Customer case

Case of technical transformation in cement mill

• 2024-09-19
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Our company carried out technical transformation in the first and second warehouses of a cement plant's grinding mill, which doubled the production capacity and reduced the cost. Let's introduce it in detail below.

Production data before technical transformation:

Cement ratio: 75% clinker + 4.5% desulfurized gypsum + 5% limestone + 7% slag + 8.5% fly ash, average production capacity of finished products: 260t/h@ratio: 370±15m2/kg; R45μm: 5%, mill work: about: 3275KW

The length of the first warehouse is ~4080mm, and it is currently a medium-wave stepped liner. The steel ball grading is: φ25mm=29t; φ20mm=22t; φ17mm=18t, the average ball diameter is 21.3mm, the theoretical filling rate is 31.2%, and the actual filling rate on the day is 29.96% (with material).

The length of the second warehouse is ~9000mm. It is currently equipped with four small corrugated lining plates and four ball retaining rings. The steel ball grading is: φ20mm=20t; φ17mm=59t; φ15mm=41t; φ12mm=34t, the average ball diameter is 15.8mm, the theoretical filling rate is 30%, and the actual filling rate on the day is 27.22% (with material).

First warehouse-feed end lining

It has just been replaced and is in good condition. The end lining adopts a lifting bar design to increase wear resistance. However, the lifting bar design will aggravate the deformation of the steel ball, and in this belt roller press cement mill system, the diameter of the steel ball is not large, so it is not necessary. It is recommended to use a flat end lining to thicken it to 90mm in the later stage.

First warehouse lining

The form is a medium-wave stepped lining, which is currently severely worn and has obvious wear grooves on the lining. This kind of grinding groove will aggravate steel wear and deformation, and the maximum lifting height of the lining is insufficient. It is recommended to replace it.

Condition of grinding body in bin 1

Steel balls are used in bin 1, which is in normal condition. The breakage and deformation rate of steel balls is normal, and the average ball diameter is visually smaller. Actual bin length: ~4080mm

Block plate on bin 2: The anti-blocking grate plate design is also adopted, and the sieve slot opening is the same as that on bin 1. The wear condition is normal, and there is obvious blockage.

Block 2 lining

The form is a four-wave small corrugated lining plate plus a four-circle ball retaining ring. The small corrugated lining plate has obvious wear, and the corrugation has been sharpened. The ball retaining ring is seriously worn and has reached the limit thickness. The height of the ball retaining ring is about 755mm, and the lower hole height is about 250mm.

Condition of grinding body in bin 2

Steel balls are also used in bin 2, and there is obvious ball wrapping phenomenon. The wear and deformation rate of steel balls is normal. The measured length of the second bin: ~9000mm

The main idea of technical transformation in the mill:

The lining form is optimized, and our company's new lightweight wear-resistant lining is adopted. The following plan has detailed descriptions;

The steel ball grading is too compact and easy to cause ball sticking, which needs to be fine-tuned. Our company will provide a reference plan for steel ball grading according to the final lining form;

Change the operating habits and avoid the vicious cycle of excessive cyclic load as much as possible.

In-mill transformation plan:

1. Replace the lightweight combined groove lifting lining in the first bin

The lightweight combined groove lifting lining is mainly used in the first bin of the cement mill with roller press. Because the in-mill ratio table of the roller mill combined grinding system has a detailed improvement, the size of the steel ball in the first bin is relatively smaller, so the first bin needs to reduce the crushing function, and at the same time, the grinding effect should be improved to a certain extent.

The lightweight combined groove lifting lining is a combined lining, which consists of two grooved lifting linings of different heights. The maximum height difference between the two liners is about 15mm, which drives steel balls of different sizes and levels during the operation of the mill, giving full play to the grinding efficiency of the steel balls.

The lightweight combined groove lifting liner is made of high chromium alloy through multiple heat treatment processes. It has high hardness, uniform texture inside and outside, good wear resistance, and excellent impact resistance, which ensures the stability and safety of the liner during use. At the same time, our company's liner is finely made, the technical standard far exceeds the national standard, the liner is light, and the average weight is only 31kg/piece, which reduces the customer's mill load to a certain extent and helps customers reduce energy consumption.

Features of lightweight combined groove lifting liner:

-The liner height is designed according to the characteristics of the mill, which is lighter than other domestic lifting liners;

-Good wear resistance, high hardness, up to 53HRC, and uniform hardness inside and outside, with small hardness deviation inside and outside;

-The product has a long service life. In the case of a remaining height of 20mm, the belt roller press combined grinding system can reach more than 6 years;

-For use with roller press mills, it increases the grinding effect;

-With a groove design, it specifies the running trajectory of the steel ball and improves the effect of one bin.

2. Replacement of lightweight functional corrugated lining with interval activation ring design in the second bin

The lightweight functional corrugated lining is a new type of corrugated lining. While providing the necessary power for the grinding movement of the steel ball, it can help the steel ball "absorb" excess materials and "release" the finer materials to the control, forming a certain material curtain, allowing the air flowing in the mill to sort, allowing the finer materials to flow further to the end of the mill, and the coarser materials to fall into the steel ball for further grinding. Its main features are as follows:

-Long service life, with an average life of more than 60,000 hours.

-The lining material is high chromium alloy, which has high hardness, good wear resistance, small internal and external hardness deviation, can maintain long-term grinding effect, and is more suitable for closed-circuit mill use.

-The average thickness of the lining is 40mm, which increases the effective volume of the mill.

-Easy to install, safe to carry, and simple to maintain.

After the technical transformation, the total weight of the cylinder liner has been reduced by 26 tons compared to the current weight, a decrease of about 31%, which greatly reduces the mill load and helps to reduce mill power consumption and protect mill slippers. In addition, the thickness of the liner after the technical transformation is thinner than the current liner, which effectively increases the effective grinding inner diameter of the mill and helps to improve production quality. At the same time, due to our company's unique design and high-quality high-chromium alloy material, the process performance of the liner is less reduced in the middle and late stages of use, ensuring stable production quality in the middle and late stages.

Under the condition that the main exhaust fan has sufficient air volume (the efficiency of the main exhaust fan is too low, and the actual air volume is less than 220,000m3/h, which cannot meet the demand for further production increase), if the liner plates, partition plates (not considering replacing the frame for the time being) and grate plates of the first and second bins are upgraded according to our plan, and the steel ball grading is adjusted accordingly, it is expected that the production can be increased by 8% (based on the current PO42.5 cement production of 260t/h) and the energy consumption can be reduced by 3%. Based on 7,000 hours/year, under normal circumstances, the profit per ton of cement is 50 yuan/ton, and the electricity fee is 0.6 yuan/kwh. Please implement it according to the actual situation of the company.