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exm301ie20051

# exm301ie20051 - MURDOCH UNIVERSITY PERTH WESTERN AUSTRALIA...

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Unformatted text preview: MURDOCH UNIVERSITY PERTH, WESTERN AUSTRALIA Semester 1 Examinations 2005 Unit EXM301 MINERAL PROCESSING I Internal & External Time Allowed 3 hours plus 10 minutes reading time INSTRUCTIONS ANSWER ANY FIVE QUESTIONS Family Name: Given Name: Student No: Signature: EXAMINATION AIDS ALLOWED Provided by the Universiﬂ GRAPH PAPER (A4 1MM) GRAPH PAPER (LOG-LOG) Provided by the Candidate CLOSED BOOK EXAMINATION CALCULATOR PERMITTED (NO QWERTY KEYBOARD) ANSWER ONLY FIVE QUESTIONS ALL QUESTIONS CARRY EQUAL MARKS AS INDICATED . a. Draw the ﬂow sheet of a typical comminution circuit and explain the purpose of each piece of equipment and its characteristic features. (5 marks) b. Discuss the commonly used tests to determine cornminution characteristics of an ore for the purpose of designing a comminution circuit. (5 marks) 0. What is meant by the critical speed of a tumbling mill and discuss how it affects the product? (5 marks) d. What are the main beneﬁts of having a circulating load in a grinding circuit? (5 marks) A sample of an ore was hatch ground in a laboratory mill. The results of the size analysis of the ground product are given in the table below. TABLE 1: Sieve Anal sis Data (%) Passin ; a. Evaluate the mean size and the parameters of the Rosin—Rammler distribution of the above product. (Rosin-Rammler paper is attached) (12 marks) b. Hence, calculate the amount of ﬁnes below 20 microns in the product. (3 marks) 0. Determine the sphericity of a cylindrical carbon particle of diameter 2 mm and 5 mm in length. (5 marks) It is required to determine the performance of an operating hydrocyclone in a typical gold plant. a. Discuss what samples should be collected and the information you would obtain from the samples? (8 marks) b. How would you analyse the data in order to obtain the cyclone characteristics in terms of its operating, corrected and reduced performance curves? (6 marks) c. Explain why the operating performance curve does not pass through the origin. (3 marks) d. Discuss why hydrocyclones are preferred over other mechanical classiﬁers. (3 marks) 4. a. Derive an expression for the fraction of particles of size d retained on a screen of square aperture size a, if the probability of passage of a particle in one attempt is p and the number of attempts it makes is n. (6 marks) b. Using a suitable expression for p above, determine the size distribution of the oversize product when a feed material whose size distribution given below is screened over a screen of aperture size 4mm. Assume that the wire thickness is negligible in comparison to aperture size and that the number of attempts made by particles during their passage over the screen is given by: n=12.65 0%) for %<0.4 = 8.62 (14%) for% >0.4 Feed size distribution ————————————————-—-————- Size Range (mm) Average (14 marks) 5. a. What are separability curves and what do they represent? (5 marks) b. The performance curves of an Operating jig and a dense medium cyclone are shown in Figure below. Estimate the cut SG, probable error and imperfections for the two devices. > (6 marks) 05- Performance curves for Jig and Dense medium cyclone 100 Iiiiassmgi .EIIIIIIIIIIIIIIIIIIIII II IIII 90 I IIIIIIII!!!IIIFII{IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIEIIIIEIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII m 80 llIIIlIIllIIIIIIIEIIIEIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII x llllllllIIIIIIIIIIIﬁlIIQIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII ,5 7o IIIIIIIIIIIIIIIIIIIIEQIQIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII a) lllIIIIIIIIIlIllIIlIIIIlIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII o 60 llllIIIIIIIIIIIIIIIIIIIIESEIIllIIIIIIIIIIIIIIIIIIIIIIIIIIII ... 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