Stages of material handling within powder processing plants

A modular structure for material handling flow is used to understand how powder processing plants work, what they do and how best they should be developed.

These distinct stages and the order in which they connect are unloading, storage, processing, mixing, blending and packing. Transfer of powders within or between stages is done by pneumatic conveying.

Stages and flow of material with powder handling systems and pneumatic conveying in the powder processing industry

Each stage will typically have custom control panels and dust collection systems. Some stages may require dehumidifiers and magnetic separator systems.

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Unloading stage of a powder processing plant

Unloading of granular and powder ingredients into a food processing plant can occur via several methods. Truck or ISO container unloading systems are used to transfer bulk volumes of material (up to 30 tonnes) into a storage area within the food processing plant. They generally require specific discharge aids such as fluidisers and aerators.

Smaller volumes of material can be brought into the plant using bulk bags (500kg to 1,500kg) or small bags (up to 25kg). The material can be sent to a storage facility; however, it is generally fed directly into the processing stage.

Bulk bag unloading systems have electric hoists that allow operators to lift and position the bags above vibratory dischargers. Small bags (25kg) can be unloaded using various types and configurations of tipping and dump systems. These are usually manual systems that deal with much smaller volumes compared to the other unloading systems. Auto debagging systems can be coupled with tipping and dump systems to improve efficiency. They cut away and remove ingredient container bags so the contents can feed automatically into the processing plant.

Systems used in unloading stage include:

  • Auto debagging systems
  • Small bag tipping and dump systems
  • Bulk bag unloading system
  • ISO container unloading systems
  • Truck unloading

Accessories used in systems within the unloading stage include:

  • Aspiration units
  • Bag lifters
  • Belt conveyors
  • BFM fittings
  • Control systems
  • Discharge aids
  • Dust collectors
  • Dust extractors
  • Dust filters
  • Electric hoists
  • Heat extractors
  • Hoppers
  • Level indicators
  • Load cells
  • Magnetic separators
  • Rotary bin dischargers
  • Rotary valves

Powder handling systems used in the unloading stage in the powder processing industry

Storage stage of a powder processing plant

There are two main storage methods for holding granular and powder ingredients within a food processing plant. Silos are used for holding large volumes (up to 75 tonnes) of dry bulk ingredients such as dairy powders, flour, sugar, starch and salt. They are generally made from mild steel, stainless steel or aluminium and deployed outside the plant; however small silos can be deployed within a plant to provide temporary storage for buffering. They can be supported using skirting or a leg structure. Most silos need to be specifically designed to meet the requirements of the food processing plant, and their design is dependent on the type and characteristics of the ingredient to be stored.

Fabric flexible silos are a special type of storage system. These are always deployed within the plant and are made from durable, tough, dust-proof and non-toxic fabric. They are made in standard sizes however they can be customised to specific dimensions. Fabric flexible silos are light and come with a galvanized steel frame that can be readily assembled. The ingredient is pneumatically loaded to the top of the fabric flexible silo and then descends by gravity. The silo fabric walls allow for a smooth discharge of the ingredient from the bottom where extraction is made either by a screw conveyor or rotary valve. The fabric is air permeable to avoid agglomeration of the ingredients via condensation.

Systems used in the storage stage include:

  • Flexible fabric silos
  • Indoor silos
  • Outdoor silos

Accessories used in systems within the storage stage include:

  • Aspiration units
  • BFM fittings
  • Bin activators
  • Control systems
  • Dust collectors
  • Dust extractors
  • Dust filters
  • Hoppers
  • Level indicators
  • Load cells
  • Magnetic separators
  • Outdoor silo ladders
  • Rotary valves
  • Screw conveyors

Powder handling systems used in the storage stage in the powder processing industry

Processing stage of a powder processing plant

Processing of granular or powder ingredients involves applying one or more operations prior to mixing, blending or packing.

Processing operations include the use of grinding systems to reduce raw ingredient particle size, or vibrating sieves and rotary sifters to remove ingredient impurities or irregularities.

Processing also involves such operations as the weighing and batching of ingredients to accurately meter ingredient volumes, which are then fed into subsequent processes or stages.

Systems used in the processing stage include:

  • Batching systems
  • Grinders
  • Rotary sifters
  • Vibrating sieves
  • Weighing systems

Accessories used in systems within the processing stage include:

  • Aspiration units
  • BFM fittings
  • Control systems
  • Cooling units
  • Dust collectors
  • Dust extractors
  • Dust filters
  • Heat extractors
  • Hoppers
  • Inspection hatches
  • Level indicators
  • Load cells
  • Magnetic separators
  • Rotary valves
  • Screw conveyors
  • Sight glasses
  • Vibrating tube feeders
  • Volumetric feeders

Find out more on mixing systems and blending systems.

Powder handling systems used in the processing stage in the powder processing industry

Mixing stage of a powder processing plant

In a granular and powder food processing plant, mixing is often associated with combining solid ingredients with large quantities of liquid ingredients.

Mixing involves combining the ingredients in a vigorous fashion to form a homogeneous product.

The mixture then either remains a liquid or becomes a semi-solid, such as a dough, paste or cream.

Mixed products are further processed by methods outside the scope of granular and powder handling.

Accessories used in systems within the mixing stage include:

  • Control systems
  • Dust collectors
  • Dust extractors
  • Dust filters
  • Hoppers
  • Magnetic separators

Find out more on processing systems and blending systems.

Powder handling systems used in the mixing stage in the powder processing industry

Blending stage of a powder processing plant

The blending of granular and powder ingredients involves combining them in a gentle fashion so that they become inseparable but not necessarily homogeneous.

Blending is associated with the combining of solids with solids, or solids with small amounts of liquids.

Examples of blends are powdered milk products, cake mixes, and colouring being added to expanded cereals.

Blended ingredients are typically transferred to the packing stage.

Components used in the blending stage include:

  • Control systems
  • Dust collectors
  • Dust extractors
  • Dust filters
  • Hoppers
  • Magnetic separator

Find out more on processing systems, and mixing systems.

Powder handling systems used in the blending stage in the powder processing industry

Packing stage of a powder processing plant

Packing includes the weighting and filling of the product into bags. There are two methods used for the packing of processed or blended products from a granular or powder food processing plant. Bulk bags filling systems handle quantities from 500 to 1500 kg while small bag filling systems process quantities up to 25 kg. Both types of systems can be fully or semi-automated.

Systems that are used in packing stage include:

  • Small bag filling systems
  • Bulk bag filling system

Accessories that are used in systems within the packing stage include:

  • Aspiration units
  • BFM fittings
  • Control systems
  • Dust collectors
  • Dust extractors
  • Dust filters
  • Hoppers
  • Load cells
  • Loading spouts
  • Magnetic separators
  • Packaging waste removal systems

Powder handling systems used in the packing stage in the powder processing industry