What is the understanding of the development history of cement clinker firing system?

The cement production process is divided into three stages, and it is customary to refer to the cement production process as "two grinding and one burning": the first stage: raw meal grinding.

Stage 2: Clinker calcination. The raw meal is added to the cement kiln and calcined until partially melted to obtain cement clinker with calcium silicate as the main component; Stage 3:

Cement grinding. The clinker is added with an appropriate amount of gypsum, and sometimes some mixed materials, which are ground together to make cement.

1. Clinker to cement is a physical grinding process, in which gypsum (retarder) must be added, and the rest are mixed materials, such as water slag, fly ash, limestone, ultrafine powder, electric furnace slag, etc., which are only used as mixtures to participate in physical grinding, and have basically no effect on cement performance. You can also add grinding aids to improve production and quality during the grinding process.

2. The size of the ratio is determined according to the number of cement, in principle, the higher the label, the smaller the amount of mixed materials, and the higher the cost.

Cement production is a state-controlled project, from the project to the construction to the acceptance to the trial production to obtain the production license, the investment in civil engineering equipment is large, the trouble is very, it is better to buy the finished cement produced by the manufacturer with a license, the quality is also guaranteed, the formula is very simple: grade cement: (clinker 28 days strength of about 56MPa) clinker about 80%, gypsum 3-5%, silica fume up to 17%, grade cement:

Clinker about 50%, gypsum 3-5%, other mixed materials about 20%, silica powder up to 25%, there are many details of ah, such as process inspection, control, management, etc., it is better to buy grade cement, add silica powder 1:3 to make concrete plates, as long as you need to add steel bars,

Summary. The finer the fineness of the raw meal, the larger the surface area of the particles, that is, in the process of heat exchange and decomposition, it is easier to exchange heat with the hot air flow, improve the heat exchange efficiency, and promote the decomposition. For the raw meal with good burnability, the effect of improving the fineness may not be very obvious, as long as the fineness of the raw meal is controlled to a certain value, there is no need to grind the raw meal very finely, wasting energy consumption; For the raw meal with poor burnability, the role of fineness is more obvious, and the raw meal can be ground finer.

In the process of cement calcination, what is the effect of the fineness of the raw meal on the calcination?

The finer the fineness of the raw meal, the larger the surface area of the particles, and the easier it is for the lead to exchange heat with the hot air flow in the process of heat exchange and decomposition, so as to improve the heat exchange efficiency and promote the decomposition of Huai. For the raw meal with good burnability, the effect of improving the fineness may not be very obvious, as long as the fineness of the raw meal is controlled to a certain value, there is no need to grind the raw meal very finely, wasting energy consumption; For the raw meal with poor burnability, the role of fineness is more obvious, and the raw meal can be ground finer.

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Drying and dehydration. Drying is the evaporation of free water from the material, while dehydration is the combined water released from clay minerals. Decomposition of carbonates.

The process by which calcium carbonate and magnesium carbonate in raw meal absorb a large amount of heat and decompose into calcium oxide, magnesium oxide and carbon dioxide. Solid-phase reactions. The cement raw meal is heated to the range of 500 1000, and the decomposition product of limestone, calcium oxide, reacts with the clay component by diffusion in the solid phase.

The main cement clinker minerals are C2S, C3A, and C4AF. Sintering of the liquid phase. The lowest temperature of the liquid phase is 1250, the liquid phase is mainly composed of iron oxide, alumina and calcium oxide, etc., mainly calcium ion diffusion and C2S reaction to form the main clinker mineral C3S of cement.

The chemical reaction from raw meal to clinker in the cement calcination process, as the temperature increases, the reaction is different at each stage.

1) 600 years ago, it was mainly the dehydration reaction of clay, the crystalline water and hydroxyl group in the clay, dehydration, the formation of alumina and silicon oxide.

2) 500-1000, in which the carbonate begins to decompose, magnesium carbonate decomposes into magnesium oxide, calcium carbonate decomposes into calcium oxide, of which the decomposition temperature of magnesium carbonate is much lower than that of calcium carbonate.

3) 800-1200, alumina, silicon oxide, calcium oxide and magnesium oxide, etc., begin to form various salts. For example: