| 1. |
- Broström, Markus, 1977-, et al.
(författare)
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Sulfation of corrosive alkali chlorides by ammonium sulfate in a biomass fired CFB boiler
- 2007
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Ingår i: Fuel processing technology. - Amsterdam : Elsevier Bv. - 0378-3820 .- 1873-7188. ; 88:11-12, s. 1171-1177
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Tidskriftsartikel (refereegranskat)abstract
- Biomass and waste derived fuels contain relatively high amounts of alkali and chlorine, but contain very little sulfur. Combustion of such fuels can result in increased deposit formation and superheater corrosion. These problems can be reduced by using a sulfur containing additive, such as ammonium sulfate, which reacts with the alkali chlorides and forms less corrosive sulfates. Ammonium sulfate injection together with a so-called in situ alkali chloride monitor (IACM) is patented and known as "ChlorOut". IACM measures the concentrations of alkali chlorides (mainly KCl in biomass combustion) at superheater temperatures. Tests with and without spraying ammonium sulfate into the flue gases have been performed in a 96MW(th)/25MW(e) circulating fluidized bed (CFB) boiler. The boiler was fired mainly with bark and a chlorine containing waste. KCl concentration was reduced from more than 15 ppm to approximately 2 ppm. during injection of ammonium sulfate. Corrosion probe measurements indicated that both deposit formation and material loss due to corrosion were decreased using the additive. Analysis of the deposits showed significantly higher concentration of sulfur and almost no chlorine in the case with ammonium sulfate. Results from impactor measurements supported that KCl was sulfated to potassium sulfate by the additive. (C) 2007 Elsevier B.V. All rights reserved.
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| 2. |
- Enestam, Sonja, et al.
(författare)
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Occurrence of zinc and lead in aerosols and deposits in the fluidized bed combustion of recovered waste wood : Part 1: Samples from boilers
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society. - 0887-0624 .- 1520-5029. ; 25:4, s. 1396-1404
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Tidskriftsartikel (refereegranskat)abstract
- Combustion of recovered waste wood (RWW) has led to increased fouling and corrosion of furnace walls, superheaters, and economizers. These problems have been associated mainly with chlorine, zinc, and lead in the deposits but also with sodium and titanium. The presence of lead and zinc compounds, especially lead and zinc chlorides, has been shown to increase the corrosivity of the deposits even at relatively low metal temperatures (230−450 °C). The present work determined experimentally the distribution and speciation of zinc and lead compounds in aerosol particles and deposits in the fluidized-bed combustion of RWW. Measurements were conducted in both a full-scale (20 MWth) plant with as-received RWW and in a pilot-scale (2 MWth) setup with as-received RWW and RWW doped with zinc and lead. The results show that the amount and speciation of zinc and lead in the deposits vary depending upon the fuel composition, flue gas temperature, and metal temperature. Both lead and zinc chlorides are found in temperature ranges typical for the primary superheater area. A caracolite-type compound [Na3Pb2(SO4)3Cl] was identified in deposits from the economizer area and K2ZnCl4 in the sub-micrometer aerosol particle fraction.
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| 3. |
- Forsberg, Christer, et al.
(författare)
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Principle, calibration, and application of the in situ alkali chloride monitor
- 2009
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics. - 0034-6748 .- 1089-7623. ; 80:2, s. 023104-1-023104-4
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Tidskriftsartikel (refereegranskat)abstract
- The extended use of biomass for heat and power production has caused increased operational problems with fouling and high-temperature corrosion in boilers. These problems are mainly related to the presence of alkali chlorides (KCl and NaCl) at high concentrations in the flue gas. The In-Situ Alkali Chloride Monitor (IACM) was developed by Vattenfall Research and Development AB for measuring the alkali chloride concentration in hot flue gases (>650 oC). The measurement technique is based on molecular differential absorption spectroscopy in the UV range. Simultaneous measurement of SO2 concentration is also possible. The measuring range is 1-50 ppm for the sum of KCl and NaCl concentrations, and 4-750 ppm for SO2. This paper describes the principle of the IACM as well as its calibration. Furthermore, an example of its application in an industrial boiler is given.
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| 4. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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Improved Process Modeling for a Lime Rotary Kiln Using Equilibrium Chemistry
- 2012
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Ingår i: Journal of engineering technology. - : American Society for Engineering Education. - 0747-9964. ; 29:1, s. 8-18
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Tidskriftsartikel (refereegranskat)abstract
- This article describes an improved process model for simulation of the manufacturing process of lime in a rotary kiln. The model simulates ideal behavior of complex chemical systems with an assumed homogenous mixing without time-dependent factors. It is a totally predictive model that excludes the empirical parameters. The model is a chemical phase equilibrium model that calculates the final product in a non-equilibrium mode, according to established methods. The phase chemistry is among the most complex found in the literature for lime manufacturing. The thermodynamic data used in the model is based on 11 components (Ca, Si, Al, Fe, K, S, Cl, C, H, O and N). The fuel has an important role in the lime manufacturing process. Special attention is required since it is fed directly into the process via the burner and can influence the process and final product. In the model, the fuel is defined in order to have it behave in a realistic way, and operational data from a full scale lime plant verify the simulation results. The simulated amounts of gas and solids correlate well with operational data. The predicting chemical composition of the product needs improvement by adding more system components and their related compounds to the thermodynamic database. Simulation results from co-combustion of coal and processed waste based fuel oil that it is a versatile tool for predicting product quality and amount, temperature profiles of the rotary kiln, and exhaust gas composition and amount.
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| 5. |
- Hökfors Wilhelmsson, Bodil, 1971-, et al.
(författare)
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A predictive chemistry model for the cement process
- 2008
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Ingår i: Zement, Kalk, Gips International. - Gutersloh, Germany : Bauverlag BV. - 0949-0205. ; 61:7, s. 60-70
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A tool has been developed that enables prediction of the chemistry in cement production with thermodynamic phase equilibrium calculations. Reactions in gas, solid and liquid phases are calculated in the process from preheating tower, including exhaust gas cleaning, through rotary kiln, clinker cooler and ends at the output of clinker. The simulated values are compared to measured or calculated data from a full scale plant. This is a cement plant producing 2000 t clinker per day using both traditional and alternative fuels. The chemistry model shows good agreement especially on material chemistry at various places in the process and on composition of the clinker. A new way to define fuels is used and is straightforward and reliable. In the future work the model has to be improved and more elements are to be added to the thermodynamic database.
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| 6. |
- Persson, Kristoffer, et al.
(författare)
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High temperature corrosion in a 65 MW waste to energy plant
- 2007
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Ingår i: Fuel processing technology. - : Elsevier B.V.. - 0378-3820 .- 1873-7188. ; 88:11-12, s. 1178-1182
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Tidskriftsartikel (refereegranskat)abstract
- Incineration of municipal solid waste is often associated with high temperature corrosion problems. This paper presents results of full-scale corrosion tests in a 65 MW waste fired combined heat and power plant. A failure case indicated alarmingly high corrosion rate of the superheater tubes. Corrosion tests with five different alloys were carried out within this work in order to determine plant specific corrosion rates on different superheater materials. Additional tests were done to determine the effect on the corrosion rate from adding chlorine containing polyvinyl chloride to the ordinary fuel mix. A corrosion probe with metal temperatures ranging from 320 degrees C to 460 degrees C was used to estimate corrosion loss and to collect deposits. The sampling was performed at a flue gas temperature of 470 degrees C for 10 days. The probe rings were analysed using scanning electron microscope and micrometer measurements to determine the deposit chemistry and corrosion rates. The results showed significant differences in corrosion rates depending on tube material. Chlorine was shown to have a key role in the corrosion process, even at these relatively low temperatures. The results indicated a chlorine induced corrosion mechanism involving volatile iron chloride with a high corrosion rate on the superheater materials typically used. Addition of extra polyvinyl chloride to the fuel mix had an increasing effect on the corrosion. (C) 2007 Elsevier B.V. All rights reserved.
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