Compressed Air

1
Compressed Air

• Technology Concept

2
Compressed Air Background

• Important industrial energy source
• Inherently inefficient
• Consumes up to 20 of industrial electrical usage

Great energy cost savings potential!
3
Lifetime Operation vs. First Cost
Typical Lifetime Compressed Air Costs Over 10
years
Assumptions include a 75-hp compressor operated
two shifts, 5 days a week at an aggregate
electric rate o 0.05/kWh over 10 years of
equipment life.
Source US Dept of Energy, Office of Industrial
Technologies Compressed Air Tip sheet 1.
http//www.oit.doe.gov/bestpractices/pdfs/compress
ed_air1.pdf
4
Compressed Air Energy

• Inefficient power source even if well maintained

Eight compressor horsepower
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Compressed Air Energy
Ratio 81
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Compressed Air System

• Supply
• Compressor
• System Controls
• Air Dryer
• Aftercoolers
• Air Filters
• Primary Storage
• Flow controls

• Distribution
• Air piping
• Filters, lubricators, regulators
• End Uses
• Pneumatic tools
• Mechanical drive
• Blowers
• Vacuum generators
• Etc . . .

7
Supply compressor types
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Supply compressors

• Reciprocating
• Very efficient
• Requires frequent maintenance
• Can be equipped for very efficient part loading
• Can be multistaged

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Supply compressors

• Rotary Screw
• Easy to install
• Enables modulation control
• Easy to maintain
• Can be single or double staged

Source ATLAS COPCO
10
Supply control types
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Variable Speed Drive Compressors

• Allows precise matching of supply and demand
• Extremely efficient at low load
• Less efficient that standard compressors at full
  load
• Retrofitting standard compressors is problematic
• Not ideal for every application
• Best for precise constant pressure applications

12
Supply dryers

• Refrigerated dryers
• Utilized mechanical cooling
• Air dew point limited by water freezing point
• (35º -40º F)
• Relatively inexpensive
• Generates condensate

Source Smargon
13
Supply dryers

• Regenerative desiccant
• Water vapor is adsorbed by desiccant fill
• Low air dew points (-40ºF to -100ºF
• Heated or unheated
• Requires 3-15 purge air
• No condensate generated

Source Palatek
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Efficient compressed air systems

• Proper performance yields
• Low operating costs
• Minimal downtime
• Clean, dry, dependable air
• Effective process control

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Why make a change?
Great energy cost savings potential!
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Technology - Common System Improvements
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Benchmarking

• Determine average power draw (kW)
• Determine total energy costs
• Determine marginal generation efficiency
  (kW/scfm)
• Calculate energy savings potential for system
  improvements
• Worksheet Estimate Your Compressed Air Cost

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Common problem areas

• Air Leaks
• No heat recovery
• High pressure drop
• Insufficient air storage
• Ineffective control strategy
• Multiple compressor operation not optimized
• Base load vs. trim compressor
• Inappropriate end uses
• Poor record keeping
• Electric usage
• Air production

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Air leaks

• When was your last leak survey?

Leak surveys should be conducted quarterly!

• Poorly maintained systems
• Up to 40 leak rate
• Pressure problems
• We need to install another compressor.

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Heat recovery

8 compressor horsepower yields 1 horsepower of
compressed air . . .
Where does the other 7 horsepower go????
HEAT.
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Heat recovery

• 80 of compressor input power may be recoverable
• Possible uses
• Space heating
• Hot water heating
• Drying/curing room heating
• Heat source for desiccant dryer
• 100 hp _at_ full load ? 300,000 Btu/hr

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Heat recovery
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Heat recovery
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Pressure drop compressor room
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Pressure drop (continued)

• Distribution
• Worksheet Calculating the Cost of High Pressure
  Drop

GOAL 0 4 psig pressure drop in compressor room
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Air storage

• Rule of Thumb 4 gallons of storage per
  compressor cfm
• Remote storage for high periodic demands
• Wet vs. dry storage
• Piping rule
• In at the bottom Out at the top!

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Air Storage Compressor Loading
100 hp compressor with load/unload controls
Loaded
Blow down
Unloaded
Unloaded
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Air Storage Compressor Loading
Inadequate Storage (1 gal/cfm)
Compressor is fully loaded (delivering air) for
130 seconds
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Air Storage Compressor Loading
Improved Storage (3 gal/cfm)
Compressor is fully loaded (delivering air) for
130 seconds
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Air Storage
Generalized energy savings for increased storage
in load/unload compressors
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Compressor controls

• Control strategies impact compressor energy
  consumption

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Compressor controls

• Using the Most Efficient Control Strategy
  worksheet

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Inappropriate End Uses

• Anything that can be done
• More effectively by another method
• More efficiently by another method

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Inappropriate End Uses - Examples

• Open blowing - Cooling, drying, clean-up
• Sparging - Aerating, agitating, oxygenating,
  percolating
• Aspirating - Inducing flow in another gas (e.g.,
  flue gases)
• Atomizing - Dispersing or delivering a liquid to
  a process as an aerosol
• Dilute phase transport - Transporting solids such
  as powders
• Dense phase transport - Transporting solids in
  batches

continued
35
Inappropriate End Uses - Examples

• Vacuum generation - used with a venturi to
  generate negative pressure mass flow
• Personnel cooling
• Open blowguns or lances
• Diaphragm pumps
• Cabinet cooling

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Application of new technologies/concepts

• Variable speed compressors
• Zero loss drains
• Air amplifying nozzles
• Solenoid shut off valves
• Demand Controller

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Zero Loss Drains

• Timer drains either
• Waste air
• Fail to remove all liquid

• Zero loss drains remove liquid with no air loss

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Air Amplifiers

• Amplifiers entrain still air to increase air flow
  from blowing components
• Advantages
• Increase blowing force
• Significantly reduced compressed air usage
• Reduced noise
• Fully adjustable
• Applications

Source ARTX
39
Electric Solenoid Valves

• Reduce leaks in piping to equipment that is shut
  off
• Timer control
• Machine panel control
• Manual control

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Demand Controllers

• Isolate supply side from demand side of system
• Appropriate only with adequate storage
• Help reduce air usage by minimizing pressure
  delivered to end users

Source Zeks Compressed Air Solutions
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Technology Next Steps
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How do I optimize the performance of my
compressed air system?

• Systems approach (supply and demand)

• Improving system performance
• Assessing the entire system
• Identifying opportunities
• Quantifying benefits and costs
• Implementing most feasible projects

• Implementation requires participation
• Production
• Maintenance
• Management

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IAC implementation trends and analysis
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How to start

• Steps in evaluating your system
• Monitoring needs
• Best Practices
• Pitfalls

Treat compressed air like a fourth utility.
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Steps to Evaluate Your System

• Determine the cost of your air
• Check for air leaks
• Replace all dirty filters with high efficiency
  filters
• Set efficient control strategies
• Base loaded compressors modulating control
• Trim compressors Load/unload control
• Pressure issues
• Check that all end use pressures are regulated
• Check for excessive generation pressure (lt10 psi
  drop between compressor and highest end user)
• Address inappropriate end uses
• Check for adequate storage (gt3 gal/cfm)
• Shut down idle compressors
• Check for moisture in storage tanks and drip legs

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Monitoring

• Air Pressure Problems
• Compressor Loading
• Power consumption
• Air Consumption
• Track using MS Excel or similar program

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Pitfalls

• Running at too high a pressure
• Considering compressed air as a free utility
• Higher pressure more air
• Adding compressor horsepower to combat pressure
  problems
• Always have a compressed air audit completed
  before adding additional compressors.
• Inadequate storage/piping

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ISO 14000

• Formalized method for identifying and documenting
  process improvements
• Can be used for benchmarking
• Proper use can lead to significantly reduced
  energy costs
• All program goals are set by company
• Benchmarking

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Benchmarking revisited

• Benchmarking should be part of a larger plan

Commit to Continuous Improvement
Implement Action Plan
Create Action Plan
Assess Performance
Set Goals
Evaluate Progress
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Assessing Resources
? GO TO? Compressed Air Resource List?

• Equipment manufacturers

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Assessment Resources

• Energy Resources Center _at_ UIC www.erc.uic.edu -
  can provide expertise in industrial compressed
  air systems, also will perform energy assessments
  for industrial clients.
• Industrial Assessment Centers http//www.oit.doe.g
  ov/iac/ - will provide energy assessments
  (including compressed air systems) free of charge
  to qualified industrial clients.
• US DOE Compressed Air Challenge Program
  http//www.compressedairchallenge.org/ -
  provides a wide range of technical assistance
  materials, tools, and services to the industrial
  market.
• National Association of Energy Service Companies
  http//www.naesco.org/ - trade organization of
  companies that will perform energy audits and
  finance improvements.
• Rutgers IAC Self Assessment Guide
  http//iac.rutgers.edu/manuals/selfassessment.pdf
  - guide to assessing industrial plants for energy
  efficiency.

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Hyperlinked Slides
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Assessment Resources

• Energy Resources Center _at_ UIC www.erc.uic.edu -
  can provide expertise in industrial steam
  systems, also will perform energy assessments for
  industrial clients.
• Industrial Assessment Centers http//www.oit.doe.g
  ov/iac/ - will provide energy assessments
  (including steam systems) free of charge to
  qualified industrial clients.
• US DOE Steam Challenge Program http//www.oit.doe.
  gov/bestpractices/steam/ - provides a wide range
  of technical assistance materials, tools, and
  services to the industrial market.
• National Association of Energy Service Companies
  http//www.naesco.org/ - trade organization of
  companies that will perform energy audits and
  finance improvements.
• Steam System Survey Guide http//www.oit.doe.gov
  /bestpractices/steam/pdfs/steam_survey_guide.pdf
  - guide to assessing industrial steam systems.
• Rutgers IAC Self Assessment Guide
  http//iac.rutgers.edu/manuals/selfassessment.pdf
  - guide to assessing industrial plants for energy
  efficiency.

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