Control method and control system for fossil fuel boiler

The invention relates to a control method and a control system for a fossil fuel boiler. The boiler comprises a plurality of soot blowing devices. The method comprises a step of estimating a load rise period of the boiler based on historic data. The method further comprises a step of determining at least one soot blowing device according to the influence of the soot blowing devices on the temperature of a reheater, wherein if the determined soot blowing device is controlled to blow soot, the temperature of the reheater is led to drop. The method further comprises a step of controlling the determined soot blowing device to blow soot in the estimated load rise period. According to the control method, the temperature of the reheater can be effectively kept within an expected range under the circumstance of reducing the use of such temperature regulation modes as spraying water to the reheater.