A charcoal retort and a method of producing charcoal

Abstract

A charcoal retort comprises an outer vessel with a region 1 suitable for burning solid fuel 25, with a vent (13, Fig. 1) allowing oxygen into the region and a flue 17 allowing the emission of gaseous

Description

The present invention relates generally to a charcoal retort and a method of producing charcoal and finds particular, although not exclusive, utility in pyrolysis of granular biomass. Charcoal is produced by strongly heating biomass (e.g. wood or other animal and / or plant materials) in minimal oxygen to remove all water and volatile constituents. This is typically carried out in a retort. According to a first aspect of the present invention, there is provided a charcoal retort comprising: an outer vessel comprising a region configured to bum solid fuel therein, a vent configured to allow oxygen into the region, and a flue separate from the vent, the flue configured to allow emission of oxidised gaseous products from the region; an inner vessel located within the outer vessel, the inner vessel configured to receive material to be pyrolyzed therein, the inner vessel comprising (i) at least one outlet through which gas inside the inner vessel can escape into the outer vessel and (ii) a baffle around each of the at least one outlet to prevent material from escaping the inner vessel; and a rotation mechanism configured to rotate the inner vessel within the outer vessel. In this way, granular material such as wood chippings and / or horse manure may be pyrolyzed within the inner vessel more effectively, as the rotation of the inner vessel allows the granular material to be continuously mixed for even heating and to permit out gassing of water and volatile constituents uninhibited by adjacent granular material. In this way, during early stages of pyrolysis water vapour from the material insider the inner vessel may pass through the outlet into the outer vessel and then out through the flue. During later stages of pyrolysis volatile and flammable constituents from the material insider the inner vessel may pass through the outlet into the outer vessel and then by burned in the region. Although solid fuel is required to initiate burning, during later stages of pyrolysis there is no need to introduce more solid fuel as the volatile and flammable constituents are sufficient to produce enough heat for continued pyrolysis. 06 09 24 In this way, material may not be lost. Within the context of this application, a retort is a vessel in which substances may be heated producing gaseous products. The outer vessel may be arranged entirely around the inner vessel, and may be a 5 firebox. The vent may comprise a grate, a single hole and / or a plurality of holes between the outside of the outer vessel and the region, to allow air into the region. The vent may be provided with a valve to control air flow, for instance round holes with a flat disc pivoted to slide over the holes. In alternative embodiments, the vent may comprise an 10 automatic air valve that may be configured to open / close a valve depending upon a temperature within the outer vessel. The flue may be provided with a chimney valve, which may be in the form of a butterfly valve, but could in principle be any form of valve including a lid. The inner vessel may be substantially cylindrical in form, for instance a drum. In 15 particular, the drum may have a diameter of between 0.5 and 2 meters, more particularly between 0.8 and 1.2 meters, for example 1 meter. The drum may have a length of between 1 and 3 meters long, in particular between 1.5 and 2.5 meters long, for example 1.9 meters long. However, the inner vessel may be any shape, as long as it can be rotated within 20 the outer vessel. The inner vessel may have at least one portion that has a circular external profile in cross-section; for example, at least one portion of the inner vessel may be cylindrical, with other portions of the inner vessel having different shapes and crosssections. The inner vessel may be removably-receivable within the outer vessel. 25 In this way, the inner vessel may be removed once pyrolysis is complete and a replacement inner vessel (pre-loaded with material to be pyrolyzed) may be received within the outer vessel. The outer vessel may be openable (e.g. hinged) and / or provided with an outer door, to permit insertion and / or removal of the inner vessel therein. 30 The outer vessel may be provided with a firebox door, to permit insertion and / or removal of solid fuel into the region. The inner vessel may be openable and / or provided with an inner door, to permit insertion of material to be pyrolyzed therein, and / or to permit removal of charcoal therefrom. For example, the inner vessel may have a lid, and the lid may be securable in place by a plurality of bolts. Alternatively or additionally, the lid may be secured in place by a clipped hoop. The inner vessel may comprise a drum which may be stood on end, have its lid removed so that the contents may be changed, and the lid bolted back in place. In alternative arrangements, the inner door and the outer door may be configured such that material to be pyro lyzed may be inserted into, and / or charcoal may be removed from, the inner vessel without removing the inner vessel from the outer vessel. The rotation mechanism may be configured to rotate the inner vessel about an axis that is substantially non-vertical, for example substantially horizontal. The rotation mechanism may comprise a plurality of rollers / wheels (e.g. two rollers and / or four wheels) upon which the inner vessel rests within the outer vessel. The retort may comprise a drive means configured to drive the rotation mechanism. The rollers / wheels may be driven by a motor or some other suitable drive means, which may form part of the retort, or may be provided separate to it. The rollers / wheels may be driven manually. Driving the rollers / wheels may cause rotation of the drum. Alternatively or additionally, the inner vessel may be driven directly by similar means, and the rollers / wheels may be freely rotating, to merely support the inner vessel. The rollers / wheels may be substantially circular, and may transfer torque between the drum and the rollers / wheels by friction. Alternatively, the rollers / wheels may be toothed, and may engage with the inner vessel like a gearwheel (the inner vessel may also be provided with cooperating teeth). The at least one outlet may comprise a single outlet or a plurality of outlets, for example two outlets, in particular more than six outlets, for example ten or twelve outlets. The inner vessel may comprise at least one fin within the inner chamber arranged to churn the material as the inner vessel is rotated. In this way, pyrolysis of the material may be improved. In some arrangements, the baffle and the fin are a single baffle-fin component configured to perform the action of both a baffle and a fin. According to a second aspect of the present invention, there is provided a system comprising: the charcoal retort of the first aspect, wherein the inner vessel is removably-receivable within the outer vessel; and a further inner vessel that is removably-receivable within the outer vessel. In this way, a second load may be pyrolyzed more quickly, as the retort is already hot. According to a third aspect of the present invention, there is provided a method of producing charcoal, the method comprising the steps of: providing a charcoal retort according to the first aspect; placing material to be pyrolyzed into the inner vessel; placing the inner vessel within the outer vessel; burning solid fuel within the region to heat the material to be pyrolyzed in the inner vessel; rotating the inner vessel within the outer vessel. Rotating could be continuous; however, in preferred arrangements, rotating is intermittent; that is, the inner vessel may be rotated for a first period of time, then left stationary for a second period of time, and then rotated again for a third period of time. This procedure could be repeated. For example, the inner vessel may be rotated for three full rotations, then held stationary for three minutes, and that sequence repeated until pyrolysis is complete. The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings. Figure 1 is a perspective view of a charcoal retort. Figure 2 is a cross-sectional view of the charcoal retort of figure 1. Figure 3 shows detail of a baffle shown in figure 2. Figure 4 is a perspective view of a charcoal retort. Figure 5 is a side plan view of a charcoal retort. Figure 6 is a cross-sectional view of the charcoal retort of figure 5. The present invention will be described with respect to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. Each drawing may not include all of the features of the invention and therefore should not necessarily be considered to be an embodiment of the 06 09 24 invention. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention. Furthermore, the terms first, second, third and the like in the description and in 5 the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other sequences than described or illustrated herein. Likewise, method steps described or claimed in a particular sequence 10 may be understood to operate in a different sequence. Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other orientations than 15 described or illustrated herein. It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence 20 or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B. Reference throughout this specification to “an embodiment” or “an aspect” 25 means that a particular feature, structure or characteristic described in connection with the embodiment or aspect is included in at least one embodiment or aspect of the present invention. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, or “in an aspect” in various places throughout this specification are not necessarily all referring to the same embodiment or aspect, but may refer to different embodiments or 30 aspects. Furthermore, the particular features, structures or characteristics of any one embodiment or aspect of the invention may be combined in any suitable manner with any other particular feature, structure or characteristic of another embodiment or aspect of the invention, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments or aspects. Similarly, it should be appreciated that in the description various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Moreover, the description of any individual drawing or aspect should not necessarily be considered to be an embodiment of the invention. Rather, as the following claims reflect, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention. Furthermore, while some embodiments described herein include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination. In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practised without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. In the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value. The use of the term “at least one” may mean only one in certain circumstances. The use of the term “any” may mean “all” and / or “each” in certain circumstances. The principles of the invention will now be described by a detailed description of at least one drawing relating to exemplary features. It is clear that other arrangements can be configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching, the invention being limited only by the terms of the appended claims. Figure 1 is a perspective view of a charcoal retort comprising an outer vessel having a lower fire box part 1 and a lid 3, connected by hinges 5. A lower flange 7 surrounds an upper perimeter of the fire box part 1 and an upper flange 9 surrounds a lower perimeter of the lid 3, the respective flanges 7, 9 arranged to seal the outer vessel when closed. A door 11 in the firebox part 1 provides access to place fuel therein. Vents 13 in the firebox part allow flow of air into the outer vessel. Each vent 13 being provided with a rotatable cover 15 to control an amount of air entering the outer vessel, thereby controlling the temperature within. A flue 17 in the lid 3 allows escape of smoke and other gases from the outer vessel. An inner vessel 19 in the form of a cylindrical drum is rested on a pair of rollers 21 within the outer vessel, which can be driven to rotate the inner vessel 19. In an external wall of the inner vessel 19 is an outlet 23 to allow gasses leave the inner vessel 19 to be expelled into the outer vessel. Figure 2 is a cross-sectional view of the charcoal retort of figure 1 along line A-A in figure 1. Arrows show the respective directions of rotation of the inner vessel 19 and rollers 21. Solid fuel is shown being burned 25 in the firebox part 1, and material to be pyrolyzed 27 is shown inside the inner vessel 19. A baffle 29 is shown surrounding an interior of the outlet 23. Figure 3 shows detail of a baffle 29 shown in figure 2. The baffle surrounds an outlet 23 in the wall of the inner vessel 19, and is provided with side walls 31 in a rotational plane of the inner vessel 19; one side wall has been removed so the internal structure can be seen The baffle is arranged to move tangentially to the right of the figure; that is rotate anti-clockwise about the axis of the inner vessel (opposite to the direction shown in figure 2). The baffle is provided with a ceiling 33 over the outlet 23 and sloping roofs 35 down form the ceiling to openings 37 at each end to allow gas to pass through. 06 09 24 On the leading edge of the baffle is a blade 39 arranged to prevent granular material from entering the opening 37. A similar blade on the trailing edge is not present, as it is not necessary; however, in embodiments where the rotational direction of the inner vessel may be reversed, such a blade 39 may be necessary at both openings 37. 5 Within the baffle, two additional outwardly-sloped barriers 41 are provided adjacent to the outlet 23 to prevent any granular material that may nevertheless have passed through the openings 37 at the leading edge from passing through the outlet 23. As the inner vessel rotates, such granular material would be directed by the outwardly-sloping barrier 41 on the leading side onto the ceiling 33, then down the sloping roof 35 10 on the trailing side. Subsequently, any granular material that had passed through the opening 37 on the leading side, would be ejected through the opening 27 on the trailing side. Figure 4 is a perspective view of a charcoal retort comprising drive rods 43 extending through side walls 45 of the firebox part 1. The drive rods 43 are rotatable via 15 a drive means (not shown) such as a motor. Figure 4 also shows the flue 17 connected to the firebox 1, as an alternative location to the lid 3. Figure 5 is a side plan view of a charcoal retort. The drive rods 43 are shown to be horizontal with respect to the firebox part 1, such that the rotational axes of the drive rods 43 are also horizontal. The drive rods 43 extend completely through the charcoal 20 retort between two side walls 45. Figure 6 is a cross-sectional view of the charcoal retort of figure 5, taken along the line B-B. Gearwheels 47 are arranged on the drive rods 43, such that the rotational axes of the gearwheels 47 are concentric with the rotational axes of their respective drive rods 43. The gearwheels 47 are arranged to transfer torque between the drive rods 43 25 and the inner vessel 19. The inner vessel 19 may also be provided with cooperating teeth to engage with the teeth of the gearwheels 47. The inner vessel 19 may be formed of a cylindrical chamber. The chamber may be rolled. The inner vessel 19 may further comprise removable caps at each end of the cylindrical chamber.

Claims

1. A charcoal retort comprising:an outer vessel comprising a region configured to bum solid fuel therein, a vent configured to allow oxygen into the region, and a flue separate from the vent, the flue configured to allow emission of oxidised gaseous products from the region;an inner vessel located within the outer vessel, the inner vessel configured to receive material to be pyrolyzed therein, the inner vessel comprising (i) at least one outlet through which gas inside the inner vessel can escape into the outer vessel and (ii) a baffle around each of the at least one outlet to prevent material from escaping the inner vessel; anda rotation mechanism configured to rotate the inner vessel within the outer vessel.

2. The charcoal retort of claim 1, wherein the inner vessel is removably-receivable within the outer vessel.

3. The charcoal retort of claim 1 or claim 2, comprising a drive means configured to drive the rotation mechanism.

4. The charcoal retort of any preceding claim, wherein the inner vessel comprises at least one fm within the inner chamber arranged to churn the material as the inner vessel is rotated.

5. A system comprising:the charcoal retort of any preceding claim, wherein the inner vessel is removably-receivable within the outer vessel; anda further inner vessel that is removably-receivable within the outer vessel.

6. A method of producing charcoal, the method comprising the steps of:providing a charcoal retort according to any one of claims 1 to 4;placing material to be pyrolyzed into the inner vessel;placing the inner vessel within the outer vessel;burning solid fuel within the region to heat the material to be pyrolyzed in the inner vessel;rotating the inner vessel within the outer vessel.06 09 24

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