Chemical Engineering homework help
Chemical Engineering homework help. Your company has decided to produce P by the reaction A → P. Unfortunately, there is a parallel reaction,
A → B. Both reactions are irreversible. Both reactions are incomplete; the reactor effluent contains reactant
A, product P and worthless by-product B.
The boiling points at 1 atm are P (30C), A (50C), and B (55C). Purifying P to 99% (minimum purity
to market) by distillation is easy, but separating A and B is more difficult.
To produce and sell product P, you need only a reactor and separator I. You have two options for the A+B
mixture in the “separator I bottoms” stream: (1) you may recycle some of the A+B mixture, for example,
by purging 50% and sending 50% through the recycle, or (2) you may purchase a second separator to
separate A from B before recycling.
Option 1: Recycling some of the A+B mixture, for example, by purging 50% and sending 50% through
the recycle.
Option 2: Adding a second separator to separate A from B before recycling.
There are two options for the reactor. Reactor Type 1 has a high conversion of A but has poor selectivity
for P over B. Another reactor has a lower conversion of A, but has better selectivity for P over B.
There are two options for separator I. Both options produce a tops product with 99% P, but differ by the
amount of P in the liquid bottoms. Separator I Type 1 recovers more of the product P (the ratio P:A in the
bottoms is <1:50). Separator I Type 2 allows more P to escape via the liquid stream, but is smaller and less
expensive to operate.
If one decides to purchase a second separator, there are two options for separator II. The expensive option
(Type 1) has an A:B ratio of 100:1 in the tops and an A:B ratio of 1:100 in the bottoms. The cheaper option
(Type 2) has an A:B ratio of 10:1 in the tops and an A:B ratio of 1:10 in the bottoms.
Because B is toxic, disposal requires special treatment and is expensive. The disposal cost is determined
by the total amount of any effluent that contains B. That is, the disposal cost for 1 kg of a mixture with
10% A and 90% B is the same as the disposal cost for 1 kg with 90% A and10% B.
Engineering and Economic Data for Manufacturing P from A.
Equipment specifications, equipment costs, operating costs, chemical costs, and disposal costs vary with
different groups.
Reactor and separator prices are given by the formula price = k (FT
)
0.6, where k is a constant and FT
is
the flow through the unit, in kg/day. For example, a reactor with double the capacity costs only 1.5 times
as much. Operating costs for reactors and separators are given by the formula operating cost = c FT
.
Operating costs for reactors and separators are given by the formula operating cost = c FT. The units
are $/year. So if c = 2500 and you have a unit operating with a flow rate of FT = 300 kg/day, the annual
operating cost is 2500 * 300 = $750,000 / year.
All economic parameters – equipment prices, operating costs, chemical prices, and disposal cost – are
constant. The process operates 365 days/year. Equipment purchase costs are paid in Year 0. The plant is
assumed to be operated at 50% capacity in Year 1 and 100% starting from Year 2. Operating costs are paid
and Revenue from P sales is received at the end of each year.
Your goal is to achieve the highest Internal Rate of Return (IRR) at the end of Year 10 by using the Net
Present Value method (NPV = 0).
Each group has to prepare a technical report to propose the most profitable route(s). Furthermore, you
need to present the mass balances and the calculations for each route. It is advised to use Excel to perform
your calculations.
Assessment
Cover sheet – 2%
Report presentation – 8%
You will be assessed by the language and structure of the report.
Outcomes/Conclusion – 10%
– You need to present the best cases scenario based on the internal rate of return. In the report, you
need to justify why you have selected one particular reactor to another and similarly to the
separator(s) based on the values of P, B and A.
Material Balances/Calculation – 10% x 8 routes (max)
– Each route should be presented in a new sheet and all the sheets are in the same excel file
– You need to demonstrate one hand calculation and attach it into your excel file
Your group report and the excel sheets have to be submitted via MyUni on 15
th May at 5pm.
———————————————————–
Monday 12pm Groups
k c
reactor, type 1 (mass outlet flow rate of reactant A/mass inlet flow rate of reactant A =15%, weigh
ratio of P:B = 2:1) $110,000 $3,000
reactor, type 2 (mass outlet flow rate of reactant A/mass inlet flow rate of reactant A =60%, weigh
ratio of P:B = 20:1) $90,000 $2,500
separator I, type 1 (99wt% P in tops, weigh ratio of P:A = 1:10 in bottoms)$60,000 $2,200
separator I, type 2 (99wt% P in tops, weigh ratio of P:A = 2:5 in bottoms)$20,000 $1,100
separator II, type 1 (mass ratio of A:B = 100:1 in tops, A:B = 1:100 in bottoms)
$80,000 $4,000
separator II, type 2 (mass ratio of A:B = 10:1 in tops, A:B = 1:10 in bottoms)
$20,000 $2,300
Reactant A into the plant at 100kg/day and it costs $85/kg.
Product P (99% P) sells for $200/kg.
Disposal of waste contaminated with B costs $30/kg.
———————————————————–
Wednesday 3pm Groups
k c
reactor, type 1 (mass outlet flow rate of reactant A/mass inlet flow rate of reactant A = 5%, weigh
ratio of P:B = 3:2) $130,000 $2,700
reactor, type 2 (mass outlet flow rate of reactant A/mass inlet flow rate of reactant A = 60%, weigh
ratio of P:B = 2:1) $90,000 $2,300
separator I, type 1 (99wt% P in tops, weigh ratio of P:A = 1:20 in bottoms)$50,000 $2,500
separator I, type 2 (99wt% P in tops, weigh ratio of P:A = 2:5 in bottoms)$20,000 $1,300
separator II, type 1 (mass ratio of A:B = 100:1 in tops, A:B = 1:100 in bottoms)$140,000 $5,000
separator II, type 2 (mass ratio of A:B = 10:1 in tops, A:B = 1:10 in bottoms)$21,000 $2,300
.
Reactant A into the plant at $500kg/day and it costs $28/kg.
Product P (99% P) sells for $110/kg.
Disposal of waste contaminated with B costs $20/kg.
———————————————————–
Wednesday 5pm Groups
k c
reactor, type 1 (mass outlet flow rate of reactant A/mass inlet flow rate of reactant A = 10%, weigh
ratio of P:B = 2:1) $120,000 $2,700
reactor, type 2 (mass outlet flow rate of reactant A/mass inlet flow rate of reactant A = 65%, weigh
ratio of P:B = 20:1) $80,000 $2,300
separator I, type 1 (99wt% P in tops, weigh ratio of P:A = 1:100 in bottoms)$50,000 $2,500
separator I, type 2 (99wt% P in tops, weigh ratio of P:A = 1:2 in bottoms)$20,000 $2,000
separator II, type 1 (mass ratio of A:B = 100:1 in tops, A:B = 1:100 in bottoms)$140,000 $5,000
separator II, type 2 (mass ratio of A:B = 10:1 in tops, A:B = 1:10 in bottoms)$21,000 $2,300
Reactant A into the plant at 300kg/day and it costs $30/kg.
Product P (99% P) sells for $105/kg.
Disposal of waste contaminated with B costs $30/kg.
———————————————————–
Net present value method
NPV Year 0 Year 1 Year 2 Year 3….. Year 10
IRR = A
Capital cost K X – – – –
Operating
cost
L – Y/2 Y Y Y
Revenue M – Z/2 Z Z Z
Total Sum of
K,L,M
– – – – –
Please look at the NPV function in Excel.