Agglomerating and drying apparatus

Details Agglomerating and drying apparatus Agglomerating and drying apparatus

2000-02-23

2001-08-07

Theisen, Mary Lynn (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Forming articles by uniting randomly associated particles

Agitating to form larger particles

C264S118000, C425S222000, C034S363000, C034S368000, C034S369000

Reexamination Certificate

active

06270708

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to agglomerating apparatus, drying apparatus, and systems including both agglomerating and drying apparatus. The invention also relates to methods for agglomerating and drying particulate materials.
BACKGROUND OF THE INVENTION
Granules are widely used in food, pharmaceutical, agricultural, paint and chemical industries. Practically every tablet we take is granulated before it is made into a tablet. Household cleaning substances, fertilizers, animal feed, sugar, salt and just about every dry item that contains multiple ingredients is used in granule form.
There are dozens of reasons why granules are used and needed. The following are four of the main ones:
1. In multi-ingredient tablet manufacturing it is important that each tablet contains the same ratio of ingredients as the overall batch, otherwise the effectiveness of every tablet will be different. The only way to avoid this problem is to convert complex powder and liquid formulas into uniform granules that contain the correct ratio of ingredients, then press the tablets from these granules. There are two criteria in manufacturing a high quality tablet. One is compressibility, which is the ability to compress the granule to bind and form a tablet. The second criterion is content uniformity which is the ability to have the same ratio of ingredients distributed throughout the entire tablet.
2. Granules flow very easily due to their uniform size and moisture level. Fine powders clog, pack or clump, and do not flow well. Process machines do not work well with powders. A solution to this problem is to convert complex powder and liquid formulas to granules.
3. Fine powders do not mix into liquids easily. Experience shows that fine particles are more difficult to mix, they clump up and float in or on top of the liquid. One solution to this problem is to convert powders into granules.
4. When multiple component mixtures are transported, due to density differences in each ingredient, heavier ones will migrate toward the bottom and lighter ones will come to the surface. To prevent this from happening, mixtures are first converted to granules.
Granules can be formed in two ways; they can be ground from a larger solid mass and then sifted to obtain the proper granule size (size reduction). This process is called Granulation. The second method is to mix the various powdered ingredients with a liquid and a binder to form larger particles (size increase). This process is called Agglomeration.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides apparatus for drying particulate material, preferably granules, which includes an enclosed path through which the particulate material is conveyed in a fluidized stream. The cross-sectional area of the path, which preferably has a spiral form, increases in the direction in which the fluidized stream flows.
Preferably, the drying apparatus includes a drying chamber having an inlet for the fluidized stream of particulate material, and an outlet for the particulate material having passed through the drying chamber. A spiral path for the fluidized stream may be defined by one or more baffles fixed within an annular drying chamber. For example, a continuous spiral baffle may be provided to form a path from the drying chamber inlet towards the outlet, the pitch of the spiral increasing with distance from the inlet to give the desired increase in cross-sectional area of the path.
It has been demonstrated that a dryer of this construction can be particularly efficient, while requiring significantly less heating energy than a comparable prior art dryer of the spray or fluidized bed types. A dryer of this construction can also readily be used in a continuous process for manufacturing granules.
In another aspect, the invention provides an agglomerator apparatus including a rotary blade assembly with a plurality of blades that are configured such that, during operation of the agglomerator, material acted on by the blades is urged to follow a generally sinusoidal path relative to a plane in which the blades are rotating. This sinusoidal motion increases the volume of material impacted by the blades and hence can be beneficial to the efficiency of the agglomerating process.
To meter the size of particles generated by the agglomerator apparatus, a mesh screen or other barrier is arranged circumferentially around the rotary blade assembly, the screen or other barrier being configured to prevent the material being agglomerated escaping from the rotary blade assembly before it has been reduced to particles of a desired size or smaller. Once the particles are sufficiently small, they will tend pass through the screen or barrier as a result of centrifugal forces acting upon them, and the particles can be collected on the radially outer side of the screen or barrier to be passed to a dryer if required. Such an arrangement has been shown to give a relatively narrow distribution of granule size, with substantially no fines (3% or less).
In a preferred form, the blades of the rotary blade assembly are arranged in a circumferential array around a central hub about which they rotate in a rotary plane. The cutting edge of each blade is defined on an outer end portion of the blade and faces the direction of rotation. The radially outer end portions of adjacent blades in the circumferential direction are angled or twisted out of the rotary plane in opposite directions about respective radial axes, in alternating fashion, so that the cutting edges of adjacent blades are respectively above and below the rotary plane.
In a further aspect, the present invention provides apparatus for agglomerating and drying particulate material which comprises an agglomerator for forming and discharging wet granules of a predetermined size or smaller, and a dryer having an inlet for wet granules from the agglomerator, an outlet for granules having passed through the dryer, and one or more baffles within the dryer defining a spiral path through which the granules pass from the dryer inlet towards the dryer outlet. The agglomerator and/or the dryer may include one or more of the features discussed above.
In yet another aspect, the present invention provides a method of drying particulate material in which the material is conveyed in a fluidized stream through an enclosed path, preferably a spiral path, which increases in cross-sectional area in the direction in which the fluidized stream flows.
The invention also provides, in a still further aspect, a method of agglomerating a particulate material which includes urging the material to follow a sinusoidal path within a rotary blade assembly during agglomeration.
Also provided by the invention is a method of preparing granules, in which a mixture is formed of particulate material and a liquid. The mixture is fed into an agglomerator and agglomerated to form granules of a predetermined size or smaller, and the granules are dried by passing them through an expanding, preferably spiral, path.
The present invention also provides a method and system for agglomerating powdered materials and liquid, that is particularly well suited for forming agglomerated material using only a very small amount of water or other liquid, and for agglomerating organic powdered materials. The powdered material is initially chilled, and the liquid (e.g., water) is evaporated to form a vapor. The warm vapor is then introduced to the chilled powder while the powder is agitated, causing the vapor to uniformly condense on the chilled powdered material for even distribution.


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Johnson and Peterson, “Agglomrization (Instantizing),”Encycl. of Food Technology, AVI Westp

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