Letter to the Editor: On the Economic Utilization of Oil Shale

A method and apparatus to conduct O 2 /CO 2 combustion or oxygen-enriched combustion. The boiler exhaust gas passes through a Gas Primer Sector (GPS) combined with the boiler to effect heat transfer to the combustion gas in indirect counter-flow heat exchange. Sharply reduced gas flows result from using largely moisture-free CO 2 as diluent for O 2 in the combustion gas which allows long residence time at low velocity for maximum heat transfer from the exhaust gas to the combustion gas. Most particulate drops out and most moisture is condensed from the cooled mostly CO 2 exhaust gas. The larger portion is blended with oxygen for the combustion gas and reheated and returned to the boiler through the integrated GPS; the smaller portion is cleaned and separated, the CO 2 released or recovered. The complete exhaust gas-combustion gas cycle may be 30 to 90 seconds and preferably about 60 seconds. The high heat capacity of CO 2 allows a much higher oxygen content in the combustion gas compared to open-cycle air combustion with a large nitrogen content of lower heat capacity. Efficiency is increased. Final exhaust gas separation and recovery is simplified. Condensate is processed to boiler feedwater or portable water quality. NO x is eliminated, mercury fume captured and CO 2 output reduced.