US3272617A - System for adding fluid fuel to furnace blast - Google Patents

Description

Sept. 13, 1966 A. A. FENNELL SYSTEM FOR ADDING FLUID FUEL TO FURNACE BLAST Filed Nov. 24. 1961 5 Sheets-Sheet l INVENTOR yQJVerZ/Zefl Sept. 13, 1966 A. A. FENNELL 3,272,317

SYSTEM FOR ADDING FLUID FUEL TO FURNACE BLAST Filed Nov. 24, 1961 5 Sheets-Sheet 2 .157 )JW/v. J m k. m) 1 5 176 I v J5? w .155 170 1% J94 J55 J40 J56 fi0 gg I J56 v 3 J74 Z0? J55 ENTOR.

p 1966 A. A.,FENNELL SYSTEM FOR ADDING FLUID FUEL TO FURNACE BLAST Filed NOV. 24, 1961 5 Sheets-Sheet 5 w w m6 My 5 M 4 a w /w w/% wmww nw w ./.M* 0 w l /%w /2 d; a 3 w 7 w, "N 3 United States Patent 3,272,617 SYSTEM FOR ADDIN G FLUID FUEL T0 FURNACE BLAST Anthony A. Fennel], Fennell Corp, 379 E. 147th St., Harvey, Ill. Filed Nov. 24, 1961, Ser. No. 154,551 7 Claims. (Cl. 75-42) This invention relates generally to the operation of a blast furnace and especially to a system for adding fluid fuel to the furnace blast.

One traditional method of making steel involves use of a blast furnace into which there is charged a burden consisting of iron ore, coke and limestone, the coke providing carbon for deoxidizing the iron ore as well as fuel for heating the burden. Modern practice calls for a decrease in the customary proportion of coke in the burden and the introduction of a fluid fuel into the air blast which is supplied to the furnace. While this practice achieves a greater tonnage output of steel per hour of operation in addition to generally improved furnace behavior, heretofore the rate of introducing the fluid fuel has been established arbitrarily and regulated manually. As a result, the furnace operation has been somewhat erratic and certain safety hazards have arisen.

Accordingly, an important object of the present invention is to provide a system for introducing fluid fuel into a blast furnace at a rate which is a constant proportion of the weight of oxidizing gas being simultaneously introduced.

Another object of the invention is to provide such a system in which the proportion of fuel to oxidizing gas can be selectively varied.

A more general object of the invention is to provide a new and improved system for automatically adding fluid fuel to a furnace blast.

Still another object of the invention is to provide a system for automatically adding fluid fuel to a furnace blast, which system is characterized by uniform flow of fuel through the several tuyeres.

And another object of the invention is to provide a system for safely and automatically adding fluid fuel to a furnace blast.

A more specific object of the invention is to provide a control system which prevents fluid fuel from backing up into the blast bustle upon clogging of a tuyere and which prevents the fuel from being introduced into the atmosphere surrounding the furnace upon the burning off of a tuyere.

Additional objects and features of the invention pertain to the particular structure and arrangements whereby the above objects are attained.

A system in accord with the invention includes means for sensing the physical conditions of a flow of oxidizing gas to a blast furnace and for supplying an output signal related to a selected percentage of the weight rate of flow of the oxidizing gas; means for regulating the flow of a fluid fuel to the tuyeres of the blast furnace; and means receiving the output signal and operating the regulating means in accordance therewith.

The invention, both to its arrangement and mode of operation, will be better understood by reference to the following disclosure and drawings forming a part thereof, wherein:

FIG. 1 is a perspective view of a blast furnace incorporating a control system constructed in accordance with the present invention and adapted for adding natural or manufactured gas to the furnace blast;

FIG. 2 is a schematic view of the blast furnace and control system of FIG. 1, illustrating in particular the components employed in proportioning the fluid fuel being introduced into the furnace blast;

FIG. 3 is a schematic view of the components of the control system which are particularly arranged to insure safe introduction of the fluid fuel;

FIG. 4 is an enlarged, central, cross-sectional view of one of the pressure switches used in the system of the invention;

FIG. 5 is an enlarged, central, cross-sectional view of a differential pressure transmitting device of the type used in the system of the invention; and

FIG. 6 is a schematic view of a modified form of the control system of the invention, particularly arranged for adding fuel oil to the furnace blast.

Referring now in detail to the drawings, specifically to FIGS. 1 and 2, a blast furnace installation indicated generally by the numeral 10 will be seen to include a blast furnace 12 comprising a tapered body 14 resting on a bosh or base 16 and having an open throat 18 at its upper end. In accordance with conventional practice, the blast furnace 12 is constructed of refractory brickwork and is intended for continuous operation, raw materials being periodically charged into the furnace through throat 18 and the steel produced in the furnace being periodically withdrawn from the bosh 16 to be cast into pigs.

Oxidizing gases, comprising air which is sometimes enriched with oxygen and which is occasionally replaced entirely with oxygen, are required in the operation of the blast furnace 12 in order that suflicient heat may be developed in the reaction mass of the furnace burden to deoxidize the iron ore to steel. In compliance with conventional operations, these oxidizing gases are directed from a supply line 20 to a header or bustle pipe 22 surrounding the blast furnace 12 in the vicinity of the juncture between the body and the bosh. In further compliance with customary practice, nozzles or tuyeres 24 are employed to direct the oxidizing gases from the bustle pipe 22 into the body of the blast furnace at various peripheral locations. Whereas two tuyeres are shown in the drawings, it is to be recognized that any number of tuyeres may be employed, large furnaces frequently utilizing as many as sixteen or eighteen tuyeres.

In accordance with the present invention, supplemental fluid fuel is introduced into the furnace, specifically into the oxidizing gases being directed through the tuyeres 24. The means for introducing this fluid fuel into the tuyeres are shown in FIG. 1 to include a supply line 26, a header 28 encompassing the furnace 12 and communicating with the supply line 26, and nozzles 30 which conduct the fluid fuel from the header 28 to the individual tuyeres 24.

Since it is intended to introduce fluid fuel into the current or blast of oxidizing gas being directed into the furnace 12 in such a manner that the rate of addition of the fuel is a constant proportion of the weight of oxidizing gas being simultaneously introduced, the system of the present invention is particularly arranged to measure the flow of oxidizing gas through the supply line 20. In addition, the system of the invention is arranged to measure both the temperature and pressure of oxidizing gas in order to correct the volumetric flow of oxidizing gas for variations in either the temperature or pressure of the supply, thus in effect determining the weight rate of flow of the oxidizing gas.

Specific means for making these measurements and performing the corrections are shown in FIG. 2. There, a primary metering device indicated generally by the numeral 32 will be seen connected in the supply line 20 upstream of the bustle pipe 22. The metering device 32 is intended to measure the gross volumetric flow of oxidizing gas through the supply line 20 and, therefore, advantageously takes the form of an orifice meter, a nozzle meter, a venturi meter or some other suitable arrangement, desirably including valving, such as the valves 34, for purposes of regulation.

The two output signals from the primary metering device 32, which differential signals are indicative of the volumetric flow of oxidizing gas, are directed to a differential pressure transmitter 36 of conventional construction, transmitter 36 being particularly arranged to convert the received information to a pneumatic signal whose magnitude is indicative of the volumetric flow through the supply line 20. While trannsmitter 36 is provided with instrument air from a line 38 and a regulator 40 and while transmitter 36 is particularly arranged to develop a pneumatic signal, the transmitter 36 ma be equally well adapted to provide either a hydraulic or an electric signal indicative of the flow of oxidizing gas.

Continuing with reference to FIG. 2, a pressure sensor or tap 42 is connected in supply line 20 adjacent the metering device 32; and the output of pressure sensor 42 is directed to a transducer 44 which receives instrument air from a line 46 through a regulator 48 and which converts the output signal of the pressure sensor to a pneumatic signal passing through conduit 50. Similarly, a temperature sensor or well 52 is connected in the supply line 20; and the output of the temperature sensor is directed to a transducer 54 which receives instrument air from a line 56 through a regulator 58 and which converts the output signal of the temperature sensor to a pneumatic signal passing through the conduit 60.

A pneumatic relay 62 receives the output signals from transducers 44 and 54 in order to convert these signals to a single output signal to be used in correcting the measured volumetric flow of oxidizing gas for variations in pressure and temperature. Relay 62 receives instrument air from a line 64 through a regulator 66; and the pneumatic output of the relay is passed through a conduit 68 to a pneumatic relay 70 which also receives the signal from transmitter 36 through the conduit 72. Relay 70 is supplied with instrument air form a line 74 through a regulator 76 and develops from its input signals a composite signal which is indicative of the weight rate of flow of the oxidizing gas passing through supply line 20.

This composite output signal is pneumatic in nature and is carried by a conduit 78 to a ratio setting device 80 where the input signal is selectively varied to represent a desired proportion of fuel to oxidizing gas. The ratio setting device 80 may conveniently take the form of a variable orifice or some other arrangement capable of establishing an output signal which is a selected fraction of its input signal. Suitable proportions of fuel to oxidizing gas have been found to be on the order of 1 or 2%.

The output of ratio setting device 80 is passed to similar control equipment associated with each of the tuyeres 24. Specifically, the pneumatic signal from devic 80 is carried by a conduit 82 which divides into branch lines 84 and 86, branch line 84 carrying the output of device 80 to a controller 88 associated with one of the tuyeres 24 and branch line 86 carrying the output signal to a controller, not shown, associated with the other one of the illustrated tuyeres. By controlling the flow of fluid fuel at each of the tuyeres from a single master signal developed by the ratio setting device 80, assurance that there will be uniform flow of fuel through all of the tuyeres is achieved.

The controller 88 operates a valve 90 which is disposed in the fuel line between header 28 and a nozzle 30 as is shown in FIG. 2. Specifically, the valve 90 is connected to a control unit 92 which is spring-loaded to direct the valve 90 normally into a closed position, unit 92 being further arranged to open valve 90 in compliance with a pneumatic signal from controller 88. Instrument air is provided to the unit 92 through a line 94, a check and throttling valve 96 being advantageously interposed between the unit 92 and the controller 88.

In order to insure proper operation of valve 90, i.e. in order to insure that the quantity of fluid fuel passing through the valve conforms with the requirement established at controller 88, means are provided for sensing the flow of the fiuid fuel at a location downstream from the valve 90. In the embodiment illustrated in FlG. 2, these means include an orifice meter indicated generally at 98 and a differential pressure transmitter 100. The orifice meter 98 includes a pair of spaced-apart orifice plates 102 and 104 which are connected in a fuel line 106 between valve and the nozzle 30. The pressure indications developed by the orifice plates 102 and 104 are conducted to the transmitter through suitable regulating valves such as the valves 108. The transmitter 100, like the transmitter 36, may be of any conventional design and configuration, a specific embodiment to be hereinafter described with reference to FIG. 5. The transmitter 100 receives instrument air from a line 110 and converts the pressure indications from orifice plates 102 and 104 to a single pneumatic signal indicative of the volumetric flow of fluid fuel passing through the line 106. This output signal from transmitter 100 is passed through a conduit 112 to the controller 88 for purposes of modifying the directed operation of valve 90 in accord with the flow of fuel actually passing through the valve. Instrument air is advantageously supplied to the controller 88 through a line 114. Furthermore, a check valve 116 may be interposed in line 106 between orifice plate 102 and nozzle 30 if desired.

Similar elements and components are arranged with the other of the tuyeres.

The embodiment of FIGS. 1-3 is particularly arranged to employ fluid fuel of a gaseous nature, such as for example natural gas or manufactured gas; and it has proved important to arrange the system of the invention in such a fashion that situations inherent from the use of fuel of this character do not present a safety hazard. The blast furnace 12 is intended to be operated at an elevated temperature, and it has been found that fuel gas can decompose at the furnace temperature to deposit carbon in the tuyeres 24. Blockages resulting from carbon deposits are capable of restricting fiow through the tuyeres and of permitting fuel gas from the nozzles 30 to backup into the bustle pipe 22. If appreciable quantities of the fuel gas collect in the bustle pipe, an explosive mixture can be developed. As will be recognized, blockage of a tuyere 24, as for example might be incurred by the deposition of carbon from decomposing fuel gas, results in a reduced flow of the oxidizing gas through the tuyere; and this fact can be employed in determining the blocked condition and compensating for it.

Moreover, the high temperature at which the furnace 12 operates can weaken and eventually destroy the connection between the tuyere and the body of the furnace, a condition frequently referred to as burning off. Upon the connection of a tuyere with the furnace so failing, the fuel gas being introduced through nozzle 30 is thereby capable of being readily discharged into the atmosphere surrounding the furnace due to the back pressure of the gases within the furnace. The resultant atmosphere about the blast furnace could develop an explosive mixture and could also present a toxicity problem to those persons working in the vicinity of the furnace. As will be recognized, the burning off of a tuyere permits more rapid flow from the bustle pipe through the remainder of the tuyere; and this increased rate of flow can be sensed and utilized in terminating the fuel flow through the damaged tuyere.

In accordance with the present invention, means are provided for sensing the flow of oxidizing gas through each of the tuyeres. Specifically, an inverted impact tube 118 is situated in each of the tuyeres intermediate the nozzle 30 and the bustle pipe 22. By inverting the impact tube, a negative pressure or vacuum signal related to the volumetric fiow through the tuyere is developed; and this pressure signal from the impact tube 118 is directed to a pair of differential pressure switches 120 and 122. In order to provide a common, high pressure reference for the switches 120 and 122, a pressure switch 124 is pneumatically connected to the bustle pipe 22 by means of a conduit 126, the output of pressure switch 124 being directed to both of the switches 120 and 122 as is shown in FIG. 2.

Switch 120 is particularly arranged for the internal contacts thereof to be closed when an excessive flow of oxidizing gas develops in the related tuyere 24, i.e., switch 120 is adapted to signal a burned off or similarly defective tuyere, this signal being passed by an electrical cenductor 128. On the other hand, switch 122 is arranged for the internal contacts thereof to close passing an electrical signal when the flow through tuyere 24 falls below a selected value as sensed by impact tube 118, i.e. switch 122 is adapted to sense obstruction of tuyere 24, the output signal from switch 122 being passed by an electrical conductor 13!).

The conductors 128 and 130 are connected to a common conductor 132 which passes the signals from switches 120 and 122 to a solenoid operated valve 134 of 3-way configuration, valve 134 exhausting the pneumatic signal from unit 92 to the atmosphere whereby to permit the spring force stored in the unit 92 to close the valve 90 terminating flow of fuel through valve 90 whenever either the switch 120 or the switch 122 passes a signal to the solenoid valve 134. If desired, a flow indicating and recording device 136 can be connected in pneumatic circuit with the controller 88 and the valve 134 so as to provide visual monitoring and permanent recordation of the operation of valve 90. Instrument air is supplied to the device 136 through a line 138.

In addition, the conductor 132 is connected with a conductor 140 in order that the signals from switches 120 and 122 can be directed to a relay station 142. The signals from switches 120 and 122 are directed from the relay station 142 to circuits, such as the circuits 144 and 146, which are connected to annunciators for audibly indicating respectively excessive fiow through a tuyere 24 and insuflicient flow therethrough. A master manual switch 148 is also connected through relay station 140 for terminating operation of the entire system should the need arise.

Automatic cessation of operation of the entire system is also desirable under certain circumstances, as for example upon failure of the fuel supply, failure of the oxidizing gas supply, or failure of the instrument air supply. For purposes of determining proper flow of the oxidizing .gas, a pressure switch 150 is pneumatically connected to the supply line by a conduit 152 whereby to sense the pressure in the line. The internal contacts of pressure switch 150 are advantageously arranged to complete a circuit passing an electrical signal through the conductor 154 to the relay station 142 upon the pressure in supply line 20 dropping below a selected value; and turning to FIG. 3, the signal thus developed by pressure switch 150 is passed by the relay station 142 by a conductor 156 to a 4-way solenoid valve indicated generally at 158. In response to the signal thus passed, the valve 158 is caused to shut off all fuel from a main gas supply line 160. Thus, fuel will not be directed into the tuyeres 24 in the absence of a proper flow of oxidizing gas.

Similarly, a pressure switch 162 is pneumatically connected to the gas line downstream from valve 158 by a conduit 164, switch 162 being arranged so that the internal contacts thereof close passing an electrical signal to relay station 142 through a conductor 166 uponthe pressure in the gas line falling below a selected value. This signal from switch 162, is, like the signal from switch 150, passed by the relay station 142 to the conductor 156 and thence to the solenoid valve 158 for shutting off the flow of fuel when the pressure thereof falls below the selected value.

The relay station 142 may be similarly arranged with appropriate sensors to detect a failure in the instrument air pressure and to direct solenoid valve 153 to take the fluid fuel supply from the blast furnace whenever the instrument air supply becomes defective.

When natural gas is employed as the fuel gas for the system of FIGS. 1-3, it is ordinarily delivered to the blast furnace area at a line pressure of 250 p.s.i.g. in order that the system may accommodate gas demands on the order of 400,000 cubic feet per hour. Continuing with reference to FIG. 3, the gas is passed by the solenoid valve 158 at the initial pressure to a series of gas regulators indicated by the numeral 170. These regulators reduce the gas pressure to a useful range of from to p.s.i.g. If it is desired to silence the noise incurred in reducing the gas pressure, a sound silencer 172 may be close-coupled with the reducers downstream thereof.

Completing the disclosed embodiment of FIGS. 1-3 is a flow measuring unit indicated generally by the numeral 174. Unit 174 includes a primary metering device 176 including orifice plate- s 178 and 180. The pressure signal from these orifice plates is suitable passed to a differential pressure transmitter 182 through a suitable system of regulating valves, such as the system of regulating valves 184. The transmitter 182 is supplied with instrument air from a line 185, and the pneumatic output of the transmitter is passed for pressure and temperature variations in the gas supply. For this latter purpose, a pressure sensor or tap 187 and a temperature sensor or well 188 are connected in the gas line 26 downstream from the orifice plates 178 and 180. The signals from the sensors 187 and 188 are passed to transducers 100 and 192 respectively, transducers 190 and 192 receiving instrument air from lines 194 and 196 in order to convert the signals from the sensors 187 and 188 to pneumatic outputs.

The output signals from transducers 190 and 192 are conducted to a pneumatic relay 198 from whence a combined signal is passed to the relay 186, relay 198 receiving instrument air from a line 200. The pneumatic output of relay 186 is passed to a meter body 202, and the determination of volumetric flow made at the meter body 202 is passed to a flow recorder 204. The pneumatic signal which indicates gas line pressure and which is passed by transducer 190 is also conducted to the recorder 204 for purposes of integrating the flow of gas. A pressure recorder 206 may be advantageously combined with the recorder 204.

If desired, the system described with reference to FIGS. 1-3 can be combined with systems for analyzing the top gas from the furnace and for determining the B.t.u. content of these exhaust gases.

The pressure switches employed in the system of the invention are pressure switches of a known and conventional structure, such as for example the pressure switch which is shown in detail in FIG. 4. There, the switch 120 will be seen to comprise a housing 210 defining a chamber 212 and a chamber 214, which chambers are separated by a flexible diaphragm 216. Because the pressure switch 120 is intended to be a pressure difference switch, the chambers 212 and 214 are connected respectively to a high pressure source and to a low pressure source as through the conduits 218 and 220 respectively. In the system of FIGS. l3, conduit 218 connects the chamber 212 to the pneumatic output of pressure switch 124 whereas conduit 220 connects chamber 214 to the output of impact tube 118.

The housing 210 also encloses a microswitch arrangement 222; and the diaphragm 216 is arranged to operate the microswitch 222 by means of a pin 224 in response to the differential pressure existing between chambers 212 and 214. Conductors 226, 228 and 230 are employed in making the desired electrical connections with the microswitch 222.

As will be recognized, the system of the invention can usefully employ pressure switches adapted to be operated from a single pressure source as well as pressure switches arranged to develop a pneumatic rather than an electrical output.

Similarly, the system of the invention is adapted to utilize differential pressure transmitters of a common type. Differential pressure transmitter 100 is selected to be such a unit; and turning to FIG. 5, the differential pressure transmitter 100 will be seen to comprise a housing 232 which encloses a diaphragm 234, diaphragm 234 separating a chamber 236 from a chamber 238. Advantageously, chamber 236 is provided with an opening 240 which is adapted to be connected to a high pressure source. In similar manner, chamber 238 is provided with an opening 242 which is adapted to be connected to a low pressure source.

A lever 244 is connected to the diaphragm 234 by a plate arrangement 246 whereby a differential pressure applied to the diaphragm 234 causes a force to act on a lever 248 which is pivotally connected to the lever 244 and which is swingably mounted about a pivot 250. The action of lever 248 is employed to operate a switch or to control a valve incorporated with the transmitter by suitable means, as by a link 252. A bellows 254 advantageously seals the lever 248 in the vicinity of pivot 250.

Construction of the system and operation thereof is believed obvious from the foregoing descriptions.

While a particular embodiment of the system of the invention has been thus far shown, it should be understood, of course, that the invention is not limited thereto since many modifications may be made. Therefore and turning to FIG. 6, a modified embodiment of the invention will be seen particularly arranged to employ fuel in the form of fuel oil. The embodiment of FIG. 6 incorporates a number of elements and components similar in nature to those employed in the embodiment of FIGS. 1-3. Accordingly, like numerals have been used to designate like parts in the two embodiments, the sufiix letter a being utilized to distinguish those elements and components associated with the embodiment of FIG. 6.

The embodiment of FIG. 6 is singular in a number of respects. First of all, an oil header 260 is arranged to replace the gas header, a supply line 262 delivering fuel oil to the header 260. The header 260 surrounds a blast furnace 12a as does a bustle pipe 220; and in addition, the oil header 260 is provided with a return line 264 in which there is installed a back-pressure relief valve 266. A substantially constant pressure in the oil header 260 is thus insured.

A controller 88a receives the fuel rate signal from a ratio setting device 80a to control the fuel valve 90a in a manner similar to the elements 88, 80 and 90 described hereinabove. However, in the embodiment of FIG. 6, monitoring of the actual flow of fuel to a given one of the tuyeres 24a is achieved by means of a rotometer 268 which is situated upstream of valve 90a in an oil line 270 connecting the valve 90a with header 260. The output signal from rotometer 268 is passed to controller 88a in order to insure that the actual flow through the valve 90a is in compliance with the demand established at the ratio setting device 80a. It is important to point out that positioning of the rotometer 268 upstream of the valve 90a insures accurate monitoring of the flow through the valve since the rotometer thereby operates at substantially constant oil pressure.

A fuel line 272 connects the valve 90a with nozzle 30a; and while nozzle 30a is merely arranged to direct a stream of the liquid fuel into the oxidizing gas being introduced into the furnace, it is to be recognized that nozzle 30a may be equally well arranged to provide atomization of the liquid fuel. A manual shut-off valve 274, a check valve 276 and a purge connection 278 are also advantageously interposed in the fuel line 272 between valve 90a and nozzle 30a.

To prevent the liquid fuel from flooding into the bustle pipe 22a upon a tuyere 24a becoming plugged, a Pitot tube 280 is installed in each tuyere 24:: between the nozzle 30a and the bustle pipe 22a. The velocity head sensed by the Pitot tube 280 is delivered to a differential pressure switch 282; and when a desired velocity head is achieved in the tuyere due to proper flow of oxidizing gas, the signal from the Pitot tube holds the contacts in the switch 282 so as to energize the coil of solenoid valve 134a thereby maintaining instrument air on the control unit 92a. Thus, valve a is held in an operative condition similar to the valve 90 described hereinabove.

Upon tuyere 24a becoming plugged or obstructed, the signal from the Pitot tube 280 decreases whereupon the differential pressure switch 282 in response opens its interal contacts to de-energize the coil of solenoid valve 134a, evacuating instrument air from the unit 92a and permitting valve 90:: to close.

The pressure switch 282 is arranged with internal contacts adapted to respond to both excessive and insfiicient oxidizing gas velocities as sensed by the Pitot tube 280. Accordingly, in the event that the tuyere 24a breaks off or burns off at the furnace 12a, the excessive flow of oxidizing gas thus incurred is sensed by the Pitot tube; and in response, the internal contacts of pressure switch 282 open to release the solenoid valve 134a and deactivate the control unit 92a whereby to close valve 90a.

The specific examples herein shown and described should be considered as illustrative only. Various changes in structure may occur to those skilled in the art; and these changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A control system comprising; a first sensing means disposed in sensible contact with a flow of reactable gas which is subject to fluctuations in its physical conditions, said first sensing means being arranged for developing a first signal indicative of the volumetric rate of flow of said reactable gas; a second sensing means disposed in sensible contact with said flow of reactable gas for developing a second signal indicative of the fluctuations of at least one of the physical conditions of said reactable gas; correction means connected to said first and second signal means for developing a third signal indicative of a corrected volumetric rate of flow of said reactable gas corrected for fluctuations of at least one of the physical conditions of said reactable gas; a plurality of nozzles receiving said flow of reactable gas and directing the same into a reaction mass; means directing a flow of fluid fuel to each of said nozzles; a plurality of means for regulating the flow of said fuel to said nozzles, one of said regulating means being operatively associated with each of said nozzles; and means individually associated with each of said regulating means for receiving said third signal and operating the associated regulating means in accordance therewith.

2. A control system comprising: means disposed in sensible contact with a flow of reactable gas which is subject to fluctuations in its physical conditions, said means being arranged for developing a signal indicative of the volumetric rate of flow of said gas corrected for changes in at least one physical condition thereof; a plurality of nozzles receiving said flow of reactable gas and directing the same into the reaction mass; means directing a flow of fluid fuel to each of said nozzles; a plurality of means for reguating the flow of said fluid fuel to said nozzles, one of said regulating means being operatively associated with each of said nozzles; means individually associated with each of said regulating means for receiving said signal and operating the associated regulating means in accordance therewith; flow sensing means measuring the flow of said fluid fuel to the corresponding nozzle and providing a signal indicative thereof; and means for modifying the operation of said regulating means in compliance with said last mentioned signal so that said flow of fluid fuel corresponds with the requirement established by said first mentioned signal.

3. A system for introducing fluid fuel into a blast furnace having a header and a plurality of tuyeres directing oxidizing gas under pressure from said header into the body of said furnace, said system comprising: means supplying fluid fuel to each of said tuyeres at a rate proportional to the weight of oxidizing gas entering said header, including a fuel line; means for sensing the impact pressure of said oxidizing gas in one of said tuyeres and for developing output signals indicative thereof; and means responsive to said output signals for terminating the flow of fuel to said one tuyere upon the flow therethrough falling above or below a selected range of values, including a valve in said fuel line and a first and a second diiferential pressure switch receiving said output signal and arranged individually to cause closing of said valve when said impact pressure is respectively above and below the selected range of values.

4. A system according to claim 3 wherein said means for sensing the impact pressure of said oxidizing gas is disposed in aid one tuyere intermediate said header and a connection with said first mentioned means.

5. A system according to claim 3 wherein said means for sensing the impact pressure of said oxidizing gas includes an inverted impact tube.

6. The method of controlling the introduction of fluid fuel into the air supply to a blast furnace comprising the steps of causing a flow of air having a variable pressure and temperature; measuring the volumetric flow of air at a first point in its path to the blast furnace; introducing fluid fuel into said flow of air at a second point downstream from said first point; sensing the pressure and temperature of said flow of air adjacent said first point; altering said measure value of volumetric flow of air in proportion to the sensed changes in pressure and temperature;

10 and regulating the volumetric flow of said fuel in accordance with the altered value of volumetric flow of air.

7. The method of controlling the introduction of fluid fuel into the air supply to a blast furnace comprising the steps of: causing a flow of air having a variable pressure and temperature; measuring the volumetric flow of air at a first point in its path to the blast furnace; introducing fluid fuel into said flow of air at a plurality of second points downstream from said first point; sensing the pressure and temperature of said flow of air adjacent said first point; altering the measured value of volumetric flow of air in proportion to the sensed changes in pressure and temperature; and individually regulating the volumetric fiow of said fuel in accordance with the altered value of volumetric flow of air.

References Cited by the Examiner UNITED STATES PATENTS 2,072,384 3/1937 Schmidt 13791 X 2,388,669 11/1945 Baker 137--88 X 2,879,056 3/ 1959 Wagner 266-29 2,938,782 5/1960 Toulmin 266-29 X 3,165,399 1/1965 Kennedy 26629 X OTHER REFERENCES Blast Furnace, Coke Oven, and Raw Materials Proceedings, vol. 20, 1961 (AIME), pp. 595-598.

JOHN F. CAMPBELL, Primary Examiner.

MARCUS U. LYONS, WHITMORE A. WILTZ,

Examiners.

D. L. REISDORF, I. C. HOLMAN, Assistant Examiners.

Claims (2)

1. A CONTROL SYSTEM COMPRISING; A FIRST SENSING MEANS DISPOSED IN SENSIBLE CONTACT WITH A FLOW OF REACTABLE GAS WHICH IS SUBJECT TO FLUCTUATIONS IN ITS PHYSICAL CONDITIONS, SAID FIRST SENSING MEANS BEING ARRANGED FOR DEVELOPING A FIRST SIGNAL INDICATIVE OF THE VOLUMETRIC RATE OF FLOW OF SAID REACTABLE GAS; A SECOND SENSING MEANS DISPOSED IN SENSIBLE CONTACT WITH SAID FLOW OF REACTABLE GAS FOR DEVELOPING SECOND SIGNAL INDICATIVE OF THE FLUCTUATIONS OF AT LEAST ONE OF THE PHYSICAL CONDITIONS OF SAID REACTABLE GAS; CORRECTION MEANS CONNECTED TO SAID FIRST AND SECOND SIGNAL MEANS FOR DEVELOPING A THIRD SIGNAL INDICATIVE OF A CORRECTED VOLUMETRIC RATE OF FLOW OF SAID REACTABLE GAS CORRECTED FOR FLUCTUATIONS OF AT LEAST ONE OF HE PHYSICAL CONDITIONS OF SAID REACTABLE GAS; A PLURALITY OF NOZZLES RECEIVING SAID FLOW OF REACTABLE GAS AND DIRECTING THE SAME INTO A REACTION MASS; MEANS DIRECTING A FLOW OF FLUID FUEL TO EACH OF SAID NOZZLES; A PLURALITY OF MEANS FOR REGULATING THE FLOW OF SAID FUEL TO SAID NOZZLES, ONE OF SAID REGULATING MEANS BEING OPERATIVELY ASSOCIATED WITH EACH OF SAID NOZZLES; AND MEANS INDIVIDUALLY ASSOCIATED WITH EACH OF SAID REGULATING MEANS FOR RECEIVING SAID THIRD SIGNAL AND OPERATING THE ASSOCIATED REGULATING MEANS IN ACCORDANCE THEREWITH.

6. THE METHOD OF CONTROLLING THE INTRODUCTION OF FLUID FUEL INTO THE AIR SUPPLY TO A BLAST FURNACE COMPRISING THE STEPS OF: CAUSING A FLOW OF AIR HAVING A VARIABLE PRESSURE AND TEMPERATURE; MEASURING THE VOLUMETRIC FLOW OF AIR AT A FIRST POINT IN ITS PATH TO THE BLAST FURNACE; INTRODUCING FLUID FUEL INTO SAID FLOW OF AIR AT A SECOND POINT DOWNSTREAM FROM SAID FIRST POINT; SENSING THE PRESSURE AND TEMPERATURE OF SAID FLOW OF AIR ADJACENT SAID FIRST POINT; ALTERING SAID MEASURE VALUE OF VOLUMETRIC FLOW OF A AIR IN PROPORTION TO THE SENSED CHANGES IN PRESSURE AND TEMPERATURE; AND REGULATING THE VOLUMETRIC FLOW OF SAID FUEL IN ACCORDDANCE WITH THE ALTERED VALUE OF VOLUMETRIC FLOW OF AIR.

Images