Förbränning av pellets framställda av defibrerad granråvara
Fuel pellets are in Sweden mainly produced from sawdust and cutter shavings. Before the pelletising process the raw material is dried to attain consistent moisture content and ground up in a hammer mill. In the densification process (pelletising) the ground material is forced through holes in a rota...
| Autor principal: | |
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| Formato: | L3 |
| Lenguaje: | sueco Inglés |
| Publicado: |
SLU/Dept. of Forest Resource Management
2008
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| Materias: |
| _version_ | 1855572002744565760 |
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| author | Henriksson, Gunnar |
| author_browse | Henriksson, Gunnar |
| author_facet | Henriksson, Gunnar |
| author_sort | Henriksson, Gunnar |
| collection | Epsilon Archive for Student Projects |
| description | Fuel pellets are in Sweden mainly produced from sawdust and cutter shavings. Before the pelletising process the raw material is dried to attain consistent moisture content and ground up in a hammer mill. In the densification process (pelletising) the ground material is forced through holes in a rotating die. This heats up the wood particles which cause them to soften and self bond. After the process the pellets are cooled, sieved and bagged.
The milling process creates a wide range of particle sizes. How the particle size distribution influences the characteristics of pellets are still rather unclear although it is generally assumed that a mixture of particle sizes will increase pellet durability. The influence of particle size distribution of a pellet on burning characteristics is not known. In pulp mills the woody raw material is usually converted into chips which thereafter are treated in a defibrator into fibre bundles. Such a material is physically different from a mill ground material.
One of the main aims of this work was to investigate the burning characteristics of pellets produced from defibrated spruce wood and to compare these pellets with pellets made from mill ground saw dust. The influence of saw dust particle size distribution on burning characteristics was also evaluated for industrially produced and laboratory made pellets.
It was found that the char combustion time of pellets made from defibrated wood was somewhat longer than that of saw dust pellets. Anyhow, the differences were not statistically significant. The particle size distribution of the saw dust did affect the burning characteristics e.g. pellets made of a coarse fraction had faster char combustion than pellets made from a fine fraction. The investigation also revealed that during the pelletising (densification) process the saw dust was grinded to smaller particle sizes. |
| format | L3 |
| id | RepoSLU12113 |
| institution | Swedish University of Agricultural Sciences |
| language | swe Inglés |
| publishDate | 2008 |
| publishDateSort | 2008 |
| publisher | SLU/Dept. of Forest Resource Management |
| publisherStr | SLU/Dept. of Forest Resource Management |
| record_format | eprints |
| spelling | RepoSLU121132017-11-07T11:17:02Z Förbränning av pellets framställda av defibrerad granråvara Combustion of pellets produced from refined Norway spruce wood Henriksson, Gunnar biobränsle defibrering pelletering partikelstorlek Fuel pellets are in Sweden mainly produced from sawdust and cutter shavings. Before the pelletising process the raw material is dried to attain consistent moisture content and ground up in a hammer mill. In the densification process (pelletising) the ground material is forced through holes in a rotating die. This heats up the wood particles which cause them to soften and self bond. After the process the pellets are cooled, sieved and bagged. The milling process creates a wide range of particle sizes. How the particle size distribution influences the characteristics of pellets are still rather unclear although it is generally assumed that a mixture of particle sizes will increase pellet durability. The influence of particle size distribution of a pellet on burning characteristics is not known. In pulp mills the woody raw material is usually converted into chips which thereafter are treated in a defibrator into fibre bundles. Such a material is physically different from a mill ground material. One of the main aims of this work was to investigate the burning characteristics of pellets produced from defibrated spruce wood and to compare these pellets with pellets made from mill ground saw dust. The influence of saw dust particle size distribution on burning characteristics was also evaluated for industrially produced and laboratory made pellets. It was found that the char combustion time of pellets made from defibrated wood was somewhat longer than that of saw dust pellets. Anyhow, the differences were not statistically significant. The particle size distribution of the saw dust did affect the burning characteristics e.g. pellets made of a coarse fraction had faster char combustion than pellets made from a fine fraction. The investigation also revealed that during the pelletising (densification) process the saw dust was grinded to smaller particle sizes. Idag används i huvudsak sågspån, kutterspån och flis som pellets råvara. Hammarkvarnar används ofta vid sönderdelning av råvaran innan pelletering. Massaindustrin däremot använder raffinörer som sönderdelare och får en s.k. defibrerad fiber vilken är helt olik den som hammarkvarnen producerar. Syftet med detta arbete var att undersöka förbränningsegenskaperna och förbränningsförloppet för pellets producerad av defibrerad granråvara. Även inverkan av råvarans fraktionsfördelning (fraktionsstorleken) på förbränningsförloppet undersöktes. Pellets pressade av två olika fraktionssammansättningar och en industriproducerad referenspellets undersöktes (förbrändes). Det som framkom antyder goda förbränningsegenskaper för raffinör pellets, däremot tycks fraktionsstorleken ha en inverkan på förbränningsförloppet. Pelleteringsegenskaperna var inte optimala för defibrerat material och det var stora problem att pressa materialet. Hållfasthet och densitet på de pellets som pressades motsvarade dock standardvärden för kommersiell pellets. Vissa intressanta observationer gjordes, bland annat att fraktionsfördelning förändrades vid pelleteringen pga. en malningseffekt i pressen. Vid slipning av pelleten upptäcktes problem med hållfastheten som antyder att tendensen till smulning är större i pelletens konvexa del sedd i pressriktningen än i den andra änden. SLU/Dept. of Forest Resource Management 2008 L3 swe eng https://stud.epsilon.slu.se/12113/ |
| spellingShingle | biobränsle defibrering pelletering partikelstorlek Henriksson, Gunnar Förbränning av pellets framställda av defibrerad granråvara |
| title | Förbränning av pellets framställda av defibrerad granråvara |
| title_full | Förbränning av pellets framställda av defibrerad granråvara |
| title_fullStr | Förbränning av pellets framställda av defibrerad granråvara |
| title_full_unstemmed | Förbränning av pellets framställda av defibrerad granråvara |
| title_short | Förbränning av pellets framställda av defibrerad granråvara |
| title_sort | förbränning av pellets framställda av defibrerad granråvara |
| topic | biobränsle defibrering pelletering partikelstorlek |