What is a dry cement kiln? Why is the kiln head fire unstable when the new dry kiln of cement heats

Refers to the cement produced by the new dry process cement production process. Its production is based on the use of new dry firing technology as the core, the use of new raw materials, fuel pre-homogenization technology and energy-saving grinding technology and equipment, the whole line of computer distribution control, to achieve cement production process automation and high efficiency, high quality, low consumption, environmental protection.

In the process of heating up the new cement dry kiln, because the cooling system of the kiln head is generally not started, the temperature of the kiln head rises slowly, the flame is unstable, and the kiln head part may be overheated, agglomeration and other problems may occur. The workarounds are as follows:1

Control the feeding speed of the kiln head to avoid excessive feed and excessive load on the kiln head. 2Adjust the combustion system, increase the air volume and improve the air-fuel ratio, and increase the kiln head temperature.

3.Strengthen the monitoring and management of the kiln head, and find and deal with the abnormal temperature of the kiln head in time. If there is a problem of overheating of the kiln head, local cooling measures can be taken, such as using water mist spray and other methods.

When the new dry kiln of cement heats up, the reasons for the instability of the kiln head fire may be as follows: 1The material density of the kiln head is uneven

In the process of heating up the new cement dry kiln, the density of materials in the kiln will change. If the density of the material in the kiln head is uneven, it will lead to the instability of the kiln fire, because the heat in the lower density part is easy to lose upward, and the heat in the higher density part is easy to conduct downward. 2.

Kiln head frit blockage: In the kiln head bucket loss area, the frit is easy to form and block the kiln head outlet, resulting in the instability of the kiln head fire. The formation of frits is usually caused by high temperatures in the kiln head area, which melts and solidifies the material.

3.Poor exhaust gas at the kiln head: The material temperature in the kiln head area is high, so the exhaust gas contains a large amount of dust and solid particles.

If the exhaust system of the rubber pants kiln head is not smooth, it will cause the gas to stay in the kiln head area for a long time, further increase the temperature of the kiln head area, and make the kiln head fire unstable. 4.Uneven cooling of the kiln head:

In the process of heating up the kiln head, if the kiln head is cooled unevenly, it will also lead to the unstable fire of the kiln head. This is usually due to a malfunction in the kiln head cooler or insufficient cooling water. Therefore, in the process of heating up the new cement dry kiln, it is necessary to pay attention to controlling the temperature and material density of the kiln head area, and ensure that the exhaust system is unobstructed and the cooler works normally to ensure the stability of the kiln head fire.

To put it simply, the dry method is to prepare the raw meal into dry powder, and the wet method is to prepare the raw meal into a slurry.

The quality of cement produced by the dry process is not as stable as that of the cement produced by the wet process.

1.The nitrogen oxides at the outlet of the preheater are the indicators of the kiln condition and the change of the firing resistance of the material, and when the change fluctuates greatly, the kiln condition changes significantly.

2.Look at the brightness of the flame at the kiln mouth, when the flame is bright and powerful, it means that the kiln condition is stable, the raw meal composition is stable and good to burn, and the flame at the kiln mouth is gray and dark, and the situation of fluttering indicates that the raw meal composition changes greatly, and there is flying sand material, and the kiln condition becomes worse.

3.The most direct thing is to see the clinker sample, granulation, and the proportion of fine powder and coarse powder of the grate cooler.

The misunderstandings of the new dry cement kiln operation mainly include: the higher the saturation ratio, the higher the clinker strength; The temperature before the kiln is low, the free calcium is high, and the kiln speed is reduced by adding coal; The flame of the kiln head is strong, and it is easy to hurt the kiln skin; Increase the internal wind of the coal injection pipe, reduce the external wind, and shorten the flame; Increase the external wind of the coal injection pipe, reduce the internal wind, and prolong the flame; It is better to be in the third quadrant of the coal injection pipe.

1) The kiln temperature increases.

2) The kiln speed is accelerated, and the unit output of the kiln is increased.

3) The kiln diameter increases.

4) The enrichment of volatile components, and the erosion of alkali, sulfur, chlorine and other components is serious.

5) The kiln system has a complex structure.

6) High requirements for energy-saving effect.

1. Dust control of limestone;

Limestone is the most widely used calcareous raw material. Its main component is CaCO3, and the grade is mainly determined by the CAO content. The CAO content of limestone used in cement production is not as high as possible, but also depends on whether its acid oxide content, such as SiO2, Al2O3, Fe2O3, etc., meets the ingredient requirements.

Harmful components such as MGO, R2O, and free SiO2 should also be controlled.

2. Quality control of clay raw materials;

The quality control of clinker is only the revision system and management: loess and clay are the most widely used. Its main components are SiO2, Al2O3 and Fe2O3.

The quality of clay is mainly measured by the chemical composition of clay (silicic acid rate, aluminum oxygen rate), sand content, alkali content, plasticity, water demand and other process properties.

After entering the factory, the materials should be stored in separate piles, and then used for laboratory testing. When storing, lay it flat and take it straight, and try to homogenize it as much as possible. Incoming clay raw materials should be sampled on time, and each batch should be fully analyzed. 3. Calibrate the quality control of raw materials.

3.quality control of gypsum;

The gypsum used as cement retarder is mainly gypsum (CaSO4·2H2O) and anhydrite (CaSO4). According to the mineral composition, it can be divided into three categories of products:

Class G gypsum: its grade is expressed by the mass percentage content of CaSO4·2H2O;

Class A anhydrite: its grade is expressed by the mass percentage of CaSO4·2H2O+CaSO4, and CaSO4 (CaSO4·2H2O+CaSO4).

M mixed gypsum: the mass percentage of CaSO4·2H2O+CaSO4 indicates its grade and caSO4 (CaSO4·2H2O+CASO4).

A batch of gypsum into the factory was sampled and tested once, and the basic analysis and inspection items were: attached water, crystal water, and sulfur trioxide content.

Quality control and standards in cement production There are two main aspects of quality management in cement production: on the one hand, it is to control the normal operation of the host equipment - kiln and mill within the scope of index control; On the other hand, it is to manage the quantity and quality of materials in various warehouses, raw materials, coal, raw meal, clinker and cement, and master the incoming and outgoing warehouses to ensure the normal operation of production. Determining quality control points and control indicators is a very important task, and we must start from the specific situation of the factory's process flow and equipment, and formulate a reasonable and feasible plan to better guide production.

The production of cement generally uses air sweep mill for grinding and drying, and the requirements for raw coal moisture have been relaxed, and the main indicator to measure the quality of coal is the level of combustion value. Here are the specific production indicators:

1. The calorific value of coal. The calorific value directly affects the temperature in the kiln, and then affects the generation of C3S, in order to ensure that the temperature in the kiln is 1450, the coal should have a higher calorific value.

2. Volatile matter of coal. When using rotary kiln, in order to ensure the smooth ignition of pulverized coal and sufficient combustion intensity, it is generally required to be between VD=18 and 30%; When the vertical kiln is used to produce cement, because the precipitation of volatile matter is carried out under anoxic conditions, in order to reduce the heat loss of Q3, it is necessary to burn coal with low volatile, and VD < 10% is appropriate.

3. Ash content of coal. The influence of ash on the calcination of cement clinker is not as great as that of calorific value and volatile matter, especially in the calcination process of vertical kiln, and the raw meal before entering the kiln should also be regarded as a kind of coal with high ash content. This is because the chemical composition of cement clinker and coal ash is basically the same, but the various components are different.

For rotary kilns, if the ash content is too high, on the one hand, it will reduce the calorific value of coal, and on the other hand, the quality of clinker will be affected because the coal ash produced after the combustion of pulverized coal falls into the clinker.

4. The coal particle size of d<6 13mm or the mixed coal of d<13 25mm is selected.

5. The water supply of coal is MT, AR < 10%.

6. Ash melting point ST>1250.

There are two main types of cement kilns, one is the kiln cylinder horizontal (with a slight inclination), and can do rotary motion called rotary kiln (also known as rotary kiln); Another type of kiln cylinder is vertically not rotating, which is called vertical kiln.