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![3.1: Schematic of an updraft gasifier [4].](profile/Amir-Mahmoudi/publication/289532943/figure/fig2/AS:670721990733835@1536923992737/1-Schematic-of-an-updraft-gasifier-4.png)
![Figure 1.3.1: Schematic of an updraft gasifier [4].](profile/Amir-Mahmoudi/publication/289532943/figure/fig2/AS:670721990733835@1536923992737/1-Schematic-of-an-updraft-gasifier-4_Q320.jpg)
![Figure 1.3.2: Schematic of a downdraft gasifier [4].](profile/Amir-Mahmoudi/publication/289532943/figure/fig3/AS:670721990742037@1536923992756/2-Schematic-of-a-downdraft-gasifier-4_Q320.jpg)
![Figure 1.3.3: Schematic of a crossdraft gasifier [4].](profile/Amir-Mahmoudi/publication/289532943/figure/fig4/AS:670721990721556@1536923992772/3-Schematic-of-a-crossdraft-gasifier-4_Q320.jpg)
Citations
... Gasification is of particular importance as it produces syngas, a mixture of H2, CO, and CO2, which can then be used for the synthesis of a plethora of chemicals and fuels. The syngas can be refined and used as a fuel itself [6]. In a traditional gasification process, the biomass is reacted with air and steam in a single reactor as seen in Figure 1. ...
... Traditional Gasifier[6] ...
This study theoretically investigates the air pollution control of a sorption enhanced reforming (SER) gasification process used to produce syngas at the University of British Columbia. The flue gas produced from the SER process is high in PM and NO2 emissions that are not within the limits set by the Metro Vancouver emissions permit. The PM and NO2 concentrations released by the SER process are 969 mg/m 3 and 1660 mg/m 3 and the Metro Vancouver permit limits are 15 mg/m 3 and 271.7 mg/m 3 , respectively. A 98% reduction is required in the PM concentration and an 83% reduction is required in the NO2 concentration to meet the Metro Vancouver permit limits. The emissions reduction was achieved through the design of an electrostatic precipitator (ESP) to reduce PM emissions and a selective catalytic reduction (SCR) process to reduce NO2 emissions. An ESP with a collection plate area of 243 m 2 and an electric field strength of 95.34 kV/m is required to achieve the PM emissions reduction. An SCR reactor with a catalyst volume of 46.76 ft 3 and a catalyst area of 5.36 ft 2 is required to achieve the NO2 emissions reduction. The stack height that is required for flue gas release according to good engineering practice is 53.3 meters. The resultant maximum ground-level centerline concentrations for the PM and NO2 after implementation of the air pollution control technologies was calculated to be 0.1 μg/m 3 and 1.73 μg/m 3 , respectively. The distance to these maximum concentrations was calculated to be 521.8 meters. 3
... The discrete particle method (DPM), developed by [42], is a numerical tool that deals with the movement and thermochemical conversion of particulate material. The DPM model considers a solid particle as an individual entity with the conversion and its motion [30,32,43]. ...
Growing energy demand and environmental concern have constantly pressured the energy industry to apply increasingly efficient combustion methods. Knowing this, and in order to take advantage of the great availability of biomass energy resources from agro-industrial processes in Brazil, the US company Brayton Energy designed a cyclonic combustion chamber as a component of an externally fired gas turbine for power generation using pulverized solid biomass fuels. In this study, numerical simulations were performed using Computational Fluid Dynamics (CFD) to evaluate the fluid dynamic design and the combustion process of biomass particles in this horizontal cyclonic combustion chamber. The simulations were performed in ANSYS FLUENT using the turbulence models RNG k-ε and SST k-ω. For the combustion simulations, the Species Transport model was used, alongside the combined method finite rate/eddy dissipation for the turbulence and the chemical reaction interactions. The Discrete Phase Model (DPM) was used for the biomass particles tracking and the Discrete Ordinates model (DO) for the radiation representation. The results of the cold-flow simulations show the profile of axial and tangential velocities within the cyclonic chamber and the formation of the recirculation zones. The recirculation zones with the RNG model showed average velocities of − 35 m/s and − 20 m/s, which indicates the possibility of flame formation inside the combustor. The temperatures of fuel particles at the outlet of the biomass feed pipe reached approximately 470 K, which is a suitable temperature and indicates that the particles are ready to devolatilize inside the combustor. Based on the contours of axial velocities inside the combustor, temperature and the release region of the volatile species, it is concluded that the design of the cyclonic chamber allows the formation of the flame inside the combustor and also the complete combustion of the biomass particles, showing that, despite needing some improvements and optimizations, this cyclonic combustion chamber can be an interesting alternative for power generation with pulverized biomass fuel.
Graphical Abstract
... The model was validated against two separate experimental works depicted in Fig. 9. Profile of the temperature growth on the bed surface was simulated using the developed model based upon the given initial and boundary conditions of the packed bed experiment by Porteiro et al. [45]. Furthermore, the model was validated against another experimental result of mass loss presented within a work by Mahmoudi [46]. The validation results prove a quite good agreement between the developed model prediction and the experiments. ...
... a Ref.[45]. b Ref.[46] ...
Biomass has great potential to meet greenhouse gas reduction and fuel supply security in the future. Although the grate biomass combustors are increasingly deployed worldwide to generate energy from solid biomass, challenges in understanding the system operation to some extent have remained. This paper analyzes the effects of fuel composition uncertainty on the biomass grate combustor’s performance, which have not been solved so far. A 1D transient numerical model of the biomass fuel bed combustion is developed. A set of thermal gravimetric analysis (TGA) experiments on randomly selected biomass particles from the same fuel supplier are conducted to achieve the proximate analysis of the particles. The Bayesian model averaging (BMA) method was exercised to deliver the fuel uncertainty into the CFD model of the fuel bed. Results revealed that the fuel composition variability can significantly affect the solid fuel conversion so that ignoring them can result in incomplete combustion. In three various scenarios proposed, combustor is analyzed: (I) using primary fuel composition given by the producer, (II) mean value of fuel composition obtained from the BMA model, and lastly (III) fuel composition under fully uncertainty conditions. Results revealed that overlooking the fuel uncertainty results in overestimating system energy output by 8.3% and also can waste 1611-kg feed annually which is roughly 5% of whole consumed fuel. Meanwhile, owing to uncertainty associated with fuel composition, flame temperature can fluctuate up to 15 °C. According to the uncertainty analysis, char content of wood pellets has dominating role in fuel quality. Finally, a life cycle analysis (LCA) is conducted for the first, second, and coal-fueled system scenarios.
... The performance of a gasifier depends majorly on the type of gasifier and its design characteristics (Laciak et al., 2016, Puig-Arnavat et al., 2010. Based on the position of air inlet and product gas outlet, gasifier can also be classified into three types: i.e. downward draft, upward draft and cross-draft gasifiers (Mahmoudi, 2015). In case of upward draft gasifier, the hot air/oxygen/steam enters the gasification unit from the bottom of the ash bed (through the grate section) of the gasifier and moves up the unit to leave from the top, whereas the biomass feed moves in downward direction (Virmond et al., 2013). ...
Currently, energy security and environmental protection are two of the major concerns the world is facing. Electricity generation, being one of the fastest growing and most polluting sectors, needs to be improved with incorporation of efficient, sustainable, cost-effective and eco-friendly fuels and methods. Biomass can be such a fuel as it is abundantly available and carbon neutral. For generation of electricity from biomass, combustion, gasification and digestion can be utilized. This chapter focusses on the biomass digestion (BD) for generation of electricity. It consists of four steps, namely, pretreatment, anaerobic digestion, gas cleaning and electricity generation. Pretreatment consists of physical, chemical and/or biological operations to expose sites for microbial attack. In anaerobic digestion, biomass is converted into biogas, mainly consisting methane (CH4), in the absence of air by the action of microorganisms. Anaerobic digestion mainly follows four major steps, i.e. hydrolysis, acidogenesis, acetogenesis and methanogenesis. The undesirable components in resultant biogas, such as hydrogen sulphide (H2S), oxygen (O2), nitrogen (N2), water (H2O), carbon dioxide (CO2) and particle traces, can cause corrosion in the downstream equipment and can reduce thermal efficiency of the process. Therefore, gas cleaning and upgradation is employed to overcome such challenges. The chemical energy of the biogas can be converted into electricity using it in external and internal combustion engines and/or fuel cells. Alternatively, pressurized steam can be produced by biogas combustion to drive steam turbines. In addition, methane-rich biogas can be utilized in a reformer to produce syngas, a mixture of carbon monoxide (CO) and hydrogen (H2), to drive combined cycle and/or to produce variety of chemicals including gaseous and liquid fuels.KeywordsBiomassDigestionBiogasRenewable energyMathematical modelLife cycle assessmentHydrolysisAcidogenesisAcetogenesisMethanogenesis
... This is deemed a limitation of the fuel bed experiment. Additionally, the predicted fuel bed conversion obtained by current simulation is in line with an earlier experiment, based on a study by Yin et al. [42], showing the contribution of drying, devolatilization, and char burnout in different lengths of a moving grate. ...
... Moreover, as drying, pyrolysis, and char oxidation happen in different lengths of the grate, the primary air distribution should be updated by the wind-box mechanism under the grate, in order to speed up the conversion process inside the fuel bed. According to Yin et al. [42,46], about 40% of primary air is injected to the fuel bed from the grate opening until complete volatile decomposition, and the rest of air is distributed between middle and last zone with a ratio of 2:1. In the utilized biomass combustor, three equal wind-boxes are equipped under the grate in which the primary air is distributed for an efficient conversion. ...
This paper analyzes a moving grate biomass boiler operating with three alternative waste fuels, including biomass pellets, wood waste, and refuse-derived fuel (RDF) from a combination of thermal, economic, and environmental perspectives. The focus of this paper is on system functionality adaptation to retrofit the current systems operational conditions. A one-dimensional numerical bed model integrated with a black-box overbed model was developed to carefully investigate the fuel bed’s thermal characteristics, as well as the boiler’s output. According to the results, the system operates more efficiently under the biomass pellets feeding and annually generates 548 GJ heat, while it drops significantly in other scenarios. The system was economically evaluated based on a 25-year life cycle cost analysis. Subsequently, an internal rate of return (IRR) of 36% was calculated for biomass pellets, while the value reduced by 50% and 27% regarding wood waste and RDF, respectively. The fuel cost was identified as the main contributor to the total life cycle cost of the heating system, regardless of which feeding fuel was utilized. A long-term environmental impacts assessment of the boiler operation emerged, to show how plant-based fuels can significantly decrease the impacts of climate change that have originated from fossil fuel usage. The current study concludes that all the proposed scenarios are feasible to different degrees, and can extensively benefit a diverse set of energy sectors.
... The idea is to observe or simulate a fuel column as it travels through the screw feeder tube, referred to as the Lagrange view (Fig. 2). For many applications a sufficient description of the conversion process is achieved [9,10] and the calculation is much faster than for more complex 3D models [11]. Thanks to short calculation times, this model allows numerous parameter variations and serves to provide the boundary conditions for subsequent 3D flow simulations of the gas phase. ...
A combined 1D-fuel-bed and 3D-CFD model for the simulation of an innovative 35 kW screw burner has been developed and validated with experiments. The 1D-fuel-bed model is a further development of a previously presented walking column approach and accounts for the special transport conditions in a screw burner. A new reduced chemical mechanism combined with the Eddy Dissipation Concept (EDC) combustion model is used in the subsequent 3D-CFD simulation. Detailed and reduced mechanisms are first compared in an opposed jet burner and then an improved reduced chemistry model is used in CFD calculations to investigate the influence of different primary and secondary air settings and to be validated with experimental data from a 35 kW prototype burner. The model enables a reasonable prediction of the trends of variations of the excess air ratio in the primary zone (primary λ) and of the global excess air on the emissions and the heat output and is therefore suitable for the design of biomass combustion systems with a moving fuel bed.
... where F c i , M i,j , F ext i , v i , ω i , and I i are respectively the contact forces, torques and external forces acting on particle i, the linear velocity, the angular velocity, and the moment of inertia. The reader is referred to the literature for more information (Hoffmann, 2014;Mahmoudi, 2016;Michael, 2014;Samiei, 2012). ...
The extended discrete element method (XDEM) multi-physics and multi-scale simulation platform is being developed at the Institute of Computational Engineering, the University of Luxembourg. The platform is an advanced multi-physics simulation technology that combines flexibility and versatility to establish the next generation of multi-physics and multi-scale simulation tools. For this purpose, the simulation framework relies on coupling various predictive tools based on an Eulerian and Lagrangian approach. The Eulerian approach represents the wide field of continuum models; the Lagrangian approach is perfect for characterising discrete phases. Continuum models thus include classical simulation tools, such as computational fluid dynamics simulation and finite element analysis, while an extended configuration of the classical discrete element method addresses the discrete (e.g., particulate) phase. Apart from predicting the trajectories of individual particles, XDEM-suite extends the application of the XDEM to estimating the thermodynamic state of each particle using advanced and optimised algorithms. The thermodynamic state may include temperature and species distributions due to chemical reaction and external heat sources. Hence, coupling these extended features with either computational fluid dynamics simulation or finite element analysis opens a wide range of applications as diverse as pharmaceuticals, agriculture, food processing, mining, construction and agricultural machinery, metals manufacturing, energy production and systems biology. © 2018 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences
... where F c i , M i,j , F ext i , v i , ω i , and I i are respectively the contact forces, torques and external forces acting on particle i, the linear velocity, the angular velocity, and the moment of inertia. The reader is referred to the literature for more information (Hoffmann, 2014;Mahmoudi, 2016;Michael, 2014;Samiei, 2012). ...
The XDEM multi-physics and multi-scale simulation platform roots in the Ex- tended Discrete Element Method (XDEM) and is being developed at the In- stitute of Computational Engineering at the University of Luxembourg. The platform is an advanced multi- physics simulation technology that combines flexibility and versatility to establish the next generation of multi-physics and multi-scale simulation tools. For this purpose the simulation framework relies on coupling various predictive tools based on both an Eulerian and Lagrangian approach. Eulerian approaches represent the wide field of continuum models while the Lagrange approach is perfectly suited to characterise discrete phases. Thus, continuum models include classical simulation tools such as Computa- tional Fluid Dynamics (CFD) or Finite Element Analysis (FEA) while an ex- tended configuration of the classical Discrete Element Method (DEM) addresses the discrete e.g. particulate phase. Apart from predicting the trajectories of individual particles, XDEM extends the application to estimating the thermo- dynamic state of each particle by advanced and optimised algorithms. The thermodynamic state may include temperature and species distributions due to chemical reaction and external heat sources. Hence, coupling these extended features with either CFD or FEA opens up a wide range of applications as diverse as pharmaceutical industry e.g. drug production, agriculture food and processing industry, mining, construction and agricultural machinery, metals manufacturing, energy production and systems biology.
... Eq. 11 to 14 for the porous media also contain source terms to account for chemical reactions, which have to be modelled adequately. For completeness it shall be mentioned that Mahmoudi has recently presented a first approach of semi resolved resolution for the fluid phase [55]. ...
A brief overview is given on the capabilities and on the current limitations of the Discrete Element Method (DEM) coupled with Computational Fluid Mechanics (CFD) to simulate chemical reacting moving granular material. An approach to resolve the internal transport and reaction phenomena in particles of complex geometry is presented. Heat and mass transfer from and to the particles are accounted for as well as heat transfer between particles and between particles and a surrounding gas phase including radiation. Gas phase reactions outside the particle interact with inner particle processes.
Examples will be shown to demonstrate the capabilities of DEM/CFD coupling. These examples are an industrial scale lime shaft kilns, the simulation of a domestic pellet stove and a grate firing system for the incineration of municipal waste. The advantages of a DEM/CFD approach will be highlighted but also the still existing drawbacks and limitations are discussed. The paper ends with an outlook on necessary developments to make DEM/CFD a standard engineering tool for chemically reacting granular material.
... Generally, the involved phenomena are highly coupled in space and time and high temperature, multi-phase flow, chemical aggressive atmospheres and particulate, poly-disperse feedstock make it very difficult to gain insights into such systems. In order to study the processes occurring in such systems multi-physics numerical modelling has been developed and improved in recent years [2,3,4,5]. Such approaches individually account for the particulate and the continuous phases present: Particulate matter treated by a discrete approach may undergo motion and thermal conversion. ...
Numerical modelling of particulate matter has gained much popularity in recent decades. Advanced Multi-physics Simulation Technology (AMST) is a state-of-the-art three dimensional numerical modelling technique combining the eX-tended Discrete Element Method (XDEM) with Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) [1]. One major limitation of this code is the lack of a graphical user interface (GUI) meaning that all pre-processing has to be made directly in a HDF5-file. This contribution presents the first graphical pre-processor developed for AMST.
