Saturday, 11 February 2017

CARBON FORMATION

'Carbon Formation
Depends on: - feedstock
- operating conditions
- catalyst
 Carbon Deposition
Carbon
Catalyst
surface
1 mm (40 thou)
 Carbon Formation
CH4 C + 2H2 (Thermal Cracking)
CO + H2 C + H2O (CO Reduction)
2CO C + CO2 (CO disproportionation
“Boudoua...Carbon Formation
 Direction of reaction determined by
process gas conditions
 Generally, CO reduction and Boudouard
are ...pH2
2
pCH4
10
1.0
0.1
550 600 650 700 750 800
Carbon Formation Zone
No Carbon
Formation
Deposition rate
< removal rate
Dep...10
0
10
1.0
0.1
550 600 650 700 750 800
0.6
0.5
0.4
0.3
Carbon Formation Zone
Temperature (°C)
Proportion of tube
length f...100
10
1.0
0.1
550 600 650 700 750 800
0.6
0.5
0.4
0.3 Carbon Laydown Zone
1100 1200 1300 1400 (°F)
Carbon Formation - Hot...Carbon Formation
C + H2O CO + H2 (CO Reduction -
in reverse!)
Catalyzed by OH-
 800
100
10
1.0
0.1
0.6
0.5
0.4
0.3
550 600 650 700 750
Increasing
Potash
Content
1100 1200 1300 1400
(°F)
Carbon Formation...Role of Alkali
 Reduces likelihood that carbon will be
formed
 Enables carbon to be removed readily
 Incorporation into...Fraction Along Tube
Inlet Outlet
Non-Alkalised
Catalyst
Rings
Optimised Shape
Inside Tube Wall
Temperature
920
(1688)
820
...Methane feed/Low heat flux
Increasing Alkali
Addition
0
Methane feed/High heat flux
Propane, Butane feeds (S/C >4)
2-3
Pro...Feedstock Natural Gas
Reforming
Non-
alkalised
Associated
Gas Ref
Lightly
alkalised
Dual Feedstock
Reforming
Moderately
al...Alternatives to Alkali
• Precious metals can also be used instead
of Ni as the catalyst
– Significant higher activity and ...














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