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exm301ie20071 - MURDOCH UNIVERSITY ‘ v PERTH WESTERN...

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Unformatted text preview: MURDOCH UNIVERSITY ‘ v PERTH, WESTERN AUSTRALIA Examinations - Semester 1, 2007 nit EXM301 MINERAL PROCESSING I ExamType - Internal & External Time Allowed 3 hours plus 10 minutes reading time INSTRUCTIONS ANSWER ONLY FIVE QUESTIONS EXAMINATION AIDS ALLOWED Provided by the Universifl GRAPH PAPER (A4 1MM) GRAPH PAPER (LOG-LOG) Provided by the Candidate CLOSED BOOK EXAMINATION CALCULATOR PERMITTED (NOT GRAPHICS) ANSWER ONLY FIVE QUESTIONS ALL QUESTIONS CARRY EQUAL MARKS AS INDICATED . How would you determine the size distribution of a SAG mill feed stream that is fed by a conveyor belt. (5 marks) . Briefly describe the requirements of a sample cutter that may be used to sample a hydrocyclone underflow stream. (5 marks) . The feed to a copper flotation circuit is prepared using a standard SABC comminution circuit. A 5kg sample of ore is taken by sampling the SAG mill discharge with a top size of 3mm, so that the assay error is kept to within :h 0.2% Cu @ 95% level of confidence. What would be the assay error if a sample of 1.0 kg is taken fiom the flotation circuit feed which has a top size of 150p? Note: liberation factor = (liberation size/particle size)'/2 (10 marks) A sample of an ore was batch ground in a laboratory mill. The results of the size analysis of the ground product are given in the table below. TABLE 1: Sieve Analysis Data Size (microns) Cum.Weight (%) Passmg 1600 . Evaluate the parameters of the Gate-Gaudin Schuhmann plot of the above product. (10 marks) . Hence calculate the amount of fines below 10 microns in the product. (5 marks) Determine the sphericity of cubic particle of side 2mm. (5 marks) Describe the characteristic features of a Rod mill, Ball mill and a SAG mill. Highlight any differences in their design and/or operation. (6 marks) . What are “seats” and explain how you would deal with seats in a comminution circuit? (4 marks) What are the main benefits of having a circulating load in a grinding circuit compared to an open circuit operation? (4 marks) . Briefly describe the following: (i) Critical speed of a tumbling mill. (2 marks) (ii) Grindability of an ore. (2 marks) (iii) Mill charge. (2 marks) Sketch a typical Grade/Recovery plot that represents a spiral concentrator performance treating a beach sand that produces a heavy mineral concentrate and a tailing. Give two measures of efficiency that can be used to enumerate the efficiency of the separation process at a given operating point. Discuss their limitations. (8 marks) . The feed to a gravity concentrator contains 10% heavy mineral. The concentrate assays 30% heavy mineral and the tailings assay 1.5% heavy mineral. Determine: (i) The mass % of the feed recovered in the concentrate. (6 marks) (ii) The separation efficiency of the separation. (6 marks) Describe the working of a spiral classifier or a hydrocyclone. (3 marks) . Explain why the performance curve of a hydrocyclone does not pass through the origin. Show how it may be modified to determine a plot that represents the “machine characteristics” of the hydrocyclone. (8 marks) The reduced performance curve of a jig is shown in Figure 1. If the jig operates at a cut specific gravity of 1.6, determine the operating performance curve of the jig. Also estimate the probable error and the imperfection. (9 marks) Discuss the factors affecting the performance of an industrial screen. (6 marks) . What are washability curves used in gravity concentration circuit design? Sketch typical curves and illustrate how they are used. (8 marks) Suggest a flow sheet to process a beach sand mineral deposit comprising of the following minerals: Ilmenite, Rutile, Zircon, Monazite and Silica gangue. (6 marks) 5! Cum Wt. % to Floats Figure 1 - 05- Reduced Performance curve of Jig 1 00 90 80 7O 6O 50 40 30 20 10 0 T71 _J___ M .L..._ l _ I— ...w... _._._l L—efie a— 0.5 0.6 0.7 0.8 0.9 1 ____'_ 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 ReducedSG ******** END OF PAPER ******** ...
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