Experimental Scale-Up and Technoeconomic Assessment of Low-Grade Glycerol Purification from Waste-Based Biorefinery

Abstract

The purification of waste-derived crude glycerol to the 2000 g scale is presented to provide a consolidated proof of concept. Starting from unprecedented low-quality glycerol from a second-generation biodiesel plant, currently disposed of at cost, a series of physiochemical steps are implemented to improve glycerol purity and recovery under relevant conditions. The study is carried out on two samples with initial purities of 38–57 wt % and ash contents of up to 16 wt %. Under the optimal process conditions, glycerol exhibits a remarkable increase to 85 wt % purity while preserving the overall glycerol recovery of the process of up to 71%. Among different purification steps, neutralization contributes to increasing the purity to 69 wt % while the remaining water and methanol evaporation have further increased the purity to >80 wt %. The adsorption step shows the smallest increase in glycerol purity despite it being required to decolorize and deodorize the final product. The developed process is further designed for industrial-scale application using Aspen Plus for a plant size of 1630 kg/h of purified glycerol which could achieve 82 wt % final purity and a maximum recovery of 77%. In addition, the process yields 315 kg/h of salable byproduct salts suitable as fertilizer and an overall CO2 emission of 0.70 ton per ton of purified glycerol mainly due to the unrecovered feedstock and solvent combustion. As a result, the proposed process implementation could generate positive revenues with a cost of the final products of €19.2 per ton.