FIELD OF INVENTION

THIS INVENTION relates to a method of drying sphagnum peat moss. It relates also to a drying apparatus for drying sphagnum peat moss.

BACKGROUND TO INVENTION

The use of sphagnum peat moss in a number of commercial applications such as the absorption and biodegradation of hydrocarbons, the bioremediation of soil contaminated with hydrocarbon pollutants, is known. Prior to use in such commercial applications, sphagnum peat moss is "heat activated" by subjecting the moss to heat treatment so as to reduce the moisture content of the moss and change the nature of the moss from hydrophilic to hydrophobic. During the heat treatment process it is important that the plant cell structure of the moss is kept intact while maintaining a required moisture content (typically 14 % to 22 % for the abovementioned commercial applications) and also retaining the humic acid content (which acts as a catalyst in the biodegradation of hydrocarbon pollutants) in the cell structure of the moss.

It is known, for example, to dry sphagnum moss using auger tubes heated by oil or gas where the moss is fed along the tubes by augers and heated

primarily by conduction heat transfer through contact with the tubes. This leads to uneven heating of the moss which often causes localized burning of the moss and makes it difficult to control the heating of the moss to achieve a desired moisture content. The augers which are required to continuously turn the moss over as it travels along the tubes, often damage the cell structure of the moss.

It is an object of the present invention to ameliorate the abovementioned problems associated with the drying of sphagnum peat moss.

SUMMARY OF INVENTION

According to a first aspect of the invention there is a drying apparatus for drying sphagnum peat moss, including

support means for supporting sphagnum peat moss to be dried; and

electromagnetic radiation generating means which is located adjacent the sphagnum peat moss and which is operable to generate electromagnetic radiation having a wavelength in a range between 10 ^"4 cm and 1 cm, for heating the moss.

The support means may be in the form of a rotatable drum having a first end, and second end, the drum having an entrance opening at the first end through which moss can be introduced into the drum and a discharge opening at the second end through which moss can be discharged from the drum.

The drying apparatus may include drive means for causing the drum to rotate, thereby causing the sphagnum peat moss in the drum to be turned over, in use.

The drum may include feeding means for feeding the sphagnum peat moss along the drum in a direction from the first end to the second end thereof.

The feeding means may include a number of curved flights which are attached to an inner side wall of the drum and which act on the moss to displace the moss along the drum as the drum rotates.

The electromagnetic radiation generating means may be in the form of a series of infrared lamps which are arranged in a lengthwise direction within the drum, for emitting electromagnetic radiation in the infrared part of the electromagnetic spectrum.

The lamps may be disposed substantially centrally within the drum, with the drum being configured to allow an optimum spacing between the infrared lamps and sphagnum moss located in the drum, of between 170 and 200 mm.

The drum may include one or more ventilation holes for venting moist air from the drum which forms due to moisture evaporation from the moss during the heating of the moss, in use.

According to a second aspect of the invention, there is provided a method of drying sphagnum peat moss, which includes heating sphagnum peat moss using the drying apparatus as defined in accordance with the first aspect of the invention, by subjecting the moss to electromagnetic radiation having a wavelength in a range between 10 ^"4 cm and 1 cm.

The method of may include heating the sphagnum peat moss by subjecting the moss to electromagnetic radiation in the infrared part of the electromagnetic spectrum.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention are described hereinafter by way of a non- limiting example of the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:

Figure 1 shows a schematic sectional side elevation of a drying apparatus for drying sphagnum peat moss, in accordance with the invention;

Figure 2 shows a schematic side elevation of the drying apparatus of Figure 1 , the vanes and the cooling system not being shown for the sake of clarity; and

Figure 3 shows a schematic sectional end view of the apparatus of Figure 1 , sectioned along section line III-III of Figure 1 , the vanes not being shown for the sake of clarity.

DESCRIPTION OF PREFERRED EMBODIMENT

With reference to the drawings, a drying apparatus for drying sphagnum peat moss, in accordance with the invention, is designated generally by the reference numeral 10. The apparatus 10 comprises, broadly, support means in the form of a rotatable drum 12 defining a longitudinal axis A, for supporting sphagnum moss 13 to be dried; and electromagnetic radiation generating means in the form of two rows of infrared lamps 14 which are disposed in the drum for heating the moss. The apparatus includes a support stand designated generally by the reference numeral 16 which is fixed to a concrete foundation 18, in an arrangement wherein the drum 12 is elevated above ground.

The drum 12 has a first end 20 and a second end 22. The first end 20 defines an entrance opening 24 through which moss can be introduced into the drum and the second end 22 defines a discharge opening 26 through which moss can be discharged from the drum.

The drum 12 includes feeding means in the form of a number of curved vanes 27 which are located within the drum and which extend inwardly from an inner side wall of the drum, for the length of the drum. In use, the vanes act on the moss within the drum, causing it to be displaced from the first end 20 to the second end 22 as the drum rotates.

The drying apparatus 10 includes a chain drive mechanism 36 for causing the drum to rotate thereby causing the sphagnum peat moss in the drum to be turned over. The drive mechanism 36 includes a chain 38 which is fixedly mounted to the drum 12 and spaced therefrom thereby to surround the drum, an electric motor 44 which drives the chain 38 via a gearbox and a sprocket 39. The apparatus 10 includes a number of circumferentially spaced radially- extending spacer rods 40 which support a spacer ring 42 to which the chain 38 is welded.

The infrared lamps 14 are arranged in two rows 14.1 in elongate housings 41 which define elongate lamp channels 55 which each extend for the length of the drum along rear sides of a different one of the rows of lamps and which are open at opposite ends thereof. The housings are mounted to a support bracket 46 which is in turn rotatably mounted to an elongate central support beam 48 which extends along the longitudinal axis A for the length of the drum 12. In an optimum arrangement, the infrared lamps 14 are 150Ow lamps and are spaced approximately 170 - 200 mm from the sphagnum moss 13 located in the drum, in use.

The support stand 16 includes a number of freely rotatable rollers 50 on which the drum is rotatably supported. More particularly, the drum defines two circumferential guide channels 52 along an external side of the drum along which the rollers 50 are guided as the drum rotates. The Applicant envisages that a pair of spaced rollers will be located in each guide channel.

The support stand includes a pair of upright posts 53.1 and 53.2 which have brackets which extend into the drum at the ends 20 and 22 thereof, respectively, to which opposite ends of the support beam 48 is fixed for supporting the beam 48 in fixed relationship relative to the drum 12.

The drying apparatus includes a cooling system including two blowers 54.1 and 54.2 which blow ambient air into the lamp channels 55 defined by the housings. The blowers 54.1 and 54.2 are connected to the lamp channels at ends thereof at the end 22 of the drum by means of ducts 56.1 and 56.2,

respectively. The cooling air flows along the lamp channels 55 and exits the lamp channels at the end 20 of the drum. The cooling system further includes an extractor fan 58 which extracts cool air from the drum via duct 60.

In use, sphagnum peat moss to be dried is introduced into the drum via the entrance opening 24. As the drum 12 rotates the curved flights act on the moss causing the moss to be displaced from the end 20 of the drum to the end 22 thereof. In a typical example, long fibre sphagnum peat moss having a Van Post grade of between 1 to 4 and a moisture content of between 33 % and 55 % is introduced into the drum at its end 20. The moss is initially subjected to heating via both rows 14.1 and 14.2 of the infrared lamps and thereafter by the lamps in the row 14.1 until slightly more than half- way along the length of the drum. As the drum rotates, the sphagnum peat moss is turned over thereby to allow effective heating of all sides of the moss. Heating of the moss within the drum causes the evaporation of moisture from the moss. Typically, the heating of the moss is sufficient for the moisture content of the moss to be lowered to 14 % to 22 % when it is discharged from the drum. Moist air evaporating from the moss is extracted via the ventilation ducts 30. The Applicant envisages that the speed of rotation of the drum will be adjusted so as to expose the sphagnum peat moss to infrared radiation for approximately 8 to 15 minutes within the drum. The infrared lamps provide for contact-less directional heat transfer to the sphagnum moss which heats the moisture in the moss without significantly increasing the temperature of surrounding materials. This reduces the risk of burning of the moss via conduction heat transfer from surrounding materials as in the case when auger tubes are used, for example, when the moss contacts the auger tubes. The drying apparatus 10 also provides for efficient use of energy for drying moss.