Fig. 2.
APP demonstration plant, Swindon, UK.
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This paper focuses on two related experiments preformed recently on APP’s demonstration plant. Wood pellet feedstock augmented with sulphur was used with a view to understanding sulphur release during gasification. After detailing the materials and methods employed, the results are presented, analysed and discussed, followed by summary conclusions.
2. Materials
Along with the actual process, the feedstock (composition detailed in Table 1) and fluid bed material (Table 2) are integral to this research. Although the plant routinely handles RDF, the experiments reviewed in this paper focus on a wood pellet feed. The pellets were sourced locally and comply with the European standard CEN/TS 14691 (Big Barn, 2012). They are cylindrical in shape, with a diameter of 6–8 mm and varying length (⩾3 mm). Virgin sawdust is used in their manufacture, derived from a mix of spruce (ca. 50%) and pine with Douglas fir (ca. 50%) (Rowley, 2013). Compositional analysis results are presented in Table 1. Generally pellets are manufactured by compressing dry sawdust or wood shreds under high pressure until the lignin softens and binds the material together (Forestry Commission, 2007). This, combined with a low moisture and ash content, makes them a clean, high energy density fuel (typically two thirds that of coal). They also have a consistent composition and flow easily, making them an ideal experimental feed. By contrast, RDF has a less consistent composition and feedrate, thus introducing more variables to experiments. This can complicate analysis as well as the reproduction of and comparison between experiments.