How to select compressed air adsorption dryer?
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Applicable to the occasions of adsorption dryer: compressed air water grade is divided into 6 levels, of which 1~3 pressure dew point are below -20℃, must use adsorption dryer to achieve. Its typical applications include photographic film, microelectronic chip (level 1, -70℃), precision spraying (Level 2, -40℃), powdery product delivery (level 3, -20℃), etc. Although some occasions to the dew point of compressed air is not very strict, but gas pipeline through below 0 ℃ environment and external thermal insulation material, no in order to prevent the transmission of residual moisture in the compressed air in the pipe frozen, it must make its dew point pressure is lower than environment can achieve low temperature, this is also adsorption of compressed air dryer shall apply in addition to water treatment.
The air dew point processed by the adsorption dryer can cover the treatment effect of the freeze dryer, so in principle all occasions using the freeze dryer can be replaced by the dryer, but the other way around is not ok. Because the energy consumption of the freeze dryer is much lower than that of the adsorption dryer, it is definitely not economical to replace the freeze dryer with the adsorption dryer.
Selection of regeneration mode: dew point of finished product and regeneration energy consumption are two major factors that must be considered when choosing adsorption dryer. Generally speaking, both can not be taken into account, that is, to obtain low dew point compressed air, it must pay more energy consumption. According to the adsorption theory, the basic form of adsorption dryer only has two kinds of thermal regeneration and thermal regeneration. No heat regenerative dryer because on the basis of pressure swing adsorption, used the short cycle of work, by its handling of the compressed air dew point both in depth and stability is better than a heat regenerative dryer, and renewable energy has been very close to the theory of the bottom line, so since there is no heat regenerative adsorption dryer, heat regenerative dryer will have a tendency to exit the application.
Selection of adsorbent: activated alumina and molecular sieve are commonly used adsorbent adsorption dryer. Both of these adsorbents have strong adsorption capacity for water vapor. Activated alumina also has a lot of excellent physical and chemical properties, so in most occasions is the choice of adsorption dryer. Especially in the case of no thermal regeneration, activated alumina is almost the natural choice for obtaining compressed air at the pressure dew point of -40℃. However, the adsorption capacity of the adsorbent in low moisture environment is far less than molecular sieve, so molecular sieve will be very useful in obtaining extremely dry compressed air (pressure dew point below -60℃). But the mechanical strength and anti-droplet performance of molecular sieve is not ideal, so it is often combined with alumina to obtain a better effect. It is not the best way to choose molecular sieve as desiccant in all occasions.
Selection of combined dryer: a freeze-drying base preprocessing in the upstream of adsorption dryer is a good process design to obtain extremely low dew point compressed air and reduce the regenerator. It is generally believed that the savings in energy costs over the lifetime of this combined application will more than offset the increased initial investment in equipment. When the operation quality of compressed air system is higher, the cascade arrangement can be selected. The rigid assembly of two different types of drying equipment together to form a so-called "modular dryer" is not necessary in most cases. A good air source system should not only provide better working conditions for each equipment in the system to play its greater effectiveness, but also take into account the convenience of daily maintenance and troubleshooting of equipment. From both points of view, the split cascade seems to be better than the "combined dryer".