6 - Ash fouling, deposition and slagging in ultra-supercritical coal power plants

Abstract

Ash deposition on heat transfer surfaces in a boiler have been a significant operational challenge for coal-fired power plants. This chapter reviews the recent literature on ash deposition in coal-fired boilers, covering the nature of minerals and inorganic matter in coal, fundamentals of inorganic reactions and ash transformation, mechanisms of ash fouling and slagging, as well as ash deposition management. The influence of the furnace operating conditions on the formation and growth of ash deposit as well as the physical and chemical characteristics of the ash deposits are also discussed in detail. Practical examples are examined to illustrate how fundamental research has advanced and can lead to satisfactory solutions to practical problems. The ash characteristics and deposition formation during the co-firing of coal and biomass are also discussed. References on ash deposition in advanced ultra-supercritical power plants is scarce in the public domain and much of the literature covered in this chapter is based on the conventional subcritical coal-fired power plants and on laboratory based fundamental research. Therefore, the extension of the discussion to ultra-supercritical coal-fired boiler applications is drawn from the author’s own research and practical problem solving experiences.