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Vacuum Distillation Technology in the Purification of Rare Earth Metals

1. Vacuum Technology Used in the Purification of Rare Earth Metals

As we all know, rare earths have made a significant contribution to the economic growth of countries around the world. They have many special functions. They are the basic raw materials for new functional materials such as rare earth permanent magnetic materials, magnetic refrigeration materials, and rare earth luminescent materials. In addition to metallurgy, petrochemicals and other traditional industries In addition, rare earths are also widely used in materials such as magnetism, optical fiber communication, superconductivity, etc., occupying an important position and promoting the development of emerging high-tech industries and modern military technology.

2. Difficult to Purify

There are 17 kinds of chemical elements in rare earth metals, which are composed of lanthanide elements and the same family of scandium and elements. Due to the close nature of the elements, the separation and purification process is complicated, and it is not easy to obtain mono-rare earth products. In the process of rare earth preparation, the empty environment is indispensable. With the deepening of research on rare metals, the requirements for its purity are getting higher and higher. At present, the methods for purifying rare earth metals mainly include electrolytic refining, vacuum remelting, air distillation, zone smelting, molten salt extraction, and solid-state electromigration. Next, let us take a look at the vacuum technology involved.

3. Vacuum Distillation Technology

The essence of vacuum distillation technology is distillation and sublimation, the difference of the vapor pressure of the elements, and the purification of rare earth metals under vacuum conditions. The requirement of this method for the purification of metals is to have a larger vapor pressure to facilitate the actual application of distillation or sublimation rate, and to be carried out at a temperature lower than the co-distillation or sublimation of its oxides. Purification of rare earth metals.

In production, as the distillation temperature increases, the distillation speed increases. In addition, the condensation rate of metal vapor is another factor in the purification of rare earth metals. If the condensation rate is greater than the distillation rate, a reflux phenomenon will occur, and the condensation rate is related to the temperature and area of the condenser, and the condensation rate is fixed. The temperature of the condenser is inversely proportional to the surface area.

The access method has low cost and high efficiency, coupled with the increasing demand for rare earth materials in our country, so vacuum distillation technology is currently one of the rare earth purification treatment methods widely used and has large-scale production capacity.

Vacuum distillation is mainly divided into (1) reduction distillation technology. The main factors that affect reduction distillation are distillation temperature, holding time, compacting density, vacuum degree, excessive washing of reducing agent, etc.; (2) vacuum distillation purification technology, which uses rare metal and The difference in vapor pressure of impurities at a certain temperature is heated under high temperature and high vacuum to separate rare earth metals from impurities, thereby obtaining high-purity rare metals.

The vacuum distillation production equipment can be a vacuum induction furnace or a vacuum resistance furnace. Among them, vacuum induction furnace has the advantages of rapid heating and cooling rate, but its temperature control accuracy is not as good as vacuum resistance furnace. Therefore, the vacuum induction furnace is suitable for large-scale production with low temperature control requirements. The vacuum resistance furnace has a slow heating and cooling rate and high temperature control accuracy. Therefore, it is convenient to control the temperature of the reduction distillation zone and the condensation zone. It has been widely used Industrial production.