Dry chalk has a modulus of 3000 MPa (for loose chalk) to 10,000 MPa (for tight) and behaves as an elastic body. The angle of internal friction is chalk, clutch under hydrostatic compression reaches 700-800.
When moistened chalk strength starts to decrease already with a moisture content of 1-2% and at a humidity of 20-30% of the compressive strength is increased by 2-3 times, while the plastic properties appear. Manifestation of visco-plastic properties of natural chalk with increasing humidity leads to serious complications in the technology in their processing. From this comes the chalk sticking to cell vehicles (excavator bucket, box truck, feeder, conveyor belt). There is a sticking roller gear grinders. This leads in some cases to the chalk production failure from lower horizons flooded, although the quality of the lower Cretaceous horizon refers to quality Cretaceous.
Natural chalk has virtually no frost, after several freeze-thaw cycles, it is divided into separate pieces of 1-3 mm size. This phenomenon, in some cases, is a positive factor. For example, when using chalk as a soil ameliorant deoxidation it is not necessary to grind to a particle size – 0.25 mm (limestone powder), and can be applied to the soil before crushed chalk – 10 mm. When freezing and thawing annual tilling the soil pieces of chalk broken and his actions on neutralization of soil stored for a long time.
As already noted, it chalks mainly consists of two main parts – the carbonate portion soluble in hydrochloric and acetic acids (calcium carbonate, magnesium) and the carbonate portion (clay, marl, quartz sand, metal oxides, etc.) Are not soluble in these acids. The carbonate of the chalk on 98-99% consist of calcium carbonate. The small amount of magnesium carbonates, which form dispersed in the bulk of magnesia chalk crystals of calcite, dolomite and siderite.
The most acceptable is the classification of the content of carbonates and brands of chalk products.
Classification of Cretaceous carbonate content and brand products from it
Chemical characterization of chalk certain Russian fields is given in Table 4. Initially it was thought that the chalk is the rock mass, which in chemical composition and physical properties of the same throughout the field. However, during prolonged operation of the field, and especially in the transition of the Cretaceous enterprise to produce higher quality products Chalk it was found that in different parts (depths) as the chalk is different in chemical composition and physico-mechanical properties. In this regard, some deposits of chalk held geological and technological mapping, in which the designated areas of quality chalk.
Cretaceous deposits of the Belgorod region have a low content of insoluble residue and a high content of carbonates. Table 1.5 shows the chemical composition of the reserves and the largest deposits of the Belgorod region.
Calcium carbonate (chalk) in the modern world industry is a commonly used material. The development of the rubber industry and the electrical, plastics, paint, and others. Industries require increasing the output of high-quality fillers, which primarily relates chalk. Annual consumption of natural chalk in lump, crushed and powdered form in developed countries exceeds 150 million tons In the US and Canada is produced annually more than 7.5 mln. T. Ground chalk, and more than 15 million. M. In Europe.
Mel is widely available filler becomes essential for many industries. A distinctive feature of this natural material is the fact that it is easily extracted and processed at relatively low cost. Extraction and processing of chalk does not cause serious environmental violations. Cretaceous Reserves are practically unlimited in many European countries, countries of the former CIS and Russia.
Powerful Cretaceous zone extends across the entire European continent, including northern France, southern England, Poland, passes through Ukraine, Russia and shifted to Asia – Syria and the Libyan desert.
Stocks chalk evenly distributed in the territories: about 48 – 50% of the reserves of quality chalk with a high content of calcium and magnesium carbonate, a minimum content of harmful impurities are concentrated in Russia; about 32 – 33% in the Ukraine and a little over 12% in Belarus. There are small reserves of deposits in Kazakhstan, Lithuania and Georgia. General balance reserves of chalk in Russia is estimated at 3.3 billion. M. With unlimited forecasted stocks.
Belgorod region has almost unlimited resources forecast chalk. Total in the region explored 29 deposits of chalk with total reserves of 1,000 million. Tons. The largest deposits of chalk are Lebedinskoye, Stoilensk and Logovskoye. At the same time at the Lebedinsky and Stoilensk deposits account for 75% of proven reserves of chalk in Belgorod region. These two deposits are exploited for the extraction of iron ore, where chalk is overburden.
Every year, these deposits mined and exported to more than 15 million blades. M. Cretaceous, where he is irrevocably lost. Only a small part (about 5.0 mln. T.) Is used for the production of cement and produce ground chalk. In addition to the traditional consumers of chalk in recent years, new consumers, such as the pulp and paper industry, where instead of kaolin began to use highly dispersed chalk. Also chalk began to apply for deoxidation of acid soils, it was shown that its activity is 30% higher than ground limestone.
Mel carbonate rock (limestone kind) is almost entirely composed of calcite (91-98,5%). Externally, it is weakly cemented white, fine-grained, stain the rock, called “writer’s white chalk.” As part of the Cretaceous, there are three basic elements of form calcium composition as the biogenic and autogenous origin. Fossils usually compose most of the species (75%). In the main part they are represented by skeletal shells of planktonic algae-coccolithophorids and foraminifera (sometimes up to 40%). skeletal remains of size is 5-10 microns. Variable, but sometimes essential (10-90%) has a calcite powder with a particle size of 0.5-2 microns. Less development belongs to the larger (5-10% m.) Well-infinite crystal of calcite. There are sinks Inoceramus (sometimes up to 13 to 20%), the remains of crinoids, sea urchins, corals. In small amounts, usually up to 5, at least up to 10-12% present pelitomorphic no carbonate impurities, mainly terrigenous, at least autogenous origin: quartz, feldspar, clay minerals (glauconite, kaolinite, hydromica, montmorillonite), opal, chalcedony, pyrite and others. In some places there are nodules of flint.
The Cretaceous strata observed sustained development of large cracks – and vertical reservoir filled with chalk flour. On the surface crack network outputs greatly thickened. When impregnated with oil chalk samples they appear hidden zhilchatye structure in the form of intertwining the smallest cracks and traces of numerous passages of worms – mud-eaters.
Accumulation of white chalk writing are a particular feature of the Late Cretaceous epoch and found in almost all layers of the Upper Cretaceous, from Cenomanian to masstrahta and inclusive. Chalk-like limestone common in the Tertiary deposits in Paleozoic Cretaceous accumulation are not stored, transformed into a variety of limestone. Possibilities of industrial use of chalk is defined as the composition of its constituent components and their structural features, on which depends mainly on the physical and mechanical properties of rocks. Mel basically – rock monomineral biohimogennogo origin, composed of calcite – CaCO3.
As part of this mineral theoretically contains 56,03% CaO and 43.97% CO2. Calcite crystallizes in the trigonal system. Cleavage is perfect for the rhombohedron. Mohs hardness scale 3, density 2.72 g / m3. The main diagnostic priznak- “boiling” of drops of hydrochloric acid (5-10%), even more violent than the smaller grains of calcite. Colour colorless crystals, white. When heated in air at a temperature of calcite is dissociated ◦S 800-900.
The percentage content of chalk carbonates characterizes its quality determines the production and availability of Chalk technology products for various sectors of the economy. The study of the mineralogical composition and textural-structural components of many papers. The chemical composition of Cretaceous rocks are more uniform in the field and are different for the main constituent elements in a small range.
Carbonate chalk part consists of three groups of components: organic residues (plant, animal); calcium crystals with well-defined edges; powdered calcite.
Organic residues -. It is the main component of chalk and consists of plankton, coccolithophorids, foraminifera and other Kokkolitoforidy- unicellular calcareous algae, from which the body remained coccoliths and rabdolity. Latest in the chalk are very rare.
Coccoliths very different flat shapes and sizes, in the range of 2-5 microns, there are milestones in calcareous sediments of the Cretaceous period, the Dnieper-Donets Basin, mostly in the form of flat plates, saucers, convex discs, sometimes mutually connected by a bridge. Rabdolity have an elongated form: the form of tubes, rods, bars or rods sometimes with a disk or bell at the end. Their content is as high as 50%. Powdered calcite, one of the constituent parts of chalk and marl, its content in some Cretaceous rocks reaches 60%.
Non-carbonate of the most represented in the chalk quartz, feldspar, opal, chalcedony, and others. The content of non-carbonate rocks is small, but they significantly complicate the technology to produce high-quality chalk powder.
Natural chalk on the physical and structural features and composition are divided into 4 types, whose characteristics are given in Table 1.1.
Classification of Cretaceous rocks.
|name of species||Physical description||Content, %|
|Swept clean||Quite easily smudged soft fine-grained rock in white.||More 95||Less 5|
|Chalk-clay (or sand)||Incompetent, fine-grained rock white, with various shades of color.||90-95||5-10|
|Cretaceous marl||Incompetent, fine-grained rock, gray, yellow, greenish and a different color.||80-90||10-20|
|chalk-like limestone||Firmly cemented, obviously crystalline rock of white, gray or yellowish color.||90||10|
Large deposits of chalk.
The largest deposits of high-quality chalk are in the Belgorod region. Explored more than 29 chalk deposits with approved reserves of 1.0 billion tonnes Projected reserves of chalk is almost unlimited. The largest proven deposits of chalk and are Lebedinskoye Stoilensk where chalk is extracted as the overburden. At Lebedinsky deposit reserves have been approved under category A + B + C1 -. 388mln.t, and on Stoylenskaya category C1 575mln.t. According to the Institute “Tsentrogiproruda” mining chalk-marl rocks in these quarries for the period until 2005 will be about 25 million tonnes each year . Of the total produced in passing swept-margelnogo only 5.0 million tons of raw materials annually consumed Oskolsky cement plant, and the rest is exported to the blades and is lost forever.
Another large deposit of high-quality chalk is Shebekino, Belgorod region. Detailed exploration work was done in this field in 1951 and later in 1972. Balance reserves on 1.01.1997g. up 23.5 million tons that the production capacity of the plant for the processing of 350 tonnes of chalk Security is about 70 years.
Under the terms used in the plant technology for the processing of chalk productive stratum of chalk in the calculation of reserves is divided into an upper part of the “dry” natural chalk with humidity around 20% and the lower part of the “wet” chalk with humidity over 20%. stocks ratio of “dry” and “wet” chalk is 2.5. The upper horizon to the absolute level of 145-150m. Cretaceous strata characterized by containing up to 96-97,5% and the insoluble residue of 1.5-2.5%. The lower horizon to the absolute level of 109 m. Contains 97,5-99% and 0,7-1,9% of insoluble residue. Chalk on Shebekinsky field chemical composition refers to high-quality chalk and is widely used in various industries (paint, rubber, wire and cable, paper, etc.)
During 1956-1957gg. It was explored new deposits of chalk in Belgorod Oblast – Petropavlovsk, located at 3 km. from the station. Belomestny South-Eastern Railway. The quality is not inferior Cretaceous chalk Shebekinsky field and some indicators even surpasses it. Net power Cretaceous strata is 30 meters. Mel goes almost to the surface and power capping is only 2-3m.
High quality natural chalk provided to JSC “Melstrom” high-quality products for many industries (paint, rubber, plastic, etc.). On the basis of its own chalk it organized the production of paints, fillers and others. Materials.
One of the oldest deposits of chalk, operated for several decades, Belgorod is located practically in the city. The geological structure of the deposit is attended, besides the upper Cretaceous strata, tertiary and quaternary sediments. On the basis of field work Belgorod combine of building materials (BKSM), which produces lime, sand-lime brick and powdered chalk. According to their chemical properties chalk this field can be attributed to the quality, but it has a dense structure and the grinding without classification to obtain conditioned product is not possible.
Among other Belgorod region with high quality chalk explored deposits may be noted Volokonovsky, Chernyansky, Fironovskoe, Churaevskoe. For fields with reserves of less quality chalk Belgorod region include Valuiskikh, Zaslonovskoe, Znamenskoye, Cossack bumps and Korochansky. Mel these deposits contain relatively low levels (82-87%) and other impurities clogged. From this deep chalk without enrichment to obtain high-quality products is not possible. Without this enriching chalk it can be used for the production of lime and used in agriculture as chemicals for soil deoxidization.
The deposits of chalk Voronezh region are turonkonyakskomu age. Chalk has a high content (do98,5%) and low content of impurities of non-carbonate – less than 2% of silica enriched amphora, brought obviously Santonian of deposits. He chalks lies in close proximity to the surface and is covered with chalk or eluvium Quaternary sediments. A characteristic feature of the Cretaceous deposits of the Voronezh region is its water saturation. The moisture content in the chalk reaches 32%, which causes serious difficulties in its production and processing. The largest deposits of the Voronezh region include Kopanischenskoe, Buturlino, Kruprennikovskoe and Rossosh.
Cretaceous strata on Kopanischenskom field varies 16,5-85 m. (Average 35 m.). Represented overburden soil and topsoil is only 1.8-2.0 m. The vertical thickness chalk divided into two packs, the lower of which contains up to 98%, and the upper somewhat smaller (96-97,5%).
Buturlino field with extremely homogeneous white chalk turunskogo tier with capacity from 19.5 to 41m. stripping capacity reaches 9.5 m. and a vegetable layer, marl, sandstone and sand-clay formations. Contents of calcium and magnesium carbonates reaches 99.3%, with a relatively small amount of non-carbonate components.
The use of chalk
Chalk natural processed in accordance with the requirements of the different degrees of purity, a necessary raw material for various industries.
Chalk production is located in the Belgorod region, because there are large reserves of this rock. In this regard, the regional center and its name-Belgorod.
The use in the manufacture of chalk as a filler can significantly reduce the cost of the finished product to improve its quality. Because, despite the low cost, chalk is an attractive combination of high whiteness, brightness, low hardness, price and practical absence of reactive impurities.
Chalk as a filler used in the production of paints and emulsions. It marks:
RC, M-3 (MNBK-3), M-5, M-90 MTD-1, BPD-2, MSK-2, M-10, M-20, M-40, M-60 Superfine, STM -10, STM-20, STM-40, Mel fine synthetic brands “K” and “C”, Chalk, precipitated.
In the production of construction and finishing materials, dry mixes, fillings. It marks: RC, BL-50, M-40, STM-10, STM-20, STM-40, 1-MTD, MTD-2, 1-MMC, MMC-2, Mel Syromolotov, MD-2, MM 2.
Fertilizers feed. MMZHP, FILLER, MD-2, MM-2, MC-1, Mel Syromolotov, Ground limestone for production of feed and feeding of animals and birds (fr.1-4 mm)
Rubber and plastic products: M-5, M-90, M-90T, M-40, the BPD-1, MTD-2, MSK-1, MMS2, MMOR.
Use of chalk in the paper industry.
In the paper industry as a filler and brightener used kaolin deposits which are located in Ukraine and Kazakhstan. In connection with the collapse of the USSR, these deposits remained outside Russia. Quality delivered kaolin clays dramatically deteriorated with an increase in their prices. It has set the paper industry Russia the question of replacing kaolin clays, calcium carbonate – chalk. This is supported by the fact that over the last decade and paper industry in Western Europe has mastered the use of chalk, and the amount of consumption is steadily increasing.
Use of chalk as a filler and pigment in the manufacture of paper and cardboard can be provided to meet the requirements of this kind of raw material, especially concerning the optical properties and size distribution.
The level of brightness of natural calcium carbonate to be used abroad as a pigment, is 90 – 95% (by Elrefo). For paper filler used natural calcium carbonate with white 85 – 95% and above. In the paper industry is used ground natural carbonate calcium high degree of dispersion. The average size of the particles of calcium carbonate (pigment) in foreign data is 0.7 – 1.0 micron particle content:
less than 2 microns – 90%;
less than 1 micron – 60%;
less than 10 microns – 35%.
For the same foreign data quality paper filler has an average particle size of 1.5 – 2.0 microns. When the content of the particles less than 2 microns – 40%, and particles of 10 microns – 95%. Some varieties of natural calcium carbonate for paper filling have an average particle size of 5.0 – 7.0 micron, but does not contain a fraction of more than 20 microns and 10 microns particle content is 95 – 99%.
High dispersion of ground calcium carbonate has a positive effect on smoothness, porosity, optical and printing properties of paper, the product is reduced abrasiveness. This is an important point, since the natural calcium carbonate abrasive greatly exceeds kaolin abrasive, resulting in premature wear of expensive components and parts papermaking equipment. Specifications on the chalk for the paper industry are given in the table.
Technical requirements on crushed chalk for the paper industry.
|№п/п||The name of indicators||chalk Mark||test|
|МБД – 83||МБД – 81|
|1||Mass fraction of calcium carbonate and magnesium carbonate in terms of calcium carbonate,%, not less||97,0||96,0||ГОСТ 21138.5|
|2||The whiteness (reflectance),%, not less||83,0||81,0||ГОСТ 16620|
|3||The residue on the sieve of 20 mm,% not more||0,5||0,5||ГОСТ 20082|
|4||Balance,% max sieve №№ 0,2,%, not bolee№ 0.09% max||0,20,4||0,30,6||ГОСТ 19286|
|5||Mass fraction of water-soluble substances,%, no more||0,2||2,5||ГОСТ 211381|
|6||Insoluble residue in hydrochloric acid,%, no more than||2,0||2,5||ГОСТ 211381|
|7||Moisture content,%, not more||10||20||ГОСТ 19219|
Indicators of the quality of paper samples for offset printing.
|№ п/п||The name of indicators||Марка мела и изготовитель|
|СП «Руслайм»МНБК – 3||ОАО «Шебекинский меловой завод»МПНБ – 2||Саженское месторождение||Чураевское месторождение|
|1||Paper Weight 1m2, g||70||70||70||70|
|2||Breaking length, m||2800||2750||2700||2800|
|3||Fracture strength (number of double folds)|
The use of chalk in the livestock industry
A significant part of chalk used in the livestock industry to feed with / farm animals and the preparation of animal feed. Special guests at the stern there is no chalk. Ministry of Agriculture in 1970 temporary technical conditions (VTU), which act so far been approved. The table shows the technical requirements for feed chalk.
Specifications on the stern chalk.
|Specifications for the Cretaceous||consumption Area|
|Mineral feeding animals and birds||feed production|
|Moisture,%, no more||10,0||10,0|
|Thinness: the residue on the sieve with a mesh of 2 mm,% by weight (no more than)||20,0||20,0|
|The content of calcium carbonate (CaCO3),%, not less than||85,0||85,0|
|The content of insoluble residue in hydrochloric acid,%, no more than||5,0||5,0|
|The content of poisonous impurities fluoride,%, no more than arsenic,%, no more heavy metals (lead, barium)% max||0,20,0150,008||0,20,0150,008|
|The impurity content of magnesium carbonate, iron oxide, aluminum oxide,%, no more||5,0||5,0|
|The content of metallic impurities up to 2 mm inclusive, mg / kg, more||100||100|
Using chalk rubber industry
As the amount of filler used in the rubber industry, chalk ranked first. This is due, on the one hand, purely economic considerations – are relatively large chalk value and opportunity without harm to rubber compounds to enter it in large numbers, on the other hand – the technical feasibility as chalk facilitates the process of manufacturing rubber products: accelerates the rubber vulcanization process, and It gives it a smooth surface. Mel is widely used also for the production of porous and spongy rubber kozhazameniteley et al. Product. Mel used by the rubber industry, must comply with the requirements of GOST 1208-66 and TU 21-01-143-68. These standards apply respectively natural chalk enriched representing a powdered product that is obtained from natural chalk by wet or dry processing, and chalk Separated being powdered product obtained from natural chalk by its crushing, drying, grinding and classifying by size a air separators. Technical requirements for the rubber industry are given in the table.
Specifications on the chalk for the rubber industry.
|The name of indicators||Norm|
|Calcium carbonate and magnesium carbonate +,%, not less||98,5|
|Sesquioxide (R2O3),%, not more||0,4|
|Insoluble residues in hydrochloric acid,%, no more than||1,3|
|Manganese,%, not more||0,01|
|Copper,%, no more||0,001|
|iron oxide (Fe2O3),%, no more than||0,15|
|Free alkali based on CaOH,%, no more than||0,01|
|Water-soluble substances,%, no more than||0,1|
|SO4 ions and Cl’ in the aqueous extract,%, not more||0,05|
|Iron extracted magnet,%, not more||0,02|
|Sand,%, no more||0,015|
|Moisture,%, no more||0,15|
|The reflection coefficient,%, not less||90,0|
|The residue on the sieve: 02%, no more than 014%, no more than 045%, no more||000,5|
Using the chalk in the glass industry.
Chalk among other carbonate rocks in the glass industry is used as a component of glass batch cooking introduced into the blend in powder form in quantities up to 30% of the final volume. Mel gives the thermal resistance of the glass, mechanical strength, resistance to chemicals and weathering. Glassworks Practice shows that the most harmful impurity in glass carbonate (chalk) are iron oxides which give the glass an undesirable green color and reduce its translucency. Harmful impurities are also elements such as TiO2, Mh3O4 and Cr2O3, however, these compounds in the chalk are extremely rare. Impurities MgO, Al2O3 are not harmful, but their number should be as constant as possible, which ensures the stability of the charge and the finished product. Mel used in the charge for the cooking window and technical glass, must meet the following requirements: CaO content should not be less than 53%; Fe2O3 content-not more than 0.1%.
In addition, in the glass industry for the production of chalk used soda. CaCO3 content (in the amount of from 1.2 MgCO3) to crushed chalk established within the 90-97% for commercial ground chalk 96-98%.
Use in the building industry chalk
One of the major consumers of chalk is the construction industry, where chalk is used for the production of cement, lime, various plastering and painting materials. Pobelochnyh chalk used for work in a soluble form of ground chalk paste and powder. to the Cretaceous requirements for production pobelochnyh works shown in the table.
to the Cretaceous requirements for the production of whitewash.
(ГОСТ 12085 – 88)
|The name of indicators||Norm|
|Calcium carbonate + magnesium carbonate,%, not less||98,2|
|Sesquioxide (R2O3),%, not more||0,4|
|The insoluble residue in hydrochloric acid,%, no more than||1,3|
|Manganese,%, not more||0,15|
|Copper,%, no more||0,001|
|iron oxide (Fe2O3),%, no more than||0,15|
|Free alkali as CaO,%, no more than||0,02|
|The water-soluble substance,%, no more||0,1|
|SO4 ions and Cl’ in the aqueous extract,%, not more||0,04|
|Iron extracted magnet,% not more||0,02|
|Sand,%, no more||0,02|
|Moisture,%, no more||0,2|
|The reflection coefficient,%, not less||90,0|
|The residue on the sieve size: 0.2%, not more than 0.14%, not more than 0.045%, not more than||001,0|
To use the chalk in the cement industry are no more restrictions in view of constant composition of chalk. Cement raw materials is regulated limit content: Magnesium oxide (not greater than 4%), sulfur trioxide (1.3%), the amount of alkali metal oxide, 1% of phosphoric anhydride and not more than 0.4% .Prevyshenie these parameters can be expected only by phosphoric anhydride .
chalk quality for production of building air mixture is regulated by the content of CaCO3, which should be at least 95%, MgCO3 and not more than 2.5%. Clay impurities in chalk should not be higher than 2% (fat lime). At a higher content of the latest news is a more skinny. For the production of the construction of hydraulic lime with clay content of more than 8% of impurities, suitable “loamy” chalk. According to lumpiness isolated group rubble mm with large pieces of the size 400-200, an average of 200 to 80, and the fine from 80 to 15. Trivia below the permissible limit should not contain more than 30%.
With the analysis of chalk market you can meet at the Academy of Industrial Markets Conjuncture report “Market of chalk in Russia.”