The document provides guidelines for safely starting up and reducing steam reforming catalyst. It discusses warm-up procedures to avoid condensation, reducing the catalyst with hydrogen or hydrocarbons, and gradually introducing feedstock. It also summarizes a case study where overfiring during start-up led to tube failures due to much higher than normal temperatures as a result of deviations from proper procedures.

1. Reduction and Start-up of
Steam Reforming
Catalyst
By:
Gerard B. Hawkins
Managing Director, CEO

2. Contents
 Introduction
 Start-up procedures
• Warm-up
• Catalyst reduction
• Feed introduction
 Case study

3. Introduction
 Steam reformer is complex
• heat exchanger
• chemical reaction over catalyst
• combustion, leading to steam generation
 Common symptoms of poor performance
• high exit methane slip
• high approach to equilibrium
• high tube wall temperature
• high pressure drop
Need properly active catalyst

4. As supplied - NiO on support
Active species - Ni crystallites
Reduction process needed:
NiO + H2 Ni + H2O
Steam Reforming Catalyst

5. 400 500 600 700 800
100
200
300
500
700
Temperature oC (oF)
Partial Pressure of H2O / Partial Pressure H2
EquilibriumConstant
Reducing Conditions
Oxidizing Conditions
(752) (932) (1112) (1292) (1472)
Reduction of Bulk Nickel Oxide

6. NiO Reduction
 Faster at high temperature
 Slower in presence of steam
 Thermodynamically, very little hydrogen
needed
 Support can affect ease of reduction

7. Catalyst Reduction
 Requires high temperature
• fire steam reformer
 Requires hydrogen
• supply H2 or reduce gas
• re-circulation or once-through
 Since little or no steam reforming is taking place,
• less heat is required to warm up gas:
 50% steam rate, with 5:1 steam: H2 ratio
requires 1/7 fuel of normal operation
Extreme danger of local
overheating!

8. Contents
 Introduction
 Start-up Procedure
• Warm-up
• Catalyst Reduction
• Feed Introduction
 Case Study

9. Warm-Up
1. Purge plant of air with N2
- must be free of hydrocarbons and carbon oxides
2. Heat reformer above condensation temperature
2. Add steam when exit header temperature 50oC
(90oF) above condensation temperature
- low pressure favours good distribution and
lowers this temperature
4. Increase steam rate to 40 - 50 % of design rate
- min 30 %
5. Stop N2 circulation
Air warm-up possible, but not for previously reduced
catalyst (possible carbon)

10. Warm-Up - Feedstock Isolation
• Before a flow of steam is established in the
steam reformer, hydrocarbons must not be
present
– Carbon formation!
• Ensure that hydrocarbon feed lines are fully
isolated
– Double-block and bleed
– Do not rely on block or control valves
• Or keep the pressure of the hydrocarbon feed
supply below hydrogen plant start-up
pressure

11. Traditionally 50oC (90oF) /hr
Modern materials 100oC (180oF) /hr
Catalyst 150 - 170oC (270 - 350oF) /hr
Warm-Up rates
 Rapid warm-up minimises energy usage/time
 Limited by mechanical considerations of steam
reformer
 Assess effect on plant equipment
• thermal expansion of inlet/exit pipes
• steam reforming tensioners
• steam reformer tubes
• refractory linings

12. • Water can damage the steam reforming
catalyst
• Temperature “shock”
• Rapid drying of “wet” catalyst
•The expansion of water to steam in the
catalyst pores causes catalyst break-up
• Pre-reforming catalyst much more sensitive
to water
• Essential to avoid condensation
Warm-up - Avoiding Condensation

13. Steam
Reformer
Cold Pipework
Steam
If upstream pipe work is cold, then it is good
practice to warm up by steam flow with vent
to prevent carry-over of water
Warm-up - Avoiding Condensation
To Vent

14. Warm-up - Condensation
Ensure that all drain points are operational
To steam
reformer
Steam
Condensate to drain

15. Temperatures
 Temperatures referred to are true catalyst
temperatures at exit of tube
 Measured temperatures during normal operation
are 10 - 100oC (18 - 180oF) cooler due to heat losses
 Most catastrophic failures of tubes in top-fired
furnaces occur during start-up
 Cannot rely on plant instrumentation during start-
up
• lower flows than normal
• higher heat losses than normal
• fewer burners can give severe local effects
Frequent visual inspection of reformer tubes and
refractory is essential during start-up

16. Effect of Pressure and Temperature
800 900 1000 1,100 1,200
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
Tube Wall Temperature oC (oF)
( 1500 ) ( 1650 ) ( 1830 ) ( 2010 ) ( 2200 )
30 bar
5 bar
Steam Reformer Tube Life

17. Contents
 Introduction
 Start-up procedure
• Warm-up
• Catalyst reduction
• Feed introduction
 Case study

18. Reduction Procedures
 Reduction with hydrogen
 Reduction with natural gas
 Reduction with other sources of hydrogen
• higher hydrocarbons
• ammonia (not discussed)
• methanol (not discussed)

19. Reduction with Hydrogen
 H2 or H2-rich gas can be added at any time
to the steam when plant is free of O2
 Steam: hydrogen ratio normally 6:1 - 8:1
 Get tube inlet temperature as high as
possible
 Increase exit temperature to design value
(>700oC/1292oF)
 Hold for 2-3 hours

20. Hydrogen Source
 Hydrogen must be
• free of poisons (S, Cl)
 Special consideration must be given to the
presence in impure hydrogen sources of
• carbon oxides
• hydrocarbons
Also applies to nitrogen (or inert) source
used for purge/warm-up

21. Carbon Oxides
 Re-circulation loop may include HDS unit
(at temperature)
 Carbon oxides above 250oC (480oF)
methanate over unsulfided CoMo catalyst
• temperature rise 74oC (133oF) per 1% CO
converted
• temperature rise 60oC (108oF) per 1%
CO2 converted
If H2 contains >3% CO or >13 %CO2
or a mixture corresponding to this,
then by-pass the HDS system

22. Hydrocarbons
 May be converted to carbon oxides in
reformer
 May crack thermally to give carbon

23. Reduction with Natural Gas
1. Warm-up as before
2. Introduce natural gas at 5% of design rate
3. Slowly increase gas rate to give 7:1 steam: carbon
over 2-3 hours
4. Simultaneously increase reformer exit temperature to
design level (>700oC/1292oF)
5. Increase inlet temperature as much as possible (to
crack natural gas to hive H2)
6. Monitor exit methane hourly: reduction complete
when methane reaches low, steady value (4 to 8
hours)

24. Reduction with Higher Hydrocarbons
 Increased possibility of carbon formation
 Great care needed
 Longer time periods needed
 More precision in all measurements
needed
 Hydrogen addition recommended
 Purification issues
Only use if absolutely necessary

25. Contents
 Introduction
 Start-up procedure
• Warm-up
• Catalyst reduction
• Feed introduction
 Case study

26. Feedstock Introduction
1. Introduce feedstock at high steam: carbon
ratio
(5:1 for natural gas; 10:1 for higher
hydrocarbons)
2. Steam reforming will give small increase in
inlet pressure, cooling of tubes, and lower
exit temperature
3. Need to increase firing to maintain exit
temperature
4. Then increase feedstock flow
5. Increase pressure to operating pressure
6. Adjust steam: carbon ratio to design

27. Feedstock Introduction
 Increase flow of natural gas to design steam:
carbon ratio (2 hours)
 Maintain exit temperature
 Check that exit methane stays low
• (reducing steam: carbon ratio will increase
methane slip and heat load)
 if not, hold at 7:1 steam : carbon for 2 hours
 Increase throughput to design level
 Increase pressure to design level
Always increase steam rate before feed rate

28. Steam Reformer Re-starts
 Shorter re-reduction recommended
• typically 4-6 hours for heavy feeds
 Not essential to carry-out reduction with
 Natural gas or light off-gas feedstock
• start-up at 50% design rate, high steam:
carbon ratio

29. Contents
 Introduction
 Start-up procedure
• Warm-up
• Catalyst reduction
• Feed introduction
 Case study

30. Case Study: Overfiring
 Large modern top-fired steam reformer
 Significant tube failures during start-up
 Caused by over-firing at start-up due to a
number of coincident factors

31. Case Study: Background
 Site steam shortages requiring conservation of
steam
 Pressure to avoid a shut-down (due to low
product stocks)
 Burner fuel usually from two sources, mixed:
• one low-calorific value
• one high-calorific value
 At time of incident, all high-calorific value
(unexpectedly) fuel received
 Operators had seen many shut-down/start-ups
during past two years

32. Case Study: Events
 Plant trip (loss of feedstock to steam reformer)
due to valve failure
 Feedstock to steam reformer not isolated
adequately by valve
 Setpoint on reformed gas pressure not reduced
 Steam introduced for plant restart at reduced
rate
 All burners lit (deviation from procedure)
Reformer tubes remained at normal
operating pressure of 16 barg (232 psig)

33. Case Study: Events (Contd.)
 Steam reformer tubes “looked normal”
 Nearly 3x as much fuel going to burners than there should
have been
 High calorific value fuel added an extra 15% heat release
 First tubes rupture
 High furnace pressure (trip bypassed)
 Oxygen in flue gas dropped to zero
 Flames seen from peep holes
 Normal furnace pressure
 Visual inspection revealed “white hot furnace” and tubes
peeling open
30minutes
Emergency Shutdown Activated!

34. Case Study: Conclusions
 Reformer exit gas temperature on panel never
exceeded 700oC (1290oF)
• cannot use this instrument as a guide to tube
temperature
 Reformer start-up at normal operating pressure
• tube failure temperature 250oC (450oF) lower
than normal for start-up
 All burners lit
• far too much heat input resulted in excessive
temperatures

35. Summary
 Start-up procedures
• Warm-up
 Feedstock isolation
 Rate
 Condensation
 True temperatures/Tube temperatures
• Catalyst reduction
 Using hydrogen
 Using hydrocarbon
 Feed introduction
• Case Study