Papers by Flemming Frandsen
European Biomass Conference and Exhibition Proceedings, 2016
A method to simulate the reaction between gaseous K-species and solid additives, at suspension fi... more A method to simulate the reaction between gaseous K-species and solid additives, at suspension fired conditions has been developed, using an entrained flow reactor (EFR). A water slurry containing solid additives (kaolin or coal fly ash) and KCl, is injected into the EFR and the solid products are collected from the cyclone and filter. The K-capture reaction is evaluated by determining the fraction of water-insoluble K in the products. The results showed that KCl can effectively be captured by kaolin and coal fly ash, forming water-insoluble Kaluminosilicates. The amount of K, captured per gram of additives, rose when increasing the molar ratio of K/(Al+Si) in the reactants. A change of the reaction temperature, from 1100 °C to 1450 °C, did not significantly influence the extent of the reaction, which is in contradiction to the trend observed in previous fixed-bed reactor studies. The method using the EFR, developed in this study, will be applied for further studies on the reaction of different additives and alkali species.
Energy & Fuels, Feb 1, 2018
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Fuel Processing Technology, 2013
Trace element partitioning in co-combustion of a bituminous coal and a solid recovered fuel (SRF)... more Trace element partitioning in co-combustion of a bituminous coal and a solid recovered fuel (SRF) was studied in an entrained flow reactor. The experiments were carried out at conditions similar to pulverized coal combustion, with SRF shares of 7.9 wt.% (wet basis), 14.8 wt.% and 25.0 wt.%. In addition, the effect of additives such as NaCl, PVC, ammonium sulphate, and kaolinite on trace element partitioning was investigated. The trace elements studied were As, Cd, Cr, Pb, Sb and Zn, since these elements were significantly enriched in SRF as compared to coal. During the experiments, bottom ash was collected in a chamber, large fly ash particles were collected by a cyclone with a cutoff diameter of~2.5 μm, and the remaining fly ash particles were gathered in a filter. It was found that when coal was co-fired with SRF, the As, Cd, Pb, Sb and Zn content in filter ash/cyclone ash increased almost linearly with their content in fuel ash. This linear tendency was affected when the fuels were mixed with additives. The volatility of trace elements during combustion was assessed by applying a relative enrichment (RE) factor, and TEM-EDS analysis was conducted to provide qualitative interpretations. The results indicated that As, Cd, Pb, Sb and Zn were highly volatile when co-firing coal and SRF, whereas the volatility of Cr was relatively low. Compared with coal combustion, co-firing of coal and SRF slightly enhanced the volatility of Cd, Pb and Zn, but reduced the volatility of Cr and Sb. The Cl-based additives increased the volatility of Cd, Pb and As, whereas addition of ammonium sulphate generally decreased the volatility of trace elements. Addition of kaolinite reduced the volatility of Pb, while the influence on other trace elements was insignificant. The results from the present work imply that trace element emission would be significantly increased when coal is co-fired with SRF, which may greatly enhance the toxicity of the dusts from coal-fired power plant.
Energy & Fuels, Feb 20, 2018
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Fuel, Apr 1, 2019
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Energy & Fuels, Jun 14, 2011
The release and transformation of inorganic elements during grate-firing of bran was studied via ... more The release and transformation of inorganic elements during grate-firing of bran was studied via experiments in a laboratory-scale reactor, analysis of fly ash from a grate-fired plant, and equilibrium modeling. It was found that K, P, S, and to a lesser extent Cl and Na were released to the gas phase during bran combustion. Laboratory-scale experiments showed that S was almost fully vaporized during pyrolysis below 700°C. Sixty to seventy percent of the K and P in bran was released during combustion, in the temperature range 900À1100°C. The release of K and P was presumably attributed to the vaporization of KPO 3 generated from thermal decomposition of inositol phosphates, which were considered to be a major source of P and K in bran. The influence of additives such as CaCO 3 , Ca(OH) 2 , and kaolinite on the release was also investigated. Ca-based additives generally increased the molar ratio of the released K/P, whereas kaolinite showed an opposite effect. Thermodynamic modeling indicated that the fly ash chemistry was sensitive to the molar ratio of the released K/P. When the molar ratio of the released K/P was below 1, KPO 3 and P 4 O 10 (g) were the main stable K and P species at temperatures higher than 500°C. Below 500°C, the KPO 3 and P 4 O 10 (g) may be converted to H 3 PO 4 (l), which may cause severe deposit build-up in the economizers of a grate-fired boiler. By increasing the molar ratio of the released K/P to above 2, the equilibrium distribution of the K and P species was significantly changed and the formation of H 3 PO 4 (l) was not predicted by thermodynamic modeling.
In the present study a method to simulate the reaction between gaseous KCl and kaolin at suspensi... more In the present study a method to simulate the reaction between gaseous KCl and kaolin at suspension fired condition was developed using a pilot-scale entrained flow reactor (EFR). Kaolin was injected into the EFR for primary test of this method. By adding kaolin, KCl can effectively be captured, forming water-insoluble K-aluminosilicate. The amount of K captured by 1 g kaolin rose when increasing the molar ratio of K/Si in the reactant. Changing of reaction temperature from 1100 °C to 1300 °C did not influence the extent of reaction, which is different from the results observed in previous fixed-bed reactor. The method using the EFR developed in this study will be applied for further systematic investigation of different additives.
A water slurry, consisting of KCl and Al-Si based additives (kaolin and coal fly ash) was fed int... more A water slurry, consisting of KCl and Al-Si based additives (kaolin and coal fly ash) was fed into an entrained flow reactor (EFR) to study the K-capturing reaction of the additives at suspension-fired conditions. Solid products collected from the reactor were analysed with respect to total and water-soluble K content to quantify the extent of the K-capturing reaction. The results showed that under suspension-fired conditions (1100 °C-1450 °C), kaolin and coal fly ash can effectively capture gaseous KCl. When increasing the mass ratio of KCl to Al-Si additives in the reactants, the conversion of KCl to K-aluminosilicate decreased. When reaction temperature increased from 1100 °C to 1450 °C, the conversion of KCl does not change significantly, which differs from the trend observed in fixed-bed reactor.
Social Science Research Network, 2022
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
insights from laboratory scale studies DTU Orbit (18/01/2019) Alkali chloride induced corrosion o... more insights from laboratory scale studies DTU Orbit (18/01/2019) Alkali chloride induced corrosion of superheaters under biomass firing conditions: Improved insights from laboratory scale studies One of the major operational challenges experienced by power plants firing biomass is the high corrosion rate of superheaters. This limits the outlet steam temperature of the superheaters and consequently, the efficiency of the power plants. The high corrosion rates have been attributed to the formation of corrosive deposits (rich in alkali chlorides) on the surfaces of the superheaters. Accordingly, an extensive number of fundamental investigations have been undertaken to understand the basic mechanisms behind the alkali chloride induced high temperature corrosion of superheaters (for example, [1–3]). However, complete understanding of the corrosion mechanism under biomass-firing conditions has not yet been achieved. This is attributed partly to the complex nature of the corrosion process sin...
Surface Engineering, 2016
Superheater tubes in biomass-fired power plants experience high corrosion rates due to condensati... more Superheater tubes in biomass-fired power plants experience high corrosion rates due to condensation of corrosive alkali chloride rich deposits. To explore the possibility of reducing the corrosion attack by the formation of an initial protective oxide layer, the corrosion resistance of pre-oxidized Al and Ti-containing alloys (Kanthal APM and Nimonic 80A, respectively) was investigated under laboratory conditions mimicking biomass-firing. The alloys were pre-oxidized at 900 o C for 1 week. Afterwards, pre-oxidized samples, and virgin non-pre-oxidized samples as reference, were coated with a synthetic deposit of KCl and exposed at 560 o C for 1 week to a gas mixture typical of biomass firing. Results show that pre-oxidation could hinder the corrosion attack; however the relative success was different for the two alloys. While corrosion attack was observed on the preoxidized Kanthal APM, the morphology of the preoxidized Nimonic 80A was significantly unaffected suggesting protection of the alloy from the corrosive environment.
Surface and Coatings Technology, 2017
Development of corrosion resistant materials in biomass fired power plants demands specific atten... more Development of corrosion resistant materials in biomass fired power plants demands specific attention since the condensation of deposits rich in KCl on heat exchanger surfaces induces severe corrosion attack, which is different from corrosion in traditional coal fired plants. Therefore, the ability of preoxidized layers formed on a commercial Cr-Ti-Al-containing Ni-based alloy (Nimonic 80A) to withstand biomass-induced corrosion was investigated. Preoxidation treatments at 900 o C in O2 and O2 + 10 vol % H2O, respectively, were conducted before samples were exposed to conditions that mimicked biomass firing. Complementary characterization methods were employed to study samples after preoxidation as well as after corrosion exposure. The oxides obtained by the preoxidation treatments protected the alloy during corrosion exposure at 560 o C for a period of 168 h. In contrast, non-preoxidized samples suffered corrosion attack and formed porous non-protective oxides containing the alloying elements, Ni, Cr, Ti and Al. The influence of the preoxidation layers on the corrosion mechanism is discussed.
Metallography, Microstructure, and Analysis, 2016
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Energy & Fuels, 2015
The variable flue gas composition in biomass-fired plants, among other parameters, contributes to... more The variable flue gas composition in biomass-fired plants, among other parameters, contributes to the complexity of high temperature corrosion of materials. Systematic parameter studies are thus necessary to understand the underlying corrosion mechanisms. This paper investigates the effect of water (H2O) vapour content in the flue gas, on the high temperature corrosion of austenitic stainless steel (TP 347H FG) under laboratory conditions, to improve the understanding of corrosion mechanisms. Deposit-coated and deposit-free samples were isothermally exposed for 72 h in a synthetic flue gas atmosphere containing either 3 vol % or 13 vol % H2O vapour. Comprehensive characterization of the corrosion products was carried out by the complementary use of microscopic, spectroscopic and diffraction based techniques. To evaluate the effect of the exposure time, results were compared to previous results with longer isothermal exposure over 168 h, and indicated that the development of a Nirich layer due to selective attack was time dependent. The increase in water vapour decreased the measurable corrosion attack, and, in addition decreased sulphation was observed. Results from the current investigation and from previously reported findings suggest that an increase in water vapour will cause competitive adsorption on active sites.
Energy & Fuels, 2015
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Co-combustion of refuse derived fuels (RDF) with coal in pulverized coal-fired power plants can p... more Co-combustion of refuse derived fuels (RDF) with coal in pulverized coal-fired power plants can potentially increase the electrical efficiency of utilizing RDF and reduce the formation of some harmful pollutants such as dioxins. The objective of this project was to provide a general assessment of the technical issues related to co-combustion of coal and RDF, and to improve the fundamental understandings of this subject. The project was carried out in collaboration between the CHEC Research Centre at DTU Chemical Engineering and DONG Energy Power A/S, and was financially supported by Energinet.dk. The project work mainly involved conducting pilot-scale experiments in the CHEC entrained flow reactor, carrying out full-scale aerosol measurements at the Esbjergvaerket (ESV), doing global equilibrium calculations, and performing thermogravimetric experiments. Through performing co-combustion experiments in the CHEC entrained flow reactor, the burnout, NO and SO 2 emissions, the transformation of ash forming species, the formation of deposits, and the partitioning of trace elements during co-combustion of coal and solid recovered fuel (SRF) were studied systematically. The effect of different coal properties, SRF properties, and mass share of SRF on co-combustion was investigated. Besides, global equilibrium calculations were conducted to interpret the results of the entrained flow experiments. The formation of fine particles during cocombustion of coal and SRF was also investigated, through performing full-scale aerosol measurements at the Esbjergvaerket (ESV). The influence of co-combustion on the concentration and composition of the fine particles was evaluated, and the impact on the dust emissions was discussed. In addition, a fundamental study on the interactions of coal and different waste materials during pyrolysis was conducted through thermogravimetric experiments. In general, the results obtained from this project have significantly improved the understandings of fuel conversion, ash transformation, ash deposition, and pollutant formation during co-combustion of coal and refuse derived fuels. These results have also provided essential knowledge regarding the fuel selection and process optimization of co-firing refuse derived fuels and coal under suspension-firing conditions. Appendixes A. Report: Solid fuel interactions in co-combustion-a literature review.
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Papers by Flemming Frandsen