What are the main technical requirements for quicklime
Lime, as an important inorganic chemical raw material, plays an irreplaceable role in various fields such as construction, environmental protection, agriculture, and water treatment. Its technical requirements cover multiple aspects such as raw material selection, production process, physical and chemical properties, and application fields. The following is a detailed discussion of the main requirements for quicklime technology.
1、 Raw material selection and classification
The main raw materials for quicklime are natural rocks rich in calcium carbonate (CaCO), such as limestone and dolomite. After high-temperature calcination and removal of carbon dioxide, the main component formed from these raw materials is the block of calcium oxide (CaO), namely quicklime.
According to the content of magnesium oxide (MgO), quicklime can be divided into calcium quicklime and magnesium quicklime. The content of MgO in calcium quicklime does not exceed 5%, while the content of MgO in magnesium quicklime exceeds 5%. In addition, quicklime can be classified into superior, first-class, and qualified products according to its quality grade. The higher the grade, the higher the total content of CaO and MgO, and the lower the slag content.
2、 Production process and technical indicators
The production process of quicklime has undergone a transformation from primitive manual operation to modern mechanized production. The traditional production process involves layering limestone and fuel (such as wood) and calcining them for one week. In modern times, mechanized and semi mechanized vertical kilns, as well as rotary kilns and boiling furnaces, are used for production, greatly reducing the calcination time. Using rotary kilns to produce lime only takes 2-4 hours, which can improve production efficiency by more than 5 times compared to using vertical kilns.
The technical indicators of quicklime mainly include the content of CaO+MgO, undigested residue content, carbon dioxide content, and slurry production. For example, the CaO+MgO content of high-quality calcium quicklime should not be less than 90%, the undigested residue content (5mm round hole sieve residue) should not exceed 5%, the carbon dioxide content should not exceed 5%, and the slurry production should not be less than 2.8L/kg. These technical indicators ensure the quality and performance of quicklime, meeting the needs of different application fields.
3、 Physical and chemical properties
Quicklime is a white or grayish white hard block that has water absorption properties and can absorb moisture and carbon dioxide from the air. When quicklime reacts with water, it produces calcium hydroxide (Ca (OH) ₂) and releases a large amount of heat, a process called lime maturation or digestion. The matured lime is called hydrated lime or hydrated lime, and its aqueous solution is strongly alkaline.
The density of quicklime is usually between 3.1 and 3.4 g/cm ³, with a melting point of 2572 ℃ and a boiling point of 2850 ℃. It is soluble in acidic water but insoluble in alcohol. Lime reacts violently with water and can be immediately heated to temperatures exceeding 100 ℃, so special caution is required when using it.
4、 Application Fields and Precautions
The application fields of quicklime are extensive, mainly including the following aspects:
Desiccant: Lime has strong water absorption properties and is a commonly used chemical absorption method desiccant. It is suitable for local specialties such as puffed food, mushrooms, and fungus, as well as products in industries such as instrumentation, medicine, clothing, electronics and telecommunications, leather, and textiles.
Building materials: Lime and limestone are widely used as building materials, and hydrated lime can be mixed into stone mortar, lime paste, lime mortar, etc., which are used as coating materials and brick and tile adhesives.
Water quality improvement and disinfection: Lime, as a disinfectant and water quality improver, can neutralize the acidity in the pool, increase the alkalinity of the water, adjust the pH value, kill pathogenic microorganisms and wild fish and shrimp, improve the sediment, increase calcium fertilizer, and improve the utilization rate of calcium and phosphorus by aquatic plants.
Industrial raw materials: Lime is also used in industries such as steel, pesticides, pharmaceuticals, leather making, and alcohol dehydration, and is an important raw material for many industries.
When using quicklime, the following points should be noted:
Long term exposure of quicklime to the air will absorb carbon dioxide and turn it into powdered calcium carbonate, which will lose its cleaning and disinfection effect. Therefore, it is best to buy and use it now, and store it in a sealed container.
Lime should be added to the slurry and sprinkled while it is hot to avoid pouring the residue into the pool, in order to prevent fish from accidentally eating it and dying.
Lime should not be used together with halogenated drugs such as nitrogen fertilizer, phosphorus fertilizer, bleaching powder, strong chlorine, dichlorvos, and copper sulfate to avoid chemical reactions, reduce effectiveness, or produce toxicity.
The technical requirements for quicklime cover multiple aspects such as raw material selection, production process, physical and chemical properties, and application fields. These requirements ensure the quality and performance of quicklime, meet the needs of different fields, and promote the development of related industries.
