JPH0776739A - Production of metal calcium - Google Patents

Abstract

PURPOSE:To efficiently produce high-purity metal Ca by housing pellets consisting of CaO and Al into a single reaction tube in which a high vacuum degree is obtainable and individual control of temp. is possible and subjecting these pellets to reduction and distillation under specific conditions. CONSTITUTION:The pellets of the CaO (quicklime) contg. MgO and metal Al are housed in the raw material zone B of the vacuum reaction tube 1. A Ca capturing cylinder (d) is installed in a zone D and an Mg capturing cylinder (e) in a zone E. While an inert gas is passed from the zone A to the zone E, the zone B is held at the evaporation temp. (about 700 deg.C) of the Mg and under a vacuum degree of about 1X10<-2>Torr to evaporate the Mg. The Mg is deposited on the capturing cylinder (e) of the zone E kept at a low temp. (about <=600 deg.C). The zone B is then heated up to about 1100 deg.C to evaporate the Ca and the temp. of the zone D is lowered to about <=700 deg.C, by which the metal Ca is deposited in the capturing cylinder (d) of the zone D. As a result, the metal Ca having extremely high purity is easily obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing high-purity metallic calcium by vacuum thermal reduction distillation in which CaO is heated and reduced under reduced pressure using Al or an Al alloy.

[0002]

2. Description of the Related Art High-purity metal Ca is used as a reducing agent for rare metals and rare earths, as an additive for alloys, and for various other purposes, and the demand is increasing in recent years. Is used as a reducing agent to reduce CaO,
By the reaction of the following formula, about 99% crude metal Ca of the first stage is obtained (first stage), 6CaO + 2Al = 3Ca + 3CaO.Al ₂ O _{3 and} then the above crude metal Ca is repeatedly distilled at 850 ° C. using a distillation furnace. , A method by a two-step method for further increasing the purity is known.

Among the impurities in the crude metal Ca obtained in the first step, Mg is directly reflected on the purity of the raw material, and metal Al used as a reducing agent also enters as impurities. This is because the behaviors of the above elements under reduced pressure and high temperature are similar. Therefore, in the conventional first-stage reduction furnace, since the temperature, vacuum degree, etc. during the reaction have large fluctuations (especially the vacuum degree has large fluctuations), it is not possible to obtain high-purity Ca with only one step. It was necessary to set up a process.

As described above, in the prior art, in order to obtain high-purity metallic Ca, two furnaces, a reduction furnace and a distillation furnace, are required, and cost and labor are required for the construction of the furnace, its management and operation. However, there is a problem that it causes an increase in cost.

[0005]

In view of the above situation, the present inventors have proposed a method for obtaining high-purity metal Ca by a single-stage process in which a two-stage process including a reduction furnace and a distillation furnace is performed. As a result of earnest research, by using a high-vacuum reaction tube having a specific structure, a reduction evaporation reaction and a purification distillation reaction can be rapidly performed, and at least 99.9% which is superior to metallic Ca obtained by a conventional two-step process. The present invention has been completed by succeeding in obtaining a high-purity product.

An object of the present invention is to provide a method for efficiently producing high-purity metal Ca by performing reduction and distillation in a single reaction tube which can obtain a high degree of vacuum and whose temperature can be controlled individually. It is in.

[0007]

In order to achieve the above object, the present invention uses Ca or Al as a reducing agent.
In the method for producing metallic calcium by heating and reducing O under reduced pressure, a high degree of vacuum is obtained, and a raw material zone, a Mg deposition zone, and a Ca deposition zone are formed inside so that the temperature of each zone can be controlled individually. The high-vacuum reaction tube described above is used to store pellets of CaO and Al or an Al alloy in the raw material zone, generate Mg-rich vapor under the conditions of vacuum degree and temperature at which Mg is reduced and evaporated, and After the Mg-rich Ca is deposited here at a low temperature, and after the vacuum and temperature conditions in which Ca is reduced and evaporated, the Ca deposition zone is cooled to deposit high-purity Ca in the Ca deposition zone. Is the main feature. In this way, in a single reaction tube, the Mg component contained as an impurity in the raw material is evaporated in advance and deposited in another zone, so that high-purity Ca can be obtained in one reduction reaction in the Ca deposition zone. You can

[0008]

[Example] Quick lime obtained by firing limestone and pulverizing it to 200 mesh or less (CaO 93.27%, MgO 6.73%)
80 parts and 20 parts of metal Al powder are mixed, and 1 kg / cm ²
A pellet having a diameter of 20 mm press-molded under the load was used as a raw material, and the raw material was housed in the position of the raw material zone B in the vacuum reaction tube where a high vacuum of at least 10 ⁻⁵ Torr shown in FIG. 1 was obtained. Further, the Ca collection cylinder (d) was installed at the position D, and the Mg collection cylinder (e) was installed at the position E. Utilizing the fact that the evaporation temperature of Mg is lower than that of Ca, the temperature of the raw material zone (700 ° C.) and the degree of vacuum (1 × 10 ^-2 T
Org), only the impurity Mg was evaporated as the first step, and Mg vapor was deposited in the collection tube (e). As for the temperature distribution in the furnace at that time, as shown in FIG. 4, the temperature is set higher than the raw material zone up to the D zone where the Ca collection tube is present, and only the E zone where the Mg collection tube is set to a low temperature (600 ° C. or lower). Keep Mg vapor deposited.

Subsequently, as shown in FIG. 2, the temperature of the raw material zone was raised to a temperature at which Ca could be evaporated (1100 ° C.) to evaporate Ca, and Ca vapor was deposited in the collecting cylinder (d). The temperature distribution in the furnace at this time is Ca as shown in FIG.
Lower the temperature of the D zone with the collecting cylinder to 700 ° C or lower,
Metal Ca was deposited by keeping the temperature at which Ca vapor could be deposited. During the reaction, an inert gas was introduced from the A zone and exhausted to the E zone side in order to ensure the flow of vapor from the raw material side to the collection cylinder side. Immediately before the two reduction processes, the reaction tube was evacuated to a vacuum as high as possible to exhaust impurities such as oxygen.

The results of analysis of the obtained deposits are shown in the table below.
The collection cylinder (d) had a value indicating a purity of 99.9% or more, and high-purity metal Ca could be obtained by one reduction.

[0011]

As described above, according to the conventional method, after the raw material CaO is reduced in the reduction furnace to obtain the crude metal Ca,
High purity C can only be obtained by repeating the distillation by transferring to a separate distillation furnace.
Although a was obtained, according to the present invention, the reduction reaction and the purification distillation can be carried out continuously and efficiently in a single reaction tube, and extremely high-purity metal Ca can be easily obtained. Therefore, the effect such as cost reduction is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic view showing the structure of a reaction tube used in the present invention.

FIG. 2 is a graph showing a change in temperature in a raw material zone of a reaction tube.

FIG. 3 is a graph showing changes in the degree of vacuum in the raw material zone of the reaction tube.

FIG. 4 is a temperature distribution diagram in the reaction tube during Mg reduction.

FIG. 5 is a temperature distribution diagram in the reaction tube during Ca reduction and distillation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction tube 2,3 Vacuum gauge 4 Heater 5 (A to E) Thermocouple for each split furnace control 6 Raw material (CaO, Al mixed pellets) d Ca collection tube e Mg collection tube

Claims (1)

[Claims] 1. Ca as a reducing agent using Al or an Al alloy
In the method for producing metallic calcium by heating and reducing O under reduced pressure, a high degree of vacuum is obtained, and a raw material zone, a Mg deposition zone, and a Ca deposition zone are formed inside so that the temperature of each zone can be controlled individually. The high-vacuum reaction tube described above is used to store pellets of CaO and Al or an Al alloy in the raw material zone, generate Mg-rich vapor under the conditions of vacuum degree and temperature at which Mg is reduced and evaporated, and After the Mg-rich Ca is deposited here at a low temperature, and after the vacuum and temperature conditions in which Ca is reduced and evaporated, the Ca deposition zone is cooled to deposit high-purity Ca in the Ca deposition zone. The method for producing metallic calcium is characterized by carrying out reduction and distillation in a single reaction tube according to.