1. Hybritec Refrigerated/Blower Purge Dryers (Combination Dryer)
The Hybritec “combination” dryer is a system that first incorporates a refrigerated dryer, which may have either an air-cooled or a water-cooled refrigeration system, to condense and remove the majority of the water vapor being carried by an untreated compressed air stream.
The “pre-treated” air is then delivered cold and saturated to an externally heated, atmospheric blower purge, desiccant dryer where the dew point is further reduced, typically to -40°F.
The very dry and cold compressed air is returned to the refrigerated dryer where it is reheated and delivered warm and dry to the air distribution system.
This combination arrangement significantly reduces both operating and maintenance costs compared to other dryer types equally capable of producing dew points as low as -40°F.
The combination system also permits the refrigerated dryer to be operated independently.
As the vast majority of compressed air applications simply require the water vapor remaining in the air after treatment to remain in the vapor state, a refrigerated dryer provides adequate drying during warm weather periods, and the blower purge dryer is typically needed in the system only during the wintertime.
As refrigeration is comparatively a very inexpensive method for dehydrating compressed air, the energy required to produce a dew point of -40°F in a compressed air stream is significantly reduced when the air is first routed through a refrigeration system before being treated by a desiccant dryer.
Refrigeration will typically remove 85% to 88% of the total amount of water vapor needing to be removed to lower the dew point of compressed air to -40°F. Consequently the desiccant dryer is challenged with only the remaining 12% to 15% of the total water removal.
Hybritec Refrigerated/Blower Purge Dryers
(Combination Dryer)
Externally
Heated
Blower
Purge
Dryer (KBD)
Dual Control
Air-cooled or Water-cooled Refrigerated
Dryer

2. Compressed Air Flow Hybritec Process Flow Diagram for -40°F PDP
Here we see the Hybritec dryer process flow for producing a
-40°F pressure dew point. Note the position of the isolation and by-pass valves, incorporating the blower purge dryer into the process air flow.
Compressed air that has been through an aftercooler (at 100 psig and 100°F in this example) enters the refrigerated dryer and passes through the primary side of the air-to-air heat exchanger where its temperature is reduced to about 70°F.
This change in temperature condenses a significant amount of the water vapor that entered the air-to-air heat exchanger. Some oil vapor may also be condensed in the air-to-air heat exchanger.
The mixture of 70°F saturated air and liquid water enters the air-to-refrigerant heat exchanger where the temperature of both is further reduced to about 38°F.
Again the change in temperature condenses more water vapor which creates more liquid water, and also condenses more oil vapor creating oil aerosols.
This mixture of 38°F saturated air, liquid water and oil aerosols enters the refrigerated dryer’s KFS separator where oil aerosols are coalesced and the liquid water, and newly formed oil droplets, are separated from the compressed air stream and removed from the system by a capacitance-sensing automatic drain.
The KFS also captures and retains solid particles 3 micron and larger.
The cold saturated air, reduced in oil aerosols and particulates, is routed through a KOR oil coalescing filter where further coalescence reduces oil aerosol concentration to 0.01 PPMw, and particles 0.1 micron and larger (ISO Class 1 for particles) are captured and retained.
The cold, saturated, oil-free and particle-free compressed air is now routed to the blower purge dryer and passed through a bed of activated alumina desiccant where the dew point of the air is reduced from 38 to -40°F.
The temperature of the compressed air will increase slightly as it moves through the desiccant bed. This is due to the heat released as water vapor is adsorbed, being carried out of the bed by the compressed air flow.
The magnitude of this temperature rise is dependent upon the air pressure at the inlet of the Hybritec system. At rated pressure, being 100 psig, the air temperature will rise to about 41°F by the time is exits the bed.
The cold, dry, oil-free air stream then passes through a one micron particulate filter where desiccant fines that migrate out of the desiccant bed in the compressed air flow, are captured and retained.
Compressed Air Flow
Air Inlet
100 psig
100°F
100°F pdp
Rated Conditions
Air Outlet
psig ≈ 85°F
-40°F pdp
HTA After-Filter
A/A HX
Repressurization and Cooling Air Solenoid Valve Closed
(Air ≈ 41°F)
Air ≈ 70°F
Bypass Valves Open
Check Valve Open
Check Valve Closed
Air ≈ 41°F °F pdp
Repressurization and Cooling Air Check Valve Closed
R-404A
A/C or W/C
A/R HX
¼” Activated Alumina
Desiccant
Check Valve Closed
Air ≈ 38°F
KFS (Separator)
Eco-Drain
Eco-Drain
KOR
Insulation:
Air ≈ 39°F

3. Ambient Air for Regeneration
Hybritec Process Flow Diagram for -40°F PDP
Regeneration of the desiccant beds of the Hybritec dryer is accomplished in the manner typical of a blower purge dryer.
A centrifugal or regenerative type blower draws in air, which will be used for regeneration, from the ambient through its inlet filter. The blower discharge pressure is typically between 1 and 3 psig, being just enough to overcome the resistance of the purge circuit. The filtered ambient air is pushed through an in-line heater, typically an immersion type, where its temperature is raised to that required to accomplish regeneration, typically 230°F to 250°F (for Hybritec dryers).
The heated ambient air is then routed through a series of check valves which separate high pressure compressed air from the low pressure regeneration air stream, then downward through the saturated desiccant bed, finally being exhausted to the ambient through the purge valve.
The heated ambient air evaporates water off the desiccant and carries it through the purge valve to the ambient. This completes the regeneration process.
Regeneration Air Flow with Blower and Heater
Air Inlet
100 psig
100°F
100°F pdp
Rated Conditions
Air Outlet
psig ≈ 85°F
-40°F pdp
HTA After-Filter
A/A HX
(Air ≈ 41°F)
Check valves separate high pressure compressed air from low pressure ambient air.
Air ≈ 70°F
Bypass Valves
Air ≈ 41°F °F pdp
R-404A
A/C or W/C
A/R HX
¼” Activated Alumina
Desiccant
Regeneration Air ≈250°F
Heater
Air ≈ 38°F
¼” Activated Alumina
Desiccant
Blower
Blower Inlet Filter
KFS (Separator)
Eco-Drain
Eco-Drain
KOR
Ambient Air for Regeneration
Note: Compressed air drying continues during regeneration phase.
Insulation:
Air ≈ 39°F

4. Cooling air ≈ 41°F - 40°F pdp taken from dried compressed air stream
Hybritec Process Flow Diagram for -40°F PDP
Cooling Phase
Air Inlet
100 psig
100°F
100°F pdp
Rated Conditions
Air Outlet
psig ≈ 85°F
-40°F pdp
HTA After-Filter
A/A HX
Cooling air ≈ 41°F °F pdp taken from dried compressed air stream
Air ≈ 41°F
The final step in preparing the desiccant bed for another drying cycle is removing the residual heat left by the regeneration process. This is accomplished by passing a small volume of dry, cool process air, taken from the outlet air stream of the on-line desiccant bed, through the freshly regenerated tower. A low cooling air flow rate (1.1% of the Hybritec dryer’s rated capacity) is achieved by allowing four (4) hours to complete the cooling process.
The cooling air enters the purge circuit through a dedicated valve, passes through an orifice where its pressure is reduced to very near atmospheric, and is then routed to the hot desiccant bed. Here again the check valves separate the high pressure compressed air from the low pressure cooling air. The cooling air also exhausts to the ambient through the purge valve.
Air ≈ 70°F
Bypass Valves
Check valves separate high pressure compressed air from low pressure ambient air.
R-404A
A/C or W/C
A/R HX
¼” Activated Alumina
Desiccant
Air ≈ 38°F
Heater
¼” Activated Alumina
Desiccant
Blower
KFS (Separator)
Eco-Drain
Eco-Drain
KOR
Note: Compressed air drying continues during the cooling phase. The blower and heater are turned off.
Insulation:
Air ≈ 39°F

5. Desiccant Dryer Valved Out for Summer Operation
Hybritec Process Flow Diagram for +38°F PDP
Here we see the Hybritec dryer process flow for producing a +38°F pressure dew point. Note the position of the isolation and by-pass valves, now isolating the blower purge dryer from the process air flow.
Compressed air that has been through an aftercooler (at 100 psig and 100°F in this example) enters the refrigerated dryer and passes through the primary side of the air-to-air heat exchanger where its temperature is reduced to about 70°F.
This change in temperature condenses a significant amount of the water vapor that entered the air-to-air heat exchanger. Some oil vapor may also be condensed in the air-to-air heat exchanger.
The mixture of 70°F saturated air and liquid water enters the air-to-refrigerant heat exchanger where the temperature of both is further reduced to about 38°F.
Again the change in temperature condenses more water vapor which creates more liquid water, and also condenses more oil vapor creating oil aerosols.
This mixture of 38°F saturated air, liquid water and oil aerosols enters the refrigerated dryer’s KFS separator where oil aerosols are coalesced and the liquid water, and newly formed oil droplets, are separated from the compressed air stream and removed from the system by a capacitance-sensing automatic drain.
The KFS also captures and retains solid particles 3 micron and larger.
The cold saturated air, reduced in oil aerosols and particulates, is routed through a KOR oil coalescing filter where further coalescence reduces oil aerosol concentration to 0.01 PPMw, and particles 0.1 micron and larger (ISO Class 1 for particles) are captured and retained.
The cold, saturated, oil-free and particle-free compressed air is now routed through the by-pass line to the secondary side of the air-to-air heat exchanger where it is reheated to about 85°F by the inlet compressed air. It then exits the air-to-air heat exchanger and is delivered to the air distribution system.
Desiccant Dryer Valved Out for Summer Operation
Air Inlet
100 psig
100°F
100°F pdp
Rated Conditions
Air Outlet
psig ≈ 85°F
39°F pdp
A/A HX
Air ≈ 39°F
Air ≈ 70°F
Bypass Valves
R-404A
A/C or W/C
A/R HX
Air ≈ 38°F
KFS (Separator)
Eco-Drain
Eco-Drain
KOR
Insulation:

6. KBD bypassed for summertime operation KBD blower purge desiccant dryer
Hybritec Combination Dryer Overview
Why Hybritec Refrigerated/Blower Purge Dryers?
Lowest year-round operating cost for -40°F pdp of any desiccant dryer
Bypass KBD in summertime, run 38°F pdp when -40°F pdp unnecessary
Low pressure drop when desiccant dryer valved out for summertime operation (3-4 psi typical)
KBD bypassed for summertime operation
85°F Air Temperature 39°F pdp
HTA After-Filter
Using a refrigerated dryer in combination with a blower purge dryer yields a surprising number of benefits.
A Hybritec dryer
* Consumes significantly less power than other types of desiccant
dryers, especially when the blower purge dryer is by-passed during
warm weather. For example
* A Hybritec dryer operating at rated conditions and producing a
-40°F dew point for 7 months of the year and 38°F dew point for the
remaining 5 months, will consume:
* 48% less power than a blower purge dryer.
* 54% less power than a heated purge dryer.
* 64% less power than a heatless dryer
Likewise by-passing the blower purge dryer and its after-filter, reduces the system pressure drop.
KBD and HTA valved out
KBD blower purge desiccant dryer

7. Less desiccant required in each tower than other desiccant dryer types
Hybritec Combination Dryer Overview
Why Hybritec Refrigerated/Blower Purge Dryers?
Lowest routine maintenance cost of any desiccant dryer
Requires far less desiccant than other desiccant dryers
Typical desiccant service life of 7 years
Valves cycle 50% less than other heated dryers, 99% less than heatless dryers
Less desiccant required in each tower than other desiccant dryer types
* Hybritec dryers also have the lowest routine maintenance costs.
As routine maintenance is minimal for refrigerated dryers, the Hybritec’s blower purge dryer becomes the primary maintenance component.
Note that the single greatest maintenance expense for any type of desiccant dryer, is replacement desiccant and the Hybritec dryer requires far less desiccant than other types and has a much longer desiccant service life years is typical.
As example consider dryers with a rated capacity of 1500 scfm (though the numbers would be proportional for other flow rates)
the average annual quantity of replacement desiccant for a heated dryer (e.g. heated purge or blower purge), which have a desiccant service life typically of 2 years, is about 1250 lb/yr for 1500 cfm.
For a heatless dryer, typically having a 5 year desiccant service life, we’ll need about 400 lb/yr for 1500 cfm, and for the Hybritec dryer, with its 7 year desiccant service life, we need about 220 lb/yr.
* Hybritec dryers also cycle their switching valves far less often
than other desiccant dryer types.
This extends valve life and reduces the number of rebuilds that will be required over the life of the dryer.

8. Less than 2 year payback at only 1,472 scfm!
Hybritec Combination Dryer Overview
Here we see the compounded effect of the lower operating and maintenance costs of a Hybritec dryer.
The chart is based on the Hybritec dryer operating continuously at -40°F pressure dew point for 7 months and 38°F dew point for
5 months each year, inlet conditions of 100 psig and 100°F saturated air, expected end user purchase costs and a power cost of 15 cents per kilowatt-hour.
Note this chart targets the northeast of the United States.
Year “zero” is the end-user purchase cost of the dryers. As you can see a 1500 cfm Hybritec dryer is more than twice the cost of the heatless or heated purge dryer, yet in less than 2 years the Hybritec dryer is the least expensive dryer to own, operate and maintain.
One caution regarding Hybritec applications please call Project Support to discuss the feasibility of a Hybritec dryer for a specific application before presenting the idea of the Hybritec system to a customer.
As the Hybritec dryer will typically (but not always) have a greater initial expense than other desiccant dryer types, for a Hybritec dryer to provide an attractive payback on its additional purchase price, certain conditions must exist.
We must be drying enough air for example
* Or have a high enough power cost
* Have near continuous operation
* Or have severe summertime inlet conditions
* Have no need for a -40°F dew point all year long
or some combination of these conditions.
We may also need to demonstrate the savings in operating and maintenance costs the Hybritec will deliver. In fact, an Operating and Maintenance Cost Analysis most often is the causal factor in securing an order for a Hybritec dryer.
To request an Operating and Maintenance Cost Analysis please contact Project Support in Fredericksburg and have all of the following information:
1) __INLET or desired __OUTLET air flow rate: _______ SCFM
2) __INLET or desired __OUTLET air pressure: _____ PSIG
3) Inlet air temperature: ____ F
4) Refrigeration system: __air-cooled or __water-cooled 
5) Period of operation: __Continuous
OR--->hr/day:____ and days/wk:____ and wk/yr:____
6) Seasonal dew point: Winter: -40°F for ____mo/yr.
Summer: +39F for ____ mo/yr.
7) What is the electrical power cost? ______$/kW-hr
With this information Kaeser will prepare an operating and maintenance cost analysis comparing the Hybritec to other dryer types.
Total Cost of Purchase, Operation and Maintenance
Less than 2 year payback at only 1,472 scfm!

9. Why Hybritec Refrigerated/Blower Purge Dryers?
Hybritec Combination Dryer Overview
Why Hybritec Refrigerated/Blower Purge Dryers?
Earlier it was mentioned that using a refrigerated dryer in combination with a blower purge dryer yields a surprising number of benefits. Here we add to the list.
As a “major” benefit in one application may be a “minor” benefit in another, the list is not given in any weighted order.
* The average cooling air flow rate is only 1.1%, with the maximum
flow rate being 2.3%.
Note this air is not “purge air” per se. The blower and heater provide the “purge air”, but the cooling air is dry air that is lost – it flows through the desiccant bed to atmosphere.
The cooling air begins flowing after the blower and heater have fully regenerated a desiccant bed. Recall the compressed air leaving the blower purge dryer is routed back through the air-to-air heat exchanger of the refrigerated dryer
Therefore the hot desiccant bed must be completely cooled so that the secondary side of the air-to-air heat exchanger does not suffer a “thermal shock”. Consequently
* Hybritec dryers exhibit no temperature or dew point spike:
Completely cooling the desiccant bed with dry air is what eliminates the temperature and dew point spike characteristic of other heated dryer types.
* High inlet air temperature affects only the refrigerated dryer:
Since the refrigerated dryer in the Hybritec system is selected to produce a consistent outlet dew point, as long as we choose the
correct refrigerated dryer the blower purge dryer is unaffected by the inlet air temperature.
* Hybritec dryers handle high inlet temperatures much better than
other heated desiccant dryer types:
Since the refrigerated dryer in the Hybritec system will always have some amount of additional capacity as an air compressor’s aftercooler begins to suffer from external fouling and its outlet air temperature begins to rise the capacity of the Hybritec system will not be immediately affected as would a heated purge or blower purge dryer.
Likewise, the Hybritec dryer will not be affected to the degree a heated dryer will be. For example
Note the capacity of heated desiccant dryers is severely impaired as the temperature of the inlet air to the dryer rises.
A rise of only 5°F above rated inlet temperature (100°F to 105°) results in a 13% decrease in capacity.
I.e. a 1000 cfm heated dryer becomes an 870 cfm heated dryer when the inlet temperature is 105°F meanwhile, a 5 degree temperature rise at the inlet of a Hybritec dryer will have no measurable effect on its capacity.
This is why:
The refrigerated dryers in a Hybritec system are our standard energy-saving designs. To keep their pressure drop to a workable level as part of a “two-dryer” system, they are rated in the Hybritec system for much less flow than they are as a “stand-alone” dryer.
This means, in the Hybritec system, we don’t want to “overflow” the refrigerated dryer for the reason of pressure drop, but, we can “over-temperature” the refrigerated dryer.
   
For example the smallest Hybritec model has a TG 301 Dual Control refrigerated dryer. As a “stand-alone” dryer, the TG 301 is rated at 1000 cfm for a 39°F dew point. In the Hybritec system it’s rated for 706 cfm.
Again, this is for the purpose of keeping the overall system pressure drop manageable, but clearly it allows for the inlet air temperature to rise above the rated 100°F in fact, all Hybritec dryers can operate without capacity loss at an inlet air temperature up to 110°F.
Note that an inlet air temperature of 110°F will reduce the capacity of a heated desiccant dryer by 26%! Now our 1000 cfm heated dryer becomes a 740 scfm heated dryer when the inlet temperature is 110°F.
Consequently a Hybritec dryer allows much more time to correct the cause of rising inlet air temperature than other types of heated dryers allow.
* Routine maintenance of the blower purge dryer in a Hybritec system
is very convenient.
Having the ability to by-pass and shut down the blower purge dryer for months at a time when sub-freezing dew points aren’t necessary, permits routine maintenance, such as filter element replacement, valve rebuilds, desiccant replacement, to be performed without having to schedule air system downtime.
Consequently the need to stock these routine maintenance items is eliminated and so is the administrative cost of that function, and in addition, warehouse space is saved.
Average cooling air flow rate is 1.1% ……….. maximum is 2.3%
No dew point or temperature spike characteristic of other heated desiccant dryers
For high inlet air temperature applications, only the refrigerated dryer must be over-sized
Tolerates elevated inlet temperatures better than other heated desiccant dryers
Refrigerated dryer always has some amount of additional capacity
Perform desiccant dryer routine maintenance without having to schedule air system down time
No need to inventory desiccant dryer parts or desiccant

10. Refrigerated dryer with energy saving controls
Hybritec Combination Dryer Overview
What Else is There to Know?
The refrigerated dryer removes about 85% of the water load permitting down-sizing the blower purge dryer
Refrigerated dryer has energy saving controls
What else is there to know?
* With the refrigerated dryer doing the majority of the work, the
blower purge dryer has much smaller blowers, heaters and desiccant
beds than other heated dryer types having the same rated flow.
* The refrigerated dryers are equipped with energy saving controls.
More on this at Slide 16.
Refrigerated dryer with energy saving controls

11. Blower purge dryer with energy management control
Hybritec Combination Dryer Overview
What Else is There to Know?
16 hour cycle time – 8 hours drying, 8 hours regenerating
Desiccant bed is cooled by dry air to eliminate dew point spikes
Blower purge dryer is equipped with Energy Management Control, matching energy consumption to demand
* The 16 hour cycle is what gives us the time to regenerate the
desiccant and then completely cool it with a low dry air flow rate.
Regeneration consists of 4 hours of blower and heater operation to dry the desiccant bed, with 4 hours allotted to completely cool the bed. Complete cooling eliminates the dew point spike characteristic of other heated dryer types.
* The blower purge dryers are equipped with our Energy Management
Control.
The Energy Management Control will keep a tower on-line until its adsorptive capacity has been fully utilized, reducing the frequency with which regeneration needs to occur.
Blower purge dryer with energy management control

12. Less thermal cycling than other heated dryers
Hybritec Combination Dryer Overview
What Else is There to Know?
Desiccant life is much longer than for other heated dryers due to:
A) Less thermal cycling (towers switch no less than every 8 hours)
B) Magnitude of the thermal cycling is greatly reduced (250°F regeneration temperature versus 380°F to 425°F)
* The longer desiccant service life of the Hybritec dryer results
from two conditions:
First, there is less thermal cycling of the desiccant.
The desiccant beds of Hybritec dryers are heated and cooled half
as often as in other heated dryer types. Recall Hybritec dryers
regenerate every 8 hours versus the 4 hours typical of other
heated dryers.
And second, the magnitude of the thermal cycling is reduced.
The typical regeneration temperature for Hybritec dryers is 230°F
to 250°F. At the end of drying when regeneration begins, the
desiccant bed is at a temperature of about 40°F. Therefore the
temperature change of the desiccant during regeneration is about
200°F (40°F to 240°F).
The typical regeneration temperature for heated dryers ranges from
380 to 425°F. The desiccant bed of a heated dryer will be about
125°F when regeneration begins, therefore the temperature change of
the desiccant can be as much as 300°F.
Less thermal cycling than other heated dryers

13. What Else is There to Know?
Hybritec Combination Dryer Overview
What Else is There to Know?
Single Skid Models
Eleven standard models with capacities from 706 to 5,295 scfm
Models available to 7,000 scfm
All models 460 VAC/3 phase/60 Hz
* We have eleven standard models, but we can design a single Hybritec system for flow rates up to 7,000 scfm.
* One power supply is available at this time, 460 volt, 3 phase,
60 Hertz. If you have a 575 volt application let Project Support know.
Note the dimensions for the “two skid” models are for the fully assembled dryer.
Drawings of both the “single skid” and “two skid” models appear on Slides 24 and 25.
Two Skid Models*
*Notes (Two skid models only):
Dimensions are fully assembled dryer
Height measurement the same for air- cooled or water-cooled models

14. What Else is There to Know?
Hybritec Combination Dryer Overview
* We can “mix and match” refrigerated and blower purge dryers for
off-standard conditions, such as low pressure applications. Let
Project Support know what you need.
* A unique feature of our system is the automated by-pass of the
blower purge dryer and the after-filter for summertime operation.
As standard, the by-pass valves are pneumatically actuated and controlled by a two-position switch in the electrical enclosure.
When the weather is warm enough a flip of the switch will simultaneously open the by-pass valve and close the isolation valves of the desiccant dryer. The desiccant dryer can then be de-energized.
When cooler weather again approaches, energize the blower purge dryer and a flip of the switch brings it back on-line.
As an option, summer/winter operation of the Hybritec dryer can be controlled automatically by a customer supplied temperature sensor, appropriately located to measure ambient air temperature.
The customer’s sensor is wired into the dryer’s electrical enclosure where our optional logic package will automatically
by-pass, or not, the blower purge dryer based on the ambient temperature. It works like this:
It’s late spring and it’s just beginning to get warmer. When the ambient temperature rises to 46°F, and stays there (or higher) for 96 consecutive hours (4 days), the controller automatically activates the by-pass valves taking the blower purge dryer off-line.
If the ambient temperature falls below 46°F, the controller will automatically bring the blower purge dryer back on-line, and it’ll remain on-line until the controller detects an ambient air temperature of 46°F (or greater) for another 4 consecutive days.
* Lead time is 14 to 16 weeks as Hybritec dryers are presently being
built in Germany.
We can probably do a little better than that, but quote the
14 to 16 weeks at this point. I’d rather under-promise and over-deliver.
What Else is There to Know?
Many combinations of refrigerated and blower purge dryers available
Sensor controlled changeover for summer / winter operation
Lead time is 14 to 16 weeks on all models
Sensor control option automatically switches isolation and bypass valves for summer / winter operation
Isolation Valves
Bypass Valve

15. Components and Requirements
Here we want to give you an understanding of what is needed for a true “combination” dryer such as the Hybritec.
It’s more than putting a desiccant dryer downstream of a refrigerated dryer, so we’ll look at some of the particulars for the refrigerated dryer, the desiccant dryer and the filtration.
We’ll also see some details of the interconnecting piping between the two dryers.
Before we continue, note that Hybritec dryers are complete packages – in the larger systems there is “some assembly required”, but you do not need to source any other components.
What is required of the refrigerated dryer?
What is required of the desiccant dryer?
What filtration is required?

16. Refrigerated dryer with demand control
Hybritec Combination Components and Requirements
Components and Requirements
Refrigerated Dryer
Must produce a 38°F air temperature at the heat exchanger
Must have demand control (load/energy matching) capability
Load/unload (digital scroll) refrigeration compressor (706 – 2,355 scfm)
Refrigeration compressor with cylinder unloading (2,940 – 5,295 scfm)
* We want a refrigerated dryer that will give us a 38 or 39°F dew
point.
Although we can size the blower purge dryer for any inlet air temperature, the closer we get to 38, the smaller the blower purge dryer will be and the lower its purchase and operating costs will be.
* We want load and energy matching capability for the refrigerated
dryer recall the refrigerated dryer does 7/8th's of the water
removal, so matching energy and load is very important feature for
the refrigerated dryer.
Hybritec models from 706 cfm (the smallest dryer) up to 2355 cfm are equipped with Kaeser’s Dual Control refrigerated dryer. Here the digital scroll compressor will load and unload to very closely match energy consumption to the load on the dryer.
Hybritec models from 2940 to 5295 cfm (our largest standard model) utilize a high capacity, open-frame, refrigerated dryer, equipped with reciprocating, semi-hermetic, refrigeration compressors having cylinder unloading.
When load on the refrigerated dryer decreases proportionately with the number of cylinder banks the compressor is equipped with, a bank of cylinders will unload.
I.e., if the refrigeration compressor has 3 banks of cylinders, two of those banks can be unloaded. Therefore one bank of cylinders will unload at 2/3rd's of the refrigeration compressor’s capacity, and the second bank of cylinders will unload when the load on the refrigerated dryer is reduced to 1/3rd of the refrigeration capacity.
Note this is not 2/3rd's or 1/3rd of the Hybritec dryer’s rated flow, it’s 2/3rd's or 1/3rd of the capacity of the refrigeration system this means we can expect unloading to occur before we reach 2/3rd's or 1/3rd of the dryer’s rated flow.
Refrigerated dryer with demand control

17. Components and Requirements
Hybritec Combination Components and Requirements
Components and Requirements
Refrigerated Dryer
Must be equipped with intermediate inlet and outlet air connections
Separator outlet (routes cold air to desiccant dryer inlet)
A/A HX secondary side inlet (accepts cold air from desiccant dryer outlet)
interconnecting piping to and from intermediate air connections must be insulated
Insulated interconnecting piping from blower purge outlet (HTA) to refrigerated dryer
* The refrigerated dryer must have 4 connections for compressed
air.
In addition to the primary “wet air” inlet and “dry air” outlet connections, we also need “intermediate” connections to route the cold air from the refrigerated dryer’s internal filtration (separator and oil coalescer) to the inlet of the blower purge dryer and a connection on the secondary side of the refrigerated dryer’s air-to-air heat exchanger so that the cold, dry air from the outlet of the blower purge dryer can be routed back through the air-to-air heat exchanger.
* As the interconnecting piping is carrying cold air, it must be
insulated.
As noted earlier, the Hybritec dryer is a complete package there is no need to supply additional insulation.
Insulated interconnecting piping from KFS/KOR outlet to blower purge dryer

18. Blower purge dryer with energy management control
Hybritec Combination Components and Requirements
Components and Requirements
Desiccant Dryer
Must be an externally heated atmospheric blower purge (KBD) type because:
Blower purge provides maximum energy savings
Heated purge (KED) provides modest energy savings
Heatless (KAD) provides no energy savings
* Of the many types of desiccant dryers available, the externally
heated, atmospheric blower purge is best suited for a combination
dryer system.
The blower purge dryer will provide the maximum energy savings while still providing enough dry process air to completely cool the desiccant beds after regeneration.
Heated purge dryers would provide some energy savings, but they consume too much process air and a large heater is necessary to achieve a -40°F dew point.
The heatless dryer provides no energy savings at all.
A refrigerated dryer upstream of a heatless dryer will not increase a heatless dryer’s capacity, nor will it reduce the volume of purge air necessary for regeneration.
Blower purge dryer with energy management control

19. Components and Requirements
Hybritec Combination Components and Requirements
Components and Requirements
Desiccant Dryer
Must have demand control (load/energy matching) capability:
Extends dryer cycle in proportion to load reduction
Must completely cool desiccant bed after regeneration:
Cannot have a temperature spike – why?
Must supply cold air to the secondary side of the A/A HX
Air ≈ 41°F °F pdp
Air ≈ 41°F
-40°F pdp
for 4 hours
Atmosphere
* The Energy Management Control (demand control) of the blower purge
dryer will provide the final measure of capacity control by
extending the time a desiccant bed can be on-line in proportion to
a reduction of the inlet water load.
* The desiccant bed must be completely cooled after regeneration to
protect the air-to-air heat exchanger of the refrigerated dryer
from a thermal shock (temperature spike), as well as providing
pre-cooling of the inlet air stream.
Air ≈ 39°F

20. 16 hour drying/regeneration cycle
Hybritec Combination Components and Requirements
Components and Requirements
Desiccant Dryer
Must have a long drying/regeneration cycle time:
16 hour cycle allows time for drying, regeneration and cooling
8 hours drying
4 hours regenerating with blower and heater
4 hours for complete dry air cooling of the desiccant bed
* The cycle time of the blower purge dryer must be long enough to
allow for drying, regenerating and cooling, while using a cooling
air flow rate as low as reasonably possible.
For this reason a 16 hour cycle was selected hours for drying with 8 hours remaining for regeneration and cooling.
Here note that although initially the perception may exist that a long cycle will unnecessarily increase the quantity of desiccant required for dehydration, recall the blower purge dryer in a Hybritec system manages only one eighth of the total water load.
SLIDE 20 cont.
For this reason a long cycle does not result in unduly large desiccant beds. In fact, as we saw earlier, the quantity of desiccant required per scfm of inlet air for the Hybritec dryer is significantly less than that required for other desiccant dryer types.
16 hour drying/regeneration cycle

21. Ambient air cooling flow path
Hybritec Combination Components and Requirements
* Desiccant bed cooling can only be done with dry air.
You will likely meet a customer who will tell you “Brand X cools the bed and doesn’t use any purge air”.
Some competitive heated dryer designs claim to eliminate the temperature and dew point spikes by cooling the desiccant bed with ambient air.
After regeneration is complete these designs simply turn the heater off and let the blower continue to run. This is an inefficient process, and it reduces the drying capacity of the desiccant beds.
This is why:
The moisture content of ambient air can be significant and in some locales for the majority of the year. This moisture is adsorbed by the desiccant during this “ambient air cooling” process (i.e. as the blower continues to run without the heater).
The adsorption of ambient moisture results in the release of heat into the desiccant bed. On humid days this additional heat can increase the cooling requirement of the bed by as much as 50%.
The adsorption of ambient humidity will also consume a significant portion of the desiccant’s dynamic adsorption capacity.
During the typical one hour ambient air “cooling” period the adsorption of ambient humidity on a humid day can utilize as much as 25% of the desiccant’s capacity.
The moisture adsorbed during the cooling period also results in a dew point spike when the tower is put back on-line.
Once again, only cooling with dry process air will eliminate the temperature and dew point spikes of heated dryers.
Components and Requirements
Desiccant Dryer
Must cool only with dry air:
Ambient air cooling adds moisture and heat to desiccant
Ambient moisture is adsorbed during this “cooling” process
Adsorption releases heat into the desiccant bed
Up to 25% of the desiccant’s dynamic adsorption capacity can be lost due to the adsorption of ambient moisture
Heater off
Blower on
Not Good
Ambient “cooling” air
inlet
Ambient air cooling flow path

22. Components and Requirements
Hybritec Combination Components and Requirements
Components and Requirements
Filtration
Desiccant bed must be protected from oil aerosols with KOR
Oil coalescer (KOR) must be installed downstream of refrigerated dryer separator and upstream of blower purge dryer
Is in the cold air stream
Must be insulated
Single skid model with integral cold oil coalescer (KOR)
* Of course we need filtration to protect the desiccant beds from
oil aerosols.
For this we use a KOR mounted downstream of the refrigerated dryer’s KFS separator and upstream of the blower purge dryer.
The Hybritec models that utilize the Dual Control refrigerated dryer, (these are the “single-skid” models) incorporate the “integral cold coalescer”, so the KOR is mounted within the dryer cabinet.
The Hybritec models incorporating the open-frame refrigerated dryers (the “two-skid” models) have a “pressure vessel” style KOR mounted in the section of interconnecting piping.
In either case the KOR is fully insulated and equipped with an automatic condensate drain.
KOR
Two skid model with pressure vessel style cold oil coalescer (KOR)

23. Particulate filter (HTA)
Hybritec Combination Components and Requirements
* The final need for filtration is to remove desiccant fines from
the outlet air of the blower purge dryer to protect the secondary
side of the air-to-air heat exchanger, and the customer’s process.
For this we use the 1 micron HTA high temperature after-filter.
The HTA filter is also in the cold air stream, so it is fully insulated as well, but does not need a condensate drain.
Note that Hybritec dryers do not exhibit temperature spikes, and the outlet air from the blower purge dryer is a constant forty-some degrees, you may wonder “Why a high temperature filter, wouldn’t a KPF-RF be just fine?” and you’d be right a KPF-RF would be just fine.
However, as the blower purge dryer in a Hybritec system is nonetheless a “heated dryer”, the expected perception of the customer for a heated dryer to have a high temperature after-filter is the reason an HTA is supplied.
* A final caution regarding filtration the manufacturers of
refrigerated dryers that I am aware of all state “non-fouling heat
exchangers” “pre-filter not required, etc”.
But we also know that even new air systems can produce significant particulate contamination in a relatively short period of time, depending on the choice of piping material.
Consequently I ask that you always consider the need for a KFS or KPF pre-filter for any refrigerated dryer including the Hybritec dryer especially since the Hybritec is the most expensive dryer on the shelf, and a pre-filter will be “chump-change” in comparison.
Components and Requirements
Filtration
Particulate filter (HTA) must be installed downstream of blower purge dryer and upstream of secondary side of refrigerated dryer A/A HX
Is in the cold air stream
Must be insulated
Doesn’t need to be high temperature filter but that’s what is supplied
Always consider the need for a KFS or KPF pre-filter for any refrigerated dryer, including Hybritec
HTA afterfilter
Particulate filter (HTA)

24. Models DTG 200/301 (706 scfm) through DTI 667/901 (2,355 scfm)
Hybritec Combination Components and Requirements
Hybritec Dryers – Single Skid Models
Models DTG 200/301 (706 scfm) through DTI 667/901 (2,355 scfm)
Ships as complete package
Interconnecting piping factory installed
Package fully insulated
Commissioning:
Make air connections
Install condensate drain lines
Supply power
Top View
Rear View
* Here we have the “single skid” models, 706 through 2355 cfm.
These are the Hybritec dryers supplied with the cabinet-style Dual Control refrigerated dryers, and they ship as a complete package, with interconnecting piping factory installed and the dryer fully insulated.
Commissioning of the single-skid models is no different than any other dryer. Make the compressed air connections, install condensate drain lines and supply power.

25. Hybritec Dryers – Two Skid Models
Hybritec Combination Components and Requirements
Hybritec Dryers – Two Skid Models
Models DTL 833/1101 (2,940 scfm) through DTL 1500/1755 (5,295 scfm)
Ships as two skids (refrigerated and desiccant) each fully insulated
Interconnecting piping ships as separate assembly but fully insulated
Dryers are positioned and interconnecting pipe assembly installed
Commissioning:
Make air connections
Install condensate drain lines
Supply power
HTA
KOR
* The “two skid” models , 2940 through 5295 cfm, are the units
supplied with the open-frame refrigerated dryers and ship in
three sections the refrigerated dryer on its own skid, the
blower purge dryer on its own skid, and the interconnecting piping
as a fully insulated sub-assembly.
For the field installation of the interconnecting piping, the necessary gaskets, flange bolts and nuts are supplied.
Commissioning of the two-skid models first requires alignment of the refrig and desiccant dryer skids and installation of the interconnecting piping. The compressed air connections can then be made, the condensate drain lines installed and power brought to each dryer skid.
Interconnecting piping assembly
Top View
KOR
HTA
Left Side View

26. Hybritec Refrigerated/Blower Purge Dryers
Is there anything else to know?
YES!
The whitepaper is on the Kaeser website
In conclusion please note:
The Hybritec dryer is a flexible drying system capable of consistent performance and reliability, with low operating and maintenance costs, that can quickly return its initial purchase price, and then provide years of ongoing energy and maintenance cost savings.
* Please read the whitepaper found on the Kaeser web site and contact
Project Support with any questions.
Text by Dave Phillips
Final proofreading by Dave Phillips on Sept 27, 2010.
Hybritec dryers are available RIGHT NOW …
Place your order!