In-situ pyrolysis behavior of lignite in a moving bed reactor

In order to obtain the feasibility of in-situ pyrolysis of high moisture content lignite and its behavior of pyrolysis, a moving bed tubular experimental reactor used for the in situ pyrolysis of lignite was built. The effects of moisture content, temperature and particle size on the mass loss, product yields and gas characteristic of the lignite pyrolysis were studied. The results show that in-situ steam evaporates from the lignite participated the char gasification and volatile steam reforming reaction. With the increase of moisture content, the in-situ steam gasification reaction of lignite is strengthened, accompanied by the rise of carbon conversion ratio. The H₂ yield increases from 277.13 mL/g to 527.77 mL/g. The gas yield increases with the rise of pyrolysis temperature, while the liquid and char yield show an opposite trend. The carbon conversion ratio increases from 38.19% to 52.74%. The increase of the particle size prolongs the residence time of moisture and volatile in the interior of the coal particle, and it can strengthen the semi-coke gasification reaction and the volatiles reforming reaction. Furthermore, the rise of particle size increases the mass transfer resistance of the pore in lignite particles, leading to the strengthened secondary reaction. The optimum lignite particle size for its in-situ pyrolysis is 1.6-3.2 mm.