What Is a Fine Bubble Generator?
A fine bubble generator is a device that generates fine bubbles, which are bubbles smaller than 100μm (0.1mm) in diameter.
Fine bubbles refer to all bubbles smaller than 100 µm in diameter. Bubbles of 1 to 100 μm are classified as microbubbles, and bubbles of 1 μm or smaller are classified as nanobubbles.
Uses of Fine Bubble Generators
Fine bubble generators are used in industries and fields where fine bubbles are used. A major characteristic of fine bubbles is that they can remain in liquids for long periods of time. This means that fine bubbles have various effects, such as purification and cleaning, and have a wide range of applications.
The following is a description of the main applications of fine bubbles.
1. Environmental Field
Fine bubbles are used for purification of rivers, lakes, marshes, and wastewater treatment.
2. Agriculture and Fisheries
Fine bubbles are very small in diameter and easily penetrate into the cells of living organisms, enabling them to deliver nutrients efficiently. Specifically, fine bubbles are used to promote growth and increase yields of agricultural, livestock, and marine products.
3. Food Industry
It is used to preserve freshness and prevent the oxidation of food products.
4. Cleaning Field
Fine bubbles are used to prevent the growth of bacteria in pipes, tanks, and other equipment by utilizing the effect of fine bubbles to inhibit the growth of microorganisms. Specifically, fine bubbles are used for toilet cleaning and washing machines.
5. Industrial Fields
Fine bubbles are also characterized by their electrification and strong adsorption properties. Therefore, they can also efficiently separate and recover metal sludge and are used for production line cleaning. It is also used for precision stripping and silicon wafer thin film separation.
Fine bubble generators can be used in a wide range of applications, from daily life to industrial use, as well as in the beauty and medical fields.
Principle of Fine Bubble Generators
The principle of fine bubble generator is to generate minute bubbles by “crushing bubbles by shearing liquid,” “precipitation of dissolved gas in liquid,” and “rapid condensation of vapor bubbles.” Note that any of these methods may contain both microbubbles of 1~100 µm in diameter and nanobubbles of 1 µm or less in diameter. If necessary, they may be separated, and such devices are available.
Types of Fine Bubble Generators
Fine bubble generators generate bubbles in three different ways: “bubble breaking by shearing the liquid,” “precipitation of dissolved gases in the liquid,” and “rapid condensation of vapor bubbles.” Specific methods belonging to each of these methods are listed below.
1. Bubble Breaking by Liquid Shear
In this method, liquid and gas are mixed, then agitated, and bubbles consisting of gas in the liquid are sheared (torn or cut off) by water flow.
Specifically, the following methods are available:
- Swirling Flow Liquid Type
Bubbles are crushed by a high-speed swirling liquid flow. - Ejector Type/Venturi Type
Bubbles are crushed by sudden pressure changes in the gas-liquid flow path. - Micropore Type
Micronization of bubbles by fine gas dispersion holes - Static Mixer Type
Shearing of bubbles by obstacles in the gas-liquid flow path
2. Precipitation of Dissolved Gas in the Liquid
This method involves mixing a liquid and gas in a supersaturated state and then applying pressure or heating to precipitate the supersaturated portion as fine bubbles. Specifically, the following methods are available:
- Pressurized Dissolution and Precipitation Method
Bubbles are precipitated by rapid decompression of a saturated - Solution Under Pressure
Heated precipitation
3. Rapid Heating of a Saturated Solution at Room Temperature to Precipitate Bubbles
Rapid Condensation of Vapor Bubbles
In this method, a mixture of liquid and gas is made into vapor, which is then quenched to generate bubbles composed of gas. Specifically, the vapor direct contact condensation method is used to refine mixed gas bubbles by direct contact condensation of vapor.
Other Information on Fine Bubble Generators
Fine Bubble Generation by Porous Ceramics
Fine bubble generators are often used to generate fine bubbles using physical changes in the gas, but they are also used to generate fine bubbles by porous ceramics. In this method, gas is injected through a ceramic membrane with fine and uniform pore size and dispersed in the liquid to generate fine bubbles.
Therefore, it is not necessary to apply a strong force to the gas or liquid when generating fine bubbles. Another advantage is that it can be used with a wide range of fluids, from watery to viscous liquids, and the amount of fine bubbles generated can be adjusted by controlling the number and length of ceramics used.