[Vertical Grinding Technology] Discussion on the Application of Grinding Aid in Cement Vertical Mill

Date: 2019-07-01 Views:

I. Overview

Cement grinding aid is a process admixture added during cement grinding. The addition of grinding aid can improve the cement grinding process and improve production efficiency without compromising cement performance. The purpose is to reduce production cost and improve cement quality. The use of grinding aids has a good improvement in cement strength, water demand, setting time, fluidity and other quality indicators as well as the suitability of cement.

The earliest appearance of grinding aids is mainly based on the ball milling process. The theoretical starting point of how to disperse the material particles is that the traditional grinding aids are mainly suitable for the ball milling process.

With the continuous improvement and improvement of vertical mill technology, it has changed the situation that the former vertical mill is only used for grinding raw materials in cement enterprises, and has gradually been approved for use in cement enterprises with unique advantages. Therefore, grinding aids adapted to the cement vertical grinding process have also emerged.

Second, the superiority of vertical grinding

Compared with the ball milling process, vertical grinding has significant advantages. It is accepted by cement companies because of its simple process, small footprint, high grinding efficiency and low energy consumption.

Compared with the ball mill, because there is no steel ball and steel section, the vertical grinding naturally avoids the impact and wear between the metal, the metal wear is small, the noise is low; and because it is the wind-sweeping grinding, its own powder-selecting function It avoids the phenomenon of over-grinding, thus reducing the consumption of useless work, and the grinding efficiency is high. Compared with the ball-milling system, the power consumption of grinding is only about 60% of the latter; it also has a simple process flow and a large single-machine output. The material has large particle size, good sealing performance, and no negative dust operation.

In terms of quality control, the finished product quality control is fast and the replacement product is flexible. The residence time of the material in the vertical mill is about 3 minutes, while the ball mill takes about 30 minutes. Therefore, the quality control index of the product when the cement is ground by the vertical mill can be quickly measured and corrected, and the fluctuation of the product composition is small. However, the short residence time of the material in the mill is also one of the drawbacks of the vertical mill for grinding cement. Since the residence time of the material in the vertical mill is very short, the qualified powder is quickly pulled out by the wind and selected as the finished product. The particle distribution is extremely narrow, the ultrafine particles are too small, and the particle distribution lacks complementarity, so the applicability to the cement is certain. Impact. On this issue, the following aspects can be solved. First, continuous improvement and improvement of vertical grinding technology to adapt to cement performance requirements; second, improve production process control, improve product quality with high operation level; third, with cement plus Improves the quality and suitability of cement.

Third, the difference between grinding aids used in the vertical grinding process and the ball milling process

The invention of cement grinding aids originates from the cement ball milling process. Based on the theory of dispersed material particles, the complex chemical or physical mechanism generated by the mixture of organic, inorganic or organic substances and inorganic substances and surfactants is used to solve the ball mill in powder. Electrostatic adsorption, flocculation, and crack healing in the process of grinding cement to achieve the purpose of increasing production, reducing energy consumption, and improving cement quality.

The vertical grinding process and the ball milling process are very different. The grinding aid used in the ball milling process mainly disperses the material, improves the looseness of the material, has a fast flow rate, and has high grinding efficiency. The vertical grinding process is just the opposite. The material flow rate is fast, and the residence time in the grinding is short. If the material is too loose, it is suspended in the grinding chamber under the action of the wind, and the grinding roller cannot be fully milled on the grinding disc. Therefore, the vertical grinding is performed. The use of improper grinding aids in the process is not conducive to the improvement of production and cement quality.

Fourth, the use characteristics and regulation of grinding aid in cement vertical grinding process

It is well known that both the ball milling process and the vertical grinding process have certain characteristic reactions in the process when using the grinding aid. The ball milling system is solved by adjusting the internal ventilation, the speed of the classifier, the grading of the steel ball (segment), and the filling rate of the grinding bodies of each bin. Although the vertical grinding system process is simple, the process parameter control is relatively complicated. Therefore, when the grinding aid is used, the process parameters should be adjusted in time.
The reason and treatment of the rough running fineness. The vertical grinding process uses a grinding aid mainly to stabilize the layer and fully grind it to make the distribution of cement particles more reasonable, so as to improve the strength of the cement and improve the applicability of the cement. Controlling fineness and increasing specific surface area are fundamental. The process parameters should be adjusted immediately when the fineness is rough. The first is to adjust the speed of the powder selection device, adjust the speed, but to control within a certain range, not blind; second is the adjustment of ventilation. The amount of ventilation plays a vital role in the control of cement quality. It mainly shows that when the ventilation volume is small, a large amount of qualified cement can not be pumped away in time, resulting in an increase in the amount of internal circulation, and the excessive air volume leads to excessive fineness. After using the grinding aid, the physical properties of the material change. Under normal circumstances, the air volume should be adjusted to reduce the wind speed to meet the quality control requirements. Third, the grinding pressure is small. When the grinding pressure is low, the material cannot be effectively milled on the grinding disc. Many coarse particles cannot be crushed due to the small grinding pressure. The pressure of the grinding roller can be given in the middle control. Generally, the pressure is set to be minimum when grinding, and as the output increases, It must be gradually pressurized, otherwise it will run rough because of the lack of ability to crush and grind. In addition, the unstable material and the poor wearability of the milled material will also affect the fineness.

Differential pressure control. Differential pressure is an important parameter for the balance of the vertical mill system. Only a stable differential pressure can contribute to the improvement of production and quality. After the grinding aid is added, the material characteristics change, and differential pressure changes may occur, mainly caused by changes in system wind and internal circulation. Fluctuations in differential pressure may cause system instability, which may be through system wind, feed volume, The adjustment of the grinding pressure is solved to ensure a stable differential pressure.

Control of mill vibration. Mill vibration is the dominant factor affecting production and quality. It mainly shows that the material layer is too high and too unstable, and the grinding material has large particle size and poor wearability. The presence of iron materials can also cause vibration. In the event of mill vibration, the parameters should be adjusted immediately to avoid the machine jumping. In general, the thickness of the layer and the grinding pressure are adjusted to control the balance of the material.

Adjustment of the grinding pressure. After using the grinding aid, as one of the important parameters of the system balance, the grinding pressure will change, and the grinding pressure also has a great influence on the feeding amount. When the grinding pressure is too large, the grinding vibration will increase due to the too thin layer; when it is too small, the material layer will be too thick, and the material cannot be effectively milled on the grinding disc. Many coarse particles cannot be crushed due to small grinding pressure. Grinding, the internal circulation increases, the slag has more differential pressure, which reduces the grinding efficiency and the fineness becomes coarser. Therefore, the grinding roller pressure can be appropriately adjusted according to the working conditions and the fineness of the grinding cement, which is beneficial to the production and quality. Improvement.

Vertical mill outlet temperature regulation. The temperature change of the vertical mill outlet reflects the residence time of the material in the mill. When the outlet temperature is too low, the inner layer of the mill is thickened, the power consumption of the grinding main motor is large, and the high temperature will cause the material layer to be too thin. Machine vibration will also have an impact on production quality. Under normal circumstances, adjust the circulating air or cold air baffle to control the outlet temperature.

The point of addition of the grinding aid. Due to the unique characteristics of the vertical grinding process, the addition point and the joining method of the grinding aid are different from those of the ball mill. The ball milling cement process can be added to the grinding material according to the layout of the process according to the principle of simple and easy operation. The grinding aid and the material will be fully mixed evenly in the grinding. The vertical grinding process is different. It belongs to the wind sweeping. The material stays in the mill for only a few minutes. The fine material is not milled and selected as the finished product. Therefore, it is obviously not suitable for the vertical grinding process to use the grinding aid directly on the grinding material. First, the slag is coarse particles, and the granules are circulated in the mill for up to several tens of times. The grinding aids are more uniformly and effectively utilized by the particles into the mill. Second, the vertical grinding process and Different ball milling processes, the material enters the grinding machine and is laid on the grinding disc, which lacks the effective mixing and mixing of the material itself. Therefore, in the use, we have made the grinding aid tiled feeder, so that the grinding aid can be evenly added to the outer circulation material. .

In short, with the use of vertical grinding technology in cement production, jiangsu LVSSN will further develop and improve the grinding aids for vertical grinding, making it more suitable for the needs of vertical grinding cement technology, saving energy and reducing cement quality. Improve the quality of cement.

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