how coarse can ball mill feed be - grinding & classification circuits - metallurgist & mineral processing engineer

how coarse can ball mill feed be - grinding & classification circuits - metallurgist & mineral processing engineer

We are looking at a 1 MTPA comminution circuit that goes from a tertiary crush to a single ball mill (closed on a cyclone cluster) to produce a 100 m P80 product. We're doing a trade-off study. Closing the tertiary on the screen or leaving it open! (The crushing plant runs 11 h per day, the mill 24 h/d.) The mill power (and media consumption) is higher and the mill grinding length is a bit longer in the open case. Is there any other side-effects associated with feeding a ball mill with 16 kW-h/tonne feed which is coarser (closed P80 of 13.4 mm vs. open P80 of 15.4 mm i.e.2 mm coarser)? Aside from the additional capital and operating costs are there any operational issues associated with feed which is coarse i.e. coarser than the selection function maximum which is at -2 mm.

High scatting rate would be the primary concern I think, and as the crusher liners wear, the situation will get worse and your throughput rate/grind size will vary. Wouldn't recommend it if this is going to be an issue.

What we're looking at is a jaw, open circuit secondary cone and an open circuit tertiary. Screens before the cones if the capacity is a problem but no recycle on the secondary or tertiary. The idea is the very cheapest get-into-operation solution. The cost of the recycle conveyors and larger screens is being avoided (and being transferred to mill op costs). What I really am interested in is whether the scatting problem is a definite or a maybe if the Bond Ball Mill Work Index were 16 kW-h/tonne? Is it a show stopper or a just more work for the FEL? What % of the feed might end up in the scats bunker? Yes the p80 being presented to the ball mill could be less, 8-10 mm as you mentioned but I'm looking at this coarse transfer size case.

If feed coarser than the selection function maximum which is at - 2 mm and ball mill is biggest, it is possible to increase circulating load to get an acceptable product P80 for ball mill. Need to check the pumps and hydro-cyclones to increase the circulating load.It is also possible to increase the number of balls of larger diameter in the mill, if the inverter is slightly increased speed.

I also agree with increasing the circulation load can assist to achieve the required p80 but do not forget that high circulating load will also lead to lower than targeted throughputs in terms of milling. The mill will be backing up due to high circulating load. Normally you need to determine the bond work index for the material you will be treating. With proper Bond work index data then your desired p80 and Milling throughputs will be easily achieved. Physical characteristics of the ore to be treated is very important and we often look at cyclone efficiency forgetting the Kilowatt hour required to reduce one short tonne of ore of an infinite size to 80% passing 100 microns.

We had designed a similar Plant to yours using closed-circuit secondary crushing only, to save on costs, and closed-circuit milled with 90mm, accepting a scats "loss"/lower grade reintroduction, as a consequence of preferential grinding. This concentrator was uprated later to series milling when increasing throughput to beyond 2.5x. I am sure that the ball size should improve the selection function peak; however, tertiary crushing/HPGR should give you a much better product than 13mm, still dry screening? Whereas, secondary closed circuit crushing to 16-18mm should be possible?

But it's a wet grinding process. We're making a 3D model of the system and applying value engineering as we go. For instance the secondary cone crusher feed chute, the screen and the discharge chute add 20 m in length (and two trestles) to the conveyor; so we would now cost the screen and additional chutes, conveyor and structural steel against a cone crusher that can handle the volume of the unscreened feed. We're trying to find the lowest capital comminution system for 1 MTPA. Almost regardless of operating costs!

At the top size you are dealing with crushers are much cheaper to run than ball mills. There are other things to consider. That is hard ore. Your ball size needs to be matched to the ore size. If it turns out you need 4 inch (100 mm) balls to handle the scats your mill liners will last a much shorter time than if you need 2 inch (50 mm) balls. In fact with rubber liners, the 4 inch balls will beat the living daylights out of the liners.

We're working with a plant where exactly what you describe for a crusher circuit going into a ball mill with hard ore is going on. If the crusher gaps or liner wear get out of hand scats can be 10 to 20% of new feed. Unless there is some preferential grinding phenomenon going on and you can throw away the scats, that high rate is not to your advantage.

Don't even think about crushing scats from a ball mill. There is so much metal (ball chips) in there the metal detection system is bypassing the crusher all the time. Of course if your ore isn't magnetic, that isn't a problem. Tramp magnets will pick the worst of the metal.

Finally don't forget to watch what kind of crushers you buy. Some are optimized for aggregate and tend to make a coarse product with a minimum of fines and some are optimized for mining and make a finer product with lots of included fines. You want the latter. The manufacturer may not tell you which is which.

I spread-sheeted the Bond new ball size formula and varied F80 and WI. To me hard is WI>18. So it seems the predicted size should be less than 4". For a 16' diameter ball mill do you have an opinion on what new ball size would be half-way liveable in terms of liner life?

A quick check of the Rowland optimum feed size for this ball mill is between 3 and 4 mm; operating either circuit you describe will be at least 15% inefficient compared a more conventional ball mill feed size. The screen doesn't matter in terms of energy efficiency; only more crushing (or a small rod mill) that will improve the energy efficiency. I doubt the opex benefit of energy efficiency will matter given the capex needed. Ball size sounds right; I get 3.5 inch top size.

I note the question is -6 months old, but there have been some really interesting recent comments.I agree that anything with a BWI>18kWh/t is a hard ore, you mention a WI of -16kWh/t - so I am assuming for my comments that the ore is of medium competency. You also mention a crusher P80 (closed) of 13.4mm or a P80 (open) of 15.4mm. My rough calculation with the above (using the open case) agrees with your ~16' (5.3m) mill size, installed power around 2.5MW.

With regards to 3.5"- 4" media, typically for Ball mills of this size (16'), max size of ball used should be around the 50-60mm. I feel that a 4 ball in a 16 Ball Mill is too large and more suited to SAG Milling. You risk damaging liners (rubber, composite or full steel) as well as trommels and feed chutes in the process. To ensure the final grind, extra EGL in the mill may be required as you rightly point out.

If the EGL is not long enough, you will not get the residence time and hence the grind you are after,The hydro-cyclones will have a hard time if set for the desired P80Increased re-circulating loadLarger than normal feed spouts needed to handle the coarser feedHigh wear on trammel screens

Another option may to consider scrapping the tertiary, and perhaps even secondary crushers (depending on Primary crusher CSS) plus screening / scalping capacities) and using HPGR as secondary crushing / primary grinding before feeding to the Ball mill. There are several iron ore flowsheets in operation that run Primary-Secondary-HPGR (dry), then wet for Ball and Regrind milling before going to product and tails.

By the way this project has been stalled due to tenure issues but the challenge (minimum cost of getting into production, even symbolically) is still worthy of consideration. The design can allow for retrofit of closed-circuit crushing, or quaternaries, HPGR, rods or even SABC but these must be paid for by sold Dore. He has suggested that squeezing down the CSS (P80 9 mm) and having a 4 mm trommel where the oversize could be re-processed (I would say parked) might be do-able at WI 16. One assumption in all this is that a ball mill is available which has lots of grinding length, and even if this were not the case a certain pre- or post-ball mill oversize could be parked providing the capital for parking was less than closing the tertiary or some other solution. The other project setting criterion is that the maintenance and operation should be suited to a remote, let's say island, location.

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hpgr vs sag - grinding & classification circuits - metallurgist & mineral processing engineer

hpgr vs sag - grinding & classification circuits - metallurgist & mineral processing engineer

Hello: I would like to start a new discussion. When HPGR should be used instead of SAGs in a grinding circuit. What are the technical advantages, sensitivity to feed distribution, hardness of ore, efficiency etc? What are the trade-offs between SAG vs HPGR grinding technologies?

HPGRs are suitable for comminution circuits that deal with ores qualified as "competent". I like to leave the term hardness out of this analysis so I recommend not using the Bond Mill work index as an indicator to decide whether to use HPGRs in a circuit or not.

Everyone in the industry is trying to have the simplest circuit possible that will deliver the lowest CAPEX and OPEX possible while allowing to reach design capacity but in case of competent ores there is no alternative other than adding "crushing power". With technology available today you will be forced to have about 3 stages of crushing before feeding a ball mill if your ore is a competent ore. HPGR is a machine that plays a role in tertiary crushing, receiving top sizes of about 45 mm and delivering product sizes of around 4 mm (this is achieved by using a classification circuit together with the HPGRs). I have seen HPGRs in circuits dealing with throughput of about 1,500 t/h of fresh feed, so you can safely assume that HPGR can be used in a wide variety of tonnages up to the limits I mention. In one place the circuit I have seen working has 3-4 HPGRs to process about 4,800 t/h. May be an easiest way to show when HPGRs are needed in a circuit is to look at those projects where a SAG mill circuit didn't reach design capacity. If I remember well ALL of the SAG circuits dealing with competent ores have been forced to add either pebble crushers or secondary crushers to reach design capacity. This situation has transformed some SAG mills into an unusual hybrid mill which looks like a SAG but that is fed with a particle size close to the typical critical size that forms inside a SAG mill, i.e particle sizes in the range of 45 mm. The critical size generated in a SAG mill when dealing with competent ores is such that these pebbles are very hard to crush and impossible to grind down in a reasonable amount of time in a regular tumbling mill. The 45 mm competent ore produced in a crusher has internal fractures that make it suitable to feed a SAG mill where these rocks are easily reduced to final SAG product.

In discussion with about this topic some time ago I asked him a similar question. He suggested the following high level guidance when thinking about the selection of equipment to treat particular ore strengths.

Above 200 use a scrubber Above 60 use AG milling Above 40 use SAG milling Above 25 use HPGR AxB very rarely goes below 25. For AG and HPRC analysis the SMC test and DWi is very important." Mike may care to clarify further?

I recommend thinking on HPGR for AxB below 40. At AxB values between 37 and 40 there may still be a trade-off between conventional SAG and HPGR circuits. Under 37 I would be very careful to have a SAG circuit in my design. In this case a secondary crusher or pebble crusher (together with big SAG grate openings) is almost a must have.

HPGR may not be the right machine for less competent ore, especially when the ore has clays. So far it looks like that there are certain ore types that require too much energy to have them ground down in a conventional SAG-Ball Mill circuit. This is the case where HPGR circuits come handy. When the ore is competent there are less fractures available so the ore gets its size reduction mainly through abrasion. You will understand that trying to abrade a 6 inches rock down to 2.5 inches may take lots of time and hence the rock just spins around the SAG mill. If you want to reach design capacity then you need more SAG mills which just take you down the path of energy waste.

For less competent ore the conventional circuit is still the best choice due to lower CAPEX. HPGR circuits needs that more real state is made available as an ore classifying system needs to be in place. This system requires the construction of conveyor belt systems which enlarge the size of a circuit.

I think, the SAG/FAG cannot simply be compared with HPGR, taking account of their very different grinding process requirements and results, even the process is dry. As an example, if you expect to grind an ore from 200 mm size to 1 mm size, the use of the HPGR instead SAG/FAG requires the addition of 12 crushing phases, consequently the FAG/SAG cannot be replaced by HPGR only. If we add the screening, handling and feeding equipment CAPEX and OPEX, the comparison work will be more complex. The complexity degree of this comparison will be higher if the process water is available, due to the significant benefits of the wet screening vs. dry screening. Another aspect, with a major impact on the screening efficiency, is the different particle forms resulted from the SAG and HPRG processes. In conclusion, the optimal grinding circuit and its equipment requires a complex study of the technical and financial aspects. Taking into consideration the different recommended utilization areas of SAG and HPGR, their limited comparison is not possible to be correctly developed.

1. Pre-crushing- three crusher MP-2500(Metso) for crushing from 300mm to 50mm. Two working and once in reserve. 2. Primary grinding- once SAG mill with size 42ft x 24ft, power motor 28MW. F80-50mm, p80- 2mm. 3. Secondary grinding- two Ball mills with size 31ft x 45ft, power motor 28MW (each). F80- 2mm, P80 - 250microns. 4. Thirty grinding- once Ball mill (analogically). F80- 350microns, P80- 150microns. 5. Capacity of flowsheet - 10 000t/h. 6. Bond index for ball mill- 12.7 KW/t. 7. Power consumption of flowsheet - 10KW/t.

So far we have clarified that HPGR doesn't replace s SAG mill and hence these two machines can't be compared. We need to compare the HPGR circuits against the SAG-crush-Ball mill and against the Crush--Ball mill circuits

A always with equipment differences "there are horses for courses" - an analogy I would like to propose is that HPGR is like a race horse, not too good in variable circumstances in the same race, no hills, no uneven ground and a fixed handicap as the main challenge to performance. All this being correct, it is the fastest horse available option to get from point A to point B.

Now a SAG, could be seen as, a pack horse, a rodeo quarter horse, show jumper and all those other equine functions that require flexibility. One clear example is the ability to change it into a large ball mill (seems quite common these days) with increased charge and higher dependence of a P80 particle reduction. Drawing a even longer bow, you tend to shoot a race horse, should it break a leg....and spend serious money to replace it....

An interesting question. Published data shows HPGR capex is typically 15% to 30% higher than a comparable SABC circuit for the hardest ores. HPGR though provides opex reductions. I am curious to see if the opex reductions have actually panned out? Any experience out there on this?

Cerro Verde actual data shows that the HPGR circuit energy consumption was 3 kWh/t less than the SAG/Ball mill circuit that was considered in the trade off studies. The initial trade off studies were expecting to have 4.2 kWH/t of less energy consumption.

HPGR may be after 5...10 years. Why? SAG mill drinks water more them HPGR. Water consumption of SAG nearly 1.0 m3/t (with thickener), HPGR have less 0.1m3/h (without thickener). After 5...10 years the capacity plant will be 70...100 Mt/y may be more. Where to look 100 million tons water? May be after 5 years will be new favorite horse. For example - microwave grinder (Pegasus).

I would recommend to see if the horse would do the work he is expected to do. You may choose a cheaper horse that may look strong but if he won't walk at the pace you want THEN you may not arrive to the cash flow town you expect.

The decision needs to include a risk analysis. My suggestion is to look at the rock "competency" or look at the axb. If axb is low I would recommend to NOT believe in the SAG design output and add some extra percentage of power needed, lets say 20% or 30% more. The reason for this is that SAG modeling tools available have the tendency to make the wrong predictions when SAG circuits deal with competent ore.

However, things are changing with SAG throughputs regularly achieving higher than rated flows and better P80 expectations. At the risk of not trying to promote our work, as these forums are not for this at all. Our work these days is actually blending ball sizes and grades to optimize the process. This is not usual as most ball makers would not be able to blend say a 5" ball with a 3" ball in a high impact SAG environment without killing the 3" media either partly or totally. This now can be done without media carnage - plus the media retains its spherical shape throughout its deployment. Take a look at this scenario - you can actually have your cake and eat it too. I believe I am keeping within the scope of the question as it does give a SAG scenario that is not possible with HPGR that has no media to play with. We calculate impact energy in relation to ball size ensuring that targeted throughputs are met - then using the grinding surface adjustability of blending we can target the grind closely as well. The question that I would like to put forward to this forum is; As SAG can have this little spoken about flexibility, how can HPGR ever hope to match this?

size of balls in SAG: 6 inch size of balls in Ball Mill: 3 inch (50%) 2 in (50%) load of balls in SAG: 14% load of balls in Ball mills: 32% f80 to SAG: 152 mm (6 inches) SAG P80: 2 inch Circuit p80: 274 microns SAG speed : 10 RPM

This scenario for the SAG mill is taken from a design criteria. P80 for the SAG is 2 inch (this p80 considers SAG discharge only). If we consider the SAG screen and pebble crusher then SAG CIRCUIT p80 = 7mm.

This one is not a design that I have encountered before which is interesting as competent 150mm SAG media can only be made by a very, very limited list of suppliers. We have theoretically designed 200mm media as an exercise targeting almost 60 as an average volumetric hardness. We may look at the modeling for a size blend which may also include a percentage of 140mm media as well for that finer P80. !2.8m SAG is also an odd one. First thought, apart from the above, is a P80 of 50mm (2") when say 15mm/20mm could be achievable even at that bond work index of 20kWt/h. as a direct mill grate discharge prior pebble crushing.

Frankly, I would really like to have a close look at this ourselves if it ever got passed the design stage. The Ball mills are a great size as well and probably very capable of better than the 274um noted as the final grind or BM discharge. A blended media size with compatible ball grades would also be interesting to run through our modeling. Totally, very interesting sets of equipment to fine tune.

I have seen a design for a similar ore who has 4 HPGRs (5,600 kw each) and 4 cone crushers (933kw each) in the secondary crusher area. It has a 60x113 primary crusher and 3 ball mills (17,000 kw each). This circuit process between 110-120 ktpd

I'm not looking to get advice on designing a new circuit but to only add facts (numbers from actual operations) to this discussion to try help Tony with his question I appreciate your passion and help with the exchange of information. Knowledge is the only thing we will leave in this world long after we are gone.

As a media supplier, I am happy to concede applications where HPGR is indeed the front runner in equipment selection. HPGR will be the better performer when you have a very consistent ore body as that machine can be specifically set up to maximize the greater ore quantities. It is when the ore body feed to processing has a wide range of ore variations that fast processing adjustment and flexibility is demanded. Then SAG takes the lead.

Higher energy-efficiency than SAG milling Finer product than cone crushing Similar transfer size to SAG milling Reduced work index of product Improved minerals liberation Reduced over-grinding and sliming Smaller footprint (m/kW) Improved delivery times Shorter installation times More rapid plant ramp-up Easier plant debottlenecking Disadvantages: Plant complexity, larger overall footprint: Closed circuit secondary and HPGR Crushers & screens Conveyors, bins & feeders Dust control Tramp metal management Capital costs: Capex differential = (ore competency-1) Capex differential = (plant capacity-1) 100,000 tpd 10% 20,000 tpd 30%Show less

1. Capacity of flowsheet - 3600t/h. This is few for SAG mill with size 12.8 meters of diameter and 7.4 meters of light (even with 20 Bond Index). 2. The work power consumption of SAG is 20,24 MW. Nearly 80% (16.3 MW) consumed to crushing large rocks from 350mm ( F80=152mm) to 56mm. Specific power consumption will be 4.3 kW/t. May be this work make in secondary crushers ( 0.7kW/t)? 3. The work power consumption of ball mills is 21.2 MW (each) and capacity of each mill is 1800 t/h. This is too few.

Mark, i understand that you want blending difference ball size for increasing capacity of mill and reducing P80? We investigated at this and head follow result. You are right about killing small balls by large balls. Ball of 4' are will killing the 1.5' ball. Therefore blend 4' & 1.5' is impossible. If use the 2'ball the lifetime of it will be short. If use only 4' so after 20...25 days the balls size curve is will be consist 80% less 3.2' (with permanent adding necessary 4' balls) and 15...20% less 1.5'. This curve will be permanently. If blending 4' with 2.5' the grade of 1.5' will be more 20%. Is it need? I think for SAG mill the load ball size will be one size. For reducing P80 this work must do Ball mill (secondary grinding) with small balls. We are load only 2.5' and this ball killed 1' ball. For more reducing P80 necessary use thirty grinding with Ball mill or Vertimill with load of 1.0'...1.5'ball etc.

However, some good up to date news for you! We have the ability to make even 5" with 3" in a blend that works in harmony - without breakage concerns. As a SAG guy you will appreciate this as a new set of options. This plan was first started in ball mills we tune, in an actual trial account, this was a start-up seasoned charge in a single stage mill where we had several sizes - the top being a 133mm and the smallest being 80mm. Commissioning was quicker and the results were very good.

I do think blending ball sizes with compatible media grades is the future and a flexibility that HPGR cannot match. At this time we are carefully planning a shift in the final grind by using a 2.8: ration of 115mm: 90mm. This should move 76% of passing 200mesh to over 80%. I would welcome your comments on this as well.

You will be amazed to see people making decisions based on CAPEX only and based on what they are used to do. If they have been operating with a SAG circuit they will have the tendency to continue doing this. The real evaluation comes from developing a trade-off where the following needs to be considered CAPEX and OPEX Revenues (coming from Metallurgical performance as Kshirasagara points out) Risks of project construction (for example, is the new site far from roads infrastructure? this puts a limitation on machine sizes sometimes) Availability of financing Investors expectations in regards to the time they will have their capital back and start making earnings. Start-up Risks (learning curve of the operators) Social Risks (dust generation for example)

I studied all comments related SAG vs. HPGR. In addition, I remarked the change of flowsheet production capacity, from 10000 t/h to 36004000 t/h. I strongly recommend you, in accordance with Juans opinion, to select the following comminution steps: 1) Crushing, from 300 to 40 mm; 2) HPGRs from F80 40 mm to P80 2 mm in closed circuit with dry screening 2 mm; 3) The under screening -2 mm will be submitted to the wet screening 0.25 mm opening; the size fractions +0.25 mm will be sent to the secondary BM and the under screening to tertiary grinding; 4) Secondary BM grinding, F80 2 mm, P80 0.25 mm; 5) Tertiary BM grinding, F80 0.25 mm, P80 0.150 mm.

Taking account of your lower production capacity, you can think to replace the two BMG phases by one VM grinding step only, able to ensure a very efficient grinding from F80 2 mm to P80 0.150 mm under very, very efficient technical and financial conditions. You can look at METSO VM 3000 or new METSO VM 5000. You can develop the VM grinding tests with METSO (USA, PA) on 60 kg ore sample and the cost of the test is about US$6000. Based on the test result you can quantify the accurate number of VMs required by your ore and production capacity. The VM is a very profitable grinding equipment, under incidence of the OPEX and even the CAPEX. Based on my rough estimate, you need 1416 VMs for your flowsheet of 3600 tph. If you need further information concerning the VMs and their high grinding efficiency, please contact me. It will my pleasure to introduce you to METSO people, USA, PA, in order to develop the VM grinding test.

Unit Eq Power Total Power Supplied kW kW MP-2500(Metso) 2 1,864 3,728 SAG mill 1 28,000 28,000 Ball mills 2 28,000 56,000 Thirty grinding- Ball mill 1 42,973 42,973 Total (kW) 130,701 Specific Energy (kwh/t) 13.07

Certainly, there will be some saving on power consumption when HPGR is used as against a SAG Mill. However, there are other factors that do affect the decision, as well. For example, abrasiveness of the ore.

We have just completed DFS for a large Zinc Mine with beneficiation plant. Carried out a trade-off between SAG Mill and HPGR. Simply because of high abrasiveness of the ore (Index = 65) the saving on power got set-off by higher consumption of wear components (Crusher Liners & Screen panels) and requirement of additional O&M staff.

Make decision on commercial recovery and grade not on equipment based. Finally it is the operator and owner who is benefited and not equipment vendor. After SAG if metallurgy fails then what to do. Who will answer, vendor or operator? Today many industries are facing serious problems in this subject. Test both particles produced form SAG and HPGR and do cost benefit analysis and then take decision. It is the final Cost of concentrate produced, quality, and quantity that will give you confidence in buying equipment. Please don t forget metallurgy part.

Please do not take offence to these remarks, as it is not meant to be so, the circuit you have mapped seems quite viable BUT an alternate SAG circuit proposal (as you see it) will make it less of an "only" alternative. VM's are also interesting to look at, as they do seem very efficient. A single stage BM we have been fine tuning has F80: 75mm and P80+: passing 200mesh and does it easily. Much better than 2mm to 150um in a single step.

You can select your flowsheet based on BM use but, as I mentioned, it is recommendable to replace the SAG equipment (F80 50 mm; P80 2 mm) by HPGRs keeping the same feed and product sizes 50 mm and 2 mm). It is your choice but, taking account of your new throughput (4000 t/h), you can look at another flowsheet variant, significantly more efficient (lower OPEX) and characterized by reduced CAPEX than comminution scenario SAG + 2 BM stages. I suggest you to consider the following grinding circuit:

1. Primary HPRG F80 50 mm, P80 3 mm, in closed circuit with dry screening 3 mm opening (3 mm instead 2 mm in order to increase the dry screening efficiency); 2. Secondary grinding, using the Metso Vertimill 3000 (F80 3 mm and P80 250 m, the last being your required final product size).

1. The Metso VMT is characterized by lower power consumption than BM (up to 35 % less power) and lower grinding media consumption than BM (up to 53% less media consumption); 2. The operation of your secondary and tertiary BMs is not situated on the optimal size range of the product size (BM optimal product size 15000900 M) in comparison with Metso VTM optimal operating range, of 100040 m; You need the final size 250 m; 3. The CAPEX and OPEX of the fine grinding circuit will be considerably reduced (screens, feeders, pipes etc.).

In order to develop this flowsheet and accurately assess the CAPEX and OPEX, you need to proceed to HPRG laboratory and, in addition, the semi-pilot tests. The VTM tests will be developed with METSO, on the ground sample resulted from HPRG semi-pilot test (3 mm size) in order to check the VTM response to the size distribution obtained from HPRG process (tests). If you need further information please do not hesitate to contact me.

1. The VMs replace 4 BM units (2 secondary and 2 tertiary) based on your assessment; The BM CAPEX are higher than 10...14 VM (about US$10 M each); The accurate VM number can be quantified based on the stirred mill test results; In addition, you will reduce the CAPEX and OPEX required by BM size classification Equipment;

I do not try to convict you to use the VMs (same situation HPGR instead SAG), but your SAG and BM grinding circuit is an old grinding concept. The final flowsheet, as I mentioned, is your choice. As an example, I would agree to use the SAG if the size reduction ratio, in one step would be 100 or higher. In addition, I kept in my mind your remark concerning the water consumption, but the minimal information package, that you provided, does not allow to select the optimal grinding circuit.

The interesting thing is that savings in maintenance manpower, steel balls and energy largely pay to have more VTMs. The payback of the extra capex is about 40 months, which is paid by the operational savings.

OPEX for Vertimil may reach values that are 18% lower than for BM circuits Now some equipment manufacturers will help to pay the initial capex to receive a payment every month for 4 years or so. I would rather have more machines to operate to have lower OPEX for the mine of the life

I agree, but our assumptions have a general character only. The sensitivity analysis of the grinding circuit (NPV and IRR) can provide the accurate response to the question VM or BM? In principle, in the case of the size reduction from 2 mm to 0.25 mm (2 stages BM), one stage VM seems to be the better variant. The 4500 Metso VM can successfully use.

SAG, HPRG, BM, VM and other industrial grinders are one generation - mechanism of energy passing are same. Primary energy from electricity net pass to motor, it pass energy to gearbox, then to drum, from it to ball, and only these acts energy (balls kinetic energy) passed to address - to rock or particle ore. If the primary energy is 100%, gearbox consumption will be 10%, consumption drum rotating 35%, to lifting balls, ore and water 55%, consumption to heating of drum, balls, ore, water, grinder "music"& "dance" 15%, to grinding rock or particle This is very "effectively", ok?

This generation is use kinetic energy by contact. The main problem is in comminution, other problem is residence time. At present time, i think, is necessary determine the concepts for new generation? In my opinion the new grinder mast be follow: 1. The energy passing to ore particle, will be without contact. For example by microwave, ultrasonic, pneumatic energy etc. 2. The manufacturing material of grinder, will be non-metallic (polymer, ceramic or carbon). 3. The residence time, will be less 1 minute. 4. Needless of water. 5. The grinding and separating of ore particles, will be in one time with one stage (one machine). 6. Installation of grinder will be self-mobile (may be fly). 7. Energy feed will be autonomy (plasma generator with buttery).

I appreciate your efforts and understand them. Your project is a big investment. As Juan and others mentioned, the right way of your work is the preliminary technical and financial study of the both variants of the comminution circuit as follows:

If the Variant B will be more profitable, I suggest you to develop the HPRG laboratory and pilot tests with the HPGR supplier (i.e. Thyssen Krupp Polysius), on 1.52 t crushed ore 300 mm size. The objective of the tests is the complete qualification of the response of your ore to the HPRG process. FYI information, the cost of the VM and HPRG tests are not expensive (VM test on 6070 kg sample, of 3 mm size about US$6000; HPRG test (laboratory and pilot, in closed circuit, about US$25000). For additional data and test development, you can contact your regional representative of the suppliers of HPGRs and VMs (Metso). Please carefully study and select the optimal screening concepts and equipment, under incidence of CAPEX and OPEX, in addition to technical criteria.

I have always wanted someone with this ability (I do not have it) to look at a hypothetical case, I say this as we are travelling down this road now and it would be wonderful if anyone could be able to calculate the possible efficiency outcome. SAG/BM circuit. SAG using 5" media with several pebble ports (4") discharging smaller media for magnetic separation and media captured is being reloaded into the BM. BM has 3" media. Now the hard part. The media retains its spherical shape throughout deployment in both SAG and BM - repeating that all media remains round throughout deployment. Small spherical ball populations grow in the BM promoting a better grind, SAG balls are not retained below say 3.5" leaving more space for new ore. The question: If the above was fully achieved, what would be the "estimated" improvement in efficiencies? I have no evidence (data) to quantify the media saving or the additional room for more ore. I also do not have an estimate of savings due to media remaining round and not losing shape. I do have one (and only one) reference for this - unused media additions to BM were reduced by 25% as this is the estimated media additions won from used round SAG media. Our aim was always to reduce costs and increase efficiencies in existing SAG/BM circuits. The HPGR and VM alternative does read well - and calculating this new efficiencies in comparison with the SAG/BM best operating scenario is probably relevant? Any thoughts or questions would be most welcome.

The technical and financial comparison BM vs. VM, based on grinding test results, is not a problem. The comparison SAG vs. HPRG is more complex and requires the good knowledge of the entire grinding circuit and its phases, including the material classification and its handling. The experimental checking of the compatibility with the ore with HPRG process is obligatory. As an example, please look at the Juan remark related to the clay content. In 2011 - 2012, I developed a similar preliminary economic assessment (PEA) for our project Roche Bay Magnetite Deposit, Nunavut Canada. Based on the RB ore characteristics, production capacity and study and test results, I selected the final scenario: Primary Crushing (from 1000 mm to 175 mm); Wet FAG/SAG (from 175 mm to 1.6 mm) followed by VM grinding (from 1.6 mm to 30 m).

The selection of the FAG/SAG as a primary grinding phase has been the result of the study of the efficiency of entire flowsheet, including magnetic separation and sulfide flotation. In spite of the higher profitability of the HPRG in comparison with FAG/SAG, the major financial impact of the efficiency of the wet ore classification and magnetic separation, on the global process efficiency, has been the final criterion of the selection of the FAG/SAG variant.

After you unload -50mm balls summary size in sag will be: 125...100mm 50%, 100...50mm 50%. All balls in sag will be have spherical shape. Unloading balls in ball mill after one day will be spherical too.

Usual SAG consumption milling mid hardness ores (say WI 16) can expect 300-400gr per tonne of ore milled. Harder ores and media breakage a take these numbers well over the KG per tonne consumption. We have seen (first hand) in access of 3kg/mt, due to unnecessary media breakage due to incorrect media grade/size selection.

Collectively all of us have the task to look closely in comparing new designs in equipment, meanwhile we also have the task to "optimize" existing equipment. Strict SAG operation does not include grinding only crack the ore and discharge with only short transitional time in the primary mill. However, now we are all seeing higher ball charges and ore levels in these primary mills. Targeting a smaller size particle (P80) is the reasoning most likely for this? Taking some work from the secondary mill(s) for an improvement in the final grind follows that same logic. Round media in the SAG mill in such cases then makes sense as round media in traditional SAG operation is no great gain (as no grinding is planned). Your percentages for media size seasoned charge distribution is similar to our own, but with pebble porting those smaller sizes should have been mostly discharged. SAG discharge being roughly classified by a screen to BM and oversize then magnetic separation and then to cyclone classification with overflow to the BM and underflow back to the SAG. Keep an acceptance of media retaining its shape throughout deployment and read further. BM operation using size/grade media blend to target the final grind - if the BM is at high efficiency then either throughput or grind can be adjusted with media selection - but not both. Recent site visits that we have had enabled both throughput and grind to be enhanced as efficiencies were low. Sorry to write these long comments about SAG/BM circuits but the point is that many circuits can be improved greatly and so may be a more accurate circuit to compare with the HPGR/VM alternative. The best thing that I see (please correct me if I am wrong), with HPGR/VM scenario is that there is far less chance of getting such a circuit operating incorrectly - simplicity is its greatest gift?

An HPGR has less things to look at, compared to a SAG or Ball mill, when trying to optimize its performance. The residence time is really short in this machine and it is really easy to take a sample to see what the outcome of a change was.

In contrast, when you change the grind media distribution in a SAG or Ball Mill you need to wait a much larger period of time until you see the final result. By that time the ore may be different, liners may be at different state of their useful life, you may have new operators, etc.

We should be ready to agree on some items that we, as a group, can accept as valid. 1. HPGR - VM is more energy efficient PROVIDED that the ore body remains very consistent. 2. HPGR - VM requires a lower skill set for operation. 3. HPGR - VM will trend out instantly if adjustments (rebuild) are required.

Laboratory and pilot HPRG tests, the last in closed circuit, aiming to qualify the response of your ore to the HPRG process; The tests will be developed on 1.21.5 t crushed ore, 50 mm size; I suggest you to select the P80 3 mm size instead 2 mm (HPRG process) in order to increase the dry screening efficiency, consequently, in order to reduce the screening CAPEX and OPEX and HPGR throughput; VM test on 60...70 kg ore, F80 3mm, necessary to the accurate quantification of the VM number/units; It is preferable, in order to reproduce the commercial operating conditions, to submit to VM test a sample resulted from the HPRG pilot test.

If you need the rough CAPEX and power consumptions required by the 6 options mentioned above, please contact me. For the current phase of your project (probably Preliminary Economic assessment or Scoping Study), the accuracy degree of my estimate is higher than the accuracy degree of your study. The VM tests will give you the very accurate VM number and power consumption. For the development of the tests, you can contact the METSO (VM) and Thyssen Krupp Polysius regional representative, or contact me in order to introduce you to METSO and TKP concerned people.

Selection -- Type of grinding system---- i. For very hard ores SAG mill. For soft ores and all FLOTATION TECHNOLOGY use HPGR. ii. Before taking decision consult Experts in Mineral processing for FLOTATION. iii. Do compare results of metallurgy for both. ivDo cost benefit analysis. v. Develop operator knowledge in controlling OPERATING PARAMETERS as per design, not as per fancy ideas given by many. Redesign if you fail to get results.( from the company who has supplied equipment.) vi. Many times ore characteristics changes as you go deep in the mine, or change location.

For all problems we have solutions. Clays in ore is 1st washed to -2mm, and +2mm. +2mm in INDIA will dry so fast that it will have hardly 6% moisture. You are giving examples of site specific. Yes you are correct if this ore is in cold countries at <10 C or where it is difficult to dry naturally. It will add to cost for drying +2 mm. 2.Let us not get confused with this subject. For some it is good for some it is not---This is based on situation, temperature, nature of ore, Flotation problems, Leaching problems, etc. 3.Anyone who want to use please do tests, and calculate cost benefit analysis form all points of view 100% then decide. It is only to know and gain more knowledge and each ones experience. Good to learn all have given reasonably good suggestions. All suggestions are very valuable and thought provoking. 4. We had very good time to learn many new concepts, practical solutions. We need not stop at one point and use age old technologies. New technologies are equally good. Let us learn how best we can make use of them. 5.Our priority is Mineral conservation, recovery, yield, simple operation, cost after installation. 6.Today Metals have become so costly that CAPEX and OPEX can be absorbed in profit.

TIGHTEST control of ore particle size throughout the "pit to product" flow sheet is agreed by all of us, as paramount. After looking at this forum contributor list, and their credentials, we can take this as 100% incontrovertible fact.

We have also discussed how that this can be done best - right on topic. Contributors have generously shared detailed firsthand information and also references to clarify points made. This has been invaluable to us all, it has certainly improved my own knowledge for one.

Agreed that this is a generalization, BUT we have, I think, given project designers a great "starting point" for initial assessment of equipment selection. The exercise has been totally worth the effort and we should all be pleased of the exchange. I do hope a balanced paper can be drafted on this very question, as it does have universal benefit.

Adaptation of HPGR as fourth stage size reducer for high clay and bit over critical moisture content feed ore is difficult because of the increase in force of cohesion for adhered fine particles on roll. This may spoil the plant reliability and operator's confidence. The same seems to be addressed by pre-screening for fines reduction, pre washing to reduce sticky adhered fine clays then dry and etc. HPGR consumes less energy for the same duty condition because

a. It works on breaking the particle to particle cleavages. The surface coatings took place at the time of ore body evolution in metamorphism may not damage to the greater extent as it happens in case of SAG - Ball mill combination. This activity may be desired or less desired for some onward separation process based on surface coatings. HPGR generates narrow band PSD particles. b. The SAG- Ball mill combination works on impacting and attrition action and the particles residence time increases with its size and density combination. This will generate slimes of high density valuable mineral particle, which is undesired activity and consumes unrequired energy. The hydro cyclones in efficiency will also add up and increase in close circuits grinding operation.

Size reduction is a liberation process which needs to be designed or focussed to felicitate more on wards separation process results. Off course selected combination essentially needs to strengthen plant reliability and economy.

The HPGR has earned a place in front end processing by being the best cost option for particle resizing, if the ore body has fixed and reliable characteristics - even I accept this and we are a ball supplier! I am content however, that the SAG mill still has greater utility in its flexibility to handle a wide range, or changing feed ore characteristic.

In the early releases there was too much expectation in HPGR ability to handle some great variations in an particular ore bodies. Careful planning of what goes in HPGR gives you the fixed and reliably fixed discharge result. I think Boddington (Australia) is happy with current results over the other option of 3 X 40' SAG mills, this will be one to research for sure.

New technologies generally take years to get traction with mining companies but once they do get something good they learn to use it well. It always needs a senior operations person to champion the cause before there is "traction". Then that is just step #1....

We have had some new developed products accepted by large mining houses and not by the smaller ones and vice it just depends on the company people to embrace new things or to even get them to consider....I have found the copper guys to be more interested in exploring things lately...(probably something to do with USD3/Pd?).

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arri | inspiring images. since 1917

arri | inspiring images. since 1917

ARRI builds global solutions business with end-to-end cine and broadcast solutions. First reference projects include mixed reality studio DARK BAY and WELT TV studios, entirely equipped with IP-based lighting technology.

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4k security cameras - cctv camera world

4k security cameras - cctv camera world

4K Security cameras by CCTV Camera World allow for the best quality image and clarity. The 4K cameras featured on this page use state of the art 8MP image sensors. This allows our 4K surveillance camera to produce an image that is nearly four times the size of a standard 1080P HD security camera. Larger sensors also capture more light, which improves low-light performance, and overall picture quality. High pixel density allows for clear digital zoom which is another great benefit of our 4K security cameras. No more worrying about pixelation when you zoom in to gather more detail like a persons face or license plate numbers. Finally, our 4K security cameras support H.265 encoding (also called HEVC or High Efficiency Video Coding), which helps keep the file size smaller without sacrificing any quality. Rest assured knowing that our security cameras capture the highest quality picture to protect your home or business. Click here to read more about 4K surveillance cameras. If you're interested in purchasing a complete surveillance system featuring these cameras, be sure to browse through our 4K security camera systems.

CCTV Camera World is proud to announce that we now carry the highest resolution IP cameras available in the security camera industry. Our line of Ultra HD (aka UHD) 4K NVR recorders and IP cameras support up to 4K resolution real-time live viewing and recording, and camera sensor resolutions of 8 megapixels and 12 megapixels. 4K security camera systems are perfect for large area coverage and identifying objects at a distance even in recorded video. You can capture video with wide-angle overviews with multiple focus points while maintaining the ability to digitally zoom in and focus on the fine details.

Depending on the size of the 4K security camera system you need, we offer network video recorders for 4K cameras in densities of 8, 16, 32, 64, and 128 channels. The 64 and 128 channel NVRs are available with hard drive Hot Swap ability which comes in handy in professional and business security projects where long term video storage is needed. Drive Hot Swap lets you replace video storage without ever having downtime.

4K security cameras are the latest and greatest in video surveillance. With image quality that is nearly 4 times that of standard HD 1080P quality, a 4K camera is a must have to capture any potential activity around your home or business. With the advent of new and more cost-effective manufacturing, a 4K surveillance camera is affordable and extremely beneficial. 4K security cameras produce amazing detail at further distances without pixelation that is common with lower video quality. You can expect to see facial detail up to 60 ft with daylight conditions when utilizing 4K security cameras and the massive amount of digital zoom they have to offer. For a comparison to lower resolution security cameras look no further than the table below. Like the saying goes a picture is worth a thousand words.

As you can see there is really no competition between the clarity of lower resolution cameras to the image our 4K security cameras capture. Even the above table cannot fully demonstrate the benefit of investing into a 4K resolution security camera system unless you see it for yourself. The much larger image size grants exceptionally better digital zoom for instances where you need facial detail and even license plate numbers.

The short answer is yes, 8MP is the same as 4K. However its important to understand the relationship between the Megapixel format and K or P format when talking about image resolutions. MP refers to Megapixel or Millions of Pixels, which is often spoke about when referring to a cameras sensor, or what a camera uses to capture video or pictures. The K or P as in 4K, 2K, 1080P, or 720P refers to the video standard that is associated with the Megapixel lens a camera uses. 8MP and 12MP are both referred to as 4K resolution, which is also known as UHD, or UltraHD. Compared to 2MP or 1080P, known as standard HD, there are approximately four times the pixels in a 4K or 8MP image. Conversely a 2K or 4MP, known as QHD or Quad HD, image has roughly half the pixels of a 8MP image. The MP number is calculated from the actual resolution that a camera produces, examples include 3000x4000 for 12MP, 3840 x 2160 for 8MP, down to 1920x1080 for a 2MP camera.

When considering a purchase that protects your home or business it is important to educate yourself of all the possibilities. With that in mind you want to ensure that you protect your investments in the best way possible. 4K security cameras allow you to rest at ease knowing you will not miss anything important that happens on your property. You do not want to sacrifice quality for the sake of saving yourself money upfront by going with a lower-end security system. Todays criminals know what they are up against, and it is easy for them to sneak around or conceal themselves from lower quality cameras. 4K security cameras greatly reduce the opportunities these subversive culprits have to avoid critical surveillance.

Mainstream CCTV cameras have been D1 resolution (704x480 pixels) for the longest time until 2014, with megapixel sensors being price prohibitive for the home or small business. As image sensor technology improves, it has gotten cheaper and allowed 1080P cameras to become so affordable that they are on pace to replace analog resolution security cameras as the base resolution for a starter system. 1080P HD security cameras are more than adequate for indoor use where the subjects are no more than 40ft away from the camera, and even for outdoor use in most cases. However, if you wish be able to zoom in and identify facial detail on recorded video at distances of 30ft or greater, that is only possible with 3mp ip cameras, or greater resolution cameras. If you're looking for the most detail at a wide angle, then 4K IP cameras are the recommended equipment.

This higher level of detail in the picture afforded by a higher pixel count makes 4K security systems ideal for high-traffic areas where detail is crucial in identifying the difference in someone dancing and fighting. Too often, lower resolution security cameras leave ambiguity lingering as to what really occurred in a surveillance video clip. 4K cameras clear up this ever so present uncertainty in video footage. Athletic fields, Schools, universities, big box retail, train/bus stations and government facilities are just a few of the industries that could benefit from these 4K security cameras.

CCTV Camera World is an established CCTV equipment distributor in the USA with shipping locations nationwide. We test every product we sell to make sure it is worthy of our name, as we stand behind all the products we sell.

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