Liquid Pool Height Research Articles

Random Packing Performance in Continuous Foam Fractionation

AbstractThe #25 teller rosette (TR) random packing was used to enhance foam drainage in foam fractionation under continuous steady‐state conditions and tested using sodium dodecyl sulfate (SDS) as a model surfactant. A column without the #25 TR served as control. The results demonstrated that the #25 TR was capable of enhancing the foam drainage and enrichment ratio while reducing the liquid holdup. The experiment was set up with optimized feed flow rate, liquid pool height, air flow rate, and SDS feed concentration. The enrichment ratio obtained by the #25 TR column was 1.76 times higher compared with the control column. Based on the mass balances and equilibrium relationship, a new method for graphical illustration of theoretical stages is also presented.

Numerical investigation on thermal characteristics and flow distribution of a parallel micro-channel separate heat pipe in data center

This study focuses on the flow distribution and heat transfer characteristics of the evaporation terminal of a micro-channel separate heat pipe (MCSHP) used in data center. A complete CFD model for the parallel tubes with simplified louvered fins of the evaporator structure was established to consider the thermal enhancement while reduce the computing costs. The CFD model was validated by comparing the cooling capacity and outlet temperature of MSCSHP with experiments. The transformation process from bubble flow to slug flow was visualized using VOF model. The simulations reveal that the maximum cooling capacity of the studied MCSHP system could reach 9610 W when the corresponding optimal refrigerant filling ratio is 65.27%. The generation and motion of vapor bubbles influence the height of liquid pool in the evaporation terminal, thus leaded to the change of effective heat transfer area. Moreover, it is found that configurations of inlet and outlet have great impacts on the distribution of mass flow and heat flux under low filling ratios. While under higher filling ratios, the heat flux distribution is not affected by these factors due to the flat tubes filled with two-phase refrigerant.

Performance of Solvent-Assisted Thermal Drainage process and its relationship to injection parameters: A comprehensive modeling

The addition of hydrocarbon solvents to the steam injection, known as Solvent-Assisted Thermal Gravity Drainage (SA-SAGD), has recently been proven to be a more energy saving and environmentally friendly method for heavy oil recovery. Nevertheless, the relationship between injection parameters and heavy oil production in conventional SAGD were always introduced to analysis the performance of SA-SAGD, which makes many confusing in the interpretation. In this paper, the heat lost to the cap rock of the reservoir is determined by taking into account not only the chamber-edge velocity, but also the temperature and mass distributions inside the chamber. Besides, by implicitly characterizing the chamber-edge shape and considering heat and solvent diffusion beyond the chamber edge, the oil rate is calculated. Then, the model couples heat and mass balance equations in the whole oil sand dynamically by considering the effect of liquid pool. This comprehensive method enables us to clearly examine the relationship between the Production-Injection Ratio (PIR) and the height of liquid pool. Lastly, the new model is verified by comparing predicted results with that of numerical simulation. The results show that, the oil rate of SA-SAGD is improved by both of the diluting effect of solvent on bitumen viscosity and a more reasonable chamber shape formed by co-injection solvent with steam. In addition, although heat-loss rate of SA-SAGD is generally smaller than that of conventional SAGD, the Steam-Oil Ratio (SOR) of SA-SAGD may even higher than that of SAGD in the late period of the process if the liquid level is extremely high. Moreover, the liquid-pool height for SA-SAGD is more sensitive to the PIR than for SAGD. Accordingly, when the effect of liquid pool on the production is considered, the PIR of SA-SAGD must be selected carefully.

Abstraction of phenol onto Pseudomonas putida and Cetyl Trimethyl Ammonium Bromide.

Foam separation, an efficient downstream processing unit operation, was tested as a post-treatment technique for phenol removal after biosorption. The biosorptive foam separation process was carried out in two stages, namely biosorption and foam separation. A minimum run resolution V central composite design with four variables (initial concentration, pH, biosorbent dosage, and time) for biosorption and three variables (liquid pool height, surfactant concentration, and air flow rate) for biosorptive foam separation was applied to optimize the process. The results showed a good fit with the proposed statistical model for removal of phenol (R2 = 0.9500) for biosorption and (R2 =0.9599) for biosorptive foam separation. In addition, the adsorption isotherm and kinetic studies revealed that the biosorption process followed the Langmuir model (R2=0.9544) and Bangham kinetic model (R2=0.9857). The adsorbed chemical species was identified by FTIR spectroscopy. Electrokinetic measurements were carried out to determine the isoelectric point (IEP) of the bacteria. The zeta potential profile of the bacteria appears to be negative throughout the range of pH examined, showing isoelectric point at a pH of 3. The recovery of phenol loaded biomass and final traces of phenol by flotation were found to be 99.95%.

Experimental Investigation on Abstraction of Phenol Onto Micrococcus lylae and Cetyl Trimethyl Ammonium Bromide

Air floatation, an efficient solid–liquid separation process, was tested as a post treatment technique for phenol removal. The results consider about the practical solutions for certain operations such as efficient solid–liquid separation, attainment of maximized percentage removal, phenol rich solution with Micrococcus lylae cells, and pure water without M. lylae cells. The two processes, biosorption and flotation, can effectively operate in combination and both the sorbent and treated water can be recycled. The effect of various operating parameters, such as initial feed concentration, equilibrium time, biosorbent dose, pH, liquid pool height, surfactant concentration, and air flow rate, was experimentally investigated. The maximum sorption capacity was found to be 303 mg/g at pH 7 and an initial phenol concentration of 500 mg/L. The higher floatability of M. lylae was obtained in a maximum time of 10 min. In addition, the adsorption isotherm and kinetic studies revealed that the biosorption process followed the Dubinin–Radushkevich model (R2 = 0.982) and pseudo‐first order kinetics with a kinetic constant of 2.6537/day. The adsorbed chemical species was identified by Fourier transform infrared (FTIR) spectroscopy. Electrokinetic measurements were carried out to determine the isoelectric point of the bacteria. The zeta potential profile of the bacteria was affected by the presence of phenol at different pH values. The recovery of phenol loaded biomass and final traces of phenol by flotation were found to be 99.91%.

Influence of various process parameters on the biosorptive foam separation performance of o-cresol onto Bacillus cereus and Cetyl Trimethyl Ammonium Bromide

Response surface methodology was used to optimize the removal of o-cresol from aqueous solution by Bacillus cereus and Cetyl Trimethyl Ammonium Bromide based hybrid technique biosorptive foam separation. The biosorptive foam separation was carried out in two stages namely biosorption and foam separation. A minimum run resolution V central composite design with five variables (initial feed cresol concentration, pH of the feed, biosorbent dosage, time and agitation speed) for biosorption and three variables (liquid pool height, surfactant concentration and airflow rate) for biosorptive foam separation were applied to optimize the process. The optimized conditions for maximum removal of cresol for biosorption were, Initial feed cresol concentration 467mg/l, pH of the feed 6.44, biosorbent dosage 1.11g, time 5.25 days and agitation speed of 195rpm for biosorption, and that for biosorptive foam separation were liquid pool height 28.38cm, surfactant concentration 0.29% and airflow rate 1.8lpm. The results showed a good fit with the proposed statistical model for removal of o-cresol (R2 = 0.9387) for biosorption and (R2 = 0.9980) for biosorptive foam separation.

Continuous foam fractionation of chromium(VI) ions from aqueous and industrial effluents

The purpose of this study was to investigate the use of foam fractionation to recover Cr(VI) ions from simulation aqueous solution and tannery effluent. The effects of operation parameters, such as air flow rate, liquid pool height, feed concentration, surfactant concentration, pH of the feed, and feed flow rate on the separation characteristics were studied in the continuous operation. Enrichment ratios of 5.2 and 4.8 with percentage removal of 65% and 61% were achieved for the removal Cr6+ ions from simulation aqueous solution and tannery effluent on the basis of optimization of parameters, respectively. As the optimized results, the air flow rate and liquid pool height were 0.1 lpm and 30 cm, feed concentration and surfactant concentration were 10 ppm and 0.1 % (w/v), pH of the feed was 6 and feed flow rate was 4 lph. The Cr(VI) concentration in the effluent was around 0.5 ppm which could meet the Bureau of Indian standards (BIS2490) wastewater discharge standards. Box–Behnken model and Analysis of Variance (ANOVA) were applied to the experimental foam fractionation studies. Response surface method with three levels of variances was used in the identification of significant effects and interaction of the above mentioned six variables in the continuous foam fractionation studies. A second order polynomial regression model has been developed using experimental data. From the results it was found that the selected variables have a strong effect on the foam fractionation and also the experimental values were in good agreement with predicted values.

CONTINUOUS FOAM SEPARATION OF HEAVY METAL IONS FROM ELECTROPLATING INDUSTRIAL EFFLUENT

Process industries generate a large amount of waste materials during either production or downstreaming operations. Among many methods available for their separation, foam separation plays a major role, especially when the concentration of undesirable components involved is very low. The success of this technique depends on the stability and characteristics of the foam. This operation is simple with less maintenance as there are no moving parts. In the present study, simultaneous removal of metal ions such as chromium (VI), copper (II), and zinc (II) from electroplating industrial effluent was carried out with sodium lauryl sulfate (SLS) as surfactant in continuous foam column. Enrichment ratios of 3.94, 4.05, and 7.96 with a percentage removal of 59.0%, 63.0%, and 99.2% were obtained for chromium (VI), copper (II), and zinc (II) ions respectively at the optimum operating parameters of 23 cm liquid pool height in column, 0.1 liter per minute (Lpm) of airflow rate, feed flow rate of 4 liters per hour (Lph), 0.1% (w/v) of SLS concentration, pH of 6.0, and at feed concentrations of 32.5, 27.0, and 23.0 ppm for chromium (VI), copper (II), and zinc (II) ions respectively. Enrichment ratio was found to increase with an increase in feed flow rate. With a decrease in concentration of the bulk solution, the separation factor was found to increase. The study indicates the feasibility of continuous foam separation for treating industrial effluents.

Nucleate boiling heat transfer from a structured surface – Effect of liquid intake

A model of the suction evaporation mode in nucleate boiling from tunnel and pore structures is presented. The model is based on the analysis by Nakayama et al. [W. Nakayama, T. Daikoku, H. Kuwahara, T. Nakajima, Dynamic model of enhanced boiling heat transfer on porous surfaces – Part II. Analytical model, ASME J. Heat Transfer 102 (3) (1980) 451–456] and L.H. Chein and R.L. Webb [A nucleate boiling model for structured enhanced surfaces, Int. J. Heat Mass Transfer 41 (14) (1998) 2183–2195]. Additionally, a detailed phenomenological model of liquid refill has been developed. It has been shown that the process of liquid refill and the time needed for it is strongly dependent on pool height. Effect of liquid pool height on bubble frequency has also been discussed. Finally, a generalized methodology is given for the prediction of boiling data from a structured surface.

Determination of operation envelopes for closed, two-phase thermosyphons

A concern in the design and operation of closed, two-phase therosyphons (CTPTs) is determining the initial filling ratio of the working fluid, as a function of CTPT dimensions, type and vapor temperature of working fluid and power throughput, to maximize performance, while avoiding potential dryout in the evaporator section. A one-dimensional, steady-state model is developed for determining the operation envelopes of CTPTs, in terms of the above parameters. The CTPT operation envelope is basically an enclosure with three boundaries. The lower boundary corresponds to when the liquid film thickness in the evaporator reaches a critical value—beyond it the liquid film could dry out—while the upper boundary corresponds to when the expanding liquid pool, due to boiling, fills the entire evaporator. The third and closing boundary corresponds to the counter-current flooding limit (CCFL) at the exit of evaporator. The correlation developed to calculate the expanded liquid pool height in the evaporator agrees with experimental data of acetone, ethanol and water to within ±8%. Also, the calculated upper and lower boundaries of the operation envelope for an ammonia CTPT are in excellent agreement with experimental data [1]. Calculations showed that increasing the CTPT diameter, evaporator length, or vapor temperature expands the operation envelope, while increasing either the condenser or the adiabatic section length only slightly changes the envelopes upper and lower boundaries.

Prediction of separation factor in foam separation of proteins

A phenomenological model has been developed for predicting separation factors obtained in concentrating protein solutions using batch-foam columns. The model considers the adsorption of surface active proteins onto the air-water interface of bubbles, and drainage of liquid from the foam, which are the two predominant processes responsible for separation in foam columns. The model has been verified with data collected on casein and bovine serum albumin (BSA) solutions, for which adsorption isotherms are available in the literature. It has been found that an increase in liquid pool height above the gas distributor and the time allowed for drainage result in a better separation. Further, taller foam columns yield poorer separation at constant time of drainage. The model successfully predicts the observed results.

A Model for Continuous Foam Concentration of Proteins: Effects of Kinetics of Adsorption of Proteins and Coalescence of Foam

Abstract A model for concentration of proteins from dilute solutions in a continuous foam fractionation column is proposed. This model accounts for (1) kinetics of adsorption of proteins in the liquid pool as well as in the foam, (2) liquid drainage from thin films due to Plateau border suction and disjoining pressure, (3) gravity drainage of liquid from Plateau borders, and (4) bubble coalescence in the foam. Protein enrichment and recovery were found to increase as the liquid pool height increased, eventually attaining constant values (corresponding to adsorption equilibrium), thus demonstrating the strong dependence of protein separation on adsorption kinetics. Higher enrichments and lower recoveries were obtained for smaller gas velocities, larger bubble sizes, and higher feed flow rates. Enrichments as well as recoveries were higher at lower feed concentrations. Coalescence was found to lead to higher enrichments and lower recoveries, this dependence being stronger for larger inlet bubble sizes.

Stability analysis of a closed thermosyphon model

The stability of a closed two-phase thermosyphon model is studied as a function of the heat input, liquid filling, viscosity, density, capillary number and two-phase flow Grashof number. It is shown that for small liquid fillings or pool heights, the liquid dries out and there are no solutions beyond this point. For relatively large liquid pool heights, the heat input, when plotted versus the respective steady-state vapour height, is approximately a quadratic expression such that there are two possible steady states for each heat input. A linear stability analysis indicates that there is a turning point at the maximum heat input at which one of the eigenvalues of the linear stability analysis becomes zero. Control parameter surfaces have been calculated in order to determine the effects of the thermosyphon length, liquid pool height, capillary number, liquid-to-vapour density and viscosity ratios, heat input, and two-phase flow Grashof number on the stability of the closed two-phase thermosyphon model. It has been found that the steady operation of a thermosyphon is insensitive to the vapour-to-liquid viscosity ratio and thermosyphon length, and very sensitive to the vapour-to-liquid density ratio. Linear and nonlinear transient analyses of the thermosyphon behaviour near the steady-state operating conditions indicate that, for large liquid fillings, there are upper limits for the heat input. Large liquid fillings may result in an unstable operation of the thermosyphon. It is also shown that a linear analysis underestimates grossly the transient behaviour of the thermosyphon operation.