FURNACE FOR PYROLYSIS

Abstract

A rotary furnace (1) for pyrolyzing a feedstock, the furnace (1) comprises a rotating vessel (12) having an upstream end (12A) with an inlet (16) for receiving feedstock and a downstream end (12B) with an outlet (17A, 17B) for egress of pyrolysis products, and a gas extraction pipe (13) extending within and along the rotating vessel (12) from the downstream end (12B), the gas extraction pipe (13) having an opening (18) upstream of the downstream end (12B) to accept gaseous components generated in use.

Claims

1. A rotary furnace for pyrolyzing a feedstock, the furnace comprising a rotating vessel having an upstream end with an inlet for receiving feedstock and a downstream end with an outlet for egress of pyrolysis products, and a gas extraction pipe extending within and along the rotating vessel from the downstream end, the gas extraction pipe having an opening upstream of the downstream end to accept gaseous components generated in use.

2. A rotary furnace according to claim 1, wherein the rotating vessel is inclined at an angle of between-4 to 15 degrees relative to the longitudinal horizontal axis.

3. A rotary furnace according to claim 1, wherein the gas extraction pipe extends less than half way along the length of the rotating vessel.

4. A rotary furnace according to claim 1, wherein the ratio of the internal width of the rotating vessel to the internal width of the gas extraction pipe is 2:1 to 4:1.

5. A rotary furnace according to claim 1, wherein the longitudinal axis of the gas extraction pipe is parallel to and offset from the longitudinal axis of the rotating vessel.

6. A rotary furnace according to claim 1, wherein the gas extraction pipe comprises a chamfered inlet for entry of gaseous components generated in use.

7. A rotary furnace according to claim 6, wherein the angle created by the chamfered inlet is 20 to 40 degrees.

8. A rotary furnace according to claim 1, wherein the rotating vessel is configured to rotate at a speed of 1 to 10 rpm.

9. A rotary kiln according to claim 1, wherein the gas extraction pipe comprises a self-cleaning device configured to contact an interior surface of the gas extraction pipe to remove debris therefrom.

10. A rotary furnace according to claim 9, wherein the self-cleaning device comprises a disc having a width substantially equal to the internal width of the gas extraction pipe.

11. A rotary furnace according to claim 10, wherein the self-cleaning device comprises a circular disc having a diameter substantially equal to the internal diameter of the gas extraction pipe.

12. A rotary furnace according to claim 10, wherein the disc is secured to a rod axially extending through the gas extraction pipe.

13. A rotary furnace according to claim 12, wherein the rod of the self-cleaning device is configured rotate about its axis.

14. A rotary furnace according to claim 12, wherein the rod of the self-cleaning device is configured to translate along its axis.

15. A rotary furnace according to claim 10, wherein the disc of the self-cleaning device is configured to extend beyond the opening of the gas extraction pipe.

16. A rotary furnace according to claim 1, further comprising a hopper.

17. A rotary furnace according to claim 1, further comprising a feeder.

18. A rotary furnace according to claim 1, further comprising a gas condensation chamber.

19. A rotary furnace according to claim 1, wherein the outlet for egress of pyrolysis products comprises a first outlet for the egress of gaseous components and a second outlet for the egress of solid pyrolysis products.

20. A method of pyrolyzing feedstock in a rotary furnace, the method comprising: a. providing a rotary furnace according to claim 1; b. locating feedstock at the inlet; c. conveying the feedstock through the rotating vessel; d. pyrolyzing the feedstock to produce gaseous components; e. removing the gaseous components from the rotating vessel via the gas extraction pipe.

Description

[0048] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0049] FIG. 1 is a cross-sectional view of the side elevation of a rotary furnace according to an embodiment of the invention;

[0050] FIG. 2 is a cross-sectional view of the rear elevation of the downstream end of the rotating vessel of the rotary furnace of FIG. 1;

[0051] FIG. 3 is the opening of the gas extraction pipe of the rotary furnace of FIG. 1;

[0052] FIG. 4 is a cross-sectional view of the side elevation of a rotary furnace comprising a self-cleaning device, according to a further embodiment of the invention FIG. 5 is a side elevation of the self-cleaning device shown in FIG. 4;

[0053] FIG. 6 is a three dimensional representation of the self-cleaning device shown in FIGS. 4 and 5.

[0054] Referring now to FIG. 1, there is shown a cross-sectional view of the side elevation of a rotary furnace 1 for pyrolyzing a feedstock according to a first embodiment of the invention.

[0055] The rotary furnace 1 comprises a hopper 10, a conduit 11, a rotating vessel 12, a gas extraction pipe 13, and a gas condensation chamber 14. The conduit 11 comprises an auger conveyor 15 extending therethrough. The rotary furnace 1 further comprises a heating means (not shown) to elevate the temperature of the feedstock to effect pyrolysis.

[0056] The rotating vessel 12 has an upstream end 12A and a downstream end 12B. The upstream end 12A has an inlet 16 for receiving feedstock. The downstream end 12B has a first outlet 17A and a second outlet 17B for the egress of pyrolysis products. In this embodiment, the first outlet 17A is configured for the egress of gaseous components, and the second outlet 17B is configured for the egress of solid products such as char.

[0057] The gas extraction pipe 13 comprises an opening 18. The gas extraction pipe 13 extends within and along the rotating vessel 12 from the downstream end 12B. The opening 18 is upstream of the downstream end 12B of the rotating vessel 12.

[0058] The gas condensation chamber 14 comprises an inlet 14A and an outlet 14B.

[0059] In this embodiment, the rotating vessel 12 is inclined at an angle A of between 4 to 15 degrees relative to the longitudinal horizontal axis H.

[0060] In this embodiment, the gas extraction pipe 13 extends less than half way along the length L of the rotating vessel 12. The gas extraction pipe 13 extends within and along the rotating vessel 12 by a length M. In this embodiment, the length L of the rotating vessel 12 is approximately 7 metres and the length M is between 2.5 to 3.0 metres, e.g. 2.8 metres, such that the gas extraction pipe 13 extends into the rotating vessel 12 by a length M that is 0.4 times the length L of the rotating vessel 12.

[0061] It has been surprisingly found that extracting gaseous components from the rotary furnace of the invention is most effective if the opening 18 of the gas extraction pipe 13 is located at a length M that is 0.4 times the length L of the rotating vessel, for example 2.8 metres to 2.9 metres from the downstream end 12B of a 7 metre long rotating vessel 12. Without wishing to be bound by any particular theory, it is thought that extracting the gaseous components at this location minimises the volume of suspended carbon particles in the volatile gas.

[0062] The longitudinal axis of the gas extraction pipe 13 is parallel to and vertically offset from the longitudinal axis of the rotating vessel 12.

[0063] Referring also to FIG. 2, there is shown a cross-sectional view of the rear elevation of the downstream end 12B of the rotating vessel 12 of the rotary furnace 1 of FIG. 1. In this embodiment, the rotating vessel 12 and the gas extraction pipe 13 are substantially cylindrical. The ratio of the internal diameter D1 of the rotating vessel 12 to the internal diameter D2 of the gas extraction pipe 13 is between 2:1 to 4:1, for example, 3:1, or 2.5:1. In an embodiment, rotating vessel 12 has a diameter of 810 mm and the gas extraction pipe 13 has a diameter of 320 mm, such that the ratio of the internal diameter of the rotating vessel 12 to the internal diameter of the gas extraction pipe 13 is approximately 2.5:1.

[0064] Referring also to FIG. 3, there is shown the opening 18 of the gas extraction pipe 13 of the rotary furnace 1 of FIG. 1. In this embodiment, the opening 18 comprises a chamfered inlet. The angle B created by the chamfered inlet of the opening 18 may be between 20 to 40 degrees, for example, 30 degrees.

[0065] Referring to FIGS. 1 to 3, the hopper 10 comprises a wide opening for receiving portions of the feedstock. In combination, the conduit 11 and the auger conveyor 18 define a feeding means, which is configured to convey feedstock from the hopper 10 to the inlet 16 of the rotating vessel 12. In this embodiment, the auger conveyor 15 is driven by an electrical motor (not shown).

[0066] The rotary vessel 12 is configured to rotate about its longitudinal axis during pyrolysis of the feedstock, for example, at a speed of between 1 to 10 rpm. The rotary vessel 12 comprises a gear system (not shown) to effect rotation whilst the remaining components of the rotary furnace 1 including the gas extraction pipe 13 remain static.

[0067] The gas extraction pipe 13 is configured to accept gaseous components generated in use of the rotary furnace 1 during a pyrolytic reaction. The opening 18 of the gas extraction pipe 13 is in communication with the inlet 14A of the gas condensation chamber 14. The gas condensation chamber 14 is configured to condense the volatile, gaseous components that enter from the outlet 17A of the gas extraction pipe 13.

[0068] In use, feedstock is loaded into the hopper 10 as a batch or continuously. The feedstock is conveyed from the hopper 10 through the conduit 11 by action of the auger conveyor 15. The feedstock enters the rotating vessel 12 through the inlet 16. The feedstock is heated to temperature suitable for pyrolysis. The rotating vessel 12 rotates about its longitudinal axis to mix the feedstock as it thermally degrades into pyrolysis products comprising gaseous components and solid char. Advantageously, the rotating vessel 12 slopes downwards from the upstream end 12A to the downstream end 12B to enable, in use, the feedstock to be conveyed along the rotating vessel 12 from the inlet 16 to the outlet 17 under the influence of gravity.

[0069] The gaseous components flow from the rotating vessel 12 through the opening 18 of the gas extraction pipe 13. Advantageously, the opening 18 being a chamfered inlet enables more effective entry of gaseous components generated in use by providing a larger surface area for the egress of gas from the rotating vessel 12 to the gas condensation chamber 14. In addition, there is less fowling caused by solid char.

[0070] The gaseous components flow through the gas extraction pipe 13, through the outlet 17A of the rotating vessel 12, and into the inlet 14A of the gas condensation chamber 14. In the gas condensation chamber 14, the gaseous components condense, and are collected through the outlet 14B.

[0071] The solid pyrolysis products, for example solid char, is collected from the rotating cylinder 12 via the second outlet 17B.

[0072] The feedstock may be tyre crumb. The rotary furnace 1 may be used to pyrolyze tyre crumb into solid char and gaseous components.

[0073] Referring now to FIG. 4, there is shown a cross-sectional view of the side elevation of a rotary furnace 4 for pyrolyzing a feedstock according to a further embodiment of the invention. The rotary furnace 4 shares many of the same features, which function in the same manner, as the rotary furnace 1 shown in FIG. 1. These features are labelled with the same reference numeral as that shown in FIG. 1 with an additional a prime (′).

[0074] The gas extraction pipe 13′ of the rotary furnace 4 further comprises a self-cleaning device 20.

[0075] Referring also to FIG. 5, there is shown a side elevation of the self-cleaning device 20 of FIG. 4 in more detail. Referring also to FIG. 6, there is shown the self-cleaning device 20 in a three dimensional view. The self-cleaning device 20 comprises a rod 21 and a circular disc 22. The circular disc 22 comprises a cut-out portion 23 such that air and other gaseous compounds are able to flow therethrough. The rod 21 is secured to the centre of the circular disc 22.

[0076] The self-cleaning device 20 is configured to contact at least a portion of the interior surface of the gas extraction pipe 13. The circular disc 22 comprises an outer diameter D3. The gas extraction pipe 13 comprises an internal diameter D4. The outer diameter D3 of the circular disc 22 is substantially equal to the internal diameter D4 of the gas extraction pipe 13.

[0077] The rod 21 is dimensioned to axially extend longitudinally through the length of the gas extraction pipe 13. The rod 21 is configured rotate about its axis and/or to translate in a direction along its axis.

[0078] The self-cleaning device 20 may have a rest position when not in use. As shown in FIG. 5, the circular disc 22 of the self-cleaning device 20 is configured to extend beyond the opening 18 of the gas extraction pipe 13.

[0079] The self-cleaning device 20 functions to remove built-up dirt and debris from the gas extraction pipe 13′ after the pyrolysis reaction has finished. Advantageously, this prevents the gas extraction pipe 13 from becoming blocked with solid pyrolysis products. More advantageously, the rotary furnace 4 does not require disassembly to clean the gas extraction pipe.

[0080] The self-cleaning device 20 may also be retro-fitted into the rotary furnace 1 of FIG. 1 to produce the rotary furnace of FIG. 4.

[0081] Advantageously, the apparatus and method according to the invention provide an efficient way to recycle feedstock, for example, waste tyre material, to produce energy-rich fuel sources. More advantageously, the apparatus enables the gaseous components of the pyrolysis products to be more efficiently recovered for use as a fuel. In addition, the self-cleaning device enables the apparatus to be kept clean and debris free such that it is able to operate efficiently, without having to dismantle the apparatus after use.

[0082] It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention.

[0083] It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.