An 1D hydrodynamic model has been simulation and developed for gas hold-up and liquid circulation velocity prediction in AIR-LIFT reactors. model is based on momentum balance equations and has been adjusted to experimental data collected on a pilot plant reactor equipped with two types of gas distributors and using water as the liquid phase.The model equations described previously constitute a set of non-linear equations which are solved by an iterative procedure (v.b) (c plus). This model has also been combined with mass transfer and the kinetics of a chemical reaction to yield a complete model of the performance of a reactor.

Polygalacturonase production under different shear stress environments by Aspergillus sp. was studied. It was found that the rate of enzyme production in the stirred tank fermentor decreased with increasing the stirrer speed in the range 300-750 rpm. On the other hand, in a split cylinder AIR-LIFT fermentor, the rate of polygalacturonase production slightly increased with increasing in AIR rate from 1.5 to 2 v.v.m (volume AIR/culture volume/minute). The maximum enzyme titres at the end of the cultivation period in the AIRLIFT fermentor were 35 unit/ml and at least twice of that obtained in agitated fermentors. Measurement of main hyphal length in agitated and AIR-LIFT fermentors suggested break up of the mycelia in the higher shear environment of stirred fermentor especially at the higher agitation rates. The similarity in the trend of the enzyme production and main hyphal length suggested a possible relationship between the morphology and productivity of the Aspergillus sp. used in the present study.

Nowadays the lack of food especially protein is the most important problem. Because of the increasing of the world population the need for food is increasing day by day for this reason researches are searching for cheap resources of protein for people. Whey is by- product of cheese factory. Whey provides ecological problems because of having high COD. According to these problems many researchers have been done on whey and different products were achieved such as single cell protein.In this research, the production of single cell protein from whey and trichosporon yeast are studied in external loop AIRLIFT reactor. Effective factors on gas hold up Such as AIR giving, ratio of down comer diameter to riser diameter and height of liquid in gas separator were studied and optimized. In this optimized situation the rate of single cell protein was achieved.The results of experiments showed that optimimum value for AIR giving intensity was 2.27 cm/s , ratio of down comer diameter to riser diameter was 0/5 cm and height of liquid in gas separator was 3 cm. In this optimum condition, the amount of single cell protein was 18.9 g/l. The rate of single cell protein in stirred reactors and bubble column was 10.38 and 17.3 g/l respectively in other's researches. In comparison, external loop AIR LIFT reactor showed an increase about 8.5 percent to bubble column and 45 percent to stirred reactor in producing single cell protein. So external loop AIR LIFT seems suitable in producing single cell protein. Producing single cell protein can be studied in other AIR LIFT reactors such as internal loop AIRLIFT reactors and obtained results can be campared with the results of this research.

In this paper, oxygen mass transfer in an AIRLIFT reactor for single step H2S removal from acid gas streams has been studied experimentally. Oxygen and nitrogen were used as gas phase. Water, Chelated iron solution (500ppm) and a slurry solution 0.08% (wt %) sulfur per 100 ml of solution of chelated iron) were used as liquid phase. Experiments were carried out in a 60 liters internal loop AIRLIFT reactor.  Results show that mass transfer coefficient (KLa) for three different types of liquid phase are almost equal. Adding of nitrogen accompanied with oxygen causes an increase in mass transfer coefficient, decreasing saturation concentration (C*) and consequently decreasing mass transfer flux. Finally, new correlations expressing variation of mass transfer coefficient in terms of AIR and nitrogen superficial velocities were presented. There is a good agreement between this work and similar experimental works.

Objective: AIR-LIFT bioreactors can play an important role in tissue engineering because of many advantages, such as; simplicity of construction, absence of moving parts, easy sterilization and low power consumption. However, optimum design of AIRLIFT bioreactors for cultivation of stem cells is still a difficult task, because of complicated relations between mixing and mass transfer, and also high sensitivity of stem cells to shear stress. In this study, computational fluid dynamics (CFD) analysis using related software was used to characterize an internal loop AIRLIFT bioreactor for stem cell proliferation. The effect of geometry parameters such as sparger position and configuration, ratio of the downcomer to the riser area (Ad/Ar), and height of liquid above (Ha) and below (Hb) of the draft tube was considered to identify the complex hydrodynamic environment as well as shear stress applied to suspension culture of stem cells. The results demonstrated that sparger position and configuration has maximum effect on shear stress exposure on cell although shear stress can be reduced with increasing Ha in this area. In addition, large Ad/Ar was found to be useful for minimum exposure shear stress on cells while it has negative effect on cell distribution as same as Hb. Therefore, optimum design of AIR-LIFT bioreactor can be achieved by CFD analyzing with comprehensive considering of hydrodynamic environment to apply this type of bioreactor in tissue engineering without performing costly time-consuming experiments.Materials and Methods: Computational fluid dynamic software (ANSYS 14.0) was used to consider geometric parameters of AIR-LIFT bio-reactor hydrodynamic environment to apply this kind of bio-reactor in tissue engineering for expanding stem cells.Results: The effect of geometry parameters such as sparger position and configuration, ratio of the downcomer to the riser area (Ad/Ar), and height of liquid above (Ha) and below (Hb) of the draft tube was considered to identify the complex hydrodynamic environment as well as shear stress applied to suspension culture of stem cells. The results demonstrated that sparger position and configuration has maximum effect on shear stress exposure on cell because of effected on bubble formation and geometry. Although shear stress can be reduced with increasing Ha in this area, in addition, large Ad/Ar was found to be useful for minimum exposure shear stress on cells while it has negative effect on cell distribution as same as Hb.Conclusion: As the above results show, optimum design of AIR-LIFT bio-reactor can be achieved by CFD analyzing with comprehensive considering of hydrodynamic environment to evaluate applicability of AIR-LIFT bio-reactor in tissue engineering without performing costly time-consuming experiments.

To study microbial oxidation of ferrous ions through the uranium bioleaching process, experiments were carried out in the internal loop AIR-LIFT reactor by Acidithiobacillus ferrooxidans. The microbial oxidation kinetics was evaluated with the Monod correlation and modified models for the substrate and product inhibition. The maximum recovery of uranium in the biological and control tests were 97.1% and 21%, respectively. Evaluation of the experimental data with the mentioned models showed that the modified model for the substrate inhibition gave a good fitting for all aeration rates. The R2-values were found to be 0.98, 0.97, 0.94 and 0.94 for the AIR superficial velocity of 0.0065, 0.0085, 0.01 and 0.015 m/s, respectively.

In this study, effects of solid concentration, temperature, and initial Fe2+ concentration on bioleaching of sulfide mineral (chalcopyrite) obtained from Sarcheshmeh Copper Mine in the region of Kerman located in the south of Iran were investigated. A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans has been isolated from a typical chalcopyrite copper concentrate of the mentioned mine. Bioleaching experiments were carried out in two batch AIR-LIFT bioreactors with recycling stream. One reactor contained 2 liters of medium and 10% (v/v) inoculums while in the other reactor, control bioleaching tests were carried out with sterilized concentrate without inoculums by the addition of 40 ml of 0.5% (v/v) formalin in ethanol. The results indicate that the efficiency of copper extraction is dependent on all of the aforementioned variables. In addition, results show that the effects of solid concentration and temperature had more effect compared to the initial Fe2+ concentration. Maximum copper recovery was achieved 70% at pH=1.5, initial Fe2+ concentration=7g/L and pulp density = 10% (w/v) in bioreactor, after 10 days.

Simulations of tware in the system of gas velocity input and the amount of retained gas in reactors AIR or AIR LIFTs. Model that rays this simulation was chosen with the condition of mass transfer can also be a liquid phase used. But in general, the program is oriented to the empirical equation of a reactor using different relations of by neural networks is developed for the solution of other answer is. Comparison between the original model and simulation model for a variety of nozzles single-input, multi-input 1 and 2 have also been made.

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Background and Objective: In This study the impacts of operating conditions such as aeration rate, the downcomer-to-riser cross-sectional area ratio (Ad/Ar), and liquid phase properties on the hydrodynamics and volumetric mass transfer coefficient in three-phase AIRLIFT reactors was investigated. Method: Experiments were conducted in external loop AIR-LIFT reactor with downcomer to riser cross-sectional area ratio (AD/AR=0. 14) and internal AIR-LIFT reactors with downcomer to riser cross-sectional area ratios 0. 36 and 1. AIR and Water were used as gas and liquid phases, respectively and activated sludge is used as the solid phase. Findings: The liquid circulation velocity, gas holdup and mass transfer coefficient increased with an increase in the superficial gas velocity, decrease the sludge concentration and decrease downcomer to riser cross-sectional area ratio. The maximum amount of gas hold up, 0. 178 in external AIR-LIFT reactor with 1%(w/w) activated sludge in superficial gas velocity 0. 24(m/s) was observed. A model to predict the effect of activated sludge concentration, the superficial gas velocity and the downcomer-to-riser cross-sectional area ratio on the mass transfer activated sludge AIRLIFT reactors provided which with the experimental results are in good agreement. Discussion and Conclusion: The evaluation of internal and external reactors performance at different concentration and superficial gas velocity show that the AIR-LIFT reactor with external loop has better performance in comparison with internal AIRLIFT reactors.