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A twenty-eight layered new polytype of cadmium iodide, designated 28Hc, with unit-cell dimensions a--4.24, c--95.69/~, is described. The detailed atomic structure has been worked out and its zigzag sequence is found to be 2222222222221111. The growth of the polytype is examined in the light of the screw dislocation theory of polytypism. The screw dislocation theory is not able to explain fully the growth of this polytype. The polytype 28Hc is so far the largest cadmium iodide polytype with a known atomic structure.

An advanced coal based power plant system that has an electrical efficiency of 60% on an HHV basis is defined. The solid oxide fuel cell (SOFC) hybrid has been shown to be an essential requirement in order to achieve such a high efficiency. The coal is gasified utilizing a high pressure air-blown advanced transport reactor (ATR). A thermo-economic analysis of this integrated gasification fuel cell (IGFC) plant is performed by comparing it to an integrated gasification combined cycle (IGCC) plant that utilizes a gas turbine combined cycle for power generation. Results of this thermo-economic analysis indicate that the required “break even” cost of the SOFC system is $400/kW on an installed cost basis such that the cost of electricity of IGFC plant is the same as that of the IGCC plant. Coproduction of H2 and capture of carbon emissions may be incorporated in the design without causing a major thermal penalty on the system performance when high temperature separation membranes are employed. An O2-blown gasifier is required for such applications. The technology development needs are addressed.