CN113686190B - System and method for comprehensively recycling and utilizing low-temperature waste heat - Google Patents

Abstract

The invention relates to the technical field of environmental protection, in particular to a system for comprehensively recovering and utilizing low-temperature waste heat, which comprises a heat discharge module, a heat pump unit and a heat utilization module; the heat utilization module comprises a deaerator system, a water treatment system, a heating boiler system and a heat network circulating water system, cold water in the heat pump unit is sent out through a cold water outlet pipe and is respectively sent into the boiler heating system, the circulating water system and the continuous sewage system, a hot water outlet pipe and a cold water return pipe are communicated in the heat pump unit, and the hot water outlet pipe is communicated with the deaerator system, the water treatment system, the heating boiler system and the heat network circulating water system. According to the invention, the flue gas waste heat is recycled, so that the flue gas exhaust temperature can be reduced, the emission of smoke dust is reduced, the generation of white smoke plume of the flue gas is reduced, meanwhile, the sensible heat and the condensation latent heat of the flue gas can be recycled, and the full utilization of waste heat resources is realized through the heat pump.

Description

A system and method for comprehensive recovery and utilization of low-temperature waste heat

Technical field

The present invention relates to the field of environmental protection technology, and in particular to a system and method for comprehensive recovery and utilization of low-temperature waste heat.

Background technique

In the process of combustion power generation, fuel is burned in the boiler, and the heat generated by the combustion is used to generate electricity and heat. However, during the working process, more heat is wasted, resulting in low combustion utilization. The wasted heat includes the following:

1. During the operation of coal-fired, gas-fired boilers, gas steam turbines and gas-fired internal combustion engine power generation, heating or cogeneration units, it is common that the exhaust gas temperature is relatively high (wet desulfurization exhaust gas temperature is 45-55℃, gas The exhaust gas temperature of the boiler or gas internal combustion engine is 80°C.)

2. Circulating cooling water discharges low-temperature waste heat into the atmosphere through the cooling tower, and at the same time consumes a large amount of cooling evaporated water.

3. Continuously pass the fixed discharge waste heat through the fixed discharge expansion vessel to cool down and neutralize the boiler wastewater. A large amount of water is needed to neutralize the high-temperature sewage. After the sewage is reduced to 30°C, it is discharged into the water treatment workshop and processed in the water treatment workshop. Afterwards, reuse.

In the process of working and living in a power plant, a certain amount of heat needs to be consumed to provide a suitable environment for equipment operation, such as:

1. At present, the raw water of most power plants needs to be heated to 25°C before entering the chemical water treatment system, and low-pressure steam extraction in the plant is used for heating, which wastes a lot of energy.

2. The desalted water inlet temperature of the boiler deaerator is generally 25°C. The other water after recovering the shaft seal cooling waste heat and the slag waste heat is generally at 50°C. It enters the deaerator and is heated by low-temperature steam in the deaerator. Chemical water treatment system 104℃ (or cold water outlet pipe 150℃), then enters the high-temperature heater, and then enters the main boiler after reheating. When the deaerator is heated, a large amount of high-grade fresh steam is used, reducing heating and power generation. Ability.

3. At present, most heating boilers use steam plus plate heat exchangers to heat the circulating water in the heating pipe network, mostly using primary high-grade fresh steam. The hot water boilers use high-temperature direct supply, and the heating network circulates water for supply and return. The temperature is generally 50-10℃.

In this way, if the heat cannot be comprehensively utilized, the operating costs of the power plant will increase and the revenue will be reduced. Therefore, the existing combustion waste heat needs to be recycled.

Contents of the invention

In order to solve the technical problems existing in the background technology, the present invention proposes a system for comprehensive recovery and utilization of low-temperature waste heat, which includes a heat discharge module, a heat pump unit and a heat utilization module. The heat discharge module includes a boiler heating system, a circulating water system and a heat utilization module. Connected to the sewage system, the heat utilization module includes a deaerator system, chemical water treatment system, heating boiler system and heating network circulating water system, and the heat discharge module and heat utilization module are connected in the heat pump unit through pipelines, so that the heat The heat in the discharge module and the heat utilization module is moved by the drive of the heat pump unit to realize the utilization of heat; the heat pump unit is connected with a cold water outlet pipe and a hot water return pipe, and the cold water in the heat pump unit is sent out through the cold water outlet pipe, respectively. It is sent to the boiler heating system, circulating water system, and continuous sewage system, where heat exchange is performed, heat is absorbed, and the heat in the boiler heating system, circulating water system, and continuous sewage system is absorbed and then passes through the hot water return pipe. The heat is recovered into the heat pump unit, and is collected in the heat pump unit to form heated water; the heat pump unit 6 is connected to a hot water outlet pipe and a cold water return pipe, and the heated water in the heat pump unit is sent out through the hot water outlet pipe, and the hot water outlet pipe The water pipes are connected to the deaerator system, chemical water treatment system, heating boiler system, and heating network circulating water system to provide heat for the deaerator system, chemical water treatment system, heating boiler system, and heating network circulating water system, and provide heated bathing The role of hot water, heated chemical water raw water, heating deaerator water inlet, heating and heating pipe network circulating water, and cooling formed after heating in the deaerator system, chemical water treatment system, heating boiler system, and heating network circulating water system The water is connected to the cold water return pipe through the pipe, and the cooling water is returned to the heat pump unit again.

Preferably, the boiler heating system includes a boiler, a dust collector, and an induced draft fan. The fuel is burned in the boiler, and the generated flue gas is filtered from the dust collector and then discharged through the induced draft fan. The boiler heating system is connected with the desulfurization tower. The flue gas generated by combustion is sent into the desulfurization tower, where it is desulfurized and purified. The exhaust pipe of the desulfurization tower is connected in the chimney, and the processed flue gas is discharged to the external environment; it is discharged from the boiler heating system The heat in the flue gas is recovered through three parts. First, a first flue gas heat exchanger is installed between the boiler heating system and the desulfurization tower. A second flue gas heat exchanger is installed on the exhaust pipe between the desulfurization tower and the chimney. The flue gas heat exchanger directly absorbs the heat in the flue gas. A slurry heat exchanger is installed on the circulating slurry pipe in the desulfurization tower to absorb the heat in the circulating slurry pipe.

Preferably, the first flue gas heat exchanger is a plate heat exchanger, which heats the high-temperature flue gas passed into the desulfurization tower to achieve the function of a medium-temperature heat source, and then sends the medium-temperature heat source to the heat pump unit for processing. use.

Preferably, the water circulation pipeline of the circulating water system is connected to the heat pump unit through a water circulation heat exchanger, and the waste heat in the circulating water is sent into the pipeline of the heat pump unit.

Preferably, the water circulation pipeline of the circulating water system is directly connected to the pipeline of the heat pump unit, so that the cooling water in the heat pump unit is directly sent to the circulating water system for use.

Preferably, the continuous sewage drainage system and the heat pump unit are connected through a continuous waste heat exchanger to perform heat exchange, so that the heat in the regular sewage discharge is absorbed and utilized, reducing waste steam emissions and the use of cooling water. At the same time, the heat of the sewage can be recovered.

A method of using a low-temperature waste heat comprehensive recovery and utilization system, including the following steps:

S1, heat recovery, including S11, S12 and S13, as follows:

S11. The flue gas discharged from the boiler heating system is sent into the desulfurization tower through the first flue gas heat exchanger. The flue gas processed in the desulfurization tower is discharged into the chimney through the second flue gas heat exchanger. The first flue gas The gas heat exchanger and the second flue gas heat exchanger are connected with the cold water outlet pipe and the hot water return pipe, and the cold water entering the first flue gas heat exchanger and the second flue gas heat exchanger absorbs the heat in the flue gas; The slurry flowing in the desulfurization tower absorbs the heat in the desulfurization tower and exchanges heat through the slurry heat exchanger. The cold water entering the slurry heat exchanger absorbs the heat of the flue gas in the desulfurization tower; the heat is sent back to the heat pump through the hot water return pipe. in the crew;

S12. The circulating water in the circulating water system flows and exchanges heat through the water circulation heat exchanger. The cold water entering the water circulation heat exchanger absorbs the heat in the circulating water of the circulating water system, and then returns it to the heat pump unit through the hot water return pipe. ;

S13. The waste discharged from the Lianding sewage system contacts the Lianding waste heat exchanger for heat exchange. The cold water entering the Lianding waste heat exchanger absorbs the heat in the waste from the Lianding sewage system. Then it is sent back to the heat pump unit through the hot water return pipe;

S2. The heated water formed in the heat pump unit is sent to the deaerator system, chemical water treatment system, heating boiler system, and heating network circulating water system respectively to provide heated bathing hot water, heated raw water, and heated deaerator The role of water inlet and heating heating pipe network circulating water is to form cooling water heated in the deaerator system, chemical water treatment system, heating boiler system, and heating network circulating water system, which is connected to the cold water return pipe through the pipeline to cool the water. The water is returned to the heat pump unit again.

Compared with the existing technology, the above technical solution of the present invention has the following beneficial technical effects: the invention can reduce the exhaust temperature of the flue gas by recovering the waste heat of the flue gas, reduce the emission of smoke dust, and reduce the generation of white plumes of the flue gas. At the same time, the sensible heat and latent heat of condensation of the flue gas can be recovered, and the waste heat resources can be fully utilized through the heat pump. At the same time, the condensed water in the flue gas can be recovered to achieve energy and water saving functions; the recovery of waste heat of the circulating water can realize the non-stop use of circulating water. Running up the tower or a small amount on the tower can not only recover the waste heat of the circulating water, but also reduce the amount of water evaporated for cooling in the cooling tower, achieving the purpose of energy and water saving; recycling the waste heat of the continuous sewage can not only reduce waste steam emissions and cooling water consumption At the same time, the heat of sewage can be recovered to achieve the purpose of energy saving and water saving.

Description of the drawings

Figure 1 is a schematic structural diagram of a system for comprehensive recovery and utilization of low-temperature waste heat.

Figure 2 is a schematic diagram of the partial connection structure of a system for comprehensive recovery and utilization of low-temperature waste heat.

Reference signs: 1. Boiler heating system; 2. Desulfurization tower; 3. First flue gas heat exchanger; 4. Second flue gas heat exchanger; 5. Slurry heat exchanger; 6. Heat pump unit; 7. Circulation Water system; 8. Connected sewage system; 9. Deaerator system; 10. Chemical water treatment system; 11. Heating boiler system; 12. Heating network circulating water system; 13. Plate heat exchanger; 14. Connected Waste heat exchanger; 15. Cold water outlet pipe; 16. Hot water return pipe; 17. Hot water outlet pipe; 18. Cold water return pipe.

Detailed ways

As shown in Figure 1-2, the invention proposes a system for comprehensive recovery and utilization of low-temperature waste heat, including a heat discharge module, a heat pump unit 6 and a heat utilization module. The heat discharge module includes a boiler heating system 1 and a circulating water system. 7 and Lianding sewage system 8, the heat utilization module includes a deaerator system 9, a chemical water treatment system 10, a heating boiler system 11 and a heating network circulating water system 12, and the heat discharge module and heat utilization module are connected through pipelines In the heat pump unit 6, the heat in the heat discharge module and the heat utilization module is moved through the drive of the heat pump unit 6 to realize the utilization of heat. The heat pump unit 6 is a device that transfers the heat energy from the low-level heat source to the high-level heat source, and absorbs the heat. Heat reuse.

The boiler heating system 1 mainly includes a boiler, a dust collector, and an induced draft fan. Fuel is burned in the boiler, and the generated flue gas is filtered from the dust collector and then discharged through the induced draft fan. The boiler heating system 1 is connected with the desulfurization tower 2 , send the flue gas generated by combustion into the desulfurization tower 2, and perform desulfurization and purification treatment in the desulfurization tower 2. The exhaust pipe of the desulfurization tower 2 is connected in the chimney, and the processed flue gas is discharged to the external environment; boiler The heat in the flue gas discharged from the heating system 1 is recovered through three parts. First, a first flue gas heat exchanger 3 is provided between the boiler heating system 1 and the desulfurization tower 2, and between the desulfurization tower 2 and the chimney. A second flue gas heat exchanger 4 is installed on the exhaust pipe to directly absorb the heat in the flue gas. A slurry heat exchanger 5 is installed on the slurry pipe circulating in the desulfurization tower 2 to absorb the circulating slurry pipe. The heat of The medium-temperature heat source is then sent to the heat pump unit 6 for utilization.

The circulating water in the circulating water system 7 and the water circulation pipe of the circulating water system 7 are connected to the heat pump unit 6 through the water circulation heat exchanger 13, and the waste heat in the circulating water is sent to the pipeline of the heat pump unit 6. The circulating water system 7 The water circulation pipeline can also be directly connected to the pipeline of the heat pump unit 6, so that the cooling water in the heat pump unit 6 can be directly sent to the circulating water system 7 for use.

The continuous sewage system 8 and the heat pump unit 6 are connected through the continuous waste heat exchanger 14 to perform heat exchange, so that the heat in the regular sewage is absorbed and utilized, reducing waste steam emissions and the use of cooling water. At the same time, the heat of the sewage can be recovered.

The heat pump unit 6 is connected with a cold water outlet pipe 15 and a hot water return pipe 16. The cold water in the heat pump unit 6 is sent out through the cold water outlet pipe 15 and sent to the boiler heating system 1, the circulating water system 7, and the continuous sewage respectively. In the system 8, heat exchange is carried out, heat is absorbed, and the heat in the boiler heating system 1, circulating water system 7, and continuous sewage system 8 is absorbed, and then the heat is recovered to the heat pump unit 6 through the hot water return pipe 16. The heated water is collected in the heat pump unit 6 .

The heat pump unit 6 is connected to a hot water outlet pipe 17 and a cold water return pipe 18. The heated water in the heat pump unit 6 is sent out through the hot water outlet pipe 17. The hot water outlet pipe 17 is connected to the deaerator system 9 and chemical water treatment. System 10, heating boiler system 11, and heating network circulating water system 12 provide heating for the deaerator system 9, chemical water treatment system 10, heating boiler system 11, and heating network circulating water system 12, providing hot water for bathing and heating. The role of chemical raw water, heating deaerator water inlet, heating and heating pipe network circulating water, and cooling formed after heating in the deaerator system 9, chemical water treatment system 10, heating boiler system 11, and heating network circulating water system 12 The water is connected to the cold water return pipe 18 through the pipeline, and the cooling water is returned to the heat pump unit 6 again.

The method of using the system for recycling and utilization of the above system includes the following steps:

S1, heat recovery, including S11, S12 and S13, as follows:

S11. The flue gas discharged from the boiler heating system 1 is sent to the desulfurization tower 2 through the first flue gas heat exchanger 3. The flue gas processed in the desulfurization tower 2 is discharged to the chimney through the second flue gas heat exchanger 4. Inside, the first flue gas heat exchanger 3 and the second flue gas heat exchanger 4 are connected with the cold water outlet pipe 15 and the hot water return pipe 16, and enter the first flue gas heat exchanger 3 and the second flue gas heat exchanger The cold water in 4 absorbs the heat in the flue gas; the slurry flowing in the desulfurization tower 2 absorbs the heat in the desulfurization tower 2, and exchanges heat through the slurry heat exchanger 5, and the cold water entering the slurry heat exchanger 5 absorbs the desulfurization tower 2 The heat of the internal flue gas; the heat is sent back to the heat pump unit 6 through the hot water return pipe 16;

S12. The circulating water in the circulating water system 7 flows and exchanges heat through the water circulating heat exchanger 13. The cold water entering the water circulating heat exchanger 13 absorbs the heat in the circulating water of the circulating water system 7, and then sends it through the hot water return pipe 16. Return to heat pump unit 6;

S13. The waste discharged from the continuous sewage system 8 contacts the continuous waste heat exchanger 14 for heat exchange, and the cold water entering the continuous waste heat exchanger 14 absorbs the waste from the continuous sewage system 8 The heat in the water is then sent back to the heat pump unit 6 through the hot water return pipe 16;

S2. The heated water formed in the heat pump unit 6 is sent to the deaerator system 9, the chemical water treatment system 10, the heating boiler system 11, and the heating network circulating water system 12 to provide heated bathing hot water and heated raw water. , heating deaerator water, heating heating pipe network circulating water, the cooling water formed after heating in the deaerator system 9, chemical water treatment system 10, heating boiler system 11, heating network circulating water system 12 passes through the pipes It is connected with the cold water return pipe 18 to send the cooling water back to the heat pump unit 6 again.

Through the design of the invention, the recovery of waste heat of flue gas can reduce the exhaust temperature of flue gas, reduce the emission of smoke and dust, and reduce the generation of white plumes of flue gas. At the same time, the sensible heat and latent heat of condensation of flue gas can be recovered, and waste heat resources can be realized through heat pumps. It can fully utilize the condensed water in the flue gas and realize the function of energy saving and water saving; the recovery of the waste heat of the circulating water can realize the operation of the circulating water without going up the tower or a small amount of the circulating water. While recovering the waste heat of the circulating water, it can Reduce the amount of water evaporated by the cooling tower to achieve the purpose of energy and water saving; recycling the waste heat of continuous discharged sewage can not only reduce waste steam emissions and the use of cooling water, but also recover the heat of the sewage to achieve the purpose of energy and water saving. .

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the scope of knowledge possessed by those skilled in the art, various modifications can be made without departing from the spirit of the present invention. Variety.

Claims (6)

1. A system for comprehensive recovery and utilization of low-temperature waste heat, which is characterized by including a heat discharge module, a heat pump unit (6) and a heat utilization module; The heat emission module includes the boiler heating system (1), circulating water system (7) and continuous sewage drainage system (8). The heat utilization module includes the deaerator system (9), chemical water treatment system (10), heating The boiler system (11) and the heating network circulating water system (12) are connected with a cold water outlet pipe (15) and a hot water return pipe (16) in the heat pump unit (6). The cold water in the heat pump unit (6) passes through the cold water outlet pipe. (15) is sent out to the boiler heating system (1), circulating water system (7), and continuous sewage drainage system (8) respectively, and absorbs the boiler heating system (1), circulating water system (7), and continuous sewage system (8). The heat in the sewage system (8) is then recovered into the heat pump unit (6) through the hot water return pipe (16); the heat pump unit (6) is connected with a hot water outlet pipe (17) and a cold water return pipe. (18), the heated water in the heat pump unit (6) is sent out through the hot water outlet pipe (17), which is connected to the deaerator system (9), chemical water treatment system (10), and heating Boiler system (11), heating network circulating water system (12), the heated water is in the deaerator system (9), chemical water treatment system (10), heating boiler system (11), heating network circulating water system (12) The cooling water formed after heating is connected to the cold water return pipe (18) through the pipeline, and the cooling water is returned to the heat pump unit (6); The method of using the low-temperature waste heat comprehensive recovery and utilization system includes the following steps: S1, heat recovery, including S11, S12 and S13, as follows: S11. The flue gas discharged from the boiler heating system (1) is sent to the desulfurization tower (2) through the first flue gas heat exchanger (3). The flue gas processed in the desulfurization tower (2) passes through the second flue gas The gas heat exchanger (4) is discharged into the chimney, and the first flue gas heat exchanger (3) and the second flue gas heat exchanger (4) are connected with the cold water outlet pipe (15) and the hot water return pipe (16). The cold water entering the first flue gas heat exchanger (3) and the second flue gas heat exchanger (4) absorbs the heat in the flue gas; the slurry flowing in the desulfurization tower (2) absorbs the heat in the desulfurization tower (2). The heat is exchanged through the slurry heat exchanger (5). The cold water entering the slurry heat exchanger (5) absorbs the heat of the flue gas in the desulfurization tower (2); the heat is sent back to the desulfurization tower (2) through the hot water return pipe (16). Heat pump unit (6); S12. The circulating water in the circulating water system (7) flows and exchanges heat through the water circulating heat exchanger (13). The cold water entering the water circulating heat exchanger (13) absorbs the heat in the circulating water of the circulating water system (7). Then it is sent back to the heat pump unit (6) through the hot water return pipe (16); S13. The waste discharged from the continuous wastewater system (8) contacts the continuous waste heat exchanger (14) for heat exchange, and the cold water entering the continuous waste heat exchanger (14) absorbs the continuous waste heat. The heat in the waste in the sewage system (8) is returned to the heat pump unit (6) through the hot water return pipe (16); S2. The heated water formed in the heat pump unit (6) is sent to the deaerator system (9), chemical water treatment system (10), heating boiler system (11), and heating network circulating water system (12) respectively. Provides heating hot water for bathing, heating raw water, heating deaerator water, heating heating pipe network circulating water, in the deaerator system (9), chemical water treatment system (10), heating boiler system (11), heating The cooling water formed after heating in the network circulating water system (12) is connected to the cold water return pipe (18) through the pipeline, and the cooling water is returned to the heat pump unit (6) again. 2. A system for comprehensive recovery and utilization of low-temperature waste heat according to claim 1, characterized in that the boiler heating system (1) includes a boiler, a dust collector, an induced draft fan, and the boiler heating system (1) and desulfurization The tower (2) is connected to send the flue gas generated by combustion into the desulfurization tower (2). The exhaust pipe of the desulfurization tower (2) is connected in the chimney. Between the boiler heating system (1) and the desulfurization tower (2) A first flue gas heat exchanger (3) is installed between the desulfurization tower (2) and the chimney. A second flue gas heat exchanger (4) is installed on the exhaust pipe between the desulfurization tower (2) and the chimney. A slurry heat exchanger (5) is installed on the circulating slurry pipeline. 3. A system for comprehensive recovery and utilization of low-temperature waste heat according to claim 2, characterized in that the first flue gas heat exchanger (3) is a plate heat exchanger. 4. A system for comprehensive recovery and utilization of low-temperature waste heat according to claim 1, characterized in that the water circulation pipeline of the circulating water system (7) is connected to the heat pump unit (6) through a water circulation heat exchanger (13) . 5. A system for comprehensive recovery and utilization of low-temperature waste heat according to claim 1, characterized in that the water circulation pipeline of the circulating water system (7) is directly connected to the pipeline of the heat pump unit (6). 6. A system for comprehensive recovery and utilization of low-temperature waste heat according to claim 1, characterized in that a continuous waste heat exchanger is used between the continuous wastewater drainage system (8) and the heat pump unit (6). (14)Connect.