Regardless of the firing method, when coal is burned, a relatively small portion of the ash will cause deposition problems. Ash passing through the boiler is subject to various chemical reactions and physical forces which lead to deposition on heat absorbing surfaces. The process of deposition and the structure of deposits are variable due to a number of factors. Particle composition, particle size and shape, particle and surface temperatures, gas velocity, flow pattern, and other factors influence the
extent and nature of ash deposition.
The two main categories of high-temperature ash deposition are called slagging and fouling. Slagging is the formation of molten, partially fused or resolidified deposits on furnace walls and other surfaces exposed to radiant heat. Slagging can also extend into convective surface if flue gas temperatures are not sufficiently reduced.
Fouling is the second form of ash deposition and is defined as the formation of high temperature bonded deposits on convection heat absorbing surfaces, such as superheaters and reheaters, that are not exposed to radiant heat. In general, fouling is caused by the vaporization of volatile inorganic elements in the coal during combustion. As heat is absorbed and temperatures are lowered in the convective section of the boiler, compounds formed by these elements condense on ash particles and
heating surface, forming a layer which aids deposition.
Areas where slagging and fouling can typically occur are shown here:
حدد منطقتك الجغرافية للاستعلام عن المبيعات أو الخدمات: