RU2706892C2 - Cryogenic heat exchanger cooling method and device and hydrocarbon flow liquefaction method - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: present invention relates to a method and a device for cooling a cryogenic heat exchanger for liquefying a stream of hydrocarbons, such as a stream of natural gas. Method includes receiving one or more refrigerant temperature readings, providing coolant temperature indication, comparing one or more coolant temperature readings with one or more corresponding predetermined threshold values and selection of one of the procedures for automatic cooling of the cryogenic heat exchanger in the warm state and automatic cooling of the cryogenic heat exchanger in the cold state based on the comparison results.

EFFECT: technical result consists in increase of heat exchanger cooling speed.

15 cl, 7 dwg

Description

Technical field

The present invention relates to a method and apparatus for cooling a cryogenic heat exchanger.

In various embodiments of the invention specifically described herein, a cryogenic heat exchanger is suitable for liquefying a hydrocarbon stream, such as a natural gas stream.

In another aspect, the present invention relates to a method for liquefying such a hydrocarbon stream.

State of the art

Several types of cryogenic heat exchangers are known. Such cryogenic heat exchangers can be used in processes for liquefying a natural gas stream to produce liquefied natural gas (LNG). In this case, the cryogenic heat exchanger is generally capable of receiving a stream of hydrocarbons to be liquefied, exchanging heat between the hydrocarbon stream and at least partially evaporating refrigerant, thereby at least partially liquefying the hydrocarbon stream and releasing at least partially liquefied hydrocarbon stream.

Depending on the type of hydrocarbon in the stream and the pressure level at which the hydrocarbon stream passes through a cryogenic heat exchanger, the typical temperature at which, for example, natural gas begins to liquefy, can be –135ºC.

However, in preparation for the normal cooling and / or liquefaction of the hydrocarbon stream, the cryogenic heat exchanger must be cooled, which may, for example, be part of the installation start-up procedure.

To prevent damage to the cryogenic heat exchanger, including, for example, leaks that may result from the uneven distribution of thermal expansion and contraction over the cryogenic heat exchanger, operators and manufacturers of such cryogenic heat exchangers generally recommend that, as far as possible, exceeding a certain predetermined maximum temperature change rate with time .

On the other hand, in order to minimize this unproductive or non-optimal production period of the cryogenic heat exchanger, operators usually want to cool the cryogenic heat exchangers at the highest possible speed.

US Pat. No. 4,809,154 describes an automated control system for liquefied natural gas plants using mixed refrigerant, which has optimized functional parameters. Optimization is carried out by adjusting parameters, such as the available number of components, composition, compression ratio of the mixed refrigerant, as well as the compressor turbine speed, in order to achieve the highest performance of each unit of the unit that consumes electricity.

In more detail, the process control system of the US '154 patent is implemented in a parallel processing computer system that allows parallel control processes to be performed on several processors with access to shared memory, which stores values that characterize the current state of each sensor and each controller associated with the production installation. To organize the work of parallel control processes, the sequence of requests and the order of responses, as well as the priority table, which is used to resolve conflicts between parallel cycles of work processes, are supported.

The '154 US patent process controller system may work appropriately to optimize or maintain the optimum amount or quality of liquefied gas produced during the liquefaction process. However, the US 15 154 patent process controller system is not suitable for controlling a cryogenic heat exchanger during initial cooling at start-up, since it requires a series of steps that cannot be processed using a system of priority and request and response tables.

WO2009 / 098278 describes a method and apparatus for cooling a cryogenic heat exchanger. The cooling is carried out in automatic mode and provides the possibility of cooling at the highest possible speed without exceeding the specified maximum rate of temperature change.

Short description

The objective of the invention is to provide a device and method that allows more flexible and faster cooling of the cryogenic heat exchanger, in particular in situations where the cryogenic heat exchanger resumes after suspension, at which the refrigerant temperature is still significantly lower than the ambient temperature. Such a situation may occur, for example, if the work was suspended for a relatively short period of time (for example, for maintenance after a forced emergency shutdown of the compressor, a usual break or stop) or even after longer suspensions (days) during which proper sheathing is carried out to keep the temperature as low as possible.

The present invention provides a device for cooling a cryogenic heat exchanger to liquefy a hydrocarbon stream, such as a natural gas stream, wherein the cryogenic heat exchanger is configured to receive a hydrocarbon stream to be liquefied and a refrigerant for exchanging heat between the hydrocarbon stream and the refrigerant, thereby at least partially liquefying hydrocarbon stream, as well as releasing at least partially liquefied hydrocarbon stream and spent refrigerant passing through cryogenic t an exchanger, while the device contains

a refrigerant recirculation circuit for recycling the spent refrigerant back to the cryogenic heat exchanger, the refrigerant recirculation circuit comprising at least a compressor, a compressor recirculation valve, a cooler and a first Joule-Thomson throttle valve;

- a programmable controller configured to perform a comparison step (502), including:

(i) receiving one or more readings of the temperature of the refrigerant, providing an indication of the temperature of the refrigerant,

(ii) comparing one or more readings of the temperature of the refrigerant with one or more corresponding predetermined threshold values, and

(iii) selection of one of the procedures for automatic cooling of a cryogenic heat exchanger in a warm state and automatic cooling of a cryogenic heat exchanger in a cold state based on the results of comparison in accordance with paragraph (ii).

After step (iii), the programmable controller is configured to perform the selected cooling procedure. It should be noted that warm and cold cooling procedures are similar procedures, which may include similar actions, but the actions are performed differently, in particular, they differ in one of the following aspects: different step sizes for opening / closing valves, different opening times / closing of valves, various threshold values for deciding on further opening / closing of valves, in particular, various values of SIT.

In particular, the cold cooling procedure is different from the warm cooling procedure, since the warm cooling procedure includes the stage of closing the throttle valve (it closes automatically or the operator is instructed to close the throttle valve), while the cooling procedure when cold, it can start when the throttle valve is open. The cold cooling procedure allows you to start lowering the temperature of the cryogenic heat exchanger from the (still) cold state (for example, from −80 ° C to −130 ° C) to the point of LNG production (approximately −165 ° C). This is described in more detail below.

The term warm cooling procedure is used to describe a cooling procedure in which the initial temperature of the refrigerant is relatively high, i.e. above a predetermined threshold, and a pre-cooling procedure may be required. An example of a warm cooling procedure is described in detail in document WO2009 / 098278, which is incorporated herein by reference.

The term cold cooling procedure is used to describe a cooling procedure in which the initial temperature of the refrigerant is relatively low, i.e. below a predetermined threshold value, and a pre-cooling procedure is not required.

The warm cooling procedure is usually applied at the first start-up of a new device or at the end of a relatively long maintenance period. However, relatively short maintenance work should be performed during the device’s service life, at the end of which the refrigerant remains relatively cold, i.e. well below ambient temperature. Instead of waiting for the refrigerant to reach a temperature that allows the warm cooling procedure, it is proposed to use the cold cooling procedure, which allows the refrigerant to cool from a relatively cold starting point. This is relatively time efficient. It also increases flexibility, as it enables automatic cooling from warm and cold conditions.

After cooling the cryogenic heat exchanger through the method described above and / or using the device described above, the hydrocarbon stream may be liquefied in one or more stages, including a heat exchange process for the hydrocarbon stream in the cryogenic heat exchanger to produce a liquefied hydrocarbon product.

In another aspect, the invention provides a method for cooling a cryogenic heat exchanger for liquefying a hydrocarbon stream, such as a natural gas stream, comprising the steps of:

- provide a cryogenic heat exchanger configured to receive a hydrocarbon stream to be liquefied and a refrigerant to conduct heat exchange between a hydrocarbon stream and a refrigerant, thereby at least partially liquefying a hydrocarbon stream, and also releasing at least partially a liquefied hydrocarbon stream and spent refrigerant, passed through a cryogenic heat exchanger,

- provide a refrigerant recirculation loop for recirculating the spent refrigerant back to a cryogenic heat exchanger comprising at least a compressor, a compressor recirculation valve, a cooler and a first throttle valve;

- perform the comparison step (502), including:

(i) receiving input signals representing sensor signals from one or more readings of a refrigerant temperature, providing indications of a refrigerant temperature,

(ii) comparing one or more readings of the temperature of the refrigerant with one or more corresponding predetermined threshold values, and

(iii) selection of one of the procedures for automatic cooling of a cryogenic heat exchanger in a warm state and automatic cooling of a cryogenic heat exchanger in a cold state based on the results of comparison in accordance with paragraph (ii).

A brief description of the graphic materials

The present invention is illustrated here only by way of example, with reference to embodiments and the accompanying schematic graphic materials, not having a restrictive nature, on which:

FIG. 1 schematically illustrates a cryogenic heat exchanger device in accordance with one embodiment of the invention;

FIG. 2 schematically illustrates a cryogenic heat exchanger device in accordance with another embodiment of the invention;

FIG. 3 schematically illustrates a block diagram of the automatic cooling of the cryogenic heat exchanger of FIG. 1 or FIG. 2;

FIG. 4 schematically illustrates the arrangement of a primary cryogenic heat exchanger in accordance with another embodiment of the invention used to conduct the test;

FIG. 5 schematically illustrates the circuit of FIG. 4 with designation of temperature and pressure control points;

FIG. 6 illustrates a block diagram of the automatic cooling of the cryogenic heat exchanger of FIG. 4 or FIG. 5

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present description, the same reference number will be assigned for the line (pipeline), as well as for the flow passing along this line (pipeline). The same reference numbers indicate similar components, flows or lines (pipelines).

Methods and devices are described using a programmable controller that is configured to receive input signals, such as user input and measurement data, for processing input signals and generating control signals such as output data and valve control signals.

The programmable controller can be made in the form of a computer containing an input / output device for receiving / transmitting signals, a storage device configured to store data, and a processor configured to communicate with the input / output device and a storage device (read, write). The specified processor is configured to read and execute program lines, for example, stored in a storage device, to perform the described method. The storage device may also (partially) be located as a separate unit available to the programmable controller.

A programmable controller can be integrated into a distributed control system (DCS), in which, for example, modules provide output through a server interface, such as OLE (embedded and composable objects), for process control (OPC), which can communicate between a computer program and various interface units that may be present in the DCS. With this arrangement, the DCS can return control, without waiting for the transfer of control to the programmable controller, which may be necessary during emergency situations or similar cases.

Automatic cooling of the cryogenic heat exchanger provides the advantage of cooling the cryogenic heat exchanger at the highest possible speed without exceeding the specified maximum rate of temperature change. When cooling a cryogenic heat exchanger with manual control, the operator usually needs to maintain wider boundaries between the rate of temperature change and the indicated maximum.

In addition, thanks to the automation described in this document, even more time-efficient cooling is provided.

In addition, the methods and devices disclosed herein can also be used to eliminate a situation in which one or more spatial temperature gradients in or around the cryogenic heat exchanger exceed the recommended maximum value (s).

The advantages of the methods and devices described herein are more pronounced for cooling counterflow cryogenic heat exchangers, preferably using external refrigerant, in which the evaporating refrigerant flows countercurrently with respect to the flow or flows that must be cooled in the cryogenic heat exchanger from the evaporating refrigerant than for cooling the direct-flow cryogenic heat exchangers.

As one skilled in the art will understand, the maximum rate of temperature change and / or the maximum spatial temperature gradient usually depends on the type and / or specific design of the heat exchanger that is being cooled. Specific recommendations regarding these values may be provided by the manufacturer.

If the cryogenic heat exchanger contains an annular space for evaporating the refrigerant and a pipe space for automatically cooling the refrigerant, the selected spatial temperature gradient may reflect the temperature difference between the annular space of the cryogenic heat exchanger and the pipe space containing the refrigerant.

There are other preferred temperature gradients that are used, for example, in circuits in which a liquid-vapor separator is provided downstream of the cooler and upstream of the first throttle valve to produce a partially condensed refrigerant and to separate a partially condensed refrigerant stream to a liquid heavy fraction of a refrigerant and a gaseous light fraction of a refrigerant, as well as to discharge a liquid heavy fraction of a refrigerant through an outlet for liquid and the release of a gaseous light fraction of the refrigerant through the gas outlet, and these fractions pass to the cryogenic heat exchanger, in which the first throttle valve is configured to control the passage of one of these fractions, preferably the light fraction of the refrigerant.

In such a scheme, the selected spatial temperature gradient may reflect one or more of the following parameters: the temperature difference in the cryogenic heat exchanger between the spent refrigerant at the gas outlet and the refrigerant at the inlet for gaseous refrigerant; and a temperature difference in the cryogenic heat exchanger between the spent refrigerant at the liquid outlet and the refrigerant at the liquid refrigerant inlet.

Other possible controlled variables include variables characterizing the operating conditions of one or more compressors, such as surge conditions. The so-called surge deviation parameter can be determined based on sensor data to quantify the deviation between surge and actual compressor operating conditions. Typical sensor data that is taken into account when determining the surge deviation parameter contains the flow through the corresponding compressor stage and the inlet and outlet pressure at the corresponding stage.

For automatic cooling of the cryogenic heat exchanger, one or more of the controlled variables may include one or both of the following: setting the first throttle valve, which is the value of the degree of opening of the first throttle valve; and setting the compressor recirculation valve, which is the value of the degree of closure of the compressor recirculation valve. The degree of opening of the first throttle valve directly affects the cooling rate of the cryogenic heat exchanger, because this is one of the factors determining the Joule-Thomson effect that occurs when the flow of refrigerant passes through the throttle valve, which determines the cooling capacity of the refrigerant. The degree of closure of the compressor recirculation valve also affects the cooling rate of the cryogenic heat exchanger, since it also affects the Joule-Thomson effect in the first butterfly valve, as this is one way of regulating the pressure and flow rate of the refrigerant.

Of course, there are other adjustable variables that can be used to control the pressure and / or flow rate of the refrigerant, for example, the speed of the compressor rotor. Thus, the compressor rotor speed can also be used as one of the controlled variables. However, unlike speed, a valve that has a relatively direct effect on pressure is a very convenient element for manipulating the control sequence.

The methods and devices described herein can be used in methods of liquefying a hydrocarbon stream, such as a natural gas stream. In this case, after cooling the cryogenic heat exchanger, normal operation follows, in which the hydrocarbon stream is cooled in the cryogenic heat exchanger before liquefaction, preferably followed by supercooling in the cryogenic heat exchanger or in the subsequent heat exchanger.

It is desirable to liquefy the flow of natural gas for a number of reasons. For example, storing and transporting natural gas over long distances is easier in the liquid than in the gaseous state, since it takes up a smaller volume and does not require high pressure for storage.

Typically, natural gas containing predominantly methane is fed to the LNG plant at elevated pressures and pretreated to produce a purified feedstock suitable for liquefaction at cryogenic temperatures. The purified gas is processed through many stages of cooling using heat exchangers to gradually reduce its temperature until liquefaction is achieved. Then, liquid natural gas, if required, is further cooled and expanded by one or more expansion steps to a final atmospheric pressure suitable for storage and transportation. Steam released at each stage of expansion can be used as a source of factory fuel gas.

It is noted that US Patent Application 2006/0213223 A1 describes a liquefaction plant and a method for producing liquefied natural gas. The control of the installation can be fully or partially automated, for example, using the appropriate computer, programmable logic circuit (PLC), using circuits with closed loop and open loop, using proportional-integral-differential (PID) control. However, US application 2006/0213223 does not propose a computer program or algorithm as described herein.

As schematically illustrated in FIG. 1, there is provided a cryogenic heat exchanger 1 adapted to receive, through a conduit 2 and an inlet 7 for a hydrocarbon stream, a hydrocarbon stream that must be liquefied in order to provide heat exchange between the hydrocarbon stream and at least partially evaporating refrigerant 3. As a result of heat exchange the hydrocarbon stream may be liquefied at least partially. Preferably, the at least partially liquefied hydrocarbon stream is discharged through the hydrocarbon stream outlet 8 and supplied to conduit 4. In the embodiment of the invention illustrated in the drawing, conduit 2 and conduit 4 are connected via pipe space 29. However, other types of heat exchangers are possible.

The cryogenic heat exchanger 1 contains an inlet 5 for incoming from the outside of the refrigerant and an outlet 6 for the spent refrigerant, which passed through the cryogenic heat exchanger. The refrigerant recirculation circuit 10 is provided for recirculating the spent refrigerant back to the inlet 5. The refrigerant recirculation circuit 10 includes at least a compressor 11, a compressor recirculation valve 12, a cooler 13, and a first throttle valve 14 (first Joule-Thomson valve).

In practical embodiments, a throttle valve may be used in conjunction with an expander. However, in particular during cooling of the heat exchanger, a throttle valve is preferably used for regulation.

In practical embodiments of the invention, the compressor may comprise a plurality of compression stages, for example 15 compression stages or more. A number of these stages, for example 15 of these stages, can be made in the form of an axial compressor or a centrifugal compressor located in one housing. Each stage may contain a special recirculation valve and / or one recirculation valve can be shared by any number of subsequent stages. Several compressors or compressor housings may be arranged in series one after another to form a compressor line. Each housing (or compressor stage) can be followed by any number of additional coolers (or intercoolers) and additional steam separators to remove any liquid from the compressed steam before passing the compressed steam to the next compression stage. After the last stage of compression, the compressed refrigerant stream can be cooled.

However, for the purpose of illustrating the present invention, in FIG. 1 and 2 schematically depict a simplified compressor circuit, with only one compressor and one recirculation valve. Next, with reference to FIG. 4-6, an example containing two compression stages is described in more detail.

In the process, the spent (at least partially evaporated) refrigerant leaves the heat exchanger 1 through the outlet 6 and at least part of it enters the suction port of the compressor 11 through the pipe 25.

The gaseous portion of the spent refrigerant stream in the conduit 25 is compressed to produce a compressed refrigerant stream 16, which is then cooled in one or more coolers, illustrated herein as cooler 13, thereby at least partially condensing the compressed refrigerant stream 16 to form a stream of at least at least partially condensed refrigerant 17. The flow of at least partially condensed refrigerant 17 expands through the first throttle valve 14 and then is supplied to the heat exchanger 1 through the inlet 5.

As illustrated in FIG. 1, the flow of refrigerant passes through the heat exchanger 1 straight through with the flow of hydrocarbons (from left to right). However, said flow can be directed countercurrently, as, for example, illustrated in FIG. 2.

In FIG. 2 illustrates an alternative cryogenic heat exchanger device that contains the same elements as in the embodiment of FIG. 1, and furthermore comprises a refrigerant tube space 15 for automatically cooling the refrigerant. In the heat exchanger 1, heat exchange occurs both of the hydrocarbon stream 2 and of the refrigerant, with the evaporating refrigerant. The compressed refrigerant stream 16 is then cooled in one or more chillers, illustrated herein as cooler 13, followed by cooling in the heat exchanger 1 through the pipe space 15, thereby at least partially condensing the compressed refrigerant stream 16 to form at least a stream partially condensed refrigerant 17. An automatically cooled stream of at least partially condensed refrigerant 17 exits the heat exchanger through the outlet 18 and is supplied through the first rosselny valve 14 before it enters through the inlet 5 to the heat exchanger 1, where it is able to at least partially evaporate.

If necessary, a refrigerant make-up system can be provided that is capable of changing the available amount of refrigerant, in particular in the case of mixed refrigerant.

The present invention relates to a device or method for cooling a cryogenic heat exchanger for liquefying a hydrocarbon stream 2, 7, 29, 8, 4, such as a natural gas stream, wherein the cryogenic heat exchanger 1 is adapted to receive a liquefied hydrocarbon stream and a refrigerant for exchanging heat between a hydrocarbon stream and a refrigerant, thereby at least partially liquefying the hydrocarbon stream, and also discharge at least partially a liquefied hydrocarbon stream and spent refrigerant an agent passed through a cryogenic heat exchanger, the device comprising

- a refrigerant recirculation circuit for recycling the spent refrigerant back to the cryogenic heat exchanger, the refrigerant recirculation circuit comprising at least a compressor 11, a compressor recirculation valve 12, a cooler 13 and a first throttle valve 14;

A single component refrigerant such as methane, ethane, propane, or nitrogen may circulate in the refrigerant recirculation loop; or a multi-component mixed refrigerant, sometimes simply referred to as mixed refrigerant (CX), based on two or more components. These components can preferably be selected from the group consisting of: nitrogen, methane, ethane, ethylene, propane, propylene, butane and pentane.

The refrigerant circuit may contain any number of separate lines or flows of refrigerant for cooling various hydrocarbon streams, as well as any number of common elements or features, including compressors, coolers, expanders, etc. Some refrigerant flows may be shared, and some flows may be shared.

In a specific embodiment of the present invention, the described method for cooling a cryogenic heat exchanger is part of a method for liquefying a hydrocarbon stream, such as natural gas from a feed stream. Similarly, the apparatus described herein can be used in such a process for liquefying a hydrocarbon stream.

The hydrocarbon stream may be any suitable hydrocarbon-containing, preferably methane-containing, stream that is to be liquefied but typically recovered from a natural gas stream obtained from natural gas or an oil reservoir. Alternatively, the natural gas stream can also be obtained from another source, also including a synthetic source, such as the Fischer-Tropsch process.

Naturally, natural gas consists mainly of methane. Preferably, the feed stream contains at least 60 mol% of methane, more preferably at least 80 mol% of methane.

The hydrocarbon feed stream may be liquefied through several stages of cooling. Any number of cooling stages can be used and at each cooling stage one or more heat exchangers can be used, and also, if necessary, each cooling stage can include one or more stages, levels or sections. At each cooling stage, two or more heat exchangers can be used connected in series, in parallel or in combination.

Suitable heat exchangers of various types are known in the art for cooling and liquefying a feed stream of hydrocarbons, and the present invention can be applied to any of them. Examples of heat exchangers of this type are heat exchangers manufactured by Air Products and Chemicals Inc. and Linde AG, which typically contain one, two, three or more ligaments.

Various devices are known in the art for suitable heat exchangers capable of cooling and liquefying a feed stream, such as a hydrocarbon stream, for example natural gas, including devices with a single component mixed refrigerant (OCX), devices with a two component mixed refrigerant (DLC), devices with a propane mixed refrigerant (C ₃ -CX) based on three or more cycles, such as, for example, the so-called APX device manufactured by Air Products & Chemicals Inc. based on C ₃ -CX-N ₂ cycles, and cascading devices, including devices with a subcooling cycle. The present invention can be applied to any heat exchanger in any of such devices and other suitable devices with some minor modifications available to a person skilled in the art.

In various devices, the cooling and liquefaction of a hydrocarbon feed stream includes two (or more) cooling steps, including a pre-cooling step and a main cooling step. Typically, in the pre-cooling stage, the hydrocarbon stream is cooled to a temperature below 0 ° C, for example, to a temperature in the range from -10 ° C to -35 ° C, and in the second stage, which may be called the main cryogenic stage, the hydrocarbon stream is cooled from a temperature of the range from -10 ° C to -35 ° C to a temperature in the range from -145 ° C to -160 ° C or even -170 ° C to liquefy the flow of hydrocarbons.

The present invention may contain one or more other or additional refrigerant circuits, for example, in a pre-cooling step. Any other or additional refrigerant circuits may, if necessary, be coupled and / or combined with the refrigerant circuit to cool the hydrocarbon stream.

As indicated above, in accordance with embodiments of the present invention, a device and method are provided for cooling the heat exchanger 1. Such cooling is required before using the heat exchanger to actually liquefy the hydrocarbon stream. Cooling procedures can be controlled using a programmable controller. Different cooling procedures can be used depending on the temperature of the refrigerant.

FIG. 3 schematically illustrates a flowchart representing steps that may be performed. After a start signal is generated in step 501 (see FIG. 3), a comparison step 502 is performed, which includes:

(i) receiving one or more readings of the temperature of the refrigerant, providing an indication of the temperature of the refrigerant,

(ii) comparing one or more readings of the temperature of the refrigerant with one or more corresponding predetermined threshold values, and

(iii) selecting one of the procedures for automatically cooling a cryogenic heat exchanger in a warm state 503 or automatically cooling a cryogenic heat exchanger in a cold state 504 based on the comparison results according to paragraph (ii).

Step 502 may include checking a state, for example, verifying that a distributed start-up system (DCS) is generating an appropriate start signal and / or checking for a heartbeat signal, that is, verifying that all relevant program modules are still active.

Step (i) may include obtaining one or more indications of a refrigerant temperature comprising at least one of the indications of a refrigerant temperature

- on the inlet side of the throttle valve 14;

- on the exhaust side of the throttle valve 14;

- on the input side of the cryogenic heat exchanger 1;

- at a point inside the cryogenic heat exchanger 1;

- on the exhaust side of the cryogenic heat exchanger 1.

For each received refrigerant temperature reading, one or more suitable temperature sensors may be provided to indicate the temperature of the refrigerant at its location.

Refrigerant temperature readings can be obtained by directly measuring the temperature of the refrigerant.

Step (i) may further include obtaining a temperature difference reading between the annulus and the tube space of the heat exchanger and / or the temperature at the bottom of the heat exchanger. These temperatures can be used throughout the procedure. All actions may have a condition check, including a temperature difference check.

There is a predetermined threshold value for each received refrigerant temperature reading, and each received refrigerant temperature reading is compared with a corresponding threshold value. The comparison is to determine whether the accepted value is greater or less than the threshold value.

For example, the refrigerant temperature at the inlet side of a cryogenic heat exchanger can be compared with a threshold value of -50 ° C to determine if the temperature is above or below -50 ° C. Alternatively, the predetermined threshold value may take any suitable value, for example, -80 ° C or -130 ° C.

If the temperature is below a threshold value, an automatic cold cooling procedure 504 is selected, and if the temperature is above a threshold, a warm cooling procedure 503 is selected.

According to another example, the temperature of the refrigerant can be compared with the first and second threshold value to determine whether the temperature is between the first and second threshold value. For example, the refrigerant temperature on the downstream side of a cryogenic heat exchanger can be compared with a first threshold value of -15 ° C and a second threshold value of -55 ° C to determine whether the temperature is between -15 ° C and -55 ° C or not. This is to prevent too large temperature differences between the refrigerant and the heat exchanger. Of course, the exact values depend on the type of heat exchanger used.

In this document, the warm cooling procedure is not described in detail. A detailed description of the warm cooling procedure is given in document WO2009 / 098278. The warm cooling procedure includes the same steps as the cold cooling procedure, but the warm and cold cooling procedures are not identical, as described in more detail below.

The first action of the cold cooling procedure is the action of determining the initial states 505, in which the initial states are determined. This action can use information about critical and non-critical initial states that can be stored in memory accessible to the programmable controller.

In the event of a critical condition, the programmable controller interrupts the procedure. The procedure can be resumed and / or re-started after the critical state has been eliminated or confirmed, and the initial states were confirmed by the operator either manually or by performing an automatic control procedure to restore the initial state. In the case of a non-critical initial state, a warning may be issued. This action 505 may further initiate monitoring of critical parameters. Only after all critical parameters are within the specified ranges, the next action begins (initial opening stage 506).

Examples of critical initial states are states in which:

- the first throttle valve 14 is not closed sufficiently (for example, it is open by more than 0.1% or another suitable value);

- the pressure in the refrigerant circuit is lower than the pressure at the outlet of the compressor 11;

- the compressor 11 is not online and does not work, which is determined by measuring the speed of the compressor (for example, the compressor is operating at least at a speed of 3400 rpm or at another suitable speed) and checking that the inlet and exhaust valves;

- the refrigerant pressure is too high (for example, above 20 bar gage (2 MPa) or another suitable value);

- The guide flap at the compressor inlet (NZV) is open.

Examples of non-critical initial states are states in which:

- there are differences in actual temperatures, for example, the temperature of the refrigerant directly upstream and the temperature directly downstream of the first throttle valve 14, and / or temperature differences;

- compressor recirculation valves are not fully open (for example, less than 99% open or less than any other suitable amount);

- the pressure of the compressed refrigerant is lower than the set minimum value (as this may slow down the cooling processes too much). As a rule, a suitable minimum value is 18 bar. (1.8 MPa).

The warm and cold cooling procedure includes an initial opening step 506, an initial opening step 506 includes initiating an initial opening of the first throttle valve 14, wherein the initial opening step of the first throttle valve 14 according to the automatic warm cooling procedure 503 is different from the initial opening step the first throttle valve 14 according to the automatic cold cooling procedure 504.

According to an embodiment of the invention, the initial opening of the first throttle valve is more in the automatic warm cooling procedure 503 than in the automatic cold cooling procedure 504.

For example, the initial opening initiated on the throttle valve 14 according to the automatic cold cooling procedure 503 may be in the range of 1 - 2%, while the initial opening initiated on the throttle valve according to the automatic cooling cooling procedure 504 may be in the range 3 - 5%.

In the automatic warm cooling procedure 503, the throttle valve 14 initially opens relatively tightly to check whether the Joule-Thomson effect occurs.

Valve opening is expressed in%, which reflects the position of the valve plug (moving part of the valve) relative to its valve seat (fixed part of the valve). It is understood that 0% means that the valve is completely closed (the valve plug on the valve seat), 100% means that the valve is fully open (the valve plug is farthest from the valve seat). It is understood that the ratio between the opening of the valve (%) and the flow rate depends on the type of valve used (for example, ball valve, disk valve, valve type linear valve, valve type quick opening valve) and therefore may differ from the ratio 1: 1.

According to an alternative embodiment of the invention, the initial opening step 506 of the first throttle valve 14 in the automatic warm cooling procedure 503 includes initiating a predetermined initial opening of the first throttle valve 14 (for example, 3-5%), wherein the initial opening step 506 of the first throttle valve 14 the automatic cold cooling procedure 504 includes determining the current opening of the first throttle valve 14 and initiating a certain current opening of the first throttle valve 14.

This allows you to start the cold cooling process without adjusting the setting of the first butterfly valve. In any case, the predetermined initial opening of the cold cooling procedure is less than the predetermined initial opening of the warm cooling procedure.

According to an embodiment of the invention, the initial opening step 506 of the cold cooling procedure 504 also includes opening the recirculation valve of the compressor 12.

This is in contrast to the warm cooling procedure 503, in which the compressor recirculation valve 12 remains closed or quickly closes during the initial opening of the warm cooling procedure. In the cold cooling procedure, the recirculation valve of the compressor 12 may already be open during the initial opening 506 of the cold cooling 504.

Opening the compressor recirculation valve as part of the initial opening phase 506 will be performed mainly in the event of a short emergency shutdown. Typically, the compressor recirculation valve will be closed during the initial opening phase 506.

According to an embodiment of the invention, the programmable controller is configured to perform, as part of the initial opening step 506, an SIT step including adjusting the opening of the first throttle valve 14 based on the determined rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve 14, in accordance with an adjustment circuit, wherein the automatic warm cooling procedure 503 and the automatic cold cooling procedure 504 have different walkings.

Both warm and cold cooling procedures 503, 504 include comparable SIT stages, but different states are used in both SIT stages to decide how to control the opening of the butterfly valve 14.

According to an embodiment of the invention, the determination of the rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve 14 is carried out by comparing two readings of the refrigerant temperature obtained at the corresponding first t ₁ and second t ₂ time points, the first and second time points are separated by a predetermined interval time, and the predetermined time interval according to the cold cooling procedure 504 is less than the predetermined time interval according to the warm cooling procedure 503.

The time interval according to the cold cooling procedure may be less than 50% of the time interval according to the warm cooling procedure.

The time interval according to the cold cooling procedure can usually be 2 minutes, while the time interval according to the warm cooling procedure can usually be 5 minutes. Therefore, in accordance with this example, SIT according to the warm cooling procedure 503 is calculated as follows: SIT _heat. (t) = (T _t-5 -T _t ) * 12 [° C / h], where SIT according to the cold cooling procedure 504 is calculated as follows: SIT _ch. (t) = (T _t-2 -T _t ) * 30 [° C / h], where t _i is the time in minutes and T is the temperature.

A specific SIT is compared with a predetermined threshold SIT to prevent cooling too quickly. For example, in accordance with the cold cooling procedure 503, the predetermined SIT threshold value may be 28 ° C. The adjustment scheme may state that if the SIT value is _cold. exceeds a predetermined threshold SIT value, for example, is higher than 28 ° C, the first throttle valve 14 will be closed with a certain set closing value (for example, 0.5%) and a predetermined waiting time (for example, 5 minutes) will be initiated before continuing to open the first throttle valve 14 with a predetermined opening value (for example, 0.2%), wherein the predetermined closing value is greater than the predetermined opening value.

Temperature measurements used to determine the appropriate rate of change of temperature (SIT) can be obtained by measuring the temperature of the refrigerant in one or more of the following places:

- on the inlet side of the throttle valve 14;

- on the exhaust side of the throttle valve 14;

- on the input side of the cryogenic heat exchanger 1;

- at a point inside the cryogenic heat exchanger 1;

- on the exhaust side of the cryogenic heat exchanger 1.

According to an embodiment of the invention, the adjustment scheme of the cold cooling procedure includes waiting for a predetermined time interval between the initiation of the initial opening of the first throttle valve and the beginning of the CIT stage. The SIT step includes (as described above) adjusting the opening of the first throttle valve 14 based on the controlled rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve 14.

Waiting for a given time interval provides a gradual decrease in pressure drop. A large pressure drop will increase the effect of J.-T. and further too quick opening can lead to an excessively high SIT.

The end of the initial opening phase 506 can be determined by determining the SIT and verifying that its value is less than a predetermined value or is within a predetermined range.

After the initial opening phase 506 is completed, the automatic cooling process in the cold state proceeds to the adjustment phase 507, which simultaneously includes:

- adjusting and closing the recirculation valve (509) and

- additional adjustment of the first throttle valve (508).

As will be described in more detail below with reference to FIG. 4-6, act 509 may include adjusting and closing the plurality of recirculation valves (509) and / or act 508 may include further adjusting the plurality of butterfly valves, in particular the first and second butterfly valves.

At act 508, the first throttle valve 14 is further adjusted. In particular, in the embodiment of the invention illustrated in FIG. 2, strong cooling can cause condensation of the refrigerant. Preferably, just before the condensation, the valve movements are slowed down, and at the moment condensation is detected, the valve can be partially closed to avoid a too high cooling rate, which otherwise would occur due to a sharp increase in flow due to condensation (often an increase of 100 t / day ( tons per day) for 10 s). After condensation is detected, the valve can be opened normally and left open until the effect of J.-T. will not decrease. Effect J.-T. can be controlled when the throttle valve is opened further, for example, based on the difference in temperature of the refrigerant upstream of the throttle valve and the refrigerant downstream of the throttle valve. It can be assumed that the effect of J.-T. present if the temperature difference exceeds 8 ° C.

Condensation can be detected by deviating from one or both of the temperature and flow readings on the butterfly valve. For the refrigerant that flows through the first throttle valve 14, the refrigerant temperature downstream of the throttle valve 14 and / or the flow rate through the throttle valve, which, in turn, can be estimated from the differential pressure in the throttle valve 14, can be used.

In preferred embodiments of the invention, the degree of closure of the throttle valve 14 cannot be greater than the minimum degree of opening corresponding to the degree of opening when starting this module.

Change in the effect of J.-T. additional throttle valve opening may be negligible. However, at the same time, the pressure of the refrigerant increases, since at the same time the action 509 of adjusting the recirculation valve 12 is performed to achieve the target deviation of the compressor pressure (or the number of compression stages). This module monitors the pressure deviation of the compressor 11 and closes the recirculation valve 12 if the pressure deviation exceeds a predetermined maximum deviation. A suitable predetermined maximum deviation is 0.3.

If there are many recirculation valves, for example, at multiple compressor stages, each recirculation valve can be adjusted separately (but at the same time), taking into account the special pressure deviation parameter for the corresponding stage through which each particular recirculation valve regulates recirculation.

Since closing the recirculation valve 12 affects the suction pressure of the compressor, it is preferable that this pressure be adjusted so that it does not fall below the recommended limit, for example, below 1.8 bar. (0.18 MPa). Closing the recirculation valve also reduces the suction pressure. Therefore, closing the recirculation valve is conditional in order to avoid lowering the suction pressure below a predetermined target value. The task is to maintain a linear change (increase) in the outlet pressure by constantly closing the recirculation valves, while controlling the pressure deviation. When the pressure deviation is less than the considered minimum level (for example, 0.1), the module is terminated. However, the pressure deviation is monitored throughout the final cooling procedure, and when the allowable pressure deviation and suction pressure are within a predetermined range, the recirculation valves close.

When the temperature of the cryogenic heat exchanger 1 reaches the operating temperature, an end signal is generated. This can be part of actions 508 and 509, each action can generate a separate end signal, or, as part of one of the actions or a separate action, a single end signal can be generated (not illustrated). When the termination signal (s) is triggered, the programmable controller can complete the automatic cold cooling procedure (step 510 in FIG. 3).

The action of the end 510 may completely close the recirculation valve 12, as far as possible, provided that the pressure deviation does not prevent this. If the pressure deviation prevents further closure of the recirculation valve when the pressure deviation is too small (usually below 0.1), a warning message may be generated and issued to notify the operator that adjustment of the BOP may be necessary. The movement of the NZV gives the same effect as closing the recirculation valve 12. However, any movement of the NZV can be limited by the molecular weight of the passing refrigerant, which must exceed a predetermined minimum value. The minimum molecular weight of a typical CX is 24 g / mol. Obviously, such a warning signal cannot be used as an additional function if there is no NZV on the compressor used.

Since the movement of the NZV is considered the last resort, it is only intended to notify the operator of the need to move the NZV instead of trying to perform any movement of the NZV under the control of an automatic procedure, as described in this document.

As soon as the recirculation valve closes completely or sufficiently, control can be transferred to the operator and / or an output condition is provided or an alert signal is generated to inform the operator of the possibility of continuing normal operation of the cryogenic heat exchanger, or the like. Alternatively, a subsequent control procedure or the like can be started, for example, conventional operation control, such as advanced process control, as described, for example, in US Pat. No. 7,266,975 and / or US Pat. No. 6,272,882, or any other type of module.

FIG. 4 illustrates a large cryogenic heat exchanger 100 integrated in a system of various pre-cooling heat exchangers served by such an additional refrigerant circuit, as well as other equipment that may be used in a hydrocarbon liquefaction plant. An additional refrigerant circuit may hereinafter be referred to as a “pre-refrigerant circuit” or “pre-refrigerant cycle”. Similarly, elements such as compressors and refrigerant may also be referred to as a “pre-refrigerant compressor” or “pre-refrigerant”.

The cryogenic heat exchanger 100 according to this embodiment of the invention will hereinafter be called the main cryogenic heat exchanger 100 in order to distinguish it from any other heat exchangers present in the embodiment of the invention. The main cryogenic heat exchanger 100 contains a warm end 33, a cold end 50 and a middle part 27. The wall of the main cryogenic heat exchanger 100 forms the annulus 110. In the annulus 110 is located:

a first pipe space 29 extending from the warm end 33 to the cold end 50, preferably extending between the inlet for the hydrocarbon stream 7 and the outlet for the hydrocarbon stream 8;

a second pipe space 28 extending from the warm end 33, preferably from the inlet for gaseous refrigerant 49a at the warm end 33 to the middle portion 27; and

a third pipe space 15 extending from the warm end 33, preferably from the inlet for liquid refrigerant 49b at the warm end 33 to the cold end 50.

To compress the refrigerant, a refrigerant compressor line is provided, symbolically illustrated herein, comprising the first and second compressors 30 and 31. Each of these compressors is equipped with several recirculation valves, which are schematically represented in this document by recirculation valves 130 and 131 in the recirculation line connecting the compressor outlet downstream of the respective coolers, with a suction port on the low pressure side.

The first refrigerant compressor 30 is driven by a suitable engine, for example, a gas turbine 35, which is equipped with an auxiliary engine 36 for starting, and the second refrigerant compressor 31 is driven by a suitable engine, for example, a gas turbine 37, equipped with an auxiliary engine (not illustrated). Alternatively, compressors 30 and 31 may be driven on a single shaft by a common motor.

During normal operation, after cooling the main cryogenic heat exchanger, a gaseous, preferably methane-rich hydrocarbon feed stream is supplied at elevated pressure through the feed pipe 20 to the first pipe space 29 of the warm end 33 of the main cryogenic heat exchanger 100. The hydrocarbon feed stream passes through the first pipe space 29 where it cools, liquefies and, optionally, is supercooled by mixed refrigerant (CX), evaporating in the annulus 110, forming a waste this refrigerant. The resulting liquefied hydrocarbon stream is removed from the main cryogenic heat exchanger 100 at its cold end 50 through line 40. The flow of hydrocarbon through the system can be controlled, for example, using a drain valve 44 provided in line 40.

Stream 40 may, if desired, pass through a suitable end evaporator system, where the pressure is reduced to storage and / or transportation pressure. Ultimately, the liquefied hydrocarbon stream is supplied as a product stream to a storage, where it is stored as a liquefied product, or, optionally, directly sent for transportation.

During normal operation and during cooling of the main cryogenic heat exchanger, the spent refrigerant is removed from the annulus 110 of the main cryogenic heat exchanger 100 at its warm end 33 through a pipe 25 and passes to a steam separator 56.

A recharge control line of refrigerant 65 is also supplied to the steam separator 56 to optionally add refrigerant components to the waste refrigerant stream. The addition of various refrigerant components is controlled by one or more valves, typically one valve per component. In this document, these valves are schematically represented as valve 66.

The evaporated spent refrigerant fraction 55, which leaves the top of the steam separator 56, is compressed in the refrigerant compressors 30 and 31 to produce a compressed refrigerant stream that is removed through line 32. Other refrigerant compressor devices are also possible.

The heat of compression is removed from the fluid passing between the two refrigerant compressors 30 and 31 through line 38 to a natural cooler 23, which may include an air cooler and / or water cooler, and / or any other type of natural cooler. Similarly, an intermediate heat exchanger (not illustrated) may be provided between two successive compressor stages of the compressor.

The compressed refrigerant stream in line 32 is cooled in the air cooler 42 and partially condensed in one or more pre-cooling heat exchangers (illustrated by reference numerals 43 and 41) due to the pre-cooling refrigerant cycle, which will be described in more detail below. Pre-cooling heat exchangers 41, 43 can operate at different pressures and / or use refrigerants of various compositions.

The partially condensed refrigerant stream 39 then passes and is introduced into the liquid / vapor separator through an inlet device, which are illustrated herein as a separator tank 45 and an inlet 46. In the separator tank 45, the partially condensed refrigerant stream is separated into a liquid, heavy refrigerant fraction (TPC) and on the gaseous, light fraction of the refrigerant (LFH). Each of these flows may be separately controlled by a throttle valve or similar device, wherein the first throttle valve 58 controls the flow of vaporous (light) refrigerant, and the second throttle valve 51 controls the flow of liquid (heavy) refrigerant.

The liquid heavy fraction of the refrigerant is removed from the separator tank 45 through line 47, and the gaseous light fraction of the refrigerant is removed through line 48. The heavy fraction of the refrigerant is supercooled in the second pipe space 28 of the main cryogenic heat exchanger 100 to produce a supercooled heavy refrigerant stream 54. The supercooled heavy refrigerant stream is removed the main cryogenic heat exchanger 100 through the pipe 54 with the possibility of expansion in a throttle device containing a second dros reset valve 51. The throttle device may further comprise a dynamic expander (not illustrated) connected in series with the second throttle valve 51, which does not need to be controlled during any cooling procedure of the main cryogenic heat exchanger.

A stream of supercooled heavy refrigerant under reduced pressure is introduced through line 52 and nozzle 53 into the annular space 110 of the main cryogenic heat exchanger 100 in its middle part 27. The heavy refrigerant stream has the ability to evaporate in the annular space 110 under reduced pressure, thereby cooling liquids in the pipe spaces 29 , 28 and 15.

The gaseous light fraction of the refrigerant removed from the separator tank 45 through line 48 passes into the third pipe space 15 in the main cryogenic heat exchanger 100, where it is cooled, liquefied and supercooled to produce a stream of supercooled light refrigerant 57. The stream of supercooled light refrigerant is removed from the main cryogenic heat exchanger 100 through a pipe 57 expandable in a throttle device containing a first throttle valve 58. At reduced pressure, it is introduced through cutting the pipe 59 and the nozzle 60 into the annular space 110 of the main cryogenic heat exchanger 100 at its cold end 50. The light refrigerant stream can evaporate in the annular space 110 under reduced pressure, thereby cooling liquids in the pipe spaces 29, 28 and 15.

Optionally (not illustrated), an additional side stream may be taken from the gaseous light refrigerant stream 48, which may be cooled, liquefied, and supercooled by one or more other cold streams in one or more other heat exchangers other than the main cryogenic heat exchanger 100. For example, it can be cooled, liquefied and supercool due to the cold emitted steam generated during the instantaneous evaporation of stream 40 in an additional terminal evaporation system. The additional supercooled side stream may be re-combined with the light refrigerant stream in line 57 or 59, in which case it requires auxiliary throttle means such as a first auxiliary throttle valve. A more detailed description of this possibility is given in US patent 6272882.

Pre-cooling heat exchangers 41, 43 operate using pre-cooling refrigerant, which may be a multi-component refrigerant or a single-component refrigerant. In this example, propane was used. The vaporized propane is compressed in a pre-cooling compressor 127, which is driven by a suitable engine, such as a gas turbine 128. A recirculation valve for the pre-cooling refrigerant compressor 129 is also provided, which is here symbolically illustrated on the line connecting the suction inlet on the low pressure side of the first compressor stages with intermediate pressure level. However, a recirculation line may optionally be provided at all or at selected compression stages.

Then, the compressed propane is condensed in the air cooler 130 and, after that, the condensed compressed propane at increased pressure passes through pipelines 135 and 136 to heat exchangers 43 and 41, which are arranged in series with each other. Before entering the heat exchanger 43, the condensed propane is allowed to expand to an intermediate pressure via a throttle valve 138. There, the propane is partially evaporated by the heat of the multi-component refrigerant in line 32, and the resulting vaporized gaseous fraction passes through line 141 to the inlet on the intermediate pressure side of propane compressor 127. The liquid fraction passes through conduit 145 to the heat exchanger 41. Before entering the heat exchanger 41, propane can be expanded yatsya to a low pressure across throttling valve 148. The evaporated propane is passed through conduit 150 to the inlet side of propane at low pressure compressor 127.

One skilled in the art will appreciate that steam separators or similar devices can be provided in any pipe that connects to the compressor inlet to avoid supplying a non-gaseous phase to the compressor. An economizer may also be provided.

This example illustrates two pre-cooling heat exchangers operating at two pressure levels. However, any number of pre-cooling heat exchangers and corresponding pressure levels can be used.

A pre-cooling refrigerant cycle may also be used to produce hydrocarbon stream 20, for example, as described below. The hydrocarbon feed, in this example, natural gas feed, passes at elevated pressure through feed line 90. The natural gas feed, which is usually a multi-component mixture of methane and heavier components, partially condenses in at least one heat exchanger 93.

In the present example, said heat exchanger operates at approximately the same pressure level as the pre-cooling heat exchanger 43, using a side-stream of pre-cooling refrigerant 137 taken from line 135. Although not illustrated in FIG. 4, conduit 137 is connected to conduit 137a. Prior to entering the heat exchanger 93, the pre-cooling refrigerant is able to expand by means of a valve 139 to approximately intermediate pressure. The resulting vaporized gaseous fraction passes through conduits 140a and 140 to conduit 141, where it is re-combined with the gaseous fraction taken from the pre-cooling heat exchanger 43. The liquid fraction of the pre-cooling refrigerant is taken from the heat exchanger 93 into the pipe 151 and supplied to the heat exchanger 91 after expansion by means of a valve 152 to approximately low pressure. Then, the evaporated pre-refrigerant refrigerant through lines 153a and 153 enters line 150.

It is noted that heat exchangers 43 and 93 and / or heat exchangers 41 and 91 can be made in the form of combined heat exchangers containing separate spaces for natural gas and for refrigerant in the pipe 32.

Partially condensed feed 92 is introduced, for example, through an inlet device 94, into a gas / liquid separator 95, which may be provided, for example, in the form of a scrubbing column or the like. In the scrubber column 95, the partially condensed feed is separated to produce a methane-rich gaseous overhead stream 97 and a liquid methane-depleted bottom stream 115.

The gaseous overhead stream 97 through line 97, through the heat exchanger 91, passes to the upper separator 102. In the heat exchanger 100, the gaseous overhead stream is partially condensed by the pre-cooling refrigerant entering through line 151, and the partially condensed overhead stream is introduced into the upper separator 102 through the inlet 103. In the upper separator 102, the partially condensed overhead stream is separated into a gaseous stream 20 (which is substantially depleted in C5 + components and / or relatively rich in methane SG compared to the feed stream) and a liquid bottom stream 105. The gaseous stream 20 forms the hydrocarbon feed at elevated pressure and enters the duct 20.

At least a portion of the liquid bottom stream 105 may be introduced through line 105 and nozzle 106 into the scrub column 95 as a return stream. The pipe 105 is provided with a flow controller (not illustrated) and / or a pump 108.

If the return flow should be less than the amount of liquid in the partially condensed gaseous overhead stream 105, then the excess can be transferred to conduit 20 through a bypass conduit (not illustrated) and a flow regulator (not illustrated). If the return flow is too small, then the external flow of the return flow, butane, respectively, may be added to the return flow from an external source (not illustrated), into a conduit 105.

The liquid bottom stream enriched in C3 + is removed from the scrubbing column 95 via line 115. It can then be removed from the process, sent to the fractionation line and / or storage / transportation and / or reboiler by any method known to a person skilled in the art.

Before starting normal operation, the main cryogenic heat exchanger, as described above, must be cooled to operating temperature. The methods and devices described herein provide automatic cooling of the main cryogenic heat exchanger. This is demonstrated by the following.

During cooling, a number of temperatures, rates of temperature changes and temperature changes at various points in and around the main cryogenic heat exchanger can be controlled by a programmable controller. This allows the programmable controller to determine the change in temperature profile over time. FIG. 5 illustrates points in and around the main cryogenic heat exchanger 100, where temperature sensors (TR20, TR25, TR33, TR40, TR47, TR48, TR52, TR54, TR57, TR59) and differential temperature sensors (TDR2547, TDR2548, TDR2715, TDR5254, TDR5759) in addition to other temperature sensors and differential temperature sensors, which are not described in this document, since their consideration is less important for the described automation.

The circuit of FIG. 5 corresponds to the circuit of FIG. 4, but reference numbers are omitted to highlight reference numbers corresponding to the various illustrated sensors. Temperature sensors are indicated by the code “TR” followed by a number corresponding to the reference number assigned to the component, flow or line (pipe) where the sensor is provided. For differential temperature sensors, the TDR code is used, followed by two two-digit numbers corresponding to the reference numbers assigned to the components, flows or lines (pipelines) between which a differential sensor is provided. Temperature sensors and differential temperature sensors generate sensor signals that can be received and monitored by a programmable controller that can use one or more signals as control parameters.

In the upper part of the main cryogenic heat exchanger 100, temperatures in conduits 57 and 59 upstream and downstream of the first throttle valve 58 were monitored using temperature sensors TR57 and TR59. The difference in these temperatures was also controlled, which can be used to determine the actual effect of J.-T. in the first butterfly valve.

The temperature difference (TDR2715) of the annulus was measured in the middle part 27 of the main heat exchanger and the tube space 15 in the middle part 27 of the main heat exchanger. In addition, the temperature of the annulus near the warm end 33 was measured using the TR33 sensor, as well as the temperature of the spent refrigerant taken from the heat exchanger through line 25 (TR25).

The inlet temperature of the heavy liquid fraction of the refrigerant can be measured using a TR47 sensor, the inlet temperature of the hydrocarbon stream immediately upstream from the main cryogenic heat exchanger 100 can be measured using the TR20 sensor, and the inlet temperature of the hydrocarbon stream immediately downstream from the main cryogenic heat exchanger 100 can be measured using a TR40 sensor.

All temperature measurements are stable and reliable with direct flow. Therefore, measurements can be unreliable from time to time, for example, at the beginning of cooling, when the inhibited gas returns to the temperature sensor. The control depends on the initial states, for example, on pressure conditions. The temperature indicating the end of cooling is the temperature measured by the TR40 sensor on the hydrocarbon product discharge line. However, at the beginning of cooling, when the flow of hydrocarbons is extremely weak, these measurements may be unreliable. Therefore, instead, at the beginning of cooling, a different temperature can be controlled, respectively, the LPC temperature measured by the TR59 sensor downstream of the first throttle valve 58. However, at the end of cooling, the control temperature will be the temperature measured by the TR40 sensor.

During cooling, several pressures and pressure drops at various points in the circuit can be controlled by a programmable controller. In FIG. 5 illustrates the most suitable pressure sensors (PR32, PR54, PR55, PR57, PR150) using the PR code followed by a number that corresponds to the reference number assigned to the component or line (pipeline) where the sensor is provided. The most important pressures to be controlled include the suction pressure of the PR150 pre-cooling compressor in line 150, the suction pressure of the mixed refrigerant compressor 30 (PR55) in line 55; and the pressure at the outlet of the mixed refrigerant compressor PR32 in the pipe 32.

These pressure sensors generate sensor signals that can be received and monitored by a programmable controller that can use one or more signals as control parameters.

After a long shutdown of the device, the pressure in the circuit can affect the cooling procedure, in particular, if the circuit has been in full recirculation for several days. When the main cryogenic heat exchanger 100 is completely cooled, minor changes in high pressure can have large consequences. In addition, before cooling, the pressures measured by PR57 and PR54 sensors can be monitored (pressure in the LPC and TPC pipes is upstream from the first (58) and second (51) butterfly valves, respectively). If these pressures are too high, any action of the valve can have faster dynamics, therefore, as the initial state, the system should have a pressure level that is less than the specified initial maximum pressure value (during the test, the pressure was 20 bar gage (2 MPa)).

For LF and TFC flows, costs can be calculated to use as managed parameters or at least parameters to be monitored. Such calculations can be based on the difference in pressure and the nominal opening of the first (58) or second (51) butterfly valves, respectively. For this purpose, pressure measurements to the first and second throttle valves can be used both on the LPF circuit and on the TPH circuit (by PR57 and PR54 sensors, respectively), and by measuring the suction pressure (PR55 sensor) of the refrigerant circuit before being supplied to the compressor.

The standard deviation of the flow measurements with a small degree of opening of the throttle valve can be quite large, which can lead to errors in its use as a monitored parameter. The linear model of LF and TFC flows was calculated as a linear model using the least squares method for all measurements with a significant degree of valve opening. According to this model, estimated flows will be determined as:

F _LFH = K _LFH · X ₅₈ · √ (PR57 - PR55); and

F _TPC = K _TPC · X ₅₁ · √ (PR54 - PR55),

where F _LFH (F _TFH ) - the consumption of LFH in the pipeline 48 (the consumption of TFH in the pipeline 47); X ₅₈ (X ₅₁ ) - the degree of opening of the first (second) throttle valve 58 (51), respectively; and K _LFH (K _TFC ) is a constant corresponding to the slope of a linear model calculated using the least squares method. It was found that the linear least squares model satisfies the required accuracy. However, other types of functions may be used instead. In particular, a quadratic function can be used to calculate the TPC flow, while a characteristic shape resembling the square root function was found for the LPC flow.

Immediately prior to performing automatic cooling, the main cryogenic heat exchanger 100 was pre-cooled by manual control to a temperature between about –25 ° C and about –35 ° C. Other tasks that were completed at this stage manually, but can also be automated and entered into the module structure, as described, include:

- adjusting the level in any stream of gas condensate liquid (liquid natural gas, usually consisting of molecules having a mass comparable with propane and above) in the extraction column (for example, a scrubber column);

- adjustment of the temperature of the stream 20;

- pressure relief in the refrigerant circuit, namely in the pipe spaces 15, 28;

- adjusting the thawing of the gas / cold gas mixture used to cool the pipes of the refrigerant circuit in the temperature range from about –25 ° C to about –35 ° C.

Further cooling of the main cryogenic heat exchanger to a working temperature below about -155 ° C, in this document to a working temperature of about -160 ° C, was achieved using the method and device for automatic cooling. Further cooling may hereinafter be referred to as “final cooling”.

Thus, as described above, step (i) may include obtaining one or more readings of the temperature of the refrigerant containing at least one of the readings of the temperature of the refrigerant for the liquid, heavy fraction of the refrigerant (TPC) and / or for the gaseous, light fraction of the refrigerant (LF) )

- on the inlet side of the throttle valve 14;

- on the exhaust side of the throttle valve 14;

- on the input side of the cryogenic heat exchanger 1;

- at a point inside the cryogenic heat exchanger 1;

- on the exhaust side of the cryogenic heat exchanger 1.

Thus, in view of the embodiment of the invention described above with reference to FIG. 4 and 5, according to an embodiment of the invention, the refrigerant recirculation circuit for recycling the spent refrigerant back to the cryogenic heat exchanger comprises a plurality of compression stages, each compression stage comprising a compressor recirculation valve (130, 131) and the adjustment step (507) includes adjusting and closing the plurality of recirculation valves (509a, 509b).

Thus, in view of the embodiment of the invention described above with reference to FIG. 4-6, according to an embodiment of the invention, a liquid / vapor separator 45 is provided downstream of the cooler 42 and upstream of the first throttle valve to provide a partially condensed refrigerant and to separate the partially condensed refrigerant stream into a liquid heavy fraction of refrigerant (TFC) ) and the gaseous light fraction of the refrigerant (LF), as well as for discharging the liquid heavy fraction of the refrigerant through the liquid outlet and discharging the gaseous light fraction of the refrigerant through the outlet for gas, moreover, these fractions pass to a cryogenic heat exchanger in which the first throttle valve is configured to control the passage of one of these fractions, preferably a light refrigerant fraction and in which the second throttle valve is configured to control the passage of the other of these fractions, preferably heavy refrigerant fractions.

Next, with reference to FIG. 6, a block diagram of the automatic cooling of the cryogenic heat exchanger of FIG. 4 or FIG. 5.

Similar to the embodiment described above with reference to FIG. 3, after a start signal is generated in step 501, a comparison step 502 is performed, which includes:

(i) receiving one or more readings of the temperature of the refrigerant, providing an indication of the temperature of the refrigerant,

(ii) comparing one or more readings of the temperature of the refrigerant with one or more corresponding predetermined threshold values, and

(iii) based on the comparison results according to paragraph (ii), the selection of one of the procedures for automatically cooling a cryogenic heat exchanger in a warm state 503 or automatically cooling a cryogenic heat exchanger in a cold state 504.

In this document, the warm cooling procedure 503 is not described in more detail. Reference is made to document WO2009 / 098278, which provides a detailed description of the warm cooling procedure.

The cold cooling procedure 504 begins by determining the initial states during step 505, preferably in the same manner as described above. Examples of critical initial states are states in which:

- there is an excess of heavy components in the hydrocarbon feed (for example, in line 20) when adjusting the flow of hydrocarbons (usually a maximum C5 + content of 0.08 mol% is allowed);

- the first and second throttle valves (58, 51) are not closed sufficiently (during testing, the degree of opening of the valves was more than 1%);

- the pressure in the refrigerant circuit (LFH and TFC) is lower than the pressure at the outlet of the compressor 31;

- one or more refrigerant compressors 30, 31 and pre-cooling refrigerant compressor 127 are not online and do not work (which, for example, is controlled by the speed of the compressor);

- the inlet and outlet valves on these compressors are not open;

- the refrigerant pressure at the outlet of the compressor 31 is too high (the test used a maximum pressure of 20 bar g. (2 MPa));

the suction pressure of the pre-cooling refrigerant compressor 127 is outside the specified pressure range (correspondingly, the range is about 0.5 bar g. (0.05 MPa));

- any existing NZV is closed insufficiently.

Examples of non-critical initial states are states in which:

- TDR5759 sensor readings are too small (the usual minimum value recommended for a spiral heat exchanger from Air Products and Chemicals Inc is 25 ° C);

- one or more recirculation valves of the refrigerant compressor (for example, 130, 131) is not open enough (during the test, an opening degree of less than 99% was used);

- the pressure at the outlet of the compressor 31 is below a predetermined minimum value (during the test, a pressure of 18 bar g.

When the initial conditions are determined and the causes of possible warnings are eliminated, actions 506 and 511 are triggered.

During the initial opening action 506, the first throttle valve 58 for controlling the flow of vaporous (light) refrigerant and the second throttle valve 51 for controlling the flow of liquid (heavy) refrigerant are set to the initial opening (506a), the initial opening according to the automatic warm cooling procedure 503 different from the initial opening stage of the first throttle valve 14 according to the automatic cold cooling procedure 504. Preferably, the initial opening of the throttle valve to apani more in procedure automatic cooling in the warm state 503 than in the procedure of the automatic cooling in a cold state 504.

Following step 506a, step 506b initiates a timeout, as described above.

The initial opening step may include initiating the initial opening of the first and second throttle valves, while the initial opening step of the first and second throttle valves (51, 58) according to the automatic warm cooling procedure is different from the initial opening step of the first and second throttle valves (51, 58 ) according to the automatic cold cooling procedure.

In particular, the initial opening of the first and second throttle valves is more in the procedure of automatic cooling in the warm state than in the procedure of automatic cooling in the cold state.

The initial opening may further include performing an SIT step, including adjusting the opening of the first and second throttle valves 51, 58 based on the determined rate of change of temperature (SIT) of the refrigerant flowing through the first and second throttle valves 51, 58, in accordance with the adjustment scheme, wherein the automatic warm cooling procedure 503 and the automatic cold cooling procedure 504 have various adjustment schemes.

In particular, the adjustment scheme of the cold cooling procedure may include waiting for a predetermined time interval between initiating the initial opening of the first and second throttle valves 51, 58 and initiating the adjustment of the opening of the first and second throttle valves 51, 58 based on a controlled temperature change rate (SIT) ) refrigerant flowing through the first and second throttle valves 51, 58.

Further, after completing step 506, the automatic cold cooling procedure includes performing an adjustment step (507), which simultaneously includes:

- adjusting and closing the recirculation valve (509) and

- additional adjustment of the first and second throttle valves (508a, 508b).

As described above, there may be a plurality of compression stages, each compression stage containing a compressor recirculation valve (130, 131), and act 509, thus, may include adjusting and closing the plurality of recirculation valves 130, 131.

The feed adjustment is controlled by act 512, which is performed simultaneously with act 507 and adjusts the feed so that:

• increase the pressure at the outlet of the compressor 31 with a linear change to the target operating pressure (during the test, 30 bar gage (3 MPa) was used);

• change the composition of the refrigerant to obtain the target composition, which may be the ultimate goal for the normal operation of the main cryogenic heat exchanger 100 or an intermediate goal.

During the cooling procedure, the target composition of the refrigerant may change. It can change gradually or stepwise when the controlled parameter reaches a predetermined value. For example, it can change as soon as the temperature measured by the TR57 sensor falls below a set value of -135 ° C or -140 ° C.

Simultaneously with steps 506 and 507, step 511 is executed that controls one or more of the recirculation valves of the pre-refrigerant compressor, presented in this document as a first stage 129 recirculation valve, which controls the flow recirculated through the first compression stage of compressor 127. The purpose of the module is to maintain the suction pressure of the pre-cooling refrigerant (in line 150 in FIG. 4) within a predetermined range, for example, 0.25-0.50 bar g. (0.025 - 0.05 MPa), but without approaching the pressure deviation, it is too close to the control boundary. Low pressure ensures that the temperature of the hydrocarbon feed gas entering the main cryogenic heat exchanger 100 (for example, via pipe 20) is of acceptable value. Therefore, the temperature in the pipe 20 does not need to be controlled or used as a condition for control in this module.

In addition, the temperature at the outlet of the pre-cooling refrigerant compressor 127 (in line 135) was not controlled, since the automatic cooling procedure used in the test did not provide for the possibility of controlling any parameter that could be used to improve the situation with a high temperature at the outlet of the refrigerant compressor pre-cooling 127. However, this can be implemented without departing from the scope of the invention.

For one or more monitored parameters, some limit values may be set. Crossing one of these boundaries (i.e., exceeding a predetermined maximum and / or minimum value) by one or more monitored parameters can lead to an alert to alert the operator, or to stop cooling, or to abort cooling, or a combination of these actions.

Typical examples of such boundary limits are:

- the specified maximum rate of temperature change (for example, 28 ° C / hour, as indicated for the cryogenic heat exchanger of Air Products) at any selected temperature, respectively, at one or more temperatures of the hydrocarbon product at a location in the pipe space 29 and / or in the exhaust pipe 40; the temperature of the spent refrigerant (for example, in the lower warm end of the annulus 33 or in the pipe 25); refrigerant temperature on the exhaust side of the first throttle valve 58 or the second throttle valve 51, or on its inlet side; any annulus temperature in the heat exchanger 1;

- the specified maximum spatial temperature gradient, reflecting a certain maximum temperature difference between two spatially separated points in or around the heat exchanger (for example, a maximum temperature difference of 28 ° C), respectively, the temperature difference TDR2547 between the light refrigerant upstream from the main cryogenic heat exchanger 100 and the spent refrigerant (also possible: TDR3347, not illustrated); the temperature difference TDR2548 between the heavy refrigerant upstream of the main cryogenic heat exchanger 100 and the spent refrigerant (also possible: TDR3348, not illustrated); TDR2715; and TDR5759;

- the specified maximum content (0.08 mol.%) of heavy components in the feed stream of hydrocarbons, which will be frozen in the main cryogenic heat exchanger 100;

- the inlet and outlet valves of the refrigerant compressor are closed;

- the maximum specified annular pressure (5 bar gage (0.5 MPa)) at the cold end of the main cryogenic heat exchanger;

- emergency shutdown detection;

- the presence of communication errors in the control system.

Obviously, other limiting boundaries can be used, for example, when using other types of cryogenic heat exchangers.

Although this was not realized during the test, it is assumed that the above-described block diagrams (as shown in Fig. 6 or similar for another circuit or heat exchanger) will be further included in a larger structure containing other previous or subsequent actions, or both. An example is illustrated in FIG. 7.

FIG. 7 illustrates an example with some tasks performed after cooling. For example, these may be intermediate tasks that must be completed before an automatic process control system can take control for normal operation. For example, module 401 controls the drain valve 44 to gradually increase the flow of hydrocarbons through pipelines 20 and 40 and pipe space 29.

Therefore, other modules can operate in parallel with module 401. As an example, module 402 is illustrated, but there may also be a module for building up any fractionation section, which can be provided downstream of any natural gas condensate extraction column to receive and further fractionate the extracted gas condensate liquids. . A person skilled in the art will be able to determine which adjustable and controllable parameters can be used, depending on the type of circuitry and equipment used.

The devices and methods described herein can be applied to cryogenic heat exchangers whenever a cryogenic heat exchanger needs to be cooled before operation. For example, it can be initial cooling or cooling after a maintenance operation, or after an emergency shutdown: the reason why the heat exchanger temperature exceeded the operating temperature does not belong to the subject matter described in this document.

One skilled in the art will understand that the present invention can be carried out in many different ways, without departing from the scope of the attached claims. The invention has been described in detail, including target values for certain controlled parameters. However, one skilled in the art will understand that these target values were selected in accordance with the specific circuitry and equipment used to conduct the test. Optimization of such target values may be required when the invention is to be carried out on a different circuit using different equipment, and therefore should not be construed as limiting the scope of the present invention.

Claims (47)

1. A device for cooling a cryogenic heat exchanger designed to liquefy a hydrocarbon stream, such as a natural gas stream, wherein the cryogenic heat exchanger is adapted to receive a hydrocarbon stream and a refrigerant to be liquefied to conduct heat exchange between the hydrocarbon stream and the refrigerant, thereby at least partially liquefying the stream hydrocarbons, and also produce at least partially liquefied hydrocarbon stream and spent refrigerant passing through a cryogenic heat exchanger, with possessive - a refrigerant recirculation circuit for recycling the spent refrigerant back to the cryogenic heat exchanger, wherein the refrigerant recirculation circuit comprises at least a compressor, a compressor recirculation valve, a cooler and a first throttle valve (Joule-Thomson); - a programmable controller configured to perform a comparison step (502), including: (i) receiving one or more readings of the temperature of the refrigerant, providing an indication of the readings of the temperature of the refrigerant, (ii) comparing one or more refrigerant temperature readings with one or more corresponding predetermined threshold values; and (iii) the choice of one of: procedures for automatic cooling of a cryogenic heat exchanger in a warm state and procedures for automatic cooling of a cryogenic heat exchanger in a cold state based on the results of comparison according to item (ii), moreover, the cooling procedure in the warm and cold state includes an initial opening step comprising initiating an initial opening of the first throttle valve, wherein the initial opening step of the first throttle valve according to the automatic cooling cooling procedure differs from the initial opening step of the first throttle valve according to the automatic cold cooling procedure condition the programmable controller is configured to, as part of the initial opening step (506), perform the SIT step, including adjusting the opening of the first throttle valve (14) based on the determined rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve (14), according to the adjustment scheme, wherein the automatic warm cooling procedure (503) and the automatic cold cooling procedure (504) include various adjustment schemes, however, the cold cooling procedure is different from the warm cooling procedure, since the warm cooling procedure includes a step where the first throttle valve is closed, while the cold cooling procedure may begin when the first throttle valve is open. 2. The device according to p. 1, characterized in that one or more readings of the temperature of the refrigerant contain at least one of the indications of the temperature of the refrigerant - on the inlet side of the throttle valve; - on the exhaust side of the throttle valve; - on the inlet side of the cryogenic heat exchanger; - at a point inside the cryogenic heat exchanger; - on the discharge side of the cryogenic heat exchanger. 3. The device according to claim 1, characterized in that the initial opening of the first throttle valve is larger in the procedure of automatic cooling in the warm state than in the procedure of automatic cooling in the cold state. 4. The device according to claim 1, characterized in that the step of initially opening the first throttle valve in the automatic cooling process in the warm state includes initiating a predetermined initial opening of the first throttle valve, the step of the initial opening of the first throttle valve in the automatic cooling process in the cold state determining the current opening of the first butterfly valve; and the purpose of determining a specific current opening of the first butterfly valve. 5. The device according to any one of paragraphs. 1-4, in which the initial opening step of the cold cooling procedure further includes opening the compressor recirculation valve. 6. The device according to p. 1, characterized in that the determination of the rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve is carried out by comparing two readings of the temperature of the refrigerant obtained at the first and second time, respectively, while the first and second moment times are separated by a predetermined time interval, the predetermined time interval according to the cold cooling procedure being smaller than the predetermined time interval according to the warm cooling procedure. 7. The device according to any one of paragraphs. 1-6, characterized in that the scheme for adjusting the cold cooling procedure includes waiting for a predetermined time interval between initiating the initial opening of the first throttle valve and initiating adjustment of the opening of the first throttle valve based on the controlled rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve. 8. The device according to any one of the preceding paragraphs, characterized in that the automatic cooling process in the cold state includes performing an adjustment step (507), which simultaneously includes - adjusting and closing the recirculation valve (509) and - further adjustment of the throttle valve (508). 9. The device according to p. 8, characterized in that the refrigerant recirculation circuit for recycling the spent refrigerant back to the cryogenic heat exchanger contains many compression stages, each compression stage contains a compressor recirculation valve (130, 131) and the adjustment step (507) includes adjustment and closing a plurality of recirculation valves (509a, 509b). 10. The device according to any one of the preceding paragraphs, characterized in that a liquid-steam separator is provided downstream of the cooler and upstream of the first throttle valve in the refrigerant recirculation loop to produce partially condensed refrigerant and to separate the partially condensed refrigerant stream into a liquid heavy fraction of refrigerant (TPC) and a gaseous light fraction of refrigerant (LF), as well as for discharging a liquid heavy fraction of a refrigerant through a liquid outlet and discharging a gaseous light fraction of a refrigerant through a gas outlet, fractions pass to a cryogenic heat exchanger in which the first throttle valve is configured to control the passage of one of these fractions, preferably a light refrigerant fraction, and in which the second throttle valve is configured to control the passage of another of these fractions, preferably a heavy refrigerant fraction. 11. The device according to p. 10, characterized in that the initial opening step includes initiating the initial opening of the first and second throttle valves, the initial opening step of the first and second throttle valves (51, 58) according to the automatic warm cooling procedure differs from the stage initial opening of the first and second throttle valves (51, 58) according to the procedure for automatic cooling in the cold state. 12. The device according to p. 10, characterized in that the automatic cold cooling procedure involves performing an adjustment step (507), which simultaneously includes - adjusting and closing the recirculation valve (509) and - further adjustment of the first and second throttle valves (508a, 508b). 13. A method of cooling a cryogenic heat exchanger for liquefying a hydrocarbon stream, such as a natural gas stream, comprising the steps of: - provide a cryogenic heat exchanger configured to receive a hydrocarbon stream to be liquefied and a refrigerant to conduct heat exchange between a hydrocarbon stream and a refrigerant, thereby at least partially liquefying a hydrocarbon stream, and also to discharge at least a partially liquefied hydrocarbon stream and spent refrigerant passing through a cryogenic heat exchanger, - provide a refrigerant recirculation loop for recirculating the spent refrigerant back to the cryogenic heat exchanger, wherein the refrigerant recirculation loop comprises at least a compressor, a compressor recirculation valve, a cooler and a first throttle valve; - perform the comparison step (502), including: (i) receiving from the sensors input signals representing the signals of one or more readings of the temperature of the refrigerant, providing an indication of the temperature of the refrigerant, (ii) comparing one or more refrigerant temperature readings with one or more corresponding predetermined threshold values; and (iii) the selection of one of the procedures for automatic cooling of a cryogenic heat exchanger in a warm state and automatic cooling of a cryogenic heat exchanger in a cold state based on the results of comparison in accordance with paragraph (ii), moreover, the cooling procedure in the warm and cold state includes an initial opening step comprising initiating an initial opening of the first throttle valve, wherein the initial opening step of the first throttle valve according to the automatic cooling cooling procedure differs from the initial opening step of the first throttle valve according to the automatic cold cooling procedure condition the programmable controller is configured to, as part of the initial opening step (506), perform the SIT step, including adjusting the opening of the first throttle valve (14) based on the determined rate of change of temperature (SIT) of the refrigerant flowing through the first throttle valve (14), according to the adjustment scheme, wherein the automatic warm cooling procedure (503) and the automatic cold cooling procedure (504) include various adjustment schemes, however, the cold cooling procedure is different from the warm cooling procedure, since the warm cooling procedure includes a step where the first throttle valve is closed, while the cold cooling procedure may begin when the first throttle valve is open. 14. A method of liquefying a hydrocarbon stream, such as a natural gas stream, comprising the following steps: - cooling a cryogenic heat exchanger designed to liquefy a hydrocarbon stream in accordance with the method of claim 13; - subsequent liquefaction of the hydrocarbon stream at one or more stages, including at least heat transfer of the hydrocarbon stream in a cryogenic heat exchanger. 15. A method of liquefying a hydrocarbon stream, such as a natural gas stream, comprising the following steps: - cooling a cryogenic heat exchanger designed to liquefy a hydrocarbon stream using a device according to any one of paragraphs. 1-12; - subsequent liquefaction of the hydrocarbon stream at one or more stages, including at least heat transfer of the hydrocarbon stream in a cryogenic heat exchanger.

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