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