Two-stage micronizer for reducing oversize particles

Details Two-stage micronizer for reducing oversize particles Two-stage micronizer for reducing oversize particles

1999-04-30

2001-09-11

Ostrager, Allen (Department: 3725)

Solid material comminution or disintegration

Apparatus

Series material flow only through plural comminuting zones

C241S261200, C241S261300, C241S275000, C241S296000, C241S297000

Reexamination Certificate

active

06286771

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for reducing the size of coal, minerals (including ores, compounds, and elements), biomass, waste, and other material. More specifically, the invention relates to a two-stage micronizing mill for reducing the size of such materials.
2. Related Art
Efficient size reduction technology through application of dual counter-rotating rotary mill design is undertaken in numerous patents. U.S. Pat. Nos. 5,275,631 and 5,575,824 to Brown et al. disclose combining such meanswith refuse separation means. U.S. Pat. No. 5,597,127 to Brown provides for finer milling. The present invention provides an improved method and apparatus for finer milling, and with particular regard to the problem of efficient reduction of oversize particles, provides for second stage selective milling integral to the mill itself, without classification and recirculation.
Classification and recirculation requires additional mechanical means which adds to capital costs. Operating costs increase also since typically discrimination is not precise and more material than necessary is returned for re-milling, including particles milled to within size specification as well as oversize particles.
The term “second-stage milling” refers to size-reduction by means of a separate type than that employed in the first stage. Here, primary milling is accomplished by attrition and impacting, while second stage reduction is accomplished by crushing, or—in the case of unfriable, fibrous materials—the crushing action results in pinching and rolling which separates fibers.
SUMMARY OF THE INVENTION
An object of this invention is to improve the size reduction technology for coal, minerals (including ores, compounds and elements), biomass, waste and other materials.
A further object of this invention is to provide more efficient and high rate means for pulverizing coal through initial milling means followed immediately by second stage milling means for reducing oversize, in order to supply a fineness grade of 99 percent smaller than 100 mesh and 80 percent smaller than 325 mesh, or similar grade also conducive to combustion with reduced nitrous oxides formation rates.
A still further object of this invention is to provide more efficient and high rate size reduction of various forms of biomass, such as wood chips, pecan shells or hybrid willow potentially useable as boiler fuel.
A further object of this invention is to provide autogenous wear resistance in milling structures.
Efficient high capacity size reduction of coal, minerals, biomass and other materials is accomplished through integrated first stage and second stage reduction means, in which a portion of the reductive work is done by passing centrally fed feed material centrifugally from rotating rings to counter-rotating rings with destructive effects, and the resulting material, significantly reduced in size, subsequently is stripped of oversize by passing through a closely spaced and specially contoured final pair of annular rings or crushing elements between which particles larger than the limited space are crushed.


REFERENCES:
patent: 1624037 (1927-04-01), Butler
patent: 2585881 (1952-02-01), Walker
patent: 3411724 (1968-11-01), Noe
patent: 4355586 (1982-10-01), Brown
patent: 4691867 (1987-09-01), Iwako et al.
patent: 5275631 (1994-01-01), Brown et al.
patent: 5449122 (1995-09-01), Berger et al.
patent: 5575824 (1996-11-01), Brown et al.
patent: 5597127 (1997-01-01), Brown
patent: 5637122 (1997-06-01), Brown
patent: 5704559 (1998-01-01), Froberg et al.

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