Thermodynamic analysis of thermochemical recovery of high temperature wastes

This paper describes a feasibility study of direct heal recovery system from high temperature wastes over 1 700 K by using objective chemical reaction, in which enthalpy-exergy diagram, so-called thermodynamic compass, is introduced for evaluating various systems. Blast furnace slag was taken as an example for the evaluation and familiar endothermic reactions in the cement production, the chemical industry, etc. were selected as a combination process for the heat recovery. Exergy analysis of cement and methanol plants was also carried out for further discussion. The results showed that decomposition of limestone, reforming of methane and gasification of carbon are the most promising for heat recovery of the high temperature wastes; various slag and LD gas, from a viewpoint of effective use of exergy, not energy. This also appeals a possibility of next generation symbiotic steelworks with heat cascade utilization, rather than heat recovery.