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[small Metal Conference dry goods] Analysis of selenium Raw material Source, Product Application, supply and demand
Jul 24,2020 11:46CST
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Source:SMM
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SMM7 March 24: today, at the "2020 small Metal Summit" hosted by SMM, Yang Wenlong, marketing director of Yunnan Copper Science and Technology Development Co., Ltd., brought a speech with the theme of "talking about the understanding and exchange of the domestic selenium industry in recent years". The speech was mainly carried out from the sources of selenium raw materials, the basic overview of product application, selenium market supply and demand and understanding, and other selenium-related understanding.

Basic general situation of raw material source and product application of selenium

1. Sources of selenium raw materials

The main results are as follows: (1) the raw material of crude selenium produced by impurity removal of anode slime in copper smelting is mainly used, and its production technology is as follows:

Fire method: high temperature oxidation volatilization, selenium gas liquid absorption, acid reduction precipitation;

The traditional furnace type is represented by rotary furnace, and the operating temperature is about 900 degrees.

At present, the high efficiency furnace is Cardol furnace-rotary oxygen-rich blowing furnace, which has higher temperature, higher impurity removal efficiency and higher flue gas treatment efficiency than rotary kiln.

Wet method: strong acid and strong oxidation leaching (close to aqua regia, the end point of selenium leaching takes the pullback of gold as the index) and precipitated under the condition of hydrochloric acid.

(2) production of acid mud, which is the precipitate of purification of smelting flue gas from other sulphide ores.

Acid mud fire method: adding alkali oxidizing roasting, mercury volatilization, alkali fixing selenium, roasting residue and then oxidizing and leaching selenium, reducing and precipitating selenium.

Wet method: that is, strong oxidation and chlorination, similar to the wet process of anode mud, acid leaching, selenium and mercury leaching, reduction and neutralization of mercury.

2. Production of SeO2

The main results are as follows: (1) the fire low temperature oxygen enrichment stirring volatilization technology has replaced the wet nitric acid oxidation process, the production cost has been reduced, and the environmental protection conditions have been improved.

(2) the main production cost is that liquid oxygen is gasified directly into the oxidation furnace, with the participation of oxidation catalyst, the combination efficiency of rich oxygen is improved, the efficiency of selenium consumption of liquid oxygen reaches 80%, and the electricity consumption of tons of selenium is about 3000 kilowatt-hours.

(3) the quality of the product is stable, and the separation efficiency of heavy metal impurities containing SeO298%, is more than 90%.

3. Sodium selenite: a low-cost production process, which is also made by mixing sodium carbonate and SeO2 directly by fire and melting at 450C.

4. In the glass industry, selenium is used instead of arsenic to purify the impurities in the glass, and the red glass is obtained because of the red principle of selenium.

5. The ceramic pigment industry mainly uses the basic principle that the selenium particles are red. When the selenium powder reduced by SeO2 at low temperature, it is generally bright red, such as nano-selenium, small particles are also red, and so on. The red glaze in daily life is generally based on selenium red, such as all kinds of red glazed tiles are sintered with selenium glaze.

6. For optoelectronic applications, selenium-based photocells were the earliest industrial solar cells. Because the price of selenium was once one million yuan, it promoted the development of silicon-based solar cells. With the development and advantages of thin-film flexible solar cell technology, taking extremely thin high-purity selenium as the capacitor base, the superiority of high photovoltaic efficiency of solar cells under the action of light was gradually conquered by modern technology and equipment. Has entered a new stage of development.

7. The great health of selenium and the application of related medicine and fertilizer.

The main selenium is an amphoteric element, that is, it has the reducibility of metals and the oxidizability of non-metals.

For general organic matter, selenium is non-metallic and can be oxidized and combined with organic matter to form stable and absorbable compounds. at the same time, under the condition of strong oxidation, selenium can combine with oxygen to prevent organic matter from being oxidized, so selenium has the ability of antioxidation. Especially for alkaline metal toxic substances which are harmful to human body, the combination of selenium can effectively inhibit its toxicity and harm human health.

The mechanism is so general for plants, animals and soil.

Therefore, selenium is widely used in crops, livestock and poultry feed, anticancer drugs and health food.

Supply and demand of selenium market and its understanding

At the beginning of 2015, with the fermentation of the Pan-Asian event, the selenium market ushered in another round of price reduction. The price of crude selenium products dumped all the way from 300000 yuan to 50, 000 or 60, 000 yuan. From 2019 to 2020, it is also the eve of the disposal of Fanya's 300-ton selenium inventory. Although the amount of selenium has little impact on the industry, selenium-related production, management and sales enterprises are more mature, and the industrial chain is more perfect, but the price of selenium has been tossed back to 60, 000 yuan. Why, thank our dealers for their respective battle, full market competition and profit-seeking bidding.

For these problems, we first analyze the supply of selenium raw materials.

(1) the expansion of production and capacity of copper smelting enterprises has promoted the stability of copper prices and doubled the supply of selenium raw materials;

(2) the maturity of the technology of extracting selenium and mercury from acid sludge from smelting flue gas promotes the supply of selenium raw materials with lower price;

(3) the industrialization scale demand of selenium products, especially the situation of electrolytic manganese industry and the full competition of procurement, the result of the price war is falling endlessly.

(4) the demand for refined selenium and high-purity selenium products, especially for high-quality selenium applications, has not increased as previously expected, but is only the initial stage of the 100-ton level.

(5) for emerging applications such as big health, feed, fertilizers and alloys, and surface treatment agents, the demand of less than 1000 tons, even if it is an order of magnitude higher than the bulk demand price of the selenium industry, cannot affect the market price. Why not do it at a lower cost? produce products with a greater difference between purchase and sales and higher profits.

(6) the impact of demand in the glass-ceramic industry is limited, and the annual demand has been basically maintained at 600 tons in the past ten years.

1. The supply situation of selenium industry in recent years.

(1) selenium production in domestic copper smelting enterprises

Ten years ago, the price of selenium products was nearly 1 million yuan, due to the doubling of the scale of the copper industry, and the demand for copper mines has increased from 4 million tons ten years ago to nearly 10 million tons in recent years. Of course, the selenium production has also increased from less than one thousand tons ten years ago. With the upgrading of selenium removal technology and equipment in recent years, the output has reached about 2600 tons per year.

The supply of selenium in Jiang Copper, Tongling and medium Copper in the top three copper smelting enterprises exceeded 1000 tons, and the output of the top ten copper smelting enterprises exceeded 2,000 tons. (Yunnan Copper now belongs to China Copper, with an annual output of not less than 500 tons of selenium.)

(2) selenium production in other industries

The sulphuric acid industry from fire sulphide ore, that is, lead and zinc industry and other industries, has an annual output of about 500 tons.

(3) the import volume of selenium products has begun to decline gradually from the previous kiloton level, and it is estimated that the import volume this year is less than 300 tons. The corresponding export volume has also increased to the same level, and now due to the impact of the epidemic, the import and export volume is limited.

The above situation shows that the raw material supply of the domestic selenium industry has reached a reasonable level from the backward technology and equipment many years ago, and now the raw material supply chain is perfect and the equipment technology has reached a reasonable level.

2. The demand of selenium industry

(1) traditional demand

A. SeO2 demand status of Electrolytic Manganese

Electrolytic manganese enterprises form an unprotected lowest price transaction model by way of bidding. The annual demand for millions of tons of electrolytic manganese does not exceed 2000 tons of selenium, that is, the annual demand for selenium is about 1500 tons, including recovery. The transaction price is the basic standard for the basic transaction price of the main selenium raw materials in the selenium industry.

B. The glass industry has a demand for 99.5% selenium of good quality and 300 tons of selenium and above. About 10% of the high-end glass in China's glass industry uses the purification and color functions of selenium, especially automotive glass and glass products.

C, the ceramic pigment industry has strict requirements for hair color impurities in selenium quality, but it can also be applied to different hair color models, such as dark red hair color, such as bright red to rose red, a small amount of tellurium needs to be added, so, in the pigment industry, the selenium quality is not less than 99.5%, generally 99.9% selenium is used, the monthly demand is about 40 tons, and the annual demand is about 400 tons.

(2) in the feed industry, studies in developed countries have shown that selenium in livestock and poultry in the breeding industry can improve human immunity, so the relevant mandatory requirements have been issued, and the supply and demand chain of selenium additives has been steadily formed through study and development in China.

According to the relevant data, the demand for mineral element additives in the domestic feed industry is more than 5 million tons, of which the demand for selenium is only 1/10000 tons. Without counting the export, the demand for selenium for feed is greater and stable than that in developed countries.

Selenium fertilizer and soil application amount, from the land application, the demonstration area is less than 10 million mu and the application amount is less than 100 tons, but the opportunity we can see is that only 1% of the land application amount has reached the demand of nearly 100 tons, and if it continues to develop, reaching more than 10%, or reaching 20% of the selenium application area, fertilizer and soil improvement will reach the demand of 1000 tons, which will compete with the previous demand for additives for industrial products.

(3) material surface treatment agents and alloy products

For example, the surface of metal materials is oxidized, the amount of anti-vulcanization alloy additive for lead-acid battery is about 100 tons, the content is not less than 99.9%, and the annual demand is less than 100 tons.

(4) the demand for optoelectronic applications of high purity materials, especially flexible thin film optoelectronic materials, is gradually increasing, with an annual stable demand of 300 tons, the industry is basically mature, and the batch can reach 800 to 1000 tons after large-scale expansion.

Comparison of supply and demand

By comparing the normal amount, the result is a 10% difference between supply and demand of selenium, which belongs to the normal range. With the increase in the field of application, especially the continuous increase in the demand for the latter two high-end applications, the market will shift, the supply will be less than the demand, and the market will shift to the seller. of course, high-quality selenium products are required to place orders with selenium products with quality certification, while selenium products containing arsenic and mercury will be restricted.

4. Is the demand and application of selenium consumptive demand or recyclable demand?

The main results are as follows: (1) except that part of selenium can be recovered from manganese slag in electrolytic manganese industry, other industries and industries have no recovery value, and the demand of other industries is stable and the demand cycle is long.

(2) selenium mineralization is due to the crystallization of nature for hundreds of millions of years and is enriched in sulfur mineralization of the same group elements. after sulphide smelting, the enriched crude selenium resources that can be used for production are formed, so, the supply of copper, lead and zinc smelting resources will also decrease sharply in the process of reducing the recent mineral supply and recycling scrap metal (within ten years), and there is no other means to form stable resource supply support.

(3) with the continuous deepening of the application of high-tech materials, selenium will also become the basic material in the material application industry, and the demand will increase steadily. In the past ten years, from the kilogram class of the research type to the small batch type, the annual demand has reached the level of 100 tons.

(4) the cycle and quantity of improved demand will be significantly longer and larger than the stable supply of resources, which has changed significantly in the past five years, especially from this year, domestic supply and demand will tend to be balanced, as may happen when supply tends to be less than demand ten years ago.

5. Yunnan Copper Science and Technology now the selenium product structure is basically combined with the above analysis to upgrade the technology and equipment, and it has been upgraded from the crude selenium product structure for many years to all levels of selenium products. The serialization, equipment and batch of selenium products from 99% to 99.999% have been completed.

Other understandings related to selenium

1. The strategic position of selenium.

(1) the basic materials necessary for thin film solar cells with high-end optoelectronic materials;

(2) stable demand for mineral elements in the development of large health industries, especially after the accumulation of material wealth, people's requirements for basic grain quality improvement, disease prevention and control, non-toxic agricultural fertilizer, etc., in which selenium will play an important role.

(3) with the gradual improvement of quality and the increase of personalized service in the feed industry, the addition of minerals in feed will obviously increase, which is more beneficial to serve the sales and quality improvement of livestock and poultry. The most obvious example is that eggs exported in the early years contain selenium, and now the eggs eaten by ordinary people are also beginning to have selenium-rich varieties.

2. Selenium is friendly to the environment.

(1) the physical and chemical properties of selenium.

Physical properties: selenium element is a red or gray powder, quasi-metal with gray metallic luster. Among the six known solid allotropes, three kinds of crystals, the gray hexagonal system is the most stable and the density is 4.81g/cm3. It also exists in three forms of amorphous solids: red and black, two kinds of amorphous glassy selenium. The former is brittle with a density of 4.26 g / cm ~ 3, the latter has a density of 4.28 g / cm ~ 3, and the other is colloidal selenium.

Brittle and poisonous. Soluble in CS2, benzene and quinoline.

It can conduct electricity, and its conductivity changes sharply with the light intensity. Semiconductors and photosensitive materials can be made.

Melting point: 217 ℃.

Boiling point: 684.9 ℃.

Chemical properties: the first ionization energy is 9.752 electron volts. Selenium burns in the air and gives off a blue flame to form SeO2 (SeO2). It can react directly with hydrogen and halogen and combine with metal directly to form selenide. It cannot interact with non-oxidizing acid, but it dissolves in concentrated sulfuric acid, nitric acid and strong alkali. SeO2 was obtained by oxidation of selenium. Hydrogen selenide dissolved in water can precipitate many heavy metal ions into selenides of particles. Selenium and metals with oxidized state + 1 can form two kinds of selenides, namely normal selenide (M2Se) and acid selenide (MHSe). The aqueous solution of positive alkali metal and alkaline earth metal selenide will dissolve the element selenium and form polyselenide (M2Sen), which is similar to sulfur to form polysulfide.

(2) Stability of selenium compounds

Because of the chemical nature of selenium, its compounds are stable enough under normal conditions and can only be separated under acidic and strong oxidation conditions, but under natural conditions, this requirement is very stringent. For alkaline metals and harmful heavy metals, stable combination can be achieved basically.

(3) the value of selenium to human beings.

Through the above materials, it is recognized that the existence of selenium is conducive to the balanced and inhibitory absorption of various mineral elements. of course, selenium is also a necessary trace element for the human body, and the appropriate proportion of selenium in the surrounding environment and food and drinking water will be beneficial to human health and disease prevention. Of course, excess can also cause poisoning. According to the relevant mouse tests, the toxicity of the lethal dose of SeO2 is similar to that of arsenic, so, Selenium-related production enterprises are defined as the production of highly toxic and dangerous chemicals.

3. Explore the prospect of selenium application.

Exploring the application of selenium has not only been driven by the obligations and interests of our practitioners in the selenium industry, but also its high-end application must rely on the efforts and research and exploration of professionals in the high-end industry. fortunately, in agricultural applications, the state has issued relevant compulsory standards, and in the field of food and drugs, I believe there will be relevant policies in the near future. The supply of selenium production resources will decline significantly, and new resources must raise the level of discovery in the past decade.

Summary

The selenium industry is a competitive industry that has been active for less than 20 years, and its output scale is relatively small in application fields from basic to high-end industries, as the main cross-industry functional additives and substrate application elements. today's scale is based on the consumption of mineral resources, with the improvement of the recovery industry in the non-ferrous metals industry, the decline of mineral supply, and the general promotion and restriction of environmental protection policies. With the development of various application ways in selenium industry, antioxidant additives used in basic industrial products will be competed by high-end selenium application products. finally, selenium products will show sufficient value and price in the market, as well as development potential.

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