US3157163A

US3157163A - Steam generating unit

Info

Publication number: US3157163A
Application number: US146123A
Authority: US
Inventors: Max H Kuhner
Original assignee: Riley Power Inc
Current assignee: Riley Power Inc
Priority date: 1961-10-19
Filing date: 1961-10-19
Publication date: 1964-11-17
Anticipated expiration: 1981-11-17

Description

Nov. 17, 1964 M. H. Kul-:NER 3,157,163

STEAM GENERATING UNIT Filed Oct. 19, 1961 INVENTOR lax H. Kahne-r combustion chamber.

United States Patent Oilice 3,l57,lb3 Patented Nov. 17, 1964 3,157,163 STEAM GENERATDJG UNT Max H. Kuhner, alrham, Mass., assigner to Riley Stoner Corporation, Worcester, Mass., a corporation of Massachusetts Filed Get. 19, 1961, Ser. No. 146,123 4- Claims. (Cl. inw-235) This invention relates to a steam generating apparatus and more particularly to apparatus arranged to produce steam for the generation of electrical power or the like.

in the design of steam generating units and, particularly, of those in an intermediate range from, say, 75,90() to 260,060 lbs. per hour, one of the drawbacks encountered is that these units are quite expensive because each unit requires an individual custom design. Furthermore, in order to obtain complete combustion of the fuel before the products of combustion pass over the convection surfaces, it has been necessary to provide an extremely large ln addition, extremely large buildings have been required to maintain such boilers; in many cases the fact that v the burners are on diiterent levels means that access can be had to the .burners only by the operator climbing on catwalks or the like. These and other difficulties have been experienced by the prior art devices and have been obviated in a novel manner by the present invention.

it is, therefore, an outstanding obiect of the invention to provide a steam generating unit of the intermediate range of sizes in which the longitudinal design may remain the same for the entire range and the capacity of the unit may be increased for a speciiic application merely by making the furnace wider.

Another object of this invention is the provision of a compact steam generating unit which is inexpensive to manufacture for a given capacity and which requires a relatively small combustion chamber.

A further object oi the present invention is the provision of a steam generating unit for use in t e intermediate range of capacity in which combustion is completed well before the products of combustion pass into the convection passes.

Another object of the invention is the provision of an intermediate range steam generating unit in which the back passes and the main combustion chamber are shaped to lit together geometrically to provide an inexpensive, compact unit.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination ol parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms as illustrated by the accompanying drawing in which:

The single ligure shows a longitudinal, vertical, sectional view of a steam generating unit embodying the principles of the present invention.

The steam generating unit, indicated generally by the reference numeral 1), is shown mounted in association v with the operating floor 1l of a building in which the unit is housed. The unit consists generally of a boiler l?. and a furnace 13 which are inter-related in the usual manner. The furnace 13 consists generally of a front wall 15:-, a rear wall l5, side walls 16, a bottom wall 17, and a roof wall ld deilning a vertically-elongated combustion chamber 19. The boiler 12 consists of an upper steam-andwater drum 2l and a lower mud drum 22 which is parallel with and spaced from the drum 2l. A. number of downcomer tubes 23 extend from the drum 21 to the drum 22. 4on the rearward side of a vertical baille 24 which extends vertically downwardly from the bottom of the drum 21. Forwardly of the baille 2d a number of riser tubes 25 connect the drum 22. to the drum 2l. A large downcomer tube 26 connects the mud drum 22 to a header 2'7 which underlies the rear portion of the bottom wall 17 and is parallel to and spaced downwardly from the drums 21 and ZZ. A number of water-wall tubes 28 extend from the header 27 up the back rear wall 15 and enter the steamand-water drum 21. Other water-wall tubes 29 extend from the header 27 along the bottom wall 17 up the front wall le and over the undersurface of the roof wall 1S to enter the steam-and-water drum 2i. Under each side wall 16 is located a longitudinal header 31 which is connected to the mud drum 22 by a downcomer 32. From each header 3l extend water-wall tubes 33 which lie along the surface of the side walls 16 and discharge into a header located above the roof wall 18, which header is also connected to the steam-and-water drum 21. A front wall 14 extends vertically upwardly from the bottom wall 17 for a short distance and then merges into a downwardlyfacing, upwardly-and-inwardly inclined portion 35 which merges with an upper vertical portion 35. This portion extends upwardly until it meets the roof wall 18. The rear wall l5 also extends vertically upwardly the same short distance above the bottom wall 17 and is then provided with a downwardly-facing, upwardly-and-forwardly inclined portion 37 which merges at its upper portion with an upper vertical portion 3?. The upper part of the rear wall l5 has the refractory removed and the water-wall tubes 2% are bent longitudinally to provide a gas oil-take 39. The space between the vertical downwardly-depending baille Zd and the upwardly-extending rear wall l5 provides a convection pass il which contains a convection superheater 4t2. @ne end of this superheater is attached to the top of the steam-and-water drum 21 and the other end is connected to the superheated steam header 43 which lies above the roof wall 18. A gas-reversal passage i4 lies between the lower end of the baille 24S and the upper surface of the mud drum 22 and another gas-reversal passage 45 underlies the rnud drum 22 and lies within an ash hopper lo whose forward wall is formed by the inclined portion 37 of the rear wail 15 and is provided with another inclined wall 47 located rearwardly of the mud drum. The upper edge of the inclined wall i7 ot the ash hopper merges with a vertical back wall lf3 which defines with the baille 24 a back pass i9 in which most of the downcomer tubes 23 reside. A series of battles 51 extend from the bailles 24 and the rear wall 4? to cause sinuous flow of gas over the bundle of downcomer tubes. Rearwardly of the steam-and-water drum 2l the gases llow up the back pass 49 over a damper S2 to a breaching 53 for disposal. The bottom of the ash hopper i7 is provided with a vertical slot S3 leading downwardly to a horizontal longitudinal passage 5d from which a number of nozzles lead through the bottom portion of the rear wall l5 into the combustion chamber 19. A motor-driven fan 5o discharges air at high velocity into the passage dll and into the nozzles S5. Extending upwardly into the hopper and into the gas passage i5 is a duct 57 having a damper 5S whose setting in the duct S7 is controlled by a manuallyoperated rod 59. Mounted on the inclined portion 35 of the front wall i4 is a burner el which is of the inter-tube directional-flame type shown and described in the patent of Craig No. 2,853,659 having a central fuel gun 62 which receives fuel from a duct 63. The burner is provided with a gas-electric ignition gun dd and is provided with a housing e5 which receives air from a duct do connected at its other end to a forced draft fan 67 and provided with an air-ilow damper d. The burner has upper vanes 6? mounted on horizontal axes and adjustable as to inclination to the horizontal by means of a control rod 71. Below the fuel gun 62 the burner is provided with lower vanes 72 also mounted for adjustment about horizontal axes by means of a control rod 73. The fuel gun o2 is shown ot the type having an outer pulverized-coal burner which receives its fuel from the fuel duct 63 and an inner gas gun 7d which receives its fuel from a gas pipe 75. it will be understood that although only one burn-er 6l is shown on the inclined portion 35 of the front wall, that any number of burners may be used and that their operating portions and areas are readily accessible from the operating floor 1l. The bottom wall 17 is provided with a slag opening 76 which is lined with water cooling pipe 77. Under the opening 76 is hung a slag tank 7S having a pool 79 of water and `at its bottom a screw-type ash conveyor 8l. Water injection pipes $2 and are located at the upper part ofthe tank 7S and are provided with nozzles for spraying a continuous stream of Water across the tank in the path of the downwardly-falling molten slag. The inclined portions 3S and 37 of the front wall i4 and rear Wall l5, respectively, define with the bottom wal i7 a high-temperature lower cell or combustion chamber S4, while the vertical portion 36 of the front wall ld and the vertical portion 3d of the rear wall l5 serve to define a narrow upper combustion chamber S5.

It will be understood that a plurality of burners E usually be provided transversely of the furnace on clined surface 35' of the front wall; there also is a of the injection nozzles 55 along the lower porti of rear wall l5. The slot 53 from the hopper the full Width of the furnace, as does the hopper itself and the recirculating gas duct 57 with its damper. A plurality of injection air fans 56 may also be used.

The operation of the apparatus will now be readily understood in view of the above description` 2l operates in the usual way with water leaving the steamand-water drum through the downcomers to YElow into the mud drum 22;. The water flows from the mud drum through the downcomers 216 and 32 into the

headers

27 and 31. From that point the water rises through the water-

wall tubes

2S, 29, and 33 and, eventually, the mixture of steam and water flows into the steam-and-water drum 2l where the steam moves to the top and the water circulates again. The steam passes through the superheater 42 into the superheated steam header 43 and is eventually used in a turbine or other steam equipment. The operation of the furnace is also in the usual manner; air from the forced-draft fan 67 flows into the burner til and into the furnace over the vanes 69 and 71?; whose angles have been set by use of the actuating handles and 73, respectively. Fuel enters the system through tl e duct 63 and the pulverized coal gun 62 as well as through the gas pipe 75 and the gas gun 74. The air and fuel mix in the combustion chamber and are ignited and maintained in ignition by the ignition gun 64. rthe rapidly-burning fuel and air mixture is directed by the vanes 69 and "2 downwardly toward the bottom wall T17 of the furnace. The burning mixture is then reversed, moves under the inclined portion 3'7 of the rear wall (which portion acts in the nature of a rear arch), and then moves vertically upwardly into the upper combustion chamber S5. lt can be seen that the upper combustion chamber 35 is quite narrow compared to the lower combustion chamber and, therefore, there is a tendency for the products of combustion to linger in the lower combustion chamber which, because of the high rate of heat release, becomes very hot and forms a high-temperature cell. The exit from the high-temperature lower combustion chamber Sd is, of course, the passage between the closest adjacent portions of the inclined portion 35 of the front wall and the inclined portion 37 of the rear wall. Heat transfer to the Water tubes takes place mainly by radiation in the entire combustion chamber i9. The products of combustion pass from the combustion chamber rearwardly through the gas off-take 39 into the convection pass #il Where it comes into heat transfer relationship to the superheater d?. and to the riser tubes The gases pass downwardly through lthe convection pass il and pass around the mud drum Z2. Some of them pass above the mud drum in the passage lil and some move down a 1 Will "ai i i r1.9 (ai dill through the hopper 45 in the passage In either case, they are reversed and move upwardly through the back pass 49 in a sinuous flow brought about by the bafdes 5l. During the reversal in the passages 44 and 45 a considerable amount of the ash in the gases is thrown by centrifugal force into the hopper 46 where it slides down the outer surface of the inclined portion 37 of the rear wall and the inner surface of the inclined wall 47, these making up thc walls of the hopper. The ash passes downwardly through the slot 53 into the passage 54 where it meets the air blast from the fan 56 and is thrown by the ejector principle into the nozzle 5S and into the hightemperature lower combustion chamber 84. The ilyash which is in this way introduced into the furnace again contains a considerable amount of unburned combustible which is now burned; the non-combustible is melted into slag by the high average temperature existing in this hightemperature cell. All of the slag formed in the hightemperature cell flows onto the inner surface of the bottom wall i7 and eventually ows through the slag opening 76 where it is cooled by the spray from the pipes SZ and and falls into the pool 79 in the slag tank 78. Eventually, it is removed from the bottom of the slag tank by the conveyor Si. it is advantageous, of course, not only to burn out the combustible left in the ash which accumulates in the hopper 46 but also this is a convenient way of disposing of the ash itself, since, as solidified slag, it is extremely concentrated in form, easy to transport and disposed of, and is saleable for use in the paving of roads and similar uses.

t may be desirable at times to regulate the temperature of steam reaching the superheated steam header 43. For this purpose, it is possible to recirculate a portion of the products of combustion. By a proper setting of the damper 5S in the duct 57, the ejector action of the air from the fan 55 passing over the bottom of the duct 57 will cause products of combustion to be drawn from the back passes of the furnace and to be thrown with the ash through the nozzle 55 into the high-temperature cell. The location of the upper end of the duct 57 is selected so that the gas drawn into the duct will be relatively free of ash; for instance, it might be located behind the mud drum 22. In any case, small amounts of llyash returned to the furnace by the gas recirculation duct are not harmful and will be disposed of in the same manner as the rest of the ash from the hopper d6. The recirculated gas, however, ilows from the nozzle 55 up along the inclined portion 37 of the rear wall l5. From there it moves up along the rear wall 15, being forced into that position by the tlame from the burner di. The gas recirculated in this manner serves two purposes. First of all, it increases the mass llow of gas which flows out of the gas olf-take 39 and down the convection pass 41 over the superheater 42, thus increasing the temperature of gas which flows from the superheater into the superheated steam header 43. The gas thus recirculated is also cooler than the gas from the flame and serves as an inert cooling blanket along the back wall, so that the flame from the burner 61 as it reverses itself and moves upwardly along the inclined surface 37 and the upper vertical portion 38 of the rear wall is maintained some distance away from the rear wall by the blanket of recirculated gas. This prevents the water-wall tubes and refractory from becoming too hot and also prevents the formation of slag deposits on these walls, tending to keep the walls clean and free of slag.

Manipulation of the

control rods

71 and 73 permits changing the angles of the varies 69 and 72 not only relative to their horizontal positions but also relative to one another, so that complete control of the flame in the hightemperature lower combustion chamber is permitted. Since the high-temperature cell brings about very complete combustion of the fuel, the gases which enter the upper combustion chamber tend to be inert and the temperature gradient from side 16 to side 16 of the unit is quite even. It is necessary, therefore, to provide only a small upper combustion chamber 85 since room for combustion is not necessary. Furthermore, this present construction provides for small distance from the front wall 14 to the rear wall 15 in the upper combustion chamber as is evident in the drawings. This permits a higher rate of transfer from the fuel to the water-wall tubes, since radiant transfer from a given particle is inversely proportional to the square of the distance from the particle to the surface in question. The need for a large combustion chamber is thus obviated, resulting in a much less expensive steam generating unit. At the same time, the fact that the inclined portion 37 of the rear wall not only serves as part of the high-temperature lower combustion charnber 84 but also as the bottom of the hopper 46 provides a geometric inter-relationship of the parts which provides a compact steam generating unit, thus requiring `a relatively small supporting structure and building for the housing of the unit.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

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 boiler having a steam-and-water drum, a furnace having front, rear, side, roof, and bottom walls defining a combustion chamber, a header parallel to the said drum underlying the floor wall of the chamber, water-wall tubes extending from the header over the oor wall, over the front wall, and along the roof wall to the steam-and-water drum, water- Wall tubes extending from the header over the rear Wall to the drum, the front wall having a downwardly-facing inclined portion adjacent the floor Wall, the rear wall having a downwardly-facing inclined portion adjacent the ffoor wall, a rear housing Wall defining with the said rear wall a back pass enclosing the said heat exchanger, the lower part of the said rear housing wall being inclined to the Vertical and lying in opposition to the said inclined portion forming a V-shaped ash hopper which underlies the drum, the said inclined portions serving to define a high-temperature lower combustion chamber with the fioor wall, the inclined portions of the front and rear walls extending toward one another, these Walls having vertical portions extending upwardly from the upper parts of the inclined portions to provide a relatively narrow upper combustion chamber, a gas off-take through the rear Wall adjacent the roof wall, a convection heat exchanger section connected to and underlying the said drum, the said section lying adjacent the vertical portion of the rear Wall and lying over the said inclined portion, and at least one burner mounted on the said inclined surface of the front wall.

2. A steam generating unit, comprising a boiler having a steam-and-water drum, a furnace having front, rear, side, roof, and bottom walls defining a combustion chamber, a header parallel to the said drum underlying the floor Wall of the chamber, water-wall tubes extending from the header over the floor wall, over the front Wall, and along the roof wall to the steam-and-water drum, Waterwall tubes extending from the header over the rear Wall to the drum, the front Wall having a downwardly-facing inclined portion adjacent the fioor wall, the rear wall having a downwardly-facing inclined portion adjacent the floor wall, a rear housing Wall defining with the said rear wall a back pass enclosing the said heat exchanger, the lower part of the said rear housing Wall being inclined to the vertical and lying in opposition to the said inclined portion forming a V-shaped ash hopper which underlies the drum, the said inclined portions serving to define a high-temperature lower combustion chamber with the floor Wall, the inclined portions of the front and rear walls extending toward one another, these walls having vertical portions extending upwardly from the upper parts of the inclined portions to provide a relatively narrow upper combustion chamber, a gas off-take through the rear wall adjacent the roofwall, a convection heat exchanger section connected to and underlying the said drum, the said section including a superheater lying adjacent the vertical portion of the rear wall and lying over the said inclined portion and receiving downwardly-flowing gas from the said off-take, and at least one burner mounted on the said inclined surface of the front wall.

3. A steam generating unit, comprising a boiler having a steam-and-water drum, a furnace having front, rear, side, roof, and bottom Walls defining a combustion chamber, a header parallel to the said drum underlying the fioor wall of the chamber, water-Wall tubes extending from the header over the floor wall, over the front Wall, and along the roof wall to the steam-and-Water drum, water- Wall tubes extending from the header over the rear wall to the drum, the front wall having a downwardly-facing inclined portion adjacent the iioor wall, the rear wall having a downwardly-facing inclined portion adjacent the floor wall, a rear housing Wall defining with the said rear wall a back pass enclosing the said heat exchanger, the lower part of the said rear housing wall being inclined to the vertical and lying in opposition to the said inclined portion forming a V-shaped ash hopper which underlies the drum, the said inclined portions serving to define a high-temperature lower combustion chamber with the floor wall, the inclined portions of the front and rear walls extending toward one another, these walls having vertical portions extending upwardly from the upper parts of the inclined portions to provide a relatively narrow upper combustion chamber, a gas off-take through the rear wall adjacent the roof Wall, a convection heat exchanger section connected to and underlying the said drum, the said section lying adjacent the vertical portion of the rear wall and lying over the said inclined portion, and at least one burner mounted on the said inclined surface of the front wall, the burner including a fuel gun and air-directing varies mounted for pivotal adjustment about horizontal axes, there being no burners on the inclined surface of the rear wall.

4. A steam generating unit, comprising a boiler having a steam-and-water drum, a furnace having front, rear, side, roof, and bottom walls dening a combustion chamber, a mud drum underlying and spaced from the steamand-Water drum, downcomer tubes connecting the two drums, a transverse header underlying the floor wall of the chamber, water-wall tubes extending from the header over the door wall, over the front wall, and along the roof wall to the steam-and-water drum, water-wall tubes extending from the header over the rear wall to the mud drum, the front Wall having a downwardly-facing inclined portion adjacent the floor Wall, the rear Wall having a downwardly-facing inclined portion adjacent the floor wall, a rear housing wall defining with the said rear wall a back pass enclosing the said heat exchanger, the lower part of the said rear housing wall being inclined to the vertical and lying in opposition to the said inclined portion of the rear wall, the said lower part and the said inclined portion forming a V-shaped ash hopper which underlies the drum, the said inclined portions serving to define a high-temperature cell with the fioor wall, and a directional dame burner mounted on the said surface of the front Wall.

References Cited in the file of this patent UNITED STATES PATENTS 1,970,109 Stratton Aug. 14, 1934 2,336,236 Foresman et al Dec. 7, 1943 2,853,059 Craig Sept. 23, 1958 2,905,155 Grossman Sept. 22,1959

FCREIGN PATENTS 759,462 Great Britain Oct. 17, 1956

Claims

1. A STEAM GENERATING UNIT, COMPRISING A BOILER HAVING A STEAM-AND-WATER DRUM, A FURNACE HAVING FRONT, REAR, SIDE, ROOF, AND BOTTOM WALLS DEFINING A COMBUSTION CHAMBER, A HEADER PARALLEL TO THE SAID DRUM UNDERLYING THE FLOOR WALL OF THE CHAMBER, WATER-WALL TUBES EXTENDING FROM THE HEADER OVER THE FLOOR WALL, OVER THE FRONT WALL, AND ALONG THE ROOF WALL TO THE STEAM-AND-WATER DRUM, WATERWALL TUBES EXTENDING FROM THE HEADER OVER THE REAR WALL TO THE DRUM, THE FRONT WALL HAVING A DOWNWARDLY-FACING INCLINED PORTION ADJACENT THE FLOOR WALL, THE REAR WALL HAVING A DOWNWARDLY-FACING INCLINED PORTION ADJACENT THE FLOOR WALL, A REAR HOUSING WALL DEFINING WITH THE SAID REAR WALL A BACK PASS ENCLOSING THE SAID HEAT EXCHANGER, THE LOWER PART OF THE SAID REAR HOUSING WALL BEING INCLINED TO THE VERTICAL AND LYING IN OPPOSITION TO THE SAID INCLINED PORTION FORMING A V-SHAPED ASH HOPPER WHICH UNDERLIES THE DRUM, THE SAID INCLINED PORTIONS SERVING TO DEFINE A HIGH-TEMPERATURE LOWER COMBUSTION CHAMBER WITH THE FLOOR WALL, THE INCLINED PORTIONS OF THE FRONT AND REAR WALLS EXTENDING TOWARD ONE ANOTHER, THESE WALLS HAVING VERTICAL PORTIONS EXTENDING UPWARDLY FROM THE UPPER PARTS OF THE INCLINED PORTIONS TO PROVIDE A RELATIVELY NARROW UPPER COMBUSTION CHAMBER, A GAS OFF-TAKE THROUGH THE REAR WALL ADJACENT THE ROOF WALL, A CONVECTION HEAT EXCHANGER SECTION CONNECTED TO AND UNDERLYING THE SAID DRUM, THE SAID SECTION LYING ADJACENT THE VERTICAL PORTION OF THE REAR WALL AND LYING OVER THE SAID INCLINED PORTION, AND AT LEAST ONE BURNER MOUNTED ON THE SAID INCLINED SURFACE OF THE FRONT WALL.