WO2019043533A1

WO2019043533A1 - Pasteurizer

Info

Publication number: WO2019043533A1
Application number: PCT/IB2018/056420
Authority: WO
Inventors: Obiro Cuthbert WOKADALA; Petrus Johannes BRITZ; Petrus Paulus Hugo SNYMAN; Phalane Sekina LEBOTSA; Tingmin YU
Original assignee: Agricultural Research Council
Priority date: 2017-08-31
Filing date: 2018-08-24
Publication date: 2019-03-07
Also published as: ZA202001317B

Abstract

This invention relates to a pasteurizer. In particular, but not exclusively, the invention relates to a pasteurizer which is also suitable for use in pasteurizing soy milk. The pasteurizer includes a pasteurizing chamber in that in turn comprises an outer tank, an annular inner tank substantially concentric to the outer tank, with the annular inner tank defining a pasteurizing section through which the liquid flows. A first heat exchange passage is defined by a hollow core of the annular inner tank, and a second heat exchange passage is defined between an outer surface of the annular inner tank and an inner surface of the outer tank. The pasteurizing chamber can be selectively configured in order for the heating gas to be directed through the first heat exchange passage only, or through both heat exchange passages.

Description

PASTEURIZER

BACKGROUND TO THE INVENTION

This invention relates to a pasteurizer. In particular, but not exclusively, the invention relates to a pasteurizer which is also suitable for use in pasteurizing soy milk. The invention also relates to a pasteurizer that is configured to be used in remote locations without an electricity supply infrastructure.

It is common practice for various consumable liquids, such as milk and fruit juices, to be treated prior to consumption in order to avoid diseases from spreading to humans, and also to destroy spoilage organisms in the untreated liquids. Thermal treatments such as pasteurization are commonly used due to their ability of killing pathogens and potentially harmful enzymes contained in the liquid. Pasteurization is the use of low- temperature heat treatment with a temperature high enough to destroy spoilage organisms, and low enough not to destroy the original characteristics of the liquid being treated. Liquids suitable for undergoing pasteurisation include, for example, various types of milk (diary, soy) as well as fruit juices.

Analysis of the dairy market value chain indicates that farmers and other producers at times lack the expertise and equipment to pasteurize milk, which is a major limitation to the marketing of milk by farmers and other producers, especially insofar as smaller scale farmers are concerned. It is also difficult to use standard existing equipment, as the necessary infrastructure that is presupposed when design pasteurizers (for example electricity for fluid distribution and heating) are not available. The same applies to the soy milk and fruit juice industries.

In addition, a specific assessment of the soya bean value chain reveals that there is a need and opportunity for investment in affordable small-medium scale technologies in poor communities which are linked to the local production of soya beans, and in particular soya bean derived products such as soy milk. Pasteurizers are the most critically limiting equipment in soy milk processing for small, medium and micro enterprises (SMMEs) because of the high cost of commercial pasteurizers. Existing pasteurizers are predominantly aimed at commercial use and require easy accessibility to resources such as electricity, which may be limited in poor, rural communities.

Pasteurization of soy milk is similar to the pasteurization of dairy milk and other dairy products. Continuous flow pasteurizers typically include a first holding reservoir for receiving milk to be pasteurized, a pasteurizing section where the milk is heated to a desired pasteurization temperature, and a second reservoir for holding the pasteurized milk after pasteurization. From the first reservoir the milk is pumped through the pasteurizing section where the milk is pasteurized. In the pasteurizing section a heat source transmits heat to the milk flowing through the section. The heat source is typically an electrical heating element. Milk that has not reached the desired pasteurization temperature does not pass through to the second reservoir but is recirculated back to the first reservoir. Milk that has reached the desired pasteurization temperature passes through to the second reservoir. The known continuous flow pasteurizers are typically powered by an external electricity source, which energizes the heating element, while also driving the pump used to displace the milk. The problem with these pasteurizers is that implementation in rural areas with limited resources is difficult.

Most conventional pasteurizers use either parallel plate heat exchangers or open pan heat exchangers. Parallel plate heat exchangers are effective, but require a significant pump head to force the liquid through the heat exchanger. Open pan heat exchangers require a low pump head, but they cannot be heated efficiently by a non-electric arrangement, and the temperature is also difficult to control. It will therefore be readily apparent that the correct design of the heat exchange mechanism will be of critical importance if pasteurizer design were to be adapted for use without external infrastructure support (e.g. an electrical gird) and if pasteurizers were to be made affordable to remote and smaller scale users.

It is an object of this invention to alleviate at least some of the problems experienced with existing commercial pasteurizers.

It is a further object of this invention to provide an alternative pasteurizer that will be a useful alternative to existing commercial pasteurizers.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention there is provided a pasteurizer including:

a first reservoir for receiving liquid to be pasteurized;

a pasteurizing chamber in fluid communication with the first reservoir, the pasteurizing chamber including :

an outer tank; and

an annular inner tank substantially concentric to the outer tank, the annular inner tank defining a pasteurizing section through which the liquid flows; a first heat exchange passage defined by a hollow core of the annular inner tank;

a second heat exchange passage defined between an outer surface of the annular inner tank and an inner surface of the outer tank; a gas burner for providing a heating gas to the pasteurizing chamber, the gas burner being substantially axially aligned with the first heat exchange passage;

a second reservoir in fluid communication with the pasteurizing chamber, the second reservoir configured to receive the pasteurized liquid for packaging;

characterised in that the pasteurizing chamber can be selectively configured in order for the heating gas to be directed through the first heat exchange passage only, or through both heat exchange passages.

There is provided for the pasteurizing chamber to be selectively configurable in order for the heating gas to be directed through the first heat exchange passage and then subsequently also through the second heat exchange passage.

The pasteurizing chamber may include a first chimney which is in flow communication with the first heat exchange passage, the first chimney located towards an upper end of the outer tank.

The pasteurizing chamber may also include a second chimney which is in flow communication with the second heat exchange passage, the second chimney located towards a lower end of the outer tank.

A flow control device, for example a damper, may be located in the first chimney in order for the first chimney to be selectively closable in order to alter the flow path of heating gas through the pasteurizing chamber.

There is provided for the first heating passage and the second heating passage to include heating fins for optimizing heat transfer into the liquid in the annular inner tank. There is also provided for a central shaft to extend co-axially inside the hollow core of the annular inner tank, and for baffles to be located on the central shaft for directing the heating gas towards an inner surface of the annular inner tank.

There is provided for the internal volume of the annular tank to include turbulence fins for ensuring that the flow regime inside the annulus is turbulent for optimized heat transfer to the fluid.

There is also provided for the pasteurizer to include a recirculation conduit for channelling liquid that is not at the desired pasteurization temperature back to the first reservoir or pasteurization chamber.

A control valve may be located in the recirculation conduit.

The control valve may be manually actuated based on a temperature reading, for example obtained from an inline temperature detector with a temperature display panel, or may alternatively be in the form of a temperature sensitive flow valve, or temperature controlled actuating valve that is actuated when a thermocouple or probe detects that the temperature has reached a predetermined set point.

In one embodiment the gas burner may include a gas thermostat for regulating the temperature within the pasteurizing chamber.

There is provided for the pasteurizer to include a pump suitable for displacing the liquid to be pasteurized.

The pump may be connected to a solar panel.

According to a further aspect of the invention there is provided a pasteurizing chamber for a pasteurizer including:

an outer tank; and an annular inner tank substantially concentrically located inside the outer tank, the annular inner tank defining a pasteurizing section through which the liquid flows;

a first heat exchange passage defined by a hollow core of the annular inner tank;

a second heat exchange passage defined between an outer surface of the annular inner tank and an inner surface of the outer tank; characterised in that the pasteurizing chamber can be selectively configured in order for a heating gas to be directed through the first heat exchange passage only, or through both heat exchange passages.

According to a still further aspect of the invention there is provided a method of operating a pasteurizer including the steps of:

- providing a pasteurizing chamber including a first heat exchange passage and a second heat exchange passage;

- enabling a heating gas to flow through the first heating passage only while the pasteurizing chamber is heated up from an ambient temperature towards an operating temperature;

- directing the heating gas to flow through the first heating passage and the second heating passage once an actual temperature is within a predetermined range below the operating temperature.

There is provided for the predetermined range is 0 to 20 °C, preferably 0 to 10 °C.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a milk pasteurizer according to the invention; Figure 2 shows a front view of the milk pasteurizer of Figure 1 ;

Figure 3 shows a top plan view of the milk pasteurizer of Figure 1 ;

Figure 4 shows a perspective view of the pasteurizing chamber of the milk pasteurizer of Figure 1 ; and

Figure 5 shows a sectioned side view of the pasteurizing chamber of

Figure 4.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Additionally, the words "lower", "upper", "upward", "down" and "downward" designate directions in the drawings to which reference is made. The terminology includes the words specifically mentioned above, derivatives thereof, and words or similar import. It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term "include" and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items. Referring to the drawings, in which like numerals indicate like features, a non-limiting example of a pasteurizer in accordance with the invention is generally indicated by reference numeral 10.

As shown in Figures 1 , 2 and 3, the pasteurizer 10 includes a first reservoir 12 for receiving a liquid, for example milk, to be pasteurized, a pasteurizing chamber 30 where the milk is pasteurized and a second reservoir 60 where the pasteurized milk is stored for packaging. The first reservoir 12 has an outlet 14 which is in flow communication with a pump 18 by way of a conduit 16. The pump 18 is configured to pump the milk from the first reservoir 12 through the conduit 16 to the pasteurizing chamber 30 where the milk is treated before exiting the pasteurization chamber 30. From here, the milk is either recirculated back into the pasteurization chamber 30 via a recirculation pipe 66 or enters the second reservoir 60 where packaging of the final pasteurized milk takes place.

The pasteurizing chamber 30, as best seen in Figures 4 and 5, comprises an outer tank or furnace chamber 32, and an annular inner tank 34 located concentrically inside the outer tank 32. A gas burner 38 and gas thermostat (not shown), for providing heat and regulating the temperature within the furnace chamber 32, is located operatively below the pasteurizing chamber, and more particularly below a hollow core of the annular inner tank 34, which in use defines a first heat exchange passage (indicated by arrows A). The internal volume 36 of the annular inner tank 34 defines a pasteurizing section through which the milk flows during pasteurization. The internal volume 36 is defined between an outer cylinder 34.1 and an inner cylinder 34.2 of the inner annular tank 34. In one embodiment of the invention it is envisaged for the pasteurizing section to be in the form of a helical coil or any other suitable conduit in which the milk can flow and through which heat can be transferred to the milk, but in the preferred embodiment shown in the drawings the pasturing section will be in the form of the annular tank. A second heat exchange passage 50 (indicated by arrows B) is defined between the operatively inner surface of the outer tank 32, and the operatively outer surface of the annular inner tank 34.

Figure 5 shows a cross-sectional side view of the pasteurizing chamber 30 with the gas burner 38 located at the bottom of the outer tank or furnace chamber 32, but axially aligned with the hollow core or first heat exchange passage 52 of the annular inner tank 34. The pasteurizing chamber 30 includes a first chimney 42 at an upper end of the furnace chamber 32 for releasing the flue gases produced by the gas burner 38. The pasteurizing chamber 32 also includes a second chimney 43 located towards a lower end of the pasteurising chamber. A valve or damper 42.1 is provided in the first chimney 42. In one operational mode (a heating mode), the damper 42.1 will be open, and the flue gas will travel upwards through the first heat exchange passage 52, and then exiting the pasteurizing chamber 30 without also going down the second heat exchange passage 50. In another operational mode (a maintaining mode), the damper 42.1 will be closed, and the flue gas will travel from the upper end of the first heat exchange passage 52 down the second heat exchange passage 50, and will exit the system via the second chimney 43.

It is envisaged for the gas burner to utilise biogas or LP gas provided by a gas cylinder 102, for example as seen in Figures 1 , 2 and 3. In one preferred embodiment of the invention the heating of the milk within the annular inner tank 36 is by direct radiant heat provided by the gas burner 38. It is, however, envisaged that in another embodiment of the invention (not shown), the gas burner 38 heats a therminol liquid in which the annulus or similar conduit is immersed. The temperature within the pasteurizing chamber 30 is controlled by a pilot flame controlled thermocouple or gas thermostat (not shown).

The second heat exchange passage 50 and the first heat exchange passage 52 are provided with heating fins 46 for facilitating enhanced heat transfer to the milk flowing in the annular inner tank 36. There are also fins or baffles 48 provided on a central shaft 54 extending along a centreline of the first heat transfer passage 52. These baffles 48 serve to direct the heating gas toward the inner surface 34.2 of the annular inner tank 36 in order to optimise heat transfer to the inner tank 36. The internal volume of the annular inner tank 36 also includes internal turbulence and heating fins 44 for ensuring that the flow of milk in the annulus 36 is turbulent, thereby further optimising heat transfer to the milk. Insulation (not shown) is provided on the inner surface of the furnace chamber 32 in order to minimize heat loss from the pasteurizing chamber 30.

In use, milk is introduced in the first reservoir 12 before it is pumped by the pump 18 to the pasteurizing chamber 30. A valve 19 is located between the first reservoir 12 and the pasteurizing chamber 30, and the milk feed rate into the pasteurizing chamber is controlled by the valve. The valve position can be regulated to switch between continuous flow operation and semi- continuous flow operation. The milk enters the annular inner tank 36 in the pasteurizing chamber 30 via an annulus inlet 22.1 located at the bottom of the pasteurizing chamber 30 and exits the annular inner tank 36 at an operatively upper section of the pasteurization chamber via an annulus outlet 22.2. The milk is heated within the annular inner tank 36 by the heat transferred from the heat exchange passages (50 and 52). The milk then exits the pasteurizing chamber 30 via the annulus outlet 22.2.

At this point the temperature of the milk is measured, and a control valve 64 is set in a position either to recirculate the milk to the pasteurization chamber 30 for a second pass, or to direct the milk into the second reservoir 60. In this embodiment the valve 64 is a manual valve (for example a ball valve), and the temperature of the milk is measured by an inline temperature detector with a display panel, but it will be appreciated that the valve may also be an automatically actuated valve that receives a control signal from a suitable thermocouple or probe. The control temperature of the milk is chosen based on the required temperature that the milk needs to reach in order for it to be considered sufficiently pasteurized. If the milk is out-of-control-temperature it is channelled back towards the pasteurization chamber 30 via the recirculation pipe 66. This ensures that the milk being pasteurized is sufficiently pasteurized before entering the second reservoir 60 for packaging or immediate consumption. The temperature will depend on the liquid that is being pasteurized, and will for example be different for fruit juices, cow milk and soy milk. The operating temperature for milk may for example be between 75 and 100°C, but for soy milk it may be between 120 and 140°C. The recirculation pipe 66 is fitted with a reservoir offtake that is linked to the first tank 12. The configuration of the first tank, and the presence of this offtake, ensures that the system is an open system without the possibility of pressure build-up during recirculation.

It is envisaged for the second reservoir 60 also to serve as a packaging station. Bottles or other suitable containers are filled with the pasteurized milk from the second reservoir 60 via a filling tap 68.

It is envisaged for all surfaces that come into contact with the milk to be made of food grade stainless steel.

The pump 18 provides the desired pressure and flow rate to the pasteurizer 10, and in particular ensures that the milk is forced through the pasteurizing chamber 30. The pasteurizer 10 also includes a solar panel 1 10 connected to an electrical box 1 12 for providing renewable power to the pump 18. Electricity is stored in a battery pack with an appropriate alternator linked to the pump, and the pasteurizer 10 therefore requires no external electricity source for powering the pump. Electricity is also not required to provide heat to the pasteurizing chamber 30 which is heated by way of LP gas or biogas. This allows the pasteurizer 10 to be suitable for rural small-medium micro enterprises with limited access to electricity.

The pasteurizer 10 is essentially a mobile unit on a base 100 fitted with wheels (not shown). This allows the pasteurizer 10 to be easily and readily movable for producing ready to consume pasteurized milk. The compact configuration of the pasteurizer 10 allows for easy mobility and use in poor communities with limited access to resources in particular electricity. A number of other advantages are associated with the new design, including:

- The pasteurizer has a product recycling functionality which enables the product to be recycled if a sufficient temperature has not been reached. This recycling functionality is currently controlled by way of a manual valve, but it will be possible to use an automated control valve at some point in the future. The recycling functionality is especially important for a free-standing pasteurizer where heating capacity is limited.

- The heat exchange configuration can be run in a single pass or a double pass configuration. Two exhausts or chimneys are provided, with a damper being located in the uppermost chimney. When the damper is open, the flue gas will pass through the inside of the heating annulus only. The flow rate, and thus heating rate, will be high, but the process will not be optimally efficient and this operational mode will accordingly be used for initial heating. Once the heat transfer arrangement has been heated, the damper will be closed, and the flue gas will be forced to flow downwardly adjacent the outer perimeter of the heating annulus. The increased pressure differential will result in reduced gas flow, and this mode of operation is ideally suited for maintaining the operational temperature once reached. It is foreseen for the pasteurizer to be switched from the single pass mode to the double pass mode when the temperature is about 10°C below the desired operating temperature.

- The annular heating arrangement is not an arbitrary choice, but is particularly useful for this kind of stand-alone pasteurizer. Parallel plate heat exchangers are effective but require a significantly higher pump head which will not be easily achievable by way of a solar pump. Open pan heat exchangers require a very low pump head, but they cannot be heated efficiently by a gas heating arrangement, and the temperature is also difficult to control. It follows that the combination of the annular heating arrangement and the solar pump is also an important aspect of the invention.

It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention. It is easily understood from the present application that the particular features of the present invention, as generally described and illustrated in the figures, can be arranged and designed according to a wide variety of different configurations. In this way, the description of the present invention and the related figures are not provided to limit the scope of the invention but simply represent selected embodiments.

The skilled person will understand that the technical characteristics of a given embodiment can in fact be combined with characteristics of another embodiment, unless otherwise expressed or it is evident that these characteristics are incompatible. Also, the technical characteristics described in a given embodiment can be isolated from the other characteristics of this embodiment unless otherwise expressed.

Claims

CLAIMS:

1 . A pasteurizer including:

a first reservoir for receiving liquid to be pasteurized;

a pasteurizing chamber in fluid communication with the first reservoir, the pasteurizing chamber including:

an outer tank; and

an annular inner tank substantially concentrically located inside the outer tank, the annular inner tank defining a pasteurizing section through which the liquid flows;

a second heat exchange passage defined between an outer surface of the annular inner tank and an inner surface of the outer tank;

a gas burner for providing a heating gas to the pasteurizing chamber, the gas burner being substantially axially aligned with the first heat exchange passage;

2. The pasteurizer of claim 1 in which the pasteurizing chamber is selectively configurable in order for the heating gas to be directed through the first heat exchange passage and then subsequently also through the second heat exchange passage.

3. The pasteurizer of claim 1 or claim 2 including a first chimney which is in flow communication with the first heat exchange passage, with the first chimney located towards an upper end of the outer tank.

4. The pasteurizer of claim 3 including a second chimney which is in flow communication with the second heat exchange passage, with the second chimney located towards a lower end of the outer tank.

5. The pasteurizer of claim 3 or 4 in which a flow control device is located in the first chimney in order for the first chimney to be selectively closable in order to alter the flow path of heating gas through the pasteurizing chamber.

6. The pasteurizer of any one of the preceding claims in which the first heating passage and the second heating passage include heating fins for optimizing heat transfer into the liquid in the annular inner tank.

7. The pasteurizer of any one of the preceding claims in which a central shaft extends co-axially inside the hollow core of the annular inner tank, and in which baffles are located on the central shaft for directing the heating gas towards an inner surface of the annular inner tank.

8. The pasteurizer of any one of the preceding claims in which an internal volume of the annular tank includes turbulence fins for ensuring that the flow regime inside the annulus is turbulent for optimized heat transfer to the fluid.

9. The pasteurizer of any one of the preceding claims including a recirculation conduit for channelling liquid that is not at the desired pasteurization temperature back to the first reservoir or pasteurization chamber.

10. The pasteurizer of claim 9 in which a control valve is located in the recirculation conduit.

1 1 . The pasteurizer of claim 10 in which the control valve may be manually actuated based on a temperature reading from an inline temperature detector with a temperature display panel.

12. The pasteurizer of claim 10 in which the control valve is a temperature controlled actuating valve that is actuated when a thermocouple or probe detects that the temperature has reached a predetermined set point.

13. The pasteurizer of any one of the preceding claims including a pump suitable for displacing the liquid to be pasteurized.

14. The pasteurizer of claim 13 in which the pump is connected to a solar panel.

15. A pasteurizing chamber for a pasteurizer including:

an outer tank; and

an annular inner tank substantially concentrically located inside the outer tank, the annular inner tank defining a pasteurizing section through which the liquid flows; a first heat exchange passage defined by a hollow core of the annular inner tank;

characterised in that the pasteurizing chamber can be selectively configured in order for a heating gas to be directed through the first heat exchange passage only, or through both heat exchange passages.

16. A method of operating a pasteurizer including the steps of:

17. The method of claim 16 in which the predetermined range is between 0 to 20 °C.

18. The method of claim 16 in which the predetermined range is between 5 to 10 °C.