Mapo Caffeine is often added to headache medications because it affects the flow
ID: 1009813 • Letter: M
Question
Mapo Caffeine is often added to headache medications because it affects the flow of blood in vessels and may enhance the pain relieving qualities of the medication. You have been tasked with evaluating one process that extracts caffeine from a coffee slurry, and you decide to study a small scale version of the process. A coffee slurry containing a mass fraction of 0.01 g caffeine/g, 0.08 g other solids/g, and 0.91 g waterlg is fed to a mixer at a rate of 850.0 g/min. NazCO3 is added to the mixer such that the mass ratio of Na2CO3 to coffee slurry is 0.0500. This aqueous solution proceeds to an extractor where CH2Cl2 is added such that the mass ratio of CH2Cl2 to coffee slurry entering the extractor is 0.410. Two streams leave the extractor The first is a mostly aqueous stream that leaves the process containing some caffeine, all of the other solids in the original slurry, all of the Na2CO3, all of the water and 2% of the mass of CH2Cl2 entering the extractor. The second stream contains the remaining caffeine and CH2Cl2, and enters an evaporator that completely vaporizes the CH2Ch. The vaporized CH2Cl2 is condensed and is merged with the fresh CH2Cl2 on the way to the extractor. The dried caffeine crystals exit the evaporator and leave the process. Of the caffeine entering the process a fraction of 0.960 the process in this product stream. Label the process flow diagram below. Label any quantities as "unknown" if you have to calculation to obtain the numeric value. DO NOT LEAVE ANY ANSWER SPACE BLAN Ima = g CH2Cl2/min g Na2CO3/min g CH2Cl2/min m5 g CH2Cl2/min m1 = g coffee slurry/m Mixer Extractor Evaporator caffeine/min g caffeine/g g mostly aqueous solution/min g other solids/g g caffeine/aExplanation / Answer
m1= 850 g//min
Caffeine entering the mixed ,m1= 850 g//min*0.01 g caffeine/g = 8.5 gms
0.96 fraction entering caffeine leaves the proces and hence caffeine leaving , m7=8.5*0.96=8.16 gms
Caffeine at the exit of extractor in the aqueous phase= 8.5-8.16= 0.34 gms
Water enteing = 850*0.91=773.5 gms
This water is withdrawn from extractor which is 773.5 gms
Na2CO3 added is expressed in terms of mass of Na2CO3/coffee =0.05
Mass of Na2CO3 added,m2 =0.05*850 gm=42.5gms
Other solids leaving the extractor= 850*0.08=68 g/min
CH2Cl2 entering the extractor .m5= 850*0.410=348.5gms/min
2% of this is removed from extractor in the aqueous stream =348.5*2/100=6.97gm/min
Total mas leaving the aqueous stream leaving the extractor, m3 = 0.34+773.5+42.5+68+6.97=891.31 g/min
This also leves along with aqueous stream from extractor
Writing overall balance m1+m2+m4=m3+m7
850+42.5+m4= 891.31+8.16
Therefore, m4= 6.97g/min
Recycled CH2Cl2 can be obtained by m4+m6=m5
Therefore, Recycle m6= 348.5-6.97=341.53 g/min
Recyle to Fresh CH2Cl2 = 341.53/6.97=49