CN210068251U - Demethanizer in ethylene production process - Google Patents

Abstract

The utility model relates to an ethylene preparation process equipment specifically is a demethanizer in ethylene preparation process, including the demethanizer, the demethanizer sets up in a barrel, still is connected with the reflux tank in the barrel, the condenser, the demethanizer, the reflux tank, the condenser is from supreme setting gradually down, the feed line is connected at the middle part of demethanizer, first gaseous phase line connection condenser is passed through at the top of demethanizer, the pipe connection reflux tank is passed through to the bottom of condenser, the reflux tank passes through the top of the liquid phase line connection demethanizer, the reflux tank passes through second gaseous phase line connection expander, the low temperature methane pipeline is connected to the expander. The utility model utilizes the high-pressure methane at the top of the demethanizer and adopts the throttling expansion principle to generate low-temperature methane which is then used for cooling through the cold box system, thereby reducing the scale of the refrigeration compressor unit and saving the long-term energy consumption; the utility model discloses utilize high potential energy, can save low temperature methane backwash pump, improve device operational benefits.

Description

Demethanizer in ethylene production process

Technical Field

The utility model relates to ethylene preparation process equipment, in particular to a demethanizer in the ethylene preparation process.

Background

Ethylene is the most basic raw material in petrochemical industry and is the tap in petrochemical industry. And preparing chemical products such as polyethylene, ethylene oxide, ethylbenzene, chloropropane, ethanol and the like at the downstream of the ethylene. The preparation method of the ethylene mainly comprises the following steps: 1. cracking hydrocarbon steam to prepare ethylene; 2. cracking naphtha to prepare ethylene; 3. preparing ethylene from methanol; 4. preparing ethylene from natural gas; 5. and (3) preparing ethylene by catalytic cracking.

In the existing steam cracking separation process, the flow of a cold box is an indispensable part, important products in the steam cracking process, such as hydrogen, methane, ethylene and ethane, need to be separated after being cooled by low-temperature refrigerant in the cold box, and the compression refrigeration cannot be obtained and the energy consumption is huge. In addition, in the traditional rectification process, a gas phase at the top of the tower enters a reflux tank after being condensed, and the gas phase needs to be pressurized by a reflux pump and then returns to the top of the tower, and the reflux pump is a vulnerable device in actual production, needs standby equipment and generates energy consumption, and generates long-term operation and maintenance cost.

SUMMERY OF THE UTILITY MODEL

The to-be-solved technical problem of the utility model is to overcome prior art's defect, provide a demethanizer device in ethylene preparation process, can reduce the scale of refrigeration compressor unit and saved long-term energy consumption to save low temperature methane reflux pump, improve device operational benefits.

In order to solve the technical problem, the utility model provides a following technical scheme:

the utility model provides a demethanizer in ethylene preparation process, be applicable to steam cracking system alkene technology, including the demethanizer, the demethanizer sets up in a barrel, still be connected with the reflux tank in the barrel, a condenser, the demethanizer, the reflux tank, supreme setting gradually is down followed to the condenser, the feed line is connected at the middle part of demethanizer, the top of demethanizer is through first gaseous phase line connection condenser, the bottom of condenser passes through the pipe connection reflux tank, the reflux tank passes through the top of liquid phase line connection demethanizer, the reflux tank passes through second gaseous phase line connection expander, the low temperature methane pipeline is connected to the expander, the expander adopts throttle expansion principle, it only relies on high pressure methane drive to need not external power, there is not the energy consumption increase.

The expansion machine is connected with a low-pressure fuel gas feeding pipeline and a high-pressure fuel gas discharging pipeline, and the high-pressure methane is used for pressurizing fuel gas of the cracking furnace generated by the system.

The demethanizer is connected with the bottom to a reboiler according to the process requirement.

The utility model discloses a work flow does:

the crude C1-C2 components separated from the cold box system are fed from the middle part of the demethanizer, the temperature of the top of the demethanizer is-95 to-100 ℃, the pressure is-3.0 MPaG, the temperature of the bottom of the demethanizer is 0 to-20 ℃, and the pressure is-3.1 MPaG. Gas phase at the top of the demethanizer is extracted and enters a condenser, the gas phase is partially condensed after exchanging heat with low-temperature ethylene refrigerant, the condensed material flows into a reflux tank at the lower part, the material is subjected to gas-liquid separation in the reflux tank, and the liquid phase reflux material automatically flows into the top of the demethanizer by virtue of high potential energy gravity generated by height difference; the gas phase discharged from the reflux tank is high-pressure methane, the high-pressure methane enters an expander device to push the expander to do work to pressurize fuel gas of the cracking furnace generated by the system, the high-pressure methane is used as cold source of a cold box when the temperature of the expander does work is reduced to-135 to-140 ℃, the low-temperature methane is used as cold source of the cold box, the temperature can be raised to 30 ℃ in the cold box through serial heat exchange, and the high-pressure methane can be used as fuel of the cracking furnace.

The utility model discloses the beneficial effect who reaches is:

1. the utility model utilizes the high-pressure methane at the top of the demethanizer and adopts the throttling expansion principle to generate low-temperature methane which is then used for cooling through the cold box system, thereby reducing the scale of the refrigeration compressor unit and saving the long-term energy consumption;

2. the utility model discloses the condenser and the reflux drum that will remove the methane tower design into the vertical equipment that is close with the tower diameter, and with the coincide of methanol tower in a barrel, utilize high potential energy, can save low temperature methane reflux pump, improve device operational benefits.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic structural view of the present invention;

in the figure: 1. a demethanizer; 2. a reflux tank; 3. a condenser; 4. a barrel; 5. an expander; 6. a reboiler; 7. a feed line; 8. a first gas phase line; 9. a liquid phase line; 10. a second gas phase line; 11. a low pressure fuel gas feed line; 12. a high pressure fuel gas discharge line; 13. a low temperature methane line.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are presented herein only to illustrate and explain the present invention, and not to limit the present invention.

Example (b):

as shown in fig. 1, a demethanizer in the process of preparing ethylene is suitable for the process of preparing olefin by steam cracking. The device specifically comprises a demethanizer 1, wherein the demethanizer 1 is connected in a cylinder 4, a reflux tank 2 and a condenser 3 are fixedly connected in the cylinder 4, and the demethanizer 1, the reflux tank 2 and the condenser 3 are sequentially arranged from bottom to top. The middle part of the demethanizer 1 is connected with a feeding pipeline 7, the top part of the demethanizer 1 is connected with a condenser 3 through a first gas phase pipeline 8, and the condenser 3 is connected with a refrigerant inlet and outlet pipeline. The bottom of the condenser 3 is connected with a reflux tank 2 through a pipeline, the reflux tank 2 is connected with the top of the demethanizer 1 through a liquid phase pipeline 9, the reflux tank 2 is connected with an expander 5 through a second gas phase pipeline 10, and the expander 5 is connected with a low-temperature methane pipeline 13. The expansion machine 5 is connected with a low-pressure fuel gas feeding pipeline 11 and a high-pressure fuel gas discharging pipeline 12, and the high-pressure methane is used for pressurizing the fuel gas of the cracking furnace generated by the system.

The demethanizer 1 is connected with the bottom part and is connected with a reboiler 6, and the reboiler 5 is connected with a refrigerant inlet pipeline and a refrigerant outlet pipeline.

The utility model discloses a work flow does:

crude C1-C2 components separated from the cold box system enter the middle part of the demethanizer 1 from a feed pipeline 7, the temperature of the top of the demethanizer 1 is-95 to-100 ℃, the pressure is-3.0 MPaG, the temperature of the bottom of the demethanizer is 0 to-20 ℃, and the pressure is-3.1 MPaG. Gas phase at the top of the demethanizer 1 is extracted and enters a condenser 3, partial condensation is carried out after heat exchange with low-temperature ethylene refrigerant, the condensed material flows into a reflux tank 2 at the lower part, the gas and the liquid of the material are separated in the reflux tank 2, and the liquid phase reflux material automatically flows into the top of the demethanizer 1 by virtue of high potential energy gravity generated by height difference; the gas phase discharged from the reflux tank 2 is high-pressure methane, the high-pressure methane enters the expansion machine 5 through the second gas phase pipeline 10, the work of the expansion machine 5 is pushed to pressurize the fuel gas of the cracking furnace generated by the system, the high-pressure methane is the temperature of the expansion machine 5 after the work of the expansion machine is reduced to-135 to-140 ℃, the low-temperature methane can be used as a cold source of a cold box after being sent out through the low-temperature methane pipeline 13, and the low-temperature methane can be heated to 30 ℃ through series heat exchange in the cold box and can be used as the fuel of the cracking.

In the actual operation, utilize the utility model discloses can realize:

1. compression refrigeration load reduction

Taking each ton of methane products produced by the demethanizer 4 as an example, through accounting, each ton of methane can generate 120kW to 140kW of refrigeration capacity for the cold box through the process, so that the refrigeration capacity requirement of ethylene, propylene or other refrigerants in the cold box system is directly reduced, and the equipment investment of the compression refrigeration unit is indirectly reduced. The expansion machine 5 does not need external power and only depends on high-pressure methane for driving, and the energy consumption is not increased.

2. The demethanizer equipment is vertically and sequentially arranged, and a low-temperature methane reflux pump is cancelled

The condenser 3, the reflux tank 2 and the demethanizer 1 are stacked from top to bottom in a cylinder, the static equipment investment is increased, the occupied area of the device is reduced, the arrangement is simpler, two low-temperature methane reflux pumps with high maintenance rate are omitted, the self-reflux is realized by depending on the gravity of materials, and the equipment investment is reduced. Statistical calculations show that each methanol reflux in a conventional process will result in about 1kW of reflux pump energy consumption. The application is a long-term benefit, reduced operating cost process improvement.

Claims (3)

1. The utility model provides a demethanizer in ethylene preparation process, a serial communication port, including the demethanizer, the demethanizer sets up in a barrel, still be connected with reflux tank, condenser in the barrel, the demethanizer, reflux tank, condenser set gradually from supreme down, the feed line is connected at the middle part of demethanizer, the top of demethanizer is through first gaseous phase line connection condenser, the bottom of condenser is through the pipe connection reflux tank, the reflux tank passes through the top of liquid phase line connection demethanizer, the reflux tank passes through second gaseous phase line connection expander, the expander is connected low temperature methane pipeline.

2. A demethanizer for ethylene production as in claim 1, wherein the expander is connected to a low pressure fuel gas feed line and a high pressure fuel gas discharge line.

3. A demethanizer for ethylene production as recited in claim 1, wherein the demethanizer is connected to a reboiler at a bottom thereof.

Images