Design of Spray column with Chemical Reaction

Problem To reduce the impurity (A) level in an organic liquid from 10000ppm to 500ppm using an aqueous solvent containing a solute (B) which reacts with A following the rate equation, rate = Kmn*[A]m * [B]n

Given dataOrganic phase flow rate = 1m3/hraq =1000 kg/m3org = 900 kg/m3aq = 1 mPasorg = 5 mPas = 0.025 N/mDistribution coefficient = 5

Co-relations usedu0 =

dp =

kd = (0.00375*u0)/(1+d/c)

kc = 0.725* (dp*u0*/c)^-0.43*(c/cD)^-0.58*(1-d)

ApproachCase 1- The rate of chemical reaction is very slow as compared to rate of mass transferCase 2- The rate of mass transfer is comparable to the rate of chemical reactionCase 3- The rate of chemical reaction is very high as compared to rate of mass transfer

Case 1 As the rate of chemical reaction is very low as compared to rate of mass transfer the concentration profile will be as below

Case 2When the rate of chemical reaction is comparable to the rate of mass transfer

Case 3As the rate of chemical reaction is very high the concentration of A in aqueous phase will be zero

AssumptionThe dispersed phase mass transfer co-efficient is very high as compared to continuous phase mass transfer co-efficientHence, resistance to mass transfer on the dispersed side is neglected

Calculations

Calculate minimum flow rate for aqueous liquid from given data Assume flow rate of aqueous liquid higher than the minimum value calculatedCalculate u0 Calculate dpCalculate f

Assume d value ranging from 0.1 times f to 0.9 times f increasing it by 0.1 every timeHence calculate vc and vdFrom the values of vc and Qc we get the column diameter.Then we calculate a = 6 d/dThen we find the no of orifices in the distributor

Then we find the values of kd and kcThen we find the relative rate of reaction as regards to the rate of mass transferBased on the relative values, we can find the volume of the contactor and the height of the contactor

Effect of water flow rate on volume

When the phases are interchangedWhen water is the continuous phase, due to Morongani effect we consider only regimes 3 and 4Calculations similar to the previous caseContinuous phase mass transfer is the controlling mechanism

Effect of %flooding on Volume

Effect of %flooding on Height

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