Air Emissions

New Technology reducing Carbon Dioxide Emissions – Kwinana
Alcoa’s global refining research and development team, the Technology Delivery Group (TDG), continued to solve environmental challenges through cutting-edge new technology in 2009.

Since 1968 TDG has been developing innovative equipment and processes for cleaner, more efficient production at Alcoa refineries worldwide, and consistently helps to solve environmental challenges through new technology. TDG employs around 80 scientists, engineers, research and support staff and is centre of excellence for Alcoa’s global refining research.

In 2009, TDG, commissioned a new process at Kwinana Refinery’s residue area which uses naturally occurring microbes to consume oxalate – saving 11,000 tonnes of carbon dioxide from going into the atmosphere each year. 

Oxalate is an unwanted impurity in the alumina refining process.  If the oxalate is not removed from the process it has an adverse impact on alumina quality and refinery productivity. The new process, known as ‘continuous biological oxalate destruction’, is an environmentally friendly solution.  It has saved the company AUD$20 million as it’s less expensive to build and run than the usual oxalate kiln, and is saving a further $2 million per year in energy costs. This equates to sustainable long-term management of oxalate, with the system expected to be rolled out globally to all Alcoa refineries.

Mercury Emission Reduction – Wagerup
The TDG conducted successful trials at Wagerup throughout 2009 to reduce mercury emissions to air.

Oxalate, as described above, is an unwanted impurity in the alumina refining process. It contains mercury which is released into the atmosphere when the oxalate is removed and burnt.  Oxalate can be stored long-term without any environmental ramifications, and this is the method Alcoa has used at two of our WA refineries over the past decade. However, storage is not an ongoing sustainable solution to the oxalate challenge. As such, the development of an alternative was essential.

TDG devised a slight change in the alumina refinery process at Wagerup, so that only very low amounts of mercury are absorbed onto the oxalate during the refining process.  This new process, which is patented by TDG, ensures that when the oxalate is burned there is little to no mercury released into the air. 

This technology has been rolled out to Alcoa’s Point Comfort refinery in the US, and is likely to be implemented full scale at Wagerup in 2011.

(Note: Due to minor differences in the Bayer refining operations at our other WA sites, the Kwinana Refinery’s oxalate does not contain mercury, while Pinjarra’s oxalate contains mercury at much lower levels compared with the oxalate at Wagerup. Therefore, the same mercury challenges don’t exist at our other WA refineries.  Despite this, Pinjarra could still benefit from similar technology and this will be investigated by TDG.)  

Liquor Burner Emissions - Kwinana
In 2009 Alcoa commissioned a study to characterise emissions from the liquor burner.  Emissions from the newly commissioned emissions reduction equipment (which is installed on the liquor burner process) were comprehensively monitored and analysed and compared against emission levels predicted in the environmental assessment for the project.

The results showed that the project was very successful in meeting its aims of significant reductions in air emissions of odour and volatile organic compounds from the Kwinana liquor burner unit (greater than a 90% reduction for most measured compounds).

Perfluorocarbon Emissions – Point Henry & Portland Aluminium
The Point Henry and Portland Aluminium Smelters are working to reduce anode effects which produce perfluorocarbon emissions (PFC) (see graph directly below). Anode effects are caused by low alumina levels in smelting pots and are a main source of direct greenhouse gas emissions from aluminium smelting.  Point Henry has seen a 55% reduction in PFC emissions since 2005, while Portland Aluminium has seen a 75% reduction since 2005.
Click image to enlarge.

Smelter Fluoride Emissions – Point Henry and Portland Aluminium
Both Point Henry and Portland Aluminium smelters continue to focus on minimising and sustaining fluoride emissions within internal (Alcoa) targets, which is reflected in the long-term historical trends (see graph directly below). Alcoa’s internal targets are more stringent than those set by the Victorian Environmental Protection Authority.

Portland Aluminium continues to progress a long-term management program for fluoride emissions, to further understand and manage the effects of low level fluoride emissions on local fauna inhabiting the land surrounding the smelter. Fluoride emissions were sustained at around 0.3kg/tonne of aluminium produced in 2009, making Portland Aluminium one of the lowest fluoride-emitting smelters in the world.

Click image to enlarge.

Sulphur Dioxide (SO₂) Emissions – Anglesea
Anglesea Power Station has had ambient air monitoring stations for SO₂ since the late 1990s.  Under certain weather and operating conditions the plant has recorded ground level concentrations of SO₂ that exceed the State Environmental Protection Policy - Air Quality Objective of 200 parts per billion over a 1 hour average.

Anglesea has adopted strategies to further improve its management of SO₂ emissions, including the development of the Air Quality Control System (AQCS). This system employs both predictive and reactive components to anticipate and react to weather conditions that potentially impact on ground level concentration of SO₂.  The AQCS provides binary instruction for control room operators to modulate the power station load (or generation) accordingly, to ensure compliance with the Air Quality Objective.

Commissioning of the AQCS commenced in late September 2009, with the system now embedded in the power station’s operation.  It should be noted that there have been no further exceedances of the Air Quality Objective limit since March 2009, which included the commissioning period of the AQCS. Anglesea Power Station was subject to an audit by an EPA Appointed auditor, which took the form of a section 53V audit (a robust audit under section 53V of the Environmental Protection Act 1970), to assess the robustness and sustainability of the station’s SO₂ management, including the AQCS, in December 2009. The results of this audit will be submitted to the Victorian EPA in quarter one 2010.

Carbon Bake Sustainability Project Emission Reductions – Portland Aluminium
A key achievement in emissions reduction was seen at Portland Aluminium in 2009. The Carbon Bakes Sustainability Project was implemented in 2008, with full commissioning at the end of quarter one 2009. The $114 million project included the refurbishment of one of the two anode baking furnaces, the installation of an additional furnace scrubbing system and a new firing system.  Monitoring during the remainder of 2009 showed improved emissions management through more efficient combustion during the baking process.  This has included an 80% reduction in Polycyclic Aromatic Hydrocarbon (PAHs) emissions from the anode baking process, and a more than 90% reduction in volatile organic compounds.

Technology Delivery Group supporting PhD Projects
The Technology Delivery Group, based at Kwinana, is sponsoring PhD projects at two Western Australia universities to further understand the atmospheric fate of emissions and their downstream impacts. Both are cutting edge, research projects with the two university supervisors world renowned in their fields.