US1959100A - Fluid heater and method of operating same - Google Patents

Description

y 15, 1934; c. w. GORDON 00 FLUID HEATER AND METHOD OF OPERATING SAME Filed Dgc. 11, 1931 3 Sheets-Sheet 2 INVENTOR 5 i (62*\ C harle s WGo'rdon,

64 61 BY 0 1 Z 70 76 re ATTORNEY M y 15 34. c. w. GORDON 1,959,100

FLUID HEATER AND METHOD OF OPERATING SAME Filed Dec. 11, 1931 3 Sheets-Sheet 3 5 INVENTOR CharleM/V Gordon ATTORNEY Patented May 15, 1934 UNITED STATES PATENT OFFICE v FLUID HEATER AND METHOD OF OPERATING SAll/IE Charles W. Gordon, Munster, Ind, assignor to The superheater Company, New York, N. Y.

Application December 1 12 Claims.

comes important that the variations of the temperature be kept within very close limits, and especially that the upper limit be not exceeded.

It is one of the main objects of my invention to provide an arrangement and a method of oper ating it which will meet these requirements. v

In order that my invention may be readily and clearly understood, I will now describe in detail three forms of apparatus selected by way of example from a number of possible embodiments of my apparatus invention and which are adapted to operate in accordance with my process invention. Said two apparatuses are illustrated in the accompanying drawings in which Fig. l is a transverse section thru an A type superheater boiler built in accordance with my invention.

Figs. 2 and 2a. show certain curves used hereinafter to explain the operation of apparatus in accordance with my invention.

Fig. 3 is a sectional view thru a Stirling type superheater boiler in accordance with my invention.

Fig. 4 is a front view of the boiler shown in Fig. 3, parts being broken away and parts being shown in section for purposes of illustration.

Fig. 5 is a fragmentary plan view of an alternative arrangement of headers for the superheater of Figs. 3 and 4.

Fig. 6 is a sectional elevation of a third form of apparatus embodying my invention.

In Fig. 1 of the drawings, 10 refers generally to the superheater boiler, which is of the Well known A-type, having an upper steam and water drum 12 and two lower water or mud drums 14, 14. set parallel to the upper drum and connected therewith by outwardly and downwardly inclined banks of generating tubes 16 and 16a. The banks.

16 and 16a lie on opposite sides of a central A- shaped combustion space 18 and the gases of combustion flow from the furnace 18 upwardly thru two gas paths each comprising one of the generating tube banks 16 or 1611 and one of the passages 20 or 20a, one on each side of the drum 12 and which unite to form the stack 24. The passages 20 and 2060 have independently operable dampers 22 and 22a. The units for superheat- 1, 1931, Serial No. 580,290

mg the steam from boiler 10 are placed above the banks 16 and 16a in passages 20 and 20a respectively. The superheater therefore is of the convection type in which the heating surface is screened from radiation emanating from the fur-- mace and a typical load-temperature curve for a superheater of this type and in the location illustrated is shown at A in Fig. 2a, curve A indicating the temperature of the steam at the superheater outlet for steam flows ranging from part load to full load. In accordance with my invention, materially more of the superheater surface is placed above one bank of generating tubes than above the other. As shown, steam from the drum 12 is conducted to inlet header 26 thru a 70.1;

conduit 28. From header 26 the steam passes thru the group of relatively large superheater units 30a located in passage 20a into the intermediate header 32.

From header, 32 the steam passes thru conduit 34 into a second intermediate header 36. From header 36 the steam passes thru the group 30 of smaller superheater units located in the passage 20 and thence into the outlet header 38.

The steam generating surface of banks 16 and 16a and heating surface of the superheater are preferably so chosen and divided between the two gas paths 20 and 200, that the final temperature of the steam delivered from the boiler is some desired maximum when the boiler is op- 35.

crating at its calculated full load and the dampers 22 and 22a are preferably so adjusted that the gas flow thru the two sides of the boiler is substantially equal. This is expected to occur where the dampers in both gas paths are wide open. With the boiler illustrated in Fig. 1 it is assumed, as indicated in Fig. 2a, that the temperature of the steam at the outlet of the superheater will attain the desired maximum of 850 deg. F. at the time the load on the boiler reaches 95.

its calculated full load of 350,000# steam per hour, the gas flow being equal thru the two banks 16 and 16a. The superheater and the turbine or other prime mover to be connected with the boiler are designed to withstand a steam temshows that the'desired maximum temperature will be exceeded at such load, some of the superheater surface is then removed so as to bring the final temperature as near as may be to the desired maximum. The superheaterbeing of the convection type, the temperature of the steam delivered by it tends to fall off with a decrease of the load somewhat as indicated in curve A provided the normal division of combustion gases through the two sides of the boiler is not disturbed. Such a curve would result in reducing the efficiency of the prime mover at such lower loads. By means of the present invention, the temperature is kept up to the desired maximum throughout the greater part of the load range. For this purpose, as the load decreases, a greater percentage of the combustion gases is diverted so as to flow over the larger section 30a of the superheater. This is accomplished, in the arrangement shown, by adjusting to the extent required the dampers 22 and 22a so as to force more of the gases to fiow through the passage 20a. Assuming that the group of units 30 contains 30% of the total superheating surface and that the group 30a contains of such surface, I have found that the temperature of the steam delivered by the apparatus can be kept substantially constant as indicated in curve B of Fig. 2a by dividing the gases at different loads between the passages 20 and 20a as indicated in Fig. 2. Under these conditions, the temperature at the outlet of the group 30a will vary with the steam flow as indicated in curve C of Fig. 2a, the remaining amount of superheat necessary to maintain the desired constant maximum temperature being supplied by the small superheat group 30.

It will be evident to those skilled in the art that the principle involved in the above described operation of apparatus shown in Fig. 1

is not limited to an A-type boiler, but can be applied to vertical water tube, semi-vertical water tube or to horizontal water tube boilers. The arrangement illustrated in Figs. 3 and 4 comprises semi-vertical type superheater boiler 40 having a front bank of generating tubes 42 and a rear bank 44 connected to parallel drums in the usual manner. The elements for superheating the steam generated in banks 42 and 44 are placed behind the front bank 42 as illustrated.

The boiler 40 is divided into two gas paths by two baflles 46, 46 which are spaced approximately at equal distances from the two side walls of the boiler and extend perpendicular to the axes of the boiler drums from points near the front edge of the front tube bank 42 entirely thru the boiler to the rear wall and the. uptakes. As shown, the baffles 46 are spaced apart from each other so that approximately one-half the generating surface lies in the space between the baffles and one-half in the space outside them. With the baffle arrangement illustrated and just described, the baliles 46 divide the boiler into a central gas path 48 and a divided path having two passages 50, 50, one along each side wall 52 of the boiler, the passages 50 being operated as a unit to form the second gas path thru the boiler. The uptake 54 is provided for the central path 48 and two uptakes 56, 56 are provided one for each of the passages 50, uptakes 54 and 56 being united in the usual manner with a chimney, not shown. A damper 58 is provided in the central uptake 54 and connected dampers 60, 60 are provided one in each of the uptakes 56. The dampers 60 are so connected that they close and open the uptakes 56 simultaneously in order that the passages 50 and uptakes 56 may in effect form a single gas path. The damper 58 being operable independently of the dampers 60, the fiow of gases thru the path 48 and the path composed of passages 50, 50 can be varied as desired by the boiler operator. As shown, the superheating surface is unequally divided between the gas path 48 and the path formed by the passages 50. As illustrated, approximately 70% of the superheating surface is allotted to the group of units 62 in path 48 and the remaining 30% of the superheating surface is allotted to the group of superheater units 64, 64 in the passages 50 taken together. The superheater boiler illustrated in Figs. 3 and 4 therefore operates in the same manner as that illustrated in Fig. 1. In Figs. 3 and 4, the units of the superheater are shown arranged in parallel. The parallel arrangement of the superheater elements is a more convenient one for the type of boiler illustrated in Figs. 3 and 4, but it is not at all essential and the units 62 may be arranged in series with units 64 whenever desired. A suitable header arrangement for this purpose is that illustrated in Fig. 5. As shown in Fig. 5, the steam from the steam space of boiler 40 enters the header 70 at both ends. The header 70, however, has partitions 72, '72 therein at points removed from its ends cutting off a central portion from the end portions so that the steam flows from the end portions of the header '70 thru units 64 into a header '74. In header '74, the steam runs toward the center portion of the header and out thru elements 62 back into the central portion of header 70. Steam is discharged from header '70 at 76.

It will be seen from the foregoing and from Figs. 2 and 211 that a boiler in accordance with my invention may be operated in accordance with a method of which the following is an illustrative example:

Assuming a boiler designed for the saturation temperature of 450 deg. F. and a calculated full load of 350,000# of steam per hour and having the proportions of the boiler described above in detail, at a steam rate of 350,000 lbs. per hour and with equal gas flow through the two gas paths, the total superheat will be 400 F. At a steam rate of 100,000# per hour and with equal gas flow thru the two gas paths the total superheat will be only 325 deg. F. Of this total, the group of units of the superheater having the large superheating surface will contribute 227 deg. F. If, however, we pass 70% of the gas over the heating surface of the group having 70% of the heating surface, the superheat obtained from the large group will increase to 340 deg. F. and that obtained from the smaller group will decrease to 60 deg. F. The sum of the superheats will then be 400 deg. F., the same as that obtained with equal gas flow in the two gas paths at the calculated full load of 350,000# steam'per hour instead of 325 deg. F. It will be seen therefore, that in accordance with the method of my invention, the temperature of the steam may be maintained substantially constant over a wide range of load and at the highest temperature which it is desirable to use in the superheater and/or prime mover without danger of overrunning the desired maximum steam temperature.

While it is obviously desirable that the draft thru the boiler be unimpeded by the dampers at the point of the maximum load, it may be that it is impractical to obtain the desired division of gas flow thru the boiler at maximum load without adjusting the dampers to some extent. However, it is preferable, when practicable, to so arrange the heating surfaces in the boiler,

" faces.

that the dampers be wide :openat the maximum expected load on the boiler. if it is found that gas flow in the parallel :gas paths .of :aiboiler is correct at the maximum expected :load, the damper in the gas path having :thegrea'ter superheating surface therein may be omitted.

In the two boilers described hereinabove, it is assumed that the two gas paths of the boiler have equal resistances so that the normal -dis tribution of gases between the paths of a given boiler at full load would be an equal on'e. However, if the paths of a given boiler have different cross-sectional areas, the -rate "of flow -:of gases at calculated full load should preferably be in proportion to the cross-sectional areas of the gas paths. It will be understood therefore that where .the following claims refer to equal rates of how, equal rates per square ioot of area of cross-section of the stream of gas is meant. However, I-do notlimit mystelfto equal rates of how in all cases.

While I have shown in Figs. 1 to 5 and described above heater installations, for example steam 'superheaters, heated solely by'convection, I do not exclude from my invention installations having certain portions heated by radiation, it being essential to my invention only that there be a convectionheated portion in each gas path thru the installation, and means whereby the proportionate amount ofgas flowing over one such convection heated portion may be varied as-compared to that flowingover another.

Also in the-arrangement illustrated in Figs. 1 to '5 inclusive, the walls-of the furnaces are not water cooled. However, this feature is becoming increasing-1y popular in steam plants and has the effect of increasing the heat absorbed "from the furnace gases prior to their contact with convection heated superheater elements, thereby increasing the variation in final temperature with variation in load at the outlet of a superheater boiler having a-given number of rows of generating tubes in front of the superheater and thereby'correspondingl-y increasing the need for regulation of the final temperature such as that 'provided by my invention.

In the apparatus illustrated in i ignfigthe boiler is shown as having two 'steam and "water drums 82 and 84 and a water ormud drum 86 an arranged and connected 'by generating and circulating tubes in the usual manner for Stirling type boilers. Boiler 80 has a large furnace 88, the lower portion of which is provided with water wall tubes 90, 90 along one or more of its wall Water "for tubes 90 maybe takenfromthe drum 84 through a downcomer '92 and delivered by such downcomer to a lower header -94 connected to one end of each of tubes 90. The upper ends of tubes 90 are connected into upper header 96 from which steam and "water is delivered to the drum 82 through a riser 98. The presence of waterwall tubes 90 in furnace 88, by lowering the temperature of the gases reaching ordinary generating surfaces makes it preferable to employ some radiant type superheater surface.

Two of the wall faces of the furnace 88 are shown as having radiant type superheater elements thereon. One of a set of such elements is indicated at 100 along the rear wall of the furnace 88 and one of another set of such elements is shown at 102 along the front wall of "the fur nace 88. In the arrangement shown, steam for elements 100 and 102 is taken from the drum 84 through connectors 104, and delivered thereby to two headers 106, 108. The lower 'ends of elements "100 connect into header 106 and steam flowing through elements 100 is delivered there- .by team upper header 108 from which it is transported by a :connecting conduit 110 to a header 1-12 forming the front face of the boiler. Steam delivered by connectors 104 to the header 108 :pases upwardly through the elements 102 and directly into the header 112. From header 112 the superheated steam passes by connectors 114 to the header 116. From header 116 steam flows through a group of convection type units 118 to an intermediate header 120. From header 120 the .steamifiows through a second group of convection :type units 122 to an outlet header 124.

The gases leaving the furnace 88 pass first through a :front tube bank 126. .After passing bank 126 the gases may flow through either one of two paths, 128 and 129 respectively. One side :of ,path 128 is defined by a bafile 130 which .runs upwardly from the mud drum 86 along the rear side of ;bank 126. The other side of the path 128 is defined by an L-shaped baths 132 which runs parallel to the :baflie 13.0 for some distance beginning at a point slightly above the level-of the upper end of baffle 130. At a point 134 :some distance above the drum 86 baflle 132 turns at substantially right angles and runs at an upward slope till it joins the rear wall 136 of the boiler. The path 129 lies above the bafile 132 between such baflie and the roof. connects with an outlet 'flue 138 for carrying off the-gases of combustion throughaport 140 in the wall 136'justbelow the bafiie 132. Path 129 connects with flue 138 through a port 142 in the wall 136 just above the bafiie 132. Ports 1'10 and :142 are :controlled by independently operable dampers 144 and 146 respectively.

Now superheater units 118 lie in path 128 and superheater units 122 lie in path 129 so that, by changing the position of dampers 144 and 146 the relative amount of combustion gases passing over the units 118 :and 122 canbe regulated. As appears in the drawings, :units 122 have a greater amount of surface than units 118 so that, by throwing :more of the gases through path 129, the final :steam temperature may be raised above what it would otherwise be at a given load on the boilerand also .so that the steam temperature maybe kept up :to a desired maximum when the load on the boiler .is below agiven predetermined point. 0n the other hand, by throwing more gases through the path 128, the final steam temperature will be kept down to the desired maxi mum when the load on the boiler is above a given ecalculated point.

Aneconomizer 150 is shown in flue 138 whereby the final temperature :of the escaping gases may be reduced to give a high overall operating efiiciency even though one of the paths 128 or 129 does not have suificient heat absorbing surface therein :to .cool the gases to the temperature at which they are ordinarily discharged.

In the curves or graphs shown in Figs. .2 and 12a of the drawings, it is assumed that the final temperature of the steam at times of low load .61

will not rise above that at maximum load. However, :some :prime movers are so constructed that they can utilize to advantage steam of higher temperature under 310W load conditions than at high load conditions. stallations to increase the temperature at the outlet of the superheater at periods of low loads as compared to that at maximum load. The apparatus in accordance with my invention can be operated 'to give this effect when desired by Path 128 It is desirable in such ini directing a large enough proportion of the heating gases thru the gas path having the greater proportion of heater surface therein. The heat losses in the steam line between the superheater and the prime mover also make it desirable at times to raise the temperature of the steam at the superheater outlet somewhat at low loads as compared to that at high loads. This is because the radiation loss from a steam line is substantially constant irrespective of the load and is sometimes sufficient to reduce the temperature of the steam at the prime mover at times of low load compared to such temperature at high load. Certain of my claims therefore are not limited to producing the maximum temperature of the fluid being heated at times of maximum gas flow.

Under normal conditions it is expected that my invention will be used primarily to increase the steam temperature under partial load conditions above what it would otherwise be. Circumstances often arise, however, in steam plant practice which raise the final steam temperature above the normal at a given load. One such circumstance, for example, is the cutting out of a feedwater heater. Cutting out an air heater has a similar effect. This is due to the fact that, when such economizer or air heater is cut out, more fuel must be burned to produce a given amount of steam. The quantity of the gas striking the convection superheater at a given load is thereby increased with a consequent increase in the final steam temperature. By controlling the dampers in the gas paths to increase the relative proportion of the gases flowing thru a path having a minor portion of the heater surface therein, my invention may be used to keep down the steam temperature under such abnormal conditions.

Another application of my invention may be made in installations operating at times at loads so high that the maximum intended steam temperature will be exceeded if the gas flow is equal in the different gas paths at such loads. In such cases, my invention is applied so as to limit the final steam temperature by using the independent dampers, or equivalent means, in the different gas paths to throw a greater portion of the gas thru the gas path having the minor portion of the heater surface therein. It will be seen that the apparatus shown in Fig. 2 has the groups of units in the different gas paths connected for flow of steam therethru in series, while the apparatus shown in Figs. 3 and 4 has groups of units connected in parallel. It will be understood further that I consider it within my invention to connect the units in one gas path in series with a portion of the units in another gas path.

It will be evident that my invention is not limited to superheating steam, but may be utilized in maintaining substantially constant temperature of a fiuid being heated at the outlet of any heating apparatus. Feed water heating is another place in the arts where my invention is plainly useful. 1

What I claim is:

l. The method of maintaining substantially constant outlet temperatures from fluid heaters having parallel gas paths and groups of 'materially unequal heating surfaces in the different paths comprising controlling the heating gases so that the heating gases flow at substantially equal rates thru the paths when the flow of fluid being heated is at a point near the maximum to produce at the same time the maximum temperature in such fluid, and increasing the relative flow of gases thru the gas path of the heater having the greater surface therein as the fluid flow decreases to substantially prevent a decrease in the fluid temperature.

2. The combination in a superheater boiler having two gas paths arranged for parallel flow of combustion gases of two sets of superheater elements, one set in each of said paths arranged to be contracted-by combustion gases of substantially the same temperature at the points of initial contact with said sets and having some superheating surface in each gas path, but materially greater superheating surface in one gas path than in the other, and means whereby the flow of gases thru the one of said paths having the lesser amount of superheating surface therein may be restricted so as to increase the flow thru the other. a

3. The boiler as set forth in claim 2 and in which the steam generating and the superheating surfaces are so proportioned and arranged that the desired maximum steam temperature occurs nearly at the maximum expected load on the boiler when the gas paths have equal rates of gas flow therethru.

4. A superheater boiler having two gas paths arranged for parallel flow of combustion gases and each having superheater elements therein substantially screened from radiation and arrangedto be contacted by combustion gases, the set of elements of one path having substantially 70% of the total of-heating surface but making initial contact with gases of substantially the same temperature as that of the gases initially contacting with the smaller set of elements and the steam generating surface and the superheating surface being so proportioned and arranged that the desired maximum steam temperature occurs at near the maximum expected load on the boiler when the gas paths have equal rates of gas flow therethru, and means whereby the flow of-gases through the one of said paths having the smaller amount of superheater surface therein may be restricted relatively tothe other.

5. The boiler as set forth in claim 4 and in which the superheating surface in one gas path is in series with that in the other path.

6. A superheater boiler having two gas paths arrangedfor parallel flow of combustion gases and having superheater elements substantially screened from radiation but arranged to be contacted by combustion gases and having some superheating surface in each gas path, but materially greatersuperheating surface in one gas path, than in the other, and means whereby the flow of gases through the one of said paths having the lesser amount of superheating surface therein may be restricted so as to increase the flow through the other the gas path having the greater amount of superheating surface having the less steam generating surface.

7. The method of operating a fluid heater having two parallel gas paths and groups of materially unequal convection type heating surfaces in said paths, the gas paths and heating surfaces having an arrangement such that the group of heating surfaces having the greater area adds a greater amount of heat to the fluid being heated than the other of said groups when the gas flow inthe two gas paths is equal in volume comprising passing all the heating gases and in equal amounts through said paths to produce a desired substantially maximum temperature at a high load on the heater and decreasing the proportion of gas in the one of said paths having the greater heating surface with increases in load on the heater to prevent said temperature from rising at loads higher than said high load and increasing the proportion of gas in the path having the greater heating surface with decreases in load to prevent it from falling at loads lower than said high load.

8. The method of operating a superheater boiler having two gas paths therethrough and superheater and generating surface in each of said paths, but having a materially greater portion of the total superheater surface in one of said paths than in the other, the generating and superheating surfaces having an arrangement such that the superheater portion having the greater surface adds a greater amount of heat to the steam than the other portion when the gas flow in the two paths is equal in volume, which comprises passing all the heating gases through said paths, but a greater portion of heating gases through the one of said paths having the greater amount of superheater surface therein at relatively low loads to maintain the temperature of steam delivered by said superheater as high as desired at such low loads and increasing the proportion of gases passing through the one of said paths having the smaller proportion of superheating surface therein at high loads to prevent the steam temperatures rising beyond the maximum desired at such high loads.

9. The method of maintaining substantially constant outlet temperatures from a fluid heater having parallel gas paths and materially unequal groups of heating surface in the different paths, the gas paths and heating surfaces having an arrangement such that the group of heating surfaces having the greater area adds a greater amount of heat to the fluid being heated than the other of said groups when the gas flow in the two paths is equal in volume comprising controlling the heating gases so that the heating gases flow at substantially equal rates through the paths when the fluid being heated is near the maximum to produce at the same time the maximum temperature in such fluid and increasing the relative flow of gases through the path of the heater having the greater heating surface therein as the fluid flow decreases to substantially prevent a decrease in the fluid temperature.

10. The method of maintaining substantially constant outlet temperatures from a superheater boiler having parallel gas paths containing nearly equal amounts of generating surface and having materially unequal amounts of superheating surface in the gas paths, the gas paths and heating surfaces having an arrangement such that the group of heating surfaces having the greater area adds a greater amount of heat to the fluid being heated than the other of said groups when the gas flow in the two gas paths is equal in volume comprising controlling the furnace gases so that they flow at substantially equal rates through said paths when the steam flow is near the maximum to produce at the same time nearly the maximum final steam temperature and increasing the relative flow of gases in the one of said paths having the greater superheating surface therein as the steam flow decreases to substantially prevent a decrease in steam temperature.

11. The method of maintaining substantially constant outlet temperature from a superheater boiler having parallel gas paths adapted for substantially equal volumes of gas flow at normal full load on the boiler and having materially unequal amounts of superheating surface in such paths, the gas paths and heating surfaces having an arrangement such that the group of heating surfaces having the greater area adds a greater amount of heat to the fluid being heated than the other of said groups when the gas flow in the two gas paths is equal in volume comprising controlling the furnace gases so that they flow at substantially equal rates through said paths when the steam flow is at normal full load to produce at the same time nearly the maximum final steam temperature, and increasing the relative flow of gases in the one of said paths having the greater superheating surface therein as the steam flow decreases to prevent a decrease in steam temperature.

12. The combination in a superheater boiler having two gas paths arranged for parallel flow of combustion gases and to receive jointly the entire flow of gases for heating the boiler of two unequal sets of superheater units, one set in each of said paths and arranged to be contacted by furnace gases, said generating surface being so arranged with respect to said sets of units that the larger set of units adds a greater amount of heat to the steam when the flow in the two gas paths is substantially equal said paths having nearly equal amounts of generating surface therein, and means whereby the flow of gases through the one of said paths having the lesser amount of superheating surface therein may be restricted so as to increase the flow through the other.

CHARLES W. GORDON.

CERTIFICATE OF CORRECTION.

Patent No. 1,959,100. May i5, 1934.

CHARLES W. GORDON.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, line 85, claim 2, for "contracted" read contacted; page 5, line 42, claim 9, before "paths" insert gas; and lines 120 to 124, claim 12, strike out the words "said generating surface being so arranged with respect to said sets of units that the larger set of units adds a greater amount of heat to the steam when the flow in the two gas paths is substantially equal" and insert the same after therein," in line 126, of same claim; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 24th day of July, A. D. 1934.

Bryan M. Battey (Seal) Acting Commissioner of Patents.

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