Direct-contact heat exchange, shale production, and slag processing as examples of new efficient technologies for power generation

Novel concepts for direct-contact gas-water heat exchangers (DCHX), in which the energy in combustion exhaust gases is recovered as 70–80 °C hot water, are described; such hot water is a considerably more valuable energy stream (e.g. for industrial process heat or district heating) than the water, at best at 50–55 °C, which emerges from a conventional DCHX, where the wet-bulb temperature of the combustion gases is the upper limit of the hot-water temperature. Escape from this constraint is achieved by one of two methods: (1) the use of a high-boiling-point liquid (an aqueous solution of lithium bromide) in the first of two coupled DCHX; or (2) the deliberate introduction of additional water into the combustion exhaust stream to raise its wetbulb temperature. Both technologies have been demonstrated at the Mary Power Plant in Turkmenia, which burns natural gas. The processing of fine shales is assessed, with a quantitative investigation of the value of the principal products and by-products: shale oil and semicoke gas for power generation, chemicals (phenols), and ash useful for the deacidification of soil to increase crops. Finally, the results of an analysis of a new technology for the production of ferrosilicates during the combustion of coal are presented.