Separation system offers coal a new hope
22 Aug 2001
Researchers at the Inorganic Membrane Technology Laboratory (IMTL) in Oak Ridge, TN have developed a means of separating and isolating hydrogen from other gases at high temperatures.
The development could be of particular significance to designers of Integrated Gasification Combined Cycle (IGCC) systems that conceptually could be 30 to 50 percent more efficient than present-day coal burning systems.
When coal is gasified, a large fraction of the very hot gas produced is hydrogen. And one way to help make a IGCC system economical is to have a unit that can separate and collect a significant portion of the hydrogen for use in more valuable ways, such as fuel for fuel cells or for use in petroleum refinery catalytic crackers.
This approach is often termed 'fuels decarbonisation,' and refers to the process of converting a hydrocarbon fuel into a fuel, i.e., hydrogen, that does not contain carbon.
But for such a process to be viable, it must include provisions for separating and capturing carbon dioxide and other oxides of carbon that are produced.
The Oak Ridge-developed gas separation system consists of a porous membrane made of a ceramic material. Molecules of hydrogen are extremely small, as compared to molecules of carbon monoxide, carbon dioxide, and hydrocarbon gases. The difference in size allows the smaller molecules of hydrogen to pass through the porous material and away from the remaining gases.
The coal-derived hydrogen may then be collected and used as a feedstock for other advanced energy producing technologies, such as hydrogen-fuelled turbines or fuel cells or for chemical and petroleum processing, such as hydrotreating.
Development of an inorganic porous membrane for separating hydrogen from very hot gases posed a technological challenge for the Oak Ridge researchers. A separation device must be able to tolerate both high temperatures and harsh environments associated with coal gasification processes. However, laboratory tests have shown that the Oak Ridge-developed system is able to function well under these conditions.
