Pyrolysis has been a useful procedure to treat waste-tire, which decomposes waste-tire at high temperature in the absence of oxygen. This thermal decomposition process generates pyrolysis oil, combustible gas, and char, which distribute in liquid phase, gas phase, and solid phase, respectively. Pyrolysis oil and combustible gas are fuels, while char is composed of carbon black and ash. Thus, char would be economically worth while to be treated before reuse. In this study, based on the resistivity difference between carbon black and ash, ash can be removed from char in the principle of electrostatic separation and thus increase the value of char.
In this study, the objective was to separate ash from char by electrostatic separation process, different char including waste-tire pyrolytic char (raw char), low pressure re-pyrolytic char, ZnO-added char (12% ZnO mixed with 600 oC re-pyrolytic cahr) and man-made char (N600 carbon black mixed with 14.5% metallic oxide) were tested. The Electro-Static Separator (ESS) was designed and constructed with two types of discharge electrodes including a needle-plate electrode (NPE) and a needle-bar electrode (NBE) and two kinds of dust feeders to generate either fine or coarse particles.
The results indicated that raw char had higher collection efficiency using the NBE system than the NPE system in the operating voltages of -7 kV to -15 kV because the surface area of the NBE system was less than the NPE system, thus led higher surface charge density for the NBE system than the NPE system, resulting in higher discharge current of the NBE system.
In order to lower resistivity and reduce deposited pyrolysis oil on char, low pressure repyrolysis process was used. Because the removal efficiency of pyrolysis oil is proportional to repyrolysis temperature, more pyrolysis oil can be removed from the surface of char, resulting in more carbon blacks exposed on the char surface as conductive material. Thus, the collection efficiency of 600 oC repyrolytic char was less than that of 400 oC repyrolytic char. Furthermore, because particle charging quantity was proportional to particle size, fine char particles had less collection efficiency than coarse char particles.
However, both raw char and repyrolytic char, the collection efficiency of carbon and ash had similar trends, suggesting that similar percentage of carbon and ash were collected on the plate and penetrated the ESS system. Therefore, the separation efficiency of carbon and ash were similar, same situation was observed for the ZnO-added char.
In order to verify the feasibility of carbon and ash separation by electrostatic separation process, N660 carbon black mixing with 14.5% man-made ash (Al2O3, ZnO and CaO composed) to simulate man-made char, which was further used to proceed the electrostatic separation experiments in this study.
The results indicated that the collection efficiency of man-made char increased with operating voltage, and the ash content seems to increase with voltage. Carbon black is a low resistivity material, which causing sparkover during the experiments, thus operating voltage cannot be regulated more than -8.25 kV. In order to verify the feasibility of carbon black and ash separation by the principle of electrostatic separation, this study applied non-linear regression to model the collection efficiency of man-made char, carbon black and ash, and further simulate the collection efficiency at higher electrical field strength. The simulated results indicated that the maximum collection efficiency of carbon and ash was approached around -10 kV/cm of carbon black and ash and their collection efficiencies were similar. The collection efficiency of ash was close to the ash content of man-made char (the collection efficiency of ash equal to the collected ash per mass of injected char), suggesting that most injected ash was collected by the ESS system. In addition, the ash content of penetration char was also simulated, the modeling results showed that the ash content of penetrated char were lower than 2%, while was relatively lower than the raw man-made char, and more than 75% injected char could penetrate the ESS system during the operation procedure. According to the modeling results, solid-solid separation technology could be more efficient if carbon and ash are independently separate particles, and lower resistivity materials would penetrate the ESS system and higher resistivity materials would be collected by the electrostatic separation process.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0706108-185149 |
| Date | 06 July 2008 |
| Creators | Lin, Chih-Feng |
| Contributors | Chih-Chieh Chen, Chung-Shin Yuan, Wen-Yin Lin, Chung-Hsuan Hung |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0706108-185149 |
| Rights | withheld, Copyright information available at source archive |
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