Recycle waste PET yarn on site by feeding waste yarn as grinded powder to improve product quality, increase energy efficiency and reduce environmental impact

Abstract

A technical approach was proposed to recycle waste PET yarn on site with the aim of building green manufacturing plant with no waste accumulation. In the recycling process, the waste PET yarn with almost infinite aspect ratio was first treated with custom-designed grinder prior to recycling, which breaks the yarn into small pieces and produce powder-like final product (waste yarn/fiber powder, WYP/WFP). Then it could be mixed with PTA and EG to form slurry and fed into manufacturing unit using well-established method rather than be fed as melt by screw-extruder that is known for its high energy intensity. Furthermore, the wetting of WYP by EG during slurry formation facilitates the de-oxygenation process and is beneficial to improve the quality of product, which produces higher quality products with lower cost compared to conventional methods. PET containing 20 wt.% WYP addition using the proposed technical approach could give best balance between performance and profit margin. The properties of the produced PET products (20% WYP addition) were found similar to that of virgin counterparts and meet the specs for various commercial application. With the help of energy benign treatment and feeding processes, the energy intensity and CO2 emission of this method compared to conventional method were reduced by 78.96% and 62.02%, respectively. The method proposed a novel energy efficient and cost-effective approach to reliably recycle waste PET to high quality PET products on site. It partially solves the problems that the industry currently encountered, such as high recycle cost, relatively low product quality, high energy intensity and low economic benefit. It moves one step forward to the greening of the manufacturing process and may help on the sustainable development of the PET industry.