A lime kiln flue gas recovery system and flue gas recovery and utilization method in steel smelting

Abstract

The present invention discloses a lime kiln flue gas recovery system and a flue gas recovery and utilization method in steel smelting, and belongs to the technical field of steel smelting resource recovery and utilization. The present invention comprises a lime production system, a fly ash utilization system, and a preheating flue gas utilization system. The lime production system is connected to the fly ash utilization system and the preheating flue gas utilization system respectively. The lime production system transports fly ash flue gas to the fly ash utilization system, the lime production system transports preheating flue gas to the preheating flue gas utilization system, and the preheating flue gas utilization system transports fuel to the lime production system through the fly ash utilization system. The present invention adopts a variety of flue gas recovery and utilization means to fully utilize the flue gas and the substances and energy derived from the flue gas recovery and utilization process, minimizes the emission of available substances and energy, and makes the flue gas generated in the lime production process and the substances and energy derived from the flue gas recovery and utilization process have a high utilization rate, significantly reduces energy consumption, reduces waste, and reduces flue gas pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recycling in steel smelting, and relates to a fume recovery system and a fume recycling method of a lime kiln in steel smelting. Background Art

[0002] During the steelmaking process, especially electric furnace steelmaking, lime is added to regulate the furnace temperature and neutralize acidic oxides within the furnace, forming stable calcium silicate and other silicate substances. This in turn promotes slag formation, reduces impurities and oxide content within the furnace, and improves molten steel quality. The installation of lime kilns within steel mills to produce lime has significantly improved the energy efficiency and economic benefits of the steelmaking process. However, the lime kiln calcination process produces a large amount of high-temperature flue gas, with temperatures reaching approximately 1150°C. This high-temperature flue gas not only contains a high amount of heat but also carries dust, sulfur dioxide, and other pollutants, which are environmentally polluting. Therefore, this high-temperature flue gas cannot be directly discharged. Instead, the high heat and pollutants contained in this high-temperature flue gas can be reused as a resource, saving energy and reducing its pollutants. Therefore, improving the utilization rate of the high-temperature flue gas generated during lime production is of great significance.

[0003] Therefore, it is necessary to provide a lime kiln flue gas recovery system and a flue gas recovery and utilization method in steel smelting, so that the high-temperature flue gas generated in the lime production process can be efficiently utilized. Summary of the Invention

[0004] In order to solve the problems in the background technology, the present invention designs a lime kiln flue gas recovery system in steel smelting combined with a flue gas recovery method, so that high-temperature flue gas can be utilized more efficiently in the lime production process, thereby achieving the purpose of saving energy consumption and reducing flue gas pollution.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] On the one hand, the present invention proposes a lime kiln flue gas recovery system in steel smelting, which includes a lime production system, a fly ash utilization system, and a preheating flue gas utilization system. The lime production system is connected to the fly ash utilization system and the preheating flue gas utilization system, respectively. The lime production system transports fly ash flue gas to the fly ash utilization system, and the lime production system transports preheating flue gas to the preheating flue gas utilization system. The preheating flue gas utilization system transports fuel to the lime production system through the fly ash utilization system.

[0007] Preferably, the lime production system includes a limestone preheater 100, a lime kiln 110, and a lime collector 190. The flue gas outlet of the lime kiln 110 is connected to the flue gas inlet of the limestone preheater 100, the fly ash outlet of the lime kiln 110 is connected to the fly ash utilization system, the lime outlet of the lime kiln 110 is connected to the lime collector 190, and a filter is installed in the pipeline connecting the flue gas outlet of the lime kiln 110 and the flue gas inlet of the limestone preheater 100.

[0008] Preferably, the preheated flue gas utilization system includes a blower 210, a three-stage heat exchanger 220, a hot blast furnace 230, and a blast furnace 240. The flue gas inlet of the three-stage heat exchanger 220 is connected to the flue gas outlet of the limestone preheater 100. The blower 210 blows cold air into the three-stage heat exchanger 220 through the air inlet of the three-stage heat exchanger 220. The air outlet of the three-stage heat exchanger 220 is connected to the air inlet of the hot blast furnace 230. The air outlet of the hot blast furnace 230 is connected to the heat source inlet of the blast furnace 240. The flue gas outlet of the three-stage heat exchanger 220 is connected to the fly ash utilization system to provide raw materials for the fly ash utilization system.

[0009] Preferably, the fly ash utilization system includes a digestion chamber 120, a desulfurization reaction chamber 130, and a gypsum collector 200. The material inlet of the digestion chamber 120 is connected to the fly ash outlet of the lime kiln 110, and the digestion chamber 120 is connected to a water source, which transports water into the digestion chamber 120. The material inlet of the desulfurization reaction chamber 130 is respectively connected to the material outlet of the digestion chamber 120 and the material outlet of the three-stage heat exchanger 220, and the material outlet of the desulfurization reaction chamber 130 is connected to the gypsum collector 200. The gypsum collector 200 is a solid-liquid separation device, and the liquid material outlet of the gypsum collector 200 is connected to the water inlet of the digestion chamber 120.

[0010] Preferably, the fly ash utilization system also includes a primary heat exchanger 150, a secondary heat exchanger 160, and a gas bin 170. The heat exchange medium inlet of the primary heat exchanger 150 is connected to the steam outlet of the digestion chamber 120, the material inlet of the primary heat exchanger 150 is connected to the material outlet of the gas bin 170, the material inlet of the gas bin 170 is connected to the gas outlet of the blast furnace 240, the material outlet of the primary heat exchanger 150 is connected to the fuel inlet of the lime kiln 110, the steam outlet of the primary heat exchanger 150 is connected to the material inlet of the secondary heat exchanger 160, and the material outlet of the secondary heat exchanger 160 is connected to the material inlet of the digestion chamber 120.

[0011] Preferably, the heat exchange medium inlet of the secondary heat exchanger 160 is connected to the boiler feed water source, and the heat exchange medium outlet of the secondary heat exchanger 160 is connected to the boiler feed water tank 180.

[0012] Preferably, the fly ash utilization system further includes a dust collector 140 , and the material inlet of the dust collector 140 is connected to the fly ash outlet of the desulfurization reaction chamber 130 .

[0013] Another aspect of the present invention provides a method for recovering and utilizing the flue gas of the above system, the method comprising the following steps:

[0014] (1) The limestone produced by steel smelting is added to the limestone preheater 100 for preheating.

[0015] (2) In step 1, the limestone is preheated and then transported to the lime kiln 110. The limestone is calcined in the lime kiln 110 to obtain lime, which is then stored in the lime collector 190. The flue gas generated by the lime kiln 110 is divided into two parts, which are transported to the limestone preheater 100 and the digestion chamber 120 respectively. The flue gas transported to the limestone preheater 100 serves as a heat source for preheating the limestone. The flue gas transported to the digestion chamber 120 contains CaO. Water is introduced into the digestion chamber 120, and the CaO in the flue gas reacts with the water in the digestion chamber 120 to generate Ca(OH)2.

[0016] (3) The Ca(OH)2 generated in step 2 is transported to the desulfurization reaction chamber 130. At the same time, the flue gas generated by the limestone preheater 100 is divided into two parts after heat exchange and cooling in the three-stage heat exchanger 220, and is transported to the hot blast furnace 230 and the desulfurization reaction chamber 130 respectively. The flue gas transported to the hot blast furnace 230 is heated and then transported to the blast furnace 240 as a heat source. The flue gas transported to the desulfurization reaction chamber 130 contains SO2, which reacts with the Ca(OH)2 entering the desulfurization reaction chamber 130 to generate CaSO3. The CaSO3 is transported to the gypsum collector 200 for solid-liquid separation. The separated solid matter is collected and stored. The separated liquid material is transported to the digestion chamber 120 to react with CaO again to generate Ca(OH)2;

[0017] (4) In step 3, the coal gas generated by the operation of the blast furnace 240 is transported to the coal gas bunker 170 for storage. The coal gas stored in the coal gas bunker 170 is transported to the primary heat exchanger 150. At the same time, in the digestion chamber 120, the reaction between CaO and water is an exothermic reaction, which heats the water in the digestion chamber 120 into steam. The steam is transported to the primary heat exchanger 150. The coal gas transported to the primary heat exchanger 150 is preheated by the steam. The preheated coal gas is transported to the lime kiln 110 as fuel.

[0018] (5) In step 4, steam enters the primary heat exchanger 150 to heat the coal gas, forming a mixture of steam and liquid water. The mixture is then transported to the secondary heat exchanger 160. The secondary heat exchanger 160 heats and cools the steam in the mixture, converting the steam into liquid water. All the liquid water in the secondary heat exchanger 160 is transported to the digestion chamber 120 to react with CaO.

[0019] Beneficial effects of the present invention:

[0020] The present invention adopts relatively rich flue gas recovery and utilization means, combines the recycling of multiple energies among the lime production system, the fly ash utilization system, and the preheating flue gas utilization system, fully utilizes the flue gas and the substances and energy derived from the flue gas recovery and utilization process, minimizes the emission of available substances and energy, thereby achieving a high utilization rate of the flue gas generated in the lime production process and the substances and energy derived from the flue gas recovery and utilization process, significantly reducing energy consumption, reducing waste, and reducing flue gas pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the flue gas recovery and utilization system of the present invention.

[0022] In the figure, 100-limestone preheater, 110-lime kiln, 120-digestion chamber, 130-desulfurization reaction chamber, 140-dust collector, 150-primary heat exchanger, 160-secondary heat exchanger, 170-gas bin, 180-boiler feed water tank, 190-lime collector, 200-gypsum collector, 210-blower, 220-third-stage heat exchanger, 230-hot blast furnace, 240-blast furnace. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0024] like Figure 1 As shown, the system includes a lime production system, a fly ash utilization system, and a preheated flue gas utilization system. The lime production system is connected to the fly ash utilization system and the preheated flue gas utilization system, respectively. The lime production system transports fly ash flue gas to the fly ash utilization system, and the lime production system transports preheated flue gas to the preheated flue gas utilization system.

[0025] During the production of quicklime, the lime production system generates high-temperature flue gas, which is sent to the preheating flue gas utilization system and the fly ash utilization system respectively. The preheating flue gas utilization system mainly recycles and reuses the heat of the flue gas, and the fly ash utilization system mainly reuses the fly ash and other substances contained in the flue gas. During the operation of the preheating flue gas utilization system and the fly ash utilization system, both the preheating flue gas utilization system and the fly ash utilization system will generate derivative substances and energy. After the derivative energy generated by the fly ash utilization system acts on the derivative substances generated in the preheating flue gas utilization system, the derivative substances generated by the preheating flue gas utilization system can be returned to the lime production system for reuse. At the same time, the derivative substances generated in the fly ash utilization system can be reused within the system, so that the high-temperature flue gas generated in the lime production process of the present invention and the derivative substances and energy for treating the high-temperature flue gas are fully utilized, which significantly reduces energy consumption, reduces waste, and reduces the pollution of flue gas.

[0026] The lime production system includes a limestone preheater 100, a lime kiln 110, and a lime collector 190. The flue gas outlet of the lime kiln 110 is connected to the flue gas inlet of the limestone preheater 100, the fly ash outlet of the lime kiln 110 is connected to the fly ash utilization system, the lime outlet of the lime kiln 110 is connected to the lime collector 190, and a filter is installed in the pipeline connecting the flue gas outlet of the lime kiln 110 and the flue gas inlet of the limestone preheater 100.

[0027] During lime production, limestone is first added to the limestone preheater 100 for preheating. The preheated limestone enters the lime kiln 110 and is calcined to obtain quicklime. The chemical reaction formula is: CaCO3=CaO+CO2. During the operation of the lime kiln 110, high-temperature flue gas is generated. The quicklime calcined in the lime kiln 110 directly enters the lime collector 190 for collection and storage, while the high-temperature flue gas is discharged from the lime kiln 110 through the flue gas outlet of the lime kiln 110 and enters the limestone preheater through the flue gas inlet of the limestone preheater 100. Since the high-temperature flue gas is at a high temperature and contains a lot of heat, the high-temperature flue gas can preheat the limestone after entering the limestone preheater 100, thereby playing a role of replacing heating and reducing energy consumption during the limestone preheating process. A filter is installed in the flue gas channel to filter dust such as fly ash brought out during the transportation of the high-temperature flue gas, thereby preventing a large amount of dust and other solid matter from entering the limestone preheater 100.

[0028] Valves can be installed on the flue gas passages between the lime kiln 110 and the limestone preheater 100 to control the flow of high-temperature flue gas, thereby adjusting the speed and amount of high-temperature flue gas entering the limestone preheater 100 according to specific production conditions.

[0029] The preheated flue gas utilization system includes a blower 210, a three-stage heat exchanger 220, a hot blast furnace 230, and a blast furnace 240. The flue gas inlet of the three-stage heat exchanger 220 is connected to the flue gas outlet of the limestone preheater 100. The blower 210 blows cold air into the three-stage heat exchanger 220 through the air inlet of the three-stage heat exchanger 220. The air outlet of the three-stage heat exchanger 220 is connected to the air inlet of the hot blast furnace 230. The air outlet of the hot blast furnace 230 is connected to the heat source inlet of the blast furnace 240. The flue gas outlet of the three-stage heat exchanger 220 is connected to the fly ash utilization system to provide raw materials for the fly ash utilization system.

[0030] The hot blast furnace 230 is one of the main supporting equipment for the blast furnace in the ironmaking plant. The hot blast furnace continuously provides high-temperature hot air of more than 1000°C for the blast furnace during operation. The hot blast furnace 230 usually uses coal gas as fuel to heat the cold air and then supplies high-temperature hot air to the blast furnace 240. The blower 210 blows cold air into the tertiary heat exchanger 220. At the same time, the flue gas in the limestone preheater 100 also enters the tertiary heat exchanger 220. Since the flue gas from the limestone preheater 100 to the tertiary heat exchanger 220 still has a certain temperature, the flue gas and the cold air exchange heat in the tertiary heat exchanger 220. The cold air is heated to a certain extent, which can reduce the heating burden of the hot blast furnace 230 on the cold air, thereby saving energy consumption of the hot blast furnace 230 and saving coal gas usage. The flue gas entering the fly ash utilization system as raw material has basically no temperature limit. Therefore, the reduction in flue gas temperature does not affect its entry into the fly ash utilization system as raw material.

[0031] The fly ash utilization system includes a digestion chamber 120, a desulfurization reaction chamber 130, and a gypsum collector 200. The material inlet of the digestion chamber 120 is connected to the fly ash outlet of the lime kiln 110, and the digestion chamber 120 is connected to a water source, which transports water into the digestion chamber 120. The material inlet of the desulfurization reaction chamber 130 is respectively connected to the material outlet of the digestion chamber 120 and the material outlet of the three-stage heat exchanger 220. The material outlet of the desulfurization reaction chamber 130 is connected to the gypsum collector 200. The gypsum collector 200 is a solid-liquid separation device. The liquid material outlet of the gypsum collector 200 is connected to the water inlet of the digestion chamber 120.

[0032] Since CaO is generated by calcination in the lime kiln 110, the high-temperature flue gas will carry fly ash during transportation. The main component of fly ash is CaO. Therefore, the fly ash is carried into the digestion chamber 120 by transporting the high-temperature flue gas, and then water is introduced into the digestion chamber 120. Then, CaO and water react to generate Ca(OH)2. The chemical reaction chamber is: CaO+H2O=Ca(OH)2. Ca(OH)2 enters the desulfurization reaction chamber 130 along the connecting channel between the digestion chamber 120 and the desulfurization reaction chamber 130. Since the lime kiln 110 usually uses fuel combustion to obtain heat during operation, fuel combustion will produce SO2. Therefore, the high-temperature flue gas contains SO2. The high-temperature flue gas enters the limestone preheater 100 to only preheat the limestone. At the same time, after heat exchange in the tertiary heat exchanger 220, the flue gas is only a temperature difference. At this point, the flue gas also contains SO2. When the SO2-containing flue gas is passed into the desulfurization reaction chamber 130, Ca(OH)2 and SO2 react to form CaSO3. The chemical reaction formula is: Ca(OH)2 + SO2 = CaSO3 + H2O. CaSO3 is gypsum. The resulting gypsum enters the gypsum collector 200 for solid-liquid separation. The gypsum collector 200 can use equipment such as a filter press to perform solid-liquid separation on the gypsum generated by the reaction. The resulting solid material is gypsum. The solid material in the gypsum collector 200 is collected and stored uniformly. The liquid obtained from the solid-liquid separation is mainly H2O. The water is returned to the digestion chamber 120, where it reacts with CaO to form Ca(OH)2. This reduces the amount of water supplied to the digestion chamber 120 from the water source, thereby saving resources. At the same time, the high-temperature flue gas is desulfurized, thereby reducing the pollutants of the flue gas.

[0033] Valves may be installed on the communication pipes between the digestion chamber 120 and the lime kiln 110, the digestion chamber and the desulfurization reaction chamber 130, etc. to control the flow rate and amount of material conveyance.

[0034] The fly ash utilization system also includes a primary heat exchanger 150, a secondary heat exchanger 160, and a gas bin 170. The heat exchange medium inlet of the primary heat exchanger 150 is connected to the steam outlet of the digestion chamber 120, the material inlet of the primary heat exchanger 150 is connected to the material outlet of the gas bin 170, the material inlet of the gas bin 170 is connected to the gas outlet of the blast furnace 240, the material outlet of the primary heat exchanger 150 is connected to the fuel inlet of the lime kiln 110, the steam outlet of the primary heat exchanger 150 is connected to the material inlet of the secondary heat exchanger 160, and the material outlet of the secondary heat exchanger 160 is connected to the material inlet of the digestion chamber 120.

[0035] Blast furnace gas is a combustible gas produced as a by-product during the blast furnace ironmaking process. It can be used as fuel in the operation of the lime kiln 110. Therefore, the gas produced by the blast furnace 240 is transported to the gas bin 170 for storage, and the gas is transported to the primary heat exchanger 150. In the digestion chamber 120, the process of calcium oxide and water reacting to form calcium hydroxide is an exothermic reaction. A large amount of heat is released during the reaction, which vaporizes the water in the digestion chamber 120 and converts it into steam. The steam is transported to the primary heat exchanger 150, which can exchange heat with the gas on the one hand, thereby improving the efficiency of the reaction. The gas temperature is increased, thereby enhancing the gas combustion efficiency and reducing energy consumption. On the other hand, the steam loses heat and turns back into liquid water. The liquid water flows from the steam outlet to the secondary heat exchanger 160. Since the liquid water entering the secondary heat exchanger 160 may carry part of the steam, in order for the steam to enter the secondary heat exchanger 160 for cooling and heat exchange, it is converted into liquid water. Then, it flows from the secondary heat exchanger 160 into the digestion chamber 120 in the form of liquid water and reacts with CaO as a raw material, which can once again reduce the water supply to the digestion chamber 120.

[0036] The heat exchange medium inlet of the secondary heat exchanger 160 is connected to the boiler feed water source, and the heat exchange medium outlet of the secondary heat exchanger 160 is connected to the boiler feed water tank 180.

[0037] The boiler feed water needs to be preheated before being supplied to the boiler, and the secondary heat exchanger 160 needs to cool the steam. Therefore, in the secondary heat exchanger 160, steam is used to preheat the boiler feed water. On the one hand, the boiler feed water is preheated, and on the other hand, the steam is cooled and converted into liquid water. No additional cooling medium is required, which is beneficial to saving energy.

[0038] The fly ash utilization system further includes a dust collector 140 , wherein a material inlet of the dust collector 140 is connected to a fly ash outlet of the desulfurization reaction chamber 130 .

[0039] Since gypsum is generated by the reaction in the desulfurization reaction chamber 130, a certain amount of desulfurization ash will be produced. In order to avoid pollution caused by the discharge of desulfurization ash, the desulfurization ash is collected in the dust collector 140 for dust removal, which is also convenient for other uses and treatments of the desulfurization ash.

[0040] The flue gas recovery and utilization method of the system of the present invention is carried out according to the following steps:

[0041] (1) The limestone produced by steel smelting is added to the limestone preheater 100 for preheating.

[0042] (2) In step 1, the limestone is preheated and then transported to the lime kiln 110. The limestone is calcined in the lime kiln 110 to obtain lime, which is then stored in the lime collector 190. The flue gas generated by the lime kiln 110 is divided into two parts, which are transported to the limestone preheater 100 and the digestion chamber 120 respectively. The flue gas transported to the limestone preheater 100 serves as a heat source for preheating the limestone. The flue gas transported to the digestion chamber 120 contains CaO. Water is introduced into the digestion chamber 120, and the CaO in the flue gas reacts with the water in the digestion chamber 120 to generate Ca(OH)2.

[0043] (3) The Ca(OH)2 generated in step 2 is transported to the desulfurization reaction chamber 130. At the same time, the flue gas generated by the limestone preheater 100 is divided into two parts after heat exchange and cooling in the three-stage heat exchanger 220, and is transported to the hot blast furnace 230 and the desulfurization reaction chamber 130 respectively. The flue gas transported to the hot blast furnace 230 is heated and then transported to the blast furnace 240 as a heat source. The flue gas transported to the desulfurization reaction chamber 130 contains SO2, which reacts with the Ca(OH)2 entering the desulfurization reaction chamber 130 to generate CaSO3. The CaSO3 is transported to the gypsum collector 200 for solid-liquid separation. The separated solid matter is collected and stored. The separated liquid material is transported to the digestion chamber 120 to react with CaO again to generate Ca(OH)2;

[0044] (4) In step 3, the coal gas generated by the operation of the blast furnace 240 is transported to the coal gas bunker 170 for storage. The coal gas stored in the coal gas bunker 170 is transported to the primary heat exchanger 150. At the same time, in the digestion chamber 120, the reaction between CaO and water is an exothermic reaction, which heats the water in the digestion chamber 120 into steam. The steam is transported to the primary heat exchanger 150. The coal gas transported to the primary heat exchanger 150 is preheated by the steam. The preheated coal gas is transported to the lime kiln 110 as fuel.

[0045] (5) In step 4, steam enters the primary heat exchanger 150 to heat the coal gas, forming a mixture of steam and liquid water. The mixture is then transported to the secondary heat exchanger 160. The secondary heat exchanger 160 heats and cools the steam in the mixture, converting the steam into liquid water. All the liquid water in the secondary heat exchanger 160 is transported to the digestion chamber 120 to react with CaO.

[0046] The present invention can achieve the purpose of controlling the material flow speed and the material inflow and outflow by installing a valve on the material flow pipeline. The material flow speed can be adjusted by different valve openings, and the material inflow and outflow can be controlled by closing or opening the valve.

[0047] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A lime kiln fume recovery system in steel smelting, characterized by: The system includes a lime production system, a fly ash utilization system, and a preheated flue gas utilization system. The lime production system is connected to the fly ash utilization system and the preheated flue gas utilization system respectively. The lime production system transmits fly ash flue gas to the fly ash utilization system, and the lime production system transmits preheated flue gas to the preheated flue gas utilization system. The preheated flue gas utilization system transmits fuel to the lime production system through the fly ash utilization system. The fly ash utilization system comprises a digestion chamber (120), a desulfurization reaction chamber (130), and a gypsum collector (200). The material inlet of the digestion chamber (120) is connected to the fly ash outlet of the lime kiln (110), and the digestion chamber (120) is connected to a water source, which transports water into the digestion chamber (120). The material inlet of the desulfurization reaction chamber (130) is respectively connected to the material outlet of the digestion chamber (120) and the material outlet of the three-stage heat exchanger (220). The material outlet of the desulfurization reaction chamber (130) is connected to the gypsum collector (200). The gypsum collector (200) is a solid-liquid separation device. The liquid material outlet of the gypsum collector (200) is connected to the water inlet of the digestion chamber (120).

2. A lime kiln fume recovery system for steel smelting according to claim 1, characterized in that: The lime production system comprises a limestone preheater (100), a lime kiln (110), and a lime collector (190); a flue gas outlet of the lime kiln (110) is connected to a flue gas inlet of the limestone preheater (100); a fly ash outlet of the lime kiln (110) is connected to a fly ash utilization system; a lime outlet of the lime kiln (110) is connected to the lime collector (190); and a filter is installed in a pipe connecting the flue gas outlet of the lime kiln (110) and the flue gas inlet of the limestone preheater (100).

3. The lime kiln fume recovery system in steel smelting according to claim 2, characterized in that: The preheated flue gas utilization system comprises a blower (210), a three-stage heat exchanger (220), a hot blast furnace (230), and a blast furnace (240). The flue gas inlet of the three-stage heat exchanger (220) is connected to the flue gas outlet of the limestone preheater (100). The blower (210) blows cold air into the three-stage heat exchanger (220) through the air inlet of the three-stage heat exchanger (220). The air outlet of the three-stage heat exchanger (220) is connected to the air inlet of the hot blast furnace (230). The air outlet of the hot blast furnace (230) is connected to the heat source inlet of the blast furnace (240). The flue gas outlet of the three-stage heat exchanger (220) is connected to the fly ash utilization system to provide raw materials for the fly ash utilization system.

4. The lime kiln fume recovery system in steel smelting according to claim 3, characterized in that: The fly ash utilization system further comprises a primary heat exchanger (150), a secondary heat exchanger (160), and a gas bin (170); the heat exchange medium inlet of the primary heat exchanger (150) is communicated with the steam outlet of the digestion chamber (120); the material inlet of the primary heat exchanger (150) is communicated with the material outlet of the gas bin (170); the material inlet of the gas bin (170) is communicated with the gas outlet of the blast furnace (240); the material outlet of the primary heat exchanger (150) is communicated with the fuel inlet of the lime kiln (110); the steam outlet of the primary heat exchanger (150) is communicated with the material inlet of the secondary heat exchanger (160); and the material outlet of the secondary heat exchanger (160) is communicated with the material inlet of the digestion chamber (120).

5. The lime kiln fume recovery system in steel smelting according to claim 4, characterized in that: The heat exchange medium inlet of the secondary heat exchanger (160) is connected to the boiler feed water source, and the heat exchange medium outlet of the secondary heat exchanger (160) is connected to the boiler feed water tank (180).

6. The lime kiln fume recovery system in steel smelting according to claim 1, characterized in that: The fly ash utilization system further comprises a dust collector (140), wherein a material inlet of the dust collector (140) is connected to a fly ash outlet of the desulfurization reaction chamber (130).

7. The method for recycling flue gas from a lime kiln flue gas recovery system in steel smelting according to claim 5, characterized in that: The method comprises the following steps: (1) Limestone produced by steel smelting is added to a limestone preheater (100) for preheating; (2) In step (1), the limestone is preheated and then transported to the lime kiln (110). The limestone is calcined in the lime kiln (110) to obtain lime, which is then stored in the lime collector (190). The flue gas generated by the lime kiln (110) is divided into two parts and transported to the limestone preheater (100) and the digestion chamber (120), respectively. The flue gas transported to the limestone preheater (100) serves as a heat source for preheating the limestone. The flue gas transported to the digestion chamber (120) contains CaO. Water is introduced into the digestion chamber (120), and the CaO in the flue gas reacts with the water in the digestion chamber (120) to generate Ca(OH)2. (3) The Ca(OH)2 generated in step (2) is transported to the desulfurization reaction chamber (130). At the same time, the flue gas generated by the limestone preheater (100) is divided into two parts after heat exchange and cooling in the three-stage heat exchanger (220), and is transported to the hot blast furnace (230) and the desulfurization reaction chamber (130) respectively. The flue gas transported to the hot blast furnace (230) is heated and then transported to the blast furnace (240) as a heat source. The flue gas transported to the desulfurization reaction chamber (130) contains SO2, which reacts with the Ca(OH)2 entering the desulfurization reaction chamber (130) to generate CaSO3. The CaSO3 is transported to the gypsum collector (200) for solid-liquid separation. The separated solid matter is collected and stored. The separated liquid material is transported to the digestion chamber (120) to react with CaO again to generate Ca(OH)2. (4) In step (3), the coal gas generated by the operation of the blast furnace (240) is transported to the coal gas bin (170) for storage. The coal gas stored in the coal gas bin (170) is transported to the primary heat exchanger (150). At the same time, in the digestion chamber (120), CaO reacts with water, which is an exothermic reaction. The water in the digestion chamber (120) is heated to steam. The steam is transported to the primary heat exchanger (150). The coal gas transported to the primary heat exchanger (150) is preheated by the steam. The preheated coal gas is transported to the lime kiln (110) as fuel. (5) In step (4), steam enters the primary heat exchanger (150) to heat the coal gas, forming a mixture of steam and liquid water. The mixture is transported to the secondary heat exchanger (160). The secondary heat exchanger (160) heats and cools the steam in the mixture, converting the steam into liquid water. All the liquid water in the secondary heat exchanger (160) is transported to the digestion chamber (120) to react with CaO.

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