Abench-scale updraft gasifier was used as a fluidizedand fixed-bed gasification unit in three modes (fluidizedbed at equivalence ratios (ER) =0. 2 and 0. 25, and a mode in fixed-bed). The experiments were done in five different temperatures (650, 700, 750, 800 and 850oC). To obtain the required data to develop a thermodynamic equilibrium model, the proximate and ultimate analysis were carried out on potato shoot as feedstock. Since the developed model is a temperature-based model, it gives different outcomes in different temperatures. The model gave a completely exact result to predict CH4 in fluidized-bed at ER=0. 25. The average error for the difference between each produced gas in experiments and the model showed the best result of the model for CO with the error of just 0. 7%. Regarding each experiment data difference with the model data, the model was more accurate to be used in fluidized-bed, especially at ER=0. 25 than the other two modes. Moreover, the best performance of the model was obtained for CO, N2 and CO2, according to the average errors. Since the maximum amount of high heating value (HHV) and carbon conversion efficiency (CCE) was observed at higher temperatures, it can be contended that the model has better performance at higher temperatures.

The main advantage of a fluidized bed is its capability in excellent gas-fuel mixing. However, due to the lacks of gas radial momentum, its lateral mixing of gas-solid is not adequate. Therefore, this research is focused on fluidized bed hydrodynamics enhancement using the modified gas distributor plate design. For getting an optimum fluidized bed hydrodynamics prediction, three different classical ANSYS Fluent drag models, namely Wen-Yu, Syamlal O’ Brien, and Gidaspow are examined first. Afterward, a novel distributor plate called swirl distributor plate (SDP) is proposed in order to enhance the gas-fuel mixing in vertical and radial directions. In terms of simulation approach, results were presented and compared with the experimental data. It has been observed that better hydrodynamics prediction is achieved by Syamlal O’ Brien drag model. The effect of SDP on gas-solid mixing was then studied numerically and compared with conventional distributor plate (CDP). Compared with CDP, better gas-solid mixing was found while the SDP was used. As a final point, gasification test was conducted in a lab scale system in order to study and compare the composition of produced syngas using both distributor plates. Based on the gasification results, SDP leads to promotion of Hydrogen and Carbon monoxide by 34. 85 and 65. 92 percent, respectively.

An Eulerian–Eulerian-based two-dimensional mathematical modeling approach for bubbling fluidized bed gasifier using FLUENT has been proposed to transfer energy, momentum, and mass between two phases namely solid and gas together with the application of the kinetic theory of solid particle flow. The modeling equation involves eight homogeneous and five heterogeneous reactions kinetics. The eddy dissipation model of FLUENT has been used to incorporate homogeneous reaction kinetics and a user-defined code has been developed that describes the kinetics of heterogeneous reactions. The simulation result shows that the exit syngas composition is in line with the experimental one and has a maximum error of around 4.05% for CO and 2.68% for hydrogen. This model has been used to study the variation in hydrogen concentration in the syngas to maximize hydrogen production based on different operating and design parameters.

This paper investigated the possibilities of using birch wood chips for fixed-bed downdraft gasification. The preliminary air gasification resulted producer gas with an average composition of 11.5% CO, 5.4% CO2, 5.9% H2, 0.38% CH4 corresponding to a mean lower heating value of about 2 MJ/kg. The approximate size of woodchips used for gasification was around 11.5 mm for a maximum solid throughput of 0.65 kg/h. The obtained equivalence ratio (ratio between actual air fuel ratio and stoichometric air fuel ratio) as a result of air and biomass feed was close to 0.45 which was stable throughout the test. Producer gas left the gasifier at ca. 150oC and was diverted for flaring owing to the level of low energy content. Despite availability, the option for gas to generate heat and electricity via integrated gas engine has not been utilized in the present case and remained for further ongoing research.

Fluidized beds are conventional components of many industrial processes, such as coal gasification for energy generation and syngas production. Numerical simulations help to properly design and understand the complex multiphase flows occurring in these reactors. Two modeling approaches are usually adopted to simulate multiphase flows: the two fluids Eulerian-Eulerian model and the continuous/discrete Eulerian-Lagrangian model. Since fluidized beds account for an extremely large number of particles, tracking each of them could not assure to get results within a reasonable computational time. The Computational Particle-Fluid Dynamics (CPFD) approach, which belongs to the Eulerian-Lagrangian models class, groups together particles with similar key parameters (e. g. composition, size) into computational units (parcels). Parcel collisions are modeled by an isotropic solid stress function, depending on solid volume fraction. In this paper, the bubbling fluidized bed (BFB) upstream gasifier of the EU research infrastructure ZECOMIX (Zero Emissions of Carbon with Mixed technologies) has been simulated using a CPFD approach via Barracuda® software. The effect of different fluidizing agent injection strategies on bed bubbling and mixing, for non-reacting cases, has been studied. The numerical results for a reacting case have been compared to the available experimental data, gathered during the coal gasification campaign. The model has proved to be very useful in the choice of the more efficient injection configuration that assures a more effective contact of the gas with the solid bed and a good bubbling fluidization regime, together with a satisfactory prediction of the outlet gas composition. The numerical approach has turned out to be robust and time-saving and allowed to dramatically reduce the computational cost with respect the classical two fluids Eulerian-Eulerian models.

The transport of sediment in open channels is a complex process, and the physics of this phenomenon have not been completely explored. The majority of research work on sediment transport has been concentrated on beds formed of the same mobile sediment and only a few researchers have been concerned with sediment motion over fixed bed. This paper reviews the state of the problem and focuses on some practical points. Sediment threshold experiments were conducted in the two types of V-shaped bottom channels. Sand and gravel particle movements were considered and the relationship between flow discharge and bed shear stress, as well as channel bed slope were found at the threshold condition. Some practical and design equations were found to be more appropriate. It may be found that the effect of cross sectional shape on sediment threshold in fixed bed channels should be examined.