US1423764A - Oil-fired steam boiler - Google Patents

Description

B. GREENFIELDI 0H. FRED STEAM BOI'LER. APPLICATION FILED MAR. I2, w29.

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through NETE@ BENJAMIN GREENFELD, OF BAR'ILESVXLLE, OKLAHOMA, ASSIGNOR,

BY MESNE ASSIGNMENTS, T0 DOHERTY RESEARCH COMPANY.

OIL-FRED STEAM BOILER.

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Specification of Letters Patent.

Patented July 25, 1922.

Application filed March 12, 1920. Serial No. 365,367.

To all whom. t may concern Be it known that I, BENJAMIN GREEN- FIELD, a citizen of the United States of America, residing at Bartlesville, in the county of Washington, State of Oklahoma, have invented certain new and useful lmprovements in Oil-Fired Steam Boilers; and l do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

rlhis invention relates to a method and apparatus for controlling combustion in oil ired steam boilers.

With the rapid development of oil for industrial fuel purposes, the combustion efficiencies obtained in burning oil have been very loW. rThis has been due mainly to the fact that the oil fuels have been burned in furnaces which are not properly constructlThe fuel losses are caused in a large degree by over-venti lation and also by under-ventilation. The under-ventilation loss is caused by an insufcient supply of air to the fuel so that the unburned fuel passes out of the stack in flue gases. rl`he common and largest loss is caused by over-ventilation in which an eX- cessive amount of air is used to burn the oil thereby giving a decreased flame temperature and causing a large amount of heat to be carried out of the stack with the flue ases.

To obtain the highest efficiency in the cembustion of oil, it is necessary to supply the oil and air for supporting combustion in such proportions that the air will just suffice to completely burn the oil and will not be in suficient excess of this amount to materially cool the flame or dilute the hot products of combustion. Because of the comparatively small volume of oil used, the proper proportioning of the oil and air requires great accuracy in the control and measurement of the oil, since a comparatively large variation from the proper proportions is caused by a comparatively small excess or deficiency in the volume of oil above or below that required for perfect combustion.

This accuracy of control of the volume of oil supplied cannotbe obtained by varying the opening of the control valves commonly used on the oil supply pipe, since the flow these valves does not follow any definite law. This is more especially the case when the volume of oil is constantly or frequently varied, with changes in the consumption of steam from the boiler. Under these conditions changes in the flow of oil through valves of this type can not be readily and accurately measured, nor can the measurement of the flow of oil be accurately transmitted to an air supply controlling device. lt has, therefore, been customary to supply air to oil fired boilers in excess of that required for perfect combustion in order to insure complete combustion and avoid the formation of soot and smoke and the Waste of fuel. Consequently, a large part of the heat of combustion is wasted in heating this excess of air rather than used in generating steam or forv other useful work.

`The primary object of the present invention is to provide a method of combustion control for oil fired boilers in which the supply of oil and air for supporting combustion is accurately controlled to give the proper proportions for the efficient combustion of the fuel.

Another object of the present invention is to provide an apparatus for controlling combustion in oil fired boilers in which the changes in the supply of oil and air for su porting combustion will be made accurate y and simultaneously.

With these and other objects in view, the invention consists in the method of and apparatus for regulating combustion in oil fired boilers described in the following specication and defined in the appended claims.

The various features of the invention are illustrated in the accompanying drawing in which Fig. 1 shows a boiler equipped with a combustion regulating apparatus embodying the preferred form of the invention. and Fig. 2 is a detail sectional view of the valve for regulating the pressure inthe oil feed tank.

In accordance with thepresent invention,

the generation of steam in the boiler is con trolled by varying the rate of feed of oil to the boiler with a corresponding and simultaneous variation of the air supply. rllhe rate of iow of oil is controlled by the steam pressure of the boiler, the control in turn being operated between definite limits of steam pressure. The steam pressure acts upon the oil in a closed feed chamber and forces the oil at variable rates into an overflow chamber through a pipe provided with a standard Sli orifice disk. A supply of oil is continuouslyv pumped from a storage tank to the feed chamber and a constant level is maintained in the latter by means of an oil overflow pipe. A small quantity of boiler steam is admitted through a ressure-reducing valve to the upper part of the feed chamber and the maximum pressure exerted by the steam is limited by means of a liquid seal pressure pipe. When the boiler steam pressure reaches a definite maximum limit under a light load, the pressure in the feed tank is released to fall to atmospheric pressure, which is the minimum feed pressure, and practically no oil is fed to the boiler furnace at this time. As the boiler steam pressure falls below this definite maximum limit with the increased consumption of steam, the pressure in the feed tank builds up to the maximum pressure producible with the liquid seal, at which time the maximum oil feed is olotained for carrying the full load of the boiler. The supply of oil at maximum feed pressure is arranged to be sufficient to carry the boiler at full load and therefore the rate of oil supply varies directly with the steam pressure between maximum noload pressure and minimum full-load pressure. The pressure maintained in the oil feed chamber is utilized to give the proper proportion of air to the oil supply. For this purpose a small amount of steam passes from the feed tank through a pipe leading to a damper-controlling mechanism which serves to control the amount of air supply to furnace to a definite proportion of the fuel being supplied. l

Referring to the accompanying drawing, oil for supporting combustion in the furnace 10 is withdrawn from an oil storage tank 12 through an outlet pipe 14 and pumped by means of a pump 16 through a delivery pipe 18 to an oil feed tank 20. The oil ills the feed tank 2() to the level of an overflow pipe 22 and returns through the overflow pipe to the tank 12. A ortion of the oil supplied to the tank 20 is orced, under a steam pressure, through an outlet pipe 24 and flows into a tank 28 through a standard orifice 26.01 other tiow controlling device. From the tank 28 the oil flows through an overflow pipe 30 to the burner 32 in the boiler furnace 10. rl`he burner 32 may be of the steam injector type or any other suitable t pe.

yrlhe pressure under which oil is forced through the orice 26 is produced in the feed tank 20 by the admission of steam from the boiler 10 and is controlled by the steam pressure in the boiler. To this end, a small amount of steam continually passes from the boiler 10 through a pipe 34 to the upper portion of the tank 20. The quantity of steam passing through the pipe 34 is controlled by means of throttle valves 36 and 38 in the pipe 34 to supply steam at a rate slightly greater than sufficient to make up for condensation losses in the'tank 20, the pressure being limited to a definite maximum by means of an excess pressure escape device. The steam pressure in the tank 20 is controlled by the steam pressure in the boiler 10 through an escape valve 40 which is governed by means of a diaphragm 42 communicating with the steam space in the boiler 10 through connecting pipes 43 and 34 (see Fig. 2). The valve 40 is normally closed by a spring 41 when the pressure transmitted through the pipes 34 and 43 is below a definite minimum 'and is open when the pres- 'sure transmitted through the pipe 43 is sufticient to depress the diaphragm 42. When the valve 40' is closed, the admission of steam from the pipe 34 gradually builds up the pressure in the tank 20 until it reaches a limit at which it escapes through the excess pressure escape device. At this pressure the oil is forced through the pipe 24 and the outlet orifice 26 to the burner 32 at the maximum rate. When the steam pressure in the boiler 10 rises to the point at which the valve 4() is opened, the pressure in the feed tank 20 drops to substantially atmospheric pressure and the supply of oil through the orifice 26 decreases to a minimum. A pilot pipe 44 leads from the overflow tank 28 to the boiler furnace 10 through which a small' amount of oil is supplied to a pilot burner in the furnace when pressure is released in the tank 20. The rate of supply of oil through the pilot pipe is regulated by means of a valve 45.

rl`he rate of supply of air for supporting the combustion of the oil fed to the furnace 10 is controlled by a damper 46 in a stack or flue 48 of the boiler furnace in such a manner that the opening for the passa e of exhaust products of combustion throug the stack 48 is approximately proportional to the rate of flow of oil through the orifice 26. 110 To this end, the damper 46 is rigidly mounted on a rotatable shaft 50, the position of which is governed by the pressure of steam passing to the feed tank 20 in such a manner that the rate of flow of gases past the damper 11a is approximately proportional to the square root of the fuel feeding steam pressure. The pressure of the steam passing through the valve- 38 to the feed tank 20 is transmitted 'through branch pipes 52 and 54 to a verti- 120 pipes 52 and 54 to the bell 56 increases, the bell rises and rotates the pulley 62 and shaft 50. rlfhe rotation of the shaft 50 by the rising ofthe bell is assisted oy a weight 66 adjustably carried on a crank arm 68 formed on the shaft 50. As the bell 56 rises, due to an increase in the pressure of steam transmitted from the pipe 34 and feed tank 20 and a corresponding increase in the rate of How of oil to the burners 38, the shaft 50 is rotated to lower the weight 66. As the shaft rotates the moment arm of the weight 66 on the shaft 5()y decreases and is proportional to the sine of the angle made by the crank arm 68 with the vertical. Since the pressure in the bell 56 must be inversely pro-- portional to the moment arm of the weight 66 in order to have an equilibrium of forces, the damper 46 continues to open as the presl sure in the bell increases until it cornes to full open position; The amount of oil passing through the orifice 26 follows the wellknown equation Q=c..t/2gh in which@ is the quantity of oil as passing through the orifice, c the orifice coefficient, a the orifice area, g the gravit-y coefficient, and h is the ypressure acting on the oil. Further, the pressure acting on the oil to cause it to flow through the orifice is the same as the pressure `acting within the damper motor 56. Accordingly with this arrangement the quantity of gas passing through theI stack 48 and the air admltted to the furnace vary approximately as the square root of the steam pressure transmitted to the bell or damper motor 56 and is thereby proportional to the rate of supply of oil to the furnace. The pressures which may be used in the bell to move the damper from closed to fully open position may be varied, by adjusting the position or amount of the weights 66 and amount of weight 64.

rfhe pressure of steam in the feed tank 2O is limited to a definite maximum by means of a. branch pipe 7 0 extending from the pipe 54 down into a water reservoir 72. IThe maximum pressure of steam in the feed tank may be altered by using pipes 70 of different lengths so as to project different distances below the level of the liquid on the reservoir 72. ln any particular installation the depth of submergence and accordingly the pressure at which oil is forced through the measuring device, are adjusted to supply sufficient fuel to maintain a full load on boiler. When once adjusted for any particular conditions the pressure limiting device however prevents the `feeding of an eX- cess of fuel above the maximum.

Due to the condensation of steam in the feed tank 20 a considerable amount of water will accumulate therein. To prevent the water formed by the condensed steam from mixing with the oil, the oil inlet and outlet pipes 18, 22 and 24 are covered by means of a bell 74 sealed at its lower end by the condensed steam andhaving a small opening 76 in its top through which it communicates with the steam space'of the feed tank. rlhe oil entering through the pipe i8 Heats on top of the water in the bell 74 and is thereby kept from mixing with the body of water. The condensed water is kept at a constant level by means of an overflow pipe 78 leadingv from the tank 20 to the water sea-l 72.

In starting the operation of the combustion regulating apparatus, communication is closed between the valve 38 and the feed tank 20 by means of a stop cock 80 on the pipe 34. The valves 36 and 38 are then opened until a small stream of gas passes through the pi es 52 and 70 and issues as a small stream o bubbles in the water seal 72. rlhe pressure between the valves 36 and 36 is then at the desired operating point, as will be indicated by the pressure auge 82. The stop cock 8O is then opened am?Y pressure builds up in the pipe 34, feed tank 20 and damper regulating bell 56; As the pressure in the tank 2O increases, oil is forced through the pipe 24 and orifice 26 at a rate increasing with the pressure until a point is reached at which steam bubbles out of the end of the pipe 70. At this pressure oil is forced through the orifice 26 at the maximum r-ate. As this maximum pressure is reached, the bell 56 is simultaneously lifted to position the damper 46 to induce the maximum air supply into the boiler. When the -steam pressure in the boiler 10 reaches a definite maximum, the pressure transmitted to the diaphragm 42 through the branch pipe 43 depresses the diaphragm .and opens the valve 40, placing the feed tank 20 into direct communication with the atmosphere. Steam is thereby exhausted from the feed tank 2O and from the pipes 34 and 52 and the damper regulating bell 56. The flow of oil through the orifice 26 thereupon drops to an amount just sufficient to supply the pilot burner through the pipe 44 and the damper 46 is rotated to approximately closed lposition by the falling of the bell 56.` As the boiler steam pressure again drops below a definite minimum, the dia* phragm 42 is raised, the v-alve 40 closed and pressure is again permitted to build up in the feed tank 20 and bell 56, simultaneously increasing the flow of oil to the boiler and the draft through the stack 48 until the maximum rate of combustion is reached.

Although the apparatus has been described as using steam pressure for forcing the oil through the feed orifice, it is obvious that compressed air or gas or other fluid under pressure might be used instead of steam.

Having described the invention, what is claimed as new is:

l. A combustion regulator for oil fired boilers which comprises a closed feed tank for oil, means for admitting fluid under fil.. m

pressure to said tank7 means governed by the steam pressure in said boiler for permitting the escape of Huid from said tank, and means governed by the fluid pressure existing in said feed tank for controlling the draft to said furnace.

2. A combustion regulator for oil fired boilers which comprises a fiow controlling device., means for feeding oil to said boiler through said device, means for slowly admitting steam under pressure to said oil feeding means. and means governed by the steam pressure in said boiler for relieving the pressure in said oil feeding means.

3. A combustion regulator for oil fired boilers which comprises a flow restricting device. means for feeding oil to said boiler through said device, means for slowly admitting fluid under pressure to said oil feeding means. means governed by the steam pressure in said boiler for permitting the escape of fluid from said oil feeding means, and means for controlling the draft to said boiler in accordance with the pressure in said oil feeding means.

l. A combustion regulator for oil fired boilers which comprises an oil feed tank. a pipe leading from said tank and provided with an outlet orifice, means for feeding oil through said outlet orifice to the burners of said boiler. a steam pipe provided with a restricted passage from said boiler to said feed tank, a steam escape valve on Asaid tank. and a diaphragm communicating with the steam space of said boiler for controlling said escape valve...

5. A combustion regulator for oil tired boilers which comprises an oil feed tank. a pipe leading from said tank and provided with an outlet orifice. means for conducting oil from said orifice to the burners of said boiler. a steam pipe provided with a restricted passage from said boiler to said feed tank. a steam escape valve on said tank. a diaphragm governed by the steam pressure of said boiler for controlling said steam escape valve. a damper for said furnace, a liquid sealed bell controlling the position oiv said damper, and means for transmitting gaseous pressure from said oil feed tank to said bell.

(i. A combustion regulator for an oil fired boiler which comprises a closed oil feed chamber. an oil compartment in said chamber. means for slowly supplying fluid to said chamber. a fiuid escape valve for said chamber controlled by the steam pressure in said boiler. a. device for limiting the maximum fluid pressure in said chamber, an oil outlet orifice conimunicating with the oil compartment in said oil feed chamber. and means connecting said outlet orifice'to the burners of said furnace.

7. ln an oil fired steam boiler. the combination of an oil feed tank, means for maintaining a constant oil level in said feed tank, an orifice outlet for oil from said tank., means for admitting steam to said oil feed tank. means governed by the pressure of steam in said boiler' for permitting the escape of steam from said oil feed tank, a damper for said boiler. and ymeans governed by the steam pressure existing in said feed tank for controlling the position of said damper.

8. In an oil fired steam boiler, the combination of a closed oil feed tank, means for maintaining a constant level of oil in said tank. means for permitting the escape of oi] in said feed tank to the burners of said furnace at a rate dependent on the pressure in said feed tank, a damper for controlling the draft to sa'd boiler, means actuated by steam pressure for controlling the position of said draft regulating damper, means for slowly admitting steam from said boiler to said oil feed tank and'to said damper controlling means, and means governed by the steam pressure in said boiler for exhausting steam or gas from said oil feed tank and damper controlling mechanism.

9. The method of regulating combustion in oil fired boilers which comprises forcing a supply of oil to' said boiler under a pressure developed by steam from said boiler, controlling said pressure by the steam pressure in saidboiler and simultaneously controlling the draft controlling damper of said furnace by the same. pressure as that used to supply oil.

10. The method of regulating combustion in oil fired boilers which comprises forcing a supply of oil to said boiler through an orifice under) pressure of steam admitted from said boiler, controlling the pressure of steam admitted to said oil by the steam pressure in said boiler, simultaneously controlling the draft controlling damper of said furnace by the pressure of steam on said oil. and limiting the pressure on said oil to a definite maximum.

11. The method of regulating combustion in an oil fired boiler which comprises forcing a supply of oil to a burner for said boiler through a flow restricting device under a pressure developed by steam from said boiler and controlling the oil feeding pressure by the pressure of steam in the boiler.

12. The method of regulating combustion in an oil fired boiler which comprises forcing a supply of oil to a burner for the boiler through a flow restricting device under a pressure developed by steam from the boiler, controlling the oil feeding pressure by the pressure of steam in the boiler, and' limiting the oil feeding pressure to a pre-determined maximum independently of the boiler steam pressure.

ln testimony whereof I affix my signature.

BENJAMIN GREENFXELD.

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