Sag mill operation pdf

The ability to mill a broad range of ore types in various circuit configurations, with reduced numbers of unit operations and a. Firstly, the advent of ring motors has removed the constraint applied by the power that a. D burgess 38 11th mill operators conference 2012 hobart, tas, 29 31 october 2012 an open circuit operation. 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. The optimal performance of agsag mills is the key to successful plant operation. Sag mill operation at cortez ccs complete comminutions. Sag semiautogenous milling circuit is described with the emphasis on the process control systems employed. Typical tests required to define a hardness variability function, are given below in figure 1. Optimization and control of a primary sag mill using real. Two vibration systems installed and in operation at gold corp penasquito on their two 2265 tph sag mils. Metso has experience of over 8,000 grinding mills globally, including manufacturing and delivering the largest sagag mills in the world. A method of c alculating autogenous semiautogenous grinding. The total volume inside the mill is given by vm 4 d2 ml 1 2lc l l 1 dtdm 3 1 dtdm 8.

A method of c alculating autogenous semiautogenous. Two silos containing merensky and ug2 ore respectively feed the mill that operates at a fixed 75% of the critical speed. The sag mill had a 68% ball charge and the power consumption was 8 kwht, which agreed well with the expected value. Various kinds of mills are there with which different material processing takes place. Efficient operation even at higher mill speeds operatorfriendly smooth mill operation significantly improve wear life can be precisely designed to handle the given capacity can be easily retrofitted to existing mills. The results have seen a decrease in process variance with an associated increase in average circuit performance.

Outotec highperformance grinding mills use advanced simulation tools for the best possible process efficiency, mechanical reliability, and maintainability. The phu kham operation has recently undergone a series of process improvements to treat the anticipated competent ores scheduled for 2017 and 2018. Your operation requires a sag or ag mill that is flexible, durable, costefficient and tailored to your specific needs and use cases. Oversize is returned to the mill by a bucket wheel and water jet.

This puts the application in the realm of dual motor, dual pinion installations. Comminution is an essential component of mineral processing operations and its proper operation and design is vital to ensure that the plant operates efficiently. The plant was designed to process 1585 h mtpof sag feed. Metso has experience of over 8,000 grinding mills globally, including manufacturing and delivering the largest sag ag mills in the world. 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. Difference between sag mill vs ball mill mech4study. Single stage sagag milling design abstract single stage semiautogenous autogenous sag milling has become a common design for a variety of ore.

Todays state of the art of electronic control allows for easy operation of the mill by means of the gearless drive. If the critical size material, typically 2550 mm, is accumulated the mill energy efficiency will deteriorate, and the mill feed. The results in sagmill line 2 are even more dramatic. Evolution of sag mill process control at the xstrata nickel. The sag mill product is then crushed to 100% passing 3. 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. Each module at waterval concentrator wvalc employs a. There are many different types of mills and many types of materials processed in them. 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. In these circuits the sag mill is the largest energy consumer. Today we will learn about difference between sag mill vs ball mill. The feed rate setpoint can then be tied into a sag mill power optimisation strategy. This puts the application in the realm of a single mill, single pinion operation. 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.

Actual comminution circuits consist in most of the cases in coarse crushing, sag milling, pebble crushing and secondary ball milling. Evolution of liner design from current to future operations. Sag mills are currently the technology of choice in hard rock milling operations for reducing primarycrushed ore to ball mill feed. The material grinding occurs during impact falling grinding balls and abrasion the particles between the balls. The sag mill has a trommel on the discharge end of it. 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. Put another way, the sag mill energy required according to this statement, is 2. The operation modes of a grinding mill with gearless drive. 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. The operations comminution circuit, which comprises of a semiautogenous sag mill and two ball mills, each with megawatts mw of installed power, was expected. In order to continuously optimize mill operation, it is vital to obtain regular measurements of the ball load and pulp position. Achieving sag mill design production at startup using best. Improved relationships for discharge in sagag mills uq espace.

Engineers have determined that the mill motor will eventually require a full rewind. The sag test reproduces commercial sag mill grinding conditions on 4. As an example, table 1 presents agsag pilot plant data for an oxide gold ore. 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. Oct 12, 2017 today we will learn about difference between sag mill vs ball mill.

High ldl signal and low bearing pressure, reduce speed and prevent metal on metal operation. 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. Pdf evolution of sag mill process control at the xstrata. If 75 percent of critical speed is considered desirable for efficient grinding in a 2. Developments in sag mill design and operation over the last few years, sag mill manufacturing technology has advanced rapidly.

Currently a number of the largest sag mills designed are installed in single stage configuration. 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. Sagwise total process control the key to efficient sag. This paper describes the methodology by which the neural network model was implemented, the considerations.

Mineral processing operations present many challenges for automatic process control due to variations in unmeasured ore properties, material transport delays. This commutation is an essential part of many processes. A sag mill is usually a primary or first stage grinder. Selection of comminution circuits for improved efficiency. Sag mill discharge control is quite involved due to few interactive. Sag mills operation data abstract comminution, particularly milling, is on average the largest consumer of energy in mining. A mill is a device that breaks solid materials into smaller pieces by grinding, crushing, or cutting.

If a sag mill has been designed with a conventional power or speci. Application of operating work indices in autogenous. In the case of the large sag mill referred to in fig. Such comminution is an important unit operation in many processes. Every mining operation has a unique grinding process.

The bounds of mill size have been pushed from two directions. Automated sag mill speed control using oncontact vibration. Because of segregation on the coarse feed stockpile, sagmill 2 receives a higher percentage of coarse material. 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.

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. In this case, mill speed is the primary manipulated variable used to control mill load. Our experts welcome the opportunity to assist you with circuit and circuit control design as well as startup, operation, and optimization of your mill. The operating principle of the ball mill consists of following steps. Evolution of sag mill process control at the xstrata. The geometry of a mill with conical ends is shown in figure 8. Sag mills are currently the technology of choice in hard rock milling operations for reducing primary crushed ore to ball mill feed. 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. 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. 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. The single stage sagag milling option is ideal for starter projects with significant exploration and expansion potential. Overview on the grinding mills and their dual pinion mill drives abstract this paper will first give a short overview of the copper mountain project in british columbia, which just has started commercial operation earlier this year.

Grinding circuit design tools, including for sag millball mill circuits, and geometallurgy energy models are available to subscribers. Modelling sag milling power and specific energy consumption. Optimizing your sag mill operation international mining. With the development of the kx3 cnc key to both is the use of precision ball. 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. Comminution, process optimization, precrushing, sag mill capacity increase. Sag mills are autogenous mills that also use grinding balls like a ball mill. Sag mill discharge control is quite involved due to few interactive variables, such as mill discharge sump level, classification. The operating principle of the ball mill primo pizza. However, sag mill weight is difficult to control as the dynamic response changes as the mill approaches maximum capacity. From startup, the mill struggled to meet the required production rates. 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.

Sag mill optimisation and increasing throughput at. Tpl is an environmentally friendly technology used to achieve higher energy efficiency from the. It uses micro infinity i to grind or mill items into their crushed variants, like ores into dusts. Outotec grinding mills optimize grinding mill performance, efficiency, and availability to ensure you meet your plants operational targets.

Semiautogenous grinding sag mill liner design and development. In the past, the way to correctly operate a sag mill was not fully understood. Each of these performance parameters peaks at different filling values. Grinding mills for mining and minerals processing metso. 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.

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. As an example, table 1 presents ag sag pilot plant data for an oxide gold ore. 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. A mill is a machine by which solid or hard materials are broken into smaller pieces by means of grinding, crushing or cutting. Pdf understanding the effects of liner wear on sag mill. The acoustic sensors ensure regular and accurate adjustments to mill loading. 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. The circuit is closed with a 600 m aperture classification screen with. Trommel undersize was pumped to a vibrating screen where the. Rajamani4, professor metallurgical engineering 1barrick cortez gold mines star hc66 box 1250. 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.