US2535679A - Process of agglomerating aerosols - Google Patents

Description

1950 c. B. HORSLEY ETAL 2,535,679

PROCESS OF AGGLOMERATING AEROSOLS -Fi1ed Sept. 12, 1946 .2510 j rs.

Patented Dec. 26, 1950 PROCESS OF AGGLOMERATING AEROSOLS Caperton B. Horsley, Stamford, Conn., and Gordon C. Seavey, Arlington, Mass, assignors to Ultrasonic Corporation, Cambridge, Mass., a corporation of Massachusetts Application September 12, 1946, Serial No. 696,628

1 Claim.

Our invention relates to the agglomeration of aerosols by sound waves.

In many industries valuable materials are lost because they are carried off in flue gases or other gas streams in the form of very finely divided particles, so fine that they are suspended in the gas. For example, sign ficant quantities of carbon black are carried off and dissipated into the atmosphere together with their flue gases. In the manufacture of several kinds of soap products large quantities are carried off and are not only lost for all practical purposes, but constitute a serious nuisance in the surrounding neighborhood. There are other instances in which aerosols are undesirable. For example, in petroleum refining there is sometimes formed a fog comprising small droplets of sulphuric acid dispersed in a gas.

We have discovered several important facts regarding the effects of sound waves upon aerosols and have invented a process, based on our discoveries, which may be followed to obtain the successful agglomeration of aerosol particles by the application of sound waves.

It can be stated as a major premise that agglomeration of aerosol particles may be brought about by increasing the collision expectancy. Inasmuch as it is not possible directly to affect the particle spacing or the particle size and shape,

the sound waves, if they are to be effective, must be applied in such a way as to increase the velocity of each particle relative to other particles.

An important feature of the invention resides in improving the process of sonic agglomeration by continuously removing agglomerates from the treating chamber and re-circulating them. Consequently there is maintained in the treating chamber a desired range of particle sizes in the aerosol undergoing treatment, since the agglomer tes maintained in the treating chamber provide in eifect more targets for the smaller particles to hit.

In the accompanying drawing there is shown schematically the arrangement of treating chamber, sound generator, and ducts by means of which our novel process may satisfactorily be carried out.

As shown in the figure there is provided a tank or chamber l0 at the top of which is mounted a sound generator or siren 12. A sound wave generator capable of producing the required acoustic intensities on a commercial scale is described in the copending applicat on Ser. No. 722,240, of Caperton B. Horsley and Richard E. Young, filed January 15, 1947 as a continuation-in-part of an earlier application Ser. No. 624,504 filed October 25, 1945, now abandoned. We have used such a generator or a modification thereof in carrying out the process herein disclosed. A conduit I4 is arranged to admit the aerosol to be treated to the interior of the chamber l0 while an outlet duct I6 is provided adjacent the top of the chamber. In order to provide for the re-circulation of some of the agglomerates leaving the chamber, there is provided a by-pass duct or conduit l8 leading from the outlet duct Hi to the inlet duct l4 adjacent its connection to the chamber I0. A small fan 20 is provided in the duct It] in order to bleed off a desired portion of the agglomerates leaving the chamber and introduce them into the untreated aerosol as it enters the treating chamber I 0. As stated above, we have found it advantageous to provide means for maintaining some of the agglomerated particles with the aerosol as it undergoes treatment rather than to permit the agglomerated particles to fall out immediately. This in efiect increases the range of mass to drag ratios. By keeping agglomerated particles in the aerosol we provide. in efiect, more targets for the smaller particles to hit. In such a case the frequency may be varied downward to correspond to the change in range of mass to drag ratios. As shown in the figure, we withdraw agglomerated particles from one portion of the treating apparatus and put them back into the aerosol at another place. The essence of the invention may be summed up broadly as recirculating agglomerated particles at a rate suificient to maintain a desirable range of particle sizes in the aerosol undergoing treatment. The process is carried on continuously; that is to say, the aerosol is continuously introduced into the treating area, some of the agglomerated particles are removed and collected, and others are recirculated to the treating area.

The process may be carried out at a fixed frequency lower than the optimum for the range of mass to drag ratios in the untreated aerosol but at or near the optimum frequency for the range of mass to drag ratios present in the treating area and comprising the original aerosol mixed with agglomerated particles.

Having thus disclosed our invention what We claim as new and desire to secure by Letters Patent of the United States is:

A process of agglomerating an aerosol, comprising passing the aerosol continuously through a chamber, subjecting the chamber and the aerosol to sound waves, withdrawing agglomerated particles from the aerosol as the treatment 3 proceeds and continuously recirculating some of the agglomerated particles through the chamber together with untreated aerosol in order to increase the collision expectancy of the particles of the aerosol.

CAPERTON B. HORSLEY. GORDON C. SEAVEY.

REFERENCES CITED Number The following references are of record in the 910 Number file of this patent:

UNITED STATES PATENTS Name Date Herbsman Dec. 2, 1930 Lewis June 30, 1931 St. Clair Sept. 24, 1940 Houghton et a1. Oct. 8, 1940 Amy Nov. 3, 1942 FOREIGN PATENTS Country 7 Date Great Britain Feb. 4, 1937

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