An evaporator is concentrating solutions coming from three different sources. The first source contains 20% NaCl by weight, the rest is water. The second source contains 10% by weight NaCl, 30% NaOH by weight, the rest water. The third source contains 25% NaCl by mole, 25 % NaOH by mole, the rest water. The feed streams are fed directly to the evaporator at the following flow rates; 100 kg/min for the first source, 7800 kg/min for the second source and 120 kg/min for the third source. If 70% of the original water is evaporated, calculate (a) composition in % by weight of the product (b) the flow rate in kg/min of the product.
1) An evaporator is concentrating solutions coming from three different sources.
The first source contains 20% NaCl by weight, the rest is water. The second
source contains 10% by weight NaCl, 30% NaOH by weight, the rest water. The
third source contains 25% NaCl by mole, 25 % NaOH by mole, the rest water.
The feed streams are fed directly to the evaporator at the following flow rates;
100 kg/min for the first source, 7800 kg/min for the second source and 120
kg/min for the third source. If 70% of the original water is evaporated, calculate
(a) composition in % by weight of the product (b) the flow rate in kg/min of the
product.
2) Two process streams are mixed to form a single stream. Only the flow in the
mixed stream is known. A soluble salt is added to one of the original streams at
a steady rate. Samples taken of this stream show it to be 4.76 % w salt. Samples
from the combined stream show 0.62% w salt. What is the ratio of the flows in
the two original streams?
3) A chemist attempts to prepare some very pure crystals of borax by dissolving
100g of Na2B4O7 in 200 grams of boiling water. He then cools the solution slowly
until some borax crystallizes out. Calculate the grams of borax recovered in
the crystals per 100 grams of initial solution (Na2B4O7 plus water), if the residual
solution at 550C after the crystals are removed contains 12.4% Na2B4O7.What is
the percent yield or percent recovery of Na2B4O7.
4) Slab building boards contain 17% moisture by weight. They are dried to a water
content of 1% by weight by circulating hot air over them. The fresh air contains
0.017 lb of moisture per pound of dry air. The exhaust air contains 0.075 lb of
moisture per pound of dry air. How many cubic feet of fresh air at standard
conditions must be used per ton of the building boards?
Step by step
Solved in 3 steps with 3 images
