What is foam generator?
Regardless of the foam generator, the basic principle of foaming is to introduce air into the foaming agent solution. The various types of changes are different in the way of introducing gas, so the effect is also different.
There are two necessary factors for the formation of foam, one is the foaming agent solution, and the other is air. Both are indispensable. Without the blowing agent solution, the liquid film surrounding the gas would not form and there would be no bubbles. And without gas, foaming agent solution alone cannot form bubbles.
In the bubble formation system, the blowing agent solution is the dispersion medium, the gas is the dispersed phase, and the gas is dispersed in the liquid to form bubbles, and then numerous bubbles form the foam. In addition to the important factor of blowing agent performance, the introduction of gas into the blowing agent solution is another important factor. The principle of the foam generator is to introduce gas into the liquid, that is, the foam generator uses a certain method to introduce the gas into the liquid. Different foaming machines have different methods of introducing gas. In general, there are several ways to introduce gas into the foaming machine:
(1) Slowly rotating blades introduce gas. This is a method of directly introducing gas into mortar (or concrete slurry) mixed with cement foaming agent. When the mixer blade pushes the slurry, air enters the slurry with the mixer blades. In addition, a large amount of air is wrapped into the slurry when the slurry is turned over, and a part of the air is brought into the slurry by the cement and aggregate. The sum of the three is the total amount of air entering the slurry. Among them, the air brought into the slurry by the stirring blade and the air wrapped by the blade turning the slurry occupy the main body.
After the air enters the slurry, the liquid containing the foaming agent surfactant surrounds the air, forming a double-electron layer liquid film at the interface between the air and the liquid, and finally forms the bubbles in the slurry in the form of air-in-liquid.
Due to the slow rotation speed of the blades and less gas introduced in this way, the amount of bubbles generated is small, the foaming effect is not good, and the efficiency is low.
(2) High-speed rotating blades introduce gas. This is a way of introducing gas into the blowing agent solution by relying on high-speed rotating blades. The introduction of the gas mainly depends on the force of the rotating blades. The blades of this type generally require high-speed rotation, the speed should be> 700 rpm, generally between 700 and 1400 r/min, and the peripheral speed of the impeller end should be> 20 m/s in order to obtain satisfactory results. A certain high speed can expose the impeller to the liquid, contact with air, and introduce air. If the speed is too low, the impeller will not be exposed to the liquid, and the amount of bleed air will be very low. The proper speed should be lower than the impeller is exposed when the liquid is rotating.
(3) The use of pressure to introduce gas. This is the most commonly used advanced air-entrained foaming method at home and abroad. It is also a more scientific air-entraining method. It is the core of the foam concrete high-pressure and medium-pressure foam generator technology.
The two methods mentioned above are slow and uneven, and the bubble diameter is large, especially the bubble diameter cannot be controlled. It is completely dependent on the randomness of the foaming machine, and cannot guarantee the small bubble diameter and uniform foam. The most critical technical indicators. At the same time, the amount of foaming is difficult to control.
In order to effectively solve the above problems, the pressure-entrained foaming method came into being. No matter in terms of foaming volume, foaming speed, foam diameter and foam uniformity, etc., they have stepped on a new level and have made great technological progress. Its main principle is to use various equipment that can generate air pressure to press air into the liquid phase to achieve uniform mixing of the two phases. Under normal pressure, it is difficult for air to enter the liquid, but under certain pressure, it becomes easier. This air pressure not only presses the gas into the liquid, but also presses the liquid into the gas. In fact, it simultaneously applies pressure. In this way, the mixing of the two phases will be fast, efficient, uniform, and have fine bubbles, which meets the ideal technical requirements for foam.
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