What composition of feed 2 will give a product composition that is 25% A, 35% B, and the rest C if feed 1 is 40% A and both feeds enter with the same mass flow rate?
Please write out the set-up of this problems, following ALL the steps given in Chapter 1
(including a title for the problem!), and number each step or set of steps in the solution using the Chapter
1 numbers and headings.
1. A steady state, constant T and P mixing process is being used to combine two input streams and
produce one output (product) stream. Feed 1 contains components A and B, Feed 2 contains components
B and C, and there is no chemical reaction.
a. Provide a title, System, Contents, Process, Assumptions, and fully labeled drawing, with all variables
defined. Make sure to include ALL composition variables on your feed arrows, even if you know they are
= 0.
b. Using the variables you have defined, write out the overall mass balance for this process. Also write
out all the stream balances (how many are there?). Given these equations, how many independent
component balances are there? Write them out.
c. How many variables are needed to fully describe this process (please count T and P separately from the
ones appearing in the material balance equations)? Now subtract the total number of equations in part b
from the total number of variables in part c (not counting T and P) to get the number of independent
specifications needed to enable you to solve this system of equations.
d. How would your answers to parts a-c change if the mixing process produced two separate phases?
Please be specific.
e. There are 2 “Givens” in the problem statement above. What are they? Write them out in terms of the
variables you have defined.
f. Below are four different problem statements that could apply to this process. For each one, please
write out the “givens” and the “finds”, including the two “Givens” from the initial problem statement
above, and solve, algebraically first, for the “find” or “finds” following the strategies given in Chapter 1.
Make sure to number and annotate all of your steps, and don’t leave any steps out!
(i) 100 kg/h of feed 1 is to be processed. Feed 1 is 50% A by weight and 50% B by weight, and
feed 2 is 20% B by weight. How much feed 2 must be fed per hour to produce a mixture that is
45% B by weight? What will the composition of the product be, and what will its flow rate be?
Which “given” in this problem statement is redundant, and therefore not independent?
(ii) What will the steady state product composition be if the feed ratio, F1:F2, is 1.5:1 and each
feed is 25% B? Can you find the product flow rate from this set of “givens”? Explain.
(iii) What composition of feed 2 will give a product composition that is 25% A, 35% B, and the
rest C if feed 1 is 40% A and both feeds enter with the same mass flow rate? What will the
product flow rate be?
(iv) What should the feed ratio, F1:F2, be if the desired product composition is 25% A, 35% B and
the rest C, feed 1 is 60% A, and feed 2 is 25% B? need all the answers
