Catalytic Steam Reforming of Gasifier Tars: On-line Monitoring of Tars with a Transportable Molecular Beam Mass Spectrometer. Milestone Completion Report

摘要

Catalytic tar decomposition remains a key technical hurdle to commercializing biomass gasification. Decomposition of the tars, i.e. catalytic steam reforming of the organic 'tar' compounds to hydrogen and carbon monoxide, increases the overall yield of fuel gas from the biomass. More importantly, it minimizes (and potentially eliminates) the need for water scrubbing of the product gases, which is expensive in terms of equipment and operation/maintenance costs and process efficiency. The work presented here is a follow-up effort to catalyst tests performed at Battelle Columbus Laboratories' (BCL) biomass gasification facility during the winter of 1999-2000. That work was performed under Department of Energy (DOE) field work proposal (FWP) No. WU94, which in turn was related to DOE Contract No. DE-FB02-98CH10942. The focus of that contract was to operate a gas turbine on biomass derived synthesis gas (more properly, and henceforth called pyrolysis gas), and to demonstrate that a BCL-patented catalyst (DN34) could effectively decompose gasifier tars. A 10-ton per day, integrated gasifier-gas turbine system at BCL's West Jefferson, OH facility was used for the contracted project. Under the FWP, NREL's Transportable Molecular Beam Mass Spectrometer (TMBMS) was installed on that system to monitor the performance of the catalyst in real-time. Difficulties with achieving suitably high temperatures in the catalytic reactor resulted in premature coking of the DN34 catalyst. Consequently, the catalyst was deactivated and virtually no tar decomposition was measured by the TMBMS. The fact that some tar was removed from the pyrolysis gas by the catalytic reactor (as measured by the collection of tar by Modified Method 5 impinger sampling) was attributed to the accumulation of high molecular weight (low vapor pressure) tar compounds on the DN34 catalyst as coke deposits.