Key Aspects of Slag Viscosity in Slagging Gasifiers
Final Report Abstract
The joint Sino-German research project “SlagVis” focused on the detailed investigation of the viscosity behavior of slags. The technological backgrounds are coal based slagging gasification processes for syngas production supplemented by co-gasification of pet coke and biomass. The slag handling is one of the main issues regarding stable gasifier operation (availability) and also further optimization of efficient gasification technologies. The research plan considered phenomena within slag flow characteristics which are still not fully understood from the scientific perspective and which also concern practical issues that limit efficient syngas production. A variety of measurement and analytical equipment and methods (high temperature viscometer, quench furnace, HT-SEM, SEM-EDX, XRF, XRD, thermochemical calculations) was applied to investigate the various factors affecting slag viscosity. The scientific objectives focused on the overall aim, to improve the measurement and prediction methods, to allow transferable viscosity predictions for industrial gasifiers. Main objectives and results (focus on German project part and joint work) include a systematic comparison of the viscosity measurement procedure at ICC and IEC, whereas for Newtonian slags an almost good reproducibility was obtained. For slags with a tendency to crystallization, different crucible and spindle material in connection with shear induced crystallization will result in significant deviations. The detailed investigation of real gasifier slags confirmed the existence of several secondary phases with impact on the bulk slag viscosity (miscibility gaps, recrystallisation, incomplete melting). To cover incomplete melting, the ash melting behavior was included into the investigations. The influence of P2O5 was systematically investigated, based on sewage sludge ashes. Main results confirm the role of P2O5 as network former. Furthermore, a viscosity anomaly was observed, based on the formation of a miscibility gap. Thermochemical calculations (FactSage) was in line with the experimental findings via quench experiments, XRD and SEM-EDX analysis. The shear induced non-Newtonian behavior with respect to the measurement system material was unexpected. It underlines the requirement for further research of the various effects on crystallization (low reproducibility of viscosity measurement for crystalline slags and almost no reliable viscosity models including crystallization). Furthermore, the role of phosphorus is much more complex due to the formation of secondary phases. Also, aspects like phosphor evaporation or iron-phosphide formation and their effects on viscosity are still not understood/investigated and underlines further need for research. This joint Sino-German project established a successful long-term cooperation between IEC and ICC.
Publications
- In-situ analysis of the effect of CaO/Fe2O3 addition on ash melting and sintering behavior for slagging-type applications, Fuel 285 (2021) 11909
W. Shi, M. Laabs, M. Reinmöller, J. Bai, S. Guhl, L. Kong, H. Li, B. Meyer, W. Li
(See online at https://doi.org/10.1016/j.fuel.2020.119090) - Meta-study on the effect of P2O5 on single phase slag viscosity and the effect of P2O5 induced liquid phase immiscibility on dispersion viscosity, Fuel 305 (2021) 121501
D.H. Schwitalla, S. Guhl, J. Körner, M. Laabs, J. Bai, B. Meyer
(See online at https://doi.org/10.1016/j.fuel.2021.121501) - The fusion mechanism of complex minerals mixture and prediction model for flow temperature of coal ash for gasification, Fuel 305 (2021) 121448
W. Shi, M. Laabs, M. Reinmöller, L. Kong, S.V. Vassilev, S. Guhl, J. Bai, B. Meyer, W. Li
(See online at https://doi.org/10.1016/j.fuel.2021.121448) - Thermochemical and analytical approach to describe secondary slag phase formation and local process conditions in a full-scale BGL gasifier, Fuel Processing Technology 217 (2021) 106833
D.H. Schwitalla, S. Guhl, M. Laabs, M. Reinmöller, J. Bai, B. Meyer
(See online at https://doi.org/10.1016/j.fuproc.2021.106833)
