Method and apparatus for separating particles

Apparatus for separating dispersed particles by means of applying sound to the dispersion through ultrasonic standing waves in a composite resonator, which composite resonator consists in sequence in its longitudinal direction of a first waveguide area, a first separation area, a middle waveguide area, a second separation area, and a third waveguide area, and which composite resonator comprises:

• a vessel containing the dispersion,
• a transducer which consists of at least one electrically driven, mechanically oscillating element, said electrical driving occurring at a frequency in the neighborhood of the characteristic frequency f.sub.o and which transducer is acoustically coupled with said vessel,
• an acoustic mirror system consisting of one or several acoustic mirrors, said mirrors reflecting sound so that standing sound waves may come about which generate sound radiation forces which act on the dispersed particles in the longitudinal direction of the standing waves, said forces driving the particles into the areas of antinodes or areas of nodes of the standing field of sound and holding them there,
• an electronic circuit, by which the drive frequency of said transducer is increased, by starting out form a minimum resonant frequency f.sub.min, of said composite resonator in a stepwise a manner from one resonant frequency f.sub.n, of said composite resonator via the respective next resonant frequency f.sub.n+1 of said composite resonator until, finally, the maximum resonant frequency f.sub.max of said composite resonator has been reached, and by which within a delay time t.sub.T, which is very small compared to the action period .DELTA.t.sub.n =t.sub.n+1 -t.sub.n of the respective frequency f.sub.n, it is reverted back to initial frequency f.sub.min, and by which furthermore said process is repeated in a cyclic manner and the position and the length of the composite resonator such-like that for any step in frequency of f.sub.n .fwdarw.f.sub.n+1, the greatest displacement of a sound antinode area to occur within a separation area is always less than a quarter of the respective initial wavelength, and that the greatest possible displacement of a sound antinode area to occur within a separation area, said displacement belonging to the total frequency deviation f.sub.max -f.sub.min, is greater than one quarter of the mean wavelength.

Apparatus for separating dispersed particles by means of applying sound to the dispersion through ultrasonic standing waves in a composite resonator, which composite resonator consists in sequence in its longitudinal direction of a first waveguide area, a first separation area, a middle waveguide area, a second separation area, and a third waveguide area, and which resonator comprises:

• a vessel containing the dispersion,
• a transducer which consists of at least one electrically driven, mechanically oscillating element, said electrical driving occurring at a frequency in the neighborhood of the characteristic frequency f.sub.o and which transducer is acoustically coupled with said vessel,
• an acoustic mirror system consisting of one or several acoustic mirrors, said mirrors reflecting sound so that standing sound waves may come about which generate sound radiation forces which act on the dispersed particles in the longitudinal direction of the standing waves, said forces driving the particles into the areas of antinodes or areas of nodes of the standing field of sound and holding them there,
• an electronic circuit, by which the drive frequency of said transducer is decreased, by starting out from a maximum resonant frequency f.sub.max of said composite resonator, in a stepwise manner from one resonant frequency f.sub.n of said composite resonator via the respective next resonant frequency f.sub.n+1 of said composite resonator until, finally, the minimum resonant frequency f.sub.min of said composite resonator has been reached, and by which within a delay time t.sub.T, which is very small compared to the action period .DELTA.t.sub.n =t.sub.n+1 -t.sub.1 of the respective frequency f.sub.n, it is reverted back to initial frequency f.sub.max, and by which furthermore said process is repeated in a cyclic manner and the position and the length of each separation area is chosen within the total length of the composite resonator such-like that for any step in frequency of f.sub.n .fwdarw.f.sub.n+1, the greatest displacement of a second antinode area to occur within a separation area is always less than a quarter of the respective initial wavelength, and that the greatest possible displacement of a sound antinode area to occur within a separation area, said displacement belonging to the total frequency deviation f.sub.max -f.sub.min, is greater than one quarter of the mean wavelength.

Apparatus for separating dispersed particles by means of applying sound to the dispersion through ultrasonic standing waves in a composite resonator, which is arranged as ring resonator which comprises:

• a vessel containing the dispersion,
• at least one transducer which consists of at least one electrically driven, mechanically oscillating element generating a first circulating resonant wave of frequency f.sub.1 and second circulating resonant wave of frequency f.sub.2 moving in an opposite direction, whereby both of said frequencies f.sub.1, f.sub.2 differ very slightly from each other, said electrical driving occurring at a frequency in the neighborhood of the characteristic frequency f.sub.0 and which transducer is acoustically coupled with said vessel, said transducer consisting of at least two piezoelectric discs with thicknesses of n times the half of the wavelength of the sound waves emitted by said transducer, n being a natural number of the group 1, 2, 3, . . . , and said discs are located at a distance from each, said distance being filed with the dispersion medium and being equal to a quarter or an uneven multiple of a quarter of the wavelength in the filling material, and said two piezoelectric discs comprise electrodes on both sides which are excited by alternating voltages and comprise periodic amplitude modulations having a temporal phase shift with regard to each other, said phase shift being equal to K.sub.2. II/2, k.sub.2 being an uneven number of the group 1, 3 5 . . , and
• an acoustic mirror system consisting of one or several acoustic mirrors which are arranged in such a manner that the deflection of the resonant ring wave takes place by means of total reflection, said mirrors further reflecting sound so that standing sound waves may come about which generate sound radiation forces, which act on the dispersed particles in the longitudinal direction of the standing waves, said forces driving the particles into the areas of antinodes or areas of nodes of the standing field of sound and holding them there.

Method for separating particles being dispersed in a dispersion medium, comprising the following steps:

• applying sound to the dispersion through ultrasonic standing waves in a composite resonator which consists in its longitudinal direction of at least one separation area and at least one waveguide area, wherein the frequencies of said sound lie in the neighborhood of the characteristic frequency f.sub.o,
• increasing the drive frequency of said composite resonator by starting out from a minimum resonant frequency f.sub.min, in a stepwise manner from the one resonant frequency f.sub.n via the respective next resonant frequency f.sub.n+1 until, finally, the maximum resonant frequency f.sub.max has been reached, wherein the position and the length of each separation area is chosen within the total length of the composite resonator such-like that for any step in frequency of f.sub.n .fwdarw.f.sub.n+1, the greatest displacement of a sound antinode area to occur within a separation area is always less than a quarter of the respective initial wavelength, and that the greatest possible displacement of a sound antinode area to occur within a separation area, said displacement belonging to the total frequency deviation f.sub.max -f.sub.min, is greater than one quarter of the mean wavelength,
• reverting back to initial frequency f.sub.min within a delay time t.sub.T, which is very small compared to the action period .DELTA.t.sub.n =t.sub.n+1 -t.sub.n of the respective frequency f.sub.n,
• repeating this process in a cyclic manner.

Method for separating particles being dispersed in a dispersion medium, comprising the following steps:

• applying sound to the dispersion through ultrasonic standing waves in a composite resonator which consists in its longitudinal direction of at least one separation area and at least one waveguide area, wherein the frequencies of said sound lie in the neighborhood of the characteristic frequency f.sub.o,
• decreasing the drive frequency of said composite resonator by starting out from a maximum resonant frequency f.sub.max, in a stepwise manner from the one resonant frequency f.sub.n via the respective next resonant frequency f.sub.n+1 until, finally, the minimum resonant frequency f.sub.min has been reached, wherein the position and the length of each separation area is chosen within the total length of the composite resonator such-like that for any step in frequency of f.sub.n .fwdarw.f.sub.n+1, the greatest displacement of a sound antinode area to occur within a separation area is always less than a quarter of the respective initial wavelength, and that the greatest possible displacement of a sound antinode area to occur within a separation area, said displacement belonging to the total frequency deviation f.sub.max -f.sub.min, is greater than one quarter of the mean wavelength,
• reverting back to initial frequency f.sub.max within a delay time t.sub.T, which is very small compared to the action period .DELTA.t.sub.n =t.sub.n+1 -t.sub.n of the respective frequency f.sub.n,
• repeating this process in a cyclic manner.