Gassing rate

The influence of gassing rate and stirrer speed on an oxidation reaction, in an aerated batch reactor, are to be investigated. The outlet gas is assumed to be essentially air, which eliminates the need for a gas balance for the well-mixed gas phase. 

Fig. 3. Response of Q and C0 profiles with different gassing rates until the reactant CA is consumed.

Apart from the critical impeller speed for solid suspension and efficient gas dispersion, flooding is also a very important phenomenon in three-phase systems. Flooding may take place at low impeller speed or high gassing rate. Under these conditions, the gas is dispersed just around the central shaft of the tank, whereas the solids are settled at the bottom. Flooding characteristics are not affected by particles. Furthermore, high-viscosity liquids are able to handle more gas before flooding than low-viscosity liquids. 

At the given gassing rate, a 0.84-m-dia. concave-blade (CD6) turbine will draw the same power. Recalculating the aeration... 

FIGURE 9.30 Changing vessel performance with agitation and gassing rates. (From Nienow et al., 1977.)... 

More recently, a range of 6-V and 12-V, 125-Ah monobloc batteries with/without catalysts have been tested under standby float conditions for extended periods at room temperature and the gassing rates recorded. The results for the 6-V batteries are presented in Table 5.8. Batteries 1 and 2 were not fitted with catalysts and had individually sealed cell compartments. Batteries 3 and 4 had a single catalyst located in a common headspace. The data obtained from tests on 12-V, 25-Ah batteries with two catalysts in the common headspace are shown in Fig. 5.14. Those without... 

Table 5.8. Gassing rates for batteries under standby service at room temperature.

L.T. Lam, H. Ceylan, N.P. Haigh, T. Lwin, C.G. Phyland, D.A.J. Rand, D.G. Vella, ALABC Project N3.1, Influence of residual elements in lead and expander materials on the oxygen- andjor hydrogen-gassing rates of lead-acid batteries. Semi-annual Report 1 July to 31 December 2001, Advanced Lead-Acid Battery Consortium, Research Triangle Park, NC, USA, 2001. 

R. P. Fishwick, J.M. Winterbottom, E.H. Stitt, "Effect of gassing rate on solid-liquid mass transfer coefficients and particle slip velocities in stirred tank reactors", Chem. Eng. Sci., 2003, 58, 1087-1093. 

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