The spent acid is injected through spray nozzles into the combustion chamber where the acid is decomposed to form sulfur dioxide, oxygen, and water vapor. During turndown conditions, strong acid is also injected through a spray nozzle into the combustion chamber. Any hydrocarbon present with the acid burns to form carbon dioxide and water vapor and supplies part of the heat required for the decomposition of acid and vaporization of water in the acid feed stream.
The combustion of H2S gas also supplies heat to the system and yields SO2 gas and water vapor. Any hydrocarbon present in the H2S gas has the same effect on the system as hydrocarbon in the spent acid feed stream. H2S gas supplied to the combustion chamber is fed into a burner nozzle.
The additional heat required to maintain the combustion chamber outlet temperature at 1,066 C is achieved by burning fuel gas. In addition, the required combustion air is preheated to reduce the gas volume that the plant must handle.
