As a large metal mine, Daye Nonferrous Tonglushan Copper Iron Mine was designed to process and produce 1.32 million tons last year. Three sets of φ 5500 * 1800 SAG mill and 2700 * 3600 ball mill respectively form three production series. The feed size of SAG mill is 350mm, and the hardness of ore is f = 8-16. In the process of mineral processing, SAG mill has many problems, mainly related to manganese steel lining plate short life, large noise and high energy consumption. It also owns a negative impact on the smooth progress of production and the physical and mental health of employees. In view of the above problems, Tonglushan Iron Mine began to use SAG mill and ball mill rubber liner produced by Kosga industrial based on Sweden Skega technology in 2010.
1.Current Application of Manganese Steel Liner
Before using mill rubber liner, the manganese steel liner was used in Tonglushan iron mine. Several years of practical production still reflects the following shortcomings.
1.1 Short service life & large installation labor load
The larger ore size can not meet the requirements of stable operation of SAG mill. To keep up with the process conditions, a certain amount of steel balls are added into SAG mill to strengthen grinding. In this way, the impact between the large ore and the steel ball accelerates the wear of the lining plate. According to Kosga statistics, the average service life of SAG mill manganese steel liner is only 2050 hours, and three sets of liner need to be replaced every year. The weight of each set is 46 tons. Among them, the maximum is half a ton and the minimum is 260 kg. It takes 8-10 days to replace one set, which has a serious negative impact on production and increases the labor intensity of workers.
1.2 Frequent interruption on working SAG MILL
SAG mill is operated in wet condition. The small range elastic deformation and rapid wear of manganese steel liner lead to frequent leakage of screw hole. Stop the machine to tighten the liner screws, causing frequent work interruption of SAG mill. According to the statistical data of several years, it is necessary to stop the machine and fasten the bolts every 28 hours. Repeated and frequent shutdown and start-up reduce the output and equipment operation rate. The service life of 800 kW Synchronous Motor is also shortened.
1.3 Big noise
Kosga industrial uses ND2 precision sound level meter to measure. The noise of single series SAG mill and ball mill running at the same time is 96dB (a), which is mainly caused by the impact of large ore and steel ball on manganese steel. Big noise causes harm to the physical and mental health of equipment operators and management difficulties.
2.Advantages of Mill Rubber Liner
After using over one year, mill rubber liner has more advantages than manganese steel liner.
2.1 Extend service life & reduce cost of liner
SAG mill of grinding floating I was installed at the end of 2010 and put into operation on January 7, 2010. The equipment has been running normally without stopping due to liner failure. Up to the end of March 2010, the autogenous mill has operated for 6,545 hours and processed 392,650 tons of raw ore. The test results show that the wear of cylinder liner with high and low lifting bars is slight, while the wear of lifting bars is large. The service conditions of mill rubber liner show that when the wear of mill lifting rod changes from high to low, replacing shell lifting rod at ore inlet and mill end outer ring lifting rod at discharge end is beneficial to keep shell liner with high and low lifting rod structure. One set of lining plate can match with two sets of end outer ring and shell high lifting rod. As a result, Tonglushan mine has replaced the worn mill lifting rod at the end of September 2011. The test results show that the liner can still work for 2,000 hours at the current wear rate. The service life of a set of mill rubber liner can reach 8,500 hours, which is more than 4 times of the service life of manganese steel liner. The reason why mill rubber liner can greatly improve its service life is due to its ability to mitigate the impact of ore and steel ball, and has strong wear resistance and corrosion resistance.
2.2 Improve equipment operation rate at lower energy consumption
The mill rubber liner with good elasticity and wear resistance can greatly reduce the slurry leakage caused by bolt loosening. According to the application statistics, the shutdown fastening bolt only occurs once or twice a month, reducing more than 40 hours. In addition, one set of rubber liner is equivalent to four sets of manganese steel liner, and the replacement cycle of mill rubber liner is short, and the replacement time is reduced by about 40 days. Therefore, the application of mill rubber liner can improve the operation rate of SAG mill equipment by nearly 18%. SAG mill is driven by an 800 kW motor at 15 rpm. Grinding can be achieved by friction and collision between lifted and thrown ores. Manganese steel liner weighs 46 tons, while mill rubber liner weighs only 15 tons. 2/3 less weight greatly reduces power consumption. In practical application, the power consumption of manganese steel liner is 10.11 kwh per ton of raw ore, while that of mill rubber liner is 7.13 kwh per ton of raw ore. The power consumption decreases by 29.47%.
2.3 Reduce industrial noise and improve working environment
The original manganese steel liner has bigger noise and higher frequency. ND2 is measured by precision sound level meter. The noise of SAG mill ore dropping area is 9.6 dB, which is harmful to the physical and mental health of mill operators and difficult to control. Ball mill with rubber liner has better shock absorption and sound insulation, and reduces noise. The test result is 90 dB. The equipment absorbs the high frequency part of the noise, and the reduced 6 dB can greatly improve the operating environment of the staff. For maintenance, the original liner should be replaced in SAG mill shell, and the maximum single piece weight is half a ton. Average piece is more than 260 kg. The maximum single weight of mill rubber liner is only 120 kg, and the general parts are only 30 kg, which brings great convenience to the installation and greatly reduces the working strength.
3.Technical and Economic Comparison between Mill Rubber Liner and Manganese Steel Liner
The mill rubber liner, which replaces the manganese steel liner, can run for 42 days, or 1,008 hours per year. With 90% operation rate and 60 tons of processing capacity, 54,432 tons of ore can be handled more. In terms of energy consumption, 974,000 kwh has been saved in 1991.
The application of Kosga industrial SAG mill rubber liner in Tonglushan iron mine shows that: mill rubber liner has better wear resistance, corrosion resistance, shock absorption, sound insulation, light weight, low maintenance, low power consumption and noise reduction performance with more than four times of service life compared with manganese steel lining plate. After using mill rubber liner, there is almost no slurry leakage in screw hole, which improves the operation rate of SAG mill and is conducive to safe and civilized production.
In conclusion, based on the development of science and technology, Kosga will continuously improve the wear-resistant materials to up the performance of mill rubber liner. Comparing with the traditional manganese steel liner, many advantages will broaden the application of SAG mill