A method for producing pharmaceutical grade magnesium oxide

Abstract

The application provides a production method of medical-grade magnesium oxide and relates to the field of medical-grade magnesium oxide. The production method of the medical-grade magnesium oxide comprises the following steps: a reaction-aging step, a multi-stage beating and washing step, a drying step, a calcining step and a post-treatment step. The production method of the medical-grade magnesium oxide can effectively balance the purity and activity requirements of the medical-grade magnesium oxide, effectively avoids the problems of low reaction efficiency, high sulfate content of the medical-grade magnesium oxide and the influence of the structure and morphology of magnesium carbonate on the quality of magnesium oxide while ensuring that the tablet hardness reaches 2.5-3 kg.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of pharmaceutical grade magnesium oxide, in particular to a production method of pharmaceutical grade magnesium oxide. BACKGROUND

[0002] Magnesium is an essential cationic element in human body, ranking the fourth in cell tissue only after potassium. Magnesium participates in all energy metabolism of human body, activates and catalyzes enzyme system, promotes completion of biochemical reaction and formation of cells. As an important raw material and auxiliary material for producing medicine, pharmaceutical grade magnesium oxide is widely used in pharmaceutical industry. The specification indexes of pharmaceutical grade magnesium oxide (including calcium oxide content, acid insoluble content, iron content, sulfate content, loss on ignition, etc.) are strictly regulated in the national pharmacopoeia. In addition to the above specification indexes, the tabletting hardness as the application performance of pharmaceutical grade magnesium oxide is also crucial. On the one hand, it can ensure that the tablets are less likely to break or wear during production, packaging, transportation, storage and patient use, effectively guaranteeing the integrity and reducing the loss of effective ingredients of the medicine. At the same time, when the patient needs to break the tablets (such as scored tablets), high tabletting hardness can produce neat fracture during breaking, reducing the generation of irregular fragments and avoiding the problem of inaccurate dosage. On the other hand, due to the hygroscopicity of magnesium oxide, high tabletting hardness can slow down the penetration speed of external moisture into the tablet, and the overall stability and storage performance of the tablet are better.

[0003] Compared with the preparation of magnesium oxide products for other purposes, the preparation of pharmaceutical grade magnesium oxide is relatively special. Its characteristics are sticky material, poor flowability, high process requirements, and it needs both a certain purity content and a certain activity, which is between ordinary high-purity magnesium oxide and active magnesium oxide. The inventors found in the production practice of pharmaceutical grade magnesium oxide that the conventional heavy magnesium carbonate, light magnesium carbonate and magnesium hydroxide cannot produce pharmaceutical grade magnesium oxide meeting the tabletting hardness requirements, and the tabletting hardness cannot reach the required 2.5-3 kg.

[0004] Further, the inventors also found that due to the poor quality and structure morphology of magnesium carbonate (the morphology cannot reach spherical shape, generally irregular morphology such as needle-like, rod-like, snowflake-like, etc.), there are problems of low reaction efficiency, influence of magnesium carbonate structure morphology on magnesium oxide quality, and high sulfate content of pharmaceutical grade magnesium oxide in the existing production of pharmaceutical grade magnesium oxide. SUMMARY

[0005] To solve the technical problems in the prior art, the present application provides a production method of pharmaceutical-grade magnesium oxide, which can effectively balance the purity and activity requirements of pharmaceutical-grade magnesium oxide, effectively avoid the problems of low reaction efficiency, magnesium carbonate structure affecting magnesium oxide quality and high sulfate content of pharmaceutical-grade magnesium oxide caused by poor quality and structure of magnesium carbonate, while ensuring the tablet hardness to reach 2.5-3 kg.

[0006] To solve the above technical problems, the technical solutions adopted by the present application are as follows:

[0007] A production method of pharmaceutical-grade magnesium oxide, comprising the following steps: reaction-aging step, multi-stage beating and washing step, drying step, calcination step, post-treatment step;

[0008] In the reaction-aging step, under stirring conditions, polyethylene glycol is added to the magnesium sulfate solution, and after uniform mixing, the first portion of sodium carbonate solution is added to the 90-95 DEG C magnesium sulfate solution, and after the addition of the first portion of sodium carbonate solution is completed, the reaction is kept warm; the second portion of sodium carbonate solution is continuously added to the 90-95 DEG C magnesium sulfate solution, and after the addition of the second portion of sodium carbonate solution is completed, the reaction is kept warm; then aging is carried out at a temperature not lower than 65 DEG C, to obtain a primary reactant;

[0009] The multi-stage beating and washing step consists of the following steps: primary beating and washing, secondary beating and washing, and tertiary leaching;

[0010] In the primary beating and washing, the primary reactant is pressure-filtered to obtain a first filter cake, which is then mixed with primary beating water and water washing aids, and subjected to primary beating to obtain a primary beating and washing material;

[0011] In the secondary beating and washing, the primary beating and washing material is pressure-filtered to obtain a second filter cake, which is then mixed with secondary beating water and water washing aids, and subjected to secondary beating to obtain a secondary beating and washing material;

[0012] In the tertiary leaching, a side washing type of leaching mode is adopted, and after the secondary beating and washing material is leached by the first portion of leaching water and the second portion of leaching water, it is pressure-filtered to obtain a tertiary leaching filter cake.

[0013] Further, in the drying step, the tertiary leaching filter cake is dried at 130-150 DEG C to a moisture content of ≤3.0wt%, to obtain a magnesium carbonate dry powder;

[0014] In the calcination step, the magnesium carbonate dry powder is calcined at 800-850 DEG C to obtain a calcined magnesium oxide semi-product;

[0015] In the post-treatment step, the calcined magnesium oxide semi-product is subjected to demagnetization and sieving, and then pulverized to an average particle size D50 of 8-10 μm, to obtain the pharmaceutical-grade magnesium oxide.

[0016] Preferably, in the reaction-aging step, the molar concentration of the magnesium sulfate solution is 2.0-2.5 mol / L, and the molar concentration of the sodium carbonate solution is 1.0-1.5 mol / L.

[0017] The volume ratio of the first sodium carbonate solution to the second sodium carbonate solution is 1.9-2.1:1.

[0018] In the magnesium sulfate solution, the first sodium carbonate solution, and the second sodium carbonate solution, the molar ratio of magnesium sulfate to total sodium carbonate is 1:1.1-1.2.

[0019] Preferably, in the reaction-aging step, the first sodium carbonate solution is added for 30-45 min, and the reaction is maintained for 20-40 min after the addition of the first sodium carbonate solution is completed.

[0020] The second sodium carbonate solution is added for 30-45 min, and the reaction is maintained for 2-2.5 h after the addition of the second sodium carbonate solution is completed.

[0021] Preferably, in the reaction-aging step, the aging time is 2-3 h.

[0022] The amount of polyethylene glycol added is 0.5-1% of the total mass of the prepared magnesium carbonate dry powder.

[0023] Preferably, in the primary beating and washing, the beating speed is controlled at 200-250 r / min, the beating temperature is 40-45℃, and the beating time is 1.5-2 h.

[0024] The amount of primary beating water used is 14-15 m 3 / ton of magnesium carbonate dry powder.

[0025] The washing aids are hexadecyltrimethylammonium bromide and ammonium bicarbonate. The amount of hexadecyltrimethylammonium bromide added is 0.5-1% of the total mass of the magnesium carbonate dry powder, and the amount of ammonium bicarbonate added is 5-10% of the total mass of the magnesium carbonate dry powder.

[0026] Preferably, in the secondary beating and washing, the beating speed is controlled at 200-250 r / min, the beating temperature is 40-45℃, and the beating time is 1-1.5 h.

[0027] The amount of secondary beating water used is 14-15 m 3 / ton of magnesium carbonate dry powder.

[0028] The washing aids are hexadecyltrimethylammonium bromide and ammonium bicarbonate. The amount of hexadecyltrimethylammonium bromide added is 0.5-1% of the total mass of the magnesium carbonate dry powder, and the amount of ammonium bicarbonate added is 2-5% of the total mass of the magnesium carbonate dry powder.

[0029] Preferably, in the third-stage leaching, the first portion of leaching water is leached from left to right, and the leaching time is 20-30 min.

[0030] The second portion of leaching water is leached from right to left, and the leaching time is 20-30 min.

[0031] The dosage of the first portion of leaching water is 9-10 m 3 / ton of dry magnesium carbonate powder.

[0032] The dosage of the second portion of leaching water is 9-10 m 3 / ton of dry magnesium carbonate powder.

[0033] Preferably, in the calcination step, the calcination time is 40-60 min.

[0034] In the post-processing step, the magnetic separation is performed by using an electromagnetic powder magnetic separator, the control excitation current is 52-55 A, and the magnetic induction intensity is 19000-20000 GS.

[0035] Further, the medical-grade magnesium oxide has a magnesium oxide content of ≥96.0 wt%, an average particle size D50 of 8-10 μm, a specific surface area of 15-25 m 2 / g, a 30-degree citric acid activity of 30-50 s, and a sulfate content of ≤0.5 wt%.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] (1) In the production method of the medical-grade magnesium oxide, in the reaction-aging step, firstly, the molar concentrations of the magnesium sulfate solution and the sodium carbonate solution are controlled as the basic conditions for synthesizing heavy magnesium carbonate with a bulk density of ≥0.5 g / mL; then, the sodium carbonate solution is added to the magnesium sulfate solution in batches, and the bulk density and particle size of the heavy magnesium carbonate are adjusted by controlling the related process parameters (such as the addition time and the reaction temperature) in the reaction and aging processes, so as to balance the purity and activity of the medical-grade magnesium oxide prepared subsequently, to avoid the adverse effects of the poor quality and structure of the magnesium carbonate on the medical-grade magnesium oxide, and to ensure that the tablet hardness reaches 2.5-3 kg; in the multi-stage beating and washing step, the sulfate attached to the primary reactant magnesium carbonate is removed through the first-stage beating and washing, the second-stage beating and washing, and the third-stage leaching; then, the medical-grade magnesium oxide is prepared through the drying step, the calcination step, and the post-processing step; the aforementioned technical means cooperate with each other and work together, which can effectively balance the purity and activity requirements of the medical-grade magnesium oxide, avoid the problems of low reaction efficiency, the influence of the structure of the magnesium carbonate on the quality of the magnesium oxide, and high sulfate content of the medical-grade magnesium oxide, while ensuring that the tablet hardness reaches 2.5-3 kg.

[0038] (2) The production method of the pharmaceutical grade magnesium oxide of the present application, the specification of the pharmaceutical grade magnesium oxide prepared by the method is shown in the following table:

[0039]

[0040] (3) The production method of the pharmaceutical grade magnesium oxide of the present application, the raw material is easy to obtain, the process flow is simple, the reaction process is easy to control, and is suitable for industrialized scale production. DETAILED DESCRIPTION

[0041] In order to have a more clear understanding of the technical features, objects and effects of the present application, the specific embodiments of the present application are described. It should be pointed out that the following detailed description is exemplary and is intended to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0042] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, "first", "second", and the like are used to distinguish similar objects, and are not intended to describe a particular order or sequence, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0043] The present application provides a production method of pharmaceutical grade magnesium oxide, which is carried out by the following process flow: magnesium sulfate, sodium carbonate → preparation → reaction and aging → cooling → filtration → washing → drying → calcination → demagnetization → screening → crushing → packaging → finished product.

[0044] The production method of the pharmaceutical grade magnesium oxide comprises the following steps: a preparation step, a reaction-aging step, a multi-stage beating and washing step, a drying step, a calcination step, and a post-treatment step.

[0045] The method of the preparation step is to use magnesium sulfate heptahydrate, sodium carbonate and deionized water as raw materials to prepare a magnesium sulfate solution with a molar concentration of 2.0-2.5 mol / L and a sodium carbonate solution with a molar concentration of 1.0-1.5 mol / L.

[0046] In the preparation step, the magnesium sulfate heptahydrate is a commercially available pharmaceutical grade magnesium sulfate qualified product, and the sodium carbonate is a commercially available pharmaceutical grade sodium carbonate qualified product.

[0047] The method of the reaction-aging step is that the magnesium sulfate solution and the sodium carbonate solution are heated to 90-95℃ respectively and kept warm; under the condition of stirring at 100-120 r / min, the polyethylene glycol is added to the magnesium sulfate solution, after uniform stirring, the first portion of the sodium carbonate solution is added to the 90-95℃ magnesium sulfate solution (attention should be paid to not adding in the reverse direction), and the adding time of the first portion of the sodium carbonate solution is controlled to be 30-45 min; after the addition of the first portion of the sodium carbonate solution is completed, the 90-95℃ temperature is kept for 20-40 min of reaction and stirring, and the second portion of the sodium carbonate solution is continuously added, and the adding time of the second portion of the sodium carbonate solution is controlled to be 30-45 min; after the addition of the second portion of the sodium carbonate solution is completed, the stirring speed is adjusted to 150-180 r / min, the 90-95℃ temperature is kept for 2-2.5 h of reaction and stirring; after the reaction is completed, the stirring speed is adjusted to 60-80 r / min, the temperature of the material during the aging is controlled to be not lower than 65℃, and after the aging for 2-3 h, the temperature is cooled to below 50℃, and the primary reactant is obtained.

[0048] In the reaction-aging step, the volume ratio of the first portion of the sodium carbonate solution to the second portion of the sodium carbonate solution is 1.9-2.1:1;

[0049] In the magnesium sulfate solution, the first portion of the sodium carbonate solution and the second portion of the sodium carbonate solution used, the molar ratio of magnesium sulfate to the total sodium carbonate (the sum of the first portion and the second portion) is 1:1.1-1.2;

[0050] The polyethylene glycol is PEG-400, and the adding amount is 0.5-1% of the total mass of the dry magnesium carbonate powder prepared by reaction, which is used to improve the reaction efficiency and adjust the particle size of the magnesium carbonate particles.

[0051] The inventors have found through a large number of experimental researches that the bulk density of magnesium carbonate is too low, which directly affects the quality of the magnesium oxide prepared by subsequent calcination, and causes the tablet hardness of the magnesium oxide used in the pharmaceutical industry to be unable to meet the predetermined requirements (the tablet hardness reaches 2.5-3 kg); and the inventors have further found that even if high-purity magnesium hydroxide with required activity and specific surface area is used as the raw material, the tabletting performance of the magnesium oxide prepared by calcination still cannot meet the predetermined requirements; and only the heavy magnesium carbonate with a bulk density ≥0.5 g / mL can be used to prepare the pharmaceutical-grade magnesium oxide meeting the tablet hardness requirements. In this step, firstly, the molar concentrations of the magnesium sulfate solution and the sodium carbonate solution are controlled as the basic conditions for the reaction and synthesis of the heavy magnesium carbonate with a bulk density ≥0.5 g / mL; then the adding method is that the sodium carbonate solution is added to the magnesium sulfate solution in batches, and the bulk density and particle size of the heavy magnesium carbonate are adjusted by controlling the related process parameters (such as the adding time and the reaction temperature) in the reaction and aging processes, so as to balance the purity and activity of the pharmaceutical-grade magnesium oxide prepared subsequently, to ensure that the tablet hardness reaches 2.5-3 kg, and to avoid the adverse effects of the quality and structure and morphology of the magnesium carbonate on the pharmaceutical-grade magnesium oxide.

[0052] The multi-stage beating and washing step comprises: a first-stage beating and washing, a second-stage beating and washing, and a third-stage elution.

[0053] The method of the first-stage beating and washing is as follows: the primary reactant is introduced into a 1# filter press, and is filtered to obtain a first filter cake with a water content of ≤50wt%; the first filter cake is introduced into a 1# beater tank, and then first-stage beating water and a water washing aid are added, the first-stage beating speed is controlled to be 200-250r / min, the first-stage beating temperature is controlled to be 40-45℃, and first-stage beating is performed for 1.5-2h to obtain first-stage beating and washing material.

[0054] In the first-stage beating and washing, the amount of the first-stage beating water is 14-15m 3 / ton of dry magnesium carbonate powder.

[0055] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of the cetyltrimethylammonium bromide CTAB is 0.5-1% of the total mass of the dry magnesium carbonate powder, and the addition amount of the ammonium bicarbonate is 5-10% of the total mass of the dry magnesium carbonate powder.

[0056] The method of the second-stage beating and washing is as follows: the first-stage beating and washing material is introduced into a 2# filter press, and is filtered to obtain a second filter cake with a water content of ≤50wt%; the second filter cake is introduced into a 2# beater tank, and then second-stage beating water and a water washing aid are added, the second-stage beating speed is controlled to be 200-250r / min, the second-stage beating temperature is controlled to be 40-45℃, and second-stage beating is performed for 1-1.5h to obtain second-stage beating and washing material.

[0057] In the second-stage beating and washing, the amount of the second-stage beating water is 14-15m 3 / ton of dry magnesium carbonate powder.

[0058] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of the cetyltrimethylammonium bromide CTAB is 0.5-1% of the total mass of the dry magnesium carbonate powder, and the addition amount of the ammonium bicarbonate is 2-5% of the total mass of the dry magnesium carbonate powder.

[0059] In the first-stage beating and washing and the second-stage beating and washing, the water washing aid ammonium bicarbonate can react with magnesium sulfate attached to the magnesium carbonate to generate ammonium sulfate, and the ammonium sulfate is easily dissolved in water and dispersed into the filtrate; in combination with the added cetyltrimethylammonium bromide CTAB, the dispersibility of the magnesium carbonate in water is improved, so that the sulfate is more easily washed away, and the washing efficiency and effect of the sulfate are further improved.

[0060] The method of the third stage washing is that the secondary pulping washing material is introduced into a 3# side washing filter press, and the side washing method is used for washing; first, the left side is introduced into the right side, and the first part of normal temperature washing water is introduced for washing for 20-30 minutes, then the right side is introduced into the left side, and the second part of normal temperature washing water is introduced for washing for 20-30 minutes, and the filter cake is pressed to a water content of ≤50wt%, to obtain the third stage washing filter cake.

[0061] In the third stage washing, the amount of the first part of washing water is 9-10m 3 / ton of dry magnesium carbonate powder;

[0062] The amount of the second part of washing water is 9-10m 3 / ton of dry magnesium carbonate powder.

[0063] In this step, the sulfate attached to the primary reactant magnesium carbonate is removed by the first stage pulping washing, the second stage pulping washing and the third stage washing; by controlling the amount of pulping water at each stage, and the composition and amount of the washing aid, the sulfate content of the product is reduced to 1-1.5wt% after the first stage pulping washing, the sulfate content of the product is reduced to 0.5-1wt% after the second stage pulping washing, and the sulfate content of the product is ≤0.2wt% after the third stage washing.

[0064] The method of the drying step is that the third stage washing filter cake is put into the feeding hopper, and is fed into the drying furnace through the feeding auger, the drying temperature is controlled to be 130-150℃, the material moisture content is dried to ≤3.0wt%, the drying is stopped, the material is scattered, the dry magnesium carbonate powder is obtained, and is discharged to the storage bin for use.

[0065] In the drying step, the magnesium oxide content of the dry magnesium carbonate powder is ≥42.0wt%, the sulfate content is ≤0.2wt%, the moisture content is ≤3.0wt%, and the bulk density is ≥0.5g / mL.

[0066] In this step, by controlling the drying temperature to be 130-150℃, the premature decomposition of part of the magnesium carbonate into magnesium oxide during the drying process is prevented, and then the morphology and structure of the magnesium carbonate are not good, which affects the quality of the magnesium oxide prepared by subsequent calcination.

[0067] The method of the calcination step is that the dry magnesium carbonate powder is put into the feeding hopper, and is fed into the rotary calcination furnace through the feeding auger, the calcination temperature is controlled to be 800-850℃, the calcination is carried out for 40-60min, the activity and specific surface area of the magnesium oxide are controlled by targeted calcination, then the calcined magnesium oxide semi-finished product is obtained after crushing, and is discharged to the storage bin for use.

[0068] In the calcination step, the calcined magnesium oxide semi-finished product has a magnesium oxide content ≥96.0 wt%, a loss on ignition ≤5.0%, a sulfate content ≤0.5%, a moisture content ≤0.5%, a citric acid activity of 40-60 s at 30 degrees Celsius, and a specific surface area of ​​10-20 m². 2 / g.

[0069] In this step, a rotary kiln is used to specifically calcine magnesium oxide at a specific temperature and time to control its activity, specific surface area, and weight loss on ignition, thereby ensuring that the pressed tablets achieve the predetermined hardness. Meanwhile, the inventors' experiments revealed that other methods, such as shuttle kilns and roller kilns, cannot produce magnesium oxide products with acceptable activity.

[0070] The post-processing method is as follows: the calcined magnesium oxide semi-finished product is fed into an electromagnetic powder magnetic separator, the excitation current is controlled at 52-55A, the magnetic induction intensity is 19000-20000GS, after demagnetization treatment, it is sieved with an 80-mesh sieve, and then crushed by an impact mill to an average particle size D50 of 8-10μm to obtain pharmaceutical grade magnesium oxide.

[0071] In this step, an electromagnetic powder magnetic separator is used to demagnetize (remove iron) the calcined magnesium oxide semi-finished product, removing some magnetic materials (such as iron) introduced during the calcination process. After removal by the demagnetizing equipment, the iron content and black spots in the product are controlled to meet the standards (10-20 black spots before demagnetization, which can be reduced to less than 5 after demagnetization). Sieving is used to remove impurities introduced during drying, calcination, and other steps, ensuring that the acid-insoluble matter meets the standards. The material is crushed using an impact mill, and the average particle size D50 must be controlled at 8-10μm. Particles that are too coarse or too fine will result in the tablet hardness not meeting the standards.

[0072] The pharmaceutical-grade magnesium oxide has a magnesium oxide content ≥96.0 wt%, a CaO content ≤0.1 wt%, an acid-insoluble matter content ≤0.1 wt%, a moisture content ≤0.5 wt%, and an iron (Fe) content ≤0.5 wt%. 3+ The content is ≤0.01wt%, the average particle size D50 is 8-10μm, and the specific surface area is 15-25m². 2 / g, citric acid activity at 30 degrees Celsius is 30-50s, black spots (5g) ≤5, loss on ignition ≤5.0wt%, sulfate content ≤0.5wt%.

[0073] The present invention will be further described below with reference to some specific embodiments.

[0074] Example 1

[0075] This embodiment provides a method for producing pharmaceutical-grade magnesium oxide, specifically:

[0076] 1. Preparation steps

[0077] The magnesium sulfate heptahydrate, sodium carbonate and deionized water are used as raw materials to prepare a magnesium sulfate solution with a molar concentration of 2.5 mol / L and a sodium carbonate solution with a molar concentration of 1.5 mol / L.

[0078] The magnesium sulfate heptahydrate is a commercially available pharmaceutical-grade magnesium sulfate qualified product, and the sodium carbonate is a commercially available pharmaceutical-grade sodium carbonate qualified product.

[0079] 2. Reaction and aging step

[0080] The magnesium sulfate solution and the sodium carbonate solution are heated to 95°C and kept at this temperature. Under the condition of stirring at 120 r / min, the polyethylene glycol is added to the magnesium sulfate solution, and after uniform stirring, the first portion of the sodium carbonate solution is added to the 95°C magnesium sulfate solution (note that the sodium carbonate solution should not be added to the magnesium sulfate solution). The addition time of the first portion of the sodium carbonate solution is controlled to be 45 min. After the addition of the first portion of the sodium carbonate solution is completed, the reaction is kept at 95°C for 30 min, and the second portion of the sodium carbonate solution is continuously added under stirring. The addition time of the second portion of the sodium carbonate solution is controlled to be 45 min. After the addition of the second portion of the sodium carbonate solution is completed, the stirring speed is adjusted to 180 r / min, and the reaction is kept at 95°C for 2 h. After the reaction is completed, the stirring speed is adjusted to 80 r / min, the temperature of the material during the aging is controlled to be not lower than 65°C, and the aging is performed for 2 h. After the aging, the temperature is cooled to below 50°C, and the primary reaction product is obtained.

[0081] The volume ratio of the first portion of the sodium carbonate solution to the second portion of the sodium carbonate solution is 2:1.

[0082] The molar ratio of the magnesium sulfate to the total sodium carbonate (the sum of the first portion and the second portion) in the magnesium sulfate solution, the first portion of the sodium carbonate solution and the second portion of the sodium carbonate solution is 1:1.2.

[0083] The polyethylene glycol is PEG-400, and the addition amount is 1% of the total mass of the magnesium carbonate dry powder prepared by the reaction.

[0084] 3. Multi-stage beating and washing step

[0085] (1) First-stage beating and washing

[0086] The primary reaction product is introduced into a 1# filter press, and is filtered to obtain a first filter cake with a water content of ≤50 wt%. The first filter cake is then introduced into a 1# beater tank, and a first-stage beating water and a water washing aid are added. The first-stage beating speed is controlled to be 250 r / min, the first-stage beating temperature is controlled to be 45°C, and the first-stage beating is performed for 2 h to obtain a first-stage beating and washing material.

[0087] The amount of the first-stage beating water is 15 m 3 / ton of the magnesium carbonate dry powder.

[0088] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of cetyltrimethylammonium bromide CTAB is 1% of the total mass of the magnesium carbonate dry powder, and the addition amount of ammonium bicarbonate is 5% of the total mass of the magnesium carbonate dry powder.

[0089] (2) Secondary pulp washing

[0090] The primary pulp washing material is introduced into a 2# filter press, and is filtered to obtain a second filter cake with a water content of ≤50wt%; the second filter cake is introduced into a 2# pulp tank, and then secondary pulp water and a water washing aid are added, the secondary pulp rotation speed is controlled to be 250r / min, the secondary pulp temperature is controlled to be 45℃, and secondary pulp washing is performed for 1.5h to obtain secondary pulp washing material.

[0091] The amount of the secondary pulp water is 15m 3 / ton of the magnesium carbonate dry powder.

[0092] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of cetyltrimethylammonium bromide CTAB is 1% of the total mass of the magnesium carbonate dry powder, and the addition amount of ammonium bicarbonate is 3% of the total mass of the magnesium carbonate dry powder.

[0093] (3) Tertiary leaching

[0094] The secondary pulp washing material is introduced into a 3# side washing type filter press, and is leached by using a side washing type leaching mode; first, the left side is used to introduce the right side to introduce the first portion of leaching water at normal temperature to leach for 30min, and then the right side is used to introduce the left side to introduce the second portion of leaching water at normal temperature to leach for 30min, and the filter cake is filtered to have a water content of ≤50wt% to obtain a tertiary leaching filter cake.

[0095] The amount of the first portion of leaching water is 10m 3 / ton of the magnesium carbonate dry powder.

[0096] The amount of the second portion of leaching water is 10m 3 / ton of the magnesium carbonate dry powder.

[0097] 4, Drying step

[0098] The tertiary leaching filter cake is introduced into a feeding hopper, and is fed into a drying furnace through a feeding auger, the drying temperature is controlled to be 140℃, and the material is dried to have a water content of ≤3.0wt%, the drying is stopped, the material is scattered, and magnesium carbonate dry powder (with a bulk density of 0.58g / mL) is obtained, and is discharged into a storage bin for use.

[0099] 5, Calcination step

[0100] The dry magnesium carbonate powder is put into the feeding hopper, fed into the rotary calcining furnace through the feeding auger, the calcining temperature is controlled at 800 ℃, and the calcining is kept for 60 min to control the activity and specific surface area of the magnesium oxide, then the calcined magnesium oxide semi-product is obtained after crushing, and discharged into the storage bin for later use.

[0101] 6. Post-treatment step

[0102] The calcined magnesium oxide semi-product is put into the electromagnetic powder magnetic separator, the excitation current is controlled at 55 A, and the magnetic induction intensity is 20000 GS, after the magnetic treatment, the 80 mesh screen is used for screening, and then the impact mill is used for crushing to an average particle size D50 of 9.3 μm to prepare the pharmaceutical grade magnesium oxide.

[0103] The quality specification of the pharmaceutical grade magnesium oxide prepared in this example is shown in the following table:

[0104]

[0105] Example 2

[0106] The present example provides a production method of pharmaceutical grade magnesium oxide, in particular:

[0107] 1. Preparation step

[0108] The magnesium sulfate heptahydrate, sodium carbonate and deionized water are used as raw materials to prepare a magnesium sulfate solution with a molar concentration of 2.0 mol / L and a sodium carbonate solution with a molar concentration of 1.5 mol / L.

[0109] The magnesium sulfate heptahydrate is a commercially available pharmaceutical grade magnesium sulfate qualified product, and the sodium carbonate is a commercially available pharmaceutical grade sodium carbonate qualified product.

[0110] 2. Reaction-aging step

[0111] The magnesium sulfate solution and the sodium carbonate solution are heated to 90 ℃ respectively and kept; under the condition of 120 r / min stirring, the polyethylene glycol is added to the magnesium sulfate solution, after uniform stirring, the first portion of the sodium carbonate solution is added to the 90 ℃ magnesium sulfate solution (note that it cannot be added inversely), and the addition time of the first portion of the sodium carbonate solution is controlled at 45 min; after the addition of the first portion of the sodium carbonate solution is completed, the reaction is kept at 95 ℃ for 30 min, and the second portion of the sodium carbonate solution is continuously added under stirring, and the addition time of the second portion of the sodium carbonate solution is controlled at 45 min; after the addition of the second portion of the sodium carbonate solution is completed, the stirring speed is adjusted to 180 r / min, and the reaction is kept at 90 ℃ for 2 h; after the reaction is completed, the stirring speed is adjusted to 80 r / min, the temperature of the material during the aging is controlled to be not lower than 65 ℃, the aging is kept for 2 h, and then the temperature is cooled to below 50 ℃ to obtain the primary reactant.

[0112] The volume ratio of the first portion of sodium carbonate solution to the second portion of sodium carbonate solution is 2:1.

[0113] The molar ratio of magnesium sulfate to all sodium carbonate (the sum of the first and second portions) in the magnesium sulfate solution, the first portion of sodium carbonate solution, and the second portion of sodium carbonate solution is 1:1.1.

[0114] The polyethylene glycol is PEG-400, and the addition amount is 1% of the total mass of the dry magnesium carbonate powder prepared by reaction.

[0115] 3. Multi-stage beating and washing steps

[0116] (1) First-stage beating and washing

[0117] The primary reactants are introduced into a 1# filter press, and the filter cake is pressed to a water content of ≤50wt%, obtaining a first filter cake; the first filter cake is introduced into a 1# beater tank, then first-stage beating water and a water washing aid are added, the first-stage beating speed is controlled at 250r / min, the first-stage beating temperature is controlled at 45℃, and first-stage beating is performed for 2h, obtaining first-stage beating and washing material.

[0118] The amount of first-stage beating water is 15m 3 / ton of dry magnesium carbonate powder.

[0119] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of cetyltrimethylammonium bromide CTAB is 1% of the total mass of the dry magnesium carbonate powder, and the addition amount of ammonium bicarbonate is 5% of the total mass of the dry magnesium carbonate powder.

[0120] (2) Second-stage beating and washing

[0121] The first-stage beating and washing material is introduced into a 2# filter press, and the filter cake is pressed to a water content of ≤50wt%, obtaining a second filter cake; the second filter cake is introduced into a 2# beater tank, then second-stage beating water and a water washing aid are added, the second-stage beating speed is controlled at 250r / min, the second-stage beating temperature is controlled at 45℃, and second-stage beating is performed for 1.5h, obtaining second-stage beating and washing material.

[0122] The amount of second-stage beating water is 15m 3 / ton of dry magnesium carbonate powder.

[0123] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of cetyltrimethylammonium bromide CTAB is 1% of the total mass of the dry magnesium carbonate powder, and the addition amount of ammonium bicarbonate is 3% of the total mass of the dry magnesium carbonate powder.

[0124] (3) Third-stage elution

[0125] The secondary pulp washing material is introduced into a 3# side washing filter press, and a side washing type of rinsing is performed. First, the left side is used to input and the right side is used to output, and normal temperature first rinsing water is introduced to perform rinsing for 30 minutes. Then, the right side is used to input and the left side is used to output, and normal temperature second rinsing water is introduced to perform rinsing for 30 minutes. The filter cake is pressed to a water content of less than or equal to 50 wt%, and a third rinsing filter cake is obtained.

[0126] The amount of the first rinsing water is 10 m 3 / ton of magnesium carbonate dry powder.

[0127] The amount of the second rinsing water is 10 m 3 / ton of magnesium carbonate dry powder.

[0128] 4. Drying step

[0129] The third rinsing filter cake is introduced into a feeding hopper, and is fed into a drying furnace through a feeding auger. The drying temperature is controlled to be 145 DEG C, and the material is dried to a water content of less than or equal to 3.0 wt%. After the drying is stopped, the material is scattered to obtain magnesium carbonate dry powder (the bulk density is 0.53 g / mL), which is discharged to a storage bin for use.

[0130] 5. Calcination step

[0131] The magnesium carbonate dry powder is introduced into a feeding hopper, and is fed into a rotary calcination furnace through a feeding auger. The calcination temperature is controlled to be 850 DEG C, and the calcination is performed for 60 minutes. The activity and specific surface area of magnesium oxide are controlled by targeted calcination. After the calcination, the magnesium oxide semi-finished product is obtained by crushing, and is discharged to a storage bin for use.

[0132] 6. Post-treatment step

[0133] The calcined magnesium oxide semi-finished product is introduced into an electromagnetic powder magnetic separator, and the excitation current is controlled to be 55 A and the magnetic induction intensity is controlled to be 20000 GS. After the magnetic treatment, the product is sieved by an 80 mesh screen, and is crushed by an impact mill to an average particle size D50 of 8.8 μm, so as to obtain the pharmaceutical grade magnesium oxide.

[0134] The quality specification of the pharmaceutical grade magnesium oxide obtained in this example is shown in the following table:

[0135]

[0136] Example 3

[0137] The example provides a production method of pharmaceutical grade magnesium oxide, and specifically comprises the following steps.

[0138] 1. Preparation step

[0139] The magnesium sulfate heptahydrate, sodium carbonate and deionized water are used as raw materials to prepare a magnesium sulfate solution with a molar concentration of 2.0 mol / L and a sodium carbonate solution with a molar concentration of 1.5 mol / L.

[0140] The magnesium sulfate heptahydrate is a commercially available pharmaceutical-grade magnesium sulfate qualified product, and the sodium carbonate is a commercially available pharmaceutical-grade sodium carbonate qualified product.

[0141] 2. Reaction and aging step

[0142] The magnesium sulfate solution and the sodium carbonate solution are heated to 95°C and kept at this temperature. Under the condition of stirring at 100 r / min, the polyethylene glycol is added to the magnesium sulfate solution, and after uniform stirring, the first portion of the sodium carbonate solution is added to the 95°C magnesium sulfate solution (note that the sodium carbonate solution should not be added to the magnesium sulfate solution). The addition time of the first portion of the sodium carbonate solution is controlled to be 40 min. After the addition of the first portion of the sodium carbonate solution is completed, the reaction is kept at 95°C for 30 min, and the second portion of the sodium carbonate solution is continuously added under stirring. The addition time of the second portion of the sodium carbonate solution is controlled to be 35 min. After the addition of the second portion of the sodium carbonate solution is completed, the stirring speed is adjusted to 150 r / min, and the reaction is kept at 95°C for 2 h. After the reaction is completed, the stirring speed is adjusted to 60 r / min, the temperature of the material during the aging is controlled to be not lower than 65°C, and the aging is performed for 2 h. After the aging, the temperature is cooled to below 50°C, and the primary reaction product is obtained.

[0143] The volume ratio of the first portion of the sodium carbonate solution to the second portion of the sodium carbonate solution is 2:1.

[0144] The molar ratio of the magnesium sulfate to the total sodium carbonate (the sum of the first portion and the second portion) in the magnesium sulfate solution, the first portion of the sodium carbonate solution and the second portion of the sodium carbonate solution is 1:1.15.

[0145] The polyethylene glycol is PEG-400, and the addition amount of the polyethylene glycol is 1% of the total mass of the dry magnesium carbonate powder prepared by the reaction.

[0146] 3. Multi-stage beating and washing step

[0147] (1) First-stage beating and washing

[0148] The primary reaction product is introduced into a 1# filter press, and the filter cake is obtained by filtering to a water content of ≤50 wt%. The first-stage beating and washing is performed by adding the first-stage beating water and the water washing aid to the first filter cake in a 1# beater tank, controlling the first-stage beating speed to be 250 r / min and the first-stage beating temperature to be 45°C, and beating for 2 h to obtain the first-stage beating and washing material.

[0149] The amount of the first-stage beating water is 15 m 3 / ton of dry magnesium carbonate powder.

[0150] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of cetyltrimethylammonium bromide CTAB is 1% of the total mass of the magnesium carbonate dry powder, and the addition amount of ammonium bicarbonate is 7.5% of the total mass of the magnesium carbonate dry powder.

[0151] (2) Secondary beating and washing

[0152] The primary beating and washing material is introduced into the 2# filter press, and is filtered to obtain a second filter cake with a water content of ≤50wt%; the second filter cake is introduced into the 2# beating tank, and then the secondary beating water and the water washing aid are added, the secondary beating speed is controlled to be 250r / min, the secondary beating temperature is controlled to be 45℃, and secondary beating is performed for 1.5h to obtain a secondary beating and washing material.

[0153] The amount of the secondary beating water is 15m 3 / ton of the magnesium carbonate dry powder.

[0154] The water washing aid is cetyltrimethylammonium bromide CTAB and ammonium bicarbonate; the addition amount of cetyltrimethylammonium bromide CTAB is 1% of the total mass of the magnesium carbonate dry powder, and the addition amount of ammonium bicarbonate is 5% of the total mass of the magnesium carbonate dry powder.

[0155] (3) Tertiary leaching

[0156] The secondary beating and washing material is introduced into the 3# side washing filter press, and is leached by using a side washing leaching mode; first, the left side is used to introduce the right side to introduce the first portion of leaching water at normal temperature to leach for 30min, and then the right side is used to introduce the left side to introduce the second portion of leaching water at normal temperature to leach for 30min, and the filter cake is filtered to obtain a tertiary leaching filter cake with a water content of ≤50wt%.

[0157] The amount of the first portion of leaching water is 10m 3 / ton of the magnesium carbonate dry powder.

[0158] The amount of the second portion of leaching water is 10m 3 / ton of the magnesium carbonate dry powder.

[0159] 4, Drying step

[0160] The tertiary leaching filter cake is introduced into the feeding hopper, and is fed into the drying furnace through the feeding auger, the drying temperature is controlled to be 150℃, and the material is dried to a water content of ≤3.0wt%, and then the drying is stopped, the material is scattered, and the magnesium carbonate dry powder (with a bulk density of 0.56g / mL) is obtained, and is discharged into the storage bin for use.

[0161] 5, Calcination step

[0162] The dry magnesium carbonate powder is put into the feeding hopper, fed into the rotary calcining furnace through the feeding auger, the calcining temperature is controlled at 830 ℃, and the calcining is kept for 45 min, so as to control the activity and specific surface area of the magnesium oxide. Then, after crushing, the calcined magnesium oxide semi-finished product is obtained, and discharged to the storage bin for later use.

[0163] 6. Post-treatment step

[0164] The calcined magnesium oxide semi-finished product is put into the electromagnetic powder magnetic separator, the excitation current is controlled at 55 A, and the magnetic induction intensity is 20000 GS. After the magnetic treatment, the product is sieved with an 80-mesh screen, and then crushed by an impact mill to an average particle size D50 of 8.6 μm to obtain the pharmaceutical-grade magnesium oxide.

[0165] The quality specifications of the pharmaceutical-grade magnesium oxide prepared in this example are shown in the following table:

[0166]

[0167] Comparative Example 1

[0168] Comparative Example 1 uses the technical solution of Example 1, and the difference lies in that:

[0169] 1) In the preparation step, the molar concentration of the magnesium sulfate solution is 1.5 mol / L, and the molar concentration of the sodium carbonate solution is 0.5 mol / L.

[0170] 2) In the reaction-aging step, the magnesium sulfate solution and the sodium carbonate solution are not heated, and the first portion of the sodium carbonate solution and the second portion of the sodium carbonate solution are added to the magnesium sulfate solution at room temperature, and the reaction is carried out at room temperature. The molar ratio of magnesium sulfate to all sodium carbonate (the sum of the first portion and the second portion) in the magnesium sulfate solution, the first portion of the sodium carbonate solution, and the second portion of the sodium carbonate solution is 1:1.

[0171] The other operations and steps are the same as those of Example 1.

[0172] The quality specifications of the magnesium oxide product prepared in Comparative Example 1 are shown in the following table:

[0173]

[0174] It can be seen that the magnesium oxide content, specific surface area, and activity of the magnesium oxide product prepared in Comparative Example 1 cannot meet the predetermined requirements, specifically, the magnesium oxide content and activity are reduced, and the specific surface area is increased, which directly affects the tabletting performance of the magnesium oxide.

[0175] Comparative Example 2

[0176] Comparative Example 2 adopts the technical solution of Example 2, the difference is that in the multi-stage beating washing step, the water washing auxiliary agent used in the first stage beating washing is omitted, and the second stage beating washing is omitted, and after the first stage beating washing is completed, the third stage leaching is directly carried out.

[0177] Other operations and steps are the same as Example 1.

[0178] The quality specifications of the pharmaceutical grade magnesium oxide prepared in Comparative Example 2 are shown in the following table:

[0179]

[0180] It can be seen that after the multi-stage beating washing in Comparative Example 2 is changed, the sulfate content of the prepared magnesium oxide product cannot meet the predetermined requirements.

[0181] Comparative Example 3

[0182] Comparative Example 3 adopts the technical solution of Example 2, the difference is that in the calcination step, the calcination temperature is set to 900℃, and the calcination time is 80min.

[0183] Other operations and steps are the same as Example 1.

[0184] The quality specifications of the pharmaceutical grade magnesium oxide prepared in Comparative Example 3 are shown in the following table:

[0185]

[0186] It can be seen that the specific surface area and activity of the magnesium oxide product prepared in Comparative Example 3 cannot meet the predetermined requirements, which is manifested as the activity of the magnesium oxide increasing and the specific surface area decreasing, directly affecting the tabletting performance of the magnesium oxide.

[0187] Comparative Example 4

[0188] The magnesium oxide products of Examples 1-3 and Comparative Examples 1-3, magnesium oxide with a particle size D50 of 16.7μm (particle size unqualified), magnesium hydroxide calcined magnesium oxide, light magnesium carbonate (bulk density 0.18g / mL) calcined magnesium oxide, ordinary magnesium carbonate (bulk density 0.25g / mL) calcined magnesium oxide, and magnesium carbonate (bulk density 0.45g / mL) calcined magnesium oxide were used to carry out powder direct tabletting (Chinese Pharmacopoeia 2020 Edition 0101 Tablets), and the tablet hardness was detected by YD-1 tablet hardness tester, and the specific results are shown as follows:

[0189]

[0190] It can be seen that, due to the deterioration of the aforementioned relevant indicators, the tablet hardness of magnesium oxide in Comparative Examples 1 and 3 could not meet the predetermined requirements. At the same time, the tablet performance of magnesium oxide calcined with magnesium oxide and magnesium hydroxide with unqualified particle size, as well as magnesium oxide calcined with magnesium carbonate with unqualified bulk density (bulk density ≥ 0.5 g / mL), could not meet the predetermined requirements.

[0191] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0192] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing pharmaceutical grade magnesium oxide, characterized by, The method comprises the following steps: a reaction-aging step, a multi-stage beating and washing step, a drying step, a calcination step, and a post-treatment step. In the reaction-aging step, polyethylene glycol is added to a magnesium sulfate solution under stirring, and after mixing, a first sodium carbonate solution is added to the magnesium sulfate solution at 90-95 DEG C, and after the addition of the first sodium carbonate solution is completed, the reaction is kept for a certain time. Then, a second sodium carbonate solution is continuously added to the magnesium sulfate solution at 90-95 DEG C, and after the addition of the second sodium carbonate solution is completed, the reaction is kept for a certain time. Then, aging is performed at a temperature of not less than 65 DEG C to obtain a primary reactant. The multi-stage beating and washing step comprises the following steps: a first-stage beating and washing step, a second-stage beating and washing step, and a third-stage washing step. In the first-stage beating and washing step, the primary reactant is pressed to obtain a first filter cake, and then the first filter cake is mixed with first-stage beating water and a water washing aid, and is subjected to first-stage beating to obtain a first-stage beating and washing material. In the first-stage beating and washing step, the water washing aid is cetyltrimethylammonium bromide and ammonium bicarbonate, the addition amount of the cetyltrimethylammonium bromide is 0.5-1% of the total mass of the dry magnesium carbonate powder, and the addition amount of the ammonium bicarbonate is 5-10% of the total mass of the dry magnesium carbonate powder. In the second-stage beating and washing step, the first-stage beating and washing material is pressed to obtain a second filter cake, and then the second filter cake is mixed with second-stage beating water and a water washing aid, and is subjected to second-stage beating to obtain a second-stage beating and washing material. In the second-stage beating and washing step, the water washing aid is cetyltrimethylammonium bromide and ammonium bicarbonate, the addition amount of the cetyltrimethylammonium bromide is 0.5-1% of the total mass of the dry magnesium carbonate powder, and the addition amount of the ammonium bicarbonate is 2-5% of the total mass of the dry magnesium carbonate powder. In the third-stage washing step, a side washing type washing mode is adopted, and after the second-stage beating and washing material is washed by first-stage washing water and second-stage washing water, the material is pressed to obtain a third-stage washing filter cake. In the drying step, the third-stage washing filter cake is dried at 130-150 DEG C until the water content is less than or equal to 3.0 wt%, and a dry magnesium carbonate powder is obtained. In the calcination step, the dry magnesium carbonate powder is calcined at 800-850 DEG C for 40-60 min to obtain a calcined magnesium oxide semi-product. The post-processing step, the calcined magnesium oxide semi-finished product is removed from the magnetic field, screened, crushed to an average particle size D50 of 8-10 μm, and a pharmaceutical grade magnesium oxide is prepared; the pharmaceutical grade magnesium oxide has a magnesium oxide content of ≥96.0 wt%, an average particle size D50 of 8-10 μm, a specific surface area of 15-25 m 2 / g, a 30-degree citric acid activity of 30-50 s, and a sulfate content of ≤0.5 wt%.

2. The method for producing pharmaceutical-grade magnesium oxide according to claim 1, characterized by, In the reaction-aging step, the molar concentration of the magnesium sulfate solution is 2.0-2.5 mol / L, and the molar concentration of the sodium carbonate solution is 1.0-1.5 mol / L. The volume ratio of the first sodium carbonate solution to the second sodium carbonate solution is 1.9-2.1:

1. In the magnesium sulfate solution, the first sodium carbonate solution, and the second sodium carbonate solution, the molar ratio of magnesium sulfate to all sodium carbonate is 1:1.1-1.

2.

3. The method of producing pharmaceutical grade magnesium oxide according to claim 1, characterized by, In the reaction-aging step, the addition time of the first sodium carbonate solution is 30-45 min, and the reaction keeping time after the addition of the first sodium carbonate solution is completed is 20-40 min. The addition time of the second sodium carbonate solution is 30-45 min, and the reaction keeping time after the addition of the second sodium carbonate solution is completed is 2-2.5 h.

4. The method of producing pharmaceutical-grade magnesium oxide according to claim 1, characterized by, In the reaction-aging step, the aging time is 2-3 h. The addition amount of the polyethylene glycol is 0.5-1% of the total mass of the dry magnesium carbonate powder prepared by reaction.

5. The method of producing pharmaceutical-grade magnesium oxide according to claim 1, characterized by, In the first beating washing, the beating speed is controlled at 200-250 r / min, the beating temperature is controlled at 40-45 DEG C, and the beating time is controlled at 1.5-2 h; The amount of primary slushing water is 14-15 m 3 / ton of dry magnesium carbonate powder.

6. The method of producing pharmaceutical-grade magnesium oxide according to claim 1, characterized by, In the second beating washing, the beating speed is controlled at 200-250 r / min, the beating temperature is controlled at 40-45 DEG C, and the beating time is controlled at 1-1.5 h; The amount of secondary pulp water is 14-15 m 3 / ton of dry magnesium carbonate powder.

7. The method of producing pharmaceutical-grade magnesium oxide according to claim 1, characterized by, In the first-stage washing, the first washing water is introduced from the left side and discharged from the right side, and the washing time is 20-30 min; In the second-stage washing, the second washing water is introduced from the right side and discharged from the left side, and the washing time is 20-30 min; The amount of the first elution water is 9-10 m 3 / ton of dry magnesium carbonate powder; The amount of the second elution water is 9-10 m 3 / ton of dry magnesium carbonate powder.

8. The method of producing pharmaceutical grade magnesium oxide according to claim 1, characterized by, In the post-processing step, the magnetic separation is performed by using an electromagnetic powder magnetic separator, the excitation current is controlled at 52-55 A, and the magnetic induction intensity is controlled at 19000-20000 GS.

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