Industrial and you can Laboratory Reactors – Chemical substances Response Hazards and you will Techniques Combination off Reactors Leave a comment

Factors Affecting the new Overall performance of Bubble 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 (K_L), but significant on mass transfer area (a). For chemical reaction controlled gas-liquid reaction (slow or very slow gas-liquid reaction) a certain minimum K_La 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.

Low Gasoline Velocity

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, (?r_A) = (?1/V_l) (?dN_A/dt), but decreases the liquid holdup (V_l). The combined effect on the rate of consumption of limiting reactants in reaction (?dN_A/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.

Functions off Fuel Stage and you may Water Stage: The new bodily attributes of the energy phase haven’t any affect the newest performance of your own line, however, the ones from the fresh new liquid phase, elizabeth.grams., skin tension, viscosity, will likely be powerful. A rise in the fresh viscosity regarding liquids stage or a decline about facial skin tension boosts the energetic interfacial city and therefore increases the size transfer rates. The clear presence of electrolyte on h2o stage effects new performance considerably. An electrolytic provider gives less bubble dimensions and therefore a amigos haciendo sitios gratis top active interfacial city and better rate away 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 K_La can be increased by as much as a factor of 3 by pulsation.

Inclusion regarding Packing otherwise Packaged Bubble Column: Adding loading reduces the axial fusion off drinking water. And this, a loaded ripple column is employed in which water backmixing is actually unwelcome. Gas-liquids reactions where nice energy shrinkage takes place in the brand new reactor have very reasonable low energy velocities, and that then cause a bad speed away from bulk transfer inside the top of the main reactor. In these instances, placing packings in the top region is beneficial. The fresh new packing boosts the effective interfacial town and gasoline holdup in order to a level. Additionally, it will bring a higher rate off mass transfer. However, a stuffed bubble column is not used if the okay good particles are present regarding the program while the catalyst or since reactant. Loading is also maybe not well-known to own very exothermic otherwise endothermic reactions, since the packed systems enjoys poor temperature transfer coefficients. Reactions like packaged towers bring poor heat transfer coefficient. Desk 21-5 reveals advantages and drawbacks between a ripple column and you can an empowered container reactor, and Table 21-6 listing commercial examples of ripple column reactor.