The sulfuric acid plant and sulphonation plant share a common sulfur melting system. After sulfur melting, the sulfur is transported to the sulfur burning furnace through a sulfur pump and burned with dry air. The dry air is dehumidified by 98% sulfuric acid in the drying absorption tower, achieving a dew point of minus 40 degrees. Then, the main blower sends the dry air to the sulfur furnace for combustion.   After combustion, SO2 is converted once through a conversion tower to produce SO3 gas. Afterwards, SO3 is absorbed by 98% sulfuric acid in the primary absorption tower, and the exhaust gas after absorption returns to the secondary conversion. The heat from the primary conversion will be transferred to the exhaust gas from the second conversion, and after the second conversion, the conversion rate can reach 99.98%. Afterwards, SO3 undergoes secondary absorption, and the exhaust gas undergoes alkaline washing in the scrubber before finally being discharged into the atmosphere. In the early stages of start-up, the scrubber will operate at full capacity to absorb a larger amount of sulfur dioxide from the initial start-up. Under normal operation, qualified discharge can be achieved without passing through the scrubber. The exhaust gas can meet the emission standards in any country under any operating conditions.   The process for energy recovery mainly involves using fire-tube boilers to recover the combustion heat generated by sulfur combustion, as well as the reaction heat generated by the first part and secondary conversions of the converter, and generate steam. Steam can be used for sulfur melting in sulfuric acid and sulphonation plants. Meanwhile, a portion of the steam can also be used for lithium bromide refrigeration in sulphonation units. The remaining steam can be used in other nearby unites. The total heat recovery rate will reach over 80%.