生物质炭煤粉高炉混合喷吹性能分析

Analysis on characteristics of blast furnace mixed injection biochar and coal

在“双碳”目标积极推进的背景下,节能减排已经成为当前钢铁工业绿色可持续发展的重要任务之一。生物质作为可再生的碳源,应用于高炉炼铁可显著降低钢铁生产的CO_(2)排放。为改善生物质原料应用于高炉喷吹的冶金性能,分别采用热解炭化和水热炭化对生物质原料进行炭化提质制备生物质炭,并探究了生物质炭与煤粉混合搭配进行高炉喷吹的可行性。结果表明,生物质水热炭和热解炭的挥发分高于烟煤,当生物质炭以5%~20%比例与煤粉混合时会使混煤的固定碳含量和发热值降低,但降低幅度较小。当生物质炭配比低于20%时,混煤无爆炸性,着火点大于350℃,满足高炉制粉和喷吹系统的安全性能要求。生物质炭具有较好的可磨性和燃烧性,能够改善混煤的制粉性能和风口前的燃烧性能。生物质热解炭灰成分中含有较高的碱金属,造成生物质热解炭混煤的灰熔点降低幅度远大于生物质水热炭混煤。通过对生物质炭混煤方案的碱负荷变化分析发现,高炉喷吹生物质热解炭对高炉冶炼碱负荷影响大于水热炭,生物质炭配比为20%,高炉喷煤比为140 kg/t时,生物质热解炭混煤方案的碱负荷增加0.3943 kg/t,生物质水热炭混煤方案的碱负荷增加0.0064 kg/t。以上分析表明,生物质水热炭能够满足高炉喷吹的各项冶金性能要求;生物质热解炭由于碱金属含量高,限制了其在高炉喷吹生产中的应用,发展生物质水热炭化技术是实现农林废弃生物质资源在高炉炼铁工序高效应用的关键。

Energy conservation and emission reduction have been elevated to the top priority for the green and sustainable growth of the iron and steel industry in light of the active promotion of the"Dual carbon"target.The application of biomass,a renewable carbon source,in blast furnace ironmaking can significantly lower the CO_(2)emissions associated with iron and steel production.To improve the metallurgical properties of biomass feedstock for blast furnace 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 ignition point greater than 350℃when the proportion of biochar is less than 20%,which satisfies the safety performance 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 pyrolysis 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 0.3943 kg/t for the pyrolysis char blending scheme and 0.0064 kg/t for the hydrochar blending scheme when the biochar ratio was 20%and the blast furnace coal injection ratio was 140 kg/t.According to the analyses presented above,biomass hydrochar can successfully meet all metallurgical performance requirements 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.