System and method for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite

Abstract

The invention provides a system and method for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite, and the system comprises a crushing and screening assembly which is used for crushing and screening the low-grade magnesite step by step to a set particle size; the first treatment assembly is connected with the crushing and screening assembly and is used for carrying out reaction treatment on the low-grade magnesite with the set particle size by utilizing a leaching solution to obtain a treatment solution, washing solid residues and then firing the solid residues into light burning powder; the second treatment assembly is connected with the first treatment assembly and is used for carrying out reaction treatment on the treatment liquid by utilizing a precipitant to obtain mother liquor and precipitation slag; washing and drying the precipitation slag, and calcining to obtain magnesium oxide; and a concentration crystallization assembly. According to the system and the method, the technical problems that the comprehensive utilization rate of low-grade magnesite is low, and magnesite products are difficult to extract are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-grade magnesite preparation, in particular to a system and method for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite. BACKGROUND

[0002] Magnesite is an important mineral resource and plays an important role in many fields, such as building material field, refractory material field, chemical industry field, ceramic industry, environmental protection field, etc. In the refractory material field, it is used in the steel industry and glass industry; in the building material field, it is used to produce magnesite cement and prepare magnesium thermal insulation materials. At present, the resource reserves of magnesite are very rich, but the high-quality and high-grade resources are less, and the low-grade magnesite resources are more. The content of magnesium oxide in low-grade magnesite is less, usually between 20-40%, and with the increasing demand for magnesite products, how to comprehensively utilize low-grade magnesite to extract useful magnesite products is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0003] The purpose of the present application is to provide a system and method for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite, to solve the technical problems of low comprehensive utilization rate of low-grade magnesite and difficulty in extracting magnesite products.

[0004] To achieve the above-mentioned purpose, according to the first aspect of the present application, a system for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite is provided, comprising: a crushing and screening assembly, which crushes and screens the low-grade magnesite to a set particle size step by step; a first processing assembly connected with the crushing and screening assembly, which is used to obtain a treatment liquid by reacting the low-grade magnesite with a leaching liquid, and to obtain light-burned powder by washing and calcining the solid residue; a second processing assembly connected with the first processing assembly, which is used to obtain mother liquor and precipitation residue by reacting the treatment liquid with a precipitant; the precipitation residue is washed, dried and calcined to obtain magnesium oxide; and a concentration and crystallization assembly connected with the second processing assembly, which is used to obtain calcium chloride by concentrating and crystallizing the mother liquor.

[0005] In some embodiments, the crushing and screening assembly comprises a first grinding part, a second grinding part and a third grinding part connected in series according to the flow direction of the low-grade magnesite; each of the first grinding part, the second grinding part and the third grinding part comprises a corresponding crushing part and a screening part; the crushing part crushes and grinds the entering low-grade magnesite and then the crushed and ground low-grade magnesite is screened by the corresponding screening part.

[0006] In some embodiments, a backflow pipe is arranged between the crushing element and the screening element in the first abrasive element, the second abrasive element and the third abrasive element, for returning the low-grade magnesite with a particle size less than a set value to the corresponding screening element for further crushing and grinding.

[0007] In some embodiments, the first processing assembly comprises a first reactor, a first filter, a first washing machine and a calcining machine; wherein the feed inlet of the first reactor is connected to the crushing and screening assembly; the liquid inlet of the first reactor is connected to the leaching liquid; the discharge outlet of the first reactor is connected to the first filter; the liquid outlet of the first filter is connected to the second processing assembly; the discharge outlet of the second processing assembly is connected to the first washing machine; the discharge outlet of the first washing machine is connected to the calcining machine.

[0008] In some embodiments, the liquid outlet of the first washing machine is connected to the second processing assembly, for feeding the magnesium-containing liquid to the second processing assembly.

[0009] In some embodiments, the second processing assembly comprises a second reactor, a second filter, a second washing machine and a calcining machine; wherein the liquid inlet of the second reactor is connected to the liquid outlet of the first filter and the liquid outlet of the first washing machine; the feed inlet of the second reactor is connected to the precipitant; the discharge outlet of the second reactor is connected to the second filter; the liquid outlet of the second filter is connected to the concentration and crystallization assembly; the discharge outlet of the concentration and crystallization assembly is connected to the second washing machine; the liquid inlet of the second washing machine is connected to distilled water; the discharge outlet of the second washing machine is connected to the calcining machine.

[0010] In some embodiments, a drying machine is arranged between the discharge outlet of the second washing machine and the calcining machine.

[0011] In some embodiments, the concentration and crystallization assembly comprises a concentration and crystallization machine, and the liquid inlet of the concentration and crystallization machine is connected to the liquid outlet of the second filter.

[0012] To achieve the above-mentioned purposes, according to the second aspect of the present application, a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride is provided, and the method comprises the following steps: The low-grade magnesite is crushed and screened by the crushing and screening assembly to a particle size of not more than 74 microns; The crushed low-grade magnesite is mixed with the leaching liquid at an addition ratio of 1:35-45 g / ml in the first processing assembly at 85-125°C for 1-3h of lifting and stirring reaction; and the reaction liquid is filtered to obtain a treatment liquid and a solid residue; the treatment liquid is fed to the downstream, and the solid residue is washed and calcined into light calcined powder; The processing liquid enters into the second processing assembly, and is reacted with the precipitant under the conditions of pH value of 9-11, temperature of 45-65℃ and stirring rate of 100-300 r / min for 1-2h, and then is filtered to obtain mother liquor and precipitate residue; the mother liquor is transported to the downstream, and the precipitate residue is washed, dried and calcined into magnesium oxide; The mother liquor is crystallized and concentrated in the crystallization and concentration assembly to obtain calcium chloride.

[0013] In some embodiments, the leaching liquid comprises ammonium salt solution with mass percentage of 15%-20%, wherein the ammonium salt solution comprises ammonium chloride; And / or, the precipitant is alkali liquor, and the alkali liquor comprises Ca(OH)2 with concentration of 0.1-0.5 mol / L, and the adding ratio of the alkali liquor to the processing liquid is (1-2):1; And / or, the solid residue is fired at temperature of 750-1000℃ for 2-4h to obtain the light-burned powder; And / or, the precipitate residue is calcined at temperature of 800-1000℃ for 2-4h.

[0014] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The figure is a structural schematic diagram of the system for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite according to an embodiment of the present application; Figure 2 The figure is a structural schematic diagram of the system for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite according to an embodiment of the present application; Figure 3 The figure is a flow chart of the method for producing magnesium oxide and calcium chloride by comprehensively utilizing low-grade magnesite according to an embodiment of the present application; In the figure, 1 is magnesite, 2 is a jaw crusher, 3 is a first screening machine, 4 is a cone crusher, 5 is a second screening machine, 6 is a ball mill, 7 is a spiral classifier, 8 is a first reactor, 9 is leaching liquid, 10 is a first filter, 11 is solid residue, 12 is a first washing machine, 13 is a firing machine, 14 is light-burned powder, 15 is magnesium-containing liquid, 16 is processing liquid, 17 is a second reactor, 18 is precipitant, 19 is a second filter, 20 is a second washing machine, 21 is mother liquor, 22 is a crystallization and concentration machine, 23 is calcium chloride, 24 is distilled water storage tank, 25 is a drying machine, 26 is a calcining machine, and 27 is magnesium oxide. DETAILED DESCRIPTION

[0016] Embodiments of the present application are described below in detail with reference to the accompanying drawings, wherein the same or similar components or components having the same or similar functions are denoted by the same or similar reference numerals throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are for the purpose of explanation only, and are not to be understood as limiting the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents falling within the spirit and scope of the appended claims.

[0017] To achieve the above-mentioned purpose, according to the first aspect of the present application, a system for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride is provided, comprising a crushing and screening assembly, a first processing assembly, a second processing assembly, and a concentration and crystallization assembly; wherein the crushing and screening assembly crushes and screens the low-grade magnesite to a set particle size in stages.

[0018] Since the low-grade magnesite contains a large amount of impurities and cannot be directly utilized, it must be treated by leaching chemical reaction before use. The present application can improve the utilization of low-grade magnesite and reduce resource waste. In the present application, the crushing and screening assembly comprises a first grinding part, a second grinding part, and a third grinding part connected in series according to the flow direction of the low-grade magnesite (low-grade magnesite 1); wherein the first grinding part, the second grinding part, and the third grinding part each include a corresponding crushing part and a screening part; the crushing part crushes and grinds the entering magnesite 1 and then sends it to the corresponding screening part for screening.

[0019] In other words, the crushing and screening assembly of the present application comprises a first grinding part, a second grinding part, and a third grinding part connected in series, wherein according to the flow direction of the magnesite 1, the magnesite 1 passes through the first grinding part, the second grinding part, and the third grinding part in sequence and is crushed and screened in stages. The first grinding part, the second grinding part, and the third grinding part each include a crushing part and a screening part, i.e. the low-grade magnesite enters the crushing part of the first grinding part, is crushed, and then enters the screening part of the first grinding part for screening, the screened magnesite 1 with a qualified particle size enters the crushing part of the second grinding part, is crushed, and then enters the screening part of the second grinding part for screening, the screened magnesite 1 with a qualified particle size enters the crushing part of the third grinding part, is crushed, and then enters the screening part of the third grinding part for screening, and the screened magnesite 1 with a qualified particle size is crushed.

[0020] For example, Figure 1As shown, the crushing and screening components of the first abrasive component are a jaw crusher 2 and a first screen 3, respectively; the crushing and screening components of the second abrasive component are a cone crusher 4 and a second screen 5, respectively; and the crushing and screening components of the third abrasive component are a ball mill 6 and a spiral classifier 7, respectively. Magnesite ore 1 is fed into jaw crusher 2 for coarse crushing, reducing the low-magnesite ore 1 to coarse particles of 20-50 mm. The discharge port of jaw crusher 2 is then connected to first screen 3, which screens the crushed magnesite ore 1 output from jaw crusher 2. The sieved low-grade magnesite coarse powder with a particle size of 20-50 mm is connected to the finished product discharge port of the first screening machine 3 through the input port of the cone crusher 4. The low-grade magnesite coarse powder enters the cone crusher 4 and is easily finely crushed. The cone crusher 4 crushes the 20-50 mm magnesite coarse powder into a fine powder with a particle size of 5-10 mm, making it easier and faster to process the low-grade magnesite in the future. The discharge port of the cone crusher 4 is connected to the second screening machine 5, which screens the low-grade magnesite fine powder output by the cone crusher 4. The low-grade magnesite fine powder with a particle size of 5-10 mm screened by the second screening machine 5 is connected to the finished product discharge port of the second screening machine 5 through the ball mill 6 and passed into the ball mill 6 for further grinding. Therefore, the provision of the cone crusher 4 allows the ball mill 6 to process more quickly during subsequent processing and preparation, reducing the grinding time of the low-grade magnesite and improving processing efficiency. The ball mill 6 further grinds the low-grade magnesite fine powder with a particle size of 5-10 mm into a low-grade magnesite powder with a particle size not exceeding 74 microns (about 200 mesh). The discharge port of the ball mill 6 is connected to the feed port of the spiral classifier 7. The low-grade magnesite powder is passed into the spiral classifier 7 for classification, wherein the discharge port of the spiral classifier 7 is connected to the first processing component, and the low-grade magnesite powder with a particle size not exceeding 74 microns is passed into the first processing component for further processing.

[0021] In some embodiments, a reflux pipe is provided between the crushing element and the screening element in the first abrasive element, the second abrasive element and the third abrasive element, for returning the low-grade magnesite whose particle size does not reach the set value screened out by the screening element to the corresponding screening element for further crushing and grinding.

[0022] It is known that a return pipe is provided between the crushing part and the screening part in the first abrasive part, the second abrasive part and the third abrasive part. Figure 1For example, the crushing part and the screening part of the first abrasive part are a jaw crusher 2 and a first screening machine 3 respectively; the crushing part and the screening part of the second abrasive part are a cone crusher 4 and a second screening machine 5 respectively; the crushing part and the screening part of the third abrasive part are a ball mill 6 and a spiral classifier 7 respectively. In this embodiment, a backflow pipe is arranged between the jaw crusher 2 and the first screening machine 3, so that the filtered end of the first screening machine 3 is connected to the feeding port of the jaw crusher 2, and the low-grade magnesite coarse particles that do not meet the particle size of 20-50 mm can be sent back to the jaw crusher 2 for further crushing. In addition, another backflow pipe is arranged between the cone crusher 4 and the second screening machine 5, so that the filtered end of the second screening machine 5 is connected to the feeding port of the cone crusher 4, and the low-grade magnesite fine powder that does not meet the particle size of 5-10 mm is sent back to the cone crusher 4 for further crushing, so that the low-grade magnesite can be kept between 5-10 mm. Finally, another backflow pipe is also arranged between the ball mill 6 and the spiral classifier 7, and the low-grade magnesite powder with a particle size greater than 74 microns can be separated and sent to the ball mill 6 for further grinding.

[0023] In this embodiment, the low-grade magnesite is put into the jaw crusher 2 for coarse crushing, and is screened by the first screening machine 3, so that the low-grade magnesite coarse particles that do not meet the particle size of 20-50 mm can be sent back to the jaw crusher 2 for further crushing, and the low-grade magnesite coarse particles with a particle size of 20-50 mm can be sent to the cone crusher 4 for fine crushing, reducing the crushing difficulty and time of the cone crusher 4. The fine crushed low-grade magnesite fine powder is screened by the first screening machine 3, and the low-grade magnesite fine powder with a particle size of 5-10 mm is transported to the ball mill 6 for further grinding. The low-grade magnesite fine powder with a particle size not meeting 5-10 mm is sent back to the cone crusher 4 for further crushing. The ball mill 6 performs ball milling on the low-grade magnesite fine powder with a particle size of 5-10 mm, and the spiral classifier 7 screens the low-grade magnesite powder with a particle size not exceeding 74 microns. The low-grade magnesite powder with a particle size exceeding 74 microns is separated and sent to the ball mill 6 for further grinding. The scheme of the present application can perform grading, grinding and screening on the low-grade magnesite, effectively improve the grinding efficiency of the low-grade magnesite, and make the low-grade magnesite powder have a small particle size, so as to improve the contact area and subsequent reaction efficiency of the low-grade magnesite powder.

[0024] In this application, the first processing assembly is connected with the crushing and screening assembly, for obtaining the treatment liquid 16 by reacting the low-grade magnesite with a set particle size with the leaching liquid 9 after treatment, and washing the solid residue 11 to be calcined into the light calcined powder 14.

[0025] The first processing assembly comprises a first reactor 8, a first filter 10, a first washing machine 12 and a calcining machine 13. The feed inlet of the first reactor 8 is connected to the crushing and screening assembly. The liquid inlet of the first reactor 8 is connected to the leaching solution 9. The discharge outlet of the first reactor 8 is connected to the first filter 10. The liquid outlet of the first filter 10 is connected to the second processing assembly. The discharge outlet of the first filter 10 is connected to the first washing machine 12. The discharge outlet of the first washing machine 12 is connected to the calcining machine 13. In other words, the feed inlet of the first reactor 8 is connected to the spiral classifier 7. The low-grade magnesite powder with a particle size of not more than 74 microns output by the spiral classifier 7 is transported into the first reactor 8. The liquid inlet of the first reactor 8 is connected to the leaching solution 9. The leaching solution 9 can be an ammonium salt solution with a mass percentage of 15%-20%, such as an ammonium chloride solution. The leaching solution 9 and the low-grade magnesite powder are mixed in the first reactor 8 at a specific ratio. In the reaction process, the slurry at the bottom of the first reactor 8 is lifted to the upper part, so that the low-grade magnesite powder can be fully stirred and contacted with the leaching solution 9. The leaching temperature is controlled between 85-125℃, and the reaction time is controlled between 1-3 hours, so that the low-grade magnesite powder can react with the leaching solution 9 to produce a double decomposition reaction. When the ammonium salt solution is an ammonium chloride solution, the chemical reaction formula is as follows: MgCO3+2NH4Cl→MgCl2+2NH3↑+CO2↑+H2O. The application realizes that the magnesite stone powder can be fully stirred and contacted with the leaching solution 9 in the first reactor 8, so that the magnesite stone powder can react with the leaching solution 9 to produce a double decomposition reaction, and the magnesium ions in the magnesite stone powder can be accelerated to be decomposed into the leaching solution 9. In addition, the leaching solution in the embodiment can also be an acidic solution such as dilute sulfuric acid, dilute hydrochloric acid or dilute nitric acid. However, the concentrated acid such as sulfuric acid, hydrochloric acid or nitric acid needs to be diluted, and it has high corrosivity. Therefore, the leaching solution is selected to be an ammonium chloride solution, which can be recycled and has high economic efficiency.

[0026] The mixture in the first reactor 8 is sent into the first filter 10 through the discharge outlet of the first reactor 8, so as to filter to produce solid residues 11 and treatment liquid 16. Therefore, the magnesium ions in the low-grade magnesite powder can be accelerated to be decomposed into the leaching solution 9, and the solid residues 11 and the treatment liquid 16 can be separated. The liquid outlet of the first filter 10 is connected to the second processing assembly, and the treatment liquid 16 is output to the downstream second processing assembly for further processing. At the same time, the discharge outlet of the first filter 10 is connected to the first washing machine 12, and the solid residues 11 are output to the first washing machine 12 for cleaning. The discharge outlet of the first washing machine 12 is connected to the calcining machine 13, and the solid residues 11 are calcined into light calcined powder 14 in the calcining machine 13, so that the residues of the magnesite stone 1 can be utilized. The prepared light calcined powder 14 can be used to prepare magnesite cement.

[0027] In some embodiments, the liquid outlet of the first washing machine 12 is connected to the second processing assembly for outputting the magnesium-containing liquid 15 to the second processing assembly.

[0028] In order to maximize the recovery of magnesium elements in low-grade magnesite, the liquid outlet of the first washing machine 12 is connected to the second processing assembly in the present embodiment. In other words, the solid residue 11 carries a certain amount of magnesium ions, such as Figure 2 As shown in the present application, the magnesium-containing liquid 15 obtained by washing the solid residue 11 is output to the second processing assembly for processing the magnesium ions, so that a magnesium-containing product with high yield can be obtained, and the magnesium ions remaining in the solid residue 11 and the leaching liquid 9 can be recovered.

[0029] In some embodiments, the magnesium-containing liquid 15 obtained by washing the solid residue 11 can be combined with the treatment liquid 16 output from the liquid outlet of the first filter 10 and then input into the second processing assembly. The magnesium-containing liquid 15 and the treatment liquid 16 in the present application will be jointly input into the second processing assembly, so that the treatment liquid 16 can combine with the magnesium ions.

[0030] In the present application, the second processing assembly is connected to the first processing assembly, and is used for reacting the treatment liquid 16 with a precipitant 18 to obtain a mother liquor 21 and a precipitate; the precipitate is washed and dried and then calcined into magnesia 27.

[0031] In the present application, the second processing assembly is connected to the first processing assembly, and is used for reacting the treatment liquid 16 with a precipitant 18 to obtain a mother liquor 21 and a precipitate; the precipitate is washed and dried and then calcined into magnesia 27.

[0032] For example, the magnesium-containing liquid 15 and the treatment liquid 16 are input into the second reactor 17, and the precipitant 18 is input into the input end of the second reactor 17. The magnesium-containing liquid 15, the treatment liquid 16 and the precipitant 18 are mixed and stirred in the second reactor 17 by upward lifting movement, and a chemical reaction occurs in the second reactor 17, including: MgCl2+2NaOH→Mg(OH)2↓+2NaCl. The second reactor 17 uniformly mixes the magnesium-containing liquid 15, the treatment liquid 16 and the precipitant 18 from bottom to top, thereby reducing the processing time and improving the efficiency.

[0033] After the reaction in the second reactor 17 is completed, a second filter 19 is connected to the outlet of the second reactor 17, and the second filter 19 is used to separate the mother liquor 21 from the magnesium hydroxide precipitate. The outlet of the second filter 19 is connected to a concentration and crystallization assembly, and the outlet of the concentration and crystallization assembly is connected to a second washing machine 20. The inlet of the second washing machine 20 is connected to a distilled water storage tank 24, and distilled water can be supplied to the second washing machine 20. The outlet of the second washing machine 20 is connected to a calcining machine 26. In some embodiments, a drying machine 25 is arranged between the outlet of the second washing machine 20 and the calcining machine 26. That is, the outlet of the second filter 19 is fixedly connected to the second washing machine 20, the outlet of the second washing machine 20 is connected to the drying machine 25, and the outlet of the drying machine 25 is connected to the calcining machine 26. The calcining machine 26 produces magnesium oxide 27.

[0034] In this embodiment, the distilled water from the distilled water storage tank 24 is used to wash the magnesium hydroxide precipitate multiple times to remove the adsorbed impurity ions. The washed magnesium hydroxide precipitate is dried by the drying machine 25 and then fed into the calcining machine 26. The temperature of the calcining machine 26 is controlled to be 800-1000°C, and the calcining time is controlled to be 2-4 hours. After the calcining is completed, the magnesium oxide 27 is produced and can be used to manufacture parts.

[0035] In this application, the concentration and crystallization assembly is connected to the second processing assembly to concentrate and crystallize the mother liquor 21 to obtain calcium chloride 23. In some embodiments, the concentration and crystallization assembly includes a concentration and crystallization machine 22, and the inlet of the concentration and crystallization machine 22 is connected to the outlet of the second filter 19.

[0036] The mother liquor 21 output by the second filter 19 can be fed into the concentration and crystallization machine 22, and heating is started. The mother liquor 21 is evaporated by the concentration and crystallization machine 22, so that the mother liquor 21 can be concentrated and the heating and evaporation are stopped when the mother liquor 21 is saturated. Forced cooling is performed to make the mother liquor 21 clean and produce calcium chloride 23. Therefore, the mother liquor 21, which is a byproduct, can be recycled and used to manufacture calcium chloride 23.

[0037] To achieve the above-mentioned purpose, according to the second aspect of the present application, a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride is provided as shown in Figure 3 By using the system in any of the above embodiments, the following steps are included: S1: The low-grade magnesite is gradually crushed and sieved to a particle size of not more than 74 microns by using the crushing and sieving assembly. S2: The crushed low-grade magnesite and the leaching liquid are mixed in the first processing assembly at an addition ratio of 1:35-45 g / ml at 85-125°C, and the mixing and reaction are performed for 1-3 hours. The reaction liquid is filtered to obtain a treated liquid and a solid residue. The treated liquid is sent to the downstream, and the solid residue is washed and calcined into light calcined powder. S3: The treatment liquid enters the second treatment assembly, and reacts at a pH value of 9-11, a temperature of 45-65℃ and a stirring rate of 100-300 r / min for 1-2 h, and then is filtered to obtain a mother liquor and a precipitate; the mother liquor is transported to the downstream, and the precipitate is washed, dried and calcined into magnesium oxide.

[0038] In S1, the low-grade magnesite is crushed and sieved to a particle size of not more than 74 microns by using a crushing and sieving assembly.

[0039] In S2, the crushed low-grade magnesite is mixed with an ammonium salt solution with a concentration of 5%-20% at an addition ratio of 1:35-45 g / ml, wherein the addition ratio of the low-grade magnesite to the leaching liquid can be 1:35 g / ml, 1:36 g / ml, 1:37 g / ml, 1:38 g / ml, 1:39 g / ml, 1:40 g / ml, 1:41 g / ml, 1:42 g / ml, 1:43 g / ml, 1:45 g / ml. When the addition amount of the leaching liquid is small, the low-grade magnesite powder cannot be fully soaked, resulting in insufficient solid-liquid contact area, and the magnesium elements inside the low-grade magnesite powder cannot be fully leached out; when the addition amount of the leaching liquid is large, the stirring resistance is large, which easily leads to internal overheating, affecting the accuracy of the reaction, and increasing the wear of the mechanical assembly.

[0040] In the process, the reaction temperature is 85-125℃, for example, the reaction temperature is 85℃, 95℃, 105℃, 115℃, 125℃, etc. The reaction of ammonium salt leaching magnesium is an endothermic reaction. When the reaction temperature is too low, such as lower than 85℃, the magnesium elements inside the low-grade magnesite powder move slowly, the leaching rate decreases, and the process time is prolonged; when the reaction temperature is too high, such as higher than 125℃, the decomposition rate increases, the raw material consumption is large, the by-products increase, and the ammonium salt itself is easily decomposed in a high-temperature environment, causing the reaction to be unstable.

[0041] Meanwhile, in the process, the solid residue is calcined at a temperature of 750-1000℃ for 2-4 h to obtain a lightly calcined powder; wherein the calcination temperature of the solid residue is 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, etc. When the calcination temperature of the solid residue is too low, such as lower than 750℃, the magnesium carbonate and basic magnesium carbonate remaining in the residue are not completely decomposed; when the calcination temperature of the solid residue is too high, such as higher than 1000℃, CaO in the residue is melted and forms clumps on the inner wall of the equipment, which easily causes safety hazards to the equipment.

[0042] In S3, the treatment liquid and the magnesium-containing liquid enter a second reactor, and a precipitant is used to react at a pH value of 9-11, a temperature of 45-65℃, and a stirring rate of 100-300 r / min for 1-2 h, and then filtered to obtain a mother liquor and a precipitate; the mother liquor is sent to a downstream, and the precipitate is washed, dried, and calcined into magnesium oxide.

[0043] The precipitant is a lye, which can be Ca(OH)2 with a concentration of 0.1-0.5 mol / L, and the addition ratio of the lye to the treatment liquid is (1-2):1, so that the reaction efficiency is higher and the raw material cost is lower, the generated calcium ions are convenient for the concentration and crystallization process, are converted into calcium chloride products, and are convenient for discharge. In addition, the lye can also be sodium hydroxide or ammonia water, but the concentration of the ammonia water needs to be increased to 15%-25%, and the ammonia water itself is volatile, and the sodium ions generated by the sodium hydroxide need to be treated by another process.

[0044] In the process, the reaction pH value is 9, 10, or 11, and the temperature is 45℃, 48℃, 50℃, 52℃, 55℃, 60℃, 65℃, etc. When the reaction temperature is too low, such as lower than 45℃, the ion reaction rate of magnesium ions and hydroxide ions is reduced, and the magnesium ions are not completely reacted, causing high residues. When the reaction temperature is too high, such as higher than 65℃, the calcium hydroxide of the precipitant is precipitated, causing an increase in impurities.

[0045] In the present application, the precipitate is calcined at a temperature of 800-1000℃ for 2-4 h, and the calcination temperature of the precipitate is 800℃, 850℃, 900℃, 950℃, 1000℃, etc. When the calcination temperature of the precipitate is too low, such as lower than 800℃, the combustion is incomplete, and the residual magnesium hydroxide exists in the product in the form of Mg(OH)2, resulting in a decrease in the purity of magnesium oxide. When the calcination temperature of the precipitate is too high, such as higher than 1000℃, the reaction is too fast, the magnesium oxide crystals grow rapidly, resulting in insufficient internal density and a decrease in overall hardness.

[0046] In order to further understand the present application, the schemes of the present application will be further described below in combination with examples. Those skilled in the art will understand that only some examples are described in the present application, and any other suitable specific examples are within the scope of the present application.

[0047] Example 1 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are as follows: the low-grade magnesite is crushed and screened in stages to a set particle size of not more than 74 microns; the crushed low-grade magnesite powder is added into a first treatment assembly at an addition ratio of 1:35 g / ml with 20% ammonium chloride in terms of mass percentage; the reaction is carried out under the condition of 85 DEG C for 3 h through lifting and stirring, and the reaction liquid is filtered to obtain a treatment liquid and solid residues; the treatment liquid is transported to a downstream, and the solid residues are washed and calcined at a temperature of 750 DEG C for 4 h to obtain light calcined powder.

[0048] The treatment liquid enters a second treatment assembly, and 0.5 mol / L Ca(OH)2 is used as a precipitant at an addition ratio of 1:1 with the treatment liquid; the treatment liquid and the precipitant are reacted at a pH value of 11, a temperature of 50 DEG C and a stirring rate of 300 r / min for 1 h, and then filtered to obtain a mother liquor and precipitated residues; the mother liquor is transported to a downstream, and the precipitated residues are washed, dried and calcined at a temperature of 1000 DEG C for 2 h to obtain magnesium oxide.

[0049] Embodiment 2 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are as follows: the crushed low-grade magnesite powder is added into a first treatment assembly at an addition ratio of 1:40 g / ml with 15% ammonium chloride in terms of mass percentage; the treatment liquid enters a second treatment assembly, and 0.1 mol / L Ca(OH)2 is used as a precipitant at an addition ratio of 2:1 with the treatment liquid; the reaction is carried out at a pH value of 9, a temperature of 65 DEG C and a stirring rate of 100 r / min for 2 h, and then filtered.

[0050] Embodiment 3 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are as follows: the crushed low-grade magnesite powder is added into a first treatment assembly at an addition ratio of 1:45 g / ml with 18% ammonium chloride in terms of mass percentage; the treatment liquid enters a second treatment assembly, and 0.3 mol / L Ca(OH)2 is used as a precipitant at an addition ratio of 2:1 with the treatment liquid; the reaction is carried out at a pH value of 10, a temperature of 60 DEG C and a stirring rate of 200 r / min for 1 h, and then filtered.

[0051] Embodiment 4 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are different from those in the embodiment 1 in the following aspects: the crushed low-grade magnesite powder is mixed with ammonium chloride with a mass percentage of 18% in a first processing assembly according to an adding ratio of 1:39 g / ml, and the mixing is subjected to lifting and stirring reaction at 125 DEG C for 1 h.

[0052] Embodiment 5 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are different from those in the embodiment 1 in the following aspects: the crushed low-grade magnesite powder is mixed with ammonium chloride with a mass percentage of 16% in a first processing assembly according to an adding ratio of 1:40 g / ml, and the mixing is subjected to lifting and stirring reaction at 100 DEG C for 2 h.

[0053] Embodiment 6 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are different from those in the embodiment 1 in the following aspects: the solid residue is washed and then calcined at 1000 DEG C for 2 h to obtain light calcined powder.

[0054] The treatment liquid enters a second processing assembly, and 0.3 mol / L Ca(OH)2 is used as a precipitant, and the adding ratio of the treatment liquid to the precipitant is 2:1; the treatment liquid and the precipitant are at a pH value of 10; the precipitated residue is washed and dried, and then calcined at 800 DEG C for 4 h to obtain magnesium oxide.

[0055] Embodiment 7 The embodiment provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are different from those in the embodiment 1 in the following aspects: the solid residue is washed and then calcined at 1000 DEG C for 2 h to obtain light calcined powder.

[0056] The treatment liquid enters a second processing assembly, and 0.3 mol / L Ca(OH)2 is used as a precipitant, and the adding ratio of the treatment liquid to the precipitant is 2:1; the precipitated residue is washed and dried, and then calcined at 800 DEG C for 4 h to obtain magnesium oxide.

[0057] Comparative Example 1 The comparative example provides a method for comprehensively utilizing low-grade magnesite to produce magnesium oxide and calcium chloride, and the process and parameters are different from those in the embodiment 1 in the following aspects: the low-grade magnesite is crushed and sieved to a set particle size of 500 meshes.

[0058] Comparative Example 2 The comparative example provides a method for producing magnesium oxide and calcium chloride by comprehensive utilization of low-grade magnesite, which has the following differences compared with example 1 in process and parameters: the crushed low-grade magnesite powder and ammonium chloride with a mass percentage of 15% are added in a first treatment assembly at an addition ratio of 1:50 g / ml.

[0059] Comparative example 3 The comparative example provides a method for producing magnesium oxide and calcium chloride by comprehensive utilization of low-grade magnesite, which has the following differences compared with example 1 in process and parameters: the treatment liquid enters a second treatment assembly, and 0.1 mol / L Ca(OH)2 is used as a precipitant with an addition ratio of 2:1 to the treatment liquid; after reacting for 2 h at a pH value of 12, a temperature of 80°C and a stirring rate of 100 r / min, filtration is performed.

[0060] Comparative example 4 The comparative example provides a method for producing magnesium oxide and calcium chloride by comprehensive utilization of low-grade magnesite, which has the following differences compared with example 1 in process and parameters: the crushed low-grade magnesite powder and ammonium chloride with a mass percentage of 20% are added in a first treatment assembly at an addition ratio of 1:35 g / ml, and the reaction is performed under elevated stirring at 50°C for 5 h.

[0061] Comparative example 5 The comparative example provides a method for producing magnesium oxide and calcium chloride by comprehensive utilization of low-grade magnesite, which has the following differences compared with example 1 in process and parameters: the crushed low-grade magnesite powder and ammonium chloride with a mass percentage of 20% are added in a first treatment assembly at an addition ratio of 1:35 g / ml, and the reaction is performed under elevated stirring at 150°C for 1 h.

[0062] Experimental example The yield and purity of the magnesium oxide and calcium chloride obtained in each example and comparative example are detected, the purity of the magnesium oxide is detected by EDTA complexometric titration (GB / T 9853-2008), and the yield is the ratio of the magnesium oxide to the low-grade magnesite powder.

[0063] The purity of the calcium chloride is detected by argentometric method (Morr method, GB / T 26520-2011), and the yield is the ratio of the calcium chloride to the low-grade magnesite powder, and the results are shown in Table 1.

[0064] Table 1 Results of yield and purity of magnesium oxide and calcium chloride obtained in each example and comparative example

[0065] As shown in Table 1, the yield of magnesium oxide after precipitation-calcination in this application is stabilized at 88-92%, and the purity can reach 96-98%, which can directly meet the requirements of industrial-grade high-purity magnesium oxide and is significantly better than the traditional calcination method.

[0066] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A system for producing magnesium oxide and calcium chloride by comprehensive utilization of low-grade magnesite, characterized in that: include: Crushing and screening components, which crush and screen low-grade magnesite ore step by step to a set particle size; a first processing assembly connected to the crushing and screening assembly, configured to treat the low-grade magnesite of a set particle size with a leaching solution to obtain a treatment solution, and to wash and then burn the solid residue into light-burned powder; a second treatment component connected to the first treatment component, for treating the treatment liquid with a precipitant to obtain a mother liquid and a precipitate residue; the precipitate residue is washed, dried, and then calcined to produce magnesium oxide; as well as A concentration and crystallization component is connected to the second processing component and is used to concentrate and crystallize the mother liquor to obtain calcium chloride.

2. The system according to claim 1, wherein: The crushing and screening assembly includes a first abrasive member, a second abrasive member, and a third abrasive member which are connected in series in sequence according to the flow direction of the low-grade magnesite; wherein the first abrasive member, the second abrasive member, and the third abrasive member each include a one-to-one corresponding crushing member and a screening member; the crushing member crushes and grinds the incoming low-grade magnesite and then transmits it to the corresponding screening member for screening.

3. The system according to claim 2, characterized in that A reflux pipe is provided between the crushing element and the screening element in the first abrasive element, the second abrasive element and the third abrasive element, for returning the low-grade magnesite sieved out by the screening element and having a particle size that does not reach a set value to the corresponding screening element for further crushing and grinding.

4. The system according to any one of claims 1 to 3, characterized in that: The first processing component includes a first reactor, a first filter, a first washing machine and a burning machine; wherein the feed port of the first reactor is connected to the crushing and screening component; the leachate is introduced into its liquid inlet; the discharge port of the first reactor is connected to the first filter; the liquid outlet of the first filter is connected to the second processing component, and the discharge port thereof is connected to the first washing machine; the discharge port of the first washing machine is connected to the burning machine.

5. The system according to claim 4, characterized in that The liquid outlet of the first washing machine is connected to the second processing component for transporting the magnesium-containing liquid to the second processing component.

6. The system according to claim 5, characterized in that The second treatment component includes a second reactor, a second filter, a second washing machine and a calciner; wherein the liquid inlet of the second reactor is connected to the liquid outlet of the first filter and the liquid outlet of the first washing machine; the precipitant is introduced into the feed port of the second reactor; the discharge port of the second reactor is connected to the second filter; the liquid outlet of the second filter is connected to the concentration and crystallization component, and its discharge port is connected to the second washing machine; the distilled water is introduced into the liquid inlet of the second washing machine, and its discharge port is connected to the sintering machine.

7. The system according to claim 6, characterized in that A dryer is provided between the discharge port of the second washing machine and the firing machine.

8. The system according to claim 6, wherein: The concentration crystallization component includes a concentration crystallizer, the liquid inlet of which is connected to the liquid outlet of the second filter.

9. A method for producing magnesium oxide and calcium chloride by comprehensive utilization of low-grade magnesite, characterized in that: Utilizing the system according to any one of claims 1 to 8, comprising the steps of: Use crushing and screening components to crush and screen low-grade magnesite step by step to a set particle size of no more than 74 microns; The crushed low-grade magnesite and the leachate are added in a first treatment component at a ratio of 1:35-45 g / ml and heated to 85-125° C. for 1-3 hours under stirring; the reaction liquid is filtered to obtain a treatment liquid and a solid residue; the treatment liquid is transported downstream, and the solid residue is washed and fired to form light-burned powder; The treated liquid enters the second treatment component, reacts with a precipitant at a pH of 9-11, a temperature of 45-65°C, and a stirring rate of 100-300 r / min for 1-2 hours, and then is filtered to obtain a mother liquor and a precipitate residue; the mother liquor is transported downstream, and the precipitate residue is washed, dried, and then calcined to form magnesium oxide; The mother liquor is crystallized and concentrated in a concentration crystallization component to obtain calcium chloride.

10. The method according to claim 9, characterized in that The leachate comprises an ammonium salt solution having a mass percentage of 15% to 20%, wherein the ammonium salt solution comprises ammonium chloride; and / or, the precipitant is an alkali solution, the alkali solution comprises Ca(OH)2 at a concentration of 0.1-0.5 mol / L, and the addition ratio of the alkali solution to the treatment solution is (1-2):1; and / or, the solid residue is calcined at a temperature of 750-1000° C. for 2-4 hours to obtain the light-calcined powder; And / or, the precipitated slag is calcined at a temperature of 800-1000° C. for 2-4 hours.

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