revamps for ageing ammonia plants
DESCRIPTION
This presentation highlights some of the retrofits that can be applied to Improve efficiency Increase productionTRANSCRIPT
Revamps for Ageing Ammonia Plants
By; Gerard B. Hawkins Managing Director
Introduction
This presentation highlights some of the retrofits that can be applied to • Improve efficiency • Increase production
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Effic
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Introduction
Why consider a retrofit? Limitations Options for retrofits Problems and Pitfalls GBHE Catalysts and Retrofits Conclusions
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
Plant Limitations Six main areas that can limit plant
performance
Primary
Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
Air Compressor and Secondary
Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
Air Compressor and Secondary
Cooling, Shifts and CO2 Removal
Plant Limitations Six main areas that can limit plant
performance
Primary
Convection Section
Air Compressor and Secondary
Cooling, Shifts and CO2 Removal
Compression
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
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
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
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
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
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
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%
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
