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Analysis of new dry process cement production process

Date:2019-06-25 15:18     writer:cement editor     Views:

According to the current and future period of China's cement industry development of the guidance document "Special Plan for Cement Industry Development" and cement industry industry development policy, revised standards for general cement, etc. The book focuses on the new dry process cement production process technology, comprehensively and systematically expounds the production methods of general cement, Portland cement clinker, raw materials and pre-homogenization, batching and raw material grinding, clinker calcination, cement The basic knowledge and skills of quality control and management of cement production, as well as the hydration and hardening of cement, cement performance, other types of cement production, energy saving and environmental protection measures for cement production, and application of cement. Let me come to understand the relevant knowledge of the cement production process.

Cement introduction

Cement: powdery hydraulic inorganic cementitious material. After adding water and stirring, it can be solidified in the air or hardened in water, and can firmly bond sand, stone and other materials together. The word cement is developed from the Latin caementum and is the meaning of gravel and schist. The mixture of early lime and volcanic ash is very similar to modern lime volcanic ash cement. Concrete made of cemented gravel is hardened not only with high strength but also against fresh water or salt water. For a long time, it has been widely used in civil engineering, water conservancy, national defense and other projects as an important cementing material.

Cement production line process

The cement production line (cement plant equipment) is a cement equipment production line consisting of a series of equipment for producing cement. It is mainly composed of crushing and pre-homogenization, homogenization of raw material preparation, preheating decomposition, firing of cement clinker, cement grinding and packaging.

Cement equipment (cement machinery, cement plant equipment) contains equipment

Cement equipment includes: cement rotary kiln, cyclone preheater, and grate cooler.

Cement rotary kiln is the main equipment for calcining cement clinker and has been widely used in cement, metallurgy, chemical and other industries. The device is composed of a cylinder body, a supporting device, a belt wheel supporting device, a transmission device, an active kiln head, a kiln tail sealing device, a combustion device and the like. The rotary kiln has the characteristics of simple structure, reliable operation and easy control of the production process.

The cyclone preheater is suitable for use in various kiln types (see the list). On the basis of the main equipment for converting and digesting imported Kawasaki Nissan 800 tons and daily production of 1000 tons of cement clinker, Nissan 500 tons and 2000 were developed. Ton five-stage suspension preheater with decomposition furnace. The preheater can be widely used in the construction and renovation of large, medium and small cement plant equipment.

The grate cooler is a quenching chiller. The principle is: blow the cold air with a blower, and quench the clinker layered on the slab to reduce the clinker temperature from 1200 °C to 100 °C. the following.

Cement production process

1. Fragmentation and pre-homogenization

(1) Breaking During the cement production process, most of the raw materials are broken, such as limestone, clay, iron ore and coal. Limestone is the raw material for producing the largest amount of cement. After mining, the particle size is larger and the hardness is higher. Therefore, the crushing of limestone plays an important role in the material crushing of cement plants.

(2) Raw material pre-homogenization Pre-homogenization technology is to use the scientific stacking and reclaiming technology to realize the initial homogenization of raw materials in the process of depositing and taking raw materials, so that the raw material storage yard has the functions of storage and homogenization.

2, raw material preparation

In the cement production process, at least 3 tons of materials (including various raw materials, fuels, clinker, mixture, gypsum) should be ground for every ton of Portland cement produced. According to statistics, the dry cement production line needs to be consumed. The power accounts for more than 60% of the power of the whole plant, of which raw material grinding accounts for more than 30%, coal grinding accounts for about 3%, and cement grinding accounts for about 40%. Therefore, rational selection of grinding equipment and process, optimization of process parameters, correct operation, and control of operating systems are of great significance for ensuring product quality and reducing energy consumption.

3, raw material homogenization

In the production process of new dry process cement, the stable raw material composition is the premise of stable clinker burning heat processing, and the raw material homogenization system plays the last role of stabilizing the raw material composition.

4, preheat decomposition

The preheating and partial decomposition of the raw material are completed by the preheater, instead of the partial function of the rotary kiln, the length of the return kiln is shortened, and the gas heat exchange process in the kiln is carried out in a stacked state, and moved to the preheater in a suspended state. Under the process, the raw material can be fully mixed with the hot gas discharged from the kiln, the contact area of ​​the gas material is increased, the heat transfer speed is fast, and the heat exchange efficiency is high, thereby improving the production efficiency of the kiln system and reducing the heat consumption of the clinker. purpose.

(1) Material dispersion

80% of the heat transfer takes place in the inlet pipe. The raw material fed into the preheater pipe, under the impact of the high-speed updraft, the material turns and moves with the airflow while being dispersed.

(2) Gas-solid separation

When the airflow carries the powder into the cyclone, it is forced to rotate in the annular space between the cyclone cylinder and the inner cylinder (exhaust pipe), and moves downward while rotating, from the cylinder to the cone It can be extended to the end of the cone and then turned up and up, and discharged by the exhaust pipe.

(3) Pre-decomposition

The emergence of pre-decomposition technology is a technological leap in the cement calcination process. It is a decomposing furnace added between the preheater and the rotary kiln, and a flue gas is used to raise the flue by the kiln tail, and a fuel injection device is provided to make the exothermic process of burning the fuel and the endothermic carbonate decomposition process. The furnace is rapidly carried out in a suspended state or a fluidized state, so that the decomposition rate of the raw material into the kiln is increased to 90% or more. The carbonate decomposition task originally carried out in the rotary kiln is moved to the decomposition furnace; most of the fuel is added from the decomposition furnace, and a small part is added by the kiln head, which reduces the heat load of the calcination zone in the kiln and extends the lining. The material life is beneficial to the large-scale production; due to the uniform mixing of the fuel and the raw material, the fuel combustion heat is transferred to the material in time, and the combustion, heat exchange and carbonate decomposition processes are optimized. Therefore, it has a series of excellent performances and features such as high quality, high efficiency and low consumption.

5. Firing of cement clinker

After the raw material is preheated and pre-decomposed in the cyclone preheater, the next step is to enter the rotary kiln for clinker firing.

In the rotary kiln, the carbonate is further rapidly decomposed and a series of solid phase reactions occur to form minerals in the cement clinker. As the temperature of the material rises, the minerals become liquid, and are dissolved in the liquid phase to react to form a large amount (clinker). After the clinker is fired, the temperature begins to decrease. Finally, the high temperature clinker discharged from the rotary kiln is cooled by the cement clinker cooler to the temperature that can be withstood by the downstream conveying, storage and cement grinding, and the sensible heat of the high temperature clinker is recovered, and the thermal efficiency and clinker quality of the system are improved.

6, cement grinding

Cement grinding is the last step in cement manufacturing and the most energy-intensive process. Its main function is to grind cement clinker (and gelling agent, performance adjusting material, etc.) to a suitable particle size (expressed by fineness, specific surface area, etc.) to form a certain particle gradation and increase its hydration area. Accelerate the hydration speed to meet the requirements of cement slurry condensation and hardening.

7, cement packaging

The cement is shipped in both bagged and bulk shipping modes.

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Active lime is produced from limestone dolomite chalk and other minerals with high calcium carbonate content by the calcination process under the temperature of 1000-1100 ° C. There are various processes for the active lime production mainly

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