US2388344A - Deaerating feed-water heater - Google Patents

Description

Nov. 6, 1945.

J. F. SEBALD 2,388,344

DEAERATING FEEDWATER HEATER Filed Oct. 5, 1944 TEE/775D VVATE'A? OUTLET 0599/ f fNVENTOR A TTORNE Y Joseph F. Sebald, Bloomfield, N.

J., asslgnor to Worthington Pump and Machinery Corporation, Harrison, N. J

a corporation of Delaware Application October 3, 1944, Serial No. 557,018

12 Claims.

The present invention relates to apparatus for heating and deaerating liquids, and more particularly to a novel method of and means for treating water for boiler feed purposes and other services requiring practically oxygen-free water. The apparatus of the present invention is of the mixing type, as disclosed in U. S. Patent' 2,308,719, and Patent 2,308,721, both of which issued January 19, 1943, in contradistinction to the atomizing and tray typ s of Water treating apparatus known in the art. Steam jet deaerating apparatuses such as are shown in the foregoing patents embody two stages of heating and deaeration, the first or primary stage consisting of a spray type direct contact heater and deaerator, and the second or secondary stage consisting of a direct contact heater and deaerator of the steam jet eductor type.

An object of the invention is to provide an apparatus for heating and deaerating liquids, wherein means are provided for recirculating processed or partly processed efliuent back through the apparatus to increase the overall time of contact of the liquid with conditions which produce completion of chemical reactions and increased deaeration.

Another object is to provide a steam jet feed- Water heater of the multistage heating and deaerating type, wherein the construction is such as to effect deaeration with a minimum steam pressure drop between the incoming steam and the steam in contact with the deaerated water in the storage space, and in which means are provided fo recirculating water from the storage or from predetermined secondary stages, either singly 0:- simultaneously, back to the primary stage to obtain improved performance of the apparatus. I

A further object is to provide a method of heating and deaerating water in which eiliuent is recirculated with incoming water to be treated in such manner as to obtain more efiective deaeration and purification.

With these and other objects in view, as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawing, showing a deaerating feedwater heater of a preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

The drawing represents a deaerating'feedwater heater in accordancewith the present invention.

Referring'more particularly to the drawing,

the feedwater heater and deaerator shown therein comprises a shell I which is circular in cross section. The lower portion'ol' this-shell provides a storage space, as shown at 2, for storing the heated and deaerated water until it is removed for use. Water to be treated is caused to pass through a vent condenser 3 which is provided with the usual water inlet 4, water outlet 5, and vent 6 for expelling the non-condensible gases liberated in the process of deaeration. To the water outlet 5 is connected a pipe I which extends through the side 8 of the shell I and through which water flows from the condenser 3 to a spray head 9, the latter being located axially of the shell I and within the initial heating and deaerating chamber or compartment Ill.

Within the shell I is mounted a horizontal partition or dished head I I with its concavity facing down. The partition II is spaced from the top I2 of the shell I to provide a passage or chamber I3 adjacent the top, and the partition is of annula contour but of smaller diameter than the shell I to provide an annular passage I4 which places the initial heating and deaerating chamber ill in communication with the passage l3. A depending flange I5 extends about the perimeter of the partition I I.

Water which enters the spray head 9 is sprayed therefrom through spring loaded valves or nozzles I 6, of any suitable ty into the initial heating and deaerating chamber I0 and in the direction of the partition II. The water emitted through the valves I6 forms fine particles in direct contact with the steam in the initial heating and deaerating chamber I0 and is heated to approximately steam temperature, in addition to being partially deaerated or degasified.

Beneath the partition II is positioneda laterally extending and downwardly inclining flange or partition II, the latter being joined to the side 8 of the shell I. The partition I! is provided with a central opening I8 of smaller diameter than the partition II, but in concentric relationship therewith. Water sprayed into the initial heating and deaerating chamber l0 falls into a collecting cone l9 beneath the partition l1. Much of the water impinging against the partition II is deflected laterally and then downwardly by'the flange I5, as at 20. The water which is deflected downwardly by the flange l5 falls on the partition I1 and is directed into the collecting cone l9, so that all the falling water is directed into the collecting cone.

In addition to the first stage of heating and deaeration, as represented by the initialheating and deaerating chamber II), the incoming water is caused to pass through two additional stages of heating and deaeration before it is delivered to the storage space 2; that is to say, through a second or intermediate stage 2|, and a third or final stage 22. All three stages are connected in series relationship, so that the incoming water passes successively from the collecting cone I9 to second and third stages 2| and 22, respectively, and then to the storage space 2.

The collecting cone I9 includes an upper wall 23 of conical contour, a bottom wall 24 of the same contour, and a vertical annular wall 25 attached to the perimeters of the two walls 23 and 24. The wall 25 is arranged co-axially with the partition I1 and is of smaller diameter than the wall 8 of the shell I to provide an annular passage 28 for steam which flows upwardly from the chamber 21. of the second stage 2| of heating and deaeration to the initial heating and deaerating chamber l8. As will be noted by reference to the drawing, the walls 23 and 24 are spaced to provide a conical space orpassage 28 for steam, which steam is admitted to the space 28 through tubes 29, the passages 30 in the tubes 29 placing the space 28 in communication with the chamber 3| of the third stage 22 of heating and deaeration.

Water in its passage from the second to the third stage of heating and deaeration falls into a collecting cone 32 arranged coaxially with the collecting cone I9. The collecting cone 32 comprises an upper conical wall 33, a bottom conical wall 34, and a vertical annular wall 35. The wall 33 is joined at its perimeter to the wall 8 of the shell I so that the chambers 21 and 3| of the second and third stages of heating and deaeration, respectively, are sealed one from the other, with exception of the passages 30 in the tubes 29. The Walls 33 and 34 are spaced to provide a conical space or passage 36 for steam utilized for heating and deaerating the water, which steam may be derived from any suitable source, such as exhaust steam from an engine or steam from the bleeder stage of a steam turbine (not shown). 1 This steam enters the space through an inlet 31, the latter opening through the wall 35 of the collecting cone 32 and extending through the wall 8 of the shell I.

The water which falls on the collecting cone I9 is further heated because of the steam circulating in the space 28, and this water, in its passage from the initial heating and deaerating stage to the second heating and deaerating stage, drains from the collecting cone I9 through a downtake pipe 38 which is coaxial with both collecting cones I9 and 32. An annular and upturned flange 39 is formed at the lower end of the downtake pipe 38, and a neck or pipe section 48 extends downwardly from the lower end of the wall 24 and into the annular cavity 4| defined by the upturned flange 39. The neck 40 is arranged concentrically of the downtake tube 38 and is of larger diameter than the latter to provide an annular passage 42 for the escape of steam from the space 28 in the collecting cone I9.

A cup-like member 43 is mounted beneath and coaxially with the downtake tube 38 which member includes an upstanding wall 44 arranged concentrically of the upturned flange 39. The wall 44 is of larger diameter than the upturned flange asaaau.

The upturned flange 39 and the neck 48 are of such relative diameters as to provide a passage 41 in continuation of the passage 42, the passage 41 being coaxial with the passage 45.

The wall 44 'coacts with the neck 40 to provide a confined mixing or combining passage 48, with the passages 45 and 41 discharging upwardly into the confined mixing passage 48, so that the water and the steam passing upwardly through the passages 45 and 41, respectively, pass through the confined mixing passage 48 in parallel flow. A flare 49 is formed at the upper end of the wall 44 so that the confined mixing passage 48 includes a portion 50 which is of gradually increasing cross-sectional area in an upward direction.

Water collecting in the member 43 is drawn up intothe confined mixing passage 48 by the eductor action of the steam from the passage 41, and the mixture of steam and water flows at a high velocity through the confined mixing passage 48. The high velocity steam and water mixture emitted from the confined mixing passage 48 impinges on the wall 24 and a baflie 5| attached to this wall, the spray being deflected by the baflle in a downward direction to the collecting cone 32.

Because of the flare 49, the mixture of steam and water flows from an area of high velocity to a gradually increasing area and reduced pressure. This results in further heating of the water to the temperature corresponding to the effective steam pressure, which is higher than the steam pressure in the initial heating and deaerating chamber l0. Only a small amount of the total steam is condensed in the confined mixing passage 48 since the water is virtually at saturated temperature. This allows nearly full flow of the steam to transmit sufficient velocity to the water to break it up into minute particles and promotes the 'final removal of oxygen and non-condensible gases. As the water and steam mixture enters the portion 50 of the confined mixing passage 48, a small amount of flashing occurs which further agitates the water particles and assists in water and gas separation prior to impingement on the battle 5|.

In passing the water stream and the steam stream emitted from the passages 45 and 41, respectively, through the confined mixing passage 48, a thermal-compression action is obtained which causes a thorough mixing of the steam and the water before they are projected into the lower pressure area for deaeration. By regulation of the relative areas of the passages 45 and 41, the quantity of steam and water may be proportionately controlled and regulated to meet the conditions of operation under which the apparatus is to work, and in accordanc with the final temperature of the water desired.

The steam and non-condensible gases in their upward travel from the second stage of heating and deaerating break through the Water film deflected by, the baille 5| and enter the initial heating and deaerating chamber I9 through the passage 26, the space between the upper end of the wall 25 and the partition H, with the steam and non-condensible gases breaking through the water film spilling from the partition I1 into the collecting cone I9. Further heatin and deaeration takes place in the initial heating and deaerating chamber I0, and part of the steam which enters this chamber is condensed, and the remainder, together with the non-condensible gases, breaks through the water spray therein and flows upwardly through the passage l4 and a central opening 52 in the partition into the space I3,

aseas-ia and into the inlet 56 leading to the vent condenser 6.

a The steam condensed in the vent condenser 3 r is returned to the initial heating and deaerating chamber In through a water sealed outlet 64, which condensate spills into the collecting cone I! for delivery to the water-flowing to the second stage of heating and deaeration.

To the lower end of the wall 34 is connected a downtake tube 55 which is provided with an upturned flange 56 at its lower end. A neck or tube 61 depends from the lower end of the wall 34 and is arranged concentrically of the downtake tube 55, with the two tubes of such relative diameters as to provide an annular passage 58 for the escape of steam from the space 36 in the collecting cone 32. The' lower end of the neck 51 extends into the annular cavity 59 defined by the flange 66 and coacts with the latter to provide an annular steam passage 66 in continuation of the passage 56.

A cup-like member 6| is mounted in the chamber 3| and includes an annular upstanding wall 62 arranged concentrically of the upturned flange 56. The wall 62 and the upturned flange 56 are of such relative diameters as to provide an annular passage 63' for the escape of water from the chamber 64 defined by the member 6|. In addition, the wall 62 is of such diameter with respect to the neck 51 as to provide an annular confined mixing or combining passage 65 which is coaxial with both passages 60 and 63, the passages 66 and 63 discharging upwardly in parallel flow into the confined mixing passage 65. A flare 66 is formed at the upper end of the wall 62 so that the confined mixing passage 65 includes a portion 61 of progressively larger cross-sectional area in an upward direction. The high velocity steam and water mixture emitted from the confined mixing passage 65 impinges on the wall 34 and a baffle 68 attached to that wall, the spray being defiectedlby the baiile in a downward direction to the storage space 2.

The steam and non-condensible gases in their upward travel from the chamber 3| of the third or final stage of heating and deaeration break through the water film deflected by the bafiie 68 and pass to the second or intermediate stage of heating and deaeration through the passages 30 in the tubes 29. It will thus be seen that the structures defining the second and third stages of heating and deaeration are generally identical. The steam enters the third stage of heating and deaeration and is first used as the heating and deaerating medium in the final stage of deaeration. From the third stage, the steam enters the I second or intermediate stage for the same purmechanical design, the steam passages 58 and 66 are larger than the corresponding passages 42 and 41 of the second stage of heating and deaeration. However, the relative areas of the passages 58 and 60 may be changed with respect to each other and with respect to the passages 42 and 41 to meet different operating conditions.

heating and deaeration. The primary stage performs the major portionof the heating and deaeration and heats the water to within a very" few degrees of the steam temperature corresponding to the pressure in that stage of the apparatus. The second stage 01 direct contact heating and deaeration heats the water essentially to steam uneconomical operation or may disturb-the nor-,

mal heat balance of the power plant system. Such a temperature depression is objectionable when the deaerating apparatus is applied with steamfrom the bleeder stage of a steam turbine.

In order to eliminate the objectionable temperature depression which takes place in the second stage of heating and deaeration, the third stage of heating and deaeration incorporated in the present apparatus is structurally similar to the structure of the second stage, but is designed to produce the heating eifect with a lesser degree of scrubbing action and turbulence to thereby heat the water only essentially to that Of steam temperature in the third stage of heating and deaeration. Because of the liberal steam passages involved, the pressure drop between the incoming steam and the steam in the compartment 3| is extremely small, and the loss of sensible heat is minimized. Of course, a certain amount of deaeration will be eifected although it will be minor as compared to the deaerating qualities of the primary direct contact stage aswell as the second stage of direct contact heating and deaeration. While two stages are illustrated in addition to the primary stage, additional stages of direct contact heating and deaeration may be added.

It will thus be seen that the invention herein shown and described embodies stages of heating and scrubbing which result in prolonged mixing and time of contact at elevated temperatures to a degree whereby more effective degasification and purification are produced. Thus the chemical reaction between the carbonates contained in the water and the added chemical compounds which may be employed in the treating process, for example, may be forced to completion by prolonged intimate mixing of the components at elevated temperatures, such as are necessary to in-' crease the rate of reaction, and that one or more of the gaseous products of the reaction may be removed from the water being processed, and the reaction made irreversible to approach come pletion.

a Means are provided for recirculating the fluid which has been processed through the apparatus or partly processed back to the initial stage of heating and deaeration. Pipes 69 and 16 communicate with the bottom portions of the cups 43 and 6|, respectively, and a pipe H leads into the bottom of the storage 2. All these pipes are connected with the inlet eye 12 of a power driven centrifugal pump 13, which may be of any approved type. Control valves 14, I5, and 16 are interposed in the pipes 66, I6, and II, respectively.

To the discharge ll of the pump 13 is connected a pipe 18 which leads into the pipe I for delivering processed or partly processed water to the incoming water to be treated.

Because of the valves 14, I5, and I6, finally treated ellluent from the storage 2 or eflluent from the two secondary stages of heating and deaeration may be recirculated individually or simultaneously back to the primary stage. Such recirculation of the eilluent increases the overall time of contact of the liquid with conditions which produce completion of chemical reactions and increased deaeration. The recirculated eifiuent is subjected to an additional treatment by increasing its time of contact in the preceding stage, which increases the amount of scrubbing and deaeration. Such recirculation also increases the combined temperature of the liquid entering the preceding stages which increases the rate of chemical action in the preceding stages. Recirculation also lends itself to more effective removal of free carbon dioxide and ammonia which are, under certain conditions, extremely difficult to remove in conventional types of deaerating apparatus. 1

A valve 19 is interposed in the pipe 78 so that the entire recirculation system may be isolated from the apparatus.

It will b understood that the invention is not to be limited to the specific construction or arrangement of parts shown, but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a liquid heating and deaerating apparatus, an initial treatment chamber, means for introducing liquid to be treated to said chamber, a plurality of supplementary treating chambers,

confined mixing passages for liquid and steam including means for delivering liquid from said initial treatment chamber to the successive confined mixing passages, said confined mixing passages each discharging liquid and steam into one of said supplementary treating chambers, means for delivering steam to one of said confined mixing passages and successively to the remainder of said plurality of mixing passages and said initial treatment chamber, and means for recirculating finally treated liquid back to the initial treatment chamber.

2. In a liquid heating and deaerating apparatus, an initial treatment chamber, means for introducing liquid to be treated to said chamber, a plurality of treatment chambers arranged in series relationship to cause liquid to be treated to flow from the initial treatment chamber to and through said plurality of treatment chambers, confined mixing passages for steam and liquid including means for delivering liquid to the successive confined mixing passages, means for introducing steam to one of said confined mixing passages and successively to the remainder of said plurality of mixing passages and to the initial treatment chamber, and means for recirculating partially treated liquid back to the initial treatment chamber.

3. A water heating and deaerating apparatus comprising a shell provided with an initial treatment chamber and a storage chamber for treated water, means for introducing water to be treated into said chamber, an intermediate treatment chamber, a first confined mixing passage for water and steam including means for delivering water thereto from said initial treatment chamher, said first confined mixing passage discharging water and steam into said intermediate treatpent chamber, a final treatment chamber defined asses in part by said storage chamber, a second confined mixing passage for water and steam including means for delivering water thereto from said intermediate treatment chamber, said second confined mixing passage discharging water and steam into said finaltreatment chamber and the storage chamber, means for delivering steam to said second confined mixing passage, means for delivering steam from said final treatment chamber to said first confined mixing passage, means for delivering steam from said intermediate treatment chamber to said initial treatment chamber, means for recirculating partially treated water back to the initial treatment chamber, and means for recirculating finally treated water back to the initial treatment chamber.

4. A water heatingand deaerating apparatus comprising a shell provided with an initial treatment chamber and a storage chamber for finally treated water, means for introducing water to be treated into said chamber, an intermediate treatment chamber, a first confined mixing passage for water and steam including a collecting. cone for delivering water to the confined mixing passage from said initial treatment chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber, a final treatment chamber defined in part by said storage chamber, a second confined mixing passage for Water and steam including a collecting cone for delivering water to said second confined mixing passage from said intermediate treatment chamber, said second confined mixing passage discharging water and steam into said final treatment chamber and the storage chamber, means for delivering steam to said second confined mixing passage, means for delivering steam from said final treatment chamber to said first confined mixing passage, means for delivering steam from said intermediate treatment chamber to said initial treatment chamber, means for recirculating partially treated water back to the initial treatment chamber, and means for recirculating finally treated water back to the initial treatment chamber.

5. A water heating and deaerating apparatus comprising a shell provided with an initial treatment chamber and a storage chamber for treated water, means for introducing water to be treated into said chamber, an intermediate treatment chamber, a first confined mixing passage for water and steam including a collecting cone for delivering water to the confined mixing passage from said initial treatment chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber, a finaltreatment chamber defined in part by said storage chamber, a second confined mixing passage for water and steam including a collecting cone for delivering water to said second confined mixing passage from said intermediate treatment chamber, said second confined mixing passage discharging water and steam into said final treatment chamber and the storage chamber, means for delivering steam from a single source to both confined mixing passages and said initial treatment chamber, means for recirculating partially treated water back to the initial treatment chamber, and means for recirculating finally treatedv water back to the initial treatment chamber.

- 6. In a water heating and deaerating apparatus, an initial treatment chamber,-means "rarintroducing water to be treated into said chamber, anintermediate treatment chamber, a first confined mixing passage for water and steam including means for delivering water thereto from said initial treatment chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber,

afinal treatment chamber, a second confined mixing passage for water and steam including means for delivering water thereto from said intermediate treatment chamber, said second confined mixing passage discharging water and steam into said final treatment chamber, means for delivering steam to said second confined mixing passage in separated heat transfer relationship to the water flowing to the second confined mixing passage, means for delivering steam from said final treatment chamber to said first confined mixing passage in separated heat transfer relationship to the water flowing to the first confined mixing passage, means for delivering steam from said intermediate treatment chamber to said initial treatment chamber, means for recirculating finally treated water back to the initial treatment chamber, and means for recirculating partially treated water from points adjacent the respective confined mixing passages back to the initial treatment chamber.

7. In a water heating and deaerating apparatus, an initial treatment chamber, means for introducing water to be treated into said chamher, an intermediate treatment chamber, a first confined mixing passage for water and steam including a collecting cone for delivering water to the first confined mixing passage from said initial treatment chamber, said first confined mixing passage discharging water and steam into an intermediate treatment chamber, a final treatment chamber, a second confined mixing passage for water and steam including a collecting cone for delivering water to said second confined mixing passage from said intermediate treatment chamber, said second confined mixing passage discharging water and steam into said final treatment chamber, means for delivering steam to said second confined mixing passage in separated heat transfer relationship to the water flowing to the second confined mixing passage, means for delivering steam from said final treatment chamber to said first confined mixing passage in separated heat transfer relationship to the water flowing to the first confined mixing passage, means for delivering steam from said intermediate treatment chamber to said initial treatment chamber, means for recirculating finally treated water back to the initial treatment chamber, and means for recirculating partially treated Water back to the initial treatment chamber.

8. In a water heating and deaerating apparatus, an initial treatment chamber, means for introducing water to be treated into said chamber, an intermediate treatment chamber, a first confined mixing passage for water and steam including a collecting cone for delivering water to the first confined mixing passage from said initial treatment chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber, a final treatment chamber, a second confined mixing passage for water and steam including a collecting cone for delivering water to the second confined mixing passage from said intermediate treatment chamber, said second confined mixin passage discharging water and steam into said final treatment chamber, means for delivering steam to said second confined mixing passage in separated heat transfer relationship to the wa ter flowing through said second mentioned collecting cone to said second confined mixing passage, means for delivering steam from said final treatment chamber to said first confined mixing passage in separated heat transfe relationship to the water flowing through said firs entioned collecting cone to said first confined mixing passage, means for delivering steam from said intermediate treatment chamber to said initial treatment chamber, valve controlled means for recirculating partially treated water back to the initial treatment chamber, and valve controlled means for recirculating finally treated water back to the initial treatment chamber,

9. A water heating and deaeratingapparatus comprising an initial treatment chamber, means for introducing water to be treated into said chamber, an intermediate treatment chamber, a first confined mixing passage for water and steam including means for delivering water,

thereto from said initial treatment chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber, a final treatment chamber, a second confined mixing passage for water and steam including means for delivering water thereto from said intermediate treatment chamber, said second confined mixing passage discharging water and steam into said final treatment chamber, means for delivering steam to said second confinedmixing passage in separated heat transfer, relationship to the water flowing to the second confined mixing passage, said final treating chamber being sealed from said intermediate treatment chamber, means defining passages for delivering steam from said final treatment chamber to said first confined mixing passage in separated heat transfer relationship to the water flowing to the first confined mixin passage, means defining an annular passage for delivering steam from said intermediate treatment chamber to said initial treatment chamber, means for recirculating partially treated water backto said first-mentioned means, and means for recirculating finally treated water back to said first-mentioned means.

10. In a liquid heating and deaerating apparatus, an initial treatment chamber, means for introducing liquid to be treated to said chamber, a plurality of supplementary treating chambers, confined mixing passages for liquid and steam including means for delivering liquid from said initial treatment chamber to the successive confined mixing passages, said confined mixing passages each discharging liquid and steam into one of said supplementary treating chambers, means for delivering steam to one of said confined mixing passages and successively to the remainder of said plurality of 'mixing passages and said initial treatment chamber, and means for recirculating partially treated liquid back to the initial treatment chamber.

11. A water heating and deaerating apparatus comprising an initial treatment chamber, means for introducing water to be treated into said initial treatment chamber, a first confined passage for water and steam including means for delivering Water thereto from said initial treatment chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber, a final treatment chamber, a second. confined mixing passage for water and steam including means for delivering water thereto from said intermediate treatment chamber. said second confined mixing passage discharging water and steam into said final treatment chamber, means for delivering steam to said second confined mixing passage in separate heat transfer relationship to the water flowing to the second confined mixing passage, said final treating chamber being sealed from said intermediate treatment chamber, means defining passages for delivering steam from said final treatment chamber to said first confined mixing passage in separate heat transfer relationship to the water flowing to the first confined mixing passage, means defining an annular passage for delivering steam from said intermediate treatment chamber to said initial treatment chamber, and means for recirculating partially treated I water back to said first-mentioned means,

12. A water heating and deaerating apparatus comprising an initial treatment chamber, means for introducing water to be treated into said initial treatment chamber, a first confined passage for water and steam including means for delivering water thereto from said initial treatment ,chamber, said first confined mixing passage discharging water and steam into said intermediate treatment chamber, a final treatment chamber, awsecond confined mixing passage for water and steam inclifding means for delivering water thereto from said intermediate treatment chamher, said second confined mixing passage discharging water and steam into said final treatment chamber, means for delivering steam to said second confined mixing passage'in separate heat transfer relationship to the water flowing to the second confined mixing passage, said final treating chamber being sealed from said intermediate treatment chamber, means defining passages for delivering steam from said final treatment chamber to said first-confined mixing passage in separate heat transfer relationship to the water flowing to the first confined mixing passage, means defining an annular passage for delivering steam from said intermediate treatment chamber to said initial treatment chamber, and means for recirculating treated water back to said first-mentioned means.

JOSEPH F. SEBALD.

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