US3357410A - Water tube heater - Google Patents

Description

Dec. l2, 1967 J. L. EOYEN 3,357,4l@

WATER TUBE HEATER Filed sept. 15, 1955 F/GZ 4, A, *m WN www1 CNTROr PANE ATTORNEYS United States Patent Giice l@ Patented Dec. l2, 196'? 3,357,410 WATER TUBE HEATER .lohn L. Boyen, Orinda, Calif., assignor to C-C Industries, a corporation of California Filed Sept. 13, 1965, Ser. No. 486,627 3 Claims. (Cl. l22-238) This invention relates to a water tube heater and more particularly to a novel fuel burning and heat transfer arrangement which provides a high degree of operating eiiiciency even when burning low-grade fuels, and a unit which is inherently more compact than those hitherto known in the art.

A problem frequently incurred in present-day field appiications of fuel-fired heaters is the proper utilization of low-grade fuels encountered in areas where availability makes such fuels the most convenient and economic to use. Although some prior art heater units may accommodate low-grade fuels, the hot gases produced usually have a relatively high degree of soot content. This is due mainly to incomplete combustion generally caused by a total flame path which may be satisfactory for higher grade fuels but inadequate to burn lower grade ones to a point where soot content is minimized. When soot-containing gases produced by such lower grade fuels come intocontact with the heat transfer elements of the unit, usually tubes arranged in a bundle through which liuid to be heated is passed, the soot tends to coat the elements and decrease the heat transfer eiliciency from the hot gas medium.

In addition, soot which persists after incomplete combustion of a fuel is usually wet which makes it particularly adhesive and chemically more active. Such soot not only tends to coat more readily the various objects with which it comes into Contact, but may contribute to harmful corrosive action, which in turn may require abnormally high held maintenance to keep the unit at a reasonably good level of operating efficiency.

Also, various prior art devices for hot Huid generation with which I am familiar are generally designed for a given amount of hot fluid output per hour for optimum operating eiliciency. Field applications which may require a range of output capacities, therefore, cannot be accommodated efficiently by such equipment; and such units ordinarily do not provide a modular and compact arrangement whereby capacity may be changed readily either at the factory or in the field. Moreover, heaters manufactured in accordance with such prior art designs normally do not lend themselves to a mode of production whereby a relatively small number of stock, oif-the-shelf components may be combined to give a range of capacities depending upon particular engineering requirements.

Thus it is an object of this invention to provide a heater for generating a hot working fluid which may effectively utilize various types of fuels including those of a low-grade type frequently encountered in the field. More specifically it is an object of this invention to provide a heater having a tubular combustion chamber in uid communication with an enclosed, hollow, transverse vessel which defines a path for conveying the hot ignited fuel from the combustion chamber to a housing within which the heat exchanger for producing the hot working uid is mounted. The combustion chamber, transverse vessel, and heat exchanger housing form a U-shaped configuration within the heater enclosure so that the mixture of fuel and air conveyed therethrough becomes highly turbulent through the transverse portion.

A feature and an advantage of the above described U-shaped continuum within whose transverse portion the ignited fuel and air mixture becomes highly turbulent, is that such turbulence delays the ignited fuel in a Zone of extended burning. Such extended burning increases the overall fuel utilization of the heater and minimizes the amount of soot which remains in the hot gas iiow.

Another object of this invention is to provide a heater of the character described above including a plenum formed within the heater enclosure and surrounding the input end of the combustion chamber. A blower is provided in fluid communication with the enclosure and atmosphere to force air under pressure into the plenum at the input end of the combustion chamber. rlfhis forced air circulation causes mixing of air with fuel supplied from a fuel injector mounted at the input end of the combustion chamber and accelerates passage of the mixture through the U-shaped gas-conveying continuum.

A feature and an advantage of this invention is that various low-grade fuels readily available in the field may be used in my novel heater and burned to a point where little if any soot content remains in the hot gas combustion product.

A more specific feature and advantage of my invention is that an effectively extended path for the burning of the causes extended burning of the mixture within a relatively compact structure. This is so due to the novel U- shaped conguration of my heater combustion chamber and adjacent gas-conveying portions which cause a highly increased turbulent flow of ignited gas before contact with the heat exchanger portion of the device. The increased turbulence of the ignited fuel and air mixture, particularly in the transverse portion of the U-shaped continuum, causes extended burning of the mixture within a relatively confined space thus obtaining many of the advantages of a long flame path.

Another advantage of the U-shaped design of the gasconveying portions of my invention is that the heat exchanger housing is folded back in parallel relationship to the fuel combustion chamber, the two being connected by the transverse vessel within which the aforementioned high zone of turbulence is accomplished. This inherently compact design is relatively more eilicient for portable field applications than conventional heater designs; and is generally adaptable to multiple arrangements of two or more units connected together in side-by-side relationship on a common base.

Another object of this invention is to provide a plenum which preheats the air before introduction into the combustion chamber and hence acts as an economizer as well as a thermal barrier against heat loss from the gas-conveying and combustion portions of the heater to the atmosphere.

A feature and an advantage to the above stated object, in addition to the increase thermal efficiency of the unit, is to maintain the outside of the heater enclosure at relatively low temperatures thus permitting the use of less heat resistant outer materials.

Numerous other objects, features and advantages will become apparent from a reading of the following specication and by referring to the accompanying drawing wherein similar characters of reference refer to the same parts in the various views.

Turning now to the drawings,

FIG. 1 is a fragmentary plan view showing a portion of one embodiment of my invention;

FIG. 2 is a sectional view taken along line 2 2 of FIG. 1;

FIG. 3 is a partial and fragmentary plan View showing a portion of one embodiment of my invention; and

FIG. 4 is a perspective view of one portion of my invention.

The invention is best understood by referring rst to FIG. 1 wherein two water tube heater units, each embodying my invention, are indicated generally at 14a and |14b. The unit at 14a is also shown in the sectional View of FIG. 2.

Although FIG. l shows my invention adapted for a typical arrangement of two units operating together in a so-called parallel hook-up, it is well understood that a single unit such as that indicated at 14a may be used alone. One of the advantages of my invention is its modular and compact arrangement so that two units may be mounted together with relative simplicity and ease. The somewhat minor changes that must be made in order to combine units is explained in greater detail below; however, for sake of clarity, the major portion of the description of my invention which follows is directed to a single `unit with the understanding that similar corresponding components may be provided inY additional units f-or parallel or multiple operation.

Attention is now directed to FIG. 2 which is a sectional elevation of a typical water tube heater indicated at 14a embodying my invention. The unitcomprises a basel or mounting structure indicated at B, an. outer insulated en.- closure indicated generally at E, and three sections of equipment mounted within the enclosure which forma generally U-shaped passageway for the combustion and utilization of tired fuel. These. three sections include the combustion chamber indicated generally at C, a turbulence-producing, transverse, crossover chamber indicated generally at D, and the water tube Ibundle chamber and flue combination indicated generally at F.

The outer. enclosure indicated. at EV comprises a pair of opposite, spaced apart walls 64 and 65; a pair of oppositespaced apart walls 66 and69. (FIG. 1) adjacent to walls 64 andl 65 and suitably connected. thereto atthe corners; roof portion 67; and' floor 68. The floor is suitably combined in a conventional manner with. structural members 71, 72, 73 and 74 which are boltedor otherwise connected together to `form the base generally indicated at B. As can be seen in FIG. 1 the base may be extended at either end of the unit, when used. either singly or in parallelk operation, to form a` structural platform upon which to mount the control panel, the feed water pump, blower, motors, and other conventional equipment necessary for the operation. of the. unit, as well as a base from which the various piping and' plumbing connectionsmay be supported. Walls 64, V 65, 266, and 69, floor 68,y and roof 67, maybe of a conventional sandwich.insulation-type construction wherein the inner and outer surfaces are made of some suitable material such as steel sheeting between which there is disposed an insulating material such as rock wool, fiber glass, or the like.

In the operation of the unit shown at 14a, fuel is conveyed to fuel nozzle 27a which may be. adapted to any suitable -fuel including, but not. limited to, gas, oil, pnl verized hydrocarbons or certain other crude fuelsv readily available at a particular place. The fuel. nozzle may also be provided with a means for igniting the fuel which is ejected therefrom under predetermined pressure and immediately thereafter mixed with additional air under pressure as is later explained more fully. The fuel injector or nozzle may be ofa type known in the art and is not further described herein; and the entire foregoing fuel injector arrangement may be referred to hereinafter as the fuel burner or fuel injector, although it is understood that combustion occurs through the combustion chamber and -portions of the transverse chamber. The burner is mounted to project through opening 81 in roof 67 and is held in place by flange 82 and suitable fasteners associated therewith. Burner 27a is surrounded by hood 83 which depends from the inner surface of roof 67 to a point just above the upper surface yof the combustion chamber indicated generally at C, forming a spaced interval indicated by the dimension 84. Positive pressure air is provided by means of motor M1 connected to blowerY 29 which discharges throughduct 31, al1 in a manner known to those Skilled in the art and not further described herein. The discharge from duct 31 is entrapped inxplenum 87, the space co-extensive everywhere between the enclosure indicated at E and the continuous envelope or continuum formed by the combustion chamber at C, the curved transverse chamber at D, and the water tube bundle chamber and flue combination indicated at F. The air under positive pressure is caused to travel in a path indicated by arrows 86 through the spaced interval having dimension 84 t0 provide the necessary combustion air for the fuel introduced to burner 27a. The air ow under pressure also causes the ame front from burner 27a to move through the combustion chamber at C with a relatively high velocity into the crossover or transverse chamber indicated generally at D.

The combustion chamber at C may be formed of a cylindrical portion 88 and an upper conical section 89 having an opening 91 through which the flame front and ignited gases under positive air flow pressure pass in the direction and path indicated by arrows 92. The lower porti-on of cylinder 88 is shaped to for-mcounter bore 93 having land surface 94. The inside diameter of the counter bore is suitably formed to fit over the outisdediameter of annular or ring portion 96 of the transverse chamber indicated at. D with land surface 94 resting on circular top lip 97 also seen in FIG. 4.

The transverseV chamber indicatedat D and' shown in FIGS. 2 and 4 may be described as defining an inner surface which approximates that of a semi-torus or toroid whose cross section may be circular and whose axis of generation lies on or near line seen in FIG. 4. The combustion chamber shell may be formed from two sections of suitable ceramic material, namely, an upper section 98: having annular or ring` portion 96, referred to above, and cylindrical or discharge portion 99; and the base portion indicated at 101. Upper portion 98 is shaped totclosely onto the base portion whose inside surfaces form al continuous toroidal or bathtub-like profile having curved portion 102 forming a trough immediately continuous-.with inside taper 103 of the opening defined by upper section 96; curved section 104 shapedr to define a trough sloping away from surface 102; and curved wall- 10S which is the relatively straight through region continuous with sections 102 and 104. Wall 105 is tangent, along its lower most'- .longitudinal elements, to a plane normal to the extension of the longitudinalv axis of the water tube bundle indicated at 61. In the region to the right lof the projection of said longitudinal axis, as viewediin FIG. y2the relatively straight through surface 105 is gradually formed into an upward curving surface 106, similar to that of surfaces 102 and 104, and termi-y nates at planar interface 107 at the contacting surface between the upper edge `of the base portion and the adjacent surface of cylindrical or discharge portion 99.

Annular or ring portion 96 forms an enclosed continuum with cylindrical or discharge portion 99 by means of saddle 95. In its entire form, the toroidally shaped transverse chamber indicated at D forms the bottom portion of a U-shaped passage whose straight legs generally comprise the combustion chamber indicated at C and the tube chamber and flue at F.

As theflame front caused by the combustion of fuel expelled? through burner 27a moves through combustion chamber C in the direction of arrows` 92 into the transverse chamber, the gas tiow is deflected by curved surfaces 102, 104 andstraight surface 105 of the initial portion of the-U to cause greatly increased gas turbulence and change ow direction indicated by the shape and position of arrows 109. The generation of gas turbulence is enhanced by tapered surface 103 which, due to its convergence in the direction of gas ow, tends to accelerate the gas just prior to its contact with deliecting surfaces 102 and104.

Asthefdirection of gas ow is changed, any soot which may be present from the use of low-grade fuels introduced to burner 27a is delayed because of the circuitous ow caused by theV increased turbulence indicated by arrows 109 and thereby exposed to a longer duration of burning than Would be the case with less turbulence or in a shorter llame front path. In this manner soot due to unburned fuel is decreased and that which is present and remains as suspended residue in the gas flow is exposed to longer and higher temperatures and hence is burned to dry ash consistency once it leaves chamber D. The now relatively soot free and high temperature gas ow continues in a curvilinear path indicated by arrows 108 through the transverse chamber and then, by the action of trough surfaces 106, in the direction of arrows 111 .toward the water tube bundle indicated at 61. The pressurized air present in plenum 87 ,continues to force the hot gases up through the spaces between the tubes of the water tube bundle in the direction of arrows 110, lwhere the heat from the hot gases is transferred through the tubes to form a mixture of hot water and steam or the like within the tubes. Soot which may still be present in the hot gas ilow is of a dry ash residue character and tends to blow through the tubes rather than adhere thereto. That which does stay on the tubes is of a relatively harmless nature being dry and less likely to be of a corrosion supporting nature. A soot blower may be added, if desired, in the vicinity of the water tube bundle to blow away even that portion of the dry soot that does remain and which may decrease the heat transfer eiliciency of the water tubes.

As explained above, however, even Without a soot blower, the water tube bundle remains relatively free of contamination and incrustation that would be formed by wet soot or excessive soot of any type. After the interaction of the hot gases upon the water tube bundle and consequent cooling as a result in the heat exchange that occurs, the gases are conveyed in the direction of arrows 112 through the ue chamber defined by casing 113 and hence out into the atmosphere in the vicinity of arrows 114.

A portion of the double spiral water tube bundle indicated at 61 is seen in FIG. 1 where a major portion of outer enclosure 113 is shown removed. High pressure feed water is introduced into the uppermost coil 116 from feed water line 62a and thence in a spiral path toward the center of the first course of said tubing. At the center of the spiral, the direction of coiling is reversed by means of reentrant curved portion 117; and the tubing then proceeds in a reversed or outward spiraling direction toward the outer periphery of the tube bundle. Once tubing 116 reaches the outer circumference of its return spiral, it is bent slightly downwardly to begin the next course of continuous tubing spiral back towards the inner region f the tube bundle whereupon a second reentrant curve portion, not shown but beneath the -iirst, is formed and the entire spiral pattern configuration is repeated. The above double spiral tubing shape is followed in a continuously repeating pattern until the tubing reaches the lower level of outlet line 63a which is best seen in FIG. 2. This mode of double spiral tubing affords an eicient conguration for use in my novel Water tube heater and has been found satisfactory to obtain maximum heat interception and transfer with the hot gases that ow -through the bundle as described above. The hot uid output at `63a may be combined with the output from another unit such as that indicated at 1417 which is conveyed by means of outlet pipe 6317 to common hot fluid header 118. The combined output of the two units thus provides a source of yhigh-pressure, low-quality steam (which may be of a high quality or of hot liquid alone by making certain modifications to the system) which may be used in a variety of processes including, but not limited to, the recovery of viscous crude in certain types of oil fields, thermal mining of selected minerals, and other applications which `utilize such high pressure hot fluid.

The control panel which I indicate at FIG. l provides 6 housing for control components of a conventional nature including those necessary to start up the fuel and air supply and operate the unit as shown, or multiple units if such be the case.

As mentioned briey in the foregoing specification, heating units embodying my invention may be combined for parallel and multiple operation with a common outlet or with individual high pressure hot fluid lines for use in a variety of combinations, depending upon the type of process being serviced. This is best understood by referring first to FIG. 3 which shows one corner of a heater unit embodying my invention similar in all respects to the unit shown generally at 14a in FIG. 1 except that no second parallel unit, such as that shown at 14b in FIG. l, is provided adjacent to the unit. Wall 66a, shown in FIG. 3, is opposite a wall such as wall 69 and, together with portions of sides such as `64, y65 and floor structure at B, comprise the enclosure for a single heater unit standing alone. Internally, bracket '77a is secured to the inside surface of wall 66a to brace the heat exchanger and flue assembly indicated at F.

When two units are to be combined, as shown in FIG. l, Wall 66a of the unit as shown in FIG. 3, and the adjacent wall of the unit with which it is to be combined, are first removed along with corresponding floor and roof portions employing expedients which are known in the art of structural frames and are not repeated here. The units may then be placed in side-by-side relationship, as shown in FIG. 1; and roof portions 67 of both units, which previously abutted their corresponding walls, such as -Wall 66a, are connected by iiller strip 76 in the parallel arrangement. Filler strips (not shown) for walls 64 and 65, and floor 68, similar to that of strip '76 for the roof portion, are also provided and relatively easily installed to complete the enclosure structure for tWo units in parallel operation. In addition, when units are combined for parallel operation, supports 77a, of the Water tube bundle enclosure and ue combination indicated at F, which are anchored to corresponding walls 66a during single unit operation, are in turn supported by an internal partial wall 78. This gives necessary structural rigidity to the support of the enclosure at F and structurally ties together internally adjacent portions of parallel units.

It is convenient to note here certain other changes which are made when single units, such as those indicated at 14a and 14h in FIG. 1, are combined in parallel arrangement; when the units are thus combined, and if the pressurized air consumption for fuel combustion and gas travel requires such change, various supporting equipment used such as blower 2.9 and motor M1, duct 2.3, and associated parts, may require substitution in part or entirely to provide added capacity. From the arrangement of the units as shown in FIG. 1, and the elimination of walls 65a to combine the units in continuous multiple arrangement, a single blower motor and duct arrangement entering into one of the units walls, as shown by duct 31 entering wall 69, provides air under a positive pressure for both units.

Although I have chosen to show two units in parallel in the arrangement shown in FIG. 1, it is understood that any number of heater modular packages, including the basic chambers indicated at C. D. and F, and corresponding outside enclosure shown in FIG. 2, could be added by merely extending the base frame indicated at B in FIGS. 1 and 2 to the appropriate and necessary length to add such units. In general, it has been found satisfactory to limit two modular heater packages such as those indicated at 14a and 1411 in FIG. 1 to a single structural base; however, this does not prevent the use of several such groups of units in side-by-side arrangement in a single multiple parallel installation.

It is also understood that, although I have described certain necessary structural and air blower modifications 7 that may be required to combine t-wo or more modular units such as those indicated at 14a and 14h in FIG. 1, certain feed water circuit modifications may also be required. If it is desired to combine the hot fluid output of two or more units into a single header, it is generally necessary to assure that the overall pressure drop through the uid circuitry of both units are individually the same or nearly so. This may be accomplished in a variety of ways known to those skilled in the fluid mechanic arts.

The foregoing specification describes one embodiment of my invention utilizing a single Water tube heater or two water tube heaters connected in parallel. However, it is understood that a number of different arrangements making certain mechanical modifications may be practiced within the spirit of my invention and scope of the appended claims.

What is claimed is:

1. In a compact heater suitable for :generating a hot Working fluid by the burnin-g of a low-grade fuel, the combination comprising: a U-shaped airtight enclosure defined by first and second hollow upright members and a transverse curved delivery conduit extending in uid communication between the lower ends of said first and second upright members, means for maintaining said transverse member and first upright member at high temperature; heat exchange means disposed only within said second upright member and spaced above the lower end thereof; means for transferring working uid through said heat exchange means; means mounted at the upper end of said first upright member for introducing fuel into said enclosure; means disposed within said first upright member for initiating the burning of said fuel;

and means for providing air to the upper end of said rst upright member under suicient pressure to produce a hot turbulent mixture of air and burning fuel in said first upright member which is subjected to further turbulence upon passage from said first upright member through said transverse delivery conduit, thereby causing extended burning of said fuel to minimize the low-heat conductive non-burned portion of said fuel that remains when said hot mixture contacts said heat exchange means in said second upright member to inhibit the deposit of the nonburned fuel portion on said heat exchange means.

2. A heater in accordance with claim 1 wherein the said conduit defines an annular ring portion adjacent the lower end of said burner, said ring portion having a tapered surface converging towards the conduit to accelerate the passage of said mixture and produce additional turbulence of said mixture as it passes from said burner to said conduit.

3. A heater in accordance `with claim 1 wherein said conduit is formed of ceramic to inhibit the loss of heat from said mixture during residence in said conduit and prior to passage to said heat exchange means.

References Cited UNITED STATES PATENTS 1,701,836 2/1929 Cannon et al. 110-28 2,035,908 3/1936 Michel 122-250 2,573,910 11/1951 Kreisinger 122-250 X 2,621,635 12/1952 Joosten 122-250 CHARLES I. MYHRE, Primary Examiner.

Claims (1)

1. IN A COMPACT HEATER SUITABLE FOR GENERATING A HOT WORKING FLUID BY THE BURNING OF A LOW-GRADE FUEL, THE COMBINATION COMPRISING: A U-SHAPED AIRTIGHT ENCLOSURE DEFINED BY FIRST AND SECOND HOLLOW UPRIGHT MEMBERS AND A TRANSVERSE CURVED DELIVERY CONDUIT EXTENDING IN FLUID COMMUNICATION BETWEEN THE LOWER ENDS OF SAID FIRST AND SECOND UPRIGHT MEMBERS, MEANS FOR MAINTAINING SAID TRANSVERSE MEMBER AND FIRST UPRIGHT MEMBER AT HIGH TEMPERATURE; HEAT EXCHANGE MEANS DISPOSED ONLY WITHIN SAID SECOND UPRIGHT MEMBER AND SPACED ABOVE THE LOWER END THEREOF; MEANS FOR TRANSFERRING WORKING FLUID THROUGH SAID HEAT EXCHANGE MEANS; MEANS MOUNTED AT THE UPPER END OF SAID FIRST UPRIGHT MEMBER FOR INTRODUCING FUEL INTO SAID ENCLOSURE; MEANS DISPOSED WITHIN SAID FIRST UPRIGHT MEMBER FOR INITIATING THE BURNING OF SAID FUEL; AND MEANS FOR PROVIDING AIR TO THE UPPER END OF SAID FIRST UPRIGHT MEMBER UNDER SUFFICIENT PRESSUR TO PRODUCE A HOT TURBULENT MIXTURE OF AIR AND BURNING FUEL IN SAID FIRST UPRIGHT MEMBER WHICH IS SUBJECTED TO FURTHER TURBULENCE UPON PASSAGE FROM SAID FIRST UPRIGHT MEMBER THROUGH SAID TRANSVERSE DELIVERY CONDUIT, THEREBY CAUSING EXTENDING BURNING OF SAID FUEL TO MINIMIZE THE LOW-HEAT CONDUCTIVE NON-BURNED PORTION OF SAID FUEL THAT REMAINS WHEN SAID HOT MIXTURE CONTACTS SAID HEAT EXCHANGE MEANS IN SAID SECOND UPRIGHT MEMBER TO INHIBIT THE DEPOSIT OF THE CONBURNED FUEL PORTION ON SAID HEAT EXCHANGE MEANS.

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