Air separator

The present invention pertains to an air separator with a stationary housing, which forms a helix when viewed in the axial direction, with a blade ring arranged stationarily in the housing with adjustable blades, and with a bladed separation wheel, which is arranged coaxially within the blade ring and rotatable around the axis of the housing. A raw material inlet opens tangentially into the annular space between the separation wheel and the blade ring, and the separation gas inlet, which is directed in parallel to the crude gas inlet, opens into the annular space between the blade ring and the helical housing. Finally, a raw material outlet is provided in the end zone of the flow in the annular space between the blade ring and the separation wheel. A coarse material outlet is arranged offset in relation to the separation gas outlet in the axial direction of the helical housing, as a result of which the helical housing has the three-dimensional shape of a worm with at least one revolution.

BACKGROUND OF THE INVENTION 
The present invention is based on an air separator with the features of the 
air separators according to WO 93/09883 of the same applicant and also 
according to German Offenlegungsschrift No. DE-OS 24,26,295. The separator 
housing is helical in both cases and in the case of the present invention, 
the separator housing has a tangential separation air inlet, an inlet for 
the material to be separated parallel to the separation air inlet, as well 
as an axial fine material outlet. The fine material outlet is preceded by 
a separation wheel, through which the material to be separated is blown 
radially from the outside to the inside, and from which the separation air 
mixed with fine material is discharged axially, is removed from the 
separator housing through the separated material outlet and is fed to, 
e.g., a filter. After tangential entry into the separator housing, the 
material to be separated rotates around the axis of the separation wheel 
on a helical path, the coarse material enters the area of the helical flow 
located radially on the outside, it is separated from the mixture of 
separation air and fine material, and leaves the separator housing through 
a coarse material outlet. 
In both cases, after tangentially entering the separator housing, the 
separation air first enters the flow channels of a blade ring with 
adjustable blades before mixing with the material to be separated takes 
place. While having the same design, the two blade rings are completely 
different due to the completely different tasks. In the case of the air 
separator according to DE-OS 24,26,295, the blade ring is the actual 
separation means, i.e., the separation of the particle containing gas 
flow, of the "material to be separated" into the fine material component, 
on the one hand, and into the coarse material component, on the other 
hand, takes place in the blade ring. Thus, the separation wheel is only an 
additional component. Based on the consideration that during of 
separation, the fine material can be contaminated with spray particles, 
which are formed after collision with other particles or after rebounding 
from the coarse material outlet, in the blade ring. The purpose of the 
separation wheel is to prevent these spray particles from entering the 
fine material outlet, and the separation wheel is therefore operated at a 
cut point which is above the coarsest cut point that can be set with the 
helical air separator, i.e., above the cut point that can be set with the 
stationary blade ring. 
The conditions are fundamentally different in the air separator according 
to WO 93/09883. The separation takes place in the separation wheel in the 
air separator described there. While the separation into fine material and 
coarse material takes place in the stationary blade ring in the first air 
separator discussed above, the separation into fine material and coarse 
material takes place in the separation wheel, i.e., in the rotating blade 
ring, in the air separator according to WO 93/09883. While a rotating 
blade ring is an additional component, which has a special function in 
terms of catching spray particles, in the first air separator, the 
stationary blade ring is an additional component in the second air 
separator, and this blade ring has a special function, which consists of 
ensuring uniform conditions for the separation air over the entire 
circumference of the separation wheel. The blades of the stationary blade 
ring are therefore designed, arranged and adjustable such that due to the 
adjustment of the blades of the stationary blade ring in the annular space 
between the blade ring and the separation wheel, a helical air separation 
can be achieved. This provides a coarser separation size than would 
correspond to the conditions prevailing at the outer edges of the blades 
of the separation wheel. Consequently, spray particles are caught in one 
case, and the flow conditions at the outlet of the blade channels of the 
separation wheel are changed in the other case. 
Regardless of this fundamental difference, the above-mentioned two air 
separators also differ by a different design of the coarse material 
discharge. In both cases, a separation air component is located radially 
on the outside and receives coarse material, which is peeled off with an 
edge. The coarse material is discharged with a screw arranged downstream 
of the edge in the case of the separator according to DE-OS 24,26,295. In 
contrast, the coarse material is peeled off by a properly arranged baffle 
plate in the case of the separator according to WO 93/09883. The baffle 
plate and especially the screw are additional components, which not only 
cause higher costs and additional weight, but are also subject to wear. In 
recognizing this circumstance, the basic task of the present invention is 
to design an air separator with the features according to the prior art 
discussed above but with neither a baffle plate nor a screw being 
necessary for discharging the coarse material. 
SUMMARY OF THE INVENTION 
The present ivnentin includes an air separator with a stationary housing 
forming a helix when viewed in the axial direction, with a blade ring 
arranged stationarily in the housing with adjustable blades, and with a 
bladed separation wheel, which is arranged coaxially within the blade ring 
and rotates around the axis of the housing, as well as with a 
particle-containing gas inlet opening tangentially into the annular space 
between the separation wheel and the blade ring and with a separation gas 
inlet, which is directed in parallel to the particle containing gas inlet 
and opens into the annular space between the blade ring and the helical 
housing, and, finally, with a coarse material outlet in the end zone of 
the flow in the annular space between the blade ring and the separation 
wheel. The helical housing has, as a result, the three-dimensional shape 
of a worm with at least one complete revolution. 
The separation wheel (7) and the helical blade ring are associated with one 
another such that the blades of the separation wheel cover, as extensively 
as possible the blades of the blade ring in both the inlet area and the 
outlet area of the separator housing. 
A coarse material outlet (8) is arranged offset in the axial direction of 
the helical housing in relation to the separation gas inlet (5) and the 
inlet (3) for the material to be separated. 
The present invention will be explained in greater detail below based on 
the drawings, with reference to an air separator typified by WO 93/09883, 
in which a separation wheel is the actual separation means, and the 
separation wheel is preceded by a blade ring, which ensures that identical 
flow conditions prevail for the separation air over the entire 
circumference of the separation wheel. The blades of the separation wheel 
should consequently be arranged and designed such that helical air 
separation, which ensures a coarser separation size than would correspond 
to the conditions prevailing at the outer edges of the blade wheel which 
acts as a separation wheel, can be achieved by adjusting the blades of the 
blade ring in the annular space between the blade ring and the blade wheel 
acting as a separation wheel. 
Even though such a separator design is a preferred design for the present 
invention, the separator design may also be based on DE-OS 24,26,295, in 
which the actual separation element is a stationary blade ring, and a 
separation wheel is arranged in this separation element only to catch 
spray particles, i.e., the blade wheel separator is operated at a cut 
point that is above the coarsest separation size that can be set with the 
helical air separator.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The separation chamber 9 is surrounded by a stationary blade ring 11. The 
guide blades 12 of the blade ring 11 are individually adjustable around 
their respective longitudinal axis 13. The blade ring 11 forms part of a 
circle that is concentric to the separator axis 6. 
A known, rotary separation wheel 14, which has blades 15, is arranged in 
the separation chamber 9 surrounded by the blade ring 11, likewise 
concentric to the separator axis 6. The annular space between the outer 
circle of the separation wheel 14 and the inner circle of the blade ring 
11 is relatively narrow, because no separation is to take place in it. The 
width of the annular space between the separation wheel and the blade ring 
is selected to be only such as is necessary with respect to the ordered 
passage of the raw material consisting of the material to be separated and 
separation air, the latter from the blade ring, into the separation wheel. 
The inlet 3 for the material to be separated opens tangentially into the 
separation chamber 9 in the area of the annular space between the blade 
ring 11 and the separation wheel 14. The separation air inlet 5 opens 
tangentially into the annular space 17 between the blade ring 11 and the 
housing, which is helical in the representation in FIG. 1. The inlet 3 for 
the material to be separated and the separation air inlet 5 are pipes 
arranged in parallel to one another. The coarse material outlet is a pipe, 
which is located opposite the separation air inlet 5 and the product inlet 
3 in the representation in FIG. 1, i.e., it is directed downward, and the 
two inlets 3, 5, on the one hand, and the coarse material outlet 8, on the 
other hand, are offset in relation to one another by at least one screw 
turn in the direction of the longitudinal axis of the separator or the 
axis of rotation of the separation wheel 14, i.e., the housing is a worm 
housing, which also appears from the representations in FIGS. 2 and 3. It 
can also be recognized from FIG. 2 that the blading of the separation 
wheel extensively covers the blades of the blade ring 11 in both the inlet 
area 3, 5 and the outlet area 8. 
The separation air flows through the flow channels between the guide blades 
12 of the blade ring 11 from the outside to the inside. The guide blades 
12 are located on a helical contour defined by the housing and are mounted 
rotatably in the housing 1 such that both the angle at which the 
separation gas flows in and the gap width between the blades 12 can be 
varied. The material to be separated is charged in on the inside of the 
guide blades 12 of the blade ring 11, and the separation gas flows through 
it intensely. Based on the prevailing flow conditions caused by the blade 
position and the shape of the blades, turbulence develops in the flow 
channels between the blades of the blade ring 11, and this turbulence 
prevents material to be separated from settling on the guide blades, and, 
finally, a three-dimensional helical or spiral flow develops in the 
separation chamber 9. 
The same physical conditions prevail in the separation wheel 14 with the 
blades 15, which is arranged concentrically in the separation chamber 9, 
but the radial and circumferential velocities are influenced here by the 
mass flow and the speed of rotation of the separation wheel 14, rather 
than by the mass flow and the blade position. To ensure that the fineness 
is determined mainly by the separation wheel 14, the cut point is set 
higher in the annular intermediate space than at the separation wheel 14. 
The outer blade ring 11 is used for only a relatively slight 
pre-separation, but especially for intensely dispersing and disintegrating 
of the material being separated. The separation proper takes place at high 
efficiency in the separation wheel. 
The fine material finally leaves the separator via the fine material outlet 
7 of the separation wheel 14; dispersed material, which circulates close 
to the blade ring 11, is thus preferably removed from the separation 
chamber via the coarse material outlet 8. Due to the offset of the 
material inlet 3 and the separation air inlet 5, on the one hand, and the 
coarse and dispersed material outlet 8, on the other hand, in the axial 
direction of the housing, the coarse material and, if present, dispersed 
material reach the area of the coarse material outlet 8 along the inside 
of the housing wall without the need for special additional built-in 
components, such as a baffle plate or a discharge screw. 
The air separator according to the present invention is shown in FIG. 2 
with the view of the separator housing 1 being in the direction indicated 
by the arrow A in FIG. 1. It shows how the product inlet or the inlet for 
the material to be separated, 3, and the separation air inlet 5, lying one 
behind the other in this view, are offset in relation to one another by 
one screw turn in the direction of the separator axis 6 and are associated 
with the separator housing 1 pointing upward (said inlets 3 and 5) and 
downward (said coarse material outlet 8). 
The guide blades 12 of the outer, static blade ring 11 are set such that 
the angle of flow through the guide blades 12 and the cross sections of 
the guide blade channels between the guide blades in the annular 
separation chamber 9 between the blade ring 11 and the blade-type 
separation wheel 14 bring about helical air separation, which ensures a 
coarser separation size than would correspond to the conditions prevailing 
at the outer edge of the blade-type separation wheel. The forces acting on 
the material being separated during the operation of the separator are 
indicated by arrows in FIG. 1. 
Since no separation is to take place in the annular space 17, this annular 
space may have a constant width, even though it may also become narrower 
in the direction of flow.