Zero Emission Coal Power, a New Concept

The Zero Emission Coal Alliance (ZECA) is developing an integrated zero emission process that will generate clean energy carriers (electricity or hydrogen) from coal. The process exothermically gasifies coal using hydrogen to produce a methane rich intermediate state. The methane is subsequently reformed using water and a CaO based sorbent. The sorbent supplies the energy needed to drive the reforming reaction and simultaneously removes the generated CO2 by producing CaCO3 The resulting hydrogen product stream is split, approximately 1/2 going to gasify the next unit of coal, and the other half being the product. This product stream could then be split a second time, part being cleaned up with a high temperature hydrogen separation membrane to produce pure hydrogen, and the remainder used to generate electricity via a solid oxide fuel cell (SOFC). The inevitable high temperature waste heat produced by the SOFC would in turn be used regenerate the CaO by calcining the CaCO3 product of the reforming stage thereby generating a pure stream of CO2. The CO2 will be dealt with a mineral sequestration process discussed in other papers presented at this conference. The SOFC has the added advantage of doubling as an oxygen separation membrane, thereby keeping its exhaust stream, which is predominantly steam, free of any air. This exhaust stream is largely recycled back to the reforming stage to generate more hydrogen, with a slipstream being extracted and condensed. The slipstream carries with it the other initial contaminants present in the starting coal. Overall the process is effectively closed loop with zero gaseous emissions to the atmosphere. The process also achieves very high conversion efficiency from coal energy to electrical energy (~ 70 %) and naturally generates a pure stream of CO2 ready for disposal via the mineral sequestration process.