US2351351A - Apparatus for dedusting comminuted soap - Google Patents

Description

June 13, 1944. B. L. MAXWELL ETAL 2,351,351

APPARATUS FOR DEDUSTING COMMINUTED SOAP Original Filed Aug. 15) 1940 Til:|.l. I Tigrz.

- I INVENTORS f BERNARD L. MAXWELL CHARLES T ATWOOD ATTORNEY- Patented June 13, 1944 orgies 2,351,351 7 APPARATUS FOR DESQEASPTING COMMINUTED Bernard L. Maxwell, Reading, and Charles 1'. At-

wood, Belmont, Mass,

assignors to Lever Brothers Company, Cambridge, Mass, a corporation of Maine Original application An Divided and this 1941, Serial No. 394,590

gust 15,1940, Serial Nd.

application May 22.

1 Claim. (01. 209-437) This invention relates to classification of finely comminuted materials, and has particular reference to an improved apparatus for separating excessively fine soap particles from comminuted soaps, and the improved soap product.

This is.a division of application Serial No.

352,738, filed August 15, 1940.

In general, the forming of comminuted soaps is accomplished by spray drying the liquid soap stock to obtain particles in characteristic granule form. The dried soap particles are classified within designated limits of particle size by a screening operation, and packaged. Commercial grades of comminuted soap ordinarily range in particle size between those particles passing a 20 mesh screen and retained by an 80 mesh screen, the oversized particles and fines being returned to the manufacturing system for reprocessing. However, with screening methods presently in use, soap fines and dust occur in the packaged product in amounts varying between 5% and 30% of the total pack.

The presence of soap fines and dust in the comminuted product is objectionable for several reasons. The fine particleshave an irritating efiect on the nasal passages. Sucha dust irritating effect may become apparent in several ways. For example, the user of a comminuted soap of undesirably high dust content may sneeze and cough on opening a package of such soap or in pouring it out for use. This-undesirable eifect is also particularly apparent in the comminuted soap manufacturing process. Objectionably large amounts of dust are formed during the,

manufacture of comminuted soap and the problem is difiicult to overcome in view of the pulverulent properties of the soap particles.

cumulation of large amounts of fines in bulk comminuted soaps during manufacture and prior tov screening leads directly to air pollution through excessive dusting, and enhances the inefiiciency of the screening operation as an accurate method of particle classification, due to clogging of the screen mesh.

It has been discovered that a comminuted soap containing in the bulk only those particles retained by a 140 mesh'sc'reen is not objectionable from the point of view of causing the nasal irritation often indicated by excessive coughing or sneezing. Removal and collection of soap dust of such fineness is not satisfactorily accomplished during the screening operation due to the tendency of the bulk soap to retain a portion of the dust, and the tendency of microscopic particles to entrain in air upon agitation, the effect of gravity thereon being negligible. Similarly, apparatus presently available for classification and dedusting of relatively hard materials such as case hardened soap drops and the like, are not adaptable to the refining of bulk comminuted soaps, due to the fragile nature of the soap particle and the tendency to crumble with excessive agitation, reducing the percentage of .packageable dedusted product.

Soap dust extracting methods heretofore emplayed in comminuted soap manufacture have been, in most cases, entirely inadequate, and in many cases the use of dust masks by workmen associated with the screening and packaging rooms is necessary.

Moreover, the wastage of soap between the spray drying and screening operations by excessive sifting or filtration from apparatus and entrainment of fine particles in the air, is considerable. It has been found that the presence of large amounts of fines in bulk comminuted soaps causes undesirable variance in bulk-weight proportions of the packaged granules.

The forming of small amounts of fines in comminuted soaps during screening and packaging is unavoidable, due to agitation of the particles inherent in these operations. However, the acsoap particles into containers.

It is an object of the present invention to provide a novel apparatus for separating excessively fine soap particlesfrom bulk comminuted soap.

Other objects and advantages will appear from the following description and drawing, wherein: 1

Figure 1 is a view in vertical section of the soap particles classifying and dedusting apparatus embodying the invention: I

Figure 2 is a similar view of a modified formof apparatus embodying the present invention; and

Figure 3 is a view in top section along the line 3-3 of Figure 2 and looking in the direction of the arrows. V

Referring to Figure '1 of the drawing, the numeral Iii indicates a tower preferably rectangular in cross-section, having a top wall II and bottom plates l2 converging to a particle discharge outlet l3. A hopper l4 discharges into a tortuous chamber I5 enclosed by a series of ramps l6 positioned to form inclined falls throughout the tower. The chamber l5 at its lower portion connects with the outlet l3, which discharges to a conveyor 24 or other devicesuitable to divert the A suction pump ll adapted to draw a flow of gaseous medium such as air through an air inlet l8 into the chamber l5 at its lower portion exhausts spent gaseous medium through an aperture in the upper wall II by means of a hood I3 and a conduit Dampers 23 in each of the conduits 22 permit of control of the rate of exhaustion of gaseous medium through each. There is also a.control damper 23' in the draw-01f conduit 20.

In operation, the pump I1 is operated to provide an airflow in chamber l5. This airflow has preferably a fixed velocity determined in accordance with the degree of particle separatory action desired. The comminuted soap product is continuously introduced into the chamber I5 through the hopper I4, falling by gravity over the inclined ramps I6 to ultimate discharge through the outlet I3. The slope of the ramps I6 is selected to permit of free gravitational fall of the particles of soap which are subjected to a series of winnowing actions asthey pass over the ends of the ramp sequences and fall by gravity through the upflowing air to the surface of the ramp next below. It is essential that the rate of feed and the slope of the ramps I6 be correlated to obtain a particle flow characterized by minimum agitation, in order to preserve the particle form of the packageable soap and avoid pulverization. The air, traveling counter to the particle fall, entrainsand carries the excessively fine particles of soap dust through the hood I9 and conduit 20 to suitable particle recovery means, not shown, such as a cyclone separator, or a dust bag for example. The degree of particle separation effected will depend upon the velocity of the flow of air in the tortuous chamber I5, which velocity may be varied as desired by proper manipulation of the damper 2|. For

example, if it is desired to separate only those dust particles passing through a 140 meshscreen from the bulk soap, a moderate counterflow velocity may be provided by opening the damper 2|. If it is desired to effect removal of all soap fines and dust passing through, for instance, an 80 mesh screen, the velocity of the counterflow may be duly increased by closing the damper 2| to exert the full efiect of the suction generated by the pump IT on the counterflow in the chamber I5.

In the modification shown in Figure 2 of the drawing, comminuted soap is introduced into the chamber I5 and a suitable gaseous counterflow generated therein, as described. By means of the auxiliary exhaust conduits 22, portions of the counterflow are exhausted from the chamber I5 at zones immediately subsequent to the winnowing operations. In this manner the dust carried by the air is immediately separated and the possibility of its return tothe downflowing mass of soap particles is minimized. Any danger of overloading of counterflow with soap dust "prior to ultimate exhaustion through the hood I9 is avoided. By proper adjustment of the dampers 23 and 23', the rate of withdrawal of portions of the airflow in the chamber I5 may be controlled in accordance with previously determined conditions of dust concentration in the soap bulk, and the airflow velocity desired at designated points along the length of the chamber I5. If I desired, additional air may be bled into the chamber at points intermediate the ends thereof to replace the dust-laden air withdrawn through conduits 22, thus avoiding operating at decreasing linear velocities from the bottom to the top of the chamber. For instance, as the maximum concentration of dust in the comminuted soap bulk will occur upon initial introduction of the soap particles into the chamber I5, it may be desirable to introduce additional air and to operate the top auxiliary conduit 22 with the damper 23 in position to restrict the flow therein and thus maintain a maximum velocity of the counterflow at the first ramp sequence. The number of auxiliary conduits 22 may be varied as desired.

The angle of incline of the ramps I6 may be determined in accordance with the relationship of the ramp slope to the desired rate of travel of the particles thereover. The rate of travel is also dependent upon the size and density of the soap particles and the velocity of the upward flow of air. By reducing the area between the ramps at points along the length of the tower I0, the velocity of the airflow will be proportionately increased at those points. It has been noted, for example, in a test unit having a capacity of 200 ounces per minute of a standard spray dried soap screen through 20 mesh and with 6 ramps or. falls at an angle of 45 degrees that a spacing of eleven inches was desirable between the inclined ramps. The air volume was about 450 cubic feet per minute and the velocity of flow about 500 feet per minute. A screen analysis of the soap originally and after treatment gives the following data:

' Screen analysis After Originally treatment Held on 20-mesl1 Held on BO-mesh Held on (SO-mesh. Held on -mesh Packable soap recovered uct having a percentage content of objection able fines and soap dust considerably under 1.0%

of the total bulk. For a given rate of feed of soap particles, which rate has an optimum value for any given size of the apparatus there will be a critical volume of airflow determined by the setting of the damper 2|, and a critical velocity of airflow, determined by the spacing between the ramps I6 and the setting of damper 2|, at which adjustment a maximum efficiency of dust separation both from the mass of soap particles as they pass from'the surface of the ramps and from the particle screen as the particles pass across; the upflowiugair. This, furthermore, as a result or our invention, may be amplified without undue loss of packable soap granules as a result of the separation.

Desirable results, we have found, may be obtained commercially by utilizing an air volume of about 6000 cubic feet per minute and an air velocity of about 600 feet per minute. When op-v erating under these conditions of air velocity and volume, the width of the unit preferably is about 10 feet and the clined ramps preferably is about twelve inches. Obviously, for commercial p rposes, a greater capacity may be obtained "by utilizing multiple towers. li'or example, a battery of three towers operating under the above conditions of air volume and velocity will have a capacity of about 40,000 lbs. of soap per hour. With this rate of feed, a material containing 3 to 4% of fines through 140 mesh is reduced in fines content to less than 1%. 5

While it is preferred to utilize the apparatus of the invention in a commlnuted soap manufacturing system prior to screening or otherwise classifying the soap particles for packaging, in order to expedite classification, the apparatus maybe used with equallysuccessful fesuts subsequent to screening, or at any other point in the manufacturing process subsequent to spray'drying of the soap particles Byincorporating the apparatus of the present invention into presently used systems for manufacturing comminuted soap, operating inemciencies incurred through air pollution and waste oi, produot through dust filtration are eliminated. fI he apparatus according to the invention provi s a bulk comminuted soap product with an eiiectively standardized bulk-weight proportion, and having a soap dust content of less than 1% prior to packaging.

While the invention has been described herein with reference to specific structure, these references are made by way of illustration. It is intended to include all equivalents within the scope spacing between the inof the invention, which is to be limited only as defined in the appended claim:

We claim:

Apparatus for dedusting soap comprising a chamber, means for introducing soap particles at the top of the chamber, a series 01' vertically spaced inclined ramps arranged in said chamber in position to support the particles in a continuous tortuous flow through the chamber and to form a series of curtains'of falling particles between the successive ramps, an exhaust'conduit connected to said chamber above the uppermost ramp, suction-producing means connected to the exhaust conduit for inducing a flow ofwinnowing air upward through said chamber and through said curtains of falling particles to produce a series of winnowing actions on the curtains of particles and for entraining the dust content of said particles and exhausting the dust-laden air from the chamber, means for admitting winnowing air to said chamber only at a point below the lowermost of said ramps, and means for simultaneously and accurately varying the velocity of flow of air through each of said curtains of falling particles including an adjustable damper movable to admit a controlled amount of supplemental air to said apparatus from the exterior said suction-producing means whereby supplemental air admitted by the damper mingles with the dust-laden air passing to said suction-pro- BERNARD L. CHARLES T. ATWOOD.

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