The invention relates to a process for the continuous preparation of oleum of
a concentration of 10 to 45% by weight of SO3 and/or sulphuric acid
of a concentration of 94 to 100% by weight of H2SO4 by combustion
of sulphur with atmospheric oxygen according to the principle of superstoichiometric
combustion, cooling the resultant sulphur-dioxide-containing gases to 350
C. to 500 C., catalytic conversion of these cooled gases to give sulphur-trioxide-containing
gases in the presence of a vanadium-containing catalyst using single or double
contact catalysis, absorption of the sulphur-trioxide-containing gases after cooling,
if appropriate removal of liquids from the gases after absorption and energy recovery,
with liquid sulphur being injected into the hot combustion gas stream perpendicular
to the main direction of flow in the form of a fan using one or more bimodal fan-type nozzles.
