Method for preparing sulfuric acid by catalytically oxidizing low-concentration sulfur dioxide in baking flue gas

The invention relates to a method for preparing sulfuric acid by catalytically oxidizing low-concentration sulfur dioxide in baking flue gas. The method comprises the following steps of (1) introducing baking flue gas into a spray absorption tower, and spraying water onto the tower bottom of the spray absorption tower for dedusting and cooling to obtain a cooled spray liquid; (2) filling cooled and dedusted baking flue gas into a wet electron exchange resin layer loaded on the spray absorbing tower, oxidizing an electron exchange resin into an oxidization type resin with oxygen in the baking flue gas, reducing the oxidation type resin into a reduction type resin by using sulfur dioxide in the baking flue gas, oxidizing the sulfur dioxide into sulfur trioxide, and spraying with the spraying absorbing tower to obtain a dilute sulfuric acid; and (3) finally exhausting the baking flue gas out of an upper layer demister layer of the spray absorbing tower. The method has the beneficial effects that scaling and blocking are avoided; the desulfurizing efficiency is high; the investment is small; and nearly zero-cost running is realized, and great social benefit and economic benefit can be created.