Analysis of solid phase formation and its impact on slag rheology

Schwitalla, Daniel; Bronsch, Arne M.; Klinger, Mathias; Guhl, Stefan; Meyer, Bernd

doi:10.1016/j.fuel.2017.04.092

Cited by 26 publications

(11 citation statements)

References 24 publications

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“…After the crystal incubation time, the time period passed until a crystal arrangement is formed was very minuscule. These findings prove that the understanding of crystallisation in oxidic slags is a crucial parameter for the stability of gasification processes [6,12,13]. Ultimately, the crystallised phases were investigated using XRD and SEM.…”

Section: Resultsmentioning

confidence: 59%

“…Although viscosity of fully liquid slag systems can be calculated sufficiently, its calculation for partly crystalline slag systems are of greater challenge [6,11]. Recent studies [12][13][14][15] indicated the impact of crystallisation on the slags viscosity. In this study, crystallisation processes in three synthetic slag systems were investigated.…”

Section: Introductionmentioning

confidence: 99%

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Investigations on Crystallization Processes of Three Oxidic Gasifier Slag Systems

Schupsky

Guo

Blanpain

et al. 2020

Journal of Energy Resources Technology

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In entrained flow gasifiers, the production of oxidic slag accompanies the gasification process. This slag forms a layer on the refractory walls, flows downwards gravitationally, and is collected in a water quench. Hence, the slag flow must be constant, since a slag blockage represents a worst-case-scenario. Crystallization of the slag increases slag viscosity, subsequently leading to a possible slag blockage. Therefore, crystallization processes in oxidic slags need to be understood and hence investigated. In this study, three artificial, coal ash related oxidic slag systems were analyzed on their crystallization behavior. Therefore, their melt behavior was investigated via hot-stage microscopy and differential thermal analysis (DTA). Additional thermochemical calculations were performed to predict crystallized phases. Subsequently, quenching experiments were conducted to generate supercooled crystallization in the slag samples. These samples were analyzed afterward via X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the morphologies of crystals were characterized/described. In-situ observations on crystallization growth were performed by using a confocal laser scanning microscope (CLSM). Finally, crystallized phases were compared with results obtained from thermochemical calculations, and the impact of kinetics on the distributed phases was discussed. The knowledge on the crystallization behavior of various phases can be transferred to other slag systems and can improve general crystallization predictions made by thermochemical calculations.

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Section: Resultsmentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Investigations on Crystallization Processes of Three Oxidic Gasifier Slag Systems

Schupsky

Guo

Blanpain

et al. 2020

Journal of Energy Resources Technology

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“…An experimental study on the crystallization characteristics of oxidic slag systems was conducted by using the CLSM setup [3]. To validate the impact of the sample state, the applied oxygen partial pressure, and the crucible material, several experiments were performed.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the demand for bridging technologies is high and the usage of gasification technology serves advantages compared to combustion plants [1,2]. Gasifiers, such as entrained flow gasifiers, are able to convert different kinds of fuels (coal, biomass, waste) into energy [3]. Also, the operation under partial load conditions gives gasification technology a high relevance by filling gaps in the power grid due to fluctuations of renewable energy production [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, this study provides helpful advice for experimental investigations of oxidic slags, to reduce sources of error and to improve the reproducibility of results. Investigations were conducted with a confocal laser scanning microscope (CLSM) [3]. The experiments proved that the usage of sample powder entails a heterogeneous crystallization even at high temperatures of above 1500 °C.…”

Section: Introductionmentioning

confidence: 99%

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The Impact of Sample Homogeneity, Crucible Material, and Oxygen Partial Pressure on the Crystallization of Fe-Rich Oxidic Slag in CLSM Experiments

Schupsky

Guo

Blanpain

et al. 2020

J. Sustain. Metall.

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Crystallization tendency and the state of oxidic slags are important influencing factors for slag viscosity and therefore slag tapping. During the gasification process slag is constantly produced and flows down the gasifier walls until it is intercepted and stored for further treatment or a possible valorisation. The kinds of fuel used for gasification lead to different kinds of slag composition likewise. Slag viscosity is strongly influenced by the composition of the slag and the temperature. However, the process of crystallization represents another major influencing factor. Slag crystallization is also affected by several parameters, whose effects need to be considered in experimental studies. This study investigated the impact of the sample state, the chosen crucible material, and the oxygen partial pressure on the crystallization of a Fe-rich oxidic slag in the confocal laser scanning microscope (CLSM) experiment. Using sample powder may lead to heterogeneous nucleation and crystallization during heating due to heterogeneous melting of the compounds. The selection of crucible material is crucial to prevent alloy formation of Fe-species with Pt-crucibles under reducing atmosphere. Finally, the partial pressure of oxygen influences the crystallization tendency as well as the morphology of the crystallized phases. These parameters impede the reproducibility of results as well as the comparison with results deriving from other experiments like sample quenching. This contribution provides an enhanced understanding of the stated parameter effects on the experimental investigation of oxidic slags using the CLSM setup and yields advice to prevent experimental influence on the results.

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