OCR Text |
Show This burner is a very simple one having a fuel injection hole inclined to its axis at the tip part. Accordingly, the price of the burner is low, and it can be said that modification of equipment such as the burner tile area is hardly necessary. So this burner is particularly suitable for application to the existing furnace. The performance of this low N O x burner in test furnace are set forth below: Fig. 6 shows the effect of excess oxygen concentration on N O emission for various kinds of fuel. In this case, N O x value decreases to a value less than half of the conventional burner. Fig. 7 shows the effect of combustion air temperature on N O emis-sion. NOx value is also extremely low, but furthermore it hardly affected by combustion air temperature. This finding together with another finding that it is hardly affected by the above-mentioned excess oxygen concentration is very advantageous in a practical furnace with a large fluctuation width in these values. °< ( / / o / * > Or1 > ! s° V C-o 4 y *£ « o y tL <- - a ^5 •Or K \ \ ) M o • A I Conventionol Model bEur nleorw NOx burner Fuel Butane ajos C Heovy oil COG ot nu 600 Conventional burner Model E low NO« burn* o • A Fuel Butane gas C Heovy oil COG 100 200 300 400 900 ComtoWton Air T«*» ("CI Fig. 7. Effect of combustion air temperature on N O emission (30° burner tile) 2-2-2. Principle and performance of improved low N O x burner (Model EE) Fig. 6. Effect of excess 02 on NO emission (30° burner tile) It is a model improved from the aforementioned Model E low N O x burner. In type diagram Fig. 8, combustion air A and fuel stream F are mutually injected in separate directions. For that reason, mixing of fuel and air is further suppressed at the initial stage of combustion, and combustion progresses gently. Consequently, the state of very uniform combustion is obtained. Furthermore, because flue gas G begins to mix in owing to momentum of combustion air in addition to an effect of a drop in oxygen partial pressure, the effect of which is called, the self flue gas recirculation, is achieved. Therefore, N O x decreasing effect also becomes large, and a decrease in the quantity of smoke is also obtained. The relation between Bacharach smoke number and N O x emission is shown in Fig. 9. Here, smoke decreases to about half of the case of 11- 4 - |