The objective of the present work was to demonstrate the possibilities to reduce the emission of fine particle forming alkali during co-combustion of wood with peat in a full scale (150 kW) grate fired boiler. For this purpose the particle emissions from a 150 kW district heating grate fired boiler situated in northern part of Kramfors, Sweden, were studied. During the experiment the district heating boiler was fired with sawdust fuel with a 0, 10 and 20 wt-% (zero, low, high) peat content respectively. Mass concentrations and particle size distribution were measured by using a DLPI (13-step low-pressure cascade impactor) with a precyclone. The particle matter was analyzed for morphology and elemental composition using SEM/EDS (Scanning electron microscopy/energy dispersive spectroscopy). In addition, chemical equilibrium model calculations were used to interpret the experimental findings. The present study clearly shows that reduction of fine particles (< 1 um) is possible when co-combusting wood pellets with peat pellets in grate fired boilers. When 10 wt % peat was added to the wood/peat fuel mixture the fraction of fine particles was significantly decreased (about half of that emitted during pure softwood pellet combustion). The fine particles were for all fuel types/mixtures dominated by potassium, chlorine, sulfur, sodium and zinc. The result from this work therefore shows that a significant reduction of fine particle alkali is possible when co-combusting wood pellets with peat. The results from the thermo-chemical calculations suggest that a significant share of the potassium is retained in the bottom ash as a K rich silicate slag and as KAlSi2O6(s) (Leucite) when co-combusting sawdust with peat. / <p>Validerat; 20110920 (anonymous)</p>
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:ltu-55062 |
| Date | January 2011 |
| Creators | Nigusie, Kiflom Gebrehiwot |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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