From raw materials to 8 steps of cement manufacturing, read everything about the production of cement
Raw Mix Proportioning and Raw Mix Design of cement The raw materials mixture is called raw mix or raw meal or kiln feed, The continuous production of high-quality cement is possible only if the raw mix possesses optimum composition, The purpose of calculating the composition of the raw mix is to determine the quantitative proportions of the components of the raw materials to give clinker the desired chemical and mineralogical composition and for smooth kiln operation. Main Parameters for Raw Mix Design, The raw mix composition is usually characterized by certain ratios called moduli. They are proportioning formulas in which percentages of various oxides as determined by chemical analysis are included., The three important moduli are lime saturation factor (LSF), silica modulus (SM), and alumina modulus (AM). Lime Saturation Factor (LSF), LSF represents the ratio of the actual amount of lime (CaO) to the theoretical lime required by other major oxides in raw mix/clinker., It is the ratio of CaO to the other three main oxides. A clinker with a higher LSF will have a higher proportion of elite than a clinker with a low LSF., Limiting the range of LSF in clinker is 0.66 – 1.02 and the preferable range is 0.92 – 0.96. Silica Modulus (SM), SM represents the proportion of SiO2 to the total of Al2O3 and Fe2O3., It is the ratio of SiO2 to the sum of Al2O3 and Fe2O3. SiO2 SM = Al2O3 + Fe2O3, A high SM means that more calcium silicates (C3S + C2S) and less aluminate (C3A) and ferrite (C4AF) are present in the clinker., In addition, it characterizes the ratio of solid/liquid and the amount of liquid phase in the clinker., Kiln process (coatings, rings, dusty clinker) is sensitive to SM changes., The limiting range of SM in clinker is 1.9 – 3.2 and the preferable range is 2.1 – 2.7. Alumina Modulus (AM), AM characterizes the raw meal/clinker by the proportion of alumina to iron oxide., It is the ratio of Al2O3 to Fe2O3. Al2O3 AM = Fe2O3, AM determines the potential proportions of aluminate (C3A) and ferrite phase (C4AF) in the clinker., In addition, it characterizes the composition of the liquid phase in the clinker, Alumina and iron oxide have flux effect., The liquid phase promotes the C3S formation., Higher iron oxide decreases the viscosity of the melt, increasing the speed of reaction between CaO and SiO2., Low alumina modulus = Easier burning due to low viscosity., Limiting the range of AM in clinker is 1.2 – 2.5 and a preferable range is 1.3 – 1.6 Raw Mix Design Calculation Prerequisites for Raw Mix Design Calculation, Raw Materials 1. Chemistry 2. Materials cost, There are many methods of calculation: from the simplest to more complicated ones., The basis for calculation is the chemical composition of the raw materials. Generally, data of chemical analysis should be accurate to two places of decimals. Results of the analysis are more than 100%, each constituent being proportionally reduced. If on the other hand, the total of constituents is less than 100 the constituents are not proportionally increased to 100. In this case, the difference from 100 is denoted as ‘rest’, so that the total of all constituents is then 100. Ingredients and properties of cement compounds Ingredients: 1. Lime (CaO):, This is the important ingredient of cement and its proportion is to be carefully maintained.,A sufficient quantity of lime forms tricalcium silicate (C3S) and dicalcium silicate (C2S), The lime in excess makes the cement unsound and causes the expansion and disintegration of the cement. , On the other hand, if the lime is deficient, it will decrease the strength of the cement and will cause it to set quickly. 2. Silica (SiO2):, It imparts strength to the cement due to the formation of dicalcium silicate and tricalcium silicate.,If silica is present in excess quantity