High-alumina cement is a special cement obtained by high-temperature calcination of bauxite and limestone as raw materials. It is widely used in metallurgy, electric power, chemical industry, shipbuilding, military industry and other fields due to its excellent high temperature resistance, corrosion resistance, chemical erosion resistance and other properties. This article will introduce the production process of high-alumina cement in detail, including the whole process from raw material selection, proportioning, calcination to finished products.

1. Selection and preparation of raw materials
The main raw materials of high-alumina cement are bauxite and limestone. In addition, some auxiliary materials are required, such as iron ore, clay, coal, etc.

Bauxite: Bauxite is the main raw material of high-alumina cement and contains rich aluminum components. The quality of bauxite directly affects the performance of high-alumina cement. Therefore, in the ore dressing process, it is necessary to ensure that the aluminum content of bauxite is high.

Limestone: Limestone is the main source of calcium. Calcium reacts with aluminum to form calcium aluminate minerals, which give cement high temperature resistance and corrosion resistance.

Iron ore and clay: These two raw materials are used in some formulas to adjust the mineral composition of cement and ensure the stability of the physical properties of cement.

2. Ratio and mixing of raw materials
In the production of high-aluminum cement, a reasonable ratio of raw materials is very important. Common high-aluminum cement raw material ratios are:

Bauxite: 60%-70%
Limestone: 25%-35%
Others: 5%-10%
Different ratios will directly affect the chemical composition and properties of cement. Through scientific ratios, high-aluminum cement is ensured to have excellent compressive strength, high temperature resistance and corrosion resistance. After the ratio is completed, all raw materials need to be fully mixed through a ball mill or other equipment to form a uniform raw material mixture.

3. Calcination of raw materials
Calcination is a key step in the production of high-aluminum cement. Rotary kilns or vertical kilns are usually used for high-temperature calcination. The calcination temperature is generally controlled between 1400-1600 degrees Celsius. The chemical reaction during the calcination process combines elements such as calcium, aluminum, and silicon in the raw materials to form the main mineral of cement-calcium aluminate minerals.

Reaction process: At high temperatures, the aluminum in bauxite reacts with the calcium in limestone to form calcium aluminate (CaO·Al2O3) minerals. During this process, some bauxite will also react with silicate minerals to form minerals such as aluminum silicate (CaO·Al2O3·SiO2), further improving the strength and durability of cement.

Temperature control: Temperature control during calcination is crucial. Too high a temperature will lead to excessive decomposition of minerals, affecting the quality of cement; too low a temperature will lead to insufficient formation of calcium aluminate minerals, affecting the hardening properties of cement. Therefore, reasonable temperature and calcination time are the key to ensuring the quality of high-alumina cement.

4. Cooling and formation of clinker
The product after calcination is called clinker. Clinker is a particle composed of various calcium aluminate minerals, usually in granular form, with a gray or gray-black color. After the calcination process is completed, the clinker needs to be cooled quickly to prevent the mineral from recrystallizing or decomposing.

Cooling is usually done in the following ways:

Water cooling: The clinker is rapidly cooled by water flow to quickly cool it down and avoid changes in the mineral structure.
Air cooling: Use cooling air to slowly cool the clinker.
The cooled clinker is the basic component of high-alumina cement, containing a certain proportion of minerals such as calcium aluminate and aluminum silicate.

5. Clinker grinding and cement forming
The cooled clinker needs to be further ground to obtain a suitable particle size. The grinding process usually uses a ball mill or a vertical mill to grind the clinker into a fine powder, and the particle size is usually controlled at a specific surface area of ​​3000-4000 cm²/g. The ground clinker will be mixed with an appropriate amount of gypsum or other retarding materials to form the final product of high-alumina cement.

Gypsum is added to adjust the setting time of cement and prevent it from setting prematurely. During the grinding process, gypsum reacts with calcium aluminate minerals in the clinker to form hydration products, thereby controlling the hardening process of cement.

6. Finished product packaging and storage
After grinding, high-alumina cement is usually in the form of gray or gray fine powder. The finished cement needs to be packaged and stored, and the packaging is generally in bagged or bulk form.

Bag: Suitable for small-scale use or retail market, usually packaged in 50 kg bags.
Bulk: Suitable for large construction sites and industrial users, usually transported and stored by bulk cement trucks.
During storage, cement needs to be kept in a dry and ventilated environment to prevent moisture absorption and agglomeration from affecting the quality of cement.
7. Finished product testing and quality control
In the production process of high-aluminum cement, every link needs to be strictly controlled to ensure the quality of the finished product. Quality control mainly includes the following items:
Chemical composition analysis: Regularly test the chemical composition of raw materials, clinker and cement through chemical analysis instruments to ensure that they meet the standards.
Physical property testing: Including tests of cement compressive strength, setting time, fluidity and other indicators.
High temperature resistance test: One of the most important properties of high-aluminum cement is high temperature resistance. Manufacturers need to conduct relevant tests regularly to ensure the stability of cement in high temperature environments.
Conclusion
The production process of high-aluminum cement requires strict control from raw material selection, proportioning, calcination to finished product processing. Each link is related to the quality of the final cement. With the continuous development of high-alumina cement technology, the production process is also being continuously optimized, gradually achieving higher production efficiency and better product performance. In the future, with the increase in market demand and the expansion of application areas, high-alumina cement will continue to play an important role in more fields.