US1736423A - Steam generator - Google Patents

Description

Nov. 19, 1929;

R. WOOD STEAM GENERATOR File Jan. 22, 1925 e Sheets-Sheet 1 i Nov. 19, 1929. w. R. WOOD STEAM GENERATOR Filed Jan. 22, 1925 6 Sheets-Sheet 2 fQ/M ATTOR/VE Y5 Nov. 19, 1929.

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x? TTO ENE 2 5 Patented Nov. .19, 1929 UNITED STATES PATEN'F: OFFICE WILFRED ROTHERY WOOD, OF LONDON, ENGLAND, ASSIGNOR TO INTERNATIONAL COMBUSTION ENGINEERING CORPORATION, OF NEW" YORK, N. Y., A CORPORATION OF DELAWARE I STEAM GENERATOR Application filed January 22, 1925, Serial No. 8,921, and in Great Britain April 9,1924.

It has been recognized that steam generators make better use of the heat of combustion of the fuel when the surfaces which transmit the heat to the water receive that 5 heat by radiation rather than by convection, and the introduction of water tubes into the furnace chamber in a position in which they are exposed to the radiant heat therein has been proposed, partly with this object and partly to protect the, Walls of the furnace from damage. As a further step in the direction of utilizing radiant heat the vertical walls of the furnace chamber have been constituted by water tubes or their equivalent placed so closely together that they enclose effectively the combustion space, or at all events relieve any enclosing wall which there may be of the functions of a furnace wall.

In this case provision of suitable water and steam drums is all that is necessary to complots the generator and a construction is obtained of much smaller, dimensions than is possible when the main water tubes are in an uptake superimposed upon the combustion chamber. This construction may be called a furnace-shaped boiler.

It suffers, however, from a serious disadvantage, namely that the cooling effect of the surfaces to which the heatv is radiated is high temperature-an objection whatever the kind of fuel used but particularly so when pulverized fuel is burnt in suspension. For in that case a large proportion of the ash leaves the chamber together with the combustion. gases at a temperature near its melting point in which condition it adheres readily to the walls of any chamber through so great that the flame of burning fuel is crease the surface available in a furnace-.

shaped boiler for absorption of radiant heat, and another object is to reduce the temperature of the ashes as they leave the chamber.

Another object of my inventionis a construction in which the water circulation shall be sufliciently rapid to prevent the tubes from becoming overheated by the gases which impinge upon them in a state of violent combustion at a high temperature.

According to my invention a furnaceshaped boiler is fired in such a manner that turbulent intermixture of the fuel and air occurs at a place as nearly as possible on the axial line of the chamber so as to localize the combustion at this place and ensure its continuance.v

This object is achieved by any method of localizing combustion but preferably that in which the fuel and air are introduced into the combustion space at two or more places in streams of such velocity and direction that tlis'yl impinge upon each other and rapidly intermix. Preferably the direction is from the sides of the furnace and such that each stream is directed more or less tangentially to a circle. There is thus produced more or less vortex movement of the air and fuel ensuring rapid intermixture and combustion.

As is known, for development of the high temperature necessary for maximum radiation, pro-heating of theair for combustion is essential; for this purpose I prefer to use a recuperator in the uptake of the boiler. This has the advantage that the combustion gases do not come into contact with the outside of the boiler so that they retain a larger quan- 'tity ofheat for the purpose in question than is the case when they are allowed to-Jreturn over the tubes. Furthermore, it is easier in this manner to realize anadvantage of my.

' externally readily accessible from all sides.

According to my invention the furnaceshaped boiler has not only its side walls formed of water. passages but also its ends, whereby further surfaces for absorption of radiant heat are provided. To permit of escape of combustion gases there must be at one or more places a sufticient'space between the water tubes or the like for this escape. Tn the path of these escaping gases there may be placed additional water tubes sulhcient to lower the temperature of'the escaping gases to that at which any ashes which they may carry are so far cooled on approaching the tubes bounding the outlet space or the aforesaid additional water tubes that they have but little tendency to adhere to'superheater tubes or chamber walls.

. This part of my invention therefore may be said to consist in providing water tube ends to the more or less box-shaped boiler. Conveniently, the escape of combustion gases is at one of these ends. Tf, in a vertical boiler the upper end is selected,'there' will be at this part a sufiicient setting apart ofthe water tubes, or such a gap in the water tubes, as may be necessary for passage of the gases and beyond this additional water-tubes ofthe boiler to have the cooling eflect already mentione One of the difliculties in connection with firing by pulverized fuel: is due tothe tendency for the ash to be carried away by the products of combustion, this ash subsequently depositin in the neighbourhood of the chimney stac' By one feature of my invention the gases leaving the furnace pass through a chamber containing means for causing deposition of ash carried by the gases.

When pulverized fuel is being burnt therey is preferably provision at the bottom of the chamber for escape of ashes which may fall,

' escape so that here also there is a spacing apart of the tubes and if necessary additional water tubes for preventin in known manner fusion of the ashes in the ash-pit, which may be the chamber referred to in the preceding paragrasph.

ince there is this necessity for an ash at the bottom T generally prefer to make the upper "end of the chamber sub- 'stantially gas-tight with water tubes. and

arrange the take-elf for the gases at the bottom.

Qther features of my invention will appear from the description of the accompany ing drawings, in wh1ch:-

Fig. 1 is a vertical section through a -furnace-shaped boiler constructed in accordance with my invention. Q

Fig. 2 is alike section on line 2-2 of Fig. 1. Fig. 3 is a horizontal section on line 3-3 of Fig. 1. f v

Fig. 4 is a 'ke section on line 44 of Fig. 5.

a temperature appreciably Fig. 5 is a vertical section of a modificaa modification of the mode of supplying fuel to the furnace.

Figs. 9 and 10 are views illustrating the flame produced by the arrangement shown in Figs. 5 and 6.

Referring to Figs. 1, 2 and 3, the combustion space A is bounded on its four vertical sides by four, sets of vertical tubes 7, 8, 9 and 10.

The upper end of the combustion space is bounded by the tubes 11 and the bottom of the combustion space is bounded by the tubes 13.

Tubes 7 enter at their upper ends the drum l4: and at their lower ends the drum 15. Tubes 9 enter at the": upper ends the drum 16 and at their lower ends the drum 17. Tubes 13 are inclined to the horizontal and at their .upper ends enter drum 17 and at their lower connected with a header 21 at the bottom and with a header 22 at the top, these headers extending respectively from drums 15 and 16. It will be seen that this arrangement of tubes 8 and 10 with their respective headers affords a connection between the diagonally opposite drums 15, 16, such thatlthere is only one generaldirection of passage of fluid from the 'lower'to the upper drum and the length of this passage is the same whichever tube conducts the fluid.

As indicatedvin 4, each of the tubes of sets 7, 8,9 and 10 have on opposite sides fins 23, so that when the tubes are assembled the fins overlap, thus making a substantially gas-tight chamber which, however, is made completely closed on its four sides and top by means of insulating material 24: and a shell 25, both of which may be of very light construction, since they have not to withstand higher than that of the water in the tubes. Tf preferred, the fins may closely abut against each other. In any case they prevent the building up of ashes between the tubes which is liable to occur if any sort of brickwork be exposed between the tubes.

The chamber thus formed is open at the bottom and communicates with an ash-pit 26 situated by an ash tunnel 27. This ash pit may contain baflies, not shown in the drawings, suitable for causing the gases to change their direction of travel and thus to comer tubes of the circulatory system. They are of such size and number that they do not hamper the extremely rapid circulation in the boiler.

The tubes 13 are upcomer tubes from drum 15 to drum 17. Tubes 7 and 9 are upcomer tubes from drums 15 and 17 respectively to drums 14 and'16 respectively, and tubes 8 and 10 are upcomer tubes from header 19 to header 20 and from header 21 to header 22 respectively.

Drum 16 is a combined steam and water h drum.

The circulation is from drum 16 to drum 15 and thence upwardly through all the tubes 7, 8, 9, 10, 13 and 11 back to drum 16.

Drum 16 is suspended from the structural steel-work 30 and this suspension, coupled with the fact that the tubes 7, 9 and 13 are bent and that the tubes 8 and 10 are connected with headers, permits the boilerto expand and contract without placing any undue stress on the parts.

For the purpose of introducing the fuel there is provided at each of the four up? right corners of the combustion space and at a level some distance below that of the drum 14, a burner 31 constructed to deliver a thin sheet of fuel, sandwiched between sheets of air, into the chamber in a substantially vertical plane.

or the purpose of admitting these burn- .ers suitable spaces are left between the tubes at the corners. The direction in which the fuel and air proceed in these burners is that indicated in Fig. 3. That is, the directions are substantially tangential to the circle indicated atthe centre of the chamber; the result of this is that when the fuel streams meet a vortex is set up, the axis of which is parallel to the line of draught. The. fuel is introduced at high velocity, preferably with a blast of carrying air by-a usual as is indicated in Fig. 5.

The main portion of air necesary for com time, the flame being short, concentrated-and ted for combustion is intensely hot. The proportion of air admitpreferafbly close to the theoretical.

' Dampers 36 form of controlled feeder mechanism, such The combustion gases leave the chamber by passing among the nest of tubes 13 which are at such a temperature that they 'cool the gasessufliciently to prevent fusion of the ash collecting in the ash-pit but not to a much lower temperature, so that the gases can superheat the steam which flows by way of pipe 38 from drum 16 through the gases passing over this superheater. After leaving the superheater the gases, still at a high temperature, pass through the recuprator 35 consisting of a box subdivided by thin metallic partitions into comparb ments 33 and 34. The hot gases pass by the compartments 33 while air is drawn through compartments 34 into the passage 35 which as branches 36 leading to the burners. control the air supply and a damper, not shown, is provided in the offtake above the recuperator.

It is to be noted in Fig. 2 that the rows of tubes 13 have different tube spacings, the tubes of the first and second rows being widely spaced whereas those of the lower rows are more closely spaced, a staggered relationship being always observed. This arrangement restricts the passage for c0mbustion gases in accordance with the shrinkage of the latter in volume due to the absorption of their sensible heat.

In theconstruction shown in Figs. 4, 5 and 6 the draught is upwards instead of downwarels. The general construction is the same as that already described but the ofitake is above the combustion space, necessitating the proper spacing apart of tubes 11. The recuperator 35 is divided, the parts being spaced to leave the flue channel 39 controlled by'valve 40. Tubes 13 above the ash-pit 26 may be reduced in number in this form since their. function is only to cool such portion of the ash as falls between them.

To suit the direction of draught the fuel is admitted at each of two opposite sides in thin spaced sheets in a downwardly inclined direction by the sets of burners 41, producing flames which impinge as indicated in Fig. 10.

The mode of firing illustrated in Fig. 8 is substantially the same but the sheets of fuel are delivered substantially horizontally and at alower level in the chamber.

In the construction shown in Fig. 7 there is a fifth drum 18 which serves as the steam drum. It is connected with drum 16 by tubes 12 and with drum 14 by the short tubes shown.

The constructions illustrated have the ad vantage that any side wall may expand with relation to any other side wall with perfect freedom and the top and bottom of the boiler may also expand without causing strains.

The term water-tube means any tube which affords passage for fluid, and includes passages in what are commonly called boiler sections.

superheater 37 placed in the'uptake 32, the

While a single row of water tubes for each vertical wall of the furnace chamber is generally sufiicient, two or more rows of tubes, preferably staggered, may be used.

No specific claim is made herein to the updraft arrangement, the same being subject matter of my copending application Serial No. 51,533, filed August 21, 1925; nor to the specific type of combustion illustrated in Figures 9 and 10, the same being the subject matter of my copending application Serial No. 51.534, filed August 21, 1925.

Having thus described the nature of the said invention and the'best means I know of carrying the same into practical efiect, I claim 1. A furnace-shaped boiler having six walls, one of which receives its circulating water from inclined Water passages defining the bottom of the combustion chamber while the opposite wall receives its water from a drum or header at the lowest point of the boiler and discharges it through inclined tubes defining the top of'the chamber.

2. A furnace-shaped boiler having an up per and a lower drum or header placed diagonally opposite to each other with respect to the combustion chamber and connected together by upright tubes constituting at least one wall of the chamber at right angles to the axes of the drums, in such a manner that fluid traveling from drum to drum through any tube of this wall passes through the same distance.

3. A furnace-shaped boiler having the circulation referred to in claim 2 wherein downcomers connect the diagonally opposite drums.

4. A stationary power boiler defining its own combustion space from an end of which the gases of combustion leave and comprised of rows of tubes with appropriate drum and header means, the tubes of the boiler being so disposed that circulation is very-rapid, means near the other end for introducing a fuel ,to be burned in space in said combustion space in a manner that the boiler is subjected to heat of convection as well as of radiation and that violent combustion occurs, a metallic air preheater, means for subjecting the heater to waste gases of combustion, means for introducing the air to the combustion space, and heat absorbing means in advance or" the heater and associated with the boiler for lowering the temperature of the gases'leaving the combustion space to a point where rapid destruction of the air preheater does not ocour.

5. A stationarypower boiler defining its own combustion space from one end of which the waste gases of combustion leave, and

largely comprised of rows of upright radiant heat tubes with appropriate drum and header means connected to secure rapid circulation, the amount of evaporating surface of the tubes defining the combustion space being such that the gases leave such space at very high temperature, convection tubes over which the gases leaving the space ass having an amount of evaporating sur ace such that the gases leave the same at high temperature, a waste gas combustion air preheater beyond such convection tubes adapted to lower the temperature of the gases so their final exit temperature is within allowable limits, and means for introducing such preheated air and fuel to be burned in space under conditions to produce violent combustion with high furnace temperature head.

' In testimony whereof l have signed my name to this specification.

WILFRED ROTHERY WOOD.

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