US2880084A - Process of preparing massive zirconium particles - Google Patents

Description

United States Patent rnocnss or PREPARING MASSIVE ZIRCONIUM PARTICLES No Drawing. Applica'tionMay 17, 1956 Serial No. 585,386

7 Claims. (Cl. 75-84.5) 1

i i The present invention relates to aprocess for preparation of massive zirconium metal and, more particularly,

to a process for preparation of massive zirconium metal from a finely divided solid mixture comprising a sodium halide and a sub-halide of zirconium. Still more particularly, the invention embodied herein relates to a sintering process for preparation of massive zirconium metal from a finely divided solid mixturecf sodium chloride and ajzirconium sub-chloride, prepared by partial reduction of zirconium tetrachloride with sodium, whereby to obmin as a product of the sintering process, massive zirconium comminutable to particles of desired particle size characteristics with minimization of production of fines.

In the usefof sodium for reduction of a zirconium tetrahalide to produce zirconium metal, a two step process can be utilized whereby, in an initial step, the zirconium tetrahalide is reacted with an amount of sodium lessthan is stoichiometrically required to complete the reduction to zirconium under conditions to produce a finely divided solid mixture of a sub-halide or halides of zirconium and the corresponding'halide of sodium. Such an initial step may be carried out at atemperature above the melting point of the sodium and below the melting point of the sodium halide or below the melting point of the resulting finely divided partially reduced mixture. Temperatures that may be suitably employed for the initial reduction step include about 175 to about 450 C. For example, whenreducing zirconium tetrachloride using sodium as the reducing agent, the initial reduction step is carried out at a temperatureabove the melting point of sodium and below the melting point of sodium chloride to produce a free-flowing, finely divided solid mixture of zirconium sub-chlorides and sodium chloride produced substantially in accordance with the following equation when the sodium is used in an amount of about 50% of that stoichiometrically required to completely reduce the zirconium tetrachloride to zirconium.

In the use of sodium for such a reaction with zirconium tetrachloride, amounts less than or more than about 50% but less than the stoichiometric amount required for complete reductionpfi the tetrachloride may be used in which case the partially reduced finely divided mixture that is obtained will contain, in addition to the sodium halide, a, mixture of sub-halides of zirconium, such as zirconium dihalide and zirconium trihalide or zirconium ice sodium halide is subjected to contact with sodium in an amount substantially suflicient to completely reduce the zirconium sub-halides to zirconium. Such a step is usually carried out by contacting the partially reduced mixture (e.g., at room temperature) with sodium and heating the mixture to a temperature (e.g., 120-200 C.) at which sodium reduction of the zirconium sub-halides is initiated. The heat of reaction from the reduction rapidly raises the temperature of the mixture to a temperature such as 800 C. or above depending on the exact intiation temperature. The mixture is then maintained at a temperature (e.g., 8l0-950 C.) which is above the melting point of the by-product sodium halide in the mixture and below the point at which zirconium seriously alloys with steel sintering pot for a period of time (usually 1 or less to 10 hours) sufficient to form massive zirconium metal. In one method for carrying out such a step, i.e., the sintering operation, sodium in an amount substantially sufiicient to effect the complete reduction of the, ZllCOlIlllllJ'l sub-halides in the finely divided solid mixture is placed in a sintering pot and cooled (e.g., to about 30 C.) before the finely divided solid mixture is added. The sintering pot is then placed in a furnace and heated until the vessel contents reach a temperature above the melting point of sodium whereby the sodium reduction of the zirconium sub-halide is initiated and the temperature of the vessel contents is then maintained at a temperature of from about 850 C. to about 950 C. until the sintering is completed and massive zirconium is formed. In another method, only a portion of the required amount of sodium is initially placed in the sintering vessel and the remainder of the required amount of sodium for complete reduction is added after the reduction reaction between the initially added sodium and zirconium sub-halides is completed.

When the sintering operation is carried out by the aforedescribed methods, it has been found that upon crushing of the product mixture, a substantial amount of undesired fines is obtained; that is for example, particles of such fineness that they pass through a 20 mesh screen. Such fine particles are objectionable as they not only complicate subsequent handling procedures (e.g., leaching and water wash treatments to remove sodium chloride) but, of considerable importance, such fines ignite very easily by means such as friction, static electricity, stray sparks, etc. Once ignited, it is extremely difficult, if at all possible, to extinguish the ignited fines whereby complete loss of product occurs.

It has now been discovered that with use of a finely divided-solid mixture of a sodium halide and a zirconium sub-halide, as may be illustrated by such a mixture comprised substantially of sodium chloride and zirconium dichloride produced by initial partial reduction of zirconium-tetrachloride with sodium as aiorediscussed, the obtainment of objectionable fines can be substantially minimized if the sintering operation (including completion of the reduction of the sub-halide) is carried out at relatively high initiation reaction temperature, such as from about 400 to about 500 C. In other Words, it has been found that if the partially reduced finely divided solid mixture is initially heated to about 400 to about 500 C. prior to contact thereof with sodium, the sintering operation results in obtainment of substantially all of the product zirconium metal in massive form of low specific surface comminutable to relatively large size particles with substantial minimization of fines formation.

In order to further described the inventiom-the following embodiments are set forth for illustration and not limitative purposes. In the described embodiment, parts are by weight unless otherwise defined.

Example] A finely divided solid mixture of substantially ZrCl -2NaCl in composition is prepared by reacting 1150 parts of zirconium tetrachloride with 430 parts of sodium at a temperature of 350-425 C., the reaction being carried out by charging the reactants in a continuous mannerinto a stirred reactor maintained under an argonblanket. r l 1580 parts of thesubstantially dry finelydivided partially reduced-mixture are placed in a sintering pot which is "thiell placed in a furnace and heated to a temperature of 450 C. (vessel contents) while maintaining the vessel contents under an argon blanket. 430 parts of sodium are then added slowly through a down pipe'in the'vessel'. The heat of reaction that occurs'upon initial addition of sodiumrapidly raises the vessel contents to a temperature of about 800 C. at which temperature the vessel contents are maintained, mainly by regulating the rate of sodium addition until the sodium addition is completed. Following the complete addition of the sodium, the temperature of the vessel contents is raised to about 950 C. and maintained thereat for one-half hour. The sintering pot and contents were then removed from the furnace and, while still at a temperature at which the by-product salt is molten, the molten salt is allowed to drain away from the zirconium sponge. The vessel contents are then removed, ground to pass through inch mesh, and leached with 1% H01 followed by a water wash to remove sodium chloride.

From such a sintering operation zirconium sponge is obtained from the crushing operation with a Brinnel hardness of 135 and in a 95% yield (560 parts) of particles of less than one quarter inch diameter but which are retained on a 20 mesh screen.

Example 2 J I For comparison purposes, a finely divided solid mixture, such as that used in Example 1, results in obtainment of only 81% of the zirconium sponge in particles of less than one quarter inch diameter but retained on a 20 mesh screen when the sintering operation is carried out by placing thev sodium in the bottom of the cool sintering pot followed by addition thereto of the finely divided solid mixture at room temperature, and subjecting the vessel contents to a sintering operation under siinilar conditions (time-temperature) as in Example 1.

Example 3 p In a manner such as described in Example 1, the finely divided partially reduced mixture is subjected to a sintering operation as described in Example l with addition of the remaining sodium for stoichiometry added to the vessel containing the finely divided mixture after the temperature of the'latter is raised to 450 C. The temperature of the contents are maintained at'825-950" C. during sodium addition by regulating the rate of sodium addition.

From such an operation, 565 parts of zirconium sponge are obtained from the crushing operation as particles-of less than inch in diameter but retained on a 20 mesh screen, i.e., the'results are comparable to those obtained in Example 1. v I

While there are above disclosed but a limited number of embodiments of the process of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed, and it is desired therefore that only such limitations be imposed on the appended claims as are stated therein.

What is claimed is:

1. A process for preparation of massive zirconium comminutable to relatively large size particles with minimized production of fines which comprises contacting with sodium a finely divided solid mixture, at a temperature of at least about 400,LC. and comprising a sodium halide and a sub-halide of zirconium, said mixture which is at said temperature being contacted with an amount of sodium sufiicient to reduce' substantially all of the zirconium sub-halide in said mixture tozirconium, and maintaining the resulting mixture at a temperature above the melting point of the by-product sodium halide but below the meltingpointof zirconium for a period of 'timesufficient to produce zirconium'in-massive form comminutable to relatively large 'size particles with mized production of fines. 1

2. A process, as defined in,clain 1 1;, wherein the finely divided solid mixture is preheated to from about 400 to about 500 CFpriO'r-to' contact with sodium.

3. A process, as defined in claim 1, wherein the finely divided solid mixture consists substantially by weight, of one part of zirconium dichlorideand two parts of sodium chloride.

4. A process, as defined in claim l,, wherein the finely divided solid mixture is at a temperature of about 400 to about 500 C. when contacted with sodium and the mixture obtained following the contact with sodium is maintained at a temperature of from about 800 to about 950 C. for a period of time sufiicient to produce zirconium in massive form comminutable to relatively large size particles with minimized production of fines.

5. A process for preparation of massive zirconium comminutable to relatively large particles with minimized formation of fines which comprises reacting zirconium tetrachloride with sodium in an amount less than stoichiometrically required to reduce said tetrachloride to zirconium to produce a finely divided solid mixture comprising sodium chloride and a sub 'chloride of zirconium, contacting said finely divided solid mixture with sodium in an amount su'fiicient to reduce substantially all of the zirconium sub-chloride in said mixture to zirconium, said mixture being at a temperature of at least about 400 0., when contacted with said sodium and maintaining the resulting mixture comprising zirconium and sodium chloride to a temperature above the melting point of sodium chloride but below the melting point of zirconium to produce zirconium in massive form comminutable to relatively large particles" with formation of fines.

6. A process, as defined in claim 5, wherein the zirconium tetrachloride is reacted with sodium in an amount of from about 25 to about 75% of that stoichiometrically required for reduction of the tetrachloride to zirconium whereby the finely divided solid mixture comprises sodium chloride and zirconium sub-chlorides.

, .7. A process, as defined in claim '5,"wherein the z'irchloride.

conium tetrachloride is reacted withsodium ilian amount of about 50% of thatstoichiom'etrically required for reduction of the tetrachloride to zirconium whereby the finely-divided'solid mixture is comprised substantially of one part of zirconium dichloride and two parts of sodium References Cited in the tile of this patent UNITED STATES PATENTS 2,607,674 Winter Aug. 19,1952

2,703,752 Glasser et al. Mar. 8, 1955 2,753,254 Rick July 3, 1956 2,758,921 Schmidt Aug. 14, 1956 FOREIGN PATENTS I 632,564 Great'Britain -2Nov. 28,, 1949 694,921 Great Britain July 29, 1953 720,517

Great Britain Dec. 22, 1954

Claims (1)

1. A PROCESS FOR PREPARATION OF MASSIVE ZIRCONIUM COMMINUTABLE TO RELATIVELY LARGE SIZE PARTICLES WITH MINIMIZED PRODUCTION OF FINES WHICH COMPRISES CONTACTING WITH SODIUM A FINELY DIVIDED SOLID MIXTURE, AT A TEMPERATURE OF AT LEAST ABOUT 400* C. AND COMPRISING A SODIUM HALIDE AND A SUB-HALIDE OF ZIRCONIUM, SAID MIXTURE WHICH IS AT SAID TEMPERATURE BEING CONTACTED WITH AN AMOUNT OF SADIUM SUFFICIENT TO REDUCE SUBSTANTIALLY ALL OF THE ZIRMAINTAINING THE RESULTING MIXTURE AT A TEMPERATURE ABOVE THE MELTING POINT OF THE BY-PRODUCT SODIUM HALIDE BUT BELOW THE MELTING POINT OF ZIRCONIUM FOR A PERIOD OF TIME SUFFICIENT TO PRODUCE ZIRCONIUM IN MASSIVE FROM COMMINUTABLE TO RELATIVELY LARGE SIZE PARTICLES WITH MINIMIZED PRODUCTION OF FINES.