1 thought on “Tone gas desulfurization and denitrification”
Phyllis
Abstract
The main influencing factors of the current status of SO2 and NOX emission and pollutants in my country's coking industry. Compared with the ammonia, limestone/limestone method, bisodium alkali method, magnesium oxide method, spray drying method , Curring -Delicate bed method, coke furnace flue gas desulfurization technology represented by low -nitrogen combustion technology, low -temperature selective catalytic reduction denitration technology, oxidation denitrification, etc. The technical principles, desulfurization and denitration efficiency, and their respective advantages and disadvantages of coke furnace flue gas desulfurization and denitration integrated technology, summarize the existence of coke furnace flue gas desulfurization and denitration technology in terms of process route selection, flue gas emissions, secondary pollution, etc. The problem. It is pointed out that the treatment of furnace flue gas pollution must effectively integrate the source control of the source, low nitrogen combustion, and end purification, and continuously strengthen the application of coke oven operation management level and new technologies.
This
The environmental pollution such as SO2 and NOX in coal -fired flue gas has seriously affected human survival and development. At present, the most effective and most widely used coal -fired flue gas SO2 and NOX pollution control measures are the technology of smoke dehydration and denitration after burning. As the second largest in the country in China, my country's coal coking consumption of about 1 billion T year, accounting for about 1/3 of the country's total coal consumption. At present, the development and application of gas desulfurization and denitration technology in the field of coal -fired power generation are relatively mature. Most coal power enterprises SO2 and NOX emissions have reached over -net standard 12017 The 23rd volume of clean coal technology in the 6th of the 6th. But as a traditional coal chemical industry, The development of my country's coking field is relatively extensive, and pollutant governance measures have been forced to implement under the continuous rigorous environmental protection policies in recent years. Most coking companies have not yet achieved effective prevention and control of scorched furnace flue gas SO2 and NOX emissions. There is a certain gap in the regulations in the Emissions of Pollutants in Chemical Industry. Because the flue gas and coal -fired power plant flue gas in terms of flue gas temperature, SO2 and NOX contents are different, so the two ones of desulfurization and denitration treatment technology do not be exactly the same. Research and practice shows that there are certain problems in the selection of craftsmanship, localization of key catalysts, and stable systems in the selection of process routes, key catalysts, and system stable operation.
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1 The current status of SO2 and NOX emissions
according to statistics, 2015 nationwide SO2 The total amount of emissions is 18.591 million t, NOX total emissions are 18.518 million t. Coal coking is one of the main sources of pollution in the field of industrial coal. Coking furnace flue gas is the most important source of exhaust gas pollution in coking enterprises. About 60%of SO2 and 90%of NOX comes from this. The SO2 concentration in the furnace flue gas is closely related to the type of fuel, the shape of the sulfur element in the fuel, the content of the fuel oxygen, and the degree of leakage of the coke furnace charcoal chamber; Time is closely related. The process of coking furnace gas as the main fuel, the direct emission concentration of SO2 in its flue gas is about 160mg/m3, and the direct emission concentration of NOX is 600 ~ 900mg/m3 (up to 1000mg/m3 at the highest); Low thermal gas (or mixed gas) is the main fuel process. The direct emission concentration of SO2 in its flue gas is 40 ~ 150mg/m3, and NOX direct emission concentration is 300 ~ 600mg/m3. It can be seen that whether the concentration of the SO2 and NOX concentration in the flue gas is difficult to stabilize the standard limit of the standard limit, whether it is not governed.
With the increasing importance to environmental protection in the country, it is imperative to discharge flue gas standards in the coking sector. Since 2017, the "Application of Settlement License Application and Technology Specifications-Jiao Jiao Chemical Industry" will be implemented for the first time, which has put forward higher requirements for the discharge of pollutants in the focusing industry. As mentioned earlier, the main technical means of SO2 and NOX discharge of SO2 and NOX in the coke furnace flue gas are the terminal desulfurization and denitrification of the end. Advantages and disadvantages, summarize the common problems of domestic coke furnace flue gas desulfurization and denitration technology, in order to provide a reference for the choice and optimization of the choice and optimization of the coking industry desulfurization and denitration technology in my country.
2 Scorching furnace flue gas desulfurization and denitrification technology
At present, the governance process of the terminal of the end -end desulfurization and denitration of coke furnace flue gas can be divided into separate desulfurization, independent denitrification, desulfurization denitrification, denitrification degradation, dehydration degradation, dehydration degradation degradation degradation, dehydration degradation degradation degradation. Three categories such as integration.
2.1 desulfurization technology
According to the type and operating characteristics of desulfurization agent, flue gas desulfurization technology can usually be divided into wet, semi -dry and dry desulfurization. At present, there are many applications in the field of burnt furnace smoke desulfurization. The semi -dry desulfurization technology represents, and the application of dry desulfurization technology is relatively rare. Therefore, this article focuses on the wet method and semi -sulfur furnace flue gas desulfurization technology.
2.1.1 Wet desulfurization technology
1) ammonia method
The principle of ammonia desulfurization is SO2 and ammonia harvesters in coke furnace flue gas After contact, chemical reactions generate NH4HSO3 and (NH4) 2so3, (NH4) 2SO3 will generate NH4HSO3 with SO2; during the absorption process, the NH4HSO3 that does not have absorption of SO2 to SO2 will be converted to (NH4) 2so3, and (NH4) 2SO3, (NH4) 2so3, (NH4) 2so3, (NH4) 2so3, 2so3, (NH4) 2so3,, (NH4) 2so3, (NH4) 2SO3,, (NH4) 2so3. In order to use the continuous conversion of (NH4) 2SO3 and NH4HSO3 to absorb SO2; (NH4) 2SO3 2SO3 through oxidation, crystallization, filtering, and drying to obtain ammonium sulfate, thereby removing SO2.
This foster foam ammonia ammonia method can reach 95%~ 99%. The utilization rate of absorbers, high desulfurization efficiency, SO2 resource utilization, simple process and process structure, non -waste residue and exhaust emissions are the main advantages of this method; however Disadvantages such as expensive, high desulfurization costs, unable to remove heavy metals, and dual evils.
2) Lemon/lime
The lime/lime stone method desulfurization process has become the most application of smoke -gas desulfurization technology due to the advantages of abundant absorption resources and low cost. This process mainly uses calcium oxide or calcium carbonate jelly to absorb SO2 in a wet washing tower, that is, the flue gas in the absorption tower with the absorbent in the absorption tower and the sprayed absorbent reaction to generate CASO3. Gylatic gypsum. The efficiency of lime/limestone method of burnt furnace can generally reach more than 95%. The advantage of lime/limestone method is the high utilization rate of absorbers, strong coal adaptability, and desulfurization by -products for comprehensive utilization, mature technology, and reliable operation. The scaling is blocked, the flue gas carrying the slurry caused "gypsum rain", and the difficulty of treatment of desulfurization wastewater is the main deficiency.
3) Double alkali method
dual -alkali method, that is, different types of alkali in SO2 absorption and absorption solution treatment. As a absorbent absorption SO2, the salt clearing solution is used to generate NA2SO3 salt solution, and then uses lime (limestone) and NA2SO3 in the reaction tank to regenerate the absorption solution. Elected. Twin alkali furnace furnace smoke desulfurization efficiency can reach more than 90%. The dual -alkali desulfurization system generally does not produce precipitation, and the absorption tower does not produce blockage and wear; Difficulties, etc., are issues that this technology needs to be solved.
4) Magnesium oxide
Magone oxide desulfurization is a more mature technology, but due to the limited reserves of magnesium oxide resource and uneven distribution, the law is worldwide It is not widely used in it; and my country's magnesium oxide resources are abundant and have unique conditions for developing magnesium oxide desulfurization. This process is to generate MGSO3 crystals with magnesium oxide pulp as an absorbent absorption SO2, and then separates, dry, and baked the MGSO3 crystals, and MGSO3 decompose the regenerative magnesium oxide and return to the absorption system. Gas can be processed into products such as sulfuric acid or sulfur. This method can be more than 95%of the desulfurization efficiency. Magnetic oxide desulfurization technology is mature and reliable, with a wide range of applications, high recycling value of by -products, and no scaling, wear, and pipeline blockage; Magnesium sources are limited and MG2 in wastewater is difficult.
2.1.2 Semi -drying method
1) Spray drying method
The extremely small fog -shaped droplets, fog -shaped droplets and flue gas form a large contact surface area, a desulfurization method of calorie exchange, quality transmission, and chemical reactions between the two phases of the gas liquid. The absorbers used in this method are generally alkali, lime milk, lime slurry, etc. At present, most devices use lime milk as an absorbent. Under normal circumstances, the spray drying furnace flue gas desulfurization effect can reach about 85%. The advantage is that desulfurization is performed in the state of qi, liquid, and solidarity. The process equipment is simple, and the generics are CASO4 and CASO3 that is easy to handle. There is no serious equipment corrosion and blockage. The automation requirements are relatively high, the amount of absorbers is difficult to control, and the absorption efficiency needs to be improved. Therefore, choosing a reasonable absorbent is a new problem facing spray drying method.
2) Circular fluidization bed method
This is based on the principle of circulating fluidized beds, and the contact time of the absorption agent and flue gas by multiple cycles of the absorbent is extended. The absorption of SO2 through the turbulence of the bed layer has greatly improved the utilization rate and desulfurization efficiency of the absorbent. The advantage of this method is that the absorption tower and its downstream equipment will not produce phenomena such as adhesion, blockage and corrosion. It has high desulfurization efficiency, low operating costs, and less discharge of desulfurization by -products. However, the core technology and key equipment of this method rely on imports, and the cost is expensive, which limits its application promotion. Therefore, the research and development of local conditions has independent intellectual property rights, which is suitable for my country's national conditions, which is the focus of researchers' attention. In addition, the calcium sulfate content of calcium sulfate in this method is greater than the content of calcium sulfate, and in order to achieve the in order to achieve The high desulfurization rate has to be operated near the flue gas dew point, which has caused the enrichment of the absorbent in the reactor. This is also the aspect of the circulating fluidized bed desulfurization process.
2.1.3 Comparison of desulfurization technology commonly used in coke furnace flue gas
The comparison of scorching furnace flue gas is compared to Table 1.
2.2 Nitrile technology
At present, the commonly used denitration technology of scorched furnace flue gas mainly includes low -nitrogen combustion technology, low -temperature selective catalytic reduction (low temperature SCR) technology and oxidation denitrification technology Wait 3.
1) Low nitrogen combustion technology
low -nitrogen combustion technology refers to NOX -based mechanism to reduce the combustion conditions to reduce NOX emissions, thereby achieving NOX in the combustion process to NOX Control of generating amount. Coking furnace heating low nitrogen combustion technology mainly includes technologies such as flue gas recycling, coking furnace segmented heating, and actual combustion temperature control. The re -cycle of flue gas is currently the relatively common low -nitrogen combustion technology in the coking field. Most of the existing coke oven in my country adopt this technology. Research and practice shows that the appropriate control of flue gas cycle 32017 The 23rd of clean coal technology in the 6th of the 6th to 20%, if it exceeds 30%, it will reduce the combustion efficiency; 25%. The heating of coke oven segments is generally used to heat up with air and gas segments to reduce the combustion strength, thereby achieving the reduction of the production of thermal nitrogen oxides. The actual combustion temperature control technology is the coke furnace temperature control system independently developed by my country. This technology can optimize the coking furnace heating system, adjust the horizontal row temperature of the coke furnace, reduce the temperature of the fire furnace operation, avoid high temperature point, reduce the excess air of the focus furnace air, Coefficient, thereby reducing NOX generation. Theoretical calculation shows that if the coke oven uses the combination of flue gas recycling and segmented heating technology, the NOX emissions can be achieved below 500mg/m3; Control at about 600mg/m3.
2) Low -temperature SCR denitrification
Compared with the flue gas of the thermal power plant, the temperature of the furnace flue gas is relatively low, generally 170 ~ 280 ° C; for this feature, related my country related country The institution has developed a low -temperature SCR coke furnace flue denitration technology, and the denitration efficiency of this technology can reach more than 70%. The low -temperature SCR coke furnace flue gas denitration process is to spray a reducing agent such as ammonia or urea in a certain temperature of flue gas. The NOX reaction is generated to generate nitrogen and water, thereby achieving the effect of denitration.
low -temperature SCR flue gas denitration technology is currently relatively mature and reliable technology in coke furnace flue denitration technology. The denitration efficiency is high and easy to control. It is safe and reliable. ; Catalyst is the core issue restricting the development of low -temperature SCR denitration technology, reducing the degree of reliance on catalyst imports, preventing catalyst poisoning, and solving the secondary pollution caused by waste catalysts.
3) oxidation denim
O n oxidation denitration technology is to use a strong oxidant to oxidize NO into high -priced nitrogen oxides, and then use alkaline solution to spray absorption of denitrification; at present The oxidant applied in the coke furnace flue gas desulfurization and denitration measures is mainly ozone and hydrogen peroxide. This method has a small area and can remove other pollutants such as mercury at the same time. However, the process has a large consumption of oxidant, high operating costs, high energy consumption, high requirements for equipment materials, and prone to secondary pollution of ozone.
2.3 Desulfurization and denitration integrated technology
This of smoke -gas desulfurization and denitration integration technology has significant advantages in economics, resource utilization rate, etc., and has become the research and utilization in recent years point. The coke furnace flue gas desulfurization and denitration integrated technology is mainly concentrated in the active coke dehydration and denitration integrated technology and liquid catalytic oxidation method.
1) Activated coke dehydration and denitration integrated technology
The active coke dehydration and denitration integrated technology. And NOX and recover sulfur resource drying smoke treatment technology. The principle of desulfurization is based on the adsorption and catalytic effect of SO2 on the active focus surface. The SO2 in the flue gas is at 110 ~ 180 ° C. The oxygen and water vapor in the flue gas react in the flue gas. Using the catalytic characteristics of the active focus, a low -temperature selective catalytic reaction is adopted, and a small amount of NH3 is distributed in the flue gas to promote the NO's selective catalytic reaction to generate harmless N2 direct emissions.
This SO2 and NOX removal efficiency can reach more than 80%. Do not consume craft water, combined with multiple pollutants, recycling sulfur resource recycling, saving investment, etc. is the advantages of coking furnace flue gas active scorching and dehydration and denitration technology; and this process route also has large active focus loss, spray ammonia causes pipelines to cause pipelines Disadvantages such as blocking and slow desulfurization rate have hindered its industrial promotion and application to a certain extent.
2) liquid catalytic oxidation method desulfurization and dehydration technology
icidal catalytic oxidation method (LCO) desulfurization and denitration technology refers With NOX continuously oxidized into sulfuric acid and nitric acid, then reacts with the addition of alkaline substances (such as ammonia, etc.) and quickly generate ammonium sulfate and ammonium nitrate. Coke furnace flue gas liquid catalytic oxidation method SO2 and NOX removal efficiency can reach 90%and 70%, respectively. The advantages of high efficiency of sulfur nitritan dehydration, no secondary pollution, and wide range of smoke temperature adaptation have made the coke furnace flue gas liquid catalytic oxidation and decar sulfur decreasing technology have a good promotion prospect; however The problems such as the loss of organic catalyst loss and equipment corrosion are still the difficulty of liquid catalytic oxidative desulfurization and denitration technology.
2.4 The current problems of the existence of scorched furnace flue gas desulfurization and denitrification technology
1) Selection of separate desulfurization and indexing combinations
according to process conditions Requirements must be carried out at high temperatures, and desulfurization must be performed at low temperature. If you choose to decaphically nitrate first and then decrease after desulfurization, you need to increase the smoke temperature from 80 ° C to more than 200 ° C before entering the denitration process, which will cause energy waste and increase corporate costs. Under the action of denitration catalysts, SO2 in flue gas is partially catalyzed to SO3, and the generated SO3 reacts with the escape NH3 and water vapor to generate ammonium sulfate. The ammonium sulfate has viscosity and corrosion, which will cause renuct catalysts and downstream equipment to cause Covering and corrosion affects the denitration effect and the service life of the equipment.
2) The problem of flue gas emissions after the furnace flue gas desulfurization and denitration
After the furnace flue gas can be discharged by the chimney directly through the desulfurization and denitrification device, it can There are two ways to discharge the chimneys of coke. If you choose to discharge directly through the chimney through the desulfurization and denitration device, when a power outage accident occurs, the flue gas must be discharged through the coke furnace chimney, and the coke oven chimney is not used for a long time. Eatsses, which causes safety accidents such as explosion; if the flue gas after desulfurization and denitrification, if the flue gas is selected to discharge through the coke furnace chimney, the current low temperature will not suck the chimney in low temperature due to the current decorative process of desulfurization and denitration. Difficulty in smoking, which causes the system resistance and chimney corrosion, which is not conducive to the stability of the entire production and purification system, and even causes safety accidents.
3) The problem of secondary contamination after the furnace flue gas desulfurization dehydration
This flue gas may produce the following pollution after decontamination and denitration A large amount of water vapor in the air and the floating microorganisms floating in the air form gas solution, which eventually leads to the occurrence of haze weather; ② ammonia desulfurization process has the problem of ammonia from volatilization and escape; ③ At present, the market prospects and sales circuits of desulfurization by -products are not Smooth, a large amount of pollution environment will be stacked; ④ The current desulfurization and denitration catalysts are mostly rigid or titanium systems. After replacement, the catalysts used have become harsh waste. If the management is improperly managed during transportation and treatment, it is easy to cause pollution.
3 Conclusion and Suggestion
1) The control of furnace furnace flue gas pollution must be effectively integrated, low nitrogen combustion, and end purification of the end; : Enterprises with conditions should use the mix of blast furnace gas or blast furnace gas and coke furnace gas as heating fuels to control the production of pollutants from the source, so as to reduce the difficulty of processing the subsequent purification system; The hydrogen sulfide and hydrogen cyanide in the furnace gas are removed as much as possible to reduce the sulfur oxide produced when the coke furnace gas is burned.
2) Strengthening the operation and management of coke oven, which has a positive role in controlling pollutant emissions. For example, by strengthening the maintenance of the furnace body, it can effectively control the leakage of the furnace. The room causes excessive standards for furnace flue gas pollutants; therefore, coking enterprises should pay attention to and adopt reliable means to strengthen the operation and management of coke oven to achieve the multiple benefits of controlling pollutant emissions, extending the life of the coking furnace, and maintaining the quality of the product.
3) The burning temperature of the flue gas has an important impact on the production of nitrogen oxides. The application of applicable low -nitrogen combustion technology can be taken from the source control pollutants; The heating method such as Qi re -circulation controls the temperature of the combustion chamber, thereby inhibiting the production of nitrogen oxides to reduce the difficulty of purifying the subsequent denitration system.
Abstract
The main influencing factors of the current status of SO2 and NOX emission and pollutants in my country's coking industry. Compared with the ammonia, limestone/limestone method, bisodium alkali method, magnesium oxide method, spray drying method , Curring -Delicate bed method, coke furnace flue gas desulfurization technology represented by low -nitrogen combustion technology, low -temperature selective catalytic reduction denitration technology, oxidation denitrification, etc. The technical principles, desulfurization and denitration efficiency, and their respective advantages and disadvantages of coke furnace flue gas desulfurization and denitration integrated technology, summarize the existence of coke furnace flue gas desulfurization and denitration technology in terms of process route selection, flue gas emissions, secondary pollution, etc. The problem. It is pointed out that the treatment of furnace flue gas pollution must effectively integrate the source control of the source, low nitrogen combustion, and end purification, and continuously strengthen the application of coke oven operation management level and new technologies.
This
The environmental pollution such as SO2 and NOX in coal -fired flue gas has seriously affected human survival and development. At present, the most effective and most widely used coal -fired flue gas SO2 and NOX pollution control measures are the technology of smoke dehydration and denitration after burning. As the second largest in the country in China, my country's coal coking consumption of about 1 billion T year, accounting for about 1/3 of the country's total coal consumption. At present, the development and application of gas desulfurization and denitration technology in the field of coal -fired power generation are relatively mature. Most coal power enterprises SO2 and NOX emissions have reached over -net standard 12017 The 23rd volume of clean coal technology in the 6th of the 6th. But as a traditional coal chemical industry, The development of my country's coking field is relatively extensive, and pollutant governance measures have been forced to implement under the continuous rigorous environmental protection policies in recent years. Most coking companies have not yet achieved effective prevention and control of scorched furnace flue gas SO2 and NOX emissions. There is a certain gap in the regulations in the Emissions of Pollutants in Chemical Industry. Because the flue gas and coal -fired power plant flue gas in terms of flue gas temperature, SO2 and NOX contents are different, so the two ones of desulfurization and denitration treatment technology do not be exactly the same. Research and practice shows that there are certain problems in the selection of craftsmanship, localization of key catalysts, and stable systems in the selection of process routes, key catalysts, and system stable operation.
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This
1 The current status of SO2 and NOX emissions
according to statistics, 2015 nationwide SO2 The total amount of emissions is 18.591 million t, NOX total emissions are 18.518 million t. Coal coking is one of the main sources of pollution in the field of industrial coal. Coking furnace flue gas is the most important source of exhaust gas pollution in coking enterprises. About 60%of SO2 and 90%of NOX comes from this. The SO2 concentration in the furnace flue gas is closely related to the type of fuel, the shape of the sulfur element in the fuel, the content of the fuel oxygen, and the degree of leakage of the coke furnace charcoal chamber; Time is closely related. The process of coking furnace gas as the main fuel, the direct emission concentration of SO2 in its flue gas is about 160mg/m3, and the direct emission concentration of NOX is 600 ~ 900mg/m3 (up to 1000mg/m3 at the highest); Low thermal gas (or mixed gas) is the main fuel process. The direct emission concentration of SO2 in its flue gas is 40 ~ 150mg/m3, and NOX direct emission concentration is 300 ~ 600mg/m3. It can be seen that whether the concentration of the SO2 and NOX concentration in the flue gas is difficult to stabilize the standard limit of the standard limit, whether it is not governed.
With the increasing importance to environmental protection in the country, it is imperative to discharge flue gas standards in the coking sector. Since 2017, the "Application of Settlement License Application and Technology Specifications-Jiao Jiao Chemical Industry" will be implemented for the first time, which has put forward higher requirements for the discharge of pollutants in the focusing industry. As mentioned earlier, the main technical means of SO2 and NOX discharge of SO2 and NOX in the coke furnace flue gas are the terminal desulfurization and denitrification of the end. Advantages and disadvantages, summarize the common problems of domestic coke furnace flue gas desulfurization and denitration technology, in order to provide a reference for the choice and optimization of the choice and optimization of the coking industry desulfurization and denitration technology in my country.
2 Scorching furnace flue gas desulfurization and denitrification technology
At present, the governance process of the terminal of the end -end desulfurization and denitration of coke furnace flue gas can be divided into separate desulfurization, independent denitrification, desulfurization denitrification, denitrification degradation, dehydration degradation, dehydration degradation degradation degradation, dehydration degradation degradation degradation. Three categories such as integration.
2.1 desulfurization technology
According to the type and operating characteristics of desulfurization agent, flue gas desulfurization technology can usually be divided into wet, semi -dry and dry desulfurization. At present, there are many applications in the field of burnt furnace smoke desulfurization. The semi -dry desulfurization technology represents, and the application of dry desulfurization technology is relatively rare. Therefore, this article focuses on the wet method and semi -sulfur furnace flue gas desulfurization technology.
2.1.1 Wet desulfurization technology
1) ammonia method
The principle of ammonia desulfurization is SO2 and ammonia harvesters in coke furnace flue gas After contact, chemical reactions generate NH4HSO3 and (NH4) 2so3, (NH4) 2SO3 will generate NH4HSO3 with SO2; during the absorption process, the NH4HSO3 that does not have absorption of SO2 to SO2 will be converted to (NH4) 2so3, and (NH4) 2SO3, (NH4) 2so3, (NH4) 2so3, (NH4) 2so3, 2so3, (NH4) 2so3,, (NH4) 2so3, (NH4) 2SO3,, (NH4) 2so3. In order to use the continuous conversion of (NH4) 2SO3 and NH4HSO3 to absorb SO2; (NH4) 2SO3 2SO3 through oxidation, crystallization, filtering, and drying to obtain ammonium sulfate, thereby removing SO2.
This foster foam ammonia ammonia method can reach 95%~ 99%. The utilization rate of absorbers, high desulfurization efficiency, SO2 resource utilization, simple process and process structure, non -waste residue and exhaust emissions are the main advantages of this method; however Disadvantages such as expensive, high desulfurization costs, unable to remove heavy metals, and dual evils.
2) Lemon/lime
The lime/lime stone method desulfurization process has become the most application of smoke -gas desulfurization technology due to the advantages of abundant absorption resources and low cost. This process mainly uses calcium oxide or calcium carbonate jelly to absorb SO2 in a wet washing tower, that is, the flue gas in the absorption tower with the absorbent in the absorption tower and the sprayed absorbent reaction to generate CASO3. Gylatic gypsum. The efficiency of lime/limestone method of burnt furnace can generally reach more than 95%. The advantage of lime/limestone method is the high utilization rate of absorbers, strong coal adaptability, and desulfurization by -products for comprehensive utilization, mature technology, and reliable operation. The scaling is blocked, the flue gas carrying the slurry caused "gypsum rain", and the difficulty of treatment of desulfurization wastewater is the main deficiency.
3) Double alkali method
dual -alkali method, that is, different types of alkali in SO2 absorption and absorption solution treatment. As a absorbent absorption SO2, the salt clearing solution is used to generate NA2SO3 salt solution, and then uses lime (limestone) and NA2SO3 in the reaction tank to regenerate the absorption solution. Elected. Twin alkali furnace furnace smoke desulfurization efficiency can reach more than 90%. The dual -alkali desulfurization system generally does not produce precipitation, and the absorption tower does not produce blockage and wear; Difficulties, etc., are issues that this technology needs to be solved.
4) Magnesium oxide
Magone oxide desulfurization is a more mature technology, but due to the limited reserves of magnesium oxide resource and uneven distribution, the law is worldwide It is not widely used in it; and my country's magnesium oxide resources are abundant and have unique conditions for developing magnesium oxide desulfurization. This process is to generate MGSO3 crystals with magnesium oxide pulp as an absorbent absorption SO2, and then separates, dry, and baked the MGSO3 crystals, and MGSO3 decompose the regenerative magnesium oxide and return to the absorption system. Gas can be processed into products such as sulfuric acid or sulfur. This method can be more than 95%of the desulfurization efficiency. Magnetic oxide desulfurization technology is mature and reliable, with a wide range of applications, high recycling value of by -products, and no scaling, wear, and pipeline blockage; Magnesium sources are limited and MG2 in wastewater is difficult.
2.1.2 Semi -drying method
1) Spray drying method
The extremely small fog -shaped droplets, fog -shaped droplets and flue gas form a large contact surface area, a desulfurization method of calorie exchange, quality transmission, and chemical reactions between the two phases of the gas liquid. The absorbers used in this method are generally alkali, lime milk, lime slurry, etc. At present, most devices use lime milk as an absorbent. Under normal circumstances, the spray drying furnace flue gas desulfurization effect can reach about 85%. The advantage is that desulfurization is performed in the state of qi, liquid, and solidarity. The process equipment is simple, and the generics are CASO4 and CASO3 that is easy to handle. There is no serious equipment corrosion and blockage. The automation requirements are relatively high, the amount of absorbers is difficult to control, and the absorption efficiency needs to be improved. Therefore, choosing a reasonable absorbent is a new problem facing spray drying method.
2) Circular fluidization bed method
This is based on the principle of circulating fluidized beds, and the contact time of the absorption agent and flue gas by multiple cycles of the absorbent is extended. The absorption of SO2 through the turbulence of the bed layer has greatly improved the utilization rate and desulfurization efficiency of the absorbent. The advantage of this method is that the absorption tower and its downstream equipment will not produce phenomena such as adhesion, blockage and corrosion. It has high desulfurization efficiency, low operating costs, and less discharge of desulfurization by -products. However, the core technology and key equipment of this method rely on imports, and the cost is expensive, which limits its application promotion. Therefore, the research and development of local conditions has independent intellectual property rights, which is suitable for my country's national conditions, which is the focus of researchers' attention. In addition, the calcium sulfate content of calcium sulfate in this method is greater than the content of calcium sulfate, and in order to achieve the in order to achieve The high desulfurization rate has to be operated near the flue gas dew point, which has caused the enrichment of the absorbent in the reactor. This is also the aspect of the circulating fluidized bed desulfurization process.
2.1.3 Comparison of desulfurization technology commonly used in coke furnace flue gas
The comparison of scorching furnace flue gas is compared to Table 1.
2.2 Nitrile technology
At present, the commonly used denitration technology of scorched furnace flue gas mainly includes low -nitrogen combustion technology, low -temperature selective catalytic reduction (low temperature SCR) technology and oxidation denitrification technology Wait 3.
1) Low nitrogen combustion technology
low -nitrogen combustion technology refers to NOX -based mechanism to reduce the combustion conditions to reduce NOX emissions, thereby achieving NOX in the combustion process to NOX Control of generating amount. Coking furnace heating low nitrogen combustion technology mainly includes technologies such as flue gas recycling, coking furnace segmented heating, and actual combustion temperature control. The re -cycle of flue gas is currently the relatively common low -nitrogen combustion technology in the coking field. Most of the existing coke oven in my country adopt this technology. Research and practice shows that the appropriate control of flue gas cycle 32017 The 23rd of clean coal technology in the 6th of the 6th to 20%, if it exceeds 30%, it will reduce the combustion efficiency; 25%. The heating of coke oven segments is generally used to heat up with air and gas segments to reduce the combustion strength, thereby achieving the reduction of the production of thermal nitrogen oxides. The actual combustion temperature control technology is the coke furnace temperature control system independently developed by my country. This technology can optimize the coking furnace heating system, adjust the horizontal row temperature of the coke furnace, reduce the temperature of the fire furnace operation, avoid high temperature point, reduce the excess air of the focus furnace air, Coefficient, thereby reducing NOX generation. Theoretical calculation shows that if the coke oven uses the combination of flue gas recycling and segmented heating technology, the NOX emissions can be achieved below 500mg/m3; Control at about 600mg/m3.
2) Low -temperature SCR denitrification
Compared with the flue gas of the thermal power plant, the temperature of the furnace flue gas is relatively low, generally 170 ~ 280 ° C; for this feature, related my country related country The institution has developed a low -temperature SCR coke furnace flue denitration technology, and the denitration efficiency of this technology can reach more than 70%. The low -temperature SCR coke furnace flue gas denitration process is to spray a reducing agent such as ammonia or urea in a certain temperature of flue gas. The NOX reaction is generated to generate nitrogen and water, thereby achieving the effect of denitration.
low -temperature SCR flue gas denitration technology is currently relatively mature and reliable technology in coke furnace flue denitration technology. The denitration efficiency is high and easy to control. It is safe and reliable. ; Catalyst is the core issue restricting the development of low -temperature SCR denitration technology, reducing the degree of reliance on catalyst imports, preventing catalyst poisoning, and solving the secondary pollution caused by waste catalysts.
3) oxidation denim
O n oxidation denitration technology is to use a strong oxidant to oxidize NO into high -priced nitrogen oxides, and then use alkaline solution to spray absorption of denitrification; at present The oxidant applied in the coke furnace flue gas desulfurization and denitration measures is mainly ozone and hydrogen peroxide. This method has a small area and can remove other pollutants such as mercury at the same time. However, the process has a large consumption of oxidant, high operating costs, high energy consumption, high requirements for equipment materials, and prone to secondary pollution of ozone.
2.3 Desulfurization and denitration integrated technology
This of smoke -gas desulfurization and denitration integration technology has significant advantages in economics, resource utilization rate, etc., and has become the research and utilization in recent years point. The coke furnace flue gas desulfurization and denitration integrated technology is mainly concentrated in the active coke dehydration and denitration integrated technology and liquid catalytic oxidation method.
1) Activated coke dehydration and denitration integrated technology
The active coke dehydration and denitration integrated technology. And NOX and recover sulfur resource drying smoke treatment technology. The principle of desulfurization is based on the adsorption and catalytic effect of SO2 on the active focus surface. The SO2 in the flue gas is at 110 ~ 180 ° C. The oxygen and water vapor in the flue gas react in the flue gas. Using the catalytic characteristics of the active focus, a low -temperature selective catalytic reaction is adopted, and a small amount of NH3 is distributed in the flue gas to promote the NO's selective catalytic reaction to generate harmless N2 direct emissions.
This SO2 and NOX removal efficiency can reach more than 80%. Do not consume craft water, combined with multiple pollutants, recycling sulfur resource recycling, saving investment, etc. is the advantages of coking furnace flue gas active scorching and dehydration and denitration technology; and this process route also has large active focus loss, spray ammonia causes pipelines to cause pipelines Disadvantages such as blocking and slow desulfurization rate have hindered its industrial promotion and application to a certain extent.
2) liquid catalytic oxidation method desulfurization and dehydration technology
icidal catalytic oxidation method (LCO) desulfurization and denitration technology refers With NOX continuously oxidized into sulfuric acid and nitric acid, then reacts with the addition of alkaline substances (such as ammonia, etc.) and quickly generate ammonium sulfate and ammonium nitrate. Coke furnace flue gas liquid catalytic oxidation method SO2 and NOX removal efficiency can reach 90%and 70%, respectively. The advantages of high efficiency of sulfur nitritan dehydration, no secondary pollution, and wide range of smoke temperature adaptation have made the coke furnace flue gas liquid catalytic oxidation and decar sulfur decreasing technology have a good promotion prospect; however The problems such as the loss of organic catalyst loss and equipment corrosion are still the difficulty of liquid catalytic oxidative desulfurization and denitration technology.
2.4 The current problems of the existence of scorched furnace flue gas desulfurization and denitrification technology
1) Selection of separate desulfurization and indexing combinations
according to process conditions Requirements must be carried out at high temperatures, and desulfurization must be performed at low temperature. If you choose to decaphically nitrate first and then decrease after desulfurization, you need to increase the smoke temperature from 80 ° C to more than 200 ° C before entering the denitration process, which will cause energy waste and increase corporate costs. Under the action of denitration catalysts, SO2 in flue gas is partially catalyzed to SO3, and the generated SO3 reacts with the escape NH3 and water vapor to generate ammonium sulfate. The ammonium sulfate has viscosity and corrosion, which will cause renuct catalysts and downstream equipment to cause Covering and corrosion affects the denitration effect and the service life of the equipment.
2) The problem of flue gas emissions after the furnace flue gas desulfurization and denitration
After the furnace flue gas can be discharged by the chimney directly through the desulfurization and denitrification device, it can There are two ways to discharge the chimneys of coke. If you choose to discharge directly through the chimney through the desulfurization and denitration device, when a power outage accident occurs, the flue gas must be discharged through the coke furnace chimney, and the coke oven chimney is not used for a long time. Eatsses, which causes safety accidents such as explosion; if the flue gas after desulfurization and denitrification, if the flue gas is selected to discharge through the coke furnace chimney, the current low temperature will not suck the chimney in low temperature due to the current decorative process of desulfurization and denitration. Difficulty in smoking, which causes the system resistance and chimney corrosion, which is not conducive to the stability of the entire production and purification system, and even causes safety accidents.
3) The problem of secondary contamination after the furnace flue gas desulfurization dehydration
This flue gas may produce the following pollution after decontamination and denitration A large amount of water vapor in the air and the floating microorganisms floating in the air form gas solution, which eventually leads to the occurrence of haze weather; ② ammonia desulfurization process has the problem of ammonia from volatilization and escape; ③ At present, the market prospects and sales circuits of desulfurization by -products are not Smooth, a large amount of pollution environment will be stacked; ④ The current desulfurization and denitration catalysts are mostly rigid or titanium systems. After replacement, the catalysts used have become harsh waste. If the management is improperly managed during transportation and treatment, it is easy to cause pollution.
3 Conclusion and Suggestion
1) The control of furnace furnace flue gas pollution must be effectively integrated, low nitrogen combustion, and end purification of the end; : Enterprises with conditions should use the mix of blast furnace gas or blast furnace gas and coke furnace gas as heating fuels to control the production of pollutants from the source, so as to reduce the difficulty of processing the subsequent purification system; The hydrogen sulfide and hydrogen cyanide in the furnace gas are removed as much as possible to reduce the sulfur oxide produced when the coke furnace gas is burned.
2) Strengthening the operation and management of coke oven, which has a positive role in controlling pollutant emissions. For example, by strengthening the maintenance of the furnace body, it can effectively control the leakage of the furnace. The room causes excessive standards for furnace flue gas pollutants; therefore, coking enterprises should pay attention to and adopt reliable means to strengthen the operation and management of coke oven to achieve the multiple benefits of controlling pollutant emissions, extending the life of the coking furnace, and maintaining the quality of the product.
3) The burning temperature of the flue gas has an important impact on the production of nitrogen oxides. The application of applicable low -nitrogen combustion technology can be taken from the source control pollutants; The heating method such as Qi re -circulation controls the temperature of the combustion chamber, thereby inhibiting the production of nitrogen oxides to reduce the difficulty of purifying the subsequent denitration system.