JPH01135515A - Method for separating substances having no specific gravity differences in fluid - Google Patents

Abstract

PURPOSE:To efficiently separate small particles from a medium having no specific gravity differences by transmitting supersonic waves into a fluid for collection of the small particles in its field in a position of the small sound pressure amplitude and for separation and extraction thereof. CONSTITUTION:A fluid with small polystyrene particles 3 suspended in a medium 2 such as salt water, etc., is placed in a cylindrical container 1 and supersonic waves are transmitted thereinto from a supersonic wave transmitter 4. The polystyrene particles 3 are collected densely in a position of the minimum sound pressure amplitude according to the distribution of the sound pressure amplitude of standing wave. The particle thus collected are separated for efficient extraction of the small particles having no specific gravity differences.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for separating substances mixed in a fluid that have substantially no difference in specific gravity.

[Prior Art] When a substance other than a medium is mixed in a fluid, that substance can generally be separated by centrifugation, but if the substance has substantially the same density as the fluid. In some cases, centrifugation cannot be used.

[Problems to be Solved by the Invention] The present invention seeks to provide a method for easily separating substances with no difference in specific gravity in the above-mentioned fluid.

[Means and operations for solving the problem] In order to achieve the above object, the method of the present invention irradiates ultrasonic waves into a fluid containing small particles with no difference in specific gravity from the medium, and A force is applied to the small particles in the direction of the small sound pressure amplitude, so that the small particles gather at a position where the sound pressure amplitude is small, and from this aggregation, a part containing a high density of small particles is separated and extracted. It is characterized by:

To explain more specifically, in general, when a small sphere with a volume V is irradiated with ultrasound, the force F due to the radiation pressure of the ultrasound acting on the small sphere is expressed by the following formula (W, L, Nyborg
Author, Ultrasound: ijs applica
tion sin medicine and biol
ogy, F, J, Fry! (1978).

F = VYWK[-V (1-y)vPr...(1) K[: Time average of kinetic energy PE: Time average of potential energy: Gradient end of space @ Niko γ: Compression of sphere and medium Sex ratio Y: a function of the density of the sphere ρS and the density of the medium ρ0, where:
If the densities of the sphere and the medium are equal (ρS=ρo),
Y=0, and the first term on the right side of equation (1) becomes 0.

And, in general, since γ is smaller than l, after all.

F oc −vP E , and a force acts on the small sphere in a direction opposite to the gradient of potential energy, that is, a force acts in the direction of the small sound pressure amplitude within the sound field.

Therefore, if a large number of small particles with the same density as the medium are mixed into the three-dimensional standing wave sound field in the medium, the small particles will eventually settle at the position where the sound pressure amplitude is minimum. By suctioning and extracting the collected part of small particles using a thin tube or the like, it is possible to separate a part containing a high density of small particles.

In this case, by irradiating ultrasound into the medium,
Since the force due to the ultrasonic radiation pressure expressed by equation (1) acts on the substance in the fluid, there is a compressibility between the fluid medium and the small particles present in it, even if there is no difference in specific gravity. If there is a difference, or a difference in the speed of sound or a difference in acoustic impedance, a non-zero finite force will be applied to the small particle, and as it moves through the fluid medium, it will be possible to move the small particle to a specific location. This makes it possible to aggregate and separate at high density.

In addition, with this method, as will be described later as an example, for example, in a standing wave sound field inside a cylinder, agglomeration of small particles as shown in Figures 82 to 4 is observed, and when the frequency of the ultrasound is changed, resonance occurs. The shape of the agglomeration changes in response to changes in the state6. Therefore, by appropriately selecting the container shape and the frequency of the ultrasonic waves, the aggregation can be further concentrated in a specific position, making it easier to extract and separate small particles. It can be done.

Note that this separation method is not limited to the case where a standing wave sound field is formed in the medium, but also in the case of a traveling wave sound field.
The OT function can be implemented by creating a spatial gradient in the potential energy (sound pressure amplitude).

[Example] Figure 1 shows the configuration of an apparatus used to carry out the separation method of the present invention, in which about 50 cm of salt water as the medium 2 is placed in a cylindrical container l made of transparent acrylic resin and having a diameter of 10 cm. A large number of polystyrene particles 3 having a diameter of about 0.5 m were suspended in the medium 2. The density of Nuga 2 was matched to that of polystyrene particles 3 by changing the salt concentration.
An ultrasonic transmitter 4 is attached to the lower surface of the cylindrical container l.

using a device like this. An attempt was made to separate the polystyrene particles 3 in a three-dimensional standing wave sound field by transmitting waves from the ultrasonic transmitter 4 to form a standing wave with the water surface.

The pressure inside the cylinder is not a plane wave but a complex pressure distribution, but the polystyrene particle 3
settles at the position where the sound pressure amplitude is minimum, making it possible to gather polystyrene particles 3 at a high density in a part of the three-dimensional pressure field inside the cylinder. By measuring the pressure distribution using a small sensor, it was confirmed that particles were concentrated in areas with low pressure.

2 to 4 show the ultrasonic transmitters 4 to 30.
It shows the agglomeration state of particles when ultrasonic waves of 35 kHz, 31.19 kHz, and 31.79 kHz are transmitted.

[Effects of the Invention] According to the separation method of the present invention, substances with no difference in specific gravity in a fluid can be simply and easily separated and extracted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus used to carry out the method of the present invention, and FIGS. 2 to 4 are explanatory diagrams showing the state of aggregation of small particles by the above-mentioned apparatus. 1. Cylindrical container, 2. Fist medium, 3ψ medium polystyrene particles, 4. Ultrasonic wave transmitter. Figure 1

Claims (1)

[Claims] 1. Ultrasonic waves are irradiated into a fluid containing small particles with no difference in specific gravity from the medium, and a force is applied to the small particles in the sound field in the direction of the small sound pressure amplitude, causing the small particles to increase the sound pressure. A method for separating substances with no difference in specific gravity in a fluid, which is characterized by aggregating substances in a position where the amplitude is small, and separating and extracting a part containing a high density of small particles due to this aggregation.