The raw materials of cement industry

Raw materials for cement production are mainly clay and carbonate rocks, and other natural raw materials and certain types of industrial waste, toxins, etc.

Carbonate rocks - it is limestone, limestone-coquina, chalk, marly limestone, marl, metamorphic or sedimentary rocks of dolomite, carbonate-clay and limestone composition. The quality and value of such species as raw materials for the creation of cement is determined by their structure and physical properties. Species worse crystal structure, compared with the amorphous structure rocks interact with other elements of the mixture during firing.

• Mel - easily rubs soft sedimentary rock, limestone kind of anointing. It is easily crushed and is a popular material for the creation of cements.

• Marl - a sedimentary rock, the transition from limestone to clay. It can be a solid or a loose structure, and varying density according to the humidity percentage of clay impurities. Building solutions based on marl are actively used in the installation of stoves and fireplaces, etc.

• limestone for cement production are preferred porous and marl species with a small threshold compressive strength and without the content of silicon inclusions.

• From argillaceous rocks used in the production of cement: loam, clay, loess, clay slate and loess.

Clay, mountain sedimentary rocks are composed of various kinds of minerals, when moistened acquire plasticity and swell. The dry cement production method of communication ability and plasticity of clay allows the granulation and briquetting flour. Called loam clay, which contains high amounts of silt and sand particles.

Shale is a dense and solid rocks that can easily flake on a small plate thickness. Regarding the clay shales have a constant composition and less humidity.

Lessa called fine-grained rock, loose and porous, consisting of the finest particles of clay material, feldspar, quartz and other silicates. Loess is not characterized by a high plasticity. Loess loam - a material with properties which is transitional between loam and loess.

Also the basic raw material in the production of various kinds are widely used in the cement additives corrective allowing to change some properties of the final product. It can be aluminous, siliceous, clay-containing additives, and fluorspar as a mineralizer (sodium fluorosilicate, gypsum, apatite, phosphogypsum, fluorite)

It should be noted that the raw material composition, both in the dry and in the wet cement production process may vary depending on the location of the cement plant, the availability of a raw material, the capabilities of the equipment, the demand for certain types of products in this region, and many others.

Limestone and clay

Limestone should meet the following requirements:

a) the content of calcium oxide (CaO) calculating the amount of calcium carbonate (CaCO3), the contents of which should be less than 75%;

b) the clay content is determined methylene solution in accordance with EN 933-9 and should not exceed 1.20 g / 100 g To test lime must be ground to a fineness of about 5,000 cm2 / g. Specific surface area is determined in accordance with EN 196-6.

c) the total organic carbon (TOC) for the EN 13639 test methods shall comply with one of the following criteria:

- LL: not exceed the mass fraction of 0.20%;

- L: must not exceed the mass fraction of 0.50%.

 

Izvestnyak- widespread monomineral rock composed of calcite; it can be easily determined by a violent reaction with hydrochloric acid. Due to the wide distribution, ease of handling and chemical properties of limestone is mined and used to a greater extent than other species, second only to the sand and gravel deposits. The limestones are of different colors, including black, but the most common breed of white, gray or have a brownish tint. The bulk density of 2.2-2.7. This soft rock, easy to scratch the knife blade. Limestone effervesce rapidly by reaction with a dilute acid. In accordance with its sedimentary origin has a layered structure. Net Limestone consists of calcite (rarely with a low content of other forms of calcium carbonate - aragonite). Present and impurities. The limestones are found in almost all continents except Australia. They were formed in different geological epochs. Seam Thickness varies from a few centimeters to hundreds of meters. The limestones are common in the United States and take up 75% of the country. In Russia, the limestone common in the central regions of the European part of, as well as common in the Caucasus, the Urals and Siberia. Limestone (in the broadest sense) have an extremely diverse range of applications. They are used in the form of lump limestone, crushed stone, piece (Saw, wall) and quarry stone, facing slabs, mineral crumbs, crushed sand, mineral powder, mineral wool, limestone powder. The main consumers - the cement industry (limestone, chalk, marl), construction (obtaining building lime, concrete, plaster, mortar, masonry walls and foundations; decorative-facing work, etc.), road and rail construction, rock placement for coastal protection and waterworks, metallurgy (limestone and dolomite - fluxes and refractories processing nepheline ore into alumina, cement and soda), agriculture (limestone flour in farming practices and animal husbandry), oil and coke, food (especially sugar), pulp and Paper, glass (limestone, chalk, dolomite), leather (limestone), rubber, cable, paint and varnish industry (chalk as a filler). Other areas of application - polishing products, non-ferrous metals and nacre (limestone), electric welding (chalk to cover the electrodes), writing chalk (chalk), insulation of building structures and technological equipment (mineral wool), etc.

Many cement plants use raw mixture of limestone and clay (or shale). Typically, these plants are being built in most limestone quarries and near the clay or shale deposits.

It should be borne in mind that not every limestone suitable for the production of portland cement. limestone deposits containing large admixtures MgC03, usually can not be used. Similarly, the presence of pyrite and gypsum inclusion can increase the content of sulfate in the cement, which is undesirable. There are deposits of chalk, littered with plenty of flint pebbles, in connection with which it is difficult to use for the production of cement.

In cases where the feed mixture to produce limestone is used with a high content of lime, it is necessary to mix with the clay-containing materials such chemical composition that could provide a given composition preparation of clinker.

 

Clay - sedimentary rock composed mainly of clay minerals; with water to form dough, dries able to maintain shape given to it, and get the hardness of stone after firing. Clay consists of one or more of kaolinite mineralovgruppy (derived from the area in China Kaolin), montmorillonite or other layered aluminosilicates (clay minerals), but may contain both carbonate and sand particles. Usually, rock-forming mineral is kaolinite clay, composition: 47% (by weight) of silicon oxide (IV) (SiO2), 39% of aluminum oxide (Al2O3) and 14% water (H2O).

Al2O3 and SiO2 - make up a large part of the chemical composition of yellow clay, brown, blue, green, purple and even black colors. Painting is caused by impurities of ions - chromophores, mainly iron valence of 3 (red, yellow) or 2 (green, bluish). The properties of clay: plasticity, fire and air shrinkage, fire resistance, caking, color ceramic crock, viscosity, shrinkage, porosity, swelling, dispersion. Clay is the most stable waterproofing - vodonepropuskaemost is one of its qualities. Due to this, the clay soil - the most stable type of soil developed on vacant lots and wasteland. Development of a plant root system clay deposits possible. Vodonepropuskaemost clay useful to preserve the quality of groundwater - a significant part of the quality of artesian springs lies between the clay layers.

Minerals contained in clays

• kaolinite (Al2O3 · 2SiO2 · 2H2O)

• andalusite, kyanite and sillimanite (Al2O3 · SiO2)

• Halloysite (Al2O3 · SiO2 · H2O)

• gibbsite (Al2O3 · 3H2O)

• Diaspora (Al2O3 · H2O)

• Aluminium oxide (Al2O3)

 

• Monotermit (0,2 [K2MgCa] 0 · Al2O3 · 2SiO2 · 1,5H2O)

• Montmorillonite (MgO · Al2O3 · 3SiO2 · 1,5H2O)

• Muscovite (K2O · Al2O3 · 6SiO2 · 2H2O)

• Cover (Al2O3 · SiO2 · 2H2O)

• Pyrophyllite (Al2O3 · 4SiO2 · H2O)

 

Proiskhozhdenie- main source of argillaceous rocks is feldspar, at which decay under the influence of atmospheric phenomena produced kaolinite and other hydrates of aluminum silicates. Some sedimentary clay formed in the process of local accumulation mentioned minerals, but most of them are deposits of water flows, dropped to the bottom of lakes and seas.

Clay - is a secondary product of the earth's crust, sedimentary rock, formed as a result of destruction of rocks during weathering.

application

• Pottery production,

• Technical ceramics,

• Production tsementa- for manufacturing cement is first extracted from limestone and clay quarries. Limestone (approximately 75% of the amount) was crushed and thoroughly mixed with the clay (about 25% of the mixture). The dosage of the raw materials is an extremely difficult process, as the lime content must meet the specified number of up to 0.1%.

These relationships are defined in the literature concepts of "lime", "flinty" and "aluminous" modules. Since the chemical composition of the starting raw materials is constantly fluctuating due depending on the geological origin, it is easy to understand how difficult it is to maintain the constancy of the modules. In modern cement plants is well established control with a computer in combination with the automatic analysis methods.

A legitimate slurry prepared according to the chosen technology (dry or wet method) is introduced into the rotary kiln (up to 200 m long and up to 2.7 m in diameter) and calcined at a temperature of about 1450 ° C - the so-called sintering temperature. At this temperature the starting material is melted (sintered), it leaves the furnace at a more or less large lumps of clinker (sometimes called Portland cement clinker). Firing occurs.

The clinker material formed by these reactions. Upon exiting the rotary kiln falls into the clinker cooler, where it is quenching from 1300 to 130 ° C. After cooling, the clinker is ground with a small amount of gypsum (6% maximum). cement grain size ranges from 1 to 100 microns. It is better to illustrate the concept of "specific surface area". If we sum the surface area of ​​the grains in one gram of cement, the cement grinding depending on the thickness are obtained value from 2000 to 5000 cm² (0.2-0.5 m²). The majority of the cement in special containers transported by road or rail. All overload produced pneumatically. A smaller part of the cement production is delivered in moisture- and razryvostoykih paper bags. Stored cement at construction sites mainly in silos.

• Application in medicine and cosmetology

The most common in nature are: red clay, white clay (kaolin), clay sandstone. Grades clay - for the production of porcelain, earthenware and refractory products - kaolin.