scholarly journals INLET TEMPERATURE INFLUENCE ON ISOTHERMAL GAS CLEANING FROM MONO-IMPURITIES BY FIXED LAYER OF ADSORBENT

2020 ◽  
Vol 63 (9) ◽  
pp. 88-92
Author(s):  
Olga N. Filimonova ◽  
Andrey S. Vikulin ◽  
Marina V. Enyutina ◽  
Alexey V. Ivanov
Keyword(s):  
Gas Flow ◽  
Physical Adsorption ◽  
Plug Flow ◽  
Fixed Bed ◽  
Initial Boundary ◽  
Gas Production ◽  
Solid Particles ◽  
Inlet Temperature ◽  
Isothermal Adsorption ◽  
Gas Cleaning

The influence of the temperature of the inlet gas containing mono-impurity was evaluated for the process of physical adsorption purification in a porous fixed bed of granular adsorbent. The theoretical analysis is based on the classical mathematical model of the isothermal adsorption dynamics in a porous stationary medium structurally made-up of the dispersed phase of solid particles, under the assumptions made: the gas to be purified contains a low-concentration mono-impurity, its motion in the adsorber is unidirectional, and the levelling effect of the velocity profile in the porous cross section environment allowed to adopt the hydrodynamic regime of plug flow; axial mixing in the gas flow  is negligible; the adsorption heat is negligible; the layer porosity is uniform; adsorption rate is determined by the sorption kinetics equation with an isotherm, obeying Henry's law. An initial-boundary-value problem is formulated for a system of first-order partial differential equations, which solution with respect to mono-impurity concentrations in the gas stream and adsorbent is obtained in an explicit analytical form using the one-sided integral Laplace transform. A comparative analysis of the computational experiment results with known experimental data showed that the proposed model with an assumptions system is quite adequate qualitatively and quantitatively describes the adsorption separation process. Using the example of an industrial adsorber functioning in the ZB-120/120 complex purification unit in a mobile gas production system, it is shown that the temperature increase by 10 K of inlet dried air after compression containing carbon dioxide reduces the working time in the adsorption stage by 45%. It has been established that the temperature change in the gas inlet flow has a significant effect on the adsorber efficiency and should be taken into account when identifying the overall characteristics of the complex cleaning unit.

A Simplified Numerical Approach to Characterize the Thermal Response of a Moving Bed Solar Reactor

2021 ◽  
Author(s):  
Assaad Al Sahlani ◽  
Kelvin Randhir ◽  
Nesrin Ozalp ◽  
James Klausner
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Energy Storage ◽  
Solid Particle ◽  
Gas Flow ◽  
Plug Flow ◽  
Fixed Bed ◽  
Flow Rates ◽  
Proposed Model ◽  
Simulation Results

Abstract Concentrated solar thermochemical storage in the form of a zero-emission fuel is a promising option to produce long-duration energy storage. The production of solar fuel can occur within a cylindrical cavity chemical reactor that captures concentrated solar radiation from a solar field. A heat transfer model of a tubular plug-flow reactor is presented. Experimental data from a fixed bed tubular reactor are used for model comparison. The system consists of an externally heated tube with counter-current flowing gas and moving solid particles as the heated media. The proposed model simulates the dynamic behavior of temperature profiles of the tube wall, gas, and particles under various gas flow rates and residence times. The heat transfer between gas-wall, solid particle-wall, gas-solid particle, are numerically studied. The model is compared with experiments using a 4 kW furnace with a 150 mm heating zone surrounding a horizontal alumina tube (reactor) with 50.8 mm OD and a thickness of 3.175 mm. Solid fixed particles of magnesium manganese oxide (MgMn2O4) with the size of 1 mm are packed within the length of 250 mm at the center of the tube length. Simulation results are assessed with respect to fixed bed experimental data for four different gas flow rates, namely 5, 10, 15, 20 standard liters per minute of air, and furnace temperatures in the range of 200 to 1200 °C. The simulation results showed good agreement with maximum steady state error that is less than 6% of those obtained from the experiments among all runs. The proposed model can be implemented as a low-order physical model for the control of temperature inside plug-flow reactors for thermochemical energy storage (TCES) applications.

scholarly journals The Numerical Modeling of Gas Movement in a Single Inlet New Generation Multi-Channel Cyclone Separator

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8092
Author(s):  
Aleksandras Chlebnikovas ◽  
Artūras Kilikevičius ◽  
Jaroslaw Selech ◽  
Jonas Matijošius ◽  
Kristina Kilikevičienė ◽  
...  
Keyword(s):  
Gas Flow ◽  
Numerical Models ◽  
Research Process ◽  
Solid Particles ◽  
Gas Flows ◽  
Cyclone Separator ◽  
Cleaning Efficiency ◽  
Gas Cleaning ◽  
Viscosity Models ◽  
New Generation

The work of traditional cyclones is based on the separation of solid particles using only the centrifugal forces. Therefore, they do not demonstrate high gas-cleaning efficiency, particularly in the cases where gas flows are polluted with fine solid particles (about 20 µm in diameter). The key feature of a new-generation multi-channel cyclone separator’s structure is that its symmetrical upgraded curved elements, with openings cut with their plates bent outwards, make channels for the continuous movement of the gas flows from the inflow opening to the central axis. The smoke flue of the vertical gas outflow is located near the cover of the separating chamber. The present work is aimed at studying the applicability of two various viscosity models and their modified versions to simulate aerodynamic processes in an innovative design for a multi-channel cyclone separator with a single inflow, using the computational fluid dynamics. The research results obtained in the numerical simulation are compared to the experimental results obtained using a physical model. The main purpose of this study is to provide information on how the new design for the multi-channel cyclone affects the distribution of gas flow in the cyclone’s channels. The modified viscosity models, k-ε and k-ω, and computational meshes with various levels of detailed elaboration were analyzed. The developed numerical models of a single-inlet multi-channel cyclone separator allow the researchers to describe its advantages and possible methods of improving its new structure. The developed models can be used for simulating the fluid cleaning phenomenon in the improved fourth-channel cyclone separator and to optimize the whole research process.

scholarly journals STEADY STATE FIXED BED COMBUSTION OF WOOD PELLETS. A SIMPLE THEORETICAL MODEL

2014 ◽  
Vol 13 (2) ◽  
pp. 59
Author(s):  
C. Pinho ◽  
T. Ferreira ◽  
E. Marques ◽  
D. Almeida ◽  
C. Pereira ◽  
...  
Keyword(s):  
Steady State ◽  
Gas Flow ◽  
Combustion Process ◽  
Fixed Bed ◽  
Solid Particles ◽  
Volatile Components ◽  
Wood Pellets ◽  
Gaseous Flow ◽  
Combustion Gas ◽  
Biomass Particles

The combustion of biomass follows a sequence of several distinct phases which begin with drying, the subsequent pyrolysis with the release of volatile components that burn in gaseous phase and finally the combustion of carbonaceous resiue, the time consuming step. For small solid fuel boilers, as it is the case of pellet boilers for domestic heating, biomass particles are continuously burned in fixed bed boilers or heaters. In these appliances the furnace is a metallic basket into which fuel particles are thrown and burn. The combustion air is introduced through orifices drilled in this metallic basket although some lateral air entrances are also found. The gaseous flow is a piston flow, the particles fall under gravity on the upper bed surface and as they burn they slowly move downwards until their size is small enough to fall down through the air entrance orifices or are dragged by the upcoming combustion gas flow. So the gaseous current has an up flow movement while the solid particles move downwards. It is assumed that the bed is at uniform temperature and all the average properties of the gaseous flow are constant with the exception of the oxygen concentration that diminishes as the gas flow rises through the bed. The mathematical development of a simple model that allows the calculation of the steady state burning time of a biomass particle in fixed bed, the amount of energy released, the fixed bed size and its particle inventory, is hereby presented. The pedagogical interest of this model is pertinent because it presents, in a synthetic way, the relative importance of the combustion kinetic, the mass transfer mechanism and the reactor fluid dynamics, upon the lifetime of a biochar particle during its combustion process.

A SIMPLIFIED NUMERICAL APPROACH TO CHARACTERIZE THE THERMAL RESPONSE OF A MOVING BED SOLAR REACTOR

2021 ◽  
pp. 1-6
Author(s):  
Assaad Alsahlani ◽  
Kelvin Randhir ◽  
Nesrin Ozalp ◽  
James Klausner
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Solid Particle ◽  
Gas Flow ◽  
Plug Flow ◽  
Fixed Bed ◽  
Tube Length ◽  
Flow Rates ◽  
Proposed Model ◽  
Simulation Results

Abstract In this paper, heat transfer model of a tubular plug-flow reactor designed and manufactured for a solar fuel production is presented. Experimental data collected from a fixed bed tubular reactor testing are used for model comparison. The system consists of an externally heated tube with counter-current flowing gas and moving solid particles as the heated media. The proposed model simulates the dynamic behavior of temperature profiles of the tube wall, gas, and particles under various gas flow rates and residence times. The heat transfer between gas-wall, solid particle-wall, and gas-solid particle are numerically studied. The model results are compared with the results of experiments done using a 4 kW furnace with a 150 mm heating zone surrounding a horizontal alumina tube (reactor) with 50.8 mm outer diameter and thickness of 3.175 mm. Solid fixed particles of MgMn2O4 with the size of 1 mm are packed within length of 250 mm at the center of the tube length. Simulation results are assessed with respect to fixed bed experimental data for four different gas flow rates, namely 5, 10, 15, 20 standard liters per minute of air, and furnace temperatures in the range of 200 to 1200 °C. The simulation results showed good agreement with maximum steady state error that is less than 6% of those obtained from the experiments for all runs. The proposed model can be implemented as a low-order physical model for the control of temperature inside plug-flow reactors.

scholarly journals MODELING OF A DUSTED GAS FLOW CLEANING PROCESS USING A KINEMATIC MODEL OF THE INTERACTION OF DISPERSED PARTICLES WITH DROPLETS IN A WET SCRUBBER

2021 ◽  
pp. 84-98
Author(s):  
I.A. Volchyn ◽  
V.A. Raschepkin
Keyword(s):  
Mathematical Model ◽  
Gas Flow ◽  
Kinematic Model ◽  
Significant Proportion ◽  
Solid Particles ◽  
Venturi Tube ◽  
Gas Cleaning ◽  
Dispersed Particles ◽  
Spray Density ◽  
Wet Scrubber

A mathematical model is proposed for the scavenging process of the dispersed particles by droplets in a wet scrubber under excess spray density in Venturi tube within kinematic approach of the interaction of particles in countercurrent gas-dispersed flows, which refines the existing engineering model, taking into account the spatial size variation of the droplets, due to their coagulation with wet slurry droplets and uncaptured particles entering a wet scrubber from the Venturi tube. The results of calculations with the adopted mathematical model showed that in case of possibility to organize the spraying of a gas flow in a scrubber with 300–500 micron droplets aerosol at a specific spray density of about 1 liter/m3, a 1–2 meters wide layer of droplets ensures effective absorption of both uncaptured PM2.5 solid particles, and the slurry droplets from the Venturi tube. The ejection of the slurry droplets into a wet scrubber from the Venturi tube, and the associated increase in the size of the scrubber droplets due to coagulation with slurry droplets, does not noticeably affect the efficiency of the dusted gas stream cleaning. An adopted mathematical model was applied to calculate the capture of particles by droplets in cylindrical and conical scrubbers. Due to the increase in a residence time of the droplets upon increased velocity of the countercurrent gas flow, the efficiency of gas cleaning from dispersed particles in a conical scrubber appears to be higher than in a cylindrical scrubber. However, with an increase in the spray density above 2 liter/m3 and with droplet diameters greater than 1000 microns, the efficiency of the conical scrubber decreases, which is associated to an increase in the escape of a significant proportion of massive drops to the walls with a reduction in the scrubber reactor cross-section.  Bibl. 21, Fig. 4.

Gasification as an optimum alternative for the sludge management

2011 ◽  
Vol 6 (4) ◽  
Author(s):  
C. Peregrina ◽  
J. M. Audic ◽  
P. Dauthuille
Keyword(s):  
Power Generation ◽  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Combined Heat And Power ◽  
Gas Production ◽  
Waste Reduction ◽  
Fluidised Bed ◽  
Sludge Management ◽  
Gas Cleaning ◽  
Cleaning System

Assimilate sludge to a fuel is not new. Sludge incineration and Combined Heat and Power (CHP) engines powered with sludge-derived anaerobic digestion gas (ADG) are operations widely used. However, they have a room of improvement to reach simultaneously a positive net power generation and a significant level of waste reduction and stabilization. Gasification has been used in other realms for the conversion of any negative-value carbon-based materials, that would otherwise be disposed as waste, to a gaseous product with a usable heating value for power generation . In fact, the produced gas, the so-called synthetic gas (or syngas), could be suitable for combined heat and power motors. Within this framework gasification could be seen as an optimum alternative for the sludge management that would allow the highest waste reduction yield (similar to incineration) with a high power generation. Although gasification remains a promising route for sewage sludge valorisation, campaigns of measurements show that is not a simple operation and there are still several technical issues to resolve before that gasification was considered to be fully applied in the sludge management. Fluidised bed was chosen by certain technology developers because it is an easy and well known process for solid combustion, and very suitable for non-conventional fuels. However, our tests showed a poor reliable process for gasification of sludge giving a low quality gas production with a significant amount of tars to be treated. The cleaning system that was proposed shows a very limited removal performance and difficulties to be operated. Within the sizes of more common WWTP, an alternative solution to the fluidised bed reactor would be the downdraft bed gasifier that was also audited. Most relevant data of this audit suggest that the technology is more adapted to the idea of sludge gasification presented in the beginning of this paper where a maximum waste reduction is achieved with a great electricity generation thanks to the use of a “good” quality syngas in a CHP engine. Audit show also that there is still some work to do in order to push sludge gasification to a more industrial stage. Regardless what solution would be preferred, the resulting gasification system would involve a more complex scenario compared to Anaerobic Digestion and Incineration, characterised by a thermal dryer and gasifier with a complete gas cleaning system. At the end, economics, reliability and mass and energy yields should be carefully analysed in order to set the place that gasification would play in the forthcoming processing of sewage sludge.

scholarly journals Development of a simplified gas ultracleaning process: experiments in biomass residue-based fixed-bed gasification syngas

2021 ◽  
Author(s):  
Christian Frilund ◽  
Esa Kurkela ◽  
Ilkka Hiltunen
Keyword(s):  
Activated Carbons ◽  
Low Cost ◽  
Fixed Bed ◽  
Carbonyl Sulfide ◽  
Gas Analysis ◽  
Small Scale ◽  
Cleaning Process ◽  
Medium Temperature ◽  
Gas Cleaning ◽  
Adsorption Affinity

AbstractFor the realization of small-scale biomass-to-liquid (BTL) processes, low-cost syngas cleaning remains a major obstacle, and for this reason a simplified gas ultracleaning process is being developed. In this study, a low- to medium-temperature final gas cleaning process based on adsorption and organic solvent-free scrubbing methods was coupled to a pilot-scale staged fixed-bed gasification facility including hot filtration and catalytic reforming steps for extended duration gas cleaning tests for the generation of ultraclean syngas. The final gas cleaning process purified syngas from woody and agricultural biomass origin to a degree suitable for catalytic synthesis. The gas contained up to 3000 ppm of ammonia, 1300 ppm of benzene, 200 ppm of hydrogen sulfide, 10 ppm of carbonyl sulfide, and 5 ppm of hydrogen cyanide. Post-run characterization displayed that the accumulation of impurities on the Cu-based deoxygenation catalyst (TOS 105 h) did not occur, demonstrating that effective main impurity removal was achieved in the first two steps: acidic water scrubbing (AWC) and adsorption by activated carbons (AR). In the final test campaign, a comprehensive multipoint gas analysis confirmed that ammonia was fully removed by the scrubbing step, and benzene and H2S were fully removed by the subsequent activated carbon beds. The activated carbons achieved > 90% removal of up to 100 ppm of COS and 5 ppm of HCN in the syngas. These results provide insights into the adsorption affinity of activated carbons in a complex impurity matrix, which would be arduous to replicate in laboratory conditions.

scholarly journals Thermochemical Heat Storage in a Lab-Scale Indirectly Operated CaO/Ca(OH)2 Reactor—Numerical Modeling and Model Validation through Inverse Parameter Estimation

2021 ◽  
Vol 11 (2) ◽  
pp. 682
Author(s):  
Gabriele Seitz ◽  
Farid Mohammadi ◽  
Holger Class
Keyword(s):  
Numerical Model ◽  
Gas Flow ◽  
Reaction Rate ◽  
Heat Storage ◽  
Bulk Material ◽  
Fixed Bed ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Thermochemical Heat Storage ◽  
Speed Up

Calcium oxide/Calcium hydroxide can be utilized as a reaction system for thermochemical heat storage. It features a high storage capacity, is cheap, and does not involve major environmental concerns. Operationally, different fixed-bed reactor concepts can be distinguished; direct reactor are characterized by gas flow through the reactive bulk material, while in indirect reactors, the heat-carrying gas flow is separated from the bulk material. This study puts a focus on the indirectly operated fixed-bed reactor setup. The fluxes of the reaction fluid and the heat-carrying flow are decoupled in order to overcome limitations due to heat conduction in the reactive bulk material. The fixed bed represents a porous medium where Darcy-type flow conditions can be assumed. Here, a numerical model for such a reactor concept is presented, which has been implemented in the software DuMux. An attempt to calibrate and validate it with experimental results from the literature is discussed in detail. This allows for the identification of a deficient insulation of the experimental setup. Accordingly, heat-loss mechanisms are included in the model. However, it can be shown that heat losses alone are not sufficient to explain the experimental results. It is evident that another effect plays a role here. Using Bayesian inference, this effect is identified as the reaction rate decreasing with progressing conversion of reactive material. The calibrated model reveals that more heat is lost over the reactor surface than transported in the heat transfer channel, which causes a considerable speed-up of the discharge reaction. An observed deceleration of the reaction rate at progressed conversion is attributed to the presence of agglomerates of the bulk material in the fixed bed. This retardation is represented phenomenologically by mofifying the reaction kinetics. After the calibration, the model is validated with a second set of experimental results. To speed up the calculations for the calibration, the numerical model is replaced by a surrogate model based on Polynomial Chaos Expansion and Principal Component Analysis.

Hydrogen Production from Ethanol Steam Reforming: Fixed Bed Reactor Design

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Pablo Giunta ◽  
Norma Amadeo ◽  
Miguel Laborde
Keyword(s):  
Steam Reforming ◽  
Flow Model ◽  
Multicomponent Mixture ◽  
Plug Flow ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Ethanol Steam Reforming ◽  
Heterogeneous Model ◽  
Ethanol Steam ◽  
Hydrogen Stream

The aim of this work is to design an ethanol steam reformer to produce a hydrogen stream capable of feeding a 60 kW PEM fuel cell applying the plug flow model, considering the presence of the catalyst bed (heterogeneous model). The Dusty-Gas Model is employed for the catalyst, since it better predicts the fluxes of a multicomponent mixture. Moreover, this model has shown to be computationally more robust than the Fickian Model. A power law-type kinetics was used. Results showed that it is possible to carry out the ethanol steam reforming in a compact device (1.66 x 10 -5 to 5.27 x 10 -5 m3). It was also observed that this process is determined by heat transfer.

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