# Evaluation and Current State of Primary and Secondary Zinc Production--A Review
## 4 Zinc Production from Secondary Resources  
Products containing zinc, e.g., galvanized steel, become a source of raw materials for recycling (this is the so-called old scrap). These products are collected and processed based on scrap availability, alloy composition (e.g., purity, etc.) and ease of processing [68]. Currently, more and more zinc is produced, and this entails the generation of many zinc-containing wastes at various stages of its production (new scrap). Table 6 presents the formation of new and old zinc scrap at different stages of zinc production, while Figure 7 shows the material cycle in zinc recycling. The primary energy Intensity of zinc production ranges from 49 to 55 GJ/tone. Energy savings due to the recycling of steel (mainly in the case of galvanized steel) and zinc can range from 60 to 75% [57]. Worldwide, approximately 20% of zinc becomes new scrap in batch and continuous galvanizing processes. Zinc concentrates have a relatively constant chemical composition, while the resulting zinc wastes contain zinc in varying amounts. Table 7 shows the characteristics of various zinc precipitations generated in the industry and during the production process. Gall-v \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Scrap Source**} & \multirow{2}{*}{**Skiimming—New**} & \multicolumn{2}{c}{**Scrap Type**} & \multirow{2}{*}{**Steel Dust**} & \multirow{2}{*}{**Recovery Process**} \\  & & & **Crap** & & **—Old Scrap** \\ \hline Brass/Bronzes & Yes & Yes & No & Remelting \\ Zn–Al alloys & No & Yes & No & Remelting \\ Galvanizing & Yes & No & Yes & New scrap—remelting, \\ Rolled zinc—Zn–Ti & No & Yes & No & Remelting \\ sheets & & & & \\ Other & Yes & Yes & Yes & New scrap—remelting, \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Sources and types of zinc scrap, worked out based on [68]. Figure 7: Material cycle in zinc recycling, figure prepared based on data taken from [69]. in the remelting of galvanized steel. The specificity of the hot dip galvanizing process causes the efficiency of zinc use is lower compared to other areas of zinc production and consumption. Zinc consumption depends not only on the thickness of the coating but also on the losses resulting from the specificity of the technology, i.e., the formation of hard zinc and galvanizing ashes, oxidation of the bath surface and formation of precipitations of solidified zinc. Studies have shown that one ton of zinc used in the hot dip galvanizing process generates 147.6 kg of hard zinc and 139.3 kg of zinc ashes. The average zinc content in hard zinc ranges from 94 to 96 wt.%, while the average zinc content in galvanizing ashes ranges from approximately 70 wt.%. This means that for each tone of SHG zinc delivered to the galvanizing plant, on average, approx. 240 kg of zinc is ineffectively used to create waste in the form of hard zinc and zinc ashes [49]. These are, of course, by-products rich in zinc, which is the raw material for the production of secondary zinc. Zinc oxidation on the surface of the galvanizing bath creates zinc oxide (galvanizing ash) contaminated with flux decomposition products. The need to clean the surface of the bath before each immersion and the emergence of the charge generates a significant amount of galvanizing ashes. Ensuring a high-quality coating requires continuous cleaning of the bath surface and periodic removal of galvanizing ashes from it. During the collection of ashes, it is also inevitable that significant amounts of \"pure\" zinc will be removed from the surface. Galvanizing ashes are, therefore, a zinc-rich waste. During galvanizing, the iron is dissolved in the bath. The source of bath contamination with iron is galvanized products, but also the dissolving galvanizing kettle and flux contaminated with iron chloride.