Method for controlling ultra-low emission of sintering flue gas

Abstract

The application discloses a method for controlling ultra-low emission of sintering flue gas, characterized in that: low-temperature sintering flue gas in a cold air large flue is introduced into a sinter ore cooling system, the sintering flue gas temperature is raised by using the sensible heat of sinter ore, then the flue gas after temperature rising is introduced into a waste heat power generation system, and the flue gas after power generation is discharged from a chimney through a main air extractor after desulfurization and denitrification. The method for controlling ultra-low emission of sintering flue gas can reduce the cost of a sintering flue gas emission reduction system, increase the waste heat power generation capacity of a sintering machine, and has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of sintering production technology, and more specifically, relates to a method for controlling ultra-low emissions of sintering flue gas. Background Technology

[0002] The Ministry of Ecology and Environment has revised the emission limits for particulate matter, sulfur dioxide, and nitrogen oxides from 20 mg / m³, 50 mg / m³, and 100 mg / m³ to 10 mg / m³, 35 mg / m³, and 50 mg / m³, respectively, based on regional requirements. All eligible steel enterprises are required to complete ultra-low emission retrofitting by 2020, 2022, and 2025. Experts point out that ultra-low emission retrofitting technology for steel sintering machine flue gas is very mature. Using technologies such as integrated activated carbon desulfurization and denitrification processes or ultra-low emission technologies from coal-fired power plants are both mature technologies. As long as the design is standardized and the engineering quality is up to standard, ultra-low emissions from steel sintering machine flue gas can be achieved, significantly reducing air pollutant emissions from steel enterprises.

[0003] Activated carbon desulfurization and denitrification require large investments and have high operating costs. Ultra-low emission technologies for coal-fired power plants generally use wet SNCR+SCR ammonia denitrification followed by desulfurization. These technologies do not fully utilize the characteristics and temperature of sintering flue gas, and require fuel to preheat the sintering flue gas, resulting in high investment and operating costs. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and provide a method for controlling ultra-low emissions of sintering flue gas that can reduce the cost of sintering flue gas emission reduction systems and increase the power generation of waste heat from sintering machines.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The method for controlling ultra-low emissions of sintering flue gas is characterized in that: the low-temperature sintering flue gas in the cold air flue is introduced into the sintering ore cooling system, the sensible heat of the sintering ore is used to raise the temperature of the sintering flue gas, and then the heated flue gas is introduced into the waste heat power generation system. After power generation, the flue gas is desulfurized and denitrified and then discharged from the chimney by the main exhaust fan.

[0006] To make the above technical solutions more detailed and specific, the present invention also provides the following further preferred technical solutions to achieve satisfactory practical effects:

[0007] The low-temperature sintering flue gas in the cold air flue enters the cooling system air inlet pipe after dust removal, and is pressurized by the first booster fan and then passed into the fume hood.

[0008] After being heated by the sensible heat of the sintered ore, the high-temperature flue gas from the fume hood is removed by dust removal and then enters the waste heat power generation system to produce high-pressure steam.

[0009] The flue gas from the medium-temperature fume hood, heated by the sensible heat of the sintered ore, mixes with the high-temperature sintering flue gas output from the hot air duct and enters the waste heat power generation system to produce low-pressure steam.

[0010] The flue gas from the medium-temperature fume hood is output from the cooling system's outlet duct, and after dust removal, it enters the waste heat power generation system.

[0011] The flue gas after passing through the waste heat power generation system is pressurized by a booster fan and then enters the dry desulfurization system for desulfurization treatment.

[0012] After desulfurization, the flue gas is pressurized by a booster fan and then enters a heat exchanger to exchange heat with the denitrified flue gas.

[0013] The flue gas output from the heat exchanger is heated to 300°C by the pipeline heater before entering the SCR denitrification system.

[0014] Compared with the prior art, the present invention has the following advantages: the method of controlling ultra-low emissions of sintering flue gas in the present invention can reduce the cost of sintering flue gas emission reduction system and increase the waste heat power generation of sintering machine, and has good application prospects. Attached Figure Description

[0015] The following is a brief explanation of the contents depicted in the accompanying drawings and the markings therein:

[0016] Figure 1 This is a schematic diagram of the low-emission control system for sintering flue gas of the present invention;

[0017] The following are labeled in the diagram: 1. Wind box, 2. Branch pipe, 3. Cold air main flue, 4. Hot air main flue, 5. Electrostatic precipitator, 6. Heat exchanger, 7. Cooling system inlet pipe, 8. First booster fan, 9. Fume hood, 10. Cooling system power generation pipe, 11. Cooling system outlet pipe, 12. First multi-tube dust collector, 13. Waste heat power generation system, 14. Second multi-tube dust collector, 15. Booster fan, 16. Dry desulfurization system, 17. Pipe heater, 18. SCR denitrification system, 19. Main exhaust fan, 20. Chimney. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and through the description of the examples.

[0019] This invention relates to a method for controlling ultra-low emissions from sintering flue gas, such as... Figure 1 As shown, the low-temperature sintering flue gas in the cold air flue 3 is introduced into the sintering ore cooling system. The sensible heat of the sintering ore is used to raise the temperature of the sintering flue gas. The heated flue gas is then introduced into the waste heat power generation system 13. After power generation, the flue gas is desulfurized and denitrified and then discharged from the chimney 20 through the main exhaust fan 19.

[0020] In this invention, the low-temperature sintering flue gas in the cold air flue 3, after dust removal, enters the cooling system inlet pipe 7 and is pressurized by the first booster fan 8 before being introduced into the fume hood 9. The high-temperature fume hood flue gas, heated by the sensible heat of the sintered ore, is then purified by the first multi-tube dust collector 12 before entering the waste heat power generation system 13 to produce high-pressure steam. The medium-temperature fume hood flue gas, heated by the sensible heat of the sintered ore, mixes with the high-temperature sintering flue gas output from the hot air flue 4 and enters the waste heat power generation system 13 to produce low-pressure steam. The medium-temperature fume hood flue gas is output from the cooling system outlet pipe 11, purified by the second multi-tube dust collector 14, and then enters the waste heat power generation system 13.

[0021] In this invention, the flue gas after passing through the waste heat power generation system 13 is pressurized by the booster fan 15 and enters the dry desulfurization system 16 for desulfurization treatment. After desulfurization, the flue gas, after being pressurized by the booster fan 15, enters the heat exchanger 6 to exchange heat with the denitrified flue gas. The output flue gas, heated by the heat exchanger, is then heated to 300°C by the pipeline heater 17 and can be introduced into the SCR denitrification system for denitrification treatment. During this process, the temperature of the denitrified sintering flue gas is reduced to 160-170°C through heat exchange with the low-temperature flue gas. This flue gas is then used for heat exchange to evaporate ammonia water in the SCR denitrification system, reducing the temperature to below 100°C, and is then discharged into the atmosphere by the main exhaust fan. The high flue gas temperature results in high desulfurization and denitrification efficiency.

[0022] This invention utilizes the high-temperature flue gas (average temperature above 320℃, accounting for 33% to 38% of the total sintering flue gas) from the 7-8 wind boxes at the tail of a large sintering machine. After dust removal, the flue gas directly enters the waste heat power generation system for power generation. The low-temperature flue gas (temperature around 80℃, accounting for 67% to 62% of the total sintering flue gas) from the low-temperature wind boxes of the sintering machine enters the sinter cooling system. The sensible heat of the sinter (temperature around 700℃ to 800℃) is used to further raise the temperature of the low-temperature sintering flue gas. The high-temperature flue gas (above 300℃) passes through the power generation pipe 10 of the cooling system, and after dust removal by the first multi-tube dust collector 12, it enters the waste heat power generation system 13. The medium-temperature flue gas (200℃ to 300℃) mixes with the high-temperature sintering flue gas and passes through the second multi-tube dust collector 14. After dust removal, the flue gas is mixed again with the flue gas from the waste heat power generation system 13. The mixed flue gas passes through the dry desulfurization system 16, and the flue gas temperature is about 100-130℃. After passing through the flue gas heat exchanger 6, the temperature is raised to 240-260℃. After being heated to 300℃ by the burner heater, it enters the medium-temperature SCR denitrification system. The temperature of the denitrified sintering flue gas is about 280-290℃. It exchanges heat with the low-temperature flue gas (100-130℃) to reduce the temperature to 160-170℃. This flue gas is then used for heat exchange to evaporate the ammonia water in the SCR denitrification system, and the temperature is reduced to below 100℃. It is then discharged into the atmosphere by the main exhaust fan. The high flue gas temperature results in high desulfurization and denitrification efficiency, reducing costs. Most of the flue gas is purified twice by electrostatic precipitator and multi-tube dust collector, which can effectively meet the requirements for ultra-low emissions of sintering flue gas.

[0023] In this invention, the wind box 1, branch pipe 2, cold and hot air flue, main exhaust fan 19, fume hood 9, and chimney 20 are commonly used equipment in sintering production. Dry desulfurization systems, booster fans, medium-temperature SCR denitrification systems, GGH heat exchangers, and electrostatic precipitators are commonly used equipment in ultra-low emission systems for sintering flue gas.

[0024] In this invention, such as Figure 1 As shown, the flue gas flow path of the high-temperature trolley air box is as follows: air box 1 → branch pipe 2 → hot air main flue 4 → second multi-pipe dust collector 14 → booster fan 15 → waste heat power generation system 13 → dry desulfurization system 16 → booster fan 15 → heat exchanger 6 (cold side) → pipe heater 17 → SCR denitrification system 18 → heat exchanger 6 (hot side) → main exhaust fan 19 → chimney 20.

[0025] like Figure 1 As shown, the flue gas flow path of the low-temperature trolley air box is as follows: air box 1 → branch pipe 2 → cold air main flue 3 → electrostatic precipitator 5 → cooling system air inlet pipe 7 → first booster fan 8 → fume hood 9 → path 1 and path 2 → waste heat power generation system 13 → booster fan 15 → dry desulfurization system 16 → booster fan 15 → heat exchanger 6 (cold side) → pipe heater 17 → SCR denitrification system 18 → waste heat power generation system 13 → heat exchanger 6 (hot side) → main exhaust fan 19 → chimney 20.

[0026] Route 1: Low-temperature section cooling flue gas → Cooling system outlet duct 11 → Second multi-tube dust collector 14.

[0027] Route 2: High-temperature section cooling flue gas → Cooling system generator pipe 13 → First multi-pipe dust collector 12.

[0028] Implementation Method 1: A 380m² sintering machine has 2 sintering blowers with a capacity of 1.2 million m³ / h, a utilization coefficient of 1.23 t / m²·h, and 7 sintering blowers with a cooling fan capacity of 260,000 m³ / h. The material layer is 900 mm thick. The sintering machine air box temperatures are shown in the table below. Each trolley has a double-row air box (south and north sides), and each air box has a branch pipe connecting to the main flue, forming a double flue. A dual-fan arrangement is used. The first three air boxes are equipped with cooling fans. The average temperature of the air box entering the waste heat power generation system is 385℃. Currently, the average emission concentrations of SO2 and NOx in the sintering flue gas are 228 mg / Nm³ and 180 mg / Nm³, respectively (the current standards for SO2 and NOx are 300 mg / Nm³ and 200 mg / Nm³, respectively). The initial power generation per ton of ore was 10.71 kWh / t of ore. No denitrification system was installed; the desulfurization cost was only 10 yuan / t of ore.

[0029] Sintering machine air box temperature, °C

[0030]

[0031] The cooling of the low-temperature sintering flue gas requires an air volume of 2 million m³ / h. The air volume for low-temperature sintering is 0.75 of the total sintering air volume, which is 1.8 million m³ / h. Supplementary air of 200,000 m³ / h can meet production needs. The first five units are equipped with cooling power generation, currently generating 16.02 kWh / t of ore. With an electricity price of 0.5 yuan / kWh, the cost reduction is 2.5 yuan / t of ore. The average emission concentrations of NOx and SO2 are 38 mg / Nm³ and 18 mg / Nm³, respectively, resulting in a cost of 15.3 yuan / t of ore. Compared to the corresponding standards of activated carbon and dry desulfurization + denitrification, this reduces operating costs by 1.7–4.7 yuan / t of ore, reduces sinter return powder by 0.8%, and reduces costs by 0.5 yuan / t of ore. The actual reduction in comprehensive cost per ton of ore is between 4.7 and 7.7 yuan. Taking 4.7 yuan as the calculation, the sintering machine produces 3.9262 million tons of sintered ore per year, and the cost reduction is about 18.453 million yuan.

[0032] Implementation Method 2: A 2×435m² sintering machine has a main exhaust fan of 2×1.5 million m³ / h and a utilization coefficient of 1.3t / m²·h. The cooling fan consists of 5×420,000 m³ / h. The sintering machine has 26 air boxes. The average temperature of the first 17 air boxes is 85℃, and the average temperature of the last 9 air boxes is 325℃. The cost of activated carbon desulfurization and denitrification for one sintering machine is 19.8 yuan / t of ore. The first two cooling fans generate electricity. The inlet air temperature is 360℃, and the waste heat power generation is 9.6kWh / t of ore. Another sintering machine uses this technology. The sintering cooling requires an air volume of 2.2 million m3 / h, and the low-temperature sintering flue gas volume is 1.96 million m3 / h, requiring 240,000 m3 / h of air for cooling. The first four cooling fans generate electricity, with an inlet air temperature of 340℃. The waste heat power generation is 16.2 kWh / t of ore. With an electricity price of 0.5 yuan / kWh, the cost reduction is calculated to be 2.53 yuan / t. The desulfurization and denitrification cost is 15 yuan / ore, reducing the cost by 3.8 yuan / t of ore. The return powder is reduced by 1%, resulting in a cost reduction of 0.63 yuan per ton of ore.

[0033] The total cost reduction is 6.96 yuan / ton of ore. The average emission concentrations of NOx and SO2 are approximately 35 mg / Nm3 and 20 mg / Nm3, respectively. The sintering machine has an annual output of 4.7502 million tons of sintered ore, resulting in a cost reduction of 33 million yuan.

[0034] This invention presents a method for controlling ultra-low emissions from sintering flue gas, fully utilizing the waste heat from the sintering machine flue gas and the sensible heat of the sintered ore to reduce the cost of the sintering flue gas emission reduction system. It fully utilizes the waste heat from the 80℃ low-temperature flue gas of the sintering machine and the sensible heat of the sintered ore to generate electricity from the sintering waste heat, increasing power generation by approximately 5 kWh / t of ore. Using the low-temperature flue gas from the sintering machine as cooling gas for the sintered ore achieves flue gas recycling, reducing the sintered ore's need for fresh air and lowering air pollution from sintering production. By using sintering flue gas to replace air in cooling the sintered ore, and with some CO combustion releasing heat, it reduces embrittlement caused by the large temperature difference between the high-temperature sintered ore and air, improving the yield and quality of the sintered ore, increasing yield by 1%. The cost per ton of sintered ore is reduced by 4-7 yuan / t of ore.

[0035] This invention provides a method for controlling ultra-low emissions from sintering flue gas. Based on the temperature distribution characteristics of sintering flue gas and the characteristics of the sintered ore cooling system, it utilizes sintering waste heat to reduce the investment and operating costs of the ultra-low emission system for sintering flue gas. This invention fully utilizes the waste heat of sintering flue gas and the sensible heat of sintered ore to reduce the cost of the sintering flue gas emission reduction system; it also increases the power generation from the waste heat of the sintering machine and improves the quality of sintered ore.

[0036] The method for controlling ultra-low emissions of sintering flue gas in this invention can reduce the cost of sintering flue gas emission reduction systems and increase the power generation from waste heat of sintering machines, and has good application prospects.

[0037] The present invention has been described above by way of example with reference to the accompanying drawings. However, the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention or any direct application to other situations shall fall within the protection scope of the present invention.

Claims

1. A method of controlling ultra-low emission of sintering flue gas, characterized in that: The low-temperature sintering flue gas in the cold air large flue is introduced into the cooling system air inlet pipe after dust removal, and is introduced into the smoke hood by the first booster fan, and the high-temperature smoke hood flue gas after the sensible heat of sinter is increased is introduced into the waste heat power generation system to produce high-pressure steam, and the flue gas after power generation is discharged into the chimney by the main exhaust fan after desulfurization and denitrification; The medium-temperature smoke hood flue gas after the sensible heat of sinter is increased is mixed with the high-temperature sintering flue gas output from the hot air large flue, and is introduced into the waste heat power generation system to produce low-pressure steam, the medium-temperature smoke hood flue gas is output from the cooling system air outlet pipe and introduced into the waste heat power generation system after dust removal, the flue gas after the waste heat power generation system is introduced into the dry desulfurization system after being pressurized by the booster fan, the flue gas after desulfurization is introduced into the heat exchanger to exchange heat with the flue gas after denitrification, the output flue gas after heating by the heat exchanger is introduced into the SCR denitrification system after being heated by the pipeline heater; The low-temperature flue gas of the sintering machine low-temperature section air tank, the temperature of which is 80℃, accounts for 67% to 62% of the total amount of sintering flue gas, is introduced into the sinter cooling system, and the sensible heat of sinter, the temperature of which is 700℃ to 800℃, is used to increase the temperature of the low-temperature sintering flue gas again, among which the high-temperature smoke hood flue gas above 300℃ passes through the cooling system power generation pipeline, is removed by the first multi-tube dust collector, and is introduced into the waste heat power generation system; The medium-temperature smoke hood flue gas of 200℃ to 300℃ is mixed with the high-temperature sintering flue gas, is removed by the second multi-tube dust collector, and is mixed with the flue gas of the waste heat power generation system again, the temperature of the mixed flue gas is about 100-130℃ after the dry desulfurization system, the temperature is increased to 240-260℃ by the flue gas heat exchanger, is heated to 300℃ by the burner heater, and is introduced into the medium-temperature SCR denitrification system, the sintering flue gas after denitrification has a temperature of about 280-290℃, and the low-temperature flue gas has a temperature of 100-130℃, and the heat exchange reduces the temperature to 160-170℃, the flue gas is used for heat exchange evaporation of the ammonia water of the SCR denitrification system, the temperature is reduced to below 100℃, and is discharged into the atmosphere by the main exhaust fan.

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