Getting Metal Out of Spices
Magnetic Separators in Spice Processing Plant
Most households have a collection of spices in one of their kitchen cupboards. Adding spices to food when cooking is now a common practice, but how are they processed and prepared?
Most spices are grown in the tropical regions of the world, with some thriving in the cool misty highlands. Many of the seed spices come from more temperate areas, such as coriander seed, which is grown in Northern India, Africa and the wheat producing areas of South Australia and Western New South Wales.
The nature of the location and how the spices are collected mean that there is a high risk of metal contamination. Most spice plants use a series of Magnetic Separators and Metal Detectors to remove and detect any problematic metal. Indeed, many UK supermarkets and food retailers (eg M & S) have strict guidelines on the use of Metal Removal equipment.
The plant shown in the flowsheet is a generalisation of a typical spice producing operation and highlights suitable locations for both Magnetic Separators and Metal Detectors.
Ideally, it is always best to remove metal before it enters the process. The metal tends to be larger in size and easier to separate. At this early stage, the delivered spices can be passed over a High Intensity Rare Earth Drum Magnet. This automatically removes magnetically susceptible metal prior to the spices moving on to storage.
Prior to Processing
Metal damages processing equipment and so it is always best practice to ensure protection by installing a Magnetic Separator. The spices can be passed over a simple Plate Magnet prior to grinding, protecting the grinding plates from damage.
At this stage, the spice may be sent directly to bagging. There are several types of Magnetic Separator that are often used to ensure a metal-free product including a Pneumatic In-Line Magnet on the pneumatic line, and a Grate Magnet or Plate Housing Magnet just prior to packing. A FS Metal Detector can also be used to remove any non-magnetic contamination.
Once the spices are mixed into a blend, they can be passed through a Centre Flow In-Line Magnet and Quicktron Metal Detector prior to storage in drums or containers. Prior to the spices being bottled, a final stage of Magnetic Separation is often used. This is commonly a form of Grate Magnet followed by a Quicktron Metal Detector. The final check on the bottled spice is often undertaken using a conveyor-type Metron C Metal Detector. The bottles are then packed ready for despatch.
The multiple stages of Metal Separation may appear excessive, but are required due to the nature of the process. Metal in a wide variety of forms can be introduced at any stage in the process, especially after grinding and mixing. Installing different designs of Magnetic Separator and Metal Detector at different points in the process will ensure the best protection against metal contamination.
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