US2534049A - Apparatus for regulating combus - Google Patents

Description

Dec. 12, 1950 c, MlLLER APPARATUS FOR REGULATING COMBUSTION IN SPREADER STOKER FURNACES Filed Feb. 20, 1948 hvvewro/e 52/715 6. MILLER BY M W Patented Dec. 12, 1950 ermaerv ee UL I Compsrrou -lnsr-n napnn sroggnn ensueons Earle, Millers Worcester, Mass assignor t nileytsiokrr G mqr m, W rces r, Mass corporation of Massachusetts Application February 20, 19 13-,Serial No. 9,899 S CIaims, (Cl. 110 191 This invention relates. to oombustionaregul ation, and more particularly to an improved apparatus forregulatingcombustion in furnaces. of the spreader stokentype.

Dhe ordinary spreader stoker furnace includes amechanism which feeds fuel ata controlledirate to arotor or distributor locatediadjacent; ansopening: in awall of;thefurnacet The distributoris rotated, usually abouta horizontal axis, and. it is provided with blades which throw: the fuel through thewalLopeningand onto a grate within the furnace tomaintain a bed: of burning, fuel. Air-is supplied: for combustion, and the finer particles of fuelburnin suspension, whereas the coarser particles fall upon the fu l bed and: are thereconsumed;

'I-wogenera-b types of combustion control: are in common use.- First there is the so-called "fioati-ng control, whereby the supplies of fuel and air are variedf-ina smooth or gradual manner in accordance with variations in the demand for heat,wi;thin a definite operatingrange. Second there is the so-called start-stop? control; whereby the supplies of fuel and airare started and stopped in accordance with the variations in the demand: for heat: Floating= contro1 pro vides more efficient operation, since; the rate of combustion is maintained closely in step with the heat requirements, and. sudden changes in' combustion conditions are largelyavoided. The operating rang e howeveris more limited, audit is diflioult to operate with such a control when the demandfor heat isvery low. "Start-stop control is well adapted for installations in which a very. wide operating range is required, and in which the demand for heat may at times beat a minimum, However, the combustion efficiency will be less, because of the sudden changes in; the combustion rate between zero. and the maximum. Furthermore, it isnot desirable to stop the rotation of the stoker distributor; for when this is done some of: the fuel may become wedged between the distributor and its housing: and thus prevent the distribu-tonfrom starting its rotation again. Also, a stationary shaft. will be, heated from onesi'de only, and this will cause distorticn of the'shaft.

It is accordingly one object of the invention to overcome these diniculties andflto, provide an pparatus for regulating combustiou in a spr ader stokerfurnace which, will realize the advantagesof the-known types oftcontiiol while avoid ns the disadvanta es thereof.

It is af-ur her abid -tor nvention t are: vide apparatus whereby elimina ion a 2; a p ader Stoker. u ac mayb re u ted as efficient, manner. throughout, a wide range oi; def mand for heat.

It is a further object of the invention 111 1211),- videz an apparatus whereby the combustion a spreader stoker furnace may be regulatedmuto; matically in a thoroughly satisfactory manner even when the demand foiyheat is very. low,

With these and other objects in view; as will be apparent to those, skilled in the art, the in; vention resides in the combination, of parts set forth in the specification and; covered by the claims appended hereto.

Referring to the drawings illustrating one em,- bodiment of the invention, and in. which likereference numerals indicate like parts, the "single figure is a somewhatv diagrammatic. side el'evatidh of a steam generating furnace fired by' a spreader Stoker and equipped with combustion regulating apparatus.

The embodiment illustrated comprises a furnace Ill having a front wall a combustio'n chamber I Z, a grate l4, and'an ash pit bran chamber I 5 beneath the gratefAtf'the' frdnt of the furnace there is provided the usual fire door I immediately above the grate, an 'uie stal ash door l1 communicatingwith the ashpit""5. Afjuel admission opening is provided iri'the wall I] above'the deer l6. spreade f'stolger or known construction is mounted on the to Pr e i l th u h h o ning UL T i stoke'rcomprises a distributor 22 rotatable about a horizontal axisadjacent the openihQ'lQ a' ref ciprocable ram 23' above the distributor tbff d e he to an h per Z4 in nota io to. .9:

ply fuel by amt to the .v T distributar 2' a he a 2% ar t driven i ,1 ii na n r' i n le t i moto i Stok r s d udes 2i t l y m unt d e d o rbl 2.1 whi h ca b m v d s a y th q is cf he ram 23 known manner between zero and'aa max um- Wh n the arm 21 is in the min m indicated by thebrolgen line 28Xthelstrol e of the ram andthe rate of teed will he master as when the arm 'is in the position indicated by, the broken line ZSJthe stroke of the ram and the rate of feed will be at a maximum. The 2-1; is biased downwardly toward its lowermostor zero position by a weight 38. Air for combustion is supplied to the .ash pit tithroughaduct 32 y h m o a a 33 d i by a e ect is new 34. The air flow is controlled by a damper oc ed With the u t s de an 31 Thi rm saee i a mantis-wh m serves to bias the damper toward its closed position.

The heat produced by the combustion of the fuel is utilized to generate steam in a boiler 49 associated with the furnace ID. This boiler comprises the usual water tubes 4| located in the path of the hot gases leaving the combustion chamber l2, and the usual steam delivery pipe 42. Upon leaving the boiler, the furnace gases flow through a duct 44 to a stack or other draft producing device (not shown). Within the duct 44 there is provided a damper 45 having an arm 46. This damper is preferably controlled automatically in known manner to maintain a predetermined pressure, slightly below atmospheric, in the combustion chamber I2. For this purpose there is shown a regulator 48 of the type disclosed in the United States patent to Temple No. 1,992,048, granted February 19, 1935. This regulator comprises a pilot valve mechanism 49 supplied with a suitable fluid under pressure through a pipe 50 and connected by tubes 52 to a hydraulic motor 53. This motor is connected to the damper arm 46 by a rod 54. The regulator 49 is connected to the combustion chamber [2 by a pipe 55.

The fuel feed and the flow of combustion air are controlled automatically in accordance with variations inthe demand for steam from the boiler 40. For this purpose there is provided an automatic regulator 51 of the type disclosed in the United States patent to Temple No. 2,049,549 granted August 4, 1936. This regulator comprises a diaphragm chamber 58 and a reversible motor 59. nected by a pipe 6| to the steam delivery pipe 42, and the motor 59 is connected by a rod 62 to a lever 63. A flexible cable 65 leads from the lever 63 over an idler sheave 66 to the damper arm 31. A second flexible cable 68 leads from the lever 63 over an idler sheave 69, thence in the form of a loop beneath an idler sheave 19, and thence over idler sheaves H and 12 to the fuel feed control arm 21. The construction is such that with the idler sheave 1!! in the position shown in full lines, a full stroke of the regulator 51 will move the arm 21 through the angle A between the broken line 29 and a broken line 13 which lies at an angle B with the broken line 28. The angle A is preferably considerably greater than the angle B. As the arm 21 is moved from the position 29 to the position 13, the damper 36 will be moved from an open position to'a nearly closed position, maintaining the proper ratio between the supplies of fuel and air at all times. The automatic control throughout the angle A will take place in a smoothly graduated or floating manner, and it will correspond to a definite range of heat demand as indicated by the steam pressure transmitted through the pipe 6| to the regulator diaphragm chamber 58. Thus, by way of ex ample, the maximum load position 29 may correspond to a steam pressure of say 200 pounds per square inch, and the position 13 may correspond to a steam pressure of say 208 pounds. While the steam pressure is at a value between these limits, the regulator 51 will hold the feed control arm 21 at a corresponding intermediate position.

If now the demand for heat should become so low as to cause the steam pressure to rise ap preciably above 208 pounds (say to 210 pounds) requiring even less fuel than is represented by the arm position 13, a further regulating means The diaphragm chamber 58 is conwill assume control to stop the fuel feed and the fan 33. For this purpose certain additional regulating apparatus is provided. Thus the idler sheave 10 is mounted on a yoke 15 which may be moved vertically by a reversible hydraulic motor 15 connected by tubes 11 to a valve mechanism 19, the latter being supplied with a suitable fluid under pressure through a pipe 99. A solenoid 8! is connected to the valve mechanism 19 to actuate the same in a known manner, the arrangement being such that when the solenoid is energized, fluid will be admitted to the upper end of the motor 18 to hold the sheave 19 in its lower or full line position. Upon deenergization of the solenoid, the motor 16 will raise the sheave 10 to the broken line position, thus slackening the cable 68 sufliciently to lower the arm 21 to the zero feed line 28. A pressure actuated master controller, such as a master switch 93 of the well-known mercury tube type, is connected to the steam pressure pipe 65. This switch may be adjusted to open when the steam pressure increases to say 210 pounds, and to close when the steam pressure decreases to say 208 pounds. The fan motor 34 is connected to a suitable source of electrical energy by means of a magnetic contactor having three normally open switches 86 and an actuating coil 81. is also provided a magnetic contactor having two normally open switches 89 and 99, and an actuating coil 9|. To ensure maintenance of fuel bed ignition during periods of low heat demand, an interval timer 93 is provided having a switch 94 which is closed at predetermined intervals by a small electric motor 95. In addition,- a source 91 of electrical energy is provided, with a manually operable switch 98 to control the same.

The various electrical connections will now be described. The solenoid 8| and the switch are connected in series across the source 91, as controlled by the switch 98. The pressure switch 83 and the coil 9! are likewise connected'in series across the source 91, and the switch 89 and the coil 81 are similarly connected in series. The switch 94 is connected in parallel with the switch 90. The motor 95 is connected across the source 91, as controlled by the switch 98.

The operation of the invention will now be ap-, parent from the above disclosure. The switch 98 will be closed, and if the steam pressure is less than 208 pounds the'master pressure switch 83 will be closed, energizing the coil 9!, so that theswitches 89 and 99 will be closed. The closed switch 89 will energize the coil 81, so the switches 86 will be closed and the fan motor 34 will bein operation to drive the fan 33. The closed switch 99 will energize the solenoid 8|, so that the valve 19 will cause the hydraulic motor 16 to hold the idler sheave 19 in its lower or full line position. The motor 95 of the interval timer 93 will close the switch 94 periodically, but this will have no effect so long as the switch 90 is closed. The stoker motor 26 will operate con-' bustion gases will generate steam in the boiler 40, and the gases will then escape at reduced temperature through the duct 44. The regulator 49 will control the damper 45 in known man- There ner'toimaintain a predetermined sub-atmospheric pressure in the combustion chamber l2. The steam will flow through the pipe ezto a place of use. Anyincrease in the demandlfor steam will tendtoreduce the-steam pressure, and vice versa. So long as the steam pressure remains within the operating range of the regulator 51, which we have assumed to. be from 200 to 208 pounds, this regulator will control the fuel feed control armZl. and the airoontrol damper 36 in asmooth or-floating manner. In other words, these parts will assumepositions varying with the steam pressure, the position of the arm 21 being somewhere between the lines 23 and 713.

If now the demand for steam decreases until the steam pressure rises to Z'iidpounds, the regulator motor 59 will be at the upper limit of its stroke, the damper 36 will benearly closed, and the stoker arm 21 will be in the position indicated by the line i3, so that the ram 23 will feed fuel at a lowrate to the distributor. If the steam pressure continues to increase and reaches 210 pounds, the master switch it will open, deenergizing the coil 9!, and opening the switches se and 99. Opening the switch as will deenergize the coilai' and thus open the switches 85, so that the motor 34 and the fan 33 will come to a stop. Opening the switch 93 will deenergize the solenoid 8!, causing the valve '59 to admit pressure fluid to the lower end of the motor '16, and the sheave 'lii will accordingly be raised to the broken line position. This will slacken the cable i8 and lower the arm 21 to the position indicated by the line 28, so that the stroke of the ram will be reduced substantially to zero. While the steam pressure remains above 208 pounds, the periodic closing of the switch 94 by the motor 95, say for two minutes out of every ten minutes, will energize the solenoid 8i and cause the sheave E0 to return to its full line position, moving the arm 2'17 to the line 13 position, and supplying a small amount of fuel to the grate M. This will ensure the maintenance of ignition in the fuel bed during long periods of low demand for steam. When the steam pressure decreases to 208 pounds, the master switch 33 will close, energizing the coil 9!, and closing the switches es and The closed switch 89 will energize the coil 8?, closing the switches as and starting the fan motor 34 and the fan 33. The closed switch 98 will energize the solenoid 8!, causing the motor '56 to lower th sheave iii and raise the fuel feed arm to the line 13 position. Thus the rate of combustion will be increased, tending to raise the steam pressure once more.

It will accordingly be seen that unless the demand for steam is very low, the combustion will be under the control of the regulator 51, and this regulator will operate in a floating manner to change the fuel and air supplies smoothly and gradually in accordance with variations in the steam pressure. Under conditions of very low demand for steam, the master switch 83 will be in control, starting and stopping the fuel feed and the forced draft fan as required to meet the steam requirements. Furthermore, if the demand for steam is low or even zero, the interval timer 93 will bring about an intermittent feed of fuel in amounts sufficient to maintain ignition in the fuel bed, the necessary air flowing past the nearly closed damper 35 by reason of the slight suction in the combustion chamber l2.

The invention makes it possible to operate the furnace automaticaly and efliciently over a very wide range of demand, in fact from zero demand up tothemaximumfuel burning capacity of the apparatus. Since the distributor 22 is rotated continuously, even understart-stop control, there of the fuel feed control arm 2:? corresponds to a relatively low range in steam pressure and to a relatively high range in demandifor heat. Similarly, the angular movement 13 corresponds to a relatively'high range in steam pressure and to arelatively low range in demand for heat.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1, In combination with a furnace for the combust/ion offuel and the production of heat, a rotatable spreader 'stoker distributor to supply fuel tothe furnace, means to continuously rotate said distributor, means to feed fuel to the distributor, a forced draft fan to supply air to the furnace, master controller responsive to changes in the demand heat, and connections from the controller to the fuel feedingmeans and the fan, effective to start and stop the fuelfeed and-the fan as the demand for heat increases and decreases while the distributor continues to rotate.

2. In combination with a furnace for the combustion of fuel and the production of heat, a rotatable spreader stoker distributor to supply fuel to the furnace, means to continuously rotate said distributor, means to feed fuel to the distributor, a forced draft fan to supply air to the furnace, an air control damper operatively associated with the fan, a master controller responsive to changes in the demand for heat over a relatively low range, an automatic regulator responsive to changes in the demand for heat over a relatively high range, connections from the controller to the fuel feeding means and the fan effective to start and stop the fuel feed and the fan as the demand for heat increases and decreases within the low range and while the distributor continues to rotate, and connections from the regulator to the fuel feeding means and the damper effective to adjust the same as the demand for heat varies within the high range.

3. In combination with a furnace for the combustion of fuel and the generation of vapor, a rotatable spreader stoker distributor to supply fuel to the furnace, means to continuously rotate said distributor, means to feed fuel to the distributor, a forced draft fan to supply air to the furnace, an air control damper operatively associated with the fan, a master controller responsive to changes in the vapor pressure over a relatively high range, an automatic regulator responsive to changes in the vapor pressure over a relatively low range, connections from the controller to the fuel feeding means and the fan effective to start and stop the fuel feed and the fan as the vapor pressure decreases and increases within the high range and while the distributor continues to rotate, and connections from the regulator to the fuel feeding means and the damper effective to adjust the same as the vapor pressure varies within the low range.

i. In combination with a furnace for the combustion of fuel and the generation of vapor, a rotatable spreader stoker distributor to supply fuel to the furnace, means to continuously rotate said distributor, means to feed fuel to the distributor, a forced draft fan to supply air to the furnace,

7 an electric motor to drive the fan, an air control damper operatively associated with the fan, a master pressure switch responsive to changes in the vapor pressure over a relatively high range,

- a first reversible motor controlled by the switch and movable through a predetermined stroke, an automatic regulator responsive to changes in the vapor pressure over, a relatively 'low range and including a second reversible motor movable through a predetermined stroke, connections from the second reversible motor to the damper to adjust the same, connections from the second reversible motor to the fuel feeding means to adjust the same between a high feeding position and a low feeding position, means connecting the first reversible motor tothe last mentioned connections to adjust the fuel feeding means between the said low feeding position and a zero feeding position, and connections from the master pressure switch to the fan motor to start and stop the same as the vapor pressure reaches respectively the lower and upper limits of the said" high range.

5. In combination with a furnace for thecombustion of fuel and the production of heat, a rotatable spreader stoker distributor to. supply fuel to the furnace, means to continuously rotate decreases within the low range and whilethe distributor continues to rotate, and connections from the regulator to the fuel feeding means eilective to adjust the fuel feed as the demand for heat varies within the high range.

' EARLE C. MILLER.

REFERENCES CITED The-following references are of record in the file of this patent:

v UNITED STATES PATENTS ,Number Name Date 1,472,280, Ousdahl Oct. 30, 1923 2,055,641 Young Sept. 29, 1936 2,205,494 Schindler June 25, 1940 2,376,701 Klinker May 22, 1945 2,385,811 Hotchkiss Oct. 2, 1945

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