State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, China
To improve the economy of the hydropyrolysis process by reducing the cost of hydrogen, it has been suggested that cheaper hydrogen-rich gases (such as coke-oven gas, synthesis gas) could be used instead of pure hydrogen. Pyrolysis of Chinese Xianfeng lignite was carried out with real coke-oven gas (COG) and synthesis gas (SG) as reactive gases at 0.1–5 MPa and at a final temperature up to 650°C with a heating rate of 5–25°C min−1 in a 10 g fixed-bed reactor. The results indicate that it is possible to use COG and SG instead of pure hydrogen in hydropyrolysis, but that the experimental conditions must be adjusted to optimize the yields of the valuable chemicals."
Another point to be made is that the Chinese researchers seem to indicate that "recycling" the synthesis gas derived from the coal decomposition back into the pyrolysis of more coal also improves the hydrogenation process.
But, definitely: A coal-use by-product of steel-making, coke-oven gas, which was once a troublesome and polluting effluent, can be collected and added to coal as an additional raw material which enhances and improves the conversion of coal into liquid fuel.