RG Mineral Systems

The behavior of mineral matter in high temperature conversion processes such as gasification and combustion is of special interest. Particularly process disturbances and wear of plant components are often linked to the ash/slag properties of the feedstock. Our goal is the chemical-mineralogical characterization of these ash forming components as well as the modelling and measurement of physical and chemical property data. Based on this information, we extend our understanding regarding the behavior of ash/slag and develop new approaches for process optimization. In addition to analytical/experimental investigation, we use thermochemical calculations to estimate the behavior of mineral components within high temperature processes.

Analytical/experimental Equipment
Current projects
Former projects / references


  • Chemical-mineralogical characterization of feedstock and process samples (slags, agglomerates, fouling layers),
  • Determination of viscosity, density, surface tension and wetting behavior of slags,
  • Experimental investigation of slag formation and the interactions between solid, liquid and gas phases at high temperatures and in different atmospheres,
  • Modelling of the ash/slag behavior on the basis of chemical equilibrium considering experimental information (slag formation and solidification, mobilizing of trace elements and extraneous materials, deposit formation/fouling, refractory corrosion).

Analytical/experimental Equipment:

  • Analysis of elements (X-ray fluorescence spectroscopy, energy dispersive X-ray spectroscopy), 
  • Phase analysis (X-ray diffraction up to 1600 °C/20 bar, different atmospheres), 
  • reflected-light and transmitted-light microscope, 
  • Scanning electron microscope (heating chamber up to 1600 °C, Environmental scanning electron microscope, EDX, WDX, EBSD), 
  • Laboratory furnace up to 1800 °C and 30 bar with different atmospheres,
  • Furnace with rapid sample quenching (1600 °C, reducing/oxidizing atmosphere),
  • Calorimetry (differential scanning calorimetry, Drop in calorimeter, up to 1700 °C),
  • Viscometer (up to 1700 °C, variable oxygen partial pressure/gas atmosphere), 
  • Thermo-optical measurement systems (inert/reducing up to 2000 °C, oxidizing up to 1700 °C, sessile drop and maximum bubble pressure-method),
  • Thermogravimetric analyzers coupled with Differential thermal analysis differential scanning calorimetry up to 1500 °C,
  • ICP-OES with electro-thermal evaporation.


  • FactSage 
  • SimuSage 

Current projects:

  • VERENA: Optimization of the COORVED gasifier pilot plant for biogenic input materials and scaling to industrial size based on advanced CFD models, joint project with TU Darmstadt, TU München, Forschungszentrum Jülich, RWE Power AG, Air Liquide F&E GmbH, GTT, Arvos GmbH, GKN Sinter Metals Filters GmbH, Clariant Produkte GmbH, SUEZ Deutschland GmbH, VER Verfahrensingenieure GmbH; FKZ: 03EE5044C, Auftraggeber BMWE, 10/2020-09/2024
  • VeRa: Investigation and evaluation of the formation potential when replacing standard fuels with biogenic substitute fuels in power plant boilers, joint project with TU Stuttgart, Forschungszentrum Jülich, Recom Services GmbH, RWE Power AG, Clyde Bergemann GmbH, EnBW Energie Baden-Württemberg AG, RWE Generation SE, LEAG; FKZ: 03EE5064C, Auftraggeber BMWE , 02/2021-01/2025
  • OptiCon: Optical Investigation of High Temperature Conversion Processes, Joint project with Friedrich-Schiller-Universität Jena, Institute of Applied Physics, project no. 03Z22F513, funder BMBF, 12/2017-11/2020
  • ZIK Virtuhcon II, Research Group Material and Process Analysis, project no. 03Z22FN12, funder BMBF, 09/2016-08/2021

Former projects / references:

  • KORRISTENT: Investigation of slagging of coal fired boilers, Joint project of TU Bergakademie Freiberg (IEC, IAC, IKGB) and Lausitz Energie Kraftwerke AG, project no. 03ET7066A, funder BMWi, 01/2016-12/2019
  • SlagVis: Key Aspects of Slag Viscosity in Slagging Gasifiers, Sino-German Joint project with State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, project no. 392218733, funder DFG, 07/2017 – 06/2020
  • HotVeGas III: General investigations on gasification based process chains, Joint Project with TU Munich, IEK-2 Forschungszentrum Jülich, GTT Technologies GmbH, RWE Power AG, Air Liquide Forschung und Entwicklung GmbH, project no. 0327773J, funder BMWi and Industrial partners, 01/2016-12/2019
  • HITECOM I und II: In situ investigation of reactive single particles by laser spectroscopic measurements, Joint project with Friedrich-Schiller-Universität Jena, Institute of Applied Physics, project no. 03Z2F511 and 03Z2F512, funder BMBF, 02/20014-01/2015 and 02/2015-01/2017
  • R&D project “Fouling free combustion of Reichwalde coal”, Joint project with Institute of Process Engineering and Environmental Technology TU Dresden, funder VATTENFALL EUROPE GENERATION AG, 10/2015-10/2017
  • ZIK Virtuhcon, Research group Multiphase Systems: support of property data acquisition for ash-slag-systems, project no. 03Z2FN12, funder BMBF, 11/2009-10/2014
  • HotVeGas I und II: General investigations on selected process steps (kinetics, slag formation) within gasifiers, Joint project, project no. 0327773B and 0327773G, funder BMWi and industrial partners, 09/2007-08/2011 and 09/2011-08/2015



Group manager:

Scientific staff:


Selected International Journal Contributions

Schwitalla, D. H.; Bronsch, A. M.; Klinger, M.; Guhl, S.; Meyer, B. (2017): Analysis of solid phase formation and its impact on slag rheology. In: Fuel (203), S. 932–941. DOI: 10.1016/j.fuel.2017.04.092.

Küster, F.; Nikrityuk, P.; Junghanns, M.; Nolte, S.; Tünnermann, A.; Ackermann, R., Richter, A.; Guhl, S.; Meyer, B. (2017): In-situ investigation of single particle gasification in a defined gas flow applying TGA with optical measurements. In: Fuel 194 (2), S. 544–556. DOI: 10.1016/j.fuel.2016.12.069.

Gonzalez, V.; Rußig, S.; Schurz, M.; Krzack, S.; Kleeberg, J.; Guhl, S.; Meyer, B. (2018): Experimental investigations on lignite char gasification kinetics using a pressurized drop tube reactor. In: Fuel 224, S. 348–356. DOI: 10.1016/j.fuel.2018.03.018.

Komarova, E.; Abosteif, Z.; Guhl, S.; Meyer, B. (2019): Brown coal char CO2 ‐gasification kinetics with respect to the char structure. Part II. Kinetics and correlations. In: Can. J. Chem. Eng. 97 (1), S. 226–237. DOI: 10.1002/cjce.23329.

Rußig, S.; Gonzalez, V.; Schurz, M.; Krzack, S.; Kleeberg, J.; Guhl, S.; Meyer, B. (2019): Particle residence time measurement in a pressurized drop-tube reactor with radioactive tracer. In: Fuel 252, S. 37–46. DOI: 10.1016/j.fuel.2019.03.134.

Gehre, P.; Preisker, T.; Brachhold, N.; Guhl, S.; Wöhrmeyer, C.; Parr, C.; Aneziris, C. G. (2020): Thermodynamic calculation and microscopic examination of liquid phase formation in MgO–C refractories contain calcium magnesium aluminate. In: Materials Chemistry and Physics 256, S. 123723. DOI: 10.1016/j.matchemphys.2020.123723.

Xuan, W.; Wang, H.; Guhl, S.; Zhang, J.; Meyer, B. (2020): Different Roles of Iron Species in the Network Structure and Viscosity of Silicate Melts. In: Energy Fuels 34 (11), S. 13698–13706. DOI: 10.1021/acs.energyfuels.0c02425.

Schwitalla, D. H.; Guhl, S.; Körner, J.; Laabs, M.; Bai, J.; Meyer, B. (2021): Meta-study on the effect of P2O5 on single phase slag viscosity and the effect of P2O5 induced liquid phase immiscibility on dispersion viscosity. In: Fuel 305, S. 121501. DOI: 10.1016/j.fuel.2021.121501.

Schwitalla, D. H.; Guhl, S.; Laabs, M.; Reinmöller, M.; Bai, J.; Meyer, B. (2021): Thermochemical and analytical approach to describe secondary slag phase formation and local process conditions in a full-scale BGL gasifier. In: Fuel Processing Technology 217 (Part 1), S. 106833. DOI: 10.1016/j.fuproc.2021.106833.

An, F.; Küster, F.: Ackermann, R.; Guhl, S.; Richter, A. (2021): Heat and mass transfer analysis of a high-pressure TGA with defined gas flow for single-particle studies. In: Chemical Engineering Journal 411 (17), S. 128503. DOI: 10.1016/j.cej.2021.128503.

Shi, W.; Laabs, M.; Reinmöller, M.; Bai, J.; Guhl, S.; Kong, L.; Li, H.; Meyer, M.; Li, W. (2021): In-situ analysis of the effect of CaO/Fe2O3 addition on ash melting and sintering behavior for slagging-type applications. In: Fuel 285, S. 119090. DOI: 10.1016/j.fuel.2020.119090.

Hommel, C.; Hassler, J.; Matschat, R.; Vogt, T.; Detcheva, A. K.; Recknagel, S. (2021): A fast and robust direct solid sampling method for the determination of 27 trace, main and minor elements in soda-lime glass based on ETV-ICP OES and using a gaseous halogenating modifier. In: Journal of Analytical Atomic Spectrometry 36 (8), S. 1683–1693. DOI: 10.1039/d1ja00081k.

Reinmöller, M.; Sieradzka, M.; Laabs, M.; Schreiner, M.; Mlonka-Mędrala, A.; Kopia, A.; Meyer, B.; Magdziarz, A. (2021): Investigation of the thermal behaviour of different biomasses and properties of their low- and high-temperature ashes. In: Fuel 301. DOI: 10.1016/j.fuel.2021.121026.

Reinmöller, M., Kong, L., Laabs, M., Ge, Z., Hommel, C., Farid, M. M.,  Shi, W., Schreiner, M., Cao, X., Guhl, S., Bai, J., Meyer, B. (2022): Methods for the determination of composition, mineral phases, and process-relevant behavior of ashes and its modeling: A case study for an alkali-rich ash. In: Journal of the Energy Institute 100, S. 137–147. DOI: 10.1016/j.joei.2021.11.001.

Laabs, M.; Schwitalla, D. H.; Ge, Z.; Kong, L.; Bai, J.; Guhl, S.; Meyer, B.  (2022): Comparison of setups for measuring the viscosity of coal ash slags for entrained-flow gasification. In: Fuel 307, S. 121777. DOI: 10.1016/j.fuel.2021.121777.