The cement mill is undoubtedly an important piece of equipment in the cement grinding station, and its quality directly determines the quality of the cement. Recently, a customer wrote to inquire about the cement mill upgrade solution. The customer said that his cement mill has only been used for two years, and the fineness of the finished cement appears to be coarse. What should I do?
AGICO CEMENT is committed to solving various problems related to cement production equipment for customers. We design cement production lines for customers and provide related configuration equipment, including the supply of related accessories. In addition, some customers are not satisfied with the existing production lines or cement production equipment. Satisfied, we also provide customers with cement plant upgrading and transformation services.
Whether the cement fineness is too coarse mainly depends on two indicators – specific surface area and sieve residue. We found two cases of cement plants that had similar situations and found that they were eliminated in sections and conducted multiple experiments to find out the problem. We use two cases to learn how to adjust the fineness of the cement mill.
Cement mill upgrade case-1
The first cement plant has qualified specific surface area. The 45-micron sieve residue has increased from less than 17% to 21%, and the 80-micron sieve residue has increased from less than 3% to 3.2%-3.6%. The cement quality is obvious. Affected, measures must be taken to ensure production, so we started to solve the problem from the following aspects.
Adjust grinding capacity
The sieve residue was too large, but the cement specific surface area was normal, so the first guess was that the grinding capacity was insufficient, so a steel section was added to the main grinding chamber. The 45 micron sieve residue dropped, but the 80 micron sieve residue was still around 4%. Failure to meet the standard of less than 3%.
Reduce the fan speed
Due to the phenomenon of ball wrapping before, the wind speed was adjusted from 650r/min to 1000r/min. However, the adjustment of the wind speed shortened the residence time of the materials in the mill and the grinding was not sufficient, so the wind speed was adjusted to 725r/min. After this move, the cement quality still did not meet the standard, but in order to prevent the balling phenomenon, the wind speed could not be reduced any further.
Adjust the grinding screen grate seam
In order to solve the problem of ball wrapping, the grate seam was adjusted from 4mm to 6mm, so it was guessed that the residence time of the material in the mill was affected, so it was adjusted back, but the cement fineness was still a little different from the standard requirements.
Check the variety and dosage of mixed materials
None of the previous changes solved the problem, and finally the problem was found in the type and dosage of mixed materials.
The company’s cement mixing materials have always used fly ash and dry slag (water slag mixed with limestone). Later, due to insufficient supply of fly ash and considering cost issues, it began to mix slag powder into the mill. When the slag powder content was less than 5%, the grinding conditions were still within the controllable range. However, after the content was increased to 15% ± 1%, the cement screening amount gradually exceeded the standard. After ball washing and grinding, the balling phenomenon was eliminated. Production returned to normal.
After testing, the dosage of slag powder should be around 5% ± 1%. With the participation of a small amount of fly ash, the slag powder content can be increased to about 13% ± 1%.
Cement mill upgrade case-2
The second cement plant also had a sudden increase in screen residue, which affected the cement quality, and began to seek solutions.
Reduce the fan speed
The method used is the same as the first one, but the effect is not obvious.
Reduce the grinding particle size of materials
The feed particle size had been increased from 12.29mm to 24.11mm due to work reasons. Now the feed particle size has been reduced and adjusted to 11.08mm, but the screen residue situation has not improved.
Adjust the grate seams of the partition board
The grate seams of the partition plate are the same as those of the first mill and screen. They are used to control the grinding time of materials in the mill. The inspection found that the grate seams of the partition plate were seriously blocked, so the partition plate was replaced and steel was added. ball to improve the grinding capacity of the equipment.
Check the powder separator system
The powder selector controls the fineness of the powder, so after the fineness becomes coarser, the powder selector will be the key inspection object. Finally, it is found that there is no abnormality in the powder selector.
Reduce production output
The purpose of reducing production output is to consume some of the large clinker particles in the mill, but the phenomenon of substandard sieve residue still exists.
Replace the air chute canvas of the powder selection machine
Various inspections and adjustments still did not work, so the powder selection system was re-inspected. Finally, it was found that the air duct of the chute of the powder selection machine was blocked and the canvas near the entrance was damaged. The air chute canvas was replaced. After the material flow rate was stabilized, the return material fluctuated. It tends to normal, but the sieve residue is getting larger and larger.
Clean laboratory testing water screen
Finally, it was found that the problem lay in the laboratory inspection water screen. After cleaning with acid, the screen residual value of the grinding material returned to normal.
To sum up, we found that when the cement mill has a coarser fineness, we can first adjust the fan speed, add steel balls or steel rods to increase the grinding capacity, adjust the partition plate or the grate slits of the grinding screen to observe whether the production of the cement mill is normal. . Then adjust the feed ratio, production output, etc. according to your actual production situation, and finally make detailed adjustments.
The above cases are only a small part of our many cement equipment upgrading and transformation projects. If you have any questions about cement equipment upgrading and transformation, please feel free to consult us.
