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Coal to Liquids – CTL
Reactors : Fixed Bed Reactor and Slurry Bed Reactor
FT Catalysts : Precipitated iron and supported cobalt
Espinoza Prime 3 offers the following CTL technology
SYNTHESIS GAS (SYNGAS)
C SOURCE + H2O + O2 CO + H2 + CO2 + H2O (Same)
FT REACTION
n CO + n(2+x) H2 (CH(2+2x))n + n H2O (Similar)
WGS REACTION
CO + H2O CO2 + H2
FISCHER-TROPSCH REACTION
Fe >> Co
For Iron and Cobalt catalysts
A SIMPLIFIED FT – PU Process Flow Diagram
Water
Light HC
HydrogenationFischer-TropschReactor
DistillationColumn
Hydrocracker
Syngascleaning
Wax
Wax
Light HC
Naphtha
Diesel
H2
H2
Wax
Secondarywax cleaning
Separator
Recycled to extinction
Espinoza Prime 3 Technological Preferences
Precipitated Fe catalyst
Supported Co catalyst
Fixed Bed Slurry Bed
Yes
YesNo
No
Fixed Bed Slurry Bed
Fe
Co
Espinoza Prime 3 Technological Preferences
SBR – Fe catFB - Co cat
Fixed Bed Slurry Bed
Fe
Co
Influence of Plant Size on Technology Selection
Plant capacity : 1000 to 3500 bpd
FB - Co cat
Fixed Bed Slurry Bed
Fe
Co
Plant capacity : 4000 to 10000 bpd
Influence of Plant Size on Technology Selection
SBR - Fe cat
Plant capacity : > 10000 bpd
From :
To :
Influence of Plant Size on Technology Selection
Summary Table for Iron vs Cobalt in Slurry Bed Reactors
Item Iron Cobalt
Activity Lower Higher
Methane Lower Higher
Diesel Yield Similar Similar
Olefin/oxygenates in products Higher Lower
Catalyst life Lower Higher
Contaminants tolerance Higher Lower
Regeneration No Yes
Mechanical Strength Lower Higher
Filterability More complex but more reliable
Simpler but less consistent
Reactor Volume Larger Smaller
Optimal H2/CO ratio in fresh feed ~ 1.7 – 1.8 ~ 2.1
CO2 Selectivity Higher Lower
Overall CO2 produced Similar Similar
Cost $/bbl - Fe : 7 to 10 Co : 30 to 35Catalyst life ~ Co 10 times larger than Fe
Higher Lower
Overall Technical Reliability High Medium
Summary Table for Iron vs Cobalt in Fixed Bed Reactors
Item Iron Cobalt
Activity Much Lower Higher
Methane Lower Higher
Diesel Yield Similar Similar
Olefin/oxygenates in products Higher Lower
Catalyst life Lower Higher
Contaminants tolerance Higher Lower
Regeneration No Yes
Mechanical Strength Lower Higher
Filterability More complex but more reliable
Simpler but less consistent
Reactor Volume Much larger Smaller
Optimal H2/CO ratio in fresh feed ~ 1.7 – 1.8 ~ 2.1
CO2 Selectivity Higher Lower
Overall CO2 produced Similar Similar
Cost $/bbl - Fe : 7 to 10 Co : 30 to 35Catalyst life ~ Co 10 times larger than Fe
Higher Lower
Overall Technical Reliability High High
Espinoza Prime 3 Technological Preferences
Low volumetric productivity. Too many reactors needed
Technological risk.
Cat/wax separation related problems may delay start-up/lower production
Precipitated Fe catalyst
Supported Co catalyst
Fixed Bed Slurry Bed
Yes
Yes
PARAMETER FIXED BED
SLURRY BED
EFFECT
Pre-shaped support Spherical, extruded(*)
Spray dried
Catalyst activity High activity
not needed
As high as
Possible.
FB: easier to devel.
and prepare
Mechanical/Chemical strength
Medium High or Low
(no medium like poorly promoted
γ-Al2O3)
FB cats need less or no structural promoters
Average pore diameter Can be large.
Smaller than
that for FB
Better diffusion for
FB catalysts
COMPARISON FOR FB AND SBR CATALYSTS
PARAMETER FIXED BED
SLURRY
BED
EFFECT
Size constraints function of ΔP and diffusion
function of filtration & fluidization
Study effect of size on performance
Effectiveness factor (η) << 1 ~ 1 FB : put metals on
accessible region
Diffusion constraints Yes Should not
be present
FB cat pre-shape and Impregnation technique important
Dispersion Function of
select, stabil.
red To etc
High: limited
by deactiv. rate
FB cats easier to
develop and prepare
COMPARISON FOR FB AND SBR CATALYSTS(Cont.)
Fixed Bed FT Reactors
Poisons remain at the top
PH2O increase,
Gas Lin Vel decrease(lower heat transfer),High ΔP
Diameter ~ 1.5 – 2”
Lower heat transfer region
PH2O and heat
transfer at Rx bottomlimit conversion
Fixed Bed Reactors : Approximate Sizing
0
1
2
3
4
5
6
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Bpd
Appro
x R
x dia
met
er (m
) .
0
100
200
300
400
500
600
Appro
x R
x w
eight (t) .
Diameter (m)
Rx Weight (t)
Fixed Bed FT Reactors
Diameter ~ up to 34’
Continuous slurrymovement. All cat inventory exposedto poisons
Good heat transferat any point
ΔP = gas distributor plus hydrostatic
Conversion limitedby max PH2O inside
reactor (towards top)
Slurry Bed FT Reactors
Slurry Bed Reactors : ApproximateSizing
0
1
2
3
4
5
6
7
8
9
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Bpd
Appro
x R
x dia
met
er (m
) .
50
100
150
200
250
300
350
400
450
500
Appro
x R
x w
eight (t) .
Diameter (m)
Rx weight (t)
Slurry Bed FT Reactors
Typical Preparation Stages for the Precipitated Fe Catalyst
Fe2O3 Fe3O4 FexCyH2 H2 (CO)
H2O
Fischer-TropschWGS
Magnetite CarbideHaematite
Iron Catalysts
Iron catalysts have a high WGS activity during FT reaction while cobalt catalysts do not.
Result : The H2/CO ratio increases during reaction.
COBALT CATALYSTS
Typically supported on an inorganic oxide
- Alumina, silica, titania, zirconia, zinc oxide, mixtures
- 10-35 wt% cobalt loading
- Typical finished catalyst cost in range of $10-30/lb
Usually with precious metal reduction promoter
- Ruthenium, rhenium, platinum, etc.
Other additives sometimes employed
- Rare earth oxides, base metals, alkalis
Must be reduced to the metal prior to reaction
- Hydrogen treatment at up to about 700-750° F
Metal concentration
Diffusion constraints,Low metal area
Radial Co Concentration Profile: Bad Impregnation
Supported Co Catalysts
Radial Co Concentration Profile: Good Impregnation
Metal concentration
Supported Co Catalysts
* We pay particular attention to the radial Co concentration profile
Co Metal Crystallites: Effect of their Size
Cobalt crystallite size
Fre
que
ncy
High metal surfaceDifficult reductionFast deactivation
Low metal surfaceEasier reductionHigher stability
* Our supported Co catalyst for fixed bed reactors has the optimum average crystallite size
Preferred Range for the H2/CO Ratio: Co Catalysts
Optimum range of H2/CO ratio in the feed : Co Catalyst
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30 40 50 60 70 80 90
CO conversion (%)
Inle
t H
2/C
O R
atio
.
Typically preferred range
Preferred Range for the H2/CO Ratio: Fe Catalysts
Optimum range of H2/CO ratio in the feed : Fe Catalyst
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30 40 50 60 70 80 90
CO conversion (%)
Inle
t H
2/C
O R
atio
.
Typically preferred range
(1) and (3)Table 3, page 366 : Fischer-Tropsch Technology. Vol 152 Studies in surface science and catalysis. A.P. Steynberg and M.E. Dry editors
(2) and (4)Table 4, page 392 : Fischer-Tropsch Technology. Vol 152 Studies in surface science and catalysis. A.P. Steynberg and M.E. Dry editors
Gasifier
Sasol-Lurgi (1)
Sasol-Lurgi (2) KRW (3)
Lurgi MPG (4)
H2/CO 1.63 2.17 0.70 0.77
H2 39 39 31 41
CO 24 18 44 53
CO2 28 31 18 4
CH4 9 11 6 0.15
N2+Ar 0 1 0 1.85
Typical Syngas Composition from Different Gasifiers (vol %)
WGS to Adapt the H2/CO in Feed for Cobaltand Iron Applications
Cobalt application (Stoichiometric ratio ~ 2.14)
Sasol-Lurgi Sasol-Lurgi KRW Lurgi MPG
CO to CO2 3.6 0 19.7 22.55
H2/CO 2.09 2.17 2.09 2.09
H2 42.6 39 50.7 63.55
CO 20.4 18 24.3 30.45
CO2 31.6 31 37.7 26.55
CH4 9 11 6 0.15
N2+Ar 0 1 0 1.85
WGS to Adapt the H2/CO in Feed for Cobaltand Iron Applications
Iron application (Stoichiometric ratio ~ 2.07)
Sasol-Lurgi (1)
Sasol-Lurgi (2) KRW (3)
Lurgi MPG (4)
CO to CO2 2 0 17.8 20.1
H2/CO 1.86 2.17 1.86 1.86
H2 41 39 48.8 61.1
CO 22 18 26.2 32.9
CO2 30 31 35.8 24.1
CH4 9 11 6 0.15
N2+Ar 0 1 0 1.85
Cobalt example.
CO conversion = 94 %. CO2 Sel = 2 %. CH4 Sel = 10 %.
Sasol-Lurgi
Sasol-Lurgi KRW
Lurgi MPG
Relative number of mols of CO converted 19.18 16.92 22.84 28.62 H2/CO ratio 1.59 2.90 1.56 1.57 Tail gas composition (relative number mols) H2 1.95 3.13 2.27 2.87 CO 1.22 1.08 1.46 1.83 CO2 31.98 31.34 38.16 27.12 CH4 10.92 12.69 8.28 3.01 N2+Ar 0.00 1.00 0.00 1.85 PERFORMANCE Rel mols CO conv. to CO2 0.38 0.34 0.46 0.57 Rel mols CO conv. to HC’s 18.79 16.58 22.39 28.05 Rel mols CO conv to C2+ 16.91 14.92 20.15 25.25 % CO in SG converted to C2+ 70.47 82.91 45.79 47.63 % C in SG converted to C2+ 32.53 30.46 32.49 44.29
Cobalt Catalysts Performance
Iron Catalysts Performance
Iron example.
CO conversion = 94 %. CO2 Sel = 20 %. CH4 Sel = 4.5 %.
Sasol-Lurgi
Sasol-Lurgi KRW
Lurgi MPG
Relative number of mols of CO converted 20.68 16.92 24.63 30.93 H2/CO ratio 1.76 6.81 1.75 1.66 Tail gas composition (relative number mols) H2 2.33 7.36 2.75 3.27 CO 1.32 1.08 1.57 1.97 CO2 34.14 34.38 40.73 30.29 CH4 10.03 11.85 7.23 1.70 N2+Ar 0.00 1.00 0.00 1.85 PERFORMANCE Rel mols CO conv. to CO2 4.14 3.38 4.93 6.19 Rel mols CO conv. to HC’s 16.54 13.54 19.70 24.74 Rel mols CO conv to C2+ 15.80 12.93 18.82 23.63 % CO in SG converted to C2+ 65.83 71.82 42.76 44.58 % C in SG converted to C2+ 30.38 26.38 30.35 41.45
Comparison of Cobalt and Iron Performance
Both catalysts show a similar performance in terms of carbon efficiency when using a coal derived syngas feed.
32
S CONTAMINANT LEVEL (ppm)
0.001’s 0.01’s 0.1’s 1’s 10’s
CLEANING COST
Fe Catalysts
Co Catalysts
EXTRA COST FOR Co CATALYSTS
COST OF FEED(S) CLEANING FOR Fe AND Co CATALYSTS
The S compounds in the feed for both catalysts have to be very low, butcobalt catalysts require an additional step to go from the low 100’s ppb (eg ~ 200)for Fe catalysts to the low 10’s (eg ~ < 20) ppb.
GasifierSyngasCleanup
Water Gas Shift
FT Reactor
H2O
H2O
O2 Source
Coal
GasifierSyngasCleanup
H2O O2 Source
Coal Water Gas Shift
FT Reactor
H2O
AdditionalSyngasCleanup
Fe BASED PROCESS
Co BASED PROCESS
~ 200 ppb S (*)
~ 20 ppb S
H2/CO ~ 1.6 - 1.9
H2/CO ~ 2.05 – 2.1
(*) M E Dry
CO2 Removal
CO2 Removal
Differences in the Fe and Co Based Processes Due to Irreversible Poisons in the Feed
