Influence of Coke Combustion on NO_x Emission during Iron Ore Sintering

Abstract

This paper explores NO x emission during iron ore sintering on a pilot-scale pot. A novel technique of using a three-layered bed structure was adopted to study the role of coke level, properties and combustion behavior on NO x emission. In addition, the lime content of the mix was also altered to understand the effect of the melt formation process. Thirteen sinter pot tests were employed to analyze the influence of coke combustion on NO x emission. As the flame front descended down the pot, NO x emission decreased because of increasing bed temperatures. For this reason, it is to be expected that increasing coke rate will result in higher sinter bed temperature and lower conversion of coke-N to NO x . However, overall NO x emission is little changed because more coke means higher N availability. Increasing basicity (CaO/SiO 2 ) from 1.9 to 2.4 in raw mix results in the decrease of NO x emission, about 5%. Increasing coke size may result in the decrease or increase of NO x emission. Placing coke particles on the outside of granules can lower NO x emission in the middle and bottom layers, by 4−15%. NO x emission in the iron ore sinter process is determined by the conversion of coke-N to NO x and nitrogen source in sinter mix. The atmosphere around coke particles is very important for NO x reduction, and NO x emission will increase by around 15% when oxygen increases by 1 vol.%. During iron ore sintering, temperature has great influence on NO x emission, with levels decreasing by 15−25% for a 100 K temperature increase.

Effects of Fuel Type and Operation Parameters on Combustion and NOx Emission of the Iron Ore Sintering Process

“…Pan et al [9] researched the impact of coke ratio and moisture content on NO x emission. Zhao et al [10] studied the influence of the fuel layered distribution on NO x emission.…”

Factors Controlling High-temperature Zone Resistance to Airflow during Iron Ore Sintering

“…The chemical composition of the raw materials is given in Table 1. 10) Base blend details are 6.5 wt.% moisture, 1.9 basicity(CaO/SiO 2 ), 5.0 wt.% SiO 2 , 1.7 wt.% MgO, 4.05 wt.% coke rate and 20 wt.% return fines.…”

The Effects of Coke Parameters and Circulating Flue Gas Characteristics on NOx Emission during Flue Gas Recirculation Sintering Process

“…The decomposition reaction of limestone occurs when the bed temperature increases to the decomposition temperature during sintering. The reaction equation and rate are modeled as Equations (9) and (10) [31].…”

“…Moreover, SO 2 and NOx emissions during sintering account for 60% and 50% of the overall emissions of SO 2 and NOx in steel production, respectively [1]. At present, new technologies for reducing NOx emission during sintering mainly include flue gas recirculation sintering (FGRS), selective catalytic reduction [2], biomass fuel [3][4][5][6], gas injection [7], and parameter control [8,9].…”