Efficient Zinc Chloride Production with A Multi-Effect Falling Film Evaporator

Abstract 

    Zinc chloride (ZnCl₂) is an inorganic compound widely valued for its versatility and the critical role it plays across industries such as pharmaceuticals, electronics, textiles, and metallurgy. As a highly hygroscopic material, ZnCl₂ readily absorbs moisture, is highly soluble in water, and forms strongly acidic solutions. Despite its usefulness, traditional methods of evaporating and concentrating zinc chloride solutions face several challenges, including high energy consumption, environmental concerns, and inefficient batch processing.

Traditional Evaporation and Drying Challenges

    Conventional zinc chloride production relies on batch evaporation with graphite evaporators, followed by drying with graphite sloping plate dryers. These methods are energy-intensive, as vapor diffuses into the air, requiring recovery systems yet offering no steam reuse. Additionally, the vapor often contains hydrochloric acid (HCl), posing operational challenges and increasing environmental pollution risks.

A Better Solution: Multi-Effect Falling Film Evaporation

    To address these limitations, our company has developed a multi-effect falling film evaporation process, which provides continuous, energy-efficient, and environmentally friendly method for producing high-purity zinc chloride solids from zinc chloride solution. This technique recycles the secondary steam generated during high-temperature concentration for preheating or initial evaporation, significantly improving thermal efficiency and reducing energy consumption.

How it works

    The proposed multi-effect evaporation concentration process for zinc chloride involves the following steps:

    1. First Effect – Initial Evaporation: The process begins with a zinc chloride solution of lower concentration (eg. 40% concentration) that is preheated in a plate heat exchanger and introduced into the Effect-I falling film evaporator. Here, the solution forms a thin film as it flows down heat exchange tubes, where steam heats the liquid. Vapor and liquid are then separated, and the secondary steam is reused in the next stage.

    2. Second Effect- Further Concentration: The concentrated solution from the Effect I evaporator is transferred to Effect II evaporator, where the process is repeated. Steam from this stage is condensed for reuse, ensuring maximum thermal efficient.

    3. High-Temperature Concentration: The zinc chloride solution of higher concentration after initial initial evaporation and further concentration, is transferred to a high-temperature concentrator where it’s indirectly heated using thermal oil (or molten salt). This process brings the solution to a dry state, producing molten zinc chloride. And the molten zinc chloride is later cooled using a screw conveyor, yielding high-purity solid zinc chloride.

Advantages of Multi-Effect Evaporation

    1. Continuous Operation: Eliminates batch-processing inefficiencies with uninterrupted evaporation and concentration.

    2. Energy Efficiency: Recycles secondary steam, significantly reducing energy consumption and operating costs.

    3. Vacuum Processing: Operates under vacuum to enable rapid heating, reduce degradation, and improve product quality.

    4. Advanced Distribution Design: Dual-layer distribution ensures uniform liquid flow, enhancing heat exchange efficiency and adaptability.

    5. Sustainability: Lower steam consumption reduces environmental impact, making it a greener option for industrial applications.

Conclusion

    The multi-effect falling film evaporation technology is a game-changer for zinc chloride production. By combining continuous operation, energy efficiency, and environmental sustainability, it addresses the shortcomings of traditional methods while offering superior performance and cost savings. This advanced technology is paving the way for more efficient and eco-friendly industrial processes, ensuring high-quality zinc chloride products for a wide range of applications. 

    If you have any projects or requirements related to zinc chloride concentration, please feel free to contact our company. We are committed to providing professional solutions and excellent service, and we look forward to collaborating with you!