US2575885A - Steam superheat control by automatic and extended-range means - Google Patents

Description

Nov. 20, 1951 H. c. MITTENDORF STEAM SUPERHEAT CONTROL BY AUTOMATIC AND EXTENDED-RANGE MEANS Filed April 1, 1948 5 Sheets-Sheet 1.

Supurhonhd Sham Tomporaiun Recordmg our I I I I I I l l I I I I I I l L- INVENTOR. Harvey C. Mittendorf Nov. 20, 1951 H. c. MITTENDORF STEAM SUPERHEAT CONTROL BY AUTOMATIC AND EXTENDED-RANGE MEANS 5 Sheets-Sheet 2 5 Filed April 1, 1948 Fig. 3.

INVEN TOR.

Harvey G. Mi'rtendorf fla'fih mr NOV. 1951 H. c. M ITTENDORF,

STEAM SUPERHEAT CONTROL BY AUTOMATIC AND EXTENDED-RANGE MEANS Filed April 1, 1948 5 Sheets-Sheet 3 Temperature INVENTOR Harvey C. Mifiendorf ATTORNEY 1951 H. c. MITTENDORF 2,575,885 I STEAM SUPERI-IEAT CONTROL BY AUTOMATIC AND EXTENDED-RANGE MEANS Filed April 1, 1948 5 Sheets-Sheet 4 Fig. 6.

Temperature of superheated Steam 65 700 750 800 52 I 69 E70 TIlIqbIe I I93 85 Burnarls/ i I I INVENTOR Harvey C. Miflendiorf Nov. 20,, 1951 H. C. MITTENDORF STEAM SUPERHEAT CONTROL BY AUTOMATIC AND EXTENDED-RANGE MEANS 5 Sheets-Sheet 5 Filed April 1, 1948 Fig. 7.

Temperature of Steam Tihuble Burners INVENTOR Harvey C. MiHendorf Ma i ATTORNEY Patented Nov. 20,1951

STEAM. SUPERHEAT CONTROL BY AUTO- MATIC AND EXTENDED-RAN GE MEANS Harvey C. Mittendorf, East Orange, N. J., as-

signor, by mesnc assignments to Combustion Engineeringsuperheater, Inc., a corporation of Delaware Application April 1, 1948, Serial No. 18,337

13 Claims. (Cl. 122-479) This inventionrelates to means for regulating the temperature of steam leaving the superheaters of conventional steam generators, and it has particular reference to an improved control of the superheated steam temperature through a unique automatic variation in the temperature of the heating gases which enter the superheater and also by a novel combination with such gas-temperature variation of bypassing a portion of the heating gases around the superheater.

In the operation of present-day steam generating units (particularly at high steam pressures and temperatures) that are equipped with builtin superheaters, it is well known that the tem perature of the superheated steam varies with fluctuations in generator steam output. Thus, when the superheater is of the convection type (as distinguished from the radiant type) a reduction of superheat occurs with a reduction in steam output and an increase of superheat accompanies an increase in output. Because this is undesirable (a substantially constant steam temperature at the superheater outlet typically is required over a wide range in generator capacity) various means have been devised to correct for these steam temperature variations.

One early-proposed method is to by-pass a portion of the heating gases around the convection superheater when the steam temperature undesirably rises and thereby correctively lower the temperature by reducing the flow of gases over the superheater, and when the superheat temperature undesirably falls to cut down the bypass flow with resultant corrective temperature raising.

Another more recently devised and even more satisfactory method of correctively adjusting the superheated steam temperature is to cause a variation in the heat absorption within the furnace from the fuel burned therein so that the gases passed over the superheater surface are at a temperature capable of producing the desired degree of superheat. A method of this nature as disclosed in the patent to Kreisihger et al. No. 2,363,875 of November 28, 194i, entitled Combustion Zone Control provides for the physical raising or lowering of the furnace flame body over a considerable distance to make use of more or less heat absorption surface in the furnace and thereby effect wide range control over the temperature of the combustion gases leaving the furnace and passing over the superheater.

Kreisingers so called tilting burner method has met with wide commercial success particularly in installations (public utility and other) where high capacity (from several hundred thousand to over one million pounds of steam per hour) and high temperature (as 700" F. and above) generating units are employed. But, past practice in effecting necessary adjustments in the burner tilt has been to use a manual rather than an automatic system of control; moreover, it has in certain installations been found desirable to supplement the tilting burner facilities by gas bypass means in order most effectively to meet superheat temperature variations which prove exceptionally wide.

Accordingly, an important object of this invention is to provide automatic control means responsive to the superheated steam temperature and effective to adjust the heat absorption within the furnace (tilting burners) in advantageous and commercially satisfactory ways.

Another object is automatically to control a by-passing of furnace gases around the superheater (by-pass damper) in comparably advantageous manner.

A further object is to provide an improved method for obtaining the desired steam temperature from the superheater by regulating both the heat absorption within the furnace and the by-passing of furnace gases around the superheater.

A still further object is to coordinate the burner tilting means with the gas by-pass means in such a way that the temperature control ranges of the two are directly additive and otherwise advantageously related.

Other objects and advantages will become apparent from the following description of illustrative embodiments of the invention when taken in conjunction with the accompanying drawings wherein:

Figure 1 is a sectional elevation of a steam generator and associated convection superheater together with tilting burner and gas by-pass fa cilities effective individually and jointlyto conshowing one arrangement for vertically tilting.

the streams of fuel and air directed thereby into the furnace;

Figures 4a-b-c indicate how the tilting burners may be adjusted respectively to locate the burning fuel flame at lowered, intermediate and raised positions in the furnace combustion chamber;

Figure is a diagram of electrical circuits organized in accordance with my invention to effect an automatic positioning of the tilting burners in a way which holds the superheated steam temperature substantially constant;

Figure 6 is a similar circuit diagram organized to extend my novel automatic regulation to the by-pass damper and arranged to apply required positioning adjustments first to the tilting burners as a primary control and then to the damper as a secondary or range-extending control; and

Figure 7 is a similar electrical diagram differing from Figure 6 in that primary control is effected by the by-pass damper (instead of the burners) and secondary control by the tilting burners (instead of the damper).

The illustrative steam generator to be benefitted The drawings hereof show my automatic control improvements applied to a steam generator represented in Figure l as comprising a furnace A fired by burners 9 and heating a boiler B equipped with a superheater S. Boiler furnaces of this general design (and having a wide range of steam output, pressure and temperature ratings) have already been extensively adopted for such uses (high-capacity and other) as supplying the turbines of electrical generators in power-stations, providing steam for the central heating of business and residential districts, and supplying steam for industrial needs.

For facilitating description it will be assumed that the represented boiler furnace has a rated generating capacity (at v100% full load) of 400,000 pounds of steam per hour; a rated operating pressure of 500 pounds per square inch, which establishes the steam saturation temperature at 470 F.; and that for all generator loadings (below, at and above 100%;rated) it is desired to hold the superheated or total steam temperature substantially constant at 750 F.

Such assumed values are obviously illustrative rather than restrictive; for as the description proceeds it will become evident that my superheat control improvements (automatic and extended range) also are useable with boiler furnaces of other capacities, characteristics and designs. Particular benefit from these improvements is received by high pressure (typified by up to 1800 p. s. i. andabove), high'steam temperature (typified by up to 1000 F. and above), high capacity typified by up to 1,000,000 pounds of steam per hour andabove) installations in which employment of a super heater such as here shown at S substantially increases the thermal efliciency of the generating unit, reduces the amount of work that must be done by the evaporative surfaces to produce the same power, and makes the steam transmittable without condensation as well as more efficiently useable by turbines and other consumption devices.

The representative boiler illustrated at B includes a lower water drum I0 plus upper steam and water drums II and I2 interconnected with the lower'drum by banks of steam generating tubes 8, I3 and [4. The superheater S is located in'the first 'pass of the boiler behind a front bank of boilertubes 8; it receives the saturated steam generated in the boiler as discharged from rear upper drum I 2 'by' way of conduits I 5. Baffles l6 and l! cause the gases from the furnace ofitake l9 to pass serially over superheater S and the lower portion of tube banks 13 and I4 and thence back and forth around bafile l8 to the boiler ofitake 2|. Heat transfer from the furnace gases to the superheater is therefore mostly by convection; reception by the superheater of radiant heat from the furnace flame being blocked by shielding baflle l6 aided by front tube bank 8.

In the superheater by-pass arrangement shown, baffle I! at the front of tube bank I3 is spaced below the upper steam and water drum H to form a by-pass entrance for some of the furnace gases; a bafile 22 behind the tube bank I3 forms the rear wall of a by-pass channel 23; both baflles l1 and 22 continue in substantially parallel spaced relation across the lower portion of rear tube bank M to form a rearward continuation of the by-pass 23; and a damper 24 lo cated at the lower end of baffies l8 and22 controls the flow of gas from furnace oiftake l9 through this by-pass 23.

Damper 24 may be opened and closed in any suitable manner such as through linkage means including a pivoted support lever 25 for the damper, connecting link 26, guided rod 21', bell crank 28 and a vertical rod 29 which is caused to move up and down by means of a motor 30 driving the rod through reduction gearing 3| and an arm 32 which transmits positioning movement from themotor to the damper. An electric motor is here shown at 30; however an air motor, hydraulic cylinder or the like obviously may be used in its place.

The ilustrative furnace A of Figure 1 has two of its walls lined with Water cooled tubes 3 as shown in Figures 1 and 2; the lower furnace portion has two opposing sides which slope inwardly to form a bottom hopper or throat 35; these sloping portions are faced with water cooled tubes 36 which continue upwardly to line the two remaining side walls of the furnace combustion chamber; and all of the wall lining tubes 34 and 36 are connected in Water circulation with boiler B in the well known manner indicated.

The vertically tiltable burners 9 Serving to fire furnace A are a group of burners arranged in the lower portion thereof as shown at 9 (see Figures 1 and 2) above the hopper 35 and there suitably located such as at or near the furnace corners as indicated in Figure 2. When so arranged the burners may satisfactorily project streams of fuel (in one or more forms as later indicated) and air into the furnace in directions tangential to the surface of an imaginary cylinder (again see Figure 2) located vertically within the furnace preferably at its center. Other burner arrangements are of course useable to fire the selected fuel (pulverized coal, oil, gas or the like).

Figure 3 shows a typical burner construction which permits either pulverized fuel or oil to be burned in the furnace alone or both to be burned simultaneously (through obvious modification gas may be substituted for either of the named fuels or gas alone may be burned); This illustrative burner comprises air chambers 43 which are connected at their sides to an air duct for supplying air thereto (as indicated in Figure 2) from a suitable source typified by conduits 42 of Figure 1.

In Figure 3 six such air ducts 43 are disclosed, the first and sixth being used to supply air alone to deflecting vanes. or'nozz1etips 5 r passa therefrom into the furnace; the second and fifth each being provided with a pulverized fuel supply pipe 39 (leading from a fuelsource. notshown) and a conduit portion extending through the duct for conveying the fuel from pipe 39 in a stream of air to a nozzle tip 4| and thence into the furnace where burning takes place; and the third and fourth air ducts 43 each being provided with an oil pipe (connected with an oil source) and a surroundingtube 46 extending through the duct to a nozzle tip 41 from which oil may be injected into the furnace for burning therein along with or instead of the pulverized fuel from nozzle tips 4 I.

Each of the represented fuel nozzle'tips 4| may be rectangular in cross section; it i located between air deflecting vanes 44 lying symmetrically above and below the tip and connected thereto by end plates adjacent the air chamber walls 43.1101"- mal to the vanes; it is rotatable vertically on pins .in horizontal bearings 48 in the end plates, the

pins being mounted on the opposite Walls of fuel conduit 40 adjacent the end of said conduit; and tip 4| and its supporting conduit 40 are formed at their juncture into a cylindrical socket joint.

The represented air nozzle tips (associated with the first and sixth air ducts 43) likewise may be rectangular in cross section; each is pro- .vided with deflecting vanes shown as supported by end plates normal to the vanes; and each is rotatable vertically on pins in the horizontal support bearings 43 carried by end plates, the pins being mounted on the opposite walls of the conduit 43.

The represented all nozzle tips 41 (associated with the third and fourth air ducts 43) are located within air deflecting vane 44a which lie symmetrically around each tip and are connected to a tip-surrounding jacket by perforated inclined spacer plates 41a and end plates normal to the vanes. Each of these tips 41 comprises an oil nozzle and a surrounding jacket; and it is rotatable vertically on pins in horizontal supporting bearings 48 in the end plates, the pins being mounted on the opposite walls of the air conduit 43 adjacent the end of tube 46.

The just-described fuel, oil and air nozzle tips 4|, 41 and 45 when turned upwardly or downwardly direct the issuing fuel and air streams accordingly; the distribution of air above and below the fuel streams issuing from each of the fuel nozzle tips 4| and 4'! remaining symmetrical for any position of the nozzle tip. The effect of simultaneously adjusting the tilt of these burner nozzles is represented in Figures 4ai-b-c and will be more fully considered later; obviously less than all of the fuel and air nozzles in each burner 9 may be so adjusted tiltwise, as the Patent 2,363,875 to Kreisinger et a1. brings out.

For imparting tilting movement to each of the burners represented nozzles 4|, 45 and 41 use is made of a positioning rod which ispivoted to an end-plate of the nozzle, offset with respect to bearing 48, and which has an exterior extension 5| connected with a bellcrank 52 that in turn receives nozzle adjusting movement from a vertical tilt rod 53. Upward movement of rod 53 tilts all of the burner nozzles (4|-45 -41) downwardly around their bearings 48 while downward movement of the rod swings all of the nozzles upwardly with respect to the horizontal. 7

Serving to impart such tilt adjusting movements to vertical rod 53 is a motor represented at 55 in Figure 3. An electric motor is here shown at 55; however, an .air motor, hydraulic cylinder or the like obviously may be used in its place. In the arrangement illustrated this burner-tilting motor 55 drives into reduction gearing 56 to rotate arm 51 and thereby move connecting link 58 joined with the lower end of tilt rod 53 as indicated. When arm 5"! has the intermediate position represented all of the burner nozzles 4|, 45 and 41 are aligned horizontally as Figures 1, 3 and 4b show; clockwise rotation of arm 51 thereupon imparts toeach of the burner nozzles an upward tilt (the same for all) above the horizontal to some position such as that of Figure 4c; and counterclockwise rotation of arm 51 similarly imparts downward tilt to all of the burner nozzles (to some position such as that of Figure 4a).

Burner adjustment affords superior temperature control In the absence of superheat control means a steam generator equipped with a convection-type superheater S and otherwise organized as shown in Figure 1 will upon changes in loading vary through objectionably wide limits the temperature of the superheated steam taken from outlet 60. Such convection-superheater apparatushas a rising steam temperature characteristic (as earlier indicated); and in going from light to heavy generator load a total rise in the named steam temperature of more than F. is not uncommon for a unit such as illustrated (when without superheat control), while in going from heavy to light load a temperature drop of similar magnitude is experienced.

Steam-utilizing requirements of the present day make superheat temperature variation of this wide magnitude (100 F. or more) unpermissible, especially in the high-temperature high-pressure installations which supply turbines and other devices whose satisfactory operation (due to carefully chosen materials and limited clearances) requires that steam temperature variation be held within relatively close limits.

The demand for constant steam temperature at the superheater outlet 60, over a wide range in generator capacity, has thus presented a significant problem. It is one in which the temperature of the products of combustion leaving the furnace must be sufficiently high to effect the necessary heat transfer, yet avoid objectionable deposition of slag on the heat absorbing surfaces. For example, if the gas temperature is high enough at partial load to obtain full superheat, then at full load it may be too high to avoid slagging; moreover, a presence of deposits on furnace wall 34-46 and on the boiler surface 8 ahead of superheater S reduces the heat absorbing capacity of those surfaces and increases the gas temperature in the superheater zone.

These critical requirements led to development of the earlier clescribed adjustable burners 9 which can be tilted upward (see Figure 40) or downward (see Figure 4a) to suit load conditions and thereby govern superheat temperature as taught by the Kreisinger et al. Patent 2,363,875 already mentioned. With this burner arrangement, applied as here illustrated to a furnace A having liberal volume, it is possible to control the furnace outlet temperature and thereby provide a positive means for regulating superheated steam temperature over a wide range in capacity.

In manipulating the burners, required temperature of the furnace outlet gas is obtained by selective use of the available furnace volume, through positioning the zone of turbulent combustion (see Figures 4a-b-c), thereby varying the effectiveness of the furnace water wall areas; such manipulation, moreover, provides for variations in the total furnace heat absorption to compensate not only for changes in load but also for changes in the cleanliness factor of the water walls 3436. Hence to maintain a given degree of superheat the burner nozzles may be directed upward as in Figure 40, either during light load periods or when the walls are clean; and downward as in Figure 4a during heavy loads or when the walls are coated with dust or slag.

Prior to the present invention such tilting adjustment of the burner nozzles has been accomplished only in comparatively large increments and only under manual control, it having been considered that such burner nozzles did not lend themselves to automatic control. Thus, all past efforts to govern the superheat temperature through automatic means have been directed at supplemental by-pass damper means (such as shown at 24 in Figure 1) and have been confined to attempts to make same positionally responsive to departures of the named temperature from a desired value.

The improved temperature regulating facilities now to be disclosed remove the foregoing and other prior limitations and for the first time make possible a satisfactory and commercially acceptable control by automatic means of the tilting burners 9 alone, of the by-pass damper 24 alone, and of the burners and damper in uniquely related combinations.

The automatic burner tilting system of Figure 5 In Figure 5 there is represented an electrical control diagram organized to effect regulation of the superheated steam temperature through a unique automatic control of the furnaces tiltable burners 9. Responding to and at all times registering the temperature of the superheated steam in outlet 60 is a recording meter represented at 62 in each of Figures 1 and 5. This meter 62 may satisfactorily be of a type utilizing athermocouple 63 in the stream of superheated steam passing through outlet 60 together with an electrical potentiometer circuit (not shown) and associated means which keep an instrument pointer 64 (of Figure 5) in a position along horizontal scale 65 accurately corresponding to and registering the superheated steam temperature in outlet 60.

Carried by pointer 64 is a contact 66 which moves horizontally therewith. As long as the superheated steam temperature stays at the dc sired value, contact 66 is disengaged from both of a pair of cooperating stationary contacts I and D; In the arrangement shown stationary contacts I and D are mounted on a slide 61 settable beneath horizontal scale 65 for the superheated steam temperature that it is desired to maintain constant. The illustrative setting shown by Figure 5'is at 750" F. This slide 61 also carries a second pair of stationary contacts Im and Dm which respectively become engaged by movable contact 66 when temperature errors registered by instrument 62 become relatively large.

The positioning motor 55 for thetilting burners 9 may satisfactorily be linked with all of the burner nozzles as shown in Figure 3. Each burner may be provided with a separate motor 55 and the motors all energized in parallel, or all four burners may receive tilting movement from only a single motor through mechanical interconnections not here shown in detail but readily providable. In the description of Figure 5 which follows the latter arrangement will be assumed; and it will therefore be considered that the single motor represented at 55 in Figure 5 simultaneously efiects the same tilting adjustment in all four of the furnace burners which are represented at 9 in Figures 1, 2 and 4.

This burner adjusting motor 55 may be of comparatively low capacity (fractional horsepower or higher as needed) suitable for energization from the control potential appearing between the two vertically-drawn supply conductors designated 12 and 76 in Figure 5. The named motor driving voltage may be either direct current (as the 110 volt control potential available in power stations) or alternating current (as 110 or 220 volts, either 25 or 60 cycles). To facilitate explanation it will be assumed that a 110 volt, 60 cycle per second alternating current voltage appears between supply conductors i2 and 16.

Current for operating burner motor 55 is at proper times fed thereto from the named source through a conductor 13. Connection (as later described) of that conductor with motor terminal R produces forward rotation which causes arm 51 to tilt all fuel and air nozzles of all burners 9 in the upward or flame-raising direction; similarly, connection of conductor 13 (again as later described) with terminal L causes motor 55 to rotate in the reverse direction and tilt (through arm 5'!) all of the burner nozzles in the downward or flame-lowering direction. In order to prevent motor 55 from moving arm 51 too far in either the upward tilting (clockwise in Figure 5) or the downward tilting (counterclockwise in Figure 5) direction, use is made of normally closed limit switches 14 and 75 respectively inserted in the raise and lower supply leads for motor 55 as per the diagram of Figure 5.

Translation of the earlier described temperature-change responses by master control instrument 52 into appropriate operations by the burner tilting motor 55 is effected through the medium of the two relays which the schematic diagram of Figure 5 illustrates at IR and DR. Each of these two relays may be of conventional type including the usual operating winding shown as a simple block directly over the relays designation plus the contacts shown immediately therebeneath and identified with the winding by a vertical dotted line. In Figure 5 both relay windings are shown de-energized and all relay contacts are shown released or open.

The first or increase relay IR is activated by master control instrument 62 whenever the, temperature of the superheated steam in outlet 60 (see Figure 1) drops below the desired value. In

such event pointer 64 moves to the left along scale 65 and carries contact 86 into engagement with stationary contact I. This completes for relay IR an energizing circuit extending from the supply conductor 12 at the left of Figure 5 through conductor 18, engaged contacts 66 and I, conductor 19, the winding of relay IR, conductor and a step timer back to the supply conductor 16 at the right of Figure 5.

Thus activated relay IR moves its normally open contact 82 upwardly to the closed position and completes for burner tilting motor 55 a forward circuit extending from supply conductor 12 through conductor 13, relay contact 82, limit switch 14, terminal R of motor 55, the motors forward driving winding, and conductor 89 to in the water walled furnace A, shortens the vertical length of furnace wall tubes exposed to intense radiation before reaching offtake l9 and thus has the effect of flowing the gases across the superheater S at a higher temperature thanbefore.

The second or decrease relay DH is activated by master control instrument 62 whenever the temperature of the superheated steam in outlet 50 (see Figure l) rises above the desiredvalue. In such event pointer 6t moves to the right along scale 65 and carries contact 66 into engagement with stationary contact D. This completes for relay DR an energizing circuit extending from the supply conductor 12 through conductor 78, engaged contacts 65 and D, conductor 84, the winding of relay DR, conductor 80, and step timer 95 to the supply conductor 76.

Thus activated relay DR moves its normally opened contact 86 upwardly to the closed position and completes for burner tilting motor 55 a reverse circuit extending from supply conductor 12 through conductor 13, relay contact 85, limit switch l5, terminal L of motor 55, the motors reverse driving winding, and conductor 89 to supply conductor 19. Thus energized the motor rotates reversely causing arm 51 to push burner member 53 upwardly and thereby tilt the fuel and air nozzles offurnace burners 9 in the downward direction. Result is to lower the flame body (see Figure 4) in the water walled furnace A, expose the combustion gases to a greater length of the vertical wall tubes 34-36, and pass those gases from offtake l9 over the superheater S at a reduced temperature.

In my new automatic control organization the foregoing corrective adjustments in burner tilt proceed: (a) in a recurrently interrupted and hence relatively slow manner as long as the temperature error remains small; but (b) continuously for faster corrective response when the error becomes large. In the system of Figure such step-type operation a is achieved by inserting the earlier-mentioned step timer 95 in the pick-up circuits for the increase and decrease temperature-adjusting relays IR and DR.

The step timer represented at 95 includes contacts 91-98 which are repeatedly closed and opened under the cyclic action of a cam H30 con tinuously rotated (at some relatively low speed such as about 1 R. P. M.) by a suitable synchronous or clock-type motor 99 energized over conductor l0! from the systems alternating current supply circuit 12-19. Motor 99 accordingly rotates timer cam Hill at the slow and uniform speed earlier assumed (1 R. P. M.); the two cam lobes represented then serve to move timer contact 98 up and down once each thirty seconds in regularly repeated cycles; and each upward movement engages contact 98 with companion contact 97 while each downward movement breaks that engagement.

For adjusting the ratio of on (engaged) to off (disengaged) periods in these recurring timer contact cycles, provision is made for moving the upper contact 91 either closer to or further away from the lower contact 98. As here shown, this provision takes the form of a second 10 cam I03 settable in different rotational positions by timer adjusting lever I04.

When lever I04 is turned counterclockwise to the extreme left each thirty second cycle of timer operation will include a five second on period during'which contacts 91-98 are engaged and a twenty-five second off period during which contacts 97-98 are disengaged; turning lever l04- clockwise increases the length of the timer on periods and decreases the length of the timer off periods; and if lever I04 is set to the extreme clockwise position timer contacts 91-98 will remain continuously engaged throughout the full thirty second cycle. In this way there is provided a simple and effective adjustment in the relative lengths of timer on andoff periods throughout a comparatively wide range.

With connections made as shown in Figure 5 the pick-up circuits for both relays IR and DR of Figure 4 have included therein the timer contacts 9l-98just described. Instead then of being continuously picked up by master control instrument 92 (over contacts 65 and I or 6B and D) each of the system relays IR and DR now is picked up only during each on period of timer contact engagement and is released during each intervening off period when timer contacts 91-98 are disengaged.

In the case of increase relay IR pick-up current supplied thereto over instrument contacts 06-1 and conductor passes through timer contacts 97-98. As long, therefore, as contacts 66-1 of master instrument 62 remain engaged relay IR picks up only when timer contacts 91-99 are together and releases each time that those contacts are recurrently separated in the manner aforesaid. Result is that relay IR in controlling the burner tilting motor 55 then runs the motor not continuously but intermittently in step with the on periods of timer 95, the motor stopping during each timer off period.

Similarly, in the case of "decrease relay DR, pick-up current supplied thereto over instrument contacts 56D and conductor Bllalso passes through timer contacts 91-98. As long, therefore, as contacts 56-D of master instrument 62 remain engaged, relay DR picks up only when timer contacts 97-98 are together and releases each time that timer contacts are recurrently separated in the manner aforesaid. Result is,

that relay DB. in controlling the burner tilting motor 55 then runs the motor not continuously but intermittently in step with the on periods of timer 95, the motor stopping during each timer oi? period.

As will now be evident, the eifect'of step timer is to slow down the speed with which each corrective adjustment of superheated steam tem"- perature is eifected by burner motor 55. This is because each on portion of the timer cycleis during corrective actionaccompanied by a run'- ning of the adjuster motor 55 and eachinter in burner tilt more fully to produce its ultimate change in superheated steam temperature before further adjustment is initiated; in this way any tendency for the regulating system to hunt by overshooting its corrective actions is eifectively cared for.

The step timer 95 obviously may be arranged to provide operating cycles (on plus ofif periods) of either greater or lesser lengththan the thirty second duration earlier assumed (to facilitate explanation). With the thirty second cycle length illustratively assumed, equal "on and off periods (fifteen seconds each) may prove most suitable for certain steam generator installations; in other installations a shorter on and a longer oil period may prove most satisfactory; and in still other steam generator installations a longer on and a shorter o period may result in the best operation. As earlier indicated, the optimum adjustment for each installation is readily effected through timer adjuster lever I04.-

In my unique control organization of Figure the step-type of corrective adjustment in the tilt of furnace burners 9- proceeds as just described only when the temperature error being corrected is relatively small, such as not more than about five degrees above or below the desired value (750 F. earlier assumed) of superheated steam temperature. Should the temperature error being corrected exceed the named limits then one or the other of a pair of auxiliary relays IF and DF is activated to take step timer 95 out of the pick-up circuits of increase and decrease relays IR and DR.

In the organization shown the first auxiliary relay IF is upon a steam temperature drop large enough to bring temperature-following contact 66 into engagement with a first large-error contact Im (of master instrument 62) energized over a circuit then completed by those contacts and represented as including conductors I8 and 83; likewise, the second auxiliary relay DF is upon a steam temperature rise large enough to bring master instrument contact 66 into engagement with a second large-error contact Dm energized over a similar circuit then completed by the con tacts just named.

In either event the activated auxiliaryrelay IF or DF closes its normally- open contact 81 or 9| and thereby connects conductor 80 (common to the pick-up circuits of increase and decrease relays IR and DR) to supply conductor 16 directly over conductor I05 instead of through contacts 9'l98 of step timer 95. Under this conditionrthe corrective operation of burner tilting motor 55 instituted by relay IR or relay DR proceeds continuously rather than intermittently, and the large-temperature error thus is correctively reduced at a faster rate than otherwise would be the case.

How the automatic control system of Figure 5 operates During operation of a steam generator such as shown in Figure 1 the firing rate of the furnace fuel is usually regulated (through conventional means forming no part of the present inventlons and hence not here shown) to maintain a specified constant steam pressure (such as the 500 p. s. i. earlier assumed) at the superheater outlet 60; moreover, as changes in the demand for generated steam may tend to increase or decrease this pressure the fuel-firing rate is (by the means named) appropriately adjusted to bring the pressure back to desired value. At the 500 p. s. i. pressure assumed this means that the saturated steam as generated in boiler B and as fed into superheater S (by way of conduits l5) has a superheater-entering temperature which stays at or very close to 470 F. regardless of whether the generator loading is high, medium or low. 7

The manner in which the complete burner-tilting system of Figure 5 performs its intended functions will now be examined in the light of the above. Assume first that master control instrument 62 of Figure 5 is set to hold contact 66 between contacts I and D when the superheated steam temperature at outlet (see Figure 1) has a. selected value of 750 F.; next that the bypass damper 24 of Figure l continuously occupies the fully closed position there shown; and finally that all of the furnace burners 9 initially have their nozzles in a substantially horizontal fueland-air-flow position as indicated by Figure 4b.

The foregoing conditions accompany some intermediate value (such as say 50% of full rating) of steam generator loading. Due to the untilted positioning of burner nozzles (as represented in each of Figures 1, 3, 4b and 5) the fuel and air streams from all of the burners 9 (see Figure 2) have an initial horizontal direction into the fur-.

nace A and cause the main flame body to center itself at and slightly above the vertical location of the burners (see Figure 4b) in the water-walled combustion chamber. The water wall length (vertically) contacted by the flame gases prior to leaving furnace offtake 19 then is such that the gases flowing over superheater S (all of them since damper 24 is closed) have a temperature proper for imparting to the steam passing through the superheater just enough heat to maintain the superheated steam leaving outlet 60 at the desired total temperature of 750 F. (assumed 470 saturated temperature of the steam entering superheater S plus. 280 F. added to that steam during passage through the superheater).

Assume now that the demand for generated steam falls off thus decreasing the steam generator loading to some lower value (such as 25% rated) at which a considerably lesser quantity of fuel is supplied to burners 9 for combustion in furnace A. The furnace flame body now burns with diminished intensity and the temperature of the furnace gases is correspondingly lowered. The resultant stepped down transfer of heat to superheater S cuts down the total steam temperature in outlet 60 to some value less than the 750 F. desired.

This temperature lowering is at once registered by master control instrument 62 which in moving indicator 64 to the left engages contact 66 with contact I to initiate an appropriate increase adjustment in the superheated steam temperature. In responding (as earlier explained) relay IR closes its contact 82 thereby completing for burner tilting motor 55 the forward circuit earlier traced to cause an upward tilting of all fuel and air nozzles of all of the furnace burners 9 as previously described.

Such upward tilting inclines the fuel streams above the horizontal (see Figure 4c) and thereby lifts the flame body to a higher position in water walled furnace A; such raising shortens the vertical length of furnace wall tubes exposed to intense radiation from the combustion gases before same reach offtake I9 and thus has the effect of flowing the gases across superheater S at a higher temperature than before; and the resultant stepping up of heat transfer to the superheater raises the temperature of superheated steam leaving outlet 69.

In responding to this corrective increas master instrument 62 moves pointer 64 to the right. When this movement reaches the desired 750 F., contact 66 separates from contact I, relay IR be- 76 comes de-energized and opens contact 82, and

motor 55discontinues its tilt raising adjustment of the fuel and air nozzles of furnace burners 9.

Obviously if the steam generator loading goes too low-a point will be reached when this upward tilting action reaches the limit of nozzle travel (a condition represented in Figure 4c) in the flame-raising direction. When this happens,

burner adjusting member 53 occupiesits limiting position of downward travel wherein actuator 90 opens limit switch 14 andthereby breaks the forward (tilt raising) driving circuit forburner motor55.

Assume-next that the steam generator loading starts to build up. More fuel is then supplied to burners 9 and the temperature of the furnace gases passing over superheater S is correspond-- ingly raised. More heat is now transferred to the steam passing through the superheater, and this isreflected by a raising of the superheated steam temperature in outlet 6|]. ment 62- registers this, brings'oontact 66 into engagement with contact D and picks up (as earlier explained) decrease relay DR to effect closure of its contact 86. That closure completes for burner tilting motor 55 the reverse circuit earlier traced to cause a downward tilting of all fuel and air nozzles of all of the furnace burners 9 as previously described.

Result of'this downward tilting is to bring the flame body back to a lower location in waterwalled furnace A and to require that the combustion gases be exposed to a greater length of the vertical wall tubes 34 and 35 (see Figures 1 and 2) before reaching furnace offtake [9. In consequence the gases flowing over superheater S now have a lower temperature than before, and the transfer of heat therefrom to the steam passing through the superheater is correspondingly cut down. This in turn reduces the temperature of the superheated steam in outlet 60 and causes master control instrument 62 to move its indicator 64 to the left.

When the superheated steam temperature has thus been correctedbackto the desiredvalue of 750 F., contact 66 disengages from contact D; relay DR is deenergized, the accompanying opening of contact 86 disconnects motor from its en-' ergi zing source, and tilt lowering adjustment in the fuel and air nozzles of furnace burners 9 is thereupon discontinued.

Further increases in steam generator loading are accompanied by further corresponding increases. in fuel supply to. and heat liberation within furnace A. Each of these increases produces a corresponding rise in superheated steam temperature (in outlet immediately followed by an appropriate further lowering of nozzle; tilt in, the:

full rated generatorload (this assumption isnot Master control instruthe tilt-raising direction.

necessarily accurate but is made to facilitate description).

Still further rises in steam generator output are accompanied by further increases in furnace fuel supply, and through the automatic control system of Figure 5 they effect additional downward tilting of the burner nozzles to fuel-streamdirecting positions below the horizontal. As the generator loading is thus progressively increased,

a point is eventually reached at which burner motor 55 has brought the fuel and air nozzles to the extreme downward limit (a condition represented in Figure 4a) in their range of tilting travel. When this happens, the limiting point of superheat control in this temperature-decreasing direction will have been reached by burners 9 and limit switch 15 then will be opened by actuator 90. To facilitate description it will be assumed that this limit switch opening occurs when the generator loading has risen to 100% of full rated value.

Upon subsequent dropping of steam generator,

load below this assumed 100 full rated value, the accompanying decrease in superheat temperature is registered by instrument 62 to pick up increase relay IR, run (over contact 82) humor motor 55 in the forward direction, and thereby adjust the fuel and air nozzles of burners 9 (from the extreme downward position of Figure 4a) in Such adjustment brings the burner flame body to a higher point in furnace A and restores the superheat temperature back to desired value.

Continued falling off in the steam generator loading acts in this manner progressively to raise the tilt of the burners fuel and air nozzles; in this way those nozzles are brought back to the substantially horizontal position (shown by Figures. 1, 3, 4b and 5) when the steam generator loading has returned to the intermediate value (as of the order of 50% rated) first assumed. at the beginning of this operation description for the Figure 5 control system.

In all of the Figure 5 adjustments in burner tilt thus far described the corrective action proceeds: (a) intermittently when the temperature error being corrected is small, due to auxiliary relays IF and DF then being de-energized and step timer then being included in the pick-up circuits of main corrective relays IR and DR; and (b) continuously when the temperature error being. corrected is large enough to engage instrument element 56 with contact Im or Dm and pickup relay IF or DF to render step timer 95 ineffective as earlier explained.

An initially large temperature error therefore produces a continuous corrective action which adjusts the temperature back toward normal at the fastest possible rate; this continuous or fast adjustment continues until the error has been reduced to only several degrees at which time instrument element 65 leaves contact Im or Dm toreinsert step timer 95 back into the main.

relay IR,DR pick-up circuit; and from then on further and final correction of the temperature error proceeds in the intermittent manner established by step timer 95 and already explained as minimizing hunting and preventing the corrective adjustment from proceeding beyond'the.=

point necessary.

Certain features of the. foregoing control facilities of Fig. 5 form the subject matter of divisional application Serial 232,488 filed June 20, 1951 under title of superheat Control by Automatic- Tilting Burner Means.

closed. The latter contact if Figure 6 In Figure '6 there is representedan electrical control diagram wherein the unique form of automatic control just explained for the furnaces tiltable burners 9 is at proper times extended to the superheaters by-pass damper represented at 24 in Figure 1. In this composite organization of Figur 6 primary control of the superheated steam temperature is assigned to the named burners and secondary control thereof to the named damper.

'All Figure elements for controlling the tilting burners 9 have been reproduced in Figure 6 and hence need not again be described. Supplementing these are the by-pass damper 24, its positioning motor 30, driving circuits for that motor including contacts 8| and 85 of relays IR and DR, a burner-actuated contact 88 in those driving circuits, and a damper-actuated contact H in the circuits which drive the burner motor 55.

The positioning motor 36 for by-pass damper 24 may satisfactorily be of comparatively low capacity (fractional horsepower or higher as needed) suitable for energization from the control potential appearing between the two vertically-drawn supply conductors l2 and 16 of Figure 6. There current for operating the damper motor 38 is at proper times fed thereto through a conductor 68.

Connection (as later described) of that conductor with motor terminal C produces forward rotation by motor 39 which causes arm 32 to move damper 24 toward the closed position represented; similarly, connection of conductor 68 (again as later described) with terminal 0 causes motor to rotate in the reverse direction and thereby move (through arm 32) damper 24 in the opening direction. In order to prevent motor 38 from moving arm 32 too far in either the damper closing (clockwise in Figure 6) or the damper opening (counterclockwise in Figure 6) direction use is made of normally closed limit switches 69 and E8 respectively inserted in the close and in the open supply leads of motor 38 as per the Figure 6 diagram.

In the fully closed damper position represented limit switch 59 has been opened, and contact H also actuated by damper arm 32 has been (in the driving circuits for burner motor 55) is closed only when damper 213 is fully closed; at all other times it remains open. Obviously, however, the system may be set up to effect closure of this contact H at given positions of damper 24 other'than the fully closed one here selected for purposes of illustration.

In the intermediate burner-tilt position (corresponding to Figure 4b) represented in Figure 6, the burner-actuated contact 88 (in the driving circuits for damper motor 30) is opened; it closes only when the burners occupy the position of maximum downward tilt as represented in Figure 4a. Obviously, however, the system may be set up to effect closure of this contact 88 at given positions of burner tilt other than the maximum downward one here selected for purposes of illustration.

How primary burner control system of Figure 6 operates In considering operation of the composite burner-damper control system of Figure 6, initijally assume (as was done in explaining Figure 5) that master control instrument 62 is set to hold element 66 between contacts I and D when the superheated steam temperature at outlet 60 (see Figure 1) has a selected value of 750 F.; that the by-pass damper 24 occupies the fully closed position shown wherein contact H assigns burner tilting motor 55 to control by relays IR and DR; and that all of the furnace burners 9 have their nozzles in a substantially horizontal fuel and air flow position (as in Figure 4b) wherein contact 88 actuated by burner tilting member 53 is open to keep damper motor 30 continuously de-energized and hence unresponsive V of generator loading the necessary regulation of steam temperature at superheater outlet 60 is accomplished through tilting burners 9 automatically adjusted as in the system of Figure 5 earlier described; and for higher values of generator loading which do not reach or exceed some predeterminedly high value, such as 100% rating for the unit, a similar statement can be made.

This is because contact 88 actuated by burner tilt rod 53 closes only when the furnace burners 9 have been adjusted to their Figure 4a position of maximum downward tilt corresponding to the assumed'100% rated generator loading. For all lesser load values this contact 88 remains open and prevents damper motor 30 from receiving driving current upon closure either of relay IRs contact 8| or of relay DRs contact 85. Damper 24 thus stays in the fully closed position represented wherein contact H maintains the forward and reverse driving circuits for burner motor 55 set up for selective completion upon respective closure of IR relay contact 82 and DR relay contact 85.

Hence within the geenrator load range cared for by tilting burners 9 the response by tilt-adjusting motor 55 to relays IR and DR is the same as in the earlier-described system of Figure 5. But, as the generator loading is progressively increased, a point is ultimately reached at which motor 55 brings the fuel and air nozzles to their limiting position of downward 'tilt as represented in Figure 4a.

When this happens, actuator opens limit switch 15 while burner tilting member 53 effectsa closure of contact 88 and thereby connects damper motor conductor 68 with the supply conductor 16. Such connection conditions damper positioning motor 30 for response to pickups on the part of relays IR and DR. As earlier indicated; the flame body within furnace A is by 'superheater S. The'resultant increase in heat transfer thereto again increases the temperature of the superheated steam in outlet .60 and causes master control instrument 62 once more to move indicator 64' to the right and bring contact 66 txvusas r 'zles'; in this way those nozzles are brought back to the substantially horizontal position of Figure 4b when the steam'generator loading has returned to the intermediate value (as of the order o'f,50% rated) first assumed at the beginning'of this'operation' description vfor the Figure 6 control system. i

i'With this system it will accordingly be seen that when the steam generator loading is in the range; below some predetermined value (here illustratively assumed as 100% rated) all corrective adjustments in superheated steam temperature are effected through the medium of tilting burners'9; that when the generator loading lies 'in the range above that predetermined value '(100,% rated assumed as aforesaid) all required controlof the superheated steam temperatureis provided through the medium of by-pass damper Zitrand that the total range of generator load variation accompanied by effective superheat temperature control thus has been increased to the sum of the two load ranges individually cared'for by the two controlling instrumentalities (tiltable burners 9 and by-pass damper 24). In the illustrative example given, the burners 9 thus 'take care of generator loadings from an extremely low value up to an assumed 100% full rated'value while the by-pass damper 24 accomplishes all necessary superheat temperature control for generatorloadings of from 100% to an assumed 12 5% rated value.

v In all'of the-Figure 6 adjustments in damper positioning and in burner tilt which have been described the corrective action proceeds: (a) intermittently when the temperature error being corrected is small, due to auxiliary relays IF and DF then being de-energized and step timer 95 then'being included in the pick-upicircuits of master relays IR and DR; and (b) continuously when" the temperature error being corrected is largeenough to engage element 66 with contact I'm or Dm and pick-up relay IF or DF to render step timer 95 ineffective as earlier explained.

I The by-pass damper 24, as well as the tilting burners :9, therefore responds to an initially large temperature error toproduce a continuous corrective action which adjusts the temperature backjtowards normal at the fastest permissible rate; this continuous or fast adjustment (by the damper or by the burners, whichever is respondingycontinues until the error has been reduced to only several degrees, at which time instrument element 56 leaves contact Im or Dm to reinsert step timer 95 back into the main relay IR'DR pick-up circuit; and from then on further and final correction of the temperature error proceeds in the intermittent manner established by step timer 95, which is eiTective to prevent corrective action overshoot (as earlier indicated)'.

Ihe primary damper control system of Figure? 20 "garded as a secondary control of superheat tem perature which serves to extend the total range of generator load variation effectively provided In the modified system of Figure 7 aisome whatjdiflferent arrangement is used in thatbypass damper 24 may be regarded as providing the primary control of superheat temperature while the furnace burners 9 supplement same only when needed to shift the damper range so as to embrace the particular value of steam'genierator'loading being dealt with. V o

Comparison of Figure 7'with Figure 6 will re veal that the Figure 7 circuit organization exactly duplicates the Figure 6 organization except for the following differences: (a) burner 'a'ctuated contact 88 of Figure 6 has been eliminated from Figure '7; (b) damper actuated contaot'lj of Figure 6. has in Figure 7 been replaced by a pair of contacts lla llb; and c) the reverse or tilt lowering driving circuit for burner motor 55 (which includes contact 86 of relay DR). is in Figure 7 carried separatelythrough damper contact 'Hb; o

These changes cause the Figure 7 systemto 0perate in the modified mannerwhich will now be explained. .Assume that. the steam generator loading has some intermediate value suchas 50% rated. Under this condition the by-pass damper 24 will be partially openedvas indicated in Fig.- ure .7 while the fuel and air nozzles of furnace 9 will also have some intermediate position in their tilt range such as the horizontal oneof Figure 4b.

.Assume next that there occurs a rise in steam generator loading which calls for greater fuel sup: ply to and heat release in the furnace, with consequent initial elevation in the temperature of the superheated steam leaving generator outlet 60. Master control instrument 62 registers this initial rise to pick-up relay DR over contact 66-D and thereby close relay contacts and 86 But, the closure of contact 86 cannot operate burner motor 55 for the reason that the reverse driving circuit therefor is now broken at damper contact H'b.

However, the closure of relay DRs contact 85 completes the reverse driving circuit for damper motor 30 (conductor 68 now being directly connected with the supply conductor 16). Motor 30 accordingly moves by-pass damper 24 in the open ing direction to divert more of the furnace gases from contact with superheater S and thereby bring the superheat steam temperature back down to the desired value. v

If the increment of steam generator load in crease was large enough to cause motor 30 thus to fully open damper 24, limit switch 10 will be opened by actuator 93 at the same time that damper contact I l b closes and connects relay DRs contact 86 with the supply conductor 12. Should contacts B6D of master instrument 62 then still be engaged, closed contact 86 of relay DR now becomes efiective to run burner motor 55 reversely and thereby tilt the fueland air nozzles of furnace burners 9 in the downward direction.

This downward tilting action by motor 55 con-.-. tinues until the superheated steam temperature: as measured by master instrument 62 returns to the desired value at which instrument contact 66 disengages from contact D to de-energize relay ,DR and thereby discontinue burner lowering operation of motor 55. Further increasesin the. generator loading repeat the just described super- 0i burner motor 55.

Itfnow thesteamageneretnmrioadiugzieiisrwith attendants. decrease: im neeeaimeii simply fi lbwering oir? the superheateit ste'am tempe master: instrument: 6-2;; engages: 'eontettz 35: with. emitiaict 151130: picksu increase relay The attendant; closure off contact: 821 cannot;- upemte? burner-motor '55 Hammer neasonzthahthe: forward? driving: oir'cuititherefbnisa nowl broltenlat 101,

the; desirecii value; relay: will: continue to:

hold bontactse 81' and": closed; Contacts?! has; nmeitect' omdamper-moton I U'ifbn thetereason thnt limit; switch: 691* has; now been: opened: by acme at'on 98;; That: opening; moreover, was'l-accom-enamed-l by a closure: ofi dampencontact: Til-(1:: to: connect: reliwyw contact I25 (in; the: burner motor: circuit)" with thezsupplwconductorr 12.

Iz'r consequence: or!" this; I -1w closure: relay 18 neontacn 82 now: drives:- dampen motor? 55 1 in the fbrwardzdireotion'towmovethetmeiianw airvnozziein of furnace: burners: 92 im the. tilt. raisi g: (iii-se tlon: Suchmovementcontinuesuntilitheiinitieiiy ibwered superheated steamr temperature is: re? stored" to: the? desired; value at which content; "*1 de energizes relay andastonsmotors 55-;

Should? the steam: generator loading nowwbe m creased the resultant riser in: superheated? steami temperature-as registered:by instrument znipicks; upw relay DE: The attendant;- closure of? relay contact 88* has' no efiecti ombumer motorvtor the reason: that thereverse driving cirouit for; thismotor isz now broken at thedamper oontaot: It (whichcloses only when byepass dam-per- N. is fully: opened). But the" attendhntaciosurwofrea my Dft'e contact E6 drives" damper motor" 30, the reverse direction and starts move-m as: dampen 2.4% in the opening direction (from the previous tully 'closediposition);

This" opening of damper 24 coxrtimie'sw eitherlmtil l the, superheated steam: temperature isbroughtbaok to normal (to-release-=reityDRgnd stop motor 30 or until" demperv lfibeoohis fully. openedto" breakthe motor" driving Qirouit at limit switch" 10 anti at the sametime toe see: Contact Hb in: the: reverse driving eircuitrflirs Burner: motor 515% In, the tbrmenevent: the corerective flictidtiais'; completed; imtiie-iatte motor: fl comes-einto' mationtto. move th uel; and. air nozzles; of? fiirna'ce; burners: 9? in: the iitrlow. ening: directionza'sw maybe-required: res-tore jthu; superheated'steamatemperatunehac I ,normztli In axll 01! the" Figure 7 adjustments? in. dampen QOSitlOII. and' in burnertfltawhibhf haveabeen: de:-* scribed: the corrective: action: (or proceeds in? termittently when the: temperature ror being: tormented? is': small} due to: auxiliary relays and; DE"- then: beingdie-energized". Emit temtim 'i 95%: then being included; the plain-up circuits: of' master control relays: IR: and" DB3? and; (Ir): proceeds c'ontinuousiys'whem the teniperetur error: large? enougitto engage? inmariimfentv ei' ment l6; canteen andi Dm andi pink-um rel-muteDmmrendemgtegium-alz inezeenw as: mien expiair redi producesaaa'continuouscorrective:fiction; (esa-imthei eamiieredescribecii systems" 0ft Figures. 5': and: 6.)5; this continuous ore-fast;adjustmentmontinuesmm til: the? error: has; been reduced to; only several degrees; and"; fromzfthena on; further a'ndi final: correction of the: temperature: error proceeds; in: theintermittent-mannersestabiishedibyntepatimen 96: to prevent. each corrective abtion from; pure ei'eeding beyonditheapoint necessaryi'.

Itiwiil. accordingly-be: seen:thatuingthezfligurex 7, cincuitmrganizationprimarycontrohofithetssunen heat'edistahiatemprature'iseffelitedi'throughthe} mediumzi'of: lay-pass dampen 24; whilezthe tiltable: furnaceburnersffl:come intuzactionilonly whenvthe? magnitudeioji augivenchunge insteamgbnerator: loading; exceeds the;temperaturezcorrectivevrange' of"? the? by-palss damper; However; a-s-gin; thevsys termofliiiguresBithemjisqprovidea -an:effectiveacony 131101: of; superheat temperature throughoutja" tqtelt rangerofeteamgeneratorloading;variationywhich is the sum of the individual ranges on the", by, pass; damper: 2.4xandaofjthstiltable furnacei bumers; 9: (each of these? two, instrumentalitiestbeing; efieotiveciniazgiyeninstallation toholdithesupez heated steam; temperature constant through and: only through; 31*? certain range; of. generator; ratingsii 7 Summary;

From the foregoing, it will aceoraingiy: that: I. haver pmvided. improved means for; in taining the, desired; steam; temperature from, the;

" convection superheaten of; arconvenuonnwett walled; steamtgenerator by autqrnetioilly; eam leting. (through tilting, burners), the fleet xiii: sorntion withinithefiirndoe :as' the, injor, basiswof control and also (when desired) the bill-iififisifig; o fifurnac gaseearounduthe suiiriieaten asq' sup piementall basis of control}. shit I nave} pro "'dd automatic, controlimansres onsive t0 the Sill? heatedilsteam tembertt'ure'a'nd uniquely e'fie'tiv' to. adjust iiix advantageous and. omnieiciallysfit isrectory Ways either'thetilting' burners-:or e by-nass damperor both ithat Iiiavecoordinateiii the heat absorption or tilting burnerjmeanswith thege kiy-pas's or'uamper eanein suoh wire? that the temperature gontroi ranges of-the two? are-additive: arid-that!haveprovided' eutomaue controi systems responsive to superheated teifn' tfe'niperaturewhioh' erefiedtive-to adjust theta ordinetedtilting; burner and liY ps'S ilfii ifls pidtefmii'id advafitgeou's' Whi actuar practice the" fierifi-diolo sd iihiqii" automatiecontrols, of the tilta'blburners 9 lies sfio'wfl' advanta es Whih; reboth Signifioatifi and; unexpected 3111 operating exper'iende thu'sk fir.- acquiredhaving demonstrated: iii-nit individiill' automatic control: 61' tilting Biififits'u it fair i ion to-end hence-much to: be preferred over dividiimi autdmitiocontrol of a' by-passu dampen.

the example; using tiltable burnrs asthe regulator of" superheated steam; temperature the r furnace exit gases; are efiectively'prevnted; from: getting: objectionaibly; hot? (high: loads; being: amcomnani'edatbyilow:flame:positionings;asushuwnjinz Eigurea 411-); whereas; if" only; a}; byL-passa d'amnen (such asazimmgure 1) dependerluppmto ac co'mpl-isir superheat regulation th'eztemperaatureiofa the: furnace: exit. gases" camnotzv be", so held; dawn. atzhighzgenerator; loadings :andobj actionable 28' g}. deposits; on. the; heating; tubes surfacesthen; ar likely to occur; additionz superior; efiflgiencyg befits transfer; the? boiler Witter is dehievd;

- *2'3. with 'the'by pass'damper M held fully closed and all superheat control provided by the tilting burners for then all furnace gases traveling through'boiler B follow the circuitous path which enables-better heat transfer than does a bypassing flow through channel 23.

Moreover, the here-disclosed tilting burner method of automatic superheat regulation involves a sweeping of the flame body up and down in the'furnace with changing generator load as diagramed by Figures 4a-b-c. Operating experience demonstrates that such recurrent change in vertical flame location gives a totally unexpected advantage of keeping the furnace walltubes 34'--36 relatively .clean and free from the slag deposits which build up when the flame isfheld in a single vertical location, as in conventional furnace organizations of the prior art.

In consequence coals and other fuels of a wider grade can be successfully burned in a furnace equipped with automatically tilted burners 9- thanin a furnace wherein the burners are not so controlled incident to superheat temperature regulation. i

The foregoing special advantages of automatic burner tilt control therefore have a wide practical significance and vastly extend the performance capabilities of steam generators such as therein considered. My inventive improvements are therefore extensive in their application and hence are not to be restricted to the specific form here disclosed by way of illustration.

What I claim is: Y

1. In a steam generator, a generally vertical furnace having a gas outlet at one end and Walls lined with water cooled tubes, burners in the vicinity of the other furnace end for introducing into the furnace at a point remote from said gas outlet streams of fuel and air which create a mass of burning gas within said tube lined walls, a superheater carrying steam from the generator and receiving heat from the furnace gases which leave said outlet, a passage through which a portion of said furnace gases may bypass around said superheater and, thereby cut down heat transfer thereto, a damper for adjusting the flow of said by-pass gases, means for tilting said burners wherebyto alter the angle to.thehorizontal of the direction of said fuel and air streams so as to bring the vertical-location within the tube lined walls of said mass of burning gas closer to or more remote from the furnaces said gas outlet, a motor for imparting tilt adjusting movement to said burners through said means, another motor for imparting position adjusting movement to said by-pass damper, an instrument for registering the temperature of the steam leaving said superheater, forward andreverse driving means for said burner motor respectively activatable by said instrument when said leaving-steam temperature falls below and risesabove a desired value and then effective respectively to adjust said burners in direction bringing said burning gas mass closer to the furnace gas outlet and in direction bringing said mass further away from said outlet, forward and reverse driving means for said damper motor respectively activatable by said instrument when said steam temperature falls below'and rises above said desired value and then effective respectively to adjust said damper in the bypass gas increasing and in the by-pass gas decreasing direction, and control transfer means for causing' -said instrument to govern as aforesaid the said burner motor driving means at times and the said damper motor driving means atrfotl'rerl times.

"2. 'Inia steam generator, a generally 'yertical furnace having a gas outlet at one end and zwalls lined with water cooled tubes, burners in .the

vicinity of the other furnace end for introducing into the furnace at a point remote from said.

gas outlet streams of fuel and air'which create a mass-ofburning gas within. said tube'linedi walls, a superheater carrying steainfrom "the generator and receiving heat from thefurnace. gases. which leave'said outlet, a passage through which a portion of said furnace gases may by-" pass around said'superheater and thereby cut down heat transfer thereto, a damper for adjust-z ing the flow ofsaid by-pass gases, means for tilting said burners whereby to alter the angle to the horizontal of the direction of said fueland air streams so to bring the'vertical location within the tube lined walls of said mass of:

burning gascloser to or more remote from the furnacessaid gas outlet, a motor for imparting" tilt adjusting movement to said burners through said means,'another motor for imparting .positionadjusting'movement to said by-pass damper,

an instrument for registering the temperature of the steam leaving said superheater, forward and reverse driving means for said burner motor respectively activatable by said instrument when said leaving-steam temperature falls-below andrises above a desired value and then effective respectively toadjustsaid burners in*direction-- bringing said burning gas mass closer to the furnace-gas outlet and in direction bringing-said mass further away from said outlet, forward and reverse driving means for said damper motor" respectively activatable by said instrument when said steam temperature falls below and rises above'said desired value and then efiective're spectively'to adjust said damper --in;theby-pass gas decreasing and in the by-pass gas increasingdirection, and control transfer means responsive to changes in steam generator loading and functioning to cause said instrument to govern the aforesaid driving means for one of the aforesaid two'motors when that loading is within a given range and to govern the aforesaid driving means for the other of those motors when the generator loading is outside of said given range.

3. In a steam generator, a generally vertical furnace having a gas outlet at one end and walls lined with water cooled tubes, burners in the vicinity of the other furnace end for introducing intothe furnace at a point remote fromssaid gas outlet streams of fuel and air which create a mass of burning gas within said tube lined walls; a superheater carrying-the generated steamand receiving heat from the furnace gases which leave said outlet; 'apassage through which a portion of 7 motor for imparting tilt adjusting movement to said burners through said means, another motor for imparting positionv adjusting movement to said by-pass damper, an instrument for registering the temperature of the steam leavingsaid superheater, forward and reverse driving means for said burner motor respectively. activatableby I 225 mstrunreno -wlien said' leaviiigwteam"j perature tailsbelow and rises abov afiesitdwelue antvthemetfeetiverespectively d =adjus' said bumers in dire'etion ibi'ing'mg said 'burn'in bririg'lngi'said "mass further'away 'from safd litl t; tbrward and reverse 'drivmg-f ieaiis fer said reverse-driving means="of said burner'motbr at" t timer effective to cause the"aforesaid 'correcfiiVe 1 operatibns of said =burnei t'ilfing Hand mamper positioning motors 'te proceed ritermittently-ancb "antime-ans"effeetive'\i heirsaid.superheated steam 25' temp'era'ture as registered'bythe iiist'ru'mentdia parts widely *fiomsaiddesired value {or musing the a'ecompanying =cor1ective operation flay *the bumertfltin'g motor 'or *the damper 'position'ing motor" then to proceed continuous'li and" iieiilce 'relativeNTastuntil the"temperaigiire errorunder "c'orrectiemhas' been broughtback 1 intdthe smallerror-range within which the step timer'wenciers "the-motor"operatien intermittentas aTbresaid;

4. m a; -steam generator, -a= mmace'havmw a heater carrying steamirom the generator-and "the'iiirection ef' saidffiiel and alt-"stream as an -Ewes-'01 raise' the vertical i'oeation within "!6r' 1mpa1 tirig *tiit- 'adjusting mevemefit td said *bumers' through *saJd means; anether mdterfr *imparting position adjusting movement 'to' said bymass dampen an instrument fer reg terir'i g sthe-i=temperaturedI the steam leavifi'g said heater; 'forward' an'd reverse 'driving niea said lanner mdtor' respectively i aetivatafile by sai'di"instrument when" said Ieavmg steam tem perature "falls below andris'es abeve a "desired value raridathen effective respectively to' 'a'rljiist znerature talls below-anti -"rises above saiii desirefl aaid lbumermotor fid'riving means' at times and inass closerite ihe furna'c'e 'outlet iand indirection wors mi anu siesta amass oil-1311mm:

gas within the tubevlined wa'-1-ls. afliiid heater marrying steamgfrom -the generator and reeei i'ing heat frbifi the 'fi rhace gases which leav said outlii passage thrfiligh 'wfileh"a pbr ti'eri df sa'id fiirnaee g'afs'es may by 'pass afciund asziid heatier an merebyi'cu t dbwn heat transfer theretoha as m 'adjjustin'g the mow or :sai'aby pass is es, meansfef tilting- 'saidburhei s whereby ito alter-Lina angle to I the horizontal 'of the cures ltion' lOf said fue'l azi'd air streams-s6 as \to lewer' 0T saise 'is'h'e ver ti'ca-l location within the f-iiz iiaic'e df -said burninggas' massga -=m'otor-' for tingtilt adjustingmovement to said' 'burnough sai'd means, 'another motor for 11map utingipositibii adjustingi movement tesaid bydamper;an-fiinstrumentfor registering the iteiziperatu'reof the steam leavingsaid-fluid eater, fb'rward andre'verse "driving ni'eans for burner" "motor 'resliecti'vely abtivata'bl by instriu'hent'wheh' sa'id leaving steamtemsamura -fans below-arid rises above a "desired "value -a nd Lthen' efiective respectively teadjust S,-idibiirhers in theflip'ward-and' in th e' downward 'id-ireetiemiorwa'rd and-"reverse drivihg 'mean's -fer sma -damper motor respectively activatabl b'y :said iristrumeht when said steam" temperature -fa1ls-beIew and-rises abovesaiddesired valueafid :the'n effeetiverespectively to adjust said damper 'cezitrolti aii'sfer" means responsive to changes in ste'am* generator' loading "and fur ctibniing "to cause said instrument to govern the f aforesaid eiivm 'gmea s-rbr: one orthearoresaid-iw mowrs f-w'her'i that" leading is wiihiri "a; given range? ma 'to igo'verii [the aforesaid driving nieans"'fpi" 'the qthero'fthose motors wh n the generator ibaajingfis eutside *of said given" range; V V

"6. In a "steam generator, :a furnace having; a gas outlet and walls lined "with water codled tii'bes; burners i'fer introducing inte "a given pertio'n' of -"said -furnace "streamsmf fuel andalir "Wfiichcrate a; mass of bur'ning gas within said 'tubeflineflwallsfiasiiperheater eariyingtthe gen- "eratezi steairvantl 'reeeiviri" -heat*TrqmTthe fur nace gases which leave said ofioletr'a'passaz ze through which :a' portion 'of :said furhaceg'ases nfiay by fP eSs around said superheater and were bycu't dawn heat; transfer thereto) a damper Pier for tilting said burners wherebytealterfthe arrgie to 'me' horizontal of the direction of "said fuel and fan streams so asto lower or raise tIie, "vertical 1 loeation within" the-furnace bfsa-idbjirnin? movement to rsaid J burners "through said "mean'sianethei"motor'for 'impartihg' -pds'ifieii ad- "justingmovement to said by pass damper, "an flinstrfirrientfon'registringflzhe' temperature bfthe "steahiilavingfsaid"superheater; forwafif and re: verse centfol iircui'tsfoi' said-burner meter "afiivatsmeby' said ifistrumerit when said'iniiiera .tuxeirespeetiv'ly. fall's blbviifafidfriss Tabdve fade-f s'iredv'alue and tlienleffeetiv rresbeetivefjatbiai'l' .ijustisaidburnersin the upWardzanddntlde downward-direction, miorward and reverseicentrel air- .1cuitsf0r= sa id .dampe1? motor activatable bYi fl-id instrument when said temperatureerespeetively zfallsebelowandurises-above said desired valuie and .themefiectiveerespectivelyitoiadjust said. damper zm-lt-he clusing eandiinwhe z'ope ningedireetiommand inieansrfori-causmg said linsfrumnvaoegoverriwas atoresaid ithe -2forward :a1id"-.-reverse .contrdl ici-r- :wardqand reverse control circuits-fof said jdamper motorat other times. r izxi'l'rlnv a steam generator, afurnace having a .gas outlet and walls lined with water, cooled g tubes, burners for introducing into a'given portion of said furnace streams of fuel and air which create a massof burning gas within said tube lined walls, a superheater carrying the generated steam and receiving heat from, the furnace gases which leave said outlet,ra passage through whichv .i a portion of said furnace gases may by-pass around'saidsuperheater and thereby cut down heat transfer thereto, a'damper for adjusting the rflowj of said by-pass -gases, means for tilting said burners whereby to alterthe angle to the horimaontalof the direction-pf said fuel and air streams r so as to lower or raise-the vertical location within the furnace of said burning gas mass, amotor for impartingtilt adjusting movement to said {burners through said means, another motor for "below and increases above said desired value are fcorrect'ed through compensating adjustments in "the positioning ofsaid damper, and means effective'atoth'er timesand governed by the position of said damper for connecting said burner 'motors'forward and reverse operating circuits in 1control"receiving relation with said first and secone. relays whereby during said other times superheated steam temperature decreases below 1 and "increases above "said desired value arecorrected through compensating adjustments in the tilting of saidbur'ners. Y j v I. '8.' In a'steam generator, a furnace having a'gas ioutlet an'd wall's'lined with water cooled tubes, burners for introducing into said'furnac'e streams of fuel and air which create a mass of burning gas within said tube linedwalls, a 'superheatencarlrying, the generatedsteamandieceiving heat from the'furnace gases which'leave said outlet, a passage through which a'portion of said furnace gases mayfby-pass around said superheater and thereby'cut down heat transfer thereto, 'a'dam'p'e'r 'ror adjusting the flow of said by-pass gases, means for tilting, said burners whereby to alter the angle 'to the horizontal of the direction of said fuel and air streams so as. to lower or raise the vertical location within the furnace of said burning gas mass, a motor for imparting tilt adjusting movement to said burners through said means, another' motor for imparting position adjusting movement to said by-pass damper, an; instrument for registering the temperature ofthe steam leaving said superheater, forward and reverse control circuits for said burner motor activatable 'by said instrument when said temperature respectively falls below and rises above a; desired value and then respectively effective to adjust said burners in the upward and in the downward direction, forward and reverse control circuits for said damper motor activatable'by said instrument when said temperature respectively. falls. below and rises above said esi d v lue a d-th n e fectiverespectively toadjust said damper in the closing and in the opening direction, ;means for causing said instrument to govern as aforesaid the forwardandreverse control circuits of said burner motor at times and the forward andreverse control circuits of said damper motor at .other times, means responsive to the difference a o id. o r qiiv O ations b rb ime tilting and damper positioning motors to proceed with relatively rapid temperature adjusting effectiveness when said difference is large and with v 9. In a steam generator, a furnace having a gas outlet and walls lined with water cooled tubes, burnersfor introducing into said furnace streams of fuel and air which create a massof burning gas within said tube lined walls, a superheatercarrying the generated steam and receiving heat from the furnace gases which leave said outlet,a pas- ,sage through which a portionof said furnace gasesmay by -pass around said superheater and thereby cut down heat transfer thereto, a damper for adjusting the flow of said by-pass gases, means-for tilting said burners whereby to alter I the angle to the horizontal of the direction of said fuel and air streams so as tolower-or raisethe vertical location withinthe furnace of said buming gas mass, a motor for imparting tilt adjusting 'movement to said v burners through said :means, another motor for imparting positionad- ,justing movement to said Icy-pass damper, an i instrument for registering the temperature of the steam leaving said superheater, a first relay activated by said instrument when saidtemperature falls below a given desired value, a second relay activated by said instrument when said rtemperature rises above said value, forward and reverse operating circuits for said burner motor, forward and reverse operating circuits for saiddamper -motor,means effective as long as said damper occupies a given position such as that of minimum .by-pass gas-flow for connecting saidburner motors forwardand reverse, operating circuits in co ntrolreceivingr relation with said first and second relays wherebysuperheated: steam tempera- -ture decreases belowand increases above said desired valuethen cause the burnermotor respectively'to adjust the tilt of said burners as appropriate to correct the; temperature, andmeans rendered effective when said burners reachagiven position: such as that of extreme downward tilt for connecting-said damper motors-forward'and and second relays as aforesaid.-; ,7 10.; In asteam generator, a" furnace having a" gas outlet and walls lined with -water cooled tubes, burners for introducing into a given portion of;s aid furnace streams offuel and airwhich fi W5fiTm 55 burning as-w thin s i tub liQQdigtW i s-1 a-su h a e KQQ KEWQB 4 .1 531E

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