Cement grinding is one of the most important links in the cement production process, and the power consumption in the grinding process accounts for about 60-70% of the total energy consumption of cement production, of which the power consumption of the finished cement grinding accounts for 30~ 40%. The grinding process of cement is a process in which the particles of cement materials (such as clinker, mixed materials and gypsum) change from large to small, and it is also an energy conversion process that converts electrical energy into mechanical energy and then into cement powder surface energy, and the energy conversion efficiency It directly determines the energy utilization rate. How to improve the energy conversion efficiency in the grinding process has become a key demand for improving grinding efficiency or energy utilization.
Energy-saving and consumption-reducing effect of grinding aids in cement production
Improve cement grinding efficiency
The dispersion of grinding aids eliminates the agglomeration of cement particles in the mill, and the ground cement particles are transported out of the mill through the grate plate in time, reducing the phenomenon of over-grinding, improving the grinding efficiency of the mill, and assisting grinding The dispersion of the agent can greatly improve the phenomenon of paste balls and paste liners in the mill, thereby reducing the negative impact of the "paste layer" buffering effect on the grinding efficiency, and improving the conversion of mill electrical energy into mechanical impact energy. Efficiency; Under the condition of keeping the distribution of cement particles unchanged, the output of the mill can be increased, and the power consumption of the cement powder mill is reduced. The production effect of grinding aid is obvious, and when the amount of the same mixture is added, the strength of cement is also increased moderately. Our company began to use liquid grinding aids gradually in 2010, from the start of the small grinding test to the production of large grinding. Statistics show that after using grinding aids, the average table effect has increased by 3 to 5t/h, and the amount of the same mixture is added. The strength of cement is increased by 1~3MPa, and the grinding efficiency is obviously improved.
Improve cement fluidity and reduce cement transportation energy consumption
Due to the dispersion of the grinding aid, the film formed on the surface of the cement particles weakens the cohesion between the cement particles and the adhesion to the cement transportation and storage equipment, and the hydrodynamic properties of the cement are improved. After the addition of grinding aids, the fluidity of general cement has improved. As the fluidity of cement improves, it can bring many advantages: ① The reduction of cement flow resistance is not easy to hang on the wall and agglomerate, which increases the storage capacity of the cement warehouse, and does not need to be cleaned frequently, saving the cost of cleaning and increasing The use efficiency of the cement warehouse; ②Reduced flow resistance of the cement can shorten the transportation and loading and unloading time of the cement, and accelerate the transportation speed of the cement. Our company has done mathematical statistics for this purpose; ③It can reduce the cement wall and long-distance transportation vehicles. Waste caused by agglomeration of bagged cement, especially the phenomenon of agglomeration of bagged cement will cause unnecessary waste to users.
Improve cement specific surface area and product quality
High-efficiency composite cement grinding aids can increase the specific surface area of cement and accelerate the rate of cement hydration. Before using grinding aids, the average cement specific surface area of our company was about 330m2/kg. After using grinding aids, the average specific surface area of cement was increased to about 345m2/kg. The effect of the composite grinding aids to enhance the excitation component can effectively improve the cement strength. To improve product quality, when the cement output is unchanged, the cement mixed with grinding aid has an increase in strength of 1 to 3 MPa in the early and later stages compared to the cement without the grinding aid. With the improvement of cement strength, it can meet the production requirements of high-quality high-grade cement and improve the competitiveness of products. Due to the enhanced effect of grinding aids, the amount of clinker can be reduced when the cement is compounded. Our company calculated that the amount of clinker added can be reduced by 3% to 5%. In this way: ① can increase the amount of mixed materials, is conducive to the use of more low-grade industrial waste residues, reduce environmental pollution, reduce production costs, increase production and efficiency and can obtain good environmental benefits; ② with the reduction of clinker consumption Under the condition that the total output of cement remains unchanged, it can reduce the consumption of raw material resources and coal and electricity energy required for the production of clinker, and reduce the emission of CO2 and dust. It has good environmental, energy and social benefits; ③ The reduction of clinker consumption can reduce the heat of hydration of cement, improve the performance of products, and achieve energy saving and consumption reduction of buildings.
Effect of Cement Grinding Aid on Cement Powder Properties and Hydration Performance
The effect of cement grinding aid on the properties of cement powder
Adding cement grinding aids in the grinding process not only affects the properties of the cement powder itself, such as particle distribution and fluidity, but also changes the cement hydration process, slurry properties and various properties of the hardened cement stone. The differences in the chemical groups and structure of grinding aids determine the improvement in the particle gradation, particle morphology, specific surface area and angle of repose of the powder, which indirectly affects the powder fluidity.
Effect of cement grinding aid on cement hydration process and cement properties
In addition to the physical modification of the cement powder properties, the use of grinding aids also indirectly affects the hydration performance of the cement particles and the properties of the hydration products, mainly focusing on the changes in the hydration process caused by the change in the distribution of cement particles and The adsorption of chemical components on the surface of the powder particles causes changes in the reaction process of the particle surface and water contact, which in turn leads to changes in the cement hydration process and product and changes in the properties of the final cement hardened slurry. After the cement particles are mixed with water, various clinker minerals on the surface of the particles immediately start to dissolve and chemically react with the water to form hydrates; after the grinding aid as a surfactant is adsorbed on the surface of the particles, the mixing water is improved. The wetting and adsorption process of the particle surface accelerates the dissolution and hydration of each mineral phase in water.
In addition, various chemical components in cement grinding aids participate in the cement hydration process (such as the hydration of C3A, C3S, etc.) and cause changes in the properties of cement paste and cement stone. It can promote the conversion of AFt to AFm, optimize the pore structure and reduce the porosity. In addition, some of the chemical components of the grinding aids stimulate the potential activity of the mixed material due to the change of the ionic environment or the acidity and alkalinity in the slurry, and a secondary hydration reaction occurs, thereby changing the physical properties of the cement stone. The introduction of different grinding aids improves the slag hydration activity and at the same time increases the dissolution of calcium and silicon ions in the hydration system.