Integrierte Vermeidung und Verminderung der Umweltverschmutzung

2.1.1.1.3 Description of techniques, methods and equipment
Chapter 2
Solid materials are commonly delivered in bags stacked on pallets or in containers. They may
also be delivered frozen, packed in standardised blocks with carton linings. They are typically
transported by forklift trucks and stored in warehouses. Larger amounts of solid raw materials
and powders are mostly delivered in bulk. These are off-loaded directly for processing or stored
in silos for future use. Solid raw materials can be conveyed by water, e.g. as is often the case for
vegetables, roots and tubers, by air, e.g. as is the case for solid particles and powder, or by
conveyor belts, elevators, screw conveyors and pumps.
Liquid materials are usually delivered in bulk tankers and then pumped into storage tanks. The
internal transport of liquid is achieved by pumping the liquid through pipework systems, which
can be extensive and complex. Smaller quantities of liquids are also delivered in mini-bulk
containers or in drums. These are then transported to storage areas by forklift trucks.
Gases like N2, CO2 and SO2 are delivered and stored in special pressurised containers. When
they are required they are connected to the system concerned and transported through the
pipework system by pressure differences. For example, SO2 is used in the processing of sugar
and wine, and N2 and CO2 in packing and chilling.
2.1.1.2 Sorting/screening, grading, dehulling, destemming/destalking and
trimming (A.2)
2.1.1.2.1 Objective
Most raw materials contain some components which are inedible or have variable physical
characteristics. Processing techniques such as sorting or screening, grading, dehulling,
destemming or destalking and trimming are necessary to obtain the required uniformity of the
raw material for further processing. A metal detector may also be used to ensure any metal
particles in the raw material are removed.
2.1.1.2.2 Field of application
These processing techniques are used as a first step in the processing of fruit and vegetables.
They are also used for meat, egg and fish processing.
2.1.1.2.3 Description of techniques, methods and equipment
Dry and wet sorting or screening is the separation of raw materials and/or slurries into
categories on the basis of shape, size, weight, image and colour. Dry sorting is applied in the
malting industry to select even sized grains. Wet sorting is used for slurries, to separate
components.
Size sorting and dry cleaning of agricultural raw materials separates solids into two or more
fractions. Size sorting is especially important for FDM products which have to be heated or
cooled, as large differences in size can lead to an over or under-processing of the product. For
size sorting, various types of screens and sieves, with fixed or variable apertures, can be used.
The screens may be stationary, rotating or vibrating. Shape sorting can be carried out manually
or mechanically with, e.g. a belt- or roller-sorter. Weight sorting is a very accurate method and
is, therefore, used for more valuable foods, e.g. for cut meats, eggs, tropical fruits and certain
vegetables. Image processing is used to sort foods on the basis of length, diameter and
appearance, i.e. surface defects and orientation of food on a conveyor. Finally, colour sorting of
defective discoloured items, can be applied at high rates using microprocessor controlled colour
sorters.
Sorting also allows the separation of some additional undesirable material at first sight, e.g.
leaves and stones, or inappropriate raw material such as immature or rotten berries, and is aimed
at ensuring that only good quality food is preserved and passed on for further processing.
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