Flue gas desulfurization consists of air pollution control technology that is used to remove sulfur dioxide from combustion gas before atmospheric release. To date, there are many processes used to remove sulfur dioxide from flue gas, such as the dry and wet systems. Among these, the semi-dry lime/limestone-gypsum process is one of the most widely used and reliable technologies available.
The semi-dry lime/limestone-gypsum process is composed of two main components; an aerosol wet scrubbing stage and a lime/limestone-gypsum filter stage. In the wet scrubbing stage, the flue gas is brought into contact with a reagent, such as lime or limestone, suspended in the form of an aerosol. The reagent captures and neutralizes the sulfur dioxide in the gas, producing a liquid by-product which contains dissolved calcium and sulfur compounds. This by-product is then treated in a settling vessel to allow for the separation of solid particles from the liquid. The liquid is then routed to the filter stage of the process, where the dissolved calcium and sulfur compounds are removed and processed.
The filter stage utilizes a bed of finely powdered lime/limestone and gypsum to capture and filter the dissolved calcium and sulfur compounds from the liquid by-product. The lime/limestone-gypsum mixture is highly efficient at binding to the dissolved sulfur dioxide, converting it to a solid form which can be easily removed from the filter. After the filter is saturated with calcium sulfate, the filter is replaced and the spent filter material is recycled for use in other applications.
The semi-dry lime/limestone-gypsum process is an effective and cost effective way of removing sulfur dioxide from flue gas. It is relatively easy to operate and maintain, and can reduce sulfur dioxide concentrations in flue gas by 95-99%. This process is widely used due to its effectiveness, low cost, and overall environmental friendliness. Additionally, the process produces a usable by-product with commercial potential; calcium sulfate can be used in a variety of applications, such as construction or fertilizer production.
The semi-dry lime/limestone-gypsum process is a widely used method which eliminates sulfur dioxide from flue gas, at an acceptable cost with little environmental impact. It is a reliable and proven technology which can be used to reduce emissions and improve air quality, while also providing a valuable by-product.
