In the industrial field, as an important secondary energy source, compressed air has a drying degree that directly affects product quality, equipment life and production efficiency. As common compressed air drying equipment, micro-thermal dryers and thermal-free dryers work based on the principle of pressure swing adsorption, there are significant differences in many aspects. A deep understanding of these differences will help companies make more scientific decisions on equipment selection and improve production efficiency. This article will explain the difference between micro-heat dryer and heat-free dryer. The following points are introduced to you.
1. Working principle: same origin but different paths
Thermal-free dryer and the micro-thermal dryer are both adsorption dryers. Relying on the adsorption effect of adsorbent on moisture, the dew point of the outlet gas can reach -40℃. However, their regeneration process is significantly different.
- The heat-free dryer is based on the principle of pressure-switching adsorption and realizes continuous drying through alternating operation of the two towers. When one adsorption tower absorbs moisture under working pressure, the other adsorption tower uses about 12% - 20% of the dry finished gas to close atmospheric pressure to purgate and regenerate the adsorbent. This process requires no external heat source and the single tower working cycle is only 5-10 minutes.
- On the basis of the heat-free dryer, the micro-thermal dryer adds a heating step for regenerative gas. After the finished gas is reduced by throttling, it enters the heater to heat up, and then enters the regeneration tower to purify the adsorbent. When the regeneration gas temperature is 50℃, the theoretical regeneration gas consumption is 8.2%; when the temperature is 70℃, the regeneration gas consumption is 3% - 4%. The water vapor pressure of the regenerated gas after heating is reduced, which can carry more water vapor, thereby improving the regeneration efficiency of the adsorbent and reducing the regenerating gas consumption.
2. Energy consumption performance: the trade-off between gas and electricity
- The heat-free dryer does not consume electricity during the regeneration process, but requires a large amount of dry finished gas as regenerating gas. Data from Shouli dryer shows that the heat-free regeneration gas consumption is ≤12%, which means that a large amount of compressed air is wasted, indirectly increasing the energy consumption of the air compressor. In a certain chemical product recycling plant, the dry back-blown air consumed by the heat-free adsorption dryer accounts for 15% of the total treated air volume.
- Although the micro-thermal dryer needs to consume a certain amount of electricity to heat the regenerated gas, the heating power consumption is usually 0.37kw/(m³/min), its regenerated gas consumption is relatively low, and the regeneration gas consumption of the Shouli micro-thermal dryer is ≤6%. Taking a certain optoelectronics industry as an example, the water-cooled and micro-heat combination dryer used originally consumes 10% of compressed air during the regeneration process, and the energy-saving effect after transformation is significant, reducing the initial investment cost of the compressor to a certain extent.
3. Drying effect and stability: the comparison of dew point
- Micro-thermal dryer: Due to heating and regeneration gas, the regeneration process of the micro-thermal dryer is more thorough, with better dew point stability, and dew point fluctuation is less than ±3℃, which can meet the requirements of continuous high-load production.
- Thermal-free dryer: Since regeneration is achieved through only decompression and purge, dew point fluctuations sometimes occur, and it is impossible to provide a stable drying effect in scenarios with high dew point requirements. In the production of semiconductors, PCB boards and electronic components, the micro-thermal regeneration dryer can better control the dew point, provide a more stable drying gas source, significantly reduce the waste rate, and extend the maintenance cycle of the equipment.
4. Accurate matching requirements
- Thermal-free dryer: suitable for small flow and intermittent gas use scenarios. The equipment structure is simple, the manufacturing process is mature, and the initial investment cost is low. For some small businesses with small gas usage and low requirements for compressed air quality, thermal dryers can meet basic drying needs at a lower cost.
- Micro-thermal dryer: More suitable for medium flow and continuous gas use scenarios, the overall cost is better than that of heat-free dryers. For example, in automotive spray workshops, micro-thermal regeneration dryers combined with multi-stage filtration technology can provide a stable gas source with a dew point of -20°C to -40°C, effectively reducing coating defects. After a certain car company adopted a micro-thermal dryer, the spray rework rate dropped from 5% to 0.8%, saving more than one million yuan in annual costs.
When enterprises choose drying equipment, the difference between micro-thermal dryers and thermally-free dryers needs to comprehensively consider factors such as gas usage demand, energy consumption cost, equipment investment, etc., and combine the characteristics of micro-thermal dryers and thermally-free dryers to make the most appropriate decisions to maximize production efficiency and resource utilization.
