Fully coupled TFM-DEM simulations to study the motion of fuel particles in a fluidized bed

2015 ◽  
Vol 134 ◽  
pp. 57-66 ◽  
Author(s):  
F. Hernández-Jiménez ◽  
L.M. García-Gutiérrez ◽  
A. Soria-Verdugo ◽  
A. Acosta-Iborra
Keyword(s):  
Fluidized Bed ◽  
Dem Simulations ◽  
Fuel Particles ◽  
Fully Coupled

scholarly journals Modelling of dynamics of combustion of biomass in fluidized beds

2004 ◽  
Vol 8 (2) ◽  
pp. 107-126 ◽  
Author(s):  
Jaakko Saastamoinen
Keyword(s):  
Particle Size ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Fuel Mixture ◽  
Linear Increase ◽  
Fuel Feed ◽  
New Process ◽  
Fuel Particles ◽  
The Stability ◽  
Fluidized Bed Boilers

New process concepts in energy production and biofuel, which are much more reactive than coal, call for better controllability of the combustion in circulating fluidized bed boilers. Simplified analysis describing the dynamics of combustion in fluidized bed and circulating fluidized bed boilers is presented. Simple formulas for the estimation of the responses of the burning rate and fuel inventory to changes in fuel feeding are presented. Different changes in the fuel feed, such as an impulse, step change, linear increase and cyclic variation are considered. The dynamics of the burning with a change in the feed rate depends on the fuel reactivity and particle size. The response of a fuel mixture with a wide particle size distribution can be found by summing up the effect of different fuel components and size fractions. Methods to extract reaction parameters form dynamic tests in laboratory scale reactors are discussed. The residence time of fuel particles in the bed and the resulting char inventory in the bed decrease with increasing fuel reactivity and differences between coal and biomass is studied. The char inventory affects the stability of combustion. The effect of char inventory and oscillations in the fuel feed on the oscillation of the flue gas oxygen concentration is studied by model calculation. A trend found by earlier measurements is explained by the model.

scholarly journals Development and assessment of speed-up algorithms for the reactive CFD–DEM simulation of fluidized bed reactors

2020 ◽  
Vol 5 (2) ◽  
pp. 278-288 ◽  
Author(s):  
Riccardo Uglietti ◽  
Mauro Bracconi ◽  
Matteo Maestri
Keyword(s):  
Fluidized Bed ◽  
Selection Procedure ◽  
Operating Conditions ◽  
Fluidized Bed Reactors ◽  
Effective Algorithm ◽  
Dem Simulation ◽  
Dem Simulations ◽  
Speed Up

PA and ISAT algorithms are developed to speed-up the CFD–DEM simulations of fluidized reactors. Also, a selection procedure of the most effective algorithm according to the operating conditions is developed, enabling the simulation of lab reactors.

scholarly journals Investigation of particle–wall interaction in a pseudo-2D fluidized bed using CFD-DEM simulations

Particuology ◽  
2016 ◽  
Vol 25 ◽  
pp. 10-22 ◽  
Author(s):  
Tingwen Li ◽  
Yongmin Zhang ◽  
Fernando Hernández-Jiménez
Keyword(s):  
Fluidized Bed ◽  
Dem Simulations ◽  
Wall Interaction

A Novel Technique for “In-Situ” Characterization of Devolatilization Rate of Solid Fuels in Fluidized Beds

2005 ◽  
Author(s):  
R. Solimene ◽  
R. Chirone ◽  
A. Marzocchella ◽  
P. Salatino
Keyword(s):  
Fluidized Bed ◽  
Fluidized Beds ◽  
Volatile Matter ◽  
Solid Fuels ◽  
In Situ Characterization ◽  
Flow Restriction ◽  
History Of ◽  
Fuel Particles

The characterization of volatile matter (VM) emission from solid fuel particles during fluidized bed combustion/gasification is relevant to reactor performance influencing the fate of VM as it results from competing phenomena of release, mixing/segregation and burn-out. The rate and the time-history of volatile matter release strongly affect axial segregation of fuel particles in the bed, favoring the establishment of the stratified combustion regime. On the other hand, the comparison between the devolatilization and radial solids mixing time scales affects the radial distribution of volatile matter across the reactor. Short devolatilization times determine VM release localized near feeding point. The knowledge of devolatilization kinetics, as determined by thermogravimetric analysis, does not take into account key process phenomena such as the effective time-temperature history of the devolatilizing particle. A novel and easy-to-use diagnostic technique for “in-situ” characterization of the devolatilization rate of fuel particles in gas fluidized beds is proposed in the present paper. It is based on the time-resolved measurement of pressure in a bench scale fluidized bed reactor equipped with a calibrated flow restriction at the exhaust. The procedure consists of the injection of a single fuel particle (or small batches of multiple particles) and continuous monitoring of the pressure in the reactor. The bed was kept at a constant temperature by external heating and fluidized with nitrogen. Gas pressure inside the reactor increases during devolatilization as a consequence of the increased flow rate, due to the emission of volatile matter, across the calibrated flow restriction at the exhaust. Experimental data are analyzed in the light of a model of the experiment based on the transient mass balance on the reactor volume referred to the fluidizing gas and to the volatile matter. The comparison between experimental pressure time series and model computations enables the characterization of the kinetic parameters of devolatilization rate for samples of different coals as well as of non-fossil solid fuels.

Catalytic Fluidized-Bed Co-Combustion of Peat and Anthracite

2019 ◽  
Vol 19 (3) ◽  
pp. 227-234
Author(s):  
N. A. Yazykov ◽  
A. D. Simonov ◽  
Yu. V. Dubinin ◽  
O. O. Zaikina
Keyword(s):  
Fluidized Bed ◽  
Catalytic Combustion ◽  
Oxide Catalyst ◽  
Fine Particles ◽  
Weight Percent ◽  
Equivalent Diameter ◽  
Coarse Particles ◽  
Fuel Particles ◽  
Fluidized Catalyst Bed ◽  
Industrial Aluminum

Results of the studies of catalytic combustion of peat, anthracite, as well as the mixture at the peat to anthracite weight percent ratio 40/60 are discussed. The degree of the mixture burning-off was shown to increase when peat evolving large quantity of volatile substances is added to anthracite. The burn-up degrees of the solid fuel particles less than 1.25 mm in size were 98.2 % of peat, 50.9 % of anthracite, 74.2 % of the peat and anthracite mixture at 700–750 °C and 1 m height bed of the industrial aluminum-copper-chromium oxide catalyst IC-12-70. In combusting coarse particles (equivalent diameter 11.6–18.6 mm) of molded peat and anthracite mixture, the burn-up degree was 80.5 % at the top of the fluidized catalyst bed. The burn-up degree of the coarse particles fed to the bottom of the fluidized bed was estimated with allowance for the burn-up degree of fine particles moving through the bed. With the coarse molded particles of the peat and anthracite mixture fed to 1 m height catalyst bed, the burn-up degree was shown to reach no less than 95 %. When the catalyst used is 2 mm in size, the peat and anthracite particles comprised in the molded fuel must be no more than 1–1.5 mm in size in order to prevent from ash accumulation in the fluidized catalyst bed.

Control of stoichiometry, microstructure, and mechanical properties in SiC coatings produced by fluidized bed chemical vapor deposition

2008 ◽  
Vol 23 (6) ◽  
pp. 1785-1796 ◽  
Author(s):  
E. López-Honorato ◽  
P.J. Meadows ◽  
J. Tan ◽  
P. Xiao
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Chemical Vapor Deposition ◽  
Young’S Modulus ◽  
Fluidized Bed ◽  
Vapor Deposition ◽  
Young's Modulus ◽  
Chemical Vapor ◽  
Carbide Coatings ◽  
Fuel Particles

Stoichiometric silicon carbide coatings the same as those used in the formation of TRISO (TRistructural ISOtropic) fuel particles were produced by the decomposition of methyltrichlorosilane in hydrogen. Fluidized bed chemical vapor deposition at around 1500 °C, produced SiC with a Young’s modulus of 362 to 399 GPa. In this paper we demonstrate the deposition of stoichiometric silicon carbide coatings with refined microstructure (grain size between 0.4 and 0.8 μm) and enhanced mechanical properties (Young’s modulus of 448 GPa and hardness of 42 GPa) at 1300 °C by the addition of propene. The addition of ethyne, however, had little effect on the deposition of silicon carbide. The effect of deposition temperature and precursor concentration were correlated to changes in the type of molecules participating in the deposition mechanism.

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