US1693794A - Electrode - Google Patents

Description

Dec- 4, 1928.

1,693,794 H. w. MATHEsoN Er M Y ELECTRODE Filed Auz- 23. 1924 v l l f Q Y HIbr/ney Patented Dec. 4, 1928.

UNITED sTATEs'f PATENT OFFICE.

rI-IOYARD W'. MATHESON AND JULIAN O. SMITH, 0I MONTREAL, QUEBEC, CANADA.

ELEQTRGDE.

Application sied August 23,. im. ,serial` Nn. 738,721.

This invention relates broadly to improvements 1n electrodes, and more particularly to electrodes for use in electric steam generating or water, lheating units ofthe water resistance type. f

l, The primary ob'ect of this invention is tok rovide a construe ion of such a type that the ormat-ion of non-condensable gases, principally hydrogen and oxygen, is greatly reduced or eliminated.

Ay further object of the invention is to secure as nearly as possible a, uniform cur.- rent density over the Whole surface of the electrode and in the Water itself between the elect-rode. Y y

A still further object of the invention is toy prov-ide construction of such a type as to ensure a vigorous circulation of the Water. n The electrodes at presentin use in Water resistance electric steam generators, such as shown inSwiss Patent No. 30,925 to ReveL'are usually cylindrical members disposed axially vertically rat such distance from a complementary electrode that a discharge may take place through intervening water, and it was previously supposed that the current density wasapprcximately uniform over the entire` surface and that the electric discharge took if place without arcing. It has been, however,

discovered that althou Y l1 the two electrode surfaces may be paralleil, the currentv density of the surface is by no means uniform, being greatest at the bottom.. This non-uniformity of current density is now believed to be due tol electro-dynamic forces and rto the largevolume of steam arising over the surface of the inner electrode, the insulating effect ofthe Steam increasing with the height of the electrode. Therefore, the current density becomes much greater at the bottom Where the steamlrn is thinnest and increases to such a point that eroiner takes place under ordinary conditions. Thermal decomposition of the steam results and 'coolingof the gases takes pla-ce so rapidly that recombinatiouof the hydrogen yand oxygen is not effected. Rapid deterioration of ythe lower parts of theelectrodes is experienced; and furthermore, the circulation of the water. in the boiler is rather poor.k .s f

The factors contributing towards the formation of hydrogen and oxygen in the steam may therefore be classified as follows (1,) Non-uniform current density of the electrode until arcing takes place, causingthermal'decomposition of the Water vapour. (2) Overheating of the electrode itself,

due to the poor circulationof the Water and the non-uniform current densit It has beenrdiscovered that in the operation of an electric boiler of the type described, the voltage drop is largely'at the surface ofthe highl tension electrode and therefore the largest evolution of steam is at the surface of the electrode; with the result that if the steam' is allowed to remain in Contact kwith the discharge surface ofthe electrode, it forms an' insulating jacket around the electrode increasing in thickness from the bottom to the ktop of the electrode and thereby increasing the current density at theloiver end ofthe electrode where the steam film `is thinnest. This increase or concentration of current density is belicvedto be largely responsible for the arcing which has been foundv to occur. The quality the Water is also a considerable faotor'in the arcing tendency at any definite voltage. If

the Water 1s impure giving lowlresistance, the voltage should be lowered in order to ma1n `tain the current density below the point at `which areing begins.

eliminate arcing and the formation of noncondensable gases by ensuring a great uniformity of current density from topl to, bottolnof the electrode and by removal of steam from the discharge surface of the electrode. The accompanying drawings show scvcl'alof the many forms `which the electrode may takel inorder to produce these results. Brieflyit may be stated vthat the electrode instead of being a single continuous surface is ypreferably madeup of a number of separateA members or segments with the objectof rpresenting a numbery of separate disrharge surfaces ivith channels between 'tor the escape ol steam. These surfaces are so disposed that the separationol steam therefrom is Yfacililated and the steam permitted to ris-e Without passing` over the discharge surfaces above. rl`he arrangement also has the disadvantage. of' ensuring' better circulation of vater in the boiler with consequent ellective cooling of the e.- ftrode.

ln the accoinpanvingry drawings Aillustrating' certain, but b v no means all possible7 einl'iodimcnts et the invention :M

Fir'. l is a vertical sectional. viev.' of a boilei` with the improved electrode therein.

Fie". Q is a cross sectional vienv on the line Q-QQFiefure l.

Fiejs. 3, l and 5 are viewsshou'ing on an enlarb'ed sifale compared with Figure l,

various forms of electrode segments.

Rete `ring` more particularly to the dra2vings. ll desigA .ates u boil-er provided with an inner shell or lining` lf2, spaced from the boiler but eleetiicallfv and mechanicallvv connected thereto. The lo ver end olI the boiler ma)- be provided with a thnvnivardljvv extending lerev or settling` chamber 13. from vv'hif'h a. bleeding pipe il leads for discharge of surplus or inpure vvater to regulate the level or electric coiiductivitv of the Water in the boiler. Tater ma)r be adiritted to the boiler by any suitable means as through a pipe l5 having communication 'with the interior of' the boiler at points around the si rfa/ce thereof.

For purposes ot illustration onlj,T one elect iode is shown disposed eoncentricallv in a boiler. and majv be regarded as connected in a single phase circuit or to one phase ot a two-phase. three-phase. or poly-phase circuit, and the boiler muy be regarded as conueeted to another phase or as nroum'led. lt will be understood that tho invention applies to anyv arrangement ot electrodes, i. e., one or more to a boiler and that the dis-- charge may be between the eletrode and the boiler or between an electrode and a coinpleinentai,r Aground member nithin the boiler or between concentricallv arranged similar electrodes.

The form ot electrode illustrated coniprises a central stem 1G and a series ol reed i'irusto-conieal plates 1T, or equivalents. supported in suitable manner troni the central stem which ma;7 also serve as an electrical conductor Yfor all the plates. lt ivill be understood. hovvever. that the plates ma)Y be Ainsulated from the stein and supplied with current by a separate conductor. PreferablyY the plates increase in outr'de and inside diameter from the lower-most ip vards but there maj; be no in'r i ease in either (haineter or the increase nav be in onli.v on. diameter. Also. the p ates are preferablyv siibstantiallj.v parallel, and if desired the lower-most magv be substantiallj.v conical as shown. rVlie outer edges o'l` the plates are prelerablv rounded but maxv be thirst:- eiualior of bulbous cro `etion as shown at itl. This arrangement of plates has the advantage not onli-,V ot giving a substantialljY uni` m distribution olf current with coolol' the electrode, but at the same time removes the steam from the active surla'ge ot the electrode.

Other vforms ol electrodes are shown in lligures il, #l and 5 and embody the use of s need bars or tubes arranged in substant ally trusto-conical 'form and provided with meansV tor supimrtng the same 'from the c-eitral stem lll. The structure shown in Figure 3 embodies a single bar or tubo ll) bent in spiral-helical form and connected, as by welding, to spacers 2O which hold the .'arious turns of the helix in properly spaced relation and which are in turn mounted on the arms ot a spider or other suitable contrivanee tor supportineT the structure from aeentral stem.

Figure l; disfloses a structure dillerincf from F l only in that the bar that ol" Figure or tube lil is replaced by a series ol rings 2l secured to the supports 20.

Figure 5 shovvs an arrangement ditlerin.r from the prt-cedingT .figures in that the bars composingY the discl'iarc'e surface are arranged to point toward the. focal point of the. trustmconical structure instead of extending cireuinterentiallv as in the previous lorms. i

In all these modifications excellent coolingv is obtained but the construction not as advantageous as the solid plate construction on account of the tendone)v for steam to riso between the bars and theretoife through the disfl'iarjgro Zones. To avoid vthis condition as much as possible the barsy should be closely spaced.

The evolution ot steam is greatest u the surface of the electrode. as previously lained, and therefore in the present seg:- mental type of electrode the discharge is betvvein the outer surfaces of the electrode segments und the inner shell. Steam formed at these outer surfaces rises into contact with the inner surface of the segment next. above and flows thence upwardly through the central orince of the annular segnient and through the correspon dintr orifices ot all segments above. ln no rase should the steam `generated at a lower segment flow in :mvVy considerable amount: over tl e acti ve surface ot any segment above. The gradual increase in diameter of the see-ments from the lowest to the highest While not essential is advantageous and serves tivo purposes: Firstly, it: ensures that little or no stam risingr from b leu vvill flou' through the discharge Zone segments abov and seeondlv. it provdes a central pass through the electrode. the cross sectional area of which passage inlof) `less than one part.

creases from bottom Ata'top to accommodate the increasing volume of steam toward the top. The establishment of ay denite current of Lsteamrising through the centre of the electrode induces a vigorous circulation of water in the boiler, which circulation of water serves touniormly cool the electrode and also to maintain the conductivity of the water substantially uniform throughout the boiler.

Many modifications may be made in the form of the electrode segments or divisions, and it will therefore be understood that the invention is not limited to the details of construction and arrangement herein illustrated, but embraces all modifications and arrangements which produce the results above described.

By the use of electrodes of the general design above described, it is found in actual practice that the amount of non-condensable gases, principally hydrogen and oxygen, is greatly reduced. The amount of hydrogen developed in an electric boiler of previously known design has been found to run between 10 to 50 parts per 1,000,000 parts of steam produced, or even more; whereas with an electrode of the type described and with Water of the same characteristics, the free hydrogen drops, to g to 5 parts per 1,000,000 parts of steamk and is usually This reduction is obtained with a definite type of water and definite current density, and it is to be understood, of course, that the amount of hydrogen will vary depending on the characteristics of the water and the current density. The folowing example of resultswill serve to illustrate.

Using an installation comprising three boilers each connected to one phase of a three-phase systempand a good commercial water, it is found that with a voltage of 6,000 and total amperage of 2,200, givingr about 24,000 kilowatts tot-al input at an average current density of .5 amperes per ysquare inch, that the average of hydrogen gas produced in a series of ten tests was .S5 parts per 1,000,000 parts of steam produced, which is approximately the same amount of hydrogen as that found in steam from ordinary coal-fired boilers.

Having thus described our invention, what we claim is v l. An electrode for water resistance steam generators and the like. comprising a series of annular superposed spaced discharge members and a central conducting and supporting stem connected to `said members at intervals around the circumference theredf, whereby a steam passage is formed Within the annul, continuous from top to bottom of the electrode.

2. An electrode for water resistance steam generators and the like, comprising a series of superposed annular {ruste-conical dis` charge members increaslng 1n diameter pmgressively from the lower-most, and a conducting and supporting stem therefor disposed within the imnulaa 3. An .electrodc'for water resistance steam generators and the like, ycomprising a series of super-posed annulaifrusto-conical discharge members increasing in diameter progressively from the lowermost and supporting means therefor disposed within the annulae.

4. An electrode for water resistance steam generators and the like, comprising a series of superposed annular discharge plates rounded at their outer edges, and a conducting and supporting stem therefordisposed within the annulae.

5.. An electrode for Water resistance steam generators and the like, comprising a series of superposed annular discharge plates thickened and rounded at their outer edges, and a conducting and supporting stem therefor disposed within the annul.

` 6. An electrode for water resistance steam generators and the like, comprising a series of frusto-conical annular plates thickened and rounded at their outer edges and nested in spaced relation, and means for supporting the plates.

7. An electrode for water resistance steam generators and the like, comprising a series of frusto-conical annular plates nested in spaced relation and progressively increasing in outside diameter from the lowermost plate upwards, and means for supporting the plates and conducting electric currentto or from the same.

8. An electrode for water resistance steam generators and the like, comprising a series of super-posed electrode members adapted to be disposed at different distances from a complementary electrode, the active surface areas of such members being proportioned to the distance from the companion electrode, the direction of current flow and the conductivity of water at different levels, to the end that a substantially uniform current density is obtained at all parts of the active surface of the electrode.

9. An electrode for water resistance steam generators for use Wit-hin a comliilementarv vdefining a vertically disposed upwardly enlarging steam flow passage, said body having passages inclining upwardly from its active surface and leading into the vertical passage for transfer of steam from the acllilive snrl'uce ol die electrode inlo the vertical passage.

ll. An electrode Comprising a seires of upwardly tapering hollow members urrzingjed in superposed relation and increusingjr progressively in diameter from the lowermostJ said members combining to deline a passage increasing' in size .from lhe holloni uinvnrdly, and menus connecting the inemhers together. 10 In witness whereof, we hare hereunto set our hands.

HOVARD YV. MATHESON. JULIAN C. SMITH.

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