Iron and steel enterprises are enterprises that consume a lot of energy. During the production process of iron and steel enterprises, while consuming a large amount of energy such as coal, fuel oil and electricity, they also produce a large amount of blast furnace gas. However, the incombustible inert gases (N2 and CO, etc.) in the blast furnace gas account for about 75%, the combustible components (CO and H2) are only about 25%, and the low calorific value is extremely low (3 050 ~ 3 470kJ/Nm3), which is quite 60% of general producer gas, 44% of converter gas, 17% of coke oven gas, 9% of natural gas, and 3% of liquefied petroleum gas. Due to the low calorific value, narrow flammable range, low combustion temperature, and unstable pressure and combustion, the flame is prone to pulsation and fire off. ?
In addition to being used as fuel in blast furnace hot blast stoves in my country's early blast furnaces, most of them were burned in vain, and the gas emission rate reached 40% to 60%. The emission rate of major iron and steel enterprises in the country is above 10%, and the annual energy consumption loss amounts to billions of yuan. After the 1980s, people had a new understanding of blast furnace gas. For example, blast furnace gas began to be used for co-firing with coal and coke oven gas to produce steam, and mixed with coke oven gas and converter gas to be used as fuel for steel rolling furnaces. Although Most of the blast furnace gas has been utilized, but no breakthrough has been made. Co-combustion, blast furnace gas will compete with solid coal powder and coke oven gas with long molecular chains for oxygen, so that the coal powder cannot be burned out well, and coke oven gas is still burning until the top of the furnace or the flue mouth. The cost of consuming high-quality fuel is high, and it also causes a waste of energy in disguise. Moreover, with the large-scale iron-making blast furnace and the development of domestic iron-making situation in recent years, the production of blast furnace gas has doubled, and the capacity and energy utilization of small-scale mixed-fired blast furnace gas boilers are far from being able to adapt to the needs of the domestic iron and steel industry. development situation. In recent years, at the same time, China has started to independently develop and introduce foreign full-fired blast furnace gas power generation technology. For example, Shougang's full-fired blast furnace gas 50MW power generation unit was built in 1993 and put into operation at the end of 1996; Baosteel's 145MW full-fired blast furnace gas power generation It was completed and put into operation at the end of the month (at that time it was the largest and most advanced blast furnace gas power generation technology in the world); at the same time, due to the country's strong support for energy-saving and emission-reduction technologies, and stricter emission standards for pollutants, many iron and steel enterprises The transformation of coal-fired boilers to blast furnace gas was carried out, such as: No. 4 boiler of Baotou Thermal Power Plant was converted to blast furnace gas, and the 75t/h pulverized coal boiler of Xiangyang Iron and Steel Thermal Power Plant was converted to blast furnace gas. So far, the effective and efficient utilization of blast furnace gas has made a breakthrough. ?
In the transformation process of coal-fired boilers to burn blast furnace gas, because the boiler fuel is changed from solid coal to gas blast furnace gas, the calorific value is greatly reduced, and the content of CO2 and N2 in the gas is large, which do not participate in the generation of heat, and cannot Combustion, on the contrary, absorbs a large amount of heat, so a large amount of heat is transferred to the flue gas, so that the amount of flue gas generated by burning blast furnace gas is much larger than that generated by burning coal; the laminar flame propagation speed of general gas is about 0.3 ～0.8m/s, while the flame propagation speed of blast furnace gas is low, the flame stability range is narrow, and its theoretical combustion temperature is low, about 1 149 ℃, so it is difficult to ignite. If the blast furnace gas entering the boiler cannot be ignited quickly, it may It is very dangerous to cause boiler explosion. Therefore, in the transformation process, on the one hand, in order to ensure the output of the boiler, on the other hand, ensure the stability of combustion. In addition to the calculation and selection of the transformation of the furnace and heating surface, the selection and transformation of the burner is also a very important part. ?
At present, the commonly used burner transformation technologies in our country are as follows:
1 Using a blunt body burner with a pre-combustion chamber?
The blast furnace gas burner is replaced with a slotted blunt body burner with a pre-combustion chamber, so that the blast furnace gas with low calorific value can be ignited quickly and stably, and burned efficiently. . The large tangential circle arrangement can further strengthen the direct washing of the flue gas on the water-cooled wall tubes, and increase the convective heat absorption of the water-cooled walls. In this way, there is a 75t/h boiler reformed by Xiangyang Iron and Steel Thermal Power Plant. ?
2 The adiabatic furnace is adopted, and the front and rear walls of the swirl burner are arranged together.
This technology adopts the largest adiabatic chamber furnace in China pioneered by Wuxi Boiler Factory, and the front and rear walls of the swirling burner are arranged. In order to ensure the stable combustion of blast furnace gas during the transformation, a heat storage and stable combustion chamber (using refractory materials and no water wall) was added to the original cold ash hopper to reduce the evaporation and heating surface of the original furnace. At the same time, in order to make the blast furnace gas pressure of each burner consistent, on the basis of conditions, an automatic regulating valve is installed on the burner or a regulating valve is installed on the gas pipeline. In this way, there is a 130t/h medium-temperature and medium-pressure boiler transformed by Baotou Steel Thermal Power Plant [2]. ?
3 Furnace stable combustion column technology?
This transformation technology greatly increases the heating area of the furnace by removing the cold ash hopper of the original boiler and straightening the water wall. In order to make the blast furnace gas burn stably in the furnace, a chimney-shaped, high-alumina refractory brick material is built in the center of the furnace for stable combustion. bring. When igniting, slowly absorb heat to increase the temperature of the stable combustion column. It is required that during operation, its temperature reaches above 1000°C. The existence of the stable combustion column improves the level of the temperature field in the burner area, making the gas burn faster and more completely, releasing more heat in a smaller area, and further increasing the temperature until it is balanced in the high temperature field Down. At the same time, the water-cooled wall absorbs more heat, and the imaginary tangent circle of the flame is tangent to the heat storage and combustion stabilization device. The unburned gas passes over the outer surface of the combustion stabilization device, and the high temperature further heats the gas to make it burn clean. In addition, the large tangential combustion increases the heat absorption of the water wall. In this way, there is a 220t/h high-temperature and high-pressure boiler transformed by Baotou Steel [3]. ?
4 Flameless burners?
In order to further reduce the volume of the combustion equipment and increase the volume heat load of the furnace, and consider the two factors of convenient operation and the number of burners, a premixed flameless burner has been developed, which is a general premixed combustible gas flow A section of porous refractory filler layer with a large volumetric heat load is installed at the outlet of the premixed burner. When the premixed gas passes through the pores of the packing layer, it is divided into many strands and burns, so that the refractory material can be kept at a high temperature, and the premixed gas can be reliably ignited quickly. Basically, no flame can be seen, or only a short flame can be seen, so it becomes a "flameless burner". Using this kind of burner can shorten the flame length when burning blast furnace gas, and at the same time, it can be used at the outlet of the premixing tube. Installing a cooling water jacket keeps the temperature of the steel pipe at a lower value and reduces the occurrence of tempering. ?
It can be seen from this that in the process of transforming coal-fired boilers into blast furnace gas, the choice of burners can be varied. Which method to use in practice should consider many factors including the cooperation between the burner and the heating surface, the limitations of the original furnace type, etc., and then make a decision after performing thermal check calculations on the boiler and the modified furnace type. It is more helpful for the transformation design to analyze the flow field after transformation through numerical simulation calculation conditionally.
Iron and steel enterprises are enterprises that consume a lot of energy. During the production process of iron and steel enterprises, while consuming a large amount of energy such as coal, fuel oil and electricity, they also produce a large amount of blast furnace gas. However, the incombustible inert gases (N2 and CO, etc.) in the blast furnace gas account for about 75%, the combustible components (CO and H2) are only about 25%, and the low calorific value is extremely low (3 050 ~ 3 470kJ/Nm3), which is quite 60% of general producer gas, 44% of converter gas, 17% of coke oven gas, 9% of natural gas, and 3% of liquefied petroleum gas. Due to the low calorific value, narrow flammable range, low combustion temperature, and unstable pressure and combustion, the flame is prone to pulsation and fire off. ?
In addition to being used as fuel in blast furnace hot blast stoves in my country's early blast furnaces, most of them were burned in vain, and the gas emission rate reached 40% to 60%. The emission rate of major iron and steel enterprises in the country is above 10%, and the annual energy consumption loss amounts to billions of yuan. After the 1980s, people had a new understanding of blast furnace gas. For example, blast furnace gas began to be used for co-firing with coal and coke oven gas to produce steam, and mixed with coke oven gas and converter gas to be used as fuel for steel rolling furnaces. Although Most of the blast furnace gas has been utilized, but no breakthrough has been made. Co-combustion, blast furnace gas will compete with solid coal powder and coke oven gas with long molecular chains for oxygen, so that the coal powder cannot be burned out well, and coke oven gas is still burning until the top of the furnace or the flue mouth. The cost of consuming high-quality fuel is high, and it also causes a waste of energy in disguise. Moreover, with the large-scale iron-making blast furnace and the development of domestic iron-making situation in recent years, the production of blast furnace gas has doubled, and the capacity and energy utilization of small-scale mixed-fired blast furnace gas boilers are far from being able to adapt to the needs of the domestic iron and steel industry. development situation. In recent years, at the same time, China has started to independently develop and introduce foreign full-fired blast furnace gas power generation technology. For example, Shougang's full-fired blast furnace gas 50MW power generation unit was built in 1993 and put into operation at the end of 1996; Baosteel's 145MW full-fired blast furnace gas power generation It was completed and put into operation at the end of the month (at that time it was the largest and most advanced blast furnace gas power generation technology in the world); at the same time, due to the country's strong support for energy-saving and emission-reduction technologies, and stricter emission standards for pollutants, many iron and steel enterprises The transformation of coal-fired boilers to blast furnace gas was carried out, such as: No. 4 boiler of Baotou Thermal Power Plant was converted to blast furnace gas, and the 75t/h pulverized coal boiler of Xiangyang Iron and Steel Thermal Power Plant was converted to blast furnace gas. So far, the effective and efficient utilization of blast furnace gas has made a breakthrough. ?
In the transformation process of coal-fired boilers to burn blast furnace gas, because the boiler fuel is changed from solid coal to gas blast furnace gas, the calorific value is greatly reduced, and the content of CO2 and N2 in the gas is large, which do not participate in the generation of heat, and cannot Combustion, on the contrary, absorbs a large amount of heat, so a large amount of heat is transferred to the flue gas, so that the amount of flue gas generated by burning blast furnace gas is much larger than that generated by burning coal; the laminar flame propagation speed of general gas is about 0.3 ～0.8m/s, while the flame propagation speed of blast furnace gas is low, the flame stability range is narrow, and its theoretical combustion temperature is low, about 1 149 ℃, so it is difficult to ignite. If the blast furnace gas entering the boiler cannot be ignited quickly, it may It is very dangerous to cause boiler explosion. Therefore, in the transformation process, on the one hand, in order to ensure the output of the boiler, on the other hand, ensure the stability of combustion. In addition to the calculation and selection of the transformation of the furnace and heating surface, the selection and transformation of the burner is also a very important part. ?
At present, the commonly used burner transformation technologies in our country are as follows:
1 Using a blunt body burner with a pre-combustion chamber?
The blast furnace gas burner is replaced with a slotted blunt body burner with a pre-combustion chamber, so that the blast furnace gas with low calorific value can be ignited quickly and stably, and burned efficiently. . The large tangential circle arrangement can further strengthen the direct washing of the flue gas on the water-cooled wall tubes, and increase the convective heat absorption of the water-cooled walls. In this way, there is a 75t/h boiler reformed by Xiangyang Iron and Steel Thermal Power Plant. ?
2 The adiabatic furnace is adopted, and the front and rear walls of the swirl burner are arranged together.
This technology adopts the largest adiabatic chamber furnace in China pioneered by Wuxi Boiler Factory, and the front and rear walls of the swirling burner are arranged. In order to ensure the stable combustion of blast furnace gas during the transformation, a heat storage and stable combustion chamber (using refractory materials and no water wall) was added to the original cold ash hopper to reduce the evaporation and heating surface of the original furnace. At the same time, in order to make the blast furnace gas pressure of each burner consistent, on the basis of conditions, an automatic regulating valve is installed on the burner or a regulating valve is installed on the gas pipeline. In this way, there is a 130t/h medium-temperature and medium-pressure boiler transformed by Baotou Steel Thermal Power Plant [2]. ?
3 Furnace stable combustion column technology?
This transformation technology greatly increases the heating area of the furnace by removing the cold ash hopper of the original boiler and straightening the water wall. In order to make the blast furnace gas burn stably in the furnace, a chimney-shaped, high-alumina refractory brick material is built in the center of the furnace for stable combustion. bring. When igniting, slowly absorb heat to increase the temperature of the stable combustion column. It is required that during operation, its temperature reaches above 1000°C. The existence of the stable combustion column improves the level of the temperature field in the burner area, making the gas burn faster and more completely, releasing more heat in a smaller area, and further increasing the temperature until it is balanced in the high temperature field Down. At the same time, the water-cooled wall absorbs more heat, and the imaginary tangent circle of the flame is tangent to the heat storage and combustion stabilization device. The unburned gas passes over the outer surface of the combustion stabilization device, and the high temperature further heats the gas to make it burn clean. In addition, the large tangential combustion increases the heat absorption of the water wall. In this way, there is a 220t/h high-temperature and high-pressure boiler transformed by Baotou Steel [3]. ?
4 Flameless burners?
In order to further reduce the volume of the combustion equipment and increase the volume heat load of the furnace, and consider the two factors of convenient operation and the number of burners, a premixed flameless burner has been developed, which is a general premixed combustible gas flow A section of porous refractory filler layer with a large volumetric heat load is installed at the outlet of the premixed burner. When the premixed gas passes through the pores of the packing layer, it is divided into many strands and burns, so that the refractory material can be kept at a high temperature, and the premixed gas can be reliably ignited quickly. Basically, no flame can be seen, or only a short flame can be seen, so it becomes a "flameless burner". Using this kind of burner can shorten the flame length when burning blast furnace gas, and at the same time, it can be used at the outlet of the premixing tube. Installing a cooling water jacket keeps the temperature of the steel pipe at a lower value and reduces the occurrence of tempering. ?
It can be seen from this that in the process of transforming coal-fired boilers into blast furnace gas, the choice of burners can be varied. Which method to use in practice should consider many factors including the cooperation between the burner and the heating surface, the limitations of the original furnace type, etc., and then make a decision after performing thermal check calculations on the boiler and the modified furnace type. It is more helpful for the transformation design to analyze the flow field after transformation through numerical simulation calculation conditionally.