The circumferential distribution of wastage on in-bed tubes in fluidized bed combustors

MacAdam, S.; Stringer, J.

doi:10.1016/0043-1648(95)07186-5

Cited by 13 publications

(4 citation statements)

References 3 publications

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“…The results of the circumferential profiles of erosion are depicted in Figure 7. The results show an erratic behaviour, different from those available in the literature [7] [8]. Measures at 135°and 225°show the highest erosion rates (which is in accordance with previous studies), but negative erosion have been found in several measures, which is not possible.…”

Section: Erosionsupporting

confidence: 84%

Experimental study of erosion in heat exchangers immersed in fluidized beds

Domínguez-Coy,

Córcoles,

Almendros-Ibáñez

2024

J. Phys.: Conf. Ser.

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Fluidized beds can be used as solar energy receivers in beam-down concentrated solar power plants. The fact that solid particles can withstand temperatures over 1,000°C is promising because it would mean higher thermal efficiencies than conventional concentrated solar power plants (CSP, that use molten salts, whose maximum operating temperature is limited to about 560°C). Nonetheless, immersed heat exchangers are exposed to erosion because fluidized particles impinge on their surfaces. The multiple variables of a multiphase flow and the uncertainties of the material detachment process make erosion a complex problem that stills not fully solved. The aim of this study is to conceive an experimental procedure to measure erosion on cylindrical probes immersed in a lab-scale high temperature fluidized bed (able to operate up to 1,000°C and atmospheric pressure), simulating a tube of a heat exchanger in a fluidized bed working at expected temperatures in CSP applications. Preliminary results at ambient temperature are presented in this study. Silica sand particles were fluidized with air and erosion was measured on cylindrical probes made of aluminium 5027. Silica sand was characterized with a microscope before and after each test to determine its size distribution and shape. Several parameters (diameter, mass, and circumferential profile) of each probe were also studied before and after each test. Different fluidization velocities were implemented to assess the influence of the flow rate on erosion.

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Section: Erosionsupporting

confidence: 84%

Experimental study of erosion in heat exchangers immersed in fluidized beds

Domínguez-Coy,

Córcoles,

Almendros-Ibáñez

2024

J. Phys.: Conf. Ser.

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“…5c and 5d. After one firing season an erosion pattern recognised as type A [16,17] and usually related to constrained particle flows in dense tube banks [18] has developed on tube 25. Type A is described as an increased erosion located at an angle of AE 30 -458 from the incoming particle stream.…”

Section: Resultsmentioning

confidence: 99%

“…This is consistent with the results in the present study, which show a very low degree of deposit formation in the same region, thus confirming a low recirculation flux. The deposits on the other tubes are mainly eroded according to a Type A pattern [16,17], suggesting that the locally high vertical particle flow has the largest impact on the tube surfaces. It must however be mentioned that due to the contamination, sand particles agglomerate to large lumps which are found in between the superheater tubes.…”

Section: Discussionmentioning

confidence: 99%

Field study on superheater tubes in the loop seal of a wood fired CFB plant

Nafari

Nylund

2004

Materials & Corrosion

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Two full scale superheaters were exposed in the loop seal of a 30 MW wood-fired CFB plant in Nässjö, Sweden, for one firing season each. Some austenitic steel tubes from the first tube bundle were reinstalled in the second superheater. The superheater tubes were made from one ferritic steel, X10 (Fe8.8Cr) and three austenitic steels; Esshete 1250 (Fe15Cr9Ni6Mn), 347H (Fe17Cr11Ni) and AC66 (Fe27Cr32Ni). Commercial coatings mainly on iron, nickel and carbide base were deposited on some of the X10 and 347H tubes.The material wastage kinetics was non-linear showing that pure corrosion and not erosion-corrosion is the major degradation mechanism in the loop seal. It is however clear that the environment is not very aggressive and the corrosion attack on the uncoated tubes is very small. The largest oxide thickness was only about 150 lm recorded on the X10 alloy. The austenitic steels mainly suffered from internal corrosion and grain boundary corrosion, the extent and distribution of which strongly depended on the alloy composition. Generally, it was more pronounced in the regions with the thinnest deposit layers.Eight out of 17 coating qualities tested were unaffected by the exposure. Corrosion was only recorded on the lowest alloyed iron based coatings. The only coatings which could not resist the conditions in the loop seal were the carbide containing Metco 3006 and Metco 3007, where severe oxidation and delamination took place. Also the thermally sprayed Inconel 625 coating delaminated, but this was rather due to a mechanical failure resulting from thermal expansion.

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“…The fact that this rig does not produce the Type B pattern was found to be due to the constrained vertical motion in the bed. When the constraint is relaxed, as shown by a computer simulation study 28 and by experiments 21 , the Type B wear pattern more commonly found in bubbling beds could be generated.…”

Section: Temperature Dependence Of Wastagementioning

confidence: 98%

High temperature degradation by erosion-corrosion in bubbling fluidized bed combustors

Hou

MacAdam²,

Niu

et al. 2004

Mat. Res.

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Heat-exchanger tubes in fluidized bed combustors (FBCs) often suffer material loss due to combined corrosion and erosion. Most severe damage is believed to be caused by the impact of dense packets of bed material on the lower parts of the tubes. In order to understand this phenomenon, a unique laboratory test rig at Berkeley was designed to simulate the particle hammering interactions between in-bed particles and tubes in bubbling fluidized bed combustors. In this design, a rod shaped specimen is actuated a short distance within a partially fluidized bed. The downward specimen motion is controlled to produce similar frequencies, velocities and impact forces as those experienced by the impacting particle aggregates in practical systems. Room temperature studies have shown that the degradation mechanism is a three-body abrasion process. This paper describes the characteristics of this test rig, reviews results at elevated temperatures and compares them to field experience. At higher temperatures, deposits of the bed material on tube surfaces can act as a protective layer. The deposition depended strongly on the type of bed material, the degree of tube surface oxidation and the tube and bed temperatures. With HCl present in the bed, wastage was increased due to enhanced oxidation and reduced oxide scale adherence

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The circumferential distribution of wastage on in-bed tubes in fluidized bed combustors

Cited by 13 publications

References 3 publications

Experimental study of erosion in heat exchangers immersed in fluidized beds

Experimental study of erosion in heat exchangers immersed in fluidized beds

Field study on superheater tubes in the loop seal of a wood fired CFB plant

High temperature degradation by erosion-corrosion in bubbling fluidized bed combustors

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