Analysis on characteristics of blast furnace mixed injection biochar and coal
Energy conservation and emission reduction have been elevated to the top priority for the green and sus-tainable growth of the iron and steel industry in light of the active promotion of the"Dual carbon"target.The appli-cation of biomass,a renewable carbon source,in blast furnace ironmaking can significantly lower the CO2 emissions associated with iron and steel production.To improve the metallurgical properties of biomass feedstock for blast fur-nace injection,this paper employs pyrolytic and hydrothermal carbonization to prepare biochar,and investigates the feasibility of mixing biochar with pulverized coal for blast furnace injection.The results showed that the volatile fraction of biomass hydrochar and pyrolysis char was higher than that of bituminous coal.The fixed carbon content and higher heating value of the mixed coal would gradually decrease when the biochar was mixed with pulverized coal at a ratio of 5％to 20％,though the reduction was only slight.The blended sample is non-explosive and has an igni-tion point greater than 350 ℃ when the proportion of biochar is less than 20％,which satisfies the safety perform-ance requirements of the blast furnace comminution and injection system.Better grindability and combustibility of biochar can increase the pulverizing and combustion performance of blended sample.The ash melting point of pyrol-ysis char blends decreases significantly more than that of hydrochar blends due to the high alkali metal content of the ash component.The increase in alkali load of pyrolysis char was substantially more than that of hydrochar when the same proportion of biochar was injected,according to calculations of the alkali load variation of the biochar blending scheme.The alkali load rose by 0.394 3 kg/t for the pyrolysis char blending scheme and 0.006 4 kg/t for the hydro-char blending scheme when the biochar ratio was 20％and the blast furnace coal injection ratio was 140 kg/t.Ac-cording to the analyses presented above,biomass hydrochar can successfully meet all metallurgical performance re-quirements for blast furnace injection,whereas biomass pyrolysis char cannot be used to blast furnace injection due to its high content of alkali metals.The development of biomass hydrothermal carbonization technology is therefore necessary to effectively use agricultural and forestry waste biomass resources in the blast furnace ironmaking process.
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