Within the RDF production process, shredding equipment plays a pivotal role in determining fuel particle size, purity, and combustion efficiency. Today, we delve into the essential shredder types used in RDF preparation, highlighting how Harden Machinery, with its deep expertise in the field, leverages innovative technology to address shredding challenges across diverse waste streams.

RDF production demands precise control over material particle size—too coarse leads to incomplete combustion, while excessively fine particles can cause dust pollution and handling issues. Given the wide variations in waste characteristics (e.g., hardness, toughness, and moisture content), selecting the right shredder is crucial. Harden Machinery, drawing on its profound understanding of solid waste properties, offers a comprehensive lineup of shredders covering primary, secondary, and fine shredding stages.

• Shredders: The Frontline of Solid Waste Processing

Single-Shaft Shredder

Single-shaft shredders are indispensable in RDF alternative fuel production.

Principle: At the core is a single high-speed rotating shaft equipped with blades that shear and tear materials against fixed knives. 

A replaceable bottom screen ensures precise particle size control. Unlike conventional crushers that rely on brute force compression, this design excels in efficiently handling tough materials while delivering uniform output sizes.

Performance: Harden's RDF series single-shaft shredders feature an intelligent feeding system and helically arranged blades, automatically adjusting push force based on material thickness to prevent jams. With alloy blades and adjustable screens, they can reduce materials to below 30mm, achieving a qualification rate of over 95%. Screens ranging from 40-100mm allow flexible adaptation to various kiln feeding requirements.

Applications: In full RDF workflows, single-shaft shredders often serve as secondary units, refining materials after primary shredding to enhance fuel uniformity. For instance, in plastic waste RDF projects, post-shredding materials can boost thermal efficiency by 8-10% during combustion, meeting the needs of a broader range of cement kiln applications.

One-Step Shredder

Building on over 1,600 successful global projects, Harden introduced a low-TCO RDF preparation solution in 2025—the one-step single-shaft shredder. This innovation targets inefficiencies and cost pain points in preprocessing, effectively turning "one shredder into an RDF factory." 

From a total cost of ownership (TCO) perspective, it minimizes footprint, reduces energy consumption per ton, and shreds over 90% of common wastes to ≤50mm in a single pass, simplifying operations and accelerating profitability in alternative fuel production.

Double-Shaft Shredder

Double-shaft shredders are among the most widely used in RDF alternative fuel preparation.

Principle: Featuring two counter-rotating shafts with interlocking blades, they deliver a combination of shearing and compression forces. This makes them ideal for highly mixed wastes containing impurities (e.g., plastics, textiles, and small metal fragments in MSW). 

The low-speed, high-torque design handles high-moisture and entanglement-prone materials, avoiding common shaft jamming issues in traditional equipment.

Performance: Harden's TD912 double-shaft shredder stands out for its robust adaptability and high throughput. It processes mixed soft and hard materials (e.g., leather scraps with metal buttons) while maintaining output sizes below 150mm and impurity separation rates above 90%. 

In a Southeast Asian MSW processing center, a single unit handles over 200 tons per day, operating fault-free for more than 3,000 hours. Safety features include overload protection that auto-stops upon encountering unbreakable objects, preventing damage.

Applications: As the initial shredding stage in RDF production, double-shaft shredders rapidly reduce material volume (up to 70% reduction), easing downstream screening and impurity removal. In industrial waste RDF projects, such as leather trimmings and textile scraps, shredded outputs can proceed directly to screening, significantly shortening the overall cycle.

Four-Shaft Shredder

Four-shaft shredders are commonly employed for electronic waste and bulky item shredding.

Principle: They operate via an upper pair of shafts for initial breaking and material distribution, followed by a lower pair for fine shearing, achieving four-stage processing: coarse, medium, fine, and shaping. Blade thickness and screen aperture provide dual control over output size, making them suitable for complex, high-purity demanding wastes (e.g., e-waste or bulky furniture).

Performance: Harden's QSH series four-shaft shredders integrate intelligence and sustainability. Independent shaft controls allow individual speed and torque adjustments, increasing shearing frequency by 30% over traditional models. 

For e-waste like circuit boards mixed with plastic casings, post-shredding purity exceeds 95%. Hybrid hydraulic-electric drives cut energy use by 20%, saving up to 12,000 kWh annually. CCTV monitoring and big data analytics enable remote parameter optimization, with fault prediction accuracy above 98%, minimizing downtime.

Applications: In high-value fuel preparation, they reduce wastes like textiles to below 30mm, meeting stringent RDF standards. They also excel in preprocessing electronic waste, as well as recycling bulky items such as mattresses and sofas.

In the journey toward RDF production from solid waste, selecting the appropriate equipment is paramount. RDF fuel quality fundamentally depends on shredder compatibility—single-shaft for precision, double-shaft for versatility, and four-shaft for depth—forming the technological backbone of the process. Harden Machinery, with its cutting-edge technology, reliable products, and superior service, injects new vitality and solutions into the solid waste management industry.