Presentation on theme: "Compressed Air Systems"— Presentation transcript:
1Compressed Air Systems Workgroup Meeting July 2014Energy EfficientCompressed Air SystemsAbdul Qayyum “Q” MohammedEngineer
2Why is this important ?Almost all Manufacturing Facilities use Compressed Air (CA)These are large systemsSmaller systems draw about 40 kW (50-hp)X 40
3Expensive Resource Only 9% ! Compressed Air (CA) is a very expensive resourceThe most expensive in many casesAbout 90% of the input energy is lost through the systemEnergy InHeatConversionPurgesAnd DrainsOnly 9% !Work OutSource: David Vanderbeek, 2011 Power Smart Forum
4Why use Compressed Air ? Simple : Its easy to use Can be used for a wide variety of applicationsAll you need is a new hose for a new applicationIn many cases it is the economically feasible option
5Well what’s the problem then? Its ease of use makes it …….…..the most misused resource
6CA FundamentalsBefore we get into energy savings opportunities lets briefly look atTypes of air compressorsReciprocatingScrewCentrifugalDifferent control strategies for the compressorsPros and Cons
7Reciprocating Compressors Simplest and oldest compressor typeSize: 1 – 600 hp
8Recips: Part Load Good part-load performance Very close to ideal compressorIdeal
9Recips: Pros and Cons Pros: Simplest and oldest compressor type Comparable full load efficiencyVery good part load efficiencyCons:Higher maintenance costs compared to the new compressor types (for larger compressors)
10Screw Compressors Currently the most commonly used compressor in industrySizes 5 – 700 hp
11Screws: Part Load Multiple control options Combinations of controls available with each compressorGives large scope for optimization*VFDs have lower full-load efficiencyThey are very efficient between45% to 80% capacity
12Screw: Pros and Cons Pros: Low maintenance Different control options work well within different systemsProper sizing is criticalLarge cost range depending onControl optionsOther additional options (oil free, integrated dryers etc.)Cons:Optimization is often neglected (or done poorly) which degrades system part-load performance
13Centrifugal Compressors Larger compressors (these are dynamic)Sizes 125 – 6,000 hp
14Centrifugal: Part Load Can be the most inefficient compressors at part loadsCombination of controls are availableControl optimization is necessary for efficiency
15Centrifugal: Pros and Cons Very high full-load efficiencyVery good for systems that have a high base loadLow maintenance if operated properlyCustomizableCan be built to match client needsOil freeCons:Slightly higher costCan be the worst at part-loadsBlow-off should be minimizedDynamic nature limits turn down ratio (to avoid surge)
16Energy Saving Opportunities There can be endless opportunities in a system.It can take couple of hours to go through them all.So, Let’s just look at the BIG hittersInappropriate usesLeaksPressureStagingOther opportunitiesAir DryingStorageFiltersHeat ReclaimThese are things we look for when we have limited time with the client.
17Let’s look at some examples. Inappropriate UsesQuestions to ask..Is CA even necessary ?It is a VERY Expensive resourceIs there an alternative that can eliminate CA use?Is CA being used effectively ?Can CA use be reduced ?PressureTimingLet’s look at some examples.
18In-appropriate use Examples To blow off a product. Good idea?Air Saver nozzles use about70% less CA
19In-appropriate use Examples CA to cool off product. …. Good Idea?200x more expensive than cooling towersEnergy Efficient Process Cooling – Dr. Kissock, University of Dayton
20In-appropriate use Examples Personal Cooling (We just saw cooling costs)Occupational Safety and Health Administration (OSHA) safety violation
21In-appropriate use Examples Drains are used to remove condensate from the systemBut do we need to lose air?No-loss Drain: Zero air lossOpen valve: Always loosing air.Timed Drain: Timing set for peak, often results in air loss
22In-appropriate use Examples Need low pressure air (20 psig) ? => Use Blowers !Blowers use about5x less energy
23List of Common Inappropriate Uses Blow-Off ApplicationsAir knivesDust collector purgesCleaning with CAPersonal coolingProcess coolingContinuous CA Use ApplicationsAerationAgitationAtomization (mixing)Transport of materialAir motors /hoistsDiaphragm pumpsAir vibratorsElectrical cabinet coolingVacuum generationVortex coolersAir CylindersAir Operated vacuum cleaners
24Energy Saving Opportunities There can be endless opportunities in a system.It can take couple of hours to go through them all.So, Let’s just look at the BIG hittersIn appropriate usesLeaksPressureStagingOther opportunitiesAir DryingStorageFiltersHeat ReclaimThese are things we look for when we have limited time with the client.
26Leaks Example Misconception “We do not have a large leak load..” On average 30%* of a facility’s compressed air is lost to leaksExample FacilityWeekendAvg. Leak Load = 50% !!In a two compressor system100 kW in Non-production ~ 100 Homes*U.S. DOE, Compressed Air Fact Sheet #7
27Strategy to Reduce Leaks Strategies we have observed:Leak reduction programsOther MethodsUse of Isolation Valves to valve off unused areasReduced pressure during non productionTurning off CA system on weekends
28Goals for Leaks Can I have Zero Leak Load ? What should I aim for ? Unfortunately, NOWhat should I aim for ?Good rule of thumb is to reduce it by 50%We have observed facilities with leak loadsAs high as 60% andAs low as 7-10% - this was accomplished overtime by reducing leaks and isolating unused areas
29Energy Saving Opportunities There can be endless opportunities in a system.It can take couple of hours to go through them all.So, Let’s just look at the BIG hittersIn appropriate usesLeaksPressureStagingOther opportunitiesAir DryingStorageFiltersHeat ReclaimThese are things we look for when we have limited time with the client.
30Reduce Pressure at End Use Did we adjust pressures at end use ? Do you need line pressure ?We recently observed a large manufacturing facility with efficient compressors…..Almost all end uses were unregulated !!!Unregulated tool~ 120 acfm95 psig~ 20% reduction !Regulated tool~ 95 acfm70 psig
31Reduce Pressure at Compressor Why is a compressor used?To pressurize the incoming air streamA compressor has to Work harder for higher PressureAir CompressorAir P2Power kWAir P1Heat out
32Reduce Pressure at Compressor Common Misconception“Raising the pressure increases capacity”Reality – It decreases compressor capacity and increases operating costsOften times other issues are compensated with pressure,Lack of storageImproper piping
33Reduced Pressure - Energy Savings Rules of ThumbCompressor Efficiency Increases by 1% for every 2 psi reduction in operation pressure
34Reduced Pressure - Benefits Energy savingsImproves compressor efficiencyReduced leak loadReduces CA use at applicationsReduced pneumatic equipment fatigueIncreases equipment life
35Goals for Reducing Pressure How low should my system pressure be?Rough rule of thumb, System Press = Min Press + 10We 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.
36Energy Saving Opportunities There can be endless opportunities in a system.It can take couple of hours to go through them all.So, Let’s just look at the BIG hittersIn appropriate usesLeaksPressureStagingOther opportunitiesAir DryingStorageFiltersHeat ReclaimThese are things we look for when we have limited time with the client.
37Staging This is one of THE most important opportunities Why? Lets look at an example (worst case)Compressor – Centrifugal with blow-off onlyWe just reduced compressed air demand by 50%How much do we save ?
38StagingCentrifugal part loadHow much do we save ? ZERO !
39Staging System Part-Load with Multiple Compressors Very Well staged multiple compressor systemPoorly staged multiple compressor system
40Staging Fundamentals Points to remember Constant speed compressors are only efficient at full loadsOperation at part loads should be minimized.You NEVER* want multiple compressors at part-load*Does not apply in special circumstances with centrifugal and VFD compressorsEliminate (or minimize) blow-off in Centrifugal compressors
41Complexities in Optimizing Staging Need to understandSystem air flow requirementsCompressor – full load efficienciesCompressor – individual part-load performanceEffect of combination of different compressors within a systemHow one staging sequence is different from the otherHow ?Metering the equipment is a startAnalysis of metered dataNeed to apply knowledge to obtainaction itemsOkay, Let’s not worry about complexities.** This is where you may want to reach out for technical assistance.Let’s look at a few case studies to understand the potential.
42Case Study 1Pre:Two new 900-hp centrifugal compressors are operated in base trim mannerProject cost ~ $800,000Both of them can modulate and then blow-offPost:Compressors are operated in parallel so thatOnly one compressor blows-off first
44Case Study 2A facility has two compressed air systems that were put in place for two different systemsPreAs often seenBoth systems were oversizedWhat's interesting is both systems operate at 95 psig.PostCombine the two compressed air systemsFacts:Engineers like factor of safety;Vendors like to sell larger compressors
45Compressor Optimization: Case Study 2 Savings ~ 20%In the new case only one compressor is part-loaded instead of two.
46Case Study 3 Manufacturing facility wanted to save energy Pre Post They thought VFD compressor is a good idea (it is, but..)PreThey bought a Oversized (215 hp) VFD compressorWhy ? Sales person recommendation ? Lack of analysis ?Issue: the VFD could not trimUsed a 250 hp load/unload as the trim insteadNot goodPostBought appropriately sized (125 hp) VFD compressorCompressor Cost ~ $150,000And changed the control sequence
47* Could have been achieved the first time if the VFD was sized right. Case Study 3Savings ~ 24%* Could have been achieved the first time if the VFD was sized right.Big Savings
48Case Study 4 Multiple facilities with multiple compressors Are more compressors better ?Is a control system better ?Is a VFD better ?
49Case Study 4 1. Poorly Staged (Manual) - 8 similar compressors 2. Staged with VFD(Pressure based)- 8 different compressorsFacility 1Facility 23. Very well staged. (Demand Based)No VFD- 8 similar but different size compressors.Facility 3
50Case Study 4 Most of the savings can be achieved by effective staging Control systems are vital for optimization in large systemsA VFD compressor can help improve your part-load performanceTypically only one effective VFD is required per systemIf sized correctly
51Its time for the Recommendations SummaryWe discussedImportance of compressed airWhy its an expensive resourceDifferent types of compressors and their controlsReciprocatingScrewCentrifugalLargest Energy savings opportunitiesIn-appropriate usesLeaksPressureStagingWe looked at a few case studiesIts time for the Recommendations
52Recommendations Pursue all the low-cost no-cost opportunities In-appropriate usesLeaksReducing pressureStaging with available control systemsConsult experts to evaluate best strategy with available controlsConsult technical experts before Investing CapitalThe last thing you want is invested capital and no savings.New compressor installationControl system upgrade
53Abdul Qayyum “Q” Mohammed Questions ?Thanks for Listening!Abdul Qayyum “Q” MohammedAdditional Slides are available at the End for Interested Partiesx308
54End Use: CA Diaphragm Pumps Facilities use CA Diaphragm Pumps.Needed for extremely corrosive or volatile fluidsHowever, in many cases diaphragm pumps are used for fluids that can be moved with a regular centrifugal pumpMotor Operated pumps use about4x less energy
55End 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 purgesBag house uses ~ 40% of system capacity
56Distribution: Storage Used to eliminate (or dampen) the variation of pressure within the system.Particularly important in systems with load/unload compressorsStorage 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
57Distribution: Storage (Cont.) How much storage should I have ?Rule of thumb 3 to 5 gal/cfm of compressor outputActual requirement depends on fluctuations in CA demand and types of compressors
58Optimize Compressed Air Drying Appropriate drying technologies should be usedCommon drying technologies in order of decreasing efficiencyRefrigerant DryersCyclingNon-CyclingDesiccant DryersHeat of Compression* (HOC)Heated desiccantHeated with Blower purgeHeated with CA purgeHeatless desiccant* HOC dryers are more efficient than refrigerated dryers
59Generation: Reclaim Heat ~ 80% of input energy is lost as heatHeat can be used for various purposesFor space heating during winterFor process use throughout the year
61Generation: Compress Outdoor Air Outdoor air is typically cooler than a mechanical roomCooler air is denser hence easier to compressFraction savings ~ 2% per 10 F reductionNote:Savings are realized in oil free compressors onlyIn oil lubricated compressors the air is mixed with hot oil before compression. This eliminates savings.Considerations should be made to avoid freezing temperatures
62What's the benefit of Energy Savings? We reduce emissionsHelps slow down global warmingHelps Protect Out planetWhat are we talking about ?Lets rephrase “What is MY benefit ?”