Treatment process for reducing flue gas emission of steel billet heating furnace

Abstract

The invention discloses a treatment process for reducing flue gas emission of a steel billet heating furnace, which comprises the following steps of: 1) optimizing a removal process of nitrogen oxides, determining that a denitration process of the heating furnace preferentially selects a low-nitrogen combustion technology, and adopting a ULF (Ultra Low Frequency) type long-flame low-NOx flame-adjusting burner which belongs to one of low-nitrogen environment-friendly burners and adopts a two-stage combustion mode; 2) desulfurization process selection: a calcium-based fixed bed dry desulfurization technology is selected for heating furnace transformation desulfurization; the granular desulfurizer adopted in the fixed bed desulfurization technology has a dust removal function, and the dust removal efficiency of the granular desulfurizer in the fixed bed can reach 90% or above under the conditions that the thickness of a granular layer is certain and the flow speed is certain. The invention aims to provide the treatment process for reducing the flue gas emission of the steel billet heating furnace, and the emission concentration of nitrogen oxides, sulfur dioxide and particulate matters in the flue gas is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas emission treatment, and in particular relates to a treatment process for reducing flue gas emission from a steel billet heating furnace. Background Art

[0002] In principle, the hourly average concentrations of particulate matter, sulfur dioxide, and nitrogen oxides emitted by heating furnaces shall not exceed 10, 50, and 200 mg / m 3 For steel enterprises that achieve ultra-low emissions, the hourly average emission concentration for at least 95% of the time periods each month must meet the above requirements.

[0003] With the rapid development of industry, the wanton emission of a large number of pollutants has caused the current environmental pollution to become more and more serious. The "Emission Standards for Air Pollutants in the Steel Rolling Industry" stipulates that the pollutant emission indicators of steel rolling heating furnaces are particulate matter, sulfur dioxide, and nitrogen oxides. Conventional heating furnaces and regenerative heating furnaces cannot guarantee that the pollutant indicators in the exhaust gas meet the specified standards by relying on the existing process control. Therefore, it is a future development trend to gradually upgrade the desulfurization and denitrification treatment technology to step-by-step heating furnaces to ensure that the heating furnaces meet the pollutant emission standards.

[0004] Therefore, the flue gas emitted by the heating furnace does not meet the requirements of ultra-low emission transformation. It is necessary to study the process suitable for the flue gas treatment of the heating furnace to reduce the nitrogen oxides, sulfur dioxide and particulate matter in the flue gas emissions of the heating furnace to meet the requirements of ultra-low emission transformation, which is of great significance. Summary of the invention

[0005] The purpose of the present invention is to provide a treatment process for reducing flue gas emissions from a billet heating furnace, thereby reducing the emission concentrations of nitrogen oxides, sulfur dioxide and particulate matter in the flue gas.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a treatment process for reducing smoke emission from a billet heating furnace, comprising:

[0008] 1) Optimization of nitrogen oxide removal process

[0009] Determine that the heating furnace denitrification process should give priority to low-nitrogen combustion technology. The specific measure is to use the ULF type long flame low NOx flame-adjusting burner, which is a kind of low-nitrogen environmentally friendly burner. It adopts a two-stage combustion method, fully utilizes the dilution effect of air classification and the in-furnace smoke flow, reduces the flame center temperature, and effectively inhibits the generation of NOx;

[0010] 2) Desulfurization process selection

[0011] The heating furnace transformation desulfurization adopts calcium-based fixed bed dry desulfurization technology; the granular desulfurizer used in the fixed bed desulfurization technology has a dust removal function. Under the conditions of a certain particle layer thickness and a certain flow rate, the dust removal efficiency of the granular desulfurizer in the fixed bed can reach more than 90%.

[0012] Furthermore, the heating furnace is a conventional walking beam heating furnace.

[0013] Furthermore, under the premise of continuous production for 72 hours and production load reaching 90%, the ultra-low emission transformation indicators of the heating furnace meet the requirements.

[0014] Furthermore, after the ultra-low emission transformation equipment of the heating furnace was put into operation, the average nitrogen oxide value was 63mg / Nm 3 , the maximum value is 120mg / Nm 3 ; The average sulfide content is 1.8 mg / Nm 3 , the maximum value is 19mg / Nm 3 ; The average particle size is 1.1 mg / Nm 3 , the maximum value is 4mg / Nm 3 , fully in line with the ultra-low emission transformation requirements.

[0015] Furthermore, the NOx emission of the heating furnace was significantly reduced after the ultra-low emission transformation, with the average value decreasing from 223 mg / m 3 Reduced to 56 mg / m 3 .

[0016] Furthermore, the SO2 emission of the heating furnace was significantly reduced after the ultra-low emission transformation, with the average value decreasing from 79 mg / m 3 Reduce to 4 mg / m 3 .

[0017] Compared with the prior art, the beneficial technical effects of the present invention are: BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings.

[0019] Figure 1 It is the NOx operation data during the production period after the ultra-low emission transformation of the heating furnace;

[0020] Figure 2 Sulfur and particulate matter operation data after ultra-low emission modification of heating furnace;

[0021] Figure 3 Comparison of NOx data before and after ultra-low emission transformation of heating furnace;

[0022] Figure 4 Comparison of sulfide data before and after the ultra-low emission transformation of the heating furnace. DETAILED DESCRIPTION

[0023] The present invention is based on the working principle of the heating furnace combustion system, and reduces flue gas emissions by optimizing the nitrogen oxide removal process and the desulfurization process, and finally meets the emission requirements. The specific process is as follows:

[0024] 1. Optimization of nitrogen oxide removal process

[0025] The heating furnace is a conventional walking beam heating furnace. The heating furnace combustion mode adopts the form of furnace top flat flame burner matching furnace wall flame regulating burner. The cold installation design output is 200 tons / hour. The fuel is high coke mixed gas with a calorific value of 2400kcal / Nm 3 , three-stage heating, using air preheating and waste heat boiler steam recovery operation mode, the heating furnace flue gas flow rate is ~123800m 3 / h, the exhaust temperature is 240~320℃, and the specific parameters are shown in Table 1.

[0026] Table 1 Heating furnace related parameters

[0027]

[0028] According to the environmental protection inspection data of the heating furnace in 2023 (see Table 2), the NOx excess rate of the heating furnace was 61.76%, the SO2 excess rate was 99.86%, and the particulate matter emission excess rate was 13.40%.

[0029] Table 2 Online detection data of heating furnace environmental protection indicators Statistical unit: mg / m 3

[0030]

[0031] It can be seen from Table 2 that the flue gas emitted by the heating furnace currently does not meet the ultra-low emission modification requirements. It is necessary to study a process suitable for the flue gas treatment of the heating furnace to reduce nitrogen oxides, sulfur dioxide and particulate matter in the flue gas emissions of the heating furnace to meet the ultra-low emission modification requirements in Document No. 35 of the Environmental Atmosphere

[2019] .

[0032] In view of the production mechanism of nitrogen oxides, the current domestic main technologies are low-nitrogen combustion technology, SCR (selective catalytic reduction) and SNCR (selective non-catalytic reduction denitrification technology).

[0033] See Table 1 below:

[0034] Table 1 Comparison of advantages and disadvantages of denitrification process technology

[0035]

[0036] After on-site research and analysis, and by comparing the advantages and disadvantages of the three denitrification processes in Table 3, it was determined that the heating furnace denitrification process gives priority to low-nitrogen combustion technology. The specific measure is to use ULF type long flame low NOx flame regulating burner, which is one of the low-nitrogen environmentally friendly burners. It adopts a two-stage combustion method, makes full use of the dilution effect of air classification and the smoke airflow in the furnace, reduces the center temperature of the flame, and can effectively inhibit the formation of NOx. This technology is mature, has high denitrification efficiency, can fully meet the requirements of ultra-low emission indicators, and is in line with the actual environmental conditions on site, with low investment costs and no additional land use. More importantly, this technology controls the generation of nitrogen oxides from the source and has good conditions for promotion to similar enterprises.

[0037] 2. Desulfurization process selection

[0038] SO2 in flue gas mainly comes from the combustion of sulfur-containing substances in blast furnace gas. The concentration of inorganic sulfur H2S in gas is usually less than 20 mg / Nm 3 , organic sulfur is relatively high, about 80-300 mg / Nm 3 Organic sulfur accounts for more than 70% of the total sulfur content in coal gas, which is the main reason for the excessive SO2 concentration in the flue gas from blast furnace gas combustion.

[0039] In view of the low efficiency of sulfide removal in coal gas, high investment, and complex subsequent operation and maintenance, and the mature flue gas desulfurization technology after combustion, high desulfurization efficiency, and moderate investment and operating costs, the current heating furnace desulfurization technology mainly selects end-of-pipe flue gas desulfurization technology.

[0040] At present, there are more than a dozen mature flue gas desulfurization processes, which can be mainly divided into wet, semi-dry and dry processes. Considering the small amount of flue gas emissions from steel rolling heating furnaces and the shortage of on-site land, domestic heating furnace desulfurization does not use wet or semi-dry desulfurization processes, but selects from dry desulfurization. Focus on activated carbon desulfurization technology, SDS sodium-based desulfurization technology, calcium-based fixed bed Desulfurization technology and high-activity calcium hydroxide desulfurization technology.

[0041] Table 4 Comparison of advantages and disadvantages of desulfurization technology

[0042]

[0043]

[0044] The selection of heating furnace desulfurization technology is mainly based on desulfurization efficiency, operation difficulty, infrastructure cost, operating cost, difficulty in handling desulfurization products, etc. By comparing the advantages and disadvantages of various flue gas desulfurization technologies, the best process suitable for heating furnace desulfurization is selected. After research and analysis: calcium-based fixed bed dry desulfurization technology has high desulfurization efficiency, desulfurization products are non-hazardous waste products, easy to handle, low flue gas temperature requirements for desulfurizers, no need to add equipment to control flue gas temperature in the heating furnace, and no need to add full-time operators after the equipment is put into operation, no special equipment, simple system, low energy consumption, small equipment footprint, etc. Therefore, calcium-based fixed bed dry desulfurization technology is selected for this heating furnace renovation desulfurization.

[0045] The particulate emission value of the heating furnace was low before the transformation, slightly exceeding the limit. In the fixed bed desulfurization technology selected this time, the granular desulfurizer has a dust removal function, and according to research, under the conditions of a certain particle layer thickness and a certain flow rate, the dust removal efficiency of the granular desulfurizer in the fixed bed can reach more than 90%. Therefore, the calcium-based fixed bed dry has a certain effect of removing particulate matter. After the flue gas is treated by the calcium-based fixed bed, the particulate matter should be able to meet the requirements of ultra-low emissions.

[0046] Based on the above analysis, the ultra-low emission transformation of the heating furnace uses low-nitrogen combustion + calcium-based fixed bed desulfurization to reduce the concentration of nitrogen oxides, sulfur dioxide and particulate matter in the flue gas. After the ultra-low emission transformation of the heating furnace was implemented, under the premise of continuous production for 72 hours and production load reaching 90%, the completion status of the ultra-low emission transformation indicators of the heating furnace is shown below Figure 1 and Figure 2 :

[0047] Depend on Figure 1 and Figure 2 It can be seen that after the ultra-low emission transformation equipment of the heating furnace was put into operation, the average nitrogen oxide value was 63mg / Nm 3 , the maximum value is 120mg / Nm 3 ; The average sulfide content is 1.8 mg / Nm 3 , the maximum value is 19mg / Nm 3 ; The average particle size is 1.1 mg / Nm 3 , the maximum value is 4mg / Nm 3 , fully in line with the ultra-low emission transformation requirements. Comparing the environmental protection operation data of the heating furnace before and after ultra-low emission, the comparison is shown in Figure 3 , Figure 4 :

[0048] Depend on Figure 3 It can be seen that the NOx emission of the heating furnace was significantly reduced after the ultra-low emission transformation, and the average value was reduced from 223mg / m 3 Reduced to 56 mg / m 3 .

[0049] Depend on Figure 4 It can be seen that SO2 emissions were significantly reduced after the ultra-low emission transformation of the heating furnace, with the average value decreasing from 79 mg / m 3 Reduce to 4 mg / m 3 .

[0050] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A process for reducing flue gas emissions from a billet heating furnace, characterized in that: include: 1) Optimization of nitrogen oxide removal process Determine that the heating furnace denitrification process should give priority to low-nitrogen combustion technology. The specific measure is to use the ULF type long flame low NOx flame-adjusting burner, which is a kind of low-nitrogen environmentally friendly burner. It adopts a two-stage combustion method, fully utilizes the dilution effect of air classification and the in-furnace smoke flow, reduces the flame center temperature, and effectively inhibits the generation of NOx; 2) Desulfurization process selection The heating furnace transformation desulfurization adopts calcium-based fixed bed dry desulfurization technology; the granular desulfurizer used in the fixed bed desulfurization technology has a dust removal function. Under the conditions of a certain particle layer thickness and a certain flow rate, the dust removal efficiency of the granular desulfurizer in the fixed bed can reach more than 90%.

2. The process for reducing flue gas emissions from a billet heating furnace according to claim 1, characterized in that: The heating furnace is a conventional walking beam heating furnace.

3. The process for reducing flue gas emissions from a billet heating furnace according to claim 1, characterized in that: Under the premise of 72 hours of continuous production and a production load of 90%, the ultra-low emission transformation indicators of the heating furnace meet the requirements.

4. The process for reducing flue gas emissions from a billet heating furnace according to claim 3 is characterized in that: After the ultra-low emission transformation equipment of the heating furnace was put into operation, the average nitrogen oxide value was 63mg / Nm 3 , the maximum value is 120mg / Nm 3 ; The average sulfide content is 1.8 mg / Nm 3 , the maximum value is 19mg / Nm 3 ; The average particle size is 1.1 mg / Nm 3 , the maximum value is 4mg / Nm 3 , fully in line with the ultra-low emission transformation requirements.

5. The process for reducing flue gas emissions from a billet heating furnace according to claim 3, characterized in that: After the ultra-low emission transformation of the heating furnace, NOx emissions were significantly reduced, with the average value decreasing from 223 mg / m 3 Reduced to 56 mg / m 3 .

6. The process for reducing flue gas emissions from a billet heating furnace according to claim 3, characterized in that: After the ultra-low emission transformation of the heating furnace, SO2 emissions were significantly reduced, with the average value decreasing from 79 mg / m 3 Reduce to 4 mg / m 3 .

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