Gasification and Fischer-Tropsch Process Wastewater Treatment

Abstract

In a method for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, a feedstock, such as municipal solid waste, is gasified in a reactor (R) and processed in a purification unit (C) to produce a first wastewater stream (1st WWT Stream) containing salts and inorganic contaminants. The first wastewater stream is treated in a treatment unit (T1) to remove inorganic contaminants derived from the synthesis gas. This treatment includes a) degassing, followed by b) neutralization of the first wastewater stream prior to treatment in a dissolved air flotation unit (72c) and filtration in a moving sand bed (72d) to remove solids and ammonia. A second wastewater stream (2nd WWT Stream), containing organic contaminants but with less salt content, resulting from the FT process is treated separately to allow reuse within the FT process.

Description

[Technical Field]

[0001] The present invention relates to a process for treating wastewater from a gasification process used to produce feedstock for the Fischer-Tropsch (FT) process for producing hydrocarbon fuels. [Background technology]

[0002] The Fischer-Tropsch process is a widely used method for producing fuel from carbon monoxide and hydrogen and can be represented by the following equation: (2n + 1)H2+ nCO → C n H 2n+2 + nH2O

[0003] The reaction is highly exothermic and is catalyzed by a Fischer-Tropsch catalyst (usually a cobalt-based catalyst) under conditions of high temperature (usually at least 180°C, e.g., 200°C or higher) and pressure (e.g., at least 10 bar). A product mixture is obtained, where n typically ranges from 10 to 120. It is preferred to minimize methane selectivity, i.e., the proportion of methane (n=1) in the product mixture, and maximize selectivity to C5 and higher paraffins (n≧5), typically at levels above 90%. It is also desirable to maximize carbon monoxide conversion.

[0004] The source of hydrogen and carbon monoxide is typically synthesis gas.

[0005] Syngas may be produced by gasifying carbonaceous materials at high temperatures, e.g., about 700°C or higher. The carbonaceous materials may be composed of any carbon-containing material that can be gasified to produce syngas. Carbonaceous materials include biomass (e.g., plant or animal matter, biodegradable waste, etc.), food sources (e.g., corn, soybeans, etc.), and / or non-food sources such as coal (e.g., low-rank coal, high-rank coal, clean coal, etc.), petroleum (e.g., crude oil, heavy oil, tar sands oil, shale oil, etc.), solid waste (e.g., municipal solid waste, hazardous waste), refuse-derived fuel (RDF), tires, petroleum coke, garbage, biogas, sewage sludge, animal waste, agricultural waste (e.g., corn stover, switchgrass, grass clippings), construction demolition, plastic materials (e.g., plastic waste), cotton ginning, landfill gas, mixtures of two or more of these, etc. The carbonaceous material may also be solid recovered fuel (SRF), which is a waste product with a relatively high calorific value typically obtained from paper, card, wood, textiles, and plastics. Summary of the Invention

[0006] Fresh syngas may be processed to adjust the molar ratio of H to CO by steam reforming (e.g., a steam methane reforming (SMR) reaction in which methane is reacted with steam in the presence of an SMR catalyst); partial oxidation; autothermal reforming; carbon dioxide reforming; or a combination of two or more thereof. For purposes of this application, such processing of syngas is broadly considered to be part of the FT process, and any wastewater stream resulting from such processing is considered to be a wastewater stream from the FT process, and not from such a gasification process.

[0007] The molar ratio of H2 to CO in the fresh syngas desirably ranges from about 1.6:1 to about 2.2:1, or from about 1.8:1 to about 2.10:1, or from about 1.95:1 to about 2.05:1.

[0008] The fresh syngas can optionally be combined with recycled tail gas (e.g., recycled FT tail gas) containing H and CO to form a reactant mixture. The tail gas optionally contains H and CO, and the molar ratio of H to CO can be 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.

[0009] The combined FT syngas feed (comprising fresh syngas in combination with recycled tail gas) desirably comprises 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.

[0010] The present invention relates to the treatment of wastewater from gasification processes that utilize municipal solid waste (MSW) or commercial and industrial waste (C&I) as gasification feedstock, particularly, but not exclusively, wastewater that tends to contain high levels of contaminants. Treatment of such wastewater and removal of contaminants has become an urgent issue.

[0011] There is demand for landfill-free disposal of MSW and C&I waste.

[0012] Additionally, there is demand for fuels derived from renewable sources. For example, the Renewable Transport Fuel Obligation (RTFO) requires UK road transport fuel suppliers (such as refiners and importers) that produce more than 450,000 litres per year to use a certain percentage of sustainable biofuels.

[0013] It is known to reuse the waste liquid of the FT process.

[0014] Furthermore, it is known, for example from WO2017 / 011025A and WO2017 / 039741A, to treat separate wastewater streams from the gasification and FT processes in a combined gasification and FT plant using MSW as a feedstock, however these patent applications do not disclose details of the wastewater treatment or the contaminants to be removed from the wastewater.

[0015] FT wastewater treatment is disclosed in WO2016193337A1, which discusses pretreating wastewater by distillation or steam stripping, removing residual wax by gravity, and feeding the resulting pretreated wastewater into a granular sludge-based anaerobic bioreactor. The document makes little mention of saltwater treatment other than ion exchange or reverse osmosis membranes.

[0016] In one aspect, the invention provides a process for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, comprising treating an aqueous effluent from the gasification with alkali to produce a first wastewater stream, treating the first wastewater stream to remove inorganic contaminants present in the aqueous effluent, and treating a second wastewater stream, different from the first wastewater stream and comprising water produced in the FT process, separately from the first wastewater stream to remove organic compounds.

[0017] The treated first wastewater stream may be discharged to the environment, and the treated second wastewater stream may be reused within the plant where it is utilized in the gasification and / or FT process.

[0018] Accordingly, the present invention also provides a process for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, comprising treating an aqueous wastewater from the gasification with alkali to produce a first wastewater stream, treating the first wastewater stream to remove inorganic contaminants present in the aqueous wastewater, treating a second wastewater stream comprising water produced in the FT process and different from the first wastewater stream separately from the first wastewater stream to remove organic compounds, wherein the treated first wastewater stream is discharged to the environment, and wherein the treated second wastewater stream is reused within the plant for use in the gasification and / or FT process.

[0019] This allows for optimal treatment of the wastewater stream: salty inorganic wastewater is treated separately from salt-free organic wastewater, which in a preferred embodiment allows for the reuse of salt-free (fresh) water within the facility for cooling water production or other resources.

[0020] The first wastewater stream may be comprised of, for example, treated aqueous effluent from any one or more of the gasification zone, partial oxidation zone, clean-up zone, and / or hydrogen / carbon monoxide ratio shift zone (e.g., water-gas shift zone).

[0021] In a preferred embodiment, the following method is provided: the below described: a. gasifying a carbonaceous feedstock, preferably comprising waste and / or biomass, in a gasification zone to produce a synthesis feedstock gas; b. optionally partially oxidizing the feed syngas in a partial oxidation zone to produce a partially oxidized feed syngas; c. feeding at least a portion of the optionally partially oxidized feed syngas to a cleaning zone to remove contaminants and provide a clean syngas; d. Optionally, shifting the hydrogen / carbon monoxide ratio of the clean syngas in a hydrogen / carbon monoxide ratio shift zone to produce a shifted clean syngas. e. Feeding the optionally shifted clean synthesis gas to a FT reaction system to produce at least one first useful product. f. optionally upgrading the first useful product in a second further reaction system to produce a second useful product; 1. A method for the production of one or more useful products (e.g., long chain hydrocarbons, etc.), comprising: The method, wherein the aqueous effluent from one or more of steps a. to c. is treated by degassing and subsequent neutralization, and the aqueous effluents from steps d. and e. (and optionally step f.) are treated separately.

[0022] Even when the feedstock is derived from MSW or C&I waste, it has generally been found that the primary wastewater stream can be economically treated to remove contaminants to meet regulatory requirements.

[0023] Preferably, the treated first wastewater stream is discharged to the environment.

[0024] Preferably, the process comprises: a) degassing, and then b) neutralization; c) preferably clarification, and d) Preferably filtering the first waste stream.

[0025] In a related aspect, the present invention provides a process for treating an effluent from a combined gasification and Fischer-Tropsch (FT) process, wherein the aqueous effluent from the gasification is treated with alkali to produce a first effluent, and the first effluent is treated to remove inorganic contaminants present in the aqueous effluent, wherein the treatment comprises: a) degassing, and then b) neutralization; c) preferably clarification, and d) Preferably filtering the first waste stream.

[0026] Preliminary degassing improves process economics by reducing the need for neutralization, releasing acid gases such as CO2 and SO2 that would otherwise require caustic soda, and maintaining a low salinity in the final treated effluent.

[0027] Furthermore, both aspects of the wastewater treatment of the present invention have been found to be significantly effective in reducing contaminants such as heavy metals, even when using relatively dirty feedstocks such as MSW and C&I waste.

[0028] Preferably, the process comprises the following additional steps: c) oxidizing the dissolved or suspended components of the neutralized first wastewater stream;

[0029] This makes it easier to remove heavy metals and reduces the COD (chemical oxidation demand) of wastewater.

[0030] Preferably, the first wastewater stream is neutralized in a reaction zone agitated by an oxidizing gas (eg, air).

[0031] This ensures thorough mixing and neutralization. It is also possible to carry out neutralization and oxidation in the same reaction vessel.

[0032] In a preferred embodiment, the reaction zone is agitated by bubble aeration in the presence of a catalyst, preferably a cobalt or iron catalyst, for oxidizing one or more of sulfites, nitrites, and arsenic compounds.

[0033] Preferably, the first wastewater stream is treated with activated carbon (preferably powdered activated carbon) to absorb organic compounds and / or heavy metals.

[0034] This allows for a significant reduction in pollutants economically.

[0035] Preferably, the treated first wastewater stream is subjected to a dissolved air flotation process to separate spent activated carbon and other suspended matter, if present.

[0036] This process is complementary to treatment with activated carbon. The suspended solids typically contain heavy metal oxides.

[0037] Preferably, the first wastewater stream is filtered through a sand filter, a multimedia filter or a membrane filter to remove residual spent activated carbon and suspended solids, if present.

[0038] This makes it possible to economically achieve near-complete clarification of wastewater.

[0039] Preferably, the first wastewater stream is treated with a flocculant, preferably an aluminum or iron based flocculant and / or a flocculation enhancing polymer, to assist in the removal of suspended solids.

[0040] This function is particularly advantageous in combination with dissolved air flotation, as it causes small particles in the wastewater to flocculate, aiding their removal in the dissolved air flotation process. Flocculants also aid in the capture of heavy metals.

[0041] Preferably, the first wastewater stream is subjected to an air or steam stripping process, preferably under alkaline conditions, to remove ammonia, which is captured and reused within the facility.

[0042] Preferably, the first wastewater stream is treated with a sulfide compound, which may be an inorganic sulfide, such as sodium sulfide, or an organic sulfide compound, preferably a heteroaromatic sulfide, most preferably an S-triazine sulfide salt, to precipitate heavy metals.

[0043] These two features are particularly advantageous when the first wastewater is made alkaline, as this further reduces the solubility of the precipitated heavy metal complexes.

[0044] The present invention also provides a plant configured to operate the process disclosed herein, which may be a combined gasification and Fischer-Tropsch (FT) plant.

[0045] Further preferred features are defined in the dependent claims.

[0046] All preferred features can be freely combined.

[0047] Preferably, the preferred process steps and combinations thereof are carried out in the order described above. [Brief explanation of the drawings]

[0048] Preferred embodiments of the present invention will now be described, by way of example only, with reference to Figures 1 to 4 of the accompanying drawings.

[0049] [Figure 1] Figure 1 is a schematic diagram of the raw material preparation facility for treating MSW and C&I waste as raw materials for the gasification-FT combined process.

[0050] [Figure 2] Figure 2 is a schematic diagram of the gasification and FT combined process using the feedstock produced by the FCF shown in Figure 1.

[0051] [Figure 3] FIG. 3 is a schematic diagram of the unit T1 (devices 72a to 72e) used to treat the first WWT (Wastewater) stream in FIG.

[0052] [Figure 4] FIG. 4 is a schematic diagram showing in more detail the arrangement of the degassing tank and the reaction tank in unit T1. DETAILED DESCRIPTION OF THE INVENTION

[0053] Feedstock Conditioning Referring to FIG. 1 , the FCF receives bagged C&I and MSW waste from a bunker (not shown) from which the bags of waste are transferred to a bag divider 1 .

[0054] Waste from the bag divider 1 is fed onto a vibrating conveyor c1 and passes under a belt magnet 2 and an eddy current rotor 3 which remove ferrous and non-ferrous metals respectively.

[0055] Oversized items are also removed at this stage.

[0056] The treated waste is sent to a density separator 4, which removes dense, non-combustible materials such as glass and rubble.

[0057] The processed waste is transported by conveyor c2 to a fine shredder 5 where the particle size is reduced to 25 mm or less.

[0058] The downsized waste is transported by conveyor c3 to belt dryer 4 where excess moisture is removed. The dried waste (typical moisture content 10 wt%) is transported to bunker 7 by conveyor c4.

[0059] Bunker 7 also accepts solid recovered fuel (SRF), a waste product with a slightly higher calorific value than MSW or C&I waste, typically derived from paper, card, wood, textiles, and plastics.

[0060] The combined material from the bunker 7 is then transferred by crane to a conveyor assembly c7, which delivers the processed feed material to a baler 8.

[0061] Gasification Referring now to FIG. 2, the baled feedstock from baler 8 is fed to feeder 12, which pressurizes the feedstock to reactor pressure and feeds it into gasifier 21 of reactor assembly R.

[0062] The reactor assembly R further includes a partial oxidation (POx) reactor 22 and a radiative cooler 23.

[0063] The gasifier 21 includes a steam reforming reactor incorporating a deep fluidized bed, and the bed operating temperature is typically 600-800°C. The fluidized bed is fluidized with superheated steam, causing the feed carbonaceous material to pyrolyze and react with the steam to produce hydrogen, carbon monoxide, and carbon dioxide.

[0064] The syngas product of the gasifier 21 is fed to the partial oxidation reactor 22, which receives the FT tail gas from the FT reactor 51 and also receives oxygen. The reactor 22 is operated at a temperature above the ash melting point for a residence time sufficient to convert the tars and oils and methane in the syngas to carbon oxides, hydrogen and water.

[0065] The synthesis gas output of the partial oxidation reactor 22 is fed to a cooler 23, which includes a radiative cooler and a convective cooler. The reactor 22 also produces molten ash, which is solidified in the cooler 23.

[0066] The HRSG (Heat Recovery Steam Generator) has a blowdown stream of water containing slag particles from the gasifier and POX. Because this stream has a relatively high concentration of suspended solids, it is sent directly to the sludge dewatering centrifuge 72e (a centrifuge, not a cyclone) to remove most of the solids before the liquid phase is co-processed with the remaining brine.

[0067] The cooled synthesis gas from cooler 23 is fed to a venturi scrubber 31 a of a gas cleaning system C, which further includes an acid gas removal unit 31 b, a compressor 41 and an acid gas removal unit 42 .

[0068] Particulate matter is removed in the Venturi scrubber 31a, and the scrubbed syngas is passed to a halide removal unit 31b, which includes a packed column through which sodium hydroxide solution is passed to absorb hydrogen chloride, bromide, and fluoride. The resulting first wastewater (WWT) stream containing halide salts is passed to a degassing tank 72a of the first water treatment assembly T1.

[0069] The synthesis gas output from the halide removal unit 31b is compressed by a compressor 41, cooled, and turned into a condensed liquid (waste liquid), which is removed from the synthesis gas and sent to a degassing tank, and then sent to a dissolved air flotation (DAF) unit 73a, which will be described later.

[0070] The compressed synthesis gas from compressor 41 is fed to acid gas removal unit 42. Acid gas removal unit 42 operates at low temperature 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 carbonyls that may be harmful to downstream process units, particularly by poisoning the FT catalyst. Unit 42 is preferably constructed using RECTISOL TM The process uses a methanol solvent, dissolved impurities are removed from the methanol solvent by staged flashing and passed to an incinerator 45. The acid gas removal unit 42 also contains a mercury guard bed for absorbing mercury.

[0071] Acid Gas Removal Unit 42 RECTISOL TM The liquid from the process and the liquid from the shift process of unit 43 are fed to DAF unit 73a via a degassing tank (not shown). The acid gas from unit 42 is fed to incinerator 45.

[0072] The absorbed carbon dioxide is regenerated and supplied to the CO2 compressor 47, which releases purified carbon dioxide into the atmosphere and produces contaminated water, which is supplied to the DAF 73a via a degassing tank (not shown).

[0073] The synthesis gas output of the acid gas removal unit 42 is fed to a shift reactor 43, which increases the hydrogen content of the synthesis gas. The shift reactor 42 communicates with a pressure swing adsorption reactor 44, which removes impurities in the hydrogen, such as carbon monoxide, carbon dioxide, methane, nitrogen, and argon. The liquid produced in the shift reactor 43 is fed to a degassing tank 72a and then to a DAF 73a.

[0074] FT synthesis The synthesis gas from reactor 43 is fed to a Fischer-Tropsch unit 51 via guard beds 48. The FT unit 51 consists of a train of three parallel FT reactors, each consisting of a shell (pressure vessel) containing four microchannel cores. Each core consists of multiple vertical and cross-flow microchannels.

[0075] The water produced in the FT reaction is supplied to a steam stripper 71 of the second water treatment assembly T2.

[0076] The FT product from FT unit 51 is fed to liquid reforming unit 61, which produces high-quality naphtha and synthetic paraffinic kerosene (SPK). The liquid reformer is configured as a recycle hydrocracker to achieve full conversion of the FT feedstock while maximizing SPK production. This is achieved through hydrocracking, hydroisomerization, and hydrotreating using appropriate catalysts.

[0077] The output of the liquid upgrading unit 61 is fed to a fractionator 62 which produces SPK as the primary fuel product. The contaminated water from the fractionator 62 is fed to a steam stripper 71.

[0078] First WWT processing Referring to Figures 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 and is equipped with a multi-stage cascade system CS to allow natural gas escape, as shown in Figure 4. The degassing tank is also equipped with an external mixer pump MP to prevent suspended solids from settling within the tank. The tank is bench-type, with the outlet piping located at the bottom to prevent solids from accumulating within the tank.

[0079] The off-gas is sent to the incinerator 45 along with other process gases. In the incinerator 45, the sulfur dioxide gas is incinerated to produce sulfur dioxide, which is then clubbed through the incinerator flue with a sodium hydroxide solution before the vent gas is released into the atmosphere.

[0080] The resulting sodium sulfite / bisulfite solution is then sent to reactor 72b, where it is oxidized to sodium sulfate in the presence of a cobalt or iron catalyst. Reactor 72b is aerated by a coarse-bubble aeration system A (Figure 4) using two fans. Aeration allows for the oxidation and precipitation of species such as sulfite / bisulfite, nitrite, and arsenic. Neutralization of the feed is achieved by the injection of sodium hydroxide. Aeration also provides effective mixing within the tank.

[0081] The spent caustic solution contains sodium sulfite and sodium bisulfite, and this wastewater, along with the deaerated water from deaeration tank 72a, is sent to reaction tank 72b, where the wastewater stream is both neutralized with sodium hydroxide and oxidized by aeration. The sulfite is converted to sulfate with the aid of a cobalt or iron catalyst. Powdered activated carbon (PAC) is also added to remove residual mercaptans, heavy metals, phenols, cresols, and other organics present in the water after deaeration (see Figures 3 and 4). Cobalt(II) chloride or ferrous chloride catalyst is added to catalyze the oxidation of sulfite to sulfate. This tank, like the subsequent DAF unit 72c, is odor-controlled.

[0082] The flow then passes to a DAF (Dissolved Air Flotation) unit 72c. A heavy metal trap (TMT-15 or similar) is dosed along with a flocculant and polymer to improve the capture of heavy metals and suspended solids in the DAF unit. An aluminum-based flocculant is then added to the DAF unit 72c via an alum dosing pump to promote flocculation.

[0083] Additionally, wash water from downstream filtration unit 72d is fed to DAF unit 72c for clarification. The solids in the degassed water are presumed to be finely divided soot particles washed from the gasifier overhead product. To remove these very fine particles, they must be agglomerated into larger flocs to facilitate clarification and removal by filtration.

[0084] A polymer, preferably a polyacrylamide anionic polymer, is added to DAF unit 72c via a polymer dosing package (not shown) to promote flocculation.

[0085] A compound such as TMT-15 (1,3,5-triazine-2,4,6-triathione sodium salt) is dosed in accordance with discharge permit limits for the precipitation of heavy metals. The floc particles float on the surface of DAF unit 72c. The solids form a sludge that is continuously scraped into a sludge hopper (not shown) for transfer to sludge dewatering centrifuge 72e, which produces a sludge cake for disposal.

[0086] The clarified water from the DAF unit 72c is then pumped to the filtration unit 72d, whereby continuous filtration is performed. The type of filtration is determined on a site-by-site basis depending on the discharge water quality requirements.

[0087] Depending on the ammonia load in the wastewater and the associated discharge permit, an ammonia stripping system may be required between the DAF unit 72c and the filtration unit 72d. The ammonia can be back-extracted by dosing with sodium hydroxide to raise the pH, followed by countercurrent back-extraction in a packed column with either air or steam as the backflow medium.

[0088] The filtrate cannot be reused as cooling water make-up due to its high total dissolved solids (TDS) levels, so it is discharged through a wastewater balancing tank (not shown), where it is mixed with other salt-containing waste streams, such as ion exchange softener regeneration brine and cooling tower blowdown.

[0089] The filtrate cannot be reused as cooling water make-up due to its high total dissolved solids (TDS) levels. Therefore, the filtrate is discharged through a wastewater balancing tank (not shown), where it is blended with other salt-containing waste streams, such as ion exchange softener regeneration brine and cooling tower blowdown. In this manner, the treated water from filtration unit 72d can be safely discharged to the environment.

[0090] The sludge from DAF unit 72c, along with the POX slag / water from unit 230, is dewatered in sludge dewatering centrifuge 72e. The centrate from centrifuge 72e is reprocessed in DAF unit 72c. The clarified water from DAF unit 72c is then further refined 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 filter (and stripping) water is then sent to a wastewater balancing tank (not shown) where it is mixed with other brine streams, including cooling water blowdown and softener regeneration brine, before being discharged to an appropriate waterway.

[0091] The saline wastewater from the scrubber unit 31a (first WWT) is led to a degassing tank 72a operating under vacuum. Referring again to Figure 4, the tank is fitted with a multi-stage cascade system CS to allow natural escape of gases.

[0092] The reactor 72a is equipped with an external mixer pump MP to prevent suspended solids from settling inside the tank. The outlet piping is a bench type with the lowest position to prevent solids from accumulating inside the tank.

[0093] The tank vent is sent to incinerator 45. Degassed water is passed forward to reactor 72b for neutralization, oxidation, and adsorption. In incinerator 45, sulfur dioxide gas is incinerated to sulfur dioxide, which is scrubbed from the incinerator flue with aqueous sodium hydroxide. The resulting sodium sulfite / bisulfite solution is sent to reactor 72b where it is oxidized to sodium sulfate in the presence of a cobalt or iron catalyst.

[0094] Reactor 72b is aerated by a coarse bubble aeration system A using two blowers. Aeration allows for oxidation and precipitation of species such as sulfite / bisulfite, nitrite, and arsenic. Neutralization of the feed is achieved by injection of sodium hydroxide. Aeration also provides effective mixing within the tank.

[0095] Powdered activated carbon (PAC) is used to remove residual mercaptans after degassing, as well as heavy metals, phenols, cresols, and other organics present in the water. Cobalt(II) chloride or ferrous chloride catalyst is dosed to catalyze the oxidation of sulfite to sulfate. This tank, like the subsequent DAF unit 72c, is odor-controlled.

[0096] The range of selected contaminants that can be addressed by the first water treatment assembly T1 is shown in Table 1 below.

[0097] [Table 1]

[0098] Processing the second WWT The treated water from the FT unit 51 and fractionation unit 62 is sent to the steam stripper 71 as described above.

[0099] The combined process water feed stream (second WWT stream) is first preheated and then flows through a packed / traded tower stripping section where it is contacted with rising steam. The steam flow rate is set in proportion to the feed flow rate. The steam volatilizes the organic matter in the feed, producing a bottoms stream of water containing small amounts of hydrocarbons. The bottoms stream is positioned to preheat the feed stream. The bottoms stream is further cooled in a wastewater cooler (not shown).

[0100] The cooled stripped water is sent to DAF unit 73b via DAF feed tank 73a for further processing. 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.

[0101] The DAF assembly described above removes any remaining free oil from the combined stream and also removes any remaining solids.

[0102] The feed is first pH adjusted with sodium hydroxide and then fed to the DAF flocculation zone, where a flocculant such as aluminum sulfate is added to cause the solids and oil droplets to aggregate into larger particles that separate from the aqueous phase.

[0103] Air for the DAF process is supplied by a dedicated compressor (not shown). This air is pressurized and dissolved in the reclaimed water stream in a contactor (not shown). When mixed with the inlet feed, the aerated water is decompressed, creating microscopic air bubbles. These bubbles attach to the flocculants and rise to the top of the DAF unit 73b, where they are removed as sludge by a skimmer (not shown) into an on-board sludge hopper (not shown). The sludge is then transported off-site by tanker.

[0104] The clarified water from the DAF unit 73b is pumped to a membrane bioreactor (MBR) 73c, which is fed with nutrients and converts organic contaminants into microbiological sludge, which can then be transported to a sewerage plant or other off-site or on-site sludge treatment facility.

[0105] The pure water from the MBR 73c is dosed with anti-rust, anti-bacterial and anti-deposition chemicals in a dosing unit 84a and then fed to a cooling tower 84b where it is cooled before the treated cooling water is fed to the units that require cooling.

[0106] Cooling water users include: Ash handling (not shown) Gasifier 21 Gas Purification Equipment C Shift Reactor 43 Incinerator 45 FT Unit 51 Fractionation 62 Wastewater treatment equipment T1, T2.

[0107] The following is further disclosed in relation to the present invention. [1] 1. A method for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, comprising: treating the aqueous wastewater from the gasification with alkali to produce a first wastewater stream; treating the first wastewater stream to remove inorganic contaminants present in the aqueous wastewater; treating a second wastewater stream, the second wastewater stream comprising water produced by the FT process and different from the first wastewater stream, separately from the first wastewater stream to remove organic compounds; The method, wherein the treated first wastewater stream is discharged to the environment and the treated second wastewater stream is reused within the plant for use in gasification and / or FT processes. [2] The process a) Degassing, and then b) neutralizing the first waste stream; The method according to [1], comprising: [3] The method of claim 2, wherein the treating further comprises: c) clarifying the first wastewater stream. [4] The method of [2] or [3], wherein the treating further comprises d) filtering the first wastewater stream. [5] Further steps as follows: c) oxidizing the dissolved or suspended components of the neutralized first wastewater stream; The method according to any one of [2] to [4], comprising: [6] The method according to any one of [2] to [5], wherein the first wastewater stream is neutralized in a reaction zone agitated by an oxidizing gas. [7] [6] The method according to [6], wherein the reaction zone is agitated by bubble aeration in the presence of a catalyst to oxidize one or more of sulfites, nitrites and arsenic compounds. [8] The method according to [7], wherein the catalyst is a cobalt catalyst or an iron-based catalyst. [9] Any of the preceding methods, wherein the first wastewater stream is treated with activated carbon to absorb organic compounds and / or heavy metals.

[10] The method according to [9], wherein the treated first wastewater stream is subjected to a dissolved air flotation step to separate spent activated carbon and other suspended solids.

[11] The method of [9 or

[10] , wherein the first wastewater stream is filtered through a moving bed sand filter, or a multimedia filter, or a membrane filter to remove the remaining spent activated carbon and suspended solids.

[12] The method according to any one of [2] to

[11] , wherein the first wastewater stream is treated with a flocculant to remove suspended solids.

[13] Any of the preceding methods, wherein the first wastewater stream is subjected to an air stripping process or a steam stripping process to remove ammonia.

[14] Any of the preceding methods, wherein the first wastewater stream is treated with sulfide to precipitate heavy metals.

[15] 10. The method of claim 9, wherein a second wastewater stream comprising water produced in the FT process and different from the first wastewater stream is cooled and then used to cool a plant utilized in the gasification and / or FT process.

[16] Any of the preceding methods, wherein gas extracted from the first wastewater stream and / or the second wastewater stream is recycled to one or both of the incinerator and sulfur scrubber.

[17] A second wastewater stream comprising water produced in the FT process and different from the first wastewater stream, comprising: a) steam stripping to remove volatile organic components, followed by b) Dissolved air flotation to remove less volatile organic components; Any of the preceding methods, wherein the method is subjected to

[18]

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

[19] The method of any of

[15] ,

[17] and

[18] , wherein the second wastewater stream is passed through a membrane bioreactor.

[20] Any of the preceding methods, wherein commercial and industrial waste (C&I) and / or municipal solid waste (MSI) is processed to form a feedstock for the gasification process.

[21] the below described: a. gasifying a carbonaceous feedstock, including waste and / or biomass, in a gasification zone to produce a synthetic feedstock gas; b. optionally partially oxidizing the feed syngas in a partial oxidation zone to produce a partially oxidized feed syngas; c. feeding at least a portion of the optionally partially oxidized feed syngas to a cleaning zone to remove contaminants and provide a clean syngas; d. Optionally, shifting the hydrogen / carbon monoxide ratio of the clean syngas in a hydrogen / carbon monoxide ratio shift zone to produce a shifted clean syngas. e. Feeding the optionally shifted clean synthesis gas to a FT reaction system to produce at least one first useful product. f. optionally upgrading the first useful product in a second further reaction system to produce a second useful product; A method according to any one of [1] to

[20] for the production of one or more useful products, comprising: The method, wherein the aqueous effluent from one or more of steps a. to c. is treated by degassing and subsequent neutralization, and the aqueous effluents from steps d. and e. (and optionally step f.) are treated separately.

[22] A combined gasification and Fischer-Tropsch (FT) plant configured to operate according to any of the methods described in [1] to

[21] .

Claims

1. 1. A method for treating wastewater from a combined gasification and Fischer-Tropsch (FT) process, comprising: treating the aqueous wastewater from the gasification with alkali to produce a first wastewater stream; treating the first wastewater stream to remove inorganic contaminants present in the aqueous wastewater; treating a second wastewater stream, the second wastewater stream comprising water produced by the F-T process and different from the first wastewater stream, separately from the first wastewater stream to remove organic compounds; the treated first wastewater stream is discharged to the environment and the treated second wastewater stream is reused within the plant for gasification and / or F-T process utilization; The method, wherein the gasification comprises gasifying a carbonaceous feedstock comprising waste and / or biomass.

2. The treatment of the first wastewater stream to remove inorganic contaminants present in the aqueous wastewater comprises: a) Degassing, and then b) neutralizing the first wastewater stream The method of claim 1 , comprising:

3. 3. The method of claim 2, wherein said treating further comprises c) clarifying said first wastewater stream.

4. 4. The method of claim 2 or claim 3, wherein the treating further comprises: d) filtering the first wastewater stream.

5. Further steps as follows: bi) oxidizing the dissolved or suspended components of the neutralized first wastewater stream; The method according to any one of claims 2 to 4, comprising:

6. The method of any one of claims 2 to 5, wherein the first wastewater stream is neutralized in a reaction zone agitated by an oxidizing gas.

7. 7. The method of claim 6, wherein the reaction zone is agitated by bubble aeration in the presence of a catalyst to oxidize one or more of sulfites, nitrites, and arsenic compounds.

8. 8. The process of claim 7, wherein the catalyst is a cobalt catalyst or an iron-based catalyst.

9. The method of any one of claims 1 to 8, wherein the first wastewater stream is treated with activated carbon to absorb organic compounds and / or heavy metals.

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

11. 11. The method of claim 9 or claim 10, wherein the first wastewater stream is filtered through a moving bed sand filter, or a multimedia filter, or a membrane filter to remove residual spent activated carbon and suspended solids.

12. The method of any one of claims 2 to 11, wherein the first wastewater stream is treated with a flocculant to remove suspended solids.

13. The method of any one of claims 1 to 12, wherein the first wastewater stream is subjected to an air stripping process or a steam stripping process to remove ammonia.

14. The method of any one of claims 1 to 13, wherein the first wastewater stream is treated with sulfide to precipitate heavy metals.

15. 15. The method of any one of claims 1 to 14, wherein a second wastewater stream comprising water produced in the FT process and different from the first wastewater stream is cooled and then used to cool a plant utilized in the gasification and / or FT process.

16. 16. The method of any one of claims 1 to 15, wherein 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. A second wastewater stream comprising water produced in the FT process and different from the first wastewater stream, comprising: a) steam stripping to remove volatile organic components, followed by b) Dissolved air flotation to remove less volatile organic components; The method according to any one of claims 1 to 16, wherein the

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

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

20. 20. The method of any one of claims 1 to 19, wherein commercial and industrial waste (C&I) and / or municipal solid waste (MSI) is processed to form feedstock for the gasification process.

21. the below described: a. gasifying a carbonaceous feedstock, including waste and / or biomass, in a gasification zone to produce a syngas; b) feeding at least a portion of the feed syngas to a purification zone to remove contaminants and provide a clean syngas; c. feeding the clean synthesis gas into an FT reaction system to produce long chain hydrocarbons; 21. A method according to any one of claims 1 to 20 for the production of one or more long chain hydrocarbons, comprising: The method, wherein the aqueous effluent from one or more of steps a. to b. is treated by degassing and subsequent neutralization, and the aqueous effluent from step c. is treated separately.

22. Partially oxidizing a feed syngas in a partial oxidation zone to produce a partially oxidized feed syngas; 22. The method of claim 21 further comprising:

23. Shifting the hydrogen / carbon monoxide ratio of the clean synthesis gas in a hydrogen / carbon monoxide ratio shift zone to produce a shifted clean synthesis gas; 23. The method of claim 21 or 22, further comprising:

24. Upgrading the long chain hydrocarbons in a second further reaction system to produce high quality naphtha and synthetic paraffinic kerosene. The method of any one of claims 21 to 23, further comprising:

25. A combined gasification and Fischer-Tropsch (FT) plant configured to operate the method of any one of claims 1 to 24.

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