| 1. |
- Lyckeskog, Huyen, 1985, et al.
(författare)
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Storage Stability of Bio-oils Derived from the Catalytic Conversion of Softwood Kraft Lignin in Subcritical Water
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:4, s. 3097-3106
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Tidskriftsartikel (refereegranskat)abstract
- The stability of lignin-derived bio-oil obtained from a continuous process [base (K2CO3)-catalyzed, using phenol as a capping agent] under subcritical conditions of water (25 MPa, 290-370 degrees C) was investigated. The lignin-derived bio-oil obtained was stored at ambient temperature for 2 years. Our results show that the base concentration in the feed solution affects the stability of this lignin-derived bio-oil during its long-term storage. It was found that, at low base concentrations (i.e., 0.4%-1.0%), the yields of all lignin-derived bio-oil fractions were relatively stable. At high base concentrations (i.e., 1.6%-2.2%), however, the yield of high-molecular-weight (high-Mw) structures increased and that of low-molecular-weight (low-Mw) structures decreased after storage. This indicated that the low-Mw materials had been polymerized to form high-Mw materials. In addition, it was found that the yield of gas chromatography-mass spectrometry (GC-MS)-identified compounds (excluding phenol) in this lignin-derived bio-oil decreased from 15% to 11%. This is probably due to the presence of solids in these lignin derived bio-oils, which promotes the catalytic polymerization reactions, suggesting that it is beneficial to remove the solids from this lignin-derived bio-oil in order to enhance its stability. Compared to the results obtained from bio-oil derived from biomass pyrolysis, our results show that bio-oil derived from the conversion of lignin in subcritical water has better chemical stability during long-term storage.
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| 2. |
- Belkheiri, Tallal, 1985, et al.
(författare)
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Effect of pH on Kraft Lignin Depolymerisation in Subcritical Water
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:6, s. 4916-4924
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Tidskriftsartikel (refereegranskat)abstract
- Softwood kraft lignin was depolymerized using subcritical water (623 K and 25 MPa) in a continuous small pilot unit. ZrO2 and K2CO3 were used as catalysts, and phenol was used as capping agent to suppress repolymerization. The effect of pH was investigated by adding KOH in five steps to the feed. The yield of water-soluble organics increased with pH. The yield of bio-oil was also influenced by the pH and varied between 28 and 32 wt %. The char yield on the zirconia catalyst showed a minimum at pH 8.1. The yield of suspended solids was low at pH below 8.1 but increased at higher pH values. The oxygen content in the bio-oil was only 15 wt %, compared to about 26 wt % in the kraft lignin.
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| 3. |
- Hagman, Henrik, 1980-
(författare)
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Co-firing complex biomass in a CFB boiler : ash transformation, corrosion control and materials selection
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The effects of greenhouse gas net emissions on global warming, stricter legislation on waste handling, and the pursuit of ever cheaper heat- and power production are all important factors driving the introduction of complex fuels in incineration plants. However - without fundamental knowledge regarding ash transformation, corrosion control, and materials selection – this introduction of potentially economically and environmentally beneficial fuels, might instead cause economic loss and environmentally adverse effects.The present work is a contribution to the transition from today's CO2 net generating energy conversion system, to a more environmentally friendly and cost-efficient one. This is done using scientific methods to generate knowledge concerning mechanisms of ash transformation, corrosion control, and materials selection, in a co-fired industrial scale circulating fluidized bed (CFB) boiler, using a novel and biomass-based fuel mix, rich in Na, K, Cl, N, S, P, Ca and Si. Fuel fractions, ashes, flue gas, deposits, and construction material samples have been collected and analyzed using various techniques, including scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray Diffraction (XRD). The experimental results have been evaluated and interpreted using chemical equilibrium calculations.The results of this work include:1) An analysis of; the failure and preventive maintenance statistics of the industrial scale CFB boiler at hand; the elemental composition of boiler ashes and deposits, the flue gas composition and elemental composition of a multitude of fuel fractions; correlations between boiler design, operational parameters, elemental composition of deposits and boiler availability; a boiler elemental mass balance revealing details regarding deposit buildup mechanisms; properties of the fly ash relevant to flue gas filter design; and findings regarding the nitrogen chemistry of the novel and nitrogen-rich fuel mix.2) Speciation and description of the overall ash transformation and fireside alloy interaction, enabling the implementation of on-line corrosion control which significantly inhibits superheater and dew-point corrosion in the boiler; and, an equation describing the sulfation potential of the fuel mix, as a result of the direct and indirect interactions between all major ash-forming elements.3) A literature review relevant for the co-fired CFB cyclone vortex finder alloy selection and corrosion at 880 °C; An alloy selection study including long term exposures of several commercially available alloys identifying materials that are more than twice as cost-efficient as the often used alloy 253MA; a suggestion of novel methods for both systematic comparison of heavily degraded alloys, and for alloy service-life estimations; a detailed analysis of heavily degraded alloys 310S, 800H/HT and 600, identifying the driving corrosion mechanisms of the VF alloy degradation, including aspects of how the alloy internal mass transport and fireside surface interaction develops over time.The knowledge gained during this project has been used in the improvement work of the Perstorp 50 MWth CFB boiler, improving the boiler availability with 7 %, reducing the overall energy conversion costs with around 1.7 MEUR/year.
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| 4. |
- Karlsson, Sofia, 1982, et al.
(författare)
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Reducing high-temperature corrosion on high- alloyed stainless steel superheaters by co-combustion of municipal sewage sludge in a fluidised bed boiler
- 2015
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 139, s. 482-493
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Tidskriftsartikel (refereegranskat)abstract
- One way of mitigating alkali chloride induced corrosion in biomass and waste-fired boilers is by using additives or by co-combustion and thereby decreasing the corrosiveness of the flue gas and deposits. The effect of co-firing digested sewage sludge with a mixture of biomass and waste (78% bark pellets + 22% Solid Recovered Fuel, denoted "SRF'') was investigated in a 12 MW circulating fluidised bed (CFB) boiler. The initial corrosion attack of the stainless steel 304L at 600 degrees C (material temperature) was investigated during 24 h exposures. The exposures were carried out in the flue gas environment from three fuel-mixes: SRF, MSS1- low (SRF with municipal sewage sludge, low dosage) and MSS2- high (SRF with municipal sewage sludge, high dosage). The results showed that the most severe corrosion attack on 304L occurred without sewage sludge in the SRF exposure. This attack was characterised by a corrosion product layer up to 100 mu m in thickness and signs of internal corrosion of the steel. The deposit in the SRF case was dominated by alkali chlorides. The exposures with co- combustion of sewage sludge, MSS1-low and MSS2- high, showed a significant decrease in corrosion. The steel sample of 304L performed especially well in the latter case when it was protected by a thin oxide of less than 0.3 mu m in thickness. This deposit was dominated by sulphate- and phosphate- containing compounds but traces of aluminium silicate compounds where also found. Furthermore, the concentration of alkali chlorides was low. Thus, the initial corrosion attack was greatly reduced by co- combustion of digested sewage sludge with SRF.
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| 5. |
- Kassman, Håkan, et al.
(författare)
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Simultaneous reduction of NO and KCl during injection of ammonium sulphate in a biomass fired BFB boiler
- 2017
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Ingår i: 12th International Conference on Fluidized Bed Technology, CFB 2017. ; , s. 1093-1101
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Konferensbidrag (refereegranskat)abstract
- Sulphate containing additives, such as ammonium sulphate (AS), are used for sulphation of KCl during biomass combustion. Another aspect with injection of AS is that a significant NOx reduction is achieved but it may also have an impact on other flue gas components. Operating parameters such as the air excess ratio and the presence of combustibles could also have an effect on the flue gas chemistry involving NO and KCl. This paper is based on results obtained from a measurement campaign during combustion of demolition wood in a 63 MWth Bubbling Fluidised Bed (BFB) boiler. Ammonium sulphate was injected for simultaneous reduction of NO and KCl at two positions in the boiler i.e. in the upper part of the combustion chamber and in the empty pass. The impact of AS on the flue gas chemistry was investigated at different operating conditions. Several measurement tools including, IACM (online measurements of gaseous alkali chlorides) and gas analysis were applied. The position for injection of AS as well as the operating parameters had an impact on the flue gas chemistry for reduction of both NO and KCl.
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| 6. |
- Mattsson, Cecilia, 1970, et al.
(författare)
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Subcritical water de-polymerization of Kraft lignin: A process for future biorefineries. Structural characterization of bio-oil and solids
- 2015
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Ingår i: NWBC 2015 - 6th Nordic Wood Biorefinery Conference. ; , s. 112-119
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Konferensbidrag (refereegranskat)abstract
- A 2D-NMR analysis was carried out on fractionated bio-oil in order to investigate the result of the subcritical water base catalysed de-polymerization of LignoBoost Kraft lignin (350 °C, 25 MPa). It was confirmed that the signals from aliphatic lignin inter-unit linkages, i.e. ß-O-4’, ß-ß’, ß-1’ and ß-5’, had disappeared in all bio-oil fractions (light oil, heavy oil and suspended solids). This means that both aliphatic carbon-oxygen (C-O) and carbon-carbon (C-C) bonds in LignoBoost Kraft lignin have been broken and an effective de-polymerization has occurred. However, re-polymerization to higher molecular weight (Mw) fractions take place simultaneously. These higher Mw fractions (heavy oil and suspended solids) were found to be re-polymerized macromolecules (Mw distribution 5.4 kDa and 19.5 kDa resp.) with new structural networks based on guaiacol/disubstituted aromatic ethers and polyaromatic hydrocarbon structures tightly bound together. In this work it has been demonstrated that the subcritical water de-polymerization process of LignoBoost Kraft lignin does function; an effective de-oxygenation of LignoBoost Kraft lignin takes place, generating a bio-oil with a low content of atomic oxygen (15 wt.%) suitable for further processing at fossil-based oil refineries.
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| 7. |
- Mattsson, Cecilia, 1970, et al.
(författare)
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Using 2D NMR to characterize the structure of the low and high molecular weight fractions of bio-oil obtained from LignoBoost (TM) kraft lignin depolymerized in subcritical water
- 2016
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 95, s. 364-377
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Tidskriftsartikel (refereegranskat)abstract
- In this work a multilevel analysis approach have been used for characterization of LignoBoostTM kraft lignin and bio-oil produced from LignoBoostTM kraft lignin using a process based on subcritical water (350 degrees C, 25 MPa). LignoBoostTM kraft lignin and the different fractions of the bio-oil (light oil, heavy oil and suspended solids) was characterized with high field NMR (18.8 T, 2D(13)C, H-1-HSQC NMR and C-13-NMR), GPC, GC-MS and elemental composition to improve understanding of the subcritical process. By using high resolution 2D HSQC NMR it was possible determine the chemical structures both on low and high molecular weight fractions of the bio-oil. It was confirmed that the signals from the aliphatic lignin inter-unit linkages, i.e. beta-O-4', beta-beta', beta-1' and beta-5', had disappeared from all of the bio-oil fractions studied. This means that both the aliphatic carbon-oxygen (C-O) and to some extent carbon-carbon (C-C) bonds in LignoBoostTM kraft lignin have been cleaved and an effective depolymerization has occurred. However, re-polymerization into higher molecular weight (Mw) fractions takes place simultaneously. These higher Mw fractions (heavy oil and suspended solids) were found to be re-polymerized macromolecules, with new structural networks based on guaiacol/disubstituted aromatic ethers and polyaromatic hydrocarbon structures bound tightly together. (C) 2016 Elsevier Ltd. All rights reserved.
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| 8. |
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| 9. |
- Viklund, P., et al.
(författare)
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Deposit chemistry and initial corrosion during biomass combustion - The influence of excess O-2 and sulphate injection
- 2015
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Ingår i: Materials and Corrosion - Werkstoffe und Korrosion. - : Wiley. - 1521-4176 .- 0947-5117. ; 66:2, s. 118-127
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of superheater tubes is a serious problem during combustion of fuels with a high content of chlorine, such as waste and certain biomasses. The alkali chlorides are released to the flue gas and may condense on the heat exchanger tubes forming corrosive, chloride-rich deposits. In this work the effect of ammonium sulphate ((NH4)(2)SO4) injection on gaseous alkali chlorides, deposit chemistry and initial corrosion attack of superheater tubes during biomass combustion have been investigated. The investigation was carried out at three different sulphate injection rates (reference, low and high) and at three air excess ratios (lambda = 1.1, 1.2 and 1.4). Short-term exposures of Sanicro 28 specimens, using temperature controlled probes, were used for deposit collection and to study the initial corrosion attack. The results showed reduced concentrations of potassium chloride in the flue gas when injecting ammonium sulphate and in particular in combination with high air excess ratios. A decrease of chlorine was also observed in the deposit, but the concentrations did not always correlate to the flue gas measurements. In particular, it was evident that a subsequent sulphation occurred on the tube surface at low air excess ratios. Metallography revealed that sulphation reactions on the tube surface, rather than in the flue gas, had a detrimental effect on the initial corrosion attack. As a consequence, the corrosion attack correlated more clearly to the KCl(g) concentration in the flue gas than the chlorine content in the deposit.
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| 10. |
- Åmand, Lars-Erik, 1957, et al.
(författare)
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Aspects on the Flue Gas Chemistry of KCl, NO and CO During Injection of Ammonium Sulphate - An Experimental Approach
- 2015
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Ingår i: 22nd International Conference on Fluidized Bed Conversion June 14-17 2015, Turku, Finland. ; , s. 583-593
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Konferensbidrag (refereegranskat)abstract
- Sulphate containing additives, such as ammonium sulphate (AS, (NH4)2SO4), are used for sulphation of KCl during biomass combustion. Another aspect with injection of AS is that a significant NOx reduction is achieved but it may also have an impact on other flue gas components such as CO. The concentration of oxygen and the presence volatile combustibles could also have an effect on the flue gas chemistry involving KCl, NO and CO. This paper is based on results obtained from two measurement campaigns during co-combustion of wood chips and straw pellets in a 12 MW circulating fluidised bed (CFB) boiler. In the first campaign, the NO reduction performance of AS, ammonia and urea was compared. In the second one, AS was injected at three positions in the boiler i.e. in the upper part of the combustion chamber, in the cyclone inlet, and in the cyclone. The impact of AS on the flue gas chemistry was investigated at three air excess ratios (λ= 1.1, 1.2 and 1.4). Several measurement tools including, IACM (on-line measurements of gaseous alkali chlorides) and gas analysis were applied. The position for injection of AS as well as the different air excess ratios had a great impact on the flue gas chemistry for especially KCl and NO.
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