GRIND­ING TECH­NOL­OGY

Metso sat down with a panel of ex­perts from its busi­ness, Alan Boyl­ston (AB), Suzy Lynch-Wat­son (SLW), Håkan Ståhlbröst (HS) and An­dré Vien (AV), to dis­cuss some of the trends and chal­lenges fac­ing min­ing pro­duc­ers of to­day. The goal: to find out how new

The Australian Mining Review - - COMPANIES GEARING UP -

Q. What are the main chal­lenges fac­ing min­ing pro­duc­ers to­day?

AB: One main chal­lenge we see for our min­ing clients in to­day’s mar­kets is how to bal­ance the in­creased pro­duc­tion needed to meet a ris­ing de­mands for met­als, with the fact that ore grades around the world con­tinue to fall.

What this means is that to even main­tain cur­rent lev­els of pro­duc­tion, mines need to process more and more raw ore, which re­quires ad­di­tional en­ergy as they ramp up pro­duc­tion.

It also trans­lates in many cases to higher in­vest­ments in equip­ment and higher op­er­at­ing costs.

In or­der to be prof­itable, mines have to re­ally zero in on ways to im­prove op­er­a­tional ef­fi­ciency.

Q. What trends are you see­ing in the in­dus­try to ad­dress these chal­lenges?

AB: The big trends are re­lated to look­ing at the many op­tions that can help to lower en­ergy costs as pro­duc­tion de­mands in­crease.

It be­comes im­por­tant to look at im­prove­ment op­por­tu­ni­ties across the en­tire process to find ways to drive down costs.

On the equip­ment side, there is more open­ness to look­ing at new ap­pli­ca­tions for older tech­nol­ogy.

For ex­am­ple, High Pres­sure Grind­ing Rolls (HPGR) have been around a long time in lime­stone, ce­ment and kim­ber­lite oper­a­tions, but ap­pli­ca­tions in­volv­ing hard ores are rel­a­tively new.

With their higher en­ergy ef­fi­ciency, HPGR’s are get­ting a se­cond look as an al­ter­na­tive to more tra­di­tional grind­ing in cer­tain ap­pli­ca­tions.

The Metso HRC3000, launched in 2015, rep­re­sents a sig­nif­i­cant tech­no­log­i­cal leap for the min­ing in­dus­try with its sim­ple yet ro­bust de­sign that max­imises en­ergy ef­fi­ciency, avail­abil­ity and re­li­a­bil­ity.

Process im­prove­ment is also what we are hear­ing more and more about from our cus­tomers.

Mines are look­ing at things like im­prov­ing blast­ing prac­tices at the mine face to re­duce feed size to the pri­mary crush­ers as well as op­ti­miz­ing mill lin­ers for longer ser­vice life and en­ergy sav­ings.

We are also see­ing the trend to­wards dig­i­tal­i­sa­tion with many mines us­ing ad­vanced process con­trols to make their oper­a­tions more ef­fi­cient and to re­duce en­ergy con­sump­tion.

All these ap­proaches are fo­cused on im­prov­ing op­er­a­tional ef­fi­ciency and mak­ing bet­ter use of en­ergy to drive down costs.

HS: I would also add that there is a trend to re­place small and medium-sized mills by fewer but sig­nif­i­cantly larger mills to han­dle the high ca­pac­i­ties re­quired.

Large mills re­quire fast and safe main­te­nance, some­thing we will con­tinue to im­prove.

How­ever, large mills also re­quire large amounts of en­ergy to op­er­ate, so I be­lieve that the fo­cus on ef­fi­ciency will in­crease.

En­ergy is ex­pen­sive and in many ar­eas be­com­ing more so with time.

Q. What tech­ni­cal im­prove­ments has Metso launched in terms of grind­ing tech­nol­ogy?

HS: Tra­di­tional hor­i­zon­tal mills are gen­er­ally not par­tic­u­larly en­ergy ef­fi­cient.

Only a very small part of the en­ergy is trans­formed into ef­fi­cient grind­ing, with the re­main­ing en­ergy chan­neled into liner and me­dia wear, heat and noise.

In terms of tech­nol­ogy, there is not much that can be done with the mill it­self ex­cept for the en­gine and drive, but it is of­ten pos­si­ble to con­trol the process bet­ter.

As an ex­am­ple, mills with vari­able speed con­trols al­low you to run the mill as fast as needed and in com­bi­na­tion with a con­trol sys­tem that au­to­mat­i­cally ad­justs speed and feed based on pa­ram­e­ters such as mill weight and noise within the mill.

You can en­sure that the mill is al­ways run­ning in the most ef­fi­cient man­ner which helps to de­crease en­ergy con­sump­tion.

New and faster sim­u­la­tion tools also al­low us to en­sure that the mill feed con­trib­utes to in­creased grind­ing ef­fi­ciency.

Pre­vi­ously sim­u­la­tions took a long time, but now we sim­u­late al­most all de­signs for larger mills.

If the grind­ing is as ef­fi­cient as pos­si­ble, you con­sume less en­ergy per ton.

SLW: Metso is al­ways look­ing to make im­prove­ments that will im­pact the grind­ing process and help clients meet their goals of in­creas­ing equip­ment avail­abil­ity and low­er­ing op­er­at­ing costs.

One re­cent ad­vance in mill lin­ing that has re­ceived a lot of at­ten­tion is the Metso Me­ga­liner made from poly­met and steel.

The lin­ers can use less ma­te­rial than pre­vi­ously since we use a ‘skip row’ de­sign, where the lin­ers now have only two-thirds of the num­ber of lifters as be­fore.

Us­ing this de­sign, we can still achieve the same lift and charge tra­jec­tory but with less liner weight.

The lower weight can make it pos­si­ble to load more in the mill and to­gether with an op­ti­mised de­sign, you can pro­duce more tons and in some cases, in­crease ef­fi­ciency.

Look­ing be­yond prod­ucts, we have also made tech­ni­cal im­prove­ments by com­bin­ing our many ser­vices of­fers to find so­lu­tions that help clients achieve lower en­ergy and higher pro­duc­tion lev­els.

This in­volves look­ing at our prod­ucts and us­ing our process, in­stru­men­ta­tion and con­trols ex­per­tise to come up with the best com­bi­na­tion of ser­vices to meet the clients’ ob­jec­tives.

For ex­am­ple, when our team is asked to as­sess why a par­tic­u­lar grind­ing cir­cuit is un­der­per­form­ing, we try to take a more holis­tic view.

Ques­tions such as ‘are the drill and blast prac­tices op­ti­mised’ and ‘is there a large vari­ance in the char­ac­ter­is­tics of the ore com­ing into the plant’ are also im­por­tant.

Of course, the grind­ing mill it­self needs to be as­sessed but the process steps be­fore and after the mill all play a part in driv­ing the over­all per­for­mance of the cir­cuit.

Q. Do you see any trends in the way equip­ment is de­signed and used, es­pe­cially as through­put ton­nages con­tinue to in­crease?

SLW: One thing that we have seen is plants look­ing at dif­fer­ent op­tions in terms of equip­ment se­lec­tion to keep en­ergy costs in check as pro­duc­tion de­mands con­tinue to in­crease.

For ex­am­ple, we are see­ing in­ter­est in Metso Ver­timill stirred milling tech­nol­ogy, par­tic­u­larly in cases where a plant needs ex­tra milling ca­pac­ity or wants to achieve a finer grind.

In the past, plants would in­vest in a se­cond ball mill to run in par­al­lel with their cur­rent one to add the ad­di­tional ca­pac­ity, but this is not al­ways an en­ergy ef­fi­cienty way of tack­ling the prob­lem.

Re­cent re­search by Mal­colm Pow­ell and Sam Pa­lan­diandy at the JKMRC showed that us­ing a ter­tiary ver­timill to in­crease cir­cuit ca­pac­ity can be 25 per cent more en­ergy ef­fi­cient com­pared with adding ex­tra ball milling ca­pac­ity in a sec­ondary grind­ing ser­vice.

The con­clu­sion was that look­ing at the per­for­mance of a sin­gle mill or piece of equip­ment is not al­ways the right ap­proach.

You re­ally need to look at how all the dif­fer­ent pieces of equip­ment in the cir­cuit work to­gether to find the most en­ergy ef­fi­cient com­bi­na­tion.

It comes down to find­ing the right ap­proach to the right ap­pli­ca­tion.

Q. What does Metso see in its field oper­a­tions as poor grind­ing prac­tices and how this can be over­come?

AV: One key thing to re­mem­ber is that even with the most mod­ern and up-to-date equip­ment, per­for­mance in the field is still de­pen­dent on how the equip­ment is op­er­ated.

Our global Process Op­ti­mi­sa­tion group has vis­ited hun­dreds of con­cen­tra­tor plants, look­ing at the com­minu­tion cir­cuits, as­sess­ing how things are set up and look­ing for im­prove­ments in terms of en­ergy ef­fi­ciency or through­put.

Most of the process bot­tle­necks we run into are not caused by the ma­chines them­selves but rather have re­sulted from the way the com­minu­tion equip­ment has been con­fig­ured or is op­er­ated.

The four most com­mon is­sues en­coun­tered re­volve around the grind­ing me­dia used in the mill, how the mill speed and liner an­gles are paired, re­ly­ing too heav­ily on rules of thumb re­lated to pro­duc­tion, and fi­nally a lack of com­mu­ni­ca­tion be­tween the mine and the plant.

Q. Can you walk us through a few ex­am­ples?

AV: Well, look­ing at grind­ing me­dia we run into sit­u­a­tions where the me­dia is too large for the ex­pected grind.

The re­sult ends up be­ing high wear rates to both the lin­ers and the me­dia and a very in­ef­fi­cient use of en­ergy.

You can also run into poor qual­ity me­dia that splits or else wears in a way that re­sults in disk shaped me­dia that does not roll as it should within the mill.

This me­dia con­sumes mill vol­ume and power but the grind­ing is very in­ef­fi­cient due to the mo­tion of the charge.

All of these fac­tors add up to in­ef­fi­cient use of en­ergy. The so­lu­tion to this would be to con­duct on­go­ing cal­cu­la­tions to en­sure the op­ti­mal size of grind­ing me­dia is used and to keep a close eye on me­dia qual­ity.

In terms of in­cor­rectly paired mill speeds with the liner an­gles, what you of­ten have is me­dia that be­comes over­thrown caus­ing dam­age to the lin­ers and to the me­dia it­self.

The way to mon­i­tor for prob­lems would be to try to get a bet­ter pic­ture of ex­actly what is hap­pen­ing in­side the mill.

This can be done in sev­eral ways. One method would be to mon­i­tor the noise lev­els within the grind­ing mill us­ing Acous­tic tech­nol­ogy such as Metso SmartEar OCS which mea­sures steel on steel im­pacts within the mill.

By mea­sur­ing the noise lev­els within the mill, you can ad­just the mill speed to com­pen­sate and bring things back in line, re­sult­ing in more ef­fi­cient grind­ing and en­ergy us­age.

We also run into sit­u­a­tions where a plant is re­ly­ing too heav­ily on rules of thumb or gen­eral as­sump­tions with­out go­ing one step fur­ther.

For ex­am­ple, we of­ten think of in­creased power draw be­ing tied to greater through­put.

But what if the prob­lem is not with the mills tum­bling speed but there is a slurry pool­ing prob­lem? In this case it is not a ques­tion of an is­sue with tum­bling ef­fi­ciency but rather with pump­ing ef­fi­ciency.

To cor­rect this, con­vert­ing a ra­dial dis­charge to a curved dis­charge could be a so­lu­tion, in­creas­ing through­put in the mill for the same en­ergy due to the higher dis­charge ca­pac­ity of the pulp dis­charge sys­tem.

Fi­nally, a lack of com­mu­ni­ca­tion be­tween the mine and the plant can be clas­si­fied as a poor grind­ing prac­tice.

A plant needs to have good vis­i­bil­ity on in­com­ing feed ma­te­ri­als, in par­tic­u­lar the ra­tio be­tween coarse and fine run of mine ore, which can vary sig­nif­i­cantly.

With­out good vis­i­bil­ity, the plant may not be able to re­act quickly enough to ad­just its op­er­at­ing pa­ram­e­ters and there­fore lose ef­fi­ciency and over­all per­for­mance.

HS: Some­times it all comes down to not look­ing at the whole process.

Many com­pa­nies are just try­ing to ac­com­plish one thing at a time, low­er­ing the price or in­creas­ing equip­ment longevity in­stead of con­sid­er­ing how to im­prove the ef­fi­ciency of its en­tire grind­ing process and re­duce the cost per pro­cessed ton.

It’s all about help­ing the cus­tomer to in­crease ef­fi­ciency based on the con­di­tions that ex­ist.

In some cases, in­vest­ments may be re­quired, such as a new liner han­dler, to max­i­mize liner size/weight and re­duce main­te­nance time.

Changes in the process or equip­ment to solve prob­lems or achieve set ob­jec­tives may be re­quired.

There re­ally is no one size fits all so­lu­tion and as a team we work on find­ing the right mix of equip­ment and ser­vices to help our clients meet their busi­ness goals.

Over the years, our clients have come to ex­pect re­sults and that is what we try to de­liver.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.