Method for sorting tires

Abstract

The present invention relates to a method for sorting tires (15) on basis of its components as well as to an apparatus for carrying out such a method. The present invention also relates to the use of scrap rubber in a pyrolysis process to obtain a char material. The method for sorting tires (15) on basis of silica content (7).

Claims

1. A method for sorting tires on basis of silica content, comprising: sorting said tires into a low silica content stream or a high silica content stream on basis of the silica content of said tires, wherein said low silica content stream consists of tires in which 90% of the tires has a silica percentage lower than 15 wt. % and wherein said high silica content stream consists of tires in which 90% of the tires has a silica percentage higher than 15 wt. %, wherein the weight percentage is based on the total weight of the tire.

2. The method of claim 1, wherein said silica content of said tires is measured by using one or more sensor-based technologies chosen from the group of electrical resistivity (ER), X-ray fluorescence (XRF), Near-infrared (NIR) and laser-induced plasma spectroscopy (LIPS).

3. The method of claim 2, wherein said silica content of said tires is measured by using X-ray fluorescence (XRF).

4. The method of claim 1, wherein non-destructed tires are sorted.

5. The method of claim 2, wherein said measurement is carried out on a tire tread surface of said tires.

6. The method of claim 1, wherein the tires to be sorted are placed on a conveyor, wherein the thus placed tires are transported by said conveyor to at least one station for measuring the silica content of said tires, wherein said station further comprises means for analyzing the data provided by said measuring method and means for providing a signal for separating the tires thus measured into said low silica content stream and said high silica content stream.

7. The method of claim 1, wherein the surface of the tires on which the measurement is to be carried out is dry.

8. The method of claim 1, wherein said high silica content stream is destructed in a destruction process into at least a tread comprising high silica content stream and a non-tread comprising high silica content stream, characterized in that the silica percentage in said tread comprising high silica content stream is in a range of 20-50 wt. %, on the basis of the total weight of said tread comprising high silica content stream, characterized in that the silica percentage in said non-tread high silica content stream is in a range of lower than 5 wt. % on the basis of the total weight of said non-tread comprising high silica content stream.

9. The method of claim 1, wherein said low silica content stream is destructed in a destruction process into at least a tread comprising low silica content stream and a non-tread comprising low silica content stream.

10. The method of claim 9, wherein the silica percentage in said tread comprising low silica content stream is in a range of lower than 5 wt. %, on the basis of the total weight of said tread comprising low silica content stream.

11. The method of claim 10, wherein the silica percentage in said non-tread low silica content stream is in a range lower than 5 wt. % on the basis of the total weight of said non-tread comprising low silica content stream.

12. The method of claim 1, wherein, said low silica content stream consists of tires in which 95% of the tires has a silica percentage lower than 15 wt. % and wherein said high silica content stream consists of tires in which 95% of the tires has a silica percentage higher than 15 wt. %, wherein the weight percentage is based on the total weight of the tire.

13. An apparatus for carrying out the method according to claim 1, said apparatus comprising means for conveying unsorted tires to a downstream located measuring station, said measuring station comprising means for measuring the silica content of said tires, said measuring station further comprising means for analyzing the data provided by said measuring means and means for providing a signal for separating the tires thus measured into said low silica content stream and said high silica content stream wherein said low silica content stream consists of tires in which 90% of the tires has a silica percentage lower than 15 wt. % and wherein said high silica content stream consists of tires in which 90% of the tires has a silica percentage higher than 15 wt. %, wherein the weight percentage is based on the total weight of the tire.

14. The apparatus of claim 13, wherein said means for measuring the silica content of said tires comprise one or more sensor-based technologies chosen from the group of electrical resistivity (ER), X-ray fluorescence (XRF), Near-infrared (NIR) and laser-induced plasma spectroscopy (LIPS).

15. The apparatus of claim 14, wherein said means for measuring the silica content of said tires comprise X-ray fluorescence (XRF).

16. The apparatus of claim 15, wherein said apparatus comprises means for positioning the tires to be sorted such that said means for measuring the silica content of said tires carry out said measurement on the tire tread surface of said tires.

17. The apparatus of claim 16, wherein said apparatus further comprises means for drying the unsorted tires, said means for drying the unsorted tires being positioned upstream from the measuring station comprising means for measuring the silica content of said tires.

18. The apparatus of claim 17, wherein said apparatus further comprises means for destructing said low silica content stream into a tread comprising low silica content stream and a non-tread comprising low silica content stream.

19. The apparatus of claim 17, wherein said apparatus further comprises means for destructing said high silica content stream into a tread comprising high silica content stream and a non-tread comprising high silica content stream.

20. A method of performing a pyrolysis process to obtain a char material, comprising: using scrap rubber from a high silica content stream consisting of tires in which 95% of the tires has a silica percentage higher than 15 wt. % obtained according to a method according to claim 1, wherein said tires mainly comprise tread parts of tires, in a pyrolysis process, wherein said pyrolysis process pyrolysis comprises at least a two-stage pyrolysis process, wherein the said two-stage pyrolysis process comprises: a) a first pyrolysis stage to obtain an intermediate char material and b) a second pyrolysis stage to obtain said char material and wherein at least one of the stages a) or b) is carried out in a rotary kiln, wherein said scrap rubber is fed into said first pyrolysis stage.

Description

(1) The sole FIGURE shows the above discussed process in a block diagram. Passenger car tires 15 are separated into silica tires 1 and non-silica tires 2. Silica tires 1 are separated into tread 3 and non-tread 4. Tread 3 is composed of high silica content 7 and low carbon black content (and having a relatively small average primary particle size) 8. Non-tread 4 is composed of low silica content 9 and high carbon black content (and having a relatively large average primary particle size) 10. Non-silica tires 2 are separated into tread 5 and non-tread 6. Tread 5 is composed of low silica content 11 and high carbon black content (and having a relatively small average primary particle size) 12. Non-tread 6 is composed of low silica content 13 and high carbon black content (and having a relatively large average primary particle size) 14.

(2) Separating these tire components will deliver more differentiated products compared to only differentiating according to silica content. The tread: non-tread separation process may require two steps: separate the tread and inner liner from the rest of the tire, for example by using a machine like a TRS T-CUT (trademark, Tire Recycling Solutions SA, for example the apparatus as disclosed in WO2015/162443), separate the tread from the inner liner, for example by using a water-jet cutter.

(3) The present invention furthermore relates to an apparatus for carrying out the method as discussed above, wherein the present apparatus comprises means for conveying unsorted tires to a downstream located measuring station, the measuring station comprising means for measuring the silica content of the tires, the measuring station further comprising means for analyzing the data provided by the measuring means and means for providing a signal for separating the tires thus measured into the low silica content stream and the high silica content stream. A computer system including software and algorithms can be used for processing the data generated by the means for measuring the silica content of the tires. A calibration curve can be mentioned here as a suitable algorithm to convert the data generated by the means for measuring the silica content of the tires into a value of the silica content.

(4) The means for measuring the silica content of the tires comprise one or more sensor-based technologies chosen from the group of electrical resistivity (ER), X-ray fluorescence (XRF), Near-infrared (NIR) and laser-induced plasma spectroscopy (LIPS), wherein it is preferred to apply a measuring method according to X-ray fluorescence (XRF). In another embodiment the apparatus further comprises means for drying the unsorted tires, said means for drying the unsorted tires being positioned upstream from the measuring station comprising means for measuring the silica content of said tires. As an example of such means for drying tires a station provided with hoses for delivering pressurized air can be mentioned. The air to be supplied can be preheated.

(5) The present invention furthermore relates to the use of scrap rubber in a pyrolysis process to obtain a char material, wherein the scrap rubber is a low silica content stream consisting of tires in which 95% of the tires has a silica percentage lower than 15 wt. % obtained according to the sorting method as discussed above.

(6) According to another embodiment It is preferred to use scrap rubber in a pyrolysis process to obtain a char material, wherein the scrap rubber is a high silica content stream consisting of tires in which 95% of the tires has a silica percentage higher than 15 wt. % obtained according to the sorting method as discussed above. Such a pyrolysis process preferably comprises at least a two-stage pyrolysis process, wherein the two-stage pyrolysis process comprises: a) a first pyrolysis stage to obtain an intermediate char material and b) a second pyrolysis stage to obtain the char material and wherein at least one of the stages a) or b) is carried out in a rotary kiln. A preferred method for such a two-stage pyrolysis process, including its process conditions, has been disclosed in the already discussed WO 2013/095145 in the name of the present inventors.

(7) The term silica as used herein refers silica or amorphous silica, silica gel. For example silica is produced by the acidification of solutions of sodium silicate. The gelatinous precipitate is first washed and then dehydrated to produce colorless microporous silica. This term also includes silica obtained from sand.

(8) The invention will be explained hereinafter by means of a number of examples in which connection it should be noted, however, that the present invention is by no means limited to such examples.

EXAMPLES

(9) The measurements were done with the industrial on-line XRF analyzer CON-X03M. XRF analyzer with so called close geometry of measuring unit was used. This means that the X-ray tube and the detector are configured so that the focal spot which is excited by primary X-ray radiation on the surface of the analyzed material (and which is seen by the detector) is placed at a distance of <5 mm from the measuring cell.

(10) The instrument has one channel (measurement point) and easily variable sample excitation conditions. Measurement conditions are specified in Table 1.

(11) TABLE-US-00001 TABLE 1 Measurement conditions Analyzer CON-X 03M X-ray tube anode material Ag Primary radiation filter No filter X-ray tube voltage 8.0 kV X-ray tube current 800 A Measurement time 10 and 300 s Ambient medium Ambient temperature/vacuum 0.15 Torr Distance between the sample and analyzer ~2 mm XRF detector Si, SDD type

(12) Measurement of Tire Tread Surface

(13) Spectra of the LS (Low silica, <10%, m/m) and HS (high silica, >10%. m/m) samples measured from the tread sides are shown in FIG. 1. For comparison FIG. 1 also shows the spectrum of a black rubber cord used for the production of conveyor belts. The material for the conveyor belt is produced by converting the corresponding polymers into a more durable rubber material via the process of vulcanization with sulfur. The intensity of Si XRF line measured for HS sample on the tread side is substantially higher than for LS sample. In contrast, Si line is much weaker for the conveyor belt rubber which is vulcanized with sulfur. It is noteworthy that the intensity of Si XRF line is in the inverse proportion to the intensity of Si line for the samples under study. The difference between Si line intensities measured for HS and LS tread surfaces is significant. The essential difference between the intensities of target spectral line for the two types of silica tires is crucial for reliable and accurate pre-sorting and separation them on the conveyor in real time.

(14) Measurement of the Side Surface of Tires.

(15) Sub-samples of the side parts of the tire were also prepared and measured. Typical spectrum of the side surface of HS tire is shown in FIG. 2 as an example.

(16) For comparison on the same FIGURE another line shows the spectrum measured on the tread sub-sample of HS tire. Therefore the difference between silica content in different parts of the tire is clearly demonstrated by the intensity of Si spectral line (FIG. 2). Si line intensity that is measured on the side surface of HS tire is much weaker compared to HS tread sample. The former is close to the intensity obtained for the tread surface of LS tire. Therefore the intensities of the Si spectral line measured for tread and side surfaces of the tire are not equal. This difference is observed both for HS and LS grades: Si line measured on the tread surface is higher in the both cases. The difference between Si line intensities of tread and side surfaces is more significant for HS tire.

(17) On basis of this measurement it is preferred that the tires must be somehow directed in a proper position on the transporting mechanism, such as a conveyor, so that the measuring unit could see the tread surface but not side surface of the tire. Thus it is preferred to apply a mechanism that could direct each tire in the vertical position before the measurement is carried out.

(18) Additional measurements have shown that a layer of water or just a humid surface of material being measured can affect readings (Si XRF line intensity) thus affecting the separation. Therefore it is preferred that the more dry the surface the tread of the tire is, the higher is the Si line intensity and the more accurate and reliable is the step of sorting. The inventors assume that the presence of water decreases the Si line intensity due to partial absorption of silicon XRF photons in water and attenuation of their energy.

(19) On basis of the above one may conclude that the intensity of Si XRF line measured for HS sample on the tread side is substantially higher than for LS sample. The essential difference between the intensities of silicon line for two types of silica tires is crucial for reliable and accurate pre-sorting and separation them on the conveyor in real time. In addition, Si line intensity measured on the tread surface of the tire is higher than on side surface both for LS and for HS grades. The difference between Si line intensities of tread and side surfaces is much more significant for HS tire. Furthermore, a water layer on the surface of the material to be measured affects readings (Si XRF spectral line intensity) in some extent. In a situation of a short time of measurement, namely in a range of about 10 seconds, it is thus preferred to measure on a dry tread surface.