For low flow rate acid gasses (<1,000 Nm3/h) or for those with a low sulfur content (H2S+oragnosulfur ≤ 5%), the Claus process is not as economical because of the low sulfur production and high operating cost.
Treating high hydrocarbon content (C3+C4+C5 ≥ 5%) acid gasses with the Claus process may cause a series of problems such as incomplete combustion of hydrocarbons, carbon deposition on the catalyst surface, poor product quality, low sulfur recovery, and high NOx emissions. If the sulfuric acid process is used, low acid concentration, severe dew point corrosion, and high capital cost will become the key concerns.
To address these issues, the incineration process can be used to convert all of the sulfur compounds in the acid gas to SO2. The incinerated flue gas from the incinerator is then treated in the ammonia desulfurization unit to produce ammonium sulfate. The treatment of low flow rate, low sulfur content, or high hydrocarbon content acid gasses with the “incineration plus ammonia desulfurization” process provides a solution with low capital cost and high operating flexibility.
If the user also has a desulfurization requirement for boiler flue gas, flue gas from the acid gas incineration before heat recovery can be combined with the boiler flue gas and treated in one ammonia desulfurization unit, thereby further reducing capital and operating costs.