Summary:
The cement production line is a complex production line specializing in the production of cement. The production line is mainly composed of crushing and pre-homogenization, raw material preparation homogenization, preheating decomposition, cement clinker burning, cement grinding and packaging, and each process is independent and interconnected.
The cement production equipments mainly include: limestone crushing, vertical grinding, pre-homogenization, kiln tail, kiln, kiln head, coal mill, cement batching, packaging system, DCS control system, etc.
1. Crushing and pre-homogenization
(1) Crushing
In the cement production process, most of the raw materials need to be crushed, such as limestone, clay, iron ore and coal. The consumption of limestone is very large in the cement production. After mining, the particle size is large and the hardness is high. Therefore, the crushing of limestone plays an important role in the material crushing of cement production.
(2) Raw material pre-homogenization
Pre-homogenization technology is to use scientific stacking and reclaiming technology to realize the initial homogenization of raw materials in the process of storing 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 three tons of materials (including various raw materials, fuels, clinker, mixture, gypsum) should be ground for one ton of silicate cement production. According to statistics, in the dry cement production line, the power consumption of grinding is about 60% of the whole plant power, 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 process of new dry cement production, stable raw material composition is the precondition of stable clinker burning thermal system, and the raw material homogenization system plays the final role in stabilizing the raw material composition.
4. Preheating decomposition
The preheating and partial decomposition of cement raw material is finished by preheater, which replaces partial function of the rotary kiln to shorten the length of the rotary kiln, and at the same time, the gas heat exchange process is carried out in the kiln 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 exchange 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 burning.
(1) Material dispersion
80% of the heat exchange 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 upward 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 upward and discharged by the exhaust pipe.
(3) Predecomposition
The emergence of predecomposition technology is a technological leap in the calcination process of cement equipment. Add a decomposing furnace between the preheater and rotary kiln, and set up fuel injection device by means of raising flue at the end of kiln to make the exothermic process of fuel burning and the endothermic process of carbonate decomposition be carried out rapidly in a suspended or fluidized state in the decomposition furnace, so that the decomposition rate of the raw material fed into the kiln is increased to 90% or more. Most of the fuel is added from the decomposition furnace, and a small part is added from the kiln head, which reduces the heat load of the calcining zone in the kiln and prolongs the life of the lining. In addition, the fuel and the raw material are evenly mixed, and the fuel combustion heat is transferred to the material in time, so that the combustion, heat exchange and carbonate decomposition processes are optimized. Therefore, it has a series of excellent performances such as high quality, high efficiency and low consumption.
5. Cement clinker burning
After the raw material is preheated and pre-decomposed in the cyclone preheater, the next step is to enter the rotary kiln for clinker burning.
In the rotary kiln, the carbonate is further rapidly decomposed and a series of solid phase reactions occur to form the cement clinker. 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, so that the thermal efficiency of the system and the quality of the clinker are improved.
6. Cement grinding
Cement grinding is the final step in the cement production, and it is also a process consumes a lot of electricity. 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 delivered in bagged or bulk.
Technology innovation:
1. High level of production technology
The entire cement production process is highly automated, high quality, environmentally friendly, safe and trouble free.
2. Good product quality
The production line homogenizes raw material components, reduces quality fluctuations, facilitates the production of higher quality clinker and stabilizes the production of the burning system.
3. Rational equipment configuration
The main equipment rotary kiln in the production line has rapid heat transfer, high thermal efficiency, larger yield per unit volume than wet cement production, low heat consumption, energy saving and high efficiency.
4. Low energy consumption
The unique design of the decomposition furnace and burner improves the utilization rate of the tertiary air at a temperature higher than 900°C, so that the heat consumption of the clinker burning is reduced by 2-3% compared with the pre-decomposition line of the same specification.
Process flow chart:
Successful cases: