US1007683A - Process of forming oxids of nitrogen. - Google Patents

Description

0, ELLIS. PROCESS OF FORMING OXIDS OF NITROGEN.

AIYLIUATION FILED JULY 29,1911.

1,007,683. Patented Nov. 7, 1911.

@YIIIIII' 5 WITNESSES:

Wim T%E PATENT oTT oE.

CARLETON ELLIS, OF MONTCLAIR, NEW JERSEY, ASSIGNOR TO ELLIS-FOSTER COIVL PANY, A CORPORATION OF NEW JERSEY.

PROCESS OF FORMING OXIDS F NITROGEN.

' following is a specification.

This 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 into contact' with an elec} tric arc, whereby a sufiicient exposure is se- .cured to saidarc to produce a maximum content of oxids of nitrogen all-as more fullyhereinafter described and claimed.

At the enormously high temperature of the electric arc nitrogen and oxygen appar ently dissociate into atoms, and these combine to form nitric oxid as follows This is probably a pure thermal effect and not due to any specific electric effect. That thermal action is sufiicient for this reaction is indicated by the work of Bunsen wlio found that in the explosion of air with hydrogen, oxids of nitrogen formed. Unfortunately, this reaction does not progress to completion. On the contrary, it is very incomplete.

As a purely thermal effect, the simple physico-chemical laws obtain. The law of mass action determines equilibrium and from the above equation we have- K. is a constant depending upon the temperature and is independent of the relative amounts of gas at the beginning of the reaction. It is of course important to de termine the most favorable temperature for Specification of Letters Patent.

Application filed July 29,

Patented Nov. '7, 1911. 1911. Serial No. 641,365.

It has been observed that the output of nitric oxid is smaller, the greater the energy which produces the arc. The electric arc consists of an interior portion which is very hot and an exterior portion,'superposed layer, or aureola which is at a lower temperature. Apparently the nitrogen and oxygen combine in the interior portion of the arc and in passing from thencethrough the aureola are cooled in so gradual a way.

that a reversal of the reaction occurs.

Hence the greater the energy supplied to thev arc, the greater the aureola an d the more extensive the decomposition of the previously formed nitric oxid. Theoretically therefore, it .would. be better to use spark (:l-ischarges, but the energy of a spark dis charge is so small that the method is not feasible. Of course with the aid'of a system of condensers the current of a spark dis-' charge might be greatly increased, but there are difliculties in the way of-carryingout such a plan commercially. Therefore it be comes desirable commercially, to make use oft-he arc in spite of its disadvantage of aureola decomposition. more essential than efficiency.

In the treatment of air byits passage across a flaming arc, great difliculty is experienced in maintaining the continuity of the arc, as theair tends to extinguish or blow out the arc. In order to secure .the rapid cooling elfect desired when. an-

intensely hot electric arc, with an extensive aureola is employed, a great excess of air is used, so that the oxidsv of nitrogen, as soon as formed, will be swept as rapidly as possible out of the aureolazone of decomposition, and cooled by contact with the surrounding air. Hence it follows that the content of oxids of nitrogen at the present time is usually not more than 1% or so of the total air passing through the electrically heated apparatus. This means not only the .handling'ofa 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 forheating up the.98% or 99% or so of air which does not enter into reaction. The

sensible heatjabsorption in this manner is very great and the arc thereforedoes not work to good advantage under such circum stances. Probably not more than 3% or 4% of the electric energy is absorbed in the Output is often lot -under steam boilers or evaporating pans,

but the generation of heat for such purposes in this way is of course costly, and uncle sirable,

Besides the flaming are mentioned above, in which the air travels transversely across the are, there also exists the method of oxidizing nitrogen; in which air is passed helically about an elongated electric arc and in which case' aureola contact is of course pronounced.

-The present invention has for its object the production of an arc of great length, so that each furnace or unit of apparatus is capable of handling a great volume of air and in which there is aminimum 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 pass in a circular path in a plane at right angles to the axis of the normal are passing between the electrodes. Preferably also I take great pains to have the air passing through the apparatus of constant'moisture content, so that variations in moisture, such as ordinarily exist in atmospheric air, do not cause variations in the rate of production of oxids of nitrogen. ,The moisture in the air apparently has no very important bearing on the speed of reaction of the oxidation processes, although it may have a very slight catalytic effect which would be exerted both in causing an acceleration in the speed of combination of oxygen and nitrogen, as well as in the reverse reaction. The essential point is, however, to have the air constant in its content of moisture, and preferably I reduce the content of moisture below that of average humidity, by passing the air over a drying substance, such as calcium chlorid, or I may remove the moisture by refrigeration, to reach a substantially constant moisture percentage.

By reference to the drawings, the manner in which the invention is carried out may be seen.

In the drawings which,for the sake of simplicity, are diagrammatic, Figure 1 shows a side elevation and Fig. 2 an end section of one form of my-apparat-us. Figs. 3, 4, 5, 6, and 7 show other forms, involv- .ing slight structural changes.

Like numerals denote like parts in the several drawings.

In Fig. l, 1 is a cylindrical furnace chamber, having the water jacket 2, and the electrodes 3, 3. 4: is a flattened portion, serving as an air distributer and heat interchanger. The air, preferably of constant moisture content, enters by the inlet 5, and is injected into the furnace tangentially as a long, flat, thin stream, which circles about the interior of the furnace, and departs at a point near its entrance. An arc is maintained between the electrodes, and in circling about this arc the air contacts with it, and oxids of nitrogen are formed. Owing to the circular travel of the air, which follows a path at right angles to the axis of thearc, oxidationtakes place in such a manner, that there is little opportunity for reverse reaction. In Fi 3, the apparatus is set horizontally, and an electro-inagnet, 7 is arranged to maintain the arc in its normal axis. vFig. 4c, shows three inlets, 5, 9 and 10 for the entering air, the outlet being at 6. Fig. 5, shows a chamber of elliptical cross section, having two arcs and provided with means for entering the airtangentially. An electro-magnet is provided at 11, and by the use of an alternating current, the arcs formed at the electrodes, 3, 3, may be caused to vibrate to and fro, using of course, a direct current to form the arc. Fig. 6, shows another form of the apparatus in which the air is entered tangentially on one side and removed on the other side after circulating about the arc in a substantially semicircular path. Fig. 7, shows a cross section of another form in which the air is entered at 5, and the outgoing gases depart through the passage 6. A direct current may be used to form the arc, and a three phase alternating current passed through the coil surrounding the furnace at 14. The air preferably enters the apparatus under considerable pressure, so that a, proper tangential whirl may be secured.

The interior of the furnace shell may be lined with ditiicultly fusible bodies having a catalytic action, and such catalysts as thorium oXid, vanadium oxid, titanium (ixid,

uranium oxid, boron oxid, aluminum oxid and the like may be applied to the interior of the furnace shell. shell may be water cooled if desired in the manner well known in the furnace art.

In preheating the air supplied to the fur-' ing retrogressive changes 'of a material character. The present process thus secures a large output with a maximum electrical efficiency and a sufficient time contact is secured to derive the necessary heating effect.

With a long are and an air current traveling from one end of the arc to the other,

there is, as stated, unavoidable protracted aureola contact so that the union and decom- The exterior of the.

- applied to gas engines may be profitably used in carrying out the foregoing process. The illustrative method herein given de-.

picts' the invention in its preferred forms,

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 the 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 of equivalency, so far as same is herein applicable.

Commercial requirements demand the operations involved in the fixation .of nitrogen to be carried out on the large scale with apparatus of extreme simplicity and units of great size. The cost of operation and depreciation charges must be very low. The present invention obtains this object in a satisfactory way. The arrangement of air travel provides a minimum of aureola contact with respect to thelength of the arc. Direct or alternating current may be used according to circumstances. A direct current ordinarily may be used to advantage when an arc is to be pulsated by magnetic control; an alternating current being used to energize the magnet.

As a matter of commercial exigency, the alternating type of current is usually most readily available, and is therefore more extensively used in electro-thermal operations. The present process is Well adapted to be carried out efficiently with an alternating current, at for example, from 3,000 to 5,000 volts; the exact voltage depending on the ,length of the arc. The current depends on the size of the apparatus and the volume of air treated, but With the latter of constant moisture content, the amperage may be relatively small, thereby reducing retrogressive changes. Convection currents are undesirable, and the circular travel of the air, in planes at right angles to the normal axis of the arc, is important for securing a satisfactory yield. Admission of the air under a substantial pressure accomplishes theprojection of an annulus of air whose particles travel in planes at right angles to the normal axis of the arc and Without any material tendency to longitudinal movement.

To recapitulate; my. invention involves the production of an arc'of great length, capable of treating a relatively large volume of air or other nitrogen-containing gas, for

.the purpose of oxidizing the nitrogen there- I of to a substantial extent and with a minimum of aureola contact and retrogressive decomposition, characterized by the passage of the air or other gas spirally and not helically around said arc; so that the gaseous current travels in a circular path substantially in a plane at right angles to the axis of the normal arc.

' hat I claim is 1. In the process of electrically oxidizing nitrogen, the step which consists in forming an annulus of nitrogen and oxygen containing gases about an arc and in causing the particles of said gases to travel in planes substantially at right angles to the normal moisture content.

2. In the process of electrically oxidizing nitrogen the step which consists in forming an elliptical annulus of nitrogen and oxygen containing gases about an arc and in causing the particles of said gases to travel in planes substantially at right angles to the normal axis of the arc, said gases being of constant moisture content.

3. The process of oxidizing nitrogen which comprises forming an electric arc and .passing'air substantially concentrically, but

not helically, about said are.

4. ,The process of oxidizing nitrogen which comprises forming an electric arc and passing air of constant moisture content substantially, concentrically, but. not helically, about said are.

5. The process of oxidizing rgnitrog'en which comprises forming an electric arc and passing preheated air of constant moisture content substantially concentrically, but not helically, about said arc.

6. The process, of oxidizing nitrogen which comprises forming an elongated electric arc and passing a gaseous mixture containing nitrogen and oxygen, substantially spirally but not helically, about said arc;

whereby a minimum of aureola contact and retrogressive decomposition is secured.

Signed at Montclair in the county -of of June 'A. D. 1911.

, CARLETON ELLIS. Witnesses:

B. M. ELLIs, NATHANIEL L. FOSTER.

Essex and State of New Jersey this 9th day

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