Absorption drying is a process in which water vapor is chemically absorbed by a special material, both solid and liquid. Sodium chloride and sulfuric acid may well be suitable for this process. However, in this case there is a risk of corrosion. With this dehumidification method a large amount of absorbent material is required and the dew point is only reduced by small values, so this method is not widespread.
It’s worth describing desiccant drying in more detail.
In this type of process, dewatering occurs by passing moist air through a desiccant material, such as silica gel. Sometimes this material is called “desiccant”. When compressed air passes through this type of drying material, moisture is removed from the air and absorbed by the desiccant. In addition to silica gel, aluminum oxide, molecular sieves and other materials can be used for these purposes. To regenerate and maintain the desiccant’s desiccant properties, it must be regenerated periodically. As a rule, adsorption dryers have two compartments, one for direct compressed air drying and another for regeneration.
These compartments are sometimes referred to as “columns”. Regeneration and dewatering in columns takes place cyclically. The value of the pressure dew point in this process can reach.40 degrees Celsius. This makes these dryers ideal for use in areas with very high compressed air drying requirements.
The process for regenerating the desiccant can vary but this determines the type of dryer. If you need a dehumidifier that stores energy it will usually be more complex and will affect the price. However, in the long run, it will save your energy costs.
Below are the methods of desiccant regeneration:
- Regeneration by blowing through is achieved by rarefying or purging compressed air. This method is used at low air flows and requires around 20% of the dryer’s capacity at 7 bar.
- Heated blowdown regeneration involves heating the rarefied blown air with an electric heater. The additional heating reduces the blowdown flow by up to 8% and energy consumption by 25%.
- Regeneration by blower with this process the ambient air is blown through an electric heater and then blown onto the absorption material to regenerate it. This eliminates the need to use compressed air for regeneration and saves up to 40% on energy costs compared to a dryer model that is not heated.
- Regeneration by means of utilization of heat generated during compression The desiccant is regenerated by the heat from the compressor during the compression process. Basically, this type of regeneration can produce a standard pressure dew point of.20 degrees Celsius. If this regeneration process is augmented with additional heating, the dew point can be reduced even further.
Obviously before starting the adsorption drying process appropriate preparation should be done to separate and drain condensate water, install an oil filter in the dryer inlet (if the compressor is lubricated with oil), after the dryer a particle filter should be installed. Note that method 4 (recovery of heat generated in compression) can only be used in the case of oil-free compressor because of the need for high compression temperatures. This type of dehumidifiers is constructed with a rotating drum that is filled with absorbent material and divided into four sectors. One of the sectors is regenerated by some hot compressed air from a compressor at about 150-190 degrees Celsius.
The regenerated air is then condensed and cooled. The condensate is drained and the air returned to the main stream via the ejector. The remaining three drum sectors are required to dry the compressed air from the compressor end-cooler.
This type of dryer does not lose compressed air and consumes power only for the rotation of the drum. The advantage is also that oil and particle filters are not necessary.
Vacuum regeneration system
Special mention should be made of vacuum regeneration. Here we would like to use the example of APD-V series vacuum regenerated desiccant dryer.
In general terms the dryer operates in the same way as the above described: It dries the compressed air produced by the compressor. The optional pre-filter cleans dust, oil and water from compressed air. Functional pre-filters increase the service life of the dryer. The final filter (optional) removes products of friction from the compressed air before it reaches the application area. The adsorption material is placed in both vessels. This material acts like a sponge and stores humidity. The accumulated humidity is then removed in the regeneration process. The two vessels work separately, which means that one side is in the process of drying air while the other side is in the process of regeneration.
Let’s take a closer look at the adsorption and regeneration processes within the presented APD-V series adsorption dryer.
From the piping system after the compressor, saturated compressed air flows into the pre-filter (dryer protection, class 0.01 μ) into the inlet opening of the dryer. The compressed air comes into contact with the adsorbent, which is filled from the bottom upwards in the vessel. In this process, moisture accumulates in the adsorbent. The dried air flows through the dryer outlet into the final filter, which eliminates the friction particles of the adsorbent.
The expansion phase begins with the opening of the expansion valve. In doing so, the regenerated vessel expands until the pressure becomes spherical. The sensor monitors this. The air outlet of the tank is muffled by the silencer and a continuous flowing noise is heard.
Four phases are required for the regeneration process:Expansion, heating, cooling and pressure build-up. Because an additional dew point control element is installed, there is a further phase. standby phase. Thus, the regeneration side is pressurized and awaits the switchover.
A vacuum pump draws in atmospheric air over the continuous outlet of the heater. The heater heats the air that is sucked through the dryer. As a result of this process, the adsorbent heats up and the previously stored humidity evaporates.Vacuum pump creates humidity in the atmosphere. This process works in the same direction as the adsorption process. The heat at the outlet of the desiccant is measured at the temperature sensor. When the temperature reaches 98 C, the heating process is terminated.
The desiccant must be cooled down to be able to absorb moisture again. To do this, the heater is turned off and the vacuum pump starts sucking the cold ambient air through the desiccant. The adsorbent is cooled down to ambient temperature. Temperature is also monitored by the temperature sensor. At a value of
50 C the vacuum pump switches off and the cooling phase ends. The direction of flow is also in the same direction as the adsorption.
After the cooling phase is finished the regenerated side is under pressure. Therefore, the valve at the top of the upper tube system is open until the pressure regulator adjusts the pressure level to that of the compressed air system. In this state, switching can be carried out without pressure shock.
When the adsorbent in the adsorber vessel is saturated (dew point becomes wetter) or the maximum adsorption time is reached, switching is carried out. The freshly regenerated adsorbent is now ready for saturation and the saturated side will be regenerated. This process changes from one vessel to the next each time.
Advantages of the vacuum regeneration system (versus blower system):
- No blowing or cooling is necessary, 100% of the volume flow is always ready for the system (with an average system flow rate of 2% is required);
- Only a final heating temperature of 98 C, caused by vacuum, is required;
- Fewer impurities in the dryer caused by vacuum;
- Lower maintenance costs due to lower heat load.
As can be seen from the description of the process, this method of vacuum regeneration is the most optimal and economical solution for compressed air desiccant drying applications.Read more about these desiccant dryer models here.
The main cause of 80% of failures and malfunctions. Poor quality air. That’s why it’s important to follow the manufacturer’s recommendations and pay special attention to compressed air treatment: removing condensate and solids.
In some cases, no additional drying is required, for example when treating general industrial air. Also an ordinary separator will cope with welding, painting and sandblasting.
The need for a dryer depends on the compressor system’s purpose and air treatment requirements.
Why do we need a dryer in a compressor?
Nowadays compressor equipment is used in every kind of way: in household appliances, cars, industrial machines and so on.д. But a compressor does not mean one cylinder of compressed air, which most imagine. A compressor is a combination of devices.
Types of dryers
Nowadays modern industry offers several types of such apparatus.
The principle of operation of this type of device consists in artificial condensation of moisture from the air mixture by cooling it. Freon, or as they are also called, refrigerator compressed air dryer for compressors can be used when the pneumatic system is located within a heated room.
Desiccant devices with cold recovery of filler properties
Compressed air from a compressor enters the tank with a filler, which is most often silica gel or any other adsorbent that retains moisture vapor. Cold regeneration is nothing more than drying the adsorbent to restore its adsorptive properties. The desiccant is regenerated with part of the dry air. One of the disadvantages of desiccant dehumidifiers after the compressor is considerable loss of compressed air during desiccant desiccant desiccant regeneration.
Such devices are most often equipped with filter elements that retain solid particles down to 0.01 μm. and some of the condensate. It is removed from the unit by a float-type condensate drain. The rest of the moisture is retained by the desiccant.
Adsorption, with hot regeneration
According to their operating principle, dryers with hot desiccant regeneration do not differ from the devices described above. The main difference is not in the method of removing moisture from the air, but in the method of restoring the properties of the adsorbent. There are four types of hot drying of the filler:
- Internal. In this type of dryers, to regenerate the desiccant, an already dry air mixture is taken and, together with the filler, is heated inside the unit using heating elements.
- External. Units with external heating use air which is heated before entering the unit.
- Recovery of desiccant by heat from compression of the air mixture. After regeneration, the moisture-enriched mixture, under pressure, is returned to the air system for reuse.
- Vacuum regeneration of the desiccant. Thanks to the vacuum pump, the air mixture is fed into the tank with the filler, creating a negative pressure inside the tank with the adsorbent.
The principle of operation of these devices is based on the retention of water molecules as the air passes through the holes in the membranes. The main advantage of such devices is durability, they do not require maintenance and power supply.
These dehumidifiers consist of several radiators which are cooled by powerful fans.
The air stream, passing through the finned tubes of the radiator, is cooled until the condensate falls out on the radiators, which is collected in the condensate receiver, and then drained. Ease of construction and durability are the main advantages of this device.
The device and principle of operation of devices for water collection, the creation of their own hands
Moisture separator for a compressor is a device that is designed to separate oil elements from the incoming air. The device is a quality filtration system. This tool has found widespread use in machine shops, as well as various production shops, where the employees have to perform large volumes of various operations.
The water separator for the compressor is a quality filter. Thanks to it, you can create optimal conditions for the operation of the equipment. The mechanism also cleans the air that comes from the pneumatic pump. moisture traps now have an oil filter or panel filter. It is needed to prepare the gas mixture. When all is cleared, it supplies the equipment with air that is completely free of moisture. Dehumidifiers are often used during sandblaster operation.
The moisture separator takes care of the air mass before it enters the air compressor. It is worth knowing that spray guns should not be operated without such a device. Otherwise they would break down prematurely. Also the quality of paint application will be greatly reduced. The air stream is thoroughly cleaned so that the output stream is free of fine solid and liquid particles.
Moisture separator for the compressor with their own hands
The device is often used of cyclone or vortex type. Such a device catches the smallest water particles very effectively thanks to the fact that inside the construction there is a whirling flow. Liquid particles settle on the inner surface of the housing. Then, clean air is fed into the compressor in a compressed state. Paddles are installed inside the structure, which helps to increase the efficiency of the appliance. Oil and water droplets are separated during the air flow. In the debugger they condense and then are expelled.
Compressed air dryers: operating principles and characteristics
The smallest particle size that a desiccant can catch has a direct influence on the final cleaning quality. For the industry they use units that are capable of fine preparation. They pick up particles as small as 5 microns from the air. The normal models, used in small plants, are generally equipped with filters capable of trapping water fractions of about 15 microns.
Before buying the equipment you should pay close attention to the maximum pressure to be maintained. Often the filter for the compressor is able to work at 7 bar. The quality of the final machining does not depend on this parameter. But you need to remember that the moisture separator must match the compressor. Compare the power and load appearing during the transfer of compressed air through the system.
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Types of moisture separators and selection criteria
For industrial and consumer applications apply several basic types of moisture traps for pneumatic equipment. Before you buy it, it is necessary to define the tasks to be performed by the equipment. This will help you choose the right type of device. Basic types of devices:
A feature of the moisture separator is that it cleans the air streams of oil, water, and solid impurities very effectively. Must be connected to an oil compressor that processes some items with high intensity. Modular filters are also used in larger plants. This design includes a moisture separator. It is a separate element, but cannot function as a filter on its own. The modules are controlled by a controller. It issues commands to all components of the unit, not just the dehumidifier.
Different areas of activity have different requirements for the degree of purification. The paint spray gun requires a filter that has a low flow rate. Fine filtration equipment well enough to meet these requirements. The filtration requirements in production are often minimal. In this case, attention is often paid to the maximum volume of air masses that can flow through. Also an important factor can be a list of particles that can catch the filter. Often a desiccant dryer is chosen for this purpose.
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If the only thing you need is to collect excess moisture, you usually buy standard dryers. Such units cannot guarantee that the air is filtered of particulate matter.
Types of compressed air dryers for compressors
Moisture traps go a long way toward helping the air gun and compressor work. With their help, they can create a stable operation of the equipment. Filters that are designed according to the cyclone type are in great demand on the market now. These units have several distinct advantages:
- 1. Pretty straightforward design that even a non-specialist can cope with.
- 2. Competitive pricing. The cost of such equipment is relatively low.
- 3. These units have a very high efficiency.
- 4. Cyclone filters are capable of trapping large condensate droplets.
- 5. The units are easy to operate and maintain.
- 6. Their design implies a coarse pre-cleaning of the air stream.
These devices are often used in small production halls. Also people buy them for domestic purposes.
moisture separator for a compressor with your own hands
It is recommended to make a self-made device according to the drawings. Moisture separator for the compressor with their own hands is often made from an old unnecessary cylinder from propane, pipes, and a fitting. The workpiece should be installed vertically in a stable position. To the top is welded (you can also use threaded connections) fitting. It is necessary for the air supply. It is desirable to mount it near the edge of the cylinder. Then, it is required to perform the inlet pipe. An ordinary metal tube is well suited for this purpose.
Make a second hole, which must be provided with a valve. It is necessary to release accumulated moisture. The hole should be placed at the bottom of the cylinder. At this stage it is necessary to make all the calculations, as well as to make the filler. Wood chips can be used for filling the tank. It is important to know that it should not be stacked tightly. The air must circulate freely.
Moisture separator with their own hands is made for use in compressors. To create will require water and oil filtering devices from the car. The inlet hole in the filter must be changed. This is done with a strong steel tube. To make the work of the finished equipment was stable, you should use the built-in mechanism. The second hole must be sealed as tightly as possible with a threaded plug. It is advisable to use a sealant for this purpose.
Between the walls of the body there is a small space in the form of a ring. It should be filled with a material that adsorbs moisture. One should not forget that the adsorbent should absorb water gradually. You need to use rubber gaskets for this. They are used as a space divider into several zones.
Compressor air dryer from a Geyser filter
Homemade equipment with silica gel
To assemble this type of device yourself, you will need a water or oil filter and silica gel. The greatest challenge during manufacture is the proper placement of the adsorbent. Work steps:
- 1. Take apart the old unwanted car filter into its elements.
- 2. If the condition of the spigot is acceptable, it can be used as an air inlet.
- 3. It is necessary to carefully inspect the filter for possible cracks or holes that can make the finished mechanism leaky. If such are found, they can be eliminated with silicone sealant.
- 4. Assemble the filter.
- 5. Fill all empty spaces with adsorbent so that no voids are left.
- 6. The upper cover must be fastened with a bolt.
You can also weld special brackets for convenience. They will be used as a fastener for the unit.
This is how the moisture and oil separators for the compressor work. To assemble such a device with your own hands is not so difficult. Moisture condenses at low temperatures. Such devices very qualitatively remove all liquid fractions from the air flow, which is then fed to the compressor. These devices have gained great popularity among professional painters.
You can assemble an oil moisture separator for the compressor with your own hands, using old unnecessary equipment. To separate the liquid from the air, you only need to pass the flow through a freezer or some other refrigeration equipment. In the process of creation there are also some difficulties. First you need to solve the problem of condensate drainage from the unit. For this purpose, a special fitting is usually welded to the freezer. It is also necessary to make a completely airtight housing.
Building a moisture separator yourself is a relatively simple undertaking that does not require much effort or time. But it is necessary to try hard in order to make the device reliable and effectively cope with its functions. A few recommendations will help:
- 1. It is necessary to match the obtained unit with the characteristics of the compressor with which it will work. These parameters must match each other. A self-made device may not be able to withstand the power of the equipment.
- 2. Only quality materials should be used for welding.
- 3. Check hoses and fittings thoroughly. The air flow must be able to pass through them without any obstruction.
- 4. To create a moisture separator, it is necessary to use high-quality sealants. After completing the assembly it is advisable to check the construction for leaks.
Moisture separators for pneumatic equipment are a fairly effective addition to. It is almost impossible to imagine these units working without them. Oil and moisture separators are able to filter the air supplied to the compressor very well.
Principle of operation of an industrial compressed air desiccant dryer
The core element of this equipment is the rotor that is filled with an adsorbing substance. Adsorbents remove moisture from the incoming pneumatic flow, after which, some of the dry air is returned to the rotor for regeneration of the adsorbents. In the case of the technology “hot regeneration” losses from pneumatic stream are 2-3%, but such dehumidifiers have a rather high cost. Dehumidifiers with “Cold regeneration” are much cheaper, but they are not designed for installation in high capacity stations and require about 15-20% of the flow for regeneration.
If you want to choose an industrial dehumidifier for the medical, food or electronics industries, or if you are going to use the station in places with low air temperatures, an adsorption dehumidifier would be an excellent choice.
How a refrigeration dryer operates
Pneumatic energy is used in many industries and applications. Compressed air is used to power a wide variety of tools and machines, including large industrial systems.
But in its composition compressed air, which is generated by compressor, has particles of moisture, dust and other substances that can adversely affect the operation of consuming equipment and pneumatic network.
Special units are used to efficiently remove moisture from compressed gas. dehumidifiers. This article describes how a refrigerated compressed air dryer for compressors and pneumatic systems works.
Working principle of the refrigeration dryer
As a rule, the relative humidity of the air supplied by a compressor varies between 30-90%. And the consequences of its possible ingress in the equipment can be very different: from corrosion of some components of the installation up to a complete breakdown in the work of the whole system. So, the removal of moisture contained in compressed air is one of the most important ways to keep pneumatic equipment safe.
One of the most common and simple methods of reducing moisture levels in compressed air is to use refrigeration dryers, which operate as any other air conditioner or refrigerator. They use freon gas as a refrigerant, which is why they are also called freon or refrigerated dehumidifiers.
The moisture in the compressed air first condenses, and then it is removed. The amount of moisture that can be condensed increases significantly as the temperature difference between the outlet and inlet air rises. The lower the cooling temperature, the less moisture remains in the compressed air.
In refrigerated dehumidifiers, the dew point value is usually 3C, which is the specific cooling air temperature at which the water vapor in the air reaches the saturation state and condenses to a dew point at a constant air pressure. The dew point gets closer and closer to the actual air temperature, depending on how much the air is saturated with water vapor.
Generally speaking, the process of operating such a dehumidifier is quite simple:
- The heat that is drawn in by the compressed air is absorbed in the heat exchanger by other, already cooled air moving in the opposite direction. No additional energy is expended at all for any of this. This is where about 60% of the moisture in the compressed air condenses.
- The compressed air itself reaches condensation temperature as it passes through a refrigerant heat exchanger and then cools down. The compressor circulates the refrigerant. Any moisture remaining in the compressed air is cooled as soon as it reaches condensing pressure, and is then automatically evacuated.
The main disadvantage of such devices may be considered the limited possibility of lowering the dew point temperature.
Refrigerated Type Compressed Air Dryer Process Animation
Where is the device in question used?? The field of application of the moisture separator for the compressor is very extensive. It is installed in the systems of automobiles, mechanical engineering equipment, aircraft construction, and so on. In this case, consider the use of a moisture separator for a compressor used in painting. Homemade or industrial design can be used in this case.
To achieve high quality painting of different surfaces can be as follows:
- It is necessary to properly adjust the compressor and competently pick up his moisture separator.
- When using a moisture separator with high efficiency, moisture in the air mass can be reduced by 90%.
- Reducing the amount of moisture in the air allows you to significantly increase the volume of air mass.
- If the humidity is high, cratering will occur. This is because the interaction of oil, oxygen and moisture creates bubbles, which significantly reduce the quality of the resulting surface.
For low-quality painting, you can use moisture separators created by your own hands. However, if you want to achieve a high result, you need to use industrial versions, which are able to reduce the humidity by at least 70%.
What to pay attention to?
As well as creating a dehumidifier for the compressor with your own hands, you should pay attention to the following indicators when buying one:
- The number of cleaning stages is an important indicator. As a rule, filtration is done in two stages: the first separates most of the water and large particles, the second is a more subtle purification. If there is only the first stage, the air quality will be low. If the design has only a fine purification, then there is a possibility of its very rapid clogging.
- Throughput capacity determines the possibility of using a moisture separator in a system with a compressor, as well as its performance. If the flow capacity is below the set standard, it will quickly fail because it will not be able to cope with the load.
- Cleaning depth. As a rule, this figure is indicated in microns. For example, the figure of 5 microns indicates that the device is able to sift out particles that have a larger size of this parameter. Smaller particles, less than 5 microns, will pass through the installed elements.
In some cases, manufacturers specify how much you can reduce the humidity of oxygen when passing it through the construction in question. With your own hands you can create a moisture separator for the compressor, which will halve the humidity, conduct a delay of particles of a few tens or hundreds of microns. However, some elements will still have to be purchased, for example, a fine purification unit.