Boiler sootblowing control system

Abstract

The invention is a method for controlling sootblowing in a power boiler or chemical recovery boiler. The method comprises assigning the sootblowers into a number of groups. Sootblowers within a group are generally adjacent to each other and cover heat transfer surfaces having similar fouling deposit formation characteristics. Each group will typically have up to 4 sootblowers. Every sootblower is assigned a weight factor which is the percentage of the total number of sootblowing cycles that the sootblower will be operative. Every sootblowing cycle in the boiler begins with the most upstream sootblower group and proceeds progressively through all of the other groups in the direction of the flow of combustion gases until the most downstream sootblower group is reached. By blowing in this manner the dislodged fouling deposits from the upstream heat transfer surfaces are swept in the direction of combustion gases. This sootblowing strategy is designed to maintain the boiler at or near maximum operating efficiency. Reduction in sootblowing steam usage is a secondary consideration, even though in one installation the usage was lowered to about two thirds of that previously needed. On-line instrumentation to determine heat transfer characteristics can be used to modify the default values of the weight factors assigned to the individual sootblowers in order to accommodate on-line changes in operating characteristics. The method is well adapted for use either in a feedback or feed forward control strategy and may also be used with a combination of these techniques.