Automation of ceramic floor tiles firing

Introduction

Construction ceramics occupies one of the leading places in construction, largely determining the overall level of construction production.

Ceramics are products and materials with stone-like properties obtained during the processing of mineral raw materials and their sintering at high temperatures. The name of ceramics comes from the Greek words "kermaike" - pottery and "kermos" - clay.

Ceramic materials are some of the most ancient artificial materials created by man. The production of construction ceramics mainly began to develop in China, the countries of the East and Central Asia.

Durability, high artistic and decorative qualities, fire resistance, waterproof, complete lack of toxicity, acid resistance determined the widespread distribution of ceramic tiles. Ceramic tiles for floors are used in industry, housing, household, public buildings with high frequency requirements with possible effects of fats and other chemical reagents, with heavy movement, as well as in rooms where the material for floors serves as a decorative element in architectural design. The material of these tiles has low porosity, high density, fire resistance, has high resistance to abrading forces.

The production of ceramic for floors includes a number of operations. Roasting is the most important operation in the production of tiles and ceramics in general.

furnaces and equipment in which heat treatment is carried out, determine the quality of the product and the degree of mastery of artistic and technical design.

The furnace in which the roasting is carried out is on the one hand a process equipment, on the other hand a thermodynamic system.

Skilled mastery of the roasting process of ceramic products is one way to reduce heat consumption, and in addition to obtaining better products.

Feasibility Study for Process Automation

The technological regulation provides for the production of floor tiles by semi-dry pressing. The main feature of semi-dry pressing of ceramic products is their formation from powders by pressing at a significant specific pressure of 1540 MPa.

The firing process is an essential step in the manufacture of ceramics. The success of this operation depends on the results of all work. Automation of the firing furnace leads to an improvement in the quality of tiles and a decrease in scrap.

Different types of furnaces are used to burn ceramics. In the burning of tiles, tunnel furnaces are mainly used.

The final evaluation of the furnace is the quality of the final product. The quality of the product depends on the maintenance of a given law of a given burning temperature curve.

The maintenance of a given temperature curve depends on the level of automation and the quality of regulation.

The relatively high heat consumption for roasting is determined by the low efficiency of the furnaces, and to reduce heat loss to the environment, recirculation of exhaust gases, etc., should be used.

Cost-effectiveness is the measurement of automation results and costs.

Technically competent automation of production releases a certain number of workers, dramatically increases production, significantly reduces its cost and improves quality. It is necessary to introduce only those technologies that have a great economic effect.

Automation of tunnel furnaces avoids a number of disadvantages and gives a significant economic effect. In most cases, automation costs do not exceed a few percent of the cost of production.

1.1 General characteristic of the production process of ceramic floor tiles by semi-dry pressing

The main technological decisions were made on the basis of the current technological process for the production of ceramic tiles for floors adopted by the Association for the Production of Building Materials and Household Appliances. The process of making tiles by semi-dry pressing involves the following groups of operations: quarrying, preparation of powder, pressing, drying and firing of the product.

Quarrying works are performed according to mining and operational conditions of clay location. Raw materials are unloaded from the wagons and fed to the clay raw material warehouse using a belt conveyor (item 1) (item 12).

Raw materials are stored in an equipped indoor warehouse. The stock of clay raw materials is maintained in the warehouse for five months.

Bulk materials (feldspar, quartz sand coming in wagons are unloaded at the materials warehouse.

The warehouses are provided with intermediate silos (3), under which plate feeders (4) are installed, which supply materials for crushing to the crusher (5) and roll crusher (13), respectively.

The following materials are used for the intended finished performance of ceramic tiles:

- clay of Veselovskoye deposit TU 2125GA388;

- clay of Stoilensky and Lebedinskoye deposit;

- Brosyakovsky and Glukhovetsky stones of wet enrichment GOST 2128882;

- dry dressing stones GOST 218575;

- quartz sand;

- nepheline silicate alumina concentrate TU 1131215065, TU 6125480;

- dolomitic materials;

sodium tripolyphosphate;

- glass drills;

- saltpeter;

- sodium nitrate;

- natural graying;

- selenium;

- chromium oxide;

- cobalt oxide;

- calcium chloride;

- calcium borate;

- zirconium concentrate;

- sodium silicofluorous;

- titanium dioxide;

- lead sucker;

- boric acid;

- technical drill;

- artificial technical cryolite;

- potash - potassium carbon dioxide;

- strontium carbonate;

- barium carbon dioxide of the highest grade.

Ground clay and loose materials are supplied to the service hoppers by the system of belt conveyors (1) and elevators (6) (3). Clays with a moisture content of more than 10% are fed to a rotary dryer (pos.16) for drying to 68%.

Materials are fed to the mill with rotating rings (pos.7). After drying and crushing, the materials are fed into intermediate silos (pos.18).

Clinker preparation is carried out by joint grinding of clay and other materials in a ball mill (item 19). The cycle was ground for 6-8 hours, depending on the fineness of the grinding required. Silicon balls (cylinders) and natural silicon pebbles are used as grinding bodies.

Ratio of material: grinding bodies: water - 1.0: 5.0: 0.86.

After the grinding cycle, the mills are automatically stopped. The finished clinker is drained by gravity into the storage pool (pos. 20) equipped with a propeller stirrer.

Clinker settings.

Humidity 39 ± 5%

The rest on the screen is 0.063 not more than 4-6%

Density 1.591.61 g/cm3

Fluidity after 30 seconds of protrusion not more than 20 seconds

Clinker stock should be 2.7 days (233.3 tons)

Finished clinker with membrane pump (pos. 22) is pumped to the supply pools (item 21) of the press powder preparation compartment.

The press powder is obtained by dewatering the clinker in a tower spray dryer (item 23).

The clinker is supplied by a plunger pump to the tower dryer via a pneumatic line under a pressure of 23 ± 0.2 bar.

The clinker is sprayed through nozzles (from 8 to 16 pieces).

Nozzle: nozzle diameter 1.8mm; the height of the snail is 8mm and 4mm.

The spray clinker jet in the drying tower is subjected to a swirling flow of hot air from a direct combustion generator at an air temperature of 450550 ° C.

Exhaust gas temperature shall be from 100120С. Discharge in the tower 2535 mm water column.

Press powder from dryer by means of belt conveyor (1) through vibrating screw (4) equipped with mesh with diameter of holes 1, 25mm, to intake funnel of elevator (6) and supplied to silos of intermediate storage (pos. 18) reversing belt conveyor (item 1).

Hold of press powder in intermediate storage silos must be not less than 48 hours. The moisture content of the press powder should be 5.5-3.3.

The press powder is fed to the press hoppers. The powder reserve on should be for 3.3 days (264 tons).

The tiles are pressed on Hydra 1400 press machines (pos. 25). Tile pressing pressure shall correspond to:

- primary 80-120 t

- secondary 1200-1300t

After pressing, the tile passes the turntable, then the tile enters the vertical dryer (pos. 26) and by transport comes for glazing (pos. 27).

The temperature at the upper point dried from 8095 ° C. The temperature of the tiles at the outlet of the dryer is not more than 65 ° C. Humidity 0.8%. Glaze and angob are prepared in a ball mill (pos.19) by joint grinding of clay materials and electrolytes (1.0: 1.5: 0.8). Balance on

screen 0063 0.4 - 0.5%. The finished glaze is pumped to a vessel with a propeller stirrer (item 32) through a screen and a separator for its intermediate storage.

Glazing is carried out by disk spraying and pulverization.

To better adhere the glaze to the biscuit and reduce generations, the tile is moistened by spraying before glazing.

Glaze consumption per tile 320x320mm 6060g.

Angob is applied to the mounting side. Decoration of tiles is carried out by method of aerograph spraying of colored suspension on the main layer.

The glazed tiles are loaded into boxes that are fed to the intermediate warehouse (item 29). The number of tiles is more than 60m2. The warehouse is designed for 5400m2.

After glazing, the tiles are fired once in a mono-annealing furnace (tunnel furnace pos. 30).

The sorting line provides separation of tiles of different quality.

Tiles come from the extractor, are sorted by the operator using encoding with magnetic signals.

The equalizer, which performs the functions of an elevator, places the tiles, depending on their quality, on various ribbons using pneumatic transport. Then the tile is packed into boxes using an automatic packaging machine. The boxes are bound, packed in film and sent to the finished product warehouse.

In this diploma project, attention is paid to

roasting process, i.e. tunnel furnace (pos. 30).

Analysis of scrap arising in the process due to its imperfection

The operation experience of this process line shows that the required product quality at the output of the analyzed process area is not always maintained.

One of the main reasons for the scrap of ceramic products is the lack of moisture of the raw materials. As a result, the integrity of the products is violated, the tiles are delaminated, cracks appear.

This issue is solved by automating the drying process.

Also, the reason for the tile failure is the lack of maintenance of a given burning temperature. As a result of re-annealing, torched tiles are obtained, cracks and chips appear. Insufficient firing results in insufficient strength and no other desired properties. Using automatic temperature control in the furnace, the scrap is reduced to 55%.