Two stages holding pyrolysis of lignite under coke-oven gas

In order to promote the commercial industrial application of coal hydropyrolysis (HyPy) in China, coke-oven gas (COG) was used to replace expensive pure hydrogen as reactive gas for HyPy, the feasibility of this replacement was evaluated by the TG/DTG. And then, basing on the HyPy characteristics of coal under COG, two stages holding a certain time at suitable temperature during HyPy of coal under COG was introduced to simulate the ultra slow heating rate and to slow the formation rate of free radicals, by this process, matching the diffusion of external hydrogen. The results showed that inexpensive COG can replace expensive pure hydrogen as reactive gas for HyPy of HM coal; The DTG profile of coal under COG showed two obvious peaks, with a secondary HyPy peak occurring at about 500 °C, and this HyPy peak is favored by very slow heating rates; Slow heating rates could be used to improve the pyrolysis behaviors under COG; Holding certain time can slow the formation rate of free radicals, prolong the time of hydrogen diffusion and the time of the hydrogen react with free radical. By this, matching the diffusion of external hydrogen with the formation of free radicals and increasing the total conversion, oil yield and enhancing the sulfur removal are achieved.