US2686499A - Fuel burning and fly ash collecting apparatus - Google Patents

Description

Aug. 17, 1954 c. H. SPARKS FUEL BURNING AND FLY ASH COLLECTING APPARATUS Filed Oct. 8, 1947 3 Sheets-Sheet l INVENTOR Cedric J /am/d (soar/ 5 ATTORNEY Aug. 17, 1954 c. H. SPARKS 2,586,499

FUEL BURNING AND FLY ASH COLLECTING APPARATUS Filed Oct. 8, 1947 's Sheets-Sheet 2 ATTO R N EY Aug. 17, 1954 c. H. SPARKS 2,636,499

FUEL BURNING AND FLY ASH COLLECTING APPARATUS Filed Oct. 8, 1947 3 Sheets-Sheet 5 INVENTOR Cad/gi o /ar0/a Jbarks ATTORNEY Patented Aug. 17, 1954 FUEL BURNING AND FLY ASH COLLECTING APPARATUS Cedric Harold Sparks, Burwocd Park, England,

assignor to The Babco Rockleigh, N. J., a, corporation of New Jersey Application October 8, 1947, Serial No. 778,641

Claims priority, application Great Britain October 14, 1946 4 Claims.

This invention relates in general to fuel burning apparatus, and more particularly to the construction and operation of a fuel burning apparatus or system whereby fuel is burned in a furna-ce and particles separated from the combustion gases are returned to the furnace for consumption of combustible matter contained in the particles. My invention especially adapted for use in vapor generating units wherein, for example, heating gases resulting from the combustion of fuel in an associated furnace are directed through a unit in a plurality of passes and wherein frequently the unit is provided at a number of points in the gas flow path with means for receiving particles carried by the gases from the furnace. In a vapor generating unit employing tubular heating surface, there may, for example, be a down pass or down passes containing vaporizing tubes and a down pass containing an economizer or air heater and below each down pass may be a hopper for the deposit of entrained particles, while a grit arrester may be provided for the deposit of further particles before the gases pass to the stack. With some methods of firing or rates of firing or with the use of some fuels the disadvantage arises that in operation an appreciable proportion of the fuel in the form of dust or grits of considerable calorific value is carried out of the furnace by the gases. The rate of deposit of particles at the different points in y the gas fiow path generally varies greatly and the calorific value of the deposits at the different points also tends to differ. As a r sult, if in an endeavor to obtain an improved fuel consumption the deposits are injected into the furnace chamber at different points across the width thereof, greatly uneven unsatisfactory combustion conditions may be produced. Apart from an unsatisfactory distribution of fuel, when the deposits are introduced in the furnace chamber by air injectors, an air injector associated with a point at which the rate of deposit is relatively low may be underloaded with particles, so that at least locally within the furnace an undesirably high excess of air is produced. Also, when there is a substantial number of points at which particles are deposited, the problem arises of accommodating in the space available the nozzles for the injection of the deposits and the supply of combustion air.

With a view to overcoming the above mentioned difficulties, it is an object of my invention, in the construction and operation of fuel burning apparatus comprising a furnace, to combine particles deposited by combustion gases at a plurality of points in the gas flow path and to convey the ck & Wilcox Company,

combined deposits through common feeding means to the furnace for the consumption of combustible matter contained in the particles.

Another object, in the construction and operation of fuel burning apparatus comprising a furnace, is to combine deposits of particles separated from combustion gases at a plurality of points in .the gas flow path and to direct the combined deposits into the furnace in streams distributed throughout a selected portion of the furnace.

An additional object, in the construction and operation of fuel burning apparatus comprising a furnace, is to provide for the reception of particles deposited by the furnace gases at a plurality of points in the gas flow path and to convey the deposits to a common collecting zone where particles deposited at the various receiving points are caused to be mingled in predetermined proportion and from which the deposits are returned to the furnace in streams respectively containing particles deposited at a plurality of receiving points.

A further object, in the construction and operation of fuel burning apparatus associated with a vapor generating unit and comprising a furnace from which heating gases are directed through the unit in a plurality of passes, is to provide for the reception of particles deposited by the furnace gases at a plurality of points in the gas flow path and at a location below a gas turning zone between two of the passes to cause the deposits to be combined in predetermined proportion for return to the furnace in streams respectively containing particles of a. plurality of deposits.

Other objects include a method of maintaining substantially uniform combustion conditions throughout the width of a grate-fired furnace by collecting particles deposited from gases discharged .from the furnace and by returning the particles .to the furnace in predetermined proportions at different locations so as to maintain a fuel bed of predetermined thickness throughout the Width of the grate.

The various features of novelty which characterize my 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 advan tages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which Ihave illustrated and described preferred embodiments of my invention.

Of the drawings:

Fig. l is a partly diagrammatic sectional side elevation illustrating a form of my invention as embodied in a vapor generating unit employing a water-tube boiler;

Fig. 2 is a view to a larger scale on the line 22 of Fig. 1 of the rear wall of the boiler furnace;

Fig. 3 is a view also to a larger scale on the line 33 of Fig. l of a grit receiving hopper below a rear portion of a tube bank of the boiler, with parts removed to show details;

Fig. 4 is a front View also to a larger scale on the line 44 of Fig. l of a grit tank receiving grits from below gas turning zones in a rear portion of the boiler; and.

Fig. 5 is a View also to a larger scale on the line 5--5 of Fig. 1 of the hopper bottom of a grit collector at the rear of the boiler.

Referring to the drawings, the boiler comprises a horizontally inclined bank I of water tubes arranged with its upper portion extending above a spreader stoker fired furnace 2 from which the gases of combustion flow upwardly over the tube bank in a first gas pass. Within the boiler setting suitable baiiles, including bafiles 3 and 4 extending transversely across the tube bank, are arranged so that the combustion gases, after flowing upwardly over the tube bank in the first gas pass, are constrained to flow over tubes of a superheater 5 arranged above the tube bank, then downwardly across an intermediate portion of the tube bank in a second gas pass 6, and then upwardly across the lower portion of the tube bank in a third gas pass 1,

Below the second and third gas passes is a gas turning zone 8 traversed by the combustion gases after leaving the second gas pass and in turning to flow upwardly to enter the third gas pass, and below this zone is a hopper 9 for the collection of particles deposited from the combustion gases during their turning movement.

At their lower ends the tubes of the tube bank I connect into a sectional header I supported below a transverse steam and water drum I I, and supplied with water therefrom through downcomer tubes l2. At their upper ends the tubes of the bank connect into a sectional header I3 connected by riser tubes to the steam and water drum I I for the passage thereto of water and of steam generated in the tube bank I. The superheater comprises two rows of tubes lying in vertical planes and extending horizontally forward in U- shaped form above the first gas pass and connected at their ends to a transverse inlet header I4 and a transverse outlet header l5 arranged vertically thereabove. Suitable steam piping IE is arranged for conveying steam to the superheater inlet header from the steam space of the steam and water drum I I.

The combustion gases, after leaving the third gas pass I, flow rearwardly within the setting and normally flow downwardly in a Vertical passage I1 within which between front and rear walls I8 and I9 are disposed upper and lower economizer sections 20 and 2I respectively. At the bottom of the vertical passage a gas duct 22 conducts the combustion gases leaving the economizer section 2| rearwardly to a grit collector 23 of any suitable kind, for instance of the multi-cyclone type, in which particles are separated from the gases and fall into the hopper bottom 24 of the collector, the gases then being conducted by an outlet duct 25 to an induced draft fan (not shown) and thence to a stack (not shown). Gases flowing into the gas duct 22 are constrained to undergo a relatively sharp turning movement in a gas turning zone 26 below the lower economizer section 2I by reason of a baffle 21 extending forwardly and downwardly from the lower edge of the rear wall I9 of the vertical passage I! and partly across the entrance to the gas duct. Particles separated from the gases during this turning movement fall into a hopper 23 arranged below the gas turning zone 26.

Within the setting rearwardly of the steam and water drum II and forwardly of the vertical gas passage 5? is an econom zer by-pass passage 29 arranged for conducting combustion gases, when desired, downwardly for passing to the gas turning zone 25 below the lower economizer section 2! without passing over the economizer section. A damper 38 situated in an opening leading rearwardly from the lower end of the by-pass passage 29 to the gas turning zone 26 is provided for preventing, when desired, the by-passing of the economizer sections. Inlet dampers 3! above the front wall I8 of the vertical gas passage and outlet dampers 32 below the lower economizer section 2| and above the gas turning zone 27 are provided for preventing, when desired, the access of combustion gases to the economizer sections.

Particles separated from combustion gases flowing in the economizer by-pass passage 29 fall into a hopper 33 provided below the by-pass passage.

The furnace 2 is supplied with coal for combustion by feeder apparatus 34 of known spreader stoker type mounted in front of apertures 35 in the front wall 36 of the furnace and adapted to project coal into the furnace for combustion therein. The feeder apparatus, as diagrammatically indicated in Fig. 1, includes a hopper 3'! into which suitably sized coal is arranged to be fed, a reciprocatory coal pusher member 38 for transferring charges of coal intermittently rearwardly from below the hopper, a coal distribution plate 39 for supporting the charges of coal during movement from below the hopper, and an overthrow rotor 48 arranged to be rotated and provided with rotor blades adapted in their rotary motion to project into the furnace coal fed by the pusher over the rear edge of the distribution plate.

The floor of the furnace is formed by a suitable endless grate of known construction consisting of transverse grate bars carried by endless chains passing over front driving sprockets 42 and rear sprockets 43, and arranged for travel of the upper run of the grate from back to front of the furnace. The grate bars are pierced for the passage therethrough of primary combustion air introduced below the upper run of the grate and provided by a forced draught fan (not shown). Nozzles 44 are provided in the front wall 36 of the furnace below the apertures 35 for the introduction of secondary combustion air.

The rear wall l' of the furnace is cooled by a row of eighteen water tubes 45 bent rearwardly in their lower lengths so as to connect at their lower ends into a transverse header l! suitably supplied with water from the steam and water drum through downcomer tubes (not shown), and extending in their upper lengths forwardly above the furnace in two rows 43 parallel to and below the upper portion of the tube bank i, and connecting at their upper ends into the lowermost parts of the upper sectional headers i3.

In the rear wall 45 opposite spaces between the second and third, the sixth and seventh, the twelfth and thirteenth, and the sixteenth and seventeenth, counting'from either end of the tube row, of the tubes 46 lining the rear wall, air nozzles 49 are provided for the admission to the furnace of secondary combustion air in streams directed forwardly and slightly downwardly towards the upper run of the grate. The nozzles 49 are supplied with air from air pipes 50 arranged at the back of the furnace and supplied from an air duct 5! connected to the outlet of a fan 52. A valve 53 in the air duct 5! is provided for controlling the quantity of secondary air admitted to the nozzles 49.

During the operation of the furnace, coal fed rearwardly from below the hoppers 3'1 by the reciprocating coal pusher members 38 and over the rear edge of the coal distribution plates 39 is projected by the rotor blades of the revolving rotors 4i! through the apertures 35 into the furnace. Some of the coal particles ignite as they pass into the flame. Most of the coal falls onto the fuel bed from near the front end to the rear end of the upper run of the grate ll within the furnace and burns out thereon, the resulting ash being deposited from the front end of the upper run of the grate into a subjacent ash hopper 8B. The mass of gases rising in the furnace, however, carry away upwardly from the fuel bed and out of the furnace fine particles which may in the aggregate have a considerable calorific value.

The hopper 9 below the second and third gas passes 6 and l in the tube bank is divided in its lower part into three limbs 8| each of which has secured thereto a respective nozzle box 82 of known. construction adapted for the entraining by an air stream of particles falling into the nozzle box from the respective hopper limb. From the nozzle boxes 82 ducts 83 lead to respective grit injector nozzles 85% placed in the rear wall is of the furnace and arranged to deliver between the fourth and fifth, the ninth and tenth, and the fourteenth and fifteenth, counting from either end of the tube row, of the tubes lining the rear wall, streams of air and entrained particles directed forwardly and slightly downwardly towards the upper run of the grate. The ducts 83 leading to the grit injector nozzles 8d connect into the nozzle boxes 32 on the forward sides thereof and air is supplied to the nozzle boxes by air pipes 85 connecting into the rearward sides of the nozzle boxes, co-axiaily with the air ducts. The air pipes connect into an air supply duct 85 connected to the outlet of the fan 52, and a valve ill in the air supply duct 88 is provided for controlling the quantity of air admitted to the air pipes.

The hopper 33 below the economizer by-pass assage 23 is divided in its lower part into two limbs from which collected particles fall through vertical chutes $39 each provided with a suitable dust non-return valve 9% to a sub- ;Iacent covered grit tank. 9!. Similarly the hopper 28 below the vertical gas passage ll containing the economizer sections is divided in its lower part into two limbs 92 from which collected particles fall through vertical chutes $3 each provided with a suitable dust non-return valve dd to the grit tank ill. The grit tank has a hopper bottom 95 which has secured thereto a nozzle box 8% for entraining in an air stream delivered by an air pipe 91 leading into the rear of the nozzle box 95 particles falling into the hoppers 83 and 23 and thence into the hopper bottom $5 of the grit tank 9!. The air pipe is supplied from an air duct 98 .connected to the outlet of the fan 52, and a valve 99 is provided for controlling the supply of air to the air pipe 91.

Connecting into the front of the nozzle box 96 coaxially with the air pipe 9'! is a pipe I Oil arranged to conduct the stream of air and entrained particles to a centrifugal separator Ill! suitably supported below the tube bank I and above the front wall I82 of the hopper 9 below the second and third passes of the tube bank. The centrifugal separator [Ell comprises a whirl chamber ms arranged with its axis vertical and to which the stream of air and entrained particles is tangentially admitted through a suitable aperture I84, a concentric diverging tubular air outlet I65, and a downwardly extending outlet Illli for separated solid material. Air leaving the separator by the air outlet H35 joins the combustion gases flowing to the third gas pass in the tube bank I. Guilding means it! is arranged below the separator into which the separator outlet discharges and a chute lit-8 conducts falling separated particles in a stream laterally to one side of the separator and discharges this stream above the dividing ridge I69 between the center hopper limb and a lateral hopper limb; and a chute I ll! conducts falling separated solid material in a separate stream laterally to the other side of the separator and discharges this stream above the dividing ridge H between the center hopper limb and the other lateral hopper limb. At the lower ends of the chutes Hill and HG discharge sleeves H2 and H3 respectively are pivoted, and rods connected to the pivoted sleeves and extending laterally outwardly therefrom to adjusting means permit of adjustment of the guiding means transversely of the ridges its and Ill for the purpose of equalizing the fall of solid material separated in the separator it! into the three hopper limbs 8!, or ensuring an otherwise suitable distribution of the particles between the three hopper limbs. Numerals l 15 and I I6 indicate the rod and adjusting means respectively in Figure 3 for the sleeve I i2.

As shown in Figure 5, the hopper bottom of the dust collector is divided into two hopper limbs Hill and below each limb a nozzle box MI is secured similar to the nozzle boxes 96 to which nozzle boxes Ml air streams are led through an air duct M2 connected to the outlet of the fan 52, and respective air pipes 543 connecting into the rear of the nozzle boxes. A valve hid in the air supply to the air duct M2 provides for control of the air supply. From the front of each nozzle box and .co-axially with the air pipe, a pipe M5 for carrying air and entrained particles separated in the dust collector connects, and the pipes 545 are arranged to conduct the air and entrained particles to respective centrifugal separators M6 arranged within the hopper 9 and with their axes in vertical planes and parallel with the sloping rear wall of the hopper. Each separator M6 is of the same type as the centrifugal separator ml already described. The separators Hit are arranged respectively above the dividing ridges between the three hopper limbs and particles separated thereby are con ducted downwardly by respective chutes M? and discharged above the said ridges, the chutes being pivoted and. provided with laterally extending rods I 48 and adjusting means iii-*3 for equalizing the distribution, or ensuring an otherwise suitable distribution, between the three hopper limbs of the particles separated in the separators M6.

Below the nozzle boxes 82, 9t, and I4! respectively pipes lfiil are provided for the withdrawal of particles if desired, for instance in the case of blockage in the respective nozzle box.

Peep hole fittings l5l are provided in the pipes H and M5 for the observation of the flow of particles entrained in the air streams. Mica panels I52 are provided in the front and rear walls of the hopper 9 slightly above the dividing ridges H38 and ill for the observation of particle fall into the hopper limbs from the sleeves H2 and H3 and chutes Hi.

In operation, particles separated from the combustion gases in the grit collector 23 and deposited in the hopper bottom therebelow, and particles received in the hoppers below the gas passages ll and 29, are transferred by the means described to the hopper 8 to unite therein with particles deposited from the gases in their turning zone 3 below the rear part of the tube bank l. The

sleeves 1 l2 and i it are adjusted in position above the dividing ridges I99 and Hi respectively so as to ensure a suitable distribution, for example, by equalizing as far as possible the distribution between the three hopper limbs 31 of the particles separated from the gases and falling into the hoppers 33 and 28. Again, the chutes Hi1 are also adjusted in position above the dividing ridges so as to ensure a suitable distribution, for example, by equalizing as far as possible the distribution between the three hopper limbs 81 of the particles separated from the gases in the grit collector 23.. The ducts 83 conveying air and entrained particles from the hopper limbs 35 are arranged to carry such quantities of air and particles that satisfactory, substantially uniform or not undesirably uneven combustion conditions are maintained across the width of the furnace, notwithstanding any differences in calorific value of the particles deposited from the different points in the gas flow path, and differences in the amounts deposited at such points. The rate of how of air through the air pipes 85 for transporting particles from the hopper limbs 8! to the furnace, and the rate of flow of air through the secondary air pipes 5i] are adjusted to values suitable for effective transport and combustion.

While in accordance with the provisions of the statutes I have illustrated and described herein the best forms of my invention now known to me those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. In fuel burning apparatus comprising a furnace arranged to supply furnace gases to heat absorbing apparatus located beyond said furnace and through which said gases are directed along a predetermined gas flow path, collector means at a plurality of points in said gas flow path for receiving entrained particles deposited by said gases, means for causing deposits of particles from the various receiving points to unite within one of said collector means, and feeding means discharging into said furnace at laterally spaced positions adjacent one end for returning the deposits from said one collector means to the furnace and to distribute the deposits across the width of the furnace, said one collector means having separate compartments within which separate masses of said returned deposits are caused to be united in predetermined adjustable proportions, said feeding means comprising separate discharge ducts communicating respectively with said separate compartments.

2. In fuel burning apparatus comprising a furnace arranged to supply heating gases to fluid heating components through which the gases are directed along a predetermined gas flow path including a downflow gas pass through one of said components, means defining a bypass section of said gas flow path for bypassing heating gas flow around said one component, means arranged to separately receive particles deposited from said gases at each of a plurality of points in the path of heating gas flow including a receiver point below said downfiow pass and a receiver below said bypass section, an auxiliary collecting chamber arranged to be fed with the deposits of particles from said receivers, a main collecting chamber in the form of a hopper and arranged to be fed with deposits of particles received from a plurality of said points including the combined deposits fed into said auxiliary chamber, and means for feeding particles from said hopper to the combustion zone of the furnace at difierent feeding points.

3. In fuel burning apparatus comprising a furnace from which the gases of combustion are discharged through a predetermined gas flow path and particles carried by said gases are deposited at successive points in said path, grit receivers at a plurality of said points arranged to separately receive the deposits of particles at the respective points, a grit collector divided into compartments, pneumatic conveying means for separately conveying to said collector the deposits of particles from the respective receivers, means for separating the conveyed particles of the respective deposits from the gaseous conveying medium while causing the separated particles to be discharged into said collector and the gaseous conveying medium to be released into said gas flow path, adjustable discharge means in said collector arranged to receive the separated particles from the respective separating means and to cause particles conveyed from therespective receivers to be proportionately discharged into each of said collector compartments, and pneumatic injection means for conveying particles from the respective collector compartments into said furnace at spaced locations.

l. In fuel burning apparatus comprising a furnace arranged to supply heating gases to fluid heating components through which the gases are directed along a predetermined gas flow path including a downflow gas pass through one of said components at a location adjacent said furnace, means arranged to separately collect particles deposited from said gases at each of a plurality of points in the path of heating gas flow including a main collector below said downflow pass and an auxiliary collector below a point in said path at a location downstream of said downfiow pass, pneumatic conveyor means for conveying to said main collector the particles deposited in said auxiliary collector, means associated with said main collector for separating the conveyed particles from the gaseous conveying medium while causing the separated particles to be discharged into said main collector and the gaseous conveying medium to be released into said gas flow path, and pneumatic means for transporting said separated particles from said main collector and in- 9 jecting said particles directly into said furnace at Number spaced locations. 2,110,452 References Cited in the file of this patent UNITED STATES PATENTS 5 Number Name Date 2,476,567 795,106 Curtis July 18, 1905 2,483,728 919,014 Hochstein Apr. 20, 1909 1,942,687 Daniels Jan. 9, 1934 1,943,949 Coghlan et a1 Jan. 16, 1934 10 f gf g 1,995,745 Morrow Mar. 26, 1935 2,029,285

Bennett Feb. 4, 1936 Name Date Moyer Mar. 8, 1938 Allen Nov. 18, 1941 Mosshart Oct. 9, 1945 Allen May 6, 1947 Sparks July 19, 1949 Glaeser Oct. 4, 1949 FOREIGN PATENTS Country Date Austria Feb. 25, 1932

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