Propane Cracking in a Micro Channel Reactor - Process ...

Intensification of the
Steam Cracking Process
Mohamed Ellob, Jonathan Lee, Arthur Gough
School of Chemical Engineering and Advanced Materials
University of Newcastle
Does Steam Cracking Need Steam

Presentation outline
Introduction
Catalytic plate reactors
Coke formation
Objectives
Benefits
Methodology
Experimental Work
Results
Conclusions

Introduction
Olefins demand in year 2005 :
Ethylene (107 million tons )
propylene (67.1 million tons )
Olefins demand growth during years(2005 –2010):
Ethylene about 4.3% per year
propylene about 5.4% per year
Olefins production capacity growth:
Ethylene about 5.4% per year
Propylene about 5.1% per year

Typical Steam Cracking Furnaces
Total Number of cracking tubes about 600
Total Reaction Volume about 45 m³
Total firebox volume about 9,000 m³
Residence Time 0.25 to 0.75 s
Firebox Efficiency about 65%

Steam function and process limitation
Enhance heat transfer
Reduce coke formation and deposition
Improve selectivity towards ethylene
Operation purposes
Coke deposition is the main process limitations
due to:
- High tube skin temperature
- High pressure drop

Exothermic
channel gas
Exothermic reaction
catalyst
Heat
Thin plate
Endothermic
channel gas
Endothermic reaction
catalyst
Catalytic Plate Reactor

Source: Velocys,(2005),olefins by high intensity oxidation, http: // www.velocys.com/Img/pdf.2250.pdf

Advantages Of Catalytic Plate Reactor
High Surface to volume Ratio
Laminar flow Conditions
High Heat transfer Coefficient
Thin Catalyst Layer Minimize Diffusion Limitation
Surface Temperature only few degrees above the
process temperature
Improved Safety and Environmental Impact
Scale-up by Numbering –up
Low Capital and operating Costs

Coke formation
Metal-catalyzed coke
Non-catalytic coke from tars
Small chemical species (coke precursors) react
with free radicals on the coke surface
Heterogeneous Catalytic
Heterogeneous non catalytic
Homogeneous non catalytic
Chemisorbed
HC. Molecule
Molecule
Radical
Coke particle
Radical on coke surface
Surface reaction
Tar droplet

Objectives
1-Study and investigate the possibility of intensifying the
thermal cracking of propane to produce ethylene through
the use of the catalytic plate reactors.
2- Reducing the coke formation and deposition.
3- Reducing the use of steam.
4- Modelling and simulation for propane cracking using
Catalytic Plate Reactor.

Benefits
Lower environmental and safety impacts.
(NO x , contaminated water, CO 2 , H 2 S)
Improved energy efficiency.
Lower capital cost.
Improved overall plant economics

Experimental setup design criteria
Allows for accurate coke measurement
Constant and uniform temperature along the reactor
Very fast cooling of reaction products
Easy to change reactor size and material

Nitrogen
To CO2
Propane
V-1 V-2 Filter-1
FIC-1
V-9
V12
V14
analyser
V-3 V-4 Filter-2
FIC-2
PI-1
PI-2
Air
V13
Reactor
V-5 V-6 Filter-3
FIC-3
Argon
V-10
V-7 V-8 Filter-4
FIC-4
Catchpot
V15
To GCs
Catchpot
V16
Propane cracker
showing flow paths
during decoke
Manometer
Knock-out
V17
Vent

Experimental variables
Reactor materials and internal coatings
Reactor channel size
Process variables ( temperature, pressure, and flow rate)
Run time length

Conversion at low and high operating parameters
Low flow rate
10 0
95
90
85
80
75
70
Conversion, %
65
60
Temperature
low
high low
high
Pressure
High flow rate
100
95
90
85
80
75
70
Conversion, %
65
Temperature
60
low
high low
high
Pressure

Coke yield vs Flow at 835 o C and 1.35 bar
Coke yield ( mg/g-propane reacted)
1.2
1
0.8
0.6
0.4
0.2
0
1.5 2 2.5 3 3.5 4 4.5 5
Flow, l/h

Coke yield vs Temperature. at 3.5 l/h and 1.35 bar
1.2
Coke yield (mg/g-propane reacted)
1
0.8
0.6
0.4
0.2
810 820 830 840 850 860
Temperature, o C

Coke yield vs Pressure at 3.5 l/h and 835 o C
Coke yield (mg/g-propane reacted)
1.1
0.9
0.7
0.5
0.3
0.1
0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8
Pressure, bar

Coke yield at low and high operating parameters
Low flow rate
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
Coke yield (mg/g-propane reacted)
Temperature
Low
High Low
High
pressure
High flow rate
0.6
0.5
0.4
0.3
0.2
Low
Coke yield (mg/g-propane reacted)
Temperature
High Low
High
pressure

Inlet of the reactor
Middle of the reactor
Outlet end of the reactor + Quenching line

UY of Ethylene at low and high operating parameters
Low flow rate
50
UY of Ethylene, Weight %
48
46
44
42
40
low
Pressure
high low
High flow rate
high
Temperature
Ultimate Yield =
Mass Ethylene Produced
Mass Propane In Feed
Assuming that the unreacted propane and
the ethane produced by one pass through
the reactor, are recycled to the feed
50
UY of Ethylene, Weight %
48
46
44
42
40
low
Pressure
high
low
high
Temperature

Conclusions
• Conversion of about 90 % can be achieved in 2 mm internal
diameter fused silica reactor without any significant
pressure drop.
• Steam use can be reduced or possibly eliminated.
• High olefins yield can be obtained without steam.
• Low acetylene and C 4+ yield.
• Run length of about 14 – 20 days was estimated to be
possible before any decoking is required. This run length
was achieved with no steam.

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