US1002249A - Electrical oxidation of nitrogen. - Google Patents

Description

G. ELLIS.

ELECTRICAL OXIDATION OF NITROGEN.

APPLIGATION FILED JUNES, 1911.

1,002,249 Patented Sept. 5,1911.

m N O WITNEStSES:

cmrinron ELLIS, or MonToLA'IR, NEW JERSE'Y, a. CORPORATION or NEW JERSEY.

To all :whom it may concern: 1 Be 1tknown that I, CARLETON ELLIS, a

' citizen of the United States, and a resident secured to saidare to ently dissociate i-nto of Montclai r, in the county of Essex and State of New Jersey, have invented certain Improvements in Electrical ing is a specification.

-Th1s invention relates to the oxidation of the nitrogen of the air by electrical means, and

relates, in particular to a specific method of bringing air 'intoconta'ct with an electric arc, whereby a sufficient exposureis produce a maximum content of oxids of nitrogen, all asmore fully hereinafter describedand claimed.

At the enormously high temperature of the electric arc nitrogen and oxygen appar atoms, andthen combine to form nitric oxid as follows This is probablya pure thermal efieet and not due to any. specific electric effect. That :therma-l actionis sufficient. for-this reaction ,is indicated by the Work of Bunsen who found that in the explosion of air with hydrogen oxids of nitrogen were formed. Un-

fortunately this reaction does not progress to completion- On-thecontrary, incomplete.-

As a purely thermal effect, the simple physico-chemical lawsobtain. The law of mass action determines equilibrium and it is very from the above equation we have K. is a constant depending upon the tem- 'action. It is of course important to determine the most favorable temperature for a maximum concentration of n1tr1c oxld. 7 It has been found that at temperatures of.

3,000 to 4,000 degrees, combination is extremely rapid.- Since however,the reaction is reversible, it is very important that the gases be quickly cooled after being exposed to such a high temperature. 1 It has been found that at-a temperature of 1700 the reaction velocity is so slow, that rover; sion to nitrogen and oxygen is" not to be feared. 1

' hot.- and aureoladecomposition.

. In the treatment of I blow out the arc;

ASSIGNOR TO -ELLIS-FOSTER COMPANY,

. ELE'GTRICAI L TOVXIDATIQN oF NITROGEN-2 i It has been observed that 7 Specification of letters Patent. Patented Spt 5, 1911, hppli cationfiled June 6, 1911. SriatNo. 631,533. v

the greaterthe energy which produces theiarc. j'The electric arc'.

consists of an interior portion which is'very an exterior portion, superposed layer, or aureola which is at a lower tem-. perature. Apparently the nitrogen and oxygen combine in the interior portion of the are and inpassing from thence through the aureola are cooled in sogradual a way that a reversal of the reaction occurs. Hence the greater-the energy suppliedto the arc, the greater the aureolaand the more extensive the decomposition of the previously formed nitric oxid. Theoretically therefore, it

would be better touse spark discharges-but the energy of a spark that the method is not with the aid of a system .of condensers the, current. of a spark discharge might be greatly increased, but there are difficulties in the way of carrying out'such a plan comdischarge is so small feasible. "Of course mercially. Therefore it is necessary to make use of the arc in sp-iteof its disadvantage of air by its passage across a flaming are, great difiiculty is ex-- '1' perienced in preserving said arc, as the air tends to extinguish or In order to secure the rapid cooling effect desired, when an intensely hot electric-arc, with an extensive aureola is employed-a great-excess of air is the continuity of used, so that the oxide of nitrogen, as soon handling of a great volume of ;air in the subsequent process of absorption, but there is also a tremendous heat loss, due to employing so costly an agent as electric energy for heating up the 98 or 99%, or so of air which does not enter into reaction. The sensible heat. absorption in -,this manner is very great and the are therefore does not Work to good advantage under such circumstances; Probably not more. than 3% or 4% of the electric energy is absorbed in the actual process of making nitric oxid. Of

course a certain portionof this heat is repass in a circular path in a plane at right-v angles to the axis of the normal are passing the production of an arcof great length, so

that each furnace or unitof apparatus is capable of handling a. great volume of air and in Wl'HCh there'is a nnnunum of aureola contact with respect to the length of the arc.

Preferably for this purpose, I form a long electric are between two electrodes, or a plurality of electrodes, and cause the air to between the electrodes, and I cause said are to be deviated from its 'normal axis into the path of said current of'air Obviously, if t-he'jarc is stationary in respect to 'the travel of the gaseous current, it is liable to be extinguished bythe'blastof air against it, andto overcome this ditliculty I cause the are to revolve about its normal axis in the path of the current of air and at a speed 5 either slightly greaterthan the rate of travel lofithe air current, or preferably at a slightly lower speed, so that a lag efiect isobt-ained,

Hence, as the are is traveling practically at the same speed as'the'air current, it is prone not to be extinguished by the said current and I thussecurethe advantage of a greatly elongated transverse are with a m nimum of aureola contact.

That is to 7 say, the extinguishing effect of the air'blast isminimizedby causing the are to travel in this manner, and the aureola contact is greatly reduced over methods which involve the travel of the air longitudinally with the are. The process therefore yields alarge output with simplicity of furnace-construe} tion, small number of units and therefore reduced labor cost and maximum electrical eiiicieney. In the accompanying drawing, means are shown for carrying out my invention.

' In Figure-1, is shown a plan view of a furnace adapted to carry out the method above indicated, and Fig. 2 is a longitudinal section of Fig. 1. a

In the drawings, 1 is a cylindrical shell or furnace, having at each end the electrodes,

2; an are 3, is formed between the elec-- trodes, 2. The normal axis of this are is indicated by 4. -The furnace shell is surrounded by electromagnets 5, ,so arranged that the magnetic effect may e caused to nected to utilize the. phase efi'ects economically. An electric current is sent through the control magnet system 5, and by means 'gentiall travel in a wave or circular path about the furnace shell. An inlet, 13, is provided for the incoming air which enters the furnace in tangential fashion, so that the air current is caused to pass around the normal axis of the arc in. a concentric way. An outlet- 14, is provided for the heated gases. The passages 6 and 7, contain respectively, the outgoing and incominggases and form a con tinuous regenerator or heat recuperator. Both the inletsand outlets have the form of slits, so that the air is caused to travelin a concentric path in a plane at right angles to the normal axis of the arc.

The initial air enters the regenerative system through the pipe 9, the amount introduced being controlledby the valve 10. It is supplied under pressure; A distributing expanded portion 8 leads from wipe 9, to the flat recuperator. An outlet or the heated gases is shown at 11, and this is provided with the regulating damper l2. 7

The. operation of the process with the illustrative apparatus described is as follows :-An are is formed between the elec trodes 2, using any suitable means for startin said are. A pressure of 4-,000 to 5,000 v0 ts maybe used and in the case ofa polyphase system severalfurnaces may be c 'nof a commutator or other distributing system ormethod of connecting, magnetism is locally established and caused to travel about the furnace shell, thereby causing the are to be deviated from its normal axis and revolve in a position between the normal axis and the furnace shellf'Air is admitted through the pipe 9,'passed along the. recuperator passage 7, enters the furnace tanat slit 13, passes concentrically about t e normal "axis 4, and leaves at the slit exit :14, passing through thegrecuperator passage 6, and to the absorbing towers, etc., by the conduit 11. The rate of movement of the'arc with respect. to the speed of travel of the air is regulated in a predetermined manner; the are being speeded. either to keep slightly in advance of t e. an current or. preferably to lag slightly, so while it is a traveling substantially at the same rate as p the current of air, its la' is suflicient to permit. of the passa eoft e majorportion of the air'currentt rough the said are. In so doing, the oxygen and the nitrogen are heated to the dissociating temperature and combine to form nitric oxid; They are qu ckly however, removed fromthe zone of reverse I decomposition, as the present arrangement. it will be seen, provides a minimum of aureola contact. In passing through the recuperator the heated gases are gradually cooled and further oxidation may take place to some extent, depending'upon the length of the recuperator. When nitric. oxid is The hot gases leaving by conduit cooled below600 it takes up further oxygen, and becomes nitrogen dioxid, N0 11, may be passed under a steam boiler for the generation ofsteam, ormaybe sent under evaporatlng pans containing liquors from absorptlon operations. From thence the gases may be conducted to a tower throughwhich lime orotheralkalis in solution or suspension is passed, so as to form a mixed nitrate or nitrite. Orthe gases may go to water absorption-towers where nitric acid is formed and recovered.-'- Y I.

'As stated, the air.which enters the'apparatusis under pressure, which pressure maybe merely sufficient to propel the air through the system and this movement of the gaseous current maybe facilitated by an exhaust pump placed in the exit con creased to 2 or 3 atmospheres in which case the concentration of the nitrogen and oxygen becomes greater as it were, that is to say, the partial pressure of the nitrogen, for example, seemingly increases, and the action of the arc ismore-efi'ective. The

presence of water vapor in the air current is detrimental to the extent that variations in the humidity of the 'air causes variations from time totime in the character of reactions andI therefore prefer to have the it at a constantdegree of humidity. Re actions between gases are generally faciliair enter the apparatus either dried to a certain definite or constant condition of dryness, orelse moisten the air so as to preserve tated by the presence of a small amount of moisture, but this amount does not need to be large and in fact, a large amount of water vapor in the aircurrent-would be detrimental, as the sensible heat'of water is verygreat and increases rapidly with" increasing temperature. In the preferred form of my invention, I therefore enter the air in the apparatus under constant condition of humidity.

The interior of the furnace shell may be 55 lined with diflicultly fusible bodies havlng a catalytic action, and such catalysts as thorium oxid, vanadium oxid, titanium oxid, uranium oxid, boron oxid, aluminum oxid and the like may be applied to the interior of the furnace shell. The exterior of theshell may be water-cooled if desired in the manner well known in the furnace art.

In preheating the air supplied to thefur- I nace, it will be evident from the foregoing vthat'it is undesirable to use a preheater of so effective a character that the entering direction, or anti-clock-wise.

gases would have a temperature above the ing retrogressive changes of a material character. The present process thus secures a large output with a maximum electrical efficlency and a sufiicien-t time contact is secured to derive the necessary heating effect by the proper advance or lag of the arc and this differential acceleration or'retardation .is regulated in a predetermined manner by magnetic control or otherwise.

' With a long are and an air current traveling from one end of the arc tothe other, there is as stated, unavoidable aureola'contact so that the union and decomposition'of oxygen and nitrogen may take place an infinite number of times, during the long period oftravel, resulting in the imperfect application. and waste of electric energy. The present process overcomes this difiiculty while taking advantage of the commercially valuable features of the long are.

The illustrative methodherein given depicts the invention in its preferred form,

but it is evident that 'various modifications may be made in the manner in which the air is caused to circulate about the normal axis of an arc, and the manner in which said are is caused to travel through the air current, and I do not wish to limit'myself to the-exact procedure herein described, but may invoke the doctrine ofequ'ivalency, so far as same is herein applicable. For example, 'the apparatus shown in the drawings may be inverted thus impelling the circular current of air in the furnace 1, in a reverse Under such circumstances, the relatively cool air enters near the top of thefurnace and becomes heated more and more. as it passes forward and downward in its reverse circular path finally coming in contact with the hottest portion of the arc and forming nitric oxid.

To preclude the possibility of disturbing eddies, care should be takento avoid too close a juxtaposition of the inlet and outlet slits. If these slits are then not properly directed a slight eddy is set up which affects the are somewhat if the latter is revolving, but not appreciably if the arc is stationary. The best method of reducing exit-eddy to a minimum is'to have the exit passage or slit, set nearly inthe line of a tangent at the point of exit. Further stability can be given the flame-in the inverted type by using air of constant moisture content under pressure. With an alternating current it often becomes desirable to introduce an inductive resistance into the circuit, usually directly in series with the arc. With very large chambers a plurality ofair inlet slits may be required tosecure the necessary momentum to the air current-and pre-- recapitulate by stating that my'invention' relates to the method and its equivalents of forming an electric arc, or plurality of arcs, preferably greatly elongated, in passing about the arc, or its normal axis or the plurality of arcs or their normal or common axis a current of air, or mixture containing cs- 'sentiallyoxygen and nitrogen, in causing the current to take a circular or substantially circular path thereabout in planes substantially at right angles thereto; in withdrawing the air after making such circuit, at a point preferably adjacent to the initiation of the circular flow, in preferably causing the arc to deviate from the normal axis by magnetic action or otherwise, and to revolve about said axis at a speed preferably slightly 0 less than the speed of the-current of air, etc., and to introduce .the air or other gaseous mixture into the electrical heating zone, preferably in a preheated state, preferably under pressure and preferably of constant moisture content.

What I claim is:

k 1. The process of oxidizing nitrogen which consists in forming an elongated electric arc, in passing a current of oxygen and nitrogen concentrically in a plane at right angles to the normal axis of said arc and in magnetically deviating said electric are into the path of the gaseous current.

' 2. The process of oxidizing nitrogen which comprises forming an electric arc, in passing a current of air at a predetermined speed concentrically about and substantially 1n a plane at right angles to the normal axis of the arc and in causing said are to be deviated 0 from its normal axis and to revolve aboutsaid axis at a predetermined speed in the gaseous current.

3. The process of oxidizing nitrogen which comprises forming an electric arc, inpassing a current of preheated air at a predetermined speed concentrically about and in planes substantially at right angles to the normal axis of said arc and in causin said are to be deviated from its normal axis, and to revolve in the said gaseous current and at a rate of speed slightly less than that of the current of the gases.

.4. The process of oxidizing nitrogen which comprises forming an electric arc, in passing a current of preheated air concentrically about and in planes substantially at right angles to the normal axis of said are and in causing said are to be diverted from its normal axis by magnetic actionandto revolve about said normal axis in the path of the gaseous current at a speed less than that of ,said gaseous current.

5. The process of oxidizing nitrogen which comprises forming an elongated electric arc, in passing a current of preheated air'of constant molsture content concentrically about and in planessubstantially at right angles to the normal axis of the arc and in causing the arc to be deviated from its normal axis and revolve thereabout at a speed sli htly less than that of the rate of travel 0 I the gaseous current.

6. The process of oxidizing nitrogen which comprises forming an electric arc, in passing a current of preheated air at a predetermined speed concentrically about substantially the entire length of the arc and in planes substantially at right angles to the normal axis of the arc and in causing said are to revolve about its normal axis by magnetic action, at a speed slightly less than that of the said gaseous current in withdrawing the' said gaseous current after it has made asubstantial circuit of the normal axis of the arc, and in transmit-ting a portion of its heat to the incoming cool air.

Signed at Montclair, in the county of Essex and State of New Jersey this 25th day of May A. D. 1910.

CARLETON ELLIS.

Witnesses: NATHANIEL L. Fos'rnn SYDNEY M. SPEDON.

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