Laboratory Testing & General Mineral Processing Engineering

Laboratory Testing & General Mineral Processing Engineering 2017-04-04T06:57:51+00:00
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Concentrator Completion Tests – Process Equipment Performance Guarantee (31 replies)

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

Which parameter (Grade, Recovery and Reagent, Utility consumption, etc.) could be defining in concentrator plant (Flotation& Grinding) performance guarantee? How can we determine the liquid damages?While recovery is a deciding factor in performance guarantee figures, however measurement of recovery in the plant could not be effected in ideally constant and unvarying conditions. Therefore such measurement should also take into consideration this fact by considering and applying the concept of standard deviation. In other words, in determination of liquidated damage, (and for example deduction of 1% of contract value for not achieving the targeted 89% recovery), different variable conditions prevailing during measurement of recovery should also be considered in view of the respective standard deviation.

Gruppen
1 year ago
Gruppen 1 year ago

There is a trade off between grade and recovery. More grade less recovery. I would prefer to penalize both. For instance 1% of the investment (of the flotation equipment, if the grade is less than 0.5% of the expected, and the recovery 2% of penalized if the recovery is lower than a certain value +/- 0.5%. Only as example. However in some cases if the recovery is lower and the grade if higher also is a compensation clause.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

Results from plant tests for process guarantees will depend on the properties of the ore being tested, compared with the properties of the ore which was tested to develop the guarantees. The plant feed should be sampled throughout the performance test, and then the sample subjected to the laboratory procedure developed for the performance guarantee. This may include reagent dosages, pH, eH, as well as the grade/recovery relationship, which can be compared using the grade/recovery curve, rather than a single point. The grade/recovery curve may shift due to conditions being closer to optimum for the laboratory conditions than for the plant conditions. Differences should be investigated.

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

Do you have any procedure about performance guarantee test?

Unterstarm
1 year ago
Unterstarm 1 year ago

Grade & Recovery are the two deciding factors in a plant along with the reagent consumption to know the health of the Unit.

Bill Fraser
1 year ago
Bill Fraser 1 year ago

There is a connection between ore mineralogy and flotation results and the information below would help you.A few aspects of the connections between ore mineralogy and flotation results at Hitura nickel mine in Finland

Abstract
The serpentinite massifs of Hitura are located in the municipality of Nivala in Central Finland. The most important sulphide minerals in the ore are pentlandite, pyrrhotite and chalcopyrite. The ore body consists of amphibolites rocks in contact with serpentinite against mica gneiss. The mean Ni grade of the ore is about 0.7%, and the highest Ni grades have been encountered in close contact. In general, the inner parts of the ore are strongly serpentinizedultramafite and some sulphides have been converted to mackinawite and valleriite. The degree of alteration varies considerably within the ore body and, correspondingly, the grain size of the sulphides varies as well. In this study, flotation tests were done with samples from different zones of the ore body. The flotation test results on the bench scale and plant scale are discussed in terms of the mineralogical features of the ore. Ores in the North Hitura zone differ from those in the South Hitura zone.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

I have no knowledge of your project, or the contract that you have negotiated, but hope that the following notes will help.

Negotiating a contract for the construction of a minerals processing plant is a complex business. The type of contract determines the shares of the risk to be taken by the owner and the contractor. The contract will cost the owner more if the contractor provides a performance guarantee. This guarantee will include equipment warranties and plant reliability to give an overall plant availability, as well as a throughput guarantee. If in addition a process performance guarantee is provided, the contractor will need some results from ore testing to determine what grade, recovery, reagent addition, etc. can be guaranteed.
If the project is expanding an existing plant, or building a new plant to treat the same ore type, results are already available. If it is a new project, a representative sample of ore needs to be taken for plant design. This sample may be made up from drill core or bulk sampling. It may represent average ore for the life of the mine, ore for the first two years, or a range of ore types and blends to allow for variability in the ore body. The test sample for the performance guarantee has to be matched with the ore treated during the plant performance tests. The sample needs to also match the Mine Production Plan.
The performance test usually requires the plant to give the required result for availability, throughput, grade and recovery during continuous running over a set time period. A suitable parcel of ore needs to be available to cover this time period. Samples may be collected hourly and composited over various times periods to provide performance data, as well as for standard comparison laboratory tests using the designed reagent scheme and dosages.
Overall it is the owner who ultimately takes the risk that the plant does not perform over the long term. There is much more money in a well-performing plant than in claiming damages from the contractor.

Bill Rico
1 year ago
Bill Rico 1 year ago

The parameters can’t be treated individually, all them are related and many times it is a chain, because it’s a multivariable operation (i.e.: more reagent=better recovery and less concentrate grade), usually the utilities consumption is constant and is used in according to the ore features. About liquid damages; could depend of the contractual conditions and this is a right of the buyer. All results depend on the route and definitions during the initial tests. In the plant’s operation is hard but possible to correct last mistakes. In other words; all can depend on the quality of the metallurgist, and the best metallurgist is the Ore processed.

Oberstorm
1 year ago
Oberstorm 1 year ago

Performance guarantee as regards feed and products at different stages in the process with weight recoveries and grade based on which we determine metal recovery , normally done based on initial test data of a representative sample or samples based on operation regime whether first 5 yrs or later. In actual plant practice, you do not get the feed characteristics as tested so it’s better to have a range for weight recoveries / grade/metal recoveries for performance guarantee purpose beyond which penalty may be charged. Al the operating parameters also need to be evaluated for performance guarantee test work.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

In my opinion, if the owner's business strategy is long term efficient and sustainable production of optimised product, then it is the owner's responsibility to ensure representivity of the samples for testing, and to match the test results with the Mine Production Plan and the ore used for the performance test. It is also ultimately the owner's responsibility to confirm the work of the contractor, in terms of fit-for-purpose, operability and maintainability of the equipment and layout proposed. A high quality owner's team, as well as the contractor's team, is essential for the success of the project. The key is for both teams to work together for mutual benefit.

Overall, although equipment warranty is essential, including capacity and availability, a process performance guarantee is probably not worth pursuing. If after all the work that has been done, the predicted results cannot be obtained, then something is very wrong with the project! Once the plant has been commissioned and is running steadily, it is the job of the metallurgists and maintenance team to aim for continuous improvement in productivity, product quality and valuable component recovery, while reducing unit costs.

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

Thanks for your comments. As I understand if the plant works steadily with normal process result after commissioning, we can accept the deliver the plant. Is it true?

Because based on my experience the guarantee figure in contract usually is not achievable during performance guarantee test.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

What you are saying is in my opinion the best way to go, provided the performance test result is achieved within a reasonable range of reagent additions, concentrate grades and recoveries. All major deviations should be removed during commissioning, including those due to grind size distribution and pulp density. However, surprises may occur. An example from my experience was flotation cells that could not produce froth. At first this was blamed on the supergene ore being treated, as opposed to the primary ore in the laboratory test program. The problem was actually the compressor for the flotation air was under specified, and was unable to generate sufficient pressure to overcome the head of slurry in the cells. So in this case, although the sample was incorrect, it was an equipment design problem, not a process problem. It is good to keep an open mind when commissioning!

To qualify my previous comment:
If a contract has already been signed which includes a process guarantee, it is likely that the contractor has included this risk in the price to be paid by the owner. In this case the owner should investigate the possibility of at least part of the contractual damages being recovered. However, unless the results show a major deviation, this should not distract from starting production and optimising the plant. As you say, it is difficult to achieve the guarantee figure, usually due to differences in the ore. If the performance test parcel is sampled and put through the developed laboratory test procedure, the payment of damages may be based on the difference between these results and the actual plant performance.

If a contract has not yet been negotiated, then if a process guarantee is to be included, then the performance test should be based on a laboratory test of the ore actually treated, rather than the results from the laboratory test sample used for design. In the long term, when the ore used for the design laboratory tests is treated in the plant, the results should be closer to or even exceed the design predicted result.

A contract which does not include a process guarantee should be considerably cheaper.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

I do know your project from several years ago when you were building a copper processing plant. From that experience you would have learnt that once the plant is commissioned - then the real work begins - how do you optimize what you have bought?

I am sure that your previously installed plants are now probably running at a greater efficiency that the equipment nameplate suggests.

Gruppen
1 year ago
Gruppen 1 year ago

How long do you think a performance test should take? And how,long the plant it should run before this test to see whether the plant is according to the design parameters? And what about the energy consumed on the process? It should also test as a guaranty?

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

I agree optimization and productivity are the real game with whatever plant has been provided. Jorge's point about energy consumption is very interesting, and is now beginning to be addressed in new plant design, especially in the energy efficiency of size reduction, including blast pattern and powder factor in the mine to reduce oversize and fines generation, where blasting may be the most energy efficient form of rock breakage. Conventional autogenous milling and HPGR are also aimed at energy efficiency, including savings on mill liners and grinding ball consumption. Another key is to reject material of no value at the coarsest possible size. Liberation tests should include both waste and valuable components of the ore. This includes selective mining before the ore reaches the stockpile, as well as ore blending.

The plant commissioning and performance testing are always under a great deal of time pressure. This is when all the money has been spent and no income produced. The mine has ramped up to full production and stockpiles are filling rapidly. Management expectations are daily increasing. Any delay in producing saleable product is very expensive, and will not be covered by contractual penalties.
Many decisions have to be made - is the ore suitable for the performance test and is there enough of it? Is it sufficiently blended to avoid unsteady plant operation? Should the mine separately stockpile surface ore in order to provide fresh ore for testing? Should the plant be started on waste or low grade ore to avoid possible losses from good ore? Should the priority be throughput, concentrate grade or recovery? Can all be achieved at once? Does it depend on the nature of the plant and the ore being treated? Is the processing stream composed of many unit processes, which could be commissioned and tested independently, or must it all be tested in one run, for example crushing section first, upgrade section later? How easy is it to evaluate performance before assay results are available is on stream analysis included which has been pre-commissioned?
The time required for the performance test is very process specific, could be anything from 48 hours to 2 weeks. This can be disrupted by breakdowns or required modifications, when the test will need to be re-started to give the required period of continuous operation.

Bob Mathias
1 year ago
Bob Mathias 1 year ago

I would say it's pretty simple. It's the combination of grade and recovery that makes the most money for the company. The two are usually inversely related and there is an optimum.

Marshal Meru
1 year ago
Marshal Meru 1 year ago

At feasibility stage, is recovery already modelled with grade, grind, reagent dosage, pH, density? Or is it usually just grade?

That plant performance guarantee should be based on lab results shows that the laboratory, most often neglected, must be built at pre-commissioning stage, if recovery has not been modelled thoroughly during feasibility study.

Furthermore, most feasibility study test work are done on samples deep in drill holes, and not commissioning ore.

I think main drivers for performance guarantee should be grade and recovery bands (at a certain confidence level), given a throughput band for a specific ore type/section of the ore body.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

The Feasibility Report should have fixed the values for throughput, concentrate grade, recovery, expected reagent dosages, pulp densities, pulp densities - in fact everything to allow the project to proceed to FEED - Front End Engineering and Design, which includes final selection of processing equipment and detailed design to connect it all together with pipes, pumps, conveyors, utilities supply and control equipment.

But, as you say, the laboratory tests have not been carried out on the ore which will actually be treated, so a practical view of the results obtained has to be taken. It is the responsibility of the owner to make sure that the ore for the performance test is as close as possible to the ore tested in the laboratory, on which the design was based. It is always good to have a laboratory on site ahead of commissioning, but other facilities elsewhere can be used, such as the original test laboratory. The issue is delay in obtaining results. However, experienced commissioning metallurgists can usually tell whether things are going right or not. An on-site metallurgical laboratory is very useful for plant optimization and testing future ore supplies.

A couple of thoughts on the grade/recovery relationship:
First, the laboratory test work and later plant optimization are based on moving the grade/recovery curve to a higher level, by using collectors with greater selectivity, depressants, modifiers, grind control, etc. It is also possible than different flotation equipment mechanisms can improve relative flotation rates.
There are many differences between the laboratory manual flotation tests and continuous plant operation, including using one sample compared with continuously varying feed, and the bias of the laboratory test operator, who is trying to get the best possible result.
The second thought relates to economic recovery, where the grade/recovery curve is optimised, but the choice of where to operate along the curve remains. For example, at times of high product prices, recovery might be favoured over grade. The trade-off is the extra value of the recovered material, compared with extra processing and concentrate transport costs. There is also a risk of introducing more penalty elements into the concentrate if high recovery is the target. Lower grade concentrate also implies higher throughput to maintain or increase overall production of the valuable component.

Hauptsturm
1 year ago
Hauptsturm 1 year ago

This is a business decision about risk sharing. Why do you want to transfer the risk? Can the guaranty be enforced if push comes to shove? Will some third party hold the guaranty, can they be trusted or will international banking laws change during the construction and commissioning phases? After the recent Russian sanctions there is lot less certainty in international banking. The equipment suppliers should be able to guaranty equipment availability and consumables (here wear components rather than reagents). Anything beyond that they ought to be doing their own drilling because they are acting as a mining company and taking a commercial position on the ore while it is still in the ground.

For some simple unit processes (such as dewatering) the full scale performance can be compared to a test sample with a defined testing procedure. This is much more difficult for a whole concentrator (hence your question!). Even for bulk commodity bene plants there is always something hidden in the ground. For polymetalic concentrators I'd guess that the drilling costs involved in getting a meaningful guaranty would be higher than the guaranty value.

What recovery would you have expected from the Bre-X deposit?

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

I agree with what you are saying - it is the responsibility of the owner/client/mining company/exploration company to provide samples for processing plant design. There are a few possibilities:-

The owner designs and arranges for the test program to be carried out by a reputable laboratory and the contractor takes responsibility for the results.

The contractor designs and carries out the test program. Either way, equipment suppliers will either have to be satisfied with test results, or will want to carry out their own tests.

The expertise required from suppliers is predictable conversion of small scale test results to full size equipment results.
Whichever way, a large quantity of sample is required to cover both average ore and variability. The sample will most likely be composited from expensive drill core at a time when the project can least afford it. The dewatering tests referred to in your comment require concentrate or tail from previous test work. It takes a lot of drill core to provide concentrate from a low grade feed.
A considerable amount of test work will have already been done by the owner as part of the ore definition program, including demonstration of economic recovery required to comply with the JORC or other codes. It reduces costs significantly if the contractor and equipment suppliers can use the information generated as a basis for design.
In conclusion, equipment manufacturers and the contractor can only give a guarantee on the ore sample tested, with perhaps a range of variability. If the performance test sample differs significantly, a guarantee cannot be enforced.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

Guarantees from suppliers are readily available; we actually do this with trials whereas we guarantee to cover any additional costs incurred when testing our media. However you do need operational data to set firm, known, ACTUAL costs to get that comparison.

Feasibility modeling is an estimate, and only that, an estimate.
Work practices are also a part of our guarantee assessment as well - for example we have seen "grind outs" as a regular practice on some sites. That is in most cases fine, but there other grind out regimes that may run for 30 minutes at full mill speed, which may actually destroy an entire ball charge - then if that practice is not negotiable we may walk away.
Commissioning clarifies design errors. We have seen commissioning pinpoint serious issues such as pipe size and pump capacities which need urgent adjustment to make the circuit work. Until that plant has run correctly for months, how would any supplier offer performance guarantees for their products.
Create a history which gives you a SOLID performance reference point to compare efficiencies before doing product evaluations.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

I agree that the plant owner must take joint responsibility with the equipment or consumable supplier to ensure that the test conditions give the best possible outcome, since this is what it is all about. This implies, as you say, that all major capacity and reliability issues have been fixed during commissioning.

There are two situations here, the first where a plant is already up and running with an established performance, which is seen as having potential for improvement. For example, grinding balls and flotation reagents. The second is a totally new plant, where the supplier may be expected to take some responsibility for equipment or consumable performance, based only on laboratory test results. There has to be some way that the owner can make a decision between different suppliers. This depends on the supplier being able to scale-up laboratory test results, normally using their own in-house data bases and procedures. Of course, the supplier may simply give indicative mass and volume capacities or consumable consumptions, leaving it up to the experience of the owner's selection team to decide which equipment is likely to perform best. It is a bit too late if after several months of steady operation, the equipment fails to meet reasonable expectations. It is also fairly easy to guarantee a performance that has already been achieved. Ultimately, capital cost often over-rides any perceived performance advantage!

Maya Rothman
1 year ago
Maya Rothman 1 year ago

Often I see grinding scenarios that leave room for improvement, they are the only ones we guarantee performance in. In 90%+ of these trials we propose zero capital cost additions but leave the site with a new control lever - how to use only media grade/size/blend to adjust the milling.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

Things very quiet in Tasmanian mining at the moment, lots of projects but no capital to get them up and running, with the low metal price outlook. Time for the next big cost reduction innovations! Do you include changes in pulp chemistry in your grinding ball tests? Not sure if it is still the same now, but first fill with high specification grinding balls can add a lot of capital to the project.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

Same over here, projects are all ready to go but the market holds them back.

Pulp chemistry is an interesting topic - but we only show interest in the PH levels and discharge particle size distribution data; these are the only grinding media related issues.
In line with the forums topic you mentioned the expense of an initial ball charge on commissioning. We like the "first fill" opportunity as we calculate where the ball charge will be after natural seasoning of sizes by percentage. With that data we usually supply about 6 to 8 different sizes in that percentage size distribution. That then brings down the "ball commissioning" down to days rather than weeks. The sooner you have trended data in your hands the sooner you can adjust the media grade/size/blend to target priorities such as grind and throughput. We are just about to complete a two year case study for a single stage BAG mill (barely autogenously grinding) - the last touch should be adding a 27% by weight addition of a 90mm ball to a top size 115mm ball. This should give us a cyclone underflow of about 90% passing 200 mesh. That is like sinking a 65' putt on an undulating green!

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

If autogenous milling was selected during process design, it looks like something went wrong with the decision-making process! Hypothetically this could be due to poor sample selection, insufficient test work, incorrect interpretation of results and over-optimistic predictions by the supplier or project team.

An alternative to adding grinding balls is optimising the feed ore size distribution to generate the optimum mill load size distribution, instead of using grinding balls to generate it in the mill. It looks like this particular mill has now become a ball mill! I have knowledge of excessive weight causing structural damage when an autogenous mill was converted to a ball mill by continually increasing the ball charge.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

You may know the name Marcus Binks (a circuit commissioning specialist), whom I first met in Tasmania. He was given the task of commissioning an AuRico site in Canada a few years ago. It was supposed to be a fully autogenously operated mill. Marcus watched it for a few days and threw in some 5" media - the mill was at operational nameplate throughput in a week or so. Fortunately for Marcus the mill bearing and structural design allowed up to a 40% ball charge. We have done assessments on AG to SAG in the past, bearing load capabilities usually only allow a 5% ball charge but also the liners needed replacement as they were extra hard and brittle and would not survive alloy steel ball impact for long. I have only seen a few AG mills that suit the strategy well, pancake mills and very low work index ore for example. It does still allow possible change to SAG in many cases.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

It is interesting in the example that a small volume of 5" media was seen to be required. This indicates that the critical size fraction was the coarsest rocks, which needed a bit of impact from the large steel balls to increase the breakage rate to give equilibrium with the new feed appearance rate. It would seem that this reduced the critical size fraction to finer than the discharge grate aperture, thus removing the bottleneck from the AG/SAG mill. The alternative for a medium critical size is to install a pebble crusher.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

I may be wrong here but would you pebble port the SAG to allow these to be separated for crusher feed? If so, then magnetically removing the steel (which can be recycled into a secondary ball mill) and screening out ball mill feed would seem the plan?

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

As you say, pebble-port grate elements would be used to release the pebble build-up, with magnetic head pulley removal of steel from the screen oversize recycle belt. This is a problem if magnetic ore is being treated, but it can be overcome. Another circuit that is possible is pebble milling instead of ball milling, using the pebbles as grinding media instead of crushing them. Usually pebble mills need to be much bigger for the same throughput, and only work for specific ore structures. Steel balls are needed to increase the breakage rate, by increasing the proportion of impact and attrition breakage compared with abrasion.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

We have found that ball milling or single stage mills can have some interesting options as well. Blended sizes of compatible ball grades - gives some top size energy and control of the small ball population for grind. We are thinking about aggressive lifter bars for ball mills as well, now that we have developed a "non spawling" ball mill and SAG mill ball....

Break that kidney area build up and pooling. Previously this was unthinkable as ball mill media was too brittle - but we have not traded off the hardness, just increased the toughness.
A awesome product.

David Kano
1 year ago
David Kano 1 year ago

Yes it is true Recovery will give a good Per, Guarantee and parameter for measurement. But you forgot costing in down line operation after recovering minerals. Grade will play a major role in down line operation. EXAMPLE: ISM>5% in Zn Con is Rejected in Imperial Smelting Process.

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