CA1112703A - Electric steam generator - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The electrodes of the steam generator are each formed as a horizontally extending disk to receive descending water jets from a distribution chamber above the electrode as well as with openings to direct water jets downwardly onto a collecting grid. The current flows from the electrodes through the water jets to evaporate part of the water to steam. Movable inter-ceptors are also mounted in the vessel to intercept the water jets for partial loads. The invention results in a reduced overall height of the generator. In a particularly useful embodiment, the water distribution means are movable to adjust the number of water jets which impinge on the electrodes while the collecting means for intercepting the excess water are stationary. Each collecting means is also located out of vertical alignment with the respective electrode. The distribution means are fixed to a rotatable pipe which serves to move the distribution means and through which water can be fed to the distribution means. The latter embodiment results in a still further reduction of the overall height of the generator.

Description

The present invention relates to an electric steam generator of the type having at least one electrode disposed in a vessel, and further including a distribution device for directing water to be evaporated against the electrode in the form of jets.
In known steam generators of this type, the electrodes are arranged vertically about a centrally located distribution device and being operatively connected to a three-phase network.
In use, a current flows through the water jets so that part of the water jets evaporates. The steam formed in this manner is collected in the vessel and is then fed to the steam consumers while the unevaporated water returns to a sump located in the lower part of the vessel and forms further current paths. If the consumption of electric power changes, a larger or smaller number of the water jets emanating from the distribution device is intercepted in these known steam generators so as not to reach the electrodes. It is a drawback of the known steam generators that because of the vertical arrangement of the electrodes and of the distribution device, the steam generator has a xelatively large overall height as, due to the curved water jets, it is necessary to provide intercept area of the ; electrodes to be of required size in vertical direction.
It is an object of the present invention to provide a steam generator of the above mentioned type, whose overall height is smaller than in the known prior art devices, and whose steam generating capacity relative to the voIume of the generator ~is increased.
The present invention solves the above object by an arrangement wherein the electrode is~formed~as a horizontally extending dish for receiving a supply of water having openings formlng outlets for the received water to form vertical water the jets. The distribution means has a chamber to receive water, ~27~3 chamber having an approximately horizontal bottom and having a group of openings above the dish-shaped electrode for directing vertical water jets against the electrode. Due to the fact that the openings in the distribution means are arranged in a horizontal plane and the electrode is in the form of a horizontal dish, the height of the electrode and thereby, the overall height of the steam generator, can be reduced substantially.
This makes it possible to accommodate the steam generator according to the present invention in a basement of a normal story height in dwellings, hospitals, and similar buildings.
Due to the dish-shaped form of the horizontal electrode and the horizontal arrangement of the openings in the distribution means, a uniform vertical straight-line path of the water jets emanating from the distribution means is obtained. This makes it possible to increase the steam generating capacity over vertically arranged electrodes.
In general terms, the present invention provides, in an electric steam generator, the combination comprising, at least one horizontal extending dish-shaped stationary electrode in said vessel for receiving and heating a supply of water and having openings therein forming outlets for the received water to form vertical water jets;
a horizontally movable water distribution means located above each of said at least one electrode for movement relative to each of said at least one electrode in a range between a first position corresponding to a partial load on the generator and a second position corresponding to a full load on the generator, said distribution means having a chamber to receive water, said chamber including a horizontal bottom having a group of openings above each of said at least one electrode for directing vertical water jets against and into each of said at least one electrode; and a water collecting .
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~2~3 means mounted in stationary manner in said vessel in a horizontal plane between said distrlbution means and each of said at least one elect~ode, said collecting means being vertically disposed below at least a portion of said distribution means when said distribution means is within said range and vertically out of alignment with each of said at least one electrode for collect:ing that portion of the water not directed at each of said at least one electrode.
The invention will now be disclosed in greater detail with reference to two embodiments of steam generators, of which one is claimed in a copending Canadian patent application s~rial No. 272,466 filed February 23, 1977 and assigned to the present applicants, the said application being a "parent" application of which the present application is a division.
In the Drawings:
Figure 1 is a vertical section of a steam generator of the "parent" application;
Figure 2 is a section along lines II-II of Figure l;
Figure 3`is a vertical section of another steam generator.according to the present invention;
Figure 4 is a partial section IV-IV of Figure 3;
Figure 5 is a partial section V-V of Figure 3;
Figure 6 is a secti.on VI-VI of Figure 4;
Figure 7 is a plan view:;of an electrode of the steam generator of Figure 3; and Figure 8 is section VIII-VIII of Figure 7.
Referri:ng to Fig. 1, the electric steam generator has a cylindrical vessel disposed on a vertical axis which is provided at the top and bottom with~a convex cover 3 and

2 respectiveIy. The diameter of the vessel l is approximately equal to the height of the vessel, so that the vessel 1 is of ~2a-~' ~

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compact shape. ~ pipe elbow 4 is connected to the lower co~er 2 and is connected via a flange joint to an intake s~ub 5 of a circulating pump 7, which is driven by an electric motor 6. An output stub 8 o~ the circulating pump 7 is flanged to a central pipe 10 which passes through the lower cover 2 and ex~ends close to the upper cover 3. The lower end of the pip~ 10 is cylindrical and ¢hanges toward the top to a triangular cross-section with rounded corners (see Fig. 2). A pipe line 50 is connected to the lower cover 2 through which feed water is supplied by means of a feed pump (not shown) and forms a sump in the lower part of vessel 1.
A plane intermediate plate 12 is provided below the mouth of the central pipe 10 in the vicinity of the upper cover

3 or at the same height as this mouth. ~his intermediate plate 12 is part of a distribution means for the water to be evaporated which water collects on the intermediate plate 12 as a layer of a certain height. At approximately half height of the vessel 1 ,- three dish-shaped electrodes 20 are provided in a horizontal plane, uniformly distributed over the circumference. Each electrode 20 consists of an approximately horizontal bottom 21 and a frame 22 welded thereto, which extends upward and has a segment-shaped top elevation (see Fig. 21. The bottom 21 is equipped with sixty-six nozzles 55, the exit openings of which are arranged at the intersection points of two families of involutes 26 whîch are mirror-symmetrical to a radial plane including the laxis of the vessel 1. Several mutually parallel grid bars 25 are fastened above the nozzles 55 in the frame 22, which form a grid and are omitted in Fig. 2 to the lef~ o~ ~he break line b for the;sake of clarity.
A colleoting grid 15 is provided below each electrode 20 which consi~ts of steel strips 16 arranged on edge side-by-~ side and rests via four legs 14 on the lower cover 2. Each :
~ ~ -3-Z7~3 electrode 20 is supported via two ceramic insulators 18 on the collecting grid 15 located underneath. Fox this purpose, the grid 15 has two overhanging plates 17. The insulators lB insulate the respective electrode 20 electrically against the collecting grid 15. Current is supplied to the three electrodes 20 via a bar 41 each of which is connec,ed at one end to the bottom 2 of an electrode 20 via a connecting strip 43 and is brought out at the other end through a radially disposed stub 42 of the vessel 1. The bars ql are enclosed by insulators 40. The three phases of a three-phase network are connected to the outer ends of the bars 41 in a manner not shown in detail.
A group of several nozzles 13 is associated with each electrode 20 and are disposed in the intermediate plate 12 to define openings through which vertical water jets are directed against the associated electrode 20. The arrangement of the nozzles 13 corresponds to that of the nozzles 55 in the electrode ~0. A pipe line 51 is connected to the vessel 1 closely below the intermediate bottom 12 and conducts the saturated steam generated in thevessel ltO the consumers (not shown).
Furthermore, the intermediate bottom 12 is pro~ided on its lower side with a pipe section 28 which is concentric with the central pipe 10 and has a flange 29 at a lower end. The flange 29 has an annular slot of circular cross-section on the upper side in which balls 30 roll and a ring 31 of angular cross-section extends over the balls~30 so that an axial bearing is formed. Three collecting trays 35 are distri~uted circumferentially over the ring 31 and~ are welded to the ring 31. Each tray 35 is associated with one of the three groups of nozzles 13 ancl can be swung into the area of the water jets coming from the nozzles 13. Each of the collecting trays 35 is provided with a spout 36 (Fig. 2~ which is pointed toward the wall of the vessel 1 and can move, together with the collecting : ~ :

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tray 35, over the openiny of a collecting pocket 38. The collecting pockets 38 are each formed by a metal sheet 56 which is welded to the inside of the vessel and extends downward to shortly above the water sump. If the collecting trays 35 are swung into the area underneath the nozzle 13, part of the water jets is therefore intercepted by means of the collectinq trays 35 and the water collected is conducted into *he collecting pockets 38, so that this intercepted water does not come into contact with the electrodes 20 and therefore does not carry current.
I'he operation of the steam generator is as follows:

By means of the circulating pump 7, water i5 drawn from the sump and pumped via the central pipe 10 onto the intermediate bottom i2, where a water layer is formed, the height of which depends on the amount of water pumped by the circulating pump 7 and on the sum total of the exit cross sections of all nozzles 13. A pipe - 52 is provided for pressure equalization between the space above and the space below the intermediate plate 12. This pipe 52 also serves as an overflow. The water collecting on the intermediate bottom 12 is distributed over the nozzle 13 and falls in a multiplicity Df ve-rtical jets onto the grid 25 of the dish-shaped electrodes 20. The water collects in these dishes forming a level. Then, the water flows via the nozzles 55 onto the collecting grid 15 underneath and from there to the sump. The current fed-in via the bars 41 flows from the dish~shaped electrodes 20 on the one hand against the falling water, to the ~-nozzles 13 and on the other hand, in the same direction as the falling water, to the collecting grid 15. The nozzles 13 as well as the connecting grids 15 are electrically con.ected ~

the vessel 1 and are at zero potential. When the current passes through the water jets, steam is generated. The steam is then collected below the intermedia~e plate 12 and leaves the vessel via the line 51.

7~3 At full load of the st:eam generator, the three collecting trays 35 are outside the area of the water jets issuing from the nozzles 13. For a smaller load, the ring 31 with the three collecting trays 35 is moved counter-clockwise in Fig. 2 by a suitable means (not shown) !30 that the collecting trays intercept a larger or smaller paxt of the water issuing from the nozzles 13. The collected water flows via the spouts 36 into the collecting pockets 38 and returns to the water sump.
By the specific arrangement of the nozzles 13 and 55 at the points of interception of two equidistant families of involutes, the number of water jets covered ~y the collect.ing trays 35 is varied approximately linearly as a function of the angle of - rotation.
It may be advan~ageous to provide partitions about~
the individual nozzles 55 at the bottom of the dish-shaped electrodes 20 in such a manner that the water leaves the dish in approximately the same axis as the water enters. It is also conceivable to arrange partitions in the dishes in such a manner that the water is no~ distributed over a larger area or a larger number of jets leaving the electrodes than corresponds approximately to the number of the jets flowing towards the electrode. Finally, the height of the partitions can be arranged in steps. In this manner, at low load, the water which is fed-in in only a few jets can be prevented from discharging from too large a number of jets.
Instead of equipping the bottoms 21 and the inter-mediate plate 12 with nozzles 55 and 13j respectively, it is also possible to work nozzle-shaped discharge openings into the bottom 21 or the plate 12 itself.
30 ~ In the steam generator shown in Figures 1 and 2~

means are provided whereby - for a partial load of the steam generator - the water flowing toward the electrode is fed only .

to a part of the ~penings in ~he electrode. This mea~s consists of a movable intercepting device which can be moved into the space be~ween the distribution device and the electrode located underneath in order to prevent more or fewer water jets from striking the electrode. However, such a steam generator still has a relatively large overall height because the distance between the upper side of the electrode and t:he underside of the intercepting device inserted below the distribution device must not be less than a certain value as otherwise there is danger of the current arcing over.
In the embodiment of Figures 3 to 8, the distribution means is arranged to be movable in a horizontal direction from its position above the electrode in a direction away from the electrode. The collecting means is mounted in stationary manner in the vessel between the water distribution means and the electrode vertically out of alignment with the electrode, to intercept the water jets which are not to strike the electrode. As the water distribution means is movable and the collecting means is stationary, the distribution means can be arranged closer to the electrode, while the collecting means remains outside of the current-carrying water jets. Thus, the overall height of the steam generator can be further reducedO
Referring to Fig. 3, the steam generator comprises a cylindrical vessel 1 which is disposed on a vertical axis and is provided at its bottom cover 2 to communicate with a suction stub 5 of a circulating pump 7. An output stub 8 of the pump 7 is connected to a flanged pipe stub 10 which is centrally located of the vessel 1 and protrudes upwardly throush the vessel bottom cover 2. The pipe s~ub 10 terminates at a flange 65 somewhat below the level of the water sump formed on the bottom 2. A bearing ring 66 of angular cross-section is arranged on ithe flange 65 to surround the flange 65 on the outside ~ . . - ' , .. 1 :

7~3 with a downward directed rim. A vertical pipe 67 is mounted on the bearing ring 66 to rotate about the axis of the vessel. This pipe 67 is formed at the lower end with an inward projecting flange 68 which rests on the bearing ring 66. The section of the pipe 67 located below the flange 68 encloses the outer circumference of the b~aring ring 66. Thus, the bearing portion is bridged by the water of the sump acting as an electric conductor. Therefore, there are only negligibly small voltage differences between the bearing surfaces, so that corrosion due to voltage differences is avoided.
The upper end of the rotatable pipe 67 terminates in a hexagonal housing 69 which has a rectangular opening 70 in each of three walls. The three openings 70 are thus arranged at an angle of 120 to each other. A distribution box 72 which is open at the top and is bolted to the respective wall of the housing 69 via gaskets (not shown) is connected to each opening 70 to form a chamber to receive water. The distribution boxes 72 have the shape of a truncated sector as seen in a top view (Fig. 4). The horizontal bottom of each distribution box 72 is provided an opening in the shape of a ring sector 73 which is covered rom below by a nozzle plate 75 which is fastened to the bottom of the distribution box 72 by means of screws 74.
The nozzle plate 75 has a group of nozzle openings 76 which are arranged in rows in such a manner that the rows are slightly askew to the axis of rotation of the pipe 67. Referring to Figs. 4 and 6, each distributlon box 72 has a slight~y inclined sheet of metal plate 79 near one boundary wall 72' which forms a slot 78 for the chamber. As shown, the slot 78 widens towards the top. The plate 79 functions as a partition to separate the slot 78 from the remainder of the chamber in the box 72 such that the slot 78 can function as an overflow opening.

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In order to drive the pipe 67, a rotatable drive shaft 80 is bolted to a cover 69' of the hexagonal housing 69 via a flange and extends through the upper end, i.e. cover 3, of the vessel 1. In addition, a stuffing gland 81 is mounted in the cover 3 to seal the drive shaft 80 in the cover 3. The drive shaft 80 is in connection wit'h drive means ~not shown~
via which a rotary motion of about 45~ can be imparted to the rotatable pipe 67 including the thrlee distribution boxes 72, and more specifically, clockwise from the position shown in Fig. 4 and back again. The collection device formed by the collecting dishes 95 is thus disposed within the vessel 1 in a stationary fashion.
As best seen from Figs. ~, 7 and ~ three horizon~lly ex-tending dish-shaped electrodes 88 are arranged underneath the full-load position of the distribution boxes 72 spaced by 120 over the circumference of the vessel 1. Each of these electrodes 88 is supported by a conductor rod 87 which projects into the vessel space radially and is mounted in a stuh 85 of the vessel. The conductor rods 87 serve to supply current and are each surrounded 2~ by an insulator 86. Each electrode 88 consists of a horizontal bottom 89 and an adjoining upward-extending frame 91. The bottom 89 is provided with nozzle outlets 90, which are arranged, corresponding to the nozzle openings 76 of the distribution boxes 72, in rows which are slightly askew to the axis of the rotatable pipe 67. Vertical partitions 94 are provided between each two adjacent rows of nozzle outlets 90 and extend from the bottom to about 2/3 of the height of the'frame 91. Collecting rods 92 are fastened to the ~rame 91 above partitions 94 and run crosswise to the ]partitions 94 and extend in the ver~ical direction. A col'lecting grid 15 is provided below each electrode 88 to collect the water jets from the electrode 88. Each collecting grid 15 is fastened to two brackets 15' which are _9_ ~ ~' '.
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welded to the inside of the vessel 1 and protrude horizontally into the vessel space (Fig. 5).
Referring to Figs. 3 and 4, a collecting means is mounted in stationary manner within the vessel 1 in a horizontal plane between each water distribution box 72 and an associated electrode 88. Each collecting means includes a collecting dish 95 which is secured, as by welding, to a vertical run-off pipe 96. ~he run off pips 96 are fastened by means of U-bolts 97 to U-shaped strip steel brackets 98, which are welded to the wall of the vessel 1. As seen in Fig. 6, the upper left boundary edge 99 of each collecting dish 95 runs approximately radially to the pipe 67 and extends, in the position of the distribution box 72 shown in Fig. 4, underneath this box 72 between the slot 78 and the row of the row of noæzle openings 76 adjacent to this slot 78.
In the operation of the steam generator, water is taken from the sump of the vessel 1 by means of the circulating pump 7 and pumped via the central pipe 10 and th~ rotatable pipe 67 into the three distribution boxes 72. ~he three dis-tribution boxes 72 thus form a water chamber in which the waterto be evaporated collects as a layer of a certain height. From the distribution boxes 72, the water passes via the nozzle openings 76 to the associated électrode 88 in the form of water jets while any excess pumped by the circulating pump 7 flows over the upper edge of the plate 79 into the overflow slot 78 and thence into the associated collecting dish 95. For full load, the distribution boxes 72 are in the position shown in Fig. 4, i.e. vertically over the electrodes 88, so that all the water jets 1ssuing from the nozzle openings 76 strike the electrodes 88. The excess water flowing out from the slots 78 returns via the collecting dishes 95 and the run off pipes 96 to the sump.: The water of the water jets coming from the boxes 72 collects row by row between the partitions 94 of the dish-shaped electrodes 88 and is distributed anew and flows via the outlets 90 to the collecting grid 15, again in the form of jets.
The three-phase current fed-in via the three conductor rods 87 flows from the dish-shaped electrodes 88 on the one hand toward the nozzle plates 75, against the falling water, and on the other hand, in the direction of the falling water, to the collecting grids 15. The nozzle plates 75 as well as the collecting grids 15 are electrically connected to the vessel 1 and are at zero potential. During the passage of the current, steam is generated which collects under the top cover 3 and is conducted via a line 51 to consumers (not shown). The amount of steam leaving the vessel 1 is replaced by feed water, which is fed to the vessel 1, via a line 50 connected to the bottom cover 2 by means of a feed water pump, not shown.
If the load is reauced, the p~pe 67 is rotated via the drive shat 80 so that the distribution boxes 72 are gradually moved away from the associated electrode 88 in the horizontal direction clockwise as viewed in Fig. 4. Thus, one jet after the other from each box 72 no longer strikes the associated electrode 88 and is received by the associated collecting dish 95 from where the water is returned to the sump via the run-off pipe 96. Accordingly, the steam generation is reduced while the electric voltage remains constant.
A man hole stub 100 is provided in the cylindrical wall of the vessel 1 through which all components of the steam generator can be brought into the vessel 1 and assembled.
The steam generator according to the invention may also be equipped with only one electrode instead of with three electrodes.
The invention is not limited to vessels with a vertical axis. It is also possible to use cylindrical vessels : ,-with a horizontal axis, in which case, the dish-shaped electrodes are arranged staggered in the direction of the horizontal axis.
Accordingly, also the distribution boxes are then arranged to be axially movable.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an electric steam generator, the combination comprising a vessel;
at least one horizontally extending dish-shaped station-ary electrode in said vessel for receiving and heating a supply of water and having openings therein forming outlets for the received water to form vertical water jets;
a horizontally movable water distribution means lo-cated above each of said at least one electrode for movement relative to each of said at least one electrode in a range between a first position corresponding to a partial load on the generator and a second position corresponding to a full load on the generator, said distribution means having a chamber to receive water, said chamber including a horizontal bottom having a group of openings above each of said at least one electrode for directing vertical water jets against and into each of said at least one electrode; and a water collecting means mounted in stationary manner in said vessel in a horizontal plane between said distribution means and each of said at least one electrode, said collecting means being vertically disposed below at least a portion of said distribution means when said distribution means is within said range and vertically out of alignment with each of said at least one electrode for collecting that portion of the water not directed at each of said at least one electrode.

2 . The combination as set forth in claim 9 which further comprises a collecting grid below each of said at least one electrode to collect the water jets from each of said at least one electrode.

3. The combination as set forth in claim 9 wherein said vessel is disposed on a vertical axis and said distribution means is rotatably mounted on said axis.

4. The combination as set forth in claim 11 wherein said distribution means includes a pipe coaxial with said axis, and wherein said generator further comprises a central pipe stub protruding into said vessel and having said pipe rotatably thereon below a level of water in said vessel and means for feeding water from within said vessel through said pipe stub into said pipe to said distribution.

5. The combination as set forth in claim 12 which further includes a rotatable drive shaft extending through an upper end of said vessel and connected to said pipe for rotating said pipe.

6. The combination as set forth in claim 13 which further comprises a stuffing gland sealing said drive shaft in said vessel upper end.

7. The combination as set forth in claim 9 wherein said distribution means includes a slot-like overflow opening adjacent said openings in said bottom, said overflow opening being disposed vertically above said collecting means to deliver overflow thereto.

8. The combination as set for h in claim 9 which includes a plurality of said electrodes and an equal number of said distribution means.