Serious slagging in the furnace of a 300MW boiler has restricted output capacity of the said boiler. Through field and laboratory tests

main reasions causing the slagging in furnace have been found

and a scheme of retrofitting the burners and comprehensive treatment has been worked out. Via adding guide-plate in the jets of primary air to reduce the deflection of gas flow

combined with methods of numerical simulation by using computer and cold model test

the variation of gas flow deflection and of flow field in the furnace before and after adding the guide-plate of primary air has been determined

and the variation of temperature field in the furnace before and after adding the said guide-plate has been calculated by using the Monte-Carlo method. Based on the results of test and calculation

the dimensions of the guide-plate are determined. After realization of the retrofitting scheme

the problem of slagging in the furnace has been solved.