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Author:
Publisher:
ISBN:
Category : Bubbles
Languages : en
Pages : 264
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Book Description
The investigation of the effect of salinity on the performance of airlift contactor was achieved using the 17L internal loop airlift system with a column height of 1.2 m, and 0.137 m diameter, and a draft tube height of 1 m. The diameters of the draft tubes were altered to vary the ratio between downcomer and riser cross sectional areas (A[subscript d]/A[subscript r]) from 0.061-1.01. The aeration was supplied in the superficial gas velocity (U[subscript sg]) from 0.01-0.07 m/s and the salinity levels were altered from 0, 15, 30, and 45 ppt. The Sauter mean diameter of the bubble appeared to be smaller in saline water than in fresh water due to two main reasons. The first one was the presence of hydrophilic repulsive force which inhibited bubble coalescence, and the second was the high Laplace pressure which promoted the breakup of the bubbles. The range of pressure difference, [delta]P, acting on the bubble which was found to promote bubble coalescence was between 15-20 N/m[superscript 2]. In saline water, the bubble size decreased with superficial gas velocity, u[subscript sg], where a reduction from 6 to 1 mm was observed with an increase in U[subscript sg] from 0.02-0.07 m/s. This was caused by the collision of bubbles at high gas hold-up in the system at higher gas flow rate which occurred at [delta]P greater than 20 N/m[superscript 2] and consequently supported bubble break-up. Axial variation in bubble size was only observed at low u[subscript sg] (less than 0.04 m/s) where bubbles in the bottom section of the airlift was larger than those in the middle and top sections. This was because the conditions in the middle and top sections were turbulent and with high [delta]P (27-65 N/m[superscript 2]), bubble break-up occurred. The effect of downcomer to riser area ratio was quite important and the highest range of [delta]P (approx. 50-97 N/m[superscript 2]) was found at the smallest downcomer area configuration which led to bubble break-up conditions. The overall volumetric mass transfer coefficient appeared lower in the saline water than in the fresh water where the levels of k[subscript L]a could be ordered from high to low as 0 ppt > 30 ppt > 15 ppt > 45 ppt. The specific area was found to be high in the saline water systems, however, the mass transfer coefficient was much higher in the fresh water system than in the saline water. The mass transfer coefficient was controlled by both natural and forced convections which were related significantly to the diameter and slip velocity of the gas bubbles.
Author:
Publisher:
ISBN:
Category : Bubbles
Languages : en
Pages : 264
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Book Description
The investigation of the effect of salinity on the performance of airlift contactor was achieved using the 17L internal loop airlift system with a column height of 1.2 m, and 0.137 m diameter, and a draft tube height of 1 m. The diameters of the draft tubes were altered to vary the ratio between downcomer and riser cross sectional areas (A[subscript d]/A[subscript r]) from 0.061-1.01. The aeration was supplied in the superficial gas velocity (U[subscript sg]) from 0.01-0.07 m/s and the salinity levels were altered from 0, 15, 30, and 45 ppt. The Sauter mean diameter of the bubble appeared to be smaller in saline water than in fresh water due to two main reasons. The first one was the presence of hydrophilic repulsive force which inhibited bubble coalescence, and the second was the high Laplace pressure which promoted the breakup of the bubbles. The range of pressure difference, [delta]P, acting on the bubble which was found to promote bubble coalescence was between 15-20 N/m[superscript 2]. In saline water, the bubble size decreased with superficial gas velocity, u[subscript sg], where a reduction from 6 to 1 mm was observed with an increase in U[subscript sg] from 0.02-0.07 m/s. This was caused by the collision of bubbles at high gas hold-up in the system at higher gas flow rate which occurred at [delta]P greater than 20 N/m[superscript 2] and consequently supported bubble break-up. Axial variation in bubble size was only observed at low u[subscript sg] (less than 0.04 m/s) where bubbles in the bottom section of the airlift was larger than those in the middle and top sections. This was because the conditions in the middle and top sections were turbulent and with high [delta]P (27-65 N/m[superscript 2]), bubble break-up occurred. The effect of downcomer to riser area ratio was quite important and the highest range of [delta]P (approx. 50-97 N/m[superscript 2]) was found at the smallest downcomer area configuration which led to bubble break-up conditions. The overall volumetric mass transfer coefficient appeared lower in the saline water than in the fresh water where the levels of k[subscript L]a could be ordered from high to low as 0 ppt > 30 ppt > 15 ppt > 45 ppt. The specific area was found to be high in the saline water systems, however, the mass transfer coefficient was much higher in the fresh water system than in the saline water. The mass transfer coefficient was controlled by both natural and forced convections which were related significantly to the diameter and slip velocity of the gas bubbles.
Author:
Publisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages : 186
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Book Description
Various configurations of external loop airlift contactor (ELALC) were examined for their hydrodynamic and mass transfer behavior using tap water. These behaviors was manipulated by changing the length of connection tubes (L[subscript c]), height of riser and downcmoer (L[subscript h]) and other configurations while keeping the ratio between downcomer and riser cross sectional area constant at 0.269. The results showed that the change of configuration could have effects on: gas holdup, liquid velocity, and gas-liquid mass transfer. Increasing L[subscript c] and L[subscript h] seemed to pose the same effect on the airlift performance. For instance, an increase in L[subscript c] from 20 to 40 cm, and Lp[subscript h] from 100 to 140 cm, could increase liquid velocity at 11.3 and 7.2%, decreased overall gas holdup at 8.6 and 3.3% and decreased the overall volumetric mass transfer coefficient at 8.2 and 5.6%, respectively. The effect of configurations on ELALC was investigated. ELALCs with inclined connection tubes and with close downcomer were compared with regular ELALC in terms of hydrodynamic and gas-liquid mass transfer behaviors. The two configurations presented large agglomerate of gas bubbles on the top connection tubes which resulted in more gas holdups and less downcomer liquid velocity when compared with regular ELALC. The mathematical model was developed based on the mass conservation principals to predict the gas-liquid mass transfer in the ELALC. Basically ELALC was represented by a series of reactors, i.e. the riser, downcomer, top and bottom connection tubes were represented by the dispersion model, and the two gas separators represented by the stirred tank model. The simulation results were found to be reasonably accurate for all experimental conditions employed in this work.
Author:
Publisher:
ISBN:
Category : Chemical reactors
Languages : en
Pages : 142
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Book Description
To investigate the influence of sparger position on the bubble size distribution in internal loop airlift contactors. To complete the examination, the effects of other main design/operating parameters, i.e. the ratio between cross-sectional areas of downcomer and riser (A[subscript d]/A[subscript r]) and the superficial gas velocity, were also considered. The aeration in the ALC was achieved via the PVC ring sparger. The number of holes in the sparger was fixed at 60. The air flow rate was controlled in a range of superficial gas velocity, u[subscript sg] , from 4 to 10 cm s[superscript -1] . The ratios between cross-sectional areas were varying from 1.4 to 0.9. The sparger position was varied by changing the position of annulus sparger (0, 6 and 12 cm above the bottom of the contactor). A photographic technique was used to measure the bubble size and its distribution. The results revealed that the Sauter mean diameter of bubble was the smallest when the sparger was located at base of the reactor, and became larger when the sparger was moved to higher positions. It should be noted that at the lowest position, the sparger position was lower than the draft tube, therefore the recirculating fluid from the downcomer pushed the new-born bubbles towards the wall of the reactor and bubble breakage was observed. In addition, bubble size was also controlled by other flow conditions in the system, especially the superficial gas velocity (u[subscript sg] ), where an increase in u[subscript sg] decreased the bubble size due to the induction of high turbulence which rendered the bubble breakup. The system operated with smaller riser area had a higher level of turbulence, thus, the average bubble size was found to be smaller than system with larger riser area. At the bottom section of the reactor, the Sauter mean bubble diameter appeared to be larger than those at the middle and top sections. In terms of gas-liquid mass transfer, the sparger at its lowest position provided the highest level of overall volumetric mass transfer coefficient in the system. The specific interfacial area at the lowest sparger position was also found to be higher that other positions which suggested that this specific interfacial area could have strong positive impact on the gas-liquid mass transfer.
Author: Diaa el Din H. El Gabbani
Publisher:
ISBN:
Category :
Languages : en
Pages : 460
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Book Description
Author: M. Y. Chisti
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 368
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Book Description
Author: Antonio Lopez
Publisher: IWA Publishing
ISBN: 1843393433
Category : Science
Languages : en
Pages : 285
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Book Description
Innovative and Integrated Technologies for the Treatment of Industrial Wastewater deals with advanced technological solutions for the treatment of industrial wastewater such as aerobic granular biomass based systems, advanced oxidation processes integrated with biological treatments, membrane contactors and membrane chemical reactors. Wastewater from pharmaceutical, chemical and food industries as well as landfill leachates are specifically considered as representative of major problems encountered when treating industrial streams. The economic and environmental sustainability of the above solutions are also reported in the book and compared with the alternatives currently available in the market by life cycle assessment (LCA) and life cycle costing (LCC) methodologies. The implementation of the considered solutions at large scale could support and enhance the competitiveness of different industrial sectors, including the water technology sector, in the global market. Innovative and Integrated Technologies for the Treatment of Industrial Wastewater also makes a contribution towards defining: new concepts, processes and technologies in wastewater treatment with potential benefits for the stable quality of effluents, energy and operational costs saving, and the protection of the environment new sets of advanced standards for wastewater treatment new methodologies for the definition of wastewater treatment needs and framework conditions new information supporting development and implementation of water legislation.
Author: Jie Bao
Publisher: Springer
ISBN: 3662483475
Category : Science
Languages : en
Pages : 161
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Book Description
This book review series presents current trends in modern biotechnology. The aim is to cover all aspects of this interdisciplinary technology where knowledge, methods and expertise are required from chemistry, biochemistry, microbiology, genetics, chemical engineering and computer science. Volumes are organized topically and provide a comprehensive discussion of developments in the respective field over the past 3-5 years. The series also discusses new discoveries and applications. Special volumes are dedicated to selected topics which focus on new biotechnological products and new processes for their synthesis and purification. In general, special volumes are edited by well-known guest editors. The series editor and publisher will however always be pleased to receive suggestions and supplementary information. Manuscripts are accepted in English.
Author: Simon Judd
Publisher: Elsevier
ISBN: 0080465102
Category : Technology & Engineering
Languages : en
Pages : 342
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Book Description
The MBR Book
Author: Hideki Tsuge
Publisher: CRC Press
ISBN: 9814463108
Category : Medical
Languages : en
Pages : 378
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Book Description
Microbubbles and nanobubbles have several characteristics that are comparable with millimeter- and centimeter-sized bubbles. These characteristics are their small size, which results in large surface area and high bioactivity, low rising velocity, decreased friction drag, high internal pressure, large gas dissolution capacity, negatively charged surface, and ability to be crushed and form free radicals. Microbubbles and nanobubbles have found applications in a variety of fields such as engineering, agriculture, environment, food, and medicine. Microbubbles have been successfully used in aquacultures of oysters in Hiroshima, scallops in Hokkaido, and pearls in Mie Prefecture, Japan. This field has shown a strong potential for growth. This book comprehensively discusses microbubbles and nanobubbles and their application in aquaculture, environment, engineering, medicine, stock raising, agriculture, and marine industry. It presents their potential as a new technology that can be utilized globally.
Author: Pauline M. Doran
Publisher: Elsevier
ISBN: 0080528120
Category : Science
Languages : en
Pages : 455
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Book Description
The emergence and refinement of techniques in molecular biology has changed our perceptions of medicine, agriculture and environmental management. Scientific breakthroughs in gene expression, protein engineering and cell fusion are being translated by a strengthening biotechnology industry into revolutionary new products and services. Many a student has been enticed by the promise of biotechnology and the excitement of being near the cutting edge of scientific advancement. However, graduates trained in molecular biology and cell manipulation soon realise that these techniques are only part of the picture. Reaping the full benefits of biotechnology requires manufacturing capability involving the large-scale processing of biological material. Increasingly, biotechnologists are being employed by companies to work in co-operation with chemical engineers to achieve pragmatic commercial goals. For many years aspects of biochemistry and molecular genetics have been included in chemical engineering curricula, yet there has been little attempt until recently to teach aspects of engineering applicable to process design to biotechnologists.This textbook is the first to present the principles of bioprocess engineering in a way that is accessible to biological scientists. Other texts on bioprocess engineering currently available assume that the reader already has engineering training. On the other hand, chemical engineering textbooks do not consider examples from bioprocessing, and are written almost exclusively with the petroleum and chemical industries in mind. This publication explains process analysis from an engineering point of view, but refers exclusively to the treatment of biological systems. Over 170 problems and worked examples encompass a wide range of applications, including recombinant cells, plant and animal cell cultures, immobilised catalysts as well as traditional fermentation systems.* * First book to present the principles of bioprocess engineering in a way that is accessible to biological scientists* Explains process analysis from an engineering point of view, but uses worked examples relating to biological systems* Comprehensive, single-authored* 170 problems and worked examples encompass a wide range of applications, involving recombinant plant and animal cell cultures, immobilized catalysts, and traditional fermentation systems* 13 chapters, organized according to engineering sub-disciplines, are groupled in four sections - Introduction, Material and Energy Balances, Physical Processes, and Reactions and Reactors* Each chapter includes a set of problems and exercises for the student, key references, and a list of suggestions for further reading* Includes useful appendices, detailing conversion factors, physical and chemical property data, steam tables, mathematical rules, and a list of symbols used* Suitable for course adoption - follows closely curricula used on most bioprocessing and process biotechnology courses at senior undergraduate and graduate levels.
