【作者】 李峰；

【导师】 储满生；

【作者基本信息】 东北大学 ， 钢铁冶金， 2022， 博士

【摘要】 我国是世界第一钢铁大国,2021年粗钢产量超10亿吨,其中近90%是通过高炉-转炉流程生产,钢铁工业的碳排放占全国碳排放总量的16%左右,故而是我国实施碳中和战略的重点领域。以氢能替代化石能源的氢冶金是通过钢铁冶炼工艺流程革新和能源结构优化,从碳还原转换为氢还原实现低碳或无碳钢铁生产的颠覆性前沿技术。氢冶金工艺主要包括富氢还原高炉、氢基竖炉直接还原、氢基熔融还原,其中,基于氢冶金的氢基竖炉-电炉短流程新工艺是目前国内外研发的热点,是我国钢铁产业实现碳中和的重要途径。国外氢冶金研发起步早、规划系统,已有生产实践和工程示范,而我国氢冶金尚处于探索阶段,仍存在诸多亟待解决的关键理论和技术难题。本研究针对氢基竖炉炉料制备、氢基竖炉直接还原工艺配置、基于不同氢源的氢基竖炉-电炉短流程新工艺质-能转换机制、能量高效利用有效途径以及绿色协调性多目标优化等关键问题进行了系统研究。氢基竖炉炉料制备及还原工艺配置实验研究表明,以国产的铁品位71.78%的超高品位铁精矿制备的氧化球团在1050℃、H2/CO=2.5(体积比,下同)和900℃、H2/CO=1.5条件下膨胀率分别达到51.20%和242.73%,发生恶性膨胀。氢基竖炉工艺宜选取品位70%左右的高品位铁精矿制备优质氧化球团,增加还原气H2含量,球团还原速率及金属化率提高,还原膨胀和还原粘结行为得到改善;随还原温度升高,氧化球团还原性指数增大,但还原膨胀率和还原粘结指数均增大。在还原膨胀和还原粘结指数允许的范围内,氢基竖炉宜采用高温高氢的工艺条件,提高产品金属化率和生产效率。氢基竖炉-电炉短流程新工艺质能平衡研究表明,氢基竖炉还原气理论需求量应同时满足炉内化学平衡和热平衡,900℃条件下,还原气成分为H2/CO=1.5、H2/CO=2.5和 100%H2时,还原气理论需求量分别为 1427.89 m3/tDRI、1601.65 m3/tDRI 和 2201.50 m3/tDRI。采用 900℃、H2/CO=1.5 的还原气在氢基竖炉内还原品位为67.89%的氧化球团,球团单耗为1.37 t,还原气消耗量588.00 m3,需补充粗煤气1281.00 m3。最终,在100%DRI条件下,基于煤制气的氢基竖炉-电炉短流程吨钢的能耗为726.29 kgce/t,品位70.10%的铁精矿消耗量为1619.68 kg/t。氢基竖炉-电炉短流程新工艺有效能利用研究表明,100%DRI、H2/CO=1.5条件下,基于煤制气的氢基竖炉-电炉短流程新工艺有效能利用率为35.93%。煤制气及净化、氢基竖炉和电炉工序有效能损失分别占总有效能损失的64.92%、12.06%和13.21%,提高气化炉内碳转化率以及粗煤气H2/CO可提升煤制气及净化工序的有效能利用率。此外,电炉炼钢时配加适量的废钢有助于提升短流程的能效,而提高还原气氢含量,会增加系统有效能的不可逆损失,导致短流程能量利用水平的下降。氢基竖炉-电炉短流程新工艺热经济学研究表明,100%DRI、H2/CO=1.5条件下,净煤气、还原气、氧化球团、DRI和钢水的单位热经济学成本分别为0.053、0.063、86.03、0.55 和 0.61 元/MJ,经济学成本分别为 0.71 元/m3、0.85 元/m3、1724.84元/t、3455.78元/t和4392.47元/t,以上产品分别对褐煤、天然气、无烟煤、还原气、含铁炉料的成本变化最敏感。当电炉DRI配比下降70%时,钢水单位热经济学成本及经济学成本分别降低0.070元/MJ和511.24元/t。还原气成分由H2/CO=1.5变为100%H2时,还原气、DRI和钢水的单位热经济学成本分别增加 33.33%、16.36%和 18.32%。氢基竖炉-电炉短流程新工艺环境绿色性研究表明,基于煤制气的氢基竖炉-电炉短流程采用100%DRI冶炼时,其生命周期总体环境影响为4.10·E-11,其中,POCP和GWP100分别贡献49.52%和41.93%,且脱碳、电炉、煤气加热工序是造成环境影响最大的工序,是短流程环境性能优化的重点环节。当DRI配比下降至30%时,短流程相比高炉-转炉长流程可实现CO2减排54.34%、节能57.96%。然而,提高还原气氢含量会降低基于煤制气的氢基竖炉-电炉短流程的环境优势,采用煤制氢的氢基竖炉-电炉短流程的能耗和碳排放分别达到了 810.28 kgce/t 和 1993.68 kg/t。基于不同氢源的氢基竖炉-电炉短流程多维度评价研究表明,基于焦炉煤气、天然气和电解水制氢的氢基竖炉-电炉短流程有效能利用率分别为45.64%、48.39%和30.68%,相较高炉-转炉长流程,可分别减少碳排放39.96%、62.80%和88.64%,但吨钢成本均高于高炉-转炉长流程,其中焦炉煤气-富氢竖炉短流程最低。在“双碳”背景下,我国近期发展氢冶金工艺的重点应为基于COG的富氢竖炉-电炉短流程,在未来,结合可再生能源制氢规模化廉价化(可再生能源电力单价降低至0.10元/kWh即与富氢竖炉-电炉短流程基本相当),逐步发展基于电解水制氢的全氢竖炉-电炉短流程。更多还原

【Abstract】 China is the largest iron and steel producer all over the world,the output of crude steel exceeds 1 billion tons in 2021,of which nearly 90%is produced through the blast furnace-basic oxygen furnace(BF-BOF)process.The iron and steel industry accounts for about 16%of the total carbon emissions of the country.Therefore,the iron and steel industry is a key area for China to implement the carbon neutral strategy.Hydrogen metallurgy,which substitutes hydrogen energy for fossil energy,is a subversive frontier technology to realize low-carbon or non-carbon steel production through process innovation and energy structure optimization.The hydrogen metallurgy process mainly includes hydrogen-enriched reduction blast furnace,hydrogen-based shaft furnace direct reduction and hydrogen-based smelting reduction.Among them,the hydrogen-based shaft furnace-electric arc furnace(HSE)process became a hot spot at home and abroad,and is an important way to achieve carbon neutral of China’s iron and steel industry.The development of hydrogen metallurgy in foreign countries started early and planned systematically with production practice and engineering demonstration.However,the research of hydrogen metallurgy in China is still at the exploratory stage,and there are still many key theoretical and technical problems remain to be solved.In this study,the key issues,such as the pellets preparation of the hydrogen-based shaft furnace,process configuration of the hydrogen-based shaft furnace,the conversion mechanism of mass and energy,effective way for efficient utilization of energy,and green coordination multi-objective optimization of the HSE process based on different hydrogen sources are systematically studied.The experimental study on the pellets preparation and process configuration of the hydrogen-based shaft furnace shows that the reduction swelling index of oxidized pellets prepared with the ultra-high grade iron concentrate with an iron grade of 71.78%reaches 51.20%and 242.73%respectively under the conditions of 1050℃,H2/CO=2.5(refers to the HYL process)and 900℃,H2/CO=1.5(refers to the MIDREX process),which means catastrophic swelling occurs during the reduction.High-grade iron concentrate with an iron grade of about 70%should be selected to prepare high-quality oxidation pellets for the hydroge-based shaft furnace,and the H2 content of the reduction gas should be increased to improve the reduction rate and metallization rate of pellets,meanwhile the swelling and sticking behavior can be improved.With the increase of the reduction temperature,the reducibility,swelling and sticking index of the oxidized pellets increased.Within the allowable range of reduction swelling and sticking index,the parameters with higher temperature and higher H2 content in the reducing gas should be adopted for the hydrogen-based shaft furnace to improve the metallization rate and production efficiency of the product.The research on the conversion mechanism of mass and energy of the HSE process shows that the theoretical demand of the reduction gas of the hydrogen-based shaft furnace depending on the chemical balance and thermal balance in the furnace at the same time.At 900℃,the theoretical demand of the reduction gas is respectively 1427.89 m3/tDRI,1601.65 m3/tDRI and 2201.50 m3/tDRI when the composition of the reduction gas is H2/CO=1.5,H2/CO=2.5 and 100%H2.When the oxidized pellets with an iron grade of 67.89%is reduced in the hydrogen-based shaft furnace at the condition of 900℃ and H2/CO=1.5,the unit consumption of pellets and reduction gas is 1.37 t and 588.00 m3,and 1281.00 m3 of crude gas needs to be supplemented.Under the condition of 100%direct reduction iron(DRI),the energy and iron concentrate with an iron grade of 70.10%consumption of the HSE process based on coal gasification is 726.29 kgce/t and 1619.68 kg/t.The research on the exergy assessment of the HSE process based on coal gasification shows that the exergy efficiency is only 35.93%under the condition of 100%DRI and H2/CO=1.5.The exergy loss of coal gasification and purification,hydrogen-based shaft furnace and electric are furnace process accounts for 64.92%,12.06%and 13.21%of the total exergy loss,respectively.Improving the carbon conversion rate in the gasifier and the H2/CO ratio of the crude gas can improve the energy utilization rate of coal gasification and purification process.In addition,the utilization of proper amount of scrap steel during electric furnace steelmaking can do helpful efforts to improve the exergy efficiency of the HSE process,while increasing the hydrogen content of the reducing gas will increase the irreversible exergy loss of the system,resulting in the reduction of the energy utilization level of the whole process.The research on the thermo-economic analysis of the HSE process shows that the unit thermoeconomic cost of the clean gas,reducing gas,oxidized pellets,DRI and steel is respectively 0.053 RMB/MJ,0.063 RMB/MJ,86.03 RMB/MJ,0.55 RMB/MJ and 0.61 RMB/MJ under the condition of 100%DRI and H2/CO=1.5.Meanwhile,the unit economic cost of the above products is 0.71 RMB/m3,0.85 RMB/m3,1724.84 RMB/t,3455.78 RMB/t and 4392.47 RMB/t,respectively.And they are respectively most sensitive to the cost changes of lignite,natural gas,anthracite,reducing gas and ferrous materials.When the DRI ratio of electric furnace is reduced from 100%to 30%,the unit thermoeconomic and economic cost of steel are reduced by 0.070 RMB/MJ and 511.24 RMB/t respectively.When the composition of reducing gas changes from H2/CO=1.5 to 100%H2,the unit thermoeconomic cost of reducing gas,DRI and steel increases by 33.33%,16.36%and 18.32%respectively.The research on the life cycle assessment of the HSE process based on coal gasification shows that,when 100%DRI smelting is adopted,the environmental impact of is 4.10·E-11,of which POCP and GWP100 contributes 49.52%and 41.93%respectively,and decarbonization,electric furnace and gas heating processes yield the greatest environmental impact and are the key links of the environmental performance optimization.When the ratio of DRI is reduced to 30%,the HSE process can achieve 54.34%of CO2 emission reduction and 57.96%of energy saving compared with the BF-BOF process.However,increasing the hydrogen content of the reduction gas will reduce the environmental advantages of the HSE process,the energy consumption and carbon emission of the HSE process based on hydrogen produced from coal reaches 810.28 kgce/t and 1993.68 kg/t respectively.The multi-dimensional assessment on the HSE process based on different hydrogen sources shows that the exergy efficiency of the HSE process based on coke oven gas,natural gas and water electrolysis is 45.64%,48.39%and 30.68%respectively.Compared with the BF-BOF process,the carbon emission of the above three processes can be reduced by 39.96%,62.80%and 88.64%respectively.However,the thermoeconomic and economic costs of the steel are all higher than that of the BF-BOF process,and among them,the production cost of the HSE process based on coke oven gas is the lowest.In light of the urgent tasks of the carbon neutral of the iron and steel industry,the HSE process based on COG should be the focus of China’s recent development of hydrogen metallurgy process.In the future,the HSE process based on hydrogen production from water electrolysis will be gradually developed,when the large-scale and low-cost hydrogen production from renewable energy realize(when the unit price of renewable energy power is reduced to 0.10 RMB/kWh,the cost of HSE process based on hydrogen production from water electrolysis is basically equivalent to the hydrogen-riched shaft furnace process).更多还原