Transcript OMA Workgroup Compressed Air: Go Sustainable Energy

Workgroup Meeting July 2014
Energy Efficient
Compressed Air Systems
Abdul Qayyum “Q” Mohammed
Engineer
Why is this important ?

Almost all Manufacturing Facilities use Compressed Air (CA)

These are large systems

Smaller systems draw about 40 kW (50-hp)
X 40
Expensive Resource

Compressed Air (CA) is a very expensive resource

The most expensive in many cases

About 90% of the input energy is lost through the system
Heat
Conversion
Purges
Energy
In
And Drains
Only 9% !
Work Out
Source: David Vanderbeek, 2011 Power Smart Forum
Why use Compressed Air ?
Simple :
 Its easy to use

Can be used for a wide variety of applications

All you need is a new hose for a new application

In many cases it is the economically feasible option
Well what’s the problem then?

Its ease of use makes it …….
…..the most misused resource
CA Fundamentals
Before we get into energy savings opportunities lets
briefly look at
 Types of air compressors
 Reciprocating
 Screw
 Centrifugal


Different control strategies for the compressors
Pros and Cons
Reciprocating Compressors


Simplest and oldest compressor type
Size: 1 – 600 hp
Recips: Part Load
 Good
part-load performance
 Very close to ideal compressor
Ideal
Recips: Pros and Cons
Pros:
 Simplest and oldest compressor type
 Comparable full load efficiency
 Very good part load efficiency
Cons:
 Higher maintenance costs compared to the new
compressor types (for larger compressors)
Screw Compressors


Currently the most commonly
used compressor in industry
Sizes 5 – 700 hp
Screws: Part Load
 Multiple
control options
 Combinations
of controls available with each compressor
 Gives large scope for optimization
*VFDs have lower
full-load efficiency
They are very
efficient between
45% to 80%
capacity
Screw: Pros and Cons
Pros:
 Low maintenance
 Different control options work well within different
systems


Proper sizing is critical
Large cost range depending on
Control options
 Other additional options (oil free, integrated dryers etc.)

Cons:
 Optimization is often neglected (or done poorly) which
degrades system part-load performance
Centrifugal Compressors


Larger compressors (these are dynamic)
Sizes 125 – 6,000 hp
Centrifugal: Part Load
Can be the most inefficient compressors at part loads
 Combination
of controls are available
 Control optimization is necessary for efficiency
Centrifugal: Pros and Cons
Pros:
 Very high full-load efficiency
Very good for systems that have a high base load
 Low maintenance if operated properly


Customizable

Can be built to match client needs
Oil free
Cons:
 Slightly higher cost
 Can be the worst at part-loads

Blow-off should be minimized
 Dynamic nature limits turn down ratio (to avoid surge)

Energy Saving Opportunities

There can be endless opportunities in a system.


So, Let’s just look at the BIG hitters





It can take couple of hours to go through them all.
Inappropriate uses
Leaks
Pressure
Staging
Other opportunities




Air Drying
Storage
Filters
Heat Reclaim
These are things we look for when
we have limited time with the
client.
Inappropriate Uses
Questions to ask..

Is CA even necessary ?



It is a VERY Expensive resource
Is there an alternative that can eliminate CA use?
Is CA being used effectively ?

Can CA use be reduced ?


Pressure
Timing
Let’s look at some examples.
In-appropriate use Examples
To blow off a product. Good idea?
Air Saver nozzles use about
70% less CA
www.thoritedirect.co.uk
In-appropriate use Examples
CA to cool off product. …. Good Idea?
200x more expensive
than cooling towers
Energy Efficient Process Cooling – Dr. Kissock, University of Dayton
In-appropriate use Examples
Personal Cooling (We just saw cooling costs)
Occupational Safety and Health Administration
(OSHA) safety violation
www.safetyposters.com
In-appropriate use Examples

Drains are used to remove condensate from the
system
 But
do we need to lose air?
Open valve: Always loosing air.
www.airbestpractices.com
Timed Drain: Timing set for
peak, often results in air
loss
www.isccompressedair.com
No-loss Drain: Zero air
loss
www.ingersollrand.com
In-appropriate use Examples
Need low pressure air (20 psig) ? => Use Blowers !
Blowers use about
5x less energy
www.aircompressorsdirect.com
www.spx.com
List of Common Inappropriate Uses
Blow-Off Applications
Air knives
Dust collector purges
Cleaning with CA
Personal cooling
Process cooling
Continuous CA Use Applications
Aeration
Agitation
Atomization (mixing)
Transport of material
Air motors /hoists
Diaphragm pumps
Air vibrators
Electrical cabinet cooling
Vacuum generation
Vortex coolers
Air Cylinders
Air Operated vacuum cleaners
Energy Saving Opportunities

There can be endless opportunities in a system.


So, Let’s just look at the BIG hitters





It can take couple of hours to go through them all.
In appropriate uses
Leaks
Pressure
Staging
Other opportunities




Air Drying
Storage
Filters
Heat Reclaim
These are things we look for when
we have limited time with the
client.
Reduce Leaks !

Leaks are lost $$$$$
www.logis-tech.co.uk
Air Power Usa
Leaks Example

Misconception “We do not have a large leak load..”


On average 30%* of a facility’s compressed air is lost to leaks
Example Facility
Avg. Leak Load = 50% !!
In a two compressor system
Weekend
100 kW in Nonproduction ~ 100
Homes
*U.S. DOE, Compressed Air Fact Sheet #7
Strategy to Reduce Leaks

Strategies we have observed:

Leak reduction programs
http://processengineering.theengineer.co.uk/

Other Methods



Use of Isolation Valves to valve off unused areas
Reduced pressure during non production
Turning off CA system on weekends
Goals for Leaks

Can I have Zero Leak Load ?
 Unfortunately,

NO
What should I aim for ?
 Good
rule of thumb is to reduce it by 50%
 We have observed facilities with leak loads


As high as 60% and
As low as 7-10% - this was accomplished overtime by reducing
leaks and isolating unused areas
Energy Saving Opportunities

There can be endless opportunities in a system.


So, Let’s just look at the BIG hitters





It can take couple of hours to go through them all.
In appropriate uses
Leaks
Pressure
Staging
Other opportunities




Air Drying
Storage
Filters
Heat Reclaim
These are things we look for when
we have limited time with the
client.
Reduce Pressure at End Use
Did we adjust pressures at end use ? Do you need line pressure ?
Unregulated tool
0.25” @ 95 psig
We recently observed a large
manufacturing facility with efficient
compressors…..
~ 120 acfm
~ 20% reduction !
Almost all end uses were unregulated
!!!
Regulated tool
0.25” @ 70 psig
~ 95 acfm
Reduce Pressure at Compressor

Why is a compressor used?
 To
pressurize the incoming air stream
A
compressor has to Work harder for higher Pressure
Air out @ P2
Power kW
Air Compressor
Air in @ P1
Heat out
Reduce Pressure at Compressor

Common Misconception
 “Raising


the pressure increases capacity”
Reality – It decreases compressor capacity and increases operating
costs
Often times other issues are compensated with
pressure,
 Lack
of storage
 Improper piping
Reduced Pressure - Energy Savings

Rules of Thumb

Compressor Efficiency Increases by 1% for every 2 psi reduction in operation
pressure
Reduced Pressure - Benefits

Energy savings
Improves compressor efficiency
 Reduced leak load
 Reduces CA use at applications


Reduced pneumatic equipment fatigue

Increases equipment life
Goals for Reducing Pressure

How low should my system pressure be?
 Rough
rule of thumb, System Press = Min Press + 10
 We
have observed a large MFG facility with CA
system at 75 psig.

This was done overtime by addressing system constraints such as
adding storage, increasing pipe diameters etc.
Energy Saving Opportunities

There can be endless opportunities in a system.


So, Let’s just look at the BIG hitters





It can take couple of hours to go through them all.
In appropriate uses
Leaks
Pressure
Staging
Other opportunities




Air Drying
Storage
Filters
Heat Reclaim
These are things we look for when
we have limited time with the
client.
Staging

This is one of THE most important opportunities

Why?

Lets look at an example (worst case)
 Compressor
– Centrifugal with blow-off only
 We just reduced compressed air demand by 50%
 How much do we save ?
Staging

Centrifugal part load
How much do we save ? ZERO !
Staging

System Part-Load with Multiple Compressors
Very Well
staged multiple
compressor
system
Poorly staged
multiple
compressor
system
Staging Fundamentals
 Points
to remember
 Constant
speed compressors are only efficient at full loads
 Operation
 You
at part loads should be minimized.
NEVER* want multiple compressors at part-load
*Does not apply in special circumstances with centrifugal and VFD compressors
 Eliminate
(or minimize) blow-off in Centrifugal compressors
Complexities in Optimizing Staging

Need toOkay,
understand
Let’s not worry about complexities.
System air flow requirements
** This is where you may want to reach out for technical
 Compressor – fullassistance.
load efficiencies
 Compressor – individual part-load performance
 Effect of combination of different compressors within a system



How one staging sequence is different from the other
Let’s look at a few case studies to understand the
How
?
potential.
Metering the equipment is a start
 Analysis of metered data


Need to apply knowledge to obtain
action items
Case Study 1

Pre:

Two new 900-hp centrifugal compressors are operated in base trim
manner



Project cost ~ $800,000
Both of them can modulate and then blow-off
Post:

Compressors are operated in parallel so that

Only one compressor blows-off first
Case Study 1 (Cont)
Savings ~ $50,000/year
Case Study 2


A facility has two compressed air systems that were put in
place for two different systems
Pre
Facts:

As often seen



Both systems were oversized
Engineers like factor of safety;
Vendors like to sell larger compressors
What's interesting is both systems operate at 95 psig.
Post

Combine the two compressed air systems
Compressor Optimization: Case Study 2
Savings ~ 20%
In the new case only one
compressor is partloaded instead of two.
Case Study 3

Manufacturing facility wanted to save energy


They thought VFD compressor is a good idea (it is, but..)
Pre

They bought a Oversized (215 hp) VFD compressor


Issue: the VFD could not trim

Used a 250 hp load/unload as the trim instead


Why ? Sales person recommendation ? Lack of analysis ?
Not good
Post

Bought appropriately sized (125 hp) VFD compressor


Compressor Cost ~ $150,000
And changed the control sequence
Case Study 3
Savings ~ 24%
Big Savings
* Could have been achieved the first
time if the VFD was sized right.
Case Study 4

Multiple facilities with multiple compressors

Are more compressors better ?

Is a control system better ?

Is a VFD better ?
Case Study 4
1. Poorly Staged
(Manual)
- 8 similar compressors
2. Staged with VFD
(Pressure based)
- 8 different compressors
3. Very well staged.
(Demand Based)
No VFD
- 8 similar but different
size compressors.
Facility 1
Facility 2
Facility 3
Case Study 4

Most of the savings can be achieved by effective staging


Control systems are vital for optimization in large systems
A VFD compressor can help improve your part-load
performance

Typically only one effective VFD is required per system
 If sized correctly
Summary

We discussed

Importance of compressed air


Different types of compressors and their controls




Reciprocating
Screw
Centrifugal
Largest Energy savings opportunities





Why its an expensive resource
In-appropriate uses
Leaks
Pressure
Staging
We looked at a few case studies
Its time for the
Recommendations
Recommendations

Pursue all the low-cost no-cost opportunities




In-appropriate uses
Leaks
Reducing pressure
Staging with available control systems


Consult experts to evaluate best strategy with available controls
Consult technical experts before Investing Capital



The last thing you want is invested capital and no savings.
New compressor installation
Control system upgrade
Questions ?
Additional Slides are
available at the End for
Interested Parties
Thanks for Listening!
Abdul Qayyum “Q” Mohammed
www.gosustainableenergy.com
614-268-4263 x308
[email protected]
End Use: CA Diaphragm Pumps
Facilities use CA Diaphragm Pumps.


Needed for extremely corrosive or volatile fluids
However, in many cases diaphragm pumps are used for fluids
that can be moved with a regular centrifugal pump
Motor Operated
pumps use about
4x less energy
www.wildenpumps.org
http://www.winter-pumpen.de/
End Use: Dust Collector Purges
CA is used in dust collector for purges.


These purges can use significant amount of air if not optimized
properly.
Control CA with solenoids to appropriately time purges
Bag house uses ~ 40% of system capacity
Distribution: Storage

Used to eliminate (or dampen) the variation of
pressure within the system.
 Particularly
important in systems with load/unload
compressors
Storage improves part
load performance of a
system with
load/unload
compressors
“Improving Compressed Air System Performance: A Sourcebook for Industry.” – US D.O.E, Nov 2003
Distribution: Storage (Cont.)

How much storage should I have ?
 Rule
of thumb 3 to 5 gal/cfm of compressor output

Actual requirement depends on fluctuations in CA demand and
types of compressors
Optimize Compressed Air Drying
Appropriate drying technologies should be used
Common drying technologies in order of decreasing efficiency
 Refrigerant
Dryers
 Cycling
 Non-Cycling
 Desiccant
Dryers
 Heat
of Compression* (HOC)
 Heated desiccant


Heated with Blower purge
Heated with CA purge
 Heatless
desiccant
* HOC dryers are more efficient than refrigerated dryers
Generation: Reclaim Heat

~ 80% of input energy is lost as heat
 Heat
can be used for various purposes
 For
space heating during winter
 For process use throughout the year
Summer
Plant
Winter
Cooling
Air
Compress
Outdoor Air
Air
Compressor
Compressed
Air To Plant
Generation: Reclaim Heat
 Example
Installation
Generation: Compress Outdoor Air

Outdoor air is typically cooler than a mechanical
room
 Cooler
air is denser hence easier to compress
 Fraction savings ~ 2% per 10 F reduction
 Note:
 Savings

are realized in oil free compressors only
In oil lubricated compressors the air is mixed with hot oil before
compression. This eliminates savings.
 Considerations
temperatures
should be made to avoid freezing
What's the benefit of Energy Savings?

We reduce emissions
 Helps
slow down global warming
 Helps

Protect Out planet
What are we talking about ?
 Lets
rephrase “What is MY benefit ?”