HotSpot: High temperature behaviour of potentially toxic and corrosive trace elements in thermal gasification systems
Final Report Abstract
In conclusion, this study revealed new findings regarding the chemical form and the concentration of the trace metals cadmium, zinc and lead under gasification-like conditions at temperatures up to 1000 °C under the influence of hydrogen sulfide, hydrogen chloride and steam. The focus was on the speciation of cadium, zinc and lead species in the gas phase and the condensate. The gaseous species were determined online by a Molecular-Beam-Mass- Spectrometer. The condensates were analysed by standard methods. The experimental data was compared with the results of thermodynamic Scheil-Gulliver cooling calculations. Further, the experimental data was used as an input for a pseudo equilibrium model aiming the determination of kinetic information of the underlying transformations. Most abundant chemical forms of lead were metallic Pb, PbCl2, PbS. In general, PbO and PbO2 are minor species as shown by the experimental findings and as predicted by the thermodynamic calculations. The additions of steam, hydrogen chloride and hydrogen sulphide have a significant influence on the chemical form and the concentration of lead species. For example, the concentration of PbCl2 increases strongly with increasing hydrogen chloride content of the atmosphere. Also the concentration of PbS increases strongly with increasing hydrogen sulphide content. The major lead condensation processes occur at temperatures below 885 °C as shown by the experimental results and by Scheil-Gulliver calculations. In general, the experimental results and the Scheil-Gulliver calculations of the gas phase show a good agreement. Increasing the amount of hydrogen sulphide lead to prevalence of PbS in the condensate. The effect of hydrogen chloride is less significant due to lower amount of PbCl2 in the condensate. Nevertheless, the amount of PbCl2 condensed at lower temperature is increasing with increasing concentration of hydrogen chloride. In the condensation experiments ZnO, ZnCl2, and ZnS were found in the deposits. The species found in the gas phase were Zn, ZnO, ZnCl2, and ZnS. The release and condensation of zinc compounds were strongly influenced by steam, hydrogen chloride and hydrogen sulphide. The comparison of the experimental results with the results of the cooling calculations performed by the Scheil−Gulliver model showed the great capacity of the model to predict the behavior of zinc under the gasification conditions taken into account. Thus, the speciation as well as the temperatures at which the species condensed and were found in the gas phase had the same trend in the calculations as in the experiments. Furthermore, the pseudothermodynamic model was found quite useful to clarify and understand the global kinetics of the experiments. The key cadmium species detected during the condensation experiments were Cd, CdCl2, and CdS. The species found in the gas phase were Cd, CdO, CdCl2, and CdS. The Scheil−Gulliver cooling model was proved to be an excellent tool for the prediction of the release and condensation of Cd. The speciation as well as the temperatures at which the species condensed and were present in the gas phase under the influence of H2O, HCl, and H2S had the same trend in the calculations as in the experimental results. In conclusion, this work lead to a more detailed understanding of the behavior (condensation and release) of cadmium, lead zinc species under gasification conditions in qualitative and quantitative meanings. Furthermore, the Scheil−Gulliver tool has been discovered to be a potent tool for obtaining reliable predictions of the behavior of this trace metal under gasification conditions. However, future work should address the interaction of hydrogen chloride and hydrogen sulphide as well as its competing behavior for the formation of cadmium, zinc and lead compounds has to be addressed in future, because both chlorine and sulphur are common fuel components, which can lead to more complex interaction with trace metals than observed in this study.
Publications
- "Influence of Steam, Hydrogen Chloride, and Hydrogen Sulfide on the Release and Condensation of Zinc in Gasification". - Ind. Eng. Chem. Res. 55 (2016), 6911-6921
Benito Abascal, M., Bläsing, M., Ninomiya, Y., Müller, M.
(See online at https://doi.org/10.1021/acs.iecr.6b01637) - Influence of Steam, Hydrogen Chloride, and Hydrogen Sulfide on the Release and Condensation of Cadmium in Gasification, Energy Fuels 30 (2016), 943–953
Benito Abascal, M., Bläsing, M., Ninomiya, Y., Müller, M.
(See online at https://doi.org/10.1021/acs.energyfuels.5b02676) - Partitioning of lead and lead compounds under gasification-like conditions, Energy & Fuels 32 (2018), 651-657
Bläsing, M., Benito Abascal, M., Ninomiya, Y., Müller, M.
(See online at https://doi.org/10.1021/acs.energyfuels.7b02803)
