Pretreatment Reactor Scaling: Comparing Conversion Performance Across Different Pretreatment Reactors

High throughput pretreatment screening provides the ability to rapidly assess and identify operating conditions for new biomass feedstocks that optimize sugar production. However, these screening techniques are typically performed on small, bench-scale systems and it is often unclear how their results are applicable to pilot- or demo-scale equipment.

The present study attempts to answer this question by systematically developing pretreatment and enzymatic hydrolysis yield data using a rapid screening technique and comparing performance results to those produced in 1-L and 4-L batch reactors as well as a (nominal) 25 dry kg/h continuous, pilot-scale horizontal reactor routinely used for pilot scale operations. The findings show that for all four reactor systems, the maximum total xylose yield from pretreatment and overall saccharification yield (a measure of the total glucose and xylose yield from pretreatment and enzymatic hydrolysis) are nearly equivalent (within experimental error). However, because of significant differences in heat and mass transfer characteristics and achievable time/temperature profiles among the various reactors, the pretreatment conditions that produce the maximum yields in each reactor did not match. While this is not an unexpected finding, it does pose a challenge to mapping operating conditions that produce equivalent results between the different reactors, and more specifically to using conditions identified in smaller scale higher throughput screening systems to inform larger scale production.

In this work we present some simple scaling heuristics that give sufficient guidance for using results from one reactor system to identify near optimum conditions for pretreatment in the other reactor systems.