VCE Environmental Science:Unit 4: Pollution

Fluoride Mitigation Strategies at Portland Aluminium

An evaluation of the strategies used to reduce fluoride pollution emitted

by the “Smelter in the Park”.

EPA Licensing of Fluoride Emissions• Portland Aluminium has an EPA Licence outlining emission limits for

fluoride. These limits are set to ensure that the design criteria are met where people may be exposed.

• Fluoride is measured inside the facility’s emission points (or stacks) and reported annually to EPA Victoria.

• Licence limits set out in EPA licences require emissions to be well within safe levels. This means that concentrations of fluoride in air around industrial facilities meet the levels that have been set to protect vegetation and grazing animals and therefore human health.

Covered electrolysis pots for smelting aluminium.

Inside Monitoring• Workers are asked to submit blood and urine

samples on a regular basis to test for fluoride absorption.

• A monitoring badge may be worn to test daily exposure rates.

• Laser-light monitoring in the pot-rooms shows green-amber-red lights for different levels of fluoride emissions (measured in parts per billion).

• If the level reaches the critical ‘red’ amount, alarms sound and workers are evacuated form the pot rooms. This only happens when smelter workers have not followed correct procedures and opened too many pots at one time.

Diagram of an Aluminium Smelting Pot

“FLUORIDE DISPERSION IN A COASTAL ENVIRONMENT” John Hill and Peter Hurley

• “Gaseous and particulate fluorides emitted from the potroom roof vents have the potential to injure vegetation and degrade ecosystem health. Fluoride dispersal is monitored within the heath, adjacent farmland and the city area.”

• “A continuous air monitoring station is maintained to the north of the smelter and supplemented with a network of rainfall monitoring sites.”

• “An updated model of fluoride dispersal using The Air Pollution Model (TAPM) was prepared to enable a review of the current monitoring program.”

• “Preliminary modelling of gaseous fluoride did not show good correlation with monitoring data until exponential decay was incorporated into the model (that is fluoride was progressively removed using an arbitrary time-based factor).”

• “This was rationalised on the basis of the reactivity of gaseous fluoride and the high aerosol load in coastal air.”

Atmospheric Monitoring

• There are many external atmospheric monitors that measure fugitive emissions from the pot rooms.

• These are located at different distances and compass points around the pot room buildings to measure fluoride (and other pollutants) during varying environmental conditions (temperature, wind speed and direction, precipitation and humidity will all effect these levels).

Monitoring water quality at Portland Aluminium

Environmental Monitoring - Animals

• Bone, tooth and horn samples are taken from the cattle that graze within the smelter boundaries, to test for fluorosis.

• Kangaroos have been affected in the past, so tail bone samples are also taken from kangaroos that have died in the area.

• Fluoride tends to replace calcium in bone and tooth enamel causing discolouration and thickening.

• Vegetation and grazing animals are more sensitive to fluoride than humans.

• Industry Licence limits set by EPA Victoria require emissions to be well within safe levels for vegetation and grazing animals. Therefore, human health is also protected.

Kangaroos and cattle have teeth and bone samples tested for fluorosis.

Environmental Monitoring - Plants

• In the 600 hectares of land surrounding the smelter, which acts as a buffer zone between the point source of emissions and residential properties, a great variety of vegetation has been planted.

• Because plants are sensitive to fluoride emissions, it is likely that they will show the first impacts of excessive fluoride pollution.

• Each year an expert botanist visits to take plant surveys to check for chlorosis (damage to leaf chlorophyll causing plants to turn yellow).

• Fluoride compounds, which occur as both gases and aerosol, cause damage to plants at concentrations about 1000 times lower than those that cause detectable human health effects. Certain plants, such as grapevines, are particularly sensitive. The Australia and New Zealand Environment Conservation Council has recommended environmental guidelines (based on damage to plants) for fluorides (ANZECC 1990)

http://www.environment.gov.au/soe/2001/publications/theme-reports/atmosphere/atmosphere05-9.html

Fluoride levels in the bones of some kangaroos near Portland Aluminium have been above desirable concentrations. The problem may be compounded by fluoride present in some fertilisers used in the region. Significant reductions in fluoride emissions from the refinery have been achieved recently through modifications to refining methods and improved pollution. There have been consistently low atmospheric fluoride concentrations near the Alcoa smelters in Victoria since 1993.

Monitor – Plan – Implement - Check

• All the effective monitoring is of no use unless a plan to reduce emissions has been prepared and implemented.

• Portland Aluminium’s plan includes the A398 fluoride recovery system, which recovers 99.8% of fluoride emissions from the pot rooms.

• Recovery and recycling of Spent Pot Lining also reduces the fluoride emissions.

General arrangement of Fluoride recovery process.

A398 Fluoride Recovery System

• The covered pots reduce the amount of particulates and gaseous emissions that escape into the pot rooms.

• The gases produced during electolysis are trapped and then piped to the A398 Recovery System which consists of a bed of fluidized alumina, which traps the fluoride emissions as they are pumped through from underneath the conveyor.

• The fluoride-rich alumina is then conveyed to the smelting pots.

• Fluoride helps to lower the melting point of the alumina so that less energy is required to produce molten aluminium.

• Less fluoride inputs are required as the about 99.8% of the fluoride is recycled in this manner.

Bank of A398 Fluoride Scrubbers

Portland Aluminium has the lowest fluoride emissions of any of the six primary aluminium smelters in Australia, according to the Australian Government “State of the Environment” report (2001). (120 tonnes/year)http://www.environment.gov.au/soe/2001/publications/theme-reports/atmosphere/atmosphere05-9.html

Alcoa Portland Plant Total Fluoride (Portland Internal Limit = 0.63 in kgF/tonneAl) (EPA limit = 418 gF/min)

Environmental Improvement Report• The Point Henry and Portland Aluminium smelters are working to reduce anode effects which produce perfluorocarbon emissions. • 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.

http://www.alcoa.com/australia/en/pdf/Sustainability_Report_2009_Final.pdf

Reducing Fluoride Pollution

Lowest Fluoride Emissions• During 2009, both Point Henry and Portland Aluminium smelters

continued to focus on minimising and sustaining fluoride emissions within internal (Alcoa) targets, which is reflected in the long-term historical trends.

• Alcoa’s internal targets are more stringent than those set by the Victorian Environmental Protection Authority.

• Portland Aluminium continued to progress a long-term management program for fluoride emissions in 2009, 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, making Portland Aluminium one of the lowest fluoride-emitting smelters in the world.

Sustainability GoalsThrough the “Sustainability Strategic Framework”, Alcoa set itself some challenging

goals, including:

• Zero fatalities and lost work day or recordable injuries.

• 25% reduction in greenhouse gas emissions by 2010, compared to the base year of 1990.

• 10% reduction in energy intensity by 2010, compared to 2000.

• 70% reduction in process water use by 2010, compared to 2000.

• 50% of Alcoa‟s fabricated aluminium output produced from recycled metal by 2020.

• 40% of Alcoa employees contributing to their communities through volunteering.

REFERENCES

• http://www.alcoa.com/australia/en/alcoa_australia/location_overview/portland.asp

• http://www.alcoa.com/australia/en/pdf/Sustainability_Report_2009_Final.pdf

• http://www.environment.gov.au/soe/2001/publications/theme-reports/atmosphere/atmosphere05-9.html

• http://aluminium.org.au/australian-aluminium/aluminium-portland

• http://www.health.vic.gov.au/environment/downloads/fluor_air.pdf