DIP_Class4_Reactor p. 1

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

Integrated Process Design

CHOICE OF REACTOR (III)

• Practical reactors• Example

DIP_Class4_Reactor p. 2

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

Choice of ReactorPractical reactors

STIRRED TANK REACTORS

• Liquid phase, homogeneous or heterogeneous (L+L, L+S, L+G, S+L+G).

Allowed reaction processes:

• Operation modes: Batch – Semi-batch – Continuous

Non-recommended processes:• Multiple in series and some in parallel (low selectivity).• High pressure.• Hazardous products.

Temperature control:• External jacket or internal coil.• External heat exchanger.• Reflux from condenser

Recommended large volume PF reactor: consider using CSTR in series.

DIP_Class4_Reactor p. 3

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

TUBULAR REACTORS

• Heterogeneous reactions (unless static mixers are used).Not-allowed reaction processes:

• Operation modes: Batch – Semi-batch.

Recommended:• Residence time controlled reactions (multiple in series and

polymeric without termination stage).

• Highly exothermic/endothermic reactions.• High pressure.

FIXED-BED CATALYTIC REACTORS

DIP_Class4_Reactor p. 4

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

‘Hot spots’: undesired reactions and catalyst degradation

• Multi-tubular.Alternatives:

• Catalyst dilution (inert solid).

Not recommended when frequent catalyst regeneration is required (alternatively a moving-bed catalytic reactor may be used).

DIP_Class4_Reactor p. 5

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

FIXED-BED NONCATALYTIC REACTORS

Gas + solid reactions:

• Non-stationary conditions: difficult to control.

Gas + liquid reactions:• Improve contact between phases.

FLUIDIZED-BED CATALYTIC REACTORS

Advantages:

• Excellent temperature uniformity.• Continuous catalyst regeneration.

Disadvantages:

• Complex hydrodynamic (bubbles).• Attrition of catalyst.

Intermediate performance between PF and CSTR models.

FLUIDIZED-BED NONCATALYTIC REACTORS

Gas + solid reactions (the same characteristics as catalytic reactors)

DIP_Class4_Reactor p. 6

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

STIRRED TANK REACTOR

TUBULAR REACTOR

FIXED-BED CATALYTIC REACTOR

FIXED-BED NONCATALYTIC REACTOR

FLUIDIZED-BED CATALYTIC REACTOR

FLUIDIZED-BED NONCATALYTIC REACTORS

• Gas phase reaction.

• Catalytic heterogeneous.

• Frequent catalyst regeneration.

FLUIDIZED-BED TOLUENE

H2

DIP_Class4_Reactor p. 7

Inte

gra

ted

Pro

cess

Des

ign

(In

teg

rati

on

)

Flow pattern:

• Toluene: main reaction PF

• H2: High concentration at the exit.

• Benzene: multiple in series PF

Excess of hydrogen:

• Shifts the competitive reaction to the left (higher selectivity)

• Reduces coke formation.

• Decreases kinetics,2

2

H Toluene

Reactor1 1 2Toluene H

c cr V

r c c /

Temperature:

• Main reaction: highly exothermic, irreversible T high (control ΔT !!)

• Secondary reaction: endothermic, equilibrium T low at the exit

• Inert: Control ΔT (cold-shot and mCp increase)

Pressure: • Main reaction : irreversible P maximum

• Secondary reaction: equilibrium Δn=0 indifferent

• Separate from CH4 to recycle.