<p>This thesis encompasses CO<sub>2</sub> mitigation using three different processes: i) natural gas-fired combined cycle with chemical looping combustion (CLC), ii) trigeneration of electrical power, hydrogen and district heating with extended CLC, iii) steam-based gasification of biomass integrated in an advanced power cycle. </p><p>In CLC, a solid oxygen carrier circulates between two fluidised-bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO<sub>2</sub> separation occurs. In this thesis, CLC has been studied as an alternative process for CO<sub>2</sub> capture in a natural gas-fired combined cycle (NGCC). The potential efficiency of such a process using a turbine inlet temperature of 1200 °C and a pressure ratio of 13 is between 52 and 53 % when including the penalty for CO<sub>2 </sub>compression to 110 bar. It is shown that this efficiency cannot be further improved by including an additional CO<sub>2</sub> turbine. Two conceivable reactor designs for CLC in an NGCC are presented. Top-firing has been studied as an option to overcome a temperature limitation in the CLC reactor system. The degree of CO<sub>2</sub> capture is shown versus the temperature in the CLC reactor and its combustion efficiency. CLC has the potential to reach both a higher efficiency and a higher degree of CO<sub>2 </sub>capture than conventional post combustion CO<sub>2</sub> capture technique. However, further research is needed to solve technical problems as, for example, temperature limitations in the reactor to reach this potential. </p><p>Extended CLC (exCLC) is introduced, in which hydrogen is not only produced but also inherently purified. The potential efficiency of a novel tri-generation process for hydrogen, electricity and district heating using exCLC for CO<sub>2 </sub>capture is investigated. The results show that a thermal efficiency of about 54% might be achieved. </p><p>A novel power process named evaporative biomass air turbine (EvGT-BAT) for biomass feedstock is presented. This process contains a steam-based gasification of biomass, which is integrated in an externally fired gas turbine cycle with top-firing. In the EvGT-BAT process, the steam-based gasification is conducted in an entrained-flow tubular reactor that is installed in the SFC as a heat exchanger. The EvGT-BAT process has the potential to generate electrical power from biomass with an efficiency of 41 %.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:kth-77 |
| Date | January 2004 |
| Creators | Wolf, Jens |
| Publisher | KTH, Chemical Engineering and Technology, Stockholm : Kemiteknik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Trita-KET, 1104-3466 ; 202 |
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