Can Ultrasonic Equipment Remove Bubbles?

Ultrasonic defoaming in dishwashing liquid is a typical application of ultrasonic liquid treatment technology in the daily chemical industry. It utilizes the cavitation effect of ultrasound to disrupt foam stability, solving foam problems during the production, storage, and use of dishwashing liquid. The following is a systematic analysis of its application scenarios, technical principles, process parameters, equipment selection, and advantages and limitations, providing practical reference for industrial production or related scenarios:

I. Core Application Scenarios (Industrial + Consumer Extension)
The foaming problem in dishwashing liquid mainly stems from the strong foaming properties of surfactants (such as LAS and AES). Ultrasonic defoaming focuses on the entire chain of "foam generation - persistence - use," with core scenarios including:

 

1. Industrial Production Stage (Core Scenarios)
Ingredient Mixing Defoaming: During dishwashing liquid production, surfactants, water, and additives (such as thickeners and fragrances) are mixed at high speed, easily generating a large amount of fine foam, leading to:

**Expansion of liquid volume, reducing equipment utilization (requiring ample space for foam);

**Foam trapping air, affecting subsequent homogenization, filtration, or filling accuracy;

**Foam residue causing uneven product appearance (such as layering, bubble marks).** Ultrasonic waves can defoam in real time during mixing or defoam in batches of foamy mixtures.

**Defoaming before filling:** During detergent filling, foam can easily cause overflow at the bottle mouth and inaccurate filling volume. Ultrasonic pretreatment can quickly break up tiny air bubbles in the liquid, improving filling efficiency and metering accuracy.

**Defoaming in storage tanks:** During the storage of finished detergent, foam may re-generate due to transportation shaking and temperature changes. Ultrasonic waves can be installed on the inner wall of the storage tank to continuously suppress foam accumulation.

2. Civil/Special Application Extensions

**Industrial Cleaning Support:** In industrial cleaning lines using detergent as a cleaning agent (such as for hardware and plastic parts cleaning), excessive foam can affect the circulation efficiency of the cleaning solution and remain on the workpiece surface. Ultrasonic waves can be integrated into the cleaning tank to defoam while cleaning.

**High-Concentration Detergent Dilution:** High-viscosity, high-concentration detergents are prone to generating stubborn foam during dilution. Ultrasonic-assisted dilution can quickly break up the foam, preventing it from lingering for extended periods after dilution.

II. Technical Principles: The Core Logic of Ultrasonic Foam Breaking
The stability of detergent foam depends on the strength of the liquid film (the repulsive force of the electric double layer formed by surfactant molecules) and gas retention (the inability of gas inside the foam to diffuse rapidly). Ultrasonic waves break up bubbles through two main effects:

 

1. Cavitation Effect (Main Cause)
When ultrasound propagates in a liquid, it forms alternating high-pressure and low-pressure zones (frequency 20kHz~1MHz). Microbubbles (cavitation bubbles) are generated in the low-pressure zone.
Cavitation bubbles rapidly collapse in the high-pressure zone, releasing instantaneous high temperatures (thousands of K) and shock waves (pressure reaching hundreds of atmospheres), directly impacting the liquid film of the foam, causing the liquid film to rupture and the foam to dissipate.

For the 10~100μm microbubbles in detergent (which are difficult for conventional defoamers to work with), the cavitation effect can precisely disrupt the surface tension balance of the liquid film, achieving deep defoaming.

2. Vibration Disturbance (Secondary Factor) The high-frequency vibrations of ultrasound are transmitted to the foam surface, causing resonance and continuous stretching and thinning of the liquid film, eventually leading to rupture due to tension imbalance.

Vibration also promotes liquid convection, accelerating gas diffusion on the foam surface and reducing foam lifespan.

Viscosity (25℃): 100~1000 mPa·s (regular detergent), low frequency and high power are preferred; if viscosity > 1000 mPa·s (concentrated type), the power density needs to be increased to 2~3 W/cm², and the processing time extended.

Foam Type: Surface foam (easily broken) can have reduced power; internal microbubbles (difficult to break) require a frequency of 50kHz or higher, combined with stirring.

 

IV. Industrial Equipment Selection Guide
Select equipment based on processing scale (laboratory/pilot-scale/mass production). Core types and applicable scenarios are as follows:

 

1. Immersion Ultrasonic Defoaming Equipment (Mainstream Mass Production Selection)

Structure: Consists of an ultrasonic generator (power supply) and an immersion transducer probe (titanium alloy, corrosion resistant). The probe is directly inserted into the liquid (storage tank, mixing vessel, buffer tank).

Advantages: Flexible installation, mobile, wide coverage, suitable for batch processing (e.g., 500L~10m³ storage tank) or production line upgrades (no modification to existing equipment required).

Selection Parameters: Select the number of probes (1~8) based on the processing capacity. Single probe power is 500W~1.5kW. For example, a 10m³ storage tank can be configured with 4 1kW probes, evenly distributed on the lower part of the tank wall (areas prone to foam accumulation).

2. Tank-type Ultrasonic Defoaming Equipment (for continuous production lines)

Structure: The transducer is embedded in the bottom/side wall of a stainless steel tank. The liquid undergoes continuous ultrasonic treatment as it passes through the tank, and is transported by conveyor belt or pipeline.

Advantages: High processing efficiency (suitable for production lines ≤5m³/h), high degree of automation, can be integrated into a buffer tank before filling.

Applicable Scenarios: Detergent mass production lines (e.g., defoaming before filling in daily chemical plants at 1~3m³/h), requiring synchronization with the production line speed (liquid residence time in the tank ≥30s).

3. Laboratory/Pilot-scale Equipment (for R&D)
Small immersion equipment (power 100~300W, frequency 28/40kHz), suitable for testing defoaming effects during the formulation development stage, or for small-batch sample preparation (≤50L). Material Requirements: Components in contact with the liquid (probe, tank) must be made of 316L stainless steel or titanium alloy to avoid reaction with surfactants and preservatives in the detergent, ensuring product purity.

 

V. Core Advantages and Limitations (Comparison with Traditional Defoaming Methods)

 

1. Advantages (Comparison with Chemical Defoamers and Mechanical Defoaming)

No Secondary Pollution: No need to add defoamers (such as silicones or polyethers), avoiding impact on the surface activity, pH value, or odor of the detergent, meeting the requirements for food-grade daily chemical products (dishwashing liquid may be used for dishwashing).

Thorough Defoaming: Highly effective against microbubbles (1~10μm), which traditional mechanical defoaming methods (such as stirring and filtering) struggle to break, while chemical defoamers have limited effect on internal bubbles.

No Impact on Product Performance: Ultrasonic waves only break down foam, without altering the detergent's viscosity, cleaning power, or stability, avoiding product stratification and deterioration in texture caused by chemical defoamers.

1. **Easy to Operate:** Automated control allows for power and time adjustment based on foam concentration, resulting in low maintenance costs (only periodic probe cleaning is required).

2. **Limitations:**
Higher Energy Consumption: Compared to chemical defoamers, ultrasonic equipment requires higher initial investment and operating energy, making it suitable for applications with high product purity requirements (e.g., high-end detergents, food-grade cleaning agents).

Limited Effectiveness in High-Viscosity Systems: If the detergent viscosity > 5000 mPa·s (ultra-concentrated type), ultrasonic wave propagation is hindered, weakening the cavitation effect. Heating (to reduce viscosity) or stirring is necessary.

Potential Temperature Increase: Prolonged high-power processing can raise the liquid temperature by 5-10°C, requiring cooling devices (e.g., chillers, jacketed tanks) to prevent impact on product stability.

 

VI. **Practical Precautions (Avoiding Pitfalls in Industrial Applications)**

Avoid Over-processing: Excessive power or duration can generate secondary bubbles (incomplete collapse of cavitation bubbles). Optimal parameters must be determined through small-scale testing (e.g., testing the defoaming effect at 20kHz, 1W/cm², and 1min).

Probe Cleaning: Thickeners and dirt in dishwashing liquid may adhere to the probe, affecting ultrasonic wave transmission. The probe surface should be cleaned regularly with water and a neutral detergent.

Uniform Distribution: In large storage tanks, probes should be evenly distributed at different heights and positions to avoid "dead zones." A stirrer can be used to improve liquid flow and ensure even defoaming.

Compatibility Testing: Newly formulated dishwashing liquids require small-scale testing to verify the cleaning power and foam stability of the product after ultrasonic treatment (a certain amount of foam should be maintained during use to avoid excessive defoaming and affecting the user experience).

Safety Protection: Low-frequency ultrasonic waves (20~40kHz) may generate noise (>85dB). Earplugs must be worn in the operating area, and the equipment must be grounded to prevent electric shock.

 

VII. Application Case References
Daily Chemical Detergent Production Line:** A factory adopted four 1kW immersion ultrasonic defoaming devices (frequency 28kHz) installed in a 10m³ mixing tank. The processing time was 3 minutes, achieving a foam removal rate of 95%, increasing filling efficiency by 30%, eliminating the need for defoamers, and raising the product qualification rate from 92% to 99%.

Industrial Cleaning Support:** A hardware parts cleaning line used detergent as a cleaning agent. Foam caused workpiece residue. Installing a tank-type ultrasonic device (frequency 40kHz, power density 1.5W/cm²) in the cleaning tank, defoaming was performed simultaneously with cleaning. The workpiece residue rate decreased from 8% to 1.2%, and the cleaning solution lifespan was extended by 50%.

Summary: The core value of ultrasonic detergent defoaming lies in "additive-free, deep defoaming," making it particularly suitable for industrial production scenarios with high requirements for product purity and performance (such as high-end detergents and food-grade cleaning agents). When selecting a model, equipment parameters should be matched based on the processing capacity, detergent viscosity, and foam type. Optimal processes should be determined through small-scale trials. Combining cooling and stirring as auxiliary methods can improve defoaming efficiency. Compared to traditional methods, although the initial investment is higher, it avoids chemical pollution, improves product quality, and in the long run aligns with the "green and safe" development trend of the daily chemical industry.