In CFB boilers supplied by JFE, advanced control is realized by adoption of the following control methods in addition to normal boiler control.

1. Boiler Master and

Fuel Injection Rate Control

Normally, with turbine generators, power generation (or power transmission) control is performed by the demand of power generation (power transmission), and the boiler master performs proportional-integral-deriv-ative control (PID control) of the main steam pressure. In the method adopted here, the output from the boiler master is used as the command value for the fuel input calorie. After assigning the input calorie rates of the respective fuels, which have been set in advance, the charging amounts of the fuels are determined from the unit calorie of each fuel. For the charging systems of each fuels, participation in boiler master pressure control (or not) is selected, and constant input calorie control is performed for the nonparticipating charging systems. With this method, it is possible to maintain a constant total input calorie and suppress fluctuations in boiler output, even when the input calorie ratios of the respective fuels are changed and during backup with another fuel due to troubles in one of the fuel charging systems.

In order to eliminate deviations in boiler master out-put and the combustion air rate due to changes in the unit calorie of the fuels, calorie compensation control is performed, in which the boiler master output is cor-rected by a compensation value obtained from the ratio of the predicted main steam flow rate obtained from the fuel charging rate in operation and the actual main steam flow rate.

2. Automation of Boiler Operation

In JFE Engineering’s CFB boilers, operation of the boiler is automated so that all processes can be per-formed using one button by an automated sequence, which includes starting and stopping of the auxiliary equipment. This also includes the turbine generator when this equipment is installed.

∙ Start sequence (auxiliary start, ignition and pressur-ization, main fuel switching, turbine start, generator circuit breaker close, load increase)

∙ Stop sequence (load decrease, generator circuit

breaker open, turbine stop, boiler stop, auxiliary stop)

Plant control in normal operation is also virtually completely automated. At the CFB plants supplied by JFE Engineering, which are currently in operation, nighttime operation is performed by a 2-person system.