جستجوی مقالات مرتبط با کلیدواژه "انتقال جرم" در نشریات گروه "محیط زیست"

CO2 concentration, as the main greenhouse gas, is growing in atmosphere and many alternatives have been investigated to deal with it. However, harnessing with the aim of biomethanation seems to be more economic.

In this study a mass transfer modeling was conducted for a biomethanation process under a batch strategy aiming at maximizing liquid active volume. The accuracy of modeling results was assessed via comparing with experimental data and kinetic results under zero-dimension study. Then one-dimensional study was conducted in order to investigate biomass and hydrogen concentration profiles within liquid phase of the bioreactor and active volume calculation. Response surface method (RSM) was also served to investigate effect of temperature, pressure and as three main factors on active volume followed by response optimization.

Model accuracy was confirmed by zero-dimension study. One-dimensional study was also revealed that biomass growth dispersion within liquid phase depends on hydrogen profile concentration on condition that both hydrogen and biomass diffusion coefficients were assumed to be equal. Their degree of magnification was 10-9  in standard conditions. RSM showed that the three studied factors significantly affected on bioreactor active volume. Meanwhile, pressure and temperature influenced the most, respectively.

A batch bioreactor with  and high pressure and temperature met optimal conditions for biomethanation; however, process economy defines operational limitations.

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.

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.

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.

 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.

The objective aim of this research was to predict dissolved oxygen (DO) concentration in a full scale activated sludge reactor. So tested a function for oxygen transfer.The activated sludge model No.1 was used to describe the biochemical processes.The function of dissolved Oxygen was used by first- order differential equations. This model was simulated by MATLAB Software. The simulated model was tested for a laboratory pilot and shahrak Ghods treatment plant. The obtained results confirmed the data obtained from the model and the experimental one.