US1685788A - Furnace regulation - Google Patents

Description

"Oct, 2, 1928.

c. H., vsMoo'r FURNACE vREGULATION Filed Dec. 16, 1926 2 Sheets-Sheet 1 ATTORNEYS Oct 2, 1928. 1,685,788

c. H. sMooT FURNACE REGULATION Filed Deo1s;.192s 2 sheets-sheet 2- Patented Oct. 2, 1928.

i UNITED STATES CHARLES H. SHOOT, OF'MAPLEWOOD, NEW JERSEY.'

FURNACE REGULATION.

Application led December 16, 1926. Serial No. 155,232.

This invention relates to the art of furnace v regulation and more generally to the art of regulation by proportionate pressures.

One purpose of my invention is to devise novel apparatus adaptedto regulate the resistance offered to the gaseous flow through a furnace to thereby effect the control of the pressure above the fuel bed.

Another purpose of my invention is to devise a complete system for automatic furnace regulation, and adjustable Vapparatus therefor, embodying the general features of centralized regulation disclosed and described in my Patent No. 1,551,272, granted August 25, 1925, an application, Ser. No. 143,309 for a reissue of which is now pending. y

Still another purpose of my invention is to utilize the air pressure from the common forced draft air duct of a boiler plant as a master controlling force for the centralized regulation of the plant.

Other purposes and novel features VWill become apparent from the description and accompanying drawings. a

In the claims annexed hereto I have not included certain of the broad features of my proportionate pressure apparatus hereinafter to be described as these features form part of the invention described in my co-pending application, Serial No. 155,231 filed December 16, 1926, and are therein broadly claimed.

For a better understanding of my invention and the advantages pertaining thereto, reference may be had to the accompanying drawings. 8

Fig. 1 is a. diagrammatic representation of a simple embodiment of my invention.

Fig. 2 is al diagrammatic representation of my invention as applied to the centralized 4o regulation of a boilerl plant.

ln Fig. 1` I have illustrated my appara-l tus for maintaining constant the resistance odieredby the fuel bed and inlet damper of a furnace to the gaseous flow therethrough. A boiler furnace, l, having a fuel bed 2, and a stack 3 .is supplied with forced draft from the blower 4 through the inlet 5. A damper 6 controls the inlet air flow and a hand operated damper 7 controls the flow of exhaust gases fromr the furnace. The operation of the damper 7 is immaterial to the embodiment of my invention disclosed in Fig. 1,v and might be` controlled automatically by the steampressure or in any other well lrnown -i manner as desired. The damper 6 is controlled according to my! invention by the` apparatus hereinafter to be described. A conduit 8 having the manually operated reducingvalves 9 and 10 leads from a point 11 located between the damper 6 and blower 4 in the inlet 5 to a point 12 within the furnace 1 and above the fuel bed 2. vA conduit 13 leads from the conduit 8 at a point intermediate the valves 9 and 10 to a chamber 14. The chamber 14 is closed by a diaphragm 15 to which is rigidly attached a rod 16. The damper 6 and rod 16 are operatively connected by link 17.

lVith a constant air pressure delivered by the blower 4, this apparatus operates to maintain constant the total resistance offered by the inlet damper and the fuel bed to the air j flow through the furnace, and therefore to maintain a constant pressure above the fuel bed according to the following theory.

During combustion there will be a flow of air through the furnace, and a consequent drop in static pressure along the path of low. The conduit Spermits a by-path How from the point 11 below the inletdamper to the -point 12 above the fuel bed, which flow, for any definite posit-ion of the valves 9 and 10 bears a definite relation to the flow through the furnace between the same two points. The static pressure within the conduit 13 and chamber 14 will be of course intermediate the pressures at the points 11 and 12, its value relative to either' of those at these two points depending upon the resistance to the flow through the conduit 8 offered by the valves 9'and 10. With the valve 9 partly closed, and thereby offering relatively large resistance, and with the valve 10 wide open and thereby offering relatively small resistance, the pressurewithin the chamber 14 will have a value closer to that at the point 12 than to that at the point 11. Conversely, with the valve 9 open and the valve 10 partly closed the pressure within the chamber will be .nearer that at 11 than that at l2. For any given inlet air pressure `the pressure at the point 12 will. depend vupon the thickness of the fuel bed and upon the setting of the inlet damper. The opposing pressures of the air within the chamber 14 and of the atmosphere act upon the diaphragm 15 to control the setting of the damper 6 by means of rod 16 and link 17, a departure from atmospheric pressure within the chamber tending to change the position of the damper to return the pressure within the ronduit to that of the atmosphere. If the pressure within the chamber'14 increases the fl (l sure above the fuel bedl at the point 12 and;

the fuel bed and inlet damper Will offer a definite resistance to the flow through the furnace. lf new, the fuel' bed becomes thin, or holes develop, the resistance offered by thebed; willy decrease, and the negative pressure at 12 therefore will, momentarily decrease and the pressure in the conduitlland chamber 14n/'ill exceed. thatV ofthe atInOs# phere. This pressure increase Willimmediately move the damper to increase its resistance until: the pressure at 12 returns to its original l Vvalue andthc pressure Within the chamber 14 returns. to that ofthe atmosphere. It follows therefore that the resistance added by the new positionof the damper must be eX- actly equalv to thedecrcase in that of the fuel bed' resistance.

creases the negative pressure aty the point 12 and decreascs'that Within the chamber 111 which latter moves the damper to offer less resistance tofloiv to return the pressure at 12 to its original value and to return the pressure Within the chamber to that ofy the atmosphere, the decrease in resistance offered by the new posit-ioniof the damper being equal to the increase in resistance offered by the thicker fuelbed.

. F or a given inlet air pressure thevalves 9 and' 10 are set according` to the pressure it is desired to maintain at the point 12 above the bed. A partial closure of the valve 9, Wit-h the val'x'fe 10 open, willy adjust the apparatus to maintain a relatively small negative pressure above the fuel bed, While a partial closure of the valve 10 with the valve 9 open Will maintain a largernegative pressure above the bed.

Vheneier the inlet air pressure changes to a new value the apparatus of Fig. loperates to` maintain a nen' pressure above the fuel bed and a new total resistance to flow between the points 11 and; 12; lf the, inlet pressure increases the pressure within the chamber 14A increases causing the damper 6 to increase its resistente to the flow until the pressure Within the chamber returns to atmospheric. This` can only occur when the negative pressure at 12 has been increasedv by an amount proportional to the positive pressure increase at 11.U The apparatus then operates to maintain constant the new and greater lvalue of the total resistance offered by the damper and rality of boilers.

Similarly an increase in the thickness of' the fuel bed momentarily in-V damper to maintain any desired negative pressure above the fuel bed. The apparatus described pern'iits of ready adjustment ifl desiredand can be usedv with or Without other regulating devices for the different elements ofcombustion in the furnace.

In Fig. 2l have illustrated diagrammatically my system ofproportionate pressurel regulation as applied to the entire combustion regulation of a plant comprising a plu- The numeral 1 indicates one of a series` of. boiler furnaces supplying steam to the common header 64:. Air is supplied to the boilers from the main (i5 fed. by the blower 4. A. damper. 6 in the air inlet 5 to the furnace 1fv controls lthe. passage of air. tor the fuel bed 21and a. damper. 7 in thestacl 3l controls theoutlet of the gases of combustion. Fuel is fed to the. furnace from the hopper G6 by the stolcr engine. 67. The air main 65 supplies air to a master controller G8 through the pipe G9 provided with the valve 69, The pipeGQcOnnectsivith the air duct 65 at a point' 63 between the blower 4l.

and the furnaces 1. There are three4 conduits 710, 71 and 725 leading from the master controller and terminating in branches to the various elements to be controlled through eachl of which conduits and branches. there Will.y be a flow of air, controlled by aredjucing. valve 7 3; Gauges 181 indicate the pressures in the conduits 70, 71 and 72 beyond the valves 73. A, gauge 1'8" indicates the pressure in` the conduit G9r between the valve 694ya andthe main G5 and a gauge 18? indica-'tes the pressure in the master controller. branch, conduit 1*;91provided.I with a valve 20 leads frointhe conduit 70 to a point 21 in the sition of,v the dan'iper- 7Hby ine-ans` of the rod,

2G rigidly attached tothe di apln'agm 25,*the lever 27 pivoted at 28 and the links 29 and 80, a slight increase in` the pressure4 Within the chamber 24h tending to slightly openr the damper 7.

' A; branch llprovidedivith a valve 32 leads from the conduit 71 to a point 33 between the tubes 22 and the fuel bed 2 of each boiler,

furnace. Connected to the con-duit 31v between, the. valve 32 andl the conduit 71 is a lill) G8 through the conduit 58.

branch 34 terminatingin a chamber 35 closed by a diaphragm 36 which is responsive to he difference between therpressure Within the chamber 35 and that of the atmosphere. As shown the diaphragm 3G controls the position of the damper 6 in the saine Way as the diaphragm controls the damper except that an increase in the pressure Within the chamber tends to close rather than to open the damper.

A suction fan 37 is driven by the stolrer 11 to run at a speed proportional to thatof the Stoker'. This fan creates a negative pressure at a point 38, which pressure varies in* versely With the square. of the fan speed7 and therefore inversely With the square of the stoker speed. A branch 39 provided with the valve 40 leads from the conduit 72 to this point of negative pressure 38 of the fan 3T. Connected to the conduit between the valve 40 and the conduit 72 is a branch 41 terminating in the chamber closed by the diaphragm 43. The diaphragm 43, moving in response tothe di'lference in the pressureivit-hin the chamber and that ofthe atmosphere, controls the supply of operating luid to the/stolzer engine 67 by the throttle 45 in the supply pipe 46 through the rod 44 at tached rigidly tio ythe diaphragm 43 andv linked to the throttle y45.

At 47 I have illust-rated a device which acts to vary the air pressure in the conduit (S5 and in the master controller 63 in inverse ratio vWith the pressureof the steam in the header 64. A chamber 48 having a diaphragm 49 receives steam from the header (i4 through the connecting pipe 50. A rod 51 is rigidly attached to the diaphragm and pushes upon a `lever 52 hinged at 53. A weight 54 is partly suspended from the end of the lever 52 and partly supported bv a rod rigidly attached to a diaphragm 5d. The haphragm 56 closes one side of a chamber 57 4A1u con'lmunication with the master controller The position of the lever 52 determines the speed of an electric nl otor 59 Which drives the blower '4 by adplstmg the electrical resistance 6() through the pin n61 and sliding contact arm G2 in the motor circuit as shown.

The .theory of the operation of the appa.- ratus disclosed in Fig. 2 similar in many respects to that given in connection with Fig. 1. At the point 63 there .is a positive pressureiicoi responding to that at the point 11 of Fig. 1, from which point there will be a by-pass iflow through the pipe 469, master controller G8. conduit 71 and branch 31 to the point 33 above the fuel bed 2. The pressure within the chamber 35 is that at a point along this by-path flow and the difference between this pressure and that of the atmosphere controls the position of the damper 6 and therefore the resist.

ance to the flow through the furnace 1 otfcrul by this damper. The damper 6 is controlled V69 corresponding to the vavle 10 and thevalve 32 corresponding to the valve 11 ot' Fig. 1.

`The negative pressure above the fuel bed is therefore cont-rolled by the damper 6 to vary proportionately `with the air duet pressure and as the pressure Within the master controller G8 also varies with the air duct pressure it follows that the negative pressure at the point 33 above the fuel bed varies with the pressure in the master controller.

Similarly there Will be a liv-pass flow from the point (S3 through the pipe (3)7 master controller 68, conduit 7() and 'branch 19 to the point 21. The pressure in the chamber 24 will be that at a pointalong this by-path flow and the difference between this pressure and that of the atmosphere will control the position of the damper 7 an increase in the pressure Witlt in the chamber tending to open the damper 7, to increase the draft suction. The increase in suction increases the negative pressure at the point 21 until the pressure Within the charnber returns to that of the atmosphere. In the same way a decrease in the pressure Within the Achamber 24 results in a decrease in the draft suction, a decrease in the negative pressure at the point 21 and the consequent return to atmospheric pressure Within the chamber 24. The setting of the valves G9 in the pipe 69, 73 in the conduit 70 and 20 in the branch 19 control the ratio between the positive pressure in the air duct or master controller and the negative pressure at the point 21.

T he pressure within the chamber 42 is that at a point along the by-path flow from the point 63 through the pipe 69, controller 68, conduit 7 2 and branch 39 to the point of negative pressure 38 of the exhaust fan 37. The difference between this pressure and that of the atmosphere controls the flow of motive fluid through the valve to the stoker engine 67 and therefore controls the speed of the stolzer engine G7 and the speed of the fan 37 as Well, an increase in the pressure Within the chamber 42 causing the stoker to speed up and therefore the negative pressure at this point 38 to increase. The negative pressure at this point 38, and therefore the square of the speed of the Stoker, is thus maintained proportional to the pressure in the airduct and so to the pressure in the n'iaster controller. the ratio depending upon the setting of the valves 69a, 73, in` the conduit 7 2 and 4() in the branch 39.

The pressures Within the chambers 24, 35 and 42 are thus regulated to that of the atmosphere, variations from which pressure in any one of these chambers causing a movelill) ment of the damper or a change in the speed lfurnace nega-tive pressures proportional. to

Vthe air main and ina-ster contr ller ('38, and

to maintain a stoker speed the square of which is proportional to these air pressures. ',lhese air pressures are maintained inversely propoi-tional` to the steam pressure in the main .header by the device il as already described7 and the ratio etween the pressure in the air inain and in the master con .'oller can be adjusted manually at the master controller by means of the valve Se, and this ratio indicated by the gauges l and 18h. between the u alive pressures at 'the poiiis 2l of all 'the ituriiaces and that within the master controller maybeadj usted by the valve 73 in the conduit TO. Similarly the valve 73 in the conduit Til permits adjustment ot the ratio between the negative pressures at the vpoints 33 ot all the boilers and t a wi* master controller, and the valve 'l t duit T2 permits au adiustiu of stoller speeds` to the pressi.

he coucontroller. The valves 20, 32 and l0 permit adjustment of these same rr;

the other 'furnaces or stolrers.

Then the regulating system is in operation an increase in` steam pressure in the maui header, indicating` drop in load on the boil-V ers, results in a decrease. ot the blower speed, a drop in the air supply main pressure, drop in the pressure in the niaster controller, a decrease in the speed ol the stoliers, an init al openingl of the inlet danipers and a closing.;` oit .the exhaust danipers to positions which will return the system to equilibrium at the new steam pressure. TVith a decrease in steam pressure the blower' and stokers speed up, the inlet dempers tend to close and the outlet dampers to open to speed up combustion to correspond with the new load on the boilers. TiVith constant sten-in pi ssuro when a change occurs in the lire bed, resulting,` in changed resistance to air liow, tl e changed pressure at the'point above the .tuel bed will cause a corresponding change in the pressure within the chamber und "l a siii'ft in the position oit' the damper l to change its resistance to the air liow'by :in amount equal and opposite to the change in the iuel bed restance.

By using the air pressure from lthe common forced dratt aff duct as the master control ling@T force I have eliminated the necessity for an auml-lary lluid pressure supply for this purpose and have di-erebyY obviated one possible source of i'ailure oit 'the apparatus that has ,hitherto been yinherent wits the niaiiator conhin the device moving;v in response to the pressure ot the atmosphere and to a pressure which is regulatedl to that o'r the atmosphere as a result of the element controlled. ln practice the pressure responsive device illustrated as the membrane l5 of l or the membrane 25, or ll oi lli 2 would control an auxiliary aplisratus operated by an external torce such as oil pressure, compressed air or electricity, this auxiliner;v apparatus then supplying the motive torce to move the damper or to change the speed ol" the Stoker. Such an auxiliary apparatus is shown in the drawing in my co- Vpendinp; application, Serial No. 155,23l above the numeral ll.

pressure. l

l have now described and illustratedviny invention applied.' to the regulation of boilr t'urnaces, but Y l do not wish to be limited such peeilic application, nor to the particular embodiments shown.

ltfis ot course apparent that certain ieatures oi my invention might advantageously beyond the scope o l' the annexed claims to employed at times without the correspond ing use of the other features and that many changes might be made in the arrangei'nent of parts or in the elenients controlled without departing from thescope ol my invention.

l claim:

l.. ln a boiler furnace havingl an inlet damper, stack damper, astoler and a blower, a control system comprising in combination a master controller connected by pipe to the air duct oi the blower, a conduit leading from the master controller to a point in the furnace just below the stack, a-valve in said conduit at the point of connection to the master controller, and a 'second valve in said conduit near the lar end thereof, means :tor controlling the stack damper by the dillerentlal between the pressure o'l' the atn'iosphere and that at a point in said conduit intermediate said valves, second conduit lea-ding` from the master controller and `wovided with a valve at the point oiI connection to the master controller, said second conduit leadingl to a point just above the fuel bed and likewise provided with a valve near the tar en d thereof, means for controlling` the inlet damper by the `ditl'lerential between the pressure of the atmosphere and that within said second conduit at a point intern'iediate the valves, an exhaust lan operated by the stoker and varying in seed with the speed of the stolrcr,

a third conduit leading from the master controller to the exhaust end oi said 'tan and having valve at the connection between the master controller and this third conduit and a second valve near the far end of the conduit, means for controlling the speed of the stoker engine by the differential of the pressure of the atmosphere and that within the conduit at a point intermediate said valves, and means for varying the air duct pressure inversely with the steam pressure.

2. In a boiler plant comprising a plurality of boiler furnaces having regulable air and fuel supplies, a control system including in combination a master vcontroller connected by pipe with the common air duct of the blower, means for causing a regulable by-path flow from said controller to a pointl in each furnace just below the stack, means for controlling the draft in each furnace in response to the differential of the pressure of the atmosphere and that at a point along said b'y-path flow, means for causing a regulable by-path flow from said controller to a point in each furnace just above the fuel bed, means folIl controlling the iiow of air through the fun nace in response to the differential of the pressure of the atmosphere and that at a point along said last mentioned by-path flow, means for creating a negative pressure proportional to the square of the speed with which the fuel is fed, means for causing a regulable ley-path flow from the master controller to a point at such negative pressure, means for regulating the speed at which fuel is fed to the furnaces in response to the differential of the pressure of the atmosphere, and that at a point along said last mentioned by-path iiow, means at the master controller for man ually adjusting all of said by-path flows and means for varying the air duct pressure inversely with the pressure of the steam from all the boilers.

3. A steam generatingfurnace including an inlet damper, an outlet damper, a regulator for one of the dampers controlled in accordance with a desired intermediate between the pressure at a point in advance of the inlet damper and at a point beyond the furnace bed, and a regulator for. the other damper controlled in accordance with a desired intermediate between. the pressure at a point in advance of the inlet damper and a point near the outlet damper.

4. In a controlsystem for. boiler plants having a plurality of boiler furnaces the combination of a blower for producing a forced draft, a device responsive to variations of steam pressure and to the pressure ofthe draft controlling the speed of the blower, in dividuz-.l combustion regulators for the several furnaces, and means for causing the variations of pressure of the dra-ft to affeet the control of each of the individual regulators.

5. A control system for boiler plants comprising in coinl'iination a master controller, means for supplying the master controller with a pos ive air pressure varying with the air duct pr ure, means for creatine' a plurality of regulable air iiows from said master controller to points of negative pressure, means for controlling an element effecting the combustion in a furnace by the differential between the pressure of the atmosphere and 'that at a point along each of said air flows, means at the master controller for adjusting each of said flows, and means for varying the air duct pressure inversely with the steam pressure.

6. In a contro system for steam generating plants having a plurality of boiler furnaces, the combination of a blower for pro ducing a forced draft, a plurality of individual combustion regulators at the several furnaces, a master controller for supplying air pressure to said individual regulators7 means for supplying air under pressure from the blower to the master controller, and means for controlling the pressure of the air fromtbe blower in accordance with variations of steam pressure.

7. A steam generating furnace including a blower and an inlet damper, aregulator for the damper and means for controlling said regulator in accordance with a desired intermediate between tlie pressure at a point in advance of the damper and at a point in the combustion chamber.

8. In a control system for steam generating plants having a plurality of boiler furnaces, the combination of a blower for producing a forced draft, a plurality of individual combustion regulators at the several furnaces, a master controllex'for supplying air pressure to said individual regulators, and

means for supplying air under pressure from the blower to the master controller.

In testimony whereof, I have signed my name to this specification.

CHARLES H. SMOOT.

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