US3593372A

US3593372A - Wet-pelletizing apparatus

Info

Publication number: US3593372A
Application number: US887031A
Authority: US
Inventors: Richard E Driscoll
Original assignee: Cities Service Co
Current assignee: Cities Service Co
Priority date: 1969-12-22
Filing date: 1969-12-22
Publication date: 1971-07-20
Anticipated expiration: 1988-07-20

Abstract

Improved wet-pelletizing apparatus having an elongated conduit wherein a bed of wetted powder particles is agitated and tumbled to form pellets. The agitation is accomplished by rotating a coaxially extending shaft which carries a multiplicity of elongated members arranged in longitudinally spaced rows along the shaft and which extend outwardly therefrom toward the wall of the conduit. A stream of liquid-pelletizing medium is injected longitudinally into the conduit from an injector oriented to provide impact with a primary row of the members in which the number of members exceeds that in subsequent rows. Better atomization, and more quick and uniform distribution of the liquid throughout the powder bed, is thereby accomplished.

Description

United States Patent inventor Richard E. Driscoll Monroe, La. Appl. No. 887,031 Filed Dec. 22, 1969 Patented July 20, 1971 Assignee Cities Service Company New York, N.Y.

WET-PELLETIZING APPARATUS Primary Examiner.l. Spencer Overholser Assistant Examiner--R. L. Spicer, Jr. Attorney-J. Richard Geaman ABSTRACT: Improved wet-pelletizing apparatus having an elongated conduit wherein a bed of wetted powder particles is agitated and tumbled to form pellets. The agitation is accomplished by rotating a coaxially extending shaft which carries a multiplicity of elongated members arranged in longitudinally spaced rows along the shaft and which extend outwardly therefrom toward the wall of the conduit. A stream of liquidpelletizing medium is injected longitudinally into the conduit from an injector oriented to provide impact with a primary row of the members in which the number of members exceeds that in subsequent rows. Better atomization, and more quick and uniform distribution of the liquid throughout the powder bed, is thereby accomplished.

PATENIEU JUL 20 m:

llIl I j I I 1 r c I c INVENTOR.

RICHD EDRISCOLL WET-PEELETIZING APPARATUS BACKGROUND OF THE INVENTION Many powdered materials canbe wet pelletized in order to increase the bulk density of the materialwhile alsomaking it easier to handle in bulk form. This may be accomplished in-an elongated conduit into which the powder and a pelletizing liquid are separately introduced and wherein the wetted powder particles are agitated and tumbled to form-wet aggregates. Both the agitation and the tumbling can be achieved by means of elongated members which are affixed to a rotating shaft and extend outwardly therefrom. After formation, the wet aggregates are then dried to'produce dry pellets. In the past, the liquid-pelletizing medium has been injected into the pelletizing conduit in a variety of ways for distribution of the liquid over the powder particles, but it has been recently determined that directing a stream of the liquid longitudinally stream, and some of the liquid is thus conveyed upon the members into the powder bed.

i It will be appreciated, therefore, that rapid uniform wetting of the powder in the manner just described is dependent upon the frequency of impacts between the elongated-members and the stream of pelletizing liquid, and that this frequency is consequently dependent upon the speed at which the shaft is rotated. However, with any particular pelletizer, both the number of agitating members inthe longitudinally spaced rows, and the speed at which the shaft is rotated must be optimized to achieve the desired agitating and tumbling effects without exceeding the structural limitations of the machine. In other words, satisfactory pelletization cannot be obtained if too many agitating members are used in the longitudinally spaced rows, and the machine will-be damaged by vibration if the shaft is rotated at too high a speed. In many cases, each longitudinally spaced row of the members will contain only about two to four members, and the shaft will be rotated at a relatively slow speed, e.g. a few hundred r.p.m. As a result, atomization and distribution of the liquid stream by impact with the rotating members has not always been entirely satisfactory.

SUMMARY OF THEINVENT-ION It is therefore an object of this invention to provide improved distribution of a liquid-pelletizing medium throughout a bed of powder that is agitated and-tumbled to form wet aggregates of the powder. Other objects and advantages .of the invention will become apparent from the following description thereof andthe appended claims.

By means of the present invention, wetted powder particles are agitated and tumbled withinan elongated conduit to form wet aggregates of the particles. For continuous operation, the conduit is provided with an inlet-opening at oneend for'the-introduction of powder at a preestablished rateand an outlet at the other end of the conduit for the discharge of the wet aggregates. A rotatable shaft extends coaxially through the con- 1 duit and a multiplicity of elongated members extend outwardly from the shaft toward. the conduit wall. These members are arranged in longitudinally spaced rows along the shaft. In order to improve atomization of the liquid-pelletizing medium and to assure quick and uniform distribution of the liquid throughout the powder bed, an injector is employed which introduces a metered stream of the liquid into the conduit in a substantially longitudinal directiomln conjunction with the injector, there exists a primary row ofelongated members which extend outwardly from said shafLThisprimary row is located upstream of subsequent longitudinally spaced rows of the members, and the number of members in the primary row is greater than the number of members in subsequent rows. Furthermore, the injector for the liquidstream is oriented toward the members of the primary row for impacting the liquid stream thereon during rotation of the shaft.

' Arranged thus, the liquid stream is disrupted more often during rotation of the shaft, at any given speed, than would occur with an equal number or fewer members in the primary row than are employed in the subsequent rows. Furthermore, since a greater number of members is wetted, the liquid is conveyed into the powder, upon the members, at a faster and more uniform rate. One advantage of the invention is the ability to wet the powder particles quickly and uniformly even when the rotational speed of the shaft is relatively low.

The number of members which can be arranged in the primary row is variable, of course, and will depend among other things upon speed, or range of speeds, at which the shaft is rotated. While in a typical case the lateral spacing between the members in the primary row will be significantly less than between members of the subsequent rows, sufficient lateral spacing to permit maximum contact between the powder particles and the wetted surface of the members is generally desirable.

As an injector for the liquid-pelletizing medium, a liquid supply conduit can extend transversally into the pelletizing conduit and can be provided with at least one orifice for discharging the liquid longitudinally into the pelletizing conduit. To additional advantage, this liquid supply conduit can be at least partially rotatable about its longitudinal axis for controlling the angle at which the liquid stream is directed toward the elongated members of the primary row.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly in section, of one embodiment of the pelletizing apparatus of this invention.

FIG. 2 is a sectional view along the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary vertical side view, in section and somewhat enlarged, of the apparatus of FIG. 1 in the vicinity of line 2-2.

DESCRIPTION OF PREFERRED EMBODIMENT In 'FIG. 1, an elongated cylindrical pelletizing zone I is enclosed by the pelletizing conduit 2. The conduit is provided with an inlet 3 for introduction of powder at a preestablished rate, and a discharge outlet 4 for the removal of wet aggregates. A rotatable shaft 5 extends coaxially through the conduit 2. The shaft is mounted by means of bearings and seals 6 which are affixed to the end'closure plates 7 of the conduit. Elongated members, generally depicted at 8, are affixed to the shaft 5 at their inner ends and extend outwardly from the shaft toward the wall of the conduit 2. The elongated members are arranged in longitudinally spaced rows'8a, 8b, 8c, 8d, etc.; along the shaft 5.

An injector assembly, generally depicted at 9, is employed for longitudinal introduction of a liquid-pelletizing medium into the pelletizing zone. A liquid supply conduit'l0 extends transversally into the pelletizing conduit 2 and is provided with'several orifices 11 whereby streams 12 of the pelletizing liquid are introduced longitudinally into the pelletizer and are directed'toward the plane of rotation of the elongated membersin row 8a,i.e. the primaryrow.

To advantage, the liquid supply conduit 10 can be at least partially rotatable about its longitudinal axis to permit variation'of the angle at which the orifices l 1, and streams 12, are directed toward the elongated members in row 8a. A locking screw 13 extends through a stationary bushing 14, and the screw can be tightened to secure the conduit 10 at a proper insertion depth and at the selected angular relationship of the orifices II with row once the conduit 10 has been positioned. A packing gland, generally represented at 15, provides a seal between the pelletizing zone and the outside atmosphere.

As previously indicated, row 8a of the elongated members is regarded as the primary row since the liquid streams 12 are directed toward it for impact with the members therein and since the number of members is greater than in subsequent rows. Atomization and distribution of the liquid is thus enhanced in the manner previously described. it can be seen in the drawings that row 8a contains eight elongated members, while

rows

8b, 8c, 8d, etc. seq. contain only two members.

It will be appreciated that rows which are considered to be subsequent, or following, with respect to the primary row are those which lie downstream therefrom in relation to the direction in which the powder bed travels through conduit 2 toward outlet 4. In the illustrated case this direction of travel is from left to right, the primary row 8a being located between the liquid injector and subsequent rows. It will be understood, however, that the primary row can instead be located to the other side of the conduit 10, and in which case the orifices 11 would be directed in an upstream relation. With this altemative arrangement, the liquid injector is thus located between the primary row and the subsequent rows.

In the drawings the elongated members 8 are all shown to be substantially identical in shape, length and diameter, but it will be appreciated that this is not essential to the invention. The members of the primary row, particularly, can have dimensions quite different from those in the subsequent rows, the purpose being to further improve atomization and distribution of the pelletizing liquid.

Although the invention has been described with reference to a liquid injector having several discharge orifices for eff cient distribution of the liquid over the members of the primary row, it will be understood that only one orifice need necessarily be employed, e. g. one which projects a sheetlike stream, or one which discharges droplets in a cone-shaped pattern. Furthermore, the invention has also been described with reference to still other specific apparatus arrangements, and it will also be understood that even other embodiments will become apparent which are within the spirit and scope of the invention as defined by the appended claims.

Therefore, what I claim is:

1. In a wet-pelletizing apparatus having:

an elongated pelletizing conduit wherein wetted powder particles are agitated and tumbled to form wet aggregates,

an inlet opening at one end of said conduit for the introduction of powder and an outlet at the other end for the removal of wet aggregates,

a rotatable shaft which extends through said conduit in coaxial relationship therewith,

a multiplicity of elongated members arranged in longitudinally spaced rows along said shaft, said members extending outwardly from said shaft toward the wall of said conduit,

the improvement for enhancing atomization and uniform distribution ofa liquid-pelletizing medium throughout the powder which comprises:

a. an injector for introducing a stream ofliquid-pelletizing medium into said conduit in a substantially longitudinal direction,

b. a primary row ofelongatcd members which extend outwardly from said shaft, the number of members in said primary row being greater than the number of members in subsequent rows, and wherein said injector is oriented toward the members of said primary row for impacting of the liquid stream thereon during rotation of said shaft.

2. The apparatus of claim 1 wherein said injector comprises a liquid supply conduit which extends transversally into said pelletizing conduit, and at least one orifice for discharging the liquid longitudinally into the pelletizing conduit.

3. The apparatus of claim 2 wherein said liquid supply conduit is at least partially rotatable about its longitudinal axis.

4. The apparatus of claim I wherein said primary row of members is located between said liquid injector and said subse uent rows ofmembers.

. The apparatus of claim 1 whereln said in ector IS located between said primary row and said subsequent rows of members.

Claims

1. In a wet-pelletizing apparatus having: an elongated pelletizing conduit wherein wetted powder particles are agitated and tumbled to form wet aggregates, an inlet opening at one end of said conduit for the introduction of powder and an outlet at the other end for the removal oF wet aggregates, a rotatable shaft which extends through said conduit in coaxial relationship therewith, a multiplicity of elongated members arranged in longitudinally spaced rows along said shaft, said members extending outwardly from said shaft toward the wall of said conduit, the improvement for enhancing atomization and uniform distribution of a liquid-pelletizing medium throughout the powder which comprises: a. an injector for introducing a stream of liquid-pelletizing medium into said conduit in a substantially longitudinal direction, b. a primary row of elongated members which extend outwardly from said shaft, the number of members in said primary row being greater than the number of members in subsequent rows, and wherein said injector is oriented toward the members of said primary row for impacting of the liquid stream thereon during rotation of said shaft.

4. The apparatus of claim 1 wherein said primary row of members is located between said liquid injector and said subsequent rows of members.

5. The apparatus of claim 1 wherein said injector is located between said primary row and said subsequent rows of members.