COMMISSIONING OF THE AMBATOVY ACID PLANTS

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COMMISSIONING OF THE

AMBATOVY ACID PLANTS

By : Werner Vorster, TBT (presenter)

Alfred Guenkel, NORAM

John Orlando, NORAM

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Project History

Plant Design and Construction Philosophy

• Single vs Double Train

• Location

• Terminology and Handover Process

Construction and Cold Commissioning

• Commissioning Delays

• Care and Maintenance during Construction

• Pressure Testing

• Cold Commissioning Failures

• Items Commissioned outside of Contract

Hot Commissioning / Start-up

• Melting Circuit

• Acid Plant

• Operational Issues

Conclusions

Contents

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Bateman was bought by the Tenova Group in the beginning of 2012

This resulted in a significant company re-organisation :

But first.....

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EP project started in Aug 2007

C contract awarded to “Bateman” in 2008 (hereinafter referred to as Tenova)

Project History

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Noram was responsible for the process engineering for the acid plant and the detailed engineering of the main acid plant vessels and equipment featuring :

• NORAM all welded stainless steel converter

• NORAM’s RFTM gas-to-gas heat exchangers

• NORAM’s sulphur furnace and sulphur guns

• NORAM’s low-pressure drop CECEBE HPTM saddle packing

• NORAM anodically protected acid coolers

• NORAM’s SMARTTM distributor with 10 drip points / m2

Project History

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Tenova was responsible for :

• Engineering of the remainder of the plant (process, mechanical, civil, structural, piping, instrumentation, electrical)

• Procurement

• Construction (except for civil works) using South African, Chinese and Malagasy Labour

Project History

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PLANT DESIGN & CONSTRUCTION PHILOSOPHY

Single vs Double Trains:

• Ambatovy’s Plant 1 rate typically varies between 30% and 60% of design.

• The constraints thus far has been outside the control of the Acid Plant

• A growing trend world wide has been to construct ever larger plants

• One has to consider the feasibility (technical and economical) of this approach especially with complex hydrometallurgical plants such as Ambatovy which typically takes many months to ramp to full production

• In this case the draw backs to having a single plant are :

o Excess acid plant capacity even when running at low rates which means lower acid temperatures, colder gas side temperatures etc all contributing to excessive corrosion rates

o Running the plant on an batching basis

o Equipment and motors operating on the turndown design limits

o There is no safety net – any operational error or equipment failure will bring down the entire facility

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Plant Design & Construction Philosophy

Single vs Double Trains:

• For Ambatovy, two smaller plants overcame these disadvantages albeit at a slightly higher CAPEX

• A single large plant is not always the incorrect choice

• Single biggest advantage of two smaller plants is have 50% capacity even if a key piece of equipment fails

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Plant Location

• Regarding plant design, as “in real estate - it is location, location, location”

• The location of the Ambatovy project on the east coast of Madagascar about 10km south of Tamatave resulting in :

• Opportunities

• Challenges


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Plant Location

• Joe Brown once said “A challenge is an opportunity to prove your abilityto yourself, and others”

• This project certainly seems to prove the point :


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Plant Location

• Close proximity of the site to the ocean

• High annual rainfall (in excess of 3,300mm per year)

Coupled with delays in overall construction schedule resulted in :

• Having to “store” some equipment in less than desirable locations

• Without (in some cases) the best protection possible against elements

This resulted in problems which only manifested itself during the cold commissioning phase and in some cases only became apparent during start-up


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Terminology and Handover :


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Schedule :

• Original construction contract start-up in Dec 2009

• The last major piece of mechanical equipment (main blower) was shipped from Germany in January 2009.

• By March 2009 all the major equipment were on site – largely being stored in the shipping containers they arrived in, until such time that they could be installed.

Due to :

• the late completion of civil works (by others)

• and construction delays as a result of the economic downturn

The acid plant construction / erection was largely completed by mid 2010 at which time cold commissioning commenced.

This process was completed toward end 2010 followed by the formal hand-over to the client in February 2011.


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“It was the best of times……”

Construction and Commissioning

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“……it was the worst of times”


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Commissioning Delays

• Originally scheduled to go directly from construction into cold commissioning to operation

Care and Maintenance During Construction / Commissioning

• All motors in excess of 150 kW were fitted with space heaters.

• Motors and gearboxes were inspected and rotated twice a week

• Motors and transformers were megger tested at regular intervals to monitor for any breakdown of the winding insulation and to serve as early warning

• Valves and instruments were kept in shipping containers until installation. Unfortunately, once installed, these items were open to the elements and left largely unprotected / uninspected.

• Catalyst was only installed at the latest possible time to prevent degradation of the catalyst.

• Once installed there was another delay prior to start-up and the client opted for nitrogen purging of the converter to prevent air and moisture ingress.

• Just prior to commissioning inspections with the client representatives, all valves etc were serviced and checked to operate correctly.


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Pressure testing during construction and commissioning

• All pressure vessels and systems were pressure tested

• The ASME certified equipment also required statutory inspection and sign-off from Madagascar government appointed Authorised Inspection Authority (AIA)

• All ASME pressure tests on site were done with demineralised water

• As far as practically possible, the water was drained and the system air dried.

• However this is not 100% possible, and, if no long term wet / dry lay-up plans are made for the critical systems, could lead to near disastrous failures, as would be illustrated later.

Protection of Castable Refractory During Delayed Start-up

• Delays in start-up caused concern that some of the castable refractory would degrade as a result of extremely high ambient temperatures with humidity approaching 100%

• The castable refractory material was coated with an organic wax

• During plant warm-up , the wax converted to water and CO2 and was vented to atmosphere


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Failures during cold commissioning

o Apart from :

• visual inspection of equipment

• bump testing of motors (pumps and agitators)

• the sulphur filters

Very little could be cold commissioned fully.

o All mechanical, piping, and electrical equipment were tested, inspected and signed off by the client’s team without any significant issues and only minor remedial work

o Instrumentation was the main area causing problems :

• Some instruments and valves were damaged during other installation activities which only manifested itself during valve stroking, point to point checks etc

• Installed instruments and valves could not receive the same care that electric motors and gearboxes (for example) received


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Cold commissioning outside of the contract

• The main blowers could not be tested (Siemens was called back at a later stage just before start-up)

• The start-up burners could not be fired and no drying / curing of the refractory could happen.

• The cooling towers and reticulation (by others)


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Start-up - Melting Circuit (end 2011)

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Design Requirements :

o 2 overflow-type melting tanks (above ground)

o Each sized for 75% of total sulphur requirement for the plant

o 3 sulphur filters (2 operational, 1 hot standby)

o 5,000m3 liquid sulphur storage

o 4% moisture content

o Prills 2-4mm in size

o 6 bar steam used for melting, 4 bar steam used for heat tracing

Start-up Problemso Frothing in the melting tanks

o Scaling of vibrating feeders

o False level measurements from the tanks

o Blockages of the overflow from the melting to the dirty tanks.


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Higher than designed moisture content

o As a result of high rainfall

o Open stockpile

o FEL operation

Line sizing on overflow

o Increase line sizing and design


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Some initial problems experienced with start burner (mostly valve failures which had to be ordered from Canada)

Plant warm-up proceeded without too much issues until Valentines Day 2012

Start-up - Acid Plant Feb 2012

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Some initial problems experienced with start burner (mostly valve failures which had to be ordered from Canada)

Plant warm-up proceeded without too much issues until Valentines Day 2012


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The cyclone passed approx 50km south of Tamatave causing significant damage and some loss of life in the rural areas of Madagascar

The town of Tamatave and the Ambatovy site escaped largely unscathed

The heat-up cycle start again and the converter was brought to temperature


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The majority of the ducts from the gas section to the absorption towers are approximately 1.9m in diameter and located approximately 10m above ground

The site maintenance team planned and executed this exceptionally well :

o ~80 people were mobilised and split into dedicated 4-5 man teams per blind

o All blinds were pulled within 3 hours and,

o The entire process was executed without a flaw


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Shortly after start-up, the acid circulation pump started tripping

o The motor was eventually replaced with larger motors

o Investigations are still underway to determine the exact cause of the problem as hydraulic calculations and field measurements indicated that the supplied motor should be functioning

The plant restarted on Sunday evening but factors outside of acid plant control contributed to frequent stoppages :

o Cooling tower and water reticulation failures.

o Power plant reliability


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Other issues :

o Some pressure measurements on the DCS were incorrect (non-running pumps showing a discharge pressure of 13 bar).

• All the instruments were re-calibrated and in this process damaged the installed gaskets.

• Replaced with hand-cut gaskets

• The inside open area of the gasket being smaller than the diaphragm of the pressure transmitter causing constant pressure onto the diaphragm therefore a constant false reading

o Increasingly, operators are extremely well computer trained but lack practical field experience

o Vent lines from the acid tanks to the stacks dipped below the acid level

o The acid sampling line from the discharge of the acid coolers to the analysers was also incorrectly located at the top of the pipe.


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Other issues :

o NAPS

• Initially successfully cold commissioned by simulating the reference and control signals.

• Improvements were made by Noram to the design of the feedback electrodes

• It was found that the passivation feedback was incorrect :

The site maintenance team unfortunately switched around some of the control cables during the electrode modifications

Further trouble shooting resulted in identifying a faulty electric component

• Installation lessons learned :

Install a junction box per cooler for the termination of both the duty and the back-up reference and control electrodes.

Signal re-transmission (mV to mA)


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Other issues - Acid Valve Tuning


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Other issues - BFW Valve

o In March 2012 weld failures started occurring on the economisers

o 2 failures simultaneously


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o Tube Cracking :

• A small welding imperfection in the piping

• The pressure testing was conducted with demineralised water almost 2 years before the failure

• No boiler preservation

o Tubesheet Failure :

• On-off control of boiler feed water flow control during heat-up (due to sizing issues with the control valve)

• Water hammer was experienced

• Cyclic, thermal shocking


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In some cases more is better (2 vs 1)

Establish a well documented and enforced care and maintenance regime prior to start-up (from the first arrival of equipment to the hand-over of the plant)

Have operators involved as soon as possible in the cold commissioning of the plant

Ensure that all control loops and valves are properly tuned as soon as possible after start-up.

Having a computer savvy operator does not ensure success – practical fault finding, investigating and understanding trends are important

Conclusions

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Documents

COMMISSIONING OF THE AMBATOVY ACID PLANTS