Low-rank Coal Gasification Studies Using the Psdf Transport Gasifier

The Power Systems Development Facility (PSDF) is an engineering scale demonstration of advanced coal based power systems, including the KBR Transport Gasifier, a hightemperature, high-pressure syngas filtration system, and a gas cleanup unit. Designed to be at a sufficient scale to test advanced power systems and components in an integrated fashion, the PSDF provides data necessary for commercial scale-up. The Transport Gasifier is a circulating fluidized bed reactor designed to operate at higher circulation rates and riser densities than conventional circulating bed units. The high circulation rates result in higher throughput, better mixing, and higher mass and heat transfer rates. Since the gasifier uses a dry feed system and does not slag the ash, it is particularly well-suited for high moisture fuels such as subbituminous coal and lignite. As of September 2006, the gasifier has achieved over 7,100 hours of gasification using subbituminous Powder River Basin (PRB) coal and over 700 hours of gasification using lignite. The gasifier has operated in both air blown and oxygen blown modes with both fuels. Using PRB coal in previous test runs, the gasifier yielded raw wet lower heating values of up to 71 BTU/SCF in air blown mode and up to 100 BTU/SCF in oxygen blown mode. These values translate into commercially projected syngas heating values of up to 147 Btu/SCF in air blown mode and up to 299 BTU/SCF in oxygen blown mode. Historically, the gasifier has maintained carbon conversions of around 95% using PRB coal. Recent gasifier configuration modifications have resulted in improvements to both the heating value and the carbon conversion. Preliminary data for PRB coal during air blown mode suggest an increase in the raw wet lower heating value to as high as 87 BTU/SCF, while the average carbon conversion increased to over 98%. This paper compares the performance of the gasifier during early testing with subbituminous coal and lignite to the preliminary results of the new gasifier configuration.