WebInternal mass transfer effects are eliminated when the internal effectiveness factor η i is equal to 1. η i approaches unity as the observable Thiele modulus Φ decreases. From Table 13.4, Φ is decreased by:. 1. Reducing the observed reaction rate r A,obs. 2. Reducing the size of the catalyst. 3. Increasing the effective diffusivity D Ae. 4. WebUnit 38 defines the Thiele modulus for first order reactions in spherical catalyst particles and demonstrates its relationship to the catalyst effectiveness factor, which ... For example, if the reaction rate is first order in A, this leads to equation (38.7) for the surface concentration of A. Substitution of equation (38.7) back into the ...
Calculations of effectiveness factors and the ... - Oxford Academic
WebThe square of the Thiele modulus has a precise physical meaning, since it compares a first-order reaction rate with a pure diffusion rate. [Pg.38] This difference is maximized, if CA.center becomes zero. Figure 4.7.1 shows the influence of the Thiele modulus on the concentration of reactant A in the center of a spherical particle ( first-order ... Web3. Effectiveness factor vs. Thiele modulus for irreversible reaction: EB = 5. can be obtained for the case m which one or more of the products decreases reaction rate because of strong adsorption on the catalyst. (b) For a given value of the Thiele modulus, reaction rate approaches zero when conversion approaches one. total foodservice uk
A First Course on Kinetics and Reaction Engineering Unit 38 ...
Web26 May 2024 · The Thiele Modulus was developed to describe the relationship between diffusion and reaction rates in porous catalyst pellets with no mass transfer limitations. … Web17 Nov 2015 · The I in the acronym applies to the mixing: there is no spatial dependence - the reaction rate is the same everywhere in the reactor. And it can be any value. The dahmkohler number included transport from bulk to the surface of the pellet, whereas thiele modulus accounts for transport from surface to inside the pellet. WebThe Thiele moduli for first-order reactions in various geometries as well as the generalized moduli applicable for other reaction orders all assume that the chemical reaction is irreversible. Studies on the first-order reversible reaction A <-> B have shown that the same q>L-ri function as in the irreversible case can be used, when the Thiele ... total food supermarket in miami 17th ave