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Minning Maintenance Realibility | Distributor Cone
The distributor cone is mounted directly below the feed well. The purpose of the distributor cone is to distribute flocculated slurry to the outside edge of the tank.
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Minning Maintenance Realibility | Overflow Arrangements
Clarified effluent typically is removed in a peripheral launder located inside or outside the tank. The effluent enters the launder by overflowing a 'V' notch or level flat weir. Uneven overflow rates caused by wind blowing across the liquid surface in large thickeners can be better controlled when 'V' notch weirs are used. The hydraulic capacity of a launder must be sufficient to prevent flooding, which can cause short-circuiting of the feed and deterioration of overflow density. |
Minning Maintenance Realibility | Underflow Arrangements
Concentrated solids are removed from the thickener by use of a centrifugal slurry pump, positive displacement pump or by gravity. The underflow arrangement must be designed to remove solids, without plugging upsets, at the maximum rate at which they will enter the thickener.
Provisions must be made to unplug or to bypass plugged piping so that solids can always be removed from the thickener to preclude their filling the thickener and stalling the mechanism. Underflow recycle back to the feed well is used in some applications to aid in flocculation of the unit during periods when the feed is reduced or interrupted.
These are two basic under flow arrangements and are as follows:
Tunnel
Centre cone pumping (open area) |
Minning Maintenance Realibility | Instrumentation
Instrumentation is used on most thickeners to measure torque in order to prevent mechanical damage to the drive or rake mechanism by actuating a rake lifting device or shutting off power to the drive in the event of an overload. Some applications also require automatic control of thickener feed or discharge to maintain acceptable performance when departure from the norm occurs.
An approximately steady state material balance must be maintained around the thickener. Although the volume of pulp in the thickener can be allowed to increase or decrease within harmless limits, it must be controlled to prevent, on the one hand, solids from overflowing the thickener and, on the other hand, the bed pressure from falling so low that the underflow density drops below desired values. Variable pumping rates can be obtained by use of variable speed pumps or flow control valves. Underflow density measurements can be made by routine checks using a device like a Marcy pulp density scale by the operator or on line through use of a density gauge. |
Minning Maintenance Realibility | Thickener Operation Rules
INPUT minus OUTPUT equals ACCUMULATION.
Excessive accumulation results in operating problems, usually requiring shutdown and
If solids are allowed to accumulate in a thickener without corrective action, one or more of the following will occur:
The pulp will begin to exit the tank with the overflow.
The underflow will become too thick to pump.
A 'doughnut' will form in the thickener and the underflow density will start to approach the feed density.
The rake mechanism will become overloaded and be stopped by the drive control.
Automatic control on a conventional thickener is usually achieved by an underflow density loop that regulates the rate of withdrawal of underflow. A turbidity meter is sometimes used to measure overflow clarity and regulate the addition of a coagulant or polymer flocculants.
These measures are not adequate on a HRT; because they would not give optimum control and could lead to excessive flocculant use. |
Minning Maintenance Realibility | HRT Control Systems
Briefly a HRT operates in the following way (see Fig 1): feed enters the feed well which is designed to promote deaeration and floc formation. If the feed has a high solids concentration, it is usually necessary to add dilution water to allow effective floc formation.
Flocculant is injected into the feed and deaeration and flocculation occurs as the feed moves down the feed well. It leaves the feed well by impinging on the deflector cone, which imparts a horizontal velocity as it enters the body of the thickener.
Most HRT control systems are based on the regulation of underflow withdrawal rate to achieve control of bed level. Hence, when any of the above parameters change the underflow valve position is regulated to increase the underflow discharge if bed level rises and vice versa. |
Minning Maintenance Realibility | HRT Control System at Sunrise Dam Gold Mine
The control system installed in the SDGM thickener is shown in fig. 2 where the underflow density is controlled by a bed mass pressure probe and the flocculation rates controlled by a bed level probe. The control strategy based on bed mass is explained below. |
Minning Maintenance Realibility | Rittershaus & Blecher (R&B) pressure filters.
The Çayeli concentrator designed nameplate capacity was 600,000 tonnes per year. Originally, three Rittershaus & Blecher pressure filters were installed: one for copper concentrate, one for zinc concentrate, and one standby for both copper and zinc concentrates. Mill throughput gradually increased after commissioning and was 896,700 tonnes in 1999. At these production levels, the filtration capacity created a bottleneck. In 1999, CBI decided to increase the mill capacity to one million tonnes per year and a fourth filter was installed ?n the year 2000 as part of the expansion plan. A LASTA M.C. automatic filter press was selected.
These filters are high-maintenance items and required dedicated mechanics to look after them as production increased. Initially, one operator was budgeted for the dewatering section, but due to the operational difficulties of these filters, this was increased to two operators per shift. In choosing a filter, the main selection criteria were low maintenance and operation costs, and the filter had to be simple to operate and robust in design. The capacity requirement was 400 dmt/day.
The MC LASTA AUTOMATIC FILTER PRESS was selected. Industrial Process Machinery (IPM) offered a model MCFHC 1500 X 40/34 for 400 dmt/day operation. The number of plates offered was 34, while the frame capacity was 40 plates.
The auxiliaries were:
one high pressure water pump for filter cloth washing, feed core clean-up, channel cleans, etc.,
one slurry feed pump, which was also retrofit to the existing copper concentrate holding tank,
one compressor, dedicated for use with the Lasta filter,
one transfer pump, to pump filtrate and filter cloth washings.
The construction contract was awarded in mid-April and commissioning of the filter started in mid- August 2000. The filter was fully commissioned by the end of September 2000.
They programmed the PLC and checked that the filter operation was satisfactory. |
Minning Maintenance Realibility | COMMISSIONING
After the usual pre-commissioning checks and dry runs, hot commissioning of the filter started on 19 August 2000. The filter exceeded its rated capacity after one month of operation. The current operational parameters are as follows:
Average Cycle Time: 11 minutes.
Average Number of Cycles: 120 per day.
Average Capacity: 518 dmt/day.
The filter is consistently exceeding its rated capacity of 470 dmt and we are very satisfied with its performance.
The press has three operational modes.
1. Manual Mode (Maintenance Mode).
2. Semi Auto Mode.
3. Auto Mode (Operation Mode).
5.1 Manual Mode
All functions are manually controlled. This mode is also called the maintenance mode and is required during maintenance.
5.2 Semi Auto Mode
The press operates and stops at the end of each phase of operation and requires restarting after each phase. This mode is used to optimise the operating conditions, especially during commissioning.
5.3 Auto Mode
The filter is started by simply pressing the start button and it completes a full cycle automatically. It does not need restarting at the end of each cycle. It stops only when the "feed tank empty" alarm is activated.
Performance Comparison
6.1.1. Capacity (Number of Cycles)
R&B filters: The rated capacities are 390 dmt/day for copper and 330 dmt/day for the zinc filters. The average cycle time is 20-25 minutes This is highly dependent on cake discharge. The
Filling
Membrane squeezing
Cake blow cycles take 12-15 minutes.
Cake discharging takes about half of die time required for the rest of tie steps. The plate-shifting mechanism is a problem and the operator is required to complete the cake discharge and clean the plates.
The plate-shifting mechanism chain and connection pieces, shifting hook, and locking hook (pawl) stick and plates often do not move. Sometimes, due to these difficulties, it is only possible to average 40-50 cycles per day. In actual operation, only about 280 dmt/day is obtained, based on availability due to operational problems which are explained below.
6.1.2 Labour Requirements
R&B filters: ÇBI employs 2 operators per shift to operate these filters due to frequent cloth changes (average 2200 cycles for one set of cloth) and platemoving problems. The seal surfaces on the sides of the plates and around the feed opening require continuous cleaning after each cycle due to the lack of an auto cloth wash provision. An auto cloth wash after each cycle is not possible with the existing design. This is explained in more detail ?n the maintenance comparison section.
6.1.3 Difficulties in Plate Shifting
R&B filters: The plates are hung on a rail with carriages. The carriages are equipped with hooks. There is a continuous running chain mechanism with shifter hooks attached. These shifter hooks catch the locking hooks (pawls) on the plate carriages and move the plates. This complex system causes frequent plate-shifting problems. This reduces the performance of the press. When plate-shifting problems start, the operator needs to climb on top of the filter to release the plates and maintenance assistance is required to change the damaged connection pieces.
6.1.4 Vibration Bars for Cake Removal
R&B filters: No vibration bars ?n design. MC LASTA filter: When cake sticks to the cloth, the cloth support bar ?s depressed due to the weight of the sticky material and blocks the photo beam. This activates a vibration cycle and shakes all the plates from both sides. The vibration cycle is also an indication of possible cloth problems, i.e., holes, blinding, etc.
6.1.5 Cake Discharge System
R&B filters: The cake falls with its own weight by gravity, and there are no additional features to help discharge the cake.
MC LASTA filter: The weight of the cake on the cloth rapidly compresses the springs which support the cloth support bars. The bars come to a sudden stop, which creates a shear effect between the cake and the filter cloth. This helps removal of the cake from the filter cloth. |
Minning Maintenance Realibility | 6.2.1 Filter Plate Repairs
R&B filters: These filters require extensive maintenance on the plates for several reasons.
The plates undergo continuous wear on the seal surfaces due to the lack of a good seal. This is due to the absence of an auto cloth wash after each cycle.
The wear surfaces are repaired by plastic welding and filling. After a while, this ?s no longer possible and the whole plate is taken out and sent away for resurfacing.
The air entry and filtrate discharge ports are not replaceable wear items; they are part of the whole plate. Any wear at these critical points means wear on the plate itself.
Damage occurs on the membrane plates. The rubber membranes are attached to the membrane plates by insertion of the sealing ring into the channel provided on the peripheries of the plates.
These channels are damaged by compression ?n time and membranes cannot be inserted anymore.
In general, plate repair is a continuous process. The plates are collected on site when they cannot be repaired with plastic welding, and are sent to Germany for resurfacing. ÇBI is looking for a local workshop to repair these plates.
MC LASTA filter: There are no membrane plates. Only chamber plates are provided. The air entry and filtrate discharge ports are replaceable units called filtrate rejecters. When worn, they are replaced. Their wear is also an indication of holes in the filter cloth.
To date, no plates have been damaged due to any other factors.
6.2.2 Cloth Change Comparison
R&B filters: The cloth is a single piece. Changing it is a time-consuming and fairly laborious job.
One part of the cloth has to be rolled, squeezed and passed through the feed opening of the plate so that it can be put on the other side of the plate.
Similarly, removing the old cloth is not easy as the cloth becomes harder and very difficult to roll back through the feed opening. It ?s common practice to cut the cloth when removing it from the plates.
MC LASTA filter: The cloth change is very easy. There are two pieces, which are hung on each side of a plate by hanging bars. The filter cloth assembly can be prepared in advance of cloth change. The odd-numbered plate cloth is equipped with a feeding device which is attached to the cloth before it is hung on the bars.
6.2.3 Plate-Moving and Shifting Mechanism
R&B filters: The chains located inside the traverse are equipped with shifter hooks, which glide over the carriages of the plate pack when the press is closed. When the press is opened, one of the shifter hooks engages, due to its own weight, on the last plate and unlocks this plate. The shifter hook now moves the plate suspended from the carriage fitted with offset rollers. This action is repeated until the last plate is opened. The offset roller movement is hindered by dirt accumulating inside the traverse rails, which are difficult to reach and clean. If the locking hooks of the carriages are not caught by the shifter hook of the chain in the proper order, men a group of plates shift together. This overloads the locking hook and the drive motor of the chain mechanism. The locking hook bends or the chain drive motor trips due to overloading. In short, the plate-shifting mechanism is complex.
MC LASTA filter: The plate-moving mechanism is rather simple. The plates are connected to each other by chains at four corners.
When the cylinder retracts, it moves the head plate backwards and the head plate pulls the rest of the plates one by one. The plates move freely on top of two side rails. The greasing of the rails makes it easy.
6.2.4 Washing System Maintenance
RifeB filters: The washing mechanism is a separate unit. It has a trolley with a moving chain and washing device. A geared motor is provided for the longitudinal and the wash travel drives. Both the washing device and the plates have to move to wash the cloth. The problems with plate moving continue during cloth washing. Each washing takes about 45 minutes if there are no problems with plate movements or washing device movements.
The cloth wash is a manual process. The filter has to be stopped and the control unit is changed to cloth wash mode. It is not practical to wash cloth after each cycle since one wash takes 45 minutes.
In addition to these problems, the washing device catches the filter cloth and sometime damages it while the sprays are in upward motion.
MC LASTA filter: The cloth wash is part of the auto cycle; it takes 40 seconds to wash all 41 plates and 40 chambers. Each plate is equipped with three cloth wash sprays as an integrated part of the cloth support bar. Water from the spray water header is connected to the cloth support bars on the even numbered plates by hoses. Wash nozzles direct wash water over the cake side of the filter cloth.
6.3 Safety and Environment
6.3.1 Leaks and Noise from Filter Plates R&B filters: Sealing surfaces deteriorate due to poor cloth washing, especially at the bottom of the plates. Cake remnants deteriorate the sealing surfaces. When the filter comes to the cake blow cycle, the compressed air leaks through these surfaces, creating dust and a shrill whistling noise. The cloth is also damaged by these surfaces.
MC LASTA filter: There is no sealing problem. The effective cloth-washing system after each cycle cleans all the surfaces of the plate. There are no leaks and there is no whistling.
6.3.2 Position and Access to Plates
R&B filters: The working platform is level with the bottom of the plates. This is necessary due to the operator assistance required in cake discharge.
In order that the top of the plates can be reached, a ladder is provided. The operator or maintenance personnel have to put on a safety belt while working on top of the filter.
MC LASTA filter: The working platform ?s located on top of the plates. The support rails, spray nozzles and cloth change bars are all accessible without the need for any safety equipment. One operator can change a filter cloth. |
Minning Maintenance Realibility | Slurry Pumps
CENTRIFUGAL SLURRY PUMPS AND SLURRY PUMPING SYSTEMS
It is very common in these same plants to use pulley and belt drives between motors and pumps. The main reason for this is that duties often change and mostly upwards after initial installation. If the pump speed is not sufficient, it is then only a matter of changing one of the pulleys to get an increased speed, a higher throughput and, alas, also a higher power consumption. To cater for such power changes, it is strongly recommended to select the initial motors with sufficient reserve power, say some 10% to 20% above the initial calculated requirement. This extra power is also handy in correcting mistakes which invariably happen due to uncertainties in friction loss predictions, as mentioned above. A bigger motor is slightly more expensive but the confidence it generates is priceless. |
Minning Maintenance Realibility | PUMP TYPES
Two types of pumps are used in the hydraulic transportation of solids: centrifugal pumps and positive displacement pumps.
Centrifugal pumps are used for flow rates from a few litres to thousands of litres per second, they can handle solid particle sizes from microscopic to large rocks up to 300 mm. Their main limitation is the fact that they can develop pressures of not much more than 7 MPa even when they are arranged in series, with say up to 8 pump stages. Their casings can be of unlined or lined design, i.e. with internal replaceable liners, which can be made of many materials from soft elastomers to hard metal alloys to suit the material pumped. The wearing parts are mostly impellers, volutes and side liners.
The majority of centrifugal pumps are horizontal, i.e. they are of end-suction, horizontal-shaft design.
Positive displacement pumps are almost invariably of the piston and diaphragm or piston and cylinder design with inlet and outlet poppet valves. They are employed in pumping through very long pipelines, say from 2 to 50 km because of their ability to generate high pressures, which are well in excess of multi-staged centrifugal pumps. Their design flow rate range is limited from 50 to 1000 litres per second, due mainly to their large physical sizes, both at low and high flows. They are most suitable for transporting slurries with high concentrations of fine particles with a maximum size of about 6 mm. The maximum particle size is dictated by the poppet valves, which can jam in semi-open position by large particles. Poppet valves are high wear items and they need frequent attention and replacement.
Impellers can be of closed design (with two shrouds) or open design (with one shroud). For critical duties, in order to reduce friction and to achieve the best possible pump performance, impeller surfaces are often machined all over or as much as physically possible and polished.
Let us consider the impeller once again. Its vanes must be thicker in slurry pumps than in water pumps to allow for wear. Because of this extra thickness, there must be fewer vanes, otherwise the passageways would be too narrow and would affect pump performance. The passageways must be made wide enough to let the largest planned solid particles to pass through without blockage. As a consequence, fluid in this impeller cannot be guided as closely as in a water impeller and this in turn results in reduced pumping head and efficiency. Unlike water pump impellers, slurry hard metal impellers are seldom machined outside and, like rubber impellers, never internally. This extra work would be a waste of money because impellers and liners have a finite life even though made of hard alloys or resilient elastomers and must be replaced when pump performance falls off.
Another factor affecting both head and efficiency in slurry pumps is the actual presence of solids in the slurry. Water flowing through a pipe changes velocity and velocity head when pipe diameters change. When velocity head increases (or decreases), it proportionally decreases (or increases) the static head in accordance with Bernouillis theorem.
When we have solid particles in a flowing slurry, water flows faster than the solids because the solids are moved along only when drag forces, generated by the faster water, overcome gravity forces. The difference between water velocity and solids velocity is called slippage. [This is mentioned also in Section 7, page 1]. The average velocity of the slurry is somewhere between the velocity of water and that of the solids.
The other important part of the slurry pump is its casing, which takes all the pressure loads. There a two main types of casings: those with internal replaceable liners and those without.
An important feature of slurry pumps is the provision for some simple means of axial adjustment of the gap between the impeller and the adjoining throatbush seal face. This can be achieved either by axial movement of the shaft, bearing assembly and impeller in the pump or by axial adjustment of the throatbush. Either method assists in maintaining pump performance as the inner component parts wear. |
Minning Maintenance Realibility | PUMP SEALING
Associated with the impeller-throatbush seal face adjustment is the means of sealing the pump against leakage along the shaft. Most pumps still use the proven and versatile water-fed gland seal, which still provides the lowest sealing costs even though it requires reasonably frequent attention by the operators.
Most slurry pumps (and many clear liquid pumps) are designed with suction diameters larger than discharge diameters. The simple aim of this design modification is to reduce suction pipe velocity and consequent friction losses, which in turn increase available NPSH. This is particularly important in slurry pumping where the density of the slurry reduces the available NPSH.
Slurry pumps with powers up to about 300 kW are almost universally driven by fixed speed motors through sets of belts and pulleys to produce different pump speeds and generate various heads. Two reasons for selecting belt drives are their low cost and the ease of changing pump speeds.
A small but growing percentage of slurry pumps above 200 kW are also direct coupled to variable speed motors or to fixed speed motors via variable speed hydraulic couplings or variable frequency controllers. |
Minning Maintenance Realibility | PUMP SPEED AND WEAR
Whenever we are dealing with centrifugal pumps we are of necessity involved with flow rates, total heads, consumed power and pump speeds. The first three parameters are closely related to the forth,
This example comes from a copper mine. The specific gravity of copper ore is S=2.85, the flow of slurry fed to the cyclone is Q=61.7L/s, the solids concentration in the slurry is Cw=40% (and Cv=19%) and the specific gravity of the slurry is Sm=1.35. |
Minning Maintenance Realibility | WARMAN 10/8 T-AHPP gland sealed pumps.
Two trains of 7 stages. Tailings application. Rubber lined casings and high efficiency, hard-metal impellers.
Duty: Q=930 m3/h, Hm=55 m per stage, Cw=55%. Drives: 315 kW, 740 r/min motors, direct coupled. |
Minning Maintenance Realibility | ASH PUMP 22x20 SRH pumps.
Two trains of 3 stages (one train shown). Tailings application. Rubber lined casings and impellers.
Duty: Q=36005000 m3/h, Hm=2431 m per stage, Sm=1.21.3. Drives: 750 kW motors with gear reducers and Variable Frequency Speed Controllers. |
Minning Maintenance Realibility | WARMAN 20/18 TU-AH pumps.
One pump per processing circuit. Mill discharge application. Rubber lined casings, hard-metal impellers and throat bushes. Duty: Q=3200 m3/h, Hm=32.5 m, Cw=62%. Drives: 600 kW motors and gear reducers. |
Minning Maintenance Realibility | WARMAN 550 U-SHDU gland sealed pump.
Mill discharge application. Hard-metal pump casing and impeller; unlined. Duty: Q=5220m3/h, 37 m, Cw=72%
Drive: 1200 kW motor with Variable Frequency Speed Controller, direct coupled. |
Minning Maintenance Realibility | Diesel Electric Power Train in Hauling Trucks
Vibration Points Mining
Shovels
Motor Generator set
Hoist and swing transmission
Haulage trucks
Diesel engine
Generator
Concentrator
SAG / Ball mills
Pumps
Conveyors |
Minning Maintenance Realibility | Shovel Vibration Monitoring
There are a total of 13 electrically-powered shovels in operation at the mine, each with a 15 m3 bucket capacity.
These comprise; Bucyrus - Erie 295 B and 195 Bl, P&H 2100 BL and Marion 201 M. At present the shovel availability is approximately 65%. Vibration monitoring has played a major part in maintaining this high level, as just one year ago the availability was 45%. The main problems encountered are with the motor-generator (MG) Set which, at costs in the region of $250000 for replacement and $100000 for repair, represents a potentially considerable maintenance cost.
The monitoring programme for the shovels covers the following items:
Motor-Generator (MG) Set unbalance and misalignment problems;
Hoist and Swing Transmission -gear and bearing problems;
Hoist Magnetorque® Drive - unbalance, bearing and operation problems. |
Minning Maintenance Realibility | Truck Vibration Monitoring
The truck fleet at the mine consists of a total of 41 Wabco, Terex and Unit Rig diesel-electric trucks, each with a capacity of 170 tons. The trucks are powered by a 1600 BHP diesel engine driving a DC generator, which in turn drives an electric motor mounted on each of the rear wheel-sets. At a cost of approximately 1 million-$ each, these trucks represent a considerable investment. |
Minning Maintenance Realibility | Concentrator Vibration Monitoring
The Autogeneous Mill
The autogeneous mills are 32 ft diameter cascade type grinding-mills, powered by two 3000 HP motors coupled by gearboxes, see Fig. 21. Because of their importance to the concentrator operation, they have number one priority in the plant. Vibration measurements at 16 measuring points are taken from the drive section of one mill at weekly intervals. |
Minning Maintenance Realibility | The most common types of problem encountered are due to installation misalignment, bearing failures and gearing problems.
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Minning Maintenance Realibility | Carbon-in-leach Process
The CIL (Carbon in Leach) circuit is an intermediate stage in the production of gold. The process involves dissolving the solid gold particles into solution using a process know as cyanidation.
The dissolved gold in solution is adsorbed onto activated carbon. When the carbon is loaded with enough gold it is removed from the circuit and sent to elution where the adsorption process is reversed and the gold is stripped off the carbon back into solution, electrowon and smelted into bars.
The remaining barren slurry reports to the tails thickener and is pumped to the tails dam.
The CIL circuit consists of two separate trains of tanks, with seven tanks in each train. In conventional CIL circuits, leaching takes place in the presence of carbon and therefore leaching and adsorption occur simultaneously. The CIL circuit at SDGM can be considered a hybrid circuit as the first tank of each train are purely leaching tanks (no carbon addition). |
Minning Maintenance Realibility | The Cyanidation Reaction
CIL technology is based on the fact that the gold dissolves readily in cyanide solutions in the presence of oxygen, and the resultant gold cyanide complex ion (molecule) is readily adsorbed onto activated carbon. The goal of leaching is to push the reaction to the right ie; consume the reactants to produce the gold complex in solution.
Therefore to leach the gold out of the ore and into solution, cyanide, and oxygen must be added to the slurry. Lime is added to the grinding circuit to modify the pH of the slurry to prevent the formation of deadly hydrogen cyanide gas. Cyanide is added in liquid form to the tanks and lime is added to the ore prior to milling. Oxygen is added in pure form, injected down the agitator shafts. |
Minning Maintenance Realibility | Factors Affecting the Rate of the Cyanidation Reaction
Size of Gold Particles
The gold must be in a fine particulate form (from the grinding circuit). The feed slurry must have an 80% passing size of 75um to achieve suitable gold recovery (refer to cyclone and grinding modules).
Free Cyanide Concentration
Increasing cyanide concentration drives the cyanidation reaction to the right. There must be sufficient free cyanide ions in solution to dissolve all the gold, otherwise it will be lost to tailings
Dissolved Oxygen
There must be sufficient entrained oxygen in the slurry. Increasing the oxygen concentration drives the reaction to the right
Slurry pH
PH modification is achieved by adding lime to the ore prior to milling which makes the slurry alkaline (high pH). The pH level in the tanks is monitored regularly by the process technician responsible for the CIL circuit.
Residence Time
Residence time in the CIL circuit is the time taken for the slurry to flow through the tanks, and is an important operational consideration. The longer the gold particles are in contact with the cyanide in the slurry the more gold that will be leached.
Residence time is determined by the volume of the tanks (which is fixed), the slurry flowrate and the slurry density.
Agitation
Effective agitation allows the reactants to intimately mix and prevents the solids from settling out, bogging the tanks.
Temperature
Higher temperatures will increase the rate of gold dissolution, however it is not economical to heat the slurry. High temperatures also reduce the capacity of carbon to adsorb gold and lower the solubility of oxygen in the slurry |
Minning Maintenance Realibility | Carbon Adsorption Theory
After the leaching process is complete, the soluble gold must be concentrated and separated from the process slurry. The method of recovery of gold from the process slurry is by carbon adsorption. |
Minning Maintenance Realibility | Trash Screens
The overflow slurry stream from the cyclone nest feeds the CIL circuit via the leach feed thickener. Before entering the leaching circuit, all the wood fibre, cloth, plastic, rocks from cyclone blowouts and other trash material must be removed from the slurry. If trash is not removed it may block the CIL interstage screens causing tank overflows and also cause problems in the elution and carbon reactivation circuit.
The cyclone overflow is fed to three trash screens, the undersize reports to the leach feed thickener feed hopper and the oversize trash material is collected and discarded. |
Minning Maintenance Realibility | Leach Feed Thickener
Slurry from the trash screens flows into the thickener feed hopper. The slurry is pumped from the hopper to the thickener where the slurry is flocculated and thickened to a density of 50% solids. The thickener underflow reports to a hopper from which the slurry is then pumped to the leach feed splitter box. |
Minning Maintenance Realibility | CIL Tanks
The major component of the CIL circuit are the two, seven tank leaching trains. The eastern, first train of tanks (train no.1, tanks 1 to 7) were part of the original plant. The western, second train of tanks (train no.2, tanks 101 to 107) was commissioned as part of the stage three plant expansion, and is very similar in design and operation as the original train apart for a few minor differences. The first tank of each train is purely a leach tank (no carbon), the remaining six are leach and adsorption (CIL) tanks. Each tank has an effective volume of 761m3 each, and operate at a leach density of 50% solids, giving a residence time of approximately 4 hrs leach (first tank) and 22 hours CIL. Tanks 1 and 101 (the leach only tanks) are the slurry feed end of trains 1 and 2 respectively, and tanks 7 and 107 the tail end
The tanks are positioned in two staggered rows. In train 1 the tanks are interconnected with open launders and gate valves, in train 2 flow between tanks involves a system of pipes and dart valves. The flow through the tanks is such that any tank in the system may be bypassed, while the circuit continues to operate with reduced volume and residence time.
The slurry from the thickener underflow is pumped to a splitter box, which distributes the feed evenly between each train. Cyanide solution is added to the leach feed (thickener underflow) hopper, distribution box and also to the first three CIL tanks of each train (tanks 2, 3, 4, 102, 103 & 104). The tanks are agitated by twin impellers, with oxygen injected through lances down the hollow agitator shafts.
Tank 1 also incorporates a multi-mix unit and recirculation pump as another means of adding oxygen to the slurry. Slurry is pumped from the base of the tank and is discharged below the slurry line at the top of the tank. Within the pipe, immediately after the pump is the multimix unit which injects oxygen into the passing slurry stream. The oxygen is injected as a fine jet of bubbles which are sheared by the slurry flow, giving good oxygen dissolution within the slurry.
Slurry flows by gravity through each train, with the overflow launder from each tank being preceded by an intertank screen that prevents the advance of carbon with the slurry. Barren slurry from the final tank of each train flows to a carbon safety screen, which prevents the loss of carbon in the instance that the final intertank carbon screen is holed. The barren slurry underflow from the safety screen reports to the tails thickener feed hopper.
Reactivated carbon is added to the final tank (tanks 7/107) of each train and is moved counter currently to the flow of slurry by centrifugal carbon transfer pumps, finally being removed for stripping from the second tank (tanks 2/102) of each train. |
Minning Maintenance Realibility | Intertank Screens
Screens are fitted in each of the CIL tanks to retain the carbon in the tank, as the circuit operates with carbon being moved counter-current to slurry flow. The screens are cylindrical and are fitted just prior to the slurry exit launder. Wiper blades with a dedicated drive motor system are installed to keep the screen surfaces free from carbon build-up. If the wiper blades fail, then carbon is carried/forced onto the screen surface by the slurry flow. This impedes the flow of slurry and may cause the tank to overflow.
The screens may also become holed due to damage or deterioration. To check whether the screens are passing carbon, a sieve is dipped into the discharge launder and inspected. The screens will also become pegged with near sized carbon and other material such as small rocks and need to be removed and cleaned/replaced regularly to prevent tank overflows. |
Minning Maintenance Realibility | Carbon Forwarding Pumps
To facilitate the counter current movement of carbon, each CIL tank has a carbon-forwarding pump.
The pumps are run on a batch schedule as required to maintain the desired carbon concentrations in the tanks. The forwarding pump from tanks 2 and 102 pumps to the loaded carbon screen where the carbon is screened from the slurry and sent to the elution column. The slurry underflow from the loaded carbon screen is returned to either tank 2, 102, 4 or 104. |
Minning Maintenance Realibility | Carbon Safety Screens
Both of the CIL trains each have a carbon safety screen over which the tail slurry from tanks 7/107 is passed.
Carbon may be present in the tailings slurry due to either:
The carbon has abraded over time and is fine enough to pass the intertank screen.
The intertank screen is holed.
The seal between the launder and the screen has deteriorated or is not seated properly, allowing carbon to pass.
If the screen wasnt present this carbon would end up in the tailings dam resulting in gold and carbon losses.
Generally the carbon on the safety screen is due to the screen being holed or the launder seal not sealing properly. This carbon is collected and put back into the circuit.
The slurry underflow from each of the carbon safety screens flows into separate tails thickener feed hoppers, from which the slurry is pumped to the tailings thickener feed box. |
Minning Maintenance Realibility | TAC Cyanide Analyser
The TAC analyser is an automatic titration unit that measures the cyanide concentration and pH of the slurry. A slurry sample from the splitter box is taken through a filtration sock and is sent by a peristaltic pump to the analyser unit. The filtered sample is titrated with silver nitrate to determine the free cyanide concentration. A probe measures the pH of the solution.
The cyanide concentration result as determined by the TAC is used in a control loop to automatically adjust the cyanide addition rate to the circuit. |
Minning Maintenance Realibility | Debex Carbon Meter
Each CIL tank is fitted with a Debex carbon meter. The meter measures the carbon concentration in the slurry. It works by sending an ultrasonic signal through the slurry, and from the loss of signal energy over the detection gap, determines the carbon concentration. The Debex system also incorporates a densiometer to account for variations in pulp density, which will alter the amount of energy absorbed from the ultrasonic pulse. |
Minning Maintenance Realibility | Leach Feed Slurry Autosampler
An autosampler intermittently takes a cut of the feed to the trash screens. The sample collects in a bucket that is removed daily by the laboratory technician. |
Minning Maintenance Realibility | Tailings Slurry Autosampler
An autosampler placed prior to each carbon safety screen takes a periodic cut of the tailings slurry from each train. |
Minning Maintenance Realibility | Waste Water Treatment
The systems treatment stages include: a
Sedimentation
Dissolved air flotation
Media filtration
Activated carbon filtration
Ultrafiltration
Reverse osmosis.
In the sedimentation process, the suspended solids in the water are gravity settled. Then, through dissolved air flotation, various colloidal materials and dispersed particles are removed.
The water is then filtered to remove residual solids that may remain after the flotation stage. The removal of any dissolved organic material is completed with activated carbon filtration, followed by ultrafiltration. The latter step ensures that any residual suspended solids, colloidal and organic matter including bacteria and viruses are removed before the water is treated using reverse osmosis.
Removing as much sediment as possible is particularly important. It protects the infrastructure investment by making certain the membranes and other equipment used for reverse osmosis are neither fouled nor harmed by the water quality. Although this is important in any treatment process, water from mining in particular is full of sediment. The final polishing step in the water treatment process, reverse osmosis desalination, ensures that any dissolved salts and heavy metals are removed from the water before it is reused |
Minning Projects | Grinding Mills
Part of the concentration plant, the grinding or tumbling mill is a large-scale grinding device (see Figure 2) used in mineral processing to grind large chunks of ore into a suitable size for the next step in the concentration process. A similar setup is used in the cement industry for crushing clinker.
There are several different types of grinding mills: ball, rod, autogenous and semi-autogenous grinding (SAG). In a ball mill, steel or stone balls are mixed with the ore and during rotation of the drum, the ore is ground by friction and compression into a suitable fineness. A rod mill uses a similar principle, but the steel or stone balls are replaced by rods to create the grinding action. In an autogenous mill, the ore itself is used in the grinding process. A SAG mill is a combination of a ball mill and an autogenous mill.
The main component of all mills is a horizontal rotating drum, typically with a rubber liner and regularly spaced lifter bars (see Figure 1). Generally, the ore is continuously fed into the drum in one end, then crushed and transported out in the other.
Figure 1: The drum interior at Garpenberg during a service stop clearly shows the rubber lifters. The rubber lifters are clearly visible.
In autogenous mills, a sufficient amount of bigger parts of ore inside the drum is critical to an effective grinding process. Maintaining particle size while minimizing equipment wear, downtime and power consumption is a challenge to production and maintenance engineers. |
Minning Projects | Al Masane Al Kobra Mining Company is a precious metals and base metals developer focused on the completion and production of the 700,000 tpa copper, zinc and precious metals Al Masane Mine in Saudi Arabia. The Al Masane Project is fully funded and permitted. As of mid 2010, the surface facilities were completed and waiting for testing prior to delivery of ore. The contract to continue mine development has been awarded and pre-production development has commenced.
Production of copper concentrate, zinc concentrate, gold and silver bullion is scheduled for the 3rd quarter 2011.
The project is located in southwestern Saudi Arabia, approximately 640 km south east of Jeddah. It lies some 414 km by a newly paved road from the port of Gizan on the Red Sea. The mines copper and zinc concentrates will be trucked to the port of Gizan and shipped to smelters in Europe or the far east.
In addition to the known ore reserves that are being developed, exploration of gossans and geochemical anomalies in the greater Al Masane area has indicated that there is a high probability of discovering additional minable resources which will increase the life of mine.
Saudi Arabia Al Masane Cu & Zn Mining & Processing & Metallurgy EPC Project (700,000tpa)
EPC contractor BGRIMM in brief
BGRIMM, incorporated in China and directly under the Chinese central government (SASAC), is a leading institute providing innovative technology, diversfied products, and process-orientated engineering services in mineral and material industries worldwide. With ISO 9001 certificate and well established multi disciplinary organization, BGRIMM takes pride to be a complete solution provider integrating R&D, engineering and equipment manufacture tailored to customer requirments and serve the mineral industry with a full range of expertise from mining to mine closure.
Process consists of:
* Mining 2,000 tonnes of ore per day
* Crushing and grinding ore
* Floatation to produce copper and zinc concentrates
* Cyanidation of tailings to produce gold/silver Dore
Transportation of concentrates to the Port of Gizan on the Red Sea for export and dore for treatment in the gold/silver refining plant in Jeddah. |
Minning Projects | Al Masane Geology and Mineralization
Three mineralized zones with massive sulfide mineable reserves have been discovered to date and outlined by 45,000 meters of diamond drilling from the surface and underground tunnels. The principal sulfide minerals in all the zones are pyrite, sphalerite, and chalcopyrite. The precious metals occur chiefly in tetrahedrite and as tellurides and electrum
INFRASTRUCTURE
300-Man single status camp for employees
Accommodation for expatriate and Saudi employees
On-site medical facility
Service building for 200 employees
On-site diesel generation consisting of our 3.2 MW generators with three in operation, until connection to National Grid
Potable water supply
Sewage treatment plant
assay laboratory |
Minning Projects | Maaden Phosphate Development
Office: Al-Khobar, Melbourne, Beijing, Abu Dhabi
Customer: Saudi Arabian Mining Company
Location: Al-Jalamid and Raz Az Zawr, Saudi Arabia
Timeframe: 2006 - ongoing
The Maaden Phosphate Development located in Saudi Arabia is one of the worlds largest producers of di-ammonium phosphate, a fertilizer for use in grain and horticulture.
This $4.5 billion (direct capital cost) phosphate project being managed by WorleyParsons focuses on the economic development of the major phosphate resource rock located at Al Jalamid. The full project development involves the design and construction of a beneficiation plant and associated infrastructure located at Al Jalamid, a major fertilizer complex and port facilities at Ras Az Zawr, a new 1400 km rail link between Al Jalamid and Ras Az Zawr for processing and a power generation plant.
The success of this world leading project is directly due to teamwork. WorleyParsons' commitment to supporting Maaden in maintaining their schedule and creating a multi-national workforce focused on safety, quality and cost has been invaluable in assisting Maaden to achieve their business objectives. |
Minning Projects | Phosphate
Phosphate is one of the most significant products of Maaden as it is made naturally of phosphorus element. It is one of three main nutrition elements in the photosynthesis and is key element of the growth of agricultural crops.
According to the Food and Agriculture Organization (FAO) of the United Nations, the global food production needs to rise by 70%, and to be doubled in developing countries, so as to meet the anticipated needs of the world population, which will reach population of 9 billion people in 2050. Thus, there will still be a need to raise the productivity of phosphate fertilizers to meet this growing demand for food.
Maaden produces ammonium phosphate, which is recently widely used in agricultural field, Diammonium Phosphate (DAP), Monoammonium Phosphate (MAP). Maaden plans to introduce new phosphate compounds to become one of the leading suppliers of phosphate fertilizer companies in the world.
KSA is rich of all raw materials and other resources available to produce and supply phosphate fertilizers to the fastest growing countries in the world, all of which are close to the Kingdom.
Maaden continues its growth in the area of phosphate, based on two of the largest companies in the world, Ma'aden Phosphate Company, which was established in partnership with SABIC and Ma'aden Waad Al Shamal Phosphate, which was created in partnership with both SABIC and the US based Mosaic, which is one of the largest producer of phosphate fertilizer in the world. |
Minning Projects | Ma'aden Phosphate Company (MPC)
With an investment of USD 5.5 Billion (SAR 21 Billion), MPC is a joint venture between Maaden and Saudi Basic Industries Corporation (SABIC), who share 70% and 30% respectively, with total production capacity of 3 Million TPA of DAP, MAP, and NP's. Each year, Maaden markets about 70% of its production from two major sites; Al-Jalamid, north of the Kingdom, where lies the phosphate mine in addition to an ore beneficiation plant; and Ras Al-Khair (RAK) site in the Eastern Province, which includes an integrated plant for the production of fertilizers and chemicals.
The mine produces about 11.6 Million TPA of phosphate ore, which undergoes the beneficiation process in the plant in order to produce nearly 5 Million TPA of beneficiated ore. MPC sought for investment in Al-Jalamid mine site, in terms of infrastructure, by constructing a power plant, potable water production and treatment facilities, a telecommunication network as well as a transportation network so as to facilitate exploration and production operations.
Phosphate concentrates are transported from Jalamid to RAK by rail for the production of phosphate fertilizers thru a number of facilities, including a phosphoric acid plant, a sulfuric acid plant, an ammonia plant, a Diammonium phosphate plant (DAP) and a desalination plant.
Based on the business relations of its founders (Maaden and SABIC), as well as the supply chain, markets and materials networks that cover the continents, MPC is growing as global company and playing an active role in this journey. |
Minning Projects | Ore beneficiation plant
In the mining industry beneficiation or benefication in extractive metallurgy, is any process that improves (benefits) the economic value of the ore by removing the gangue minerals, which results in a higher grade product (concentrate) and a waste stream (tailings). Exemplary beneficiation processes are froth flotation and gravity separation. |
Minning Projects | Flotation Cells
The froth flotation process is commonly employed for the selective separation of a mineral species from a liquid solid suspension of both valuable and unwanted gangue mineral particles
A mechanical flotation cell essentially consists of a vessel or a tank fitted with an impeller or rotor. The impeller agitates the slurry to keep particles in suspension, disperses air into fine bubbles and provides an environment in the cell tank for interaction of bubbles and hydrophobic particles and their subsequent attachment and therefore separation of valuable mineral particles from the undesired gangue mineral particles. The bubble particle aggregates move up in the cell by buoyancy and are removed from the cell lip into an inclined drainage box called a launder. |
Minning Projects | Size Control
Size control is the tool for improvement of the size fractions in the process stages and in the final products. For the coarser part of the process, screens are used (in practise above 1-2 mm). In the finer part we have to use classification with spiral classifiers, see section 4. |
Minning Projects | Secondary crusher Type
In a rock crushing circuit, the second stage normally starts to be of importance for control of size and shape. Because of this the jaw crusher, in most cases, is disqualified as secondary crusher.
Instead the cone crusher is used more frequently. Also in comminution (crushing and grinding) circuits for ore and minerals the cone crusher is frequently used as the secondary stage, see 3:4. Using a secondary HSI means as always a restriction in feed hardness and abrasiveness. |
Minning Projects | Final crushing stage More than just crushing
For many rock and gravel crushing circuits the final crushing stage is of special interest. The final sizing and shaping will take place in this stage influencing the value of the final product.
For hard, abrasive rock circuits Cone crushers, Vertical Shaft Impactors (VSI) or High Pressure Grinding Rolls (HPGRs) can be used |
Minning Projects | VSI A rock on rock autogeneous crushing impactor
Horizontal impactors normally use rock to metal impaction. This means a restriction in crushing circuits with hard feed material, when wear can be dramatically high.
The VSI Impactor of Barmac type is using a rock-to-rock impaction technology where most of the design is protected by rock, see below. This means that we can use the advantages of the impaction techniques also in hard, abrasive rock operations.
The crushing action takes place in the rock cloud in the crushing chamber, not against the rock protection |
Minning Projects | High Pressure Grinding Rolls (HPGRs) - HRC
HPGRs utilize two counter-rotating tires one fixed and one floating in order to effectively crush ore. Hydraulic cylinders apply very high pressure to the system, causing inter-particle comminution as the feed travels between the two tires.
The basic operating principle behind HPGRs makes them very energy efficient |
Minning Projects | rinding Introduction
Size reduction by crushing has a size limitation for the final products. If we require further reduction, say below 5-20 mm, we have to use the processes of grinding. Grinding is a powdering or pulverizing process using the rock mechanical forces of impaction, compression, shearing and attrition
Grinding Tumbling mills
Wet or dry Primary, coarse grinding (up to 400 mm feed size) Grinding media is grinding feed High capacity (short retention time) Sensitive to feed composition (critical size material), |
Minning Projects | Semi Autogenous (SAG) mill
Wet or dry Higher capacity than A-G mill grinding Primary, coarse grinding (up to 400 mm feed size) Grinding media is grinding feed plus 4-18% ball charge (ball dia.100-125 mm) High capacity (short retention time) Less sensitive to feed composition (critical size material), see data sheet 3:44 |
Minning Projects | Size Control
In mineral processing practices we have two methods dominating size control processes:
Screening using a geometrical pattern for size control
Classification using particle motion for size control
There are many types of screens, but they can be reduced to the four types shown below. |
Minning Projects | Classification Introduction
For size control of particles finer than 1 mm, we are moving out of the practical range of conventional screens. Classification is the process of separating particles by size into two or more products according to their behaviour in air or water (liquids).
Classification methods
Wet classification with hydrocyclones using separation by centrifugal force covering the size range of 100 10 micron (typical)
Wet classification with spiral classifiers using separation by gravity covering the size range of 100 1000 micron (typical)
Dry classification using separation by centrifugal force covering the range of 150 5 micron (typical). |
Minning Projects | Hydrocyclone
Centrifugal forces classify solids by size (mass). High mass particles closer to outer wall reporting to underflow. Low mass particles closer to the centre reporting to overflow.
Hydrocyclone design
1. Vortex finder 2. Inlet head 3. Spigots (apex) 4. Overflow elbow 5. Feed inlet 6. Barrel 7. Cones 8. Cone extension |
Minning Projects | Spiral classifier
By combining a gravity settler of rectangular section with a sloped transport spiral for the sediment we have a spiral classifier |
Minning Projects | Enrichment Washing
Washing, mainly used in the enrichment process of industrial minerals, coal, aggregates, sand and gravel, normally with the products in solid form (size = 1 mm and coarser)
Separation, mainly used in the enrichment processes of metallic minerals and high value industrial minerals, normally with the products in liberated particle form (size = 1mm and smaller)
Washing is the simplest method of enrichment used to improve the value of rock and mineral fractions from sand size and upwards. Removing of surface impurities like clay, dust, organics or salts is often a must for a saleable product.
Different techniques are used depending on how hard these impurities are attached to the rock or mineral surface, see section 5 |
Minning Projects | Tumbling scrubber
If solids of rock, gravel or minerals contain a high and sticky content of clay and dirt that has to be removed, wet screening is normally not effective enough. A medium speed washing drum for scrubbing solids against solids is then the option. The drum is relatively short in relation to its diameter. Water requirements per ton is the same as for wet screening. Typical capacities 8 120 t/h. |
Minning Projects | Attrition scrubber
These scrubbers are mainly used for washing of material below 10 mm in size. Very high energy inputs are possibly used for washing of silica sand for glass making and cleaning of foundry sand. The machine is also suitable for clay blunging and lime slaking, |
Minning Projects | Wash water treatment closed system
After recovery of coarser material the fines can be treated in a closed system recovering all process water and bringing the fine solids into a transportable form. |
Minning Projects | Enrichment Separation
Most value minerals (both metallic and industrial) are priced by their purity. After liberation by size reduction and size control all minerals are free to be separated from each other.
Depending on the properties of the individual minerals they can be recovered by different methods of separation |
Minning Projects | Upgrading
After the enrichment operation we end up with a value product (concentrate) and a non-value product (tailings). These products are probably not sellable nor disposable due to the content of process water, particle size, or chemical composition.
By upgrading we mean the methods of increasing the value of these products by sedimentation, mechanical dewatering, drying, calcining or sintering and recovering the process water from the tailings, making them disposable, see section 6. |
Minning Projects | Separation by shaking tables
A cross stream of water transports material over the table to riffles running perpendicular to the direction of feed. Particles build up behind each riffle and stratification occurs with heavier particles sinking to the bottom. The light particles are carried over each riffle to the tailings zone. The shaking action of the tables carries the heavy particles along the back of each riffle to the concentrate discharge. |
Minning Projects | Separation by flotation
Flotation is a mineral separation process, which takes place in a water-mineral slurry. The surfaces of selected minerals are made hydrophobic (water-repellent) by conditioning with selective reagents. The hydrophobic particles become attached to air bubbles that are introduced into the pulp and are carried to a froth layer above the slurry thereby being separated from the hydrophilic (wetted) particles. In addition to the reagents added, the flotation process depends on two main parameters.
Retention time needed for the separation process to occur determines the volume and number of flotation cells required.
Agitation and aeration needed for optimum flotation conditions, determine the type of flotation mechanism and the power input required. |
Minning Projects | Flotation circuit layout
Flotation circuit designs vary in complexity depending primarily on the type of mineral, degree of liberation of valuable minerals, grade (purity) of the product and the value of the product. |
Minning Projects | Reactor cell flotation system (RCS)
The RCSTM (Reactor Cell System) flotation machine utilizes the patent protected DVTM (Deep Vane) mechanism. Flow pattern characteristics are |
Minning Projects | DR Flotation cell system
The Reactor Cell System Flotation Machine is the preferred choice for many mineral flotation applications. The DR design may be specified for certain applications, particularly where de-slimed coarse particles have to be handled such as in glass and potash processing. Features of the DR design are as follows. |
Minning Projects | Column flotation cells
Column flotation cells, like mechanical cells, are used to perform mineral separations. Column cells do not use mechanical agitation (impellers). Instead, mixing is achieved by the turbulence provided by the rising bubbles. Columns are mostly used to produce final grade concentrates because they are capable of high selectivity. Other features which distinguish them from mechanical cells are their shape, bubble generation system and the use of wash water. An optimum flotation circuit is a combination of mechanical cells and column cells
Applications for flotation columns include:
Sulfides Iron ore Phosphate Coal Industrial minerals Potash
With upgrading we understand, the further processing of the final products from the enrichment stages in a process.
This is valid both concerning the valuable minerals (the concentrate) and the waste minerals (the tailings). In the first case upgrading means improving the product value by bringing the concentrate to transportability or into a completely dry form. Processing can also go further to calcining and sintering. On the tailing side upgrading means that waste material (wash water, process effluents etc.) is properly taken care of in order to protect the environment, to recover process water and to turn certain portions into valuables. |
Minning Projects | Sedimentation
Sedimentation is a continuous solid-liquid separation process with settling of solids by gravity.
Clarification is the process for removal of solids from a dilute solid/liquid suspension.
Thickening is the process for concentrating particles in a supension by gravity compression |
Minning Projects | Flocculation
All sedimentation technologies are related to particle size. One way of improving the settling speed generally is therefore to increase the size of the particles. Fine particles can be connected together by coagulation or flocculation. The settling rate of the combined particles will be higher than that of each individual particle. This can also be applied prior to mechanical dewatering. |
Minning Projects | Flocculation system
A handling system is needed for flocculent utilisation. This comprises provision to mix, store and dilute the polymer. The dilute polymer is then mixed with the feed slurry and allowed to condition (or age) before a sedimentation or dewatering process. |
Minning Projects | Conventional clarifier
Clarification is achieved when the liquid upstream velocity VL (rise rate) is lower than the sedimentation velocity of the solids VS |
Minning Projects | Conventional clarifier sizing
Clarifier diameter is selected to give a suitable upstream velocity (m/h). Sizing is usally done using Surface Load, meaning the volume of slurry m3/h fed per m2 of clarifier surface. Typical surface loads are given below. |
Minning Projects | Conventional thickener
Continuous thickening to give the required solids concentration in the underflow depends on balancing the volumetric solids flow rate at a critical concentration with the diameter of the thickener. |
Minning Projects | Conventional clarifier/thickener Design
Bridge type
For smaller thickeners, up to 30 40 m diameter, the rakes and drive mechanism are supported on a bridge superstructure, which straddles the tank as shown.Centre pier type
For tanks over 30 40 m diameter a bridge structure will be impractical. The mechanism and rakes are therefore supported from a centre pier and the bridge is only used for access and to support feed pipe and launder. |
Minning Projects | Inclined Plate Settler IPS
The inclined plate settler consists of two main components, the upper tank containing the lamella plates inclined at 55° and the lower conical or cylindrical sludge container.
The feed for the inclined plate settler enters through vertical chambers on either side of the lamella packs and passes into each plate gap through slotted feed ports.
Clarification takes place above the suspension inlet so there is no mixing of the clarified fluid with the incoming feed.
Above each pack is a full-length overflow launder fitted with throttling holes to create a slight hydraulic back pressure on the incoming feed stream. This method of feed control guarantees equal distribution to all lamella chambers with minimum turbulence at the entry points.
The solids settle onto and slide down each lamella plate to the sludge container where the solids are further thickened and compressed with the assistance of the raking system |
Minning Projects | Mechanical dewatering Introduction
Mechanical dewatering means mechanical removal of liquids from a slurry to obtain the solids in a suitable form and/or recovery of a valueable liquid for:
Further processing Transportation Agglomeration Disposal Recovery of valuable liquids |
Minning Projects | Gravimetric dewatering
When the particles in a slurry are too coarse for the capillary forces to trap the water, the use of gravity is enough to remove the water and give at least transportable solids.
|
Minning Projects | Al Jalamid Beneficiation Plant 12Mtpy
Dec 17, 2007
RIYADH, Saudi Arabia, 17 DEC 07: Ma'aden has today signed the final two major plant contracts for its mega phosphate project. The contracts are for the power & desalination plant as well as the beneficiation plant of what will be the worlds largest fully integrated phosphate fertilizer complex.
The power and desalination plant which will be located at the phosphate processing complex at Ras Az Zawr will be undertaken by Hanwha Engineering and Construction Corporation (Hanwah) of Korea. The value of the contract is US$280 million.
The beneficiation plant will be located at the phosphate mine site in Al Jalamid in the north of the Kingdom. The US$350 million contract was won by Guizhou Hongfu Industry and Commerce Development Co. Ltd. (Hongfu) of China.
Speaking at the signing ceremony for the two contracts, Ma'aden President and CEO, Dr Abdallah Dabbagh said, As with the other major contracts for the phosphate project, we have scoured the globe for the right partners with the right experience and expertise. Both Hanwah and Hongfu have met our specific criteria and I am very pleased to welcome them both to this monumental project.
The signing of these two contracts means now that all major plant contracts have been agreed. Work at the Ras Az Zawr site has already begun with the driving of piles for the sulphuric acid plant and started basic construction of foundations. This project is now very much a reality and on track to deliver the first phosphate fertilizer to waiting markets to feed the world in the last quarter of 2010. |
Minning Projects | Power & Desalination Plant
Site mobilisation for the power and desalination plant will commence in January 2008 with construction stating in May of that year. The plant is expected to be completed and fully operational by the middle of 2010.The power plant consists of 2 x 66% Siemens Condensing Steam Turbines & Generators, with an output of 126.76MW base load and 146.53MW peak load. The phosphate project is expected to be a net exporter to the grid of approximately 10MW, depending on final load examination.
The desalination plant will utilise Entropie Multi Effect Distillation (MED) and can process up to 40,000 cubic metres per day. The plant will also include storage facilities for desalinated, process and potable water. |
Minning Projects | Beneficiation Plant
Construction on the beneficiation plant at Al Jalamid will commence in April 2008, with completion expected by May 2010.
The beneficiation plant is required to remove calcium and magnesium carbonates from the phosphate deposit run-of-mine ore to produce 4.63 MTPY dry phosphate concentrate suitable for use in the manufacture of phosphoric acid.
The beneficiation plant physical limits are comprehensive, starting with the primary crusher located in the mine area, an overland conveyor, run of mill (ROM) storage, crushing and milling circuit, de-sliming, conditioning, flotation, dewatering, filtration, wet concentrate storage, concentrate drying, and rail car load-out, pumping plant tailings to the tailings dam, as well as a central control building and fuel & chemical reagent storage tanks.
The Scope of Work includes the provision of all professional and technical services, labour, equipment, facilities and materials and all other functional services necessary and required to engineer, procure, construct, commission and performance test the beneficiation plant facilities on a lump sum turn key basis, as defined in the contract. |
Minning Projects | About Maaden
Ma'aden was established as a Saudi Arabian joint stock company in March 1997 to facilitate the development of Saudi Arabias non-petroleum mineral resources and to diversify the Kingdoms economy away from the petroleum and petrochemical sectors. Maaden is engaged in the development, advancement and improvement of all aspects of the mineral industry, mineral products and by-products and related industries in Saudi Arabia. In July 2008 Maaden offered 50% of the companys shares for subscription in a successful SR 9.25 billion IPO. Maaden has progressed towards realizing its vision of building a world class mineral enterprise and its mission of being a profitable, publicly owned, international mining company, while maintaining the utmost concern for human resources, health and safety, environmental and social issues. |
Minning Projects | Involved in Projects management in varying capacity, prepare close out reports for Al Jalamid
projects, involve in reviewing the design of the new assets water treatment plant, new 2 impact
crushers, rod mill and belt filter. Supervision of assets construction. Prepare scope of work for all modification to plant, prepare commissioning procedures, witness the performance tests, etc. |
Minning Projects |
Involved with PMC team in pre-commissioning and commissioning of the 3 GE/GTG and main
substation building, this included review method statements, the walk down, generate punch list, test
packages and witnessing the hydro tests
Involved in field checking equipment installations against P&ID, liasing with beneficiation Contractor with respect to construction schedule, developing and categorizing of punch list to achieve mechanical
completion. |
Minning Projects | XXX has assisted as a technical expert with Pre-commissioning and commissioning of the beneficiation plant including the following sub-systems: Primary crusher, secondary crusher, stacker and reclaimer, milling and desliming systems, reverse flotation,
wet concentrate storage, drying and tailings disposal.
Monitored and supervised the beneficiation plant reliability and preliminary performance tests.
During reliability and performance tests a number of problems were identified that needed to be
attended to before the handover of the plant. These are summarised as: Water shortage - The basic design of the beneficiation plant was assumed that the fresh water required to run the plant at 100% designed capacity is 801m3/hr, in addition to 726 m3/hour as a make-up water used from filtrate and tailings thickener overflow water recycled directly into grinding and Desliming circuit. During
plant operation and due to collector residual in the recycled water which resulted in failure of grinding-
Desliming system performance. The contractor was obliged to use a 726m3/hr of raw water to compensate the contaminated recycled water. The maximum water available from the 7 water wells at AJ is 1050m3/hr
Accordingly, the shortage in water required to run the plant at maximum capacity is 726 m3/hr. The
contractor is working on solution to resolve this problem
Excessive foaming - This problem is preventing the plant to operate over 70% of the designed capacity
Lower grade- The average grade obtained during preliminary performance test is 31.5% P2O5 versus the designed grade 32.5% P2O5
Action: The contractor Wengfu has worked on several modifications to the tailings thickener in order to improve the thickener performance. After the modification the overflow process water quality has been
improved and the foaming was less. A further modification will be carried out on thickener feeding pipes and installing a new pipeline from overflow tank to process water tank in milling and Desliming area. The
contractor has submitted a technical and financial proposal to MPC to resolve the water shortage problem. A
detailed laboratory tests were carried out by Wengfu in China to determine the ultimate design for the required water treatment facility. |
Minning Projects | Project located in the northern region of the Kingdom, The site is situated 23km from Al Jalamid village and 20km inside the desert. Al Jalamid village is located between Ar'ar and Turaif, about 100km from Ar'ar. Site
location is 31° 30' 51.7"N, 39° 57' 13.7"E (WGS84)
This Project is to economically mine the Al Jalamid phosphate deposit at a rated capacity of 5.0 Mtpy of concentrate and produce 2.9 Mtpy of diammonium phosphate fertilizer (DAP)
The Al Jalamid phosphate deposit will be strip-mined and the ore processed in a beneficiation plant at Al
Jalamid. The phosphate concentrate will then be railed approximately 1200 Km to fertilizer production
facilities located at Ras Az Zawr, on the Arabian Gulf shoreline, 85 Km north of Al-Jubail
At the fertilizer complex at Ras Az Zawr, the phosphate concentrate will be processed to produce DAP, in an integrated fertilizer complex consisting three Sulphuric Acid plants, three Phosphoric Acid plants, one
Ammonia plant and three DAP plants and the related infrastructure to support these plants. Port facilities will
be constructed to ship the product to market.
Both the Al Jalamid mine site and the fertilizer complex at Ras Az Zawr are green field sites and will
therefore require significant infrastructure development, both of a social and industrial nature. |
Minning Projects | The beneficiation plant will utilize the process developed by SAPC and refined by Litwin to produce 5.020 million tones per year (dry basis) of concentrated phosphate rock. The beneficiation process involves particle size reduction using crushers and rod mills followed by desliming, froth flotation to remove carbonates, concentrate dewatering, drying and storage, concentrate reclaim and rail load out, waste disposal, and process water recovery and distribution. Other facilities will include Power plant. Water and wastewater treatment facilities, maintenance shops, warehousing complex, Administrative offices and a Bachelors' Community. |
Minning Projects | Trucks
Komatsu 830E, 930E and 630E
930E and 630E - used for removal of overburden
630E used to take ore to dump pad
Service intervals
250 Hr service Service Sheet
Change engine oil, radiator coolant samples
500 Hr
750 Hr
1000 Hr
1250 Hr
1500 Hr
1700 Hr
2000 Hr Major Maintenance
Major equipment in the trucks, gear boxes, air cooling systems and hydraulic systems |
Minning Projects | Electrical Shovels (Liebherr 996 , Komatsu & Hitachi) |
Minning Projects | Wheel Loaders
To be used in the dump pads
Caterpillar 992 |
Minning Projects | Excavators
Used for construction of roads and pits |
Minning Projects | Water Carts
Used foe dust impressing |
Minning Projects | Pit dewatering pumps
To evacuate pits during rainy season, Aker Wirth Pumps |
Minning Projects | FIX PLANT
Bull Horn Crusher/ feeder and hopper arrangement
Ore is fed into a Hopper and then transported to the crusher with the help of conveyors
There is a different control room for the crusher
Major reliability issues with bull Horn Crushers is,
Cracks in the Horns
Bondi Product melt and become one product
Feeder is a critical equipment in the plant
Crusher maintenance 2 day / 5 Day
Pully system bent up pully
Conveyors
Conveyor arrangement
Pulley vibration check 6 weeks
Lube Schedule take sample
Check Oil Levels
Greasing
Thermography for bearing
PI Progress book
Normally the thermography is done in 4.30 am in the morning and put a tag, a note on a book and then create a WO (Work Order)
Belt Inspection
Every 3 months Planned shutdown ( 5 days )
Every 1 year MSD June/Aug ( 8-12 days ) |
Minning Projects | Mine Fixed are is two parts
Dry Area
In a mine where there is crushing
Wet Area
Grinding and rest |
Minning Projects | Gyratory Crusher -> 2 X Cone Crusher ( Serial and no stand by crusher) Banana Screen/ Vibratory Screen
During Grinding water is added to the system |
Minning Projects | Reliability Issues
Roller damage
Belt damage
Hopper liner worn and damage |
Minning Projects | RCA Analysis
Power Plant General 15 MW , Piston damage
/back pressure exhaust Cracker muffler
Power plan is totally unmanned and have 5 engines = 3 (Run) + 2 (Standby)
Engine is 4.2 MW
Type of oil 320 or 220 oil |
Minning Projects | SAG Mill Grate Ball/SAG Mill
Liner replacement in a Shutdown, every 8 12 months
Ball feed conveyor
Grate reliability Issue. The solution was
SWI Standard Work Instructions
Check Hardness ( Hardness test Brinell hardness test)
QA assurance from supplier
Relining machine Replace grates |
Subsets and Splits
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