US1584480A - System of combustion control - Google Patents

Description

May 11 1926. 1,584,480

G. SIMMONS SYSTEM OF COMBUSTION CONTROL Filed June 6, 1923 s Sheets-Sheet 1 I (5'. SIMMONS SYSTEM OF comaugwion 'CONTROL' May 11 1926.

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- 1 1,584,480 G. SIMMONS Y SYSTEM OF comgps'rlow CONTROL May 11 1926.

Filed June 6, 1923 5 Sheets-Sheet 5 K abrdbnsimm is 1 nyenTor- Patented May 11, 1926.

STATES PATENT OFFICE.

GORDON SIMMONS, OF BALTIMORE, MARYLAND, ASSIGNOR 0F ONE-HALF.T0 A. D. LESPERANCE, OF BALTIMORE, MARYLAND.

SYSTEM OF COMBUSTION CONTROL.

Application filed June 6, 1923. Serial No. 643,677.

My invention relates to an improved system of combustion control, and has for its object an improved system of controlling the generation of steam in a steam generating lant.

A further object of my invention is'the providing of an automatic system of control of steam generating plants.

A further object of my invention is a temperature system of combustion control;

A further object of my invention is an alarm indication of combustion conditions in a steam generating plant.

With the foregoing and other objects in view, my invention consists of the methods employed, combination and arrangements of systems and improvements thereof, alarms and indicating means as hereinafter specifically described and illustrated in the accompanying drawings, wherein is shown the preferred embodiment of the combination of systems and indicating means of my invention, but it is understood that changes, variations, and modifications may be resorted to which come within the scope of the claims hereunto appended.

In the drawings hereunto attached is shown an apparatus arranged to carry out the various objects of my invention, but I do not wish to be limited to the arrangement shown nor the apparatus or means shown, as there are various ways of accomplishing the various functions of the installations by vastly different appliances.

For a better understanding of my invention, I have shown in Fig. 1 an installation of a return tubular boiler, stoker fed, as may be found in a modern steam plant, with the various cont-rolling features illustrated as I have installed the same, including certain new features which I will'describe and claim hereafter in other applications.

Figure 2 is a theoretical diagram of a single tube of a boiler plant, for technical discussion better to understand the various functions involved in this application, and Figure 3 is a diagram of a boiler in its relative position to the stack control, especially whena plurality of boilers are used in battery, and shows a modified form of damper and fuel control.

Figure 4 shows the entire apparatus combining the control of a single boiler with a battery control. ,p

Similar numerals refer to similar parts and appliances throughout the several views.

1 is a boiler, in Fig. 1, return tubular. 2 is the stoker. 8 is the stoker operating means which in the drawings is shown as a steam engine. 4 is the stoker operating control means, which in the drawing is electrically controlled by mechanism hereinafter described. 5 is an improved bridge wall permitting the introduction of air at a desirable point in the combustion'chamber. 6 is the air inlet control damper operated by electro-magnetic controlling means, 7 and the uptake damper 8 is in a similar manner operated simultaneously therewith in the layout shown in Fig. 1. 9 is a thermocouple inthe combustion chamber. 10 is a thermocouple in the exit gases. 11 is a temperature recording controller well known in the art, such as the Taylor instrument or similar device as manufactured by the Leeds & Northrup Company, illustrated in Brewer Patent #1,356,804, of October 26, 1920, which I have adopted and by certain changes in the connections, and improvements which I will more definitely describe in another application made applicable for adoption to the subject matter of this application. Two such controllers may be used for simplified connections, as found commercially. 12 is an electrical relay for operating Stoker operating control means 4.- which is shown in the drawing as an electrically operated steam valve. 13, 14, and 15 are red, white, and blue signal lights respectively. 16 is a klaxon horn. 17 is an inlet duct in the bridge wall surmounted by a perforated refractory tile 18 for diffusing the air and heating same.

When a water tube boiler is used, it is difficult or almost impossible to use a thermocouple in the combustion chamber. I avail myself of the well known principle that the flue gas content of CO is a function of or varies as the theoretical temperature of combustion, the CO content being measured by the thermal conductivity of the products of combustion, with reference to air. I use this means which is accurate for all practical purposes, in conjunction with my actual temperature readings of the exitcal CO, cell in the passage of the gases. I

each other in the operation of my apparatus.

The operation of my apparatus is as fol-' lows :.Fig. 1 shows. an ordinary return tubular boiler in partial sectional elevation, with a thermocouple located at each end thereof. The temperature as measured in the combustion chamber at A is a function of the temperature of combustion and is always less than this temperature, and is within the safe working limits of the thermocouple to stand, which makes this method a practical one. Furthermore, a variation in the temperature of combustion promptly affects the thermocouple so located, there be ing little lag and it has been found that if a temperature at this point is maintained between 1,700 degrees Fahr. and'1,800 degrees Fahnthat a reasonably hightemperature of combustion is maintained, but not too high, which might clinker the coal, burn grate bars, or even effect disastrously the furnace linings.

A substantial part of the heat of the fuel is delivered directly to the boiler by radia tion, and some. of the heat is also radiated to the boiler setting and rejected to the ash pit. This loss is unavoidable, and its elimination is not contemplated by this method.

What is contemplated is, the substantial -maintenance of two fixed temperatures at two definite locations in the gas passages of a boiler installation, in combination with a uniform steam pressure, which can be demonstrated to mean depending upon the temperatures held A definite combined boiler and furnace efliciency. v

A reasonably definite temperature of combustion.

A definite. and stack. 7

A definite ratio of air to steam, or in other words, the control of air supply to the known heat loss to the furnace in step with the steam flow from the boiler.

It further becomes apparent that whenburning a low grade, low ash fusing coal, that if combustion chamber temperature is held at a sufficiently lower temperature than would be usual in the case of a high grade coal, clinkering can be redu ed to any de-' terminable extent or eliminated if the ash fusing point of the coal is known and the temperature of combustion kept below such temperature by proper'setting of the control points in 11.

This is accomplished by ascertaining a number of different furnace temperatures with an optical pyrometer and simultaneously reading the corresponding temperatube surrounded by a cooling medium as water, both at a fixed temperature. The arrows show the path of the gases of combustion and the thermocouples located at each end thereof, measure in this particular case and for this discussion, 1,800 degrees Fahr. and 500 degrees Fahr. respectively, giving an actual working condition observed.

We then have in a sense, what amounts to a Venturi meter, where in place of a pressure drop, we measure a temperature drop. And since we are interested in heat delivery to the cooling medium, in this case, water under approximately 125 lbs. pressure at a temperature for this discussion, 350 -deg., we have an efficient form of heat meter.

The principle of its operation is based upon the well known law of heat transfer when heated gases flow through or around a boiler tube, as follows :The heat available for absorption is proportional to the product of the weight of the gases flowing and the difference in the temperature of the gases and the wall of the tube.

. Therefore, if a substantially constant difference in temperature is maintained between the point of ingress and egress of the gases, as at A andB, the heat available for steam generation is weight of the gases flowing.

the air supply to the furnace is so con-- trolled by the incremental movement of the main stack damper caused by slight variations in the steam pressure or other means, in combination" with the incremental move ment of the individual boiler damper actuatedby tem erature controlled means, that a substantia 1y constant and predetermined temperature at A is maintained, the number of pounds of air will be in a definite ratio tothe number of pounds of steam,

which ratio can be varied to suit any condiproportional to the dilution of the heat of the gases caused by the aforementioned excess air, the above named temperatures are not maintained. The temperature at A drops and assum-. ing there is a reasonable load on the boiler,

the temperature atfB rises.

- combustion conditions.

This phenomenon isused as the basis for an alarm indication of excess air, and in,

combination with the other apparatus and means shown can be made to control said It is worthy of note that the alarmindication of high stack temperatures also functions for sooty fines or high overloads and the reason is manifest In welloperated plants the fines are regu larly blown and, ample number of boilers are usedtmpreven-t a greatly overloaded condition. 125 to 17 5 per cent of builders rating appears to be the eflicient operating load of.

the average boiler.

Again referring to Fig. 1 and the stokcr controlas shown, the particular installation I as installed provides for a greatly lessened coal feed when the temperature at A exceeds 1900 deg. Fahr. Manifestly the coal feed can, by suitable well known electric solenoid valves and relays, be varied at will by the said temperature actuated means included in the commercial recording temperature controllerilhistrated at the top of Figure 1 controlled the temperatures at-A or B or both in an almost infinite number of combinations, and similarly a great number of different means can be used for controlling the air supply from a temperature di'l'- fcrence caused by the passage of the products of combustion throughthe boiler.

In the particular installation shown in Fig. 3,,the individual stoker engine speed for each boiler is varied by the usual balanced steam valve in the steam line operated by a. differential lever 20, "one side of, the lever being connected by chain to the damper regulator 21 operating main stack damper :22 by variations in steam pressure, and the other side'of lever 20 connected also by chain L to the piston of a regulator 23 operated by a pilot controlled in turn by a diaphragm'affccted by changes in the overfire vacuum from over-fire vacuum.- The balanced valve 24 is connected to the center of the differential lever 20 so that equal movements of the lever in opposite directions will cause no move anent in the controlled valve.

Assuming then, a low steam pressure and control from point B.

the valve 24 and the consequent'stoker speed will be very much lessthan with a low steam pressure and thin fuel bed.

, Hi 11 combustion chamber temperature as at A does not necessarily mean high citiciency. It may mean that the zone of chemical combination of the combustible with the 1 oxygen present, has been moved further back near the tubes, and the result of this is that complete combustion is arrested at this point r with consequent fuel loss and smoke. The relay 12 and solenoid steam valve 4 as shown in Fig. 1 retard the coal feed when this con dition occurs.

Separate control points in the temperature recording controller 11, operate the red, and white signal lights over boiler. In this par ticular installation and so theoperation can be more. easily understood, we will assign different temperatures for the different control points. The red light will show from zero to 1600 .deg. F. The red and whitelights showing a fair combustion condition, will both light from 1600 to 1700 deg. F. The white light onlyowillshow above 1700 deg. F. showing good combustion, and the stoker valve will close at 1900-deg. F. The blue light is operated only by the temperature of, the exitvgases of its particular boiler The klaxon in series with the common wire to all blue lights, is common to the battery of boilers, but in the'drawing'Fig. 1 is across the blue light circuit as that is for a single boiler. The controller operates the blue light and klaxon at 580 deg. F. at point B. A separate controller as they are found commercially wouldbe necessary to The magnetic regulators 7 operated across the red and white signal lights, said lights 13 and 14 being operated intermittently, control the individual boiler dampers 8. Manifestl'y, when both red and white lights are on, the regulator is inoperative since the magnets 26 (gppose each other and the two opposed springs 27 hold armature and pilot valve 28 in neutral position. Choke valves 25, hand adjusted, makes the movement of the damper slu gish and weight 29 provides =2 for quick opening and slow closing until it strikes against a stop (not shown), set to prevent the fires assuming a banked condi tion, in other words to prevent the dampers from "fully closing.

The main damper regulator. 21 prevents popping and governs the position of the damper 22 in'accordance with the steam pressure.

This system of control then, is designedto. accomplished the following objects To assign the bulk of the load to those boilers whpse fires are in better condition to carry it.

To notify fireman by red'light that damper.

/ fines are foul, boiler is overloaded, or a preon particular boiler is gradually closing account improper condition of fire or falling off in load. 1

To warn fireman by blue light over particular boiler andby the klaxon horn, that ventable amount of excess air is present account of hole in his fire, thin fuel bed, fire move the ash.

operating.

Automatically'to slow up stoker engine when temperature in combustion chamber becomes too high for good efliciency, fusing point of the coal or the fire brick.

To notify fireman which fires are in good dooropen, or automatic damper control not condition so that he can work on the fires most needing his attention.

To automatically control and maintain efiicient-combustion conditions without outside intervention, it being the firemans duty to keep coal hopper full and periodically re= In Figure 4, I have shown in a single .figure the entire apparatus combining the control of the single boiler as shown in Figure 1, with a battery control as shown in Fi ure 3. The operation of the device is as follows: The various devices are set to give proper controkwith a' definite kind of coal, a definite overfire vacuum and a definite steam pressure. The device 23, which is well known, will maintain the damper 6 in such position that the overfire vacuum is at 'the tenth inch A lower steam pressure probably results, and this causes the Mason steam pres sure regulator 21 (this also being well known) to operate the battery damper, opening this damper and simultaneously raising the left hand end of the equalizing lever 20, the right hand end of which has been raised slightly by the closing, of the damper 6, the

result being that eachof these movements tends to openthe balanced valve 24 and to cause the stoker engine 3 to feed fuel at a faster rate.

Under certain circumstances, the regulator 21 is not called upon to act since'the raising of the lever 20 by the closing of the .damper 6 will itself cause the proper correction .in stoker speed so as to build the fire bed to the. proper thickness. The regulators 21 and 23 operate together to govern the valve 24 and usually in conjunction, but

if b chance the requirements for steam shou d drop when the damper 6 is being closed due to the thinning of the fire bed, no change in the stoker engine speed would be required, and the .proper compensation would be obtained by the simultaneous raising of the right hand end of the lever and the lowering of the left hand end of the lever.

lVe will assume, as in the first instance,

of the instrument 23 is constant, and con-' sequentlythe rate of flow of gas through the boiler changes irrespective of the condi tion of the fuel bed, and this change is at a definite rate corresponding to the definite change in steam pressure affecting the instrument 21. Assumin the right hand side of lever 20 to be fixed, t e fuel feed, through its connection from the instrument 21 to the left hand-side of lever 20, will also vary the stoker speed at a definite rate with definite changes in steam pressure affecting the instrument 21, and, therefore, the rate of feeding fuel and the rate of flow of gases through the boiler are in definite ratio one to the other. v

Assuming, however, that due to change 1n pressure of the steam operatingthe stoker engine 3 or a variation in the friction load, would cause this ratio of gas flow to fuel feed to vary from the predetermined rate.

The left hand side of lever 20 will compen sate for suchchanges in stoker speed so that fuel will be fed at the rate at which it is burned because if the fuel bed should become too thick because the fuel was not being burned at the rate fed, damper 6 would necessarily open to maintain the fixed overfire vacuum of one-tenth of an inch, through the instru cut 23, and this in turn would cause the rig t hand side of lever 20 to lower, slowing up stoker speed until the fuel already fedwas consumed. In the event of fuel being burned at a more rapid rate than being fed by stoker 3, the pressure necessary to overcome resistance of the fuel bed'would not be so great, and instrument 23 would slightly close the damper ti as previously-explained, raising the right hand side of lever 20, causing stoker engine 3 to feed fuel at a more rapid rate to replace fuel already burned.

We will now replace individual uptake damper 8 controlled by instrument 7, which is actuated by mechanism which. is in turn controlled by instrument 11 and actuated by instrument 19. As long as the CO content of the combustion gases remains at. a pre- 1 determined standard, no change in the position of damper .8 will occur. 'We will as- H the rate of feeding air and fuel is not being maintained at the predetermined standard, or that the quality of the fuel has changed or that a hole in the fire has occurred. This would cause the Shakespear CO cell to operate the device 11 which governs the instru- -ment 7, controlling in turn the position of the furnace uptake damper 8. If the CO content has dropped, the damper 8 will close slightly and progressively at timed intervals until the CO content is returned to normal.

The closing of the damper 8 will reduce the rate or volume of the gases through the furnace and consequently, affect the overfire vacuum and'through the instrument 23 will close under incremental movements the damper 6, causing an increased speed of the stoker engine. If, instead of falling, the

percentage of CO should arise, the Shakespear cell 19-would cause the damper 8 to open by means of the devices 11 and 7 in the same manner, that is, by incremental movement of the damper 8, or these parts could be arranged so that upon increase in the CO, content, the damper 8 would open Wide.

Should the CO content continue to rise so that the damper 8 remains in wide open position, the Shakespear cell -1.9 would operate the instrument 11 and relay 12' to close the electrically'operated steam valve 4, slowing the speed of stoker engine 3 to an idling speed or stop it altogether, this, of course,

being absolutely independent of the position of the balanced steam valve 2%, and such ac-. tion will obviously cause lowering of the CO content until normal CO. ratio is had, at which time the electrically operated valve 4 will again open wide, leaving the control of the stoker engine entirely with the balanced valve 24.

Having thus described my invention, what I claim and desire to secure by Letters Patent is 1. The combination with a boiler, a furnace, fuel feeding means, and air control means, of mechanism for governing both of said means to maintain a predetermined temperature difference betweentwo definite locations in the gas passage.

2. The combination with a boiler, a .furnace, fuel feeding means, and air control means, of mechanism for governing both of said means to maintain a predetermined temperature difference between the front and rear ends ,of the boiler.

3. In a boiler assembly, a furnace,'a boiler,

an automatic sfuel feeder, means controlled by the combustion chamber temperature for controlling the fuel feeder speed as a function of the steam pressure and of the over fire vacuum.

.4. In a boiler assembly, a fuel feeder, a governing means therefor, a differential mechanism connected to said governing means, means governed by the steam pres sure, means governed by the over-fire I vacuum, and means for connecting each of said last two mentioned means separately with said mechanism so that they act in conjunction or in opposition to alter the position of said fuel feed governing means.

5. In a steam generating plant, an automatic fuel feeder, an air supply means, steam pressure responsive means, over-fire vacuum responsive means, temperature responsive means, means governed by the last three mentioned means for controlling the air supply means, and means governed by the steam pressure responsive means and by the over- -fire vacuum responsive'means for controlling the fuel feeder.

6. In a steam generating plant, means for controlling the rate of supply of air to the furnace, means responsive to changes in the combustion chamber temperature for governing said air control means, steam pressure means independent of said last men tioned means for modifying the control of the air supply means, and over-fire vacuum responsive means acting in conjunction with said temperature responsive means to alter the ratio of flow'of air to the furnace.

7 In a boiler assembly, a device responsive to changes in steam pressure for altering the rate ofsupply of air, and means responsive to changes in the rate of supply of air for altering the rate of supply of fuel to maintainsuch rate of supply of fuel in a definite ratio to the rate of supply of air.

8. In a system for maintaining a definite ratio of fuel to air in a steam generating plant, an automatic fuel feeder, and means responsive to changes in the rate of air flow eonnou SIMMONS.

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