“In response to the unique characteristics of rare earth resources, China has developed a series of world-leading rare earth extraction and separation technologies, which have been applied on a large scale in the industry and achieved China’s international status as a major rare earth producer.” March 31 – April 1, the first strategic resources comprehensive utilization forum held in Hengyang, Hunan, around the solution to the development of the rare earth industry constraints of resources and environmental major problems, the Chinese Academy of Engineering academician Huang Xiaowei introduced the latest progress of green extraction and separation technology of rare earth resources.
China’s rare earth resources distribution presents the “South heavy North light” characteristics, located in Baotou City, Inner Mongolia Autonomous Region, Baiyun Ebo mixed rare earth ore, is the world’s first light rare earth ore; Southern ionic rare earth ore is rich in valuable medium and heavy rare earth resources, is a new generation of information technology, national defense industry and other indispensable key raw materials, but the extraction and separation of difficult.
In the past decade or so, Huang Xiaowei led his team to develop a new process of separating and purifying rare earths by magnesium bicarbonate method and a new process of integrating ionic rare earth ore leaching and extracting, which is a green and low-carbon metallurgical technology tailored to China’s light and medium-heavy rare earth resources.
Enhancement of rare earth resource utilisation and product quality
Baiyun Ebo mixed rare earth ore is a polymetallic coeval deposit, consisting of cerium fluorocarbon ore and monazite ore, which is recognized as a difficult smelting ore in the world, and its reasonable development and utilization has a pivotal impact on the global rare earth pattern.
It is understood that at present, Baotou mixed rare earth ore is mainly used in the third generation of sulfuric acid smelting and separation developed by China Youyan Group (formerly Beijing General Research Institute of Non-ferrous Metals), which has the advantages of low cost, large scale and easy continuous production, but there is a bottleneck of magnesium sulfate wastewater difficult to recycle and calcium sulfate scaling, and the level of resource utilization and green development needs to be further enhanced.
To solve the above problems, Huang Xiaowei led his team to successfully develop a new process for the separation and purification of rare earths by magnesium bicarbonate. The new process consists of two core technologies, including the saponification of magnesium bicarbonate extraction transition separation of rare earths and calcium elements directional control technology, continuous scale preparation of magnesium bicarbonate solution and material recycling technology, which can solve the recycling of high salt wastewater and calcium sulfate scaling problems in the separation process of conventional mineral-based rare earth smelting, and achieve efficient and clean production.
“Using the magnesium sulphate wastewater generated from the Baotou rare earth mine smelting and separation process, as well as the CO_2 recovered from the rare earth saponification extraction and other processes, magnesium bicarbonate solution is prepared by continuous carbonation scale, replacing magnesium oxide, liquid alkali or liquid ammonia for saponification extraction transition separation of rare earths, ultimately realising low carbon, low salt and no ammonia nitrogen emissions from the rare earth extraction and separation process. ” Huang Xiaowei introduced, the new process to make rare earth extraction rate of 99% or more, rare earth purity greater than 99.99%; to achieve the recycling of water, magnesium and CO_2 resources, to avoid calcium sulfate scaling, aluminum and iron impurities on the extraction process, improve the utilization of rare earth resources and product quality.
“With the original method, the rare earth extraction tank and equipment on calcium sulfate scaling, hundreds of workers clean up 1-2 times a month. After adopting the new process, it is only cleaned 1-2 times a year.” Huang Xiaowei said, the technology in the smelting and separation of Baotou rare earth mine in Gansu rare earth company and other popular applications since the production workers welcome.
Making medium and heavy rare earth extraction more efficient and environmentally friendly
For southern ionic rare earth mines, which are rich in strategic resources of medium and heavy rare earths, China has invented a unique ammonium sulphate in situ leaching – ammonium bicarbonate precipitation enrichment process to achieve large-scale development. It is understood that the process is lengthy, the rare earth recovery rate is low, ammonia and nitrogen pollution is serious, and a large amount of radioactive decontaminated slag and radioactive acid soluble slag is produced.
Huang Xiaowei introduced the newly developed green extraction technology called the new ionic rare earth ore leaching integration process. The eco-friendly magnesium salt composite system replaces the traditional ammonium sulphate leaching ionic rare earth ore, and the low concentration leaching solution replaces the traditional ammonium bicarbonate precipitation rare earth enrichment process with a non-equilibrium centrifugal extraction rare earth enrichment process, directly producing a high concentration mixed rare earth chloride solution product, reducing the process by 5 procedures, increasing the rare earth recovery rate by 10%-20%, eliminating ammonia and nitrogen pollution at source, and No radioactive waste residue is produced.
In 2016, Chalco Guangxi Rare Earth Company’s mine completed a phase I project, using this technology for the first time to achieve the industrial application of ionic rare earth ore low concentration leach solution direct extraction enrichment, medium and heavy rare earth extraction recovery rate of 99% or more, to solve the long-term plague of ionic mining enterprises containing radioactive slag pollution problem. Later on, several production demonstration lines were built in Guangxi, Fujian and Jiangxi rare earth mines.
In the same year, China Nonferrous Metals Industry Association results evaluation meeting site, results evaluation experts agreed that: the new technology is a major change in the production process of ionic rare earth ore, the overall leading in the world rare earth metal selection and separation technology level.