Simulation and analysis of an integrated steam pyrolysis system

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School of Engineering | Master's thesis
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(15) + 120 s. + liitt. 18
The conceptual design of an integrated system for steam pyrolysis is presented. For the biomass input of 1 kg, pyrolysis enthalpy of 1639 kJ resulted from calculation is discussed as a reasonable estimation for pyrolysis of softwood. Four cases of pyrolysis using steam and nitrogen were simulated. Overall, for the combustion bed temperature of 850°C, if there is sufficient steam for the low-pressure steam turbine, all steam pyrolysis systems can always operate self-sufficiently. Additionally, if a high preheated air temperature is required, partial char combustion can be better deployed for steam pyrolysis than in the case of conventional N<sub>2</sub> operation. Moreover, the steam-to-biomass mass ratios determine the capacities of turbines and a low steam-to-biomass mass ratio contributes to a stable electricity output. Only when the pyrolysis enthalpy is estimated to be above 2.0 MJ per kg of biomass input, the highest electricity output is attributed to the case of N<sub>2</sub>. Otherwise, with the same combustion bed temperature and same pyrolysis enthalpy, the case for steam-to-mass ratio of 0.34 always represents highest electricity output. For a biomass input of 3 kg/s, the system can generate approximately 3 MW of excess power. As preliminary optimization results, three integrated systems with steam-to-biomass mass ratios of 0.34, 0.67 and 0.5 are proposed as optimum cases under electricity-, bio-oil-and operation-dominated scenario designs. Moreover, the system with steam to biomass mass ratio of 0.5 can be considered as the candidate for future multi-objective optimization results.
Järvinen, Mika|Yang, Weihong
Thesis advisor
Kohl, Thomas
Kantarelis, Efthymios
bio-oil, pyrolysis enthalpy, steam pyrolysis, system integration