US3265039A

US3265039A - Burning chamber cells formed by horizontal partition-forming tubes

Info

Publication number: US3265039A
Application number: US400046A
Authority: US
Inventors: Ralph D Winship; Paul C Anderson
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1964-09-29
Filing date: 1964-09-29
Publication date: 1966-08-09
Anticipated expiration: 1983-08-09

Description

Aug. 9, 1966 R. D. WINSHIP ET AL 3 I BURNING CHAMBER CELLS FORMED BY HORIZONTAL Filed Sept. 29, 1964 PARTITION-FORMING TUBES 6 Sheets-Sheet 1 7 INVENTORS kALP/f P. WINS/17F PAUL C. ANVLRSO/V Aug. 9, 1966 R wms ET AL 3,265,039

BURNING CHAMBER CELLS FORMED BY HORIZONTAL 6 Sheets-Sheet 2 Filed Sept. 29, 1964 Aug. 9, 1966 R. D. WINSHIP ET AL 3,265,039

BURNING CHAMBER CELLS FORMED BY HORIZONTAL PARTITION-FORMING TUBES Filed Sept. 29, 1964 6 Sheets-Sheet :5

Aug. 9, 1966 R. D. WINSHIP ET AL 3,265,039

BURNING CHAMBER CELLS FORMED BY HORIZONTAL PARTITION-FORMING TUBES Filed Sept. 29, 1964 6 Sheets-Sheet 4 FIG. 4

Aug. 9, 1966 R. D. WINSHIP ET AL 3,265,039

BURNING CHAMBER CELLS FORMED BY HORIZONTAL PARTITION-FORMING TUBES Filed Sept. 29, 1964 6 Sheets-Sheet 5 FIG. 5

Aug. 9, 1966 R. D. WINSHIP ET AL 3,265,039 BURNING CHAMBER CELLS FORMED BY HORIZONTAL PARTITION-FORMING TUBES Filed Sept. 29, 1964 6 Sheets-Sheet 6 FIG. 6

United States Patent The present invention relates to a vapor generator incorporating a tubular furnace construction provided with means for burning fuel in a pile at the bottom thereof and for the discharge of hot combustion gases into heat transfer relation with steam generating surface forming the furnace walls. More particularly, the invention relates to the novel construction of a fluid cooled, multicell combustion chamber for a tubular furnace in which cellulosic fuel, such as wood, bark, 'bagasse and the like, is employed as the principal burning medium. The combustion chamber is provided with air passage means for delivering combustion air to the fuel cells about their entire periphery in order to enhance the combustion of fuel therein.

Furnaces having a combustion chamber formed as a plurality of burning cells are old in the art. However, in the past such cells have been formed either entirely, or in great part, by refractory brick as exemplified by the conventional Dutch oven type of combustion chamber. The use of refractory in furnaces employing cellulosic fuels has been found to be undesirable, first, because of the high initial cost of the refractory material and secondly, because of the outage time and expense required for maintenance of the refractory which is subject to spalling and fluxing by the fuel and ash.

The present invention pnovides a furnace construction of the type described in which the combustion chamber is divided into a plurality of burning cells without the need for refractory material. The combustion chamber of the instant invention is divided into cells by means of tubular partition means, the tubes of which conduct vaporizable fluid and form part of the steam generating circuit of the generator. Thus, the combustion chamber is rendered harmless of the deleterious effects of cellulosic fuels having a high moisture content.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter which illustrate and describe the preferred embodiments of the invention.

In the drawings:

FIGURE 1 is a sectional side elevation of the vapor generator embodied in the invention;

FIGURE 2 is an isometric representation of the combustion chamber embodied in the invention;

FIGURE 3 is an enlarged sectional elevation showing the lower portion of the vapor generator;

FIGURE 4 is a section taken along line 4-4 of FIG- URE 3 and FIGURE 5 is a section taken along line 5-5 of FIG- URE 3.

FIGURE 6 is a section taken along line 66 of FIG- URE 3.

In the illustrative embodiment of the invention shown in FIGURES l, 2 and 3, a vapor generator 10 incorporating a wood burning furnace is arranged in association with a natural circulation boiler section comprising a bank of upright tubes 12 having offset ends connected to upper and

lower drums

14 and 16, respectively. It is to be understood, however, that the instant invention is 3,25fl39 Patented August 9, 1966 equally applicable to boilers employing other than natural fluid circulating systems. The furnace is formed of upright, tubular walls which define a furnace chamber 18 and which includes a front wall Ztl, a rear wall 22 and opposing side walls 24. The upper portion of the front wall 20 is extended over the top of the furnace chamber 18 to the drum 14 and forms a roof 26. The rear Wall 22 terminates adjacent the lower drum 16, in spaced relation to roof 26, so as to provide a combustion gas passage 28, between

drums

14 and 16, through which gaseous products of combustion are discharged from the furnace chamber 18 and directed over the boiler tubes 12. In the gas passage 28 tubes 30 are provided downstream of the boiler tubes 12 for preheating the incoming feedwater and tubes 32 are provided upstream thereof for superheating the steam emitted from the upper drum 14.

The bottom of the furnace chamber 18 is defined by sloping extensions of the tubes forming the front wall 20 which extend across the furnace chamber thereby defining the floor 34. At the bottom of the furnace chamber 18 is located the combustion chamber 36, described in greater detail hereinafter. All boundaries of the furnace chamber 18 are fluid cooled by means of upwardly extending, fluid conducting tubes 38 which line the respective walls and through which liquid is circulated in parallel with the natural circulation of liquid through the boiler tubes 12. The tubes 38 lining the walls of the furnace chamber 18 are provided throughout substantially all of the heating surface with tangent spacing. Other tube spacing arrangements can, however, be employed without departing from the scope of the invention. For example, other furnace constructions such as fusion Welded wall, fin welded membranous wall or integral finned tube walls are equally suitable. The tubes 38 lining the side walls 24 connect at their lower end to headers 40 located at the base of the furnace and at their upper ends to upper headers 42. The tubes lining the rear wall 22 extend from the lower drum 16 to a lower header 44 located adjacent the furnace bottom while the tubes that line the roof 26, front wall 20 and floor 34 extend from the upper drum 14 to a header 46 adjacent the bottom of the rear wall. The

headers

44 and 46 are positioned adjacent to but spaced from one another to provide clearance for ash removal through doors 4% located in the rear wall. The

lower headers

40, 44 and 46 are supplied with vaporizable fluid by means of downcomer conduits 49 that connect with the lower drum 16. Fuel feeding conduits 5d capable of depositing cellulosic fuel such as wood, bark, bagasse and the like into the combustion chamber 36 are provided in the furnace front wall 20. These conduits are adapted to deposit fuel into the combustion chamber 36. Intermediate the height of the furnace chamber 18 is also positioned a plurality of burners 52 capable of burning auxiliary fuel such as pulverized coal, oil or gas. In the arrangement shown in FIGURE 1 the burners 52 are located at the corners of the furnace chamber formed between

walls

20, 22 and 24 and are adapted for tangential firing within the furnace chamber. On the other hand however, the burners 52 could be mounted in opposite walls for oppose-d firing. An air chamber 54 encloses the burners 52 and supplies them with combustion air.

The combustion chamber 36 located at the bottom of the unit is lined with tubes 56 that connect with the tubes 38 lining the

respective furnace walls

20, 22 and 24. These tubes 56 are of reduced diameter being connected to the tubes 38 by means of transition pieces 58. Being of smaller diameter than the tubes 38, the tubes 56 are therefore provided with spaces therebetween. These spaces are filled by a metallic web or membrane indicated as 60 which are provided with spaced openings 62 to effect communication between an air duct 64 that surrounds the bottom of the unit and the combustion chamber. The air duct 64 is adapted to supply the combustion chamber with the necessary air required to burn fuel deposited therein. The air duct 64 is provided with partitions 66 which divide the duct into distinct elevations of air admission. Each of the elevations of air admission can be controlled by dampers such that air can be admitted to the combustion chamber 36 through the upper elevation 66, the lower elevation, or both depending on the height of the fuel pile being burned. More or less elevations can be employed.

As shown best in FIGURE 2 the combustion chamber 36 is divided into a pair of spaced burning cells 68 by means of a tubular partition that extends across the combustion chamber parallel to the floor 34 between the front wall 20 and rear wall 22. The partition is formed by laterally spaced sides 70 and a roof 72 that define a central air pasage 74 communicating with the air duct 64 through the front wall 20. The tubes forming the partition roof 72. are provided on tangent spacing and connect at their lower end with the lower front wall header 46. These tubes extend initially upwardly from the header to the top of the partition sides 70 and then are substantially normally offset and extend across and along the tops of the sides to the front wall 20 where they are offset vertically into alignment with the tubes 38 that line the front wall. The tubes thereafter extend parallel with the tubes 38 that form the front wall vertically upwardly through the height of the furnace chamber 18 and across the top of the furnace thereby forming part of the roof 26 Where they connect with the upper drum 14. The tubes that form the partition sides 70 are of a somewhat lesser diameter than the tubes that form the roof 72. These tubes are provided with the same spacing as the vertical tubes 56 that line the combustion chamber 36 so as to provide similar spaces between the tubes. These spaces are similarly filled with a web 69 provided with openings 62 to obtain communication between the control air passage 74 and the cells 68. The partition side tubes emanate from the lower front wall header 46 radially communicating with the header at points angularly spaced from the points of communication of the tubes forming the floor 34 as shown in FIGURE 3. These tubes extend parallel to the floor 34 across the bottom of the combustion chamber from the rear wall 22, through the front wall 20 to a point therebeyond where the tubes of opposite sides 79 are oppositely offset with right angle bends and caused to extend to the extremities of the front wall. Here the tubes are again offset as shown best in FIGURES 3 and 5 to bring them into alignment with the tubes 38 lining the front wall whereupon they extend vertically through the height of the furnace chamber 18, across the top of the chamber thereby lining a portion of the roof 26 and terminate in the upper drum 14.

The operation of the illustrated embodiment of the invention is as follows. Feedwater is admitted to the upper drum 14 where it mixes with the separated, saturated fiuid located therein and flows through downcomer tubes in the boiler bank 12 to the lower drum 16 from whence it is conducted by the conduits 49 to the

lower headers

40, 44 and 46 at the base of the unit. From these headers the downcomer fluid is caused to flow upwardly through the tubes 38 lining the walls of the furnace and through those that form the sides 70 and roof 72 of the central air passage 74 where heat is extracted from the gases generated in the furnace chamber transforming some of the fluid into steam which collects in the upper drum 14 where separation or other processing occurs before the steam passes to the superheater 32 where an additional amount of heat is extracted from the combustion gases thereby raising the temperature of the steam. From the superheater 32 the steam is removed from the unit and conducted to a point of use.

Fuel in the form of wood, bark, bagasse or the like is admitted into the combustion chamber 36 through the fuel feed conduits located in the furnace front wall 20. The fuel is dumped into piles within one or both of the cells 68 where combustion occurrs. At the same time hot air is admitted to the hot air duct 64 which surrounds the combustion chamber 36 and also to the central air passage 74- which is in communication with the hot air duct. Control of air admission to one or more of the air duct elevations can be maintained by means of dampers (not shown) which govern the operability of the elevations. One or more of the elevations can be operated depending upon the depth of the fuel piles within the combustion chamber 36. Spent fuel can be removed from the combusion chamber cells through the ash removal door 48.

At the same time as, or independently of, burning within the combustion chamber 36 the auxiliary fuel burners 52 and be fired to generate gases within the furance chamber 18, which gases similarly flow in a vertical direction through the furnace chamber 18 and thence through the gas outlet passage 28 and out of the unit into an air heater '76 or other ancillary equipment before egressing from the stack.

One of the more important features derived from the novel means employed for dividing the combustion chamber into cells is the fact that, because of the instant arrangement the entire furnace chamber is unobstructed by divider walls that would prevent the use of tangentially fired auxiliary burners. The burners can be mounted in the corners of the furnace and directed so as to fire in an imaginary circle so as to achieve all of the beneficial results inherent in tangential firing. Likewise, the use of opposed burners rather than tangentially oriented burners would be benefitted by an unobstructed furnace chamber in that high heat release rates can be accommodated within the furnace chamber without the danger of slagging or overheating a tubular surface that would otherwise be relatively close to the burners.

Another beneficial result is that a lesser number of tubes is required to completely line the central air passage when the partition forming tubes are horizontally oriented than is required when vertically arranged tubes are employed thereby giving rise to lower fabrication and installation costs.

The illustrated combustion chamber arrangement further provides a structure adapted for operation at relatively high rates of combustion and capable of accommodating cellulosic fuels having a relatively high moisture content. The fuel burning cells formed by the central partition are able to receive combustion air around their entire periphery thereby effecting a more uniform and therefore more efficient burning with each of the cells. The uniform distribution of air in this manner also results in more intimate mixture of fuel and air which contributes to the burning efficiency which occurs within the combustion chamber. Such construction also permits separate operation of each cell thereby permitting continuous operation of the furnace since one cell can continue to operate while the other is shut down for the dumping of spent fuel or the like.

Furthermore, the invention enhances the burning fuels having a high moisture content. By locating the watercooled cells in the bottom of a furance chamber having auxiliary fuel burners, the radiant effect of the flame provided by the auxiliary burners is available for drying processes thereby eliminating much of the moisture from the fuel prior to their combustion in the cells.

It will be understood that various changes in the de tails, materials, and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. A vapor generator having rectangularly disposed walls defining a vertically extending furnace chamber;

substantially vertically arranged vapor generating tubes lining said walls; a combustion chamber capable of supporting combustion of cellulosic fuel positioned subjacent to and communicating with said furance chamber; substantially vertically extending extensions of said vapor generating tubes lining the Walls of said combustion chamber; first air passage means surrounding said combustion chamber; partition means dividing said combustion chamber into a plurality of burner cells, said partition means comprising rectangularly disposed rows of substantially horizontally arranged, parallel tubes extending between opposed walls of said combustion chamber, said rows defining second air passage means therethrough, said partition means'including spaced, parallel sides and a roof traversing the top of said sides; the tubes forming said sides extending to the exterior of said vapor generator and there being laterally and vertically offset to connect with a first portion of said vapor generating tubes; the tubes forming said roof being vertically offset to connect directly with a second portion of said vapor generating tubes; and means for effecting communication between said air passage means and said burner cells.

2. A vapor generator having rectangularly disposed walls forming a vertically extending, undivided furnace chamber; tubes lining the walls of said furnace chamber; fluid fuel burner means positioned for operation in said furnace chamber; a combustion chamber adapted to burn piles of cellulosic fuel positioned subjacent to, and in open gaseous communication with, said furnace chamber; tubes in fluid communication with said furance chamber tubes lining the walls of said combustion chamber; tubes in at least one of said walls being downwardly slopingly displaced across the bottom of said combustion chamber to form the floor thereof upon which said piles are burned; means for passing combustion air through the walls of said combustion chamber; partition means extending upwardly from the floor of said combustion chamber to a height substantially coincident with the height of the combustion chamber dividing said combustion chamber into a plurality of burner cells comprising rows of parallel tubes forming an air passage having oppositely spaced sides and a roof extending between opposed walls of said combustion chamber parallel to the floor thereof, said air passage tubes being displaced at their upper ends to connect with tubes in the adjacent furnace chamber wall and means for passing combustion air from said air passage to said burner cells.

3. A vapor generator as recited in claim 2 including tubes lining said combustion chamber walls being coaxial with, but of smaller diameter than, said furance chamber tubes thereby providing spaces between said combustion chamber tubes; a metallic membrane filling said spaces; and means forming openings in said metallic membrane for passing combustion air to said burner cells.

4. A vapor generator as recited in claim 3 wherein said partition means comprises rows of parallel tubes defining an air passage having oppositely spaced sides and a roof traversing the tops of said sides; said side forming tubes being vertically spaced; a metallic membrane filling said spaces; means forming openings in said metallic membrane for passing combustion air from said air passage to said burner cells; said side-forming tubes being oppositely displaced at their upper ends to connect with said furnace chamber tubes forming spaced portions of said adjacent furnace chamber wall; and said roof-forming tubes being vertically offset into communication with said furnace chamber tubes.

5. A vapor generator as recited in claim 4 including means forming openings in said adjacent furnace chamber wall and said side-forming tubes extending through said wall openings to the exterior of said combustion chamber and there being displaced to connect with said furnace chamber wall tubes.

6. A vapor generator as recited in claim 3 including means forming an air duct surrounding the walls of said combustion chamber; said combustion wall tubes being common with said air duct and means connecting said air passage in communication with said air duct.

References Cited by the Examiner UNITED STATES PATENTS 1,792,068 2/ 1931 Caracristi l22235 2,114,619 4/1938 Ward l107 2,637,306 5/ 1953 Marquez et al. 122240 2,875,735 3/1959 Falla 1222 3,156,219 11/1964 Zoller 122510 CHARLES I. MYHRE, Primary Examiner.

Claims

1. A VAPOR GENERATOR HAVING RECTANGULARLY DISPOSED WALLS DEFINING A VERTICALLY EXTENDING FURNACE CHAMBER; SUBSTANTIALLY VERTICALLY ARRANGED VAPOR GENERATING TUBES LINING SAID WALLS; A COMBUSTION CHAMBER CAPABLE OF SUPPORTION COMBUSTION OF CELLULOSIC FUEL POSITIONED SUBJACENT TO AND COMMUNICATION WITH SAID FURNACE CHAMBER; SUBSTANTIALLY VERTICALLY EXTENDING EXTENSIONS OF SAID VAPOR GENERATING TUBES LINING THE WALLS OF SAID COMBUSTION CHAMBER; FIRST AIR PASSAGE MEANS SURROUNDING SAID COMBUSTION CHAMBER; PARTITION MEANS DIVIDING SAID COMBUSTION CHAMBER INTO A PLURALITY OF BURNER CELLS, SAID PARTITION MEANS COMPRISING RECTANGULARLY DISPOSED ROWS OF SUBSTANTIALLY HORIZONTALLY ARRANGED, PARALLEL TUBES EXTENDING BETWEEN OPPOSED WALLS OF SAID COMBUSTION CHAMBER, SAID ROWS DEFINING SECOND AIR PASSAGE MEANS THERETHROUGH, SAID PARTITION MEANS INCLUDING SPACED, PARALLEL SIDES AND A ROOF TRAVERSING THE TOP OF SAID SIDES; THE TUBES FORMING SAID SIDES EXTENDING TO THE EXTERIOR OF SAID VAPOR GENERATOR AND THERE BEING LATERALLY AND VERTICALLY OFFSET TO CONNECT WITH A FIRST PORTION OF SAID VAPOR GENERATING TUBES; THE TUBES FORMING SAID ROOF BEING VERTICALLY OFFSET TO CONNECT DIRECTLY WITH A SECOND PORTION OF SAID VAPOR GENERATING TUBES; AND MEANS FOR EFFECTING COMMUNICATION BETWEEN SAID AIR PASSAGE MEANS AND SAID BURNER CELLS.