Gas separation: processes – Sound waves used
Patent
1996-02-28
1998-10-20
Bushey, C. Scott
Gas separation: processes
Sound waves used
55277, 55318, 95 30, 96175, B01D 5108
Patent
active
058241361
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the purification of a gas by scrubbing and to a device, namely a vertical-axis Venturi column, for carrying out said process.
The present invention in fact constitutes an improvement to the scrubbing processes for the purification of gases contaminated by liquid and/or solid particles (aerosols), wherein a scrubbing liquid is atomized in co-current with the contaminated gas. The vesicles of said scrubbing liquid intercept the contaminating particles carried by said gas. Such processes have been carried out particularly in devices such as Venturi scrubbers or vertical-axis Venturi columns of circular cross-section. Said scrubbing liquid is injected into the gas to be purified, upstream of or at the entrance of the throat of the Venturi(s).
2. Description of Related Art
According to the prior art, processes for the purification of gases contaminated by liquid and/or solid particles, in a vertical-axis Venturi column, have been particularly described and carried out, said processes comprising: atomization of a scrubbing liquid in a rising stream of the gas to be purified, said scrubbing liquid being injected in a direction substantially perpendicular to that of said stream; and scrubbing liquid entrained by said gas stream and laden with contaminants.
Elimination of the vesicles is understood as meaning any of the chemical engineering operations whose purpose is to eliminate from a gas at least some of the particles, in this case vesicles, suspended in said gas.
Such scrubbing processes for the purification of gases in a vertical-axis Venturi column equipped with a Venturi of circular cross-section are described in greater detail later on in the present text with reference to FIG. 1. As indicated above, the present invention constitutes an improvement to such processes.
According to the prior art, acoustic processes have also been proposed for the purification of gases contaminated by solid and/or liquid particles. The shifting of the contaminating particles which is due to the acoustic field causes two phenomena contributing to the purification of the gas: limit the agglomeration volume; and particles in the case of a polydisperse aerosol. The resulting change in the size distribution of the aerosol affords a significant reduction in the component for which the conventional separation processes are the least effective.
There are very few industrial apparatuses which utilize such acoustic agglomeration. It is possible to mention a few applications, mainly on the pilot scale, in the world, and a few laboratory-scale embodiments in France, especially the one described by C. A. Stokes, Sonic agglomeration of carbon black aerosol, Chem. Eng. Progr. 46(8): pages 423-432(1950).
Acoustic agglomerators principally consist of a large coagulation chamber (6 to 9 m in height) in which the treated gases, circulating at low velocity (2 to 5 m/s), are subjected to the action of an acoustic wave emitted by a sonic generator, which is generally a siren in industrial applications and an electric loudspeaker in pilot plants. (The residence time of the gases inside said chamber must be sufficient.)
At the exit of the agglomeration chamber, where the acoustic conditioning takes place which increases the median diameter of the contaminating particles so as to facilitate their subsequent capture, the gases pass through a dust-eliminating or vesicle-eliminating device such as a cyclone, multicyclones, packed column or filter medium.
The phenomena of acoustic precipitation on the walls by means of a field with a high intensity of the order of W/cm.sup.2 make a major contribution to the purification of the gases in this type of apparatus, mainly in the case of vesicle elimination by means of a packed bed, sieve or filter medium.
Inside an acoustic agglomeration chamber, it is possible to spray in countercurrent with the gas to be treated. In such a case, the drops of sprayed liquid entrain the contaminating particles which have previ
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patent: 5197399 (1993-03-01), Mansour
IEEE Transactions On Ultrasonics Engineering, vol. UE-10 No. 2, pp. 91-95, Sep. 1963.
Bushey C. Scott
Societe Generale Pour les Techniques Nouvelles -SGN-
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