A hot blast stove combustion air and gas preheating system

Abstract

The utility model belongs to the field of smelting reduction ironmaking technology, concretely relates to a hot blast furnace combustion air and gas preheating system for improving the combustion air and gas preheating temperature of hot blast furnace to meet the hot blast temperature requirement of Hismelt ironmaking process. It comprises a smelting reduction furnace, a waste heat boiler, a cyclone dust collector, an air preheater, a dust collector, a combustion air fan and a hot blast furnace. The smelting reduction furnace is connected with the exhaust hood, the cyclone dust collector, the air preheater, the dust collector and the hot blast furnace in sequence. The combustion air fan is connected with the air preheater and the hot blast furnace in sequence. The utility model has the following advantages: the waste heat of coal gas is fully utilized, the high-temperature coal gas directly enters the air preheater to heat the combustion air, and the waste heat utilization efficiency is higher; the combustion air is heated to above 300 DEG C after the air preheater, the coal gas temperature is reduced to about 500 DEG C, and the hot blast furnace is used for burning the furnace, so that the target of 1200 DEG C hot blast temperature can be achieved; the system structure is simple, and the operation is reliable.

Description

Technical Field

[0001] This utility model belongs to the field of molten reduction ironmaking technology, specifically relating to a hot blast stove combustion air and gas preheating system for increasing the preheating temperature of combustion air and gas in a hot blast stove to meet the hot blast temperature requirements of the Hismelt ironmaking process. Background Technology

[0002] The molten reduction ironmaking process mentioned above is Hismelt ironmaking.

[0003] Hismelt ironmaking directly uses iron ore powder and coal powder, eliminating the coking and sintering processes. The smelting process involves directly injecting iron ore powder and granulated coal into the slag-iron molten pool through iron ore powder lances and granulated coal lances, while hot air is injected from the top of the reduction furnace into the space above the molten pool. The oxygen in the hot air burns with the CO and hydrogen produced by the reduction reaction in the molten pool, providing heat for the reaction in the molten pool.

[0004] The gas produced by the molten reduction furnace has a temperature of over 1400℃. After being cooled by the exhaust hood, the gas temperature is below 900℃. The gas passes through a cyclone dust collector and then through a waste heat boiler to produce steam, where it is cooled to ≤200℃. Then it enters a bag filter for purification, and the purified gas enters the clean gas pipeline.

[0005] The system is equipped with a hot blast stove to heat the cold air from the blower. To improve the heating capacity of the hot blast stove, the combustion air and gas need to be preheated. A plate heat exchanger is used to preheat the combustion air and gas with the 350°C exhaust gas generated by the hot blast stove combustion. However, due to the low temperature of the exhaust gas as a heat source, the preheating temperature can only reach 150–180°C. Furthermore, the calorific value of the gas produced by Hismelt ironmaking is low, only 2800–3000 kJ / m³. 3 The hot air temperature can only reach around 1050℃, but the process requires a hot air temperature of 1200℃.

[0006] Reference: In page 559 of "Blast Furnace Design: Theory and Practice of Ironmaking Process Design" published by Metallurgical Industry Press, it is stated that if the preheating temperature of the combustion air is increased by 100℃, the theoretical combustion temperature will increase by 31℃; if the preheating temperature of the coal gas is increased by 100℃, the theoretical combustion temperature will increase by 52℃.

[0007] To address the problems in the prior art, this utility model provides a preheating system for combustion air and gas in a hot blast stove, which achieves the purpose of increasing the hot blast temperature by significantly increasing the preheating temperature of the combustion air and gas. Summary of the Invention

[0008] Definition: High-temperature coal gas refers to coal gas that has been cooled to below 900℃ by an exhaust hood and then subjected to coarse dust removal by a cyclone dust collector.

[0009] Technical problems to be solved

[0010] By making reasonable use of the heat of high-temperature coal gas, the temperature of coal gas and combustion air in the hot blast stove can be increased, and a hot air temperature of 1200℃ can be achieved without adding natural gas and with a relatively low calorific value of coal gas.

[0011] To address the above problems, the following technical solution is provided:

[0012] A hot blast stove combustion air and gas preheating system, through a unique design, achieves efficient preheating of combustion air and gas. It includes a molten reduction furnace, an exhaust hood, a cyclone dust collector, an air preheater, a dust collector, a combustion air blower, and a hot blast stove. The molten reduction furnace is sequentially connected to the exhaust hood, cyclone dust collector, air preheater, dust collector, and hot blast stove. The combustion air blower is sequentially connected to the air preheater and hot blast stove. The air preheater is used to heat the combustion air with high-temperature gas from the cyclone dust collector.

[0013] Preferably, the air preheater has a cylindrical structure, consisting of an outer shell, conduits, and end plates. End plates are fixedly installed at both ends inside the outer shell, and multiple conduits are evenly installed on the end plates. One end of the air preheater is provided with a gas inlet and an air outlet on the side wall; the other end is provided with a gas outlet and an air inlet on the side wall. High-temperature gas flows inside the conduits, and combustion air flows between the outer shell and the conduits. The combustion air and the high-temperature gas flow in opposite directions.

[0014] Preferably, the shell, duct, and end plate of the air preheater are made of 310S, which has good high-temperature resistance and can work stably in high-temperature environments. The shell adopts internal and / or external insulation, with the internal insulation using 100mm thick lightweight spray paint and the external insulation using ceramic fiber cotton, which improves the heat exchange efficiency of the air preheater and reduces heat loss.

[0015] Preferably, the dust collector is a bag filter, and the filter bag material is one of cloth bag, ceramic filter bag, or stainless steel wire filter bag. The cloth bag has a temperature resistance of ≤280℃; the ceramic filter bag has a temperature resistance of ≤800℃; and the stainless steel wire filter bag has a temperature resistance of ≤500℃. The appropriate filter bag material is selected according to the temperature of the gas after the air preheater.

[0016] Preferably, the dust collector inlet is connected to the gas compressor outlet, or the dust collector outlet is connected to the gas compressor outlet; the gas compressor inlet is connected to a clean gas pipeline. The temperature of the gas entering the hot blast stove is adjusted by adding a portion of clean gas to reach the required process temperature.

[0017] Preferably, the hot air furnace is connected to the desulfurization and denitrification device and the chimney.

[0018] Furthermore, the gas generated by the molten reduction furnace has a temperature of ≥1400℃. After being cooled by the exhaust hood, the gas temperature is ≤900℃. The gas is then divided into two paths after passing through a cyclone dust collector. One path enters the air preheater, while the other path is cooled to ≤200℃ by the waste heat boiler before entering the bag filter for purification. The purified gas then enters the clean gas pipeline.

[0019] Compared with existing technologies, this solution has the following advantages:

[0020] 1. Make full use of the waste heat of coal gas. High-temperature coal gas is directly fed into the air preheater to heat the combustion air. Compared with high-temperature coal gas entering the waste heat boiler to produce steam, heating the combustion air with high-temperature coal gas has a higher waste heat utilization efficiency.

[0021] 2. After passing through the air preheater, the combustion air is heated to over 300°C, and the gas temperature is reduced to around 500°C. This gas is then used in the hot blast stove to achieve the target hot blast temperature of 1200°C.

[0022] 3. This design has a unique concept, a simple system structure, and reliable operation. Attached Figure Description

[0023] Figure 1 This is a flow chart of the hot blast stove combustion air and gas preheating system.

[0024] Figure 2 This is a schematic diagram of a heat exchanger.

[0025] Legend markings

[0026] 1. Melting reduction furnace; 2. Exhaust hood; 3. Cyclone dust collector; 4. Air preheater; 41. Shell; 42. Pipe; 43. End plate; 44. Gas inlet; 45. Gas outlet; 46. Air inlet; 47. Air outlet; 5. Combustion fan; 6. Dust collector; 7. Waste heat boiler; 8. Bag filter; 9. Hot air furnace; 10. Gas compressor.

[0027] 11 Desulfurization and denitrification unit; 12 Chimney; 13 Clean gas pipeline; Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily implement it. The present invention may be embodied in many different forms and is not limited thereto.

[0029] Example 1 (with attached) Figure 1 , Figure 2 For reference, the following explanation is provided:

[0030] The hot blast furnace combustion air and gas preheating system includes a melting reduction furnace 1, an exhaust hood 2, a cyclone dust collector 3, an air preheater 4, a dust collector 6, a combustion air blower 5, and a hot blast furnace 9. The melting reduction furnace 1 is sequentially connected to the exhaust hood 2, the cyclone dust collector 3, the air preheater 4, the dust collector 6, and the hot blast furnace 9. The combustion air blower 5 is sequentially connected to the air preheater 4 and the hot blast furnace 9. The air preheater 4 is used to heat the combustion air with the high-temperature gas from the cyclone dust collector 3.

[0031] The exhaust hood 2 is a waste heat utilization device connecting the molten reduction furnace 1 and the cyclone dust collector 3. It consists of a round pipe and a mode wall installed on the inner wall of the pipe. Demineralized water flows through the mode wall. The gas generated by the molten reduction furnace 1 at a temperature of over 1400°C enters the exhaust hood 2. The heat of the gas is transferred to the demineralized water to generate steam. When the gas reaches the outlet of the exhaust hood 2, the temperature drops to the gas temperature of 900°C to 600°C.

[0032] The high-temperature coal gas mentioned is the coal gas produced by smelting in the molten reduction furnace 1, cooled by the exhaust hood 2, and coarsely dusted by the cyclone dust collector 3 (coal gas temperature: 900℃~600℃, dust content: ≤10g / Nm³). 3 ).

[0033] The air preheater 4 has a cylindrical structure, consisting of an outer shell 41, a conduit 42, and an end plate 43. The end plate 43 is fixedly installed at both ends of the inner shell 41, and multiple conduits 42 are evenly installed on the end plate 43. One end of the air preheater 4 is provided with a gas inlet 44 and an air outlet 46 on the side wall; the other end is provided with a gas outlet 45 and an air inlet 47 on the side wall.

[0034] The outer shell 41, duct 42, and end plate 43 of the air preheater 4 are made of 310S material; the outer shell adopts internal and external insulation.

[0035] The dust collector 6 is a bag filter, the filter bag material is ceramic filter bag, and the working temperature is 650℃.

[0036] Furthermore, the gas temperature generated by the molten reduction furnace 1 is ≥1400℃. After being cooled by the exhaust hood 2, the gas temperature is ≤900℃. The gas is divided into two paths after passing through the cyclone dust collector 3. One path of gas enters the air preheater 4, and the other path of gas is cooled to ≤200℃ by the waste heat boiler 7. Then, it enters the bag filter 8 for purification. The purified gas enters the clean gas pipeline 13.

[0037] The preheated combustion air and gas are used to burn the hot blast stove 9. The waste flue gas generated from burning the stove is treated by the desulfurization and denitrification device 11 and then discharged through the chimney 12. The burned hot blast stove is used to heat the cold air, which is then sent to the melting reduction furnace 1 after being heated to above 1200°C.

[0038] A shut-off valve (not shown) is installed on the gas pipeline connecting the air preheater 4 and the hot blast stove 9 to cut off the gas supply when the hot blast stove is stopped.

[0039] The gas pipeline connecting the air preheater 4 and the hot blast stove 9 is also equipped with a flow regulating valve (not shown) to regulate the amount of gas during the hot blast stove firing process.

[0040] The combustion air pipe connecting the air preheater 4 and the hot blast stove 9 is equipped with a shut-off valve (not shown) to cut off the combustion air when the hot blast stove is stopped.

[0041] The combustion air pipe connecting the air preheater 4 and the hot blast stove 9 is also equipped with a flow regulating valve (not shown) to regulate the amount of combustion air during the hot blast stove firing process.

[0042] The working system of hot blast stove 9: Hot blast stove 9 includes a combustion chamber and a regenerable type. The combustion chamber is equipped with gas and combustion air burners. The regenerable type is filled with refractory checker bricks as a heat storage body. When the hot blast stove is working, the high-temperature flue gas generated by combustion in the combustion chamber heats the heat storage body. Then the furnace is stopped, and cold air is introduced into the hot blast stove. The cold air exchanges heat with the heat storage body and is heated into hot air.

[0043] It is equipped with three hot air furnaces 9, two of which are for firing the furnace and one for heating the cold air.

[0044] Some process parameters:

[0045] The required air volume for smelting in smelting reduction furnace 1 is 140,000 m³. 3 / h, requires heating with a hot air furnace.

[0046] The required combustion air volume for the hot blast stove is 60,000 m³. 3 / h, 50°C before entering the air preheater, 400°C after exiting the air preheater

[0047] Gas required for hot blast stove combustion: 80,000 m³ 3 / h, 750℃ before entering the air preheater, 540℃ after exiting the air preheater

[0048] Air preheater 4 heat exchange area: 500m² 2

[0049] The calorific value of the gas used in the hot blast stove is 2800 kJ / m³. 3

[0050] The temperature of the hot air heated by the hot air furnace is 1250℃.

[0051] Example 2

[0052] Everything else is the same as in Example 1.

[0053] The inlet pipe of dust collector 6 is connected to the outlet of gas compressor 10, and the inlet of gas compressor 10 is connected to clean gas pipe 13. By adding a portion of clean gas into the outlet pipe of dust collector 6, the temperature of the gas entering hot air furnace 9 is adjusted to reach the required process temperature. The filter bags of dust collector 6 are cloth bags.

[0054] Some process parameters:

[0055] Hot air furnace heating air volume: 140,000 m³ 3 / h

[0056] Combustion air volume: 60000m³ 3 / h, 50°C before entering the air preheater, 300°C after exiting the air preheater

[0057] Gas volume: 60,000 m³ 3 / h, 750℃ before entering the air preheater, 350℃ after exiting the air preheater, mixed with 20000m³ 3 The temperature of the purified coal gas is 260℃ per hour.

[0058] Air preheater heat exchange area: 500m² 2

[0059] Calorific value of coal gas: 3000 kJ / m³ 3

[0060] Hot air temperature: 1200℃.

[0061] The required air volume for smelting in smelting reduction furnace 1 is 140,000 m³. 3 / h, requires heating with a hot air furnace.

[0062] The required combustion air volume for the hot blast stove is 60,000 m³. 3 / h, 50°C before entering the air preheater, 400°C after exiting the air preheater

[0063] Gas required for hot blast stove combustion: 80,000 m³ 3 / h; of which 60000m 3 / h air preheater, 750℃ before entering the air preheater, 350℃ after exiting the air preheater, then 20000m³ is added at the inlet of dust collector 6. 3 / h of clean coal gas, the temperature of the mixed coal gas is 260℃, and after dust removal by the dust collector, it is used for firing in the hot blast stove.

[0064] Air preheater 4 heat exchange area: 500m² 2

[0065] The calorific value of the gas used in the hot blast stove is 2800 kJ / m³. 3

[0066] The temperature of the hot air heated by the hot air furnace is 1250℃.

[0067] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A preheating system for combustion air and gas in a hot blast stove, characterized in that, It includes a molten reduction furnace, an exhaust hood, a cyclone dust collector, an air preheater, a dust collector, a combustion blower, and a hot air furnace; the molten reduction furnace is connected in sequence to the exhaust hood, the cyclone dust collector, the air preheater, the dust collector, and the hot air furnace; the combustion blower is connected in sequence to the air preheater and the hot air furnace; the air preheater is used to heat the combustion air with high-temperature coal gas from the cyclone dust collector.

2. The hot blast stove combustion air and gas preheating system according to claim 1, characterized in that, The air preheater has a cylindrical structure, consisting of an outer shell, conduits, and end plates. End plates are fixedly installed at both ends inside the outer shell, and multiple conduits are evenly installed on the end plates. One end of the air preheater has a gas inlet and an air outlet on the side wall; the other end has a gas outlet and an air inlet on the side wall. High-temperature gas flows inside the conduits, and combustion air flows between the outer shell and the conduits, with the combustion air and high-temperature gas flowing in a countercurrent.

3. A preheating system for combustion air and gas in a hot blast stove according to any one of claims 1 or 2, characterized in that, The outer shell, duct, and end plate of the air preheater are made of 310S; the outer shell is insulated with internal heat and / or external heat.

4. The hot blast stove combustion air and gas preheating system according to claim 1, characterized in that, The dust collector is a bag filter, and the filter bag material is one of cloth bag, ceramic filter bag, or stainless steel wire filter bag.

5. The preheating system for combustion air and gas in a hot blast stove according to claim 1, characterized in that, The dust collector inlet is connected to the gas compressor outlet, or the dust collector outlet is connected to the gas compressor outlet; the gas compressor inlet is connected to a clean gas pipeline, and the gas temperature entering the hot air furnace is adjusted by adding a portion of clean gas.

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