JPS58141349A - Production of high purity calcium - Google Patents

Abstract

PURPOSE:To produce high purity calcium of low Mg content inexpensively by subjecting crude metallic calcium to preliminary distillation under a specific temp. range then to vacuum redistillation. CONSTITUTION:Crude metallic calcium is subjected to preliminary distillation for about >=10hr, more preferably >=12hr at about 630-700 deg.C under vacuum, preferably about 10<-2>-10<-3>Torr, then the temp. is increased to about 900-920 deg.C and the crude metallic calcium is subjected to regular distillation under the reduced pressure, whereby the high purity calcium of an extremely low Mg content is obtained in high yields. If the temp. of the above-mentioned preliminary distillation is >=700 deg.C, the performance for separating Mg is low and if the temp. is <=630 deg.C, sufficiently high rate of distillation is unobtainable. A higher effect is obtained if the crude metallic calcium is subjected to the preliminary distillation for a long time at a relatively low temp.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-purity calcium by removing magnesium from metallic calcium (Ca) by a distillation method.

Calcium metal is usually CaO and AI! FiAl again!
It is produced by a vacuum thermal reduction method in which the alloy is heated in a vacuum retort. Calcium produced by vacuum thermal reduction contains Mg and AI! , Mn, Fe, Si, and other impurities are unavoidable. Methods for reducing these impurities include carefully selecting and using highly pure raw materials, installing a baffle in a part of the condenser to absorb and remove impurities, and redistilling crude metals. Ru. However, no matter which method is used, it is difficult to reduce Mg, which has a vapor pressure close to that of Ca.

For example, A. H. Wilhelm et al. charged 75 kp of crude metal calcium into a retort and heated it to a pressure of 2 Torr.
The results of redistillation at 900° C. for an XIO time in a He atmosphere of φ are reported. According to it, AI in Ca!
Although impurities such as , Mn, Fe, Si, N, and 0 are reduced, Mg is 0.5 wt% before and after redistillation, indicating that it is difficult to remove by redistillation method. . In addition, regarding the reduction method of Mg, W, J, MeCr
Early uses a sliding condenser during re-distillation? This paper reports on a method for condensing by moving the condenser position in six stages. According to this method, metallic Ca with an Mg content of 3 ppm or less can be obtained by charging lkp of metallic Ca, but the yield is as low as about 35%, and the equipment is too low. It is complex and difficult to implement economically.

The present invention aims to eliminate these drawbacks and provide high purity calcium with a low Mg content at a low cost.

The present invention was conceived as a method for easily separating Mg from metallic Ca by studying the vapor pressures of Ca and Mg and clarifying conditions for preferentially distilling Mg. Experimental Results In the distillation of crude Cm containing impurities, when the activity coefficient of Mg is assumed to be 1 in a Ca-Mg alloy system, the evaporation amounts Wca and WMg of Ca and Mg are given by the following equation as a function of temperature.

Here, T: Distillation temperature 0K NMfl x Mole fraction of Mg in metal Ca: 1 The larger the value of WMg/WCa, the more preferentially Mg evaporates, so according to the above equation, the lower the temperature, the higher WMg/vCa. Mg is preferentially evaporated.

However, if the distillation temperature is too low, Mg will not evaporate.

As a result of various experiments taking these points into consideration, we have found a method for efficiently and significantly reducing Mg.

Next, the experimental results will be explained based on the figures.

Figure 1 shows that 6 kg of crude calcium metal containing 0.5 to 2.0 Mg is charged into a distillation retort furnace, and the pressure is 3XIOT.
The relationship between the condensation position and Mg content weight when redistilled at orr and unidirectionally condensed in a condenser is shown. Pre-distillation for preferential evaporation of Mg is carried out at 600°C to 720°C.
The main distillation of Ca was carried out for 4 hours at 900°C. The distilled metal was collected by condensing from one direction into a cooled condenser. Among the condensed metals, Mg, which is distilled in the initial process, precipitates near the tip of the condenser, so by removing this part after cooling and recovery,
Metallic calcium with low Mg content can be obtained.

In the distillation process of Ca, impurities having a vapor pressure lower than that of Ca are concentrated in the residual metal, so that the obtained metallic calcium has extremely high purity.

When the preliminary distillation temperature reaches 720°C, the WMυV (4 ratio) becomes low, resulting in poor Mg separation ability, and when it is below 600°C, a sufficient distillation rate cannot be obtained.

Figure 2 shows the preliminary distillation temperature at 65°C in an experiment similar to the above.
The results are shown when the temperature was 0°C and the treatment time was varied from 3 hours to 16 hours. From the results shown in FIG. 2, it can be seen that the longer the pre-distillation time, the more Mg evaporates.

The treatment time must be kept within the preliminary distillation temperature range for at least 10 hours, preferably 12 hours or more, and it is effective to treat at a relatively low temperature for a long time. Appropriate temperature and time of pre-distillation can be selected from the required Mg-containing cap of calcium metal and from economic point of view.

Considering equipment conditions, reaction efficiency, and the crystalline state of the metal produced, the processing atmosphere is 1 f2-1.
It is most effective to process under reduced pressure of 0-'rorr.

630 to 700 for separate distillation of Mg in this pressure range
It is necessary to control the temperature within as narrow a range as possible.

According to the method of the present invention, impurities in calcium, particularly magnesium, can be easily removed as necessary by simply changing the distillation temperature.

Furthermore, by selecting and cutting the distance from one end face of the capacitor depending on the desired purity of calcium, it is possible to obtain calcium with high purity in a good yield.

Example: 6 kg of crude metallic calcium obtained by vacuum thermal reduction method was charged into a retort for redistillation, and the pressure was adjusted to 10-2 to 1O'''3.
Torr was maintained and preliminary distillation was carried out at a temperature of 650-670°C for 16 hours. Then the temperature was increased from 900℃ to 920℃.
The main distillation was carried out for 4 hours.

The distilled metal was cooled from one direction on the condenser surface to condense and precipitate. After cooling, the condensed metal is collected and cut off at a distance of 1 crn from one end of the capacitor, and the Mg content o, os
5 kg of high purity calcium of less than ts was obtained with a yield of 8
It was 0chi. The grades of metallic calcium before and after the redistillation treatment were as follows.

Moreover, the yield when the Mg content was 0.01% or less was 55%.

Further, the yield of metallic calcium with an Mg content of 0.01% or less was 55%.

According to the present invention, Mg, Al1Mn,
High purity calcium with extremely low Fe and Zn content can be obtained in good yield.

[Brief explanation of the drawing]

Figures 1 and 2 show the condensation position and Mg in the condenser.
It is a figure showing the relationship of content. Patent applicant Showa Denko Co., Ltd. agent Patent attorney Sei Kikuchi Procedural amendment (spontaneous) September 1980 IZ Commissioner of the Patent Office Kazuo Nasugi 1 Case indication 1982 Patent ■ No. 21237 No. 26 Invention Name: Process for producing high-purity calcium 3, relationship with the amended case Patent applicant address: 13-9 Shiba Daimon-chome, Aba-ku, Tokyo Name: C20
0) Showa Denko Co., Ltd. Representative Yasunobu Hiromoto No. 1 Agent Address No. 13-S, Shiba Daimon-chome, II-ba-ku, Tokyo Showa Denko Co., Ltd. 105 03-432-5111 (Representative)
1) 6. Contents of amendment The description in Book 11111 has been amended as follows. (1) Line 9 of the third car, “Wca” is rWc! a Correct as J. (2) R6N119 row, r6kgJ to r4, 8 kg
Correct with J. (3) Delete lines 11R7142 to 3. (4) On page 87, line 9, after "yield", add "[based on 6 kg of crude metal calcium]". (2)

Claims (1)

[Claims] A method for producing metallic calcium with a low magnesium content, which comprises performing preliminary distillation at 630°C to 700°C, in a method for highly purifying metallic calcium by a reduced pressure redistillation method.