The following piece is an excerpt from an article written by Charles R. Harbison and presented at the 10th Annual Bulk Material Handling Seminar in 1977. It has since been edited and condensed for the purpose of this article.
ABSTRACT
Agglomeration is an old technique. Awareness of its value is just beginning to be realized in industries outside the iron ore ranges. Upgrading size of fines created during process phases enables more complete utilization of raw materials and is a method for diminishing environmental problems. This paper outlines many of the techniques available with special emphasis on pelletizing and related techniques using pelletizing equipment. A simple explanation of what takes place in the pelletizing equipment should enable better evaluation for the use of this rather simple process technique.
Size Control Through Agglomeration
Most often, when the subject of size control of bulk solids is discussed, size reduction is what first comes to mind. Particularly in the mining and quarrying industry, size control is primarily a concern of size reduction. Sometimes, this means going very small to obtain mineral liberation.
We are rarely content with the size of the bulk solids we must work with. We crush, grind, pulverize, screen and re-screen until we arrive at a material size considered most economical or desirable for the particular process or product we are dealing with.
In the matter of course, either accidently or purposely, we end up doing more size reduction than is desirable with large quantities of material or product too finely divided for further economic or practical processing, use, handling or even disposal. What was until all too recently considered a disposal problem was in reality unused or wasted resources. Now with increasing frequency these materials are being reclaimed through agglomeration.
Agglomeration is an old idea to many of us, but new and unexplored to many more of us and universally miss-spelled by secretaries everywhere.
Agglomerate: to heap up, join, to gather into a mass: cluster
Agglomeration is further defined by the various techniques implemented. William Engelleitner, a long-time industry expert, presented an excellent paper entitled, “Agglomeration of Dusts – the effect of Agglomeration on Materials Handling and Bulk Transportation of Fine Materials” at the 7th Annual Bulk Materials Handling Seminar. Engelleitner listed and defined the following fourteen agglomeration techniques:
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1. Pelletizing Rolling fines into a pellet or a ball, in the presence of moisture, either in an inclined disc, a drum or a cone-shaped device. Usually refers to minerals agglomeration. |
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2. Balling Same as pelletizing; in a narrower sense means “green- balling” or producing a moist ball as opposed to the complete process of balling and heat treating. {Note: this term is used extensively on the iron range for pelletizing. For the purpose of this paper, pelletizing and balling will be used synonymously.} |
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3. Micropelletizing Producing very small, tiny agglomerates or irregular pellets without a high degree of compaction, such as in dust collector fines agglomeration. {Note: In several industries producing the highest quality pellets in mesh sizes up to 50 mesh is micropelletizing. This may also be accomplished to varying degrees in some of the mixing equipment but is best accomplished in the pin mills or pelletizing equipment.} |
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4. Conditioning A fluffing, tumbling and wetting action with some degree of agglomeration, but no pelletizing. {Note: This can be accomplished in several types of equipment: mixers, blenders, pug mills, pin mills (mixers), mullers or pelletizing equipment.} |
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5. Instantizing An expression used primarily in the food industry to describe the agglomeration of powdered food base materials by mechanical and chemical means. |
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6. Briquetting The process of shaping fine materials into briquettes of pillow, droplet or almond shape, usually in a continuous double-roll press. |
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7. Compaction The process of force compressing fines between two smooth rolls to produce a sheet, which is then typically broken into flakes, or compacts. |
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8. Tabletting The process of producing wafers or spheres in continuous tablet presses by filling a die and stamping out the preforms. Usually limited to pharmaceuticals, powder metals, and ceramics. |
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9. Extrusion Forcing a mass of fines through augers and an orifice to produce a shaped, elongated agglomerate, cylinder, or rod. Used in ceramics, animal feeds, and plastics, but also metal powders and metallic shapes. |
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10. Induration The firing of pellets (greenballs), such as taconite ore concentrate. This is done on a grate, grate-kiln, or in a shaft furnace at temperatures above 2000º F. |
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11. Sintering Heat-fusing of a mass of mixed ore fines into a cinder which becomes hard and slag-like at temperatures of 1,500º F and above. |
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12. Nodulizing Sometimes used to describe rolling of a mass into balls, or nodules, in a rotary kiln, such as for cement, ore concentrates, or refractories. |
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13. Granulating Same as pelletizing, i.e., pellet forming, except that granulation usually refers to smaller pellets, such as fertilizers. (Drum Granulation – Pan Granulation) {Note: This is the fertilizer industries term for pelletizing or micropelletizing, generally 6 x 16 mesh. The equipment is normally drum or pan “granulators” (Pel1etizers).} |
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14. Prilling Forming of spherical agglomerates from hot melt concentrates, such as urea, ammonium nitrate, caustic soda or sulphur. The melt is sprayed from a shot tower against an updraft of cooling air, thus agglomerating into prills in suspension. |
FEECO has been manufacturing agglomeration equipment such as pelletizers, rotary drum agglomerators, pin mixers, and paddle mixers since 1961. We also have the ability to run agglomeration feasibility tests in our laboratory testing and tolling facility. For more information on our agglomeration equipment, or agglomeration feasibility testing, contact us today!
is the author of this post. She has been part of the FEECO Marketing Team for 2 years, and has gained her knowledge from interviewing FEECO engineers, as well as spending time in the FEECO testing & tolling facility. At FEECO -- We Build BIG Stuff! Check out our website and social networks below to see some of the equipment we manufacture...
