The use of lime on a personal plot. Features of the use of slaked and quicklime substances

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

What is slaked lime?

Lime is a material that is obtained by firing a rock belonging to the carbonate category. This 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 material in question 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 is approximately the same as the ambient temperature.

The slaking of lime is directly carried out by mixing quicklime - that is, calcium oxide - with water. This procedure is accompanied by a noticeable heat release - about 67 kJ per mole.

Slaked lime - material that can be used:

1. as part of whitewash;
2. to protect wooden structures from destruction and fire;
3. for the preparation of various mortars;
4. to reduce water hardness;
5. in the production of various fertilizers;
6. as a food supplement;
7. for disinfection purposes during dental procedures.

Let us now study in more detail the specifics of the main raw material used to obtain 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 limestone, i.e. calcium carbonate.

When interacting with water, quicklime turns into slaked lime - while, as we noted above, heat is released. When mixed with acids, the substance in question forms salts. When 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. as well as slaked lime - as a food additive;
4. for cleaning flue gases from sulfur dioxide.

Other methods of using the material in question are also known. For example - as the main "warming" substance in specialized dishes that heats drinks on their own.

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

Comparison

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

Having determined what is the difference between canceled and, let us fix the conclusions in the table.

Lime is a product of the processing of chalk, limestone and other minerals from the carbonate group. The main rock-forming elements in it are calcite and. Both of these substances are widely used for feeding garden and garden crops both in industrial agriculture and in private farms. They are used to treat plants in order to protect against pests, and to improve the soil in various ways.

The most commonly used slaked lime. The extinguishing process is easy to do yourself. It is based on the reaction of the interaction of water and lime powder, and proceeds rather quickly, over several tens of minutes. During the interaction of these components, lime is "melted" and processed into a form that is more convenient for use and safe for plants. There is a little secret of making slaked lime - it is undesirable to fill it hot water, since the higher the temperature of the liquid, the less nutrients will be retained in the final product.

So why is lime so useful for the garden and garden? In accordance with the classification of calcareous - dolomite rocks (according to Vishnyakov), it contains (depending on the composition of the source), calcium, magnesium and potassium, moreover, potassium - in an oxide form easily assimilated by plants. But a large share in the composition of limestone or dolomite belongs, of course, to calcium. For many millennia, the remains of living organisms have accumulated in different places on our planet - skeletons, shells, shells, which over time have been compressed into limestone. Also, for many tens of centuries, dolomite fractions, which are of inorganic origin, were deposited on the mountain slopes. Both of these substances are used to make quicklime and have the same range of uses. But for some gardeners and gardeners, the difference between them is fundamental. What is it? Let's try to figure it out in the next section.

Is lime mineral or organic?

It has become very popular in recent decades healthy eating... This trend involves the use of only natural fruits and vegetables for cooking, grown without the use of agrochemicals. Following it, many summer residents and small farmers strive to grow organic products. This concept does not accept the use of mineral and synthesized fertilizers for feeding. In this regard, the question arises - is it possible within the framework of ecologically cleaner production the use of lime in the garden? What class of fertilizers does it belong to?

This is where the catch lies. The fact is that, depending on the source substance, lime can be both mineral and organic fertilizer. If it is obtained from CaMg (CO 3) 2 dolomite, then it is mineral fertilizer, since the original substance in this case is a mineral, sedimentary carbonate rock. The origin does not diminish the advantages of dolomite lime as a fertilizer, but it partially imposes restrictions on it for use in farms focused entirely on organic farming.

Calcium lime for soil, as mentioned above, is a substance that has an organic nature of origin, so it can be used in gardens and vegetable gardens, the owners of which practice natural farming. It is divided into two types - quicklime (CaO), and slaked lime - fluff Ca (OH) 2. Both types, with reasonable handling and compliance with the application rate, are safe for humans and plants, which confirms the fact that this type of lime is used even in food Industry, as an additive, marked E-529.

Lime properties

IN agriculturethe use of garden lime is widespread. Despite the fact that many plants cannot tolerate an excess of calcium, it is an indispensable element in many life processes that occur in all plant organisms. Its presence in the soil complex is necessary to retain hydrogen ions in it, which helps calcium to maintain a favorable level of environmental reaction. This item provides the following functions:

1. Calcium protects crops from various diseases, strengthening their own immunity. Soil liming helps to activate the activity of nodule bacteria, which retain nitrogen in the ground from the air that gets to the roots during loosening. This helps to improve the quality of plant nutrition, and, accordingly, to increase their resistance to various harmful counterparties.
2. Transport of carbohydrates in plant tissues. Calcium promotes better dissolution of elements in the aquatic environment.
3. Strengthening the walls of blood vessels, along which aqueous solutions of vital substances move. This property, to a large extent, contributes to a more active and high-quality development of the root system. Moreover, these elements are vital for plant nutrition.
4. The introduction of lime is necessary during formation. Ca is a catalyst that activates the activity of beneficial microorganisms that release nitrogen from organic matter and mineralize it. Also, this element contributes to the formation of humus, as it accelerates the decomposition of organic matter.
5. One of the most useful properties lime is considered to be its ability to reduce soil acidity. But, this substance not only normalizes the reaction of the upper soil layer, but also improves it chemical composition, neutralizing the effect of toxic metals - iron, aluminum and manganese. Also, bleach has a positive effect on the structure of the soil, making it less free-flowing and more lumpy.

Lime is actively used in agriculture for various purposes. In plant growing, the following are the most relevant:

The use of lime to normalize soil acidity

This procedure should be performed once every 4-5 years, on lands subject to intensive exploitation - once every three years. Also, you should always pay attention to external signs, with the help of which the earth itself signals that its composition has changed. A sign of desperate acidification of the beds is green moss, which quickly begins to overgrow the edges of the earth. Also on elevated level acidity is indicated by plants such as horsetails and wormwood. If these unexpected guests have appeared on your site, it's time to liming the soil.

The application rates are as follows:

• On heavy clay soils - from 450 to 800 g / m2 It is necessary to follow the rule - the higher the pH value, the less lime is added.
• On lighter, loams and alumina - from 350 to 600 g / m2.
• On the lightest, sandy lands, lime for the soil is applied (depending on the pH factor), in an amount of 250 to 500 g / m2.

The use of lime in the garden is possible in conjunction with organic fertilizers, that is, it can be entered simultaneously with them. But this mixing method imposes certain restrictions on the introduction of certain types of lime powder - dolomite, calcareous tuff, marl, fluff, cement dust, and even chalk should not be mixed with organic matter. That is, only calcium organic matter - ground limestone - can be mixed with natural fertilizers.

Video: mini-film about soil liming and acidity reduction

Protecting trees from pests with whitewashing

In spring, you can see orderly rows of trees and shrubs with whitewashed trunks in almost every village in our country. Naturally, this is not done for beauty, but in order to protect trees from pests. Whitewashing trees with lime is included in the planned processing of all fruit farms in our country and abroad, since this measure is cheap and very effective.

Trees are not only whitened in spring. Many gardeners do this before winter. Both the first and the second method have a mass of followers, and each has its own advantages and disadvantages.

Autumn whitewashing and clay coating protects the tree trunk from sudden changes in temperature, and the milk of lime acts as a peeling, helping to remove dead layers of bark. But this is where all its advantages, for the most part, end. Under the influence of precipitation (snow and rain), after snowmelt, the trunks are stored in best case, half a layer of autumn whitewash. This is not enough to protect the tree from solar overheating, which is especially dangerous for young seedlings of the second or third year of life.

Spring whitewash, in addition to protection from the scorching sun rays, it also perfectly protects from awakened insects that have wintered in the ground or in leaves, and tried to encroach on your apple trees. A white belt will block their way. But, there is an opinion that the autumn whitewashing will be able to drive out insects hiding under the bark for wintering. Yes, this is true, but only for a neglected garden that has not been cultivated before. Trees, which have been regularly treated with lime every spring since planting, are simply not carriers of insect pests.

Preparation is always necessary before whitewashing. It consists in removing the upper, dead layer of the bark, the sinuses of which serve as an excellent shelter for both larvae and adults. The bark is cleaned and burned without fail. Then the tree is treated with a pre-prepared solution.

It is necessary to dilute lime for whitewashing with the following components:

1. Lime - 1 kg;
2. Water - 10 liters;
3. Copper sulfate - 200 g;
4. dry - 1 kg;
5. Clay - 300 g.

After thorough mixing, this solution is left to swell. After 2-3 hours, you can start processing. It must be remembered that in order to obtain a high-quality and viscous solution, it is not enough to dilute lime for whitewashing, it is fundamentally important to add all the components specified in the recipe to it, only in this case it is guaranteed positive effect from this procedure.

Video: an alternative example of whitewashing trees

Some interesting facts about lime

• Liming acidic soils in the recommended quantities, has a positive effect on population growth. They reproduce slowly in acidic soils, and their lifespan is also noticeably reduced if they live in highly acidic soil.
• can replace lime in its absence. It lowers soil acidity and is valuable potash fertilizer... But this fertilizer will have to be applied in larger quantities than limestone or dolomite.

• One of the common mistakes gardeners make when normalizing the acidity of the soil in their area is replacement of quicklime with gypsum. It's pointless, since gypsum does not lower acidity. It is introduced only into saline soils to improve their reclamation, as it crystallizes excess salt.
• The frequency of using garden lime directly depends on what fertilizers are used on the site. If - liming is done more often. And the use contributes to the natural maintenance of a neutral pH - balance, therefore, with regular introduction of organic matter, additional lime treatment may not be required.
• Not all cultures love lime. Some categorically do not tolerate it. For example, such as, sorrel, peas, parsley, zucchini and pumpkin. In gardening, it is also possible to distinguish plants that sharply negatively react to the introduction of limestone, dolomite, tuff - these are chokeberries, gooseberries, raspberries and blueberries. From field crops, the introduction of lime is contraindicated for flax, it loves acidic soils.

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

Limestone is usually mined open way in the quarries. Dense calcareous-magnesian rocks explode. To do this, first, with the help of shock-rotary machines (with hard rocks) or rotary drilling (with rocks of medium strength), wells with a diameter of 105-150 mm and a depth of 5-8 m and more are drilled at a distance of 3.5-4.5 m from one another. They are filled with 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 the occurrence of limestone in deposits (in terms of chemical composition, strength, density, etc.) necessitates selective mining of useful rocks. Selective mining of limestone increases the cost of the product, therefore, when determining the technical and economic feasibility of developing certain deposits, careful geological exploration is required.

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

High-quality lime can only be obtained by firing carbonate rocks in the form of lumps that differ little in size. When firing the material in pieces of different sizes, unevenly burnt lime is obtained (the fines are partially or completely burnt, the core of large pieces is not burnt). In addition, when loading shaft furnaces with pieces different sizes the degree of filling of the furnace is significantly increased, and, consequently, the gas permeability of the material decreases, which complicates the firing. Therefore, before 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 advisable to burn limestone separately in fractions of 40-80, 80-120 mm in diameter, and in rotary kilns - 5-20 and 120-40 mm.

Since the size of blocks of mined rock often reaches 500-800 mm or more, it becomes necessary to crush them and sort the entire mass obtained after crushing into the desired 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 working fractions to the plant.

Roasting is the main technological operation in the production of air lime. At the same time, a number of complex physical and chemical processes take place that determine the quality of the product. The purpose of firing is the fullest possible decomposition (dissociation) of CaCO3 and MgCO3-CaC03 into CaO, MgO and CO2 and obtaining a high-quality product with an optimal microstructure of particles and their pores.

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

The decomposition reaction (decarbonization) of the main component of limestone, calcium carbonate, proceeds according to the scheme: CaCO3 ^ Ca04-CO2. Theoretically, 179 kJ or 1790 kJ per 1 kg of CaCO3 is consumed for decarbonization of 1 mole of CaCO3 (100 g). In terms of 1 kg of CaO obtained, the costs are equal to 3190 kJ.

Dissociation process of calcium carbonate - reversible reaction. Its direction depends on the temperature and partial pressure of carbon dioxide CO2 in a medium with dissociating calcium carbonate.

Since CaO and CaCO3 are solids and their concentrations per unit volume are constant, the dissociation constant is / (DIs \u003d Cso2. For a gas, its concentration can be expressed through the partial pressure, then /

Dissociation of calcium carbonate is possible only if the dissociation pressure is greater than the partial pressure of CO2 in the environment. At ordinary temperature, decomposition of CaCO3 is impossible, since the dissociation pressure is negligible. It was found that only at 600 ° C in an environment devoid of carbon dioxide (in vacuum), the dissociation of calcium carbonate begins, and it proceeds very slowly. With a further increase in temperature, the dissociation of CaCO3 accelerates (7).

At 880 ° C, the dissociation pressure (elasticity) reaches 0.1 MPa. At this temperature (it is sometimes called the decomposition temperature), the pressure of carbon dioxide during dissociation exceeds the external atmospheric pressure, therefore, the decomposition of calcium carbonate in an open vessel proceeds intensively. This phenomenon can be conditionally compared with the intense release of steam from a boiling liquid.

At temperatures above 900 ° C, an increase in it for every 100 ° C accelerates the decarbonization of limestone by about 30 times. Practically in kilns, decarbonization begins at a temperature on the surface of the pieces of about 850 ° C with a CO2 content in the exhaust gases of about 40-45%. The rate of limestone decarbonization during firing also depends on the size of the pieces to be fired and their physical properties.

The decomposition of CaCO3 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 of the dissociation zone inside the piece increases with an increase in the firing temperature (8). In particular, at 800 ° C the rate of dissociation zone movement is about 12 mm, and at 1100 ° C it is 14 mm per hour, that is, it goes 7 times faster than at 800 ° C.

Quality Construction Air Lime depends not only on the content of free calcium and magnesium oxides in it, but also on the microstructure of the product, determined by the size and shape of CaO and MgO crystals, as well as the size of the pores and their distribution in the mass of the substance.

With the true density of calcite, the main component of limestone, 2.72 g / cm3, 1 g of the substance occupies an absolute volume of 1: 2.27 \u003d 0.36 cmg \\ From 1 g of calcite during firing, 0.56 g of calcium oxide is formed, which at a density of 3 , 4 g / cm3 occupies a volume of 0.56: 3.4 \u003d 0.16 cm3, i.e., 2.25 times less than the initial calcite. If we assume at the same time that calcium oxide will be evenly distributed in the volume of the initial calcite and will occupy half of this volume, then the other half will be represented by pores of various sizes, penetrating the mass of lime.

In fact, the average density of limestones of various deposits, depending on their chemical and petrographic composition, density, microstructure, as well as firing conditions, varies in different ways. Usually, at low firing temperatures (850-900 ° C), pieces of lime from limestones of various deposits only slightly decrease in volume, although sometimes a slight increase is observed. When the firing temperature rises to 1000 and especially to 1200-1300 ° C, the volume usually decreases significantly. Exceptions are rare.

Naturally, a decrease in volume is accompanied by a decrease in the total porosity of the pieces and an increase in their average density. If the average density of lime obtained by burning at 850-900 ° C reaches 1.4-1.6 g / cm3, then for lime burnt at 1100-1200 ° C, it rises to 1.5-2.5 g / cm3 and more (per piece). It is characteristic here that the density of pure calcium oxide, according to BN Vinogradov, practically does not depend on the firing temperature in the range of 650-1500 ° C and is equal to 3.43 g / cm3. During firing, there is a rapid rearrangement of the trigonal crystal lattice of calcite into cubic calcium oxide.

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

The specific surface area of \u200b\u200bsuch lime, according to the research of R. Gaul and F. Raal, reaching about 50 m2D, 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. The influence of the shape of calcium oxide crystallites on the technical properties of lime has not yet been studied.

An increase in the firing temperature to 900 ° 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 m2 / g, which should have a negative effect on 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 calcining limestone at temperatures of about 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.

Finally, firing at 1400 ° C and above causes an increase in the average density, a sharp decrease in porosity and the formation of calcium oxide crystals and their conglomerates of significant sizes - 10-20 microns and more (9), which predetermines their slow interaction with water, which is characteristic of burnt lime. ...

Some impurities in limestones, especially ferruginous ones, contribute to the rapid growth of calcium oxide crystals and the formation of "burnout" even at temperatures around 1300 ° C. This necessitates firing raw materials with such impurities at lower temperatures.

Burn in lime adversely affects the quality of the solutions and products manufactured on it. Delayed slaking of such lime, which usually occurs in an already set mortar or concrete, causes mechanical stresses and, in some cases, material destruction. Therefore, the best lime will be calcined at the lowest temperature that ensures complete decomposition of calcium carbonate and fuel economy.

Selecting the firing temperature for limestone also depends on the presence of magnesium carbonate impurities in it. Unlike calcium carbonate, MgCO3 decomposes when heated at a lower temperature: the beginning is about 400 ° C and complete dissociation at 600-650 ° C. The reactivity of the resulting MgO, like CaO, decreases significantly with an increase in the firing temperature. Already at 1200-1300 ° C, tightly fired magnesium oxide is obtained - periclase, which practically does not possess astringent properties and only with very fine grinding begins to slowly interact with water. Sufficiently active magnesium oxide is obtained by firing dolomites and dolomitized limestones at 850-950 ° C.

Since limestone is fired at a higher temperature than is necessary for the decomposition of magnesium carbonate, lime with a significant content of magnesium oxide in it is slaked slowly. Therefore, carbonate rocks with a high content of magnesium carbonate should be burned at temperatures no higher than 900-1000 ° C. Otherwise, the astringent properties of magnesium oxide will not be used, the resulting lime may be characterized by an uneven change in volume.

During the firing of limestones with clay and sandy impurities, reactions occur in the solid state between CaCO3, MgC03, CaO and MgO and the acidic oxides Si02j A1203 and Fe203 contained in these impurities. At high temperatures (800-1200 ° C and more), the mobility of anions and cations, forming a crystal lattice of these substances, increases significantly. As a result, there is an intensive exchange of crystal lattice elements and the formation of silicates, aluminates and calcium ferrites. Therefore, in addition to the predominant amount of free calcium oxide, the composition of limestone roasting products usually includes dicalcium silicate (3-2CaO-SiO2, mono-calcium aluminate CaO-A1203 and dicalcium ferrite 2CaO "Fe203.

The reaction rate between CaO and acidic oxides increases with increasing temperature. The more clay and sandy impurities in limestone, the more calcium oxide binds to these compounds, the slower the lime is slaked and the more pronounced its hydraulic properties. According to GOST 9179-77, in well-burnt lime, the content of free calcium and magnesium oxides must be at least 90%. In modern factories with pure raw materials, lime is obtained with an activity of up to 95% or more.

For practical purposes, such indicators as the yield of lime from a unit mass of the fired material, its consumption per unit mass of the resulting lime, as well as the theoretically possible and practically obtained activity of lime during the firing of one or another type of raw material, are important. All these indicators are determined with an accuracy sufficient for practice. a. V. Volzhensky's formulastaking into account the chemical composition of the fired material.

With the degree of decarbonization equal to one, it is possible to establish the theoretical lime yield from raw materials of a given chemical composition. At present, in modern factories and installations, even when producing soft-fired lime, the degree of decarbonization reaches 0.95-0.98.

It should be noted that when lime is calcined in transfer furnaces, it is enriched with fuel ash in an amount of about 1% of the raw material mass. This circumstance is not taken into account in the above formulas, since it has little effect on the final values.

The name "lime" comes from Greece, it means "unquenchable". This word is applied to such materials that have been in the use of mankind for a long time. The properties of this substance were discovered randomly, it found application in various fields, its behavior was tested in different situations, tried, made mistakes, checked again, and as a result, properties were deduced that are still used by mankind in many fields of activity.

Nowadays there is a substance called slaked lime, this article will talk about the properties of this material, how it is obtained, where it is used.

Arriving at a store selling building materials among the assortment of goods, you can see a substance in a bucket that has the inscription "Silicate concrete", its composition will indicate what it contains slaked lime... Undoubtedly, many are interested in information about this material. Slaked lime has a formula of this type: Ca (OH) 2, this is a substance of a strong base, it can be found under other names, for example:

1. Calcium hydroxide.

Fluff lime is white, powdery substance, almost insoluble in water. It was found that what colder water, the less soluble the lime. When a reaction with an acid occurs, certain calcium salts are released, if mixed with sulfuric acid, water and calcium sulfate will be released. When the solution is in the air, interaction with carbon dioxide will occur, and the solution will acquire a cloudy hue. The result of this reaction is due to the interaction of water and calcium carbonate. With the continuation of the bubbling of carbon dioxide, as a result of the reaction, calcium bicarbonate will be released, it will be destroyed if the temperature of this solution is increased.

Interaction carbon monoxide and lime at temperatures closer to 400 C will give hydrogen, carbonate. Such a substance has reactive properties with respect to salts, this happens in the case when the result of the process is the appearance of a precipitate, also in the case of mixing fluff with sodium sulfite, in this case the result of the reaction will be the appearance of sodium hydroxide, calcium sulfite.

The material from which lime is made

There are two types of substance: slaked and quicklime... To get slaked, you need to extinguish a certain substance. It is customary to extinguish any compound with water. It has such a name as quicklime. By adding water to such a substance, slaked lime is obtained.

Using slaked lime

Slaked lime is used in the following cases:

In addition to all of the above, it is used in many other industries, she is needed almost everywhere.

Slaked lime and quicklime are different. Quicklime is calcium oxide, and slaked is calcium hydroxide, which is another substance formed as a result of quenching.

Slaked lime

It is a white powder that is difficult to dissolve in water., the base is quite strong, capable of reacting with acids, in this case a neutralization reaction occurs, calcium salts are formed. The density is 2.211 g / cm, melting occurs at a temperature of 5120C, its formula is Ca (OH) 2. The receipt of the material occurs when the interaction of quicklime, calcium oxide, which is quicklime, with water occurs, this process is called quenching. During quenching, strong heating occurs, 65 kJ per mole, equal to 1160 kJ per 1 kilogram of calcium oxide. The temperature at which extinguishing occurs can even ignite wood.

Lime classes

Fluffy who called construction, has the form of air, ensuring the hardening of mortar or concrete, retains strength under dry conditions, another type is hydraulic, which provides hardening of solutions or concrete, provides strength in water and in air. Quicklift air-type fluff has three types: dolomite, magnesian, and calcium... The type depends on how much magnesium and calcium metal oxides are contained. The aerial form has two types: quicklime, quenched, quenched also has the name hydrated. It is obtained by quenching dolomite, magnesian, and calcium.

The hydraulic type is divided into two types: highly hydraulic as well as weakly hydraulic... Fractional composition is divided into types: powdery, lumpy, crushed. Powdery is obtained by breaking, quenching, and also by hydration of the type of lump lime, it can be of two types: which has additives, and which does not. Lime is divided into classes according to the time during which slaking occurs. It is fast-extinguishing, which is extinguished no more than eight minutes, medium-extinguishing, it is extinguished up to 25 minutes, and slowly extinguishing, its extinguishing time is more than 25 minutes.

The use of slaked lime

This material has found quite a lot of use:

Also fluff lime has found application in many other industries and situations: it is used to obtain different connections calcium, for carrying out the neutralization of various solutions, this applies, for example, to waste water; in the production of various organic acids, and many other applications. In the food industry it is used as a food additive E526. Calcium hydroxide solution is also called lime water... This water is used to determine the presence of carbon dioxide.

Lime milk is a suspension, in other words, a suspension of calcium hydroxide. This liquid is white and opaque. Such a substance is used in order to produce sugar, to prepare certain mixtures that are made to treat various diseases in plants, and also to whitewash trees and trunks. In addition, there is a positive experience of using lime in dentistry for disinfection of tooth canals. Chemical and physical indicators correspond to GOST 9179–77.

Lime can rightfully be included in the list of the most commonly used materials. However, we use it not only in finishing works, but also in a variety of tasks where the properties of lime are ideal.

This material is called calcium hydroxide. It is obtained from calcium oxide (quicklime) by interaction of the latter with water. A so-called quenching reaction occurs, which can take less than 8 minutes and more than 25 minutes. Depending on this, lime, quicklime usually in the form of lumps gray shade, are subdivided into fast, medium and slow extinguishing.

The quenching process is chemical in nature, and a large amount of heat is generated during it. Water evaporates, and we can observe this vapor during the process. When slaking lime, fluff or dough is obtained. The latter has unique propertiesallowing it to be stored for a long time in the ground. It is noteworthy that in this case specifications material only grows, since the remaining particles are extinguished during storage.

Spheres of application of hydrated lime

• Whitewashing premises and other surfaces, including tree trunks, thus protected from pests;
• Use in brickwork... Most often - in the oven masonry. In this case, we can talk about the highest adhesion to a brick or cinder-concrete surface;
• It is used as a wood finish. However, in this case it is necessary to use plaster mesh or shingles.
• Preparation of a lime mortar that has been used since ancient times. For the preparation of the solution, three to four parts of sand and one part of slaked lime are used. In the process, water is released, which is a disadvantage, therefore, in rooms created using this solution, always high humidity... So the cement almost completely replaced this solution over time;
• Silicate concrete preparation. This concrete differs from simple concrete by accelerated hardening time;
• Bleach production;
• Leather tanning;
• Neutralization of acidic soils and fertilizer production. In this case, the introduction of lime into the soil occurs after plowing in the spring and autumn periods of the year;
• Lime milk and lime water. The former is used to prepare mixtures for combating 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 supplement E526.
• In fact, there are many ways to use lime. We have listed only a few of them.

How to properly store slaked lime

In case if it comes about winter period, then lime storage in the ground is carried out at least 70 cm deep. 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, it is about curing for at least a month. If the solution will participate in the laying, then two weeks will be enough.

• If you are preparing a lime-based solution, then in this case perfect solution will gradually add pre-sifted sand to the dough. Kneading 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 to mortar gypsum, you will significantly increase the setting time. The setting time in this case is estimated to be approximately 4 minutes. In the case of the addition of cement, hardening occurs over a longer period of time. A clear solution of lime sets 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 poured 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 lime of medium or slow slaking. A pit is dug, at the bottom of which a container for a solution is installed in the form wooden box with a damper at the bottom created using a fine mesh. Lumps are put in a box and filled with water. Water is added as the fragments disintegrate into smaller ones. As soon as all the fragments are extinguished, and the final product is ready-made milk of lime, we drain excess waterpushing back the flap. After that, the lime porridge is covered with a layer of sand of 10 centimeters, which will prevent it from drying out;
• Method 3: Fluff can be prepared by pouring lime with water in equal proportions. During the quenching process, the mixture is stirred. However, you need to be careful not to bend over during periods of the highest heat generation in order not to breathe in vapors.

Lime is a Greek word that has its own meaning. Literally translated, it means "unquenchable". It is one of those materials that have existed since time immemorial. It has long been used by humanity for their own purposes. Oddly enough, its properties were determined completely by accident. But they began to apply the material in many areas, through errors and trial, one might say, blindly. Lime - universal materialwhich is still used today.

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

Material history

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

If we recall the history of ancient China, the workers stabilized the soil with limestone cement and laid the masonry of their famous Great Wall of China. Its length is 2500 km. It is amazing that it has survived to this day, and today we can contemplate its greatness. Over time, lime has become a key ingredient in the preparation of fertilizers used in agriculture.

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

Raw material production

We already know that lime is a rock product. It is mined by firing in special furnaces from limestone, dolomite and chalk. The output is material in the form of white lumps, or, as it is also called, a lumpy "boiling pot". This is quicklime. The mining process takes place in special factories, from where lime is delivered further. "Kipelka" is the initial product, from which other types will be further produced. Chemical formula material - CaO (calcium oxide).

The raw materials ready after firing are not used for mortars and cement, since they have the ability to absorb moisture very strongly, and also contributes to the formation of fungal mold on the walls. Nevertheless, boiling water is quite in demand in the construction industry, namely for the manufacture of cinder concrete, silicate bricks, dyes and mixtures for plaster.

Depending on the time during which it is possible to extinguish the lump "boiling pot", it is divided into 3 types. The first of these is quick-drying lime. The time it takes to pay off is up to 8 minutes. The second type is medium damping, which comes in 25 minutes. Well, the last type is slow-extinguishing, which takes 25 minutes or more to get to the condition. So smoothly we moved on to another type of material - slaked lime.

Slaked lime

Differences between slaked and quicklime, how are they expressed? The name itself already shows the difference between the materials. If the usual raw material has the formula CaO, then the slaked material is obtained by adding water: CaO + H 2 O \u003d Ca (OH) 2. This is the quenching process. It is noteworthy that when mixing raw materials with water, a violent reaction occurs, in which great amount heat and smoke. The water literally boils. That is why lump lime is called "boiling water". The output is a hydrated fluff.

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

How to make a slaked fluff

For the production of slaked lime, some rules must be followed. Dehydration (quenching process) is required outdoors. The raw material itself must be placed in a tank or container. Since a fairly large amount of steam will be released in the process, you need to protect yourself. The material itself can also harm humans and even burn the skin. That is why it is necessary to protect the skin of the hands and the whole body, eyes and respiratory tract. You cannot do without a suit or special clothing, gloves, glasses and a respirator. Then everything will be safe for your health.

It is important to remember that there is no need for haste in this matter. The qualities of quicklime can vary, one is extinguished quickly, the other takes a long time. If you do not bring the whole thing to the end, then it is possible that the material will smoke in the finished plaster. When using slow-drying lime, it is not recommended to immediately fill it with water. Better to do it in small portions. Medium and fast-extinguishing are poured until the steam has completely disappeared in order to prevent burnout.

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

There will be more lime after dehydration. From 1 kg of quicklime material, 2 or more can be obtained. Slaked lime and quicklime the difference is obvious. But where are these materials used?

Application in construction

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

It is a material with binder properties, which is obtained as a result of firing followed by processing of carbonate rocks... Among them: calcareous-magnesian minerals, limestone, chalk. Lime, in its various forms, is used in almost all areas of human activity, including the construction industry.

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

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

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

How to extinguish lime correctly

Slaked lime is on sale in building stores, but you can cook it yourself. First you need to figure out what it is slaked lime. This material is obtained by treating lump of quicklime with water.

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

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

• Put in the prepared container required amount source material.
• Pour it with COLD water in a 1: 1 ratio. During the initial interaction with water, lime behaves very violently and heats up very much. At this point, you especially need to remember about safety rules.
• Quicklime from different manufacturers, made from different raw materials, may differ in properties. Therefore, it is better to fill it with water in several steps to ensure uniform quenching.
• In the first half hour, the composition must be constantly mixed. Then the container must be closed and left alone for at least two weeks. Practice shows that the longer the exposure, the better the fluff turns out.

It is best to cook the fluff outdoors, as it is unhealthy and unsafe to extinguish lime at home, indoors. The consistency of hydrated lime may require additional dilution immediately prior to use.

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

After the preparation of slaked lime, during the first filling with water, unquaked pieces are necessarily left. They can form as a result of incomplete firing or, conversely, burnout. So you shouldn't throw them away right away. It is necessary to fill again clean water and use as directed. And after secondary processing - dispose of.

What is the difference between slaked lime and quicklime

Burnt limestone instantly enters into a chemical reaction with water, therefore, it cannot be used as a pure binder. However, quicklime has found its use in the manufacture of cinder concrete, coloring compounds, silicate bricks, cellular and heavy silicate concrete. It is difficult to do without it in the process of wastewater and flue gas treatment. Quicklime is an excellent fertilizer for reducing the acidity of the soil and increasing its fertility.

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

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

Scope of slaked lime application in construction production and finishing works are wide enough. Cooking masonry, plaster mortars, lime-based silicate concrete makes them especially flexible and workable. In addition, it is used as a whitewash material, as well as in the production of bleach, in the leather and food industries.

Conditions for safe storage of hydrated lime

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

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

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

First aid for lime burns

If, nevertheless, the precautions for extinguishing did not help and the lime got on the skin, then the measures should be taken immediately. For burns quicklime it is necessary to free the victim from stained clothing, remove the substance from the affected area with a dry napkin or rag. Wash this place thoroughly big amount running water. Then treat with a 2% solution boric acid and apply a bandage of sterile material with synthomycin ointment or Vishnevsky balm. And immediately seek help from a medical facility.

Any soil actively used in agriculture begins to oxidize over time. The use of lime in this case helps to adjust the pH balance and increase soil fertility. Experts advise how and in what cases it is appropriate to use slaked and quicklime calcium oxide.

The use of lime at their summer cottage: technology

Lime is a good fertilizer for the site. But if misused, it will be useless. Handling the substance requires compliance with the following conditions:

1. Dosage accuracy. Exceeding the norm will cause an excessive shift in the balance towards alkalinity, which will also negatively affect crops. The amount of fertilizer applied is determined by the type of plant and the level of acidity of the soil.
2. Timeliness of introduction. Depending on the type of lime, it is added to the soil in spring or autumn.
3. Correct combination with other dressings and fertilizers. In particular, calcium oxide neutralizes the effect. It is not efficient to apply both fertilizers at the same time.

Attention! Lime is found in significant quantities in ground chalk, dolomite flour, open-hearth slag, lake lime deposits, cement dust, tuff, shale ash and other fertilizers.

Large farms for have a scientific and technical basis: special equipment or reagents (litmus paper). In the conditions of a personal plot or summer cottage, the pH level and feasibility can be determined based on external signs:

• in spring the land is violent and in short term cover powerful weeds;
• the surface of the soil is covered with a whitish coating;
• in the pits, lakes are formed with rusty water and an iridescent film on the surface.

Follow the instructions

Moss, wild mustard, cornflower, cinquefoil, daisy, sorrel, mint, plantain testify to the acidic state of the soil. About neutral - nettle, clover, quinoa. They grow on slightly alkaline soil berry bushes... But the higher this indicator, the fewer plants able to live in such a land.

Council. IN living conditions the acidity of the land on the site is easy to determine using a home experiment. Take a soil sample from the garden bed, pour a few drops of vinegar on it. If the soil hiss, then the reaction of acetic acid with alkali has taken place. The soil in this case can be either neutral or alkaline.

How is slaked lime used

The main direction is to improve soil fertility by influencing its structure and pH level. The use of lime is relevant when this parameter is 5.5 (sometimes 6.0) or lower. In addition, calcium oxide is used for:

• whitewashing trees;
• disinfection of the instrument;
• counteracting pests and their larvae;
• protecting brick and wood surfaces from mold.

To affect acidity, lime can simply be scattered on the beds in a dry state. After watering or rain, it will dissolve in the water and penetrate deeper. Detailing the rates of application of the substance for different types soils:

• pH not higher than 4.5: for clayey - 0.5 kg / sq. m, for sandy ones - 0.3 kg / sq. m;
• pH 4.6-5: clay - 0.3 kg / sq. m, sandy - 0.2 kg / sq. m;
• pH 5.1-6: only clayey - 0.2 kg / m2.

Attention! Lime rates are adjusted depending on the plant. Often these corrections are determined by the depth of the roots.

The disinfecting properties of lime are used for all kinds of work on the site. In particular, for a long time and successfully it has been used to produce spring whitewash trunk:

• for 1 bucket of water (8-10 l), dilute 2 kg of substance, 1.5 kg of clay and 300 g of copper sulfate. Alternatively, add 2.5 kg of lime, 100 g of wood glue, 500 g of copper sulfate to the same volume of liquid;

• stir thoroughly until creamy. In the second version of the solution, he must be allowed to brew;
• evenly thin layer Apply 3-4 mm to the barrel;
• after a while, repeat the application.

Council. Make sure that no streaks form on the barrel during operation. Whitewashing in some cases is allowed in the fall. Sometimes a little hellebore is added to the solution to protect the wood from rodents.

Application of quicklime

Such a substance is in pieces after heat treatment of limestone. It remains quicklime before contact with moisture and is suitable for weed control:

• first clear the area of \u200b\u200bunwanted plants;
• cover the beds with chopped herbicide.

Attention! In a similar way, you can add quicklime only twice a season at a dosage of 150 g / sq. m.

Experts recommend putting the substance into action immediately after purchase, since it is difficult to store it in a quick state. Lime can also be combined with other fertilizers. For example, it interacts well with ash. In exceptional cases, the dosage can be increased to 200 g / m2.

The correct introduction of quicklime is for digging to a depth of about 20 cm. If you are going to cut the dose, then you need to bury it not so deeply. You can also treat bushes or trees with this type of lime, armed with a wide brush. Just clean the trunk of rotting or old bark first. Lime has widespread use on the site, but you need to use it only with preliminary calculations.

How to add lime to the soil: video

Lime is a word of Greek origin and means "unquenchable". Belongs to those materials that have accompanied humanity since time immemorial. Its properties were discovered, probably by accident, and it found application in different areas through trial and error, so to speak, blindly. Consider the difference between slaked and quicklime.

People still did not know anything about calcium and its compounds with coal and oxygen, but they already realized that mountain limestone is good building material, and that by firing some rocks: limestone, chalk, dolomite and others, you can get a substance that has binding properties.

The ancient Chinese stabilized the soil with lime cement and strengthened the masonry with their Great Wall with a length of 2500 km, fertilizers used in agriculture were subsequently made on the basis of lime.

Quicklime

Currently, the quicklime obtained as a result of firing is not used as cement, due to its ability to absorb moisture and cause fungal mold on the walls, but in the construction industry it is in demand for the production of cinder concrete, paints, silicate bricks and plastering materials.

Quicklime (or calcium oxide with an admixture of other oxides, primarily magnesium oxide) is used to neutralize wastewater and flue gases, and to paint buildings. It is found in many foods as an emulsifier, binding substances that by their nature resist dissolution in each other, such as water and oil.

Slaked lime

Slaked (or hydrated) lime is formed as a result of interaction with water. Calcium oxide, of which quicklime is composed, is converted to calcium hydroxide, generating abundant heat in the form of steam.

Depending on the quenching method, we can get:

• lime water;
• suspension (milk of lime);
• dry calcium hydroxide (fluff).

Quenching method

Quicklime may differ in its qualities, so you should not rush into the process, and, possibly, increase the slaking time so that poorly quenched lime does not smoke in freshly laid plaster, which has gotten water.

Slowly extinguishing lime is best poured in several steps. A substance with a fast or medium quenching term is poured in until the steam stops to avoid burnout. Be careful not to let the boiling lime get on your hands and face. To avoid burns, protect yourself with long gloves, a respirator, and special goggles.

In general, the specific dosage of water in the process directly depends on the purpose of the future substance. General sense household use lime is to prevent unwanted activity of microorganisms.

Application

• Lime fertilizers since ancient times they have been used in agriculture to increase soil fertility and for liming, that is, to lower acidity. Solid lime fertilizers such as chalk, limestone, dolomite are ground or burned before being applied to the soil. Soft lime fertilizers work more efficiently and are applied to the soil without preprocessing - natural dolomite flour, lake lime (drywall), limestone tuff, marl. Lime fertilizers include rock processing products: quicklime burnt lime (ground or lumpy) and fluff (slaked lime), as well as industrial waste such as cement dust, white powder, blast-furnace slag, shale and peat ash, defecation mud, and others.
• Painting trees.Dissolve 1 kg of lime in 4 liters of water. After a couple of days, the solution is ready for use.
• Spraying plants.Add to lime water copper sulfate and two hours after preparation, they begin to spray.
• Whitewashing ceilings and walls.Here the proportion will be different: 1 kg of lime per 2 liters of water. Then add water until the desired consistency is obtained. Let the solution stand for a couple of days and strain it.
• Fluff (or dry calcium hydroxide) perfectly copes with the functions of protecting against moisture, disinfecting and improving the binding qualities of cement and concrete mortars.