Trial Application Effect of Rubber Lining at End of Ball Mill of China Aluminum Guangxi Branch

17-06-2019

Authors:Kosga engineering technology Gloria Li


The mill system of alumina plant of China Aluminum Guangxi Branch has been using steel liner since it was put into operation. The production practice for many years has proved that the steel liner has poor wear resistance, short life, high weight, high energy consumption, high noise, slow installation of liner and many dangerous factors, high cost and poor economic benefit.

Rubber liner is a kind of macromolecule compound. The synthetic rubber with high elasticity and excellent wear resistance is chosen as the main body, and a certain proportion of natural rubber is added to obtain good dispersion, uniformity and co-vulcanization. Kosga's company proves that the use of rubber liner can prolong the life of liner, reduce costs, reduce the labor intensity of maintenance workers, improve the operating environment of operators, and produce good economic and social benefits.


1. Grinding process and operating conditions

The ore used in the alumina plant of China Bauxite Guangxi Branch is diaspore bauxite, which is the hardest, most difficult to grind and most insoluble bauxite known. The wear of liner is caused by impact, abrasion and corrosion. It is observed that the steel balls and materials brought up by the rotating cylinder begin to fall from about 2 meters high, which has a great scouring force on the end liner. The steel liner can not bear the erosion and wear of the material under such bad working conditions, so its life is short.

Fig. 1 is a sketch of the grinding system operation flow. According to the characteristics of bauxite ore in Guangxi Branch of China Bauxite, Kosga developed a new grinding process of one stage bar grinding, two stage ball grinding and slurry classification using hydrocyclone. Qualified ore pulp is obtained by rod mill, ball mill grinding and hydrocyclone classification and sent to high pressure digestion. The overflow mill is used to 3600x8500m.


2 Problems

ZG32Cr2SiMnMoTiRe steel liner was used at the end of ball mill. The liner has a shorter service life, with an average service life of 3642 hours, while the cylinder liner has a service life of 7600 hours. The life of the end liner is different from that of the cylinder liner, which makes it difficult to replace the end liner.When replacing the end liner, 130 tons of steel balls in the mill are discharged, and the workload of refilling steel balls is very heavy. At the same time, manganese steel plate is often used in the later stage, because of loose bolts and leakage of ore in the cylinder, it has to stop processing. Frequent start-up of the mill not only affects the production efficiency, but also easily causes equipment damage. In addition, the annual consumption of spare parts, maintenance costs are higher.

Ball mill rubber lining

3. Use of rubber liner at the end of ball mill

Pre-test

In order to solve the problems of short service life and difficult replacement of end steel liner, in May 2014, China Aluminum Guangxi Branch and KOSGA Industrial Company jointly formed a key research group to change end steel liner of ball mill to rubber liner. The application technology of the two kinds of liner was compared and analyzed, and some physical phenomena of the two kinds of liner were measured. The test and monitoring showed that the steel ball had greater resilience when it fell to the rubber lining board. The test steel ball fell from 1 meter height to the rubber lining board, and its rebound height was 200 mm to 250 mm, while there was almost no rebound when it fell to the steel lining board. The wear of liner is caused by impact, abrasion and corrosion. The steel balls and materials brought by the rotating cylinder drop from about 2 meters high, which has a great impact on the end liner, while the rubber liner has a strong resilience and wear resistance. By comparison, in January 2015, the trial of replacing steel liner with heat-resistant and acid-alkali-resistant rubber liner at the feed end of No. 1 ball mill was carried out. Fixed liner was installed with original bolt holes. Some unused bolt holes were blocked with rubber blocks to prevent leakage in operation, and the mill barrel did not need to be changed.


4 Use effect

It is found that the corrosion resistance and wear resistance of rubber liner are superior to that of steel liner. The average service life of end liner of ball mill after using rubber liner is 8609 hours, which is 2.4 times as long as that of steel liner. The application of rubber liner in the industrial and mining conditions of high temperature, high alkali concentration and high hardness of raw material grinding in China Aluminum Guangxi Branch has been proved to be feasible over the past two years. The use of rubber liner has the following advantages:

(1) Extend the service life of liner greatly, reduce the consumption of liner and save the cost of spare parts;

(2) The time of replacing liner during shutdown is shortened, and the utilization rate of ball mill is increased.

(3) The single weight of rubber liner is about 50kg, which is much lighter than 205KG of steel liner, so it can reduce the difficulty and labor intensity of replacing liner and improve the safety of installing and replacing liner.

(4) Reduce the number of mill failure downtime. Frequent start-up of ball mill not only affects production efficiency, but also easily causes equipment damage. After changing rubber liner, the problem is solved better.

(5) Reduce power consumption. The weight of rubber liner is 9 tons lighter than that of steel liner, which can reduce the load of motor and reducer and improve the operating conditions of driving mechanism.

(6) It can prolong the service life of other running parts of the mill, such as large ring gear.

(7) Reduce noise and improve working conditions on site.


5. Economic Benefit Analysis

Kosga Engineer Statistics.The running time of the three mills is 9725 hours per year./pcs


6. Calculating the annual consumption of spare parts and overhaul fees for the end steel liner of the three billiard ball mills before transformation

Average Service Life of Steel Lining Plate at End of Ball Mill: 3642 Hours/Table


Total replacement quantity of end steel liner plate of ball mill: 9725 hours to 3642 hours/set = 2.67 sets/year price of end steel liner plate of ball mill: 95248 yuan


Total cost of spare parts for end steel liner of ball mill: 2.67 x 95248= 254,312 yuan/year


Overhaul cost of end steel liner of ball mill: 2.67 x 9800= 26,166 yuan/year


Total consumption of spare parts and overhaul cost for end steel liner of ball mill: 254,300 + 26,200 = 280,050 yuan/year


Annual Consumption Spare Parts and Maintenance Cost Calculation of Ball Mill End Replaced with Rubber Lining Plate


Average service life of rubber liner at end of ball mill: 8609 hours/set


Total replacement amount of rubber liner at end of ball mill: 9725 hours to 8609 hours per unit = 1.13 units per year


The price of rubber liner at the end of ball mill is 82133 yuan per unit.


Total cost of spare parts for rubber liner at end of ball mill: 1.13 x 82133 = 92800 yuan / year


Overhaul fee for rubber liner at end of ball mill: 1.13 x 4500 = 5,085 yuan/ year


Direct economic benefit of ball mill end replaced with rubber liner 280,500 - 97900 = 182,600 yuan /year


After using rubber liner, the service life is greatly prolonged, the labor intensity of liner replacement is reduced, the danger of operation is reduced, the operation rate of mill is increased, the production of alumina is stabilized, the cost of spare parts and the consumption of electric energy are further reduced, and good economic and social benefits are produced, which is helpful for the popularization of rubber liner in other mills. Use provides reliable protection

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