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Show X o z CU U 3 CO CO CU £ 130 120 110 100 90 80 70 60 Burner No. 2 Ob j ecjt to be Burn'er treated JIo.l t lb -JU3JJ 4|U-JQ-" 0.50.71.01.2 Air distribution of burner No. 1 (%) Total air-fuel ration: 1.12 - 1.19 Total gas consumption: 250 m3/h Fig. 91 Off stoichiometric combustion data of heating furnace Furnace temperature "15 14 13 12 II W For off stoichiometric combustion, no-extra cost for equipment is required as it can be practiced only by simple valve operation. For low temperature furnace, or even for high temperature furnace such as heating furnace for forging, care shall be paid to the safety of combustion or to the discharging of non-combustion substance, when the furnace temperature is being increased. In an example of a butch type heating furnace for forging with two burners, the furnace is operated with normal air ratio when the temperature is being raised and the operation is switched to off stoichiometric combustion by electrical signal when the furnace temperature exceeds about 1000°C intending to solve the above problem. To be more specific, the air pressure applied on the diaphragm of the equalizing valve is changed by electrical signal for the switching to the off stoichiometric combustion as shown in Fig. 92 of which NOx chart is shown'in Fig. 93. S - 84 - |