Superb quality compressed air is an essential ingredient for an efficient and productive plant. One crucial step to ensure quality air is drying.
When air is compressed, the moisture naturally present in ambient air is concentrated, causing condensation. A dryer eliminates this moisture before it can get into the air network, where it can wreck havoc on equipment, processes and products and bring production to a grinding halt.
There are three general types of dryers: refrigerant, desiccant, and heat of compression. You’re probably familiar with the well-established desiccant and refrigerant dryer technologies. However, there are many advantages offered by today’s most advanced dryer technology, Heat of Compression. Let’s take a quick look at all three technologies.
Refrigerant Dryers
A refrigerant dryer uses a refrigerant circuit and heat exchanger(s) to pre-cool air, refrigerate it to remove moisture vapor via condensation, and then reheat the air to prevent pipe sweating downstream. Refrigerant dryers can lead to a pressure dew point (PDP) as low as +37.4°F/+3°C for many applications where there is a need for dry air. They can be used at different pressures and consume no processed compressed air. The main types of refrigerant dryers, include:
- Direct expansion dryers
- Fixed speed non-cycling dryers that run continuously regardless of varying load conditions
- Fixed speed cycling dryers that shut down at lower loads to save energy and restart when required
- Variable speed dryers that cycle automatically according to demand
Desiccant Dryers
A desiccant dryer consists of two towers filled with desiccant such as activated alumina, silica gel or molecular sieve. While one tower is drying compressed air, the other is being regenerated. Desiccant dryers can achieve dew points as low as -40°F/-40°C and -100°F/-70°C. The three types of desiccant dryers, include:
Heat of Compression (HOC) Dryers
Compressing any gas, including air, produces heat. Heat of Compression drying recycles heat energy from the compressor to regenerate the desiccant. An HOC dryer requires only a very small amount of electric power for regeneration, and operation is continuous and fully automatic. When used in place of a refrigerant or desiccant dryer, it also eliminates the related power consumption (direct or purge). Atlas Copco’s unique zero purge technology consumes no compressed air due to purge, so there is no need to oversize the compressor installation to compensate for purge losses.
Later this week, we’ll discuss how to determine which dryer is right for you.
