Recently, air pollution legislations suchas the Clean Air Act to reduce the amount of air pollution are increasingworldwide. The Clean Air Act address numerous air quality problems. One ofthese problems is acid rain caused by sulfur dioxide and nitrogen oxideemissions from fossil-fueled power plants and other industrial andtransportation sources. Sulfur oxides and nitrogen oxides (NOx) are recognizedas harmful pollutants and great efforts are underway to remove these toxicgases. Under emission regulatory requirements and legislation to reduce theemission of these air pollutants, power plants in particular have installed"flue gas desulfurization systems" also known as scrubbers.

Wet flue gas desulfurization or scrubbersystems are an excellent way of reducing the sulfur dioxide emissions caused bycoal combustion boilers. The flue gas discharged from the boiler is fed intothe absorber. In the absorber, a mixture of water and pulverized limestone is sprayedon the flue gas. The limestone slurry absorbs the sulfur dioxide (SO2) containedin the flue gas reducing the emission of sulfur. The limestone reacts with theSO2 to produce calcium sulfite. The calcium sulfite then reacts withoxygen and is then finally removed as gypsum. The limestone slurry and gypsumslurry are very abrasive. Magnetic flow meters are normally used to measure andcontrol the flow of the limestone slurry to the sprayers.