Technology

Controlling humidity is important for human health and for comfort, for this reason air humidity control technology is very important. It is vital for many processes and the use or storage of certain products. Dehumidifiers are used wherever one wants to control humidity, not just in very humid or damp areas.

By classifying your application according to the solution we want to provide, we have some examples:

• Corrosion prevention:
  • Using a DH can save the security and armed forces millions of Eurosin the storage of materiel such as aircraft, tanks, and naval vessels.
  • It helps to prolong the life of printed circuits in the computer hardware which might otherwise suffer micro-corrosion.
  • It reduces the servicing costs and increases the rapid response availability of power turbines.
  • It enables the batteries, including lithium batteries, to be produced on an industrial scale. Lithium corrodes at a very low ambient humidity.
• Condensation prevention:
  • Dehumidifiers enhance visibility and conditions for sports, as well as prolonging the durability of sports facilities with ice rinks.
  • Water treatment plants cut maintenance costs and prevent serious corrosion problems if the humidity in control and pumping rooms is controlled.
  • Large metal parts in ships, pipes and off-shore structures withstand sea conditions if they are painted in a dry atmosphere.
  • Dehumidifiers can boost production of plastic injectors that produce toys, bottles and automobile parts.
• Preventing micro-organisms from forming:
  • The life of priceless works of arts can be extended and their appearance preserved by controlling the humidity of their surroundings.
  • Plant and crop seeds can be conserved to be used when needed in the sowing season or to preserve the species.
  • Some foods such as milk powder or cocoa can be stored for longer without spoiling.
  • Brewers can store their raw materials and produce their beer without the quality being impaired when the air humidity is controlled at various stages of the process.
• Storage of hygroscopic materials:
  • Sweets can be manufactured and conserved in their wrappers without deteriorating thanks to the dry atmosphere.
  • Domestic and car windows and windscreens will not shatter thanks to a hygroscopic membrane that requires very dry air when it is being applied in layers.
  • Semi-conductor production (with very hygroscopic polymers) and the manufacturing of chemicals and pharmaceuticals can be carried out to the highest quality standards in an atmosphere with controlled humidity in what are known as clean rooms.
  • Sugar can be transported and stored without blockages thanks to dry air jets.
• Drying products at low temperatures
  • The coatings used on sweets and tablets can be made on an industrial scale thanks to dry air.
  • Tomatoes and milk can be converted to powder thanks to a highly efficient drying process.
  • The proccesing of the serrano ham is aided by our dehumidifiers: The curing can take place in less time and it is not necessary to do it in zones of high heights (the mountain).
  • Gelatin capsules are a relatively new way of delivering medication and can be mass produced thanks to these systems.

It is important to understand the difference between absolute humidity and relative humidity. Relative humidity expresses the relationship between the amount of humidity in the air and maximum amount of humidity that the air can support at a certain temperature. It is always contingent upon this temperature. Air can contain much more humidity when the air is warmer. (Illustration showing a glass of water from the BTI) Specific humidity expresses the humidity content in grams per kg of dry air. This magnitude is separate from the temperature. Our dehumidifiers are designed to dry air down to very low levels of humidity, removing from the nominal air an average of 5 grams of vapour per kg of dry air.  This is contingent upon the nominal flow (more drying if we move less air), the reactivation energy (the greater the energy the dryer the air) and the conditions of the air as it enters the unit (the more humid the air, the more it is dried).

We have manufactured units that dry air up to  a dew point of -70°C. This is required in special applications such as semi-conductor or lithium batteries manufacturing.

It is true that these units consume quite a lot of energy but more than 80% of that energy is calorific. If the installation has residual heat such as steam, heating oil or hot water, it can be taken from that. It can also be produced through primary energy with units reactivated by a natural or propane gas burner.

For all units we can reduce the energy consumption with alternative methods. In our compact ranges, we have purge sectors in the rotor that leverage the wheel’s heat inertia to reduce the heater’s energy consumption. Also, the very hot dessicant of the first angles does not dry sufficiently and this leads the heat to be recovered here.

In our A series we include plate heat recuperators and in the DFRIGO series the plate recuperator is fully integrated between flows also with the aim of reducing the injection temperature.

The advantage of silica gel in solid form and constant reactivation is the reduction in the preventive maintenance workload:

• Supervision and filter-changing.
• Checking the tension and replacing the belt of the rotor traction traction.
• Supervision of the condition of the rotor surface. Where applicable, cleaning the rotor surface (compressed air and water) if required.
• Replacing the joints between sectors of the rotor and perimeter.

Faults may be caused by a failure of the reducer motor or to some resistance of a blown heater. The most serious faults are highly unusual in our equipment.

The silica gel rotor has an unlimited useful life. This is the big difference between it and the absorption-based dessicant systems that use lithium chlorate. Users of these rotors know that unfortunately their useful life does not usually last more than 5 years.

The most usual reason for having to replace the silica gel rotor is under-performance when receiving dirt in the process air that ends up encrusted inside the wheel and reduces its performance. Proper filter maintenance eliminates this possibility and a good cleaning operation can solve this problem. Instructions on this are included in the manual.

In addition, the rotor body is made of glass fibre and can be damaged by an impact with mechanical objects.

Dehumidifiers are generally dimensioned by the humidity load they have to dry in kg/hr. Therefore, we must quantify the loads:

• Ventilation (knowing the most unfavourable status of the outside air humidity).
• Seepage (being mindful of the above and with experience).
• Humidity produced by humans (according to the activity and clothing).
• Humidity emitted by water surfaces.
• Humidity emitted by products.
• Humidity emitted by diffusion from walls and floors.temperature using integrated post-heating coils.

Once we have quantified the loads we must be clear about the set point requested (T and RH or RP, never just RH). According to the power source for the reactivation (electricity, steam, natural gas, etc.) where the dehumidifier is placed in the room and whether or not the temperature is treated as part of the process, we can define the solution precisely. The existence of cooled water in the installation can help to reduce the size of the unit needed by integrated pre-cooling coils (mechanical pre-drying) and can also help to control the temperature using integrated post-heating coils.

The drying capacity of the units is directly proportional to the power we feed to the reactivation of the dessicant rotor. The greater the power supplied, the greater the unit’s drying capacity. The humidity probe must be linked proportionately to the control signal of this reactivation coil. Sensitive temperature regulation must be performed only via the control of the sensitive treatment coils downstream of the rotor but integrated in our unit and managed by our regulator. The pre-treatment coils can also be controlled with the Fisair regulator.

Maintenance of Fisair dehumidifiers is very simple and does not require special training. All that is needed is to read the manuals carefully and use original Fisair replacement parts. These can be sourced from distributors of the Fisair international partners: www.fisair.com/contact which also offer specialized after-sales service. Fisair responds to requests for replacement parts in less than 24 hours.