The project uses ammonia water with a concentration of about 8.77% provided by the owner as an absorbent to absorb SO2 in the exhaust gas discharged from the sulfur recovery device. The exhaust gas temperature at the inlet of the desulfurization system is 750°C, the exhaust gas volume is 25,651Nm3/h, and the SO2 concentration in the exhaust gas is about 1526mg/Nm3. The system is equipped with a fire-tube waste heat boiler and an economizer. The high-temperature waste gas at 750°C recovers the waste heat through the waste heat boiler to produce about 9.5t/h of saturated steam of 1.5MPa. The waste gas temperature is lowered to 150°C and then enters the desulfurization tower. Concentration, absorption, desalination, and fog removal are performed in sequence to reduce the SO2 content in the exhaust gas to below 35mg/Nm3, and the net flue gas is discharged through the 60-meter-high tower top chimney, and ammonium sulfate products with a moisture content of less than 5% are obtained at the same time.