AU594323B2

AU594323B2 - Electrode configuration for a high voltage electric boiler

Info

Publication number: AU594323B2
Application number: AU53861/86A
Authority: AU
Inventors: Curtis J. Diedrick
Original assignee: Vapor Corp
Current assignee: Vapor Corp
Priority date: 1985-02-28
Filing date: 1986-02-21
Publication date: 1990-03-08
Anticipated expiration: 2006-02-21
Also published as: IN165994B; FI87011C; GB2172480A; GB2172480B; FR2587450B1; FR2587450A1; FI87011B; AU5386186A; CA1244864A; FI860843A0; FI860843A; BR8600838A; GB8605065D0; JPS61211601A

Description

i:

AUSTRALIA

Patents Act 594323 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: 3 g '7 Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: j i !UL-V r~ tt:L_-ii cLII~: 0 ti a0 0 APPLICANT'S REF.: HSI 1075 Name(s) of Applicant(s): VAPOR CORPORATION o oa o o o o "cAddress(es) of Applicant(s): o0 o o0 Actual Inventor(s): Address for Service is: 0 A Address for Service is: 6420 West Howard Street Chicago, Illinois 60648 UNITED STATES OF AMERICA CURTIS JOSEPH DIEDRICK PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000 Complete Specification for the invention entitled: "ELECTRODE CONFIGURATION FOR A HIGH VOLTAGE ELECTRIC BOILER" The following statement is a full description of this invention, including the best method of performing it known to applicant(s): Pl9/3/84 PHILLIPS ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia P17/2/83 Page 0- ELECTRODE CONFIGURATION FOR A HIGH VOLTAGE ELECTRIC BOILER Ig-T eEending application S/N 706,219, filed on February 28, 198 =se disclosed an improved method for controlling steam outputf^t c ntical boiler. The specification of S/N 706,219 and any al-ow e ndments BACKGROUND OF THE INVENTION This invention relates generally to high voltage electric boilers, and more particularly to high voltage electric boilers utilizing water jet electrodes.

High voltage electric boilers of the type utilizing Sflowing water or termed "water jet" electrodes, have been in use for a considerable period of time. Operation of 0 0 15 this type of unit has been described as early as 1935 in S° 0 Volume XXII, Number 3 of the Brown Boveri Review. In ,this type of u water flowing under pressure and directed toward high voltage electrodes is utilized to conductively heat the flowing water internal of a large .o 20 pressure vessel having insulated high voltage electrodes.

Generally speaking, units of this type are operated with three sets of high voltage electrodes, accommodating 0 widely used, three-phase electrical distribution.

Typically, units of this type operate at voltages as high as 15,000 volts phase-to-phase, generating steam at o"SO" capacities of up to 50 megawatts power input.

Although many boilers operating at lower voltages, i.e. less than 15 kilovolts (KV) phase-to-phase, are highly reliable and provide satisfactory operation, it has been necessary to supply an increasing number of units for operation at the higher end of the range, i.e.

closer to 15 KV and most recently, market demands have 4. The basic application referred to in paragraph 2 of this Declaration first application made in a Convention country in respect of the invention the subject of the application.

DECLARED Chi .cag. .lli Qi th o 6 Page 2 made it necessary to develop units capable of operating as high as 24 KV phase-to-phase volts. This trend is due to increased experience with higher distribution voltages on the part of electrical utilities, allowing them to take advantage of reduced transmission line costs. An additional market factor adding to the necessity for higher voltage operation arises from desire on the part of boiler operators to operate directly from primary distribution circuits, thus overcoming the initial costs and operating power losses of a step-down distribution transformer.

In applying boilers to the now required higher voltages, units of this type have encountered an increasing number of internal flashovers, particularly at higher 15 power levels. Applicant has discovered that in designs o used today, this flashover phenomena is largely due to Soo° jet interaction adjacent the internal boiler electrodes, 0 and$bg developed a novel electrode jet distribution 00 °configuration which essentially avoids the above men- So 20 tioned problems.

Accordingly, it is an object of this invention to provide an improved jet electrode, high voltage electric 0oo°° boiler capable of operating at phase-to-phase voltages/' oO o0 b 25 kilovolts.

It is an additional object of this invention to o 0o0 provide a water jet formation and cooperating jet electrode configuration which minimizes internal boiler flashovers due to jet interaction.

o0:0 It is yet an additional object of this invention to 30provide a jet electrode, high voltage electric boiler wherein critical dimensions relating to jet formation and high voltage electric spacing are identified; and the effects of jet disintegration due to multiple jet collisions have been eliminated.

It is a further object of this invention to provide a high voltage, water jet electrode boiler wherein the critical relationships between water conductivity and jet formation/electrode relationships are observed.

SUMMARY OF THE INVENTION The present invention provides an electi'ic boiler of the water jet electrode type, comprising; a tank for containing pressurized steam; a substantially vertically disposed electrode in said tank, said electrode having a flow channelling section for receiving water jet electrode flow and said electrode being electrically insulted from the tank; a substantially cylindrical water jet header having an inner chamber and on outer substantially vertical surface, said outer surface being spaced from said electrode and in vertical alignment with said channelling section; a plurality of tubular jet forming nozzles in said header surface each having an axial flow length of about nine inches in said header, and having a first discharge end intersecting said outer surface and a second open inlet end in said header, each nozzle axis defining an angle of degrees with said outer surface of said header; a jet discharge orifice defined by the intersection of said nozzles and said outer surface; and a critical ratio of said radial spacing to said nozzle o axial flow length of less than 1.88.

The present invention also provides an electric boiler of the water jet electrode type, comprising; a tank for containing pressurized steam; a substantially vertically disposed, high voltage electrode in said tank having a jet contact surface intermediate cooperating flow channelling edges, and said electrode being electrically insulated from said tank; a substantially vertically disposed, substantially cylindrical feedwater header having an inner chamber and an outer surface, said outer surface in vertical alignment with and separated from said contact surface and flow channelling edges by a radial distance of about sixten inches; a plurality of substantially vertically aligned tubular jet forming nozzles of about nine inches in length in said headers, each of said nozzles angularly intersecting said header surface at a first end, and having a second open end in said chamber, said angle and length determining a falling jet trajectory such that successive vertically descending jets traverse said distance, and said trajectories intersect forming a composite jet electrode wherein said composite jet and contact surface intersection lies within said channelling edges.

Further, the present invention provides a method of decreasing high voltage electrode contact area current density in an electric boiler of the water jet electrode type having a plurality of substantially vertically disposed tubular jet forming nozzles contained in a feedwater header and a substantially vertically parallel and radially spaced high voltage electrode, comprising the steps of; lengthening each nozzle in said header to a length of about nine inches; increasing the jet delivery angle such that said jet and said header form an angle of about sixty degrees; o said lengthened nozzle positioned at an increased o angle generating a plurality of flowing water jets each said jet having a falling vertical trajectory, said trajectories 0 intersecting and combining in an integrated combination flow jet, said falling jets and combined flow jet traversing a radial space of about sixteen inches; positioning said 0° electrode within said integrated jet trajectory so as to intercept said combined flow jets at a point of minimal jet interaction, wherein the area of jet contact on said high voltage electrode surface is maximized.

[-3a- Page 4 discovered contributes to effectively reducing the dynamic internal spacing of the boiler during flow conditions associated with power outputs, particularly when operating near maximum boiler ratings.

Utilization of the combination structure disclosed and claimed herein allows operation of boilers at substantially higher distribution voltages with acceptable internal arcing, and greatly reduces internal arcing or boiler "trips" in present lower voltage units.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent upon reading the following detailed description, and upon reference to the drawings in which: Figure 1 is a partially sectioned drawing of a atconventional water jet electrode boiler, particularly showing the water jet distribution header and high 0 voltage electrode in section.

Figure 2 is a section of the boiler of Figure 1 .o o 20 along the lines 2-2, particularly showing in tear-away, the generation of water jet electrodes and impingement on the channeling or collecting high voltage electrode for a single phase of high voltage.

Figure 3 is a section of an electric water jet P I quec -9n 25 electrode boiler similar to that inV a however, cono 0 structed with the objects and principles of the disclosed invention.

Figure 3a is a partial section of a high voltage o o electrode boiler showing the relationship of receiving *0 4 O 30 electrode and distribution header, and particularly showing the trajectory of interfering jets present in typical units in use today.

Figure 4 is a transverse section of Figure 3 along the lines 4-4, particularly showing the formation of a Page conventional water jet electrode wherein jet impingement or collision results in electric flashover.

While the improved electric boiler of the invention will be described in connection with the preferred embodiment disclosed, it will be understood that this particular embodiment is not intended to limit the invention to that embodiment. On the contrary, applicant intends to cover all alternatives, modifications, and cqivalents as may be included within the spirit and L0 scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION With particular reference to Figures 1 and 2, the boiler consists of an outer tank or pressure vessel 2, aa 15 containing the jet electrode feedwater header assembly 4, Ssupplying water forming the water jet electrodes 6 from 0@00 water flowing through a plurality of nozzles 8. Also internal of the boiler pressure vessel or tank, are the a. 00 0 high voltage electrodes 10. Typically, three-phase power S 20 is utilized to generate steam, therefore as disclosed (reference Figure three internal, high voltage electrode assemblies 10 are shown cooperating with three sets of nozzles or jet electrodes 8. The asspmblies o 0 include a high voltage feed through insulated 13, providing a pressure isolating electrical connection supplying current from an outside power source to the internal electrode 10. More particularly, current flow through the insulator 13 energizes the electrode flow channel 11.

Jet electrodes 6 striking the channel initiate water S 30 heating. It should be noted that in the interest of clarity, Figure 1 indicates a single set of nozzles 8, water jet electrodes 6, and high voltage receiving electrode 10. Also internal of the high pressure boiler tank is the delivery portion of the feedwater pump 12, having internal portions of its housing 14 with an inlet 16, and an outlet terminated by a feedwater delivery conduit 18. Intermediate the pump outlet and conduit 18 is a control valve and actuator assembly 20 having an actuator outside the tank 2 operating a valve closure member 21. As will be discussed later, positioning the member 21 adjusts feedwater delivery of the pump 12 to the header 4.

As shown, (reference Figure the feedwater delivery conduit provides a sufficient level of water, typically 22, within the header 4, allowing the water to flow outward from the nozzles 8 forming jet electrodes 6 which impinge on the high voltage receiving electrode 10. As shown in Figure i, the jet electrodes 6 enter the electrode 7 striking its backwall target plate 11. Coalescing jets form a vertically descending stream of feedwater exiting the electrode assembly 10 at a Slower flow section 24. The vertically flowing feedwater stream i passes through the lower electrode flow section 24 in a stream 26. The vertically flowing stream 26 continues downward until it contacts the return or counter electrode 28 where the portion of current entering the boiler via the electrode assembly 10 not returned to the electrical return via the water S jets 6 is conducted to the electrical return or boiler 0 0, et o housing. It should be noted that the stream 26 and counter electrode 28 contribute substantially to the steam generated by the boiler.

A level sensor 30 of conventional boiler feedwater level control provides inputs of additional feedwater in accordance S with feedwater needs dictated by steam demand.

Figures 3 and 3a, show a partial cross-section of a jet electrode formation and high voltage electrode construction.

Each construction utilizers, as in the above described unit, a pressurized tank 2 containing a high voltage electrode assembly supplied with high voltage from a terminal 15 through an insulated bushing 13 and having a connected water jet channelling portion 11. Typically, said channelling portion has a length of 75 inches. Centrally located within the tank 2 is a jet distribution header 4 containing a cylindrical portion having a plurality of vertically disposed orifices terminating an associated plurality of flow control nozzles 8 located R'19 internal of the header assembly 4. Each nozzle 8 has an open -6end in communication with the water level 22 of the header cylindrical portion and an end terminated by the jet forming orifice In operation, with reference to Figure 3a, with the header water level as indicated at 38, feedwater outflow from the vertically oriented orifices results in a vertical column of water jet electrodes 6 traversing the distance 48, between the cylindrical header surface 37, and the internal or flow channelling portion 11 of the electrode assembly 10. Nozzles 8 are inclined at an angle 7 from a perpendicular to the header surface 37. Each nozzle 8 has a predetermined length 9.

As shown, jet electrode trajectories from the high level 39 to low level 40 produce interference or jet intersection S occurring typically in the region shown as 41. With further a Ue reference to Figure 4, the jet collisions produced by the E o° intersections at 41, result in spreading of the agglomerated water flow with a substantial portion of the now mixed flow, i.e. a ragged jet having components of 39 and 40. Jet collision alters initial jet size to the extent that deflected Ut jets 42 are produced from interaction at 41 of jets 39 and Under these conditions, feedwater having an electric t potential close to that of the electrode header 4 is now

IIO

0, directed toward an outer surface portion 50 of the flowguide 17. As the electrode assembly 10 operates at phase voltage potential, current flow through the jet occurs along the path OVI 43, having a length 49. As the path 49 is substantially less Zo C than that of the direct path 48, flashover occurs between electrode surface 50 and header surface in the vicinity indicated as 3. This flow results in greatly decreased flashover distance and subsequent arcs depicted along path 43.

Applicant's discovery of the jet impingement phenomena has let to the jet electrode forming and high voltage electrode configuration disclosed herein, and particularly shown in Figure 3. With reference to Figure 3, as described above, the electrode assembly 10 and header 4 are contained internal of a pressure vessel or tank 2. The header assembly 4 utilizes a plurality of jet nozzles 8, terminated at one end by flow control orifices 5 and in fluid communication with header ,1AZ9_ feedwater at its opposite end. As shown, the tubular axis of -7each nozzle 8 is inclined from the perpendicular of header surface 37 at the critical angle 46. Additionally, critical lengths developed include the nozzle length 47 and the distance or radial spacing between the header cylindrical surface 37 and the high voltage electrode flow channelling surface 11 shown as 48. As indicated in further reference to Figure 3, utilizing the critical constants determined by applicant, upper water jet electrode trajectory 39 and lower jet trajectory 40, combine or agglomerate over a substantially larger vertical portion of the in electrode surface 11. Also, it has been determined that the jet collisions or interactions such as 41 are greatly diminished or nonexistent, thereby eliminating the tendency to arc caused by electtrode jets with diverse velocity components 42 (reference Figure Further, due to the relatively low velocity pressure at the header upper end, the top jets are S more likely to produce jet disintegration. Thus, in a preferred form the jet forming nozzles are at least the top four nozzles of the header.

Applicant has also discovered that the increased area of jet combination, relative to current flow, results in substantially reduced current density at the jet ir\pingement area 51 on surface 11 of the electrode assembly 10. Local heating and deterioration of the electrode is thus substantially reduced. A continuing problem in presently used jet electrode boilers is generation of hydrogen (H 2 and Soxygen (02) at electrode surfaces. It is well known that 4 reduced electrode current density minimizes gas formation through increased recombination. Improved recombination therefore results in decreased H2 and 02 generation.

Application of applicant's discovery in the torm of the disclosed embodiment has resulted in substantial improvement in high voltage jet electrode boiler operation. Applicant has observed a 67% increase in operating voltage and a 50% increase in boiler capacity at no increased jet electrode feedwater pump powe requirements.

Typical critical constants determined by applicant which produce the above mentioned improvements in boiler operation are a jet electrode nozzle length 47 of 9 inches, and an angle o~3K 46 of 300 between the nozzle axis and a -8- A

.A

Page 9 horizontal radius perpendicular to the header cylindrical surface. Spacing 48 of the high voltage electrode/header orifice discharge surface, in keeping with applicant's inventive concepts, is 16 ig inches.

The boiler further includes terminating the lower end of the ,,high voltage electrode assembly 10 in a flow section 2+ channeling combined water flow 26 from the jet electrodes 6 toward a return water counter electrode or grid 30, operating at the potential of the tank or power ground. Channeled jet electrode water passes through the counter electrode, returning to the lower portion of the tank where, typically, a return water level 32 is maintained during operation.

Those skilled in the electric boiler arts will readily understand that all jet electrode feedwater in electrode boilers is maintained at a closely controlled value of electrical conductivity, through the use of added chemicals.

Applicant has further discovered that operating at an electrode voltage of 20 KV allows reduction of the feedwater conductivity from the ordinarily used value of 2,000 micromhos to approximately 1,700 micromhos which still obtains the 50% increase in boiler output. Those 0 skilled in the electric boiler arts will readily understand that this reduction in jet electrode feedwater conductivity results in a frther reduction in the amount of hydrogen and oxygen formation at the surface 11 of boiler high voltage electrode assembly oa Those skilled in the electric boiler art will further readily understand that a number of conventional boiler auxiliary controls such as water level indicator, feedwater inlet, safety pressure valve, and others are as shown and indicated on attached Figures 1 and 2. Since these components do not form a part of the invention, no ,o~~g Page further explanation of their function will be contained herein.

In operation, water contained at the level 32 within the boiler pressurized tank 2 enters the pump inlet 16, and is delivered to the header 4 via the pump outlet conduit 18. The water level 22 essentially determines the amount of boiler steam outlet delivered to the load, since the number of jet electrodes 6 generated is direct- 6r~r 3b3 ly related to the water level 22 X in the header 4.

Feedwater of controlled conductivity exiting the nozzles 8 and forming the jet electrodes 6, strikes or impinges the central portion 11 of the h gh voltage electrode assembly 10 (reference Figure 2X) Since the tank 2 and nozzles 8 operate at essentially neutral ground, whereas the high voltage electrode operates at the phase voltage of the electric power supply, conductive water of the jet 6 is heated through current flow, generally raising its temperature and generating steam. As indicated above, the quantity of steam generated and, to some extent, its S0 20 pressure is directly determined by the number of jets and quantity of water exiting the nozzles as determined by the header water level. As only a small amount of the 0o0 jet electrode water is heated to a temperature suffio ciently high to generate steam, the cumulative water flow from the nozzles 8 and jets 6, now flowing vertically 1 downward in the flow channel 11 of the high voltage electrode assembly 10, exits the high voltage electrode at 26. At this point, the jet electrode return water is essentially at the electric potential of the high voltage 0o 30 electrode. Therefore, as shown, the electrode exit flow passes through a return water counter electrode 30. As the electrode 30 is at neutral ground or tank potential, current flow through exit flow generates additional steam within the return flow 28. All non-vaporized water returns to the lower portion of the tank 2, typically

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Page 11 maintaining a level 32. The volume of water contained at level 32 is functional in that it serves as a "stilling" or quieting volume, tending to reduce turbulence at the pump inlet.

Thus it is apparent that there has been provided in accordance with applicant's discovery and invention, an improved, high voltage, water jet electrode boiler that fully satisfies the objects, aims and advantages set forth above. While a disclosed improvement in water jet electrode/high voitage electrode configuration has been described in conjunction with a particular unit, applicant contends that many alternatives, modifications, and variations will be apparent to those skilled in the electric boiler arts in the light of applicant's foregoing description. Accordingly, applicant intends to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

Therefore, I claim: S4o ear a

Claims

2. A boilet according to claim 1 wherein said spacing is about 16 inches. ta 3. A method of decreasing high voltage electrode contact area current density in an electric boiler of the water jet electrode type having a plurality of substantially vertically disposed tubular jet forming nozzles contained in ooaa a feedwater header and a substantially vertically parallel and radially spaced high voltage electrode, comprising the steps of; lengthening each nozzle in said header to a length of about nine inches; increasing the jet delivery angle such that said jet and said header form an angle of about sixty degrees; said lengthened nozzle positioned at an increased angle generating a plurality of flowing water jets each said jet having a falling vertical trajectory, said trajectories -12- i, intersecting and combining in an integrated combination flow jet, said falling jets and combined flow jet traversing a radial space of about sixteen inches; positioning said electrode within said integrated jet trajectory so as to intercept said combined flow jets at a point of minimal jet interaction, wherein the area of jet contact on said high voltage electrode surface is maximized.
4. an electric boiler of the water jet electrode type, comprising; a tank for containing pressurized steam; a substantially vertically disposed, high voltage electrode in said tank having a jet contact surface intermediate cooperating flow channelling edges, and said electrode being electrically insulated from said tank; a substantially vertically disposed, substantially cylindrical feedwater header having an inner chamber and an outer surface, said outer surface in vertical alignment with and separated from said contact surface and flow channelling edges by a radial distance of about sixten inches; a plurality of substantially vertically aligned a tubular jet forming nozzles of about nine inches in length in said headers, each of said nozzles angularly intersecting said header surface at a first end, and having a second open end in said chamber, said angle and length determining a falling jet trajectory such that successive vertically descending jets traverse said distance, and said trajectories intersect forming a composite jet electrode wherein said composite jet and contact surface intersection lies within said channelling edges. An electric boilet according to claim 4 wherein said plurality of vertically aligned, tubular jet forming nozzles are at least the top four nozzles of said header.
6. An electric boiler according to claim 1 substantially as herein described with reference to Figure 3.
7. A method according to claim 3 substantially as herein described with reference to Figure 3. 7 UIM-13- -FV 0 eNT
8. An electric boiler according to claim 4 substantially as herein described with reference to Figure 3. DATED: 4 JANUARY, 1990 PHILLIPS ORMONDE &FITZPATRICK Attorneys For: VAPOR CORPORATION i. 4 4* It 4 -14-