Typical controlled variables Plant Data analysis Approach to equilibrium Prediction of remaining catalyst life Tube wall temperature measurement

1. Normal Operation of Steam
Reformers on Hydrogen
Plants
By:
Gerard B. Hawkins
Managing Director, CEO

2. Contents
 Typical controlled variables
 Plant data analysis
 Approach to equilibrium
 Prediction of remaining catalyst life
 Tube wall temperature measurement

3. Typical Controlled Variables
 Process gas exit temperature
 Process gas and steam inlet temperature
 Steam/carbon ratio
 Process pressure
 Furnace parameters
• Air preheat temperature
• Excess air

4. ExitMethaneSlip(mol%Dry)
Catalyst
Activity
40%
200%
Plant Rate
130%
80%
Exit
Pressure
-1 bar
+1 bar
Exit
Temp(oC)
-10
-20
+20
+10
Steam
Ratio
-10%
-8%
+8%
+10%
5
4
3
2
1
0
Reformer Optimization : Hydrogen Reformer
(Top-Fired) Exit Temperature 856oC (1573oF)
Note relatively small changes in exit
temperature or steam to carbon ratio
can have significant effect on exit
Methane slip
Catalyst activity has relatively less
impact

5. Catalyst
Activity40%
60%
80%
150%
200%
Exit
Temp(oC)
+10
-20
Steam
Ratio
+10%
-10%
Exit
Pressure
-1bar
+1bar
Plant Rate
120%
110%
90%
80%
8
6
4
2
Methane-SteamApproach
Temperature(oC)Reformer Optimization : Hydrogen Reformer
(Top-Fired) Exit Temperature 856oC (1573oF)
Catalyst activity has relatively more
impact on methane-steam approach to
equilibrium temperature

6. MaximumTubeWall
TemperatureoC(oF)
Catalyst
Activity40%
200%
60%
Plant Rate
110%
90%
80%
120%
Exit
Temp(oC)
-10
-20
+10
+20
Steam
Ratio
(Small
effect)
890
(1634)
880
(1616)
870
(1598)
860
(1580)
850
(1562)
Exit
Pressure
(Small
effect)
Reformer Optimization : Hydrogen Reformer
(Top-Fired) Exit Temperature 856oC (1573oF)
If exit temperature remains constant,
then catalyst activity has relatively more
impact on maximum tube wall
temperatures

7. Monitoring Operations
 Furnace Inspection
• tube appearance
• refractory condition
 external hot-spots
• burns
 flame characteristics
 Steam reformer exit temperature measurement
• subheader/pigtail temp, measurements
 burner trimming
 Feedstock purification performance
 sulfur/chlorides etc

8. Hot Band Hot Tube SettlingGiraffe
Necking
Tiger
Tailing
Reformer Tube Appearance

9. Contents
 Typical controlled variables
 Plant data analysis
 Approach to equilibrium
 Prediction of remaining catalyst life
 Tube wall temperature measurement

10. Plant Data Analysis
 Important to cross-check measured data
• gas compositions
 inlet steam reformer
 exit steam reformer
 exit shift reactors(s)
• pressures/temperatures at these points
• flowrates
 recycle hydrogen
 hydrocarbon feedstocks
 steam (need also steam/BFW HTS feed
quench)
 fuel & air

11. Plant Data Analysis
 Match measured plant data with heat/mass balance
• if good match, then data accurate
• if poor match, then errors in plant data
 Total plant data computer fitting program
• can use product rates and compositions etc for
cross-checking of data
• can suggest likely sources of measurement error

12. Plant Data Analysis
 Total plant data fitting
• CO conversion across shift converter(s)
 temperature increase very accurate due to
multiple thermocouples
 cross-checks CO analysis AND steam rate
• Product rate/composition (methanator exit or
PSA product and offgas)
 cross-checks feed rate, steam rate and
methane in reformer exit analysis
• Methanator temperature rise
 cross-checks CO slip from LTS and CO2 slip
from CO2 removal system

13. Steam Reformer
Feed flow (Nm3/hr)
Steam flow (tonne/hr)
Exit gas temperature (oC)
Exit gas composition (mol % dry)
H2
N2
CH4
CO
CO2
Exit gas flow (Nm3/hr)
Steam : dry gas ratio
Equilibrium temperature (oC)
Approach to M/S equilb.(oC)
Steam : carbon ratio
Measured
Value
1975
11.2
750.0
65.27
-
4.65
9.02
21.05
7.009
Best Fit
Value
2459
11.1
765.0
71.37
0
3.23
8.63
16.77
8634
1.1745
755.5
9.5
5.575
Percentage
Error
24.5
-1.1
1.4
-9.3
-
30.5
4.3
20.3
Plant data Verification - Poor Fit

14. Plant Data Verification - Poor Fit
 Poor fit
 Areas to check
• feed flowrate
• exit methane
• exit CO/CO2
Feed flowrate originally quoted as 1.156 tonne/hr naphtha
- Revised to be 1.59 te/hr naphtha

15. Plant Data Verification - Revised Fit
Steam Reformer
Feed flow (Nm3/hr)
Steam flow (tonne/hr)
Exit gas temperature (oC)
Exit gas composition (mol % dry)
H2
N2
CH4
CO
CO2
Exit gas flow (Nm3/hr)
Steam : dry gas ratio
Equilibrium temperature (oC)
Approach to M/S equilb.(oC)
Steam : carbon ratio
Measured
Value
2644
11.2
750.0
65.27
-
4.65
9.02
21.05
5.244
Best Fit
Value
2554
11.2
758.0
71.33
0
3.23
8.68
16.76
8954
1.1384
758.1
0
5.442
Percentage
Error
-3.4
0.3
0.8
-9.3
-
30.4
3.8
20.4

16. Plant Data Verification - Revised Fit
 Better fit for flowrate
 Significant error still on reformer exit gas
analysis
 CH4
 CO/CO2
Methane slip originally quoted as 4.65 mol %(dry)
- Revised to 3.56 mol % (dry)

17. Plant Data Verification - Final Fit
Steam Reformer
Feed flow (Nm3/hr)
Steam flow (tonne/hr)
Exit gas temperature (oC)
Exit gas composition (mol % dry)
H2
N2
CH4
CO
CO2
Exit gas flow (Nm3/hr)
Steam : dry gas ratio
Equilibrium temperature (oC)
Approach to M/S equilb.(oC)
Steam : carbon ratio
Measured
Value
2644
11.2
750.0
69.86
-
3.56
8.24
18.34
5.244
Best Fit
Value
2554
11.2
758.0
71.33
0
3.23
8.68
16.76
8954
1.1384
758.1
0
5.442
Percentage
Error
-3.4
0.3
0.8
-2.1
-
9.4
5.3
8.6

18. Plant Data Measurement - Problem
Areas
 Sampling/analysing exit gas compositions
 Exit temperature from reformer
 Flow measurement

19. Exit Gas Composition
 CO shift reaction can occur if not quench
cooled quickly
 CO2 may dissolve in water
• dry gas analysis!
 Analysis of sample must be taken in the
same time frame as the process data
recording

20. Exit Reforming
Catalyst
(mol % dry)
"Shifted" Sample
Analysis
(mol % dry)
CH4 4.4 4.2
CO 13.8 10.3
CO2 8.6 11.4
H2 71.9 72.8
N2 1.3 1.3
CO>CO2 CO<CO2
“Shifting” in Gas Sample
Note also reduction in CH4

21. Exit Temperature
 Heat/mass balance requires temperature exit
catalyst
 Plant temperature measurement often at inlet to
waste heat boiler
• large heat losses possible
 outlet pigtails, headers, transfer mains
Top-fired : 10-20oC (18-36oF) heat loss
Side-fired : 25-35oC (45-63oF) heat loss
(Air ingress at base of steam reformer can lead to further cooling)

22. Note that hydrocarbon composition variations
may effect the metered accuracy and also the
steam/carbon ratio calculation
Flow Measurement
 Hydrocarbon feedstock generally high accuracy
• “costing” meter
• multiple feed streams may be less accurate
 Steam flow often less accurate
• error in steam/carbon ratio can have a
significant effect on heat/mass balance

23. Plant Data Analysis
 Best to record trends
• relative changes partially remove
 measurement errors
 Monitor monthly/quarterly
• measures of catalyst activity
 methane slip
 assuming constant operating conditions
• approach to equilibrium
• tube wall temperature

24. Plant Data Analysis

25. 0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 10 20 30 40
MethaneSlip(mol%)
Months on line
Plant Data Analysis
NaturalGasRate(x1000
Nm3/hr)
8
6
4
2

26. Contents
 Typical controlled variables
 Plant data analysis
 Approach to equilibrium
 Prediction of remaining catalyst life
 Tube wall temperature measurement

27. Approach Tms = Actual T gas - Equilibrium T gas
(A.T.E.)
Measured Calculated
• Measure of catalyst activity
• If ATE = O, system at equilibrium
• As catalyst activity decreases, ATE increases
Approach to Equilibrium
CH4 + H2O CO + 3H2⇔

28. Calculation of Approach to
Equilibrium
1. Take gas samples and record steam
reformer exit temperature
2. Calculate wet reformer exit composition
- Hydrogen atom molar balance (inlet/exit)
- Calculate steam in exit gas
- Convert exit dry gas to wet gas composition
3. Calculate equilibrium temperature
corresponding to this exit composition
- Use tables or equations
4. Calculate approach to equilibrium

29. Contents
 Typical controlled variables
 Plant data analysis
 Approach to equilibrium
 Prediction of remaining catalyst life
 Tube wall temperature measurement

30. Case Study
 Terraced wall reformer
 How much longer will catalyst last (from
Jan’08)
 Change-out when?
• September ‘08
• April ‘09
• September ‘09

31. 11/Apr/06 03/Oct/06 27/Mar/07 18/Sep/07 12/Mar/08
1,320
1,340
1,360
1,380
1,400
1,420
6
7
8
9
10
Date
MethaneSlip(m
Outlet Temperature Methane Slip
Steam Reformer Performance
GBH Enterprises Ltd.

32. 10/Feb/04 22/Dec/05 02/Nov/05 12/Sep/06 24/Jul/07 04/Jun/08
0
Design EOR
Design SOR
Catalyst On- line: Oct ‘02
01/Apr/03
10
20
30
40
Date
ApproachtoEquilibrium(oF)
Catalyst Performance Monitoring
GBH Enterprises Ltd.

33. 1,300
1,400
1,500
1,600
1,700
Date
01/Apr/05 26/May/06 20/Jul/07 12/Sep/08 06/Nov/09
Design temperature
Tube wall temperatures (Top)
Tube wall temperatures (Bottom)
Tube Wall Temperatures
TubeWallTemperature(oF)
GBH Enterprises Ltd.

34. 0 0.2 0.4 0.6 0.8
1260
1360
1460
1560
Fraction down Tube (%)
Tube Wall Temperature Process Gas
Delta T
1
Tube Wall Temperatures
GBH Enterprises Ltd.

35. Bottom minus Top
01/Apr/06 26/May/07 20/Jul/08 12/Sep/08 06/Nov/09
0
20
40
60
80
100
120
140
-9oF/year
Tube wall Temperatures
Date
GBH Enterprises Ltd.

36. June 06 June 07 June 08 Sep 08 Sep 09
Exit CH4 (mol% dry) 7 7 7 7 7
Exit Temp oC
(oF)
787
(1432)
789
(1452)
795
(1463)
795
(1463)
795
(1463)
Max Tube Temp oC
(oF)
829
(1524)
831
(1528)
838
(1540)
838
(1540)
838
(1540)
M/S Equilib. Approach oC
(oF)
10
(18)
12
(22)
13
(23)
14
(25)
15
(27)
Steam Reformer Data
Looks OK to September ‘09 BUT……..….

37. 0 0.2 0.4 0.6 0.8 1
500
600
700
800
900
Fraction from inlet of tube
Carbon
Formation Catalyst ageing
New catalyst
Carbon Formation
GBH Enterprises Ltd.

38. Activity Decay Factor
 Need to consider carbon formation
• Accurate model of catalyst activities needed to
correctly simulate catalyst ageing
 Take data at different times and calculate
relative activity
• for terraced wall reformer
 (i) top 30% slowly poisoned
 (ii) middle 30% very slowly poisoned
 (iii) bottom 40% sinters very slowly
(i) and (ii) account for delta T
(iii) accounts for increased approach
GBH Enterprises Ltd.

39. Jan
02
May Sep Jan
03
May Sep Jan
04
May Sep Jan
05
May Sep
0
50
100
150
200
250
Today September
‘04
September
‘05
Carbon
margin
Date
CarbonMargin(oF)
Carbon Margin with Time
GBH Enterprises Ltd.

40. Activity
(arbitrary)
Time (years)
Carbon forming
region
Initial sintering
"Stable"
activity
Margin
Period where carbon
can be formed at
anytime due to
variation in process
conditions
Catalyst Deactivation (Schematic)
GBH Enterprises Ltd.

41. Conclusions #1
 In terms of M/S Approach and Tube Wall
Temperatures, can run till September ‘05
 Concern about carbon margin from April ‘05
onwards
• options
 change April ‘05 - CHOSEN OPTION
 OR run with spare on site and change
September ‘05
GBH Enterprises Ltd.

42. Conclusions #2
• Sometimes difficult for operator to predict
change-out requirement
– Couldn’t rely on M/S Equilibrium Approach
and Tube Wall Temperature trending
– Needed complex reformer simulation
• HOWEVER, recording of historic data from
start-of-run conditions allowed accurate
assessment by the catalyst vendor
– Take data from SOR!
GBH Enterprises Ltd.

43. Contents
 Typical controlled variables
 Plant data analysis
 Approach to equilibrium
 Prediction of remaining catalyst life
 Tube wall temperature measurement
GBH Enterprises Ltd.

44. Importance of Tube Wall
Temperature Measurement
 Need accurate information
• Tube life !
• Artificial limitation on plant rate
GBH Enterprises Ltd.

45. TubeLife(Years)
850
(1560)
900
(1650)
950
(1740)
1000
(1830)
0.1
0.2
0.5
1
2
5
10
20
Design
Effect of Tube Wall Temperature on
Tube Life
Temperature oC (oF)
+ 20oC
+ 36oF
GBH Enterprises Ltd.

46. Tube Wall Temperature Measurement
 Contact
• surface Thermocouple
 “Pseudo-contact”
• Gold Cup Pyrometer
 Non-contact
• disappearing filament
• infra-red optical pyrometer
• laser pyrometer
GBH Enterprises Ltd.

47. Surface Thermocouples
 Continuous measurement, by condution
 “Slotting” can weaken tube wall
 Spray-welding leads to high readings
 Short, unpredictable lives (6-12 months)
Not commonly used for steam reformer tubes
GBH Enterprises Ltd.

48. Disappearing Filament
 Hand held instrument
 Tungsten filament superimposed on
image of target
 Current through filament altered until it
“disappears”
 Current calibrated to temperature
 Range 800-3000oC (1470 - 5430oF)
Very operator sensitive
Largely displaced by IR
GBH Enterprises Ltd.

49. Infra-red Pyrometer
 Easy to use
 Need to correct for
emissivity and reflected
radiation
 Inexpensive
GBH Enterprises Ltd.

50. Radiation Methods
 Measure emitted energy at given wavelength
 Use Planck’s Law to give temperature
 Correction factors needed
• target emissivity
 real versus black body
• reflected radiation
GBH Enterprises Ltd.

51. Tw
"e" is the emissivity
of the tube
Target Tube
Tt
Refractory Wall
Measured
Temperature
Tm
Flame Tf
e
The Effect of Reflected Radiation from
Target Surroundings

52. Measured True Averaged
target target background
temperature temperature temperature
e = emissivity
r = reflectance
= (1-e)
Temperature Correction
E (Tm) = e E (Tt) + r E (T’w)
GBH Enterprises Ltd.

53. 0.7 0.75 0.8 0.85 0.9 0.95 1
Difference in wall and target
temperature oC (oF)
300
200
100
Deg C Deg F
(540 F)
(360 F)
(180 F)
200
150
100
50
0
392
302
212
122
0
Target Emissivity
Error in measured tube temperature
Theoretical Effect of Wall Temperature
(0.9 micron pyrometer)
GBH Enterprises Ltd.

54. Laser Pyrometers
 Laser pulse fired at target and return signal
detected
 Can determine target emissivity
 Must correct for background radiation
 High speed selectivity
 Very accurate for flat surfaces
GBH Enterprises Ltd.

55. TUBE
Laser
Pyrometer
Laser Pyrometer - Angle of Incidence
Scattered laser pulse
GBH Enterprises Ltd.

56. Gold Cup Pyrometer
 Excludes all reflected radiation
 Approximates to black body conditions
 High accuracy/reproducibility
 But…..
• limited access
• awkward to use
GBH Enterprises Ltd.

57. Tube
Furnace Wall
Water
Cooling
To
Recorder
Gold Cup
Lance
*
Gold Cup Pyrometer
GBH Enterprises Ltd.

58. Accurate Temperature Measurement
 Combination of IR pyrometer and Gold
Cup
• Gold Cup allows us to calculate “e”
• Full accurate survey of reformer
possible with IR
GBH Enterprises Ltd.

59. • Measure Tt using Gold Cup
• Measure Tm and Tw using Infra Red Pyrometer
• Calculate e
Calculate "e"Use IR to give Tt with measured
T’w and Tm and calculated e
Accurate Temperature Measurement
E (Tm) = e E (Tt) + (1-e) E (T’w)
GBH Enterprises Ltd.

60. A
a (Nearby tubes)2
Background Temperature
Measurement
Background Measurement for Tube A
a1
Refractory
Wall
GBH Enterprises Ltd.

61. 950
900
850
800
750
1742
1652
1562
1472
1382
Temperature(oC)
Temperature(oF)
0 0.2 0.4 0.6 0.8 1
Uncorrected
Pyrometer
Corrected Pyrometer
Calculated
= Gold Cup Measurements
Fraction down tube
Comparison of IR pyrometer and
Calculated Tube Wall Temperature
Measurements
GBH Enterprises Ltd.

62. Tube Wall Temperature
Measurement - Conclusions
 IR typically reads high
• top-fired reformer 32oC (58oF)
• side-fired reformer 50oC (90oF)
 IR with Gold Cup “calibration”
• top-fired reformer 2oC (4oF)
• side-fired reformer 16oC (29oF)
GBH Enterprises Ltd.

63. Summary
 Effect of operating variables on performance
 Plant data analysis
• fitting plant data
• problem areas
 reformer exit temperature
 flow errors
 sample analysis shifting
 Approach to equilibrium
 Prediction of remaining catalyst life
 Tube wall temperature measurement
GBH Enterprises Ltd.