Biomass gasification methanol production wastewater treatment system

Abstract

The utility model discloses a wastewater treatment system for methanol preparation through biomass gasification, and relates to the technical field of wastewater treatment. The method comprises the following steps: washing decoking wastewater is subjected to an oil removal process and then enters a steam stripping ammonia distillation facility, after ammonia nitrogen and part of total nitrogen are removed through steam stripping ammonia distillation, the wastewater enters an oxidation cyanogen breaking process, and effluent after oxidation cyanogen breaking enters a production wastewater treatment unit; the process flow of the production wastewater treatment unit is as follows: wastewater enters a hydrolysis acidification tank after being homogenized and regulated by a production wastewater regulating tank, effluent of the hydrolysis acidification tank enters a two-stage AO biochemical tank, effluent of the hydrolysis acidification tank enters a secondary sedimentation tank, and effluent of the secondary sedimentation tank is discharged after reaching the standard through a Parshall tank and a discharge tank; the clean wastewater treatment unit is formed by sequentially connecting the clean wastewater output end with a clean wastewater adjusting tank, a coagulation tank, a flocculation tank and a sedimentation tank. According to the utility model, the sludge yield is reduced, and the standard discharge of effluent is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to wastewater treatment technical field, concretely relates to the production wastewater treatment system of biomass gasification methanol. BACKGROUND

[0002] Biomass energy is an important renewable energy, directly or indirectly from photosynthesis of plants, generally from agricultural and forestry waste, household garbage and livestock manure, etc., which can be converted into solid, liquid and gaseous fuels through physical conversion (solid fuel), chemical conversion (direct combustion, gasification, liquefaction), biological conversion (such as fermentation into methane) and other forms. Due to the characteristics of environmental friendliness, low cost and carbon neutrality, the development and utilization of biomass resources has attracted high attention, and as the most potential renewable energy, it has become the fourth largest energy after coal, oil and natural gas.

[0003] Methanol is one of the three basic chemical raw materials, widely used in organic synthesis, dyes, pesticides, pharmaceuticals, coatings and other industries, and its deep processing products have reached more than 120 kinds.

[0004] Biomass methanol technology refers to the biomass raw material (straw, branches and other materials) entering the gasification unit through the crushing conveying machine, reacting with oxygen and steam produced by gasification in the gasification furnace to produce crude synthesis gas. The crude synthesis gas is subjected to a series of processes such as dust removal, tar removal, desulfurization, shift conversion, decarburization, etc. to obtain synthesis gas that meets the needs of methanol synthesis. The synthesis gas is synthesized into crude methanol product under the action of catalyst, and the refined methanol product is obtained by rectification. The wastewater produced by the above process needs to be treated before being discharged.

[0005] Biomass gasification synthesis gas contains many impurities, including tar, hydrogen cyanide, thiophene, mercaptan, sulfide and other pollutants, and the composition is complex. After water washing, the washing and de-tarring wastewater contains a large amount of tar, COD, NH3-N and aromatic polycyclic compounds and other difficult-to-degrade organic substances. The wastewater needs to be pretreated by appropriate method before entering the whole plant wastewater treatment station and being combined with other wastewater for subsequent treatment.

[0006] Biomass methanol wastewater mainly includes continuously discharged gasification washing and de-tarring wastewater, methanol rectification wastewater and intermittently discharged device floor flushing water, equipment cleaning wastewater, etc. Among them, the gasification washing and de-tarring wastewater has the largest water quantity and the worst water quality.

[0007] According to the current literature and patent retrieval, the research progress of biomass gasification and washing coke wastewater treatment technology (Li Jian, etc.) is summarized, including dilution, transpiration, coagulation, adsorption, filtration, and pretreatment technology of adding chemical reagents; biochemical treatment technology of aerobic biological treatment and anaerobic biological treatment, and oxidation technology of wet oxidation, supercritical water oxidation, incineration, and plasma. The patent "biomass gasification wastewater treatment device" (CN206328292U) provides an oil separation + first coagulation + air flotation + ozone oxidation + anaerobic + A / O biochemical contact oxidation + second coagulation + second ozone oxidation + MBR membrane separation treatment process, but the process is only for biomass gasification wastewater, and does not consider the overall consideration of methanol distillation and other process device wastewater in biomass methanol production. Through retrieval, there is no related patent, literature and example of biomass methanol wastewater treatment process. Utility model content

[0008] The utility model provides a wastewater treatment process suitable for this production process for each process of biomass methanol production, which is used for solving the problems of high content of tar, ammonia nitrogen and COD in biomass gasification washing and descaling wastewater, and comprehensively considering other process wastewater of the whole plant, realizing classified collection, quality treatment and standard discharge of wastewater.

[0009] The purpose of the utility model can be realized by the following technical schemes:

[0010] A biomass gasification and methanol wastewater treatment system, which comprises a washing and descaling wastewater pretreatment unit, a production wastewater treatment unit and a clean wastewater treatment unit;

[0011] The washing and descaling wastewater pretreatment unit is connected with an oil removal unit, a stripping ammonia evaporation facility and an oxidation cyanide breaking process in sequence at the output end of the washing and descaling wastewater;

[0012] The production wastewater treatment unit is connected with a production wastewater adjusting pool, a hydrolysis acidification pool, an A / O biochemical pool, a secondary sedimentation tank and an external discharge pool in sequence at the output end of each device production wastewater;

[0013] The clean wastewater treatment unit is connected with a clean wastewater adjusting pool, a coagulation tank, a flocculation tank and a sedimentation tank in sequence at the output end of the clean wastewater;

[0014] The output end of the oxidation cyanide breaking process is connected with the production wastewater adjusting pool, the output end of the sedimentation tank and the secondary sedimentation tank is connected with a sludge concentration tank, and the output end of the sedimentation tank is connected with the external discharge pool.

[0015] In the above system, the oil phase output end of the coalescence oil remover is connected with a waste oil dehydration tank; and the solid phase output end of the impeller air flotation and the dissolved air flotation is connected with a dregs tank and a dregs dehydration device.

[0016] In the system, the secondary sedimentation tank has another output end connected with the high-density sedimentation tank, the ozone catalytic oxidation tower, the degassing tank and the external discharge tank in sequence.

[0017] In the system, the oil removal unit comprises an oil-water separation settling tank, a coalescence oil removal device, an impeller air floatation device and a dissolved air floatation device connected in sequence.

[0018] A method for treating wastewater generated in the production of methanol from biomass gasification by using the system, comprising the following steps:

[0019] (1) After the washing and decoking wastewater is subjected to the oil removal process, the wastewater is introduced into the ammonia stripping facility, and after the ammonia nitrogen and part of the total nitrogen are removed through the ammonia stripping, the wastewater is introduced into the oxidation cyanide breaking process, and the effluent is introduced into the production wastewater treatment unit after the oxidation cyanide breaking;

[0020] (2) The process flow of the production wastewater treatment unit is as follows: the production wastewater is homogenously adjusted in the production wastewater adjusting tank, and then introduced into the hydrolysis acidification tank, and the effluent of the hydrolysis acidification tank is introduced into the two-stage AO biochemical tank, and the effluent is introduced into the secondary sedimentation tank, and the effluent of the secondary sedimentation tank is introduced into the Bartha tank and the external discharge tank to be discharged after reaching the standard;

[0021] Preferably, the high-density sedimentation tank and the ozone catalytic oxidation tower are arranged as security measures, when the monitoring of the external discharge water exceeds the standard, the effluent of the secondary sedimentation tank is switched to the high-density sedimentation tank to remove the suspended solids, and then the effluent is introduced into the ozone catalytic oxidation tower to further remove the refractory COD in the wastewater, and then the effluent is introduced into the degassing tank to remove the residual ozone, and then discharged into the external discharge tank;

[0022] (3) The clean wastewater treatment unit is the output end of the clean wastewater, which is connected with the clean wastewater adjusting tank, the coagulation tank, the flocculation tank and the sedimentation tank in sequence.

[0023] In the method, the washing and decoking wastewater is sequentially subjected to the oil-water separation settling tank, the coalescence oil removal device, the impeller air floatation device and the dissolved air floatation device in sequence.

[0024] The washing and decoking wastewater is subjected to the oil-water separation settling tank for 1-3 hours, an automatic oil skimmer is arranged in the oil separation tank, the coalescence oil removal device removes most of the dispersed oil and part of the emulsified oil in the wastewater by using the large difference in affinity between the oil and water and the characteristics of the material, the oil droplets are captured on the coalescence material, gradually form an oil film, and are separated from the water under the action of the water force and the buoyancy; the coke oil separated from the coalescence oil removal device is sent to the waste oil dehydration tank for dehydration, and then sent out for disposal.

[0025] The impeller air flotation and dissolved air flotation further remove emulsified oil to make the oil content in the sewage meet the subsequent stripping ammonia feed water requirements. During the operation of the impeller air flotation machine, the gas-liquid mixing machine self-aspirates gas and forms micro-nano bubbles. The gas quantity is adjusted by controlling the number of revolutions to adapt to the fluctuation of the water quality. The gas-liquid mixing machine aspirates the gas in the air flotation machine and circulates internally. The scum formed in the process is automatically discharged by the scum scraper. The effluent of the impeller air flotation enters the dissolved air flotation. The scum of the two-stage air flotation is collected and concentrated by the scum tank and then sent to the scum dewatering unit.

[0026] Preferably, a PAC and anionic PAM dosing point are arranged at the front end of the water inlet pipeline of the impeller air flotation machine. The PAC solution is first added, mixed by the pipeline mixer, and then the anionic PAM solution is added after flowing through a pipeline with a length of 6 m in the sewage pipeline.

[0027] In the above method, the stripping ammonia is composed of an ammonia stripping tower, a reboiler, a fractionating device, a condenser, a feed preheater, a wastewater cooler, a lye tank, a concentrated ammonia water tank, and a concentrated ammonia water pump. The ammonia stripping tower is heated by steam to distill the ammonia in the washing and decoking wastewater. The ammonia gas taken from the side is condensed by the ammonia fractionating device, and the liquid phase returns to participate in the gas-liquid mass transfer. The uncondensed gas phase continues to enter the condenser to be cooled into 18% to 20% concentrated ammonia water. The wastewater at the bottom of the tower is cooled to 30 to 40°C by the cooler and then enters the next process.

[0028] The oxidation cyanide is oxidized by the alkaline chlorination method in two stages. In the first stage, the pH value of the stripping ammonia effluent is adjusted to 10 to 11, and sodium hypochlorite solution is added. The reaction time is 10 min, and the cyanide is oxidized to sodium cyanate. In the second stage, hydrochloric acid is added to adjust the pH value of the wastewater to 8.5 to 9, and sodium hypochlorite solution is continuously added to completely oxidize the cyanide to CO2 and N2. The reaction time is 5 to 15 min.

[0029] In the above method, the production wastewater in step (2) is washing and decoking wastewater pretreatment effluent, methanol rectification device wastewater, tank area equipment cleaning wastewater, tank area and automobile loading and unloading platform floor washing wastewater, initial rainwater, and plant area domestic sewage.

[0030] In the above method, the solid output ends of the sedimentation tank and the secondary sedimentation tank are connected to the sludge thickening tank and the sludge dewatering machine in sequence.

[0031] In the above method, the coagulation tank, the flocculation tank, and the sedimentation tank are used to remove part of the suspended solids in the circulating water blowdown wastewater backwash wastewater. The effluent of the sedimentation tank is sent to the external drainage tank.

[0032] Specifically as follows:

[0033] (1) Washing and decoking wastewater pretreatment of biomass gasification:

[0034] The main pollutants of the biomass gasification and washing coke wastewater are tar, NH3-N, CODcr, HCN, TP and a small amount of suspended solids. The tar is complex, containing organic pollutants such as phenol, naphthalene, pyridine, anthracene, benzene and other heterocyclic and polycyclic aromatic hydrocarbon compounds (PAHs), and exists in the wastewater in the form of unstable particles in the form of oil-in-water. The utility model adopts the process of "oil separation + coalescence oil removal + impeller air flotation + dissolved air flotation + stripping ammonia + oxidation cyanide breaking", the tar-containing wastewater is first removed from most of the floating oil through an oil separation tank, and then removed from dispersed oil and part of emulsified oil in the water through a coalescence oil removal device, the affinity of oil and water two phases to the coalescence material is greatly different, the oil droplets are captured by the coalescence material and retained on the material surface and in the gap to form an oil film, when the oil film increases to a certain thickness, the oil film falls off into larger oil droplets under the action of water force and buoyancy. The larger oil droplets after coalescence are easily separated from the water. The effluent enters two-stage air flotation (impeller air flotation + dissolved air flotation) to further remove emulsified oil so that the petroleum in the sewage is less than 30 mg / L, meeting the requirements of the water inlet of the stripping ammonia. The gas-liquid mixer of the air flotation machine can self-suck gas and form micro-nano bubbles, and the gas quantity is adjusted by controlling the number of revolutions to adapt to the fluctuation of the water quality. The tar in the oil separation tank and the coalescence oil removal device is sent to a waste oil dehydration tank, and after collection and dehydration, is sent out for disposal, and the dregs are collected and concentrated in a dregs tank and then sent to a sludge dehydration unit.

[0035] (2) Production wastewater treatment

[0036] The biomass methanol production washing and coke removal wastewater is pretreated and combined with other production wastewater for treatment, and the wastewater still has high CODcr and NH3-N concentrations after being combined, so a denitrification and decarburization process needs to be selected, and the utility model / the utility model adopts the biochemical method of "hydrolysis acidification + two-stage A / O" process for denitrification and decarburization. The production wastewater and the pretreated washing and coke removal effluent enter a production wastewater adjusting tank, the effluent of the adjusting tank enters a hydrolysis acidification tank to improve the B / C value, and then enters two-stage AO to remove most of the organic matters, ammonia nitrogen and total nitrogen in the incoming water, and then enters a secondary sedimentation tank to remove suspended solids and colloids, the effluent is lifted to a monitoring tank by a pump, and "high-density sedimentation tank + ozone catalytic oxidation tower" security facilities are arranged to further reduce the suspended solids and CODcr, and the effluent enters the monitoring tank after degassing to reach the standard.

[0037] In the technical scheme of the utility model, a steam coil is arranged in the waste oil dehydration tank to heat the waste oil, and the outside is heat-insulated, so that the waste oil is kept at a certain temperature, and the oil-water separation is further strengthened. The tank body is provided with a breather valve and a single valve, and the single valve is connected with a pipeline to convey the oil gas to a waste gas treatment facility. The waste oil after dehydration is sent out for disposal, and the wastewater is returned to the production wastewater adjusting tank.

[0038] The impeller air flotation function is further used for removing emulsified oil so that the oil content in the sewage meets the subsequent biochemical treatment water inlet requirement.

[0039] In the technical scheme of the utility model, PAC (polyaluminium chloride) and anion PAM (anionic polyacrylamide) dosing points are arranged on the front end water inlet pipeline of the impeller air flotation machine, PAC solution is first added, mixed by a pipeline mixer and then anion PAM solution is added after flowing through a certain length of pipeline in the sewage pipeline.

[0040] In the technical scheme of the utility model, the production wastewater treatment adopts a treatment process of "adjustment + hydrolysis acidification + two-stage A / O + secondary sedimentation tank + monitoring pool".

[0041] In the technical scheme of the utility model, the function of the production wastewater adjustment tank is to mix and adjust the washing and decoking pretreatment effluent and other process device wastewater to be homogeneous.

[0042] In the technical scheme of the utility model, the two-stage A / O is a two-stage anoxic-oxic denitrification and decarburization process.

[0043] In the technical scheme of the utility model, the carbon source is self-produced crude methanol of the biomass methanol production process device, and the alkalinity is sodium carbonate solution.

[0044] In the technical scheme of the utility model, the efficient sedimentation is a flocculation-coagulation-precipitation process used for removing total phosphorus and suspended solids in the production wastewater.

[0045] In the technical scheme of the utility model, the ozone catalytic oxidation uses a tower reactor with a catalyst arranged therein to further remove COD in the high-density tank effluent and improve the wastewater biodegradability.

[0046] In the technical scheme of the utility model, the degassing tank is provided with aeration facilities to realize the functions of rapid mixing of the wastewater and other clean wastewater sent to the monitoring pool from the plant and deodorization.

[0047] The utility model technical scheme, the outer drainage monitoring pool sets up pH, COD, TN, NH3, TP water quality on -line analyzer.

[0048] Beneficial effect:

[0049] The biomass methanol production wastewater treatment process provided by the utility model / utility model can effectively remove tar, ammonia nitrogen and cyanide in biomass gasification scrubbing and decoking wastewater, combine pretreated effluent and other process device wastewater for comprehensive treatment, reduce the dosage of carbon source and other reagents and related reagents and operation cost, further reduce sludge production, and ensure that the effluent meets the discharge standard. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 Biomass gasification methanol production wastewater treatment process flow chart. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the utility model / utility model technical scheme, the utility model / utility model will be described in detail below in combination with specific embodiments.

[0052] As Figure 1 A biomass gasification methanol production wastewater treatment system, the system comprises a scrubbing and decoking wastewater pretreatment unit, a production wastewater treatment unit and a clean wastewater treatment unit;

[0053] The scrubbing and decoking wastewater pretreatment unit is connected with an oil removal unit, a stripping ammonia evaporation facility 5 and an oxidation cyanide breaking process 6 in sequence at the output end of the scrubbing and decoking wastewater;

[0054] The production wastewater treatment unit is connected with a production wastewater conditioning tank 9, a hydrolysis acidification tank 10, an A / O biochemical tank 11, a secondary sedimentation tank 12 and an external drainage tank 16 in sequence at the output end of each device production wastewater;

[0055] The clean wastewater treatment unit is connected with a clean wastewater conditioning tank 17, a coagulation tank 18, a flocculation tank 19 and a sedimentation tank 20 in sequence at the output end of the clean wastewater;

[0056] The output end of the oxidation cyanide breaking process 6 is connected with the production wastewater conditioning tank 9, the output end of the sedimentation tank 20 and the secondary sedimentation tank 12 is connected with a sludge concentration tank, and the output end of the sedimentation tank 20 is connected with the external drainage tank 16.

[0057] The oil phase output end of the coalescence oil remover 2 is connected with a waste oil dehydration tank 7, and the solid phase output end of the impeller air flotation 3 and the dissolved air flotation 4 is connected with a dregs tank 8 and a dregs dehydration device.

[0058] The secondary sedimentation tank 12 has an output end connected with a high-density sedimentation tank 13, an ozone catalytic oxidation tower 14, a degassing tank 15 and a water discharge tank 16 in sequence.

[0059] The oil removal unit comprises, in sequence, an oil-water separation settling tank 1, a coalescence oil removal device 2, an impeller air floatation device 3 and a dissolved air floatation device 4.

[0060] A biomass gasification methanol production wastewater treatment process, the wastewater discharge amount and water quality of each device are shown in Table 1.

[0061] Table 1 wastewater discharge amount of each device

[0062]

[0063]

[0064]

[0065] The design water quality of the inlet and outlet of the washing and decoking wastewater pretreatment unit and the production wastewater treatment unit is shown in Table 2 and Table 3 respectively.

[0066] Table 2 design water quality parameters of the inlet and outlet of the washing and decoking wastewater pretreatment unit

[0067]

[0068]

[0069] Table 3 design water quality parameters of the inlet and outlet of the production wastewater treatment unit

[0070]

[0071] (1) Washing and decoking wastewater pretreatment

[0072] The normal water amount of the biomass gasification washing and decoking wastewater is 43.5m 3 / h, and the main pollutants are tar (978mg / L), NH3-N (200mg / L) and COD (2900mg / L), HCN (70.7mg / L) and a small amount of sulfide and suspended solids.

[0073] The wastewater flows into the treatment area under pressure, first enters the oil-water separation settling tank. The oil-water separation settling tank V = 130m 3 . The oil separation outlet water enters the coalescence oil removal device, and two devices are set, and the design scale of a single device is 40m 3 / h. After the wastewater passes through the oil separation tank and the coalescence oil removal device, the tar content is reduced from 978mg / L to 200mg / L. The water content of the oil in the coalescence oil removal device is 60%, and after dehydration in the oil dehydration tank, the water content is reduced to 5%, and the corresponding continuous oil amount is about 0.04m 3 / h.

[0074] The water from the coalescence oil remover enters two-stage air flotation. A 10% PAC solution is added to the water inlet pipeline of the impeller air flotation machine at a dosage of 80 mg / L. The wastewater and the PAC are mixed in the pipeline mixer, and then a 0.2% anionic PAM solution is added to the pipeline at a dosage of 5 mg / L after the wastewater flows through a 5-10 s wastewater pipeline length. The water from the impeller air flotation enters the second-stage dissolved air flotation, and a 60 mg / L PAC solution and a 2 mg / L PAM solution are added at the front end. The tar content in the water from the air flotation is reduced to 30 mg / L, and the water enters the ammonia stripping facility. One ammonia stripping tower with a DN1000 / 1800 and a material of 316L is provided, and a feed preheater F=200 m 2 , a reboiler F=220 m 2 , a splitter F=140 m 2 , and a wastewater cooler F=120 m 2 are provided, each of which is provided with one.

[0075] The water from the ammonia stripping enters two-stage cyanide breaking reactors. In the first stage, the pH value of the water from the ammonia stripping is adjusted to 10-11, a 5% sodium hypochlorite solution is added, and the reaction time is 10 min to oxidize cyanide to sodium cyanate. In the second stage, hydrochloric acid is added to adjust the pH value of the wastewater to 8.5-9, and a 5% sodium hypochlorite solution is continuously added to completely oxidize cyanide to CO2 and N2, and the reaction time is 15 min. The water from the cyanide breaking enters the production wastewater treatment unit.

[0076] (2) Production wastewater treatment

[0077] The pretreated biomass gasification and descaling wastewater is sent to the production wastewater homogenizing pool together with other production wastewater.

[0078] The normal water quantity of the production wastewater is 52.4 m 3 / h, and the residence time in the production wastewater homogenizing pool is 13.6 h. The homogenized water enters the hydrolysis acidification pool with a residence time of 8 h, and then enters the AO biochemical pool.

[0079] The AO biochemical pool is in parallel operation in two series and is watered by a water distribution channel. The total volume of the two series is 750 m 3 for the A pool and 2618 m 3 for the O pool, and the residence times are 14.3 h and 49 h, respectively.

[0080] The AO biochemical pool adopts a large reflux ratio, and the mixed liquid reflux ratio is 450%. The O pool of the AO biochemical pool is a four-corridor type, and the wastewater advances in the pool by plug flow.

[0081] The sludge reflux ratio of the AO biochemical pool is 100%.

[0082] Carbon source, alkalinity and nutrient salt need to be added in the AO tank. Carbon source is crude methanol produced by the process device, with a dosage of 440 mg / L, which is equivalent to 29 L / h. Alkalinity is 10% Na2CO3 solution, with a dosage of 538 mg / L, which is equivalent to 281 L / h. Nutrient salt is 5% sodium phosphate, with a dosage of about 12 L / h.

[0083] A gas distribution system and aeration system are arranged in the O tank, and micro-porous aerators are used for aeration, with a gas-water ratio of 20.

[0084] The biochemical effluent flows to the secondary sedimentation tank by itself, with a surface hydraulic load of 0.5 m 3 / (m 2 ·h) and a sedimentation time of 4 h. The amount of residual sludge is 232.7 kg / d (dry).

[0085] The effluent from the secondary sedimentation tank enters the high-density sedimentation tank, with the following parameters:

[0086]

[0087]

[0088] The effluent from the high-density tank is pumped to the ozone catalytic oxidation tower (3.6 m x 10.5 m), with a contact time of 1 h. Two 5 kg / h ozone generators are used.

Claims

1. A biomass gasification to methanol wastewater treatment system, characterized in that: The system comprises a washing and decoking wastewater pretreatment unit, a production wastewater treatment unit and a cleaning wastewater treatment unit; The washing and decoking wastewater pretreatment unit is connected with an oil removal unit, a stripping ammonia evaporation device (5) and an oxidation cyanide breaking procedure (6) in sequence at the output end of the washing and decoking wastewater; The production wastewater treatment unit is connected with a production wastewater conditioning tank (9), a hydrolysis acidification tank (10), an A / O biochemical tank (11), a secondary sedimentation tank (12) and an external discharge tank (16) in sequence at the output end of the production wastewater of each device; The cleaning wastewater treatment unit is connected with a cleaning wastewater conditioning tank (17), a coagulation tank (18), a flocculation tank (19) and a sedimentation tank (20) in sequence at the output end of the cleaning wastewater; The output end of the oxidation cyanide breaking procedure (6) is connected with the production wastewater conditioning tank (9), the output end of the sedimentation tank (20) and the secondary sedimentation tank (12) is connected with a sludge concentration tank, and the output end of the sedimentation tank (20) is connected with the external discharge tank (16).

2. The biomass gasification to methanol wastewater treatment system of claim 1, wherein: The oil phase output end of the coalescence oil remover (2) is connected with a waste oil dehydration tank (7); the solid phase output end of the impeller air flotation (3) and the dissolved air flotation (4) is connected with a scum tank (8) and a scum dehydration device.

3. The biomass gasification to methanol wastewater treatment system of claim 1, wherein: The secondary sedimentation tank (12) has another output end connected with a high-density sedimentation tank (13), an ozone catalytic oxidation tower (14), a degassing tank (15) and the external discharge tank (16) in sequence.

4. The biomass gasification to methanol wastewater treatment system of claim 1, wherein: The oil removal unit comprises an oil-water separation settling tank (1), a coalescence oil remover (2), an impeller air flotation (3) and a dissolved air flotation (4) connected in sequence.

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