GB2331353A

GB2331353A - Charcoal manufacture

Info

Publication number: GB2331353A
Application number: GB9824862A
Authority: GB
Inventors: Robin Webster
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-11-12
Filing date: 1998-11-12
Publication date: 1999-05-19
Also published as: GB2331353A9; GB9824862D0; GB9723782D0

Abstract

The present invention relates to charcoal manufacture. In particular, it relates to an improved design of charcoal burner or retort. There is described a retort for the production of charcoal from woody material, the retort comprising a casing including two horizontal cylindrical (typically circular) charcoal ovens and defining a firebox between the two ovens; wherein each oven is provided with an exhaust flue which, in use, directs exhaust gases produced as the woody material is converted to charcoal, into the firebox.

Description

CHARCOAL MANUFACTURE The present invention relates to charcoal manufacture In particular, it relates to an improved design of charcoal burner or retort.

The process for the production of charcoal from woody materials is an ancient one. Based on the traditional methods, charcoal is conventionally produced in kilns comprising two stacked rings fitted with a lid and chimneys. The kiln is filled with wood and a fire is lit in the middle. The chimneys are moved around two or three times during the burning process, which can take up to 30 hours. There is no guarantee of even burning and thus no guarantee as to the quality of charcoal obtained The kilns are emptied by removal of the top ring and someone climbs inside This inevitably results in damage to the charcoal There have been many attempts to improve the yields and process times from the traditional methods None of the improved methods are entirely satisfactory For example, EP-A-0 335 044 and US 4 935 099 both describe highly complex apparatus The apparatus of FR 2 677 661 requires ground excavations for its installation. W096/29378 describes an apparatus which it is claimed provides yields of up to 50% and a turnaround time of around 2 hours, but the apparatus is operated under considerable pressure The present invention seeks to overcome the disadvantages in the prior art by providing an essentially simple, but effective, improved charcoal retort According to the present invention, there is provided a retort for the production of charcoal from woody material, the retort comprising a casing including two horizontal cylindrical charcoal ovens and defining a firebox between the two ovens, wherein each oven is provided with an exhaust flue which, in use, directs exhaust gases produced as the woody material is converted to charcoal, into the firebox Preferably, the exhaust flue is also open to the atmosphere but can be stopped, thereby allowing regulation of the temperature of the firebox

Preferably, the exhaust flue is mounted upon the door of each oven.

Preferably, each oven includes a rake comprising a disc of a shape corresponding to the cross-section of the oven and a handle extending the length of the oven In use, the disc of the rake sits at the end of the oven remote the door Typically, the ovens have a circular cross-section.

The above and other aspects of the present invention will now be described in further detail, by way of example only, with reference to the accompanying figures in which Figure 1 is a front view of an embodiment of a charcoal retort in accordance with the present invention; Figure 2 is a side view of the embodiment of Figure 1, and Figure 3 is a schematic plan view of the embodiment of Figure 1 showing the layout of the principle components Referring to the figures, there is shown a charcoal retort 10 comprising an outer casing 11 defining generally a firebox Within the casing 11 are mounted two horizontal, cylindrical charcoal ovens 12,13 A fire 14 is made between the ovens 12,13 and accessed through a fire door 15. A screen of fire bricks (not shown) is provided between the fire 14 and each oven 12,13, for improved distribution of heat and to avoid direct contact between the fire and the metal of the oven Fire door 15 includes a smaller viewing and ventilation port 16. Each oven is provided with a respective oven door 20, 21, the left hand one of which is shaded for clarity in Figures 1 and 2.

At the rear of the firebox are provided suitable fire exhaust means, in the form, as shown, of two chimneys 22,23.

Each oven door 20,21 includes a flue 25 which includes (shown as a dotted line on door 21 in Figure 1) an inlet 26 from the oven and two outlets, an upper outlet 27 and a lower outlet 28 Upper outlet 27 exhausts gases emitted from the carbonisation process to atmosphere. Lower outlet 28 exhausts such gases to a horizontal flue pipe 30 within the firebox and adjacent the fire. The flue pipe 30 includes a plurality of exhaust ports 31 directing the exhaust gases into the fire, where the gases, which include combustible compounds, are burned, thus reducing the amount of fuel required by the fire Upper outlet 27 is closed with a removable stop (not shown) The stop ensures that essentially all the exhaust gases pass into the firebox. However, that may result in excessive temperatures in the firebox. Accordingly, the stop can be removed as required to modulate the temperature. Typically, removal of the stop will be a manual operation. Alternatively, temperature probes could be provided in or on the firebox and removal of the stop, completely or partially, may be automated.

In the preferred embodiment shown, the apparatus also includes a rake 40 for assisting in removal of the charcoal from each oven (for clarity, a rake is shown only in oven 13 of Figure 3) The rake 40 consists of a plate 41, the shape of which corresponds to the cross-sectional shape of the oven (that is to say, the plate is typically a circular disc), connected to a long handle 42. In use, the rake 40 sits with the plate 41 at the rear of the oven and the handle 42 extending towards the front of the oven and resting on the floor of the oven The basic process for the conversion of wood into charcoal is well documented and will not be described in further detail here.

In use, a rake 40 is placed in each oven as described above and the oven is stacked with charcoal In a typical retort having a generally square plan and in which each oven is around 1m in diameter, around 1 tonne of wood can be converted into charcoal The doors 20,21 are closed and the flues 25 are stopped The firebox is fed with, typically, waste wood and lit. For around % hour, the fire bums solely on the waste wood. Thereafter, the temperature in the ovens increases sufficiently to drive off organic vapours from the wood. These vapours enter the firebox through flue pipes 30 where it is burned The opening of the ventilation port 16 is adjusted to

maintain the fire at the desired level. After around 6 hours, depending largely upon the water content of the wood in the ovens, the conversion of wood into charcoal is complete and the ovens may be left to cool down.

The quantity of organic vapours driven off from the wood will vary from batch to batch. If the vapours are excessive and lead to an undesirable excess temperature in the firebox, the flow of vapours into the firebox can be moderated by removal of the stops in the flues 25 Moisture from the wood is drained through vents (not shown) in the floor of each oven Once the oven has cooled, the doors are opened and the charcoal is removed very quickly into a receptacle placed under the oven by simply pulling on the handle 42 of the rake 40 This method of removal results in reduced breakage of the charcoal The whole process takes 12-16 hours from start to finish (perhaps 18-24 hours if the wood is excessively wet) and produces a yield of high and uniform quality charcoal of around 30% This is contrasted with conventional round kiln methods which give yields of around 10% and, including stacking and emptying, take around 2 days to complete a 4.5 tonne batch.

Further evidence of the improved efficiency of the apparatus of the present invention is provided by the fact that there is generally very little smoke emitted The retort can be mounted upon a chassis (not shown) to raise it off the ground The legs of the chassis can be height adjustable. Thus, the retort is easily set up for use with no requirement for major construction works as is the case with the prior art devices described above. Furthermore, the high yields mean that the retort can be of a size which makes it readily transportable.

Claims

Claims 1 An apparatus for the production of charcoal from woody material, the retort comprising a casing including two horizontal cylindrical charcoal ovens and defining a firebox between the two ovens; wherein each oven is provided with an exhaust flue which, in use, directs exhaust gases produced as the woody material is converted to charcoal, into the firebox.
2 An apparatus as claimed in Claim 1 wherein the exhaust flue is also open to the atmosphere but can be stopped to allow regulation of the temperature of the firebox
3 An apparatus as claimed in Claim 1 or Claim 2 wherein the exhaust flue is mounted upon the door of each oven.
4 An apparatus as claimed in any one of Claims 1 to 3 wherein each oven is provided with a rake comprising a disc of a shape corresponding to the cross-section of the oven and a handle extending the length of the oven 5 An apparatus as claimed in any preceding claim wherein the ovens have a circular cross-section 6 An apparatus for the production of charcoal substantially as herein described with reference to the accompanying drawings.