Processing cement
Mining and Quarrying
The production of cement begins with the extraction of raw materials via mining and quarrying. Once a suitable large deposit has been found, the production of cement begins. Firstly the raw material, limestone, clay, iron ore, is blasted or drilled into depending on the depth of the deposit. The most central materials such as limestones will generally be mined on site and secondary materials will generally be mined on a nearby quarry. Whilst blasting any raw materials, site managers need to ensure that the best routine of blasting is practiced so that dust, vibration and noise pollution are kept to a minimum^(1). The blasted rocks will most often be of varying diameters and must be transported to a crushing plant. Crushing plants are set up close of the mining sites to reduce transportation costs and increase productivity and efficiency. Backhoe loading truck with blasted material ^(4)
Crushing and Grinding
The raw materials firstly go through a screening process which ensures only the required materials are crushed and no time and energy is wasted in processing waste constituents. Once the excessively large rocks are crushed into the desired size, the next step is ensuring the right chemical composition of your cement. Typical additives include sand, to increase the silicon oxide composition as well as iron ores to maintain the proportions of iron oxides. The next step is grinding which can be achieved one of two ways:
Wet process – The raw materials are firstly grinded to particles less than 75 microns and then fed into a rotating mill and mixed with water. This results in “slurry” being formed. The slurry has easy flow ability and is extremely malleable. The next step is ensuring the chemical composition is balanced throughout and finally it is stored away in tanks.
Dry Process – The raw materials are again grinded into powder form and sent into either a rotating ball or a vertical roller. The materials are then dried using waste gases from other stages of the production cycle. The dry material exiting the kiln is called “kiln feed” and is stored away for later use.

Clinker production
Clinkers are 3 -25 mm nodules produced through a series of chemical reactions (also known as pyroprocessing)^(2). Both wet and dry processes go through the same chemical enhancements. Firstly any moisture that may have built up during storage is evaporated; next calcining takes places, forming calcium oxide which reacts with the secondary materials including sand, clay, iron, etc^(1). This results in the formation of a black lumpy product called clinker. The clinker is then fed into a rotary kiln fired by coal to temperatures of up to 2700 degrees Celsius^(3). The Slurry requires a much longer time in the kiln due to its higher water content than the dry process “kiln feed”. The next stage is cooling the clinkers in a clinker cooler. Cooling methods include reciprocating gate, planetary and rotary. Essentially all methods use the same technique allowing air to flow through the clinkers for long enough to dissipate heat so that the clinkers can be used in the next stage of processing. Clinkers ^(2)

Finishing Grinding
The final stage determines the characteristics of your cement. Additives such as gypsum are mixed and grinded with the clinkers using ball and roller mills. The amount of gypsum (usually 3-5%) and other additives will determine the performance and setting characteristics of the cement. Once the clinkers are well crushed and mixed into the desirable size, the cement is ready for packaging and transportation.
Hot Clinkers ^(2

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The most interesting aspects of the Project
Concrete is the second most consumed product
Concrete has become a necessity for industrial development over the last century. It is currently the second most consumed product on earth only after water. Any human built landform will almost always require concrete including bridges, roads, concrete slabs, reservoirs and many more structures that improve the lifestyle of communities around the world.

Sewerage Sludge as an alternative fuel source
Sewerage sludge which has been idly left for many years has been found to have the capacity to replace fossil fuels. Although this is not going to overtake the current major sources of fuel, it can be large enough to power kiln in cement production, thereby reducing the reliance on coal. Hence it is a good method for cement production companies to reduce costs and use up waste materials in an effective manner.

Bibliography (1) “Cement Process”, Essroc Italcementi Group, last update: 2011, accessed on 15/10/2012. http://www.essroc.com/default.aspx?pageid=183 (2) ‘Clinker (cement)’, Wikipedia the free encyclopedia, last update: 5/10/2012, accessed on 15/10/2012. http://en.wikipedia.org/wiki/Clinker_(cement) (3) ‘Cement and Concrete Basics’, Portland Cement Association, last accessed on 15/10/2012 http://www.cement.org/basics/howmade.asp (4) “Manufacturing - the cement kiln”, Understanding Cement, last update: 2011, accessed on 15/10/2012. http://www.understanding-cement.com/kiln.html