Desiccant Air Dryer vs. Refrigerated – Compressed Air Dryer Types
A lot of industrial processes require a steady flow of moisture-free, compressed air to optimize productivity. The presence of water vapor in circulating air might alter chemical reactions involved in the manufacturing process and lead to the creation of poor-quality products.
For instance, food and beverage manufacturers routinely use air in their packing process and the retention of moisture will diminish the shelf life of the food items.
To overcome this challenge, many industrial players use air drying systems to improve the quality of air in their processes. Different types of air dryers are available with unique principles of operation.
In this article we will consider desiccant dryers and their refrigerated counterparts, comparing their functions and key features.
Compressed Air Dryer Types
One of the major issues operators of compressed air systems must contend with is air dryer selection. Most times industrial operators have difficulties deciding whether to opt for a refrigerated type dryer or a desiccant air dry. Each of these air compressor dryer types has its unique working principle, advantages, and drawbacks.
A typical desiccant air dryer setup consists of towers that contain hygroscopic material (desiccant beads) that absorb water from compressed air circulated through them. Most desiccant dryers are regenerative setups with timers and dew point monitors which determine moisture saturation levels.
Some models contain windows with indicator beads that change color to indicate water saturation. While the desiccant in one tower is used to remove moisture from the compressed air, the second tower is regenerated using either a heated or heatless method.
Heated Desiccant Regeneration
These desiccant types utilize heat to regenerate the desiccant materials. A heat source is used to rapidly evaporate water from saturated hygroscopic beads. This method of regeneration requires significant amounts of electricity to effectively carry out compressed air drying.
Heatless Desiccant Regeneration
Heatless desiccant dryers utilize a portion of the generated dried air to eliminate moisture from the saturated desiccant in a regenerating tower. A major advantage of using a heatless regenerative dryer is its energy-saving quality. Desiccant material can be efficiently dried without utilizing external energy, which helps reduce operating costs significantly.
Refrigerated Air Dryer
Refrigerated compressed air dying systems function on the principle of condensation to achieve air moisture removal. At very low temperatures, water suspended in the air as vapor will condense into liquid form. A refrigerated type air dryer facilitates this process by lowering air temperatures to very low ranges allowing most of the water in the air to be precipitated. Refrigerated air dryers come as two variants: cycling and non-cycling types.
Cycling type refrigerated dryers function similarly to typical refrigerator units. These devices possess the ability to regulate their cooling capacities to alter cooling according to compressed air demands. Regulator valves alter the flow of refrigerant through the compressor unit in response to the moisture level within the dryer setup.
This feature makes cycling refrigerated dryers efficient. Cycling air dryers may be one of three types: thermal mass, variable speed drive, or digital scroll.
This type of air dryer runs a continuous cooling cycle by constantly circulating refrigerant through its circuit independent of moisture levels. Temperature regulation is achieved using hot gas bypass valves which recirculate the refrigerant. While non-cycling refrigerant dryers are cheaper than cycling types, they are generally less efficient.
Membrane Air Dryer
These dryer types are composed of selective membrane microtubules that selectively retain water vapor. When a stream of saturated compressed air is passed through this membrane system, the moisture is retained while dry air is released at the outlet. Membrane dryers are particularly suited to isolated locations where a constant flow of compressed air is required.
NiGen uses similar membrane technology in our nitrogen generators for Oil and Gas.
When to Use Desiccant Dryer vs. Refrigerated Air Dryer
Deciding on what type of air dryer to use for your process depends on the consideration of several factors including:
- Dew point requirements
- Installation, operating and maintenance costs
For industrial drying applications where dry air is required (metal finishing, beverage, and food processing), the use of a desiccant dryer is ideal. Water vapor in compressed air passed through a desiccant dryer is more thoroughly eliminated than any other drying method.
Desiccant dryers operate at significantly lower dew points which facilitates the elimination of moisture more efficiently than a refrigerated dryer.
By comparison, refrigerated air dryers are typically operated at higher dew points than desiccant dryers. These dryer types are ideal for manufacturing operations where some degree of retained moisture (ISO Quality Classes 4, 5 and 6) is acceptable.
An additional benefit of deciding on a refrigerated air dryer is the lower overall cost of purchase, operation, and maintenance when compared to the cumulative expenditures on a desiccant dryer.
Differences Between an Air Dryer vs. Water Separator
An air dryer and a water separator differ on the state of the fluids for which they are employed. While an air dryer is designed to remove vaporized water from compressed air (a mixture of gases), a water separator (also known as an oil-water separator) operates on the principle of the immiscibility of oil and water (both liquids) to separate the two.
NiGen Has Reliable Air Drying Solutions
At NiGen we are dedicated to providing our clients with the most efficient air drying solutions best suited to their unique process needs. We offer cost-effective rental services on high-quality compressed air desiccant dryers guaranteed to cater to your specialized compressed air-drying needs.
Contact us online today to learn more about our products and services.