Definition - What does Unslaked Lime mean?
Unslaked Lime, also known as calcium oxide is an inorganic material that is used for wastewater treatment and cement production. It contains carbonates, oxides and hydroxides in predominating quantities. It has white crystalline solid appearance with a very high melting point of 2572 degree Celsius. It is manufactured by heating limestone, coral, seashells or chalk, which are mainly composed of calcium carbonate.
Other uses of unslaked lime include:
- Building and engineering materials
- Producing chemical feed stocks
- Producing chemicals
- Refining sugar
Petropedia explains Unslaked Lime
Unslaked Lime has an adhesive property with bricks and stones hence it is used as a binding material in masonry works. It is also used in whitewashing as a wall coat so that the white wash adheres to the wall.
It is broadly classified in three types:
- Pure - Also known as fat, rich, air, slaked, slack, pickling, hydrated and high-calcium lime. It consists primarily of calcium hydroxide and may contain up to 5% other ingredients.
- Hydra - Also called water lime or hydrated lime. It contains lime with silica and/or alumina and sets with exposure to water. It can be set underwater.
- Poor lime - Also known as lean or meager lime. Poor lime sets and cures very slowly and has weak bonding.
Nearly 45% of lime or calcium oxide is used in the steel industry. It is also used in the production of other metals. For example, it is used to remove silicates from alumina before the alumina is reduced to aluminum metal.
Unslaked lime is used in stack gas scrubbers to reduce sulfur dioxide emissions from power plants. It is also added to sewage to remove phosphates. Lime is used to pretreat water supplies to decrease the acidity and soften drinking water. A variety of other industrial processes also make extensive use of unslaked lime or calcium oxide.