Sludge hydrothermal carbonization waste heat heating system and method based on absorption heat pump

Abstract

This invention belongs to the field of waste heat utilization technology in hydrothermal carbonization, and relates to a sludge hydrothermal carbonization waste heat heating system and method based on an absorption heat pump. It includes: a sludge hydrothermal carbonization subsystem, a dehydration heat exchange subsystem, and an absorption heat pump subsystem. The dehydration heat exchange subsystem includes a filter press, a product cooler, a drying device, a filtrate heat exchanger, a condensate tank, and a first wastewater storage tank, connected in sequence. The absorption heat pump subsystem includes a generator, a condenser, an evaporator, an absorber, a solution pump, a solution heat exchanger, a pressure reducing valve, and a second wastewater storage tank, connected in sequence. The input end of the absorber is used to connect to the output end of the heating device, and the output end of the condenser is used to connect to the input end of the heating device. This invention utilizes primary flash steam, secondary flash steam, and dehydrated filtrate to heat the return water of the heating network through the absorption heat pump subsystem to obtain heating hot water, solving the problems of high energy consumption and low waste heat recovery rate in existing sludge treatment methods.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology in hydrothermal carbonization, and specifically discloses a sludge hydrothermal carbonization waste heat heating system and method based on an absorption heat pump. Background Technology

[0002] With the acceleration of urbanization, the amount of sludge generated from sewage treatment has surged. This sludge is rich in harmful substances and highly perishable, posing a serious threat to the ecological environment. Currently, hydrothermal carbonization of sludge is a promising technology for sludge resource utilization. It can directionally convert the organic matter in sludge into high-value-added hydrothermal carbon in a high-temperature, high-pressure water environment, thus shifting the focus of waste treatment from cost burden to resource recycling. In particular, the hydrothermal carbonization reaction itself is a massive energy carrier conversion process; the high-temperature slurry contains abundant thermal energy. Therefore, developing and utilizing the waste heat from the hydrothermal carbonization process to construct an integrated technology for treatment-conversion-energy supply is a core direction for overcoming the current high energy consumption and low waste heat recovery rate in sludge treatment.

[0003] In sludge treatment, the existing waste heat recovery methods mainly involve generating flash steam through flash evaporation. For example, CN202311034593.9 discloses a high-efficiency and energy-saving hydrothermal carbonization device and its application, which recycles the flash steam generated in the flash tank to the heat exchanger of the preheater to achieve waste heat recovery. However, the utilization efficiency is low due to the limitation of indirect heat exchange. CN201410031217.9 discloses a sludge treatment method based on hydrothermal carbonization, which recycles the flash steam generated by flash evaporation at atmospheric pressure to the heat exchanger to achieve waste heat recovery. However, flash evaporation at atmospheric pressure reduces the grade of the flash steam, limiting the waste heat recovery rate. Summary of the Invention

[0004] The purpose of this invention is to provide a sludge hydrothermal carbonization waste heat heating system and method based on an absorption heat pump, which solves the problems of high energy consumption and low waste heat recovery rate in existing sludge treatment.

[0005] The specific solution of the present invention is as follows:

[0006] A waste heat heating system based on sludge hydrothermal carbonization using an absorption heat pump, comprising: Sludge hydrothermal carbonization subsystem, dewatering heat exchange subsystem, and absorption heat pump subsystem; The sludge hydrothermal carbonization subsystem includes a pulverizer, a slurry preheating tank, a slurry pump, a hydrothermal carbonization tank, a primary flash tank, and a secondary flash tank connected in sequence. The slurry preheating tank is connected to the primary flash tank. The dehydration heat exchange subsystem includes a filter press, a product cooler, a drying device, a filtrate heat exchanger, a condensate tank, and a first wastewater storage tank connected in sequence. The filter press is connected to the slurry output end of the secondary flash tank, and the filtrate heat exchanger is connected to the filter press, the condensate tank, and the first wastewater storage tank respectively. The absorption heat pump subsystem includes a generator, condenser, evaporator, absorber, solution pump, solution heat exchanger, pressure reducing valve, and a second wastewater storage tank connected in sequence. The generator is connected to the steam output end of the secondary flash tank, the solution heat exchanger is connected to the generator, one end of the pressure reducing valve is connected to the solution heat exchanger, and the other end of the pressure reducing valve is connected to the absorber. The evaporator is connected to the second wastewater storage tank and the filtrate heat exchanger respectively. The input end of the absorber is used to connect to the output end of the heating device. The absorber is connected to the condenser, and the output end of the condenser is used to connect to the input end of the heating device.

[0007] Preferably, the volume of the slurry preheating tank is the same as the volume of the hydrothermal carbonization tank.

[0008] This invention also relates to a method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump, used to implement the aforementioned waste heat heating system for sludge hydrothermal carbonization based on an absorption heat pump, comprising: The sludge undergoes a hydrothermal carbonization reaction through a sludge hydrothermal carbonization subsystem to obtain hydrothermal carbonized slurry; After the hydrothermal carbonization reaction is completed, the hydrothermal carbonization slurry is flashed to obtain flash steam. The flash steam is used to preheat the slurry preheating tank and drive the absorption heat pump subsystem. After the flash evaporation process, the hydrothermal carbonization slurry is mechanically dehydrated, dried, and heat-exchanged through the dehydration and heat exchange subsystem to obtain hydrothermal carbon and condensed hot water at a set temperature. The condensed hot water at the set temperature is then transported to the absorption heat pump subsystem. Based on the condensate at a set temperature, the heat pump subsystem heats the return water of the heating network to obtain heating hot water.

[0009] Preferably, the hydrothermal carbonization slurry includes: The sludge is fed into a pulverizer for pulverization to obtain sludge slurry. The sludge slurry is transported to a slurry preheating tank for preheating treatment; After preheating, the sludge slurry is pumped to a hydrothermal carbonization tank for hydrothermal carbonization reaction to obtain hydrothermal carbonized slurry.

[0010] Preferably, the temperature of the hydrothermal carbonization reaction is 180℃-260℃.

[0011] Preferably, the hydrothermal carbonization slurry is flash-treated to obtain flash steam, which is then used to preheat the slurry preheating tank and drive the absorption heat pump subsystem, including: The hydrothermal carbonized slurry is transported to the primary flash tank, and primary flash steam is obtained by primary flashing through the pressure difference between the primary flash tank and the hydrothermal carbonization tank. The primary flash steam is then transported to the slurry preheating tank for preheating treatment. After the first-stage flash evaporation is completed, the hydrothermal carbonization slurry is transported to the second-stage flash tank. Second-stage flash steam is obtained by using the pressure difference between the second-stage and first-stage flash tanks. The second-stage flash steam is then transported to the generator to drive the absorption heat pump subsystem.

[0012] Preferably, the pressure range for the first-stage flash evaporation is 0.1 MPa-2.5 MPa, and the pressure range for the second-stage flash evaporation is 0.1 MPa-0.5 MPa.

[0013] Preferably, obtaining hydrothermal carbon and condensed hot water at a set temperature includes: After the secondary flash evaporation, the hydrothermal carbonized slurry is transported to a filter press for mechanical dewatering to obtain dewatered filtrate and semi-dry hydrothermal carbon. The semi-dry hydrothermal charcoal is conveyed to a product cooler for cooling to obtain cooled charcoal cake. The cooled charcoal cake is conveyed to a drying device for drying to obtain hydrothermal charcoal. Meanwhile, after the dehydrated filtrate is transported to the filtrate heat exchanger, the dehydrated filtrate exchanges heat with the condensate in the condensate tank to obtain condensed hot water and filtrate wastewater at the set temperature. The filtrate wastewater is then transported to the first wastewater storage tank for storage.

[0014] Preferably, the working fluid of the absorption heat pump subsystem is a lithium bromide solution.

[0015] Preferably, based on condensate at a set temperature, the heating system heats the return water of the heating network to obtain heating hot water, including: After the secondary flash steam is delivered to the generator, the lithium bromide solution in the generator is heated to produce steam and concentrated lithium bromide solution. In the generator, the concentrated lithium bromide solution and the dilute lithium bromide solution from the absorber, which has been pressurized by the solution pump, exchange heat in the solution heat exchanger. After the concentrated lithium bromide solution cools down, it is sent to the absorber through the pressure reduction valve. After the dilute lithium bromide solution is preheated, it is sent to the generator. Meanwhile, the condensed hot water at the set temperature is delivered to the evaporator, where the refrigerant absorbs heat and evaporates to produce evaporated water vapor and condensed wastewater, which is then delivered to the second wastewater storage tank. After the evaporated water vapor is transported to the absorber, the concentrated lithium bromide solution in the absorber absorbs the evaporated water vapor to obtain a dilute lithium bromide solution and heat of absorption. The heat is absorbed to heat the return water of the heating network after passing through the absorber to obtain semi-hot water for heating, and then the semi-hot water for heating is delivered to the condenser. The generated water vapor is transported to the condenser for condensation and heat release, which is then used to heat the semi-hot water for heating to obtain hot water for heating.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention deeply couples the sludge hydrothermal carbonization subsystem with the absorption heat pump subsystem. Through the integration of two-stage flash evaporation-dehydration filtrate heat exchange-absorption heat pump, it achieves multi-gradient recovery and utilization of waste heat and heating with near-zero energy consumption, thereby effectively reducing energy consumption, improving waste heat recovery and utilization rate, and generating heating benefits. First, the sludge dewatering performance is improved through a sludge hydrothermal carbonization subsystem, enhancing subsequent mechanical dewatering capabilities. Second, primary flash steam is used to preheat the sludge slurry, enabling the recovery and utilization of waste heat from hydrothermal carbonization and reducing energy consumption. Then, secondary flash steam is used as the driving heat source for an absorption heat pump subsystem, and the condensed hot water obtained by heat exchange between the dewatered filtrate and condensate is used as the low-temperature heat source for the absorption heat pump subsystem. This allows the absorption heat pump subsystem to output the required heating energy without consuming external heat energy. The heat absorbed in the absorber and the condensed heat in the condenser are used to sequentially heat the return water of the heating network to obtain heating hot water, thus recovering the waste heat from hot water carbonization and converting it into effective heating energy. This significantly reduces system energy consumption and carbon emissions, lowers costs, and greatly improves waste heat recovery and utilization rates, resulting in significant environmental and economic benefits. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a waste heat heating system based on sludge hydrothermal carbonization using an absorption heat pump, as described in an embodiment of the present invention.

[0018] Figure 2 This is a flowchart of a waste heat heating method for sludge hydrothermal carbonization based on an absorption heat pump, as described in an embodiment of the present invention.

[0019] Reference numerals: 1-Pulverizer, 2-Slurry preheating tank, 3-Slurry pump, 4-Hydrothermal carbonization tank, 5-First-stage flash tank, 6-Second-stage flash tank, 7-Filter press, 8-Product cooler, 9-Drying device, 10-Filtrate heat exchanger, 11-Generator, 12-Condenser, 13-Evaporator, 14-Absorber, 15-Solution heat exchanger, 16-Solution pump, 17-Pressure reducing valve, 18-Condensate tank, 19-First wastewater storage tank, 20-Second wastewater storage tank. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] A waste heat heating system based on sludge hydrothermal carbonization using an absorption heat pump, such as Figure 1 As shown, it includes: Sludge hydrothermal carbonization subsystem, dewatering heat exchange subsystem, and absorption heat pump subsystem; The sludge hydrothermal carbonization subsystem is responsible for sludge crushing, preheating, hydrothermal carbonization, and flash evaporation. The dehydration heat exchange subsystem is responsible for mechanical dehydration, drying, and generating condensed hot water at a set temperature. The absorption heat pump subsystem is used to drive the absorption heat pump through a low-grade heat source (such as flash steam) to enhance the thermal energy of the low-temperature heat source and heat the return water of the heating network to meet the heating demand.

[0022] The sludge hydrothermal carbonization subsystem includes a crusher 1, a slurry preheating tank 2, a slurry pump 3, a hydrothermal carbonization tank 4, a primary flash tank 5, and a secondary flash tank 6 connected in sequence. The slurry preheating tank 2 is connected to the primary flash tank 5. The dehydration heat exchange subsystem includes a filter press 7, a product cooler 8, a drying device 9 connected in sequence, as well as a filtrate heat exchanger 10, a condensate tank 18, and a first wastewater storage tank 19. The filter press 7 is connected to the slurry output end of the secondary flash tank 6, and the filtrate heat exchanger 10 is connected to the filter press 7, the condensate tank 18, and the first wastewater storage tank 19 respectively. The filtrate heat exchanger 10 can be a plate heat exchanger. The absorption heat pump subsystem includes a generator 11, a condenser 12, an evaporator 13, an absorber 14, a solution pump 16, a solution heat exchanger 15, a pressure reducing valve 17, and a second wastewater storage tank 20, connected in sequence. The generator 11 is connected to the steam output end of the secondary flash tank 6. The solution heat exchanger 15 is connected to the generator 11. One end of the pressure reducing valve 17 is connected to the solution heat exchanger 15, and the other end of the pressure reducing valve 17 is connected to the absorber 14. The evaporator 13 is connected to the second wastewater storage tank 20 and the filtrate heat exchanger 10, respectively. The input end of the absorber 14 is used to connect to the output end of the heating device. The absorber 14 is connected to the condenser 12, and the output end of the condenser 12 is used to connect to the input end of the heating device.

[0023] Preferably, the volume of the slurry preheating tank 2 is the same as the volume of the hydrothermal carbonization tank 4.

[0024] This invention also relates to a method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump, used to implement the aforementioned waste heat heating system for sludge hydrothermal carbonization based on an absorption heat pump, such as... Figure 2 As shown, it includes: S1. The sludge undergoes a hydrothermal carbonization reaction through the sludge hydrothermal carbonization subsystem to obtain hydrothermal carbonized slurry. The sludge is fed into crusher 1 for crushing to obtain sludge slurry. The sludge slurry is transported to slurry preheating tank 2 for preheating treatment; After preheating, the sludge slurry is transported to the hydrothermal carbonization tank 4 by the slurry pump 3 for hydrothermal carbonization reaction to obtain hydrothermal carbonized slurry; the temperature of the hydrothermal carbonization reaction is 180℃-260℃.

[0025] S2. After the hydrothermal carbonization reaction is completed, the hydrothermal carbonization slurry is flashed to obtain flash steam. The flash steam is used to preheat the slurry preheating tank 2 and drive the absorption heat pump subsystem. After the hydrothermal carbonization reaction is completed, the hydrothermal carbonized slurry is transported to the primary flash tank 5. Primary flash steam is obtained by using the pressure difference between the primary flash tank 5 and the hydrothermal carbonization tank 4. The primary flash steam is then transported to the slurry preheating tank 2 for preheating treatment. The pressure range of the primary flash is 0.1MPa-2.5MPa. After preheating treatment, the temperature range of the sludge slurry in the slurry preheating tank 2 is 30℃-120℃.

[0026] By using primary flash steam to preheat the sludge slurry in slurry preheating tank 2, the waste heat from hydrothermal carbonization can be recovered and utilized, reducing the energy consumption of hydrothermal carbonization.

[0027] After the first-stage flash evaporation is completed, the hydrothermal carbonization slurry is transported to the second-stage flash tank 6. Second-stage flash evaporation is carried out through the pressure difference between the second-stage flash tank 6 and the first-stage flash tank 5 to obtain second-stage flash steam. The second-stage flash steam is then transported to the generator 11 to drive the absorption heat pump subsystem. The pressure range of the second-stage flash evaporation is 0.1MPa-0.5MPa, and the temperature range of the second-stage flash steam is 100℃-152℃.

[0028] By utilizing secondary flash steam as the driving heat source for the absorption heat pump subsystem, the operation of the absorption heat pump subsystem can be driven without consuming external heat energy.

[0029] Among them, flash evaporation can be carried out in multiple stages to further improve the recovery and utilization rate of waste heat.

[0030] S3. After the flash evaporation process, the hydrothermal carbonization slurry is mechanically dehydrated, dried and heat-exchanged through the dehydration and heat exchange subsystem to obtain hydrothermal carbon and condensed hot water at a set temperature. The condensed hot water at the set temperature is then transported to the absorption heat pump subsystem. After the secondary flash evaporation, the hydrothermal carbonized slurry is conveyed to filter press 7 for mechanical dewatering, resulting in solid-liquid separation and obtaining dewatered filtrate and semi-dry hydrothermal carbon; the moisture content of the semi-dry hydrothermal carbon is less than 60%. The semi-dry hydrothermal charcoal is transported to product cooler 8 for cooling treatment to obtain cooled charcoal cake, thus completing the preparation work before drying. The cooled charcoal cake is conveyed to the drying device 9 for drying to obtain hydrothermal charcoal; the moisture content of the hydrothermal charcoal is less than 20%.

[0031] Meanwhile, after the dehydrated filtrate is transported to the filtrate heat exchanger 10, the dehydrated filtrate exchanges heat with the condensate in the condensate tank 18 to obtain condensed hot water and filtrate wastewater at a set temperature. The filtrate wastewater is then transported to the first wastewater storage tank 19 for storage.

[0032] The temperature range for the set temperature of the condensing hot water is 30℃-60℃.

[0033] By using the heat exchange between the dehydrated filtrate and the condensate to obtain condensed hot water at a set temperature as a low-temperature heat source for the absorption heat pump subsystem, waste heat can be further recovered and utilized, thereby improving the waste heat recovery and utilization rate.

[0034] S4. Based on the condensate at the set temperature, the heat return water of the heating system is heated through the operating absorption heat pump subsystem to obtain heating hot water.

[0035] The working fluid of the absorption heat pump subsystem is a lithium bromide solution.

[0036] After the secondary flash steam is delivered to generator 11, the lithium bromide solution in generator 11 is heated, causing the water in the lithium bromide solution to evaporate and precipitate, thereby increasing the concentration of the lithium bromide solution, resulting in steam and concentrated lithium bromide solution. The concentrated lithium bromide solution in generator 11 exchanges heat with the dilute lithium bromide solution from absorber 14 after being pressurized by solution pump 16 in solution heat exchanger 15. After the concentrated lithium bromide solution is cooled, it is depressurized through pressure reducing valve 17 and then sent to absorber 14. After the dilute lithium bromide solution is preheated, it is sent to generator 11, thus completing the circulation of lithium bromide solution. Meanwhile, the condensed hot water at the set temperature is used as the low-temperature heat source of the absorption heat pump subsystem. After the condensed hot water at the set temperature is delivered to the evaporator 13, the liquid refrigerant in the evaporator 13 absorbs heat and evaporates to obtain evaporated water vapor and condensed wastewater. The condensed wastewater is then delivered to the second wastewater storage tank 20. After the evaporated water vapor is transported to the absorber 14, the concentrated lithium bromide solution in the absorber 14 absorbs the evaporated water vapor, thereby reducing the concentration of the concentrated lithium bromide solution and obtaining a dilute lithium bromide solution and absorbing heat. The heat is absorbed to heat the return water of the heating network through the absorber 14 to obtain semi-hot water for heating, and the semi-hot water for heating is then transported to the condenser 12. The generated water vapor is transported to the condenser 12 for condensation and heat release, and the condensation heat is used to heat the semi-hot water for heating to obtain hot water for heating; the temperature range of the hot water for heating is 65℃-95℃.

[0037] By utilizing secondary flash steam and condensed hot water at a set temperature, the absorption heat pump subsystem can output the heat energy required for heating without consuming external heat energy. The heat absorbed in the absorber 14 and the condensed heat in the condenser 12 are used to heat the return water of the heating network of the heating device to obtain heating hot water. This realizes the integrated utilization of waste heat from the hydrothermal carbonization process and its conversion into effective heating energy, significantly reducing the system's energy consumption and carbon emissions, lowering costs, and greatly improving the waste heat recovery and utilization rate, resulting in significant environmental and economic benefits.

[0038] Among them, the absorption heat pump subsystem can be a dual-effect absorption heat pump subsystem or a triple-effect absorption heat pump subsystem, which can achieve higher performance when the driving heat source temperature allows.

[0039] Example 1 Sludge with a moisture content of 88% and a weight of 1000 kg is crushed by crusher 1 to obtain sludge slurry. The sludge slurry is then transported to slurry preheating tank 2 for preheating treatment for 0.5 h.

[0040] After preheating, the sludge slurry is transported to the hydrothermal carbonization tank 4 by the slurry pump 3 for hydrothermal carbonization reaction. The hydrothermal carbonization reaction is carried out at a pressure of 2.5 MPa, a temperature of 220℃, and a time of 1.5 h. After a series of reactions such as hydrolysis, dehydration, and decarboxylation are completed, hydrothermal carbonized slurry is obtained.

[0041] After the hydrothermal carbonization reaction is completed, the high-temperature and high-pressure hydrothermal carbonization slurry is transported to the first-stage flash tank 5. The pressure of the hydrothermal carbonization slurry drops instantly from 2.5 MPa to the first-stage flash pressure of 1.3 MPa. During this process, some of the water in the hydrothermal carbonization slurry is rapidly vaporized, achieving first-stage flash evaporation and obtaining 56.9 kg of first-stage flash steam. The first-stage flash steam is then transported to the slurry preheating tank 2 for preheating treatment, which can preheat the sludge slurry in the slurry preheating tank 2 from 25°C to 62.09°C.

[0042] After the first-stage flash evaporation is completed, the hydrothermal carbonization slurry is transported to the second-stage flash tank 6. The pressure of the second-stage flash evaporation is 0.29 MPa. The second-stage flash evaporation is carried out through the pressure difference between the second-stage flash tank 6 and the first-stage flash tank 5 to obtain 107.73 kg of second-stage flash steam. The driving steam mass flow rate is 0.02 kg / s. The second-stage flash steam is transported to the generator 11 through the heat insulation pipe to drive the absorption heat pump subsystem.

[0043] After the secondary flash evaporation, the hydrothermal carbonization slurry is conveyed to the filter press 7 for mechanical dewatering to obtain dewatered filtrate and semi-dry hydrothermal carbon; the semi-dry hydrothermal carbon is conveyed to the product cooler 8 for cooling treatment to obtain cooled carbon cake; the cooled carbon cake is conveyed to the drying device 9 for drying to obtain hydrothermal carbon.

[0044] After the dehydrated filtrate is transported to the filtrate heat exchanger 10, the 132.4°C dehydrated filtrate exchanges heat with the 25°C condensate in the condensate tank 18 to obtain 35°C hot condensate and filtrate wastewater. The 35°C hot condensate is transported to the evaporator 13 at a flow rate of 0.684 kg / s, and the filtrate wastewater is transported to the first wastewater storage tank 19 for storage.

[0045] A secondary flash steam-driven absorption heat pump subsystem operates, heating the lithium bromide solution in generator 11 to produce steam and concentrated lithium bromide solution. The steam is then transported to condenser 12 for condensation and heat release, and through solution pump 16 and pressure reducing valve 17, the concentrated lithium bromide solution exchanges heat with the dilute lithium bromide solution in absorber 14 at solution heat exchanger 15. After cooling, the concentrated lithium bromide solution is transported to absorber 14, and after preheating, the dilute lithium bromide solution is transported to generator 11. Simultaneously, 35°C condensed hot water... The liquid refrigerant in evaporator 13 undergoes heat absorption and evaporation to obtain evaporated water vapor and condensed wastewater. The condensed wastewater is then transported to the second wastewater storage tank 20. After the evaporated water vapor is transported to absorber 14, the concentrated lithium bromide solution in absorber 14 absorbs the evaporated water vapor to obtain a dilute lithium bromide solution and absorbed heat. Then, the absorbed heat is used to heat the 50°C return water from the heating network that has passed through absorber 14 to obtain semi-hot water for heating. The semi-hot water for heating is then transported to condenser 12, where the condensed heat is used to heat the semi-hot water for heating to obtain 70°C hot water for heating.

[0046] As can be seen, the above system and method achieve zero-energy heating, with the heat source entirely derived from waste heat within the system. The total energy consumption for sludge treatment is 865.175 MJ, while the heating power is 74.15 kW. Without waste heat recovery, the total energy consumption would be 1094.5 MJ, thus reducing energy consumption by 21.04% and generating enough heat to sustain 1483 m³ of sludge. 2 The benefits of heating the building area; therefore, compared with the case of no waste heat recovery, the present invention saves 20.94 kgce of primary energy.

[0047] Example 2 Sludge with a moisture content of 88% and a weight of 1000 kg is crushed by crusher 1 to obtain sludge slurry. The sludge slurry is then transported to slurry preheating tank 2 for preheating treatment for 0.5 h.

[0048] After preheating, the sludge slurry is transported to the hydrothermal carbonization tank 4 by the slurry pump 3 for hydrothermal carbonization reaction. The hydrothermal carbonization reaction is carried out at a pressure of 2.5 MPa, a temperature of 220℃, and a time of 1.5 h. After a series of reactions such as hydrolysis, dehydration, and decarboxylation are completed, hydrothermal carbonized slurry is obtained.

[0049] After the hydrothermal carbonization reaction is completed, the high-temperature and high-pressure hydrothermal carbonization slurry is transported to the first-stage flash tank 5. The pressure of the hydrothermal carbonization slurry drops instantly from 2.5 MPa to the pressure of the first-stage flash tank 1.4 MPa. During this process, some of the water in the hydrothermal carbonization slurry is rapidly vaporized, and 50.18 kg of first-stage flash steam is obtained. The first-stage flash steam is transported to the slurry preheating tank 2 for preheating treatment, which can preheat the sludge slurry in the slurry preheating tank 2 from 25°C to 57.92°C.

[0050] After the first-stage flash evaporation is completed, the hydrothermal carbonization slurry is transported to the second-stage flash tank 6. The pressure of the second-stage flash evaporation is 0.43 MPa. The second-stage flash evaporation is carried out through the pressure difference between the second-stage flash tank 6 and the first-stage flash tank 5 to obtain 90.19 kg of second-stage flash steam. The driving steam mass flow rate is 0.017 kg / s. The second-stage flash steam is transported to the generator 11 through the heat insulation pipe to drive the absorption heat pump subsystem.

[0051] After the secondary flash evaporation, the hydrothermal carbonization slurry is conveyed to the filter press 7 for mechanical dewatering to obtain dewatered filtrate and semi-dry hydrothermal carbon; the semi-dry hydrothermal carbon is conveyed to the product cooler 8 for cooling treatment to obtain cooled carbon cake; the cooled carbon cake is conveyed to the drying device 9 for drying to obtain hydrothermal carbon.

[0052] After the dehydrated filtrate is transported to the filtrate heat exchanger 10, the filtrate at 146.2°C exchanges heat with the condensate at 25°C in the condensate tank 18 to obtain condensed hot water at 35°C and filtrate wastewater. The condensed hot water at 35°C is transported to the evaporator 13 at a flow rate of 0.621 kg / s, and the filtrate wastewater is transported to the first wastewater storage tank 19 for storage.

[0053] A secondary flash steam-driven absorption heat pump subsystem operates, heating the lithium bromide solution in generator 11 to produce steam and concentrated lithium bromide solution. The steam is then transported to condenser 12 for condensation and heat release, and through solution pump 16 and pressure reducing valve 17, the concentrated lithium bromide solution exchanges heat with the dilute lithium bromide solution in absorber 14 at solution heat exchanger 15. After cooling, the concentrated lithium bromide solution is transported to absorber 14, and after preheating, the dilute lithium bromide solution is transported to generator 11. Simultaneously, 35°C condensed hot water... The liquid refrigerant in evaporator 13 undergoes heat absorption and evaporation to obtain evaporated water vapor and condensed wastewater. The condensed wastewater is then transported to the second wastewater storage tank 20. After the evaporated water vapor is transported to absorber 14, the concentrated lithium bromide solution in absorber 14 absorbs the evaporated water vapor to obtain a dilute lithium bromide solution and absorbed heat. Then, the absorbed heat is used to heat the 50°C return water from the heating network that has passed through absorber 14 to obtain semi-hot water for heating. The semi-hot water for heating is then transported to condenser 12, where the condensed heat is used to heat the semi-hot water for heating to obtain 70°C hot water for heating.

[0054] As can be seen, the above system and method achieve zero-energy heating, with the heat source entirely derived from waste heat within the system. The total energy consumption for sludge treatment is 881.407 MJ, while the heating power is 65.33 kW. Without waste heat recovery, the total energy consumption would be 1094.5 MJ, thus reducing energy consumption by 19.47% and generating enough heat to sustain 1306.6 m³ of heating. 2 The benefits of heating the building area; therefore, compared with the case of no waste heat recovery, the present invention saves 18.78 kgce of primary energy.

[0055] Example 3 Sludge with a moisture content of 88% and a weight of 1000 kg is crushed by crusher 1 to obtain sludge slurry. The sludge slurry is then transported to slurry preheating tank 2 for preheating treatment for 0.5 h.

[0056] After preheating, the sludge slurry is transported to the hydrothermal carbonization tank 4 by the slurry pump 3 for hydrothermal carbonization reaction. The hydrothermal carbonization reaction is carried out at a pressure of 2.5 MPa, a temperature of 220℃, and a time of 1.5 h. After a series of reactions such as hydrolysis, dehydration, and decarboxylation are completed, hydrothermal carbonized slurry is obtained.

[0057] After the hydrothermal carbonization reaction is completed, the high-temperature and high-pressure hydrothermal carbonization slurry is transported to the first-stage flash tank 5. The pressure of the hydrothermal carbonization slurry drops instantly from 2.5 MPa to the first-stage flash pressure of 1.1 MPa. During this process, some of the water in the hydrothermal carbonization slurry is rapidly vaporized, achieving first-stage flash evaporation and obtaining 71.93 kg of first-stage flash steam. The first-stage flash steam is then transported to the slurry preheating tank 2 for preheating treatment, which can preheat the sludge slurry in the slurry preheating tank 2 from 25°C to 70.98°C.

[0058] After the first-stage flash evaporation is completed, the hydrothermal carbonization slurry is transported to the second-stage flash tank 6. The pressure of the second-stage flash evaporation is 0.31 MPa. The second-stage flash evaporation is carried out through the pressure difference between the second-stage flash tank 6 and the first-stage flash tank 5 to obtain 89.77 kg of second-stage flash steam. The driving steam mass flow rate is 0.017 kg / s. The second-stage flash steam is transported to the generator 11 through the heat insulation pipe to drive the absorption heat pump subsystem.

[0059] After the secondary flash evaporation, the hydrothermal carbonization slurry is conveyed to the filter press 7 for mechanical dewatering to obtain dewatered filtrate and semi-dry hydrothermal carbon; the semi-dry hydrothermal carbon is conveyed to the product cooler 8 for cooling treatment to obtain cooled carbon cake; the cooled carbon cake is conveyed to the drying device 9 for drying to obtain hydrothermal carbon.

[0060] After the dehydrated filtrate is transported to the filtrate heat exchanger 10, the 134.6°C dehydrated filtrate exchanges heat with the 25°C condensate in the condensate tank 18 to obtain 35°C hot condensate and filtrate wastewater. The 35°C hot condensate is transported to the evaporator 13 at a flow rate of 0.54 kg / s, and the filtrate wastewater is transported to the first wastewater storage tank 19 for storage.

[0061] A secondary flash steam-driven absorption heat pump subsystem operates, heating the lithium bromide solution in generator 11 to produce steam and concentrated lithium bromide solution. The steam is then transported to condenser 12 for condensation and heat release, and through solution pump 16 and pressure reducing valve 17, the concentrated lithium bromide solution exchanges heat with the dilute lithium bromide solution in absorber 14 at solution heat exchanger 15. After cooling, the concentrated lithium bromide solution is transported to absorber 14, and after preheating, the dilute lithium bromide solution is transported to generator 11. Simultaneously, 35°C condensed hot water... The liquid refrigerant in evaporator 13 undergoes heat absorption and evaporation to obtain evaporated water vapor and condensed wastewater. The condensed wastewater is then transported to the second wastewater storage tank 20. After the evaporated water vapor is transported to absorber 14, the concentrated lithium bromide solution in absorber 14 absorbs the evaporated water vapor to obtain a dilute lithium bromide solution and absorbed heat. Then, the absorbed heat is used to heat the 50°C return water from the heating network that has passed through absorber 14 to obtain semi-hot water for heating. The semi-hot water for heating is then transported to condenser 12, where the condensed heat is used to heat the semi-hot water for heating to obtain 70°C hot water for heating.

[0062] As can be seen, the above system and method achieve zero-energy heating, with the heat source entirely from waste heat within the system. The energy consumption for the entire sludge treatment is 830.57 MJ, while the heating power is 62.87 kW. Without waste heat recovery, the energy consumption of the entire system would be 1094.5 MJ, thus reducing energy consumption by 24.11% and generating enough heat to sustain 1257.4 m³ of heating capacity. 2The benefits of heating the building area; therefore, compared with the case of no waste heat recovery, the present invention saves 20.03 kgce of primary energy.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sludge hydrothermal carbonization waste heat heating system based on an absorption heat pump, characterized in that, include: Sludge hydrothermal carbonization subsystem, dewatering heat exchange subsystem, and absorption heat pump subsystem; The sludge hydrothermal carbonization subsystem includes a pulverizer, a slurry preheating tank, a slurry pump, a hydrothermal carbonization tank, a primary flash tank, and a secondary flash tank connected in sequence, with the slurry preheating tank connected to the primary flash tank; The dehydration heat exchange subsystem includes a filter press, a product cooler, a drying device, a filtrate heat exchanger, a condensate tank, and a first wastewater storage tank connected in sequence. The filter press is connected to the slurry output end of the secondary flash tank, and the filtrate heat exchanger is connected to the filter press, the condensate tank, and the first wastewater storage tank respectively. The absorption heat pump subsystem includes a generator, a condenser, an evaporator, an absorber, a solution pump, a solution heat exchanger, a pressure reducing valve, and a second wastewater storage tank, connected in sequence. The generator is connected to the steam output end of the secondary flash tank, the solution heat exchanger is connected to the generator, one end of the pressure reducing valve is connected to the solution heat exchanger, and the other end of the pressure reducing valve is connected to the absorber. The evaporator is connected to the second wastewater storage tank and the filtrate heat exchanger, respectively. The input end of the absorber is used to connect to the output end of the heating device, the absorber is connected to the condenser, and the output end of the condenser is used to connect to the input end of the heating device.

2. A sludge hydrothermal carbonization waste heat heating system based on an absorption heat pump according to claim 1, characterized in that: The volume of the slurry preheating tank is the same as that of the hydrothermal carbonization tank.

3. A method for heating using waste heat from sludge hydrothermal carbonization based on an absorption heat pump, characterized in that, To implement the sludge hydrothermal carbonization waste heat heating system based on any one of claims 1-2, the system comprises: The sludge undergoes a hydrothermal carbonization reaction through a sludge hydrothermal carbonization subsystem to obtain hydrothermal carbonized slurry; After the hydrothermal carbonization reaction is completed, the hydrothermal carbonization slurry is flashed to obtain flash steam. The flash steam is used to preheat the slurry preheating tank and drive the absorption heat pump subsystem. After the flash evaporation process, the hydrothermal carbonization slurry is mechanically dehydrated, dried, and heat-exchanged through the dehydration and heat exchange subsystem to obtain hydrothermal carbon and condensed hot water at a set temperature. The condensed hot water at the set temperature is then transported to the absorption heat pump subsystem. Based on the condensate at a set temperature, the heat pump subsystem heats the return water of the heating network to obtain heating hot water.

4. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 3, characterized in that, The obtained hydrothermal carbonization slurry includes: The sludge is fed into a pulverizer for pulverization to obtain sludge slurry. The sludge slurry is transported to a slurry preheating tank for preheating treatment; After preheating, the sludge slurry is pumped to a hydrothermal carbonization tank for hydrothermal carbonization reaction to obtain hydrothermal carbonized slurry.

5. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 4, characterized in that: The temperature for hydrothermal carbonization is 180℃-260℃.

6. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 3, characterized in that, The process of flash-evaporating the hydrothermal carbonized slurry to obtain flash steam, and then using the flash steam to preheat the slurry preheating tank and drive the absorption heat pump subsystem, includes: The hydrothermal carbonized slurry is transported to the primary flash tank, and primary flash steam is obtained by primary flashing through the pressure difference between the primary flash tank and the hydrothermal carbonization tank. The primary flash steam is then transported to the slurry preheating tank for preheating treatment. After the first-stage flash evaporation is completed, the hydrothermal carbonization slurry is transported to the second-stage flash tank. Second-stage flash steam is obtained by using the pressure difference between the second-stage and first-stage flash tanks. The second-stage flash steam is then transported to the generator to drive the absorption heat pump subsystem.

7. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 6, characterized in that: The pressure range for the first-stage flash evaporation is 0.1 MPa to 2.5 MPa, and the pressure range for the second-stage flash evaporation is 0.1 MPa to 0.5 MPa.

8. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 6, characterized in that, The process of obtaining hydrothermal carbon and condensed hot water at a set temperature includes: After the secondary flash evaporation, the hydrothermal carbonized slurry is transported to a filter press for mechanical dewatering to obtain dewatered filtrate and semi-dry hydrothermal carbon. The semi-dry hydrothermal charcoal is conveyed to a product cooler for cooling to obtain cooled charcoal cake. The cooled charcoal cake is conveyed to a drying device for drying to obtain hydrothermal charcoal. Meanwhile, after the dehydrated filtrate is transported to the filtrate heat exchanger, the dehydrated filtrate exchanges heat with the condensate in the condensate tank to obtain condensed hot water and filtrate wastewater at the set temperature. The filtrate wastewater is then transported to the first wastewater storage tank for storage.

9. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 6, characterized in that: The working fluid of the absorption heat pump subsystem is a lithium bromide solution.

10. A method for heating waste heat from sludge hydrothermal carbonization based on an absorption heat pump according to claim 9, characterized in that, The condensate, based on a set temperature, is heated by an absorption heat pump subsystem to obtain heating hot water for the heating system's return network, including: After the secondary flash steam is delivered to the generator, the lithium bromide solution in the generator is heated to produce steam and concentrated lithium bromide solution. In the generator, the concentrated lithium bromide solution and the dilute lithium bromide solution from the absorber, which has been pressurized by the solution pump, exchange heat in the solution heat exchanger. After the concentrated lithium bromide solution cools down, it is sent to the absorber through the pressure reduction valve. After the dilute lithium bromide solution is preheated, it is sent to the generator. Meanwhile, the condensed hot water at the set temperature is delivered to the evaporator, where the refrigerant absorbs heat and evaporates to produce evaporated water vapor and condensed wastewater, which is then delivered to the second wastewater storage tank. After the evaporated water vapor is transported to the absorber, the concentrated lithium bromide solution in the absorber absorbs the evaporated water vapor to obtain a dilute lithium bromide solution and heat of absorption. The heat is absorbed to heat the return water of the heating network after passing through the absorber to obtain semi-hot water for heating, and then the semi-hot water for heating is delivered to the condenser. The generated water vapor is transported to the condenser for condensation and heat release, which is then used to heat the semi-hot water for heating to obtain hot water for heating.

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