Clean carbon capture technology

2017/03/15

Clean carbon capture technology

Coal-powered power stations are becoming more environmentally friendly

In the course of Project SCARLET, scientists at the TU Darmstadt have succeeded in developing the so-called Carbonate Looping process for the reduction of CO2 emissions during power plant operations almost to the point of market readiness.

Jochen Hilz, Dr.-Ing. Jochen Ströhle, Prof. Dr.-Ing. Bernd Epple (von links) in derCO2-Versuchshalle, in der sich die 1 MW-Versuchsanlage befindet. Bild: Katrin Binner
Jochen Hilz, Dr.-Ing. Jochen Ströhle, Prof. Dr.-Ing. Bernd Epple (from left to right) in the CO2 testing facility, which houses the 1 MW experimental pilot plant. Photo: Katrin Binner

By the time Professor Bernd Epple of the TU Darmstadt‘s Institute for Energy Systems and Energy Technology opens the final symposium of the European-wide Project SCARLET these coming days, several milestones will have been reached. Over the past three years, Professor Epple, a mechanical engineer, and his ten German and international project partners have developed the technical prerequisites for the industrial deployment of the Carbonate Looping process. This process can be used to separate more than 90 per cent of the CO2 released during the combustion of fossil fuels. Retrofitting existing power generation facilities and industrial plants with this technology would allow them to be operated in a much more environmentally-friendly manner.

Based on data measured at a 1 Megawatt (MW) experimental facility, Professor Epple and his team have developed scaling tools for industrial plants with which they have conducted model calculations and computer simulations. They have proven that the new process is more cost effective and energy efficient than competing processes. They presented plans for a complete pilot project plant for the coal-fired power plant Émile Huchet in Saint-Avold in France, with a total output of 20 MW.

“If the funding details were already clarified at this point”, says Dr. Jochen Ströhle, Senior Research Scientist at the Institute for Energy Systems and Technology at the TU Darmstadt and Project SCARLET coordinator, “then this could be the first industrial scale pilot project to be launched. “All the necessary planning, including a cost schedule and a risk assessment are already on the table”. The acronym “SCARLET” stands for “Scale up of Calcium Carbonate Looping Technology for Efficient CO2 Capture from Power and Industrial Plants”. The European Union has provided five million euro in project funding, and the overall budget was over seven million euro.

How does the carbonate looping process work?

Schematische Darstellung des Carbonate-Looping-Verfahrens. Abbildung: Prof. Bernd Epple / Grafik: Ulrike Albrecht
Carbonate looping process. Table: Prof. Bernd Epple / Desgin: Ulrike Albrecht.

Carbonate Looping involves two chemical reactions continuously running in two interconnected fluidized bed reactors. In the first fluidized bed reactor, the absorber, a powder of burnt lime or calcium oxide (CaO) is contacted with the CO2 in the power station exhaust to form calcium carbonate (CaCO3). The calcium carbonate then is transferred in the second of the two fluidized bed reactors, known as the regenerator, where high temperatures force out the CO2 bound as the calcium carbonate thereby producing burnt lime and CO2 once again. The released CO2 can then be used for other purposes or stored whilst the burnt lime is returned to the first fluidized bed reactor. The material needs to be replaced after several dozen cycles, but the depleted lime can then be used in cement production making it a valuable raw material rather than a waste product.

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