Decanter centrifuge for food processing (DDF): oil separation, protein recovery, and clarification

A decanter is a horizontal-axis sedimentation centrifuge. Inside, a conical-cylindrical bowl rotates at high speed to generate centrifugal forces many times greater than gravity. The denser solid phase is pushed to the bowl wall; a scroll (conveyor screw) rotating at a differential speed relative to the bowl scrapes and transports the solid cake toward the conical end for discharge, while the lighter liquid phase overflows at the opposite end. This allows continuous separation without stopping the machine to discharge solids, as is required with batch filtration.

For food applications, the advantages of this mechanism are an enclosed flow path, continuous processing, and ease of cleaning — factors critical to maintaining ingredient quality and safety. Separation performance (cake dryness, liquid-phase clarity) is adjusted via bowl speed, scroll differential speed, and feed flow rate, typically managed by a PLC controller.

In oil processing, raw material after milling or pressing forms a mixture of oil, water, and solid residue. The DDF decanter separates the solid phase from the oil–water liquid phase, enabling effective oil recovery and reducing losses carried away with the solids. For vegetable oil, fish oil, or other oil-separation products, the decanter handles high-solids-content streams that a disk-stack separator cannot handle directly.

After the decanter step, the oil–water stream, now largely free of solids, is typically fed to a disk-stack separator for fine separation of oil from water. This two-stage combination is a standard arrangement in oil processing lines, where the decanter handles coarse solid–liquid separation and the separator handles fine liquid–liquid separation.

Many processing streams require protein recovery or solid removal to clarify the product: starch suspensions, plant or animal protein liquors, dairy streams, and by-products. The DDF decanter concentrates and separates the solids (cake, protein precipitates) from the liquid phase in a continuous flow, recovering valuable ingredients and reducing the load on downstream filtration steps.

Because food-grade decanters process consumable products directly, contact surfaces are made from AISI 304/316 stainless steel, with easy-disassembly design and cleanability (CIP depending on configuration). This is the core distinction from industrial (DDI) or environmental (DDE) decanters, which prioritise mechanical durability and sludge dewatering over food hygiene standards.

When selecting a decanter for a food processing line, the key parameters to define are: feed characteristics (viscosity, solids content, particle size), separation objective (oil recovery, protein recovery, or clarification), required flow rate, and hygiene requirements. The DDF series covers a flow rate range of 1–180 m³/h and bowl diameters of 200–800 mm depending on model, serving facilities from small workshops to large-capacity production lines.

Larger bowls and higher speeds provide greater throughput and separation efficiency but bring higher costs and operational demands. For some feeds, adding a flocculant polymer is necessary to improve solid separation — dosage depends on the nature of the liquid. Sample testing and pilot trials are the practical approach to finalising the configuration; detailed model specifications are confirmed by the manufacturer based on actual operating conditions.