How a Nozzle Separator Works

A nozzle separator belongs to the disc-stack (or disc-bowl) family of centrifuges. The mixture spins inside a bowl at very high speed, generating centrifugal force many thousands of times gravity, which drives denser solids and heavier liquid outward while lighter clarified liquid moves toward the center and out.

What distinguishes a nozzle separator is how it removes solids. A set of small nozzles is spaced around the widest part of the bowl. Concentrated solids collect at the bowl periphery and are discharged continuously through these nozzles as a thick slurry, while the clarified liquid leaves separately. This lets the machine run nonstop on feeds with a steady, moderate solids load.

Inside the bowl sits a stack of closely spaced, cone-shaped discs. Their purpose is to shorten the distance a particle has to travel to be separated. Instead of settling across the full radius of the bowl, a particle only has to reach the nearest disc surface, a very short distance, before it is carried outward along the disc to the bowl wall.

Because the stack packs a large effective settling area into a compact bowl, a disc-stack machine can process high flow rates and separate fine particles and closely matched liquids. The many thin channels between discs are what give this design its high clarifying capacity for its size.

The nozzle design suits feeds that carry a fairly constant, moderate concentration of solids that need continuous removal, rather than occasional bursts. As solids concentrate at the bowl wall, they flow out through the nozzles as a controlled underflow while the process runs.

Nozzle size and number set the solids discharge rate, so they are matched to the feed. Some designs recirculate part of the concentrate to keep the discharge consistent. Typical applications include yeast and biomass concentration, starch processing, protein recovery, and other high-volume biological and food streams where solids must come off continuously.

This continuous discharge distinguishes a nozzle separator from a self-cleaning (solids-ejecting) disc centrifuge, which holds solids in the bowl and periodically shoots them out in intermittent bursts. A nozzle machine instead bleeds solids off steadily.

Nozzles erode as abrasive concentrate passes through them, and worn or blocked nozzles change the solids discharge and separation, so they are inspected and replaced as wear parts. The disc stack can scale, corrode, or foul, which reduces clarifying performance and must be cleaned or renewed.

The bowl runs at very high speed, so the spindle, bearings, drive, and seals carry heavy loads and wear over time, and the rotating assembly must stay precisely balanced. A rebuild typically covers the nozzles, disc stack, bearings, spindle, and seals, followed by high-speed balancing and a test run before return to service.