Calcium Hydroxide - China

Brief Overview

Calcium hydroxide does not occur naturally since it reacts readily with water (to form hydrated lime) and carbon dioxide to form limestone. This is an exothermic reaction which releases a lot of heat, thus caution must be taken. Calcium oxide vary in the degree of crystallization and cohesion of the crystalline mass and the homogeneity of the matrix.

Manufacturing Process

Method 1: Calcium carbonate is reacted with hydrochloric acid to generate calcium chloride. After which, ammonia is added for neutralization and left to stand for precipitation to occur. The solution is filtered, and sodium bicarbonate is added to generate a calcium carbonate precipitate.

Method 2: Calcium carbonate is heated to a higher temperature to undergo thermal decomposition to form calcium oxide or burnt lime. Calcium oxide is then treated or slaked with water to produce calcium hydroxide on a commercial scale:

CaO + H₂O → Ca(OH)₂

The calcium oxide is broken down into fine particles of calcium hydroxide in this hydration reaction, which occurs in a continuous hydrator. The particle sizes can be modified through milling to ensure consistent particle size.

Food Industry

Calcium hydroxide is used to produce beverages like alcohol and soft drinks. Calcium hydroxide is prevents fruits from ripening before they are shipped to the grocery store. It is also applied in preparing a traditional Swedish food called Lutefisk. 

Sewage treatment Industry

Calcium hydroxide is used as a flocculant in water and sewage treatment. 

Other Applications

Calcium hydroxide is used to produce ammonia gas by reacting it with ammonium chloride. It is also used as an intermediate to produce sodium hydroxide in the paper industry.