Low-temperature economizer system and coal power generation equipment

Abstract

The invention relates to the technical field of coal-fired thermal power generating units, in particular to a low-temperature economizer system and coal-fired power generating equipment, which comprises a shell-and-tube heat exchanger and a plurality of groups of plate heat exchangers, the plate heat exchangers are arranged in a flue at the tail of a boiler, and heating medium water is arranged in the plate heat exchangers; boiler tail flue gas exchanges heat with heat medium water in the plate heat exchanger and then is cooled and discharged, and the heat medium water after heat exchange with the flue gas is subjected to heat exchange through the shell-and-tube heat exchanger and then returns to the plate heat exchanger to continuously cool the boiler tail flue gas; the internal medium of the shell-and-tube heat exchanger is condensed water; a soot blower is arranged in an upstream flue of the plate heat exchanger and used for removing soot of the plate heat exchanger. According to the system, traditional H-shaped finned tube or spiral finned tube heat exchange is abandoned, the plate heat exchanger is matched with the shell-and-tube heat exchanger to circulate the heating medium water and exchange heat for flue gas at the tail of the boiler, and compared with traditional H-shaped finned tube or spiral finned tube heat exchange, dust accumulation and blockage can be effectively prevented, and stable operation of the low-temperature economizer system is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature economizer transformation, and particularly to a low-temperature economizer system and a coal-fired power generation device. Background Art

[0002] Coal-fired power generation is a process in which the chemical energy released by coal combustion is used to heat water into steam, which then drives a steam turbine to drive a generator to generate electricity. The boiler is the "heart" of the coal-fired power system. Through the chemical energy released by coal combustion, water is heated into steam, which then drives a steam turbine to drive a generator to generate electricity. In order to reduce the heat loss of boiler flue gas and improve the operation economy of the power plant, and to achieve the comprehensive goals of low-temperature dust removal and energy conservation, most boilers are currently equipped with low-temperature economizers. The low-temperature economizer is generally installed in the tail flue of the boiler, using low-temperature flue gas to heat the boiler feed water, converting the waste heat of the flue gas into the internal energy of water, reducing the flue gas temperature, and reducing heat loss.

[0003] The existing types of low-temperature economizers are mainly H-type finned tubes or spiral finned tubes. The H-type finned tube is composed of a base tube and symmetric H-type fins on both sides. The fins and the base tube are fixed by high-frequency welding or laser welding. The heat transfer mechanism is usually to form a channel perpendicular to the flue gas flow direction through the H-type fins, forcing the flue gas to flow across the fin surface laterally to enhance the degree of turbulence. On the water side, the water flow in the base tube is single-phase or vapor-liquid two-phase flow, and the convection heat transfer is enhanced through the fins. The flue gas resistance is low and it is suitable for high-dust flue gas environments; the structure of the spiral finned tube is mainly to wind a spiral metal strip on the outer surface of the base tube and form continuous fins through high-frequency welding. The spiral fins guide the flue gas to form a rotating flow field on the flue gas side, prolong the residence time of the flue gas, and enhance heat transfer, with the characteristics of large heat transfer area and high heat transfer efficiency. However, in actual applications, after long-term operation, referring to Figure 1 ... the most prominent problem of the low-temperature economizer is ash fouling. When the ash fouling is serious, it will affect the output of the induced draft fan, thus affecting the load-carrying capacity of the unit. To avoid ash accumulation, if the low-temperature economizer is installed between the air preheater and the electrostatic precipitator and fails to operate due to low temperature, it will not only cause the flue gas temperature to rise and the coal consumption of the unit to increase, but also affect the dust removal efficiency of the electrostatic precipitator, seriously affecting the dust removal pressure of downstream equipment. In severe cases, the chimney dust emission will exceed the standard, and the unit will be forced to reduce the load operation, and the ash fouling problem cannot be fundamentally solved. Therefore, the ash fouling of the low-temperature economizer is a long-term difficult problem. How to improve the long-term stable operation of the low-temperature economizer is an important topic related to the safety and economy of the power plant, and the optimization transformation of the low-temperature economizer is an inevitable trend.

[0004] In view of the problem of high energy consumption caused by easy ash fouling of the low-temperature economizer in the prior art, the present invention provides a low-temperature economizer system.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a low-temperature economizer system, which includes a shell-and-tube heat exchanger and several groups of plate heat exchangers. The plate heat exchangers are arranged in the flue at the tail of the boiler and are internally provided with heating medium water. After the flue gas at the tail of the boiler exchanges heat with the heating medium water inside the plate heat exchanger, it is cooled and discharged. The heating medium water after exchanging heat with the flue gas returns to the plate heat exchanger through the shell-and-tube heat exchanger to continue cooling the flue gas at the tail of the boiler. The medium inside the shell-and-tube heat exchanger is condensate water. A soot blowing device is arranged in the flue upstream of the plate heat exchanger for removing ash from the plate heat exchanger.

[0007] Optionally, two groups of plate heat exchangers are provided and are arranged in series in the flue at the tail of the boiler in sequence. Each group of plate heat exchangers includes several heat exchange plates arranged in the flue at the tail of the boiler.

[0008] Optionally, the heat exchange plates are corrugated heat exchange plates.

[0009] Optionally, the material of the heat exchange plates is ND steel, and the surface of the heat exchange plates is treated with an enamel anti-corrosion process.

[0010] Optionally, a heating medium water pump is arranged between the heating medium water output end of the shell-and-tube heat exchanger and the heating medium water input end of the plate heat exchanger.

[0011] Optionally, an expansion tank is connected between the heating medium water output end of the shell-and-tube heat exchanger and the heating medium water input end of the plate heat exchanger for supplementing the heating medium water.

[0012] Optionally, the soot blowing device includes several acoustic soot blowers arranged upstream of the flue gas of the plate heat exchanger. The acoustic soot blowers are arranged in the flue at the tail of the boiler in a grid array manner, and the air source of the acoustic soot blowers comes from the ash conveying air compressor system.

[0013] Optionally, the ash conveying air compressor system includes an air source primary control valve, an air source secondary control valve, an air source electric main valve, a pressure reducing valve, a steam-water separator, and a soot blowing control valve that are sequentially connected to the boiler steam source main pipe. The output end of the soot blowing control valve is connected to the acoustic soot blower.

[0014] Optionally, the outlet flue gas temperature of the plate heat exchanger is 2°C to 3°C higher than the flue gas acid dew point, and the inlet temperature of the heating medium water of the plate heat exchanger is greater than or equal to 75°C.

[0015] The present invention also provides a coal-fired power generation device, which includes the above-mentioned low-temperature economizer system.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a low-temperature economizer system, which includes a shell-and-tube heat exchanger and several groups of plate heat exchangers. The plate heat exchangers are arranged in the flue at the tail of the boiler, and hot medium water is provided inside. After the flue gas at the tail of the boiler exchanges heat with the hot medium water inside the plate heat exchanger, it is cooled and discharged. The hot medium water after exchanging heat with the flue gas returns to the plate heat exchanger through the shell-and-tube heat exchanger to continue cooling the flue gas at the tail of the boiler. The medium inside the shell-and-tube heat exchanger is condensate water. A soot blowing device is arranged in the flue upstream of the plate heat exchanger for removing ash from the plate heat exchanger. This system abandons the traditional H-type finned tubes or spiral finned tubes for heat exchange, and uses plate heat exchangers to absorb the waste heat of the flue gas at the tail of the boiler. Since the inside of the plate heat exchanger is composed of a series of corrugated metal plates stacked together, thin rectangular channels are formed between the plates, enabling strong turbulence to be formed when the fluid flows between the plates, which helps to reduce the deposition of dirt on the surface of the plates. Compared with the traditional H-type finned tubes or spiral finned tubes for heat exchange, it can effectively prevent ash accumulation and blockage. To prevent the internal pressure head of the plate heat exchanger from exceeding the bearing pressure range of the plate heat exchanger, the circulation of the hot medium water is coordinated with the shell-and-tube heat exchanger, ensuring that the hot medium water can continuously and stably transfer heat. While enabling the system to operate efficiently, the condensate water inside the shell-and-tube heat exchanger is used for heat exchange to buffer the pressure on the plate heat exchanger and avoid the failure of the plate heat exchanger caused by excessive pressure head. The soot blowing device arranged in the flue upstream of the plate heat exchanger can effectively remove the ash on the surface of the plate heat exchanger, preventing the dust carried in the flue gas from depositing on the surface of the plate heat exchanger, thereby ensuring the stability of the flue gas flow and the economizer system.

[0018] Two groups of the plate heat exchangers are provided and are arranged in series in the flue at the tail of the boiler in sequence. Each group of plate heat exchangers includes several heat exchange plates arranged in the flue at the tail of the boiler. This structure can effectively increase the heat exchange process and contact time between the flue gas and the hot medium water. When the flue gas passes through the first group of heat exchangers, part of the heat is absorbed by the hot medium water and the temperature decreases, but it still carries a certain amount of waste heat. After entering the second group of heat exchangers, it continues to exchange heat with the hot medium water, enabling the heat in the flue gas to be more fully recovered. This hierarchical heat exchange can not only effectively avoid the problem of uneven heat exchange caused by large changes in flue gas temperature in a single group of heat exchangers, but also improve the overall heat exchange efficiency. In addition, during the operation of the boiler, the load changes, resulting in changes in the flue gas flow rate and temperature. The two groups of plate heat exchangers are arranged in series, and the operating state of each group of heat exchangers can be flexibly adjusted according to the actual load condition of the boiler, enabling this economizer system to better adapt to different working conditions and improving the operation stability and reliability.

[0019] The heat exchange plate is a corrugated heat exchange plate. The surface of the corrugated heat exchange plate is undulating like waves. Compared with a flat plate, its surface area is significantly increased. At the same time, the presence of the corrugations will change the flow state of the fluid, causing the fluid to form strong turbulence between the heat exchange plates. When the flue gas flows through the corrugated surface, due to the blocking and guiding effects of the corrugations, the fluid velocity and direction constantly change, generating eddies and disturbances, which can break the fluid boundary layer, reduce the thermal resistance, and promote the rapid transfer of heat.

[0020] The material of the heat exchange plate is ND steel, and the surface of the heat exchange plate is treated with an enamel anti-corrosion process. This not only ensures that the heat exchange plate has good structural strength, but also after being treated with the enamel anti-corrosion process, it can have better corrosion resistance and wear resistance, preventing corrosive substances in the flue gas from damaging the heat exchange plate.

[0021] A hot medium water pump is arranged between the hot medium water output end of the shell-and-tube heat exchanger and the hot medium water input end of the plate heat exchanger. The setting of the hot medium water pump can ensure that the hot medium water circulates between the two heat exchangers at a stable flow rate and speed, guaranteeing the stability and heat exchange efficiency of the economizer system.

[0022] An expansion tank is connected between the hot medium water output end of the shell-and-tube heat exchanger and the hot medium water input end of the plate heat exchanger, which is used to supplement the hot medium water to ensure the stability of the flow rate of the internal hot medium water circulation.

[0023] The soot blowing device includes a number of acoustic soot blowers arranged upstream of the flue gas of the plate heat exchanger. The acoustic soot blowers are arranged in the flue at the tail of the boiler in a grid array manner, and the air source of the acoustic soot blowers comes from the ash conveying air compressor system. The acoustic soot blowers arranged in a grid array in the flue at the tail of the boiler can cover the entire heating surface area of the plate heat exchanger, avoiding ash cleaning dead corners and ensuring that the ash accumulation in each corner can be affected by the sound waves. At the same time, it prevents the arrangement of the soot remover from affecting the effective flow of the flue gas. Using the ash conveying air compressor system as the air source of the acoustic soot blowers realizes the integrated utilization of resources within the system, eliminating the need to separately equip the acoustic soot blowers with compressed air generating equipment, reducing the equipment investment cost and operating cost.

[0024] The ash conveying air compressor system includes a primary steam source control valve, a secondary steam source control valve, a main pneumatic control valve, a pressure reducing valve, a steam-water separator, and a soot blowing control valve that are sequentially connected to the boiler steam source main pipe. The output end of the soot blowing control valve is connected to a sonic soot blower. The series design of the primary steam source control valve and the secondary steam source control valve can effectively control the steam source pressure and prevent damage to subsequent equipment caused by excessive pressure or fluctuations. The steam-water separator effectively removes moisture and droplets in the compressed air through the centrifugal separation principle, ensuring that the gas entering the sonic soot blower is dry and clean. The setting of the soot blowing control valve makes the start, stop, and adjustment of the sonic soot blower more flexible, enabling precise control according to actual needs. By providing a corresponding power source for the sonic soot blower through the ash conveying air compressor system equipped in the existing boiler system, the operation and maintenance costs and retrofit costs of the system can be effectively reduced.

[0025] The outlet flue gas temperature of the plate heat exchanger is 2°C to 3°C higher than the flue gas acid dew point, and the inlet temperature of the heat transfer medium water of the plate heat exchanger is greater than or equal to 75°C, which is more conducive to the effective recovery of flue gas waste heat.

[0026] A coal-fired power generation device includes the above-mentioned low-temperature economizer system. Due to the equipped low-temperature economizer system, this coal-fired power generation device has the characteristics of good economy and environmental protection, low retrofit costs and operation costs, making it an ideal choice for the retrofit of old power plants and the optimization of newly built units. Description of the Drawings

[0027] Figure 1 It is a diagram of ash accumulation and blockage in the existing low-temperature economizer. Among them, a is a diagram of ash accumulation and blockage in H-shaped finned tubes, and b is a diagram of ash accumulation and blockage in spiral finned tubes.

[0028] Figure 2 It is a schematic structural diagram of a low-temperature economizer system of the present invention.

[0029] Figure 3 It is a schematic diagram of the flue gas waste heat absorption process of a low-temperature economizer system of the present invention.

[0030] Figure 4 It is a physical diagram of the plate heat exchanger of a low-temperature economizer system of the present invention.

[0031] Figure 5 It is a physical diagram of the corrugated heat transfer plate of a low-temperature economizer system of the present invention. Among them, a is an overall view of the heat transfer plate, and b is a cross-sectional view of the heat transfer plate.

[0032] Figure 6 It is a structural diagram of the soot blowing device of the present invention.

[0033] Figure 7 It is a schematic diagram of the layout points of the sonic soot blower.

[0034] Among them, 1 is a plate heat exchanger, 2 is a shell-and-tube heat exchanger, 3 is a soot blowing device, 4 is a heat medium water pump, 5 is an expansion tank, 31 is an acoustic soot blower, 32 is a main pipe of boiler steam steam source, 33 is a primary steam source control valve, 34 is a secondary steam source control valve, 35 is a main electric air valve, 36 is a pressure reducing valve, 37 is a steam-water separator, 38 is a first float steam trap, 39 is a second float steam trap, 40 is a steam trap control valve, 41 is a soot blowing control valve, and 42 is an acoustic soot blowing control mechanism. Specific embodiments

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0036] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0037] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0038] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, or the orientations or positional relationships in which the products of the invention are usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated devices or elements must have specific orientations, be constructed and operated in specific orientations, and therefore should not be construed as limiting the present invention. In addition, terms such as "first" and "second" are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0039] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0040] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if the terms "set", "installed", "connected", "connected" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0041] The following further elaborates on the present invention with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0042] See Figure 1 , the existing types of low-temperature economizers are mainly H-type finned tubes or spiral finned tubes. During long-term operation, the more prominent problems of low-temperature economizers are wear, corrosion, leakage, ash fouling, etc. When the ash fouling is serious, it will affect the output of the induced draft fan, thereby affecting the load-carrying capacity of the unit. Analyzing the difficult problems of wear, corrosion, leakage, and ash fouling of the low-temperature economizer, it is found that wear, corrosion, leakage, and ash fouling often interact with each other and form a vicious cycle. For example, the wear problem will cause leakage, and after leakage, it will cause ash fouling. The ash fouling will increase the flow velocity and exacerbate the wear, and at the same time, it will also cause corrosion. Similarly, corrosion will also cause leakage, ash fouling, and aggravated wear. To address the above problems, see Figure 2 and Figure 3 , the present invention discloses a low-temperature economizer system, including a shell-and-tube heat exchanger 2, a soot blowing device 3, and several groups of plate heat exchangers 1;

[0043] The plate heat exchanger 1 is arranged in the flue at the tail of the boiler and is internally provided with heating medium water. After the flue gas at the tail of the boiler exchanges heat with the heating medium water inside the plate heat exchanger 1, it cools down and is discharged. The heating medium water after exchanging heat with the flue gas returns to the plate heat exchanger 1 through the shell-and-tube heat exchanger 2 to continue cooling the flue gas at the tail of the boiler. The medium inside the shell-and-tube heat exchanger 2 is condensate water. The soot blowing device 3 is arranged in the upstream flue of the plate heat exchanger 1 and is used for removing ash from the plate heat exchanger 1. A heating medium water pump 4 is arranged between the heating medium water output end of the shell-and-tube heat exchanger 2 and the heating medium water input end of the plate heat exchanger 1 to ensure the internal heating medium water circulation. Preferably, valves are arranged at both ends of the heating medium water pump 4, and a standby heating medium water pump is connected in parallel. When the heating medium water pump 4 is under maintenance or fails, it is convenient for disassembly and to ensure the effective circulation of the heating medium water. An expansion tank 5 is connected between the heating medium water output end of the shell-and-tube heat exchanger 2 and the heating medium water input end of the plate heat exchanger 1 to supplement the heating medium water. The input end of the heating medium water tank 5 is connected to the tap water source. Valves are arranged at both ends of the expansion tank 5 to control the input and output of the water inside the heating medium water tank 5. A drain valve is arranged between the expansion tank 5 and the heating medium water pump 4 to adjust the heating medium water circulation flow rate or to facilitate the discharge of the internal heating medium water during maintenance or repair. Preferably, an ash hopper is arranged at the bottom of the plate heat exchanger 1 to collect the ash blown between the heat exchange plates and prevent the accumulation of ash from affecting the heat exchange effect of the low-temperature economizer system. The ash in the ash hopper is transported to the ash conveying main pipe of the electrostatic precipitator by pneumatic conveying.

[0044] Determine the layout method of the low-temperature economizer system according to the on-site space position. If the on-site space is limited and high-temperature and low-temperature segmented layout is required, that is, the plate heat exchanger 1 is set as two groups and arranged in series in the flue at the tail of the boiler in sequence; see Figure 4 and Figure 5 . Each group of plate heat exchangers 1 includes a number of heat exchange plates arranged in the flue at the tail of the boiler. Preferably, the heat exchange plates are corrugated heat exchange plates, made of ND steel, and the surface is treated with an enamel anti-corrosion process to improve the wear resistance and corrosion resistance of the plate heat exchanger 1. In order to prevent the pipeline from being pulled and cracked due to the thermal expansion and displacement of the plate heat exchanger 1, the fixed end and the expansion end of the plate heat exchanger 1 need to be designed during the retrofit design. A bellows expansion joint is arranged at the expansion end to absorb the expansion amount.

[0045] See Figure 6 and Figure 7 . The soot blowing device 3 includes a number of acoustic soot blowers 31 arranged upstream of the flue gas of the plate heat exchanger 1. The acoustic soot blowers 31 are arranged in the flue at the tail of the boiler in a grid array manner, and the air source of the acoustic soot blowers 31 comes from the ash conveying air compressor system. At the same time, a 10m 3The gas storage tank; the acoustic soot blower 31 is composed of a swirl spray chamber and a resonance chamber. Compressed air enters the swirl chamber, is accelerated and pressurized, and is sprayed into the resonance chamber to form a recoil flow. The recoil flow and the incident fluid converge and collide at high speed at the port of the resonance chamber, thereby forming fluid friction and instantaneously generating high-intensity sound waves to achieve soot blowing. Preferably, during the arrangement of the acoustic soot blower 31, it is arranged in an array according to the grid method, with one acoustic soot blower 31 arranged per square meter on average to ensure that it will not affect the inlet air flow of the plate heat exchanger 1. The ash conveying air compressor system includes a steam source primary control valve 33, a steam source secondary control valve 34, an air source electric main valve 35, a pressure reducing valve 36, a steam-water separator 37, and a soot blowing control valve 41 connected in sequence to the boiler steam source main pipe 32. The output end of the soot blowing control valve 41 is connected to the acoustic soot blower 31; the lowest end of the steam-water separator 37 is connected to a first float trap 38 and a second float trap 39 in sequence; the lowest point between the steam-water separator 37 and the soot blowing control valve 41 is connected to a drain control valve 40 to access the drain circuit to the drain expander, and the drain control valve 40 is connected to the second float trap 39; the soot blowing device 3 further includes an acoustic soot blowing control mechanism 42, and the acoustic soot blowing control mechanism 42 is electrically connected to the soot blowing control valve 41, the drain control valve 40, the steam source primary control valve 33, the steam source secondary control valve 34, and the air source electric main valve 35. A number of pressure gauges are provided between the steam-water separator 37 and the boiler steam source main pipe 32, and the pressure gauges are electrically connected to the acoustic soot blowing control mechanism 42.

[0046] Before the transformation, it is necessary to test the flue gas resistance, flue gas flow rate, and velocity field to provide boundary conditions for the numerical simulation before the low-temperature economizer transformation. Numerical simulation is carried out in the inlet flue of the low-temperature economizer, and according to the simulation results, a flow guide plate is installed to ensure that the relative standard deviation of the inlet velocity field uniformity is less than 15%, and the flow deviation of different flues is less than 10%. During the adjustment process, the flow rate of the condensed water inside the shell-and-tube heat exchanger 2 can be adjusted to adjust the temperature of the heat medium water. The outlet flue gas temperature of the plate heat exchanger 1 is 2°C - 3°C higher than the flue gas acid dew point, and the inlet temperature of the heat medium water of the plate heat exchanger 1 is greater than or equal to 75°C. According to the original design coal and the common coal quality of the power plant, calculate the acid dew point and determine the inlet water temperature and outlet flue gas temperature of the plate heat exchanger 1; the calculation formula for the flue gas acid dew point temperature is as follows:

[0047]

[0048] Among them, t Dp is the flue gas acid dew point temperature; t Dp.o is the dew point temperature of water vapor in the flue gas; S ar,zs is the received-base converted sulfur content; α fh is the share of fly ash in the fuel ash, taking 0.9 for pulverized coal furnaces; A ar,zs is the received-base converted ash content.

[0049] The present invention also provides a coal-fired power generation device, which includes the above-mentioned low-temperature economizer system. Due to the configuration of the above-mentioned low-temperature economizer system, the coal-fired power generation device has good economy and environmental protection, and has characteristics such as low retrofit cost and operation cost, making it an ideal choice for the retrofit of old power plants and the optimization of newly built units.

[0050] In summary, the present invention provides a low-temperature economizer system and a coal-fired power generation device. The low-temperature economizer system abandons the traditional H-type finned tubes or spiral finned tube heat exchange, and uses a plate heat exchanger in cooperation with a shell-and-tube heat exchanger to circulate the heat transfer medium water and exchange heat with the flue gas at the tail of the boiler. Compared with the traditional H-type finned tubes or spiral finned tube heat exchange, it can effectively prevent ash accumulation and blockage, and ensure the stable operation of the low-temperature economizer system.

[0051] The above are only the preferred embodiments of the present invention, and are not used to limit the technical solutions of the present invention. Those skilled in the art should understand that without departing from the spirit and principle of the present invention, the technical solutions can be subject to several simple modifications and substitutions, and these modifications and substitutions also fall within the protection scope covered by the claims.

Claims

1. A low-temperature economizer system, characterized in that, It includes a shell-and-tube heat exchanger and several groups of plate heat exchangers. The plate heat exchangers are arranged in the flue at the tail of the boiler and are internally provided with heating medium water. After the flue gas at the tail of the boiler exchanges heat with the heating medium water inside the plate heat exchanger, it is cooled and discharged. The heating medium water after exchanging heat with the flue gas returns to the plate heat exchanger through the shell-and-tube heat exchanger to continue cooling the flue gas at the tail of the boiler. The internal medium of the shell-and-tube heat exchanger is condensate water. A soot blowing device is arranged in the flue upstream of the plate heat exchanger for removing ash from the plate heat exchanger.

2. The low-temperature economizer system according to claim 1, wherein The plate heat exchangers are set to two groups and are arranged in series in the flue at the tail of the boiler in sequence. Each group of plate heat exchangers includes several heat exchange plates arranged in the flue at the tail of the boiler.

3. The low-temperature economizer system according to claim 2, characterized in that, The heat exchange plates are corrugated heat exchange plates.

4. The low-temperature economizer system according to claim 2, characterized in that, The material of the heat exchange plates is ND steel, and the surface of the heat exchange plates is treated with an enamel anti-corrosion process.

5. The low-temperature economizer system according to claim 1, wherein, A heating medium water pump is arranged between the heating medium water output end of the shell-and-tube heat exchanger and the heating medium water input end of the plate heat exchanger.

6. The low-temperature economizer system according to claim 1, wherein An expansion tank is connected between the heating medium water output end of the shell-and-tube heat exchanger and the heating medium water input end of the plate heat exchanger for supplementing the heating medium water.

7. The low-temperature economizer system according to claim 1, characterized in that, The soot blowing device includes several acoustic soot blowers arranged upstream of the flue gas of the plate heat exchanger. The acoustic soot blowers are arranged in the flue at the tail of the boiler in a grid array manner, and the gas source of the acoustic soot blowers comes from the ash conveying air compressor system.

8. The low-temperature economizer system according to claim 7, characterized in that, The ash conveying air compressor system includes a steam source primary control valve, a steam source secondary control valve, an air source electric main valve, a pressure reducing valve, a steam-water separator, and a soot blowing control valve that are sequentially connected to the boiler steam source main pipe. The output end of the soot blowing control valve is connected to the acoustic soot blower.

9. The low-temperature economizer system according to any one of claims 1-8, characterized in that The flue gas temperature at the outlet of the plate heat exchanger is 2°C to 3°C higher than the acid dew point of the flue gas, and the inlet temperature of the heating medium water of the plate heat exchanger is greater than or equal to 75°C.

10. A coal-fired power generation device, characterized in that, It includes the low-temperature economizer system according to any one of claims 1-9.

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