Portland Cement Manufacturing
What is Portland cement? Portland cement derives its name from Portland, England, in many cases, also called silicate cement. It is a kind of hydraulic cementing material made of calcium silicate cement clinker, limestone or blast furnace slag (less than 5%), and an appropriate amount of gypsum. At present, Portland cement has been widely used in residential construction, traffic construction, large-scale water conservancy construction, civil engineering, etc.
For different applications, Portland cement is classified into various types. Ordinary Portland cement (OPC) refers to Portland cement containing 5 ~ 20% of active mixing material. The Portland cement with a higher proportion of admixture (more than 20%) is usually named by the admixture, such as Portland pozzolan cement, Portland fly ash cement, Portland slag cement, etc.
|Lime (CaO)||60 to 67%|
|Silica (SiO2)||17 to 25%|
|Alumina (Al2O3)||3 to 8%|
|Iron oxide (Fe2O3)||0.5 to 6%|
|Magnesia(MgO)||0.1 to 4%|
|Sulphur trioxide (SO3)||1 to 3%|
|Soda and/or Potash (Na2O+K2O)||0.5 to 1.3%|
Chemical Composition of Portland Cement
The main components of Portland cement include calcium oxide (CaO), silicon dioxide (SiO2), aluminum oxide (Al2O3), and iron oxide (Fe2O3). They account for more than 95% of the total cement composition. In addition, there are other oxides like magnesium oxide (MgO), sulfur trioxide (SO3), titanium dioxide (TiO2), phosphorus pentoxide (P2O5), potassium oxide (K2O), sodium oxide (Na2O), etc., accounting for less than 5% of the total amount. These components that make up raw materials react at high temperatures and finally form compounds tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite. The tricalcium silicate and dicalcium silicate determine the strength of Portland cement, in which the tricalcium silicate mostly affects the early strength. Tricalcium aluminate causes the initial setting of Portland cement.
Features of Portland Cement
Portland cement has a high setting and hardening speed, and high strength, especially its early strength growth rate. It is suitable for high-strength concrete structures, prestressed concrete engineering, and projects with high early strength requirements.
High Hydration Heat
The rich content of carbon disulfide in Portland cement leads to its high heat release, high release speed, and high strength in the early stage. If it is used in winter construction, freezing damage can be avoided.
Good Wear Resistance
Portland cement features high strength, good wear resistance, and small dry shrinkage, which can be widely used in pavement and ground engineering.
High Alkalinity & Carbonization Resistance
Portland cement has the feature of strong alkalinity, high density, and strong carbonation resistance. When the steel bar is buried in an alkaline environment, a layer of gray passivation film will be formed on the surface, which can keep the steel bar from rusting for decades.
Small Dry Shrinkage
A large amount of calcium silicate hydrate will be produced during the hardening process of Portland cement. As a result, cement stone has high density, less free moisture, and is not easy to produce dry shrinkage cracks. Therefore, Portland cement can be used in concrete engineering in a dry environment.
Good Frost Resistance
Portland cement mixture is not easy to bleed, and the density of hardened cement stone is large, so the frost resistance is better than other general cement. It is suitable for concrete engineering under repeated freeze-thaw action in severe cold areas.
Portland Cement Manufacturing Process
The Portland cement manufacturing process can be divided into 6 steps: raw material crushing, pre-homogenization, fine grinding, clinker production, cement grinding, cement packing, etc. In these processes, we need the assistance of different kinds of cement equipment, such as cement kilns, cement mills, and cement crushers. The specific manufacturing processes are as follows:
Step 1: Raw Material Crushing
After cement raw materials are mined, most of them should be crushed into small particle sizes. Coal, the main fuel for cement production, also needs to be broken in advance. In this step, all of them should be crushed by special crushing mills and then transported to the pre-homogenization yard by belt conveyor.
Step 2: Pre-homogenization
The pre-homogenization refers to the preliminary homogenization of cement raw materials and fuel raw materials through the application of scientific stacking and reclaiming technology in the process of material storing and taking. In this step, the stacker is applied to pre-homogenize and stack raw materials in layers. Then the scraper reclaimer takes out raw materials and sends them to the batching station helped by the belt conveyor.
Step 3: Fine Grinding
After the raw material batching is completed, cement raw meals (calcareous raw materials, clayey raw materials, and a small number of corrective materials) need to be further ground by raw mills to realize a certain fineness, appropriate chemical composition, and uniform structure so that they can meet the calcination requirements of various cement kilns. The frequently used raw mills include cement ball mills, cement vertical mills, Raymond mills, etc. The air-swept coal mill is used for coal grinding.
Step 4: Clinker Production
Clinker production is the most critical stage in the cement manufacturing process. At present, the new dry process clinker production technology is the most advanced clinker production method. It has the advantages of high efficiency, energy-saving, and high production quality. By this production method, the raw meal powder will be pre-decomposed in a cyclone preheater and calciner first, and then enter a cement kiln to be calcined under high temperature. After that, the calcined clinker will be cooled by the grate cooler and stored in the clinker warehouse.
Step 5: Cement Grinding
After calcination, the clinker needs to be mixed with gypsum and additives to meet the requirements of different properties. Then, they will be ground by cement mills to appropriate particle size, forming a certain particle gradation, which increases the hydration area and accelerates the hydration speed.
Step 6: Cement Packing
Cement packing is the last step in the cement manufacturing process. After the cement powder is discharged from the unloading system at the bottom of the cement silos, it will be sent to the cement packaging machine by the bucket elevator. In the packing machine, they are packaged into bags and then transported to different sales markets.
Why Choose AGICO Portland Cement Manufacturing Plant
AGICO is a reliable cement plant manufacturer. We can help you to establish your Portland cement manufacturing plants.