WO2022166159A1 - Deep purification system and method for coke oven gas - Google Patents

Abstract

The present invention belongs to the field of coke oven gas purification and provides a deep purification system and method for coke oven gas. By providing a pre-washing tower as a super-gravity rotating device, debenzolized coke oven gas can be subjected to preliminary impurity removal in the pre-washing tower by means of a super-gravity rotating technology, so that dust, benzene, tar, naphthalene, ammonia, sulfur and other harmful substances in the debenzolized coke oven gas are removed deeply, the problem that excessive sulfur and ammonia in the coke oven gas may affect stable operation of a system is solved, and the problem that the tar and naphthalene in the coke oven gas may cause blockage in a compression system is also solved. By means of devices such as a desulfurization tower, a heat regeneration tower, a washing tower, an azeotropic tower, a methanol-water separation tower, a methanol-rich flash tank, and a four-phase separator, a system for further removing complex impurities from coke oven gas by means of a low-temperature methanol washing technology is provided, so that an air purification index is ensured, and the problem that coking desulfurization waste liquid cannot be radically treated can be solved by means of a methanol regeneration cycle.

Description

System and method for deep purification of coke oven gas technical field

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

Background technique

Coke oven gas is an important by-product obtained in the coking process. In recent years, the research on the composition of coke oven gas has been quite mature. Coke oven gas belongs to natural gas with medium calorific value, with hydrogen content of 50% to 60% and methane of 22% to 24%, which contains huge utilization value. When producing coke, a large amount of coke oven gas will be produced. If 430 cubic meters of coke oven gas is produced by producing 1 ton of coke, the amount of coke oven gas generated in my country is basically maintained at 180 billion cubic meters throughout the year, of which about 45-50% The coke oven gas is returned to the coke oven, and the remaining coke oven gas is equivalent to more than twice the designed annual gas transmission volume of the national "West-East Gas Pipeline". Therefore, how to recycle coke oven gas is of great significance to realize the recycling of resources and the sustainable development of economy. Before the comprehensive utilization of coke oven gas, the purification of coke oven gas has become the top priority. Before the comprehensive utilization of coke oven gas, the purification of coke oven gas has become the top priority, and the core problem in the purification of coke oven gas is desulfurization.

At present, the commonly used desulfurization methods for coke oven gas are dry desulfurization and wet desulfurization. Dry desulfurization mainly uses the desulfurization catalyst synthesized by ferric hydroxide and other preparations to remove H ₂ S in the gas, and the regenerated desulfurizer can be reused. Dry desulfurization is mainly used in coke oven gas desulfurization with small gas volume or secondary desulfurization with high desulfurization accuracy. Wet desulfurization process is to use liquid desulfurizer to remove H ₂ S and HCN in coke oven gas. Currently commonly used wet desulfurization methods include improved ADA method, naphthoquinone method, glue method, FRC method, TH method, HPF method, PDS method. method, OPT method, complex iron method, ammonia water catalysis method. Large-scale coking enterprises usually use wet desulfurization. In the wet desulfurization process, in order to avoid the accumulation of side reaction salts in the desulfurization waste liquid, a small amount of waste liquid will be discharged. The previous measure is to send the discharged desulfurization waste liquid to the coal blending system, but this method will cause environmental problems and pollute the environment.

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 treatment method for desulfurization waste liquid has not been established in China. In summary, coke oven gas desulfurization is faced with the high investment and cost of dry desulfurization, which cannot meet the requirements of large-scale coke oven gas, and the traditional wet desulfurization has the problem that waste liquid cannot be treated. In addition, in the current deep purification process of coke oven gas, the accuracy of desulfurization and naphthalene removal is insufficient, and the safe-stable-normal-full-optimal operation of the subsequent devices cannot be guaranteed. It is mainly manifested in the following three aspects: (1) The coke oven gas after deep purification contains sulfur and ammonia exceeding the standard, which affects the normal operation of subsequent purification and synthesis.

Generally, when coke oven gas is only used as fuel gas, H ₂ S is required to be less than 500mg/Nm ³ and ammonia content is less than 100mg/Nm ³ , but in actual operation, acid gas and ammonia may exceed the standard, which will affect 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 for use, and the change in the use of coke oven gas has resulted in the design index of the original coke oven gas deep purification far from meeting the requirements of the current use index.

(2) The deeply purified coke oven gas contains tar and naphthalene, which seriously affects the normal operation of the compressor. The main reason is that the coke oven gas entrains tar and high naphthalene content, and the temperature rises during compression. The compressor is blocked by naphthalene, which makes the compressor unable to operate normally and is forced to stop maintenance. Sometimes it is necessary to stop for repair after only 1-2 days of operation, which makes the production very passive.

(3) The desulfurization agent for fine desulfurization is invalid in advance due to abnormal rough desulfurization, which affects the production operation, mainly due to the penetration of sulfur.

technical problem

In order to solve the technical problems that the current coke oven gas in the deep purification process will affect the stable operation of the rear system, cause compressor blockage, and cause premature failure of the desulfurizing agent for fine desulfurization and increase operating costs, the present invention provides a coke oven gas. The deep purification system and method.

technical solutions

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is: a deep purification system for coke oven gas, which comprises a prewash tower, a desulfurization tower, a thermal regeneration tower, a water washing tower, an azeotrope tower, a methanol water separation tower, a Methanol flash tank and four-phase separator, 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 passes through the first heat exchange The separator is connected to the gas phase inlet at the bottom of the prewash tower, the liquid phase outlet at the bottom of the prewash tower is connected to the feed port of the four-phase separator, and the gas outlet of the prewash tower passes through the first compressor, the second heat exchanger and the third The heat exchanger is connected with the air inlet at the lower part of the desulfurization tower, the air outlet at the top of the desulfurization tower is connected with the second heat exchanger, and the liquid outlet at the bottom of the desulfurization tower is connected with the liquid phase inlet at the upper part of the prewash tower through the second compressor, The liquid outlet in the middle and lower part of the desulfurization tower is connected with the liquid inlet of the methanol-rich flash tank through the fourth heat exchanger, and the gas outlet at the top of the methanol-rich flash tank is connected with the air inlet in the middle and upper part of the water washing tower. The gas outlet is connected with the desulfurization waste gas pipeline, the liquid outlet at the bottom of the methanol-rich flash tank is connected with the liquid inlet in the middle and upper part of the thermal regeneration tower through the fifth heat exchanger, and the liquid outlet at the bottom of the thermal regeneration tower passes through the third compressor and The fifth heat exchanger is connected with the liquid inlet at the upper part of the desulfurization tower, the air outlet at the top of the thermal regeneration tower is connected with the air inlet at the lower part of the water washing tower through the sixth heat exchanger, and the sixth heat exchanger is connected with the inlet of the condensate storage tank. The liquid outlet, the liquid outlet of the condensate storage tank is connected with the liquid inlet of the upper part of the thermal regeneration tower, the gas outlet at the top of the water washing tower is connected with the desulfurization waste gas pipeline, and the liquid outlet at the bottom of the water washing tower is connected with the feed inlet of the four-phase separator Connection, the gas phase outlet of the four-phase separator is connected to the air inlet in the middle of the azeotrope column, the heavy phase fluid outlet of the four-phase separator is connected to the heavy oil pipeline, the light phase fluid outlet of the four-phase separator is connected to the light oil pipeline, and the four-phase fluid outlet is connected to the light oil pipeline. The intermediate phase fluid outlet of the separator is connected with the liquid inlet in the middle of the azeotrope column through the fourth compressor and the seventh heat exchanger, the air outlet at the top of the azeotrope column is connected with the air inlet at the lower part of the washing tower, and the air outlet at the bottom of the azeotrope column is connected with the inlet. The liquid outlet is connected with the liquid inlet in the middle of the methanol-water separation tower through the fifth compressor, the air outlet at the top of the methanol-water separation tower is connected with the air inlet in the middle of the thermal regeneration tower, and the liquid outlet at the bottom of the methanol-water separation tower is connected with the first. Seven heat exchanger connections.

Optionally, the pre-wash tower includes a transmission device, a rotating shaft and a pre-wash shell, the transmission device is connected with one end of the rotating shaft, and the other end of the rotating shaft is connected with a rotor, the rotor is arranged in the middle and lower part of the inner cavity of the pre-wash shell, and the pre-wash shell is installed. A gas outlet is connected to the middle of the top of the pre-washing shell, a liquid-phase outlet is connected to the bottom of the pre-washing shell, a gas-phase inlet is connected to the bottom of one side of the pre-washing shell, and a liquid-phase inlet is connected to the upper part of the other side of the pre-washing shell. The phase inlet is connected with an L-shaped liquid pipeline. The vertical tube of the L-shaped liquid pipeline extends to the middle of the rotor. Several liquid phase nozzles are installed on the vertical tube of the L-shaped liquid pipeline. 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 gasket, and the two sides of the middle of the bottom of the rotor and the rotating shaft are respectively separated by a second gasket and a first gasket. Three gaskets are sealed, and the rotor is filled with a packing layer inside.

Optionally, the four-phase separator includes 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; the inlet section I is provided with a gas-liquid separator, The baffle plate and the sedation plate, the feed port is set outside the separation shell and connected to the top of the separation shell, the gas-liquid separator is installed under the feed port, the bottom end of the sedation plate is connected with the bottom of the separation shell, and the top of the baffle plate is connected to the separation shell. The top of the shell is connected and located between the gas-liquid separator and the sedation plate; the settling and 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 collection tank, a light-phase fluid The fluid collection tank and the intermediate phase fluid overflow weir, the heavy phase fluid overflow weir is arranged on one side of the coalescer and connected with the bottom of the separation shell, the top of the heavy phase fluid collection tank is connected with the bottom of the separation shell and is located between the coalescer and the separation shell. Between the heavy-phase fluid overflow weirs, a first liquid level gauge is installed on the top and bottom of the sidewall of the heavy-phase fluid collection tank. The bottom of the heavy-phase fluid collection tank is connected with a heavy-phase fluid outlet. A second liquid level gauge is installed on the top and bottom of the separation shell. The light-phase fluid collection tank is arranged on one side of the heavy-phase fluid overflow weir. The front wall of the light-phase fluid collection tank is the light-phase fluid overflow weir. The height of the fluid overflow weir is lower than the height of the back wall of the light-phase fluid collection tank. The top and bottom of the light-phase fluid collection tank are each provided with a third level gauge, and the light-phase fluid collection tank is connected to the bottom of the light-phase fluid collection tank. The outlet, the light phase fluid outlet is located outside the separation shell, a mist eliminator is arranged above the light phase fluid collection tank, the gas phase outlet is arranged outside the separation shell and connected to the mist eliminator, and the intermediate phase fluid overflow weir is arranged in the light phase fluid. One side of the collection tank is 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 collection tank, and the top and bottom of one side of the intermediate phase fluid overflow weir are each provided with a fourth Liquid level gauge, the bottom of the separation shell on one side of the overflow weir of the intermediate phase fluid is connected with an outlet of the intermediate phase fluid.

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.

Optionally, the top end of the sedation plate is at the same level as the second liquid level gauge at the top of the separation shell; the bottom end of the baffle is 400-500mm higher than the top of the sedation plate, and the bottom end of the baffle is lower than the gas-liquid separator The bottom end is not less than 200mm, 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 end of the light-phase fluid collection tank, and the light-phase fluid The height of the overflow weir is 1/2-3/4 of the diameter of the four-phase separator, the height of the back wall of the light-phase fluid collection tank is 200mm higher than the bottom end of the demister, and the height of the overflow weir of the intermediate-phase fluid is higher than that of the light-phase fluid overflow. The height of the weir is 20-100mm lower.

A deep purification method for coke oven gas, the deep purification method adopts the above deep purification system for coke oven gas, which comprises the following steps: S1, coke oven gas after eluting benzene and coke oven gas after deep purification by desulfurization tower When the heat is exchanged to 20-25℃, the coke oven gas after heat exchange is sent to the pre-wash tower from the lower part of the pre-wash tower, and the gas detergent from the bottom of the desulfurization tower is pressurized and sent to the pre-wash tower from the upper part of the pre-wash tower ; Among them, the pre-washing tower is a supergravity rotating device; S2, the coke oven gas after heat exchange and the gas detergent are in countercurrent or cross-current contact in the pre-washing tower for pretreatment, and the pre-treated gas detergent is in the pre-washing tower. Under the action of supergravity, the coke oven gas is collected in the inner wall of the pre-washing tower and discharged to the four-phase separator; 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 after deep purification in the desulfurization tower After deep cooling to -22 ~ -28 ℃, it enters the desulfurization tower, and the impurities in the coke oven gas are removed through two stages in the desulfurization tower, and the deeply purified coke oven gas is obtained. After heating, 42-50% of the deeply purified coke oven gas is depressurized to 8-10kPa and used for coke oven heating as return gas, and the rest is used for chemical production; S4, sulfur-containing methanol obtained from desulfurization in the lower part of the desulfurization tower The rich liquid is reheated to 25~35℃ and then enters the methanol-rich flash tank for decompression flash evaporation. The flash pressure is 2-8 bar. The flashed gas is recovered by the washing tower and then discharged as desulfurization waste gas. The flash rich liquid at the bottom of the 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 to -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 washing tower for washing, and the coke oven gas after washing by the water washing tower is discharged into the system as desulfurization waste gas; S5, the pre-washing tower pretreated gas detergent It is mixed with the methanol-containing solution discharged from the bottom of the water washing tower, and the mixed mixture is sent to the four-phase separator for gas-liquid separation. The dissolved gas separated by the four-phase separator is discharged to the azeotropic tower for washing, and the four-phase separator is separated out The tar dust is discharged from the heavy-phase fluid outlet of the four-phase separator, the naphtha separated by the four-phase separator is discharged from the light-phase fluid outlet of the four-phase separator, and the middle phase separated by the four-phase separator is used as a gas detergent. The waste water discharged from the methanol water separation tower is heated to 80-100 °C and then sent to the azeotrope tower to recover the detergent by pressure; S6, the non-condensable gas at the top of the azeotrope tower is washed by the water washing tower to recover methanol and used as desulfurization waste gas The methanol/water mixture at the bottom of the azeotrope column is pressurized and sent to the methanol-water separation column for rectification and purification, the methanol vapor at the top of the methanol-water separation column is returned to the middle of the thermal regeneration tower, and the methanol-water separation column at the bottom of the methanol-water separation column is discharged from the system. The wastewater is cooled and sent out of the system.

Optionally, the operating conditions of the prewash tower are: operating temperature 15-20°C, operating pressure 3-6 kPa, packing specific surface area 500-4000 m ² /m ³ , packing rotation frequency 30-60 Hz, gas-liquid ratio 1000 ~6000.

Optionally, the gas scrubber includes at least methanol and crude benzene.

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 less than or equal to 0.1 ppm, the carbon dioxide content is less than or equal to 2.5%, and there is no tar dust, naphthalene and ammonia.

Optionally, the consumption of the gas detergent in the prewash tower is 0.20-0.32kg/m ³ coke oven gas; the consumption of lean methanol in the desulfurization tower is 1.30-1.50kg/m ³ coke oven gas; The content of NH ₃ in methanol is less than 20×10 ^{- 6} ppm, and the pH value is 8-10.

beneficial effect

The beneficial effects of the invention are as follows: by setting the pre-washing tower and setting the pre-washing tower as a super-gravity rotating device, the coke oven gas after debenzene removal can be preliminarily removed by the super-gravity rotating technology in the pre-washing tower, Through the pretreatment of the pre-washing tower, harmful substances such as dust, benzene, tar, naphthalene, ammonia and sulfur in the coke oven gas after removing benzene can be deeply removed, which solves the problem that the excessive sulfur and ammonia in the coke oven gas will affect the The problem of the stable operation of the system 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 blockage of the compression system, and avoids the blockage abnormality that may be caused in the subsequent section. Further, by setting equipment such as desulfurization tower, thermal regeneration tower, water washing tower, azeotrope tower, methanol water separation tower, methanol-rich flash tank and four-phase separator, a low-temperature methanol washing technology is provided to further remove The system of impurities with complex components in coke oven gas can not only ensure the purification gas index, but also solve the problem that the coking desulfurization waste liquid cannot be treated radically through methanol regeneration and recycling, and also solve the desulfurization agent that can cause fine desulfurization due to abnormal rough desulfurization The problem of increasing operating costs due to early failure.

Through the system and method provided by the embodiments of the present invention, the requirements of pressurized transportation of coke oven gas and subsequent deep purification are met, and the purpose of purification of the production chemical synthesis system is achieved. The invention has the advantages of low investment, small equipment volume and floor space, high removal efficiency of impurities such as tar dust and naphthalene in coke oven gas, low energy consumption and high washing efficiency. In addition, the deep-purified coke oven gas does not need to be desulfurized after being returned to the coke oven, and no intractable desulfurization waste liquid is generated, so that the fine desulfurization catalysis and service life of the subsequent production of chemical products can be extended by at least one year.

Description of drawings

FIG. 1 is a schematic diagram of the system composition of the present invention.

Fig. 2 is the structural representation of the prewash tower in Fig. 1.

FIG. 3 is a schematic structural diagram of the four-phase separator in FIG. 1 .

Embodiments of the present invention

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

As shown in FIG. 1 , an embodiment of the present invention provides a deep purification system for coke oven gas, which includes a prewash tower 1, a desulfurization tower 8, a thermal regeneration tower 3, a water wash tower 4, an azeotrope tower 5, and a methanol-water separation tower. Tower 6, methanol-rich flash tank 7 and four-phase separator 2, the prewash 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 with the gas phase inlet 103 at the bottom of the prewash tower 1 through the first heat exchanger 9, the liquid phase outlet 102 at the bottom of the prewash tower 1 is connected with the feed port 201 of the four-phase separator 2, and the The gas outlet 107 is connected to the air inlet at the lower part of the desulfurization tower 8 through the first compressor 10, the second heat exchanger 11 and the third heat exchanger 12, and 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 prewash tower 1 through the second compressor 14, and the liquid outlet at the middle and lower part of the desulfurization tower 8 is connected to the methanol-rich flash tank 7 through the fourth heat exchanger 13. The liquid inlet is connected, the air outlet at the top of the methanol-rich flash tank 7 is connected with the air inlet in the upper part of the water washing tower 4, the air outlet at the top of the water washing tower 4 is connected with the desulfurization waste gas pipeline, and the outlet at the bottom of the methanol-rich flash tank 7 is connected. The liquid port is connected to the liquid inlet in the upper part of the heat regeneration tower 3 through the fifth heat exchanger 15, and the liquid outlet at the bottom of the heat regeneration tower 3 is connected to the upper part of the desulfurization tower 8 through the third compressor 16 and the fifth heat exchanger 15. The liquid inlet is connected, and the air outlet at the top of the thermal regeneration tower 3 is connected with the air inlet at the bottom of the water washing tower 4 through the sixth heat exchanger 17, and the sixth heat exchanger 17 is connected to the liquid inlet of the condensate storage tank 22. The liquid outlet of the storage tank 22 is connected to the liquid inlet of the upper part of the thermal regeneration tower 3, the gas outlet of the top of the water washing tower 4 is connected to the desulfurization waste gas pipeline, and the liquid outlet of the bottom of the water washing tower 4 is connected to the feed port of the four-phase separator 2. 201 is connected, the gas phase outlet 202 of the four-phase separator 2 is connected with the air inlet in the middle of the azeotrope column 5, the heavy-phase fluid outlet 203 of the four-phase separator 2 is connected with the heavy oil pipeline, and the light-phase fluid outlet 204 of the four-phase separator 2 is connected Connected with 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 azeotrope column 5 through the fourth compressor 18 and the seventh heat exchanger 23, and the air outlet at the top of the azeotrope column 5 is connected to the liquid inlet. The air inlet at the bottom of the washing tower 4 is connected, the liquid outlet at the bottom of the azeotrope tower 5 is connected with the liquid inlet in the middle of the methanol water separation tower 6 through the fifth compressor 24, and the air outlet at the top of the methanol water separation tower 6 is connected with the thermal regeneration. The air inlet in the middle of the tower 3 is connected, and the liquid outlet at the bottom of the methanol-water separation tower 6 is connected with the seventh heat exchanger 23 .

The system of the invention is applied to the coke oven gas after initial cooling, electric tar trapping, precooling, desulfurization, intermediate cooling, ammonia removal, final cooling and eluting of benzene, and is used to remove dust, benzene and tar contained in the coke oven gas. , naphthalene, ammonia and various forms of sulfur and other impurities, to meet the needs of coke oven gas pressurized transportation and subsequent deep purification to meet the purification needs of the production chemical synthesis system.

Optionally, as shown in FIG. 2 , the pre-wash tower 1 includes a transmission device 101 , a rotating shaft 115 and a pre-wash housing 108 , the transmission device 101 is connected to one end of the rotating shaft 115 , and the other end of the rotating shaft 115 is connected to the rotor 104 , and the rotor 104 The gas outlet 107 is connected to the middle of the top of the pre-wash housing 108 , the liquid phase outlet 102 is connected to the bottom of the pre-wash housing 108 , and the bottom of one side of the pre-wash housing 108 A gas phase inlet 103 is connected, a liquid phase inlet 109 is connected to the upper part of the other side of the pre-washing shell 108, and an L-shaped liquid pipeline is connected to the liquid phase inlet 109. The vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor 104, and the L Several liquid phase nozzles 111 are installed on the vertical pipe of the shaped liquid pipeline, a demister 106 is installed on the top of the inner cavity of the pre-washing 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 the first gasket 110 , the middle of the bottom of the rotor 104 and the shaft 115 are sealed by the second gasket 112 and the third gasket 113 respectively, and the interior of the rotor 104 is filled with There is a filler layer 114 .

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

Optionally, as shown in FIG. 3, 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 The inlet section I is provided with a gas-liquid separator 206, a baffle 207 and a sedative plate 208. The feed port 201 is set outside the separation shell 218 and is connected to the top of the separation shell 218. The gas-liquid separator 206 is installed in the feed port 201 Next, the bottom end of the sedation plate 208 is connected to the bottom of the separation shell 218, and the top of the baffle plate 207 is connected to the top of the separation shell 218 and is located between the gas-liquid separator 206 and the sedation plate 208; The collection section III is provided with a heavy-phase fluid overflow weir 217, a heavy-phase fluid collection tank 219, a light-phase fluid collection tank 220, and an intermediate-phase fluid overflow weir 216, and the heavy-phase fluid overflow weir 217 is set at the One side of the coalescer 209 is connected to the bottom of the separation shell 218, the top of the heavy-phase fluid collection 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, and the heavy-phase fluid collection tank A first liquid level gauge 213 is installed on the top and bottom of the side wall of 219, a heavy-phase fluid outlet 203 is connected to the bottom of the heavy-phase fluid collection tank 219, and the separation shell 218 above the heavy-phase fluid collection tank 219 is installed at the top and the bottom. There is a second liquid level gauge 212, the light-phase fluid collection tank 220 is arranged on the side of the heavy-phase fluid overflow weir 217, and the front wall of the light-phase fluid collection tank 220 is the light-phase fluid overflow weir 214, and the light-phase fluid overflows The height of the weir 214 is lower than the height of the rear wall 215 of the light-phase fluid collection tank 220. The top and bottom of the light-phase fluid collection tank 220 are respectively provided with a third liquid level gauge 210, and the bottom of the light-phase fluid collection tank 220 is connected with a third liquid level gauge 210. The light phase fluid outlet 204, the light phase fluid outlet 204 is located outside the separation shell 218, a mist eliminator 222 is arranged above the light phase fluid collection tank 220, and the gas phase outlet 202 is arranged outside the separation shell 218 and is connected with the mist eliminator 222, The 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 rear of the separation shell 218 form an intermediate phase fluid collection tank 221. The top and bottom of the phase fluid overflow weir 216 are respectively provided with a fourth liquid level gauge 211 , and the intermediate phase fluid outlet 205 is connected to the bottom of the separation shell 218 on the intermediate phase fluid overflow weir 216 side.

Among them, the gas-liquid separator 206 and the sedation plate 208 are the conventional components of the inlet section I, wherein the main function of the gas-liquid separator 206 is to realize the gas-liquid pre-separation. The uniform initial distribution or redistribution at the top of the packing or at a certain height is used to improve the effective surface of mass transfer and heat transfer, improve the interphase contact, and thus improve the separation efficiency of the tower. The main function of the sedation plate 208 is to slow down the two-phase fluctuation in the liquid phase area of the inlet section I, and also have the function of liquid-liquid-liquid pre-separation, but mainly to suppress the fluctuation 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 fluctuation of the liquid phase region of the settling separation section II.

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.

Optionally, the top end of the sedation plate 208 is at the same level as the second liquid level gauge 212 located at the top of the separation housing 218; It is not less than 200mm below the bottom end of the gas-liquid separator 206 .

Optionally, the height of the coalescer 209 is the same as the height (H1) of the light-phase fluid overflow weir 214, and the height of the heavy-phase fluid overflow weir 217 is higher than the bottom end 200- of the light-phase fluid collection tank 220. 500mm, 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 collection tank 220 is 200mm higher than the bottom end of the mist eliminator 222, and the middle The height (H3) of the phase fluid overflow weir 216 is 20-100 mm lower than the height of the light phase fluid overflow weir 214.

Three overflow weir plates, heavy phase fluid collection tank 219 and light phase fluid collection tank 220 are set in the collection section III, the heavy phase fluid overflow weir 217 , the light phase fluid overflow weir 214 and the intermediate phase fluid overflow weir 216 and the intermediate phase fluid collection tank 221 three liquid phase collection tanks, so the length of the collection section III of the four-phase separator 2 is longer than that of the ordinary separator, but also because of this setting, the liquid-liquid interface during the operation can be better controlled , so as to ensure the stability of the separation process, thereby reducing or avoiding the impact of fluctuations in working conditions on the process of sedimentation and separation section II. The control of the liquid-liquid interface of the four-phase separator 2 in the embodiment of the present invention comes from two aspects: one is that the structure of three overflow weirs and three liquid-phase collecting grooves makes the liquid-liquid interface simultaneously affected by the light phase/intermediate The control of the hydrostatic pressure of the phase and the heavy phase is relatively stable; the second is that the light-phase fluid collection tank 220 and the intermediate-phase fluid collection tank 221 provide buffer space for the fluctuation of the upstream and downstream (inlet and outlet) flow during the operation, thereby The influence of working condition fluctuations on the separation process of the settling section is reduced or avoided. By arranging components such as the sedative plate 208 and the coalescer 209, a low lateral flow rate is ensured, so that the fluid in the liquid phase has sufficient residence time to achieve liquid-liquid-liquid sedimentation separation, and at the same time is conducive to the sedimentation or buoyancy of the dispersed phase, and also Reduce the fluctuation of the liquid phase, shorten the separation time, and reduce the size of the equipment.

All the four-phase separators 2 shown in FIG. 3 are used in the present invention, which comprehensively considers the influencing factors of the pressure distribution at the end of the sedimentation separation section II under the actual separation conditions, including: the height of the light-phase fluid overflow weir 214 and the pressure distribution of the three weir plates. It is determined by the height difference, the thickness of the liquid layer at the top of the overflow weir, the flow rate of the liquid layer at the top of the overflow weir and the flow resistance at the bottom of the light phase collection tank 220 .

The embodiment of the present invention also provides a deep purification method for coke oven gas, the deep purification method adopts the above deep purification system for coke oven gas, which includes the following steps: S1, the coke oven gas after eluting benzene is first The heat exchanger 9 and the second heat exchanger 11 exchange heat with the coke oven gas after deep purification in the desulfurization tower 8 to 20-25°C, and the coke oven gas after heat exchange is sent to the prewash tower 1 from the lower part of the prewash tower 1 At the same time, the gas detergent from the bottom of the desulfurization tower 8 is pressurized by the second compressor 14 and sent to the pre-wash tower 1 from the upper part of the pre-wash tower 1; wherein, the pre-wash tower 1 is a supergravity rotating device.

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

S2, the coke oven gas after heat exchange and the gas detergent are contacted in the pre-washing tower 1 in countercurrent or cross-current for pretreatment, and the pre-treated gas detergent is in the pre-washing tower 1 under the action of the supergravity of the pre-washing tower 1. The inner wall is collected and discharged to the four-phase separator 2 .

Since the coke oven gas after eluting benzene includes impurities such as dust, benzene, tar, naphthalene, ammonia, and various forms of sulfur, the embodiment of the present invention first uses the pre-wash tower 1 of the supergravity rotation technology to elute the benzene. The obtained coke oven gas is pretreated to preliminarily remove impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur in the coke oven gas after eluting the benzene.

Specifically, in the pre-wash tower 1, the gas detergent is evenly distributed through the liquid phase nozzles 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 detergent is split into The liquid microelements (liquid film, liquid filaments and droplets) are contacted with the benzene-eluted coke oven gas in countercurrent to remove impurities in the benzene-eluted coke oven gas. Since the prewash tower 1 is a supergravity rotating device, the embodiment of the present invention uses the supergravity rotating technology to remove impurities. The cutting particle size of the supergravity rotating technology reaches the order of magnitude of 10 ^-8 m, and the particle size of the gas detergent after passing through the packing layer 114 almost reaches the molecular level, and then it is aggregated in the supergravity rotating device and extracted together with impurities. In the embodiment of the present invention, the coke oven gas after eluting benzene is pretreated by using the supergravity rotation technology, which can strengthen the washing effect, reduce the particle size of the washing, and at the same time, through the liquid phase spray and the action of supergravity, the droplets are distributed It is more uniform, and the contact surface with impurities in coke oven gas is larger, thereby improving the elution effect of impurities. The supergravity rotating device has the characteristics of good particle trapping effect, small gas phase pressure drop, and the rotating packing is not easy to be blocked, so as to achieve the deep removal of dust, benzene, tar, naphthalene, ammonia and sulfur and other harmful substances in the coke oven gas. , so as to meet the coke oven gas pressurized transportation and subsequent deep purification, and achieve the purpose of purification of the production chemical synthesis system. The coke oven gas after removing impurities is defrostered by the demister 106 to obtain pretreated coke oven gas, and the gas detergent after removing impurities is thrown to the inner wall of the pre-washing shell 108 and flows into the fourth phase through the liquid phase outlet 102. Phase separator 2.

The pretreatment of coke oven gas is tested under different temperatures, pressures and detergents. It is found that naphthalene in coke oven gas is easy to crystallize at <20°C. In order to avoid the blockage of equipment and pipelines caused by naphthalene crystallization at low temperature, in the embodiment of the present invention, a pre-wash tower 1 is newly added, and pre-wash methanol is used to remove naphthalene in the coke oven gas. Since the pre-wash methanol contains crude benzene, both benzene and naphthalene are aromatic compounds. According to the similar compatibility principle, naphthalene is basically dissolved in the gas detergent.

Further, in the embodiment of the present invention, it is determined through experiments that the most suitable temperature for the best pretreated coke oven gas is 20-25° C. The gas cleaning agent at least includes methanol and crude benzene, and the gas cleaning agent can also include desalinated water, ethanol, washing One or a combination of two or more of oil and tar, when the temperature of the gas scrubber is less than 20°C, has a good pretreatment effect. Under these conditions, after pretreatment of benzene-eluted coke oven gas, practice has proved that the collection efficiency of tar dust reaches more than 99%, and the particles of more than 3 μm can be completely removed; the removal rate of naphthalene is more than 80%. ; The removal rate of tar and dust is more than 60%; the removal rate of organic sulfur is more than 85%; the removal rate of ammonia is more than 50%; the removal rate of benzene is more than 50%; The removal rate makes the pretreated coke oven gas meet the requirements of subsequent compression and deep purification.

S3, the pretreated coke oven gas is pressurized to 0.3-1.0 MPa by the first compressor 10, and then subjected to primary cooling in the second heat exchanger 11 with the coke oven gas deeply purified by the desulfurization tower 8, and then passes through the second heat exchanger 11. The third heat exchanger 12 is cryogenically cooled to -22～-28°C and then enters 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 deeply purified coke oven gas. After the furnace gas is reheated by the first heat exchanger 9 and the second heat exchanger 11, 42-50% of the deeply purified coke oven gas is decompressed to 8-10kPa and used as the return gas for coke oven heating, and the rest for the production of chemicals.

S4, the sulfur-containing methanol rich liquid obtained from desulfurization in 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 flashing under reduced pressure, and the flash pressure is 2-8 bar, The flashed gas is discharged from the system as desulfurization waste gas after the methanol is recovered by the water washing tower 4, and 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 thermal regeneration tower 3. Regeneration is carried out, the regenerated lean methanol is pressurized by the third compressor 16, 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, and obtained from the top of the thermal regeneration tower 3. The sulfur-containing gas 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 washing tower 4 for washing, and the coke oven gas washed by the washing tower 4 is discharged into the system as desulfurization waste gas.

The gases flashed from the methanol-rich flash tank 7 are H ₂ , CH ₄ and the like. The sulfur-containing gas obtained from the top of the thermal regeneration tower 3 is a gas with a higher concentration of H ₂ S. The methanol solution absorbing acid gas components is regenerated and recycled by means of vacuum flash evaporation and heating regeneration. When the lean methanol temperature is -20～-40℃, it can not only meet the requirement of desulfurization precision, but also can be cooled by common cooling medium.

S5, the pretreated gas detergent in the pre-wash tower 1 is mixed with the methanol-containing solution discharged from the bottom of the water wash tower 4, and the mixed mixture is sent to the four-phase separator 2 for gas-liquid separation. The dissolved gas is discharged to the azeotrope 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 separated by four phases. The light phase fluid outlet 204 of the device 2 is discharged, and the intermediate phase separated by the four-phase separator 2 is used as a gas detergent. 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 passed through. The fourth compressor 18 is pressurized and sent to the azeotrope column 5 to recover the detergent.

The pre-treated gas detergent in the pre-wash tower 1 contains impurities such as tar, dust, crude benzene, naphthalene, ammonia, and organic sulfur.

S6, the non-condensable gas at the top of the azeotrope tower 5 is washed with water to reclaim the methanol as the desulfurization waste gas discharge system, and the methanol/water mixture at the bottom of the azeotrope tower 5 is sent to methanol water after being pressurized by the fifth compressor 24 The separation tower 6 is rectified and purified, the methanol vapor at the top of the methanol water separation tower 6 is returned 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 sent out to the system.

The methanol in the desulfurization tower 8 absorbs the NH ₃ in the process gas while absorbing the acid gas, which will affect the low temperature methanol washing system (desulfurization tower 8, thermal regeneration tower 3, water washing tower 4, azeotrope tower 5, methanol water Separation tower 6 and methanol-rich flash tank 7) cause a certain impact. The solubility of NH 3 in methanol at low temperature is much higher than that of acid gases such as CO ₂ and H ₂ S in methanol, therefore, it is easy to accumulate in the methanol wash system. Acid gases such as CO ₂ and H ₂ S dissolved in methanol will reduce the pH value of methanol and cause corrosion of the equipment in the low temperature methanol washing system. In order to reduce the corrosion of the equipment, prolong the service life and operation cycle of the equipment, the current low-temperature methanol washing process will allow a certain content of NH ₃ in the system. The solubility of NH 3 in methanol at room temperature is more than 10 times that of H ₂ S. More than 60 times of CO ₂ , the methanol containing NH ₃ finally enters the thermal regeneration tower 3 for regeneration, the NH ₃ dissolved in methanol will be desorbed in the thermal regeneration tower 3, and the acid gas enters the thermal regeneration tower 3. Water cooler, because the water cooler cools the acid gas, the methanol in the acid gas is condensed down. However, the content of NH ₃ in the low-temperature methanol washing system must be strictly controlled. If the content of NH ₃ is low, the corrosion of equipment will be aggravated _; Heat exchanger; when the NH ₃ content is high to a certain extent, it will cause the sulfur content in the process gas to exceed the standard. Therefore, it is necessary to control the NH content in the low _- temperature methanol washing system. Therefore, in the embodiment of the present invention, the ammonia concentration needs to be controlled within a certain range during purification, that is, the lean methanol used in the cycle is maintained (in the desulfurization tower 8, the thermal regeneration tower 3 , the water washing tower 4, the azeotrope tower 5, the methanol water separation tower 6, the methanol-rich flash tank 7 and the four-phase separator 2) The NH ₃ content is less than 20 × ^10-6 ppm ^, and the pH value is 8-10 .

Depending on the concentration of H ₂ S in the coke oven gas, the solubility in methanol is 0.9-6Nm ³ H ₂ S/m ³ at 0.3-1.0MPa, temperature -20～-40℃, CO ₂ is 0.3-1.0MPa, temperature The solubility in methanol at -20～-40°C is 0.8～5Nm ³ CO ₂ /m ³ , and the amount of lean methanol in the desulfurization tower 8 can be determined (that is, the amount of lean methanol entering the desulfurization tower 8, including the amount from the thermal regeneration tower 3 The lean methanol entering at the bottom of the tower and the methanol supplemented by the external cut-off time) are 1.30-1.50kg/m ³ coke oven gas.

Coke oven gas has complex components and many impurities. Its gas components include CO, H ₂ , CO ₂ , CH ₄ , H ₂ S, organic sulfur, C ₂ H ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , HCN, N ₂ , Ar and tar, fatty acid, monophenol, compound phenol, naphtha, anthracene oil, naphthalene oil, fly ash, etc. In these components, except for CO, H ₂ effective components and CH ₄ , N ₂ , Ar and hydrocarbon inert gases, all other components including CO ₂ and sulfide are harmful impurities that need to be removed. The daunting task of purification. With the implementation of policies such as coking enterprises withdrawing from the city and entering the park, upgrading and transformation, large-scale and high-end development have become the development direction of the coking industry, and the requirements for coke oven gas desulfurization have also increased. The use of low-temperature methanol cleaning method can clean Remove various harmful components in coke oven gas, such as CO ₂ , H ₂ S, COS, C ₄ H ₄ S, HCN, NH ₃ , H ₂ O, hydrocarbons above C ₂ (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 the complex sulfur impurities in the coke oven gas can not only ensure the purification gas index, but also solve the problem that the coking desulfurization waste liquid cannot be radically treated through methanol regeneration and recycling.

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

Optionally, the gas scrubber includes at least methanol, washing oil and tar.

Optionally, after the desulfurization tower 8 removes the impurities in the coke oven gas in two stages, the sulfur content in the coke oven gas after deep purification is less than or equal to 0.1 ppm, the carbon dioxide content is less than or equal to 2.5%, and there is no tar dust, naphthalene and ammonia.

Optionally, the amount of the gas detergent in the pre-wash tower 1 (ie the amount of detergent entering the pre-wash tower 1 from the bottom of the desulfurization tower 8 ) is 0.20-32 kg/m ³ coke oven gas.

Further, the general coke oven gas composition is shown in Table 1 below.

.

Since the CO ₂ content in coke oven gas is less than 3%, and the sulfur content in coking coal is 0.7%, the sulfur concentration in large-scale coal gasification gas is 4-8 times higher than that in large-scale coal gasification gas. The hydrogen sulfide concentration tower is used to increase the concentration of acid gas, and the required acid gas concentration can be recovered by the heat regeneration tower 3 and the waste gas is concentrated and processed by the water washing tower 4 to achieve the required acid gas concentration. 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, small footprint and good environmental protection benefits.

It can be understood that the above embodiments are only exemplary embodiments adopted to illustrate the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, without departing from the spirit and essence of the present invention, various modifications and improvements can be made, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (10)

1. A deep purification system for coke oven gas, characterized in that it comprises a prewash tower (1), a desulfurization tower (8), a thermal regeneration tower (3), a water washing tower (4), an azeotrope tower (5), methanol water Separation tower (6), methanol-rich flash tank (7) and four-phase separator (2), the prewash 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 with the gas phase inlet (103) at the bottom of the prewash tower (1) through the first heat exchanger (9), and the liquid phase outlet at the bottom of the prewash tower (1) is connected (102) is connected to the feed port (201) of the four-phase separator (2), and the gas outlet (107) of the prewash tower (1) passes through the first compressor (10), the second heat exchanger (11) and the The third heat exchanger (12) is 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), and the liquid outlet at the bottom of the desulfurization tower (8) The outlet is connected to the liquid phase inlet (109) in the upper part of the prewash tower (1) via the second compressor (14), and the liquid outlet in the middle and lower part of the desulfurization tower (8) is connected to the methanol-rich flasher via the fourth heat exchanger (13). The liquid inlet of the steaming tank (7) is connected, the air outlet at the top of the methanol-rich flash tank (7) is connected with the air inlet in the middle and upper part of the water washing tower (4), and the air outlet at the top of the water washing tower (4) is connected with the desulfurization waste gas pipeline connection, the liquid outlet at the bottom of the methanol-rich flash tank (7) is connected with the liquid inlet in the upper part of the thermal regeneration tower (3) through the fifth heat exchanger (15), and the liquid outlet at the bottom of the thermal regeneration tower (3) The third compressor (16) and the fifth heat exchanger (15) are connected with the liquid inlet at the upper part of the desulfurization tower (8), and the air outlet at the top of the thermal regeneration tower (3) is connected with the sixth heat exchanger (17) through the sixth heat exchanger (17). The air inlet at the lower part of the washing tower (4) is connected, the sixth heat exchanger (17) is connected to the liquid inlet of the condensate storage tank (22), and the liquid outlet of the condensate storage tank (22) is connected to the thermal regeneration tower (3). ) upper liquid inlet is connected, the air outlet at the top of the water washing tower (4) is connected with the desulfurization waste gas pipeline, and the liquid outlet at the bottom of the water washing tower (4) is connected with 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 azeotrope column (5), and 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 (2) is connected to the light oil pipeline, and the intermediate-phase fluid outlet (205) of the four-phase separator (2) is connected to the common via the fourth compressor (18) and the seventh heat exchanger (23). The liquid inlet in the middle of the boiling tower (5) is connected, the air outlet at the top of the azeotrope tower (5) is connected with the air inlet at the bottom of the water washing tower (4), and the liquid outlet at the bottom of the azeotrope tower (5) is compressed by the fifth The machine (24) is connected with the liquid inlet in the middle of the methanol water separation tower (6), the air outlet at the top of the methanol water separation tower (6) is connected with the air inlet in the middle of the thermal regeneration tower (3), and the methanol water separation tower (6) ) at the bottom of the liquid outlet is connected to the seventh heat exchanger (23).
2. The deep purification system for coke oven gas according to claim 1, wherein the prewash tower (1) comprises a transmission device (101), a rotating shaft (115) and a prewash shell (108), and the transmission device (101) 101) is connected with one end of the rotating shaft (115), the other end of the rotating shaft (115) is connected with a rotor (104), the rotor (104) is arranged in the middle and lower part of the inner cavity of the pre-washing shell (108), and the A gas outlet (107) is connected to the middle of the top, a liquid phase outlet (102) is connected to the bottom of the pre-washing shell (108), and a gas-phase inlet (103) is connected to the bottom of one side of the pre-washing shell (108). The upper part of the other side of the body (108) is connected with a liquid phase inlet (109), the liquid phase inlet (109) is connected with an L-shaped liquid pipeline, and the vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor (104), and the L-shaped A number of liquid phase nozzles (111) are installed on the vertical pipe of the liquid pipeline, a demister (106) is provided on the top of the inner cavity of the pre-washing shell (108), and the bottom of the demister (106) is connected to the rotor (104) A partition plate (105) is installed between the tops, the middle of the top of the rotor (104) and the partition plate (105) are sealed by a first gasket (110), and the two sides of the middle of the bottom of the rotor (104) are connected to the shaft (115) A second gasket (112) and a third gasket (113) are used to seal the space between them, respectively, and the interior of the rotor (104) is filled with a packing layer (114).
3. The deep purification system for coke oven gas according to claim 1 or 2, wherein the four-phase separator (2) comprises a separation shell (218), and the inner cavity of the separation shell (218) is from left to right It is divided into inlet section (I), sedimentation separation section (II) and collection section (III);

   The inlet section (I) is provided with a gas-liquid separator (206), a baffle plate (207) and a sedation plate (208), and the feed inlet (201) is provided outside the separation shell (218) and is connected with the separation shell (201). 218) is connected at the top, the gas-liquid separator (206) is installed under the feed port (201), the bottom end of the sedation plate (208) is connected with the bottom of the separation shell (218), and the top of the baffle plate (207) is connected with the separation shell ( 218) The top is connected and located between the gas-liquid separator (206) and the sedation 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), heavy phase fluid collection tank (219), light phase fluid collection tank (220) and intermediate phase fluid overflow weir (216), the heavy phase fluid overflow weir (217) is arranged in the coalescer One side of (209) is connected to the bottom of the separation shell (218), the top of the heavy-phase fluid collection 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 installed on the top and bottom of the side wall of the heavy-phase fluid collection tank (219), and a heavy-phase fluid outlet (203) is connected to the bottom of the heavy-phase fluid collection tank (219). , a second liquid level gauge (212) is installed on the top and bottom of the separation shell (218) above the heavy-phase fluid collection tank (219), respectively, and the light-phase fluid collection tank (220) is arranged at the heavy-phase fluid overflow weir ( 217) side, the front wall of the light-phase fluid collection tank (220) is a light-phase fluid overflow weir (214), and the height of the light-phase fluid overflow weir (214) is lower than the back of the light-phase fluid collection tank (220). The height of the wall (215), a third liquid level gauge (210) is provided at the top and bottom of the light-phase fluid collection tank (220), and a light-phase fluid outlet (204) is connected to the bottom of the light-phase fluid collection tank (220). ), the light-phase fluid outlet (204) is located outside the separation shell (218), a mist eliminator (222) is arranged above the light-phase fluid collection tank (220), and the gas phase outlet (202) is arranged outside the separation shell (218) and connected with the mist eliminator (222), the intermediate phase fluid overflow weir (216) is arranged on one side of the light phase fluid collection tank (220) and connected with the bottom of the separation shell (218), and the intermediate phase fluid overflow weir (216) ) and the space at the end of the separation shell (218) to form an intermediate phase fluid collection tank (221), and a fourth liquid level gauge (211) is provided at the top and bottom of one side of the intermediate phase fluid overflow weir (216). An intermediate phase fluid outlet (205) is connected to the bottom of the separation shell (218) on one side of the phase fluid overflow weir (216).
4. The deep purification system for coke oven gas according to claim 3, wherein 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 .
5. The deep purification system for coke oven gas according to claim 3, characterized in that, the top of the sedation plate (208) and the second liquid level gauge (212) located at the top of the separation shell (218) are at the same level; The bottom end of the baffle plate (207) is 400-500mm higher than the top end of the sedation plate (208), the bottom end of the baffle plate (207) is not less than 200mm lower than the bottom end of the gas-liquid separator (206), and the coalescer (209) The height of the weir is the same as the height of the light-phase fluid overflow weir (214), the height of the heavy-phase fluid overflow weir (217) is 200-500mm higher than the bottom end of the light-phase fluid collection tank (220), and the light-phase fluid overflows The height of the 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 collection tank (220) is 200mm higher than the bottom end of the mist eliminator (222), and the middle-phase fluid The height of the overflow weir (216) is 20-100 mm lower than the height of the light phase fluid overflow weir (214).
6. A deep purification method of coke oven gas, the deep purification method adopts the deep purification system of coke oven gas according to any one of claims 1 to 5, and is characterized in that, comprises the following steps:

   S1, the coke oven gas after eluting benzene and the coke oven gas deeply purified by the desulfurization tower (8) exchange heat to 20-25°C, and the coke oven gas after heat exchange is sent to the prewashing tower from the lower part of the prewashing tower (1). In the tower (1), the gas washing agent from the bottom of the desulfurization tower (8) is pressurized and fed into the prewashing tower (1) from the upper part of the prewashing tower (1); wherein, the prewashing tower (1) is a supergravity rotating device;

   S2, the heat-exchanged coke oven gas and the gas detergent are contacted in the pre-wash tower (1) in counter-current or cross-current for pretreatment, and the pre-treated gas detergent is in the pre-wash tower (1) under the action of hypergravity. The inner wall of the prewash tower (1) is collected and discharged to the four-phase separator (2);

   S3, the pretreated coke oven gas is pressurized to 0.3-1.0 MPa and then subjected to primary cooling with the deeply purified coke oven gas in the desulfurization tower (8), and then enters the desulfurization tower after deep cooling to -22～-28°C (8), in the desulfurization tower (8), the impurities in the coke oven gas are removed through two stages to obtain deeply purified coke oven gas. After the deeply purified coke oven gas is reheated, 42-50% of the depth purification After the coke oven gas is decompressed to 8-10kPa, it is used as the return gas for coke oven heating, and the rest is used for the production of chemicals;

   S4, the sulfur-containing methanol-rich liquid obtained from desulfurization at the lower part of the desulfurization tower (8) is reheated to 25-35° C. and then enters the methanol-rich flash tank (7) for flashing under reduced pressure. The flashing pressure is 2-8 bar, and the flashing The outgoing gas is discharged from the system as desulfurization waste gas after the methanol is recovered by the water washing tower (4), and the flash 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, and the sulfur-containing gas obtained at the top of the thermal regeneration tower (3) is cooled and the entrained methanol is recovered. The water washing tower (4) is then sent for washing, and the coke oven gas after washing by the water washing tower (4) is discharged into the system as desulfurization waste gas;

   S5, the gas washing agent after the pretreatment of the pre-washing 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, and the four-phase The dissolved gas separated by the separator (2) is discharged to the azeotrope column (5) for washing, and 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). , 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 passed through methanol as a gas detergent The waste water discharged from the water separation tower (6) is heat-exchanged to 80-100° C. and then sent to the azeotrope tower (5) under pressure to recover the detergent;

   S6, the non-condensable gas at the top of the azeotrope tower (5) is discharged from the system as the desulfurization waste gas after the methanol is recovered by washing with the washing tower (4), and the methanol/water mixture at the bottom of the azeotrope tower (5) is pressurized and sent to methanol The water separation tower (6) is rectified and purified, the methanol vapor at the top of the methanol water separation tower (6) is returned 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 and sent out to the system.
7. The method for deep purification of coke oven gas according to claim 6, wherein the operating conditions of the prewash tower (1) are: an operating temperature of 15 to 20°C, an operating pressure of 3 to 6 kPa, and a packing specific surface area of 500 to 500°C. 4000m ² /m 3 , the packing rotation frequency is 30～60Hz, and the gas-liquid ratio is 1000～6000.
8. The method for deep purification of coke oven gas according to claim 6, characterized in that, the gas cleaning agent at least comprises methanol and crude benzene.
9. The method for deep purification of coke oven gas according to claim 6, characterized in that, after the desulfurization tower (8) removes impurities in the coke oven gas in two stages, the sulfur content in the coke oven gas after the deep purification is less than or equal to 0.1ppm , carbon dioxide content ≤ 2.5%, no tar dust, naphthalene and ammonia.
10. The deep purification method of coke oven gas according to claim 6, is characterized in that, the consumption of gas detergent in described prewash tower (1) is 0.20-0.32kg/m ³ coke oven gas; desulfurization tower (8) The consumption of medium and lean methanol is 1.30-1.50kg/m ³ coke oven gas; the NH ³ content in the recycled lean methanol is less than 20×10 ^-6 ppm, and the pH value is 8-10.