ATAC i system - Energimyndigheten

7. Evaluation and reporting.
2
So far, activities have only been carried out in the three first steps (due to that until recently
there was no PhD candidate available). Step 2 is completed and the current activities focus on
establishment of a strategy for the experiments.
Results
Process evaluation
The process evaluation focussed on integration of the air separation unit (ASU) with the
power process, and design of a flue gas treatment scheme. Thus, a process scheme is proposed
and evaluated. Also, emission data were obtained together with estimates of the investment
cost of the plant. Commercial state-of-the-art data from an existing 2x865 MW power plant
(Lippendorf) and commercial design data of large-scale ASU and auxiliary components
(compressors, separators etc.) were used as bases for the study.
The ASU is integrated with the power cycle and optimized with respect to purity of the
product gas (95% O2). Since no air pre-heater is needed in the O2/CO2 plant, there is extra
heat available, compared with the reference plant. Also, heat is recovered from the flue gas
condenser introduced. Different alternatives for the use of these heat flows are proposed, such
as heating of the Nitrogen flow in the ASU. Intercooling of the compressors, cooling to
condensate the flue gas and to bring the carbon dioxide in a liquid state are provided by the
ordinary cooling tower. Significant energy savings were obtained from the process
integration.
The flue gas treatment passage consists of units for cleaning from particulates, water
condensation, dehydration, compression of the flue gas and separation of non-condensable
gases. To meet the requirements for transport of the flue gas with respect to hydrate formation
and corrosion, the gas is dehydrated after the traditional flue gas condensers. The process
suggested permits deposition of the sulfur dioxide solved in the liquid carbon dioxide, i.e.
there is no need for a conventional desulfurization unit. After dehydration the flue gas is
compressed to 58 bars and cooled to 15°C, i.e. the carbon dioxide and sulfur dioxide are
transformed to liquid state, and the non-condensable gases are separated. Before
transportation, the pressure of the carbon dioxide is increased to a suitable level with a pump.
The proposed plant, forms a near zero emission plant as 99.5% of the CO2 is separated from
the flue gas, and very low levels of sulfur emissions, particulates and low emissions of nitrous
gases are achieved.
Since the O2/CO2 plant needs no desulfurization unit the total investment cost (including the
ASU) is similar to that for a conventional. The extra energy consumption for the CO2
separation and liquefaction reduces the output from the plant to 700 MW, compared to 865
MW of the reference plant.
Based on the results of the process evaluation, an abstract has been submitted to the GHGT6
conference (Int. Conf. on Greenhouse Control Technologies).
Test rig with instrumentation
Detailed dimensioning of the test rig and design of measurement plan is carried out at present
and is also the main focus of the activities in the near future. Since there is now a PhD