How is raw cement cooked and the difference between raw cement and clinker

Cement is finely ground and mixed by limestone, clay and iron ore powder in proportion, and the mixture at this time is called raw meal. Then calcination is carried out, the general temperature is about 1450 degrees, and the product after calcination is called clinker. Then the clinker and gypsum are ground together and mixed in proportion to be called cement.

The cement at this time is called ordinary Portland cement.

Cement is generally divided into ordinary Portland cement, Portland cement mixed with mixed materials and special cement. Portland cement mixed with mixed materials is to add other substances to ordinary Portland cement in proportion and certain processing procedures to achieve special effects, such as slag cement, porosyl Portland cement, fly ash Portland cement, composite Portland cement and so on. The raw materials of these cements are more active mixed materials or non-reactive mixed materials than the original ordinary Portland cement.

Special cement is somewhat different in material stage and production process, for example, the material of high-alumina cement (aluminate cement) is bauxite and limestone after calcination to obtain clinker, and then ground to become aluminate cement.

There are other characteristics of cement that are less useful, so let's talk about it to the landlord. For example, white cement is mainly used for decoration projects, and the materials are pure kaolin, pure quartz sand, and pure limestone, and the mature material is calcined at a suitable temperature.

There are two methods of raw meal preparation: dry and wet.

In the dry preparation process, limestone and other large hard raw materials, according to the traditional process, are first crushed to a block with a size of about 100mm, or then crushed to a block of less than 25mm for a second time (in recent years, a lump process of crushing to less than 25mm has been developed). Clay and other water-containing raw materials should be dried and then sent to the mill in proportion to limestone, iron ore, etc., ground into fine raw meal, input into the mixing warehouse, stirred with compressed air in the warehouse, and adjust the composition to qualified raw meal.

The main difference between the wet process and the dry process is that the clay is first washed with water into a slurry and ground together with limestone and iron ore until the water content is about 35 years. The main advantage of dry preparation of raw meal is that the heat consumption of calcined cement clinker is lower than that of wet process, and the heat consumption per kilogram of clinker is only required, while the wet process requires. However, the composition of the raw meal prepared by wet process is more homogeneous.

In recent years, some advanced dry production cement plants have adopted measures such as raw material pre-homogenization and automatic control of raw meal composition to ensure the uniformity of raw meal composition.

The grinding of raw meal is carried out in different types of mills, mainly ball mills, tube mills, vertical mills and intermediate discharge mills that dry and grind at the same time. In order to save the electric energy of the grinding process and improve the efficiency of the mill, closed-circuit (circle flow) grinding is often used in production, that is, the material out of the mill first passes through a particle classification equipment and a powder separator, and the fine particle part is selected as the product, and the coarse particle part is returned to the mill to continue grinding. Closed-circuit grinding can increase the output of open-circuit grinding (without separator grading) by about 15 25 and reduce over-grinding.

The disadvantage is that the equipment investment is large, and the operation and management are more complicated. In recent years, a new type of vertical roller mill with a separator has been adopted, which completes crushing, grinding, drying and grading in the same unit.

The cement is finely ground and mixed by limestone, clay and iron ore powder in proportion.

Cement is made of limestone, clay and silica as the main raw materials, which are crushed, batched and ground to make raw meal, fed into the cement kiln to calcine the mature material, and added an appropriate amount of gypsum (sometimes mixed with mixed materials or admixtures) to grind finely.

The production of cement can generally be divided into three processes: raw meal preparation, clinker calcination and cement making.

1. Raw meal grinding.

There are two types: dry and wet. The dry method generally adopts a closed-circuit operating system, that is, after the raw materials are ground by the mill, they enter the separator for sorting, and the coarse powder flows back into the mill and then grinds the operation, and most of the materials are dried and ground in the mill at the same time, and the equipment used includes tube mill, intermediate unloading mill and roller mill. The wet process usually uses an open-circuit system such as a tube mill or a baseball mill that does not return through the mill at one time, but there are also closed-circuit systems with classifiers or arc screens.

2. Calcination.

There are two main types of equipment for calcining clinker: vertical kiln and rotary kiln, vertical kiln is suitable for small production scale factories, and large and medium-sized factories should use rotary kiln.

3. Grinding. <>

Fine grinding of cement clinker is usually carried out using a coil-flow grinding process (i.e. closed-circuit operating system). In order to prevent dust from flying in production, cement plants are equipped with dust collection equipment. Electrostatic precipitators, bag collectors and cyclone dust collectors are commonly used dust collection equipment in cement plants.

The differences between these two materials are as follows:1. Composition differences: cement raw meal includes limestone, clay, iron ore and other raw materials, while clinker is the product formed after calcination of these original materials at high temperatures.

2. Differences in physical properties: cement raw meal has a low density and large particles; The clinker has a higher density and finer particle size distribution, while the clinker has a stronger chemical reaction ability and a shorter hardening time.

3. Differences in chemical properties: clinker contains more compounds such as silica and alumina, and its chemical properties are more active than cement raw meal. After mixing, grinding, adding water and other processes, the cement clinker can be virtualized to form a cement colloid that sets and hardens.

First of all, it is necessary to know the reasonable mineral composition of cement, and in order to obtain such cement, it is necessary to analyze the composition of raw coal. Limestone composition. Iron powder ingredients.

and clay components, through a reasonable mix of raw materials, after a reasonable firing calcination of mature materials, by mixing an appropriate amount of mixed materials and gypsum after grinding into cement.

The cement raw meal formula is divided into the black material of the vertical kiln plant or the white raw material of the rotary kiln, first, the raw material of the vertical kiln mainly has, clay, iron powder, limestone, coal, which is the main and essential, but according to the composition of the raw materials, the raw materials need to be corrected, such as aluminum-containing less bauxite, fly ash, coal gangue.

There are alternatives to clay, there are gangue, shale, etc.

Iron powder substitutes include lead-zinc smelting slag, copper slag, etc., in order to save coal and increase production in the kiln, you can also add mineralizers, fluorite, phosphogypsum, coal saving agents, etc. Combined with the above-mentioned raw materials to develop a three-rate value that is in line with your own production, this is generally OK.

Second, the white raw material of the rotary kiln does not need to put coal first, and the others are similar to the vertical kiln.

Raw meal is the raw material for the production of cement, such as limestone, clay, iron powder, etc., which is crushed, dried and ground into powder by a ball mill according to the formula, which is raw meal.

Clinker, that is, the raw meal with fuel (some with coal, some without the white raw meal) according to a certain system into the kiln calcining, after a high temperature of more than 1350 degrees, a series of chemical reactions, the generation of calcium silicate-based minerals, is called clinker.

After clinker plus about 5% gypsum and a certain proportion of mixed materials are ground into powder by a ball mill, it is cement.