Research On Combustion Behavior Of Pulverized Coal Injection Into COREX Melter Gasifier

COREX process was the first smelting reduction ironmaking technology for industrialization production. The process made important progress which smelted with non-coking coal and pure oxygen to get high quality hot metal. Lump coal was the main fuel for the COREX process, but it was very limited, large amount of coal powder was gotten before the charge. The problem could be resolved, if pulverized coal was injected into COREX melter-gasifier. It was very important to study the combustion behavior of pulverized coal in melter-gasifier for the design and optimization of COREX pulverized coal injection (PCI) technology.Some index of COREXC3000 was used in order to calculate and analysis the tuyere raceway, the theoretical combustion temperature and the influence of PCI on COREX melter gasifier. According to the similar principle, thermal model and cold model were designed. On the thermal furnace, a lot of experiment was carried out, including of coal's granularity, volatile matter, combustion condition and injection position et al. Coal's residence time and trajectory in COREX melter-gasifier were analysized on the cold furnace. Combustion efficiency of coal in COREX tuyere raceway was studied by mathematical model. According to the thermal decomposition mathematical model of coal particle, the devolatilization efficiency was studied when pulverized coal was injected from the upper position.The experiment research showed: the granularity scope of pulverized coal could be relaxed, but the ratio of -200mesh must be guaranteed. The combustion efficiency and devolatilization efficiency of mixed granularity injection were obviously higher than the average calculated data. The combustion efficiency and devolatilization efficiency of bituminous were higher than anthracite's at the same granularity. The granularity had less influence on bituminous than anthracite. The idea combustion efficiency and devolatilization efficiency could be gotten for bituminous as long as the granularity reached to some extent. For anthracite, the combustion efficiency could be improved with the granularity became more and more fine. Coal was an accelerator itself, the combustion efficiency could be improved when different coals were mixed. A certain proportion of anthracite was added into the pulverized coal which was screened from the process, the combustion efficiency and devolatilization efficiency would not decline obviously. The concentration of carbon monoxide or oxygen had obvious influence on the combustion efficiency, but less influence on the devolatilization efficiency. The influence of carbon monoxide concentration was obvious for big particals, while oxygen concentration was obvious for fine particals. The combustion efficiency and devolatilization efficiency when pulverized coal was injected from upper position were lower than below position injection. It was possible that the injection ratio reached to 30% for the COREX process. Granularity was the major factor to combustion efficiency, while volatile matter was the major factor to devolatilization efficiency. Volatile matter was the major factor to blow-off and quantity of surplus coal's volatile matter.The research by mathematical model showed: The combustion efficiency of pulverized coal in COREX raceway could keep above 65%, when the mean partical size was 0.075mm and the injection ratio was under 125kg/tFe for COREXC3000 PCI. The thermal decomposition completed basically in 0.2 seconds when coal was injected from upper position, the thermal decomposition of the residual volatile matter need a longer period of time, the residual volatile matter should not influent on production obviously. Temperature, granularity and volatile matter had obvious influence on thermal decomposition rates.