Dispersed air flotation as a pretreatment process for seawater desalination

2012 ◽  
Vol 12 (4) ◽  
pp. 431-438 ◽  
Author(s):  
Hossam Altaher ◽  
Emad ElQada ◽  
Waid Omar
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Seawater Temperature ◽  
Operating Conditions ◽  
Oxygen Absorption ◽  
Aeration Tank ◽  
Overall Mass Transfer Coefficient ◽  
Air Flotation

Pretreatment of seawater before reverse osmosis (RO) processes with dispersed air flotation involves a change in oxygen concentration in seawater. In order to understand this phenomenon, a series of experimental aeration studies was conducted. Aeration tests were performed under different operating conditions of seawater temperature, flow rate of the air and depth of the water in the aeration tank. The experimental results show that the overall mass transfer coefficient increases by increasing air flow rate. A measured increase in the overall mass transfer coefficient was observed with elevation of the temperature from 24 to 38 °C. The estimated value of activation energy of oxygen absorption in seawater is 42.5 kJ/mol. The value of the overall mass transfer coefficient is found to be affected by diffuser type and stirrer speed as these parameters influence the bubble size and the surface area available for mass transfer of oxygen from air bubbles to seawater.

scholarly journals Mass Transfer in Multiphasic Gas/Liquid/Liquid Systems. KLa Determination Using the Effectiveness-Number of Transfer Unit Method

Processes ◽  
2018 ◽  
Vol 6 (9) ◽  
pp. 156 ◽  
Author(s):  
Éric Dumont
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Gas Flow ◽  
Absorption Capacity ◽  
Operating Conditions ◽  
Transfer Unit ◽  
Liquid Systems ◽  
Overall Mass Transfer Coefficient

The Effectiveness-Number of Transfer Unit method (ε-NTU method) was applied to determine the overall mass transfer coefficient, KLa, of operating gas-liquid absorbers treating Volatile Organic Compounds (VOCs). This method requires the knowledge of the operating conditions (gas flow rate, QG; liquid flow rate, QL; scrubber volume V), the measurement of gaseous concentrations at the inlet, CGin, and at the outlet, CGout, of the contactor (in order to determine the effectiveness of the absorber ε) and the calculation of the Henry coefficient of the VOC between the gas and the liquid phases (HVOC). Coupled with the “equivalent absorption capacity” concept, the ε-NTU method was used to determine KLa of absorbers contacting a gas and a mixture of water and a Non Aqueous Phase, successfully. The method, validated from literature data for configurations countercurrent scrubbers and stirred tank reactors, could be used to simply determine the overall mass transfer coefficient of systems for which the standard KLa determination methods still remain non-reliable or inaccurate (viscous solvents, mixture of immiscible liquids, fermentation broths…).

scholarly journals An Experimental Investigation of Overall Mass Transfer coefficient ( K_Ga ) of 〖CO〗_2 absorption using Monoethanolamine(MEA) and Diethanolamine(DEA) in a Bubble Column Reactor (BCR)

2020 ◽  
Vol 13 (1) ◽  
pp. 67-73
Author(s):  
Elaf Thamera ◽  
Salih Abduljabbar Rushdi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Gas Flow ◽  
Bubble Column ◽  
Bubble Column Reactor ◽  
Air Flow Rate ◽  
Column Reactor ◽  
Overall Mass Transfer Coefficient

In this work, an absorption technology   was used actually to investigation the  mass transfer coefficient of carbon dioxide from a gaseous mixture (air, carbon dioxide) in  blended solution Monoethanolamine (MEA) and Diethanolamine (DEA)  in a bubble column reactor (BCR) . The bubble column reactor(BCR) was made of Plexiglas with 1.5 m high and 0.1 m inside diameter. The overall mass transfer coefficient (  was evaluated at different operating conditions , gas flow rate, air Flow rate ,liquid flow rate .Where the gas flow rates were 10, 15 and 20 L /min ,  air flow rate 100,150 and 200 L/h ,and liquid flow rate 5 ,10,15 L /min . This experiment  by   using  continuous   process with helping centrifugal  pump  . High-performance gas chromatographic (GC) was performed to evaluate  loading during absorption experiment . The  experimental results have shown that the   loading in range of  0.581-1.367 (mol  /mole amine),and the maximum value of overall mass transfer coefficient ( KG) was 0.04 S-1 .

Influence of Physical Properties of Phases on Hydrodynamics and Mass Transfer Characteristics of a Liquid-Liquid Circular Microchannel

2016 ◽  
Author(s):  
Mehdi Sattari-Najafabadi ◽  
Bengt Sundén ◽  
Zan Wu ◽  
Mohsen Nasr Esfahany
Keyword(s):  
Mass Transfer ◽  
Physical Properties ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Rate Ratio ◽  
Operating Conditions ◽  
Flow Rate Ratio ◽  
Internal Diameter ◽  
Volumetric Mass Transfer Coefficient

The influences of operating conditions and physical properties of the two phases on the hydrodynamics and mass transfer in a circular liquid-liquid microchannel have been investigated. The polytetrafluoroethylene (PTFE) microchannel has an internal diameter of 0.7 mm and a T-shaped mixing junction. Sodium hydroxide solution was used as the aqueous phase. N-hexane and toluene were employed as the organic phases to investigate the effect of physical properties. Regarding the results, at constant total flow rate, raising the flow rate ratio enhanced the overall volumetric mass transfer coefficient. Using toluene as the organic solvent enhanced the overall volumetric mass transfer coefficient in average by 64.7% and 100.27% comparing to n-hexane-water at flow rate ratio of 1 and 0.5, respectively. This increment resulted in a decrement in the required mass transfer time and length in the microchannel. The length of the slugs had no considerable variation as n-hexane was replaced with toluene. Thus, the significant improvement of the overall volumetric mass transfer coefficient was because of the increment of the overall mass transfer coefficient, not the specific interfacial area.

scholarly journals Investigation of overall mass transfer coefficient of CO2 absorption in packed Column

2020 ◽  
Vol 13 (2) ◽  
pp. 153-157
Author(s):  
Zahraa N. Abd ◽  
Salih A. Rushdi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Continuous Process ◽  
Packed Bed Reactor ◽  
Absorption Time ◽  
Overall Mass Transfer Coefficient

Mixtures of different types of amine solution Monoethanolamine, Diethanolamine, and Triethanolamine were experimentally used to investigate the overall mass transfer coefficient (KGa) at different operating parameters. The experiments were made in a packed bed reactor (PBR) with 75 cm in high and10 cm inside diameter as a gas-liquid contactor at 25℃ and atmospheric pressure, using a simulation gaseous mixture (air, carbon dioxide)  with recycle stream (semi-continuous process). Experimental design process Taguchi was employed. Four factors and three levels were chosen and exploded using L9 (3 ^4) orthogonal array design. These parameters for semi-continuous  process were namely: gas flow rate 5,10,and 15 L/min ,airflow rate80,90,and 100 L/h, liquid flow rate 400,450,and 500 mL/min  and time absorption time  30,45,and 60min . A Shimadzu GC-8A Gas Chromatograph with a thermal conductivity detector was used to measure the CO2 concentration absorbed in aqueous blended solution. The maximum value for CO2 loading was 8.622 (mol CO2/mol amine) at 15 L/min gas flow and 450 mL/min liquid flow and 100 L/h airflow for 60 min from absorption time. The results showed that the max value of KGa is 0.048 S-1.

scholarly journals Optimization in the Absorption and Desorption of CO2 Using Sodium Glycinate Solution

2018 ◽  
Vol 8 (11) ◽  
pp. 2041 ◽  
Author(s):  
Pao Chi Chen ◽  
Sheng-Zhong Lin
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Bubble Column ◽  
Absorption Efficiency ◽  
Operating Conditions ◽  
Flow Rate Ratio ◽  
Optimum Operating ◽  
Co2 Absorption

This study used sodium glycinate as an absorbent to absorb CO2 in the bubble column scrubber under constant pH and temperature environments to obtain the operating range, CO2 loading, and mass transfer coefficient. For efficient experimentation, the Taguchi method is used for the experimental design. The process parameters are the pH, gas flow rate (Qg), liquid temperature (T), and absorbent concentration (CL). The effects of the parameters on the absorption efficiency, absorption rate, overall mass transfer coefficient, gas–liquid molar flow rate ratio, CO2 loading, and absorption factor are to be explored. The optimum operating conditions and the order of parameter importance are obtained using the signal/noise (S/N) ratio analysis, and the optimum operating conditions are further verified. The verification of the optimum values was also carried out. The order of parameter importance is pH > CL > Qg > T. Evidence in the 13CNMR (Carbon 13 Nuclear Magnetic Resonance) spectra shows that the pH value has an effect on the solution composition, which affects both the absorption efficiency and mass transfer coefficient. There are 18 experiments for regeneration, where the operating temperature is 100–120 °C. The heat of regeneration was measured according to the thermodynamic data. The CO2 loading, the overall mass transfer, and the heats of regeneration correlation are also discussed in this work. Finally, an operating policy for the CO2 absorption process was confirmed.

scholarly journals Effect of pH and Gas Flow Rate on Ozone Mass Transfer of Κ-Carrageenan Solution in Bubble Column Reactor

REAKTOR ◽  
2019 ◽  
Vol 18 (04) ◽  
pp. 177 ◽  
Author(s):  
Aji Prasetyaningrum ◽  
Dyah Arum Kusumaningtyas ◽  
Purbo Suseno ◽  
Ratnawati Ratnawati
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Gas Flow ◽  
Bubble Column ◽  
Operating Conditions ◽  
Bubble Column Reactor ◽  
Gas Flow Rate ◽  
Column Reactor

This research was conducted to calculate the mass transfer coefficient value for ozonation reaction of κ-carrageenan solution in the bubble column reactor. Ozone gas was produced using ozone generator type corona discharge. In this study, operating conditions were regulated at ozone gas flow rate 2- 5 L min-1, pH 4-10, and temperature 29 ± 1 oC. Samples were tested every 5 minutes to determine the dissolved ozone concentration. The results showed that dissolved ozone concentrations increased with increasing ozonation time and ozone gas flow rate. However, a very high gas flow rate can increase turbulence so that the mass transfer coefficient (kLa) value decreased. In alkaline conditions, the formation of free radicals (HO*) increases so that the amount of dissolved ozone decreases. The kLa value of ozone gas in κ-carrageenan solution is slightly lower than the kLa value of the ozone gas in the water. The results of this study indicate that (kLa) ozone gas in water is 0.131 / minute while the value (kLa) in κ-carrageenan solution is 0.128 / minute.

scholarly journals Mass Transfer Correlation and Optimization of Carbon Dioxide Capture in a Microchannel Contactor: A Case of CO2-Rich Gas

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5465
Author(s):  
Nattee Akkarawatkhoosith ◽  
Wannarak Nopcharoenkul ◽  
Amaraporn Kaewchada ◽  
Attasak Jaree
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Co2 Capture ◽  
Volumetric Flow Rate ◽  
Absorption Efficiency ◽  
Operating Conditions ◽  
Molar Ratio ◽  
Volumetric Mass Transfer Coefficient

This work focused on the application of a microchannel contactor for CO2 capture using water as absorbent, especially for the application of CO2-rich gas. The influence of operating conditions (temperature, volumetric flow rate of gas and liquid, and CO2 concentration) on the absorption efficiency and the overall liquid-side volumetric mass transfer coefficient was presented in terms of the main effects and interactions based on the factorial design of experiments. It was found that 70.9% of CO2 capture was achieved under the operating conditions as follows; temperature of 50 °C, CO2 inlet fraction of 53.7%, total gas volumetric flow rate of 150 mL min−1, and adsorbent volumetric flow rate of 1 mL min−1. Outstanding performance of CO2 capture was demonstrated with the overall liquid-side volumetric mass transfer coefficient of 0.26 s−1. Further enhancing the system by using 2.2 M of monoethanolamine in water (1:1 molar ratio of MEA-to-CO2) boosted the absorption efficiency up to 88%.

scholarly journals Ionic Mass Transfer at Point Electrodes Located at Cathode Support Plate in an Electrorefining Cell in Presence of Rectangular Turbulent Promoters

2022 ◽  
Vol 14 (2) ◽  
pp. 880
Author(s):  
Tondepu Subbaiah ◽  
Ponnam Vijetha ◽  
Barsha Marandi ◽  
Kali Sanjay ◽  
Manickam Minakshi
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Current Density ◽  
Limiting Current ◽  
Forced Circulation ◽  
Support Plate ◽  
Limiting Current Density ◽  
Overall Mass Transfer Coefficient

Current density plays a major role in deciding the plant size, current efficiency, and energy consumption in electrorefining cells. In general, operating current density will be 40% of the limiting current density. Forced circulation of the electrolyte in the presence of promoters improves the mass transfer coefficient. In the present study, rectangular turbulence promoters are fitted at the bottom side of the cell to improve the mass transfer coefficient at the cathode support plate. The limiting current density technique is used to measure the mass transfer coefficient. The variables covered in the present study are the effects of flow rate, promoter height, and spacing among the promoters. The electrolyte consists of copper sulfate and sulphuric acid. At a regulated flow rate, the electrolyte is pumped from the recirculation tank to the cell through an intermediate overhead tank. The limiting current density increased with an increasing flow rate in the presence of promoters, and thus the overall mass transfer coefficient on the cathode support plate also improved. With an increase in the flow rate of the electrolyte from 6.67 × 10−6 to 153.33 m3/s, limiting current density increased from 356.8 to 488.8 A/m2 for spacing of 0.30 m, with a promoter height of 0.01 m. However, it is noteworthy that when the promoter height is increased from 0.01 to 0.07 m, the overall mass transfer coefficient is found to increase up to 60%, but with the further increase in the promoter height to 0.30 m the mass transfer coefficient starts to decrease. Therefore, the optimized cell parameters are established in this work. The current sustainable concept of employing rectangular turbulence promoters will bring benefits to any precious metal refining or electrowinning tank house electrolytes.

scholarly journals Packed bed absorption column: Hydrodynamics and mass transfer

2019 ◽  
pp. 260-267
Author(s):  
Milan Sovilj ◽  
Branislava Nikolovski ◽  
Momcilo Spasojevic ◽  
Sinisa Mauhar
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Gas Mixture ◽  
Countercurrent Flow ◽  
Air Velocity ◽  
Absorption Column ◽  
Overall Mass Transfer Coefficient

This paper presents the results of the determination of the hydrodynamic characteristics and mass transfer in the pilot plate absorption column. The experimental values of the pressure drop in the countercurrent flow of air and water through the column were obtained. The graphic dependence of the pressure drop of air per unit height of the layer of packing (?P/h) on the apparent air velocity (Ug) through the dry charge was shown to be in the form of a quadratic function. From the graphical function which shows the dependence of the pressure drop per unit height of the layer of filling (?P/m) on the apparent air velocity during the countercurrent flow of the phases (water and air), three fields of the interaction of the phases were observed: a) the area of low load, at low apparent air velocities, b) the area of high load, at higher air velocities, and c) the flooding area, when the liquid completely fills the cavities and the working gas in them starts bubbling. The overall mass transfer coefficient (Kg) of the air-CO2-water system depends on the flow rate of the gaseous phase and the composition of the starting gas mixture (air-CO2). With the increase in the total gas flow rate, with a constant composition of the starting gas mixture and constant fluid flow, the overall mass transfer coefficient increases. Increasing the amount of CO2 in the starting gas mixture at a constant flow rate of fluid and a constant ratio of the molar flow of the inert in the liquid and the gas-phase (L'/G') decreases the overall mass transfer coefficient.

Absorption of oxygen into solutions of polymers

1986 ◽  
Vol 51 (10) ◽  
pp. 2127-2134 ◽  
Author(s):  
František Potůček ◽  
Jiří Stejskal
Keyword(s):  
Mass Transfer ◽  
Aqueous Solutions ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Flow Rate ◽  
Liquid Flow ◽  
Flow Curve ◽  
Liquid Flow Rate ◽  
Polymer Concentration ◽  
Newtonian Liquids

Absorption of oxygen into water and aqueous solutions of poly(acrylamides) was studied in an absorber with a wetted sphere. The effects of changes in the liquid flow rate and the polymer concentration on the liquid side mass transfer coefficient were examined. The results are expressed by correlations between dimensionless criteria modified for non-Newtonian liquids whose flow curve can be described by the Ostwald-de Waele model.

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