2. Three major types of reformer
Each tackles the duty in different ways
No clear best choice
Choice dictated by Contractor history
3. Top Fired
Usually Single box with Multiple rows
of tubes.
Heat load for a Top fired, is in the top
one third of the reforming section.
Peak tube wall temperature is is this
region
Pencil Type Flames required
Side Fired/Foster Wheeler
Side Fired Reformers are usually
made up of several identical cells, with
each having a single row of tubes
The aim of the side fired design is to
achieve a more even heat flux profile
over the length of the tube, by locating
burners the full height of the box.
5. Majority of plants have Top Fired Reformers
Some have Foster Wheeler Reformers
A few have Side Fired Furnaces
Lurgi plants often have an oxygen blown secondary
A few plants have a pre reformer (Statoil and M5000)
6. Methanol reformers are large
Largest reformer has 960 tubes
Two to three times the size of an ammonia reformer
Many reformers in the range 600-900 tubes
Why is this ?
All reforming is done in this reformer
There is no secondary
Therefore choose the cheapest design and easiest to
scale up
Therefore use Top Fired - Why ?
7. Capital Cost
For a reformers of the same size a Top Fired furnace
has less equipment than Side Fired or Foster Wheeler
FW and SF duplicate a lot of equipment as there are 2
cells
Side fired are generally less heavily loaded - they have
a higher capacity
8. Operational Costs
Top fired have a higher radiant efficiency
Typically 50-60%
Side fired furnaces have a lower efficiency
Typically 40-45%
Maintenance Costs
Side Fired reformers have more burners
By a factor of 5 over Top Fired
By a factor of 2 over Foster Wheeler
Side Fired refractory temperatures are higher
9. Name Methanol Ammonia
Steam to Carbon 2.8-3.2 3.0-3.4
Pressure (bara) 15-20 30-35
Exit 1y
Temperature (°C) 860-880 740-780
Exit 2y
Temperature (°C) n/a 960-980
Tube Count 900-1000 300-400
Maximum TWT (°C) 900-950 800-850
H2 70-73 54-58
CO 14-16 10-12
CO2 7-9 8-10
CH4 2-3 0.1-1.0
N2 0-1 22-26
Comparison of Flowsheets
Typical Conditions
10. On most methanol plants we only have a primary
reformer
Therefore must minimize methane slip from primary
Methane is an inert in the loop
Just like ammonia
Represents an inefficiency
Must be purged out - lose reactants
Purge is burned in reformer
Typically 2/3 of the reformer fuel
(Some plant do sell it !)
11. Must therefore run at highest outlet temperature
There is no secondary to drop slip down to very low
levels
A steam to carbon of 2.8 to 3.3 allows MPS to be used
from steam turbine
Balances out MPS balance
Run at low pressure to minimise methane slip
Does increase compression costs
12. No requirement for nitrogen to be added to the process
In fact do not want nitrogen
It’s an inert and will reduce loop efficiency
Oxygen plants are traditionally expensive
Oxygen blown secondary’s have a poor track record
Many failures due to poor burner design
Many failures due to poor vessel/refractory design
Flame temperature is very high (2000°C)
13. Historically plants were never built with them
No need for feedstock flexibility
Licensed contractors have their own primary reformer
design - based on JMC design in many cases
Topsøe do include them - problems with MgO hydration
Similar to ammonia plants
Therefore there is no great driving force for inclusion
Until now
Mega plants are at limit of reformer design
15. Nearly all heat transfer is by radiation
Radiation from the fluegas to the tubes
Little direct radiation from refractory to tube
Refractory acts as a reflector
Radiation from flame to tube at tube top
19. Same for both types
Nearly all heat transfer is by radiation from flames and
refractory
Major portion is from refractory
Some from flame (especially in FW)
Some from fluegas
Heat is transferred from flame to the walls
By convection
20. Typical catalyst is VSG-Z101
Required to prevent carbon formation
Heat fluxes are very high 100-160 kW/m²
For plants with really high heat fluxes us VSG-Z101
Only two plant shave giant installed
Pressure drop is not an issue (no air compressor)
Heat transfer and carbon formation ARE issues
22. Exit temperatures are higher
Therefore inside tube wall temperatures are higher
Heat fluxes are higher
Top fired between 100-140 kW/m²
But some in range 140-160 kW/m²
Ammonia plants typically 80-120 kW/m²
These conditions favor carbon formation
23.
24. Several N American
Operators had failures
at bottom of the tubes
Simulations said lots of
margin
New peepholes
installed and
temperatures measured
Must hotter than
expected
25.
26.
27. Found in Canada
Unusual Temperature
distribution
Checked using dry
powder
Up flow at walls
Flame impingement
Modelled using CFD
28.
29.
30.
31.
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