2010 Volume 52 Issue 162 Pages 280-288
Industrial once-through boilers regulated by “Boiler Safety Rules (in Japan)” were developed for increasing equivalent output (i.e. increasing heat release rate in furnace) against universal environmental standards have been more made more rigorous. Since this boiler type at the age 1960, boiler efficiency increases up to 96%, and also low emission technologies under high heat release rater were developed continuously against from low quality fuel as heavy oils spread at the Oil-Shocks to natural gas. At present, main fuels for boilers are shifted from regulated A-oil to natural gas (methane) due to environmental requirements and unstable global oil markets. Environmental standards qualities are more severely restricted about fixed emission facilities. Based on these environmental backgrounds, the progressive pre-mixed gas combustion techniques applied using flat surface burners against water tube bundle were developed and applied to low NOx emission as “Non-furnace combustion technique”. Approximately zero NOx emissions achieved with reducing catalysis and “Non-furnace combustion technique” at theoretical combustion air ratio that fuel gas flow controlled with sensing O2 concentration in combustion gas at exit. Based on this technique, the emissions of NOx and CO reduced within a few ppm at O2≒0~0.05% (nearly theoretical air ratio range).
