Pure hydrogen gas production in a coal supercritical water gasification system with CO2 as transporting medium
Weizuo Wang, Qiuyang Zhao, Bingru Lu, Jinwen Shi, Hui Jin
Abstract
Supercritical water gasification (SCWG) technology was a clean coal conversion and utilization technology, which could decompose low-grade coal into gaseous products and make efficient and clean use of them. However, system with H 2 O transporting had much energy consumption on heating transporting medium and side reactions at heating process would weaken the gasification effect. Considering the advantages of low critical point and low specific heat capacity of CO 2 , and the precedent of CO 2 as a transport medium in non-supercritical systems, CO 2 was expected to become a transport medium in supercritical water gasification systems and to achieve the goal of improving the gasification effect of heating process and reducing energy consumption. A supercritical water coal gasification system of was established with lignite as raw material in this paper. Production yields of gasification with CO 2 as the transporting medium at different working conditions were investigated. CO 2 and H 2 O were used as the transporting medium of the system, contrastively. Compared with H 2 O-transporting system, production of H 2 and CO 2 in CO 2 -transporting system decreased while that of CH 4 and CO increased as well. Furthermore, both energy and exergy efficiency of CO 2 -transporting system were higher than that of H 2 O-transporting system. The result proved the superiority of CO 2 as the transport medium of supercritical water gasification system.