DEPOSITION IN POWER PLANTS - MECHANISMS AND IMPACT

Maintaining the high purity of boiler water, feedwater and steam is critically important for ensuring reliability in utility power generating systems. By understanding how contaminants enter or are generated in steamside equipment, mechanisms of transport and deposition of impurities, and the root causes of damage such as corrosion and scaling, it should be possible to define water and steam quality limits to eliminate or ameliorate the problems requiring unscheduled outages. In addressing one facet of this goal, a fundamental assessment of deposition mechanisms has been undertaken. Relevance of each mechanism to the power generation cycle, including the ambient conditions present in the feedwater and steam equipment, has been identified. This assessment is based on i) review of existing literature and discussions with experts to characterize the fundamental processes; ii) discussions with power industry personnel and contractors to provide insight into the role of various deposition mechanisms at specific areas within the steam generation cycle; and iii) evaluation of suspected and novel deposition mechanisms which warrant further research. The results of this study have been incorporated into two extended tables for ease of identification and indexing. It is envisioned this study will facilitate understanding of how basic deposition processes function in steam cycle equipment, and help focus resources on poorly understood areas. Topics recommended for future research include mechanisms for formation, transport, and deposition of colloids under steam cycle conditions, and mechanisms involving electrostatic and magnetic facilitation of deposition.