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Show Unlie SOx, not all the ni-trogen content in fuel turns into NO but only 30 to 40%. However, the nitrogen content in fuel is related to sulfur content, and the fuel with less sulfur contains less nitrogen proportionally. Accordingly, the effect of quality improvement of NOx fuel or conversion into gas fuel such as LNG is significant. Quality improvement of fuel is effective not only to NOx but also to SOx and dust. Generally speaking, generation of NOx by different types of fuel can be summarized in the order of coal>asphalt>heavy oil C>heavy oil B>heavy oil A>light oil>kerosene>LPG>city gas>carbon oxide>methanol>H2 Fig.6 General relation between air ratio and NOx quantity Air ratio Alteration of operating air ratio range(low oxygen operation) The relationship between the air ratio of NOx generation and NOx generation can be classified into three patterns as shown in Fig-6. The most foundamental one of the three patterns is the curve (a), which shows the maximum value of NOx at an air ratio. It is decided depending on the range of operating air ratio and fuel/air mixing characteristic in the combustion chamber to which pattern the data of actual measurement belongs. In other words, if the operating range of a combustion equipment is larger than the peak point of (a) curve, the pattern is (b) curve, and if the range is smaller than the peak point, the patter is (c) curve. Moreover, the air ratio at the peak point tends to move to the side of lower air ratio. From this, it can be generalized that the peak point deflects to the side of lower air ratio with liquid than with solid, and with gas fuel than with liquid fuel. However, 8 . n _ |