WO2020051631A1

WO2020051631A1 - A dryer

Info

Publication number: WO2020051631A1
Application number: PCT/AU2019/050958
Authority: WO
Inventors: Gregory Warren Weir
Original assignee: Solarkilns Holdings Pty Ltd
Priority date: 2018-09-10
Filing date: 2019-09-06
Publication date: 2020-03-19
Also published as: AU2019101792A4; AU2019338924A1

Abstract

A dryer (100), for drying a product, has a first zone (122) and a second zone (124). The dryer has a heating distribution system that is configured to distribute heat to at least the second zone (124) to maintain the second zone at an operating temperature that is equal to or higher than the first zone. The dryer also has a wall arrangement (160) for physically separating the first zone from the second zone. In use, the product is first located in the first zone (122) to be p re-dried and is then moved to the second zone (124) for further drying.

Description

A dryer

Field of the Invention

[0001] The invention relates to a dryer. More particularly, the invention relates to a kiln, a method drying a product, a controller arrangement for a kiln, and a method of modifying a kiln.

Background

[0002] Existing solar drying kilns collect solar energy and use the collected solar energy as heat to dry a product (which may be timber, fruits, leaves or herbs for example). A problem with solar drying kilns operation is their dependence on solar intensity and heat energy supply, which is often highly variable on any day or within any daylight solar cycle. To compensate for this high variability, some existing kilns operate with an acceptance that the kiln will produce intermittently and without adequate control to minimise risks (for example fungal attack), while some other existing kilns operate in a hybrid mode in which solar heat is supplemented with heating from fuel fed burners for example. The supplementary heating in these hybrid kilns overcomes the large and otherwise uncontrollable variations in energy supply and output from solar-only kilns during normal weather and climate cycles. However, the existing hybrid kiln solution is costly and has impacts on the environment due to its emissions.

[0003] Existing kilns, including those solar drying kilns and hybrid solar drying kilns described above, operate based on drying schedules that impose stepped increases in temperature as the process reaches completion. This drying method is unsympathetic to low levels of heat energy and air temperature. As the processes reaches completion, the temperature levels must be progressively increased in order maintain a suitable drying speed. When a higher temperature is required (particularly at the later stages or final stage of completion) and cannot be met by the available energy supply at any time, the drying progress slows down significantly and often stops completely. The available cooler conditions or potentially warm ambient air cannot be exploited at these higher temperature stages. When the available energy is inadequate to complete the final stage in the drying process, the product would only be at a semi -dried state. In addition, this drying method would require higher maximum process temperatures and creates the need for supplementary heating. In particular, the speed and extent to which the process temperature increases during any set of climate circumstances are governed by the volume or thermal mass of the load and its absorption effects, which limit the extent to which the process air can be heated at a given time and solar/climate circumstances.

[0004] Most existing kilns implement batch drying with conventional schedules, which further compound the problems noted above and further limit the kiln performance. Batch drying is common to the timber drying industry. Whole batches (or loads) are in their entirety subjected to the same increasingly severe conditions and generally higher temperatures as the drying process proceeds from its wettest state to its final driest state. The fact that the entire batch is exposed to the same, rising temperature and reducing humidity conditions in the kiln means that the process in any sunlight or weather period or circumstances more regularly would still reach a point later in the process where the whole batch stops drying (particularly at the later drying stage and the final drying stage). The batch drying approach would still regularly create situations where supplementary heating (e.g. by a large heater and a large volume of fuel) would be required to complete the drying process.

[0005] In this context, there is a need for a method and system that is capable of maximising drying performance over a wide range of variable conditions including solar energy availability and weather conditions.

Summary of the Invention

[0006] According to an aspect of the present invention, there is provided a dryer for drying a product, the dryer including: a first zone; a second zone; a heating distribution system that is configured to distribute heat to at least the second zone to maintain the second zone at an operating temperature that is equal to or higher than the first zone; and a wall arrangement for physically separating the first zone from the second zone, wherein, in use, the product is first located in the first zone to be pre-dried and is then moved to the second zone for further drying. [0007] Each zone is preferably an enclosed space. The space is enclosed in the sense that heat in the space is substantially retained in the space.

[0008] The heating distribution system may be configured to distribute heat to the first zone. The heating distribution system may be configured to distribute heat to the second zone to maintain the operating temperature of that zone at a predetermined temperature. The heating distribution system is preferably configured to distribute heat to the first zone in the event that there is surplus energy after the operating temperature of the second zone is at the predetermined temperature. Alternatively, the heating distribution system may be configured to distribute heat to the first zone if the heat is not sufficient to raise and/or maintain the operating temperature of the second zone at a desired operating temperature.

[0009] Preferably, in use, the product is dried in a plurality of batches, wherein each batch is separately moved through the first zone for pre-drying and subsequently through the second zone for further drying. When a first batch of product is pre-dried in the first zone and moved to the second zone, a second batch of product is moved to the first zone for pre-drymg. The first zone is preferably an earlier drying zone or a pre-drying zone, while the second zone is preferably a later drying zone or a final drying zone.

[0010] The dryer is preferably a kiln. For example, the dryer may be a solar drying kiln that operates based at least in part on solar energy. The heating distribution system may include one or more solar collection modules for collecting solar energy that is distributed as heat to the zone(s). The solar collection module is preferably a photovoltaic module. The dryer may be a hybrid kiln that is operable in a solar mode in which the hybrid kiln operates substantially solely with heat generated from solar energy and a heated mode in which the hybrid kiln operates to dry the product substantially solely with heat generated from supplemental heating means. The supplemental heating means may be a fuel-based heating means, i.e. that operates on other than solar energy. The hybrid kiln may be operable in a multi-mode in which the hybrid kiln operates to dry the product with heat generated from solar energy, or with heat generated from the supplemental heating means, or with a combination of heat generated from solar energy and heat generated from the supplemental heating means.

[0011] The dryer may further include an air-flow control unit for controlling an air flow through each zone. The air flow control unit preferably includes one or more fan arrangements that are located in each respective zone at or substantially near an entry point of product into the respective zone. The fan arrangement(s) for each zone may be located at a plenum wall in each respective zone.

[0012] The dryer may include an interior vent operable to allow heat to be vented from the second zone to the first zone, or vice-versa. The interior vent may be provided in the wall arrangement and may be operable to vent heat from the second zone to the first zone in the event that the second zone is already at the desired operating temperature. In addition or alternatively, the dryer may include an exterior vent operable to allow heat to be vented from either one of the zones externally to atmosphere.

[0013] The dryer further includes a controller arrangement for monitoring operating conditions of the zones and for controlling the heat distribution system based on the operating conditions of one or all zones and/or operator settings. The operating conditions may include at least one of ambient temperature, ambient humidity, ambient solar radiation, ambient light intensity, ambient wind speed, ambient barometric pressure, dryer temperature, dryer humidity, diyer air circulation speed, product moisture content, and product drying rate. For example, based on any of these operating conditions, the controller arrangement controls the heating distribution system to adjust the distribution of heat to the zone(s).

[0014] The dryer may further include a conveyor system for conveying the product to a respective one of the zones and/or from a respective one of the zones, wherein the controller arrangement is configured to control the operation of the conveyor system to convey the product to and/or from the respective zone. The dryer may have an entry location into the dryer for wet product and an exit location from the dryer for dried product that is adjacent to the entiy, wherein the conveyor system preferably includes at least two conveyor lines that are parallel to each other for conveying the product from the entry location to the exit location. Alternatively, the dryer may include an entry location for wet product into the dryer and an exit location for dry product from the dryer that is on an opposite side of the dryer to the entry location, wherein the conveyor system preferably includes one conveyor line for conveying product from the entry location to the exit location. The conveyor line from the entry location preferably leads into the first zone, while conveyor line from the second zone preferably leads towards the exit location.

[0015] The controller arrangement may be configured to control the operation of the conveyor system to convey the product from one zone when the product in the one zone has a moisture content at or below a moisture content threshold. A moisture content of product in the final zone is preferably a desired moisture content of the product, while the moisture content of product in the pre-drying zone is preferably higher than the moisture content lower than the desired moisture content. The moisture content of the product from the first zone to the second zone is preferably decreasing. In some embodiments, for example on high intensity solar days and weather, the zones may be configured such that the moisture content of product in the first zone is the same as the moisture content of the product in the second zone. Where the product is timber for example, the desired moisture content level may be about 10% to 15%. Where the product is dried fruit for example, the desired moisture content level may be about 8%. Where the product includes leaves for example, the desired moisture content level may be about 6%.

[0016] The controller arrangement may be configured to control the operation of the conveyor system to convey the product from one zone to the next zone an amount time after the product's moisture content has reached a moisture content level. For example, the controller arrangement may control the operation of the conveyor to convey the product after a few minutes or hours after the product's moisture content reaches the moisture content level. Alternatively, the controller arrangement may be configured to control the operation of the conveyor system as soon as the product's moisture content has reached the moisture content level. [0017] The dryer may further include one or more sensors for sensing one or more operating conditions of the dryer and/or the product. The one or more operating conditions may include at least one of ambient temperature, ambient humidity, ambient solar radiation, ambient light intensity, ambient wind speed, ambient barometric pressure, dryer temperature, dryer humidity, dryer air circulation speed, product moisture content, and product drying rate. The controller arrangement is preferably in communication with the one or more sensors and is configured to monitor the operating condition(s) to determine when the product should be moved from the zone. Preferably, the one or more sensors include a moisture content sensor and the controller arrangement is configured to monitor the moisture content of the product to determine when the product should be moved from the zone.

[0018] The one or more sensors may include at least one moisture content sensor in each zone. A respective zone preferably includes one moisture content sensor at an exit from the respective zone to a next zone. Each respective zone further preferably includes one moisture content sensor at an entry into the respective zone from a previous zone. The moisture content sensor(s) may be preferably used to determine when the product should be moved from the zone(s).

[0019] The one or more sensors may include temperature sensors, each temperature sensor is configured to detect the temperature of a respective one of the zones, wherein the controller arrangement is in communication with the temperature sensors and is configured to monitor the detected temperature to determine if the heating distribution system should distribute more or less heat to the zone(s).

[0020] The one or more sensors may further include humidity sensors, each humidity sensor is configured to detect a humidity of a respective one of the zones, wherein the controller arrangement is in communication with the humidity sensors and is configured to monitor the detected humidity to determine if the heating distribution system should distribute more or less heat to the zone(s).

[0021] The dryer may further include an extraction unit for removing air from a respective one of the zones upon determining, based on sensor measurements, that air in the respective zone is moisture-laden or excessively saturated. The sensor measurements may be obtained from a humidity sensor for example. Additionally or alternatively, the sensor measurements may be obtained from a moisture content sensor. At least one of the zones may be divided into two or more sub-zones, and the dryer includes two or more sensors distributed along a length of the respective zone along which the product is conveyed, each sensor being configured provide measurements of air in a respective one of the sub-zones from which measurements the moisture content or the saturation of air in the sub-zone can be determined. Each sensor may be associated with a respective extraction unit for extracting air from the sub-zone. The dryer may further include a dehumidification system for receiving and dehumidifying air from the extraction unit to produce dry air that is provided to the respective zone or to the respective sub-zone via a ventilation unit. In the example where the zone is divided into two or more sub-zones, the dryer may include two or more ventilation units, each ventilation unit being associated with a respective one of the sub-zones for providing dry air to the respective sub-zone.

[0022] The wall arrangement may include a separator that separates the dryer into two halves, one half corresponding to the first zone and another half corresponding to the second zone. The separator may be formed of plastic, metal, or timber for example. The wall arrangement preferably acts as a barrier that thermally insulates the first zone from the second zone. The barrier separates the zones of normally different drying settings and conditions depending on the stage of the drying process being conducted.

[0023] The dryer may further include one or more additional zones, the wall arrangement being configured or arranged to physically separate the additional zones from each other and from the first and second zones, and the heating distribution system is for controlling heat distribution to at least one of the one or more additional zones such that the zones have different operating temperatures and the product to be dried is moved from zone-to-zone from the lowest temperature zone to the highest temperature zone. The zones may define a sequence through which the product is moved to be dried. The second zone may be the last zone in the sequence, with the one or more additional zones preferably being in between the first and last zones in the sequence. Each additional zone preferably defines an intermediate drying stage. The zones preferably normally have stepped increases in operating temperature from zone-to-zone according to the sequence. On high quality drying days (e.g. during days with a high solar intensity), two or more or all of the zones may be configured to provide the same temperature such that the two or more or all of the zones provide a final drying stage for the product.

[0024] The wall arrangement preferably divides the dryer into a plurality of sectors, each sector including a respective one of the zones. The sectors preferably have the same size. The sectors may alternatively have different sizes. For example, the first zone may be larger than the second zone. Alternatively, the second zone may be larger than the first zone.

[0025] The heating distribution system may be configured to distribute heat from one zone to another zone if the heat from the heat distribution system for the one zone is not sufficient to cause the operating temperature of the one zone to meet a desired operating temperature. Thereby, while the heat for that one zone would be insufficient to bring the operating temperature of that one zone to the desired operating temperature for that one zone, that heat could be sufficient to bring another earlier zone to an operating temperature that is suitable for that another earlier zone.

[0026] At least one of the zones may include one or more flexible walls that are expandable outwardly from an original state towards the product located in the tunnel in order to force the airflow to pass through the product. Preferably, the one or more flexible walls expand outwardly from the original state to contact the product. The one or more walls are preferably contractable when the product is to be removed from the zone. The one or more walls may be contractable to the original state. The dryer may include an inflation fan for controlling the expansion of the one or more walls.

[0027] According to another aspect of the present invention, there is provided a dryer for drying a product, the dryer including: a zone in which the product is locatable, the zone having one or more flexible walls for surrounding the product; and an airflow arrangement to control an airflow through the zone, the flexible wall(s) being configurable to expand outwardly towards the product to force the airflow provided by the airflow arrangement to pass through the product. [0028] Preferably, the one or more flexible walls expand outwardly from an original state to contact the product. The one or more walls are preferably contractable to the original state when the product is to be removed from the zone. The dryer may include an inflation fan for controlling the expansion of the one or more walls.

[0029] The zone with the wall(s) outwardly expanded preferably has a space, in which the product is located, that is smaller than a space of the zone with the wall(s) contracted or in the original state.

[0030] The dryer may include the features of the dryer of the previous aspect described above.

[0031] According to another aspect of the present invention, there is provided a method of drying a product using a dryer having a first zone, a second zone, a heating distribution system that is configured to distribute heat to at least the second zone, and a wall arrangement for physically separating the first zone from the second zone; the method including: operating the heat distribution system to maintain the second zone at an operating temperature that is equal to or higher than the first zone; locating a first batch in the first zone for dying using at least the ambient conditions; and locating, when the first batch is pre-dried in the first zone, the first batch to the second zone for further drying.

[0032] The dryer may include the features of the dryer of the previous aspect described above.

[0033] The method may further include locating a second batch in the first zone when the first batch is in the second zone. Preferably, the method includes separating the product to be dried into a plurality of batches including the first batch and the second batch. When one batch of product is pre dried in the first zone and moved to the second zone for further drying, another batch is moved to the first zone for pre -drying.

[0034] The method may further include operating the first and second zones at a similar operating temperature. For example, on high quality drying days (e.g. during days with a high solar intensity), the two zones may be configured to provide the same operating temperature such that the two zones provide a final drying stage for the product.

[0035] According to a further aspect of the present invention, there is provided a controller arrangement for controlling an operation of a dryer for drying a product, the dryer including: a first zone, a second zone, a heating distribution system that is configured to distribute heat to at least the second zone, and a wall arrangement for physically separating the first zone from the second zone; the controller arrangement including at least one processor that is configured to: monitor operating conditions of the first zone and of the second zone; and transmit a signal when the operating condition of either zone reaches a desired operating condition.

[0036] The dryer may include the features of the dryer of the previous aspect described above.

[0037] The controller arrangement may be further configured to control the heat distribution system to maintain the second zone at an operating temperature that is equal to or higher than the first zone.

[0038] The controller arrangement may be further configured to control a vent between the first zone and the second zone. Preferably, when an operating temperature of the second zone exceeds a desired operating temperature, the controller arrangement is configured to transmit the signal for operating the vent to cause the heat to be transferred, via the vent, from the second zone to the first zone.

[0039] The operating conditions may include at least one of ambient temperature, ambient humidity, ambient solar radiation, ambient light intensity, ambient wind speed, ambient barometric pressure, dryer temperature, dryer humidity, dryer air circulation speed, product moisture content, and product drying rate.

[0040] The signal may be a control signal for a conveyor system that conveys the batch(es) of product from zone to zone, wherein the controller arrangement is configured to transmit the control signal to the conveyor system and the control signal causes the conveyor system to convey the product from one zone to another zone.

[0041] According to another aspect of the present invention, there is provided a method of modifying a dryer, the method including: installing a wall arrangement in the dryer to create two or more physically separate zones; and configuring a heat distribution system to distribute heat to at least one of the zones to maintain that zone at an operating temperature that is equal to or higher than the other zones.

[0042] The dryer may include the features of the dryer of the previous aspect described above.

[0043] The two or more zones define a sequence of zones through which a batch of product to be dried progresses. The product's moisture content in a batch is preferably decreasing as it progresses from zone to zone according to the sequence. The operating temperature of the different zones preferably increases from zone to zone according to the sequence. For example, the operating temperature of the earlier zones in the sequence is lower than the operating temperature of the later zones in the sequence. A relative humidity of the different zones preferably decreases from zone to zone according to the sequence. For example, the relative humidity of the earlier zones in the sequence is higher than the relative humidity of the later zones in the sequence.

Brief Description of the Drawing

[0044] The invention will now be described, by way of non-limiting example only, with reference to the accompanying drawing, in which:

Figure 1 is schematic drawing of sectional top view of a kiln according to an embodiment of the present invention.

Detailed Description

[0045] Figure 1 illustrates a dryer in the form of a kiln 100 for drying a product. The product 200a includes, but is not limited to, high density products such as timber and low density products such as fruit, thin veneer and herb/leaf products. The kiln 100 is a solar drying kiln that operates based at least in part on solar energy. The kiln 100 can optionally operate in a hybrid mode with supplemental heating. The supplemental heating may be provided by a fuel-based heating source for example. The kiln 100 has a greenhouse structure with solar energy collection modules (e g. photovoltaic modules). For example, the greenhouse structure has solar panels mounted on a roof thereof for collecting solar energy. The kiln is not limited to a greenhouse structure and could include other structural type solar dryers.

[0046] Wet product 200a to be dried enters the kiln 100 through an entry point 121 in direction A, while dried product 200b exits the kiln 100 through an exit point 123 in direction B. The first direction A and the second direction B are parallel and ran in opposite directions to each other. The entry point 121 is adjacent to the exit point 123 on the same side of the kiln 100. It will be readily appreciated that, in other embodiments, the entry point and exit point could be on different sides of the kiln. For example, the wet product could enter the kiln at one end and dry product could exit the kiln from an opposite end of the kiln (i.e. the conveyor provides a single straight direction through the kiln).

[0047] The kiln 100 has a conveyor system having a first conveyor 162 for conveying product through the kiln in the first direction A, a side transfer conveyor 164 for moving the product at the end of the first conveyor sideways (i.e. laterally or transverse to the first direction A), and a second conveyor 166 for conveying the product back through the kiln 100 through the second zone 124 in the second direction B. The side transfer conveyor 164 is located externally to the kiln 100. In other embodiments, the side transfer conveyor could be inside the kiln. Alternatively, the conveyor system could have a U-shaped conveyor path with the first and second conveyor forming the straight sections of the U-shaped conveyor path. In yet other embodiments, instead of conveyors, the kiln may utilize trolleys or other methods for transporting the batches of product through the kiln.

[0048] To dry a wet product, the product is normally separated into a plurality of batches. The size of each batch will depend on the product to be dried (e.g. whether it is a high density product or low density product), and physical dimensions and operating conditions of the kiln 100 or ambient conditions at the time. Each batch is loaded onto the conveyor system and conveyed through the kiln 100.

[0049] The kiln 100 includes a first zone 122 and a second zone 124, and a wall arrangement 160 physically separating the two zones.

[0050] The wall arrangement 160 is a separator that divides the kiln into two halves - the first half corresponds to the first zone 122, while the second half corresponds to the second zone 124. In other embodiments, the zones could have different sizes. The size of the zone would depend at least on the quality of ambient air. For example, where the kiln is in a typical tropical location, the first zone could be smaller than zone the first second zone where night temperatures would rarely fall below 25°C to 30°C, in which wet material can be dried very quickly and to an extent that final drying of the material can be readily be finished off in the second zone. The wall arrangement 140 is a separator or barrier in the form of a central dividing wall. The wall extends from the floor to the ceiling of the kiln, and extends from one wall to an opposite wall of the kiln. Thereby, the wall arrangement creates the two physically separate zones 122, 124. In this way, two different drying environments can be maintained in the kiln 100. The wall arrangement is made from a substantially low thermally conductive material. For example the wall arrangement is made from plastic. Alternatively, the wall arrangement may be made from metal. Further alternatively, the wall arrangement may be made from timber. Where the kiln is for drying plywood veneer leaf, the wall arrangement may be plywood for example.

[0051] Each zone 122, 124 has their own operating conditions and provide different drying stages (or different drying environments) for the product. The operating conditions include at least one of ambient temperature, ambient humidity, ambient solar radiation, ambient light intensity, ambient wind speed, ambient barometric pressure, kiln temperature, kiln humidity, kiln air circulation speed, product moisture content, and product drying rate. [0052] The kiln 100 includes sensors for sensing one or more of those operating conditions of the kiln and/or of the product. Each zone 122, 124 includes sensor for sensing the operation conditions of that zone. Based on the sensed operating condition in one of the zones, the product is automatically moved, using the conveyor system, from that zone. The sensed operating conditions are also used to adjust the operation of the heating distribution unit. For example, if the sensed operating temperature in one zone is too low, the heating distribution system can be adjusted to increase the operating temperature so that it reaches the desired operating temperature for that zone. Similarly, if the sensed operating temperature in one zone is too high, the heating distribution system can be adjusted to reduce the operating temperature so that it reaches the desired operating temperature for that zone. The excess heat from that one zone can be utilized in the other zone.

[0053] The sensors include at least one moisture content sensor in each zone 122, 124. The moisture content sensor in the first zone 122 is located at an exit from the first zone, which is opposite to the kiln wall where the entry point 121 is located. Similarly, the moisture content sensor in the second zone 124 located at an exit from the second zone, which is opposite to the kiln wall where the exit point 123 is located. The conveyor system 162, 164, 166 is operated to move the batch of product from one zone if the moisture content of that batch of product, as sensed by the respective moisture content sensor in that zone, reaches a predefined desired threshold. Where the product is timber for example, the desired moisture content level for the product from the second zone is about 10% to 15%. Where the product is dried fruit for example, the desired moisture content level for the product from the second zone is about 8%. Where the product includes leaves for example, the desired moisture content level for the product from the second zone is about 6%.

[0054] The sensors can include temperature sensors for detecting the operating temperature of a respective one of the zones 122, 124. The sensors can also include humidity sensors for detecting an operating relative humidity of a respective one of the zones 122, 124. The detected zone temperature and/or relative humidity are used to determine whether the heating distribution system should be adjusted to provide more or less heat to the respective zone. [0055] In some embodiments, these humidity sensors, or other humidity sensors, are used to determine if a set point humidity is reached in a respective one of the zones 122, 124 or in a sub-zone within a respective one of the zones 122, 124. These, or these other, sensors are distributed along a length of the respective zone along which the product is conveyed. For example, a respective one of the zones may be divided into two or more sub-zones, each sub-zone having a respective humidity sensor for measuring the humidity in that sub-zone. The set point humidity may for example be a dew point or near-dew point, at which point water droplets begin to condense in the respective zone or in a sub-zone in the respective zone. These, or these other, humidity sensors are in communication with a controller that is configured to, upon determining based on measurements from these, or these other, humidity sensors that the set point humidity is reached, operate an extraction unit (e.g. a fan unit or vent unit) to remove the air from the respective zone or from the sub-zone in the respective zone. Removing the air with high moisture content from the zone allows for drier air, supplied from the fan arrangement located at or near the start of the zone, to reach the later sections in the zone and to provide effective drying of the product in those later sections. In other examples, the controller may be further configured to operate a ventilation unit (e.g. a fan unit) to supply dry air to the respective zone or to the sub-zone in the respective zone. In these other examples, the air that is removed from the respective zone or from the sub-zone via the venting/extraction unit is passed through a dehumidifier system to remove the moisture from the air and to produce dry air. In these other examples, the dry air from the dehumidifier system is returned to the respective zone or to the sub zone via the ventilation unit. The dehumidifier system may be a dehumidifier system that is described in PCT patent publication no. WO/2011/146993 titled 'Solar-powered drying, heating and air- conditionmg system', by the present inventor, published on 1 December 2011. Other sensors, such as moisture content sensors for example, may be used instead of, or in addition to, the humidity sensors to determine when the air in a zone or sub-zone becomes moisture-laden or excessively saturated, and needs to be removed and/or dehumidified. In some embodiments of the solar drying kiln, it would be preferable to divide a zone into two or more sub-zones, with each sub-zone having its own humidity sensor, extraction unit, and optionally ventilation unit, so that the varying air conditions and the varying evaporation levels throughout the zone (which would occur due to the varying levels of solar energy received by the kiln) can be segmented into the different sub-zones and more easily tracked and processed accordingly in order to improve the overall drying efficiency of the kiln.

[0056] Each zone 122, 124 defines a substantially closed enclosure for containing the product with its own drying condition. Each zone 122, 124 has its own controller for adjusting, monitoring, and maintaining the operating conditions of the respective zone. Alternatively, one controller may be provided for adjusting, monitoring, and maintaining the operating conditions of both zones generally separately and optionally (e.g. on high solar intensity days) acts together as one. The first zone 122 makes use of lower operating conditions (e.g. lower operating temperatures) to pre-dry the batch(es) in the first zone, while the second zone 124 makes use of higher operating conditions (e.g. higher operating temperatures) to further dry/fmish drying the product.

[0057] Each zone 122, 124 has a cross-section that is substantially larger than the batches to allow the batches to pass through the zone in their respective trolleys on the conveyor system. The zone includes walls that define a tunnel through airflow passes to reduce the product's moisture content. The gap between the product and the walls of each zone defines an airflow path of least resistance. Airflow that is provided by the airflow arrangement of the kiln would be more likely to flow through this path of least resistance instead of going through the product. It is desirable to get as much air to flow through the batch of product, instead of around the batch of product, in order to reduce the product's moisture content.

[0058] In order to force more airflow through the product, each zone 122, 124 has flexible walls that surround the product. The flexible walls may be a canvas or plastic bladder inside rigid outer walls of the zone. The flexible walls have an original state in which the product to be dried can be located in the respective zone. Once located, an inflation fan is operated (e.g. turned on) that causes the flexible walls to expand outwardly towards the product to preferably contact the product. That is, the flexible walls preferably embrace or hug the batch of product. When the inflation fan is operated to expand the flexible walls, the cross-section of the respective zone becomes substantially smaller (i.e. the tunnel defined by the zone becomes more restricted). The airflow arrangement of the kiln is then operated to provide airflow through the respective zone. The outwardly expanded flexible walls force more airflow through the product.

[0059] Once the product's moisture content level has reached a desired moisture content level, the inflation fan is operated (e.g. turned off) to deflate the flexible walls. Thereby, the flexible walls contract back to its original state allowing the batch of product to be removed from the zone and allowing a new batch of product to be located in the zone for drying.

[0060] As described above, the kiln 100 can be operated in a hybrid mode with supplemental heating where the kiln 100 can operate substantially solely with heat generated from solar energy and/or the kiln 100 can operate substantially solely with heat generated from means other than solar energy (e g. from a fuel-based source). In a first mode, the kiln operates to dry the product with heat generated from solar energy. In a second mode, the kiln operates to dry the product with heat generated from the means other than solar energy. In a third mode, the kiln operates to dry the product with a combination of heat generated from solar energy and heat generated from the means other than solar energy. For example, in the event that the second zone 124 does not have a high enough operating temperature to reduce the moisture content to a final desired moisture content, the hybrid kiln is operated in either the second or third modes. The supplementary heating provided in the hybrid kiln would be minimal compared to the hybrid kiln of the existing kilns described above. By decreasing the moisture content from the product in stages making use of the natural/ambient energy resources available, only a small amount of supplementary heating would be required (e.g. during a low solar intensity period) to finish off the drying process.

[0061] In other embodiments, the kiln may include more than two physically separate zones (e.g. three zones, four zones, etc.). In these other embodiments, the wall arrangement includes one or more walls for physically separating the zones. The kiln could, for example, have a plurality of zones arranged in a 1 x 2 arrangement, 2 x 1 arrangement, 3 x 1 arrangement, a 1 x 3 arrangement, a 2 x 2 arrangement, etc. That is, the zones could be arranged in the kiln in one column with the plurality of zones as rows of that column, or arranged in one row with the plurality of zones as columns of that row, or arranged in multiple rows and multiple columns in a m x n arrangement where m and n is any non-zero and positive integer. In addition, the size of each zone could be the same as or different than the other zone(s).

[0062] The kiln 100 further includes a heating distribution system (not shown) for distributing heat to the first zone 122 and to the second zone 124. The heating distribution system collects energy for distribution from solar energy collection modules and from supplementary heating sources (e.g. a fuel based heating source). The heating distribution system 100 maintains the second zone 124 at an operating condition that is higher than the first zone 120. The first zone 122 could be operated based solely on ambient conditions without any external heating being provided the solar energy collection sources or by the supplementary heating. However, in some arrangements, if the heat for the second zone 124 is insufficient to bring the temperature of the second zone 124 to a desired operating temperature, that heat is provided to the first zone 122. Also, in some arrangements, any surplus heat after the second zone 124 reaches a desired operating temperature is provided, by the heating distribution system, to the first zone 122.

[0063] The desired operating temperature for the different zones depends at least on the product to be dried. Where the kiln includes more than two zones, the desired operating temperature of the different zones will also depend at least on the number of zones present. For example, food or bio products for example will typically require a maximum operating temperature in the second (final) zone 124 of 40°C in order to avoid the chemical and nutrient constituents from breaking down at higher temperatures. Other products including plywood will typically require a maximum operating temperature of 50°C to 75°C in the second (final) zone 124, which would be normal upper limits of a solar drying kiln. The operating temperature of the first (earlier) zone 122 will vary depending on natural/ambient conditions available. Each zone progressively dries the products as the products progress in batches from one zone to the next zone so that the batch of product at the final zone is able to be dried to their desired moisture content level. The progressive drying of the product continues to take place even when subjected to ambient temperatures as low as 5°C and as high as 95% humidity. At times where the second zone is using all of the available energy to reach the desired operating temperature to finish off drying the product or when the finishing process stops at night when there is no heating available to meet the desired operating temperatures for the second zone, the first zone will still be operable at its operating temperatures (intermediate to the final desired operating temperature) to pre-dry other batches of products. The first zone can continuously pre-dry other batches of product during periods where the second zone does not have sufficient energy to meet its desired operating temperatures, so that when there is sufficient energy available (e.g. during the next solar energy period), the second zone would be able to finish off drying those batches of product. Thereby, having the separate zones with different drying conditions speeds up the drying process and increases productivity.

[0064] The kiln 100 further includes a controller arrangement for controlling an operation of a kiln 100. The controller includes one or more computer processing units that are configured to execute computer instructions to cause the processing unit(s) to control the operation of the kiln 100. The controller arrangement is configured to control the operation of the heating distribution system and the conveyor system. The controller arrangement is also configured to control the supplementary heating operations in the hybrid mode of operation. The controller arrangement receives inputs from the sensors previously described above (including the moisture content sensors, the temperature sensors, and the humidity sensors). The controller arrangement is configured to control the operation of the conveyor system 162, 164, 166 and heating distribution system described previously above.

[0065] The controller arrangement is also configured to monitor the current status and heat output by the heating systems. For example, when the controller arrangement detects that the solar energy period is over or senses that the heat output for the second zone is not sufficient to bring the second zone to its desired operating temperature, the controller arrangement is configured to cause the second zone to maintain the second zone at the lowest possible relative humidity until the next solar energy period or until the supplementary heating is operated. The controller arrangement controls at least the airflow arrangement to maintain the relative humidity of the second zone. While the second zone is maintained at the lowest possible humidity, the first zone continues to pre-dry other batches of product. [0066] If the measured moisture content of the product in a respective one of the zones reaches a desired moisture content level (as sensed by the moisture content sensor), the controller arrangement operates the conveyor system to move the product from the respective zone. On the other hand, if the moisture content of the product in the respective zone is at or below a desired moisture content level, the controller arrangement does not operate the conveyor system. In those cases, particularly for the product in the second zone, the controller arrangement can operate the kiln 100 in the hybrid mode to control the supplementary heating source to provide supplementary heating to the respective zone if the moisture content of the product in the respective zone is at or below a desired moisture content level. For example, the controller arrangement operates the supplementary heating source where the moisture content is one of 5%, 10%, 20% or 30% higher than the desired moisture content level.

[0067] If the measured operating temperature of a respective one of the zones 122, 124 is at or below a desired operating temperature, the controller arrangement operates the heating distribution system to provide extra heating to the respective zone. Where the measured operating temperature is above the desired operating temperature, the controller arrangement controls the heating distribution system to transfer heat to the other zone to increase the temperature of that other zone by operating a vent 156 (described in further detail below) in the wall arrangement 156. For example, during periods of high solar intensity, the controller arrangement is configured to operate the vent 156 so that the two zones 122, 124 have substantially similar operating conditions.

[0068] Similarly, if the measured operating humidity of one of the zones 122, 124 is above a desired humidity, the controller arrangement operated the fan arrangements 182, 184 (described in further detail below) to increase the air flow through the zone to decrease the humidity of that zone.

[0069] Thereby the kiln 100 is able to positively exploit the whole range of solar and ambient conditions in the normal course that that the kiln could be naturally exposed to in order to provide efficient drying to the product. Available solar energy can be concentrated into one or more electively chosen parts of the drying process. By breaking down the load into different stages conducted in different zones, the lull variety of ambient airborne heat energy and conditions can be positively exploited at any time during the drying process.

[0070] The batches are progressed, independently and separately of each other, through two separate smaller and more manageable zones 122, 124 of the kiln 100 that operate separately or in parallel to each other in order individually or optionally to collectively perform the whole drying process. The zones 122, 124 may individually optionally receive all, part of or none the heat energy from a collector system, reducing the thermal mass/energy ratio and concentrating heat energy in the zones to increase the operating temperature under conditions where solar energy availability is less than optimal.

[0071] The kiln 100 has an air flow system including two fan arrangements 182, 184. Each fan arrangement operates in a respective one of the zones 122, 124, and are located at or substantially near the start of the respective conveyor 162, 164 in the zone. The air flow system circulates process air- stream through the kiln 100. The entry point of circulation kiln air through the end-section zones instead of into the comparably larger whole outer wide-face of the load according to the existing batch kiln systems described above is important. This arrangement focuses or concentrates available heat so that the larger dosage of heat energy per circulation air volume and smaller relative load mass enables substantially higher upper temperature levels in all conditions.

[0072] The first zone 122 is a pre-drying zone for pre-drying very wet material can successfully exploit generally lower temperature ambient temperatures and conditions at any stage during the diurnal solar and varied weather cycles, without additional solar heat energy. The first zone 122 may be used 24 hours per day as a preparatory first-stage 'pre-drier' to reduce moisture of stock in preparation for a faster stage conducted in a final -drying zone optionally during the following daylight period. At times of high solar intensity and ambient temperature, the first zone 122 may be used as a full process system or zone converting product from its wettest state to required final dry state in the same zone. [0073] Optionally directing all heat energy to the second zone 124 to increase the operating conditions of the second zone 122 at the expense of operating the first zone 122 at lower operating conditions does not significantly impact the first zone 122. Rather, a large positive impact is provided on the temperature levels, drying rate, uniformity of production, length of production day and demands for supplementary heat in the dry heat-dependent zone.

[0074] The comparative temperature gain in the second zone 124 is mainly due to the fact the drying load thermal mass/energy ratio is doubled or greatly improved depending on the selected design dissection that may optionally include different sizes and numbers for the zones used in customer-specific customisations .

[0075] In fact, the consequential gain from concentrating energy and achieving higher and more reliable and predictable temperature in the second zone 124 increases its drying rate and offsets the small change on the first zone 122 only marginally so that drying rate of the whole load is improved over a 24-hour period. The process benefits substantially because the length of time in any day that the dry end zone can achieve its required optimal drying temperatures in order complete the process may otherwise be more substantially increased regardless of solar intensity as may be impacted by afternoon and morning angulation and collector orientation issues and by highly variable cloud cover or ambient humidity levels for example.

[0076] Unlike those existing kilns described previously above that cannot effectively function without supplementary heating, or to have passed a point in the process where it could potentially exploit ambient conditions, the kiln 100 allows for substantial 'pre-drying' to continue when there is inadequate heat to finish the process, for examples at night and during days of low quality solar insolation. At all times, the first zone 122 can continue to exploit ambient air to prepare substantial quantities of pre-dried (partially dried) product to quickly complete in the second zone 124 when heat energy is available or when the operator opts to apply smaller amounts of supplementary energy.

[0077] Because the second zone 124 includes a very small cross section and because small batches of product are passed through the second zone having small volumes of product and small thermal mass, the amount of heat energy required to create the operating temperature increase needed for successful final-stage drying for the second zone 124 is very small when compared to that needed for a whole batch approach of the existing kilns described previously above for example. Capital and operating costs of required heaters is therefore substantially smaller because supplemental heating would not, or only rarely, be needed.

[0078] In addition, when seasonal or variable weather trends allow larger than normal amounts of heat collection, and hence process temperature opportunity, both zones 122, 124 can be selectively used as final drying units instead of as separate parts of a whole drying process. That is, when larger than normal amount of heat is collected (e.g. on high solar intensity days), the surplus or excess heat is used to raise the operating condition of the first zone 122. In the days following a heavy ram event and monsoonal cloudiness event that negatively impact final stage dry productivity, solar insolation and collection generally peak due to the removal of dust from the atmosphere by precipitation. During these peaks, the first and second zones could be operated as a single zone with a high and uniform operating temperature to increase production and to offset losses caused by the weather that caused the losses in the first instance.

[0079] Each zone 122, 124 is controlled by a respective controller. The controllers may be part of the controller arrangement previously described above.

[0080] Each zone 122, 124 incorporates its own plenum wall 132, 134 that spans half of each end of the kiln 100. Each plenum wall 132, 134 includes a respective fan arrangement 182, 184, respective process temperature and humidity sensing unit(s), and respective humidification vents 152, 154. The plenum wall 132, 134 spans half the kiln width and extends from the centrally located separator of the wall arrangement 140 to a side wall of the kiln. The fan arrangement 182, 184 in the plenum wall 132, 134 creates a negative and positive pressure zone on both sides or ends of the circulating air-stream. The controller arrangement can be utilized to operate any number of fans in this arrangement. The kiln 100 allows for the amount of heat energy required to heat air to ideal temperatures at the same required flow speed or rate to be substantially less than (about 15%) of that required for the existing batch kiln systems described previously above. The change in direction and reduction in the process air-entry area delivers more than 6 times the energy to the same volume of entry-point air. Combined with the fact that the load mass to be heated has been reduced by 50% by having the kiln structure and load physically separated into different zones, the result is that the extent, uniformity and predictability of process temperature can be greatly improved even when available solar heat energy is less than optimal. A low amount of solar heat energy is needed to achieve a specific air temperature and relative humidity outcome because only half the absorbing thermal mass is provided. At a reduced circulation air flow rate, air heating requirement of only 15% compared to the existing kiln systems. A small amount of solar heat then becomes more effective in the closing stages of the process.

[0081] Arrows FI, F2 in Figure 1 show the direction of flow from the fans 182, 184 along the top of the tunnels. Arrows F3, F4 in Figure 1 show the direction of circulation airflow through the tunnels, aided by the positive pressure imposed on the tunnel entrance at the furthest end away from the plenum walls and also by the suction effect created by the fans on the plenum end of the tunnels where the tunnels effectively end. In the preferred embodiment, they end approx. 1.6m from the outer end walls of the kiln 100.

[0082] The solar air heating system includes the solar air heating system of PCT patent publication no. WO 2011/146993 A1 titled 'Solar-powered drying, heating and air-conditioning system' published on 1 December 2011. The system includes outer cavity and/or external solar collection systems that perform a variety of functions using an array of sensing devices and complex software for their range of functions. The external collector/ air conditioning system includes a series of air inlet and solar heat outlet fans that act independently on east and west sides depending on the current angle of solar insolation and several other variables. The system discharges solar heated air when available into the kiln circulation air stream, from re-entry points at the top of the same side in which the solar energy is collected. [0083] The kiln 100 provides a system for transfer and concentration of heat from both sides of the whole structure and collector into the driest and most heat dependent side/zone of the kiln in the enclosure. This zone may preferably contain semi -dry material approaching from other zones and concluding the final stages of the process. The result is that approximately 100% of the heat energy from the exchanger is then directed and exposed to only half or part of the load mass. The result of this change in design is that the load mass absorption of heat energy is half of that of the existing batch kiln systems at any given time during the drying cycle when the system is directed by the controller to do so. The result is that higher temperatures and drying rates can be achieved for longer periods of time every day when solar heat energy is less than optimal. The final zone reaches required finishing temperatures earlier each morning and may be maintained later each afternoon when intensity decreases. Depending on operator control setting options, the severity of conditions in the zone may be increased to increase drying speed and progression of finished units of dry product to completion. Improved drying productivity and reliability can thus be achieved by the current art even in lower quality sunlight periods and without supplementary energy.

[0084] Having vents 156 allows for any concentration of heat energy into the second zone 124 (if it reaches excessive levels of temperature during peak periods of solar intensity or during deliberate cooling periods that may be prescribed by the operating system) to be transferred to the first zone 122. Transfer to other zones may occur, depending on individually modified designs and on the basis of the measured temperature differential between the current maximum set zone temperature and the measured actual zone temperature as determined by the controller unit.

[0085] Additional 'vent' fans 152, 154 in the kiln are operated when heated air in the driest zone becomes excessively saturated. This heated heavily moisture laden air may be treated as a valuable by-product of the final zone 124 directed to the earlier zone 122 containing wetter product that may constructively recycle this otherwise wasted product. A controller includes a simple operator selector switch that may, depending on the current selected function of the zones, be used to direct vented hot saturated air through either of the normal atmospheric venting system or to preferably be recycled via the vent 156 in the wall arrangement. [0086] The separate controllers may be optionally all used by the operator to each serve zones used as full process dryers converting product from wet to dry final stage, or alternatively separately as parts of a multi-stage process commencing with pre-drying (wet material) and concluding with “final drying” finished product ready for use. By using a selector switch, the operator may direct solar heated air from the collection system to prioritised multiple zones and may set controllers to operate at final drying temperatures and humidity levels so that final stage dry product may result from each zone. This feature is particularly useful at times of peak solar activity allows for multiple zones to be used as finishing stages.

[0087] Embodiments of the present invention allow for a range of variable (e.g. weather dependent) operating conditions to be optimally exploited conditions to maximise solar energy in the drying process. In particular, when the temperature conditions are unsuitable or fall short of needs for the later/final stages of the drying process, these conditions would be often suitable for the initial/earlier stages of the drying process. For example, at the early drying stages, the product can often be dried substantially and quickly without any solar heat energy and using only ambient air conditions. The currently available energy can be used to provide different drying conditions to smaller batches of product located in different zones. When a batch in one zone reaches a dry or semi dry state, that batch is moved onto the next zone for further drying, or left aside for the next stage/zone while another batch is moved into the one zone.

[0088] When the heated air reaches excessive saturation or humidity levels for that stage of the process, the heated air is vented to another (previous) zone to utilize/recycle the energy in the heated air. A load containing material at various drying zones from wettest to driest states offers an alternative recycling destination and use for the otherwise wasted heat energy by-product.

[0089] Embodiments of the present invention concentrates finite and variable energy to lengthen and add reliability to the final stage processing step and to provide flexibility to the drying system to exploit the cooler night and times when the final stage simply cannot be conducted using solar heat energy alone. [0090] The kiln 100 has two physically separate zones 122, 124 that are individually controlled and that can interact with each other to increasing drying efficiencies.

[0091] The first zone 122 is a pre-drier zone, while the second zone 124 is a finishing final-drier zone for facilitate continuing high levels of semi-dried stock preparation during the otherwise fuel supplemented or inactive night period when energy is insufficient to finish the process.

[0092] By dividing the kiln 100 into two zones 122, 124, with each zone having its own moisture content/drying state, the product can be dried in batches in stages and at any time. The heat energy from the second zone 124, which would otherwise normally be wasted as part of the dehumidification function, can be recycled for use in the first zone 122.

[0093] The air flow system controls process airflow circulation along the structure in order concentrate heat energy to the air entry point of the load via a smaller and more concentrated area.

[0094] By having the entry point 121 adjacent to the exit point 123 in the kiln 100, the product can be practically transferred to loading and unloading zones that are close to each other. This aids recirculation of trolleys and handling costs.

[0095] Collected solar heat energy is provided to the zone 122 that most requires the heat energy at a given time.

[0096] The kiln 100 is configured to selectively transfer all or most of the available collected solar heat energy to the zones 122, 124 as a balancing mechanism to optimise production during cycles of solar activity, weather and climate. The kiln 100 is configured to selectively transfer all or most of the available collected solar heat energy at a given time to separate zones that form part of the drying process in order better exploit climate and diurnal temperature conditions that might otherwise impede the process. [0097] The kiln 100 is configured to selectively transferring excess energy that may become surplus from the second zone 124 that normally receives and requires most heat energy to the first zone 122 that generally needs it least.

[0098] The kiln 100 is configured to use ambient air during a full day-long cycle of solar energy availability and cyclically warming and cooling ambient air.

[0099] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

[00100] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavor to which this specification relates.

[00101] Throughout this specification and the claims which follow, unless the context requires otherwise, the word 'comprise', and variations such as 'comprises' and 'comprising', will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A dryer for drying a product, the dryer including: a first zone; a second zone; a heating distribution system that is configured to distribute heat to at least the second zone to maintain the second zone at an operating temperature that is equal to or higher than the first zone; and a wall arrangement for physically separating the first zone from the second zone, wherein, in use, the product is first located in the first zone to be pre-dried and is then moved to the second zone for further drying.

2. The dryer of claim 1, wherein each zone is an enclosed space.

3. The dryer of claim 1 or 2, wherein the heating distribution system is configured to distribute heat to the first zone.

4. The dryer of claim 3, wherein the heating distribution system is configured to distribute heat to the second zone to maintain the operating temperature of that zone to a predetermined temperature, and wherein the heating distribution system is configured to distribute heat to the first zone in the event that there is surplus energy after the operating temperature of the second zone is at the predetermined temperature.

5. The dryer of any one of claims 1 to 4, wherein the dryer is a solar drying kiln.

6. The dryer of any one of claims 1 to 5, wherein the heating distribution system includes one or more solar energy collection modules for collecting solar energy that is distributed as heat to the zone(s).

7. The dryer of any one of claims 1 to 6, further including an air-flow control unit for controlling an air flow through each zone.

8. The dryer of any one of claims 1 to 7, further including an interior vent operable to allow heat to be vented from the second zone to the first zone, or vice-versa.

9. The dryer of claim 8, wherein the interior vent is operable to vent heat from one of the zones to the other zone in the event that the operating temperature of the one zone is at a desired operating temperature.

10. The dryer of claim 8 or 9, wherein the wall arrangement includes the interior vent.

11. The dryer of any one of claims 1 to 10, further including a controller arrangement for monitoring operating conditions of the zones and for controlling the heat distribution system based on the operating conditions.

12. The dryer of claim 11, further including a conveyor system for conveying the product from zone to zone, wherein the controller arrangement is configured to control the operation of the conveyor system to convey the product from one zone to the next zone.

13. The dryer of claim 12, wherein the controller arrangement is configured to control the operation of the conveyor system to convey the product from one zone to the next zone when the product in the one zone has a moisture content reaches or is below a moisture content threshold.

14. The dryer of claim 13, further including a moisture content sensor for detecting a moisture content of the product in a respective one of the zones, wherein the controller arrangement is in communication with the moisture content sensor and is configured to operate the conveyor system to convey the product from the respective zone when the detected moisture content reaches or is below the moisture content threshold.

15. The dryer of any one of claims 11 to 14, further including temperature sensors, each temperature sensor is configured to detect the operating temperature of a respective one of the zones, wherein the controller arrangement is in communication with the temperature sensors and is configured to monitor the detected operating temperature to determine if the heating distribution system should distribute more or less heat to the zone(s).

16. The dryer of any one of claims 11 to 15, further including humidity sensors, each humidity sensor is configured to detect a relative humidity of a respective one of the zones, wherein the controller arrangement is in communication with the humidity sensors and is configured to monitor the detected relative humidity to determine if the heating distribution system should distribute more or less heat to the zone(s).

17. The dryer of any one of claims 1 to 16, further including: an extraction unit for removing air from a respective one of the zones upon determining, based on sensor measurements, that air in the respective zone is moisture-laden or excessively saturated.

18. The dryer of claim 17, further including a dehumidification system for receiving and dehumidifying air from the extraction unit to produce dry air that is provided to the respective zone via a ventilation unit.

19. The dryer of any one of claims 1 to 18, wherein the wall arrangement includes a separator that separates the dryer into two sectors, one sector corresponding to the first zone and another sector corresponding to the second zone.

20. The dryer of any one of claims 1 to 19, further including one or more additional zones, the wall arrangement being configured or arranged to physically separate the additional zones from each other and from the first and second zones, and the heating distribution system is for controlling heat distribution to at least one of the one or more additional zones such that the zones have different operating temperatures and the product to be dried is moved from zone- to-zone from the lowest temperature zone to the highest temperature zone.

21. The dryer of claim 20, wherein the zones define a sequence through which the product is moved through to be dried, the sequence defining stepped increases in temperature from zone -to -zone.

22. The dryer of any one of claims 1 to 21, wherein the wall arrangement divides the dryer into a plurality of sectors, each sector including a respective one of the zones.

23. The dryer of claim 22, wherein the sectors have the same size.

24. The dryer of any one of claims 1 to 23, wherein at least one of the zones includes one or more flexible walls that are expandable outwardly from an original state towards the product located in the tunnel in order to force the airflow to pass through the product.

25. A dryer for drying a product, the dryer including: a zone in which the product is locatable, the zone having one or more flexible walls for surrounding the product; and an airflow arrangement to control an airflow through the zone, the flexible wall(s) being configurable to expand outwardly towards the product to force the airflow provided by the airflow arrangement to pass through the product.

26. The dryer of claim 24 or 25, wherein the one or more flexible walls are expandable outwardly from the original state to contact the product.

27. The dryer of any one of claims 24 to 26, wherein the one or more walls are contractable to the original state when the product is to be removed from the zone.

28. The dryer of any one of claims 24 to 27, further including an inflation fan for controlling the expansion of the one or more walls.

29. A method of drying a product using a dryer having a first zone, a second zone, a heating distribution system, and a wall arrangement for physically separating the first zone from the second zone; the method including: operating the heat distribution system to maintain the second zone at an operating temperature that is equal to or higher than the first zone; locating a first batch in the first zone for drying using at least the ambient conditions; and locating, when the first batch is pre-dried in the first zone, the first batch to the second zone for further drying.

30. The method of claim 29, wherein the method includes locating a second batch in the first zone when the first batch is in the second zone.

31. A controller arrangement for controlling an operation of a dryer for drying a product, the dryer including: a first zone, a second zone, a heating distribution system that is configured to distribute heat to at least the second zone, and a wall arrangement for physically separating the first zone from the second zone; the controller arrangement including at least one processor that is configured to: monitor operating conditions of the first zone and of the second zone, and transmit a signal when the operating condition of either zone reaches a desired operating condition.

32. A method of modifying a dryer, the method including: installing a wall arrangement in the dryer to create two physically separate zones; and configuring a heat distribution system to distribute heat to at least one of the zones to maintain that zone at an operating temperature that is equal to or higher than the other zone.