PETpla.net Insider 03 / 2016

MATERIAL / RECYCLING 10 PET planet insider Vol. 17 No. 03/16 www.petpla.net Polymetrix EcoSphere technology Energy and yield optimised Polymetrix’ EcoSphere technology brings to the market the very latest technological developments in bottle grade virgin PET production. EcoSphere technology answers the rising demand for energy-saving along with process reliability and increased yield, while maintaining polymer quality. Among the key features of EcoSphere is the link between melt phase and solid phase polymerisation, which allows the recovery of energy from the melt phase for reduced energy consumption but still leaves the option for independ- ent operation. The low transition viscosity from the melt phase to the solid phase is said to assure maximum quality of the final PET. Polymetrix asserts that the technology en- ables improved economies of scale, with a capacity of circa 1mio./t in one installation. At first glance, the EcoSphere Technology appears to be simply the link from the continuous melt phase polymerisation (CP) to solid state polymerisation (SSP) but without intermediate storage of amorphous PET pellets. This allows heat to be recovered from the PET melt for the crystallisation step. (Fig.1) Polymetrix says that closer exami- nation will show that the technology offers users opportunities for improve- ments in process reliability, energy efficiency, plant layout and capac- ity, as well as product quality. The EcoSphere system comprises one or multiple underwater pelletising lines feeding an actively heated crystal- liser. The main equipment for solid state polymerisation (SSP) is similar to conventional nitrogen SSP but with the difference that crystallisation is smaller, a deduster is added and, for preference, with gas cleaning by an EG scrubber column. Nitrogen crystal- lisation is also an option. (Fig.2) Conventional SSP in traditional, or established systems, typically uses PET with a relatively low start- ing IV and is more or less independ- ent from the CP plant, which means that energy recovery from the melt is impossible. While energy recov- ery technology was developed in the 1960s for a wide range of starting IVs, it was commercialised in large scale only for direct melt processes, which make the transition from the melt to the solid phase treatment at a relatively high starting IV. This left customers with a dilemma: they could opt for energy savings or elect for the quality advantages of the lower start- ing IV – but not both. Fig.3: Energy costs and quality comparison Fig.1: Process flow conventional CP/SSP and EcoSphere technology Fig.2: Process flow detail EcoSphere technology