US2809096A - Process for generating sodium monoxide - Google Patents

Description

Oct. 8, 1957 HULSE PROCESS FOR GENERATING SODIUM MONOXIDE Filed Sept. 10, 1953 IN VENTOR ROBERT E. HULSE ATTORNEY Distillers and Chemical Corporation, a corporation of Virginia Application September. 10,1953, Serial No. 379,427

2 Claims. (Cl. 23--184) This invention is a new and useful process for the generationof sodium monoxide and is a. continuation-inpart of my prior application, now abandoned, Serial No. 274,927 filed March 5, 1952. The invention will befully understood from the following description read in conjunction with the drawing, which is a diagrammatic showing of apparatus in which my invention may be carried into effect.

In the ordinary process for the manufacture of sodium monoxide, metallic sodium is added continuously or inter mittently to amass of sodium monoxide maintained in an oxidizing atmosphere at a temperature between 130 and 400 C. The sodium is present in minor amounts, ordinarily from 1-5 of the total, and the sodium monoxide functions as a diluent to disseminate the sodium, improve contact between it and the oxidizing agent, and to provide heat ballast. In this process it is diff cult to obtain complete oxidation of the sodium and-the product ordinarily contains considerable very fine materialwhich, in the ultimate utilization of the sodium monoxide, is apt to be both disagreeable and dangerous.

One object of my invention is to oxidize the sodium quantitatively and easily to sodiummonoxide. Another objective is to produce a product within any desired range of particle sizes which shall be free-flowing and also free fromdust.

in the first stage of my invention I maintain a mass of sodium monoxide, in the form of particles, in a state of continuous movement and/ or agitation in an atmosphere substantially free from oxygen and inert with respect to both sodium monoxide and sodium. Any of the inert gases or mixtures thereof will function as inert atmosphere. The preferred gas is nitrogen. As commercially produced this contains traces of oxygen. Amounts of oxygen ranging up to one mol percent can be tolerated, although I prefer to work with an atmosphere containing not over one-half mol percent. Within these limits the sodium functions as a true metal with sufiicient interfacial tension or wetting action to form a surface film on the particles of monoxide. With increasing amounts of oxygen above these limits, oxidation proceeds actively and the interfacial tension or wetting action is negatived by the development of an oxide film covering the sodium. During this stage the temperature is maintained at a point above the melting point of sodium and preferably below 250 C. To the mass of sodium monoxide particles in said inert atmosphere I add sodium to the extent of a minor part by weight of the sodium monoxide, i. e., from 1-10% and preferably from 35% by weight of the sodium monoxide. At this temperature and under these conditions the sodium disseminates uniformly throughout the mass of sodium monoxide, superficially wetting the individual particles and forming a film of elemental sodium surrounding each particle. Within this temperature range the filming of the elemental sodium upon the particles of sodium monoxide will ordinarily be. fully completed within a period of from 30-45 minutes- All of the sodium may be added initially or the sodium may be ire Estates Patent fit 2,809,096 Patented Oct. 8, 1957 2 added gradually during this period or during the initial stages thereof.

Whenever the. sodium has, become uniformly and sub stantially entirely distributed as a film. upon the particles of sodium. monoxide, the inert, atmosphere. is replaced with anoxygen-containing gas which may be either air or air enriched withioxygenor relatively pure oxygen. The atmosphere operates tooxidize the superficial film. of elemental sodium uniformly and completely. to sodium monoxide. It will, then be present as a surface layer of sodium monoxide surrounding the original particle. During the oxidation stage I prefer to maintain a temperature between 200 and 300 C. and since the oxidation is exothermic, it will benecessary to coolthe, system in some way to abstract the. excess heat. ElementaLsodium isv not added duringthe oxidation stage. The oxidizing atmosphere is replenishedand maintaineduntil at least the major part, and preferably substantially all of the sodium, is oxidized to monoxide.

The two stages are-preferablycarried out continuously, i. e., by the continued addition of sodium to a mass, of sodium monoxide particles in. a condition of motion or agitation, in. an'inert atmosphere, and. by the continuous abstraction from said mass of sodium monoxide particles wetted with. a superficial film of metallic sodium, which particles are continuously introduced into a second mass composedof sodiummonoxide particles andsodium, present as asuperficial film upon these particles, in an oxidizing atmosphere, with the result that the sodium is undergoing continuous oxidation to sodium monoxide. As stated, the temperature in the first stage is preferably below 250 C. and in the second stage. preferably between 200 and 300 C. (Preferably these stages. are: operated in combination as a unitary continuous process.) Bot first. and secondstages are preferably operated at constant volume; any excess of particles over that necessary to maintain this volume is continuously abstracted from the second stage, apart of the same is withdrawn from the system for commercial utilization while the remainder is recycled to the first stage to again function as a carrier for sodium. If the second stageis operated at a higher temperature than the first stage, the particles may be cooledin transit, so that they arrive at thefirst stage atthe proper filming. temperature.

Inthis way it is possible to build up particles of sodium monoxide of substantially any desired size which, because of their mode of formation, are free from dust and relatively pure. Because of their method of formation, the particles so formed have a pearl-like structure and are composed of successively formed layers of sodium monoxide. In the preferred method of operation the sodium monoxide particles resulting from the second stage are classified, with the result that a particular range of particles most suitable for utilization in other industries, is separated and withdrawn. This cut will be composed of rounded particles which are free-flowing and substantially free from dust. The over-size from the classifying operation is preferably reground and, together with the under-size, is returned to the first stage, to be again built up into particles Qff the optimum .size. for commercial utilization.

Referring to the drawing 1 designates, a reactor of the rotary type provided with circular rims 2. and 3 rotatably carried by flanged wheels, such as 4 and 5. Suitable provision is made for driving at least some of the wheels to rotate the reactor. Suitable provision (not. shown) is also. made for heating the reactor, if desired, to initiate reaction. Inasmuch as the reaction to be carried out in the reactor is exothermic in character, provision is also made for abstracting the excess heat to keep the reactants down to the desired operating temperature, and this provision is diagrammatically indicated by pipe 61:011-

trolled by valve 7 discharging into shower head 8. Material may be introduced to the reactor through pipe 11 controlled by valve 12 discharging into conveyor 13 consisting of worm 14 driven by any suitable means diagrammatically indicated by 15 and housed in pipe 16 which extends into the interior of the reactor. Pipe 16 is in turn surrounded by pipe 17. The space between the exterior of pipe 16 and the interior of pipe 17 forms an annular duct extending into the interior of the reactor and is connected to pipe 18 controlled by valve 19. The space between the exterior of pipe 17, which is stationary, and the end 21 of reactor 1, which is rotatable, is sealed by stuffing box 22.

At the other end of the reactor conveyor 23 extends to a point within reactor 1. This consists of worm 24 driven by any suitable means diagrammatically indicated by 25 and housed in pipe 26 which extends to a point within the reactor terminating in trough 27. Pipe 26 is surrounded by pipe 28. The space between pipes 26 and 28 forms an annular duct extending into the interior of the reactor and communicates with pipe 31 controlled by valve 32. The end 33 of the reactor carries lifts, such as 34, adapted during rotation of the reactor, to lift material contained therein, and discharges into the open top of trough 27, so that it may be withdrawn from the reactor by the operation of worm 24. Material so withdrawn may be discharged through pipe 35 discharging into vibrating screens 36. Of these the topmost screen 37 is preferably about 20 mesh. The material retained on this screen is diverted through pipe 38 to grinder diagrammatically indicated by 39. Material passing through screen 37 is discharged onto screen 41, which is preferably about 40 mesh. The material retained on screen 41 which will be 20-40 mesh is discharged through chute 42 into tank 43. Material passing through screen 41 which will be finer than 40 mesh is caught in pan 44 and discharged thence through tube 45 into pipe 46. The grinder 39 is operated to yield a product which will pass 40 mesh and the combined products from grinder 39 and pan 44 are picked up and transported by enclosed conveyor 47 which may be of the so-called Redler type. Provision is made for cooling material transported by this conveyor diagrammatically indicated by pipe 49 controlled by valve 50 discharging through shower head 51 by which coolant may be distributed over the outer surface of the conveyor housing.

The Redler conveyor 47 discharges through pipe 52 into mixer 53, which is of the enclosed type, consisting of tank 54 provided with cover 55 and provided also with a mixer bar 56 driven by any suitable means diagrammatically indicated by 57. Provision is made for the controlled introduction of sodium into the tank 54 from tank 61 through pipe 62 controlled by valve 63. Any excess of material within the tank 54 over that necessary to maintain level 64 will automatically flow off through pipe 65 discharging into pipe 11.

Provision is made for operating the mixer under a controlled atmosphere and to this end a gas, such as nitrogen, may be introduced through pipe 66 controlled by valve 67 passing through the mixer and thence countercurrent to the incoming material in conveyor 47 and thence out of the system through pipe 68 controlled by valve 69.

Material in the mixer 53 may be held at any predetermined temperature by indirect heat exchange with a liquid circulated through jacket 70. Material may be introduced into mixer 53 when desired through pipe 71 controlled by valve 72.

When starting up the system mixer 53 is purged with nitrogen fed through pipe 66 and exhausted through pipe 68. Reactor 1 is purged with dry air through pipe 31 and exhausted through pipe 18. Sodium monoxide is then introduced into mixer 53 through pipe -71 by opening valve 72. The temperature of mixer 53 is brought up to 130-200 C. by circulation of a suitable hot liquid 4 in jacket 70. Reactor 1 is brought up to 200300 C., preferably 200250 C., by indirect heating, usually oil or gas-fired.

Sodium is added from tank 61 through pipe 62 to the extent of about 35% of the sodium monoxide coming into the mixer through pipe 71. During this stage the mixer bar 56 is continuously operated and the inert gas is continuously supplied through pipe 66 so that the mixing is at all times conducted in an inertatmosphere and no oxidation of the sodium occurs. The result of this procedure is to cause the sodium to distribute itself uniformly over the particles of sodium monoxide in the mixer, forming a thin film of elemental sodium over the surface of each such particle. The supply of sodium and sodium monoxide is continued in this manner, and when the amount of sodium monoxide carrying the surface film of elemental sodium has accumulated in mixer 53 in excess of that necessary to maintain level 64, the excess moves continuously through pipe 65 into pipe 11, from which it is forced by conveyor 13 into reactor 1.

Reactor 1 is kept in slow rotation. By the application of heat or coolant, the contents are held at a temperature broadly within the range of 400 C., usually within the range of ZOO-300 C. and preferably Within the range of ZOO-250 C. An oxidizing gas, such as air or air enriched in oxygen, or relatively pure oxygen, is passed in through pipe 31. If the gas contains nitrogen, the exhausted residue consisting principally of nitrogen, is withdrawn through pipe 18. Sodium monoxide carrying the superficial film of sodium is supplied to the reactor from mixer 53 at such a rate that the average dwell in the reactor is approximately 1-2 hours. The oxidizing gas is supplied at such a rate as to provide an excess of oxygen over that stoichiometrically corresponding to the sodium introduced during the same period. As a result of the foregoing the film of sodium introduced into the reactor 1 as a surface film surrounding the particles of sodium monoxide, is substantially all oxidized to form a surface layer of sodium monoxide surrounding the original particle. Sodium monoxide is continuously removed from reactor 1 by conveyor 23 discharging into pipe 35. Particles which are over-size, i. e., over 20 mesh, are retained on screen 37 and diverted through tube 38 to grinder 39 by which they are reduced to below 40 mesh and fed into pipe 46. Of the particles passing through screen 37 and which are minus 20 mesh, the particles above 40 mesh are retained on screen 41 and diverted through pipe 42 into tank 43. These particles which will fall within the range of 20-40 mesh are freeflowing and substantially free from dust. The particles passing through screen 41 and which are minus 40 mesh are diverted from pan 44 through tube 45 into the pipe 46, by which together with the particles from grinder 39, they are transferred by the conveyor 47 back into the mixer 53. They are cooled en route by water or other suitable coolant spread over conveyor 47 from the shower head 51, and thereby brought down to the temperature obtaining in mixer 53. As soon as sodium monoxide arrives at mixer 53 from Redler conveyor 47, the supply of sodium monoxide particles through pipe 71 is discontinued and the system is thereafter continued in operation, adding sodium to the extent of 35% of the incoming sodium monoxide from conveyor 47 and abstracting particles of sodium monoxide of from 20-40 mesh through pipe 42. Because the particles generated in the operation of the process are built up by the formation of successive layers of sodium monoxide, they are freefiowing and free from dust. While I have described abstracting a cut of such particles of from 2040 mesh, it will of course be understood that in commercial practice the range of particle sizes abstracted will be that required by the market. The under-size particles are of course recycled through the system until they have become built up to the desired size. In general the sizes of screens 37 and 41 should-be adjusted to take out a 5 relatively narrow out since the amount of sodium monoxide recirculated will run from 19-33 times the amount by weight which is withdrawn through pipe 42. The system may be continued in operation until it becomes necessary to shut down for maintenance.

I claim:

1. The continuous process of preparing sodium monoxide in the form of nuclear particles of sodium monoxide surrounded by a film of sodium monoxide, which comprises the step of continuously introducing nuclear particles of sodium monoxide into a mixing zone, separately introducing molten metallic sodium into said mixing zone in an amount of about 1% to about 10% of the weight of said nuclear particles, maintaining the materials in said mixing zone in a state of continuous agitation and in a temperature range from the melting point of elemental sodium to about 250 C., preventing the oxidation of the metallic sodium in said mixing zone by maintaining in said mixing zone an atmosphere inert in relation to metallic sodium and to sodium monoxide at the temperature in said mixing zone, thereby coating said nuclear particles of sodium monoxide with a film of metallic sodium, withdrawing particles so coated from said mixing zone and introducing them continuously into an oxidizing zone, controlling the temperature of the material in said oxidizing zone to maintain it within the range of about 130 C. to about 400 C., continuously introducing into said oxidizing zone an oxidizing atmosphere providing an amount of oxygen substantially greater than stoichiometrically equivalent to the metallic sodium present, thereby oxidizing the film of metallic sodium surrounding said nuclear particles substantially completely to sodium monoxide and continuously withdrawing nuclear particles of sodium monoxide surrounded by a film of sodium monoxide from said oxidizing zone.

2. Process according to claim 1 in which the material continuously withdrawn from said oxidizing zone is divided into at least two portions, including a portion serving as the process product and a portion which is recycled to said mixing zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,685,520 Carveth Sept. 25, 1928 2,279,088 Gilbert Apr. 7, 1942

Claims (1)

1. THE CONTINUOUS PROCESS OF PREPARING SODIUM MONOXIDE IN THE FORM OF NUCLEAR PARTICLES OF SODIUM MONOXIDE SURROUNDED BY A FILM OF SODIUM MONOXIDE, WHICH COMPRISES THE STEP OF CONTINUOUSLY INTRODUCING NUCLEAR PARTICLES OF SODIUM MONOXIDE INTO A MIXING ZONE, SEPARATELY INTRODUCING MOLTEN METALLIC SODIUM INTO SAID MIXING ZONE IN AN AMOUNT OF ABOUT 1% TO ABOUT 10% OF THE WEIGHT OF SAID NUCLEAR PARTICLES, MAINTAINING THE MATERIALS IN SAID MIXING ZONE IN A STATE OF CONTINUJOUS AGITATION AND IN A TEMPERATURE RANGE FROM THE MELTING POINT OF ELEMENTAL SODIUM TO ABOUT 250*C., PREVENTING THE OXIDATION OF THE METALLIC SODIUM IN SAID MIXING ZONE BY MAINTAINING IN SAID MIXING ZONE AN ATMOSPHERE INERT IN RELATION TO METALLIC SODIUM AND TO SODIUM MONOXIDE AT THE TEMPERATURE IN SAID MIXING ZONE, THEREBY COATING SAID NUCLEAR PARTICLES OF SODIUM MONOXIDE WITH A FILM OF METALLIC SODIUM, WITHDRAWING PARTICLES SO COATED FROM SAID MIXING ZONE AND INTRODUCING THEM CONTINUOUSLY INTO AN OXIDIZING ZONE, CONTROLLING THE TEMPERATURE OF THE MATERIAL IN SAID OXIDIZING ZONE TO MAINTAIN IT WITHIN THE RANGE OF ABOUT 130*C. TO ABOUT 400*C., CONTINUOUSLY INTRODUCING INTO SAID OXIDIZING ZONE AN OXIDIZING ATMOSPHERE PROVILDING AN AMOUNT OF OXYGEN SUBSTANTIALLY GREATER THAN STOICHIOMETRICALLY EQUIVALENT TO THE METALLIC SODIUM PRESENT, THEREBY OXIDIZING THE FILM OF METALLIC SODIUM SURROUNDING SAID NUCLEAR PARTICLES SUBSTANTIALLY COMPLETELY TO SODIUM MONOXIDE AND CATINUOUSLY WITHDRAWING NUCLEAR PARTICLES OF SODIUM MONOXIDE SURROUNDED BY A FILM OF SODIUM MONOXIDE FROM SAID OXIDIZING ZONE.

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