Saturday, 11 February 2017

Primary Reforming Flowsheets


The Theory and Practice
of
Steam Reforming
By:
Gerard B. Hawkins
Managing Director, CEO
 Contents
 Steam reforming reactions
 Steam reforming catalyst
 Equilibrium considerations
 Carbon formation
 Poisonin...Steam Reforming of Methane
CH4 + H2O CO + 3H2 (Steam Reforming))
CO + H2O CO2 + H2 (water Gas Shift)
• Overall strongly en...Steam Reforming of Heavier
Hydrocarbons
CnHm + nH2O nCO + (n+m/2)H2
 Still endothermic
 Easier than methane
 More prone...Contents
 Steam reforming reactions
 Steam reforming catalysts
• catalyst activity
• catalyst development and testing
• ...Steam Reforming Catalyst
 Steam reforming can be done without
catalyst, but needs very high temperatures
• partial oxidat...Steam Reforming Catalyst Activity
 Reaction highly endothermic
• may be limited by process of getting
heat in to reactant...Activity Testing
 Define some measure of reaction
• exit methane
 Measure for a range of catalysts under
fixed condition...Reactants
Products
Reaction
Gas Film
• Two types:
- molecular diffusion
- Knudsen diffusion
Diffusion Effects
Bulk Gas Bul...Diffusion Processes
 Molecular diffusion, Dm
• determined by rate at which molecules collide
with each other
• depends on...Check for Knudsen Diffusion
 Mean free path of molecules must be greater
than pore radius for Knudsen diffusion to
domina...Steam Reforming Catalyst Activity
 Intrinsic activity (chemical reaction only)
 Extrinsic activity (includes heat and ma...Pressure bar (psi)
Catalyst B
Catalyst A
1
(14.5)
10
(145)
20
(290)
Pressure Dependence
 Adsorption
Desorption
Adsorption
Dehydrogenation
Surface Reaction
**
OH2 C + 2H2 CH4
*
H2O CO + H2
CH4
Surface Science
 Nickel crystallites
No further reaction Reaction zone
Catalyst Pellet
Pore
Reactants
Products
Effect of gsa
 Steam Reformer Tubes
 Need to get a lot of heat in
• narrow bore tubes
 High temperatures and pressures
• tubes in creep...850
(1560)
900
(1650)
950
(1740)
1000
(1830)
Temperature oC (oF)
0.1
0.2
0.5
1
2
5
10
20
Design
Effect of Tube Wall Temper...850
(1560)
900
(1650)
950
(1740)
1000
(1830)
Temperature oC (oF)
0.1
0.2
0.5
1
2
5
10
20
Design
Effect of Tube Wall Temper...





https://image.slidesharecdn.com/theoryandpracticeofsteamreforming-130729071412-phpapp01/95/theory-and-practice-of-steam-reforming-23-638.jpg?cb=1375082097TemperatureDegC(DegF)
Tube Wall Temperature Limit
Poor stability
Good stability
Days on Line
0 1,000500100 200 300 400 600...Contents
 Steam reforming reactions
 Steam reforming catalysts
 Equilibrium considerations
• equilibrium curves
• effec...Methane Steam Equilibrium
CH4 + H2O CO + 3H2
P [CH4] P [H2O]
Kms =
P [CO] P [H2] 3
– equilibrium tables
– equilibrium curv...

Equilibrium curves
(methane)
508
203
102
Equilibrium%CH4(drybasis)
Pressure(psig)
Pressure(barg)
Steam Ratio
2.0
3.0
4.0
5...Equilibrium curves
(methane)
Pressure : 30 bar (435 psi)
Temperature : 850°C (1562°F)
Steam:Carbon Ratio : 3.5
What is exi...
















































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