|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;
No degradation during absorption-regeneration; and
Tolerance to oxygen and contaminants in gas.
Chilled Ammonia Process Update (EPRI and Alstom)