Cement production introduction
Cement is among the most critical materials (bonding agent) in the building sector. It can be produced in a very simple procedure and at reasonable price, the finished product is just not damaging to the atmosphere, and it can be recycled.
There has been a considerable raise within the utilization of cement more than the past couple of years. The demand is expected to boost further inside the future as, specially in Asia and Latin America, infrastructure measures and housing might be intensified. You will discover double-digit growth rates in cement production mainly in China, but additionally in India, Indonesia, Malaysia plus the Philippines. A number of Middle East and African nations are also rising their cement production.
FAG, as a rolling bearing manufacturer, has to prepare for the expanding demand for bearings applied in machines for cement production.
The most necessary supplies for cement production are:
• limestone (Ca0) ca. 65 %
• clay (Si02 ca. 20 %; AL203 ca- 5 % and Fe203 ca. 3 %)
• additives (modest amounts)
Cement producer plants are ordinarily erected close to massive limestone deposits. If the geological structure with the limestone isn't homogeneous, additives must be admixed during the preparation method.
Limestone deposits are virtually unexhaustible so that the availablity of this raw material for cement inside the future is ensured. gold processing equipment
Crushing limestone, alumina etc.
Limestone, alumina and so on. are quarried or mined in quarries or pits and subsequently decreased to sizes ranging from 12 to 80 mm.
The following machines are mainly employed for crushing these supplies:
• Jaw crushers (see section 1.2.1)
• Cone crushers (see section 1.two.2)
• Hammer crushers (see section 1.two.3)
furthermore, tertiary crushers might be utilized, in combination with vibrating screens, for crushing/grading.
Drying/mixing
The material broken in the crushers is taken to drying plants by truck or belt conveyors. Inside the drying procedure the moisture is lowered to approx. 8 to 15 %, according to the further size reduction method. Through the drying approach, additives can already be admixed. The material is then put in intermediate storage.
Coarse grinding
State-of-the-art coarse grinding systems are generally vertical roller grinding mills (see section 1.2.4) or roller presses (see section 1.2.5). On account of their slighter energy consumption, these systems are gradually replacing ball tube mills (see section 1.two.6) which are still used, in combination with an impact mill or as independent units for coarse grinding. Within the coarse-grinding procedure the final grain sizes of approx. 0.1 mm necessary for the further cement production approach are produced.
Burning the raw meal/cooling the clinkers
In so-called cyclone preheating plants and succeeding rotary kilns the raw meal is continously heated from ambient temperature to approx. 1500 °C and discharged as granulated cement clinker.
The burning of raw meal to clinker constitutes a complex approach. It consists of precisely defined actions and is consistently monitored. Huge rotary kilns today can be approx. 6 m across and 100 m long, reaching throughputs of up to about 10,000 t per unit and day.
The power carriers employed for preheating and heating in preheating plants and for "burning" the material in rotary kilns are coal, oil and all-natural gas. Which of these fuels are ultimately utilised depends upon their price and availability.
Where coal is employed as power carrier, coal crushers are frequently employed in cement plants for size reduction and fine grinding. Normally, these coal crushers are smaller vertical rolling mills similar to those utilized for grinding raw meal. As a rule, numerous machines are run in parallel operation, grouped into units.
As the roller grinding mills have to cope with extremely adverse ambient circumstances the bearings frequently fail due to wear to ensure that there's a constant demand for new bearings. There's also a continuous demand for bearings for beater wheel mills which are utilized for coal crushing. stone processing plant
Rotary kilns are typically radially supported in hydrostatic bearings. Having said that, for some years now, support roller units with rolling bearings have also been used, fig. 22. The FAG product Programme consists of such units. Axial support with the rotary kiln is constantly effected by assistance rollers (fig. 23) which in turn are supported in rolling bearings.