| 1. |
- Fleig, Daniel, 1980, et al.
(författare)
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Conversion of Sulfur during Pulverized Oxy-coal Combustion
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 25:2, s. 647-655
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Tidskriftsartikel (refereegranskat)abstract
- On the basis of experiments in the Chalmers 100 kW(th) oxy-fuel test facility, this study presents an analysis of sulfur chemistry of pulverized lignite combustion, comparing oxy-fuel and air-fired conditions. Four test cases were investigated: an air-fired case, two oxy-fuel cases with dry recycling (30 and 35 vol % O-2), and one oxy-fuel case with wet recycling (43 vol % O-2 on a dry basis). The amounts of sulfur in the flue-gas, ashes, and condensed water from the condenser were quantified, and a sulfur mass balance was established. The composition of the ashes and the ash-forming matter in the fuel was analyzed. The ashes were investigated by X-ray diffraction, while the size of fuel and ash particles was determined by laser diffraction. In general, the results show that the lignite has a high sulfur self-retention by ash, especially in oxy-fuel combustion. The experiments also show that the conversion of fuel S to SO2 from oxy-fuel combustion is around 35% lower compared to air-fired conditions, whereas the flue-gas concentration of SO2 is higher in oxy-fuel combustion because of the absence of air-borne nitrogen.
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| 2. |
- Fleig, Daniel, 1980, et al.
(författare)
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Evaluation of SO3 Measurement Techniques in Air and Oxy-Fuel Combustion
- 2012
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 26:9, s. 5537-5549
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Tidskriftsartikel (refereegranskat)abstract
- SO2 is enriched in wry-fuel combustion due to flue-gas recycle, and a significant higher SO3 concentration can be expected compared to air-firing. Since SO3 can cause high and low temperature corrosion, it is important to measure the SO3 concentration under oxy-fuel fired conditions. However, measurement of SO3 is not straightforward, since SO3 is a highly reactive gas. This paper presents an experimental study in the Chalmers oxy-fuel test unit, comparing different SO3 measurement techniques applied during oxy-fuel and air combustion. Propane (60 kW(th)) was used as fuel and SO2 was injected in the oxidizer to generate a controllable amount of SO3. The SO3 concentration was measured with four techniques: the controlled condensation method, the salt method, the isopropanol absorption bottle method, and with the Pentol SO3 monitor (previously: Severn Science analyzer). The controlled condensation method was used as the standard for comparison. Additionally, the acid dew-point temperature was measured with a dew-point meter. The controlled condensation and the salt method gave comparable results, and the repeatability with these methods was good. The SO3 concentrations measured with the Pentol SO3 monitor differed in average less than 20% from the SO3 concentrations obtained with the controlled condensation method. With the isopropanol absorption bottle method, a large amount of the SO2 was absorbed in the isopropanol solution, which gives a positive bias if the SO2 is oxidized to sulfate in the isopropanol solution. This was minimized by reducing the measurement time, bubbling argon through the absorption bottles after the measurement to force the SO2 out, and analyzing the solution immediately after the measurement. No principal differences between measuring the SO3 concentration during oxy-fuel combustion and air-firing were obtained. However, a correction factor for the mass flow meter of the Pentol SO3 monitor has to be used because of the high CO, concentration during oxy-fuel operation.
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| 3. |
- Fleig, Daniel, 1980, et al.
(författare)
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Influence of Operating Conditions on SO3 Formation during Air and Oxy-Fuel Combustion
- 2012
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 51:28, s. 9483−9491-9491
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Tidskriftsartikel (refereegranskat)abstract
- Because SO3 participates in both high- and low-temperature corrosion processes, there is a general concern about the SO3 formation under oxy-fuel fired conditions. This work has the aim to evaluate the influence of combustion parameters on the formation of SO3. Experiments were conducted in oxy-fuel and air-fired experiments with propane as fuel and injection of SO2 in the oxidizer. The SO3 concentration was measured with a controlled condensation method at the furnace outlet as well as in the flame. The experiments show that the gas-phase is an important contributor to SO3 formation and that the SO3 formation is strong during burnout of the fuel. In oxy-fuel combustion with wet flue-gas recycle (FGR), more SO3 was formed than during dry FGR at similar temperature conditions, which indicates that H2O enhances SO3 formation. The experiments also show that the SO3 formation rises with an increase in furnace temperature. Because temperature and residence time in the furnace increases with reduced FGR ratio, the FGR ratio directly influences the SO3 formation in oxy-fuel combustion. This was obvious during the experiments, and the SO3 concentration rose with a reduced FGR ratio.
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| 4. |
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| 5. |
- Fleig, Daniel, 1980, et al.
(författare)
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SO3 Formation under Oxyfuel Combustion Conditions
- 2011
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 50:14, s. 8505-8514
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Tidskriftsartikel (refereegranskat)abstract
- The sulfur chemistry in oxyfuel combustion systems has received growing attention lately. The formation of SO(3) is of special concern, because of the elevated SO(2) concentrations found in oxyfuel, compared to air-fuel conditions. The present study focuses on the gas-phase chemistry and examines the impact of different combustion parameters and atmospheres on the formation of SO(3) in oxyfuel and air-fuel flames, using a detailed gas-phase model. The work also includes a summary of the presently available SO(x) data from experiments in laboratory and pilot-scale combustors. The reviewed experimental data, as well as the modeling results, show significantly increased SO(3) concentrations in oxyfuel, compared to air-fuel conditions. The modeling results reveal a complex behavior of the SO(3) formation, which is influenced by direct and indirect effects of the SO(2), O(2), NO(x), and CO content in the flue gas. One of the main contributors to the increased SO(3) concentration in oxyfuel, compared to air-fuel conditions, is the high concentration of SO(2) in oxyfuel combustion. The modeling also shows that the stoichiometry, residence time, and flue-gas cooling rate are critical to the SO(3) formation. Thus, in addition to the stoichiometry of the flame, the flue-gas recycling conditions are likely to influence the formation of SO(3) in oxyfuel combustion.
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| 6. |
- Fleig, Daniel, 1980, et al.
(författare)
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Sulphur chemistry in oxy-fuel combustion
- 2009
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Ingår i: VDI-Berichte. - 0083-5560. - 9783180920566 ; 2056:24. Deutscher Flammentag, s. 289-294
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 7. |
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| 8. |
- Fleig, Daniel, 1980, et al.
(författare)
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The fate of sulphur during oxy-fuel combustion of lignite
- 2009
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 1:1, s. 383-390
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work focuses on the sulphur chemistry in oxy-fuel combustion of lignite. Comparison is made with air-fired conditions, and the main combustion products containing sulphur (ash, SO2, SO3 and H2S) are examined by modelling and experimental data. The conversion of fuel-S to SO2 is lower in oxy-fuel than in air-fuel conditions and the SO2 concentration per unit energy supplied is therefore reduced. The modelling shows that the SO3 concentration is about four times greater than the concentration in air-firing. High SO3 and H2O contents in the oxy-fuel flue gas during wet recycling increase the acid dew-point by 20 to 30 K.
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| 9. |
- Fleig, Daniel, 1980, et al.
(författare)
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The Sulphur Mass Balance in Oxy-Fuel Combustion of Lignite
- 2009
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Ingår i: 1st OXYFUEL COMBUSTION CONFERENCE: September 8-11, 2009, Cottbus, Germany.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents an experimental study of the sulphur chemistry in oxy-fuel combustion of pulverized lignite. It has been observed that the emission of sulphur dioxide (SO2) by unit energy supplied is lower in oxy-fuel combustion than in air combustion [1-5] but the reason for this is not clear. In order to validate previous work and to clarify this difference the present work compares the amount of emitted SO2 in air and oxy-fuel combustion (wet and dry flue-gas recycle). Furthermore, the amounts of sulphur in the ash and in the water of the flue-gas condenser were determined to make a mass balance and to verify the measured amount of SO2 in the flue gas.
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| 10. |
- Vainio, Emil, et al.
(författare)
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Experimental evaluation and field application of a salt method for SO3 measurement in flue gases
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:5, s. 2767-2775
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an SO3 measurement technique was evaluated and developed. In the method, a salt is used to capture gaseous SO3/H2SO4. Various salts were tested to evaluate the suitability to measure SO3/H2SO4 without interference from SO2. Salts tested include NaCl, KCl, K2CO3, and CaCl2. The salts were tightly packed into a Teflon tube, and the gas was fed through the salt tube with subsequent reaction between SO3/H2SO4 and the salt with formation of sulfates of the respective salt. After the measurement, the salt was dissolved in water, and the solution was analyzed for sulfate ions. The SO3/H2SO4 concentration in the flue gas could then be determined because the gas volume flowing through the salt was measured together with the amount of sulfate bound in the salt. The method was tested in laboratory conditions, in a 100 kW(th) test unit during air-firing and oxy-fuel combustion, and in an industrial boiler. A first attempt to continuously measure SO3/H2SO4. indirectly with an FTIR, by measuring the release of HCl in the sulfation of KCl, was also made. The conversion of SO3 to H2SO4 in flue gas conditions is discussed. It was found that at the measurement conditions almost all SO3 is present as H2SO4. Therefore, the laboratory study was made with gaseous H2SO4 instead of SO3. The laboratory tests showed that all salts captured all H2SO4. The best selectivity toward H2SO4 was shown for NaCl and KCl; no significant amount of SO2 was captured in these salts. An in situ implementation of the salt method using KCl as salt was used during heavy oil combustion in a Kraft recovery boiler. The salt method showed to be an accurate, inexpensive, and easy way to measure SO3/H2SO4. in flue gases.
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