THERMAL DAMAGE: The environment near the incinerator burner flame can easily reach 3000o F or higher. Loss of temperature control or selection of materials with poor high temperature properties account for most thermal damage.
Metal Selection: Since incinerators operate at high temperatures, carbon steel can't be used in certain areas. Burner parts are normally constructed of 304, 316 or 310 stainless steel in order to handle normal flame temperatures. Operation with corrosive wastes may require use of Inconel, Hastelloy or other specialty metal for both temperature and chemical resistance. The degree of air cooling and radiation affect metal selection. Incinerating acid wastes usually requires flue gas scrubbing. A scrubber circulating 15% HCl at 200o F may require Zirconium or nonmetallic construction - even Hastelloy may prove inadequate at an acid temperature above 150o F. Trial-and-error or past experience with similar waste may be required for a long lasting design.
Source of problem: Wrong metal selected for the waste or combustion products being handled.
Refractory Selection: An operating temperature above the service limit for a particular refractory can weaken or melt the refractory. Operation under reducing conditions (starved air) in the furnace reduces the service limit of most refractories by several hundred degrees (use 400oF as a rule of thumb). Reducing operation can cause severe shrinkage in phosphate bonded refractories (causing large cracks in castable refractory or collapse of large sections of brick linings). Waste containing certain ashes, particularly sodium compounds, can create corrosive deposits which dissolve certain refractory constituents, thinning the lining in a matter of months.
Source of problem: Improper refractory selection or placement.
Radiation / Convection: Waste gases must be transported to the incinerator and then injected into the burner or furnace at the proper location and velocity for stable operation. Intermittent flow may allow hot flue gases to circulate back into the waste delivery hardware, overheating carbon steel or nonmetallic materials. Maintaining minimum flow or using a different material of construction can solve the problem. Hot refractory radiates heat, and a straight view line into an exterior waste gas plenum or duct can allow localized overheating some distance from the heat source. A change of sight line or use of high temperature materials can be a solution.
Source of problem: Improper configuration, flow control or materials of construction.