In order to adapt to the changes in the coal market and satisfy the relative requirements

the1 025t/h boilers in 4×300 MW units of Zhanjiang Electric Power Company were retrofitted

the fuel was changed into bituminous coal with high volatile matters and the capacity of both the boiler and the turbine was enlarged.After the retrofitting

coking problem easily occurred in the boiler.Thus

the furnace coking risk was assessed by numerical simulation

and the boiler integral transformation scheme was proposed

which includes the pulverizing system retrofitting

changing the burners

increasing the heating surface area

applying horizontal bias burner

reducing the excircle diameter

and other anti-fouling measures.After this transformation

the boilers can safety burn bituminous coal with volatile content of above 40%(dry ash free basis)

and the fouling situation turned well

the boiler maximum continuous rating reached1 077t/h

the boiler efficiency was enhanced to 93.22%

and the steam temperature

steam pressure and steam flow rate all met the design requirements.However

due to low ash melting point

serious coking will occurred when burning Indonesia coal and Shenhun coal purely.It is recommended these two coals blending ratio be lower than 50%.