APPARATUS AND METHOD FOR VACUUM MICROWAVE-DEHYDRATING OF ORGANIC MATERIALS

APPAREIL ET METHODE DE DESHYDRATATION SOUS VIDE PAR MICRO-ONDES DE MATIERES ORGANIQUES

English Abstract

This invention relates to an apparatus and method, namely a continuous vacuum
microwave dehydrator, to evaporate water from water containing organic
materials by
means of microwave and vacuum. The vacuum chamber has an inlet port for the
introduction of the organic material to be dehydrated and a discharge port for
removal of
the dehydrated organic material. The apparatus has at lease 2 microwave
sources and
microwave transparent windows on the top of the vacuum chamber for
transmission of
microwave radiation from microwave sources into the vacuum chamber. In the
vacuum
chamber, a combination of a conveyor belt and a rotary drum handling soft,
sticky or crispy
organic material to be dehydrated is provided.

Claims

Patent:
APPARATUS AND METHOD FOR VACUUM MICROWAVE-DEHYDRATING OF
ORGANIC MATERIALS
CLAIMS
1. An apparatus for dehydrating organic material, comprising:
A vacuum chamber having a loading port for introduction organic material into
the
vacuum chamber and a discharge port for removal of the dehydrated organic
material;
The apparatus has at least 2 microwave sources and corresponding microwave
transparent windows on the top of the vacuum chamber for transmission of
microwave radiation from microwave sources into vacuum chamber;
The apparatus has an endless conveyor belt disposed longitudinally in vacuum
chamber to receive organic material to be dehydrated from the loading port and
convey the organic material to another end of the conveyor belt;
The apparatus has a rotary drum exposed longitudinally in vacuum chamber under
the conveyor belt in parallel;
means for loading the organic material input loading port of the vacuum
chamber;
means for transferring partially dehydrated organic material from conveyor
belt to
rotary drum;
means for rotating the rotary drum inside the vacuum chamber;
means for discharging the dehydrated organic material from the vacuum chamber
at
the discharge port.
2. An apparatus according to claim 1, wherein rotary drum exposed under the
conveyor belt, the rotary drum is in parallel with the conveyor belt.
3. An apparatus according to claim 1, wherein rotary drum, is made of
microwave
transparent low dielectric material.
4. An apparatus according to claim 1, wherein conveyor belt, is made of
microwave
transparent low dielectric material.
5. An apparatus according to claim 1, wherein rotary drum, having a plurality
of fins
exposed on the inner surface of the rotary drum to stir and transfer organic
material
toward discharge port.
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6. An apparatus according to claim 1, in the vacuum chamber 1, vacuum
microwave
dehydrating chamber is subdivided into several zones by means of metal plates
18
having an opening for passage of the conveyor belt and rotary drum 10.
7. An apparatus according to claim 1 and 3, the rotary drum sits on drive
wheels to be
able to rotate clockwise and counter-clockwise.
8. A method for dehydrating an organic material, comprising the steps of:
Load organic material to be dehydrated into vacuum chamber;
Distribute the loaded organic material on the conveyor belt evenly;
The conveyor belt with organic material on it passes subdivided vacuum
microwave
dehydrating zones;
At the end of the conveyor belt, partially dehydrated organic material is
collected and
guided into the rotary drum exposed under the conveyor belt.
In the rotary drum, partially dehydrated organic material is stirred and
conveyed from
one end of the rotary drum to another end. During transferring, the organic
material is
dehydrated by the microwave power that has been partially absorbed by organic
material on the conveyor belt.
At the other end of rotary drum, one or several holes on the rotary drum allow
dehydrated organic material to be dropped into the discharge port. By passing
through
an air-lock mechanism, the dehydrated organic material is discharged from the
vacuum
chamber eventually.
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Date Recue/Date Received 2021-02-04

Description

Patent:
APPARATUS AND METHOD FOR VACUUM MICROWAVE-DEHYDRATING OF
ORGANIC MATERIALS
DESCRIPTION
Field of the invention
The invention pertains to apparatus and method for vacuum microwave
dehydrating of
organic materials such as fruits and dairy products.
Background of the invention
The dehydration of various organic materials by exposure to microwave
radiation at
reduced atmospheric pressures is well known. Vacuum microwave dehydration
processes
may accordingly permit dehydration to occur in the absence or reduction of
oxygen, and
without exposing the material that is being dehydrated to significantly
elevated
temperatures, thereby yielding dried products that may have better physical,
organoleptic
and/or chemical qualities as compared to dried products obtained using other
known
dehydration processes such as hot air drying.
Beyond the apparatus for the purpose of research and pilot trial, to
commercial scale
production equipment, organic materials such as agricultural products are
often done at a
reduced pressure in a pressure tight dry chamber in which one or more
microwave heating
sources are arranged. Liquid products are usually pumped into the drying
chamber for
treatment where they are evenly distributed on an endless conveyor belt which
guides
them past the microwave heating sources from loading end of the drying chamber
to the
discharge end, as presented in the patent US4045639A and EP292053361. In these
apparatuses, the electrical field increases as the amount of energy absorbed
by the
quantity of product present decreases, this decrease being due to evaporation
and removal
of the water as heating progresses. The critical value of the electrical field
is thus reached
quickly, and to prevent the ionisation that would result there from the
electrical field,
microwave power must be reduced, which leads to a decrease in the rate of
drying and the
use of the apparatus below its maximum yield. To avoid the issue of ionisation
without
reducing microwave power, one idea is to introduce recycling water load to
absorb extra
Date Recue/Date Received 2021-02-04

microwave power as present in the patent CA2781644C. But a big portion of the
microwave power will be wasted on the water load.
On the other hand, due to natural unevenness of the organic products, such as
varieties on
sizes, shapes and moisture content, it is difficult to get uniform final
product from a
conveyor belt in terms of moisture content. Since microwave field distribution
in the
vacuum microwave dryer can never be even, uneven drying is a common issue to
belt type
vacuum microwave dehydrators.
Mainly for obtaining evenly dried products, tumbling type of vacuum microwave
dehydrators are also widely used in commercial applications. Patent US 10,
178, 873 B2
and EP0113900B1 present similar concepts in which the product is tumbled in
rotary
drums. The difference between the 2 ideas is whether the drums, as material
carriers, stay
in the vacuum microwave chamber or be loaded in and out from the vacuum
microwave
chamber with organic products. But many organic products are not suitable for
tumbling,
especially if they are in high moisture contained (like watermelon chops),
sticky (like fruit
pulps) or crispy (like tofu or cheese chips). The tumbling type of vacuum
microwave has
the same issue as belt type vacuum microwave dehydrators that microwave power
has to
be reduced when organic products getting lower moisture to avoid ionisation
and product
burning, which leads to a decrease in the rate of drying and the use of the
apparatus below
its maximum yield.
The key factor which permits the apparatus and method innovation of this
patent is the
specific layout and concurrent use of both tumbling and belt type vacuum
microwave
drying, enabling the ability to dry organic materials of almost all physical
properties,
including liquid, pulp, solid and bulk.
Brief description of the invention
According to the present invention, there is a vacuum microwave dehydrator for
the
continuous evaporation of a moisture containing material and preferably for
the dehydration
of water containing organic materials.
In accordance with the invention, the vacuum microwave dehydrating apparatus
comprises
a housing forming a closed elongated space, named vacuum chamber. The vacuum
chamber has an inlet port for the introduction of the organic material to be
dehydrated and
a discharge port for removal of the dehydrated organic material. The apparatus
has at least
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2 microwave sources and microwave transparent windows on the top of the vacuum
chamber for transmission of microwave radiation from microwave sources into
the vacuum
chamber. The apparatus has an endless conveyor belt disposed longitudinally in
the
vacuum chamber to receive organic material to be dehydrated from the inlet
port and
convey the organic material to the other end of the conveyor belt. In the same
vacuum
chamber, the apparatus has a rotary drum to receive partially dried organic
materials out of
the conveyor belt to continue the vacuum microwave dehydration process until
the organic
material reaches desired moisture. The rotary drum is located in parallel
directly under the
conveyor belt. The partially dehydrated organic material is tumbled in the
rotary drum and
transferred from one end of the rotary drum to another end of the rotary drum,
in which,
partially dehydrated organic material absorbs the remaining microwave power
that passed
through the organic materials on the conveyor belt. During the whole
dehydrating process,
the organic material to be dehydrated will essentially move through the vacuum
microwave
chamber twice: once on the conveyor belt and once in the rotary drum. Thus, in
the
vacuum chamber, there is always enough load to absorb microwave power and
organic
material is uniformly dehydrated.
According to another aspect of the invention, there is provided an apparatus
for
dehydrating organic materials, the vacuum microwave dehydrating apparatus
comprises a
vacuum chamber. The vacuum chamber has an inlet port for the introduction of
the organic
material to be dehydrated and a discharge port for removal of the dehydrated
organic
material, at least 2 microwave sources and microwave transparent windows on
the top of
the vacuum chamber for transmission of microwave radiation from microwave
sources into
vacuum chamber, a conveyor belt and a rotary drum located under the conveyor
belt.
Preferably the vacuum microwave dehydrating chamber is subdivided into several
zones
by means of metal plates having an opening for passage of the conveyor and
rotary drum.
According to another aspect of the invention, there is provided a method for
dehydrating
organic materials. A combination of a conveyor belt and a rotary drum handling
soft, sticky
or crispy organic material to be dehydrated is provided. The organic material
to be
dehydrated is pumped or loaded through an air-lock mechanism into the vacuum
microwave chamber in which the pressure is less than atmospheric pressure. In
the
vacuum microwave chamber, organic material to be dehydrated is distributed
evenly onto
the conveyor belt. The conveyor belt conveys the organic material to pass
through the
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vacuum chamber from one end to another, while the microwave power is applied
to
partially dehydrate the organic material. At the end of the conveyor belt, the
partially
dehydrated organic material is more rigid and less sticky. The partially
dehydrated organic
material then falls into the rotary drum through a hopper. In the rotary drum,
the organic
material is mixed and stirred to be evenly dehydrated by absorbing the
microwave power
which has been partially absorbed by organic material above on the conveyor
belt. The
dehydrated organic material will be discharged from the discharge port of the
vacuum
chamber through an air-lock mechanism.
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Date Recue/Date Received 2021-02-04