AU3777100A

AU3777100A - Improvements in drying nuts and seeds

Info

Publication number: AU3777100A
Application number: AU37771/00A
Authority: AU
Inventors: Roy Victor Andrews
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-05-28
Filing date: 2000-05-29
Publication date: 2000-11-30

Description

P/00/011 Regulation 3.2 9* n.e

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S S COMMONWEALTH OF AUSTRALIA Patents Act 1990 COMPLETE SPECIFICA TION FOR A S TANDARD PA TENT

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Name of Applicant Actual In ventor(s): Address for Service: ROY VICTOR ANDREWS ROY VICTOR ANDREWS

AHEARNS

Patent Trade Mark Attorneys GPO Box 1149 Brisbane Queensland 4001 IMPROVEMENTS IN DRYING NUTS AND

SEEDS"

Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me: -1- "IMPROVEMENTS IN DRYING NUTS AND SEEDS" THIS INVENTION relates to improvements in the drying of nuts and seeds, and more particularly to an improved method for drying nuts and seeds, and an apparatus for carrying out the improved method.

In this specification, particular reference will be made to the drying of madacamia nuts (Macadamia spp, eg. M. ternifoilia; M. integrifolia). However, it will be appreciated that the invention is applicable generally to the drying of nuts and seeds.

The drying of nuts and seeds has been carried out in the past by placing the nuts or seeds in a heated air stream for an extended period of time, relying on diffusion of moisture through *the shell or integument to reduce the overall moisture content of the nut or seed. However, diffusion rates are quite slow through the shells or integuments, particularly in the case of thick shells surrounding nuts. Macadamia nuts in particular have a *hard, tough, thick shell, making the drying of this type of nut energy inefficient using the traditional drying process.

S 20 One object of the present invention is to provide an improved method for drying nuts and seeds. Another object of the invention is to provide an apparatus for drying nuts and seeds.

With the foregoing in view, this invention resides broadly in a method of drying nuts or seeds, including: heating the nuts or seeds in a heated, dry air stream until equilibrium in temperature and moisture content of the air stream is substantially reached; reducing the pressure of the atmosphere surrounding the nuts or seeds until a new equilibrium is substantially reached; -2- 0 0 0*0* restoring, or at least partially restoring, the pressure of the air stream, and repeating the foregoing steps until the nuts or seeds achieve a desired moisture content.

In another aspect, this invention resides broadly in a method of drying nuts or seeds, including: providing an air stream; reducing the temperature of the air stream sufficiently to substantially dry the air stream; heating the dried air stream; contacting the heated dry air stream with the nuts or seeds, and reducing the pressure of the heated dry air stream at predetermined intervals.

Preferably, the method further includes arranging the nuts or seeds into a bed, and recirculating the air stream by directing the air stream from the bed, drying the air stream by removing as least some of the moisture therefrom, heating the air stream and returning the air stream to the bed. It is also preferred that the pressure of the atmosphere surrounding the nuts or seeds initially be substantially atmospheric pressure and that the pressure be reduced by directing some of the recirculating air from the air stream. If desired, the air stream may be filtered.

In another aspect, this invention resides broadly in drying apparatus for drying nuts or seeds, including: a blower for creating an air stream; holding means for holding the nuts or seeds in contact with the air stream; 0 0 20 *a -3air conditioning means in fluid communication with the air stream for conditioning the temperature and humidity of the air stream, and pressure reduction means in fluid communication with the air stream for selectively reducing the atmospheric pressure of the air stream.

Preferably, the air conditioning means heats and dries the air supplied to the blower. It is also preferred that the air stream be recirculated through a recirculation duct. It is further preferred that pressure reduction means be provided by e* *another blower (referred to hereinafter as a "pressure reduction blower", which is operable to remove at least some of the air from the air stream, thereby reducing the pressure thereof. In a e preferred arrangement, the pressure reduction means is 15 selectively operable to enable the drying apparatus to be operated in a repeated cycle in which air is recirculated at atmospheric pressure for part of the cycle, and at a reduced .pressure for the remainder of the cycle. In an alternative form, the blower and pressure reduction means may be embodied together, S 20 such as by providing the blower in concert with a flow diverting valve or baffle whereby the induced air flow from the blower may be selectively directed through the recirculation duct or be diverted from the recirculation duct to selectively create a reduction in pressure in the recirculation duct and holding means, thereby reducing the pressure of the atmosphere surrounding the nuts or seeds as required. An air inlet is preferably included in the recirculation duct upstream of the air conditioning means and is selectively openable to permit air to enter the recirculation duct to restore atmospheric pressure -4therein. The air inlet may be provided by the pressure reduction blower being left inoperable, and being arranged to permit backflow of air when in an inoperable state. The flow diverting valve is operable to divert at least some of the airflow from the blower, but it will be appreciated that in order to create a strong vacuum, the pressure reduction blower will divert as much airflow as is practical from the air stream.

Preferably, the holding means includes a silo having a support therein for supporting the nuts or seeds in contact the air stream and has a temperature probe inserted therein for *o measuring the temperature of the air in the holding means, there being a controlling connection to the heating means for cutting goo* off the heating if the temperature in the holding means exceeds a desired or required level. Preferably, the air conditioning 15 means includes complementary parts of a heat pump, and is more e preferably contained entirely within the recirculation duct, the complementary parts being a condenser for heating the air and an evaporator for drying the air. Humidity measuring means is preferably interposed in the recirculation duct after the filter S 20 and before the air inlet so that the humidity of the recirculating air may be measured at a location suitable for determining whether the nuts or seeds have achieved a desired level of moisture. A filter may interposed in the recirculation duct for filtering air passing from the holding means, particularly for nuts or seeds having a friable shell or husk which may become entrained in the air stream.

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate two preferred embodiments of the invention, and wherein: Fig. 1 is a schematic diagram of a drying apparatus according to the invention, and Fig. 2 is a schematic diagram of another drying apparatus according to the invention.

Referring to Fig. 1, the drying apparatus 10 includes a silo 11 having a screen 12 for supporting a bed of macadamia nuts 13.

The screen is near to, but spaced from the lower end of the silo.

The bed of nuts may be increased to a nut bed height shown by the dashed line at 14. The silo also has a nut inlet 15 near the top and a nut outlet 16 in the side close to the bottom of the silo, but at level with the screen, which is sloped to permit the nuts to roll out. A silo outlet 31 leads from the top of the silo, and a silo inlet 32 leads into the bottom of the silo, to and from a recirculation duct 35 respectively.

Within the recirculation duct 35 there is provided a heat pump shown generally at 20 and having a condenser 21 and an evaporator 22 which are operated by a compressor 24, all of which S 20 are mounted within the recirculation duct. A drain pan 23 is located below the evaporator 22 to collect moisture condensation which trickles from the evaporator when the drying apparatus is in operation drying the nuts. The heat pump is shown generally in a lower portion of the recirculation duct, and it will be appreciated that the heat pump would not typically be located in an elevated position.

Also within the recirculation duct 35 is a blower located immediately upstream from the condenser, and which is operable to blow air through the recirculation duct in the -6direction of the arrows with reference numerals 18. The air stream thus created also passes through the bed of nuts 13 in the direction of the arrows with reference numerals 19.

A humidistat 29 is provided in the recirculation duct downstream from the silo outlet for measuring the moisture content of the air stream and provide a comparative signal for controlling the initiation of the changeover of the cycle. After the initial changeover, the cycling of pressure is controlled by a timer 28.

A pressure reduction blower 26 is provided on the input to ""*the blower 25 for exhausting its output to the outside of the recirculation duct, thereby reducing the atmospheric pressure within the recirculation duct and the silo. For restoration of .normal atmospheric pressure, the pressure reduction blower is turned off, the pressure reduction blower being so formed and *arranged that air may flow therethrough in the reverse direction when it is inoperative. However, there is a delay after start up of the evaporator cooling cycle before air is introduced in order to avoid humidity from the outside air entering the silo. A wind "20 vane 34, anemometer or flow measurement probe 34 is provided .i downstream from the silo outlet controlling the speed of the pressure reduction blower and/or for measuring the air flow rate of the air stream.

The operation of the drying apparatus is controlled and automatic. During normal operation, (that is, at substantially atmospheric pressure), the pressure reduction blower 26 is not operational. The blower 25 has a variable speed control to compensate for changes in air flow resistance in the bed of nuts and by the different modes of operation of the drying apparatus.

The air stream passes through the screen and bed of nuts upwardly, and through the silo outlet and into the recirculation duct. From there, the air stream passes the fan speed controller and the humidistat, whereupon its moisture content is measured.

The air stream then passes through the evaporator, which cools the air to remove at least some of the moisture contained therein, and passes through the condenser, which heats the air stream to a temperature close to, but not exceeding 70 0

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however, the air is closer to 20 0 C when is passes through the bed of nuts 13. The moisture collected in the drain pan is removed at regular intervals in this part of the cycle.

For the depressurised part of the cycle, the pressure reduction blower is activated to direct its output to the outside S through the air outlet, thereby reducing the pressure to approximately 10 to 20 cm Hg below atmospheric pressure. If *4*S there is an increase in the moisture content during this part of the cycle above a desired limit, the normal operation of the drying apparatus is resumed, and the process repeated until a desired level of moisture is achieved in the bed of nuts.

S 20 Referring to Fig. 2, the other drying apparatus 40 is shown with the same features being given the same reference numerals as Fig. 1, and is arranged in a similar form thereto.

However, within the recirculation duct 35 there is provided a blower 45 operable to blow air through the recirculation duct in the same manner as described above with reference to Fig. i, the air stream thus created passes through the bed of nuts 13 in the direction of the arrows 19 and through the ricirculation duct in the direction of the arrows 18.

-8- A filter 30 is also provided in the recirculation duct downstream from the silo outlet 31. The filter is for collecting dust which might become entrained in the air stream after passing through the bed of nuts 13. The humidistat 29 is provided in the recirculation duct 35 downstream from the filter 30 for measuring the moisture content of the air stream and to provide a comparative signal for controlling the initiation of the changeover of the cycle.

A diverter baffle 46 is provided on the output from the blower for diverting as much as possible of its output to the outside of the recirculation duct through an air outlet 47, thereby reducing the atmospheric pressure within the recirculation duct and the silo. For restoration of normal :atmospheric pressure, an air inlet 48 is provided downstream from the humidistat, however, there is a delay after start up of the evaporator cooling cycle before air is introduced in order to avoid humidity from the outside air entering the silo. The wind vane 34 is provided downstream from the air inlet for measuring the air flow and regulating the airflow over the evaporator coil.

The operation of the other drying apparatus of Fig. 2 is similar to that of Fig. i, being controlled and automatic. During normal operation, the diverter baffle 46 directs all of the output from the blower through the silo by way of the silo inlet 32. The air stream passes through the screen and bed of nuts upwardly, and through the silo outlet and into the recirculation duct. From there, the air stream passes through the filter, whereupon it has any dust substantially removed, past the humidistat, whereupon its moisture content is measured, past the air inlet and wind vane, where its flow rate is measured. The air -9stream then passes through the evaporator, which cools the air to remove at least some of the moisture contained therein, and passes through the condenser, which heats the air stream before it returns to the blower. The moisture collected in the drain pan is removed at regular intervals in this part of the cycle.

For the depressurised part of the cycle, the diverter baffle is actuated to direct as much as possible of the output from the blower to the outside through the air outlet, thereby reducing the pressure below atmospheric. The air outlet includes a nonreturn valve to prevent backflow of air into the system. The remainder of the output from the blower is directed through the silo and around the recirculation duct in the same manner as with the normal operation, however, it is not necessary to run the *heat pump 20 during this part of the cycle. If there is an increase in the moisture content during this part of the cycle :.above a desired limit, the normal operation of the drying apparatus may be resumed, and the process repeated until a desired level of moisture is achieved in the bed of nuts. To 0**e return the system to atmospheric pressure, the air inlet 28 is 20 opened for a short period of time.

In reducing the pressure surrounding nuts having an air space between the kernel and the shell, it is believed that there is a net transport of air through the shell, carrying with it the equilibrated moisture content thereof into the reduced pressure atmosphere surrounding the nuts. For nuts or seeds, including the macadamia nuts, it is believed that reducing the pressure enhances the transport of moisture into the surrounding atmosphere. When repressurised with dry air, the dry air penetrates any shells which had a net loss of air in the reduced pressure part of the cycle, and permits the moisture in the nuts or seeds inside their shells to equilibrate their moisture content with the dryer air thus penetrating the shells.

Although the invention has been described with reference to specific examples, it will be appreciated by persons skilled in the art that the invention may be embodied in many other forms and fall within the broad scope and ambit of the invention as defined by the following claims.

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Claims

2. A method of drying nuts or seeds, including: providing an air stream; reducing the temperature of the air stream sufficiently to substantially dry the air stream; heating the dried air stream; contacting the heated dry air stream with the nuts or seeds, a aS Sae 20 and reducing the pressure of the heated dry air stream at predetermined intervals. 2. A method according to Claim 1 or Claim 2, and including arranging the nuts or seeds into a bed, and recirculating the air stream by directing the air stream from the bed, drying the air stream by removing as least some of the moisture therefrom, heating the air stream and returning the air stream to the bed. -12-
3. A method according to any one of the preceding claims, wherein the pressure of the atmosphere surrounding the nuts or seeds is initially substantially atmospheric pressure and the pressure is reduced by directing some of the recirculating air from the air stream.
4. Drying apparatus for drying nuts or seeds, including: a blower for creating an air stream; holding means for holding the nuts or seeds in contact with the air stream; air conditioning means in fluid communication with the holding means for conditioning the temperature and humidity of the air stream, and *e .0pressure reduction means in fluid communication with the air stream for selectively reducing the atmospheric pressure thereof. 0**0 a Drying apparatus according to Claim 4, and including a recirculation duct for recirculating the air stream. 0000 rr 20 6. Drying apparatus according to Claim 4 or Claim 5, wherein the pressure reduction means includes a pressure reduction blower operable to remove at least some of the air from the air stream thereby reducing the pressure thereof.
7. Drying apparatus according to Claim 6, wherein the pressure reduction blower is adapted to permit backflow of air when not in an operating state. -13-
8. Drying apparatus according to any one of Claims 4 to 7, wherein the holding means includes a silo having a support therein for supporting the nuts or seeds in contact the air stream and a temperature probe inserted therein for measuring the temperature of the air in the holding means.
9. Drying apparatus according to Claim 8, and including a controlling connection to the heating means for cutting off the heating if the temperature in the holding means exceeds a desired or required level. *-woe:
10. Drying apparatus as substantially hereinbefore described with reference to Fig. 1
11. Drying apparatus as substantially hereinbefore described with reference to Fig. 2. Dated this 29 t h day of May 2000 20 20 ROY VICTOR ANDREWS by his Patent Attorneys AHEARNS