New high-pressure dry-solids feed pump could make high-efficiency, lower-emission gasification economically competitive
In a project (DE-FC26-04NT42237) funded by the US Department of Energy’s Office of Fossil Energy, Pratt & Whitney Rocketdyne has developed a high-pressure dry-solids feed pump that could make gasification economically competitive by improving efficiencies and introducing low-rank Western coal as a viable feedstock option.
|A rendering of the Pratt & Whitney Rocketdyne high pressure, dry-solids feed pump. Source: NETL. Click to enlarge.|
The first Pratt & Whitney Rocketdyne commercial-scale high-pressure dry-solids feed pump was commissioned at the Environmental and Engineering Research Center on 10 April 2012. There it will undergo 9–12 months of demonstration-scale testing to determine the pump’s flexibility in handling feed types, particle sizes, and pressure ranges. If successful, Pratt & Whitney Rocketdyne will make the pump available to industry for commercial use.
The project is a collaborative effort among Pratt & Whitney Rocketdyne, the Office of Fossil Energy’s National Energy Technology Laboratory (NETL), ExxonMobil Research and Engineering Company, Alberta Innovates – Energy and Environment Solutions, and the Environmental and Engineering Research Center at the University of North Dakota.
Today’s commercial dry-feed gasification systems are limited to processing pressures of about 450 psi. Pratt & Whitney Rocketdyne’s feed pump more than doubles those pressures to 1,000 psi. Higher system pressures mean higher system efficiencies; higher efficiencies translate into less coal used to produce power and other products. Capital, operations, and maintenance costs are lower and resources are extended.
Add in the ability of the Pratt & Whitney Rocketdyne system to feed low-rank coal into gasifiers, and costs are further reduced. Low-rank coal contains less energy per pound than higher-ranked bituminous coal, so it is typically considered too low in energy density for current slurry-fed gasification systems.
However, approximately 50% of the coal produced in the United States is low-rank sub-bituminous coal and lignite, mined predominantly in the Western states. The ability of the system to use these lower-cost feedstocks can further enhance the option of gasification. India, China, Turkey, Australia, and Eastern Europe also have considerable reserves of low-rank coal.
Coal gasification plants have been shown capable of exceeding stringent regulations for air- and solids-emissions. Coal gasification also produces a CO2 stream that is ready for capture, utilization, and storage. However, capital and operational costs have prohibited the widespread adoption of gasification, especially for power production—a major source of anthropogenic carbon dioxide (CO2) emissions.
Gasification-based power generation in general uses about half the water consumed by combustion-based coal power production. Compared to conventional slurry-feed gasification systems, the Pratt & Whitney Rocketdyne feed pump further reduces water use by cutting or eliminating its addition.