Revamps for Ageing Ammonia Plants
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Revamps for Ageing Ammonia Plants
By; Gerard B. Hawkins Managing Director
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Introduction
This presentation highlights some of the retrofits that can be applied to • Improve efficiency • Increase production
Safe
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Effic
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Rel
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Thro
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Envi
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ent
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Introduction
Why consider a retrofit? Limitations Options for retrofits Problems and Pitfalls GBHE Catalysts and Retrofits Conclusions
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Why Consider a Retrofit?
Plant is • Inefficient • Has poor economics • Production can be increased by
elimination of bottlenecks Retrofits generally are more cost
effective than new plant builds
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Plant Limitations Six main areas that can limit plant
performance
Primary
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Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
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Air Compressor and Secondary
Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
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Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
Air Compressor and Secondary
Cooling, Shifts and CO2 Removal
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Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
Air Compressor and Secondary
Cooling, Shifts and CO2 Removal
Compression
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Plant Limitations • Six main areas that can limit plant performance
Primary
Convection Section
Air Compressor and Secondary
Cooling, Shifts and CO2 Removal
Compression
Ammonia Synthesis
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Pre-Reformers
Installation of pre-reformer helps to de bottleneck • The primary reformer - reduced box
duty • The convection section - heat removal • Eliminates heavies/ poisons
Can increase plant rate by up to 11%
Will affect steam balance
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Change Catalyst Shape and Size
By optimizing catalyst size can • Reduce pressure drop by up to 33% • Reduce carbon formation potential
By changing to VULCAN VSG-Z101 can • Reduce ATE/CH4 slip • Reduce Tube Wall Temperatures • Reduce carbon formation potential • Optimize catalyst loading even further
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Primary Reformer Re-Tube
By re-tubing reformer can generate large benefits • Reduce pressure drop by 20% • Improve radiant efficiency • Reduce tube wall temperature • Increased plant rate by 3.5% • Further optimize catalyst loading to
generate even more benefits
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Combustion Air Pre-heat Installed on many modern plants Has been retrofitted to many plants Must have high stack temperature Allows for large improvements in radiant
efficiency • Use less fuel
Can allow for plant increases Will increase NOx levels
• May require NOx reduction system
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Options for Secondary Reformers
Install High Intensity Burner Gun
Install improved catalyst • Reduce installed
volume - up to 45% • Increase mixing volume
Add excess process air • Requires H2 recovery in
loop
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VULCAN SG Delta Retrofit for Shift Vessels
By installing a specialized support system we can reduce pressure drop significantly
GBHE can offer the VULCAN SG Delta which can reduce pressure drop by 50%
Allows plant rate increases of up to 0.5%
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CO2 Removal Retrofits
Can uprate CO2 removal by • Changing packing • Use more efficient solution
Either will help to reduce reboiler duties • In turn allows reduction in steam to carbon
ratio GBH Enterprises range of catalysts are
designed to operate under these lower steam to carbon conditions
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Water Removal from Synthesis Gas
Use either molecular sieves or ammonia washing
Can feed synthesis gas to converter inlet • Reduces ammonia content of gas inlet
converter therefore increases production • Reduced refrigeration load • No loss of reactants in purge gas
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Converter Retrofits
Convert to axial-radial or radial flow Utilize smaller catalyst
• Since reaction is diffusion limited increases reaction rate and therefore increased production
• Can improve efficiency by 0.5-1.0 GJ/t • Must look at rest of plant
Converter exit piping and exchangers
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Converter Retrofits Often link with modifications to circulator
• Reduce circulation rate and hence power requirement
If converter already modified then can • Modify converter again
Use heat exchange rather than quench • Install high activity catalyst
VULCAN Series VSG-A101 low pressure synthesis
Can be utilized up to 150 bara
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Converter Retrofits
Further Options • Add a booster converter
Utilize when main converter has reached limit Can achieve up to 30% capacity increases Will need modifications to rest of the plant
• Add a synthesis gas converter - for example as done in the Uhde DPUP Utilize when main converter has reached limit Can achieve up to 30% capacity increases Will need modifications to rest of the plant
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Hydrogen Recovery Can increase plant capacity by up to 5%
with no other modifications Either
• Cryogenic • Membrane
If adding excess air to the secondary then must install hydrogen recovery • Even greater capacity increases are achievable
since methane slip has been reduced
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Other Retrofits
Addition of Saturator Fuel gas preheat Synthesis gas machine suction
chilling Modification of synthesis gas
machine internals Install AGHR in parallel to existing
Waste Heat Boiler Upgrade utilities
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Other Options There are other options There are a number of operational
modifications that will improve plant performance for no cost • Reduction in steam to carbon • Raising primary exit temperature • Reduce excess air/oxygen in reformer
Energy Audits will help to identify these areas and the benefits of changing process parameters
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Plant Revamp Selector Ammonia – Capacity Increases
What capacity increase is required ?
>15%
Front End Catalyst change Re-tube New burner gun VULCAN SG Delta
<5%
Front End SC Reduction Pre-reformer
5-15%
Compression/Loop Syn gas drying High activity catalyst H2 recovery Chill Syn Gas
Front End Parallel AGHR Re-tube Loop Booster converter MUG converter
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Plant Revamp Selector Ammonia – Efficiency Improvements
What efficiency improvement is required ?
>1 GJ/t <0.1 GJ/t
Front End SC Reduction Fuel preheat CO2 solution change Saturator Chill syngas
0.1-1 GJ/t Front End Combustion air preheat
None
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Problems and Pitfalls Contractor and Contract
Must carefully select partners • Must have domain knowledge
Design and operations • Must have correct tools • Must be able to supply correct level of detail
for study Must select appropriate contract type
• LSTK or Reimbursable • Both have advantages and disadvantages
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Problems and Pitfalls Modelling Capability
Must use correct tools Model the whole plant using a
flowsheeting package • Must include all unit operations • Must develop a robust base case • Must validate against plant data • Must understand deviations • Then develop the retrofit case
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Problems and Pitfalls Retrofit Details
The customer and engineering contractor must determine • Precise scope for retrofit • Responsibilities • Key deliverables • A detailed and consistent design basis • Time scale and milestones • Review schedules
Summarize as Good Project Management
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Problems and Pitfalls Design Basis
Engineering contractor must conduct on site visit • Must work with client • Collect representative plant data • Model and understand plant data • Discuss discrepancies and eliminate • Identify bottlenecks • Identify opportunities for improvement
These form the core of the design basis
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Problems and Pitfalls HAZOPs and Commissioning
Must use systematic review method to highlight potential problems with retrofit • HAZOPs are a well proven system • Requires time and buy in from all parties • Results as good as quality of people !
Retrofit will change plant parameters • Must update PFDs and P&IDs • Must update operating instructions • Must take additional care during start up
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What Can GBHE Catalysts Offer?
GBHE Catalysts Process Technology has developed a detailed flowsheeting package
GBHE Modelling for AMMONIA includes
• Detailed primary reformer model • Models for secondary reformers, shifts, methanation and
ammonia synthesis • Can model in detail the synthesis gas machine
Unified, consistent and intelligent process model
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What Can GBHE Catalyst Process Technology Offer?
Detail catalyst unit operation models such as the Industry leading VULCAN REFSIM program • Also models for other catalyst unit operations
Detail non-catalyst unit operation models such as • Heat exchange programs • Finite Element Analysis • CFD modelling
One stop shop
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What Can GBHE Catalysts Offer?
Domain Knowledge • Operations
Many staff have operations background
Troubleshooting clients plants • Design
Many staff have detailed engineering background
Engineers work on design daily Work with leading contractors
on front end and detailed design issues
Catalysts
Consulting Services
Domain Knowledge
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What Can GBHE Catalysts Offer?
Can supply any level of detail for retrofit
Scoping studies • Front End • What are the best options
Front End Engineering • Flowsheets and design of key components
Detailed Engineering • Design of all components of retrofit
A one stop shop for all your revamp requirements
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One Stop Shop Case Study Re-tube – Present Model
Plant Operator
Concept Engineer
Tube Supplier
Catalyst Vendor
Tube Installer
Catalyst Handler
No Communication
Detailed Engineer
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One Stop Shop Case Study Re-tube – “One Stop Shop” Model
Plant Operator
GBHE Concept Engineer
Tube Supplier
Tube Installer
Catalyst Handler
Detailed Engineer
Seamless Minimum Cost
Maximum Benefit
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Case Study - How GBHE Works Strong position due to credibility from previous
work Uprate projects
• Feasibility Process Uprate study on Naphtha 115%, 130% or 150% cases
• FEEP (Front End Engineering Package, what would be needed?)
115% FEEP adopted • Option evaluations and natural gas feed
conversion Followed by full Engineering Detail Design Also additional design work on Desulfurization
Design Study
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Conclusions Many options for retrofitting an ammonia
plant Must select correct options based on
• Require capacity increase • Present bottlenecks
Must select the right contractor GBHE has all the right expertise and
knowledge to develop and design retrofits
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