Reduction & Startup of Pre-reforming Catalysts
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Reduction and Start Up of Pre-reforming
Catalyst
Gerard B. Hawkins Managing Director
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Prereformer Startup
Drying Heating Startup Reduction
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Catalyst Drying
For catalyst subjected to low temperatures
Dry using Nitrogen 175 to 250°C NG can be used below 200°C 4 to 24 hours Dry air, not suitable for prereduced First startup of prereduced
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Catalyst Heating
Normally heated using nitrogen Absorbed moisture Initial heating rate, 50°C per hour Max temp differential in bed 100°C At 200°C, 70°C per hour Heating till peak 400°C, min 370°C High circ rate, max pd 2 bar
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Catalyst Heating continued
Warm-up rates Rapid warm-up minimises energy
usage/time Traditional constraints of equipment Controllability Limited by mechanical considerations of
vessel Catalyst, 150-170oC per hour
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Catalyst Heating continued
Limits on impurities Oxygen 1% vol Carbon Dioxide 1% vol Carbon Monoxide 1% vol Methane 1% vol Hydrogen 1% vol Ethane 100 ppm vol Sulfur 0.2 ppm vol
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Catalyst Heating continued
Holding at temperature Not recommended 2% hydrogen added Temperature reduced to 350°C
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Catalyst Startup
When operating temperature has been achieved:
Check for build up of carbon oxides and hydrocarbons
Add of 10% Hydrogen Followed by steam Introduce process feed, maintain safe
S:C
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Condensation Ensure steam lines warm and low points
drained
Pre-reformer Cold Pipework
Steam
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Heating using Natural Gas
Using NG as heating medium No impurities Immediate startup 50°C per hour, max differential 100°C At 200°C introduce steam
• Min S:C 0.3kg/kg at 200°C • Min S:C 0.5kg/kg at 400°C to 450°C • Increase to design feed and S:C
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Reduction of Unreduced Catalyst
Unreduced catalyst As supplied - NiO on support Active species - Ni Crystallites Reduction process needed:
NiO + H2 Ni + H2O
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Reduction of Unreduced Catalyst
Reduction aspects Bed temperature 450°C and 500°C 12 to 16 hours
Hydrogen must be
• free of poisons (S, Cl) Special consideration must be given to the
presence in impure hydrogen sources of • carbon oxides • hydrocarbons
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Reduction of Catalyst continued
Reduction procedure Hydrogen set at 15 –25% Slowly increased to 50% Regularly check hydrogen levels Water cooled and collected
Reduction complete 85% of reduction water collected Consumption of hydrogen stopped
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Pre-reformer Objectives
Remove the restriction on the ID Fan to allow rate increase to Design MTPD
Improve efficiency by recovering additional process heat from flue gas
Pre-reformer aims:
• Reduce primary reformer firing • Reduce flue gas temperature to ID fan • 4 Year design life • Install during next turnaround • Maintain operating flexibility
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Pre-reformer Installation
Pre- Heating
Re- Heating
Gas/Steam
Pre-reformer
500ºC
500ºC 450ºC
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Pre-reformer Installation New Pre-Reformer
New Vessel and Piping Integration with Flue Duct By-pass Quench Arrangement
Duct Modifications New Coils • Reheat Post Pre-reformer • Cold’ Feed Pre-heater • Natural Gas Pre-heater • Process Air Pre-heater • Superheater Coil Existing Coils • Check New Duty Performance
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Pre-reformer Installation
GBHE / HAISO– Technology Supplier
Axial flow with 2 Thermowells 6m3 bed of Catalyst
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Planned Procedure •Commissioning smooth minimal changes to normal
plant start up – Pre-reformer bypassed initially – Quench controls primary inlet until production achieved – Process gas slowly introduced to pre-reformer –As inlet exit valves fully open, by-pass closed –Quench valve closed as endotherm takes place
•
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