7 research outputs found
SÄgspÄnets malningsgrad
I denna undersökning har torkat sÄgspÄn malts med olika sÄllgrovlekar (2 mm, 4 mm, 6 mm och 8 mm) och anvÀnts för pelletstillverkning. Som jÀmförelse har icke malt, endast material som passerar 4 x 4 mm anvÀnts. Materialen har konditionerats till fukthalter mellan 10 % och 13 % innan pelletering. Försöken gjordes pÄ SLU:s pilotanlÀggning med en kapacitet pÄ ca 400 kg/h.
Under försöken uppmĂ€ttes energiĂ„tgĂ„ng vid malning, energiĂ„tgĂ„ng vid pelletering samt fysikaliska kvalitetsegenskaper pĂ„ produkten. Ăven askhalter, extraktivĂ€mnesinnehĂ„ll och styckedensitet pĂ„ pellets producerade av olika spĂ„nfraktioner uppmĂ€ttes.
TvÄ prover, pellets tillverkade av 8 mm spÄn och 2 mm spÄn, togs ut för att studera emissioner av kolmonoxid, koldioxid och metan vid lagring och för att se om det Àr skillnader mellan pellets tillverkade av olika grovt malda rÄvaror.
Resultaten visade att spĂ„nets malgrad pĂ„verkar framför allt bulkdensiteten pĂ„ produkten genom att mer finmalt spĂ„n ger en högre bulkdensitet. Ăvriga kvalitetsparametrar pĂ„verkades i mindre grad eller inte alls av spĂ„nets malgrad.
Det Àr ocksÄ möjligt att producera pellets av acceptabel kvalitet helt utan malning av spÄnet. Endast en bortsÄllning av övergrovt material verkar vara tillrÀckligt för att ge en acceptabel rÄvara.
Emissionstesterna visade att det Àr ingen skillnad mellan pellets tillverkade av spÄn malt pÄ 2 mm sÄll och spÄn malt pÄ 8 mm sÄll. ExtraktivÀmneshalten i pelleterat material var nÄgot lÀgre Àn i den icke pelleterade rÄvaran. Detta beror antagligen pÄ lÀttflyktiga Àmnen som avgÄr vid de förhöjda temperaturerna som uppstÄr i pelletringsprocessen
Using macromolecular composition to predict optimal process settings in ring-die biomass pellet production
This study was performed to investigate if the process settings that give high pellet durability can be modelled from the biomassâ macromolecular composition. Process and chemical analysis data was obtained from a previous pilot-scale study of six biomass assortments that by Principal Component Analysis (PCA) was confirmed as representative for their biomass types: hardwood, softwood bark, short rotation coppice (SRC), and straw and energy crops. Orthogonal Partial Least Squares Projections to Latent Structures (OPLS) models were created with the content of macromolecules as factors and the die compression ratio and the feedstock moisture content at which the highest pellet durability was obtained as responses. The models for die compression ratio (R2X = 0.90 and Q2 = 0.58) and feedstock moisture content (R2X = 0.87 and Q2 = 0.60), rendered a prediction error for obtained mechanical durability of approximately ±1%-unit, each. Important factors for modelling of the die compression ratio were: soluble lignin (negative), acetyl groups (negative), acetone extractives (positive), and arabinan (positive). For modelling of the feedstock moisture content, Klason lignin (negative), xylan (positive), water-soluble extractives (negative), and mannan (negative), were the most influential. Results obtained in this study indicate that it is possible to predict optimal process conditions in pelletizing based on the macromolecular composition of the raw material. In practice, this would mean a higher raw material flexibility in the pellet factories through drastically reduced risk when introducing new raw materials
Pelleting torrefied biomass at pilot-scale â Quality and implications for co-firing
The co-firing of solid biofuels in coal plants is an attractive and fast-track means of cutting emissions but its potential is linked to biomass densification. For torrefied materials this topic is under-represented in literature. This pilot-scale (121â203 kg hâ1) pelleting study generated detailed knowledge on the densification of torrefied biomass compared to untreated biomass. Four feedstock with high supply availability (beech, poplar, wheat straw and corn cob) were studied in their untreated and torrefied forms. Systematic methods were used to produce 180 batches of 8 mm dia. pellets using press channel length (PCL) and moisture content (MC) ranges of 30â60 mm and 7.3â16.6% (wet basis) respectively. Analysis showed that moderate degrees of torrefaction (250â280 °C, 20â75 min) strongly affected pelleting behaviour. The highest quality black pellets had a mechanical durability and bulk density range of 87.5â98.7% and 662â697 kg mâ3 respectively. Pelleting energy using torrefied feedstock varied from â15 to +53 kWh tâ1 from untreated with increases in production fines. Optimal pelleting MC and PCL were reduced significantly for torrefied feedstock and pellet quality was characterised by a decrease in mechanical durability and an increase in bulk density. Energy densities of 11.9â13.2 GJ mâ3 (as received) were obtained
Complications and survival after surgical treatment of 214 metastatic lesions of the humerus
Background: The humerus is the second most common long-bone site of metastatic bone disease. We report complications, risk factors for failure, and survival of a large series of patients operated on for skeletal metastases of the humerus. Materials and methods: This study was based on 208 patients treated surgically for 214 metastatic lesions of the humerus. Reconstructions were achieved by intramedullary nails in 148, endoprostheses in 35, plate fixation in 21, and by other methods in 10. Results: The median age at surgery was 67 years (range, 29-87 years). Breast cancer was the primary tumor in 31%. The overall failure rate of the surgical reconstructions was 9%. The reoperation rate was 7% in the proximal humerus, 8% in the diaphysis, and 33% in the distal part of the bone. Among 36 operations involving an endoprosthesis, 2 were failures (6%) compared with 18 of 178 osteosynthetic devices (10%). In the osteosynthesis group, intramedullary nails failed in 7% and plate fixation failed in 22%. Multivariate Cox regression analysis showed that prostate cancer was associated with an increased risk of failure after surgery (hazard ratio, 7; P < 0.033). The cumulative survival after surgery was 40% (95% confidence interval [CI] 34-47) at 1 year, 21% (95% CI, 15-26) at 2 years, and 16% (95% CI, 12-19) at 3 years. Conclusions: Our method of choice is the cemented hemiprosthesis for pathologic proximal humeral fractures and interlocked intramedullary nail for lesions in the diaphysis. Pathologic fractures in the distal humerus are uncommon and associated with a very high reoperation rate. Level of evidence: Level IV, Case Series, Treatment Study. (C) 2012 Journal of Shoulder and Elbow Surgery Board of Trustees