| 1. |
- Berguerand, Nicolas, 1978, et al.
(författare)
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Producer Gas Cleaning in a Dual Fluidized Bed - a Comparative Study of Performance with Ilmenite and a Manganese Oxide as Catalysts
- 2012
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 2:3, s. 8-252
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Tidskriftsartikel (refereegranskat)abstract
- Secondary catalytic gas conditioning is one strategy to eliminate tars formed in a producer gas during biomass gasification. However, most catalysts tend to lose their tar reforming activity after short period of operation due to carbon formation. A novel technique for catalytic gas cleaning based on two interconnected fluidized beds has been investigated; this technique can be applied to all types of gasifiers. The idea is to reform the tar components into useful molecules - even at high tar contents - by means of a circulating catalyst. More precisely, the producer gas is cleaned with catalyst in one of the reactors, referred to as the fuel reactor (FR), while the catalyst is continuously regenerated in another reactor, the air reactor (AR). The system described here is coupled with the Chalmers 2-4 MWth biomass gasifier while the AR is fed with nitrogen-diluted air. The effect of different catalysts on both the tar content and the gas composition was investigated. Some of the tested materials do not only reform tars, they also influence the H2/CO-ratio in a beneficial manner; in particular, ratios closer to 3 in the reformed gas are favorable if subsequent methanation is implemented. In this paper, comparative results based on testing with manganese- and iron-based catalysts are presented. The former is a manufactured catalyst while the latter is a natural ore. Results suggest that both show satisfying ability for regeneration from carbon deposits. Higher temperature enhances tar decomposition during experiment with both catalysts. Moreover, the iron-based catalyst enhances water gas shift activity, which in turns impacts the total amount of produced gas. On the other hand, the manganese-based catalyst seems to display higher propensity for tar conversion.
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| 2. |
- Berguerand, Nicolas, 1978, et al.
(författare)
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Producer Gas Cleaning in a Dual Fluidized Bed Reformer using Two Catalysts
- 2011
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Ingår i: Compendium of the International Conference on Polygeneration Strategies11. ; , s. 9-
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Konferensbidrag (refereegranskat)abstract
- The most elegant method to remove tars out of producer gas from biomass gasification is catalytic hot gas cleaning. However, most catalysts are poisoned after short operation due to carbon formation or by other contaminants on their active sites. A novel technique for catalytic gas cleaning based on two interconnected fluidized beds has been investigated. The idea is to reform the tar components into useful molecules by means of a circulating catalyst, also called oxygen carrier in the following. The producer gas is cleaned in one of the reactors, referred to as the fuel reactor (FR), while it is continuously regenerated in the air reactor (AR). The two reactors are separated by loop seals in such a way that gas leakage is prevented between the reactors while solid circulation occurs. By varying the circulation rate of material in the system, the residence time in the raw gas stream and the frequency of regeneration can be adjusted. Meanwhile, the required amount of oxygen for partial oxidation of the tars is transferred. The system described here is coupled with its FR to the Chalmers 2-4 MWth biomass gasifier while the AR is fed with nitrogen-diluted air. In preliminary tests, the effect of different catalysts on both the tar content and the gas composition was investigated. Some of the tested materials do not only reform tars, they also influence the H2/CO-ratio in a beneficial manner. In this paper, comparative results based on testing with manganese and iron based catalysts are presented. Results suggest that both show satisfying ability for regeneration from carbon deposits. Higher temperature enhances tar removal during experiment with both catalysts. Moreover, the iron-based catalyst enhances water gas shift activity, which in turns impacts the total amount of produced gas. On the other hand, the manganese-based catalyst seems to express higher propensity for tar conversion. These observations elicit an interesting flexibility of the process as a judicious set of catalyst in coordination with pertinent operating conditions can be chosen to achieve desired purposes.
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| 3. |
- Berguerand, Nicolas, 1978, et al.
(författare)
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Use of Nickel Oxide as a Catalyst for Tar Elimination in a Chemical-Looping Reforming Reactor Operated with Biomass Producer Gas
- 2012
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 51:51, s. 16610-16616
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Tidskriftsartikel (refereegranskat)abstract
- A secondary tar-cleaning process based on Chemical-Looping Reforming (CLR) was investigated for upgrading biomass producer gas, derived from the Chalmers University of Technology 2-4 MW indirect gasifier. The experiments were conducted in a bench-scale CLR reactor using a manufactured nickel oxide (NiO) catalyst. Although Ni is a well-documented and efficient steam-reforming catalyst, it is susceptible to rapid deactivation under tar-rich conditions. The aim of this study was to explore the advantages of CLR as a gas-cleaning application, a process which offers continuous regeneration of the carbon deposits on catalysts. The tar-reforming performance of this Ni material and its influence on the gas composition and in particular its potential to increase the H2/CO ratio, were studied. The system was tested at reforming temperatures that ranged from 700°C to 880°C and at oxygen concentrations of 1.0% and 2.2% in the inlet feed to regenerator section. The results confirm the strong ability of the catalyst to reform tars. Higher process temperatures clearly promoted tar conversion, with 96% overall conversion at 880°C (99% if benzene is excluded), as compared with 45% conversion at 700°C. The hydrogen production was favored when temperature was raised. Though, a maximum ratio H2/CO of 2.2 was observed at 750°C. Finally, no time-on-stream deactivation of the catalyst in the CLR was observed during the test, which lasted almost 7 hours.
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| 4. |
- Hermansson, Sven, 1978, et al.
(författare)
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On-line monitoring of fuel moisture-content in biomass-fired furnaces by measuring relative humidity of the flue gases
- 2011
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 89:11, s. 2470-2476
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Tidskriftsartikel (refereegranskat)abstract
- Combustion of biomass for heat and power production is continuously growing in importance, because of incentivesfor replacing fossil energy resources with renewable ones. In biomass combustion, the moisture content of the fuel isan essential operation parameter, which often fluctuates for biomass fuels. Variation in moisture content complicatesthe operation of the furnaces and results in an uncertainty in the energy content of the fuel delivered to a plant.The fuel moisture-content in a furnace may be determined either by direct measurement on the entering fuel or bymeasuring the moisture and oxygen contents of the flue gases deriving the moisture content of the fuel. However,reliable methods of a motivated cost for the small to medium-scale furnaces are today not available. An exception isif the furnace is equipped with flue-gas condenser, which can be used to estimate the moisture content of the fluegases. A limitation of this method is, though, that not all furnaces have flue-gas condensers and that the measuredsignal has an inherent time delay.In thiswork, measurement of the relative humidity (RH) of the flue gases froma furnace is investigated as the centralcomponent in the on-line monitoring of the moisture content of the fuel in a furnace. The method was analysedwith humid air in a laboratory environment and tested for accuracy and dynamical behaviour in two biomass-firedheat-production units, one circulating fluidised-bed boiler (CFB) and one grate furnace. The results show that themethod, which is easy to calibrate on site, can be used to predict the moisture content of the biomass fuel in thegrate furnace with very good precision (
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| 5. |
- Leffler, Tomas, 1962, et al.
(författare)
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Combined measurement techniques for fast detection of alkali release in fluidized bed combustion
- 2021
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Ingår i: CFB 2021 - Proceedings of the 13th International Conference on Fluidized Bed Technology. ; , s. 339-344
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Konferensbidrag (refereegranskat)abstract
- This study presents an approach combining three alkali-measuring techniques to quantitatively measure the released alkali compounds during the thermal conversion of biomass and Municipal Solid Waste (MSW) in fluidized bed reactors. The method includes measurements of alkali-containing species in the gas phase, as aerosols, or taken up by the bed material. Two techniques are used for online alkali detection in the flue gas: An In-situ Alkali Chloride Monitor (IACM), and a Surface Ionisation Detector (SID). The third technique is an Electronic Tongue (ET) used for the post-analysis of alkali content in the bed material. These three techniques form a method used to determine the alkali present in gaseous state (IACM), as aerosols (SID), and in the bed material (ET). The use of these techniques can enable the determination of optimal intervals to regenerate the bed material and to avoid bed agglomeration, slagging and fouling, as well as high-temperature corrosion.
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| 6. |
- Leffler, Tomas, 1962, et al.
(författare)
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Monitoring of bed material in a biomass fluidized bed boiler using an electronic tongue
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 340
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conversion of biomass fuel mixes in fluidized beds can cause agglomeration. To counteract agglomeration, bed material is gradually exchanged with virgin bed material, and this results in increased disposal of used bed material. Furthermore, the bed material exchange represents a costly option, as it involves a cost for virgin bed material, for landfill, and for unplanned downtime of the plant. This paper presents a novel method for the evaluation of bed material quality: the electronic tongue (ET). Evaluation of bed material quality can contribute toward decreasing the cost of unnecessary exchanges of bed material. The proposed method was tested on bed material sampled on an almost daily basis from a commercial fluidized bed boiler during several months of operation. A two-electrode ET was used for the evaluation of the bed material quality. The analysis relied on pulsed voltammetry measurements and multivariate data analysis with Principal Component Analysis (PCA). The results suggest that it is possible to follow bed material changes and that the ET, after further development, may be used to optimize the material flows connected to the bed material. Further research is being conducted to optimize the ET's performance and its application in monitoring bed material.
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| 7. |
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| 8. |
- Lind, Fredrik, 1978, et al.
(författare)
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Ilmenite and Nickel as Catalysts for Upgrading of Raw Gas Derived from Biomass Gasification
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:2, s. 997-1007
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Tidskriftsartikel (refereegranskat)abstract
- Two metal oxides, naturally occurring ilmenite (iron titanium oxide) and manufactured nickel oxide supported on an α-Al2O3 matrix (NiO/AL2O3), were compared as catalysts for secondary biomass gas upgrading. The experiments were conducted in a Chemical-Looping Reforming (CLR) reactor, which combines biomass gas upgrading with continuous regeneration of coke deposits. The CLR system was fed with a tar-rich producer gas from the Chalmers 2–4 MW biomass gasifier, and the possibilities to reduce the tar fraction and to increase the yield of hydrogen were evaluated for temperatures between 700°C and 880°C. A system-wide molar balance was established, to enable calculations of tar removal efficiency on a mass basis; these results were further compared with those for the more widely used tar-to-reformed gas ratio, yielding tar concentrations in units of gtar/Nm3gas. Both materials exhibited activity with respect to tar decomposition and increased the yield of hydrogen. In addition, both tar removal and hydrogen production were increased with increases in temperature. All the phenolic compounds and a large proportion of the one-ring branched tars were decomposed at 800ºC by the two catalysts, despite the fact that the tar load in the raw gas was as high as 30 gtar/Nm3gas. Results from the mole balance showed that it is important to specify on what basis the tar removal efficiency is calculated. The tar removal efficiency was calculated to 95% for the Ni/Al2O3 catalyst at 880°C and to 60% for the ilmenite catalyst at 850°C on tar-to-reformed gas basis. When the produced permanent gases were removed from the reformed gas the same calculations yielded the tar removal efficiency of 86% and 42% respectively. The testing of serial samples of the effluent stream from the regeneration reactor for carbon oxides showed that coke was removed from the catalyst, and no deactivation by coke deposits was detected during the 8 hours of operation of the CLR reactor.
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| 9. |
- Lindmark, Hampus, 1992, et al.
(författare)
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A material degradation study of novel FeCrAl alloys, stainless steels and nickel base alloy in fluidized bed heat exchangers of a waste-fired CFB boiler
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to evaluate the material degradation resistance of two newly developed FeCrAl alloys exposed within the loop seal region of an 85 MWth waste-fired CFB boiler in Sweden. In addition to the FeCrAl alloys, two commercial austenitic stainless steel and one nickel base (Ni-base) alloy were also studied. The samples were exposed for 6 and 12 months by clamping half-moon rings onto tubes of the installed superheater bundle, achieving a material temperature of 500–520 °C. The material degradation of the samples was assessed by evaluating material loss using an ultrasonic thickness gauge in combination with a scanning electron microscope (SEM). Microstructural analysis was carried out using SEM coupled with Energy-dispersive X-ray spectroscopy (EDX). Both FeCrAl alloys showed promising results achieving material losses in the same range as the investigated austenitic stainless steels and the Ni-base alloy. A thin inward-growing Cr/Al-rich and thick outward-growing Fe-rich oxide were present for the FeCrAl alloys, and an internal nitridation zone was formed in the material matrix close to the metal/oxide interphase. The material loss and extent of the corrosion attack for the austenitic stainless steels varied depending on the alloy composition. However, the corrosion attack remained similar, as all the austenitic steels suffered from internal and intergranular corrosion. For the Ni-base alloy, the attack was defined by an internal Cr-rich oxide formation with no intergranular corrosion. This study suggests that the novel FeCrAl alloys provide satisfying resistance towards corrosion and erosion of the fluidized bed heat exchangers in the loop seal region of a waste-fired boiler. In addition, the stainless steel SX and the Ni-base alloy Sanicro® 69 performed well. Furthermore, the results revealed that corrosion rather than erosion was the dominating degradation process of the investigated samples, as deposit formation was observed on most of the samples as well as corrosion product layers. Thus, the erosive aspect of the attack was expected to be minor.
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| 10. |
- Maric, Jelena, 1983, et al.
(författare)
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Using a manganese ore as catalyst for upgrading biomass derived gas
- 2013
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Ingår i: International Conference on Polygeneration Strategies, Wien.
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Konferensbidrag (refereegranskat)abstract
- Secondary catalytic tar cleaning has been evidenced as a promising technology for upgrading gas derived from biomass gasification. When applying this technology downstream a biomass gasifier, the tar fraction in the raw gas can be reduced and the content of hydrogen can be increased. In this work, experiments have been conducted in a Chemical-Looping-Reforming (CLR) reactor. The present reactor system features a circulating fluidized bed as the reformer section, which offers a higher gas-solids contact time than a bubbling bed configuration previously tested. All experiments were performed using raw gas from the Chalmers 2-4 MWth biomass gasifier as feedstock to the reactor system. The catalyst inventory consisted of a natural manganese ore and its activity was evaluated at three different temperature levels - 800oC, 850oC and 880oC - and with an oxygen content of 2.2%, corresponding to a theoretical air-to-fuel ratio of 0.06. Experimental results showed that the manganese ore exhibits catalytic activity with respect to tar conversion and a tar reduction of as much as 72% was achieved at 880oC. Moreover, this material showed high activity towards hydrogen production.
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