| 1. |
- Larsson, Stefan, et al.
(författare)
-
Characteristics of anadromous whitefish (Coregonus lavaretus (L.)) rivers in the Gulf of Bothnia
- 2013
-
Ingår i: BIOLOGY AND MANAGEMENT OF COREGONID FISHES - 2011. - 9783510470662 ; 64, s. 189-201
-
Konferensbidrag (refereegranskat)abstract
- In order to study anadromous whitefish spawning river requirements, we sampled 41 rivers in the Gulf of Bothnia for newly hatched whitefish larvae for one to three consecutive years. Chemical and morphological data (e.g. flow rate, topography, pH, estuary fetch and distance to coastal sandy areas) were collected for each river. Newly-hatched whitefish were caught in 19 rivers whereas whitefish were not confirmed present in 22 rivers. By applying partial least squares discriminant analysis (PLS-DA), data for rivers confirmed to support whitefish were contrasted with data for rivers in which whitefish were not found. The single most important factor was annual average water flow rate. Whitefish larvae were observed in 93% of the rivers with annual mean flow rate > 5 m(3) s(-1) (N = 14). In contrast, newly-hatched whitefish were only found in 22% of the smaller rivers (N = 27).
|
|
| 2. |
- Agar, David, et al.
(författare)
-
A systematic study of ring-die pellet production from forest and agricultural biomass
- 2018
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 180, s. 47-55
-
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.
|
|
| 3. |
|
|
| 4. |
- Agar, David, et al.
(författare)
-
Pelleting torrefied biomass at pilot-scale – Quality and implications for co-firing
- 2021
-
Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 178, s. 766-774
-
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.
|
|
| 5. |
- Averheim, Andreas, et al.
(författare)
-
Separate hydrolysis and fermentation of softwood bark pretreated with 2-naphthol by steam explosion
- 2024
-
Ingår i: Biotechnology for Biofuels and Bioproducts. - : BioMed Central (BMC). - 2731-3654. ; 17:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: 2-Naphthol, a carbocation scavenger, is known to mitigate lignin condensation during the acidic processing of lignocellulosic biomass, which may benefit downstream processing of the resulting materials. Consequently, various raw materials have demonstrated improved enzymatic saccharification yields for substrates pretreated through autohydrolysis and dilute acid hydrolysis in the presence of 2-naphthol. However, 2-naphthol is toxic to ethanol-producing organisms, which may hinder its potential application. Little is known about the implications of 2-naphthol in combination with the pretreatment of softwood bark during continuous steam explosion in an industrially scalable system.Results: The 2-naphthol-pretreated softwood bark was examined through spectroscopic techniques and subjected to separate hydrolysis and fermentation along with a reference excluding the scavenger and a detoxified sample washed with ethanol. The extractions of the pretreated materials with water resulted in a lower aromatic content in the extracts and stronger FTIR signals, possibly related to guaiacyl lignin, in the nonextractable residue when 2-naphthol was used during pretreatment. In addition, cyclohexane/acetone (9:1) extraction revealed the presence of pristine 2-naphthol in the extracts and increased aromatic content of the nonextractable residue detectable by NMR for the scavenger-pretreated materials. Whole-slurry enzymatic saccharification at 12% solids loading revealed that elevated saccharification recoveries after 48 h could not be achieved with the help of the scavenger. Glucose concentrations of 16.9 (reference) and 15.8 g/l (2-naphthol) could be obtained after 48 h of hydrolysis. However, increased inhibition during fermentation of the scavenger-pretreated hydrolysate, indicated by yeast cell growth, was slight and could be entirely overcome by the detoxification stage. The ethanol yields from fermentable sugars after 24 h were 0.45 (reference), 0.45 (2-naphthol), and 0.49 g/g (2-naphthol, detoxified).Conclusion: The carbocation scavenger 2-naphthol did not increase the saccharification yield of softwood bark pretreated in an industrially scalable system for continuous steam explosion. On the other hand, it was shown that the scavenger's inhibitory effects on fermenting microorganisms can be overcome by controlling the pretreatment conditions to avoid cross-inhibition or detoxifying the substrates through ethanol washing. This study underlines the need to jointly optimize all the main processing steps.
|
|
| 6. |
- Björkman Björkelund, Karin, et al.
(författare)
-
Factors at admission associated with 4 months outcome in elderly patients with hip fracture.
- 2009
-
Ingår i: AANA Journal. - 0094-6354. ; 77:1, s. 49-58
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this descriptive cohort study was to describe patients with hip fracture on the basis of ASA physical status and to identify preoperative risk factors associated with postoperative outcome up to 4 months after surgery. Data were collected prospectively through the Swedish National Hip Fracture and Anesthetic registers and retrospectively from medical and nursing records. The 428 patients (aged > or = 65 years) with hip fracture were consecutively included. Multiple logistic regression analyses were used to identify factors predicting each of 4 outcomes. Risk factors for a poorer 4-month survival after hip fracture were ASA physical status 3 and 4, more extensive fractures, 85 years or older, male sex, and dependency in living. Mortality within 4 months was significantly associated with ASA physical status 3 and 4, age 85 years or older, male sex, dementia diagnosis, fewer than 8 correct answers on the Short Portable Mental Status Questionnaire, 4 or more prescribed drugs, hemoglobin level less than 100 g/L, creatinine level more than 100 micromol/L, dependency in living, inability to walk alone, and fracture other than undisplaced intracapsular. Elderly patients with hip fracture should be identified immediately at admission regarding risk factors leading to a poorer survival and more complications.
|
|
| 7. |
- Björkman Björkelund, Karin, et al.
(författare)
-
Reducing delirium in elderly patients with hip fracture: a multi-factorial intervention study.
- 2010
-
Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; Apr 7, s. 678-688
-
Tidskriftsartikel (refereegranskat)abstract
- Background: There is an evident need for improved management of elderly patients with trauma in order to avoid common and troublesome complications such as delirium. The aim of this study was to investigate whether an implementation of a multi-factorial program including intensified pre-hospital and perioperative treatment and care could reduce the incidence of delirium in elderly patients with hip fracture, cognitively intact at admission to the hospital. In addition, we explored the factors that characterize patients who developed delirium. Methods: A prospective, quasi-experimental design was used. A total of 263 patients with hip fracture (>/=65 years), cognitively intact at admission, were consecutively included between April 2003 and April 2004. On 1 October 2003, a new program was introduced. All patients were screened for cognitive impairment within 30 min after admission to the emergency department using The Short Portable Mental Status Questionnaire (SPMSQ). To screen for delirium, patients were tested within 4 h of admission and thereafter daily, using the Organic Brain Syndrome scale. Results: The number of patients who developed delirium during hospitalization was 74 (28.1%), with a decrease from 34% (45 of 132) in the control group to 22% (29 of 131) in the intervention group (P=0.031). Patients who developed delirium were statistically older, more often had >4 prescribed drugs at admission and scored less well in the SPMSQ test. Conclusion: The use of a multi-factorial intervention program in elderly hip fracture patients, lucid at admission, reduced the incidence of delirium during hospitalization by 35%.
|
|
| 8. |
- Björkman Björkelund, Karin, et al.
(författare)
-
The influence of perioperative care and treatment on the 4-month outcome in elderly patients with hip fracture.
- 2011
-
Ingår i: AANA Journal. - 0094-6354. ; 79:1, s. 51-61
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this descriptive cohort study was to identify perioperative risk factors associated with postoperative outcome up to 4 months after surgery in elderly patients with hip fracture. Data were collected prospectively through the Swedish National Hip Fracture, the local Acute and Emergency, and Anesthesia registers, and retrospectively from medical and nursing records. The 428 patients (aged > or = 65 years) with hip fracture were consecutively included. Multiple logistic regression analyses were used to identify factors predicting each of 4 outcomes. Perioperative risk factors predicting death within 4 months after surgery were fasting time of 12 or more hours and blood transfusion of 1 U or more. Risk factors predicting postoperative confusion were postoperative oxygen saturation less than 90% and fasting time 12 hours or longer. Risk factors predicting in-hospital complications were transfusion of 1 or more units of blood, preoperative oxygen saturation less than 90%, and fasting time 12 hours or more. Risk factor predicting length of stay longer than 10 days was blood transfusion of 1 U or more. To minimize morbidity and mortality, providers should increase efforts to optimize the patients' oxygen saturation and hemoglobin level and reduce fasting time and waiting time for surgery.
|
|
| 9. |
- Björkman Björkelund, Karin, et al.
(författare)
-
The Organic Brain Syndrome (OBS) scale: a systematic review.
- 2006
-
Ingår i: International Journal of Geriatric Psychiatry. - : Wiley. - 1099-1166 .- 0885-6230. ; 21:3, s. 210-222
-
Forskningsöversikt (refereegranskat)abstract
- Background/Objective The Organic Brain Syndrome (OBS) Scale was developed to determine elderly patients' disturbances of awareness and orientation as to time, place and own identity, and assessment of various emotional and behavioural symptoms appearing in delirium, dementia and other organic mental diseases. The aim of the study was to examine the OBS Scale, using the eight criteria and guidelines formulated by the Scientific Advisory Committee of the Medical Outcomes Trust (SAC), and to investigate its relevance and suitability for use in various clinical settings. Method Systematic search and analysis of papers (30) on the OBS Scale were carried out using the criteria suggested by the SAC. Results: The OBS Scale in many aspects satisfies the requirements suggested by the SAC: conceptual and measurement model, reliability, validity, responsiveness, interpretability, respondent and administrative burden, alternative forms of administration, and cultural and language adaptations, but there is a need for additional evaluation, especially with regard to different forms of reliability, and the translation and adaptation to other languages. Conclusions The OBS Scale is a sensitive scale which is clinically useful for the description and long-term follow-up of patients showing symptoms of acute confusional state and dementia. Although the OBS Scale has been used in several clinical studies there is need for further evaluation. Copyright (c) 2006 John Wiley & Sons, Ltd.
|
|
| 10. |
- Borén, Eleonora, et al.
(författare)
-
Off-gassing from 16 pilot-scale produced pellets assortments of torrefied pine : impact of torrefaction severity, storage time, pelletization parameters, and pellet quality
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Off-gassing from wood pellets poses risks in large scale handling chains - yet little is known on off-gassing from pellets of torrefied wood. This study reports CO, CO2, and O2 concentrations in off-gases during storage of 16 torrefied and two untreated pellets assortments. According to an experimental design, pellets were produced in pilot scale from pine chips torrefied at five different set points. Off-gassing was assessed in relation to storage conditions, torrefaction and pelletization parameters, and pellet quality. Pellets from the most severely torrefied pine formed CO, CO2, and consumed O2 similarly to untreated pellets. Off-gassing was positively correlated to pellet moisture content; however, the most severely torrefied also retained the least moisture. Open air storage (20–270 days) of torrefied chips prior to pelletization did not affect off-gassing levels. Results are important for safe handling; torrefied pellets can cause comparable levels as untreated pellets of CO, CO2, and O2.
|
|
| 11. |
- Borén, Eleonora, et al.
(författare)
-
Off-gassing from pilot-scale torrefied pine wood chips : impact of torrefaction severity, cooling technology, and storage time
- 2020
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 202
-
Tidskriftsartikel (refereegranskat)abstract
- During handling and storage of conventional wood pellets, O2 depletion as well as CO and CO2 off-gassing can reach acutely hazardous levels and certain Volatile Organic Compounds (VOCs) may reach concerning levels from an occupational health and safety perspective. With new thermally pre-treated biomass commodities entering consumer markets, corresponding knowledge is needed on these assortments' off-gassing behaviour. In this study, relative concentrations of VOCs, CO, CO2, and O2 in the closed storage space of five different pilot-scale torrefied pine wood chip assortments were monitored over 12 days. The VOCs composition in the storage space differed between torrefaction treatment settings; terpenes decreased while furans and lignin degradation products peaked at narrow ranges with increased torrefaction severity, indicating that VOC off-gassing composition of individual compounds is highly specific. Generally, VOC amounts decreased with storage time, but for the mildest torrefied chips certain VOCs increased, predominantly compounds of higher volatility such as hexanal, acetone, and 2-pentylfuran. Also, the newly produced torrefied chips were cooled with two different post-process technologies: i) heat exchanging, and ii) heat exchanging with additional water spraying. Water spraying resulted in higher VOC concentrations, stronger O2 depletion, and factor four higher concentration of CO2 in the storage headspace.
|
|
| 12. |
- Borén, Eleonora, 1985-
(författare)
-
Off-gassing from thermally treated lignocellulosic biomass
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Off-gassing of hazardous compounds is, together with self-heating and dust explosions, the main safety hazards within large-scale biomass storage and handling. Formation of CO, CO2, and VOCs with concurrent O2 depletion can occur to hazardous levels in enclosed stored forest products. Several incidents of CO poisoning and suffocation of oxygen depletion have resulted in fatalities and injuries during cargo vessel discharge of forest products and in conjunction with wood pellet storage rooms and silos. Technologies for torrefaction and steam explosion for thermal treatment of biomass are under development and approaching commercialization, but their off-gassing behavior is essentially unknown.The overall objective of this thesis was to provide answers to one main question: “What is the off-gassing behaviour of thermally treated lignocellulosic biomass during storage?”. This was achieved by experimental studies and detailed analysis of off-gassing compounds sampled under realistic conditions, with special emphasis on the VOCs.Presented results show that off-gassing behavior is influenced by numerous factors, in the following ways. CO, CO2 and CH4 off-gassing levels from torrefied and stream-exploded biomass and pellets, and accompanying O2 depletion, are comparable to or lower than corresponding from untreated biomass. The treatments also cause major compositional shifts in VOCs; emissions of terpenes and native aldehydes decline, but levels of volatile cell wall degradation products (notably furans and aromatics) increase. The severity of the thermal treatment is also important; increases in torrefaction severity increase CO off-gassing from torrefied pine to levels comparable to emissions from conventional pellets, and increase O2 depletion for both torrefied chips and pellets. Both treatment temperature and duration also influence degradation rates and VOC composition. The product cooling technique is influential too; water spraying in addition to heat exchange increased CO2 and VOCs off-gassing from torrefied pine chips, as well as O2 depletion. Moreover, the composition of emitted gases co-varied with pellets’ moisture content; pellets of more severely treated material retained less moisture, regardless of their pre-conditioning moisture content. However, no co-variance was found between off-gassing and pelletization settings, the resulting pellet quality, or storage time of torrefied chips before pelletization. Pelletization of steam-exploded bark increased subsequent VOC off-gassing, and induced compositional shifts relative to emissions from unpelletized steam-exploded material. In addition, CO, CO2 and CH4 off-gassing, and O2 depletion, were positively correlated with the storage temperature of torrefied softwood. Similarly, CO and CH4 emissions from steam-exploded softwood increased with increases in storage temperature, and VOC off-gassing from both torrefied and steam-exploded softwood was more affected by storage temperature than by treatment severity. Levels of CO, CO2 and CH4 increased, while levels of O2 and most VOCs decreased, during storage of both torrefied and steam-exploded softwood.CO, CO2 and O2 levels were more affected by storage time than by treatment severity. Levels of VOCs were not significantly decreased or altered by nitrogen purging of storage spaces of steam-exploded or torrefied softwood, or controlled headspace gas exchange (intermittent ventilation) during storage of steam-exploded bark.In conclusion, rates of off-gassing of CO and CO2 from thermally treated biomass, and associated O2 depletion, are comparable to or lower than corresponding rates for untreated biomass. Thermal treatment induces shifts in both concentrations and profiles of VOCs. It is believed that the knowledge and insights gained provide refined foundations for future research and safe implementation of thermally treated fuels as energy carriers in renewable energy process chains.
|
|
| 13. |
- Borén, Eleonora, et al.
(författare)
-
Off-gassing of VOCs and permanent gases during storage of torrefied and steam exploded wood
- 2017
-
Ingår i: Energy & Fuels. - Washington : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 31:10, s. 10954-10965
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal treatment for upgrading of low-value feedstocks to improve fuel properties has gained large industrial interest in recent years. From a storage and transport perspective, hazardous off-gassing could be expected to decrease through the degradation of reactive biomass components. However, thermal treatment could also shift chemical compositions of volatile organic components, VOCs. While technologies are approaching commercialization, off-gassing behavior of the products, especially in terms of VOCs, is still unknown. In the present study, we measured off-gassing of VOCs together with CO, CO2, CH4, and O2 depletion from torrefied and steam exploded softwood during closed storage. The storage temperature, head space gas (air and N2), and storage time were varied. VOCs were monitored with a newly developed protocol based on active sampling with Tenax TA absorbent analyzed by thermal desorption-GC/MS. High VOC levels were found for both untreated and steam exploded softwood, but with a complete shift in composition from terpenes dominating the storage gas for untreated wood samples to an abundance of furfural in the headspace of steam exploded wood. Torrefied material emitted low levels of VOCs. By using multivariate statistics, it was shown that for both treatment methods and within the ranges tested, VOC off-gassing was affected first by the storage temperature and second by increasing treatment severity. Both steam exploded and torrefied biomass formed lower levels of CO than the reference biomass, but steam explosion caused a more severe O2 depletion.
|
|
| 14. |
- Borén, Eleonora, et al.
(författare)
-
Reducing VOC off-gassing during the production of pelletized steam-exploded bark : impact of storage time and controlled ventilation
- 2018
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 32:4, s. 5181-5186
-
Tidskriftsartikel (refereegranskat)abstract
- Volatile organic compound (VOC) off-gassing behavior of thermally treated biomass intended for bioenergy production has recently been shown to be vastly different from that of untreated biomass. Simple measures to reduce emissions, such as controlled ventilation and prolonged storage time, have been suggested but not yet studied in detail. In the present study, we monitored how VOC off-gassing was reduced over time (24–144 h) in enclosed storage with and without ventilation. Steam-exploded bark was collected directly from a pilot-scale steam explosion plant as well as before and after subsequent pelletizing. Active Tenax-TA absorbent sampling of VOCs was performed from the headspaces of a bench-scale sample storage setup. The impact of storage time and ventilation on VOC levels was evaluated through multivariate statistical analysis. The results showed that relative VOC concentrations in the headspace were reduced by increased storage time, with heavier VOCs reduced at a higher rate. VOC composition was neither reduced nor shifted by controlled intermittent ventilation during storage; instead, VOC levels equilibrated at the same levels as those stored without ventilation, and this was independent of the process step, storage time, or number of ventilations.
|
|
| 15. |
- Borén, Eleonora, et al.
(författare)
-
Reducing VOCs off-gassing during production of pelletized steam exploded bark : impact of storage time and controlled ventilation
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- VOC off-gassing behavior of thermally treated biomass intended for bioenergy production has recently been shown to be vastly different to that of untreated biomass. Simple measures to reduce emissions, such as controlled ventilation and prolonged storage time, has been suggested but not previously studied in detail. In the present study, we monitored how VOC off-gassing was reduced over time (24–144h) in closed storage with and without ventilation. Steam exploded bark was collected directly from a pilot scale steam explosion plant, and before and after subsequent pelletizing. Storage and active sampling of VOCs in the headspace was done in a bench-scale set-up using Tenax-TA absorbent. The impact of storage time and ventilation to reduce VOCs was evaluated through multivariate statistical analysis. The results showed that VOC concentrations in the headspace were reduced by increased storage time, and that heavier VOCs reduced faster. No impact on either reducing or shifting VOC composition could be achieved by controlled ventilation during storage; instead, VOCs emitted to the same concentrations anew, independent of process step, storage time, or number of ventilations.
|
|
| 16. |
- Borén, Eleonora, et al.
(författare)
-
VOC off-gassing from pelletized steam exploded softwood bark : emissions at different industrial process steps
- 2018
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 171, s. 70-77
-
Tidskriftsartikel (refereegranskat)abstract
- Formation of hazardous gases during transport and storage of biomass for large-scale bioenergy production is an important safety concern. While off-gassing has been addressed in numerous studies for raw woody biomass, very few describe it in the context of biomass for bioenergy production pre-treated by thermal technologies such as steam explosion. Volatile Organic Components (VOCs) are expected to be altered by the treatment, but until now there is no research published on VOC profiles of steam exploded materials in industrial scale. In the present study, VOCs emitted from the products were evaluated by sampling from different production steps from steam explosion of softwood bark, and following the production chain including also pelletization. Off-gasses were actively sampled using Tenax TA absorbent and analyzed by GC-MS. The VOC formation dependency of operation and storage conditions at different process steps was evaluated by multivariate statistical analysis. We showed that the different process steps along the production line was the main influencing factor for VOC off-gassing amounts, with highest VOC levels directly after the steam explosion process. Treatment severity mainly altered the relative composition of VOC profiles with more terpenes emitted from milder treatment, whereas more severe treatment shifted VOCs composition to contain more furans, e.g. furfural. In summary, treatment by steam explosion leads to potentially problematic VOC off-gassing profiles from the material, and levels vary considerable along the production line. The findings are important from a fuel handling and working environment perspective.
|
|
| 17. |
- Bozaghian Bäckman, Marjan, et al.
(författare)
-
Bed material performance of quartz, natural K-feldspar, and olivine in bubbling fluidized bed combustion of barley straw
- 2024
-
Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 364
-
Tidskriftsartikel (refereegranskat)abstract
- The present study investigates how three different silicate-based bed materials behave in bubbling fluidized bed combustion of a model agricultural residue with respect to ash composition, namely barley straw. Quartz, natural K-feldspar, and olivine were all used in combustion at 700 °C, and the resulting layer formation and bed agglomeration characteristics were determined. Based on this, a general reaction model for bed ash from agricultural residues was proposed, taking into account the reactivity of the different silicates investigated towards the main ash-forming elements K, Ca, and Si. The proposed reaction model links bed material interaction with K-rich bed ash to the degree of polymerization of the silicate bed material, where addition reactions occur in systems with high polymerization, predominately in quartz, and substitution reactions dominate for depolymerized silicates such as K-feldspar and olivine.
|
|
| 18. |
|
|
| 19. |
- Bozaghian, Marjan, et al.
(författare)
-
Combustion characteristics of barley straw stored with CaCO3 during fluidized bed combustion using quartz and olivine as bed materials
- 2017
-
Konferensbidrag (refereegranskat)abstract
- In order to achieve a continuous feedstock supply for power plants a large quantity of harvested material must be stored for long-term periods. During storage, especially during right conditions of temperature, moisture and oxygen, solid agricultural fuels are susceptible to microbial activities. Microbial respiration not only leads to loss of organic carbon, but also to an increased temperature in the stored fuel which may lead to self-ignition. There is on-going work studying the effect of adding Ca as CaO or CaCO3 during storage of straw with the aim of creating an unfavorable alkaline microenvironment that prevents microbial growth during storage. The effect of this amendment during storage is still being explored, but the effect in the combustion step of the process in terms of determining the potential of Ca-additives to positively affect overall ash chemistry have yet to be certainly quantified. Utilization of agricultural crops for energy purposes in heat and power plants has proven to be challenging in numerous ways. Compared to woody fuels, agricultural fuels can cause severe ash-related operational problems in combined heat and power plants through by fouling, slagging and/or bed agglomeration due to their high concentrations of inorganic constituents. The objective of the present study is therefore to determine the fouling and bed agglomeration characteristics during fluidized-bed combustion of barley straw stored with different dosages of Ca to biomass with the main ash-forming elements shown in Figure 1, using two types of bed materials, quartz and olivine.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
- Bozaghian, Marjan, et al.
(författare)
-
Combustion characteristics of straw stored with CaCO3 in bubbling fluidized bed using quartz and olivine as bed materials
- 2018
-
Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 212, s. 1400-1408
-
Tidskriftsartikel (refereegranskat)abstract
- The addition of Ca-containing compounds can reduce mass loss from agricultural biomass during storage. The resulting alkaline environment is detrimental to microorganisms present in the material. Theoretical analysis of Ca-containing biomass suggests that combustion properties are improved with respect to slagging. To validate the theoretical calculations, barley straw was utilized as a typical model agricultural biomass and combustion characteristics of straw pre-treated with 2 and 4 w/w% CaCO3 for combined improvement of storage and combustion properties were determined through combustion at 700 degrees C in a bench-scale bubbling fluidized-bed reactor (5 kW) using quartz and olivine sand as bed materials. The combustion characteristics were determined in terms of elemental composition and compound identification in bed ash and bed material including agglomerates, fly ash, particulate matter as well as flue gas measurements. The addition of CaCO3 to straw had both positive and negative effects on its combustion characteristics. Both additive levels raised the total de fluidization temperature for both quartz and olivine, and olivine proved to be less susceptible than quartz to reactions with alkali. With Ca-additives, the composition of deposits and fine particulate matter changed to include higher amounts of KCl potentially leading to higher risk for alkali chloride-induced corrosion. Flue gas composition was heavily influenced by CaCO3 additives by significantly elevated CO concentrations likely related to increased levels of gaseous alkali compounds. The results suggest that it is necessary to reduce gaseous alkali compounds, e.g. through kaolin or sulphur addition, if alkali-rich straw is to be co-combusted with Ca-rich biomass or large amounts of Ca-additives.
|
|
| 23. |
- Bozaghian, Marjan, et al.
(författare)
-
Does mechanical screening improve fuel properties? Effects of mechanical screening of stored logging residue chips on ash chemistry and other parameters relevant for combustion
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Forestry and the forest industry plays an important role in the Swedish economy. From forest operations and at sawmills and pulp and paper mills several by-product assortments are generated and these are providing the basis for the highly developed Swedish bioenergy sector. Logging residues constitute a major resource and is utilized as fuel in heat and power plants. However, due to a relatively low heating value and high management costs, this resource is still underutilized. Logging residue chips have irregular particle size, high moisture content (30-60%) and high ash content (8-15 %) and these features cause most of the problems encountered during the operation of feeding systems and combustion processes. Ash, present both in endogen plant tissues and as extrinsic matter such as sand and clay minerals, is of especially big concern for small-size plants. In this on-going work screening of logging residue chips was performed. Different mechanical screening methods was applied with the aim to provide a homogenous fuel with a higher quality for combustion purposes. Through screening, the chemical fuel composition is also altered and this affects combustion behavior and ash chemistry. The objective of the present study is to, from a combustion process perspective with emphasis on ash chemistry, evaluate the overall effects of different screening procedures when applied on stored logging residue chips.
|
|
| 24. |
- Bozaghian, Marjan, et al.
(författare)
-
Does Mechanical Screening of Contaminated Forest Fuels Improve Ash Chemistry for Thermal Conversion?
- 2020
-
Ingår i: Energy and Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 34, s. 16294-16301
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of mechanical screening of severely contaminated forest fuel chips was investigated, focusing on main ashforming elements and slagging tendency and other properties with relevance for thermal conversion. In this study, screening operations were performed according to practice on an industrial scale by combining a star screen and a supplementary windshifter in six different settings and combinations. Mechanical screening reduced the amount of ash and fine particles in the accept fraction. However, the mass losses for the different screening operations were substantial (20−50 wt %). Fuel analyses of the non-screened and the screened fuels showed that the most significant screening effect was a reduction of Si and Al, indicating an effective removal of sand and soil contaminations. However, the tested fuel’s main ash-forming element’s relative concentration did not indicate any improved combustion characteristics and ash-melting behavior. Samples of the accept fractions and non-screened material were combusted in a single-pellet thermogravimetric reactor, and the resulting ashes’ morphology and elemental composition were analyzed by scanning electron microscopy−energy dispersive X-ray spectrometry and the crystalline phases by powder X-ray diffraction. Results from both these analyses confirmed that screening operations had no, or minor, effects on the fuels’ ash chemistry and slagging tendencies, i.e., the fuels’ proneness to ash melting was not improved. However, the reduction of ash and fine particles can reduce slagging and other operational problems in smaller and more sensitive combustion units.
|
|
| 25. |
- Broche, Ludovic, et al.
(författare)
-
Dynamic Mechanical Interactions Between Neighboring Airspaces Determine Cyclic Opening and Closure in Injured Lung
- 2017
-
Ingår i: Critical Care Medicine. - 0090-3493 .- 1530-0293. ; 45:4, s. 687-694
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: Positive pressure ventilation exposes the lung to mechanical stresses that can exacerbate injury. The exact mechanism of this pathologic process remains elusive. The goal of this study was to describe recruitment/derecruitment at acinar length scales over short-time frames and test the hypothesis that mechanical interdependence between neighboring lung units determines the spatial and temporal distributions of recruitment/derecruitment, using a computational model. Design: Experimental animal study. Setting: International synchrotron radiation laboratory. Subjects: Four anesthetized rabbits, ventilated in pressure controlled mode. Interventions: The lung was consecutively imaged at - 1.5-minute intervals using phase-contrast synchrotron imaging, at positive end expiratory pressures of 12, 9, 6, 3, and 0 cm H2O before and after lavage and mechanical ventilation induced injury. The extent and spatial distribution of recruitment/derecruitment was analyzed by subtracting subsequent images. In a realistic lung structure, we implemented a mechanistic model in which each unit has individual pressures and speeds of opening and closing. Derecruited and recruited lung fractions (F-derecruaed, F-recruited) were computed based on the comparison of the aerated volumes at successive time points. Measurements and Main Results: Alternative recruitment/derecruitment occurred in neighboring alveoli over short-time scales in all tested positive end-expiratory pressure levels and despite stable pressure controlled mode. The computational model reproduced this behavior only when parenchymal interdependence between neighboring acini was accounted for. Simulations closely mimicked the experimental magnitude of F-derecruited and F-recruited when mechanical interdependence was included, while its exclusion gave F-recruited values of zero at positive end -expiratory pressure greater than or equal to 3 cm H2O. Conclusions: These findings give further insight into the microscopic behavior of the injured lung and provide a means of testing protective-ventilation strategies to prevent recruitment/derecruitment and subsequent lung damage.
|
|
