Note: Descriptions are shown in the official language in which they were submitted.
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l Background
Granular bed filters have at least an inlet screen and in
some cases a bed support screen. See U.S. Patents 3,410,055 and
3,798,882.
~hen the temperature of the gas being filtered is high,
surh as above 1600F, and/or contains for example 1.4% hydrogen sul-
fide, the metallurgical requirements prohibit the use of metallic
bed support screens or perforated plates. For the same reasons, an
inlet screen cannot be used.
The problem solved by this invention is the provision of a
granular bed filter lacking an inlet screen and lac~ing a support
screen in a manner whereby the granular bed material is not lost
during operation or during backwashing of the granular material which
at least in part is subjected to cleaning by fluidization.
Summary of the Invention
The granular bed filter of the present invention includes
a housing having an inlet and an outlet. Walls of the housing are
arranged so as to define at least one U-shaped passageway between
~ the inlet and outlet. A bed of granular filter material is supported
-~ 20 in said passageway for filtering dirty gas flowing from said inlet
to said outlet.
In the preferred embodiment of the present invention, the
cross sectional area of the passageway at the end thereof communicat-
ing with the outlet is greater than the corresponding area of the
end of the passageway communicating with the inlet. Also, the size
of the granular material in said passageway and exposed to the inlet
is smaller than the size of the granular material in said passageway
and exposed to the outlet.
It is an object of the present invention to provide a
granular bed filter capable of operating at high temperatures without
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1 a support screen or inlet screen while at the same time providing a
granular bed filter which may be backwashed by fluidizing at least
part of the granular material.
Other objects will appear hereinafter.
For the purpose of illustrating the invention, there is
shown in the drawings a form which is presently preferred; it being
understood, however, that this invention is not limited to the pre-
cise arrangements and instrumentalities shown.
Figure 1 is a vertical sectional view through a granular
bed filter in accordance with the present invention.
Figure 2 is a transverse sectional view taken along the
line 2-2 in Figure 1.
Figure 3 is a perspective view partially cut away for il-
lustrating another embodiment of the present invention.
Figure 4 is a sectional view taken along the line 4-4 in
Figure 3.
Referring to the drawing in detail, wherein like numerals
indicate like elements, there is shown in Figure 1 a granular bed
filter in accordance with the present invention designated generally
as 10.
The filter 10 includes a housing 12 having an inlet mani-
fold 14 and an outlet manifold 16. The inlet manifold 14 is separated
from the outlet manifold 16 by a partition wall 18. It will be noted
that the partition 18 divides the interior of the housing 12 in a
manner so that the inlet manifold 14 is substantially smalle} in
cross sectional area than the outlet manifold 16.
The filter 10 includes a plurality of filter chambers
having an inlet end communicating with the inlet manifold 14 and an
outlet end communicating with the outlet manifold 16. The walls of
the housing 10 for defining the filter chambers are preferably pre-
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fabricated so as to have their inlet end secured in a cut-out opening
in the partition wall 18. Tn ~igure 1, the housing 12 includes filter
chambers 20 and 22 which are identical. Hence only Eilter chamber 22
will be described in detail.
The filter chamber 22 is U-shaped in transverse section as
shown in Figure 1 with a curved top wall 24 and a curved bottom wall
26 interconnected by side walls 28 and 30. The distance between the
side walls 28 and 30 is less than the transverse dimensions across
the housing 12 as shown in Figure 2.
An end wall 32 interconnects the upper edge of the walls
24, 26, 28 and 30 at the inlet end thereof. An inlet opening 34 is
provided in the bottom wall 26. The filter chamber 22 communicates
with the outlet manifold 16 by way of an outlet opening 36. While
it is preferred to have the opening 36 at an elevation above the
elevation of opening 34, they may be substantially the same elevation.
The bight portion and the portion of the legs of the filter
chamber 22 is filled with a bed of granular material 38. The granular
material 38 is preferably a coarse material such as Alundum particles
having transverse dimensions of approximately one-quarter inch.
On the inlet end of the granular material 38, there is provided a
thin layer 40 of fine granular material such as that disclosed in my
above-mentioned application and the above-mentioned patents.
The cross sectional area of the filter chamber 22 adjacent
the outlet opening 36 is substantially greater than that of the filter
chamber 22 adjacent the inlet opening 34. In other words, the
top and bottom walls 24, 26 are divergent adjacent the outlet opening
36. m e purpose of the enlarged cross sectional area adjacent the
- outlet opening 36 is to reduce the superficial gas velocity thereby
compensating for any increase in pressure drop due to the
*Trademark
10~`1961
1 length of the filter path through the granular materials 38 and 40.
The layer of granular material 40 is spaced from the elevation of
the inlet opening 34 by a distance 90 that the layer of granular
material 40 may be fluidized in the space thereabove without flowing
out of the opening 34. This feature is explained in greater detail
in my above-mentioned co-pending application. With the layer of
granular material 40 having a thickness of three inches, the upper
surface thereof will be spaced from the lower edge of opening 34 by
a distance of approximately seven inches.
The interface between the coarse granular material 38 and
the layer 40 of fine granular material is preferably horizontally
disposed to assure uniform fluidizing reverse flow gas distribution.
During backwashing, the layer 40 of granular material will be fluid-
ized into the space thereabove without any lifting or fluidizing of
the coarse granular material 38. The large interface between the
materials 38, 40 assures that the reverse flow cleaning gas velocity
will be insufficient to fluidize the coarse granular material 38.
The interface between the materials 38, 40 extends across the full
width and length of the inlet end of the filter chamber 22.
Dirty gas at an elevated temperature with or without high-
ly corrosive components is introduced into the inlet manifold 14.
The dirty gas enters the filter chambers 20, 22 through the inlet
opening, is filtered as it passes downwardly through the layer 40
of fine granular material, is further filtered as it passes through
the granular material 38, and then exits into the outlet manifold
16. When it is desired to clean the filter beds, backwash gas such
as air is introduced into the outlet manifold 16 at a low pressure
such as 80 psi above the operating pressure in manifold 16. The
backwash gas flows through the coarse granular material 38 and
envelopes any accumulated dust in the interstices between the coarse
10~ ~9~;1
1 granular materi~l 38. The backwash gas then passes upwardly through
the interface between materials 38, 40 and fluidizes the granular
material 38 into the space thereabove but below the elevation of
the inlet opening 34. The backwash gas then passes out the inlet
opening 34 into the inlet manifold 14. Accumulated contaminants in
the layer 40 of granular material is removed therefrom as the mater-
ial is fluidized.
In Figures 3 and 4, there is illustrated another embodiment
of the present invention designated generally as 10'. The filter
10' includes a housing defined by the outer pipe 42 and the inner
pipe 44 coupled together by way of a partition wall 46 which divides
the annular space between the pipes into an inlet manifold 48 and an
outlet manifold 50. It will be noted that the pipes 42, 44 are non-
concentric so as to define a U-shaped passageway between the mani-
folds 48 and 50 with the larger cross sectional area of the passage-
way being provided adjacent the outlet manifold 50 for the reasons
discussed above. Dirty gas is supplied to the inlet manifold 48 by
way of the conduit 54r
Clean gas from the outlet manifold 50 flows into the pipe
44 by way of holes 52. The filter 10' may have a plurality of fil-
ter chambers along the length of the pipes 42, 44. The ends of pipe
42 are closed at each end by an end wall whereas the pipe 44 may be
open at both ends or may be closed at one end depending upon the de-
sired distribution of the clean àir therewithin. The U-shaped pass-
ageway is filled with the granular material, coarse and fine as des-
cribed above. The elevation of the fine granular material i8 spaced
below the inlet opening 56 in accordance with the description set
forth above so that the fine granular material is not lost when being
backwashed.
When filters 10 and 10' are used with high temperature
and/or corrosive gases, the walls of the housings may be made from
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1 ceramic or refractory material. Preferably, the walls of the housing
exposed to contact with the dirty corrosive gas are made from metal
coated on its exposed surface with a thin layer of ceramic in accor-
dance with conventional procedures utilized heretofore for making
kitchen sinks, bathtubs, and the like. As will be apparent from the
above description and the illustration in the drawings, the filter
of the present invention is easily fabricated from readily available
materials requiring little machining. For e~ample, the embodiment
in Figures 3 and 4 has the advantage of permitting the use of readily
available tubes with tube 44 being surrounded by tube 42. The U-
shaped passageway, divergent at its outlet end, is attained by posi-
tioning the tubes so as to be non-concentric. The absence of inlet
screens or support screens decreases the cost of the filter while
at the same time eliminating a component which is highly subject
to corrosion.
The present invention may be embodied in other specific
forms without departing from the spirit or essential attributes
thereof and, accordingly, reference should be made to the appended
claims, rather than to the foregoing specification as indicating the
scope of the invention.
