Lime quicklime. Lime quicklime. Application

Up to a certain time, air lime in construction was used only in the form of dies. IV Smirnov in the thirties proposed the use of the substance in a different way. He, and later Osip BV, showed that under certain conditions, the material can harden hydrated. This process is similar to the hardening of Portland cement or gypsum.

general information

Lime is a generally accepted concept throughout the world, conditionally combining the products of roasting (and later processing) of chalk, limestone and other carbonate rocks. Classification is carried out in accordance with the chemical composition. As a rule, the word "lime" means lime quicklime and the product of its interaction with water. This material can be in powdered, ground form or as a test. The formula of quicklime is CaO. This compound is a roasting product in which calcium oxide acts as the main chemical component. It actively interacts with water. As a result of hydration, slaked lime is formed - Ca (OH) ₂ .

Classification

According to the chemical composition, an air mixture (consisting predominantly of magnesium and calcium oxides) and hydrate (containing a large number of iron, aluminum and silicon oxides) is separated. The industry uses lime quicklime construction lumpy and powdery. The latter is also divided into two types. The first is quicklime lime. The second type is obtained by applying a special technology. The quenching of magnesian, calcium and dolomitic lime with the use of a limited amount of water produces slaked lime (puschku). There are other species. They include, in particular, chloric and sodium lime.

Production

The lime is made of quick lime using natural calcium-magnesium rocks. They mainly include calcium and magnesium carbonate . They also contain impurities of clay and sand. During the heat treatment (when heated) in the furnace to a temperature of 800 to 1200 degrees, the calcium-magnesium rocks begin to decompose. As a result of this process, magnesium (MgO) and calcium (CaO) oxides are formed, as well as carbon dioxide.

Technology of obtaining a mixture of fine grinding

Lime quicklime is obtained by grinding the mixture in conventional ball mills. Their work is carried out in a closed cycle with a separator separating particles of the necessary dimensions. In some cases, two separators are placed in the unit in series. This greatly increases productivity. To date, questions on the fine grinding of lime are not sufficiently developed. In the selection of mills and grinding schemes, it is necessary first of all to take into account the degree of firing of the material (strong-, medium- or soft-burned product). It is necessary to take into account the presence of overheating, underburning, the presence of solid inclusions. Strongly and medium-lime lime is more appropriate to grind, acting on its particles by abrasion and impact. This is what happens in ball mills. It should be noted that the propensity of solid particles to aggregate requires short mills and rapid removal of fine fractions from the total mass of the milled mixture, as well as the use of methods that reduce aggregation.

Application of quicklime and its products

This substance is widely used in various spheres of human activity. The largest consumers include: ferrous metallurgy, agriculture, sugar, chemical, pulp and paper industry. It is also used in the construction industry. Of particular importance is the connection in the field of ecology. Lime is used to remove flue gas oxide from sulfur oxide. The compound is also capable of softening water and precipitating the organic products and substances present in it. In addition, the use of quicklime provides neutralization of natural acidic and waste water. In agriculture, when in contact with soils, the compound removes acidity that is harmful to cultivated plants. Lime quicklime enriches the soil with calcium. Due to this, the workability of the land is increased, the rotting of humus is accelerated. At the same time, the need to introduce nitrogen fertilizers in large doses is reduced. Hydrate mixture is used in poultry and livestock for feeding. This eliminates the lack of calcium in the diet. In addition, the compound is used to improve the overall sanitary conditions when maintaining and breeding livestock. In the chemical industry, hydrated lime and sorbents are used to produce fluoride and calcium hydrochloride. In the petrochemical industry, the compound neutralizes acid tar, and also acts as a reagent in basic inorganic and organic synthesis. Lime is widely used in construction. This is due to the high environmental friendliness of the material. The mixture is used in the preparation of binders, concretes and mortars, the manufacture of products for construction.

Lime quicklime. Benefits

Lime quicklime, as already mentioned above, is used in the manufacture of concretes and solutions. This connection has several advantages. In particular, in comparison with hydrated lime in the form of a test or powder, the finely divided mixture leaves no waste. At the same time, all its components are used most rationally during hardening. Lime quicklime has a lower water requirement. In addition, its specific surface area is also much smaller. In this regard, the "workability" of concrete or a solution based on CaO is obtained with a reduced volume of water. Reducing the water demand of concrete and mortar mixes increases their strength during hardening. When hydrated in the already prepared mixtures, lime binds more water (at the transition to hydrate - up to 32%). This contributes to the production of products, concretes and solutions of increased density and strength. In the process of hydrate hardening of quicklime ground lime, a significant amount of heat is released. In this regard, products based on this compound at lower (below zero) temperatures harden more quietly and have better strength indicators, because the surrounding conditions provide rapid heat removal and reduction of thermal stresses. It is these advantages that determine the widespread use of СаО in the construction industry.

How to get quality concrete and mortar mixes?

With hydrated hardening of quicklime, good results are possible if a number of conditions are met. First, the mixture must be finely ground. It is also necessary to observe a certain ratio of lime and water. In the process of hardening, optimal heat removal is necessary or other methods should be used that do not allow the heating of hardening concrete or solutions to temperatures capable of causing intense evaporation of moisture (especially when boiling). It is also important to stop mixing the mixture at a certain stage of the lime hydration process.

Storage and Cost

The price of lime quicklime depends on the variety, type and quantity in which the material is needed. So, for example, the cost of a bag is from 300-400 rubles, and tons - from 8-10 thousand rubles. The product is stored in warehouses with mechanized unloading and loading. The duration of the compound should not exceed five to ten days (in order to avoid carbonization and hydration of calcium oxide). To the consumer lime quicklime or ground is dispatched in containers, bituminized bags or in wagons equipped for its transportation, or in autocement trucks. Packing in bags is carried out with the use of modern units with shaking devices. In bags, the product should be stored no longer than fifteen days.