| 1. |
- Agar, David, et al.
(författare)
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A systematic study of ring-die pellet production from forest and agricultural biomass
- 2018
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 180, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- Continuous global growth in the pellet production industry and renewable energy policy targets have driven interest in under-utilised lignocellulosic biomass. In this comprehensive study, pelleting trials were systematically carried out using a pilot-scale ring-die pellet press with eight different biomass feedstock; logging residues, pine bark, wheat straw, reed canary grass, coppiced willow, poplar and beech. A standard spruce/pine sawdust blend was pelleted as a reference material.Pellets were produced from feedstock at four different moisture content levels, through two press channel lengths and three replicate steady-state sampling periods. A total of 192 batches of 8 mm diameter pellets were produced within a press channel length and moisture content range of 30-60 mm and 9-17% respectively. Pellet production had a range of 141-206 kg h(-1) and relatively good pellet quality was achieved for a majority of the studied feedstock. The best pellet batches had a mechanical durability and bulk density range of 91-99% and 532-714 kg m(-3) respectively, corresponding to an energy density range of 8.3-12.5 GJ m(-3) (as received). The extruded pellet temperature ranged between 99 and 131 degrees C and was correlated to pellet bulk density for hardwoods, pine bark and forest residues. The normalised energy (reference value of 1) used in pelleting all materials varied between 0.76 and 1.3 being highest for the hardwoods and lowest for straw and forest residues.
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| 2. |
- Agar, David, et al.
(författare)
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Pelleting torrefied biomass at pilot-scale – Quality and implications for co-firing
- 2021
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 178, s. 766-774
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Tidskriftsartikel (refereegranskat)abstract
- 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 (121–203 kg h−1) 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 30–60 mm and 7.3–16.6% (wet basis) respectively. Analysis showed that moderate degrees of torrefaction (250–280 °C, 20–75 min) strongly affected pelleting behaviour. The highest quality black pellets had a mechanical durability and bulk density range of 87.5–98.7% and 662–697 kg m−3 respectively. Pelleting energy using torrefied feedstock varied from −15 to +53 kWh t−1 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 11.9–13.2 GJ m−3 (as received) were obtained.
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| 3. |
- Bernesson, Sven, et al.
(författare)
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Glycerin från omförestring av vegetabiliska oljor som tillsatsmedel : praktiska försök med pelletering och eldning av några biobränslen
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- During transesterification of vegetable oils in particular, but also animal fats and used frying oils, glycerine is obtained as a by-product. It is important for transesterification economics that the glycerine by-product can be sold for the best possible price. In Sweden today, glycerine is often sold to biogas production for a few Swedish crowns per kilo. If other markets where glycerine replaces a more expensive product can be found, the willingness to pay for glycerine will increase. This project examined whether glycerine can be used as an additive in pelleting some biofuel types, and the value it would have in this use. The project investigated admixtures of appropriate amounts of glycerine of varying quality during pelleting of some types of fuel (straw, reed canary grass and pine wood). To determine how these affect pellet quality, the function of the pellet press, pellet storage properties, the risk of harmful emission levels of carbon monoxide (CO), nitrogen oxides (NOx), sulphur oxides (SO2) and aldehydes during incineration of the pellets, the risk of ash sintering and the risk of corrosive deposits in flue gas channels were examined. In addition, the commercial value of the glycerine when added to pellets was estimated. Pelleting trials were conducted using 1% and 5% admixtures of four types of glycerine in three types of fuel. Two of the glycerine products were alkaline, originating from alkaline transesterification of rapeseed oil, and two were acidic, originating from acid esterification/transesterification followed by alkaline transesterification, of rapeseed oil in one case and used frying oil in the other. The fuel types were pine wood, reed canary grass and straw. After pelleting, pellet durability, the amount of fine fraction and bulk density were measured. Chemical analyses were performed of glycerine types, fuel types and glycerine/fuel mixtures to evaluate ash melting behaviour and the risk of corrosion associated with alkali chlorides. Pellets from the trials were stored for 6 months, during which time moisture uptake and the incidence of mould were studied. After the storage experiments, pellet durability was measured again. Wherever possible, the experimental design was evaluated statistically using multivariate data analysis. About half the samples were incinerated and emissions of CO, NOx, SO2, particulate matter, acrolein and formaldehyde were measured. In addition, the average temperature and maximum temperature during incineration were measured and the amount of combustion residues and their content of unburned and sintered material were determined. Some ash samples from the combustion of glycerine/pine wood mixes were sent for chemical analysis. The admixture of glycerine in the fuel types generally resulted in pellets with lower durability, higher proportion of fines (fine fraction) and significantly lower bulk density. However, pellets with the same or slightly better durability and the same or lower proportion of fines were obtained by admixture of 1% acidic glycerine to the fuel types. The specific energy consumption for pelleting the fuels containing glycerine was generally lowered, which may have been due to the lubricating properties of the glycerine. The addition of glycerine in all cases resulted in a decrease in pellet bulk density. Reed canary grass had the best durability, least share of fines and highest bulk density, while straw usually had the worst durability, highest share of fines and lowest bulk density. During the storage experiments the pellets took up some water, but never to such a level that the storability was compromised. Pellets with glycerine took up more water, often an increasing amount with increasing glycerine content. Mould was not found in any pellets from any experiment. Durability deteriorated more frequently with higher glycerine content, and thus low durability in the pellets at the outset. The initial moisture content and thus the type of fuel were also of great importance for moisture absorption. Straw contained most moisture from the start and took up the most water. In addition, durability decreased most for straw during storage. During incineration, the main problem with an increasing admixture of glycerine in the fuels was an increasing amount of particles in the flue gas. Calculations of potassium (K) losses with the flue gases, based on analysis of fuels and their ash composition, suggested that this increased sharply with increasing admixture of glycerine. For example, incineration of pine wood with about 1% added glycerine increased the amount of K leaving with the flue gases to the level observed with straw incineration. There seemed to be a close link between the amount of particles in the flue gas and the amount of K released. It is therefore likely that addition of glycerine will cause problems with corrosive deposits in the flues for fuels that normally do not present such problems. However, with fuels that normally give rise to such problems, e.g. straw, it is likely that there will be little obvious difference. Glycerine (acid) containing sulphur can probably prevent particle release and thus lower the risk of corrosion associated with alkali chlorides in the flue gas. The emissions of acrolein and formaldehyde did not increase as might be expected in experiments with glycerine admixture. The levels of acrolein were below the detection limit, and the levels of formaldehyde were very low. Emissions of CO, NOx and SO2 varied widely between experiments in a more or less random way. However, CO emissions may have increased with lower pellet quality. Sulphur dioxide should be produced during incineration of pellets with high sulphur levels. Ash melting point declined in pine wood in particular on addition of glycerine, but also in reed canary grass. The ash melting point for straw was not affected at all by glycerine admixture. The reason why pine wood ash was more sensitive is that the amounts produced from pine are so small that properties of the glycerine ash can have an impact even at small admixture rates. The K content of reed canary grass is so low that very little glycerine with high K content is required before its properties start to become apparent. However, straw has a high initial content of an ash that is already high in K, so the K content of glycerine ash is les obvious even at rather high admixture rates. Calculations using key numbers showed that the ash melting point of reed canary grass in particular should be lowered by the admixture of glycerine, but also that of pine wood to a lesser degree, from an initially high level. Straw ash should scarcely be affected at all. High losses of K in the flue gases can suppress the problem of ash melting point depression in bottom ash. Some of the glycerine types initially had high contents of methanol. It is important that this can be removed, as it constitutes a fire hazard during pelleting and also during transport and handling of the glycerine. High methanol concentrations are also a human health risk, as methanol is toxic. The commercial value of the glycerine is at one of three different levels depending on how it functions when mixed in different fuels. A) If glycerine admixture degrades a good fuel such as wood in terms of the risk of acid deposits in the flue so much that it is similar to straw as a fuel, glycerine value has a negative value. B) On admixture of glycerine in a poor fuel, such as straw, the properties of the glycerine are not evident and its value based on the energy is therefore the same as for the pure fuel. This is currently approximately SEK 0.6-0.9/kg glycerine, which can be compared with the current price of SEK 1/kg for glycerine in biodigestion applications. These factors combined make it difficult to find a profitable use for glycerine as an additive in pelleting or when used as fuel. Glycerine would therefore not be of commercial interest for use in these applications. C) If the glycerine acts as an additive in very small amounts at pelleting, most likely as a lubricant, the value would then be about SEK 3/kg. However, only small amounts would be used in this application, probably just a few hundred tonnes per annum. The advice to the industry is that glycerine should not be used in pelleting as it probably does not work well for this application. If glycerine is incinerated, it should be co-fired with a poor fuel, so as not to impair the properties of the fuel. Glycerine is probably more profitable in applications other than fuel to produce heat. At low addition rates glycerine could probably act as a lubricant during pelleting of certain fuels. However, more research is required to determine whether glycerine can act as a lubricant along with some cheap binding agent in pelleting of fuels
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| 4. |
- Finell, Michael, et al.
(författare)
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Sågspånets malningsgrad : inverkan på pelletskvalitet : pelletplattformen II
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna undersökning har torkat sågspån malts med olika sållgrovlekar (2 mm, 4 mm, 6 mm och 8 mm) och använts för pelletstillverkning. Som jämförelse har icke malt, endast material som passerar 4 x 4 mm använts. Materialen har konditionerats till fukthalter mellan 10 % och 13 % innan pelletering. Försöken gjordes på SLU:s pilotanläggning med en kapacitet på ca 400 kg/h. Under försöken uppmättes energiåtgång vid malning, energiåtgång vid pelletering samt fysikaliska kvalitetsegenskaper på produkten. Även askhalter, extraktivämnesinnehåll och styckedensitet på pellets producerade av olika spånfraktioner uppmättes. Två prover, pellets tillverkade av 8 mm spån och 2 mm spån, togs ut för att studera emissioner av kolmonoxid, koldioxid och metan vid lagring och för att se om det är skillnader mellan pellets tillverkade av olika grovt malda råvaror. Resultaten visade att spånets malgrad påverkar framför allt bulkdensiteten på produkten genom att mer finmalt spån ger en högre bulkdensitet. Övriga kvalitetsparametrar påverkades i mindre grad eller inte alls av spånets malgrad. Det är också möjligt att producera pellets av acceptabel kvalitet helt utan malning av spånet. Endast en bortsållning av övergrovt material verkar vara tillräckligt för att ge en acceptabel råvara. Emissionstesterna visade att det är ingen skillnad mellan pellets tillverkade av spån malt på 2 mm såll och spån malt på 8 mm såll. Extraktivämneshalten i pelleterat material var något lägre än i den icke pelleterade råvaran. Detta beror antagligen på lättflyktiga ämnen som avgår vid de förhöjda temperaturerna som uppstår i pelletringsprocessen.
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| 5. |
- Grimm, Alejandro, et al.
(författare)
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Drying recycled fiber rejects in a bench-scale cyclone : Influence of device geometry and operational parameters on drying mechanisms
- 2017
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 167, s. 631-640
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Tidskriftsartikel (refereegranskat)abstract
- Significant amounts of waste sludge and rejects are generated by pulp and paper mills, and stricter environmental regulations have made waste handling a global challenge. Thermochemical conversion of mechanically dewatered by-products is expensive and inefficient due to their high moisture content; therefore drying is a vital unit operation in waste management. This paper reports results from drying of light coarse fiber reject in a bench-scale cyclone that allows changes in geometry. For the sake of comparison, convective fixed-bed drying tests were also performed. The results showed that the drying rate in the cyclone was hundreds of times higher than in the fixed-bed. For cyclone drying, the inlet air velocity was the most important factor in both determining the drying rate and residence time of the material. This led to the hypothesis that grinding of the reject particles due to particle-wall and particle-particle collisions play a crucial role in enhancing the efficiency of heat and mass transfer. In addition to inlet air velocity, cyclone geometry was the main factor that determined particle residence time, as drying air temperature mainly determined drying rate.
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| 6. |
- Grimm, Alejandro, et al.
(författare)
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Slagging and fouling characteristics during co-combustion of Scots pine bark with low-temperature dried pulp and paper mill chemical sludge
- 2019
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 193, s. 282-294
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Tidskriftsartikel (refereegranskat)abstract
- This paper shows how chemical sludge (CS) generated during wastewater treatment at a paperboard mill can be quickly dried at low-temperature and employed in bark-fired boilers to reduce slagging and corrosion problems. By using a cyclone-dryer operated at an inlet-air velocity of 110 m/s and a temperature of 90 degrees C, the dry-matter content of CS was increased from approximately 19 to 82%. The residence time of CS inside the cyclone was approximately 2 s when using the inlet-air velocity mentioned above. Disaggregation of the feedstock caused by collisions with the cyclone wall and between particles played a crucial role in enhancing the efficiency of heat and mass transfer. Three co-pelletized mixtures of Scots pine bark (SPB) and dried-CS were combusted in a 40 kW fixed-bed burner. Flue gas analysis was performed with a gas analyser. Coarse and fine ash were analysed by SEM-EDS and XRD. NOx, and SO2 emissions increased with increasing amount of CS in the mixtures. Mono combustion of SPB resulted in a large quantity of slag (i.e., molten ash) with a high degree of sintering (i.e., hardness of the slag), and ash deposits formed on heat transfer surfaces were rich in K2SO4 and KCI. Mixtures of SPB and CS were less prone to slagging, and the amount of alkali chloride in the deposits was reduced in favour of alkali sulphate formation.
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| 7. |
- Hallor, Karolin Hansén, et al.
(författare)
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Fusion of the EWSR1 and ATF1 genes without expression of the MITF-M transcript in angiomatoid fibrous histiocytoma
- 2005
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Ingår i: Genes, Chromosomes and Cancer. - : Wiley. - 1045-2257 .- 1098-2264. ; 44:1, s. 97-102
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Tidskriftsartikel (refereegranskat)abstract
- Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor that usually occurs in children and young adults. Only two cases of AFH with genetic rearrangements have been reported previously; both of these had a FUS-ATF1 fusion gene. We have studied an AFH from a 9-year-old boy whose tumor displayed a t(12;22)(q13;q12) as the sole cytogenetic aberration. FISH,RT-PCR, and sequence analyses revealed an EWSR1-ATF1 fusion gene that has previously been reported in clear cell sarcoma (CCS), a soft tissue sarcoma that is morphologically and clinically distinct from AFH. This study thus has demonstrated that the EWSR1-ATF1 chimera represents a fusion gene that can be associated with different tumor types. Simultaneous expression of the EWSR1-ATF1 and MITF-M transcripts in CCS has led to the proposal that the MITF-M promoter is transactivated by EWSR1-ATF1. The AFH, however, did not express the MITF-M transcript, supporting the theory that MITF-M expression in CCS is a reflection of its cellular origin, rather than a consequence of the presence of an EWSR1-ATF1 fusion protein. Activation of the EWSR1-ATF1 oncogene is probably an early step in the transformation process, but the overall gene expression patterns are likely to vary considerably between AFH and CCS, in keeping with their clinicopathologic differences.
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| 8. |
- Larsson, Sylvia, et al.
(författare)
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Temperature controlled feed layer formation in biofuel pellet production
- 2012
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 94, s. 81-85
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Tidskriftsartikel (refereegranskat)abstract
- A pilot scale pelletizing system (capacity: 300 kg/h) with integrated die temperature control was built and evaluated using reed canary grass as a model raw material. A pelletizing series was performed using a full factorial design having independent factors such as die temperature (35-65 C), raw material moisture content (12-15% w.b.), and raw material temperature/steam conditioning (0-2 kg/h), with continuous or discontinuous feed layer formation as responses. Die temperature was the most influential parameter on feed layer formation and was negatively correlated to continuous feed layer formation. An immediate response, changing discontinuous production patterns into continuous was experienced when die temperature was lowered by the temperature control system. Further, a partial least squares discriminant analysis model, using the experimentally varied parameters, predicted continuous or discontinuous feed layer formation with 100% accuracy. Thus, die temperature control can be considered as a fast and efficient method for overcoming feed layer losses in pelletizing.
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| 9. |
- Larsson, Sylvia, et al.
(författare)
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Using the macromolecular composition to predict process settings that give high pellet durability in ring-die biomass pellet production
- 2021
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 283
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed to investigate if the process settings that give high pellet durability can be modelled from the biomass’ 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.
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| 10. |
- Mäkelä, Mikko, et al.
(författare)
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Convective drying of industrial sludge materials with a high-velocity pilot cyclone
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In response to the growing need of economically viable sludge drying technologies and respective resource recovery, a convective high-velocity pilot cyclone was set-up at the Biofuel Technology Centre, Swedish University of Agricultural Sciences in Umeå, Sweden. In essence this process entails feeding (≤900 kg/h) a material to a heated low-temperature high-velocity inlet air flow (capacity ca. 13·103 m3/h) allowing moisture removal and respective shaping/separation of particles. Primarily this equipment is expected to provide improvements to the drying efficiency of challenging waste-water treatment sludge materials, whilst enabling simultaneous particle separation based on physical phenomena. Hence preliminary testing of a fibre reject stream from a local paper mill was performed, followed by a detailed optimisation of respective drying efficiency in early fall 2013. The process set-up will be presented followed by discussion of material characteristics and attained results.
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