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However, in this case the ARD of tray efficiency is 13.0% between this investigation and the modified AIChE method for 50 points. It shows that the modified AIChE method can also be employed to estimate the tray efficiency of air-water-solid particles system.

Beenackers and Swaaaij [79] have studied the influence of solid particles on gas-liquid mass transfer and reported the method of calculating the volumetric liquid-side mass transfer coefficients at the gas-liquid interface kLa, from which tray efficiency for gas-liquid-solid particles system can be deduced [80]. kLa is solved by with index "0" indication of no solids present.

We select a three-phase system, e.g. propylene (gas) - benzene (liquid) - Silica gel (solid particles) to test the modified AIChE method. The calculated values of tray efficiency from the method of using k, a are compared with those from the modified AIChE method under the same conditions. The results are listed in Table 4 where hw = 40mm. The results of two methods are in good agreement with the difference less than 5%. It is shown that the modified AIChE method is suitable for either air-water-solid particles or organic gas-organic liquid-solid particles system.

However, it may be expected that the actual tray efficiency is greater than the calculated values coming from both the modified AIChE method and the method of using kLa. It is known that kLa is the product of k, and a, in which a (m2 m"3) is gas-liquid contact area and not changed whether or not chemical reaction takes place, but kL will increase if chemical reaction in the liquid phase is considered. The reason is that mass transfer is enhanced due to rapid chemical reaction, which can be described by enhancement factor EA.

Ea is defined as the ratio of JA (molar flux of component A, kmol m"2 s"1) with particles, to JA with the same but inert particles, in which JA is evaluated at the same overall driving force. Inert means that neither the particles nor components produced from the particles participate in the reaction as a reactant or a catalyst. Further, inert particles don't adsorb the gas phase component transported towards the bulk of the liquid phase, nor any other reactant or reaction product. Even so, it seems that the designed result is safe and conservative because we take on as the tray efficiency smaller than actual into consideration.

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