从生命周期评价视角看钢铁企业“煤改天然气”

Evaluation on the “coal to natural gas” in iron and steel enterprises from the perspectives of life cycle assessment

当前环保压力下,钢铁企业成为控煤的主要对象,煤改天然气是一个重要控煤举措。文章从生命周期评价视角分析了钢铁企业主要工序将煤替换为天然气的节能环保效益。在目前冶炼技术和工艺水平下,焦炭作为高炉骨架和还原剂,还不能被替代,因此炼焦煤不能被天然气所替换。自备电厂"煤改天然气"可实现碳排放降低33%,SO_2降低36%,粉尘降低82%,固废降低99%,但NO_x排放反而会上升38%。俄罗斯等国天然气替代喷吹煤的实践结果表明,高炉焦比全部上升,从而导致生命周期煤耗没有明显降低,没有明显地起到节能减排作用。焦炉、焙烧炉等炉窑经常使用喷吹煤粉掺混混合煤气,这种情景下煤粉替代为天然气,可取得良好的环境效益。

Under the current environmental pressure, iron and steel enterprises have become the main target of coal control, and “coal to natural gas” is an important coal control measure. From the perspective of life cycle assessment, the paper analyzed the energy and environmental benefits of “coal to natural gas” in iron and steel enterprises. At the current metallurgical technology and level, coke as a blast furnace skeleton and a reducing agent cannot be replaced, so coking coal cannot be replaced by natural gas. The power plant “coal to natural gas” can reduce carbon emissions by 33%, SO 2 by 36%, dust by 82%, and solid waste by 99%, but NO x emissions will increase by 38%. The practice of replacing coal with natural gas in Russia and other countries shows that due to the increase of coke ratio, the life cycle coal consumption has not been significantly reduced, and there is no obvious effect on energy conservation and emission reduction. Coke ovens, lime kiln and other furnaces often use pulverized coal mixed gas and in this scenario,“coal to natural gas” can achieve good environmental benefits.