Secondary reactions suppression during fuel fast pyrolysis in an infrared heating apparatus for the fixed bed pyrolysis process with internals

To probe the primary reaction characteristics in coal pyrolysis, the suppression of secondary reactions was systematically examined and optimized by pyrolyzing a kind of compressed thin-layer coal sample in an infrared (IR) heating device with the high heating rate. The effect of pyrolysis temperature, thin-layer thickness, and reactor structure on product distribution and component was comprehensively examined. In the tested experimental temperature range from 600 to 1000 degrees C, by reducing the thin-layer thickness to 1.5 mm, the yields of fuel gas and tar increased synchronously, and the volume yields of H-2 and CO were improved obviously. By comparing with the pyrolysis of a single thin-layer coal sample and the samples of one piece of coal and one piece of char together, one can see that there were serious interactions between char and volatile, leading to the decrease of tar yield and the increase of its fractions with the high boiling temperature. On this basis, by removing the gas distributor in the adopted pyrolyzer, the tar yield was raised further, reaching the 1.56 times of G-K assay. And its components became much light due to the less pitch generation. Moreover, the tested gas components, such as H-2, CO, CH4, and CO2, were greatly promoted. Finally, the results demonstrated the availability of thin-layer coal pyrolysis method and the optimized reactor restructure in the suppression of secondary reactions