 |
|
On other pages here we’ve talked about removing water from the compressed air via a number of different methods including after coolers and refrigerant dryers.
Now we’ll explore some additional options.
Desiccant Dryers
Some applications require the compressed air to be 'bone dry'. The air will have a dew point down to the minus temperatures, in some cases down to -100 deg. F.
This means that as long as the temperature in the system is higher than that -100 deg. F, no more water can condense out of that air anywhere in the plant.
There are costs associated with this type of system, and, as we always say, you only want to treat your air to the level of dryness that you need.
Desiccant dryers can be relatively small, in-line type, or twin tower units with regenerative capabilities for high compressed air-flow systems.
Simple, in-line desiccant dryers are uncomplex, relatively low cost, are easy to install, and work! They contain a desiccant chemical that is consumed as water is adsorbed.
You would install the in-line desiccant filter immediately just before the application for air.
It's recommended that you install a general purpose filter just upstream from the desiccant, as the G.P. filter will remove any free water before it can into, and overload, the desiccant unit. The desiccant will remove free water, but it's preferred application is to remove water vapour, and the dry the air to the point where it's dew point will be well below the temperature of the application. If it does this, there's no more condensation downstream from the desiccant dryer.
Some in-line desiccant dryers need to be drained regularly as their function leads to a pool of water and desiccant chemical in the bottom of the housing, which, if not drained, will ultimately destroy the unit's capacity for drying air.
The in-line units will require periodic charging with the desiccant itself, and this means that you have to know when to do it, and of course someone has to do it.
This is an important maintenance issue, and is one of the down-sides of the in-line systems, particularly in the many industries that, of late, have more maintenance work to do in the plant than their down-sized maintenance staff can cope with.
If you need "bone dry" air, in your application, there's another alternative.
 |
The twin tower desiccant dryer has two desiccant dryers built into one system. Periodically, usually based on time, the system will cause a valve to shift, and the air from the compressor will change flow paths from one tower to the other.
Once air is flowing through the new path, dry air from that tower is used to "regenerate" the desiccant in the now unused tower. In this case "regenerate" means to dry the desiccant in the tower.
After a certain time period, the valve shifts again, and the compressed air flows to the tower with the dry desiccant, and the dry air is used to "regenerate" the desiccant in the other tower.
These units are sized based on the expected flow rates of your compressed air system and the level of dryness required.
They are often classified as heatless, meaning that no external heat is generated to help dry the desiccant. Some units do heat the air to speed the drying process.
In time, these twin-tower units will require maintenance. In the shorter term, they provide very dry air for the whole plant, negating the need for in-line units to be placed throughout the whole facility.
To top
