subject: Controlling Emissions Of Hydrogen Sulfide [print this page] Hydrogen Sulfide is dangerous to the environment, colorless, very poisonous, highly flammable gas with the characteristic foul odor of rotten eggs. With density greater than air, it tends to accumulate at the bottom of poorly ventilated spaces. Although very pungent at first, it quickly deadens the sense of smell, so potential workers may be unaware of its presence until it is too late. 800 ppmv is the lethal concentration for 50% of humans for 5 minutes exposure.
A common off-gas produced in the Steel and Mining industry is Hydrogen Sulfide. At even very low concentration levels H2S is considered a fatal gas. H2S is commonly reduced by thermal oxidation to SO2 and SO3 for possible usage in other plant processes or if not utilized for other applications may be removed by the use of a wet scrubber.
Air pollution control by industrial engineers and H2S application specialist haveoften decided to use direct fired thermal oxidizer systemsforthe treatment of H2S and CS2 pollutants.
Many, after being involved with high fuel costs have devoted the time in research and product development to design and manufacture a regenerative thermal oxidizer that workswith much reduced fuel consumption.
ARegenerative Thermal Oxidizer (RTO) is utilized to improve fuel efficiencies and to reduce NOX production that normally comes with a standard Direct-Fired Thermal Oxidizer.
Many steel and mining facilities are currently utilizing Direct-Fired Thermal Oxidizers and have more recently realized that a Regenerative Thermal Oxidizer would be a better piece of equipment when considering a direct fired thermal oxidizer's usage of fuel costs.
Many limiting factors have to be considered while designing the H2S reduction thermal oxidizer. Some considerations include; blocking any H2S from possible leakage from the regenerative thermal oxidizer system, leaking can cause premature degradation and drastically reduce the overall life of the equipment; blocking any possible fatal H2S gas to be emitted directly into the immediate atmosphere causing severe health and safety issues.
Many systems have the potential of high operating pressures, consideration should be given to flow and metal thickness design. Many systems that have been installed have not taken into considerationhigh pressures which resulted in duct protrusion and fractured welded seams emittingexposure of high levels of H2S.
Design considerations should also be given to the type and metal thickness to obtain high outlet temperatures. These temperatures need to be above any possible condensation levels of by-products, this will reduce any formation of sulfuric acid within the exhaust system. With the high outlet temperatures the exhaust may be used to generate high pressure steam which may be used in steam operations or to power a turbine creating offset electricity.
Sample ports allow the periodic testing of the stack and inlet process streams to monitor H2S values. In certain global areas regulations may also require continuous monitoring of SO2 emissions. In determining whether or not to apply waste heat recovery to regenerative thermal oxidizer on plant size and utility costs. Economic evaluations comparing regenerative thermal oxidizers with and without waste heat recovery should be performed.
