GB1568357A

GB1568357A - Method and apparatus for the treatment of vulcanized material in particulate form

Info

Publication number: GB1568357A
Application number: GB47199/75A
Authority: GB
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1976-11-09
Filing date: 1976-11-09
Publication date: 1980-05-29

Description

(54) AN IMPROVED METHOD AND APPARATUS FOR THE TREATMENT OF VULCANIZED MATERIAL IN PARTICULATE FORM (71) We, DUNLOP LIMUED, a British Company, of Dunlop House, Ryder Street, St. James's, London S.W.1, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - The present invention relates to an improved method and apparatus for the treatment of vulcanized material in particulate form so as partially or wholly to de-vulcanize the material.

It is known to recover vulcanized natural or synthetic rubber for re-use by reducing an article containing or consisting of the rubber, such as a pneumatic tyre, to particulate form and removing non-rubber com- ponents. The vulcanized rubber particles are known as "rubber crumb" and this can be subjected to mechanical working and or chemical treatment at least partially to devulcanize the rubber which can then be revulcanized when used to form a new article or compounded in a given proportion with new natural or synthetic rubber.

The re-vulcanised material is known as "re-claim rubber".

A principal object of the present invention is to provide an improved method and apparatus for the de-vulcanization or partial de-vulcanization of rubber crumbs to improve its properties and facilitate its re-use in re-claim rubber.

According to the present invention there is provided a method of treating a vulcanized material so as to de-vulcanize at least partially at least some of the material, the method comprising dropping the material in particulate form through an annular flame in a burner chamber to subject all sides of the flow of particles to the action of flame.

Preferably the particles pass through the flame in a low oxygen environment, in order to avoid partial or total combustion of the finer particles.

In accordance with another aspect of the present invention there is provided apparatus for treating a vulcanized material in particulate form so as to de-vulcanize at least partially at least some of the material, the apparatus comprising a feed tube for the particles opening downwardly into a burner chamber and an annular burner opening surrounding the feed tube and connectable to sources of air and fuel gas arranged so that mixed fuel gas and air emitted from the opening will provide an annular flame surrounding the lower end of the feed tube.

Preferably the opening is arranged to provide a tubular flame coaxial with the tube and extending therebeneath into the chamber.

A water cooling duct may be arranged to surround an upper part of the feed tube.

A plurality of feed tubes may be provided in spaced parallel relation at the top of the burner chamber, each being surrounded by a respective annular burner opening connectable to sources of fuel gas and air.

A housing may be provided extending across the top of the burner chamber, the housing comprising top and bottom plates each formed with a plurality of mutually spaced openings, each opening in the top plate being coaxially aligned with a paired opening in the bottom plate, the feed tubes being joined at their upper ends to the top plate to extend downwardly through the housing, each surrounding and sealed with respect to a respective opening in the top plate, and the lower ends of the tubes being located coaxially within the respective openings in the bottom plate and spaced therefrom so that the lower end of each tube is surrounded by an annular burner opening communicating with the interior of the housing, means being provided for admitting air to the interior of the housing and pas sages for fuel gas being provided surrounding the openings in the bottom plate of the housing each connectable to a source of fuel gas and each being formed with a gas emission slit opening into the respective burner opening.

In this construction the fuel gas passages may be defined between the bottom plate of the housing and a gas passage plate located inside the housing parallel with the bottom plate and formed with openings each coaxially aligned with one of the openings of the bottom plate, each plate having a tubular extension surrounding each opening therein directed toward the other plate and the tubular extensions of the bottom plate being received in the tubular extensions of the gas passage plate with clearances between the associated extensions such that slits for gas emission are formed between the two tubular extensions surrounding each feed tube, said slits opening outwardly of the housing coaxially with respect to said tube.

Water cooling passages may be defined between the top plate of the housing and a water passage plate located inside the housing parallel with the top plate and formed with openings each surrounding and sealed with respect to a respective one of the feed tubes.

The or each feed tube may open at its upper end to an admission chamber for untreated material, which is preferably connected to a source of gas or low or nil oxygen content so that the material passes through the feed tubes in the presence of said gas. Means is preferably provided for maintaining a flow of said gas from the admission chamber through the feed tubes into the lower chamber so that the material is in the presence of less oxygen than there is in air when subjected to the flame treatment. In this way the danger of continuing self-combustion of the particles following flame treatment is avoided.

Preferably the burner chamber opens downwardly to a plenum through which a conveyor moves for carrying away the flame treated material, and preferably the plenum is connected by a duct to the admission chamber and a fan is provided in the duct for re-circulating the products of combustion from the burner chamber back to the admission chamber, so that the material passes through the feed tubes of the burner assembly in an atmosphere of high CO2 content and low oxygen content.

A preferred embodiment of the invention will now be described with reference to the accompanying drawing, in which: Figure 1 is a side elevation, mainly in section, of apparatus in accordance with the invention, and Figure 2 is a sectional view of a detail of the apparatus of Figure 1.

The illustrated apparatus for the treatment of vulcanized material in particulate form comprises a burner chamber 10 opening downwardly into a plenum 11, a burner head assembly 12 across the top of the burner chamber 10 and an admission chamber 13 above the burner head assembly 12.

Referring to Figure 2, a plurality of feed tubes 14 extend through the burner head assembly 12 between the admission chamber 13 and the burner chamber 10 whereby a continuous vertical passage for particulate material extends from the top of the admission chamber 13 to the bottom of the plenum 11. A hopper 15 for vulcanized material in particulate form is located above the admission chamber 13 and an auger 16 is provided in the admission chamber for maintaining a controlled flow of the material downwardly to the feed tubes 14.

As shown in Figure 2 the burner head assembly 12 comprises a top plate 21 and a bottom plate 22 between them defining a housing through which the feed tubes 14 extend. The top plate 21 is formed with a number of openings 23 each sealed to the upper end of a respective one of the feed tubes 14 and the bottom plate 22 is formed with an equal number of openings 24 paired in coaxial alignment with the openings 23 and slightly larger than the latter so that an annular gap is left between the free, lower end of each feed tube 14 and the openings 24 surrounding it.

Located inside the housing defined between the top plate 21 and the bottom plate 22 and parallel therewith is a gas passage plate 25 which has openings 26 coaxial with the openings 24 in the bottom plate. In the formation of the gas passage plate 25 the material of the plate is deformed downwardly around each opening 26 therein to provide a tubular extension which, in the assembled condition of the burner head assembly, surrounds the associated feed tube 14 in spaced relation thereto and extends into an associated opening 24 of the bottom plate 22, a slit being left between the tubular extension and the oDening 24 so that fuel gas can be emitted.

The sDace enclosed between the plates 22 and 25 is in communication with a fuel gas admission line 17 whereby fuel gas will be emitted from the slit surrounding the bottom end of each feed tube 14.

Located on one side of the burner head assembly 12 is a fan unit 19 arranged to nrovide a forced draught of air into the housing. Some of this air will be discharged through the annular slit surrounding the bottom end of each feed tube 14 between it and the tubular extension from the associated aperture 26 in the gas passage plate.

The remainder of the air will be discharged from the housing through a plurality of additional tubular extensions extending from additional apertures in the gas passage plate 25 one of which is indicated at 36. The bottom plate 22 is formed with a number of additional apertures 37 corresponding to the apertures 36 and axially aligned therewith, a gas emission slit being provided between each additional aperture 37 in the bottom plate and the tubular extension from an aperture 36 extends thereinto.

Surrounding the top end of each feed tube 14 is a water cooling manifold defined between the top plate 21, the feed tubes 14 and a water passage plate 28 inside the housing and parallel with the plates 21 and 22, the plate 28 having openings corresponding and coaxial with the openings 23 of the top plate 21. In the formation of the water passage plate 28 the material of the plate is deformed upwardly around each aperture therein to provide a tubular extension which is sealed, in the assembled burner head, to the feed tube 14 which it surrounds. The manifold is connected at opposite sides of the burner head assembly 12 to a water inlet 27 and a water outlet 27A whereby cooling water may be circulated through the manifold to cool the upper part of the burner head assembly 12.

In use, fuel gas emitted from the slits between the plates 22 and 25 mixes with air from the fan 19 emitted from the tubu lar extension of the apertures 26 and 36 of the plate 25 and is ignited in the burner chamber 10 to form flames extending into the burner chamber from the plate 22 either parallel with or coaxially with respect to each feed tube 14. Suitable ignition means (not shown) is located in the burner chamber 10 to ignite the mixture emitted from each opening 24 of the burner head hous ing.

The upper run of an endless conveyor 34 passes across the bottom af the plenum 11 to carry away treated material from the open bottom end 31 of the chamber 10.

At the end of the plenum 11 remote from the bottom end 31 of the burner chamber a duct 32 extends upwardly from the plenum to a centrifugal fan 33 which communicates on its output side with the admission chamber 13 via a branch pipe 38. The plenum 11, duct 32, branch pipe 38 and the admission chamber 13 thus form with the burner chamber 10 a closed system through which the products of combustion of the burner head 12 can be re-circulated by the fan 33 to the input side of the burner head assembly 12. The sides (not shown) of the plenum 11 are close to the upper run of the conveyor 34 and curtains 39 and 40 are provided at its opposite ends to exclude air from entering the plenum. The rubber crumb in the hopper 15 will inhibit air entry into the admission chamber 13.By these measures the presence of air in the burner chamber 10 is minimised and the material passes through the feed tubes 14 to be flame treated in an atmosphere with a high CO. and a low or nil oxygen content so that the danger that the rubber crumb will catch fire or that combustion of the rubber crumb will continue after the flame treatment is mitigated or averted.

Due to the action of the fans 19 and 33 the pressure within the plenum 11 will be above atmospheric and there will be a leakage from the system of exhaust gases from the burner 12 under the curtains 39 and 40 and alongside the conveyor 34, but this loss will be constantly made up by the operating burner. Damping means 41 may be provided in the duct 32 for controlling pressure in the plenum 11 and scrubber means 42 may also be included in the duct 32 for removing volatiles from the exhaust gases before their re-circulation to the burner.

In use of the apparatus illustrated vulcanized rubber in particulate form is loaded into the hopper 15. The auger 16 is operated to obtain a desired rate of flow of the particulate material into the admission chamber 13. A mixture of gas and air emitted from the slits between the plates 25 and 22 of the burner head assembly is ignited in the burner chamber 10 to provide a flame from each additional aperture pair 36 and 37 and a tubular flame surrounding the bottom end of each feed tube 14.

The particulate material drops through the feed tubes 14 and is treated by the tubular flame surrounding each tube, and thereafter falls through the plenum 11 onto the conveyor 34 which removes the treated particulate material by passing it out of the plenum 11 under the curtain 40. The fan 19 is operated to provide combustion air through the apertures 36 and the slits surrounding the feed tubes 14 and the fan 33 is operated to re-cycle the products of combustion from the output (lower) side of the burner head assembly 12 to its input (upper) side so that the incoming, untreated material passes through the feed tubes 14 in an atmosphere deficient in oxygen.

The fan 19 and the fuel gas supply through the inlet 17 are controlled to burn the fuel gas stoichiometrically below the burner assembly 12, fuel gas being emitted both through the apertures 24 and through the apertures 37.

The burner ports additional to those provided to surround each feed tube 14, namely those provided by the apertures 36 and 37, mav be dispensed with but the presence of such additional ports will provide additional heat in the burner chamber 10, if this provides desirable, and supplementary de vices in the burner chamber 10, such as flame sensing electrodes (not shown) may be associated with the additional flame ports so that these will not be contaminated by the flame-treated material passing out from the feed tubes 14.

By subjecting divided flows of the parti culate material to annular flames the ma terial receives a uniform treatment which is adaptable to achieve different desired effects. For example, by the method and by using the apparatus of the invention substantially the whole of each particle may be recovered to an unvulcanized condition.

WHAT WE CLAIM IS : - 1. A method of treating a vulcanized material so as to de-vulcanize at least par tiallv at least some of the material, the method comprising dropping the material in particulate form through an annular flange in a burner chamber to subject all sides of the flow of particles to the action of flame.

2. A method as claimed in claim 1, wherein the particles are passed through the flame in a low oxygen environment, in order to avoid partial or total combustion of the finer particles.

3. Apparatus for treating a vulcanized material in particulate form so as to devulcanize at least partially at least some of the material, the apparatus comprising a feed tube for the particles opening downwardly into a burner chamber and an annular burner opening surrounding the feed tube and connectable to sources of air and fuel gas arranged so that mixed fuel gas and air emitted from the opening will provide an annular flame surrounding the lower end of the feed tube.

4. Apparatus as claimed in claim 3, wherein the opening is arranged to pro vide a tubular flame coaxial with the tube and extending therebeneath into the chamber 5. Apparatus as claimed in claim 3 or claim 4, wherein a water cooling duct is arranged to surround an upper part of the feed tube.

6. Apparatus as claimed in any of claims 3-5, wherein a plurality of feed tubes are provided in spaced parallel relation at the top of the burner chamber, each being surrounded by a respective annular burner opening connectable to sources of fuel gas and air.

7. Apparatus as claimed in claim 6, wherein a housing is provided extending across the top of the burner chamber, the housing comprising top and bottom plates each formed with a plurality of mutually spaced openings, each opening in the top plate being coaxially aligned with a paired opening in the bottom plate the feed tubes being joined at their upper ends to the top plate to extend downwardly through the housing, each surrounding and sealed with respect to a respective opening in the top plate, and the lower ends of the tubes being located coaxially within the respective openings in the bottom plate and spaced therefrom so that the lower end of each tube is surrounded by an annular burner opening communicating with the interior of the housing, means being provided for admitting air to the interior of the housing and passages for fuel gas being provided surrounding the openings in the bottom plate of the housing each connectable to a source of fuel gas and each being formed with a gas emission slit opening into the respective burner opening.

8. Apparatus as claimed in claim 7, wherein the fuel gas passages are defined between the bottom plate of the housing and a gas passage plate located inside the housing parallel with the bottom plate and formed with openings each coaxially aligned with one of the cpenings of the bottom plate, each plate having a tubular extension surrounding each opening therein directed toward the other plate and the tubular extensions of the bottom plate being received in the tubular extensions of the gas passage plate with clearances between the associated extensions such that slits for gas emission are formed between the two tubular extensions surrounding each feed tube. said slits opening outwardly of the housing crr axially with respect to said tube.

9. Apparatus as claimed in claim 7 or claim 8, wherein water cooling passages are defined between the top plate of the housing and a water passage plate located inside the housing parallel with the top plate and formed with openings each surrounding and sealed with respect to a respective one of the feed tubes.

10. Apparatus as claimed in any of claims 3--9. wherein the or each feed tube opens at its upper end to an admission chamber for untreated material.

II. Apparatus as claimed in claim 10, wherein said admission chamber is connected to a source of gas of low or nil oxygen content so that the material passes through the feed tubes in the presence of said gas.

12. Apparatus as claimed in claim 11, wherein means is provided for maintaining a flow of said gas from the admission chamber through the feed tubes into the lower chamber so that the material is in the presence of less oxygen than there is in air when subjected to the flame treatment.

13. Apparatus as claimed in any of claims 3-12, wherein the burner chamber opens downwardly to a plenum through

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. vices in the burner chamber 10, such as flame sensing electrodes (not shown) may be associated with the additional flame ports so that these will not be contaminated by the flame-treated material passing out from the feed tubes 14. By subjecting divided flows of the parti culate material to annular flames the ma terial receives a uniform treatment which is adaptable to achieve different desired effects. For example, by the method and by using the apparatus of the invention substantially the whole of each particle may be recovered to an unvulcanized condition. WHAT WE CLAIM IS : -

1. A method of treating a vulcanized material so as to de-vulcanize at least par tiallv at least some of the material, the method comprising dropping the material in particulate form through an annular flange in a burner chamber to subject all sides of the flow of particles to the action of flame.

4. Apparatus as claimed in claim 3, wherein the opening is arranged to pro vide a tubular flame coaxial with the tube and extending therebeneath into the chamber

5. Apparatus as claimed in claim 3 or claim 4, wherein a water cooling duct is arranged to surround an upper part of the feed tube.

which a conveyor moves for carrying away the flame treated material.

14. Apparatus as claimed in claim 13, wherein the plenum is connected by a duct to the admission chamber and a fan is provided in the duct for re-circulating the products of combustion from the burner chamber back to the admission chamber, so that the material passes through the feed tubes of the burner assembly in an atmosphere of high CO2 content and low oxygen content.

15. Apparatus for treating a vulcanized material in particulate form constructed and arranged substantially as herein described and as shown in the accompanying drawings.

16. A method of treating a vulcanized material so as to de-vulcanize at least partially at least some of the material by means of the apparatus claimed in any of claims 3-15 substantially as herein described.

Reference has been directed in pursuance of section 9, subsection (1) of the Patents Act 1949, to patent No 1,501,865.