Because sodium hydroxide is too alkaline, desulfurization with sodium hydroxide will cause secondary pollution, so there is no single use of sodium hydroxide as desulfurizer. Sodium hydroxide is commonly mixed with lime for desulfurization, which is called double alkali process. The by-product of lime desulfurization process is calcium sulfate. Sodium hydroxide can increase the reaction rate. Magnesium hydroxide is usually obtained by reaction with water. Magnesium hydroxide is the main part of desulfurization process. Magnesium hydroxide desulfurization reaction produces magnesium sulfite. Magnesium sulfite is obtained by aeration reaction.