JAKINS, Andrew (Erf 5082 Main Road, Hout Bay, 7806 Cape Town, ZA)
HETHERINGTON, Grahame Alan (506 Shorham, 199 Beach RoadThree Anchor Bay, 8005 Cape Town, ZA)
JAKINS, Andrew (Erf 5082 Main Road, Hout Bay, 7806 Cape Town, ZA)
| CLAIMS:
1. A method of optimizing the utilization of the processing capacity of a material processing plant for processing a solids-containing flowable process material having variable material properties, supplied from a single feed source, wherein the material processing plant includes a first processing unit for processing a first grade of the process material at optimal efficiency and a second processing unit for processing a second grade of the process material at optimal efficiency, the method including:
sorting the process material prior to processing by the material processing plant, into:
said first grade;
said second grade; and
a middling grade having a material property between that of the first and second grades and which can be processed at optimal efficiency by both of the first and second processing units;
directing the first grade process material to a first processing stream for processing by the first processing unit;
directing the second grade process material to a second processing stream for processing by the second processing unit; and
directing the middling grade process material to the first and second processing streams whenever the first and second processing units have spare processing capacity, thereby to balance the flow of middlings grade process material between the first and second process streams so as to maximise utilization of the processing capacity of both the first and second processing units.
2. The method as claimed in claim 1 , which includes sorting the process material into grades according to particle size distribution, with the first grade having a relatively finer particle size distribution, the second grade having a relatively coarser particle size distribution and the middling grade having a particle size distribution between that of the first and second grades.
3. An apparatus for optimizing the utilization of the processing capacity of a material processing plant for processing a solids-containing flowable process material having variable material properties, supplied from a single feed source, wherein the material processing plant includes a first processing unit for processing a first grade of the process material at optimal efficiency and a second processing unit for processing a second grade of the process material at optimal efficiency, the apparatus including:
sorting means for sorting the process material prior to processing by the material processing plant, into:
said first grade;
said second grade; and
a middling grade having a material property between that of the first and second grades and which can be processed at optimal efficiency by both of the first and second processing units;
first flow directing means for directing the first grade process material to a first processing stream for processing by the first processing unit;
second flow directing means for directing the second grade process material to a second processing stream for processing by the second processing unit; and balancing means for directing the middling grade process material to the first and second processing streams whenever the first and second processing units have spare processing capacity, thereby to balance the flow of middling grade process material between the first and second streams so as to maximize utilization of the processing capacity of both the first and second processing units.
4. The apparatus as claimed in claim 3, wherein the sorting means is operable to sort the process material into grades according to particle size distribution wherein the first grade has a relatively finer particle size distribution, the second grade has a relatively coarser particle size distribution and the middling grade has a particle size distribution between that of the first and second grades.
5. The apparatus as claimed in claim 3 or claim 4, wherein the apparatus is adapted for use with process material in the form of mined ore. |
METHOD AND APPARATUS FOR OPTIMISING THE UTILIZATION OF THE PROCESSING CAPACITY OF A MATERIAL PROCESSING PLANT
FIELD OF INVENTION
This invention relates to a method and apparatus for optimising the utilization of the processing capacity of a material processing plant.
BACKGROUND TO INVENTION
The usual practice for the processing of solids-containing flowable material having a variable material property, for example, mined ore such as kimberlite or alluvium, supplied from a single feed source, is for the feed material to be graded into two size fractions or grades upstream of the material processing plant. Each grade is fed into a processing stream for processing by a processing unit of the processing plant. The particle size cut-off point according to which the material is graded, is selected taking into account the anticipated or design particle size distribution throughout the process material and the processing capacity of each processing unit in order to maximize utilization of the processing capacity of both processing units. As such, in order to achieve full capacity utilization of both processing units, the actual particle size distribution must be exactly the same as the design particle size distribution and remain constant. In practice, however, the particle size distribution varies, often significantly, within a range of sizes. In order to
address the problem of the actual particle size distribution not matching the design particle size distribution, a number of approaches have been taken, such as:
1 ) increasing the processing capacity of the processing units - this approach, however, often involves significant additional cost and a sensible cost/benefit trade off would likely not cover all variations in the design particle size distribution nor the life of a mine.
2) reducing the head feed rate to both processing streams when the maximum processing capacity of one of the processing units is achieved - this approach can be extremely costly as it has a direct bearing on revenue.
3) over-feeding one or both of the processing streams - this approach leads to sub-optimal efficiencies, revenue loss and usually is only available as an option where relatively small variations in particle size distribution, are involved.
4) feeding excess process material in one of the processing streams to the other processing stream - this leads to sub-optimal process efficiencies.
The above approaches are clearly not ideal and have the disadvantages mentioned hereinabove.
SUMMARY OF INVENTION
According to the invention there is provided a method of optimizing the utilization of the processing capacity of a material processing plant for processing a solids-containing flowable process material having variable material properties, supplied from a single feed source, wherein the material processing plant includes a first processing unit for processing a first grade of
the process material at optimal efficiency and a second processing unit for processing a second grade of the process material at optimal efficiency, the method including:
sorting the process material prior to processing by the material processing plant, into:
said first grade;
said second grade; and
a middling grade having a material property between that of the first and second grades and which can be processed at optimal efficiency by both of the first and second processing units;
directing the first grade process material to a first processing stream for processing by the first processing unit;
directing the second grade process material to a second processing stream for processing by the second processing unit; and
directing the middling grade process material to the first and second processing streams whenever the first and second processing units have spare processing capacity, thereby to balance the flow of middling grade process material between the first and second process streams so as to maximise utilization of the processing capacity of both the first and second processing units.
The method may include sorting the process material into grades according to particle size distribution, with the first grade having a relatively finer particle size distribution, the second grade having a relatively coarser and the middling grade having a particle size distribution between that of the first and second grades.
According to a second aspect of the invention there is provided an apparatus for optimizing the utilization of the processing capacity of a material processing plant for processing a solids-containing flowable process material having variable material properties, supplied from a single feed source, wherein the material processing plant includes a first processing unit for processing a first grade of the process material at optimal efficiency and a second processing unit for processing a second grade of the process material at optimal efficiency, the apparatus including:
sorting means for sorting the process material prior to processing by the material processing plant, into:
said first grade;
said second grade; and
a middling grade having a material property between that of the first and second grades and which can be processed at optimal efficiency by both of the first and second processing units;
first flow directing means for directing the first grade process material to a first processing stream for processing by the first processing unit;
second flow directing means for directing the second grade process material to a second processing stream for processing by the second processing unit; and
balancing means for directing the middling grade process material to the first and second processing streams whenever the first and second processing units have spare processing capacity, thereby to balance the flow of middling grade process material between the first and second streams so as to maximize utilization of the processing capacity of both the first and second processing units.
The sorting means may be operable to sort the process material into grades according to particle size distribution wherein the first grade has a relatively finer particle size distribution, the second grade has a relatively coarser particle size distribution and the middling grade has a particle size distribution between that of the first and second grades.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features of the invention are described hereinafter by way of a non- limiting example of the invention, with reference to and as illustrated in the accompanying diagrammatic drawings and tables. In the drawings:
Figure 1 shows a schematic block flow diagram illustrating a prior art process for sorting a solids-containing flowable process material prior to processing the material in a material processing plant;
Figure 2 shows a schematic block flow diagram illustrating a method of optimising the utilization of the processing capacity of a material processing plant, in accordance with the invention;
Figure 3 shows a schematic perspective view of an apparatus in accordance with the invention;
Figure 4 shows a schematic sectional perspective view of the apparatus of Figure 3, sectioned along section line IV-IV of Figure 3;
Figure 5 shows a schematic sectional perspective view of the apparatus of Figure 3, sectioned along section line V-V of Figure 3;
Figure 6 shows a schematic side view of the apparatus of Figure 3;
Figure 7 shows a schematic top plan view of the apparatus of Figure 3;
Figure 8 shows a schematic sectional end view of the apparatus of Figure 3, sectioned along section line VIII-VIII of Figures 6 and 7;
Figure 9 shows a schematic sectional end view of the apparatus of Figure 3, sectioned along section line IX-IX of Figures 6 and 7;
Figure 10 shows a schematic sectional end view of the apparatus of Figure 3, sectioned along section line X-X of Figures 6 and 7;
Figure 1 1 shows a schematic perspective view from one side, of the reservoirs of the apparatus of Figure 3;
Figure 12 shows another schematic perspective view from an opposite side, of the reservoirs of the apparatus of Figure 3; and
Figure 13 shows a schematic sectional perspective view of the reservoirs of the apparatus of Figure 1 , sectioned along section line XIII-XIII of Figure 12.
In the tables:
Table 1 illustrates the variation in the actual particle size distribution of head feed process material compared to the design particle size distribution; and
Table 2 provides data illustrating a comparison of the overall capacity utilization of the prior art material processing method depicted in Figure 1 with that of the method in accordance with the present invention depicted in Figure 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
With reference to Figure 1 of the drawings, a prior art method of processing a solids-containing flowable process material of variable size, prior to processing the material in a material processing plant, is illustrated. The head feed supply of process material which, in this instance, is mined ore such as kimberlite or alluvium having a size range from A mm to G mm, is fed into a sizing facility where the feed material is graded into two size fractions or grades. More particularly, the process material is sized into a fine size fraction and a coarse size fraction at a particle size cut-off point of D mm. The fine size fraction contains particle sizes ranging in size from A mm to particle sizes of less than D mm, whereas the coarse size fraction contains particles having particle sizes of D mm to G mm. The fine size fraction is conveyed to process stream No. 1 which has a maximum processing capacity of 50 tons per hour (tph). The coarse size fraction is conveyed to process stream No. 2 having a maximum processing capacity of 70 tph. The process material in process streams No. 1 and No. 2 is processed separately in processing units No. 1 and No. 2, respectively. The particle size cut-off point and the processing capacity of each of the two processing units is determined by the anticipated particle size distribution ("PSD") of the mined ore in order to achieve full capacity utilization of both processing units. In practice, however, the PSD varies, often significantly, within a range of sizes. It will be appreciated that processing unit No. 1 is operable to process the process material of process stream No. 1 , but is not capable of processing the coarser process material of process stream No. 2 at optimal efficiency. Similarly, the processing unit No. 2 is operable to process the process material of process stream No. 2 but is not capable of processing the finer process material of process stream No. 1 at optimal efficiency.
With reference to Figure 2 of the drawings, a method of optimizing the utilization of the processing capacity of a material processing plant, in accordance with the invention, is illustrated. The process material in this example is dense media in the form of mined ore such as kimberlite or alluvium, having a variable particle size. A single head feed of the process
material having a particle size range between A mm to G mm is conveyed to a sizing facility (1 ) in which the process material is sized into three size fractions or grades. More particularly, the sizing facility sorts the process material into a fine size fraction having a size range of A mm to C mm, a middling size fraction from C mm to E mm and a coarse size fraction of E mm to G mm. After sorting, the three size fractions are fed into surge bins (2), (3) and (4), respectively. The fine size fraction is conveyed from the fine fraction surge bin (2) to process stream No. 1 (5), whereas the coarse size fraction is conveyed from the coarse fraction surge bin (4) to process stream No. 2 (6). As for the prior art process illustrated in Figure 1 , the maximum processing capacity of process stream No. 1 is 50 tph and the maximum processing capacity of process stream No. 2 is 70 tph. Processing unit No. 1 (7) which forms part of a material processing plant, is operable to process the process material in process stream No. 1. Process material in process stream No. 2 is conveyed to processing unit No. 2 (8) at the material processing plant, for processing by processing unit No. 2.
The middling size fraction of the process material is conveyed from the middling fraction surge bin (3) to one of the process stream No. 1 and the process stream No. 2 for processing in one of the processing unit No. 1 or the processing unit No. 2. It will be appreciated that processing unit No. 1 is operable to process the fine size fraction and the middling size fraction at optimal efficiency, whereas processing unit No. 2 is operable to process the coarse size fraction and the middling size fraction at optimal efficiency. The processing unit No. 1 is, however, not capable of processing the coarse size fraction at optimal efficiency, and the processing unit No. 2 is not capable of processing the fine size fraction at optimal efficiency.
The middling size fraction is directed from the middling fraction surge bin (3) to the process stream No. 1 and to the process stream No. 2 in amounts relatively proportional to the available processing capacity of each of the first and second processing units. This permits the flow of middling size fraction process material to be balanced between process stream No. 1 and process
stream No. 2 so as to maximise utilization of the processing capacity of both of the processing unit No. 1 and the processing unit No. 2.
With reference to Table 1 , examples of the actual variation of PSD of a head feed of process material compared to a design PSD, are provided. In a first example ("Case I"), it can be seen that the actual PSD of the head feed is generally finer than the design PSD. In a second example ("Case II"), it can be seen that the actual PSD of the head feed is generally coarser than the design PSD. In the given examples, the cut point is a particle size of 8 mm.
With reference to Table 2, the effect of the variation in the actual PSD of the head feed is demonstrated using the Case I and Case II examples illustrated in Table 1 in relation to the prior art method of processing material depicted in Figure 2 and also the material processing method in accordance with the present invention. With specific reference to the prior art processing method, Table 2 shows the effect on overall processing capacity utilization as the PSD of the head feed becomes finer (Case I) or coarser (Case II) than the design PSD. For the examples given, it is clear that as the head feed material becomes finer, the processing capacity of process unit No. 1 is fully utilized as relatively more feed material falls into the size range A mm to D mm. It can be seen from the PSD shown in Table 1 for the Case I example, that 65 tph of the process material would report to the finer size fraction and 55 tph would report to the coarse size fraction if the material feed rate was maintained at 120 tph. As the processing capacity of process unit No. 1 is 50 tph, the head feed rate has to be slowed down to 50/65 = 77% of 120 tph = 92 tph. As a result, 50 tph is reported to processing unit No. 1 and 42 tph is reported to processing unit No. 2. A surge facility would only delay the timing at which the head feed rate would need to be reduced. The processing capacity of the processing unit No. 2 drops to 60% resulting in an overall capacity utilization for the processing plant of 77%. Similarly, as the actual PSD becomes coarser as is demonstrated by the Case II example in Table 2, the head feed rate must be slowed down from the ideal maximum of 120 tph. If the material feed rate was maintained at 120 tph, 85 tph of coarse size fraction would report to
processing unit No. 2. The feed rate therefore has to be cut back to 70/85 = 83% of 120 tph = 99 tph. As a result, 70 tph is reported to processing unit No. 2 and 29 tph is reported to processing unit No. 1.
From Table 2 it can be seen that for the material processing method of the present invention, as the head feed PSD varies, the maximum overall capacity utilization of the processing units is achieved by simply varying the amount of the middling size fraction which is directed to process stream No. 1 and process stream No. 2 to top up the finer size fraction and the coarse size fraction, respectively. The middling size fraction is directed to the processing stream No. 1 and No. 2 whenever excess processing capacity becomes available thereby to achieve optimal processing efficiencies and maximum overall utilization of the processing capacity of the processing units over a wide variation in the PSD of the head feed.
The Applicant believes that implementation of the method defined hereinabove in accordance with the present invention, will result in significant cost savings in capital expenditure on processing units as processing units need not be over-sized in terms of processing capacity in order to cater for variations in PSD. Furthermore, the operating costs associated with oversized installations will be obviated. The method also reduces the risk of bottlenecking and other problems occurring during a material processing operation, due to variations in the PSD of the feed material.
With reference to Figures 3 to13, an apparatus for optimising the utilization of the processing capacity of a material processing plant, in accordance with, the invention, is designated generally by the reference numeral 10. The apparatus 10 is adapted for use in implementing the method in accordance with the invention, described hereinabove and illustrated in Figure 2. The apparatus 10 is operable to sort the dense media process material prior to processing of the process material in process units No. 1 and No. 2 of the material processing plant. The apparatus 10 comprises, broadly, a first surge reservoir 12, a second surge resorvoir 14, sorting means in the form of a shaker 16 and a frame 18.
The surge reservoir 12 feeds the processing stream No. 1 with process material and the surge reservoir 14 feeds the processing stream No. 2 with process material. As described hereinabove, the process material of the process stream No. 1 is conveyed to the processing unit No. 1 for processing and the process material of the process stream no. 2 is conveyed to the processing unit No. 2 for processing. Each reservoir 12 and 14 is defined by walls 32. The first reservoir 12 and the second reservoir 14 are located adjacent one another and divided by a dividing wall 20.
The shaker 16 is located on the frame 18 in an arrangement wherein it extends longitudinally along the dividing wall 20. The shaker 16 includes a coarse sieve 22 and a fine sieve 24. The shaker 16 is fed from a head feed supply of the process material which is fed onto the coarse sieve 22 via a hopper (not shown).
The coarse sieve 22 is disposed above the fine sieve 24. The sieves 22 and 24 are inclined slightly to assist process material which is too large to pass through a particular one of the sieves 22,24 to travel downwards along the sieve when shaken.
With reference to Figure 8, process material which is sized larger than the perforations in the coarse sieve 22 (i.e the coarse size fraction having a PSD of E mm to G mm) collects on the coarse sieve 22 and travels along the sieve until it drops off the lower end of the coarse sieve at region 40. The apparatus 10 includes first flow directing means in the form of a slanted plate 26 which is located below region 40. The plate 26 extends between the dividing wall 20 and the upper ends of the reservoirs 12, 14. Coarse size fraction process material which drops from the shaker 16 along region 40 falls onto the plate 26 which directs the coarse size fraction to the first surge reservoir 12.
With reference to Figure 10, the fine sieve 24 allows process material having a size less than perforations in the fine sieve 24 (i.e the fine size fraction having a PSD of A mm to C mm) to fall through the fine sieve 24, along a
region 44. The apparatus 10 includes second flow directing means in the form of a slanted plate 30 which is located under region 44. The plate 30 extends between the dividing wall 20 and the upper ends of the reservoirs 12, 14. Fine size fraction process material which drops from the shaker 16 along region 44 falls onto the plate 30 which directs the fine size fraction to the second surge reservoir 14.
With reference to Figure 9, the process material which is small enough to pass through the coarse sieve 22, but too large to pass through the fine sieve 24 (i.e. the middling size fraction having a PSD of C mm to E mm), is discharged along a region 42 into the reservoirs 12, 14 via a chute 36. The throat of the chute 36 is intersected and divided in half by part 28 of the dividing wall 20. The part 28 is as high, or slightly higher, than the lower end of the chute. As such, part of the middling grade material is discharged into the first reservoir 12 and part of the middling grade material is discharged into the second reservoir 14. In use, if one of the reservoirs 12, 14 is filled to a height beyond the lower end of the chute 36, the part of the throat of the chute through which middling grade material is discharged into that reservoir is blocked off by the build-up of middling grade material and the middling grade material is thus necessarily directed to the other reservoir.
The chute 36 and part 28 of the dividing wall 20 intersecting the chute thus provide balancing means for balancing the amount of process material within the surge reservoirs 12, 14.
It will be appreciated that the exact configuration of the apparatus may vary considerably while incorporating the essential features of the invention as defined hereinabove. The Applicant envisages that a number of different designs of the apparatus, which incorporate the essential features of the invention, may be used to implement the method in accordance with the invention.
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