Conditioning process for dust-containing waste gas

Claim 1

A process for conditioning a dust containing gas stream prior to its introduction into an electrostatic separator comprising: introducing molten sulfur into a furnace; introducing combustion air into said furnace at a constant rate in an amount of 4.5 to 5 times that required for stoichiometric combustion of the maximum sulfur rate; combusting said sulfur in said furnace to produce a gas mixture containing air and SO 2 ; exhausting the gas mixture from the furnace; introducing said gas mixture into a catalytic converter; converting SO 2 to SO 3 in said catalytic converter; exhausting an SO 3 -containing gas stream from the catalytic converter; introducing the SO 3 -containing gas stream into the dust containing gas through distribution means; interrupting the sulfur feed when the temperature in the area of the distribution means falls below a critical value, the critical value being determined so as to avoid sulfuric acid corrosion; measuring a parameter of the gas stream when exhausted from the electrostatic separator and controlling the introduction of sulfur into said furnace in dependence on the measurement; maintaining a constant amount of thermal energy supplied to the furnace by controlling the sulfur feed rate and by controlling an amount of preheat added in a preheater to the combustion air prior to its introduction into said furnace, the amount of preheat being controlled in dependence on the sulfur feed rate; and regulating the temperature of combustion air supplied to the preheater.