As pressure mounts to reduce the amount of carbon dioxide emissions, a development by Bath University could radically improve the clean-up process. Siobhan Wagner reports
A technology that could drastically reduce the amount of pollution emitted by a range of industrial processes promises to be less cumbersome and more energy efficient than systems now used to clean process waste.
The technology, which was developed by two chemical engineering researchers at Bath University, traps carbon dioxide and other pollutants so they can be removed and possibly recycled back into the production process.
It has industrial backing from Colin Billiet, the former chief executive of Domnick Hunter Group, an international filtration supplier. Billiet is now working with the University of Bath on the spin-out venture, Nano-Porous Solutions, which intends to develop and further commercialise the technology for buyers in the beverage and petrochemical industry.
The technology uses hollow fibres packed with nano-sized pores, which trap volatile hydrocarbons and other gases so they can be removed from the air flow. The gases can then be de-absorbed from the fibres by heating them in a process called temperature swing absorption or by vacuuming it out through vacuum swing absorption. The gas, which does not undergo any chemical change in the procedure, can then be recycled.
Early trials have shown the technology uses less than five per cent of the energy needed by thermal air pollution control systems such as thermal oxidisers and combustion systems.
Devices using the hollow fibre technology could be tailored to remove or recycle a range of gases by varying the composition of fibres used. The fibres can be spun with a high surface area-to-volume ratio, so they are not only efficient but also sufficiently compact to suit applications in which space is a particular constraint.
’There are some membranes available to remove CO2 but they are limited by the area available,’ said Semali Perera, one of the developers. ’If you look at the ceramic membranes, then you’re looking at about 300sq m/cu m. But the hollow fibre system we’re applying would have over 3,000 sq m surface area per cu m. The greater the surface area, the more CO2 you can capture.’
In an application being considered for the beverage industry, the researchers have designed polymeric hollow fibres tailored to capture CO2, which will be recycled back to the bottling plant for carbonating drinks.
Current systems are cumbersome. Amine scrubbing technology consists of 20-40m high absorption towers, in which exhaust gas is bubbled through an amine solution used as an absorption liquid. In another desorption tower, the carbon dioxide-loaded liquid is heated to free the gas. If used in the food and beverage industry, the gas must go through more purification so there are no contaminants in the recycle stream.
Perera said the hollow-fibre system does not need an additional purifying system but one could be developed with a simple additional fibre system.
The potential of this technology is huge. According to DEFRA, emissions of CO2 in the UK were over 500 million tonnes in 2005 — about two per cent of global man-made emissions.
In 2005 the Commons Science and Technology Committee stressed the importance of zero-emission processing plants and encouraged greater use of CO2 capture, re-use and storage.
Perera said the hollow fibre system could help industries reach a zero-emissions goal. ’Our main task, when we design processors is to reduce emissions and recycle as much as possible, so I think this technology does exactly that,’ she said.