One based on exhaust gas recirculation o 2 -co 2 Combustion-supporting pellet production process and preparation system

Abstract

The invention discloses a pellet production technology and preparation system based on exhaust circulation O2-CO2 combustion supporting, and belongs to the field of pellet environment-friendly efficient preparation production in the ferrous metallurgy process. The physical heat of exhaust in the production process is used for drying and preheating of pellets, and the exhaust containing high-concentration CO2 is directly mixed with or mixed with industrial pure oxygen after being purified to serve as combustion-supporting gas of fuel. According to the pellet production technology and preparation system, the waste heat of the exhaust is sufficiently utilized, and the heat utilization efficiency of the pellet preparation system is improved; approximate zero input of nitrogen of the pellet preparation system is achieved, and the generation amount of NOx in the production process is decreased from the source; and the exhaust containing the high-concentration CO2 can be used for preparing industrial grade / food grade CO2 with low cost, and a CO2 recycling and emission reduction approach is provided.

Description

technical field [0001] The invention belongs to the field of green and high-efficiency preparation and production of pellets in iron and steel metallurgical processes, and specifically relates to a method based on tail gas circulation. 2 -CO 2 Combustion-supporting pellet production process and preparation system. Background technique [0002] Most of the chemical reactions in the blast furnace ironmaking process are carried out between the gas phase and the solid charge, which requires that the filling layer in the furnace has good air permeability, and the charge has a certain particle size and uniformity; with the large-scale development of the iron and steel industry, taste The output of relatively high iron ore with appropriate particle size has dropped sharply, and after a large amount of development and utilization of lean iron ore resources, a large amount of finely ground iron concentrate powder less than 0.074mm has been provided through the mineral processing pro...

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Problems solved by technology

[0005] However, due to the late start and short development time of my country's pellet industry, there are still some problems in the pellet production process of grate machine-rotary kiln-circular cooler, and there is a big gap with foreign advanced enterprises in terms of energy saving and emission reduction, such as It is said that coke oven / blast furnace gas or pulverized coal is often used as fuel in the rotary kiln at present, and the air is used for combustion to provide the heat required for pellet drying, preheating and roasting. However, due to the large amount of N in the furnace atmosphere 2 , the high temperature of the flame combustion front leads to NO in the exhaust gas x The concentration exceeds the standard and a large amount of emissions, generally speaking, the NO in the tail gas of the process x The concentration is 100mg / m 3 Above, if pure oxygen is used as a combustion aid, it will cause the flame combustion front temperature to exceed 2500°C, which will seriously affect the life of the rotary kiln wall refractory material; secondly, during the operation of the equipment, the fuel and power consumption is high, and the CO 2 Large emissions, according to statistics, the pellet preparation process CO 2 Emissions account for about 11.5% of steel industry emissions, mainly because nitrogen in the air absorbs a lot of heat, and the physical heat carried by nitrogen in the tail gas has a low utilization efficiency

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