2009

www.eAmmonia.com

The 54th Annual AIChE

Ammonia Safety Symposium

54th AIChE Ammonia Safety Symposium

In September, 310 engineers from about 40 countries and 110 companies attended the AIChE’s 54th

Ammonia Safety Symposium at the Hyatt Regency in Calgary, Alberta. The conference venue was

downtown and the weather was ideal. Many attendees took the opportunity to visit nearby Banff, the

Canadian Rockies, and Lake Louise.

The symposium’s keynote speaker was Yara International’s Tore K. Jenssen. His speech, which was

presented via video, concerned ammonia production and climate change. Tore has 35 years of experience with

safety and environmental issues. Following are a few of the points that he made. Tore accepts that the climate

is changing but believes more discussion is needed on how best to counter the change. Yara’s greenhouse gas

emissions come mainly from its ammonia and nitric acid plants.

EU regulations come into play between 2013 and 2020 and will be based on 2005 to 2007 emission

figures. EU ammonia producers may have to buy allowances since the proposed bench-marking level is 1.5

tonnes of CO2 per tonne of NH3. China and Russia have higher emissions than the EU but have no pending

regulations. Tore sees the need to educate regulators since the fertilizer industry is part of the solution to CO2

emission reductions. For instance, trees consume CO2, but, without fertilizer, the world would need to claim

more farmland from the remaining forested areas.

Summaries of conference papers that dealt specifically with safety are:

Explosion of a Benfield Solution Storage Tank

In December 2006, an explosion occurred in a Benfield solution storage tank at Borealis Agrolinz’s

ammonia plant in Austria. During hot work to install an additional vent on the tank, the roof blew off.

Investigations and laboratory tests carried out in association with the University of Erlangen identified the root

cause as the evolution of hydrogen.

CO2-containing solutions could produce significant quantities of hydrogen in alkaline conditions. Large

capacity tanks for holding solution could be dangerous even though combustible substances seem to be absent.

The author suggested installing nitrogen blanketing on solvent storage tanks to prevent the build-up of

flammable gases such as hydrogen.

Failure of Process Air Compressor and Gear Box

The process air compressor installed in QAFCO’s Ammonia-2 plant in Qatar experienced a major failure

in its high-pressure stage. The failure started with axial displacement of the rotor, followed by increased radial

vibrations from increased torque loading. The coupling failed and the rotor fractured almost simultaneously.

Two high-level alarms in the third-stage separator signalled condensate carryover that led to choking of the

suction impeller eye, high torque overload, and coupling failure. QAFCO found that the third-stage cooler

trap-and-drain bypass line had choked with rusty carbon steel corrosion deposits.

IFFCO’s Aonla Ammonia Plants

IFFCO discussed three separate incidents in its ammonia plants in Aonla, India:

• Damage to a 20-inch gate valve in the rich solution line at the CO2 absorber outlet. Sudden opening of

the absorber outlet trip valve caused it and downstream piping to vibrate and shift position. IFFCO

repaired the piping and its support.

• Damage to a 16-inch butterfly valve in the ammonia synthesis loop. The spindle on a

butterfly valve at the waste-heat boiler inlet sheared off and allowed high-pressure syngas to escape.

IFFCO replaced the valve actuator.

• Failure of an isolation valve in K2CO3 service. Large-scale leakage occurred through the CO2 absorber

outlet upstream from the hydraulic turbine. Throttling had eroded and corroded the valve body.

IFFCO replaced the valve.

Ice Removal from an Ammonia Storage Tank’s Annular Space

Orica has used acoustic emission techniques for several years to monitor the integrity of its ammonia

storage tank in Kooragang Island, Australia. In 2001, it detected high levels of acoustic emission, indicating

that the tank was at risk of failing. Further investigation found that a 0.4-inch layer of ice had formed over the

inner tank in addition to a 12-inch layer of ice/perlite matrix around the circumference of the tank at the floor-

to-wall junction. Failure to purge the tank’s annular space with nitrogen caused the problem, albeit

unintentionally. A dehumidified-air reticulation system removed the ice from the outside of the inner tank. On

completing the ice removal project in 2008, an acoustic emission test showed the tank was in good condition.

Implosion of a Titanium Liner

A vessel’s titanium liner collapsed under vacuum during a startup of Incitec Pivot’s (IP) urea plant in

Brisbane, Australia. The operator had not followed the normal startup procedure. IP replaced all the internals

and titanium liner with duplex plates, conducted a HAZOP analysis, and installed instrumentation to prevent a

recurrence.

Fire in Ammonia Synthesis Start-up Heater

In September 2008, during a restart of Yara’s ammonia plant in Tertre, Belgium, the startup heater’s coil

ruptured and a fire ensued. External local corrosion was to blame. Creep damage had caused significant

thinning of the coil. Yara has instituted a risk-based inspection program to prevent similar incidents from

occurring.

Corrosion Caused Primary Reformer Tube Failures in Qatar

After finding significant corrosion on reformer tubes in two ammonia plants, QAFCO replaced 65

reformer tubes in 2007. High levels of H2S in the reformer fuel gas had contributed to the corrosion.

Modifications to the combustion air distribution system increased the air flow and the excess oxygen to two

percent.

Roundtable Workshop on the Thursday

The topics covered included:

• Tube rupture in the high-pressure stripper of a new urea plant

• Unusual dry-gas seal failure and subsequent syngas compressor fire

• Advantages and disadvantages of an E work permit

• Procedural controls in a mature ammonia facility

• A CO2 line explosion and urea high-pressure flush header rupture

• Pigtail nipping – a failure incident, learning from experience

• Primary reformer explosion.

The 2010 meeting will be in San Francisco, California.