Celestite (strontium ore) beneficiation and processing method
Strontium is an alkaline earth metal smallest element in abundance. The main minerals are lapis lazuli and strontium carbonate. It can be prepared by electrolytically melting cerium chloride. Used in the manufacture of alloys, photocells, and analytical chemistry, pyrotechnics, etc. The mass number 90 is a radioactive isotope that can be used as a beta-ray source with a half-life of 25 years. Earthworms, strontium, calcium and magnesium are both alkaline earth metals and are also abundant in the earth's crust.
Celestite production is not aimed at obtaining high grade concentrates. Most of the world's lapis lazuli resource-owning countries have integrated the production of primary products (original or concentrate) with antimony-containing compounds (salt salts such as SrCo 3 ). This determines the production of lapis lazuli and its strontium salt, including the two parts of mineral processing and strontium salt production and processing technology.
(1) Mineral processing method
Re-election is the most common method used in lapis lazuli dressing. The most common structural process is the process of jigging-shaker. Jigging is used to process coarse materials and shakers are used to process fine grade materials.
After the ore is crushed and crushed to less than 12 mm, the granules of each group larger than 1 mm are separately selected for jigging, and the fine granules of less than 1 mm are separately selected by shaker. The comprehensive index of re-election is: concentrate yield is 45.38%, concentrate grade (SrSo 4 ) is 86.12%, and recovery rate is 83.31%. The middle mines of the jigging and shaker can be recovered by three methods such as magnetic separation, re-election and flotation after crushing and grinding, but the index of the flotation scheme is the best. Note that in the flotation sludge and dispersion suppressing limonite ore, after with Na2CO 3 and Na 2 SiO 3 slurried, pH is preferably controlled at between 8 and 9.5, with oleic acid as collector agent, The slurry temperature should be greater than 25 °C. In addition, the structure of the flotation process has a greater impact on product quality. When the flotation feed is taken as 100%, the yield of flotation concentrate is 44.50%, and the concentrate grade (SrSO 4 ) is 86.04%. It is 95.68%.
(2) Processing technology
In the strontium ore processing, the lapis lazuli concentrate is actually processed into various strontium salts such as SrCo 3 , Sr(No 3 ) 2 , SrCl 2 and SrTiO 3 . However, among the many strontium salts, the most important one is SrCo 3 , which is not only the most widely used, but also the most widely used, and can be converted into other forms of strontium salts.
The production methods of SrCo3 mainly include reduction method and metathesis method, but the former is mostly. However, the technical requirements for strontium carbonate products at home and abroad are slightly different.
The reduction method is also called black ash method, that is, after high temperature roasting, SrSo4 is converted into SrCo3. The main chemical reactions are:
SrSo 4 +2C 1300°C SrS+2CO 2 ↑(1)
SrS+NaCo 3 Na 2 S+SrCo 3 ↓ (2)
Or: SrS+Co 2 SrCo 3 ↓+So 2 ↑(3)
The metathesis method mainly uses a soda ash or ammonium hydrogencarbonate to undergo a metathesis reaction with diatomite after calcium removal to form crude cesium carbonate. Acid-soluble, refined and then reacted with soda ash or ammonium bicarbonate to form SrCo3.
Both the double decomposition method and the reduction method have their own strengths. In terms of product quality, the difference between the two is small; but in terms of cost, because the meta-decomposition process is long and requires a lot of chemical raw materials, the cost is more than 40% higher than the reduction method. This is perhaps one of the main reasons why most manufacturers choose the reduction method. The biggest advantage of the double decomposition method is that the waste liquid is easy to handle, which is not comparable to the reduction method.
The pollution of sulfur-containing waste liquid in the production of reduction has attracted the attention of countries all over the world. In the past few years, the Lishui Chemical Plant in Jiangsu Province has tried to treat the ammonium sulphate waste liquid by gas stripping method, and has received good results. The foreign country replaces Na 2 Co 3 with Co 2 to carbonate the SrS refining liquid, thus avoiding sulfur-containing waste. The production of liquid. At present, there are still a number of new processes and new equipment being tested. Reducing pollution is one of the main directions in the development of the reduction method.
A new method currently being tested in the country is to directly convert SrSo 4 into SrCo 3 by means of leaching, which is extremely attractive for reducing costs and reducing pollution. The specific method is to directly leach the lapis lazuli concentrate by using a sodium carbonate solution as a leaching agent. The ore used in the test is a natural high-grade lapis lazuli ore. The ore is crushed, ground, and sieved into several grades of -65+100, -100+150, -150+200, -200+250, -250+325 mesh for testing. The content of (Ba+Ca) impurities in the sample was <1%. The leaching test was carried out in a 0.25 L flask. The leaching agent Na2Co3 concentration was 0.2 mol, the leaching time was 300 min, the temperature was 328 K, and the pH was 8-12. Analysis of the results showed that the leached products were all SrCo 3 . This method is currently in the experimental phase.
The new technologies introduced in the past two years in China mainly include calcium method and thermal method.
The main process of the calcium method is the reduction-metalysis one-step conversion method, which is black ash mainly composed of ruthenium chloride, and then refined by water, refined and then reacted with ammonium hydrogencarbonate to prepare SrCo3. The main chemical reactions are:
SrSo 4 +4C+CaCl 2 SrCl 2 +CaS+4CO↑
SrCl 2 +NH 4 HCo 3 SrCo 3 ↓+NH 2 ↑
A chemical plant in Sichuan Province has used this process to produce qualified SrSo 4 products. Ore Sichuan Dazu, copper beams, Aikawa production celestite containing SrSo 4 70% ~ 85%, CaSo 4> 8% ~ 15%, BaSo 4 3% ~ 15%; SrSo 3 product purity of 97%, CaCo 3 ≤1.
The shortcoming of this process is that the intermediate agent CaCl 2 in the calcium production has a great influence on the product cost. Recently, the price of CaCl 2 has risen, which has led to an increase in the cost and price of SrCo 3 . In addition, in the precipitation reaction, the aqueous solution of ammonium hydrogencarbonate is largely lost; in the separation of alkaline earth metals, the loss rate of strontium salt is relatively high.
The thermal method is a new process based on the reduction method. The process was designed by the Sichuan Huzhou Chemical School and the Sichuan South-East Geological Team to handle the only diamond-mining mine in Sichuan. The process is as follows: firstly mixing the antimony ore and coke in a certain ratio, and then calcining at a high temperature of 1290 ° C; the clinker containing Sro and other metal oxides is leached with water to prepare a crude mash; after precipitation, filtration After removing impurities, NH 4 HCo 3 is added to form a SrCo 4 precipitate; finally, it is separated, dried, and pulverized to obtain a product.
The joint factory has used this process to produce the province's first-class SrSO3 products with an annual output of 500t. The raw materials used were the Linglong Mine in Tongliang County, Sichuan Province. The ore contains SrCo 3 79.39%; CaCo 3 19.06%; NgCo 3 0.3%; Fe 2 O 3 0.31%. The purity of SrCo 3 is as high as 98.69%; Fe 2 O 3 0.0054%; CaO 0.22%; C1-0.009%; all indexes exceed Sichuan foreign trade standards. Almost all products are exported. In addition, the final leaching residue in the production process can also be used in the construction industry. The clear liquid separated from the slurry is dilute ammonia water, which can be used for agricultural production and also recovers ammonia hydrogencarbonate. This allows the raw materials to be comprehensively utilized. At present, the main problem in production is that the process conditions of calcination and leaching are difficult to control, and the ruthenium in the ore is difficult to be recycled, and the ruthenium contained in the leaching residue needs to be recovered by acid treatment.
The processing of other tellurides and metal ruthenium is based on SrCo3:
The SrCo 3 is placed in a cylinder reactor, and concentrated nitric acid is added to react to form a cerium nitrate product:
SrCo 3 +2HNo 3 Sr(No 3 ) 2 +H 2 O+Co 2 ↑
Barium chloride is obtained by the action of barium carbonate and hydrochloric acid:
SrCo 3 +2Hcl 〖FY 2 〗 SrCl 2 +H 2 O+Co 2 ↑
The cerium oxide can be obtained by heating cerium carbonate. The metal ruthenium can be obtained by a thermal reduction reaction of ruthenium oxide with aluminum metal, or an oxide of molten ruthenium or electrolysis of ruthenium chloride.
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