[filinho1990]

Hey,

can someone please help me? I have one problem that I have to solve, but unfortunately I don't know if my result is correct.
Could someone please look at my work and tell me if I did any mistake?
I would be very grateful for any help.
 
Regards,
Filip
 
Description of my problem could be seen here and solution down under:
 
Roasted copper ore containing the copper as CuSO4 is to be extracted in a counter-current
stage extractor. Charge consists of 10 tons of inert solids, 2 tons of
copper sulfate (CuSO4), and 0.5 ton of water. The strong solution produced is to
consist of 90% H2O and 10% CuSO4 by weight. The recovery of CuSO4 is to be 98% of
that in the ore. Pure water is to be used as the fresh solvent. After each stage, 1 ton of
inert solids retains 2 tons of water plus the copper sulfate dissolved in that water.
Equilibrium is attained in each stage. How many stages are required?
 
 
2 t CuSO4.....100%                                                       1.96t.....10%
      x       ...98%                                                             x.....90%
                                         
x=1.96 t CuSO4                                                                                                                     x=17.64 t H2O
 
extract:   1.96 t CuSO4/17.64 t H2O = 1.12 t CuSO4/10 t H2O
 
raffinate:
 
0.04 t CuSO4/10 t inert solid
 
As base we define 10 t of inert solid (without H2O and CuSO4)
 
CuSO4 in: 2 t
 
CuSO4 out:
 
0.04 +(1.12 /(1.12 +10) *(S-20+0.5)) = 0.101*S - 1.924
 
 
CuSO4 in = CuSO4 out
 
2 = 0.101*S - 1.924
 
S = 38.85 t H2O  (amount of solvent)
 
 
ya = ((20*1.12/(1.12+10)) + (1.12/(1.12+10)*(38.85-20+0.5)) - 2 ) / 38.85
ya = 0.0505
 
yb = 0
 
ya* = 1.12/(1.12+10) = 0.101
 
yb* = 0.04/20 = 0.002
 
Number of stages:
 
N=log(yb - yb*/(ya-ya*)) / log(yb-ya/(yb*- ya*))
 
N=4.8=5