Method for continuous zero-carbon preparation of basic magnesium sulfate whiskers from phosphate tailings

Abstract

The invention discloses a method for continuous zero-carbon preparation of basic magnesium sulfate whiskers from phosphate tailings, which comprises the following steps: recovering phosphate concentrate and removing iron and aluminum from the phosphate tailings through acidolysis to obtain magnesium hydroxide precipitate and calcium solution; and adding a sulfuric acid solution and a crystal modifier into the magnesium hydroxide precipitate, uniformly mixing, and adding into a continuous crystal transformation kettle for reaction to obtain the basic magnesium sulfate whisker. The method has the characteristics of high phosphate concentrate recovery rate, high product added value and environmental protection.

Description

Technical Field

[0001] The invention relates to the field of phosphate ore in non-metallic minerals, and in particular to a method for continuously preparing basic magnesium sulfate whiskers with zero carbon from phosphate tailings. Background Art

[0002] Phosphate ore needs to be separated and enriched through mineral processing to meet the requirements of the phosphorus chemical industry [Guo Wenda, Lu Haolong, Jiang Yuanting, et al. Research progress analysis of phosphate collectors and their mechanism of action [J / OL]. Comprehensive utilization of minerals. https: / / link.cnki.net / urlid / 51.1251.TD.20240802.1352.009]. In high-magnesium low-grade phosphate ore, impurities mainly exist in the form of dolomite, which contains a large amount of MgO. When the MgO content in phosphate ore is too high, MgO will have adverse effects on the production of phosphoric acid, ammonium phosphate and other acid-based phosphate fertilizers, such as fertilizer withdrawal effect, filtration difficulty, and phosphate fertilizer moisture absorption.

[0003] At present, the industry generally uses the reverse flotation method for magnesium removal pretreatment of phosphate ore, but this method will produce a large amount of flotation tailings. The current treatment method of phosphate tailings is to build a reservoir for storage, which occupies a large amount of land. The harmful components and residual mineral processing agents in it will enter the soil, destroy the soil structure, cause soil degradation, and cause environmental problems such as vegetation destruction and water pollution, as well as the safety risk of dam breach.

[0004] The main minerals in phosphate tailings are dolomite, apatite and quartz. Acid solution is added to the phosphate tailings, and the acid reacts with dolomite to obtain soluble salts, and the solid-liquid separation is carried out to achieve the enrichment and recovery of apatite in the tailings. For example, nitric acid is used to react with phosphate flotation tailings, and the resulting magnesium-containing solution is neutralized with lime milk to obtain a magnesium hydroxide product [Chen Xiaolin, Liu Daijun, Tan Deqin, et al. Study on the process of preparing magnesium hydroxide from phosphate tailings by nitric acid removal of magnesium [J]. Chemical Minerals and Processing, 2012, (3): 6-8]. Using lime milk to adjust the pH value of the acid leaching solution to remove iron and aluminum will increase the calcium content in the solution and increase the difficulty of post-treatment of the magnesium removal solution; the iron-aluminum mixture obtained by precipitation is difficult to be recycled; and the prepared magnesium hydroxide product has low added value.

[0005] The phosphate tailings are mixed with a dilute acid solution for a primary acid hydrolysis to form a primary pulp, the pH value of the primary pulp is controlled to be 2.0-5.0, and the primary pulp is stirred; then, the primary pulp is subjected to solid-liquid separation to obtain a primary acid hydrolysis solution and a primary tailings; when the Mg content in the primary acid hydrolysis solution is higher than 5000 mg / L, magnesium hydroxide is extracted by chemical precipitation; thereafter, the primary tailings are mixed with a dilute acid solution for a secondary acid hydrolysis to form a secondary pulp, the pH value of the secondary pulp is controlled to be less than 2.0, and the secondary pulp is separated into a secondary tailings; The secondary slurry is separated into solid and liquid to obtain a secondary acid solution and quartz tailings; then, an alkaline substance is added to the secondary acid solution to precipitate phosphate, and phosphate is obtained after solid-liquid separation; the dilute acid solution of the primary acid solution and the secondary acid solution is a hydrochloric acid solution and / or a sulfuric acid solution; the alkaline substance is calcium oxide powder, calcium hydroxide and / or ammonia water [Yu Yaohui. A method for step-by-step extraction of phosphorus from phosphate tailings and comprehensive utilization of all components, China, 202310339468[P].2023.04.03]. Dissolving apatite with acid, adding alkaline substances to precipitate phosphate, and using alkaline substances to neutralize phosphoric acid will increase costs. Using two acid solutions increases the process flow and production costs. The magnesium hydroxide product obtained has low added value.

[0006] The phosphate tailings are calcined to obtain calcined phosphate tailings powder; the calcined phosphate tailings powder is mixed with water and a leaching agent to perform a leaching reaction, and filtered to obtain a leachate and a phosphate concentrate; the leachate is mixed with sulfuric acid to perform a calcium precipitation reaction, and filtered to obtain calcium sulfate and a calcium precipitation filtrate; the calcium precipitation filtrate is mixed with hydrofluoric acid to perform a magnesium precipitation reaction, and filtered to obtain magnesium fluoride and a magnesium precipitation filtrate; the leaching agent is one or more of organic small molecule acids, and the organic small molecule acids include malic acid, anhydrous citric acid, monohydrate citric acid and lactic acid [He Dongsheng, Li Zhili, Tang Yuan, et al. A method for enriching phosphate concentrate using phosphate tailings to produce calcium sulfate and magnesium fluoride, China, 202410417849[P]. 2024.04.09]. The phosphate tailings are calcined to increase production costs. Hydrofluoric acid is highly corrosive and expensive, which is not conducive to industrial application. The magnesium fluoride product fails to increase the added value of magnesium itself.

[0007] Basic magnesium sulfate whisker is an environmentally friendly magnesium salt whisker material with a chemical formula of MgSO4·5Mg(OH)2·3H2O. Due to the particularity of its structure and composition, this material not only has good mechanical properties unique to general whisker materials, but also has good flame retardant effect during thermal decomposition at high temperatures. For example, basic magnesium sulfate whiskers are synthesized by hydrothermal method using magnesium hydroxide and magnesium sulfate heptahydrate as raw materials [Jiang Demin, Li Shunmei, Li Qingqing, et al. Hydrothermal synthesis of basic magnesium sulfate whiskers from magnesium hydroxide and magnesium sulfate heptahydrate [J]. Inorganic Salt Industry, 2023, 55(12): 74-81].

[0008] The use of intermittent reactors for whisker preparation has low production efficiency and high production costs. A system for continuous whisker production is developed to achieve continuous whisker production, improve production efficiency and reduce production costs.

[0009] The content of magnesium sulfate in the raw material is much greater than the stoichiometric amount of magnesium sulfate in the whiskers, resulting in more residual magnesium sulfate in the process flow, which reduces production efficiency. By adding a crystal-changing agent, the dissolution characteristics of magnesium hydroxide and the growth characteristics of whiskers are changed, the content of magnesium sulfate in the raw material is reduced, and the production efficiency of the product and the utilization efficiency of the equipment are improved.

[0010] The magnesium hydroxide precipitate extracted from the phosphate tailings is used as the raw material to prepare the basic magnesium sulfate whisker, which has the characteristics of resource recycling, avoids the intermediate link of purchasing raw materials, improves the production efficiency of the product, and has good economic benefits.

[0011] In order to achieve high-quality utilization of phosphate tailings resources, improve production efficiency, avoid waste generation and reduce production costs, it is necessary to develop new methods for the efficient separation of the components of phosphate tailings and achieve efficient production of high value-added products. Summary of the invention

[0012] In order to solve the problems existing in the prior art, the present invention provides a method for continuously preparing basic magnesium sulfate whiskers from phosphate tailings with zero carbon. Compared with the existing technical solutions, the method has the characteristics of high production efficiency, low cost, and green environmental protection, and has significant economic and social benefits.

[0013] A method for continuously preparing basic magnesium sulfate whiskers from phosphorus tailings with zero carbon content comprises the following steps in sequence:

[0014] Water and organic mixed acid are added to the phosphate tailings to react, and a mixed solution and phosphate concentrate are obtained by liquid-solid separation; ammonia water and a water reducing agent are added to the mixed solution, the pH value of the solution is controlled to be 2.5-3, and an iron precipitate and an iron removal liquid are obtained by liquid-solid separation; ammonia water and a particle size regulating agent are added to the iron removal liquid, the pH value of the solution is controlled to be 5-6, and the liquid-solid separation is performed to obtain an aluminum precipitate and an aluminum removal liquid; ammonia water and a magnesium regulating agent are added to the aluminum removal liquid, the pH value of the solution is controlled to be 9.5-11, and the liquid-solid separation is performed to obtain a magnesium hydroxide precipitate and a calcium solution; sulfuric acid solution and a crystal-changing agent are added to the magnesium hydroxide precipitate, the mixture is evenly mixed, and then the mixture is added to a continuous crystal-changing kettle for reaction to obtain basic magnesium sulfate whiskers; the continuous crystal-changing kettle consists of a pressurized column, a pipeline kettle, and a cooling kettle, and the electric energy used by the continuous crystal-changing kettle is one of photovoltaic, wind power, and hydropower.

[0015] The amount of water added is 300-500% of the mass of the phosphorus tailings; the organic mixed acid is prepared by adding one of acetic acid and tartaric acid into nitric acid, and the amount of the organic mixed acid added is 100-200% of the mass of the phosphorus tailings.

[0016] The water reducing agent is one of polycarboxylic acid, sulfonated melamine formaldehyde resin and naphthalenesulfonic acid formaldehyde condensate, and the added amount is 0.1-0.5% of the mass of the phosphorus tailings.

[0017] The particle size regulating agent is one of polyethylene glycol, ammonium acetate and ammonium oxalate, and the added amount is 0.1-0.5% of the mass of the phosphate tailings.

[0018] The magnesium adjusting agent is one of polyvinyl alcohol, polyethylene glycol octylphenyl ether and polyacrylamide, and the added amount is 0.1-0.5% of the mass of the phosphate tailings.

[0019] The amount of sulfuric acid solution added is 10-30% of the mass of the phosphate tailings.

[0020] The crystal-changing agent is one of disodium ethylenediaminetetraacetate, sodium phosphate and polyacrylamide, and the added amount is 0.1-0.5% of the mass of the phosphate tailings.

[0021] The reaction temperature in the pipeline kettle is 185-225° C., and the reaction time is 70-110 minutes.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] In the phosphorus tailings, the amount of water added is 300-500% of the mass of the phosphorus tailings, and the amount of organic mixed acid added is 100-200% of the mass of the phosphorus tailings, both of which can achieve the purpose.

[0024] Commonly used acids for acid hydrolysis of phosphate tailings are sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid. Nitric acid has strong reactivity, and the obtained nitrates are all soluble in water, which is convenient for separation from apatite. After the leaching solution removes iron, aluminum, and magnesium, the final calcium ammonium nitrate solution can be used as a water-soluble fertilizer to achieve full utilization of tailings. However, nitric acid is a strong acid that easily causes strong local acidity in the reaction system, leading to the dissolution of apatite and reducing the recovery rate of phosphorus. Add one of acetic acid and tartaric acid to nitric acid to obtain an organic mixed acid. Under the action of nitric acid, the organic acid acetic acid or tartaric acid reacts with the phosphate tailings to obtain corresponding salts, such as calcium acetate and magnesium acetate. The organic acid and its corresponding salt form a buffer solution, which is conducive to the stability of the pH value of the reaction system and ensures that the pH of the reaction system is 2.0-2.3. The organic mixed acid is one of acetic acid and tartaric acid added to nitric acid, tartaric acid is solid, and acetic acid is glacial acetic acid. The amount of addition is 5-30% of the total mass of the organic mixed acid, which can achieve the purpose. The nitric acid is a nitric acid solution, and its concentration is 5-40%, which can achieve the purpose. The content of nitric acid in the mixed acid is calculated according to the HNO3 in the solution. The total amount of organic acid is calculated according to the amount of HNO3 and tartaric acid, or HNO3 and glacial acetic acid. Water is first added to the phosphate tailings, and then the organic mixed acid is added; the organic mixed acid is added at a rate of 5-50% of the total amount added per hour, and the stirring rate of the phosphate tailings slurry is 200-1000 rpm, and a high-grade phosphate concentrate is obtained, and the recovery rate of apatite is greater than 98%.

[0025] Using ammonia water as the pH regulator of the leaching solution can increase the nitrogen content of the water-soluble fertilizer and make it easier to separate it from other substances.

[0026] Adding ammonia water and water reducing agent to the mixed solution, controlling the pH value of the solution to 2.5-3, iron precipitation can be obtained, the purpose is achieved, the iron removal rate is 99-99.9%, and the purity of the iron precipitation is 99.9-99%. Increasing the pH value of the solution is conducive to the complete removal of trivalent iron ions and improving the purity of the solution. The iron precipitate is iron hydroxide, which is a colloid and usually carries more solution, resulting in a decrease in its purity. The water reducing agent is one of polycarboxylic acid, sulfonated melamine formaldehyde resin, and naphthalenesulfonic acid formaldehyde condensate, all of which can achieve the purpose. The water reducing agent is adsorbed on the surface of the iron hydroxide colloid, releasing the solution wrapped in the colloid, improving the purity of the iron hydroxide, and avoiding the loss of the leachate. The iron hydroxide precipitate usually contains more than 30% water. By adding a water reducing agent, its water content is less than 10%. The obtained iron hydroxide precipitate can be used as an iron source for iron phosphate to achieve high-quality utilization. The iron hydroxide precipitate can also react in a continuous crystallization reactor to generate iron oxide, which can be used as a pigment; the iron oxide crystallization temperature is 180-240°C and the crystallization time is 2-8 hours.

[0027] The equipment for solid-liquid separation is a plate and frame filter press, which has the characteristics of high efficiency and low cost.

[0028] Ammonia water and particle size regulator are added to the iron removal liquid, and the pH value of the solution is controlled to 5-6, and aluminum precipitate can be obtained to achieve the purpose. The aluminum removal rate is 99-99.9%, and the purity of the aluminum precipitate is 99.9-99%. The aluminum precipitate is aluminum hydroxide precipitate. The particle size regulator can control the particle size of the aluminum precipitate to obtain nano aluminum hydroxide powder, which is conducive to the high-quality utilization of aluminum hydroxide. The particle size regulator is one of polyethylene glycol, ammonium acetate, and ammonium oxalate, which can achieve the purpose. The obtained aluminum hydroxide precipitate has a particle size of less than 100 nanometers. Nano aluminum hydroxide powder can also be reacted in a continuous crystallization reactor to prepare nano alumina, and its particle size is less than 100 nanometers, the crystallization temperature is 220-280℃, and the crystallization time is 2-8 hours. Nano aluminum hydroxide powder and nano alumina powder can be used to produce fine alumina ceramics to achieve high-quality utilization.

[0029] Adding ammonia and magnesium adjusting agent to the aluminum removal liquid, controlling the solution pH value to 9.5-11, can obtain magnesium hydroxide precipitation, achieve the purpose, and the magnesium removal rate is 80-90%. The magnesium adjusting agent controls the size of the magnesium hydroxide particle size, which is conducive to the growth of basic magnesium sulfate whiskers. If the particle size is too small and dissolves too quickly, the whisker length is relatively low. If the particle size is too large and dissolves too slowly, the whisker growth time is too long, affecting the production efficiency. The magnesium adjusting agent is one of polyvinyl alcohol, polyethylene glycol octylphenyl ether, and polyacrylamide, which can achieve the goal. The grain size of magnesium hydroxide is 0.8-5.0 microns.

[0030] Sulfuric acid solution and a crystal-changing agent are added to the magnesium hydroxide precipitate, mixed evenly, and then added to a continuous crystal-changing kettle for reaction to obtain basic magnesium sulfate whiskers. The sulphuric acid solution is dilute sulphuric acid with a concentration of 5-40%. The amount of sulphuric acid solution added is calculated according to the H2SO4 in the solution, and the purpose can be achieved.

[0031] The sulfuric acid solution reacts with magnesium hydroxide to obtain magnesium sulfate, which provides magnesium sulfate raw material for the growth of basic magnesium sulfate whiskers.

[0032] The crystal-transforming agent is one of disodium ethylenediaminetetraacetate, sodium phosphate and ammonium polyacrylamide, all of which can achieve the purpose. The crystal-transforming agent can promote the dissolution of magnesium hydroxide and the growth of whiskers in one-dimensional direction, so as to achieve adjustable aspect ratio of whiskers.

[0033] As the reinforcing phase of the composite material, whiskers are not conducive to dispersion in the matrix if their diameter is too small; if their aspect ratio is too large, the whiskers are easily entangled, which is also not conducive to dispersion; increasing the whisker diameter and controlling the aspect ratio are conducive to reducing the application cost of the whiskers.

[0034] The continuous crystallization kettle consists of a pressure column, a pipeline kettle, and a cooling kettle, which are connected by flanges. The continuous crystallization kettle is an open high-pressure container, which avoids the characteristic of traditional autoclaves that they can only produce intermittently. It realizes continuous production, improves production efficiency, and reduces production costs. The feed of the continuous autoclave is raw material slurry, which is a mixed liquid of magnesium hydroxide, sulfuric acid, and crystallization agent, and the discharge of the angle valve is product slurry.

[0035] The pressurized column consists of a hollow cylinder, a pressure relief valve and a feed valve. The feed valve is a one-way valve, also known as a check valve or non-return valve, which prevents the slurry from flowing in the opposite direction. The column is 10-400 meters high, and the height can be selected according to the design requirements. The pressure is transmitted to the pipeline kettle by the weight of the slurry and the pressure of the pump feeding the slurry; the higher the column, the greater the weight of the slurry, and the simpler the system control. The intelligent control system is used to adjust the pressure of the pump feeding the slurry to ensure that the pressure generated by the pressurized column is balanced with the saturated water vapor pressure in the pipeline kettle to ensure the temperature in the kettle is stable. The pressure relief valve is the slurry discharge port. When the pressure of the pressurized column exceeds the saturated vapor pressure of the pipeline kettle at a given temperature, the slurry is automatically discharged and discharged into the slurry pool to ensure the pressure stability in the pipeline kettle and the safety of the system, that is, overpressure protection. The slurry pressure measurement adopts one of the isolated diffused silicon sensitive elements and ceramic capacitor pressure sensitive sensors, which can achieve the purpose. The control system of the continuous crystallization kettle adopts a DCS control system, which has the characteristics of stable operation. The column body of the pressure column is arranged vertically, which is beneficial to reducing the occupied area.

[0036] The pipeline kettle is used for the growth of basic magnesium sulfate whiskers. The pipeline kettle is a cylindrical hollow pipeline with a constriction and a flange at one end, and a sealed end with a circular tubular hole on the upper side and a flange connected; a magnetic stirrer is installed on the pipeline kettle, which has the characteristic of easy sealing. The pipeline kettle is equipped with a steam jacket and is heated by steam. The heating steam is generated by the green power boiler, and the low-temperature steam is circulated back to the boiler. The pipeline kettle can also be heated by heat transfer oil, which can also achieve the purpose; the heat transfer oil is heated by green power resistance elements. Green power is one of photovoltaic, wind power, and hydropower, all of which can achieve the purpose.

[0037] The cooling kettle is a cylindrical hollow pipe with circular constrictions and flanges at both ends of the pipe. A magnetic stirrer is installed on the cooling kettle, which has the characteristic of easy sealing. The slurry flow at the outlet of the cooling kettle is controlled by an angle valve, that is, an angle stop valve. The angle valve has the characteristics of simple flow path, small dead zone and eddy zone, and small flow resistance. It is suitable for occasions containing suspended matter and granular fluids. The angle valve opening is automatically controlled by the DCS system to ensure that the discharge amount of the angle valve is balanced with the feed amount of the pressurized column, and to ensure the stability of the pressure and temperature in the pipeline kettle. The part where the angle valve contacts the slurry adopts ceramic lining to increase the service life of the angle valve. The material of the ceramic lining is one of alumina and zirconium oxide, which can achieve the purpose. The kettle wall of the cooling kettle is equipped with a water cooling jacket to cool the slurry and realize heat recovery. The temperature of the slurry discharged from the cooling kettle is 20-50℃, which avoids the difficulty of recovering the water vapor discharged and causing heat loss.

[0038] The material of the continuous crystallization kettle is one of carbon steel and stainless steel, both of which can achieve the purpose. The inner wall of the continuous crystallization kettle and the contact surface of the material are lined with one of polytetrafluoroethylene and para-polyphenylene, both of which can achieve the purpose; the material has the characteristics of high temperature resistance, wear resistance and corrosion resistance. The stirring blade of the magnetic stirrer is made of one of carbon steel and stainless steel, both of which can achieve the purpose. It is also wrapped with polytetrafluoroethylene or para-polyphenylene to prevent corrosion and extend the service life. This continuous crystallization kettle can also be used for the crystallization of iron hydroxide and aluminum hydroxide.

[0039] The pump connected to the pressurized column is a screw pump or a plunger pump, both of which can achieve the purpose. For a screw pump, when the motor drives the pump shaft to rotate, the screw rotates around its own axis on the one hand, and rolls along the inner surface of the bushing on the other hand, thus forming a sealed chamber of the pump to transport the fluid; it has the characteristics of good variable adjustment, uniform flow and stable pressure. The plunger pump relies on the reciprocating motion of the plunger in the cylinder to change the volume of the sealed working chamber to achieve fluid transportation, and has the advantages of high rated pressure, compact structure, high efficiency and convenient flow regulation.

[0040] The electricity used in whisker preparation is one of photovoltaic, wind power, and hydropower, all of which are green electricity. Green electricity is stabilized by battery storage and then used to power the equipment. Green electricity has the characteristics of no carbon dioxide emissions and zero carbon. Green electricity storage uses sodium ion batteries, which have the characteristics of stable power and low cost. The electrical equipment used in whisker preparation includes agitators, pumps, control valves, heating equipment, and automatic control systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the structure of the continuous crystal rotating kettle involved in the present invention. DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with specific embodiments.

[0043] A method for preparing basic magnesium sulfate whiskers from phosphorus tailings continuously and zero carbon, comprising the following steps: adding water and organic mixed acid to the phosphorus tailings for reaction, liquid-solid separation to obtain a mixed solution and phosphorus concentrate; adding ammonia water and a water reducer to the mixed solution, controlling the pH value of the solution to 2.5-3, liquid-solid separation to obtain an iron precipitate and an iron removal liquid; adding ammonia water and a particle size regulating agent to the iron removal liquid, controlling the pH value of the solution to 5-6, liquid-solid separation to obtain an aluminum precipitate and an aluminum removal liquid; adding ammonia water and a magnesium regulating agent to the aluminum removal liquid, controlling the pH value of the solution to 9.5-11, liquid-solid separation to obtain a magnesium hydroxide precipitate and a calcium solution; adding sulfuric acid solution and a crystal conversion agent to the magnesium hydroxide precipitate, mixing well, and then adding to a continuous crystal conversion kettle for reaction to obtain basic magnesium sulfate whiskers. The amount of sulfuric acid solution and crystal conversion agent added to the magnesium hydroxide precipitate, the crystal conversion temperature and crystal conversion time, the diameter of the basic magnesium sulfate whiskers and the aspect ratio are shown in Table 1.

[0044] Table 1

[0045]

[0046] It can be concluded from Example 1 to Example 15 that the embodiments of the present invention can all be implemented and can achieve the purpose of the invention, and the present invention is not limited to these embodiments.

Claims

1. A method for preparing basic magnesium sulfate whiskers from phosphorus tailings continuously with zero carbon, characterized in that: The method comprises the following steps: adding ammonia water and a particle size regulating agent to a solution after recovering phosphate concentrate and removing iron from phosphate tailings by acid hydrolysis, controlling the pH value of the solution to be 5-6, performing liquid-solid separation, and obtaining aluminum precipitate and aluminum removal liquid; adding ammonia water and a magnesium regulating agent to the aluminum removal liquid, controlling the pH value of the solution to be 9.5-11, performing liquid-solid separation, and obtaining magnesium hydroxide precipitate and a calcium solution; adding sulfuric acid solution and a crystal-changing agent to the magnesium hydroxide precipitate, mixing them evenly, and then adding them to a continuous crystal-changing kettle for reaction, and obtaining basic magnesium sulfate whiskers; the continuous crystal-changing kettle comprises a pressure column, a pipeline kettle, and a cooling kettle, and the electric energy used by the continuous crystal-changing kettle is one of photovoltaic power, wind power, and hydropower.

2. A method for continuously preparing basic magnesium sulfate whiskers from phosphate tailings with zero carbon as claimed in claim 1, characterized in that: The particle size regulating agent is one of polyethylene glycol, ammonium acetate and ammonium oxalate, and the added amount is 0.1-0.5% of the mass of the phosphate tailings.

3. A method for continuously preparing basic magnesium sulfate whiskers from phosphate tailings with zero carbon as claimed in claim 1, characterized in that: The magnesium adjusting agent is one of polyvinyl alcohol, polyethylene glycol octylphenyl ether and polyacrylamide, and the added amount is 0.1-0.5% of the mass of the phosphate tailings.

4. A method for continuously preparing basic magnesium sulfate whiskers from phosphate tailings with zero carbon as claimed in claim 1, characterized in that: The amount of sulfuric acid solution added is 10-30% of the mass of the phosphate tailings.

5. A method for continuously preparing basic magnesium sulfate whiskers from phosphate tailings with zero carbon as claimed in claim 1, characterized in that: The crystal-changing agent is one of disodium ethylenediaminetetraacetate, sodium phosphate and polyacrylamide, and the added amount is 0.1-0.5% of the mass of the phosphate tailings.

6. A method for continuously preparing basic magnesium sulfate whiskers from phosphate tailings with zero carbon as claimed in claim 1, characterized in that: The reaction temperature in the pipeline kettle is 185-225° C., and the reaction time is 70-110 minutes.

Images