Fracionamento da fração sólida obtida na pirólise de resíduos plásticos utilizando destilação molecular de filme descendente

Abstract

The large generation of plastic waste entails the need for recycling methods for the reduction and recovery of these materials. Molecular distillation technology is a viable process to separation high value-added products. One of the methods of recycling of polymer waste that is being increasingly used is the pyrolysis that treats these residues and has as products liquid, gaseous and solid fractions. The waxes obtained by the pyrolysis of high density polyethylene (HDPE) have several applications and can be fractionated by molecular distillation. Thus the use of molecular distillation for wax fractionation was studied. For this, the Falling Film molecular distillation at pilot plant scale it was used for the processing of a polyethylene wax (PE-Wax). Response surface methodology and desirability function were used to build predictive models for distilled percentage (DP), pseudocomponent 1 recovery in distillate (Ps1(D)) and distilled/feed ratio (D/F) of the combined effects of molecular distillation's independent variables including evaporating temperature (EVT), feed flow rate (FF) and condenser temperature (CT). The results show that response surface curves of DP, Ps1(D) and D/F displayed a similar relationship with respect EVT and maximum values of responses. The theoretical model and the multi-response optimization give decision criteria about the operative conditions during molecular distillation of PE-Wax. Under optimum conditions, the highest DP, Ps1(D) and D/F (21.96 %, 88.38 % and 0.1505, respectively) were obtained at an EVT of 184 °C, a FF of 1.91 L/h, a CT of 44.02 °C at 0.1 Pa. To obtain wax by the pyrolysis method was performed the study of the best conditions of the pyrolysis process to obtain waxes, temperatures of 425 to 450 °C were evaluated. The wax obtained in pyrolysis was evaluated by physical-chemical characterization to indicate possible commercial uses. The results obtained indicate that this wax can be fractionated by molecular distillation.