Mass transfer coefficient dynamic method

This research used mechanically agitated tank reactor system shown in Fig. 1. The reactor, 102 mm in diameter and 165 mm in height, was made of transparant pyrex glass and was equipped with four baffles, 120 mm in length and 8 mm in width, and six blades disc turbine impeller 45 mm in diameter and 12 mm in width. The impeller was rotated by electric motor with digital impeller rotation speed indicator. Waterbath thermostatic, equipped with temperature controller was used to stabilize reactor temperature. Gas-liquid mass transfer coefficient kia was determined using dynamic oxygenation method as has been used by Suprapto et al. [11]. 

By the dynamic method, the oxygen concentration was measured as shown in Figure P7.6. The static volume of a fermentation broth, the flow rate of air, and the cell concentration were 11,1.51 min", and 3.0 g-dry cell 1 , respectively. Estimate the oxygen consumption rate of the microbes and the volumetric mass transfer coefficient. 

Gas-Liauid Hydrogen Transport. Using a dynamic method (ref. 15), the gas-liquid mass transfer coefficient I a for hydrogen into toluene was measured in the 50 ml reactor. The autoclave was pressurized to an initial pressure Pt and then stirring was staned. The rate of mass transfer as a function of time and in terms of P[ and the final pressure P2, is given by Equation 1. 

The liquid-solid mass-transfer coefficient can also be measured by the reverse process, namely adsorption on a solid from solution. Furusawa and Smith (1973) studied adsorption of benzene from aqueous solution on to activated carbon particles. The concentration of benzene in the liquid was monitored by a gas chromotograph. The liquid-solid mass-transfer coefficient from such a dynamic adsorption method can be obtained from the expression (Furusawa and Smith, 1973)... 

Lee and Dudukovic [18] described an NEQ model for homogeneous RD in tray columns. The Maxwell-Stefan equations are used to describe interphase transport, with the AIChE correlations used for the binary (Maxwell-Stefan) mass-transfer coefficients. Newton s method and homotopy continuation are used to solve the model equations. Close agreement between the predictions of EQ and NEQ models were found only when the tray efficiency could correctly be predicted for the EQ model. In a subsequent paper Lee and Dudukovic [19] presented a dynamic NEQ model of RD in tray columns. The DAE equations were solved by use of an implicit Euler method combined with homotopy continuation. Murphree efficiencies calculated from the results of an NEQ simulation of the production of ethyl acetate were not constant with time. 

Without cell respiration, the overall mass balance for the biological dynamic method simplifies from Eq. (4.30) to Eq. (4.28). The volumetric mass transfer coefficient ki a is then evaluated by integrating Eq. (4.28) and plotting ln[(C - Cl)/(C - C )] as a function of time, where kj a is the slope of the resulting line, or by curve fitting the data with a nonlinear regression software package. 

Andre, G., Moo-Young, M., and Robinson, C.W. (1981), Improved method for the dynamic measurement of mass transfer coefficient for application to solid-substrate fermentation, Biotechnology and Bioengineering, 23(7) 1611-1622. 

Tribe, L.A., Briens, C.L., and Margaritis, A. (1995), Determination of the volumetric mass transfer coefficient (kLa) using the dynamic gas out-gas in method Analysis of errors caused by dissolved oxygen probes, Biotechnology and Bioengineering, 46(4) 388-392. 

In the calculation of the predicted response curves the axial dispersion coefficient and the external mass transfer coefficient were estimated from standard correlations and the effective pore diffusivily was determined from batch uptake rate measurements with the same adsorbent particles. The model equations were solved by orthogonal collocation and the computation time required for the collocation solution ( 20 s) was shown to be substantially shorter than the time required to obtain solutions of comparable accuracy by various other standard numerical methods. It is evident that the fit of the experimental breakthrough curves is good. Since all parameters were determined independently this provides good evidence that the model is essentially correct and demonstrates the feasibility of modeling the behavior of fairly complex multicomponent dynamic systems. 

Gas-Liquid Mass-Transfer and Reaction Rates. Experimentally, one of the easiest ways to determine the overall gas-liquid mass-transfer coefficient in unsparged agitated tanks is measurement of pressure drop, where Ki a is the mass-transfer coefficient (s ), Cg is the instantaneous gas concentration in the liquid, and Cg is the equilibrium gas concentration in the liquid. This is also commonly known as the dynamic method (62), and it has been used in catalytic work (63). 

The textbook entitled Environmental Chemodynamics (Thibodeaux, 1996) was the first unified attempt to address multimedia chemical mass transfer in natural systems such as air, water, soil, sediments, etc. Arguably, mass transfer is the key chemo-dynamic process responsible for the presence of many anthropogenic chemicals worldwide as trace contaminants and these chemicals achieving pollutant levels at many locales. Mass transport coefficients (MTCs) are the kinetic parameters that quantify chemical movement rates within and between these natural media. Coefficient estimation methods based upon theoretically sound transport mechanisms... 

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