 The most sophisticated technology for
the treatment of the concentrated substrate is the combined drying and granulation
process, offering a homogenous
and dry granulate as the final product and a maximum reduction
of volume.
- Prior to drying the concentrated
liquids from the evaporation
plant are mixed with the solids out of the press station.
This mixture is injected into the fluidized bed drier.
The ready granulate contains the organic substance and all mineral
salts - which mainly are valuable plant nutrients - out of the
fermented organic material. It is easy to handle and to store
and can be applied to the field like a mineral fertiliser.
Furthermore, it easily can be customised concerning its nutrient
contents by adding mineral fertilisers during or before the drying
process.
The fluidized bed drier provides high rates of heat and mass
transfer as well as homogeneous conditions in the process chamber.
This produces a uniform end product of high quality.
The fluidized bed is generated by a suction and/or pressure fan.
The fluidization medium is hot steam in a closed circuit. At
the start of the drying process, the fluidization vessel is refilled
with seed particles on which the fluidized bed is built up.
A heat transfer system supplies the required thermal energy.
The substrate is held in an intermediate storage tank from which
it is pumped to the fluidization vessel. Here, it is sprayed
into the bed. At this point, granules begin to form in the fluidization
vessel. When the required particle size is reached, granules
are continuously discharged via a classifying discharge unit.
Because of the nature of the process, the medium discharged from
the fluidization vessel contains fine particles. This material
is separated in a cyclone with a hose filter downstream. The
cyclone product is returned to the fluidization vessel.
The liquid entering the plant with the feed is cleaned by a cyclone
and used for the heating of the evaporation unit. The exhaust
air is eliminated via the dust filter downstream.
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