White Cement Manufacturing
What is white cement? White cement, also called white ordinary Portland cement, is a kind of hydraulic cementing material, which is made of white cement clinker with low iron oxide content, gypsum, and other mixed materials. It is similar to the common gray Portland cement in function, physical property, and other aspects except for its high degree of whiteness.
Compared with the ordinary Portland cement, the white cement manufacturing process is more complex. As for application, white cement can be used as building decoration materials, craft product materials, waterproof materials, floor tile materials and so on in many industries.
White Cement Application
As a type of special cement, white cement is the largest production scale of decorative cement variety. Although its performance is not as outstanding as the ordinary Portland cement, it is widely used in construction and many other fields. In the construction industry, white cement can be used to make guard rail with fine texture, the decorative finish of walls, concrete members, water stone, artificial stone, floor tile, sculpture products, color cement, cement paint, white concrete, etc. Besides, it can also be used as a tile grout, binding agent, and waterproof coating. It is ubiquitous in our lives and has high economic benefits.
White Cement Plant
The production process of white Portland cement is quite different from ordinary Portland cement. It is unique in both process flow and cement equipment selection. In white cement plants, the main manufacturing process includes six steps: raw material crushing, raw material grinding, clinker calcination, clinker cooling, cement grinding, and cement packing. AGICO provides white cement plant EPC projects with a daily capacity of 1000 to 10000 tons.
Raw Material Crushing
To ensure the complete removal of impurities in raw materials, prevent affecting the quality of white cement, the cement raw material crushing should be combined with multiple screening and washing processes. We usually adopt the jaw crusher as the primary crusher and hammer crusher as the second stage crusher.
Raw Material Grinding
Silica materials in cement raw materials are ground separately by wet grinding equipment, while other materials such as limestone are ground by cement vertical mill. The wet grinding equipment is equipped with a rubber liner or ceramic liner. And the grinding roller and grinding disc in the cement vertical mill adopt alloy material to reduce the mixing of metallic iron so that avoid affecting the color and brightness of white cement.
After the cement raw material is ground and pre-homogenized, it is pre-decomposed by cyclone preheater and calciner, and then calcined at high temperature in cement rotary kiln, until the cement clinker is formed. During these processes, the waste gas discharged from cyclone preheater can be reused to dry raw materials by cement vertical mill for reducing energy consumption.
The calcined clinker usually has a high temperature, so we need to cool it effectively. In white cement plants, this process is combined with clinker bleaching. The discharged high-temperature clinker will first enter the bleaching machine to be cooled to 500-600 ℃, and then into the grate cooler to be cooled below 100 ℃. The hot gas discharged from the grate cooler can be reused as secondary air of rotary kiln and tertiary air of calciner.
Cement ball mill is the most frequently used cement mill in the clinker grinding stage. To avoid the mixing of iron oxide, the high chromium alloy materials are applied for the compartment board, lining plate, and grinding medium. During the grinding process, we add gypsum and other materials into the mill to give the white cement a certain property.
Cement packing is the last stage in white cement manufacturing. After the cement powder is fed from the cement silo into the cement packing machine, they are packed in bags and stored in a warehouse waiting for shipping.
How to Improve the Whiteness of White Cement
Whiteness is an important quality index of white Portland cement. Compared with gray cement, white cement must meet the requirements of whiteness besides strength, stability, and other technical indexes. To obtain the white cement clinker with good brightness, the following measures should be taken.
Choose the right raw materials
We should use cement raw materials with low content of metal oxides, such as limestone, kaolinite, pyrophyllite, sand, etc.
Choose the right fuel
The fuel ash also contains metal oxides, which will affect the whiteness of cement. We can use heavy oil or natural gas instead of coal as the burning fuel.
Choose the right raw mill and cement mill
We should choose the cement grinding equipment with high grinding efficiency and replace the grinding medium, lining plate, and other parts in the mill with ceramic or pebble materials.
Choose the right way to cooling
Clinker can significantly improve whiteness by quench cooling. The premise is that the temperature of the clinker should be kept at 1300℃ before cooling.
White Cement Vs Ordinary Portland Cement
Both white Portland cement (P.W) and the ordinary Portland cement (P.O) are made from clay, limestone, gypsum, and iron ore. To produce white cement, we usually adopt kaolinite, pyrophyllite, and other raw materials that contain less level of iron, manganese, chromium, and magnesium oxides, because it’s these substances that give conventional cement its gray color. Therefore, the real secret of white cement is its raw material.
The production process of white cement is more complicated than ordinary Portland cement. It has more steps in the raw material preparation and adds a bleaching process. So the ordinary Portland cement costs about half as much to produce as white cement. In the choice of cement mill, we tend to use ceramic mill liners and grinding equipment for white cement production, because ceramic equipment avoids the mixing of color-altering oxide.
The ordinary Portland cement is suitable for the construction of bridges, highways, buildings and other large-scale concrete structures. It is more widely applied than white Portland cement. White cement, also known as decorative cement, is commonly used to increase the ornamental value of bridges and architectures. During the production, we can add different colors to white cement by mixing color pigments.