General production process description

The manufacture of ceramic products takes place in different types of kilns, with a wide range of raw materials and in numerous shapes, sizes and colours. The general process of manufacturing ceramic products, however, is rather uniform, besides the fact that, for the manufacture of wall and floor tiles, table- and ornamentalware (household ceramics), sanitaryware and also technical ceramics, often a multiple stage firing process is used. In general, raw materials are mixed and cast, pressed or extruded into shape. Water is regularly used for a thorough mixing and shaping. This water is evaporated in dryers and the products are either placed by hand in the kiln (especially in the case of periodically operated kilns) or placed onto carriages that are transferred through continuously operated kilns. In most cases, the kilns are heated with natural gas, but liquefied petroleum gas, fuel oil, coal, petroleum coke, biogas/biomass or electricity are also used.

An irreversible ceramic structure for the product is reached during the firing process in the kiln. This demands a very accurate temperature gradient during firing to ensure that the products obtain the right treatment. Afterwards controlled cooling is necessary, so that the products release their heat gradually and preserve their ceramic structure. Then products are packed and stored for delivery.

Regarding the standard conditions for measurements of volume flows and concentrations, see the following definitions, which are also stated in the Glossary:

Storage and transport of raw materials

The mining of clay, kaolin, clayey materials, feldspar, quartz and most of the other raw materials used, usually takes place in mines or quarries and in some cases the clay is also obtained from riversides near the production plant (for instance in the Netherlands).

Transportation to the production plant is mainly undertaken by truck but also by railway, or if the mine or quarry is located very near to the production plant, conveyor belts can also be used. Depending on their characteristics and the stage of processing, the raw materials are stored in open stockpiles, warehouses which are subdivided into boxes, large volume feeders, tempering silos, ageing silos, souring silos or dry silos. The silos are equipped with level indicators, overload valves and filters or gas displacement units, where displaced dusty air is blown off.

Some materials are also delivered in liquid or slurry form and therefore are stored in tanks or other vessels. The equipment for transportation within the plant is chosen according to the characteristics of the material conveyed, such as granularity, resistance to attrition and flowability, temperature, flowrate and the given space. The materials are moved with mine hoists such as bucket elevators, chain conveyors, screw conveyors, pneumatic conveyors and slides. The casting slip is partly pumped though pipelines.

Date: 2016-01-05; view: 936