A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry

Abstract

The utility model belongs to solid waste resource utilization technical field especially relates to a kind of production system for preparing high-purity magnesium sulfate with solid waste magnesite slurry, it is characterized in that, including solid waste pretreatment unit, reaction kettle, separation unit, drying unit and circulation unit, solid waste pretreatment unit includes crusher and bunker, reaction kettle is lined with enamel, with frequency conversion stirrer and temperature controller, reaction kettle is connected with high-position sulfuric acid tank outlet, high-position sulfuric acid tank is connected with sulfuric acid batching tank by pipeline, sulfuric acid pump, separation unit includes first stage electric centrifuge and second stage electric centrifuge, two-stage electric centrifuge between magnesium sulfate tank and crystallization tank are equipped, circulation unit includes PE mother liquor tank and mother liquor pump, final product is magnesium sulfate heptahydrate or anhydrous magnesium sulfate with water content≤0.5%.The utility model has the advantages that:low-activity solid waste magnesite slurry is converted into >99% purity magnesium sulfate, realizes solid waste high-value utilization conversion, and "zero" wastewater discharge is achieved in whole process.

Description

Technical Field

[0001] This utility model belongs to the field of solid waste resource utilization technology, and in particular relates to a production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry. Background Technology

[0002] Magnesite is a magnesium carbonate mineral and a major source of magnesium. When calcite is reacted with a magnesium-containing solution, it transforms into magnesite, thus magnesite belongs to the calcite group. Magnesium-rich rocks can also be transformed into magnesite. Magnesite is white or grayish-white with a vitreous luster; iron-bearing magnesite will appear yellow to brown. It is granular if crystallized, and massive if not crystallized. Besides being used to extract magnesium, magnesite can also be used as a refractory material and in the production of magnesium compounds.

[0003] The beneficiation process of magnesite generates solid waste, known as tailings. These tailings generally require treatment to meet environmental protection requirements and be converted into resource-efficient products. Currently, there are two methods for treating magnesite tailings: wet and dry processes. Wet treatment involves separating the waste through washing and biochemical methods for secondary utilization, producing calcium magnesium phosphate fertilizer. This method recovers more magnesite resources, and the generated organic matter can be used for biomass fuel. Magnesite slurry is generally classified as a solid waste product of wet processing.

[0004] Dry processing: The tailings are dried, crushed, and magnetically separated to remove excess material and recover magnesite resources, producing calcium magnesium phosphate fertilizer. Simultaneously, the tailings from dry processing can be used to manufacture building materials such as bricks and concrete. Magnesia tailings contain abundant phosphorus, calcium, and magnesium, and can not only be used to produce calcium magnesium phosphate fertilizer but also to extract magnesium compounds suitable for industries such as ceramics, textiles, and coatings. Although magnesite tailings are mineral processing waste, they are not purely industrial solid waste but rather a usable resource. Through wet and dry processing, the tailings can be made into calcium magnesium phosphate fertilizer and other useful substances can be extracted, playing a positive role in environmental protection and resource utilization.

[0005] Currently, the accumulated amount of solid waste from industrial by-product magnesite (such as mine tailings) exceeds 1 billion tons per year, and traditional landfill methods pollute water and soil (Mg). 2+ The leaching rate is >5%; however, existing solid waste utilization processes require high-temperature activation (800℃↑), consuming up to 1.5 tons of standard coal per ton of product. Furthermore, direct discharge of acid hydrolysis mother liquor leads to sulfuric acid waste (30%↑) and acidic wastewater pollution. Therefore, for solid waste magnesite slurry, a more feasible resource reuse solution needs to be developed to provide an effective solution for the resource utilization of industrial solid waste, which will play a positive role in improving the current state of magnesite mining in my country. Utility Model Content

[0006] The purpose of this invention is to provide a production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry, overcoming the shortcomings of existing technologies, realizing high-value utilization of solid waste, converting low-activity solid waste magnesite slurry into magnesium sulfate with a purity of >99%; zero waste discharge, with 100% of the residue (mainly SiO2 / Al2O3) used for special cement and building materials; and closed-loop circulation of mother liquor in the process to reduce external pollution to the environment.

[0007] To achieve the above objectives, this utility model employs the following technical solution:

[0008] A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry includes a solid waste pretreatment unit, a reaction vessel, a separation unit, a drying unit, and a circulation unit. The solid waste pretreatment unit includes a crusher and a silo. The reaction vessel is lined with enamel and equipped with a frequency converter and a temperature controller. The reaction vessel is connected to the outlet of a high-level sulfuric acid tank. The high-level sulfuric acid tank is connected to a sulfuric acid batching tank via pipelines and a sulfuric acid pump. The sulfuric acid batching tank is connected to a soft water pipe and a concentrated sulfuric acid pipe. The separation unit includes a first-stage electric centrifuge and a second-stage electric centrifuge. A magnesium sulfate tank and a crystallization tank are located between the two electric centrifuges. The drying unit is a vibrating fluidized bed dryer. The circulation unit includes a PE mother liquor tank and a mother liquor pump. The PE mother liquor tank is located between the second-stage electric centrifuge and the reaction vessel. The final product is magnesium sulfate heptahydrate or anhydrous magnesium sulfate with a moisture content ≤0.5%.

[0009] Furthermore, the crusher is a disc crusher or a rod mill.

[0010] Furthermore, the exhaust port of the reactor is connected to a CO2 distillation column via a pressurization pipeline and a pressurization pump.

[0011] Furthermore, the outlet of the vibrating fluidized bed dryer is connected to two sets of packaging machines.

[0012] Furthermore, at least one of the first-stage electric centrifuge and the second-stage electric centrifuge is an LGZ flat-plate vertical scraper automatic unloading intermittent centrifuge.

[0013] Furthermore, the crystallization tank has a vertical, cone-shaped structure that is wider at the top and narrower at the bottom, and is equipped with a spiral-type stirring paddle inside.

[0014] Furthermore, the packaging machine is connected to an inert gas tank via a pipeline.

[0015] Compared with the prior art, the beneficial effects of this utility model are:

[0016] 1) The low-activity solid waste magnesite slurry is converted into magnesium sulfate with a purity of >99%, which improves its application value and realizes the high-value utilization and transformation of solid waste; zero waste discharge is achieved, and the residue (mainly SiO2 / Al2O3) is 100% used for special cement and building materials; the mother liquor is recycled in a closed loop in the process, with a recycling rate of ≥90%; the solid waste is utilized by direct acid hydrolysis technology, eliminating the need for calcination activation and saving energy of ≥30%; dual centrifugal separation + mother liquor recycling makes the magnesium recovery rate >93% and the acid utilization rate reach over 98%;

[0017] 2) The entire process implements a synergistic mechanism of "solid waste activation - low temperature reaction - cascade separation - material recycling": a liquid-solid separation enhancement system is constructed through a two-stage centrifuge, so that the clear liquid extraction rate reaches more than 98%; a vibrating fluidized bed is used to replace the traditional drying equipment, forming a uniform heat transfer field in the high temperature dehydration stage, which can effectively prevent crystal aggregation and dissolution; metal ion pollution is strictly controlled by using a PE material mother liquor tank and a closed-loop pipeline system to ensure that the purity of magnesium sulfate at the end is >99%, and finally achieves a 100% solid waste disposal rate and achieves "zero" wastewater discharge throughout the entire process. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow structure of an embodiment of this utility model;

[0019] In the diagram: 1-crusher, 2-silo, 3-reactor, 4-first-stage electric centrifuge, 5-magnesium sulfate tank, 6-magnesium sulfate pump, 7-crystallization tank, 8-second-stage electric centrifuge, 9-mother liquor tank, 10-mother liquor pump, 11-vibrating fluidized bed dryer, 12-sulfuric acid pump, 13-packing machine, 14-high-level sulfuric acid tank, 15-sulfuric acid batching tank. Detailed Implementation

[0020] The technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this utility model, but not all embodiments.

[0021] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] The components of the present invention embodiments described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0023] See Figure 1 This is a schematic diagram of the process flow for preparing high-purity magnesium sulfate from solid waste magnesite slurry using a closed-loop chemical method. The process includes a solid waste pretreatment unit, a reaction vessel 3, a separation unit, a drying unit, and a circulation unit. The solid waste pretreatment unit includes a crusher 1 and a silo 2. In the solid waste pretreatment unit, the crusher 1 pulverizes the solid waste magnesite slurry raw material to 100-200 mesh, with a specific surface area ≥450 m². 2 / kg. The reactor 3 is lined with enamel and equipped with a frequency converter and a temperature controller. The reactor 3 is connected to the outlet of the high-level sulfuric acid tank 14. The high-level sulfuric acid tank 14 is connected to the sulfuric acid mixing tank 15 via pipelines and sulfuric acid pump 12. The sulfuric acid mixing tank 15 is connected to a soft water pipe and a concentrated sulfuric acid pipe. The concentrated sulfuric acid pipe is connected to a concentrated sulfuric acid tank. The separation unit includes a first-stage electric centrifuge 4 and a second-stage electric centrifuge 8. A magnesium sulfate tank 5 and a crystallization tank 7 are located between the two electric centrifuges. The magnesium sulfate tank 5 is connected to the crystallization tank 7 via pipelines and a magnesium sulfate pump 6. The drying unit is a vibrating fluidized bed dryer 11. The circulation unit includes a PE mother liquor tank 9 and a mother liquor pump 10. The PE mother liquor tank 9 is located between the second-stage electric centrifuge 8 and the reactor 3 to achieve closed-loop circulation of the mother liquor. The sulfuric acid mixing tank 15 contains 20% dilute sulfuric acid as the reaction mother liquor. The reaction in reactor 3 is controlled at 65-85℃ and 200-400rpm for 3-6 hours; the final product is magnesium sulfate heptahydrate or anhydrous magnesium sulfate with a moisture content of ≤0.5%.

[0024] In this embodiment, the raw material components in reactor 3 are in the following weight proportions: 100 parts solid waste magnesite slurry, 500-800 parts 20% dilute sulfuric acid, and 1-2 parts magnesium oxide. The first-stage electric centrifuge 4 and the second-stage electric centrifuge 8 are LGZ flat-plate vertical scraper automatic unloading intermittent centrifuges. The crystallization tank 7 has a vertical, tapered structure with a wider top and narrower bottom, and is equipped with a ribbon-type agitator. Magnesium sulfate solution is sent to the crystallization tank 7 for evaporation and crystallization. To further improve resource utilization, a CO2 distillation column can be connected to the exhaust port of reactor 3 via a pressurization pipeline and a booster pump to achieve CO2 recovery. The working principle of the CO2 distillation column is based on the difference in boiling points between carbon dioxide and other components. The mixture is heated to vaporize CO2 into steam. The steam exchanges heat with the descending liquid in the column, further vaporizing the lighter components (such as CO2) and condensing the heavier components back to the bottom of the column. The CO2 gas is bottled under high pressure and can be used as a filling gas for carbonated beverages or in gas-shielded welding applications.

[0025] The drying temperature of the vibrating fluidized bed dryer 11 is set according to the product type. The outlet of the vibrating fluidized bed dryer 11 is connected to two sets of packaging machines 13, corresponding to the packaging of magnesium sulfate heptahydrate and anhydrous magnesium sulfate with a moisture content ≤0.5%. To prevent the product from reacting with CO2 in the air and affecting product quality, the packaging machine 13 can be connected to an inert gas tank via pipeline for inert gas protection during the packaging process.

[0026] The process equipment composition of this utility model embodiment is shown in Table 1, and the process flow steps are shown in Table 2.

[0027] Table 1

[0028]

[0029] Table 2

[0030]

[0031] In this embodiment of the invention, solid waste magnesite is crushed to 100-200 mesh and added to an enamel-lined reactor in a specific ratio with 20% dilute sulfuric acid circulating mother liquor to form a slurry chemical reaction system. The system consists of 100 parts solid waste magnesite slurry, 600 parts 20% dilute sulfuric acid, and 1 part magnesium oxide, with magnesium oxide acting as an activating agent to promote the reaction. The reaction in reactor 3 is controlled at 65-85℃ and 200-400 rpm for 3 hours to achieve a low-temperature, high-efficiency conversion (MgCO3 + H2SO4 → MgSO4 + CO2↑ + H2O). The reaction slurry is pumped to the first-stage electric centrifuge 4 for primary separation: the magnesium sulfate clear liquid enters the magnesium sulfate tank 5, and the silicon-aluminum based residue is used for special cement production, realizing the resource utilization of the residue; the magnesium sulfate clear liquid is transferred to the crystallization tank for evaporation and concentration to form a saturated magnesium sulfate solution, and then undergoes secondary separation through the second-stage electric centrifuge 8: the separated heptahydrate magnesium sulfate enters the vibrating fluidized bed dryer 11, is dried below 40℃ to prepare heptahydrate magnesium sulfate product, and is dehydrated at 200-300℃ to prepare anhydrous magnesium sulfate (moisture content ≤0.5%); the dilute sulfuric acid mother liquor produced in the secondary separation is introduced into the PE mother liquor tank 9, and returned to the reaction vessel 3 through the mother liquor pump 10 and pipeline to achieve closed-loop recycling.

[0032] This utility model's process fully implements a synergistic mechanism of "solid waste activation - low-temperature reaction - tiered separation - material recycling": a liquid-solid separation enhancement system is constructed through a two-stage centrifuge, achieving a clarified liquid extraction rate of over 98%; a vibrating fluidized bed replaces traditional drying equipment, forming a uniform heat transfer field during the high-temperature dehydration stage, effectively preventing crystal aggregation and dissolution; and a PE mother liquor tank and closed-loop pipeline system are used to strictly control metal ion contamination, ensuring a final magnesium sulfate purity >99%. Ultimately, it achieves a 100% solid waste disposal rate, a mother liquor recycling rate ≥90%, and zero wastewater discharge throughout the entire process.

[0033] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry, characterized in that, The system includes a solid waste pretreatment unit, a reaction vessel, a separation unit, a drying unit, and a circulation unit. The solid waste pretreatment unit includes a crusher and a silo. The reaction vessel is lined with enamel and equipped with a frequency converter and a temperature controller. The reaction vessel is connected to the outlet of a high-level sulfuric acid tank. The high-level sulfuric acid tank is connected to a sulfuric acid batching tank via pipelines and a sulfuric acid pump. The sulfuric acid batching tank is connected to a soft water pipe and a concentrated sulfuric acid pipe. The separation unit includes a first-stage electric centrifuge and a second-stage electric centrifuge. A magnesium sulfate tank and a crystallization tank are located between the two electric centrifuges. The drying unit is a vibrating fluidized bed dryer. The circulation unit includes a PE mother liquor tank and a mother liquor pump. The PE mother liquor tank is located between the second-stage electric centrifuge and the reaction vessel. The final product is magnesium sulfate heptahydrate or anhydrous magnesium sulfate with a moisture content of ≤0.5%.

2. The production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry according to claim 1, characterized in that, The crusher is a disc crusher or a rod mill.

3. The production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry according to claim 1, characterized in that, The exhaust port of the reactor is connected to a CO2 distillation column via a booster pipeline and a booster pump.

4. A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry according to claim 1, characterized in that, The outlet of the vibrating fluidized bed dryer is connected to two sets of packaging machines.

5. A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry according to claim 1, characterized in that, At least one of the first-stage electric centrifuges and the second-stage electric centrifuges is an LGZ flat-plate vertical scraper automatic unloading intermittent centrifuge.

6. A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry according to claim 1, characterized in that, The crystallization tank has a vertical, cone-shaped structure that is wider at the top and narrower at the bottom, and is equipped with a spiral-type stirring paddle inside.

7. A production system for preparing high-purity magnesium sulfate from solid waste magnesite slurry according to claim 4, characterized in that, The baling machine is connected to an inert gas tank via a pipeline.

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