Dehumification System Applications

When hygroscopic ingredients are weighed and mixed, it is important that the products' weight is not influenced by absorption of moisture from the surrounding air.

In powder form, moisture will affect the flow, caking, compaction and strength properties of the manufactured solid form.

Yeast, moulds and bacteria require a certain amount of moisture to support growth. Controlling relative humidity is probably one of the most important factors in maintaining a sterile environment. A cool dry environment generally enables faster production, a better quality product and a longer shelf life. The majority of tableting processes require humidity control between 20 and 35%RH at 21 to 24°C.

Moisture Loads

In most pharmaceutical systems, the greatest moisture load is from the fresh air component which is typically between 5 and 20% of the total supply air volume. Depending on moisture gains across the room, it may only be necessary to “deep dry” the fresh air component using a pre-cooling coil (> 10°Cdp) and a desiccant dehumidifier (< 10°Cdp).

Dehumidifier capacity is controlled by an RH sensor installed in the return air duct. This simple design is often adequate to maintain the required RH in the room.

Air conditioning systems with a low fresh air volume and rooms with excessive moisture gains from high infiltration rates (negative room pressures), frequent door usage, product load, etc, will normally require all the fresh air and a proportion of the return air to be dried.

In the confectionery industry the quality of the finished product is paramount. Close control of air humidity during the various manufacturing processes is now considered essential to maintaining these high standards.

Fat blooming and sugar blooming are two common problems when both manufacturing and storing chocolate. Both kinds of blooming can occur a few hours after production, and also some time during storage if the ambient air is too humid. The relative humidity should not exceed 60 % RH during manufacture and storage.

Using dry air when cooling chocolate products in cooling tunnels prevents condensation forming on products and inside the tunnel. This enhances hygiene levels and products do not become sticky or stick to  the conveyor belt.

It is necessary to maintain control over the ambient humidity when sugar-coating products. Quality is impaired if the ambient humidity is too high, and products readily stick to one another. During the damp season, the humidity also means that the drying time– and hence also the coating time – is extended. With dehumidification, you ensure that the same drying time and quality are applicable all year round.

Package

The packaging process can be improved using dry air as this ensures that products do not become stuck on machinery or wrappings. Boxes and stacking trays become stuck in packaging machines if they are damp.

Sugar

Sugar becomes sticky or even dissolves if the ambient humidity is too high. When storing sugar loose or in sacks, therefore, it is a good idea to control the ambient humidity on the storage premises. If sugar is stored in silos, these silos can be ventilated with dehumidified air.

In the food industry the quality of the finished product is paramount. Close control of air humidity during the various manufacturing processes is now considered essential to maintaining these high standards.

Dry products

When manufacturing or storing dry products such as soups or broths, it is important to dehumidify the premises as the ingredients might otherwise clump together when being mixed or in their packaging. This assures production quality and allows the same production rate to be maintained all year round.

Spray towers and pneumatic conveyor systems

The main air can ideally be predried when drying products in spray towers (and also fluidised beds). This prevents seasonal variations in production capacity. The product is cooled in a cooling stage before being packed; rehumidification of the product is prevented if the cooling air is dried.

Air used in pneumatic systems can be dried in order to prevent rehumidification and conveyor blockages. If the air is not predried, there is a risk of rehumidification of the dried powder when it is cooled.

When storing cheese for ripening, maintaining temperature and humidity levels within tight tolerances is important to the quality and flavour of the cheese.

Drying

When drying food, a higher, more consistent level of quality is achieved if drying takes place at lower humidity levels. This enhances the quality and retains even more of the flavour.

Meats and meat processing require strict hygiene so as to be able to guarantee the quality of the products. With dehumidification you can achieve enhanced hygiene standards, fewer production standards and no condensation. 

Meat processing

As meat products are processed on cold premises, condensation often forms on ceilings and cold surfaces.  This condensation can result in dripping from the ceiling, with subsequent reductions in hygiene standards. 

Dehumidification is used to regulate relative humidity so as to create the right indoor climate. The temperature can also be controlled via DST dehumidifiers.

Dry air gives slaughterhouses a number of advantages:

• The ceilings are free of condensation. The risk of contamination is reduced greatly if relative  humidity is kept below 65 -70% RH

• The premises dry more quickly after cleaning, keeping downtime to a minimum. 

• A more pleasant working environment for the people working on the premises.

• No slippery floors or harsh indoor air.

• When the problems with condensation are rectified, less cleaning is needed in refrigerators, for example.

Without dehumidification the ambient air entering the building through the conveyor feed apertures will lead to ice and frost formation which will eventually lead to the malfunction of the conveyor machinery and associated proximity / optical sensors. Frost build up on the product is undesireable. 

The icing, fogging and frost problem can be virtually eliminated by the installation of a desiccant dehumidifier to provide dry air into the plant. This will create a much safer and more pleasant working environment resulting in increased productivity. Down time for defrosting and cleaning will be drastically reduced. The working environment will be more worker friendly.

A dehumidified environment will pay for itself in many ways.

Dry air storage is used for a variety of materials, such as corn, coffee, powders, sugars and electronic equipment. Using air is far more economical than heating and ventilating large storage areas.

Corrosion

Merchandise manufactured in materials such as iron and steel, demand low humidity. Vehicles, aircraft, machines and tools do not rust if the surrounding air is kept at a relative humidity below 50%.

Mould

Organic materials such as leather and paintings, contain micro-organisms. These can develop into fungus and mould, but will not occur if the relative humidity level is kept below 70%.

Bacteria

Bacteria requires a high humidity to survive and to multiply. If the humidity level of the surrounding air is kept below 50%, most bacteria will not survive. The limit is especially important when storing food products which are susceptible to bacter

Injection and blow moulding operations utilise thermoplastics which are heated to plasticity and shaped into forms using a mould. During this process, if moisture is present in the raw material it boils, releasing vapour that can cause both structural and cosmetic imperfections to the finished product.

To ensure that the end product is defect free, raw materials must be free of moisture before being processed. Many of today’s plastic resins are hygroscopic (high affinity for absorbing moisture).

To reduce forming time and increase production volumes, the majority of systems employ the use of chilled water to reduce the mould temperature. Generally, the cooler the mould, the faster the process cycle. However, operating at low mould temperatures will create problems with condensation, especially in summer. This can result in unacceptable water marks on the product as well as corrosion of expensive moulds and guide pins, necessitating repair or replacement.

The problem can easily be overcome by simply increasing the mould surface temperature. However, as this will result in longer cycle times and reduced output, it is not the ideal solution.

By incorporating a desiccant dehumidifier the air dewpoint can be controlled. Lower mould temperatures can then be achieved without the risk of condensation.

Desiccant dehumidifiers are also used when storing expensive moulds. There is no need to waste time and effort greasing the moulds prior to storage. If the relative humidity is maintained below 45%, moulds can be stored safely without risk of rust formation (irrespective of store temperature).

Places in a power station where drying is recommended during shut down include:

Generator - it is important to keep the windings dry to prevent corrosion and ensure a shorter starting time. Dry air can also supplement generator heaters.

Condenser - must be kept dry after flushing to allow recoating of water boxes and tube plates.

Re-heater - tubes are thinner than super heater tubes and more susceptible to corrosion. Inter-granular attacks on austenic stainless steel can be minimised using dry air.

Feed & Condensate pipes - important to eliminate internal corrosion on pipes as oxides can contaminate feed water.

Boiler - surface temperatures of fireside boiler tubing drop below the dew-point and form condensate. The condensate reacts with sulphurous parts of the ash and acid deposits and hydrolyses, forming a highly acidic solution. The end result is rapid, localized attack of the metal surface.

Reactor vessel - Where access is

 required, dry air is required to purge out CO2, eliminate corrosion and to dry the graphite prior to refilling with CO2

In water works and pumpstations, there will often occur problems with condensation on cold surfaces.

A DST dehumidifier will reduce the humidty in the air and the result will be a humidity problems in water works and pumpstations often occur during the months with highest humidity.

With a controlled level of humidty, there will be no condensation, and therefor no problems with corrosion or a poor indoor climate. A lower humidity also improves general safety of electrical equipment.

Moisture will not condense on a surface if the air in contact with it has a dew point lower than the surface temperature.

In the early 70's, NATO organisations began to use desiccant dehumidifiers to protect valuable military equipment against degradation from airborne moisture.

This has now become routine for militaries all over the world. Inactive ships, tanks, aircraft, weapons and supplies are maintained in a state of readiness by dry air storage.

This technology provides an increased combat readiness whilst significantly reducing maintenance costs.

 • The stored equipment does not require regular inspection or maintenance, thereby saving on both time and human resources

 • There will be negligible material degradation and sensitive electronic equipment is kept in good working order, ultimately increasing combat readiness.

Water damages often occurs in narrow and cold buildings. In those kinds of environments, the equipment must be robust, easy to install and easy to handle.

All DST dehumidifiers for water damage restoration are in stainless steel and are developed to endure tough environments.

They also have standard sized hoses to simplify air connections.

• The smallest DST dehumidifier DR-010B is only 12 kg.

• The Aquasorb A-30B/Bp does not need any wet air outlet since it condenses out the water into a container.

• For serious water damages, Recusorb R-060BR is often used, which can be equipped with a wagon.

DST can also offer RZ rental units (RZ units) for rental business in cases of very serious water damage and when there is aneed for very large quantities of dry air.

There is tremendous potential to utilise the benefits of dry air in the shipping industry. Above all, you can minimise downtime in port for tankers that are changing cargo. A mobile dehumidifier will shorten the drying process.

Dehumidifying cargo holds

Hygroscopic cargo such as coffee, tea, tobacco, paper and powder are particularly affected by humidity during global transit. As sea temperatures fall, air in the cargo hold cools causing a rise in the internal relative humidity - often to the point where condensation is formed.

Dehumidification of oil platforms and ships

Combined with the aggressive nature of salt, humidity is a major cause of corrosion to marine structures. It can dramatically reduce the lifetime of machinery and seriously affect the reliability of electrical equipment.

Whilst it may not be practical or necessary to protect equipment in constant use, humidity control should be considered during lay-up or refit. Machinery, empty tanks and holds, accommodation, offices and other unheated spaces will certainly benefit from environmental protection by dehumidification.

Moisture is a major enemy in the fight to preserve antiques and artefacts that form an important part of our heritage.

Paintings, furniture, linens and other organic materials contain micro organisms which thrive and multiply in high humidity conditions - invariably causing irreversible damage.

Valuable metallic objects and structures stored in museums are susceptible to oxidisation and corrosive degradation.

To avoid expensive and complicated restoration costs, environmental conditions (which are naturally aggressive), will require adjustment and control.

If the relative humidity is maintained within limits using a desiccant dehumidifier, no micro organism or bacteria activity will occur and metallic surfaces will be free from corrosion.

Storage tents are used to quickly gain extra space and for storage. Customers renting a plastic hall, expect their material to be protected from damages such as corrosion or rust.

In a plastic hall, condensation easily occurs in the ceiling. When it drips down, it will damage material in the storage.
 
With a dehumidifier, you can control the level of humidity in the tent. To avoid mould, the relative humidity should be kept below 70 %, and to avoid corrosion, the relative humidity should be kept below 50%.

Corrosion damage can lead to large costs in bridge construction worldwide. The bridge construction is assured against corrosion through development of an environment that keeps a maximum of 50% RH around the steel construction.

Corrosion of mild steel components and high tensile support wires can soon compromise structural integrity resulting in safety issues, costly traffic restrictions and ultimately bridge closure.

The girders, on which the tracks lay upon, can be protected against corrosion by the circulation of dry air through the truss, whereas the corrosion protection paint is expensive and demands maintenance.

Painting the bridge increases the weight. Even affixed constructions can be dehumidified instead of using corrosion protection paint. A dehumidifier demands minimal maintenance and saves a lot of time compared to personnel applying corrosion protection paint. Corrosion protection is also necessary in spots very difficult to reach and dry air is often the preferred method.

Since wood swells as it absorbs water, and contracts as it releases water, both it's moisture content and dimensions are influenced by the relative humidity of the surrounding air.

Damp wood is heavy and difficult to work whilst dry wood will warp and split.

The desired moisture content of both softwoods and hard woods is dependent to some extent on the type of wood, and on the intended use.

Moisture content of wood

The aim of dehumidification in wood stores for the wood products industry is always to attain a constant indoor climate so that the supplier of wood products can guarantee the high, consistent quality of its goods for end-customers. Recusorb works with heat recovery and can use steam, electricity, gas or hot water as regeneration power source. For companies with access to hot water, it can be especially beneficial that Recusorb works with heat recovery, to save energy-costs.

Wood moisture content is equal to the weight of water contained in the wood divided by the oven-dry weight of the wood, expressed as a percent. A wood moisture content of 8 to 10% is achieved at 40% to 55% relative humidity. Heated wood stores have an unpredictable effect on the wood's moisture content as temperature influences the relative humidity - albeit uncontrolled.

A desiccant dehumidifier maintains the store relative humidity within the desired range irrespective of the store temperature. The climate will remain constant and the wood will be maintained at the correct moisture content.

Suppliers wishing to guarantee the quality of their wood product should consider using desiccant dehumidifiers in their stores. If wood is stored in a humidity controlled single skin PVC building, there is the added advantage of low air infiltration rates (low moisture gains), so operating costs are kept to an absolute minimum.

Seibu Giken DST technology is effective for Supermarket and refrigeration efficiency by:

- Maintaining store humidity down between 30-50%rh

• Improve shopper comfort

• Save energy with payback between 1-3 years

• Reducing HVAC energy with Dedicated Outdoor air System design

• Reducing compressor power with low humidity (reduce 10% rh reduce power in 10%)

• Reducing defrost and strip heat

• Reduce fan energy and duct size

• Heating cold isles with dry air

• Reverse cycle heating

Many configurations are available to suite local utility costs and HVAC designs.

- Econosorb  EF series is a “World s First” Desiccant DX refrigeration system developed by DST in 1985 and Is able to reduce 22g/kg in Hong Kong to 8g/kg and 6g/kg if required with a commercially priced Desiccant DX system. Using waste condenser heat for extra capacity at low dewpoints.  (Usually 0.4kWi/L)

- Consorb CF series is a conventional desiccant system which can use waste heat solar gas or electric to dehumidify to dewpoints to 3.5g/kg.  (Usually 1.7kW heat/L)

- Frigosorb can be used where wet air is inconvenient to be removed (Usually 0.6kWi/L)

Once we understand your system we can offer practical ways to customise and optimise dehumidification of your supermarket system.