Coal-fired steam back pressure machine distributed energy supply simplified heat recovery system and method

Abstract

The present invention discloses a coal-fired steam back pressure machine distributed energy supply simplified heat recovery system and method, which relates to a distributed energy supply heat recovery system, and is used to solve a series of problems in the prior art, such as drainage leakage, pipeline heat dissipation loss, and complex installation and construction, caused by the complexity of the heat recovery system. The system includes a back pressure machine, a generator, a heat network heat exchanger, and a condensate pump, and also includes a deaerator, wherein the deaerator is a built-in deaerator, the back pressure machine is connected to the generator, the back pressure machine input end receives main steam through a steam pipeline, the back pressure machine output end is respectively connected to the deaerator steam input end and the heat network heat exchanger steam input end through a steam pipeline, the heat network heat exchanger steam output end is connected to the condensate pump input end through a water pipeline, and the condensate pump output end is connected to the deaerator hot water input end through a water pipeline. The simplified heat recovery system can achieve the purpose of reducing costs and realizing economic benefits.

Description

Technical Field

[0001] The present invention relates to the field of gas thermal energy technology, and more specifically to a coal-fired steam back pressure machine distributed energy supply simplified heat recovery system and method. Background Art

[0002] In the field of thermal technology, according to the first law of thermodynamics, in the Rankine cycle, the more extraction and heat recovery stages there are, the higher the thermal cycle efficiency. The extraction stages of thermal power plants are optimized to "3 high, 4 low, and 1 deoxygenation", which can ensure the uniform enthalpy rise of water in each stage of heaters and reduce the cold source loss of the steam turbine. At the same time, the complexity of the heat recovery system also brings about a series of problems such as drainage leakage, pipeline heat dissipation loss, and complex installation and construction. Therefore, for the distributed energy supply system of coal-fired steam back pressure machine, from the perspective of heating, it has no cold source loss. Therefore, it is not advisable to add a complex extraction and heat recovery system to the back pressure unit with a small volume and limited installed capacity to increase the power generation. This requires a new type of simplified heat recovery system for distributed energy supply of coal-fired steam back pressure machine. Summary of the invention

[0003] One object of the present invention is to provide a simplified heat recovery system and method for a coal-fired steam back pressure machine distributed energy supply, which can simplify the heat recovery system, thereby achieving the purpose of reducing costs and realizing economic benefits.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A coal-fired steam back pressure machine distributed energy supply simplified heat recovery system, the system includes a back pressure machine, a generator, a heat network heat exchanger and a condensate pump, wherein the system also includes a deaerator, wherein the back pressure machine is connected to the generator, the input end of the back pressure machine receives main steam through a steam pipeline, the output end of the back pressure machine is respectively connected to the deaerator steam input end and the heat network heat exchanger steam input end through a steam pipeline, the heat network heat exchanger steam output end is connected to the condensate pump input end through a water pipeline, and the condensate pump output end is connected to the deaerator hot water input end through a water pipeline.

[0006] In a further technical solution of the present invention, the deaerator is a built-in deaerator. Specifically, the built-in deaerator is a new type of deaerator, which abandons the deaerator head of the traditional deaerator and only retains the water tank part of the deaerator. The deoxygenation function in the deaerator tower of the original traditional deaerator is transferred to the water tank of the deaerator, and the deoxygenation and water storage functions appear in the water tank at the same time. Its advantages include eliminating the large diameter opening of the traditional vertical deaerator, reducing the local stress of the deaerator, and improving the safe operation factor of the deaerator. In addition, a new nozzle is used to improve the deoxygenation effect.

[0007] In a further technical solution of the present invention, the built-in deaerator does not have a deaerator head of a spray-type deaerator and an opening with a diameter greater than 800 mm of a vertical deaerator, and the built-in deaerator is provided with a compound steam-jet nozzle. The built-in deaerator is provided with a compound steam-jet nozzle, which consists of a shell, a steam-jet nozzle located in the middle of the shell and a nozzle located at one end of the shell. A tangential water inlet groove is provided on the circumferential wall of the shell, and steam enters the shell through the middle steam-jet nozzle.

[0008] In a further technical solution of the present invention, the output end of the built-in deaerator is directly connected to the boiler through a water pipeline, and the evaporation capacity of the boiler does not exceed 130 t / h.

[0009] In a further technical solution of the present invention, the built-in deaerator adopts a fixed and sliding pressure operation mode to make the dissolved oxygen content of the deoxygenated water ≤5 μg / L in a working state.

[0010] In a further technical solution of the present invention, the main steam output by the back pressure machine to the deaerator is the heating medium of the deaerator.

[0011] In a further technical solution of the present invention, the main steam output by the back pressure machine to the heat network heat exchanger is the heat exchange medium of the heat network heat exchanger.

[0012] Another object of the present invention is to provide a method for implementing simplified energy supply and heat recovery by using a distributed energy supply and simplified heat recovery system of a coal-fired steam back pressure machine in any of the above technical solutions, which comprises:

[0013] In the heat recovery system, only a built-in deaerator is provided, and no high-pressure heater and low-pressure heater are provided, thereby simplifying the heat recovery system of the conventional coal-fired power generation unit.

[0014] Another object of the present invention is to provide a method, namely, a method for achieving simplified energy supply and heat recovery by using the aforementioned coal-fired steam back pressure machine distributed energy supply and simplified heat recovery system, characterized in that: the method includes: the main steam coming out of the boiler is divided into two exhaust steam paths after passing through the back pressure machine, one exhaust steam path is directly sent to the deaerator; the other exhaust steam path is directly sent to the heat network heat exchanger, heat is exchanged through the heat network, and then the heat network return water absorbs the exhaust steam heat, so that the heat network return water temperature is increased, and then sent to the heat network user, the other exhaust steam path is condensed after heat exchange with the heat network return water to form condensed water, which is sent to the deaerator through a condensate pump, and the exhaust steam path sent to the deaerator is used as the heating medium of the condensed water to heat the condensed water.

[0015] Another object of the present invention is to provide a drain system, which includes the above-mentioned coal-fired steam back pressure machine distributed energy supply simplified heat recovery system, a drain expansion tank and a drain water tank, and the drain water tank also plays the role of replenishing water for the low-level water tank.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. The present invention simplifies the heat recovery system of conventional coal-fired power generation units. Only a deaerator is provided in the heat recovery system, and high-pressure and low-pressure heaters are removed, thereby reducing initial investment costs, reducing operation and maintenance costs, and achieving economic benefits.

[0018] 2. The present invention adopts a built-in deaerator, abandons the deaerator head of the traditional deaerator, cancels the large-diameter opening of the traditional vertical deaerator, reduces the local stress of the deaerator, and improves the safe operation factor of the deaerator.

[0019] 3. The system of the present invention has a simple design, compact structure, and convenient maintenance. During operation, there is very little exhaust loss, which saves operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0021] Figure 1 A distributed energy supply and heat recovery system provided by a preferred embodiment of the present invention is shown;

[0022] Figure 2 The following are the implementation steps of a distributed energy supply and heat recovery system provided by a preferred embodiment of the present invention;

[0023] Figure 3 The composite steam jet nozzle used in the built-in deaerator of the present invention is shown. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0025] like Figure 1It is a simplified heat recovery system for distributed energy supply of coal-fired steam back pressure machine, the system includes a back pressure machine, a generator, a heat network heat exchanger and a condensate pump, the system also includes a deaerator, wherein the back pressure machine is connected to the generator, the input end of the back pressure machine receives main steam through a steam pipeline, the output end of the back pressure machine is respectively connected to the steam input end of the deaerator and the steam input end of the heat network heat exchanger through a steam pipeline, the steam output end of the heat network heat exchanger is connected to the input end of the condensate pump through a water pipeline, and the output end of the condensate pump is connected to the hot water input end of the deaerator through a water pipeline. By setting in this way, the heat recovery system of conventional coal-fired power generation units is simplified.

[0026] In the above embodiment, the deaerator is a built-in deaerator because: this deaerator has a strong ability to cope with load changes, and compared with the traditional deaerator, the deaerator head of the traditional deaerator can be discarded, so that the built-in headless deaerator does not have the vibration phenomenon when the conventional deaerator is started, and does not require the large diameter opening of the traditional vertical deaerator, thereby reducing the local stress of the deaerator and improving the safe operation factor of the deaerator. Because the deaerator adopts a new nozzle, the deaerator has a good deoxidation effect and high reliability.

[0027] Furthermore, traditional deaerators need to open holes with a diameter of generally φ1600~φ2400 on the water feed tank, which is 0.4~0.8 times the diameter of the water feed tank, exceeding the requirements of GB150-98 "Steel Pressure Vessels", weakening the strength and rigidity of the water feed tank, and generating high local stress and deformation at the connection between the deaerator head and the water feed tank, causing cracks inside the water feed tank, especially a large number of cracks in the weld area, threatening the safe operation of the deaerator.

[0028] The present invention uses a built-in deaerator, abandons the deaerator head of the traditional deaerator, and only retains the water tank part of the deaerator, and transfers the deoxygenation function in the deaerator tower of the original traditional deaerator to the water tank of the deaerator. The deoxygenation and water storage functions appear in the water tank at the same time, so that the large diameter opening required by the traditional deaerator is no longer needed, and only a diameter opening of less than 800mm is needed, which reduces the local stress of the deaerator and improves the safe operation factor of the deaerator.

[0029] In a conventional deaerator, steam and water are ejected from separate nozzles, and the deoxygenated water is fully heated by reverse flow heating, delayed heating of fillers, and other methods, thereby achieving the purpose of deoxygenation. In a further embodiment of the present invention, the built-in deaerator is provided with a composite steam jet nozzle, which is composed of a shell, a steam jet nozzle and a nozzle, wherein the steam jet nozzle is arranged in the shell, and the steam jet nozzle is connected to one end of the nozzle. By adopting the above-mentioned new nozzle, the deoxygenation effect is good and the reliability is high.

[0030] In the above embodiment, when the built-in headless deaerator is started, there is no vibration phenomenon when the conventional deaerator is started. The heating steam exhausted from the back pressure machine is sent from underwater, so that the overall working temperature of the deaerator is reduced, and the metal thermal fatigue life is greatly improved. In specific operation, the output end of the built-in deaerator is directly connected to the boiler through a water pipeline. The built-in deaerator adopts a fixed and sliding pressure operation mode to make the dissolved oxygen content of the deoxygenated water ≤5μg / L in the working state.

[0031] In a further embodiment, the main steam output by the back pressure machine to the deaerator is the heating medium of the deaerator. In this embodiment, the main steam from the boiler drives the generator to generate electricity and go online after the back pressure machine does work, and the exhaust steam of the back pressure machine is divided into two paths, one of which is sent to the deaerator as the heating medium of the deaerator to heat the feed water. The other path is sent to the heat network heat exchanger, heat is exchanged through the heat network, and then the heat network return water absorbs the exhaust steam heat, so that the return water temperature of the heat network is increased, and then it is sent to the heat network user. The exhaust steam of the back pressure machine is condensed after heat exchange with the heat network return water, and is sent to the deaerator through the condensate pump. It can be seen that in this embodiment, the main steam output by the back pressure machine to the heat network heat exchanger is the heat exchange medium of the heat network heat exchanger.

[0032] In the traditional heat recovery system, the main purpose of "three highs and four lows" is to reduce the loss of cold sources and increase power generation. For the distributed energy supply system of coal-fired steam back pressure machine, the important role of high and low pressure heaters is to increase the inlet water temperature of the boiler, improve boiler efficiency, reduce the amount of steam discharged from the turbine to the condenser, reduce energy loss, and improve the circulation efficiency of the thermal system. The inlet water temperature requirement of the boiler is mainly related to the layout of the boiler heating surface. Usually, when the boiler capacity is 130t / h and above, the inlet water temperature of the high temperature and high pressure boiler needs to reach 215℃. Therefore, a high and low pressure heater is often required to heat the inlet water temperature to meet the requirements. When the capacity is less than 130t / h, the inlet water temperature of the high temperature and high pressure boiler is about 158℃.

[0033] In one embodiment, the function of the low-pressure heater is to utilize the steam that has done partial work in the steam turbine and draw it into the heater to heat the feed water, thereby increasing the temperature of the water, reducing the amount of steam discharged from the steam turbine to the condenser, reducing energy loss, and improving the cycle efficiency of the thermal system.

[0034] For a boiler with an evaporation capacity not exceeding 130 t / h, the heat recovery system of the present invention and the above-mentioned built-in deaerator of the present invention can ensure the inlet water temperature requirement of the boiler without setting a heater.

[0035] Compared with the traditional heat recovery system, the system of the present invention reduces the high-pressure heater and the low-pressure heater. Although the power generation capacity is slightly reduced after the high-pressure heater is removed, it is beneficial to reduce the initial investment cost and the operation and maintenance cost. Moreover, the system of the present invention can mainly provide heat without the loss of cold source.

[0036] refer to Figure 2 and Figure 3 The method for implementing simplified energy supply and heat recovery by using the coal-fired steam back pressure machine distributed energy supply and simplified heat recovery system in the above embodiment is:

[0037] In the heat recovery system, only a built-in deaerator is provided, and no high-pressure heater and low-pressure heater are provided, thereby simplifying the heat recovery system of the conventional coal-fired power generation unit. The working principle of the composite steam jet nozzle in the built-in deaerator is explained below in combination with the working mode of the traditional deaerator.

[0038] In traditional deaerators, steam and water are sprayed out from separate nozzles, and the deoxygenated water is fully heated through methods such as reverse flow heating and delayed heating of fillers, thereby achieving the purpose of deoxygenation.

[0039] The built-in deaerator uses a new type of composite steam jet nozzle ( Figure 3 The steam jet nozzle consists of a shell, a steam jet nozzle and a nozzle ( Figure 3 The steam jet nozzle is located in the middle of the shell, and the nozzle is located at one end of the shell. Figure 3 It can be seen that water (condensed water) and steam (steam from the back pressure machine) enter from different positions in the same nozzle. Several tangential water inlet grooves are opened on the circumferential wall of the shell. The water enters the inside of the shell from the outside of the shell through the tangential water inlet grooves and forms several rotating water flows. The middle steam jet nozzle converts the pressure energy of the steam entering the outside of the shell into velocity energy. The steam at the outlet of the steam jet nozzle reaches a higher flow rate, forming a high-speed steam jet flow. On the one hand, this high-speed steam jet flow drives the rotating water flow forward in the shell, and hits the rotating water flow at the nozzle outlet, increasing the atomization power of the water flow; after leaving the nozzle, this steam diffuses from the center of the atomization cone to the surroundings, so that the atomized water droplets are evenly heated. It can be seen that the steam and water undergo preliminary heat exchange in the nozzle, and after spraying out of the nozzle, the steam and water are both in the form of mist, which further enhances the heat exchange effect.

[0040] The present invention also provides another embodiment of a drain system, which includes the simplified heat recovery system of the coal-fired steam back pressure machine distributed energy supply, a drain expansion tank, and a drain water tank (the drain water tank also plays the role of a traditional low-level water tank) in the above embodiment. In this embodiment, the present invention adopts a simplified heat recovery system, simplifies the three-stage high-pressure heater and the four-stage low-pressure heater, and also optimizes the drain points set behind each stage of the heater. That is, the traditional drain system needs to be equipped with a drain water tank and a drain expansion tank after each stage of the heater, and a low-level water tank for water replenishment. Compared with the traditional drain system, the present invention only needs to set up a drain expansion tank and a drain water tank (which combines a conventional low-level water tank), thereby reducing the floor space. These technical effects are all due to the use of the simplified heat recovery system of the present invention.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A coal-fired steam back pressure machine distributed energy supply simplified heat recovery system, comprising: Back pressure machine, generator, heat network heat exchanger and condensate pump, characterized by: The system also includes a deaerator, wherein The back pressure machine is connected to the generator, The back pressure machine input end receives main steam through a steam pipeline. The output end of the back pressure machine is connected to the steam input end of the deaerator and the steam input end of the heat network heat exchanger through a steam pipeline. The steam output end of the heat network heat exchanger is connected to the input end of the condensate pump through a water pipeline. The condensate pump output end is connected to the deaerator hot water input end through a water delivery pipeline; The deaerator is a built-in deaerator; the built-in deaerator does not have a deaerator head of a spray type deaerator and a hole with a diameter greater than 800 mm of a vertical deaerator; The output end of the built-in deaerator is directly connected to the boiler through a water pipeline; the evaporation capacity of the boiler does not exceed 130t / h, and only the built-in deaerator is arranged in the heat recovery system, and no high-pressure heater and low-pressure heater are arranged; The built-in deaerator is provided with a compound steam jet nozzle, which consists of a shell, a steam jet nozzle located in the middle of the shell and a nozzle located at one end of the shell. A tangential water inlet groove is opened on the circumferential wall of the shell, and steam enters the shell through the middle steam jet nozzle.

2. The coal-fired steam back pressure machine distributed energy supply simplified heat recovery system according to claim 1, characterized in that: The built-in deaerator adopts a fixed and sliding pressure operation mode to make the dissolved oxygen content of the deoxygenated water ≤5 μg / L in the working state.

3. A hydrophobic system, characterized in that: The drain system includes the distributed energy supply and simplified heat recovery system of the coal-fired steam back pressure machine according to any one of claims 1 to 2, a drain expansion tank and a drain water tank, and the drain water tank also serves as a water replenishment for the low-level water tank.

4. A method for realizing simplified energy supply and heat recovery by using the distributed energy supply and simplified heat recovery system of a coal-fired steam back pressure machine according to any one of claims 1 to 2, characterized in that: The method comprises: The main steam from the boiler is divided into two exhaust paths after passing through the back pressure machine. The exhaust steam is sent directly to the deaerator; The other exhaust steam is directly sent to the heat exchanger of the heating network, and then the heat exchange is carried out in the heating network. Then the heat of the exhaust steam is absorbed by the return water of the heating network, so that the return water temperature of the heating network is increased, and then it is sent to the users of the heating network. The exhaust steam of the other route is condensed after heat exchange with the return water of the heating network to form condensed water, which is sent to the deaerator through the condensate pump. The exhaust steam sent to the deaerator is used as a heating medium for the condensed water to heat the condensed water.

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