Ever heard of cryogenic carbon capture?

Ever heard of cryogenic carbon capture?

One of the problems facing the energy industry, worldwide, is the rising level of atmospheric carbon dioxide (CO2). American company Sustainable Energy Solutions (SES) is developing a technology called cryogenic carbon capture to address this issue. CLAIRE RENCKEN investigates.

Based in Orem, Utah, in the United States, SES was founded in 2008 in response to a growing need for solutions to sustainability problems within the energy industry. SES is committed to developing solutions to problems such as the rising level of atmospheric CO2, resulting from increasing use of fossil fuels such as coal, oil, and natural gas. CO2 is a greenhouse gas and may change the climate in unexpected ways.

There is currently no worldwide plan to curb these emissions. SES is focused primarily on the development and commercialisation of cryogenic carbon capture (CCC), a patented technology developed in 2008.

Fossil fuels currently provide over three-quarters of the world’s energy, and the adoption of renewable energy to replace fossil fuels will take decades. Until then, CO2 emissions must be drastically reduced to avoid further climate change. CCC has the potential to reduce carbon emissions from fossil-fuelled power plants by up to 99 percent, at half the cost of current state-of-the-art carbon capture processes.

CCC uses phase change to separate CO2 from exhaust or process gases. In CCC, the CO2 is cooled to such a low temperature (about -140°C) that it desublimates – or changes from a gas to a solid. The solid CO2 is separated from the remaining gas, pressurised, melted and delivered at pipeline pressure.

The captured CO2 can be used in many applications, including enhanced oil recovery and production of biofuels. The gas that remains after the CO2 and other pollutants have been removed is almost pure nitrogen, and can be safely released into the atmosphere. In addition, CCC removes other pollutants such as mercury. The pollutants are captured using the same desublimation mechanism used to capture the CO2.

In greenfield installations (where no pollutant removal systems existed before), the pollutant capture capability of CCC can  offset the cost of traditional pollutant removal systems. At lower temperatures, higher quantities of the pollutants are captured. At low enough temperatures, the exhaust exiting the stack actually has less CO2 content than the surrounding air.

In such installations, the warm exhaust gas entering the CCC process can first be used to heat the water that feeds into the boiler. This boosts the steam cycle efficiency and power output of the plant. The plant can, therefore, provide more power for the same initial investment.

Thus, CCC can capture carbon for a fraction of the cost and energy of current methods. When considering the additional benefits of pollutant capture and steam cycle integration, the cost is even lower.

Existing carbon capture technologies aren’t cheap. According to the National Energy Technology Laboratory (NETL), a current state-of-the-art amine absorption process would cost US$ 69 (around R840) per tonne of avoided CO2. The same reduction of carbon emissions can be achieved using CCC at a cost of US$ 35 (more than R420) per tonne avoided. When considering the cumulative effects of CCC’s additional benefits, the cost drops to only US$ 14 (R170) per tonne avoided.

CCC also requires only half the energy of an amine absorption process. Energy requirements for carbon capture technologies are often reported as “parasitic load”, which is the fraction of power generated by the plant that is used by the carbon capture system. The parasitic load of the base CCC process, with no plant integration, is about 14 percent, compared to 28 percent for the amine absorption process.

CCC’s energy efficiency and low parasitic load are mainly as a result of effective heat integration. The cold products, including solid CO2, are used to cool the flue gas entering the process.

The energy storing implementation also allows for very efficient grid-scale energy storage, enabling better use of renewable energy sources and virtually eliminating CCC’s parasitic load during peak demand times.

It could be many years before technologies such as CCC reach South Africa, but let’s hope they do!

Bringing together Africa’s energy leaders

Every year, the Africa Energy Indaba brings together international and continental experts to share their insights and solutions to Africa’s energy crisis, while simultaneously exploring the vast energy development opportunities on offer in Africa.

That was again the case on February 17 and 18, at the Sandton Convention Centre in Johannesburg. Delegates came from across the continent to debate and exchange solutions to Africa’s energy challenges, while the exhibition component was a significant marketplace for African and international stakeholders looking for, and doing, business in Africa’s energy sector.

There were several panel discussions during the conference, the first of which was about developing an appropriate mix of resources to deliver Africa’s economic potential. The session was facilitated by Accenture Strategy’s Arthur Henna. Panel members included: Quantum Power’s Dr Louis van Pletsen; Prof Mosad Elmissiry, of the New Partnership for Africa’s Development (NEPAD) agency; Bonang Mohale, from Shell South Africa; and Gloria Magombe from the Zimbabwe Electricity Regulation Authority.

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