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 use 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 that workplace 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 being exposed harmful effects vapors, 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 the following materials:

Stock up on the required amount of material. Once you have selected 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 hold the required amount of 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 school chalk for writing as a starting material.
• 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 a wide range of applications in various areas . The substance is used in the 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 white color, 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 chemical substance, including the construction of 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 certain types of 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;
• improves plant nutrition;
• 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 normalizing the acidity of the soil in a garden plot, one of the common mistakes of the 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 lime cement was produced, which instantly hardened when absorbed by 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 development of construction technologies, the solution contains a couple of key types:

• 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 walls, but in the construction industry it is popular for making slag concrete, paint elements, sand-lime bricks (its weight) and plasters.

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

It is from the method of slaking that different variations of lime are obtained:

• 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 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 it will lead to detrimental effects on human health.

Before using lime, be sure to read the recommendations on the product packaging or find out the details of how to manipulate 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;
• arises It's a dull pain in the area of ​​the alimentary 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, the appearance of diarrhea may occur (this means the presence of a 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 cardiac suppression and breathing 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 is a versatile material that 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 accompanied by noticeable heat release - about 67 kJ per mole.

Slaked lime- material that can be used:

1. as a component of whitewash;
2. to protect 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 general case obtained through 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 a raw material for the production of sand-lime bricks;
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 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 it is possible complete removal carbon dioxide 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 mainly of calcium hydroxide Ca(OH) 2, as well as magnesium hydroxide Mg(OH) 2 and not large quantity 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. Limestones contain 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 calcareous-magnesian rocks are white, but they are often colored by iron oxide impurities 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 the optimal firing temperature should be (900 - 1150 ˚C) to obtain soft-burnt lime. Such 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 occurrence of limestone in deposits (in terms of chemical composition, strength, density, etc.) necessitates the 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 immersed in 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 be obtained only by burning carbonate rock in the form of pieces that differ little in size. When firing the material in pieces of different sizes, unevenly burned lime is obtained (the fines are partially or completely burned, 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 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 of the production flow diagram

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. Disadvantages of rotary kilns - high consumption metal 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, different methods are used. 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 rotating kiln, and from there into the refrigerator. With this method of operation of the kiln, the heat consumption for firing is reduced to 4000 - 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, 80% of the fractionated limestone is burned 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 – Bottom part ovens. 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. Perhaps also education significant amount burnout due to 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 the 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 (dissociation elasticity) 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. Thus, the average density of lime obtained at 850-900˚C reaches 1.4-1.6 g/cm 3 , and for burnt lime at 1100-1200˚C 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 the 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 the rapid growth of Ca oxide crystals and the formation of burnout even 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 quantity 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 a 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 stationary 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 is the outer diameter of the 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. " Guidelines" 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 specifications material only increases, 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 drawback, so there is always high humidity in rooms created using this solution. So cement almost completely replaced this solution over time;
• Preparation of silicate concrete. This concrete is different from ordinary accelerated time hardening;
• 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 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 container for the solution is installed in the form of a wooden box with a damper 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 have been extinguished and the final product is ready-made lime milk, drain excess water by moving the flap. 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

Quicklime is calcium oxide. It is obtained in laboratories and industrially from natural materials. The substance is actively used in construction and industry.

Physical properties

Calcium oxide is an inorganic crystalline substance in the form of a white or gray-white powder, odorless and tasteless. The solid crystallizes into cubic face-centered crystal lattices like sodium chloride (NaCl).

Rice. 1. Cubic face-centered crystal lattices.

A general description of the substance is presented in the table.

Calcium oxide is a caustic substance belonging to the second hazard class. It exhibits aggressive properties when interacting with water, forming slaked lime.

Rice. 2. Calcium oxide powder.

Receipt

Calcium oxide is also called burnt lime due to the method of production. Quicklime is produced by heating and decomposing limestone - calcium carbonate (CaCO 3).

This is a natural substance found in the form of minerals - aragonite, vaterite, calcite. Included in marble, chalk, limestone.

The reaction for producing calcium oxide from limestone is as follows:

CaCO 3 → CaO + CO 2 .

In addition, quicklime can be obtained in two ways:

• from simple substances, building up the oxide layer on the metal -

  2Ca + O 2 → 2CaO;

• during heat treatment of calcium hydroxide or salts -

  Ca(OH) 2 → CaO + H 2 O; 2Ca(NO3)2 → 2CaO + 4NO2 + O2.

Reactions occur at high temperatures. The combustion temperature of limestone is 900-1200°C. At 200-300°C, oxide begins to form on the metal surface. For the decomposition of salts and hydroxide, a temperature of 500-600°C is required.

Chemical properties

Calcium oxide is a higher oxide and exhibits maximum oxidizing properties. The compounds interact with inorganic substances and free halogens. Basic Chemical properties oxide are given in the table.

Application

The oxide is used in the food industry as:

• flour and bread improver;
• food additive E529;
• acidity regulator;
• yeast nutrient medium;
• catalyst for hydrogenation (addition of hydrogen) of fats.

In addition, quicklime is used in the chemical and construction industries for the production of various substances:

• oils;
• calcium stearate;
• grease;
• fireproof materials;
• gypsum;
• high alumina cement;
• sand-lime brick.

Rice. 3. Cement, brick, gypsum are obtained from calcium oxide.

What have we learned?

Calcium oxide or quicklime is a crystalline substance that reacts violently with water and forms slaked lime. Widely used in industry, in particular food and construction. Registered as food additive E529. It has high melting and boiling points and is soluble only in glycerol. Formed when calcium carbonate is burned. It exhibits oxidizing properties, forms salts with oxides and acids, and interacts with carbon and aluminum.

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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 firing in specially equipped kilns at temperatures from 1000 to 1200 degrees carbonate rocks. Thermally treated lime takes the form of irregularly shaped pieces, which are subject to various processing during further use.

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 quenching, a dense mass is formed, used in different areas.
• 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

The production of slaked and quicklime is subject to special requirements regulated by 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 certain requirements for its storage and transportation. Quicklime must be protected from moisture, since moisture ingress and heat release can cause a fire.

The lime conformity certificate 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 diseases respiratory tract. 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 latter’s name 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. Construction lime is used to introduce it as a plasticizer into concrete mixtures and solutions. Construction lime is produced in lumps, in the form of small fluff or lime paste.
• Hydraulic lime- a product of firing 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 Bleaching lime packaging Bleaching 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 firing of the starting material is carried out in different furnaces. 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

Lime used for preparing concrete mortars 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 redecorating 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. 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 prevents outbreaks intestinal infections and other epidemics.

Constant consumption of such water leads to allergic reactions, promotes 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 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.

price

practicality

appearance

ease of manufacture

labor intensive to use

environmental friendliness

final grade

Quicklime 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.

Quicklime building lime is a white substance with a crystalline structure. Its formation occurs during the firing of chalk, dolomite, limestone and other minerals of the calcium-magnesium type. In this case, the proportion of impurities cannot be higher than 6-8%. In general, the formula of the compound can be represented as CaO, although it also contains magnesium oxides and other compounds.

Pictured is calcium oxide (quicklime)

The material is manufactured in accordance with the requirements of GOST 9179-77 under the name “Construction lime. Technical conditions". It is made from carbonate rocks using additives of a mineral nature: quartz sand, blast furnace or electrothermophosphorus slag, etc.

According to the requirements of the state standard, it is necessary to grind to such a size that the residue after passing through sieve No. 02 and No. 008 is no higher than 1.5% and 15%, respectively.

Quicklime is classified as hazard class 2. Pure air-type lime can be of 1st, 2nd and 3rd grade, with impurities - 1st and 2nd grade. Hydrated lime has grades 1 and 2.

Quicklime production

In the past, limestone was heat treated to form lime. In recent years this method is used less and less because the reaction produces carbon dioxide. Alternative method is the thermal decomposition of calcium salts containing oxygen.

The first stage is limestone extraction, which is carried out in a quarry. First, the rock is crushed, sorted, and then fired. Firing is carried out in kilns, which can be rotary, shaft, floor or ring.

In most cases, shaft-type furnaces are used, which operate on gas, in a pour-over method or with remote fireboxes. The greatest savings come from devices that operate using the pouring method on anthracite or lean coal. The production volume using such furnaces is around 100 tons per day. Their disadvantage is the high degree of contamination with fuel ash.

You can get purer lime in a device with an external firebox, which runs on wood, brown coal or peat, or in a gas device. However, the power of such furnaces is much lower.

The highest quality is obtained from a substance processed in a rotary kiln, but such mechanisms are used quite rarely. Ring-type and floor-type furnaces have low power and require large volumes of fuel, which is why they are not installed at new enterprises.

Stages of lime production at the plant:

Varieties

Construction lime is divided into two types: air and hydraulic. Air lime makes it possible to harden concrete under normal conditions, and hydraulic lime – both in dry conditions and in aquatic environment. Therefore, air lime is suitable for ground work, and hydraulic lime is suitable for the construction of bridge supports.

Based on the nuances of processing the burned material, lime is isolated various types:

• Lump lime It is made in the form of a mixture of pieces of different sizes. It consists mainly of calcium oxides (the predominant part) and magnesium. It may also contain aluminates, silicates and ferrites of magnesium or calcium, which are formed during firing, and calcium carbonate. It does not perform the function of an astringent ingredient.
• Ground lime They are made by grinding lump lime, so their composition is almost identical. It is used in unslaked form. This avoids waste and speeds up hardening. Products made from it have excellent strength properties, they are waterproof and have a high density. To speed up the hardening process of the material, calcium chloride is added, and to slow down hardening, sulfuric acid or gypsum is added. This helps prevent cracks from appearing after drying. Ground lime is transported in sealed containers made of paper or metal. It can be stored for no more than 10-15 days in dry conditions.
• Hydrated lime– a highly dispersed dry compound formed during slaking of lime. It contains calcium and magnesium hydroxides, calcium carbonate and other impurities.
• When liquid is added in a volume that is sufficient for the oxides to turn into hydrates, a plastic mass is formed, which has the name lime dough.

The most popular in use today are slaked and quicklime.

Photos of different types of quicklime

Lump quicklime Ground quicklime Lime paste

Areas of use

For many years, lime cement was produced from quicklime. It hardens well in the air, but absorbs a lot of moisture, which is why fungus appears on the walls. Therefore, now in the construction industry, quicklime is in much less demand than before. It is one of the components in the production of plaster materials, sand-lime bricks, slag concrete, paints, etc.

Lime can be worked with in winter, since slaking produces heat, which maintains the temperature of the mixture during the hardening period. You cannot use it for the production of cement for finishing fireplaces and stoves, because under the influence of temperature it emits carbon dioxide.

Another area of ​​application of lime is Agriculture and gardening. It is well suited for treating plants against pests and fertilizing acidic soils. Ground limestone is a raw material in the production of livestock feed and poultry feed.

Flue gases and wastewater are neutralized using quicklime. It is also used to paint various surfaces. The use of lime in the country and for vegetable gardens is very popular.

Quicklime is in demand even in the food industry. It is found in many products in the form of emulsifier E-529. It is an ingredient that helps to mix substances that are immiscible in nature (let's say water and oil).

Application of quicklime:

Cancellation rules

The quenching process occurs according to the formula:

CaO + H2O = Ca(OH)2 + 65.1 kJ.

Lime powder is diluted in water, which reacts with calcium (or magnesium) oxide. Hydroxide is formed and copious discharge heat, causing the water to become steam. Water vapor loosens the mixture, and instead of lumps, fine powder is formed.

Depending on the slaking period, lime is of the following types:

1. quick-extinguishing (maximum 8 minutes);
2. medium-extinguishing (maximum 25 minutes);
3. slow-extinguishing (at least 25 minutes).

The duration of extinguishing is calculated from mixing with water until the temperature of the mixture stops increasing. Usually the specific time is indicated on the packaging.

Using slaking you can make hydrated lime (called fluff) or lime paste. To get it out, you need to pour 70-100% of its weight of water into the lime. It is usually made in factories, in special hydrators.

To make lime dough, liquid and powder must be taken in a ratio of 3-4:1. It is done mainly on a construction site. To make a plastic mass, it is kept for at least 2 weeks in a special pit.

What happens when slaking lime?

Scheme of lime slaking Heat release process

How to extinguish lime yourself

Quenching must be carried out according to the rules so that no metal oxides remain, otherwise the quality of the mixture will be much worse. To carry out complete extinguishing, at least a day is needed, preferably about 36 hours.

Procedure:

1. Pour lime into the container. The use of metal containers is allowed, but they must not be rusty.
2. Pour in powder cold water calculated at 1 liter (if fluff is made) or 0.5 liter per 1 kg (if lime dough is made).
3. Mix the mass. You need to stir it several times as soon as the formation of steam begins to decrease.

Remember:

• If the lime is slowly slaking, it is better to pour in water in several stages.
• If the lime is moderately or rapidly slaking, it should not be allowed to burn out. Water must be added to it until the formation of steam stops.
• If lime is used to whitewash a room, take 2 liters of water per 1 kg. Then add more water to get the desired consistency. The solution is left to stand for 48 hours and filtered. It is applied with a spray gun or brush.
• To whiten trees, the proportion of water and powder should be 4:1. This solution also needs to be left for two days before whitewashing.
• If lime is needed to spray plants against pests, the solution is mixed two hours before use. Pour in a lot of water and add copper sulfate.
• To reliably protect your eyes and skin when extinguishing, you need to wear safety glasses and long rubber gloves. Drops of slaked lime may cause severe burns if they come into contact with the skin. While preparing the mixture, do not lean over the container so that water vapor does not cause burns.

The following video will tell you about the features of treating lime burns:

Pros and cons of the material

Advantages of quicklime over slaked lime:

1. no waste;
2. more low level water absorption;
3. possibility of working in winter;
4. good level of strength;
5. wide scope of application.

The main disadvantage of quicklime is its danger to human health. Therefore, you should act carefully so that particles do not get into the mucous membranes or into the lungs.

You need to work in a room that can be ventilated, and best of all, in an open space.

If it is not possible to ventilate the room, you should wear a respirator or a special bandage. And so as not to have to treat an eye burn, you must wear safety glasses when extinguishing the lime.

average cost

Currently, at least 26 specialized factories are engaged in the production of quicklime in our country. Also, equipment for burning limestone is installed at many enterprises that produce cellular concrete and sand-lime brick.

The average price for quicklime varies between 3-5 thousand rubles. per ton.

Material such as slaked lime has been known to mankind since ancient times. Due to its beneficial properties, its use has not lost its relevance to this day. The difference concerned only the expansion of the scope of use.

In order to understand how this happened, it is necessary to find out what formula does slaked lime have, and how does this affect its interaction with other substances.

In real life, slaked lime is not always produced under conditions where there are no additional substances. Magnesium is often added to the reaction, etc. This is necessary to enhance certain properties of the material that will result from the interaction of all components.

Names used

Due to the fairly wide distribution of slaked lime in different regions of the world, as well as in different fields of activity, it was called differently. Among the most popular and common names, it is worth highlighting the following:

• calcium hydroxide.
  

  This term reflects the formula of the substance, since it consists of Calcium and Hydroxide. It is used in scientific and technical literature.

  Today, this term has replaced other names in many areas.

• slaked lime. about its application. This name came about due to the fact that substance is produced by extinguishing(that is, adding water).

• lime milk.
  

  This is lime, which occurs as a result of too much slaked lime when combined with aqueous solutions and directly with water.

  It looks a little like milk in color.

• lime water. This term means a translucent solution obtained after filtration.

• fluff lime or lump lime.
  

  Such material is obtained in cases where long time the substance is not used.

  During this period it begins from environment absorb carbon dioxide, thereby hardening.

There are also a number of other names and terms that are commonly used in relation to slaked lime. All of them have been used in one way or another over a certain period, or are currently used.

Formula and composition of the substance

The composition of slaked lime is quite simple and understandable. This substance consists only of calcium oxides, connected to each other in a certain sequence. The preparation of calcium hydroxide is also considered elementary. They have been able to produce it for many thousands of years.

To do this, you just need to add water to the calcium oxide, after which these components need to be mixed well and thoroughly.

The chemical formula of slaked lime is written as Ca(OH)2. The process for obtaining calcium hydroxide is as follows: CaO + H2O = Ca(OH)2.

When calcium oxide is poured with water, lime is obtained, the characteristics of which directly depend on the time of exposure of the initial components to each other.

If stirring lasted up to 8 minutes, then we can talk about quick-quenching lime, about 25 minutes - medium-quenching, and more than half an hour - long-quenching. Slaked lime formula Ca(OH)2 is compound, water solution which alkali has.

Technical properties

The formula of slaked lime has been known in chemistry for a long time. Today it is even studied in the school course of this subject. Often during lessons, in the presence of a teacher, children extinguish calcium oxides, noticing a violent reaction with the release of heat.

But making calcium hydroxide on an industrial scale is a slightly different process that requires certain rules and standards.

It is regulated in the Russian Federation by special regulatory documents entitled . This is what all manufacturers of this substance should focus on.

Among the requirements that must be met, it is worth noting the following:

• the manufacturer must use only carbonate rocks with the possibility of using a small amount of mineral supplements. Each type of lime has its own volume of additional substances that can be added to it. It is defined by GOSTs and cannot be violated.
• is produced in three grades. It should not contain any additives. Powdered lime with additional inclusions can be produced in two different grades;

• slaked material is also divided into two types - with and without additives.

• calcium lime should be predominantly calcium based. The amount of magnesium oxide (MgO) in it should not exceed 5 percent.
• According to GOSTs, dolomitized lime can contain magnesium oxide (MgO) up to 20 percent.
• dolomitic lime is considered a material in which Magnesium oxide (MgO) occupies up to 40 percent of the total volume.

• Hydraulic lime includes in its component composition such substances as silica, iron oxides, and clay.

The properties of lime primarily depend on two main factors, which are the manufacturing process and the firing of the rock. Heat treatment creates durable fragments of quicklime material in the kiln.

The whiter it turns out, the higher quality the product can be considered. In turn, some types of lime have a grayer color.

When quicklime comes into contact with water, it releases the gas that is present inside. After this, the material goes into a fluid state.

Its concentration directly depends on how much water was used. The strength of the substance may vary, which is influenced by technological manufacturing features. There can be hard fired material, medium fired material and soft fired material.

Manufacturing method

In general, the entire lime procurement process consists of only two production stages:

• extraction directly of the limestone rock itself and the additives that are used. For the lump type, production waste is often used;
• firing of prepared rocks in specially created furnace devices at high temperatures.

Limestone, in turn, is mined in quarries. characteristics of quarry sand. For this, an open method is used. The rock is split using explosives. If you carry out selective mining, you obtain raw materials that are homogeneous in their chemical composition, which subsequently makes the material of higher quality.

The preparatory process of raw materials obtained in a quarry involves crushing them into small pieces. However, they must be homogeneous. This is due to the high temperature in the furnaces, which is capable of destroying too small particles, and not completely burning the entire volume of too large particles.

Roasting is the main step in the production of air lime. The temperature regime must directly correspond to the impurities that are in the rock.

The process itself must meet all technology requirements, since any violation can lead to the resulting substance being of low quality. For example, too burnt lime dissolves quite poorly in water.

In addition, it has a relatively higher density, which negatively affects the preparation of solutions. about the density of river sand. Various kilns are used for the firing process. IN Lately use shaft and rotating tubular products.

The first ones are distinguished by the fact that in them the process occurs continuously, which makes it more economical and cost-effective. The latter allow you to achieve the highest quality, since in them the temperature effect on the rock occurs most evenly and correctly from the point of view of technology.

Manufacturers have also additionally developed devices that allow rock to be fired in a fluidized bed or in a suspended state.

They are used primarily on the smallest particles of material. The disadvantage of such production is its rather low efficiency.

Scope of application

Due to its properties, slaked lime has gained a very wide range of applications. It is used both for personal purposes by many people and in industry, both in the construction of various types of objects and for disinfection. It is worth highlighting the following specific methods of using this substance:

• for whitewashing trees– lime helps protect them from certain types of pests;

• when whitewashing interior spaces disinfection facilities;

• for painting wooden products to extend their service life, thus protecting them from rotting and fire processes;

• for the manufacture of, used primarily for disinfection;

ChlorineCombining solution that increases crop productivity;

to neutralize increased acidity in cases of use in compounds with Ca;

for the manufacture of food additives, primarily E526;

to detect the presence of carbon dioxide;

in sugar production using lime milk;

if necessary, disinfection of teeth in dental clinics.

In addition to the above areas, soda lime is used for many other purposes. soda lime formula. First of all, it was influenced by her very beneficial features and technical specifications.

In addition, the production of such material is very easy and not difficult.

For more information about using lime, watch the video:

Maintaining the working condition of the substance

The cost of lime today is not very high, which is due to its widespread production and the simplicity of the production process. But, despite this, having purchased this material, you need to understand how you can extend the life of its working condition.

• if the density of the material changes due to moisture evaporates from it, you can just add a little water to it;
• when using slaked lime, it must be stirred all the time;
• add water until the material stops absorbing it;
• to store lime, it is necessary to cover it on top with a layer 20 centimeters high;
• if a large volume of material is stored in winter open ground, It's worth protecting it from frost. To do this, you need to fill the top with sand, on top of which add a layer of soil. heat capacity of sand;
• You should not use material that contains sawdust, inclusions or lumps. This can significantly affect the integrity of the surface being treated;
• If lime is used to prepare a solution, it must be aged for at least two weeks. For plastering work should be extended to 4 weeks.

If all the above requirements are met, slaked lime will be used quite well for various purposes without any problems. If they occur, this may indicate poor quality of the material, and not the conditions of storage and use.

Conclusion

The formula for slaked and quicklime is already known a long period time, while the use of these materials has a long history. For this period they have not lost any of their relevance and usefulness, both for individuals and for society as a whole.

The industrial production of this material contributes to industrial development and improvement of many technologies. That is why it is very important that the production process is carried out strictly according to GOST standards and in accordance with certain rules. In this case, the use of lime will be beneficial and useful.