Basic principles in the cement industry
Cement contains two basic materials, lime and clay, the latter to which we add the basic materials are smooth, alumin and iron oxide.
The lime and clay materials are crushed in the crushing machines and mixed together in proportions determined by the laboratory and grinded in the grinding machines and then passed through the oven, which has a temperature of about 1430 ° C. Then we get clinker. We add to this article other articles. We enter it into the grinding machine and then we get the cement material which is put in bags and then packed.
Cement is formed as raw materials of two basic materials are lime stone and clay clay and two additional materials are added depending on the circumstance and nature of each plant namely sand, iron ore iron and sand and is called iron and sand corrective materials any material to correct the proportions to be accessed, sometimes comes the child and stone with a high proportion of sand You do not need to add limestone sand is mainly CaCo3 calcium carbonate but in nature there are many impurities such as SiO2 and Al2O3 and Na2O3 and Fe2O3 and others such as potassium, chlorine and others
The girl consists of 50% SiO2 and 14-16% Al2O3 and the rest is CaO, Na2O, Fe2O3 and others potassium, chlorine and others
Sand consists mainly of SiO2 in the range of 70% and the rest is Al2O3, Na2O3, Fe2O3, CaO and others such as potassium, chlorine, etc.
Iron is mainly composed of Fe2O3 We talked about the composition of cement in terms of raw materials We will talk about the composition of cement in other chemical terms and link it with raw materials and why we chose these materials consists of four oxides are SiO2 and Al2O3 and CaO and Fe2O3 The main source of CaO is limestone where CaCo3 turns to CaO at high temperatures, as will be seen later the primary source of Al2O3 is the child The primary source of SiO2 is sand The primary source of Fe2O3 is iron but I would like to draw your attention to some points • Although SiO2 50% of the child we did not add To get the SiO2, but we added the Fella to get the Al2O3 • But do not mind that we actually benefit from the presence of SiO2 in the girl as well as the rest of the elements • These raw materials are added in certain proportions and enter a huge mill to grind to a high degree of smoothness and this mill is called raw mill mill does not occur any mill Chemical but only grinding of raw materials and the benefit of this grinding increase the surface area of the granules in order to enter chemical reactions until all particles are exposed to reactions • The proportions in raw materials are approximately 75% of the stone and 20% of the clay and 3% of the sand and 2% of iron and these rates vary Depending on the results and analysis is taken into account In these ratios are three coefficients: L S F, lime saturation coefficient and S.M, which is silica coefficient and alumina coefficient A.M.
After the raw material comes out of the mill, it enters a silo for storing and stirring the raw material only and its usefulness is stirring
Then start the first stages of chemical reactions in a huge building called the tower or the preheater, which is five cyclone, above some and calciner and cyclone is a huge tank and the calciner is a huge tank but it has a flame and they are all connected to each other
And the usefulness of this tower is
1- Heating the raw material and preparing it to enter the furnace 2- Converting the CaCo3 to CaO because we have mentioned that the stone is made of CaCo3 and we need in the industry for CaO and this conversion is done according to the following equations CaCo3 CaO + Co2 at a temperature of 850 ° C and thus be the four oxides Ready to react in the oven
• The raw material enters the furnace, which is a huge cylinder with a simple angle at a laterally horizontal rotation and a huge flame inside it. • Inside the furnace, the four oxides combine into a so-called clinker phases. • C3S, C2S, C3A, C4AF. These four materials are the clinker. It is worth mentioning that the preceding four compounds are abbreviated to the following: • C abbreviation for CaO • A for abbreviation for Al2O3 • S for abbreviation for SiO2 • F for abbreviation for Fe2O3 • C3S is three molecules of CaO combined with a molecule of SiO2. Thus, temperatures reach 1450 degrees at the end of the furnace fire area at the flame • After the furnace enters the produced material called clinker to cooler for sudden cooling and its usefulness cooling clinker and prevent the reverse reaction and disintegration of the four clinker phases to the oxides of its component Cement industry. • Then add raw gypsum and calcium sulphate composition CaSO4.2H2O to clinker and enter together a mill called cement mill cement and the final product is cement • Add gypsum within 5% and its usefulness to regulate the doubt time for cement • In the clinker stages of C3A doubts instantaneously when adding water but we We add gypsum to delay the time of doubt • Gypsum consists of CaSO4.2H2O and this article combines with the C3A, a substance called Eterenget surrounding the C3A and delayed from the time of water to the C3A and thus delayed from the time of doubt
