In case of domestic pyrolysis dry distillation gassification technology, it stays at the stage of its early introduction and development. Moreover, the companies possessed of this technology are limited to Japan and some countries in Europe, and domestic operative performance of this system is nominal, so there exist a lot of difficulties in securing its basic data. In addition, considering its operation and management, there happens a corrosion of metals by the production of corrosive gases in time of combustion of waste, and there arise a problem of occurrence of low temperature corrosion on exterior casing or gas ducts of a combustion chamber due to the high temperature corrosion around the burner of an incinerator, lowering the durability of an incinerator. Therefore, this study looked at the problems arising in time of incineration by understanding the characteristics of the pyrolysis dry distillation gassification incinerating facility, and did research on the improvement plan for durability of an incinerator for more economic, efficient waste incineration.

Characteristics of the exhaust gas of a commercial scale (7.2 ton/day) municipal wastes incinerator with recirculation of its high temperature combustion gas were investigated. High temperature combustion gas made by incineration was entrained by an air jet and re-used for incineration. Air was preheated to 384-512oC and diluted to have an oxygen concentration of 16-17%. Incineration of municipal wastes with the preheated and diluted air made extremely uniform and stable flames. Concentrations of nitric oxide (NOx), carbon monoxide (CO), oxygen (O2), and carbon dioxide (CO2) in flue gas were measured at the boiler exit and the stack, simultaneously. Averaged concentrations of NOx and CO were reduced to 54.2 ppm and 3.1 ppm at the boiler exit and to 49.8 ppm and 6.0 ppm at the stack, respectively, at a reference oxygen concentration of 12% without any post treatment of NOx and when the averaged outlet temperature of the combustion chamber was 904oC. The measured NOx emission was only 29% of that of a conventional municipal incinerator. Simultaneous reduction of NOx and CO is significant. Averaged concentrations of O2 and CO2 were 9.7% and 8.6% at the boiler exit and 14.6% and 4.9% at the stack, respectively.

It is known that lowering of peak temperature of flame reduces NOx emission in combustion process. Low oxygenconcentration of diluted combustion air reduces peak flame temperature, but makes flame unstable. So increasing oftemperature of reactants is needed to enhance flame stability. Mixing of high temperature combustion gas with combustionair makes low oxygen concentration and increases air temperature simultaneously. Low oxygen concentration ofcombustion air reduces peak temperature of flame and increased air temperature makes flame stable by enhancement ofcombustion reaction. Special apparatus for recirculation of high temperature combustion gas should be needed, becausegeneral blower cannot be used to return the gas of almost 1,000oC. Air jet type recirculation apparatus has been developedand installed in a commercial scale of 7.2ton/day incinerator and estimated. Oxygen concentration and temperature ofair mixed with inhaled high temperature combustion gas by the apparatus are 16.24~17.78%, 384~512oC, respectively,in a steady state of incineration.