Production of ceramic floor tiles

Introduction

Ceramic floor tiles belong to the group of ceramic stone products, the distinctive feature of which is high density and high resistance to abrasion forces. Thanks to these properties, ceramic tiles are widely used for flooring in various industrial, residential and socio-cultural buildings. Mainly these tiles are used in the following rooms:

1) where there are extremely high requirements for cleanliness (enterprises of the food industry, hospitals, schools, household premises, sanitary units of buildings, etc.);

2) where the floors are exposed to fats, acids, alkalis and other chemicals (chemical industry enterprises, laboratories, machine rooms of power plants, factories, etc.);

3) where the floors due to the large movement of people are subjected to severe abrasion (railway stations, metro stations, etc.);

4) where floors are a decorative element in the architectural design of premises (lobbies of public buildings, clubs, theaters, shops, etc.).

Sometimes ceramic tiles for floors, due to their significant chemical stability, are used as lining material for chemical equipment, acid reservoirs II T. P.

Ceramic floor tiles are among the relatively new building materials. Their production, based on the pressing of semi-dry masses at high pressure, arose in the second half of the XIX century. as a result of the development of mechanical engineering and the appearance of appropriate press equipment.

In recent years, the main technical and economic indicators of tile plants have improved significantly: labor productivity and cost of production. A large role in this, together with the commissioning of new capacities, was played by the work carried out at the plants to intensify and improve technological processes and mechanization of production, as well as the replacement of obsolete low-capacity equipment with new ones.

Selection and justification of production flow chart

1) mass preparation

High requirements for the physical and mechanical properties and appearance of floor tiles determine the need to pay great attention to the careful preparation of masses and use various methods of its preparation in the curtain of the bridge depending on the quality of the raw materials used. In the production of tiles, three methods of processing raw materials and preparing masses are changed: semi-dry, plastic and wet, or slip .

The semi-dry method is used in the manufacture of tiles from high-quality homogeneous clays that do not require additives. This method of preparing masses is common in factories where homogeneous Nikolaev, Nikiforov, Chachayar and some other clays are used for the production of tiles.

The process scheme of mass preparation according to this method involves crushing wet clay in a jet, drying in a drying drum to a humidity of 7-8% and storing dry clay for 12 15 hours. in hoppers where it is cooled to ambient temperature. Cooled clay is crushed on runners, after which it is sieved on sieve-burata and fed into silos of ground clay stock, and from there - into presses for forming tiles.

There is also another option for preparing masses in a semi-dry way, which gives better products. Initial materials are previously finely ground in mills till the residue on the sieve is 1600 otv/cm2 - not more than 5%, at least 70% must pass through the sieve 6400 otv/cm2. The humidity of the powders is 3-5 °/o. Crushed materials are loaded simultaneously into periodic mixers with rotating bowls and Lancaster-type blades.

Dry mixing is carried out for about 8 minutes, then, using spray nozzles, water is supplied to the mixer to moisten the mass to 8-9 °/o. After that, mixing takes place for another 5-6 minutes. The thus obtained humidified mixture is transferred to a granulator, where a powder suitable for pressing is obtained.

The use of dry mixers can achieve good mixing and distribution in the total weight of coloring additives, the amounts of which do not exceed 5%. labor productivity at dry method is twice as high as that at wet method.

The plastic method is used when using highly plastic hard-to-filter clays, to which melts and dyes are added in small amounts.

The plastic method of mass preparation is used in some factories using Nikiforov, Nikolaev and Chachayar clays for the production of tiles.

In this case, after crushing in the jet, the clay enters the continuous mixing runners, where it is mined in a plastic state. If dry clay enters the runners, it is adjusted to the state of working dough. In the process of washing, the clay acquires the required uniformity; various mineral impurities present in it are evenly distributed in the total mass, which leads to uniformity of color and eliminates contamination of the surface of the finished product with flies and smelts.

The washed mass is squeezed out in the form of cylinders through the runners' bottom into the receiving funnel of the belt press and the roller is moulded from it. The roller with a moisture content of 22-23% enters the tunnel dryers by car, where it is dried to 7-8%, and then subjected to milling and pressing. In some cases, in the absence of runners, they can be replaced by a brick-making unit consisting of blade, stirrers, rollers and a belt press. The advantage of this process scheme is its versatility. Along with the production of tiles from natural raw materials, masses with dyes can be obtained from it. It should be noted that the described clay mass processing scheme improves the appearance of the tiles compared to dry.

The wet method, usually used for the preparation of porcelain and faience, is also used for the production of ceramic flooring boards when using inhomogeneous and hard-to-sinter clays. This method is widely used in the production of floor tiles from multicomponent masses and in the introduction of significant amounts of melts and dyes into the mass composition.

The essence of the method is as follows. Coarsely ground clay materials are dissolved in water in vertical or horizontal bolts for 1.5 - 2 hour. Steam is fed into the bolts to accelerate the process. The obtained liquid mass is filtered through 2500 or 4900 otv/cm2 sieves to remove harmful impurities (pyrite, colchedane, coarse sand, limestone, etc.) and drained into a mixing pool. It is also supplied with dehydrating and coloring additives, as well as melts, which are previously ground in ball mills of wet milling. In some cases, clay materials and hard additives are co-milled in a ball mill. The duration of such milling is 10 - 12 hours.

The disadvantage of co-grinding materials is that harmful impurities easily released from clays after they are dissolved and cut through sieves, in this case, are ground and remain in the mass. However, as a result of fine grinding, the "harmful" influence of most impurities is significantly reduced.

In mixing pools equipped with propeller mixers, the liquid mass is thoroughly mixed and then membrane pumps supply it to filter presses, where it is dehydrated to residual humidity - 22-24%.

The filtration process, depending on the plasticity of the masses, lasts from 3 to 12 hour. at a pressure of up to 12 atm. To accelerate the process, the mass is heated with sharp steam to 50 °. From the filter presses, the mass in the form of cakes enters the carrot, where it is cut into small pieces, and then the drying drum for grinding, sifting and pressing. Sometimes the cakes are dried in tunnel dryers.

The peculiarity of the masses for making floor tiles is that the amount of introduced scavenging materials, melting dyes, usually ranges from 5 to 25%, which makes their equal distribution difficult. In this case, the wet process is of particular value since it ensures that any number of components are evenly distributed in the mixture and that the resulting mass is completely homogeneous. In addition, the wet method allows the use of inhomogeneous clays or those in which impurities are present and in the form of large inclusions, interlayers, etc.

The wet method allows the use of multicomponent masses, which greatly expands the raw material base. The mass composition of a large number of components allows you to adjust the individual properties of the finished products, reduce the tendency of tiles to deformation and

cracking during drying and firing.

Despite the advantages of the wet method, its widespread introduction into the production of floor tiles is associated with significant difficulties. To date, materials are processed at small-scale ball mills and periodically operating filter presses, the maintenance of which is very difficult. In addition, it requires large production areas.

For our company, we choose a semi-dry method of preparing raw materials, since it is the simplest, less labor-intensive than the rest, provides high labor productivity and, with clear compliance with technology, obtaining high-quality products. In addition, it is widely used in the use of homogeneous and high-quality sentinel clays, which are our raw materials.

Drying of tiles

In most cases, the pressed tiles are dried to a moisture content of not more than 2% prior to firing. Only in some plants where roasting is carried out in batch or gas-chamber furnaces, the tiles are loaded into capsules and sent to the roasting furnace, bypassing pre-drying. However, firing without pre-drying results in an increase in fracture failure, slows down the firing process and significantly reduces the productivity of the furnaces.

The drying process consists in removing moisture from the surface of the articles and moving it from the inner layers to the outer layers. The phenomenon of the transfer of moisture from the surface of the product to its washing coolant (air or flue gases) is called external diffusion. The rate of external diffusion depends on the temperature, humidity and speed of air movement. The movement of moisture from the depth of the article to its surface through the capillaries is called internal diffusion and its speed is determined by the moisture conductivity of the clay, temperature and humidity difference in the direction of movement of moisture.

Although semi-dry tiles contain a small amount of moisture and hardly shrink during drying, they must be dried carefully. The fact is that when pressing, some internal stresses appear in the tiles, which can also cause fracturing during an improperly organized drying mode. Safe drying occurs when the external and internal diffusion rates are approximately equal.

Very often, during the initial drying period of ceramic articles, they are warmed up in a humid environment. Moisture removal at this time almost does not occur from the products. When dry-compacted tiles are dried, such a method is unsuitable. The strength of such tiles depends largely on the amount of water present in the pores between the clay particles. The forces compressing the mass of the tile are proportional to the coefficient of surface tension of the water. When the crude is heated, the surface tension of the water decreases, respectively, the connectivity of the mass and the ability of the products to withstand the available stresses decrease. However, if the heating of the crude is accompanied by the extraction of moisture from its surface, then as water is removed, the strength of the product increases; under the influence of attraction forces, mass particles approach and meniscus diameters in capillaries decrease.

If the article is heated without sufficient water diversion, and especially with some condensation of moisture on its * surface, then its strength decreases, and the stresses present in it can lead to cracks.

The tiles should be dried in a humid environment at an elevated heat carrier temperature.

During artificial drying of tiles, flue gases and hot air are used as heat carrier, taken from tunnel furnaces and from cooling chambers of periodic or gas-chamber furnaces, as well as flue gases obtained during gas combustion in special sub-furnaces, and air heated in air calorifers.

Countercurrent tunnel dryers have become the most common in the production of tiles, in which tile cars move in the direction opposite to the direction of movement of the coolant.

Tiles can be dried on storeys of oven cars, on drying cars equipped with retractable or removable shelves, as well as in capsules. Carriage shelves are made from woven or stamped metal mesh, sometimes from sheet steel and fixed in the frame from angular steel. In our scheme, we use drip drying in a tunnel dryer.

If the tiles are dried in capsules, they are loaded directly near the presses, after which the capsules are installed on the cars and sent to the dryer. Drying in capsules is slower than on shelf wagons, but in this method, the pen-masonry of dried tiles from drying wagons in capsels falls away, which allows significantly reducing labor costs and avoiding mechanical damage to dried raw materials.

Tile Sorting

After firing, the tiles are sorted by colors, shades and other qualitative features. To sort tiles by size in accordance with the tolerances established by the standard, special sorting machines are used.

Machine performance - 60 tiles per minute. Here, using the lever system, its size is automatically measured. If the size of the tile corresponds to the calibration setting of the station, a special electromagnetic device is triggered, and the tile falls on a belt conveyor located under the chain conveyor and moving in a direction perpendicular to its movement. If the external dimensions of the tile are smaller than the calibration size to which the station is tuned, the electromagnetic device does not operate and the leads of the chain conveyor send the tile to the next sorting station.

Tiles rejected during sorting, having cracks, broken utes or ribs, smelting and other defects on a part of the face, are cut off on special machines. Thus, square tiles are rectangular and triangular (types 4, 5, 6, 7 and 8), and hexagonal tiles are tetrahedral and pentahedral (types 11, 12, 13 and 14).

After sorting, the tiles are stacked in packs of 20 pieces each. The packs are packed in paper and bandaged with twine.

керамические плитки.dwg