Hydrogen And Power Cogeneration Process Analysis And Economic Evaluation Of Biomass Gasification Coupled Chemical Chain Technology

Hyodrogen and electricity are deemed as the two major clean energy carriers, while they are mainly produced by fossile fuels, such as coal, natural gas, etc. The controversy between the shortage of the fossile fuel and the pollution brought by the utilization of fossil fuels has gradually became the main stone that restricts the sustainable development of human beings. Biomass appears for its abundant storage, low pollution, and high heating value and has been widely developed and used at the present time. Chemical looping technology is a newly combustion technology and has a high combustion efficiency and in-situ separation CO2 characters. In this paper, the biomass was chosen as the feedstock, and two processes were put forward, they were biomass gasification coupled with iron-based chemical looping process for the cogeneration of hydrogen and electricity, and biomass gasification integrated with calcium looping process for the congeneration of hydrogen and electricity. Those two processes were evaluated from thermodynamics and economics point of view, and compared with the conventional biomass gasification for the production of hydrogen and electricity cogeneration.The Aspen Plus simulation software was employed to simulate the three kinds of processes. Some parameters were chosen and defined as the evaluation indicators, they are hydrogen yield, hyodegn efficiency, electricity efficiency, cumulative efficiency, exergy efficiency, carbon capture efficiency, and specific CO2 emission. The effect of gasification temperature (Tg,650-900?), steam to biomass mass ratio in the gasifier (STBR,0.4-0.9), the solid to steam molar ration (STSR,0.1-0.6) in the fuel reactor for the iron-based chemical looping shystem, Fe/FeO to steam molar ratio(FeTSR,0.5-1.0) in the steam reactor, the CaO to CO molar ratio (CTCR,0.8-1.8) and the steam to CO molar ratio (STCR,1.0-3.5) in the absorption reactor for the calcium looping process, on the evaluation indicators were studied. The thermodymanic analyzes shown that:1) for the conventional biomass gasification for the production of hydrogen and electricity process, when Tg=800?, STBR=0.6, the hydrogen yield was 13.82%, the cumulation efficiency was 52.53%, the exergy efficiency was 45.55%,the carbon capture was zero, and the specific CO2 emission was 608.94 kg/MWh; 2) for the biomass gasification coupled with iron-based chemical looping process for the cogeneration of hydrogen and electricy, when Tg=750?, STBR=0.5, STSR=0.4, FeTSR=0.8, the hydrogen yield was 15.39%, the cumulation efficiency was 55.80%, the exergy efficiency was 48.12%,the carbon capture was 99.9%, and the specific CO2 emission was 215.68 kg/MWh;3) similarly, for the biomass gasification coupled with calcium looping process for the cogeneration of hydrogen and electricy, when Tg=750?, STBR=0.5, CTCR=1.2, STCR=3.0, the hydrogen yield was 14.62%, the cumulation efficiency was 43.39%, the exergy efficiency was 37.77%,the carbon capture was 99.9%, and the specific CO2 emission was 217.87 kg/MWh. The exergy calucaltion results demonstrated that for the both the conventional biomass gasification for the production of hydrogen and electricity process and the biomass gasification coupled with iron-based chemical looping process for the cogeneration of hydrogen and electricy, the highest exergy destruction rate unit was gasification section (almost 30%), followed by heat recovery and steam generation section (almost 12%). While for the biomass gasification coupled with calcium looping process for the cogeneration of hydrogen and electricy, the higest exergy destruction rate was taken place at gasification section (almost 22%), followed by calcium looping section (almost 21%) and heat recovey and steam generation section (almost 12%), in that order.The overall capital investment, operation and maintenance cost, and the levilized cost of energy were adopted as the economical evaluation indicators. The economical anlysis for the upper three kinds of hydrogen and electricy cogeneration processes exhibited that economic indicators for the conventional biomass gasification for the production of hydrogen and electricity process was prior to another two processes. However, the biomass gasification coupled with iron-based chemical looping process for the cogeneration of hydrogen and electricy, and the biomass gasification coupled with calcium looping process for the cogeneration of hydrogen and electricy were prior than the conventional biomass gasification for the production of hydrogen and electricity process (when the CO2 capture unit using the MEA absorbing method (assuming carbon capture was 90%) was added) with 24% and 8.8% in the field of levilized cost of energy, respectively. It was demonstrated that the chemical looping process has a better economical property, and when the chemical looping thechnolgy was applied to the hyodrogen production filed, which could substitute the water shift reactor and PSA equipment for the convnetial hydrogen technology, and lower the levilized cost of hydrogen production.