US3117560A

US3117560A - Steam generating unit

Info

Publication number: US3117560A
Application number: US166984A
Authority: US
Inventors: Max H Kuhner
Original assignee: Riley Power Inc
Current assignee: Riley Power Inc
Priority date: 1962-01-10
Filing date: 1962-01-10
Publication date: 1964-01-14
Anticipated expiration: 1981-01-14

Description

Jan. 14, 1964 M. H. KUHNER 3,117,560

STEAM GENERATING UNIT Filed Jan. 10, 1962 2 Sheets-Sheet 1 INVENTOR. max H. Kuhner H 'rney Jan. 14, 1964 M. H. KUHNER 3,117,560

STEAM GENERATING UNIT Filed Jan. 10, 1962 2 Sheets-Sheet 2 JNV ENTOR.

max H. Kuhnev WWW ii ior% ey United States Patent Q STEAM GENERATING UNIT Max H. Kuhner, Oahham, Mass., assiguor to Riley Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Filed Jan. 10, 1962, Ser. No. 166,984 2 Claims. (Cl. 122478) This invention relates generally to a steam generating unit and more particularly to apparatus arranged to produce steam by burning fuel in a combustion chamber and bringing the resultant gases into heat exchange relationship with fluidand vapor-containing tubes. This is a continuation-in-part of patent application Serial Number 781,662, filed December 19, 1958, now abandoned.

It is customary in the art of steam generation to design each individual unit on a custom basis; that is to say, since every particular installation involves factors such as capacity, pressure, temperature, fuel and the like which differ from every other unit previously produced by a given manufacturer, it is necessary to design a unit which is particularly adapted to the circumstances of that unit. The design and construction of steam generating units in this manner is very expensive because of the fact that each step of the design and manufacturing operation is unique; in the manufacturing process, for instance, it is impossible to make use of standard units in the manner common in other industries to reduce the unit cost. These and other difficulties experienced with the prior art devices of this type have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the present invention to provide a steam generating unit of such a design that, irrespective of the particular fuel used, the capacity of the unit may be increased in the design stage merely by increasing the width by a proportionate amount.

It is another object of this invention to provide a steam generating unit having unusual superheat and reheat temperature control characteristics and in which the efficiency produce a substantially flat superheat-load characteristic curve without danger of tube fouling and slagging.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however,

of but a few of the various ways in which the principles of the invention may be employed.

In said annexed drawings:

FIG. 1 is a vertical sectional view of a steam generating unit embodying the principles of the present invention, and

FIG. 2 is a vertical sectional View of a steam-and-Water drum associated with the unit shown in FIG. 1.

Referring first to FIG. 1, wherein are best shown the general features of the invention, the steam generating unit, indicated generally by the reference numeral 11 is shown as comprising a furnace 11 and a boiler 12, the furnace producing in the usual manner hot products of combustion which pass in heat exchange relationship to the boiler. The furnace 11 is provided with a front wall 13, a rear wall 14, and side walls 15, defining a combustion chamber 16. A bottom 17 is formed at the lower portion of the furnace underlying the combustion chamher 16 and is of the water-cooled type consisting of a horizontal bank of water-filled tubes covered with a high temperature refractory material. A slag opening 18 is formed in the central portion of the bottom 17 and the edge of the opening is provided with a slag darn 19 of the usual type. A short distance above the bottom 17 the front and

rear walls

13 and 14 are provided with inwardly-diercted arches or

abutments

21 and 22, respectively. Lying between them is a restricted passage .23. The

abutments

21 and 22 and the bottom 17 serve to define a restricted high-temperature chamber 24. Mounted on the lower sides of the

abutments

21 and 22 are directional-flame inter-tube

burners

25 and 26 which are of the type shown and described in thepatentof Craig, No. 2,759,460.

Wind boxes

27 and 28 extend around the outer portions of the

burners

25 and 26, respectively, and the wind boxes are connected toa duct 2? surrounding the furnace just above the level of the

abutments

21 and 22. Solid fuel enters the system from a bunker 31 and passes through a feeder 3:2 to a ball mill pulverizer 33; puverized coal then passes through ducts 34 and 35 to the

burners

25 and 26, respectively. It will be understood, of course, that, although pulverized coal is shown as being the fuel in the preferred embodiment, the principles of the invention are as readily applicable to the burning of gas, oil or other similar fuels.

At the upper part of the combustion chamber 16 the front Walls 14 are provided with arches or

abutments

36 and 37 respectively, which define a restricted passage 38 lying therebetween. It will be understood that the

abutments

21, 22, 36 and 37 are formed by bends in tubes which cover the surfaces of the

walls

13 and 14, as well as the side Walls 15. Some distance above the

abutments

36 and 37 the furnace is provided with a roof 39. The roof, the

walls

13, 14 and 15 and the

abutments

36 and 37 define a superheater pass 41 having an outlet 42 at its upper end in the wall 13. A duct 43 extends from the outlet 42 to a regenerative air heater 44. The section of the duct between the outlet and the air heater is provided with a venturi 45 for the measurement of gas flow and with a hopper 46 located at the outer side of a bend in the duct, which hopper is adapted to receive dust and cinders. The other side of the air heater is connected to a stack 37 of the usual type. Incoming air is supplied to the duct 29 by means of a fan 48 whose outlet is connected to the air heater 44 and the fan is connected, in turn, to a duct 49 leading to the air duct 29 carrying air to the

burners

25 and 26.

The boiler 12 is provided with a steam-and-water drum 51 which is connected bydowncomer tubes 52-to

headers

53 and 54 underlying the floor 17 of the furnace. Tubes extend from the

headers

52 and 54 upwardly above the surfaces of the furnace, forming so-called water walls,

and, as has been stated, are bent outwardly to define the

abutments

21, 22, 36 and 37. A large number of the tubes lying along the front wall 13 leave the water wall at the innermost point of the abutment 36 and extend vertically upwardly to form a supporting wall 55; in the same way, some of the tubes lining the rear wall "14 leave the abutment 37 at its innermost position and extend vertically upwardly to form a supporting tube wall 56; the tubes in the

walls

55 and 56 are sufficiently widely spaced to permit flow of gas therethrough. The tube wall 35 and the front wall 13 define a front pass 57 and a similar rear pass 58 is defined by the tube wall 56 and the rear wall 13 of the furnace, while the remaining area between the tube wall 55 and the tube wall 56 is a central pass 56. The tubes lining the rear wall 14 of the furnace, including the tubes in the tube wall 56, join the steam-and-water drum at its rear portion, while the tubes lining the front wall 13, including those which form the tube wall 55, join the steam-andwater drum 51 at its forward portion. The tubes lining the side wall 15 also are joined to the steam-and-water drum at its front portion.

The upper part of the steam-and-Water drum 51 is connected to a small steam header 61 which, in turn, is connected to the lower ends of sets of superheater platens 62 and 63, associated with the front wall 13 and the rear wall 14, respectively. Each of the platens 62 consists of a number of tubes in substantially tangential relationship originating at their lower ends in a short vertical header 64 and terminating at their upper ends in a horizontal outlet header 65 which resides within the abutment 36. Similarly, each of the platens 63 associated with the rear wall 14 originates in a short vertical header 66 located outside the rear wall 14 some distance above the abutment 22 and terminates in a short horizontal outlet header 67 located within the abutment 37. It will be understood that there are a substantial number of platens 62 associated with the front wall 13 and a similar number of platens 63 associated with the rear wall 15, these being evenly spaced across the width of the combustion chamber 16. It should be noted that the innermost edges of the platens 62 and 63 do not extend further into the combustion chamber than the

abutments

21, 22, 36 and 37 and, thus, in a sense, they reside within pockets formed at the front and rear of the furnace. The

outlet headers

65 and 67 associated with the platens 62 and 63 are joined together and to the in-put side of a spray-type desuperheater 68, the outlet of which is connected to the lower end of a secondary superheater section 69 which resides partly in the center pass 59 and partly in the front pass 57, the upper end being connected to a superheated steam header 71 which, in turn, is connected to the high-pressure section of a steam turbine, not shown. A return line 72 from the turbine is connected to the upper end of a primary reheater section 73 located partly in the center pass 59 and partly in the rear pass 58. The lower or output end of the reheater section 73 is connected to the lower end of a secondary reheater section 74 which is located in the rear pass 58 only. The upper end of the reheater section 74 is connected to a reheated steam header 75 which, in turn, is connected to the low-pressure section of the steam turbine.

Referring to FIG. 2 which shows the details of the steam-and-water drum 51, it can be seen that the downcomer tubes 52 are connected into the drum, as are the steaming tubes 76 originating in the rear wall 14, and the steaming tubes 77 originating in the front wall 13 and the side walls 15. The drawings also show the manner in which the tubes 78 leave the drum to connect to the header 61. It will be understood that the elongated drum is at least as long as the furnace is wide. It will also be understood that the

tubes

76 and 77 and 78 are located in the portions of the drum between the ends. A bafiie plate 79 extends lengthwise f the drum in the lower portion thereof and forms a completely sealed receptacle which is open upwardly and is connected to the downcomer tubes by means of fittings 81. On the side of the drum adjacent the tubes 77 the bafile plate 79 is formed to provide a vertical portion at the upper edge of which is mounted a bracket 82 supporting the lower end of a series of bafile plates 83 which are suitably fastened to the drum at the upper end; a similar bracket 84 extending from the opposite upper edge of the bafl'le plate 79 supports the lower end of similar bathe plates 85 adjacent the opening of the tubes 76 into the drum. Running centrally down the middle of the drum is a feed water pipe 86 which is connected to the input leg of U-shaped

condenser members

87 and 88 located immediately inwardly of the bafile plates 83 and 85, respectively. The

condenser elements

87 and 88 are of the type shown in the patent to Andrews No. 2,424,212, issued July 22, 1947. The other leg of the condenser 87 is provided with a downwardly-turned 4 fitting 89 and the condenser $3 is provided with a similar fitting 91, the lower ends of the fittings residing well within the trough formed by the baflie plate 79. The condensers are, of course, covered with fins to promote heat exchange between the steam passing thereover and the feed water running on the inside of the tubes.

Underlying the entrance to the tubes 78 in the upper central portion of the drum is a trough 92 suitably supported and having fastened to its upper lateral edges

drier cartons

93 and 94 whose upper edges are suitably fastened and sealed against the surface of the drum on the opposite sides of the entrances to the tubes 78. From the bottom of the trough 92 extend

drain pipes

95 and 96 on opposite sides of the feed water pipe 86, the ends of the drain pipes residing well within the down-comer tubes 52 and being slightly flared to increase the ejector action of the fluid flowing down the down-comer tube to create a withdrawal of fiuid from the

pipes

95 and 96 and the trough 92.

The operation of the apparatus will now be readily understood in view of the above description. Fuel enters the furnace in the usual manner, after suitable pulverization, through the

burners

25 and 26 and is mixed with the air originating in the

windboxes

27 and 28. Combustion takes place in the high-temperature chamber 24 underlying the

abutments

21 and 22 and the hot products of combustion pass upwardly through the furance. The combustion gas how is distributed between the front pass 57, the rear pass 58, and the central pass 59 by means of

dampers

97, 98 and 99 residing in the outlet 42 of the superheater pass 41. A suitable bafile 101 serves further to separate the pass 57 from the remainder of the upper part of the furnace. The gas passes through the duct 43, through the venturi 45 where the amount of flow is measured, and through the air heater 44 to the stack 47. In the hopper 46 a certain amount of the unburned particles are deposited, and in the air heater 44 the gas, of course, comes into heat exchange relationship with the incoming air which originates in the fan 48 passing through a duct 49 to the burners. Feed water entering through the feed water pipe 36 passes through the

condensers

87 and 88 and is introduced into the trough formed by the baffle plate 79; it then flows downwardly through the downcomer tubes 52 to the

headers

53 and 54. The water is distributed by these headers into the water-wall tubes lining the

walls

13, 14, and 15 of the furnace and they flow upwardly in these walls. At some point during the upward journey through the tubes, the water is converted to steam; the steam eventually leaves the

tubes

76 and 77 and enters the steam-and-water drum. The steam originating in the tubes 77 passes over the bafiie plates 83, thus removing the larger particles of water. The steam then passes through the condenser 87 in which a certain amount of steam is condensed, thus wetting the surface of the condenser and providing the steam with a purifying action. The steam then passes over the upper lip of the trough 92, through the drier carton 93 and out of the drum through the tube 78 to the header 61; the same action takes place in the steam emerging from the tube 76. This steam passes through the baffle plates 85, over the condenser 88, and through the drier carton 94 before entering the tubes 98. The steam which arrives at the header 61 eventually passes downwardly to the header 66 and into the tubes forming the platens 62 and 63. While the steam is in the platens it receives heat mainly by radiation from the gases passing upwardly through the combustion chamber 16. A certain amount of convection heat exchange takes place, of course, but because of the fact that platens do not extend out beyond the abutments, the heat received is to a great extent that of radiation. In any case, all steam passing through the platens 62 and 63 eventually passes through the desuperheater 68 where the temperature is reduced by a water spray in accordance with a measurement of final steam temperature aided by controls which do not form a part of this invention and, therefore, are not shown. The superheated steam leaves the desuperheater 68, enters the lower end of the secondary superheater 69, and passes through the sinuous coils thereof to emerge into the superheated steam header 71 on its way to the turbine. After passing through the turbine and having a considerable portion of its thermal energy converted into mechanical power, the steam returns in the line 72 and passes downwardly to the primary reheater 73, eventually passing into the secondary reheater 74 in which the flow is in the same direction as gas flow. It will be noted that the heat exchange relationship between the gas and the two reheater sections is conductive. Manipulation of the

dampers

97, 98 and 99 proportions the gas in its flow through the passes 57, 5S and 59.

It should be noted that an econornizer section 103 extends across the top of passes 57, 58 and 59 While an economizer section 102 lies in the front pass 57 only. The feed water passes through the economizer section N2 in the same direction as the gas fiow while it passes through the economizer section 103 in counter-flow, the upper end of the section 162 being connected to the feed water pipe 86 while the upper end of the economizer section 103 is connected to the feed water pump in the usual manner.

Because the inter-tube, directional-flame burners of the furnace are all located at one elevation in two opposed walls of the furnace and because the types of fuel to be burned require no change in burner location, it is possible to adapt as standard an ideal furnace configuration. The dimensions of the two opposed burner walls and the height of the furnace may, thus, remain the same for all capacities for which this design is used. Only the distance between the side walls and the furnace width need be changed to adopt the design for larger or smaller steam generating capacity. The changein furnace width is proportional to the number of burners required for the quantity of fuel to be burned.

Because combustion is completed in this furnace substantially within the high temperature chamber 24, the use of radiant superheater platens is practical and safe. When radiant steam-superheating surfaces are used along the walls of the conventional front-fired or tangentiallyfired furnaces, flame control is very critical; in these cases flame impingement on steam heating surfaces must be avoided top revent damage of the radiant tubes. The present invention permits the use of radiant superheater platens placed over the upper section of the burner walls. It would be the usual practice to place the radiant superheater platens on 24" to 30" centers. They are not subject to direct flame impingement but receive radiant heat from the high temperature chamber of the furnace. They also receive a certain amount of convection heat from the combustion gas passing vertically upwardly from the furnace and, thus, flowing parallel with the vertical superheater tube platens. The heating surface of the radiant superheater platens can be so proportioned to the convection superheater surface that an almost constant final temperature can be produced over a very wide range of steam load. The drooping effect of heat absorption by radiation with increasing steam flow is ideally balanced with the rising characteristic of convection heat absorption in the convection superheater. The spray-type desuperheater placed between the radiant and the convection sections of the superheater need be of relatively small capacity to maintain the specified final steam temperature over a wide range of load. Note that the saturated steam enters the low end of the radiant superheater platens where combustion gas temperature is highest and where cooling of the platen tubes is most important. Note also that the entire superheater system is completely drainable. This permits rapid start-up of the boiler because time need not be wasted in evaporating the condensate from the usual hanging superheater loops to open the superheated tubes to steam passage.

The reheater is of the convection type and is also fully drainable. Reheat steam temperature is controlled by the use of gas flow proportioning dampers located beyond the econ om-izer where the average flue gas temperature is below 800 F. Combustion gas flow is divided so that the quantity required to produce the specified final reheat temperature must pass over the reheat surface while the rest of the gas flows over the economizer surface. Sub stantially all of the combustion gas passes over the convection superheater regardless of the position of the gas proportioning dampers. While the boiler is being brought up to pressure and until steam flow through the re'heater is established, the rehcater gas pms is completely closed so that the reheater surface is well protected against excessive temperatures until the turbine is in operation and reheat steam flow is established. This feature again permits rapid build-up of pressure because the firing rate need not be gradually raised for the protection of the uncooled reheater surface.

By placing the superheater and economizer surfaces above the furnace, the stack effect of the vertically rising combustion gas assists in overcoming friction loss so that the draft loss through the boiler is lower than with the conventional front-fired design where convection surfaces are placed in a second down-pass. The overall height of the structure is, however, not much greater than for the Well-known front-fired arrangement. Liberal height is desirable for high pressure natural circulation boilers to insure good-circulation by having high columns of solid water in the large feeder pipes supplying the water to the steaming section of the furnace. Withfurnace designs of the type shown, heat is released within the lowest section of the furnace; circulation in the furnace wall tubes is, thus, much more secure than with horizontally-fired furnaces where the burners are placed a considerable distance above the furnace fioor.

The present invention inconpor-ates the feature of having the steam-carrying tubes entering the steam release drum on both side of the vertical center line. The rate of steam release per linear foot of drum length may thus be almost double thatof the earlier designs in which steam carrying tubes enter-the drum over only one side, usually the front half of the drum shell. The compact design shown permits hanging or suspension of the entire boiler unit on comparatively simple structural steel framing. The standardized cross-sectional elevation of the boiler should resolve in savings of manufacturing cost and engineering.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in the following claims or the equivalent of such be employed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1. A steam generating unit, comprising (a') a vertically-elongated furnace,

(b) a coiler having a steam-and-water drum containing two sets of steam-cleaning apparatus one on either side of the vertical centerline of the drum,

(0) steam purifier apparatus in the drum,

(0.) water-walls defining a combustion chamber,

(e) a slag basin at the lower portion of the combustion chamber havin a centrally-located tap hole,

(f) two of the water-walls being in opposed relation and being vertical throughout most of their heights,

(g) a lower abutment extending from each of the said two opposed water-walls a short distance above the slag basin, each abutment extending horizontally completely across the width of its water-wall, the abutments extending toward one another on the same level to define a restricted passage therebetween,

(12) directional-lame inter-tube burners mounted on the undersides of the abutments and directed toward the slag basin, the abutments defining with the slag basin a high-temperature cell in which combustion is substantially completed during operation, the upper abutments extending from each of the said two water-walls at the upper end of the combustion chamber, the upper abntrnents defining therebetween a restricted furnace outlet passage,

(i) a convection pass extending upwardly from the said furnace outlet passage, the steam-and-water drum being located above the superheater pass,

(j) superheater platens constituting primary superheate-r sections extending inwardly from the said opposed water-walls and extending vertically for a substantial portion of the distance from the lower to the upper abutment of a given Water-wall,

(k) a substantial number of water-wall tubes leaving each upper abutment and extending upwardly through the convection pass to define it into a front portion, a rear portion, and a central portion,

(1) a secondary superheater section extending across the lower part .of the front and central portions and arranged to carry steam therethrough in the direc tion of gas flow,

(m) a primary reheater section located in the upper parts of the rear and central portions for fiow of steam therethrough in counter-fiow,

(u) a secondary reheater section located in the lower part of the rear portion for flow of steam therethrough in the direction of gas flow,

(0) an economizer having a high-temperature section located in the upper part of the front pass for how of feed water in the direction of gas flow and having a low-temperature section extending across the uppermost part of the front, central and rear portions for flow of feed water in counterflow,

(p) and dampers located in the upper part of the said portions to control the flow of gas therethrough, the tubes originating in one of the said opposed Waterwalls terminating at one side of the said drum to supply steam to one set of steam-cleaning apparatus and the tubes tt'rom the other of said opposed waterwalls terminating at the other side of the drum to supply steam to the other set of steam-cleaning apparatus.

2. A steam generating unit, comprising (a) a vertically-elongated furnace,

(b) a boiler having a steam-and-water drum containing two sets of steam-cleaning apparatus one on either side of the vertical centerline of the drum,

(0) steam purifier apparatus in the drum,

(d) water-walls defining a combustion chamber,

(e) a slag basin at the lower portion of the combustion chamber having a centrally-located tap hole,

(7) two of the water-walls being in opposed relation and being vertical throughout most of their heights,

([1) directionahfianie inter-tube burners mounted on the undersides of the abutments and directed toward the slag basin, the abutments defining with the slag basin a high-temperature cell in which combustion is substantially completed during operation, the upper abutments extending from each of the said two Water-walls at the upper end of the combustion chamber, the upper abutments defining therebet-ween a restricted furnace outlet passage,

(1') a convection pass extending upwardly from the said furnace outlet passage, the steam-and-water drum being located above the superheater pass,

(j) a substantial number of water-wall tubes leaving each upper abutment and extending upwardly through through the convection pass to define it into a front portion, a rear portion, and a central portion,

(k) a superheater section extending across the convection pass and arranged to carry steam therethrough in the direction of gas flow,

(I) a reheater section located in the convection pass for flow of steam therethrough in counter-flow,

(m) an economizer having a section located in the convection pass for flow of feed water in the direction of gas flow,

-(n) and dampers located in the upper part of the said portions, to control the flow of gas therethrough, the tubes originating in one of the said opposed waterwalls terminating atone side of the said drum to supply steam to one set of steam-cleaning apparatus and the tubes from the other of said opposed waterwalls terminating at the other side of the drum to supply steam to the other set of steam-cleaning apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 2,628,598 Van Brunt Feb. 17, 1953 2,715,451 Raynor Aug. 16, 1955 2,815,007 Sprague et al. Dec. 3, 1957 2,821,175 Seidl Jan. 28, 1958

Claims

1. A STEAM GENERATING UNIT, COMPRISING (A) A VERTICALLY-ELONGATED FURNACE, (B) A COILER HAVING A STEAM-AND-WATER DRUM CONTAINING TWO SETS OF STEAM-CLEANING APPARATUS ONE ON EITHER SIDE OF THE VERTICAL CENTERLINE OF THE DRUM, (C) STEAM PURIFIER APPARATUS IN THE DRUM, (D) WATER-WALLS DEFINING A COMBUSTION CHAMBER, (E) A SLAG BASIN AT THE LOWER PORTION OF THE COMBUSTION CHAMBER HAVING A CENTRALLY-LOCATED TAP HOLE, (F) TWO OF THE WATER-WALLS BEING IN OPPOSED RELATION AND BEING VERTICAL THROUGHOUT MOST OF THEIR HEIGHTS, (G) A LOWER ABUTMENT EXTENDING FROM EACH OF THE SAID TWO OPPOSED WATER-WALLS A SHORT DISTANCE ABOVE THE SLAG BASIN, EACH ABUTMENT EXTENDING HORIZONTALLY COMPLETELY ACROSS THE WIDTH OF ITS WATER-WALL, THE ABUTMENTS EXTENDING TOWARD ONE ANOTHER ON THE SAME LEVEL TO DEFINE A RESTRICTED PASSAGE THEREBETWEEN, (H) DIRECTIONAL-FLAME INTER-TUBE BURNERS MOUNTED ON THE UNDERSIDES OF THE ABUTMENTS AND DIRECTED TOWARD THE SLAG BASIN, THE ABUTMENTS DEFINING WITH THE SLAG BASIN A HIGH-TEMPERATURE CELL IN WHICH COMBUSTION IS SUBSTANTIALLY COMPLETED DURING OPERATION, THE UPPER ABUTMENTS EXTENDING FROM EACH OF THE SAID TWO WATER-WALLS AT THE UPPER END OF THE COMBUSTION CHAMBER, THE UPPER ABUTMENTS DEFINING THEREBETWEEN A RESTRICTED FURNACE OUTLET PASSAGE, (I) A CONVECTION PASS EXTENDING UPWARDLY FROM THE SAID FURNACE OUTLET PASSAGE, THE STEAM-AND-WATER DRUM BEING LOCATED ABOVE THE SUPERHEATER PASS,