The historical and economic situation. Raw material deposits

Economically attractive destination for doing business is the construction, especially construction materials. This industry is characterized by high profitability and return. Among other construction materials, cement production takes perhaps a central place - this is one of the major materials used in construction.

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.

Production and processing of limestone

Limestone is mainly mined in quarries, open way. Limestone, clay or sand without impurities rare. Limestone is carried out mainly by drilling and blasting, sometimes is mined using rippers and buldozerov.Dlya that are well diameter 100... 300 mm, arranged in one or several rows in a staggered manner, laying explosives and carry out a massive explosion. Sinking wells are using the rope-drum machines, pneumatic or percussion drill stankov.V Recently, use powerful, cone drills with capacity of up to 30 m / h.Pogruzku rock by excavators with bucket capacity of up to 8 m3 or pogruzchikami.Vzorvannnaya ore is transported to the crushing plant which can be operated in one or two stages. For loading blasted rock using excavators or loaders. If necessary, crushed rock released into the washing drums of clay and sand contamination. Limestone deposits only contains some minor amount of impurities, so that cleaning may be needed. Then blown and washed material is classified by size into separate factions firing in the kiln and for sale.

From limestone also produce ground limestone, which produces fine grinding with simultaneous drying, for example, used high-speed hammer mills.

Blasted ore dump transported to the crushing plant, which can operate single or multistage.

lime burning

The aim is to convert lime calcining calcium carbonate to calcium oxide. Theoretically it requires 3154 kJ / kg CaO (at 20 ° C) for this purpose. At 900 ° C CO2 partial pressure reaches 1 bar. Almost lime calcination temperature is much higher. A number of users (for example, steel mills), are willing to except a low residual content of CO 2 is also good reactivity, which can be obtained only in certain types of furnaces. For this purpose, along with the quality of the calcined product (chemical composition, crystal structure), first acts as a sintering temperature, which define the pore structure calcine. Later in detail describes the most important reactions and processes for lime burning.

Burning lime

Lime burning process is the decomposition of calcium carbonate chemically produced at a temperature of 900 to 1100 degrees to form carbon dioxide and lime-kipelki.Obzhig lime produced in a variety of kilns - oven-pit-heap furnace, the furnace floor, and a ring furnace blast furnaces of various designs. These ovens, like an oven and stove-pit-heap of the most primitive and used in large quantities prior to firing izvesti.Ustroystvo furnace pits following: prepared a round hole with a diameter of 3 to 5 meters, with a depth of at least 2 meters, then it is laid out a set of large pieces stone, put them on top of the limestone is calcined to the whole pit was zapolnena.Snaruzhi limestone coated with clay, thus it is necessary to leave a few holes to make it go where flue gases and carbon dioxide. Combustion of fuel occurs in ochelke that formed the vault and walls yamy.Vo the combustion of coal or peat ochelke equip grate and podduvalo.Pech heap has a different device: made of limestone, which will be fired, spread wall to a height of half a meter. Thus it should be a gap width of one meter, and from that point in the direction from the center are laid out two more walls having a length half metra.Rasstoyaniem between these walls and to a half meters. Laid wall overlap calcining stone in the form of arches, forming this ochelok for later burning topliva.Pod ochelka center in the roof need to leave a hole through it to pass the flue gases. On top of the arches fit scalding stone in the form of a circular heap, having a diameter of 4-6 meters and a height of 4-5 meters, all exterior daubed glinoy.Napolnye oven arranged on a more complex principle. The firm ground sees a square pit with dimensions of sides of 4.5 meters and a depth of 2 meters. On its bottom laid ochelkovye channels made of stone, having a height of about 0.6 meters, they will be burning fieldstone topliva.Sverhu channels overlap, and the limestone is calcined fit across the width of the furnace resulting layers. Such furnaces have a width up to 4 meters and a length of 6 to 13 meters and a height of 3.5 metra.V primitive furnaces above difficult to achieve uniform lime burning process. The most sophisticated kilns are limestone mines pechi.Ih daily output ranges from two to fifty tons, depending on the size of the furnace itself.