In the smelting and acid making process, there are generally purification acid coolers, drying acid coolers, first suction acid coolers, and second suction acid coolers. The purified acid cooler is mainly used for reducing the temperature of dilute acid, and the medium is generally dilute sulfuric acid and water with a concentration of about 5-20%. The medium for the dry acid cooler is sulfuric acid and water with a concentration of 93-96%. The medium for the first and second suction acid coolers is concentrated sulfuric acid and water with a concentration of about 98.5%.