# Material balance without chemical reactions

This is a practice question that I am trying. I am a student learning about material balance- I am trying to find the mass composition of stream D. The one written in pencil is the values that I have found in advanced-

My attempt-

I have made a material balance around separator 2 ignoring the recycle stream, I done up a component X balance-

$1250 X + (120 \times 0.3) = (379.08 \times 0.374) + (90.92 \times 0.222)$

I solve for x $= 0.10076$

Similarly,I done up a component Y balance-

$125 Y + (120 \times 0.7) = (379.08\times0.626) + (90.92\times 0.778)$

I solve for Y $= 0.1792$

I know this is wrong as the composition of X and Y total does not add up to 1. Where did I go wrong or what must I do ?

## 1 Answer

How do you get D = 1250?

Should it be A + B - C ie 450 + 130 - 230 = 350 based on separator 1 only, ie what leaves separator 1.

Then when you include separator 2 the +900 will give 1250 arriving at separator 2.

• Oh.., i spotted my mistake.. should not use 1250 which is (350+900) if I am ignoring the recycle stream. Thanks ! – user185692 Feb 22 '18 at 5:34