CENG0035 Minerals usage, extraction, and processing

Coursework – 30 % of the module.

To be submitted via Moodle before 09:00 on Wednesday 4th  December 2024

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Coursework outline

The industries considered within this module all have a range of unit operations and processes that transform natural resources into usable products.

This coursework looks at questions, both qualitative and quantitative that discuss the refining of these natural resources in the mining and nuclear sectors. You must show your working out in each question to gain full marks, correct answers will only receive a single mark without it.

Please note. In order to randomise each of your coursework, each coursework will be linked to your student number, which is an eight-digit number;

The fourth and fifth digits correspond to XX, the sixth and seventh to YY and the eighth to W;

E.g.: 22163849; XX = 63 and YY = 84 and W = 9.

Please write your student number and the XX, YY and W values at the start of the coursework.

100 Marks

Coursework – Part 1

In this part, we examine two different process flows for metalliferous ores: froth flotation and heap leaching/solvent extraction. Variations on these two processes are used to concentrate metals derived from their host minerals.

1) PROCESS MANAGEMENT

a)  Why do we need to decrease the size of our ore particles down, regardless of whether we follow the froth flotation route, or the heap leaching/solvent extraction route? (2 Marks)

b)  If we are to follow the froth flotation route, what would be an appropriate cut size be for our feed particle size to fall below, and why? Use an example to  help explain your answer. (3 Marks)

2)  COMMINUTION MASS BALANCE

The flow-rate of ore into your comminution stage is 1YY5 t hr-1 . This ore is crushed, and then milled. There is a single stage of milling, followed by a hydrocyclone. The hydrocyclone underflow (particles that are too large) is  returned to the mill.

2W % of the solids that leave the mill (and enter the hydrocyclone) go to the underflow and are recycled for further milling.

a)  Draw the process flow diagram. (4 Marks)

b)  What is the total flowrate of solids through the mill? Show your working. (3 Marks)

c)  What is the purpose of the hydrocyclone in this circuit? (2 Marks)

d)  Would we normally expect just one mill and one hydrocyclone at a mine site? Explain your answer. (3 Marks)

3) FROTH FLOTATION

A bank of three flotation cells (as part of a larger flotation facility)

cumulatively recovers a proportion of tin bearing cassiterite from the milled ore.

a)  Calculate the cumulative grade-recovery from the following data for a bank of three flotation cells. The flotation feed rate is 1YY5 t hr-1  solids, with a grade of 0.5W % tin. You must show your calculations for the marks.

Remember that grade is the proportion of metal in ore in this case, and recovery is the proportion of metal recovered to the concentrate.

N.B., in reality, the tin bearing cassiterite is concentrated over numerous banks of cells that perform. different functions to maximise recovery.

b)  Is your cumulative recovery value realistic? Explain you answer. (2 Marks)

c)  A section of the plant treats 160+XX0 t hr-1 of ore containing 0.W7 + 0.60 % tin (which is still associated with cassiterite), and quartz-feldspar gangue. There are no other minerals in the ore. The plant can be operated at two conditions:

•    Condition 1: A tin recovery of 8W % and a concentrate grade of 38.1 % (high grade, low recovery).

•    Condition 2: A tin recovery of 93 % and a concentrate grade of 2W.8 % (low grade, high recovery).

The smelter pays 83 % of the market price for the mass of tin in the concentrate, and charges $ 1200 per tonne of concentrate as a treatment charge (for removing the associated gangue). The current tin price is $ 22500 per tonne.

Calculate:

i.     How many tonnes of tin enter the plant every hour? (2 Marks)

ii.     How many tonnes of tin and total concentrate are produced every hour for each of the two conditions? (4 Marks)

iii.     What is the concentrate value per hour for each of the two conditions? (4 Marks)

iv.     If the tin price increases (say to $ 3W400 per tonne), should the plant operate at a higher or lower recovery condition? Explain and justify your answer. (5 Marks)

v.     In terms of environmental issues, is a higher tin price favourable or unfavourable? Explain your answer. (2 Marks)

4)  SOLVENT EXTRACTION

A solvent extraction (SX) plant comprises 1 extraction stage and 1 stripping stage. The flowrate of pregnant leach solution (PLS) into the  plant is 1500 m3  hr-1 , with a Tin (Sn) content of 6 kg/m3  solution. The loaded electrolyte feed to the EW plant has a Sn content of 6W kg/m3 solution. The organic phase consists of extractant LIX900 in kerosene.

a)   Draw the flowsheet and label all streams with all the information provided. (6 Marks)

b)   The efficiency of the extraction stage is 92-W %. The ratio of the organic phase (m3) to aqueous (m3) phase across the extraction stage is 1.4:1.

An extractant, contained within in the organic phase is used to strip (collect) the tin from the PLS. A 1 % solution of the extractant in the organic phase can collect 0.1+0.XX kg Sn from the PLS, for every 1 m3 of the organic phase.

What percentage concentration of extractant is required in the organic to receive the tin transferring from the PLS?

As part of your answer, you should calculate the volume of the organic phase. (5 Marks)

c)   The depleted electrolyte from the electrowinning circuit contains 40 kg m3 solution. What is the flowrate of the loaded electrolyte stream? (4 Marks)

d)   What happens to the tin in the electrolyte solution? Describe the process and the outcomes. (4 Marks)

64 marks in total for part 1

Coursework – Part 2

In this part, we examine the production of nuclear power and the nuclear fuel cycle.

1) NUCLEAR POWER

a)  Write out the decay reaction series for uranium-235 going through one

stage of alpha (α) decay followed by one stage of beta (β-) decay. (1 Marks)

b)  Describe the process of producing uranium fuel from mined uranium. (4 Marks)

c)  Describe the process of producing electrical energy from uranium fuel. (4 Marks)

d)  Choose two of the aspects you have described in parts b) and/or c);

highlight one safety concern for each and then explain what technique(s) can be used to mitigate the risk. (4 Marks)

2)  URANIUM FUEL PRODUCTION

The burning of fuel is not 100 % efficient, a typical reactor will burn 7W % of the U235  in the fuel, 2 % of the U238  in the fuel will also be burnt. In this question consider a reactor that uses uranium fuel with an enrichment of 2.1+0.YY % and a tails assay of 0.25 %.

a)  How much uranium feed to the enrichment plant is required to produce 1 kg of uranium fuel? (3 Marks)

b)  What percentage of this uranium feed is burnt for conversion into electrical power, assuming no losses in the fuel rod fabrication? (3 Marks)

c)  The uranium deposit at Cigar Lake (Canada) has an average grade of 15 % U3O8 , how much of this ore needs to be mined for the reactor to have burnt 10 kg of uranium? (4 Marks)

d)  Comment on your answer to part c). (1 Mark)

3)  NUCLEAR PLANT DESIGN AND SAFETY

The Finish company, TVO, is considering restarting plans to build a fourth reactor at Olkiluoto. The two designs currently under consideration for the fourth reactor are an Evolutionary Pressure Vessel Reactor (EPR) and an Advanced Boiling Water Reactor (ABWR).

a)  Describe the technical similarities and differences between these two reactors. (4 Marks)

b)  Which of the two you think would be the best option for TVO and why? Consider financial, social and safety elements as well as technical differences (8 Marks)

36 marks in total for part 2

100 marks in total for the coursework.