US2370897A - Temperature control means - Google Patents

Description

March 6, 1945. A. J. wHrrcoMB TEMPERATURE oo NTRoL 'MEANS Filed Jan. 24, 1941 f sa INVENTOR Arthur J. Wh 'comb Patented Mar. 6, 1945 l TEMPERATURE CONTROL MEANS y Arthur Whitcomb, Chlcagoilll., assignor to Freyn Engineering Company, Chicago, Ill., a

corporation of Maine Application January 24, 1941, Serial No. 375,163

' (ci. ass- 15) 7 Claims.

The present invention relates @to improvements in temperature control means.

The present invention is applicable to and will be described in connection with means for controlling the temperature within the dome of a blast furnace stove, though as the description proceeds itA willbe apparent that the invention has a broader application.

The modern blast furnace gas stove burner affords such close control of excess air that the products of combustion may be limited to as little as 0.5 per cent of oxygen. Combustion temperatures may range from 2000 to 2400 deg. F. when burning blast furnace gas which ranges from 88 to 96 B. t. u. per cubic foot. In view of the high rate 0f combustion required to maintain line heats in the neighborhood of 1400 to 1500 deg. F., there is danger of exceeding the safe working temperature of the combustion chamber, the top checkerbrick and the dome lining. If excessive temperatures are maintained. glazing and dropping of the brick may result. Even deformation of the top layers of the checkers r may occur due to such high temperatures. It has been common practice to equip the domes of blast furnaces with thermocouples and pyrometers, the readings serving as guides to the stove tenders for the manual operation of the burners.

United states Letters' Patent No. 1,817,219,`

granted August 4, 1931, in the name of Frederick H. Willcox and John C. Hayes, Jr., discloses and claims apparatus for .controlling the delivery vof combustion air to a blastfurnace stove, said apparatus including means for varying the quantity of'air deliveredproportionally to the presence of the blast furnace gas-delivered to the stove burner. The present invention contemplates a control embodying certain ofthe principles of said Leters Patent No. 1,817,219, it being preferred to utilize an adjustable speed direct current motorl for operating the blower to supply the combustion air, speed adjustment during at least a part of the speed range being obtained by adjustment of the ileld strength of the motor.

, A blast furnace stove is a heat storage medium` heat absorbing media are at low temperature, it

is possible and desirable to supply a quantity of combustion air which will give emcient combustion and which will also give thel highest posa lean fuel is used-namely. blast furnace gas, and as high a fiametemperature as can be obtained by burning cold blast furnce gas with cold air is desirable. This high iiame tempera- 'ture is advantageous in that it increases the temperature difference between the flame and the refractories, thereby increasing the rate of heat transfer to the latter. y

As the heating cycle progresses, the temperature of the refractories increases. A point is finally reached when the refractories in the combustion chamber attain as high a temperature as is safe for them. However, the refractories in the checker portion of the stove have' not yet been raised sufficiently in temperature. Therefore,`further operation oi' the stove onA gas is required.

It would perhaps be possibleI to continue opera? tions `safely by decreasing the rate f fuel input, thereby restricting the temperature attained by the refractcries in the combustion chamber of the stove. However, this would not be desirable as the restricted heat input would mean a greatly delayed rate of heating the checker brick in the stove and would not utilize all available fuel.

It is preferable to continue the original rate of heat input,l i. e., fuel input. but to prevent the refractories in the combustion chamber from attaining an excessive temperature by the expedient of increasing the input of combustion air whereby to restrict the flame temperature to a suillciently low value so that there is substantially no temperature difference between the ame andthe refractories in the combustion chamber. 1n this manner the heating of the checkers or the stove can be continued at the original rate of heat input without jeopardiz'ing the refractories in the combustion chamber and the dome of the stove.

It is well known to blast furnace operators that in heating up a blast furnace stove the rate of heat absorption-when the stove is relatively cold' is so high that the dametemperature is decidedly limited. In other words, though the blast furnace gas being delivered to the stove has a possibility of a llame temperature in the neighborhood of 2300 or .24001 F., the relatively cool refractories within the stove absorb heat so rapidly that llame temperature may not reach more than 1800" to1900'F. Under these conditions it has been common practice to supply y n all of the gaseous fuel available and to supply Aan amount of combustion air to produce the sible name temperaturel in view oi' the fact that Il most efficient burning to achievea flame tem-l perature as high as possible. This ratio of coni-l bustion air to gaseous fuel. according to well known practice, has been maintained until the vulnerable parts of the stove have reached their highest safe temperature. Using speciilc iigures by way of example, the highest'safe temperature.

of the stove may' be in the neighborhood of '21002 whereas thev possible ilame temperature of the gaseous fuel may be'in the neighborhood of .2400 F. It has long been realized that the continuing supply vof flame at excess temperature in proximity to the parts of the stove which have v. already acquired their maximum safe temperature of 2100' endangers the stove. However, as has been well understood. the checkers within the stove may be far below their desired temlectiveiy bridge 'the lpair or contacta' Id or the Dairot contacts Il.

The numeral Il indicatesa relay provided with the switch ll-8. the closing coil Il-C and the opening coil IS-O for said switch.

.Adjacent terminals or the` coils `le-c and is--o are connected to the electric conductor I1. One

of the contacts It and one of the contacts I are jointly connected to the electrical conductor I 'perature when this dangerous condition in a more -vu'lnerable'p'art of the stove, such as the dome.- has been reached. 4

It is desirable that a name temperature be maintained as high as possible to heat these checkers without overheating the vulnerable parts oi' the stove which have already reached their maximum temperature of 2100 F. Accordingly it is' desirable to continue the supplying of gas with an amount of' combustion air mixed therewith t0 pl'vide this temperature inv thev neighborhood o f 2100*.`

It may be stated. therefore, that the heating cycle of a blast furnace stove is divided into two stages: (a) before the vulnerable parts of the Aso stove have achieved their critical temperature,e

inwhich case the most eilicient ratiovbetween gas and vair should be maintained, sind (b) after the vulnerable parts of the stove4 have achieved their critical temperature, during which stage the'fullamount of available gas should be delivered with an excess supply of air to hold the flame temperature to the critical value o f the' neighborhod of this critical temperature.

I8, said conductors I1 and I8 forming the two sides-of an electric circuit. It will be clear that when the pointer Il is in\brid8ln8 relationship with the .contacts II-Il the coil It-C will be connected in circuit across the electrical conductors I'I 'and Il. When said pointer Il is in bridging relationship with the contacts li-ll the `opening coil Ie-O is connected in circuit across'the electrical conductors I1 and I8. SaidY coils' II-C and ie--O have the function. respectively, of closing or opening the switch IB-S forming part of the relay I8. The relay Ie is ofthe type wherein theswitch Ie-B, after being closed by energization of the coil l8-C, will remainclosed until the opening coil Il--Ois energized. -Buch relays are available commercially 4' and need not be described in detail.

The numeral is. indicates a relay having the operating winding I0-W and the switch le-S. Said switch IU-S i8 adapted in its biased posi-- tion toshort-circuit the resistor 20.

When the switch IO-Svof the relay I0 is closed, the winding IO-W of the relay I0 isconnected in' circuit across the electrical conductors I1-#I8 and willv move the switch -ISL-S out of its biased position, thereby removing the shortcircuit'from across the resistor 20. f

The numeral 2i .indicates a burner for. directing gas andair to the stove I0. The numeral 1 22 indicates al conduit for delivering gas to said An object of the present invention is to prol vide means f or protecting ya stove or the like of variations in gas pressure, which control means includes means for modifyingsaid mixture if and when predetermined temperatures are attained. A further object is to provide a stove burner .control vmechanism well adapted to meet 4the needs of commercial Operation. vFurther objects will appear as the description proceeds. f

The one tlg-ure of the drawing illustrates di'- `agrammatically one embodiment of the present invention applied to a blast furnace stove.

' .A blast furnace'stove is.indicated by the numeral I0. The'numeral II indicates a thermocouple; or other. temperature responsive device. whichis electrically connected to a meter I2, which may be of the well known indicating and recording type. Sucl'i meters are commercial equipment and need not-be described in detail. The movable pointer I8 of said meter is adapted at two regions of its range of movement to seprovide la control means burner II. and the-'numeral 23 indicates a motor driven blower for directing air to said burner 2i. The motor of .said blower 2l i's provided with the seid winding u, one terminal of which is connected to the electrical conductor Il andthe other terminal of which is connected to the governing means '25. Said governing means 2l includes the variable resistor 2e, the effective resistance of which is controlled by means of i the movablecontact Il. Accordingly the blower 23 will be'controlled to maintain one denite ratio of vair to gas supply when the meter I2 indicates a predetermined maximum temperature and another dennite ratio of air to sas supply.'

when said meter indicates a predetermined lower temperature. Saidgoverning means 2i may be connected up to beresponsive to the pressure l of gas admitted to the burner 2l, according to the principles set forth in Letters vPatent No. '1,817,210 above referred to. Certain mechanism for accomplishing this purpose is illustrated in the drawing. in which conduit 2l leads from the conduit 2! to the diaphragm housing 2l'.- The diaphragm (not shown) in said housing is connected to the rod Il. which through the link'II controls the levert! te swing about the f pivot II. .Said lever 32 carries the contact 21 at rometer I I is actuatedfin response to temperature changesin the dome of the stove Il to control the position of the pointer Ilot the meter It.

Y aardse? 3 When the meter I2 indicates an'aximum safe temperature, the pointer I3 bridges the contacts II-H, energizingthe coil IB-C to close 'the switch ls-s. c1osure or the switch Is-s results in the energization of the winding I9-W,

opening the short-circuit around the resistor II. By reason of the insertion of the resistor 2l in circuit, the speed of the motor driven blower 23 is `increased, so that, considering any given' gas pressure, there is an increase in the quantity of air delivered to the stove IIJ. In this man-l ner an excess amount of air is supplied to re- 'strict'the temperature in the dome "of the stove.

III-S in its unbiased position. As the dome' temperature continues to decrease, the pointer I3 will move into bridging relationship with the contacts I5, thereby energizing the opening coil IB-O of the relay I6 and opening the switch IB-S thereof, allowing the switch Iii-S to again move into short-circuiting relationship with the resistor 2U, causing the slowing down of the motor driven blower 23.

Under these conditions the eld winding 24 is responsive directly to the governing means 25, which operates, as above explained, to vary the pressure deliveredby the blower 23 in accordance with variations in pressure in the gas supply conduit 22, as fully explained in Letters Patent No. 1,817,219 above referred to.

The present invention has the advantage that relativelyiast rates of combustion may be safely utilized and relatively high quantities oi heat can be stored in the stove without the need for close watchfulness on the part of the stove tender and without danger of overheating the dome. Due to the sensitivity of the equipment the temperature of the stove dome can be maintained within close limits.

for selecting the higher ratio of air to gas upon u attainment of a predetermined high temperature and for' restoring `the lower`ratio of -air to gas upon the attainment of a predetermined lower temperature.

2. In combination, a burner, meansl for sup- Dlyhs gas to said burner, means for supplying air to said burner, said air supplying means being adapted to\supply a substantial excess of air above that required for eicient combustion of any normal gas quantity supplied to said burner, means for providing two predeterminedv ratios between the amount of air and the amount of gas supplied to saidburner by said supplying means independently of any control of the supply of said gas, thev lower of said ratios having just sumcient air to provide eilicient combustion, the higher of ysaid ratios providing an excess of air which is high enough to substantially reduce the combustion temperature, temperature responsive means. and a relay controlled by said temperature responsive means, said relay being adapted to select the higher ratio of air to gas upon attainment of a certain predetermined position by said temperature responsive means and to hold said higher predetermined ratio of air to gas until said temperature responsive means attains a predetermined different position responsive to a predetermined lower temperature.

3. In a blast furnace stove installation, in combination. a blast furnace stove having atemperature responsive member in the portion thereof most vulnerable to excessive heat consaid stove, means for delivering combustible gas to said stove, said air delivering means beingadapted to supply a substantial excess of air above thatl required for eiiicient combustion of Though-a preferred embodiment of the present invention` has been described in detail, many modiiications will occur to those skilled'in the art. It is intended to cover all such modifications that fall within the scqpe of the appended claims. y

What is claimed is: i. In combination, a. burner, means for supplying gas to said burner, means for supplying combustion air to said burner, said air supplying means being adapted to supply a substantial excess of air above that required for efilcient combustion of any normal gas quantity msupplied to said burner, means for providing two predetermined ratios between the amount .of air and the amount of gas supplied to said burner by said supplying' means independently of any control of the supply of said gas, the lower of said ratios having Just sufiicient air to pro- .vide emcient combustion, the higher of said ratios providing an excess oi air which 1,5A high enough tosubstantially reduce the combustion temperature, temperature responsive means, and means controlled by'said temperature responsive means.

any normal gas quantitysupplied to said stove, means for providing two predetermined ratios between the supply of said air and the supply of said gas delivered to said stove independently of any control of the supply of said gas, the lower of said ratios having just suiiicientair to-l provide ei'licien't combustion, the higher of said ratios providing an excess of air which is high enough to substantially reduce the combustion temperature, and means responsive to said temperature responsive member for. selecting the higher ratio of said air to said gas when said temperature responsive member, indicates a predetermined high temperaturev and for restoring the lower of said ratios when said temperature responsive member indicates a lower temperature.

4. In heat transfer mechanism, subject to alternate stages of receiving heat and giving oi heat, in combination, a heat ltransfer member having a temperature responsive member in the portion thereof vulnerable to excessive heat conditions, said heat transfer member being pro- .vided with a burner, means for supplying gas to ratios providing an excess of air. which is high v enough .to substantially reduce the combustion temperature. and means responsive to ,said temdelivering means being adapted to `supply a sub-- l stantial excess oi.' air above that required for emcient combustion of any normal gas quantity supplied to said burner, means for maintainin'! two predetermined ratios between the amount of air'and the amount of gas suppliedl to said burner independently of any control of the supply of said gas, the lower of said ratiosI having just suillcient'air to provide ei'ilcient combustion, the

predetermined ratios between the amount of and the amount ofg'as supplied to said burner by said supplying means independently .oi any control of the supplyof said gas, the lower of said' ratios having just sumcient air to provide eflicient combustion, the higher of said ratios v providing an excess of air which is high enough attainment ofa'predetermined high'temperature higher of said ratios providing anexcess of air' which is high enoughftn substantially reduce ther combustion temperature, and means responvsive to temperature at said vulnerable portion operative when the temperature at said vulnerablel portion reaches a predetermined value to select the higher ratio of air to gas, vwhereby during the iirst stage of the cycle of heating said stove the ratio of air to gas is maintained for the production of maximum combustion temperature and after said vulnerable portion has acquired l a predetermined critical temperature the ratio oi' air to gas is increased to limit said combustion temperature to a value safe with respect to saidcriticaly temperature of said vulnerable portion.

6. In combination, a burner, means for supl plyingv gas to said burner, means for supplying combustion air to said burner, said air supplying means being adapted to supply a substantial excess of air above that required for eiliclent comsald burner, governing means for providing two Patent No.4 2,570,897.

to substantially reduce the combustion temperature, temperaturey responsive means, and means controlled by said temperature responsive means for selecting the higher ratio of air to gas supply'for increasing the delivery o! air upon the as indicated by said temperature responsive 7. In heat transfer mechanism, subject t0 a1- ternate stages of receiving heat and giving of! y heat, in combination, a lheat transfer member having a temperature responsive member inthe portion thereof vulnerable toexcessive heat'conditions,` said heat transfer member being provided with a burner, means for supplying gas to said burner, vmeans for supplying combustion air to said burner, said air supplying means being adapted to supply a substantial excess of air above that required for sufiicient combustion of any normal quantity supplied to said burner,

means for-providing two predetermined ratiosbetween the amount of air and the amount of gas supplied tofsaid burner -independentlv of v the combustion temperature, and means responsive to said temperature responsive means for selecting the higher ratio of air to gas when said temperature responsive member indicates a predetermined high temperature and for selecting the'lower predetermined ratio of air to l gasA when said temperature responsive member vbustion of any normal gas quantity supplied to ARTHURJ. wHITcoMB'.

indicates a lower temperature. Y

` ARTHUR J. WHITCOMB.

March 6, 1914.5,

It is hereby eertifiedthat error appears in the printed specifiation of' theabove nunb ered patent requiring. correction as folloN's: Page 1,'f1rst column, line 56, for the word "presencef' read pressure-f; Kline liO, for' "Leters" read Letters-- Signed and sealed this l (Seal) l 'Y and. that the said Letters Patent Vshould be read witl'iriiiis correction therein 'that the same may eon'f'onn to .the record of 19th day .of June, A. D. 1945.

'Leslie'Fra-zer Acting commissioner ofrecerles.

delivering means being adapted to `supply a sub-- l stantial excess oi.' air above that required for emcient combustion of any normal gas quantity supplied to said burner, means for maintainin'! two predetermined ratios between the amount of air'and the amount of gas suppliedl to said burner independently of any control of the supply of said gas, the lower of said ratiosI having just suillcient'air to provide ei'ilcient combustion, the

predetermined ratios between the amount of and the amount ofg'as supplied to said burner by said supplying means independently .oi any control of the supplyof said gas, the lower of said' ratios having just sumcient air to provide eflicient combustion, the higher of said ratios v providing an excess of air which is high enough attainment ofa'predetermined high'temperature higher of said ratios providing anexcess of air' which is high enoughftn substantially reduce ther combustion temperature, and means responvsive to temperature at said vulnerable portion operative when the temperature at said vulnerablel portion reaches a predetermined value to select the higher ratio of air to gas, vwhereby during the iirst stage of the cycle of heating said stove the ratio of air to gas is maintained for the production of maximum combustion temperature and after said vulnerable portion has acquired l a predetermined critical temperature the ratio oi' air to gas is increased to limit said combustion temperature to a value safe with respect to saidcriticaly temperature of said vulnerable portion.

6. In combination, a burner, means for supl plyingv gas to said burner, means for supplying combustion air to said burner, said air supplying means being adapted to supply a substantial excess of air above that required for eiliclent comsald burner, governing means for providing two Patent No.4 2,570,897.

to substantially reduce the combustion temperature, temperaturey responsive means, and means controlled by said temperature responsive means for selecting the higher ratio of air to gas supply'for increasing the delivery o! air upon the as indicated by said temperature responsive 7. In heat transfer mechanism, subject t0 a1- ternate stages of receiving heat and giving of! y heat, in combination, a lheat transfer member having a temperature responsive member inthe portion thereof vulnerable toexcessive heat'conditions,` said heat transfer member being provided with a burner, means for supplying gas to said burner, vmeans for supplying combustion air to said burner, said air supplying means being adapted to supply a substantial excess of air above that required for sufiicient combustion of any normal quantity supplied to said burner,

means for-providing two predetermined ratiosbetween the amount of air and the amount of gas supplied tofsaid burner -independentlv of v the combustion temperature, and means responsive to said temperature responsive means for selecting the higher ratio of air to gas when said temperature responsive member indicates a predetermined high temperature and for selecting the'lower predetermined ratio of air to l gasA when said temperature responsive member vbustion of any normal gas quantity supplied to ARTHURJ. wHITcoMB'.

indicates a lower temperature. Y

` ARTHUR J. WHITCOMB.

March 6, 1914.5,

It is hereby eertifiedthat error appears in the printed specifiation of' theabove nunb ered patent requiring. correction as folloN's: Page 1,'f1rst column, line 56, for the word "presencef' read pressure-f; Kline liO, for' "Leters" read Letters-- Signed and sealed this l (Seal) l 'Y and. that the said Letters Patent Vshould be read witl'iriiiis correction therein 'that the same may eon'f'onn to .the record of 19th day .of June, A. D. 1945.

'Leslie'Fra-zer Acting commissioner ofrecerles.

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