Note: Descriptions are shown in the official language in which they were submitted.
5~
SPECIFICATION
This invention relates to an improved process and
system for effecting pneumatic conveyance of solids, and has
for its particular object to provide an improved process and
apparatus for effecting the pneumatic transport of solids at
consistent and controlled rates and high solids to gas ratios.
Prior art Patent No. 3,230,016 dated January 18, 1966
describes a novel and successfully used method of feeding solids.
However, that process and apparatus have limitations for some
applications which have been overcome by the present invention
and thus broaden its commercial importance and potential
acceptance. The invention described herein resides in an improved
process for effecting continuous, non-cyclic conveyance of
particulate or powdered solids, in a completely automatic
mode~ whereby it is possible for the user to program the feed
rate of a single or multiple ~treams of solids into a process
operating at any desired pressure from super-atmospheric to sub-
atmospheric levels and to measure and record the amount of
solids being fed and transported.
Prior art systems are available for feedlng solids
continuously but these systems utilize a multiplicity of vessels,
the feed from which is cyclically interrupted, and/or mechanically
rotated parts such as rotary valves which are subject to wear
and leakage and are not well adapted to high pressure applications
particularly where mul~iple streams are required such as when
feeding pulverized coal to a blast furnace having typically as
many as twelve tl2)to forty (40)tuyeres.
The process and equipment described in this inveniion
are particularly useful for the feeding of particulate or
pulverized coal ~o the tuyeres of a blast furnace for the replace-
ment of expensive liquid or gaseous hydrocarbons currently us~d
2 1~ ~
~ ~P~53~
as auxiliary blast furnace fuel, or in those blast ~urnaces
that do not employ auxiliary fuel injection this invention permits
the substitution of 10% to 30-~ of the ex~ensive burden coke
which is less expensive coal. In some blast furnace operations
it is desired to adjust the amount of injected fuel in one or
more tuyeres in proportion to the change in blast air for those
particular tuyeres. In these applications the proportionality
signal from the flow in each tuyere can be utilized to adjust
the flow of coal by the unique characteristics of the process
of this invention. In some prior art feeding systems it was a
desired cha.acteristic to maintain a constant ratio between the
coal fed and the accompanying gas. In the application of the
sub~ect invention to blast fuxnace operation it is unnecessary
and undesirable to maintain the solids/conveying gas ratio
constant since the feeding system employs a high solids:gas
ratio in any event and the amount of conveying gas is therefore
relatively unimportant in proportion to the normal amount of
blast air. The maintenance of a fixed solids: g~s ratio is un-
desirable because it is a needless instrumentation expense and
it removes flexibility of other control functions.
A similar use of this invention is for the feeding of
finely ground coke bre~ze or coal to the tuyeres of iron melting
cupolas to provide operating economies and areater o~erational
~lexibility.
By means of a novel logic and electronic signal system
t~e weight of material in the injector ~essels is transformed
to a feed rate measuring and control system which is uni~ue
primarily because the rate of flow from the Primary Injector is
being measured and controlled substantially continuously even
during ~he period when a batch of material is being transf~rred
753~
from the Storage Injector to the Primary Injector to replenish
the portion of material fed over a period of time. A further
optional but desirable feature of the invention is the use of a
special pressure balanced e~pansion joint between the Storage
S Injector and Primary Injector which because of its pressure
compensating feature exerts a very low thrust load on the vessels
due to the pressure therein, thus permitting very accurate
weight measurements by the load cell systems proviaed with the
injector vessels.
Accordingly, an important aspect of the invention resides
in an improved process for effecting pneumatic conveyance of
particulate solid materials comprising introducing a gas into the
lower portion of a mass of such material maintained in a container,
hereinafter referred to as a Primary Injector vessel, under
positive pressure thereby "fluffing" but not fluidizing the
material, flowing said material admixed with gas downwardly from
the Primary Injector vessel through one or more annular passages
into one or more connecting conduits, introducing additional gas
into sa.id conduit, or each of said conduits, upstraam from behind
the point of introduction o~ said solids~as mixture thereinto
and conductin~ said solids to ultimate use, providing a second
container, hereinafter referred to as the Storage Injector, or
storage vessel which is isolated from the Primary Injector by
cyclically controlled valves, located immediately above said
~5 Primary Injector and which performs the function o~ a lock-
~opper, or optionally located in the same or different level ~rom
the Primary Injector but interconnected by transport pipe and
valves in which case the container is referred to as a Feed
Injector. The purpose of the Storage Injector or ~eed Injector
is to automatically re~ill the Primary Injector on demand and in
37
such a manner that the flow of solids from the Primary Injector
is not interrupted or changed by reason of the refilling operation,
and during which time as well as during times when the filling
operation is not taking place the weight rate of material being
~ed is being measured and controlled by no~el means. Said means
incorporates the use of load cell systems utilizing weight
measurement cells mounted within the structural support systems
for the injector vessels and electronic devices as hereinafter
described.
Two optional electronic control systems ma~ be utilized
for the automatic control of the feed rate of solids flowing
from the Primary Injector. In both such optional methods the
load cell system produces a millivolt electrical signal which
decreases in proportion to the weight of material in the Primary
Injector vessel. In optional Method A, in addition to the
millivolt signal from th~ load cell system, an electronic device
referred to as a ramp generator produces an electronic signal
proportional to the desired weigh~ rate of solids flow ~rom the
Primary Injector o~ the eed system. This signal is
continuously and automatically compared to the electric signal
from the load cell system. If there is a deviation in the two
values, the pressure in the Primary Injector is automatically
changed to adjust the feed rate by employing the ~eeding system
process control fe~tures e~plained herein. In optional Method B,
the loss~in-weight si~nals ~rom ~he load ceïl 6ystem is converted
to a rate ~ignal by a microprocessor. ~n adjustable eed rate
signal is generated by a supplemental microprocessor unit. This
signal is compared to that generated ~rom the load cell system
and any deviation in the two values causes the feed rate to be
3~ adjusted as in optional ~.ethod A~
3'7
In accorclance with a broad aspect of the invention there is
provided a process for pneumatically conveying solid particles at a con-
trolled rate through a conduit system to a delivery point wherein the over-
all transit includes a significant horizontal component, the steps of:
(a~ producing a fluent mass of said particles moving down-
wardly in a zone which communicates at the bottom thereof directly through
a topside connection into said conduit system,
(b) arranging a portion of said solid particles in the lower
part of said zone into a form approximating a substantially symmetrical
inverted-conical annulus mass converging toward the axis of said cone and
said topside connection,
(c) forming a particulate solids-gas mixture having a minor
proportion by weight of said gas mixed therewith by introducing and dis-
tributing a gas into said conical annulus mass of particles at a rate
sufficient to place the same in the lower part of said zone in a fluent
condition without active fluidization of same and to maintain said zone
under positive pressure relative to the pressure at ssid delivery point,
(d) continuously flowing said particulate solids-gas mixture
from the bottom of said zone downwardly through said topside connection
and into a mixing zone in said conduit system,
(e) introducing a stream of additional gas at,a controlled
rate into said particulate solids-gas mixture after it has passed through
said topside connection in lateral line of flow relative to said stream of
additional gas to form a final gas-solids mixture, and
(f) conducting said final gas-solids mixture out of said mix-
ing zone as a continuation of the flow to said delivery point.
In accordance with another broad aspect of the invention there
is provided apparatus for effecting pneumatic conveyance of particulate
solids comprising:
(a) container means having a lower part which comprises an
inverted conical section,
-5a-
~ !
.. ... .
37
(b~ a double cone baffle mounted centrally within said con-
tainer means composed of two cones each of which is smaller than said
conical section and which are joined base to base and with an axis common
to that of said container means with the wall of the lower cone of said
double cone baffle being substantially parallel to the coextensive wall
of said inverted conical section and forming an annular space therebetween,
(c) said container means having a solids charging inlet near
its top and being adapted to hold gases at elevated pressures,
(d) means for introducing a gas into said annular space,
(e) means for controlling the pressure in said container
means,
(f) means forming a mixing chamber under said container
means with an inlet passageway connecting the bottom of said inverted
conical section with the top of said mixing chamber, and said mixing
chamber having a discharge passageway,
(g) means for supplying a controllable amount of gas to one
side of said mixing chamber,
(h) a conduit system,
(i) means to conduct particulate solids pneumatically out
2Q of said discharge passageway of said mixing chamber and to said conduit
system,
(j) supply means for supplying a predetermined amount of
particul.ate solids to the upper zone of said container means during the
period when said particulate solids are flowing from said mixing chamber
into said conduit system,
(k) means for controlled venting of gas from said container
means during the periods when said supply means is supplying solid
material to said container, and,
(1) means for measuring the weight rate of solid material
3Q flowing from said container.
In accordance with another broad aspect of the invention there
-5b-
~ '7~37
is provided apparatus for eEEectlng pneumatic conveyance of particulate
solid materials comprising:
(a) a container, the lower part of which comprises at least
one inverted conical section having mounted centrally therewithin a double
cone baffle composed of two cones joined base to base and arranged so that
the walls of the lower cone of said double cone baffle are substantially
parallel to the walls of said inverted conical section,
(b) a solids charging inlet near the top of said container,
said inlet being provided with means for withholding internal pressure,
(c) means for introducing and distributing a gas into the
annular space between said lower cone and said inverted conical section,
(d) means for controlling the pressure in said container,
(e) a mixing chamber under said container with a passageway
connecting the bottom of the inverted conical section o:E said container
with the top of said mixing chamber,
(f) means for supplying a controllable amount of gas to one
side of said mixing chamber,
(g) means to conduct material pneumatically out of said mixing
chamber,
(h) means for supplying a predetermined amount of particulate
solid material to an upper zone above said lower part oE said container
during the period when said solid material is flowing from the mixing
chamber into a conduit system,
(i) means for controlled venting of gas from said container
during the period when said means (h) is supplying solid material to
the container,
(j) means for measuring and contro:Lling the weight rate of
solid material flowing from container.
~'7~37
A manner of carrying the invention into effect will
now be describea with particular reference to the accompanying
drawings wherein:
FIGURE 1 is a flow diagram of the process of this
invention amplified to show th~ general external shape and
relative positioning of the principal apparatus elements:
FIGURE 2 is a side view partly in cross section of a
discharge zone from the Primary Injector vessel and associated
equipment;
FIGURE 3 is a plan view taken along line 3 - 3 of
FIGURE 2;
FIGURE 4 is a side view partly in cross section of the
discharge zone of the Storage Injector;
FIGURE 5 is a sectional side view of the gas-solids
mixing unit or T;
FIGURE 6 is a side view in cross section of a single
discharge outlet in a multi-outlet nest of a Primary Injector
vessel having a total of eight (8) feed outlets; and
FIGURE 7 is a plan view of the entire multi-outlet
Primary Injector vessel taken on line 7 - 7 of FIGURE 6.
In the flow diagram of FIGURE 1, particulate solids
of appropriate particle si~e for end use which have been charged
through valve lOd are discharged from storage vessel 10 into
Primary Injector 12 through valve 14b in conduit 14. A compatible
gas is introduced into the lower zone of Primary Injector vessel
12 through pipe 16 and valve 16a and into Storage Injector 10
through pipe 18 by means of valve 18a or through pipe 18c by
means of valve 18b in the manner hereinafter described. Discharge
conduit 20 leads rom the bottom of Injector vessel 12 through
valve 22 into mixin~ unit 24 shown in detail in FIGURE 5. Gas is
'7S;3~
;i!~ supplied through gas flow control valve ~ to arm 26 of the
~ .~ ..., ,; .
mixing unit and the mixture of gas and solids is discharged from
arm 28 of the unit into apparatus 13 which generally represents
the process and/or equipment being supplied with material by
means of the subject invention.
From the upper zone of injector vessel 12 a gas dis-
charse conduit 30 leads to atmospheric discharge conduit 32 through
valve 34 and to Storage Injector pressuxe equalization conduit
36 which is provided with a valve 38.
One important feature of the invention resides in the
method of discharging the solids from the injector vessel 12
for entrainment in the conveying gas. Suitable apparatus
therefor is shown in detail in FIGURE 2. It will be noted that
the configuration of the bottom of vessel 12 is conical and
mounted centrally therewithin is double cone 40, the outer
surface of the lower inverted cone of double cone 40 being roughly
parallel to, and substantially spaced apart rom, the wall 41
of the conical bottom of vessel 12~ The spacing between double
cone 40 and wall 41 is, of course, subject to considerable
variation. Generally, the width of said annular passageway will
vary from about 1 to 3 times the width of bottom opening 49.
The apex of each of the cones of double cone 40 for best
efficiency describes an angle of about 45 although some
departure from this angularity in both directions is permissable
between the limits of approximately 27 and 60. This angle
depends on the properties of the material being processed. ~n
any case the angle of flare of the bottom vessel 12 must be
roughly in accord with that of the apex of the inverted cone o
double cone 40O It should also be noted that for some uses ~he
inverted cone may be truncated
~ ~37537
Extending through the conical wall 41 of the vessel
bottom are gas injection nozzles 42 which preferably lie somewhat
below the horizontal midsection or widest horizontal section of
double cone 40 as shown in FIGURE 2, or at said midsection, but
may in some cases be slightly above said midsection. These
nozzles 42 are supplied with gas from pipe 16, the flow thereto
being controlled by valve 44. A suitable deployment of nozzles
42 is shown in the plan view of FIGURE 3. Other spacing and
positioning of the nozzles 42 may be used within the contemplation
of this invention. For example the nozzles 42 may be mounted
completely inside the wall 41 of vessel 12, such as on the
inverted portion of double cone 40.
As has been indicated above, Storage Injector 10 may
be cvnstructed similarly to the Primary Injector 12 but prefer-
ably with approximately one-half its active volume; however,
for simplicity, it is preferred to employ the construction
illustrated in FIGURE 4. The double cone 40, attached to the
bottom wall by several spider flanges 46 (two shown), as, in
fact, the double cone is attached to the bottom section of vessel
10 serves the same purpose as in vessel 12. However, the gas
jets may be omitted when feeding free-flowing materials.
rrhe mixing unit 24 in which the particulate solid is
entrained in the conveying gas is shown in detail in FIGURE 5D
This is connected to conduit 20 below valve 22. The mixing unit
is provided near the upper inlet end with an orifice 54, of
frustoconical shape. Pipe 26 is the diluter gas inlet branch of
the mixing unit, and pip2 28 iS the outlet for the mixture of
gas and particulate material. The inlet branch is equipped
with an insert pipe 27 which has an inside dimater approximately
one-half that of the outlet branch 28.
53~
~ low diagram shown in FIGURE 1 also shows additi~nal
critical elements consisting of vessel support lugs lOa and
12a; load cells lOb and 12b, and vessel supports lOc and 12c.
Supports lOc and 12c must be integrated with an overall support
structure have sufficient strength and rigidity that movement
due to imposed operating loads can be accurately measured by
means of load cells lOa and 12b and not influenced by external
restraining forces. Expansion element 14a in line 14 is
provided to permit unrestricted movement ofvessel 12 due to the
change in weight of the contents of the vessel.
Instrument l~d provides an electric signal which is
proportional to the weight rate desired for the feeding system
and which rate is adjustable. Instrument 12e continuously
compares the output signal from the load cell system with the
signal from element 12d and sends a modulating signal to
instrument 12f which controls pressure regulator valve 16a.
Although the process of this invention can be carried
out using the single cone injector vessel of FIGW~E 2, it is
often desirable to employ an injector vessel having a plurality
of conical discharge ~ones when the material must be delivered
simultaneously to several points such as to the tuyeres of a
blast furnace. Such multi-cone apparatus is illustrated by
FIGURES 6 and 7, in which eight cones 60 are deployed around the
bottom of a Primary Injector vessel in such a manner that
there are no dead spaces within the vessel for the accumulation
of materials being conveyed when all ~eed points being provided
are in useO
The process is carried out inapparatus such as that
described above in the following manner. Primary Injector vessel
1~ is initially charged with particulate solid material to a level
~ ~7537
such that an electric signal transmitted by the load cell weigh
system shows that said level is above a pre-established "low
level" point. Fill valve 14~ in line 14 is closed as is valve
38 in line 36. A flow of gas is controlled by valve 16a which
automatically regulates the flow to establish the pressure in
Primary Injector vessel at a predetermined value higher than
in receiving vessel 13. Gas flow through line 26 is regulated
by flow control valve 26a at a rate precalculated to result in
a velocity, at operating pressure conditions, somewhat above
that at which the solids being fed will settle in the pipe.
Typically this velocity is between 30 and 40 feet per second at
the position i~mediately downstream of mix-T 24. The flow of
pressurizing gas to line 16 through diffuser nozzles 42 maintains
the bed of solids in the lower section of vessel 12 in somewhat
open condition but not in the state of agitation and suspension
commonly encountered in fluidized beds. In other words a
function of the inflowing gas i5 to lubricate flow of solids out
of the vessel while maintaining the pressure at the level
required to produce the desired flow rate of solids from the
vessel. For convenience, this condition may be termed "fluffing".
Without this particular form of conditioning, flow of most types
of solids from a vessel, even under pressure, cannot be maintained
at the precisely controlled, consistent rates required for the
functions achieved by this invention.
After the gas flows are established, as previously des-
cribed, and feed valve 22 is opened, the solid material flows
under pressure from vessel 12 in~o the mixing uni~ 24 ~see FIGURE 5),
for an~ given pressure in the vessel~ the size of orifice 54 and
the amount of gas flowing through 26 determines the rate of solids
flow through pipe 28 for uses such as those hereinafter described.
753~
Conduit 30 is connected by valve 38 into conduit 36
which equalizes the pressure in vessels 12 and 10 during replen-
ishment of injector vessel 12 with solids from Storage Injector
10, the valve in conduit 14 being opened for the purpose,
and the material flowing by gravity from one vessel to the other.
The pressures in the vessel ordinarily being eaual, although
under some conditions, e.g., when transferring materials having
poor ~low properties, the pressure may be higher in vessel 10
than in vessel 12. In that case valve 38 will remain closed
until after valve 14b is substantially open and at which time
a controlled volume of "fluffing" gas is admitted to vessel
10 through line 18 by means of valve 18a and distributed by
difuser nozzles as in vessel 12.
Storage Injector vessel 10 is supported so that its
weight will not interact with vessel 12, and a load, cell system
with a suitable number of load cells 10b, normally three or four
are provided. This weigh system has multiple uses, including a)
to determine the correct weight of material used for filling the
vessel 10 through valve 10d in line 10e during which time the
vessel i5 at atmospheric pressure and valve 10f in line 68 is
open; b) to provide an accurate batch weight measurement of
material being cycically charged into the continuously feeding
Primary Injector vessel 12; and c) to integrate its weighing
signal with the signals from the Primary Injector load cell
system at the appropriate tLme. That integrating feature of
the system permits control of the rate of material being discharged
from the Primary Injector during the time material is being
transferred from vessel 10 to vessel 1?. Otherwise, those periods
of time would be disruptive to the automatic control of the
feeding system. It should be understood that all of the valve
t753 ~
unctions referred to herein are preferably caused to
open or close by means of pneumatic operators and that the
operating cycle is dictated by a cycle lo~ic system which ukilizes
conventional mechanical-electric relays or a pro~rammable
controller coupled with either analog or digital control
instruments. A further option is to perform all of the control
functions with a suitably pro~rammed microprocessor.
While this invention is valuable because of its
characteristic of operating at high solids-to-gas ratios, the
invention has great value in many pneumatic transport applications
requiring a controlled solids feed rate. Not only is the process
uni~ue in its ability to control solids flow rates precisely,
but it is also applicable at solids flow rates as low as one
pound a minute into a gas stream of any quantity. In such
cases the soli~s-to-gas weight ratio is determined by process
requirements rather than energy re~uirements for the transport
system. Of even greater value is the fact that the invention can
be utilized or feeding large weights of materials into processes,
e.g., in coal gasification processes a single feed system can
readily accommodate feed rates of 150 tons per hour of prepared
coal and can accurately sub-divide this into many controlled
streams as re~uired by the process desi~ner.
The amount of gas flowing through the material in
vessel 12 and into the discharge pipe 20 relative to that entering
at the mixing unit will depend on the material bein~ conveyed.
Using comparatively large, uniform sized material, the flow of
conveying gas through the vessel will be appreciable at hi~h
vessel ressures and may approach 100~ of the total conveying gas.
With a finely divided material, there may be little flow of gas
through the material in vessel 12. Re~ardless of the amount of
:~lB'75~37
gas flowing through the vessel, a satisfactory con~eyance of a
given material is made possible by proper selection of the vessel
pressure, the solids-to-~as ratio, the size of the conduits
in the mixing unit, the size of the pipe line re~uired to
move the desired amount of material, and the a~ount of gas used
to supplement that flowing with the solids discharging from the
vessel. Generally, the higher the pressure inside the Primary
Injector, the higher the flow rate of solids--everything else
being equal. However, the volume of supplemental ~as (~as
entering the mixing unit throu~h pipe 26) results in an inverse
relationship with respect to the amount of solids injected at
any given and constant vessel pressureO This combination of
direct proportionality with vessel pressure and inverse
proportionality with diluter gas provides a flexible means for
control of the solids flow rate whi~h is particularly useful when
using multiple feed points requiring the same or varying solids
flow rates among the multiple lines.
In the illustrative embodiment, the preferred range
of particle sizes of the material to be conveyed is minus 1/8",
with a relatively uniform weight percentage on each of the
intermediate screens; in other words, a normal ag~regate
distribution such as is obtained when breaking coal. Under
certain conditions, however, an aggre~ate up to 1/2' in size can
be handled. It is possible to convev certain aaaregates
containing as much as approximately 90% by weiqht of minus 200
mesh particles, provided somewhat more "fluffing gas" is permitted
to enter the vessel through nozzles 42 and vented by means of
valve 34 through line 32. However, such fines should not be so
small or of such a nature that they agglomerate. Since the
velocities are low in the normal practice of this lnvention,
~'7~i37
size degradation of the particles is minimized in contrast to
the attrition of particles normally occurring in regular pneumatic
conveying systems.
The process of this invention is particularly useful
for the injection of dry, pulverized coal into the tuyeres of a
blast furnace. It appears possible thereby to replace up to at
least 30~ of the weight of coke normally used in the charge to
the blast furnace, which will greatly improve the economics
of iron and steel production. Many modern blast furnaces utilize
liquid or gaseous hydrocarbons as auxiliary fuels for replace-
ment of part of the chaxge coke. However, the increasing cost
and reduced supply of these materials make the present invention
particularly important. Furthermore substantially more coke can
be replaced when injecting dry coal than when injecting liquid
or gaseous fuels.
A typical application of the process and apparatus
of this invention is as follows:
A Primary Injector vessel having a storage capacity of
25 tons of prepared coal is located approximately 200 feet from
a blast furnace. The Primary Injector vessel is equipped with
twenty-five (25) outlets, each having the needed associated
equipment including a mixing unit. Each mixing unit is connected
to a 3/4" nominal pipe size line, which, in turn, is connected
to an alloy steel or water cooled lance mounted so as to feed
into a blast furnace.
The Primary Injector is filled automatically, on 1QW
level demand signal, from a pressurized storage vessel located
immediately above. The pressure in the Primary Injector is
approximately thirty-five pounds above the pressure in the
tuyeres, which is approximately forty pounds gauge pressure
14
~3'7~i3~
during blast. The pressure of the blast-air is somewhat variable
which would result in a variable rate of flow of injection coal
except that one of the novel features of the feeding process
automatically adjusts the pressure in the injection vessel to
maintain the coal rate desired by the operator who "sets"
the desired rate on the instrument control panel. Likewise all
gas flows are automatically maintained from the master control
panel within which the valve sequencing logic is also
controlled to provide continuous and automatic operation A
typical rate of coal injection is approximately twenty pounds
per minute in each of the twenty-five tuyeres at a solids-to-air
weight ratio of approximately 10:1.
Another example of the use of this feedinq process
involves the injection of comminuted, dry coke breeze into the
tuyeres of an iron melting cupola. In most large iron foundries
such as those owned by automobile manufacturers, iron for castin~s
is melted in cupolas into which heated air is blasted into the
furnace throuqh multiple tuyeres near the base of the furnace.
Charge material may consist of scrap steel, iron, steel and
iron bri~uettes and the like, and screened foundry coke. In
the pre-screening of coke before use in the cupola lar~e amounts
of breeze (approximately minus 1 inch) are accumulated which has
relatively low sales value. When this relatively inexpensive
coke breeæe is prepared to a size of approximately minus 10
2S mesh and dried, its cost is of the order of one-third that of
char~e coke. Such material can be used by the process of this
invention to replace from about 10% to 20% of the coke char~ed,
with substitution ratios of from about 1.0 to 2.0 pounds of
coke removed per pound of coke fines injected, with a substantial
saving in cost of production~
7~37
A specific example of the use of the process of
this invention for the injection of coke fines through the
tuyeres of an iron producing cupola is as follows: A 122"
diameter cupola operating with 25,000 - 27,000 SCFM bla~t air
at 1200~F has ten tuyeres, five of which were equipped for
coke injection. ~his cupola was melting 50 to 60 tons per hour
of 37% returns, 55~ iron and steel briquettes, and 8% steel
bundles. The Primary Coke Injector was constructed in accordance
with this invention except that cupola operation does not
require the rate control instrumentation on an absolutely contin-
uous basis since the operator monit4rs the feed rate to the
cupola by observing the iron melting process and chemistry
of the iron product. This permits the interruption of the
feed rate measurement system for short periods during replenishing
of the supply of coke injected which in this case was provided
by a Feed Injector. In the operation described in this example
the iniector supplied coke fines at the rate of 18 pounds per
minute evenly distributed in five injection lines and the
average replacement of charge coke was 1.3 pounds per 1.0 pound
of injected breeze witll an overall saving of 13~ of the charge
coke.
16
