WO2004037949A1

WO2004037949A1 - Apparatus for pyrolysis of shredded tyres

Info

Publication number: WO2004037949A1
Application number: PCT/HU2003/000087
Authority: WO
Inventors: István LEKRINSZKI
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-10-28
Filing date: 2003-10-28
Publication date: 2004-05-06
Anticipated expiration: 2005-04-28
Also published as: AU2003280029A1

Abstract

The invention is an apparatus for pyrolysis of shredded tyres, the apparatus comprising a reactor (10), an external casing at least partly surrounding the reactor (10), a combustion space between the external casing and the reactor (10), a rotatable agitating member arranged within the reactor (10), a discharging mechanism arranged at the bottom of the reactor (10), and a charging mechanism arranged at the top of the reactor (10), the charging mechanism comprising an upper slide-valve (21) and a lower slide-valve (22). According to the invention, the charging mechanism is equipped with a liquid cooling above the lower slide-valve (22), and the lower slide-valve (22) has a transfer opening (24) with a diameter larger than that of a pipe end cross section (23) leading the shredded tyre into the transfer opening (24).

Description

APPARATUS FOR PYROLYSIS OF SHREDDED TYRES

TECHNICAL FIELD

The invention relates to an apparatus for the pyrolysis of shredded tyres.

The number of used tyres is growing significantly world-wide, and this reflects a rising tendency. For example, in Hungary as much as 300,000 t (tons) of used tyres are currently unprocessed, and this volume grows annually at the rate of 50,000 1 - the quantity officially sold in trade.

Due to the fact that reversible processes take place when manufacturing rubber, the breaking down of the basic materials of used tyres to components can be carried out by closed-system pyrolysis, as a result of which steel fibres, pyro-oil, gas and carbon black can be obtained. Except for the steel, these materials are extremely valuable fuels. The process of pyrolysis consists of heating in an enclosed space, a so-called reactor, followed by the cooling and condensation of hot gases leaving the reactor. The cost efficiency of the process is determined by the energy input of pyrolysis.

BACKGROUND ART

Prior art pyrolysis reactors are suitable for the processing of whole or shredded tyres. When processing whole tyres, the cost of shredding is eliminated, but the reactor must be very large, and in addition it is very complicated to charge and discharge the reactor. This problem can be avoided if shredded material is used. In this case, however, the shredding costs must not make the process uneconomic.

Apparatuses suitable for the pyrolysis of shredded tyres are described for example in HU 1853 U and WO 03/029384 Al The apparatus described in WO 03/029384 A1 comprises a reactor, an external casing at least partly surrounding the reactor, a combustion space between the external casing and the reactor, a rotatable agitating member arranged within the reactor, a discharging mechanism arranged at the bottom of the reactor, and a charging mechanism arranged at the top of the reactor, wherein the charging mechanism comprises an upper slide-valve and a lower slide-valve. The double locking of the charging mechanism is advantageous, because it simply ensures the feed-in of the shredded tyres (upper slide-valve) and protection against gas leakage (lower slide-valve).

However, it is a disadvantage of the prior art double slide-valve structures that under operating conditions, because of the inner temperature of the reactor reaching 400 to 600 °C, the two slide-valves are heated to several hundred degrees. The shredded rubber to be fed in is in direct contact with the top surface of the closing blade of the upper slide-valve, consequently the rubber burns on this part due to the high temperature, and this burnt rubber hinders the proper operation of the slide-valve. It is also a problem that the fed in rubber pieces drop onto the closing surfaces of the lower slide-valve, and by burning on they deteriorate the quality of gas-tight closure, in fact in an extreme case the escaping of gas is not prevented at all.

It is also a disadvantage of prior art apparatuses that the closing member of the discharging mechanism is not aligned with the bottom plate of the reactor, consequently the pieces of wire in the shredded tyres get tangled up and block the discharging opening, thereby preventing discharge.

Another known problem is that the burner heads introducing the heat necessary for pyrolysis and reaching into the combustion space cannot be directed straight to the reactor as a result of the damaging effect of the flame.

Therefore, the burner heads are usually directed tangentially to the cylindrical reactor. Using this design, however, because the introduced heat is not directed straight to the reactor, the efficiency of the apparatus is lower. Furthermore, there is no solution for the problem of uniformly guiding and distributing hot gases introduced by the burner heads over the external wall of the reactor.

DISCLOSURE OF INVENTION

It is an object of the invention to provide an apparatus for the pyrolysis of shredded tyres, which does not have the above mentioned disadvantages of prior art apparatuses.

The inventive idea is that if proper cooling is applied above the lower slide-valve of the charging mechanism, and furthermore, if we make sure by appropriate guiding that pieces falling down during the charging process do not contact the high temperature sections of the lower slide-valve, the objet outlined above can be achieved.

Accordingly, the invention is an apparatus for pyrolysis of shredded tyres, the apparatus comprising a reactor, an external casing at least partly surrounding the reactor, a combustion space between the external casing and the reactor, a rotatable agitating member arranged within the reactor, a discharging mechanism arranged at the bottom of the reactor, and a charging mechanism arranged at the top of the reactor, the charging mechanism comprising an upper slide-valve and a lower slide-valve. According to the invention, the charging mechanism is equipped with a liquid cooling above the lower slide-valve, and the lower slide-valve has a transfer opening with a diameter larger than that of a pipe end cross section leading the shredded tyre into the transfer opening.

By liquid cooling, we make sure that the inner temperature of 400 to 600 °C of the reactor does not appear in the section between the two slide-valves.

According to our experiments, by appropriate water cooling, a temperature of

200 °C can be maintained in the section between the two slide-valves, and less than 100 °C above the upper slide-valve. The narrowed cross section of the feed-in pipe end ensures that the rubber pieces do not fall on the closing surfaces of the lower slide-valve.

The liquid cooling is preferably formed as a circulated water cooling and is arranged below a closing member of the upper slide-valve at least on a portion of the external surface of a housing of the upper slide-valve.

The pipe end cross section leading the shredded tyre into the transfer opening is preferably formed by a lower flange of a guiding ring narrowing down conically. This guiding ring can be simply produced, and easily secured by welding above the lower slide-valve.

To eliminate the above mentioned discharging problem, a particularly preferred embodiment of the invention is characterised in that the discharging mechanism has a closing member of a truncated cone shape narrowing upwards, which in its closed position fitting into a complementary opening formed in a bottom part of the reactor has a top surface aligned with an inner surface of the bottom part. This structure will ensure that the pieces of wire in the shredded tyres do not get tangled up and block the discharging opening, thereby preventing discharge. Preferably, a circular sealing for preventing escape of gases from the reactor is arranged at the cone-surface of the closing member.

The problems of tangentially oriented burner heads can be eliminated, if according to a preferred embodiment, heat deflection wall(s) are arranged in the combustion space for directing the heat of burner head(s) to the wall of the reactor. Heat deflection plates arranged along a rising spiral line on the external reactor wall can be used expediently to uniformly distribute and guide the hot gases emitted by the burner heads. The spiral line has a preferred elevation angle of 10 to 30 degrees. The agitating member preferably comprises a vertical shaft, a horizontal lower support bar and a horizontal upper support bar both secured to said vertical shaft, and two opposite spiral plate ribbons arranged in a rising spiral way along the wall of the reactor, each of said spiral plate ribbons connecting an end of the lower support bar with an end of the upper support bar. The elevation angle of the spiral plate ribbons is preferably less than 30 degrees, and their distance from the inner wall of the reactor is at least 10 mm.

BRIEF DESCRIPTION OF DRAWINGS

The invention will hereinafter be described on the basis of preferred embodiments depicted by the drawings, where

Fig.1 is a schematic view partly in cross-section of a pyrolysis apparatus according to the invention, Fig. 2 is a view of an inventive charging mechanism partial in cross- section,

Fig. 3 is a schematic diagram partly in cross-section of a discharging mechanism according to the invention,

Fig. 4 is a sectional view taken along plane A-A of Fig. 1 , Figs. 5A and 5B are side view and bottom view drawings depicting the location of heat deflecting plates and

Fig. 6 is a schematic three-dimensional view of an agitating member according to the invention.

MODES FOR CARRYING OUT THE INVENTION

The pyrolysis apparatus shown in Fig. 1 comprises a reactor 10 known per se, an external casing 11 at least partly surrounding reactor 10, a combustion space 12 between the external casing 11 and the reactor 10, an agitating member 13 driven by a motor 16 and arranged in a way to allow rotation in the reactor 10, a discharging mechanism 14 at the bottom of the reactor 10, and a charging mechanism 15 mounted at the top of the reactor 10. The charging mechanism 15 comprises a motor-driven upper slide-valve 21 and lower slide-valve 22. Above the lower slide-valve 22, the charging mechanism 15 is fitted with fluid cooling, in a way to be described later on.

The discharging mechanism 14 is connected to a discharge opening 30 formed on a bottom plate 17 of the reactor 10. Into the bottom part of the space between the casing 11 and the reactor 10, burner heads 40 supplying heat (Fig. 4) are directed, and their heat is tangentially guided to the wall of the reactor 10 by heat deflection walls 18.

Fig. 2 shows the charging* mechanism 15 in details. As a closing member, the upper slide-valve 21 preferably includes a closing blade 29, which enables the feed of the shredded tyres from the feeding tank 25. The closing member of the lower slide-valve 22 is a wedge-shaped closing tongue 26 preventing gas leakage, which closing tongue fits tightly into the complementary housing of the slide-valve 22. In the fully pulled out position of the closing tongue 26, the transfer opening 24 of the slide-valve 22 is fully opened. The transfer opening 24 is depicted by dashed lines in Fig. 2.

In the course of charging, first the lower slide-valve 22 is opened, and then in a fully open position thereof, the closing blade 29 of the upper slide- valve 21 is pulled aside. Once the charging is completed, first the closing blade 29 of the upper slide-valve 21 is pushed into closed position, and when shredded rubber no longer drops into the transfer opening 24 of the lower slide- valve 22, the latter is also closed. The escaping of gas eventually trapped between the two slide-valves 21 and 22 is prevented by stuffing boxes known per se fitted on the moving bars of the closing members.

According to the invention, the charging mechanism 15 above the lower slide-valve 22 is fitted with a liquid cooling. This can be preferably implemented by cooling water circulated through an inlet stub 28B and an outlet stub 28K, and consequently, the cooling effect can be achieved for example in the section below the closing blade 29 of the upper slide-valve 21 housing by external circulation, i.e. by means of a cooled housing 28. The cooling water can be circulated in a way known perse.

By means of this liquid cooling, the inner temperature of the reactor of

400 to 600 °C will not appear on the closing blade 29 of the upper slide-valve

21. According to our experiments, by appropriate water-cooling, a temperature of 200 °C can be maintained in the section between the two slide-valves 21 and

22, while above the upper slide-valve 21 a temperature of less than 100 °C can be maintained. By keeping the closing blade 29 of the upper slide-valve 21 at a temperature lower than 100 °C, it is ensured that shredded rubber to be introduced fails to burn on the closing blade, and hence it cannot prevent the appropriate operation of the slide-valve.

The wedge shaped closing tongue 26 performs closure by tightly fitting into a finely machined surface in the housing of the slide-valve 22. It is required for the appropriate operation of the charging mechanism 15 that the lower slide- valve 22 preventing the leakage of a high temperature gas ensures an appropriate gas-tight closure. To do so, it is necessary to make sure that at the time of charging, shredded rubber falling from the upper slide-valve 21 into the transfer opening 24 of the lower slide-valve 22 does not fall onto the closing surfaces of the lower slide-valve 22, because in this case the rubber burns on the closing surfaces, thereby deteriorating and in extreme cases even preventing gas-tight closure.

To prevent this, according to the invention, the transfer opening 24 of the lower slide-valve 22 is of a larger diameter than that of a pipe end cross section 23 ending into the transfer opening 24 for introducing the shredded tyre into the transfer opening 24. This pipe end cross section 23 is preferably formed by a lower flange of a guiding ring 27 narrowing downwards and welded above the closing tongue 26 to the housing of the lower slide-valve 22. In the pyrolysis apparatus for shredded tyres, during pyrolysis steel fibres escape from the shredded rubber, and create a mixture of 400 to 600 °C temperature with the carbon black in the rubber. Under the effect of the heat, the softening steel fibres may be tangled, and combined into a large bundle they may clog the discharge opening. This especially occurs if the escaping steel fibres get stuck in any obstacle or uneven surface on the bottom plate of the apparatus.

To solve the discharging problem mentioned in the introduction, according to a specially preferred embodiment of the invention shown in Fig. 3, the discharging mechanism 14 has a closing member 31 of a truncated cone shape narrowing upwards, which - in its closed position fitting into the complementary opening 30 formed in the bottom part of the reactor 10 - has a top surface 31' in the same plain as the inner surface 17' of the bottom plate 17. This structure prevents the wire pieces of the shredded tyres to get tangled in a way so as to prevent discharge at the discharge opening 30.

The closing member 31 is arranged on a lever 33 that can be rotated around a shaft 34. Preferably, a round or circular sealing 32 is arranged on the external conical surface of the closing member 31 to prevent the outflow of the gases from the reactor 10. For improving the sealing, the closing member 31 of truncated cone shape can be divided in two parts in the depicted way, and the soft flexible sealing 32 can be fitted between the matching disk-shaped parts in a way that an axial displacement against one another is ensured. In this way, a compression of the two parts provides a perfect seal upon closure.

In the case of an apparatus according to this preferred embodiment, the above mentioned discharging problems do not arise, therefore it becomes possible to process shred tyres of a larger size than before, in this way improving the cost efficiency of the system. The cost efficiency of heating in an enclosed space, i.e. pyrolysis is determined basically by the amount of energy input. This energy input is defined by two processing steps: the energy demand of shredding prior to pyrolysis and the energy demand of heating. The apparatus according to the invention is suitable even for processing shreds of an 80 x 120 mm size on average. This size can be achieved already in a single shredding phase, consequently no subsequent shredding is required, and this improves the cost efficiency of the process.

In a way shown in Fig. 4, the two burner heads 40 ending tangentially in the combustion space supply the heat input required for the pyrolysis. The heat deflection walls 18 arranged in the combustion space guide the heat of the burner heads 40 tangentially to the wall of the reactor 10, thereby greatly improving the efficiency of the apparatus.

A further substantial improvement of the efficiency can be achieved by fixing heat deflection .plates 19 in a spirally rising arrangement on the external wall of the reactor 10 - which is preferably of a conic design at its bottom part - as shown in Fig. 1 , 5A and 5B. According to our experiments, it is advantageous if the spiral line has an elevation angle of 10 to 30 degrees. The heat deflection plates 19 are preferably made of the same material as that of the reactor 10. By means of the heat deflection plates 19, the heat transfer surface is many times larger, and a more uniform distribution of the heat input is ensured.

Fig. 6 shows an example embodiment of the agitating member 13, which includes a vertical shaft 50, a horizontal lower support bar 51 and a horizontal upper support bar 52 both fixed to vertical shaft 50, as well as two spiral plate ribbons 53, 54 each arranged raising upwards along the wall of the reactor 10, and each connecting one end of the lower support bar 51 with one end of the upper support bar 52. The oppositely arranged spiral plate ribbons 53, 54 are preferably made of flat steel. The function of the agitating member 13 is mixing the shredded rubber gently, and at the same time providing good heat transfer. According to our experiments, this function can be ensured by the above described ribbon agitator in the most advantageous way if the elevation angle of the spiral plate ribbons 53, 54 is less than 30 degrees, and their distance from the inner wall of the reactor 10 is at least 10 mm.

In this case, the agitating member 13 moves the material to be mixed gently, without bending the wire bits while ensuring an appropriate agitating effect, and in this way the metal fibres slowly released from the disintegrating material under the impact of the heat will not get tangled. The lower support bar 51 is preferably of a flat design, and its angle of inclination as against the plane of the bottom plate 17 is 10 to 20 degrees, and its distance from the bottom plate 17 is not more than 5 mm. Such design of the lower support bar 51 is advantageous for preventing the formation of wire bundles on the bottom plate 17.

For a person skilled in the art it can be perceived that the apparatus according to the invention resolves the problems mentioned in the introduction advantageously.

It can be seen further, that the preferred embodiments of the invention as described above are only examples, and within the scope of protection further modifications and changes are possible. The fluid cooling can be for example implemented in a different way, a different design of the reactor or casing can be applied or the number of burner heads and/or heat deflection walls may be other than two. The casing may fully enclose the reactor. Instead of the narrowing ring, a different similar solution implementing an appropriate inlet pipe end cross section may be applied.

Claims

1. An apparatus for pyrolysis of shredded tyres, the apparatus comprising a reactor, an external casing at least partly surrounding the reactor, a combustion space between the external casing and the reactor, a rotatable agitating member arranged within the reactor, a discharging mechanism arranged at the bottom of the reactor, and a charging mechanism arranged at the top of the reactor, the charging mechanism comprising an upper slide-valve and a lower slide-valve, c h a r a c t e r i s e d in that the charging mechanism (15) is equipped with a liquid cooling above the lower slide-valve (22), and the lower slide-valve (22) has a transfer opening (24) with a diameter larger than that of a pipe end cross section (23) leading the shredded tyre into the transfer opening (24).

2. The apparatus according to claim 1 , characterised in that the liquid cooling is formed as a circulated water cooling and is arranged below a closing member of the upper slide-valve (21 ) at least on a portion of the external surface of a housing of the upper slide-valve (21 ).

3. The apparatus according to claim 1 , characterised in that the pipe end cross section (23) leading the shredded tyre into the transfer opening (24) is formed by a lower flange of a guiding ring (27) narrowing down conically.

4. The apparatus according to any of claims 1 to 3, characterised in that the discharging mechanism (14) has a closing member (31) of a truncated cone shape narrowing upwards, which in its closed position fitting into a complementary opening (30) formed in a bottom part of the reactor (10) has a top surface (31 ') aligned with an inner surface (17') of the bottom part.

5. The apparatus according to claim 4, characterised in that a circular sealing (32) for preventing escape of gases from the reactor (10) is arranged at the cone-surface of the closing member (31 ).

6. The apparatus according to any of claims 1 to 5, characterised in that heat deflection wall(s) (18) are arranged in the combustion space (12) for directing the heat of burner head(s) (40) to the wall of the reactor (10), the burner head(s) (40) ending tangentially in the combustion space (12).

7. The apparatus according to any of claims 1 to 6, characterised in that heat deflection plates (19) are arranged along a rising spiral line on the external wall of the reactor (10).

8. The apparatus according to claim 7, characterised in that the spiral line has an elevation angle of 10 to 30 degrees.

9. The apparatus according to any of claims 1 to 8, characterised in that the agitating member (13) comprises a vertical shaft (50), a horizontal lower support bar (51 ) and a horizontal upper support bar (52) both secured to said vertical shaft (50), and two opposite spiral plate ribbons (53, 54) arranged in a rising spiral way along the wall of the reactor (10), each of said spiral plate ribbons (53, 54) connecting an end of the lower support bar (51 ) with an end of the upper support bar (52).

10. The apparatus according to claim 9, characterised in that the elevation angle of the spiral plate ribbons (53, 54) is less than 30 degrees, and their distance from the inner wall of the reactor (10) is at least 10 mm.