新型VESTA甲烷化工艺路线探究

分析了现有煤制合成天然气技术主要存在的问题，介绍了新型无循环、适应宽氢碳比的VESTA甲烷化技术。VESTA甲烷化技术的显著特征是利用合成气中的CO₂和外加水蒸汽来控制甲烷化反应温升，不需要操作条件苛刻的循环气压缩机；在甲烷化反应之前对原料气只脱硫、不脱碳，甲烷化反应之后再集中脱碳；经中试试验得出原料气中的H₂/CO比不影响最终的SNG产品指标；甲烷化后的粗SNG产品气中的CO₂体积分数高达71%，因而可在脱碳前低成本联产中压液体CO₂产品。这部分液体CO₂产品除了可用泵增压输送到粉煤气化单元用作输送气体外，还可以直接作为副产品为企业增加收益，并间接降低了碳排放。新型VESTA甲烷化技术与现有带循环压缩机的甲烷化技术相比，不但更容易操控，而且还提高了操作的稳定性和安全性，同时又能极大地降低净化装置、甲烷化装置及SNG干燥装置的投资和能耗。因此，采用VESTA甲烷化技术，能有效地提高煤制合成天然气的市场竞争力。

The new methanation process of VESTA

The existing coal-to-SNG process was analyzed, and a new methanation process of VESTA, which was without recycle compressor and adapted to the wide H₂/CO ratio, was introduced. The remarkable feature of VESTA technology was that the temperature of methanation reaction can be controlled by the use of CO₂ in syngas and additional steam without the need for recycle compressors. Before methanation, only sulfides were removed from the feedstock gas and no carbon dioxide was removed, and then carbon dioxide was removed after the methanation reaction. The results of pilot test showed that the H₂/CO ratio in the feed syngas did not affect the quality of the final SNG product. The concentration of CO₂ in crude SNG was as high as 71%. Therefore, medium pressure liquid CO₂ products can be produced at low cost before CO₂ removal. This liquid CO₂ product not only can be pumped to the pulverized coal gasification unit as the transport gas, but also can be used as a by-product to increase the profits of the enterprise and indirectly reduce carbon emissions. Compared with the existing methanation technology with recycle compressors, the new VESTA methanation technology was not only easier to operate, but also improved the stability and safety of operation, and greatly reduce the investment and energy consumption of purification unit, methanation unit and SNG drying unit. Therefore, the use of VESTA methanation technology can effectively improve the market competitiveness of coal-to-SNG.