Patent ID: 8679447

Claim:
A process for producing sulfur trioxide from a replenished circulating inventory of sulfur dioxide, which process comprises: A) dividing a stream of gaseous SO 2 into a first gaseous SO 2 stream and a second gaseous SO 2 stream, adding a controlled amount of pure oxygen into the first gaseous SO 2 stream and concurrently and separately feeding (i) the resultant oxygenated first gaseous SO 2 stream into an upstream stage of a sulfur burner having an upstream stage and a downstream stage, and (ii) the second gaseous SO 2 stream into the downstream stage of said sulfur burner while concurrently feeding molten sulfur into said upstream stage of the sulfur burner so that additional SO 2 is formed in the sulfur burner via a continuous exothermic reaction taking place in said sulfur burner, said first and second feeds reducing the temperature of the exothermic reaction in the sulfur burner, and the proportions of pure oxygen and sulfur being fed to the sulfur burner providing a gaseous exit stream of gaseous SO 2 and free oxygen; B) feeding said gaseous exit stream into a catalytic SO 3 converter that consumes all of the incoming oxygen and converts a portion of the SO 2 in the converter to SO 3 so that an exit stream of SO 2 and SO 3 is formed in a molar ratio in the range of about 7:1 to about 25:1; C) cooling the exit stream of SO 2 and SO 3 by indirect heat exchange with said recycle stream of gaseous SO 2 of A) whereby the temperature of said recycle stream of A) is increased to ensure continuous operation of the sulfur burner, and whereby a cooled exit stream of SO 2 and SO 3 is formed; D) separating the cooled stream of SO 2 and SO 3 into a gaseous or liquid stream of SO 3 for recovery or use, and a gaseous recycle stream of SO 2 ; E) feeding fresh make up SO 2 and/or sulfur into said gaseous recycle stream of SO 2 and adjusting the temperature of the resultant SO 2 stream by heat exchange to form the stream of gaseous SO 2 that is divided in A).