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    89 aziz 89 aziz Presentation Transcript

    • Integration of Supercritical Water Gasification and Combined Cycle Processes for Microalgae Mumbai, December 10-12, 2013 M. Aziz, T. Oda, T. Kashiwagi
    • Microalgae Utilization Superiority of microalgae compared to terrestrial one (high efficient solar energy conversion and nutrient acquisition, effective CO2 absorption, etc.) Numerous microalgae utilization (energy, feed-stock, etc.) Microalgae utilization processes Problems :  Lack of matured technologies for utilization  Low energy-returned on energy-invested (EROEI) 4th ICAER 2013, Mumbai 2
    • Microalgae Gasification Conventional thermal gasification • High temperature (about 900ºC) • Drying required Gasification Utilization of microalgae for power generation can be an option in the future electricity supply, especially providing the base load electricity Supercritical water gasification • Supercritical condition • No drying required 4th ICAER 2013, Mumbai 3
    • Proposed Utilization Process Integration of Supercritical Water Gasification and Combined Cycle Processes Carbon neutral process Outline of the material and energy circulation in the proposed system. 4th ICAER 2013, Mumbai 4
    • Supercritical Water Gasification  Thermochemical conversion utilizing supercritical water properties • Pressure > 22.1 MPa • Temperature > 374 ºC  Produced syngas: CO, hydrogen, methane, etc.  Advantages • Lower water density  decrease in static relative dielectric constant • Significantly lower hydrogen bond • Higher gasification efficiency • Single homogeneous phase of fluid • Faster chemical reaction • No drying required  Disadvantages • Higher energy to provide high pressure and temperature • Requires further technological development 4th ICAER 2013, Mumbai 5
    • Enhanced Process Integration  Huge energy consumption in process utilization  The conventional energy recovery technology cannot recover significantly the energy involved in the process Advanced System = Exergy Recovery + Process Integration Enhanced Process Integration (EPI) Characteristics of EPI - Exergy rate elevation and its recovery - Optimal and effective heat coupling (sensible, latent, etc.) - Integration with other processes to minimize exergy destruction 4th ICAER 2013, Mumbai 6
    • Concept of Exergy Recovery Exergy Recovery Heat Cascade T Qheat exchange Qheat exchange T T1 T1 Effluent Effluent Tb Tm in Tb’ Tb Feed Tm in Feed T0 T0 Q Q T-Q diagram of SHR process T-Q diagram of self-heat exchange process Based on pinch technology Maximum heat recovery/circulation No effective heat coupling Effective and optimal heat coupling Large exergy destruction Minimum exergy loss 4th ICAER 2013, Mumbai 7
    • Integrated Conventional Gasification Drying Gasification Combined cycle Schematic diagram of integrated conventional gasification and combined cycle 4th ICAER 2013, Mumbai 8
    • Integrated Conventional Gasification Process flow diagram of integrated conventional gasification and combined cycle 4th ICAER 2013, Mumbai 9
    • Proposed Integrated SCWG and CC Gasification Combined cycle Basic schematic diagram of proposed integrated SCWG and combined cycle 4th ICAER 2013, Mumbai 10
    • Proposed Integrated SCWG and CC Exergy elevation Highest energy recovery Process flow diagram of proposed integrated SCWG and combined cycle 4th ICAER 2013, Mumbai 11
    • Calculation Conditions Proximate and ultimate analysis of Spirulina sp. Properties Proximate analysis (wt.% db) Moisture Ash Volatile matter Fixed carbon Ultimate analysis (wt.% db) Carbon Hydrogen Nitrogen Sulfur Oxygen Calorific value (MJ kg-1) Value Gasification condition 8.04 6.98 68.15 16.83 42.83 6.02 4.09 0.49 46.57 18.5 Assumptions during calculation 1. 2. 3. 4. 5. The minimum approach temperature in all heat exchangers is 10 K The flow rate of microalgae is 1 ton h-1 Fresh microalgae has a moisture content of 90 wt.% wb The adiabatic efficiency of the compressor and turbine (steam/gas) are 87% and 90%, respectively Heat loss is neglected Properties Gasifier pressure (MPa) Gasifier temperature (C) Gasification efficiency (%) HX min. temp. approach (C) HX pressure drop (%) Pump efficiency (%) Fluidizing particles Particle diameter (mm) Density (kg m-3) Void fraction Gasification products (mol %) CO C2H6 and C3H8 CH4 CO2 H2 Gasification catalyst Catalyst to sample ratio 4th ICAER 2013, Mumbai Value 25 700 100 10 2 90 Alumina particles 100 3,400 0.5 3.1 4.9 18.1 27.8 46.1 Ru/TiO2 2 12
    • Results – Gasification Efficiency Correlation between the amount of steam flown into SCWG reactor with net generated electricity and total electricity generation efficiency • • High electricity generation efficiency could be achieved (up to about 50%) As the amount of steam flowing to SCWG reactor decreases, the generated electricity and generation efficiency increases accordingly 4th ICAER 2013, Mumbai 13
    • Summary 1. Microalgae has a very potential for energy utilization. Unfortunately, its high moisture content leading to difficulties in transportation, storage, thermal efficiency, etc. Hence, innovative technology is required to increase its energy efficiency 2. Gasification of microalgae could be achieved through conventional thermal gasification and supercritical water gasification 3. Integrated supercritical water gasification and combined cycle based on the enhanced process integration has been developed well 4. The total energy efficiency could be increased leading to its high opportunities for application 4th ICAER 2013, Mumbai 14
    • Close 4th ICAER 2013, Mumbai 15