With specialty gas manufacturer BOC Process Gas Solutions (now a part of the Linde Group), WRI is advancing a novel technology for the lower-cost production of oxygen that takes advantage of the oxygen storage properties of the mineral perovskite.
With oxycombustion technology, fuel is combusted in pure oxygen, and flue gas is recycled into the furnace to maintain optimum burning conditions. Because oxycombustion excludes nitrogen, the CO2-rich flue gas can be captured at a relatively low cost and sequestered.
The cost of oxygen, however, is a major issue in the development of sequestration-ready power systems. The BOC Group, the world’s second largest industrial gas company, has developed a technology known as CAR (Ceramic Autothermal Recovery) for oxygen production and supply to oxygen-fired boilers with flue gas recycle.
When two beds are operated in a cyclic process, the process is continuous; air is passed through one bed to allow sorption and storage of oxygen, and steam or hot flue gas is passed through the other bed to release the stored oxygen for use in the boiler. The flue gas recycle dilutes the oxygen, moderating temperatures and allowing conventional or existing equipment to be used.
The CAR process represents a major advancement in air separation technology, as the cost of producing oxygen using CAR is estimated to be 20 to 30 percent lower than using cryogenic air separation.
WRI collaborated with the BOC Group on early-stage tests of the CAR technology under the Department of Energy’s Jointly Sponsored Research Program. The testing was conducted at WRI’s Combustion Test Facility (CTF), a 30-lb/hr coal-burning furnace that mimics a utility boiler.
As a part of a $6.1 million U.S. DOE demonstration project, the BOC Group, WRI, and Alstom Power Service are fast-tracking the development and testing of oxycombustion.
WRI and the BOC Group are currently fabricating a 0.7-ton/day (O2) pilot-scale CAR unit for testing at WRI’s coal Combustion Test Facility.
The CAR technology is based on sorption and storage of oxygen at high temperatures (~ 600-800 ºC) in a fixed bed containing mixed ionic and electronic conductor materials. The stored oxygen is released for use in the boiler by partial pressure reduction using a sweep gas such as hot recycled flue gas, steam or a combination.