How does a compressed heat dryer perform? How to solve the malfunction?

Compressed heat dryers use medium-high temperature compressed air discharged from an oil-free compressor to regenerate the adsorbent. The moisture content of the regeneration gas is very high, and the pressure dew point can often reach 60-70 degrees. When it enters the adsorption tower and contacts the adsorbent in a cold state, water vapor is very likely to condense, producing liquid water droplets. Therefore, when selecting an adsorbent, activated alumina or waterproof silica-alumina gel with liquid water droplet resistance should be used to avoid the risk of adsorbent bed failure caused by gas water condensation. In particular, it is not recommended to use molecular sieves that will fail when encountering liquid water droplets in compressed heat.

The medium-high temperature oil-free compressed air discharged from the compressor of the compressed heat dryer enters the adsorption tower (in the opposite direction of adsorption), heats the adsorption bed and desorbs moisture, and the regenerated gas leaves the tower to form basically saturated regenerated tail gas. The regenerated tail gas then enters the cooler for cooling and then enters the adsorption tower for adsorption. After heating, a small amount of finished gas at the dryer outlet is depressurized, the adsorbent in the tower is cooled, and the cooled tail gas is discharged. It should be pointed out that the drum cold air further dehydrates and regenerates with the help of bed heat, reduces the remaining adsorption capacity of the adsorption tower, further improves the dew point potential, and is a very important auxiliary regeneration process.

　　However, some problems often occur when using a compressed heat dryer. So how should we solve the problem after it occurs?

　　The compressed air entering the compressed heat dryer is saturated air at a constant temperature. Under the same pressure conditions, for every 5-degree increase in temperature, the saturated moisture will increase by about 30%. In other words, the humidity load of the adsorption dryer increases by about 30%. In addition, the adsorption capacity of the adsorbent decreases as follows. As the temperature increases, if the compressed air inlet temperature increases, the drying efficiency of the adsorption dryer will decrease. For every 5-degree increase in the outlet dew point of the output gas, the inlet temperature will increase by 8-10 degrees. Therefore, the adsorption dryer will lower the inlet air temperature.

　　The waste gas of oil-free piston air compressors (excluding labyrinth, positive pressure protection packing, and low-power oil-free compressors) contains a certain amount of lubricating oil depending on the structure and specifications, approximately 6-15 mg/m3. Depending on the efficiency of the oil-gas separator and the exhaust temperature, the oil content of the oil-injected screw air compressor is comparable to that of the oil-free piston type, and can generally be considered to be 5-15 mg/m3, and their median value is 10 mg/cubic meter.

　　When the compressed heat dryer is running, the regeneration gas flow rate cannot be adjusted arbitrarily. In addition, in the case of an adsorption dryer, the instantaneous flow rate of the regeneration gas cannot be too small. Otherwise, the heat transfer efficiency of the regeneration gas as a heat medium will decrease, and local overheating will occur without heating, affecting the structure and performance of the adsorbent. At the same time, if the flow rate is too low, the airflow through the adsorption layer may short-circuit, forming a "tunnel effect", resulting in uneven heat transfer and ineffective desorption.