scholarly journals Segregation patterns in gas-fluidized systems

2001 ◽  
Vol 433 ◽  
pp. 347-356 ◽  
Author(s):  
M. A. GILBERTSON ◽  
I. EAMES
Keyword(s):  
Phase Diagram ◽  
Flow Rate ◽  
Gas Flow ◽  
Fine Particles ◽  
Lower Layer ◽  
Critical Value ◽  
Coarse Particles ◽  
Gas Velocity ◽  
Gas Flow Rate ◽  
Horizontal Band

The formation of segregation patterns in initially homogeneous, fluidized, binary mixtures of particles has been studied. The adjustment of the bed depends on the proportions of fine and coarse particles in the mixture and the gas flow rate relative to the minimum fluidization velocities of the two components. The particles are immobile until the gas flow rate is sufficiently large to fluidize the mixture of particles. When the gas flow rate exceeds this critical value, alternating vertical bands of coarse and fine particles form. At a second critical gas velocity this pattern breaks down and the more familiar pattern of a mixed horizontal band on top of a layer of coarse particles forms. A phase diagram, constructed from experimental observations, shows the conditions for which each of these regimes exists. Its structure is explained in terms of the fluidization and consequent mobility of the mixture components. When horizontal bands are present, the thickness of the lower layer of coarse particles decreases with increasing gas flow rate depending on the proportion of fine particles in the bed. This, and its development, can be understood by analogy with the sedimentation of particles through a turbulent fluid. The experiments imply that the efficiency of mixing by the bubbles in the fluidized bed is very much less than that expected from gas bubbles in a liquid.

Augmentation of the Performance of Batch Electrocoagulation Unit by Using Gas Sparging

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Ahmed Hassan Elshazly
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Dye Removal ◽  
Gas Velocity ◽  
Gas Flow Rate ◽  
Flow Rates ◽  
Gas Sparging ◽  
Current Densities ◽  
Superficial Gas Velocity ◽  
Time Of Operation

The present work investigates the effect of gas sparging in improving the performance of a batch electrocoagulation unit used to treat wastewater generated from the dyeing industry. Monopolar cylindrical aluminum electrodes were used. Many variables were investigated such as superficial gas velocity, current density, initial dye concentration, area ratio (cathode/anode), time of operation and the effect of adding chemical coagulant as FeSO4. The results show that the percentage of dye removal has been increased by a factor ranging from 2.52 to 5.14 by increasing the gas flow rate from 0.4 to 0.8 liter/min respectively and that about 93.5 percent of the dye can be removed within 60 minutes. Also it was found that using gas sparging is more efficient than adding chemical coagulant as ferrous sulfate for the removal of dye from wastewater. The power consumption for the unit was measured for different gas flow rates and different current densities; the results show that lower gas flow rate can improve the economy of the process.

Augmentation of the Performance of Batch Electrocoagulation Unit by Using Gas Sparging

2011 ◽  
Vol 312-315 ◽  
pp. 700-707 ◽  
Author(s):  
A.H. El-Shazly
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Dye Removal ◽  
Ferrous Sulphate ◽  
Gas Velocity ◽  
Gas Flow Rate ◽  
Gas Sparging ◽  
Current Densities ◽  
Superficial Gas Velocity ◽  
Time Of Operation

The aim of the present work is to investigate the effect of gas sparging in improving the performance of a batch electrocoagulation unit used for the treatment of wastewater generated from dyeing industry. Monopolar cylindrical aluminum electrodes were used. Many variables were investigated such as superficial gas velocity, current density, initial dye concentration, area ratio (cathode/anode), time of operation and the effect of adding chemical coagulant as Fe (SO4). The results show that the % dye removal has been increased by a factor ranging from 2.52 to 5.14 by increasing the gas flow rate from 0.4 to 0.8 liter/min, respectively, and that about 93.5% of the dye can be removed within 60 minutes. Also it was found that using gas sparging is more efficient than adding chemical coagulant as ferrous sulphate for the removal of dye from wastewater. The power consumption for the unit was measured for different gas flow rates and different current densities; the results show that lower gas flow rate can improve the economy of the process.

Effect of Hole Distance and Hole Number on Bubble Behavior during Gas Injection with Multi-Hole Orifices

2011 ◽  
Vol 295-297 ◽  
pp. 1113-1119 ◽  
Author(s):  
Fang Jiang ◽  
Guo Guang Cheng
Keyword(s):  
Physical Model ◽  
Flow Rate ◽  
Gas Flow ◽  
Gas Injection ◽  
Critical Value ◽  
Refining Process ◽  
Hole Diameter ◽  
Gas Flow Rate ◽  
Bubble Behavior ◽  
Hole Number

Physical model experiments have been performed to clarify the effect of hole distance and hole number of multi-hole orifices on bubble behavior during metal refining process. It is found kA/V firstly decreases and then increases with the hole distance increasing. However, kA/V shows little further increase when hole distance exceeds a critical value. There exists an optimal hole distance for the multi-hole orifice, which is dependent on the gas flow rate, the hole diameter and the hole number in the multi-hole orifice. kA/V firstly increases with the hole number increasing, and then remains unchanged when hole number exceeds a critical value. There also exists an optimal hole number for the multi-hole orifice, which is closely related to the gas flow rate.

scholarly journals PURIFICATION OF SMOKE AND PROCESS GASES IN DIRECT-FLOW CYCLONES

2021 ◽  
Vol 56 ◽  
pp. 44-50
Author(s):  
Valeriy S. Toptalov ◽  
◽  
Nikolai A. Martsulevich ◽  
Oleg M. Flisyuk ◽  
◽  
...  
Keyword(s):  
Particle Size ◽  
Flow Rate ◽  
Gas Flow ◽  
Velocity Profiles ◽  
Geometric Parameters ◽  
Gas Velocity ◽  
Gas Flow Rate ◽  
Direct Flow ◽  
Calculation Results ◽  
Process Gases

In this work, gas velocity profiles in the separating chamber of a direct-flow cyclone are obtained, and a method for calculating its efficiency is proposed. The method allows us to trace the influence of the geometric parameters of the chamber, the particle size and the gas flow rate on the degree of its purification. The calculation results are confirmed by numerous experiments

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.

On the Influence of Fluctuating Flow Rate Upon the Performance and Behaviour of Isothermal Reacting Systems

1998 ◽  
Vol 63 (6) ◽  
pp. 881-898
Author(s):  
Otakar Trnka ◽  
Miloslav Hartman
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Fluidized Bed Reactor ◽  
Computational Techniques ◽  
Continuous Stirred Tank Reactor ◽  
Gas Flow Rate ◽  
Solid Reaction ◽  
Continuous Stirred Tank ◽  
And Performance ◽  
Reacting Systems

Three simple computational techniques are proposed and employed to demonstrate the effect of fluctuating flow rate of feed on the behaviour and performance of an isothermal, continuous stirred tank reactor (CSTR). A fluidized bed reactor (FBR), in which a non-catalytic gas-solid reaction occurs, is also considered. The influence of amplitude and frequency of gas flow rate fluctuations on reactant concentrations at the exit of the CSTR is shown in four different situations.

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