- Energy savings of 30 million yuan (£3.4m)
- Boosted production efficiency
- High quality and strength of fibres
A top global producer of polyester industrial yarn, with annual production output of 200,000 tons, conducted a major investment into improving energy consumption and reducing carbon emissions during manufacturing. The new production lines were designed on a 'direct melt-spinning' production method with ambitious productivity targets. The economic benefit of the project was expected to be 3 billion yuan per annum.
The production method consists of four main steps:
- The melting kettle melts the PET to create a basic polyester melt
- The melt is sent to the viscosity enhancement kettles through pipelines, where its viscosity is increased until it reaches a specific level
- Each viscosity enhancement kettle is connected to 2 to 10 spinning units, which are equipped with 2 to 4 spinning boxes
- The spinning units convert the viscous melt into industrial yarn
To maximise production efficiency for both energy and emissions at each stage, it is important to optimise the melt viscosity. During the initial production stages, it’s crucial for the 'base polyester' to maintain a low viscosity and ensure optimal flow and pumpability through the melt-pipes.
The first polymerisation kettle ensures the polyester reaches the desired viscosity for efficient transportation, before moving onto the next kettle where the melt viscosity reaches the desired level for melt spinning.
Viscosity measurement is also critical to achieve the desired properties for the final product. By exploiting the direct correlation between viscosity and molecular chain length, the strength and quality of the fibres can be controlled in real-time. This results in two main benefits. Production output of high-quality yarn, and the ability to adjust the process to produce different yarn types.
XL7 viscometers are installed directly in the melt-pipes to allow operators to manage pumpability at every stage of the reaction, significantly reducing energy costs. Due to the scale of the operation, the saving from energy consumption alone was expected to be roughly 30 million yuan (£3.4m) per annum.
This production method is a triple win. It solves the challenge of handling highly viscous melt, allows for flexible and efficient production of various types of PET, and delivers on the ambitious efficiency and emissions targets.