Spheronizer — Extrusion Spheronization for Pellets

The QZL spheronizer turns wet extrudate into highly spherical pellets of 0.5–2.0 mm. It is the rounding stage in the extrusion spheronization route, used where the product needs pellets rather than granules — capsule filling, controlled-release cores and traditional Chinese medicine pills.

Six models cover 2.5 to 300 kg/h, from formulation development through to production.

Where the spheronizer sits in the process

Spheronization is one stage of four, and each stage constrains the next:

The most common cause of poor pellets is not the spheronizer. A wet mass that is too dry produces extrudate that shatters into fines instead of rounding; too wet, and the pellets agglomerate into oversize lumps. The spheronizer can only round what the extruder gives it.

How it works

Wet granules from the extruder are fed onto a rotating centrifugal friction plate. With the blower running, three forces act on the material at once:

• air buoyancy from the annular gap around the plate,
• centrifugal force from plate rotation, and
• gravity.

Together these drive the material into a rope-like ring that rotates around the bowl. Each particle is repeatedly thrown outward, lifted, and folded back into the rope — first breaking the extruded strands into short cylinders, then rounding those cylinders into spheres as the edges are worn down.

The specially designed rotor structure is what produces high sphericity: the friction pattern on the plate governs how the rope circulates, and a stable rope is what gives an even, narrow size distribution.

Features

• Highly spherical pellets of 0.5–2.0 mm
• Rounds rod-shaped extrudate into round pellets in a single operation
• Specially designed rotor structure for high sphericity
• Simple operation with a short production cycle
• Stainless-steel contact parts
• Six plate sizes from 230 to 1300 mm

Applications

• Pharmaceutical — capsule pellets, controlled- and sustained-release cores, pellets for coating
• Traditional Chinese medicine — pills
• Food — spherical granules and instant products
• Cosmetics, dyes and pigments
• Ceramic industry

Technical specifications

Capacity is stated as a range because residence time depends on the formulation. A mass that rounds quickly leaves the machine sooner and gives higher throughput; one that needs a longer cycle to reach the target sphericity gives less. Take the table as a selection guide and confirm the figure against your own material.

Why pellets rather than granules

Pellets are chosen when the downstream process needs a predictable surface:

• Coating. A sphere with a narrow size distribution presents consistent surface area per unit mass, so a film applied in a fluid bed coater gives a predictable release profile. An irregular granule coats unevenly, and releases unevenly.
• Capsule filling. Free-flowing spheres of even size fill capsules to a consistent weight.
• Multiparticulate dosing. A dose split across many pellets is less sensitive to the failure of any one of them than a single monolithic unit.
• Density and strength. Spheronized pellets are denser and more robust than porous granules, and survive handling and coating better.

If the product is destined for tablet compression rather than capsules or coating, porous granules usually serve better than dense pellets — a fluid bed granulator or high-shear granulator is then the right equipment, and spheronization is not required.

Selecting a spheronizer

The formulation is the variable that decides whether the route works at all. Not every material can be extruded and spheronized: the wet mass must be plastic enough to extrude cleanly and cohesive enough to round without disintegrating. That is established by trials, not by specification.

Trials

Plan development work on the actual formulation. Plate speed, residence time, load and moisture interact, and the settings that give good sphericity for one product will not transfer unchanged to another.

Record the conditions that produced acceptable pellets together with the size distribution, sphericity and yield used to judge them. Scale-up between plate sizes changes the rope circulation pattern, so each scale needs its own confirmation.

Request a configuration

Tell us the formulation, target pellet size, required throughput and what happens downstream — capsule filling, coating or direct use. We will propose a QZL model and advise how it should sit alongside your extruder and dryer. Where extrusion spheronization is the wrong route for the product, we will say so.