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Title: Oxidation and Condensation of Zinc Fume From Zn-CO 2-CO-H 2O Streams Relevant to Steelmaking Off-Gas Systems

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-CO 2-CO-H 2O 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 H 2O or CO 2 does not occur above 1108 K (835 °C) even for highly oxidizing streams (CO 2/CO = 40/7). Rate expressions that correlate CO 2 and H 2O 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 $$ \left(\frac{-50.2 kJ/mol}{RT}\right) $$ (pZnpCO 2 $-$ PCO/K eqCO 2) $$\frac{mol}{m^2 x s}$$ Rate $$ \left(\frac{mol}{m^2s}\right) $$ = 32.9 exp $$ \left(\frac{-13.7 kJ/mol}{RT}\right) $$ (pZnPH 2O $-$ PH 2/K eqH 2O) $$\frac{mol}{m^2 x s}$$. 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 CO 2 and H 2O 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, CO 2:CO ratios, and H 2O partial pressures.
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  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
Publication Date:
Report Number(s):
LA-UR-16-25438
Journal ID: ISSN 1073-5615; TRN: US1702323
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Metallurgical and Materials Transactions. B, Process Metallurgy and Materials Processing Science
Additional Journal Information:
Journal Volume: 48; Journal Issue: 2; Journal ID: ISSN 1073-5615
Publisher:
ASM International
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1364542