Depending on a physical state of raw mix, Portland cement clinker production is classified under the following technologies:
- If a raw mix is prepared as raw mix suspension in water - slurry - wet production technology is being used;
- If a raw mix is prepared as dump granules - semi-wet or semi-dry technology is being used;
- If a raw mix is prepared as dry powder - dry technology is being used.
Cement production begins with quarrying limestone and its crushing in jaw and hammer crushers. Clay is the other component of cement production. Clay is being received from quarry and modified to wet suspension - clay slurry - in a clay wash mills. Clay slurry is being pumped to raw mills through intermediate volumes; crushed limestone and raw mix corrective materials- iron ore and sand - are also fed to raw mills. Raw materials are grinded and blended in the raw mill, transforming them to the quite fluid smooth suspension, having 35-38 % of moisture and called slurry. Before feeding it to a rotary kiln the slurry is being stored and constantly blended in containers, called slurry basins.
Slurry is fed from slurry basins into the kiln, which is with a little slope and is rotated around its axis by engines. Therefore this kin is called rotary kiln.
Wet production process is used in Akmenes cementas. Raw mix is burned in
a long rotary kiln with diameter Æ 5 x 185 m.
Raw mix (in a case of Akmenės cementas AB - raw mix suspension - slurry) is heated up to 1450 °C in a rotary kiln and this results in a final black, nodular product known as "clinker" which is suddenly cooled by environment air to 50 - 90 ° C and has the desired hydraulic properties. In such a way produced Portland cement clinker is a main constituent of cement production.
Grinded in the mill coal is used as the fuel in a rotary kiln. As a fuel used tyres are fed as well. During the day, 350 tonnes of coal and 35 tonnes of used tyres are being used in rotary kiln. Fume formed in a rotary kiln, is purified by electro-precipitators before releasing them to atmosphere.
Overall plant productivity, its energy efficiency is essentially based by equipment, producing main cement production constituent - rotary kiln for clinker burning, which together with its subsidiary equipments uses 35 % of all electricity and 90 % of all plants' technological fuel demand.
Cement (as a final product in the form of fine powder) is manufactured by grinding Portland cement clinker with gypsum and other additives in particular grinding mechanism - cement mill - till fineness indicated in a standard specifications is achieved. Fineness of the cement, amount of gypsum added, and the amount of other additives added are all varied to develop a desired performance in each of the final cement products.
Additives for cement grinding- pozzolanic materials, limestone and slag - are dried in a dryer before feeding them to the cement mills.
Each cement type is stored in an individual bulk silo until needed by the customer. Bulk cement can be loaded into truck, rail, or ship depending on the customer's needs. Cement can also be packaged and distributed by truck or rail.
Detail description and layouts of cement production technology is available here.
