corin holmes, jenike & johanson: investigating the effects of larger particles on...
DESCRIPTION
Corin Holmes, Technical Officer, Jenike & Johanson Pty Ltd delivered this presentation at the 2013 FE Tech Conference. The event focussed on the economics of processing and the beneficiation of iron ore. In light of the slowdown in demand for iron ore and pricing decreases, the need to process more efficiently and cost effectively is a challenge. The conference examined on how we can achieve greater value from the iron ore supply chain, with topics addressing optimisation and streamlining processes, applying improved technologies, understanding the ore body and how to properly characterise it, knowing the steel makers needs. For more information please visit the conference website: http://www.informa.com.au/fe-techTRANSCRIPT
Bulk Solids: Science / Engineering / Design
Jenike & Johanson
Investigation into the Effects of Larger
Particles on Proctor/Fagerberg
Transportable Moisture Limit Test
Method
By:
Corin Holmes, MSc Eng.
Technical Officer
Bulk Solids: Science / Engineering / Design
Definitions
IMSBC Code – International Maritime Solid Bulk Cargoes Code
2012 Edition
• Appendix 2 – Defines test procedures to determine TML
Bulk Solids: Science / Engineering / Design
Definitions
Transportable Moisture Limit (TML):
The TML value is the moisture content of a bulk material above
which it is considered unsafe to transport in a bulk carrier as it may
liquefy
Bulk Solids: Science / Engineering / Design
Definitions
Liquefaction:
Occurs when the volume of spaces between particles reduces,
causing pore water pressure to rise, reducing the shear strength of
the particles.[2]
[2] Bulk Cargo Liquefaction (Iron Ore Fines and Nickel Ore), Standard Cargo,
February 2011, pp. 2
Material in a liquid-like flow state
Bulk Solids: Science / Engineering / Design
How to Determine TML
• Flow Table Test
• Penetration Test
• Proctor/Fagerberg Test
• Procedures for each test method are given in Appendix 2 of the
IMSBC Code
• We will focus on Proctor/Fagerberg test method
Bulk Solids: Science / Engineering / Design
Importance of TML
• There is clear need to accurately determine a maximum
moisture content of a bulk material for safe transport in bulk
cargoes.
• In 2009 two ships, the Asian Forest and the Black Rose
capsized and sank following liquefaction of iron ore cargoes
after being loaded in Indian ports during the monsoon
season.[3]
• In 2010 there was a further loss of three bulk carriers
carrying nickel ore loaded in Indonesia.[4]
[3] Bilbrough, A., et al., Circular: India – Safe Shipment of Iron Ore Fines from Indian Ports, The
London P&I Club, Dec 13, 2010 pp. 1
[4] Bulk Cargo Liquefaction (Iron Ore Fines and Nickel Ore), Standard Cargo, February 2011, pp. 2
Bulk Solids: Science / Engineering / Design
• Cell Volume = 1000 cm3
• Minimum of 5 test points (from dry to almost saturated)
• Material is dried prior to test
• Material filled into cell in 5 equal amounts
• Tamper mass, drop height, number of tamps
• Intersection of void ratio curve and 70% of saturation = TML
value
• Maximum particle size of 5 mm
Summary of Proctor/Fagerberg Test
Method
Bulk Solids: Science / Engineering / Design
Output of the Proctor/Fagerberg Test
Method
Gross Water Content [% by Mass]
Vo
id
R
atio
Bulk Solids: Science / Engineering / Design
•Particle Density – Heavy reliance on this figure but nowhere in
the code does it clearly define how this value is measured
•Consolidation Pressure – Does tamping the material surface 25
times over five layers equate to a compacted density like that
which would be seen by a material in a bulk vessel?
•Segregation & Whipping – Does liquefaction by whipping really
occur in a ships hold? Does segregation? Do they play a role in
potential liquefaction?
Proctor/Fagerberg Method Questioned
Bulk Solids: Science / Engineering / Design
•Starting Moisture Content – Does drying out the material fully alter
the material properties?
•Conservatism – Why is the TML value determined to be at the
intersection of void ratio curve and 70% of saturation as the test
method outlines? Perhaps 80 - 85% is still conservative enough?
•What about particle size? Why was 5mm chosen?
Proctor/Fagerberg Method Questioned
Bulk Solids: Science / Engineering / Design
J & J Study
Study was conducted to explore the effects of particle
size on TML values
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
Jenike & Johanson (J&J) investigated the effects of including >5
mm particles in the Proctor/Fagerberg test procedure, and the
resultant determination of TML values.
•The inter-particle void space in a material compacted per the
Proctor/Fagerberg TML test procedure will vary depending on the
sample’s particle size distribution (PSD).
•The finer fraction of a bulk material tends to carry a higher
proportion of the moisture than the coarser fraction.
•Determining the TML value on coarser particle distributions may
result in a different TML value than that determined for the minus
5mm fraction alone.
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
Determine TML values for a single sample of Australian Iron Ore
which was divided into four subsamples; separated by their
respective size distributions.
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
TML determination of each subsample
Bulk Solids: Science / Engineering / Design
J & J Study Part 1
• To examine the sensitivity of moisture content to PSD, Sample 3 was
adjusted to its average TML value of 9.6% moisture
• It was then quartered and sieved to produce three subsamples with
maximum particle size to match those of Samples 1, 2, and 3
• The moisture contents (wet basis) for each of these subsamples
were determined
Bulk Solids: Science / Engineering / Design
J & J Study Part 1 Summary
• Coarser samples often yield lower TML values
• The finer fractions of the ore have higher moisture contents
than the coarser or full size distributions
Bulk Solids: Science / Engineering / Design
J & J Study Part 2
6 Types of Iron Ore
12 mm x 0 mm
TML
5 mm x 0 mm
TML
Bulk Solids: Science / Engineering / Design
J & J Study Part 2
5 mm x 0 mm
Samples Adjusted to TML
MC %
12 mm x 0 mm
MC % MC %
12 mm x 5 mm
Split
Bulk Solids: Science / Engineering / Design
J & J Study Part 2 Results
Bulk Solids: Science / Engineering / Design
J & J Study Part 2 Results
In five of the six samples tested the moisture content of
the -5 mm fractions were higher than the TML values
determined for the -5 mm subsamples.
The -5 mm fraction is ~78% of the sample.
Bulk Solids: Science / Engineering / Design
J & J Study Summary
•The moisture content varied as a function of the sample’s
particle size distribution.
•The fine fraction of an ore will tend to have a higher
moisture content than the full size distribution, since the
finer fractions of a bulk material tend to carry a higher
proportion of moisture than the coarser fractions do.
Bulk Solids: Science / Engineering / Design
J & J Study Summary
• Measured TML values may either increase or decrease
as materials become coarser,
• If the TML value is measured using >5 mm top size:
• overall moisture content of the whole material is
below the TML value determined for 12mm x 0mm
• moisture content of the <5 mm could be above the
TML value determined for 12mm x 0mm
• May even be above the 5mm x 0mm determined
TML value.
Bulk Solids: Science / Engineering / Design
J & J Study Summary
TML = 8.6%
12mm x 0mm
TML = 8.8%
5mm x 0mm
Bulk Solids: Science / Engineering / Design
J & J Study Conclusion
• Iron ores shipped in other locations around the globe at
>TML values measured.
• If the standard is changed to include, as an example,
TML determination at 80% or 85% of saturation, then
care must be taken.
• The fines present in the sample might be even closer to
their liquefaction value especially if >5 mm are included
in the determination of the TML value
More research needs to be done to investigate this issue
Bulk Solids: Science / Engineering / Design
Questions?
Corin Holmes, MSc Eng
Technical Officer
Jenike & Johanson Perth, WA