What is a refrigerated air dryer used for? Principle & applications analysis

Writer： admin Time：2022-09-16 00:00:00 Browse：491℃

Refrigerant air dryer is an important compressed air treatment equipment. We usually use refrigerated air dryer to remove moisture or water. At the same time, it can also reduce the air temperature. Finally we can get 2~10℃ pressure dew point. In fact, refrigeration dryer uses the method of freezing and dehumidification. That is, use the heat exchange of refrigerant and compressed air. Then control its temperature and dew point.

As we all know, many industries have high requirements for compressed air quality. These industries are below, such as pharmaceutical, food, spraying, printing, textile and so on. If only install desiccant air dryer, it may not meet these requirements. Therefore, usually also need to install a refrigerated compressed air dryer.

Why need a refrigerant compressed air dryer?

Compressed air is very important source of production power. But we generally do not use it directly. Because air condenses in the pipeline, there will be a lot of moisture and oil. As the pressure increases, the temperature decreases. The moisture content of saturated humid air is reduced. So water condensation will increase. Suppose there is a 55kW screw air compressor. It operates at an ambient temperature of 24°C. In addition, the relative humidity is 75%. It will produce about 280 liters of water per day. These moisture and oil will corrode pipes and equipment. Besides, it will also affect product quality. The main hazards caused by water in compressed air are as follows:

① Firstly, the condensed water will take away the lubricate oil on the pneumatic equipment. So it will reduce the equipment efficiency;

② Secondly, the water will also accelerate the wear of the valves in the pipeline. Finally cause failure of pneumatic control equipment.

③ Thirdly, cause the pipeline and equipment to corrode. Besides, sometimes water freezing will occur in the lower part of the pipeline. Then there is a danger of the pipeline bursting;

④ High moisture content in compressed air will also directly affect product quality. For example, it will affect the quality of food and pharmaceuticals. In addition, if there are water mist, it will affect the spray painting quality.

The function of refrigerated air dryer:

It is precisely because of the above hazards that we need a refrigerant dryer. We need it to purify the impurities in the compressed air. It effectively removes moisture. So the dew point of our refrigeration air dryer can reach 2~10℃. Moreover, it can also lower the temperature. This will protect piping and equipment. Guarantee the stability of production. At the same time, ensure the quality of industrial production.

In addition, we usually also use refrigerated air dryer together with desiccant dryer. It plays an important role in the performance of the regenerative air dryer. Some industries have high requirements for dew point. 2~10℃ can not meet the requirements. So we need an adsorption air dryer. But if there is only the desiccant dryer, the dew point is often difficult to reach. Besides its running load will be very large. Therefore, it generally require pre-cooling of compressed air.

Then we need to install the refrigerated air dryer before it. Perform preliminary cooling and dewatering. This can help to play the role of the adsorbent. It also reduces the consumption of regeneration air. So reduce economic losses.

How does refrigerated air dryer work?

Firstly, the compressed air enters the precooler and heat exchanger. After initial cooling, it produces condensed water. There are also dusts inside. Then enter the evaporator of refrigerated air dryer. Deep cooling is done here. At the same time, the dew point reaches 2~10℃. They are discharged from the separator. In fact, the low-temperature air is not directly discharged at this time. Instead, go back to the heat exchanger. Output after heating. Thereby we get the clean compressed air.

On the other hand, the compressor outputs high-pressure refrigerant. Then the cooler cools it down. And make it liquid. After filtration, send them to capillary or expansion valve. Afterwards, the liquid refrigerant enters the evaporator. Refrigerant cools the air. At the same time, it will absorb the heat of the compressed air. Then conver the liquid refrierant into a gaseous state. Finally repeat the above heat exchange process.

Applications of refrigerant air dryer in different industries:

Compressed air is an important energy source for industrial production. Refrigeration dryer can purify compressed air. It has been widely used in various industries. Let’s talk about the most common industries that use refrigerant air dryer:

(1) Refrigerated compressed air dryer for laser cutting

Good air source quality is necessary for the laser cutting industry. If there are water mist and oil, they will be sprayed on the protective mirror surface. So it will seriously affect the transmission of the laser beam. Ultimately will also affect the cutting quality. The workpieces will have problems such as burrs and rough cutting surfaces. At the same time, oil and water will adhere to the laser cutter. This affects aesthetics. More seriously, it may cause damage to the laser head.

In the laser cutting industry, we need remove three types of compressed air pollutants:

① Water —— Use a refrigerated air dryer and a desiccant dryer. Removes most of the water content in compressed air. Bring the pressure dew point to around -20 to -40°C.

② Oil vapor —— Use a precision oil-removal filter. It can remove oil from compressed air.

③ Dust —— use the post dust removal filter. It’s to ensure that dust does not enter the laser cutting equipment. Avoid dust contamination on optical lenses.

Therefore, we recommend the following compressed air system: air compressor + air storage tank + refrigerant dryer + adsorption dryer + precision filters. In this way, it can guarantee the air quality for laser cutting. So as to improve the efficiency and quality of laser cutting!

(2) Refrigerant air dryer for PET bottle molding

What’s PET bottle molding? Injection molding of thermoplastic resin. Get tubular plastic parison. Afterwards, place it in a split mold while still hot. Immediately after the mold closing, introduce compressed air into the parison. Inflate the plastic parison against the inner wall of the mold. Finally cool and demould. So we obtain various plastic bottle products.

In the blow molding industry, the working pressure of compressed air is relatively high. Generally reach 3.0MPa or 4.0MPa. Under this pressure, a lot of gaseous water and oil pollutants will accumulate. This causes defects in various blow molding products: It will cause pockmarks or dirt on the surface of plastic bottles. In addition, it will also affect the stability of PET bottle stereotypes.

Therefore, it is particularly important to use a refrigerant air dryer. It effectively removes moisture and impurities. And help PET bottles fully crystallize at the moment of setting. Of course, here we need to use medium and high pressure refrigerated air dryer.

(3) Refrigerated air dryer for textile industry

The textile industry is inseparable from air compressors. Rotary screw compressor is an important power source for the production of textile enterprises. There are many production processes in the textile industry. The demand for air consumption in different processes is quite different. Therefore, the demand for air compressors is also relatively large.

Air-jet looms are the equipment that uses the most compressed air. At the same time, air-coated wire and texturing machines also require compressed air. And so do drying and transportation of chips in the chemical fiber industry. These machines require a stable air supply. It also requires the compressed air to be dry, oil-free and clean. Refer to the operating requirements of various air-jet looms. The quality indicators of the compressed air are mainly as follows:

① Firstly, remove the liquid water effectively. And remove as much gaseous moisture as possible. The pressure dew point should be below 10℃;
② Secondly, remove the oil vapors 0.8~1.0 μm;
③ Thirdly, remove dust particles above 0.3~1.0 μm;

Therefore, we have to install a refrigerated air dryer and precision filters. Use them to ensure the quality of compressed air. Only in this way, it can guarantee the stability of textile production. At the same time, it can reduce the harm to textile equipment products to a minimum standard.

(4) Refrigeration air dryer for food industry

Compressed air has wide application in the food industry. For example, beer, monosodium glutamate, lactic acid, beverages, and food fermentation all require it as a power source. All pneumatic components and solenoid valves also need compressed air.

We need it to control the filling, packaging and bottling automation process. The transportation, fermentation and spraying of powdered substances also require completely pure compressed air.

If there contains oil or other impurities, it will cause pollution. In the food industry, there cannot be any small contamination. Otherwise, it may bring physical hidden danger to consumers. On request, the air quality must meet the Class 2 standard in the food industry. Besides, compressed air dew point should be below -40°C.

So must clean it first. The compressed air system includes air compressor, air receiver, filters and dryers, etc. The pressure dew point of refrigerant air dryer can only reach +2°C to +10°C. It cannot meet the air quality requirements of the food industry. Therefore, it must also add a desiccant air dryer. Of course, refrigerated air dryer is also necessary. Otherwise, it is impossible and difficult to meet the requirements.

(5) Refrigerant air dryer for spray painting

As we all know, the spraying industry relies heavily on compressed air. Therefore, it is also very important to pay attention to the quality of compressed air. We generally have certain requirements for the aesthetics of the sprayed appearance. For example in car spray painting, if there are bubbles and pitting, it basically needs to be reworked. Of course, spraying in different industries has different requirements for the moisture content of compressed air.

① Car spraying and metal spray painting

The requirements for automotive spraying are the highest. Firstly, there must use the refrigerated air dryer. But it also needs to install a desiccant dryer. However, in many car beauty shops, there is basically no need for a dryer. Because the air consumption is too small, it is not necessary to use it.

Metal products generally require smooth appearance. It is the same as the requirements for car spraying. It is not recommended to use only a refrigerant dryer for drying.

② Wood product spraying, building decoration

Most of the wood products are furniture spraying. Its requirements are not high. In addition, architectural decoration, such as stair railings, wall spraying, do not have very high requirements for appearance. Therefore, it only needs to use the refrigerated dryer as a separate drying machine;

③ Nano spraying, art spray painting

This is the high-end spraying industry. This type of spraying has high requirements for appearance aesthetics. And the spray material is relatively expensive. Rework costs are also high. Therefore, it is not recommended to only use the refrigerated air dryer. In many cases, it is necessary to install an adsorption dryer.

(6) Refrigerated air dryer for pharmaceutical industry

In pharmaceutical factories, compressed air is also widely used. For example, filling machines and granulators of preparations need it. In addition, pulping, filling and packaging machines are also require it. There are two types of compressed air in the pharmaceutical industry: one is a general oil-lubricated compressed air system. It’s for the pneumatic components of the instruments. They do not come into direct contact with medicines. The other is an oil-free compressed air system. They come into direct contact with medicines. It is important to note that even oil-free air contains a lot of water and impurities.

Of course, the latter is currently most used by drug manufacturers. In order to ensure the air quality, its purification requirements are extremely strict. Compressed air systems are subject to validation. Only in this way can we meet the production requirements and pass the GMP certification inspection. Air source in pharmaceutical industry should meet the ISO8573.1-2001 standard. That is, the dew point should be at least -40°C. Solid particles sizes ≤ 0.1 microns. Oil content≤0.1mg/m³.

So we need to use refrigerated air dryer and desiccant dryer to remove moisture. And it also requires to install precision filters. Moreover, their materials must be 304 stainless steel.