To reduce NOx emission based on optimizing the existing states of coarse coke breeze during iron ore sintering process

Abstract

With the development of the iron and steel industry, the amount of NOx emissions is increasing year by year, and this causes environmental pollution in forms such as acidic rain and photochemical smog, which greatly threatens human health and social development. The iron and steel industry is one of the major sources of NOx emissions, accounting for more than 10% of the total NOx emissions, and the iron ore sintering process is one of the major sources of NOx emissions in the iron and steel industry, as it accounts for more than 50% of the total emissions of iron and steel plants. Hence, it is extremely urgent to reduce NOx emissions under the current high requirements of environmental protection. Since sintering gas is characterized by large volume, high dust and oxygen content, low NOx concentration, and the presence of SO2, available technologies used in De-NOx have the disadvantages of low efficiency and high investment and cost. Presently, how to cost-effectively reduce the NOx emission of the iron ore sintering process is a new challenge in the iron and steel industry. In the sintering process, NOx is mainly generated in the combustion of solid fuels, which is affected by the existing states of coarse solid fuels. Hence, the combustion behaviors of uncovered and coated coarse coke breeze and the effects of their addition methods on the NOx emission and the bonding strength of the sinter were investigated by the visible micro sintering and combustion equipment. Then, the optimal existing state of coarse coke breeze was explored by sinter pot tests. The results show that compared with the uncovered coarse coke breeze, the NOx emission decreases by 56% when coarse coke breeze is coated with calcium ferrite fines. As the coarse coke breeze is separated and controlled to be in an uncovered state, then it is added into the sintering materials after first mixing process, NOx emission increases by about 56% and the strength of the sinter decreases. The maximum concentration of NOx and conversion rate of N element decrease by 8% and 27%, respectively, when the coke breeze is a coated state by controlling in the size of 0.50−3.15 mm, respectively. The sinter indexes are also improved.

Keywords

• iron ore sinter
• nox
• solid fuel
• existing state
• combustion behavior
• adding method