1. Heatless Desiccant Dryers
Presenting. . .
Heatless
Desiccant Dryers

2. HHE – HHL – HHS Desiccant Dryer Features
Industrial grade desiccant beads offer enhanced surface area and high crush strength which prolongs bed life
Tower sized so that air velocity through the bed won’t fluidize the desiccant bed, reducing bed movement and dusting
Up-flow drying design allows water and heavy contaminants to drop out as the air enters a tower
Large flow diffusers ensure even flow distribution
Separate fill and drain ports for ease of desiccant replacement

3. HHE – HHL – HHS Desiccant Dryer Features
Pressure vessels are CRN and ASME Certified
Heavy duty mufflers for quiet operation ( extra muffler core supplied when shipped )
NEMA 4 / 4X electrical construction is standard
Pressure relief valve standard

4. Operating pressures and temperatures
Maximum Pressure
150 psig Standard
250 psig Optional
Maximum Inlet Temperature
140 deg F or 60 deg C
Maximum Temperature
120 deg F or 49 deg C
Minimum Pressure
60 psig for 150 psig machine
120 psig for 250 psig machine
Minimum Temperature
35 deg F or 2 deg C
-20 deg F or –29 deg C **
** With low ambient package

5. Desiccant Fundamentals

6. Desiccant Beads 1/8” Activated alumina Large surface area
High crush strength
Highly abrasive
All Kaeser desiccant dryers use 3mm (1/8”) spherical activated alumina desiccant beads.
Activated alumina is made of aluminum oxide which is basically the same chemical compound that makes up sapphires and rubies but does not contain the impurities that give those gems their color.
- Looking at the magnified section of the desiccant bead, you can see that there are numerous chasms and peaks on each bead instead of having a smooth surface.
These chasms and peaks add an incredible amount of surface area to each bead which is why they are so good for our application. The more surface area, the more moisture they hold.
To give you a rough idea of how much surface area, imagine a 1 square inch cube filled with desiccant beads. This small amount of desiccant has the same area as a football field.
- These beads also have a high crush strength. It takes 30 psi to crush a bead. One bead on the floor by itself doesn’t pose much of a threat. However, just 10 beads together means the crush strength just multiplied to 300 psi.
Be extremely careful when changing desiccant, if there is a bunch on the floor, don’t step on it because you will more than likely go for a ride.
- Desiccant is also very abrasive and creates large amounts of dust when replacing old desiccant or doing an initial fill. We recommend wearing a dust mask and having plenty of drinking water on hand when doing this job.

7. Adsorption Process Stage 1:
Water vapor moves from areas of higher concentration to areas of lower concentration
The compressed air stream is saturated with water vapor when it leaves the air compressor and passes through the piping system.
As you can see in the picture, the air stream is the high concentration area, the desiccant bead is the lower concentration area.

8. Adsorption Process Stage 2:
Water vapor molecules come in contact with the surface of the bead and are adsorbed
As the air stream moves across the desiccant bead and comes in contact with the peaks and chasms that create the large surface area, the water molecules adsorb onto the surface.
In other words, the molecules cling to the rough areas of the bead. The air molecules continue on and are dry after depositing their water vapor onto the bead.

9. Adsorption Process Stage 3:
Water vapor builds up on surfaces, eventually becoming dense enough to change states into a liquid
As more air flows across the bead, water vapor continues to build on the surface of the bead. Eventually, the vapor becomes dense enough to change from a vapor to liquid water.
Think of it like raindrops on your windshield. When it first starts raining, the drops are small. When they hit your windshield they stay in one spot for a while. As more and more of these small drops gather, they gain mass and form to make larger drops.

10. Adsorption Process Stage 4:
Heat is released as water is adsorbed (1250 BTU’s per pound of water)
As more and more water is adsorbed, heat is released. This heat is used to regenerate the desiccant (dry the desiccant in the offline tower).
1250 BTU’s are produced per pound of water adsorbed.
A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F.
This is the standard measurement used to state the amount of output of any heat generating device.
You might be able to imagine it this way. Take one gallon (8 pounds) of water and put it on your stove. If the water it 60 degrees F. and you want to bring it to a boil (212 degrees F.) then you will need about 1,200 BTUs to do this.

11. Adsorption Process Stage 5:
The desiccant adsorbs water until the concentration of water vapor equals that of the compressed air stream
As more and more water is adsorbed, heat is released. This heat is used to regenerate the desiccant (dry the desiccant in the offline tower).
1250 BTU’s are produced per pound of water adsorbed.
A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F.
This is the standard measurement used to state the amount of output of any heat generating device.
You might be able to imagine it this way. Take one gallon (8 pounds) of water and put it on your stove. If the water it 60 degrees F. and you want to bring it to a boil (212 degrees F.) then you will need about 1,200 BTUs to do this.

12. Operating Principles
Compressed air passes through a vessel filled with desiccant
Water vapor is captured on the surface of the desiccant by the process called adsorption
Dry air exits the dryer
There are 2 towers (tanks) filled with desiccant on the dryer. One tower is used for drying the compressed air while the other is regenerating. A controller switches towers based on criteria entered so each has time to dry air and regenerate the desiccant when not drying. As the dryer operates, it switches towers based on the cycle time.
All Kaeser dryers are up-flow design meaning the air flows in from the bottom of the tank and exits at the top. This increases air contact time with the desiccant beads. Also we can use gravity to help as water is heavier than air and tends to drain downward.
Water vapor is adsorbed on the surface of the desiccant beads.
As the beads adsorb the moisture from the air stream, the air continues to flow upward through the remaining beads and the dry air exits the dryer and out into the customer’s plant.

13. Inlet & Outlet switching valves automatically shifts to the low pressure side of circuit
Shuttle valve life tested to over 500,000 cycles
Shuttle valve position memory ensures drying continues, even with the loss of electrical power to the dryer

14. HHE Controller Solid state controller in polycarbonate box
NEMA 4/4X, IP66 rated
10 minute fixed time ONLY
Amber tower status lights
12 volt DC coil voltage

15. HHL Controller

16. HHL Controller Left Tower Pressure Switch LED On = Switch Closed
Off = Switch Open
Left Tower Drying LED
Left inlet Valve LED
On = Valve Open
Off = Valve Closed
Left Purge Valve LED
On =Valve Open
Off =Valve Closed
Left Tower
Regenerating LED
Filter Maintenance LED
ISO Class Selector Switch
Power On LED
On/Off switch
Communications Icon
Right Inlet Valve LED
Right Tower Pressure Switch LED
Right Tower LED
Energy Savings Selector Switch
Maintenance Reminder LED
Right tower Regenerating LED
Alarm LED
Reset Switch
(Normal Maintenance Reminder & Alarm)
Right Purge Valve LED
Operating Cycling LED’s
ISO class 1-4 and Manual Cycle (Test Mode)
Energy Savings Icon
Energy (Purge) Savings LED’s

17. HHS Controller

18. HHS Controller Left Tower Pressure Switch LED On = Switch Closed
Off = Switch Open
Left Tower Drying LED
Left Inlet Valve LED
On = Valve Open
Off = Valve Closed
Left Purge Valve LED
Left Tower
Regenerating LED
Filter Maintenance LED
Vacuum Fluorescent
Text Display
2 Line x 16 Character
“Select” Switch
Power On LED
On/Off switch
Communications Icon
Right Inlet Valve LED
Right Tower Pressure Switch LED
Right Tower Drying LED
“Enter”Switch
Maintenance Reminder LED
Right Tower Regenerating LED
Alarm LED
Reset Switch
(For Maintenance Reminder & Alarm)
Right Purge Valve LED

19. ISO 8573.1 Air Quality Classes

20. 40 – 3000 SCFM Air Flow Schematic
Inlet shuttle valve
Outlet shuttle valve
Muffler
Right Tower Purge -Depressurization Valve
Left Tower Purge- Depressurization Valve

21. 40 – 3000 SCFM Sequence of Operation
Compressed air flows through inlet shuttle valve (A) to Tower 1 where the air is dried
After the air is dried it flows through outlet shuttle valve (B) and then to the dryer outlet
15% of the dried air branches off of the outlet, flows through the purge orifice, and then through the adjustable purge rate valve

22. 40 – 3000 SCFM Sequence of Operation
The purge flow that has been throttled to near atmospheric pressure is directed to tower 2
When the purge air passes over the desiccant it removes the water vapor that was deposited there when the tower was on line drying
The purge air exits through valve (D) (normally closed) purge/repress valve, then out of the muffler (C) to atmosphere

23. 40 – 3000 SCFM Sequence of Operation
After time has elapsed valve (D) closes allowing tower 2 to re-pressurize slowly
Adequate time is allowed to fully re-pressurize tower 2 before switch over
After a controlled time period purge/repress valve (E) opens
The inlet and outlet shuttle valves will shift. Tower 2 will
Tower 2 is now drying the main air stream and Tower 1 is being regenerated

24. 4100 – 5400 SCFM Airflow Schematic
Purge check valve
Orifice
Purge adjust valve
Outlet check valve
Left Tower
Right Tower
Muffler
Purge Valve
Air Inlet
Inlet valve

25. 4100 - 5400 SCFM Sequence of Operation
Air enters through inlet switching valve (Normally Open) UP through the left tower where it is dried
The dry air flows through the outlet check valve and out the dryer outlet
A portion of the dry air (15 percent) branches off from the main air stream before the outlet
The purge air is controlled by the adjustable purge rate valve and goes through the single orifice

26. 4100 - 5400 SCFM Sequence of Operation
The purge air that is throttled to near atmospheric pressure goes through the purge check valve and DOWN through the right tower
The dry air removes the water vapor that was deposited while the tower was on line drying
The purge air passes through the purge/repress valve (normally closed) and out through the muffler to atmosphere

27. 4100 - 5400 SCFM Sequence of Operation
After time has allotted the purge/repress valve closes allowing the right tower to re-pressurize slowly
Adequate re-pressurization time is allowed so the the tower is fully pressurized before switchover