Study on heat exchangers and industrial absorption column for drying polyethylene terephthalate

Abstract

This study proposes the use of mass balance and the method of McCabe-Thiele in the absorption column for the removal of drying air humidity with ethylene glycol and energy balances in heat exchangers for the determination of the optimum operating conditions of a factory to produce recycled polyester fibers from polyethylene terephthalate (PET) flakes. The evaluation of these machines involved the combination of variables such as temperature, flow rate, specific heat, and operational efficiency to guarantee the correct adjustment of the physicochemical properties of the fluids and materials of the process. The efficiency of the absorption column was determined at 25%, and a diagram correlating ethylene glycol humidity, the dew point of the drying air, and the efficiency of humidity removal from the PET flake dryer were constructed to define what is the most appropriate configuration for operation. By the graph curves, it was found that the humidity of ethylene glycol for absorption should be inferior to 1% (w/w) to guarantee a dew point < -27°C at 175°C of the drying air introduced in the dryer, which would finally promote a removal with efficiency superior to 91% of the PET flake humidity for values < 0.005% (w/w).

Keywords

• humidity. dew point. pet flakes. polyester. mccabe-thiele