In-wood grinding and screening of forest residues for biomass feedstock applications

Dukes, C. Cory; Baker, Shawn A.; Greene, W. Dale

doi:10.1016/j.biombioe.2013.02.032

Cited by 28 publications

(27 citation statements)

References 12 publications

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“…25% during a time study of a small mechanical screen. The share of delay times during a time study of a grinder/trammel screen system, reported by Dukes et al [23], was even higher, ranging from 34% to 60% of the total scheduled time. Thus, there is still a strong need to carry out long-term studies on machines that can be used to screen woodchips in order to achieve more reliable estimates of delay times.…”

Section: Discussionmentioning

confidence: 86%

“…In contrast, fine particles reduce the air circulation within the woodchip piles, which decreases drying speed and increases the risk of self-combustion and spore formation due to microbial activity and fungal infestation [21]. Previous studies on screening machines already have shown that it is possible to remove fine and/or oversize particles [14,[20][21][22][23]. However, the machines tested within these studies differed in terms of throughput capacity and working principle: trommel screens and vibrating desks are only able to remove fine particles from the material stream, whereas star screens are able to separate woodchips into three fractions.…”

Section: Discussionmentioning

confidence: 99%

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Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues

Huber

Kroisleitner

Stampfer

2017

Forests

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Low harvesting costs and increasing demand for forest-derived biomass led to an increased use of full-tree (FT) harvesting in steep terrain areas in Austria. Logging residues, as a by-product of FT harvesting, present an easily accessible bioenergy resource, but high portions of fine particles and contaminants like earth particles and stones make them a complex and difficult fuel, as they affect storage capability, conversion efficiency, or emission rates adversely. The present research focuses on the productivity and performance of a star screen, which was used to remove fine and oversize particles from previously chipped, fresh Norway spruce (Picea abies (L.) Karst.) logging residue woodchips. Three screen settings, which differed in terms of different rotation speeds of the fine star elements (1861 rpm, 2239 rpm, 2624 rpm) were analyzed. Time studies of the star screen were carried out to estimate screening productivity and costs. Furthermore, 115 samples were collected from all material streams, which were assessed for particle size distribution, calorific value, ash content, and component and elemental composition. Average productivity was 20.6 tonnes (t) per productive system hour (PSH 15 ), corresponding to screening costs of 9.02 €/t. The results indicated that the screening of chipped logging residues with a star screen influenced material characteristics of the medium fraction, as it decreased the ash content, the incidence of fine particles, and the nutrient content. The different screen settings had a noticeable influence on the quality characteristics of the screening products. An increase of the rotation speed of the fine stars reduced screening costs per unit of screened material in the medium fraction, but also lowered screening quality.

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Section: Discussionmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues

Huber

Kroisleitner

Stampfer

2017

Forests

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“…Our findings showed that slash material had a significantly higher ash content compared with the other material types. Dukes et al (2013) analyzed the ash content of two residue types: larger residues from delimbing with a pull-through delimber and branches, and bark removed from a chain flail machine. They found a 4 and 11.9% ash content for the two material types, respectively.…”

Section: Feedstock Quality and Implications For Managementmentioning

confidence: 99%

“…The presence of ash in feedstock reduces thermochemical conversion efficiencies in processes, such as gasification and pyrolysis (Lacey et al, 2015). Research on methods to reduce ash content in feedstocks have suggested better material handling techniques to minimize contamination (i.e., soil and sand) and mechanical screening to sort out smaller fractions in "hog fuel" which are typically heavier in contamination (Dukes et al, 2013;Greene et al, 2014). In addition to contamination, bark has been found to be a contributor to ash content (Lehtikangas, 2001;Flibakk et al, 2001;Picchio et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Quality of Feedstock Produced from Sorted Forest Residues

Bisson

Han²

2016

AJBB

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Emerging biomass conversion technologies, such as small scale mobile biochar or pyrolysis/torrefaction machines, aim to use forest residues left after extracting merchantable timber from timber harvest or fuel reduction thinning operations. The residues generated from these operations typically produce low quality feedstock which may not be suitable for new biomass conversion technologies. In an effort to increase feedstock quality, our study separated sub-merchantable trees and tops from piled limbs during the timber harvest. A portion of the separated material was further processed to remove limbs to create five material types: processed and unprocessed, conifer and hardwood stem wood, and slash (stems, limbs and chunks). These materials were comminuted with a disc-chipper or a grinder. The quality of the feedstock produced was characterized by moisture content, particle-size distribution, bulk density, and ash content. Moisture content of sample collected ranged from 19 to 29%. The mean geometric lengths for unprocessed hardwood, unprocessed conifer, processed hardwood, processed conifer, and slash were 20.60, 18.27, 18.16, 17.41, and 47.47 mm, respectively. The bulk density of the five material types ranged from 137.20 -322 kg/m 3 . The least amount of ash were observed in processed conifer samples (0.27%) and greatest in ground slash (1.5%). The results showed that a high quality feedstock can be produced by separating stem wood from other residues during a harvest.

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“…Systems based on comminution at the landing increase the payload of trucks, since the comminuted material is less bulky, and thereby reduce transport costs (Eriksson et al 2014a;Eriksson et al 2014b). Screening also reduces the amount of fine material contaminants at the source and increases the quality of the produced fuel (Eriksson et al 2013;Dukes et al 2013;Laitila and Nuutinen 2015). Thanks to screening, an ash content of 0.4-2.3% for ground stumps has been reported, while the wood-matter losses have been rather nominal (Laitila and Nuutinen 2015).…”

Section: Procurement Of Stumps and Delimbed Stems For Fuelmentioning

confidence: 99%

The cost competitiveness of conifer stumps in the procurement of forest chips for fuel in Southern and Northern Finland

Laitila¹,

Ranta²,

Asikainen³

et al. 2015

Silva Fenn.

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• Pre-grinding and integrated screening is a way of guaranteeing fuel quality, but, when the stumps' ash content is six per cent or below, the procurement costs are higher than with grinding of stumps at the plant. Because of high transportation costs, stump harvesting is the most profitable in Southern Finland, where there is greater availability of stumps than in Northern Finland. AbstractThe aim of this study was to evaluate cost competitiveness, at regional level, of various systems for stump transportation and grinding, and to compare the results to the procurement costs of delimbed stems from early thinnings at the stand and regional level. The accumulation and procurement costs of stumps and delimbed stems were estimated within a 100-kilometer radius from two power plants located in Kouvola and in Kajaani. The analyses were performed as simulated treatments in clear cuts and thinnings of young stands, using existing productivity and cost functions, alternative ash percentages for stump wood, and yield calculations based on the forest industry regeneration felling stand data and the sample plots data of the National Forest Inventory of Finland. The results were expressed as Euros per solid cubic meter (€ m -3 ) and Euros per megawatt hour (€ MWh -1 ).The results highlight the need to improve stump fuel quality and increase the heating value. The procurement cost of stumps was about 1 € MWh -1 lower in Kouvola compared to Kajaani, when using conceivable ash content of 6% for stumps ground at the plant, and ash content of 1.5% for stumps pre-ground at the roadside landing. The procurement costs of stumps were, on average, 0.55 € MWh -1 lower compared to delimbed stems in Kouvola, and on average 0.6 € MWh -1 higher in Kajaani. Pre-grinding and integrated screening is a feasible way to guarantee the fuel quality expressed as ash content already at roadside landings, but the procurement costs are higher compared to grinding stumps at the plant, when the ash content of ground stumps is 6% or less.

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In-wood grinding and screening of forest residues for biomass feedstock applications

Cited by 28 publications

References 12 publications

Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues

Performance of a Mobile Star Screen to Improve Woodchip Quality of Forest Residues

Quality of Feedstock Produced from Sorted Forest Residues

The cost competitiveness of conifer stumps in the procurement of forest chips for fuel in Southern and Northern Finland

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