Note: Descriptions are shown in the official language in which they were submitted.
~S~.3~
The present invention relates to a high temperature electronic
furnace suitable for converting fly ash into mineral wool.
Mineral wool is a fine fibrous "wool-like" material, typically
made by blowing a srnall stream of molten rock or similar material, such as
coal ash, with a jet or stream or fluid. The action of the jet of fluid
blows the mineral stream into fine fibrous material which hardens before
the fibers reach the floor.
T~e manufacturing process requires that the fly ash be melted
and poured within critical temperature and pour rate tolerances. For
example, fly ash typically melts and pours at around 2765 degrees
Fahrer~eit. However, at this temperature, the fly ash is a gummy mass,
whereas at 2875 degrees Fahrenheit the fly ash flows like water. Moreover,
the diameter of the resultant fibrous strains is highly dependent upon the
temperature of the molten fly ash. Accordingly, it is essential that any
furnace used to melt fly ash for the production of mineral wool have the
capacity to control the temperature of the fly ash to precise tolerances,
on the order of 5 to lO degrees centigrade while processing large continuous
volurnes of fly ash on the order of 40,000 lbs./hr for weeks at a time.
However, no known prior art furnace has this degree of control over the
te~nperature of high volume molten fly ash.
In the past, attempts have been made to u-tilize electronic fur-
naces to melt fly ash and produce mineral wool. For example, U.S. Patent
No. 2,817,695 issued to I~lrtwig discloses an electronic furnace and electrode
structure designed for the melting of refractory materials such as mineral
wool. Ilartwig employs three main electrodes spaced 120 degrees from one
another in a plane. A nozzle assernbly is moveably positioned along
a line perpendicular to the plane of the main electrodes at the center
'`1--
'~ ~
.3lr~
point of the three electrodes. The no~zle assembly is cooled
below oxidation temperature by coolant flow in a nozzle support
assembly.
_artwig recognizes the need to provide accurate temperature
control and attempts to accomplish this control by cooling the
no~zle assembly and by supplying heat to the nozzle in accordance
with temperature measurement of melted product passing through
the nozzle assembly. Hartwig suggests that one way of achieving
the requisite control is to apply an electrical potential between
the nozzle and a selected one of the main electrodes to effect
resistive heating of the melted product at the nozzle. ~owever,
except for stating that auxiliary power to the nozzle is turned
on after the nozzle assembly has been properly positioned,
Hartwig prov:des no teaching of how the suggested resistive
heating of the melted product adjacent the nozzle is to be accom-
plished. Instead, Hartwig concentrates on the structure of cool-
ant passages in the nozzle assembly. ,
U.S. Patent NoO 3,147,328 issued to Le Clerc deBussy dis-
closes an electric glass making furnace which employs: three
primary electrodes angularly spaced 120 degrees apart in a plane;
a first conductive disc positioned along a line perpendicular to
the plane of the main electrodes and which passes through the
center of the three primary electrodes, and with the first disc
having a passageway through which melted glass may pass out of
the vessel; a plurality of auxiliary starting electrodes located
above the plane of the three primary electrodes and moveably
positioned adjacent the opening of the passageway in the first
disc; and a second disc moveably positioned along the above~
mentioned line of the first disc to form a slot between the first
..3~
and second discs which slot is substantially on the same plane as
the median plane of the primary electrodes.
In operation of the _e Clerc deBussy device, with the second
; disc in a separated position, the starting electrodes are moved
together three centimeters from each other adjacent the opening
of the passageway in the first disc, and are electrically ener-
gized to melt glass adjacent the first disc. The glass between
the starting electrodes is also heated with a blow pipe. The
~starting electrodes are withdrawn as the glass begins to melt and
`the primary electrodes are energized. When the glass adjacent
the first disc is in a liquid state, the second disc is brought
into position above the first disc and is also supplied with
electrical energy.
According to Le Clerc deBussy, in the course of normal oper-
ation, a major part of the current in the primary electrodes
travels from a primary electrode through the glass, from the
glass to the two discs, and then to the glass and finally to
another primary electrode. The electrical circuit diagram sup-
plied with Le Clerc deBuss_ shows the primary electrodes to be
energized by a three-phased current source, and shows the first
and second discs to be energized by single-phase current drawn
from the main three-phase power supply.
Le Clerc deBussy recognizes that the hottest region in the
molten glass is created between the two discs and the primary
electrodes. However, the electrical and mechanical configuration
of Le Clerc deB ssy does not provide control of temperatures
adjacent the passageway which would be sufficient to provide for
high volume melting of fly ash as is reauired in a high volu,e
mineral wool manufacturing process. Instead, according to Le
Clerc deBussy, only a small stream of glass is pulled through the
-3-
slit between the two discs and sucked thro~gh the passâgeway of
the first, lower, disc.
Other examples of electronic furnaces are provided by U.S.
Patent Nos. 3,876,817 and 3,659,029 also issued to Le Clerc
deBussy and by ~.S. Patent No. 3,983,309 issued to Faulkner et
al. However, none of these additional patents teaches a furnace
;arrangement or method of operation which provides for the
required amount of temperature control to accomplish large scale
melting of fly ash.
10 ~ It is, therefore, an object of the present invention to
provide a furnace and method of operation which can effectively
convert large quantities of fly ash into mineral wool.
Another object of the present invention is to provide a fur-
nace and method of operation which permits large scale conversion
of fly ash into mineral wool through the use of multiphase elec-
tric current;
A further object of the present invention is to provide an
electronic furnace and method which is capable of electronically
generating a large amount of heat at a precisely controlled tem-
2J perature over an exit orifice of a mel~ing vessel in ord~r to
permit large amounts of fly ash immediately over that orifice to
be raised to a precise temperature and to permit controlled flow
of that fly ash through the orifice to produce large quantities
of mineral wool.
Additional objects and advantages of the invention will be
set forth in part in the description which follows, and in part
will be obvious from the description or may be learned by
practice of the invention. The objects and advantages of the
!linvention may be realized and obtained by means of the instru-
mentalities and combinations particularly pointed out in the
appended claims.
Summary of the Invention
; To achieve the foregoing objects, and in accordance with the
purposes of the invention as embodied and broadly described
herein, a melting furnace is provided which comprises: (a) a
vessel for receiving product to be melted, the vessel having a
product exit orifice; (b) a plurality of primary electrodes for
defining primary current paths adjacent the orifice; (c) a con-
trol electrode means for defining a current path to the orifice;
and (d) a circuit means for energizing the primary electrodes
with multiphase current and for time-sharing the multiphase cur-
rent with the control electrode.
It is preferable that the vessel include a nozzle which
defines the product exit orifice, the nozzle having an upper sur-
face which contains the orifice, a channel having a smallerinternal diameter than the orifice which channel extends through
the nozzle, and a conical indent on the upper surface which coup-
les the orifice to the channel. The nozzle preferably further
includes a lower surface opposite the upper surface having an
opening to the channel, the opening being surrounded by a convex
proturbance of the lower surface. It is also preferable that ,he
circuit for energizing the primary electrode and for time-sharing
the multiphase current with the control electrode also provides a
return path for the multiphase current through the nozzle.
In a more narrow sense, the present invention contemplates a
melting furnace comprising: (a) a vessel for receiving product
to be melted, the vessel having in a lower po~tion thereof a
nozzle which contains an upper surface, and a product exit ori-
fice in the upper surface through which melted product may pass
30 1l out of the vessel; (b) first, second and third primary electroaes
for defining primary current paths between the electrodes to heat
product adjacent the orifice, with the primary current paths and
orifice lying in the same plane; (c) a control electrode having
an electrically conductive surface located within the vessel on a
line which is both perpendicular to the plane and passes through
the orifice, the electrically conductive surface of the control
;electrode being moveable along that line; and (d) a circuit for
; sequentially replacing each pri~ary electrode electronically with
the control electrode.
10 ; It is preferable that the above-mentioned circuit for
sequentially replacing each primary electrode electronically with
the control electrode includes the capacity for controlling the
replacement of each primary elec~rode in response to the tempera-
ture of the product passing through the orifice and/or in
response to the rate of flow of product through the orifice.
That circuit also preferably further includes the capacity for
altering the position of the control electrode in response to the
temperature of product passing through the orifice and/or in
response to the rate of flow of product through the orifice.
The furnace contemplated by the present invention in a pre-
ferred embodiment further includes the capacity for altering the
position of melted product adjacent to the orifice. This capac-
ity is preferably achieved by providing inner and outer side
walls to form the vessel, and providing a plurality of fluid flow
passages in the side walls of the vessel for cooling selective
portions of the vessel. These fluid flow passages are positioned
vertically adjacent one another in the side walls of the vessel.
Accordingly, selective control of the rate of coolant flow
ithrough the fluid flow passages affects the positioning of melted
product adjacent the orifice.
.
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It is also contemplated to be within the scope of the
present invention to provide a method for controlling the melting
of product in a vessel having a nozzle which defines a product
exit orifice, a plurality of primary electrodes which define
primary current paths adjacent the orifice, and a moveable elec-
trode, comprising the steps of: (a) energizing the primary elec-
trodes with sufficient multiphase current to maintain a pool of
melted product adjacent the orifice; (b) positioning the moveable
electrode closer to the orifice than any of the primary elec-
trodes; and (c) sequentially replacing each primary electrodeelectronically with the moveable electrode.
The above-mentioned method also preferably includes the
steps of regulating the replacement of each primary electrode in
accordance with the temperature of product passing through the
orifice, varying the positioning of the moveable electrode in
response to the temperature of product passing through the ori
fice; regulating the replacement of each primary electrode in
accordance with the rate of flow of product through the orifice;
and/or controlling the positioning of the moveable electrode in
response to the rate of flow of product through the orifice.
The method of the present invention further preferably
includes the step of melting solidified product in the orifice of
the nozzle by moving the moveable electrode adjacent to the ori-
fice, and supplying electrical current between the moveable elec-
trode and the nozzle sufficient to melt the product in the-orifice. The method further preferably includes the step of ter-
minating the flow of melted product through the orifice by with-
drawing the moveable electrode from the vicinity of the orifice.
The step of terminating the flow of melted product also includes
the step of increasing the coolant flow adjacent the nozzle.
The accompanying drawings which are incorporated and constitute
a part of the speciEication, illustrate a preferred embodiment of the
invention, and , together with the general description of the inven-tion
given above and -the de-tailed description of the preferred embodiment given
below, serve to explain the principles of the invention.
Fig. 1 schematically illustrates a melting furnace incorporating
the teachings of the present invention;
Fig. 2 is a cross-sectional view of a nozzle and nozzle support
incorporating the teachings of the present invention;
Fig. 3, which appears on the same sheet as Fig. 1, is a top view
of a schematic illustration of the positioning of primary electrodes in
accordance with the teachings of the present invention;
Figs. ~A and 4B provide a sectioned side view, and a top view
of a vessel incorporating the teachings of the present invention;
Figs. ~A, 5B, and 5C provide a top view, end view, and side view,
of a primary electrode in accordance with the teachings of the present
invention;
Fig. 6 provides a side view of a control electrode in accordance
with the teachings of the present invention; and
Fig. 7, which appears on the same sheet as Fig. 2, provides an
electrical diagram of a control circui-t incorporating the teachings of the
present invention.
The above general description and the follaw~g detailed des-
cription are merely illustrative of the generic invention and additional
modes, advantages, and particulars to this invention will be readily
suggested to those skilled in the art without departing from the spirit and
scope of the invention.
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36~
Reference will now be made to the present preferred embodimen-t
of the invention as illustrated in the accompanying drawings.
In Fig. 1 there is schematically shown a vessel 10 for receiving
product 12 to be melted, such as fly ash. me fly ash is introduced into
vessel 10 through an opening 14 at the top of the vessel. A second opening
or product exit orifice 16 is located near the bottom of the vessel to permit
melted product to exit the vessel. ~lore specifically, orifice 16 is formed
in a nozzle 18, which nozzle is in turn mounted on a nozzle assembly 20.
A cooling mechanism 22 is provided within nozæle support 20 and is controlled
by a nozzle coolant valve 24. First, second and third primary electrodes 26,
28, and 30 are shown positioned within vessel 10 to surround orifice 16.
A more detailed description of vessel 10, nozzle 18, nozzle
su~port 20, and primary electrodes 26,28 and 30 is provided below with
respect to Figs. 2-5.
Fig. 2 shows a cross-sectional view of nozzle 18 and nozzle
support 20. More specifically, nozzle 18 comprises a hollow cylinder 40
preferably constructed of moly~denum which is capable of withst~nding
exposures to melted product up to about 4700 Fahrenheit degrees. If the
temperatures of melted product adjacent orifice 18 is intended to exceed
4700 degrees Fahrenheit, ~ ~n orifice 18 may be fabricated of graphite.
m e top of cylinder 40 is closed with a plug 42 also made of moly~denum.
Cylinder 40 and plug 42 preferably canprise a single integral structure.
Plug 42 has an upper surface 44 which contains orifice 16. A channel 46
passes through plug 42 which channel has a
_ g _
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smaller internal diameter than the diameter of orifice 16 and
'~hich channel extends through plug 42 to the interior of cylinder
40. A conical indent 48 on upper surface 42 couples orifice 16
to channel 46.
Plug 42 of nozzle 18 further includes a lower surface 50
opposite upper surface 44 and having an opening 52 to channel 46.
Opening 52 is surrounded by a convex proturbance 54 of lower sur-
face 50.
The diameter of channel 46 is preferably on the order of two
and one half inches to accommodate a flow rate of 40,000 lb/hr.
of melted fly ash. The length of channel 46 is preferably six
times greater than the diameter of channel 46. The long length
of channel 46 and the upper angle created by conical indent 48
cause a stream of melted p;od~ct to stabiliz^ as the product
flows through nozzle 18. The convex proturbance 54 on lower sur-
face 50 prevents the melted material from splashing or wicking to
the side of nozzle support 20 upon exit-from nozzle 18.
Nozzle support 20 is preferably made of copper, stainless
steel, or black iron. Support 20 comprises an outer conical wall
60, and an inner conical ia]l 62 which form a watertight com-
par~ment 64 therebetween. Pipe 66 extends into compartment 64
and terminates at end 68 adjacent nozzle 18. A second pipe 70
also extends into compartment 64, and terminates at end 72 near
the lower portion of nozzle support 20. Accordingly, coolant
such as water may enter compartment 64 through pipe 66 and exit
compartment 64 through pipe 70. Nozzle 18 is mounted in elec-
trical contact, and heat conducting contact with nozzle support
20 by means of threads 74 to the upper end of support 20 and is
" therefore cooled in accordance with the temperature of support
20.
--10--
513~
No~zle support 20 is mounted to the base of vessel 10 by
support 80. Support 80 includes a circular channel 82 dimen-
sioned to receive the lower end of support 20. Channel 82 is
filled with insulating cement 84 of high alumina no. 22, to
maintain electrical isolation between the electrical combination
of nozzle 1~ and support 20, and the walls of vessel 10. Base 82
contains a centered circular opening 86. Opening 90 in the base
of vessel 10 permits melted product to pass from the interior of
nozzle support 20, through opening 86 of base 80, to the exterior
of vessel 10. Insulators 91 and 93 are also provided in the
vessel of nozzle 10 to electrically isolate pipes 66 and 70 from
vessel 10.
To protect nozzle 18 from oxidation, the interior of nozzle
support 20 may be flooded with an inert gas such as nitrogen.
Specifically, a ring-spray valve 92 may be positioned in the
interior circumference of support 20, and contain openings 94 for
release of nitrogen in the direction of nozzle 18. A supply pipe
96 is provided to deliver nitrogen to spray nozzle 84.
Figs. 4A and 4B show a preferred config-lration of vessel 10,
having exterior side walls 100 and interior side walls 102 of
vessel 10. Baffles 104, 106, 108 and 110 extend vertically up
the sides of vessel 10 to divide the opening between side walls
100 and 102 into four separate fluid-tight compartments 112, 114,
116, and 118. Each compartment 112-118, has its own input port
120, and its own exit port 122. Vessel coolant valves 124 con-
trol the flow of coolant into input ports 120. Thus each com-
partment 112-118 is positioned vertically adjacent another in the
side walls of vessel 10, and, through the independent operation
of valves 124, each compartment provides an independent means for
cooling a particular vertical quadrant of vessel 10.
!
--11--
In Fig. 4A, an opening 126 is shown through the side of vessel 10
which receives one of prim~ry electrodes 26, 28, or 30.
Figs. 5A-5C illustrate a preferred ~mbodiment of primary electrodes
26, 28 and 30. me primary electrodes each include a fan-shap~d tip 150
which is made out of moly~denum or graphite. Tip 150 is supported by an
electrode assembly 152 which includes a heavy wall, hol~low pipe 154 con-
structed of stainless steel, copper, or black iron. Tip 150 has a cylindrical
portion 156 which slides into first end 158 of pipe 154 and is held rigidly
in place by pipe 154. The remaining portion 160 of the in-terior of pipe 154
is hollow. A fluid input pipe 162 extends frcm the extreme end 164 of pipe
154 opposite tip 150 into interior section 160. Fluid input pipe 162
terminates adjacent the beginning of cylindrical portion 156 of tip 150.
A pipe cap 166 permits insertion of pipe 162 i~to the interior of pipe 154
and seals end 164 of pipe 154. Outlet pipe 168 is inserted through the side
walls of pipe 154 adjacent cap 166 and provides an exit for coolant intro-
duced into interior space 160 through pipe 162.
A pressure valve 170 also communicates through the walls of pipe
154 to interior passage 160 to privide a release escape in the event any
steam pockets build up within the interior of the electrode.
An insulation block 172 surrounds pipe 154 and permits electric-
ally insulative mounting of the primary electrodes into vessel 10.
As can best be seen from Figs. 2 and 3, primary electrodes 26,
28 and 30 are positioned to define pri~Ery current paths 180 adjacent that
portion of nozzle 18 which defines- product exit orifice 16. Preferably,
25 conductive surfaces 182 of electrodes 26, 28 and 30 are convexed in shape,
and are positioned to tend to equalize the length of primary current paths
180 between adjacent primary electrodes 26, 28 and 30.
- 12 -
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As may best be seen frcm Fig. 2, the bottom surface 184 of tips
L50 lies generally in the same plane as upper surface 44 of nozzle 18 in
which orifice 16 is defined. mUs, primary current paths 180 between elec-
trodes 26, 28 and 30 also lie substantially in the same plane as upper sur-
face 44. This orientation of electrodes 26, 28 and 30 helps to assure that
a pool of melted product will lie immediately above orifice 16.
In accordance with the present invention there is provided
control electrode means for defining a current path to the means which def~
ines the product exit orifice. For example, as illustratively shown in Fig.
1 a control electrode 200 is provided having an axis position collineæ
with the axis of channel 46 in nozzle 16. Control electrode 200 is mounted
to be moveable along its longitudinal axis by means of a motor, hydraulic
lift, or other control mechanism schematically shown by motor 202 in Fig. 1
A more detailed diagram of a preferred e~bodiment of control
electrode 200 is shown in Fig. 6. A solid cylindrical electrode tip 204
is provided at one end of electrode 200. Tip 204 is preferably constructed
of molybdenum or graphite, depending upon the temperature of the bath which
tip 204 must sustain. A hollow support pipe 206 is pro~ided to hold electrode
204 in a desired position. A threaded stud 208 is provided at one end of
support pipe 206 for attaching electrode tip 204 to support pipe 206. An
electrically conductive pipe cap 210 is provided at the opposite end of
support pipe 206 from tip 204. The interior of support pipe 206 between
threaded stud 208 and pipe cap 210 forms a hollow fluid-tight passage 212.
An input ooolant pipe 214 is inserted through a wall of pipe 206 and term-
inates in interior passage 212 near threaded stud 208. An exit path is
provided from passage 212 through exit pipe 216 positioned coincident with
the longitudinal axis of pipe cap
.'~ - 13
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210 An electrical connector 218 is also coupled to pipe cap 210
~to provide electrical access to electrode 200.
Further in accordance with the present invention, there is
provided circuit means for energizing the primary electrode means
with multiphase current and for time-sharing the multiphase cur-
rent with the control electrode means.
As illustratively shown in Fig. 1, there i5 provided a con-
trol circuit 300 which provides over lines 302, 30~, and 306,
~-S~'~' ~/f
three phase current to primary electrodes 26, 28 and 30,\. A line
303~,electrically connects control circuit 300 to control elec-
trode 200. As will be explained in more detail in connection
with ~ig. 7, control circuit 300 operates to time-share the mul-
tiphase current supplied over lines 302, 304, and 306 with the
control electrode 200 over line 308. More specifically, control
circuit 300 operates to sequentially replace each primary elec-
trode 26, 2B and 30, with control electrode 200. When so
replaced, the current intended for primary electrode 26~ 28 or 30
instead passes through control electrode 200. This creates an
electrically imbalanced load which causes generation of an addi-
tional current path from control electrode 200 to nozzle 18.
This additional control path increases the temperature of product
adjacent the additional current path in the vicinity of orifice
16. The control of current through this additional current path
provides a vehicle for precisely regulating the temperature of
product adjacent orifice 16. The greater the amount of time con-
trol electrode 200 is electrically positioned in place of one
primary electrode 26, 28 or 30, the greater the amount of current
in the additional current path adjacent orifice 15.
, .. . ..
3~
Preferably, the amount of time--sharing permit.ted by control
circuit 300 is dependent up~n the temperature of product passing through
orifice 16. The temperature of product passing through orifice 16 is, in
turn, determined by temperature sensor 320 which is positioned below open-
ing 90 of vessel 10. Temperature sensor 320 may, for example, c~nprise a
device commercially identified by the n~ne Williamson Temperature Control.
The output of temperature sensor 320 is coupled by line 322 to an input of
control circuit 300.
The amount of time-sharing by control electrode 200 may also be
varied depending upon the rate of flow of product through orifice 16. Tb
determine the rate of flcw of product through orifice 16 one or more load
cells 326 continuously measure the weight of vessel 10 and transmit a signal
indicating that weight over line 328 to control c.ircuit 300. The signaL over
line 328 is, therefore, indicative of the rate of flow of product through
orifice 16.
The physical distance between conductive surface 220 at the end
of control electrode 200 and orifice 16 also affects current flcw adjacent
orifice 16. T~e closer conductive surface 220 is to orifice 16, the greater
the temperature of product adjacent orifice 16 for a given amount of current.
me distance between conductive surface 220 and orifice 16 is controlled by
an output signal from control circuit 300 delivered over line 324 to motor
202.
Accordingly, control circuit 300 governs the position of conduc-
tive surface 220 of control electrode 200 as a function of the temperature
of the product passing through orifice 18 as determined by temperature
sensor 320, and/or as a function of the rate of flow of product through
orifice 16 as determined by the operation of load cell 326.
3~
A schematic diagram of control circuit 300 is prcvided in Fig. 7.
As shown in Fig. 7 a multiphase power scurce 400 is coupled to a delta
configuration multiphase transformer 402. Secondaries 404, 406, and 408 of
power transform~r 402 are connected in a wye configuration. The common
point 409 of the wye configuration of secondaries 404, 406 and 408 is
coupled by line 410 to nozzle 18 to provide a return current path for
current passing through control electrode 200. Variable position taps 412,
414 and 416, are coupled through switches 418, 420 and 422, respectively,
to primary electrodes 26, 28 and 30. With switches 418, 420 and 422 in
position A, secon~aries 404, 406, and 408 are coupled respectively to
primary electrodes 26, 28 and 30. Although switches 418, 420 and 422 are
illustratively shown to be double-throw, single-pole switches, they may in
fact comprise portions of a high power SCR switching circuit such as the
Hallman Model No. PA-l, which may be opened or closed depending upon the
signals generated by control unit 424 over lines 426, 428, and 430, respect-
ively.
Switches 418, 420 and 422 are shown in Fig.7 to have second
positions B in which position these switches connect secondaries 404, 406,
and 408 respectively to control electrode 200 through line 308. Thus,
each switch 418, 420 and 422 is capable of electrically replacing or sub-
stituting a primary electrode 26, 28 and 30, respectively, with control
electrode 200. Preferably, switches 418, 420 and 422 are moved sequentially
frcm position A to position B and returned to position A at zero cross-over
points of the current appearing in secondaries 404, 406, and 408. These
cross-over points may be determined by cross-over point sensors 432, 434,
and 436 which are electrically coupled to secon~aries 402, 406 and 408,
respectively.
53~
The substitutions may last for as long as a single cyele, or for
several cycles, deFending upon the amount of current necessary to be diverted
to control electrcde 200 to maintain the desired temperature as deteeted by
temperature sensor 320, and/or the desired rate of flc~ as detected by load
cell 326. As additional current is requiredl the amount of substitution by
s~itches 418, 420 and 422 is increased by control unit 424. When the input
from load cell 326, and temperature sensor 320 indicate that less current
is required, the amount of substitution by switches 418, 420, and 422 is
decreased.
Additional control over the temperature adjacent orifice 16 is
provided by the operaticn of motor 202. ~hen additional temperature is re-
quired adjacent orifice 16, motor 202 may be operated by a signal from
control unit 424 over l.ine 324 to mo~7e surface 220 of eontrol eleetrode
200 closer to orifice 16, and, in the converse, to move surface 220 further
5 away when less temperature is required.
m e control unit 424 is also coupled by line 442 to nozzle
coolant valve 24, and by line 444 to vessel coolant val~res 124. As stated
before, nozzle coolant valve 24 controls the flow of eoolant through cooling
meehanism 22 of nozzle support assembly 20. More specifically, valve 24
controls the flow of fluid through pipes 66 and 70 in Fig. 2. Vessel coolant
val~7es 124 are illustratively shown in Figs. 4A and 4B as governing the flow
of coolant allc~ed into chambers 112, 114, 116 ~n~ 118 of vessel 10. As
will be explained below, the operation of nozzle coolant valve 24 permits the
the selective freezing of procluct in orifice 16 to elose off and terminate~
the flow of procluct through nozzle 18, and the operation of vessel coolant
valves 124 operate to help selectively position the pool of melted product
adjaeent orifiee 16.
3.~ ;ic~
In operation, product to be melted, preferably minerals ccmmonly
referred to as fly ash, is intxoduced into vessel 10 through opening 14,
in sufficient quantity to covex orifice 16, pr.imary electxodes 26, 28 and
30, and control electrode 200. TV begin the melting process, control electrode
200 is moved into a position whexeby lower conductive surface 220 is immed-
iately adjacent, but not touching, uppex surface 44 oE nozzle 18.
Electrical energy .is thereaft~x supplied to primary electxodes26, 28 and 30 through secondaries 404, 406 an~ 408. In addition, switches
418, 420 and 422 are opexated to provide time-sharing of the current supplied
to primary electrodes 26, 28 and 30 with control electrode 200. The amount
of time-sharing is increased until the temperature between lower surface 220
of control electrode 200 and upper surface 44 of nozzle 18 is sufficient
to melt product adjacent orifice 16. As the melting process continues, nozzle
control valve 24 is opened to provide coolant flow through pipes 66 and 70
of nozzle support assembly 20 sufficient to assure that the pcol of melted
product adjacent orifice 16 does not come in contact with nozzle support 20.
AS the pool adjacent orifice 16 grows, conductive surface 220 of
control electrode 200 may be withdrawn through operation of motor 202 from
surface 44 of hozzle 18 and the amount of time-sharing by control electrode
200 may be reauced through the operation of switches 418, 420 and 422.
When the pool of melted product finally reaches conductive sur-
faces 182 of primary electrodes 26, 28 and 30, the operation of control
electrode 200 may be temporarily suspended, and conductive surface 220 may
even be moved even further from surface 44 of nozzle 18. When the conductive
pool reaches
- 18 -
conductive surfaces 182 of prim~ry electrode 26, 28 and 30, a low current
between the primary electrodes may maintain that pool in a melted state.
If it is not desired to begin pouring operation, nozzle control valve 24
may be further opened to increase the cooling of nozzle support assembly
20, and thereby solidified melted product in p~ssage 46 of nozzle 18 to
plug nozzle 18 aad prohibit additicnal flow of product fron the melted
pool thrcuyh nozzle 18.
m ereafter, a pour operation may begin by moving control electrode
200 back toward nozzle 18, until conductive surface 220 of control elec~rode
200 is again immediately adjacent, but not touching, upper surface 44 of
nozzle 18. The time-sharing process then commences, within time-sharing of
current frcm secondaries 404, 406, and 408 with control electrode 200,
until the intensity of current between control electrode 200 and nozzle 18
is sufficient to melt out the plug which had been formed in channel 46 of
nozzle 18. m ereaEter, co~ductive surface 220 of control electrode 200 is
once again moved back from upper surface 44 of nozzle 18, but preferably
remains at a position cle~rly closer orifice 16 than any of primary electrodes
26, 28 or 30. For example, if passage 46 has an internal diameter of approx-
imately two and one-half inches, conductive surface 220 is ideally position-
ed on the order of one-half of an inch ab~ve upper surface 44 in order to
accomplish melting of product solidified in channel 46, and is thereafter
preferably positioned anywhere bet~een one-half to three inches above sur-
face 44 depending upon the desired pour rate, the conductivit.y of the
product to be melted, the amount of curre~t supplied by secondaries 404,
406 and 408, and the amount of time-sharing provided by switches 418, 420
and 422.
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~ 3
Measurement by load cell 326 indicates a continuous weight
of vessel 10 and product 12. With a known fixed amount of
product 12 being continuously added to vessel ]0, for example
40,000 lbs per hour, a rate of flow of product through orifice 16
less than 40,000 lbs per hour will be evidenced by an increase in
the reading of load cell 326, and a pour rate of greater than
40,000 lbs per hour will be indicated by load cell 326 as a dec-
rease in the overall weight of vessel 10 and product 12. Control
-circuit 300 must be set up to either increase the amount of
time-sharing by control electrode 200 and/or decrease the amount
of distance between conductive surface 220 of control electrode
200 and orifice 16 in the event load cell 326 indicates that the
pour rate must be increased. A converse operation must occur
through the operation of control circuit 300 in the event load
cell 326 indicates that the pour rate must be decreased.
Similarly, temperature of melted product passing through the
orifice 16 is detected by temperature sensor 326, and used to
control the operation of control circuit 300.
Furthermore, the temperature of coolant passing through com-
partments 112, 114, 116, and 118 of vessel 10 may be continuously
detected to determine the location of the melted pool formed by
electrodes 26, 28 and 30. If, for example, the temperature of
coolant exiting the cornpartment 114 on the extreme left-hand side
of vesssel 10 is warmer than the coolant exiting the compartment
118 on the right-hand side of vessel 10, this indicates that the
pool of melted product is not directly centered over orifice 16,
and instead has shifted to the left. To control the shift of the
position of the pool of melted product, vessel cooling valves a25
are reset to increase the relative flow OL coolant through the
-20-
left-hand quadrant of vessel 10, and thereby shift the pool of
melted product back into a centered position over orifice 16.
Accordingly, the present invention provides apparatus and
methods for definitively controlling the temperature of product
immediately adjacent a product exit orifice of a vessel, the flow
rate of product passing through that orifice, and the position of
a pool of melted product surrounding that orifice.
~ dditional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader as-
pects is therefore not limited to the specific details, represen-
tative apparatus, an illustrative example shown and described.
Accordingly, departures may be made from such details without
departing from the spirit or scope of applicantls general inven-
tive concept.