Heat transfer considerations in design of a batch tube reactor for biomass hydrolysis

Biologic conversion of inexpensive and abundant sources of cellulosic biomass offers a low-cost route to production of fuels and commodity chemicals that can provide unparalleled environmental, economic, and strategic benefits. However, low-cost, high-yield technologies are needed to recover sugars from the hemicellulose fraction of biomass and to prepare the remaining cellulose fraction for subsequent hydrolysis. Uncatalyzed hemicellulose hydrolysis in flow-through systems offers a number of important advantages for removal of hemicellulose sugars, and it is believed that oligomers could play an important role in explaining why the performance of flow-through systems differs from uncatalyzed steam explosion approaches. Thus, an effort is under way to study oligomer formation kinetics, and a small batch reactor is being applied to capture these important intermediates in a closed system that facilitates material balance closure for varying reaction conditions. In this article, heat transfer for batch tubes is analyzed to derive temperature profiles for different tube diameters and assess the impact on xylan conversion. It was found that the tube diameter must be <0.5 in. for xylan hydrolysis to follow the kinetics expected for a uniform temperature system at typical operating conditions.