luanshya's recommendations

8/14/2019 Luanshya's Recommendations

1/20

Luanshya Report

by

Ramoutar Seecharran

(Ken)September 2009


2/20

2

REVENUE vs GRADE

28

28.5

29

29.5

30

30.5

31

31.5

32

1.2 1.25 1.3 1.35 1.4 1.45

REVENUE ($/lb)

CONS

GRADE

(%Cu

LUANSHYAs RECOMMENDATIONS

A visit was made to Luanshya concentrator in September 2009. Observationswere made. The author has 16 years experience in the Luanshya plant, 6 yearsin a senior position, in charge of operations and maintenance. Theserecommendations are based on those observations made and the authorsknowledge of the mine. The synergies derived can be replicated at the Chambishimine, wherever possible, for the enhanced profitability and efficiency of thegroup.

RECOMMENDATIONS

1. The installation of a regrind mill should be seriously considered.Regrinding of copper rougher concentrate prior to cleaning will have athree-fold effect, namely: The concentrate will be of a higher grade, approximately 29-31% Cu is

anticipated. Entrained cobalt in copper concentrate will be minimized. Most

smelters do not pay for cobalt content of copper concentrate, as thecontained cobalt is lost in slag. And,

Referring to Figure 1, does a plant always strive to operate at theoptimum profitability point? Assuming it was budgeted to operate at a

concentrate grade of 30% Cu but during a part of the period the plantoperated at (30%) for the remainder of the period so that on average a grade of30% is achieved. If so, a loss of revenue is incurred during bothscenarios. It is best to operate in the oval area. This gives a factor ofsafety to plant operators. Regrinding of rougher concentrate beforefinal cleaning will guarantee operating in the oval area.

A regrind mill is available on the property, it needs refurbishing and pipe workinstallation to be able to carry out this function.

Figure 1: Revenue

vs Concentrate

grade


3/20

3

2. Utilising forged grinding balls as opposed to cast balls will be moreeconomical. The forging process compresses and strengthens the grinding ball.

Very often, a poorly cast ball can end up being porous on the inside, Figure 2.The lines of stress travel from one void to another and such a ball shattersprematurely when compressed in the mill, Figure 3!A shattered ball does nothave the kinetic energy to break rock and it sits in the mill taking upuseful space and consuming power! If cast balls are to be used, and theyare to be sourced from within Zambia, then Zamchin is the best manufacturer inthe country. Crasters from Zimbabwe must be avoided at all cost; they producethe most inferior balls. The Chinese forged balls manufacturers are quiteconsistent in quality, Table 1. If the combined buying power of Luanshya andChambishi is used as leverage, a more favourable price might be negotiated.THE RULE OF THUMB IN CHOOSING A MILL BALL IS HARDNESS;

CHOOSE A BALL WITH ROCKWELL HARDNESS (HRC) IN EXCESS OF 55OR A BRINELL HARDNESS (HBN) IN EXCESS OF 450. The forging processchanges the balls microstructure from that resembling pearlitic to martensitic.Compacting the grain structure in the process and densifying the ball at thesame time. We then get a ball of uniform hardness, unlike a cast ball which ismuch softer in the centre, Figure 4.


4/20

4

Figure 2: Section of a poorly cast mill ball

Figure 3: Shattered mill ball

Figure 4: Hardness across a cast mill ball

BRINELL HARDNESS ACROSS BALL

0

50

100

150

200

250

300

350

400

450

500

1 2 3 4 5 6 7 8


5/20

5

Table 1: List of popular mill ball manufacturers, those shaded green areacceptable manufacturers and should be pursued

3. Star rotors on flotation machines should be rotated every year.This will prolong the life of the rotor and even out wear, guaranteeing celldynamics over a longer period of time.

4.A feed well must be installed in the Baluba and Luanshya 250thickeners. Figure 5. The need for this will become evident in the coldseason. Pulp entering the thickener could be about 28o Celsius whileambient temperature at 0300 hours might be as low as 3 degrees. Thiswill set up a convectional circulation in the thickeners and it will bringslimes to the surface, they will then short circuit towards the overflowlaunder, leading to a dirty supernatant overflow. This is often reported bythe plant operators as a SLIMING THICKENER. A feed well will ensurethat the feed solids is fed below the teeter zone, which will act as a filter,and prevent fine slimes from rising to the surface. Conveyor belting boltedto a steel ring can be used.


6/20

6

Figure 5: Proposed feed well installation on Baluba and Luanshya 250

tailings thickeners

5. Workers must be sensitized to cost and the cost of productionevery minute of the day. It is advisable that popular items and their costsbe displayed at prominent points so that the workforce can get anunderstanding of the cost, eg safety boots, 1 kg of grease, a loader tyre.

A litre of diesel etc. Production cost in /lb must be displayed atprominent points as and when they are updated.

6.A rapid response team should be found in every section of thecompany in order to safeguard lives, curtail injuries and protect thecompanys assets in the event of an emergency such as fire, flooding,chemical spills, sabotage etc. Such team should hold regular practicesessions and drills. Any member, who misses two consecutive practicesessions, should be replaced. Every member of the team should be paid abonus to motivate them. They should all be familiar with the geography oftheir section, the areas posing hazards, emergency switches and isolatingvalves, emergency telephones etc.

7. The use of synthetic oils in underground loaders must beimplemented. They can withstand overheating better than mineral oils.The poor ventilation conditions underground make them susceptible tooverheating and subsequent engine seizures.

8. Wherever possible, froth pipes should be changed to openlaunders. An open launder allows the froth to aerate, Figure 6, so whenit enters a pump box, there is no overflowing and pumping efficiencyimproves. In addition, an open launder provides a gentler flow into thesump and minimises additional air entrainment from a high velocitydownward cascade. When overflowing occurs, plant operators instinctivelyslow down the flotation cells; this leads to a reduction in copper andcobalt recoveries.


7/20

7

Figure 6: Open froth launder, allows aeration of froth

9. The use ofHigh Density Poly Ethylene (HDPE) pipes instead of steel pipes

for slurry handling applications should be pursued, Figure 7. HDPE pipeshave six major advantages, namely: They are cheaper than steel pipes They are easier to fabricate than steel pipes, thermal welding is used,

Figure 8. Joining plastic pipes is much faster than arc welding of steelpipes

Skilled boilermakers are not required for their fabrication The risk of accidents is greatly reduced Expensive welding rods and gaskets are not required They are highly versatile and can be welded into a shape which a

metal pipe cannot be fabricated into, Figure 9.

Figure 7: HDPE pipe used for slurry handling


8/20

8

Figure 8: Thermal welding of HDPE pipe

Figure 9: 13 pieces of plastic welded into a triple bend

10.Lime and cyanide, used for cobalt depression, should be added tothe feed end of the mills, and not the discharge end, the reasonsbeing: The minerals need to be coated with cyanide and lime as soon as

they are broken in order to enhance the effect of depression, and


9/20

9

Using lime in the grinding circuit reduces mill balls and linersconsumption. The chemistry being, MOST OF THE IRON ISDISSOLVED AS IRON HYDROXIDE, THIS IN TURN, INTRODUCESHYDROGEN INTO THE PULP FROM THE DECOMPOSITION OF WATER

AS HYDROXIDE IS FORMED. PULP ACIDITY, AND ULTIMATELY METALCONSUMPTION, IS INCREASED FURTHER. The problem is exacerbatedwhen grinding in a pulp of pH below 5.5.

11.A culture of good housekeeping must become an essential part of life inthe flotation plant. Spillage, if not immediately cleaned up, startstarnishing.A tarnished sulphide mineral particle is slower to floatand stands a greater chance of reporting as tailings, leading tocopper and cobalt losses!

12.The mine should aim to operate between $1.5 and $2.0 perpound of copper produced after cobalt credit. The clear patchshown in the 5-year copper price chart, Figure 10. For a production costlower than this, a bonus could be paid to everyone employed at themine; the mechanism of such a bonus will need further calculations.Cobalt credit in the range of $15.00 - $18.00/lb should be used in

financial modelling. The clear patch in Figure 11.13.Reprocessing of 14 Shafts surface waste should be seriously

considered, Appendix I. This will constitute a variable cost andshould be very profitable. Blockage of the tails race has been aregular problem in the past, especially since the closure of the Luanshyaconcentrator, it is believed that the reduced throughput does not provideenough transport velocity to keep the tailings particles in suspension andsedimentation rapidly follows, especially during periods when the grindcoarsens, and plant throughput is reduced. The reprocessing of 14Shafts surface waste will alleviate this problem and utilize the excess

capacity available in the plant. The increased throughput through theplant will make the flow of tailings in the tails race easier.

Figure 10 5-year copper price chart, clear patch denotes target


10/20

10

Figure 11: 4-year cobalt price chart, clear patch indicates selling price

to be used in financial modelling

14.It is cheaper to crush than to mill ore. As a result, the crushing plantmust produce the finest product which will not restrict throughput. In sodoing: Milling rate will increase Grinding media consumption will reduce, and Milling power consumption will also reduce

The last two items comprising the most expensive part of thegrinding process.15.Good environmental stewardship must be on the mind of every

employee at the mine at all times. Luanshya is the last of the

Copperbelt mine along the Kafue Rivers catchment area and theunpolluted integrity of the river, Figure 12, must be maintained.


11/20

11

Figure 12: The Kafue River in the vicinity of Luanshya

16.Multiskilling of operators must continue throughout the year.This will allow plant management to: Select the best operators for a particular section, leading to improved

plant efficiency and encourage a culture of continuous improvement Assist in the smooth running of the plant during periods of

absenteeism, illness or leave, compassionate or planned.17. A culture ofzero tolerance must pervade the entire mine. Thefts,

dishonesty, alcoholism, drug abuse and similar misdemeanors should notbe tolerated!

18.Depending on the price of cobalt, a special section in the mine can be setup to extract cobalt ore from the closed (back) draw points if theeconomics make it feasible. This must be kept separate from normaloperations, or else, mine grade will drop. At Baluba, it is common forcobalt mineralization to extend about 1.5m into the hanging and footwalls beyond the copper contact, Figure 13. Here again, extracting andprocessing such material constitutes a variable cost component, as thefixed costs have already been incurred.

Figure 13: Sketch showing extension of cobalt mineralization into

hanging and foot walls of the Baluba orebody

19.Managers in all Departments must be proactive about safety andlead from the front. They must personally conduct the Departmental

safety audits.20.All managers must develop a culture of continuous improvementand must inculcate such attributes in their subordinates. Targets set andachievements must be reported in their monthly reports.

21. To encourage the workers to think of continuous improvement, asuggestion scheme should be introduced. 25% of the anticipatedannual savings should be paid to the worker who promoted thesuggestion, at a well-publicised public event.

22. One crusher, and its ancillary equipment (oil pump, screen, grizzley,


12/20

12

electrics etc.), is to be maintained each day of the week. There arefive crushers installed, two Standards and three Short heads. This willensure that the crushers are in perfect condition to execute Item 14above. Being a job that is carried out every week on similar equipment,the quality of workmanship and the time of carrying out such tasks, willimprove with time as mechanical proficiency improves.

23. A froth ring should be installed in the concentrate thickenersFigure 14, to prevent froth reporting to the settling ponds, Figure 15.The method involved is very simple, Figure 16. This froth ring should beconcentric with the overflow launder of the thickener. At the best oftimes, settlement in the settling ponds in inefficient, and if material doessettle there, Copper and Cobalt could be tied up for as long as threemonths, affecting cash flow. When the ponds are excavated and the wetconcentrate is drying in the sun, it acts as a bait for thieves! In the past,thieves have been known to set up camp on the old tailings dam,opposite the concentrate drying pad, just waiting for an opportune timeto pounce!

Figure 14: Froth ring required in concentrate thickeners


13/20

13

Figure 15: Concentrate thickener without froth ring

Figure 16: Installation of froth retaining ring on concentrate

thickener

Operators should be trained to recognise the copper and cobalt minerals.24.The sheen and texture of the froth can be used as a guide. Based onthis knowledge, they should then be taught how to cut the froth layer to

maximize copper to copper concentrate and cobalt to cobaltconcentrate. Figure 17.


14/20

14

Figure 17: Methodology of cutting flotation froth

ACKNOWLEDGEMENTS

The author wishes to express profound gratitude to the management and

staff of CNMC Luanshya for offering him the opportunity to conduct thisstudy. The hospitality was heartening and made the homecoming a warm andmemorable one. The support of Mauritanian Copper Mines for making this trippossible at such short notice is also acknowledged. It is hoped that the linksestablished will enhance the entente cordiale between the two companies toenhance their efforts in efficiency enhancement.

RAMOUTAR SEECHARRANPlant Superintendent

APPENDIX I

SUPPLEMENTING PLANT FEED WITH SURFACE WASTE


15/20

15

This report, explains in details the costing and logistical implications which wereinvolved in treating waste rock from 14 Shaft and it contains proposals forutilizing excess plant capacity to continue the exercise. SINCE THIS PRACTICECONSTITUTES A VARIABLE COST COMPONENT, IT WILL HELP INDILUTING THE EFFECTS OF FIXED COSTS, AND MAKE THE OPERATIONMORE PROFITABLE. In addition, taking up the surges in tonnage supply fromthe mine will guarantee better plant control.

1: Assumptions:

The plant will process up to 3 000 tonnes of waste per day, working 24hours per day, this equates to 10 trucks of 15 tonnes capacity per hour.

Tipping of the ore will be done on the Cable Belt transfer conveyor, TB1,feed end. Tipping will be carried out North and South, thus allowing twotrucks to tip simultaneously, in a safe manner.

Figure 18: TB1 conveyor, waste to be dumped at tail end

Loading of trucks will take place at two points on the waste dump, thiswell ease congestion, and facilitate the smooth flow of traffic.

Since the waste was primary crushed before being tipped, there will be noneed for blasting. Large rocks will be shifted aside and manual labourused to break them before loading.

Since the waste is predominantly copper bearing, the chemical reagentsassociated with cobalt processing (lime, cyanide and dithiophosphate) willnot be required, contributing to significant cost savings.


16/20

16

Figure 19: Balubas milling section

2: Calculations:

3 000 tonnes per day. Feed grade 0.55% Cu, for average case scenario, 0.45% Cu for worst

case scenario, and 0.40% Cu for extreme worst case scenario. Plant recovery 65% total Cu, although higher recoveries can be expected

as shown below at the Frontier mine 50kms away, part of the samegeological formation called the Lufilian Arc.

Figure 20: Average grade waste rock treatment at Frontier mine

WASTE ROCK TREATMENT

66.0

71.0

76.0

81.0

86.0

91.0

0.14 0.24 0.34 0.44 0.54

GRADE % Cu

RECOVERY(%)


17/20

17

Figure 21: Low grade waste rock treatment at Frontier mine

Smelter/refinery combined recoveries 95%. Processing cost 7/lb recoverable copper for average case scenario,8/lb for worst case scenario and 10/lb for extreme worst case scenario

due to increased mill balls usage. Mining and transporting cost to plant, max 5kms, 5/lb recoverable

copper for average case scenario, 7/lb for worst case scenario and 9/lbfor extreme worst case scenario, because of the larger volume of barrenrock at the lower grade to be transported.

Overheads and contingencies, 3/lb recoverable copper for average casescenario, 4/lb for worst case scenario and 5/lb for extreme worst casescenario.

LME selling price of copper $1.10/lb, for average case scenario $1.00/lbfor worst case scenario and $0.90/lb for extreme worst case scenario.Figure 22.

2.1 Average Case Scenario

1. Production, volume and cost:

WASTE ROCK TREATMENT LOW GRADE

60.0

65.0

70.0

75.0

80.0

85.0

90.0

0.14 0.24 0.34 0.44

GRADE (%Cu)

RECOVERY(%)


18/20

18

(3 000X0.55X0.65X0.95)*2 205/100 22 466 lbs of copperper day.@ $1.10/lb $24 712 per day in revenue,say $24 500

2. Operating Cost: 22 466*(7+5+3)/100 $3 370, say $3 500 inexpenses

3. Profit: Daily profit is expected to be $24 500 - $3 500 = $21 000Operating 350 days per year gives $7.3m, or $0.61m per month profit

2.2 Worst Case Scenario

1. Production, volume and cost:(3 000X0.45X0.65X0.95)* 2 205/100 18 381 lbs of copper perday.@ $1.00/lb$18 380 per day in revenue,say $18 000

2. Operating Cost: 18 381*(8+7+4)/100 $3 492, say $3 500 inexpenses

3. Profit: Daily profit is expected to be $18 000 - $3 500 = $14 500Operating 350 days per year gives $5.07m, or $0.42m per monthprofit

2.3 Extreme Worst Case Scenario

1. Production, volume and cost:(3 000X0.40X0.65X0.95)*2 205/100 16 339 lbs of copperper day.@$0.90/lb$14 705 per day in revenue,say $14 500

2. Operating Cost: 16 339*(10+9+5)/100 $3 921, say$4 000 in expenses

3. Profit: Daily profit is expected to be $14 500 - $4 000 = $10 500Operating 350 days per year gives $3.67m, or $0.30m per month

profit

2.4 Extreme Worst Case Scenario, with doubled cost

Production, volume and cost:1.

(3 000X0.40X.65X.95)*2 205/100 16 339 lbs of copperper day.@$0.90/lb$14 705 per day in revenue,say $14 500

2. Operating Cost: 16 339*(20+18+10) $7 842 say


19/20

19

$8 000 in expenses3. Profit: Daily profit is expected to be $14 500 - $8 000 = $6 500

Operating 350 days per year gives $ $2.27m, or $0.19m per monthprofit

3: Conclusions:

The above presentation shows conclusively that the surface waste fromthe defunct Luanshya mine could be reprocessed profitably.

The copper price used is extremely low, current and long term sellingprice is expected at least double of what was used in this financial model,Figure 23.

The plant recovery used is very low, as the circuit is optimized; at least75% recovery is expected. Frontier mine 50kms away achieved inexcess of 80% recovery, Figures 20 and 21!

The costs expected to be incurred will definitely be lower, they will just beincremental costs, as excess plant capacity will be utilized with the sameequipment and labour force. The model assumed that waste wouldhave been treated by itself.

Considering the three points just made, above, the economics sways wellin favour of treating mine waste.

The mine manager could have a financial model on his computer, as theLME price increases; he will calculate when 18 Shafts and 28 Shaftswaste can be trucked into the plant from Mpatamatu.

While 14 Shafts waste is being processed, unemployed youths will beplaced on the two Mpatamatu waste dumps to hand pick copper rocks,they will be paid according to the copper content of such ore. This will

enhance community participation in the operation of the mine. This could become a model for the rest of the Copperbelt to follow,

utilising the vast tonnages mine waste discarded on surface, at everycopperbelt mine. But as the connotations which go with the name, thismaterial is often overlooked. This project will prove that with innovation,experience and ingenuity, such waste can be converted to a valuableresource to benefit the country, and reflect the proactive approach of thecompany.

The surface waste which is seen as an environmental eye sore will beprocessed and the ensuing waste deposited in the tailings dams in aresponsible manner.

The concentrate produced is deemed to be sweet for smelting. This isattributed to the high pyrite content which makes it exothermic (gives offheat, and saving on smelting fuel). In addition, it contributes to a lowviscosity slag, thus improving smelter recovery. Figure 22.


20/20

20

Figure 22: Sweet flotation concentrate, cherished by all smelters

Figure 23: 15-year copper price graph,..clear patch shows the

very conservative price band used in this financial model

RAMOUTAR SEECHARRAN (KEN)

luanshya's recommendations

Documents