文档介绍：DESIGN METHODOLOGY III:
RECYCLE STRUCTURE
OF THE PROCESS
GOAL --Determine alternate recycle structures
for the process based on reactor operating
requirements.
11/29/99 Recycle Structure 1
RECYCLE STRUCTURE FOR SINGLE REACTION SYSTEM
Purge
Vapor Phase Recycle
Products
Fresh Reaction Separation
Feed System System Byproducts
Liquid Phase Recycle
11/29/99 Recycle Structure 2
REASONS FOR RECYCLE
u Recycle unreacted reactants
ð Conversion limitations
ð Excess reactant to shift equilibrium
u Recycle diluent
ð Reactor heat management
ð Flammability constraints
u Recycle “to extinction”
ð Recycle byproduct to equilibrium - production
11/29/99 Recycle Structure 3
EXAMPLE #1. EFFECT OF POSTION
ON EQUILIBRIUM CONVERISION
Delta
0
0 1 2 3 4 5
fA0/fB0
A + B ⌠ C
Delta = extent of reaction for Ky = Yc/YaYb =
fA0 = feed rate of A, fB0 = feed rate of B =
fC0 = 0.
11/29/99 Recycle Structure 4
REACTOR CONSIDERATIONS
u Heat management
ð What is the adiabatic temperature change?
ð If excessive (more than 25 C), must modify design
ØDiluent
ØHeating (endothermic) or cooling (exothermic)
u Equilibrium
ð Modify operating conditions
Ø Change temperature or pressure
Ø Use excess of one reactant in feed
11/29/99 Recycle Structure 5
EXAMPLE #2: HEAT MANAGEMENT
USING A DILUENT