Calculation of the portion of air in drying units used for cold regeneration of the adsorbent

The process of cold regeneration of the adsorbents in drying units is carried out by a portion of already dried air without heating it. It simplifies the design, reduces the cost, but reduces the productivity of the installation. At hot temperature and atmospheric air humidity, this part (portion) of the air can be unacceptably large, therefore it is important to determine its value before the design work starts. The use of an I-d humid air diagram is limited by the errors of graphical constructions. Thus, the development of a method for pre-design calculation of the portion of dehumidified air for cold regeneration of the adsorbent is an urgent task. The development of a method for engineering calculations of the real process of cold regeneration of an adsorbent is possible only with simplifying assumptions that make it possible to develop a method suitable for pre-design engineering calculations. The study is carried out using a method based on the theory of “wet-bulb temperature”. It considers heat and mass transfer processes in a local boundary layer of an evaporating water film washed by a plane-parallel and stationary flow of unsaturated air. The authors have conducted a detailed study of the real processes of heat and mass transfer during cold regeneration of granular adsorbent with dried air. The calculation of the change in moisture content and air temperature in two layers of adsorbent has been performed under the assumption that the temperature of the wet-bulb thermometer is the same in all layers of the adsorbent during the entire cold regeneration phase. The temperature and relative humidity of the air at the end of the regeneration phase have been calculated based on the initial state of the dried air used for regeneration of the adsorbent. The developed algorithm of the method is illustrated by a numerical example. The results obtained using the presented methodology allow us to conclude that the model is adequate and that the research goal has been achieved. The reliability of the results is evident due to the application of basic physically easy to understand thermodynamic patterns. The technique can be used when performing pre-design calculations of air dehumidification systems of compressor stations, which have certain requirements for the moisture content of compressed air.