کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6467925 1423261 2017 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Numerical investigation of the outward growth of ZnS in the removal of H2S in a packed bed of ZnO
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی مهندسی شیمی (عمومی)
پیش نمایش صفحه اول مقاله
Numerical investigation of the outward growth of ZnS in the removal of H2S in a packed bed of ZnO
چکیده انگلیسی


- We model the outward growth and void formation seen in sulfidation of ZnO.
- Model accounts for nucleation-growth of voids, diffusion of reactants and reaction.
- Micro-scale model is used in a packed bed model that includes intra-pellet diffusion.
- The outward growth of the grains can cause to pore clogging in a pellet.
- Pore clogging leads to incomplete conversion of ZnO pellets in a packed bed.

Sulfidation of zinc oxide is a viable option for the removal of hydrogen sulfide from raw syngas and biogas. Recent experiments showed that sulfidation of nanoscopic zinc oxide particles leads to an outward growth and the formation of voids inside the particles. In this work, we derive a micro-scale model to describe this phenomenon. The model accounts for nucleation and growth of voids inside the particles, diffusion of Zn and O through the product layer, and deposition of the solid product at the particle surface as a result of the reaction between ZnO and H2S. The model is thus opposite to the well known shrinking core model where an inward growth of the product layer is assumed. To explore the effect of the outward growth on the dynamics of a packed bed adsorber the micro-scale model is combined with a macro-scale model that accounts for intra-pellet diffusion and convection along the packed bed. In the limit of fast nucleation and growth of voids inside the zinc oxide particles, the micro-scale model shows a qualitatively similar conversion profile to the shrinking core model, while when nucleation controls an inflection point in conversion profile is found. On the macro-scale, the outward growth can cause the clogging of pores inside the pellets which prevents the pellets from reaching full conversion. This leads to shorter breakthrough times of the packed bed due to the sealing of unreacted zinc oxide. Our results thus provide a possible explanation of the incomplete conversion of zinc oxide in packed beds.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Engineering Science - Volume 158, 2 February 2017, Pages 328-339
نویسندگان
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