Effect Of Aeration Rate Research Articles

Effect of aeration rate and influence of pCO2 in large-scale cultures ofCatharanthus roseus cells

Effect of aeration rate and influence of pCO2 in large-scale cultures ofCatharanthus roseus cells

Characterization of bioreactors by in-situ fluorometry

A new microfluorometer with a special fiberoptic for the simultaneous detection of two different wavelengths was developed. Several tracers were tested for reactor characterization at different wavelengths, and the influence of the pH value and culture medium components on fluorescence was studied. In CST bioreactors, the effect of aeration rate and stirrer speed on the fluorescence can be used for reactor characterization. Mixing time experiments were performed in two different bubble columns.

Effects of process variables on the residence time distribution of a solid in a continuously operated flotation cell

Effects of aeration rate, slurry flow rate, stirring rate, pulp density, and particle size on the residence time distribution of a solid in a continuously operated flotation cell under non-flotation conditions (no frother, no concentrate removal) have been examined. The mixing behaviour of the solid in the cell has been quantitatively analysed using a multiple parameter approach. The results indicate that only a part of the cell volume behaves as a perfect mixer, the remaining being dead. The exit residence time distribution E( t) and the mean residence time ( t ) of solid are described by: E(t)= Q V eff exp − Q V eff t and t= V eff Q where Q is the volumetric slurry flow rate. For the variables ranges examined, it is observed that the aeration does not have any significant effect on the mixing behaviour, V eff increases with increasing slurry flow rate and stirring rate but decreases with increasing pulp density. The mean residence time, on the other hand, increases with increasing stirring rate, decreases with increasing slurry flow rate and pulp density, and exhibits a maximum with respect to particle size. Following empirical equation correlating the effective volume of the cell with the operating variables for a unisize feed is obtained: V eff V =0.249 D i ρ N μ 1.962 Q ρ D i μ −1.472 Q VN 1.711 B −0.32 where B is the weight fraction of solid in the pulp.

The effect of aeration rates on odour and solids of pig slurry

The effects of various aeration rates on the levels of Total Solids (TS) and odour in pig slurry were studied over a period of 4 months in 1·5-litre laboratory scale digesters stirred at 80 rpm at approximately 20°C. The levels (g litre −1) of TS and VS in the slurry were 63·7 (±2·7) and 54·1 (±2·7), respectively. The maximum oxygen transfer rates to the digesters were estimated to be 118·4, 23·8, 15·9 and 3·1 mg O 2 litre −1 h −1. The results of this study indicated that all treated effluents had significantly (P < 0·05) lower levels of solids than untreated wastes. The reduction in the levels of TS associated with these aeration rates were 35%, 20%, 25% and 26%, respectively. Redox values (E cal(mV)) became more negative with decreasing aeration, providing an indication of the degree of anaerobiosis in each digester. The values were approximately −20(±4), −253(±6), −251(±8) and −321(±5) for the four aeration rates examined. Odours associated with each of the treatments were determined by a panel (odour threshold dilution (OTD) and odour offensiveness) and by chemical means (volatile sulphides, ammonia). Aeration rates of 15·9 to 23·8 mg O 2 litre −1 h −1 ( redox ⋍ −250 mV) reduced the OTD by more than 80% and the levels of volatile sulphides and ammonia by 95% compared with unaerated wastes. Increasing aeration approximately sixfold resulted in a positive level of dissolved oxygen (> 1 mg litre −1) in the treated effluent and reduced the OTD and the levels of volatile sulphides and ammonia by a further 15% and 4%, respectively. Odour offensiveness, the most subjective of the measures of odour, also decreased, with increasing aeration.

The effects of aeration rate, particle size and pulp density on the flotation rate distributions

The apparent flotation rate distributions have been estimated from the flotation kinetic data by the numerical inversion of the Laplace transform. The distributions have been analyzed for their dependence on aeration rate, particle size and initial pulp density. The distribution function remains unaltered, but the argument of the function, the apparent flotation rate, is rescaled with change in the rate of aeration and particle size. The scaling factor increases rapidly with the rate of aeration and exhibits a characteristic maximum for intermediate particle size. The calculated distributions are approximately independent of the initial pulp density when dilute, but show marked divergence for concentrated pulps. Some implications of these results for modelling of flotation circuits are briefly discussed.

The Interaction of pH and Aeration in CI Uptake by Barley Roots

AbstractThe uptake of Cl by excised roots of barley (Hordeum vulgare L.) from KC1 solution maintained at high pH was markedly reduced by high rates of aeration, whereas K uptake was scarcely affected. Aeration rate had relatively minor effects at low pH. The effect of high aeration rate at pH 9 could be overcome by the use of buffered solutions. In unbuffered solutions the H resulting from the excess cation uptake together with that produced from respiratory CO2 was sufficient to materially reduce the pH of the solution. The reduction in pH favored the uptake of Cl which is adversely affected by high pH. The effect of aeration rate could be explained in terms of root induced pH changes and film diffusion involving the solution film adjacent to the root surface.