matt duxbury, asia iron australia extension hill magnetite project - case study: corrosion...
DESCRIPTION
Matt Duxbury, Manager- Infrastructure Services, Asia Iron Australia Extension Hill Magnetite Project presented this at the 3rd Annual Slurry Pipeline Conference. The Conference focuses on the design, construction, operation and maintenance of mineral slurry pipelines. For more information, visit http://www.informa.com.au/slurrypipelineconferenceTRANSCRIPT
Corrosion Mitigation Alternatives
for Slurry Pipelines
Asia Iron Australia Pty Ltd
Matt Duxbury - Manager Infrastructure Services
3rd annual Slurry Pipeline Conference
13-14 November, 2013 * Duxton Hotel, Perth
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Presentation Outline
1.Extension Hill Magnetite Project
2.Historical approach to assessing corrosion mitigation
3. EHPL’s approach
4. What did we find?
4. What are we doing now
6. Concluding remarks
Asia Iron Group
Ownership Structure
• 60% Chongqing SoE
• 40% Private PRC
• SoE involvement
completed October
2010
Extension Hill Project
280 km from Geraldton
6 – 8 Bt of ore
6
Slurry Pipeline - Proven
technology
Da Hong Shan – 4MTpa
Samarco – 13MTpa
Extension Hill -10MTpa
Length in km
Elev
atio
n in
me
ters
2,000
400
In conclusion I Say
To the slurry pipeline industry 1. More work is needed on understanding the chemistry
• It is not reassuring to be advised that testing shows this or that is indeterminate, variable, uncertain etc…
• There should be scientific explanations, mechanisms,
2. More co-operation and reporting of operations is needed. Extensive literature searches revealed a dearth of papers.
3. The pipeline owners, designers and corrosion specialists need to get together and bring the two areas together to bear on the problem
Finally for Extension Hill 1. For EHPL the jury is still out! We have to decide by Feb/March
2012.
2. Is it chemical treatment, HDPE liner, epoxy liner, combinations, other, all are on the table?
7
Slurry Pipelines Summit, Perth, 28 & 29 November 2011
EHPL Pipeline Parameters
Slurry System.
• 288km, 20”, design point 10MTpa
• Minimum design velocity 1.5m/s
• Single pump station, inlet pressure 230bar
• 67% CW design point
Water pipelines, Return and Borefield
• Return water line 20” 1,000 m3/hr flush , 650 m3/hr normal operations
• Single pump station
• Borefield, 37 km to mid point of return water line. 650 m3/hr injected at the mid point of the return water line, 20” to mid line, 22’ mid line to mine.
Context EHPL Project • Slurry pipes are industrial “dirty water” pipelines
• WA ground water is generally corrosive to bare steel
• EHPL water is 500ppm Cl-, 1,200 TDS,
• Traditional approach is ph control or use a liner
• Liner for EHPL is a $150m decision
• Oil&gas use production gas, vacuum de-aeration, and Nitrogen to deoxygenate large quantities of sea water, 2,500m3/hr, to <20ppb, finished with oxygen scavengers where needed,
• Gold industry micro bubble Oxygen into cyanide slurry mix to increase oxygen in solution
• Looking to combine this experience, and
• Looking at the oxygen scavenging capacity of magnetite
Comment on Oxygen & Chlorides
• I’ve seen more than one case of using a nitrogen blanket to control Oxygen ingress in test rigs
• All use ppm oxygen sensors
• Corrosion of iron in an aqueous solution is supported
down to about 20ppb • Chlorides act to depassivate in ph controlled pipelines,
which promotes pitting at depassivated sites
• General corrosion too high without passivation
• ph control is compromised by high chlorides causing pitting,
• Finally it doesn’t take much to set up pitting sites which persist under protective scales,
• So recommendation under these circumstances is LINE IT!!!
Context – Industry Corrosion
Testing • Test rigs use ER and LPR probes and measure O2 ppm
• Samples of actual materials and water in the presence of
proposed pipeline coupon and record corrosion rates.
• Tests run with various chemical treatments,
• Results often variable and not definitive. Two sets of tests,
2005 and 2008, both indicated uncertainty,
• No one could explanation the results in terms of the main
chemical reactions at play, so how can chemical treatment
be reliably? And over the length and life of the pipeline
• Operation are poorly executed and experience poorly
recorded and shared with other users
• The chemistry over the length and life of a pipeline is very
complex
Corrosion Test Rig
Nitrogen Blanket Removing
Oxygen – Passing Nitrogen Blanket
pbb
ppm ppb
ppm 50ppbg
9ppm
Nitrogen removing oxygen static
Nitrogen blanket
ppm
ppb
Return water pipeline • Steel coupon
only • Relatively
large surface area
• Sub 20ppb in 12 hours
• 65km of the pipeline
10ppm
Same period. looks like zero on the ppm scale
The actual water, and pipe’s impact on dissolved oxygen
20ppb
Slurry pipe steel coupon plus concentrate
Same period. looks like zero on the ppm scale
12ppb
Sub 20ppb in 11 hours 40 minutes
Comment on Oxygen Chlorides
• It is not uncommon to used a nitrogen blanket to control Oxygen in corrosion test rigs
• All use ppm oxygen sensors
• Corrosion in an aqueous solution is supported
down to about 20ppb • Chlorides act to depassivate in ph controlled
pipelines, which promotes pitting at depassivated sites
• With general corrosion too high without passivation and with high chlorides causing pitting with ph controlled pipelines – recommendation is LINE IT!!!
Two Test results for
Magnetite Concentrate
• Magnetite reduces ph enough to allow recommencement of corrosion over the time scale of EHPL’s slurry transport, i.e. 50 hrs,
• ph did not decrease as much with increased Chloride level – unexplained
• A possible mechanism is that Fe hydroxides form, and the resulting H+ neutralises ph
Lime addition to ph 10.5
ph hours
Start 10.5 0
Mid 10.06 25
End 8.53 50
Magnetite as an Oxygen Scavenger
• EHPL’s magnetite is a weak oxygen scavenger,
reducing native level of 9ppm to about 4ppm
over the 50 hours of the tests,
• Out next set of tests will include elevated
temperature and retention time. Product comes
out of the grinding process at 50-60DegC
• Reaction rate doubles for every 10DegC
increase, (tests were done at 25DegC)
• Oxygen is the key - no oxygen no corrosion!
Some Traps!
• Soduim sulphide begins to disassociate at 6bar and is completely disassociated by 9bar. It takes about 30minutes to complete its work in the 15 -25deg C range? And yet I know it is used in slurry pipelines at these pressures.
• Testing cannot replicate the entire length of a pipeline conditions, and our 50hour test is a very poor attempt to replicate conditions over the length of the pipeline
• Let me make some observations for future testing
Developing New Understandings
• We have been working with Professor Rolf Gubner, the Chevron Chair of The Corrosion Centre at Curtin to plan the next set of tests
• We need to get back to basic chemistry so that the principle chemical reactions are understood
• We need to think about the length of the pipelines and the changing set of parameters over the length and over time,
• For unlined pipes we need to set up a rigorous corrosion control processes, starting from hydro testing to project life’s end, and the best way to progress is,
• That we need to use real conditions to develop our understanding and operating pipelines are the only real source of data for this analysis!
Thank you
Questions