Method and system for treating waste materials

Abstract

A method for treating waste material, including human and / or animal digestive waste and / or plant-derived waste, is provided. The method includes receiving a waste material input into a reactor pressure vessel, heating and pressurizing the reactor pressure vessel to perform a hydrothermal carbonization process on the waste material, separating a liquid portion from a solid component of a product produced through the hydrothermal carbonization process, and performing a gasification and / or pyrolysis process on the solid component to produce synthesis and / or pyrolysis gases. A system for performing the method is also provided.

Description

[Technical Field]

[0001] SUMMARY OF THE DISCLOSURE The present disclosure relates to methods and systems for treating waste materials. [Background technology]

[0002] In the UK, the involuntary release of untreated sewage into lakes, rivers and oceans through combined storm overflows (CSOs) has become a significant problem, causing highly harmful pollution to the environment and the public. This problem is exacerbated by population growth and rapid urbanization, which will increase the amount of sewage sludge generated. Sustainable and efficient sludge disposal is absolutely necessary for a resilient, strong and sustainable society, especially one that aspires to a circular economy.

[0003] In highly industrialized societies, sewage waste is treated in wastewater treatment plants. A portion of the solid portion of the waste is collected as it reaches the treatment plant; this portion is called primary sludge. The remainder, which makes up the majority of the sludge, is "principally" fed to bacteria. The bacteria are very efficient at consuming the waste, converting as much as 80% of it into biomass (secondary sludge), which also must be disposed of. Overall, the disposal of primary and secondary sludge can account for 60% of a wastewater treatment plant's operating costs.

[0004] Sewage waste is also a significant problem in remote areas not connected to modern sewerage infrastructure. In rural areas of industrialized countries or urban areas of low- and middle-income countries (LMICs), on-site sanitation systems (OSS) are preferred. In OSS, fecal sludge must be stored locally and collected, making its disposal problematic and expensive. Disposal of such sludge is complicated by the fact that, on the one hand, it is a resource rich in energy, nitrogen, and phosphorus. On the other hand, these sludges are pollutants, containing a wide range of micropollutants, including powerful oxygen-depleting carbon sources, greenhouse gases (nitrous oxide and methane), eutrophication-inducing nutrients (nitrogen and phosphorus), pathogens, and plastics, endocrine-disrupting compounds, drug-resistance genes, and heavy metals. However, water is the most troublesome component. Raw sludge is 97–99% water, but it can be thickened to 90–95% water or actively dewatered to 15–40% solids.

[0005] The water industry has developed successful and sophisticated strategies for the disposal of biosolids, the UK industry term for both primary and secondary sludge. They are typically processed in anaerobic digesters (AD), which recover energy and reduce biomass volume. The resulting sludge is typically disposed of, and the solution must be treated. Currently, the UK produces around 8,500 tonnes of sludge per day, 87% of which is disposed of in land, which is not a robust and sustainable solution. Summary of the Invention [Problem to be solved by the invention]

[0006] While energy produced through AD is a welcome contribution to our net-zero target, some of the phosphorus may be captured by chemical precipitation, and the availability of land for sludge disposal (land banks) is a current cause for concern for the industry. Concerns about emerging pollutants and the Environment Agency's River Pollution Act may restrict land disposal. Therefore, innovative technological solutions must be developed urgently. The success of such solutions would have a significant impact on public health and the environment. [Means for solving the problem]

[0007] According to an aspect of the present disclosure, there is provided a method for treating waste material, including, for example, human and / or animal digestive waste and / or plant-derived waste, which may or may not have undergone anaerobic and / or aerobic digestion processes, pretreatment, e.g., with biological processes, and / or pretreatment steps with anaerobic, aerobic, and / or anoxic bacteria. The method includes receiving the waste material input into a reactor pressure vessel, heating and pressurizing the reactor pressure vessel to perform a hydrothermal carbonization procedure on the waste material, separating at least a portion of the liquid from the solid component (wet hydrochar) of the product produced through the hydrothermal carbonization procedure, and performing a pyrolysis and / or gasification process, e.g., pyrolysis process, on the solid component, e.g., the residual solid component, to produce synthesis gas and, optionally, pyrolysis gas, e.g., volatile hydrocarbons and / or organic compounds, e.g., respectively.

[0008] Locating hydrothermal carbonization technology upstream of thermal gasification technology is beneficial when processing biosolids, biomass, and organic matter because hydrothermal carbonization removes nitrogen-containing compounds and increases the C / O and C / H ratios of the hydrochar for subsequent gasification and production of low-NOx, high-heat-value syngas.

[0009] Positioning the hydrothermal carbonization and thermal gasification technologies in this manner retains any unhydrolyzed chemicals within the solid hydrochar fraction, which is subsequently gasified and converted into beneficial syngas and a high-ash carbon residue, thus eliminating microplastics, per- and polyfluoroalkyl substances, and antibiotics. Additionally, the generation and capture of thermal and electrical energy from the combustion of the high-heat-value syngas can be used to supply the thermal and electrical energy needs of both technologies.

[0010] By linking these two technologies, integrating the generated thermal and electrical energy as well as waste heat, and including the principle of process concentration in the design of hydrothermal carbonization reactors and expansion vessels, innovative technological solutions have been developed to address and handle the problem of contaminated sludge disposal into land banks.

[0011] The method can include drying the separated solid component (wet hydrochar) to a target moisture content. The wet hydrochar can be dried directly using a rotary dryer. The wet hydrochar can be dried, for example, using waste heat recovered from the hydrothermal carbonization stage. Waste heat in the form of hot combustion gases can be diverted to convectively dry the wet hydrochar from a starting solids content of between 40% and 70% to a final solids content of at least 90% (by mass). The waste heat can be fed directly to the rotary dryer in either a co-current or counter-current direction.

[0012] The waste material may include, for example, digested sludge produced through anaerobic and / or aerobic digestion of human and / or animal digestive waste and / or plant-derived waste. The digested sludge may be treated with a flocculant or coagulant.

[0013] The reactor pressure vessel can be heated to a reaction temperature greater than 160°C, e.g., between 160°C and 260°C, or greater than 180°C, e.g., 200°C, to carry out the hydrothermal carbonization procedure. The reactor pressure vessel can be heated at a rate between 2°C per minute and 5°C per minute for 60 to 90 minutes until the reaction temperature is reached. The reactor pressure vessel can be maintained at the reaction temperature for between 30 and 240 minutes or between 30 and 60 minutes. In one example, the reactor pressure vessel can be maintained at the reaction temperature for approximately 4 hours. The reaction temperature and pressure of the reactants in the reactor pressure vessel can be maintained to create subcritical conditions with respect to the water in the reactor pressure vessel, e.g., where the water behaves as a subcritical fluid. The reaction temperature and pressure of the reactants in the reactor pressure vessel can be configured to reduce the dielectric constant of the water in the reactor pressure vessel to the same as the dielectric constant of the nitrogen-containing compound and the phosphorus-containing compound. For example, the reaction temperature and pressure of the reactants in the reactor pressure vessel can be configured to reduce the dielectric constant of water in the reactor pressure vessel to a value below 40, e.g., between 20 and 30, e.g., between 20 and 25.

[0014] The operating temperature of the high-pressure reactor can be selected based on the desired outcome of the process, which can be one or more of: (i) high hydrochar yield, (ii) high nutrient recovery, (iii) specific distribution of heavy metals between the solid and aqueous phases, or any other desired outcome.

[0015] The hydrothermal carbonization procedure can be carried out as a series of consecutive batch operations carried out using multiple reactor pressure vessels configured to receive waste material in sequence and carry out the hydrothermal carbonization procedure at time periods offset from one another by less than the total duration of the hydrothermal carbonization procedure.

[0016] The method can further include discharging the product of the hydrothermal carbonization step to an expansion vessel at a pressure lower than the reactor pressure vessel, for example, prior to separating the liquid from the solid components and / or prior to drying the wet hydrochar. In some arrangements, the method can include discharging the product of the hydrothermal carbonization step to two or more expansion vessels in parallel at a pressure lower than the reactor pressure vessel.

[0017] The method can include, for example, circulating gas from the expansion vessel through a gas heat exchanger configured to transfer heat from the expansion vessel to the input waste material before it is received in the reactor pressure vessel. Additionally or alternatively, the method can include circulating the separation liquid through a liquid heat exchanger configured to transfer heat from the separation liquid to the input waste material before it is received in the reactor pressure vessel. The gas heat exchanger can be located downstream of the liquid heat exchanger with respect to passage of the input waste material into the reactor pressure vessel.

[0018] The liquid can be separated from the solid components through a physical separation process. For example, the liquid can be separated from the solid components using a filter press or a solid / liquid centrifuge. The separated liquid can be extracted as fertilizer, e.g., a fast-release nutrient liquid fertilizer, and / or fed to an anaerobic digester to produce biogas and / or to reduce the carbonaceous oxygen demand of the treated water, e.g., before discharging it to the environment. The separated liquid can be further processed and / or mixed with the carbonaceous residue, e.g., a high-ash carbonaceous residue, produced through the method, for example, depending on its composition.

[0019] The method may further include burning the synthesis gas produced through the gasification process, and optionally pyrolysis gases, e.g., volatile hydrocarbons and organic compounds, in a gas generator to generate electricity. The electricity generated by the gas generator may be used, for example, to power a heater for the reactor pressure vessel during steady-state operation of the method. The method may include providing electricity from a source separate from the gas generator to heat the reactor pressure vessel during a start-up procedure. Optionally, the electricity generated by the gas generator may be used to power other electrical equipment in the plant in which the method is performed.

[0020] The method may further include sending a portion of the produced syngas as input to the gasification process. This portion of the produced syngas may be combusted to heat the reactants of the gasification process. The method may further include, for example, providing a combustible gas as input to the gasification reactor from a source separate from the gasification reactor, such as natural gas, propane, liquefied petroleum gas (LPN), and / or liquefied natural gas (LNG), during a start-up procedure for the waste material treatment method. The combustible gas may be combusted to heat the reactants of the gasification process during a start-up procedure for the waste material treatment method. The combustible gas may no longer be provided as input to the gasification process, with the syngas being available to be combusted to heat the reactants.

[0021] The method can include circulating combustion gases, for example, from a gas generator, gasifier, ground flare, or burner, around the reactor pressure vessel to heat the reactor pressure vessel and carry out the hydrothermal carbonization procedure. The combustion gases fed over the separated solids can be the combustion gases circulated around the reactor pressure vessel.

[0022] The method may further include circulating combustion gases resulting from combustion to heat the reactants of the gasification process to heat input waste materials upstream of and / or within the reactor pressure vessel. During steady-state operation, the hydrothermal carbonization high-pressure reactor may be heated solely using waste heat (combustion gases), e.g., from gasification. The or each reactor pressure vessel may include a heating jacket, and combustion gases may be passed through the heating jacket from a thermal gasifier, e.g., a shroud exhaust of the thermal gasifier. Thermal energy is transferred from the hot combustion gases to the reactor pressure vessel to heat the contents of the reactor pressure vessel to a desired operating temperature. During start-up, a natural gas / propane burner may be used to heat the reactor pressure vessel by passing the hot combustion gases through the heating jacket to heat the contents of the reactor pressure vessel to a desired operating temperature. The method may further include cleaning the synthesis gas produced through the gasification process to remove contaminants from the synthesis gas before using it for other purposes as part of a waste treatment process.

[0023] The method may further comprise feeding a further input of comminuted, optionally non-biodegradable waste material to the gasification process.

[0024] The method may further include recycling at least a portion of the contaminants, such as tar and / or oil, removed from the synthesis gas as input to the gasification process.

[0025] According to another aspect of the present disclosure, there is provided a system for treating waste materials, including human and / or animal digestive waste and / or plant-derived waste, which may or may not have undergone processes such as anaerobic digestion and / or aerobic digestion, e.g., pretreatment by biological processes, and / or pretreatment steps with anaerobic, aerobic, and / or anoxic bacteria. The system includes a reactor pressure vessel assembly including one or more reactor pressure vessels for receiving an input of the waste material and heating and pressurizing the waste material therein to perform a hydrothermal carbonization procedure on the waste material, a separation unit for separating liquids from solid components produced through the hydrothermal carbonization procedure, and a gasification reactor vessel for receiving the solid components and performing a gasification and / or pyrolysis process therein on the separated solids, e.g., to produce synthesis and / or pyrolysis gases, respectively.

[0026] The reactor pressure vessel assembly may further include one or more expansion vessels for receiving the product of the hydrothermal carbonization procedure, known as hydrochar slurry, from the one or more reactor pressure vessels at a pressure lower than that of the reactor pressure vessels.

[0027] The system can further include a gas heat exchanger configured to receive gas from the one or more expansion vessels and transfer heat from the gas to the input waste material. The gas received from the one or more expansion vessels can comprise, e.g., primarily comprise, steam. The system can further include a liquid heat exchanger configured to receive liquid, sometimes known as nutrient-rich treated water, separated by the separation unit and transfer heat from the liquid to the input waste material. The gas heat exchanger can be located downstream of the liquid heat exchanger, for example, with respect to passage of the input waste material through the gas heat exchanger and the liquid heat exchanger into the reactor pressure vessel assembly.

[0028] The system can further include a direct rotary dryer for removing moisture from the wet hydrochar (separated solid components), which can be a dryer for removing moisture by convective drying using waste heat from the hydrothermal carbonization procedure.

[0029] The system may further include a gas generator for generating electricity using the syngas produced through the gasification reactor. The reactor pressure vessel assembly may include one or more electric heaters for heating the reactants in the reactor pressure vessel. The electric heaters may be electrically connected to the gas generator. Additionally or alternatively, the reactor pressure vessel assembly may include one or more jackets, e.g., each disposed around the reactor pressure vessel. The jackets may be configured to receive heated gas, such as combustion gas from a natural gas / propane burner and / or the gasification reactor vessel, to heat the reactants in the reactor pressure vessel.

[0030] The system may further include a syngas cleaning unit for removing contaminants, such as acid gases, tar, oil, and / or entrained solids, from the syngas produced in the gasification reactor vessel. The syngas cleaning unit may be disposed between the gasification reactor vessel and the gas generator (and / or ground flare, if provided) with respect to the syngas flow. The syngas cleaning unit may include a wetted wall scrubber. The wetted wall scrubber may include multiple spray nozzles for spraying water to increase the contact area between the syngas and the water. The syngas cleaning unit may further include one or more baffles configured to facilitate turbulent flow of gas passing therethrough. In some configurations, the syngas cleaning unit may include a cyclone for removing entrained solids, and / or a dry scrubber system and / or an aqueous scrubber system, such as a venturi quench, cyclone scrubber, and / or packed bed scrubber for removing aerosol tar and / or oil and acid gases present in the syngas. The syngas cleaning unit may include a condenser configured to remove moisture from the saturated syngas prior to combustion in the gas generator. The system may further include a pollutant recirculation duct for recirculating at least a portion of the pollutants, such as tar, removed from the syngas to the gasification reactor.

[0031] The gasification reactor may include one or more burners for burning gas to heat the reactants in the gasification process. The system may include a syngas supply duct for supplying syngas removed by the gasification reactor to the one or more burners, e.g., from downstream of the syngas cleaning unit. The burners may be further configured to burn natural gas / propane / LPG / LNG to heat the reactants in the gasification reactor, e.g., during start-up of the system, when insufficient syngas is available to heat the gasification reactor.

[0032] The reactor pressure vessel assembly can include multiple reactor pressure vessels and one or more expansion vessels. The reactor pressure vessels can be configured to store reactants and products at a higher pressure than the expansion vessels. The expansion vessels can be configured to receive products of the reactions in the respective reactor pressure vessels.

[0033] The reactor pressure vessel assembly can be configured to operate in a continuous series of batch procedures in which reactants are sequentially charged to the reactor pressure vessels. Products of the reactions in the reactor pressure vessels can be sequentially removed to an expansion vessel. Hydrothermal carbonization procedures can be carried out over alternating periods in the sequential reactor pressure vessels.

[0034] The reactor pressure vessel assembly may further include one or more ducts for directing gas from the expansion vessel to one or more heat exchangers for heating the reactants entering each of the reactor pressure vessels. The ducts may be arranged such that gas from the expansion vessel flows to a heat exchanger configured to heat the reactants within the next of the reactor pressure vessels receiving the reactants in a successive series of batches.

[0035] The system may include a combustion gas duct for directing combustion gases from the gasification reactor to the reactor pressure vessel assembly. The system may further include one or more combustion gas heat exchangers, e.g., combustion gas heating jackets, for transferring heat from the combustion gases to the waste material input to the reactor pressure vessel assembly.

[0036] According to another aspect of the present disclosure, there is provided a reactor pressure vessel assembly including a plurality of reactor pressure vessels and one or more, e.g., single or a corresponding number of expansion vessels, wherein the reactor pressure vessels are configured to store reactants and products at a pressure higher than the expansion vessels, optionally each expansion vessel being connected to a different one of the reactor pressure vessels, and wherein the expansion vessels are configured to receive products of a reaction in the reactor pressure vessels, e.g., the respective reactor pressure vessels.

[0037] The reactor pressure vessel assembly may further include one or more ducts for directing gas from the expansion vessel to one or more heat exchangers for heating reactants entering or within each of the reactor pressure vessels.

[0038] The reactor pressure vessel assembly can be configured to operate in a continuous series of batch procedures in which reactants are sequentially charged to multiple reactor pressure vessels, products of the reactions in the reactor pressure vessels are sequentially removed to an expansion vessel, and hydrothermal carbonization procedures are carried out over alternating time periods in the successive reactor pressure vessels.

[0039] The duct can be arranged so that gas from the expansion vessel flows to a heat exchanger configured to heat the reactants within the next of the reactor pressure vessels that receive the reactants in a successive series of batches.

[0040] Each reactor pressure vessel may be associated with a heater, e.g., an electric heater, for heating the reactants therein. Each reactor pressure vessel may be associated with a heat exchanger, e.g., a heating jacket, for receiving combustion gases and transferring heat from the combustion gases to the reactants in the corresponding reactor pressure vessel.

[0041] The system can further include a dryer, such as a direct rotary kettle, for drying the separated solid component to a target moisture content using a convection drying process.

[0042] The system may include, for example, a ground flare unit configured, during its start-up procedure, to receive and burn syngas from, for example, the syngas cleaning unit to generate combustion gases that are fed to a dryer to heat the reactor pressure vessel and / or to dry the separated solid components.

[0043] The system may include, for example, a generator combustion gas duct configured to direct combustion gases from the gas generator to the reactor pressure vessel assembly for heating the reactor pressure vessel assembly during steady-state operation thereof.

[0044] The system may include, for example, one or more burners for providing hot combustion gases for heating the reactor pressure vessel assembly during its start-up procedure.

[0045] To avoid unnecessary duplication and repetition herein, certain features will be described only with respect to one or more aspects or embodiments of the invention. However, it will be understood that, where technically possible, a feature described with respect to any aspect or embodiment of the invention can be used with any other aspect or embodiment of the invention. For example, a feature described with respect to a first aspect mentioned can be combined with a feature of a second aspect mentioned.

[0046] For the purpose of offering a clearer understanding of the present invention and to show more clearly how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: [Brief explanation of the drawings]

[0047] [Figure 1] 1 is a schematic diagram of a system for treating waste materials including biosolids, such as human and / or animal digestive waste and / or plant derived waste, which may or may not have undergone anaerobic and / or aerobic digestion in accordance with an arrangement of the present invention. [Figure 2] 1 is a flow diagram illustrating a method for treating waste materials including biosolids, such as human and / or animal digestive waste and / or plant derived waste, which may or may not have undergone anaerobic and / or aerobic digestion, according to an arrangement of the present invention. [Figure 3] FIG. 1 is a schematic diagram of another system for treating waste materials including biosolids, such as human and / or animal digestive waste and / or plant derived waste, which may or may not have undergone anaerobic and / or aerobic digestion in accordance with an arrangement of the present invention. [Figure 4] 1 is a flow diagram illustrating another method for treating waste materials including biosolids, such as human and / or animal digestive waste and / or plant derived waste, which may or may not have undergone anaerobic and / or aerobic digestion according to an arrangement of the present invention. Modes for carrying out the invention

[0048] Referring now to FIG. 1, a system 2 for treating waste materials is described below. The system may be a system for treating waste materials including biomass and / or biosolids, such as human and / or animal digestive waste and / or plant-derived waste, which may or may not have undergone anaerobic and / or aerobic digestion. As noted above, biosolids may refer to primary sludge, secondary sludge, mixed sludge, digested sludge, and / or activated sludge that has been thickened and / or dewatered to a solids concentration of 5-40%. The system includes a reactor pressure vessel assembly 10 that includes one or more reactor pressure vessels 12, sometimes referred to herein as high-pressure reactors. System 2 further includes a separation unit 20 and a gasification reactor assembly 30.

[0049] The reactor pressure vessel assembly 10 includes an input for receiving waste materials, such as primary sludge, secondary sludge, mixed sludge, digested sludge, and / or activated sludge that has been thickened and / or dewatered to a solids concentration of 5-40% containing biosolids and / or biomass, e.g., human and animal aerobic or anaerobic digestion metabolites, and / or plant waste. These waste materials may contain both dead and live microorganisms. The sludge fed to the input can be produced through a sludge thickening process that alters, e.g., reduces, the moisture content of the sludge to about 5-40% solids. Thus, the sludge fed to the reactor pressure vessel assembly 10 can include about 10-20% solids, e.g., biomass-containing solids, and about 80-90% liquid, e.g., moisture. In some configurations, the biosolids can include a flocculating agent or coagulant. The digested sludge introduced into reactor pressure vessel assembly 10 may be received in one or more of one or more reactor pressure vessels 12 .

[0050] The reactor pressure vessel assembly 10 can be configured to heat and pressurize the sludge within the reactor pressure vessel 12 to carry out a hydrothermal carbonization procedure.

[0051] When organic materials such as biosolids and biomass are exposed to subcritical hydrothermal carbonization conditions, they begin to hydrolyze, thereby removing (cleaving) oxygen-, nitrogen-, and phosphorus-containing compounds from the solid material. Additionally, nitrogen-containing compounds are converted to ammonium and phosphorus-containing compounds are converted to phosphate ions under neutral and slightly basic pH conditions.

[0052] The objectives of the hydrothermal carbonization process can be one or more of the following: (i.) chemically dewatering the organic solids in the feedstock to increase the carbon-to-oxygen and / or carbon-to-hydrogen ratios of the solid component of the sludge (hydrochar); (ii.) recovering nitrogen- and phosphorus-containing compounds by "cleaving" these compounds from the organic solids in the feedstock and solubilizing them in the aqueous hydrochar slurry; (iii.) hydrolyzing microplastics, per- and polyfluoroalkyl substances, and antibiotics into their respective harmless soluble by-products; (iv.) killing bacteria / microorganisms present in the feedstock by exposing them to high temperatures and pressures; (v.) rupturing / lysing plant and animal cells present in the feedstock to release intracellular fluids into the hydrochar slurry; and (vi.) separating a portion of the water present in the hydrochar slurry by generating steam through pressure throttling control.

[0053] During the hydrothermal carbonization process, the solids of the sludge, e.g., biosolids-containing compounds and / or biomass-containing compounds, can be converted into carbon-containing molecules that are more suitable for use as reactants, e.g., suitable for pyrolysis and / or gasification, e.g., as described below, in a pyrolysis process and / or a gasification process, respectively. More specifically, to perform the hydrothermal carbonization process, the sludge can be heated to a reaction temperature greater than 160°C, greater than 170°C, or greater than 180°C, e.g., between 160 and 260°C. For example, the sludge can be heated to about 200°C and a reaction pressure greater than 0.6 MPa, greater than 1.5 MPa, or greater than or equal to 2 MPa, e.g., between 0.6 and 4.7 MPa, or between 2 and 2.5 MPa. The reactor pressure vessel can be heated at a rate of between 2 degrees Celsius and 5 degrees Celsius per minute for 60 to 90 minutes until the reaction temperature is reached. The sludge can be maintained at the reaction temperature and pressure for between 30 and 240 minutes, or between 30 and 60 minutes. In one example, the reactor pressure vessel can be maintained at the reaction temperature for greater than 3 hours, such as about 4 hours, or for greater than 4 hours.

[0054] The operating temperature of the high-pressure reactor can be selected based on the desired results, which can be one or more of: (i) high hydrochar yield, (ii) high nutrient recovery, (iii) specific distribution of heavy metals between the solid and aqueous phases, or any other desired result.

[0055] The reactor pressure vessel assembly 10 can include multiple reactor pressure vessels 12. In the arrangement shown in FIG. 1, the reactor pressure vessel assembly 10 includes four reactor pressure vessels 12. However, in other arrangements, the reactor pressure vessel assembly 10 can include any other number of reactor pressure vessels, such as between two and four pressure vessels. The reactor pressure vessel assembly 10 can be configured to perform the sludge hydrothermal carbonization process in a series of batch operating modes similar to that of a continuous process. For example, the treatment, e.g., heating and pressurization, of the sludge in each of the reactor pressure vessels can be alternated by periods that are shorter than the total duration the sludge is treated in the reactor pressure vessel. For example, heating of the sludge in each of the pressure vessels can begin between about one and two hours after heating of the sludge in another of the pressure vessels begins.

[0056] During the start-up procedure of the system, input biosolids and / or biomass may be loaded into each of the reactor pressure vessels 12. However, due to the staggered initiation of processes in each reactor pressure vessel, the completion times of processes in each of the reactor pressure vessels 12 will be staggered, and it will be appreciated that during steady-state operation of the system, the loading of reactor pressure vessels for subsequent batches may also be staggered, e.g., such that the reactor pressure vessels are loaded in sequence.

[0057] The reactor pressure vessel assembly 10 can include one or more heaters 11 for heating waste materials within the reactor pressure vessel, e.g., reactants for a hydrothermal carbonization process. For example, the reactor pressure vessel assembly 10 can include a heater 11 associated with each respective reactor pressure vessel 12. The heaters can be electric heaters. During a start-up procedure of the system 2, power can be supplied to one or more of the heaters from a source external to the system, such as an electrical grid, to heat the reactor pressure vessel 12 to reaction temperatures. However, as described below, during steady-state operation of the system 2, the power to power one or more heaters 11 can be generated within the system 2.

[0058] At the reaction temperature and pressure, the dielectric constant of the water in the sludge can be reduced to a point where it is the same as the dielectric constant of nitrogen- and phosphorus-containing compounds that may be present in the input feedstock or hydrochar slurry. For example, the reaction temperature and pressure of the reactants in the reactor pressure vessel can be configured to reduce the dielectric constant of the water in the reactor pressure vessel to a value lower than 40 or lower than 30, such as between 20 and 30 or between 20 and 25. This allows these ionic components to dissolve from the hydrochar solids into the aqueous phase. Furthermore, under the subcritical conditions of hydrothermal carbonization, microplastics, perfluoroalkyl and polyfluoroalkyl substances, and drug resistance genes are hydrolyzed into their respective harmless soluble components. Therefore, the water solubility / miscibility of macronutrient substances, such as nitrogen and / or nitrogen-containing compounds, can be increased compared to atmospheric temperature and pressure. Furthermore, the hydrothermal carbonization process can release nitrogen and / or nitrogen-containing components from the solid components of the sludge. Therefore, the conditions of the hydrothermal carbonization process cause nitrogen-containing compounds, such as nitrogen and ammonium, present in the sludge to be optionally released from the solids and then dissolved in the water. Furthermore, the removal of oxygen-containing compounds increases the C / O (carbon to oxygen) and C / H (carbon to hydrogen) ratios of the hydrochar solids, which significantly improves the heating value of the pyrolysis gas or the heating value of the synthesis gas when pyrolyzed or thermally gasified, respectively.

[0059] In some configurations, reactive, e.g., nucleophilic, materials such as organic acids and / or calcium oxide can be added to the reactor pressure vessel to facilitate the hydrolysis reaction, e.g., the release of ammonium, during the hydrothermal carbonization process. The released ammonium can then become dissolved in the water.

[0060] In addition to facilitating the dissolution of nitrogen and nitrogen-containing compounds into the moisture and, optionally, their release from the solids of the sludge, the carbonization reaction conditions can also induce the release of other organic and / or inorganic materials from the solids, e.g., macronutrients such as phosphorus, potassium (and phosphorus- and potassium-containing compounds), and / or the dissolution of such materials into the moisture.

[0061] The reactor pressure vessel assembly 10 can include one or more expander vessels 14. The product of the hydrothermal carbonization process, e.g., a hydrochar slurry, can be removed from the reactor pressure vessel 12 into one or more expander vessels 14 at a lower pressure than the reactor pressure vessel 12. The product of the hydrothermal carbonization process can include between 10% and 20% solids. The hydrochar slurry can be discharged from the reactor pressure vessel into the expander vessels under gravity. For example, the pressure in the expander vessels can be about atmospheric pressure. A pressure drop, e.g., a sudden pressure drop, of the hydrothermal carbonization products in the one or more expander vessels can cause structural rupture of the solid components of these products, thereby releasing, for example, additional amounts of nitrogen, phosphorus, potassium (as well as nitrogen-, phosphorus-, and potassium-containing compounds) and organic matter from the solids into the product liquid. Additionally, discharging the product of the hydrothermal carbonization process into the expansion vessel 14 can disrupt any bacteria, e.g., pathogenic bacteria and / or microorganisms, present in the product. Thus, the product of the hydrothermal carbonization process in the expansion vessel can be sterile. Again, additionally, discharging the product into the expansion vessel 14 can convert up to 20% (by mass) of the water in the hydrochar slurry into steam, for example, substantially instantaneously.

[0062] 1, the reactor pressure vessel assembly 10 includes a single expansion vessel 14 configured to receive hydrothermal carbonization products from each of the reactor pressure vessels 12. However, in other arrangements, any other number of expansion vessels 14 may be provided. For example, a number of expansion vessels 14 corresponding to the number of reactor pressure vessels 12 may be provided. In such an arrangement, an expansion vessel may be associated with, e.g., each of, one or more of the reactor pressure vessels 12 and configured to receive products therefrom. In one or more arrangements, for example, two expansion vessels 14 may be provided for all or each reactor pressure vessel 12.

[0063] System 2 may further include a gas heat exchanger / vapor concentrator 4. Gas heat exchanger / vapor concentrator 4 may be configured to receive gases, such as steam, from expansion vessel 14 and transfer heat from these gases to waste materials input to reactor pressure vessel assembly 10. System 2 may include one or more ducts 16 for directing gases, such as steam, from expansion vessel 14 to gas heat exchanger 4.

[0064] A separation unit 20 may be provided downstream of the reactor pressure vessel assembly 10. The separation unit 20 may be configured to receive the product of the hydrothermal carbonization process. For example, the separation unit 20 may be configured to receive the product of the hydrothermal carbonization process from the reactor pressure vessel 12 or the expansion vessel 14 (if present). In some configurations, the system 2 may include a slurry pump configured to transfer the hydrochar slurry from the expansion vessel 14 to a buffer / holding vessel (not shown) positioned upstream of the separation unit 20, which may deliver the slurry to the separation unit. The buffer / holding vessel may be thermally insulated. The hydrochar slurry may then be delivered from the buffer / holding vessel to the separation unit at a temperature of 20-80°C.

[0065] After the hydrothermal carbonization reaction product has been removed from the reactor pressure vessel 12 and / or expansion vessel 14, a brief spray of pressurized municipal water can be provided into the vessels to help flush out any remaining hydrochar solids and minimize fouling of these vessels.

[0066] The separation unit 20 can be configured to separate at least a portion of the liquid present in the hydrothermal carbonization process product from the solid components. For example, the separation unit 20 can be configured to separate at least a portion of the water present in the product along with any materials dissolved in the water. The separated solid components may be referred to as wet hydrochar.

[0067] The separation unit 20 can be configured to separate liquid from solid components through a physical separation process, such as a physical dewatering process. For example, the separation unit 20 can include a filter press. Alternatively, the separation unit 20 can include any other device suitable for separating at least a portion of the liquid, e.g., moisture, present in the hydrothermal carbonization product from the solid components, such as a solid / liquid centrifuge. When the separation unit includes a filter press, the hydrochar slurry can be pumped to a pressure of 4 to 17 bar absolute. The filter press can be operated in a fed batch mode or a continuous mode. The output from the separation unit can include a solid content of 40 to 70%.

[0068] System 2 may include a liquid heat exchanger 6. Liquid heat exchanger 6 may be configured to receive the liquid separated by the separation unit and transfer heat from the liquid to the waste material being input into reactor pressure vessel assembly 10. Liquid heat exchanger 6 may be positioned upstream of heat exchanger 4 with respect to the flow of waste material through heat exchanger 4 and liquid heat exchanger 6. In some arrangements, system 2 may include a buffer tank 7, which may be insulated. Buffer tank 7 may be configured to store the liquid separated by separation unit 20 until needed to heat the waste material being input into the reactor pressure vessel, for example, until the next batch of sludge is input into one or more of reactor pressure vessels 12. System 2 may further include a pump 8 for pumping liquid from separation unit 20 and / or buffer tank 7 to liquid heat exchanger 6.

[0069] The system 2 may further include one or more liquid ducts 18 for conveying the liquid separated by the separation unit 20, for example through a buffer tank 7 and / or a pump 8, to a liquid heat exchanger.

[0070] As discussed above, one or more macronutrient materials, such as nitrogen, potassium, phosphorus, nitrogen-containing compounds, potassium-containing compounds, phosphorus-containing compounds, and organic compounds, e.g., soluble organic compounds, may be dissolved in or mixed with the liquid product of the hydrothermal carbonization process. Such materials may be undesirable for inclusion as reactants in the gasification process to produce synthesis gas, as described below. Therefore, the concentration of such materials in the solid phase product can be reduced by separating at least a portion of the liquid from the solid component of the hydrothermal carbonization product.

[0071] The liquid separated from the hydrothermal carbonization process can be stored for use in another process. For example, the stored liquid can be used in a process to produce fertilizer, e.g., a nutrient-fast release liquid fertilizer, and / or can be fed to an anaerobic digester to produce biogas and / or to reduce the carbonaceous oxygen demand of the treated water, e.g., before discharge to the environment. The separated liquid can be further processed and / or mixed, e.g., depending on its composition, with the carbonaceous residue, e.g., a high-ash carbonaceous residue, produced through the gasification reactor. The liquid separated from the product of the hydrothermal carbonization process may be referred to as nutrient-rich treated water.

[0072] The gasification reactor assembly 30 includes a gasification reactor vessel 32 arranged to receive the solid components separated from the product of the hydrothermal carbonization process and the residual liquid that was not separated. The gasification reactor assembly 30 is configured to perform a pyrolysis and / or gasification process, e.g., a thermal gasification process, on the solid components within the gasification reactor to produce, for example, synthesis and / or pyrolysis gases, respectively. In other words, the gasification and / or pyrolysis process can produce a mixture of synthesis gas and hydrocarbons, e.g., volatile hydrocarbons. Features described herein with respect to gasification can also be applied to pyrolysis, and vice versa. Similarly, features described herein with respect to synthesis gas can also be applied to pyrolysis gases, and vice versa. The solid components separated from the product of the carbonization procedure and the residual moisture can form reactants for the gasification process within the gasification reactor.

[0073] Hydrochar, preferably containing at least 90% (by mass) solids, can be buffered and / or metered and / or continuously fed to the gasification reactor. During the gasification process, moisture present in the reactants can be superheated to steam, and the moisture can react with carbon-containing materials in the solid components. More specifically, moisture can react with solid carbon in a water-gas reaction to produce hydrogen and carbon monoxide, with carbon monoxide in a water-gas shift reaction to form hydrogen and carbon dioxide, and with hydrocarbons in a steam reforming reaction to produce carbon monoxide and hydrogen. Other side reactions may also occur within the gasification reactor.

[0074] The gasification reactor assembly 30 can include an indirectly heated rotary kettle. Alternatively, the gasification reactor assembly can include a fixed-bed gasifier. Again, alternatively, the gasification reactor assembly can include any other suitable gasifier.

[0075] The gasification reactor assembly 30 can include one or more burners 34 configured to heat reactants, for example, to generate superheated steam. The burners can be dual / multi-fuel burners that can be configured to operate using natural gas, e.g., methane, propane, liquefied petroleum gas (LPN), and / or liquefied natural gas (LNG), and / or syngas (or a mixture of syngas and hydrocarbons, e.g., volatile hydrocarbons). These burners can be positioned equidistantly along the heated length of the reactor shell to provide the thermal energy needed to carry out the gasification reaction. Each burner can be independently controlled based on the temperature measured by one or more temperature sensors, e.g., respective temperature sensors, located within the gasification reactor assembly, e.g., on the shroud. The burners can be configured to maintain independent temperature setpoints up to and including 1000°C. This can allow the heated length of the rotating reactor shell to have a desired temperature or desired temperature profile for additional operational flexibility.

[0076] During the start-up procedure of system 2, natural gas, propane, LPN, and / or LNG can be supplied from a source external to system 2, for example, from the grid, and burned by the burners of the gasification reactor assembly to heat the reactants. Natural gas can be supplied through natural gas inlet 38, while during steady-state operation of system 2, as described below, syngas produced through the gasification process can be supplied to the burners and used to heat the reactants in the gasification reactor vessel.

[0077] The gasification reactor assembly 30 may include a combustion air inlet 36 for supplying oxygen or air, e.g., ambient air, to one or more burners 34. A blower, e.g., a constant speed blower, may be configured to provide the combustion air needed to operate the gasification reactor both during startup and / or steady state. Nitrogen may be supplied through nitrogen inlet 39 for selective purging and sealing at the feed and discharge ends of the reactor and appendages. Nitrogen may be supplied to the system to reduce the risk of syngas emissions to the environment and air ingress into the gasification system.

[0078] In addition to syngas, the products of the gasification process may include a high-ash carbon residue and / or biochar, which can be removed from system 2 through biochar outlet 33. Due to the nature of the gasification process, the biochar may not contain microplastics, per / polyfluoroalkyl substances, and / or antibiotics. The carbon residue may include metals contained in the initial feedstock, e.g., soft metals and heavy metals. In some arrangements, the carbon residue may include a majority of the metals present in the initial feedstock. In some arrangements, the biochar can be mixed with liquid separated from the products of the hydrothermal carbonization process.

[0079] The syngas removed from the gasification reactor may include acid gases, entrained solids, tar, oil, and / or oil aerosols. System 2 may further include a syngas cleanup unit 40. The syngas cleanup unit 40 may be located downstream, for example, immediately downstream, of gasification reactor assembly 30 with respect to the flow of syngas from the gasification reactor assembly to receive the syngas produced through the gasification reaction.

[0080] The syngas cleanup unit 40 may be configured to remove contaminants from the syngas produced through the gasification reactor assembly 30. In particular, the syngas cleanup unit may be configured to remove entrained solids (e.g., carbonaceous solids), acid gases such as hydrogen chloride and hydrogen sulfide, oil, and tar. The syngas cleanup unit 40 may include a cyclone configured to recover solids / fines entrained in the dirty syngas. Additionally or alternatively, the syngas cleanup unit 40 may include a dry scrubber and / or an aqueous scrubber, such as a Venturi quench, a cyclone scrubber, a packed-bed scrubber, and / or a wetted-wall scrubber, where the aqueous scrubber may be configured to remove tar and / or oil present in the dirty syngas and neutralize the acid gases. The cyclone and the aqueous scrubber may be arranged in series. For example, the dry scrubber and / or the aqueous scrubber may be arranged downstream of the cyclone. The syngas cleaning unit can include multiple spray nozzles to increase the contact area between the syngas and the circulating water to improve pollutant removal rates. Additionally or alternatively, the syngas cleaning unit can include any other device suitable for removing one or more pollutants from the syngas, such as baffles to facilitate turbulent gas flow.

[0081] The syngas exiting the aqueous scrubber system may be saturated with water. The system may further include a condenser 46 for condensing water vapor from the syngas produced through the gasification reactor assembly. As depicted, the condenser 46 may be located downstream of the syngas cleanup unit 40 with respect to the syngas flow. The water condensed from the syngas by the condenser 46 may be combined with the contaminants removed from the syngas by the syngas cleanup unit 40. In some arrangements, the condenser may be located as part of the syngas cleanup unit 40. For example, the condenser may be located in series with the aqueous scrubber downstream of the aqueous scrubber.

[0082] The water from the aqueous scrubber system may contain unreacted caustic solution and reactive salts from the acid gas neutralization. This water stream may be stored and treated, for example, before being discharged to a municipal sewer network through wastewater outlet 35. The solids / fines recovered from the cyclone may be added to the high ash carbon residue from the gasification reactor and / or the dried hydrochar fed to the gasification reactor, depending on the composition, e.g., average composition, of this material.

[0083] System 2 may include a gas supply duct 42 for supplying synthesis and / or pyrolysis gas to the burner of the gasification reactor assembly. The gas supply duct 42 may extend from a location downstream of the synthesis gas cleaning unit 40 and optionally downstream of the condenser 46 relative to the synthesis / pyrolysis gas flow to the burner 34. As described above, during steady-state operation of system 2, the clean synthesis and / or pyrolysis gas may be burned by the burner 34 within the gasification reactor assembly 30 to heat reactants for the gasification process. In this manner, fuel for the burner from a source external to the system may not be required when system 2 is operating at steady state.

[0084] The system 2 may include a combustion gas recirculation duct 38 configured to recirculate the products of combustion of the natural gas, syngas, and / or pyrolysis gases in the burner 34 to a combustion gas heat exchanger 19 located on the reactor pressure vessel assembly. The combustion gas heat exchanger 19 may be configured to transfer heat from the combustion gases to the reactor pressure vessel 12. After passing through the combustion gas heat exchanger, the combustion gases may be exhausted from the system.

[0085] System 2 may further include a contaminant recycle duct 338 (shown in FIG. 3) for recycling at least a portion of the contaminants, such as tars and / or oils, removed from the syngas in syngas cleanup unit 40, e.g., organically or synthetically derived hydrocarbons, optionally containing chains of five or more carbon molecules, to gasification reactor vessel 32 as reactants for the gasification process. Alternatively, the contaminants may be removed from the system.

[0086] System 2 may further include a generator 50. The generator may be configured to receive the syngas produced through the gasification reactor assembly 30, for example, after being cleaned by the syngas cleaning unit 40 and optionally after passing through a condenser 46, and to burn the syngas to generate electricity. The generator may be any suitable generator. For example, the generator may include a gas turbine for burning the syngas to drive the generator.

[0087] In some arrangements, the generator 50 may be electrically connected to the reactor pressure vessel assembly 10, for example, to its heater 11. During steady-state operation of the system, power from the generator 50 may be used to heat the reactants in the reactor pressure vessel 12 and to carry out a hydrothermal carbonization process of the waste material. In some arrangements, the electricity generated by the gas generator may be used to power other electrical equipment at the plant in which the system 2 is installed.

[0088] In some arrangements, the electrical power generated by the generator 50 by consuming, e.g., burning, the syngas produced through the gasification reactor assembly may be greater than the electrical power required to heat the reactor pressure vessel 12 to perform the hydrothermal carbonization process of the waste material. In such arrangements, the electrical power may be supplied to an electrical system external to the system 2, e.g., an electrical grid or an electrical energy storage system such as a battery system. Accordingly, the system 2 may include electrical terminals 52 for electrically connecting the generator 50 to an external electrical system.

[0089] As described above, during steady-state operation of the system, the energy input requirements for the hydrothermal carbonization and gasification steps can be satisfied by combusting synthesis and / or pyrolysis gases (or a mixture of synthesis gases and hydrocarbons, e.g., volatile hydrocarbons). Thus, system 2 may not require energy from an external source to continue operating at a steady state stage, and energy can be extracted during steady-state operation as excess synthesis and / or pyrolysis gases and / or output as electricity through terminals 52.

[0090] Referring to Figure 2, a method 200 for treating waste materials will now be described. The method may be performed using the system 2 described above. For example, one or more of the things in method 200 may be performed sequentially during a start-up procedure for system 2. Alternatively, the things in method 300 may be performed substantially simultaneously and continuously, e.g., in a series of successive batches, during steady-state operation of method 200.

[0091] The method includes a first step 202 of receiving an input waste material, for example, into a reactor pressure vessel of reactor pressure vessel assembly 10. The waste material includes biosolids and / or biomass, e.g., compliant biosolids and / or non-compliant biosolids, and moisture. For example, the waste material may include primary sludge, secondary sludge, mixed sludge, digested sludge, and / or activated sludge that has been thickened and / or dewatered to a solids concentration of 5-40%. The waste material may include a solids concentration of 10-20%.

[0092] The method further includes a second step 204 of heating the reactor pressure vessel to perform a hydrothermal carbonization process, e.g., a biosolids and / or biomass hydrothermal carbonization process. Specifically, the reactor pressure vessel can be heated to a reaction temperature greater than 160°C, e.g., between 160°C and 260°C, or greater than 170°C, or greater than 180°C, e.g., about 200°C, and can reach a reaction pressure greater than 1.5 MPa, or greater than or equal to 2 MPa, e.g., between 2 MPa and 2.5 MPa. The reactor pressure vessel can be heated at a rate between 2°C per minute and 5°C per minute for a period of 60 to 90 minutes until the reaction temperature is reached. The waste material can be maintained at the reaction temperature and pressure for a period of between 30 and 240 minutes, e.g., about 4 hours or more, or between 30 and 60 minutes.

[0093] The hydrothermal carbonization process may be carried out as a series of consecutive batch operations carried out using multiple reactor pressure vessels configured to receive the waste material in sequence.

[0094] The hydrothermal carbonization product may contain 10% or more solids, e.g., 10-20% solids. In a first example, the hydrothermal carbonization product exits the reactor pressure vessel assembly at a temperature of about 100 degrees Celsius or higher.

[0095] The method 200 may further include discharging the product of the hydrothermal carbonization process from the reactor pressure vessel to one or more expansion vessels, such as the expansion vessel 14 described above, prior to separating the liquid from the solid components. The product of the hydrothermal carbonization process may be at a lower pressure in the expansion vessels than in the reactor pressure vessel.

[0096] The method further includes a third step 206 of separating liquids, such as water and materials dissolved therein, from the solid component (hydrochar) produced through the hydrothermal carbonization process.

[0097] The method further includes a fourth step 208 of performing a gasification process, eg, a thermal gasification process such as pyrolysis, on the separated solid components to produce synthesis gas.

[0098] The method 200 may further include, for example, circulating a gas, such as steam, from the expansion vessel through a gas heat exchanger, such as gas heat exchanger 4, configured to transfer heat from the expansion vessel gas to the input waste material prior to receiving the waste material into the reactor pressure vessel.

[0099] The method 200 can further include, for example, circulating the separated liquid from the third process through a liquid heat exchanger, such as liquid heat exchanger 6, configured to transfer heat from the separated liquid to the input waste material, before receiving the waste material into the reactor pressure vessel. A gas heat exchanger can be located downstream of the liquid heat exchanger relative to the passage of the input waste material into the reactor pressure vessel assembly.

[0100] The input waste material may be at ambient temperature before passing through the gas and liquid heat exchangers and may be at a temperature of up to 80 degrees Celsius when it enters the high pressure reactor vessel.

[0101] The method 200 may further include burning the syngas produced through the gasification process in a gas-powered generator, such as generator 50, to generate electricity. The electricity generated by the generator may be used, for example, to power a heater for the reactor pressure vessel during steady-state operation of the method. The method may further include providing electricity from a source separate from the generator to heat the reactor pressure vessel during a start-up procedure.

[0102] The method may further include providing a combustible gas, such as natural gas, propane, LPN, and / or LNG, as input to the gasification process from a source separate from the gasification reactor during a start-up procedure for the method of treating the waste material. The combustible gas may be combusted, for example, in the burner 54 of the gasification reactor assembly 30 to heat the reactants of the gasification process during a start-up procedure for the method of treating the waste material.

[0103] The method may further include delivering a portion of the produced synthesis and / or pyrolysis gas as input to the gasification process. This portion of the produced synthesis gas may be combusted, for example, by the burner 34 of the gasification reactor assembly, to heat the reactants of the gasification process. During steady-state operation of the method, for example, once synthesis gas is available to be combusted to heat the reactants, combustible gas may no longer be provided as input to the gasification process.

[0104] The method 200 may further include recirculating combustion gases produced from combustion in the burner to heat reactants of the gasification process to heat input waste material upstream of and / or within the reactor pressure vessel of the reactor pressure assembly.

[0105] During steady-state operation of the method, the waste material within the reactor pressure vessel may be heated using any combination of gas heat exchangers / steam condensers, and / or liquid heat exchangers, and / or recycled combustion gases resulting from combustion in burners, for example, circulated through one or more jackets, e.g., respectively, disposed about the reactor pressure vessel, and / or combustion gases from a gas generator for heating the reactants of the gasification process, and / or using a heater, e.g., electric heater 11, located within the reactor pressure vessel assembly. As noted above, heater 11 may be powered using electricity generated by generator 50.

[0106] However, during the start-up procedure of the present method, the heaters of the reactor pressure vessel assembly alone may be used to provide heat to the reactor pressure vessel.

[0107] The method may further include cleaning the synthesis gas produced through the gasification process to remove contaminants from the synthesis and / or pyrolysis gas. The synthesis gas may be cleaned before it is used for other purposes as part of the method for treating waste. In particular, the synthesis gas may be cleaned before being combusted by a gas generator to generate electricity and / or before being fed to the burner of a gasification reactor assembly. The synthesis gas may be cleaned using the synthesis gas cleaning unit described above. The method may further include recycling at least a portion of the contaminants removed from the synthesis gas as input to the gasification process.

[0108] Additionally or alternatively, the method may include passing the synthesis and / or pyrolysis gas through a condenser to remove water vapor from the synthesis gas, for example, before the synthesis gas is used for other purposes as part of the method. The synthesis gas may be passed through a condenser after removing contaminants.

[0109] Referring to FIG. 3, a system 300 for treating waste materials according to another arrangement of the present disclosure will now be described. System 300 may be similar to and may include system 2 described above with reference to FIG. 1. Features described above with respect to system 2 equally apply to system 300, and vice versa. In particular, features described below with respect to system 300 may be provided as part of system 2. System 300 may be a system for treating waste materials including biomass and / or biosolids, such as human and / or animal digestive waste and / or plant-derived waste, which may or may not have undergone anaerobic and / or aerobic digestion. System 300 includes a reactor pressure vessel assembly 10 including one or more reactor pressure vessels 12 and one or more expansion vessels. System 300 further includes a separation unit 20 and a gasification reactor assembly 30. In addition, system 300 may further include a syngas cleanup unit 40 and / or a generator 50.

[0110] System 300 differs from System 2 in that the reactor pressure vessel assembly includes a jacket 302 disposed around reactor pressure vessel 12 for circulating combustion gases around the reactor pressure vessel for heating reactants within the reactor pressure vessel. The system can include one or more first natural gas / propane burners 372 configured to burn natural gas, propane, LPN, and / or LNG to generate hot combustion gases for circulating through the jacket. During start-up of system 300, first natural gas / propane burner 372 can be activated to heat the reactor pressure vessel. In this case, additional heaters, such as the electric heaters described above with reference to FIG. 1, can be omitted.

[0111] The jacket 302 may be configured to receive combustion gases from the gasification reactor 32 and / or the generator 50. During steady-state operation of the system 300, the reactor pressure vessel may be heated solely by the heat of the combustion gases from, for example, the gasification reactor and / or the generator 50. As depicted, the system 300 may include a generator combustion gas duct 376 for conveying the combustion gases from the generator 50 to the jacket 302. In such an arrangement, the first natural gas / propane burner 372 may not be operated during steady-state operation of the system 300.

[0112] The or each reactor pressure vessel 12 may be rotated about an axis having a vertical component, such as a vertical axis, using an electric or hydraulic motor. This may ensure that combustion gases are evenly distributed across the face area of each vessel. The or each reactor pressure vessel may contain internal baffles to help mix / distribute the feedstock as it rotates, facilitating even heat transfer, and limit fouling.

[0113] System 300 further includes a feedstock preparation unit 310. Waste materials input to system 300 may be received in the feedstock preparation unit before being delivered to reactor pressure vessel 12. Feedstock preparation unit 310 may include one or more feedstock holding tanks 312. In the arrangement shown in Figure 3, feedstock preparation unit 310 includes two first feedstock holding units.

[0114] The feedstock preparation unit is configured to ensure that the feedstock is delivered to the reactor pressure vessel at or within a desired input range of solids concentration and / or temperature.

[0115] Feedstock (including biosolids) can be received into the feedstock preparation unit through the first waste input 314, for example, from a conventional wastewater treatment plant. The feedstock can be received into the first feedstock holding tank 312a of the feedstock preparation unit. The feedstock received through the first waste input 314 can have a solids concentration between 5% and 40%. A desirable input solids concentration range for the feedstock to the reactor pressure vessel can be between 10% and 20%. For example, dilute wastewater (treated or untreated) from a wastewater treatment plant can be received into the feedstock preparation unit 310 through the second waste input 316. The feedstock preparation unit can be configured to mix the dilute wastewater received from the second waste input 316 with the feedstock received from the first waste input 314.

[0116] The system 300 can further include an organic waste input 315 for organic waste, such as organic waste containing high concentrations of one or more of cellulosic, lignocellulosic, and / or lignin compounds. For example, the organic waste can include chicken manure, olive pomace, wheat husks, biomass debris, etc. The mixed extracted waste biomass can contain solids in concentrations ranging from 1% to 100%. The remaining amount is believed to be primarily water. The organic waste can be fed as input to the feedstock preparation unit along with waste material and, optionally, dilute wastewater. Thus, for example, the organic waste can be fed as input to the reactor pressure vessel along with waste material and wastewater.

[0117] The presence of organic waste in the feedstock can improve the immobilization of soft and heavy metals present in the biosolids with the solid carbon present in the organic waste during the hydrothermal carbonization process. Additionally or alternatively, the heavy metals and solid carbon can be forged together at high temperatures in the gasification reactor to form a non-leachable mineral matrix, i.e., a high-ash carbon residue, which can improve the absorption of compounds into the nutrient-rich treated water, as described below.

[0118] The feed slurry in the first feedstock holding tank 312a can be pumped through a liquid heat exchanger 6 to receive heat from, for example, the nutrient-rich treated water. The heat from the nutrient-rich treated water can be received at a temperature of 20-80°C. The feedstock slurry in the first feedstock holding tank 312a can be pumped through a liquid heat exchanger to the second feedstock holding tank 312b. The feedstock slurry in the second feedstock holding tank can be pumped through a gas heat exchanger 4 to receive latent heat from, for example, a gas, such as steam, from the expansion vessel 14. The feedstock slurry pumped through the gas heat exchanger can be returned to the second feedstock holding tank before being fed to the reactor pressure vessel. For example, a desirable input temperature range for waste materials fed to the reactor pressure vessel for a hydrothermal carbonization process can be between 15°C and 100°C.

[0119] In gas heat exchanger 4, the steam can be condensed into potable water, which can be removed from the system through potable water removal 318. The nutrient-rich treated water from liquid heat exchanger 4 can be diverted to product mixing / absorption unit 360 (described in more detail below) and / or removed as a nutrient-rich treated water removal product. The nutrient-rich treated water can either be used as a fast-release liquid fertilizer formulation or fed to an anaerobic digester for biogas production and carbonaceous oxygen demand reduction before the "clean" water is discharged to the environment.

[0120] The system 300 may further include a dryer unit 330 configured to remove entrained moisture from the wet hydrochar using, for example, a convective drying method to produce a dry hydrochar having a predetermined moisture content. The wet hydrochar removed from the separation unit 14 may be fed to the dryer unit via a screw conveyor. The dryer unit 330 may include a direct rotary dryer. Hot combustion gases from the jacket 302 of the high-pressure reactor vessel, for example, circulated through the jacket, may be diverted to the dryer unit 330 through a combustion gas dryer duct 332. The combustion gases may pass through the dryer unit in either a cocurrent or countercurrent direction relative to the feed of the wet hydrochar. The dryer unit may contain internal lifters configured to lift the hydrochar solids within the dryer for mixing with the hot combustion gases. The hydrochar may be dried to a solids concentration of at least 90% and removed from the dryer unit for feeding to a gasifier. The wet combustion gases may exit the dryer unit through wet combustion gas duct 334 carrying entrained steam.

[0121] The system 300 may further include a dryer exhaust gas cleaning unit 340. The dryer exhaust gas cleaning unit may receive the wet combustion gases from the dryer unit through a duct 334. The wet combustion gases may be received by the dryer exhaust gas cleaning unit at a temperature above the dew point temperature of these gases to avoid condensation. The dryer exhaust gas cleaning unit may be configured to remove and recover solid hydrochar used to dry the wet hydrochar and entrained within the wet combustion gases. The dryer exhaust gas cleaning unit may include a cyclone or bag filter to remove the solid hydrochar. The wet combustion gases may then be removed from the system 300 through a wet combustion gas outlet 342.

[0122] The system 300 may further include a shredded (comminuted) non-biodegradable waste input 336. The shredded non-biodegradable waste may also be referred to as "shredded screening." The shredded screening material may be fed to the gasification reactor 30, for example, if it is available from a wastewater treatment plant. The shredded screening may include any combination of inorganic (non-metallic) waste materials, including plastics (PP, HDPE, LDPE, PVC, PS, PET, and other plastics), synthetic rubbers (household cleaning gloves, "medical" gloves, other rubbers), and / or various synthetic household waste materials (such as wet wipes, hygiene products, and cleaning supplies). The shredded screening may be added to the dry hydrochar and thoroughly mixed to uniformly distribute the shredded material within the hydrochar before feeding it to the gasification reactor.

[0123] Additionally or alternatively, as described above, the tar and / or oil collected by the syngas cleaner 40 can be recycled to the gasification reactor as an optional feedstock and carbon recovery method. It is contemplated that the tar and / or oil can be added to the dried hydrochar, for example, in addition to or as an alternative to shredded screening, and mixed, e.g., thoroughly mixed, to uniformly distribute these materials within the hydrochar prior to feeding to the gasification reactor. The tar and / or oil can be fed to the gasification reactor through contaminant recirculation duct 338.

[0124] The system 300 may further include a gasification feedstock blending unit 335 configured to blend, e.g., uniformly blend, the hydrochar, tar and / or oil, and / or shredded screening collected by the syngas cleaner. For example, the gasification feedstock blending unit 335 may include a high shear mixing screw positioned within a mixing trough.

[0125] System 300 may further include a ground flare unit 350. During startup and shutdown of system 300, the syngas produced through the gasification process may be off-specification and unsuitable for powering generator 50. Additionally, hot combustion gases during startup may be required to heat the high-pressure reactor vessel and to dry the wet hydrochar. Ground flare unit 350 may be configured, for example, to receive syngas from the cleanup unit during system startup and / or shutdown and react the syngas with oxygen to produce hot combustion gases, which may be directed to the high-pressure reactor vessel, e.g., jacket 302, through ground flare combustion gas duct 378.

[0126] During steady-state operation of the system, the syngas from the purification unit 40, e.g., all of it, can be delivered to the generator 50, and the ground flare unit 350 can be maintained in standby mode with a pilot flame. The hydrothermal carbonization and convective drying can then be carried out using waste heat in the form of hot combustion gases from the gasification reactor and the generator. However, when, e.g., ambient temperatures are very low and heat is being lost to the environment through the interconnecting piping, the hot combustion gases diverted to the hydrothermal carbonization and convective drying can be supplemented, e.g., with hot combustion gases from the ground flare unit 350, as needed.

[0127] The system 300 may further include a hydrogen separation unit 380. The hydrogen separation unit may be configured to receive the purified syngas from the purification unit 40 and separate and concentrate the hydrogen gas present therein. In particular, the hydrogen separation unit may be configured to use pressure swing adsorption and / or membrane technology to separate and concentrate hydrogen. The composition and moisture content of the dry hydrochar feedstock delivered to the gasifier may affect the concentration of hydrogen in the syngas. In arrangements where hydrogen gas is a desired product from the system 300, the hydrogen separation unit may operate to separate and purify hydrogen from the remaining volatile organic compounds in the purified syngas. The syngas remaining after hydrogen separation may contain high concentrations of carbon monoxide, volatile hydrocarbons, and volatile organic compounds and may have a high heating value. The remaining syngas may be supplied to the ground flare unit 350 and / or the generator 50.

[0128] System 300 may further include a mixing / absorption tank 360. The mixing / absorption tank may be configured to receive the nutrient-rich treated water that has passed through liquid heat exchanger 4 and at least a portion of the solid product removed from the gasification reactor. These two streams may be mixed to produce a controlled-release solid nutrient fertilizer formulation for agricultural markets that is removed from the clarification / mixing tank through a controlled-release solid nutrient fertilizer outlet 362.

[0129] Furthermore, the large surface area of the carbon residue can be used to capture and store phosphate and ammonium ions contained in the nutrient-rich treated water, releasing these nutrients into the soil at a slower rate than liquid fertilizer. As noted above, including organic / biomass waste in the feedstock during the hydrothermal carbonization process can lead to the production of a carbon residue with improved adsorption properties. In particular, the large surface area of mesopores present in the high-ash carbon residue improves the retention of ammonium ions present in the nutrient-rich carbon residue during adsorption. This can limit the runoff of these nutrients and potential contamination of shallow groundwater aquifers. The filtered residual treated water can be anaerobically digested for biogas production and reduced carbonaceous oxygen demand before discharging the "clean" water to the environment, for example, through the water outlet 364.

[0130] System 300 may further include a second natural gas / propane burner 374. During a start-up procedure of system 300, the second natural gas / propane burner may be configured to burn natural gas and / or propane and deliver hot combustion gases to the dryer unit 330 for drying the wet hydrochar therein. During steady-state operation and / or when there is sufficient heat energy in the hot combustion gases extracted from jacket 302 around high-pressure reactor vessel 12 to the dryer unit to dry the hydrochar to a desired solids percentage, for example, by mass, second natural gas / propane burner 374 may be shut off and no longer burn natural gas and / or propane.

[0131] Referring now to Figure 4, a method 400 for treating waste materials will now be described. The method may be performed using system 300, described above. Method 400 may be similar to and may include method 200, described above. Features described with respect to method 200 may equally apply to method 400, and vice versa. For example, during a start-up procedure for system 2, one or more of the things in method 400 may be performed sequentially. Alternatively, during steady-state execution of method 400, multiple things in method 400 may be performed substantially simultaneously and sequentially, for example, in a series of consecutive batches.

[0132] The method includes first receiving 402 an input of waste material, for example, into a reactor pressure vessel of reactor pressure vessel assembly 10. The waste material includes biosolids and / or biomass and moisture. For example, the waste material can include primary sludge, secondary sludge, mixed sludge, digested sludge, and / or activated sludge that has been thickened and / or dewatered to a solids concentration of 5-40%.

[0133] The method further includes a second step 404 of heating the reactor pressure vessel to perform a hydrothermal carbonization process, for example, a hydrothermal carbonization process of biomass.

[0134] The method 400 can include expanding 405, discharging the product of the hydrothermal carbonization process into an expansion vessel, e.g., expansion vessel 14, at a pressure lower than that in the reactor pressure vessel in which the hydrothermal carbonization process was performed, e.g., atmospheric pressure. As discussed above, a pressure drop, e.g., a sudden pressure drop, of the hydrothermal carbonization product in one or more expander vessels can lead to structural rupture of the solid components of these products, which can then release additional amounts of nitrogen, phosphorus, potassium (and nitrogen-, phosphorus-, and potassium-containing compounds), and organic matter from the solids into, e.g., the liquid and / or gas phases of the product. In addition, discharging the product of the hydrothermal carbonization process into expansion vessel 14 can disrupt any bacteria, e.g., pathogenic bacteria, present in the product. Thus, the product of the hydrothermal carbonization process in the expansion vessel can be sterile. Again, by discharging the product into expansion vessel 14, up to 20% (by mass) of the water in the hydrochar slurry can be converted to steam, e.g., substantially instantaneously. Expanding 405 can include removing vapors released from the product.

[0135] The method further includes a third step 406 in which liquids, e.g., water and materials dissolved in the water, are separated from the solid components (hydrochar) produced through the hydrothermal carbonization process through a separation unit, such as separation unit 14 described above.

[0136] The method further includes drying 408 the separated solids to a desired percentage (by weight) for input to the gasification process, for example, using drying unit 330. The separated solids can be dried, for example, using a convective drying process by circulating hot combustion gases through a dryer unit.

[0137] The method further includes a fourth step 410 in which a gasification process, eg, a thermal gasification process such as pyrolysis, is carried out on the separated solid components to produce synthesis gas.

[0138] The method may further include a fifth step 412 in which the syngas produced through the gasification process is cleaned, for example, using syngas cleaning unit 40, so that the syngas is suitable for use in a power generator, such as power generator 50. For example, in the fifth step, the dirty syngas may be passed through a cyclone or other device to remove entrained solids from the syngas, and / or may be passed through an aqueous scrubber or a dry scrubber to remove acid gases, oil, and / or tar from the syngas. In the fifth step 412, for example, the syngas that has been passed through the aqueous scrubber may be passed through a condenser to remove moisture from the syngas.

[0139] The method 400 may further include sixthly using the cleaned syngas to generate electricity, for example, by combustion, for example, via a generator 50 .

[0140] While the present invention has been described by way of example and with reference to one or more illustrative examples, it will be appreciated by those skilled in the art that the invention is not limited to the disclosed examples and that alternative examples could be constructed without departing from the scope of the present invention as defined by the appended claims. [Explanation of symbols]

[0141] 2. Systems for treating waste materials 4 Gas heat exchanger 6 Liquid heat exchanger 40 Syngas Cleaning Unit 50 Generator

Claims

1. 1. A method for treating waste materials including human and / or animal digestive waste and / or plant derived waste, comprising: receiving a charge of waste material into a reactor pressure vessel; heating and pressurizing the reactor pressure vessel to carry out a hydrothermal carbonization process of the waste material; Separating at least a portion of the liquid from the solid component of the product produced through the hydrothermal carbonization process; performing a gasification and / or pyrolysis process on the solid components to produce synthesis and / or pyrolysis gases; A method comprising:

2. 2. The method of claim 1, wherein the waste material comprises primary sludge, secondary sludge, mixed sludge, digested sludge, and / or activated sludge that has been thickened and / or dewatered to a solids concentration of 5 to 40%, for example, produced through anaerobic and / or aerobic digestion of human and / or animal digestive waste and / or plant derived waste.

3. 3. The method of claim 1 or claim 2, wherein the reactor pressure vessel is heated to a reaction temperature greater than 160 degrees Celsius, such as to a reaction temperature of 200 degrees Celsius, to carry out the hydrothermal carbonization step.

4. 4. The method of claim 3, wherein the reactor vessel is maintained at the reaction temperature for between 30 and 240 minutes, or between 30 and 60 minutes, such as about 4 hours.

5. 5. The method of any one of claims 1 to 4, wherein a reaction temperature and pressure of the reactants in the reactor pressure vessel are maintained to achieve subcritical conditions for water in the reactor pressure vessel.

6. 6. The method of claim 5, wherein the reaction temperature and pressure of the reactants in the reactor pressure vessel are configured to reduce a dielectric constant of water in the reactor pressure vessel to below 40, such as between 20 and 30, e.g., between 20 and 25.

7. 7. The method of claim 1, wherein the hydrothermal carbonization process is carried out as a continuous series of batch operations using a plurality of reactor pressure vessels configured to receive the waste material in sequence, and wherein the hydrothermal carbonization processes are carried out for periods offset from one another by periods less than the total duration of the hydrothermal carbonization process.

8. discharging the product of the hydrothermal carbonization process into an expansion vessel at a pressure lower than that of the reactor pressure vessel prior to separating the liquid from the solid components; 8. The method of any one of claims 1 to 7, further comprising:

9. circulating the gas from the expansion vessel through a gas heat exchanger configured to transfer heat from the expansion vessel gas to the input waste material before the waste material is received in the reactor pressure vessel; 9. The method of claim 8, comprising:

10. circulating the separated liquid through a liquid heat exchanger configured to transfer heat from the separated liquid to the input waste material before the waste material is received into the reactor pressure vessel; 10. The method of claim 1, comprising:

11. 11. The method of claims 9 and 10, wherein the gas heat exchanger is located downstream of the liquid heat exchanger relative to the passage of the input waste material into the reactor pressure vessel.

12. 12. The method of any one of claims 1 to 11, wherein the liquid is separated from the solid components through a physical separation process.

13. 13. The method of any one of claims 1 to 12, wherein the liquid is separated from the solid components using a filter press.

14. 14. The method of claim 12 or claim 13, comprising drying the separated solid component to a target moisture content using a convection drying process.

15. 15. The method of any one of claims 1 to 14, further comprising combusting the synthesis and / or pyrolysis gases produced through the gasification and / or pyrolysis process in a gas generator to generate electricity.

16. 16. The method of claim 14 or claim 15, wherein drying the separated solid components comprises feeding combustion gases, e.g., from the gas generator and / or burner, onto the separated solid components, e.g., directly in a rotary dryer.

17. 17. A method according to claim 15 or claim 16, wherein the electricity generated by the gas generator is used to power a heater for the reactor pressure vessel, for example during steady state performance of the method.

18. 18. The method of any one of claims 15 to 17, including providing electricity from a source separate from the gas generator to heat the reactor pressure vessel during a start-up procedure.

19. 19. The method of any one of claims 1 to 18, comprising circulating combustion gases, for example from the gas generator or burner, around the reactor pressure vessel to heat the reactor pressure vessel and carry out the hydrothermal carbonization process.

20. 20. The method of claims 19 and 16, wherein the combustion gas fed over the separated solids is combustion gas circulated around the reactor pressure vessel.

21. delivering a portion of the produced synthesis gas as input to the gasification process, the portion being combusted to heat the reactants of the gasification process; 21. The method of any one of claims 1 to 20, further comprising:

22. 22. The method of any one of claims 1 to 21, further comprising providing a combustible gas from a source separate from the gasification reactor, such as natural gas, as an input to the gasification process during a start-up procedure for the method of treating waste material, wherein the combustible gas is combusted to heat the reactants of the gasification process during the start-up procedure for the method of treating waste material.

23. 23. The method of claims 21 and 22, wherein the combustible gas is no longer provided as an input to the gasification process once the synthesis gas is available to be combusted to heat the reactants.

24. circulating the combustion gases resulting from the combustion for heating the reactants of the gasification process to heat the input waste material upstream of and / or within the reactor pressure vessel; 24. The method of any one of claims 20 to 23, further comprising:

25. cleaning the synthesis gas produced through the gasification process to remove contaminants from the synthesis gas before the synthesis gas is used for other purposes as part of a method for treating waste; 25. The method of any one of claims 1 to 24, further comprising:

26. recycling at least a portion of the contaminants removed from the synthesis gas as input to the gasification process; 26. The method of claim 25 further comprising:

27. 27. The method of any one of claims 1 to 26, further comprising providing a separate input of comminuted, optionally non-biodegradable waste material to the gasification process.

28. 1. A system for treating waste materials including human and / or animal digestive waste and / or plant derived waste, comprising: a reactor pressure vessel assembly including one or more reactor pressure vessels for receiving an input of waste material and for heating and pressurizing said waste material within said vessel to carry out a hydrothermal carbonization process of said waste material; a separation unit for separating liquid from solid components produced through the hydrothermal carbonization process; a gasification reactor vessel for receiving the solid components and performing a gasification and / or pyrolysis process on the separated solid components within the gasification reactor vessel to produce synthesis and / or pyrolysis gases; A system including:

29. 30. The system of claim 28, wherein the reactor pressure vessel assembly further comprises one or more expansion vessels for receiving products of the hydrothermal carbonization process from the one or more reactor pressure vessels at a pressure lower than that of the reactor pressure vessel.

30. a gas heat exchanger / steam condenser configured to receive gas, e.g., steam, from the one or more expansion vessels and transfer heat from the gas to the input waste material; 30. The system of claim 29, further comprising:

31. a liquid heat exchanger configured to receive the liquid separated by the separation unit and transfer heat from the liquid to the input waste material; 31. The system of any one of claims 28 to 30, further comprising:

32. 32. The system of claims 30 and 31, wherein the gas heat exchanger is located downstream of the liquid heat exchanger relative to the passage of the input waste material into the reactor pressure vessel assembly.

33. a gas generator for generating electricity using the synthesis gas produced by the gasification reactor; 33. The system of any one of claims 28 to 32, further comprising:

34. the reactor pressure vessel assembly includes one or more electric heaters for heating the reactants within the reactor pressure vessel; the electric heater is electrically connected to the gas generator; 34. The system of claim 33.

35. 35. The system of any one of claims 28-34, further comprising a syngas cleanup unit for removing contaminants from the syngas produced in the gasification reactor vessel.

36. 36. The system of claims 34 and 35, wherein the syngas cleaning unit is provided for the syngas flow between the gasification reactor vessel and the gas generator.

37. 37. The system of claim 35 or claim 36, wherein the syngas cleaning unit comprises a wetted wall scrubber.

38. 38. The system of any one of claims 35 to 37, further comprising a pollutant recycle duct for recycling pollutants removed from the synthesis gas to the gasification reactor.

39. the gasification reactor includes one or more burners for burning gas to heat reactants in the gasification process; the system including a syngas supply duct for supplying syngas extracted by the gasification reactor to the one or more burners; 39. A system according to any one of claims 28 to 38.

40. the reactor pressure vessel assembly includes a plurality of reactor pressure vessels and one or more expansion vessels; the reactor pressure vessel is configured to contain reactants and products at a pressure greater than that of the expansion vessel; the expansion vessels are configured to receive products of the reaction within each of the reactor pressure vessels.

40. A system according to any one of claims 28 to 39.

41. 41. The system of claim 40, wherein the reactor pressure vessel assembly is configured to operate in a continuous series of batch procedures wherein reactants are charged to the plurality of reactor pressure vessels in a sequential manner, products of the reactions in the reactor pressure vessels are removed in a sequential manner to an expansion vessel, and the hydrothermal carbonization process is carried out over alternating time periods in the sequential reactor pressure vessels.

42. 42. The system of claim 41, wherein the reactor pressure vessel assembly further comprises one or more ducts for directing gases from the expansion vessel to one or more heat exchangers for heating reactants entering each of the reactor pressure vessels.

43. 43. The system of claim 42, wherein the duct is arranged such that gas from the expansion vessel is directed to the heat exchanger configured to heat the reactants within a next one of the reactor pressure vessels for receiving the reactants in the successive series of batches.

44. 44. The system of any one of claims 28 through 43, including a combustion gas duct for directing combustion gases from the gasification reactor to the reactor pressure vessel assembly, and one or more combustion gas heat exchangers for transferring heat from the combustion gases to the waste material input into the reactor pressure vessel assembly.

45. 45. The system of any one of claims 28 to 44, further comprising a dryer, such as a direct rotary kettle, for drying the separated solid component to a target moisture content using a convection drying process.

46. 46. A system as claimed in claim 33, or any one of claims 34 to 45 when dependent on claim 33, including a generator combustion gas duct configured to direct combustion gases from the gas generator to the reactor pressure vessel assembly, for example for heating the reactor pressure vessel assembly during steady state operation of the system.

47. 47. The system of any one of claims 28 to 46, including one or more burners for providing hot combustion gases to heat the reactor pressure vessel assembly, for example during a system start-up procedure.

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