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- Anerud, Erik, et al.
(författare)
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Evaluation of the performance of a three-dimensional vibrating test rig for cleaning stumps
- 2012
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Ingår i: Australian Journal of Agricultural Engineering. - 1836-943X. ; 3, s. 51-58
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Tidskriftsartikel (refereegranskat)abstract
- It has been shown that vibrating devices can successfully be used for separation and removal of unwanted/contaminant material, for both laboratory and full-scale industrial purposes. The presence of impurities on energy-rich softwood stumps is a major drawback when using stumps as fuel, since it leads to high ash content. Vibration methods can be an efficient approach to remove excess impurities and achieve acceptable ash content. Stumps are usually shaken in connection with harvesting and stored afterwards to facilitate the removal of contaminants. The required storage duration can lead to high dry matter losses and a faster and efficient cleaning method such as vibration is highly desirable. This study evaluated the performance of an adjustable three-dimensional vibrating test rig designed to assess the cleaning efficiency of vibration-based methods. Vibrating parameters such as acceleration amplitude, frequency and displacement of the test rig were determined for 12-24 mm distance between eccentric weight centre of mass and the rotating shaft of electric motors at rotation velocity 19.16-29.17 Hz. The acceleration amplitude ranged from 1.38 to 5.71 g. The parameters could be repeated irrespective of direction and number of vibration directions. The test rig was therefore considered to be a reliable tool for determining and evaluating the efficiency of vibration in removing contaminants from stumps.
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- Anerud, Erik, et al.
(författare)
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Fuel quality of Norway spruce stumps - influence of harvesting technique and storage method
- 2011
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 26, s. 257-266
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Tidskriftsartikel (refereegranskat)abstract
- The interest in using stump biomass as a biofuel has recently increased in Sweden. The uneven consumption of wood fuel during the year creates a need for storage. This study examined the properties of stump biomass and how they vary at two sites in Sweden depending on harvesting technique, storage method and storage period. Norway spruce stumps, extracted using three different stump harvesting heads (Pallari, Rotary Cutter and Aalto), were stored in windrows or heaps. After 3 months, stumps stored in heaps were gathered into windrows. The fuel quality parameters moisture content (MC), ash content (AC) and calorific value (CV) were evaluated on five occasions in the period May 2008-September 2009. After 16 months of storage, the MC in all treatments had decreased to <25% (wet basis). Average AC decreased from 3.8% to around 1% (dry basis), whereas CV marginally increased. Stumps split during harvesting dried better than those harvested in one piece. The influence of storage method was minimal, although initial storage in heaps allowed better drying in the stumps harvested in one piece. In general, fuel quality improved in all treatments after storage.
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- Anerud, Erik
(författare)
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Stump as a fuel : the influence of harvesting technique and storage method on fuel quality of Norway spruce
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Uncertain long-term availability of fossil fuels and the negative environmental impact of using it have created an urgent need for reliable renewable energy sources. Wood fuel, particularly forest residues is one of these sources which are in high demand in Sweden today. Stumps can be used as a complement to these, since they contain high concentrations of energy-rich lignin and extractives. However, stump removal can have negative environmental effects such as reduction of biodiversity and disturbance of nutrient balance in the soil. As to the fuel quality of stump biomass, there are some concerns connected with the utilisation of stumps since presence of excessive contaminants leads to high ash contents which reduce its value as fuel and causes operating problems. To ensure the supply of fuel of acceptable quality, an optimal system for harvesting, handling, and storage must be devised for stump procurement. The main aim of this work was to evaluate various stump harvesting techniques, storage methods (windrow or heaps), and different storage durations at two geographical locations and examine their effect on the fuel quality of Norway spruce stump biomass. Fuel quality parameters moisture content, ash content and calorific value were evaluated on five occasions during May 2008 - September 2009. Stump harvesting techniques that split the stumps allowed better drying during 13 months of storage. Storage method had no clear effect on these stumps. The ash content decreased considerably, particularly when transport and crushing took place at temperatures exceeding 0°C. In general, fuel quality was improved in all treatments after storage. However, as the storage time progressed, the net energy increment became continuously smaller due to the increased substance losses.
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- Anerud, Erik
(författare)
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Stumps as fuel : the influence of handling method on fuel quality
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wood fuels make a key contribution to renewable energy sources in the Nordic countries. The growing demand for forest biomass can be partly met by utilising energy-rich stumps left after clear cutting. As fuel, stump wood is commonly associated with a high presence of contaminants, resulting in high ash content. The concentration of contaminants depends on factors such as soil type, weather conditions, harvesting method, storage duration and other handling operations. The high ash content is a major drawback when using stump wood as fuel. Handling methods that could improve fuel quality are therefore highly desirable. To produce a fuel of acceptable quality, i.e. with low moisture and ash content and high energy value, the above-mentioned factors require evaluation and quantification. In this thesis, various handling methods within the supply chain for Norway spruce stump and their effects on the biomass as fuel are evaluated. The following handling processes are dealt with: harvesting technique, pre-treatments including stump splitting/fractionation and cleaning using vibration or sieving, storage methods and storage duration. Choice of stump harvesting head proved to have an impact on fuel quality, as splitting of stumps during extraction allowed better drying during storage. Such stumps could be stored directly in windrows, since no difference could be established between this method and storage in heaps prior to windrow storage. In general, storage improved fuel quality. Changes in fuel quality parameters do not reflect the whole picture, however, since dry matter losses occur during storage, and therefore the storage period should be kept as short as possible. During winter months, when demands for fuel are highest, stump ash content can be high, since frozen contaminants are difficult to detach from stumps during transport. To achieve acceptable fuel quality during high demand periods, long storage duration or a pre-treatment involving additional stump cleaning is required. Fuel quality was clearly improved by vibration-based cleaning before the comminution of stumps or by sieving stump wood after crushing. These methods can allow stump wood fuel of acceptable quality to be supplied within a harvesting season.
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