CSIRO has developed a relatively simple and environmentally friendly catalytic technology that reduces the odours of industrial processes.

 

When the breeze passes over the industrial suburbs of most Australian cities, it bears the whiff of industry.

 

This gaseous cocktail poses no dire threat to human health, but it is offensive to the nose, and prolonged exposure may cause headaches, nausea and respiratory ailments.

 

CSIRO chemical engineer Dr Manh Hoang says the problem is largely one of perception, not hazard. He says the human nose is particularly sensitive to the sulfur-rich organic compounds that dominate the mix, most notably hydrogen sulfide, or ‘rotten-egg gas’.

 

Current technologies

 

Current deodorising technologies for industry include dilution, masking or neutralising agents, high-temperature (greater than 800 °C) oxidation, wet scrubbing, adsorption and biofiltration. But each technology has its problems:

 

• High-temperature oxidation is energy-intensive and can produce sulfur and nitrogen oxide compounds, which are air pollutants.
  'The catalytic equipment can be scaled to an individual company’s requirements.'
  Dr Manh Hoang, CSIRO chemical engineer
• Masking and neutralisation consume large quantities of expensive chemicals and may create even more offensive odours.
• Wet scrubbing transfers odour compounds from air to water, leaving another waste disposal problem.
• Biofiltration plants, which use microbes to break down the offensive compounds, are suitable for large gas flow rates and are cheap to operate, but require large-scale treatment plants. 

Towards a cleaner industrial environment

 

Dr Hoang’s team has developed an alternative low-temperature technology that can tackle the problem at the source, by trapping and catalytically destroying the offending gases.

 

The catalytic converter is a lightweight, highly porous ceramic, wash-coated with the CSIRO catalyst. It provides a very large surface area for catalysis within a relatively compact volume.

 

Inside the converter, foul-smelling sulfur-containing organic compounds are burnt at temperatures between 80 °C and 300 °C in the presence of the catalyst, and are oxidised into odourless, non-toxic compounds. The low-temperature process consumes minimal amounts of fossil fuel.

 

Dr Hoang says the technology can be used to treat exhaust gases from industrial processes, or to strip gaseous pollutants from liquid industrial effluents or sewage after solids have been removed.

 

Factories can use the converter to recycle their own water or use it to irrigate parks and gardens.

 

The catalyst has a long life and is inexpensive. It has been tested it in a pilot plant for more than 1000 hours – six weeks – of continuous operation, with no significant decline in its efficiency.

 

The catalytic equipment can be scaled to an individual company’s requirements and can accommodate low or high gas flow rates.

 

Creating value

 

A major advantage of the our technology is that the converter’s size means that factories do not have to install expensive ducting to collect contaminated air and pipe it to a central disposal plant. Small plants can be installed at the source of the odours.

 

Dr Hoang believes the new low-temperature catalysis technology has considerable export potential, because of its relatively low cost and low energy consumption. CSIRO is currently negotiating with an Australian company interested in commercialising it.