1. Field of the Invention
The subject invention relates to an apparatus for treating particles, such as treating ammonium sulfate granules with an anticaking agent.
2. Description of Related Art
The prior art is replete with various methods of applying coatings, typically in a liquid form, to solid particles. Many of these prior art systems use a horizontally rotational chamber or drum where a stream of a liquid coating is applied as the particles roll within the drum. Examples of these drum type systems are disclosed in U.S. Pat. Nos. 5,443,637 and 5,501,874. These drum systems require large amounts of space and energy to operate. Also, these systems can be expensive to construct, maintain and install Other prior art systems utilize other rotational parts for applying the coating, which can likewise be expensive and are also prone to failure. For example, U.S. Pat. Nos. 4,596,206 and 2,862,511 utilize rotary applicators for applying a liquid coating. As other examples, U.S. Pat. No. 4,275,682 utilizes rotating conical plates for dispersing the liquid coating and U.S. Pat. No. 4,520,754 discloses a device that applies an electrical charge to the particles, which are then coated by a rotational applicator with the coating containing an opposite charge.
In order to avoid the pitfalls with the above designs, the prior art has developed alternative systems, such as shown in U.S. Pat. No. 5,993,903, which minimize the number of moving parts. The '903 patent discloses a device having a number converging and diverging conical cones with a number of spray applicators disposed along a length thereof. The '903 patent, however, does not optimize a throughput of the number of particles passing through the device with an amount of coating being sprayed. In other words, the '903 patent fails to provide an optimum throughput of particles relative to the amount of coating being sprayed to achieve a desired percentage of particles covered. The '903 patent simply sprays the particles at each intersection of the converging and diverging cones without any efforts to optimize the efficiency of the coating process.
In addition, the prior art does not address the issue of the coating sticking to the components of the system itself. In other words, during operation, the coating can become caked onto various components of the system, thereby reducing the effectiveness of the system.
Accordingly, there remains a need to develop a device with a minimal number of moving parts that efficiently treats a relatively large throughput of particles while avoiding the deficiencies associated with the coating caking onto various components.
An apparatus for treating a plurality of particles with a coating. The apparatus comprises a feed chute having an inlet for receiving the particles and an outlet for discharging the particles A diffuser is disposed adjacent the feed chute with the diffuser having an angled wall and a base for intersecting the particles discharged from the outlet and for creating a curtain of particles about the diffuser. An applicator is mounted adjacent the base of the diffuser for spraying the coating downwardly away from the diffuser into a predefined pattern. An exit chute is disposed about the diffuser for capturing the curtain of particles with the exit chute including a deflector for intersecting the curtain of particles and redirecting the particles into the predefined pattern of the coating,. A heating element is mounted to the deflector for maintaining a predetermined temperature of the deflector thereby preventing accumulation of the coating on the deflector.
Accordingly, the subject invention provides an apparatus for efficiently treating a large amount of particles with a minimal amount of coating and for ensuring that the coating does not become caked on certain components of the apparatus.
Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, an apparatus in accordance with the subject invention is generally shown at 20 in
A screen 34 is mounted within the feed chute 22 for sifting the plurality of particles before the particles intersect the diffuser 26. The screen 34 has a plurality of openings of a predetermined size wherein any particles larger than this predetermined size cannot pass through the screen 34. It should be appreciated that the openings may be of any suitable size or configuration. In one contemplated embodiment, the size of each of the openings is one square inch. Preferably, the size of the openings is based on the size of a gap between the feed chute 22 and the diffuser 26. The screen 34 is therefore provided to prevent clogging of the particles between the feed chute 22 and the diffuser 26. As shown in
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The particular method steps of treating the plurality of particles with the coating utilizing the apparatus 20 of the preferred embodiment will now be discussed in detail with reference to
The plurality of particles pass through the feed chute 22 and about the diffuser 26 at a high throughput rate such that the subject invention can efficiently treat a large volume of particles in a relatively short period of time. It should be appreciated that the speed of the material passing through the apparatus 20 can vary depending upon the type of particle and particle size. One non-limiting example includes the throughput of the particles passing through the feed chute 22 and about the diffuser 26 at a rate of 200 to 40,000 lbs per hour As another non-limiting example, the throughput of the particles can pass through the feed chute 22 and about the diffuser 26 at a rate of 10,000 to 25,000 lbs per hour. The throughput of the particles can be determined by any suitable device or calculation.
The coating is sprayed from the applicator 44 downwardly away from the diffuser 26 toward the deflector 66 of the exit chute 24 in a predetermined pattern. In the embodiment illustrated, the coating is sprayed downwardly in a cone shaped pattern defining an outer periphery of the sprayed coating. It should be appreciated that the coating could be sprayed in alternative patterns so long as the coating is sprayed downwardly toward the deflector 66. The coating may be sprayed downwardly in a hollow cone shaped pattern for spraying a substantial portion of the coating directly toward the deflector 66 Alternatively, the coating may be sprayed downwardly in a solid cone shaped pattern for spraying a portion of the coating directly toward the deflector 66 and spraying another portion of the coating below the deflector 66 into the discharge portion 70 of the exit chute 24. In either case, the outer periphery of the coating will intersect a portion of the deflector 66. As illustrated, the outer periphery of the coating intersects the deflector 66 approximate the width of the base 42 of the diffuser 26. Preferably, the coating is further defined as an anticaking agent. Even more preferably, the coating is petroleum wax that is heated before being sprayed The heated deflector 66 ensures that the heated wax coating does not cake or otherwise accumulate on the deflector 66, which would reduce the effectiveness of the deflector 66. In addition, maintaining the heated wax coating on the deflector 66 allows the coating on the deflector 66 to be applied to particles intersecting the deflector 66 (discussed below) below the outer periphery of the coating, thereby improving the overall process.
The curtain of particles falling from the base 42 of the diffuser 26 are captured by the exit chute 24 and intersect with the deflector 66 to redirect the particles into the predetermined pattern of the coating for treating each of the particles with the coating. Preferably, the particles intersect with the deflector 66 to redirect the particles into the pattern before any of the particles are treated with the coating. In other words, the particles remain untreated as the curtain of particles fall about the diffuser 26 and are redirected by the deflector 66,. Hence, the particles are preferably only treated after the particles change direction into the outer periphery of the sprayed coating. This feature of the invention is perhaps best illustrated in
Due to the spray pattern and the redirection of the particles, the coating can be sprayed in a relatively low throughput rate in comparison to the high throughput rate of particles passing through the apparatus 20. Again, it should be appreciated that the coating may be sprayed at any suitable rate without deviating from the overall scope of the subject invention In one non-limiting example, the coating can be sprayed at a rate of 15 to 80 lbs per hour, preferably twenty-five lbs per hour. Preferably, at least twenty five percent of the particles intersecting the deflector are treated during the process. Even more preferably, approximately thirty-five to fifty percent of the particles intersecting the deflector are treated. As non-limiting examples, it has been found that less than fifty percent of ammonium sulfate particles need to be covered to prevent anti-caking of these particles. As another non-limiting example, it has been found that nearly one-hundred percent of ammonium nitrate particles need to be covered to prevent anti-caking of these particles. It should be appreciated, that the percent of coverage for the particles is dependent upon the type of particle, size of the particle, atmospheric conditions, as well as a number of other factors Hence, the percent of coverage can vary greatly without deviating from the overall scope of the subject invention. The subject invention therefore defines an efficient method treating a large amount of particles with a minimal amount of coating while ensuring that the coating does not cake or accumulate on the deflector 66.
The treated particles are then discharged out of the exit chute 24 and accumulate along the exit conveyor 32. As discussed above, particles that exceed a predetermined size will be re-routed down a bypass chute 36 to a bypass conveyor 38.
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The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.