Concept of expert system for boiler fouling assessment

Abstract

The expert system for fouling assessment development is one of the possible approachs to the mitigation of deposit formation on boiler heat transfer surfaces. This paper presents the evaluation of the diagnostic variables and their domain based on the criteria for the fouling assessment. In agreement with the boiler furnace design, respective fields for the deposit control are selected to be instrumented with the ‘clean’ radiation heat flux and ‘not-cleaned’ radiation heat flux for the on-line reading. The ratio of the ‘clean’ and ‘not-clean’ radiation heat flux is proved to be a sensitive diagnostic variable for the deposit thickness. The rate of change of radiation heat flux ratio, together with the efficiency of the heat transfer surface, are diagnostic variables used for the design of the expert system knowledge base. The knowledge base structure is based on the object oriented concept. In this respect the FOULING object is defined. Its structure is composed of the respective attributes and values linked with the number of situations to be selected for the assessment. The examples given are related to a 300 MWe power-plant boiler furnace. It includes the number of situations reflecting different deposit formation situations: total and upper level of side surface of fouling deposit.