Wet Grinding and Granulating Machine: Maximize Quality in Plastic Recycling

A Wet granulating and pelletizing machine Is essential for professional recyclers aiming for high-quality end materials from contaminated plastic streams. Unlike standard dry grinding, this technology integrates an intensive washing process directly in the cutting chamber. This not only results in an efficient reduction in size but also produces cleaner 'flakes' (pellets) that are ready for further processing.

For companies in the recycling industry, this means a shorter processing line, lower operational costs, and an end product with a higher market value. We are seeing an increasing demand for these machines due to the stricter requirements for recycled material (scrap). Rumtoo Machine This article provides a technical analysis of wet granulation, the critical differences with dry methods, and practical guidelines for selecting the right machine for your production line.

What is a Wet Granulation and Pelletizing Machine Exactly?

At its core, a wet granulation and pelletizing machine (also known as a wet granulator or washing granulator) is a heavy-duty industrial reducer designed to process large quantities of water during the cutting process. It is specifically developed for the plastic recycling sector to process contaminated post-consumer or post-industrial plastics.

The machine reduces materials such as PET bottles, agricultural films, or hard plastic crates into uniform granules (usually 10mm to 16mm). The unique aspect is the simultaneous introduction of water into the cutting chamber. This water serves three critical functions that are missing in dry grinding:

Cleaning by friction:

1. The high speed of the rotor creates intense turbulence and friction between the plastic and the water. This effectively loosens labels, adhesive residues, sand, organic waste, and residual fluids from the plastic. Thermal control:
2. The mechanical cutting of plastic generates significant frictional heat. Without cooling, plastics with a low melting point (such as LDPE or PET) can soften or melt, leading to clogging and blocking of the machine. Water absorbs this heat directly. Lubrication and transport:
3. Water acts as a lubricant between the blades and the material, reducing wear. Additionally, it helps to quickly transport the reduced material through the sieve bed, increasing the throughput capacity. ⚠️ Differentiation from Other Sectors

of powders with a liquid to form larger granules. In plastic recycling, where we focus, it means

%

High (requires extensive extraction)

Life Span of Blades

Longer (less heat, water lubricates, dirt washes away)

Shorter (higher friction and temperature)

Quality of End Product (Flakes)

Pre-washed, cleaner, ready for friction washing directly

Dusty, contains all original contamination

The 4 Decisive Advantages for Recyclers

Implementing a wet granulation and pelletizing machine in your washing line offers concrete operational and financial benefits. According to industry organizations such as Plastics Recyclers Europe, the purity of the material is the most important factor for high-quality recycling.

1. Superior Quality of the Granulate

Through the "pre-washing effect" in the cutting chamber, a large part of the abrasive contamination (such as sand and glass) is removed in the first step. This protects the downstream machines (such as friction washers and float-zinc tanks) and ensures a much cleaner end product. Cleaner flakes mean a higher selling price per ton.

2. Increased Process Stability and Capacity

• Heat is the enemy of efficient granulation. When plastic warms up, it expands and cuts less well. In severe cases, it melts on the rotor blades. The constant water flow keeps the cutting chamber cool, allowing the machine to run at maximum capacity without thermal interruptions. The water washes the granules that are the correct size directly through the sieve, preventing "over-grinding" (the creation of unusable dust). 3. Significantly Longer Life of Wear Parts
• Blades and sieves are important cost items in maintenance. In dry grinding of contaminated plastic, sand and grit act like sandpaper on your blades. In a wet granulator, the water acts as a buffer and quickly washes away abrasive particles. In combination with the lower working temperature, blades of high-quality tool steel (such as D2) retain their sharpness significantly longer. This reduces downtime for changing or sharpening blades. 4. A Safer and Cleaner Working Environment
• The grinding of plastics, especially old films or hard plastics, normally generates enormous amounts of dust and microplastics that are harmful to workers and can pose explosion hazards. A wet granulator binds this dust directly in the water. This eliminates the need for expensive and complex extraction systems around the granulator and ensures a working environment that meets strict health and safety standards. Primary Applications and Materials
• Wet granulation machines are the standard choice in washing lines for various material streams: PET Bottle Recycling:

Essential for removing paper/PP labels and adhesive residues from the PET flakes. The friction in the water loosens the labels.

LDPE/LLDPE Films (Agricultural and Post-Consumer):

These films often contain a lot of sand, soil, and organic material. Wet grinding is the only way to effectively reduce these materials without the machine getting stuck due to heat or excessive wear from sand.

The type of rotor must match your material. An open rotor with obliquely placed blades (cutting edge) is ideal for films and bottles, as it requires less energy and provides a clean cut. For heavy blocks or thick-walled crates, a heavier, closed rotor is needed. Make sure the blades are made of high-quality steel such as D2 or comparable alloys that are resistant to both impact and corrosion from water.

Waterproof Enclosure and Bearings

This is the critical difference from a converted dry granulator. A true wet granulator has a fully enclosed cutting chamber to prevent leaks. Even more importantly: the bearings must be located outside the cutting chamber ("outboard bearings") and equipped with high-quality seals. This prevents water and fine dust from entering the bearings, which is the most common cause of early machine failures. Accessibility for Maintenance Despite the longer lifespan, blades must be replaced and screens cleaned. Choose a machine with a hydraulically removable hopper and screen holder. This reduces maintenance downtime from hours to minutes. Quick access is also crucial in case an unexpected foreign object (such as metal) enters the machine.

Rumtoo RTM-W Series: Robust Wet Granulators

Our RTM-W series is specifically designed for the harsh conditions of 24/7 recycling operations. With external bearings, D2 steel blades, and heavy-duty waterproof enclosures, we offer reliability for processing PET, films, and hard plastics.

By combining reduction and cleaning intelligently in one process step, you increase the efficiency of your line, lower maintenance costs, and deliver a cleaner product ready for the next step in the recycling process. Investing in the right wet granulation technology is investing in the sustainability of your recycling business.

Looking for a wet grinding and granulating machine? Rumtoo offers robust wet granulators that simultaneously reduce and wash plastic. Improve your granule quality and efficiency.

Wet Grinding and Granulating Machine: Efficient Plastic Recycling