COMPRESSED AIR
desiccant dryer experiences a high pressure drop, the compressor discharge pressure must be set higher, which increases energy and operating costs. The need for extra pressure requires more energy to produce, and in extreme circumstances may even require a larger output compressor to compensate for an output loss through the dryer, which in some cases can be as much as 20 per cent.
Therefore, it is important to select desiccant dryers that offer a very low pressure drop – below 0.2 bar for most models – as well as the most efficient regeneration process. In recent years, newer dryer technologies with state-of-the-art Elektronikon energy management controls, such as Dewpoint Dependent Switching, have been introduced to fulfil this requirement. The principle is simple. A dewpoint sensor will delay switching towers until the dewpoint falls. This cycle time extension can generate energy savings of up to 90 per cent.
DRYERS’ RELATIVE LIFE CYCLE COST - HEATLESS V. HEATED BLOWER When calculating lifecycle costs, a heatless desiccant dryer may be considered to be more expensive to own because it uses a substantial volume of compressed air for purging during regeneration. Typically, average purge air takes up to 16-20 per cent of the rated flow capacity of a heatless dryer. Despite these losses, the heatless dryer remains a popular choice because of its simplicity and reliability. However, if we compare the total cost of ownership between the two types of dryer over a 10-year lifetime, the heated blower purge type of unit has the advantage over the heatless desiccant method by some 40 per cent.
Although power costs for the heating process would amount to 30 per cent as opposed to zero, this difference is considerably outweighed by the compressed air output losses from the purging operation, which equates to 80 per cent of the TCO.
In terms of other component costs, there are now newer and more advanced dryer technologies, such as the latest models in Atlas Copco’s BD+ range that will guarantee a dew point down to -40°C and are capable of achieving -70°C. Furthermore, the zero purge losses achieved by the industry-leading BDZP dryers, operating with an inlet flow rate of 300 l/s with a system pressure of 7 Bar G, could see annual savings in the region of £10-14k, based on average kW/ hr rates and when running 24/7 all year round.
The overall conclusion is that for more demanding installations where a negative dew point is required adsorption dryers are regarded as the only valuable solution. But it is a solution that comes with a caveat.
Although the initial purchase price of a heatless desiccant dryer may appear to be attractive, the running costs are extremely high in comparison to other dryer systems. This type of dryer can best be used in applications with a low amount of running hours, or as a back-up unit in a compressed air network to take over in case of issues with the main dryer. On balance, it would appear that dryers featuring heated blower purge with zero purge cooling are the most economical alternative.
Atlas Copco
www.atlascopco.com/en-uk
FACTORY&HANDLINGSOLUTIONS | JUNE 2020 15
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
