Limestone and what is obtained from it surrounds a person all his life. Most people do not even think about this fact, although the plaster on the wall is a derivative of this rock. The formula of limestone is very simple, it is the usual calcium carbonate CaCO₃, but much more can be said about it, and this information concerns not so much chemistry as geology and biology.

Chronicle of bygone eras

Before talking about what limestone is, it is worth talking about calcium, its basis. This element is the fifth most abundant on Earth and its share in the earth's crust is slightly more than 3%. But it was his circulation in nature that played and plays a role in the formation of limestone.

In nature, there is a so-called carbonate equilibrium, expressed by the equation:

CaCO₃+H₂O+CO₂=Ca (HCO₃) ₂+Ca² ⁺+ 2HCO₃⁻

This state has a preponderance in one direction or another, depending on the content carbon dioxide dissolved in water. The more it is, the more the equilibrium shifts to the right, and vice versa. Living organisms play a significant role in this process, especially since the time of the oxygen catastrophe.

Cyanobacterial mats and stromatolites

Life originated on earth under anaerobic conditions. There was no free oxygen in the Earth's atmosphere; it is possible that the primary composition of the gases was a mixture of hydrogen and helium. As volcanism intensified, the primary atmosphere was replaced by a secondary one, consisting of carbon dioxide, methane and ammonia, and possibly water vapor.

As a whole (slabs), limestone is widely used in finishing works, in the form of crushed stone - in the production of concrete. It is lighter than granite: the density of this rock is 2.6 t/m³. In terms of its strength, it is inferior to other materials, it barely reaches 41 MPa, and in the wet state this figure decreases to 35 MPa. On the other hand, limestone does not transmit radiation, and it is possible and even necessary to use this material in residential premises: it is rare that a stone is able to maintain an optimal microclimate in a house so well.

Lime- white crystalline substance. This is a concept generally accepted throughout the world, conditionally combining the products of roasting (and subsequently processing) of chalk, limestone and other carbonate rocks. As a rule, the word "lime" refers to quicklime and the product of its interaction with water. This material may be in powdered, ground or dough form. The formula for quicklime is CaO.

See also:

STRUCTURE

Calcium oxide is a white crystalline substance that crystallizes in a cubic face-centered crystal lattice, similar to sodium chloride. Point group: m3m (4/m 3 2/m) - hexoctahedral. Space group Fm3m (synthetic). Syngony is cubic. Cell parameters a = 4.797Å. Unit cell volume V 110.38 ų (calculated from unit cell parameters).

PROPERTIES

The molar mass is 55.07 grams/mol. The density is 3.3 grams / centimeter³. The melting point is 2570 degrees. The boiling point is 2850 degrees. The molar heat capacity (under standard conditions) is 42.06 J/(mol K). Enthalpy of formation (under standard conditions) is -635 kJ/mol

Calcium oxide (formula CaO) is a basic oxide. Therefore, it can: – dissolve in water (H 2 O) with the release of energy. This produces calcium hydroxide. This reaction looks like this: CaO (calcium oxide) + H 2 O (water) \u003d Ca (OH) 2 (calcium hydroxide) + 63.7 kJ / mol; – react with acids and acid oxides. This forms salts. Here are examples of reactions: CaO (calcium oxide) + SO 2 (sulphurous anhydride) \u003d CaSO 3 (calcium sulfite) CaO (calcium oxide) + 2HCl (hydrochloric acid) \u003d CaCl 2 (calcium chloride) + H 2 O (water).

MORPHOLOGY

Based on the nuances of processing the burnt material, lime is isolated various kinds:
lump lime It is made in the form of a mixture of pieces of different sizes. It consists mainly of oxides of calcium (the predominant part) and magnesium. Also, it may include 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 raw form. This avoids waste and accelerates hardening. Products made from it have excellent strength properties, they are water resistant and have a high density. To speed up the hardening process of the material, calcium chloride is added, and to slow down the hardening, sulfuric acid or gypsum is added. This prevents the appearance of cracks after drying. Ground lime is transported in sealed containers made of paper or metal. It is allowed to store it no more than 10-15 days in dry conditions.
Hydrated lime- a highly dispersed dry compound formed during lime slaking. It consists of calcium and magnesium hydroxides, calcium carbonate and other impurities.
When a liquid is added in a volume that is enough for the oxides to turn into hydrates, a plastic mass is formed, which has the name of lime paste.

ORIGIN

In the past, heat treatment of limestone was performed to form lime. In recent years, this method has been used less and less because carbon dioxide is released as a result of the reaction. Alternative method is the thermal decomposition of calcium salts containing oxygen.

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

In most cases, shaft-type furnaces are used, which operate on gas, in bulk or with remote furnaces. The greatest savings are provided by devices that work in a bulk way on anthracite or lean coal. The volume of production with the help of such furnaces is around 100 tons per day. Their disadvantage is high degree fuel ash pollution.

You can get purer lime in a device with an external firebox that 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 in the substance processed in a rotary kiln, but such mechanisms are used quite rarely. Ring and floor type furnaces have low power and require large volumes of fuel, so they are not installed at new enterprises.

APPLICATION

The properties and structural features of lime contribute to its widespread use in many areas of the national economy. The main area in which lime is used is construction and design. Limestone buildings are a landmark not only in Malta. Although not in such quantities, there are buildings made of sedimentary rock in other states. So, in Russia, many churches were built from limestone, for example, the Trinity Cathedral and the Assumption Cathedral of the Kremlin in Moscow, the Church of the Intercession on the Nerl. Lime cement was also made from lime, with the help of which they built residential buildings, but at present it has ceased to be used, because houses accumulate dampness if cement and lime are used.

Not only wall blocks are made of limestone, but slabs for cladding, paving floors and sidewalks. The rock goes to the foundations of buildings. The stone is crushed and added to the road surface. True, it is used only on the tracks of the second category. So called roads for special needs, not subjected to constant loads. Limestone is also used as a raw material in soap making, printing and fertilizer production. In the food industry, stone is used as a filter in the manufacture of sugar.

Limestone water filters are built into hydraulic structures. To do this, use a porous stone, not a crystalline structure. In addition, rock is a component of concrete. Limestone is needed in the glass industry. Here, rock with a predominance of calcium oxide is used. It should be at least 53 percent. Calcite is a mineral, while limestone is a rock, that is, a composition of many minerals. Limestone is called a monomineral rock. This means that there is always more calcite in it than other elements, but this does not mean that it is the only one.

Registered in the food industry as food additive E-529.

Lime (English Lime) - CaO

CLASSIFICATION

OPTICAL PROPERTIES

CRYSTALLOGRAPHIC PROPERTIES

dot group	m3m (4/m 3 2/m) - hexoctahedral
space group	F m3m
Syngony	cubic
Cell Options	a = 4.797Å

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 make a waterproof lubricant for boats. Quicklime was also used as a fuel for cooking and heating water. Today, quicklime is used in many industrial processes. Thus, there are many reasons why you may need to get this substance. Fortunately, cheap and widely available materials are used to produce quicklime. With a little effort, you can get quicklime at home.

Steps

Necessary materials and tools

Wear safety goggles. When receiving quicklime and working with it, you must be extremely careful. Quicklime is a very dangerous substance, it reacts with water. Protective clothing must be worn when working with it. First of all, protect your eyes and skin. Quicklime can cause burns if it comes in contact with the eyes or skin, which can lead to 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 vapors are also dangerous. In order not to be exposed harmful effects fumes, work in a well-ventilated area and wear protective gear.

Choose a source of calcium carbonate. The first step is to find the source materials. These materials can be purchased at a gardening supply store, a hardware store, or a building supply store. The main initial component is rocks, which include calcium carbonate. The following materials can be used to obtain quicklime:

Stock up on the required amount of material. Once you have selected a suitable source of calcium carbonate, get enough of it. Whatever material you use is not 100% calcium carbonate, so you should stock up on it.

Get an oven. To get quicklime, you will need a kiln. It should be large enough to hold the required amount of material.

Avoid calcium sulfate. Under no circumstances should materials and mixtures containing calcium sulfate be used. 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.

Getting quicklime

• If you want to get slaked lime, sprinkle some water on the quicklime. The lime will sizzle and crumble, and as a result, you will get calcium hydroxide, that is, slaked lime. If you put slaked lime in water for several hours, it will dissolve and you will get lime water. In this case, the water will acquire a milky color.
• Store quicklime in an airtight container as it readily absorbs carbon dioxide from the air, resulting in calcium carbonate.

Warnings

• When conducting chemical experiments, be sure to observe safety precautions.
• Be 100% sure that you are going to heat calcium carbonate and not calcium sulfate. Do not use school chalk for writing as a starting material.
• Quicklime enters into an exothermic reaction with water, during which a large amount of heat is released, and in this case, splashing of boiling water and flying particles of caustic quicklime should be avoided.

Quicklime has a wide range of applications in various fields.. The substance is used in the construction industry. Tree whitewashing stands out mandatory procedure because this measure is inexpensive.

Calcium oxide in nature exists 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, limestone.

In the production of lime, part of the inclusions does 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 calcium aluminoferite crystals, which are characterized by a rounded shape of a yellowish, brown to black tint. Based on these characteristics, there are varieties of lime:

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

• as whitewash;

• construction for concrete mixtures, bricks;

• chlorine disinfectant. instructions for the use of 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 given up on using chemical, including the construction of houses, because quicklime accumulates moisture.

In the chemical industry, lime is used in the synthesis of organic compounds. It is possible to work with lime in the cold season, because when quenching, enough heat is generated, and the temperature is maintained. Do not use with any building heating device as liquefied CO2 is produced.

In the garden

Huge use of quicklime received in the garden. her formula. For example, this substance is vegetation processing from insects and as top dressing for the soil. In crushed form, it is considered a raw material in the manufacture of animal feed.

The prepared solution is used to paint a variety of surfaces. The substance is also included in many products, which are referred to as the E-529 emulsifier.

In horticulture

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 being added to the soil.

Soft additives function more efficiently because they do not require pre-treatment. Liming is carried out once every 2 years. 150 grams are needed per 1m² substances. It is important to carry out liming in the same way.

It is necessary to adhere to certain principles:

• lime is introduced without combination with humus (otherwise there is a threat to lose nitrogen);
• powerful enough material that is useful for certain types of soil;
• application rationally on heavy soil;
• it should be kept outside.

The problem is that when combined with water, lime can warm up. There are volatilizations that bring only harm to the human body.

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

In the country

Quicklime has found wide distribution in various works in summer cottages. These include tree painting. in the ratio of 1 kg of the mixture to 4 liters of liquid. After two days, the composition can be applied.

Also lime carry out sprinkling of crops. A fungicide is added to the lime water and after 2 hours they start spraying the plants.

Lime is used for whitewashing ceilings and walls. about puttying the walls under the 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 density.

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 the growth of the root system and is especially important at the very beginning of development.

The main purpose of calcium is as follows:

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

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

The use of quicklime in horticulture contributes not only to the normalization of the upper soil cover, but also to the improvement of the chemical composition. Helps to eliminate the influence of toxic metals.

Exceeding the application rate is undesirable for the culture. Too alkaline soil reduces the absorption of many required micronutrients, including Ca. However, please note that the poor quality of liming in some cases due to the addition of lime to the soil along with humus.

Therefore, as a rule, combinations are formed that cannot dissolve, and this is considered an absolutely futile process for the development of plants. Horticultural crops begin to experience a deficiency of the required nutrients, so there is no crop.

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

If lime gets into the mucous membranes, immediately go to the doctor. Wash hands and face after work.

It is not necessary to use lime along with compost, as a chemical reaction may occur when they come into contact. Liming of acidic soils in the recommended proportions favorably affects the increase in the population of earthworms, which slowly breed in oxidized soils.

Their lifespan is greatly reduced when they inhabit such an environment. Wood ash can replace lime and also favorably affect the soil.

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

When normalizing the acidity of the soil in the garden plot, one of the gardener's frequent misses is the replacement of quicklime with gypsum.

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

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

From this it follows that with the systematic supply of organic matter, auxiliary treatment with a chemical substance is most likely not needed.

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

In construction

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

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

It is forbidden to apply to processing of furnaces. kiln brick sizes. When exposed to flame and high temperatures, toxic carbonic anhydride is released from this element.

Thanks to the formation of building technologies, the solution contains a couple of key types:

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

For more information about quicklime, see the video:

The difference between quicklime and slaked

What is the difference between slaked lime (formula) and quicklime? Quicklime is not used as a cement due to its ability to absorb water and create mold on the walls, but in the construction industry it is popular for making cinder block, colorful 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 quenching method that different variations of lime are obtained:

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

Operation Precautions

When working with a ground substance, the lungs should be protected from the dust formed on the mucous membranes. Therefore, ventilate the building regularly. best method protection from toxic attack is to carry out work on the street.

When such a requirement is not feasible, apply protective bandage, gloves and a special mask.

Store the substance in an airtight container, as it freely draws CO2 from the atmosphere, forming calcium carbonate.

Symptoms of poisoning

Any chemical element if misused 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 the manipulation of the substance from a specialist or seller.

Intoxication manifests itself as follows:

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

Actions for a burn

First of all instantly carry out abundant and scrupulous washing of the affected area, and most importantly purified water. The largest accumulation of the chemical is in the conjunctival sac, so be sure to give great attention to cleansing the eyes and eyelids.

After that, you need to wait for an ambulance for effective treatment in the hospital. 0.5% composition of amethocaine is instilled into the eye - a strong anesthetic. By activity, it significantly exceeds novocaine. With the help of a wet swab, tweezers and a needle, particles of the substance are removed.

After the removal of the substance, another washing of the mucous membranes is carried out with plain water, and then with a special 0.9% aqueous solution sodium chloride.

Then apply an ointment containing 5% chloramphenicol.

In this way, both eyes are washed and treated, and then a bactericidal bandage is used. Subsequent therapy is prescribed by an ophthalmologist.

Conclusion

Lime is a versatile material that is still used today. The advantage of quicklime is 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 the particles do not get into the eyes or into the respiratory tract.

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

What is slaked lime?

Lime- this is a material that is obtained by roasting a rock that belongs to the category of carbonate. It can be, for example, limestone or chalk. Lime consists mainly of oxides or hydroxides (depending on the specific type of material) of metals such as calcium and magnesium (as a rule, calcium oxide or hydroxide occupies the largest volume). The considered material is widely used in construction.

If we talk about the slaked variety of lime, then 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 temperature of the surrounding air.

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

Slaked lime- material that can be used:

1. as an integral part of whitewash;
2. to protect wooden structures from destruction and fire;
3. in order to prepare various building solutions;
4. to reduce water hardness;
5. in the production of various fertilizers;
6. as a food supplement;
7. for disinfection 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 thus calcium oxide. In industry, this material is generally obtained by heat treatment of limestone, i.e. calcium carbonate.

When interacting with water, quicklime turns into slaked lime - in this case, 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 used most often:

1. as a raw material for the production of silicate bricks;
2. as a refractory material;
3. like slaked lime - as a food additive;
4. for purification of flue gases from sulfur dioxide.

Other ways of using the material in question are also known. For example - as the main "warming" substance in specialized utensils, which independently heats drinks.

Quicklime looks most often like a granular bulk material. If you feel 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, interacts weakly with water).

Having determined the difference between hydrated and quicklime, we fix the findings in the table.

1-2 Initial data

Production of lump quicklime in shaft kilns

1. Productivity, m 3 / year 60000

2. Materials used Shell limestone

3. Maximum fineness

raw materials D max, mm 500

4. Fraction of the finished product 80-120

1-2 Introduction

Building air lime is a product obtained from calcareous and calcareous-magnesian carbonate rocks by firing them until the complete removal of 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 more of these impurities, hydraulic lime is obtained as a result of firing.

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

Distinguish the following types of air lime: quicklime lump; ground quicklime; hydrated lime (fluff); lime paste.

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

CaO. In a small amount, it may contain 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 oxides of calcium and magnesium.

Ground quicklime is a powdered product of fine grinding of lump lime. In chemical composition, it 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 vaporous water, providing

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

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

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

They belong to sedimentary rocks and are widely distributed 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 as two minerals, calcite and aragonite.

Pure calc-magnesian rocks - white color, however, they are often colored with impurities of iron oxides in yellowish, reddish, brown and similar tones, and with carbonaceous impurities - in gray and even black colors. The amount and type of impurities in carbonate rocks, the particle size of impurities, as well as the uniformity of their distribution in the groundmass, to a large extent affect 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.

Usually clean and dense limestones are fired at 1100 - 1250 ˚С. The more carbonate rock contains impurities of dolomite, clay, sand, etc., the lower should be the optimum firing temperature (900 - 1150 ˚С) to obtain soft-burned lime. Such lime is well quenched by water and gives a dough with high plastic properties.

Gypsum impurities are undesirable. When contained in lime, even about

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

lime and causing phenomena associated with the concept of "burnout".

The physical and mechanical properties of the rocks also affect the technology of lime. 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). Pieces of rock should be homogeneous, non-layered; they must not crumble and break into smaller pieces during heating, firing and cooling.

Coarse-grained limestones, consisting of calcite crystals 1–3 mm in size, tend to crumble during firing. Soft varieties of lime-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 process

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

Limestones are usually mined in open pits. Dense calc-magnesian rocks explode. To do this, first, using percussion-rotary (for hard rocks) or rotary drilling (for medium-strength rocks), wells with a diameter of 105 - 150 mm and a depth of 5 - 8 m or more are drilled at a distance of 3.5 - 4.5 m from one another . They lay the proper amount of explosive (igdanite, ammonite) depending on the strength of the rock, the thickness of the reservoir 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 the selective development of useful rock. Selective limestone mining increases the cost of the product, therefore, when determining the technical and economic feasibility of developing certain deposits, thorough geological exploration is necessary.

research.

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

rail and water transport.

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

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

gas permeability of the material, which makes firing difficult.

Therefore, prior to firing limestone is properly prepared: sorted according to the size of the pieces and, if necessary, larger oversized pieces are crushed.

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

5 - 20 and 20 - 40 mm.

Since the sizes of blocks of extracted rock often reach

500 - 800 mm and more, then it becomes necessary to crush them and sort the entire mass obtained after crushing into the desired fractions. This is carried out on 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 working fractions to the plant.

Burning- main. technological operation in the production of air lime. At the same time, 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 there are clay and sandy impurities in the raw materials, then during firing between them and carbonates, reactions occur 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 is spent on decarbonization of 1 mole of CaCO 3 (100 g).

1 kg CaCO 3 . In terms of 1 kg of CaO obtained in this case, 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 the burnout of the surface layers of the 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 pieces of medium size.

The main difference in the technologies for the production of quicklime is in the method of firing.

1-4 Selection and description of the technological scheme of production

Rotary lime kilns make it possible to obtain high quality soft-burned lime from limestone and soft carbonate rocks (chalk, tuff, shell rock) in the form of small pieces. Rotary kilns allow full mechanization and automation of the firing process. Finally, they can use all types of fuel - pulverized solid, liquid and gaseous.

The equivalent fuel consumption 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 power consumption.

For burning lime, rotary kilns 30 - 100 m long, 2 - 4 m in diameter, with 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 per full volume of the firing drum. With an increase in the length of the furnaces, their productivity increases, and fuel consumption decreases.

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

heaters into which the lump material intended for firing is directed. From here, with a temperature of 500 - 800˚С, it enters the rotary kiln, and from it to 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 methods are used, which are a combination of a shaft kiln with a diameter of up to 6 - 8 m with a rotary kiln with a diameter of about 2.5 m. 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 designed primarily for the production of lime from small lumps and even powdered materials has been carried out. Such methods make it possible not only to use fines, but also to sharply intensify the firing process and increase the specific productivity of the 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. The firing of the material in a fluidized bed up to 1-1.2 m high lasts 10-15 minutes. The operation of these furnaces is easily amenable to full automation.

The use in the lime industry of installations for burning carbonate rocks in a fluidized bed makes it possible to rationally use large quantities of fine 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 divided particles of carbonate raw materials are carried away by a stream of hot gases and are burned. Calcined lime is deposited from the gas stream in dust settling devices.

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

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

Depending on the type of fuel used and the method of its combustion, shaft furnaces are distinguished that operate on short-flame solid fuel, which is usually introduced into the furnace along with the material being fired; because limestone and bush fuel are loaded into the mine in alternating layers, then sometimes this method of firing is called bulk, and the furnaces themselves are bulk; on any solid fuel, gasified or burned in remote flows placed directly at the furnace; on liquid fuel; on gas fuel, natural or artificial.

According to the nature of the processes occurring in the shaft furnace, there are three zones in height: heating, firing and cooling. In the heating zone, which includes upper part furnaces with a space temperature not 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, due to the heat exchange between them and the loaded material, are cooled and then removed to the top of the furnace.

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

Cooling zone- The bottom of the oven. In this zone, the lime is cooled from 900˚С to 50-100˚С by the air coming from below, which then rises to the firing zone.

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

Disadvantages of shaft kilns: lime is contaminated with ash and residues of unburned fuel. It is also possible the formation of a significant amount of overburning due to the contact of red-hot pieces of anthracite or coke with the fired material. This is especially noticeable in case of violation of the thermal regime and excessive forcing of furnaces 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, the chemical composition of limestone, the type of fuel and the required quality of lime.

Based on the above, we select a shaft furnace.

Rice. 1 Technological scheme for the production of lumpy quicklime

lime in shaft kilns.

2

1

Rice. 2 Chemical - technological scheme

1 - stage of preparation of raw materials for chemical transformations; 2- chemical transformations; 3- obtaining and fine-tuning the target products.

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

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 solid substances and their concentrations per unit volume are constant, the dissociation constant K dis \u003d P CO 2. Consequently, the 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 the dissociation pressure or the dissociation elasticity.

The 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 a medium devoid of CO 2 (in 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˚С, the pressure (dissociation elasticity) reaches 0.1 MPa at this temperature (it is sometimes called the decomposition temperature), the pressure of carbon dioxide during dissociation exceeds Atmosphere pressure, therefore, the decomposition of calcium carbonate in an open vessel proceeds intensively. This phenomenon can be compared with the intensive release of steam from a boiling liquid.

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

The rate of limestone decarbonization 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 in the entire mass of the piece, but begins from its surface and gradually penetrates to its inner parts. The speed of movement from the dissociation zone into the piece increases with increasing firing temperature. In particular, at 800˚С, the dissociation zone displacement rate is approximately

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

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

Decarbonization of limestones at low temperatures (800-850˚С) 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 thinnest capillaries with a diameter of about 8 * 10 -3.

The specific surface 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 mass of calcium oxide is difficult.

Increasing the firing temperature to 900˚С and especially to 1000˚С leads to the growth of calcium oxide crystals up to 0.5–2 µm 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 roasting limestone at a temperature of 900 ° C. Firing at higher temperatures leads to further growth of calcium oxide crystals up 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 limestone, especially ferruginous, contribute to rapid growth crystals of Ca oxide and the formation of burnout and at temperatures around 1300˚С. This makes it necessary to burn raw materials with such impurities and at lower temperatures.

Burning in lime adversely affects the quality of solutions and products manufactured on it. Belated extinguishing of such lime flowing usually already in the set mortar or concrete causes fur. stress and, in some cases, destruction of the material. Therefore, the best would be lime burnt at a minimum temperature, which ensures complete decomposition of carbon dioxide Ca and fuel economy

2. SPECIAL PART

The developed processing unit 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 not more than 5 km, by rail. We choose vehicles, which will simplify the 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 the jaw crusher is a large amount of energy consumed, large power losses, give grains of a flaky shape.

Because 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 less energy consumption, less power of the electric motor.

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

2-2 Calculation of the developed redistribution.

Definition of the annual working time fund:

T year \u003d (D-V-P) ∙ S ∙ T cm;

T year = (365-100-10) ∙8∙1=2040h.

T year - annual fund of working hours of technological repartition, h;

D\u003d 365 - the number of calendar days in a year;

AT- the 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 public holidays per year; P=10

With– number of shifts per day С=1;

T cm- the duration of the shift; T cm \u003d 8 h.

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

,

if M o and M p are given as a percentage of M n,

where M n - the amount of raw materials that should be processed for the year.

M p - technological losses; M p \u003d 3.5

M o \u003d 0 - the amount of waste.

M k - the amount of material in a useful product produced per year.

,

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

units.

M is the amount of material in a unit of production; m=1.1

M k \u003d 60000 ∙ 1.1 \u003d 66000 (m 3 / year)

(m 3 / year)

According to the material balance of a given redistribution, its required hourly productivity is determined:

, where

P required - the required hourly productivity of the device.

M up - the amount of materials re-introduced into the process at

operation of the apparatus in a closed cycle; M up = 0.

P required \u003d 33.5 m 3 / h.

2-3 Machine calculation.

The required number of devices for the implementation of a given process is determined by the formula:

,

where P is the required amount of a piece of equipment.

P required - required hourly productivity

calculated process.

K p - coefficient of performance reserve. This

the coefficient must be greater than 1.05;

P e - operational performance of the selected apparatus.

P=0.054 hence 1 crusher KKD 1200 / 150

CALCULATION OF A CONE CRUSHER

General information about cone crushers.

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

Rice. 2.1 Scheme of the structure of the cone crusher of coarse crushing.

Crushing of 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 enters the hole located eccentrically on the shaft.

Cone crushers are characterized by: B - the width of the feed opening, C - the width of the discharge slot, C - the smallest size of the crusher slot.

The size of cone crushers for coarse crushing is usually characterized by the width of the feed opening B and the width of the discharge opening C. 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 gripping angle is usually within 24-28˚, the 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 any 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 crushed pieces is more uniform.

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

Determination of crusher performance.

Performance of cone crushers P(m 3 / h) with large cones is determined by the formula:

,

where D to - the outer diameter of the movable cone, m;

r is the radius of the circle described by the point of the axis of the movable

cone lying in the plane of the unloading gap, m

b 1 - the smallest width of the unloading gap or width

parallel zone when cones approach, m

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

α 1 and α 2 are the angles between the vertical and the generators of the cones,

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

K p - coefficient of loosening of the crushed material

(K p \u003d 0.25 - 0.6)

ρ is the density of crushed material;

P \u003d 117 (m 3 / h)

Determining the power of the crusher engine.

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

,

where σ is the compressive strength of the material, N/m2

E - the modulus of elasticity of the material, N / m 2

D n - the lower diameter of the movable cone, m

d – diameter of unloaded pieces of material, m

D is the diameter of the 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 of production of building materials" graduate School» 1990.

3. N.K. Morozov "Mechanical equipment of precast concrete plants". Kyiv "High School" 2977.

4. Tkachenko G.A. " Guidelines". Rostov-on-Don State Academy of Civil Engineering.

1-1 Initial data

1-2 Introduction

1-3 Theoretical foundations of processes

1-4 Selection and description of the technological scheme of production

1-5 System analysis of the technological process

2-1 Description of the developed technological stage

2-2 Calculation of the developed technological stage

2-3 Apparatus calculation

Lime can rightly be included in the list of the most commonly used materials by man. At the same time, we use it not only in finishing works, but also in a number of tasks where the properties of lime are ideally suited.

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

The quenching 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 slaking lime, a 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 quenched during storage.

Areas of application of slaked lime

• Whitewashing of premises and other surfaces, including tree trunks, thus protected from pests;
• Use in masonry. Most often - in the laying of the stove. In this case, we can talk about the highest adhesion to a brick or cinder block surface;
• Used as a finish on wood. However, in this case, it is necessary to use a plaster mesh or shingles.
• Preparation of lime mortar, which has been used since ancient times. To prepare the solution, three to four parts of sand and one part of slaked lime are used. Water is released during the process, which is a disadvantage, therefore, in rooms created using this solution, there is always high humidity. So the cement has almost completely displaced this solution over time;
• Preparation of silicate concrete. This concrete differs from simple concrete in accelerated setting time;
• Production of bleach;
• leather tanning;
• Neutralization of acidic soils and production of fertilizers. At the same time, lime is applied to the soil after flares in the spring and autumn seasons;
• 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. With the help of slaked lime, the canals of the teeth 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 store slaked lime

In case if we are talking about the winter period, then storage of lime in the ground is carried out at least at a depth of 70 cm. In this case, the dough will be protected from freezing.

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

• If you are preparing a mortar based on lime, then the ideal solution would be to gradually add pre-sifted sand to the dough. Gradually kneading is carried out 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. In this case, the setting time is estimated to be approximately 4 minutes. In the case of the addition of cement, hardening occurs over a longer period of time. pure solution lime seizes for a very long time.

3 ways to slake lime

• Method 1: Lime clods are laid in layers 25 centimeters thick. After that, they are watered with water and covered with wet sand from above. The slaking process takes about two days, after which the lime can be used;
• Method 2: In the case of lime of medium or slow slaking. A hole is dug, at the bottom of which a solution container is installed in the form of a wooden box with a shutter at the bottom, created using a fine mesh. Lumps are placed in a box and filled with water. Water is added as the fragments break up into smaller ones. As soon as all the fragments are extinguished, and the final product is ready-made milk of lime, we drain the excess water by moving the damper. After that, lime porridge is covered with a layer of sand of 10 centimeters, which will protect it from drying out;
• Method 3: Pushenka can be prepared by pouring lime with water in equal proportions. During the quenching process, the mixture is stirred. However, one must be careful not to bend over during periods of the highest heat generation, so as not to breathe in vapors.

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Some of the materials used today in various fields have been known for a long time, and their properties, as a rule, were determined quite by accident. Lime is one of these materials. By this word, which comes from the Greek "asbestos", which means "inextinguishable", they mean quicklime, which is successfully used today in many industries.

Peculiarities

Quicklime is a product of roasting rocks mined in special mines. A special furnace is used as a tool, and the materials used to obtain the final product are limestone, dolomite, chalk and other rocks of the calcium-magnesium type, which are sorted by size and crushed before firing if the particles exceed the allowable dimensions.

The design of the furnaces used for roasting rock can be different, but the ultimate goal is always the same - to obtain material suitable for further use.

The shaft type furnace, where gas is used as fuel, is one of the most popular designs. The reason for their popularity is quite banal: the cost of processing the material is low, and the final product is of very good quality.

Furnaces that use coal as fuel and the firing process is based on the pouring principle of operation are gradually becoming a thing of the past. Although this method of processing the material is more economical and productive, but due to emissions into the environment, it is becoming less and less common.

Due to the high cost of the firing process, even more rarely are kilns with a rotating design that allow you to get the final product. highest quality. Remote fired kilns ensure purity and a minimum percentage of impurities in the final firing product. This type of furnace, in which solid fuel is used for heating and maintaining the temperature, has a small power compared to similar designs, therefore, it is not widely used.

The type of ring and floor ovens was developed a very long time ago. Compared to more modern designs, they have lower productivity and consume more fuel during processing, so they are gradually being phased out of production, being replaced by more advanced types of furnaces.

The substance obtained as a result of firing has a white tint and a crystalline structure with a small proportion of impurities. As a rule, their value does not exceed 6-8% in the total mass. The generally accepted chemical formula for quicklime is CaO, or calcium oxide.

The composition of the substance may also include other compounds, most often it is magnesium oxide - MgO.

Specifications

Any materials extracted from nature and subjected to industrial processing have a certain standard, and quicklime is no exception. For quicklime, which belongs to the second hazard class used in construction, there is a quality standard - GOST No. 9179-77, which clearly spells out the physical and chemical parameters of this material.

According to the prescribed requirements, the lime particles after grinding must have a certain size. To determine the degree of grinding, a sample is taken and sifted through sieves with different cells. The amount of sifted lime is expressed as a percentage. When passing through a sieve with cells No. 02, 98.5% of the substance of the total mass of the sample should be sieved, and for a sieve with smaller cells No. 008, 85% of the substance is allowed to pass.

According to technical requirements, admixtures are admissible in lime. This composition is divided into two grades: the first and second. Pure lime is characterized by three grades: the first, second and third.

To determine the grade of lime, indicators are used: active CO + MgO, active Mg, CO2 level and unextinguished grains. Their number is indicated as a percentage, the numerical indicator of which depends on the variety, the presence or absence of additives in the samples, as well as on the breed. If, according to some indicators, a lime sample corresponds to different grades, then the indicator with the value corresponding to the lowest grade is taken as the basis.

For chemical analysis, as well as the determination of the physical and mechanical properties of the samples, are based on GOST-22688.

Advantages and disadvantages

Like any other material, lime has its advantages and disadvantages. As a rule, it is compared with slaked lime. The main advantage of the material is a wide range of applications and a fairly low cost of the final product. When working with this material, regardless of the industry, there is no waste, which is very beneficial from an economic point of view.

The material perfectly absorbs moisture, which allows it to be successfully used as an additional element in the preparation of mortars and concrete mixtures to increase their density and strength. The release of a large amount of thermal energy by the material during hydration allows solutions containing quicklime to harden more evenly, and, as a result, have improved strength indicators of the resulting surface.

The only disadvantage of this material is its high toxicity.

How is it different from slaked?

Slaked lime is a modified quicklime product, it is obtained by adding water to the original composition. As a result chemical reaction, occurring according to the CaO + H? O → Ca (OH) ? type, is released into the surrounding space significant amount thermal energy, and calcium oxide is converted into calcium hydroxide.

The two types of lime also differ in other parameters, namely, in the percentage of indicators specified in GOST No. 9179-77 and the number of varieties. Slaked (hydrated) lime is characterized by 2 grades.

The values ​​of the indicator of active CO + MgO differ in two types of lime. For slaked lime without additives, depending on the variety, their quantitative content ranges from 70-90% (for calcium composition) and 65-85% (for magnesian and dolomite), and in slaked lime they are only 60-67%. In compositions with additives, active CO + MgO in calcium, magnesia and dolomite mixtures of quicklime are in the range of 50-65%, and in hydrated this indicator is only 40-50% lower.

Such an indicator as active MgO is completely absent in hydrated lime. In quicklime, this figure varies depending on the origin of the material. In calcium lime, it is only 5%, in magnesian lime - 20%, and in dolomite - 40%.

The level of CO in quicklime without additives is in the range of 3-7% (for a calcium mixture) and 5-11% (for magnesia and dolomite), in the hydrate composition the indicator does not exceed 3-5%. In compositions with additives, the level of CO? somewhat reduced. For calcium lime, it is in the range of 4-6%, for the other two types of quicklime - 6-9%. In the hydrate composition, the level of CO? – from 2 to 4%.

The indicator of not extinguished grains is relevant only for quicklime. For the first grade of calcium lime, 7% of a substance not participating in the reaction is allowed, 11% for the second and 14%, and in some cases 20% for the third grade. For the magnesian and dolomite composition, this figure is slightly higher. In the first grade, 10% is allowed, in the second - 15%, and in the third - 20%.

Kinds

Quicklime is classified according to many indicators, allowing it to be divided into different subspecies. According to the degree of grinding of particles, there are lumpy and ground lime. Lumps are characteristic of the lumpy appearance various shapes, fraction and size. In addition to calcium oxides, which are the main component, and magnesium oxide, which is present to a lesser extent in the composition, there may be other additives in the mixture.

Depending on the degree of burning of the lumpy material, medium burnt, soft burnt and hard burnt lime are distinguished. The degree of firing of the material subsequently affects the time taken for the quenching process. During the firing process, the composition is enriched with aluminates, silicates and magnesium or calcium ferrites.

The degree of roasting is affected by the time the product is in the kiln, the type of fuel and temperature. With the pouring firing method, where coke is used as a fuel, and the temperature in the furnace is maintained at a level of about 2000 ° C, carbide (CaC?) is obtained, which is subsequently used in various fields. Lump lime, regardless of how and to what extent it was calcined, is an intermediate and therefore undergoes further processing: grinding or slaking.

The composition of the ground mixture is not much different from the lumpy one. The difference lies only in the size of the lime particles. The grinding process is used for more convenient operation of calcium oxide. Crushed granulated or ground quicklime reacts faster with other components compared to the lumpy type.

According to the degree of grinding of particles, crushed and powdered lime are distinguished. Crushers and mills can be used for grinding, depending on the required particle sizes. When choosing mills and grinding schemes, they are guided by the degree of lime roasting, and also take into account the presence of solid inclusions and flaws in the firing process (underburning or overburning). Particles of material burned to a high or medium degree are crushed by impact and abrasion in special containers of ball mills.

The lumpy mixture is used to obtain different types slaked lime. The quenching process (inorganic chemistry) occurs very rapidly, water boils during the reaction, so the lumpy mixture is called "boiling". Different percentages with water give compositions of different consistency. There are three types of slaked lime: limestone milk, limestone dough and hydrated fluff.

Limestone milk is a suspension, where a fraction of the particles are dissolved, and the other is in suspension. To obtain such a consistency, water is required in excess, as a rule, 8-10 times more than the mass of the product.

To obtain lime dough, less water is required, but its amount is still several times greater than the mass of lime prepared for slaking. As a rule, in order to obtain the desired pasty consistency, water is added to the product, which is 3-4 times larger than the main substance by weight.

A powder mixture or hydrate fluff is prepared in a similar manner, but the amount of added water is less than for a pasty or liquid composition. Fine powder or fluff, depending on the percentage in the composition of aluminoferrites and silicates, is divided into air and hydraulic types of lime.

The time required for the slaking reaction makes it possible to classify quicklime into fast-slaking, medium-slaking and slow-slaking. The quick-extinguishing type includes compositions, the conversion of which takes no more than 8 minutes. If the quenching reaction takes longer, but the transformation does not last longer than 25 minutes, then such a composition is classified as a medium quenching type. If the quenching reaction takes more than 25 minutes, then such a composition belongs to the slow-extinguishing type.

Special varieties of calcium quicklime include chlorine and soda mixture. The chlorine composition is obtained by adding chlorine to slaked lime. Soda lime is a reaction product of soda ash and calcium hydroxide.

Scope of application

Quicklime can be used in various fields of human activity. It is most widely used in construction and everyday life. The material is used as an additional component for the preparation of cement mortars. Its astringent properties give the necessary plasticity to the mixture, and also reduce the hardening time. Lime is used as an additional component in the production of silicate bricks.

Lime-based solutions are used for whitewashing various indoor surfaces. This method of processing ceiling and wall surfaces is still relevant to this day, since lime is one of the materials that is very affordable, and the decorative effect it creates is no worse than from expensive paints and varnishes.

In agriculture and horticulture, lime is also an important component. It is used to reduce acidity and enrich the soil with calcium. The quicklime composition applied to the soil contributes to the retention of nitrogen in the soil, while activating the work of beneficial microorganisms and stimulating the growth of the root system of plants.

Quicklime also has a negative impact on crop pests. For preventive measures, aimed at fighting insects, lime is used as a solution with which to spray plants or process the lower part of tree trunks. For animals, lime is a source of calcium, so it is often given as a top dressing.

In everyday life and medical institutions, bleach is used as an excellent disinfectant. The solution from it kills most of the known pathogenic microorganisms, inhibiting the growth and their further development. Quicklime also helps in the neutralization of household gases and sewage.

In the food industry, lime is known as the E-529 emulsifier. Its presence makes it possible to improve the mixing process for components whose structure does not allow them to connect correctly.

How to breed?

Quicklime is packaged by manufacturers in bags. As a rule, a bag of 2-5 kg ​​is enough for processing plants and whitewashing fruit trees. In order to dilute lime correctly, it is necessary to prepare a container and follow the procedure.

Before diluting lime, it is necessary to choose a container that is suitable in size and material. The volume of the container is selected based on the expected volume, and the material of the utensils can be any, even metal utensils can be used, as long as it is free of chips and rust.

price

practicality

appearance

ease of manufacture

laboriousness in 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, dolomites, 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 contains magnesium oxides and other compounds.

In the photo, calcium oxide (quicklime)

The material is manufactured in accordance with the requirements of GOST 9179-77 under the name “Building lime. Specifications". 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 a sieve No. 02 and No. 008 is not higher than 1.5% and 15%, respectively.

Quicklime is referred to the 2nd hazard class. Pure lime of the air type can have the 1st, 2nd and 3rd grade, with impurities - the 1st and 2nd grade. Hydrated lime has the 1st and 2nd grade.

Quicklime production

In the past, heat treatment of limestone was performed to form lime. In recent years, this method has been used less and less because carbon dioxide is released as a result of the reaction. An alternative method is the thermal decomposition of calcium salts containing oxygen.

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

In most cases, shaft-type furnaces are used, which operate on gas, in bulk or with remote furnaces. The greatest savings are provided by devices that work in a bulk way on anthracite or lean coal. The volume of production with the help of such furnaces is around 100 tons per day. Their disadvantage is the high degree of fuel ash pollution.

You can get purer lime in a device with an external firebox that 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 in the substance processed in a rotary kiln, but such mechanisms are used quite rarely. Ring and floor type furnaces have low power and require large volumes of fuel, so they are not installed at new enterprises.

Stages of lime production at the plant:

Varieties

Building lime is divided into two types: air and hydraulic. Air lime makes it possible to set concrete under normal conditions, and hydraulic lime makes it possible to set concrete 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 burnt material, various types of lime are distinguished:

• lump lime It is made in the form of a mixture of pieces of different sizes. It consists mainly of oxides of calcium (the predominant part) and magnesium. Also, it may include 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 raw form. This avoids waste and accelerates hardening. Products made from it have excellent strength properties, they are water resistant and have a high density. To speed up the hardening process of the material, calcium chloride is added, and to slow down the hardening, sulfuric acid or gypsum is added. This prevents the appearance of cracks after drying. Ground lime is transported in sealed containers made of paper or metal. It is allowed to store it no more than 10-15 days in dry conditions.
• Hydrated lime- a highly dispersed dry compound formed during lime slaking. It consists of calcium and magnesium hydroxides, calcium carbonate and other impurities.
• When a liquid is added in a volume that is enough for the oxides to turn into hydrates, a plastic mass is formed, which has the name lime test.

The most popular in use today are slaked and quicklime.

Photo of various types of quicklime

Lump quicklime Ground quicklime Lime dough

Areas of use

For many years lime cement was produced from quicklime. It freezes well in air, but absorbs a lot of moisture, which causes fungus to appear on the walls. Therefore, now quicklime is much less in demand in the construction industry 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 the winter, as the slaking generates heat that maintains the temperature of the mixture during the hardening period. You can not take it for the production of cement for finishing fireplaces and stoves, because under the influence of temperature it releases carbon dioxide.

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

With the help of quicklime, flue gases and waste water are neutralized. It also paints 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 present in many products in the form of E-529 emulsifier. It is an ingredient that helps mix substances that are immiscible in nature (say, water and oil).

Application of quicklime:

Cancellation Rules

The quenching process occurs according to the formula:

CaO + H2O \u003d Ca (OH) 2 + 65.1 kJ.

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

Lime, depending on the period of slaking, is of the following types:

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

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

With the help of quenching, you can make hydrated lime (which is called fluff) or lime dough. To get out, you need to pour 70-100% of water from its weight into lime. They usually do it in factories, in special hydrators.

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

What happens when lime is slaked

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 a container. Metal containers are allowed, but they must not be rusty.
2. pour powder cold water at the rate of 1 liter (if fluff is being made) or 0.5 liters per 1 kg (if lime dough is being 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 slow-extinguishing, it is better to pour water in several steps.
• If the lime is medium or fast extinguishing, it must not be allowed to burn out. Water must be added to it until the formation of steam stops.
• If lime is used to whitewash the room, take 2 liters of water per 1 kg. Then more water is added to get the right consistency. The solution is defended for 48 hours and filtered. Apply it with a spray gun or brush.
• To whitewash trees, the proportion of water and powder should be 4:1. This solution also needs to be defended for two days before whitewashing.
• If lime was needed to spray plants from 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 goggles and long rubber gloves. Drops of slaked lime on the skin can cause severe burns. During the preparation of the mixture, do not bend over the container so that the water vapor does not cause burns.

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

Pros and cons of the material

Advantages of quicklime over slaked lime:

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

The main disadvantage of quicklime is its danger to human health. Therefore, you should act carefully so that the particles do not get on the mucous membranes or in 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 in order not to have to treat an eye burn, it is necessary to extinguish lime in goggles.

average cost

Now at least 26 specialized plants are engaged in obtaining quicklime in our country. Also, equipment for burning limestone is installed at many enterprises that produce cellular concrete and silicate brick.

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