(4 points)) Pure KN0s is made from a crude salt mixture(gg wt% KNO, and 1 wt% Na
ID: 637769 • Letter: #
Question
(4 points)) Pure KN0s is made from a crude salt mixture(gg wt% KNO, and 1 wt% NaC) by the process illustrated below. The Dissolver is maintained at 70°C where the solubility is 138 lb KNO/100 Ilb H,0. The Separator is maintained at 30°C where the solubility is 45.8 lb KNO100 lb H20. The solid product stream contains 83.6 lbymin of pure KNO). 50.0 lb/min are removed in a purge stream that contains a mixture of KN03, NaCl, and water. What is the flow rate (Ib/h) of the recycle stream? 2. 100% Water Solid KAio Dissolva Soluhon Recycie bimin NadExplanation / Answer
Crude salt mixture (99wt% KNO3 &1wt% NaCl)
solubility in dissolver =138 lb KNO3/100 lb H2O
solubility in Separator =45.8 lb KNO3/100 lb H2O
Product stream P= 83.6 lb/min of pure KNO3
Purge stream = 50 lb/min (KNO3,H2O & NaCl)
to calculate the flow rate of recycle stream
Feed crude = 100 lb/min
Assuming system under steady state
Mass in = mass out
mass of solid in + mass of water in =Solid product stream + Purge stream
100 + W =83.6 +50
W= 33.6 lb/min
As we are getting product flow rate = 83.6 lb/min
the stream coming out from separator must contain 45.6 lb KNO3/100 lb H2O it will be saturated as we get crystals out of it
And there is shouldnt be accumlation of NaCl in the syatem
NaCl in feed = NaCl in purge = 1 lb/min
so purge will contain 49 lb/min of water & KNO3
as the solubility is 45.8 in 145.8 of KNO3 - water mixture
x/49 = 45.8/145.8
x = 15.3923182441701 lb/min of KNO3 in purge
water in purge = 49-15.3923182441701= 33.6076817558299 lb/min
Purge mass fraction = mass fractions in recycle
Water = 0.672153635116598 KNO3 =0.307846364883402 NaCl = 0.02
In dissolver
solubility = 138 lb KNO3 /238 lb of water + KNO3
water in dissolver = water fed + water from recycle
water in dissolver =33.6 + 0.672153635116598*R
KNO3 in dissolver = fed KNO3 + KNO3 from recycle
KNO3 in dissolver= 99+0.307846364883402 *R
assuming dissolver contain saturated solution with given solubility
Therefore = KNO3 in dissolver/water in dissolver = 138 lb KNO3 /100 lb H2O
1.38 = (99+0.307846364883402 *R)/(33.6 + 0.672153635116598*R ?)
46.368 + 0.9275720165R =99+0.307846364883402 *R
0.6197256516R = 52.632
R=84.92790296 lb /min
I hope it will help !!
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