Development Program to Estimate the Suitable of Raw Materials to Produce Cement

Raw material composition plays an essential role on the lining life of cement rotary kiln.They are obtained from hard rock quarries that represent the first step in the cement manufacturing process. That raw materials are transported to AlKufa cement plant then crushed and ground to very fine powder and then blended in the correct proportions.This research aims to study suitable rations of raw materials to produce cement in al Kufa cement plant in Iraq. Through a software program, suitale raw materials ratios for the clinker were estimated, then chemical and physical tests for clinker and cement according to Iraqi Standard Specification were done to recognize the effects on the properties of cement such as the ratios of major and minor oxides, Lime saturations factor (LSF), Silica Modulus (SM) Alumina Modulus (AM), compressive strength, setting time and soundness.


b. Thermal Treatment:
Burning of the raw mix is generally carried out at 1450-1500°C. Excessive high burning temperature results in a great stress on the kiln and the refractory lining, more fuel consumption,reduction in cement strength and larger alite crystal .
On increasing holding time, C3A content may decrease, C4AF may increase, C2S may decrease, C3S may increase. Rapid burning is always favored as because fine grains of C2S formed which accelerate theinteraction of C2S, CaOand liquid. Thermal activation can be enhanced by either with mechanical (vibratory mill) or chemical (mineralizer) activation. Mechanical activation gives better results than chemical.

c. Liquid Phase Formation:
The amount of liquidformed, its appearance temperature, viscosity, surface tension and ionic mobility in the clinkerization process.

d. Clinker Quality:
The burnability becomes worse as C3S content increases while an increasing C3A and C4AF, the burnability improves. e. Kiln Atmosphere: A reducing atmosphere during burning affect the colour of the clinker by reducing iron oxide,enhancing C3A, decreasing C4AF, C3S.

Experimental Materials:
Field visits were implemented during 2016 to Al-Kufa Cement plant in Iraq to view the rotary kiln of cement manufacturing. Chemical and physical tests for clinker and cement according to Iraqi Standard Specification were done to recognize the effects on the properties of cement. A software program was achieved to calculate the ratios of the raw materials of clinker.

Calculations of Mixing Ratios For Raw Materials:
A software program is achieved to calculate the mixing ratios of raw materials for the production of the final mixture of the resistant clinker and this program requires: 1-Chemical analysis tests for the raw materials, shown in table 2 that represents the chemical tests of the raw materials. The percentages of the mixing of the raw materials in the process of production of the Al-Kufa Cement plant in Iraq during 2016 is listed in tables below using the software program.

4.Conclusions
1-The basis for this property is well-burned clinker with consistent chemical composition and free lime. There are only two reasons for the clinker free lime to change in a situation with stable kiln operation: variation in the chemical composition of the kiln feed or variations in its fineness. Variations in fineness depend on possible changes in raw materials or in operation of the raw mill. Variation in chemical composition is related to raw mix control and the homogenization process. 2-Refractory chemistry is important because it helps determine if a given product is compatible with certain applications. Although the chemical composition alone is not a suitable criterion to define product usage. 3-The finer the raw mix will have to be ground to ensure satisfactory combination at acceptable kiln temperatures. When decarbonation is complete at about 1100 C, the feed temperature rises more  rapidly. Lime reacts with silica to form belite (C2S) but the level of unreacted lime remains high until a temperature of ~1250 C is reached. This is the lower limit of the rmodynamic stability of  alite (C3S). At ~1300 C partial melting occurs, the liquid phase (or flux) being provided by the  alumina and iron oxide present. The level of unreacted lime reduces as C2S is converted to C3S. The process will be operated to ensure that the level of unreacted lime (free lime) is below 3%. 4-As the clinker passes under the flame it starts to cool and the molten C3A and C4AF, which constitute the flux phase, crystallize. This crystallization is normally complete by the time the clinker exits the rotary kiln and enters the cooler at a temperature of 1200 C. Slow cooling should  be avoided as this can result in an increase in the belite content at the expense of alite and also the formation of relatively large C3A crystals which can result in unsatisfactory concrete rheology . 5-Higher amount of sandstone is hard to burn in kiln because it consumes large amount of coaml and it even increases free lime. 6-Percentage of C3S content in clinker in increased. Alite hardens the cement faster and contributes to early strength formation. It resistant to sulfur attack hence high strength of C3S will increase the strength at all ages. 7-Lime saturations factor (LSF), Silica Modulus (SM) and Alumina Modulus (AM) and variations in clinker quality on the limit. It can be decreased by carrying out various steps at different level which reduces the deviations of blending efficiency, raw mill feed, kiln feed and clinker compositions and its minerals. 8-LSF should be in the range of 92%±1, but minimum value obtained is 89% . To determine the silica and the SM minimum value obtained is 2.3 and it goes to a maximum value of 2.65. The minimum AM value obtained is 0.7 and it goes to a maximum value of 0.9. The importance of the calculation is preparation a kiln feed mixture with a suitable content of calcium carbonate (61-65%) to avoid hard burning process at high content of calcium carbonate content, as well as to avoid friction resulting from the silica on the formed coat on the internal kiln wall when calcium carbonate content is low. 9-When the LSF is above 0.95 there is an excess of lime, which cannot be combined no matter how long the clinker is fired and this remains as free lime in the clinker. As a low level of uncombined lime must be achieved the influence of LSF on the content of C3S and C2S. 10-The higher silica modulus (SM) the less molten liquid or flux is formed. This makes clinker combination more difficult unless the LSF is reduced to compensate. The flux phase facilitates the coalescence of the clinker into nodules and also the formation of a protective coating on the refractory kiln lining. 11-High Alumina Modulus (AM) cements will have a high C3A content, and this can be disadvantageous in certain cement applications, where it is desired to minimize the concrete temperature rise. 12-The SO3 have to be closely controlled because they are volatilized in the kiln and can cause severe operational problems associated with their condensation and the formation of build-ups in the kiln.