ABSTRACT
The ENEL S.p.a. research programme into the reduction of SOx and NOx emissions by addition of chemically reactive materials to the combustion gases of power station boilers includes detailed studies of the effects on the deposition of inorganic material on fireside heating surfaces. Calcium hydroxide has been used to absorb SOx, and urea to reduce NOx in trials during station normal operation, both were injected at the upper part of the combustion chamber. Air-cooled probes were used to determine the deposition rate of solid material from the gases entering the superheater and the air heater at a power station burning Colombian coal. Results are presented showing the total deposition rate and the composition of the water-soluble material, including solution pH, fluoride, chloride, sulphite, sulphate, ammonium, sodium, potassium, magnesium and calcium, at probe metal temperatures of 540 to 700°C at the superheater and 85 to 105°C at the air heater. The implications for fouling and corrosion of the heating surfaces are considered.
