A high-pressure gas phase fluid pressure energy recovery system for dry gas recovery device

Abstract

The invention discloses a high-pressure gas phase fluid pressure energy recovery system of a dry gas recovery device, comprising a catalytic dry gas unit, a coking dry gas unit and a mixed dry gas unit. The catalytic dry gas unit comprises a buffer tank a, a dry gas compressor, a C4 absorption tower a, a C4 analysis tower a, a decarbonization tower a, a desulfurization tower a and a dearsenic-mercury tower a. The coking dry gas unit comprises a buffer tank b, a first-stage dry gas compressor, a decarbonization tower b, a second-stage dry gas compressor, a C4 absorption tower b, a C4 analysis tower b, a dearsenic-mercury tower b and a concentration compressor. The upper end of the C4 absorption tower b is connected with a gasoline absorption tower through a pipeline. The mixed dry gas unit comprises a buffer tank c, a mixed dry gas compressor, a liquid separator and an ethane tower. The upper and lower ends of the ethane tower are respectively connected with a reflux tank and a light hydrocarbon tower, so as to solve the energy loss caused by the pressure reduction of the high-pressure gas phase through a regulating valve and the problem of pipeline frosting. The efficient output of ethylene, ethane and light hydrocarbons facilitates the realization of the process steps of the latter stage.

Description

Technical Field

[0001] The present invention relates to a pressure energy recovery system, and more specifically, to a high-pressure gas phase fluid pressure energy recovery system of a dry gas recovery device, and belongs to the field of petrochemical industry. Background Art

[0002] At present, the catalytic dry gas from the catalytic cracking unit cannot be efficiently fed into the cracking gas compression unit of the ethylene unit after being compressed and absorbed by shallow cold oil; the coking dry gas from the coking unit is pressurized by the compressor, and cannot be combined with the gas phase from the outlet liquid separator of the mixed dry gas compressor, so it cannot be pressurized together by the concentrated gas compressor and sent to the ethane tower; the isomerized gas and the disproportionate fuel gas are compressed, condensed and separated, and the liquid phase is sent to the ethane tower, and the gas phase cannot be absorbed by shallow cold oil together with the coking dry gas from the coking unit to obtain the carbon two concentrated gas, and the process of reducing the pressure of the high-pressure fluid after being treated by the catalytic dry gas unit, the coking dry gas unit and the mixed dry gas unit causes a large waste of fluid mechanical energy and a huge loss of economic benefits, which is not conducive to saving efficient new energy. After the high-pressure gas phase is reduced in pressure by the regulating valve, it absorbs heat and causes frosting of the pipeline. In severe cases, it can cause freezing and blockage of the pipeline, causing the membrane separation device to stop working or even damage the membrane components. Summary of the invention

[0003] In order to solve the above-mentioned problems of the prior art, the present invention provides a high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device having the technical characteristics of simple structure, convenient operation, improved energy utilization, and the ability to efficiently produce raw gas.

[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0005] A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device comprises a catalytic dry gas unit, a coking dry gas unit and a mixed dry gas unit. The catalytic dry gas unit comprises a buffer tank a, a dry gas compressor, a C4 absorption tower a, a C4 analysis tower a, a decarbonization tower a, a desulfurization tower a and a arsenic-mercury removal tower a which are sequentially connected through pipelines. The upper end of the arsenic-mercury removal tower a is connected to an ethylene-rich gas compression unit to an ethylene cracking gas compression unit through a pipeline. The upper end of the C4 absorption tower a is connected to a gasoline absorption tower through a pipeline. The upper and lower ends of the gasoline absorption tower are respectively connected to a membrane separation unit and a gasoline stabilization tower. The tail gas of the membrane separation unit is connected to a pressure energy recovery device. The pressure energy recovery device is respectively connected to a power grid and a fuel gas pipeline network. The upper end of the gasoline stabilization tower is connected to the fuel gas pipeline network through a pipeline.

[0006] The coking dry gas unit comprises a buffer tank b, a first-stage dry gas compressor, a decarbonization tower b, a second-stage dry gas compressor, a C4 absorption tower b, a C4 analysis tower b, an arsenic and mercury removal tower b, and a concentration compressor, which are connected in sequence through pipelines. The upper end of the C4 absorption tower b is connected to the gasoline absorption tower through a pipeline.

[0007] The mixed dry gas unit includes a buffer tank c, a mixed dry gas compressor, a separator tank, and an ethane tower which are connected in sequence through pipelines. The upper and lower ends of the ethane tower are respectively connected to a reflux tank and a light hydrocarbon tower. The reflux tank removes ethane gas to an ethylene cracking furnace through a pipeline. The upper end of the light hydrocarbon tower is connected to a light hydrocarbon separation device through a pipeline. The lower end of the light hydrocarbon tower is connected to a gasoline stabilization tower through a pipeline. The separator tank is connected to a pipeline between a second-stage dry gas compressor and a carbon four absorption tower b through a pipeline. The concentration compressor is connected to the ethane tower through a pipeline.

[0008] Preferably, the lower end of the C4 analysis tower a is connected to the C4 absorption tower a through pipeline No. 1, and the lower end of the C4 analysis tower b is connected to the C4 absorption tower b through pipeline No. 2, and both pipeline No. 1 and pipeline No. 2 are connected to compression pumps.

[0009] Preferably, the pressure energy recovery device includes a turbine expander, and the turbine expander is connected to the tail gas of the membrane separation unit through pipeline No. 3, and the pipeline No. 3 is connected with PI (pressure sensor), valve No. 1, filter, and XV valve in sequence in the direction from the membrane separation unit to the turbine expander, and the filter is connected with PDI (differential pressure transmitter), and the turbine expander goes to the fuel gas pipeline network through pipeline No. 4, and the pipeline No. 4 in the direction from the turbine expander to the fuel gas pipeline network is connected with an on-off valve and valve No. 2 in sequence, and pipeline No. 5 is connected between the inlet end of the valve No. 1 and the outlet end of the valve No. 2, and the pipeline No. 5 is connected with a stop valve, and the stop valve is communicatively connected to PI, and the turbine expander is connected with a generator to generate electricity and connect to the power grid.

[0010] Preferably, the turbo expander is also connected to a condensate drain line, and two NC valves are connected to the condensate drain line.

[0011] Preferably, the membrane separation unit removes crude hydrogen to PSA via a pipeline.

[0012] Preferably, the turbo expander model is TG220.

[0013] Preferably, the generator is connected to the transmission of the turbo expander via a sliding coupling, and the sliding torque of the sliding coupling is 2.5 times the rated torque of the generator.

[0014] Beneficial effects: It solves the energy loss caused by the pressure reduction of high-pressure gas through the regulating valve and the problem of pipeline frosting; effectively recovers the pressure energy of high-pressure gas phase fluid and reduces energy loss; generates electricity through pressure energy recovery, thereby improving the overall economic benefits of the device (power generation 1037kW×8400hrs / year=8.711 million kWh / year, 0.57 yuan / kwh, electricity fee income 4.97 million / year); can efficiently output ethylene, ethane, and light hydrocarbons to facilitate the implementation of the subsequent process steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the overall principle block diagram of the present invention.

[0016] Figure 2 It is a schematic structural diagram of the pressure energy recovery device of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings, but the present invention is not limited to the following embodiments.

[0018] like Figure 1-2 The figure shows a specific embodiment of a high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device. The embodiment is a high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device, comprising a catalytic dry gas unit, a coking dry gas unit, and a mixed dry gas unit. The catalytic dry gas unit comprises a buffer tank a, a dry gas compressor, a C4 absorption tower a, a C4 analysis tower a, a decarbonization tower a, a desulfurization tower a, and an arsenic removal and mercury tower a, which are connected in sequence through pipelines. The upper end of the arsenic removal and mercury tower a is connected to an ethylene-rich gas to ethylene cracking gas compression unit through a pipeline. The upper end of the C4 absorption tower a is connected to a gasoline absorption tower through a pipeline. The upper and lower ends of the gasoline absorption tower are respectively connected to a membrane separation unit and a gasoline stabilization tower. The tail gas of the membrane separation unit is connected to a pressure energy recovery device. The pressure energy recovery device is respectively connected to the power grid and a fuel gas pipeline network. The upper end of the gasoline stabilization tower is connected to the fuel gas pipeline network through a pipeline.

[0019] The coking dry gas unit comprises a buffer tank b, a first-stage dry gas compressor, a decarbonization tower b, a second-stage dry gas compressor, a C4 absorption tower b, a C4 analysis tower b, an arsenic and mercury removal tower b, and a concentration compressor, which are connected in sequence through pipelines. The upper end of the C4 absorption tower b is connected to the gasoline absorption tower through a pipeline.

[0020] The mixed dry gas unit includes a buffer tank c, a mixed dry gas compressor, a separator tank, and an ethane tower which are connected in sequence through pipelines. The upper and lower ends of the ethane tower are respectively connected to a reflux tank and a light hydrocarbon tower. The reflux tank removes ethane gas to an ethylene cracking furnace through a pipeline. The upper end of the light hydrocarbon tower is connected to a light hydrocarbon separation device through a pipeline. The lower end of the light hydrocarbon tower is connected to a gasoline stabilization tower through a pipeline. The separator tank is connected to a pipeline between a second-stage dry gas compressor and a carbon four absorption tower b through a pipeline. The concentration compressor is connected to the ethane tower through a pipeline.

[0021] Process flow: After the catalytic dry gas from the catalytic cracking unit is compressed and absorbed by shallow cold oil, the crude ethylene gas obtained enters the refining part, and the ethylene-rich gas obtained after removing impurities such as arsenic, mercury, sulfur, O2, NOx and most of CO2 is sent to the ethylene cracking gas compression unit;

[0022] The coking dry gas from the coking unit is pressurized by a compressor and merged with the gas phase from the outlet separator of the mixed dry gas compressor. After being absorbed by shallow cold oil, the concentrated gas is obtained. After arsenic and mercury are removed from the concentrated gas, it is pressurized by the concentrated gas compressor and sent to the ethane tower.

[0023] After compression, condensation and phase separation, the liquid phase from the isomerized dry gas and the disproportionated fuel gas is sent to the ethane tower, and the gas phase is sent to the ethane tower together with the compressed coking dry gas from the coking dry gas unit, and the carbon two concentrated gas is obtained by shallow cold oil absorption, and then pressurized to obtain ethane-rich gas at the top of the ethane tower, which is sent to the ethylene cracking furnace after passing through the reflux tank. The kettle logistics of the ethane tower is sent to the light hydrocarbon tower together with the extracted carbon four, and the light hydrocarbon products are obtained at the top of the light hydrocarbon tower and sent to the light hydrocarbon separation device. The kettle logistics of the light hydrocarbon tower is sent to the gasoline stabilization tower for recycling;

[0024] The methane hydrogen from the two shallow cold oil absorption parts carries part of the C4 absorbent into the gasoline absorption tower, and heavy naphtha is used as the gasoline absorbent to absorb C4. The rich gasoline that absorbs C4 is sent to the gasoline stabilization tower together with the light hydrocarbon tower bottom logistics to separate C4 and gasoline components. The C4 absorbent recovered from the top of the gasoline stabilization tower is returned to the shallow cold oil absorption unit for recycling. Part of the lean gasoline in the gasoline stabilization tower bottom is recycled, and the other part is sent to the downstream device as a gasoline product. The methane hydrogen tail gas that has not been absorbed is sent to the membrane separation unit, and the methane hydrogen is separated by the membrane. Unit, the crude hydrogen is sent to the PSA device, and the membrane separation tail gas is sent to the pressure energy recovery device. The pressure energy recovery device is connected to the power grid and the fuel gas pipeline network respectively. Power generation and fuel gas recovery are achieved through the pressure energy recovery device. In the traditional technology, 21t / h of tail gas (temperature 100℃, pressure 3.4MPa) is produced after membrane separation absorption. The tail gas needs to be connected to the fuel gas pipeline network with a pressure of 0.7MPa. The pressure drop is as high as 2.7MPa. The pressure loss causes a large waste of fluid mechanical energy and a huge loss of economic benefits.

[0025] The lower end of the C4 analysis tower a is connected to the C4 absorption tower a through pipeline No. 1, and the lower end of the C4 analysis tower b is connected to the C4 absorption tower b through pipeline No. 2. Compression pumps are connected to the pipeline No. 1 and pipeline No. 2 to facilitate circulation operation.

[0026] In a preferred embodiment, the pressure energy recovery device includes a turbine expander, and the turbine expander is connected to the tail gas of the membrane separation unit through a No. 3 pipeline. In the direction from the membrane separation unit to the turbine expander, the No. 3 pipeline is connected with PI, No. 1 valve, filter, and XV valve in sequence. The filter is connected with PDI, and each valve is a solenoid valve, which is shaped to adjust the on-off through the PI and PDI sensor information. The turbine expander goes to the fuel gas pipeline network through a No. 4 pipeline. In the direction from the turbine expander to the fuel gas pipeline network, the No. 4 pipeline is connected with an on-off valve and a No. 2 valve in sequence. A No. 5 pipeline is connected between the inlet end of the No. 1 valve and the outlet end of the No. 2 valve, and a stop valve is connected to the No. 5 pipeline. The stop valve is connected to the PI communication connection. The turbine expander is connected with a generator, and the generator generates electricity and is connected to the power grid, so that the membrane separation tail gas is reduced in pressure and expanded at the expansion end through the expansion unit, and the output mechanical energy drives the generator to convert the mechanical energy The generated electricity is incorporated into the internal power grid of the device for use by the internal electrical equipment of the device. The exhaust gas after decompression and expansion enters the system fuel gas pipeline network. The exhaust gas expander can adapt to the changes in exhaust gas flow and pressure caused by different working conditions of the upstream gas. When the power generation device itself fails, the expander inlet shut-off valve is urgently closed, and the bypass regulating valve is quickly opened to allow the exhaust gas to pass through the bypass. It is preferred to use a radial flow expander with advanced aerodynamic design to maximize the isentropic efficiency. The turbine expander is an integrated gear connection, and the casing is directly mounted on the gearbox. The turbine expander and the gearbox share a high-speed shaft. A blade system (adjustable nozzle) is provided around the turbine expander impeller to adjust the process gas flow by changing the flow area. The nozzle blade has a simple structure and can achieve impact-free deceleration while providing the widest possible flow range. The blade pivots in clockwise and counterclockwise directions around one of its mounting bolts.

[0027] In a preferred embodiment, the turbine expander is also connected to a condensate discharge line, and two NC valves are connected to the condensate discharge line to provide operational safety.

[0028] In a preferred embodiment, the membrane separation unit removes the crude hydrogen through a pipeline to the PSA device. The ethylene cracking gas compression unit, ethylene cracking furnace, light hydrocarbon separation device, and PSA device in the present application are not the technical key points of the present application scheme. They all belong to the lower process steps and are not introduced in detail.

[0029] In a preferred embodiment, the turbine expander model is TG220, the mechanical energy of the expander is recovered, the generator is connected to the transmission of the expander by a sliding coupling, and the generator is connected to the transmission of the turbine expander by a sliding coupling. The generator is designed to rotate counterclockwise at a speed of 3017rpm, and is a self-ventilated, fully enclosed compact three-phase asynchronous motor. The generator shaft itself is supported by bearings, and the bearings are lubricated with oil from the oil system. The sliding coupling is designed to have a sliding torque of 2.5 rated torques of the generator, so that the turbine can be protected when a grid short circuit occurs on the generator. The technical parameters of the expander are as follows:

[0030] project parameter project parameter Type Expander Minimum speed rpm 28638 model TG220 Maximum continuous speed rpm 30196 medium Membrane separation tail gas Tripping speed rpm 30781 Design flow rate Nm3 / h 25678 First critical speed rpm 9030 Design pressure MPa 4.0 Second critical speed rpm 16027 Test pressure MPa 6.0 Gear Ratio 9.74 Inlet pressure MPa 3.38 Generator rated power KW 1285 Exhaust pressure MPa 0.7 Generator rated speed rpm 3018 Design temperature ℃ -28 / 130 Generator rated current A 86.7 Inlet air temperature℃ 100 Voltage V 10000 Exhaust temperature℃ 7.5 Generator first critical speed rpm 719 Design power KW 1037 Generator second critical speed rpm 2105 Rated speed rpm 29388 Synchronous speed rpm 2866

[0031] For turbo expander operation steps:

[0032] 1. Check the process pipeline at the inlet of the expander: Confirm that there is no pressure in the expander body, remove the filter of the inlet pipeline, and remove the pipeline between the filter and the body. Reinstall the filter and pipeline after cleaning.

[0033] 2. Alignment of the unit: Remove the coupling, disconnect the flanges of the inlet and outlet pipes of the expander, and use a laser alignment instrument to check the alignment of the unit. After the alignment is qualified, connect the inlet and outlet pipes, check the pipes for stress-free, and perform precise alignment of the unit.

[0034] 3. Internal inspection of the expander: remove the expander volute and the upper connecting rod of the nozzle. Check the internal condition of the machine body to prevent foreign matter from entering the machine body and causing damage to the unit when starting the machine. After the inspection is qualified, restore the machine body.

[0035] 4. Lubricating oil system inspection and commissioning: Check that the lubricating oil system pipeline connections have been installed and that all instruments are complete and easy to use. Add lubricating oil to the oil tank and the oil tank liquid level is normal. Commission a set of lubricating oil filters, a set of lubricating oil coolers, commission the accumulator, and confirm that the accumulator pressure is 0.15MPa. Commission the lubricating oil, control oil self-operated regulating valve and pump outlet self-operated regulating valve. Confirm that the lubricating oil flow is correct and start the oil pump. Open the valve to the high-level oil tank, confirm that there is oil passing through the return oil sight glass on the overflow pipeline, open the accumulator to charge the oil, commission the oil mist separator of the oil tank, and commission the electric heater at the bottom of the oil tank.

[0036] 5. Check and put the sealing system into use: Open the valve for low-pressure nitrogen to the system, introduce nitrogen, and adjust the nitrogen pressure of the system to the normal 0.6-0.8MPa. Put the on-site pressure gauge, pneumatic diaphragm regulating valve, pressure transmitter, and differential pressure transmitter of the sealing system into use. Put the isolation gas, secondary sealing gas, and primary sealing gas into use. Before the expander is started, introduce the process gas at the inlet of the expander to replace the primary sealing nitrogen used before starting, so as to realize the automatic switching of the primary sealing gas source between process gas and nitrogen.

[0037] 6. Inspection and commissioning of cooling water system: Open the cooling water inlet and outlet valves from the system, open the high point vent on the outlet pipe to exhaust air, close the drain valve after water is seen, and confirm that the cooling water system is operating normally.

[0038] 7. Generator no-load test run: Confirm that all electrical signals have met the start-up conditions, and the generator-related interlocking, alarm, and indication have been completed and meet the start-up conditions. Start the generator, confirm that the motor direction is correct, the vibration and temperature are normal, run for 2 hours and all parameters are stable, and then stop the generator.

[0039] 8. Start-up and operation: Confirm that all parameters of the unit instruments are normal, interlocking debugging is completed, and all local and remote transmission instruments are in use. Check the air tightness of the filter and inlet and outlet pipes to confirm that there is no leakage. The generator is powered on, and the start-up fast closing valve of the expander inlet is slowly opened, and the unit is gradually brought into normal operation according to the start-up curve of the expander.

[0040] Finally, it should be noted that the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device, characterized in that: It comprises a catalytic dry gas unit, a coking dry gas unit and a mixed dry gas unit. The catalytic dry gas unit comprises a buffer tank a, a dry gas compressor, a C4 absorption tower a, a C4 analysis tower a, a decarbonization tower a, a desulfurization tower a and a dearsenic-mercury tower a which are connected in sequence through pipelines. The upper end of the dearsenic-mercury tower a is connected to an ethylene-rich gas compression unit through a pipeline. The upper end of the C4 absorption tower a is connected to a gasoline absorption tower through a pipeline. The upper and lower ends of the gasoline absorption tower are respectively connected to a membrane separation unit and a gasoline stabilization tower. The tail gas of the membrane separation unit is connected to a pressure energy recovery device. The pressure energy recovery device is respectively connected to the power grid and a fuel gas pipeline network. The upper end of the gasoline stabilization tower is connected to the fuel gas pipeline network through a pipeline. The coking dry gas unit comprises a buffer tank b, a first-stage dry gas compressor, a decarbonization tower b, a second-stage dry gas compressor, a C4 absorption tower b, a C4 analysis tower b, an arsenic and mercury removal tower b, and a concentration compressor, which are connected in sequence through pipelines. The upper end of the C4 absorption tower b is connected to the gasoline absorption tower through a pipeline. The mixed dry gas unit includes a buffer tank c, a mixed dry gas compressor, a separator tank, and an ethane tower which are connected in sequence through pipelines. The upper and lower ends of the ethane tower are respectively connected to a reflux tank and a light hydrocarbon tower. The reflux tank removes ethane gas to an ethylene cracking furnace through a pipeline. The upper end of the light hydrocarbon tower is connected to a light hydrocarbon separation device through a pipeline. The lower end of the light hydrocarbon tower is connected to a gasoline stabilization tower through a pipeline. The separator tank is connected to a pipeline between a second-stage dry gas compressor and a carbon four absorption tower b through a pipeline. The concentration compressor is connected to the ethane tower through a pipeline.

2. A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device according to claim 1, characterized in that: The lower end of the C4 analysis tower a is connected to the C4 absorption tower a through pipeline No. 1, and the lower end of the C4 analysis tower b is connected to the C4 absorption tower b through pipeline No.

2. Compression pumps are connected to the pipeline No. 1 and the pipeline No.

2.

3. A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device according to claim 1 or 2, characterized in that: The pressure energy recovery device includes a turbine expander, and the turbine expander is connected to the tail gas of the membrane separation unit through pipeline No.

3. In the direction from the membrane separation unit to the turbine expander, the pipeline No. 3 is connected with a pressure sensor, a valve No. 1, a filter, and an XV valve in sequence, and the filter is communicated with a differential pressure transmitter. The turbine expander goes to the fuel gas pipeline network through pipeline No.

4. In the direction from the turbine expander to the fuel gas pipeline network, the pipeline No. 4 is connected with an on-off valve and a valve No. 2 in sequence, and a pipeline No. 5 is connected between the inlet end of the valve No. 1 and the outlet end of the valve No. 2, and a stop valve is connected to the pipeline No.

5. The stop valve is communicated with the pressure sensor, and the turbine expander is connected with a generator to generate electricity and connect to the power grid.

4. A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device according to claim 3, characterized in that: The turbo expander is also connected to a condensate discharge line, and two NC valves are connected to the condensate discharge line.

5. The high-pressure gas phase fluid pressure energy recovery system of the dry gas recovery device according to claim 1, characterized in that: The membrane separation unit removes crude hydrogen through a pipeline to PSA.

6. A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device according to claim 3, characterized in that: The turbo expander model is TG220.

7. A high-pressure gas phase fluid pressure energy recovery system for a dry gas recovery device according to claim 6, characterized in that: The generator is connected to the transmission of the turbo expander via a sliding coupling, and the sliding torque of the sliding coupling is 2.5 times the rated torque of the generator.

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