Oxidation and Condensation of Zinc Fume From Zn-CO₂-CO-H₂O Streams Relevant to Steelmaking Off-Gas Systems

Journal Article · Mon Jan 23 00:00:00 EST 2017 · Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science

DOI:https://doi.org/10.1007/s11663-016-0910-8· OSTI ID:1364542

Bronson, Tyler Mark ^[1]; Ma, Naiyang ^[2]; Zhu, Liang Zhu ^[3]; Sohn, Hong Yong ^[4]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. ArcelorMittal Global R&D, East Chicago, IN (United States). East Chicago Lab.
3. Univ. of Utah, Salt Lake City, UT (United States). Dept. Materials Science and Engineering
4. Univ. of Utah, Salt Lake City, UT (United States). Dept. of Metallurgical Engineering

Here the objective of this research was to study the condensation of zinc vapor to metallic zinc and zinc oxide solid under varying environments to investigate the feasibility of in-process separation of zinc from steelmaking off-gas dusts. Water vapor content, temperature, degree of cooling, gas composition, and initial zinc partial pressure were varied to simulate the possible conditions that can occur within steelmaking off-gas systems, limited to Zn-CO₂-CO-H₂O gas compositions. The temperature of deposition and the effect of rapidly quenching the gas were specifically studied. A homogeneous nucleation model for applicable experiments was applied to the analysis of the experimental data. It was determined that under the experimental conditions, oxidation of zinc vapor by H₂O or CO₂ does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO₂/CO = 40/7). Rate expressions that correlate CO₂ and H₂O oxidation rates to gas composition, partial pressure of water vapor, temperature, and zinc partial pressure were determined to be as follows: Rate $$ \left(\frac{mol}{m^2s}\right) $$ = 406 exp $$ \left(\frac{-50.2 kJ/mol}{RT}\right) $$ (pZnpCO₂ $$-$$ PCO/K_eqCO₂) $$\frac{mol}{m^2 x s}$$ Rate $$ \left(\frac{mol}{m^2s}\right) $$ = 32.9 exp $$ \left(\frac{-13.7 kJ/mol}{RT}\right) $$ (pZnPH₂O $$-$$ PH₂/K_eqH₂O) $$\frac{mol}{m^2 x s}$$. It was proven that a rapid cooling rate (500 K/s) significantly increases the ratio of metallic zinc to zinc oxide as opposed to a slow cooling rate (250 K/s). SEM analysis found evidence of heterogeneous growth of ZnO as well as of homogeneous formation of metallic zinc. The homogeneous nucleation model fit well with experiments where only metallic zinc deposited. An expanded model with rates of oxidation by CO₂ and H₂O as shown was combined with the homogenous nucleation model and then compared with experimental data. The calculated results based on the model gave a reasonable fit to the measured data. For the conditions used in this study, the rate equations for the oxidation of zinc by carbon dioxide and water vapor as well as the homogeneous nucleation model of metallic zinc were applicable for various temperatures, zinc partial pressures, CO₂:CO ratios, and H₂O partial pressures.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC52-06NA25396
• OSTI ID: 1364542
• Report Number(s): LA-UR-16-25438; TRN: US1702323
• Journal Information: Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science, Vol. 48, Issue 2; ISSN 1073-5615
• Publisher: ASM International
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE