CN214881311U

CN214881311U - Deep purification system for coke oven gas

Info

Publication number: CN214881311U
Application number: CN202120350103.6U
Authority: CN
Inventors: 王贵; 左永飞; 张琦宇; 施福富; 范辉; 关杰; 郝成浩; 尚书娟; 刁秀辉; 李刚; 周恩利
Original assignee: Sedin Engineering Co Ltd
Current assignee: Sedin Engineering Co Ltd
Priority date: 2021-02-08
Filing date: 2021-02-08
Publication date: 2021-11-26
Anticipated expiration: 2031-02-08

Abstract

The utility model provides a deep purification system of coke oven gas belongs to coke oven gas purification field. Through setting up the prewashing tower for hypergravity rotary device for the coke oven gas after the benzene removal can carry out the preliminary desorption of impurity through hypergravity rotary technology in the prewashing tower, with harmful substance such as dust, benzene, tar, naphthalene, ammonia and sulphur in the coke oven gas after the degree of depth desorption benzene removal, solved the problem that sulphur in the coke oven gas, ammonia exceed standard and can influence back system steady operation, still solved the problem that tar in the coke oven gas, naphthalene can cause compression system to block up. The system for further removing the impurities with complex components in the coke oven gas by adopting the low-temperature methanol washing technology is provided through equipment such as a desulfurizing tower, a thermal regeneration tower, a water washing tower, an azeotropic tower, a methanol-water separation tower, a methanol-rich flash tank, a four-phase separator and the like, so that the purified gas index can be ensured, and the problem that the coking desulfurization waste liquid can not be treated radically can be solved through the methanol regeneration recycling.

Description

Deep purification system for coke oven gas

Technical Field

The utility model relates to a coke oven gas purifies technical field, especially relates to a deep purification system of coke oven gas.

Background

Coke oven gas is an important byproduct obtained in the coking process, and the research on the composition of coke oven gas has become quite mature in recent years. The coke oven gas belongs to medium-heat value natural gas, the hydrogen content is 50-60%, and the methane content is 22-24%, wherein the coke oven gas has great utilization value. A large amount of coke oven gas can be generated while producing coke, if the generation amount of the coke oven gas in China is calculated according to the condition that the coke oven gas for producing 1 ton of coke generates 430 cubic meters, the generation amount of the coke oven gas in the whole year is basically maintained at 1800 billion cubic meters, wherein about 45-50% of the coke oven gas returns to the coke oven, and the rest coke oven gas is equal to over 2 times of the gas transmission amount in the design year of 'west gas and east gas transmission' in China. Therefore, how to recycle the coke oven gas has important significance for realizing the cyclic utilization of resources and the sustainable development of economy. The purification of the coke oven gas becomes the most important thing before the coke oven gas is comprehensively utilized. The purification of the coke oven gas becomes the key before the comprehensive utilization of the coke oven gas, and the core problem in the purification of the coke oven gas is desulfurization.

At present, dry desulfurization and wet desulfurization are commonly used as desulfurization methods for coke oven gas. The dry desulfurization is mainly to remove H in coal gas by using a desulfurization catalyst synthesized by ferric hydroxide and other preparations₂S, the regenerated desulfurizer can be reused. The dry desulfurization is mainly applied to the desulfurization of coke oven gas with small gas quantity or the secondary desulfurization with high desulfurization precision. The wet desulfurizing process is to utilize liquid desulfurizing agent to eliminate H from coke oven gas₂S and HCN, and the currently commonly used wet desulphurization comprises an improved ADA method, a naphthoquinone method, a glue method, an FRC method, a TH method, an HPF method, a PDS method, an OPT method, an iron complex method and an ammonia water catalysis method. Wet desulfurization is commonly employed by larger coking enterprises. In the wet desulfurization process, a small amount of waste liquid is discharged in order to avoid accumulation of side reaction salts in the desulfurization waste liquid. The prior measure is to send the discharged desulfurization waste liquid into a coal blending system, but the mode can cause environmental problems and pollute the environment.

Along with the coming of new environmental protection policies, the treatment of the desulfurization waste liquid becomes a great problem in the coking industry, and a relatively complete, economic and environmental-friendly desulfurization waste liquid treatment method is not formed at home until now. In conclusion, the coke oven gas desulfurization is faced with the problems that the investment and cost of dry desulfurization are too high, the scale requirement of coke oven gas cannot be met, and the waste liquid cannot be treated in the traditional wet desulfurization. In addition, in the deep purification process of the coke oven gas, the precision of desulfurization, naphthalene removal and the like is insufficient, and the safe-stable-normal-full-excellent operation of a subsequent device cannot be ensured. The main expression is in the following three aspects:

(1) the deeply purified coke oven gas contains excessive sulfur and ammonia, and normal operation of subsequent purification and synthesis is influenced.

When the coke oven gas is used as fuel gas, the requirement is H₂S is less than 500mgNm³Ammonia content of less than 100mg/Nm³However, the acid gas and ammonia in actual operation exceed the standards, which affects the stable operation of the system. Along with the expansion of coking scale and industrial aggregation, the coke oven gas becomes an important chemical raw material gas for use, and the change of the application of the coke oven gas causes that the design index of the deep purification of the original coke oven gas can not meet the requirement of the current use index.

(2) The coke oven gas after deep purification contains tar and naphthalene, which seriously affects the normal operation of a compressor, and is mainly caused by the fact that the coke oven gas contains the tar and the naphthalene is high in content, and the tar is gasified and coked when the gas temperature is increased during compression; and naphthalene is condensed and crystallized to cause naphthalene blockage of the compressor, so that the compressor cannot normally run and is forced to stop repairing, and the compressor is stopped for repairing only by opening for 1-2 days, so that the production is quite passive and is usually the situation of 1 opening for 2 spare or 1 opening for 3 spare.

(3) The desulfurization agent of the fine desulfurization is failed in advance due to abnormal rough desulfurization, which affects the production operation, mainly sulfur penetrates, and the desulfurization agent is forced to be replaced in advance, so that the desulfurization agent is replaced frequently, and the operating cost is increased.

Disclosure of Invention

In order to solve the technical problem that the desulfurizer which can influence the stable operation of the back system, can cause the blockage of the compressor and can cause the fine desulfurization fails in advance to increase the operating cost in the deep purification process of the coke oven gas at present, the utility model provides a deep purification system of the coke oven gas.

In order to solve the technical problem, the utility model discloses a technical scheme is:

the deep purification system of coke oven gas comprises a prewashing tower, a desulfurizing tower, a thermal regeneration tower, a washing tower, an azeotropic tower, a methanol-water separation tower, a methanol-rich flash tank and a four-phase separator, wherein the prewashing tower is a supergravity rotating device, and the four-phase separator is a horizontal three-weir type gas-liquid separator, wherein: the gas holder is connected with a gas phase inlet at the lower part of the prewashing tower through a first heat exchanger, a liquid phase outlet at the bottom of the prewashing tower is connected with a feed inlet of a four-phase separator, a gas outlet of the prewashing tower is connected with a gas inlet at the lower part of the desulfurizing tower through a first compressor, a second heat exchanger and a third heat exchanger, a gas outlet at the top of the desulfurizing tower is connected with a second heat exchanger, a liquid outlet at the bottom of the desulfurizing tower is connected with a liquid phase inlet at the upper part of the prewashing tower through a second compressor, a liquid outlet at the middle lower part of the desulfurizing tower is connected with a liquid inlet of a methanol-rich flash tank through a fourth heat exchanger, a gas outlet at the top of the methanol-rich flash tank is connected with a gas inlet at the middle upper part of the washing tower, a gas outlet at the top of the washing tower is connected with a desulfurization waste gas pipeline, a liquid outlet at the bottom of the methanol-rich flash tank is connected with a liquid inlet at the middle upper part of the heat regenerating tower through a fifth heat exchanger, a liquid outlet at the bottom of the heat regenerating tower is connected with a liquid inlet at the upper part of the desulfurizing tower through a third compressor and a fifth heat exchanger, an air outlet at the top of the thermal regeneration tower is connected with an air inlet at the lower part of the water washing tower through a sixth heat exchanger, the sixth heat exchanger is connected with a liquid inlet of a condensate storage tank, a liquid outlet of the condensate storage tank is connected with a liquid inlet at the upper part of the thermal regeneration tower, a liquid outlet at the bottom of the water washing tower is connected with a feed inlet of a four-phase separator, a gas phase outlet of the four-phase separator is connected with an air inlet at the middle part of the azeotropic tower, a heavy phase fluid outlet of the four-phase separator is connected with a heavy oil pipeline, a light phase fluid outlet of the four-phase separator is connected with a light oil pipeline, a middle phase fluid outlet of the four-phase separator is connected with a liquid inlet at the middle part of the azeotropic tower through a fourth compressor and a seventh heat exchanger, an air outlet at the top of the azeotropic tower is connected with an air inlet at the lower part of the water washing tower, a liquid outlet at the bottom of the tower is connected with a liquid inlet at the middle part of the methanol-water separation tower through a fifth compressor, an air outlet at the top of the azeotropic tower is connected with an air inlet at the middle part of the thermal regeneration tower, and a liquid outlet at the bottom of the methanol-water separation tower is connected with the seventh heat exchanger.

Optionally, the prewashing tower comprises a transmission device, a rotating shaft and a prewashing shell, the transmission device is connected with one end of the rotating shaft, the other end of the rotating shaft is connected with a rotor, the rotor is arranged at the middle lower part of an inner cavity of the prewashing shell, a gas outlet is connected in the middle of the top of the prewashing shell, a liquid outlet is connected at the bottom of the prewashing shell, a gas inlet is connected at the bottom of one side of the prewashing shell, a liquid inlet is connected at the middle upper part of the other side of the prewashing shell, an L-shaped liquid pipeline is connected to the liquid inlet, a vertical pipe of the L-shaped liquid pipeline extends to the middle part of the rotor, a plurality of liquid nozzles are installed on the vertical pipe of the L-shaped liquid pipeline, a demister is arranged at the top of the inner cavity of the prewashing shell, a separation plate is installed between the bottom of the demister and the top of the rotor, the middle part of the top of the rotor and the separation plate are sealed by a first sealing gasket, and the middle part of the two sides of the bottom of the rotor and the rotating shaft are respectively sealed by a second sealing gasket and a third sealing gasket, the rotor is filled with a filler layer.

Optionally, the four-phase separator comprises a separation shell, and an 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, a baffle and a calming plate, the feeding hole is arranged outside the separation shell and is connected with the top of the separation shell, the gas-liquid separator is arranged below the feeding hole, the bottom end of the calming plate is connected with the bottom of the separation shell, and the top end of the baffle is connected with the top of the separation shell and is positioned 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 collection groove, a light phase fluid collection groove and an 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 end of the heavy phase fluid collection groove is connected with the bottom of the separation shell and positioned between the coalescer and the heavy phase fluid overflow weir, the top and the bottom of the side wall of the heavy phase fluid collection groove are respectively provided with a first liquid level meter, the bottom of the heavy phase fluid collection groove is connected with a heavy phase fluid outlet, the top and the bottom of the separation shell above the heavy phase fluid collection groove are respectively provided with a second liquid level meter, the light phase fluid collection groove is arranged on one side of the heavy phase fluid overflow weir, the front wall of the light phase fluid collection groove is the light phase fluid overflow weir, the height of the light phase fluid overflow weir is lower than that of the rear wall of the light phase fluid collection groove, and the top and the bottom in the light phase fluid collection groove are respectively provided with a third liquid level meter, the bottom of the light phase fluid collecting tank is connected with a light phase fluid outlet, the light phase fluid outlet is positioned outside the separating shell, a demister is arranged above the light phase fluid collecting tank, the gas phase outlet is arranged outside the separating shell and connected with the demister, an intermediate phase fluid overflow weir is arranged on one side of the light phase fluid collecting tank and connected with the bottom of the separating shell, the intermediate phase fluid overflow weir and the space at the tail of the separating shell form an intermediate phase fluid collecting tank, the top and the bottom of one side of the intermediate phase fluid overflow weir are respectively provided with a fourth liquid level meter, and the bottom of the separating shell on one side of the intermediate phase fluid overflow weir is connected with an intermediate phase fluid outlet.

Optionally, the length ratio of the inlet section i, the settling separation section ii and the collection section iii is 1: 3.2-4.2: 2.

Optionally, the top end of the ballast plate is at the same level with a second liquid level meter positioned at the top of the separation shell; the bottom end of the baffle is 400 mm higher than the top end of the calming plate, the bottom end of the baffle is not less than 200mm lower than the bottom end of the gas-liquid separator, the height of the coalescer is the same as that of the light-phase fluid overflow weir, the height of the heavy-phase fluid overflow weir is 200mm higher than that of the bottom end 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 height of the rear wall of the light-phase fluid collecting tank is 200mm higher than that of the bottom end of the demister, and the height of the intermediate-phase fluid overflow weir is 20-100mm lower than that of the light-phase fluid overflow weir.

The utility model has the advantages that:

the pre-washing tower is arranged and is a super-gravity rotating device, so that the debenzolized coke oven gas can be subjected to primary impurity removal in the pre-washing tower through a super-gravity rotating technology, and harmful substances such as dust, benzene, tar, naphthalene, ammonia, sulfur and the like in the debenzolized coke oven gas can be deeply removed through pretreatment of the pre-washing tower, so that the problem that the stable operation of a rear system is influenced by the over-standard sulfur and ammonia in the coke oven gas is solved, and the stability of the operation of the system can be improved; the problem that the compression system is blocked due to tar and naphthalene in the coke oven gas is solved, and the possible blocking abnormity in the subsequent working section is avoided. Further, by arranging equipment such as a desulfurizing 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 for further removing impurities with complex components in the coke oven gas by adopting a low-temperature methanol washing technology is provided, so that the purified gas index can be ensured, the problem that coking desulfurization waste liquid cannot be treated radically can be solved by methanol regeneration and recycling, and the problem that the desulfurizing agent for fine desulfurization is failed in advance to increase the operating cost due to the fact that coarse desulfurization is abnormal is solved.

Through the system and the method provided by the embodiment of the utility model, the pressurizing and conveying requirements of the coke oven gas and the subsequent deep purification requirements are met, and the purpose of purifying the production chemical synthesis system is achieved. The utility model has the advantages of less investment, small equipment volume and occupied area, high efficiency of removing impurities such as tar dust, naphthalene and the like in the coke oven gas, low energy consumption, high washing efficiency and the like. In addition, through the utility model discloses need not to desulfurize again after coke oven gas after the deep purification returns the coke oven, also do not have the desulfurization waste liquid of intractable to produce for follow-up production chemical products fine desulfurization catalysis and life prolong more than one year at least.

Drawings

Fig. 1 is a schematic diagram of the system of the present invention.

FIG. 2 is a schematic view of the structure of the preliminary washing column in FIG. 1.

Fig. 3 is a schematic diagram of the structure of the four-phase separator of fig. 1.

Detailed Description

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

As shown in fig. 1, the embodiment of the utility model provides a deep purification system of coke oven gas, it includes prewashing tower 1, desulfurizing tower 8, thermal regeneration tower 3, washing tower 4, azeotropic tower 5, methanol-water separation tower 6, rich methyl alcohol flash drum 7 and four-phase separator 2, prewashing tower 1 is hypergravity rotary device, and four-phase separator 2 is horizontal three weir type gas-liquid separator, wherein: the gas holder is connected with a gas phase inlet 103 at the lower part of the prewashing tower 1 through a first heat exchanger 9, a liquid phase outlet 102 at the bottom of the prewashing tower 1 is connected with a feed inlet 201 of a four-phase separator 2, a gas outlet 107 at the bottom of the prewashing tower 1 is connected with a gas inlet at the lower part of a desulfurizing tower 8 through a first compressor 10, a second heat exchanger 11 and a third heat exchanger 12, a gas outlet at the top of the desulfurizing tower 8 is connected with the second heat exchanger 11, a liquid outlet at the bottom of the desulfurizing tower 8 is connected with a liquid phase inlet 109 at the upper part of the prewashing tower 1 through a second compressor 14, a liquid outlet at the middle lower part of the desulfurizing tower 8 is connected with a liquid inlet of a methanol-rich flash tank 7 through a fourth heat exchanger 13, a gas outlet at the top of the methanol-rich flash tank 7 is connected with a gas inlet at the middle upper part of a water-washing tower 4, a gas outlet at the top of the water-washing tower 4 is connected with a desulfurization waste gas pipeline, a liquid outlet at the bottom of the methanol-rich flash tank 7 is connected with a liquid inlet at the middle upper part of a heat-regeneration tower 3 through a fifth heat exchanger 15, a liquid outlet at the bottom of the thermal regeneration tower 3 is connected with a liquid inlet at the upper part of the desulfurizing tower 8 through a third compressor 16 and a fifth heat exchanger 15, a gas outlet at the top of the thermal regeneration tower 3 is connected with a gas inlet at the lower part of the water washing tower 4 through a sixth heat exchanger 17, the sixth heat exchanger 17 is connected with a liquid inlet of a condensate storage tank 22, a liquid outlet of the condensate storage tank 22 is connected with a liquid inlet at the upper part of the thermal regeneration tower 3, a liquid outlet at the bottom of the water washing tower 4 is connected with a feed inlet 201 of a four-phase separator 2, a gas phase outlet 202 of the four-phase separator 2 is connected with a gas inlet at the middle part of the azeotropic tower 5, a heavy phase fluid outlet 203 of the four-phase separator 2 is connected with a heavy oil pipeline, a light phase fluid outlet 204 of the four-phase separator 2 is connected with a light oil pipeline, a middle phase fluid outlet 205 of the four-phase separator 2 is connected with a liquid inlet at the middle part of the azeotropic tower 5 through a fourth compressor 18 and a seventh heat exchanger 23, a gas outlet at the top of the azeotropic tower 5 is connected with a gas inlet at the lower part of the water washing tower 4, the liquid outlet of 5 bottoms on azeotropic tower is connected through the inlet in fifth compressor 24 and 6 middle parts of methanol-water separation tower, and the gas outlet at 6 tops on methanol-water separation tower is connected with the air inlet in 3 middle parts on heat regenerator column, and the liquid outlet of 6 bottoms on methanol-water separation tower is connected with seventh heat exchanger 23.

The system of the utility model is applied to the coke oven gas after primary cooling, electric tar catching, precooling, desulfurizing, intercooling, ammonia removal, final cooling and benzene elution, and is used for removing the impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur contained in the coke oven gas so as to meet the requirements of pressurizing and conveying the coke oven gas and subsequent deep purification and reach the purification requirement of a chemical production synthesis system.

Optionally, as shown in fig. 2, the prewashing tower 1 includes a transmission device 101, a rotating shaft 115 and a prewashing housing 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 disposed at the middle lower part of the inner cavity of the prewashing housing 108, a gas outlet 107 is connected to the middle of the top of the prewashing housing 108, a liquid outlet 102 is connected to the bottom of the prewashing housing 108, a gas inlet 103 is connected to the bottom of one side of the prewashing housing 108, a liquid inlet 109 is connected to the middle upper part of the other side of the prewashing housing 108, an L-shaped liquid pipeline is connected to the liquid inlet 109, a vertical pipe of the L-shaped liquid pipeline extends to the middle of the rotor 104, a plurality of liquid nozzles 111 are mounted on the vertical pipe of the L-shaped liquid pipeline, a demister 106 is disposed at the top of the inner cavity of the prewashing housing 108, a partition plate 105 is mounted between the bottom of the demister 106 and the top of the rotor 104, a first seal 110 is disposed between the top of the rotor 104, the two sides of the middle of the bottom of the rotor 104 are sealed with the rotating shaft 115 through a second sealing gasket 112 and a third sealing gasket 113 respectively, and the interior of the rotor 104 is filled with a packing layer 114.

Optionally, the porosity of the filler layer 114 is 80% to 99%; the filler of the filler layer 114 adopts large corrugated wire mesh filler and small corrugated wire mesh filler. The small corrugated filler with the length accounting for 5% -10% of the radius of the prewashing shell 108 is arranged near the rotating shaft 115, preferably 5% -8%. The average pore diameter of the large corrugated wire mesh packing is 5-10 mm, and preferably 4-8 mm; the average pore diameter of the small corrugated wire mesh packing is 1-5 mm, preferably 2-4 mm. The packing mode is beneficial to uniform atomization of liquid-phase washing liquid, the impurity trapping effect is improved, the large-ripple packing can reduce the gas-liquid phase resistance, and the anti-blocking capacity of the packing is improved.

Optionally, as shown in fig. 3, the four-phase separator 2 includes a separation shell 218, and an inner cavity of the separation shell 218 is divided into an inlet section i, a settling 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 is connected with the top of the separation shell 218, the gas-liquid separator 206 is arranged below the feed inlet 201, the bottom end of the calming plate 208 is connected with the bottom of the separation shell 218, and the top end of the baffle 207 is connected with the top of the separation shell 218 and is positioned 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 fluid collection groove 219, a light phase fluid collection groove 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 is connected with the bottom of the separation shell 218, the top end of the heavy phase fluid collection groove 219 is connected with the bottom of the separation shell 218 and is positioned between the coalescer 209 and the heavy phase fluid overflow weir 217, the top and the bottom of the side wall of the heavy phase fluid collection groove 219 are respectively provided with a first liquid level meter 213, the bottom of the heavy phase fluid collection groove 219 is connected with a heavy phase fluid outlet 203, the top and the bottom of the separation shell 218 above the heavy phase fluid collection groove 219 are respectively provided with a second liquid level meter 212, the light phase fluid collection groove 220 is arranged on one side of the heavy phase fluid overflow weir 217, the front wall of the light phase fluid collection groove 220 is a light phase fluid overflow weir 214, and 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 groove 220, a third liquid level meter 210 is respectively arranged at the top and the bottom in the light phase fluid collecting tank 220, a light phase fluid outlet 204 is connected to the bottom of the light phase fluid collecting tank 220, the light phase fluid outlet 204 is positioned outside the separating shell 218, a demister 222 is arranged above the light phase fluid collecting tank 220, the gas phase outlet 202 is arranged outside the separating shell 218 and is connected with the demister 222, an intermediate phase fluid overflow weir 216 is arranged at one side of the light phase fluid collecting tank 220 and is connected with the bottom of the separating shell 218, the intermediate phase fluid overflow weir 216 and the space at the tail part of the separating shell 218 form an intermediate phase fluid collecting tank 221, a fourth liquid level meter 211 is respectively arranged at the top and the bottom at one side of the intermediate phase fluid overflow weir 216, and the intermediate phase fluid outlet 205 is connected to the bottom of the separating shell 218 at one side of the intermediate phase fluid overflow weir 216.

Wherein gas-liquid separator 206 and calming plate 208 are conventional components of inlet section i, wherein gas-liquid separator 206 has the primary function of achieving gas-liquid pre-separation, and may take a variety of forms in practical application, and functions to provide uniform initial distribution or redistribution of liquid at the top of the packing or at a certain height, to enhance the effective surface for mass and heat transfer, to improve phase-to-phase contact, and thereby to enhance the separation efficiency of the column. The main function of the static plate 208 is to slow down the two-phase fluctuation of the liquid phase region of the inlet section I, and also to have the function of liquid-liquid pre-separation, but mainly to inhibit the fluctuation to provide stable operation conditions for the sedimentation separation section II. The coalescer 209 is primarily intended to enhance the separation efficiency by promoting coalescence of the light phase (e.g., oil droplets) on the plate surface, and also has the function of suppressing fluctuation of the liquid phase region in the settling section ii.

Optionally, the top end of the ballast plate 208 is at the same level as the second level gauge 212 at the top of the separation housing 218; the bottom end of the baffle 207 is 400 mm and 500mm higher than the top end of the sedation plate 208, and the bottom end of the baffle 207 is not less than 200mm lower than the bottom end of the gas-liquid separator 206.

Alternatively, the height of the coalescer 209 is the same as the height of the light phase fluid weir 214 (H1), the height of the heavy phase fluid weir 217 is 500mm above the bottom end of the light phase fluid collection tank 220, the height of the light phase fluid weir 214 is 1/2-3/4 of the diameter of the four phase separator, the height of the back wall 215 of the light phase fluid collection tank 220 (H2) is 200mm above the bottom end of the demister 222, and the height of the intermediate phase fluid weir 216 (H3) is 20-100mm below the height of the light phase fluid weir 214.

The three overflow weir plates of the heavy phase fluid overflow weir 217, the light phase fluid overflow weir 214 and the middle phase fluid overflow weir 216, the three heavy phase fluid collecting tanks 219, the light phase fluid collecting tank 220 and the middle phase fluid collecting tank 221 are arranged in the collecting section III, so that the length of the collecting section III of the four-phase separator 2 is larger than that of a common separator, but the liquid-liquid interface in the operation process is well controlled due to the arrangement, the stable operation of the separation process is ensured, and the influence of working condition fluctuation on the process of the sedimentation separation section II is reduced or avoided. The embodiment of the utility model provides an in the four-phase separator 2 the control at liquid-liquid interface derive from two aspects: the three overflow weir plates and the three liquid phase collecting groove structures enable a liquid-liquid interface to be simultaneously controlled by hydrostatic pressure of light phase/intermediate phase and heavy phase, so that the liquid-liquid interface is relatively stable; the light phase fluid collecting tank 220 and the intermediate phase fluid collecting tank 221 provide buffer space for fluctuation of upstream and downstream (inlet and outlet) flow in the operation process, so that influence of fluctuation of working conditions on the separation process of the settling section is reduced or avoided. By arranging the components such as the static plate 208, the coalescer 209 and the like, the liquid-liquid sedimentation separation can be realized by ensuring the lower transverse flow velocity to ensure that the liquid in the liquid phase region has enough residence time, meanwhile, the sedimentation or the buoyancy lift of the dispersed phase is facilitated, the fluctuation of the liquid phase region is also reduced, the separation time is shortened, and the size of the equipment is reduced.

The utility model discloses an all adopt four-phase separator 2 shown in FIG. 3, it includes to synthesize the influence factor that considers the pressure distribution of II terminal separation sections of actual separation operating mode subsides: the height of the light phase fluid weir 214 and the difference in height of the three weirs, the slice thickness at the weir crest and the slice flow rate at the weir crest and the flow resistance at the bottom of the light phase collection tank 220.

The deep purification method of the coke oven gas of the deep purification system of the coke oven gas comprises the following steps:

s1, exchanging heat between the coke oven gas after benzene elution and the coke oven gas after deep purification of the desulfurizing tower 8 in the first heat exchanger 9 and the second heat exchanger 11 to 20-25 ℃, sending the coke oven gas after heat exchange into the prewashing tower 1 from the lower part of the prewashing tower 1, and simultaneously sending a gas detergent from the bottom of the desulfurizing tower 8 into the prewashing tower 1 from the upper part of the prewashing tower 1 after being pressurized by the second compressor 14; wherein, the prewashing tower 1 is a supergravity rotating device.

The coke oven gas after benzene elution contains impurities such as dust, benzene, tar, naphthalene, ammonia, sulfur in various forms, and the like. Generally, the coke oven gas after benzene elution contains 5-15mg/m of tar dust³10-200mg/m of naphthalene³Ammonia 15-100mg/m³Sulfur is less than 500mg/m3 and other trace impurities.

S2, the coke oven gas after heat exchange and the gas detergent are in countercurrent or cross-current contact in the prewashing tower 1 for pretreatment, and the pretreated gas detergent is collected on the inner wall of the prewashing tower 1 under the supergravity action of the prewashing tower 1 and then discharged to the four-phase separator 2.

Because the coke oven gas after benzene elution comprises impurities such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur, the embodiment of the utility model provides an earlier through adopting the prewashing tower 1 of hypergravity rotation technique to carry out the preliminary desorption coke oven gas after benzene elution and impurity such as dust, benzene, tar, naphthalene, ammonia and various forms of sulfur in the coke oven gas after benzene elution.

Specifically, in the prewashing tower 1, the gas detergent is uniformly distributed through the liquid phase nozzles 111 of the prewashing tower 1 and then enters the packing layer 114, and under the action of the transmission device 101, the rotating shaft 115 and the rotor 104, the gas detergent is split into liquid microelements(liquid film, liquid silk and liquid drop) and the coke oven gas after benzene elution are in countercurrent contact to remove the impurities in the coke oven gas after benzene elution. Because prewashing tower 1 is hypergravity rotary device, makes the embodiment of the utility model provides an utilize the rotatory technique of hypergravity to carry out the desorption of impurity. The cutting grain diameter of the super-gravity rotating technology reaches 10^-8m, the particle diameter of the coal gas washing agent passing through the packing layer 114 almost reaches the molecular level, and the coal gas washing agent is gathered in the supergravity rotating device and then removed together with impurities. The embodiment of the utility model provides an utilize the hypergravity rotation technique to carry out the preliminary treatment to the coke oven gas after eluting the benzene, can strengthen the washing effect, reduce the particle diameter cutting size of washing, simultaneously through liquid phase spraying and hypergravity effect under, make the liquid drop distribution more even, bigger with the impurity contact surface in the coke oven gas to promote the elution effect to impurity. The supergravity rotating device has the characteristics of good particle trapping effect, small gas phase pressure drop, difficult blockage of the rotating filler and the like, so that harmful substances such as dust, benzene, tar, naphthalene, ammonia, sulfur and the like in the coke oven gas are deeply removed, the pressurized conveying and the subsequent deep purification of the coke oven gas are met, and the purpose of purifying the production chemical synthesis system is achieved. The coke oven gas after impurity removal is defoamed by the demister 106 to obtain pretreated coke oven gas, and the gas detergent after impurity removal is thrown to the inner wall of the prewashing shell 108 and flows into the four-phase separator 2 from the liquid phase outlet 102.

The coke oven gas pretreatment is that naphthalene in the coke oven gas is easy to crystallize and separate out at the temperature of less than 20 ℃ through tests under different temperatures, pressures and detergents. In order to avoid the blocking of equipment and pipelines caused by naphthalene crystallization at low temperature, the embodiment of the utility model provides a through newly-increased prewashing tower 1 to utilize prewashing methyl alcohol to desorption naphthalene in the coke oven gas. Because the pre-washed methanol contains crude benzene, the benzene and the naphthalene belong to aromatic compounds, and the naphthalene is dissolved in the gas detergent according to the similar compatibility principle.

Furthermore, the embodiment of the utility model provides a confirm through the experiment that the most suitable temperature of best preliminary treatment coke oven gas is at 20-25 ℃, and the gas detergent includes methyl alcohol and crude benzol at least, and the gas detergent can also include one or two kinds and the combination of more than two kinds in desalinized water, ethanol, wash oil and tar, has fine preliminary treatment effect when the gas detergent temperature is less than 20 ℃. After the coke oven gas after benzene elution is pretreated under the conditions, practice proves that the collection efficiency of tar ash reaches more than 99 percent, and particles with the particle size of more than 3 mu m can be completely removed; the removal rate of naphthalene is more than 80%; the removal rate of tar and dust reaches more than 60 percent; the removal rate of the organic sulfur reaches more than 85 percent; the removal rate of ammonia reaches more than 50 percent; the removal rate of the benzene reaches more than 50 percent; the removal rate enables the pretreated coke oven gas to meet the requirements of subsequent compression and deep purification.

S3, pressurizing the pretreated coke oven gas to 0.3-1.0MPa by a first compressor 10, performing primary cooling on the pretreated coke oven gas and the coke oven gas deeply purified by a desulfurizing tower 8 in a second heat exchanger 11, performing deep cooling to-22 to-28 ℃ by a third heat exchanger 12, then feeding the coke oven gas into the desulfurizing tower 8, removing impurities in the coke oven gas in the desulfurizing tower 8 by two stages to obtain the deeply purified coke oven gas, reheating the deeply purified coke oven gas by the first heat exchanger 9 and the second heat exchanger 11, reducing the pressure of 42-50% of the deeply purified coke oven gas to 8-10kPa to serve as return gas for heating the coke oven, and using the rest of the gas for producing chemicals.

S4, reheating the sulfur-containing methanol rich liquid obtained by desulfurizing the lower part of the desulfurizing tower 8 to 25-35 ℃ by a fourth heat exchanger 13, entering a methanol-rich flash tank 7 for decompression flash evaporation, wherein the flash evaporation pressure is 2-8bar, the flashed gas is discharged out of the system as a desulfurization waste gas after methanol is recovered by a water washing tower 4, reheating the flashed rich liquid at the bottom of the methanol-rich flash tank 7 to 80-100 ℃ by a fifth heat exchanger 15, entering a heat regeneration tower 3 for regeneration, pressurizing the regenerated poor methanol by a third compressor 16, cooling to-20-40 ℃ by the fifth heat exchanger 15, sending to the upper part of the desulfurizing tower 8 as an absorbent, cooling the sulfur-containing gas obtained at the top of the heat regeneration tower 3 by a sixth heat exchanger 17, recovering the entrained methanol by a condensate storage tank 22, sending to the water washing tower 4 for washing, and discharging the coke oven gas washed by the water washing tower 4 as the desulfurization waste gas out of the system.

The gas flashed out from the methanol-rich flash tank 7 is H₂、CH₄And the like. Sulfur-containing gas obtained from the top of the thermal regeneration tower 3Is H₂Gas with higher S concentration. The methanol solution absorbed with the acid gas components is recycled after regeneration through the operation means of decompression flash evaporation, heating regeneration and the like. When the temperature of the poor methanol is-20 to-40 ℃, the requirement of desulfurization precision can be met, and the cooling of a common cooling medium can be used.

S5, mixing the coal gas washing agent pretreated by the prewashing tower 1 with the methanol-containing solution discharged from the bottom of the water washing tower 4, sending the mixed mixture to a four-phase separator 2 for gas-liquid separation, discharging the dissolved gas separated by the four-phase separator 2 to an azeotropic tower 5 for washing, discharging tar dust separated by the four-phase separator 2 from a heavy-phase fluid outlet 203 of the four-phase separator 2, discharging naphtha separated by the four-phase separator 2 from a light-phase fluid outlet 204 of the four-phase separator 2, and sending an intermediate phase separated by the four-phase separator 2 as the coal gas washing agent to the azeotropic tower 5 for recycling the washing agent after heat exchange of the wastewater discharged by the methanol-water separation tower 6 through a seventh heat exchanger 23 to 80-100 ℃ and pressurization through a fourth compressor 18.

The gas washing agent pretreated by the prewashing tower 1 contains impurities such as tar, dust, crude benzene, naphthalene, ammonia, organic sulfur and the like.

S6, washing the non-condensable gas at the top of the azeotropic tower 5 by a water washing tower 4 to recover methanol, discharging the methanol as desulfurization waste gas out of the system, pressurizing the methanol/water mixture at the bottom of the azeotropic tower 5 by a fifth compressor 24, sending the methanol/water mixture to a methanol-water separation tower 6 for rectification and purification, returning the methanol steam at the top of the methanol-water separation tower 6 to the middle part of the thermal regeneration tower 3, and cooling the wastewater at the bottom of the methanol-water separation tower 6 by a seventh heat exchanger 23, and then sending the wastewater out of the system.

The methanol in the desulfurizing tower 8 absorbs the NH in the process gas while absorbing the acid gas₃This has an effect on the low-temperature methanol washing system (the desulfurizing tower 8, the thermal regeneration tower 3, the water washing tower 4, the azeotropic tower 5, the methanol-water separation tower 6, and the methanol-rich flash tank 7). NH at low temperature₃The solubility in methanol is much higher than that of CO₂And H₂Since acidic gases such as S have solubility in methanol, they are likely to accumulate in the methanol washing system. CO 2₂And H₂After the acidic gases such as S and the like are dissolved in the methanol, the pH value of the methanol is reduced, and a low-temperature methanol washing system is arrangedAnd (4) preparing for corrosion. In order to reduce the corrosion of equipment and prolong the service life and the operation period of the equipment, the existing low-temperature methanol washing process allows a certain content of NH in the system₃NH at ambient temperature₃The solubility in methanol is H₂S is more than 10 times of CO₂Multiple 60 of NH₃The methanol finally enters a thermal regeneration tower 3 for regeneration, and NH dissolved in the methanol₃The acid gas is desorbed in the thermal regeneration tower 3 and enters a water cooler at the top of the thermal regeneration tower 3 along with the acid gas, and the methanol in the acid gas is condensed because the water cooler cools the acid gas. But NH must be strictly controlled₃Content in low-temperature methanol washing system, if NH₃The low content can cause the aggravation of equipment corrosion; NH (NH)₃If the content of the ammonium salt is high, the ammonium salt in a methanol thermal regeneration system is crystallized, and a heat exchanger at the top of a thermal regeneration tower 3 is blocked; when NH is present₃The content of sulfur in the process gas exceeds the standard to a certain extent. Therefore, NH in the low-temperature methanol washing system must be well controlled₃Content, therefore the embodiment of the present invention needs to control the ammonia concentration in a certain range during purification, i.e. to maintain the NH in the poor methanol (circulating in the desulfurizing tower 8, the thermal regeneration tower 3, the water washing tower 4, the azeotropic tower 5, the methanol-water separation tower 6, the methanol-rich flash tank 7 and the four-phase separator 2) which is recycled₃The content is less than 20 × 10^－ ⁶ppm and pH value of 8-10.

According to H in the coke oven gas₂The solubility of the S in methanol is 0.9-6 Nm at 0.3-1.0MPa and-20-40 deg.C³H₂S/m³，CO₂The solubility in methanol at 0.3-1.0MPa and-20-40 ℃ is 0.8-5 Nm³CO₂/m³It is possible to determine the amount of the lean methanol in the desulfurizing tower 8 (i.e., the amount of the lean methanol introduced into the desulfurizing tower 8 including the lean methanol introduced from the bottom of the thermal regeneration tower 3 and the additional methanol for the external cut-off time) to be 1.30 to 1.50kg/m³Coke oven gas.

The coke oven gas has complex components and a plurality of impurities, and the gas components comprise CO and H₂、CO₂、CH₄、H₂S, organic sulfur, C₂H₄、C₂H₆、C₃H₈、C₄H₁₀、HCN、N₂Ar and tar, fatty acid, monophenol, polyphenol, naphtha, anthracene oil, naphthalene oil, fly ash, etc. Removing CO and H from these components₂An active ingredient and CH₄、 N₂Ar and hydrocarbons other than inert gas, all other components including CO₂And sulfides are harmful impurities to be removed, and the purification task is difficult. Along with the implementation of policies of going back to the city and entering the garden, upgrading and transforming and the like of coking enterprises, the large-scale and high-end coking industry is developed, the requirement for coke oven gas desulfurization is increased, and various harmful components such as CO in the coke oven gas can be cleanly removed by adopting a low-temperature methanol cleaning method₂、H₂S、COS、C₄H₄S、HCN、NH₃、H₂O、C₂The above hydrocarbons (including light oil, aromatic hydrocarbon, naphtha, olefin, colloid substance, etc.) and other carbonyl compounds, etc., which cannot be achieved by any other purification process. In addition, the low-temperature methanol is adopted to elute and remove the sulfur impurities with complex components in the coke oven gas, thereby not only ensuring the index of purified gas, but also solving the problem that the coking desulfurization waste liquid can not be treated radically through the regeneration and recycling of the methanol.

Alternatively, the operating conditions of the prewash column 1 are: the operation temperature is 15-20 ℃, the operation pressure is 3-6 kPa, and the specific surface area of the filler is 500-4000 m²/m³The rotating frequency of the filler is 30-60 Hz, and the gas-liquid ratio is 1000-6000.

Optionally, the gas scrubbing agent comprises at least methanol, wash oil and tar.

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

Optionally, the amount of the gas detergent in the prewashing tower 1 (namely the amount of the detergent entering the prewashing tower 1 from the bottom of the desulfurizing tower 8) is 0.20-32kg/m³Coke oven gas.

Further, the general coke oven gas composition is shown in the following table one:

watch 1

Due to CO in the coke oven gas₂The content is less than 3%, and coking coal sulphur content is 0.7%, compares the sulphur concentration improvement 4-8 times in large-scale coal gasification coal gas, consequently for large-scale coal gasification technology, the embodiment of the utility model provides a need not improve the concentration of acid gas through hydrogen sulfide concentration tower, through thermal regeneration tower 3 and concentrate the waste gas that will be received through the processing of washing tower 4 can reach the acid gas concentration recovery sulphur concentration of requirement. Therefore, compared with a large coal gasification process, the embodiment of the utility model has the effects of shortening the whole follow-up flow, obviously reducing the investment, occupying small area and having good environmental protection benefit.

It is to be understood that the above embodiments are merely exemplary embodiments that have been employed to illustrate the principles of the present invention, and that the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. The deep purification system of coke oven gas is characterized by comprising a prewashing tower (1), a desulfurizing 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 prewashing tower (1) is a supergravity rotating device, and the four-phase separator (2) is a horizontal three-weir gas-liquid separator, wherein: the gas holder is connected with a gas phase inlet (103) at the lower part of the prewashing tower (1) through a first heat exchanger (9), a liquid phase outlet (102) at the bottom of the prewashing tower (1) is connected with a feed inlet (201) of the four-phase separator (2), a gas outlet (107) of the prewashing tower (1) is connected with a gas inlet at the lower part of the desulfurizing tower (8) through a first compressor (10), a second heat exchanger (11) and a third heat exchanger (12), a gas outlet at the top of the desulfurizing tower (8) is connected with the second heat exchanger (11), a liquid outlet at the bottom of the desulfurizing tower (8) is connected with a liquid phase inlet (109) at the upper part of the prewashing tower (1) through a second compressor (14), a liquid outlet at the middle lower part of the desulfurizing tower (8) is connected with a liquid inlet of the methanol-enriched flash tank (7) through a fourth heat exchanger (13), a gas outlet at the top of the methanol-enriched flash tank (7) is connected with a gas inlet at the middle upper part of the water washing tower (4), a gas outlet at the top of the water washing tower (4) is connected with a desulfurization waste gas pipeline, a liquid outlet at the bottom of the methanol-rich flash tank (7) is connected with a liquid inlet at the middle upper part of the heat regeneration tower (3) through a fifth heat exchanger (15), a liquid outlet at the bottom of the heat regeneration tower (3) is connected with a liquid inlet at the upper part of the desulfurization tower (8) through a third compressor (16) and the fifth heat exchanger (15), a gas outlet at the top of the heat regeneration tower (3) is connected with a gas inlet at the lower part of the water washing tower (4) through a sixth heat exchanger (17), the sixth heat exchanger (17) is connected with a liquid inlet of a condensate storage tank (22), a liquid outlet of the condensate storage tank (22) is connected with a liquid inlet at the upper part of the heat regeneration tower (3), a liquid outlet at the bottom of the water washing tower (4) is connected with a feed inlet (201) of a four-phase separator (2), a gas phase outlet (202) of the four-phase separator (2) is connected with a gas inlet at the middle part of the azeotropic tower (5), a heavy phase fluid outlet (203) of the four-phase separator (2) is connected with a heavy oil pipeline, a light phase fluid outlet (204) of the four-phase separator (2) is connected with a light oil pipeline, a middle phase fluid outlet (205) of the four-phase separator (2) is connected with a liquid inlet in the middle of the azeotropic tower (5) through a fourth compressor (18) and a seventh heat exchanger (23), a gas outlet in the top of the azeotropic tower (5) is connected with a gas inlet in the lower part of the water washing tower (4), a liquid outlet in the bottom of the azeotropic tower (5) is connected with a liquid inlet in the middle of the methanol-water separating tower (6) through a fifth compressor (24), a gas outlet in the top of the methanol-water separating tower (6) is connected with a gas inlet in the middle of the heat regeneration tower (3), and a liquid outlet in the bottom of the methanol-water separating tower (6) is connected with the seventh heat exchanger (23).

2. The deep purification system of coke oven gas as claimed in claim 1, wherein the prewashing tower (1) comprises a transmission device (101), a rotating shaft (115) and a prewashing shell (108), the transmission device (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 at the middle lower part of the inner cavity of the prewashing shell (108), the middle of the top of the prewashing shell (108) is connected with a gas outlet (107), the bottom of the prewashing shell (108) is connected with a liquid outlet (102), the bottom of one side of the prewashing shell (108) is connected with a gas inlet (103), the middle upper part of the other side of the prewashing shell (108) is connected with a liquid inlet (109), the liquid inlet (109) is connected with an L-shaped liquid pipeline, the vertical pipe of the L-shaped liquid pipeline extends to the middle part of the rotor (104), and a plurality of liquid nozzles (111) are arranged on the vertical pipe of the L-shaped liquid pipeline, the top of prewashing casing (108) inner chamber is equipped with demister (106), install division board (105) between demister (106) bottom and rotor (104) top, it is sealed through first sealed pad (110) between rotor (104) top middle and division board (105), it is sealed through second sealed pad (112) and third sealed pad (113) respectively between rotor (104) bottom middle both sides and pivot (115), rotor (104) inside packing has packing layer (114).

3. The deep purification system of coke oven gas as claimed in claim 1 or 2, wherein the four-phase separator (2) comprises a separation shell (218), the inner cavity of the separation shell (218) is divided into an inlet section (I), a settling 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 with the top of the separation shell (218), the gas-liquid separator (206) is arranged below the feed inlet (201), the bottom end of the calming plate (208) is connected with the bottom of the separation shell (218), and the top end of the baffle (207) is connected with the top of the separation shell (218) and is positioned between the gas-liquid separator (206) and the calming plate (208); the sedimentation separation section (II) is provided with a coalescer (209); the collecting 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 a middle phase fluid overflow weir (216), the heavy phase fluid overflow weir (217) is arranged on one side of the coalescer (209) and is connected with the bottom of the separating shell (218), the top end of the heavy phase fluid collecting tank (219) is connected with the bottom of the separating shell (218) and is positioned between the coalescer (209) and the heavy phase fluid overflow weir (217), the top and the bottom of the side wall of the heavy phase fluid collecting tank (219) are respectively provided with a first liquid level meter (213), the bottom of the heavy phase fluid collecting tank (219) is connected with a heavy phase fluid outlet (203), the top and the bottom of the separating shell (218) above the heavy phase fluid collecting tank (219) are respectively provided with a second liquid level meter (212), the light phase fluid collecting tank (220) is arranged on one side of the heavy phase fluid overflow weir (217), the front wall of the light phase fluid collecting tank (220) is a light phase fluid overflow weir (214), the height of the light phase fluid overflow weir (214) is lower than that of the rear wall (215) of the light phase fluid collecting tank (220), a third liquid level meter (210) is respectively arranged at the top and the bottom in the light phase fluid collecting tank (220), the bottom of the light phase fluid collecting tank (220) is connected with a light phase fluid outlet (204), the light phase fluid outlet (204) is positioned outside the separating shell (218), a demister (222) is arranged above the light phase fluid collecting tank (220), the gas phase outlet (202) is arranged outside the separating shell (218) and is connected with the demister (222), a middle phase fluid collecting tank overflow weir (216) is arranged at one side of the light phase fluid collecting tank (220) and is connected with the bottom of the separating shell (218), the middle phase fluid overflow weir (216) and the space at the tail part of the separating shell (218) form a middle phase fluid collecting tank (221), the top and the bottom of one side of the intermediate phase fluid overflow weir (216) are respectively provided with a fourth liquid level meter (211), and the bottom of the separation shell (218) of one side of the intermediate phase fluid overflow weir (216) is connected with an intermediate phase fluid outlet (205).

4. The deep purification system for coke oven gas as claimed in claim 3, wherein the length ratio of the inlet section (I), the settling separation section (II) and the collection section (III) is 1: 3.2-4.2: 2.

5. the deep purification system for coke oven gas as claimed in claim 3, wherein the top end of the ballast plate (208) is at the same level with the second liquid level meter (212) located at the top of the separation housing (218); the bottom end of the baffle (207) is 500mm higher than the top end of the calming plate (208), the bottom end of the baffle (207) is not less than 200mm lower than the bottom end of the gas-liquid separator (206), the height of the coalescer (209) is the same as that of the light-phase fluid overflow weir (214), the height of the heavy-phase fluid overflow weir (217) is 500mm higher than that of the light-phase fluid collection 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 collection tank (220) is 200mm higher than that of the bottom end of the demister (222), and the height of the intermediate-phase fluid overflow weir (216) is 20-100mm lower than that of the light-phase fluid overflow weir (214).