scholarly journals Nanopowder Fluidization Using the Combined Assisted Fluidization Techniques of Particle Mixing and Flow Pulsation

2019 ◽  
Vol 9 (3) ◽  
pp. 572 ◽  
Author(s):  
Syed Ali ◽  
Avijit Basu ◽  
Sulaiman Alfadul ◽  
Mohammad Asif
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Substantial Reduction ◽  
Data Acquisition System ◽  
Gas Flow Rate ◽  
Flow Pulsation ◽  
Pressure Transducers ◽  
Particle Mixing ◽  
Group A ◽  
Sensitive Pressure

In the present study, we report the fluidization behavior of ultrafine nanopowder using the assisted fluidization technique of particle mixing, which was further superimposed with the pulsation of the inlet gas flow to the fluidized bed. The powder selected in the present study was hydrophilic nanosilica, which shows strong agglomeration behavior leading to poor fluidization hydrodynamics. For particle mixing, small proportions of inert particles of Geldart group A classification were used. The inlet gas flow to the fluidized bed was pulsed with a square wave of frequency 0.1 Hz with the help of a solenoid valve controlled using the data acquisition system (DAQ). In addition to the gas flow rate to the fluidized bed, pressure transients were carefully monitored using sensitive pressure transducers connected to the DAQ. Our results indicate a substantial reduction in the effective agglomerate size as a result of the simultaneous implementation of the assisted fluidization techniques of particle mixing and flow pulsation.

Predicting bed dynamics in three-phase, fluidized-bed biofilm reactors

1994 ◽  
Vol 29 (10-11) ◽  
pp. 231-241 ◽  
Author(s):  
H. T. Chang ◽  
B. E. Rittmann
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Liquid Flow Rate ◽  
Gas Flow Rate ◽  
Biofilm Growth ◽  
Biofilm Thickness ◽  
Three Phase ◽  
Proper Design

This paper presents a unified model that inter-relates gas flow rate, liquid flow rate, and hold-ups of each of the liquid, gas, and solid phases in three-phase, fluidized-bed biofilm (TPFBB) process. It describes how carrier properties, biofilm properties, and gas and liquid flow velocities control the system dynamics, which ultimately will affect the density, thickness, and distribution of the biofilm. The paper describes the development of the mathematical model to correlate the effects of gas flow rate, liquid flow rate, solid concentration, and biofilm thickness and density. This knowledge is critically needed in light of the use of TPFBB processes in treating industrial wastewater, which often has high substrate concentration. For example, the proper design of the TPFBB process requires mathematical description of the cause-effect relationship between biofilm growth and fluidization.

scholarly journals Deagglomeration of Ultrafine Hydrophilic Nanopowder Using Low-Frequency Pulsed Fluidization

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 388 ◽  
Author(s):  
Ebrahim H. Al-Ghurabi ◽  
Mohammed Shahabuddin ◽  
Nadavala Siva Kumar ◽  
Mohammad Asif
Keyword(s):  
Fluidized Bed ◽  
Low Frequency ◽  
Frequency Domain Analysis ◽  
Wave Flow ◽  
Velocity Change ◽  
Pressure Transducers ◽  
Wide Range ◽  
Transient Data ◽  
Flow Pulsations ◽  
Sensitive Pressure

Low-frequency flow pulsations were utilized to improve the hydrodynamics of the fluidized bed of hydrophilic ultrafine nanosilica powder with strong agglomeration behavior. A gradual fluidization of unassisted fluidized bed through stepwise velocity change was carried out over a wide range of velocities followed by a gradual defluidization process. Bed dynamics in different regions of the fluidized bed were carefully monitored using fast and sensitive pressure transducers. Next, 0.05-Hz square-wave flow pulsation was introduced, and the fluidization behavior of the pulsed fluidized bed was rigorously characterized to delineate its effect on the bed hydrodynamics by comparing it with one of the unassisted fluidized bed. Flow pulsations caused a substantial decrease in minimum fluidization velocity and effective agglomerate diameter. The frequencies and amplitudes of various events in different fluidized bed regions were determined by performing frequency domain analysis on real-time bed transient data. The pulsations and their effects promoted deagglomeration and improved homogeneity of the pulsed fluidized bed.

scholarly journals Hydrodynamics of Pulsed Fluidized Bed of Ultrafine Powder: Fully Collapsing Fluidized Bed

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 807 ◽  
Author(s):  
Mohammad Asif ◽  
Ebrahim H. Al-Ghurabi ◽  
Abdelhamid Ajbar ◽  
Nadavala Siva Kumar
Keyword(s):  
Fluidized Bed ◽  
Ultrafine Particles ◽  
Frequency Domain Analysis ◽  
Wave Flow ◽  
Pressure Transducers ◽  
Flow Pulsations ◽  
Mass Flow Controllers ◽  
Analog Output ◽  
Sensitive Pressure ◽  
Complete Collapse

The processing of fine and ultrafine particles using a fluidized bed is challenging in view of their unpredictable hydrodynamic behavior due to interparticle forces. The use of assisted fluidization techniques in such cases can be effective in improving the bed hydrodynamics. This work investigates the dynamics of pulsed fluidized bed of ultrafine nanosilica subjected to square-wave flow pulsations. The pulse duration used in this study is sufficient to allow the complete collapse of the pulsed fluidized bed between two consecutive flow pulsations. The proposed pulsation strategy is carefully implemented using electronic mass flow controllers with the help of analog output signals from data acquisition system. Given that the different regions of the fluidized bed exhibit varying dynamics, which together contribute to overall bed dynamics, the bed transients in the upper, central, and lower regions of the fluidized bed are monitored using several sensitive pressure transducers located along the height of the bed. The effect of the flow pulsation on the hydrodynamics of the fluidized bed is rigorously characterized. A significant reduction in the minimum fluidization velocity was obtained and an increase in the bed homogeneity was observed due to flow pulsations. The frequency domain analysis of the signals clearly delineated the frequency of the various events occurring during the fluidization.

Statistical study of fluctuation of gas flow rate in caps in fluidized-bed processing units

1982 ◽  
Vol 43 (3) ◽  
pp. 949-951
Author(s):  
A. P. Baskakov ◽  
V. G. Tuponogov ◽  
N. F. Filippovskii
Keyword(s):  
Fluidized Bed ◽  
Flow Rate ◽  
Gas Flow ◽  
Statistical Study ◽  
Gas Flow Rate

scholarly journals Empirical correlation for prediction of the elutriation rate constant

2003 ◽  
Vol 7 (2) ◽  
pp. 43-58 ◽  
Author(s):  
Valentino Stojkovski ◽  
Zvonimir Kostic
Keyword(s):  
Steady State ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Rate Constant ◽  
Flow Rate ◽  
Gas Flow ◽  
Particle Density ◽  
Coarse Particles ◽  
Gas Flow Rate ◽  
Mean Size

In vessels containing fluidized solids, the gas leaving carries some suspended particles. This flux of solids is called entrainment, E or carryover and the bulk density of solids on this leaving gas stream is called the holdup. For design we need to know the rate of this entrainment and the size distribution of these entrained particles Rim in relation to the size distribution in the bed, Rib, as well as the variation of both these quantities with gas and solids properties, gas flow rate, bed geometry and location of the leaving gas stream. Steady-state elutriation experiments have been done in a fluidized bed 0,2 m diameter by 2,94 m high freeboard with superficial gas velocities up to 1 m/s using solids ranging in mean size from 0,15 to 0,58 mm and with particle density 2660 kg/m3. When the fine and coarse particles were mixed, the total entrainment flux above the freeboard was increased. None of the published correlations for estimating the elutriation rate constant were useful. A new simple equation, which is developed on the base of experimental results and theory of dimensional analyses, is presented.

SCIENTIFIC AND ENGINEERING PRINCIPLES OF EFFICIENT FUEL USE AND ENVIRONMENTALLY FRIENDLY GAS COMBUSTION IN STOVE PLATES. PART 1. MODERN STATE-OF-THE-ART AND DIRECTIONS FOR IMPROVEMENT THE GAS BURNING IN DOMESTIC GAS COOKERS

2017 ◽  
pp. 3-18 ◽  
Author(s):  
B.S. Soroka ◽  
V.V. Horupa
Keyword(s):  
Natural Gas ◽  
Flow Rate ◽  
Gas Flow ◽  
Renewable Energy Sources ◽  
Combustion Process ◽  
Orifice Diameter ◽  
Firing Process ◽  
Gas Flow Rate ◽  
Gas Combustion ◽  
Gas Stoves

Natural gas NG consumption in industry and energy of Ukraine, in recent years falls down as a result of the crisis in the country’s economy, to a certain extent due to the introduction of renewable energy sources along with alternative technologies, while in the utility sector the consumption of fuel gas flow rate enhancing because of an increase the number of consumers. The natural gas is mostly using by domestic purpose for heating of premises and for cooking. These items of the gas utilization in Ukraine are already exceeding the NG consumption in industry. Cooking is proceeding directly in the living quarters, those usually do not meet the requirements of the Ukrainian norms DBN for the ventilation procedures. NG use in household gas stoves is of great importance from the standpoint of controlling the emissions of harmful components of combustion products along with maintenance the satisfactory energy efficiency characteristics of NG using. The main environment pollutants when burning the natural gas in gas stoves are including the nitrogen oxides NOx (to a greater extent — highly toxic NO2 component), carbon oxide CO, formaldehyde CH2O as well as hydrocarbons (unburned UHC and polyaromatic PAH). An overview of environmental documents to control CO and NOx emissions in comparison with the proper norms by USA, EU, Russian Federation, Australia and China, has been completed. The modern designs of the burners for gas stoves are considered along with defining the main characteristics: heat power, the natural gas flow rate, diameter of gas orifice, diameter and spacing the firing openings and other parameters. The modern physical and chemical principles of gas combustion by means of atmospheric ejection burners of gas cookers have been analyzed from the standpoints of combustion process stabilization and of ensuring the stability of flares. Among the factors of the firing process destabilization within the framework of analysis above mentioned, the following forms of unstable combustion/flame unstabilities have been considered: flashback, blow out or flame lifting, and the appearance of flame yellow tips. Bibl. 37, Fig. 11, Tab. 7.

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