TYRE CARCASS PYROLYSIS SYSTEM

Abstract: The system comprises a pyrolysis chamber (2) having a tyre carcass inlet port and communicating with at least a duct for supplying combustion air, the pyrolysis chamber further communicating with a steam generator (4) and having a stationary bottom of frustum of cone shape coaxially communicating with the combustion air duct, rotating arm members being moreover provided, associated with the statio­ nary bottom, adapted to cause waste unburnt material to be discharged from an outlet port formed through the stationary bottom.

Description: BACKGROUND OF THE INVENTION The present invention relates to a pyrolysis system which has been specifically designed for the pyrolysis of tyres,which system is provided with cleaning means and means for improving the combustion. As is known worn tyre carcass material can be burnt to provide useful power,for example in the form of pressurized hot steam. To this end large size burning systems have been already designed which,because of the large size and weight of the main components thereof,must be constructed in situ and in which the problems of improving combustion and removing the steel cords included in the tyres being burnt have been solved by mounting the tyre combustion chamber,essentially consisting of a cylindrical drum,on a rotating supporting system, able of rotating about a near horizontal axis which substantially coincides with the geometrical axis of the combustion chamber. A rotating combustion chamber having a very great size and weight,however,requires very complex and expensive driving means,as well as thermal insulation means,and,because of these reasons, the duration of these rotating chambers is rather short. Stationary combustion chamber systemsare also known which, however, are affected by further drawbacks, the most important of which are that the combustion can be scarcely maintained and that the metal waste cord included in the modern tyres can be hardly removed from the carcass material being burnt. For example the US-A-2 402 436 patent discloses an incinerating apparatus for incinerating waste material which, however, woud not suitable for processing worn tyres, and having the features of the preamble of claim 1. SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to overcome the above mentioned drawbacks by providing a tyre pyrolysis system which is very efficient and reliable, and comprises means for continuously and automatically improving the combustion of the tyres as well means for automatically removing all of the unburnt material, such as steel cords and the like. Another object of the present invention is to provide a tyre pyrolysis system which has a comparatively reduced size and which can be constructed starting from easily commercially available elements and materials susceptible to be pre-assembled. According to one aspect of the present invention, the above mentioned objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a tyre pyrolysis system, having the features of the characterizing portion of Claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed description of a preferred, though not exclusive, embodiment of a tyre pyrolysis system according to the invention which is illustrated,by way of an indicative but not limitative example,in the figures of the accompanying drawings,in which: figure 1 is a schematic cross-sectional view illustrating the tyre pryolysis system according to the present invention; figure 2 is a vertical cross-section of the pyrolysis chamber included in the tyre pyrolysis system according to the present invention; and figure 3 is a horizontal cross-section view of the pyrolysis chamber. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the figures of the accompanying drawings, the tyre pyrolysis system provided with cleaning means and means for improving the combustion of the tyres,according to the present invention,comprises a pyrolysis chamber 2 communicating with a combustion air inlet duct 16, which will be disclosed in a more detailed way hereinafter, and a tyre carcass material inlet port thereat a reciprocating carriage 1 operates for supplying said pyrolysis chamber with the tyres to be burnt. At the top of the mentioned pyrolysis chamber 2 a further duct 3 extends which communicates the pyrolysis chamber 2 with a steam generator, said duct 3 being so designed and arranged as to form an extension of the pyrolysis chamber. The steam generator 4 is provided with a tube nest coupling a lower chamber to a upper chamber, therein there is arranged water to be vaporized; during the operation of the system,the combustion or fuel gases will release the main portion of their thermal contents to a secondary loop consisting of the tube nest,in order to generate steam by indirectly heating the water circulating inside said tube nest which is so arranged and sized as to fully exploit the combustion gas heat. Downstream of the steam generator 4 there is provided a heat exchanger,indicated at 5, which operates to further exploit the residue heat of said flue or combustion gases.This heat exchanger consists of an apparatus like the steam generator, but of less size, and it has usually a double function of preheating the steam generating water and further reducing the fume temperature so as to supply the fume cleaning apparatus 6 with fumes of comparatively low and safe temperature. More specifically the fume cleaning apparatus 6 is also able,in addition to properly cleaning the combustion fumes,to recover possible raw unburnt materials to be recycled to further chemical processes. As shown,the fume cleaning apparatus 6 communicates with a stack 7 provided for discharging the cleaned fumes into the atmosphere and further comprises a fan provided for holding the system under a partial vacuum to supply the combustion or pyrolysis chamber with the combustion supporting air and for providing a constant combustion fume flow rate through the overall system. According to the invention,the pyrolysis system is controlled by an electronic central controlling unit 8 adapted to properly control and adjust all of the operating parameters of said system. In order to hold at an optimum set value the steam generator supplying gas temperature, in the post-combustion zone at the inlet of said duct 3, there is provided a secondary-fuel burner 10 which is also able of operating as a heater during the system starting step and which automatically operates only as the temperature at the inlet of the steam generator decreases under a precisely set value even if the combustion chamber is in a saturation condition. In order to hold the proper vacuum condition in the combustion or pyrolysis chamber,there is provided an automatic gate adjusting device 11, which is arranged downstream of the cleaning apparatus 6,whereas a possible lacking of oxygen in the combustion supporting gas is compensated by a fan 12 which is arranged in the duct 3,and a possible low speed of the combustion fumes is compensated by a further fan 13 which is controlled by a gate 14 adapted to remove the gases downstream of the steam generator 4 and supply the removed gases to the pyrolysis chamber,in order to increase the gas current flow rate. A main feature of the present invention is that the combustion or pyrolysis chamber is provided with a frustum of cone shaped bottom 15 which coaxially communicates with the combustion air inlet duct 16, coupled to rotating means 17 able of rotating it about its axis. Combustion air is supplied by means of a main fan 18 supplying with air the combustion air inlet duct 16,which is coupled with two or more arms 19 provided for scraping the frustum of cone shaped bottom 15. More specifically,the arms 19 continuously entrain and displace the tyres being burnt so as to increase the combustion air amount supplied to said burning tyres,said arms being also so designed and arranged as to cause steel cords and other unburnt materials to be ejected from the discharging opening or port 20,provided at the periphery of the bottom 15,which steel cords and unburnt materials will be conveyed by an endless conveyor 21 away from the system. During the operation of the pyrolysis system,after having reached a minimum temperature of 600-700°C,by burning secondary fuel materials, such as naphta,gases and the like by means of the burners 9 and 10, the system is started by an electric command sent to the central control unit 8;in this way the system will be able of automatically operating, the operating parameters being continuously monitored by a plurality of sensors (not shown). In this connection it should be pointed out that the operation of the system will depend on the following operating parameters :the temperature in the combustion or pyrolysis chamber, the saturation status of the steam generator,the vacuum conditions in the combustion air supplying duct, the fume or flue gas speed and the burning material/combustion air ratio. With respect to the combustion chamber temperature the tyre supply system is so designed that the tyres to be burnt are supplied only if the temperature in the combustion chamber is included within a set temperature range and that the rubber material amount in said combustion chamber does not exceed a set amount,specifically selected for an optimal operation of the pyrolysis system. In this connection,it should be pointed out that the tyres to be burnt are continuously moved, in order to continuously expose to the flame new tyre material,so as to efficiently control the combustion of said tyres. Moreover,in order to provide an optimal temperature for the steam generator feeding gas, the secondary fuel burner 10 is so designed and arranged as to operate automatically only if the temperature at the inlet of said steam generator decreases under a precisely set value,as above already mentioned. Like control operations can be carried out by driving the gate 11 so as to maintain a set vacuum and control the burning oxygen amount,by operating the fan 12,and increase the flue gas rate or speed,by operating the fan 14. During the operation of the pyrolysis system,in particular, the loading device 1,which is controlled by the central control unit 8,will supply the combustion chamber with a tyre which,by gravity, will fall on the frustum of cone shaped bottom 15 which forms the floor of the combustion chamber,as indicated at 22,said supplied tyre being indicated at 23. In this connection it should be apparent that this way for supplying the tyre to be burnt is very suitable for starting an efficient tyre combustion since the linear contact between the frustum of cone shaped bottom and a face of the tyre is adapted to fully expose to the burning flame all of the combustible surface. Starting from these favorable conditions, and in order to prevent the tyre carcass from collapsing and choking the flame, the rotating arms 19 will engage the burning tyre so as to cause it to continuously slide against the frustum of cone shaped bottom ;in this way the friction between said bottom and the carcass tyre will generate passive resistance forces able of continuously turning and/or tilting the tyre, thereby continuously improving the burning flame owing to a constant supply of combustion air through the duct 16. Another important function of the rotating arms 19,in combination with the frustum of cone shape of the bottom,is that of continuously removing from the combustion chamber the steel cords and other unburnt materials. In fact,as the combustible rubber which, together with the steel cords or belts forms the tyre carcass,is gasified,all of the tyre carcass structure tends to be deformed and slide on the frustum of cone shaped bottom and the metal parts are entrained on bottom diameters which correspond to the diameters thereat there is formed the outlet port 20. From this moment,the mentioned rotating arms 19 will cause all of the waste materials, both of metal and non metal nature,to be expelled,which ejecting effect is aided by combustion air entering the combustion chamber through the rotating arm 19 and impinging on the flame just on the diameters thereat waste materials deposit so as to hold this region at a temperature adapted to hold in a brittle condition the steel cords which will be crushed by the rotating arms 19 to a size permitting said cords to easily passing through the outlet port or opening 20. In order to prevent the combustion waste materials collected on the edges of the outlet 20 from progressively choking this outlet,a cleaning device has been provided adapted to clean waste material away from said outlet. More specifically,this cleaning device comprises a swinging operating arm 24 pivoted,through the pivot pin 25,on the outside of the combustion chamber,and the end portion of which,indicated at 26,is able to engage the outlet 20 edge for removing cyclically therefrom the built in waste material. In this connection it should be apparent that said rotating arms are so designed and arranged that said end portion 26 can easily reach the combustion chamber. At the reference number 28 there has been indicated the cleaning device driving member which can consist of an electric motor or pneumatic means or any other suitable driving means. Figures 2 and 3,in particular,show the cleaning device at a rest condition,and the operating condition of this device is shown in figure 2 by the broken line. The rotating arms 19 can be made of a refractory metal material and they are held at a suitable not destructive temperature by the air impinging thereon through the fan 18. While the invention has been disclosed and illustrated with reference to a preferred embodiment thereof,it should be apparent that the disclosed embodiment is susceptible to several modifications and variations all of which will come within the spirit and scope of the appended claims.

Claims: 1. A tyre pyrolysis system comprising a tyre pyrolysis chamber (2) communicating with a duct for pyrolysis tyre carcass material, and including a frustum of cone shaped bottom (15) associated with rotating means (17) and cooperating with two frustum of cone tubular arms (19) extending from a vertical combustion air supplying duct (16) near said bottom and each having a respective open free end, a discharging outlet (20) for discharging unburnt materials from said tyre pyrolysis chamber, and first combustion air fan supply means (18) for supplying a combustion air stream through said duct, characterized in that said system further comprises, for improving the combustion of said tyres, a secondary fuel burner (10) communicating with said combustion gas converging duct (3), second combustion air supplying fan means (12) arranged in said duct (3), third combustion gas removing fan means (13), first control gate means (14), said third fan means (13) and first gate means being arranged in a return duct coupling said steam generator (1) and said pyrolysis chamber (2), and second control gate means (11) communicating a flue has cleaning apparatus with said stack (7), in that said tubular arms are formed as a single piece with said combustion air supply duct (16), that said combustion air is ejected with a set flow-rate exclusively from each of said open ends of said arms and that said chamber (2) has the top thereof defining a combustion gas conveying duct (3) for supplying with combustion gases a steam generator (4) comprising a water tube nest thereon said combustion gases impinge and coupling a lower water chamber and an upper water chamber of said steam generator (4). 2. A system according to claim 1, characterized in that it further comprises, downstream of said steam generator (4), a heat exchanger (5), said flue gas cleaning apparatus (6) and a stack (7). 3. A system according to claim 1, characterized in that said tubular arms (19) substantially lead to said discharging outlet (20). 4. A system according to claim 1, characterized in that said system comprises a cleaning device arranged at said discharging outlet and adapted to remove therefrom said ejected waste material so as to prevent said discharging outlet from being chocked, said cleaning device comprising a swinging arm (24) pivoted on the outside of said pyrolysis chamber, the end portion of said swinging arm being adapted to scrape away from the edge of said discharging outlet (20) said ejected waste material.

Inventors: MARANGONI, CARLO
Applicants: MARANGONI MECCANICA S.P.A.
Application year: 1988
Main classification: C10B53
IPC codes: F23G5, F23G7