Supply Side Review: Heat of Compression-Type Dryers

The supply side of a compressed air system has many critical parts that factor in to how well the system operates and how easily it can be maintained.   Dryers for the compressed air play a key role within the supply side are available in many form factors and fitments.  Today we will discuss heat of compression-type dryers.

Heat of compression-type dryer- Twin Tower Version

Heat of compression-type dryers are a regenerative desiccant dryer that take the heat from the act of compression to regenerate the desiccant.  By using this cycle they are grouped as a heat reactivated dryer rather than membrane technology, deliquescent type, or refrigerant type dryers.   They are also manufactured into two separate types.

The single vessel-type heat of compression-type dryer offers a no cycling action in order to provide continuous drying of throughput air.  The drying process is performed within a single pressure vessel with a rotating desiccant drum.  The vessel is divided into two air streams, one is a portion of air taken straight off the hot air exhaust from the air compressor which is used to provide the heat to dry the desiccant. The second air stream is the remainder of the air compressor output after it has been processed through the after-cooler. This same air stream passes through the drying section within the rotating desiccant drum where the air is then dried.  The hot air stream that was used for regeneration passes through a cooler just before it gets reintroduced to the main air stream all before entering the desiccant bed.  The air exits from the desiccant bed and is passed on to the next point in the supply side before distribution to the demand side of the system.

The  twin tower heat of compression-type dryer operates on the same theory and has a slightly different process.  This system divides the air process into two separate towers.  There is a saturated tower (vessel) that holds all of the desiccant.  This desiccant is regenerated by all of the hot air leaving the compressor discharge.  The total flow of compressed air then flows through an after-cooler before entering the second tower (vessel) which dries the air and then passes the air flow to the next stage within the supply side to then be distributed to the demand side of the system.

The heat of compression-type dryers do require a large amount of heat and escalated temperatures in order to successfully perform the regeneration of the desiccant.  Due to this they are mainly observed being used on systems which are based on a lubricant-free rotary screw compressor or a centrifugal compressor.

No matter the type of dryer your system has in place, EXAIR still recommends to place a redundant point of use filter on the demand side of the system.  This helps to reduce contamination from piping, collection during dryer down time, and acts as a fail safe to protect your process.  If you would like to discuss supply side or demand side factors of your compressed air system please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

Heat of compression image: Compressed Air Challenge: Drive down your energy costs with heat of compression recovery: https://www.plantservices.com/articles/2013/03-heat-of-compression-recovery/

 

What’s The Big Deal About Clean Air?

Compressed air isn’t called manufacturing’s “Fourth Utility” (the first three being electricity, water, and natural gas) for nothing. Pneumatic tools are popular because they’re often so much lighter than their electric counterparts. Compressed air can be stored in receiver tanks for use when other power supplies are unavailable or not feasible. Many compressed air operated products can be made to withstand environmental factors (high/low temperature, corrosive elements, atmospheric dust, oil, other contaminants, etc.,) that would make electric devices very expensive, unwieldy, or impractical.

One of the most valuable considerations, though, is that your compressed air system is, by and large, under your control.  The type and capacity of your air compressor can be determined by your specific operational needs.  The header pressure in your supply lines is based on the applications that your air-operated devices are used for.  And the performance & lifespan of every single component in your compressed air system is determined by the care you take in maintaining it.

I covered the importance of compressed air system maintenance in a blog a while back…today, I want to focus on clean air.  And, like the title (hopefully) makes you think, it’s a REALLY big deal.  Consider the effects of the following:

Debris: solid particulates can enter your air system through the compressor intake, during maintenance, or if lines are undone and remade.  If you have moisture in your air (more on that in a minute,) that can promote corrosion inside your pipes, and rust can flake off in there.  Almost all of your air operated products have moving parts, tight passages, or both…debris is just plain bad for them.  And if you use air for blow off (cleaning, drying, etc.,) keep in mind that anything in your compressed air system will almost certainly get on your product.

Your compressed air system may be equipped with a main filter at the compressor discharge.  This is fine, but since there is indeed potential for downstream ingress (as mentioned above,) point-of-use filtration is good engineering practice.  EXAIR recommends particulate filtration to 5 microns for most of our products.

Water: moisture is almost always a product of condensation, but it can also be introduced through faulty maintenance, or by failure of the compressor’s drying or cooling systems.  Any way it happens, it’s also easy to combat with point-of-use filtration.

EXAIR includes an Automatic Drain Filter Separator in our product kits to address both of these concerns.  A particulate filter element traps solids, and a centrifugal element “spins” any moisture out, collecting it in the bowl, which is periodically drained (automatically, as the name implies) by a float.

Point of use filtration is key to the performance of your compressed air products, and their effectiveness. Regardless of your application, EXAIR has Filter Separators to meet most any need.

Oil: many pneumatic tools require oil for proper operation, so, instead of removing it, there’s going to be a dedicated lubricator, putting oil in the air on purpose.  Optimally, this will be as close to the tool as possible, because not all of your compressed air loads need oil…especially your blow offs.  If, however, a blow off device is installed downstream of a lubricator (perhaps due to convenience or necessity,) you’ll want to do something about that oil. Remember, anything in your system will get blown onto your product.

If this is the case, or you just want to have the cleanest air possible (keep in mind there is no downside to that,) consider an EXAIR Oil Removal Filter.  They come in a range of capacities, up to 310 SCFM (8,773 SLPM,) and the coalescing element also offers additional particulate filtration to 0.03 microns.

In closing, here’s a video that shows you, up close and personal, the difference that proper filtration can make:

If you’d like to discuss or debate (spoiler alert: I’ll win) the importance of clean air, and how EXAIR can help, give me a call.

Russ Bowman
Application Engineer
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Crank Up The Heat (and Static)

The outside temperature is beginning to drop which means the thermostat in my house is getting a workout. I don’t mind the colder temps but my wife on the other hand likes it pretty toasty during the winter months. I am usually downstairs in the living room, so I don’t feel the full effect of the increased heat but our house isn’t as fortunate. The majority of our house has hardwood floors so as the inside temperatures rise and the furnace brings in more of that dry outside air to heat up, it also dries out the hardwood which begins to separate and make a nice creaking sound. We started using humidifiers upstairs and on the main floor to replace some of the moisture lost due to the increased makeup air from the outside.

Another concern with dry air is it creates static electricity.  There are a ton of natural insulators in your house, like carpet or shoes with rubber soles just to name a few, that make it all too easy to build up a static charge and deliver a nice shock. Case in point, over the weekend I was downstairs working and asked our oldest son if he could help me out and get his baby brother out of the pack-n-play. Of course, without hesitation, (heavy sarcasm) he shuffled across the carpet and reached down for his brother, then ZAP! I actually heard the shock before the screams started! I quickly made the realization that I will soon be adding a third humidifier for downstairs as well!

Static electricity is a common nuisance in industrial settings also. It can lead to damaged product, shorting of electrical components, printing or labeling errors, spark generation or cause harmful shock to an operator. EXAIR offers a wide variety of Static Eliminators that are capable of neutralizing the surface static of a material or object to ensure proper operation in many manufacturing processes. For example, our Super Ion Air Knife is a great choice for printing/labeling applications or cleaning a web. With applications requiring more of a focused airflow, we offer our Ion Air Cannon or Ion Air Jet. The Ion Air Gun is the perfect choice for a manual, surface treatment. We also offer our Ionizing Bars and Ionizing Point for close proximity static elimination, where compressed air isn’t available.

An easy way to pinpoint the location and level of static is by using our Model # 7905 Digital Static Meter. The Digital Static Meter is a handheld, portable device that is capable of reading static within 1″ of the surface, up to  +/- 20 kV with 5% accuracy. Once the static has been located, we can then make the best recommendation for a Static Eliminator that will meet the application requirements.

Static Meter
Easy to use, Digital Static Meter to pinpoint static charge. Calibrated to NIST standards.

If static is a concern in any of your processes, or if you need help in making the best selection, please contact an application engineer for assistance.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

Winter Cold = Static Issues

Winter is fast approaching us here in Cincinnati, which can mean just about anything, temperature and weather wise. For instance, 2 years ago we had a very mild winter, with warmer than usual temperatures and very little snow. I can remember golfing in December, January and even in to February, which was awesome! But last year however was much different. We experienced a very harsh winter with extreme low temperatures (several -0°F days) and a steady amount of snowfall – I know I felt like I was shoveling the driveway and sidewalk about every 2 days! The weather was so bad that local schools ran out of snow days.

brrr
There’s no stopping winter’s cold, dry air from causing static problems – solve them with our static eliminators!

The lower temperatures mean turning up the heat on the thermostat, which is going to dry out the air. As a result of the dry air, a common problem is ESD (ElectroStatic Discharge) or static electricity. All of us at some point have probably brushed our feet on the carpet to build up a charge, then “reached out and touched someone” to give them a little jolt. While this may seem slightly humorous, the truth is, static electricity can be quite problematic.

Some common static issues:

  • Spark or shocks to personnel
  • Damage to sensitive electrical components
  • Jamming of machines
  • Particulate clinging to the surface of an object
  • Unable to separate sheets or product sticking together

EXAIR offers an extensive catalog of Static Eliminators to eliminate these common issues:

Ion Air Knives – Provides a laminar sheet of high velocity, ionized airflow. Available up to 108” single-piece lengths.

Ionizing Bars – Capable of eliminating surface static within 2” of the bar.

Super Ion Air Wipe – 360° uniform ionized airflow, ideal for ionizing extruded shapes, hose, pipe, cable etc.

Ion Air Cannon – Concentrated ionized airflow, effective up to 15 feet.

Ion Air Gun – Static eliminating, hand-held air gun, allowing easy operation.

Ion Air Jet – Static eliminating spot cleaner, available in permanent or flexible mounting.

Ionizing Point – Single point ionizer, delivering a high concentration of positive and negative ions.

We also offer our Model # 7905 Digital Static Meter, allowing you to pinpoint the source of the static. Capable of reading up to +/- 20 kV with 5% accuracy (+/-) when measured at a distance of 1”.

If you are experiencing a static issue with your process, please contact an application engineer for assistance.

Justin Nicholl
Application Engineer
justinnicholl@EXAIR.com
@EXAIR_JN

 

Brrr! image courtesy Neil Turner  Creative Commons License