| 1. |
- Lyckeskog, Huyen, 1985, et al.
(author)
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Catalytic depolymerisation and conversion of Kraft lignin into liquid products using near-critical water
- 2014
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In: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 86, s. 67-75
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Journal article (peer-reviewed)abstract
- A high-pressure pilot plant was developed to study the conversion of LignoBoost Kraft lignin into bio-oil and chemicals in near-critical water (350◦C, 25 MPa). The conversion takes place in a continuous fixed-bed catalytic reactor (500 cm3) filled with ZrO2 pellets. Lignin (mass fraction of approximately 5.5%) is dispersed in an aqueous solution containing K2CO3(from 0.4% to 2.2%) and phenol (approximately 4.1%).The feed flow rate is 1 kg/h (reactor residence time 11 min) and the reaction mixture is recirculated internally at a rate of approximately 10 kg/h. The products consist of an aqueous phase, containing phenolic chemicals, and a bio-oil, showing an increased heat value (32 MJ/kg) with respect to the lignin feed. The 1-ring aromatic compounds produced in the process are mainly anisoles, alkylphenols, guaiacols and catechols: their overall yield increases from 17% to 27% (dry lignin basis) as K2CO3 is increased.
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| 2. |
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| 3. |
- Belkheiri, Tallal, 1985, et al.
(author)
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Kraft Lignin Depolymerization in Near-Critical Water: Effect of Changing Co-Solvent
- 2014
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In: Cellulose Chemistry and Technology. - 0576-9787. ; 48:9-10, s. 813-818
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Journal article (peer-reviewed)abstract
- As part of developing a process to valorize lignin in a pulp mill with lignin separation, the depolymerisation of lignin to valuable chemicals was investigated in near-critical water. This was done by using methanol as co-solvent and hydrogen donor, phenol to suppress repolymerization (e.g. formation of char), and ZrO2 as a heterogeneous catalyst, with potassium carbonate as a co-catalyst. The reaction was carried out in a continuous flow fixed-bed reactor (500 cm(3)), at 280-350 degrees C and 25MPa. An important aspect is to suppress char formation. Therefore, the char formation was studied by using different concentrations of methanol and phenol. The char yield varied between 14% and 26%. When using methanol as the only co-solvent, the char yield decreased with increasing methanol concentration. Adding phenol resulted in a further decrease. The reactor outlet consisted mainly of two liquid phases, an aqueous and an oil phase, mixed together. The chemical analysis of the aqueous phase showed the presence of mainly phenolic compounds, for instance guaiacol, catechol, phenol and cresol.
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| 4. |
- Berglin, N., et al.
(author)
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Pilot-scale combustion studies with kraft lignin in a powder burner and a CFB boiler
- 2010
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In: Tappi Journal. - 0734-1415. ; 9:6, s. 24-30
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Journal article (peer-reviewed)abstract
- Processes have been developed to produce a solid biofuel with high energy density and low ash content from kraft lignin precipitated from black liquor. Pilot-scale tests of the lignin biofuel were carried out with a 150 kW powder burner and a 12 MW circulating fluidized bed (CFB) boiler. Lignin powder could be fired in a powder burner with good combustion performance after some trimming of the air flows to reduce swirl. Lignin dried to 10% moisture content was easy to feed smoothly and had less bridging tendencies in the feeding system than did wood/bark powder. In the CFB boiler, lignin was easily handled and cofired together with bark. Although the filter cake was broken into smaller pieces and fines, the combustion was not disturbed. When cofiring lignin with bark, the sulfur emission increased compared with bark firing only, but most of the sulfur was captured by calcium in the bark ash. Conventional sulfur capture also occurred with addition of limestone to the bed. The sulfur content in the lignin had a significantly positive effect on reducing the alkali chloride content in the deposits, thus reducing the high temperature corrosion risk.
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| 5. |
- Elled, Anna-Lena, 1975, et al.
(author)
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Composition of agglomerates in fluidized bed reactors for thermochemical conversion of biomass and waste fuels Experimental data in comparison with predictions by a thermodynamic equilibrium model
- 2013
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In: Fuel. - : Elsevier BV. - 0016-2361. ; 111, s. 696-708
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Journal article (peer-reviewed)abstract
- Controlled combustion tests of biomass were performed in the 12 MWth circulating fluidized bed (CFB) boiler located on the campus of Chalmers University of Technology. The aim was twofold: to investigate the composition of agglomerated material and also to highlight the reasons for sintering and agglomeration during thermochemical conversion of biomass and wastes in fluidized bed reactors using quartz sand as bed material. Bed ash from three different tests regarding fuel or fuel mixtures (wood with straw, bark, and bark with refused derived fuel) was analysed to determine the ash elements using: (a) inductive coupled plasma (ICP) equipped with optical emission spectroscopy (OES) and (b) scanning electron microscopy equipped with an electron dispersive X-ray spectrometer (SEM-EDX). Chemical equilibrium calculations were also performed to support the interpretation of the experimental findings. It was found that the combination of (i) well controlled full-scale tests in a fluidized bed boiler, (ii) the use of line-scans by the EDX spectrometer of the SEM on bed samples and (iii) thermodynamic equilibrium modelling is a powerful tool in understanding the phenomena of bed agglomeration using quartz sand.
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| 6. |
- Elled, Anna-Lena, 1975, et al.
(author)
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Sewage sludge as a deposit inhibitor when co-fired with high potassium fuels
- 2010
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In: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 34:11, s. 1546-1554
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Journal article (peer-reviewed)abstract
- The objective of this work is to survey the fate of potassium in the gas phase of a fluidised bed boiler and gain deeper understanding of the involved mechanisms during co-firing of municipal sewage sludge with biomass containing high amounts of potassium and chlorine. The results show that formation of alkali chlorides in the flue gas and corrosive deposits on heat transfer surfaces can be controlled by addition of municipal sewage sludge even though the fuel is highly contaminated with chlorine. The beneficial effects are partly due to the content of sulphur in the sludge, partly to the properties of the sludge ash. The sludge ash consists of both crystalline and amorphous phases. It contains silica, aluminium, calcium, iron and phosphorus which all are involved in the capture of potassium. (c) 2010 Elsevier Ltd. All rights reserved.
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| 7. |
- Karlsson, Sofia, 1982, et al.
(author)
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Reducing High Temperature Corrosion when Burning Waste by Adding Digested Sewage Sludge
- 2011
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In: Swedish - Finnish Flame Days, January 26-27 2011 in Piteå, Sweden, The Swedish and Finnish National Committees of the International Flame Research Foundation (IFRF) and The Scandinavian - Nordic Section of the Combustion Institute (SNCI).
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Conference paper (other academic/artistic)abstract
- The presence of alkali chlorides are well known to cause high temperature corrosion during combustion of biomass and waste. Low alloyed steels as well as stainless steels are experiencing an accelerated corrosion attack in such environments. Even though more highly alloyed steels (i.e. higher Cr/Fe ratio in the steel) are being used, there is only a small decrease in corrosion rate compared to low alloyed steels. To maintain the corrosion rates at an acceptable level the temperature of the superheaters (used for steam production to the steam turbine) of the boiler have been lowered. However, this causes a decrease in power production when the driving force for waste-to-energy boilers in the future is to increase the power production by increasing the temperatures of the steam from the final superheater stage.One of the reasons for the corrosive behavior of alkali chlorides towards stainless steels is the formation of alkali chromates. It has been shown that alkali chlorides react with chromium in the initial formed protective oxide on stainless steel:1/2Cr2O3(s) + 3/4O2(g) + H2O(g) + 2KCl(s) K2CrO4 (s) + 2 HCl(g) This result in a chromium depleted oxide which is converted into an iron-rich fast-growing oxide. This oxide has much poorer protective properties as it has higher diffusion rates compared to chromium rich oxides. Furthermore, the iron rich oxide is also more susceptible towards chlorine induced corrosion by chlorine ions penetrating the oxide scale. This leads to the formation of transition metal chlorides (e.g. FeCl2) at the metal/oxide interface causing poor scale adherence.A way to mitigate the alkali chloride induced corrosion is by introducing fuel additives and thus, changing the flue gas chemistry and furthermore the deposit composition. In this study, the effect of digested sewage sludge as fuel additive was investigated at the 12MW circulating fluidized bed (CFB) boiler at Chalmers University of Technology. The initial corrosion attack of the stainless steel 304L(Fe18Cr10Ni exposed at 600°C (material temperature) was investigated during 24h exposure of three different environments. Deposit analysis by means of XRD and IC were carried out using Sanicro 28 (Fe35Cr27Ni31) as sample ring. The exposures were denoted “RDF” (a reference exposure 80%Bark + 20%RDF), “SjöMed” (80%Bark + 20%RDF with sewage sludge from Sjölundaverket (medium dosage)) and “HimHög” (80%Bark + 20%RDF with sewage sludge from Himmerfjärdsverket (high dosage)).The results showed that the most severe corrosion attack of 304L occurred in the “RDF” exposure. The corrosion attack was characterized by an up to 100µm thick corrosion product layer and signs of internal corrosion of the steel. The deposit in the RDF exposure was dominated by alkali chlorides. The exposures with sewage sludge additions, “SjöMed” and “HimHög”, showed a remarkable decrease in corrosion rate. 304L performed especially well in the “HimHög” exposure, the steel ring was protected by a thin oxide, less than 0.3µm in thickness. Furthermore, the deposit was dominated by sulphate- and phosphate containing compounds. The presence of alkali chlorides was low.
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| 8. |
- Kassman, Håkan, 1962, et al.
(author)
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Ammonium Sulphate and Co-Combustion with Peat – Two Strategies to Reduce Gaseous KCl and Chlorine in Deposits during Biomass Combustion
- 2010
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In: In Proceedings from: "Impacts of Fuel Quality on Power Production & Environment", Lapland, Finland, August 29th - September 3rd 2010.
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Conference paper (other academic/artistic)abstract
- Combustion of a biomass with an enhanced content of chlorine (Cl) can result in operational problems including deposit formation and superheater corrosion. The strategies to reduce such problems include co-combustion and the use of additives. The positive effects of such measures are mainly due to sulphation of the alkali chlorides (KCl for biomass) to less corrosive alkali sulphates or capture of released alkali (K) in components such as potassium aluminium silicates. A mixture of wood pellets and straw pellets was fired in a 12 MW circulation fluidised bed (CFB) boiler. PVC was added to the fuel in order to achieve a further enhanced reference level of gaseous KCl during certain tests. Two strategies were applied to decrease the risk for superheater corrosion by reducing gaseous KCl and content of chlorine in deposits. The strategies were sulphation of KCl by injection of ammonium sulphate and co-combustion with peat. During co-combustion of biomass with peat both sulphation of KCl and capture of released K in ash components can be of importance. The results were evaluated by means of several advanced measurement tools including IACM (on-line measurements of gaseous KCl), deposit measurements (chemical composition in collected deposits, initial corrosion), ash analysis (chemical composition in fly ashes). The overall performance was better for ammonium sulphate, which significantly reduced gaseous KCl. Meanwhile almost no chlorine was found in the deposits. Only a minor reduction of gaseous KCl was obtained during co-combustion of biomass with peat although the chlorine content in the deposits was greatly reduced.
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| 9. |
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| 10. |
- Kassman, Håkan, 1962, et al.
(author)
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Measures to reduce chlorine in deposits: Application in a large-scale circulating fluidised bed boiler firing biomass
- 2011
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In: Fuel. - Amsterdam : Elsevier BV. - 0016-2361 .- 1873-7153. ; 90:4, s. 1325-1334
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Journal article (peer-reviewed)abstract
- Combustion of biomass with a high content of alkali (mainly potassium, K) and chlorine (Cl) can result in operational problems including deposit formation and superheater corrosion. Among the measures applied to decrease such problems are co-combustion and the use of additives. The positive effects of these measures are to a large extent either sulphation of the alkali chlorides (KCl) to less corrosive alkali sulphates or capture of alkali from KCl during release of HCl. A test campaign was carried out in a large-scale circulating fluidised boiler fired with biomass where the measures applied were sulphation by ammonium sulphate and co-combustion with peat. Their performance was evaluated by means of several advanced measurement tools including: IACM (on-line measurements of gaseous KCl); a low-pressure impactor (size distribution and chemical composition of extracted fly ash particles) and deposit measurements (chemical composition in collected deposits). The overall performance was better for ammonium sulphate, which significantly lowered KCl in the flue gas. Meanwhile no chlorine was found in the deposits. Only a minor reduction of gaseous KCl was obtained during co-combustion with peat although the chlorine content in the deposits was greatly reduced. These findings were supported by the results from the impactor measurements. (C) 2010 Elsevier Ltd. All rights reserved.
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