US2311350A - Method and apparatus for controlling combustion - Google Patents

Description

Feb. 16, 1943. RlCHARDSON 2,311,350

METHOD AND APPARATUS FOR CONTROLLING COMBUSTION Filed Dec. 26, 1939 AWE/Wax? I W/T/YESS: f d l pgfiar con Ir Q 25?.

Patented Feb. 16, 1943 UNITED STATES! PATENT OFFICE METnon 'AND APPARATUS ron. ooN'moL- LING comnusrron Edward Adams Richardson, Bethlehem; Pa. Application December 26,1939, Serial No.'311,063 12 Claims. (01." 158-7) This invention is directed to improved methods and apparatus for controlling the rate and nature of reaction between fluids, more particularly the reaction between an oxygen-containing gas and a gaseousor gas-suspended fuel, known as combustion. V

In accordance with this invention such control is exercised by causing one of the reactants, as, for example, fuel gas, to flow in a relatively thin stream along the inner face of 'a wall of, for example, a combustion chamber, the velocity of the entering stream being such that the continuity thereof as a relatively thin stream or layer will be maintained for a considerable distance from the point of admission, while the second reactant, as, for example, air, is directed into the stream so formed at right angles'by being passed through the wall, which is, of course, permeable thereto, and at velocities too low to interfere with the fiowbf the first re-* actant as a thin stream.

By varying, within the limits of low velocity used, the rate of flow of the second reactant through any particular section of the permeable wall, a close control of the rate of reaction in the thin layer of mingling reactants just inside such section may be obtained,so that, if the reaction is one of combustion, precise point to point control of the heat produced over the entire permeable wall may be had.

Such control may most easily be obtained by dividing the outer face of the permeable wall into any desired number of sections, each'fed with one of the reactants, as air, at an independently controllable pressure. In this way, varying pressures within the reaction zone may be exactly counter-balanced, and sufilcient excess pressure applied to cause the reactant to pass through the permeable wall at the desired rate.

It will be appreciated that the permeable wall,

in order not only to permit a fluid to pass therethrough, but also to insure that such fluid pass substantially uniformly through the entire section of wall and leave the inner face thereof everywhere at low velocities, of theorder of 1 foot per minute to feet per second, must conform to rather definite specifications, which are hereinafter set out, and that the use of a ported wall, of the type, for example, illustrated in British Patent No. 18,471 of 1914 to Chantraine, is definitely excluded.

My invention may best befurther described by reference to the accompanying drawing, which illustrates a preferred embodiment thereof, and in which- The single figure is a view in vertical section of a furnace embodying my invention.

In the figure shown in the drawing'the combustion chamber I is formed with a hearth 3,

provided with ports 5 communicating with chamber I and thence through fiues 9 and H with a stack (not shown) ,and with ports or slots 13 for the admission of fuel gas from channels IS, in turn supplied from conduits l1. Enclosing chamber I on the sides (except for a door-not shown) and on top is a permeable, refractory wall I9. An outer shell 2| surrounds the structure and is spaced from the permeable wall 9 to form, with the partitions 23, a plurality of air supply chambers 25. Vertical partitions may also be present, if desired. Each chamber 25 is supplied with air under any desired pressure from the manifold Zll and leaders 29, while the rate at which air is supplied toany particular chamber, and hence the pressure obtaining in the chamber and the velocity of flow through the particular section of the permeable wall l9 fronting the chamber, may be regulatedby operation of valves 3!.

- The permeable wall mmust be constructed to pass fluid through the pores of the material thereof, at least through a portion of the thickness, so that the fluid flow may be fairly uniform therethrough. So constructed, the velocity of fluid approach to the wall will be very low, often barely detectible, and the velocity of fluidleaving the hot face will be increased only, and approximately, in the ratio of the hot to the cold fluid volume.

However, the wall may be composed of two or more layers. The outer layer will, in general, be the heat insulating layer. It may not be adapted to the highest temperatures which may be found in the wall. The hotter portions of the wall may be of a refractory body, preferably permeable. It may happen in some cases, how

ever, that tile or brick or the like of refractory refractory face shall be of highly heat conductive material and be permeable, since the temper-' ature gradient will be much less in this layer than in the other layers of low heat conductivity, and thi wall may then be free from spalling tendency. In such case, the other "layers may be bodies of granular or other loose material suitably-arranged to give adequate resistance to heat flow while being reasonably free to yield under expansion tendencies which might crack or break a solid wall.

It will also be necessary to arrange the wall material in such fashion as to furnish adequate resistance to flow at some layer of the wall, or in the wall itself, to insure reasonable uniformity of flow in those cases where a considerable pressure drop occurs in the width of a zone measured in the direction of flow of the thin stream passing the face of the wall.

In other words, the wall will be permeable, not perforated throughout; and if perforated at all, only with fine holes for a part of the wall thickness; the wall will have adequate insulating power; it will have an adequate resistance to fluid'flow. A wall not meeting these requirements is little suited to the invention 1'. have described. However, it is to be understood that I may, if I so desire, regulate in manufacture the permeability of the wall coursewise or transversely of the passing fluid to secure more perfect control of the flow, or to offset a pressure drop varying over the face of th wall. Primarily, however, regulation will be through control of fluid admission to a plurality of zones, unless adequate uniformity may be secured in one zone.

In operation a fuel gas will be fed to the furnace through valved conduits l1 and will flow into the combustion chamber I through ports l3. 'I'hese ports or slots are rather narrow and the gas'stream accordingly flows into the chamber at relatively high velocities, of the order of 1 ft. per sec. to 50 ft. per second, sufllcient to maintain, aided by the buoyant action of the gas as it becomes heated, a relatively thin blanket of gas over the surface of the side walls, and to a considerable degree over the inner surface of the roof. 7 I

As indicated, the fuel gas. will ordinarily be fed into the chamber from adjacent the lower edges of the walls, but where the gas stream may be guided and forced to the walls in other ways, as by the retort body in a retort furnace, the fuel gas may be introduced elsewhere, even at the top of the chamber.

Air for combustion, which may be preheated, will be fed into the chambers 25 through manifolds 21 and leaders 29, the rateof supplybeing controlled by valves 3|, and flow slowly combustion takes place has been bounded diagrammatically by the dash line A, and while, of

course, in actual fact no such sharp line of de-' marcation can be drawn, nevertheless combustion will take place substantially entirely within the zone between the permeable wall l9 and the this luminous blanket. The products of combustion do not reach the furnace contents until combustion has beensubstantially complete, and these inert gases, as indicated diagrammatically in the drawing, form a protecting and enveloping blanket for the material to be heated before they pass out through the ports 5 and chambers 1 into the flues 9 and II and thence to the stack.

With the furnace contents heated largely by heat radiated from the flame blanket .formed in the combustion zone closely adjacent the combustion chamber walls, the amount of heat radiated from any particular wall section may be closely controlled just as in an electrically heated furnace where heat is radiated from wall elements. Such control is accomplished, as indicated, by controlling the pressure of the air supply in any one of the chambers 25, with resultant control of the rate of flow of air through the corresponding section of permeable wall 19. In this manner the intensity of combustion and hence the degree of heat developed may be closely controlled from point to point along the combustion chamber wall, a result heretofore impossible in gas-fired furnaces.

It will be appreciated that while fuel gas has been described as entering through the ports l3 and air as being supplied to the chambers 25,

the procedure may, if desired, be reversed, air being supplied through ports I3 and the fuel gas to the various chambers 25 without departing from the scope of my invention and without altering the principles employed.

Moreover, the apparatus and principles described herein may be utilized even where the rethrough the permeable wall l9, leaving the inner that air for combustion reaches the stream of fuel gas flowing coursewise therein. As indicated, the velocity of the air leaving the inner face of the permable wall is so low that the flow of the stream of fuel gas is not interfered with but continues as a thin'layer adjacent the combustion chamber wall. In the drawing, the zone in which action involved is not one of combustion, and where the purpose of the point to point control in the reaction zone is not so much the control of heat to be radiated to a material to be heated, as in the embodiment previously described, but the maintenance of any desired temperature level in the reaction zone.

It will be appreciated that neither of the reactants need be a true gas, it being suflicient that the reactant behave as a whole like a gas. It may contain solid or liquid particles in suspension, which, since the flow velocities are small, must be quite fine. Of course, it is preferred that any fluid passing through a permeable wall be free of solid, and also of liquid particles which may be crackable, and contain at most accidental dust. It is permissible, however, to carry in suspension either finely divided liquids or solids in the gaslike body passing over the face of the wall, and it is immaterial to this invention how such admixture is produced. Neutral, as well as reactant vapor or gas may be present. It is only necessary that the mixture flow like a gas, and have reactant present in some form. The term gaslike has been'used in the claims to refer broadly to all reactants having this property, whether truly gaseous or not.

inner face of said wall, at least a portion of the said wall being permeable, and flowing the second reactant through said permeable portion and into said stream-substantially at right angles to itscourse and at a velocity not inexcess of about five feet per second whereby the 'fiow of the second reactant does not substantially interfere with the continued coursewise movement of said stream and combustion takes place substantially which is in no way limited thereto, but is defined solely by the claims hereinafter set forth.

This application is filed as and constitutes a continuation in part of my application Serial No. 47,355, filed October 30, 1935. l

What I claim and desire to protect by" Letters Patent is:

1. The method of controlling the combustion of a gas-like fuel with air which comprises flowing one of the reactants as a thin stream having definite continuity in the direction of flow, and flowing the second reactant into said stream substantially at right angles to its course and ata velocity too low to interfere substantially with the continued coursewise movement of said stream, whereby combustion takes place substantially only in a zone defined by the boundaries of said thin stream.

2. The method of controlling the combustion of a gas-like fuel with air which comprises flowing one of the reactants into a combustion zone closely adjacent a wall thereof at a velocity sufiiciently high for the said reactant to flow as a thin stream having definite continuity along the inner face of said wall, at least a portion of the said wall being permeable, and flowing the second reactant through said permeable portion and into said stream substantially at right angles to its course.

and at a velocity too low to interfere substantially with the continued coursewise movement of said stream, whereby combustion takes place substantially only in a zone defined by the boundaries of said thin stream.

3. The method of controlling the combustion of a gas-like fuel with air which comprises flowing one of the reactants as a thin stream having definite continuity in the direction of flow, and flowing all the second reactant required in combustion into said stream substantially at right angles to its course and at a velocity too low to interfere substantially with the continued coursewise movement of said stream, whereby combustion takes place substantially only in a zone defined by-boundaries of said thin stream, and varying the rate of flow of said second reactant, within the limits of velocity so imposed, at different points coursewise of said thin stream.

4. The method of controlling the combustion of a gas-like fuel'with air which comprises flowing one of the reactants as a thin stream having definite continuity in the direction of flow, and flowing the second reactant into said stream substantially at right angles to its course andat a velocity not in excess of about five feet per second whereby the flow of the second reactant does not substantially interfere with the continued coursewise movement of said stream and combustion takes place substantially only in a zone defined by the boundaries of said thin stream.

5. The method of controlling the combustion of a gas-like fuel with air which comprises flowing one of the reactants into a combustion zone closely adjacent a wall thereof at a velocity sufficiently high for the said reactant to flow as a only in a zone defined by-theboundaries of said thin stream. I

6. The method of controlling the combustion of a gaseous fuel with air which comprises flowing the gaseous fuel as a thin stream having definite continuity in the direction of fiow, and flowing air into said stream substantially at right angles to its course and at a velocity too low to interfere substantially with the continued coursewise movement of said stream, whereby combustion takes place substantially only in a zone defined by the boundaries of said thin stream.

7. The method of controlling the combustion of a gaseous fuel with air which comprises flowthin stream having definite continuity along the 7:;

ing the gaseous fuel as a thin stream'having definite continuity in the direction of flow, and flowing air into said stream substantially at right angles-to its course and at a velocity too low to intefere substantially with the continued coursewise movement of said stream, whereby combustion takes place substantially only in a zone defined by the boundaries of said thin stream, and varying the rate of flow of air, within the limits of velocity so imposed, at different points coursewise of said thin stream, so as to control the rate of combustion from point to point within the said combustion zone.

8. The method of controlling the reaction of two gas-like bodies which comprises flowing one of the reactants as a thin stream having definite continuity in the direction of flow, and flowing the second reactant into said stream substantially at right angles to its course and at 2. velocity too low to interfere substantially with the continued coursewise movement of said stream, whereby reaction takes place substantially only in a zone defined by the boundaries of said thin.

stream.

9. The method of controlling the reaction of two gas-like bodies which comprises flowing'one of the reactants as a thin stream having definite continuity in the direction of flow, flowing the second reactant into said stream substantially at right angles to its course and at a velocity too low to interfere substantially with the continued coursewise movement of said stream, whereby reaction takes place substantlally only in a zone defined by the boundaries of said thin stream, and varying the rate of flow of said second reactant, .within the limits of velocity so imposed, at diflerent points coursewise of said thin stream, so as to control the rate of reaction from point to point within the said reaction zone.

two miscible fluids which comprises flowing one of the reactants as a thin stream having defl nite continuity in the direction of flow, flowing the second reactant into said stream substantially at right angles to its course and at 9. velocity too low to interfere substantially with the continued coursewise movement of said stream, I

10. The method of controlling the reaction of r from: point to'point within the said reaction zone. v

11. A furnacecomprising a floor, walls form- 'ing with said floor a combustion chamber, at

least portions of said walls being so constructed 4 as to permit air to pass therethrough and leave the inner face thereof only at'low velocity, and the walls being votherwise impermeable, said floor being provided with a narrow slot extending therethrough adjacent the lower edge of at least one of said walls so as to direct a gas-like fuel admitted through said slot along the inner face ofsaid wall, and means for supp yin air under controlled pressure to the outer face of said permeable portions of the walls.

12. A furnace comprising. a floor, walls forming with said floor a combustion chamber, at

least portions of said walls being so constructed as to permit air to pass therethrough and leave theinner face thereof only at low velocity, and the walls being otherwise impermeable, said floor being provided with a narrow slot extending therethrough adjacent the loweredge'of at least one of said walls so as to direct a gaslike fuel admitted through said slot along the inner face of said wall, means for supplying air under controlled pressure to the outer face of said permeable portions of the walls, and means for independently varying the pressure of air supplied to different sections of said permeable portions. l EDWARD {\DAMS RICHARDSON.

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