Retrofit of a 75T/H PC-Fired Boiler Into a Coal/Gas Co-Firing One

For full use of low heat value of coke oven gas and operation under conditions of coal, gas and coal/gas, a previously 75t/h PC-fired boiler was retrofitted: six gas burners with dual-passage were installed under the originally PC-fired burners and tangentially arranged with a larger combustion circle and declined axes; the pulverized coal fired burners were declined downward 8∼10° so as to control the flame center; the heating surface of slag cooling tube and economizer were extended. The operation and test after the retrofit showed that: the combustion was very stable and temperature of the superheated steam was between the normal range under all conditions of load and fuel; the maximum steam rate was 59t/h and temperature of the exhaust flue gas was lower than 160°C under gas condition while gas flow was at 26000 Nm3/h; the maximum steam rate was 81t/h and temperature of the exhaust flue gas was lower than 147°C under coal condition; the maximum steam rate was 77t/h and temperature of the exhaust flue gas was about 155°C under coal/gas condition.