Process : Stage 1

Raw Materials

Cement is primarily a processed mixture of limestone, sand, shale, clay, and iron ore of which limestone forms the major ingredient. Limestone is usually mined on site while the other minor ingredients may be mined either on site or in nearby quarries. A series of controlled blasts are administered for extracting huge masses of limestone rock from the quarry's rock walls. The shock blast technology used by APCL ensures minimum levels of vibration, noise and dust emission.

Raw Material Processing

At the crushing plant, a series of crushers and screens reduce the limestone rocks to a size less than 10 mm. The crushed material is stored in linear stockpiles for further processing.

Other additive materials like sand, shale, clay, and iron ore will be crushed and stored in separate linear stockpiles for later use.

Process : Stage 2

Raw Material Grinding

Raw material grinding is carried out through a dry process, wherein, each of the raw materials is fed in the right proportion to attain the desired chemical composition before being fed to a rotating ball mill. The raw materials are then dried with waste process gases and ground to less than 90 microns in size. The resultant mixture of material is known as "raw meal".

The raw meal is stored in a vertical continuous blending cum storage silo where it is pneumatically blended to ensure a uniform chemical composition. The thoroughly homogenized mixture is then fed to the pre heater.

Coal Crushing and Grinding

Coal is brought in from indigenous sources and also imported from Indonesia, Malaysia and South Africa. They are  then blended together to achieve a uniform heat value. The coal mixture is then crushed and ground in a ball mill up to 75 microns in size and stored in fine coal hoppers.

Process : Stage 3

Pyroprocessing

Pyroprocessing is carried out in a 5 stage preheater, calciner and rotary kiln with cooler. It takes place inside the pre-heater tower which is about 90 meters in height.

Raw meal from the storage silo is extracted at a defined rate and fed at the top of the pre-heater tower while being subjected to high temperatures at every single stage of the 5 stages. High temperatures free the raw meal of all moisture and also do the preheating. After 4 stages, the raw meal enters the ‘calciner’ wherein calcium carbonate in the raw meal is decomposed into calcium oxide and carbon dioxide. The material is then fed to rotary kiln.

The pre-heater tower and rotary kiln are made of a steel casing and lined with special refractory materials to protect it from not only the high temperatures in the kiln but also from reactions with the raw meal and gases in the kiln, abrasion and mechanical stresses induced by deformation of the kiln shell as it rotates.

In the kiln, the calcination process is completed as the raw meal burns at 14500 C with fine coal fed in from the kiln inlet and mixing chamber. The raw material inside the kiln liquefies and begins to flow like red hot lava. During this heat treatment of raw meal, calcium oxide reacts with silica, alumina and iron oxides to form crystals of calcium silicates, calcium aluminates and calcium alumino ferrites etc. This process is called sintering. The reaction results in nodular product known as "clinker" which has the desired hydraulic properties.

The red-hot clinker is discharged from the rotary kiln into a clinker cooler. Large cooling fans blow air through the red hot clinker cooling it down on its way out. The hot kiln gases are captured using the reverse air bag house. The clinker cooler is primarily meant to transfer heat from the clinker to the pyroprocessing system in the form of hot gases, hence optimizing the whole system by reducing fuel consumption and improving overall energy efficiency.

Clinker leaving the clinker cooler is at a temperature of 1000 C capable of being handled by standard conveying equipment. Clinker is then stored in well sheltered stock piles.

Process : Stage 4

Final Grinding and Storage

The black, nodular clinker, Gypsum and Fly-ash are stored in separate hoppers ready to follow the course of final grinding. From the hoppers the clinker along with gypsum and fly-ash are ground together in ball mills in defined proportions to form the final cement products. Fineness of the final products, amount of gypsum added, and the percentage of fly-ash added are all varied to develop the product variants and different grades of cement.

Process : Stage 5

Distribution and Dispatch system

Each product variant is stored in an individual bulk storage silo ready to be dispatched. Cement is packed in bags using roto packers and is distributed by road ways or rail ways as per requirement. Customers may also demand cement to be dispatched in bulk tankers. Cement can also be packaged in eco-friendly paper bags before being distributed by road ways or railways.