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Despite tremendous effort to model fluidized bed biomass gasifiers, as major sustainable waste-to-energy devices, current equation-oriented approaches suffer from implementation difficulties. In this research, a comprehensive cocurrent sequence-based process model is introduced to simulate bottom-fed bubbling fluidized bed biomass gasifiers (BFBGs). The gasifiers include two operating regions, namely dense bed and freeboard. The dense bed is divided into several sections of logically ordered ideal reactors to describe the behavior of interacting phases, i.e., bubble and emulsion. The bubble phase is well characterized by an ideal plug flow reactor (PFR), and the emulsion phase is simulated as a continuous stirred-tank reactor (CSTR). The freeboard is successfully mimicked with a PFR. Hydrodynamic and kinetic submodels describe physical and chemical phenomena taking place in the gasifiers, respectively. A dynamic two phase model is adopted as the hydrodynamic submodel, and the kinetic submodel is derived from the literature. Several sets of experimental data from biomass gasifiers with various biomass feedstocks are analyzed to evaluate the reliability of the proposed model. Close agreement between the experimental data and the model shows that the proposed simple and in-hand method is able to predict the behavior of complex BFBGs. Finally, the modeling package is used to optimize the hydrogen production, H 2 /CO, and hazardous gas emission in BFBGs. The proposed model can be integrated into the industrial process simulators such as AspenOne modules to represent highly nonideal reactors.

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Sequential modular simulation (SMS), as a new modelling approach, was developed to simulate the photocatalytic oxidation (PCO) of gaseous pollutants in fluidized bed reactors. In the experimental part, the PCO of gaseous acetone was studied in a fluidized bed photo-reactor (FBPR) and the influence of operating conditions (inlet concentration, relative humidity (RH) and superficial gas velocity) on both acetone conversion and mineralization was investigated. It was found that the RH, as a key factor in PCO reactions, had a contradictory effect on the conversion and mineralization of acetone. In the modelling part, the bed was divided into several sections in which the bubble and emulsion phases were considered as a plug flow and a completely mixed flow reactor, respectively. Dynamic two-phase model was adopted as the hydrodynamic sub-model and the Langmuir-Hinshelwood (LH) mechanism as the kinetic sub-model. Kinetic constants of the latter sub-model were estimated using experimental data from the literature. A new dimensionless number (HA number) was introduced to determine the optimum number of sections, as the most important factor in model predictions. The performance of the proposed model was compared with the experimental data obtained in this study and several sets of experimental data from the literature. The results showed that the simple and easy-to-achieve approach, which has the capability of integrating into the industrial process simulators such as Aspen Plus © and Aspen HYSYS © , can be used to simulate the behaviour of non-ideal FBPRs in PCO processes.

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