Question

A 30 wt % solution of NaOH is diluted in a mixer to 5 wt%. If the streams entering and leaving the mixer are at 40 oC, find the heat removed from the mixer on a basis of 100 kg of feed solution.

Answer 1

Explanation:

It is given that 100 kg feed solution  contains 30 wt% solution NaOH.  Hence, feed contains 70 kg of water and 30 kg of NaOH.

Therefore, mixer outlet shows 5 wt% NaOH.

Let us assume that the mixture outlet be F kg  so, by applying mass balance of NaOH we get the value of force as follows.

          $F \times 0.05$ = 30

                 F = 600 Kg

In that 30 kg is NaOH and 570 kg is water  which also means that initially water present is 70 kg. And, additional water added is 500 kg .

Thus, water feed rate is 500 kg/hr.