Answer: The pre-filter of the adsorption dryer is used to remove solid and liquid pollutants in the compressed air and extend the service life of the desiccant layer (especially oil pollution will cause the desiccant to fail due to "poisoning"). The high-efficiency oil removal filter assembled with the precision oil removal filter element can reduce the oil content index of the filtered gas to 0.01~0.5mg/m³, which can effectively prevent the adsorbent poisoning caused by trace oil accumulation and ensure the service life of the dryer for more than 5 years.