Waste valorization in fluidized bed reactor: Statistical assessment of particle segregation in binary mixtures of sand and Tetra Pak residues

Abstract

The fluidized bed reactor is an alternative for aluminum recovery and waste valorization of polyolefins from the polyethylene/aluminum composite (LDPE/Al). The sand is typically added as an inert particle into the fluidized bed to enhance heat and mass transfer. Such addition, however, can lead to particle segregation and compromise the reactor start-up. As a research novelty, this paper uses a 33-factorial experimental design with three central points to assess particle concentration uniformity in a fluidized bed composed of LDPE/Al and sand mixtures. A statistical procedure permits an evaluation of the factors effect of the LDPE/Al mass fraction (XC% w/w), the air velocity ratio (V/Vmf), and the diameter ratio of LDPE/Al and sand (dC/dS) on the bed mixing index (IM). Results show that only the dC/dS and V/Vmf ratio affects the IM. Data analysis reveals that fluidized beds reach axial particle uniformity with 0.67 dC/dS, 10 % V/Vmf, and 15% wt. LDPE/Al composite. The statistical model developed accurately predicts the IM, with an error of less than 15%. Such results allow applying a fluidized bed for waste-derived fuels, aluminum recovery from carton packaging wastes, and energy saving of 0.745 MWh per each ton of recovered carton package annually.