Lime is a material with astringent properties.

It is extracted by roasting and further processing of carbonate fossil rocks.

Lime in a wide variety of forms is used in almost all areas of human activity. What is quicklime? The formula of this substance is also indicated.

Quicklime is a white substance with a crystalline structure.

The formation of this material occurs during the firing of chalk, limestone, as well as dolomites or any other minerals related to calcium-magnesium rock.

The amount of impurities in such material cannot exceed 6-8%. The formula of quicklime is described as follows: CaO, but the composition of this substance may include magnesium oxides and other chemical compounds.

This material is produced in accordance with established GOST 9179-77. The substance is produced from carbonate rocks with a certain mineral content.

In accordance with the requirements of established state standards, lime must be crushed to such a fraction that the number of large fragments after screening does not exceed 1.5-15%.

A substance such as quicklime is classified in the second hazard class. Hydrated lime belongs to grades 1 and 2.

Varieties

What mixtures contain quicklime? The formula and use of this substance are interdependent.

Lime used as a building material is divided into 2 types: hydraulic and air.

Air lime allows concrete to harden under normal conditions. Hydraulic substance can perform binding properties even in an aquatic environment, so this material is often used for the construction of bridge supports.

Processing features divide the material into several subtypes:

• Lump lime is produced in the form of a mixture of lumps of varying sizes. The substance often consists of calcium oxides. Most of it contains magnesium. The material may also contain aluminates, silicates, or ferrites, which are formed during the firing process. This substance is not a binder.
• Ground lime is produced by the lump grinding method, so the composition of these two varieties is the same. This substance is used in quicklime form so that the hardening process can be accelerated and waste generation can be avoided. Calcium chloride is added to improve hardening. If it is necessary to slow down this process, sulfuric acid or gypsum is added to the lime composition. Transportation of material is carried out in containers made of metal and paper. This material can be stored for about 10-15 days.
• Hydrated lime is formed during the slaking process. The composition of such material includes magnesium and calcium hydroxides, carbonate and other components.
• Lime paste is formed by adding enough water to cause the oxides to become hydrates.

Quicklime and slaked substances are the most popular today.

Production

Pure quicklime is rarely found today, despite the long history of the use of this substance in many sectors of life.

The production of such building material involves a specific chemical process.

Lime is produced by several methods:

• Thermal decomposition of rock is considered a traditional and quite expensive method, the use of which requires special equipment. Its main disadvantage is the release of a small amount of carbon dioxide.
• Processing of calcium salts, which contain various acids. This is an alternative technique that is becoming increasingly popular today. The firing process does not consume much oxygen, so the substance is environmentally friendly.

For heat treatment special equipment is used for raw materials. Developed modern technological devices make it possible to use less expensive and harmful methods for extracting quicklime.

Let's look at several types of modern stoves:

• The most popular is the so-called shaft stove, which consumes gas. Thanks to this device, good quality lime is produced at an affordable cost.
• Installations operating on the pour-over principle are much less common. Used for heating coal. This is considered the most economical and productive method, the main disadvantage of which is the large amount of emissions into the environment.
• The rotary kiln makes it possible to produce high-quality lime, but the production cost is relatively high.
• The design of the stove with a removable firebox allows you to obtain pure lime with a minimum amount of all kinds of impurities. The stove can run on solid fuel, and its performance is quite comparable to its analogues.
• Ring and floor units are practically not used because their productivity is very low. Old products are still in use, but modern equipment is gradually pushing them out of the market.

The technical characteristics of the substance are determined by the established state quality standard. The manufactured product belongs to category 2 of chemical hazard.

Application

As mentioned above, in a wide variety of different areas activities, a material such as quicklime is used. The formula and the production of this substance in large quantities make it accessible and practical to use. The largest consumers of such material include:

• Metallurgy industry.
• Sugar production.
• Agriculture.
• Chemical industry.

CaO is naturally used even in the construction industry. In the field of ecology this chemical compound is of serious importance. The substance is used for cleaning flue gases from the sulfur and oxide they contain. This compound promotes the precipitation of organic substances in water and its subsequent softening.

The use of quicklime helps to neutralize the components in Wastewater Oh. If lime comes into contact with the soil, the acidity level decreases and the conditions for growing crops improve. Quicklime helps increase calcium levels in the soil. Thus, tillage of the soil is greatly facilitated and the process of humus decay is significantly accelerated.

How to slak lime - on video:

12.11.2018

What is the formula for quicklime. Production of lump quicklime

Quicklime, also known as calcium oxide (CaO), is a caustic, alkaline substance. It has been used for centuries for a variety of purposes: as a mortar, a flux, for grain processing, and to create a waterproof lubricant for boats. Quicklime was also used as fuel for cooking and heating water. Today, quicklime is used in many industrial processes. So, there are many reasons why you might want to get this substance. Fortunately, quicklime is made from cheap and widely available materials. With a little effort, you can make quicklime at home.

Steps

Required materials and tools

Wear safety glasses. When obtaining quicklime and working with it, you must be extremely careful. Quicklime is a very dangerous substance; it reacts with water. When working with it, you should wear protective clothing. The first thing to do is protect your eyes and skin. If it comes into contact with eyes or skin, quicklime will cause burns, which can cause serious injury. To avoid this, be sure to use the following:

Make sure the work area is well ventilated. In addition to the risk of burns if quicklime comes into contact with the skin and eyes, its fumes are also dangerous. To avoid exposure to harmful fumes, work in a well-ventilated area and use protective equipment.

Select a source of calcium carbonate. The first step is to find the source materials. These materials can be purchased at a gardening, hardware or building supply store. The main initial component is rocks that contain calcium carbonate. To obtain quicklime you can use following materials:

Stock up on the required amount of material. Once you have chosen a suitable source of calcium carbonate, obtain sufficient quantities. Whatever material you use, it is not 100% calcium carbonate, so you should buy extra.

Get a stove. To produce quicklime you will need a kiln. It must be large enough to accommodate required amount material.

Avoid calcium sulfate. Under no circumstances should you use materials or mixtures that contain calcium sulfate. When heated, calcium sulfate decomposes into calcium oxide and sulfur trioxide, which is a poisonous gas. This gas can cause serious harm to you, your family and pets.

Obtaining quicklime

• If you want slaked lime, sprinkle a little water on the quicklime. The lime will fizz and crumble, resulting in calcium hydroxide, which is slaked lime. If you put slaked lime in water for several hours, it will dissolve and you will get lime water. The water will become milky in color.
• Store quicklime in an airtight container because it easily absorbs carbon dioxide from the air, resulting in the formation of calcium carbonate.

Warnings

• When conducting chemical experiments Be sure to follow safety precautions.
• Make sure you are 100% sure that you are heating calcium carbonate and not calcium sulfate. Do not use as source material school chalk for writing.
• Quicklime reacts exothermically with water, generating large amounts of heat, and in this case, beware of splashing boiling water and flying particles of caustic quicklime.

Quicklime has extensive applications in various fields. The substance is used in construction industry. Whitewashing trees is a mandatory procedure, since this measure is inexpensive.

Calcium oxide exists in nature as ordinary limestone, which is modified to oxide by heat treatment. This element has a white color and a crystal structure. Its production occurs during the firing of chalk, dolomite, and limestone.

When producing lime, some of the inclusions do not exceed 8%. The combination formula is presented as CaO, despite the fact that there are other components of mineral origin in the composition.

Scope of use

The main hydraulic qualities are determined by the number of silicates and crystals of calcium aluminoferite, which are characterized by a rounded shape of a yellowish, brown to black hue. Based on these characteristics, there are varieties of lime:

• garden, used to enrich the soil with an acidity coefficient;

• as a whitewash;

• construction for concrete mixtures, bricks;

• chlorine disinfectant. instructions for using bleach.

In the process of changing the chemical composition, structure and properties of metal alloys, it is used as a cleaning component.

Most people have stopped using the chemical, including building houses, because quicklime accumulates moisture.

In the chemical industry, lime is used in the synthesis of organic compounds. You can work with lime during the cold season, because when slaking, enough heat is generated and the temperature is maintained. Do not use any building heating device when treating as liquefied CO2 is generated.

In the garden

Quicklime is widely used in the garden. its formula. For example, this substance carries out vegetation treatment from insects and as a soil amendment. In crushed form, it is considered a raw material for the production of animal feed.

The prepared solution is used to paint various surfaces. The substance is also included in many products called emulsifier E-529.

In gardening

Lime fertilizers have long been used in agriculture to increase soil fertility and for the purpose of liming, including reducing the percentage of acidity.

Hard lime fertilizers, for example, chalk, limestone, are ground or burned before adding to the soil.

Soft additives function more efficiently because they do not require advance processing. Liming is carried out once every 2 years. 150 grams needed per 1 m² substances. It is important to carry out liming equally.

Certain principles must be adhered to:

• lime is added without combining it with humus (otherwise there is a risk of losing nitrogen);
• quite powerful material that is useful for individual types soil;
• rational use on heavy soil;
• It should be stored outside the premises.

The problem is that when combined with water, lime can warm up. Volatilization occurs, causing only harm to the human body.

It is possible to combine with sulfuric acid and wood ash. The latter option does not contain chlorine, so it is good to use for plants that react negatively to chlorine. bleach formula.

In the country

Quicklime is widely used for various works in summer cottages. These include painting trees in the ratio of 1 kg of mixture per 4 liters of liquid. After two days, the composition can be used.

Also with lime Sprinkling of crops is carried out. Fungicide is added to lime water and after 2 hours they begin to spray the plants.

Lime is used for whitening ceilings and walls. about plastering walls under wallpaper.

Remember that for this procedure the ratio is completely different: 1 kg of product per 2 liters of water. Then add liquid gradually until the solution is the desired thickness.

Then the substance settles for two days, after which it must be filtered.

Almost all gardeners know that some crops do not tolerate an excessive predominance of Ca. However, calcium is the main source for stimulating root growth and is especially important at the very beginning of development.

The main purpose of calcium is as follows:

• protects culture from diseases;
• activates the work of nodule microorganisms;
• retains nitrogen in the soil;
• does better food plants;
• increases resistance to various harmful conditions;
• helps components dissolve in liquid;
• a key element for the formation of the root system;
• promotes accelerating the decomposition of organic matter.

The ability to reduce soil subacidity is one of the most desirable qualities that fluff lime has.

The use of quicklime in gardening helps not only to normalize the topsoil, but also to improve the chemical composition. Helps eliminate the influence of toxic metals.

Exceeding the application rate is undesirable for the crop. Too alkaline soil reduces the availability of many essential microelements, including Ca. However, please note that poor liming quality in some cases caused by adding lime to the soil along with humus.

Therefore, as a rule, combinations are formed that cannot be dissolved, and this is considered an absolutely wasteful process for the development of plants. Garden crops begin to lack the required nutrients, so there is no harvest.

It is best to apply lime in the fall or spring after preliminary digging. In this case, the substance eventually seeps into the ground immediately after rain. During the work period, it is necessary to adhere to measures to protect against the influence of lime.

If lime gets into your mucous membranes, immediately go to the doctor. After work, you should wash your hands and face.

Lime should not be used with compost as a chemical reaction may occur when the two come into contact. Liming acidic soils in the recommended proportions has a beneficial effect on increasing the population of earthworms, which slowly breed in oxidized soils.

Their period of existence is significantly reduced when they live in such an environment. Wood ash can replace lime and also have a beneficial effect on the soil.

It reduces soil subacidity and is considered an important potassium supplement. However, this fertilizer will need to be applied in larger proportions than any other options.

When soil acidity is normalized to garden plot One of the common mistakes of a gardener is replacing quicklime with gypsum.

This is impractical; for example, gypsum does not reduce subacidity, but is used exclusively in saline soils for the purpose of improvement, since it crystallizes excess sulfate.

The frequency of using garden lime directly depends on the type of fertilizer. When mineral, liming is done more often. And the use of natural additives helps to naturally maintain the acid-base balance.

It follows from this that with a systematic supply of organic matter, auxiliary treatment with a chemical substance will most likely not be needed.

It should also be taken into account that not all vegetables prefer lime treatment.

In construction

Quicklime has become widely used in construction. From element for a long time was produced lime cement, which immediately hardened when absorbing CO2 in the open air. proportions of cement-lime mortar for plaster.

In today's construction it infrequently used due to significant levels of water absorption. The accumulation of moisture from inside the walls often led to the growth of bacteria and mold.

Do not use in ovens. kiln brick dimensions. When exposed to flame and high temperatures, toxic carbon anhydride is released from this element.

Thanks to the formation construction technologies the solution contains a couple of key species:

• air type used for ground construction work;
• hydraulic type for the production of special construction mixtures. Most of all it is used in the construction of bridges.

For more information about quicklime, watch the video:

The difference between quicklime and slaked

What are the differences between slaked lime (formula) and quicklime? Quicklime is not used as cement due to its ability to absorb water and cause mold on the walls, but in the industry construction work it is popular for making slag concrete, colorful elements, sand-lime bricks (its weight) and plasters.

Quicklime is used to eliminate sewer water and gases formed in the chimney.

It is from the method of extinguishing that one obtains different variations lime:

• lime liquid;
• suspension;
• hydrate slaked lime. about its application.

Precautions during operation

When working with the ground substance, you should protect your lungs from getting the resulting dust on the mucous membranes. Therefore, ventilate the building regularly. The best method of protection against toxic attack is to work outdoors.

When such a requirement is not feasible, it should use a protective bandage, gloves and a special mask.

The substance must be stored in an airtight container, since it freely draws CO2 from the atmosphere, forming calcium carbonate.

Symptoms of poisoning

Any chemical element, if used incorrectly, will lead to harmful consequences for human health.

Before using lime, be sure to read the recommendations on the product packaging or find out the details of handling the substance from a specialist or seller.

Intoxication manifests itself as follows:

• burn of the oral cavity, which is expressed by swelling, increased blood flow and sudden, severe pain;
• aching pain occurs in the area of ​​the digestive tract;
• the intensity of pain depends on the amount of exposure to the chemical element;
• there is a strong craving for drinking liquids;
• later, nausea and bloody vomiting, diarrhea may occur (this means the presence of through hole in the wall of the gastrointestinal tract, accompanied by the entry of its contents into the free abdominal cavity);
• the appearance of asthma attacks;
• increased dosage of chemical stimulates the suppression of cardiac and respiratory work, but as a result of the manifestation of a state of shock.

Actions in case of a burn

First of all, instantly Carry out copious and thorough rinsing of the affected area, and most importantly, purified water. The largest accumulation of the chemical is in the conjunctival sac, so be sure to pay great attention to cleansing the eyes and eyelids.

Then you need to wait for an ambulance for effective treatment in the hospital. A 0.5% composition of amethocaine, a strong anesthetic, is instilled into the eye. It is significantly more active than novocaine. Using a wet swab, tweezers and a needle, particles of the substance are removed.

After removing the substance, the mucous membranes are washed again with plain water, and then with a special 0.9% aqueous solution of sodium chloride.

Then apply an ointment containing 5% chloramphenicol.

Both eyes are washed and treated in this way, and then a bactericidal dressing is used. Subsequent therapy is prescribed by an ophthalmologist.

Conclusion

Lime – universal material, which is still used today. The advantages of quicklime include the absence of waste, a low level of liquid absorption, the ability to work in winter, and is also widely used in everyday life.

The main disadvantage is the threat to well-being. It is necessary to work with the substance carefully so that particles do not get into the eyes or respiratory tract.

Lime is traditionally used in 2 varieties - slaked and quicklime. What are these and other materials?

What is slaked lime?

Lime- this is a material that is obtained by firing rocks belonging to the carbonate category. This could be, for example, limestone or chalk. Lime is composed primarily of oxides or hydroxides (depending on the specific type of material) of metals such as calcium and magnesium (usually calcium oxide or hydroxide is the largest). The material in question is widely used in construction.

If we talk about slaked lime, it is presented in the form of an alkaline substance - calcium hydroxide. This material most often looks like a white fine powder, slightly soluble in water. Its temperature to the touch approximately corresponds to the ambient temperature.

Lime is slaked directly by mixing quicklime - that is, calcium oxide - with water. This procedure is accompanied by a noticeable heat release - about 67 kJ per mole.

Slaked lime- material that can be used:

1. How component whitewash;
2. for guard wooden structures from destruction and fire;
3. for the purpose of preparing various mortars;
4. to reduce water hardness;
5. in the production of various fertilizers;
6. as a food additive;
7. for disinfection purposes during dental procedures.

Let us now study in more detail the specifics of the main raw material used to produce calcium hydroxide, that is, quicklime.

What is quicklime?

The substance in question is therefore calcium oxide. In industry, this material is generally obtained through the heat treatment of limestone, that is, calcium carbonate.

When interacting with water, quicklime turns into slaked lime - and, as we noted above, heat is released. When mixed with acids, the substance in question forms salts. If it is heated strongly with carbon, calcium carbide will form.

Quicklime is most often used:

1. as raw material for production sand-lime brick;
2. as a fire-resistant material;
3. like slaked lime - as a food additive;
4. for cleaning flue gases from sulfur dioxide.

There are other ways to use the material in question. For example, as the main “warming” substance in specialized containers that independently heat drinks.

Quicklime most often looks like granular bulk material. If you touch it without gloves, you can feel the heat, since the substance immediately reacts with moisture on the surface of the skin of the hands - this process is accompanied by heat generation.

Comparison

The main difference between slaked lime and quicklime is the chemical formula. The first substance is an alkali, calcium hydroxide. The second is calcium oxide (when mixed with water, it also forms slaked lime, which, in turn, weakly interacts with water).

Having determined what the difference is between slaked and quicklime, let’s record the conclusions in the table.

1-2 Initial data

Production of lump quicklime in shaft kilns

1. Productivity, m 3 /year 60000

2. Materials used Limestone shell rock

3. Maximum size

raw materials D max, mm 500

4. Finished product fraction 80-120

1-2 Introductory part

Construction air lime is a product obtained from calcareous and calc-magnesian carbonate rocks by firing them until carbon dioxide is completely removed and consisting mainly of calcium oxide. The content of impurities of clay, quartz sand, etc. in carbonate rocks should not exceed 6 - 8%. With a larger amount of these impurities, hydraulic lime is obtained as a result of firing.

Air lime belongs to the class of air binders: at normal temperatures and without the addition of pozzolanic substances, it hardens only in an air environment.

The following types of air lime are distinguished: quicklime lump; ground quicklime; hydrated lime (fluff); lime dough.

Quicklime lump is a mixture of pieces of various sizes. By chemical composition it consists almost entirely of free calcium and magnesium oxides with a predominant content

SaO. It may contain small amounts of undecomposed calcium carbonate, as well as silicates, aluminates and ferrites of calcium and magnesium formed during firing during the interaction of clay and

quartz sand with calcium and magnesium oxides.

Ground quicklime is a powdered product of fine grinding of lump lime. Its chemical composition is similar to lump lime.

Hydrated lime is a highly dispersed dry powder obtained by slaking lump or ground quicklime with an appropriate amount of liquid or vapor water, providing re-

the passage of calcium and magnesium oxides into their hydrates. Hydrated lime consists predominantly of calcium hydroxide Ca(OH) 2, as well as magnesium hydroxide Mg(OH) 2 and a small amount of impurities (usually calcium carbonate).

The quality of air lime is assessed by various indicators, the main of which is the content of free calcium and magnesium oxides in it (lime activity). The higher their content, the higher the quality

The starting materials for the production of air lime are many varieties of calc-magnesian carbonate rocks (limestones, chalk, dolomitized limestones, dolomites, etc.), all

they belong to sedimentary rocks and are widespread in

territory of our country. The composition of limestones includes calcium carbonate CaCO 3 and a small amount of various impurities (clay, quartz sand, dolomite, pyrite, gypsum, etc.).

Theoretically, calcium carbonate consists of 56% CaO and 44% CO 2. It occurs in the form of two minerals - calcite and aragonite.

Pure calc-magnesian rocks - white, however, they are often colored by impurities of iron oxides in yellowish, reddish, brown and similar tones, and by carbonaceous impurities in gray and even black colors. The amount and type of impurities in carbonate rocks, the size of impurity particles, as well as the uniformity of their distribution in the bulk are largely reflected in the technology of lime production, the choice of kilns for firing, the optimal temperature and duration of firing, as well as the properties of the resulting product.

Typically, clean and dense limestones are fired at 1100 - 1250 ˚C. The more carbonate rock contains impurities of dolomite, clay, sand, etc., the lower it should be optimal temperature firing (900 - 1150 ˚С) to obtain soft-burnt lime. This lime is easily slaked with water and produces dough with high plastic properties.

Gypsum impurities are undesirable. When the lime content is even about

0.5 - 1% gypsum greatly reduces the plasticity of lime paste. Ferrous impurities (especially pyrite) significantly affect the properties of lime, which already at 1200˚C or more cause the formation of low-melting eutectics during the firing process, promoting the intensive growth of large crystals of calcium oxide, which slowly react with water during quenching

lime and causing phenomena associated with the concept of “burnout”.

The physical and mechanical properties of rocks also affect lime technology. Only those rocks that are characterized by significant mechanical strength are suitable for firing in high shaft kilns.

(compressive strength not less than 20 - 30 MPa). The rock pieces must be homogeneous and non-layered; they should not crumble or break into smaller pieces during heating, firing and cooling.

Coarse-crystalline limestones, consisting of calcite crystals 1-3 mm in size, tend to crumble during firing. Soft varieties of calcareous-magnesian rocks (chalk, etc.) must be fired in kilns in which the material is not subjected to strong grinding (rotating, etc.).

1-3 Theoretical basis of the process

The production of lump quicklime consists of the following main operations: extraction and preparation of limestone, preparation of fuel and calcination of limestone.

Limestone is usually mined in open pits. Dense calc-magnesian rocks are blasted. To do this, first, using rotary impact drilling machines (for hard rocks) or rotary drilling machines (for medium-hard rocks), wells with a diameter of 105 - 150 mm, a depth of 5 - 8 m or more, are drilled at a distance of 3.5 - 4.5 m from one another . They contain the appropriate amount of explosive (igdanite, ammonite) depending on the strength of the rock, the thickness of the formation and the required dimensions of the stone.

The sometimes observed heterogeneity of limestone occurrence in deposits (in terms of chemical composition, strength, density, etc.) necessitates selective development of useful rock. Selective extraction of limestone increases the cost of the product, therefore, when determining the technical and economic feasibility of developing certain deposits, careful geological exploration is necessary

research.

The resulting mass of limestone in the form of large and small pieces is loaded into vehicles, usually with a single-bucket excavator. Depending on the distance between the quarry and the plant, limestone is delivered to the plant by conveyor belts, dump trucks,

by rail and water transport.

High-quality lime can only be obtained by burning carbonate rock in the form of pieces that differ little in size. When firing material in pieces different sizes the result is unevenly burnt lime (the fines are partially or completely burnt, the core of large pieces is unburnt). In addition, when loading shaft furnaces with pieces of different sizes, significantly

the degree of filling of the furnace increases, and therefore decreases

gas permeability of the material, which makes firing difficult.

Therefore, before firing, the limestone is prepared accordingly: sorted by size of the pieces and, if necessary, larger oversized pieces are crushed.

In shaft kilns it is most advisable to burn limestone separately in fractions 40 - 80, 80 - 120 mm in diameter, and in rotary kilns -

5 - 20 and 20 - 40 mm.

Since the size of blocks of mined rock often reaches

500 - 800 mm or more, then there is a need to crush them and sort the entire mass obtained after crushing into the required fractions. This is carried out in crushing and screening plants operating in an open or closed cycle using jaw, cone and other types of crushers. It is advisable to crush and sort limestone directly at the quarry and deliver only the working fractions to the plant.

Burning- main. technological operation in the production of puffed lime. In this case, a number of complex physical and chemical processes occur that determine the quality of the product. The purpose of firing is the most complete decomposition (dissociation) of CaCO 3 and MgCO 3 CaCO 3 into CaO, MgO and CO 2 and obtaining a high-quality product with an optimal microstructure of particles and their pores.

If the raw material contains clay and sand impurities, then during firing, reactions occur between them and carbonates with the formation of silicates, aluminates and calcium and magnesium ferrites.

The decomposition reaction (decarbonization) of the main component of limestone - calcium carbonate - proceeds according to the following scheme: CaCO 3 ↔CaO + CO 2. Theoretically, 179 kJ or 1790 kJ per

1 kg CaCO 3 . In terms of 1 kg of CaO obtained, the costs are equal to

The duration of firing is also determined by the size of the pieces of the fired product. To increase the productivity of lime kilns and reduce burnout of the surface layers of pieces, it is desirable to reduce their size within acceptable limits. When firing pieces of various sizes, the process mode is determined based on the time required for firing medium-sized pieces.

The main difference in the technologies for producing lump quicklime is the firing method.

1-4 Selection and Description technological scheme production

Rotary lime kilns produce soft-burnt lime High Quality from limestone and soft carbonate rocks (chalk, tuff, shell rock) in the form of small pieces. Rotary kilns allow for complete mechanization and automation of the firing process. Finally, they can use all types of fuel - pulverized solid, liquid and gaseous.

The consumption of equivalent fuel in rotary kilns is significant and reaches 25 - 30% of the mass of lime, or 6700 - 8400 kJ per 1 kg. The disadvantages of rotary kilns are high metal consumption per 1 ton of power, increased capital investment and significant energy consumption.

For lime burning, rotary kilns with a length of 30 - 100 m, a diameter of 2 - 4 m, an inclination angle of 3 - 4˚ and a rotation speed of 0.5 - 1.2 rpm are used. Their specific daily productivity reaches 500 - 700 kg/m 3 based on the full volume of the roasting drum. As the length of furnaces increases, their productivity increases and fuel consumption decreases.

To reduce fuel consumption for burning lime in rotary kilns and to utilize the heat of gases leaving the kilns at a temperature of 750 - 800˚C, use different ways. In particular, behind the stoves they put

heaters into which lump material intended for firing is directed. From here, at a temperature of 500 - 800˚C, it enters the rotary kiln, and from there into the refrigerator. With this method of operation of the kiln, the heat consumption for firing is reduced to 4600 - 5030 kJ/kg of lime.

A variety of types are used, which are a combination of a shaft kiln with a diameter of up to 6 - 8 m with a rotating kiln with a diameter of about 2.5 m. In this case, small-piece fractionated limestone is burned 80% in a shaft using coke and finally in a rotary kiln. The daily productivity of such an installation reaches 400 - 500 tons with a heat consumption of about 4200 kJ/kg.

In recent years, intensive development of methods and installations has been carried out, designed primarily for the production of lime from finely lumpy and even dusty materials. Such methods make it possible not only to use fines, but also to sharply intensify the firing process and increase the specific productivity of installations.

Calcination of limestone in a fluidized bed according to technical and economic indicators, it is characterized by high removal and increased fuel consumption - 4600 - 5480 kJ per 1 kg of lime. Firing the material in a fluidized bed up to 1-1.2 m high lasts 10-15 minutes. The operation of these furnaces can easily be fully automated.

The use in the lime industry of installations for calcining carbonate rocks in a fluidized bed makes it possible to rationally use large quantities of small fractions of raw materials, usually formed in quarries, as well as in factories equipped with shaft kilns and even rotary kilns. The disadvantage of these installations is the increased consumption of fuel and electricity.

Calcination of crushed limestone in suspension experimentally carried out in cyclone furnaces. In them, finely ground particles of carbonate raw materials are carried away by the flow of hot gases and burned. Burnt lime is deposited from the gas flow in dust settling devices.

The choice of the type of lime kiln is determined by the productivity of the plant, the physical and mechanical properties and chemical composition of limestone, the type of fuel and the required quality of lime.

The most widely used are shaft furnaces, which are a hollow cylinder with an outer steel casing about 1 cm thick and an internal refractory lining, vertically mounted on a foundation. These furnaces are characterized by continuous operation, reduced fuel and electricity consumption, as well as ease of operation. Their construction requires relatively small capital investments.

Depending on the type of fuel used and the method of its combustion, there are shaft furnaces operating on short-flame solid fuel, which is usually introduced into the furnace along with the material being fired; because limestone and cluster fuel are loaded into the shaft in alternating layers, then sometimes this method of firing is called pour-over, and the kilns themselves are called pour-over; on any solid fuel, gasified or burned in external flows placed directly near the furnace; liquid fuel; on gas fuel, natural or artificial.

According to the nature of the processes occurring in the shaft furnace, three zones are distinguished in height: heating, firing and cooling. In the heating zone, which includes the upper part of the furnace with a space temperature of no higher than 850˚C, the material is dried and heated by rising hot flue gases. Organic impurities also burn out here. The rising gases, in turn, are cooled due to the heat exchange between them and the loaded material and are then removed to the top of the furnace.

Firing zone placed in the middle part of the furnace, where the temperature of the fired material varies from 850˚C to 1200˚C and then 900˚C; Here the limestone decomposes and carbon dioxide is removed from it.

Cooling zone– lower part of the furnace. In this zone, the lime is cooled from 900˚C to 50-100˚C by air coming from below, which then rises to the burning zone.

The movement of air and gases in shaft furnaces is ensured by the operation of a fan, which pumps air into the furnace and sucks flue gases out of it. The countercurrent movement of the fired material and hot gases in a shaft furnace allows the heat of the exhaust gases to be well used for heating the raw materials, and the heat of the fired material for heating the air flowing into the firing zone. Therefore, shaft furnaces are characterized by low fuel consumption. The consumption of equivalent fuel in these kilns is approximately 13-16% of the mass of burnt lime, or 3800-4700 kJ per 1 kg.

Disadvantages of shaft furnaces: lime is contaminated with ash and the remains of unburned fuel. It is also possible that a significant amount of burnout may occur as a result of the contact of hot pieces of anthracite or coke with the material being fired. This is especially noticeable when the thermal regime is violated and the furnaces are overpowered due to high firing temperatures.

The choice of the type of lime kiln is determined by the productivity of the plant, the physical and mechanical properties of the chemical composition of limestone, the type of fuel and the required quality of lime.

Based on what is written above, we choose a shaft furnace.

Rice. 1 Technological diagram for the production of lump quicklime

lime in shaft kilns.

2

1

Rice. 2 Chemical process flow diagram

1- stage of preparing raw materials for chemical transformations; 2- chemical transformations; 3- obtaining and finishing of target products.

If we consider the firing process in a shaft kiln, we can clearly distinguish three stages.

The process of dissociation of calcium carbonate (the main part of the raw material) is a reversible reaction. Its direction depends on the temperature and partial pressure of carbon dioxide in a medium with dissociating calcium carbonate.

Since CaO and CaCO 3 are not solids and their concentrations per unit volume are constant, the dissociation constant is K dis = P CO2. Consequently, dynamic equilibrium in the system under consideration is established at a certain and constant pressure P CO2 for each given temperature and does not depend on either the amount of calcium oxide or the amount of calcium carbonate present in the system. This pressure equilibrium is called dissociation pressure or dissociation elasticity.

Dissociation of calcium carbonate is possible only if the dissociation pressure is greater than the partial pressure of CO 2 in environment At ordinary temperatures, the decomposition of CaCO 3 is impossible, since the dissociation pressure is negligible. It has been established that only at 600˚C in an environment devoid of CO 2 (in a vacuum) does the dissociation of calcium carbonate begin, and it proceeds very slowly. With a further increase in temperature, the dissociation of CaCO 3 accelerates.

At 880˚C, the pressure (elasticity of dissociation) reaches 0.1 MPa; at this temperature (sometimes called the decomposition temperature), the pressure of carbon dioxide during dissociation exceeds atmospheric pressure, so the decomposition of calcium carbonate in an open vessel proceeds intensively. This phenomenon can be compared to the intense release of steam from a boiling liquid.

At temperatures above 900˚С, increasing it for every 100˚С accelerates the decarbonization of limestone by about 30 times. Practically in furnaces, decarbonization begins at a temperature on the surface of the pieces of 850˚C with a CO content in the exhaust gases of about 40-45%.

The rate of decarbonization of limestone during firing also depends on the size of the fired pieces and their physical properties. properties.

The decomposition of CaCO 3 does not occur immediately throughout the entire mass of the piece, but begins from its surface and gradually penetrates to its internal parts. The speed of movement from the dissociation zone into the piece increases with increasing firing temperature. In particular, at 800˚C the speed of movement of the dissociation zone is approximately

2 mm, and at 1100˚С - 14 mm per hour, i.e. goes faster.

Based on the above, the quality of air lime will be determined by the firing temperature. So average density lime obtained at 850-900˚С reaches 1.4-1.6 g/cm 3 , and for burnt lime at 1100-1200˚С it rises to 1.5-2.5 g/cm 3 or more (in a piece). During firing, there is a rapid restructuring of the trigonal crystal lattice of calcite into cubic calcium oxide.

Decarbonization of limestone at low temperatures (800-850˚C) leads to the formation of calcium oxide in the form of a mass of spongy structure, composed of crystals about 0.2-0.3 microns in size and penetrated by the finest capillaries with a diameter of about 8 * 10 -3.

The specific surface area of ​​such lime, reaching about 50 m 2 /g, should predetermine the high reactivity of the product when interacting with water. However, this is not observed, apparently because the penetration of water through narrow pores into the calcium oxide mass is difficult.

An increase in the firing temperature to 900˚C and especially to 1000˚C causes the growth of calcium oxide crystals to 0.5-2 microns and a significant decrease in the specific surface area to 4-5 m 2 /g, which should negatively affect the reactivity of the product. But the simultaneous appearance of large pores in the mass of the material creates the prerequisites for the rapid penetration of water into it and their vigorous interaction. The most energetic interaction is characterized by lime obtained by burning limestone at temperatures of 900˚C. Firing at higher temperatures leads to further growth of calcium oxide crystals to 3.5-10 microns, a decrease in specific surface area, shrinkage of the material and a decrease in the rate of its interaction with water.

Some impurities in limestones, especially ferruginous ones, contribute to rapid growth Ca oxide crystals and the formation of burnout and at temperatures around 1300˚C. This makes it necessary to burn raw materials with such impurities and at lower temperatures.

Burnout in lime has a detrimental effect on the quality of solutions and products made with it. Belated slaking of such lime, which usually leaks already in the set mortar or concrete, causes fur. stress and, in some cases, material destruction. Therefore, the best option would be burnt lime at a minimum temperature, ensuring complete decomposition of Ca2 carbonate and fuel economy.

2. SPECIAL PART

The developed processing stage consists of raw material extraction, transportation, storage, crushing, and roasting.

Transportation can be carried out by belt conveyors, if the distance from the quarry to the plant is no more than 5 km, or by rail. We choose vehicles, which will simplify access to the quarry and mechanization at the plant during unloading.

Storage can be in open and closed warehouses. Now closed warehouses are used, as they protect against environmental aggression.

Crushing can be done in jaw crushers if the feed material is hard or medium hard. The disadvantage of a jaw crusher is the large amount of energy consumed, large power losses, and produces flake-shaped grains.

Because the loaded material (limestone, shell rock) is soft, then we choose a cone crusher. The advantage of a cone crusher is the absence of idling, and therefore lower energy consumption and lower electric motor power.

Disadvantages: complex in design and require strict adherence to technological conditions for installation, systematic care and maintenance by qualified personnel.

2-2 Calculation of the developed processing area.

Determination of the annual working time fund:

T year = (D-V-P)∙S∙T cm;

T year =(365-100-10) ∙8∙1=2040h.

T year – annual fund of working hours of technological processing, h;

D=365 – number of calendar days in a year;

IN– number of days off. With a five-day work week, taking into account

4 working Saturdays a year; (B=52∙2-4=100)

P– estimated number of holidays per year; P=10

WITH– number of shifts per day C=1;

T cm– duration of the shift; T cm =8h.

Next, we calculate the material balance of the given technological process. The type of material balance depends on the task at hand. For example, the material balance for a component can be calculated using the formula:

,

if M o and M n are specified as a percentage of M n,

where Mn is the amount of raw materials that should be received for processing per year.

M p – technological losses; M p =3.5

M o =0 – amount of waste.

M k – amount of material in useful product, released per year.

,

where P year is the annual productivity of the enterprise in natural terms

units.

M – quantity of material per unit of production; m=1.1

M k = 60000∙1.1=66000 (m 3 / year)

(m 3 / year)

Based on the material balance of a given process, its required hourly productivity is determined:

, Where

P required – the required hourly productivity of the device.

Mrez – the amount of materials re-introduced into the process at

operation of the device in a closed cycle; M ascend =0.

P required = 33.5 m 3 / h.

2-3 Calculation of the device.

The required number of devices to implement a given process is determined by the formula:

,

where P is the required number of units of equipment.

P required – required hourly productivity

the calculated process.

Кр – productivity reserve coefficient. This

the coefficient must be greater than 1.05;

P e – operational performance of the selected device.

Р=0.054 therefore 1 crusher KKD 1200 / 150

CALCULATION OF A CONE CRUSHER

General information about cone crushers.

In cone crushers, the crushing element is a movable cone placed inside a fixed cone (Fig. 2.1.)

Rice. 2.1 Diagram of the design of a coarse cone crusher.

Crushing of the material is carried out in an annular working space between two truncated cones. The movable cone is tightly mounted on the shaft, the lower end of which freely fits into a hole eccentrically located on the shaft.

Cone crushers are characterized by: B – width of the loading opening, B – width of the discharge slot, C – smallest size crusher slots.

The size of cone crushers for coarse crushing is usually characterized by the width of the loading hole B and the width of the discharge hole B. The size of cone crushers for fine and medium crushing is characterized by the diameter D of the lower base of the crushing cone.

The grip angle is usually within 24-28˚, productivity, depending on the size of the machine, ranges from 25 to 3500 t/h.

The advantage of cone crushers over jaw crushers is the continuity of the crushing force acting at each moment along some generatrix of the cone. As a result, the productivity of cone crushers is greater, and the energy consumption for crushing is less than in jaw crushers. The size of the crushed pieces is more uniform.

The disadvantages include the complexity of the design, large height, which increases the cost of manufacturing and repairing crushers, as well as their unsuitability for grinding viscous and clayey materials.

Determination of crusher performance.

Cone crusher performance P(m 3 / h) with large cones is determined by the formula:

,

where D k – outside diameter movable cone, m;

r – radius of the circle described by the point of the axis of the moving

cone lying in the plane of the unloading slot, m

b 1 – the smallest width of the unloading slot or width

parallel zone when cones approach each other, m

l – length of the parallel zone, m (l=0.08 dm)

α 1 and α 2 – angles between the vertical and the generatrices of the cones,

r o – angular speed of rotation of the eccentric, rad/s.

Кр – coefficient of loosening of crushed material

(K p =0.25 – 0.6)

ρ – density of crushed material;

P=117 (m 3 / h)

Determination of crusher engine power.

The motor power N(kW) of cone crushers with steep cones is determined by the formula:

,

where σ is the compressive strength of the material, N/m 2

E – elastic modulus of the material, N/m 2

D n – lower diameter of the movable cone, m

d – diameter of unloaded pieces of material, m

D – diameter of loaded pieces of material, m

η – drive efficiency (η= 0.8-0.85)

N=11.62 (kW).

Bibliography:

1. A.V. Volzhensky “Mineral binders” Stroizdat, 1986 – 464 p.

2. A.G. Komar, Yu.M. Bazhenov, L.M. Sulimenko “Technology for the production of building materials” “ graduate School" 1990.

3. N.K. Morozov “Mechanical equipment of prefabricated reinforced concrete plants.” Kyiv "Higher School" 2977.

4. Tkachenko G.A. "Methodological instructions". Rostov-on-Don State Academy of Construction.

1-1 Initial data

1-2 Introductory part

1-3 Theoretical foundations of processes

1-4 Selection and description of production flow diagram

1-5 System analysis of the technological process

2-1 Description of the technological stage being developed

2-2 Calculation of the developed technological stage

2-3 Apparatus calculation

Lime can rightfully be included in the list of the most commonly used materials by humans. At the same time, we use it not only in finishing work, but also in a whole range of tasks where the properties of lime are ideal.

This material is called calcium hydroxide. It is obtained from calcium oxide (quicklime) by reacting the latter with water. A so-called quenching reaction occurs, which can occur in less than 8 minutes and more than 25 minutes. Depending on this, quicklime, usually in the form of lumps of a gray hue, is divided into fast-, medium- and slow-slaking.

The extinguishing process is chemical in nature, and during it a large amount of heat is released. Water evaporates, and we can observe this steam during the process. When lime is slaked, fluff or dough is obtained. The latter has unique properties, allowing it to be stored for a long time in the ground. It is noteworthy that in this case the technical characteristics of the material only increase, since the remaining particles are extinguished during storage.

Areas of application of slaked lime

• Whitewashing of premises and other surfaces, including tree trunks, thus protected from pests;
• Use in brickwork. Most often - in stove masonry. In this case, we can talk about the highest adhesion to a brick or cinder concrete surface;
• Used as a wood finish. However, in this case it is necessary to use plaster mesh or shingles.
• Preparation of lime mortar, which has been used since ancient times. To prepare the solution, use three to four parts of sand and one part of slaked lime. During the process, water is released, which is a disadvantage; therefore, in rooms created using this solution, there is always high humidity. So cement almost completely replaced this solution over time;
• Preparation of silicate concrete. This concrete differs from simple concrete in its accelerated hardening time;
• Production of bleach;
• Leather tanning;
• Neutralization of acidic soils and production of fertilizers. In this case, lime is added to the soil after flashing in the spring and autumn period of the year;
• Lime milk and lime water. The first is used to prepare mixtures to combat plant diseases. And the second is for detecting carbon dioxide;
• Dentistry. Using slaked lime, tooth canals are disinfected;
• Food additive E526.
• In fact, there are a lot of ways to use lime. We have listed only some of them.

How to properly store slaked lime

If we are talking about the winter period, then lime is stored in the ground at a depth of at least 70 centimeters. In this case, the dough will be protected from freezing.

Depending on the purpose, the dough is kept for a certain time. In the case of use in plaster solutions, we are talking about keeping it for at least a month. If the solution is involved in the masonry, then two weeks will be enough.

• If you are preparing a lime-based solution, then the ideal solution would be to gradually add pre-sifted sand to the dough. Mixing is carried out gradually to form a homogeneous mass. Subsequently, you can strain the finished solution through a sieve, removing everything that prevents it from being homogeneous;
• By adding gypsum to the lime mortar, you will significantly increase its setting time. It is estimated that in this case the setting time is approximately 4 minutes. In the case of adding cement, hardening occurs over a longer period of time. A pure lime solution takes a very long time to set.

3 ways to slak lime

• Method 1: Lime lumps are laid in layers 25 centimeters thick. After this, they are watered with water and covered with wet sand on top. The slaking process takes about two days, after which the lime can be used;
• Method 2: In the case of medium or slow slaking lime. A hole is dug, at the bottom of which a solution container is installed in the form wooden box with a flap at the bottom created using a fine mesh. The lumps are placed in a box and filled with water. Water is added as the fragments break down into smaller ones. Once all the fragments are extinguished and the final product is ready-made lime milk, drain off the excess water by moving the valve. After which the lime porridge is covered with a 10-centimeter layer of sand, which will protect it from drying out;
• Method 3: Fluff can be prepared by pouring lime with water in equal proportions. The mixture is stirred during the quenching process. However, you need to be careful not to bend over during periods of highest heat generation, so as not to breathe in the fumes.

Other entries Replacing G4 halogen lamps with LED lamps

This is a material with the properties of a binder, which is obtained as a result of firing and subsequent processing of carbonate rocks. Among them: calc-magnesium fossils, limestone, chalk. Lime, in its various forms, is used in almost all areas of human activity, including the construction industry.

In its pure form, it is a colorless substance that is quite poorly soluble in water. Consists of two main components: CaO and MgO. The following types of lime are known:

• Slaked has the formula Ca(OH)2. In turn, it is divided into hydrate or fluff and lime dough.
• Quicklime - CaO. Depending on the processing method, lump or ground lime is produced after firing.
• The formula of bleach is Ca(Cl)OCl. This variety is an excellent disinfectant.
• Soda consists of slaked lime and caustic soda (sodium hydroxide) NaOH. It has a specific meaning and is mainly used where neutralization of carbon dioxide is necessary.

In the construction industry and the production of building materials, all modifications of slaked and quicklime are used.

How to slak lime correctly

Slaked lime is available in hardware stores, but you can make it yourself. First you need to figure out what slaked lime is. This material is obtained by treating lump quicklime with water.

Important! Lime is a caustic substance; it should not come into contact with the skin or eyes. Therefore, you should work with it using personal protective equipment: gloves, goggles, respirator, durable workwear.

To work, it is necessary to prepare a container of sufficient volume, without corrosion. In production, special pits are used. You will need lump quicklime and a mixing device. You can use a convenient wooden stick; even a shovel handle will do. Further:

• The required amount of starting material is placed in the prepared container.
• Fill it with COLD water in a 1:1 ratio. Upon initial interaction with water, lime behaves very violently and gets very hot. At this moment, you especially need to remember the safety rules.
• Quicklime from different manufacturers, made from different raw materials, may differ in properties. Therefore, it is better to fill it with water in several stages to ensure uniform extinguishing.
• In the first half hour, the composition must be constantly stirred. Then the container must be closed and left alone for at least two weeks. Practice shows that the longer the exposure, the better the quality of the fluff.

It is best to prepare fluff in the open air, since slaking lime at home or indoors is harmful to health and unsafe. Immediately before use, the consistency of slaked lime may require additional dilution.

The easiest way to determine the readiness of the mixture is by looking at the mark on the stick. If, when mixing the fluff, a clear trace of white remains on it, then the composition is ready. How to dilute lime to the desired density? Just add water and mix thoroughly. After the extinguishing process has gone through, the material is no longer so dangerous.

After preparing slaked lime, when pouring water for the first time, some unslaked pieces will always remain. They can form as a result of incomplete firing or, conversely, overburning. So you shouldn’t throw them away right away. We need to fill it up again clean water and use as intended. And after secondary processing - dispose of it.

What is the difference between slaked lime and quicklime?

Burnt limestone instantly enters into a chemical reaction with water, so it cannot be used as a binder in its pure form. However, quicklime has found its application in the production of slag concrete, painting compositions, sand-lime bricks, cellular and heavy silicate concrete. It is difficult to do without it in the process of wastewater and flue gas treatment. Quicklime serves as an excellent fertilizer for reducing soil acidity and increasing its fertility.

The main difference between slaked and quicklime is their composition and properties. The quenching procedure converts calcium oxide into hydroxide, completely changing the characteristics of the source material. As a result you can get:

• calcium hydroxide in dry form (fluff);
• lime dough;
• lime milk;
• lime water.

Areas of application of slaked lime in construction industry and finishing work is quite wide. The preparation of masonry, plaster mortars, and silicate concrete based on lime makes them especially plastic and easy to lay. In addition, it is used as a whitewashing material, as well as in the production of bleach, in the leather and food industries.

Conditions for safe storage of slaked lime

Unlike quicklime, slaked construction lime can be stored for a very long time without changing its composition and properties. But subject to certain rules.

• The material should be stored at positive outside temperatures.
• If slaked lime is stored in a street pit, then for the winter it should be covered with a layer of sand 200 mm thick, and 700 mm of soil should be poured on top.
• You can use thermal insulation materials for shelter, if available.

Lime is a material with a high degree of moisture absorption, therefore, when frozen, it can lose its binding properties and the ability to adhere well to other materials. This is an important reason to ensure normal storage conditions.

First aid for lime burns

If, nevertheless, precautionary measures during extinguishing did not help and lime got on the skin, then measures must be taken immediately. In case of burns with quicklime, it is necessary to free the victim from soiled clothing and remove the substance from the affected area with a dry cloth or rag. Wash the area thoroughly with plenty of running water. Then treat with a 2% solution boric acid and apply a bandage of sterile material with syntomycin ointment or Vishnevsky balm. And immediately seek help from a medical facility.

Lime hydrate (fluff, slaked lime), the formula of which is Ca (OH)2, does not require special conditions storage The material may be kept in an open space. All you need is a canopy to protect it from precipitation.

To completely extinguish fifty-six kilograms of lime into powder, about forty liters of water should be consumed, which is about sixty-nine percent of the volume of lime taken. If less liquid is taken, the process will be incomplete.

If slaked lime is produced in a confined space and does not have the opportunity to be removed, the process will be complete even if less liquid is used. However, the amount of water should be close to the theoretically required one.

When it comes into contact with H2O, the “boiling liquid” (what lime is made from) begins to absorb it. During the process, the raw material cracks, gradually crumbling into the finest powder. In this case, a large amount of heat is generated.

The purer the lime, the more completely and quickly it disintegrates during the slaking process. The result is a fluff powder that is more delicate and voluminous. Slaked lime has a volume three to three and a half times greater than the original raw material. This increase occurs with quite a large force. This factor is used, for example, when splitting stones. It should, however, be said that such a strong increase becomes possible due to the loosening of the substance, that is, the total pore volume becomes larger.

Slaked lime is usually produced in a factory. The most common method is in which a pile formed from pieces of “boil” on a board platform or compacted area is started to be watered, sprinkled with a layer of sand. Sand is necessary to retain water vapor.

Another, less economically profitable and therefore less commonly used method of production is the method of immersion in water. Pieces of “boiling water” are placed in baskets (iron or woven from willow twigs) and lowered into H2O. Keep the raw material until the water begins to turn white. It should be said that this method very labor intensive.

The most advanced method is considered to be the conversion of raw materials into powder by exposure to hot steam. To extinguish using this method, an iron cauldron is used, which is quite durable and has a tightly closed neck. The container is equipped with a pressure gauge and the required amount of raw material is poured into the boiler, taking into account the resulting increase in volume. Then pour in the required amount of water and, having hermetically closed the container, begin to rotate it. This speeds up the disintegration process. Under the influence of high pressure, the temperature in the boiler rises to one hundred degrees. As a result, extinguishing is carried out completely and quickly.

Slaked lime is poorly soluble in water. When sand and lime paste are mixed, a solution is obtained that is quite widely used in finishing, in particular

Lime for soil is an important component of high fertility. About 10 million hectares of arable land in Ukraine have increased acidity, while a slightly acidic or neutral environment is suitable for the growth, development and ripening of most crops. An effective way to increase the productivity of soils with high acidity is liming.

General information and main characteristics

Lime is a binding material that is obtained by firing and further processing of chalk, limestone and other calc-magnesian rocks. The term translated in Greek means “unquenchable.”

The material consists of a mixture of calcium oxide CaO and magnesium MgO. Lime is used in ferrous metallurgy, construction, pulp and paper industries, the chemical industry and agriculture.

Recognized as environmentally friendly safe material, well tolerated by allergy sufferers. But when the substance is extinguished, there is a possibility of getting burns and harmful effects of the released vapors on the mucous membranes of the respiratory system and eyes. When working with the material, it is important to follow safety precautions.

Varieties

There are different types of lime:

• quicklime (formula CaO);
• slaked lime (formula Ca(OH)2);
• soda lime (obtained by mixing slaked lime Ca(OH)2 and NaOH);
• bleach (formula Ca(Cl)OCl).

Quicklime (“kipelka”) is distinguished by its snow-white color. The substance boils when it reacts with water, releasing a large amount of heat. Most often used in the construction industry, metallurgy, and sugar production. In the food industry it is known as food additive E529.

Quicklime has also found its use in “self-heating” dishes. A container with a small amount of calcium oxide is placed between the two walls of the glass; after piercing the water reservoir, a reaction occurs, during which heat is released.

Slaked lime (hydrate, “fluff”) is a white powder that is difficult to dissolve in water. The scope of application is wide: construction industry, production of lime fertilizers, neutralization of soils with high acidity, water softening, dental industry, horticulture, textile industry and others. In the food industry it is known as the food additive E526.

Soda lime has the appearance of a white porous mass, serves to absorb carbon dioxide and water ( excess moisture from the air). It is used in diving equipment, gas masks, ventilators, and laboratory equipment.

Bleach solution is more commonly known as "bleach". Scope of application: disinfection and bleaching.

Features of using lime

For the temperate zone, there is a need for liming of acidic soils due to their physicochemical composition. Without the application of lime, erosion develops, soil depletion occurs and yields decrease.

Signs of acidification:

• whitish tint of soil;
• poor growth of alfalfa, clover, winter wheat;
• pronounced podzolic horizon (about 10 cm);
• development of weeds - pickleweed, sorrel, creeping buttercup, white beet.

The effect of use is to neutralize excess levels of soil acidity. Calcium content is the key to effective plant growth. It activates fertility, increasing the availability of nutrients for cultivated crops. Interacting with iron and aluminum, lime serves as a catalyst for the decomposition of organic matter, the release of nitrogen and the activity of microorganisms in the root area.

Application in agriculture helps to provide plants with microelements and improve soil structure. Any time of year is suitable for application, preferably before winter. The optimal frequency of application is annually.

The following crops are sensitive to acidity levels: fodder and sugar beets, alfalfa, peas, cabbage, wheat, barley, sunflower, legumes and others. Yields on acidic soils may decrease by 15-20%.

Application rates:

• for sandy soil type or light loam - 250-400 g/sq.m.;
• for medium or heavy loam - 350-600 g/sq.m.

When lime is added to the soil, the yield of winter wheat increases to 5.5 centners/ha, potatoes up to 20 centners/ha, perennial grasses up to 10 centners/ha, sugar beets up to 50 centners/ha. Application lime fertilizers increases the content of vitamins in hay, grain, silage, starch in potatoes, sugar in root vegetables. Feeding animals with the obtained feed reduces the incidence of disease in young animals and increases growth.

Lime differs from other fertilizers in its low price. The effect of its application lasts for 5-20 years and depends on the composition of the soil and the applied dose.

Release form and price of lime in Ukraine

Hydrated lime is produced in the form of powder, lime paste, lime milk:

• Hydrated lime (fluff) is a fine, light-colored powder.
• Lime paste is a dough-like plastic mass consisting of hydrated lime and water.
• Lime milk is a milky aqueous suspension.

The approximate price in Ukraine is 900-2600 UAH/t, depending on packaging and volume.

Transportation and storage

Slaked lime for Agriculture transported by road and rail. Fertilizer is packaged in paper bags, and in bulk form special containers are used. It is advisable to use a covered body or wagon. When transported outdoors, lime must be additionally protected from the effects of precipitation.

According to the hazard class, the material is classified as a low-hazard substance. Storage is organized in rooms with ventilation and protection from moisture.

Manufacturers

LLC “Ukrspetsizvest”, PJSC “Dneprazot”, PJSC “Industry”, etc.

DEFINITION

Slaked lime(calcium hydroxide) under normal conditions is a white powder that decomposes without melting when heated (Fig. 1).

It is poorly soluble in water (a dilute alkaline solution is formed). Exhibits basic properties and reacts with acids. Absorbs carbon dioxide from the air.

Rice. 1. Slaked lime. Appearance.

A solution of slaked lime in water is called lime water.

Chemical formula of slaked lime

The chemical formula of slaked lime is Ca(OH) 2. It shows that this molecule contains one calcium atom (Ar = 40 amu), two hydrogen atoms (Ar = 1 amu) and two oxygen atoms (Ar = 16 amu. m.). Using the chemical formula, you can calculate the molecular weight of slaked lime:

Mr(Ca(OH) 2) = Ar(Ca) + 2×Ar(H) + 2×Ar(O);

Mr(Ca(OH) 2) = 40 + 2×1 + 2×16 = 40 + 2 + 32 = 74

Graphic (structural) formula of slaked lime

The structural (graphic) formula of slaked lime is more visual. It shows how atoms are connected to each other inside a molecule (Fig. 2).

Rice. 2. Graphic formula for slaked lime.

Ionic formula

Slaked lime is a diacid base that can dissociate into ions in aqueous solution according to the following equation:

Ca(OH) 2 ↔ Ca 2+ + 2OH -

Examples of problem solving

Exercise	Determine the molecular formula of a compound containing 49.4% potassium, 20.2% sulfur, 30.4% oxygen, if the relative molecular mass of this compound is 3.95 times the relative atomic mass of calcium.
Solution	The mass fraction of element X in a molecule of the composition NX is calculated using the following formula: ω (X) = n × Ar (X) / M (HX) × 100% Let us denote the number of moles of elements included in the compound as “x” (potassium), “y” (sulfur) and “z” (oxygen). Then, the molar ratio will look like this (the values ​​of relative atomic masses taken from D.I. Mendeleev’s Periodic Table are rounded to whole numbers): x:y:z = ω(K)/Ar(K) : ω(S)/Ar(S) : ω(O)/Ar(O); x:y:z= 49.4/39: 20.2/32: 30.4/16; x:y:z= 1.3: 0.63:1.9 = 2: 1: 3 Means simplest formula compounds of potassium, sulfur and oxygen will have the form K 2 SO 3 and molar mass 158 g/mol. Let's find the true molar mass of this compound: M substance = Ar(Ca) × 3.95 = 40 × 3.95 = 158 g/mol M substance / M(K 2 SO 3) = 158 / 158 = 1 This means that the formula for the compound of potassium, sulfur and oxygen is K 2 SO 3 .
Answer	K2SO3

Exercise	Determine the molecular formula of calcium nitrate, in which the mass ratios of calcium, nitrogen and oxygen are 10:7:24. The relative molecular weight of calcium nitrate is 164.
Solution	In order to find out what kind of relationship they are in chemical elements in the composition of the molecule it is necessary to find their amount of substance. It is known that to find the amount of a substance one should use the formula: Let's find the molar masses of calcium, nitrogen and oxygen (we'll round the values ​​of relative atomic masses taken from D.I. Mendeleev's Periodic Table to whole numbers). It is known that M = Mr, which means M(Ca) = 40 g/mol, Ar(N) = 14 g/mol, and M(O) = 32 g/mol. Then, the amount of substance of these elements is equal to: n (Ca) = m (Ca) / M (Ca); n(Ca) = 10 / 40 = 0.25 mol n(N) = m(N)/M(N); n(N) = 7 / 14 = 0.5 mol n(O) = m(O)/M(O); n(O) = 24 / 16 = 1.5 mol Let's find the molar ratio: n(Ca) :n(N):n(O) = 0.25: 0.5: 1.5= 1: 2: 6, those. the simplest formula for a compound of calcium, nitrogen and oxygen is CaN 2 O 6 and a molar mass of 164 g/mol To find the true formula of an organic compound, we find the ratio of the resulting molar masses: M substance / M(CaN 2 O 6) = 164 / 164 = 1 This means that the formula for the compound of calcium, nitrogen and oxygen is CaN 2 O 6 or Ca(NO 3) 2. This is calcium nitrate.
Answer	Ca(NO3)2

Lime is widely used in the production of building materials and as a raw material for the treatment of certain surfaces. Lime is produced by burning carbonate rocks in specially equipped kilns at temperatures from 1000 to 1200 degrees. Thermally treated lime takes the form of pieces irregular shape, which in the process of further use are subject to various processing.

Chemical formula and composition of lime

For the production of lime, no chemical catalysts are used; the main condition for its production is only the appropriate thermal regime. Thanks to this, during the manufacturing process a completely natural material is produced; the lime contains small admixtures of clay.

Limestone has the formula CaCO3, as it is predominantly composed of calcium. During the process of temperature exposure, carbon dioxide is released and the produced raw materials have the formula CaO.

The process of contact of lump lime with water looks like this - CaO + H2O? Ca(OH)2, there is a specific term for this reaction called lime slaking.

Slaked lime can be in several states:

• Fluff or fine powder is obtained by mixing pieces of lime with water, and the percentage of moisture should be from 60 to 70%.
• Lime paste is a combination of the starting material with water; it requires approximately 3.5 times more. As a result of this suppression, a dense mass is formed, used in various fields.
• If you dilute pieces of lime with water in a ratio of 1:10, you can get lime milk. This slaked lime is used for whitewashing the interiors of buildings, facades, and outbuildings.
• If slaked lime is not used for a long time, the reverse process occurs, that is, the solution absorbs carbon dioxide and hardens. On sale you can most often find lime - fluff or lump.

Photo of ground building lime

Technical properties

There are special requirements for the production of slaked and quicklime, regulated by the state standard (GOST 9179-77):

1. In the production of lime, only carbonate rocks and a certain amount of mineral additives are used. The volume of additives should not exceed the amount specified in the standards for a particular type of lime.
2. Quicklime is divided into three grades and should not contain additives; powdered lime with additives is available in two grades; slaked lime may or may not have additives and is divided into two grades.
3. The main component of calcium lime is calcium; the percentage of MgO should not be more than 5.
4. Dolomitized lime contains MgO up to 20%
5. Dolomite up to 40% MgO.
6. Hydraulic may include silica, iron oxides, and a small amount of clay.

The properties of lime are determined by the rocks used during firing and the manufacturing process itself. As a result of the heat treatment of limestone, strong pieces of quicklime emerge from the kilns; its color depends on the additives present; the whiter the shade, the higher the grade of the material. Dolomitic and hydraulic lime have a grayish tint.

– this is a substance known to almost everyone, which is in demand in various fields. It is indispensable in the production of concrete, mortar, binders, artificial stone, all kinds of parts, etc.

Upon contact with water, carbon dioxide is released and the lime turns into a liquid state, the concentration of which depends on the amount of water. Depending on the firing process and temperature, you can obtain lime of varying strength - hard burnt, intermediate and soft burnt.

As a building material, soft-burnt is more common; it has the following characteristics:

• Smallest grain size.
• Less density.
• The shortest extinction period. Hard burnt turns into a liquid state in 10 minutes, soft burnt in three minutes.

During the process of slaking lime, heat is generated, so if safety precautions are not followed, you can get a severe burn.

The density of quicklime depends on the temperature used in the kilns. Lime fired at 800 degrees has a density of 1.6; increasing the temperature to 1300 degrees makes it possible to obtain pieces of raw material with a density of 2.9 g / cm3.

According to the hazard class, lime is classified as a low-hazard substance. But there are requirements for its storage and transportation certain requirements. Quicklime must be protected from moisture, since moisture ingress and heat release can cause a fire.

The certificate of conformity for lime must contain information about its grade, percentage of impurities, and condition. The certificate is issued to certain organizations that comply with GOST for the production of this building material.

Lime is well tolerated by people with allergic respiratory diseases. But at the same time, we must not forget that when extinguishing the material, it is possible to get burns, and the vapors released at this time are dangerous for the mucous membranes of the respiratory tract and eyes. If you follow safety precautions when working with lime, it is completely safe and not harmful to health.

It is obtained by mixing unslaked lime with water, the name of which is calcium oxide. The chemical process of quenching is accompanied by an increase in temperature

Brands and some types of lime

Lime is divided by grade and by the primary raw material used.

The type and grade of lime determines the main scope of its application:

• Construction lime made from calcium and magnesium rocks. Building lime is used to introduce it as a plasticizer into concrete mixtures, solutions. Construction lime is produced in lumps, in the form of small fluff or lime paste.
• Hydraulic lime- a product of calcination of limestone containing from 6 to 20% clay impurities. This type of lime is used for the production of low-grade concrete, since along with high strength it has low ductility. Hydraulic lime is often used in the construction of buildings whose operation involves being in a humid environment.
• Lump lime This is a semi-finished product used for the manufacture of powdered raw materials or solutions. Lumps of lime are stored in closed warehouses, protected from moisture. Lump lime is sold for the preparation of whitewash solutions.
• Garden lime necessary for enriching acidic soils. In acidic soils, the calcium content is minimal, which leads to poor plant growth and development. The introduction of slaked and quicklime into the soil is carried out in spring or autumn and preferably during rains, so the limestone dissolves better. Do not apply lime at the same time as using other fertilizers, and during work you must protect your eyes and hands.
• Soda (soda) lime- a porous white mass, which is a mixture of caustic soda and slaked lime. Soda lime is used as an absorber of carbon dioxide and moisture from the air. It is used in chemical laboratories, for the production of gas masks, and diving equipment. In medicine it is used as a sorbent for anesthesia machines and pressure chambers.
• Bleaching powder obtained through a complex combination of free chlorine and calcium hydroxide. Chloride of lime has strong disinfectant properties and was previously used in its pure form in healthcare institutions. Today, bleach is used to disinfect toilets, cesspools, and to produce disinfection solutions. Bleach also has bleaching properties.

Photo of soda and bleach

Soda Lime Packaging Soda Lime Packaging Bleach Lime Bleach Lime

Mining and production technology

Lime production mainly consists of two stages:

1. Extraction of limestone and other used rocks. To produce lump lime, waste from industries that use limestone for other purposes can also be used.
2. Firing prepared rocks.

Limestone is mined in open pits using explosives. Selective mining of rocks makes it possible to prepare raw materials that are uniform in density and chemical composition, which affects the quality of subsequently produced lime.

The preparation of raw materials is carried out by crushing them. Since the temperature in ovens is set in advance, the use of fractions that differ greatly in size leads to the fact that small pieces can burn out, and large ones cannot be completely cooked.

Limestone roasting is the main technological stage in the production of puffed lime. Depending on the content of impurities, different temperature conditions are used. All technological conditions must be met, since burning of limestone leads to the formation of material with low quality characteristics. Burnt lime is poorly soluble in water, has a high density and has a negative effect on concrete solutions.

The starting material is fired in different ovens. Shaft furnaces are widely used; they are characterized by a continuous cycle of operation, efficiency, and ease of control. Rotary kilns produce soft burnt lime of the highest quality.

Installations have been developed and are used that allow firing of material in a fluidized bed or in a suspended state. Such installations are good for firing the smallest fractions of rocks, but they are characterized by low efficiency.

Educational film about lime, how it is made, what it is made from and where it is used:

Lime substitute

Used for cooking concrete solutions lime can be replaced with its analogues. Builders use Azolit, Tsemplas, Zetesol. All of these are plasticizers and they are all endowed with some better and some worse qualities compared to lime. Therefore, the decision on choosing an analogue should be made specifically in each case.

Dolomite flour is dolomite ground into a fine powder. The scope of its use is limited to soil fertilization. Liming allows you to improve the biological and physical properties of the soil, enhances plant nutrition, and allows you to get rid of pests.

How to distinguish chalk from lime

Sometimes it is necessary to distinguish chalk from lime; this can be done in several ways:

• Lump lime dissolves in water with a characteristic hiss and splash. This reaction does not occur with chalk.
• Chalk is calcium carbonate, and lime is calcium hydroxide. If you drop acid on the chalk, it will hiss; the lime will not react with the acid. The acid can be hydrochloric or acetic.
• Chalk is washed off quickly and without residue from your fingers under running water, lime becomes soapy and is quite difficult to remove.
• Surfaces whitened with chalk are smeared quite intensively; this does not happen with lime.

Lime is one of the most inexpensive materials For cosmetic repairs premises. Lime solution is used for both buildings and outbuildings.

Lime with sawdust as insulation

Sawdust from different types of trees is often used as insulation for walls, attics and floors. But they have a significant drawback - the possibility of rotting and the development of insects. This problem can be eliminated by adding lime to the sawdust.

The prepared sawdust must be mixed with fluff lime, it must be taken approximately 10% of the bulk of the shavings. Both materials are mixed well in a container and used to fill voids. You can also prepare a non-flowing material from sawdust and lime.

To prepare it you will need 10% lime, 5% gypsum and the rest of sawdust. The dry mixtures are mixed and diluted with water until a viscous mass is formed, which is used immediately. The liquid mass must be prepared in small portions, since the gypsum sets very quickly.

Water purification

To purify water, bleach is used, which has high disinfection properties. Chlorination of water allows you to avoid outbreaks of intestinal infections and other epidemics.

Constant consumption of such water leads to allergic reactions and contributes to the formation of carcinogens in the body. In water, chlorine can combine with other substances, which affects the appearance of intoxications.

In order to reduce the effect of chlorine on the body, it is necessary to drink water that has been passed through carbon or other high-quality filters. At the same time, bleach is considered one of the most effective means; it prevents the occurrence of cholera and dysentery. Bleach must be used to disinfect wastewater.

Lime - Greek word, which has its own meaning. Literally translated, it means “unquenchable.” This is one of those materials that have been around since time immemorial. Humanity has been using it for its own purposes for a long time. Oddly enough, its properties were determined completely by accident. But they began to apply the material in many areas, through errors and trials, one might say, blindly. Lime is a versatile material that is still used today.

Due to its properties, the material is used in different industries, which are different from each other. In this article we will look at how the material is extracted, how slaked lime differs from quicklime and in what areas it is used.

History of the material

In ancient times, when people still did not understand anything about calcium and its compounds with oxygen and coal, they realized something. What exactly? Through scientific research, it was found that limestone has excellent properties, especially as a building material. In addition, if you burn some rocks, such as limestone, dolomite, chalk, etc., you will get a substance that has binding properties.

If we recall the history of ancient China, workers used limestone cement to stabilize the soil and lay the masonry of their famous Great Chinese wall. Its length is 2500 km. The amazing thing is that it has survived to this day, and today we can contemplate its greatness. Over time, lime has become a key component in the preparation of fertilizers used in agriculture.

There are two types of material: slaked and quicklime. How is this or that type obtained? What is the difference between them? Let's find out the answers to these questions.

Production of raw materials

We already know that lime is a product of rock. It is mined by firing in special kilns made of limestone, dolomite and chalk. The output is material in the form of white lumps, or as it is also called - lump “boil”. This is quicklime. The extraction process takes place in special factories, from where the lime is transported further. “Kipelka” is the initial product from which other types will be produced. The chemical formula of the material is CaO (calcium oxide).

The raw material, ready after firing, is not used for mortars and cement, as it has the ability to absorb moisture very strongly, and also contributes to the formation of fungal mold on the walls. Nevertheless, boiling water is quite in demand in the construction industry, namely for the production of slag concrete, sand-lime brick, paints and mixtures for plaster.

Depending on the time it takes to extinguish the lump “boil”, it is divided into 3 types. The first of them is quick-slaking lime. The time required to repay it is up to 8 minutes. The second type is medium-extinguishing, which reaches in 25 minutes. Well, the last type is slow-extinguishing, which needs 25 minutes or more to reach condition. So we smoothly moved on to another type of material - slaked lime.

Slaked lime

The differences between slaked and quicklime, how are they expressed? The name itself already shows what the difference between the materials is. If the usual raw material has the formula CaO, then the slaked material is obtained by adding water: CaO + H 2 O = Ca(OH) 2. This is the process of extinction. It is noteworthy that when the raw material is mixed with water, a violent reaction occurs, which releases a huge amount of heat and smoke. The water is literally boiling. That is why lump lime is called “boiling lime”. The output is hydrated fluff.

From the lump “boiler” you can get different subtypes: ground quicklime, hydrated fluff, limestone dough or milk. Depending on the amount of water added for slaking, dough or milk is obtained. For example, to obtain limestone dough, the reaction liquid requires 3-4 times more than the material itself. And if you need to get limestone milk, then the amount of liquid increases 8-10 times.

How to produce slaked fluff

To produce slaked lime, you need to follow some rules. Dehydration (quenching process) must be carried out in the open air. The raw materials themselves must be placed in a tank or container. Since quite a large amount of steam will be released during the process, you need to protect yourself. The material itself can also cause harm to humans and even burn the skin. That is why it is necessary to protect the skin of the hands and the entire body, eyes and respiratory tract. You cannot do without a suit or special clothing, gloves, goggles and a respirator. Then everything will be safe for your health.

It is important to remember that there is no need to rush in this matter. The qualities of quicklime can vary, some slak quickly, others take a long time. If you do not complete the whole thing, it is possible that the material will smoke in the finished plaster. When you use slow-slaking lime, it is not recommended to immediately fill it with water. It's better to do this in small portions. Medium and fast-extinguishing are poured until the steam completely disappears to prevent burnout.

Note! Freshly slaked lime may have residues of the original material. They are extinguished again and then removed.

After dehydration, the amount of lime will be greater. From 1 kg of quicklime you can get 2 or more. There is a clear difference between slaked lime and quicklime. But where are these materials used?

Application in construction

The main area in which slaked and quicklime is used is construction. Lime is an excellent binding material. One of its advantages is environmental friendliness and naturalness. It is completely harmless to humans. We have already spoken a little about the use of quicklime raw materials, but these are not all aspects. It is necessary for the production of dry construction mixture, mortar and plaster composition. In addition, by adding lime to concrete products, they become much stronger, more moisture-resistant and denser.

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