A freeze-dryer is a machine that first freezes hydrated substances into a solid state and then vaporizes the solid water into a gas to remove moisture and preserve the substance. During the compressed air drying process, the freeze-drying is to lower the temperature of the compressed air, allowing the moisture in the compressed air to separate out.
The working principle of the refrigerated dryer is to cool compressed air to a certain dew point using refrigerants, separating super-saturated water, and then separating the liquid water through a gas-liquid separator to achieve drying. However, the dew point value at the equipment outlet cannot reach temperatures below the freezing point of water. Its significant feature is its continuous operation capability, no need for regeneration, and low energy consumption.
Adsorption dryers utilize various adsorbents such as silica gel, activated alumina, and molecular sieves to absorb moisture from compressed air, achieving the drying goal. This method allows for the easy reduction of the pressure dew point of compressed air to temperatures below the freezing point of water. However, due to the limited adsorption capacity of the adsorbents, a two-tower or more alternating adsorption method is necessary, and the drying of compressed air should be continuous. There are many types of dryers on the market, all of which employ the adsorption dehydration principle. The difference lies in the regeneration method.
The differences between freeze-dryers and adsorption dryers aren't just in their principles; they also encompass performance, operating costs, maintenance costs, and acquisition costs, among others. For more detailed information, please refer to the following article.
One: Performance Differences
Cooling dryers are more energy-efficient and cost-effective than adsorption dryers. Additionally, their pressure dew point is typically above 3°C, which is sufficient for most manufacturing processes. For applications requiring higher levels of dryness in compressed gases, adsorption dryers are a better choice.
Section Two: Operational Cost Differences
The two devices differ in the dew point values they can achieve in the compressed air they process, making them unsuitable for simple substitution. Therefore, the operational costs are not comparable. Their distinctions are more relevant when comparing with similar devices, such as the use of different types of heat exchangers, various refrigerants, and so on.
Maintaining Costs
The freeze-dryer utilizes a sealed refrigeration system, where the refrigerant is not exposed to the atmosphere, resulting in lower maintenance costs for the system.
Absorptive dryers involve frequent valve switching between absorption towers, and those with thermal regeneration also experience high and low temperature switching, resulting in relatively high maintenance costs for the valves. Additionally, absorptive dryers require regular replacement of the absorbent, leading to even higher maintenance expenses.
Section 4: Purchase Cost
Based on current market sales prices, adsorption dryers with the same gas treatment capacity are priced higher than their refrigeration counterparts within the same brand.
