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During the operation of high-foaming wastewater evaporators, large amounts of stable foam are easily formed due to the presence of large amounts of surfactants, organic matter, and other foam-prone components in the wastewater. This foam can occupy the effective space within the evaporator, reducing heat transfer efficiency, increasing energy consumption, and even leading to unstable equipment operation or wastewater overflow, disrupting normal production operations. To address this issue, defoamers are widely used in the evaporation treatment of high-foaming wastewater.

Defoamers primarily work by reducing the surface tension of the liquid film, destabilizing the foam and causing it to break down. Defoamers typically consist of an active ingredient and a carrier. Active ingredients can range from silicone to non-silicone, making it crucial to select the appropriate defoamer based on the specific wastewater properties.

The following describes defoamers for high-foaming wastewater evaporators from several perspectives:

1. Main Types of Defoamers

Based on their chemical composition, defoamers can be divided into silicone and non-silicone defoamers. Silicone defoamers, primarily composed of polydimethylsiloxane, exhibit high surface activity, quickly disrupting foam structures, and are suitable for a variety of wastewater environments. Non-silicone defoamers primarily include polyethers and fatty alcohols. These defoamers perform better in certain wastewater conditions, particularly high temperatures or high acidity and alkalinity. Choosing the appropriate defoamer requires careful consideration of factors such as the wastewater's composition, temperature, and pH.

 

2. Defoamer Usage

Defoamers are typically added in two ways: continuous and intermittent. Continuous addition is suitable for situations where foam is constantly generated. A metering pump is used to evenly inject the defoamer into the evaporator feed or circulation system. Intermittent addition is suitable for situations where foam generation fluctuates significantly. Manual or automatic addition is required depending on the foaming situation. Defoamer dosage must be strictly controlled. Excessive use may increase wastewater treatment costs and even affect subsequent treatment processes. Insufficient use will fail to effectively suppress foam. It is generally recommended to determine the optimal dosage through pilot testing and adjust it based on actual operating conditions.

3. Defoamer Performance Evaluation Indicators

Key indicators for evaluating defoamer performance include defoaming speed, foam suppression durability, temperature resistance, acid and alkali resistance, and compatibility. Defoaming speed refers to how quickly foam breaks down after defoamer addition; foam suppression durability indicates the defoamer's ability to suppress foam regeneration; temperature resistance and acid and alkali resistance reflect the defoamer's stability at high temperatures or extreme pH levels; and compatibility refers to whether the defoamer reacts adversely with other wastewater components, potentially affecting treatment effectiveness. A comprehensive evaluation of these indicators allows selection of a defoamer suitable for a specific wastewater treatment scenario.

4. Impact of Defoamers on Evaporator Operation

Appropriate use of defoamers can improve evaporator efficiency. Reducing foam fully utilizes the heat transfer area within the evaporator, improving heat energy utilization and reducing steam consumption. This enhances equipment operational stability, reduces maintenance downtime due to foaming, and extends equipment life. Defoamers also help improve effluent quality, preventing foam from carrying impurities that could affect subsequent treatment processes.

5. Economic Analysis of Defoamers

The cost of defoamers primarily consists of procurement and dosing costs. Procurement costs depend on the type and dosage of defoamer, while dosing costs involve equipment modifications or labor costs. Although defoamers increase treatment costs, overall operating costs can be optimized by improving evaporator efficiency, reducing energy consumption, and reducing maintenance costs. For example, some cases have shown that appropriate defoamer use can reduce evaporator steam usage, resulting in RMB savings. Both direct costs and indirect benefits should be considered in an economic analysis.

6. Considerations for Defoamer Selection

When selecting a defoamer, the wastewater characteristics must be fully considered. For example, high-salt wastewater may require a defoamer with good salt tolerance; high-temperature wastewater requires a defoamer that maintains activity at high temperatures. Environmental friendliness is also a key factor. Select defoamers that are easily degradable and non-toxic to avoid secondary pollution to subsequent treatment or the environment. It is recommended to verify the effectiveness of defoamers through laboratory and field trials to ensure their suitability.

7. Development Trends in Defoamers

 With advances in wastewater treatment technology, defoamers are also evolving. New defoamers are placing greater emphasis on environmental friendliness and efficiency, such as those based on biomass to reduce chemical residues. Specialized defoamers for wastewater from specific industries (such as textiles and food processing) are increasing in popularity, improving the targetedness and efficiency of treatment. Future research in defoamers may include multifunctional composite products that can both defoam and assist in the removal of certain pollutants, further enhancing the overall effectiveness of wastewater treatment.

Defoamers play a crucial role in high-foam wastewater evaporators. Proper selection and use of defoamers can effectively improve evaporator operating efficiency and stability, while reducing treatment costs. In practical applications, defoamers must be scientifically selected based on wastewater characteristics and treatment requirements, and dosing strategies must be continuously optimized to achieve cost-effective treatment.