Sag mill operation pdf

With the development of the kx3 cnc key to both is the use of precision ball. Because of segregation on the coarse feed stockpile, sagmill 2 receives a higher percentage of coarse material. Pdf evolution of sag mill process control at the xstrata. The results in sagmill line 2 are even more dramatic. In sag mill operation, the grinding rate passes through a minimum at a critical size chapter 5, which represents material too large to be broken by the steel grinding media, but has a low selfbreakage rate. Modelling sag milling power and specific energy consumption. The plant was designed to process 1585 h mtpof sag feed. The sag mill had a 68% ball charge and the power consumption was 8 kwht, which agreed well with the expected value.

Today we will learn about difference between sag mill vs ball mill. In this training module, well cover the workings of a semiautogenous grinding mill, or sag mill, thats designed to be the first stage of a grinding circuit. A sag mill is usually a primary or first stage grinder. This commutation is an essential part of many processes. In a continuously operating ball mill, feed material fed through the central hole one of the caps into the drum and moves therealong, being exposed by grinding media. In the case of the large sag mill referred to in fig. Maximising your sag mills performance semiautogenous sag mills represent a major portion of the comminution taking place in the processing plant and are by far the largest consumer of power, making their optimisation paramount. Improved relationships for discharge in sagag mills uq espace. The sag mill is 26 diameter x 123 egl and powered by 4,500 hp motor driven by a variable speed lci drive that can control the mill speed from 36% to 80% of critical speed depending on ore type and operational demands. Difference between sag mill vs ball mill mech4study. This video was made for the sag conference, in which a company wanted to show a visual walkthrough of the sag mill, from the beginning of its processes to.

Todays state of the art of electronic control allows for easy operation of the mill by means of the gearless drive. As an example, table 1 presents ag sag pilot plant data for an oxide gold ore. Comminution, process optimization, precrushing, sag mill capacity increase. Sag mills are currently the technology of choice in hard rock milling operations for reducing primarycrushed ore to ball mill feed. This puts the application in the realm of dual motor, dual pinion installations. In the past, the way to correctly operate a sag mill was not fully understood. If the sag mill is not intended to be the ratelimiting step in a process plant, then it is best to adjust the sag load and power to hold a constant tonnage to satisfy another constraint elsewhere. If the mill feed setpoint is changed, then the actual feed rate needs to stabilise at the new target in a short period of time. The circuit is closed with a 600 m aperture classification screen with. D burgess 38 11th mill operators conference 2012 hobart, tas, 29 31 october 2012 an open circuit operation. In these circuits the sag mill is the largest energy consumer. There are many different types of mills and many types of materials processed in them. Sag mills are autogenous mills that also use grinding balls like a ball mill.

Outotec highperformance grinding mills use advanced simulation tools for the best possible process efficiency, mechanical reliability, and maintainability. The acoustic sensors ensure regular and accurate adjustments to mill loading. Our experts welcome the opportunity to assist you with circuit and circuit control design as well as startup, operation, and optimization of your mill. Automated sag mill speed control using oncontact vibration. The optimal performance of agsag mills is the key to successful plant operation. The operating principle of the ball mill primo pizza. Application of operating work indices in autogenous. The operations comminution circuit, which comprises a semiautogenous sag mill and two ball mills, each with megawatts mw of installed power, was expected to be sag mill limited when. Two vibration systems installed and in operation at gold corp penasquito on their two 2265 tph sag mils. Optimization and control of a primary sag mill using real. Sag mill discharge control is quite involved due to few interactive variables, such as mill discharge sump level, classification. Every mining operation has a unique grinding process. Achieving sag mill design production at startup using best.

A method of c alculating autogenous semiautogenous. Uniquely, the sag mill can use grinding balls made from various materials to increase energy efficiency resulting in. It uses micro infinity i to grind or mill items into their crushed variants, like ores into dusts. As an example, table 1 presents agsag pilot plant data for an oxide gold ore. Metso has experience of over 8,000 grinding mills globally, including manufacturing and delivering the largest sagag mills in the world. Cadia concentrator 1 sag mill back in operation following repairs and a period of operational testing, concentrator 1 sag mill at cadia is now operating at full capacity. The knowledgescape strategys ability to maintain smooth and stable operation of the mill was more apparent when contrasted to the dcs control on the difficult line. Your operation requires a sag or ag mill that is flexible, durable, costefficient and tailored to your specific needs and use cases. Although the overall wio is close to the bwi, the calculated figures would suggest that the ag sag mill is very inefficient, while the ball mill is significantly more efficient than bond would predict. This puts the application in the realm of a single mill, single pinion operation. Closing the primary mill may result in an improvement in operating efficiency for some operations, or may facilitate a reduction in the primary mill product size. Typical tests required to define a hardness variability function, are given below in figure 1. A mill is a device that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Ag and sag mills are now the primary unit operation for the majority of large grinding circuits, and form the basis for a variety of circuit configurations.

The ability to mill a broad range of ore types in various circuit configurations, with reduced numbers of unit operations and a. A control strategy recently implemented on a large variablespeed sag mill at mmgs century zinc operation in australia is shown in the chart found on pg. Trommel undersize was pumped to a vibrating screen where the. Sag mills operation data abstract comminution, particularly milling, is on average the largest consumer of energy in mining. Such comminution is an important unit operation in many processes. Maintaining the sag mill weight at the optimum value is critical for achieving maximum grind rate efficiency and mill production powell, m. In this case, mill speed is the primary manipulated variable used to control mill load. The results have seen a decrease in process variance with an associated increase in average circuit performance. Semiautogenous grinding sag mill liner design and development.

Selection of comminution circuits for improved efficiency. The operations comminution circuit, which comprises of a semiautogenous sag mill and two ball mills, each with megawatts mw of installed power, was expected. Rajamani4, professor metallurgical engineering 1barrick cortez gold mines star hc66 box 1250. Tpl is an environmentally friendly technology used to achieve higher energy efficiency from the. Sagwise uses acoustic sensors and proprietary process control software to predict and adjust the sag mill operation according to impacts on your mill and other main process variables. Nowadays, the more successful plants are those that have adopted effective and efficient strategies to optimize their plant operation.

This paper describes the methodology by which the neural network model was implemented, the considerations. Pdf understanding the effects of liner wear on sag mill. Each mill is equipped with a 2 x 8500hp dual pinion drive system. Sagwise total process control the key to efficient sag.

If 75 percent of critical speed is considered desirable for efficient grinding in a 2. Although the overall wio is close to the bwi, the calculated figures would suggest that the agsag mill is very inefficient, while the ball mill is. Sag mill optimization using model predictive control. Although plant staff was reasonably satisfied by the performance of an expert system that was controlling their mill, they suspected that improvement was still pos sible. The material grinding occurs during impact falling grinding balls and abrasion the particles between the balls. Jan 08, 2016 in this training module, well cover the workings of a semiautogenous grinding mill, or sag mill, thats designed to be the first stage of a grinding circuit. Sag mill operation at cortez ccs complete comminutions. Evolution of liner design from current to future operations. The single stage sagag milling option is ideal for starter projects with significant exploration and expansion potential. The sag test reproduces commercial sag mill grinding conditions on 4. Grinding mills for mining and minerals processing metso. High ldl signal and low bearing pressure, reduce speed and prevent metal on metal operation. A method of c alculating autogenous semiautogenous grinding.

The operating principle of the ball mill consists of following steps. From startup, the mill struggled to meet the required production rates. Outotec tpl our unique outotec tpl technology improves grinding process efficiency the primary grinding process can be intensified for hard ores and material transport can be improved for soft ores. Optimizing your sag mill operation international mining. Evolution of sag mill process control at the xstrata nickel. Sag mill optimisation and increasing throughput at. The geometry of a mill with conical ends is shown in figure 8. If the critical size material, typically 2550 mm, is accumulated the mill energy efficiency will deteriorate, and the mill feed. If a sag mill has been designed with a conventional power or speci. The total volume inside the mill is given by vm 4 d2 ml 1 2lc l l 1 dtdm 3 1 dtdm 8. Outotec grinding mills optimize grinding mill performance, efficiency, and availability to ensure you meet your plants operational targets. The sag mill has a trommel on the discharge end of it. Single stage sagag milling design abstract single stage semiautogenous autogenous sag milling has become a common design for a variety of ore. Engineers have determined that the mill motor will eventually require a full rewind.

Oversize is returned to the mill by a bucket wheel and water jet. Grinding circuit design tools, including for sag millball mill circuits, and geometallurgy energy models are available to subscribers. Posted by matrix on 21st march 2007 sanjeev latchireddi, chief process engineer grinding americas, outokumpu technology, looks at the shift from ball mills to sag mills. However, sag mill weight is difficult to control as the dynamic response changes as the mill approaches maximum capacity. Various kinds of mills are there with which different material processing takes place. The operation modes of a grinding mill with gearless drive. Each of these performance parameters peaks at different filling values. Comminution is an essential component of mineral processing operations and its proper operation and design is vital to ensure that the plant operates efficiently. Developments in sag mill design and operation over the last few years, sag mill manufacturing technology has advanced rapidly.

Metso has experience of over 8,000 grinding mills globally, including manufacturing and delivering the largest sag ag mills in the world. The bounds of mill size have been pushed from two directions. Evolution of sag mill process control at the xstrata. Morrison et al 2011 stated that the ab value generated from the drop weight tester dwt is equal to only 40 per cent. Sag mill is an investment that can produce handsome returns if extra production is needed or simply to give the mine the option to mill the hardest ores at design throughput rates. Sag mill discharge control is quite involved due to few interactive. The phu kham operation has recently undergone a series of process improvements to treat the anticipated competent ores scheduled for 2017 and 2018.

The feed rate setpoint can then be tied into a sag mill power optimisation strategy. Currently a number of the largest sag mills designed are installed in single stage configuration. Mineral processing operations present many challenges for automatic process control due to variations in unmeasured ore properties, material transport delays. A mill is a machine by which solid or hard materials are broken into smaller pieces by means of grinding, crushing or cutting. Put another way, the sag mill energy required according to this statement, is 2. Evolution of liner design from current to future operations julius stieger1, process superintendent dave plummer2, process maintenance planner sanjeeva latchireddi3, chief process engineer raj k. Two silos containing merensky and ug2 ore respectively feed the mill that operates at a fixed 75% of the critical speed. Oct 12, 2017 today we will learn about difference between sag mill vs ball mill. The sag mill product is then crushed to 100% passing 3. In order to continuously optimize mill operation, it is vital to obtain regular measurements of the ball load and pulp position. Evolution of sag mill process control at the xstrata nickel raglan operation erik bartsch1, chief engineer guy comeau2, senior metallurgist colin hardie3, former chief metallurgist 1 process control group, xstrata process support 6 edison rd, falconbridge, ontario p0m 1s0 ph.