Introduction Background Radiation and Temperature Measurement Reformer Survey Inputs Other Troubleshooting Tools Safety Preparation Onsite Data Collection TWT Survey Observation/Troubleshooting Modelling and Analysis Results/Outputs Case Studies Conclusions Case Study 1 Case Study 2 Case Study 3 Conclusions

1. Steam Reformer Surveys
Gerard B. Hawkins
Managing Director
Techniques for Optimization of
Primary Reformer Operation

2.  Introduction
 Background Radiation and Temperature
Measurement
 Reformer Survey Inputs
 Case Study 1
 Case Study 2
 Case Study 3
 Conclusions

3.  Reformer is at the heart of the plant
◦ Converts feed gas to Syngas
◦ Complex operation
◦ Integrated design
◦ Main energy consumer
◦ Most expensive single plant item
 Reformer is often a throughput constraint

4.  Combination of techniques used
 Tube Wall Temperature measurement
 Plant heat & mass reconciliation
 Reformer simulations
 Output provides assessment of
 Catalyst performance
 Reformer operation
 Operating limits
 Tube life estimation

5.  Introduction
 Background Radiation and Temperature
Measurement
 Reformer Survey Inputs
 Case Study 1
 Case Study 2
 Case Study 3
 Conclusions

6. Tube Wall

7.  Background radiation affects readings
 Minimize errors when using IR pyrometer
◦ Use emissivity setting of 1.00
◦ Use correction formula
 Post processing calculation
 Use Gold Cup pyrometer

8. Reformer Surveys
TWT Survey (Optical Pyrometer)
Gold Cup:
•Most accurate temperature
measurement
•Eliminates the effects of background
radiation
•Limited number of tubes can be
measured
•Large cumbersome equipment
•Significantly more readings on side
fired furnaces

9. Reformer Surveys
TWT Survey (Optical Pyrometer)
Optical Pyrometer:
•Good for taking 'lots' of readings
•Most tubes are visible
•Easy to use
•Portable
•Absolute figures not accurate
•Relative figures are more accurate

10. Reformer Surveys
TWT Survey (Optical Pyrometer)
•Measures total radiation from target
•Picks up radiation from
•refractory
•flue gas
•other tubes
•Can not distinguish between
•radiation emitted and radiation
reflected
•Measured temperature is high
•Typically 68-104°F (20-40°C)

11. Reformer Surveys
TWT Survey (Optical Pyrometer)
•Cyclops 52/153 has narrow bandwidth
•0.8-1.1 micron
•Reduces radiation from flue gas effect
•Ensure that reading taken at 90° to
tubes
•Both vertically and horizontally
•It is possible to correct for these
radiation effects
•Temperature to Fourth Power
•Lots of data should eliminate random
errors

12. Reformer Surveys
TWT Survey (Optical Pyrometer)
•Correct to minimize background radiation
effects
•Use a Stefan-Bolzman Equation
Tt = {(Tm
4 - [1 -e] Tw
4)/e}0.25
• Tt : True temperature
• Tm : Measured temperature
• Tw : Background temperature
• e : emissivity

13. Reformer Surveys
TWT Survey (Optical Pyrometer)
•Must correct measured temperatures
•For background readings use
temperatures from:
•Refractory (walls, floor and roof)
•Use following expression
Tw = {1/N *( TW1
4 + TW2
4+ TW3
4 .…+ TWN
4)}0.25
•N is number of readings

14. Reformer Surveys
TWT Survey (Optical Pyrometer)
•Pyrometer used with an emissivity of 1
•Emissivity of 0.85 used in correction
•Plant data reconciled and furnace
modelled in ASPEN HYSYS V8
•Corrected temperature compared to
simulated values

15. 830
790
750
710
Temperature
ºC
40
35
30
25
20
15
10
5
A
B
C
D
E
F
G
H
Row
Tube
Num
ber
Hot Zone
Cold Zones

16.  Introduction
 Background Radiation and Temperature
Measurement
 Reformer Survey Inputs
 Case Study 1
 Case Study 2
 Case Study 3
 Conclusions

17.  Tube wall temperature survey
◦ Tube temperatures
◦ Background temperatures
 Process operating data collection
◦ Pressure, Temperature, Flows
 Chemical analysis of all streams
 Radiant and convection section data
◦ Geometry, Layouts …

18.  VULCAN CERES - data fitting package used
to reconcile data
 The use VULCAN REFSIM to model furnace
 Close H&M balance on process and flue
gas using Aspen HYSYS V8
 Allow certain values to float
 Wider data envelope = better fit

19.  VULCAN REFSIM - fully coupled computer
model
◦ Radiant heat transfer in flue gas
◦ Heat transfer inside tubes
◦ Reaction kinetics inside tubes
 Radiation based on proven theory
 Tubeside based on operating plant data

20. Heat Flows
Radiation
Convection
Tube Fluegas Flame Wall

21. 680
700
720
740
760
780
800
820
840
860
0 0.2 0.4 0.6 0.8 1 1.2
Fractional Distance Down Tube
Temperature(°C)
Simulation
Measured

22.  Fire Extinguisher
◦ Inject via side peepholes or burner ignition port
◦ Check for flue gas maldistribution
◦ See case study 1
◦ Can use K2CO3
 Fuel gas pressures
◦ Check for fuel mal-distribution
◦ Use standard pressure gauge

23.  Combustion air pressure
◦ Use standard manometer
◦ Check by row and then by burner
 Visual Inspection
◦ Look at tubes, refractory and burners
◦ Check for deviations from expectation
 Design Philosophy
◦ Check for deviations from expectation

24.  Check wind box pressure
◦ Ensure even firing through out furnace
 Check oxygen levels
◦ Ensure even combustion air flow
 Thermal Imaging
◦ Check for refractory damage

25. Reformer Surveys
Summary
A Reformer Survey involves:
•Collection and analysis of data from both
the process and flue gas sides
•Assess the performance of the reformer
•Assess the performance of the catalyst
Collecting data from the whole reformer
minimizes errors.

26. Reformer Surveys
Summary
Typical outputs from a Reformer Survey
includes:
• Catalyst performance
• Real tube skin temperature
• Reformer balance
• Efficiency gains
• Benchmarking

27. Reformer Surveys
Content
• Introduction
• Safety
• Preparation
• Onsite Data Collection
• TWT Survey
• Observation/Troubleshooting
• Modelling and Analysis
• Results/Outputs
• Case Studies
• Conclusions

28. Reformer Surveys
Introduction
• Primary is the most complicated and
expensive piece of equipment on the
plant
•Heat transfer - Provides sensible heat
and heat of reaction
•High pressure and very high
temperature
•Data collection can highlight trends
•Reformer survey required to allow full
diagnosis

29. Main additional risks are burns and
overheating,
◦ Burns from exposed hot surfaces
◦ Radiation burns via open peepholes
◦ Burns due to hot gas or flames
◦ Heat stroke/Dehydration

30. In addition to standard PPE the following
should be considered,
◦ Heat resistant gloves
◦ Flame retardant overalls
◦ Furnace eye protection

31. Reformer Surveys
Typical Work Remit
Typically a reformer survey consists of a
number of actions:
•Preparation
•On-site data collection
•Tube wall temperature measurement
•Observations and trouble shooting
•Modelling and analysis
•Report writing

32. Reformer Surveys
Preparation
Usually carried out prior to site visit and
would normally include:
• A wish list of requirements from the plant
• Mechanical design of the reformer
• Piping and instrument drawings
• Process flow diagrams
• Any known process problems

33. Reformer Surveys
On-site Data Collected
•Feed, Steam, Fuel, Combustion air
data including,
•Flows
•Pressures
•Temperatures
•Gas analysis from on line analyzers
& laboratories
•Reformer dimensions
•Tube temperatures using an optical
pyrometer (or gold cup)

34. Reformer Surveys
Tube Wall Temperature Survey
•Tube skin temperature used to fit
temperature profile
•Generates an activity figure
•No one ideal method of
measurement
•Two methods currently used
•Optical Pyrometer
•Gold Cup
•Both have advantages and
disadvantages

35.  Introduction
 Background Radiation and Temperature
Measurement
 Reformer Survey Inputs
 Case Study 1
 Case Study 2
 Case Study 3
 Conclusions

36. • Large scale ammonia plant
• Tube temperatures split in box
• No apparent process reason
Hot Zones
Cold Zones

37. • Eliminated other possibilities
• Maldistribution due to
• Process gas
• Fuel gas
• Firing
• Only left with combustion air
• Subsequent shut down
• Found one of the two air dampers stuck
• Repaired

38. • After shut down temperatures were

39.  Survey highlighted an
problem on the
furnace
 By working closely
with plant personnel,
determined root cause
 Subsequent work
proved root cause
 Problem worth
US$750,000 per year

40.  Customer complained of high ATE
 Survey found
◦ High box pressure (-2 or -3 mm H2O)
◦ Afterburning in centre of furnace but O2 levels exit
box in excess of 2.5 %
◦ Cool outer rows
◦ Hot centre rows

42.  Design of combustion
air duct was
symmetrical
 Combustion air and
flue gas fans at limit
 Insufficient driving
force to get air to
centre of furnace
 Cause after burning

43. • Survey on plant found odd temperature
distribution
• Not explained by burner pressure
• Not explained by combustion air mal-
distribution
10
18
26
34
42
50
58
66
2
3
4
5
860
880
900
920
940
860
880
900
920
940
Temperature
940+
932 to 940
924 to 932
916 to 924
908 to 916
900 to 908
892 to 900
884 to 892
876 to 884
868 to 876
860 to 868
Row Number
Tube Number

44.  Checks on furnace geometry highlighted
an issue
◦ Outer lanes were the same size as the inner
lanes
◦ Outer row of burners were rated at 70% of
the inner burners
 Injected dry powder from fire
extinguisher into furnace
◦ Unusual flow patterns

47.  Computational Fluid Dynamics was used
to model reformer in detail
Burners
Tunnel
Ports
Velocity
Vectors

48. A B C D E F Tube Number

49.  CFD simulations matched the observations
from the plant
◦ Dry powder tests and TWT measurements
 Three proposed solutions to eliminate the
effect
◦ Increase burner size to match tunnel size
◦ Decrease furnace width to match burner size
◦ Increase velocity through the burners

50. 70% 100%
burner burner
100% 100%
burner burner
70% 100%
burner burner
Recirculating
Case
Solution 1 Solution 2
100%
2.1 m
100%
2.1 m
100%
2.1 m
100%
2.1 m
70%
1.5 m
100%
2.1 m

51.  Solution 1 - Requires 100% burner in
outside rows
◦ Difficult to achieve
◦ Requires either
 Modification of burners
 Replace with 100% burners
◦ But too much heat flux
◦ Must increase process gas flow
◦ Install orifice plates inlet all tubes
◦ Outer rows are larger than inner

52.  Solution 2 is to reduce furnace width so
outer lane width matches the 70%
burners
◦ Requires modification to refractory
◦ Increase in number of ports on the outer
rows of tunnels
 Solution 3 - Increase velocity through
outer row of burners
◦ 154% of existing velocity

53.  Highlighted a mal-distribution
 Costing plant approximately US$350,000 in
lost production
 Reduce peak tube temperatures
 Methodology proved initial theory
 Allowed for a set of solutions to be
proposed

54.  Visual Inspection
◦ Look at tubes, refractory and burners
◦ Inspect external casing
◦ Check for deviations from expectation
 Design Philosophy
◦ Check for deviations from expectation
 Fuel gas pressures
◦ Check for fuel mal-distribution
◦ Use standard pressure gauge

55.  Combustion air pressure
◦ Use standard manometer
◦ Check by row and then by burner
 Fire Extinguisher
◦ Inject via side peepholes or burner
ignition port
◦ Check for flue gas maldistribution
◦ See case study 3
◦ Can use K2CO3

56.  Check wind box pressure
◦ Ensure even firing through out furnace
 Check oxygen levels
◦ Ensure complete combustion
◦ Ensure even combustion air flow
 Thermal Imaging
◦ Check for refractory damage

57. Reformer Surveys
Modelling and Analysis
Computer packages used:
• VULCAN REFSIM
• Heat and Mass Transfer in radiant
box
•Aspen HYSYS
• Flowsheeting package
• VULCAN TP3 or VULCAN CERES
•Match data between models

58. Reformer Surveys
Modelling and Analysis - VULCAN
REFSIM
•Developed using research and plant
data
•Accurate analysis of Radiant box
•Results are:
•Kinetic model
•Equilibrium model
•Tube wall temperatures & margins
•Pressure drops
•Carbon laydown prediction

59. Reformer Surveys
Modelling and Analysis – Aspen HYSYS V8
•Flowsheeting package
•Contains VULCAN REFSIM Reformer and
Reactor models
•Used for detail modelling of the plant
•Both front end and loop
•Steam system
•Heat recovery
•Results include:
•Flow sheet of the plant
•Heat loads of coils and exchangers

60. Reformer Survey
Results - Statistical Temp. Analysis
•Look at various splits of box
•Depending on design and size
•Look at
•Average
•Maximum
•Minimum
•Standard deviation
•Spreads
•Three dimensional plots
•Frequency plots
•Compare to others

62. Reformer Survey
Frequency and Cumulative Plot
Frequency Plot for the Bottom Corrected TWT's
0
5
10
15
20
25
0
-840
840
-850
850
-860
860
-870
870
-880
880
-890
890
-900
900
-910
910
-920
920
-930
930
-940
940
-950
950
-960
960
-970
970
+
Temperature Range, C
Percent
0
10
20
30
40
50
60
70
80
90
100
Btm Corrected (%) Btm Corrected Cumulative (%)

63. • Detailed heat and mass balance of
Primary reformer
• Using kinetics and equilibrium
• Pressure drop prediction
• Process and tube temperature profiles
• Flowsheet of plant
• Ideas for plant improvements
• Efficiency or Rate increases

64. Reformer Survey
Tube Wall Temperature Results
•Max tube wall temperature
•Predicted by VULCAN REFSIM
•Tube wall temperature margin is
•Predicted by VULCAN REFSIM
•Worst case analysis
•Based on GBHE Codes
•Based on 100,000 hours
operation

65.  Introduction
 Background Radiation and Temperature
Measurement
 Reformer Survey Inputs
 Case Study 1
 Case Study 2
 Case Study 3
 Conclusions

66. Reformer Surveys
GBHE Tube wall Temperature Margins
•Based on
•inlet pressure
•hoop stress calculation
•GBHE Tube wall temperature margins
do not include
•transient stresses (Start Ups/Shut
Downs)
•longitudinal stresses
•bending stresses
•weld region stresses

67. Reformer Surveys
General Conclusions
Indications of:
•Tube appearance
•Hot spots or bands
•The operation of reformer
•Optimization
•Current catalyst performance
•Benchmarking
•Instrument Calibration
•Oxygen levels

68. • Air damper stuck
• Air preheater leaks
• Correct exit temperatures
• Flue gas recirculation
• Flue gas maldistribution
• Explanation of early tube failures

69.  Accurate assessment of reformer
requires
◦ Tube wall temperature survey
◦ Extensive data collection
◦ Data reconciliation by H&M balance
◦ Fully predictive reformer model
 All of the above used together

70.  Proven and robust methodology
◦ Used on over 30 plants
 Allows identification of problems
◦ Identified NEW issues with designs
 Has saved customers money
◦ Short Term - Efficiency/Production
improvements
◦ Long Term - Extended tube life