scholarly journals Experimental Evaluation of Napier Grass Gasification in an Autothermal Bubbling Fluidized Bed Reactor

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1517 ◽  
Author(s):  
Ramin Khezri ◽  
Wan Azlina Wan Ab Karim Ghani ◽  
Dayang Radiah Awang Biak ◽  
Robiah Yunus ◽  
Kiman Silas
Keyword(s):  
Fluidized Bed ◽  
High Performance ◽  
Maximum Yield ◽  
Substantial Effect ◽  
Napier Grass ◽  
Small Scale ◽  
Fluidized Bed Reactors ◽  
Direct Combustion ◽  
Bubbling Fluidized Bed ◽  
Fluidized Bed Gasifier

Air gasification of Napier grass (NG) was studied with the target of producing combustible synthesis gas to be used in direct combustion for power generation. A small-scale autothermal bubbling fluidized bed gasifier was used to investigate the effect of reactor temperature, equivalence ratio (ER), and static bed height (SBH) on gasification performance and combustibility of the producer gas. The main generated species in syngas were identified through gas chromatography (GC) analysis. Minimum fluidization conditions were determined at different levels of SBH. Experiments carried out with two intentions of first, to achieve the highest composition of combustible species to ensure the maximum Lower Heating Value (LHV) of syngas and second, to obtain a high performance process with maximum yield of syngas and minimum residues. The results showed that the temperature and ER have significant effects on syngas yield and composition. SBH was found have a substantial effect on the production of H2 and CO. The results from this study was compared to other gasification studies from literature which have evaluated biomass gasification in bubbling fluidized bed reactors with different scales but almost similar method of experimentation. The purpose of verification was to demonstrate the effect of different reactor scales and heating characteristics on the results.

scholarly journals Study on the enhancement of hydrogen generation via biomass gasification in fluidizedbed reactors

2019 ◽  
Vol 83 ◽  
pp. 01001
Author(s):  
Yau-Pin Chyou ◽  
Po-Chuang Chen ◽  
Der-Ming Chang ◽  
Keng-Tung Wu ◽  
Rei-Yu Chein
Keyword(s):  
Fluidized Bed ◽  
Hydrogen Generation ◽  
Preliminary Test ◽  
Clean Energy ◽  
Biomass Gasification ◽  
Fluidized Bed Reactors ◽  
Carbon Abatement ◽  
Bubbling Fluidized Bed ◽  
Fluidized Bed Gasifier ◽  
Solid Biomass

In this study, solid biomass is gasified in fluidized-bed reactors, to investigate the effect of various means on syngas composition, especially for enhancing hydrogen content in the production gas. Conventionally, air is supplied to the reactor as gasification medium, which inevitably results in a high nitrogen content in the syngas. Alternatively, steam or oxygen-rich gas can be supplied to improve the syngas characteristics. On the other hand, a so-called “indirect gasification technology” realizes the whole conversion processes in dual reactors, for combustion and gasification, respectively; moreover, solid materials are circulated through two reactors, while gaseous streams in between are separated from each other. Hence, this system features the advantage of producing near nitrogen-free syngas in the gasifier, with air as oxidant in the combustor. Baseline experiments with various operating parameters, including air equivalence ratio (ER) and temperature, were firstly performed in a 30 kWth bubbling fluidized-bed gasifier; then, trial tests were conducted with the aforementioned operational and constructional factors. The preliminary test data show positive trends for the enhancement of hydrogen generation via biomass gasification. Further efforts will be pursued to establish a data base, which would be beneficial to extensive researches on clean energy and carbon abatement technologies.

Numerical Approaches for Modeling Gas–Solid Fluidized Bed Reactors: Comparison of Models and Application to Different Technical Problems

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Peter Ostermeier ◽  
Annelies Vandersickel ◽  
Stephan Gleis ◽  
Hartmut Spliethoff
Keyword(s):  
Calcium Carbonate ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Fluid Model ◽  
Industrial Applications ◽  
Small Scale ◽  
Fluidized Bed Reactors ◽  
Discrete Phase Model ◽  
Technical Problems ◽  
Numerical Approaches

Gas–solid fluidized bed reactors play an important role in many industrial applications. Nevertheless, there is a lack of knowledge of the processes occurring inside the bed, which impedes proper design and upscaling. In this work, numerical approaches in the Eulerian and the Lagrangian framework are compared and applied in order to investigate internal fluidized bed phenomena. The considered system uses steam/air/nitrogen as fluidization gas, entering the three-dimensional geometry through a Tuyere nozzle distributor, and calcium oxide/corundum/calcium carbonate as solid bed material. In the two-fluid model (TFM) and the multifluid model (MFM), both gas and powder are modeled as Eulerian phases. The size distribution of the particles is approximated by one or more granular phases with corresponding mean diameters and a sphericity factor accounting for their nonspherical shape. The solid–solid and fluid–solid interactions are considered by incorporating the kinetic theory of granular flow (KTGF) and a drag model, which is modified by the aforementioned sphericity factor. The dense discrete phase model (DDPM) can be interpreted as a hybrid model, where the interactions are also modeled using the KTGF; however, the particles are clustered to parcels and tracked in a Lagrangian way, resulting in a more accurate and computational affordable resolution of the size distribution. In the computational fluid dynamics–discrete element method (CFD–DEM) approach, particle collisions are calculated using the DEM. Thereby, more detailed interparticulate phenomena (e.g., cohesion) can be assessed. The three approaches (TFM, DDPM, CFD–DEM) are evaluated in terms of grid- and time-independency as well as computational demand. The TFM and CFD–DEM models show qualitative accordance and are therefore applied for further investigations. The MFM (as a variation of the TFM) is applied in order to simulate hydrodynamics and heat transfer to immersed objects in a small-scale experimental test rig because the MFM can handle the required small computational cells. Corundum is used as a nearly monodisperse powder, being more suitable for Eulerian models, and air is used as fluidization gas. Simulation results are compared to experimental data in order to validate the approach. The CFD–DEM model is applied in order to predict mixing behavior and cohesion effects of a polydisperse calcium carbonate powder in a larger scale energy storage reactor.

CFD-DEM Modeling of CO2 Capture using Alkali Metal-Based Sorbents in a Bubbling Fluidized Bed

2014 ◽  
Vol 12 (1) ◽  
pp. 441-449 ◽  
Author(s):  
Zhonglin Zhang ◽  
Daoyin Liu ◽  
Yaming Zhuang ◽  
Qingmin Meng ◽  
Xiaoping Chen
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Fluidized Bed Reactors ◽  
Solid Sorbents ◽  
Bubbling Fluidized Bed ◽  
Shrinking Core ◽  
Simulation And Experiment ◽  
Kinetics Simulation ◽  
Reaction Processes ◽  
Back Mixing

Abstract This paper describes a CFD-DEM modeling of CO2 capture using K2CO3 solid sorbents in a bubbling fluidized bed, which takes into heat transfer, hydrodynamics, and chemical reactions. Shrinking core model is applied in reaction kinetics. Simulation and experiment results of bed pressure drop and CO2 concentration in the reactor exit agree well. Instantaneous dynamics as well as time-averaged profiles indicate detailed characteristics of gas flow, particle motion, and chemical reaction processes. The simulation results show an obvious core-annular flow and strong back-mixing flow pattern. CO2 concentration decreases gradually along the bed height, while regards on the lateral distribution CO2 concentration near the wall is lower than that in the middle zone where gas passes through faster. The effect of bubbles on CO2 reaction is two-sided: it can promote mixing which strengthens reaction, while it can be a short pass of gas which is not beneficial to reaction. The simulation is helpful for further understanding and optimal design of fluidized bed reactors of CO2 capture.

Sign in / Sign up

Export Citation Format

Share Document