煤和焦炉气联供制烯烃过程的建模模拟与分析

摘要

Olefins are one of the most important platform chemicals. Developing coal-to-olefins (CTO) processes is regarded as one of promising alternatives to oil-to-olefins process. However, CTO suffers from high CO2 emission due to the high carbon contents of coal. In China, there is 7×1010 m3 coke-oven gas (COG) produced in coke plants annually. However, most of the hydrogen-rich COG is utilized as fuel or discharged directly into the air. Such situation is a waste of precious hydrogen resource and serious economic loss, which causes serious environmental pollution either. This paper proposes a novel co-feed process of coal and COG to olefins in which CH4 of COG reacts with CO2 in a dry methane reforming unit to reduce emissions, while the steam methane reforming unit produces H2-rich syngas. H2 of COG can adjust the H/C ratio of syngas. The analysis shows that the energy efficiency of the co-feed process increases about 10 %, while at the same time, CO2 emission is reduced by around 95 % in comparison to the conventional CTO process.%由于煤富碳少氢，煤制烯烃过程生产1 t产品将排放约5.8 t CO2。与此同时，中国焦炭工业每年产生约7×1010 m3的副产物焦炉气，这些富氢的焦炉气大多被燃烧或直接排放进入大气，对环境造成严重影响的同时还浪费了巨大的经济价值。本文对焦炉气辅助煤制烯烃的新过程进行了建模模拟与系统分析。焦炉气与煤元素互补，焦炉气中的H2可用来调节合成气的氢碳比；CH4可通过甲烷水蒸气重整和甲烷干重整两个过程，提高合成气的氢碳比的同时降低煤制烯烃过程排放的CO2，提高碳元素利用率，实现节能减排。这个新的联供过程的能效比煤制烯烃过程提高了约10个百分点，而CO2排放量则减少了约95%。