A system for deep utilization of waste heat from flue gas of steelmaking electric furnace

Abstract

The present invention discloses a system for intensively utilizing waste heat from flue gas in steelmaking electric furnaces, comprising a flue gas system, a low-pressure steam system, a molten salt heat exchange and storage system, a high-pressure steam system, and a power generation system. By providing the low-pressure steam system, the high-pressure steam system, and the molten salt heat exchange and storage system, the present invention can smooth out large fluctuations in the temperature and flow of flue gas from the electric furnace, recover waste heat from flue gas in the entire temperature range, and overcome the drawback of existing flue gas recovery methods that can only produce low-parameter steam. The system simultaneously produces low-pressure steam and high-temperature, high-pressure steam, improving the quality of waste heat recovery. This system can bring considerable benefits to steel companies and solve the problems of low waste heat recovery rates and low recovered steam parameters in existing flue gas recovery methods.

Description

Technical Field

[0001] The present invention relates to the field of waste heat utilization, and in particular to a steelmaking electric furnace flue gas waste heat deep utilization system. Background Art

[0002] Compared to the lengthy converter steelmaking process, electric furnace steelmaking offers significant advantages, including shorter processes, lower investment, faster construction, and improved energy conservation and emission reduction. This is particularly true for carbon reduction, which holds significant promise for the development of steel companies in the context of carbon neutrality. Currently, electric furnace steel production accounts for approximately 36% of total global steel production, while in my country, this percentage remains less than 10%, leaving significant room for growth. The my country Iron and Steel Association projects that this percentage will reach 30% by 2035, representing approximately 300 million tons annually.

[0003] Compared to foreign EAFs that use pure scrap steel for smelting, my country, due to limited scrap steel resources and electricity constraints, often adds large amounts of molten iron to replace scrap steel during EAF steelmaking. The molten iron ratio can reach as high as 80%. At the same time, as the molten iron ratio increases, flue gas temperature and dust content rise significantly, placing higher performance requirements on the accompanying flue gas cooling and dust removal systems. During the smelting process, the temperature and flow rate of EAF flue gas fluctuate significantly, ranging from a low of around 200°C to a high of 1400°C or even higher. The flue gas volume of a 100-ton EAF ranges from tens of thousands of standard meters per hour to over 200,000 standard meters per hour. To meet the requirements of the dust removal system, the EAF flue gas must be cooled to below 180°C. According to statistics, heat removed by cooling water, flue gas, and dust during EAF smelting accounts for over 10% of the total heat input to the furnace, and can even approach 30% when large amounts of molten iron are added.

[0004] Currently, the primary cooling method for electric furnace flue gas in China is a hybrid of water and air cooling. The process is as follows: After the furnace is powered on, primary flue gas is extracted from the fourth port through the furnace cover. It is then cooled in stages, passing through a water-cooled elbow, a water-cooled sliding sleeve, a water-cooled settling chamber, and a water-cooled flue. It then passes through an air cooler or a spray cooling tower to approximately 200°C. It is then thoroughly mixed with secondary exhaust gas at approximately 45°C collected by an ambient dust hood. Finally, it is removed by a bag filter and discharged to the atmosphere by a dust removal fan. This hybrid water-and-air cooling method effectively reduces flue gas temperature and efficiently captures flue gas dust. However, it requires a large cooling system, consumes large amounts of cooling water and electricity, and has high operating costs. Furthermore, a significant amount of high-quality heat contained in the high-temperature flue gas is not recovered. Some steel companies also use methods such as scrap preheating, vaporization flues, heat pipe waste heat boilers, and water pipe waste heat boilers to recover waste heat from the flue gas. However, these methods suffer from incomplete waste heat recovery across temperature ranges, low waste heat recovery rates, and low recovered steam parameters. The development of electric furnace flue gas waste heat recovery equipment with stable operation, high waste heat recovery rate and high waste heat recovery quality is of great significance to reducing the cost of electric furnace steelmaking and improving the energy conservation and carbon reduction level of steel enterprises. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention designs a steelmaking electric furnace flue gas waste heat deep utilization system to solve the problems of low recovery rate of existing electric furnace flue gas waste heat and low recovery steam parameters.

[0006] The present invention adopts the following technical solutions:

[0007] A steelmaking electric furnace flue gas waste heat deep utilization system, comprising a flue gas system, a low-pressure steam system, a molten salt heat exchange and storage system, a high-pressure steam system and a power generation system;

[0008] The flue gas system includes an electric furnace, a flue before the settling chamber, a combustion settling chamber, a flue after the settling chamber, a fan and a dust removal connecting flue which are connected in sequence;

[0009] The low-pressure steam system includes a deaerator, a heat accumulator, an external steam superheater, a low-pressure steam drum, a flue gasification heat exchanger, a settling chamber gasification heat exchanger, a low-pressure evaporator, a low-pressure economizer and corresponding connecting pipes;

[0010] The molten salt heat exchange and storage system includes a high-temperature molten salt tank, a medium-temperature molten salt tank, a low-temperature molten salt tank, a high-temperature molten salt heat exchanger, a medium-temperature molten salt heat exchanger and corresponding connecting pipes;

[0011] The high-pressure steam system includes a high-pressure preheater, a high-pressure evaporator, a high-pressure steam drum, a high-pressure superheater, a high-pressure economizer and corresponding connecting pipes;

[0012] In the low-pressure steam system, the deaerator inlet is connected to the feedwater, the deaerator outlet is connected to the low-pressure economizer inlet and the high-pressure economizer inlet respectively, and the low-pressure economizer outlet is connected to the water inlet of the low-pressure drum. The water outlet of the low-pressure drum is connected to the flue vaporization heat exchanger inlet, the settling chamber vaporization heat exchanger inlet, and the low-pressure evaporator inlet respectively. The flue vaporization heat exchanger outlet, the settling chamber vaporization heat exchanger outlet, and the low-pressure evaporator outlet are connected to the steam-water mixture inlet of the low-pressure drum. The steam outlet of the low-pressure drum is connected to the inlet of the heat accumulator; the outlet of the heat accumulator is connected to the inlet of the external steam superheater.

[0013] In the high-pressure steam system, the outlet of the high-pressure economizer is connected to the water inlet of the high-pressure preheater, the water outlet of the high-pressure preheater is connected to the water inlet of the high-pressure steam drum, the water outlet of the high-pressure steam drum is connected to the water inlet of the high-pressure evaporator, the outlet of the high-pressure evaporator is connected to the steam-water mixture inlet of the high-pressure steam drum, the steam outlet of the high-pressure steam drum is connected to the steam inlet of the high-pressure superheater, and the steam outlet of the high-pressure superheater is connected to the power generation system;

[0014] In the molten salt heat exchange and heat storage system, the outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the high-pressure superheater, the molten salt outlet of the high-pressure superheater is connected to the molten salt inlet of the high-pressure evaporator, the molten salt outlet of the high-pressure evaporator is connected to the molten salt inlet of the high-pressure preheater, the molten salt outlet of the high-pressure preheater is connected to the molten salt inlet of the low-temperature molten salt tank, the molten salt outlet of the low-temperature molten salt tank is connected to the inlet of the medium-temperature molten salt heat exchanger, the outlet of the medium-temperature molten salt heat exchanger is connected to the inlet of the medium-temperature molten salt tank, the outlet of the medium-temperature molten salt tank is connected to the inlet of the high-temperature molten salt heat exchanger, and the outlet of the high-temperature molten salt heat exchanger is connected to the inlet of the high-temperature molten salt tank.

[0015] Preferably, the flue vaporization heat exchanger is installed in the flue before the settling chamber.

[0016] Preferably, the settling chamber vaporization heat exchanger is installed in the combustion settling chamber.

[0017] Preferably, the high-temperature molten salt heat exchanger, medium-temperature molten salt heat exchanger, low-pressure evaporator, high-pressure economizer, and low-pressure economizer are installed in the rear flue of the settling chamber in sequence from front to back.

[0018] Preferably, the external steam superheater is installed in the low-pressure steam drum.

[0019] Preferably, a low-pressure feed water pump is connected between the deaerator outlet and the low-pressure economizer inlet, and a high-pressure feed water pump is connected between the deaerator outlet and the high-pressure economizer inlet.

[0020] Preferably, the molten salt heat exchange and heat storage system also includes a high-temperature molten salt pump, a low-temperature molten salt pump and a medium-temperature molten salt pump. The outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the high-pressure superheater through the high-temperature molten salt pump, the molten salt outlet of the low-temperature molten salt tank is connected to the inlet of the medium-temperature molten salt heat exchanger through the low-temperature molten salt pump, and the outlet of the medium-temperature molten salt tank is connected to the inlet of the high-temperature molten salt heat exchanger through the medium-temperature molten salt pump.

[0021] Preferably, the outlet of the high-temperature molten salt heat exchanger is connected to the inlet of the medium-temperature molten salt tank through a bypass.

[0022] Preferably, the power generation system includes a back-pressure steam turbine and a generator, the back-pressure steam turbine is connected to the generator; the steam outlet of the high-pressure superheater is connected to the inlet of the back-pressure steam turbine, and the steam outlet of the back-pressure steam turbine is connected to the heat user.

[0023] Preferably, the outlet of the external steam superheater is connected to a heat user.

[0024] The beneficial effects of the present invention are as follows: (1) by setting up a low-pressure steam system and a high-pressure steam system, the waste heat of each temperature section of the flue gas can be recovered, thereby improving the waste heat utilization rate and the quality of waste heat recovery; (2) the system can generate high-temperature and high-pressure steam for steam turbine power generation to supplement the steelmaking power gap on site, and can also generate low-pressure steam for process use or heating, with considerable economic benefits; (3) a low-pressure vaporization cooling heat exchanger is set in the flue before the settling chamber where the flue gas temperature is the highest and in the combustion settling chamber, which can quickly reduce the high-temperature flue gas to a suitable temperature and reduce the dust accumulation on the subsequent heat exchange surface, and avoid the risks brought by the setting up of a high-pressure heat exchange surface, thereby ensuring the stable and safe operation of the entire system; (4) three molten salt tanks with different temperatures are set up and the waste heat of the high-temperature flue gas is absorbed through a reasonable process, thereby eliminating the influence of large fluctuations in the flue gas temperature on the quality of recovered waste heat, keeping the molten salt temperature in the high-temperature molten salt tank stable, and providing a stable heat source for the high-pressure steam system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the present invention;

[0026] In the figure: 1. Water supply, 2. Low-pressure water supply pump, 3. High-pressure water supply pump, 4. Heat user, 100. Flue gas system, 101. Electric furnace, 102. Flue duct before settling chamber, 103. Combustion settling chamber, 104. Flue duct after settling chamber, 105. Fan, 106. Dust removal connecting flue, 200. Low-pressure steam system, 201. Deaerator, 202. Regenerator, 203. External steam superheater, 204. Low-pressure steam drum, 205. Flue gasification heat exchanger, 206. Settling chamber gasification heat exchanger, 207. Low-pressure evaporator, 208. Low-pressure economizer, 300. Molten salt heat exchange and storage system, 301. High-temperature molten salt tank, 302. High-temperature molten salt pump, 303. Medium-temperature molten salt tank, 304. Low-temperature molten salt tank, 305. Low-temperature molten salt pump, 306. Medium-temperature molten salt pump, 307. High-temperature molten salt heat exchanger, 308. Medium-temperature molten salt heat exchanger, 400. High-pressure steam system, 401. High-pressure preheater, 402. High-pressure evaporator, 403. High-pressure steam drum, 404. High-pressure superheater, 405. High-pressure economizer, 500. Power generation system, 501 Back-pressure steam turbine, 502. Generator. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings:

[0028] Example: Figure 1 As shown, a steelmaking electric furnace flue gas waste heat deep utilization system includes a flue gas system 100, a low-pressure steam system 200, a molten salt heat exchange and storage system 300, a high-pressure steam system 400 and a power generation system 500.

[0029] The flue gas system 100 includes an electric furnace 101, a flue 102 before the settling chamber, a combustion settling chamber 103, a flue 104 after the settling chamber, a fan 105 and a dust removal connecting flue 106, which are connected in sequence.

[0030] The low-pressure steam system 200 includes a deaerator 201, a heat accumulator 202, an external steam superheater 203, a low-pressure steam drum 204, a flue gasification heat exchanger 205, a settling chamber gasification heat exchanger 206, a low-pressure evaporator 207, a low-pressure economizer 208 and corresponding connecting pipes.

[0031] The molten salt heat exchange and storage system 300 includes a high-temperature molten salt tank 301, a high-temperature molten salt pump 302, a medium-temperature molten salt tank 303, a low-temperature molten salt tank 304, a low-temperature molten salt pump 305, a medium-temperature molten salt pump 306, a high-temperature molten salt heat exchanger 307, a medium-temperature molten salt heat exchanger 308 and corresponding connecting pipes.

[0032] The high-pressure steam system 400 includes a high-pressure preheater 401, a high-pressure evaporator 402, a high-pressure steam drum 403, a high-pressure superheater 404, a high-pressure economizer 405 and corresponding connecting pipes.

[0033] The power generation system 500 includes a back-pressure steam turbine 501 and a generator 502 .

[0034] Accordingly, the flue evaporation heat exchanger 205 is installed in the flue 102 before the settling chamber, the settling chamber evaporation heat exchanger 206 is installed in the combustion settling chamber 103, and the high-temperature molten salt heat exchanger 307, the medium-temperature molten salt heat exchanger 308, the low-pressure evaporator 207, the high-pressure economizer 405, and the low-pressure economizer 208 are installed in the flue 104 after the settling chamber, in order from front to back. The external steam superheater 203 is installed in the low-pressure steam drum 204.

[0035] In the low-pressure steam system 200, external feedwater 1 is connected to the inlet of the deaerator 201. The outlet of the deaerator 201 is connected to the inlets of the low-pressure feedwater pump 2 and the high-pressure feedwater pump 3, respectively. The outlet of the low-pressure feedwater pump 2 is connected to the inlet of the low-pressure economizer 208, which in turn is connected to the water inlet of the low-pressure steam drum 204. The water outlet of the low-pressure steam drum 204 is connected to the inlet of the flue gasification heat exchanger 205, the inlet of the settling chamber gasification heat exchanger 206, and the inlet of the low-pressure evaporator 207, respectively. The outlets of the flue gasification heat exchanger 205, the settling chamber gasification heat exchanger 206, and the low-pressure evaporator 207 are connected to the steam-water mixture inlet of the low-pressure steam drum 204. The steam outlet of the low-pressure steam drum 204 is connected to the inlet of the heat accumulator 202. The outlet of the heat accumulator 202 is connected to the inlet of the external steam superheater 203, and the outlet of the external steam superheater 203 is connected to the heat user 4.

[0036] In the high-pressure steam system 400, the outlet of the high-pressure feed water pump 3 is connected to the inlet of the high-pressure economizer 405, the outlet of the high-pressure economizer 405 is connected to the water inlet of the high-pressure preheater 401, the water outlet of the high-pressure preheater 401 is connected to the water inlet of the high-pressure steam drum 403, the water outlet of the high-pressure steam drum 403 is connected to the water inlet of the high-pressure evaporator 402, the outlet of the high-pressure evaporator 402 is connected to the steam-water mixture inlet of the high-pressure steam drum 403, the steam outlet of the high-pressure steam drum 403 is connected to the steam inlet of the high-pressure superheater 404, the steam outlet of the high-pressure superheater 404 is connected to the inlet of the back-pressure steam turbine 501, and the steam outlet of the back-pressure steam turbine 501 is connected to the heat user 4.

[0037] In the molten salt heat exchange and heat storage system 300, the outlet of the high-temperature molten salt tank 301 is connected to the molten salt inlet of the high-pressure superheater 404 through the high-temperature molten salt pump 302, the molten salt outlet of the high-pressure superheater 404 is connected to the molten salt inlet of the high-pressure evaporator 402, the molten salt outlet of the high-pressure evaporator 402 is connected to the molten salt inlet of the high-pressure preheater 401, the molten salt outlet of the high-pressure preheater 401 is connected to the molten salt inlet of the low-temperature molten salt tank 304, and the molten salt of the low-temperature molten salt tank 304 is connected to the molten salt inlet of the high-pressure evaporator 402. The outlet is connected to the inlet of the medium-temperature molten salt heat exchanger 308 through the low-temperature molten salt pump 305, the outlet of the medium-temperature molten salt heat exchanger 308 is connected to the inlet of the medium-temperature molten salt tank 303, the outlet of the medium-temperature molten salt tank 303 is connected to the inlet of the high-temperature molten salt heat exchanger 307 through the medium-temperature molten salt pump, the outlet of the high-temperature molten salt heat exchanger 307 is connected to the inlet of the high-temperature molten salt tank 301, and at the same time, the outlet of the high-temperature molten salt heat exchanger 307 is connected to the inlet of the medium-temperature molten salt tank 303 through a bypass.

[0038] The electric furnace flue gas waste heat recovery process based on the present invention is briefly described as follows:

[0039] During the steelmaking process, flue gas continuously exits the fourth outlet of the electric furnace 101, flowing sequentially through the pre-settling chamber flue 102, the combustion settling chamber 103, and the post-settling chamber flue 104. It is then drawn by fan 105 to the dust removal connecting flue 106 and then to the dust removal system. In the pre-settling chamber flue 102 and the combustion settling chamber 103, the CO in the flue gas mixes and burns with the incoming air, while the majority of the dust settles and separates in the combustion settling chamber 103. As the flue gas flows from front to back, it exchanges heat with the flue evaporation heat exchanger 205, the settling chamber evaporation heat exchanger 206, the high-temperature molten salt heat exchanger 307, the medium-temperature molten salt heat exchanger 308, the low-pressure evaporator 207, the high-pressure economizer 405, and the low-pressure economizer 208. The flue gas cools to below 180°C before entering the dust removal system for complete dust removal.

[0040] The external feed water 1 enters the deaerator 201 for deoxygenation. The deoxygenated water passes through the low-pressure feed water pump 2 and enters the low-pressure economizer 208, and then passes through the high-pressure feed water pump and enters the high-pressure economizer 405.

[0041] After entering the low-pressure economizer 208, the deoxygenated water exchanges heat with the flue gas therein and then enters the low-pressure drum 204 through its water inlet. The saturated water in the low-pressure drum 204 enters the flue gas vaporization heat exchanger 205, the settling chamber vaporization heat exchanger 206, and the low-pressure evaporator 207 through its water outlet. After absorbing heat from the flue gas, it vaporizes and enters the low-pressure drum 204 through the steam-water mixture inlet as a steam-water mixture. After steam-water separation, the steam in the low-pressure drum 204 enters the heat accumulator 202 through the steam outlet. When external steam supply is required, the steam in the heat accumulator 202 enters the external steam superheater 203 installed in the low-pressure drum 204 through its outlet. Because the pressure of heat accumulator 202 is lower than that of low-pressure drum 203, the temperature of the saturated steam in heat accumulator 202 is lower than that of the saturated steam in low-pressure drum 203. The saturated steam from heat accumulator 202 absorbs heat in external steam superheater 203, becoming low-pressure superheated steam, which is then supplied to heat user 4. In this embodiment, the low-pressure superheated steam has a pressure of 1.35 MPa and a temperature of 205°C.

[0042] In order to prevent the water entering the high-pressure steam drum from being too under-temperatured, a high-pressure preheater is provided between the high-pressure economizer 405 and the high-pressure steam drum 403 . Deoxygenated water from the high-pressure feedwater pump 3 enters the high-pressure economizer 405, where it exchanges heat with the flue gas. It then enters the high-pressure preheater 401, where it exchanges heat with molten salt. After being heated to an appropriate temperature, it enters the high-pressure steam drum 403. The saturated water in the high-pressure steam drum 403 enters the high-pressure evaporator 402 through the water outlet. There, it exchanges heat with the molten salt, vaporizing it. Then, it enters the high-pressure steam drum 403 through the steam-water mixture inlet as a steam-water mixture. After steam-water separation, the steam in the high-pressure steam drum 403 enters the high-pressure superheater 404 through the steam outlet. There, it exchanges heat with the high-temperature molten salt, generating high-temperature, high-pressure superheated steam. The superheated steam is drawn from the steam outlet of the high-pressure superheater 404 and enters the back-pressure turbine 501, driving it to rotate. The back-pressure turbine 501, in turn, drives the generator 502 to generate electricity. The low-pressure superheated steam after power generation is discharged from the back-pressure turbine 501 and sent to the heat user 4. In this embodiment, the high-temperature and high-pressure superheated steam used for power generation has a pressure of 9.8 MPa and a temperature of 480°C; the low-pressure superheated steam has a pressure of 1.35 MPa and a temperature of 205°C.

[0043] To ensure stable production of high-temperature, high-pressure superheated steam for power generation, a molten salt heat exchange and storage system 300, consisting of three molten salt tanks, is deployed. In this embodiment, the high-temperature molten salt tank 301 stores high-temperature molten salt above the set temperature (510°C in this embodiment), providing a stable heat source for the high-pressure steam system. The low-temperature molten salt tank 304 stores cold salt (280°C in this embodiment) after heat exchange with the high-pressure steam system 400, providing a heat-absorbing medium for waste heat recovery from the medium-temperature flue gas. The medium-temperature molten salt tank 303 stores molten salt within a certain temperature range (350°C to 510°C in this embodiment), providing a heat-absorbing medium for waste heat recovery from the high-temperature flue gas. When high-temperature, high-pressure steam is needed to generate electricity for the power generation system 500, the high-temperature molten salt in the high-temperature molten salt tank 301 is pumped into the high-pressure superheater 404 via the high-temperature molten salt pump 302. The saturated steam from the high-pressure steam drum 403 is superheated in the high-pressure superheater 404. The steam then enters the high-pressure evaporator 402, where it heats and vaporizes the saturated water from the high-pressure steam drum 403. The steam then enters the high-pressure preheater 401, where it heats the unsaturated water from the high-pressure economizer 405 to an appropriate temperature to facilitate its entry into the high-pressure steam drum 403. After releasing heat, the molten salt, at a temperature of approximately 280°C, flows out of the high-pressure preheater 401 and enters the low-temperature molten salt tank 304. The molten salt in the low-temperature molten salt tank 304 is then pumped into the medium-temperature molten salt heat exchanger 308 via the low-temperature molten salt pump 305. After absorbing waste heat from the flue gas, the salt enters the medium-temperature molten salt tank 303. Depending on the flue gas temperature at the inlet of the high-temperature molten salt heat exchanger 307, the molten salt in the medium-temperature molten salt tank 303 has two operating modes: when the flue gas temperature at the inlet of the high-temperature molten salt heat exchanger 307 is higher than the set temperature (540°C in this embodiment), the medium-temperature molten salt is pumped from the medium-temperature molten salt tank 303 to the high-temperature molten salt heat exchanger 307 through the medium-temperature molten salt pump 306, absorbs the high-temperature waste heat of the flue gas and is heated to above the set temperature (510°C in this embodiment), and then is sent to the high-temperature molten salt tank 301 for storage; when the flue gas temperature at the inlet of the high-temperature molten salt heat exchanger 307 is not higher than the set temperature (540°C in this embodiment), the medium-temperature molten salt is pumped from the medium-temperature molten salt tank 303 to the high-temperature molten salt heat exchanger 307 through the medium-temperature molten salt pump 306, exchanges heat with the flue gas (is heated by the flue gas or heats the flue gas), and then is sent back to the medium-temperature molten salt tank 303 through a bypass.In this way, when the temperature of the flue gas passing through the high-temperature molten salt heat exchanger 307 is not high enough to heat the medium-temperature molten salt to the required temperature (510°C in this embodiment), the medium-temperature molten salt from the medium-temperature molten salt tank 303 is not sent to the high-temperature molten salt tank 301 after flowing through the high-temperature molten salt heat exchanger 307, but circulates between the medium-temperature molten salt tank 303 and the high-temperature molten salt heat exchanger 307 through a bypass. On the one hand, it avoids not sending molten salt below the set temperature (510°C in this embodiment) into the high-temperature molten salt tank 301, thereby ensuring the stability of the molten salt temperature in the high-temperature molten salt tank 301. On the other hand, the circulation of the medium-temperature molten salt between the medium-temperature molten salt tank 303 and the high-temperature molten salt heat exchanger 307 achieves the purpose of smoothing the flue gas temperature fluctuation, which is beneficial to the smooth heat exchange of the subsequent heat exchange surface.

[0044] By providing a low-pressure steam system 200, a high-pressure steam system 400 and a molten salt heat exchange and heat storage system 300, the present invention can smooth out large fluctuations in the temperature and flow of electric furnace flue gas, recover the waste heat of electric furnace flue gas in the entire temperature range, and overcome the disadvantage that the existing electric furnace flue gas recovery method can only produce low-parameter steam. At the same time, it produces low-pressure steam and high-temperature and high-pressure steam, improves the quality of waste heat recovery, and can bring considerable benefits to steel enterprises.

[0045] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A steelmaking electric furnace flue gas waste heat deep utilization system, characterized by: It includes a flue gas system, a low-pressure steam system, a molten salt heat exchange and storage system, a high-pressure steam system and a power generation system; The flue gas system includes an electric furnace, a flue before the settling chamber, a combustion settling chamber, a flue after the settling chamber, a fan and a dust removal connecting flue which are connected in sequence; The low-pressure steam system includes a deaerator, a heat accumulator, an external steam superheater, a low-pressure steam drum, a flue gasification heat exchanger, a settling chamber gasification heat exchanger, a low-pressure evaporator, a low-pressure economizer and corresponding connecting pipes; The molten salt heat exchange and storage system includes a high-temperature molten salt tank, a medium-temperature molten salt tank, a low-temperature molten salt tank, a high-temperature molten salt heat exchanger, a medium-temperature molten salt heat exchanger and corresponding connecting pipes; The high-pressure steam system includes a high-pressure preheater, a high-pressure evaporator, a high-pressure steam drum, a high-pressure superheater, a high-pressure economizer and corresponding connecting pipes; In the low-pressure steam system, the deaerator inlet is connected to the feed water, the deaerator outlet is connected to the low-pressure economizer inlet and the high-pressure economizer inlet respectively, the low-pressure economizer outlet is connected to the water inlet of the low-pressure drum, the water outlet of the low-pressure drum is connected to the flue vaporization heat exchanger inlet, the settling chamber vaporization heat exchanger inlet, and the low-pressure evaporator inlet respectively, the flue vaporization heat exchanger outlet, the settling chamber vaporization heat exchanger outlet, and the low-pressure evaporator outlet are connected to the steam-water mixture inlet of the low-pressure drum, the steam outlet of the low-pressure drum is connected to the inlet of the heat accumulator; and the outlet of the heat accumulator is connected to the inlet of the external steam superheater; In the high-pressure steam system, the outlet of the high-pressure economizer is connected to the water inlet of the high-pressure preheater, the water outlet of the high-pressure preheater is connected to the water inlet of the high-pressure steam drum, the water outlet of the high-pressure steam drum is connected to the water inlet of the high-pressure evaporator, the outlet of the high-pressure evaporator is connected to the steam-water mixture inlet of the high-pressure steam drum, the steam outlet of the high-pressure steam drum is connected to the steam inlet of the high-pressure superheater, and the steam outlet of the high-pressure superheater is connected to the power generation system; In the molten salt heat exchange and heat storage system, the outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the high-pressure superheater, the molten salt outlet of the high-pressure superheater is connected to the molten salt inlet of the high-pressure evaporator, the molten salt outlet of the high-pressure evaporator is connected to the molten salt inlet of the high-pressure preheater, the molten salt outlet of the high-pressure preheater is connected to the molten salt inlet of the low-temperature molten salt tank, the molten salt outlet of the low-temperature molten salt tank is connected to the inlet of the medium-temperature molten salt heat exchanger, the outlet of the medium-temperature molten salt heat exchanger is connected to the inlet of the medium-temperature molten salt tank, the outlet of the medium-temperature molten salt tank is connected to the inlet of the high-temperature molten salt heat exchanger, and the outlet of the high-temperature molten salt heat exchanger is connected to the inlet of the high-temperature molten salt tank; The flue evaporation heat exchanger is installed in the flue before the settling chamber; The high-temperature molten salt heat exchanger, the medium-temperature molten salt heat exchanger, the low-pressure evaporator, the high-pressure economizer, and the low-pressure economizer are installed in the rear flue of the settling chamber in sequence from front to back; The external steam superheater is installed in the low-pressure steam drum; The outlet of the high-temperature molten salt heat exchanger is connected to the inlet of the medium-temperature molten salt tank through a bypass.

2. A steelmaking electric furnace flue gas waste heat deep utilization system according to claim 1, characterized in that: The settling chamber vaporization heat exchanger is installed in the combustion settling chamber.

3. The steelmaking electric furnace flue gas waste heat deep utilization system according to claim 1 is characterized in that: A low-pressure feed water pump is connected between the deaerator outlet and the low-pressure economizer inlet, and a high-pressure feed water pump is connected between the deaerator outlet and the high-pressure economizer inlet.

4. The steelmaking electric furnace flue gas waste heat deep utilization system according to claim 1 is characterized in that: The high-pressure steam system also includes a high-temperature molten salt pump, a low-temperature molten salt pump and a medium-temperature molten salt pump. The outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the high-pressure superheater through the high-temperature molten salt pump, the molten salt outlet of the low-temperature molten salt tank is connected to the inlet of the medium-temperature molten salt heat exchanger through the low-temperature molten salt pump, and the outlet of the medium-temperature molten salt tank is connected to the inlet of the high-temperature molten salt heat exchanger through the medium-temperature molten salt pump.

5. The steelmaking electric furnace flue gas waste heat deep utilization system according to claim 1 is characterized in that: The power generation system includes a back-pressure steam turbine and a generator, wherein the back-pressure steam turbine is connected to the generator; the steam outlet of the high-pressure superheater is connected to the inlet of the back-pressure steam turbine, and the steam outlet of the back-pressure steam turbine is connected to a heat user.

6. The steelmaking electric furnace flue gas waste heat deep utilization system according to claim 1, characterized in that: The outlet of the external steam superheater is connected to a heat user.

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