Moisture is the enemy. Keeping the compressed air you utilize moisture-free is critical to the lifespan of your compressed air equipment. There are two predominant ways to dehydrate the air you use: Refrigerated Dryers and Deliquescent Desiccant Dryers. Van Air Systems’ single tower deliquescent compressed air dryers are ideal for a wide range of applications. These compressed air dryers protect against freeze-ups in the winter and excessive moisture in the summer. Van Air Systems’ Compressed Air Dryers may be installed inside or outside and are ideal for low or high-pressure applications. Also, with no moving parts or electrical components, deliquescent compressed air dryers can be applied in dirty, dusty, and hazardous locations, too. However, choosing between a refrigerated or a deliquescent air dryer is dependent on the acceptable moisture content or pressure dew point (PDP) requirement for your application.
Refrigerated dryers are the most common type of dryers used in the service and manufacturing industries. Companies that only require pressure dew points of 40-60 degrees F(ISO Quality Classes 4, 5 & 6) are the companies that mostly use refrigerated dryers. If your application requires ultra-dry air or is likely to operate in below-freezing conditions, desiccant air dryers are a necessity. When compared to refrigerated dryers, deli(deliquescent) single tower dryers (otherwise known as pressure vessels, receiver tanks, or membrane dryers) are extremely competitive on performance and maintenance expenses with less moving parts. In most cases, a deliquescent dryer can achieve similar dew points as refrigerated dryers.
There are two types of refrigerated dryers: cycling and non-cycling. These dryers work by dropping the inlet temperature and condensing the moisture in the air down to ~40–50°F dew point. Refrigerated dryers cannot achieve temperatures less than freezing, so they are slightly limited in just how much moisture they can remove. They chill the compressed air to 30–40°F at which water vapor is condensed into a liquid and then expelled from the system via water-traps and automatic drain valves. The cool dry air then is typically re-heated to around room temperature before exiting the dryer and going into production lines, reducing condensation on the compressed air pipes. Refrigerated dryers require power and must remain indoors for proper operation. They also cannot achieve dew points below freezing and often set their dew points above 40 degrees to prevent freezing up the refrigerated dryer.
Some desiccants absorb moisture, but some – like what we’re discussing in this article – are used to control the amount of water in gaseous streams by absorbing the moisture and changing the physical state of the desiccant into a liquid brine solution. As the wet gas passes over the top of the deliquescent desiccant, the moisture in the compressed air will coat the surface of the tablet. As more moisture is attracted to the tablets, the tablet will start to slowly dissolve one layer at a time. Think of an Everlasting Gobstopper–the tablet will shed layer after layer until the entire tablet is dissolved and you have a puddle of liquid brine solution in the drain reservoir of the pressure vessel. Deliquescent desiccants are a dependable, cost-effective, and energy-free tool for a wide range of industrial drying applications. One type of desiccant known as Dry-O-Lite, is a chemical drying agent specifically formulated by Van Air Systems for single tower deliquescent air dryers and natural gas pipeline dryers. Dry-O-Lite is a dense hygroscopic tablet that absorbs water vapor from streams of compressed air or gas. In a Deli Dryer, wet compressed air enters the bottom of the dryer and flows upward through a bed of deliquescent desiccant, which absorbs moisture as it slowly dissolves. Condensate drops to the bottom of the vessel to be drained. Dry compressed air would then exit the top of the vessel. A truly unique feature of a deli dryer is that the customer can use multiple dryers in series to achieve even lower dew points.
One of the benefits of deliquescent air dryers over refrigerated dryers is that it can operate at a consistently low dew point. Deliquescent desiccants are based on a principle called Dew Point Suppression. Just like the name indicates, these dryers will reduce the inlet dew point based on the type of deliquescent desiccant being used. By using dew point suppression, we can achieve ultra-low dew points simply by sending cooler air into the deli dryer. For example, our desiccants will suppress the inlet dew point by 20°F for Dry-O-Lite (DOL for short) all the way down to 63°F.
The main benefit to using deliquescent dryers are when placed outside. As inlet conditions change, dryers will adapt to those changes and keep your dew point well below ambient conditions, never needing to worry about moisture in your lines again. Van Air System has a variety of deliquescent desiccants that they manufacture based on the needs of your application.
Not only do refrigerated dryers cost more for the initial purchase, but they also prove to be very costly to operate throughout their lifetime. A brand new refrigerated dryer can expect to operate only a few years before receiving some form of necessary, and often costly, maintenance. The life span of these dryers is very dependent on where they are installed, and how they are maintained. A neglected system, installed outdoors in a rugged environment such as our ready-mix plant, can expect to ingest cement dust and will most likely overheat due to the dust accumulating on the heat exchanger. If these same dryers experience winter temperatures below 39°F, you can also expect to see lines freeze up and block all airflow. Best case scenario, in these situations, operators will need to go out with blow torches to heat up the pipes and restore flow to the lines. This all means the same thing–operating a refrigerated dryer in non-ideal locations, will lead to excessive downtime and lost production. Conversely, a Deliquescent Dryer excels in colder temperatures and achieves better and better dew points. When installed and maintained properly, you will not have to worry about freeze-ups.
Keep in mind that deli dryers have a LOWER initial investment when compared to refrigerated dryers and operating costs are minimal. “Keep it full of desiccant and keep it drained of liquid” is the moto. Also having lower maintenance expenses compared to refrigerated dryers is an added benefit. Maintenance on a single tower deliquescent dryer is simple:
Deliquescent dryers require no power, come with a 10-year warranty, and can be installed anywhere–indoors or out. This life span exceeds any form of compressed air dryer option on the market. The fact that no electricity is required to operate and that they require no purge loss, makes deliquescent dryers the most economical option based on their flexible nature and performance capabilities. Deliquescent dryers are a preferred option for troublesome environments such as ready-mix/asphalt plants, lumber yards, feed mills, remote locations, shipyards, portable blasting & painting, rail yards, natural gas dehydration, sugar mills, and almost any industrial setting requiring dry air.
It is crucial when talking about compressed air and wanting to prevent moisture from forming inside the piping. Van Air Systems D-Series Compressed Air Dryers, are single tower deliquescent compressed air dryers for stationary applications that focus on eliminating all moisture from your compressed airlines. For customers that care about the quality of their compressed air and natural gas, the deli dryer is a great solution. When using 10BF, users can achieve a 63° suppression in their dew point. This means that with a 100° inlet temp, the outlet dew point exiting a deli dryer is going to be 37°F. If you installed the dryer outside in the northern part of the USA and were able to achieve inlet temperatures to the dryer of 40°F, your exiting dew point would be -5°F.
Whether your application is low pressure or high pressure, warm temperatures or cold, indoor or outside installation; the Van Air Systems’ Single Tower Deliquescent Dryer is the right solution for your application. It is by far the most versatile drying method on the market and will adapt to your changing conditions thought out the year. If you work in an industrial plant, blast rooms, paint booths, rail yards, gas landfills, or asphalt plants; call Van Air Systems and we will help select a compressed air dryer suitable for your application.