Pump Technology Melt Pump Technology for Production of Bioplastic PLA

Editor: Ahlam Rais

The Maag Group has supplied its latest state of the art x6 class melt pump technology for the first fully integrated sugar-to-PLA (polylactic acid) plant in China. The plant is based on a Sulzer technology and key equipment for converting lactide into PLA.

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Maag Group’s Vacorex x⁶ class polymer extraction gear pump ideally fulfills modern polymer production processes.
Maag Group’s Vacorex x⁶ class polymer extraction gear pump ideally fulfills modern polymer production processes.
(Source: Maag Group)

The lactic acid and lactide production is made from sugars (in this case won out of locally grown corn). Not only is the plant reducing the carbon footprint because of using plant-based resources instead of hydrocarbons but by using the company’s pump technology, the specific energy requirement is further optimized.

The firm’s pumps are used in the polymerization reaction stage, making sure that the efficient Sulzer SMRTM reactors are working smoothly in all operating conditions. But they are also used in the devolatilization stage, where, a minimum level is required when unreacted lactide is removed from the PLA melt to achieve a good product quality. In the last stage, the company’s melt pumps are used to build up the necessary pressure to process the melt through the downstream equipment, up to the underwater pelletizer.

The melt pump technology’s key feature is the reduced back-flow to lower the energy consumption. The melt pump helps to save up to 50 % energy and reduces material recirculation in the pump of about 50 %, states the company.

While the reduction of 50 % of energy is possible in exceptional cases and in extreme operating conditions only, the trend is true for all the applications when the firm’s technology is used. With the energy saving, also the CO2 footprint is reduced, adds the company. But the pumps offer far more than that. The high efficiency of the pumps is offering a wider operating range as compared to other state of the art technologies. It allows for example that low viscous pre-polymer can safely be processed through the Sulzer plug flow reactor when the polymer conversion is progressing and the viscosity is continuously increasing in the same, opines the firm.

The high efficiency of the technology keeps the bearing temperatures lower than in former pump technologies, allowing always a stable film of polymer, lubricating the turning shaft. The favorable shaft geometry, where the length over center distance ratio has increased, allows the operation of extraction pumps at a lower fill level than it was ever possible before at a given connection size to the vessel, mentions the company.

Only like this the PLA can fully be concentrated. But also, the reliability has increased. Not only are the bearing surfaces almost 30 % bigger, providing a better cushioning, but the pump is also working with bigger gaps, allowing potentially small foreign particles entering the system to pass the pump easier without damaging it, concludes the company.