The Cavitation Pulper

Many valuable raw materials can only be recycled inadequately with conventional technology (standard pulpers, pulping drums, etc.) or with very high energy consumption, especially cellulose-based composites and hard-to-recover grades.

Multi-material multilayer plastic packaging (“MMPP”)

• Composites and composite packaging (e.g. beverage carton packaging)
• Papers from waste (paper and cardboard from lightweight food packaging)
• Metallized packaging (e.g. aluminium-vaporized paper packaging)

Hard-to-recover grades („h2r”)

• Coated paper and cardboard (e.g. paper cups and tableware)
• Kraft paper and cardboard (e.g. sack paper)
• Cores and core wrapping paper products
• Wet-strength papers (e.g. labels)
• Release liner / Siliconized papers
• Barrier papers, consisting of various barrier layers

With the cavitation process, almost the entire fiber content can be recovered from these materials. The technology can also be used to treat and clean plastics in order to improve their quality (e.g. removing stuck-on paper labels, cleaning foils, etc.).

The Cavitation Pulper (“CP” for short) is an innovative and patented system for the efficient separation of fibrous and composite materials (or non-fiber materials) using the purely physical principle of targeted cavitation to separate the molecular compounds in the raw material.  The CP system consists of an airtight tank with an agitator (HC spiral rotor), which is driven by an energy-efficient direct drive, and a vacuum pump. The cavitation effect is generated by the vacuum pump, which creates a vacuum inside the tank. In combination with rotor recirculation, the raw material is separated very efficiently.

The main advantages compared to conventional technology:

• Significantly lower specific energy consumption (up to 50% energy savings)
• No use of chemicals or hot water necessary
• Processing of “MMPP” and “hard to recycle” raw materials
• Higher cost and resource efficiency due to improved fiber yield

As a result, the use of cavitation technology allows the packaging industry, for example, to make greater use of composite materials that were previously inadequately recyclable (avoiding plastic waste and conserving resources). Furthermore, a reduction in the formation of bacteria and yeasts can be observed in contaminated raw materials.

To operate the recycling plant, the raw material is delivered in bales (optionally in bulk), de-wired and fed into the cavitation pulper with the addition of water. The cavitation process separates the raw material into a fiber and non-fiber fraction. The entire content is then fed into the downstream peripheral equipment.

• Fibers as a final product: After separation from the reject stream, the pulp enters further cleaning and dewatering stages. After final drying, the pulp is either produced as a fiber bale (Option 1) or after initial dewatering as crumbled stock or bulk material (Option 2).
• Reject as a final product: After the cavitation pulper, the reject fraction passes through various sorting and washing stages and is available either as compressed and wired bales or as loose bulk material. The reject quality meets the requirements for further material processing. Subsequent PolyAl processing can be taken into account by RT in an overall plant concept.

The following illustrations are examples of the processing of used beverage cartons (UBC) and are taken from a fiber processing plant that has already been implemented with the innovative cavitation pulper concept.

The processing of MMPP materials (e.g. UBC) produces reject quantities that are mainly sent for thermal recycling today. Repulping Technology and Partner and its partner company offer a highly efficient closed-loop solution for the complete recycling of composite materials. The rejects produced after the RT process are virtually fiber-free and are fed directly into the PolyAl recycling plant. The process in detail:

• Step 1: Shredding and intermediate storage - to ensure a continuous process
• Step 2: Washing and separating - fibers, impurities and aluminum are sorted out
• Step 3: Drying - via a centrifugal dryer
• Step 4: Sifting - separation of light and heavy plastic parts
• Step 5: Agglomeration and extrusion - production of end products

A complete closed-loop solution for composite and MMPP materials is now possible. Recycling rates > 90% can be achieved.

Project approaches

Total costs of around EUR 15 million are estimated for an autonomous recycling plant (“greenfield”) with an annual capacity of around 40,000 tons of input material. The dried fiber bales can be sold to customers with the best prices. Alternatively, the plant can be located close to a fiber-receiving paper mill or integrated into it (“brownfield”). This eliminates the need for costly pulp drying and thus minimizes energy and transport costs to increase profitability. The revenues from the operation of such a recycling plant result from the additional payment of the dual systems (for example for fractions 512 and 550), as well as from the sale of pulp to the paper industry.

Increasingly, the recovered composite materials (films) can also be sold at a profit, or additionally processed by other systems (e.g. PolyAl processing) and used as a raw material for new plastic production. This provides a complete, closed-loop solution. This highly efficient overall solution from Repulping Technology and its partners is unique and enables end customers to meet the (PPWR) quota compliance of the recycling quotas required in the future.

Due to the increasing requirements for the recycling of packaging and the associated recycling quotas, e.g. from the PPWR legislation (applicable from 26.01.2025), such recycling capacities are increasingly necessary on the market. There are already bottlenecks in Germany, such as paper and cardboard from lightweight food packaging (Papers from waste), which is putting disposal companies under increasing pressure.

The range of services offered by Repulping Technology GmbH & Co. KG:

1. Preparation of a technical and commercial feasibility study (technical system concept with investment/operating costs and profitability analysis)
2. Engineering phase: preparation of planning documents and final offer
3. Holistic realization partner for the construction of the recycling plant