sylvite

Natural potassium bearing minerals

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Potash refers to natural potassium bearing minerals. Including potash rock Potash magnesite 、 Carnallite , magnesium sulfate, potassium chloride, etc. Potash is generally soluble and has high purity. Potash deposits exist on the surface of the crust or in the brines of lakes and oceans that are about to dry up. The most important potash deposits are found in Germany, Russia, Canada, Italy, France, Spain and the United States. 95% of the world's potash products are used as fertilizers, and 5% are used in industry. In April 1839, a potash deposit was discovered when Germany was drilling a salt mine. Since then, the potash industry has been developed, resulting in a rapid increase in the application of potash fertilizer. In 1904, the Germans discovered potash deposits in the Upper Rhine River. In 1910 and 1915, two potash deposits in Germany and France began industrial scale production. stay the First World War Previously, Germany almost controlled the world's potash market. In 2005, more than one-third of the potash products in the international potash market came from Canada.^[1]

The potash deposits and brines of potash bearing salt lakes found in the world are distributed in 26 countries on six continents, especially Canada, Kazakhstan, Russia and Poland.

Chinese name: sylvite
Composition: KCl， Often contains bromine

Crystal: Cube
Specific gravity: 1.97—1.99

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brief introduction

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Potash refers to the mineral containing potassium, which is divided into solubility Potash minerals and Insoluble Potassic aluminum silicon Acid salt Minerals. 95% of the world's potash products are used as fertilizers, and 5% are used in industry.

sylvite

Potash deposits include soluble potassium bearing minerals and brines, which are formed by evaporation, concentration and sedimentation of potassium bearing water bodies. Soluble solid potash deposits (such as Sylvite 、 Carnallite 、 Polyhalite Etc.) and containing potassium brine 。 Potash ore is mainly used to produce potash fertilizer. The main products are potassium chloride and potassium sulphate It is one of the three indispensable fertilizers for agriculture. Only a small amount of products are used in industry as chemical raw materials.

China has identified that the reserves of potash resources are not large, and it is difficult to meet the demand of agriculture for potash fertilizer. Therefore, potash mine is listed as one of the urgently needed minerals by the state.

The name derives from Sylvite, a German chemist.

Physical and chemical properties

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sylvite

Crystal system and space group: equiaxed crystal system, Fm3m; Cell parameter ：a0=0.6278nm

Form: the crystal is usually cubic, occasionally Octahedron , aggregates are usually granular or dense granular, and are produced in crusty, massive or granular form

Color: colorless and transparent when pure, often slightly white, gray, slightly blue, yellow, purple or red

Stripes: white

Transparency: Transparent - Translucent

Gloss: glass luster

Hardness: 1.5-2

Cleavage and fracture: three groups of mutually perpendicular cleavage, uneven fracture

Specific gravity: 1.99g/cm3; g/cm3

Other properties: bitter, salty and astringent, easily soluble in water. Flame reaction Purple

chemical composition

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K 52.5%，Cl 47.5%。 Often containing trace Rb, Cs Isomorphism Mixtures and inclusions, etc.

Identification characteristics

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sylvite

Soluble in cold water like salt, but bitter and astringent

Origin

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It is a kind of evaporative sedimentary mineral, which is deposited from saline solution, so it is commonly used in drying salt lake Medium, and Halite , gypsum Polyhalite 、 Carnallite and Anhydrite Symbiosis; The world is rich in potash resources. Countries with rich reserves include Canada, Kazakhstan, Poland, Iran, Russia, etc. The main source of potash in China is Qinghai qaidam Modern salt lakes, Xinjiang Lop Nur Modern salt lake and Yunnan Mengyejing solid potash mine.

purpose

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potash fertilizer

Potash ore is mainly used for manufacturing industrial potassium compounds and potash fertilizer; 95% of the world's potash products are used as fertilizers, and 5% are used in industry. In the chemical industry, about 30 kinds of products are composed of potassium, mainly potassium chloride 、 Potassium hydroxide 、 potassium sulphate 、 Potassium carbonate 、 Potassium cyanide 、 potassium permanganate 、 Potassium bromide 、 potassium iodide Etc. According to industrial use, 35% is used for production of cleaning agent, 25% is used for production of carbonate and Nitrate The form is used in glass and ceramic industry, 20% is used in textile and dyeing, and 13% is used in chemical production; The rest is used in the canning industry Leather industry , Electrical and metallurgical industry Etc. Chlorate, superphosphate and nitrate of potassium are manufactured match , fireworks, explosives and important raw materials for rockets. Potassium compounds are also used in printing, batteries Electronic tube , photography, etc industrial sector In addition, it is also used for the heat treatment of aviation gasoline, steel and aluminum alloy.

Potassium fertilizer is one of the three major agricultural fertilizers crop It has obvious effect of increasing production. Potassium fertilizer is mainly potassium chloride and potassium sulfate, which belongs to acid fertilizer. The large amount of potassium chloride is suitable for rice, wheat, corn, cotton and other crops, and chlorine is not harmful to them; Potassium sulfate is suitable for hemp, tobacco, sugarcane Grape , beet, tea, etc cash crop 。

Distribution

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Sylvite

China's potash reserve is 1.1 billion tons in KCl (2009 ore reserve Notification).

China has proved reserves Of mining area It is mainly distributed in Qinghai, Yunnan, Shandong, Xinjiang, Gansu, Sichuan and other provinces and regions. Qinghai Province Qaidam Basin The Chaerhan Salt Lake is an area rich in potash salt lake brine resources in China, with an area of more than 5800 square kilometers potassium chloride ； The Lop Nur Salt Lake in Xinjiang, discovered and evaluated in recent years, has been produced on a large scale and is known as the largest potash fertilizer production base in China. Mengyejing potash deposit in Simao area, Yunnan Province, is the first continental ancient solid potash deposit discovered in 1963 in China.

Soluble potash found in China Resource reserves Not large, it is still difficult to meet the demand of agriculture for potash fertilizer. Therefore, potash mine is listed as one of the urgently needed mineral resources by the state.

Process characteristics

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Carnallite

Compared with other general minerals, potash minerals have their own technological characteristics: (1) soluble: most potash minerals are soluble in water, and more than other minerals Salt minerals The solubility of is even higher. Therefore, more favorable conditions are needed for the formation of the deposit. After the formation, it may be dissolved or transformed into potassium free minerals under the influence of surface water or groundwater. In mining and utilization, special measures should also be taken to fully consider the characteristics of potash mines.

Polyhalite

(2) Variability: potash minerals are easy to change Mineralization During this period, the influence of surface water or groundwater with different concentrations or components, or the influence of temperature changes, may change them from one mineral to another, which is one of the reasons why the mineral composition of potash deposits is relatively complex. This easy to change feature, of course, also puts forward a subject that needs special attention for the mining and utilization of potash mines. Temperature changes mother liquor The change of composition, the change of brought in water and other factors all have their particularity. (3) Similarity: physical property They are very similar to each other. The density is less than 3 g/cm, the hardness is less than 4, and the color is also similar. Therefore, it is difficult to identify with naked eyes.

(4) With Hygroscopicity Most potash minerals have certain hygroscopicity and are easy to deliquescence. This is the characteristic of both raw ores mined and finished products processed. Therefore, moisture-proof and anti caking measures shall be taken during transportation and storage. The main potash minerals, according to the decreasing degree of hygroscopicity, can be arranged as follows: carnallite Anhydrous potassium magnesite 、 Potash magnesite , sylvite.

(5) Composition complexity: potash minerals are mostly associated with halite when forming deposits, and sometimes the content of halite is much more than that of potash; Secondly, it always contains some sulfate Class A, carbonate and clay And other impurities. Therefore, in the process of processing and utilization, it brings certain difficulties to the separation, resulting in complex process flow and affected product quality.

Potassium salt standard

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Orthoclase

1. The influence of useful elements and main associated elements on raw materials The grade of useful elements determines the processing method of raw materials. When dissolving Crystallization method When processing potash ore, it mainly requires the grade of useful elements in the ore; Instead, use Flotation method In addition to the requirements Ore grade In addition, there is another Water insoluble substance , especially the requirement of fine mud content.

Rock salt, water insoluble matter, calcium, magnesium and other minerals are the main factors affecting product quality Associated minerals 。 It affects its application in chemical industry and other industrial fields.

2. National standards

Since China's potash mines and processing plants (such as potash fertilizer plants) are a consortium, the final inspection is the quality of processed products. Therefore, there is no unified standard for potash ore. The national standard for potassium chloride products is applicable to Salt field Potassium chloride products for industrial or agricultural use produced by flotation or solution crystallization of sun dried carnallite and potash salt ores.

Other potassium salts

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potassium sulphate

Potassium sulfate powder

Colorless or white crystals, particles or powders. Odorless. It tastes bitter. Hard. Stable in air. 1g dissolved in 8.3ml water, 4ml boiling water, 75ml glycerol , insoluble in ethanol. potassium chloride 、 ammonium sulphate It can increase its solubility in water, but it is almost insoluble in saturated ammonium sulfate solution. The aqueous solution is neutral with a pH of about 7. relative density 2.66。 Melting point 1067 ℃. The main uses are serum albumin Biochemical test, catalyst for Kjeldahl nitrogen determination, preparation of other potassium salts chemical fertilizer , Drugs, Preparation Glass 、 alum Etc.

Aluminium potassium sulfate

Potassium aluminum sulfate crystal

Potassium aluminum sulfate, colorless crystal or powder. Odorless, slightly sweet, astringent and astringent. The crystal water is lost by weathering in dry air, and it dissolves and drips in humid air. Soluble in glycerol , soluble in water, the aqueous solution is acidic, hydrolysis Later Aluminium hydroxide Colloidal sediment. Insoluble in alcohol and acetone 。 The melting point is 92.5 ℃. When the sulfuric acid is dried at 60~65 ℃, 9 molecules of water are lost, and at 200 ℃, 12 molecules of crystal water are lost completely, which can be decomposed at higher temperature Sulfur trioxide 。

Potassium bromide

Potassium bromide, chemical formula KBr, relative molecular mass ：119.00。 Colorless crystal or white powder with strong salty taste, and the light color turns yellow. Slightly Hygroscopicity 。 1g is dissolved in 1.5ml water, and the water solution is neutral. Relative density (d254) 2.75. Melting point 730 ℃. Boiling point 1435 ℃. Irritating. It is mainly used for spectral analysis and drop analysis to determine copper and silver, Polarographic analysis Indium, cadmium and arsenic. Developer. Pesticide analysis,

Potassium cyanide

White round hard block, granular or crystalline powder, highly toxic. Deliquescence in wet air and release trace amount of Hydrogen cyanide Gas. It is easily soluble in water and slightly soluble in alcohol. The aqueous solution is strongly alkaline and hydrolyzes quickly. Density 1.857g/cm ^ 3, boiling point 1497 ℃, melting point 563 ℃. Contact with skin wounds or inhalation of trace powder can lead to poisoning and death. Contact with acid can release highly toxic hydrogen cyanide gas, and Chlorate or Sodium nitrite Mixing can cause explosion.

potassium nitrate

Potassium nitrate is widely used in agricultural market. Potassium nitrate belongs to Binary compound fertilizer 。 Potassium nitrate is chlorine free potassium and nitrogen Compound fertilizer ， Phytonutrients The total content of potassium and nitrogen can reach about 60%, with good physical and chemical properties. Potassium nitrate applied to tobacco has high fertilizer efficiency, is easy to absorb, promotes early seedling development, increases tobacco yield, and plays an important role in improving tobacco quality.

Current situation and trend

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1. Development and utilization status, existing problems and solutions

sylvite

Not many potash resources have been found in China, and potash fertilizer production cannot meet the growing domestic demand, most of which rely on imports. The application ratio of nitrogen, phosphorus and potassium fertilizer in China is only about 1:0.28:0.1, which is greatly different from the world average ratio (about 1:0.47:0.34). In view of the shortage of potash resources, in addition to actively doing a good job in the exploration, development and utilization of domestic resources, it is also necessary to make full use of foreign resources, consider investing in the development of potash mineral resources in neighboring countries, and establish a foreign ore supply base.

2. Development trend

Due to the lack of soluble potash ore, more attention has been paid to the development and utilization of a wider range of potassium resources (insoluble potassium resources), such as alunite Potash feldspar , containing potassium Sand shale Etc. Alunite contains about 10% K2O, except that it can be used for extraction alum In addition, it can also be used to produce potash fertilizer.

Raw material characteristics

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（1） Soluble potash mineral

Soluble potash minerals include various potassium containing minerals formed in nature chloride 、 sulfate 、 Nitrate 、 borate And double salts containing sodium, magnesium and calcium. They can become anhydrous or aqueous compounds, some of which also contain trace elements such as Li, Rb, Cs, Sr, Br, I, B, etc. Main minerals There are sylvite, carnallite, sylvite magnesite Anhydrous potassium magnesite And polyhalite, etc.

1. Potassium rock salt (KCl)

Chemical composition: K 52.4%, Cl 47.6%. It often contains liquid and gaseous inclusions: mainly nitrogen, followed by Carbonic acid gas , hydrogen and methane, sometimes helium. NaCl and Fe2O3 are common in mechanical mixture. The isomorphic mixture is usually KBr (below 0.1%) and a very small amount of RbCl and CsCl.

Crystal form: equiaxed crystal system. The crystal is cube or cube and octahedron Polymorph The aggregate is usually dense granular block, sometimes with layered structure.

Physical property: pure sylvite is colorless and transparent, but it can be red, rose, yellow and milky white (including fine bubbles) due to impurity pollution. Glass luster. The hardness is 1.5~2, brittle, and the specific gravity is 1.97~1.99. The cleavage is perfectly parallel to the pole. It has a spicy taste. Easily soluble in water and hygroscopic.

2. Carnallite (MgCl2 · KCl · 6H2O)

Chemical composition: K 14.1%, Mg 8.7%，Cl 38.3%，H2O 38.9%。 Containing a small amount Isomorphism The mixture Br (below 0.2%), Rb, Cs (several ten thousandths), occasionally containing Li, Te. The mechanical mixture includes NaCl KCl、CaSO4、Fe2O3、 Clay, brine droplets and gaseous inclusions (N2, H2, CH4 mixed gas )。

Crystal form: rhombic biconical symmetry. There are few crystals, most of which are dense granular blocks, and vein carnallite is fibrous.

Physical properties: pure, colorless and transparent, often dyed red, brown and yellow due to impurities. The glass luster of the fresh fracture surface quickly darkens in the air Grease sheen 。 The hardness is 2-3, and the specific gravity is 1.6. Fragile without cleavage, with irregular fracture or shell shape. With strong hygroscopicity, it is easy to deliquescence in the air. It tastes hot and bitter. It emits strong fluorescence. When dissolved in water, it makes a special cracking sound, which is caused by containing bubbles under high pressure.

3. Potassium salt magnesite (KCl · MgSO4 · 3H2O)

Chemical composition: K 15.7%, Mg 9.8%，Cl 14.2%，SO 38.6%，H2O 21.7%。

Crystal form: monoclinic system. single crystal (flat or columnar) rare, usually Fine grain Massive aggregates, some of which are fibrous in the pores. The cleavage edge is complete.

Physical property: colorless, but often dyed red or grayish yellow by the iron contained therein. Glass luster. The hardness is 2.5~3, and the specific gravity is 2.15. Easily soluble in water. It tastes bitter and salty. No water absorption.

4． Anhydrous potassium magnesite (K2SO4·2MgSO4)

Chemical composition: about 22.2% K2O, MgO 19.43%，SO3 57.87%， It contains a small amount of bromine.

Crystal form: equiaxed crystal system, triangular tetrahedron symmetric form. Crystals are rare and often present as granular blocks or dispersed particles.

Physical property: light gray to colorless. No cleavage, Conchoidal fracture 。 Glass luster, brittle, hardness 3-4, specific gravity 2.83. The crystals are often wrapped with halite, anhydrite and other substances. Dissolve slowly in water. It turns white when heated slightly.

5. Polyhalite [K2MgCa2 (SO4) 4 · 2H2O]

Chemical composition: K 12.9%, Mg 4.03%，Ca 13.29%，SO 63.73%，H2O 5.98%。

Crystal form: Triclinic system , axisymmetric form. However, the crystals are rare, often appearing as dense granular blocks, or fibrous or flaky aggregates.

Physical properties: transparent and colorless, sometimes white or slightly gray, light yellow, flesh red, sometimes brick red. Glass is shiny, but often dull. The hardness is 2.5~3, and the specific gravity is 2.72~2.78. One group of cylindrical surfaces is completely cleaved. Slightly salty and spicy. Dissolve in water and leave gypsum.

6. Potassium magnesium alum [K2Mg (SO4) 2 · 4H2O]

Chemical composition: K2O 25.69%, MgO 10.99%，SO3 43.67%，H2O 19.65%。

Crystal form: Monoclinic system , cylindrical symmetry. It is generally a block aggregate.

Physical property: transparent, colorless or light yellow. waxy luster To glass luster. Shell like fracture. It tastes bitter. The hardness is 2.5~3.0. Specific gravity 2.201.

7. Soft potassium magnesite [K2Mg (SO4) 2 · 6H2O]

Chemical composition: K2O 23.39%, MgO 10.01%，SO3 39.76%，H2O 26.84%。

Crystal form: monoclinic system. Cylindrical symmetry. Aggregates are fine grained or Fibrous 。

Physical property: transparent, colorless or white, sometimes light red, light yellow and gray due to impurities. Glass luster. It has a bitter taste. Easily soluble in water. Specific gravity 2.1, hardness 2.5.

8. Potassium gypsum (K2SO4 · CaSO4 · H2O)

Chemical composition: K2O 28.68%, CaO 17.08%，SO3 48.75%，H2O 5.49%。

Crystal form: monoclinic system, cylindrical symmetry. Cleavage parallel and complete, clear. The aggregate is plate shaped and leaf shaped.

Physical property: colorless, or light yellow and milky white due to impurities. Glass luster. Shell like fracture. Hardness 2.5, specific gravity 2.579. Slightly soluble in water.

Optical characteristics: biaxial negative crystal, with a refolding rate of 0.018.

Insoluble

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Insoluble potassium bearing minerals, mainly potassium and aluminum Silicate mineral And potassium rich rocks, mostly based on Rock forming mineral It occurs in various rocks, such as feldspar and mica, and is widely distributed in nature. The most common minerals are:

1. Orthoclase K [AlSi3O3], containing K2O 16.5%

Monoclinic system The crystal is usually short columnar or thick plate. Meat red, light yellow red, glass luster, hardness 6~6.5. Orthoclase mainly occurs in acid, alkali and part of neutral igneous rock Medium, such as Granite 、 Syenite 。 Also produced in various gneiss And migmatite, sedimentary rock It is also distributed in.

2. Nepheline Na [AlSiO4] also contains K2O

Nepheline forms a continuous series of Na [AlSiO4] and K [AlSiO4] solid solutions at high temperature, and the content of K [AlSiO4] molecule varies between 5% and 20%. Nepheline has been used to produce potash fertilizer abroad.

3. Alunite K2SO4 · Al2 (SO4) 3 · 2Al2O3 · 6H2O

Alunite mineral Trigonal system It is usually a fine-grained, dense and massive aggregate. The pure one is colorless, white, but often with light yellow. Glazing or Earthy Luster 。 The hardness is 3.5~4, and the specific gravity is 2.6~2.9. Alunite is intermediate acid volcano The altered products of extrusive rocks are widely distributed in Anhui, Zhejiang and other provinces, and are produced in lava And volcanic tuff. Alunite can be used to produce potassium alum, potassium sulfate, etc.

Sustained development

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Recently, with the theme of "sustainable development of potash and potash fertilizer in China" China Inorganic Salt Industry Association The seventh annual meeting of potash (fertilizer) industry branch was held in Shanghai. The conference was jointly sponsored by the Potash (Fertilizer) Industry Branch of China Inorganic Salt Industry Association and the Research Center for Resources, Environment and Food Security of China Agricultural University. Relevant leaders of the National Development and Reform Commission, the Ministry of Commerce and the head of the Soil and Fertilizer Department of the National Agricultural Technology Promotion Service Center Li Rong Wu Mingyu, President of China Inorganic Salt Industry Association, Tao Lianyin, Secretary General, and Li Gang, President of Potash (Fertilizer) Industry Branch attended the meeting. Liu Fuchang, the secretary general of the industry branch, presided over and read out the work report. Qi Zhaoying, the deputy secretary general, made a report on the operation of China's potash and potash fertilizer industry this year. Nearly 200 people from the potash and potash fertilizer industries at home and abroad attended the event to discuss the development of the industry.

sylvite

In view of the development of potash in China, Wang Xiaofeng, Deputy Director of the Industry Development Department of the China Petrochemical Federation and Secretary General of the China Inorganic Salt Industry Association, put forward strategic thinking on the development of China's potash fertilizer industry. He believes that the current mining should prevent the overexploitation of domestic potassium resources, or it may cause problems such as resource waste, comprehensive utilization can not keep up, and the service life of production equipment is too short.^[2]

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