Abstract
The gasification kinetics of bituminous coal char was investigated in a mixture of CO2, H2O, CO, H2, and N2 under isothermal conditions. In addition, the impacts of gasification temperature, gasification time, and gas composition on the gasification process were analyzed. As the experimental results suggest, there is a significant increase of the carbon conversion degree of bituminous coal char not just when gasification temperature and time increase, but also when H2 and CO concentration decreases. The kinetics of bituminous coal char in the gasification process was successfully modeled as a shrinking unreacted core. It is concluded that the gasification of bituminous coal char is controlled by an internal chemical reaction in the early stage and diffusion in the later stage. The activation energies of bituminous coal char gasification for different stages were studied. Moreover, it is proposed for the first time, to our knowledge, that the diffusion-control step is significantly shortened with the decrease of the CO2/H2O ratio. As scanning-electron-microscopy results suggest, bituminous coal char gasified in CO2/H2O = 1/3 atmosphere has numerous inner pores (0–5 m). Therefore, in the process of gasification, the inner pores provide a gas channel that reduces the gas diffusion resistance and thus shortens the diffusion-control step. These results can serve as a reference for industrialized application of the technology of coal gasification direct reduced iron.
Highlights
China has established the World’s most enormous iron and steel industry in the last few decades [1]
Studies on bituminous coal char gasification were systematically carried out using a mixture
Studies on bituminous coal char gasification were systematically carried out using a mixture of of CO2, H2 O, carbon monoxide (CO), H2, and N2 under isothermal conditions
Summary
China has established the World’s most enormous iron and steel industry in the last few decades [1]. China’s scrap resources are in short supply and the iron and steel industry has caused increasingly serious environmental pollution, contrary to China’s sustainable development strategy. The blast furnace (BF) iron-making process is the most important critical process for the iron and steel industry [2]. The BF iron-making process has several fatal weaknesses. The reduction of CO2 emissions from the iron and steel industry has a significant impact on global CO2 emission reduction [3,4]. The tonnage energy consumption of steel enterprises is 600 kgce/t
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