US3719472A

US3719472A - Process for the purification of beryllium metal

Info

Publication number: US3719472A
Application number: US00090307A
Authority: US
Inventors: F Lerman
Original assignee: National Destillers and Chemical Corp
Current assignee: Millennium Petrochemicals Inc
Priority date: 1970-11-17
Filing date: 1970-11-17
Publication date: 1973-03-06
Anticipated expiration: 1990-03-06

Abstract

Beryllium metal is produced from impure beryllium or in situ reduced beryllium containing materials by solid phase separation from a molten mixture of beryllium-rich aluminum and/or silicon.

Description

United States Patent 91 Lerman [451 March 6, 1973 PROCESS FOR THE PURIFICATION OF BERYLLIUM METAL [75] Inventor: Frank Lerman, Cincinnati, Ohio [73] Assignee: National Distillers and Chemical Corporation, New York, N.Y.

[22] Filed: Nov. 17, 1070 [21] Appl. No.: 90,307

FOREIGN PATENTS OR APPLlCATlONS 1,435,134 3/1966 France ..75/84 OTHER PUBLICATIONS Reprint from Encyc. of Chem. Tech., Vol. 2, pp. 7-14, lnterscience Encyclopedia, New York, 1948. Kjellgren, Beryllium, Brush Beryllium Company, Cleveland.

Primary Examiner-Benjamin R. Padgett Assistant ExaminerR. E. Schafer AttorneyAllen A, Meyer, Jr.

[5 7 ABSTRACT Beryllium metal is produced from impure beryilium or in situ reduced beryllium containing materials by solid phase separation from a molten mixture of berylliumrich aluminum and/or silicon.

12 Claims, 5 Drawing Figures PATEHTEDHAR 81973 SHEET 2 BF 3 535% $09 ooom CON: m o

PROCESS FOR THE PURIFICATION OF BERYLLIUM METAL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process for beryllium metal treatment and purification.

2. Description of the Prior Art In present commercial methods, beryllium metal is usually produced from beryl ore. The beryl ore is generally fused and chemically treated to solubilize the beryllium values. These values may then be extracted with water or acid, and it is necessary to further chemically treat the values to separate impurities (primarily silicon and aluminum compounds) and to further react the beryllium values to produce beryllium hydroxide.

The beryllium hydroxide is then calcined to beryllium oxide or further chemically treated to produce other beryllium compounds, most commonly beryllium fluoride, which is the major intermediate used in beryllium production today.

In the United States, the most commonly used method of producing beryllium metal involves the reduction of beryllium fluoride by magnesium in an electric furnace. Magnesium is reacted with beryllium fluoride at temperatures of about 900C. After reaction, the mixture is then heated to approximately l300C. in order to fuse the beryllium metal present into beads or pebbles.

The beryllium beads or pebbles thus formed are vacuum melted to volatilize residual fluorides and magnesium. The beryllium is then cast into ingotsfpulverized into a fine powder and pressed into blocks.

In France, beryllium metal is typically made by the electrolytic reduction of beryllium chloride with magnesium metal in a fused salt bath. Beryllium metal is produced in flake form.

another method of producing beryllium metal involves the reduction of beryllium halides (particularly the chloride) by sodium. Beryllium chloride is typically produced by the chlorination of beryllium intermediate compounds, such as beryllium oxide, hydroxide, or sulphate. One experimental process involves the chlorination of beryl ore directly to beryllium chloride. When utilizing beryllium chloride, it is generally necessary that the beryllium chloride be purified. This is done to separate any silicon, aluminum, or other chloride impurities present. Selective volatization and condensation of the chlorides are generally practiced.

Beryllium-copper alloys are made by melting and reacting a mixture of beryllium oxide, copper and powdered carbon in an electric furnace at temperatures as high as 2,000C. The molten copper dissolves the beryllium metal as formed and thus promotes the reduction reaction.

It can be seen that the above operations generally involve multi-step processes and use costly and time-consuming preliminary separation and purification methods, often at high temperature and primarily to remove aluminum and silicon.

The novel process of this invention, involves a simple direct step for treating and purifying impure or in situ reduced beryllium metal, at temperatures substantially below the melting point of metallic beryllium, that can eliminate many of the preparatory separation and purification steps required by the prior art.

SUMMARY OF THE INVENTION Applicant has found that beryllium metal containing aluminum and/or silicon, and other impurities, may be treated and purified by a selective solid-phase precipitation from liquid mixtures of beryllium and materials such as aluminum metal and/or elemental silicon. Impure beryllium is added to, or beryllium formed in situ by the chemical or electrolytic reduction of beryllium containing materials combines with, a molten mixture containing aluminum and/or silicon. A beryllium-rich molten mixture is formed that remains liquid at temperatures appreciably below the melting point of pure beryllium. Upon controlled cooling of the liquid mixture, only solid beryllium particles are separated therefrom. These beryllium particles are separated from the liquid mixture, or from the slag layer that may cover the liquid mixture, by standard solid--liquid separation processes, and then further purified by known methods.

A simple process is thus provided for the direct separation of impurities, avoiding many of the expensive preliminary chemical treatments and separation steps of the prior art for removing aluminum, silicon and other impurities. In addition, operation is at relatively low, safe temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a liquid--solid phase diagram for the two component system beryllium-aluminum.

FIG. 2 is a liquid--solid phase diagram for the two component system beryllium-silicon.

FIG. 3 is an estimated liquid--solid phase diagram for the three component system beryllium-aluminum-sil- FIG. 4, an alternate view of FIG. 3, is a liquid--solid phase diagram for the three component system beryllium--aluminum-silicon.

FIG. 5 is a horizontal projection of FIG. 3. It represents a liquid--solid phase diagram for the three component system beryllium-aluminum-silicon, and includes isothermal solidification lines for beryllium in the molten mixtures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS,

This invention is a novel, direct method fortreating and purifying beryllium metal at temperatures appreciably below the melting point of beryllium.

The process of this invention basically comprises forminga liquid mixture of beryllium, aluminum and/or silicon, precipitating solid, purified beryllium particles from the liquid mixture by cooling, and then separating the solid particles from the liquid and other impurities which may be present.

By the term precipitation" is meant that the beryllium separates from the liquid mixture or molten mass. Precipitation is thus the act of a substance separating from a solution in a concrete state in consequence of some chemical or physical change, as by the action of cooling. The precipitate may fall to the bottom or may float at or near the top.

In the following discussion, the term liquid mixture or melt signifies an all-liquid composite of beryllium and/or aluminum and/or silicon or the nonsolid portion of such a composite. From the context of the discussion, it will be apparent that at times, the terms will denote (l) a mixture containing beryllium and/or aluminum and/or silicon that has been heated to a temperature to melt the mixture completely; (2) the completely molten mixture before or after the addition of beryllium (in the discussion relating to the formation and beryllium-enrichment of the mixture); and (3) the liquid portion of the total mixture which has been cooled and has precipitated solid beryllium.

However, it must be understood that impurities can be present in the liquid mixture. Impurities introduced with the beryllium into molten aluminum and/or silicon mixture may be of many types. They could be: the residual impurities from beryllium ores; the converted impurities and reagents in winning, concentrating, convetting and purifying the beryllium values during the many process steps between the ore and the reducible beryllium compound; and the unconverted materials, reaction media and by-products resulting from the reduction of the beryllium compound to the metal form. Impurities could remain with the reduced beryllium through incomplete purification, be purposefully left in for more economical purification in accordance with the present process, or through conducting the reduction process chemically or electrolytically in situ as described above.

Depending on the prior processing and the kind of ores, reagents, and reaction media used and intermediate materials formed, the impurities could be the elemental substances; the reduced materials from the ores as silicon, aluminum and iron; the unconverted excess of the reducing agents as sodium, magnesium, or carbon; and process contaminents such as iron and carbon from the container vessel walls. They could be compounds of these elementaL substances such as oxides of aluminum, silicon and beryllium from the ores; as halide compounds of the elemental substances, that is, by-products resulting from the conversion of impure beryllium compounds to the reducible beryllium fluoride or beryllium chloride; or the fusible reaction media introduced for the chemical or electrolytic reduction such as magnesium fluoride or sodium chloride. They could be other undesired compounds such as the carbides and nitrides of the elemental substances.

Of all the possible impurities that may be present when beryllium is dissolved in the molten aluminum-silicon mix, volatile impurities such as sodium, many of the chlorides and some fluorides, can be vaporized and vented from the system for subsequent condensation or disposal. Elemental metals and silicon, like beryllium, become part of the melt. The remaining materials will combine as a fused salt mass or slag above the molten liquid mixture of beryllium, aluminum and/or silicon.

The molten slag can be removed by any state of the art means such as skimming, decanting or liquid drawoff. If the slag is not removed before cooling the liquid mixture, precipitated beryllium from the liquid metal will rise and become suspended in the slag layer, concentrating at the bottom or top of the layer depending on the density of the slag. The slag layer can then be separated from the liquid mixture and the beryllium recovered from the liquid, or from the cooled and solidified slag, by standard physical methods.

If little or no slag is present above the liquid mixture, the precipitated solid beryllium can be separated from the liquid mixture by physical means such as skimming, decanting or filtering; then washed or pressed free of the liquid metal clinging to it; then further purified as required. A

Elemental substances such as aluminum and silicon dissolve in the liquid mixture together with the beryllium and become part of the mixture for dissolving and precipitating more beryllium. Other materials in the molten mixture, such as magnesium and iron, in low concentrations, would have little effect on the later precipitation or resulting purity of the solid beryllium. When detrimental concentrations of such impurities build up in the molten mass, the molten mass must be cleaned up or replaced.

It will be obvious that if sufficient amounts of impurities are present, such will be harmful to the system. However, the exact amount of impurities which may be acceptable in a system will vary from producer to producer, and no set limit can be provided for this figure. Preferably, the amount of impurities present is maintained at a value less than 5 percent, and most preferably around 1 percent or less, with the remainder of the system being the essential constituents of the liquid mixture or melt, i.e., beryllium, aluminum and/or silicon.

As indicated above, the liquid mixture may be formed by the addition of impure beryllium to a liquid mixture containing the components aluminum metal and/or silicon, or the beryllium may be formed in situ by chemical or electrolytic reduction to yield beryllium metal.

The liquid mixture is formed, initially, by elevation of the materials to a temperature above which the mixture is completely melted. As the following discussion will make clear, this temperature can vary considerably, depending on the constituents used, the concentration of the constituents, and if beryllium is initially present or not. Although any temperature above the melting point of the mixture can be used, usually a temperature of from 10 to 50C greater than that at which the mixture under consideration is completely melted is used to provide sufficient rapidity of melting. The liquid mixture can be held at this temperature indefinitely without beryllium precipitation. Obviously, temperatures so high as to cause volatilization of the essential constituents of the liquid mixture should be avoided, or temperatures which might damage process equipment. Other than these factors, the upper temperature limit is substantially non-critical.

When it is desired to begin solid beryllium precipitation, it is necessary to begin cooling the liquid mixture. As cooling proceeds, solid, purified beryllium particles are precipitated from the liquid mixture. The temperature of precipitation is dependent upon the liquid mixture concentration. The solid beryllium may then be separated hot from the liquid mixture or from the covering slag that may be formed.

However, separation from the hot molten mixture or covering slag which is formed is not mandatory. In brief, (this aspect of the invention is explained in full detail at a late point of the specification) other metals, or silicon, which are present will begin to co-precipitate with the beryllium if the beryllium is not removed hot at temperatures above what may be termed the "coprecipitation temperature for the system being treated. However, if the beryllium particles rise to the top of the liquid mixture or enter the covering slag (if present), a rapid cooling of the liquid mixture to solidification will minimize mixing of impurities with the prior precipitated beryllium or beryllium-slag layer. The cooling from a point just above the co-precipitation temperature to solidification should be as rapid as possible, and can vary greatly depending on the impurity level acceptable, e.g., the slower the rapid cooling is, the greater the impurity concentration will be.

Having thus described in some detail the liquid mixtures which are used in the present invention, it is appropriate to turn to a general discussion of the beryllium precipitation conditions which are used.

The beryllium enriched melt should have a composition weight ratio greater than about two parts of beryllium to about three parts of silicon. Melts having composition weight ratios below about two parts beryllium to three parts silicon will, on cooling, precipitate silicon particles, except at aluminum weight concentrations at above about 90 percent when aluminum metal particles will precipitate out from the melt.

The higher the beryllium content and the lower the silicon to aluminum ratio in the melt, the greater the yield of precipitated beryllium. In this respect, about a 12 to 1 weight ratio, or higher, of aluminum to silicon gives the optimum yields of beryllium in a single melting and cooling cycle.

In the following discussion, the terms composition and points will be used interchangeably because of the fact in discussing the phase diagrams, the points thereon actually represent various compositions, whether they are elemental, two-component compositions, or three-component compositions. The points generally refer to the composition of liquid mixtures or melts, that is the beryllium and/or aluminum and/or silicon concentrations of all-liquid mixtures or the liquid portion of mixtures containing solids, usually beryllium. Also, in the phase diagrams FIGS. 1 to 4, the vertical position of the points indicate the temperature level of the mixtures designated. Further, the abbreviations Be, Al, and Si will be used interchangeably with beryllium, aluminum, and silicon.

After the liquid mixture, which must contain beryllium, aluminum and/or silicon, is formed, there are only two critical conditions which must be observed prior to the time at which one desires to begin precipitation.

First, the liquid mixture should be of sufficiently uniform concentration so that zones of extreme concentrational variation are avoided. Second, the liquid mixture should be at a temperature above that at which beryllium precipitates. This temperature will vary greatly. However, the following material will enable one to determine, for any beryllium, aluminum and/or silicon system, operable pre-precipitation temperatures, operable and preferred beryllium precipitation conditions, and when to halt beryllium precipitation for optimum results.

Reference should now be made to the drawings for a full understanding of the present invention wherein like figures are used to denote the same composition.

FIG. I is a phase diagram of the Al-Be system with liquid, solid--liquid and solid phases shown thereon.

The binary eutectic point for this system is shown thereon, at about 644C and 1.4% Be, as letter (A).

FIG. 2 is a two-component phase diagram for the Si- Be system with the liquid phase, solid phase and phases where solid Be and a melt and solid Si and a melt exist indicated thereon. The binary eutectic point for this system is shown thereon, at l,090C and 39% Be, as letter (B).

FIG. 3 is a three-component phase diagram for the Be-Si-Al system. The surface defined by the vertical Be and Si lines is the two-component phase diagram of FIG. 2. The surface defined by the vertical Si and Al lines is the two-component phase diagram for the Si-Al system. The rearmost surface defined by the vertical Be-Al lines is the two-component phase diagram of FIG. 1. The Be-Al binary eutectic point at 644C is represented by letter (A), the Be-Si binary eutectic point at 1,090C by letter (B), the Al-Si binary eutectic point at 577C by letter (C), the Be-Al-Si ternary eutectic point at about 500C by letter (D), the Be melting point at 1,280C by letter (E), the Si melting point at 1,420C by letter (F), and the Al melting point at 660C by letter (G). The ternary eutectic point for the system beryllium-aluminum-silicon is at around 90 percent aluminum, 7.5 percent silicon and 2.5 percent beryllium.

Points (a) to (e) represent liquid mixtures initially at I,200C having the following starting compositions:

a. 57% Be-43% Al b. 61% Be-3% Si-36% Al c. 65% Be-7% Si-28% Al d. Be-20% Si-I0% Al e. Be-25% Si These compositions represent those used in the examples, and will be discussed at a later point in the specification.

The surface identifiable as (EBDA) is the beryllium-- liquid surface, the phase boundary between the melt above and the solid Be plus melt below. Eutectic lines (AD), and (CD) are shown in FIGS. 3 to 5 joining each of the binary eutectic points (A), (B) and (C), respectively, to the ternary eutectic point (D). 7

FIG. 4 is another view of the ternary phase diagram of FIG. 3 taken with the vertical Al-line in front. For purposes of simplicity the (a) to (e) composition points and their liquid composition cooling lines are not shown thereon.

FIG. 5 is a horizontal projection or view from the top of FIG. 3 with an estimated series of isothermal lines thereon, one of them, the curved line designating the 1,150C. temperature level, is indicated as HJ, and that designating the 1,100C. temperature level is KL. Both of these isotherm lines are indicated in FIG. 4.

Cooling is represented on the phase diagrams by a composition point-one of the points (a) to (e)-moving downward through the successive temperature levels. If the point represented the total mixture system, it would move vertically downward (since the overall composition remains constant) as long as no material is removed from the mixture. However, the composition point is considered to be the composition of an allliquid mixture or the liquid portion of the mixture. Therefore, on cooling, the point will move vertically downward as long as the mixture is wholly liquid. But on reaching the interface line or surface between allliquid or melt and beryllium solid plus melt, the liquid concentration point will move along the line or surface, downward, away from the 100% Be vertical line, and toward lower beryllium concentration as solid beryllium precipitates from the melt.

In simplest terms, effective Be precipitation for any of the two-component systems of FIGS. 1 and 2 will generally be from a point where the liquid mixture intersects the interface line of the liquid phase and the phase where Be plus a melt exists to a point just above the binary eutectic point. For a two-component system, the binary eutectic point is the co-precipitation temperature heretofore referred to. Cooling of the melt must either be discontinued before the melt reaches the binary eutectic point, or else the liquid mixture must be rapidly cooled through the binary eutectic point to solidification.

For a threecomponent Be-Al-Si system, as shown in FIG. 3, effective Be precipitation can be from any point where the liquid mixture intersects the surface defined by the Be-Al, Be-Si and Al-Si phase lines (the surface indicated by EBDA) to a point where the composition intersects either a line joining any binary eutectic point to the ternary eutectic point (an eutectic line) or where the composition intersects the ternary eutectic point itself. The same rapid cooling procedure or halting of cooling as described for the two-component systems may then be used.

Further, as the above explanation makes clear, for any liquid mixture formed of beryllium, aluminum and/or silicon, certain critical conditions must be observed prior to precipitation. The beryllium concentration, as well as the mixture temperature of the liquid must be above the binary eutectic point, ternary eutectic point or the point in the eutectic lines that designates the same aluminum to silicon ratio as the specific liquid used. Otherwise, silicon and/or aluminum c'ould precipitate out from the liquid mixture along with the beryllium. This will be lower than the melting point of beryllium (approximately 1,280C) and higher than the tertiary eutectic point, which is at approximately 500C.

The co-precipitation temperature" is the temperature at which aluminum a'nd/or silicon will begin to precipitate from the cooled liquid mixture along with the solid beryllium particles. This will occur when the binary or ternary eutectic point of the two or three component system is reached, or when a eutectic line is reached.

Having thus described the basic factors involved in the precipitation of Be in accordance with the present invention, it is now appropriate to turn to some practical examples of the operation of the present invention.

Turning first to an examination of FIG. 1, a liquid-- solid phase diagram for the two-component system Al- Be where the horizontal legend represents the percent of aluminum of the total amount of aluminum and beryllium, and the vertical legend represents the temperature of the binary system in degrees C, point (a) of FIG. 1 represents an Al-Be mixture at a temperature of 1,200C., which is sufficient to melt the 43 percent aluminum mixture. The following discussion will illustrate what occurs during the process of this invention where a 43% Al--5 7% Be liquid mixture is cooled.

As mixture (a) is cooled from 1,200C, its composition will stay constant until the temperature is such that the liquid--solid interface is intersected. For composition (a), this is at approximately 1,I60C. At this point, the liquid mixture which had heretofore been homogeneous because it was a complete melt becomes a heterogeneous system, i.e., as the composition intersects the liquid--solid interface, beryllium will begin to precipitate. While the overall system composition will stay constant, the liquid mixture concentration, with decreasing temperature, will follow the liquid-solid interface line and, at any given temperature, the liquid mixture will have the concentration represented by a point on the liquid -solid interface. As cooling proceeds, reference to FIG. 1 shows that the liquid mixture decreases in beryllium content. This is due to the fact that solid beryllium is precipitating therefrom. At about 644C., the liquid mixture reaches the melting point of the liquid mixture, and solidification will occur at 644C. At this point, only 1.4% Be remains in the system, and the remainder has been precipitated therefrom in the form of solid, purified Be particles. The total temperature decrease has been from 1,200 to 644C. A temperature decrease of from 1,200C. to I,OOOC. will enable all but 10 percent of the Be in the liquid mixture to be precipitated therefrom. Accordingly, from the viewpoint of the amount of cooling required, it can be seen that operation down to about 1,000C. would be greatly preferred, for thereafter a more significant temperature decrease is required to precipitate smaller amounts of Be.

The total temperature range of precipitation, as represented by FIG. 1 for the Al-Be system, is thus from about 644C. (below 644C solidification will occur) up to a temperature of about 1,280C., where the liquid mixture would be almost pure Be.

With reference to FIG. 2, FIG. 2 is a liquid-solid phase diagram for the two-component system Si-Be.

The horizontal legend represents the percent of Si in the Si-Be system, and the vertical legend represents the temperature in degrees Centigrade.

An explanation of the process of this invention for the Si-Be system will be given with reference to a composition represented in FIG. 2 by point (e), which comprises approximately 25% Si and Be. Initially, at point (e), the Si-Be is in the Si-Be liquid mixture area, and of course is a homogeneous system. As mixture (e) is cooled, the composition thereof will stay constant until the temperature is such that the liquid--solid interface line is reached. At this point, a heterogeneous system is formed, i.e., Be begins to precipitate. While the overall system composition stays constant, the liquid mixture concentration, with decreasing temperature, will follow the liquid--solid interface line and will have the composition indicated thereon. The beryllium precipitating therefrom will have the composition represented at the 0% Si or Be line. The liquid mixture will decrease in beryllium concentration until, in this instance, the Si-Be binary eutectic point is reached at approximately I,090C. At this point, Be will not precipitate alone therefrom and a decrease in temperature will first solidify the complete composition and then merely further lower the temperature thereof. At the binary eutectic point approximately 39 percent of the Be remains in the liquid mixture. Thus, for composition (e), the amount of Be therein has been decreased from 75 to 39 percent.

From a review of FIG. 2, it will be apparent that the range of effective precipitation includes compositions containing at least 39% Be at a temperature range of from about 1,090C up to about the melting point of pure Be at compositions approaching pure Be. Obviously, at concentrations less than 39% Be, one would not proceed if one wished to obtain Be alone since one would only precipitate Si with the Be at lower Be concentrations.

ln simplest terms then, the range of effective operation of the present invention for the precipitation of Be from an Al-Be system is represented in FIG. 1 by that area bounded by the solid--liquid interface (AE) and a horizontal line representing the Al-Be binary eutectic temperature. For the Si-Be system the area of effective operation is represented in FIG. 2 by that area bounded by the solid--liquid interface (EB) and the horizontal line representing the binary eutectic temperature of the Si-Be system.

With specific reference to FIG. 3, beryllium-rich liquid solutions are represented by points (a) through (e). Points (a) and (e) represent the two-component mixtures57 percent beryllium and 43 percent aluminum for (a) and 75 percent beryllium and 25 percent silicon for (e)discussed above. Point (b) corresponds to a three-component mixture of 61 percent beryllium, 3 percent silicon and 36 percent aluminum. Point (c) corresponds to a liquid mixture of 65 percent beryllium, 7 silicon and 28 percent aluminum. Point (d) corresponds to a three-component mixture of 70 percent beryllium, 20 percent silicon and 10 percent aluminum. The reaction conditions will be discussed in the specific examples set out below; the following paragraphs are merely to explain the theory for the precipitation process.

When beryllium-rich solutions with either aluminum or silicon as shown by points (a) and (e) of FIG. 3 or 5 are cooled, the points representing two-component liquid concentrations will move vertically downward to meet the beryllium-liquid lines, (EA) and (EB), where solid beryllium starts to precipitate out from the liquid. On further cooling, the points, representing liquid concentration, move down along the beryllium-liquid lines with continued beryllium precipitation until, unless cooling is stopped, they reach the low eutectic points, (B) and (A), of intersection of two liquid-solid lines. The downward movement represents cooling or temperature drop.

When the beryllium-rich liquid solutions shown by points (b), (c) and (d) of FIG. 3 and FIG. 5 are cooled, the points representing the three-component liquid concentrations will move vertically downward to meet the beryllium--liquid surface, (EBDA), where solid beryllium starts to precipitate out from the liquid. On further cooling, the points representing the three-component liquid concentrations move down along the beryllium--liquid surface with continued beryllium precipitation until, unless cooling is stopped, they reach an eutectic line, (BD) or (AD), or intersection of two liquid-solid surfaces [or, for (b), the tertiary eutectic point (D)]. On further cooling, impurities will coprecipitate from the liquid along with the beryllium.

Thus, by controlled cooling and proper initial liquid concentrations, beryllium can form liquid solutions with aluminum and/or silicon at temperatures appreciably below its melting point, and precipitate out as purified particles by cooling to temperatures, approaching in one case, to as low as about 500C.

It shall be understood that in the present invention the rate of cooling of the liquid mixture is non-critical and can vary greatly. This is due to the fact that various sizes of melts will be treated in accordance with this invention. Obviously, it will be easier to remove heat from a small melt than from a large melt, and the cooling will be more rapid with a small melt, i.e., the rate of cooling will depend on the size of the batch, the composition of the melt, and the type and size of the container used to hold the batch. Further, the degree of agitation and the method of cooling will effect the rate of cooling of the liquid mixture. It can generally be stated that slower cooling, without agitation, yields larger and less pure solid beryllium particles. Accordingly, it will sometimes be advisable to cool fairly rapidly with agitation. Further, as will be apparent, the rate of cooling need not be constant but can vary significantly from any one value. As a matter of fact, since it is actually quite difficult to maintain a constant rate of cooling, due to the many factors involved in cooling even a small melt, generally cooling will be nonuniform, and such is perfectly acceptable.

The only criteria which must be observed with respect to the cooling is that cooling not be so rapid as to prevent the precipitation of beryllium, i.e., with a very small melt one would not wish to solidify so rapidly that a solid mass is formed before the density difference between solid beryllium and the melt would permit separation. However, with large melts such will hardly be a problem.

Usually, in view of the fact no external cooling means, such as a jacket, refrigerator coils in the liquid mixture, etc. would be required, cooling is simply permitted to proceed by halting heating and allowing the natural flow of the air to cool the melt container. If desired, blowers of any type could be used to increase this natural cooling, and the liquid mixture could also be cooled by any state of the art cooling means, such as liquid streams (water) actually sprayed over the exterior of the container, a cooling jacket with a refrigerant circulated therein, refrigerator coils actually in the interior of the container etc. However, most of such means are costly and complicated, and while some savings in time may be achieved, one still obtains the same product.

In any case, no matter how cooling is performed, it is necessary to either separate the Be while hot, or else to cool quickly through the co-precipitation temperatures.

Separation before cooling is preferred. However, if after the beryllium particles rise to the top, rapid cooling through the eutectic temperatures to solidification will limit the mixing of the prior precipitated beryllium with the solidified melt.

With reference to points (a) through (c) of FIGS. 3 and 5, the following examples illustrate the separation of pure beryllium particles from the beryllium-aluminum-silicon three-component system and from the beryllium-aluminum and the beryllium-silicon twocomponent systems. In all examples, the beryllium-rich melts are, at the start, in a one-phase liquid state at 1,200C.

EXAMPLE la On cooling a two-component 57 percent beryllium and 43 percent aluminum liquid mixture (denoted by letter (a) in FIGS. 1, 3 and 5) from 1,200C to l,l60C., solid beryllium starts to precipitate from the melt. Further cooling continues to precipitate purified beryllium solids, with the liquid concentration becoming progressively poorer in beryllium as it moves toward the binary eutectic point. On stopping the cooling at 920C., an estimated 96 percent of the beryllium in the original melt precipitated as solid beryllium particles. If the cooling were continued to 800C., about 98 percent precipitates. At the binary eutectic temperature of about 644C., about 99 percent of the beryllium leaves the melt before solid aluminum starts precipitating also.

EXAMPLE Ib On cooling a three-component 61 percent beryllium 3 percent silicon and 36 percent aluminum liquid mixture (denoted by letter (b) in FIGS. 3 and 5) to l,l40C., solid beryllium starts to precipitate from the melt. Further cooling continues to precipitate pure beryllium solids, with the liquid concentration becoming progressively poorer in beryllium, but remaining at a constant 12 to 1 aluminum to silicon ratio.

When the cooling is stopped at about 740C. about 93.7 percent of the beryllium of the original melt has precipitated as purified solid beryllium particles which may be recovered. The remaining melt has an estimated concentration of 9 percent beryllium, 7 silicon and 87 percent aluminum.

Cooling to the eutectic concentration (2.5 percent beryllium-7.5 percent silicon-90 percent aluminum) at an estimated 500C gives a 98.4 percent beryllium solids yield. However, at the eutectic point, silicon and aluminum solids start precipitating with beryllium to yield an impure solid mixture.

EXAMPLE lc A three-component 65 percent beryllium, 7 percent silicon and 28 percent aluminum mixture is cooled to 1,l30C. This is represented by the letter (0) in FIGS. 3 and 5. Precipitation of purified beryllium starts at l,l30C. Further cooling to 725C. precipitates approximately 90.5 percent of the beryllium present in the melt. This leaves a melt concentration of approximately 15 percent beryllium, 17 percent silicon and 68 percent aluminum. The aluminum-silicon weight ratio of the melt remains constant at approximately 4 to 1.

Further cooling to 620C. yields a total of 94 percent of the beryllium as a precipitate, but the beryllium-silicon liquid eutectic line is reached, and silicon begins to precipitate with the beryllium. Further cooling would move the melt concentration, represented as letter (c) in FIGS. 3 and 5, along the eutectic line toward the eutectic point, with continued co-precipitation of beryllium and silicon.

EXAMPLE Id Upon cooling a percent beryllium, 20 percent silicon and 10 percent aluminum melt from 1,200 to l,l60C. (represented by letter (d) in FIGS. 3 and 5) precipitation of pure beryllium begins. The weight ratio of aluminum to silicon in this melt is l to 2. Further cooling to 960C. yields about 78 percent of the beryllium as a solid precipitate. The melt concentration, upon precipitation of 78 percent of the beryllium, is approximately 34 percent beryllium, 44 percent silicon and 22 percent aluminum. Further cooling to the eutectic line, at approximately 930C, would yield about 82 percent beryllium solids, with the precipitation of silicon beginning.

EXAMPLE Ie Upon cooling a percent beryllium and 25 percent silicon liquid mixture to 1,1 C. (represented by letter (e) in FIGS. 2, 3 and 5) beryllium solids come out of the melt. Further cooling to 1,100C. yields about 75% of the beryllium from the melt. Continued cooling to the binary eutectic temperature of l,090C. would precipitate a total of about 78.7 percent of the beryllium before silicon leaves the melt in solid form.

In each of the above examples, the beryllium solids which have precipitated upon cooling to a temperature above the eutectic temperatures may be separated from the molten mixture by standard solid--liquid separation techniques, examples of which are skimming, centrifuging, filtering and the like.

If a molten slag has formed on the liquid surface, unless previously removed, it will suspend the solid beryllium particles. For heavy slags, the solid beryllium will tend to concentrate and float on it. By heating above the melting point of beryllium, a liquid layer or pool of beryllium would form on the slag. For light slags, the solid beryllium particles would tend to concentrate between the slag layer and the underlying melt of aluminum and/or silicon.

If the precipitated beryllium is not separated hot, rapid cooling of the melt through the eutectic temperatures to solidification will limit mixing of impurities with the beryllium that has previously precipitated above the eutectic temperature.

In any case, the slag and beryllium would be removed together or separately from the silicon-aluminum melt while in the hot state or when cooled and solidified.

Various types of metallurgical furnaces, coal, oil, gas-fired or electrically heated (resistance, are or induction), of the stationary, rocking, rotating or tilting type may be used to carry out the heating and melting, reduction, cooling and separating operations. However, furnaces such as used for melting beryllium (e.g. high frequency induction furnaces) would be particularly suited for the process where impure beryllium is added to the charge, providing adequate modifications are made for the cooling and separating operations.

Where chemical or electrolytic reduction in situ takes place, equipment similar to that used in the specific reductions would be used, modified for adequate heating, cooling and separating operations. For example, one could modify and use for the chemical reduction of beryllium compounds an arc-resistance steel furnace, lined with a refractory or a corrosion-resistant metal, such as is used in the direct reduction of beryllium oxide with copper to make beryllium-copper master alloys. Here the electrical heating circuit extends from the metal or carbon electrode rods to the melt or charge.

Where reduction is electrolytic, the furnace and electrolytic cell may be a corrosion-resistant steel pot, externally heated, that serves as a material container and a cathode. The graphite anode extends through the cover. Such equipment is used in the electrolysis of beryllium chloride in molten sodium chloride for the production of beryllium metal.

Since hot beryllium reacts with oxygen and nitrogen and with many other gases, a vacuum or a protective atmosphere of argon or hydrogen, etc. is needed in the processing of beryllium. The pot, crucible or cell containing the melt or material charge must be tightly sealed. In the container or its cover are inlets or outlets for inert gases, volatile reactants and products, for the material charge and for the draw-off of liquids or solids.

Indirect cooling of the melt can be accomplished by air cooling, by circulating gases, water or other fluids and by water or oil quenching. Cooling can be done with the melt in place in the furnace, after the pot or cell has been removed from the furnace, or in auxiliary containers into which the melt is drawn off or poured.

I Cooling is done slowly, usually by air or gas, with the melt unstirred or with slow stirring while the solid beryllium metal is precipitating out and rising to the surface of the melt of aluminum and/or silicon with beryllium. Unless the precipitated beryllium or its mixture with slag is removed while hot, the melt is rapidly cooled to solidification by quenching or liquid cooling to limit mixing of aluminum, silicon or other impurities with the prior precipitated beryllium above the melt.

EXAMPLE II To a dried mixture of 48 grams of aluminum, 3 grams of silicon and 200 grams of sodium chloride in a stainless-steel reactor pot, lined with molybdenum and fitted with a stirrer and a thermowell, is added 80 grams of a dry beryllium chloride and 46.3 grams of sodium.

The entire charge is set into a small tilting electric induction furnace and heated under an argon blanket to 750C. to start the reduction reaction. The reaction heat brings the temperature to above 800C. The charge is further externally heated to 960C. Stirring is started and continued for minutes to complete the reaction and affect the solution of the beryllium into the molten aluminum-silicon mixture. The stirring is stopped and the reactor pot is removed from the furnace. The pot is allowed to stand for about one-half hour and air cool to a temperature of 650C. to permit precipitation of solid beryllium particles from the melt. Then the pot is water quenched to room temperature.

The solidified contents of the pot are removed. The upper salt layer is physically separated from the solidified aluminum-silicon-beryllium, and the remaining salt is water washed from the solidified metal mix. The salt is then dissolved in cold water and filtered, leaving a beryllium metal residue. This is water washed and dried. About 6 grams of beryllium are thus recovered. This is the part of the 9 grams of beryllium produced from the beryllium chloride in the sodium reduction that was dissolved and then, on cooling,

precipitated from the molten aluminum-silicon. The other 3 grams from the reduced beryllium chloride are dissolved and remain in the aluminum-silicon mix.

EXAMPLE III The aluminum-silicon mix containing beryllium that is recovered from the run of Example II is thoroughly dried in a cleaned pot and melted with the addition of 40 grams of beryllium metal under a blanket of argon gas by heating in the furnace to about 1,150C. Stirring is started and continued for 15 minutes. The stirring is then stopped and the pot is allowed to stand for about one-half hour and air cool outside the furnace to a temperature of about 650C. The pot is water quenched to room temperature. The solidified contents of the pot are removed. The upper half of the solidified mass is shown to be of very high beryllium content.

The recovered beryllium is generally cleaned of adhering impurities by standard washing techniques. For example, molten sodium metal or salts may be utilized for washing, or water and water solutions may be used when the beryllium has cooled.

The beryllium-poor aluminum-silicon mix is reused by reheating and enriching with impure beryllium added or formed in situ. The cooling process will then be repeated on the enriched molten mixture in order to produce more beryllium particles.

1f aluminum and/or silicon is lost from the mix, this may be made up by the addition of aluminum and/or silicon or by the reduction of their oxides or salts. Excessive build-up of silicon and/or aluminum in the melt is drawn off before reusing and enriching the melt.

It will be appreciated by one skilled in the art that the purity of the final beryllium metal product will depend on the thoroughness of its separation from the molten aluminum-silicon mixture or from the slag and on the subsequent final purification of the beryllium as, or if, required.-

It is believed that the temperatures, compositions, etc. of the liquid will be obvious from the heretofore offered discussion. However, certain preferred and most preferred ranges exist, and the following discussion will provide illustrative examples thereof. All percentages are in percent by weight based upon the Be, Al and/or Si in the liquid mixture.

Estimated Limits for Beryllium Precipitation Preferred Begin 1270-1000 97-40 1-20 2-40 End 1205-950 46-325 18-225 36-45 Most preferred Begin 1215-1035 85-46 5-18 -36 End 1000-960 40-34 -22 40-44 0% Aluminum Preferred Begin 1277-1140 99-55 0 1-45 End 1 150-1095 60-40 0 40-60 Most preferred Begin 1220-1150 90-60 0 10-40 End 1140-1110 55-45 0 45-55 Thus, it can be seen that applicant has provided a method for producing purified beryllium particles without the necessity of many of the extensive preliminary processing steps for concentration, purification and fine particle subdivision commonly utilized in the present commercial production of beryllium.

While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A process for producing beryllium which comprises:

a. melting a reducible beryllium compound, reducing agent and reducing media into a liquid mixture containing a member selected from the group consisting of aluminum, silicon and mixtures thereof.

b. reducing the beryllium compound in situ to impure beryllium metal at a temperature sufficient to provide a mixture of the beryllium metal and said member from said group,

c. cooling the mixture from step (b) to precipitate purified solid beryllium particles from the mixture, and

d. separating said purified beryllium particles from said mixture.

2. A process as in claim 1, where said mixture after step (c) is rapidly cooled to solidification and then the purified beryllium is separated therefrom.

3. A process as in claim 1 wherein said liquid mixture comprises aluminum.

4. A process in claim 2 wherein said liquid mixture comprises aluminum.

5. A process as in claim 1 wherein said liquid mixture comprises silicon and said mixture is cooled to a point no lower than the binary eutectic point of the beryllium-silicon mixture formed during step (b).

6. A process as in claim 2 wherein said liquid mixture comprises silicon.

7. A process as in claim 1 wherein said liquid mixture comprises both aluminum and silicon.

8. A process as in claim 2 wherein said liquid mixture comprises both aluminum and silicon.

9. A process as in claim 8 wherein said mixture of beryllium, silicon and aluminum is cooled to a point no lower than the corresponding eutectic temperature of said beryllium, aluminum and silicon mixture.

10. A process as in claim 9 wherein said beryllium, aluminum and silicon mixture has a composition weight ratio greater than about two parts beryllium to about three parts silicon.

11. A process as in claim 1 wherein there is formed a layer of impurities or slag on said mixture which contalns said precipitated beryllium and from which, upon solidification, said beryllium is separated.

Claims

1. A process for producing beryllium which comprises: a. melting a reducible beryllium compound, reducing agent and reducing media into a liquid mixture containing a member selected from the group consisting of aluminum, silicon and mixtures thereof. b. reducing the beryllium compound in situ to impure beryllium metal at a temperature sufficient to provide a mixture of the beryllium metal and said member from said group, c. cooling the mixture from step (b) to precipitate purified solid beryllium particles from the mixture, and d. separating said purified beryllium particles from said mixture.

3. A process as in claim 1 wherein said liquid mixture comprises aluminum.

4. A process in claim 2 wherein said liquid mixture comprises aluminum.

6. A process as in claim 2 wherein said liquid mixture comprises silicon.

11. A process as in claim 1 wherein there is formed a layer of impurities or slag on said mixture which contains said precipitated beryllium and from which, upon solidification, said beryllium is separated.