A multi-stage energy utilization thermal dehydration process system for solid waste with high moisture content

Abstract

A multi-stage thermal dehydration process system for high-moisture-content solid waste is disclosed. This system includes an indirect heating evaporator, a direct contact heat extractor, an indirect heat exchanger, a secondary condenser, a preheater, a mixer, a hot water buffer tank, an airflow dryer, a primary heater, a secondary heater, an energy return unit, a dehumidifying condenser, and a cooling tower. The two-stage thermal dehydration process system of this invention features independent feed and discharge. Through multi-stage utilization of waste heat energy and the selection of water as the energy transfer carrier, efficiency is maximized. Furthermore, the system meets the long-distance energy transfer requirements between the two dehydration stages, solving the problems of corresponding equipment arrangement, mutual interference between feed and discharge, and synchronous equipment operation in two-stage thermal dehydration processes.

Description

Technical Field

[0001] This invention relates to the field of dewatering technology for solid waste with high moisture content, and specifically to a thermal dewatering process system that utilizes energy in multiple stages. Background Technology

[0002] Existing thermal dehydration processes often involve multi-stage energy utilization, with feed and discharge processes frequently interfering with each other and limited application scenarios. The two-stage thermal dehydration system of this invention features independent feed and discharge processes. By utilizing waste heat energy in multiple stages and selecting water as the energy transfer medium, it can achieve… To maximize efficiency, the system meets the long-distance energy transfer requirements between the two-stage dewatering equipment, solving the problems of corresponding equipment layout, mutual interference between feed and discharge, and synchronous operation of equipment in the two-stage dewatering process. Summary of the Invention

[0003] The purpose of this invention is to provide a thermal dehydration process system for solid waste with high moisture content, capable of... Maximize efficiency utilization to achieve the goal of energy saving and efficiency improvement.

[0004] The technical solution of this invention is:

[0005] A multi-stage energy utilization thermal dehydration process system for high-moisture-content solid waste includes an indirect heating evaporation device, a direct contact heat extractor, an indirect heat exchanger, a secondary condenser, an airflow drying device, a primary heater, a secondary heater, an energy self-return device, and a dehumidifying condenser. The system is characterized by further including a preheater, a mixer, a hot water buffer tank, a cooling tower, a boiler feedwater system, a deodorization / incineration system, and a wastewater treatment system.

[0006] The indirect heating evaporation equipment is a first-stage dehydration device. The solid waste input end is connected to the preheater, which is connected to the indirect heating evaporation equipment. The bottom of the indirect heating evaporation equipment is provided with a discharge port. The indirect heating evaporation equipment heats and dehydrates the solid waste using saturated steam. The exhaust gas outlet of the indirect heating evaporation equipment is connected to one input port of the direct contact heat extractor. The exhaust gas outlet of the direct contact heat extractor is connected to one end of the secondary condenser.

[0007] The circulating water of the direct contact heat extractor is connected to the indirect heat exchanger via a water pump, and the water is circulated between the direct contact heat extractor and the indirect heat exchanger; the hot water outlet of the indirect heat exchanger is connected to one end of the hot water buffer tank, and the other end of the hot water buffer tank is connected to the second inlet of the mixer via a water pump.

[0008] The airflow drying equipment is a two-stage dehydration device. It has a high-moisture-content solid waste inlet at the top and a discharge outlet at the bottom. The hot air inlet of the airflow drying equipment is connected to one end of the secondary heater; the other end of the secondary heater is connected to the hot air outlet of the primary heater. The secondary heater heats the hot air using saturated steam. The hot water outlet of the secondary heater merges with the hot water outlet of the indirect heating evaporation device. The hot air outlet of the airflow drying equipment is connected to the first input port of the energy return device. The other end of the energy return device is connected to the dehumidifying condenser. The hot air outlet of the dehumidifying condenser is connected to the second input port of the energy return device. The hot air from the energy return device ultimately connects to the hot air inlet of the primary heater to complete the circulation.

[0009] Preferably, the solid waste from the indirect heating evaporation equipment is input through the preheater, the hot water inlet of the preheater is connected to the hot water outlet of the primary heater, and the hot water outlet of the preheater is connected to the boiler makeup water system of the thermal power plant.

[0010] Preferably, the exhaust gas outlet of the secondary condenser is connected to the deodorization system / incineration system.

[0011] Preferably, the condensate outlets of both the secondary condenser and the dehumidifying condenser are connected to the wastewater treatment system.

[0012] Preferably, the high-temperature and high-pressure steam-water mixture generated by the indirect heating evaporation equipment is connected to the first inlet of the mixer via a drain valve, the outlet of the mixer is connected to the hot water inlet of the primary heater, and the hot water outlet of the primary heater is distributed to the preheater and the indirect heat exchanger via pipelines.

[0013] Preferably, the circulating cooling water for both the dehumidifying condenser and the secondary condenser is supplied through the cooling tower. The circulating water outlet of the cooling tower is distributed to the dehumidifying condenser and the secondary condenser by a water pump, and the circulating water inlet of the cooling tower is also connected to the dehumidifying condenser and the secondary condenser.

[0014] Beneficial effects:

[0015] The thermal dehydration process system of this invention employs multi-stage energy utilization. It extracts waste heat from the exhaust gas generated by the first-stage dehydration equipment through surface heat exchange, uses hot water as an energy transfer carrier, and then mixes it with high-temperature hydrophobic water to heat the circulating hot air in the second-stage dehydration equipment, thereby achieving… Maximizing efficiency. This invention features two-stage solid waste dewatering with independent feed and discharge, while also meeting the long-distance energy transport requirements between the two dewatering devices. It solves the problems of corresponding equipment layout, mutual interference between feed and discharge, and synchronous operation of equipment in two-stage dewatering processes, thus achieving energy saving and efficiency improvement. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system of the present invention;

[0017] Among them, the following components are included: 1. Indirect heating evaporator; 2. Direct contact heat extractor; 3. Indirect heat exchanger; 4. Secondary condenser; 5. Preheater; 6. Mixer; 7. Hot water buffer tank; 8. Airflow drying equipment; 9. Primary heater; 10. Secondary heater; 11. Energy return device; 12. Dehumidifying condenser; 13. Cooling tower; 14. Boiler water supply system; 15. Deodorization system / incineration system; 16. Wastewater treatment system. Detailed Implementation

[0018] The overall process of a multi-stage energy utilization thermal dehydration process system for solid waste with high moisture content is as follows: Figure 1 As shown, it includes an indirect heating evaporator 1, a direct contact heat extractor 2, an indirect heat exchanger 3, a secondary condenser 4, a preheater 5, a mixer 6, a hot water buffer tank 7, an airflow drying device 8, a primary heater 9, a secondary heater 10, an energy return device 11, a dehumidifying condenser 12, a cooling tower 13, a boiler feedwater system 14, a deodorization system / incineration system 15, and a wastewater treatment system 16.

[0019] The high-moisture-content solid waste energy multi-stage thermal dehydration process system mainly includes a two-stage dehydration process. The first-stage dehydration utilizes indirect heat transfer between steam and the material. The residual heat of the evaporated waste gas is extracted through water, and then mixed with high-temperature hydrophobic material to heat the circulating hot air in the second-stage dehydration equipment, thereby achieving... Maximizing efficiency.

[0020] The indirect heating evaporation equipment 1 is a first-stage dehydration device. The heat source is saturated steam. The feed is solid waste with a moisture content of 60%-80%, and the output moisture content can reach 35% to facilitate subsequent solid waste transportation and treatment. The moisture in the solid waste is heated and evaporated to form waste steam, the outlet of which is connected to an input port of the direct contact heat extractor 2. It should be noted that the indirect heating evaporation equipment 1 may include a thin-film evaporator, a thin-layer dryer, a paddle dryer, a horizontal disc dryer, a vertical disc dryer, etc., and multiple devices can be used in parallel. The number and form are not limited; that is, hot water from multiple first-stage dehydration devices can be mixed and fed into the mixer 6, and distributed to multiple second-stage dehydration devices as a heat source.

[0021] The direct contact heat extractor 2 utilizes atomized circulating water for direct contact heat exchange with waste gas, reducing the waste gas temperature from approximately 100℃ to approximately 75℃. The heat-exchanged waste gas then enters the secondary condenser 4 for further cooling, and through indirect heat exchange with cooling circulating water, the temperature is reduced to approximately 45℃. The heat-exchanged circulating water is then pumped into the indirect heat exchanger 3, where it indirectly heats the water in the hot water circulation system at the other end. It should be noted that the heat extracted from the waste gas can be transferred to downstream energy utilization equipment using fluids such as gas, oil, or water as carrier gases. However, gases have a lower density; to carry the same amount of energy, their volume is only one-thousandth that of water, and their specific heat is one-third that of water. Therefore, for the same amount of heat transfer, the diameter of the gas transport pipeline is much larger than that of water, and the power of the gas transport fan is much greater than that of the water pump, resulting in higher transport costs. Furthermore, using heat transfer oil can lead to secondary pollution problems such as leaks, resulting in high long-term operation and maintenance costs. Therefore, using water as the heat extraction carrier solves the problems of equipment layout limitations and long-distance transport.

[0022] The indirect heat exchanger 3 has a heat source of spray water circulation at one end and a cold source of hot water circulation at the other end. The spray water temperature drops from about 95°C to about 73°C, and the hot water temperature rises from about 70°C to about 90°C. The hot water outlet of the indirect heat exchanger 3 is connected to one end of the hot water buffer tank 7, and the other end of the hot water buffer tank 7 is connected to the second inlet of the mixer 6 via a water pump. The 100°C high-temperature and high-pressure steam-water mixture generated by the indirect heating evaporation device 1 is drained through a drain valve and then connected to the first inlet of the mixer 6. The two inlets of the mixer 6 maximize the utilization of the waste heat from the first-stage dehydration and the waste heat from the drain, respectively. The extracted heat is used as the heat source carrier for the subsequent second-stage dehydration through hot water.

[0023] The output port of the mixer 6 is connected to the hot water input port of the primary heater 9, and the hot water temperature can reach about 90°C. The circulating air of the secondary dehydration equipment is heated through indirect heat exchange. The hot water output port after heat exchange is distributed to the preheater 5 and the indirect heat exchanger 3 through pipelines, and the hot water temperature is about 70°C.

[0024] The preheater 5 preheats the solid waste with a water content of 60%-80% by using the hot water output from the primary heater 9. This indirectly increases the initial temperature of the solid waste, thereby reducing the consumption of saturated steam during the first-stage dehydration. The hot water outlet of the preheater 5 is connected to the boiler water supply system 14 of the thermal power plant, meaning that the condensate generated during the first-stage dehydration process is ultimately supplied to the boiler system 14 of the thermal power plant.

[0025] The airflow drying equipment 8 is a two-stage dehydration device. It has a high-moisture-content solid waste inlet at the top and a discharge outlet at the bottom, with its inlet and outlet independent of the first-stage dehydration equipment. The airflow drying equipment 8 heats and evaporates the material through direct contact between hot air and the solid waste. The hot air inlet temperature can reach 80℃, and the outlet temperature is approximately 55℃. The hot air outlet of the airflow drying equipment 8 is connected to the first input port of the energy return unit 11, and the other end of the energy return unit 11 is connected to the dehumidifier condenser 12. The hot air outlet of the dehumidifier condenser 12 is connected to the second input port of the energy return unit 11. The hot air from the energy return unit 11 is ultimately connected to the hot air inlet of the primary heater 9 to complete the circulation. During this process, the hot air carries moisture, which is cooled and condensed into water at the hot end of the energy return unit 11 before entering the dehumidifier condenser 12 for further cooling and dehumidification, restoring the hot air to its original moisture content for continued recycling. This air then returns to the cold end of the energy return unit 11, undergoes heat exchange, and enters the primary heater 9. The temperature of the hot air before heating is about 50°C. The primary heater 9 heats the hot air with 90°C hot water generated by the first-stage dehydration, raising the temperature to about 80°C. The hot air outlet is connected to one of the inlets of the secondary heater 10. When the hot air temperature cannot reach 80°C, that is, when the heat generated by the first-stage dehydration process is less than the heat required for the second-stage dehydration, the circulating hot air needs to be supplemented with heat. By supplementing the secondary heater 10 with saturated steam, the circulating gas can be heated a second time to ensure the stable operation of the subsequent second-stage dehydration. After heat exchange, the saturated steam is used as high-temperature condensate and can be connected to the hot water outlet of the indirect heating evaporation device 1 for convergence.

[0026] The cold side of both the dehumidifying condenser 12 and the secondary condenser 4 uses circulating cooling water supplied by the cooling tower 13. The circulating water outlet of the cooling tower 13 is distributed to the dehumidifying condenser 12 and the secondary condenser 4 via a water pump, and the circulating water inlet of the cooling tower is also connected to the dehumidifying condenser 12 and the secondary condenser 4. Both portions of cooling water serve as the cold-side medium of the heat exchangers, used to reduce the humidity of the circulating air during the second-stage dehydration and to reduce the temperature of the exhaust gas after the first-stage dehydration, respectively. The temperatures of the cooling water before and after heat exchange are approximately 33°C and 45°C, respectively. The dehumidifying condenser 12 is equipped with a condensate outlet connected to the wastewater treatment system 16.

[0027] The exhaust gas outlet of the secondary condenser 4 is connected to the deodorization system / incineration system 15, and the exhaust gas is finally treated by subsequent deodorization or incineration. The condensate outlets of the secondary condenser 4 and the dehumidification condenser 12 are both connected to the sewage treatment system 16, and are finally treated by subsequent sewage treatment processes.

Claims

1. A multi-stage energy utilization thermal dehydration process system for solid waste with high moisture content, comprising an indirect heating evaporator (1), a direct contact heat extractor (2), an indirect heat exchanger (3), a secondary condenser (4), an airflow drying device (8), a primary heater (9), a secondary heater (10), an energy return device (11), and a dehumidifying condenser (12), characterized in that, It also includes a preheater (5), a mixer (6), a hot water buffer tank (7), a cooling tower (13), a boiler feedwater system (14), a deodorization system / incineration system (15), and a wastewater treatment system (16). The indirect heating evaporation device (1) is a first-stage dehydration device. The solid waste input end is connected to the preheater (5), and the preheater (5) is connected to the indirect heating evaporation device (1). The bottom of the indirect heating evaporation device (1) is provided with a discharge port. The indirect heating evaporation device (1) heats and dehydrates the solid waste with saturated steam. The exhaust gas outlet of the indirect heating evaporation device (1) is connected to one input port of the direct contact heat extractor (2). The exhaust gas outlet of the direct contact heat extractor (2) is connected to one end of the secondary condenser (4). The circulating water of the direct contact heat extractor (2) is connected to the indirect heat exchanger (3) via a water pump, and the water is circulated between the direct contact heat extractor (2) and the indirect heat exchanger (3); the hot water outlet of the indirect heat exchanger (3) is connected to one end of the hot water buffer tank (7), and the other end of the hot water buffer tank (7) is connected to the second inlet of the mixer (6) via a water pump; The airflow drying device (8) is a two-stage dehydration device. It has a high moisture content solid waste inlet at the top and an outlet at the bottom. The hot air inlet of the airflow drying device (8) is connected to one end of the secondary heater (10). The other end of the secondary heater (10) is connected to the hot air outlet of the primary heater (9). The secondary heater (10) heats the hot air with saturated steam. The hot water outlet of the secondary heater (10) is connected to the hot water outlet of the indirect heating evaporation device (1). The hot air outlet of the airflow drying device (8) is connected to the first input port of the energy return device (11). The other end of the energy return device (11) is connected to the dehumidifying condenser (12). The hot air outlet of the dehumidifying condenser (12) is connected to the second input port of the energy return device (11). The hot air of the energy return device (11) is finally connected to the hot air inlet of the primary heater (9) to complete the circulation.

2. The energy multi-stage utilization thermal dehydration process system for high-moisture-content solid waste according to claim 1, characterized in that, The solid waste of the indirect heating evaporation equipment (1) is input through the preheater (5), the hot water inlet of the preheater (5) is connected to the hot water outlet of the primary heater (9), and the hot water outlet of the preheater (5) is connected to the boiler water supply system (14).

3. The energy multi-stage utilization thermal dehydration process system for high-moisture-content solid waste according to claim 1, characterized in that, The exhaust outlet of the secondary condenser (4) is connected to the deodorization system / incineration system (15).

4. The energy multi-stage utilization thermal dehydration process system for high-moisture-content solid waste according to claim 1, characterized in that, The condensate outlets of the secondary condenser (4) and the dehumidifying condenser (12) are both connected to the wastewater treatment system (16).

5. The multi-stage energy utilization thermal dehydration process system for high-moisture-content solid waste according to claim 1, characterized in that, The high-temperature and high-pressure steam-water mixture generated by the indirect heating evaporation device (1) is connected to the first inlet of the mixer (6) via a drain valve. The outlet of the mixer (6) is connected to the hot water inlet of the primary heater (9). The hot water outlet of the primary heater (9) is distributed to the preheater (5) and the indirect heat exchanger (3) via pipelines.

6. The energy multi-stage utilization thermal dehydration process system for high-moisture-content solid waste according to claim 1, characterized in that, The circulating cooling water for the dehumidifying condenser (12) and the secondary condenser (4) is provided by the cooling tower (13). The circulating water outlet of the cooling tower (13) is distributed to the dehumidifying condenser (12) and the secondary condenser (4) by a water pump. The circulating water inlet of the cooling tower (13) is also connected to the dehumidifying condenser (12) and the secondary condenser (4).

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