Exhaust from incinerators and fossil-fuel power plants are required to pass through an SO2 Scrubber before entering the atmosphere. SO2 Scrubbing, also known as Flue-Gas Desulfurization (FGD), can remove 90-99% of SO2. SO2 Scrubbers are large vertical tanks that perform a series of processes on the exhaust.
- The wet scrubber has the advantages of high SO2 removal efficiencies, good reliability, and low flue-gas energy requirements.
- In addition, it is capable of removing from the flue gases residual particulates that might have escaped the particulate-removal system.
Sulfur dioxide is a reactive gas – so when it meets other gases within the earth’s atmosphere, a fine, secondary particle forms. Emissions from automobiles and trucks, industrial processes, wood-burning stoves and forest fires, and surface mining and agriculture activities also contribute to the formation of fine particles. An abundance of these fine particles, or SO2, within the atmosphere could impact our health and the environment.
In 1971, the United States Environmental Protection Agency first established air quality standards relating to SO2 and fine particles, and updates the standards periodically. All Duke Energy plants continuously monitor emissions to ensure air quality regulations are met.
Once sulfur is burned and produces SO2, the exhaust gas passes through the scrubber where a spray mixture of limestone (or other chemical reagent) and water reacts with the SO2. The reaction enables the SO2 to be removed before it’s released into the atmosphere. Duke Energy’s newer scrubbers are typically designed to remove 95% or more of the SO2 from the exhaust gas. The white plume that comes out of the stack is water vapor.
When SO2 combines with limestone, a primary byproduct is calcium sulfate, commonly known as synthetic gypsum. A recyclable product, synthetic gypsum is used in the manufacturing of wallboard and cement, and as a soil amendment in agricultural and construction applications.
Much of the synthetic gypsum produced from Duke Energy’s scrubbers is reused in these and other applications. Unused byproducts are properly disposed of in approved landfills.
- Steel and Mining industry,
- Electric power plants,
- Oil and gas extraction operations,
- Oil refineries,
- Pulp and paper mills,
- Sewage treatment plants,
- Large poultry farms ,
- Portland cement kilns,
- Municipal waste landfills,
- Coke ovens,
- Sulfur products and hydrogen sulfide production,
- Asphalt production and storage etc.