In The Field

IUPAC ’09: Carbon capture conundrums


Back in my youth, when deciding what subjects to study at school and university I wanted to make sure that I would come out versed in something that would be of use to the wider world, perhaps even do some good. I chose chemistry. It’s clear from conferences like this that many chemists are interested in the subject for similar reasons.

Climate change is a big topic that chemists are tackling. This morning’s session on carbon capture and storage being a good example.

This is a technology intended to clean up coal-powered power stations by scrubbing out carbon dioxide from flue gas, and compressing it to be stored elsewhere – anywhere but into the atmosphere.

There are a number of problems that chemists are looking at. Today kicked off with a talk by Gary Rochelle from the University of Texas at Austin. He took us through the major considerations that are needed for the solvent that is used to collect the carbon dioxide from the gas. The standard at the moment is something called MEA, monoethanolamine. Rochelle’s fundamental physical chemistry calculations on this and other candidate solvents showed that there isn’t a simple one-size-fits-all solvent. The considerations are: capacity of the solvent to hold carbon dioxide; how much the solvent degrades when heated; how fast the reaction is; how much heat it requires.

Some of these properties are better in different solvent, he says, which are again different in different plants. Another good candidate solvent looks to be piperazine.

Then we heard from Trevor Drage from Nottingham University, UK, about using solids not liquid solvents to strip out the carbon dioxide. His systems are a long way from being scaleable but show promise. On paper, he said, solid sorbets could reduce energy loading in the systems by 30 – 50%. These systems are amine polymers loaded onto porous silica-based materials, or basic nitrogen in an activated carbon matrix.

One area that is often overlooked, says Drage is the regeneration of these sorbents and how the carbon dioxide is removed so they can be reused.

Matthew Hunt is from Doosan Babcock, a Scottish-based company

spending a lot of effort in scaling up CCS technology, with demonstration plants in Canada. This is just a 4 tonne plant so far, which is no real use for a power plant which will need to porcess 850 tonnes of carbon dioxide a day, he said. But according to Hunt, the company is on track to full-scale post-combustion carbon dioxide removal by 2014.

Of course, the impetus for these small demonstration scale plants needs to come from government, and the feeling in certain quarters of this meeting at least, was that not enough push, and not enough decisiveness is being shown to make the technology viable.

My hope is that in 2014 we are not still at the stage where academics working in small groups are showing results of small scale CCS projects and saying that scale up is needed urgently.

Image: representation of MEA


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