m. maleki moghaddam

Comminution is the most energy intensive operation which constitutes the major portion of operating and capital costs of the mineral processing plants.  Working at the maximum operating capacity of comminution equipment plays a significant role in the efficiency of the circuit.  Also, due to the effect of crusher efficiency on the downstream circuit performance, optimization of the crushing circuits has received considerable attention.  In this research, the effect of feed chute design on tertiary cone crusher performance at the Sarcheshmeh copper complex was studied.  A close monitoring of the performance crusher revealed that main problems were high fluctuations of power draw and uneven and high-rate wear of crusher liners.  Such pitfalls were clear evidences of an improper feeding arrangement into the crusher.  Accordingly, various feed chute designs were employed in the simulations by an in-house developed DEM software called KMPCDEM© to find more uniform feed distribution on the distribution plate of the crusher.  Results showed that by changing the shape of feed chute from cubic to cylindrical, decreasing its surface area from 0.34 to 0.24 m2 and increasing the cylinder length above and below the feed chute plate from 0 to 45 cm and from 53 to 95 cm, respectively, uniform feed distribution was obtained.  After installing the new feed chute design in the plant, a detail monitoring over a period of 15 months showed a reduction of the standard deviation of crusher power draw from 13 to 3 kW.  A better crusher control caused choke feeding.  Therefore, 36% increase in the crusher throughput and finer and narrower product size distribution occurred.  Furthermore, the life of crusher liners increased from 8 months to 15 months on account of more uniform and lower rate of wear on mantle and liners.

Hydrocyclone is one of the main important equipment applied for the classification of materials in mineral processing plants. Presence of coarse particles in the hydrocyclone overflow adversely affects the performance of the downstream processes. This research was carried out to provide a solution for these problems by using vibrational wave analysis. The results of vibrometer analysis showed that the average rate of vibrational signal increased from 6 dB at normal condition to 11 dB at the chock condition and variation increased more than 2 times. To stabilize the hydrocyclone vibratory behavior, a rubber layer was fitted under the hydrocyclone base and tightened with an equal torque. In order to reduce the cost and increase the accuracy of the work a piezoelectric sensor was manufactured and installed by designing the printed circuit board and installing an alarm. Analysis of piezoelectric sensor data showed that the average vibrational amplitude increases from 13 dB at normal time to 23 dB during clogging. The size distribution results showed that the amount of K80 (the size at which 80% of the particles are smaller) increased from 119 microns under normal conditions to 725 microns during clogging due to the miss classification of materials transferred to the overflow. This result indicated by using these sensors the efficiency of mineral processing circuits increases significantly.

The energy consumed by the comminution equipment accounts for the main part of the operating cost of the mineral processing plants. In order to conserve energy, attempts were made to increase the efficiency of the conventional comminution equipment. As a case study, in this research work, a process audit was carried out in the comminution plant of the Steel-Sirjan Iron Ore Complex in order to find the low-cost solutions to improve the product quality and decrease the maintenance and operating costs. Three main steps of the audit were (1) studying the operating manuals and checking the standard process procedures, (2) process data analyzing, and (3) proposing and implementing the proper solutions. Plant audit revealed a low equipment efficiency. The main defects were the crusher operation in the half-full condition, high pressure grinding roll (HPGR) operation in a non-standard condition, high amounts of rejected materials in the HPGR circuit, and low efficiency of the screen. Following this, a series of modifications were made in the crushing and grinding circuit. This consequently caused an increase of 9.3% in the crushing plant throughput in the choked condition of the crushers as opposed to the half-full condition. By increasing the HPGR operational pressure and the hopper level, BBWI of the HPGR product in the super-choked condition was decreased from 16± 0.20 kWh/t to 14.9± 0.25 kWh/t. By modifying the screen process, the circulating load decreased from 79% to 59%, and the screen efficiency increased from 63.5% to 89.5%.The energy consumed by the comminution equipment accounts for the main part of the operating cost of the mineral processing plants. In order to conserve energy, attempts were made to increase the efficiency of the conventional comminution equipment. As a case study, in this research work, a process audit was carried out in the comminution plant of the Steel-Sirjan Iron Ore Complex in order to find the low-cost solutions to improve the product quality and decrease the maintenance and operating costs. Three main steps of the audit were (1) studying the operating manuals and checking the standard process procedures, (2) process data analyzing, and (3) proposing and implementing the proper solutions. Plant audit revealed a low equipment efficiency. The main defects were the crusher operation in the half-full condition, high pressure grinding roll (HPGR) operation in a non-standard condition, high amounts of rejected materials in the HPGR circuit, and low efficiency of the screen. Following this, a series of modifications were made in the crushing and grinding circuit. This consequently caused an increase of 9.3% in the crushing plant throughput in the choked condition of the crushers as opposed to the half-full condition. By increasing the HPGR operational pressure and the hopper level, BBWI of the HPGR product in the super-choked condition was decreased from 16± 0.20 kWh/t to 14.9± 0.25 kWh/t. By modifying the screen process, the circulating load decreased from 79% to 59%, and the screen efficiency increased from 63.5% to 89.5%.

The effect of shell liners on mill performance has been the subject of various studies, but little known about the effect of dry SAG mills end liners on throughput and grinding efficiency. In particular, in the case of dry Aerofall mill types where it has been claimed that the end liners play a key role in the crushing and grinding actions. This paper experimentally characterizes the role of end liners in dry SAG mills with the objective of obtaining a thorough understanding of the effects of end liners design on the load trajectory and SAG mill performance. It was thought the characterization study will lead to design new end liners which eliminate or reduce the shortcomings of the current liners and improve the comminution efficiency mainly by prolonging liner life. The test works conducted in a scale down mill with a diameter of 1m indicated that conventionally used "deflector" type liners did not provide efficient environment for grinding. Direct observations obtained from the model mill during tests by various visualization techniques, along with simulations using the KMPCDEM software were the main sources of understanding flow behavior of charge inside the mill. In this research, to improve the grinding efficiency, a new design using low profile end liners incorporating radial ribs of proper height was investigated. The special design of model mill made it possible to increase the radial ribs height in steps of 6mm up to 18.5mm. The transparent end of the mill enabled accurate trajectory determination by image analysis. The results indicated that the new lower height profile deflectors and 15.5mm-height (14.5cm in industrial scale) radial ribs improved the mill performance while avoiding excessive pressure drop across the mill and wear on the liner. The image analysis showed that the use of new liners increased the distribution of coarse particles across the mill cross section from 28% to 35%. A new liner design was proposed by decreasing the number of liners in each slice from 5 to 4 pieces. The thickness of the inner head liners reduced from 45cm to 30cm and the outer deflector liners replaced by14.5 cm radial ribs. The distance between the feed and discharge liners increased from the original 115cm to 176cm which increased the effective length of the mill by 53%. The new design reduced the weight and volume of end liners by 9% and 23%, respectively. On account of installation of the new liners in Aerofall SAG mills the throughput increased from 441 to 465 t/h, the product size decreased from 519 to 480 μm and the amount of recycled material from the SAG mill product decreased from 10 to 6%. The most significant improvement was observed in the liner life; an increase of 50 to 200 % in liner life depending on the location of end liners was achieved. The relining time also reduced by 37.5% with the new liners.