The proven reserves of boron ore in China are 49.08 million tons, ranking fourth in the world, with 90% of the reserves distributed in Tibet, Liaoning, and Qinghai regions. At present, the high-grade boron ore in China is being depleted year by year, and the vast majority of the remaining boron ore resources are of low grade, difficult to develop, and complex in processing technology, such as the Wengquangou boron iron ore in Fengcheng, Liaoning, the magnesium salt ore deposited in the salt lake of Tibet, the low grade boron ore coexisting with various borate salt mines at the bottom of Dachaidan Lake in Qinghai, and the low grade boron magnesium ore in Northeast China.

Liaoning boron iron ore

The Fengcheng boron magnesium iron ore deposit in Liaoning has a proven B2O3 reserve of 21.84 million tons, accounting for 58% of the total reserves in the country. The characteristics of this deposit are: firstly, multi-element symbiosis, with high iron, boron, and magnesium contents; Second, there are many kinds of useful minerals and gangue minerals in ores, nearly more than 60 kinds. The main useful minerals are boehmite and magnetite, gangue minerals are serpentine and clinoptilolite, and trace minerals are uraninite and boehmite; Third, the ore structure is complicated. Different ore types in different ore sections belong to contact metamorphic deposits. magnetite and fibrous ludwigite are mainly decomposed from ludwigite by heating. Therefore, except for a small amount of primary magnetite and tabular columnar ludwigite, most of magnetite and fibrous ludwigite have very fine disseminated grain size. Their symbiotic relationship is very close, and the crystal connection is complex, showing crisscross, grid, radial, pointy Various structures such as tree branches. This extremely irregular contact pattern brings great difficulties to the dissociation of magnetite and boehmite.

Boron iron ore beneficiation and separation

The iron concentrate obtained by traditional beneficiation methods cannot meet the requirements of steel production for iron concentrate, and the grade of boron concentrate cannot meet the requirements of boron product production for boron ore. Subsequently, based on the physicochemical properties of boron iron ore, a combined beneficiation method of magnetic separation, gravity separation, and stage grinding was used to separate boron iron concentrate containing 53% to 55% iron and boron concentrate containing more than 12% B2O3.

The boron containing iron concentrate obtained from beneficiation can be used for the production of boron containing pig iron in the ironmaking industry, replacing some boron iron alloys as raw materials for wear-resistant castings; As a boron containing additive in the production of sintered ore and pellets in the ironmaking industry; Further separation and treatment can be carried out to effectively separate boron and iron from boron containing iron concentrate, resulting in boron free iron and high-grade, highly active boron rich slag.

Chemical treatment and comprehensive utilization of boron iron ore

Units such as Tianjin Institute of Chemical Technology and Zhengzhou Research Center for Comprehensive Utilization of Mineral Resources directly use acid/alkali treatment to obtain boric acid or borax, while valuable elements such as iron and magnesium remain in the waste slag after boron extraction; Then, the waste slag from boron extraction is treated to extract products such as iron and magnesium. At present, this method has not been industrialized, mainly due to the fact that the boron, iron, and magnesium obtained from boron iron ore after chemical treatment are all lean ores, with high acid and alkali consumption, high production costs, difficulty in treating process waste liquid, and environmental protection issues that need to be addressed.

Pyrolysis separation process of boron iron ore

There are two process routes for pyrometallurgical separation: blast furnace method and solid-state reduction) melting separation method.

The blast furnace method involves removing some silicon and aluminum from the boron iron ore through beneficiation, and then sintering and briquetting it into the blast furnace for smelting. The products are boron containing pig iron and boron rich slag. This process underwent industrial experiments during the "Eighth Five Year Plan" period, completing key tasks such as beneficiation, block making, 13m blast furnace boron iron separation, boron rich slag slow cooling, boron extraction, application of boron containing pig iron, and environmental governance; During the "Tenth Five Year Plan" period, industrial experiments were conducted again. Further research work is needed to achieve long-term stable industrial production.

The solid-phase reduction melting separation method is to reduce the iron oxide in the ore to metallic iron using non coking coal in the solid state, using the raw ore of boracite or the boracite treated with tailings; The reduced ore is melted in an electric furnace to obtain boron free iron and highly active boron rich slag. Due to issues with production equipment, this research work has only been carried out to scale up in the laboratory.

Research Progress on Solid Boron Deposits in Salt Lakes of Tibet

The overall grade of Tibetan magnesium boron ore is high, with low impurity content and low processing difficulty. Among them, magnesium boron ore with B2O3>30% can be directly used for the production of alkali free glass fibers without processing. Tibet is located on a plateau with inconvenient transportation and does not have the basic conditions to build factories and process boron ores locally. All magnesium and boron ores are transported to the mainland. In the process of extensive mining, the method of "using rich to abandon poor" has been used to reduce costs, resulting in serious deterioration of magnesium and boron ore resources. The abandoned magnesium and boron ores amount to millions of tons, with B2O3B<20% and MgO around 20%.

In order to utilize these resources, multiple research units have conducted systematic research on the enrichment, beneficiation, and processing techniques of boron magnesium ore. There are two main processes for producing boric acid from magnesium boron ore: sulfuric acid one-step method and two-step method; The one-step process technology route is mature, with high decomposition rate and complete decomposition of boron ore. However, with changes in boron ore composition and content, the difficulty of controlling boric acid yield and product quality increases; The advantages of the two-step process are good product quality and high boron yield, but the process flow is long. The problem with the sulfuric acid process is the recovery of boric acid mother liquor. Generally speaking, 8-10 tons of mother liquor are discharged for every 1 ton of boric acid produced, which not only causes resource waste and increases production costs, but also generates a large number of pollutants, causing damage to the environment. Especially for magnesium boron ores with high magnesium content, the acid consumption during the production of boric acid is high, the boron yield is low, the production cost is high, the mother liquor discharge is large, and the environmental pressure is high. Numerous domestic researchers have conducted extensive research on the issue of boron yield in the production of boric acid. Mainly by improving the process flow and recovering boron and magnesium from the mother liquor of boric acid, in order to balance the production cost of boric acid.

Application of Low Grade Boron Mine in Dachaidan Lake, Qinghai Province

The reserves of the Dachaidan Lake boron mine, calculated based on B2O3, reach 4.06 million tons. In the early years, resources were damaged due to the indiscriminate development of high-grade solid boron mines. However, the current boron mine reserves are still over 3 million tons, which has the resource advantage of developing the production of borax and boric acid. The mass fraction of B2O3 in the lakeside boron ore of Dachaidan Lake is generally lower than 10%, with some boron ore grades reaching 13% to 17%. Boron ore with a mass fraction of over 15% can be directly utilized, while low-grade boron ore with a mass fraction of 6% to 9% has complex composition, multiple types of associated minerals, high impurity content, especially containing a large amount of gypsum and carbonate. Direct use in boron product processing has high production costs, complex process flow, and low boron yield Problems such as large amount of waste residue generated.

Another characteristic of the low-grade boron ore in Dachaidan is that with the mining of high-grade boron ore, the composition of the boron ore has undergone significant changes, transforming from boron ore mainly composed of cubic boron ore and sodium borosilicate to boron ore mainly composed of columnar boromagnesite. Therefore, when designing the process, it is necessary to consider both the boron ore grade and the variation of the ore type.

In 1993, the Qinghai Salt Lake Research Institute of the Chinese Academy of Sciences completed the research on the practical process of producing borax from five low-grade boron ores at the bottom of the Qaidam Lake, and conducted a preliminary scale-up test. The test results show that the consumption of decomposing agent in the process of decomposition can be reduced by 40%, and the decomposition rate of boron ores can reach 92%, improving the crystallization rate of borax and product quality. At present, Lanzhou Branch of the Chinese Academy of Sciences and Qinghai Salt Lake Research Institute are jointly committed to the research of comprehensive utilization technology suitable for the change of low grade boron ore in Dachaidan.

Researchers from Hunan, Liaoning, Jilin, Tibet, Henan and other provinces have also successively conducted research on the enrichment, processing technology, and comprehensive utilization of local low-grade boron mines, mainly using flotation and roasting methods. There is also a one-step process of ammonium chloride decomposition of boron ore to produce boric acid, and a by-product of magnesium containing calcium carbonate. This method is used to decompose low-grade Changning boron ore in Hunan, and the average yield of total B2O3 reaches 80.76% to 87.98%. In addition, Qinghai Chemical Design Institute has conducted research on the enrichment and processing process of low-grade boron ore, as well as the recovery and utilization process of boron in the enriched tailings. By adopting this enrichment and processing route, the boron ore grade can be increased by 30% to 35%, and the boron yield can be greater than 80%.