The problem of the very limited resources in our country accelerated our drive to locate new resources and to reduce energy consumption. One approach to energy conservation is chemical recycling, which not only reduces consumption but also increases the efficiences of resource utilization.
Considerable amounts of waste polymeric material (five to ten percent of the total product) in the polyester fiber manufacturing process are offering the prime incentives for the waste polyethylene terephthalate (PET) recycling.
In this project, recycling of the waste PET was studied by employing depolymerization to a lower molecular weight monomer or oligomer (BHET) in a continuous two-stage alcoholysis process. In a small-scale depolymerization process, the effect of reaction temperature, residence time and recycle ratio in the average degree of polymerization of the depolymerized oligomer were experimentally investigated.
It was found that the optimum conditions were as follows :
reaction temperature 240-250℃
residence time 10 $\min$
recycle ratio 2 : 1
The plant was scaled up for an estimated waste of 4 tons/day processing, based on the optimum conditions obtained, and its economic feasibility was studied.
A total investment was estimated to be 82.9 million won, with annual savings of 340 million won, which appears to be economically very attractive.