16-01: Development of a pilot-scale packed bed Ammonia Fiber Expansion (AFEXTM) process

Pretreatment of biomass at regional depots could simplify feedstock supply logistics for the emerging biofuels industry. AFEX is a solid-to-solid biomass pretreatment process, generating a storable product that is readily densified and transported.  These unique features make AFEX one of the few pretreatment processes that can be decoupled from the centralized biorefinery and located closer to the farm.  However, AFEX process designs that have been proposed for commercial-scale biomass treatment have used complex and costly operations. For depot operation, an AFEX process combining mechanical simplicity with low equipment cost must be developed. 

MBI has demonstrated at laboratory scale a mechanically-simple AFEX process that exploits the high porosities of biomass packed beds to facilitate ammonia transport and recovery, while providing pretreatment efficacy equal to benchmark stirred batch treatment.  Results from the laboratory scale reactors show ammonia recovery of >96%, with 70-80% yield of available sugars from treated biomass.  A preliminary technoeconomic analysis of a depot treating 100 tons of corn stover per day shows that the packed bed design offers greater than 50% capital cost reduction compared to conventional AFEX process designs.  MBI is testing the scalability of packed bed AFEX with a pilot-scale reactor system, scheduled to be online February 2013, with a bed size approximately 50 times larger than laboratory scale, and 50 times smaller than depot scale.  Details of the pilot plant process design, construction, and operation will be presented, and results of corn stover pretreatment in the laboratory and pilot scale packed bed reactors will be compared.