HRSG-Nitrates

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4400.jpg
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"Overview of an area where SCC occurred. Finned pipes are used to increase the surface area of the heat exchangers. 3B - Cross section of tube material reveals stress corrosion cracking. (ref 53, 56, 58, 63). (Foto KEMA)."
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"SEM image of the microstructure of a 15Mo3 steel that showed nitrate induced SCC. (ref 53, 56, 58, 63). (Foto KEMA). "
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Carbon WDX mapping of the same area in picture 4421 shows the distribution of carbon (white is carbon, black is no carbon). The pearlite islands are normal in this material. The large amount of ternary cementite that has deposited on the grain boundaries is not normal, however. (ref 53, 56, 58, 63). (Foto KEMA).
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Correlation between measured and calculated critical nitrate concentrations of steels tested in ammonium nitrate solutions of varying nitrate concentrations. (ref 53, 56, 58, 63).
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"Pourbaix diagram of iron. Shaded areas indicate danger zones where SCC caused by nitrates, phosphates, carbonate/bicarbonate and hydroxide respectively can occur. (ref 53, 56, 58, 63). "
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"The water vapour pressures from the water vapour table. A gas with 6.5 v% H2O has a vapour pressure of 49.7 mm Hg (100 v% water has a vapour pressure of 758 mm Hg) and a dewpoint of 38 °C. (ref 53, 56, 58, 63)."
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"Dew points of SO3 at various water contents of the gas, calculated from the formula of Verhoff. (ref 53, 56, 58, 63)."
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"Dew points of SO2 at various water contents of the gas, calculated from the formula of Kiang. The SO2 dew points for all gasses are lower than the water dew point of the gasses. (ref 53, 56, 58, 63). "
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"Dew points of HCl at various water contents of the gas, calculated from the formula of Kiang and the water vapour table. (ref 53, 56, 58, 63)."
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"Dew points of NO2 at various water contents of the gas, calculated from the formula of Perry and the water vapour table. (ref 53, 56, 58, 63)."
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Theoretical curves for the rate of acid deposition according to the calculations of Land3. (ref 53, 56, 58, 63).
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Acid deposition rates in case of sulphuric acid condensation of gas A. (ref 53, 56, 58, 63).
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Acid deposition rates in case of nitric acid condensation of gas B. (ref 53, 56, 58, 63).
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Phase diagram of sulphuric acid Land3 (PH2O + PH2SO4 = 0.1 atm). (ref 53, 56, 58, 63).
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Vapour pressures of nitric acid and water as a function of acid strength and temperature. (ref 53, 56, 58, 63).
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"The solubility of ammonium nitrate in water (weight% on x-axis) versus the temperature (°C). Ammonium nitrate has 5 modifications: I: cubic, II tetragonal: III: orthorhombic, IV: orthorombic and V tetragonal. Very concentrated ammonium nitrate solutions can be formed well above the boiling point of water. (ref 53, 56, 58, 63)."
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4454.jpg
Properties of a saturated solution of calcium nitrate in water (see Table 6 for explanations). The lines a, b and c give density (a), content of calcium nitrate (b) and vapour pressure (c). (ref 53, 56, 58, 63).
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Schematic view of the condensation processes in the insulation for a start-up and a normal operation condition. The casing surface is on position zero, the liner is on position 25 cm. The dotted lines refer to the dew points of the various gasses. (ref 53, 56, 58, 63).
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Correlation between measured and calculated critical nitrate concentrations of steels tested in ammonium nitrate solutions of varying nitrate concentrations. (ref 53, 56, 58, 63).
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Histogram of the C-steels and low-alloyed steels from the database for intergranullar corrosion in ammonium nitrate environments. (ref 53, 56, 58, 63).