Service life of desiccant in adiabatic regenerative dryer
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Colleagues, I have a question to ask. The desiccant in the heat-regeneration dryer used by my company has been in use for 6 months, and when it was opened, it was found that a small portion of the desiccant had turned yellow or iron-red. Is this caused by the moisture and oil contained in the unpurified air? The desiccant in question comes from a manufacturer in Nantong City, and no instructions were provided regarding its use. What is the typical usage period for the desiccants used in your respective organizations?
I’m not sure whether your company uses silica gel or microspherical alumina as desiccants in its heat-regenerative dryers. Generally, an oil remover should be installed before the regenerative dryer to prevent oil from contaminating the desiccant. If the desiccant turns yellow or iron-red, it is due to moisture and oil present in the unpurified air, which causes the desiccant to become ineffective； Silicone has low strength; it breaks down when exposed to moisture, which reduces its service life and requires replacement after each cycle ； Microspherical alumina has good strength; as long as it is not contaminated by oil, it can be used for over 2 years without any problems. The key is to operate the oil remover before the dryer properly.
The desiccant used in our company is activated alumina in the form of balls, with a particle size of around 5 mm. We used it for over 2 years from the time it was first put into use, but during that period we noticed that the unpurified air contained water and oil. This was particularly evident in winter, as it sometimes caused some of the pipelines to freeze. In the past two years, we have shortened the duration of use, but we still find water in the unpurified air
It depends on the configuration of your piping system: 1. Whether there is an oil removal filter, 2. a water removal filter, and 3. where the equipment is used. However, based on what you’ve described, it seems that the pipes may not have been treated to prevent rusting, nor has the interior of the dryer been protected against rust. Generally, desiccants can be used for 2-3 years without any problems
There must be an oil remover in front of a heat-free regeneration dryer; otherwise, the desiccant will become ineffective very quickly. Your situation indicates that the desiccant has already partially lost its effectiveness. Activated alumina balls are commonly used as desiccants, while high-quality heat-free regeneration dryers use molecular sieves for this purpose. The normal service life is 5 years.
We also have oil removers here, but I’m not sure about their effectiveness in removing oil. Waste water is discharged regularly, and it seems to contain a considerable amount of oil. The dryer is a finished product without any access holes; it’s a product from Nantong. Judging from the desiccant taken out from its interior, no anti-corrosion measures have been applied inside it.
If, as mentioned above, the wastewater contains a high amount of oil, then there may be a problem with the air supply. Also, check whether the oil removal filter element that has been installed is contaminated, which may result in poor oil removal performance.
How can one know that the oil in the compressed air has been removed?