WO1999016848A1

WO1999016848A1 - Continuous recovery of combustible gases from tires

Info

Publication number: WO1999016848A1
Application number: PCT/CA1998/000906
Authority: WO
Inventors: Alain Mineau; Yvon Laverdure; Sylvain Martel; Jean-François BROUILLETTE
Original assignee: Thermex Energy Recovery Corp.
Priority date: 1997-09-29
Filing date: 1998-09-24
Publication date: 1999-04-08
Also published as: AU9248798A

Abstract

A plurality of sublimation chambers (1, 3) are provided and a remnant material conveyor (9) is mounted opposite them. A tire conveyor (37) alternately feeds the chambers so that when tires are being treated in one chamber other chambers are being filled with additional tires. Each chamber is associated with a burner (5, 7) and air input (55) to convert the tires into combustible gas, and a device (21) which scrapes away any char and steel belt material left in the chamber after a conversion operation. A control is provided to ensure a continuous production of combustible gases by alternating the operation in the chamber.

Description

CONTINUOUS RECOVERY OF COMBUSTIBLE GASES

FROM TIRES

TECHNICAL FIELD

This invention relates to a process and a system for converting tires or the like into combustible gases in an continuous, non-stop manner. More particularly, the present invention is concerned with a process and a system which operate continuously and which make it possible to provide a continuous supply of combustible gases by alternating the operation of at least two sublimation chambers which feed their output of gaseous products into a single line of combustible gases, the latter to be used immediately in a burner, a condenser or the like.

BACKGROUND ART It is well known that there are millions of used tires which are disposed in tire sites and which, in addition to deteriorating the environment, constitute a source of pollution and a serious fire hazard. There is thus an urgent need to provide a specific use for these products which is clean, economical and substantially improves the environment. U.S. Patent 5,295,499 discloses a dry distillation gas generator wherein used tires are thermally decomposed to produce dry distillate gases. After the dry distillation, the remains cannot be recycled because at the end of the operation the temperature is too high, making the carbon particles and steel truly non-usable, so that they have to be disposed of. The reason for this is that as the reaction proceeds, the temperature goes up to 250-350°C where it reaches a plateau, which is followed by a sudden rise to about 700°C, which is believed to be the reason why carbon particles and steel are converted to useless material.

U.S. Patent 3,362,887 discloses treating refuse and garbage in a first chamber for a preliminary treatment, and transferring the refuse and garbage thus treated in the first chamber, into a second chamber for a final treatment.

U.S. Patent 4,839,151 discloses a recovery process for used tires in which char is separated from steel and glass and is thereafter recovered.

U.S. Patent 4,900,401 discloses a complex continuous pyrolysis system for tire shreds. U.S. Patent 5,286,374 discloses a process for cracking waste rubber tires which is characterized by critical temperature ranges and the use of a mica catalyst. It will therefore be seen that there is a need for a system which is continuous and efficient in converting whole or shredded tires into useful combustible gases and which does not produce unrecoverable useless materials.

It is therefore an object of the present invention to provide a system of recycling whole or shredded tires to provide a source of low cost energy.

It is another object of the present invention to provide a system which is cost effective for owners of storage sites, waste management authorities, landfill sites, waste collectors and industries seeking an economical source of supplemental or replacement energy.

DISCLOSURE OF INVENTION

These and other objects of the present invention may be achieved in a process and a system for continuously converting tires into combustible gases. The process comprises the steps of providing a plurality of sublimation chambers; feeding a predetermined quantity of whole or shredded tires into at least one sublimation chamber; igniting the tires while introducing air into the above sublimation chamber at a pressure between about 0.1 and about 0.6 lb/in above atmospheric; maintaining ignition of the tires therein until the temperature of the gases exiting from the above sublimation chamber is between about 40° and 65°C, and then stopping the ignition; adjusting and modulating the quantity of air introduced in the above sublimation chamber so as to obtain a predetermined quantity of energy produced by combustion of the gases exiting from the sublimation chamber, said predetermined quantity amounting to at least about 2,000,000 BTU; stopping gasification of the tires when temperature inside the sublimation chamber reaches at most about 500°C and before initiation of carbon black combustion in the above sublimation chamber; cooling the remnant material formed in the above sublimation chamber to a temperature which prevents combustion of the carbon black; scraping away all material remaining in the above sublimation chamber; and repeating the above steps in at least one additional sublimation chamber in a time frame to provide a continuous production of the combustible gases.

During ignition of tires air is introduced into the above sublimation chamber at a pressure which is preferably between about 0.25 and 0.40 lb/in above atmospheric. Gasification of the tires may be terminated by injection of steam or an inert gas into the above sublimation chamber. When steam is used to terminate the combustion it will remove gases and oil present in the carbon black, so that during that stage of the process there will be a mixture of oil, steam and gases produced by the process, and this mixture will be condensed and/or burned. Usually, there are provided two sublimation chambers and they alternately operate so as to provide a continuous production of combustible gases.

Of course any combination of any number of sublimation chambers is possible according to the invention as will be appreciated by one skilled in the art. After the treatment is terminated the remnant material present in the sublimation chamber is normally cooled with steam followed by water shower.

In accordance with a preferred embodiment a conveyor is provided outside the sublimation chambers and the remnant material is scraped away onto this conveyor to be disposed of.

The system according to the invention comprises a plurality of sublimation chambers; means for feeding a predetermined quantity of whole or shredded tires into the sublimation chambers, and control means to alternate the feeding from at least one sublimation chamber to other sublimation chambers. Each chamber comprises means for igniting the whole or shredded tires and means for introducing air into the above chamber at a pressure between about 0.1 and about 0.6 lb/in² above atmospheric; a gas outlet enabling combustible gases obtained from the tires to exit from the above sublimation chamber; a tire feeding trap door and means to open the trap door when the feeding means are in operation to feed the above sublimation chamber; an exit door and means for opening and closing the exit door; an access door opposite the exit door and means for opening and closing the access door; means extending through the same access door until reaching the exit door for scraping away remnant material remaining on the floor of the sublimation chamber after a complete cycle when substantially all tires present therein have been converted into combustible gases, the remnant material then being scraped away from the sublimation chamber through the scraping means. The system also comprises conveyor means to receive the scraped away remnant material; first control means effective to maintain the tires ignited until the temperature of the combustible gases which exit from the sublimation chamber is between about 40° and 65°C, and to stop the ignition of the tires when the temperature has reached about 40° to 65°C; second control means enabling to adjust and modulate the quantity of air introduced in the above sublimation chamber so as to obtain a predetermined quantity of energy produced by combustion of the gases exiting from the sublimation chamber, said predetermined quantity amounting to at least about 2,000,000 BTU, preferably about 5,000,000 to 13,000,000 BTU; third control means for stopping gasification of the tires when temperature inside the sublimation chamber reaches at most about 500°C, and before any initiation of carbon black combustion in the sublimation chambers; means for cooling remnant material formed in the sublimation chambers to a temperature which prevents combustion of the carbon black and for flushing out gases remaining in said sublimation chamber together with oil present in said carbon black; and means for alternating treatment in the sublimation chambers in a time frame to provide a continuous production of the combustible gases. Preferably the system includes two sublimation chambers spaced from one another. In this case, the conveyor means may be disposed between the two sublimation chambers so as to receive remnant material exiting from the respective exit doors thereof.

The feeding means preferably comprises a tire conveyor having an articulated portion enabling to feed the first sublimation chamber when in upwardly raised position and the second sublimation chamber when the articulated portion is lowered at the level of the conveyor.

In accordance with another preferred embodiment, the igniting means are provided in the wall of the sublimation chambers, and the sublimation chambers each have a floor formed with openings mounting air diffusers enabling air to be injected into the sublimation chambers.

BRIEF DESCRIPTION OF DRAWINGS

Other details and characteristics of the invention will be described as the description follows with reference to the annexed drawings, in which:

FIG. 1 is a longitudinal cross-section view of a system according to the invention;

FIG. 2 is a top view of the same;

FIG. 3 is a top view of the bottom of a sublimation chamber; and FIG. 4 is a partial cross-section view of air diffusers and nozzles used for injecting air into a sublimation chamber at the bottom thereof.

MODES FOR CARRYING OUT THE INVENTION

With reference to the drawings, more particularly Figs. 1 and 2, it will be seen that the system which is illustrated essentially comprises two sublimation chambers 1 and 3. The two chambers are generally identical except for a few details, as will appear hereinafter. The two sublimation chambers 1 and 3 are conventional and both operate when two conventional burners 5 and 7 are activated mounted in the walls thereof as shown. In addition bottom floor 23 of each sublimation chamber (Figs. 3 and 4) is formed with a plurality of air diffusers 55 which are well known in the art and may be constructed as shown particularly in Fig. 4. These air diffusers are preferably distributed as shown in Fig. 3 for better results. In less than one hour the thermal process becomes self-sustaining and only requires regular air inflow through air diffusers 55, as mentioned above. Also, when the burners are operated to ignite the load of tires 57, sufficient air is introduced through diffusers 55 to provide in the sublimation chamber a pressure between about 0.1 and about 0.6 lb/in², preferably between about 0.25 and 0.40 lb/in above atmospheric.

As illustrated in Figs. 1 and 2, the two sublimation chambers 1 and 3 are disposed side by side while leaving enough space between them to mount remnant material conveyor 9 therebetween. A means, not shown, such as an electrical motor is used when remnant material is being dumped thereon to operate conveyor 9. Again referring to these drawings, it will be seen that both sublimation chambers 1 and 3 are generally identical, except for a few details that will be discussed later. For ease of description, sublimation chamber 1 will now be described in detail. It comprises a tire feeding trap door 1 1 which opens through a lifting means, not shown, when sublimation chamber 1 is not in operation and tires are intended to be fed therein. Sublimation chamber 1 also comprises an exit door 13 which is provided on one side of the chamber as shown. This door operates by being slidably liftable by means of an hydraulic cylinder 15. Of course, another lifting system could also be used without departing from the invention. Also provided, there is a ram access door 17 exactly opposite exit door 13. Ram access door 17, as is the case with exit door 13 is also slidably liftable by means of an hydraulic cylinder 19. The sublimation chamber also comprises ram 21 which is only schematically illustrated in the drawings and which is operated by means of an hydraulic cylinder, not shown. Ram 21 is mounted to extend through ram access door, all through sublimation chamber 1 while following bottom 23 thereof, until reaching exit door 13. It will be realized that ram 21 will scrape away any remnant material which remains on bottom 23 of sublimation chamber 1 , after a complete cycle, as will be seen later, when substantially all tires present in sublimation chamber 1 have been converted into combustible gases. The ram will then push the remnant material onto conveyor 9. Finally, sublimation chamber 1 is provided with gas security valve 25 and exhaust flue 26 which receives all combustible gases which are produced in the chamber while the latter is in operation. The gases are normally sent to burner 59 (Fig. 2), via line 51 , or if desired, they may be partly converted into oils in condenser 61 , as is well known in the art.

Turning now to sublimation chamber 3, the latter will be seen to be generally identical to chamber 1 except that the ram access door, the exit door and the ram are mounted in a mirror-like arrangement. So, sublimation chamber 3 correspondingly has a trap door 27, an exit door 29, a ram access door 31, a ram 33, a safety valve 35 and an exhaust flue 36 which also communicates with gas line 51. To feed both sublimation chambers 1 and 3, the system comprises a tire conveyor 37 which is mounted in known manner above the chambers, as shown. As illustrated, in order to facilitate an alternate feeding of sublimation chambers 1 or 3 through trap door 11 or trap door 27, tire conveyor 37 is constructed of two sections 39 and 41, the latter being provided with an articulated part 43. So, when it is intended to feed sublimation chamber 1, articulated part 43 is lifted in the direction of arrow 45 thereby isolating section 39 and enabling the conveyor to feed all the tires into sublimation chamber 1 via trap door 11. Conversely, when it is intended to stop the feeding into sublimation chamber 1 , and initiate the feed into sublimation chamber 3, articulated part 43 is lowered in the direction of arrow 47 until it fits exactly with the free end of conveyor section 39, which will permit the tires to continue into conveyor section 41 in the direction of arrow 49 until they reach trap door 27 which, as will be discussed later, will automatically open.

To operate the system there is provided an automatic multifunction control which is not illustrated but which can easily be designed by anyone skilled in the art so as to be effective to carry out the following operations. At the start a means is provided so that trap door 11 is opened and all remaining doors are closed while tire conveyor 37 is put into operation. When a predetermined quantity of tires have been introduced into sublimation chamber 1 , the control is programmed to automatically close trap door 11, lower articulated part 43 of tire conveyor 37, open trap door 27 and initiate gas burner 5 and 7 which are stopped after about 15 minutes. While this is taking place the tires which are in sublimation chamber 1 begin to be converted into combustible gases under the conditions mentioned above, and the gases exit the chamber through gas flue 26 and will finally be delivered into a gas line 51 to be condensed at 61 or burned at 59. At the same time additional tires are being dumped into sublimation chamber 3 through trap door 27. When the tires in sublimation chamber 1 have been substantially converted into combustible gases, the remnant material generally consists of about 10% steel belts and about 20% carbon char with respect to the initial mass of tires.

At this time the control operates to lift exit door 13 and ram access door 17, after which ram 21 is caused to extend through ram access door 17, all through the width of sublimation chamber 1 while scraping away any char and steel belt on the floor of sublimation chamber 1 , until the char and steel belt are dumped onto conveyor 9 which will deliver this material for disposal, such as by recycling, as is well known to those skilled in the art. Of course the automatic multifunction control is also designed to adjust the introduction of steam and water, respectively to remove oil from carbon particles and cooling the solid residues.

In the meantime the control acts to initiate the conversion of tires in sublimation chamber 3 in the same manner as the previous operation in sublimation chamber 1. So when gas production in sublimation chamber 1 is terminated, the control immediately acts to start the production in sublimation chamber 3 with the result that there is always a continuous production of combustible gases from tires.

Claims

CLAIMS:

1. Process for the continuous conversion of whole or shredded tires or the like into useful combustible gases which comprises the following steps: providing a plurality of sublimation chambers; feeding a predetermined quantity of whole or shredded tires into at least one sublimation chamber; igniting said tires while introducing air into said at least one sublimation chamber at a pressure between about 0.1 and about 0.6 lb/in above atmospheric; maintaining ignition of said tires therein until temperature of gases exiting from said at least one sublimation chamber is between about 40┬░ and 65┬░C, and then stopping said ignition; adjusting and modulating the quantity of air introduced in the above sublimation chamber so as to obtain a predetermined quantity of energy produced by combustion of the gases exiting from the sublimation chamber, said predetermined quantity amounting to at least about 2,000,000 BTU; stopping gasification of said tires before any initiation of carbon black combustion in said at least one sublimation chamber; cooling remnant material formed in said sublimation chamber to a temperature which prevents combustion of said carbon black; scraping away all material remaining in said at least one sublimation chamber; and repeating the above steps in at least one additional sublimation chamber in a time frame to provide a continuous production of said combustible gases.

2. Process according to claim 1 wherein said predetermined quantity amounts to between about 5,000,000 and 13,000,000 BTU.

3. Process according to claim 1 wherein during ignition of tires air is introduced into said at least one sublimation chamber at a pressure between about

ΓÇóy

0.25 and 0.40 lb/in above atmospheric.

4. Process according to claim 1 wherein gasification of the tires is terminated by injection of steam into said at least one sublimation chamber.

5. Process according to claim 3 which comprises removing oil and gases present in said carbon black with said steam and thereafter burning a mixture of said oil, said combustible gases and said steam.

6. Process according to claim 1 wherein gasification of the tires is terminated by injection of an inert gas into said at least one sublimation chamber.

7. Process according to claim 1 which comprises providing at least two sublimation chambers and alternately operating said two chambers so as to provide a continuous production of combustible gases.

8. Process according to claim 1 wherein cooling of the remnant material is carried out with steam followed by water shower.

9. Process according to claim 1 which comprises providing a conveyor outside said sublimation chambers and scraping away said remaining material onto said conveyor.

10. System for continuously converting whole or shredded tires into useful combustible gases, which comprises: a plurality of sublimation chambers; means for feeding a predetermined quantity of tires or the like into said sublimation chambers, and control means to alternate said feeding from at least one sublimation chamber to the other said sublimation chambers; each said chamber comprising: means for igniting said whole or shredded tires and means for introducing air into said chamber at a pressure between about 0.1 and about 0.6 lb/in above atmospheric; a gas outlet enabling combustible gases obtained from said tires to exit from said sublimation chamber; a tire feeding trap door and means to open said trap door when said feeding means are in operation to feed said sublimation chamber; an exit door and means for opening and closing said exit door; an access door opposite said exit door and means for opening and closing said access door; means extending through said same access door until reaching said exit door for scraping away remnant material remaining on the floor of said sublimation chamber after a complete cycle when substantially all tires present therein have been converted into combustible gases, said remnant material then being scraped away from said sublimation chamber through said scraping means; said system also comprising: conveyor means to receive said scraped away remnant material; first control means effective to maintain said tires ignited until temperature of the combustible gases which exist from said sublimation chambers is between about 40┬░ and 65┬░C, and to stop said ignition when said temperature has reached about 40┬░ to 65┬░C; second control means enabling to adjust and modulate the quantity of air introduced into said sublimation chamber so as to obtain a predetermined quantity of energy produced by combustion of gases exiting from the sublimation chamber, said predetermined quantity amounting to at least about 2,000,000 BTU; third control means for stopping combustion of said tires before initiation of carbon black combustion in said sublimation chambers; means for cooling remnant material formed in said sublimation chambers to a temperature which prevents combustion of said carbon black and for flushing out gases remaining in said sublimation chamber together with oil present in said carbon black; and means for alternating treatment in said sublimation chambers in a time frame to provide a continuous production of said combustible gases.

11. System according to claim 10 which comprises two sublimation chambers spaced from one another, said conveyor means being disposed between said two sublimation chambers so as to receive remnant material exiting from the respective exit doors thereof.

12. System according to claim 11 wherein said feeding means comprise a tire conveyor, having an articulated portion enabling to feed the first sublimation chamber when in upwardly raised position and the second sublimation chamber when said articulated portion is lowered at the level of said conveyor.

13. System according to claim 12 wherein the igniting means are provided in walls of said sublimation chambers, and said sublimation chambers each have a floor formed with openings mounting air diffusers enabling to inject air into said sublimation chambers.