Karl Uhl uses Drypoint AC adsorption dryers

Karl Uhl in Bochum, Germany, has used the special dryer technology of Beko Technologies for its cold-regenerated adsorption dryers.

The company selected three Beko Drypoint AC adsorption dryers, which are able to limit the pressure drop (including pre- and after-filter) to 0.25bar on average.

This corresponds to an improvement of more than 50 per cent compared with conventional constructions.

The energy efficiency of the Drypoint AC adsorption dryers is achieved through a range of specific measures.

For instance, Beko uses inclined-seat valves with large orifice cross sections to minimise the flow resistance.

Direct mounting of the valves at the pressure vessels, as well as rectilinear piping without redundant changes in direction, have the same effect.

Moreover, flow-optimised Clearpoint compressed-air filters, including a Bekomat 20 FM condensate drain with a filter management, are employed as standard.

The large desiccant bed also contributes significantly to the low-pressure drop.

This results in additional capacity to maintain the full dryer performance, for example, at a sudden high-volume flow or a low operating pressure.

An adjustable regeneration air nozzle allows changeovers to other operating conditions and provides additional operational reliability regarding the dosage of the correct and most profitable amount of regeneration air.

The control, with an accurately defined programme run, is said to be capable of distinguishing between a planned interruption of the operating sequence and a breakdown of the power supply.

It is claimed that the top priority during the mobile employment is process reliability.

The operational reliability of the dryers is of vital importance for the employment in mobile Karl Uhl compressed-air stations, according to the company.

During an external interruption of the power supply, conventional cold-regenerated adsorption dryers are overloaded and lose their function.

This results in water introduction into the compressed-air system.

In contrast, the concept of Drypoint AC prevents undesired loading of the dryer during a power interruption and ensures full operational capability; the compressed-air system remains dry.

In cold-regenerated adsorption dryers, both desiccant containers are under alternating pressure.

The dryers, including all fittings, are constructed to be durable throughout alternating pressure operation.

Their suitability for unlimited load alterations prolongs their service life and excludes any risk for the operator and for the entire system.

The devices are also claimed to be suitable for discontinuous operation.

Reduction of the regeneration air according to the needs of the customer takes place through coupling with the compressor, in line with the principle of the compressor synchronisation control.

A load-independent control can be retrofitted upon request.

With this control, the saving potentials of a dryer are used particularly efficiently and the operating costs are reduced even further.

A claimed advantage of the Beko Drypoint AC dryers is the retrofitability of the load-dependent control through a simple add-in.

In contrast, other manufacturers' devices normally require a costly replacement of the complete control unit.

For the specific application at Karl Uhl, the stable pressure dew point of -40C of the Drypoint AC dryers employed there is also important.

This pressure dew point is intended to ensure trouble-free operation, even during the winter months, and protects the pneumatics of the gas pumping station in the outer area against freezing.

Sven Stampa, who is responsible for the engineering/plant construction division at Karl Uhl, said: 'Ease of installation and maintenance are two particular factors that should be [focused on] where mobile compressed-air stations are concerned, because, first of all, it must be possible to arrange everything optimally here in a crowded space.

'Second, the future service personnel should be able to act without problems quickly and safely in the plant,' he added.

The Drypoint AC adsorption dryers allow for these points in many respects.

For example, all components of the devices are accessible from the front.

Therefore, demounting and mounting of the pipe bridge are not required when replacing the desiccant.

In addition, each desiccant container is equipped with an accessible overhead service sleeve.

When delivered by Beko, dryers up to a volume flow size of 800m3/hr are, as a matter of course, already mounted by the manufacturer and are ready to operate.

Even problem-free transport was taken into consideration and the devices were integrated as standard into a lift-truck-suitable supporting frame.

Stampa said: 'The sum of all these properties makes the Beko adsorption dryers ideally suited for use in our mobile compressed-air stations.' The units consist of two firmly interconnected sea containers, the sides of which are open up to ceiling height.

They form a room with a length of 6m, a width of 5m and a height of 2.5m.

The interior, which is also insulated against noise and temperature, accommodates three oil-injected, air-cooled screw compressors with an operating energy input of 22kW each.

Downstream of these, there is a 3,000-litre compressed-air tank as a buffer tank and three high-capacity adsorption dryers with the corresponding compressed-air filters, condensate drains and a dew-point control.

All installed resources are connected via signalling lines with an equipment cabinet, which is also mounted in the container.

In cold-regenerated adsorption dryers, the treatment of the desiccant takes place without the additional application of heat - via an energy-consuming heating system.

Thus, a part of the dried volume flow is diverted.

This partial flow, also referred to as purge air, expands to a pressure slightly above the atmospheric pressure and is, therefore, extremely dry.

The purge air is led through the compressed-air container to be regenerated and absorbs the moisture accumulated in the desiccant.

Via an outlet valve, the purge air finally emerges into the environment.

Cold-regenerated adsorption dryers are said to be simple to set up and are applicable even at high ambient temperatures.

They are also claimed to have fast drying and regeneration times, offering regeneration without the supply of extra energy.

However, a disadvantage of conventional standard adsorption dryers is their system-inherent compressed-air pressure drop, resulting among other things from the divergence of purge air and the function of the pre- and after-filters.

This deficiency ultimately needed to be compensated by increased compressor performance, involving a higher energy input.

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