- Title
- Beneficiation of pyrolysis-derived waste tyre char by blending with torrefied wood and microalgae to produce solid fuel
- Creator
- Dube, Cleopatra Thulani
- Subject
- Pyrolysis
- Subject
- Solid fuel reactors
- Date Issued
- 2021-12
- Date
- 2021-12
- Type
- Master's theses
- Type
- text
- Identifier
- http://hdl.handle.net/10948/58439
- Identifier
- vital:59241
- Description
- he thermal decomposition of waste tyres via pyrolysis is considered to be amongst the most promising methods of recycling tyres due to its minimal environmental impact (in terms of reduction in pollution). During pyrolysis, tyres are thermally degraded in an inert environment to produce gas, oil and char. The gas and oil have promising commercialization prospects while the char remains a pollutant despite the strides made in a lot of research to upgrade the char to carbon black, activated carbon and even for reuse as a filler in tyre manufacture. For pyrolysis to be profitable, or worthy of investments, all three of its products (oil, char and gas) need to be valorised. Pyrolysis-derived tyre chars (PT-char) have an energy value equivalent to high rank coals, however, the use of PT char as a solid fuel is uncommon due to the high contents of sulphur and mineral matter as well as low volatile matter content of the PT-char. As such, the combustion of PT-char is characterised by high ignition temperature, low thermal reactivity, and no flame formation due to the low amounts of volatile matter. On the other hand, biomass are clean, renewable feedstock, having low sulphur and mineral matter contents, as well as high thermal reactivity. The blending of PT-char with biomass could potentially improve the combustion properties of PT-char and minimise the release of toxic emissions from the char, and thus, could make PT-char suitable for use as a fuel source. In this study, PT-char was blended with torrefied wood and microalgae biomass to demonstrate the suitability of using PT-char-biomass-fuel blend as an energy feedstock. To this effect, a mixture design of experiments was used to formulate the PT-char biomass blends and regression analysis was employed to select an optimum blend formulation for the combustion and mechanical properties of the blends. Proximate analysis results showed a non-linear increase in the volatile matter and a non-linear decrease in the fixed carbon and ash yield as the biomass ratio increased. The calorific value also increased on an additive basis with increasing biomass proportion. The elemental analysis results showed a decrease in the calcium, zinc and bromine contents and an increase in the potassium and iron contents increased with increasing biomass proportion. Likewise, the sulphur content decreased while the oxygen, hydrogen and nitrogen contents increased with increasing biomass ratio. vi Thus, the fuel properties of the blends improved with increasing biomass ratio and without compromising the calorific value of the PT-char. Moreover, the TG-MS analysis showed that the PT-char and the respective blends did not show any release SO2 up to 650°C. Thus, making the fuel suitable for use in low temperature applications such as household and certain boilers. The results of the regression analysis showed that the blend formulation with the highest proportions of biomass, thus C55-T30-M15, is the optimum blend to produce a solid fuel with a low initial decomposition (214°C) and char ignition temperatures (532°C) as well as maximum burn-out temperature (640°C). In essence, the high thermal reactivity of PT-char is improved when both biomasses are loaded at maximum ratios as per the experimental design. The results of the MS showed a decrease in CO2 and NO2 emissions with increasing biomass proportion. The optimum blend (C55-T30-M15) was found to have a comparably higher gross calorific value (26 MJ/kg), lower sulphur content (1.1 wt.%), low ash yield (11wt.%) and lower concentration of minerals (i.e. zinc) than raw PT-char. In addition, the volatile matter content of the blend (20 wt.%) was found to be higher than that of PT-char and the ignition temperature of the optimum fuel blend was relatively lower and its burnout temperature higher than that of PT char. The MS results revealed that the CO2 and NO2 emissions were higher in the optimum blend than the PT-char. The mechanical properties of the pellets; impact resistance and compressive strength increased with increasing biomass blending ratio and even more so with increasing microalgae ratio. The C55-T30-M15 and C75-T10-M15 were selected as optimum blends using regression analysis and both blends exceeded the benchmark for mechanical properties except for water resistance. The blending did not improve the water resistance and all the blends did not meet the minimum threshold for water resistance. Overall, the blending of PT-char with torrefied wood and microalgae biomass has shown to improve the fuel properties PT-char, and therefore, making it a suitable potential fuel source.
- Description
- Thesis (MSc) -- Faculty of Science, 2021
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (xxi, 192 pages)
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
- Rights
- All Rights Reserved
- Rights
- Open Access
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NMU School of BioMolecular and Chemical Sciences
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Dube, C.pdf | 4 MB | Adobe Acrobat PDF | View Details Download |