Gasification and fischer-tropsch process wastewater treatment

Abstract

In a process for treating wastewater from a combined gasification and Fischer-Tropsch (F-T) process, feedstocks such as municipal solid waste are gasified in a reactor (R) and treated in a purification unit (C) that produces a first wastewater stream (first WWT stream) containing saline and inorganic contaminants. The first wastewater stream is treated in a treatment unit (T1) to remove inorganic contaminants originating from the syngas. This treatment includes a) degassing, and subsequently b) neutralizing the first wastewater stream, followed by treatment in a dissolved air flotation unit (72c) and filtration in a moving sand bed or similar device (72d) to remove solids, and a stripping process to remove ammonia. A second wastewater stream (second WWT stream) containing organic contaminants but with low salinity originates from the F-T process and is treated separately to allow for recycling within the F-T process.

Description

Technical Field

[0001] This invention relates to a method for treating wastewater from a gasification process. The gasification process is used to generate hydrocarbon fuels for use in the Fischer-Tropsch (FT) process. Background Technology

[0002] The Fischer-Tropsch process is widely used to produce fuels from carbon monoxide and hydrogen, and can be expressed by the following formula:

[0003] (2n+1)H2 + nCO → C n H 2n+2 +nH2O

[0004] The reaction is highly exothermic and catalyzed by a Fischer-Tropsch catalyst (typically a cobalt-based catalyst) under elevated temperatures (typically at least 180 °C, e.g., 200 °C or higher) and pressures (e.g., at least 10 bar). A product mixture is obtained, and n typically ranges from 10 to 120. It is desirable to minimize methane selectivity, i.e., the proportion of methane (n = 1) in the product mixture, and to maximize selectivity for C5 and higher (n ≥ 5) alkanes, typically to a level of 90% or higher. Maximizing carbon monoxide conversion is also desirable.

[0005] Hydrogen and carbon monoxide are typically used as feedstocks for syngas.

[0006] Syngas can be produced by gasifying carbonaceous materials at elevated temperatures (e.g., about 700°C or higher). Carbonaceous materials can include any carbon-containing material that can be gasified to produce syngas. Carbonaceous materials can include biomass (e.g., plant or animal matter, biodegradable waste, etc.), food resources (e.g., corn, soybeans, etc.) and / or non-food resources such as coal (e.g., low-grade coal, high-grade coal, clean coal, etc.), oil (e.g., crude oil, heavy oil, bituminous sands, shale oil, etc.), solid waste (e.g., municipal solid waste, hazardous waste), waste-derived fuel (RDF), tires, petroleum coke, garbage, waste, biogas, sewage sludge, animal manure, agricultural waste (e.g., corn stalks, switchgrass, haystacks), demolition materials, plastic materials (e.g., plastic waste), cotton gin waste, landfill gas, and mixtures of two or more of these. Carbonaceous materials can also be solid recycled fuel (SRF), which is typically derived from waste with a high calorific value from paper, cards, wood, textiles, and plastics.

[0007] Fresh syngas can be treated by steam reforming (e.g., steam methane reforming (SMR), in which methane reacts with steam in the presence of a steam methane reforming (SMR) catalyst); partial oxidation; autothermal reforming; carbon dioxide reforming; or a combination of two or more of these to adjust the molar ratio of H2 to CO. In this application, such treatment of syngas is broadly considered as part of the FT process, and any wastewater stream generated by such treatment is considered to originate from the FT process rather than from the gasification process itself.

[0008] The molar ratio of H2 to CO in fresh synthesis gas is ideally in the range of about 1.6:1 to about 2.2:1, or about 1.8:1 to about 2.10:1, or about 1.95:1 to about 2.05:1.

[0009] Fresh syngas may optionally be combined with recycled tail gas (e.g., recycled FT tail gas) that also contains H2 and CO to form a reaction mixture. The tail gas may optionally contain H2 and CO, with the molar ratio of H2 to CO ranging from about 0.5:1 to about 2:1, or from about 0.6:1 to about 1.8:1, or from about 0.7:1 to about 1.2:1.

[0010] The combined FT syngas feed (including fresh syngas combined with recycle tail gas) ideally contains H2 and CO in a molar ratio ranging from about 1:1 to about 2.1:1, or from about 1.7:1 to about 2.0:1, or from about 1.7:1 to about 1.9:1.

[0011] This invention relates, particularly but not specifically, to the treatment of wastewater from gasification processes that use municipal solid waste (MSW) or commercial and industrial waste (C&I) as gasification feedstock, which often produce wastewater with high levels of pollutants. The treatment of such wastewater and the removal of these pollutants are pressing issues.

[0012] MSW and C&I waste disposal that does not involve landfill is required.

[0013] In addition, fuels derived from renewable resources are required. For example, the Renewable Transport Fuels Convention (RTFO) mandates that more than 450,000 liters of road transport fuel supplied to UK suppliers (such as refineries and importers) each year use a certain proportion of sustainable biofuels.

[0014] The recycling of wastewater from the FT process is well-known.

[0015] Furthermore, it is known, for example, from WO2017 / 011025A and WO2017 / 039741A, that separate wastewater streams from the gasification and FT processes are treated in combined gasification and FT units utilizing MSW as feedstock. However, these patent applications do not disclose details of wastewater treatment or the removal of contaminants from the wastewater.

[0016] WO2016193337A1 discloses FT wastewater treatment, which discusses pretreatment of wastewater by distillation or steam stripping, removal of residual wax by gravity, and feeding the pretreated wastewater into an anaerobic bioreactor based on granular sludge. Apart from ion exchange or reverse osmosis, this document pays little attention to the treatment of brine streams. Summary of the Invention

[0017] In one aspect, the present invention provides a method for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, wherein an aqueous effluent from the gasification is treated with an alkali to produce a first wastewater stream, and the first wastewater stream is treated to remove inorganic contaminants present in the aqueous effluent, and a second wastewater stream, comprising water produced in the FT process and distinct from the first wastewater stream, is treated separately from the first wastewater stream to remove organic compounds.

[0018] The treated first wastewater stream can be discharged into the environment. The treated second wastewater stream can be reused in equipment using gasification and / or FT processes.

[0019] Therefore, the present invention also provides a method for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, wherein the aqueous effluent from the gasification is treated with alkali to produce a first wastewater stream, and the first wastewater stream is treated to remove inorganic contaminants present in the aqueous effluent, and a second wastewater stream comprising water produced in the FT process and different from the first wastewater stream is treated separately from the first wastewater stream to remove organic compounds, wherein the treated first wastewater stream is discharged into the environment, and the treated second wastewater stream is reused within the equipment using the gasification and / or FT process.

[0020] This offers the advantage of optimizing wastewater flow treatment. Saline inorganic wastewater is treated separately from non-salt wastewater rich in organic matter. In a preferred embodiment, this allows for the reuse of saline (fresh) water within the facility for cooling water makeup or other resources.

[0021] The first wastewater stream may, for example, contain treated aqueous effluent from any one or more of the gasification zone, partial oxidation zone, cleaning zone, and / or hydrogen to carbon monoxide ratio conversion zone (e.g., water-gas conversion zone).

[0022] In a preferred embodiment, a method for producing one or more useful products (such as, for example, long-chain hydrocarbons) is provided, comprising:

[0023] a. Gasify carbonaceous feedstock, preferably including waste and / or biomass, in the gasification zone to produce crude syngas;

[0024] b. Optionally, the crude syngas is partially oxidized in the partial oxidation zone to produce partially oxidized crude syngas;

[0025] c. At least a portion of the optionally partially oxidized crude syngas is supplied to a clean area to remove contaminants and provide clean syngas;

[0026] d. Optionally, the hydrogen to carbon monoxide ratio of the clean syngas is changed in the hydrogen to carbon monoxide ratio changing zone to produce changed clean syngas.

[0027] e. Optionally modified clean syngas is supplied to the FT reaction train to produce at least one first useful product;

[0028] F. Optionally, the first useful product is modified in a second further reaction queue to produce a second useful product.

[0029] The aqueous effluent from one or more of stages a to c is treated by degassing and subsequent neutralization, while the aqueous effluent from stages d and e (and optionally stage f) is treated separately.

[0030] It has been found that even if the raw materials are derived from MSW or C&I waste, the first wastewater stream can usually be treated economically to remove contaminants and meet regulatory requirements.

[0031] Preferably, the treated first wastewater stream is discharged into the environment.

[0032] Preferably, the process includes:

[0033] a) Degassing, and subsequently

[0034] b) Neutralization

[0035] c) Preferably clarified, and

[0036] d) Preferred filtration

[0037] First wastewater flow.

[0038] In one related aspect, the present invention provides a method for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, wherein the aqueous effluent from the gasification is treated with an alkali to produce a first wastewater stream, and the first wastewater stream is treated to remove inorganic contaminants present in the aqueous effluent, wherein the treatment includes:

[0039] a) Degassing, and subsequently

[0040] b) Neutralization,

[0041] c) Preferably clarified, and

[0042] d) Preferably, filtration

[0043] First wastewater flow.

[0044] The preliminary degassing step reduces the need for neutralization and improves the economics of the process. Acidic gases such as CO2 and SO2 are released, which would create caustic requirements without a preliminary degassing step. This also helps to maintain low salinity in the final treated effluent.

[0045] Furthermore, the wastewater treatment of the present invention has been found to be highly effective in reducing heavy metals and other pollutants in both aspects, even when using relatively dirty raw materials such as MSW or C&I waste.

[0046] Preferably, the method includes the following further steps:

[0047] c) Oxidize the dissolved or suspended components of the first wastewater stream after neutralization.

[0048] This helps remove heavy metals and reduce the chemical oxygen demand (COD) of wastewater.

[0049] Preferably, the first wastewater stream is neutralized in a reaction zone stirred by an oxidizing gas (e.g., air).

[0050] This ensures complete mixing and thus neutralization, and also makes it possible to carry out neutralization and oxidation in a single and identical reaction vessel.

[0051] In a preferred embodiment, the reaction zone is stirred by bubble aeration in the presence of a catalyst, preferably a cobalt catalyst or an ferrous catalyst, for the oxidation of one or more of sulfites, nitrites and arsenic compounds.

[0052] Preferably, the first wastewater stream is treated with activated carbon (preferably powdered activated carbon) to absorb organic compounds and / or heavy metals.

[0053] This makes it possible to significantly reduce pollutants in an economical way.

[0054] Preferably, the treated first wastewater stream undergoes a dissolved air flotation process to separate used activated carbon and other suspended solids (if present).

[0055] This process complements the treatment of activated carbon. Suspended solids typically include heavy metal oxides.

[0056] Preferably, the first wastewater stream is filtered using a sand filter, multimedia filter, or membrane filter to remove any remaining used activated carbon and suspended solids (if present).

[0057] This feature makes it possible to clarify wastewater almost completely in an economical way.

[0058] Preferably, the first wastewater stream is treated with a coagulant, preferably an aluminum or iron-based coagulant and / or a flocculation-promoting polymer, to help remove suspended solids.

[0059] This feature is particularly advantageous when combined with dissolved air flotation, as it agglomerates small particles in the effluent and facilitates their removal by dissolved air flotation. The flocculant also helps capture heavy metals.

[0060] Preferably, the first wastewater stream undergoes an air or steam stripping process, preferably under alkaline conditions, to remove ammonia. The stripped ammonia is captured and reused within the facility.

[0061] Preferably, the first wastewater stream is treated with sulfides. The sulfides can be inorganic sulfides, such as, for example, sodium sulfide, or organic sulfides, preferably heteroaromatic sulfides, and most preferably S-triazine sulfide salts, to precipitate heavy metals.

[0062] When the first wastewater stream is made alkaline, these last two characteristics are particularly advantageous when combined, as this further reduces the solubility of precipitated heavy metal complexes.

[0063] The present invention also provides an apparatus configured to perform the methods disclosed herein. This apparatus may be a combined gasification and Fischer-Tropsch (FT) unit.

[0064] Other preferred features are defined in the dependent claims.

[0065] All preferred features can be combined in any way.

[0066] Preferably, the preferred process steps and combinations thereof are performed in the order described above. Attached Figure Description

[0067] The following is for reference only to the attached diagram. Figures 1 to 4 Preferred embodiments of the invention are described by way of example, wherein:

[0068] Figure 1 This is a schematic diagram of a feedstock conditioning facility used to process MSW or C&I waste into feedstock for gasification and FT combined processes;

[0069] Figure 2 It is by using Figure 1A schematic diagram of the combined process of gasification of feedstock generated by FCF and FT;

[0070] Figure 3 It is used for processing Figure 1 A schematic diagram of unit T1 (devices 72a-72e) of the first WWT (wastewater) flow, and

[0071] Figure 4 This is a more detailed schematic diagram showing the arrangement of the degassing tank and reaction tank in unit T1. Detailed Implementation

[0072] Raw material adjustment

[0073] refer to Figure 1 The FCF shown receives bagged C&I and MSW waste from a hopper (not shown), and the bags of waste are transferred from the hopper to the bag splitter 1.

[0074] Waste from bag splitter 1 is supplied to vibrating conveyor c1, which passes under belt magnet 2 and eddy current rotor 3, which remove ferrous and nonferrous metals respectively.

[0075] During this stage, oversized items are also removed.

[0076] The processed waste is then conveyed to density separator 4, which removes high-density materials such as non-combustible glass and gravel.

[0077] The processed waste is then transferred by conveyor C2 to fine crusher 5, which reduces the particle size to 25 mm or smaller.

[0078] The reduced-size waste is then transferred to belt dryer 4 via conveyor c3, where excess moisture is removed. The dried waste (typically with a moisture content of 10 wt%) is then transferred to hopper 7 via conveyor c4.

[0079] Hopper 7 also receives solid recycled fuel (SRF), a type of waste with a slightly higher calorific value than MSW and C&I waste, and typically originates from paper, cards, wood, textiles, and plastics.

[0080] Then, the combined material from hopper 7 is transferred by crane to conveyor assembly c7, which supplies the processed raw material to baler 8.

[0081] gasification

[0082] Now for reference Figure 2 The raw materials from the baler 8 are supplied to the feeder 12, which pressurizes the raw materials to the reactor pressure and supplies them to the gasifier 21 of the reactor assembly R.

[0083] The reactor assembly R also includes a partial oxidation (POx) reactor 22 and a radiation cooler 23.

[0084] Gasifier 21 includes a steam reforming reactor combined with a deep fluidized bed, with the bed operating temperature typically between 600 and 800°C. The fluidized bed uses superheated steam to fluidize and pyrolyze the carbonaceous material of the feedstock and react it with the steam to form hydrogen, carbon monoxide, and carbon dioxide.

[0085] The syngas products from gasifier 21 are supplied to partial oxidation reactor 22, which also receives FT tail gas from FT reactor 51 as well as oxygen. Reactor 22 operates at a temperature above the ash melting point with sufficient residence time to convert tar and oil, as well as methane from the syngas, into carbon oxides, hydrogen, and water.

[0086] The syngas output from the partial oxidation reactor 22 is supplied to a cooler 23, which includes radiative and convective cooler units. The reactor 22 also produces molten ash that solidifies in the cooler 23.

[0087] The HRSG (Heat Recovery Steam Generator) has a discharge stream containing slag particles from the gasifier and POX. The concentration of suspended solids in this stream is relatively high, so it is fed directly to the sludge dewatering centrifuge 72e (a centrifuge instead of a hydrocyclone) to remove most of the solids before co-treatment with the remaining brine in the liquid phase.

[0088] Cooled synthesis gas from cooler 23 is supplied to venturi scrubber 31a of gas purification unit C, which further includes acid gas removal unit 31b, compressor 41 and acid gas removal unit 42.

[0089] Particulate matter is removed in a Venturi scrubber 31a, and the resulting scrubbed syngas is conveyed to a halide removal unit 31b. The halide removal unit 31b includes a packed column through which a sodium hydroxide solution absorbs hydrochloride, bromide, and fluoride. The resulting first wastewater (WWT) containing halide salts is then conveyed to a degassing tank 72a of the first water treatment assembly T1.

[0090] The syngas output from the halide removal unit 31b is compressed in the compressor 41, then cooled, and the condensate (wastewater) is then removed from the syngas and supplied to the degassing tank and then to the dissolved air flotation (DAF) unit 73a, which is discussed below.

[0091] Compressed synthesis gas from compressor 41 is supplied to acid gas removal unit 42, which operates at cryogenic and high pressure and uses methanol as a solvent to remove hydrogen sulfide, carbonyl sulfide, carbon dioxide, and trace impurities (such as hydrogen cyanide, ammonia, formic acid, and metal carbonyl compounds) that could otherwise be harmful to downstream processing units, particularly by poisoning the FT catalyst. Unit 42 preferably uses RECTISOL. TM The process involves removing dissolved impurities from the methanol solvent through progressive flash evaporation and conveying them to incinerator 45. The acid gas removal unit 42 also includes a mercury protection bed for absorbing mercury.

[0092] RECTISOL from acid gas removal unit 42 TM Liquid from the process and the conversion process in unit 43 is supplied to DAF unit 73a via a degassing tank (not shown). Acid gas from unit 42 is supplied to incinerator 45.

[0093] The absorbed carbon dioxide is regenerated and supplied to CO2 compressor 47, which discharges the purified carbon dioxide into the atmosphere and also produces polluted water, which is supplied to DAF 73a through a degassing tank (not shown).

[0094] The syngas output from the acid gas removal unit 42 is supplied to the shift reactor 43, in which the hydrogen content of the syngas is increased. The shift reactor 42 is connected to a pressure swing adsorption reactor 44, in which impurities such as carbon monoxide, carbon dioxide, methane, nitrogen, and argon are removed from the hydrogen. The liquid produced in the shift reactor 43 is supplied to a degassing tank 72a, and then to a DAF 73a.

[0095] FT synthesis

[0096] Syngas from reactor 43 is supplied to Fischer-Tropsch unit 51 via guard bed 48. FT unit 51 comprises three parallel FT reactors in a queue, each reactor consisting of a shell (pressure vessel) containing four microchannel cores. Each core consists of multiple vertically and cross-flowing microchannels.

[0097] The water produced in the FT reaction is supplied to the stripping tower 71 of the second water treatment unit T2.

[0098] The FT products from FT unit 51 are supplied to liquid reforming unit 61, which produces high-quality naphtha and synthetic paraffinic kerosene (SPK). The liquid reforming unit is configured as a circulating hydrocracker to achieve complete conversion of the FT materials while maximizing SPK yield. This is achieved through hydrocracking, hydroisomerization, and hydrotreating using appropriate catalysts.

[0099] The output of the liquid reforming unit 61 is supplied to the fractionator 62, which produces SPK as the main fuel product. Wastewater from the fractionator 62 is supplied to the stripping tower 71.

[0100] The first WWT processing

[0101] refer to Figure 2 , 3 And 4, the first WWT stream from the Venturi scrubber 31a is degassed in the degassing tank 72a. This degassing tank operates under vacuum, as... Figure 4 As shown, it is equipped with a multi-level cascaded system (CS) to allow gas to escape naturally. The degassing tank is equipped with an externally mounted mixing pump (MP) to prevent suspended solids from settling inside the tank. The tank is also benched, with the outlet pipe located at the lowest point to prevent solids from accumulating in the tank.

[0102] The exhaust gas, along with other process gases, is sent to incinerator 45. In incinerator 45, the sulfur-containing gas is burned into sulfur dioxide, and then the gas is scrubbed from the incinerator flue with sodium hydroxide solution before being released into the atmosphere.

[0103] The resulting sodium sulfite / sodium bisulfite solution is also sent to reaction vessel 72b for oxidation to sodium sulfate in the presence of a cobalt or ferrous catalyst. Reaction vessel 72b is then aerated via a coarse bubble aeration system A. Figure 4 Two blowers are used for aeration. Aeration allows for the oxidation and precipitation of substances such as sulfites / bisulfites, nitrites, and arsenic. Neutralization of the feed is accomplished by adding sodium hydroxide. Aeration also effectively mixes the tank.

[0104] The used caustic solution contains sodium sulfite and sodium bisulfite. This wastewater is mixed with degassed water from deaerator 72a and supplied to reactor 72b, where the wastewater stream is both neutralized by sodium hydroxide and oxidized by aeration. Sulfites are converted to sulfates with the aid of a cobalt or ferrous catalyst. Powdered activated carbon (PAC) is also added (see [link to Powdered activated carbon]). Figure 3 and Figure 4 This process removes residual thiols after degassing, as well as any heavy metals, phenols, cresols, or other organic compounds that may be present in the water. Cobalt(II) chloride or ferrous chloride catalyst is added to catalyze the oxidation of sulfites to sulfates. This tank, and subsequently DAF unit 72c, is subject to odor control.

[0105] The stream is then conveyed to DAF (dissolved air flotation) unit 72c. A heavy metal removal agent (TMT-15 or similar), along with a coagulant and polymer, is added to improve the capture of heavy metals and suspended solids in the DAF unit. An aluminum-based coagulant is then added to DAF unit 72c via an aluminum alum metering pump to promote coagulation.

[0106] The wash water from the downstream filtration unit 72d is also supplied to the DAF unit 72c for clarification. It is assumed that the solids in the degassed water are fine particulate matter washed out from the gasifier overhead product. To remove these very fine particles, they must aggregate into larger flocs for easier removal through clarification and filtration.

[0107] A polymer, preferably anionic polyacrylamide polymer, is added to DAF unit 72c via a polymer metering package (not shown) to promote flocculation.

[0108] TMT-15 (sodium 1,3,5-triazine-2,4,6-trithione) or similar substances are added for heavy metal precipitation, subject to emission permit restrictions. The flocculent particles float to the surface of DAF unit 72c. The solids form sludge, which is continuously scraped onto a sludge hopper (not shown) for transfer to a sludge dewatering centrifuge 72e, which produces a sludge cake for disposal.

[0109] The clarified water from DAF unit 72c is then pumped to filtration unit 72d. This provides continuous filtration. The type of filtration will vary depending on the location, depending on the effluent quality requirements.

[0110] Depending on the ammonia load in the wastewater and relevant discharge permits, an ammonia stripping system may be required between DAF unit 72c and filtration unit 72d. Ammonia can be stripped by increasing the pH value with the addition of sodium hydroxide, followed by countercurrent stripping in a packed tower using air or steam as the stripping medium.

[0111] The high total dissolved solids (TDS) level of the filtrate hinders its recirculation as cooling water makeup. Therefore, the filtrate is discharged through an effluent balance tank (not shown). Here, it is mixed with other saline waste streams, such as ion-exchange softener regenerated brine and cooling tower discharge.

[0112] The high total dissolved solids (TDS) level of the filtrate hinders its recirculation as cooling water makeup. Therefore, the filtrate is discharged through an effluent balance tank (not shown). Here, it is mixed with other saline waste streams, such as ion-exchange softener regeneration brine, and the cooling tower discharge. In this way, the treated water from filtration unit 72d is safely discharged into the environment.

[0113] Sludge from DAF unit 72c is dewatered in sludge dewatering centrifuge 72e together with POX slag / water from unit 230. The centrifuge sediment from centrifuge 72e is reprocessed in DAF unit 72c. Clarified water from DAF unit 72c is then further polished in filtration unit 72d. Ammonia stripping with air or steam may optionally be included here if required by pollution load and discharge permit conditions. The filtered (and stripped) water is then sent to an effluent balance tank (not shown), where it is mixed with other brine streams, including cooling water discharge and softener regeneration brine, before being discharged into a suitable waterway.

[0114] The saline wastewater from scrubber unit 31a (first WWT) is directed to deaeration tank 72a, which operates under vacuum. (See again...) Figure 4 The tank is equipped with a multi-level cascade system (CS) to allow the gas to escape naturally.

[0115] Reactor 72a is equipped with an externally mounted mixing pump MP to prevent suspended solids from settling inside the tank. The tank is also stepped, with the outlet pipe located at the lowest point to prevent solids from accumulating in the tank.

[0116] The exhaust gas from the tank is directed to incinerator 45. The degassed water is then conveyed forward to reaction vessel 72b for neutralization, oxidation, and adsorption. In incinerator 45, the sulfur-containing gas is burned to sulfur dioxide, which is then scrubbed from the incinerator flue with a sodium hydroxide solution. The resulting sodium sulfite / sodium bisulfite solution is also sent to reaction vessel 72b for oxidation to sodium sulfate in the presence of a cobalt or ferrous catalyst.

[0117] Reactor 72b is aerated using two blowers via a coarse bubble aeration system A. Aeration allows for the oxidation and precipitation of substances such as sulfites / bisulfites, nitrites, and arsenic. Neutralization of the feed is accomplished by adding sodium hydroxide. Aeration also effectively mixes the contents of the reactor.

[0118] Powdered activated carbon (PAC) can also be added to remove residual thiols after degassing, as well as certain heavy metals, phenols, cresols, or other organic compounds that may be present in the water. Cobalt(II) chloride or ferrous chloride catalyst is added to catalyze the oxidation of sulfites to sulfates. This tank, and the subsequent DAF unit 72c, is subject to odor control.

[0119] Table 1 below shows the range of selected contaminants that the first water treatment component T1 can treat.

[0120] Table 1

[0121]

[0122] *Includes As, Hg, Ni, Cd, Cu, Pb, Cr, Co, Ga, Mo, V, and Zn.

[0123] The handling of the second WWT

[0124] As described above, process water from FT unit 51 and fractionation unit 62 is sent to stripping tower 71.

[0125] The combined process water feed stream (second WWT stream) is first preheated and then flows downwards through the packed / tray stripping section, where it comes into contact with rising steam. The steam stream is proportionate to the feed stream. The steam volatilizes most of the organic contents in the feed, resulting in a bottom water stream containing a small amount of hydrocarbons. This bottom stream is arranged to preheat the feed stream. The bottom stream is further cooled in an outlet cooler (not shown).

[0126] Cooled stripping water is fed through DAF feed tank 73a to DAF unit 73b for further treatment. DAF feed tank 73a receives wastewater streams from compressor 41, gas removal unit 42, shift reactor 43, and CO2 compressor 47. These additional streams are degassed before entering the tank to release entrained gases, including carbon dioxide.

[0127] The aforementioned DAF component removes any remaining free oil and any residual solids from the combined stream.

[0128] The feed is first pH-corrected with sodium hydroxide before being supplied to the DAF coagulation zone. A coagulant, such as aluminum sulfate, is added to coagulate solids and oil droplets into larger particles, thereby separating them from the aqueous phase.

[0129] Air for the DAF process is supplied by a dedicated compressor (not shown). The air is dissolved under pressure into the recirculating water flow in a contactor (not shown), and the aerated water is depressurized as it mixes with the incoming feed to generate microbubbles. These bubbles adhere to the aggregated particles and cause them to float to the top of DAF unit 73b, where they are removed as sludge by a skimmer (not shown) and fed into a built-in sludge hopper (not shown). The sludge is then transported off-site by tanker truck.

[0130] Clarified water from DAF unit 73b is pumped to membrane bioreactor (MBR) 73c, which is supplied with nutrients and converts organic pollutants into microbial sludge, which can be transferred to a wastewater treatment plant or other off-site or on-site sludge treatment facilities.

[0131] Purified water from MBR 73c is given anti-corrosion, antimicrobial, and anti-deposition chemicals in metering unit 84a, and then supplied to cooling tower 84b for cooling. The treated cooling water is then supplied to the units that need cooling.

[0132] Cooling water is used for the following purposes:

[0133] • Ash treatment (not shown)

[0134] ·Vapor 21

[0135] • Gas purification unit C

[0136] • Shift reactor 43

[0137] ·Incinerator 45

[0138] ·FT Unit 51

[0139] · Fractional distillation 62

[0140] • Wastewater treatment units T1 and T2.

Claims

1. A method for treating wastewater from a combined gasification and Fischer-Tropsch process, wherein an aqueous effluent from the gasification is treated with an alkali to produce a first wastewater stream and a second wastewater stream, and the first wastewater stream is treated to remove inorganic contaminants present in the aqueous effluent, the second wastewater stream comprising water produced in the FT process and distinct from the first wastewater stream, the second wastewater stream being treated separately from the first wastewater stream to remove organic compounds, wherein the treated first wastewater stream is discharged into the environment and the treated second wastewater stream is reused within equipment used in the gasification and / or FT process, and wherein the gasification comprises the gasification of carbonaceous materials, the carbonaceous materials comprising waste and / or biomass.

2. The method of claim 1, wherein the processing comprises: a) Degassing, and subsequently b) Neutralize the first wastewater flow.

3. The method according to claim 2, wherein the treatment further comprises c) clarifying the first wastewater stream.

4. The method according to claim 2 or 3, wherein the treatment further includes d) filtering the first wastewater stream.

5. The method of claim 2, further comprising the following steps: c) Dissolved or suspended components of the first wastewater stream neutralized by oxidation.

6. The method of claim 2, wherein the first wastewater stream is neutralized in a reaction zone stirred by an oxidizing gas.

7. The method according to claim 6, wherein the reaction zone is aerated and stirred in the presence of a catalyst to oxidize one or more of sulfites, nitrites and arsenic compounds.

8. The method according to claim 7, wherein the catalyst is a cobalt or iron catalyst.

9. The method according to claim 1, wherein the first wastewater stream is treated with activated carbon to absorb organic compounds and / or heavy metals.

10. The method of claim 9, wherein the treated first wastewater stream undergoes a dissolved air flotation process to separate used activated carbon and other suspended solids.

11. The method according to claim 9 or 10, wherein the first wastewater stream is filtered by a moving bed sand filter, or a multi-media filter, or a membrane filter to remove any remaining used activated carbon and suspended solids.

12. The method according to claim 2, wherein the first wastewater stream is treated with a coagulant to remove suspended solids.

13. The method according to claim 1, wherein the first wastewater stream is subjected to an air stripping process or a steam stripping process to remove ammonia.

14. The method of claim 1, wherein the first wastewater stream is treated with sulfides to precipitate heavy metals.

15. The method of claim 1, wherein a second wastewater stream, which contains water generated in the FT process and is different from the first wastewater stream, is cooled and subsequently used to cool equipment used in the gasification and / or FT process.

16. The method of claim 1, wherein the gas extracted from the first wastewater stream and / or the second wastewater stream is recycled to one or both of the incinerator and the sulfur scrubber.

17. The method of claim 1, wherein a second wastewater stream, which contains water generated in the FT process and is different from the first wastewater stream, is subjected to: a) Steam stripping to remove volatile organic compounds, and subsequently b) Dissolved air flotation to remove organic components with low volatility.

18. The method of claim 17, wherein the second wastewater stream is treated with an aluminum-based coagulant and / or a flocculation-promoting polymer to remove suspended solids.

19. The method according to any one of claims 15, 17 and 18, wherein the second wastewater is passed through a membrane bioreactor.

20. The method of claim 1, wherein commercial and industrial waste and / or municipal solid waste are treated to form feedstock for the gasification process.

21. A method for preparing one or more useful products according to any one of claims 1-20, comprising: a. Gasifying carbonaceous material in a gasification zone to produce crude syngas, the carbonaceous material comprising waste and / or biomass; b. Supply at least a portion of the crude syngas to a clean area to remove contaminants and provide clean syngas; c. Supply the clean syngas to the FT reaction queue to produce at least one first useful product; The aqueous effluent from one or more of stages a to b is treated by degassing and subsequent neutralization, while the aqueous effluent from stage c is treated separately.

22. The method of claim 21, wherein, The method further includes: The crude syngas from step a) is partially oxidized in a partial oxidation zone to produce partially oxidized crude syngas; and / or The hydrogen to carbon monoxide ratio of the clean syngas from step b) is shifted in a hydrogen to carbon monoxide ratio shifting zone to produce shifted clean syngas; and / or In a second further reaction queue, the first useful product from step c) is modified to produce a second useful product.

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