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Alstom Signs Two Development Contracts for Carbon Capture Technology

Schematic of the chilled ammonia capture system. Click to enlarge. Source: EPRI, Alstom.

Alstom has signed two development contracts for its chilled ammonia-based CO2 capture technology, one with E.ON for a power plant in Sweden, and one with Statoil for the Mongstad refinery in Norway.

In March, Alstom and American Electric Power (AEP) signed an agreement to bring the Alstom advanced sorbent CO2 capture process to full commercial scale of up to 200 MW at an AEP site in Oklahoma by 2011. (Earlier post.)

E.ON. With E.ON, Alstom will launch a 5MW CO2 capture demonstration plant at Karlshamn Power Plant in southern Sweden. The demonstration plant will use Alstom’s chilled ammonia-based technology and is expected to begin operation in 2008. The companies plan to introduce the technology in other Swedish power plants after technical evaluation.

Statoil. The project with Statoil covers the design and construction of a 40MW test and product validation facility at Statoil’s Mongstad refinery in Norway. This facility will be designed to capture at least 80,000 tons per year of CO2 from flue gases from the refinery’s cracker unit or from a new combined heat and power plant being built by Statoil and scheduled to be in operation by 2010. The test and product validation facility is expected to enter operation by 2009-2010 with the first operation and testing phase to last 12-18 months.

Both parties intend that this facility will lead to technical advances and the construction of a larger CO2 capture unit that may eventually capture over 2 million tons per year of CO2 at Mongstad.

Alstom’s technology. Alstom’s chilled ammonia process is one of several new processes being explored for post-combustion capture. Research suggests that chilled ammonia-based CO2 capture can remove up to 90% of the CO2 from flue gases. Although there are several proposed techniques that can separate carbon dioxide from the other gases (such as MEA, Mono-Ethanol Amine scrubbing), Alstom’s chilled ammonia process reduces the amount of energy used to capture CO2 (energy loss). Studies by EPRI have indicated that ammonia scrubbing results in a 10% energy loss, while the older MEA (amine scrubbing) cuts generated power by 29%.

In the chilled ammonia capture system, flue gas is cooled to 0-10°C, condensing water and removing residual contaminants. This also reduces flue gas volume, increasing the concentration of CO2. This cooled gas then flows to the absorber, which operates at 0-10°C for high CO2 capture and low ammonia emission.

There, the ammonia reacts with CO2 and water to form ammonia carbonate or bicarbonate. Raising the temperature to 120°C or more and pressure to above 20 bar reverses the reaction, generating a high pressure CO2 stream with low moisture and ammonia concentration. The CO2 can then be processed for sequestration. Other advantages of the system include:

  • High capacity for CO2 per unit of solution;

  • High pressure regeneration;

  • Low-cost reagent;

  • No degradation during absorption-regeneration; and

  • Tolerance to oxygen and contaminants in gas.




I've read the linked paper which suggests after some calculations the energy penalty is around 10%, better than some claims for enhanced oxygen combustion. This is surprising since it involves a lot of cooling. The scaled up tests should reveal how it copes with hot dusty flue gas rather than lab CO2 and also whether escaped ammonia will be a smelly problem. Those are big ifs.

Paul Dietz

This is surprising since it involves a lot of cooling.

Presumably, a great deal of that energy could be recovered with appropriate heat exchangers. After all, oxyfuel combustion involves even more cooling (of the incoming air, to perform cryogenic separation), but most of that 'cold' is recycled.

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