Conversion of biomass materials into gaseous products. Final report - Operation of the PDU

Abstract

Studies were completed on the Garrett Energy Research and Engineering Company's multiple hearth furnace for the thermal conversion of biomass into a medium Btu gaseous product. Initial work on a two foot diameter, single hearth reactor provided comprehensive design data through an examination of the pertinent variables over a fairly wide range of operations. Kinetic and dynamic models were obtained for each of the reaction stages that would occur within a multiple hearth reactor. This data led to the design and construction of a process development unit (PDU) which consisted of four, four foot diameter hearths capable of processing six wet tons (50% moisture), or three dry tons of biomass per day through the steps of preheating, drying, pyrolysis, combustion, and gasification. Operation of the PDU included 10 to 20 runs on each of these steps, and work was completed with a five day, 24 hour per day, continuous operation. Process design, capital and operating costs, and an economic analysis based on this data indicated that no cost, 50% moisture manure could produce about a 300 Btu gas with a breakeven price of $4 per million Btu's in a 100 dry ton per day unit and $2.40 per million Btu'smore » in a 300 tons per day unit. These favorable results lead to a recommendation that further work should be done, optimizing the performance of the PDU and testing other potential biomass feed materials for their specific design characteristics.« less