Zhao Hengqin, Ma Hualong, Hu Hongjie, Zhang Keren
(National Engineering Technology Research Center for Comprehensive Utilization of Non-metallic Mineral Resources, Zhengzhou 450006, Henan; Zhengzhou Institute of Mineral Comprehensive Utilization, Chinese Academy of Geological Sciences, Zhengzhou 450006, Henan )
The abstract introduces the basic characteristics and comprehensive development situation of insoluble potassium-containing rocks at home and abroad, and recommends development and utilization through a comprehensive utilization model. Insoluble potassium-containing rocks are widely distributed in my country. As the available potassium-containing resources become increasingly scarce, the value mining and development of large amounts of insoluble potassium-containing rocks have attracted more and more attention. Based on many years of research and practice on insoluble potassium-containing rocks, some analyzes and comparisons were made on the characteristics, potential value, and development and utilization status of insoluble potassium-containing rocks for reference during development and utilization [1-6].
Keywords: insoluble potassium-containing rocks; basic characteristics; potential value; development and utilization.
About the first author: Zhao Hengqin, researcher, engaged in the comprehensive utilization and development of mineral resources and research on new chemical materials.
1. Types and distribution characteristics of insoluble potassium-containing rocks in my country
Insoluble potassium-containing rocks widely exist in my country and are distributed in almost every province. According to the main minerals contained, it mainly includes the following types: nepheline, mung bean, potassium feldspar, and potassium-containing sandy shale.
1) Nepheline: It is a potassium-containing aluminosilicate mineral with the chemical formula (Na, K) 2O·Al2O3·(2 +n) SiO2, n=0~0.2, A mineral containing relatively little silicon among insoluble potassium-containing rocks. Gejiu, Yunnan, Pingli, Shaanxi, Baicheng, Xinjiang and other places have large typical mineral deposits, among which the Gejiu deposit in Yunnan has reserves of more than 30×108t.
2) Potassium-bearing tuff: It is a kind of potassium-rich volcanic tuff. Its chemical composition is K2O·Al2O3·10SiO2. It is the highest potassium-containing insoluble potassium-containing rock. A type of ore. Mainly distributed in Sichuan and Shaanxi. Sichuan mung bean rock is generally produced in the lower part of the Leikoupo Formation of the Middle Triassic, and is often used as the floor of dolomite or gypsum salt layer. It can be divided into two types. One is potassium-rich tuff, which is mainly distributed in northeastern Sichuan. According to the analysis of rock composition in Kaixian County, the K2O content is high, generally 9.8% to 12.05%, with an average of 10.9%; the other is hydromicitized tuff. Mainly distributed in southern and southwestern Sichuan, most of them are volcaniclastic rocks formed by strong hydromicitization, mainly hydromica. This type of rock also contains potassium hydromica clay rock, which is generally of low grade. Petrochemical analysis of Weiyuan County K2O is 5.60% ~ 7.46%, and the grade and thickness changes are relatively stable.
3) Potash feldspar: It is also a typical aluminum silicate mineral. Its chemical formula is (Na, K) 2O·Al2O3·6SiO2. It is a potassium-containing mineral with a high silicon content. Mineral, strong chemical stability, difficult to dissolve in acid and alkali. According to existing surveys, the K2O content of potassium-containing rocks represented by potassium feldspar is between 8% and 15%, with an average of 10%. They are found almost all over the country, and their geological reserves are estimated to be hundreds of billions of tons.
4) Potassium-bearing sandy shale: It is a mixed insoluble potassium-containing rock, with a K2O content generally between 4% and 15%. The mineral composition of most mineralization zones is generally characterized by potassium feldspar associated with glauconite. Large deposits with huge reserves have been discovered in Henan, Shaanxi, Inner Mongolia and other places.
2. The resource value of insoluble potassium-containing rocks in my country and the significance of its development and utilization
(1) Insoluble potassium-containing rocks are important potassium-containing resources in my country
my country is a country with a severe shortage of potassium salt. It imports a large amount of potassium fertilizer from abroad every year. In 2005, the country's potash fertilizer imports were 883×104t, accounting for 19.9% ??of world trade volume, making it the second largest importer in the world. As a major agricultural country in the world, due to the shortage of potassium fertilizer, the ratio of basic chemical fertilizers nitrogen, phosphorus and potassium has been out of balance for a long time. The ratio of nitrogen to potassium fertilizer has long been hovering below 1:0.2, which is lower than the world average of 1:0.30. my country's long-term inability to be self-sufficient in potassium fertilizer has become a major obstacle to agricultural development. Potassium salt's dependence on foreign resources has reached 90%. Utilizable potassium salt has become one of the non-metallic minerals in short supply in my country.
The main reason for this situation is that my country's available potassium salt resources, that is, water-soluble potassium salt resources, are very few and are very unevenly distributed, with more than 95% distributed in the western region. Therefore, in addition to strengthening the search for water-soluble potassium salt resources in geological work in the future, the development and utilization of a large number of insoluble potassium-containing rocks has become a major event in my country's economic development.
(2) Insoluble potassium-containing rocks are also important alternative aluminum resources in my country
According to statistics from the Ministry of Land and Resources and China Aluminum Corporation, my country’s largest alumina producer, my country’s current aluminum The resource guarantee period of earth minerals is about 10 years, which is far from the resource guarantee requirement of more than 50 years usually required by the non-ferrous metal industry. Non-bauxite aluminum resources are widely distributed in my country, and its extraordinary reserves can be seen from the fact that the average alumina content in the earth's crust is about 17%. The crux of the matter is how to find economically viable technologies to replace aluminum resources with these abundant non-bauxite minerals. As an aluminosilicate mineral, potassium-containing rock is an alternative mineral species for non-bauxite to replace aluminum resources in the future. If the technical problems of its use as a substitute for aluminum resources can be solved, it will provide an opportunity for my country to develop and utilize non-bauxite to replace aluminum. The utilization of resources such as clay, albite, and alunite sets an example and provides strong resource guarantee for the healthy development of the aluminum industry.
(3) Insoluble potassium-containing rocks are also important silicon fertilizer resources in my country
Carrying out research on the comprehensive utilization of insoluble potassium-containing rocks will help to open up new sources of resources for silicon fertilizer production and provide Provide technical support to enhance the value of aluminosilicate resources abundant in my country.
Potassium-containing rocks contain more than 60% silica. However, due to its poor solubility and low effective silicon content, its efficiency as a silicon fertilizer is poor. Silicon fertilizer, a newly developed chemical fertilizer at the end of the 20th century, is considered by the international soil community to be the fourth plant nutrient element after nitrogen, phosphorus and potassium. Silicon fertilizer is a soluble mineral fertilizer containing mainly calcium acid. It is non-toxic, odorless, non-corrosive and not easy to drain. It is widely used in crops such as rice, wheat, corn, cotton, peanuts, rape, sugar cane, fruits and vegetables. Most of the silicon required by crops is provided by the soil, but very little silicon in the soil can be absorbed by plants. Surveys by relevant departments show that 70% of the soil in the Yangtze River Basin in my country is deficient in silicon, and about half of the soil in the Yellow River, Huaihai and Jiaodong Peninsula areas is deficient in silicon, and the areas lacking silicon are gradually expanding. Silicon is an important nutrient required for the growth of crops. After crops absorb silicon, it can promote root growth and development, improve resistance to lodging, pests and diseases, drought resistance, cold resistance and nutrient absorption. It can also improve the quality of crops, which is in line with modern "green food" "Development requirements. Therefore, if the silicon contained in the potassium extraction technology can be comprehensively utilized as a source of long-lasting silicon fertilizer raw materials, it will help to open up new sources of resources for silicon fertilizer production in my country. Currently, the Zhengzhou Institute of Comprehensive Mineral Utilization of the Chinese Academy of Geological Sciences is conducting research on the comprehensive utilization of potash-containing shale in Linzhou, with a view to obtaining potassium salt, aluminum hydroxide and silicon fertilizer to achieve their comprehensive utilization.
3. Research and development status of insoluble potassium-containing rock resources
(1) Research and development status of foreign insoluble potassium-containing rock resources
For insoluble potassium-containing rocks, relevant foreign Research and development are only carried out in a few countries, typically the former Soviet Union.
In the former Soviet Union, due to the relative scarcity of bauxite resources, some alumina plants used potassium-containing shale as raw material to produce alumina and comprehensively utilized it to recover potassium. There are also industrial production plants. Typical enterprises include Pikalev Aluminum Plant, which uses potassium-containing rock nepheline as raw material to produce alumina, with potassium carbonate and sodium carbonate as by-products; Kirovabad Aluminum Plant, which uses alunite as raw material to produce alumina. The by-products are sulfuric acid, potassium sulfate and vanadium pentoxide. The former uses an alkali method and the latter uses an acid method. Their research and industrialization technologies focus on extracting alumina, taking into account the recovery of potassium salt, and the residue is used as building material auxiliary materials or directly as building materials and raw materials.
Research on the comprehensive utilization of potassium feldspar, which is the most difficult to process in potassium-containing shale, foreign ores have low iron content, relatively high purity of potash feldspar minerals, and simple mineral embedding relationships, and most processes are simple. After beneficiation and iron removal, it can be used as high-quality potassium feldspar raw material for ceramics and glass. There is no mature technology that can be used for reference in comprehensive chemical treatment.
(2) Domestic research and development status of insoluble potassium-containing rock resources
Domestic research on potassium-containing rocks began in the 1960s, and research using Yunnan nepheline is relatively typical. The processes used include hydrochemical methods and sintering methods, and investors are currently planning to invest in industrial practice in Yunnan.
For the research and development technology of insoluble potassium-containing rocks (hereinafter referred to as potassium-containing rocks), domestic research can be summarized as follows.
1) Potassium-containing rock minerals, mainly potash feldspar, are used as raw materials for ceramics and glass through mineral processing. This has mature industrial practice in China. Generally, it is required that the raw ore has a simple inlay relationship, the potassium feldspar mineral has good purity, and it is easy to beneficiated and remove impurities. For ores with complex embedded distribution relationships, it is generally not applicable due to the poor effect of mineral processing and impurity removal. The Zhengzhou Institute of Comprehensive Mineral Utilization of the Chinese Academy of Geological Sciences has conducted beneficiation experiments on some domestic insoluble potassium-containing rock minerals, mainly focusing on potassium feldspar ores. The purpose is to reduce iron-containing impurities in the ores to meet the requirements of raw materials for glass and ceramic production. need.
2) Recover and utilize potassium through kiln dust volatilization method. The essence of this method is to use potassium-containing rocks as cement raw materials. At high temperatures, part of the potassium oxide volatilizes and is enriched in the kiln dust, and then the potassium is recovered through the kiln dust. Due to the limitation of volatilization rate, the recovery rate of potassium is low.
3) Salt sodium roasting method. The essence of this process is to use the good permeability of sodium ions and the chemical activity of chlorine radicals to destroy the stable chemical structure of potassium-containing rocks at high temperatures, thereby converting potassium into soluble potassium chloride. The disadvantages of this method are low recovery rate, serious equipment corrosion, large environmental pollution, and it is currently difficult to industrialize.
4) Acid treatment of potassium-containing rocks. The essence of this process is to destroy the structure of potassium-containing rocks through heated acid hydrolysis. Processes derived from this method include HCl method, H2SO4 method, nitric acid method, ammonium sulfate roasting method, water alum method, basic aluminum sulfate method, etc., and many patents have been published. However, due to the simple structure and low value of the end product, difficulty in acid regeneration, serious equipment corrosion, and high environmental management costs, it is difficult to achieve industrialization.
5) Bacterial potassium solution. This process uses bacteria to dissolve silicon minerals, thereby destroying the structure of potassium feldspar and obtaining soluble potassium. At present, the most widely used bacterial species are mainly silicate bacteria. Silicate bacteria have significantly different potassium-solubilizing effects on minerals with different crystal structures. In contrast, the potassium-solubilizing effect of silicate bacteria on illite (potassium is present in the interlayer domain) is significantly stronger than that on potassium feldspar (potassium is present in the structural gaps). Under the conditions where a variety of minerals exist, bacteria will show obvious differences in the strength or speed of their action due to different mineral crystal structures, thus causing varying degrees of damage to different types of minerals. The destructive effect of silicate bacteria on minerals varies depending on the origin of the mineral, the degree of crystallization of the mineral, and the condition of the associated minerals. This process should be a better method with the development of biotechnology, but at present, it is limited to high bacterial cultivation costs and little prospect for industrialization. Research on the comprehensive utilization of shale will help to tap the economic value of insoluble potassium salt resources, alleviate the shortage of water-soluble potassium salt resources in my country, open up new resources and new technologies for potassium salt/potash fertilizer production in my country, and contribute to ensuring and improving Henan Province Even the potassium resource reserves available for agriculture in my country have important scientific and technological significance.
Figure 1 Comprehensive utilization process flow of insoluble potassium-containing rock sintering method
6) Alkaline treatment of potassium-containing rocks. The alkali process includes high-temperature hydrochemical process, lime sintering process, soda-lime sintering process and other derived alkali processes. The essence of this process is to convert aluminum into soluble sodium aluminate, potassium aluminate, and calcium aluminate in a high-temperature and high-alkali water system, or in the presence of high-temperature lime, etc., and convert silicon into calcium silicate. Aluminum and potassium are recovered, and the residue is used as building materials or to produce silicon fertilizer. The biggest feature of this method is that it can achieve comprehensive utilization, the equipment is relatively simple, it is easy to close the loop, and the environmental pollution is very small. Another feature of this method is that it uses an alkaline process. The potassium produced and recovered is in the form of relatively high-value potassium carbonate and potassium hydroxide, and the aluminum is in the form of high-value chemicals alumina, such as diaspore and active oxidation. Aluminum, easily soluble alumina, ultra-white ultra-fine alumina, etc. exist in the form of silicon fertilizer or building materials, which are used in large quantities. This has laid a good market economy for the development and utilization of potassium-containing rocks towards industrialization. Base.
The Zhengzhou Institute of Mineral Comprehensive Utilization of the Chinese Academy of Geological Sciences has conducted research on Shanxi Zijinshan Mine and Shandong Potassium Feldspar Mine. The comprehensive yield of potassium has reached more than 70%, and the comprehensive yield of alumina has reached 65%. The residues are all used as cement raw materials. . The project has won the Science and Technology Progress Award from the Ministry of Land and Resources. On the basis of this method, a study conducted by relevant domestic scientific research institutions on potassium-rich slate in Baotou in 2003 showed that the alkali method is still the best process for treating potassium-containing rocks. Figures 1 and 2 show the typical process diagrams of these two alkali processes for treating potassium-containing rocks.
Figure 2 Process flow of high-pressure hydration method
IV. Development and utilization suggestions
1) According to the current research status of potassium-containing rocks at home and abroad, my country will In the development and utilization of potash-containing rocks, we should focus on the process technology route and final product design. On the technical route, we should proceed in the direction of simple, easy, economical and reasonable processes. The design of the final product should be based on the principle of maximizing the extraction of useful components potassium and aluminum, and finding the use of residual silicon. At the same time, it should be based on the principle of maximizing the value of potassium and aluminum products, and silicon The selection of products should be based on the principle of large usage. Only in this way can the value of potash-containing shale be fully exploited and truly put into practical use.
2) The country or relevant provinces should concentrate their R&D efforts on priority development of mining areas with better transportation, hydropower, etc., as well as mining conditions, taking into account the industrial status of surrounding areas, and select areas that have resources and are close to large cement Develop potassium-containing rocks in the market or agricultural fertilizer market area, so that a virtuous cycle can be achieved from the beginning.
References
[1] Zhao Hengqin, et al. High-pressure hydrochemical leaching of potassium feldspar. China Manganese Industry, 2002, (1): 27-29, 43
[2] Niu Xuguang, et al. Research on potassium-solubilizing activity of silicate bacteria. Soil Bulletin, 2005, (6): 950-953
[3] Zhao Hengqin, et al. Potassium Research on comprehensive utilization of feldspar by soda-lime sintering method. Nonmetallic Minerals, 2003, (1): 24-29
[4] Wang Rufu, et al. Research on the conversion of insoluble potassium-containing rocks into calcium silicate and potassium fertilizer. Journal of Chengdu University (Natural Science Edition), 1999, (2): 45-49
[5] Li Hua, et al. Laboratory research on improving potassium feldspar conversion rate. Chemical Minerals and Processing, 1999 , (12): 6-9
[6] Xue Yanhui, et al. New method for comprehensive development and utilization of potassium feldspar. Nonmetallic Minerals, 2005, (4): 48-50
An Analysis on the Research and Development Status Quo of Resources of Insoluble Potassium-bearing Ore
Zhao Hengqin, Ma Hualong, Hu Hongjie, Zhang Keren
（China National Engineering Center for the Multipurpose Utilization of Nonmetallic Mineral Resources; Zhengzhou Minerals Resources Multipurpose Utilization Institute, CAGS, Zhengzhou 450006, Henan, China)
Abstract: Some characteristics of insoluble potassium-bearing ore were introduced.The technology and methods for their comprehensive development were also reviewed simultaneously with corresponding research practices. Some suggestions on comprehensive development and utilization of resources were put forward.
Key words: Potassium-bearing ore, Analysis.