Interactions between corncob and lignite during temperature-programmed co-pyrolysis

Abstract

Interactions between feedstocks during pyrolysis of coal–biomass blends, and their impacts on product distribution and conversion behavior during utilization, need to be understood if we are to successfully develop systems for the effective co-utilization of biomass and coal. A novel two-stage fixed-bed reactor containing three quartz tubes was designed and used in this study to investigate these interactions, with particular emphasis on the impact on product distribution and char properties. The results show that interactions exist during co-pyrolysis of corncob and lignite blends, which increase overall tar yields and decrease overall gas yields compared with those obtained from pyrolysis of unblended feedstocks, with the interactions between corncob volatiles and lignite playing a dominant role. It is also shown that interactions between chars and volatiles can impact on the reactivity of chars to O2. Consistent with our expectations, there is a link between potassium content in char and its reactivity; however, it is found that for lignite chars in particular the potential impact of potassium is dominated by the changes of char chemical structure. The effect of potassium content is the opposite to that of char chemical structure, leading to significant complexity in determining the net result of any co-pyrolysis interactions on char reactivity. This highlights the importance of understanding these complex interactions to develop the industrial scale co-gasification systems and adjust the distributions of products.