The document summarizes research on oxygen mass transfer in a bubble column with non-Newtonian fluids. Xanthan gum solutions were used to simulate activated sludge viscosity. Clean water tests were conducted with different airflow rates and Xanthan gum concentrations. The results showed that increasing fluid viscosity through higher Xanthan gum concentration decreased oxygen transfer rates, but this could be offset by increasing airflow rates. Higher airflow increased shear and disrupted flocs, decreasing viscosity and improving oxygen transfer.
Presentation given by Auli Niemi of Uppsala University on "PANACEA & TRUST Projects Status update" at the EC FP7 Projects: Leading the way in CCS implementation event, London, 14-15 April 2014
The New Capillary Number Parameterization for Simulation in Surfactant FloodingPremier Publishers
The Capillary number hypothesis is very empirical in Surfactant flooding Enhanced Oil Recovery (EOR) method. which is of modest experience on the North Sea and many other offshore platforms. The capillary number drives the force wetting processes, which is controlled by the balance between capillary and viscous forces. The mobilization of oil trapped in pores of water-wet rock is steered by capillary number that is typically within specific ranges (〖10〗^(-5) to〖 10〗^(-4)). There is high uncertainty and confusion in the parameterization of capillary number formula, as every quantity is given on a macroscale level. As demonstrated herein, a new microscopic capillary number parameterization was proposed. This paper is written to improve the numerical formulation of capillary number in surfactant flooding model. The new formula for capillary number was derived based on existing equations as a function of residual oil saturation and tested. Thus, the proposed mobility mechanism easily accounts for a broader critical range of capillary number (〖10〗^(-6) to〖 10〗^(-4)) in comparison with available models with a critical capillary number (〖10〗^(-5) to〖 10〗^(-4)). We used an existing model to quantify the effect of capillary number on a miscible and immiscible relative permeability curves by computing the interpolation parameter F_kr as a tabulated function of the Logarithm (base 10) of the capillary number using a new capillary number formulation.
On Similarity of Differential Capacity and Capillary Pressure FractalKhalid Al-Khidir
On Similarity of Differential Capacity and Capillary Pressure Fractal Dimensions for Characterizing Shajara Reservoirs of the Permo-Carboniferous Shajara Formation, Saudi Arabia
Optimum replacement depth to control heave of swelling claysAhmed Ebid
The behavior of unsaturated swelling soils under changing of moisture content was intensively studied by many researchers since the 1950’s. Many proposed formulas and techniques were used to classify, describe and predict the swelling behavior and parameters of such type of soil. On the other hand, many techniques are used to allow structures to be founded on swelling soils without suffering any damages due to the soil heave. Replacing the swelling soil with granular mixture is one of the most famous and cheapest techniques especially in case of light structures on shallow layer of swelling soil. The aim of this research is to develop a simplified formula to estimate the heave of swelling soil considering the effect of replaced layer. The developed formula is used to estimate the required replacement depth to avoid damage due to excessive heave.
The effect of solids on the behaviour of the downcomer of a jameson celleSAT Journals
Abstract The effect of solids on the behaviour of the downcomer of a Jameson cell was studied in terms of the hydrophobic/hydrophilic character of the solids. Hydrophobic (carbon), and hydrophilic (silica sand) solids were used, separately. The experiments were carried out under controlled conditions of gas flow rate, pulp flow rate, and pulp consistency. The observed operating variables were the extension of the downcomer operating regions (pulp jet, mixing, and collection) and gas hold-up. It was observed that gas bubbles are smaller and more uniform in size when the pulp is comprised of silica (hydrophilic particles), as compared with pulps consisted of carbon (hydrophobic particles). When measuring a profile of gas holdup in the separation cell, experimental results show that a more homogeneous radial holdup distribution is achieved in the case of a slurry with silica sand rather than the pulp made of carbon. Key words: Jameson cell, downcomer, separation cell, superficial phase velocity, gas hold-up, hydrophobic solids, hydrophilic solids.
Mesoscopic simulation of incompressible fluid flow in porous mediaeSAT Journals
Abstract
Lattice Boltzmann method is used to simulate cavity driven fluid flow in porous media. A square cavity is considered with the top
lid moving with uniform velocity and other sides kept stationary. Simulation is carried out for values of Darcy number ranging
from 10-6 to10-2 at Reynolds number 10 and 100. Influence of Darcy number and Reynolds number is investigated on velocity
profiles and the streamline plots. Half-way bounce back boundary conditions are employed in the numerical simulation. The
numerical code is first verified with the results available in the literature and then used to simulate the Newtonian fluid flow in
porous media. The Darcy number and the Reynolds number were observed to have great influence on the flow properties and the
location of the primary vortex. Simulation was carried out for a 100100 mesh grid and a fine agreement is established theories
in incompressible fluid flow.
Keywords: Lattice Boltzmann method, incompressible flow, porous media
The dependencies of total pressure, velocity, vorticity, turbulent length, turbulent dissipation, turbulent viscosity, turbulent energy and turbulent time of moving fluid from a straight pipe length of a circular cross section are presented in graphical and mathematical forms. Changing analysis of considered parameters was performed at mass flow rates of 0.45, 1.0 and 1.5 kg/s. A transition boundary of laminar flow of fluid to turbulent flow is at the distance of 2/5 of length from the inlet of the pipe (at accepted total length of the pipe of 1000 mm).
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Presentation given by Auli Niemi of Uppsala University on "PANACEA & TRUST Projects Status update" at the EC FP7 Projects: Leading the way in CCS implementation event, London, 14-15 April 2014
The New Capillary Number Parameterization for Simulation in Surfactant FloodingPremier Publishers
The Capillary number hypothesis is very empirical in Surfactant flooding Enhanced Oil Recovery (EOR) method. which is of modest experience on the North Sea and many other offshore platforms. The capillary number drives the force wetting processes, which is controlled by the balance between capillary and viscous forces. The mobilization of oil trapped in pores of water-wet rock is steered by capillary number that is typically within specific ranges (〖10〗^(-5) to〖 10〗^(-4)). There is high uncertainty and confusion in the parameterization of capillary number formula, as every quantity is given on a macroscale level. As demonstrated herein, a new microscopic capillary number parameterization was proposed. This paper is written to improve the numerical formulation of capillary number in surfactant flooding model. The new formula for capillary number was derived based on existing equations as a function of residual oil saturation and tested. Thus, the proposed mobility mechanism easily accounts for a broader critical range of capillary number (〖10〗^(-6) to〖 10〗^(-4)) in comparison with available models with a critical capillary number (〖10〗^(-5) to〖 10〗^(-4)). We used an existing model to quantify the effect of capillary number on a miscible and immiscible relative permeability curves by computing the interpolation parameter F_kr as a tabulated function of the Logarithm (base 10) of the capillary number using a new capillary number formulation.
On Similarity of Differential Capacity and Capillary Pressure FractalKhalid Al-Khidir
On Similarity of Differential Capacity and Capillary Pressure Fractal Dimensions for Characterizing Shajara Reservoirs of the Permo-Carboniferous Shajara Formation, Saudi Arabia
Optimum replacement depth to control heave of swelling claysAhmed Ebid
The behavior of unsaturated swelling soils under changing of moisture content was intensively studied by many researchers since the 1950’s. Many proposed formulas and techniques were used to classify, describe and predict the swelling behavior and parameters of such type of soil. On the other hand, many techniques are used to allow structures to be founded on swelling soils without suffering any damages due to the soil heave. Replacing the swelling soil with granular mixture is one of the most famous and cheapest techniques especially in case of light structures on shallow layer of swelling soil. The aim of this research is to develop a simplified formula to estimate the heave of swelling soil considering the effect of replaced layer. The developed formula is used to estimate the required replacement depth to avoid damage due to excessive heave.
The effect of solids on the behaviour of the downcomer of a jameson celleSAT Journals
Abstract The effect of solids on the behaviour of the downcomer of a Jameson cell was studied in terms of the hydrophobic/hydrophilic character of the solids. Hydrophobic (carbon), and hydrophilic (silica sand) solids were used, separately. The experiments were carried out under controlled conditions of gas flow rate, pulp flow rate, and pulp consistency. The observed operating variables were the extension of the downcomer operating regions (pulp jet, mixing, and collection) and gas hold-up. It was observed that gas bubbles are smaller and more uniform in size when the pulp is comprised of silica (hydrophilic particles), as compared with pulps consisted of carbon (hydrophobic particles). When measuring a profile of gas holdup in the separation cell, experimental results show that a more homogeneous radial holdup distribution is achieved in the case of a slurry with silica sand rather than the pulp made of carbon. Key words: Jameson cell, downcomer, separation cell, superficial phase velocity, gas hold-up, hydrophobic solids, hydrophilic solids.
Mesoscopic simulation of incompressible fluid flow in porous mediaeSAT Journals
Abstract
Lattice Boltzmann method is used to simulate cavity driven fluid flow in porous media. A square cavity is considered with the top
lid moving with uniform velocity and other sides kept stationary. Simulation is carried out for values of Darcy number ranging
from 10-6 to10-2 at Reynolds number 10 and 100. Influence of Darcy number and Reynolds number is investigated on velocity
profiles and the streamline plots. Half-way bounce back boundary conditions are employed in the numerical simulation. The
numerical code is first verified with the results available in the literature and then used to simulate the Newtonian fluid flow in
porous media. The Darcy number and the Reynolds number were observed to have great influence on the flow properties and the
location of the primary vortex. Simulation was carried out for a 100100 mesh grid and a fine agreement is established theories
in incompressible fluid flow.
Keywords: Lattice Boltzmann method, incompressible flow, porous media
The dependencies of total pressure, velocity, vorticity, turbulent length, turbulent dissipation, turbulent viscosity, turbulent energy and turbulent time of moving fluid from a straight pipe length of a circular cross section are presented in graphical and mathematical forms. Changing analysis of considered parameters was performed at mass flow rates of 0.45, 1.0 and 1.5 kg/s. A transition boundary of laminar flow of fluid to turbulent flow is at the distance of 2/5 of length from the inlet of the pipe (at accepted total length of the pipe of 1000 mm).
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
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The dissolved oxygen (DO) content of water bodies is an indicator of water quality and hence a measure of ability of water to sustain aquatic life. Hydraulic phenomena such as hydraulic drops and hydraulic jumps can increase the amount of DO in the water by creating turbulent conditions. The main reason for this oxygen transfer is the air entrainment into the flow through large number of air bubbles that helps in air-water transfer. The present study investigates the effect of different weir types and hydraulic jump on their aeration efficiency. Two types of weirs namely rectangular and triangular weirs were used in the study. Also, the hydraulic jump was studied as an aeration agent. From the experimental results, it was found that the triangular weir provides greater aeration efficiency of 0.1948 as compared with rectangular weir that had aeration efficiency of 0.1012. On the other hand, the hydraulic jump showed aeration efficiency of 0.14285. As the weirs are more efficient than hydraulic jump, they are most applicable in the field. Also, weir structures are less expensive when compared with the structural arrangement required for the formation of hydraulic jump.
Keywords: Dissolved oxygen, Aeration efficiency, Weir, Hydraulic jump
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Abstract Water model experiments have been carried out in a 1/30th scaled down model of the 100 ton LD converter in order to investigate the effect of changing the lance height and the gas flow rate on the penetration depth of liquid with different exit diameters. It is found the penetration depth increases with decreasing nozzle diameter, decreasing the lance height and with increase the gas flow rate. Gas jets impinging onto a gas–liquid interface of a liquid pool are also studied using computational fluid dynamics modeling, which aims to obtain a better understanding of the behavior of the gas jets. The gas and liquid flows are modeled using the volume of fluid technique. The governing equations in the axisymmetric cylindrical coordinates are solved by the CFD simulation using FLUENT. The computed results are compared with experimental result and it isfound a good match with all the data. Keywords: LD process, Water Modeling, Penetration Depth, Volume of Fluid, CFD.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Arsenic removal by adsorption on activated carbon in a rotating packed bed
abstract_Vincenzo_Ciancia_MS_Thesis
1. Scuola Politecnica e delle Scienze di Base
Department of Civil, Architectural & Environmental Engineering
Master Thesis in
Environmental Engineering
Oxygen mass transfer in a bubble
column with non-Newtonian fluids
Supervisors: Author:
Prof. Francesco Pirozzi Vincenzo Ciancia
Prof. Diego Rosso M67000071
Academic Year 2013-2014
2. ABSTRACT
Every community produces both liquid and solid wastes and air emissions.
The term wastewater refers to water that has been adversely affected in quality
by any anthropogenic influence (human waste, septic tanks, sewage, urban rain-
fall, groundwater infiltrated into sewage, industrial site drainage, etc.). In order
to protect the environment and the human health, treating wastewater is essen-
tial. As reported in Metcalf and Eddy (2003) “the ultimate goal of wastewater
engineering is the protection of public health in a manner commensurate with
environmental, economic, social and political concerns”.
The activated sludge process is the most used process to treat wastewater. It is
based on aerobic degradation of wastewater components by using a suspended
growth of microorganisms. The process is highly efficient and easily to manage
but requires an aeration tank to feed oxygen to the biological colony of microor-
ganisms. Under the energy and sustainability point of view, the activated sludge
process has a big disadvantage: about 60÷70% of the total energy consumption
of a whole municipal wastewater treatment plant is used for aeration (Jiang and
Stenstrom, 2012).
1
3. Abstract
Under these circumstances, the target of wastewater treatment industries is about
designing an aeration process to transfer the highest amount of oxygen from gas
phase to the liquid phase with the highest efficiency and the lowest costs. Taking
into account these aspects it is important to comprehend the properties of the
liquid in which the oxygen mass transfer process occurs. As a result, an accurate
knowledge of the sludge characteristics and behavior is fundamental.
In this thesis, we investigated the effect of the sludge viscosity on the character-
istics of the aeration process. This situation is highly effective in MBRs where
the high MLSS concentration causes a significant increase of sludge viscosity and
widely effects the aeration process.
In order to simulate the behavior of activated sludge, different aqueous solution
of Colloidal Silica (CS) and Xanthan Gum (XG) were prepared and their rheo-
logical behavior was determined by using a rotational rheometer.
1 foot
3½ feet
Figure 1: Tank setup
2
4. Oxygen mass transfer in a bubble column with non-Newtonian fluids
By using a laboratory scale tank (Fig. 1), the oxygen transfer efficiency pa-
rameters were calculated through the Clean Water Test procedure by using the
US Standard (ASCE, 2006). Values of the volumetric mass transfer coefficient
KLa20, Standard Oxygen Transfer Rate (SOTR) and Standard Oxygen Trans-
fer Efficiency (SOTE), obtained at various airflow rates, were correlated with
liquid’s viscosity.
We observed (Fig. 2) that the Xanthan Gum solutions perfectly simulate the
behavior of MBRs activated sludge. The rheograms regarding the Xanthan Gum
(in color) are mostly equal to the rheograms of a MBRs activated sludge (in
gray). In particular, we noticed that the behavior of 1 g/L solution of Xanthan
Gum is completely comparable to the behavior of 16 g/L MLSS concentration of
MBRs sludge.
0 50 100 150 200 250 300 350 400 450 500
0
2
4
6
8
10
12
14
Shear rate, ˙γ [1/s]
Shearstress,τ[Pa]
C = 0.5 g/L C = 1 g/L C = 3 g/L C = 5 g/L
C = 16 g/L C = 20 g/L C = 26 g/L C = 31 g/L
Figure 2: Rheograms of Xanthan Gum solutions vs. MBRs Activated Sludge
3
5. Abstract
An overall of forty-seven Clean Water tests (Tab. 1) were conducted at three
different Xanthan Gum concentrations (0 g/L – 1 g/L – 2.5 g/L) and at three
different airflow rates (25 SCFH – 30 SCFH – 40 SCFH).
Table 1: Configurations adopted for the clean water tests
System Aeration device Fluid
(a) Coarse bubble diffuser Tap Water
(b) 7mm Nozzle Tap Water
(c) 3mm Nozzle Tap Water
(d) 3mm Nozzle 1 g/L aqueous solution of XG
(e) 3mm Nozzle 2.5 g/L aqueous solution of XG
We observed that the values of KLa20 and SOTR increase linearly as the airflow
rate increases while the values of SOTE are constant or slightly decrease.
0 0.5 1 1.5 2 2.5 3
0
2
4
6
8
10
12
14
16
18
20
Xanthan Gum Concentration, [g/L]
KLa20[1/h]
25 SCFH 30 SCFH 40 SCFH
Figure 3: Evolution of the overall gas transfer coefficient as a function of the
Xanthan Gum concentration (3mm nozzle)
4
6. Oxygen mass transfer in a bubble column with non-Newtonian fluids
For the 3mm nozzle, the values of KLa20, SOTR and SOTE at a specific air-
flow rate decrease as the Xanthan Gum concentration, or the liquid viscosity,
increases. As result, the increasing of fluid’s viscosity, negatively influences the
oxygen mass transfer.
For any airflow, the KLa20 reduction (Fig. 3) becomes equal to an average of
11% when the Xanthan Gum concentration increases to 1 g/L and to 59% when
the Gum content is 2.5 g/L. The reduction of KLa20 is due to the increase of
the coalescence process. The liquid viscosity promotes the coalescence: bubbles
combine in clusters and form large bubbles. Large bubbles have smaller inter-
facial area (a) and a high rising velocity that keep them in the liquid shorter,
allowing less time for the oxygen to dissolve.
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
3.5
4
Xanthan Gum Concentration, [g/L]
SOTR[g/h]
25 SCFH 30 SCFH 40 SCFH
Figure 4: Evolution of the Standard Oxygen Transfer Rate as a function of the
Xanthan Gum concentration (3mm nozzle)
For each airflow, both the Standard Oxygen Transfer Rate (Fig. 4) and the
Standard Oxygen Transfer Efficiency (Fig. 5) reduce to an average of 14% and
52% when the Xanthan Gum concentration is 1 g/L and 2.5 g/L, respectively.
5
7. Abstract
The values of SOTE are quite the same for any airflow rate.
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
3.5
4
Xanthan Gum Concentration, [g/L]
SOTE[%]
25 SCFH 30 SCFH 40 SCFH
Figure 5: Evolution of the Standard Oxygen Transfer Efficiency as a function
of the Xanthan Gum concentration (3mm nozzle)
The results we obtained are very important. We showed that when the Xanthan
Gum concentration increases, the amount of oxygen transferred in water (SOTR)
decreases. Nevertheless, at a specific concentration of Xanthan Gum and almost
at the same efficiency, we can increase the oxygen transferred by increasing the
airflow rare. Specifically, when the airflow is increased, the low decrease in ef-
ficiency is totally negligible compared to the big increase of oxygen transferred.
As observed, an increase in airflow corresponds to an increase of the shear rate in
the system. In other words, the shear rate promotes the oxygen transfer.
An explanation of this effect on real wastewater treatment plant can be found by
analyzing the structure of the activated sludge. When the MLSS concentration
increases, the filamentous organisms tend to flocculate in a large-scale network,
creating flocs. During this process a large amount of water is incorporated into
the particle structure. When the shear rate increases, the floc is disrupted and
6
8. Oxygen mass transfer in a bubble column with non-Newtonian fluids
more water becomes available in the system, making the viscosity decreasing. As
a result, the oxygen transfer process is improved.
In order to better understand the fluid dynamic of the system, we calculated the
gas holdup fraction εG:
εG =
VG
VG + VL
=
H − H
H
[%] (1)
where VG and VL are the gas and liquid volumes while H and H are the height
of aerated liquid and the clear liquid height.
When the liquid viscosity increases, at a specific airflow rate, the gas holdup
fraction decreases (Fig. 6 and 7) because the total gas volume VG in the system
reduces. As observed before, an increment of the liquid viscosity promotes the
coalescence phenomenon.
0 0.5 1 1.5 2 2.5 3
0
1
2
3
4
5
6
7
8
Xanthan Gum Concentration, [g/L]
Gashold-upfraction,εG[%]
25 SCFH 30 SCFH 40 SCFH 60 SCFH
Figure 6: Gas holdup fraction for the 3mm nozzle as a function of the Xanthan
Gum Concentration
7
9. Abstract
(a) (b)
(c) (d)
Figure 7: Gas holdup at specific airflow rate at different Xanthan Gum Con-
centration (a – 25 SCFH; b – 30 SCFH; c – 40 SCFH; d – 60 SCFH)
8
10. BIBLIOGRAPHY
ASCE (2006). Measurement of Oxygen Transfer in Clean Water. American
Society of Civil Engineers, Reston, VA, asce/ewri 2-06 edition.
Jiang, P. and Stenstrom, M. (2012). Oxygen transfer parameter estimation:
Impact of methodology. Journal of Environmental Engineering, 138(2):137–
142.
Metcalf and Eddy (2003). Wastewater Engineering: Treatment and Reuse.
Tchobanoglous, G.; Burton, F.L.; Stensel, H.D. McGraw-Hill Education, 4th
edition.
9