Note: Descriptions are shown in the official language in which they were submitted.
~G3 ~3
The present invention relates to the manufacture of particles of
controlled size from feed material which is either an oxide or in situ pro-
duced oxide. Oxide particles of a controlled range of sizes are needed for
various applications such as pigments, flame retardants, and the like. Their
production by prior art modes has been either economically infeasible or less
than satisfactory from a quality standpoint.
The physical properties of oxide materials of the inorganic type
in a finely divided form vary considerably with their average particle size
and range of particle sizes in a given sample. Certain useful properties
associated with specific particle sizes of oxide materials and particle size
distribution have been simply unavailable because neither the average size nor
the size distribution required are attainable using known techniques.
Accordingly, alternative methods and apparatus for the inexpensive production
of finely divided inorganic oxide materials of controlled size are needed.
In one yrior art arrangement, a feed material such as a metallic
salt is introduced into a plasma reactor, or its tail flame, to vaporize the
feed which is subsequently quenched to form an oxide of some average particle
size. However, quite often neither the average size nor the range of sizes
have been capable of sufficient control to guarantee an output product of
commercial utility and value.
Accordingly, it would be advantageous to be able to produce finely
divided compounds, such as oxide compounds, of controlled average particle
size and controlled particle size distribution. It would also be advantageous
to utilize efficiently plasma reactions for the production o finely divided
solid materials. In particular, it would be advantageous to produce by
plasma reaction and quenching techniques antimony oxide of submicron size.
Therefore, the present invention provides a method of obtaining
from a suitable feed material a particulate product of controlled particle
size characteristics comprising the steps of: establishing a plasma reaction
zone of high temperature relative to the vaporization temperature of said
- 1 .~
1~963'~3
material; introducing said feed material into said plasma reaction zone to
produce an effluent containing said feed material in a substantially complete-
ly vaporized form; passing said effluent to a quenching zone of lower pressure
than that of said plasma reaction zone; and applying a quenching medium to
said effluent in said quenching zone in controlled manner to obtain said
particulate product.
According to a first preferred embodiment of the method of the
present invention there is provided in a method of producing relatively fine
oxide particles of controlled average size and range of sizes from a feed
material of relatively coarse oxide particles, the steps comprising
establishing a plasma reaction zone of high-temperature relative to the
vaporization temperature of said feed material; introducing said feed material
into said plasma reaction zone to produce an effluent containing said feed
material in a substantially completely vaporized form; passing said effluent
to a quenching zone of lower pressure than that of said plasma reaction zone;
and applying a quenching medium to said effluent in said quenching zone in
predetermined volume, proximity and direction relative to that of said effluent
to said reaction product to condense oxide particl0s therefrom of size and
range of sizes controlled by said predetermined volume, proximity and direc-
tion of said quenching medium relative to said effluent.
Advantageously, with respect to the method of the present inven-
tion, the feed material is passed from a first chamber of relatively high
pressure to a second chamber of relatively low pressure within said reaction
zone, the relatively low pressure of the second chamber being greater than
that of the quenching zone. Also advantageously, the quenching medium is
applied in direct counterflow to the effluent although the quenching gas may
be directed at an angle to the path of the effluent.
According to another preferred embodiment of the method of the
present invention there is provided the method of obtaining from a suitable
oxide feed material a particulate product of controlled particle size char-
1~9632~
acteristics comprising the steps of: establishing a hot plasma gas environ-
ment in a reaction zone; introducing feed material into said reaction zone;
causing said plasma gas in said reaction zone to thoroughly mix in heat
exchange relationship with said feed material; vaporizing said feed material
in said reaction zone to form an effluent; passing the effluent from said
reaction zone into a quenching zone through a constricted passageway; in said
quenching zone, directing quenching gas from a source toward said effluent
emerging from said reaction zone to form a particulate product; controlling
particle size formation as a function of the position of the quenching gas
source relative to said constricted passageway; and recovering particulate
material from said effluent. Advantageously with respect to this other embodi-
ment the position of the quenching gas source relative to said constricted
passageway is adjusted to selectively govern the velocity at which the quench-
ing gas meets the effluent emerging from the constricted passagewayO Also
advantageously the volume of the quenching gas directed toward the effluent
is sufficient to cause substantially immediate cooling thereof to a point at
which condensation of oxide particles therefrom takes place.
According to another aspect the present invention provides plasma
reactor apparatus suitable for the formation of particulatesfrom a suitable
feed material comprising: means forming a first plasma reaction chamber
communicating with a plasma reactor operable to establish in said first
reaction chamber a plasma environment at a temperature effective to vaporize
such feed material and form an effluent; means defining an inlet to and an
outlet from said first reaction chamber; means forming a second reaction
chamber having an inlet in fluid communication with the outlet of said first
reaction chamber; effluent outlet means formed in said second reaction chamber;
means forming a quenching chamber in fluid communication with and enclosing
said effluent means; means in said quenching chamber forming at least one
quench medium discharging passageway adapted to supply and direct quenching
medium to effluent emerging from said effluent outlet means for condensing
-- 3 --
' :~
particulate material from said effluent; and means to collect such particulate
material from said quenching chamber.
According to a first preferred embodiment of the apparatus of the
present invention there is provided plasma reactor apparatus suitable for the
formation of particulates from a suitable feed material comprising: means
forming a first plasma reaction chamber communicating with a plasma reactor
operable to establish in said first reaction chamber a plasma environment at
a temperature effective to vaporize such feed material and form an effluent;
means defining an inlet to and an outlet from said first reaction chamber;
means forming a second reaction chamber having an inlet in fluid communication
with the outlet of said first reaction chamber; effluent outlet means formed
in said second reaction chamber; means forming a quenching chamber in fluid
communication with and enclosing said effluent outlet means; means in said
quenching chamber forming at least one quench medium discharging passageway
spaced from and surrounding said effluent outlet means and positioned to sup-
ply and direct quenching medium to effluent emerging from said effluent outlet
means for condensing from said effluent particulate material having particle
size characteristics functionally related to the distance between said quench
medium discharging passageway and said effluent outlet means; and means to
collect such particulate material from said quenching chamber.
Advantageously the apparatus includes means for selectively ad-
justing the position of the quench medium discharging passageway with respect
to the effluent outlet means. Preferably, the quench medium discharging pas-
sageway comprises spaced orifices along the passageway for directing the
quenching medium into the path of the effluent. More than one quench medium
discharging passageway may be used and they are advantageously in spaced
relationship to both the effluent outlet means and each other. The quenching
chamber itself may be conical in shape.
The effluent outlet means of the apparatus may comprise a single
outlet connecting the second reaction chamber to the quenching zone. In this
case the means forming the quench medium discharging passageway may be toroidal
-- 4 --
1~9~i32~3
in configuration; the toroidal axis of which may be in substantial alignment
with the central axis of the effluent. The surfaces surrounding the single
outlet may be located by any suitable means. The effective size of the single
outlet may also be varied by any suitable means to vary the amount of effluent
passing therethrough.
According to a further preferred embodiment of the apparatus of
the present invention there is provided plasma reactor apparatus suitable for
the formation of particulate oxides from a suitable feed material capable of
providing an in situ oxide comprising: plasma reactor means for establishing
a high temperature plasma environment; a first reaction chamber communicating
with said plasma reactor for vaporizing feed material to form an effluent,
said first reaction chamber having an inlet for feed material and an outlet
for said effluent; a second reaction chamber; means forming a constricted
fluid passageway between said first reaction chamber and said second reaction
chamber; means forming radially spaced effluent outlets from said second
reaction chamber; a quenching chamber surrounding and enclosing said radially
spaced effluent outlets; quench medium discharging means in said quenching
chamber, said quench medium discharging means being spaced from and surround-
ing said radially spaced effluent outlets for supplying a quenching medium to
effluent from said radially spaced effluent outlets to condense oxide particles
therefrom; and means for collecting said oxide particles.
Advantageously the further preferred embodiment of the apparatus
includes a quench medium discharging means comprising a ring having a plurality
of spaced apertures directed toward the path of the effluent emerging from the
radially spaced effluent outlets.
More particularly, the process and apparatus of the present in-
vention involve the use of plasma reactions but they differ materially from
those of the prior art in specific process steps as well as the particular
apparatus utilized. Feed material of an oxide or a substance capable of
producing an in situ oxide is introduced into a plasm environment in a reaction
lG9632~31
zone which may include chambers for imposing and maintaining specific process
conditions. The feed material is vaporized and the resultant effluent from
the reaction zone is quenched selectively and controllably to induce the
formation of a particular end product of desired particle size characteristics.
A predetermined result is obtainable by selective control of the
process variables of pressure, temperature, quench rate and quench disposition
with respect to the vaporized effluent emanating from the plasma reactor. The
invention is applicable to oxide compounds such as antimony oxide, titanium
dioxide, silicon dioxide, zirconium oxide, iron oxide, aluminum oxide, zinc
oxide, tin oxide, tungsten oxide, molybdenum oxide, copper oxide, nickel oxide,
and alloys thereof.
While the specific form of the invention described relates to
oxide compounds as set forth above, other oxide compounds of particular par-
ticle size may also be manufactured and produced in accordance with the inven-
tion, using apparatus disclosed therein, so long as necessary intrinsic
parameters dictated by the chemical and physical nature of the feed material
are considered. Also halides of various metals may be processed in order to
produce an in situ oxide which may be converted to particles of controlled
size in the micron or submicron range.
Thus, the invention relates to the production of finely divided
particulate materials of controlled particle size, including submicron sizes.
Usually, the feed materials will be of an average particle size which is
large relative to the output which is desiredO
In general terms, the practice of the present invention involves
the establishment of a high-temperature plasma gas environment in a reaction
zone, introducing a relatively coarse particulate feed material to react with
the plasma gas or its tail flame in the reaction zone to produce an effluent
containing vaporized feed material, plasma gas and carrier gas if such is
used to introduce the feed material. The reaction zone may include a first
chamber of decreasing cross-section and a second reaction chamber of uniform
-- 6 --
3~
cross-section larger than that of the outlet from the first reaction chamber
and a reactant gas may be introduced before the total effluent passes from
the reaction zone into a quenching zone where quenching gas is directed in a
controlled manner toward the effluent for producing particles having a pre-
determined average particle size and a predetermined particle size distribution.
In a typical situation, the average particle size of the feed is larger than
that desired in the end product which will have not only a smaller average
particle size than the feed but also limited particle size distribution.
By selectively maintaining a differential pressure between the
reaction zone and the quenching zone; by providing a quench medium in proximity
to the effluent entering the quenching zone; by controlling the discharge of
the quench medium in relation to the discharge of the effluent; and by closely
controlling the ratio of quench volume to the volume of effluent, the resultant
average particle size and particle size distribution of the output product can
be selectively maintained and adjusted. As the quench volume is increased
with respect to the effluent volume, the average output particle size is
reduced. As the quench discharge means is brought closer to the effluent
discharge means, the effective velocity of the quench at the point of contact
with the effluent is increased and quenching time is decreased which also
tends to reduce the average particle size.
The range of particle size distribution is also determined by con-
trol of the quenching medium dischargeO For example, a narrow range of par-
ticle size distribution is accomplished by, insofar as possible, quenching all
the effluent from the reaction zone simultaneously; the range of particle
sizes increasing or decreasing, respectively, with increase or decrease in the
displacement of the quench discharge from the effluent discharge.
As a specific example, having established the product through-put
rate and remaining system variables, if the desired output is a product having
an average particle size in the submicron range, and having a particle size
distribution as narrow as possible (i.e. approaching uniform particle size),
1~9632i~
then the quenching medium will be discharged closely adjacent the effluent
from the reaction zone to increase its effective velocity and assure intimate
turbulent mixing of the effluent and the quenching medium; also, the volume
of the quenching medium will be sufficient to quench all of the effluent in
the shortest possible time.
A preferred system for practicing the invention includes a plasma
generator for establishing plasma environment and a communicating feed inlet.
Connected to the plasma generator is a first reaction chamber having a decreas-
ing cross-section. That is, the inlet or plasma generator end of the first
reaction chamber is of a greater cross-sectional area than the outlet end.
The outlet end is connected to a second reaction chamber of constant cross-
sectional area greater than the outlet end. The second reaction chamber has
radially spaced outlets which communicate with an enclosing quenching chamber.
One or more annular or ring quench medium discharging members within the
quenching zone surround the second reaction chamber. Quenching gas from the
annular members is directed to the effluent emerging through the outlets of the
second reaction chamber along a path either normal to the path of the emerging
effluent, in direct counterflow, or in both those directions. The oxide
particles of selected size formed by the quenching operation are accumulated
in a collection chamber.
In drawings which illustrate embodiments of the invention:
Figure 1 is a block diagram of a preferred form of the process and
apparatus of the invention;
Figure 2 is a sectional partial view of the plasma generator and
reaction and quenching zone portions of the apparatus of the invention;
Figure 3 is a schematic sectional view of key components of the
apparatus utilized in practicing the process depicted in Figure l;
Figure 4 is a fragmentary view of the annular quenching members of
the quenching zone;
Figure 5 is a cross-sectional view taken along the line 5-5 of
lG~3~3~3
Figure 4;
Figure 6 is a fragmentary view in cross-section of an alternate
structural embodiment of the invention;
Figure 7 is a cross-sectional view taken along line 7-7 of Figure
6;
Figure 8 is a cross-sectional view taken along line 8-8 of Figure
6;
Figure 9 is a schematic illustration of a refinement of the
apparatus of the invention showing an electrically heated effluent exit port
at which quenching gas is radially directed; and
Figure 10 is a schematic illustration of an exit port of adjust-
': able size.
Figure 1 is a block diagram showing a preferred embodiment of the
overall process of the invention.
A plasma arc generator 200 with an appropriate cooling means 201
is powered by a DC power source 202 and fed a nitrogen stabilizer gas from a
source 204. The stabilizer gas is heated by the plasma arc in the plasma arc
generator 200. The resulting tail flame from the plasma arc generator is di-
rected into a top reactor 208 which includes an inlet and a constricted outlet.
: 20 A relatively coarse oxide feed material is supplied to the inlet from a
source 206 and, if in particulate form, may be conveyed by a fluid carrier
from a carrier source 210.
Essentially complete vaporization of the feed occurs in the top
reactor 208 and the effluent passes through the constricted outlet to a bottom
reactor 212. Any feed material not vaporized in the top reactor 208 is
vaporized in the bottom reactor 212. An oxidizer 214 provides an oxidizing
medium to the bottom reactor 212 if needed to maintain stoichiometry. Effluent
from the bottom reactor 212 is fed to the quench zone 216 which is supplied
with a quench gas from the quench source 217. The vaporized feed in the
effluent thus condensed is first collected directly from the quench zone 216
3~i~
and remaining effluent is passed to a filter 218 from which additional product
is collected. The exhaust gas from the filter 218 then passes through a
scrubber 220 and is discharged.
In Figure 2, there is shown a feeder 2 for supplying feed material
which, in this embodiment, is a particulate material. The feeder 2 operates
in conjunction with a carrier gas line 4 through which feed gas, in this
instance, air, is supplied under pressure. The feed gas carries the parti-
culate material, here, for example, antimony oxide of random particle size
averaging 5 microns, into the tail flame generated by a conventional plasma
arc generator 6. The plasma generator 6 includes a stabilizer inlet 8, a
cathode 10, and an anode 12. The plasma generator is cooled conventionally by
a coil through which water flows from an inlet 22 to an outlet 24.
Disposed beneath the generator 6 is reaction zone 14 having at
least one exit port 16 communicating with a surrounding quenching chamber 18.
Positioned in the top of the quenching chamber 18 is a manifold 26 connected
from quench rings(not shown) to a quench gas supply means 28.
A conduit 20 is connected to the bottom of the quenching chamber
18 to carry off reaction products and gases. The conduit 20 is water cooled
by conventional means and leads to a bag house or filter assembly 32. In the
filter assembly 32, purge gas, such as air, is introduced via inlets 34 and
stripped out solid product is recovered through an outlet 36. From the bag
house 32, a conduit 38 carries the gases into a scrubber 40 from which clean
gas is recovered via a conduit 42. A second outlet 44 leads to a scrubbing
solution vat 46 for return of the scrubbing solution. The scrubbing solution
is returned to the scrubber 40 by means of a pump and conduit 48. What has
been described is one overall system useful in the practice of the invention.
Figure 3 is a fragmentary view of key elements of a preferred
embodiment of the invention. The lower portion of a conventional plasma
reactor head 52 is shown as having a central plasma arc flow passageway 54
intersected by feed and carrier entrance ports 56. The feed, carrier and
- 10 -
plasma tail flame discharge into a communicating upper reactor 58 which has a
generally truncated conical interior diminishing from an inlet 60 to an outlet
62.
The upper reactor 58 is constructed of an outer stainless steel
housing 64 and a refractory liner 66 made, for example, of alumina. The upper
reactor 58 is disposed above and in communication with a lower reactor 68.
The lower reactor 68 is made of the same or similar materials as the upper
reactor 58 including, for example, a stainless steel housing 70 and an interior
refractory liner 72. The lower reactor 68 has an entrance port 74 connected
to a supply of gas, such as oxygen, which may be introduced into the chamber
of the lower reactor 68.
Adjacent the bottom of the lower reactor 68 a plurality of slag
exits 78 are formed in the reactor wall as at 76. The exits lead upwardly to
a slag collector 80 which surrounds the bottom of the reactor 78 and serves
as a depository for slag and other wastes produced in the reaction chambers.
Equally spaced radial exit ports 82 are formed through the wall
of the lower reactor 68 and lead to a quench zone 84. The quench zone 84 is
defined by a generally conical shell which may be of stainless steel generally
enclosing the upper and lower reactors. A broad flange 86 forms the top wall
of the quench chamber and openings are formed in that wall to accommodate the
manifold 26 which is connected to concentric quench rings 88 and 90.
Quench gas, such as air, is fed through the manifold 26 to the
quench rings 88 and 90. Spaced orifices 92 are formed in the quench ring 88
and these may, for example, be oriented to direct quench gas radially inwardly
in the general direction of the lower reactor exit ports 82 from which effluent
from the reaction chambers emerges. The quench ring 90 is shown here as having
spaced orifices 94 oriented to direct quench gas in a direction generally
normal to effluent emerging from exit ports 82.
The proximity and angle of direction of the quench gas to the
outlets 82 as well as the size, number, and spacing of the quench rings will
- 11 -
~9963~
selectively determine the average size of the particles and the particle size
distribution of the material recovered. The manifold 26 is slidably mounted
in the top wall 86 so that the quench rings and manifold assembly can be
selectively raised and lowered with respect to the exit ports 82. Adjustable
clamping seals 25, which seals may be operated manually, surround the manifold
members at their points of passage through the top wall 86 and the mounting
is such that an individual quench ring or combinations of rings may be raised
and lowered. Additional quench rings may be employed if desired. Generally,
if the quench rings are positioned relatively close to the exit ports 82, the
size of the particles formed during the quenching process will be reduced.
Conversely, if the quench ring assembly is positioned relatively far from the
exit port 82, the size of the particles produced during quenching will be
larger.
As noted above, quench gas orifices 94 are disposed about the
lower surface of the ring 90 so that quench gas will be directed essentially
normal to the path of effluent emerging from the exit ports 82. The quench
openings 92 are disposed about the inner surface of the quench ring 88 so that
the quench gas will be directed in counterflow to effluent emerging from the
exit ports 82. The quenching effect of quench gas from the quench ring 88 is
maximized when the quench ring is lowered to a point where the orifices 92
confront the exit ports 82. If it is contemplated that the inner quench ring
88 normally will be in a position somewhat above the exit ports 82, the
openings 92 could be disposed in the lower surface of the quench ring 88 like
those in the quench ring 90.
The size and number of spaced lower reactor exit ports 82, in
conjunction with the size of the outlet 62 of the upper reactor 58 relative
to the entry to the lower reactor 68, set up differential pressures and tem-
peratures not only between the upper reactor 58 and the lower reactor 68 but,
more importantly, between the reaction zone which includes both reactor cham-
bers and the quenching zone 84. Feed material is substantially completely
- 12 -
1 ~G32i~
vaporized in the total reaction zone because the pressure and temperature
differentials between the two reactors cause a turbulent and thorough mixing
of the plasma gases and the feed material in the upper reactor 58, maximizing
the transfer of heat from the plasma gases to the feed material. Substantially
all the feed material is rapidly mixed and vaporized in the upper reactor.
The lower reactor is configured and sized to provide a residence time for the
mixture of plasma gases and feed material to permit essentially complete
vaporization of any feed material not vaporized in upper reactor 58 as well
as a locus for the introduction of reactant gas, if needed.
The exit ports 82 are so located that any tendency for a few
particles to shoot through the entire reaction zone without vaporization is
inhibited and, in fact, is minimized when the ports 82 are axially normal to
the opening 62. The exit ports also contribute in large measure to the
establishment of temperature and pressure differentials between the reaction
zone and the quenching zone 84. Also, of course, the pattern of effluent
discharge into the quenching chamber is determined in large degree by the
disposition of the exit ports. The temperature and pressure in the two cham-
bers which constitute the reaction zone are maintained at values preventing
condensation and undesired particle formation in those chambers. The conical
wall configuration of the quenching chamber 84 (shown in Figure 2) aids in
effective quenching causing the vaporized feed from the lower reactor 68 to
condense out in finely divided particulate form. Efficient recovery of the
output product is accomplished in accordance with known techniques utilizing
cyclone, bag house or like recovery methods.
Where the feed material is a silicate or other substance which is
to be reduced and subsequently oxidized, the in situ reactants are carried
through the reaction zone 68 with a residence time effective to allow adequate
mixing and reaction prior to exiting through the ports 82.
Figures 4 and 5 illustrate typical disposition of the quench rings
88 and 90, relative to the quenching chamber 84. A plurality of bores or
- 13 -
ial963;;~3
apertures are formed in the top 86 and a manifold feed, not shown, may be
connected to each of the individual header pipes 96. The header pipes are
connected to spaced quench rings, for example, 88, 90, 83, 85, 87, 89, 91 and
93. A valve 95 may be connected to each header 96 so that quench gas of
fluid may be selectively directed through one or more of the concentrically
placed quench rings, depending on the particular particle size distribution
and average particle size desired in the end product. Any one or combination
of the quench rings may introduce the quenching gas and, in each instance,
the quench rings are provided with spaced orifices like 92 and 94 in the
quench rings 88 and 90, respectively, as illustrated in Figure 3. As with the
spaced apertures in the quench rings 88 and 90, the rings 83, 85, 87, 89, 91
and 93 are formed with apertures to provide a desired flow direction relative
to that of the effluent from the lower reaction chamber 68.
As effluent emerges from the exit ports 82 it encounters one or
more streams of quenching medium angularly directed from one or more concen-
trically placed quench rings so as to condense in finely divided form the
vaporized product entrained and contained within the effluent. The closer the
discharge of the quench gas to the effluent emerging from the exit ports 82,
the smaller average size and distribution average of the end product collect-
ed. If the smaller quench rings relatively near the ports 82 are activated,
the average particle size of product resulting from a given run will be
minimized and can be in the submicron range. To maximize the average particle
size and distribution, the quench rings furthest from the exit ports are
activated. Examples of the relationship of the quench rings to reactor
discharge and the effect on recovered product are given hereinafter but gener-
ally, the volume ratio of quench gas to effluent from ports 82 is in the
range 1:1 to 10:1.
In Figures 6, 7 and 8, an alternate embodiment is illustrated. It
includes an upper reactor 102 forming a reaction zone 104 of substantially
uniform diameter and communicating with a lower reactor 106 forming a second
- 14 -
l(g~G~
reaction zone 108, the zones 104 and 108 communicating through a transition
zone of decreasing diameter 110 formed by the refractory liner 112 in lower
reactor member 106. Although no plasma head is shown, it would be as illus-
trated in Figure 3, positioned above the upper flange 114 which forms the top
boundary of the quench zone 116 surrounding the lower reactor 106. An inlet
118 to the second reaction zone permits oxygen or a reducing reagent to be
introduced. The lower reactor 106 has circumferentially spaced exit ports or
orifices 120 opening into the quench zone 116.
In this instance, the spaced outlet ports or apertures 120 are
tapered with their large ends facing the surrounding quench zone 116. As in
the embodiment of Figures3, 4 and 5, concentric quench rings of various radii
surround the exit ports 120.
In Figure 9, a second alternative quench ring arrangement is
schematically illustrated. Here, a first reactor 124 communicates with a
second reactor 126. A single exit port or orifice 128 communicates with a
quench zone 1300 The pressure and temperature differential between the second
reactor 126 and the quench zone 130 is suitably maintained by the size of the
singular exit orifice 128. The walls of the orifice 128 are heated by an
electrically energized heating element 132 to prevent condensation or accumul-
ation of condensed solids around or within the orifice. A pair of quench rings
134 and 136 are suitably supported within the quench zone 130, spaced from and
concentric with the orifice 128. That is, the quench rings lie in planes
normal to the central axis of the orifice with their axes substantially align-
ed with that of the orifice.
Spaced, inwardly directed apertures 130 and 140 are formed in the
quench rings 134 and 136, respectively, so as to direct the quenching medium
radially inwardly into the flow path of the effluent emerging from the orifice
128. The quench rings 134 and 136 are supported from and communicate with a
common quench supply means. The assembly is selectively adjustable along the
longitudinal axis of the orifice 128. The operation and performance of the
- 15 -
i3Zi3
apparatus and process are similar to that previously described in connection
with other embodiments of the invention.
Figure 10 schematically illustrates an optional valved orifice
which permits selective adjustment of the pressure and temperature differential
between the reaction chamber and quench zone. In this view,the lower portion
of the reactor 144 is shown as having a single exit port 146, which may or may
not be heated, communicating with a quench zone 148. A support 145 having a
bore 150 is provided opposite the exit port 146. Slidably disposed in the
bore 150 is a valve steam 152. The stem 152 carries an integral tapered valve
and movement of the stem by means not shown adjusts the position of the head
154 relative to the exit port 146 varying the effective exit area. The valve
stem 152 may be electrically heated also so as to prevent particle formation
thereon. The relative pressure and temperature between the reaction zone and
quenching æone 148 thus may be selectively varied to obtain particulate mate-
rial of a desired size.
A series of runs was made using antimony oxide (Sb203) of a par-
ticle size in the 1 to 5 micron range as the feed material. The oxide was fed
into the reactor of the type illustrated in Figure 3. The exit ports or ori-
fices were approximately one-half inch in diameter and were spaced circum-
ferentially of the lower reactor member as in the embodiment depicted in
Figure 3. The results of these runs are illustrated below in Table I. In
Table I, "Air Quench SCFH" designates the flow of air to the quench ring or
rings in standard cubic feed per hour; the "Quench Ratio" defines a ratio
where the numerator is the total gas input to the system, less quench gas, plus
the feed expressed in standard cubic feed per hour and the denominator is
quench gas expressed in standard cubic feet per hour; "Cal. Temp. C" desig-
nates the calculated temperature in degrees Celsius of the upper reaction
zone; "Feed Rate lb/hr" designates the rate, in pounds per hour, of feed
delivery to the plasma reactor; "Oxygen to Reactor SCFH" designates the amount
of oxygen supplied to the plasma reactor in standard cubic feet per hour; and
- 16 -
328
"Particle Size Population DistributionMass %--Microns" is used to designate
the percentage of the total particulate recovery which is within various
designated ranges, expressed in microns.
- 17 -
- lG~16~'8
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- 18 -
i3~3
In the first run, No. 1, two quench rings were utilized, one
12" in diameter and the other 30" in diameter. The quench rings were approxi-
mately 30-l/4" above the eight exit ports in the lower reactor member communi-
cating to the quench zone. In run No. 2, the 12" quench ring was lowered to
approximately 6-1/4" above the exit ports while the 30" quench ring remained
at the original height. In run No. 3, the only quench ring utilized was the
smaller quench ring which was lowered to approximately 2" above the exit
ports. In this instance, one of the exit ports was heated while the remaining
seven exit ports remained unheated. About the one heated port, an annular
quench ring was disposed in the manner illustrated in Figure 9. From Table I,
it is apparent that there is a shift toward an output of relatively small
submicron particle sizes and away from larger particle sizes as the space
between the quench ring and the exit ports is decreased. For example, com-
paring runs 1 and 2, antimony oxide having a particle size distribution with
a major portion of average size less than 0.1 micron is obtained where the
quench gas, in this instance, air, is discharged close to the exit ports.
Also, run No. 3, empirically illustrates the fact that the closer the quench
gas discharge to the exit ports, the smaller the average particle size of the
processed material obtained and the narrower the particle size distribution.
In order to ascertain the effect of the amount of quench medium
on the inventive apparatus and process, a number of runs were made utilizing
the type of reactor configuration illustrated in Figure 3. Data on these
runs is found in Table II in which column designations are as in Table I.
Eight spaced l/2" diameter exit ports and a single diameter quench ring were
utilized. The quench ring was positioned in each of the runs approximately
6-l/4" to 6-l/2" above the exit ports. The feed material was antimony oxide
having a typical particle size in the 1-5 micron range.
- 19 -
1~9~3~
O N
A I O
O
OLr~ In
o ~
.,1 . O O
:~: N
o\ O
In N
1/~ 1 N N
~ O O
.~
O
o
~ I
.,1
~ O
a
~ o `D
N N _I
~1 0 _I
0~
N
a~ o ~ _~
N I
~) O
O N N
~rl
t~) O N
V
~3 0 N N
o o
O ~ U)
.~ ~ N ~
a~ ~,9 al oo
_I
. ~ r~ ~7
N t
_I N
rC ~ ~1
~.,1
3 t~ ~ L~
O' D!: N N
h a~ ~ 00 00
c~ O' U) N N
~ . ,_ ~_
- o --I N
~:: Z ~J _~
- 20 -
~?632~ ~
It is apparent from Table 2 that as the ratio of quench medium
in this particular instance, air, is increased relative to the amount of
effluent emerging from the reactor, the particle size distribution is reduced
and the average particle size is smaller.
Another series of runs was made utilizing a reactor configuration
of the type illustrated in Figure 9. In this embodiment, a 6" quench ring was
positioned approximately 1" from the single exit port and a 9" quench ring
was positioned approximately 2" from the exit port or 1" from the 6" quench
ring. The orifices in the quench rings were disposed to direct quench medium
towards and into the flow path of the effluent emerging from the single exit
port. That is, the direction of flow of the quench medium includes one com-
ponent in counterflow to the flow of effluent from the exit port and one
component normal to the direction of said effluent flow. The feed material
used for runs 6, 7 and 8 was of 1.3 micron Fisher-average particle size and of
commercial, high tint antimony oxide. The results of these runs are tabulat-
ed below in Table III, the column designations again being identical to those
of Table I.
i3~i3
o
U~ o
V
o
~ U~
O t N ~ ~1
h o o o o
V V
o
o\
V~ I t~ I~ I~
~ o o o
,1
~ 1~') N 0~
D . ~ ~C) t'')
h o
.,1
r~
g ~ o
~1 ~ ~ ~ n
C~ o
O ~`t
~ o C~
N ~1 ~ N 1~
'U~ O ~`t ~t ~`t
_I
t~
_I N Lr) Il~
O t~ ~ ~t
H ~ V L~ Lr~
1:~ h
~ td ~N N N
O C~ C~t O O O
h u~
~rS
ct ~- ~ ~ a~
~t ~ .~ N N O
_I ~
_t ~ C~ a~ N
~ O~ O
o .~ t
t~ O ~ ~ _I
~rl .... ..
td
~ ~ C~
h a) ~ ~ _I ~o
u~
O'u~ ~ ~U)
~ Z; ~ N ~
- 22 -
l~G3Z~
Table IV lists operating parameters of the runs set forth in
Table III. The data is correlated with the general system description given
in Figure 1, the reference numbers in the left-hand column of Table IV identify-
ing elements of the apparatus shown in Figure 1.
TABLE IV
Run No. (1) (2) (3)
D. C. Power (202) 52.8 53.6 51.8
KW Gross
Coolant Loss (201) 16.15 16.4 15.2
KW Loss
Total Power to N2 Stabilizer 36.65 37.2 36.6
KW Net
N2 Stabilizer Supply (204) 413 413 413
SCFH
Air Feed SCFH (210) 455 485 489
*2 Supply (214) 102 102 102
SCFH
Total Gas to Reactor 970 1000 1004
SCFH
Sb2 Total (206) 60.5 83 72.5
Feed lbs.
Feed Time (hr.) 0.5 0.67 0.67
*Sb203 Feed (206) 121 124.5 109
lb./hr.
Sb203 eed 161 166 145
SCFH
Total Gas Inc. Feed 1131 1166 1149
*Quench Air SCFH (217) 3513 3513 5166
*Quench Ratio 3:1:1 3:1 4:5:1
Calculated Temp. K (208) 2270 2250 2300
*Calculated Temp. C (208) 1997 1977 2027
Products - Bag (218) 49.5 66 69.5
*Repeat of information in Table III
Various modes of practicing the present invention are possible.
It should be obvious to those skilled in the art that different feed materials
and modification in materials of construction and equipment may be made
- 23 -
1~9~:i32~
without departing from the scope of the invention. In some instances, metal
oxide materials may be utilized as the starting materials and in other in-
stances, a halide may be used either singularly or in conjunction with
another oxidizable material wherein simultaneous oxidation is had with the
production of single or mixed oxide particles.
In some instances, oxygen and/or oxidizable materials will be
fed into the reaction zones, in a manner as described hereinbefore for anti-
mony oxide, and wherein the stoichiometric chemistry is maintained so as to
obtain desired oxide materials of selected particle size.
One such instance occurs with a zinc oxide feed. Using a reactor
as illustrated in Figure 3, zinc oxide is fed into the reactor while maintain-
ing a sufficient temperature to vaporize the zinc oxide (for example, greater
than 1975C). Effluent is directed through the reaction chamber into a
quenching zone and zinc oxide of predetermined average particle size and
particle size distribution is recovered.
In another instance, a feed material such as silicon dioxide,
having a boiling point of 2230C, is fed to a reactor of the configuration
of Figure 3. Reactor design varies according to operating temperatures and,
here zirconia is a suitable material for use as the reactor liner. Typically,
relatively high temperature reactors are smaller than relatively low tempera-
ture reactors but even with a feed such as silicon dioxide, an output of
controllable average particle size and particle size distribution may be had.
Although it is possible to produce an output of large particle
size, it is more often the goal to obtain an output of submicron size. A
variety of feed materials may be used including tin oxide, titanium oxide,
iron oxide, and tungsten oxide and the output particle size may be chosen by
selectively varying the operating parameters and physical disposition of
elements of the apparatus as disclosed above. That is, first by maintaining
a differential pressure of about 2 or 3 lb./sq.in. above the atmospheric
pressure in the quenching zone; second, by providing a quench medium in
- 24 -
1~3~3~1~
proximity to the effluent exiting into the quenching zone; and, third, by
closely controlling the amount of quench gas volume to the volume of the
effluent, the resultant particle size and the range of sizes of the recovered
products can be selectively maintained. Although some interaction occurs, the
parameters are independently and jointly adjustable with shifts as noted
above toward larger or smaller output particle size in greater or lesser
ranges.
It has been noted that an oxidizer ~or a reducing gas, depending
upon the type of feed material) may be introduced in the second reaction
chamber. Insofar as feeds such as antimony oxide or zinc oxide are concerned,
the oxidizer is useful in small amounts not so much for control of particle
size as to prevent the nitrogen of the feed gas from joining with the oxygen
from the vaporized feed. In such conditions, particularly with antimony oxide,
a discolored output product may result.
The system has been described in connection with a gas quenching
medium. However, a liquid quench could be used to provide a colloidal suspen-
sion useful in certain industrial processes, such as fabric treating. In the
apparatus of Figure 2, for example, a water quench could be supplied through
the manifold 26 so that effluent from the exit port 16 forms with the water a
colloidal suspension. The suspension may be recovered directly from the
bottom portion of the quench tank 18 and there would be no need for the filter
32 and other downstream apparatus.
The invention should not be limited to the details of preferred
embodiments shown and described.
- 25 -
