Mechanisms of Fouling, Slagging and Corrosion by Pulverized Coal Combustion

摘要

The objective of this program is to conduct a detailed and comprehensive study of the mechanisms of fouling, slagging and corrosion in pulverized coal combustors by employing well controlled model systems which simulate the coal combustion environment. A combustion test rig was designed, constructed and calibrated for parametric tests in which the following variables were evaluated: Non-condensing alkali (NaCl), condensing alkali (Na sub 2 SO sub 4 , K sub 2 SO sub 4 ), alkali ratio (Na/K) - melting point depression, inert particles (Al sub 2 O sub 3 ), reactive particles (SiO sub 2 and Fe sub 2 O sub 3 ), ash viscosity (SiO sub 2 , Al sub 2 O sub 3 , CaO, Fe sub 2 O sub 3 glasses), sulfur (SOx gas, SO sub 42- ), incomplete combustion - reducing agent (carbon), reactive surface area (SiO sub 2 particle size > standard SiO sub 2 particle size), gas stream and particle velocity, and tube material and tube temperature. Four target tube materials were employed: SiC (2000 exp 0 F), Hastelloy X (1600 exp 0 F), Croloy (1100 exp 0 F) and SA-210 (800 exp 0 F). Particulate fouling species used in the rig tests ranged from SiO sub 2 and Al sub 2 O sub 3 to complex glasses simulating coal ash. In reviewing the wealth of information generated in the test program, a number of significant findings emerge as being most urgent to fouling/slagging: Target tube temperature, viscosity profile, fouling medium particle size and shape, reactivity of fouling medium, aerodynamic flow, dewpoint/condensation of sulfates, particle loading rate, and surface finish. Four approaches are recommended as being potentially capable of reducing fouling and slagging: Chemical control, mechanical erosion (deposit removal), aerodynamic optimization, and elimination of tube corrosion by ceramic coatings. 46 refs., 105 figs., 23 tabs. (ERA citation 10:023746)