煤和焦炉气联供制合成天然气过程的建模、模拟与分析

近年来中国的煤制天然气项目快速发展。然而煤制天然气项目的CO₂排放量大、污水产量高难处理,生产过程能效低。与此同时,中国焦炭工业每年产生约700亿立方米的副产物焦炉气,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,同时还浪费了巨大的经济价值。煤和焦炉气联供制天然气新工艺可有效解决这些问题。焦炉气与煤元素互补,焦炉气中的氢气可用来调节合成气的氢碳比;甲烷可通过甲烷干重整过程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。本文针对煤和焦炉气联供制天然气这个新的工艺过程进行建模、模拟与分析,发现新过程的能效比煤天然气烃过程提高了约8个百分点,而CO₂排放量则减少了约60%。

Modeling,simulation and analysis for coal and coke-oven gas to synthetic natural gas

Coal to synthetic natural gas (SNG) process is regarded as one of promising way to tackle with haze in north China and is developed rapidly in China. However, coal to SNG processes suffer from the high energy consumption and 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. 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 causes serious economic loss and environmental pollution either. The co-feed process of coal and COG to SNG is a promising solution for these problems. In the co-feed process, CH₄ of COG reacts with CO₂ in a dry methane reforming unit to reduce emissions and H₂ of COG can adjust the H/C ratio of syngas. This paper makes a modeling, simulation and system analysis for the co-feed process of coal and COG to SNG. The results show that the energy efficiency of the co-feed process increases by 8%, while at the same time, CO₂ emission is reduced by 60% in comparison to the conventional coal to SNG process.