Items Impacting this new Overall performance of your own Ripple Line Reactor
Superficial gas velocity : Increase in superficial velocity increases gas holdup, the effective interfacial area and the overall mass transfer rate. Further, an increase in superficial gas velocity decreases the size of bubbles, thus increasing the interfacial area of contact between the gas and liquid. The effect of superficial gas velocity is negligible on the mass transfer coefficient (KL), but significant on mass transfer area (a). For chemical reaction controlled gas-liquid reaction (slow or very slow gas-liquid reaction) a certain minimum KLa must be achieved to overcome the effect on mass transfer. It is recommended to keep the superficial gas velocity less than or equal to 10 m/s.
Superficial Gasoline Acceleration
Backmixing: Studies have shown that gas flow in bubble column operates in the plug flow manner without any backmixing while a considerable amount of backmixing in the liquid phase is observed. Backmixing in the liquid phase decreases the concentration of liquid reactant and thus the rate of chemical reaction. Consequently, it decreases the overall rate of reaction. Use of packings, trays or baffles reduces liquid backmixing and thus reduces dilution of reactants by products. Hence, this technique provides higher concentrations of reactant and a higher rate of chemical reactions, (?rA) = (?1/Vl) (?dNA/dt), but decreases the liquid holdup (Vl). The combined effect on the rate of consumption of limiting reactants in reaction (?dNA/dt) must be checked before using any internal in the bubble column. In the case of highly exothermic gas-liquid reactions, backmixing in the liquid phase is desirable to control the nature of the reaction or its temperature. In such cases, placing packings to improve the overall rate makes temperature control very difficult because it increases the heat duty required and decreases the heat transfer coefficient.
Characteristics away from Energy Phase and you can H2o Stage: Brand new bodily properties of your own gas phase don’t have any affect this new abilities of your column, but that from the fresh new drinking water phase, e.grams., epidermis pressure, viscosity, might be serious. A rise in brand new viscosity regarding liquids phase or a decline from the body stress escalates the energetic interfacial city thus advances the size transfer rate. The clear presence of electrolyte about water phase effects the newest overall performance greatly. An electrolytic services gives quicker ripple proportions and therefore a top productive interfacial area and better price from bulk import.
Pulsation: The performance of bubble columns can be improved by pulsation. For very low superficial velocity of gas (0.8 to 2.4 cm/s), the value of KLa can be increased by as much as a factor of 3 by pulsation.
Inclusion off Loading otherwise Packed Bubble Line: Including packing decreases the axial fusion out of h2o. And therefore, a stuffed ripple column can be used where drinking water backmixing was unwanted. Gas-liquids responses in which good-sized gas shrinkage happens in the newest reactor have very reasonable shallow gas velocities, and therefore after that trigger a poor speed off mass transfer in the the top a portion of the reactor. In these instances, position packings about top region is effective. Brand new loading increases the productive interfacial city and fuel holdup to a degree. it brings a high rate regarding mass transfer. not, a stuffed ripple column isn’t used if okay solid particles can be found about program just like the stimulant or as reactant. Packing is even perhaps not prominent to have very exothermic otherwise endothermic responses, since the packaged towers possess worst temperatures import coefficients. Responses eg manufactured towers give poor heat transfer coefficient. Desk 21-5 suggests the pros and drawbacks ranging from a bubble column and you can a motivated container reactor, and you can Dining table 21-six listings industrial examples of bubble column reactor.