Acid rain is due to the presence in the atmosphere of SO2 and NOx which, after a series of reactions, are deposited as nitric and sulphuric acid in the form of rain. Particulate matter is known to cause serious respiratory diseases.
Carbon sequestration is a method that allows the reduction of CO2 by capturing it at its source (e.g. a power plant) and storing it in non-atmospheric reservoirs such as geologic or oceanic reservoirs (Herzog). The Sleipner project is a working example of carbon sequestration technology. Off the coast of Norway in the North Sea, it is in fact the world's first commercial CO2 capture and storage project collecting about one million metric tons of CO2 each year since it was opened in 1996 (Sleipner CO2 project).
The term "scrubber" is used to refer to a group of air pollution control devices that aid the removal of fine particles and/or gases (especially acid gases) from industrial exhaust streams. Scrubbers work by either physically removing substances from the exhaust gas stream or by chemically neutralising them so that they cannot do any harm once released into the environment.
Wet scrubbing is used to clean gases from pollutants and particulates by putting in contact the exhaust gas stream with the scrubbing solution. The scrubbing solution can simply be water for the removal of dust or a chemical solution which contains reagents that can specifically target certain compounds. Removal efficiency of pollutants is improved by increasing residence time in the scrubber or by the increase of surface area of the scrubber solution.
2.2. Dry scrubbing
Dry scrubbing is generally used to remove acid gases, such as SO2, primarily from combustion sources. All dry scrubbing systems consist of two main devices: 1) a device to introduce a solid sorbent material into the gas stream; and 2) a particulate control device to remove reaction products, excess sorbent material, any particulate matter already in the flue gas.
2.3. Seawater scrubbing
The natural buffering capacity of seawater can be taken advantage of by using it as a sorbent in a scrubbing system. When SO2 comes into contact with seawater a reaction takes place between the SO2 and the CaCO3 present in the seawater, producing CaSO4 and CO2. This reaction is complete in a very short time, so the equipment required for seawater scrubbing can be compact.
3.1. Primary measures
Primary measures can be applied pre-combustion. In Bowin low NOx technology, air and