US1742999A - Method and apparatus for treating liquids - Google Patents

Description

Jan., 7, 1930., .1. R. MCDERMET METHOD AND APPARATUS FOR TREATING LIQUIDS Filed Sept. 5, 1924 2 Sheets-Sheet l INVENTOR Jan. 7, 1930. J. R. McDERME-r 1,742,999

METHOD AND APPARATUS FOR TREATING LIQUIDS Filed Sept. 5, 1924 2 Sheets-Sheet 2A INVEN-roR ',q Ma

7m`mw Patented Jan. 7, 1930 UNITED STATES PATENT OFFICE.

JOHN 1%. MCDERMET, OF J'EANNETTE, PENNSYLVANIA, ASSIGNOB T0 ELLIOTT PANY, F PITTSBURGH, PENNSYLVANIA, A CORPORATION 0F PENNSYLVANIA METHOD AND APPARATUS FOR TBEATING LIQUIDE Application led September 5, 1924. Serial No. 738,087.

The present invention relates broadly to the degasiflcation or deaeration ofliquids, and more particularly to the treatment of feed water. such for example, as fed to boilers,

5'economizers and the like, for eifecting the removal of air and other entrained gases therefrom.

It has heretofore been proposed to utilize heaters of the through or thoroughfare l0 type, both in condensing and non-condensing plants. It has also been proposed to use heaters of the induction type' in a similar manner. y, Each of these types of heaters is well known commercially and each is recognized as having certain desirable characteristics. As disclosed in my copending applications, Serial N o. 535,744.- filed February 1l, 1922 and Serial No. 582,151 filed August 16, 1922, very advantageous results may be produced by combining the two types of heaters in such manner that they both operate on the water being'treated, each heater modifying theaction of the other. -This broad combination is covered in my applications referred to. d 4

It will be understood that the term thoroughfare heater as used is definitiveA of the type of heater, preferably of the open contact type, havin an excess Iof steam supplied thereto over an above that required to heat the water, both the heating steam and the excess steam ente in the heater and the excess then passin ot er connections. Its characteristic, t erefore, is that there is a thoroughfare flow of steam through the heating chamber and this is the only oonstructional limitation which the designation of t-he heater carries with it. The term induction heater as used herein is deinitive of the type of heater in which the steam is drawn thereinto by the cooling effect of the water being heated. Preferably, the water in distribute condition is heated b contact with the steam. Its characteristic, therefore, is an induced flowwhich is generally proportionate to the work being done, and this 'is the only constructional limitation which the designation or description carries with it.

For purposes of a clearer understandin of the present invention, it may be pointe out that the air content dissolved, in water is partly a function of Water temperature and partly a function of air tension in the atmosphere in which the water is agitated, as, for example, a heater. The minlmum air ten# sion, and therefore the ideal limit which can be secured in a heater of the open contact type in which steam is the heating medium,

is obviously the ai-r tension of the incoming steam. This is almost infinitesimal, particularly where the steam has been generated from degasified water. Any process of condensation by decreasing the condensible portion of the heating medium inevitably increases the noncondensible portion thereof, which is air. f

From the standpoint of air tension, a thoroughfare heater is highly desirable, as it is able to approach the ideal limit referred to,

provi ded the condensation of steam which occurs therein is substantially inappreciable. From an economical standpoint, however, a ythoroughfare heater is not desirable in vmost lpower plants, because the uncondensed steam passing therethrough to other connections is ordinarily not recoverable.

An in( uction heater, on the contrary, operates in a different sense from a heat balance standpoint in that virtually all the steam coming to it is utilized, neglecting onl the small lamount which passes therefrom t rough the vent as a mixture with air. The induction heater, therefore, by condensing substantially all of the condenslble portion ofthe vapor' vmixture coming to it, necessarily increases the proportion of air. This is undesirable from the standpoint of deaeration. From the heat transfer standpoint, however, without regard to deaeration the inductionheater is much more eficient and to a large extent is4 the only commercially utilized heater in power plants.

' I have discovered that it is possible to so combine these two ty "es of heaters that the thoroughfare heater ctions primarily for the purpose of deaeration, and the induction `heater primarily for the purpose of heating the water before it passes to the thoroughfare heater. While the division of work may be varied as desired, it is preferable that the thoroughfare heater be devoted to the duty of deaerating without doing substantially any heating, its capacity being based upon the fact that none of'its tray surface is devoted to heating. In like manner, the induction heater should be devoted substantially en-V tirely to heating duty without any attempt at the process of deaeration therein. This division of work is desirable for the obvious reason that if the major part of the heating medium is condensed in the induction heater and the major part of the heating is accomplished in this heater, virtually all of the heating medium coming to the thoroughfare heater will ass to the inductionheater. By reason of t is condition, the thoroughfare heater will have the advantages of the two fundamentals of high temperature with correspondingly low air solubility, and low air Lension substantially equivalent to that of the heating medium.

From practical experience I have found that a combination of heaters of the character referred to gives most satisfactory performance and operates very advantageously at low initial air content. It is to be eX- pected, however, that any air liberated in the thoroughfare heater ultimately arrives in the induction heater, since the two heaters are in series. Having arrived in the induction heater as one component of a mixture, its relative amount is increased due to the condensation in the heating process ofthe other component, which is steam. The air concentration in the inductionheater limits the temperature of the water leaving the heater and accordingly the amount of air liberated in' the deaeration process, to a certain degree, alters the temperature relationship between the two heaters and inevitably in a series effect, one heater of which is designed to do no heating, the failure of one of the heaters to heat imposes the heating duty on the other.

As the result of the foregoing, with high initial content in the water to be deaerated, it is impossible by a practical arrangement of sizes to so perfect the combinationy that the ideal upon which the design is based, namely that the thoroughfare heater do the deaerating and the induction heater the heating, is possible of attainment. The liberation of air depreciates the performance of the induction heater and when this performance is depreciated, the necessary heating capacity to attain the desired temperature must be assumed by the thoroughfare heater. The tray areas in the thoroughfare heater, however, are proportioned from the standpoint of deaeration, and any use of them for purely heating purposes depreciates the whole unit as a deaerator. p

From a practical standpoint, it is necessary if the unit is to be a successful dcaerator, to have the water arrive in the thoroughfare heat-er at substantially the temperature of the steam, since no deaeration can be accomplished until such a temperature has been reached. The present invention has primaily for its object the provision in a combination of heaters of this charatcer, of means to insure the desired temperature in the water supplied to the thoroughfare heater whereby the thoroughfare heater is relieved of the duty of heati-n such as would be imposed thereon by the ailure of the induction ,heater under normal conditions of high initial air content.

In the accompanying drawings, I have shown for purposes of illustration only, a preferred embodiment of the present inventlon, it being understod that the drawings do not define the limits of myy invention, as changes in the cons-truction and operation disclosed therein may be made without departing'from the spirit of the invention or scope of my broader claims.

In the drawings:

Figure l is a 'diagramatic side elevation, partly broken away, of one form of apparatus for carrying out the present invent-ion;

Figure 2 is a vertical transverse sectional Vview through the apparatus illustrated in Figure 1, certain of theparts being shown in elevation; and

Figure 3 is a detail view, illustrating a slightly modified embodiment lof the invention.

In carrying out the present invention, there may be provided an induction heater 2 having a manifold 3 for suplying the water to be treated, the outletsy from the manifold preferably discharging above a plurality of spray pans or other agitating means 5 over f.

which the water is adapted to flow in' cascade. The induction heater is preferably in superimposed relationship to a thoroughfare heater 6 havin one or more vapor connections 6a extending upwardly therefrom and into the induction heater. Liquid from the induction heater is adapted to flow into the thoroughfare heater through one or more connections 7, each communicating at one end with the bottom of the induction heater and at the other end discharging into the upper portion of the thoroughfare heater. The thoroughfare heater is also preferably provided with agitating means 8 herein illustrated as comprising a series of pans arranged .to cause the entering liquid to flow through vthe vapor space of thel thoroughfare heater other tube pass 14 to the connection 15 leading to the manifold 3. Within the connection 15 is arranged a valve 16 adapted to be automatically operated in accordance with the liquid level in the thoroughfare heater by means of a float 17 operatively connected thereto. The vapor space of the induction heater has an operative connection 18 Iwith the vapor space of the condenser 9.

Arranged within each of the water connections 7, preferably adjacent the end thereof, communicating Wlth the induction heater 2 is a steam injector 19 which may comprise a plurality of tubes communicating' with a header 20 having a steam inlet 21. Preferably these tubes extend into the connections 7 in such manner as to discharge steam in the direction of the flow of water therethrough. lt is well recognized that any attempt to 1nject steam below the surface of a body of water meets a resistance equal to the hydrostatic head of the submerged orifice through which the steam is to be discharged. lf, however, the steam is discharged into a pipe line in which the direction of the steam dischar e and the direction of the water flow are t e "-same,the two factors will be mutually acceleradvantage that it is readily accessible and can be repaired without the necessity of going into the interior of either of the heaters. During the operation of the apparatus there will usually be a solidbody of water within the connections 7, thereby insuring eiiicient heat interchange by this steam injection. lt furthermore makes it unnecessary to utilize any of the capacity of the induction heater for the concentrating of a solid body of water and insures a less expensive initial cost for the reason that the induction heater may be designed solely from the standpoint of heating surface.

In practice, the steam for operating the injector nozzles approximates about l2 inches of mercury and may be derived from a separate source of steam supplyjor by a reducing back ressure valve incorporated in the steam supp y line, this valve being of a pressure loaded type so as to impose sucient pressure on the line to create the. temperature diderential of approximately 12 inches of mercury to operate the jet and permit any surplus of steam amounting in practice to approximately 98 percent to pass onward and enter the thoroughfare heater and fulfill its normal function.

In the accompanying drawings I have illustrated the latter method of steam supply comprising a main inlet 22 leading directly to the thoroughfare heater 6 and having therein a diderentially unbalanced valve 23 which may be loaded in any desired manner, as by a spring 24. Steam may be supplied to the valve 23 through a connection 25 having a bypass cooperating with the connection 21 for supplying the steam to the auxiliary heating means within the connections 7.

ln some cases it may be desirable to operate the apparatus at a temperature corresponding to a pressure which is below atmospheric pressure. ln such cases the ondenser 9 will tend to withdraw the released vapors and gases from the apparatus and thereby maintain the desired thermal conditions therein. lt will be understood that for this purpose the particular design of the condenser may be changed in accordance with the conditions under which it is desired to operate the apparatus. By utilizing such a condenser, not only are the'desirable thermal conditions maintained within the heater, but the sensible heat of the released vapors andgases is conserved and imparted to theincoming water for preheating the same. l

When operating under subatmos heric conditions as just described, it will obvious that there may exist within the steam supply connection 25 a steam pressure which is also subatmospheric. As the present state of the art dictates the advisability of maintaining steam supply lines under a pressure which is at least atmospheric, it is undesirable to have the pressure conditions within the connection 25 transmitted to the steam supply line 26.

lf such conditions were maintained in the steam supply line, there would be a correspending tendency toward air infiltration which would not only contaminate the Water but would impair the eiiiciency of the apparatus. ln order to prevent such an lindesirable condition, there may be provided within the line 26 a balanced valve structure 27 having a piston or diaphragm 28 subjected on one side to atmospheric pressure through a port 29 and on the other side to pressure within the connection 25 through a passage 30. The pressure within the connection 25 may be adjustably augmented by a loading spring 31 whereby the desired operating conditions of the valve will be insured. ln this manner either atmospheric orsubatmospheric conditions may be maintained in the supply line 26, irrespective of the conditions existing within the apparatus or the connection 25.

`With contemplated developments in the art,

4the use of a balanced valve in the steam supply line may be rendered unnecessary as the supply of steam at subatmospheric pressures may be made possible. lt will be understood tot i l out.

therefore that while such a valve, or some equivalent means, is both necessary and de-` sirable in certain installations, the .operation of the present apparatus is not. necessarily dependent thereon in certain cases.

If desired, I may substitute for the balanced valve' a thermostatic valve operated in accordance with the temperature within the induction heater, as disclosed in my copending'application Serial No. 582,151, hereinbefore referred to. Such a modification is illustrated in Figure 3. In this figure there is illustrated a valvel 32 having a controlling element 33 within the induction heater, preferably adjacent the bottom thereof, so as to be within the comparatively small body of liquid maintained therein by reason of the location of the inlets to the connections 7. In this manner the admission of steam to the thoroughfare heater is regulated in propor-v tion as the admission of water to the induction heater varies the temperature therein. In accordance with the present state of the art, it is customary vto withdraw the exhaust steam, which is almost universally employed as heating steam for boiler feed water, from the auxiliaries which produce it at substantially atmospheric pressure. It may -be desirable, however, as before referred to, to effect deaeration at temperatures below atmospheric, for example between 140 and 212c F. If atmospheric steam in excess is admitted to the thoroughfare heater, it will obviously be impossible to maintain the de` sired low pressure temperature therein while, on the other hand, if a deficiency only of steam is available, the pressures would drop below atmospheric and a vacuum would be produced on the valve 32. Without the valve this pressure would be transmitted t0 the supply line with the objections before pointed This makes it only necessary to protect the apparatus per se against air infiltration. The thermostatic valve, where employed, further constitutes an automatic means for prevent-ing undue condensation of steam within the thoroughfare heater, such as would impair its operating efficiency.

If it were possible in commercial practice to obtain steam for heatin purposes entirely free of dissolved gases, ie operation 0f an apparatus of this character would be greatly simplified. As this is not possible, however, the provision of the vents orconnections 18 for the induction heater for the purpose of removing non-condensible gases therefrom is necessary. It is impossible in condensation work to secure an entirely steam-free vent mixture and these vents therefore conduct a mixture of steam and air. vSince the induction heater is of necessityAa/good heating means but an imperfect condensing means, this vent may at times carry away a very considerable portion of steam which without the condenser 9A would represent a loss. The

Vejector 11 cooperating with the condenser by its aspirating action induces a steam How into the thoroughfare heater, through such heater and then into the induction heater, the

condensible portion being condensed within the condenser and the heat thereby recovered.

It is desirable that the heat exchange means comprisingv the induction heater, the thoroughfare heater and thepcondenser shall all operate under a vacuum corresponding very closely lto atmospheric pressure, minus the vapor tension of the water in the induction heater. The condenser is therefore further desirable, as it obviates the necessity of providing an ejector having an air ejecting ca-` pacity large enough for aspirating a large quantity of steam from the induction heater.

The condenser by its action secures economy in ejection capacity. If ther condenser was of suiicient capacity to'accomplish its duty4 automatically, there wouldbe a rush of steam through the thoroughfare heater into the induction heater and thence into the condenser. By making the condenser of proper size,

there is provided an automatic regulation inthat if its heating duty is exceeded,'the ejectionI capacity of the ejector will be automatically diminished by reason of the overload of steam received thereby. It will be apparent that the value ejection capacity as used herein its rated in termsof air or non-condensiblegas removal Where a reduction 1n ejection capacity, as referred to, will automatically lower the vacuum and increase the absolute pressure in the induction heater. As the pressure in this heater rises, the temerature will also tend to rise, thereby tending to limit the further admission of steam to the thoroughfare heater either through the balanced pressure valve or the thermostatic valve.

During the operation of the apparatus, cold water enters the condenser and recovers the heat from the vented mixture and then c passes lnto the induction `heater flowing therethrough in broken up condition and then y partial air tension ywithin the thoroughfare eater, it is to be expected that under certain conditions the air concentration in the induction heater may `reach such a point as to interfere with the desired temperature con-V ditions therein. In such cases the admission of steam through the auxiliary heating means 19 enables the desired temperature conditions to be maintained and the water supplied to the thoroughfare heater without throwing any additional load onto the thoroughfare heater such as would impair its eiiiciency from a deaerating standpoint. In actual practice an amount of steam will be supplied to the auxiliary lheating means suflicient to at least raise the temperature of the water passing through the connections 7 by an amount equal to the depression in the induction heater by reason of-increased air concentration therein.

In order to provide a continuous record of temperature, and to provide for accurate regulation of'temperature, there may be provided an indicating or recording thermometer connected -to both the induction and 4thoroughfare heaters.

The accompanying drawingsmay be considered as largely diagrammatic for the purpose of illustrating the invention. For the sake of a clear understanding, I have illustrated the heaters as comprising separate chambers. It will be obvious, however, that the same operation and results would te obtained by providing a common enclosing shell with a thoroughfare tray section or compartment and an induction tray section or compartment. In such a` construction the entering water would iirst preferably pass, as illustrated, through the vent condenser as thecooling medium for the vented vapors which lleave the induction compartment or heatingsectionof the deaerating apparatus; this water would be distributed by the tray section in the induction compartment. The entering steam would pass horizontally through the lower for air separating tray compartment. In passing through this compartment, the steam sweepsthe air with it and then rises vertically through the port or ports provided, to the heating or induction compartment. The water in v turn Hows through the connections provided into the lower or deaerating compartment, whereby a counter dow of air and water is obtained.

The advantages of the present invention ffision in an apparatus of. this character of ,means permitting operation at any desired temperature conditions without dan er of air infiltration into the steam supply ine and without the possibility of steam Waste from. theapparatus.

said heater, means controlling the lsteam supi ply to said heater through said inlet to prevent increase in air tension therein, heating means inducing a steam 'low through the heater `and supplying heated water to lsaid connection, and means in said connection for supplying additional heat to the water therein. l

' 3. In a feed water treating apparatus, a thoroughfare heater, an induction heater for delivering heated water thereto, a vapor connection betweenl said heaters, a water connection between said heaters, and means for injecting steam into the water passing from the induction heater to the thoroughfare heater through said water connection.

4. In an apparatus for heating and deaerating water, a plurality of heating means in series, a pipe connection for passing heated liquid from one of said heaters to the next heater of said series, and means in said pipe connection for further heating the water fio-wing therethrough.

5. An apparatus for deaerating liquids, comprisin two separate sets of liquid agitating and liquid passes in" series, means for supplying steam to the systems in series with the steam supply initially to the system last receiving liquid, and heating means intermediate the systems for compensating for temperature depression in the first system.

6. An apparatus for deaerating liquids, comprising two liquid agitating .and distributing systems over which the liquid passes in series, means for supplying steam to the systems in 4series with the steam supplyl initially to the system last receiving liquid, and heating means intermediatethe systems for injecting steam into the liquid in the d1- rection of its flow.

mediate the systems for inpctlilnglstean into t e iqui conthe liquid passing throug nection to maintain a constant temperature of liquid to the last system irrespective of initial air content of the liquid,

'stributiiig trays over which the y 8. Apparatus for deaerating liquids, comprising a lower tray section, an upper tray section, connections for feeding liquid into the uppertray section and thence to the lower traysection, connections for supplying` steam to the lower tray section and thence to the upper traysection, and means intermediate the tra sections forvarying the temperature of the i u id during its passage from one section to t e other. i

9. Apparatus for deaerating liquids, comprising a lower tray section, an upper tray section, connections for feeding liquid into the upper tray section and thence to the lower tray section, connections for supplying steam to the lower tray section and thenceto the upper tray section, and 'means intermediate the tra sections for injecting steam into the liquid caving the'uppcrtraysection..

y10. Apparatus for deaerating liquids, com,- prising a lower tray section, an upper tray section, connections for feeding liquid into the upper tray section and thence to the lower tray section, connections for supplying steam to the lower tray section and thence to the upper tray section, and supplemental heatin means intermediate the tray sections.

11. eaerating apparatus, comprising an induction section, a thoroughfare section, means for producing a liquid flow through said sections in one direction and a steam flow through said sections in a counter direction,Y

and means for injecting steam into the liquid in the ldirection of liquid flow'duringits passage from one section to theother.

12. Deaerating apparatus,`compris1ng an induction section, a` thoroughfare section, means for producing a liquid flow through said sections in one direction and a steam flow through said sections in a counter direction,

supplemental Yheating means for the liquid flowing from one section tothe other, and liq- Huid distributing means in each of said sections. p I A 13. Deaerating apparatus, comprising an Y induction section, a thorou hfare section means l.for producing a liqui ow through said sections-in one direction and a steam flow through said sections in a counter direction. means for injecting steam into the liquid during its passage from'one section to the other, and liquid distributing means in each of said sections. Y 4

14. Decorating apparatus, comprising an induction section, a thoroughfare section,

means 'for producing a liquid flow through said'sections in one direction and a steam flow' v through said sections in a counter direction means for injecting steam into the` liquil in the direction of hquid flow during its passage from one section to the other, and liquid distrbutin means in each of said sections. 15. In a eed water heating s stem, lan induction heater, a thoroughfare eater, a wa ter connection between said heaters constituty ertothe other.

ing a water concentrating space for the inheater, and means delivering heating steam to the water in said connection.

17. In a feed water heating system, an induction heater, a thoroughfare heater, a water connection between said heaters constituting a water concentrating space for the induction heater, means for supplying steam initially to the thoroughfare heater, means for supplying water initially to the induction heater, andv means for injecting heating steam intov the water in the direction of itsv flow.

18. In the method of treating li: uid, the steps consisting in heating a liqui by the condensation of a heating medium, passing the heated liquidl intothe'vapor s ace 0f a second heater, heating the liquid uring its passage to the secondheater before it reaches said vapor space to an amount required to compensate for caused by air concentration during the first heating, and controlling the supply of liquid in accordance with demands for treated liquid. j y A 19. In the method of treating liquid,.'the

steps consisting in'heating a liquid, passing sage to the second heater 4under such conditions that the velocity action df the steamand water is mutually agcelerating l 20. In the method of treating liquid, the

steps consisting in heating a liquid in a heater by vthe condensation of a heating medium, v

temperature ldepression liopassing the heated liquid to a second heater,

further heating the liquid therein by the condensation of a heating medium, and compensating for the decreased heating eiciency concentration therein, by` injecting a heating 'medium intothe liquid in the direction of its travel during its passage from one heat- 21. In the method oftreating liquid, the

i steps consisting in heating a liquidA by the condensation of a heating medium, passing the heated liquid to a second heater, and;

i heating Vthe liquid during its passagejto and: VYbefore it enters the second heater to an" 'lac-1:'y

amountrequired to compensate for of the first heater caused,l by increased air directly thereto.

ature depression caused by air concentration during the first heating.

22. Inthe method of treating liquid, the steps consisting in supplying the same to a heater and heating the same therein by an induccdflovv of heating medium substantially proportional to the Work being done, passing the heated liquid to a second heater, passing the heating medium for the first heater through the second heater. maintaining a relatively low air tension in the second heater by the first heater, and heating the liquid during its passage to and before it enters the second heater to an amount required to compensate for temperature depression in the first heater'caused by increased air concentration therein.

23. In the method of treating liquid, the

ste s consisting in supplying the same to an in uction heater, heating the same therein, passing the heated liquid to a thoroughfare heater through a de ned liquid flow path, passing the heating medium', from the thorou hfare heater to the induction heater throug a separate defined fiovv path and maintaining a relatively loW air tension 1n the thoroughfare heater by the induction heater, and heating the liquid in said defined liquid flow path during the flow of the liquid from the induction heater to the thoroughfare heater. v,

24; Apparatus for deaerating liquids, comprising a plurality of'heating means in series, a pipe connection for passing heated liquid from-'one of said heaters to the next heater of said series, and heating means in said pipe connection for further heating the water flowingA therethrough, said heating means Vhaving a 25. Apparatus for deaerating liquids, comprising a plurality of heating means in series, a connection for passinghheated yliquid from one of said heaters to t c next heater of vsaid series, and heating means in said connection for further heatingA the water flowing 26. Deaerating apparatus,

therethrough, said heatin means having a steam connection leading irectly thereto for 4 discharging the steam into said liquid in the direction of liquid flow through-said connection.

comprising separate heatin chambers, water connections for said c arnbers, steam connections for said chambers independent of the water connections, and means for increasin the temperatureof the Water flowing throng one of said water connections'.

27. Deaerating apparatus, comprising an induction heater having a plurality of trays therein, a thorou hfare heater having a plurality of trays t erein, a water connection -from the induction heater to the vthoroughfare heater, a vvapor connection from the thoroughfare heater to the Ainduction heater,

,steam connection leading and means for increasing the temperature of the Water passing through said water connection.

28. Deaerating apparatus, comprising an induction heater having a plurality of trays s therein, a thoroughfare heater having a plurality of trays therein, a Water connection from the induction heater to the thoroughfare heater,.a vapor connection from the thoroughfare heater to the induction heater, and means for increasing the temperature of the Water passing through said Water connection, said means comprisinga steam nozzle structure dischargin into the Water in the direction of Water ow through said connection.

29. Deaerating apparatus, comprising a heating chamber having Va plurality of trays therein, a second heater having a plurality' of trays therein, means for delivering water to said trays, means for heating the water in its passage over said trays, a water concentrating space intermediate said trays for Water heated in the first heater, and means for further heating water in said space during its passa e to the second heater.

30. n the method of deaerating, the steps comprising subjecting the water to contact with steam in a plurality of stages and supplying heating steam intermediate certain of said stages to heat the water and to increase its velocity.

31. Deaerating apparatus, comprising a thoroughfare heater, an induction heater,

said thoroughfare heater havin a vapor space and a liquid s ace, means or supplying steam to both o said heaters, means for passing the liquid from sald mduction heater to the vapor space of the thoroughfare heater, and means for heating the liquid durprior to entryinto -heater into the induction heater, and suppl .ing additional heatto the liquid interme iate 'the' induction heater and the thoroughfare heater.

InI testimonywhereof I have hereunto set m hand.

y JOHN R. MODERMET.

eater, continuously passing-'s'ubstan-y y

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