Heating system and method for heating primary air and low-temperature flue gas using economizer feed water

Abstract

The present invention belongs to the technical field of ultra-low flue gas emission processes for waste incineration power plants, and specifically relates to a heating system and method for heating primary air and low-temperature flue gas using economizer feedwater. The heating system includes a deaerator, a feedwater pump, an economizer, at least one air preheater, a flue gas purification system, a primary air circulation heating system, and a low-temperature flue gas heating system. The feedwater pump generates a first high-pressure feedwater, which is passed into the economizer. The economizer outputs undersaturated water, which is then passed into the flue gas purification system and the air preheater for heating the low-temperature flue gas and primary air. The high-temperature flue gas passes through the economizer, and the flue gas output from the economizer is passed into the flue gas purification system. The flue gas purification system uses the flue gas and undersaturated water output from the economizer to heat the low-temperature flue gas. The present invention solves the problems of high energy consumption and system complexity caused by the use of high-quality steam to heat the primary air and low-temperature flue gas system in the flue gas heaters before the air preheater and SCR.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-low emission technology of flue gas from waste incineration power plants, and particularly relates to a heating system and method for heating primary air and low-temperature flue gas by utilizing economizer feed water. Background Art

[0002] With the increasing proportion of waste incineration, improving the efficiency of waste incineration power plants has become a major research topic. Because the flue gas generated by waste incineration contains corrosive gases such as HCl and SO₂ and has a high ash content, the superheated steam temperature must not exceed 450°C to prevent high-temperature corrosion in the waste heat boiler (WHRB), resulting in poor economic efficiency for waste incineration power plants. To prevent low-temperature corrosion and ash blockage in the air preheater (APH), the APH uses steam from the primary extraction of the turbine and saturated steam from the drum to heat the primary air, resulting in high-quality steam consumption and poor power plant economics. In the flue gas purification process, to control the nitrogen oxide content in the stack below 50 mg / Nm₃, a low-temperature SCR (SCR) denitrification reaction temperature must reach above 175°C. However, the flue gas temperature after passing through the semi-dry reactor and bag filter drops to 145°C. Therefore, a flue gas heater is required between the bag filter and the low-temperature SCR to raise the flue gas temperature by 30°C. Saturated steam from the drum is generally used to heat the flue gas to ensure effective denitrification, resulting in high-quality steam consumption and poor power plant economics. Steam-heated heat exchangers also require a drain system that uses traps or flash tanks to recover drain water to the deaerator. The air preheater and flue gas heater systems of waste incineration power plants consume high-quality steam, resulting in high steam consumption and poor plant economics. Furthermore, the use of traps or flash tanks can lead to problems such as water hammer vibration in the piping caused by the vaporization of drain water, complicating the system.

[0003] In order to avoid the consumption of high-quality steam and improve the economy of the power plant, the present invention simultaneously heats the primary air temperature to 220°C and the flue gas temperature before the SCR to above 175°C. The heaters are both heated by high-temperature feed water at the economizer outlet, and the system is simplified for easy operation. Summary of the Invention

[0004] The present invention provides a heating system and method for heating primary air and low-temperature flue gas by using economizer feed water, which mainly solves the problems of high energy consumption and complex system caused by the use of high-quality steam to heat the primary air and low-temperature flue gas system in the flue gas heaters before the hollow pre-processor and SCR in waste incineration power plants.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a heating system for heating primary air and low-temperature flue gas using economizer feed water, comprising a deaerator, a feed water pump, an economizer, at least one air preheater, a flue gas purification system, a primary air circulation heating system, and a low-temperature flue gas heating system;

[0006] In the primary air circulation heating system, the feed water pump generates the first high-pressure feed water, which is fed into the economizer. The economizer outputs undersaturated water, which is then fed into the flue gas purification system and air preheater for heating low-temperature flue gas and primary air.

[0007] The flue gas purification system for deacidification and dust removal outputs feed water to the deaerator, and the air preheater outputs feed water to the deaerator. The deaerator thermally deoxidizes the feed water output by the flue gas purification system, the feed water output by the air preheater, and the connected condensate to form first condensed water, which is then fed into the feed water pump to form a primary air circulation heating system.

[0008] Low-temperature flue gas heating system: the high-temperature flue gas generated by garbage incineration passes through the economizer, and the flue gas output from the economizer is introduced into the flue gas purification system. The flue gas purification system uses the flue gas output from the economizer and the undersaturated water output from the economizer to heat the low-temperature flue gas.

[0009] As a further preferred embodiment of the present invention, the flue gas purification system includes a semi-dry reaction tower, a bag filter, a water-feed flue gas heater and a low-temperature SCR which are sequentially arranged along the flue gas flow direction.

[0010] As a further preferred embodiment of the present invention, it further includes a first water supply, a second water supply, a steam drum, a third water supply, and a fourth water supply, wherein:

[0011] The undersaturated water output by the economizer is divided into the first feed water and the second feed water. The first feed water is passed into the steam drum, and the second feed water is divided into the third feed water and the fourth feed water. The third feed water is passed into the flue gas purification system for low-temperature flue gas heating, and the fourth feed water is passed into the air preheater for primary air heating.

[0012] As a further preferred embodiment of the present invention, the air preheater further includes two outlet air ducts and one inlet air duct, the two outlet air ducts are arranged on the same side of the air preheater, and the two outlet air ducts are located above the inlet air duct.

[0013] As a further preferred embodiment of the present invention, the air preheater adopts a high-fin serpentine tube type and is arranged in a staggered vertical manner; the feed water flue gas heater adopts a high-fin serpentine tube type and is arranged in a staggered manner.

[0014] A heating method for a heating system that utilizes economizer feedwater to heat primary air and low-temperature flue gas is also provided, including a heating method for a primary air circulation heating system and a heating method for a low-temperature flue gas heating system. The specific steps are as follows:

[0015] The heating method of the primary air circulation heating system comprises the following steps:

[0016] Step 1-1: Generation of the first high-pressure water supply:

[0017] The first condensate formed in the deaerator is passed into the feed water pump, and the feed water pump increases the pressure of the first condensate to form the first high-pressure feed water;

[0018] Step 1-2, generation of undersaturated water:

[0019] The first high-pressure feed water formed in step 1-1 is passed into the economizer, and is heated by the economizer to generate undersaturated water with a water temperature above 230°C;

[0020] Steps 1-3, primary air heating:

[0021] The first feed water of undersaturated water with a temperature of above 230°C generated in step 1-2 is passed into the steam drum, and the fourth feed water is passed into the air preheater for heating the primary air in the air preheater. During the heating of the primary air, the utilized feed water is passed into the deaerator;

[0022] Steps 1-4, Circular Heating:

[0023] Repeat steps 1-1 to 1-3 to achieve circulating heating of the primary air;

[0024] The heating method of the low-temperature flue gas heating system includes the following steps:

[0025] Step 2-1, generation of low-temperature flue gas:

[0026] The high-temperature flue gas generated by garbage incineration is passed into the economizer, heated by the economizer, and then passed into the semi-dry reaction tower. After being treated in the semi-dry reaction tower, it is passed into the bag dust collector, and after being treated in the bag dust collector, low-temperature flue gas is generated;

[0027] Step 2-2, low-temperature flue gas heating:

[0028] The water supply flue gas heater is combined with the third water supply of undersaturated water with a temperature of more than 230°C generated in step 1-2 to heat the low-temperature flue gas generated in step 2-1;

[0029] Step 2-3, denitrification treatment:

[0030] In step 2-2, the low-temperature flue gas is heated to 180°C and sent to the low-temperature SCR for denitrification.

[0031] As a further preferred embodiment of the present invention, in step 2-2, the utilized feed water is passed into a deaerator.

[0032] As a further preference of the present invention, in step 1-1, condensate needs to be introduced into the deaerator, and the condensate, the feed water after being utilized in step 1-3, and the feed water after being utilized in step 2-2 are all introduced into the deaerator for thermal deoxygenation to form a first condensate of 0.27 MPa / 130°C.

[0033] As a further preferred embodiment of the present invention, the primary air in steps 1-3 needs to be heated to above 220°C.

[0034] Through the above technical solution, compared with the existing technology, the present invention has the following beneficial effects:

[0035] 1. The present invention adopts the feed water at the economizer outlet to heat the primary air and low-temperature flue gas, and the air preheater air duct adopts a one-inlet and two-outlet layout type.

[0036] 2. The water intake point of the air preheater in the present invention is from the economizer outlet water supply, and the air preheater outlet water supply is sent to the deaerator for recycling through an electric pressure reducing valve, which is completely different from the existing air preheater system.

[0037] 3. The structure and layout of the air preheater heat exchange tube of the present invention adopts a high-fin serpentine tube type, a staggered vertical arrangement (the air duct is arranged vertically), and the material is g20+1070 aluminum alloy. The primary air and flue gas flow rate is designed to be around 10m / s. The structure is compact, the footprint is small and the heat transfer coefficient is high.

[0038] 4. The structure and layout of the heat exchange tubes of the water-feeding flue gas heater of the present invention adopt a high-fin serpentine tube type with a staggered arrangement. The flue gas flow rate is designed to be around 10m / s. The structure is compact and the heat exchange efficiency is high.

[0039] 5. The present invention passes the high-temperature flue gas generated by garbage incineration into the economizer to heat the first high-pressure feed water. The flue gas at the economizer outlet drops to 190°C and then enters the flue gas purification system; the condensed water enters the deaerator for thermal deoxidation to form the first condensed water, and the first condensed water is sent to the feed water pump through the condensate pipe to increase the pressure. The pressurized first condensed water becomes the first high-pressure feed water, which is passed into the economizer through the fifth feed water pipe and heated to undersaturated water.

[0040] 6. In the present invention, the undersaturated water is divided into a first water supply and a second water supply through a first regulating valve. The first water supply enters the steam drum through a first water supply pipe, and the second water supply is led to a second regulating valve through a second water supply pipe. The second regulating valve divides the second water supply into a third water supply and a fourth water supply. The third water supply is led into a water supply flue gas heater through a third water supply pipe to heat the low-temperature flue gas to 175°C; the fourth water supply is led into an air preheater through a fourth water supply pipe to heat the primary air to 220°C.

[0041] 7. The second outlet water supply pipe of the air preheater of the present invention is reduced in pressure to 0.7 MPa by the second electric pressure reducing valve and sent to the deaerator for recycling; the first outlet water supply pipe of the water-feeding flue gas heater is reduced in pressure to 0.7 MPa by the first electric pressure reducing valve and sent to the deaerator for recycling; it is passed into the deaerator for thermal deoxidation together with the condensate, and finally enters the economizer for recycling.

[0042] 8. In the present invention, a flow meter is installed on the fifth water supply pipe to monitor the feed water flow entering the economizer, and pressure and temperature measuring points are set on the fifth water supply pipe to monitor the feed water pressure and temperature entering the economizer; pressure and temperature measuring points are set on the first water supply pipe to monitor the feed water pressure and temperature entering the steam drum, and reflect the undersaturated water temperature at the economizer outlet; the feed water flow entering the feed water flue gas heater is controlled by the first regulating valve, and a flow meter is installed on the third water supply pipe to monitor the feed water flow entering the feed water flue gas heater, and a temperature measuring point is set on the third water supply pipe to monitor the feed water temperature entering the feed water flue gas heater; the feed water flow entering the air preheater is controlled by the second regulating valve, and a flow meter is installed on the fourth water supply pipe to monitor the feed water flow entering the air preheater, and a temperature measuring point is set on the fourth water supply pipe to monitor the feed water temperature entering the air preheater.

[0043] 9. In the present invention, a temperature measuring point is set on the second outlet water supply pipe, and the outlet water supply temperature of the air preheater is controlled below 130°C; a second electric pressure reducing valve is installed on the second outlet water supply pipe, and switch valves are installed before and after it to reduce the water supply pressure entering the deaerator to 0.7MPa for recycling; a temperature measuring point is set on the first outlet water supply pipe, and the outlet water supply temperature of the feed water flue gas heater is controlled at about 160°C; a first electric pressure reducing valve is installed on the first outlet water supply pipe, and switch valves are installed before and after it to reduce the water supply pressure entering the deaerator to 0.7MPa for recycling; that is, the present invention sets temperature measuring points and electric regulating valves on the system pipeline to control the working medium flow and temperature at various places of the air preheater and the feed water flue gas heater, so that the system operates in the best state, the system is economical and stable and reliable, the structure is simple, and the operation is also simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below with reference to the accompanying drawings and examples.

[0045] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0046] In the figure: 1. High-temperature flue gas; 2. Economizer; 3. Semi-dry reaction tower; 4. Bag filter; 5. Low-temperature flue gas; 6. Feedwater flue gas heater; 7. First electric pressure reducing valve; 8. Low-temperature SCR; 9. Undersaturated water; 10. First feedwater pipe; 11. Steam drum; 12. Second feedwater pipe; 13. Third feedwater pipe; 14. Fourth feedwater pipe; 15. Air preheater; 16. Second electric pressure reducing valve; 17. Condensate; 18. Deaerator; 19. Condensate pipe; 20. Feedwater pump; 21. Fifth feedwater pipe; 22. Inlet air duct; 23. Outlet air duct; 24. Flue gas purification system; 25. First regulating valve; 26. Second regulating valve; 27. Second outlet feedwater pipe; 28. First outlet feedwater pipe. DETAILED DESCRIPTION

[0047] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0048] In the description of the present invention, it should be understood that the terms "left side," "right side," "upper," "lower," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Terms such as "first" and "second" do not indicate the importance of components and therefore should not be construed as limitations on the present invention. The specific dimensions used in this embodiment are intended only to illustrate the technical solution and do not limit the scope of protection of the present invention.

[0049] The existing technology uses high-quality steam extracted from turbines or drums 11 to heat the primary air and low-temperature flue gas 5 before the SCR process. This high-quality steam is consumed by the heat exchanger, resulting in poor power plant economics. Furthermore, the steam heater drain system is complex, requiring equipment such as steam traps and flash tanks. The steam easily vaporizes, causing water hammer vibration in the drain pipes. This poses operational risks and shortens the life of the drain pipes. To address these issues, the following embodiments are provided:

[0050] Example 1

[0051] This embodiment provides a preferred embodiment, a heating system that uses economizer feed water to heat primary air and low-temperature flue gas, such as Figure 1 As shown, the heating system includes a deaerator 18, a feed water pump 20, an economizer 2, at least one air preheater 15, a flue gas purification system 24, a primary air circulation heating system, and a low-temperature flue gas heating system.

[0052] The above-mentioned primary air circulation heating system further comprises a water feed pump 20 that generates a first high-pressure feed water, the first high-pressure feed water is passed into the economizer 2, the economizer 2 outputs undersaturated water 9, and the undersaturated water 9 output by the economizer 2 is passed into the flue gas purification system 24 and the air preheater 15 for heating the low-temperature flue gas 5 and the primary air.

[0053] Specifically, this embodiment also includes a first water supply, a second water supply, a steam drum 11, a third water supply, and a fourth water supply. The undersaturated water 9 output by the economizer 2 is divided into a first water supply and a second water supply. The first water supply is introduced into the steam drum 11, and the second water supply is divided into a third water supply and a fourth water supply. The third water supply is introduced into the flue gas purification system 24 for heating the low-temperature flue gas 5, and the fourth water supply is introduced into the air preheater 15 for primary air heating.

[0054] Specifically, the air preheater 15 further includes two outlet ducts 23 and one inlet duct 22. The two outlet ducts 23 are disposed on the same side of the air preheater 15 and above the inlet duct 22. Primary air enters through the inlet duct 22 and exits through the two outlet ducts 23. Preferably, the air preheater 15 employs a high-fin serpentine tube type and is arranged in a staggered vertical configuration.

[0055] The flue gas purification system 24 for deacidification and dust removal outputs feed water to the deaerator 18, and the air preheater 15 outputs feed water to the deaerator 18. The deaerator 18 thermally deoxidizes the feed water output by the flue gas purification system 24, the feed water output by the air preheater 15 and the connected condensate 17 to form the first condensed water, and the first condensed water is passed into the feed water pump 20, thereby forming a primary air circulation heating system.

[0056] Specifically, the economizer 2 is arranged on the heating surface at the rear of the boiler, and uses the water supplied by the fifth water supply pipe 21 to reduce the high-temperature flue gas at the rear of the boiler to a specified flue gas temperature. The air preheater 15 is a device that preheats the air entering the incinerator to mix with the fuel.

[0057] The above-mentioned low-temperature flue gas 5 heating system, further, the high-temperature flue gas generated by garbage incineration passes through the economizer 2, and the flue gas output by the economizer 2 enters the flue gas purification system 24, and the flue gas purification system 24 uses the flue gas output by the economizer 2 and the undersaturated water 9 output by the economizer 2 to heat the low-temperature flue gas 5.

[0058] Specifically, the flue gas purification system 24 includes a semi-dry reaction tower 3, a bag filter 4, a water-feed flue gas heater 6, and a low-temperature SCR 8, which are arranged in sequence along the flue gas flow direction. The semi-dry reaction tower 3 is a device that sprays a deacidifying agent to remove acidic gases from the flue gas generated by waste incineration. The bag filter 4 uses textile filter bags to filter dust from the flue gas generated by waste incineration. The water-feed flue gas heater 6 heats the low-temperature flue gas 5 that passes through the bag filter 4. The low-temperature SCR 8 uses a denitrification catalyst to remove nitrogen oxides from the flue gas generated by waste incineration.

[0059] This embodiment also provides a heating method, which includes a heating method for a primary air circulation heating system and a heating method for a low-temperature flue gas 5 heating system. The specific steps are as follows:

[0060] The heating method of the primary air circulation heating system comprises the following steps:

[0061] Step 1-1: Generation of the first high-pressure water supply:

[0062] The first condensate formed by the deaerator 18 is passed into the feed water pump 20, and the feed water pump 20 increases the pressure of the first condensate to form the first high-pressure feed water;

[0063] Specifically, the deaerator 18 needs to be fed with condensate 17 with a temperature range of 70°C to 110°C. The condensate 17, the feed water used in step 1-3, and the feed water used in step 2-2 are all fed into the deaerator 18 for thermal deoxygenation to form a first condensate of 0.27MPa / 130°C.

[0064] Step 1-2, generation of undersaturated water 9:

[0065] The first high-pressure feed water formed in step 1-1 is passed into the economizer 2, and is heated by the economizer 2 to generate undersaturated water 9 with a water temperature above 230°C;

[0066] Steps 1-3, primary air heating:

[0067] The first feed water of the undersaturated water 9 with a water temperature above 230°C generated in step 1-2 is passed into the steam drum 11, and the fourth feed water is passed into the air preheater 15 for heating the primary air passed into the air preheater 15. During the heating of the primary air, the utilized feed water is passed into the deaerator 18.

[0068] Specifically, the primary air needs to be heated to above 220°C.

[0069] Steps 1-4, Circular Heating:

[0070] Repeat steps 1-1 to 1-3 to achieve circulating heating of the primary air;

[0071] The heating method of the low-temperature flue gas 5 heating system comprises the following steps:

[0072] Step 2-1, generation of low-temperature flue gas 5:

[0073] The high-temperature flue gas generated by the incineration of garbage is passed into the economizer 2, heated by the economizer 2, and then passed into the semi-dry reaction tower 3. After being treated in the semi-dry reaction tower 3, it is passed into the bag filter 4. After being treated in the bag filter 4, low-temperature flue gas 5 is generated. The temperature range of the low-temperature flue gas 5 is 140℃~160℃.

[0074] Step 2-2, heating of low-temperature flue gas 5:

[0075] The water supply flue gas heater 6 combines the third water supply of undersaturated water 9 with a water temperature above 230° C. generated in step 1-2 to heat the low-temperature flue gas 5 generated in step 2-1, and the water supply is then fed into the deaerator 18 after being utilized.

[0076] Step 2-3, denitrification treatment:

[0077] In step 2-2, the low-temperature flue gas 5 is heated to 180° C. and sent to the low-temperature SCR 8 for denitrification treatment.

[0078] Specific instructions:

[0079] Economizer 2 uses the high-temperature flue gas generated by waste incineration to heat the first high-pressure feedwater entering economizer 2, forming undersaturated water 9. The temperature of the undersaturated water 9 is required to be at least 30°C below the saturated water temperature. Furthermore, if the boiler steam parameters are 4MPa / 400°C and the saturated water temperature is 260°C, the temperature of the undersaturated water 9 at the economizer 2 outlet is approximately 230°C. If the boiler steam parameters are 6.4MPa / 450°C and the saturated water temperature is 287°C, the temperature of the undersaturated water 9 at the economizer 2 outlet is approximately 257°C. If the steam parameters are 13MPa / 430°C / 410°C and the saturated water temperature is approximately 330°C, the temperature of the undersaturated water 9 at the economizer 2 outlet is approximately 250°C. In other words, the temperature of the undersaturated water 9 at the economizer 2 outlet is consistently above 230°C, regardless of the steam parameters.

[0080] The utilized flue gas discharged from the economizer 2 enters the ultra-low emission flue gas purification system 24. The flue gas passes through the semi-dry reaction tower 3, the bag filter 4, the water-feed flue gas heater 6, and the low-temperature SCR 8 in sequence for deacidification and dust removal. Preferably, the temperature of the low-temperature flue gas 5 generated after passing through the bag filter 4 is between 140°C and 160°C. Since the optimal reaction temperature of the low-temperature SCR 8 is 180°C, a water-feed flue gas heater 6 is required between the bag filter 4 and the low-temperature SCR 8. The fourth water feed at the outlet of the economizer 2 is used to heat the low-temperature flue gas 5 at the outlet of the bag filter 4 from 140°C to 160°C to 180°C, and then it is sent to the low-temperature SCR 8 for denitrification.

[0081] One boiler is equipped with one air preheater 15. The air preheater 15 includes two outlet air ducts 23 and one inlet air duct 22. The primary cooling air enters from the inlet air duct 22, and the hot air is extracted from the two outlet air ducts 23 and evenly sent to the domestic waste incineration boiler to assist combustion.

[0082] The undersaturated water 9 at the outlet of the economizer 2 is divided into a first water supply and a second water supply through the first regulating valve 2525. The first water supply is passed into the steam drum 11 through the first water supply pipe 10 for recycling, and pressure and temperature measuring points are set on the first water supply pipe 10. The second water supply is passed to the second regulating valve 26 through the second water supply pipe 12, and a flow meter is installed on the second water supply pipe 12. The second regulating valve 26 divides the second water supply into a third water supply and a fourth water supply. The third water supply is passed into the water supply flue gas heater 6 through the third water supply pipe 13 for heating the low-temperature flue gas 5. The fourth water supply is passed into the air preheater 15 through the fourth water supply pipe 14 for heating the primary air. Preferably, flow meters and thermometers are installed on both the third water supply pipe 13 and the fourth water supply pipe 14.

[0083] In the water supply flue gas heater 6, the third water supply heats the low-temperature flue gas 5 from 145°C to 175°C. A temperature measuring point is set on the first outlet water supply pipe 28 of the water supply flue gas heater 6. The water supply flow entering the water supply flue gas heater 6 is adjusted according to the operating load, and the outlet water supply temperature of the water supply flue gas heater 6 is controlled at 160°C. Specifically, the water supply flue gas heater 6 adopts a high-fin serpentine tube type with a staggered arrangement. The flue gas flow rate is designed to be 10m / s, and the heat transfer coefficient is higher than 30W / (m 2 Since the outlet water pressure of the flue gas heater 6 is relatively high, a first electric pressure reducing valve 7 is installed on the first outlet water supply pipe 28 to reduce the water pressure to 0.7 MPa and send the water to the deaerator 1818 for recycling.

[0084] In the air preheater 15, the fourth water supply is used to heat the primary air to 220°C, and the water supply temperature is reduced to below 130°C after use. Specifically, a temperature measuring point is set on the fourth water supply pipe 14, and the water supply flow entering the air preheater 15 is adjusted according to the operating load to control the outlet water supply temperature of the air preheater 15 below 130°C. The air preheater 15 adopts a high-fin serpentine tube type, staggered vertical arrangement, and the primary air flows from bottom to top. The material is g20+1070 aluminum alloy. The primary air flow rate is designed to be around 10m / s, so as to achieve a small footprint and a heat transfer coefficient higher than 30W / (m 2 Since the outlet water pressure of the air preheater 15 is relatively high, a second electric pressure reducing valve 16 is installed on the second outlet water supply pipe 27 of the air preheater 15 to reduce the water pressure to 0.7 MPa and send the water to the deaerator 18 for recycling.

[0085] Specifically, since the temperature of the undersaturated water 9 at the outlet of the economizer 22 is relatively high and is not saturated, the primary air temperature can be heated to about 220°C and the low-temperature flue gas 5 can be heated to 175°C, thereby avoiding problems such as water hammer vibration caused by steam in the first water supply pipe 10, the second water supply pipe 12, the third water supply pipe 13, the fourth water supply pipe 14, and the fifth water supply pipe 21. It also completely solves the problem of waste of high-quality steam caused by using steam to heat the primary air and flue gas, thereby improving the economy of the power plant.

[0086] Condensate 17, the feedwater used in steps 1-3, and the feedwater used in step 2-2 are all passed into the deaerator 18 for thermal deoxygenation, forming first condensate at 0.27 MPa / 130°C. The first condensate enters the feedwater pump 20 through the condensate pipe 19 for boosting, becoming a first high-pressure feedwater at 5.3 MPa / 130°C (the outlet pressure of the feedwater pump 20 is determined by the pressure of the steam drum 11). The first high-pressure feedwater enters the economizer 22 through the fifth feedwater pipe 21, where it absorbs waste heat from the high-temperature flue gas 1, raising the temperature of the first high-pressure feedwater to above 230°C. The exhaust gas temperature at the economizer 21 outlet is reduced to below 190°C before entering the flue gas purification system 24. Condensate 17 and feedwater are continuously recycled in the economizer 22, the air preheater 15, and the feedwater flue gas heater 6. Preferably, the fifth feedwater pipe 21 is equipped with a pressure gauge, flow meter, and thermometer.

[0087] This implementation scheme, based on waste incineration boiler structures with varying steam parameters, comprehensively compares and analyzes heaters with different heating media, along with a detailed analysis of the air preheater 15 and feedwater flue gas heater 6 systems. The result is an energy-efficient and simple heating system. This implementation scheme utilizes only undersaturated water 9 at the economizer 2 outlet to heat the primary air and low-temperature flue gas 5, replacing high-quality saturated steam and turbine extraction, resulting in superior economic efficiency. See the table below.

[0088] Taking 2x750t / d, furnace calorific value 1800kcal / kg, medium temperature and sub-high pressure 6.4MPa / 450℃ as an example, the economic performance of the air preheater 15 and the feed water flue gas heater 6 is calculated and analyzed. The results are as follows:

[0089]

[0090] Each furnace is equipped with only one air preheater 15. Air preheater 15 utilizes high-finned serpentine tubes in a staggered vertical arrangement. With a designed air velocity of 10 m / s, air preheater 15 offers high heat exchange efficiency, a small footprint, and a compact equipment layout. The outlet feedwater of air preheater 15 is designed to be below 130°C. System piping uses only subcooled water, eliminating the need for steam traps. This prevents steam from entering the feedwater piping, causing water hammer vibration and extending its service life.

[0091] The water supply flue gas heater 6 adopts high-finned serpentine tubes with staggered arrangement. The flue gas flow rate is designed to be 10m / s. The water supply flue gas heater 6 has high heat exchange efficiency and compact equipment layout. The outlet water supply of the water supply flue gas heater 6 is designed to be about 160℃. The first outlet water supply pipe 28 only outputs supercooled water, and there is no need to configure a steam trap, which avoids operational problems such as water hammer vibration caused by steam in the water supply pipe and increases the operating life.

[0092] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such herein, will not be interpreted in an idealized or overly formal sense.

[0093] The meaning of "and / or" in this application means that both situations where each exists alone or both exist at the same time are included.

[0094] The term “connection” as used in this application may mean a direct connection between components or an indirect connection between components via other components.

[0095] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A heating system for heating primary air and low-temperature flue gas using economizer feedwater, comprising a deaerator, a feedwater pump, an economizer, at least one air preheater, and a flue gas purification system, characterized in that: The heating system comprises: In the primary air circulation heating system, the feed water pump generates the first high-pressure feed water, which is fed into the economizer. The economizer outputs undersaturated water, which is then fed into the flue gas purification system and air preheater for heating low-temperature flue gas and primary air. The flue gas purification system for deacidification and dust removal outputs feed water to the deaerator, and the air preheater outputs feed water to the deaerator. The deaerator thermally deoxidizes the feed water output by the flue gas purification system, the feed water output by the air preheater, and the connected condensate to form first condensed water, which is then fed into the feed water pump to form a primary air circulation heating system. Low-temperature flue gas heating system: The high-temperature flue gas generated by garbage incineration passes through the economizer, and the flue gas output from the economizer is introduced into the flue gas purification system. The flue gas purification system uses the flue gas output from the economizer and the undersaturated water output from the economizer to heat the low-temperature flue gas; The flue gas purification system includes a semi-dry reaction tower, a bag filter, a water-feeding flue gas heater and a low-temperature SCR, which are arranged in sequence along the flue gas flow direction; It also includes the first water supply, the second water supply, the steam drum, the third water supply, and the fourth water supply, among which: The undersaturated water output by the economizer is divided into the first feed water and the second feed water. The first feed water is passed into the steam drum, and the second feed water is divided into the third feed water and the fourth feed water. The third feed water is passed into the flue gas purification system for low-temperature flue gas heating, and the fourth feed water is passed into the air preheater for primary air heating.

2. A heating system for heating primary air and low-temperature flue gas using economizer feed water according to claim 1, characterized in that: The air preheater also includes two outlet air ducts and one inlet air duct. The two outlet air ducts are arranged on the same side of the air preheater, and the two outlet air ducts are located above the inlet air duct.

3. A heating system for heating primary air and low-temperature flue gas using economizer feed water according to claim 2, characterized in that: The air preheater adopts high-fin serpentine tube type and is arranged in staggered vertical arrangement; the water supply flue gas heater adopts high-fin serpentine tube type and is arranged in staggered arrangement.

4. A heating method for a heating system using economizer feed water to heat primary air and low-temperature flue gas according to any one of claims 1 to 3, characterized in that: The heating method includes a heating method for a primary air circulation heating system and a heating method for a low-temperature flue gas heating system. The specific steps are as follows: The heating method of the primary air circulation heating system comprises the following steps: Step 1-1: Generation of the first high-pressure water supply: The first condensate formed in the deaerator is passed into the feed water pump, and the feed water pump increases the pressure of the first condensate to form the first high-pressure feed water; Step 1-2, generation of undersaturated water: The first high-pressure feed water formed in step 1-1 is passed into the economizer, and is heated by the economizer to generate undersaturated water with a water temperature above 230°C; Steps 1-3, primary air heating: The first feed water of undersaturated water with a temperature of above 230°C generated in step 1-2 is passed into the steam drum, and the fourth feed water is passed into the air preheater for heating the primary air in the air preheater. During the heating of the primary air, the utilized feed water is passed into the deaerator; Steps 1-4, Circular Heating: Repeat steps 1-1 to 1-3 to achieve circulating heating of the primary air; The heating method of the low-temperature flue gas heating system includes the following steps: Step 2-1, generation of low-temperature flue gas: The high-temperature flue gas generated by garbage incineration is passed into the economizer, heated by the economizer, and then passed into the semi-dry reaction tower. After being treated in the semi-dry reaction tower, it is passed into the bag dust collector, and after being treated in the bag dust collector, low-temperature flue gas is generated; Step 2-2, low-temperature flue gas heating: The water supply flue gas heater is combined with the third water supply of undersaturated water with a temperature of more than 230°C generated in step 1-2 to heat the low-temperature flue gas generated in step 2-1; Step 2-3, denitrification treatment: In step 2-2, the low-temperature flue gas is heated to 180°C and sent to the low-temperature SCR for denitrification treatment.

5. The heating method according to claim 4, wherein: In step 2-2, the utilized feed water is passed into the deaerator.

6. The heating method according to claim 5, wherein: In step 1-1, condensate needs to be introduced into the deaerator. The condensate, the feed water after being utilized in step 1-3, and the feed water after being utilized in step 2-2 are all introduced into the deaerator for thermal deoxygenation to form the first condensate at 0.27 MPa / 130°C.

7. The heating method according to claim 6, wherein: In steps 1-3, the primary air needs to be heated to above 220°C.

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