RU2564377C1 - System for study of high-temperature deposits - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: system for study of high-temperature deposits comprises the device for heating of local sections operated on the basis of catalytic flameless oxidation of gaseous hydrocarbon fuel which contains, at least, one catalytic heater consisting of two identical semi-cylindrical catalytic elements of radial type, where the thermal flow is sent towards the imagined axis of the cylinder and which fasten to the respective identical semi-cylindrical metal casings; one or several branch pipes for fuel supply the quantity of which depends on the heater length.

EFFECT: creation of experimental units for study of high-temperature deposits with heating systems which provide uniform heating, high control of thermal flow, safe operation and, at the same time, simplify the access to the test site for execution of necessary measurements, installation works, avoidance of electric isolation.

8 cl, 6 dwg

Description

The present invention relates to technology for heating individual sections in devices designed to simulate conditions and study the formation of deposits at elevated temperatures (high temperature deposits). The invention relates to a heating method and a device operating on the catalytic combustion (oxidation) of gaseous hydrocarbon fuel.

The study of the formation of deposits on hot surfaces is a very difficult task and is expensive. Adjustable conditions test benches for the study of scale formation are used both in commercial companies and in universities around the world. An experimental bench usually consists of a line (pipe) along which fluid flows, a cooling system, and a test site. A line can be part of a circulation loop. In this case, the stand includes a container where the working fluid is stored. The test site is part of the line, usually in the form of a pipe, which is heated to raise the temperature of the working fluid in such a way as to create conditions for the formation and deposition of sediments. In this case, the processes of formation and deposition of sediments are recorded and analyzed by various methods. In order to obtain reliable and reproducible research results and accurate calculations, it is extremely important to ensure reproducible experimental conditions, in particular, to maintain a uniform heat flow transmitted by the working fluid at the test site. In existing technologies, in the study of high-temperature deposits, heating is used with the help of fire heaters (furnaces), electric heaters, heated coolants. However, all of the above methods have disadvantages.

In patent US 4176544, G01N 17/00, 12/04/1979 for the supply of heat in the test area using an electric heater. When using such heating, it is difficult to control the heat flux transmitted by the working fluid, which can lead to irreproducibility of measurements and results.

When heated using a coolant, including the use of shell-and-tube heat exchangers, it is difficult to maintain a constant heat flow inside the test section, which can lead, as in the previous case, to the irreproducibility of measurements and results.

An example of an experimental setup using electric heating in a pre-heating section and in a test section is described in WO 2012131281 A1, G01N 17/00, 04/10/2012. Heat is generated by passing electric current through the metal walls of the pipeline. Electric heating allows you to precisely control and measure the heat flux and temperature of the metal surface. However, with such electrical heating, the design of the device is complicated by the use of special electrical insulation, which should be used in flange connections and measuring systems. In addition, the generated electric and magnetic fields can affect the behavior of certain types of deposits.

The invention solves the problem of creating experimental installations for the study of high-temperature deposits with heating systems that provide uniform heating, high heat flow control, safe operation and, at the same time, simplify access to the test site for the necessary measurements, installation work, as well as refusal electrical isolation.

The problem is solved by a system for studying high-temperature deposits designed to study the formation of deposits, which includes a device for heating local areas, based on the catalytic flameless oxidation of gaseous hydrocarbon fuel, which contains at least one catalytic heater, consisting of two identical semicylindrical radial-type catalytic elements in which the heat flux is directed towards the imaginary axis of the cylinder and which are stronger tsya identical to the corresponding semi-cylindrical metal shell; one or more nozzles for fuel supply, the number of which depends on the length of the heater.

The catalytic heater comprises an additional fastening system for connecting the two parts of the heater to each other in the working position and an additional support system for fixing the heater in the desired position in the working position.

The catalytic heater uses various types of gaseous hydrocarbon fuels, preferably methane and a mixture of propane and butane.

The catalytic heater has a design with an open structure in relation to the environment, providing natural air access and oxygen diffusion to the surface of the catalyst for fuel oxidation, as well as the subsequent removal of hot fuel combustion products, or, alternatively, has forced air circulation in the heating and exhaust system gases.

A system may include more than one catalytic heater. In this case, the catalytic heaters are arranged sequentially directly one after another, to ensure continuous heating; or at some distance from each other to ensure the alternation of heated and unheated areas.

The system contains a heat flow and temperature control system, which is controlled by actuating shut-off and control valves to regulate one or several parameters based on the signals of the respective sensors, including fuel consumption, composition of the fuel mixture, and fuel to air ratio.

The application of the system for heating a test section, usually a pipeline with a test fluid passing through it, in devices for studying the formation of deposits, as well as for preheating the test liquid before entering the test section of a plant for studying the formation of deposits, is described.

The system consists of a device for heating the test section, which is a linear section of the pipeline with the test fluid circulating through it. The heating is carried out in a certain part of the test site using at least one catalytic heater operating on gas hydrocarbon fuel and consisting of two identical semi-cylindrical catalytic elements; each element consists of a catalytic layer in which flameless combustion of fuel takes place, is coaxial to the test site and ensures uniform heating of the outer surface of the pipeline. Fuel is supplied to each semi-cylindrical catalytic element through one or more pipes, depending on the length of the heating section. In an alternative modification using several separate catalytic heaters installed on the test site, various temperature profiles can be created along the test site to study deposits, including alternating cold and hot zones.

In another alternative modification, in addition to the previous one, one or more short catalytic heaters are used in sections of the pipeline through which the working fluid is supplied, up to the test section in the direction of movement of the liquid, for preheating the test liquid so as to provide a given temperature of the liquid at the inlet to test site.

In all modifications, gaseous hydrocarbon fuel is supplied directly to the catalytic layers through the supply pipes, and oxygen to the catalytic layers is supplied from the ambient air due to diffusion. Fuel reacts with oxygen on the surface of the catalyst. The reaction products are discharged into the environment through the free annular space between the pipeline and the inner surface of the heater. Air and exhaust gases may be vented by natural convection or forced circulation. In the case of forced circulation, air is supplied through the air supply system, and gaseous products of combustion are discharged through the gas exhaust system. Heaters can be adapted to various types of fuel, expanding their temperature range depending on the calorific value of the fuel and other parameters of the catalytic combustion of fuel. The heat flow, the temperature of the catalyst, the walls of the pipe, the liquid at the outlet of the test section can be easily and accurately controlled using a control system based on signals from a number of sensors installed in different places of the pipeline and heating device, as well as adjusting the flow rate of fuel supplied to each catalytic heater, fuel mixture and fuel to air ratio. With the use of several catalytic heaters, a centralized control system can monitor and control these indicators as a whole or separately.

The main advantage of catalytic heating compared to heating systems using traditional furnaces or heated secondary liquids is to provide more uniform heating. Compared to electric heating, the present invention eliminates the need for electrical insulation of the flanges at the test site, which greatly simplifies the design. Easy installation and dismantling, safety of flameless catalytic combustion and design when there is no explosive air-fuel mixture are also additional advantages of the invention.

The invention is illustrated by the following drawings.

FIG. 1 is a general diagram of a device for researching high temperature deposits.

FIG. 2 is a cross section of a test section of a pipeline and a heating device.

FIG. 3 is a cross-sectional view of a catalytic heater 9.1-9.2 shown in FIG. 2.

FIG. 4 is a view in longitudinal section of a catalytic heater and several nozzles for supplying fuel.

FIG. 5 is a longitudinal sectional view of a series of heaters.

FIG. 6 is a longitudinal sectional view of a catalytic heater equipped with sensors and a control system.

In FIG. 1 shows a general diagram of a device for studying the formation of high temperature deposits. The device usually, but not necessarily, consists of a reservoir 1, where the working fluid is stored; pre-heating section 2; pump 3; circulation lines 4; cooling section 5 and test section 6. The test fluid circulates in the direction of the arrow indicated in the figure. Pipes are usually insulated. The test section 6 is usually a linear section of the pipeline with a fluid circulating through it, inside which there is a section 7, which is heated by means of a heating element 8 to increase the temperature of the working fluid and contribute to the formation of deposits. The pipeline may have a circular cross section (pipe), an annular cross section (pipe in the pipe), or other shape.

The invention suggests that the heating element 8 is a radiation heater operating on the catalytic combustion of gas hydrocarbon fuel. FIG. 2 and 3 illustrate, respectively, an axial longitudinal sectional view of a test section and a cross-section along lines 9.1-9.2 of an embodiment according to the present invention. The heat flux is uniformly supplied to the outer surface of the section of the test pipeline 10, presented in the form of a pipe in the drawings, but is not limited to this form. The catalytic heater consists of two identical semi-cylindrical catalytic elements 11.1, 11.2 for flameless catalytic combustion of fuel located coaxially to the pipe, and provides a radial heat flux to the outer surface of the pipe, as shown by arrows in FIG. 3. Fuel is supplied through pipes 12.1, 12.2. Oxygen from ambient air, due to diffusion, penetrates the catalytic layer, reacting with the supplied gaseous fuel on the surface of the catalyst. When using the diffusion type of fuel combustion, the formation of explosive mixtures is absent, which ensures safe operation. The reaction products, which include water and carbon monoxide (CO ₂ ), as well as excess air are discharged from the surface of the catalyst through the space between the pipeline and the heaters into the environment. The catalytic layers 11.1, 11.2 are fixed on two identical semi-cylindrical metal casings 13.1, 13.2, which provide mechanical support for the semi-cylindrical catalytic elements and feed pipes. Support elements for fixing the catalytic heaters in the desired position can also be attached to metal casings. Both semi-cylindrical catalytic elements in mounted and operational condition can be connected to each other using an additional fastening system 14.1-14.2.

In another embodiment, when heating of long sections of the pipeline is required, longer semi-cylindrical catalyst elements 15.1-15.2 can be used, as shown in FIG. 4. In this case, several nozzles supplying gas fuel can be used to ensure uniform distribution of fuel throughout the catalytic bed. In figure 4, in each semi-cylindrical catalytic element, three nozzles are used (16.1, 16.3, 16.5 and 16.2, 16.3, 16.6, respectively), but the number of nozzles may vary depending on the particular case.

In other embodiments, several short catalytic heaters can be installed to study the effects of alternating cold and hot zones or to simulate temperature profiles. The use of separate heaters allows each of them to work under different modes, on different amounts and types of fuel. Catalytic heaters can be placed one after another to provide continuous heating, or separated to provide alternation of heated and unheated areas. One such modification is shown in FIG. 5, where two short catalytic heaters 17.1 and 17.2 are installed in separate areas of the test site. Each of these catalytic heaters has the same characteristics as the catalytic heater in the modification shown in FIG. 2 and 3.

In another alternative modification, one or more catalytic heaters are used in the pipe section to the test section in order to preheat the liquid and achieve a certain liquid temperature at the inlet of the test section. The description of catalytic heaters in this case is similar to that described previously. Differences may lie in the location of the catalytic heaters on the pipe, in the characteristics of the pipe and the operating modes of the heaters.

To start, catalytic heaters must be preheated to a temperature when external heat supply is no longer required and the required catalyst temperature sufficient for stable catalytic combustion of fuel is maintained due to the heat generated during fuel combustion. For this, known methods of preheating the catalyst can be used, including flaring fuel, electric heating, catalytic heating with gas hydrogen-containing mixtures, heating with hot air from an external source.

Various gases can be used as fuel. Depending on the chemical composition of the gases used, the composition of the catalyst and the main parameters of the gas combustion process can vary. Preferred gases contain a propane-butane mixture with an ignition temperature of about 200 ° C and methane with an ignition temperature of about 450 ° C.

In all modifications, the heating system includes a control system capable of regulating the heat flux, the temperature of the catalyst, the pipe walls or the temperature of the test fluid at the outlet by changing one or more process parameters, such as fuel consumption, fuel composition and air / fuel ratio, by based measurements using appropriate sensors. A modification including a control system and sensors is shown in FIG. 6.

Temperature sensors 18.1, 18.2 are designed to measure the temperature of the pipe walls, temperature sensors 19.1, 19.2 are designed to measure the temperature in the catalyst bed. The temperature can be controlled at one or more points within the heated area. Devices 20 and 21 include sensors for monitoring fluid flow characteristics, which may include temperature, pressure, and flow. Devices 22.1-22.2 comprise valves for controlling fuel consumption and / or fuel composition and at least flow sensors. The signals from various sensors are transmitted to the control system 23. This system is used to control the operation of the catalytic heater and to control the composition and flow rate of gas fuel supplied to each heating element in the required quantity by actuating the corresponding control valves. If forced air circulation is used, the air-to-fuel ratio is also monitored.

If multiple catalytic heaters are used, the control system can centrally process all the data at once. The control of various heaters can be performed independently of each other or in combination with each other. The control system may use conventional control schemes, control algorithms, control based on predictive models or other control algorithms. At all times, the temperature of the catalyst must be maintained above the ignition temperature and can reach values up to 700 ° C and higher.

Claims (8)

1. System for the study of high-temperature deposits, including a device for heating local areas, operating on the basis of catalytic flameless oxidation of gaseous hydrocarbon fuel, which contains at least one catalytic heater, consisting of two identical semicylindrical catalytic elements of radial type, in which the heat flow is directed to the side of the imaginary axis of the cylinder and which are attached to the corresponding identical semi-cylindrical metal casings; one or more nozzles for fuel supply, the number of which depends on the length of the heater, 2. The system according to p. 1, characterized in that the catalytic heater contains an additional fastening system for connecting two parts of the heater to each other in the working position, 3. The system according to p. 1, characterized in that the catalytic heater contains an additional support system for fixing the heater in position. 4. The system according to claim 1, characterized in that the catalytic heater uses various types of gaseous hydrocarbon fuel, preferably methane and a mixture of propane and butane. 5. The system according to p. 1, characterized in that the catalytic heater has a structure with an open structure in relation to the environment, providing natural air access and oxygen diffusion to the surface of the catalyst for fuel oxidation, as well as the subsequent removal of hot products of fuel combustion, or, alternatively, it has forced air circulation and exhaust. 6. The system according to p. 1, characterized in that it contains at least two catalytic heaters located in series directly immediately after one another, to ensure continuous heating; or at a certain distance from each other to ensure the alternation of heated and unheated areas. 7. The system according to claim 1, characterized in that it contains a heat flow and temperature control system that is controlled by actuating shut-off and control valves with the aim of regulating one or more parameters based on the signals of the respective sensors, including fuel consumption, fuel composition mixtures, the ratio of fuel to air. 8. The use of the system according to any one of paragraphs. 1-7 for heating a test section, typically a pipeline with a test fluid passing through it, in a scale formation study unit or for preheating a test liquid before entering a test section of a scale formation study unit.

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