Supporting the Chemical Dissolution of PET with Glycol
Our recycling history started way back in the 70ies when hardly anybody else was talking about it. Our film silo was one of the first technologies in the market for in-house recycling. The silo was designed to store and mix shredded pieces of film, which were then fed to the extruder for further processing.
Our story continued with the development of the first backflush screen changer in 1989. Already almost entirely automated, the BKG® HiCon™ K-SWE/RS was able to process material with higher contamination grades and was a significant first step down the road for more sustainability – at a time when this was not such a buzzword yet.
Specifically Designed for PET
The journey continued with further developments improving the classic mechanical recycling process. The overall goals were more filtration area, more pressure consistency, and producing less scrap /waste. With the launch of the BKG® HiCon™ V-Type 3G, designed explicitly for PET, we provide a system that is a filter capable of processing high throughputs at maximum pressure consistency.
Mechanical Recycling is not enough
It is obvious that the recycling goals can't be met with just mechanical recycling, and material quantity and quality requirements have increased substantially. Besides the milestones currently made in different chemical recycling applications, glycolization has become an efficient method to process higher throughputs with high recycled material contents. With the price decline for virgin PET, larger-scale plants are more economically efficient than smaller production lines, which spurred the need for higher tonnages. The consistent call for more sustainability in the plastic industry has also led to new laws and regulations which force producers to increase their use of recycled material significantly, and the industry needs to react.
We have been providing equipment for the chemical dissolution of PET with glycol for major industry partners, steadily increasing capabilities, performance, and end-product quality.
The Process
After pre-treatment, the PET flakes are blended with glycol to break up the polymer chains. The mix is then fed into the extruder. The next step is a pre-filter which catches the larger dirt particles. We provide several filtration options, but the BKG® HiCon™ K-SWE-4K has proven to be the most efficient. It provides a large filtration area and manages throughputs up to 8000 kg/h. In addition, it protects the following /booster pump, which provides the needed pressure for the fine filtration process, where the BKG® HiCon™ V-Type 3G comes into play. In combination with the BKG® FlexDisc™ (we call it BKG® rPET Power²), the BKG® HiCon™ V-Type 3G can reach a filtration area of up to 12800 cm² resulting in high tonnages of recycled material per hour and is therefore capable of matching the need for high capacities.
V3G + FlexDisc = rPET Power²
Fine Filtration
The pre-and fine filtration is of utmost importance for this process. The cleaner the material is before it enters the reactor, the more efficient the re-polymerization process. Clean material reduces residence time in the reactor while being easy to mix to reach maximum homogeneity. The tandem filtration ensures that the recycled material is extremely clean and can be further processed without any trouble.The PET-Glycol mix has a very low viscosity, and our BKG® filtration systems have effective sealing methods and tolerances to prevent leakages. The low viscosity level has a significant advantage – the lower the viscosity, the finer the filtration can be used. With our BKG® filtration system, fine filtration down to 40µm is possible, so even microscopic contaminants are removed from the melt efficiently.
After being combined with virgin material, capacities of up to 30 tons of r-PET pellets with 20% recycled material content are achievable, depending on process parameters, feedstock, and filtration fineness.
Benefits
The newest developments include intelligent sensor locations for the most efficient pressure monitoring to improve pressure consistency and protect downstream components from overpressure. With several small process adaptions, We reduced the amount of material loss during backflushing to below 1.5%, resulting in significant savings, especially in this large-scale environment.
V3G + FlexDisc = rPET Power²
The BKG® HiCon™ V-Type 3G with the FlexDisc™ combines the advantages of piston filtration technology with the capabilities of large-area filtration. The process-independent backflushing procedure and the large filtration area ensure maximum product quality, minor operator intervention, and reduced operating costs.