Zinc oxide is a crucial inorganic compound widely used in industries such as rubber, ceramics, coatings, and pharmaceuticals. Its production primarily falls into two categories: the indirect process (French process) and the direct process (Waelz process), with the choice depending on raw material sources and product purity requirements.
Core Advantages of Direct Process Zinc Oxide: Cost-Effectiveness and Raw Material Flexibility
As a leading provider of thermal solutions, Jiangsu Jufeng Thermal Technology Co., Ltd. specializes in direct process (rotary kiln) zinc oxide production. This method, specifically the Waelz process, is renowned for its exceptional raw material adaptability and cost efficiency. It can process large volumes of various zinc-bearing wastes (such as smelting dust and leaching residues) and low-grade zinc ores, making it a key technology for resource recycling.
Detailed Steps of the Direct Process Rotary Kiln Production
1.Raw Material Preparation
Zinc ores or zinc-containing wastes are crushed and ground to a suitable particle size (typically 80-100 mesh) to ensure uniform reactions.
2.Mixing and Blending
The processed zinc-bearing material is precisely blended with a reductant (e.g., coke powder, anthracite coal) to form the kiln feed.
3.Reduction and Calcination
The blended feed is fed into an inclined rotary kiln. In the high-temperature zone (1000–1300°C), zinc oxide in the feed is reduced by carbon to form metallic zinc vapor.
4.Oxidation and Collection
The zinc vapor travels with the gas flow toward the kiln's end, where it is rapidly oxidized upon contact with introduced excess air, forming fine zinc oxide particles. The flue gas then passes through a multi-tube cooler for initial settling, followed by efficient capture in a large baghouse dust collector to obtain the final zinc oxide product.
5.Environmental Protection and By-Product Treatment
The production off-gas is treated by a complete system for waste heat recovery, desulfurization, denitrification, and advanced dust removal, ensuring compliant emissions. The kiln residue is assessed for resource recovery or safe disposal, enabling cleaner production.
Product Characteristics and Applications of Direct Process Zinc Oxide
Zinc oxide produced by this method offers a wide purity range (typically 90%-99%), meeting diverse industrial needs. It is primarily used in ceramic glazes, general rubber products, glass manufacturing, and certain chemical applications, where it offers outstanding cost-performance.
In contrast, indirect process zinc oxide uses high-purity zinc ingots as feedstock, yielding products with purity exceeding 99.7%. It primarily serves high-end applications like premium rubber, pharmaceuticals, and electronics, where extreme purity is critical.
