A method to reduce NO in sintering flue gas X Methods of emission

Abstract

This invention discloses a method for reducing NO in sintering flue gas. X The main approach to reducing emissions is to address the NO content in existing sintering flue gas. X The technical problem is high emissions. The technical solution is to reduce NO in sintering flue gas. X The emission reduction methods include: 1) ore blending, with the following mass percentages of each component in the sintering ore blend: 3%–8% high-sulfur iron ore powder, 66%–75% rich hematite powder, 4.0%–5.0% solid fuel, 8%–15% of quicklime, dolomite, and limestone, and 5%–10% sintering return ore; 2) mixing and granulation; 3) sintering with exhaust gas, after which the finished sinter is obtained, and samples are taken to test the drum strength and sulfur content of the sinter; 4) desulfurization and denitrification treatment of the sintering flue gas. The NOx mass concentration in the sintering flue gas after the integrated desulfurization and denitrification treatment by circulating fluidized bed combined with ozone is ≤35 mg / m³. 3 SO2 mass concentration ≤ 5 mg / m³ 3 .

Description

Technical Field

[0001] This invention relates to a sintering flue gas control technology, and particularly to a method for reducing NO in sintering flue gas. X Specifically, methods for reducing emissions involve lowering NO in sintering flue gas through sintering ore blending and flue gas desulfurization and denitrification. X The method for measuring emissions belongs to the field of sintering and flue gas treatment technology in the iron and steel metallurgy industry. Background Technology

[0002] With the implementation of ultra-low emission standards for sintering flue gas in the steel industry, the purification of pollutants in sintering flue gas urgently needs to be addressed. Currently, sintering flue gas desulfurization and purification technology is very mature and can meet emission standards; therefore, the NOx emission from sintering flue gas is crucial. X It has become the primary pollutant for steel enterprises. With the continuous development and innovation of flue gas denitrification technology, the integrated desulfurization and denitrification technology of circulating fluidized bed combined with ozone is also being put into practical application in the purification of sintering flue gas.

[0003] More than 90% of the nitrogen oxides in sintering flue gas exist in the form of NO, which is poorly soluble in water (solubility less than 0.1 g / dm³). 3 NO, in its higher valence state, cannot be effectively absorbed by the desulfurization system. X They have high solubility in water; for example, the solubility of NO2 and N2O5 is 213 / dm³. 3 and 500 / dm 3 It is more easily absorbed. Therefore, ozone oxidizes the poorly soluble NO into the easily soluble high-valence state NO. X Then, denitrification is carried out using a subsequent circulating fluidized bed semi-dry desulfurization process.

[0004] Currently, the main measures taken are to control the amount of nitrogen-containing organic matter introduced into the fuel, strictly control sintering process parameters, and research and develop the use of NO. X Measures such as absorption catalysts can be used to reduce NO X Emission concentration, but when the nitrogen oxide concentration in the inlet flue gas exceeds 300 mg / m³ 3 At that time, the denitrification system could not meet the NO requirements. X Emission concentration ≤35mg / m³ 3 Environmental protection requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a method for reducing NO in sintering flue gas. X The main approach to reducing emissions is to address the NO content in existing sintering flue gas. X The technical problem of high emissions; the method of this invention reduces NO emissions in sintering flue gas. X Emission concentration ≤35mg / m³ 3 .

[0006] The technical concept of this invention is to produce sinter by incorporating high-sulfur iron ore powder into a sintering mixture and then performing exhaust sintering. The sintering flue gas generated during the exhaust sintering process is treated by an electrostatic precipitator at the die head, and then ozone is introduced. The ozone reacts with NO in the sintering flue gas to form higher valence NO. X The sintering flue gas is then transported to a circulating fluidized bed semi-dry desulfurization system for desulfurization and denitrification treatment. The sulfides in the sintering flue gas are converted into calcium sulfate and calcium sulfite after desulfurization treatment, and the nitrogen compounds in the sintering flue gas are converted into calcium nitrate and calcium nitrite after denitrification treatment. Finally, the sintering flue gas is purified and then discharged.

[0007] The technical solution adopted in this invention is a method for reducing NO in sintering flue gas. X The method for determining emissions includes the following steps:

[0008] 1) Ore blending: The mass percentage of each component in the sintering ore blend is as follows: 3%–8% high-sulfur iron ore powder, 66%–75% rich hematite powder, 4.0%–5.0% solid fuel, 8%–15% of quicklime, dolomite, and limestone, and 5%–10% sintering return ore. The sum of the mass percentages of each component is 100%. The binary basicity R2 of the sinter is controlled at 1.80–1.90, and the mass percentage of MgO in the sinter is 1.40%–1.60%.

[0009] 2) Mixing and granulation: The prepared sintered ore raw materials are loaded into a primary mixer for mixing. Water is added and stirred to form a primary mixture with a H2O mass percentage of 6.4% to 6.6%. The primary mixture is then loaded into a secondary mixer for granulation. Water is added and stirred to form a secondary mixture with a H2O mass percentage of 6.7% to 6.9%.

[0010] 3) Exhaust sintering: The secondary mixture is placed on the sintering trolley for exhaust sintering. The exhaust negative pressure is controlled at 14-17 kPa and the ignition temperature is 1050-1100℃ during the sintering process. After sintering, the finished sinter is obtained. Samples are taken to test the drum strength and sulfur content of the sinter.

[0011] 4) The sintering flue gas undergoes desulfurization and denitrification treatment. The flue gas generated during sintering is drawn into the main flue and first passes through an electrostatic precipitator at the machine head for dust removal. After dust removal, the SO2 and NO content in the sintering flue gas before desulfurization and denitrification treatment is monitored online. X Concentration; then ozone is introduced into the sintering flue gas after it has been treated by the electrostatic precipitator at the die head. The ozone reacts with the NO in the sintering flue gas to form NO in a higher oxidation state. X The sintering flue gas, after ozone oxidation, is then transported through pipelines to an absorption tower for desulfurization and denitrification treatment. The levels of SO2 and NO in the desulfurization and denitrification treated sintering flue gas are monitored online. X concentration.

[0012] Furthermore, the mass percentage content of the high-sulfur iron ore powder components described in this invention is as follows: TFe 56%–62%, SiO2 4%–8%, CaO 1%–2%, MgO 1%–3%, Al2O3 1%–3%, S 2%–4%, and the sum of other contents is 1%–5%.

[0013] The mass percentage composition of the rich hematite ore powder is as follows: TFe 60%–66%, SiO2 2%–8%, CaO 0.5%–2%, MgO 0.01%–2%, Al2O3 0.1%–2%, S 0.001%–1%, and the sum of other contents is 1%–5%.

[0014] The sinter produced by the method of this invention has a sulfur content ≤0.020%; a drum strength of 79%–82%; a sinter yield of 80%–82%; and a sinter utilization coefficient of 1.23–1.31 t / m. 2 ·h.

[0015] The NOx concentration in the sintering flue gas after integrated desulfurization and denitrification treatment with circulating fluidized bed and ozone is ≤35mg / m³. 3 SO2 concentration ≤ 5 mg / m³ 3 The flue gas emission indicators and sinter technical indicators all meet environmental protection and quality requirements.

[0016] The rationale for the process parameters adopted in the method of this invention is as follows:

[0017] 1. Setting the proportion of high-sulfur iron ore powder in sintering raw materials

[0018] Adding high-sulfur iron ore powder to the sintering mixture can increase the SO2 concentration in the sintering flue gas after ignition and sintering. SO2 can consume free radicals X (H, OH, and O) and simultaneously affect their reaction with NH4+. i The reaction causes NH i +X→NH i-1 The +HX equilibrium shifts to the left, preventing N formation, and the reaction NH + NO → N2 + OH occurs. Therefore, increasing the SO2 concentration in the sintering flue gas helps reduce NO formation during the sintering process and lowers the NO content in the sintering flue gas. X concentration.

[0019] In the circulating fluidized bed combined with ozone integrated desulfurization and denitrification process, SO2 in the sintering flue gas is hydrolyzed to form It then undergoes a redox reaction with NO2 in the flue gas, the reaction formula is:

[0020]

[0021] Because the desulfurization reaction of sintering flue gas occurs simultaneously, it can promote the hydrolysis of SO2. This promotes NO2 absorption, so a high SO2 concentration in the flue gas must be maintained.

[0022] The applicant discovered through extensive research that the suitable SO2 concentration in the circulating fluidized bed synergistic ozone integrated desulfurization and denitrification process is 1500–2000 mg / m³. 3 Iron ore powder that can increase the SO2 concentration in sintering flue gas is selected, in which sulfur mainly exists in the form of pyrite. The proportion of high-sulfur iron ore powder added is calculated based on the sulfur content of the iron ore powder, the decomposition ratio of sulfur, and the appropriate SO2 concentration in the sintering flue gas. Taking all factors into consideration, this invention limits the mass percentage of high-sulfur iron ore powder in the sintering raw materials to 3% to 8%.

[0023] Based on the redox interaction mechanism among flue gas components, the method of this invention increases the SO2 concentration in sintering flue gas through ore blending, thereby reducing NO in the flue gas during the sintering process. X Concentration; subsequent desulfurization and denitrification are carried out using a circulating fluidized bed combined with ozone integrated desulfurization and denitrification process, which can also promote the reduction of NO in the desulfurization and denitrification process. X Absorption improves the denitrification rate and achieves NO reduction in sintering flue gas. X Emission concentration ≤35mg / m³ 3 Ultimately, the goal is to ensure that both flue gas emission indicators and sinter technical indicators meet environmental protection and quality requirements.

[0024] Compared with existing technologies, this invention has the following positive effects: 1. Existing ore blending technologies formulate blending schemes based on the SO2 emission concentration in sintering flue gas and the sulfur content control requirements of sintered ore, strictly controlling the total sulfur content. This places high demands on the sulfur content of iron ore, generally requiring the purchase of low-sulfur iron ore, which is more expensive than high-sulfur iron ore. The method of this invention can increase the proportion of high-sulfur ore used in the sintering blending structure, reducing the cost of sintering blending. 2. The method of this invention can not only inhibit the generation of nitrogen oxides during sintering, but also reduce the NO2 content in sintering flue gas before desulfurization and denitrification treatment. X Concentration can also promote the reduction of NO in desulfurization and denitrification processes. X The gases are absorbed, ultimately ensuring that both flue gas emission indicators and sinter technical indicators meet environmental protection and quality requirements. 3. The method of this invention is easy to implement, has very obvious effects, and significantly reduces production costs. Detailed Implementation

[0025] The present invention will be further described below with reference to Examples 1-4 and Comparative Example 1, as shown in Tables 1-3.

[0026] A sintering method for reducing NOx emissions from sintering flue gas includes the following steps:

[0027] 1) Ore blending: The mass percentage of each component in the sintering ore blend is as follows: 3%–8% high-sulfur iron ore powder, 66%–75% rich hematite powder, 4.0%–5.0% solid fuel, 8%–15% of quicklime, dolomite, and limestone, and 5%–10% sintering return ore. The sum of the mass percentages of each component is 100%. The binary basicity R2 of the sinter is controlled at 1.80–1.90, and the mass percentage of MgO in the sinter is 1.40%–1.60%.

[0028] 2) Mixing and granulation: The prepared sintered ore raw materials are loaded into a primary mixer for mixing. Water is added and stirred to form a primary mixture with a H2O mass percentage of 6.4% to 6.6%. The primary mixture is then loaded into a secondary mixer for granulation. Water is added and stirred to form a secondary mixture with a H2O mass percentage of 6.7% to 6.9%.

[0029] 3) Exhaust sintering: The secondary mixture is placed on the sintering trolley for exhaust sintering. The exhaust negative pressure is controlled at 14-17 kPa and the ignition temperature is 1050-1100℃ during the sintering process. After sintering, the finished sinter is obtained. Samples are taken to test the drum strength and sulfur content of the sinter.

[0030] 4) The sintering flue gas undergoes desulfurization and denitrification treatment. All flue gas generated during the sintering process is drawn into the main flue and first passes through an electrostatic precipitator at the machine head for dust removal. After dust removal, the SO2 and NO content in the sintering flue gas before desulfurization and denitrification treatment is monitored online. X Concentration; then, the sintering flue gas, after being treated by the electrostatic precipitator at the die head, is introduced into ozone. The ozone reacts with the NO in the sintering flue gas to form higher oxidation states of NO. X The sintering flue gas, after ozone oxidation, is then transported through pipelines to an absorption tower for desulfurization and denitrification treatment. The SO2 and NO content in the desulfurization and denitrification treated sintering flue gas is monitored online. X concentration.

[0031] In Examples 1-4 of this invention, the target basicity of the sinter is 1.85, the mass percentage of MgO in the sinter is 1.40%, and the solid fuel is coke powder, accounting for 4.8% of the mass percentage of the sintering raw materials.

[0032] Table 1. Sintering batching ratio (mass percentage) of embodiments of the present invention / %

[0033]

[0034] Table 2 Quality Indicators of Sintered Ore in Embodiments of the Invention

[0035]

[0036] Table 3 Emission indicators of sintering flue gas in embodiments of the present invention

[0037]

[0038] Examples 1-4 show that after adding high-sulfur iron ore powder to the sinter, both the sinter quality indicators and flue gas emission indicators meet the requirements. However, as the proportion of high-sulfur iron ore powder increases, the SO2 concentration in the sinter flue gas before desulfurization and denitrification treatment increases, and the NO concentration in the sinter flue gas before desulfurization and denitrification treatment also increases. X The concentration of NO decreased significantly after desulfurization and denitrification treatment in the sintering flue gas. X The concentrations also decreased, all below 35 mg / m³. 3 .

[0039] Comparative Example 1 did not include high-sulfur iron ore powder in its sintering raw materials. Its sintering utilization coefficient, sinter drum strength, and yield were slightly worse than those of the Example 1. The sulfur content in the sinter was comparable to that of the Example 1. The NO content in the sintering flue gas after desulfurization and denitrification treatment was lower. X Concentration higher than 35 mg / m 3 .

[0040] In summary, increasing the SO2 concentration in sintering flue gas by adding high-sulfur iron ore powder can not only reduce the NO content in the sintering flue gas before desulfurization and denitrification treatment, but also improve the overall efficiency of sintering flue gas. X It can also reduce the NO concentration in sintering flue gas after desulfurization and denitrification treatment. X The emission concentration will ultimately ensure that both the flue gas emission indicators and the sintered ore technical indicators meet environmental protection and quality requirements.

[0041] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for reducing NOx emissions in sintering flue gas, characterized in that, The method includes the following steps: 1) Ore blending: The mass percentage of each component in the sintering ore blend is as follows: high-sulfur iron ore powder 3%–8%, rich hematite powder 66%–75%, solid fuel 4.0%–5.0%, quicklime, dolomite, and limestone (total) 8%–15%, and sintering return ore 5%–10%. The sum of the mass percentages of each component is 100%. The binary basicity R2 of the sinter is controlled at 1.80–1.90, and the mass percentage of MgO in the sinter is 1.40%–1.60%. The mass percentage of the high-sulfur iron ore powder component is as follows: TFe 56%–62%, SiO2 4%–8%, CaO 1%–2%, MgO 1%–3%, Al2O3 1%–3%, S 2%–4%, and the sum of other contents is 1%–5%. 2) Mixing and granulation: The prepared sintered ore raw materials are loaded into a primary mixer for mixing. Water is added and stirred to form a primary mixture with a H2O mass percentage of 6.4% to 6.6%. The primary mixture is then loaded into a secondary mixer for granulation. Water is added and stirred to form a secondary mixture with a H2O mass percentage of 6.7% to 6.9%. 3) Exhaust sintering: The secondary mixture is placed on the sintering trolley for exhaust sintering. The exhaust negative pressure is controlled at 14-17 kPa and the ignition temperature is 1050-1100℃ during the sintering process. After sintering, the finished sinter is obtained. Samples are taken to test the drum strength and sulfur content of the sinter. 4) The sintering flue gas undergoes desulfurization and denitrification treatment. The flue gas generated during sintering is drawn into the main flue and first passes through an electrostatic precipitator at the machine head for dust removal. After dust removal, the SO2 and NO content in the sintering flue gas before desulfurization and denitrification treatment is monitored online. X Concentration; then ozone is introduced into the sintering flue gas after it has been treated by the electrostatic precipitator at the die head. The ozone reacts with the NO in the sintering flue gas to form NO in a higher oxidation state. X The sintering flue gas, after ozone oxidation, is then transported through pipelines to an absorption tower for desulfurization and denitrification treatment. The levels of SO2 and NO in the desulfurization and denitrification treated sintering flue gas are monitored online. X concentration.

2. The method for reducing NOx emissions in sintering flue gas as described in claim 1, characterized in that, The mass percentage of the components in the hematite rich ore powder is as follows: TFe 60%–66%, SiO2 2%–8%, CaO 0.5%–2%, MgO 0.01%–2%, Al2O3 0.1%–2%, S 0.001%–1%, and the sum of other contents is 1%–5%.

3. The method for reducing NOx emissions in sintering flue gas as described in claim 1, characterized in that, The NOx concentration in the sintering flue gas after integrated desulfurization and denitrification treatment with circulating fluidized bed and ozone is ≤35mg / m³. 3 SO2 concentration ≤ 5 mg / m³ 3 .

4. The method for reducing NOx emissions in sintering flue gas as described in claim 1, characterized in that, The finished sinter contains ≤0.020% sulfur by mass; the drum strength of the sinter is 79%–82%; the yield of the sinter is 80%–82%; and the sinter utilization coefficient is 1.23–1.31 t / m. 2 ·h.

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