A heating system for deep recovery and utilization of waste heat from coal-fired power plants

Abstract

The present invention relates to the field of industrial waste heat utilization and energy, and in particular to a heating system for deep recovery and utilization of waste heat from a coal-fired power plant, comprising heat medium water, which passes through a heat medium water heat exchange circuit composed of a low-temperature heat exchanger, a high-temperature heat exchanger and an evaporator in sequence under the action of a first water pump, and an ejector heat pump heating system for heating a heat pump medium in parallel with the evaporator, wherein the ejector heat pump heating system comprises a condenser, and the heat pump medium is divided into two paths after passing through the outlet of the condenser, the first path passes through a liquid reservoir, an evaporator and an ejector in sequence and enters the condenser inlet; the second path passes through a liquid reservoir, a boiler and an ejector in sequence and enters the condenser inlet. The present invention achieves maximum heat absorption by uniformly mixing the heat pump medium that has absorbed the heat of the flue gas and the auxiliary steam system respectively through an ejector, and transfers the heat through a condenser connected to a heat network system to achieve heat network heating, thereby realizing the recovery and utilization of low-grade heat from the boiler.

Description

Technical Field

[0001] The present invention relates to the field of industrial waste heat utilization and energy, and in particular to a heating system for deep recovery and utilization of waste heat from a coal-fired power plant. Background Art

[0002] my country's energy endowment determines that thermal power generation will dominate in the long run. Thermal power generation mainly generates electricity by heating steam with coal to drive steam turbines. The combustion process will produce harmful gas pollutants such as nitrogen oxides and sulfur dioxide. The removal of sulfur dioxide is mainly carried out by the limestone-gypsum wet desulfurization method. This method uses limestone as a desulfurization absorbent. The limestone is crushed and ground into powder and mixed with water to form an absorption slurry. The absorption slurry is fully contacted and mixed with the flue gas in the desulfurization absorption tower. The sulfur dioxide in the flue gas reacts chemically with the calcium carbonate in the slurry to achieve the purpose of removing sulfur dioxide from the flue gas. After wet flue gas desulfurization, the flue gas temperature is directly reduced from 100-180℃ to about 50-55℃. However, the main factor affecting the efficiency of the boiler is the exhaust loss carried away by the boiler flue gas. How to effectively utilize the heat carried in the boiler exhaust, deeply utilize this part of the heat to achieve the purpose of waste heat utilization, and reduce exhaust losses is an effective way to improve boiler efficiency.

[0003] At present, waste heat utilization is mainly achieved by installing a low-temperature economizer before wet flue gas desulfurization. The flue gas temperature before wet flue gas desulfurization is directly cooled from 100-180℃ to 80-95℃ through a heat exchanger, and this part of the heat is used to heat the feed water. Therefore, the feed water is first heated in the low-temperature economizer before entering the drum, which reduces the heat absorption of the feed water on the heating surface. The low-temperature economizer can be used to replace part of the more expensive evaporation heating surface to increase the feed water temperature, absorb the heat of the low-temperature flue gas, and reduce the exhaust temperature. At the same time, the entry of feed water into the drum will reduce the wall temperature difference, reduce thermal stress accordingly, extend the service life of the drum, effectively reduce coal consumption, and improve boiler efficiency. However, in the boiler exhaust loss, the low-temperature flue gas of 50-55℃ after wet flue gas desulfurization accounts for the main part of the boiler exhaust loss, but this part of heat is basically difficult to use due to its low temperature, low grade, few utilization methods, and high utilization cost.

[0004] In addition, the heating systems of coal-fired power plants basically mostly use auxiliary steam to directly heat the return water of the heating network. After the water in the heating network is heated to the heating temperature, it is sent to the heating network pipeline to achieve the heating purpose. Although this heating system is simple, it has not achieved optimization in terms of heating heat source and has the problem of high coal consumption. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a heating system for deep recovery and utilization of waste heat from coal-fired power plants. By utilizing large temperature difference heating technology and using an ejector heat pump as a driving medium, the low-grade waste heat of the boiler can be used as part of the heating source. Compared with the traditional heating system, this heating system uses the low-temperature heat of the boiler for heating water in the hot network, and then uses auxiliary steam for heating. The waste heat utilization rate is high, the energy-saving effect is obvious, the operation and investment costs are moderate, and it has good application prospects.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A heating system for deep recovery and utilization of waste heat from a coal-fired power plant comprises heat medium water. The heat medium water, under the action of a first water pump, sequentially passes through a heat medium water heat exchange circuit consisting of a low-temperature heat exchanger, a high-temperature heat exchanger and an evaporator. An ejector heat pump heating system for heating a heat pump working medium is connected in parallel with the evaporator. The ejector heat pump heating system comprises a condenser. The heat pump working medium is divided into two paths after passing through the outlet of the condenser. The first path sequentially passes through a liquid reservoir, an evaporator and an ejector and then enters the condenser inlet; the second path sequentially passes through a liquid reservoir, a boiler and an ejector and then enters the condenser inlet.

[0008] Preferably, a first regulating valve is provided on the evaporator outlet and the ejector inlet pipeline, a second regulating valve is provided on the boiler outlet and the ejector inlet pipeline, a second water pump and a third regulating valve are provided on the liquid reservoir outlet and the boiler inlet pipeline in sequence, and a third water pump and a fourth regulating valve are provided on the liquid reservoir outlet and the evaporator pipeline in sequence.

[0009] Preferably, the boiler inlet is connected to the auxiliary steam system through a pipeline, and the boiler outlet is connected to the condenser through a pipeline.

[0010] Preferably, the condenser is connected to a heating network system.

[0011] Preferably, the inlet and outlet of the high-temperature heat exchanger are connected to the dust collector outlet and the desulfurization tower inlet through pipelines respectively.

[0012] Preferably, the inlet of the low-temperature heat exchanger is connected to the outlet of the desulfurization tower through a pipeline.

[0013] Preferably, the heat pump working fluid is a medium-high temperature refrigeration working fluid.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention absorbs waste heat in flue gas through a heat medium water heating system, and transfers the heat to a heat pump working fluid through an evaporator, thereby realizing energy recovery of waste heat in flue gas; by connecting an auxiliary steam system with a boiler, waste heat in the auxiliary steam system is transferred to a heat pump working fluid through the boiler, thereby realizing heat recovery of the auxiliary steam system. The key point of the present invention is that the heat pump working fluid that has absorbed the heat of flue gas and the auxiliary steam system respectively is evenly mixed through an ejector to realize maximum heat absorption, and the heat is transferred out through a condenser connected to a heat network system to realize heat supply in a heat network, thereby realizing recovery and utilization of low-grade heat from the boiler. Compared with a traditional heating system, this heating system utilizes low-temperature heat from the boiler for heating water in the heat network, has a high waste heat utilization rate, has obvious energy-saving effect, has moderate operation and investment costs, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a heating system for deep recovery and utilization of waste heat from a coal-fired power plant;

[0017] In the figure: 11. dust collector; 12. high-temperature heat exchanger; 13. desulfurization tower; 14. low-temperature heat exchanger; 15. evaporator; 16. first water pump; 21. ejector; 22. boiler; 23. liquid storage tank; 24. first regulating valve; 25. second regulating valve; 26. third regulating valve; 27. fourth regulating valve; 28. second water pump; 29. ​​third water pump; 31. condenser. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. It is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention.

[0019] Reference Figure 1 The present invention discloses a heating system for deep recovery and utilization of waste heat from a coal-fired power plant, including heat medium water. The heat medium water, under the action of a first water pump 16, sequentially passes through a heat medium water heat exchange circuit composed of a low-temperature heat exchanger 14, a high-temperature heat exchanger 12 and an evaporator 15. An ejection heat pump heating system for heating a heat pump working medium is connected in parallel with the evaporator 15. The ejection heat pump heating system includes a condenser 31. The heat pump working medium is divided into two paths after passing through the outlet of the condenser 31. The first path sequentially passes through a liquid reservoir 23, an evaporator 15 and an ejector 21 and then enters an inlet of the condenser 31; the second path sequentially passes through a liquid reservoir 23, a boiler 22 and an ejector 21 and then enters an inlet of the condenser 31.

[0020] Specifically, the heat of the heat medium water heat exchange loop comes from the waste heat of flue gas. The flue gas in the present invention passes through the dust collector 11, the high-temperature heat exchanger 12, the desulfurization tower 13 and the low-temperature heat exchanger 14 in sequence, and finally the treated flue gas enters the chimney. The function of the low-temperature heat exchanger 14 and the high-temperature heat exchanger 12 in the present invention is to transfer the heat absorbed from the flue gas to the heat medium water. This process realizes the recovery of the waste heat of the flue gas. The heated heat medium water enters the evaporator 15 and transfers the heat to the heat pump working medium passing through the evaporator 15; the boiler 22 in the present invention is connected to the auxiliary steam system. By absorbing the heat of the auxiliary steam system, the heat pump working medium passing through the boiler 22 is heated. This process realizes the heat recovery of the auxiliary steam system. The heat pump working medium heated by the boiler 22 and the evaporator 15 respectively enters the ejector 21 at the same time. The heat pump working medium fully mixed after being mixed in the ejector 21 enters the condenser 31, and its heat energy is transferred to the heat network system through the condenser 31, thereby realizing the heat supply of waste heat recovery.

[0021] A first regulating valve 24 is provided on the pipeline between the outlet of the evaporator 15 and the inlet of the ejector 21, a second regulating valve 25 is provided on the pipeline between the outlet of the boiler 22 and the inlet of the ejector 21, a second water pump 28 and a third regulating valve 26 are provided on the pipeline between the outlet of the liquid reservoir 23 and the inlet of the boiler 22 in sequence, and a third water pump 29 and a fourth regulating valve 27 are provided on the pipeline between the outlet of the liquid reservoir 23 and the evaporator 15 in sequence.

[0022] Specifically, the first regulating valve 24 and the second regulating valve 25 are used to adjust the flow rate of the heat pump working fluid entering the ejector 21 so as to achieve the purpose of sufficient mixing of the heat pump working fluid. The heat pump working fluid in the present invention can be a medium-high temperature refrigeration working fluid, such as R141b.

[0023] The third regulating valve 26 and the fourth regulating valve 27 are used to adjust the flow rate in the pipeline after being pressurized by the water pump so that the heat pump working fluid in the pipeline can fully absorb the heat of the evaporator 15 and the boiler 22 to achieve maximum heat recovery.

[0024] The working principle of the present invention is as follows: by utilizing the large temperature difference heating technology, taking the ejector heat pump as the driving medium, absorbing the waste heat in the flue gas through the heat medium water heat exchange system, and transferring the heat to the heat pump working fluid through the evaporator 15, by connecting the boiler 22 with the auxiliary steam system, and transferring the heat in the auxiliary steam system to the heat pump working fluid through the boiler 22, and finally mixing through the ejector 21, the low-grade waste heat in the boiler of the condenser 31 is transferred to the heat network to achieve the ultimate heating purpose. Compared with the traditional heating system, this heating system utilizes the low-temperature heat of the boiler for heating the water in the hot network, has a high waste heat utilization rate, obvious energy-saving effect, moderate operation and investment costs, and has good application prospects.

[0025] The above is a specific implementation of the embodiment of the utility model. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the utility model. These improvements and modifications should also be regarded as the scope of protection of this application.

Claims

1. A heating system for deep recovery and utilization of waste heat from a coal-fired power plant, comprising heat medium water, wherein the heat medium water, under the action of a first water pump (16), sequentially passes through a heat medium water heat exchange circuit consisting of a low-temperature heat exchanger (14), a high-temperature heat exchanger (12) and an evaporator (15), It is characterized in that An ejector heat pump heating system for heating a heat pump working medium connected in parallel with the evaporator (15), the ejector heat pump heating system comprising a condenser (31), the heat pump working medium being divided into two paths after passing through the outlet of the condenser (31), the first path passing through the liquid reservoir (23), the evaporator (15) and the ejector (21) in sequence and then entering the inlet of the condenser (31); the second path passing through the liquid reservoir (23), the boiler (22) and the ejector (21) in sequence and then entering the inlet of the condenser (31); The inlet of the boiler (22) is connected to the auxiliary steam system through a pipeline, the outlet of the boiler (22) is connected to the condenser through a pipeline, and the condenser (31) is connected to the heat network system.

2. A heating system for deep recovery and utilization of waste heat from a coal-fired power plant according to claim 1, It is characterized in that A first regulating valve (24) is provided on the pipeline between the outlet of the evaporator (15) and the inlet of the ejector (21); a second regulating valve (25) is provided on the pipeline between the outlet of the boiler (22) and the inlet of the ejector (21); a second water pump (28) and a third regulating valve (26) are provided on the pipeline between the outlet of the liquid reservoir (23) and the inlet of the boiler (22); and a third water pump (29) and a fourth regulating valve (27) are provided on the pipeline between the outlet of the liquid reservoir (23) and the evaporator (15).

3. According to claim 2, a heating system for deep recovery and utilization of waste heat from a coal-fired power plant, It is characterized in that The inlet and outlet of the high-temperature heat exchanger (12) are respectively connected to the outlet of the dust collector (11) and the inlet of the desulfurization tower (13) through pipelines.

4. According to claim 3, a heating system for deep recovery and utilization of waste heat from a coal-fired power plant, It is characterized in that The inlet of the low-temperature heat exchanger is connected to the outlet of the desulfurization tower (13) through a pipeline.

5. A heating system for deep recovery and utilization of waste heat from a coal-fired power plant according to any one of claims 1 to 4, It is characterized in that The heat pump working fluid is a medium- and high-temperature refrigeration working fluid.

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