Theoretical and Practical Evaluation of the Feasibility of Zinc Evaporation from the Bottom Zinc Dross as a Valuable Secondary Material

Abstract

This study presents a theoretical and practical evaluation of zinc evaporation from bottom zinc dross (hard zinc) as a secondary zinc source (zinc content approximately 94–97%), which originates in the batch hot-dip galvanizing process. The thermodynamics of the zinc evaporation process were studied under the normal pressure (100 kPa) in the inert atmosphere, using argon with flow rate 90 mL/min. Samples were subjected to the evaporation process for 5, 10 and 20 min under the temperature of 700 °C and 800 °C, respectively. For the theoretical thermodynamic study, HSC Chemistry 6.1 software was used and final products, as well as residuals after the evaporation process, were analyzed by SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray). Calculated and experimental argon consumption in the process of zinc evaporation has been compared. A high purity zinc with efficiency over 99% was reached. Due to a dynamic regime, argon consumption at the temperature of 700 °C and 800 °C were 7 times and 3 times, respectively, less than calculated.

Zinc Evaporation from Brass Scraps in the Atmosphere of Inert Gas

“…As previously noted, analysing the zinc evaporation from the liquid copper alloy is a complex process due to its heterogeneous nature, and its resultant rate is affected by the mass transfer phenomena both in the liquid phase and in the gas phase in addition to the chemical affinity. Kinetically, this process may be divided into the following three essential stages [30]:…”

“…As previously noted, analysing the zinc evaporation from the liquid copper alloy is a complex process due to its heterogeneous nature, and its resultant rate is affected by the mass transfer phenomena both in the liquid phase and in the gas phase in addition to the chemical affinity. Kinetically, this process may be divided into the following three essential stages [ 30 ]: Zinc transfer from deep inside of the liquid alloy to the interface; Zinc evaporation from the liquid metal–gas phase interface; Zinc vapour transfer from the interface into the deeper part of the gas phase. …”

“…This may indicate the importance of the topic with which research teams around the world are dealing. The authors of [30] presented the results of studies on the evaporation of zinc from zinc-bearing waste generated in the process of galvanizing steel surfaces. The process was carried out at a pressure of 100 kPa in a helium atmosphere and a process temperature of 700 to 800 • C. The result of these tests was obtaining zinc with a purity of 99 wt.%.…”

Development and Modification of New or Recycled Materials and Technological Processes towards Sustainable Development

“…The eleven research articles offer promising studies from various scientific fields with potential practical applications. Bottom zinc dross, as a valuable secondary material, is investigated in the paper by Pauerová et al [6]. The recycling of cable waste and its application use are explored by Wędrychowicz et al [7].…”