prosess model for series of isothermal constant holdup CSTR.
1. CSTR with variable hold up
Active Learning Assignment
on
Prepared By:
Patel Meet J. (150490105035)
Guided By:
Prof. Darshan Sarang
Asst. Professor
Chemical Engg. Dept.
S. N. Patel Institute of Technology
and Research Centre
Chemical Engineering Department
SEMESTER – VIII
SUBJECT – PMSO (2180503)
2. 2
Process model for series of isothermal constant hold up CSTR:-
F0
F1
CA1
F2
CA2 F3
CA3
V1
K1
T1
V2
K2
T2
V3
K3
T3
• Basis and Assumptions
A → B (first order reaction)
Compositions are molar and flow rates are volumetric
Constant V, ρ, T
• Overall Mass Balance
𝑑ρ𝑉
𝑑𝑡
= ρ𝐹0 − ρ𝐹1 = 0 i.e. at constant V, F3 =F2 =F1 =F0 ≡ F
So overall mass balance is not required!
3. 3
• F0 = Volumatric flow rate to tank-1
• CA0 = Inlet concentration
• V1 = Volume of CSTR-1
• K1 = Rate constant
• ρ = Constant Density
• Changes from previous case:
V of reactors (and F) varies with time,
Reaction is nth order(Where n=1)
• Parameters to be known:
k1, k2, k3, n
• Disturbances to be specified:
CA0, F0
• Unknown variables:
CA1, CA2, CA3, V1, V2, V3, F1, F2, F3
4. 4
• Component A mass balance on each tank :-
𝑑𝐶 𝐴1
𝑑𝑡
=
𝐹
𝑉1
𝐶 𝐴0 −
𝐶 𝐴1 − 𝑘1 𝐶 𝐴1
𝑑𝐶 𝐴2
𝑑𝑡
=
𝐹
𝑉2
𝐶 𝐴1 − 𝐶𝐴2 − 𝑘2 𝐶 𝐴2
𝑑𝐶 𝐴3
𝑑𝑡
=
𝐹
𝑉3
𝐶 𝐴2 − 𝐶𝐴3 − 𝑘3 𝐶 𝐴3
kn depends upon temperature
kn = k0 e-E/RTn where n = 1, 2, 3
Specified variables F and CA0 known but not constant.
Simplify the above constant V, T and putting
τ = V/F
5. 5
• If throughput F, temperature T and holdup V are same in all tanks, then for τ = V/F .
𝑑𝐶 𝐴1
𝑑𝑡
+ 𝐶 𝐴1 𝑘 +
1
τ
=
1
τ
𝐶 𝐴0
𝑑𝐶 𝐴2
𝑑𝑡
+ 𝐶𝐴2 𝑘 +
1
τ
=
1
τ
𝐶 𝐴1
𝑑𝐶 𝐴3
𝑑𝑡
+ 𝐶𝐴3 𝑘 +
1
τ
=
1
τ
𝐶 𝐴2
• In this way, only forcing function variable to be specified is CA0.