In order to fully use the coke oven gas with low calorific value to realize mixedly burning coal gas and pulverized coal

the burners and heating surface of a 75 t/h pulverized coal(PC) boiler in Inner Mongolian Yuanxing Energy Co Ltd has been retrofitted

six gas burners with dual-passage being additionally installed below the original PC-fired burners

and tangentially arranged on a large circle and declined downward;the nozzles of original PC-fired burners being declined downward for 8~10 ℃

and the heating surface of slag-cooling tubes and economizer being increased.After retrofitting

operation and test show that the combustion is stable and the superheated steam temperature is in the normal range under all conditions of load and fuel.During the time of burning coal gas only

the output capacity of boiler can reach 59 t/h

temperature of discharged flue gas being lower than 160 ℃;in case of mixedly burning coal gas and PC

the maximum steam flow rate can reach 77 t/h

temperature of discharged flue gas being about 155 ℃;under condition of burning PC only

the output capacity of boiler being enhanced to 81 t/h

and temperature of discharged flue gas being lower than 147 ℃.