| 1. |
|
|
| 2. |
- Andersson, Sven B, 1952, et al.
(författare)
-
N2O-Emissions from Fluidized Bed Combustion
- 1988
-
Ingår i: Proceedings of IEA AFBC Technical Meting held in November 1988 in Amsterdam, The Netherlands.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Nitrous oxide, N20, is formed during combustion. In flames the N20 is removed because of the fast destruction at high temperatures. At the temperatures of fluidized bed combustion the destruction is much slower and N20 will leave the system, normally at a concentration of 50-200 ppm when burning coal. Using the results of the preliminary model in a CFB, it can be assumed that:- N20 is formed from char nitrogen in the bottom bed because of reactions in the pores of the particle. - Only some N20 is formed when NO is reduced during its journey up through the combustion chamber. - N20 is formed from HCN. This is a slow process (taking seconds) and it therefore takes place principally above the bottom bed.
|
|
| 3. |
- Barisic, Vesna, et al.
(författare)
-
The Role of Limestone in Preventing Agglomeration and Slagging during CFB Combustion of High-Phosphorous Fuels
- 2008
-
Ingår i: Proceedings Poster Session for World BioEnergy 2008 Conference & Exhibition on Biomass for Energy, 27-29 May 2008, Jönköping - Sweden. ; , s. 259-263
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- ABSTRACT: This paper presents key observations on the role of limestone in preventing bed agglomeration during combustion of a high-phosphorous fuel in CFB boilers. Composition of the bed material samples was analyzed using X-ray fluorescence, and scanning electron microscope combined with an energy dispersive X-ray analyzer (SEM/EDXA). It has been demonstrated that during combustion of the high-phosphorous fuel in CFB conditions, addition of limestone reduces or prevents bed agglomeration and formation of slag by interfering with the ash chemistry, and not by simple dilution of the reacting system. The role of limestone can be summarized as: 1) to provide calcium for the reaction with phosphorous forming high-temperature-melting calcium phosphates instead of low-temperature-melting potassium phosphates, and 2) to coat silica particles preventing the reaction of potassium (calcium) phosphates and silica from fluidizing sand, which can form low-temperature-melting potassium (calcium) silicates, especially relevant for fluidized bed combustion conditions.
|
|
| 4. |
- Dam-Johansen, Kim, et al.
(författare)
-
Influence of SO2 on the NO/N2O chemistry in fluidized bed combustion 2. Interpretation of full-scale observations based on laboratory experiments
- 1993
-
Ingår i: Fuel. - 0016-2361. ; 72:4, s. 565-571
-
Tidskriftsartikel (refereegranskat)abstract
- In circulating fluidized bed combustion of coal, significant interactions between desulfurization by limestone and emissions of nitrogen oxides (NO, N2O) are generally observed. In order to facilitate interpretation of experimental results obtained in a 12 MW circulating fluidized bed boiler, a series of laboratory tests have been carried out. The tests include homogeneous CO and HCN oxidation in the presence of different concentrations of SO2, CO oxidation catalysed by calcined and partly sulfated limestone particles, and formation and reduction of NO and N20 over bed material containing char. The presence of SO2 in the gas is shown to decrease the rate of homogeneous CO and HCN oxidation and thereby change the product distribution of the nitrogen-containing species. Unlike sulfated limestone, calcined limestone (CaO) is shown to be a good catalyst for oxidation of CO. A lower mean CO concentration is therefore expected in fluidized bed combustors during injection oflimestone. This indirectly influences the nitrogen chemistry. Finally, the influence of NO and O2 on the formation of N2O from char was studied.
|
|
| 5. |
- Davidsson, Kent, 1967, et al.
(författare)
-
Countermeasures against alkali-related problems during combustion of biomass in a circulating fluidized bed boiler
- 2008
-
Ingår i: Chemical Engineering Science. ; 63, s. 5314-5329
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work was to study different ways to mitigate alkali-related problems during combustionof biomass in circulating fluidized beds. Wood chips and wood pellets were fired together withstraw pellets, while the tendency to agglomerate and form deposits was monitored. In addition to areference case, a number of countermeasures were applied in related tests. Those were addition of elementalsulphur, ammonium sulphate and kaolin to a bed of silica sand, as well as use of olivine sand andblast-furnace slag as alternative bed materials. The agglomeration temperature, composition and structureof bed-ash samples were examined. The flue-gas composition, including gaseous alkali chlorides, wasmeasured in the hot flue gases and in the stack. Particles in the flue gas were collected and analysed forsize distribution and composition. Deposits were collected on a probe in hot flue gases and their amountand composition were analysed. Addition of kaolin was found to be the best method to counteract theagglomeration problem. The deposition problem is effectively counteracted with addition of ammoniumsulphate, while kaolin is too expensive to be used commercially against deposits, and sulphur is lesseffective than ammonium sulphate.
|
|
| 6. |
|
|
| 7. |
- Davidsson, Kent, 1967, et al.
(författare)
-
Potassium, chlorine, and sulfur in ash, particles, deposits, and corrosion during wood combustion in a circulating fluidized-bed boiler
- 2007
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 21:1, s. 71-81
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of the addition of chlorine and/or sulfur to the fuel on fly ash composition, deposit formation, and superheater corrosion has been studied during biomass combustion in a circulating fluidized-bed boiler. The chlorine (HCl (aq)) and sulfur (SO2 (g)) were added in proportions of relevance for the potassium chemistry. The composition of the bottom and the fly ashes was analyzed. Gas and particle measurements were performed downstream of the cyclone before the convection pass and the flue gas composition was recorded in the stack with a series of standard instruments and an FTIR analyzer. At the position downstream of the cyclone, a deposit probe was situated, simulating a superheater tube. Deposits on the probe and initial corrosion were examined. It is concluded that addition of sulfur and chlorine increases the formation of submicron particles leading to deposition of potassium sulfate and chloride. The results compare well with earlier work based on laboratory-scale experiments concerning effects of chlorine and sulfur on potassium chemistry.
|
|
| 8. |
- Derda, Patrycja, et al.
(författare)
-
Fate of Alkali Metals during Co-Combustion of Biodiesel Residues with Coal in a Semi-Industrial CFB Boiler
- 2008
-
Ingår i: 9th International Conference on Circulating Fluidized Beds, CFB 2008, in Conjunction with the 4th International VGB Workshop on Operating Experience with Fluidized Bed Firing Systems; Hamburg; Germany; 13 May 2008 through 16 May 2008. - 9783930400577
-
Konferensbidrag (refereegranskat)abstract
- The use of biodiesel, especially of Rapeseed Methyl Ester (RME), has recently increased inthe European countries. This gives rise to an increasing amount of after production residues. Rapeseedcake is the main residue of the RME production process, and may become available in large amounts forenergy recovery. Since rapeseed cake contains high levels of alkali metals, it may cause bedagglomeration, deposit formation and corrosion upon combustion in fluidized beds.This paper presents the fate of alkali metals formed during co-combustion of coal and up to 25% ofrapeseed cake pellets in a 12 MW Circulating Fluidized Bed Boiler at Chalmers University ofTechnology (Sweden). Standard fuel analyses combined with sequential leaching and SEM/EDX, showedthe alkali entering the boiler. Gaseous emissions, bed samples, fly ash and deposits were analyzed inorder to monitor the alkali metals distribution. Gaseous alkali chlorides were measured upstream from theconvective pass at a flue gas temperature of 800 oC using an In-situ Alkali Chloride Monitor (IACM). Inthe same location, deposits were collected on a deposit probe fitted with rings for SEM/EDX analysis.Re-circulated bed material was analyzed as well.Two-day tests showed successful co-firing of up to 25% rapeseed cake on energy basis in the semiindustrialfluidized-bed boiler. Alkali metals were enriched in fly ash. No significant difference could benoticed in the distribution of alkali metals when increasing the share of rapeseed cake from 15% to 25%on energy basis. In the near future, further studies will be carried out to determine the influence oflimestone on the performed tests.
|
|
| 9. |
- Elled, Anna-Lena, 1975, et al.
(författare)
-
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
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 111, s. 696-708
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 10. |
- Elled, Anna-Lena, 1975, et al.
(författare)
-
Influence of phosphorus on sulphur capture during co-firing
- 2006
-
Ingår i: Fuel. ; 85, s. 1671-1678
-
Tidskriftsartikel (refereegranskat)abstract
- Interference from phosphorus on sulphur capture during co-firing of sludge with wood has been investigated in a circulating fluidised bed boiler.Chemical equilibrium analyses were performed on the combustion system to complement the experimental results. It was found that the relativelyhigh content of phosphorus in municipal sewage sludge interferes with the sulphur capture by occupying calcium, which otherwise would beavailable for reaction with sulphur. This fact must be taken into account when sulphur capture strategies are decided for reduction of sulphurdioxide emissions from sewage sludge as an additional fuel.q 2006 Elsevier Ltd. All rights reserved.
|
|
