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Final Mini project
Transcript of Final Mini project
2. Description of Gas Absorption Column
3. Application of Mass Transfer Theories
4. CO2 reacting system
5. Mathematical Modeling of Process
6. Equation Organization
7. Verification and validation of the model Introduction Aim is formulating a mathematical model and
compare the result with the Chemical reactor design
approach on the basis of chemical reaction,
the amount of absorbed carbon dioxide CO2
into dilute sodium hydroxide NaOH. Gas absorption column titration techniques were used for the analysis. Gas Absorption Column Application of Mass Transfer Theory consider the interface between the gas phase
and the liquid phase, As shown Roll # 09-CH-39
Roll # 09-CH-53
Roll # 09-CH-55 Syed Shah Jehan Gillani
Rana Muhammad Uzair
Muhammad Saleem A major Unit Operation in the Process industry
Selective Removal of selected components of mixture by absorption into suitable liquid
can be accelerated by adding specific substance chemical reacting with solute being absorbed.(Chemisorption)
Diffusion, Solubility and Chemical reaction constant are the factors that controls the rate of absorption Here we concern the reaction of materials originally present in different phases.
Following factors determine how we approach process:
1. The Over all rate expression
2. Equilibrium solubility
3. The contacting scheme Have to account for mass transfer resistance
(to bring the reactants closer.)
Resistance of chemical reaction step.
Every thing developed on the basis of Two Film theory Conventional Packed Column
Often used when purpose is to selective absorption of one component
Liquid is Distributed over packing giving larger area of contact for both phases.
Pressure drop for gas is relatively low
Valueable for treating large volume of gases. Two-film theory
1. W.G. Whitman, Chem. & Met. Eng., 29 147 (1923).
2. W. K. Lewis & W. G. Whitman, Ind. Eng. Chem., 16, 215 (1924).
P. V. Danckwerts, Trans. Faraday Soc., 46 300 (1950).
P. V. Danckwerts, Trans. Faraday Soc., 47 300 (1951).
P. V. Danckwerts, Gas-Liquid Reactions, McGraw-Hill, NY (1970).
R. Higbie, Trans. Am. Inst. Chem. Engrs., 31 365 (1935).
Surface renewal theory
P. V. Danckwerts, Ind. Eng. Chem., 43 1460 (1951).
Rigorous multicomponent diffusion theory
R. Taylor and R. Krishna, Multicomponent Mass Transfer,
Wiley, New York, 1993. 1. A stagnant layer exists in both the gas and the liquid phases.
2. The stagnant layers or films have negligible capacitance and hence a local steady-state exists.
3. Concentration gradients in the film are one-dimensional.
4. Local equilibrium exists between the the gas and liquid phases as the gas-liquid interface
5. Local concentration gradients beyond the films are absent due to turbulence. As the Chemical reaction depletes the conc. at the liquid side so enhance the conc. driving force.
Look the profile with chemical reaction. LIQUID DESCENSDES AND GAS ASCENDS IN THE COLUMN
LIQUID SOLVENT ENTERS FROM TOP GAS MIXTURE ENTERS FROM BOTTOM. RXN Kinectics of system In a solution of NaOH this reaction is
followed instantaneously by: NaOH completely dissociates to
form OH- ions.
Which reacts with CO2. Kinetics Note first of all that the concentration
of the OH- ion,
will be very much greater than the concentration of the carbon dioxide in the solution.
The reaction can therefore be treated as
a pseudo first order reaction
with a rate constant: corresponding to an overall reaction LIQUID GETS DISTRIBUTD THROUGH DISTRIBUTION PLATE ON TOPGAS IS INJECTED THROUGH GAS INJECTION PLATEA liquid seal is present at bottom.
impurity gets absorbed into liquid due to interaction between liquid and gas. Chemical Reactor Design Approach MH ^2 = Max. possible conversion in film with max transport through film Hatta Number For Pseudo 1st Order Material Balance across a Differential Balance Model of Absorption For Steady state Due to chemical Reaction
Ca = 0 in bulk liquid Where E is absorption Enhancemen factor due to chemical reaction Enhancement Factor =
rate of take of A when reaction Occur / Rate of take up of A for straight mass transfer Gas Film Liquid Film That was all about what we have learnt during the course of Chemical Plant Design Lab.