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"Tubes damaged by erosion-corrosion because of the erosive action of the soot blowers. (foto KEMA) (ref 50, Fig 1)."
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"The topotactically grown corrosion scale. In the oxide layer many sulphides are found. The sulphides have also grown in the cracks of the oxide. (foto KEMA) (ref 50, Fig 2)."
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"At the metal-oxide interface the element Cl is sometimes found. In a few cases this resulted in severe intergranular corrosion. (foto KEMA) (ref 50, Fig 3)."
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"A Scanning Electron Microscope image, the places of presence of heavy metals are blue (detail of Figure 1). (foto KEMA) (ref 50, Fig 4)."
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Typical Alligator Skin Cracks in one of the tubes at the rear water wall. (foto KEMA) (ref 50, Fig 5).
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The high-sulphide (yellow color) layer on the corrosion probe, after 4 weeks of operation. (foto KEMA) (ref 50, Fig 6).
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The oxide layer after adjustment of the burners and air curtain introduction. The layer is more protective now. (foto KEMA) (ref 50, Fig 7).
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The calculated and measured corrosion rate constants in a sulphidising gas. (foto KEMA) (ref 50, Fig 8).
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An example of calculating the corrosion at 375 °C of the tube wall based on the data of the gas measurements. A parabolic corrosion rate has been assumed. (foto KEMA) (ref 50, Fig 9).
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Figure 1. Optical microscopic image of the fire side tube deposit.
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Figure 2 SEM Backscatter electron image. The white particles contain lead.
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Figure 3. Decay chain of 238U
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The thermodynamically stable constituents of lead in an oxidizing gas environment O1. The lead condensation (dewpoint) temperature is 880°C at respectively 50 vppm HCl. (ref 51).
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In the oxidizing gas environment O2 the lead condensation (dewpoint) temperature is 770 °C at respectively 500 vppm HCl. (ref 51).
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In the oxidising gas O3 with 5000 vppm HCl lead condensates at 660 ° . (ref 51).
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The thermodynamically stable constituents of lead in the reducing gas environment R1. The lead condensation (dewpoint) temperatures are 680 °C at 500 vppm H2S and respectively 50 vppm HCl. (ref 51).
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In the reducing gas R2 with 500 vppm H2S and 500 vppm HCl Pb condensates at 670 °C . (ref 51).
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Lead has a condensation (dewpoint) temperature of 495 °C in the reducing gas R3 with 500 vppm H2S and 5000 vppm HCl. (ref 51).
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Lead condensates at 650, °C in the reducing gas R4 with 500 vpmm HCl and 50 vppm H2S. (ref 51).
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The lead condensation (dewpoint) temperature is 670 °C in the reducing gas environment R2at 500 vpmm HCl and respectively 500 vppm H2S. (ref 51).
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Pb condensates at 680 °C in the reducing gas environment R5 with at 500 vpmm HCl and 5000 vppm H2S. (ref 51).
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Cross section of one of the deposition probes after an exposure period of 4 months. The element Pb is present on the white areas on the interface between the thick porous deposit of fly ash and the outer oxide layer. (foto KEMA)(ref 51).
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Layer structure on a evaporator tube at oxidising and reducing firing conditions. (ref 37, Fig 2)
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Cross section of oxide layer on a evaporator tube in the DSM demonstration project (foto KEMA) (ref 37, Fig 3)
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Cross sections of samples exposed in sulfidising gas at 450°C. Samples C and D were exposed in NaCl containg sulfidising gas. (foto KEMA) (ref 37, Fig 4)
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Cross sections of samples exposed in sulfidising gas B with sodiumsulphate on the samples at 450°C. (foto KEMA) (ref 37, Fig 5).
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Tubes with Alligator Skin Cracking published in EPRI-rapport CS-4969 (Cialone, 1986). (ref 37, Fig 6).
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Figure from EPRI-rapport CS 4969. Photo A: cross section of of a crack filled with oxide and sulfide. Photo B: detail of the oxide and sulphide filled "Alligator Skin Crack". (ref 37, Fig 7).