Performance analysis of a multistage internal circulation liquid desiccant dehumidifier

A novel multistage internal circulation liquid desiccant dehumidifier (MICLDD) is proposed for feed air drying of air compressors in a cryogenic air separation unit (ASU). The dehumidifier is designed in a multistage structure, in which the packing bed and cooling module are layered separately inside each stage. The solution concentration and flow rate can be evenly distributed according to the moisture content distribution along the dehumidification process using the internal circulation structure. A numerical model validated by using experimental data from previous literatures, is employed to simulate the heat and mass transfer process within the dehumidifier. Effects of the inlet parameters and the number of packing stages on the dehumidification performance are investigated. Results show that the dehumidification efficiency is mainly affected by the mass flow rate of desiccant solution and increases with the mass flow rate of desiccant solution. With the increase of packing series, the heat and mass transfer area increases proportionally, so the dehumidification efficiency is improved. Compared to the structure of the packed tower with cooling tubes proposed in Ref. 1121, the dehumidification efficiency of the MICLDD can be improved by 7.3% with the same pump power consumption.