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Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes
Van der Westhuizen, L. 2025. Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/cda9abbd-6a95-474d-b0a9-30...
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| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614067754008576 |
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| access_status_str | Open Access |
| author | Van der Westhuizen, Lodewicus |
| author2 | Gorgens, Johann F. |
| author_browse | Gorgens, Johann F. Van der Westhuizen, Lodewicus |
| author_facet | Gorgens, Johann F. Van der Westhuizen, Lodewicus |
| author_sort | Van der Westhuizen, Lodewicus |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Van der Westhuizen, L. 2025. Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/cda9abbd-6a95-474d-b0a9-30f9f2f58bb9 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132353 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:46:09.042Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132353 Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes Van der Westhuizen, Lodewicus Gorgens, Johann F. Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering. Lignocellulose -- Biotechnology Coal -- Combustion Binders (Materials) Briquets (Fuel) Environmental impact analysis UCTD Van der Westhuizen, L. 2025. Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes. Unpublished doctoral dissertation. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/cda9abbd-6a95-474d-b0a9-30f9f2f58bb9 Thesis (PhD)--Stellenbosch University, 2025. ENGLISH ABSTRACT: Coal is a major energy resource globally and will be for the foreseeable future. In addition to greenhouse gas (GHG) emissions, coal utilisation also results in the production of coal-fines, which represent an environmental and economic burden. Co-utilizing sustainable, lignocellulosic biomass for briquetting of coal-fines allows their use in existing coal-infrastructure, posing as a realistic and easily implementable solution to valorising coal-fines discards whilst reducing coal dependency. This investigation explores the technical, economic, and environmental feasibility of steam-exploded lignocellulose as a binder and fuel for coal-fines briquetting. Pilot-scale experimental investigations evaluated the performance of steam-exploded lignocellulose binders produced from various feedstocks, including sugarcane bagasse (SCB), corn stover (CS), black wattle (BW), and pine. SCB was used for screening and optimization, revealing that steam explosion temperature, briquetting temperature, and binder addition rate were key factors in producing strong briquettes. Optimal steam explosion conditions of 190°C for 15 minutes were identified for SCB, with a synergistic effect between briquetting temperature and binder addition, resulting in briquettes with tensile compressive strengths of 1205 kPa at 100°C and 17.8% binder addition. Briquettes showed acceptable water resistance, maintaining structure after immersion and exhibiting a water absorption index of 82%. Briquettes retained their integrity during pyrolysis at 600°C but lost about 90% of their original strength. SCB and CS outperformed BW and pine in producing stronger briquettes. The binding mechanism was primarily due to high aspect ratio fibres formed during steam explosion, which enabled mechanical interlocking with coal-fines. SCB, CS, and BW fibres underwent defibration, increasing aspect ratio, while pine particles fractured, resulting in lower aspect ratios and weaker briquettes. Excessively high lignin content was detrimental to briquettes strength, but reducing the lignin content too severely (to 6wt%) resulted in an approximately 40% reduction in briquette strength. Briquette water resistance decreased with an increase in (hydrophilic) hemicellulose content. Steam explosion treatment could be optimised to effectively co-produce water-soluble xylan-derived xylo-oligosaccharides (XOS) at acceptable yields and high-performing binders (solids), for strong briquettes. Introducing dilute-alkali impregnation (2.5%-5% Na2CO3 or NaOH) prior to steam explosion reduced xylose and degradation products, yielding 50.7% XOS with no significant xylose formation and briquettes with strengths comparable to those without alkali treatment. However, reduced hemicellulose removal due to alkali catalysis negatively impacted water resistance. Co-producing XOS with binders from SCB in a biorefinery linked to a sugar mill, reduced the minimum selling price (MSP) of the binder from $396/t (without co-products) to $280-290/t, resulting in effective binder costs of $28-50.5/t briquettes at binder inclusion levels of 10%-18%. A case study showed that binder addition rates of up to 10.8% were economically viable, not exceeding briquette costs of $50/t and with significant GHG emission reductions compared to lumped coal utilisation. Greater binder addition rates further reduced emissions, but also increased costs disproportionally, justifiable only with higher carbon taxes. Producing SCB-only pellets by its combination with pretreated SCB as binder was found to be financially unfeasible due to a high MSP of $250/t, greatly exceeding the existing market prices for wood pellets. This dissertation demonstrates the techno-economic and environmental feasibility of using steam-exploded lignocellulose as a binder for coal-fines within a biorefinery context. This technology adds value to both lignocellulosic residues and coal-fines, potentially expanding the range of renewable energy solutions that can reduce society's dependence on fossil fuels. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Doctoral 2025-06-04T12:55:48Z 2025-06-04T12:55:48Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132353 en Stellenbosch University 261 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Lignocellulose -- Biotechnology Coal -- Combustion Binders (Materials) Briquets (Fuel) Environmental impact analysis UCTD Van der Westhuizen, Lodewicus Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes |
| title | Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes |
| title_full | Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes |
| title_fullStr | Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes |
| title_full_unstemmed | Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes |
| title_short | Techno-economic and environmental investigation of steam-exploded lignocelluloses as binder for coal-fines briquettes |
| title_sort | techno economic and environmental investigation of steam exploded lignocelluloses as binder for coal fines briquettes |
| topic | Lignocellulose -- Biotechnology Coal -- Combustion Binders (Materials) Briquets (Fuel) Environmental impact analysis UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132353 |
| work_keys_str_mv | AT vanderwesthuizenlodewicus technoeconomicandenvironmentalinvestigationofsteamexplodedlignocellulosesasbinderforcoalfinesbriquettes |