Flood regime

The flooding regime (above point C and C in Figs. 8.15 and 8.18a) This region is characterised by instability, entrainment, and poor efficiency and is therefore avoided. 

Table 13.1 Frequency of flood regimes and the estimated extend of the related floodplains with prevailing associated vegetation.

The isothermal expansion power is the energy supplied to the system by the gas stream dispersing the gas in the liquid. When the power due to the impeller rotation is less than the isothermal expansion power of the gas, the flooded regime which is characterized by gas rising unhindered near the impeller shaft prevails. The distribution of gas in the tank is non-uniform. 

Depending on the kind of the substance they are designed to process, separators can be labeled as gas-oil separators and "gas separators (Fig. 2.1). Gas-oil separators are used for separation of oil from oil gas, and gas separators - for separation of natural gas from droplets of condensate, water, and solid particles. Gas separators, as a rule, process gas-liquid mixtures with a rather small content of the liquid phase. But they can also operate in the so-called flood regime (when a large volume of liquid enters the separator as a result of accidental injection of water or accumulation of condensate in pipes). 

Countercurrent flow of gas and flowing sohds inside the packed bed has some analogies with gas-liquid systems, as preloading, loading, and flooding regimes. However, in many aspects, the nature of these phenomena are different and equations for gas-liquid systems cannot be applied to flowing solids systems. 

FIGURE 5.5 (See colour insert.) Flooding regimes in the Venezuelan Llanos (by R. Schargel and J.G. Quintero). 

FIGURE 13.12 Results of predictive control of for free radical polymerization of Am in semibatch operation. In batch mode, decreases monotonically in time. By computing conditions for isoreactivity (Equation 13.63c) constant during the reaction was achieved. By operating Am flow into the reactor in the flooded regime (Equation 13.63b), a predictable increase in during the semibatch reaction was achieved. Adapted with permission from Kreft T, Reed WF. Predictive control and verification of conversion kinetics and polymer molecular weight in semi-batch free radical homopolymer reactions. Eur Polym J 2009 45 2288-2303. 

The hysteresis observed for the prepare drop of Holpack packing (Fig. 10 of Chapter 2) leads to hysteresis of die liquid-side controlled volumetric mass transfer coefficient [30. In Fig. 11, Ch pt 2, the value of KlO at liquid superficial velocity equal to 0.00S7 m /(m s) in the flooding regime versus the velocity wo is presented. 

Because of the strong increasing of the pressure drop in the flooding regime, Ihe combined arrangement of Ifae packings is to be recommended only for cases when the increase of the pressure drop docs not lead to worsening of the economical parameters of the process. 

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