US2038580A - Method and apparatus for generating steam - Google Patents

Description

April 28, 1936. w p LA M T I 2,038,580

METHOD AND APPARATUS FOR GENERATING STEAM 9 sheets-sheet 1 Filed Jan. '7, 1927 ATTORNEYj FEED INVENTOR Mum DOI/GMSM/VINT 'April 28, 1936- w. D. LA MONT METHOD AND APPARATUS FOR GENERATING STEAM Filed Jan. '7, 1927 9 Sheets-Sheet 2 April 28, 1936. w p LA MONT I 2,038,580

METHOD AND APPARATUS FOR GENERATING STEAM Filed Jan. '7, 1927 9 Sheets-Sheet 3 INVENTOR M44 TEI? 0006M! MNQA/T ATTdRNEYfl Ji /MM A ril 28, 1936. w. D. LA MONT V METHOD AND APPARATUS FOR GENERATING STEAM 9 Sheets-Sheet 4 Filed Jan. '7, 1927 3 Z M. 3 Z w /.M m 4 f F mw/ m ,9 E ,wwirlT \\\\\\\\\\\\S III 4 0 a n J 4. a 7 2 3 3 jaw ' INVENTOR W44 rm 5006M: Z/Wwvr ATTORNEYS INVENTOR L ATTORNEYS 9 Sheets-Sheet 5 w. D. LA MO NT METHOD AND APPARATUS FOR GENERATING STEAM Filed Jan. 7, 1927 April 28, 1936.

A nl 28, 1936- w. D. LA MONT METHOD AND APPARATUS FOR GENERATING STEAM 9 Sheets-Sheet 6 Filed Jan. 7, 1927 T mm TM N A W J m 9 R w M AITORNEYj April 28, 1936. A w. D. LA MONT 2,038,580

METHOD AND APPARATUS FOR GENERATING STEAM Filed Jan. 7, 1927 9 Sheets-Sheet '7 INVENTOR W44 75/? 0006/45 ZA/Vm/T Ma 5W A'ITORNEYJ April 28, 1936. w 11 LA MONT 2,038,580

METHOD AND APPARATUS FOR GENERATING STEAM Filed Jan. 7, 192 7 9 Sheets-Sheet 9 l I V f 5 1' 1 I 757 fi/j/i'm w i 0 FEED 19/ /7j /fl3 fulll l v y/wz' I j Patented Apr. 28, 1936 METHOD AND APPARATUS FOR- GENERATING STEAM Walter Douglas La Mont, Larchmont, N. "2., as-

signor to La Mont Corporation, New York, N. .Y., a corporation of New York Application January 7, 1927, Serial No. 159,572

30 Claims. (01. 122-1) This invention relates to methods of generating steam and other vapors and to generators therefor.

In the past it has been proposed to increase 5 the efiiciency of steam generators by auxiliary apparatus which serves to heat up the feed water and which .may be placedin the stack of I the generator furnace or any other suitable point. Economizers of the common type represent a 10 distinct improvement in generator efiiciency but they are open to a number of disadvantages. Thus; for example, the circulation of water or other liquid through the tubes is relatively slow, as only the water actually transformed into steam 15 in the steam generator has to be made up by the introduction of fresh amounts of feed water. This relatively sluggish flow renders the economizer eements liable to the formation of scale and when the steam demands on the generator 20 are'very variable it sometimes happens that a temporary cessation in steam demand with a corresponding cessation of flow of Water through the economizer is not accompanied by a corresponding combination of a liquid heating means performing the function of an economizer with primary vapor generators which combination avoids-in part or in who-1e the disadvantages inherent in 35 economizers hitherto used. A further object of the present invention consists in an improvement of the circulation of primary vapor generators whereby the combination increases the efliciency of. the generator, not only by an economizer action but by an actual increase of generator efilciency within the generator itself. Other and further advantages and objects of the invention will be apparent from the following more detailed description taken in conjunction with the draw- 45 ings which illustrate some typical modifications of the present invention. I f Essentially the present invention consists of one or more primary steam generators and an associated auxiliary heating circuit provided with a positive independent circulation from which circulation water is fed to the steam generators in accordance with their demands. In the preterred embodiments of the present invention the pressure in the auxiliary circuit is substantially the same or slightly more than in the steam generator. I do not claim in this application positively circulated auxiliarycircuits in which notable amounts of vapor are generated at a pressure materially higher or lower than that obtaining in the steam generator or generators, this forming part of the subject matter of my copending application, Serial No. 115,169, filed June While in its broader aspects the present invention is not concerned with any particular type of positively circulated auxiliary heating circuit,

in its preferred and more specific embodiments the present invention includes auxiliary econom'zer circuits in which the water is circulated through the heating elements in the form of a film and in some of. the modifications preferably in the form of a film on the inside of tubular heating elements which for brevity will be termed La Mo-nt film tubes and which may advantageously embody some or most of. the structural 20 features of the La Mont film tube steam generators such as are described in my prior patent, No. 1,545,668, and my co-pending application, Serial No. 32,064, filed May 22, 1925.

Film tube economizers with the extraordinarily high heat transfer which the film principle makes possible, particularly when associated with a suitable arrangement of tubes so as to achieve advantageous gas velocities and hydraulic mean depths, are particularly important in economizer circuits and present in these circuits even greater increases in efiiciency than in steam generators, since economizers are commonly operated by means of heat sources at a relatively much lower initial temperature than is the case with steam generators. Accordingly the high efiiciency of La Mont film tube economizer circuits permits a very great increase in over-all efiiciency since the temperature of stack gases, where the economizer is placed in the stack of a generator, or of other waste heat gases may be reduced to a very low figure.

In the ordinary economizer in which the Water is circulated directly in series through the economizer into the generator the object is not does not occur reduces theheat transfer efficiency of the elements. It'is therefore the practice in common types of economizers to prevent the formation of any considerable amounts of steam.

The positively circulated auxiliary economizer circuits of the present invention may be run on this same general principle, that is, with the object of generating as little steam as possible. With a positively circulated economizer circuit it is, however, possible to separate out steam easily and readily and to unite the steam with that of the main generator or to use it separately. Such a circuit which performs the function of an economizer and an auxiliary generator and which at times may perform solely the one function or solely the other or a combination of both will hereafter be referred to as an economizer generator circuit and it is an advantage of some of the more specific embodiments of the present invention that valuable economies can be effected by utilizing economizer generator circuits. This is particularly true when film tube circuits of the La Mont type are used for the reason that with high stack temperatures such as are frequently encountered with common types of mass boiling generators when they are forced to very high ratings, the amount of heat available in the stack gases and which may be absorbed by suitable film tubes is greatly in excess of the amount of heat necessary to heat up the feed water for the steam generator. In such cases, steam may be generated in smaller or larger quantities in a film tube economizer generator circuit and a maximum. utilization of the heat of the gases may thereby be realized. Moreover the system is extremely flexible and wide variations in stack gas temperature or volume or both may be taken care of by -an economizer generator circuit of moderate size. The constant circulation of water prevents the burning out of tubes and aids .in maintaining freedom from scale, and wide fluc- N tuationsin stack gas heat content and volume can be taken care of by generating more E less .steam in'the economizer generator circuit.

The amount of water circulated through the economizer circuits or economizer generator circuits of the present invention may vary within wide limits. The amount of circulation is in most cases a compromise. For maximum thermal efliciency the circulationshould be practi cally no greater than the amount of feed water introduced, so that the water entering the coolest portion of the economizer elements is at, a minimum temperature and is thereby capable of abstracting a maximum of heat from the stack gases, particularly where the latter flow over the economizer elements counter to the flow of water in'contact therewith, the most efficient and preferred arrangement. It is, however, not possible to take care of considerable fluctuations of feed water demands of a steam generator with a circulation which is so small and if full tubes are utilized the water velocity through the tubes may be insufiicient to assure the prevention of steam locking, and to provide for a' desirable scouring action to maintain the tubes free from scale. When film tube economizer elements are used the circulation can be very greatis necessary with full tubes.

1y reduced because the travel of the film requires a very much smaller volume of water than In all cases, however, the circulation must be determined in order to achieve a maximum of safety and thermal efficiency and this invention is not essentially concerned with any definite circulation amounts which must be determined for each individual case in accordance with the operating conditions encountered in the particular installation.

When full tube economizer circuits or economizer generator circuits are utilized they will in general maintain a pressure substantially the same as that in the main generator or rather slightly in excess so as to effect feeding. When, however, film economizer circuits are used it is usually not practical tomaintain a pressure in the economizerelements themselves which is equal to that of the steam generator unless the economizer is also a generator of considerable amounts of steam. Accordingly, in the ordinary film tube economizer circuit of the present invention suitable valves must be provided in conjunction with the circulating pump or other device, so that while the pressure in the economizer elements themselves and in many cases throughout the connections between the elements and the suction of the pump, is much lower than that obtaining in the steam generator and may in fact-be but little, if any, above atmospheric pressure, the pressure in the por-' treme cases may be maintained by the drop in pressure through the film element injection nozzles or orifices, although, for most purposes, this drop in pressure is insufiicient and is diiiicult to regulate.

The maintenance of the proper pressure and the amounts of water fed from the economizer circuit into the steam generator or in the case of a plurality of generators into the different generators, can be effected by manual control or by automatic control or by a combination of the two. I prefer, in most cases, to provide suitable water levels in the film economizer elements or their connections and in the steam generator and operate their valves controlling the amount of water fed from the economizer circuit into the generator and the pressure in the pump discharge circuit from these various levels. It will be clear to the skilled engineer that a very large number of possible control modifications can be used to bring about this effect. Some arrangements which I have found to be desirable in certain cases are illustrated in the drawings but it should be clearly understood that the invention is in no sense limited to these particular control arrangements and, on the contrary, any suitable control may be used andthe proper control or combinations of controls will be determined by the skilled circulating pump is not under great pressure and the problem of suitable stufling boxes to prevent leakage is greatly simplified and where the pres sure is not greater than that of the atmosphere, practically nonexistent.

The same lower pressure permits the introduc-, tion in this portion of the circuit of relatively large drums or other vessels without excessively heavy construction. While it is an advantage to keep the actual circulation through the film elements at a very low amount when compared to the amount of feed water introduced there is a distinct advantage in providing a satisfactorily large reserve volume in the circuit to take care of sudden fiuctuations in demand. This can be done simply in film economizer circuits by means of relatively thin walled drums or other storage reservoirs which can be inserted in the low pressure portion of the circuit. The large volumes of water which may thus be retained in the circuit without decreasing its thermal efiiciency also renders it a simple and easy matter to separate the impurities from the feed water by well known purification processes. It is an added advantage therefore of film tube economizer circuits that simple and reliable means for removing solids from the feed water can be incorporated in them without the necessity of expensive structure.

The advantages of low pressure in a portion of the economizer circuit are particularly simply and easily obtained with film economizer circuits. It should be understood, however, that a similar advantage can be obtained in full element economizer circuits although not as readily. The invention therefore includes circuits having zones of low pressure, irrespective of whether the circuits utilize film elements or full elements.

In the general description which has been given above film elements and full elements have been discussed as two sharply divided and qualitatively difierent systems. As a matter of fact, however,

there is no absolutely sharp line since, if the amount of water introduced into the top of an element is gradually increased the film which I first forms will increase in thickness until the .thermal efficiency throughout.

element approaches a condition in which it is difiicult to determine whether it is a full element or whether a true film exists for the full length of the tube element. Thus, for example, as the amount of water introduced into a tube is gradually increased, the tube may be full for a short distance from the top and the water may then gradually form a film. The present invention is therefore not limited to two definitely demarcated types of economizer circuits and includes any positively circulated economizer circuit whether film or full element or some intermediate condition.

The combinations which are possible particularly with economizer generator circuits render the present invention extremely flexible in its application, particularly to installations operated by a plurality of heat sources which may be intermittent or fluctuating and also installations in which a very variable steam demand is present. Such combinations automatically adjust themselves to varying demands and maintain a high Economizer circuits of the present invention may be associated with any known types of steam generator, whether film tube, water tube, fire tube or flash, and this wide range of applicability is one of the advantages of the invention.

The invention will be described in greater detail in connection with the drawings, in which Figure 1 is .a diagrammatic section through a film tube generator and economizer generator situated in the same stack; 7

Figure 2 is a similar section of a modified type of film tube generator and film tube economizer having series gas fiow;

Figure 3 illustrates a film tube generator and separately heated economizer;

Figure 4 illustrates a vertical water tube boiler with an economizer in the stack;

Figure 5 illustrates an inclined water tube boiler with an economizer in the stack;

Figure 6 illustrates a combination of a positive ly circulated water tube generator and a common type of water tube generator having convection circulation;

Figure 7 illustrates the combination of two separate water tube boilers associated with a single economizer circuit;

Figure 8 illustrates the combination of a water wall, a common type of water tube generator and a fire tube economizer;

Figure 9 illustrates the application of an economizer circuit of the present invention to a common type of water tube generator and feed water heater; and

Figure 10 is an enlarged sectional detail of a header and a portion of a tube showing the injection orifices.

In the constructions shown in Figure l, a conventional type of film tube. generator is shown having upperheaders l,lower headers 2, tubes 3, a pot 9 and a pump 4. The circulation is from the pump 4 through the pipe 5 into the upper headers I which are provided with orifices as shown in Figure 10 whence the water fiows in the form of film down through the tubes 3 into the lower headers 2 and into the pot 9 where steam is separatedand taken off through the pipe 6 provided with a control valve 1 and excess water is returned to the pump through the pipe 8.

The economizer which is located in the stack above the film tube generator consists in upper headers I I, lower headers l2, tubes l3, pot l9, pump l4 and circulating pipes l5 and I8 connecting the pump'with the upper headers II and pot l9 respectively. A steam take-off from the pot I9 is effected through the pipe l6 provided with a control valve ll, the pipe joining the main steam pipe 6,. The water circuits of the economizer and the generator are connected through the 131128 2| which leads from the pipe 15 to the pipe 8 and is provided with a control valve 22. Feed water for both, systems is introduced into the pipe I5 through the pipe 23 provided with a control valve 24. The pots 9 and I9 are provided respectively with water level controls In and 20 which in turn actuate the valves 22 and 24.

being generated and passing off through the pipe 6. At the same time water is being circulated through the economizer circuit by means of the pump l4, the pressure of the two circuits being substantially the same. Obviously, of course, the pressure in pipe 5.is slightly higher than in the pipe 8 to compensate for the pressure drop through the orifices in the upper headers l and correspondingly the pressure in the pipe I 5 is slightly in excess of that in the pipe l8. As the water level falls in the pot 9 and connecting pipe 8, the water level control I0 operates to open the valve 22, permitting water from the pipe l5 to fiow into the pipe 8 and therefore into the circulation of the generator circuit. This results in a lowering of the water level in the pot I!) of the economizer and the associated pipe l8 and causes thewater level control 20 to operate the valve 24 introducing feed water into the pipe I5, whence it is circulated through the headers ll and tubes l3 and is heated by the gases passing up the stack.

The economizer circuit may be run either as a straight economizer or as an economizer generator by opening or closing the valve II. If the circuit is run with the tubes l3 full of water it is possible to run the circuit either as a straight economizer or as an economizer generator. If, however, the headers II are provided with injection orifices as shown in Figure and the cir: cuit is operated as a film tube circuit the valve I! is preferably permitted to remain open and the circuit then operates as an economizer generator, any steam generated being separated in is kept "at a minimum as it is cooled by the incoming .feed water for both circuits and. it is therefore possible to reduce the temperature of "the stack gases to a very low point with correspondingly high over-all efiiciency. Wide fluctuations in firing and in the rating under which the main generator operates are easily taken care of, as even if the rating is increased to the point where .thestack gases are very hot, the economizer generator "canreadily take care of the extra heat by the evolution of an increased amount of. steam which is added to that of the main generator and utilized.

It should be ,understood that Figure 1 and the other drawings in this application are purely diavided with any of the structural features or acgrammatic and many structural features and accessories which are unnecessary to show the novel methddsgof operation of the present invention have been omitted for the sake of simplicity. Of

course, in actual installation such suitable structural features and accessories, such as safety valves, blow-offs and the like .will be included. Inv general, the'film tube generators and'economizer generator circuits shown in Figure 1 may be processories which are described and illustrated in my prior patent and application above referred to.

As the temperature of the heating gases decreases they shrink in volume and it isdesirable in many cases to reduce the gas passage correspondingly in order to maintain high velocity which is desirable in effecting efficient heat transfer. In the drawings this effect has been achieved bydecreasing the spacing of the tubes l3 inthe direction of gas flow. Obviously, of course, a similar arrangement can be utilized in connection with the tubes 3 and in general such modifications of the structure and arrangement of the generators as may prove desirable are included in the present invention.

In Figure 2 a film tube generator and associated film tube economizer isshown, but no provision is made for generating and separating any considerable volumes of steam in the economizer circuit. Similar elements bear the same numerals as in Figure 1 Instead of providing a steam outlet from the pot is of the economizer both the water and any steam which may be formed pass through the pipe l8 connecting pot [9 with the pump I4. In this pipe 18 is the large tank 25 where impurities introduced by the feed water may be separated. The pressure the economizer tubes themselves is very much lower than that in the main generator and accordingly a suitable throttle valve 26 is provided in the pipe I IS in order to reduce the pressure to a suitable box of the pump tight is practically eliminated due to the low pressure. A further advantage lies in the fact that since the pressure in the elements I3 is very much lower than in the main generator, the water temperature is correspondingly low throughoutthe full length of the tubes and therefore the stack gases can be reduced to an exceedingly low temperature and in general to a considerably lower temperature than is possible when economizer generators are run at the same pressure as the main generator as illustrated in Figure 1. i

A modified feed control is'shown, the water level I0 not only controlling the valve 22 but also the feed valve 24 which introduces feed water into both systems. Obviously, of course, a separate water level can be provided on the tank 25, for controlling the -valve 24, as is shown in Figure 1. In fact, either method of control canbe used in connection with either system and any other suitable control method may be substituted therefor. In this respect the drawings are not intended to limit the invention but merely illustrate a number of suitable modifications.

In Figure 3 a separately heated economizer circuit is shown, the type illustrated being conn'ected to a source of intermittent waste heat such as, for example, a water gas plant, a suitable valve 26 being provided to control the heating gas flow. The economizer generator circuit is connected to the main generator circuit in the same manner as in Figure 1 andthe same parts are designated by the same numerals. A very efficient utilization of waste heat is made possible by the fact that whenever the waste heat gases flow through the economizer generator their heat is absorbed and efficiently utilized either in the form of sensible heatof the water introduced into the main steam generating circuit or in the form of steam when the amount of waste heat is sufficient to raise steam. Wide fluctuations in amount and duration of waste heat are easily taken care of by the arrangement shown which is very flexible and is applicable to a number of different types of installation.

Instead of waste heat a separately fired economizer may be used and in certain cases is advantageous. Thus, for example, a cheap fuel, such as, for example, low grade coal slack or breeze can be used, requiring a steady even firing and the main steam generator may be fired by powdered coal or oil or some other source of heat which can be varied rapidly. The relatively low temperature which is produced by firing the low grade fuel is effectively utilized as the economizer generator circuit may be efficiently operated at very low ratings.

A single separately heated economizer-generator circuit may be associated with a. single main generator or a plurality of economizer circuits maybe associated with a single generator or a single economizer circuit with a plurality of generators. The most satisfactory and eflicient arrangement will be determined in any case by the It should be noted that. the invention is not skilled engineer and the present invention is not in any sense limited to the particular arrangement shown.

Figure 4 illustrates a combination of a positively circulated economizer generator with a vertical water tube boiler of the Wickes type. The Wickes boiler, which is of conventional design, consists in an upper drum 21, lower drum 28, front water tubes 29, rear water tubes 30 and a bafile 3!. The circulation in the Wickes boiler is the usual convec tion circulation and is ordinarily downward in the tubes 30 and upwardin the tubes 29. Steam is separated in the drum .21 passing out through the pipe 32 controlled by the valve 33.

The economizer which is placed in the stack is of similar design to that shown in Figure 1, consisting in upper headers H, lower headers l2, pot l9 and tubes l3. The steam space of the pot I9 is connected to the steam space of the drum 2! by means of the pipe 16 provided with a check valve 34. Water from the pot l9 passes through the pipe l8 into the pump l4, whence it is circulated back to the upper headers H through the pipe ISL Feed is introduced into the-pipe I5 near the upper headers I I by means of the pipe 23 controlled by the valve 24, which'is in turn actuated by the water level control 20 operating on the water level in the pipe I8 and pot I9. A valve 35a is also provided in the pipe I5 when it is desired to run the economizer as a film tube economizer without generating steam. The circulation in the economizer circuit is precisely the same as that described in Figure l and any steam generated mixes with the steam in the Wickes boiler. The check valve 34, however, takes the place of the manually adjustable valve H in Figure 1, and prevents back flow of steam from the Wickes boiler to the economizer circuit, should the latter at any time be at a lower pressure.

Feed is introduced into the Wickes boiler from the pipe l5'through the pipe 36, controlled by the valve 31, which is in turn actuated by the water level control 38 operating on the upper drum 21. Preferably, the pipe 36 is carried into the drum 28 and discharges directly into the bottom of the tubes 29 in order to effect a maximum improvement of circulation in the. Wickes boiler. In many cases it is desirable to provide the pipe with nozzies which actually project into the tubes 29.

In operation, water is circulated through the economizer circuit either in a full tube or film tube condition and any steam which is generated passes off through the pipe l6 and check valve 34 into the drum 21. When the economizer circuit is operated as a film tube economizer generator, the operation is the same. When, however, it is operated as a film tube economizer without generaiion of steam the pressure normally in'the tubes l3 will be lower than that which obtains in the Wickes boiler and accordingly it is necessary to introduce a pressure transformer between the junction of the pipes l5. and 36 and the upper headers I l in order to permit the maintenance of a higher pressure in the pipe 36 than that which obtains in the tubes l3. A simple throttle valve 35a can be used as pressure transformer or any other suitable device may be substituted.

The feed into theWickes boiler is controlled by the water level control 33 which determines the amount of water fed from the pipe l5, whereas the feed into the economizer circuit is controlled by the water level control 26, the control arrangement being similar to that shown in Figure 1.

limited to the particular arrangement of controls and other devices which are illustrated in the The arrangement shown in Figure 4 is an unusually efilcient arrangement since it renders practical operation of the Wickes type of boiler at relatively high ratings which would otherwise be very wasteful owing to the fact that the Wickes type of boiler cannot ordinarily be forced to high ratings without very serious stack losses. The

highly efiicient arrangement of economizer elements serves to absorb the heatof the stack gases,

even when unusually high ratings are necessary.

A serious disadvantage of the Wickes type of boiler is thus overcome and the present invention makes it possible to utilize Wickes boilers for purposes for which they were but poorly suited. A further advantage of the modification shown is that it can be embodied in existing installations with a minimum of rebuilding, thus making possible the economic utilization of the old installations which had outgrown their usefulness and also makes it possible to carry peak loads economically with boilers which had been designed for much smaller loads. Gas velocity is maintained throughout the whole economizer by progressive decrease in size of the gas passages to make up for shrinkage due to cooling.

In the modification illustrated a single economizer is associated with a single generator but obviously, of course, one economizer may be used to take care of a number of generators.

Figure 5 illustrates an economizer circuit associated with inclined tube water tube boiler of conventional design. The boiler consists in a drum 31, front headers 38, rear headers 39 and tubes 40, pipes 4| and. 42 connecting the drum to' the headers 38 and 39 respectively. Steam is taken off through the pipe 43 controlled by the throttle valve 44. The circulation is of the usual convection type.

The economizer circuit is similar to that shown in Figure 2 and the corresponding parts bear the same numerals. In operation, feed water is introduced through the pipe 23 controlled by the valve 24 which is actuated by the water level control 20 and is circulated by means of the pump 14 through the tubes l3, the pressure being reduced by the pressure transformer 26 which is situated in the pipe [5. The film tubes or elements l3 therefore operate at a very low pressure which may be but little, if any, above atmospheric pressure. It is thus possible to reduce the temperature of the stack gases to an exceedingly low figure and a relatively large settling tank and water reservoir 25 can be provided without entailing expensive construction. The low pressure also renders the problem of tight stufling boxes in the pump l4 relatively simple.

Water for the water tube generator is fed through the pipe 45 which connects the pipe IS with the pipes 42. A suitable control valve 46 is provided in the pipe 45 and is actuated by a water level control 41 operating on the drum. The advantages of a low pressure in the heating elements of the economizer circuit shown in Figure 5 are, of course, the same as those described in connection with Figure 2. Similar economizer circuit arrangements are possible with othef'common types of boilers and only one or two typical boilers are shown in the drawings, the invention not being limited thereto nor to the particular combination shown. Thus, for example, in Figure 4, an economizer generator circuit isshown associated with a Wickes type boiler, whereas in Figure 5 a straight film economizer circuit is shown in connection with an inclined tube water tube boiler. Obviously, of course, a lower pressure economizer circuit can be associated with a Wickes type boiler or an economizer generator circuit with an inclined water tube boiler such as that shown in Figure 5 In general, the particular type of economizer or economizer generator circuit to be used in any particular installation will be determined by the skilled steam engineer in accordance with the operating conditions and structural features of the installation.

In theforegoing figures special forms of economizer circuits resembling La Mont film tube generators in their general arrangement have been shown. For many, if not most purposes, this general type of economizer circuit or economizer generator circuit is the most suitable and constitutes the preferred form. Other types of posi tively circulated economizer circuits may, however, be used and in some cases present advantages. Such an arrangement is shown in Figure 6, where a single pass Edgemoor boiler is shown redesigned to give a positive circulation and acting as an economizer generator in association with a Ladd type water tube boiler.

The Edgemoor boiler consists in an upper steam drum 48, lower drum 49, generating tubes 50, rear drum 5|, return circulation tubes 52 and pump 53. The tubes 52 unite in a header 54 which is connected to the suction of the pump 53 by the pipe 55. From the discharge of the pump 53 the pipe 56 connects to the drum 49. The circuit is completed by the pipes 51 and 58 which join the steam and water spaces respectively of the drums 48 and 5 I. The pipe 56 is provided with a control valve 59 actuated bya water level 60 which operates on the drum 48. A conventional design of superheater and feed .water preheater or economizer is shown associated with the Edgemoor boiler. This preheater consists of pipes 6| which join headers 62 and 63, feed water being introduced through the pipe 64 into the latter header and. the heated water, together with any'steam formed passing into the drum 5| through the pipes 65.- Saturated steam from the drum 5| may either be taken off directly through the pipe 66 controlled by the valve 6! or in usual operation is passed through the pipe 68 into the header 69 of the superheater and thence through the superheater tubes 'I0 and out into the superheating steam pipe II.

A conventional Ladd type water tube boiler is shown consisting in upper drum I2, lower drum I3 and three sets or bundles of tubes I4, 15, and 16 with associated bailles TI and I8. As is usual in v the Ladd type construction the lower drum I3 is divided into a large chamber 19 and a small chamber 190. by the baffle 80, the tube bundles I4 and I5 connecting the upper drum 12 with the space 13, whereas the rear tube bundle 16 connect-s thespace 19a with the upper drum. Feed water is introduced from the discharge of the pump 53 through the'pipe 8| into the space 19a of the lower drum. A control valve v82 is provided in the pipe 8I and is actuated by a'water level control 83 operating on the upper drum I2. The circulation in the Ladd generator is the usual convection circulation in the tube bundles I4 and I5. Feed water passes up through the bundle I6 into the upper drum aiding this circulation.

The combination of a single economizer generator circuit with two common types of water boiler is shown in Figure '7. The two boilers illustrated are a bent tube boiler of the Stirling type consisting in upper drums 84, 85, and 86 and a lower drum 8! which is connected to the upper drums by the tube bundles 88, 89 and 90 respectively. Steam and water spaces of drums 85, and 86, are connected by pipes 9| and 92 respectively. The second generator is a conventional type of cross drum inclined tube water tube boiler consisting in a steam drunY 93, tube headers 94 and 95, collector drum 96, generating tubes 91 and return tubes 98, the drums 93 and 96 being connected with theheaders and 94 by the pipes 99 and I00, respectively. Steam is taken off in the usual manner from the drums 86 and 93 by steam pipes not shown. The gas circulation through the generators is indicated by the arrows and induced draft is produced by two stack fans IN and I02 respectively, which discharge into ducts I 03 and I 04 provided respectively with control dampers I 05 and I06. The two ducts join into a single stack I01 in which a film tube economizer generator is located. The generator consists in an upper collector header I08, upper headers I09, lower headers 0, tubes III and a pot or collector II2. Circulation is downwardly from the lowest point of the pot I I2 through the pipe II3 to the pump II4, whence the water passes up through the pipe II5 into the upper collector header I08.- Feed is introduced into the pipe II5 from the pipe II6 controlled by the valve II] which is in turn actuated by a water level control II8 operating on the pipe II3. Any steam generated is separated in the pot H2 and passes oif through a. steam pipe I I9 controlled by a valve I20.

Feed water for the two water tube generators is taken from the pipe II5 through the T I2I and pipes I22 and I23 provided respectively with control valves I24 and I25 which are in turn actuated by the water level controls I26 and I2! operating on the drums 85 and 93 respectively. I

In operation each of the water tube generators vcanbe separately fired and operated independently, the amount of feed waterv introduced being constantly controlled by the respective water level controls. The waste heat ln the stack gases from the two generators is efliciently utilized in the economizer generator circuit which generates steam at substantially the same'pressure as the two generators, which steam may be, if desired,

mixed with the steam from the two main generators. At the same time, feed water for all three systems is introduced into the pipe I I5 and thence into the top of the elements I I I. As a resultthe temperature of the water-e tering the top of the tubes or elements I I I is ve low owing to the relatively large proportion of feed water to water circulated from the pump II4. A very efficient utilization of the stack heat is thereby 1 assured.

The draft through the water tube generators is controlled by the dampers I05 and I06 and in fact the whole operation of the water tube genber of the economizer. The water in this upper erators is substantially independent although if desired the generators may be fired together. Two different types of water tube generators have been shown arranged in a battery but ,obviously the generators may be of the same'type and a much larger number may be associated together placed in the stacks which provide draftv for the batteries and it is an advantage that in the case of old installations the economizer generator circuits of the present invention can be installed without radical rebuilding.

Figure 8 illustrates a combination of an economizer circuit using a fire tube economizer with a water tube steam generator and with a water wall enerator associated therewith. The water wall the return pipes I32. A circulation pipe I33 connects the steam space of the drum I28 with the steam space of the drum I3I, and serves to permit the circulation both of steam and water. The design of the generator is similar to that of the well known Edgemoor single pass generator.

The furnace walls are protected by water walls consisting in upper headers I34, I35 and I36, lower tubes are separated inthe lower headers i31, I38

and I39, and the steam passes ofi through the branched pipe I46 which connects with the steam pipe I41 from the drum I3I. The pipe is provided with a suitable valve I48.

In the stack of the furnace a fire tube economizer is placed, consisting of a shell I49, upper head I50,- lower head II and fire tubes I52. A perforated plate I53 is mounted a short. distance below the upper head I56 and fits loosely around the fire tubes, so that substantially annular orifices are formed between the tubes and the plate. The economizer is thereby divided into a small upper water chamber between the head I59 and the plate I 53 and a larger main chamber between the plate I53 and the lower head |5I. In this lower chamber a water level is maintained by means of the water level control I54 operating on the valve I55 in the feed water line I56. If desired, the water level may be maintained in tank I56 instead of in the main chamber. Water is circulated from the water. space of the economizr through the pipe I51 into a slow point or treatment tank I58 and thence by the pump I5 9 through the pipe I60 into the upper water chamchamber then trickles down through the annular orifices forming a film on the outside of the fire tubes and the advantages of high heat absorptionwhich are provided by the film, are obtained. Any

steam generated passes oif through the pipe -I6I either into the main steam pipe I41 or into a separate pipe I62, the former being provided with a valve I63 and the latter with a valve I64, while a third valve I65 is placed in the pipe I6I between the two outlet pipes. It is therefore possible to pass the steam from the economizer either out through the pipe I62 or into the pipe I41 or part through one pipe and part through the other, as may be required by the particular operatingconditions.

Feed water for the water tube boiler is taken from the pipe I60 throughthe pipe I66 into the lower drum I29, a branch pipe I61 carrying water to the pipe I44 in the water wall system. This latter pipe may advantageously be provided with a valve I68 controlled by a water level control I69 operating on any of the lower headers of the water wall, and shown for example, in the drawings as operating on the lower header I39. A similar. control of feed can be used in connection with the water tube boiler.

In operation, feed water for all three systems is taken into the economizer circuit through the pipe I56, is heated in the economizer with or without the generation of steam, purified by the settling or treating tank I58 and then forced by the pump I59 through the economizer circuit and also into the circuits of the water tube boiler and the water wall system. The economizer circult may be run at the same pressure as exists in the water Wall boilers and in the wafer tube boiler or a lower pressure may exist in the actual heating elements of the economizer circuit. This can be efiected by partially closing the thro'tle valve I16 which is situated in the pipe I69. When, of course, the pressure in the economizer is lower than in the other two generators any steam generated must be permitted to pass off through the separate pipe I62, which can be effected by a suitable operation of the valves I64 and I65. Operating the economizer at a lower pressure than that obtaining in the generators is frequently highly advantageous since it is thus possible to use a much lighter construction of economizer and treating tank than would be possible if high pressures were used and at the same time, the lower pressure with corresponding lower temperature in the economizer permits the reduction of the stack gases to a temperature which is considerably lower than that possible when the economizer is run at the same pressure as the main generator. This effects a notable saving in heat, particularly when the main generator and the water walls are run at very high ratings which would normally result ina considerable heat loss due to high stack gas temperatures.

Figure 9 illustrates a simple applicalion of an An economizer generator comprising upper headers I16, lower headers I11 and tubes I18 is placed in the stack and the heating chamber is progressively decreased in cross-section in the direction of gas flow in order to maintain uniform velocity in the steadily shrinking gas stream.

Water and steam from the lower headers I11 are discharged into the tank I18 through the pipe I19. From the bottom of this tank, water is fed into the rear header I13 of the generator through the pipe I80, pump I8I and pipe I82. The pump is driven by an electric motor or steam turbine I83 controlled from the water level I84 on the drum I1I. Steam which is separated in the tank I18 passes out through, the valved pipe I85 provided with a check valve I86. The economizer circuit may be operated at the same pressure as the generator in which case the steam from the pipe I85 may be passed into the boiler lead I81 through the pipe I88, the combined output passing through the main steam pipe I89 controlled by the throttle I90 and finally entering the high pressure stage of a turbine I9I.

A feed water heater- I92 provided with the usual trap- I93'and filtering layer I94 is arranged so that it takes the overflow from the tank I18 through.the valved pipe I95. Feed water isintroduced through the valved pipe I96 and introduction is controlled by a water level I91 operating on the feed water heater. Steam is bled from the intermediate pressure section of the turbine through the pipe I98 into the feed water heater where it heats up the incoming water. The water from the lower portion of the feed water heater is forced by' the pump feed 200- through the pipe I99 into the upper header I16 of the economizer circuit.'

Under normal operation, the feed pump 209 runs at constant speed and continuously circulates water through the pipe I99 into the econornizer which may be of the full tube, film tube, 01' any intermediate type. The suction of the pump 298 is constantly provided with a water head by the water level control I91 which determines the amount of feed water input. The water passing through the economizer tubes I18 is heated and may generate steam at apressure equal to that of the generator or at a lower pressure. When operating at the same pressure, with the steam pipe I85 connected through the pipe I88 to the steam line of the main generator, the check valve I86 prevents back-flow of steam and insures even operation. The water separated from the steam in the tank I18 is fed in varying amounts into the main generator, the rate .being varied by the speed of operation of the pump IBI, which is, in turn, controlled by the water level in the drum I1I. Normally, the pump 290 is set to deliver sufficient water to take care of the maximum feeding rate of the pump I8I, although this is not essential. Whenever the feeding rate of the pump I8I drops below the rate at which water flows into the tank'I18, the water level in the latter rises and overflows into the feed water heater where the water may be further heated together with the cold incoming feed by means of the steam bled from the turbine. Thence, the partially heated water is again circulated through the economizer. The amount of steam bled from theturbine may be controlled by the valve 2M which may advantageously be an automatic valve and may be controlled by .the water level control I91 or by the pressure in the feed water heater or. by thermostatic means. f

The installation illustrated in Fig. 9 represents a very simple means of utilizing installations which are already in use and which may be provided with feed water heaters. A minimum of rebuilding or redesigning is necessary. Where new installations are made, it is usually unnecessary to provide a feed water heater as the economizer due to its higher efliciency is usually sufficient to supply the adequate amount of preheating. Wherever desired, however, a feed water heater may be associated with economizers of the present invention.

In Figs. 1 to 8, the control of feed into the main generator is usually shown as effected by the opening and closing of a valve in the piping from the economizer circuit to the generator. In Fig.

9, however, the control is shown as effected by va-' riation of the speed of the pump feeding the generator and a similar method may be utilized in connection with the other modifications shown in the other figures of the drawings. The drawings are intended to illustrate a number of possiblecontrol modifications, but, of course, they cannot exhaust the field of practical combinations, and it should be clearly understood that the invention is not limited to the precise details and arrangements set forth in the various-.figures.

In the figures, regulation of feed has been by opening and closing valves or by varying the speed of a pump. Control may also be eifected by intermittent operation of the circulating pump of the economizer circuit, that is to say, when the feed demand ceases, the pump can be caused to stop and when demand again rises, the pump starts up again. Combinations of pump speed control and valve opening may, of course, also be used and are covered in the invention.

The invention has been illustrated in connection with a number of common types of boilers which are only a few illustrations of a number of possible combinations. The invention is in no sense limited in its utility to combinations with the generators shown. Thus, for example, insteadof the water tube or film tube generators which have been illustrated, the economizer or economizer generator circuits of the present invention may be associated with many types of fire tube boilers and such combinations present marked advantages for certain uses.

The preferred type of economizer circuit in which the water is circulated through the heating elements in the form of a film at a pressure which is relatively low and which permits the provision of settling and purifying tanks of economical construction is not limited in its usefulness to generators of the water, film or fire tube type. On the contrary, the possibility of far reaching purification by physical or chemical means renders this type of economizer advantageous for use in connection with flash boilers where the scaling problem is sometimes also serious. A further advantage of thepreferred modification lies in the fact that the relatively'large treatment tanks which are possible when the pressure is low permit the support of considerable volumes of water. This is of importance where the feed into the generator is intermittent as'the economizer can continue to run and abstract heat from the gases, the heat being stored in the volume of water contained in the economizer circuit. Where, the economizer circuit also generates steam, the steam automatically constitutes a heat storage.

It is an advantage of the preferred modification i-t is claimed as new is ii. Apparatus for the generation of steam comprising in combination, a steam generator, an auxiliary circuit, said auxiliary circuit containing heating elements,. means for circulating water positively and continuously through said elements in amounts insufficient to completely fill said elements but greater than the amount which can be evaporated in said elements under maximum heating conditions, means for feeding water irorn said auxiliary circuit into the generator", and means for'introducing feed water into the auxiliary circuit. 4

2. Steam generating apparatus comprising in combination a steam generator, a positively cir-'- culated auxiliary circuit, means for feeding water from said auxiliary circuit to the generator, means for introducing feed water into said auxiliary circuit, a water level in said generator, a water level in said auxiliary circuit, means operated by the generator water level for controlling the feed of water from the auxiliary circuit into the generator, and means operated by the water level of the auxiliary circuit for controlling the introduction of feed water in the auxiliary circuit.

3. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit, said circuit including heating elements,

means for positively and continuously circulating water therethrough in amounts insuflicient to fill the elements but greater than the amount of water which can be evaporated by passage there: throughunder maximum heating conditions, means for maintaining a high pressure in at least a portion of the auxiliary circuit between the cir culating means and the heatingelements, means for maintaining a relatively low pressure in the heating elements and in the connections from the elements to the circulating means, water treating means located in said low pressure portion of the circuit, means for feeding water from said high pressure portion of the circuit into the steam generator, and means for introducingfeed water into the auxiliary circuit.

4. Steam generating apparatus comprising in combination a steam generator, an auxiliary heating circuit, comprising heating elements, means -for positively and continuously circulating water through tlie heating elements, means for separating any steam generated in said elements; means for feeding water from said auxiliary circuit to the water circuit of the steam generator, connecting means from the steam space of the steam separator in the auxiliary means for insuring positive distribution of the water to each element and a connection from said auxiliary circuit to the generator whereby water is delivered thereto under action of said pump.

6. Apparatus for the generation of steam comprising in combination a steam generator, a positively, circulated auxiliary circuit including economizer elements, means for limiting the quantity of water introduced into said elements to amounts insuiiicient to completely fill them and means for feeding water from said circuit to iliary circuit betweenthe circulating means and the heating elements, means for maintaining a relatively low pressure in the heating elements and in the connections from the elements to the circulating means, water treating means located in said low pressure portion of the circuit, means for feeding w er from said high pressure portion of the circuiti to the steam generator, and means for introducing feed water into the auxiliary circuit.

8. A vapor generator heated by heating gases, economizer elements arranged in the path of said, heating gases, means for introducing feed into one end of each element in amount normally insuificient to fill the elements, and means for introducing unevaporated liquid from the other ends of the elements into. the generator, said means including a pressure transformer whereby the economizer elements may be operated at a 'high pressure in at least a portion of the auxpressure different from that obtaining in the vapor generator.

- combination a steam generator, a positively ciroulated auxiliary circuit including economizer elements, means for supplying water to said elements and for insuring positive distribution thereof to each individual element and means for feeding water from said auxiliary circuit, to said generator.

10. Steam generating apparatus comprisingin combination a steam generator, an auxiliary circuit, said circuit including heating elements, means for positively circulating water there, through, means for maintaining a high pressure in at least a portion of the auxiliary circuit between the circulating means and the heating elements, means for maintaining a relatively low pressure in the heating elements, and means for feeding water from said high pressure portion of the circuit into the steam generator.

11. Steam generating apparatus comprising combination a steam generator, an auxiliary circuit connected therewith, said circuit including heating elements, headers supplying said elements and havingjet orifices whereby the water is circulated through the elements in amounts insuificient to fill them but greater than that which can be evaporated in passing. through the elements under minimum heating conditions, said jet orifices also maintaining a high pressure in at least a portion of the auxiliary circuit between the circulating means and the receiving ends of the heating elements, and means for maintaining a relatively low pressure in the heating elements.

12. Steam generating apparatus in luding a steam generator and an'auxiliary cir it including economizer elements, means to feed water to the circuit and from the circuit to the steam generator, and means for insuring the positive distribution of the water to each of the economizer elements and its passage therethrough priorto its introduction into the generator.

13. Steam generating apparatus according to claim 12 in which a pump circulates water through said auxiliary circuit and elements in one direction and in which the feed water is introduced into the circuit between the pump and the elements and beyond the point in the circuit where water is fed therefrom to the generator.

14. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit in which are included heating elements sub- Jected-to the heat of a lower heat zone than that of the steam generator, means for circulating water through said elements in amounts insufllcient completely to fill said elements but greater than the amounts which can be evaporated therein in passage of the water therethrough, and means for delivering to the steam generator water from said auxiliary circuit.

15. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit in which are included heating elements subjected to the heat of a lower heat zone than that of the steam generator, means for circulating water through said elements in amounts insufiicient to fill the elements but greater than the amounts which can be evaporated therein in passage of the water therethrough, means for maintaining a relatively high pressure in at least a portion of the auxiliary circuit between the circulating means and the heating elements, means for maintaining at least in the heating elements a relatively low pressure, and means for delivering water to the generator from said high pressure portion of the circuit.

16. Steam generating apparatus comprising incombination a steam generator, an auxiliary cir' cuit in which are included heating elements subjected to the heat of a lower heat zone than that of the steam generator, means for circulating water through said elements in amounts insufiicient to fill the elements but greater than the amounts which can be evaporated therein in passage of the water therethrough, means for maintaining at least in'the heating elements of the auxiliary circuit a pressure relatively low with respect to the pressure in the steam generator, and means for delivering water to the steam generator from said circuit.

1'7. A vapor generating apparatus comprising a vapor generator, an auxiliary heating element, means independent of the'vapor generator for introducing from a source outside the vapor generator into one end of the element the liquid to be vaporized, means for limiting the water as it enters the element to an amount insuflicient to 1111 the cross-sectional area available for flow through the element, and means for delivering to the vapor generator unevaporated liquid from the other end of said element.

, 18. A vapor generating apparatus comprising a vapor generator, an auxiliary heating element, means independent of the vapor generator for introducing into one end of the element the liquid to be vaporized in an amount insumcient to fill the element but greater than can be evaporated therein in passage therethrough, means connected to the other end of the element for separating from the liquid any vapor formed in the passage of the liquid through the element, and means for delivering to the vapor generator the un evaporated liquid.

19. A vapor generating apparatus comprising a vapor generator, a plurality of auxiliary heating elements, means independent of the vapor generator for introducing in parallel into the elements at one end of each thereof the liquid to be vaporized in quantity in excess of that which can be evaporated in its passage through the elements, means for insuring the distribution or the water to each element in an amount insufficient to fill the available cross-sectional area of said element, and means for delivering to the vapor generator the unevaporated liquid dis charged from the elements.

20. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit connected thereto in which are included heating elements, means for maintaining a circulation producing pressure in the circuit, and means at the water inlet to the elements providing a pressure drop in the water entering the elements, whereby different degrees of pressure are maintained in the different parts or the circuit. 4

21. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit connected thereto in which are included heating elements, means for maintaining a circulation of water in the circuit, auxiliary heating means also in said circuit for heating with steam the water in circulation, and means for introducing steam into said auxiliary heating means.

22. Steam generating apparatus according to claim 21 in which also is included in the circuit means for separating from the water discharged from the heating elements any steam discharged therewith, and means for delivering said separated water to said auxiliary heating means.

23. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit connected thereto in which are included heating elements, means for circulating water through the circuit, means for variably delivering water from said circuit to the generator, auxiliary water heating means connected to the circuit, and means for delivering to said auxiliary water heating means the excess water flowing in the circuit and not delivered to the generator.

24. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit in which are included heating elements, means for circulating water through said circuit, means for feeding water from said circuit to the steam generator, and means operated in accordance with variations in the amount of water present in the circuit to control the amount of water circulated through the elements.

25. Steam generating apparatus comprising in combination a steam generator, an auxiliary circuit in which are included heating elements, means for circulating water through said circuit, means for introducing water into said circuit, means for feeding water from said circuit to the steam generator, and means arranged to control cooperatively the introduction of the water into the circuit and the feeding of the water to the steam generator.

26. Steam generating apparatus comprising in combination a steam generator, an economizer, means for feeding to the economizer at one end thereof the water to be evaporated and causing it to flow in the economizer uni-directionally in individual paths, means for positively distributing water to each of said individual paths, means for delivering to the steam generator the water heat- 27. The method of heating feed water for delivery to a steam generator, which comprises delivering the feed water into heat exchanging relation to heating gases, positively distributing the water to a plurality of individual paths and causing it to flow while in said heat exchanging relation uni-directionally in said paths so as to be progressively heated therein, delivering water to the steam generator after passage thereof out of said heat exchanging relation to replace that evaporated in the steam generator, and returning for redelivery into said heat exchanging relation and for distribution and unidirectional flow in said individual paths any water in excess of that delivered to the steam generator.

28. The method of preheating a liquid for delivery to a vapor generator, which comprises causing the liquid to flow in heat exchanging relation to-a source of heat while flowing in a cir cuit auxiliary to the vapor generator, causing liquid to be delivered from said circuit to the vapor generator to replace the liquid evaporated in said generator, and effecting a positive distribution of the liquid to a plurality of individual paths for flow of the liquid therein while in said heat exchanging relation with said source of heat.

29. The method of preheating a liquid for delivery to a vapor generator, which comprises causing liquid from a source independent of the vapor generator to flow in heat exchanging relation to a source of heat through a positively defined path of liquid flow, limiting the amount of liquid flowing through said path with respect to the cross-sectional area available for flow in said path so that said liquid flow does not fill said cross-sectional area, and delivering to the vapor generator the heated liquid after discharge from flow through said positively defined path in said heat exchanging relation.

30. The method of preheating a liquid for delivery to a vapor generator, which comprises causing liquid from a source independent of the vapor generator to flow in heat exchanging relation to a source of heat through a positively defined path of liquid flow, limiting the amount of liquid flowing through said path with respect to the cross-sectional area available for flow in said path so that said liquid flowing in amount greater than in the'evaporation thereof during its flow in said heat exchanging relation does not fill said crossasectional area, and delivering to the vapor generator the heated liquid in excess of any evaporated while flowing in said path.

WALTER DOUGLAS LA MONT.

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