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Патент USA US3078661

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Feb. 26, 1963
H. J. DELFS
3,078,651
APPARATUS FOR CLASSIFYING AIR-DUST MIXTURE
Filed Dec. 12, 1958
Hans (f ‘Deli-f5
IN VEN TOR.
BY
ATTORNEY
A
llnited States Patent
1
2
3,078,651
provided ‘with a stepped grid so designed as to form a
cone substantially concentric with the guide cone.
Hans Jurgen Delis, Hambnrg-Sasel, Germany, assignor to
Filed Dec. 12, 1958, Ser. No. 779,985
3 Claims. (Cl. 55-422)
This invention relates to a classi?er for classifying a
dust-air mixture preferably from a ?ne grinding pulverizer
with air swept discharge.
It is known to classify the dust-‘air mixture of direct
?ring pulverizers with the air of centrifugal forces. The
Patented Feb. 26, 1963
In a preferred form of the invention, the classi?er is
APPARATUS FUR CLASSIFYHNG Am
DUST MKXTURE
Eabcock 8: Wilcox Limited, London, England, a com
party of Great Britain
3 £78,651
5
The stepped grid can be advantageous formed by sub
stantially concentric superposed rings, the diameter of
which increases upwardly, the diameter of the lower ring
being approximately that of the raw material chute enter
ing the pulverizer. The rings of the stepped grid of the
classi?er may consist of rings formed by strips or bars
of metal.
'Several discharge tubes or outlet ducts for the dust
air mixture leaving the classi?er may be provided so that
a uniform distribution of the mixture to several points
of use is possible.
dust~air mixture to be classi?ed is conducted through a 15
The stepped grid may be suspended with the reversal
ring of tangentially directed guide vanes so that the dust
ring ‘and arranged so as to be adjustable in height. Thus,
air mixture entering the classi?er is set in rotation and
the free cross-section of the annular gap between the
centrifugal forces act on each dust particle. Since the
stepped grid and the inner guide cone wall can be varied.
centrifugal force is proportional to the mass and velocity
Thus, the velocity of the dust-air mixture passing through
of a particle, the larger particles are subjected to a ‘greater 20 the gap can be varied to produce different ?nenesses of
centrifugal force than the smaller particles when the com
the ?nished material leaving the classi?er. The spacings
posite mixture is giving a circular motion. The known
between the rings forming the stepped grid can ‘also be
centrifugal classi?ers are based on this principle where
adjustable, if desired.
the oversized particles which ‘are, for example, not Suit
The classi?er of the present invention has yet further
able for suspension burning, are returned to the grinding 25 advantages, as compared with the known centrifugal clas
process.
si?er. The raw material chute passing through the clas
It has been found in practice that with the increased
si?er into the pulversizer may ‘be vertical or arranged
boiler outputs and the necessary correspondingly large
diagonally through the space ‘between the classi?er cover
pulverizers, classi?cation of the dust-air mixture with the
and the stepped grid. This results in a very considerable
known centrifugal classi?ers can be effected only incom
adaptability of the arrangement of the classi?er of the
pletely or with dif?culty. With such large pulverizers,
the centrifugal classi?ers would have to have a very large
volume and, as a result, could ‘be accommodated within
invention so as to accommodate the various spacing re
quirements with regard to pulverize feeding and discharge.
‘In addition, the classi?er of the present invention has a
the pulverizer housing only with dif?culty or not at all.
lower air flow resistance than a centrifugal classi?er and
This is particularly true in the case of a direct ?ring pul 35 is simpler ‘and cheaper to manufacture.
verizer because the available space within or closely ad
Further details of the invention are found in the follow
jacent the pulverizer is ordinarily insu?icient. The dis
ing description of a preferred example of the invention
charge of the dust-air mixture from the pulverizer, which
as shown diagrammatically on the drawings, where:
is usually e?ected through a single line also leads to dii?
*FIG. 1 is a vertical section of a classi?er constructed
culties particularly with regard to the distribution of the
in accordance with the present invention as arranged on
dust-air mixture to the points of use, as, for example,
‘a pulverizer housing; and
to individual burners.
FIG. 2 is a plan view of the classi?er shown in FIG.
The invention avoids the above drawbacks met with
1 with the cover of the classi?er partly removed.
in practice in that the dust-air mixture is ?rst reversed
The classi?er arranged on mill housing 1 has a conical
in the classi?er and thereafter slowed down so that classi 45 shell 2 and is closed at the top by cover 3. Immersion
?cation is carried out substantially without utilizing cen
tubes 4 are passed through cover 3 for the removal of
trifugal force.
the dust-air mixture from space 5, while the raw material
In the classi?er in accordance with the invention, the
is passed by a chute 6 into the grinding space of a mill,
separation capacity, contrary to known centrifugal clas
which is only shown in outline. In this example of execu
si?ers, is independent of the size of the classi?er.
50 tion the chute ‘6 passes vertically through space 5. It
In a preferred form of the invention, the dust-air mix~
can, however, also be passed diagonally through space 5
ture is subdivided into individual separate streams after
to meet prevailing conditions. In the conical section 2 of
completion of the classifying process so that the distribu
the classi?er a guide cone 7 is provided, the outer wall 8
tion difficulties mentioned above do not occur. In ac—
of which is spaced from the classi?er outer wall 2, thus
cordance with the invention, the classi?er for carrying 55 forming an annular gap 9. Above the guide cone 7 a
out the process is characterized in that the classi?er cone
is provided with a special guide cone having a reversal
reversal ring 10 together with the stepped grid 11 is
suspended in the upper part of the classi?er. The stepped
grid 11 is formed by rings 12 made of flats arranged
concentrically to chute 6, with a diameter increasing from
spaced therefrom that the sum of its free cross-sectional 60 below upwardly. The spacing of the stepped grid 11 from
ring disposed above it to receive the dust-air mixture. A
stepped grid is provided adjacent the guide cone and so
area is greater than the free cross-sectional area of the
the inner wall 13 of guide cone 7 can be varied by adjust
ing means 14, so that an annular gap 15 with varying
cone wall. In moving between these two parts, the dust
cross section can be created which simultaneously results
air stream is abruptly diverted by the reversal ring while
in an alteration in the degree of ?neness of the ?nished
retaining a relatively high velocity and is then divide-d 65 material.
into a plurality of small streams in the stepped grid. As
The air stream laden with milled material coming for
‘a result of the cross-sectional ratios indicated, a con
example from a direct ?ring mill is conveyed through
siderable reduction in velocity occurs so that the grits or
annular gap 9 in the direction arrowed, reversed by re
oversized dust particles are separated out of the mixture
versing ring it} and reaches annular gap 15, and is then
and are returned to the raw material inlet, while air and 70 split up by stepped grid 11 while being reversed into
the ?ne particles are removed from the space above the
many part streams. Since the sum of the free cross sec
stepped grid.
tions in stepped grid 11 is greater than the free cross sec
annular gap between the stepped grid and the inner guide
3,078,651
3
tion of the annular gap 15, this results in a slowing down
of the stream again diverted by the stepped grid so that
separation of the grits results, which are led to the raw
material inlet, while air and‘?nes are conveyed from space
5 via one or several immersion tubes 4 to their point of
use, the distribution of the air stream with ?nished ma
terial being effected in the classi?er after classi?cations
has been completed.
The classi?er in accordance with the invention is not
4
face of said grid being substantially equally spaced
throughout its entire extent from the inner surface of said
element to de?ne a second annular mixture flow passage
way or" substantially uniform width therebetween, for dis
tribution of dust-air mixture flow upwardly through said
grid toward said outlet and to thereby cause separation of
coarse dust from said mixture, and means for adjusting the
width between the inner surface of said element and said
grid to control the size of coarse dust removed from said
restricted in application to direct ?ring mills for fuels, but 10 dust-air mixture.
can with equal advantage be used in all cases, where
classi?cation of a dust~air mixture is involved, for ex
ample, when grinding mineral such as limestone, arti?cial
fertilizers, and the like.
3. Apparatus for classifying a dust-air mixture for re
moval of the coarse dust from the mixture which com
prises an inverted frusto-conical casing having a closed
base with a dust-air outlet therefrom, an element having
The invention is moreover not restricted to the use of 15 inner and outer inverted frusto~conical surfaces coaxially
positioned within said casing, said outer surface cooperat
air as carrier for the dust-air mixture, but can, of course,
also be applied when instead of air some other gas is
used as carrier medium.
What is claimed is:
ing with said casing to de?ne an upwardly and outwardly
extending annular passageway therebetween, means for
passing a dust-air mixture upwardly through said annular
1. Apparatus for classifying a dust-air mixture for re 20 passageway, a reversal ring positioned at the upper end
of said annular passageway to direct the flow of said mix
moval of the coarse dust from the mixture which com
ture inwardly and downwardly along the inner surface
prises an inverted frusto-conical casing having a closed
of said element toward a centrally positioned coarse mate
base with a dust-air outlet therefrom, an element having
rial discharge opening, a stepped grid formed by a plu
inner and outer inverted frusto-conical surfaces coaxially
positioned within said casing, said outer surface cooperat 25 rality of radially spaced ring members the spaces de?ned
by said ring members having a flow area greater than
ing with said casing to de?ne an upwardly and outwardly
the flow area of said annular passageway, the lower sur~
extending annular passageway therebetween, means for
face of said grid being substantially equally spaced
passing a dust-air mixture upwardly through said annular
throughout its entire extent from the inner surface of
passageway, a reversal ring positioned at the upper end of
said annular passageway to direct the flow of all of said 30 said element to define a second annular ?ow passageway
of substantially uniform width therebetween, and means
for adjusting said grid to vary the substantially uniform
of said element toward a centrally positioned coarse ma
width between said inner surface and the grid to control
terial discharge opening, and a stepped grid formed by
‘the size of coarse dust removed from said dust-air
a plurality of radially spaced ring members and forming
an upward ?ow passageway between the ring members 35 mixture.
having a total flow area greater than the ?ow area of said
mixture inwardly and downwardly along the inner surface
annular passageway, the lower surface of said grid being
substantially equally spaced throughout its extent from
the inner surface of said element to de?ne a second annu
lar mixture flow passageway of substantially uniform 40
width therebetween for distributed upward ?ow of air
entrained ?ne dust through said grid.
2. Apparatus for classifying a dust-air mixture for re
moval of the coarse dust from the mixture which com
prises an inverted frusto-conical casing having a closed 45
base with a dust-air outlet therefrom, an element having
inner and outer inverted frusto-conical surfaces coaxially
positioned within said casing, said outer surface cooperat
ing with said casing to de?ne an upwardly and outwardly
extending annular passageway therebetween, means for 50
passing a dust-air mixture upwardly through said annular
passageway, a reversal ring positioned at the upper end
of said annular passageway to direct the flow of all of said
References Cited in the ?le of this patent
UNITED STATES PATENTS
83,506
137,438
154,412
193,242
378,507
759,553
919,249
1,598,261
1,818,905
Justi ________________ __ Oct. 27,
Grassler ______________ __ Apr. 1,
Nesmith _____________ __ Aug. 25,
Grace _______________ .._ July 17,
Henderson et al. ______ __ Feb. 28,
Rood _______________ __ May 10,
Ruddiman ___________ __ Apr. 20,
Swem _______________ __ Aug. 31,
McGee ______________ __ Aug. 11,
2,039,692
Van Tongeren _________ __ May 5, 1936
2,205,336
2,580,317
2,641,335
Beach ______________ __ June 18, 1940
Pekar et al. __________ __ Dec. 25, 1951
Berg _________________ __ June 9, 1953
2,804,171
Yellott et a1 __________ .. Aug. 27, 1957
160,100
Great Britain ________ __ Mar. 17, 1921
365,858
Great Britain ________ __ Jan. 28, 1932
mixture inwardly and downwardly along the inner surface
FOREIGN PATENTS
of said element toward a centrally positioned coarse ma
terial discharge opening, a stepped grid formed by a
plurality of radially spaced ring members, the lower sur
1868
1873
1874
1877
1888
1904
1909
1926
1931
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