Bed material cohesion and loss of fluidization during fluidized bed combustion of midwestern coal

Dawson, M.R.; Brown, Robert C.

doi:10.1016/0016-2361(92)90158-k

Cited by 33 publications

(15 citation statements)

References 6 publications

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“…Dawson and Brown [20] reported that sticky aluminosilicate material acted as a glue to form agglomerates when burning high sulphur coal in a laboratory-scale FBC. In combustion of low-rank coals with a high content of sulphur and sodium, Manzoori et al [21,22] showed the presence of a molten phase coating, which is rich in sodium, calcium and sulphur.…”

Section: Formation and Identification Of Coating Layermentioning

confidence: 99%

Agglomeration in bio-fuel fired fluidized bed combustors

Lin

Dam‐Johansen

Frandsen

2003

Chemical Engineering Journal

253

140

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Section: Formation and Identification Of Coating Layermentioning

confidence: 99%

Agglomeration in bio-fuel fired fluidized bed combustors

Lin

Dam‐Johansen

Frandsen

2003

Chemical Engineering Journal

253

140

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“…In particular, the mineral matter behavior is still to some extent unknown. There are indications from the combustion of other types of biomasses that the mineral matter in those may sometimes cause ash-related problems during combustion. − …”

Section: Introductionmentioning

confidence: 99%

Ash Behavior in a CFB Boiler during Combustion of Salix

et al. 1997

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A study on the combustion characteristics of Salix viminalis, a fast growing willow, was conducted at a 12 MW circulating fluidized bed boiler. The purpose of the study was to increase the understanding of the mineral matter behavior in the boiler and to foresee possible bed agglomeration or slagging and fouling problems that may occur during the combustion of this type of fuel. Special focus was given to the impact of ash chemistry on the slagging, fouling, and bed agglomeration. Samples from all ingoing (bed material, fuel) and outgoing solid material streams (secondary cyclone and bag filter) as well as from the bed and the return leg were collected and analyzed chemically. Selected bed samples and ash samples were also analyzed with a scanning electron microscope (SEM/EDAX). Deposit samples were collected at the cyclone inlet and from two different locations in the convective path using specially designed surface temperature-controlled deposit probes. All collected probe deposits were photographed and characterized visually. Selected samples from both windward (front) side and leeward (back) side of the sampling probes were analyzed chemically as well as with SEM/EDAX. In addition to these samples, the boiler operation was monitored carefully. This included collection of operational data (fuel feed, air distribution, and total air), collection and monitoring of pressure drops in the furnace, flue gas temperature profiles, and emissions. Multicomponent multiphase thermodynamic equilibrium calculations were then performed for predictions of the fly ash thermal characteristics, using the fly ash chemical composition as input data. The thermal characteristics, i.e., the melting behavior, were predicted for the different ash samples and compared with the results from the full scale fouling measurements. The paper discusses the impact of the ash chemistry on the bed agglomeration and fouling tendency found during the combustion tests and draws conclusions about their relevance to the operation of the boiler.

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“…Controlling agglomeration and subsequent defluidization is thus critical for any commercial fluidized-bed process. Many investigations have been performed with the aim of understanding the agglomeration/defluidization phenomena in fluidized beds in the combustion or gasification of coal, − combustion of petroleum coke, , combustion or gasification of biomass, − and co-combustion or co-gasification of biomass with coal. , …”

Section: Introductionmentioning

confidence: 99%

“…4. A commercially available clay called Snobrite, which is rich in kaolinite, was added to coal during the series of eight gasification tests at the end of the testing program.…”

mentioning

confidence: 99%

Control of Agglomeration during Circulating Fluidized Bed Gasification of a South Australian Low-Rank Coal: Pilot Scale Testing

et al. 2016

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In this paper, results are presented of experiments performed to assess control techniques to counteract the operational problems of agglomeration during gasification of a South Australian low-rank coal in a pilot scale circulating fluidized bed gasification (CFBG) plant. Kaolinite-rich clay additives were used in the experiments in order to reduce the problems associated with sodium present in coals. The effect of refreshing and removing the bed material during continuous gasification was also studied experimentally. Agglomerates were observed to form during tests that occurred without the addition of kaolinite; the joints of the agglomerates were found to be comprised principally of sodium and silicon, presumably as sodium silicates. Sodium silicates were also observed to contribute to deposition of bed material and ash in some parts of gasifier. Deposition occurred mainly just above the air delivery inlets to the riser and at the bottom of the recirculation leg. At both of these points, local higher temperatures than in the other parts of the gasifier would be expected, with temperature having a large influence on the viscosity and stickiness of silicate layers and their tendencies to stick to reactor surfaces. The addition of kaolinite clay reduces the formation of sodium silicates. Instead, sodium reacts with kaolinite to form sodium aluminosilicates, which do not melt at fluidized bed gasification conditions. Agglomeration during normal operating conditions was not observed during clay addition tests. These results further show that the formation of coating and agglomerates in the sand bed can be practically eliminated, and with fine-tuning of the Kingston coal gasification process, the problem of agglomeration and/or defluidization can potentially be overcome during operation of a commercial-scale gasifier.

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Bed material cohesion and loss of fluidization during fluidized bed combustion of midwestern coal

Cited by 33 publications

References 6 publications

Agglomeration in bio-fuel fired fluidized bed combustors

Agglomeration in bio-fuel fired fluidized bed combustors

Ash Behavior in a CFB Boiler during Combustion of Salix

Control of Agglomeration during Circulating Fluidized Bed Gasification of a South Australian Low-Rank Coal: Pilot Scale Testing

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