BACKGROUND From the mid 1930's until the 1970's, sphagnum peat was harvested in blocks, directly from partially drained fields. These blocks were then stored so as to dry them naturally. After a year of drying, the peat blocks were bulked, sieved and packaged for sale. This method, being less efficient, had the advantage of keeping the fibers intact at the time of harvesting.

The methods of harvesting and packaging have much changed. Presently, peat is harvested by means of vacuums, after repetitive harrowing, thus allowing the peat to be naturally dried by sunlight and by wind. The so dried peat is then sieved and packaged by means of automatic presses. This method of harvesting has some inconveniences, wherein the most important ones are presented herein below.

Fibers deterioration Fibers deterioration has several different origins, including repetitive harrowing and handling of peat, which bring about different consequences, including amongst others, the loss of the peat's water retention properties and quality.

Repetitive harrowing and the use of heavy equipment during peat harvesting can damage the peat's fiber, which has the effect of reducing its water retention capacity, its grading, and its quality. Knowing that quality peat is found on the surface, its quality reduces over the years, and such is linked to the amount of exploitation. Moreover, decomposed peat is much more fragile during mechanical operation, which destroys the fiber structure of the sphagnum peat, and thus reduces its water retention.

Because of the use of this peat harvesting method, the peat fiber undergoes an oxidation, such being due to peat's exposure to air. Due to water drainage, oxygen is mixed into peat, thus increasing the oxidation of the organic material and increasing the C02 emissions from the exploited field. If the surface of peatland has been exploited for many years, the peat found in deeper portions of the peatland decomposes and becomes less attractive for horticultural uses.

Production deficiencies The known methods of harvesting peat also create production problems, which are due to the ever so changing climatic conditions from one year to another. This problem brings about different consequences.

A first problem may involve the maintenance of an increased inventory so as to compensate for any inventory shortages during wet years.

Then, it is necessary to have a large exploitation area. In order to harvest 800 m3 of peat by year, an exploitation area of one hectare is necessary. This implies that for a harvest of 300 000 compressed bales of 6 ft3 each, an exploitation area of 150 hectares is necessary. Thus, peatland exploitation necessitates good infrastructure as well as involves high operational costs. Moreover, the distance between peatlands is an important factor in that it involves transportation costs for transporting peat from the peatland to the packaging factory.

A second problem involves the considerable starting costs and as well as the preparation of the harvesting site. To the starting cost, one should also include construction costs, for example the cost of constructing access trails to the peatland, a garage and personnel facilities.

A third problem involves the cost of draining the peatland. Moreover, dependently of the region, the concentration of suspended material in water is regulated. Also, the cost of maintaining a decantation basin is high.

Finally, the known methods of harvesting require the purchase of numerous pieces of mobile equipment.

Peatland restoration The known methods of harvesting allow for the restoration of peatlands only after fifteen years have passed since the beginning of exploitation. Presently, the cost for any kind of restoration process is high and represents a significant portion of the total cost of peat site.

The known methods of harvesting affect the environment in several ways and do so more importantly in large areas, wherein peat is being exploited.

Also, by using the method of vacuum harvesting, other inconveniences, which should be considered, are dust emissions from vacuums and the effect of wind on peat stacks. Dust emission norms, which are imposed by different provincial ministries, are difficult to respect.

The drainage of large areas brings about, for its part, a decrease in water levels and also an increase in the level of suspended particles in drained areas.

By using the known methods, the risk of fires is very high. The exploited area has to remain dry in order to use the process of harvesting by vacuum. Different factors may contribute to the ignition of fires, and such include : the heat of a motor; the movement of all-terrain vehicles; small fruit pickers and finally the self- ignition of stacks, such occurring when the temperature becomes too high.

Geographic location The harvesting of raw materials is being more and more done towards northern areas, which brings about other consequences, such as: difficult access; less hours of light, decreased number of harvesting days and the difficulty to find competent manpower to operate the harvesting equipment.

Market By using the traditional methods of harvesting it is also difficult to keep a significant portion of the market share ; to guarantee a constant product quality; and to respect the client's quality standards.

First of all, with regard to keeping market share, the known methods of harvesting render production very dependent on climatic conditions. If the conditions are not favourable, there will be a rarity of the product on the market.

During unfavourable seasons, if peat is unavailable, substitution or replacement products are used, and sometimes, even if peat were to become available, the client does not necessarily use it. The arrival of new peat replacement products, such as coco fibers, bark compost and synthetic fiber residues, also render the situation difficult.

Second of all, by using the traditional methods, it is difficult to guarantee a peat having a constant quality since it is only the more fibrous peat (peat found on the

surface) that is first harvested. Consequently, it becomes essential to continuously exploit new sites in order to guarantee a supply of different grades of peat, which permits to offer a constant peat quality.

Third of all, by using the traditional methods it is more difficult to respect the quality standards. The market demands a peat fiber with little dust. However, with the known methods, it is necessary to regularly harrow the fields to improve the drying process. This operation brings about deterioration in fiber quality, which means that the new fields must be opened so as to be able to mix fibrous peat with a grade of peat that is more decomposed. This operation is costly and renders certain sites non-efficient, such also depends on the price of peat, which is set by the market. Certain sites do not have any new fields to open, yet they still possess a significant amount of peat that is slightly deteriorated. It is therefore more and more difficult to make mixes of fibrous peat and decomposed peat.

Drying of fibrous material Some of the methods of drying fibrous material, such as sphagnum peat, are described herein above.

Drying by hot air with oil or gas Due to the high temperatures reached by this type of drying, the fiber is both physically and chemically damaged. Moreover, this type of drying incurs high- energy costs.

Microwave drying This type of drying requires a large drying zone. Microwave drying is also costly and requires a significant capital investment. Moreover, the moisture content of

the peat has to be less than 25% at the inlet of the dryer in order for the step of drying to be efficient. This constraint is problematic since the initial moisture content of natural peat ranges from 95 to 98%.

Fluidized bed The use of a fluidized bed incurs a high dust production, since air is blown through the peat. Moreover, this technology is expensive and requires a major investment as well as incurs high operational costs, which are related to the high consumption of energy. Another disadvantage associated with this technology is that it breaks the fiber. The latter is due to the movement of the material when it is blown by air.

Filter press The use of a filter press also incurs physical damages to the fiber, since the pressure needed to attain prescribed moisture content level damages the fiber.

Moreover, the use of such a technique lacks productivity.

Sphagnum peat possesses a high water retention capacity. For example, it can retain about 15 to 25 times its weight in water. However, in order to render this product marketable, its moisture content must be lowered to a value in the order of 40%. The known methods, natural drying by sun or by wind, combined with a vacuum harvesting, do not guarantee a production or a uniform quality, over the course of time, in this case years.

There is thus indeed a need for a drying apparatus and method that minimize the loss of the fiber characteristics and quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide a drying apparatus and method that satisfy the above-mentioned needs.

According to the present invention, there is provided a method for drying harvested organic fibrous material having a predetermined moisture level. The method comprises the steps of feeding the fibrous material to be dried on a supporting surface permeable to air and drying the fibrous material by drawing air through the fibrous material by means of at least one plenum located under the supporting surface, and thereby obtaining a dried fibrous material. The method also comprises the step of unloading the dried fibrous material from the supporting surface.

According to the present invention, there is also provided a drying apparatus for drying harvested organic fibrous material having a predetermined moisture level.

The drying apparatus comprises at least one plenum having an air inlet and an air outlet in fluid communication with each other and a supporting surface permeable to air to support the fibrous material to be dried. The supporting surface covers the air inlet of the at least one plenum. The drying apparatus also comprises at least one fan operatively connected to the air outlet to draw air through the air inlet, into the at least one plenum and out of the air outlet, thereby causing a circulation of the air through the fibrous material supported on the supporting surface and drying the fibrous material.

Advantageously, the method and the drying apparatus according to the present invention minimizes the loss of the fibers'properties and quality.

Still, another object of the present invention is to provide a method and a drying apparatus for drying harvested organic fibrous material in which the fibrous material is dried by drawing air through the fibrous material and into the plenum.

Another object of the present invention is to provide a method and a drying apparatus capable of reducing the moisture content of moist fibrous material.

In accordance with a preferred embodiment, the supporting surface is a belt conveyor used to move the fibrous material to be dried over the air inlet of the plenum in a continuous manner. The belt conveyor has a first end to receive the fibrous material to be dried and a second end opposite to the first end to discharge a dried fibrous material.

In accordance with another preferred aspect, the drying apparatus further comprises a chimney operatively connected to each one of said at least one fan to evacuate air drawn out of the air outlet away from the air inlet.

In accordance with another preferred embodiment, the method for drying harvested organic material has the following advantages: - reducing the amount of manpower required; - increasing productivity; - reducing fiber damage during the harvesting process; - reducing the dependency of fiber production to climatic conditions; - reducing the amount of capital investment required for purchasing harvesting equipment; - reducing the harvesting area; - reducing the polluant emissions; - using a minimum energy; - reducing the negative impacts on the flora and fauna; and - accelerating the restoration process.

In accordance with still another preferred embodiment, the drying apparatus is both of economic construction and use, as well as consuming a low amount of energy.

Yet, in accordance with another preferred embodiment, the method and drying apparatus are capable of removing a maximum of moisture content from sphagnum peat.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and advantages of the invention will become apparent upon reading the detailed description and upon referring to the drawings in which: Figures 1a and 1b are flowcharts illustrating different steps of a method for drying fibrous material according to the present invention.

Figure 2 is a schematic view of a drying apparatus according to a first preferred embodiment of invention, with the supporting surface removed for clarity.

Figure 3 is a schematic view of the drying apparatus of Figure 1, showing a supporting surface to support fibrous material, along with the supporting surface.

Figure 4 is a schematic view of a drying apparatus according to a second preferred embodiment of invention.

Figure 5 is a schematic view of a drying apparatus according to a third preferred embodiment of invention.

Figure 6 is a schematic view of a drying apparatus according to a fourth preferred embodiment of invention.

Figure 7 is a schematic view the drying apparatus of Figure 5, with a distribution system for distributing the fibrous material onto the belt conveyor.

DESCRIPTION OF PREFERRED EMBODIMENTS In the following description, similar features in the drawings have been given similar reference numerals and in order to weight down the figures, some elements are not referred to in some figures if they were already identified in a precedent figure.

Before the present invention is disclosed and described, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the description and appended claims, the term"peat"refers to the expression"fibrous material"and vice-versa. However, it should be noted that the use of such a term and/or example is not intended, by any means, to limit the scope of the present invention and that other types of fibrous material could be considered. Such fibrous material may include organic material like algae, cotton, bark, leaves, shrubs, grass and others, which can be dried by making use of the present invention.

As illustrated in Figures 1a and 1b, a method for drying organic fibrous material according to the present invention could have the following main steps, which are described hereinafter: Step 1: Harvesting of the fibrous material 52 Step 2: Treatment of fibrous material Step 2.1 : Primary pressing of fibrous material 52 Step 2.1. 1: Primary fluffing of the fibrous material 54 Step 2.1. 2: Primary screening of the fibrous material 56 Step 2.2. : Secondary pressing of the fibrous material 58 Step 2.2. 1: Secondary fluffing of the fibrous material 60 Step 2.2. 2: Secondary screening of the fibrous material 62 Step 3: Drying of the fibrous material 64

Step 1 : harvesting of the fibrous material 52 In this first step of this method, the organic fibrous material, for example peat, is directly harvested on a partially drain peatland, preferably by means of industrial excavator (or trencher). The peat is harvested at a depth which can generally vary from one to four meters, and such depends on the thickness of the available peat and on the peat's degree of decomposition, which can be between H1 and H4, according to Von Post scale. The so harvested peat can have a moisture content varying between 92 and 95%. Following the harvesting step, the peat is transported, for example by truck, to a site wherein the second step of the process according to the present invention is carried out.

Step 2 : treating of the fibrous material The step of treating fibrous material could be done prior to the step of drying the fibrous material. The object of this step is to mechanically work the fibrous material so as to reduce its moisture content. In doing this step of treating the fibrous material before the step of drying the fibrous material, the principal parameters of the step of drying the fibrous material are optimised, such includes : reducing the drying time and reducing the amount of energy consumed. However, it is worth noting that the step of treating the fibrous material is optional and that it can be omitted before proceeding to the step of drying the fibrous material. The step of treating the fibrous material is not necessary to succeed, but it greatly improves the total efficiency of the process.

The step of treating the fibrous material can be characterised by the removal of a certain amount of water from the fibrous material so as to reduce its moisture content to predetermined values, for example between 80 and 89%.

In a preferred embodiment of the invention, when the fibrous material to dry is peat, the preferred way of going about this step is to use presses, which can be divided into two steps, which respectively are: the first and second pressing of peat.

It is worth noting that other mechanical processes such as one or more centrifuging systems, a negative pressure or vacuum system could be used as alternatives to the presses.

Step 2. 1 : primary pressing 52 In the first step of the process of treating the peat, the peat can be introduced in a. press, for example a piston press. This first step consists in extracting a surplus of water from the peat. The object of this first step is to reduce the moisture content of the peat to a predetermine value, for example a value between 80 and 89%. This predetermine value could vary with the efficiency of the type of system used and the type of fibrous material to be dried. The press could be designed in such manner so as to extract about 30 pounds of water per cubic foot of peat.

The press may be either mobile or fixed, and such depends on the distance between the peatland and the peat treatment center. It could be advantageous to carry out the first pressing step on the same site where the first step of the process (i. e. the step of peat extraction) is done so as to reduce the amount of water in the harvested peat; reduce the weight of the harvested peat before transporting it to the site where the subsequent steps of the process are done and to reduce the transportation costs. Following this step of pressing, the peat is transported, for example by truck, to a site wherein the subsequent steps of the process are to be done.

In another preferred embodiment, the press used for the primary pressing of the peat can be combined with other systems of the subsequent steps so as to obtain a continuous process.

Step 2. 1. 1 : primary fluffing 54 Following the step of primary pressing, there is a step of primary fluffing. The first fluffing step is done by means of a disc screen, which is known to person skilled in the art, or with any other type of equipment, which is deemed to be efficient in fluffing peat.

The object of the first fluffing step is to treat the harvested peat for the next step of the process, which could be the second pressing step of peat. The first fluffing step consists in reducing the pressed peat into aggregates while preserving the fiber, in other words to delicately undo the peat into pieces. The object of this fluffing step is to modify the size of the pieces of pressed peat in order to facilitate the pressing of peat in the second pressing step. Another object of this step is to allow for a better water percolation in the peat.

Following this first fluffing step, the peat can be transported, for example by means of a conveyor, on a site wherein the next step of the process is carried out. In order to reduce the production costs associated to the handling and the transport of the peat, it is recommended that all the subsequent steps of the process, including the first fluffing step, be done in close proximity to one another.

Step 2. 1. 2 : primary screening 56 Following the first fluffing step or before the drying step, there could be a first screening step. This screening step is done by means of a pin auger, which is known to a person skilled in the art.

The object of the first screening step is to treat the harvested peat before the drying step of the method. The screening step consists in eliminating undesirable

particles from the peat, such as roots and branches. The object of the first screening step is to improve the uniformity of the peat obtained by the process.

Step 2. 2 : secondary pressing 58 ) This second pressing step consists in removing the surplus of water from the peat. The object of the second step is to reduce the moisture content of peat at a predetermined value, which is for example between 70 and 75%. This predetermined value may vary with the efficiency of the systems used and the type of fibrous materials to be dried.

For example, for this second pressing step, the press could be designed in such manner so as to remove between 300 kg by cubic meter of peat.

Following this second pressing step, the peat could be transported, for example by means of a conveyor, on a site wherein the next step of the process is carried out.

Step 2. 2. 1 : secondary fluffing 60 A second fluffing step follows the secondary pressing. Again, this step could be done by means of a disc screen, which is either known to a person skilled in the art, or with any other piece of equipment, which is deemed efficient in fluffing peat.

The object of the secondary fluffing step is to treat the peat obtained from the secondary pressing. The second fluffing step consists in reducing the pressed peat into smaller particles thus permitting a homogeneous mixture of fibres. The object of this step is to increase the peat's permeability to air.

Following the second fluffing step, the peat could be transported, for example by means of a conveyor, on a site wherein the next step of the process is carried out.

Step 2.2. 2 : secondary screening 62 A secondary screening step can be conducted following the second fluffing step or the first screening step. This step is conducted by means of a pin auger, which is known to a person skilled in the art.

The secondary screening step consists in eliminating undesirable particles, such as roots and branches from the peat. The object of the secondary screening step is to improve the quality of the peat produced by the process. Following this secondary screening step, the peat could be transported, for example, by means of a conveyor, on a site wherein the next step of the process is carried out.

Step 3 : drying of fibrous material 64 Better shown in Figure 1b, the preferably so treated fibrous material is dried in a drying apparatus according to the present invention which is described herein after. The drying of the fibrous material consists in removing a surplus of water from the fibrous material by: - feeding 66 the fibrous material to be dried on a supporting surface permeable to air; - drying 68 the fibrous material by drawing air through the fibrous material by one or more plenum located under the supporting surface, and thereby obtaining a dried fibrous material. The method also comprises the step of unloading the dried fibrous material from the supporting surface ; and - unloading 70 the dried fibrous material from the supporting surface.

The object of this third step is to reduce the moisture content in the fibrous material to a predetermine moisture content, which can be for example between 40 and 50% in the case of peat. This value may vary depending on the type of fibrous material to be dried. The airflow rate and temperature of the drying apparatus could also be adjustable with regard to the type of fibrous material to be dried, and such also is a function of the moisture content of the fibrous material to be dried when it is at the inlet of the drying apparatus and the ambient air conditions, in particular the moisture content of the ambient air.

Drying apparatus As shown in Figures 2 and 3, in a first preferred embodiment, the drying apparatus of the present invention, also referred to as a dryer, has a suction plenum 2 having an air inlet 4 and an air outlet 6 in fluid communication with each other and a fan 8 to draw air from the plenum 2.

Preferably, a chimney 10 is operatively connected to the fan 8 to evacuate air drawn out of the air outlet 6 away from the air inlet 4, thereby avoiding any re- circulation of the evacuated air into the plenum 2.

Better shown in Figure 2, the air inlet 4 is completely covered of a supporting surface 12. The supporting surface 12 is fabricated in a material permeable to air, for example a woven filament made of polyethylene terephthalate (PET). This type of material allows air to pass through the supporting surface 12. The' supporting surface 12 supports a layer of fibrous material 14 to be dried, and such is done without letting any fibrous material 14 to enter the suction plenum 2.

The fan 8 is used to draw ambient air over the fibrous material in the air inlet 4, through the plenum 2 and out of the air outlet 6 towards the exterior of the dryer via the chimney 10, thereby causing a circulation of the air through the fibrous material 14 supported on the supporting surface 12 and drying the fibrous

material. While passing through the fibrous material 14, the air absorbs the moisture present in the fibrous material 14, thus drying the fibrous material 14.

Referring now to Figure 3, there is shown a second preferred embodiment of the present invention. In order to increase the air capacity to capture moisture contained within the fibrous material 14, a heating element 22 could be located within the additional air duct 16, between an air inlet 18 and an air outlet 20. The heating element 22 thus heats the air before its circulates through the fibrous material 14 to be dried. n'comparison to ambient air, the so heated air captures a superior amount of water when it passes through the fibrous material 14.

Because of the fan 8, the outside (atmospheric) air is brought into an air duct 16 having an air inlet 18 and an air outlet 20 of the same. The air inlet 18 and air outlet 20 of the air duct 16 are in fluid communication with each other. The air outlet 20 is adjacent to the supporting surface 12.

The air duct 16 preferably has a pyramidal shape to direct the airflow over the plenum 2 but could have any other suitable shape.

In Figure 4, there is show a third preferred embodiment of the present invention the dryer having a series of plenums 2 aligned side by side. Each plenum 2 could be operatively connected one respective fan 8. Alternatively, the plenums 2 could be all operatively connected to one single fan 8 (not shown).

As shown, a chimney 10 could be operatively connected to each one of the fans 8 to evacuate air drawn out of the air outlet away from the air inlet.

The supporting surface 12 is a belt conveyor 24 that forms a buckle around the plenums 2. The belt conveyor 24 has a first end 26 to receive the fibrous material 14 to be dried and a second end 28 to discharge the dried fibrous material.

The belt conveyor 24 could be guided by guiding rollers 30 which are driven by a motor 32, for example an electric motor, in such manner that the belt conveyor 24 is moved around the plenums 2, and above the air inlets 4 of the plenums 2.

It is worth noting that the series of plenums 2 could be replaced by one or more plenums 2 of larger dimensions (not shown). This also implies that the fans 8 associated to each of the plenums 2 can be replaced by one or more large capacity fans 8. The combination of fans 8 and plenums 2 can be done to simplify the complexity of the system and reduce the related costs.

The use of a plurality of plenums 2, as well as the belt conveyor 24 in a closed buckle formation allows to produce a continuous drying where the fibrous material 14 is deposited at the first end 26 of the belt conveyor 24 and moves above the plenums 2 in a direction 34, in order to finally exit at the second end 28 of the belt conveyor 24.

As shown in Figure 7, the positioning of the fibrous material 14 on the belt conveyor 24 could be done by a distribution system to control the output of fibrous material such as the width and length of the layer of the fibrous material 14 on the belt conveyor 24 and the distribution uniformity of the fibrous material 14. This distribution system is, for example, constituted of an oscillating conveyor 72 and an equalizer. The oscillating conveyor 72 is driven by a motor 68 and the guiding rollers 70. The oscillating conveyor 72 has an outlet end 74 in communication with the first end 26 of the belt conveyor 24 and can be moved laterally over the belt conveyor 24 by following a guide 76.

The fibrous material 14 could also be feed to the belt conveyor 24 by a feeding device, such as another conveyor 38 to convey the fibrous material 14 to be dried onto from the belt conveyor 24. The conveyor 38 has an outlet end 40 in communication with the first end 26 of the belt conveyor 24 to feed the fibrous material 14 to be dried to the belt conveyor 24.

At the second end 28 of the belt conveyor 24, there could be an unloading device, such as a discharge conveyor 42 to convey the dried fibrous material 14 away from the belt conveyor 24. The discharge conveyor 42 has an inlet end 44 in communication with the second end 28 of the belt conveyor 24 to receive and unload the dried fibrous material 14 from the belt conveyor 24.

Now turning to Figure 5, there is shown a fourth preferred embodiment of the dryer of the present invention showing the plenums 2 covered by a shelter 46.

The shelter 46 is provided with an inlet 48 and an outlet 50, each one located at an extremity of the shelter 46 so as to allow fibrous material 14 to enter the shelter 46 by the inlet 48 and exit by the outlet 50. The inlet 48 and outlet 50 also allow for a controlled air opening into the dryer. The shelter 46 isolates the direction of the airflow in order to avoid moist air expulse by the chimneys 10 from being re-circulated through the dryer via the suction plenums 2. Such a re- circulation would risk reducing the efficiency of the dryer.

Design, capture profile and positioning of the in let 48 and outlet 50 of the shelter 36 may vary according to the design of the other components of the dryer, for example the chimneys 10, the suction plenums 2, etc.

In all the described embodiments hereinabove, the percentage moisture content of the fibrous material 14 could be modified by varying the drying time of the fibrous material 14 in the dryer. The drying time can be modified by controlling the motor 32 to decrease or increase the speed of the belt conveyor 24 in the direction 34.

Consequently, if the speed of the belt conveyor 24 is increased, the amount of air that passes in the fibrous material 14 in a given time is decreased. The total exposition time of the fibrous material 14 to the drying air is thus decreased.

Accordingly, the amount of water removed from the fibrous material 14 is decreased.

If the speed of the belt conveyor 24 is reduced, the amount of air passing in the fibrous material 14 in a given time is increased. The total exposition time of the fibrous material 14 over the air inlets 4 is thus increased. Accordingly, the amount of water removed from the fibrous material 14 is increased.

Varying the airflow rate of the fan 8 can also modify the percentage moisture content of the fibrous material 14. If the airflow rate, produced by fan 8 increases, the amount of air that passes through the fibrous material 14 also increases, thus increasing the amount of water removed from the fibrous material 14.

If the airflow rate produces by the fan 8 decreases, the amount of air that passes through the fibrous material 14 decreases, thus decreasing the amount of water removed from the fibrous material 14.

Advantageously, in all of the preferred embodiments described hereinabove, the dryer could be automated and controlled by an automatic control system, which could be administered by a programmable controller PLC or by a conventional computer so as to minimize human intervention.

There are three types of data, which could be continuously monitored in order to have an optimal drying efficiency. These data include : - temperature of ambient air; - the relative moisture content of ambient air; and - average moisture content of the fibrous material 14 at the second end 28 of the belt conveyor 24.

The data relating to the temperature and moisture content of the air could be collected with a meteorological station installed close to the belt conveyor 24,

while the data relating to moisture content of the fibrous material 14 could be collected with an infrared detector installed at the second end 28 of the belt conveyor 24.

A mathematical algorithm could be used to determine the optimal drying speed.

Of course, the drier the air is, the shorter of the drying time will be, since the air passing through the fibrous material 14 will advantageously capture the water particles. The same phenomenon also occurs with warm air.

Data entry will be done automatically. The only human intervention that would be required is the use of an operator who enters on an interface (i. e. a keypad) the desired moisture content of the fibrous material 14, which is to come out of the second end 28 of the belt conveyor 24.

In another preferred embodiment, the dryer according to the present invention could be provided with a mixing system (not shown). Such a system can be used to avoid a creation of preferred routes during the drying process of the fibrous material 14. These preferred routes must be eliminated in order to have a good drying efficiency and to avoid an air loss in portions of the fibrous material 14, which are drier than others.

A mixing system allows the fibrous material 14 to be continuously re-equalized, and such may depend of the speed at which of the belt conveyor 24 is functioning. This system can be installed at a mid-point of the belt conveyor 24.

However, it is worth noting that such a system can be installed along the whole length of the belt conveyor 24, and this depends on the ease at which the fibrous material 14 can create preferred routes.

In another preferred embodiment, the speeds of the fans 8 of the dryer could be controlled with frequency modifiers. Such is done to optimize the drying efficiency of the dryer in function of the moisture content of the fibrous material 14 to dry

(for example peat) on the belt conveyor 24. In this manner, it is possible to increase the airflow rate at the first end 26 of the belt conveyor 24, where the material has high moisture content. Similarly, the airflow rate can be decreased in sections close to the extremity of the belt conveyor 24 where the moisture content of the fibrous material 14 is smaller.

For example, the suction pressure of the fans 8 is in the order of 1kPa for a rate of 60-65 m3/min by m2 of belt conveyor 24.

In another preferred embodiment, the dryer could be provided with a system for levelling material (for example peat) of a certain thickness on the belt conveyor 24. In effect, it is advantageous to maintain a constant and uniform level (thickness) of fibrous material 14 on the belt conveyor 24. This thickness is preferably in the order of 5 to 10 cm, but could be otherwise. This system primarily could consists of the oscillating conveyor 72 and the equalizer previously described.

In another preferred embodiment, the dryer could be provided with a cleaning system, for example a brush, which is positioned underneath a return line of the belt conveyor 24, and close to the belt conveyor's drive system. An object of this system is to remove any fibrous material 14 particles that may obstruct the "pores"of the belt conveyor 24 and thus reduce the airflow rate, which passes through the belt conveyor 24. Such a reduction of the airflow rate reduces the drying efficiency of the dryer. The air cleaning system can also be positioned after the plenums 2 so as to remove and/or capture any fibrous material 14 particles that may be lodged in the belt conveyor 24.

Although preferred embodiments of the present invention have been described in detail herein and illustrated in the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the present invention.