How to pre-treat compressed air to prevent carbon molecular sieves from being poisoned and extend the service life of carbon molecular sieves?
Because the carbon molecular sieves in the nitrogen generation unit have very high requirements for the quality of compressed air, and the gas temperature in the compressed air is high, it also contains a large amount of moisture and certain dust and oil mist. Therefore, before the compressed air enters the nitrogen generation unit, it must undergo cooling, dehumidification, deoxygenation, dust removal, etc. The equipment for this purpose is mainly for this purpose.
The purification treatment of compressed air is of vital importance. Users must not ignore this point! Because the quality of compressed air purification directly affects the service life of carbon molecular sieves, and thus directly affects the long-term effective use of the nitrogen generation machine. Once the carbon molecular sieves are “poisoned” by oil or water, the nitrogen generation machine will have a decrease in efficiency and the indicators cannot reach the normal level.
The dehumidification of compressed air is mainly carried out by refrigeration dryers or (and) adsorption dryers. The refrigeration dryer uses R-134a or R-22 refrigerants as coolants to cool the gas in the compressed air, and the gaseous water and oil are cooled to liquid state, and then removed. The specific operation should refer to the instructions for the use of the refrigeration dryer. The adsorption dryer uses a recyclable drying agent as the adsorbent, using the principles of pressure change and gas expansion to adopt the separation process of pressure swing adsorption to remove the moisture from the compressed air.
If the nitrogen dew point is not too low (≤ -40℃ at normal pressure), a single refrigeration dryer is sufficient; if the nitrogen dew point is lower (≤ -60℃ at normal pressure), a refrigeration dryer and an adsorption dryer should be configured simultaneously. Refrigeration dryers have two cooling methods: air-cooled and water-cooled. When the processing air volume is less than 12-20 m3/min, air-cooled type can be used. Adsorption dryers have two types: no heat regeneration and micro heat regeneration. Both have certain losses in air volume, the no heat regeneration drying device generally has an air loss of 10%-15%, and the micro heat regeneration drying device generally has an air loss of 4%-8%. Therefore, when configuring the adsorption drying device, the exhaust volume of the air compressor should be considered.
The deoxygenation and dust removal of compressed air mainly use multi-stage filters of different types and different filtration accuracies. The filter removes contaminants (water, oil, particles, odors) in the medium through many microporous fiber materials or activated carbon. All filters have the functions of dehumidification, deoxygenation and dust removal, but different types of filters have different main functions. The main function of the main pipeline filter is to remove dust and liquid water; the initial filter mainly performs the first-stage oil removal; the fine filter mainly further removes oil to make the medium have very little oil content; the activated carbon oil removal filter mainly performs deep oil removal and adsorption of hydrocarbons and odor removal. The configuration of the filter mainly depends on the quality of the compressed air discharged by the air compressor. If the configuration is too little, the compressed air cannot be fully purified and cannot meet the quality requirements of the nitrogen generation machine, which is not allowed; if the configuration is too much, although the treatment effect of the compressed air is good, it will cause more pressure loss in the pipeline and also result in high costs, which is unnecessary. Generally speaking, for oil-free air compressors, one or two stages of filters should be configured, mainly for dust removal and dehumidification; for air compressors with oil, three to four stages of filters should be configured.
