How dust forms on the heating surfaces of waste heat boilers on rotary furnaces firing raw and caustic magnesite

Conclusions

The manner in which dust deposits form on the walls of the gas duct and heating surfaces of boiler utilizers attached to rotary furnaces firing magnesite was clarified.

It was found that in firing raw and caustic magnesite as a result of dissociation, oxidation, distillation, and evaporation the dust-laden flue gases are enriched with sulfur trioxide, vapors of alkali and fluorine which, being absorbed, are condensed onto the fine particles of dust, and reacting with them and between themselves, form simple and complex sulfates of alkaline and alkaline-earth compounds and magnesium fluoride, causing the formation of a deposit on the walls of the gas duct and surface of the pipes of the boiler until they are completely blocked and stop the furnace.

The formation and rate of growth of the bonded strong deposits depend on the amount of active dust entering the furnace from the electric filters and hence on the concentration of sulfates of alkali and alkaline earths and magnesium fluoride, on the dust content, temperature, and flow velocity of the flue gases.