Deep purification system and method for coke oven gas

Abstract

The present invention provides a deep purification system and method for coke oven gas, and belongs to the field of coke oven gas purification. By setting the pre-washing tower as a super gravity rotating device, the coke oven gas after debenzenization can be preliminarily removed of impurities by super gravity rotating technology in the pre-washing tower, so as to deeply remove harmful substances such as dust, benzene, tar, naphthalene, ammonia and sulfur in the coke oven gas after debenzenization, solve the problem that excessive sulfur and ammonia in the coke oven gas will affect the stable operation of the subsequent system, and also solve the problem that tar and naphthalene in the coke oven gas will cause the compression system to be blocked. Through equipment such as a desulfurization tower, a thermal regeneration tower, a water washing tower, an azeotropic tower, a methanol-water separation tower, a methanol-rich flash tank and a four-phase separator, a system using low-temperature methanol washing technology to further remove impurities with complex components in coke oven gas is provided, which can not only ensure the purified gas index, but also solve the problem that the coking desulfurization waste liquid cannot be radically treated through methanol regeneration and recycling.

Description

Technical Field

[0001] The invention relates to the technical field of coke oven gas purification, and in particular to a deep purification system and method for coke oven gas. Background Art

[0002] Coke oven gas is an important by-product obtained during the coking process. In recent years, the research on the composition of coke oven gas has been quite mature. Coke oven gas is a medium calorific value gas with a hydrogen content of 50% to 60% and a methane content of 22% to 24%, which contains huge utilization value. A large amount of coke oven gas is produced while producing coke. If it is calculated that 430 cubic meters of coke oven gas is produced for 1 ton of coke, the annual coke oven gas production in my country is basically maintained at 180 billion cubic meters, of which about 45-50% of the coke oven gas returns to the coke oven, and the remaining coke oven gas is equivalent to more than twice the annual gas transmission volume of the national "West-East Gas Transmission". Therefore, how to recycle and utilize coke oven gas is of great significance to the realization of resource recycling and sustainable economic development. Before the comprehensive utilization of coke oven gas, the purification of coke oven gas has become a top priority. Before the comprehensive utilization of coke oven gas, the purification of coke oven gas has become a top priority, and the core issue in the purification of coke oven gas is desulfurization.

[0003] At present, the commonly used desulfurization methods for coke oven gas are dry desulfurization and wet desulfurization. Dry desulfurization mainly uses a desulfurization catalyst synthesized from iron hydroxide and other preparations to remove H2S from coal gas, and the regenerated desulfurizer can be reused. Dry desulfurization is mainly used for desulfurization of coke oven gas with a small gas volume or secondary desulfurization with high desulfurization accuracy. The wet desulfurization process uses a liquid desulfurizer to remove H2S and HCN from coke oven gas. Currently, the commonly used wet desulfurization methods include improved ADA method, naphthoquinone method, gum method, FRC method, TH method, HPF method, PDS method, OPT method, complex iron method, and ammonia catalysis method. Large-scale coking enterprises usually use wet desulfurization. In the process of wet desulfurization, a small amount of waste liquid will be discharged in order to avoid the accumulation of side reaction salts in the desulfurization waste liquid. The previous measure was to send the discharged desulfurization waste liquid into the coal blending system, but this method would cause environmental problems and pollute the environment.

[0004] With the introduction of new environmental protection policies, the treatment of desulfurization waste liquid has become a major problem in the coking industry. So far, a relatively complete, economical and environmentally friendly desulfurization waste liquid treatment method has not been formed in China. In summary, the desulfurization of coke oven gas faces the problem of high investment and cost of dry desulfurization, which cannot meet the requirements of large-scale coke oven gas production, while the traditional wet desulfurization has the problem of waste liquid being unable to be treated. In addition, in the current deep purification process of coke oven gas, there is still insufficient precision in desulfurization and naphthalene removal, which cannot guarantee the safe, stable, normal, full and optimal operation of subsequent equipment. It is mainly manifested in the following three aspects:

[0005] (1) The sulfur and ammonia content of coke oven gas after deep purification exceeds the standard, affecting the normal operation of subsequent purification and synthesis.

[0006] Generally, when coke oven gas is used only as fuel gas, H2S is required to be less than 500mg / Nm 3 , ammonia content is less than 100mg / Nm 3 However, in actual operation, acid gas and ammonia sometimes exceed the standard, affecting the stable operation of the system. With the expansion of coking scale and industrial agglomeration, coke oven gas has become an important chemical raw material gas. The change in the use of coke oven gas has caused the original design indicators of coke oven gas deep purification to be far from meeting the current use indicators.

[0007] (2) The tar and naphthalene content in the deeply purified coke oven gas seriously affects the normal operation of the compressor. The main reason is that the coke oven gas contains high levels of tar and naphthalene. When compressed, the temperature rises and the tar gasifies and forms coke. In addition, the naphthalene condenses and crystallizes, causing naphthalene blockage in the compressor. The compressor cannot operate normally and is forced to stop for repairs. Sometimes the compressor has to be stopped for repairs after only 1-2 days of operation, making production very passive. It is often the case that 1 is in operation and 2 are on standby or 1 is in operation and 3 are on standby.

[0008] (3) Due to the abnormal coarse desulfurization, the desulfurizer of fine desulfurization fails prematurely, affecting the production operation, mainly due to sulfur breakthrough, and the desulfurizer is forced to be replaced in advance. As a result, the desulfurizer is frequently replaced, and the operating cost increases. Summary of the invention

[0009] In order to solve the technical problems that the deep purification process of coke oven gas currently affects the stable operation of the subsequent system, causes compressor blockage, and causes the desulfurization agent of fine desulfurization to fail prematurely, thereby increasing operating costs, the present invention provides a deep purification system and method for coke oven gas.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0011] A deep purification system for coke oven gas comprises a pre-wash tower, a desulfurization tower, a heat regeneration tower, a water washing tower, an azeotropic tower, a methanol-water separation tower, a methanol-rich flash tank and a four-phase separator, wherein the pre-wash tower is a supergravity rotating device, and the four-phase separator is a horizontal three-weir type gas-liquid-liquid-liquid separator, wherein: the gas cabinet is connected to the gas phase inlet at the bottom of the pre-wash tower through a first heat exchanger, the liquid phase outlet at the bottom of the pre-wash tower is connected to the feed port of the four-phase separator, and the gas outlet of the pre-wash tower is connected to the desulfurization tower through a first compressor, a second heat exchanger and a third heat exchanger. The air inlet at the lower part of the sulfur tower is connected, the air outlet at the top of the desulfurization tower is connected to the second heat exchanger, the liquid outlet at the bottom of the desulfurization tower is connected to the liquid phase inlet at the top of the pre-washing tower through the second compressor, the liquid outlet at the middle and lower part of the desulfurization tower is connected to the liquid inlet of the methanol-rich flash tank through the fourth heat exchanger, the air outlet at the top of the methanol-rich flash tank is connected to the air inlet at the middle and upper part of the water washing tower, the air outlet at the top of the water washing tower is connected to the desulfurization waste gas pipeline, the liquid outlet at the bottom of the methanol-rich flash tank is connected to the liquid inlet at the middle and upper part of the heat regeneration tower through the fifth heat exchanger, and the bottom of the heat regeneration tower is connected to the liquid inlet at the middle and upper part of the heat regeneration tower. The liquid outlet at the top of the desulfurization tower is connected to the liquid inlet at the top of the desulfurization tower through the third compressor and the fifth heat exchanger, the gas outlet at the top of the thermal regeneration tower is connected to the gas inlet at the bottom of the water washing tower through the sixth heat exchanger, the sixth heat exchanger is connected to the liquid inlet of the condensate storage tank, the liquid outlet of the condensate storage tank is connected to the liquid inlet at the top of the thermal regeneration tower, the gas outlet at the top of the water washing tower is connected to the desulfurization waste gas pipeline, the liquid outlet at the bottom of the water washing tower is connected to the feed port of the four-phase separator, the gas phase outlet of the four-phase separator is connected to the gas inlet in the middle of the azeotropic tower, the gas outlet of the four-phase separator is connected to the gas inlet in the middle of the azeotropic tower, and the gas outlet of the four-phase separator is connected to the gas inlet in the middle of the azeotropic tower. The phase fluid outlet is connected to the heavy oil pipeline, the light phase fluid outlet of the four-phase separator is connected to the light oil pipeline, the intermediate phase fluid outlet of the four-phase separator is connected to the liquid inlet in the middle of the azeotropic tower via the fourth compressor and the seventh heat exchanger, the air outlet at the top of the azeotropic tower is connected to the air inlet at the bottom of the water washing tower, the liquid outlet at the bottom of the azeotropic tower is connected to the liquid inlet in the middle of the methanol-water separation tower via the fifth compressor, the air outlet at the top of the methanol-water separation tower is connected to the air inlet in the middle of the heat regeneration tower, and the liquid outlet at the bottom of the methanol-water separation tower is connected to the seventh heat exchanger.

[0012] Optionally, the pre-wash tower includes a transmission device, a rotating shaft and a pre-wash shell, the transmission device is connected to one end of the rotating shaft, and the other end of the rotating shaft is connected to a rotor, the rotor is arranged in the middle and lower part of the inner cavity of the pre-wash shell, the top middle of the pre-wash shell is connected to a gas outlet, the bottom of the pre-wash shell is connected to a liquid phase outlet, the bottom of one side of the pre-wash shell is connected to a gas phase inlet, the middle and upper part of the other side of the pre-wash shell is connected to a liquid phase inlet, the liquid phase inlet is connected to an L-shaped liquid pipeline, the vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor, and a plurality of liquid phase nozzles are installed on the vertical pipe of the L-shaped liquid pipeline, a demister is provided at the top of the inner cavity of the pre-wash shell, a partition plate is installed between the bottom of the demister and the top of the rotor, the middle of the top of the rotor and the partition plate are sealed by a first sealing gasket, the middle of the bottom of the rotor and the rotating shaft are sealed by a second sealing gasket and a third sealing gasket on both sides, and the inside of the rotor is filled with a packing layer.

[0013] Optionally, the four-phase separator comprises a separation shell, and the inner cavity of the separation shell is divided into an inlet section I, a sedimentation separation section II and a collection section III from left to right;

[0014] The inlet section I is provided with a gas-liquid separator, a baffle and a calming plate. The feed port is arranged outside the separation shell and connected to the top of the separation shell. The gas-liquid separator is installed below the feed port. The bottom end of the calming plate is connected to the bottom of the separation shell. The top end of the baffle is connected to the top of the separation shell and is located between the gas-liquid separator and the calming plate. The sedimentation separation section II is provided with a coalescer. The collection section III is provided with a heavy phase fluid overflow weir, a heavy phase fluid collecting tank, a light phase fluid collecting tank and an intermediate phase fluid overflow weir. The heavy phase fluid overflow weir is arranged on one side of the coalescer and connected to the bottom of the separation shell. The top end of the heavy phase fluid collecting tank is connected to the bottom of the separation shell and is located between the coalescer and the heavy phase fluid overflow weir. A first liquid level gauge is respectively installed on the top and bottom of the side wall of the heavy phase fluid collecting tank. The bottom of the heavy phase fluid collecting tank is connected to the heavy phase fluid outlet. The top and bottom of the separation shell above the heavy phase fluid collecting tank are each provided with a first liquid level gauge. A second liquid level gauge is installed, the light phase fluid collecting tank is arranged on one side of the heavy phase fluid overflow weir, the front wall of the light phase fluid collecting tank is the light phase fluid overflow weir, the height of the light phase fluid overflow weir is lower than the height of the rear wall of the light phase fluid collecting tank, a third liquid level gauge is respectively arranged at the top and the bottom of the light phase fluid collecting tank, the bottom of the light phase fluid collecting tank is connected with a light phase fluid outlet, the light phase fluid outlet is located outside the separation shell, a demister is arranged above the light phase fluid collecting tank, the gas phase outlet is arranged outside the separation shell and connected to the demister, the intermediate phase fluid overflow weir is arranged on one side of the light phase fluid collecting tank and connected to the bottom of the separation shell, the intermediate phase fluid overflow weir and the space at the tail of the separation shell form an intermediate phase fluid collecting tank, a fourth liquid level gauge is respectively arranged at the top and the bottom of one side of the intermediate phase fluid overflow weir, and the bottom of the separation shell on one side of the intermediate phase fluid overflow weir is connected with the intermediate phase fluid outlet.

[0015] Optionally, the length ratio of the inlet section I, the sedimentation separation section II and the collection section III is 1:3.2-4.2:2.

[0016] Optionally, the top of the calming plate is at the same horizontal plane as the second liquid level gauge located on the top of the separation shell; the bottom of the baffle is 400-500mm higher than the top of the calming plate, and the bottom of the baffle is not less than 200mm lower than the bottom of the gas-liquid separator. The height of the coalescer is the same as the height of the light phase fluid overflow weir, the height of the heavy phase fluid overflow weir is 200-500mm higher than the bottom of the light phase fluid collecting tank, the height of the light phase fluid overflow weir is 1 / 2-3 / 4 of the diameter of the four-phase separator, the rear wall height of the light phase fluid collecting tank is 200mm higher than the bottom of the demister, and the height of the intermediate phase fluid overflow weir is 20-100mm lower than the height of the light phase fluid overflow weir.

[0017] A deep purification method for coke oven gas, the deep purification method adopts the above-mentioned deep purification system for coke oven gas, and comprises the following steps:

[0018] S1, the coke oven gas after benzene washing is heat exchanged with the coke oven gas after deep purification in the desulfurization tower to 20-25°C, the coke oven gas after heat exchange is sent to the pre-washing tower from the lower part of the pre-washing tower, and the gas scrubber from the bottom of the desulfurization tower is pressurized and sent to the pre-washing tower from the upper part of the pre-washing tower; wherein the pre-washing tower is a super gravity rotating device;

[0019] S2, the coke oven gas after heat exchange and the gas scrubber are contacted in a pre-wash tower in countercurrent or crosscurrent for pre-treatment, and the pre-treated gas scrubber is collected on the inner wall of the pre-wash tower under the action of super gravity of the pre-wash tower and then discharged to a four-phase separator;

[0020] S3, the pre-treated coke oven gas is pressurized to 0.3-1.0 MPa and then subjected to primary cooling with the coke oven gas deeply purified in the desulfurization tower, and then subjected to deep cooling to -22--28°C before entering the desulfurization tower, where the impurities in the coke oven gas are removed in two stages to obtain deeply purified coke oven gas, and after the deeply purified coke oven gas is reheated, 42-50% of the deeply purified coke oven gas is decompressed to 8-10 kPa and used as return gas for coke oven heating, and the rest is used for the production of chemicals;

[0021] S4, the sulfur-containing methanol rich liquid obtained by desulfurization at the bottom of the desulfurization tower is reheated to 25-35°C and then enters the methanol-rich flash tank for reduced pressure flash evaporation. The flash pressure is 2-8 bar. The flashed gas is discharged from the system as desulfurization waste gas after methanol is recovered by the water scrubber. The flashed rich liquid at the bottom of the methanol-rich flash tank is reheated to 80-100°C and then enters the thermal regeneration tower for regeneration. The regenerated lean methanol is pressurized and cooled to -20--40°C and then sent to the upper part of the desulfurization tower as an absorbent. The sulfur-containing gas obtained at the top of the thermal regeneration tower is cooled and the entrained methanol is recovered and then sent to the water scrubber for washing. The coke oven gas washed by the water scrubber is discharged from the system as desulfurization waste gas;

[0022] S5, the gas scrubber pretreated by the pre-scrubber is mixed with the methanol solution discharged from the bottom of the scrubber, and the mixed mixture is sent to a four-phase separator for gas-liquid separation. The dissolved gas separated by the four-phase separator is discharged to an azeotropic tower for washing. The tar dust separated by the four-phase separator is discharged from the heavy phase fluid outlet of the four-phase separator, and the naphtha separated by the four-phase separator is discharged from the light phase fluid outlet of the four-phase separator. The intermediate phase separated by the four-phase separator is used as a gas scrubber, and the wastewater discharged from the methanol-water separation tower is heat-exchanged to 80-100° C. and then pressurized and sent to an azeotropic tower to recover the scrubber;

[0023] S6, the non-condensable gas at the top of the azeotropic tower is washed with water in a water washing tower to recover methanol and then discharged from the system as desulfurization waste gas. The methanol / water mixture at the bottom of the azeotropic tower is pressurized and sent to the methanol-water separation tower for distillation and purification. The methanol vapor at the top of the methanol-water separation tower returns to the middle of the thermal regeneration tower, and the waste water at the bottom of the methanol-water separation tower is cooled and sent out of the system.

[0024] Optionally, the operating conditions of the pre-wash tower are: operating temperature 15-20°C, operating pressure 3-6 kPa, filler specific surface area 500-4000m 2 / m 3 , the packing rotation frequency is 30-60Hz, and the gas-liquid ratio is 1000-6000.

[0025] Optionally, the coal gas scrubber includes at least methanol and crude benzene.

[0026] Optionally, after the desulfurization tower removes impurities in the coke oven gas in two stages, the sulfur content in the coke oven gas after deep purification is ≤0.1ppm, the carbon dioxide content is ≤2.5%, and there is no tar dust, naphthalene and ammonia.

[0027] Optionally, the amount of gas scrubber in the pre-wash tower is 0.20-0.32 kg / m 3 Coke oven gas; the amount of lean methanol in the desulfurization tower is 1.30-1.50kg / m 3 Coke oven gas; the NH3 content in the recycled lean methanol is less than 20×10 －6 ppm, pH value is 8-10.

[0028] The beneficial effects of the present invention are:

[0029] By setting a pre-washing tower and setting the pre-washing tower as a super gravity rotating device, the coke oven gas after debenzenization can be preliminarily removed of impurities in the pre-washing tower through the super gravity rotating technology. Through the pretreatment of the pre-washing tower, the dust, benzene, tar, naphthalene, ammonia and sulfur and other harmful substances in the coke oven gas after debenzenization can be deeply removed, which solves the problem that the excessive sulfur and ammonia in the coke oven gas will affect the stable operation of the subsequent system, and can improve the stability of the system operation; it also solves the problem that the tar and naphthalene in the coke oven gas will cause the compression system to be blocked, and avoids the blockage abnormality that may be caused in the subsequent process. Further, by setting a desulfurization tower, a thermal regeneration tower, a water washing tower, an azeotropic tower, a methanol-water separation tower, a methanol-rich flash tank and a four-phase separator and other equipment, a system using low-temperature methanol washing technology to further remove impurities with complex components in the coke oven gas is provided, which can not only ensure the purified gas index, but also solve the problem that the coking desulfurization waste liquid cannot be radically treated through methanol regeneration and recycling, and also solve the problem that the desulfurization agent of the fine desulfurization will fail prematurely due to abnormal rough desulfurization and increase the operating cost.

[0030] The system and method provided by the embodiment of the present invention meet the requirements of pressurized transportation of coke oven gas and subsequent deep purification, and achieve the purpose of purification required by the production chemical synthesis system. The present invention has the advantages of low investment, small equipment volume and floor space, high efficiency in removing impurities such as tar dust and naphthalene from coke oven gas, low energy consumption, and high washing efficiency. In addition, the coke oven gas deeply purified by the present invention does not need to be desulfurized again after returning to the coke oven, and no difficult-to-treat desulfurization waste liquid is generated, so that the subsequent production of chemical products fine desulfurization catalysis and service life are extended by at least one year. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the system composition of the present invention.

[0032] Figure 2 yes Figure 1 Schematic diagram of the structure of the pre-wash tower.

[0033] Figure 3 yes Figure 1 Schematic diagram of the structure of the four-phase separator. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0035] like Figure 1As shown, an embodiment of the present invention provides a deep purification system for coke oven gas, which includes a pre-wash tower 1, a desulfurization tower 8, a thermal regeneration tower 3, a water washing tower 4, an azeotropic tower 5, a methanol-water separation tower 6, a methanol-rich flash tank 7 and a four-phase separator 2, wherein the pre-wash tower 1 is a supergravity rotating device, and the four-phase separator 2 is a horizontal three-weir type gas-liquid-liquid-liquid separator, wherein: the gas cabinet is connected to the gas phase inlet 103 at the bottom of the pre-wash tower 1 through the first heat exchanger 9, the liquid phase outlet 102 at the bottom of the pre-wash tower 1 is connected to the feed port 201 of the four-phase separator 2, and the gas outlet 107 of the pre-wash tower 1 is connected to the first compressor 10, the second heat exchanger 9, and the gas outlet 107 of the pre-wash tower 1 is connected to the feed port 201 of the four-phase separator 2. The heat exchanger 11 and the third heat exchanger 12 are connected to the air inlet at the lower part of the desulfurization tower 8, the air outlet at the top of the desulfurization tower 8 is connected to the second heat exchanger 11, the liquid outlet at the bottom of the desulfurization tower 8 is connected to the liquid phase inlet 109 at the upper part of the pre-washing tower 1 through the second compressor 14, the liquid outlet at the middle and lower part of the desulfurization tower 8 is connected to the liquid inlet of the rich methanol flash tank 7 through the fourth heat exchanger 13, the air outlet at the top of the rich methanol flash tank 7 is connected to the air inlet at the middle and upper part of the water washing tower 4, the air outlet at the top of the water washing tower 4 is connected to the desulfurization exhaust gas pipeline, and the liquid outlet at the bottom of the rich methanol flash tank 7 is connected to the liquid inlet at the middle and upper part of the heat regeneration tower 3 through the fifth heat exchanger 15. The liquid outlet at the bottom of the thermal regeneration tower 3 is connected to the liquid inlet at the top of the desulfurization tower 8 through the third compressor 16 and the fifth heat exchanger 15. The gas outlet at the top of the thermal regeneration tower 3 is connected to the gas inlet at the bottom of the water washing tower 4 through the sixth heat exchanger 17. The sixth heat exchanger 17 is connected to the liquid inlet of the condensate storage tank 22. The liquid outlet of the condensate storage tank 22 is connected to the liquid inlet at the top of the thermal regeneration tower 3. The gas outlet at the top of the water washing tower 4 is connected to the desulfurization waste gas pipeline. The liquid outlet at the bottom of the water washing tower 4 is connected to the feed port 201 of the four-phase separator 2. The gas phase outlet 202 of the four-phase separator 2 is connected to the gas inlet in the middle of the azeotropic tower 5. The four-phase separator The heavy phase fluid outlet 203 of the four-phase separator 2 is connected to the heavy oil pipeline, the light phase fluid outlet 204 of the four-phase separator 2 is connected to the light oil pipeline, the middle phase fluid outlet 205 of the four-phase separator 2 is connected to the liquid inlet in the middle of the azeotropic tower 5 via the fourth compressor 18 and the seventh heat exchanger 23, the air outlet at the top of the azeotropic tower 5 is connected to the air inlet at the bottom of the water washing tower 4, the liquid outlet at the bottom of the azeotropic tower 5 is connected to the liquid inlet in the middle of the methanol-water separation tower 6 via the fifth compressor 24, the air outlet at the top of the methanol-water separation tower 6 is connected to the air inlet in the middle of the thermal regeneration tower 3, and the liquid outlet at the bottom of the methanol-water separation tower 6 is connected to the seventh heat exchanger 23.

[0036] The system of the present invention is used to remove impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur contained in the coke oven gas after primary cooling, electrostatic tar capture, precooling, desulfurization, intermediate cooling, ammonia removal, final cooling and benzene elution, so as to meet the needs of pressurized transportation of coke oven gas and subsequent deep purification, and achieve the purification needs of the production chemical synthesis system.

[0037] Alternatively, if Figure 2As shown, the pre-wash tower 1 includes a transmission device 101, a rotating shaft 115 and a pre-wash shell 108, the transmission device 101 is connected to one end of the rotating shaft 115, the other end of the rotating shaft 115 is connected to a rotor 104, the rotor 104 is arranged in the middle and lower part of the inner cavity of the pre-wash shell 108, the top middle of the pre-wash shell 108 is connected to a gas outlet 107, the bottom of the pre-wash shell 108 is connected to a liquid phase outlet 102, the bottom of one side of the pre-wash shell 108 is connected to a gas phase inlet 103, the middle and upper part of the other side of the pre-wash shell 108 is connected to a liquid phase inlet 109, and the liquid phase inlet 109 is connected to L shaped liquid pipeline, the vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor 104, a plurality of liquid phase nozzles 111 are installed on the vertical pipe of the L-shaped liquid pipeline, a demister 106 is provided on the top of the inner cavity of the pre-wash shell 108, a partition plate 105 is installed between the bottom of the demister 106 and the top of the rotor 104, the middle of the top of the rotor 104 and the partition plate 105 are sealed by a first sealing gasket 110, the middle of the bottom of the rotor 104 and the rotating shaft 115 are sealed by a second sealing gasket 112 and a third sealing gasket 113 respectively, and the inside of the rotor 104 is filled with a packing layer 114.

[0038] Optionally, the porosity of the packing layer 114 is 80% to 99%; the packing of the packing layer 114 is made of large corrugated wire mesh packing and small corrugated wire mesh packing. A small corrugated packing having a length of 5% to 10% of the radius of the pre-wash shell 108 is arranged near the rotating shaft 115, preferably 5% to 8%. The average pore size of the large corrugated wire mesh packing is 5 to 10 mm, preferably 4 to 8 mm; the average pore size of the small corrugated wire mesh packing is 1 to 5 mm, preferably 2 to 4 mm. This packing method is conducive to the uniform atomization of the liquid phase washing liquid and improves the capture effect of impurities. The large corrugated packing can reduce the gas-liquid phase resistance and improve the anti-clogging ability of the packing.

[0039] Alternatively, if Figure 3As shown, the four-phase separator 2 includes a separation shell 218, and the inner cavity of the separation shell 218 is divided into an inlet section I, a sedimentation separation section II and a collection section III from left to right; the inlet section I is provided with a gas-liquid separator 206, a baffle 207 and a calming plate 208, the feed inlet 201 is arranged outside the separation shell 218 and connected to the top of the separation shell 218, the gas-liquid separator 206 is installed below the feed inlet 201, the bottom end of the calming plate 208 is connected to the bottom of the separation shell 218, the top end of the baffle 207 is connected to the top of the separation shell 218 and is located between the gas-liquid separator 206 and the calming plate 208; the sedimentation separation Section II is equipped with a coalescer 209; the collection section III is provided with a heavy phase fluid overflow weir 217, a heavy phase fluid collecting tank 219, a light phase fluid collecting tank 220 and an intermediate phase fluid overflow weir 216, the heavy phase fluid overflow weir 217 is arranged on one side of the coalescer 209 and connected to the bottom of the separation shell 218, the top of the heavy phase fluid collecting tank 219 is connected to the bottom of the separation shell 218 and is located between the coalescer 209 and the heavy phase fluid overflow weir 217, the top and bottom of the side wall of the heavy phase fluid collecting tank 219 are respectively equipped with a first liquid level gauge 213, and the bottom of the heavy phase fluid collecting tank 219 is connected to the heavy phase fluid outlet 2 03, a second level gauge 212 is installed on the top and bottom of the separation shell 218 above the heavy phase fluid collection tank 219, the light phase fluid collection tank 220 is arranged on one side of the heavy phase fluid overflow weir 217, the front wall of the light phase fluid collection tank 220 is the light phase fluid overflow weir 214, the height of the light phase fluid overflow weir 214 is lower than the height of the rear wall 215 of the light phase fluid collection tank 220, a third level gauge 210 is installed on the top and bottom of the light phase fluid collection tank 220, the bottom of the light phase fluid collection tank 220 is connected to the light phase fluid outlet 204, and the light phase fluid outlet 204 is located in the separation shell 21 8 outside, a demister 222 is arranged above the light phase fluid collecting tank 220, the gas phase outlet 202 is arranged outside the separation shell 218 and connected to the demister 222, the intermediate phase fluid overflow weir 216 is arranged on one side of the light phase fluid collecting tank 220 and connected to the bottom of the separation shell 218, the intermediate phase fluid overflow weir 216 and the space at the tail of the separation shell 218 form an intermediate phase fluid collecting tank 221, a fourth liquid level gauge 211 is respectively arranged at the top and bottom of one side of the intermediate phase fluid overflow weir 216, and the bottom of the separation shell 218 on one side of the intermediate phase fluid overflow weir 216 is connected to the intermediate phase fluid outlet 205.

[0040] Among them, the gas-liquid separator 206 and the calming plate 208 are conventional components of the inlet section I. The main function of the gas-liquid separator 206 is to realize gas-liquid pre-separation. There are many forms in practical applications. Its function is to evenly distribute or redistribute the liquid on the top of the packing or at a certain height to increase the effective surface of mass transfer and heat transfer, improve the contact between phases, and thus improve the separation efficiency of the tower. The main function of the calming plate 208 is to slow down the two-phase fluctuations in the liquid phase area of ​​the inlet section I. It also has the function of liquid-liquid-liquid pre-separation, but it mainly suppresses the fluctuations to provide stable operating conditions for the sedimentation separation section II. The coalescer 209 mainly improves the separation efficiency by promoting the coalescence of the light phase (such as oil droplets) on the plate surface, and also has the function of suppressing the fluctuations in the liquid phase area of ​​the sedimentation separation section II.

[0041] Optionally, the length ratio of the inlet section I, the sedimentation separation section II and the collection section III is 1:3.2-4.2:2.

[0042] Optionally, the top of the calming plate 208 is at the same horizontal plane as the second liquid level gauge 212 located at the top of the separation shell 218; the bottom of the baffle 207 is 400-500mm higher than the top of the calming plate 208, and the bottom of the baffle 207 is not less than 200mm lower than the bottom of the gas-liquid separator 206.

[0043] Optionally, the height of the coalescer 209 is the same as the height (H1) of the light phase fluid overflow weir 214, the height of the heavy phase fluid overflow weir 217 is 200-500 mm higher than the bottom of the light phase fluid collecting tank 220, the height of the light phase fluid overflow weir 214 is 1 / 2-3 / 4 of the diameter of the four-phase separator, the height (H2) of the rear wall 215 of the light phase fluid collecting tank 220 is 200 mm higher than the bottom of the demister 222, and the height (H3) of the intermediate phase fluid overflow weir 216 is 20-100 mm lower than the height of the light phase fluid overflow weir 214.

[0044] By setting three overflow weir plates, namely, the heavy phase fluid overflow weir 217, the light phase fluid overflow weir 214 and the intermediate phase fluid overflow weir 216, and three liquid phase collecting tanks, namely, the heavy phase fluid collecting tank 219, the light phase fluid collecting tank 220 and the intermediate phase fluid collecting tank 221, in the collection section III, the length of the collection section III of the four-phase separator 2 is greater than that of the ordinary separator. However, due to such a setting, the liquid-liquid interface during the operation is better controlled, thereby ensuring the stable progress of the separation process, thereby reducing or avoiding the influence of the operating condition fluctuation on the sedimentation separation section II process. The control of the liquid-liquid interface of the four-phase separator 2 in the embodiment of the present invention comes from two aspects: first, the three overflow weir plates and the three liquid phase collecting tank structures make the liquid-liquid interface simultaneously controlled by the static pressure of the light phase / intermediate phase and the heavy phase fluid, so it is relatively stable; second, the light phase fluid collecting tank 220 and the intermediate phase fluid collecting tank 221 provide a buffer space for the fluctuation of the upstream and downstream (inlet and outlet) flow during the operation, thereby reducing or avoiding the influence of the operating condition fluctuation on the sedimentation separation process. By providing components such as the calming plate 208 and the coalescer 209, a lower lateral flow velocity is ensured so that the fluid in the liquid phase has sufficient residence time to achieve liquid-liquid-liquid sedimentation separation, which is beneficial to the sedimentation or buoyancy of the dispersed phase, reduces the fluctuation of the liquid phase, shortens the separation time, and reduces the size of the equipment.

[0045] All the inventions used Figure 3 The four-phase separator 2 shown is designed by comprehensively considering the factors affecting the pressure distribution at the end of the sedimentation separation section II under actual separation conditions, including: the height of the light phase fluid overflow weir 214 and the height difference of the three weir plates, the liquid layer thickness and liquid layer flow rate at the overflow weir top and the flow resistance at the bottom of the light phase collection tank 220.

[0046] The embodiment of the present invention further provides a deep purification method for coke oven gas, wherein the deep purification method adopts the deep purification system for coke oven gas, and comprises the following steps:

[0047] S1, the coke oven gas after benzene elution is heat-exchanged with the coke oven gas deeply purified by the desulfurization tower 8 in the first heat exchanger 9 and the second heat exchanger 11 to a temperature of 20-25°C, and the coke oven gas after heat exchange is sent into the pre-washing tower 1 from the lower part of the pre-washing tower 1, and at the same time, the gas scrubber from the bottom of the desulfurization tower 8 is pressurized by the second compressor 14 and sent into the pre-washing tower 1 from the upper part of the pre-washing tower 1; wherein the pre-washing tower 1 is a super gravity rotating device.

[0048] After benzene is removed, the coke oven gas contains impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur. Usually, the coke oven gas after benzene is removed contains 5-15 mg / m 3 , naphthalene 10-200mg / m 3 , ammonia 15-100mg / m 3 , sulfur less than 500mg / m 3and other trace impurities.

[0049] S2, the coke oven gas after heat exchange and the gas scrubber are contacted in countercurrent or crosscurrent in the pre-wash tower 1 for pre-treatment, and the pre-treated gas scrubber is gathered on the inner wall of the pre-wash tower 1 under the super gravity of the pre-wash tower 1 and then discharged to the four-phase separator 2.

[0050] Since the coke oven gas after benzene is eluted contains impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur, the embodiment of the present invention first pre-treats the coke oven gas after benzene is eluted by using a pre-washing tower 1 using ultra-gravity rotation technology to preliminarily remove impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur in the coke oven gas after benzene is eluted.

[0051] Specifically, in the pre-wash tower 1, the gas scrubber is evenly distributed through the liquid phase nozzle 111 of the pre-wash tower 1 and then enters the packing layer 114. Under the action of the transmission device 101, the rotating shaft 115 and the rotor 104, the gas scrubber is split into liquid micro-elements (liquid film, liquid filaments and liquid droplets) and countercurrently contacts with the coke oven gas after benzene is eluted to remove impurities in the coke oven gas after benzene is eluted. Since the pre-wash tower 1 is a super gravity rotating device, the embodiment of the present invention uses super gravity rotating technology to remove impurities. The cutting particle size of the super gravity rotating technology reaches 10 -8 The particle size of the gas scrubber after passing through the packing layer 114 is almost at the molecular level, and then it is aggregated in the supergravity rotating device and removed together with the impurities. The embodiment of the present invention uses supergravity rotating technology to pre-treat the coke oven gas after eluting benzene, which can enhance the washing effect and reduce the particle size cutting size of the washing. At the same time, through liquid phase spray and supergravity, the droplet distribution is more uniform, and the contact surface with the impurities in the coke oven gas is larger, thereby improving the elution effect of impurities. The supergravity rotating device has the characteristics of good particle capture effect, small gas phase pressure drop, and the rotating filler is not easy to be blocked, so as to achieve the deep removal of harmful substances such as dust, benzene, tar, naphthalene, ammonia and sulfur in the coke oven gas, thereby meeting the coke oven gas pressurized transportation and subsequent deep purification, and achieving the purpose of purification of the production chemical synthesis system. The coke oven gas after impurities are removed is defoamed by the demister 106 to obtain pretreated coke oven gas. The gas scrubber after impurities are removed is thrown to the inner wall of the pre-washing shell 108 and flows into the four-phase separator 2 from the liquid phase outlet 102.

[0052] The coke oven gas pretreatment is tested under different temperatures, pressures, and detergents to find that naphthalene in the coke oven gas is easy to crystallize and precipitate at less than 20°C. In order to avoid the blockage of equipment and pipelines caused by naphthalene crystallization at low temperatures, the embodiment of the present invention adds a pre-wash tower 1 and uses pre-wash methanol to remove naphthalene from the coke oven gas. Since the pre-wash methanol contains crude benzene, benzene and naphthalene are both aromatic compounds. According to the principle of similar compatibility, naphthalene is basically dissolved in the gas detergent.

[0053] Furthermore, the embodiment of the present invention determines through experiments that the most suitable temperature for pre-treating coke oven gas is 20-25°C, the gas scrubber includes at least methanol and crude benzene, and the gas scrubber may also include one or two or more of desalted water, ethanol, washing oil and tar, and the gas scrubber has a good pre-treatment effect when the temperature is less than 20°C. After the coke oven gas after benzene is eluted is pre-treated under these conditions, practice has proved that the capture efficiency of tar dust reaches more than 99%, and particles larger than 3μm can be completely removed; the removal rate of naphthalene is more than 80%; the removal rate of tar and dust reaches more than 60%; the removal rate of organic sulfur reaches more than 85%; the removal rate of ammonia reaches more than 50%; the removal rate of benzene reaches more than 50%; this removal rate enables the pre-treated coke oven gas to meet the requirements of subsequent compression and deep purification.

[0054] S3, the pretreated coke oven gas is pressurized to 0.3-1.0MPa by the first compressor 10 and then cooled in the second heat exchanger 11 together with the coke oven gas deeply purified by the desulfurization tower 8, and then deeply cooled to -22~-28℃ by the third heat exchanger 12 before entering the desulfurization tower 8, and the impurities in the coke oven gas are removed in two stages in the desulfurization tower 8 to obtain deeply purified coke oven gas, and the deeply purified coke oven gas is reheated by the first heat exchanger 9 and the second heat exchanger 11, and 42-50% of the deeply purified coke oven gas is depressurized to 8-10kPa and used as return gas for coke oven heating, and the rest is used for the production of chemicals.

[0055] S4, the sulfur-containing methanol rich liquid obtained by desulfurization at the lower part of the desulfurization tower 8 is reheated to 25-35°C by the fourth heat exchanger 13 and then enters the methanol-rich flash tank 7 for reduced pressure flash evaporation. The flash pressure is 2-8 bar. The flashed gas is discharged from the system as a desulfurization waste gas after recovering methanol through the water scrubber 4. The flashed rich liquid at the bottom of the methanol-rich flash tank 7 is reheated to 80-100°C by the fifth heat exchanger 15 and then enters the hot regeneration tower 3 for regeneration. The regenerated lean methanol is pressurized by the third compressor 16 and cooled to -20--40°C by the fifth heat exchanger 15 and then sent to the upper part of the desulfurization tower 8 as an absorbent. The sulfur-containing gas obtained at the top of the hot regeneration tower 3 is cooled by the sixth heat exchanger 17 and the entrained methanol is recovered by the condensate storage tank 22 and then sent to the water scrubber 4 for washing. The coke oven gas washed by the water scrubber 4 is discharged from the system as a desulfurization waste gas.

[0056] The gas flashed out of the rich methanol flash tank 7 is H2, CH4, etc. The sulfur-containing gas obtained at the top of the thermal regeneration tower 3 is a gas with a high H2S concentration. The methanol solution absorbing the acidic gas component is regenerated and recycled by means of reduced pressure flash evaporation, heating regeneration and other operating methods. When the lean methanol temperature is -20 to -40°C, it can meet the requirements of desulfurization accuracy and can also be cooled by common cooling media.

[0057] S5, the gas scrubber pretreated by the pre-wash tower 1 is mixed with the methanol-containing solution discharged from the bottom of the water washing tower 4, and the mixed mixture is sent to the four-phase separator 2 for gas-liquid separation, the dissolved gas separated by the four-phase separator 2 is discharged to the azeotropic tower 5 for washing, the tar dust separated by the four-phase separator 2 is discharged from the heavy phase fluid outlet 203 of the four-phase separator 2, and the naphtha separated by the four-phase separator 2 is discharged from the light phase fluid outlet 204 of the four-phase separator 2, and the intermediate phase separated by the four-phase separator 2 is used as a gas scrubber. The waste water discharged from the methanol-water separation tower 6 is heat exchanged to 80-100°C by the seventh heat exchanger 23 and then pressurized by the fourth compressor 18 and sent to the azeotropic tower 5 to recover the scrubber.

[0058] The gas scrubber after pretreatment in the pre-wash tower 1 contains impurities such as tar, dust, crude benzene, naphthalene, ammonia, and organic sulfur.

[0059] S6, the non-condensable gas at the top of the azeotropic tower 5 is washed with water in the water washing tower 4 to recover methanol and then discharged from the system as desulfurization waste gas, the methanol / water mixture at the bottom of the azeotropic tower 5 is pressurized by the fifth compressor 24 and then sent to the methanol-water separation tower 6 for distillation and purification, the methanol vapor at the top of the methanol-water separation tower 6 returns to the middle of the thermal regeneration tower 3, and the waste water at the bottom of the methanol-water separation tower 6 is cooled by the seventh heat exchanger 23 and then sent out of the system.

[0060] The methanol in the desulfurization tower 8 absorbs NH3 in the process gas while absorbing acidic gases, which will have a certain impact on the low-temperature methanol washing system (desulfurization tower 8, thermal regeneration tower 3, water washing tower 4, azeotropic tower 5, methanol-water separation tower 6 and methanol-rich flash tank 7). The solubility of NH3 in methanol at low temperatures is much higher than that of acidic gases such as CO2 and H2S in methanol. Therefore, it is easy to accumulate in the methanol washing system. After acidic gases such as CO2 and H2S are dissolved in methanol, the pH value of methanol will be reduced, causing corrosion of the low-temperature methanol washing system equipment. In order to reduce equipment corrosion and extend the service life and operation cycle of equipment, the current low-temperature methanol washing process will allow a certain amount of NH3 to exist in the system. At room temperature, the solubility of NH3 in methanol is more than 10 times that of H2S and more than 60 times that of CO2. Methanol containing NH3 eventually enters the thermal regeneration tower 3 for regeneration. NH3 dissolved in methanol will be desorbed in the thermal regeneration tower 3. As the acid gas enters the water cooler at the top of the thermal regeneration tower 3, the methanol in the acid gas is condensed because the water cooler cools the acid gas. However, the content of NH3 in the low-temperature methanol washing system must be strictly controlled. If the NH3 content is low, it will cause the corrosion of the equipment to intensify; if the NH3 content is high, it will cause the ammonium salt of the methanol thermal regeneration system to crystallize and block the heat exchanger at the top of the thermal regeneration tower 3; when the NH3 content is high to a certain extent, it will cause the sulfur content in the process gas to exceed the standard. Therefore, the NH3 content in the low-temperature methanol washing system must be well controlled. Therefore, the embodiment of the present invention needs to control the ammonia concentration within a certain range during purification, that is, to maintain the NH3 content in the circulating lean methanol (circulated in the desulfurization tower 8, the thermal regeneration tower 3, the water washing tower 4, the azeotropic tower 5, the methanol-water separation tower 6, the rich methanol flash tank 7 and the four-phase separator 2) less than 20×10 －6 ppm, pH value is 8-10.

[0061] Depending on the concentration of H2S in coke oven gas, the solubility in methanol at 0.3-1.0MPa and temperature -20 to -40℃ is 0.9 to 6Nm 3 H2S / m 3 The solubility of CO2 in methanol at 0.3-1.0MPa and temperature -20 to -40℃ is 0.8 to 5Nm 3 CO2 / m 3 , it can be determined that the amount of lean methanol in the desulfurization tower 8 (i.e. the amount of lean methanol entering the desulfurization tower 8, including the lean methanol entering from the bottom of the thermal regeneration tower 3 and the methanol supplemented from the outside during the off-time) is 1.30-1.50 kg / m 3 Coke oven gas.

[0062] Coke oven gas has a complex composition and contains many impurities. Its gas components include CO, H2, CO2, CH4, H2S, organic sulfur, C2H4, C2H6, C3H8, C4H 10, HCN, N2, Ar, tar, fatty acids, monophenol, compound phenol, naphtha, anthracene oil, naphthalene oil, fly ash, etc. Among these components, except for CO, H2 effective components and CH4, N2, Ar and hydrocarbons, which are inert gases, all other components including CO2 and sulfide are harmful impurities that need to be removed, which shows the arduousness of the purification task. With the implementation of policies such as the withdrawal of coking enterprises from the city and entering the park, upgrading and transformation, scale and high-end have become the development direction of the coking industry, and the requirements for coke oven gas desulfurization have also increased. The low-temperature methanol washing purification method can cleanly remove various harmful components in coke oven gas, such as CO2, H2S, COS, C4H4S, HCN, NH3, H2O, hydrocarbons above C2 (including light oil, aromatic hydrocarbons, naphtha, olefins and colloids, etc.) and other carbonyl compounds, which cannot be achieved by any other purification process. In addition, the use of low-temperature methanol to elute and remove complex sulfur impurities in coke oven gas can not only ensure the purified gas indicators, but also solve the problem that the coking desulfurization waste liquid cannot be completely treated through methanol regeneration and recycling.

[0063] Optionally, the operating conditions of the pre-wash tower 1 are: operating temperature 15-20°C, operating pressure 3-6 kPa, filler specific surface area 500-4000m 2 / m 3 , the packing rotation frequency is 30-60Hz, and the gas-liquid ratio is 1000-6000.

[0064] Optionally, the coal gas scrubber includes at least methanol, wash oil and tar.

[0065] Optionally, after the desulfurization tower 8 removes impurities in the coke oven gas in two stages, the sulfur content in the coke oven gas after deep purification is ≤0.1ppm, the carbon dioxide content is ≤2.5%, and there is no tar dust, naphthalene and ammonia.

[0066] Optionally, the amount of gas scrubber in the pre-scrubber 1 (i.e., the amount of scrubber entering the pre-scrubber 1 from the bottom of the desulfurization tower 8) is 0.20-32 kg / m 3 Coke oven gas.

[0067] Furthermore, the general composition of coke oven gas is shown in Table 1 below:

[0068] Table 1

[0069]

[0070] Since the CO2 content in coke oven gas is less than 3%, and the sulfur content in coking coal is 0.7%, the sulfur concentration in coal gas is 4-8 times higher than that in large-scale coal gasification, the embodiment of the present invention does not need to increase the concentration of acid gas through a hydrogen sulfide concentration tower, and can achieve the required acid gas concentration and sulfur recovery concentration through a thermal regeneration tower 3 and concentrating the waste gas through a water scrubber 4. Therefore, compared with a large-scale coal gasification process, the embodiment of the present invention has the effects of shortening the entire subsequent process, significantly reducing investment, occupying a small area, and having good environmental benefits.

[0071] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A coke oven gas purification system, characterized in that: The coke oven gas first passes through a pretreatment system of primary cooling, electric tar capture, precooling, desulfurization, intermediate cooling, ammonia removal, final cooling and benzene elution to remove dust, benzene, tar, naphthalene, ammonia and various forms of sulfur impurities contained in the coke oven gas. The coke oven gas after benzene elution enters a deep purification system. The deep purification system includes a pre-washing tower (1), a desulfurization tower (8), a thermal regeneration tower (3), a water washing tower (4), an azeotropic tower (5), a methanol-water separation tower (6), a methanol-rich flash tank (7) and a four-phase separator (2). The pre-washing tower (1) is a supergravity rotating device, and the four-phase separator (2) is a horizontal three-weir type gas-liquid-liquid-liquid separator, wherein: the gas cabinet is connected to the gas phase inlet (103) at the lower part of the pre-washing tower (1) through a first heat exchanger (9). The liquid phase outlet (102) at the bottom of the pre-wash tower (1) is connected to the feed port (201) of the four-phase separator (2); the gas outlet (107) of the pre-wash tower (1) is connected to the air inlet at the bottom of the desulfurization tower (8) via the first compressor (10), the second heat exchanger (11) and the third heat exchanger (12); the air outlet at the top of the desulfurization tower (8) is connected to the second heat exchanger (11); the liquid outlet at the bottom of the desulfurization tower (8) is connected to the liquid phase inlet (109) at the top of the pre-wash tower (1) via the second compressor (14); the liquid outlet at the middle and lower part of the desulfurization tower (8) is connected to the liquid inlet of the methanol-rich flash tank (7) via the fourth heat exchanger (13); the air outlet at the top of the methanol-rich flash tank (7) is connected to the air inlet at the middle and upper part of the water washing tower (4); The gas outlet at the top of the washing tower (4) is connected to the desulfurization waste gas pipeline, the liquid outlet at the bottom of the methanol-rich flash tank (7) is connected to the liquid inlet at the middle and upper part of the thermal regeneration tower (3) through the fifth heat exchanger (15), the liquid outlet at the bottom of the thermal regeneration tower (3) is connected to the liquid inlet at the upper part of the desulfurization tower (8) through the third compressor (16) and the fifth heat exchanger (15), the gas outlet at the top of the thermal regeneration tower (3) is connected to the gas inlet at the lower part of the water washing tower (4) through the sixth heat exchanger (17), the sixth heat exchanger (17) is connected to the liquid inlet of the condensate storage tank (22), the liquid outlet of the condensate storage tank (22) is connected to the liquid inlet at the upper part of the thermal regeneration tower (3), the liquid outlet at the bottom of the water washing tower (4) is connected to the feed port (201) of the four-phase separator (2), and the four-phase separator (2) is connected to the feed port (201) of the four-phase separator (2). The gas phase outlet (202) of the four-phase separator (2) is connected to the air inlet in the middle of the azeotropic tower (5), the heavy phase fluid outlet (203) of the four-phase separator (2) is connected to the heavy oil pipeline, the light phase fluid outlet (204) of the four-phase separator (2) is connected to the light oil pipeline, the intermediate phase fluid outlet (205) of the four-phase separator (2) is connected to the liquid inlet in the middle of the azeotropic tower (5) via the fourth compressor (18) and the seventh heat exchanger (23), the air outlet at the top of the azeotropic tower (5) is connected to the air inlet at the bottom of the water washing tower (4), the liquid outlet at the bottom of the azeotropic tower (5) is connected to the liquid inlet in the middle of the methanol-water separation tower (6) via the fifth compressor (24), the air outlet at the top of the methanol-water separation tower (6) is connected to the air inlet in the middle of the thermal regeneration tower (3),The liquid outlet at the bottom of the methanol-water separation tower (6) is connected to the seventh heat exchanger (23); The pre-wash tower (1) comprises a transmission device (101), a rotating shaft (115) and a pre-wash shell (108); the transmission device (101) is connected to one end of the rotating shaft (115); the other end of the rotating shaft (115) is connected to a rotor (104); the rotor (104) is arranged in the middle and lower part of the inner cavity of the pre-wash shell (108); the middle of the top of the pre-wash shell (108) is connected to a gas outlet (107); the bottom of the pre-wash shell (108) is connected to a liquid phase outlet (102); the bottom of one side of the pre-wash shell (108) is connected to a gas phase inlet (103); the middle and upper part of the other side of the pre-wash shell (108) is connected to a liquid phase inlet (109); the liquid phase inlet (109) is connected to the liquid phase outlet (102); An L-shaped liquid pipeline is provided, wherein the vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor (104), and a plurality of liquid phase nozzles (111) are installed on the vertical pipe of the L-shaped liquid pipeline. A demister (106) is provided at the top of the inner cavity of the pre-wash shell (108), and a partition plate (105) is installed between the bottom of the demister (106) and the top of the rotor (104). The middle of the top of the rotor (104) and the partition plate (105) are sealed by a first sealing gasket (110), and the two sides of the middle of the bottom of the rotor (104) and the rotating shaft (115) are sealed by a second sealing gasket (112) and a third sealing gasket (113) respectively. The inside of the rotor (104) is filled with a packing layer (114); The four-phase separator (2) comprises a separation shell (218), wherein the inner cavity of the separation shell (218) is divided from left to right into an inlet section (I), a sedimentation separation section (II) and a collection section (III); The inlet section (I) is provided with a gas-liquid separator (206), a baffle (207) and a calming plate (208); the feed port (201) is provided outside the separation shell (218) and is connected to the top of the separation shell (218); the gas-liquid separator (206) is installed below the feed port (201); the bottom end of the calming plate (208) is connected to the bottom of the separation shell (218); the top end of the baffle (207) is connected to the top of the separation shell (218) and is located between the gas-liquid separator (206) and the calming plate (208); the sedimentation separation section (II) is provided with a coalescer (209); the collection section (III) is provided with a heavy phase fluid overflow weir (217), a heavy phase A fluid collecting tank (219), a light phase fluid collecting tank (220) and an intermediate phase fluid overflow weir (216); a heavy phase fluid overflow weir (217) is arranged on one side of the coalescer (209) and connected to the bottom of the separation shell (218); a top of the heavy phase fluid collecting tank (219) is connected to the bottom of the separation shell (218) and is located between the coalescer (209) and the heavy phase fluid overflow weir (217); a first liquid level gauge (213) is respectively installed on the top and bottom of the side wall of the heavy phase fluid collecting tank (219); a heavy phase fluid outlet (203) is connected to the bottom of the heavy phase fluid collecting tank (219); and a separation shell (218) above the heavy phase fluid collecting tank (219) is provided. 8) A second liquid level meter (212) is installed at the top and bottom, respectively; the light phase fluid collection tank (220) is arranged on one side of the heavy phase fluid overflow weir (217); the front wall of the light phase fluid collection tank (220) is the light phase fluid overflow weir (214); the height of the light phase fluid overflow weir (214) is lower than the height of the rear wall (215) of the light phase fluid collection tank (220); a third liquid level meter (210) is installed at the top and bottom of the light phase fluid collection tank (220); the bottom of the light phase fluid collection tank (220) is connected to a light phase fluid outlet (204); the light phase fluid outlet (204) is located outside the separation shell (218); the light phase fluid collection tank (220) is provided with a light phase fluid outlet (204); the light phase fluid outlet (204) is located outside the separation shell (218); A demister (222) is arranged above the separation shell (20), a gas phase outlet (202) is arranged outside the separation shell (218) and is connected to the demister (222), an intermediate phase fluid overflow weir (216) is arranged on one side of the light phase fluid collection tank (220) and is connected to the bottom of the separation shell (218), the intermediate phase fluid overflow weir (216) and the space at the tail of the separation shell (218) form an intermediate phase fluid collection tank (221), a fourth liquid level gauge (211) is respectively arranged at the top and bottom of one side of the intermediate phase fluid overflow weir (216), and the bottom of the separation shell (218) on one side of the intermediate phase fluid overflow weir (216) is connected to the intermediate phase fluid outlet (205).

2. The coke oven gas purification system according to claim 1, characterized in that: The length ratio of the inlet section (I), the sedimentation separation section (II) and the collection section (III) is 1:3.2-4.2:

2.

3. The coke oven gas purification system according to claim 2, characterized in that: The top of the calming plate (208) is at the same level as the second liquid level gauge (212) located at the top of the separation shell (218); the bottom of the baffle (207) is 400-500 mm higher than the top of the calming plate (208), and the bottom of the baffle (207) is not less than 200 mm lower than the bottom of the gas-liquid separator (206); the height of the coalescer (209) is the same as the height of the light phase fluid overflow weir (214), and the heavy phase fluid overflow weir (215) is the same as the light phase fluid overflow weir (216). The height of the flow weir (217) is 200-500 mm higher than the bottom of the light phase fluid collecting tank (220), the height of the light phase fluid overflow weir (214) is 1 / 2-3 / 4 of the diameter of the four-phase separator, the height of the rear wall (215) of the light phase fluid collecting tank (220) is 200 mm higher than the bottom of the demister (222), and the height of the intermediate phase fluid overflow weir (216) is 20-100 mm lower than the height of the light phase fluid overflow weir (214).

4. A method for purifying coke oven gas, the method adopting the coke oven gas purification system according to any one of claims 1 to 3, characterized in that: The steps include: S1, the coke oven gas after benzene washing is heat exchanged with the coke oven gas after deep purification in the desulfurization tower (8) to a temperature of 20-25°C, the coke oven gas after heat exchange is sent from the lower part of the pre-washing tower (1) to the pre-washing tower (1), and at the same time, the gas washing agent from the bottom of the desulfurization tower (8) is pressurized and sent from the upper part of the pre-washing tower (1) to the pre-washing tower (1); wherein the pre-washing tower (1) is a super gravity rotating device; S2, the coke oven gas after heat exchange is contacted with the gas scrubber in a countercurrent or crosscurrent manner in a pre-scrubbing tower (1) for pre-treatment, and the pre-treated gas scrubber is collected on the inner wall of the pre-scrubbing tower (1) under the action of super gravity of the pre-scrubbing tower (1) and then discharged to a four-phase separator (2); S3, the pre-treated coke oven gas is pressurized to 0.3-1.0 MPa and then subjected to primary cooling with the coke oven gas deeply purified in the desulfurization tower (8), and then subjected to deep cooling to -22~-28°C before entering the desulfurization tower (8), where the impurities in the coke oven gas are removed in two stages in the desulfurization tower (8) to obtain deeply purified coke oven gas, and after the deeply purified coke oven gas is reheated, 42-50% of the deeply purified coke oven gas is depressurized to 8-10 kPa and used as return gas for coke oven heating, and the rest is used for the production of chemicals; S4, the sulfur-containing methanol rich liquid obtained by desulfurization at the bottom of the desulfurization tower (8) is reheated to 25-35°C and then enters the methanol-rich flash tank (7) for reduced pressure flash evaporation. The flash pressure is 2-8 bar. The flashed gas is discharged from the system as desulfurization waste gas after methanol is recovered by the water scrubber (4). The flashed rich liquid at the bottom of the methanol-rich flash tank (7) is reheated to 80-100°C and then enters the thermal regeneration tower (3) for regeneration. The regenerated lean methanol is pressurized and cooled to -20--40°C and then sent to the upper part of the desulfurization tower (8) as an absorbent. The sulfur-containing gas obtained at the top of the thermal regeneration tower (3) is cooled and the entrained methanol is recovered and then sent to the water scrubber (4) for washing. The coke oven gas washed by the water scrubber (4) is discharged from the system as desulfurization waste gas. S5, the gas scrubber pretreated by the pre-scrubber (1) is mixed with the methanol-containing solution discharged from the bottom of the water scrubber (4), and the mixed mixture is sent to the four-phase separator (2) for gas-liquid separation. The dissolved gas separated by the four-phase separator (2) is discharged to the azeotropic tower (5) for washing. The tar dust separated by the four-phase separator (2) is discharged from the heavy phase fluid outlet (203) of the four-phase separator (2), and the naphtha separated by the four-phase separator (2) is discharged from the light phase fluid outlet (204) of the four-phase separator (2). The intermediate phase separated by the four-phase separator (2) is used as a gas scrubber and is heat-exchanged to 80-100° C. with the wastewater discharged from the methanol-water separation tower (6) and then pressurized and sent to the azeotropic tower (5) to recover the scrubber; S6, the non-condensable gas at the top of the azeotropic tower (5) is washed with water in the water washing tower (4) to recover methanol and then discharged from the system as desulfurization waste gas. The methanol / water mixture at the bottom of the azeotropic tower (5) is pressurized and sent to the methanol-water separation tower (6) for distillation and purification. The methanol vapor at the top of the methanol-water separation tower (6) is returned to the middle of the thermal regeneration tower (3). The waste water at the bottom of the methanol-water separation tower (6) is cooled and sent out of the system.

5. The method for purifying coke oven gas according to claim 4, characterized in that: The operating conditions of the pre-wash tower (1) are: operating temperature 15-20°C, operating pressure 3-6 kPa, filler specific surface area 500-4000 m2 / m3, filler rotation frequency 30-60 Hz, and gas-liquid ratio 1000-6000.

6. The method for purifying coke oven gas according to claim 4, characterized in that: The coal gas scrubber at least includes methanol and crude benzene.

7. The method for purifying coke oven gas according to claim 4, characterized in that: After the desulfurization tower (8) removes impurities from the coke oven gas in two stages, the sulfur content in the coke oven gas after deep purification is ≤0.1ppm, the carbon dioxide content is ≤2.5%, and there is no tar dust, naphthalene and ammonia.

8. The method for purifying coke oven gas according to claim 4, characterized in that: The amount of gas scrubber in the pre-wash tower (1) is 0.20-0.32 kg / m3 coke oven gas; the amount of lean methanol in the desulfurization tower (8) is 1.30-1.50 kg / m3 coke oven gas; the NH3 content in the recycled lean methanol is less than 20×10-6 ppm, and the pH value is 8-10.

Images