Insights into the co-pyrolysis interaction of cellulose and Zhundong coal via ReaxFF molecular dynamics simulation

Abstract

Experiments on the co-pyrolysis of coal and cellulose were conducted using a fixed-bed reactor in this paper. The results demonstrated that co-pyrolysis increases gas and char yields while reducing tar yield. The reactive force field molecular dynamics (ReaxFF MD) was then used to simulate co-pyrolysis in order to analyze the mutual reaction between coal and cellulose from the perspective of carbon skeleton, enabling the co-pyrolysis mechanism to be examined precisely. The results demonstrated that co-pyrolysis accelerates the crosslinking of cellulose fragments and coal char. The cellulose-derived component in cross-linked char (char products containing both cellulose and coal fragments) rises from 0.21 wt% at 2000 K to 12.82 wt% at 3000 K, resulting in higher char production. The examination of the yields and distribution of co-pyrolysis products at 2400 K reveals that the volatiles generated by cellulose and coal char undergo mainly crosslinking reaction, resulting in a lower tar yield and a higher inorganic gas yield. Due to the combination of oxygen-containing functional groups in the coal char with cellulose volatiles and free hydroxyl groups, the oxygen-containing active functional groups were consumed, rendering the cross-linked char more stable and inactive, thereby suppressing coal polymerization.