Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
Liquid atomizing nozzle
BACKGROUND OF THE INVENTION
1. Filed of the invention:
The present invention relates to a liquid atomizing nozzle
used in the field of spray drying, humid pelletizing, coating,
combustion and the like, and the nozzle is especially suited for
atomizing liquid materials having high viscosity or containing
bulky solid materials.
2. Description of the prior art:
Liquid atomizing nozzles having compressed air power
sources are widely used in such fields of spray drying, coating
works of liquid materials. The nozzle is basically composed of
a liquid supplying pipe and a compressed air supplying pipe
coaxially arranged outside of the liquid supplying pipe. By
means of compressed air from the head of air supplying pipe
blasting at a high speed in the axial direction, the liquid
pushed or sucked outward from the head of liquid supplying pipe
is sheared and atomized.
The amount of liquid processed by this kind of coaxial
double-pipe liquid atomizing nozzles is usually from several
liter/hr to dozens liter/hr, because atomizing features of the
nozzles worsens when the nozzle is enlarged analogously in
proportion to increased amount of liquid to be processed
(increased ratio of compressed air and flattened distribution of
atomized liquid particles).
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Since an enlarged diameter of liquid supplying pipe worsens
the atomizing features, diameters of liquid supplying pipe are
set at around 0.5-3.0mm. Accordingly, liquid atomizing nozzles
of this type are not suitable for atomizing liquids of so highly
viscous as scores of thousands cP (centipoise) or those
containing bulky solid materials. Further, atomizing nozzles of
this type are too narrow in spray angles to be employed as
atomizing equipments of spray dryers that they can not
substitute for pressurized spray nozzles having spray angles of
larger than 70 degree. For relatively low viscous (below 500
cP) liquids capable of being atomized with pressurized spray
nozzles, conventional double-pipe fluid atomizing nozzles
require 2-5 times more atomizing energy (kw) than that required
by pressurized spray nozzles. This is the reason why large
capacity double-pipe fluid atomizing nozzles are not so popular.
SUMMARY OF THE INVENTION
The present invention is directed to provide a liquid
atomizing nozzle capable of atomizing liquid materials of highly
viscous or containing bulky solid materials charged not only at
a small feed rate but also at several thousands liter/hr rate,
by which the liquid is atomized and sprayed uniformly with a
predetermined spray angles.
The liquid atomizing nozzle according to the present
invention comprises a liquid supplying pipe; a cylindrical
chamber for whirling of air being connected at one end with the
liquid supplying pipe, having an inside diameter larger than
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inside diameter of the liquid supplying pipe, and being provided
with one or more through holes for passing through pressurized
air in the direction tangential to circular internal surface of
the cylindrical chamber; an orifice disposed at the top of the
cylindrical chamber and having a circular opening of smaller
than inside diameter of the cylindrical chamber; and an external
cylinder covering over the cylindrical chamber and at least a
part of the liquid supplying pipe and being provided with a
pressurized air supplying pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig.1 is a longitudinal section of the liquid atomizing
nozzle according to the present invention; Fig.2 is a
longitudinal section of the liquid supplying pipe; Fig.3 is a
longitudinal section of the cylindrical chamber; Fig.4 is a
sectional view seen along A-A of the cylindrical chamber of
Fig.3; Fig.5 is a longitudinal section of the orifice; Fig.6 is
a view of the orifice of Fig.5 seen from the direction C; Fig.7
is a longitudinal section of the external cylinder; Fig.8 is a
longitudinal section of a seal cap; Fig.9 is a longitudinal
section of the liquid atomizing nozzle equipped with a reverse
conical body and a disc-type liquid distributor; Fig.10 is a
side view of the reverse conical body; Fig.11 is sectional view
of the orifice used in combination with the reverse conical
body; Fig.12 is a top view of the disc-type liquid distributor;
Fig.13 is sectional view along D-D of the disc-type liquid
distributor of Fig.12; Fig.14 is a top view of a disc-type
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liquid revolving plate; Fig.15 is a side view of the disc-type
liquid revolving plate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The liquid atomizing nozzle according to the present
invention will be explained by reference to the attached
drawings.
Reference number 1 indicates the liquid supplying pipe, and
the pipe is connected with the cylindrical chamber for whirling
of air 2 at one end exemplified by the left end in Fig.l. The
cylindrical chamber 2 has a cylindrical shape having inside
diameter larger than inside diameter of the liquid supplying
pipe l, and is provided at the cylindrical portion with one or
more through holes 3 for passing through pressurized air in the
direction tangential to circular internal surface of the
cylindrical chamber. As shown by Fig.4 by the cross-sectional
view, a plurality of the through holes 3 for passing through
pressurized air may be disposed along the same circumference
(c.f. Fig.4) or in rows in axial direction of the cylindrical
chamber (e.g. at A-A and B-B in Fig.3). A plurality of through
holes may be arranged along the same circumfere~ce and a
plurality of circumferential arrangements may be disposed in
rows in the axial direction. The orifice 4 having the circular
opening 5 of smaller than inside diameter of the cylindrical
chamber is disposed at the head of the cylindrical chamber 2.
Further, the external cylinder 6 is so disposed as to cover the
cylindrical chamber 2 and at least a part of the liquid
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supplying pipe 1, and the pressurized air supplying pipe 7 is
connected therewith. Reference number 9 is a seal for sealing
the other end of the external cylinder 6, and reference number 8
is a seal cap.
S The liquid atomizing nozzle according to the invention can
be assembled easily by steps of inserting the liquid supplying
pipe 1 into a connection opening disposed at the bottom of the
cylindrical chamber 2; inserting into the external cylinder 6
the cylindrical chamber attached with the liquid supplying pipe;
fastening the orifice 4 to front end of the external cylinder 6
to fasten the front end of the cylindrical chamber 2; engaging
the seal cap 8 having a through hole for the liquid supplying
pipe 1 at the back end of the external cylinder 6; and turning
thus assembled nozzle to air-tight or water-tight by means of
applying appropriately sealing materials. Disassembling or
exchanging such parts as the cylindrical chamber 2 and/or
orifice 4 can be done easily.
Working mechanism of the liquid spray nozzle of the present
invention will be explained hereunder. Liquid material supplied
into the cylindrical chamber 2 through the liquid supplying pipe
1 is revolved and accelerated in the cylindrical chamber by
virtue of the pressurized air coming in at a high speed from the
through holes 3 in the direction tangential to circular internal
surface of the cylindrical chamber. The accelerated revolving
liquid material moves by means of centrifugal force toward
internal surface of the cylindrical chamber, turns to thin film,
moves toward the circular opening 5, and is sprayed therefrom
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with accompaniment of whirling air stream. In this case, fine
liquid particles are accompanied by air stream ejected into the
cylindrical chamber. Other liquid flows in a thin film state
along the internal surface of cylindrical chamber, atomized at
S the opening 5 of orifice and sprayed.
In conventional liquid spray nozzles utilizing compressed
air, the nozzle has structural features that the pressurized air
and the liquid are maintained separately until reaching at the
head of double-pipe fluid atomizing nozzle, and suction,
shearing and atomizing occur instantly upon contacting at the
front end of the double-pipe. In this case, the pressurized air
discharged in high speed from outside pipe induces highly
negative pressure around the front end portion to cause the
liquid being sucked from the inner pipe and sheared. However,
due to simultaneous sucking of air from outside of the system, a
large portion of kinetic energy of the compressed air is wasted
for accelerating the external air.
On the other hand in the atomizing nozzle of the present
invention, the nozzle has the structural features that the
liquid material is revolved and accelerated in the cylindrical
chamber by the ejected pressurized air to be atomized partly,
and the remaining portion is forwarded to the orifice under film
state of accelerated revolution. For example, when a compressed
air of 3 kg/cm2 pressure is employed, around 2 kg/cm2 pressure
is consumed in the cylindrical chamber and the remaining
pressure becomes the kinetic energy for spraying from the
orifice, though the ratio varies in accordance with ratios of
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the area of circular opening 5 of orifice to the total cross-
sectional area of through holes 3 for compressed air. As the
result, the portion of energy consumed for atomizing liquid is
larger than that of conventional spray nozzles.
Ratios of necessary amount of the compressed air to the
amount of liquid varies widely in accordance with properties of
the liquid (viscosity, surface tension, size of solid material,
etc.) and average particle sizes desired. The compressed air
employable is 4-7 kg/cm2 pressure, as general purpose air
compressors usually have 7 kg/cm2 specifications. Air through
holes of the cylindrical chamber are set to have (total) cross-
sectional area allowing to pass through a predetermined amount
of air under pressure difference of 1 kg/cm2 lower than the set
air pressure. The orifice is set to have an opening area
capable of passing a predetermined amount of air under 0.5-1.5
kg/cm2 pressure difference. A too large orifice opening area
results lowered axial velocity by comparison with the whirling
velocity, which causes difficulty in atomizing liquid film rings
at the orifice portion. Thus, unfavorably larger particles tend
to appear in outward direction, though a widened spray angle may
be obtainable. From this viewpoint, the ejecting air at the
opening of orifice preferably has a velocity corresponding to
0.5-1.5 kg/cm2 pressure difference. In order to attain desirous
atomization with such a small amount of pressurized air, it is
quite important to select properly the (total) cross-sectional
area of the air through holes in the cylindrical chamber and
opening area of the orifice. It is preferred that the ratio of
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diameter of the circular opening 5 of orifice / inside diameter
of the cylindrical chamber 2 is in the range of 1 : 1.5-4.0; and
the ratio of area of the circular opening 5 of orifice / total
cross-sectional area of throuqh holes 3 opened tangentially to
circular internal surface of cylindrical chamber is in the range
of 1 : 0.2-lØ
Different from conventional liquid atomizing nozzles
employing two fluids, the nozzle according to the present
invention can employ an enlarged diameter liquid supplying pipe
thanks to being scarcely affected on the atomizing features by
pipe diameters, and the diameter of orifice can also be
enlarged. Accordingly, it is possible to atomize liquid
materials not only in large amount or of high viscosity but also
containing coarse solid materials. Since the atomized liquid
particles possess higher revolving momentum and lower axial
velocity in comparison with those of conventional nozzles, the
atomized liquid particles can be spread so broadly as to be
beneficial for usages in spray dryers.
In order to enlarge further the spray angle, a reverse
conical body lO is disposed coaxially inside of the opening 5 of
the orifice 4 as shown in Fig.9, which enables a spray angle of
near to that of pressure spray nozzles. Fig.10 shows the
reverse conical body 10 attached to the connecting rod 11. By
fixing the end of connecting rod 11 to the head of the liquid
supplying pipe 1, the reverse conical body 10 can be disposed
coaxially inside of the opening 5 of the orifice 4. In this
case, the circular opening 5 of the orifice 4 is preferably
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shaped into the reverse conical shape, as shown in Fig.11. As
mentioned previously, a liquid material passed into the
cylindrical chamber 2 from the liquid supplying pipe 1 is
dispersed, revolved and accelerated in the cylindrical chamber
by virtue of the pressurized air coming into at a high speed
from the through holes 3 in the direction tangential to circular
internal surface of the cylindrical chamber, and is transformed
to thin liquid film through centrifugal force, and transferred
toward internal surface of the cylindrical chamber. In order to
enhance transferring the liquid material to internal surface of
the cylindrical chamber, a disc-type liquid distributor 12
having a plurality of liquid ejecting holes 13 (top view:
Fig.12; sectional view: Fig.13) placed evenly and concentrically
is preferably disposed (in the cylindrical chamber) at a place
between the one or more through holes 3 for passing through
pressurized air in the direction tangential to the circular
internal surface of the cylindrical chamber and the connecting
portion of the liquid supplying pipe (cf. Fig.9). When the
reverse conical body 10 is disposed in the opening 5 of the
orifice 4 as shown by Fig.9, since front end of the liquid
supply pipe 1 is clogged by the connecting rod 11 of the reverse
conical body 10, it may be so arranged as the liquid material
can be supplied to end portion of the cylindrical chamber 2
through the side hole 14 disposed near front end of the liquid
supplying pipe 1, and the liquid supplied is introduced around
internal surface of the cylindrical chamber 2 through the liquid
ejecting hole 13 of the disc-type liquid distributor 12. Even
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when the reverse conical body 10 is not attached, liquid
distributor 12 can be disposed effectively.
In order to provide the liquid material with rotary
movement prior to be charged to bottom portion of the
cylindrical chamber 2, a disc-type liquid revolving plate 15,
shown by Fig.14 in top view and by Fig.15 in side view, having
one or more of inclined slits 16 circumferentially for revolving
liquid is disposed effectively (in the cylindrical chamber) at a
place between the one or more through holes for passing through
0 pressurized air in the direction tangential to the circular
internal surface of the cylindrical chamber and the connecting
portion of the liquid supplying pipe. For conventional nozzles
of coaxial double-pipe fluid atomizing nozzles, the larger the
difference in discharge velocities between the liquid material
and the swift air stream, the larger the shearing and atomizing
effects. Thus, a heightened supply pressure of the liquid
material for increasing the discharge velocity worsens atomizing
to results in adverse effects. In the present invention,
arrangement of the inclined slit 16 enables pressurized supply
of the liquid and decreases greatly the amount of pressurized
air, which solves the essential defect of conventional double-
pipe fluid atomizing nozzles. The present nozzle can be
installed for existing spray dryers in place of pressurized
spray nozzles, and atomization of highly viscous liquid
materials unable to be atomized so far becomes feasible.
When the present nozzle is employed for a spray dryer, the
nozzle is to be inserted close to the hot air supplying portion.
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In that case, since the cylindrical chamber 2 and the liquid
supplying pipe 1 are covered with the external cylinder 6,
overheating and charring of the liquid can be prevented
effectively.
When the cylindrical chamber and the orifice is so
fabricated as not to be integrated but to be separable as shown
in the Figs, parts having respectively several kinds of cross-
sectional area enable nozzles capable of being combined suitably
for processing various liquid materials. In ordinary double-
pipe fluid atomizing nozzles, preparation of scores kind of
nozzles of the same series are required usually, since the
amount of liquid material to be processed by one specified
nozzle is narrowly restricted. In the present invention, 5
kinds of nozzle openings corresponding to orifice diameters can
manage liquid materials amounting to several liter/hr - several
thousands liter/hr. By combining cylindrical chambers having
several kinds of (total) air through hole diameters with
orifices having several kinds of opening sizes, optimum
atomization features are available.
In the present invention, nozzles having optional lengths
for the liquid supply pipe and for the external cylinder can be
fabricated, and even extremely lengthy ones are manageable by
mere increases in costs added for the increased weight of pipe
materials. Even when the head portion of nozzle is inserted
into high temperature regions of a spray dryer or drying-
incinerator, connecting portions of the liquid supplying pipe
and pressurized air supplying pipe remain outside of the
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inserting portion of nozzle, which enables easy releasing of
connection pipes and hoses. Further, since the nozzle is
overhauled easily for cleaning without using special tools, the
nozzle is suitable for uses in food industries and changeover of
multiple products.
[Example 1]
Waste liquors of SHOUCHU spirit contains 90% or more of
water and includes grain shells of several mm and fibrous
materials of several tens mm. Though those apparently solid
materials as dehydrated activated sludges can be incinerated
with rotary kilns, waste liquors of SHOUCHU spirit are not
treated similarly because of being truly liquid materials.
However, by use of the liquid atomizing nozzle according to the
present invention having the under-mentioned specification,
waste liquors of SHOUCHU spirit could be atomized and sprayed in
a rotary kiln for evaporating main portion of the water, and the
residue was deposited on the kiln wall. The deposit was a solid
material containing about 50% of water and resembled to
dehydrated activated sludges, which was easily incinerated in
the kiln and turned to ash. Since bulky solid materials hinder
the atomization, they must be crushed for processing with a
spray dryer, but they cause almost no trouble in incinerating in
a kiln.
Inside diameter of liquid supplying pipe : 09.5 mm
Diameter of orifice opening : 07.5 mm
Amount of liquid supplied : 600L/Hr
Air pressure : 3kg/cm2
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Amount of pressurized air supplied : 0.6Nm3/min
[Example 2]
A viscous liquid of over 20,000 cP which was unable to be
atomized by use of a spray dryer with a small pressurized spray
5 nozzle was turned to dried powder by use of the liquid atomizing
nozzle according to the present invention having the under-
mentioned specification. The pressurized spray nozzle exhibited
a spray angle of larger than 70~ for a low viscosity liquid.
Though the present atomizing nozzle without the reverse conical
body exhibited about 30~ of spray angle but provided atomized
liquid capable of being dried without adhesion to turn into
dried powder of good quality.
Inside diameter of liquid supply pipe : 07.Omm
Diameter of orifice opening : 04.Omm
Amount of liquid supplied : 40L/Hr
Air pressure : 3kg/cm2
Amount of pressurized air supplied : 0.2Nm3/min
Average particle size : 25
