The use of a novel chemical system towards improving waste tyre pyrolysis and the quality of waste tyre pyrolysis products
- Authors: Tsipa, Phuti Cedric , Iwarere, Samuel
- Date: 2023-12
- Subjects: Tires -- Recycling , Rubber chemicals , Rubber, Reclaimed
- Language: English
- Type: Doctorial theses , text
- Identifier: http://hdl.handle.net/10948/62666 , vital:72912
- Description: Pyrolysis process is one of the most efficient methods in the waste tyre recycling sector at this moment, hence the attention it is receiving. However, this process has some limitations, with the main one being that it is non-conventional and typically energy intensive. In addition, its resultant products have been reported to have significantly poorer properties relative to their virgin counterparts, making it difficult to incorporate them in the mainstream of raw materials. For instance, waste tyre pyrolysis oil typically has poor fuel properties, high sulfur content, high amount of polycyclic aromatic hydrocarbons (PAHs) and strong unpleasant odour; on the other hand, the quality of the recovered carbon black is dependent on the feedstock and the pyrolysis process conditions. Hence the need for further research and development to make the process effective and improve the quality of resultant products. The aim of this research project was to study the impact of pre-pyrolysis treatment of tyre crumbs and post-pyrolysis treatment of the oil using a novel chemical system on the quality/composition of the resultant products. In addition, the study compared the impact of pre- and post-pyrolysis treatments on the optimum pyrolysis time and temperature (energy). The equipment employed in this study included a vertical fixed bed pyrolysis pilot reactor (modified to suit the reaction/experiment) as well as characterization techniques such as fourier transform infrared (FTIR), elemental analysis (carbon, hydrogen, nitrogen and sulfur – CHNS analysis), gas chromatography coupled to mass spectrometer (GCMS), gas chromatography coupled to flame photometric detector (GCFPD), thermo-gravimetric and derivative analysis (TG/DTG isothermal analysis, and proximate analysis) and scanning electron microscope (SEM). The highlight of the findings is that chemically pre-treating tyre crumbs with a mixture of protonic acid and organic solvent before pyrolysis significantly lowered the temperature required to pyrolyze them, from around 400-500 ℃ to 100-115 ℃. This meant that by using the chemical treatment on waste tyres a lot of energy can be saved. In addition, the sulfur content in the oil fraction was reduced from a total of 1.7 wt% to a total of about 0.2 wt%. This also showed that the contaminants in oil were significantly reduced. The oil was condensed into three (3) collectors for fractionation; in collector 2 was about 54 % of the total oil with sulfur content of about 0.015 wt%. The PAHs amounts were also lowered, as literature indicated that PAHs are mostly formed at around 600-700 ℃. It was also found that the oil produced from post-pyrolysis treatment of oil has a petroleum-like smell, whereas the pre-pyrolysis treated oil has a tyre-like pungent odour. Furthermore, the post-pyrolysis treated oil contains higher contents of alkanes and benzene, toluene, xylene (BTX). Findings of this study have a profound potential impact on the waste tyre recycling industry; for example, reduced production energy cost due to lowered temperature required for pyrolysis, improved quality of the products such as lowered sulfur and PAHs content as well as improved quality of the residual char and odour. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
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- Date Issued: 2023-12
Method development for chemolysis of waste tyres and characterization of the components
- Authors: Tsipa, Phuti Cedric
- Date: 2018
- Subjects: Composite materials , Rubber Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36694 , vital:34044
- Description: Chemolysis method for degradation and extraction of waste tyres for production of oil was developed. This method consist of three different solvent systems; firstly, the selective solvent system capable of extracting the process oil used in the production of tyres. This solvent system follows a phase transfer catalysis reaction, which is a reaction with a solvent consisting of two phases. Second system is a Destructive solvent system, which is capable of breaking down the polymer chains within the rubber matrix. It follows phase transfer catalysis reaction. Lastly, the collecting/wash solvent system, which is capable of collecting the remaining extracts in the residual crumb. Three products where obtained from this method: Liquid (oil), Gas and Solid (char), with the oil plus char being the focus of this study. Characterizations were carried out to obtain the quality of the oil recovered. Various analytical techniques were used to achieve the aims and objectives of this study, this involved Fourier Transform Infra-red spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) spectroscopy, High-resolution Thermogravimetric analysis (Hi-resTM TGA), Gas Chromatography coupled to Mass spectroscopy (GC-MS) and Simulated Distillation D86 (SIMDIST D86). Hydrocarbon compounds and market value acids where identified with reference to standards ran on the GC-MS. Market value acids were quantified to obtain the exact amount present in the extracted oil, the amounts for dodecanoic acid, hexadecanoic acid, heptadecanoic acid and octadecanoic acid were 0.73%, 5.1%, 0.49% and 9.98% respectively. Approximately 15% of this market value acid are present in the extracted oil. Internal GC-MS library and Retention Index (RI) methods with the help of NIST library were also used for compounds identification. A total of 53 compounds were successfully identified. SIMDIST D86 analysis showed that the petroleum fractions present in the total extracted oil were Heavy naphtha 0.73%, Kerosene 3.23%, Distillate fuel oil 6.27%, Light vacuum gas oil 57.93% and Heavy vacuum gas oil 31.83%. Hi-resTM TGA was used to characterize the char recovered for thermal properties. Chemolysis char showed relatively similar thermal stability compared to commercial N115 carbon black. The chemolysis method of oil extraction from waste tyres reported in this thesis shows promise in terms of both the routine of execution, quantification of market value constituents of the oil and chemical details of both the tyre derived oil and char.
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- Date Issued: 2018