A system and method for multi-stage heat treatment of solid waste using steam hydrothermal methods

Abstract

This invention relates to a system and method for the hydrothermal staged heat treatment of solid waste, comprising a solid raw material feeding unit, a premixing tank, a steam inlet unit, a hydrothermal reaction unit, a discharge tank, a water washing and filtration unit, an oil-water separation unit, and a drying unit. Raw materials and hot water enter the premixing tank, then enter the hydrothermal section of the hydrothermal reaction unit, where they mix, fluidize, and react with steam from the high-level and low-level steam sections. Hydrothermal char is discharged to the discharge tank, washed, and filtered, and then enters the drying unit for drying. The filtrate is returned to the oil-water separation unit, and the separated aqueous phase is sent back to the premixing tank to mix with and preheat the raw materials. The premixing, heating jacket, combined hydrothermal and steam sections, and internal and external circulation within the reactor greatly promote the mixing of raw materials and the aqueous phase, improve the three-phase turbulence of the reactor, enhance mass and heat transfer efficiency and reaction rate, and improve reaction temperature uniformity and product quality stability.

Description

Technical Field

[0001] This invention relates to a system and method for multi-stage steam-hydrothermal heat treatment of organic solid waste. Background Technology

[0002] Current research on the conversion of organic solid waste mainly focuses on the preparation of fuels and chemicals. Hydrothermal methods can convert organic solid waste into functionalized carbon materials, which can be effectively used in the adsorption of heavy metal ions and electrochemistry, and can also be used to prepare high-quality biomass pellets. Hydrothermal methods are typically carried out at 180-350℃ under pressure, offering mild reaction conditions, controllable temperature, compact structure, and low energy consumption. Traditional hydrothermal technologies, including hydrothermal liquefaction, hydrothermal carbonization, and supercritical water gasification, typically employ liquid-solid two-phase or gas-liquid-solid three-phase reactors. Due to the presence of the solid phase and the limitations of gas-liquid-solid mixing, the mass and heat transfer and reaction rates of these reactors are restricted. Traditional stirred tank reactors, with their shaft seals, are generally used at atmospheric or low pressures and cannot withstand high pressures under hydrothermal conditions. Fluidization technology, on the other hand, offers significant advantages in two- and three-phase mixing. It not only promotes multiphase turbulence and mixing, enabling multi-stage processing, improving system efficiency, mass and heat transfer, and reaction rates, but also facilitates product diversification and reduces floor space. Furthermore, it can withstand higher pressures, achieving combined heat and power generation. It can prepare various adsorbents, catalysts, and functional carbon materials, as well as biofuel oils, chemicals, and hydrogen-rich gases, demonstrating substantial technological advantages and broad application prospects. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of uneven temperature, unstable quality of carbon-based products, serious pollution, and poor economic efficiency and market flexibility in traditional biomass hydrothermal processes. By selecting additives and solvents, improving reactor structure, and optimizing various process parameters, multi-stage heating and multi-stage reaction are achieved in a single reactor, improving bed temperature uniformity and product quality stability, efficiently preparing gas-liquid-solid products, enhancing the pore distribution structure and adsorption performance of carbon-based materials, and improving product distribution by controlling process parameters. Various biomass-derived fuels and chemicals can be prepared, achieving polygeneration.

[0004] The technical solution to achieve the objective of this invention is: a system and method for multi-stage steam-hydrothermal heat treatment of solid waste. The system includes a solid raw material feeding unit, a premixing tank, a steam-hydrothermal reaction unit, a steam inlet unit, a discharge tank, a water washing and filtration unit, an oil-water separation unit, and a drying unit, all connected sequentially. The solid raw material feeding unit includes a closed hopper and a screw feeder. The screw feeder is connected to the premixing tank. The premixing tank is connected to the steam-hydrothermal reaction unit via a feed pump and piping. The steam inlet unit is connected to the steam-hydrothermal reaction unit and the drying unit. The steam-hydrothermal reaction unit is connected to the discharge tank. The discharge tank is connected to the water washing and filtration unit. The water washing and filtration unit is connected to the heating jacket of the steam-hydrothermal reaction unit, the oil-water separation unit, and the drying unit. The oil-water separation unit is connected to the premixing tank. The drying unit is connected to the heating jacket of the steam inlet unit and the steam-hydrothermal reaction unit.

[0005] The aforementioned system for multi-stage steam-hydrothermal heat treatment of solid waste includes a steam-hydrothermal reaction unit comprising a low-level steam section, a high-level steam section, a hydrothermal section, a circulation section, and a heating jacket. The steam-hydrothermal reaction unit adopts a vertical structure combining multi-stage mixing, multi-stage heating, upper and lower circulation, and internal and external heating. The heating jacket is placed outside the hydrothermal section to indirectly heat the reactor. The circulation section connects the bottom of the steam-hydrothermal reaction unit and the top of the hydrothermal section through a circulation pump and pipe fittings, transporting the liquid-solid mixture at the bottom of the reactor back to the top of the reactor. This promotes turbulence and liquid-solid mixing, improves the temperature uniformity of the reactor, enhances mass and heat transfer and reaction rate, and increases the conversion rate and system thermal efficiency.

[0006] The aforementioned system for multi-stage steam-hydrothermal heat treatment of solid waste connects the steam inlet unit to the low-level steam section, high-level steam section, heating jacket, and drying unit of the steam-hydrothermal reaction unit via pipes, fittings, and valves. The steam pipes of the low-level and high-level steam sections can be configured as spiral coils, vertical serpentine coils, or annular coils. The coils or serpentine coils have holes with a size of 1-5 mm. Steam is injected upward and / or horizontally through these holes, or simultaneously upward and downward, which promotes gas-liquid-solid fluidization and bed turbulent mixing, enhances mass and heat transfer, and improves system efficiency. The steam flow rate is controlled by a steam regulating valve.

[0007] The aforementioned system for multi-stage steam-hydrothermal heat treatment of solid waste connects the low-level steam section, high-level steam section, heating jacket, and drying unit of the steam inlet unit and the steam-hydrothermal reaction unit. The heating jacket is connected to the outlet pipes of the steam inlet unit, the drying unit, and the heating jacket via valves, pipes, and fittings. Steam from the steam inlet unit and the drying unit enters the heating jacket from the top, and the outlet pipe of the heating jacket discharges from the bottom. The outlet pipe of the heating jacket is connected to the water washing and filtration unit, achieving integrated water washing and liquid-solid separation, thereby improving the purity and quality of carbon-based products.

[0008] The aforementioned system for multi-stage heat treatment of solid waste using steam and hydrothermal methods includes a solid raw material feeding unit comprising a closed hopper and a screw feeder. The closed hopper and the screw feeder are connected together. The screw feeder is connected to a premixing tank. The premixing tank is connected to a steam and hydrothermal reaction unit, an oil-water separation unit, and the screw feeder via a pump and pipe fittings. The screw feeder is connected to the upper part of the premixing tank. The premixing tank has a stirring mechanism inside.

[0009] The above-mentioned solid waste steam hydrothermal multi-stage heat treatment system has a heating jacket outlet pipe connected to a water washing and filtration unit, which is connected to an oil-water separation unit and a drying unit. The oil-water separation unit separates the liquid phase from the water washing and filtration unit to form an oil phase and a water phase. The water phase is returned to the premixing tank, and the oil phase is transported downstream for treatment and purification. The drying unit is connected to a steam inlet unit and a heating jacket. The drying unit adopts a direct or indirect heating mode. The superheated steam from the steam inlet unit provides heat to the drying unit. After drying, the superheated steam becomes saturated steam or hot water, which then enters the heating jacket. The water vapor generated by the material during the drying process also enters the heating jacket to provide indirect heating for the hydrothermal section of the steam hydrothermal reaction unit.

[0010] The present invention has the following positive effects: (1) The present invention system, through the improvement of reactor structure, selection of additives and solvents, arrangement of reactor heating jacket and internal circulation system, constructs a solid waste heat treatment system with multi-stage heating, multi-stage reaction, steam-hydrothermal combination, internal fluidization turbulence and internal and external circulation combination, and indirect and direct heating combination, to prepare high-quality carbon-based products and realize the multi-product production of gas, liquid and solid products; (2) The steam-hydrothermal reactor is divided into a low-level steam section, a high-level steam section and a hydrothermal section. The low-level steam section and the high-level steam section are located in the lower part of the reactor and pressurized steam is introduced here to improve the fluidization gas and the required temperature of the reactor. The hydrothermal section The hot water comes from the premixing tank and is fed into the top of the hydrothermal section by the feed pump. The steam from the steam inlet unit and the dryer enters the heating jacket and condenses to provide heat for the hydrothermal section. The circulating pump transports the liquid-solid mixture that settles in the steam section to the top of the hydrothermal section to realize the internal circulation of the reactor, which promotes the fluidization turbulence and bed temperature stability of the reactor, and improves the mass transfer and heat transfer efficiency and reaction rate. (3) The condensate from the reactor heating jacket enters the water washing and filtration unit to wash and filter the hydrothermal carbon. The filtered solid product enters the drying unit to dry and obtain the product. The liquid stream enters the oil-water separation unit. After oil-water separation, the water phase enters the premixing unit. The mixing tank then enters the hydrothermal section of the steam-hydrothermal reactor to achieve external water circulation, and the oil phase is recycled downstream; (4) The steam pipes of the low-level steam section and the high-level steam section of the steam-hydrothermal reaction unit can be set as spiral coils, vertical snake tubes, or annular coils. The coils or snake tubes have holes with a hole size of 1-5mm. Steam is injected upward and horizontally through the pipe holes, and can also be injected upward and downward at the same time, which promotes gas-liquid-solid fluidization and bed turbulent mixing, strengthens mass and heat transfer, and improves reaction rate and system efficiency; (5) The solid raw material feeding unit includes a closed hopper and a screw feeder. The screw feeder has the function of conveying The functions of feeding, squeezing and sealing are connected to the premixing tank and are also mutually isolated by material sealing. The screw feeder is connected to the upper part of the premixing tank. The water phase of the oil-water separation unit also enters from the upper part of the premixing tank. The premixing tank has a stirring mechanism inside, which strengthens the mixing of solid raw materials and water phase; (6) Water washing and filtration are integrated, which improves the purity of carbon-based products and oil phase yield. Filtration can be carried out by various centrifuges, filter presses, leaf filters, etc., in vacuum or pressurized operation. Drying equipment includes various fluidized bed dryers, rotary dryers, etc., using direct or indirect heating mode, and can also be carried out in vacuum or pressurized operation. Steam can be recovered, which improves the thermal efficiency of the system. Attached Figure Description

[0011] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0012] Figure 1 This is a schematic diagram of the system and structure of the present invention;

[0013] in:

[0014] 1. Steam-hydrothermal reaction unit; 2. High-level steam section; 3. Low-level steam section; 4. Heating jacket steam inlet pipe; 5. Heating jacket; 6. Heating jacket water outlet pipe; 7. Hydraulic section; 8. Circulation section; 9. Feed pump; 10. Circulation pump; 11. Steam inlet unit; 12. Steam regulating valve; 13. Premixing tank; 14. Screw feeder; 15. Locking hopper; 16. Discharge tank; 17. Water washing and filtration unit; 18. Drying unit; 19. Oil-water separation unit. Detailed Implementation

[0015] (Example 1, see...) Figure 1 )

[0016] This embodiment includes a solid raw material feeding unit, a premixing tank 13, a steam-hydrothermal reaction unit 1, a steam inlet unit 11, a discharge tank 16, a water washing and filtration unit 17, an oil-water separation unit 19, and a drying unit 18, connected in sequence. The solid raw materials are agricultural and forestry waste, kitchen waste, etc. The solid raw material feeding unit includes a closed hopper 15 and a screw feeder 14. The screw feeder 14 has conveying, extrusion, and material sealing functions, feeding the solid raw materials into the premixing tank 13. The water separated by the oil-water separation unit 19 enters from the top of the premixing tank 13 and mixes with the solid raw materials. The premixing tank 13 has a propeller-type agitator inside to ensure uniform mixing of the liquid and solid phases. The feed pump 9 is connected to the bottom of the premixing tank 13 and feeds the liquid-solid mixture into the top of the hydrothermal section 7 of the steam-hydrothermal reaction unit 1. The steam from the steam inlet unit 11 and the drying unit 18 enters the top of the heating jacket 5 through the heating jacket steam inlet pipe 4. In the hydrothermal section 7, after the steam releases heat and condenses, the condensate is discharged from the bottom of the heating jacket 5 through the heating jacket outlet pipe 6 and enters the water washing and filtration unit 17. While the liquid-solid two-phase mixture is heated by the steam in the heating jacket 5, it gradually falls to the high-level steam section 2 and the low-level steam section 3 by gravity. The steam pipes of the high-level steam section 2 and the low-level steam section 3 are annular coils with pipe holes inside. The diameter of the holes is 2mm. After the steam from the steam inlet unit 11 enters the low-level steam section 3 and the high-level steam section 2, it is sprayed vertically upward and downward, which plays a role in fluidizing, agitating, mixing and heating the liquid-solid mixture. After the steam condenses and releases heat, the condensate is collected at the bottom of the steam hydrothermal reaction unit 1. The liquid-solid mixture at the bottom of the reactor is transported to the top of the hydrothermal section 7 by the circulation pump 10, forming an internal circulation that runs through the upper and lower parts of the reactor. This effectively enhances the degree of liquid-solid turbulence and the uniformity of mixing, and improves the mass transfer and heat transfer efficiency and reaction rate.

[0017] The liquid and solid products at the bottom of the reactor are discharged under constant pressure to the unloading tank 16, and then enter the water washing and filtration unit 17 to achieve integrated water washing and filtration. The washing water comes from the outlet pipe 6 of the heating jacket and adopts a continuous pressure filter. Feeding, filtration, washing, purging and cake discharge are continuous operations. After water washing and filtration, the filtrate enters the oil-water separation unit 19 for oil-water separation. The separated aqueous phase enters the premixing tank 13 to form an external circulation, which reduces water and energy consumption, reduces pollutant discharge, and improves the system thermal efficiency. The oil phase is sent downstream to separate various fuels and chemicals. The filtered cake is sent to the drying unit 1. 8. The dryer adopts a fluidized bed dryer and an indirect drying mode with superheated steam. After the superheated steam is cooled, it enters the heating jacket 5 directly through the steam inlet pipe 4 to heat the hydrothermal section 7. The water in the solid product evaporates and also enters the heating jacket 5 through the steam inlet pipe 4, which greatly improves the thermal efficiency of the system. In order to improve the quality of carbon-based products or increase the yield of oil-phase chemicals, additives (such as iron salts, urea, acetic acid, etc.) can be added to the solid raw material feeding unit or the premixing tank 13, or solvents / extractants (such as toluene) can be added to the oil-water separation unit 19, thereby improving product quality and enhancing process flexibility.

[0018] (Example 2, see) Figure 1 )

[0019] The difference between this embodiment and embodiment 1 is as follows: the solid raw materials are municipal sludge and industrial sludge; the steam pipes of the high-level steam section 2 and the low-level steam section 3 are spiral coils with pipe holes inside, the diameter of which is 1 mm; the steam from the steam inlet unit 11 enters the low-level steam section 3 and the high-level steam section 2 and is sprayed out in the vertical and horizontal directions; the water washing and filtration unit 17 adopts a continuous pressure leaf filter; and the drying unit 18 adopts a direct superheated steam drying mode. The other system components are the same as those in embodiment 1.

[0020] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for multi-stage steam-hydrothermal heat treatment of solid waste, comprising a solid raw material feeding unit, a premixing tank (13), a steam-hydrothermal reaction unit (1), a steam inlet unit (11), a discharge tank (16), a water washing and filtration unit (17), an oil-water separation unit (19), and a drying unit (18) connected in sequence. The solid raw material feeding unit includes a closed hopper (15) and a screw feeder (14). The screw feeder (14) is connected to the premixing tank (13). The premixing tank (13) is connected to the pipe fittings and the steam-hydrothermal reaction unit (1) through a feed pump (9). The steam inlet unit is connected to the premixing tank (16). Unit (11) is connected to steam hydrothermal reaction unit (1) and drying unit (18). Steam hydrothermal reaction unit (1) is connected to unloading tank (16). Unloading tank (16) is connected to water washing and filtration unit (17). Water washing and filtration unit (17) is connected to heating jacket (5), oil-water separation unit (19), and drying unit (18) of steam hydrothermal reaction unit (1). Oil-water separation unit (19) is connected to premixing tank (13). Drying unit (18) is connected to steam inlet unit (11) and heating jacket (5) of steam hydrothermal reaction unit (1). The steam-hydrothermal reaction unit (1) includes a low-level steam section (3), a high-level steam section (2), a hydrothermal section (7), a circulation section (8), and a heating jacket (5). The steam-hydrothermal reaction unit (1) adopts a vertical structure with multi-stage mixing, multi-stage heating, upper and lower circulation, and internal and external heating. The heating jacket (5) is placed outside the hydrothermal section (7). The circulation section (8) is connected to the bottom of the steam-hydrothermal reaction unit (1) and the top of the hydrothermal section (7) through a circulation pump (10) and pipe fittings. The steam inlet unit (11) and the steam hydrothermal reaction unit (1) are connected to the low-level steam section (3), the high-level steam section (2), the heating jacket (5), and the drying unit (18). The heating jacket (5) is connected to the steam inlet unit (11), the drying unit (18), and the water outlet pipe (6) of the heating jacket (5) through valves, pipes, and fittings. The steam from the steam inlet unit (11) and the drying unit (18) enters the heating jacket (5) from the top and exits from the water outlet pipe (6) at the bottom of the heating jacket (5). The water outlet pipe (6) of the heating jacket (5) is connected to the water washing and filtration unit (17).

2. The system for multi-stage steam-hydrothermal heat treatment of solid waste according to claim 1, characterized in that... The steam inlet unit (11) is connected to the low-level steam section (3), high-level steam section (2), heating jacket (5), and drying unit (18) of the steam hydrothermal reaction unit (1) through pipe fittings and valves. The steam pipes of the low-level steam section (3) and the high-level steam section (2) are set as spiral coils, vertical snake tubes, and annular coils. There are holes on the pipes of the coils or snake tubes. The steam flow rate is controlled by the steam regulating valve (12).

3. The system for multi-stage steam-hydrothermal heat treatment of solid waste according to claim 1, characterized in that... The closed hopper (15) and the screw feeder (14) are connected. The premixing tank (13) is connected to the steam-hydrothermal reaction unit (1), the oil-water separation unit (19) and the screw feeder (14) through the pump and pipe fittings. The screw feeder (14) is connected to the upper part of the premixing tank (13). The premixing tank (13) has a stirring mechanism inside.

4. The system for multi-stage steam-hydrothermal heat treatment of solid waste according to claim 1, characterized in that... The drying unit (18) adopts a direct or indirect heating mode.

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