Modelling alkali chloride superheater deposition and its implications

Pyykönen, Jouni; Jokiniemi, Jorma

doi:10.1016/s0378-3820(02)00240-0

Cited by 39 publications

(24 citation statements)

References 26 publications

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“…-the formation of molten phase above the protective oxide scale supporting iron oxide protective scale dissolution by "fluxing" [8,9], -the acceleration of the kinetic of sulfatation of alkali chloride above 650°C [18] that promotes induced deposit corrosion and "active oxidation" [4,7]. …”

Section: Discusionmentioning

confidence: 99%

“…Formation of eutectic compounds with lower melting temperature will enhanced fluxing mechanism at lower flue gas temperature. On the other hand, Pykkonen et al [7] demonstrate that sulphatation of alkali chloride will be limited by SO 2 transport and concentration close to the deposit. This can explain the remaining chlorine detected in deposit and oxide scale with chlorine rich ash (ash 3).…”

Section: Fig 9 Effect Of Ash Composition On Corrosion Rate At 654°cmentioning

confidence: 99%

“…-deposit induced corrosion and sulfidation of condensed chlorides [7], -molten salts eutectics induce rapid dissolution of protective oxide scales and metallic tubes("fluxage") [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Lab-Scale Study on Fireside Superheaters Corrosion in MSWI Plants

Brossard

Lebel

Rapin

et al. 2009

17th Annual North American Waste-to-Energy Conference

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Combustion of the municipal waste generates highly corrosive gases (HCl, SO 2 , NaCl, KCl and heavy metals chlorides) and ashes containing alkaline chlorides and sulphates. Currently, corrosion phenomena are particularly observed on superheater's tubes. Corrosion rates depend mainly on installation design, operating conditions i.e. gas and steam temperature and velocity of the flue gas containing ashes. This paper presents the results obtained using an innovative laboratory-scale corrosion pilot, which simulates MSWI boilers conditions characterized by a temperature gradient at metal tube on the presence of corrosive gases and ashes. The presented corrosion tests were realized on carbon steel at fixed metal temperature (400°C). The influence of the flue gas temperature, synthetic ashes composition and flue gas flow pattern were investigated. After corrosion test, cross section of tube samples were characterised to evaluate thickness loss and estimate corrosion rate while the elements present in corrosion layers were analysed.Corrosion tests were carried out twice in order to validate the accuracy and reproducibility of results. First results highlight the key role of molten phase related to the ash composition and flue gas temperature as well as the deposit morphology, related to the flue gas flow pattern, on the mechanisms and corrosion rates.

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Section: Discusionmentioning

confidence: 99%

Section: Fig 9 Effect Of Ash Composition On Corrosion Rate At 654°cmentioning

confidence: 99%

See 1 more Smart Citation

Lab-Scale Study on Fireside Superheaters Corrosion in MSWI Plants

Brossard

Lebel

Rapin

et al. 2009

17th Annual North American Waste-to-Energy Conference

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“…When there are solid particles in the carrier gas, the supersaturated vapours condense on them and they are carried to cold walls thermophoretically (Gökoglu & Rosner 1986;Castillo & Rosner 1988, 1989Neu, Bonilla & Carpio 2009). This heterogeneous condensation is important in aerosol formation (Davis 1983;Friedlander 2000;Peeters, Luijten & van Dongen 2001), fouling and corrosion in biofuel plants (Pyykönen & Jokiniemi 2003), outside vapour deposition processes used for making optical fibres (Filippov 2003;Tandon & Murtagh 2005), chemical vapour deposition, vapour condensation and aerosol capture by cold plates or rejection by hot ones (Rosner 2000).…”

Section: Introductionmentioning

confidence: 99%

Theory of homogeneous vapour condensation and surface deposition from boundary layers

Camejo¹,

Bonilla²

2012

J. Fluid Mech.

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Homogeneous condensation of vapours mixed with a carrier gas in the stagnation point boundary layer flow near a cold wall is considered. There is a condensation region near the wall with supersaturated vapour. Assuming that the surface tension times the molecular area is much larger than the thermal energy far from the wall, droplets are nucleated exclusively in a narrow nucleation layer where the Zeldovich flux of clusters surpassing the critical nucleus size is at a maximum. The vapour condenses in the free molecular regime on the droplets, which are thermophoretically attracted to the wall. Unlike the narrow condensation region for heterogeneous condensation on solid particles, in the case of homogeneous condensation the condensation region is wide even when the rate of vapour scavenging by droplets is large. A singular perturbation theory of homogeneous vapour condensation in boundary layer flow approximates very well the vapour and droplet density profiles, the nucleation layer and the deposition rates at the wall for wide ranges of the wall temperature and the scavenging parameter B. A key point in the theory is to select a trial vapour number density profile among a one parameter family of profiles between an upper and a lower bound. The maximum of the Zeldovich flux for supercritical nuclei provides the approximate location of the nucleation layer and an approximate droplet density profile. Then the condensate number of molecules and the vapour density profile are calculated by matched asymptotic expansions that also yield the deposition rates. For sufficiently large wall temperatures, a more precise corrected asymptotic theory is given.

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“…A study on fume particle and condensable alkali chloride vapor behavior in a superheater tube was carried out by Pyykonen and Jokiniemi [4]. Two models of boundary layer aerosol behavior were presented.…”

Section: Introductionmentioning

confidence: 99%