A preparation method and device for calcium-removed magnesium-rich recrystallized dolomite

Abstract

The present invention discloses a method and device for preparing calcium-removed magnesium-rich recrystallized dolomite, the method comprising: preparing a reaction solution 1, wherein the Ca in the reaction solution 1 is 2+ Mg 2+ 、Na + The ion concentration is equal to the Ca in standard seawater 2+ Mg 2+ 、Na + Ion concentration value; prepare reaction solution 2, CO3 in reaction solution 2 2‑ Ions and Ca in reaction solution 1 2+ The ion concentration is consistent, and the Na + Ions and Na in reaction solution 1 + The ion concentration is consistent; a configured basic reaction solution is added to the reactor; the prepared magnesium-rich carbonate seed is added to the basic reaction solution in the reactor; reaction solution one and reaction solution two are injected into a reaction vessel via a peristaltic pump, and a gas source of different components is supplied during the reaction to adjust the pH value of the solution in the reaction vessel. The pH is lowered and raised in a continuous alternating manner day and night, and a dolomite sample with a high magnesium-calcium ratio is obtained after 30-60 days. The present invention achieves the preparation of dolomite by decalcification and magnesium-rich recrystallization under normal temperature and pressure laboratory conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of dolomite preparation, and in particular relates to a method and a device for preparing calcium-depleted and magnesium-enriched recrystallized dolomite. Background Art

[0002] Synthesizing stoichiometric protodolomite under normal laboratory conditions at room temperature and pressure is quite difficult. However, under specific conditions, such as microbial mediation and catalysis by negatively charged species, protodolomite can be precipitated from brines with a high Mg:Ca ratio. Dolomite deposits of both microbial and inorganic origin also occur in modern sediments and ancient sedimentary formations. However, the "protodolomite" initially precipitated is of low purity and low order, consisting of a mixture of calcium and magnesium carbonates. This requires repeated cycles of dissolution and precipitation to be converted into stoichiometrically highly ordered dolomite.

[0003] Under normal temperature and pressure laboratory conditions, it is relatively easy to precipitate non-stoichiometric magnesium-rich carbonates. In modern natural environments and ancient sedimentary formations, magnesium-rich carbonates such as high-magnesium calcite are widely distributed, but because their characteristics are not obvious, they have not received widespread attention and have not been linked to dolomitization. The latest research shows that dolomite is difficult to grow under natural environmental conditions, even in highly supersaturated solutions, and the reason is not hydrated Mg. 2+ The strong dehydration kinetic barrier of ions is not the primary barrier, but rather the initially precipitated cationic disordered surface of dolomite. When a dolomite layer grows on a disordered dolomite substrate, the atomic mismatch between the surface growth layer and the underlying disordered substrate generates strain energy as high as 15 kJ / mol. This high stress can inhibit further crystal growth. A weakly acidic, unsaturated solution with a low pH value preferentially dissolves these disordered regions, thereby increasing order during reprecipitation.

[0004] However, in the current existing technology, there is no method or device that can prepare dolomite by calcium-depleted magnesium-enriched recrystallization under laboratory conditions at normal temperature and pressure, which limits the in-depth study of the causes of dolomitization. Summary of the Invention

[0005] In view of the above analysis, the embodiments of the present invention aim to provide a method and apparatus for preparing calcium-depleted magnesium-enriched recrystallized dolomite, so as to solve one or more of the above problems existing in the prior art.

[0006] The object of the present invention is achieved like this:

[0007] On the one hand, a method for preparing calcium-depleted magnesium-rich recrystallized dolomite is provided, comprising:

[0008] Step 1: Prepare reaction solution 1. The Ca 2+ Mg 2+ 、Na+ The ion concentration is equal to the Ca in standard seawater 2 + Mg 2+ 、Na + Ion concentration value;

[0009] Step 2: Prepare reaction solution 2. CO3 in reaction solution 2 2- Ion concentration and Ca in reaction solution 1 2+ The ions are the same, Na in the reaction solution 2 + Ion concentration and Na in reaction solution 1 + Ion concentration is consistent;

[0010] Step 3, adding the configured basic reaction solution into the reactor;

[0011] Step 4: adding the prepared magnesium-rich carbonate rock seeds to the basic reaction solution in the reactor;

[0012] Step 5: Inject reaction solution 1 and reaction solution 2 into a reaction vessel through a peristaltic pump to react with a basic reaction solution added with magnesium-rich carbonate rock seeds; during the reaction, the pH value of the solution in the reaction vessel is adjusted by supplying gas sources of different components, and the pH is lowered and raised in a continuous alternating manner day and night, and a dolomite sample with a high magnesium-calcium ratio is obtained after 30-60 days.

[0013] Furthermore, in step 1, the reaction solution 1 is prepared according to the following steps:

[0014] Weigh the required weight of NaCl, CaCl2, and MgCl2 compound powders, add deionized water to a container to dissolve them, and add water to the preset volume. After stirring evenly, pour it into the pre-cleaned injection container one to complete the preparation of reaction solution one.

[0015] Furthermore, in step 2, the reaction solution 2 is prepared according to the following steps:

[0016] First, add 1 / 4 deionized water to a container, then add the required weight of NaCl powder and the remaining 3 / 4 deionized water in sequence, mix well, then add Na2CO3 powder, add water to the preset volume, stir evenly, and pour the prepared reaction solution 2 into the pre-cleaned injection container 2 to complete the preparation of reaction solution 2.

[0017] Furthermore, in step three, the basic reaction solution is a NaCl solution with a concentration of 0.45M.

[0018] Furthermore, in step 4, the steps of preparing magnesium-rich carbonate rock seeds are:

[0019] High-magnesium calcite or magnesium-containing limestone with uniform composition and structure and Mg / Ca ratio>5 is selected, crushed to 60-80 mesh, washed and dried to obtain the prepared magnesium-rich carbonate rock seeds.

[0020] Furthermore, in step five, the reaction solution 1 and the reaction solution 2 are injected into the reaction container via a peristaltic pump at a rate of 7 μl / min; the gas supply pressure of the gas source is 1-1.2 bar.

[0021] Furthermore, in step 5, the following gas supply method is used to continuously lower and raise the pH value day and night:

[0022] During the day, pure CO2 gas or a mixture of CO2 and N2 is continuously supplied to maintain the solution pH at 6-6.3, allowing CaCO3 to dissolve preferentially.

[0023] Pure N2 gas is continuously supplied at night to maintain the solution pH at 7.5-7.8, and MgCO3 with strong anti-dissolution ability continues to be enriched in the sediment.

[0024] Furthermore, in step 5, before continuously alternating between lowering and raising the pH value day and night, the process further includes:

[0025] At the initial stage of the reaction, air cleaned with a NaCl solution was continuously supplied to the reaction vessel for 5 consecutive days to stabilize the pH value of the solution at 8.1 to 8.4.

[0026] Furthermore, in step five, on the first day of the initial reaction, the first gas cylinder supplies cleaned air into the reaction vessel at a first flow rate v1; from the second day to the fifth day, the first gas cylinder supplies cleaned air into the reaction vessel at a second flow rate v2, v2 = (1.1-1.5)·v1.

[0027] On the other hand, a decalcified and magnesium-rich recrystallized dolomite preparation device applied to the above-mentioned decalcified and magnesium-rich recrystallized dolomite preparation method is also provided, including a reaction container, an injection container 1, an injection container 2, a first gas cylinder, a second gas cylinder and a third gas cylinder.

[0028] Furthermore, the reaction container serves as a reaction site for preparing dolomite and is pre-filled with a basic reaction solution; injection container one and injection container two are respectively connected to the reaction container through a liquid supply pipeline, injection container one is filled with reaction liquid one, and injection container two is filled with reaction liquid two, and a peristaltic pump is provided on the liquid supply pipeline, through which reaction liquid one and reaction liquid two are supplied into the reaction container to react with the basic reaction solution to generate a dolomite sample with a high magnesium-calcium ratio; the first gas cylinder, the second gas cylinder and the third gas cylinder are connected to the reaction container through a gas supply pipeline, and can independently provide the gas required for the reaction into the reaction container; wherein the first gas cylinder is a cleaning bottle, which is connected to the atmosphere, and the cleaning bottle is pre-filled with NaCl solution for cleaning the air supplied to the reaction container; the second gas cylinder is an N2 gas cylinder, which is filled with pure N2 gas at a certain pressure; the third gas cylinder is a CO2 gas cylinder, which is filled with pure CO2 gas at a certain pressure.

[0029] Furthermore, the gas supply pipeline includes three branch gas lines and one main gas line. The first gas cylinder, the second gas cylinder and the third gas cylinder are respectively connected to a branch gas line. The three branch gas lines are connected to the main gas line, and the main gas line is connected to the reaction container.

[0030] Furthermore, a valve is provided on each branch gas line, and a main valve is provided on the main gas line.

[0031] Furthermore, the decalcified magnesium-rich recrystallized dolomite preparation device also includes an air distribution mechanism, which has a disc and an air pipe. The disc is horizontally arranged in the reaction vessel, and the interior of the disc has an air storage cavity. The air pipe is arranged through the bottom wall of the reaction vessel, and the air storage cavity is connected to the main air path through the air pipe. The top surface and / or bottom surface of the disc are distributed with multiple air vents, and the air vents are connected to the air storage cavity.

[0032] Compared with the existing technology, the method and device for preparing calcium-depleted magnesium-rich recrystallized dolomite provided by the present invention realize the preparation of dolomite by calcium-depleted magnesium-rich recrystallization under normal temperature and pressure laboratory conditions, which has positive significance for in-depth research on the causes of dolomitization.

[0033] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of the present invention will be described in the following description, and some advantages will become apparent from the description or be learned through practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0035] Figure 1 This is an operational flow chart of the method for preparing calcium-depleted and magnesium-enriched recrystallized dolomite provided by the present invention;

[0036] Figure 2 This is a schematic structural diagram of the device for preparing calcium-removed and magnesium-rich recrystallized dolomite provided by the present invention;

[0037] Figure 3 A schematic diagram of the partial structure of a device for preparing calcium-depleted and magnesium-rich recrystallized dolomite provided by the present invention;

[0038] Figure 4 This is a schematic structural diagram of another device for preparing calcium-depleted and magnesium-enriched recrystallized dolomite provided by the present invention.

[0039] Reference numerals:

[0040] 10. Reaction vessel; 21. Injection vessel 1; 22. Injection vessel 2; 23. Liquid supply pipeline; 24. Peristaltic pump; 31. First gas cylinder; 32. Second gas cylinder; 33. Third gas cylinder; 34. Branch gas line; 35. Main gas line; 40. Sampling channel; 51. Disc; 511. Vent; 52. Air pipe; 53. Rotary joint; 54. Driven gear; 61. Motor; 62- Driving gear. DETAILED DESCRIPTION

[0041] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] To facilitate understanding of the embodiments of the present application, the following will be further explained with reference to specific embodiments in conjunction with the accompanying drawings. The embodiments do not constitute a limitation of the embodiments of the present application. In the accompanying drawings, the sizes and relative sizes of the components may be exaggerated for clarity and / or descriptive purposes. When the exemplary embodiments can be implemented differently, the specific process sequence may be performed in an order different from that described. For example, two consecutively described processes may be performed substantially simultaneously or in an order opposite to that described. In addition, the same reference numerals represent the same components.

[0043] The terms used herein are for the purpose of describing specific embodiments and are not intended to be restrictive. As used herein, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, the features, integral bodies, steps, operations, parts, assemblies and / or their groups stated are explained, but the presence or addition of one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups is not excluded. It should also be noted that, as used herein, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values and / or the values provided that will be recognized by those of ordinary skill in the art.

[0044] Example 1

[0045] The inventors have found that the pH value of the solution fluctuates frequently above and below the saturation of calcium magnesium carbonate (CaMg(CO3)2-CaCO3), and the dissolution-reprecipitation cycle of magnesium-rich carbonate triggered is a key factor in the precipitation and formation of dolomite in the laboratory and natural environment. This process occurs not only in the syn-sedimentary stage of magnesium-rich carbonate, but also after diagenesis. With magnesium-rich carbonate rock as the seed, when the pH value of the solution decreases, CaCO3 dissolves preferentially (decalcification), so that MgCO3 with strong anti-dissolution ability is enriched in the sediment (magnesium-rich), and dolomite is formed through "dissolution precipitation decalcification and magnesium-rich recrystallization". This process does not require the additional addition of external magnesium. However, there is no method and device in the prior art that can prepare dolomite by decalcification and magnesium-rich recrystallization under normal temperature and pressure laboratory conditions, which affects the in-depth study of the causes of dolomitization.

[0046] Based on this, a specific embodiment of the present invention discloses a method for preparing calcium-depleted magnesium-rich recrystallized dolomite, which is carried out under normal temperature and pressure laboratory conditions. The operation process is as follows: Figure 1 As shown, the preparation method includes steps 1 to 5, which are specifically as follows:

[0047] Step 1: Prepare reaction solution 1. The Ca 2+ Mg 2+ 、Na + The ion concentration is equal to the Ca in standard seawater 2 + Mg 2+ 、Na + Ion concentration value.

[0048] According to the Ca content in standard seawater 2+ Mg 2+ 、Na+ Ion concentration value, using deionized water and CaCl2, MgCl2, NaCl three compound powders to prepare the reaction solution 1, the Ca 2+ Mg 2+ 、Na + The ion concentration is equal to or approximately equal to the Ca in standard seawater 2+ Mg 2+ 、Na + The error of ion concentration value is no more than 5%. + The concentration is 0.45M, Ca 2+ The concentration was 10.5 mM, Mg 2+ The concentration is 54mM.

[0049] For example, the volume of the reaction solution 1 is 0.5 L, and the weights of the NaCl, CaCl2, and MgCl2 compound powders weighed to prepare the reaction solution 1 are as follows:

[0050] NaCl=0.45mol / L*0.5L*(23+35.5)g / mol=13.1625g;

[0051] CaCl2·2H2O=10mmol / L*0.5L*(40+71+36)g / mol / 1000=0.735g;

[0052] MgCl2=54mmol / L*0.5L*(24+71)g / mol / 1000=2.565g;

[0053] Prepare reaction solution 1 according to the following steps: weigh NaCl, CaCl2, and MgCl2 compound powders according to the above weights, add deionized water to a container to dissolve, and add water to a preset volume, such as 0.5 L. Stir evenly with a rotor and pour into the previously cleaned injection container 1 to complete the preparation of reaction solution 1.

[0054] Step 2: Prepare reaction solution 2. The volume of reaction solution 2 is equal to the volume of reaction solution 1. The CO3 in reaction solution 2 2- Ion concentration and Ca in reaction solution 1 2+ The ion concentration is consistent, and the Na + Ion concentration and Na in reaction solution 1 + The ion concentration is consistent.

[0055] For example, the volume of the reaction solution 2 is 0.5 L, according to CO3 2- With Ca 2+ The concentration of Na in the reaction solution 2 is consistent. + Ion concentration and Na in reaction solution 1 +The ion concentration is consistent, and the weight of the Na2CO3 and NaCl compound powders is:

[0056] Na2CO3=10mmol / L*0.5L*106g / mol / 1000=0.53g

[0057] NaCl=(0.45mol / L-10mmol / L / 1000*2)*0.5L*(23+35.5)g / mol=12.5775g.

[0058] Prepare reaction solution 2 according to the following steps: first add 1 / 4 deionized water to a container, then add the weighed NaCl powder and the remaining 3 / 4 deionized water in sequence, mix well, and then slowly add Na2CO3 powder. When adding Na2CO3 powder, stir while adding to prevent rapid precipitation. Finally, add water to the preset volume, such as 0.5L. After stirring evenly with a rotor, pour the prepared reaction solution 2 into the pre-cleaned injection container 2 to complete the preparation of reaction solution 2.

[0059] Step three, adding the configured basic reaction solution into the reactor.

[0060] For example, the basic reaction solution is a 0.45M NaCl solution with a volume of 0.5 L. The mass of NaCl powder required to prepare the basic reaction solution is:

[0061] NaCl=0.45mol / L*0.5L*(23+35.5)g / mol=13.1625g;

[0062] The weighed NaCl powder was dissolved in deionized water and stirred evenly with a rotor to obtain a basic reaction solution.

[0063] Step 4: prepare magnesium-rich carbonate rock seeds, and add the prepared magnesium-rich carbonate rock seeds to the basic reaction solution in the reactor.

[0064] Specifically, use a 500 ml reaction container to peel and weigh 1 g of magnesium-rich carbonate rock seeds, then peel it again and pour in the basic reaction solution prepared in step 3, add a rotor, and cover the reaction container with a container lid. Use a marker to draw a marking line along the upper liquid surface to prevent large liquid level fluctuations in subsequent experiments.

[0065] The steps of preparing magnesium-rich carbonate rock seeds are as follows: selecting high-magnesium calcite or magnesium-containing limestone with uniform composition and structure and Mg / Ca ratio>5, crushing it to 60-80 mesh, washing and drying it to obtain the prepared magnesium-rich carbonate rock seeds.

[0066] Step 5: Inject reaction solution 1 and reaction solution 2 into a reaction vessel through a peristaltic pump to react with the basic reaction solution added with magnesium-rich carbonate rock seeds; during the reaction, the pH value of the solution in the reaction vessel is adjusted by supplying gas sources of different components, and the pH value is adjusted by lowering and raising the pH value in a continuous alternating manner day and night, with an alternating interval of 12 hours. After 30-60 days, a dolomite sample with a high magnesium-calcium ratio is obtained.

[0067] Step 5 also includes: device connection and preliminary preparation steps, as follows:

[0068] Before injecting the prepared reaction solutions 1 and 2, turn off the switches on injection container 1 and injection container 2. Connect injection container 1 and injection container 2 to the silicone tube (inner diameter 0.38mm) on the peristaltic pump. After connection, turn on the switches on injection container 1, injection container 2, and the peristaltic pump to quickly exhaust! The gas source uses three gas cylinders, which are connected to the reaction containers via gas supply pipelines (such as silicone tubes).

[0069] In this embodiment, the three gas cylinders can independently supply different gas sources to the reaction vessel, or two or all three can simultaneously supply different gas sources to the reaction vessel. The first gas cylinder is a purge cylinder, connected to the atmosphere. The purge cylinder is pre-filled with a 0.1-0.2M NaCl solution. Air is purge-cleaned by bubbling with the NaCl solution in the purge cylinder before being supplied to the mixed reaction solution in the reaction vessel. The second gas cylinder is an N2 gas cylinder, and the third gas cylinder is a CO2 gas cylinder. Gas lines or valves on the gas cylinder ports allow for the separate supply of N2 or pure CO2 gas, or the simultaneous supply of a mixture of N2 and CO2.

[0070] In one optional embodiment, during the reaction process, reaction solution 1 and reaction solution 2 are injected into the reaction container through a peristaltic pump at a rate of 7 μl / min, with a flow rate of 10 ml per day; the gas supply pressure of the three gas cylinders is 1-1.2 bar, such as 1.1 bar.

[0071] At the initial stage of the reaction, air cleaned with NaCl solution is continuously supplied to the reaction vessel to stabilize the pH value of the solution at 8.1 to 8.4. Specifically, on the first day of the initial reaction, the first gas cylinder supplies cleaned air to the reaction vessel at a first flow rate v1, and the reaction is continued for 1 day; after 1 day of continuous reaction, from the second day to the fifth day, the first gas cylinder supplies cleaned air to the reaction vessel at a second flow rate v2, where v2 = (1.1-1.5)·v1. During this process, due to the entry of CO2 in the air, the pH value of the mixed reaction solution in the reaction vessel will decrease. After 5 consecutive days of reaction, the pH value of the mixed reaction solution in the reaction vessel is basically stabilized at 8.1 to 8.4, generating carbonate mineral precipitation (CaMg(CO3)2-CaCO3);

[0072] On the first day after 5 days of continuous reaction (7:00-19:00), that is, at 7:00 a.m. on the 6th day, the gas cylinder is directly switched to continuously supply pure CO2 gas or a mixture of CO2 and N2 during the day, with the proportion of CO2 in the mixture being not less than 90%, and the pressure P of the supplied gas being 1-1.2 bar, so that the pH value continues to decrease and is maintained at 6-6.3. When the pH value of the solution drops to this range, CaCO3 dissolves preferentially.

[0073] After 12 hours of reaction, the gas cylinder was switched at 19:00 on the 6th day, and pure N2 gas was continuously supplied at night (19:00-7:00) to increase the pH of the solution, so that the pH of the solution was basically maintained at 7.5-7.8, and MgCO3 with strong anti-dissolution ability continued to be enriched in the sediment.

[0074] Until 7:00 a.m. the next day, the supply of pure N2 gas is stopped, the gas cylinder is switched, and pure CO2 gas or a mixture of CO2 and N2 is continuously supplied during the day to lower the pH of the solution, and it drops again to 6-6.3; according to the above day and night alternation process, the day and night cycle reaction is repeated continuously for 30-60 days to obtain a dolomite sample with a high magnesium-calcium ratio.

[0075] The preparation principle of decalcified and magnesium-rich recrystallized dolomite is as follows: During the reaction process, when the pH of the solution decreases, the precipitated CaCO₃ preferentially dissolves (decalcifying), allowing the more resistant Mg-CO₃ to accumulate in the sediment (enriching magnesium), initiating the "decalcification and magnesium-rich recrystallization" process without the need for additional magnesium. During the day, pure CO₂ gas or a mixture of CO₂ and N₂ is continuously fed to lower the pH, initiating the "decalcification and magnesium-rich recrystallization" process. At night, pure N₂ gas is fed to raise the pH, causing carbonate minerals to precipitate and recrystallize. This repeated cycle, with periodic pH fluctuations, allows magnesium-rich carbonates to continuously "decalcify and recrystallize," ultimately forming dolomite with a high Mg / Ca ratio. This experimental method, characterized by frequent pH fluctuations and multiple cycles of carbonate dissolution and reprecipitation, can improve the order of the precipitated dolomite. In mixed growth zones of calcium-magnesium carbonates, calcium-rich domains, hydrated carbonate domains, and disordered domains preferentially dissolve. Once stronger Mg-CO₃ bonds form within the structure, they resist dissociation during dissolution, leading to magnesium enrichment in the carbonate. Under weakly acidic conditions, the preferential dissolution order of carbonate minerals is: aragonite → calcite → disordered dolomite → magnesite → ordered dolomite. High mol% MgCO₃ carbonate precursors are required, and nonequilibrium localized dissolution is precisely the process that preferentially removes low-Mg minerals. Weakly acidic, unsaturated solutions with low pH values preferentially dissolve these disordered domains, thereby increasing order during reprecipitation.

[0076] Step five also includes: collecting the prepared dolomite sample with a high magnesium-calcium ratio, as follows:

[0077] Place the entire reaction container (sealed container lid) in an ultrasonic cleaner for ultrasonic cleaning. Separate the dolomite sample and the reaction container by following the steps below: TM Place a 0.2μm cellulose nitrate filter membrane in a filtration device. Pour all the solution in the reaction vessel into the filtration device. Connect a suction pump to the bottom of the filtration device. Turn on the suction pump and increase the pressure knob to accelerate filtration. Be careful to rinse the sediment on the inner wall of the filtration device onto the filter membrane. Use alcohol for the final rinse to accelerate sample drying. Turn off the suction pump, return the pressure knob to zero, disassemble the filtration device, clean the upper part and set aside. Remove the filtered sample with tweezers and place it in an oven to dry overnight at 35°C. This completes the collection of the high magnesium-calcium ratio dolomite sample.

[0078] In one optional embodiment, LiCl is added to the prepared reaction solution 1 as a tracer. Subsequently, lithium isotope testing is performed on the prepared dolomite sample, and the relationship between lithium isotopes and pH is determined based on the test results. Of course, B(OH)3 can also be added to the reaction solution 1 as a tracer to study the relationship between B isotopes and pH, and the corresponding LiCl and B(OH)3 are also added to the prepared base reaction solution.

[0079] Step five also includes: regularly collecting liquid samples during the reaction process. If a rotor is used to stir the reaction mixture, the rotor stirring is stopped 30 minutes before sampling (switch off) to allow the particles in the solution to settle and facilitate the extraction of solution samples. After the samples are numbered, the pH value of each sample is measured separately. After the sampling is completed, the rotor switch is turned on, the knob is turned up, and the stirring is continued at a rotor speed of 120-150rpm. Optionally, solid particles and liquid samples can be collected once a week. By measuring the solution composition, Mg / Ca ratio, Mg, B, Li isotopes and pH value of the mixed reaction solution for each sampling, the changes in the particle composition and morphological structure of the prepared high magnesium-calcium ratio dolomite sample with electron microscopy over time can be used to help understand the formation and growth process of dolomite.

[0080] Compared with the existing technology, the method for preparing calcium-depleted magnesium-rich recrystallized dolomite provided in this embodiment is easy to operate and realizes the preparation of dolomite by calcium-depleted magnesium-rich recrystallization under laboratory conditions of normal temperature and pressure, which has positive significance for in-depth research on the causes of dolomitization.

[0081] Example 2

[0082] Another specific embodiment of the present invention is as follows Figures 2 to 4 As shown, a preparation device for calcium-removed magnesium-rich recrystallized dolomite is disclosed, comprising:

[0083] The reaction vessel 10 is used as a reaction site for preparing dolomite. The reaction vessel 10 is pre-filled with a basic reaction solution.

[0084] Injection container 1 21 and injection container 2 22 are each connected to the reaction container 10 via a liquid supply line 23. The liquid supply line 23 uses a silicone tube with an inner diameter of 0.38 mm. The injection container 1 21 contains reaction solution 1, and the injection container 2 22 contains reaction solution 2. A peristaltic pump 24 is provided on the liquid supply line 23. The peristaltic pump 24 supplies the reaction solution 1 and the reaction solution 2 into the reaction container 10 to react with the basic reaction solution to generate a dolomite sample with a high magnesium-calcium ratio. Switches are provided at the liquid outlets of the injection container 1 21 and the injection container 2 22.

[0085] The first gas cylinder 31, the second gas cylinder 32 and the third gas cylinder 33 are connected to the reaction container through a gas supply pipeline, and can independently provide the gas required for the reaction into the reaction container; among them, the first gas cylinder 31 is a cleaning cylinder connected to the atmosphere, and the cleaning cylinder is pre-filled with NaCl solution for cleaning the air supplied to the reaction container; the second gas cylinder 32 is an N2 gas cylinder, which is filled with pure N2 gas at a certain pressure; the third gas cylinder 33 is a CO2 gas cylinder, which is filled with pure CO2 gas at a certain pressure.

[0086] In this embodiment, the basic reaction solution is a NaCl solution with a concentration of 0.45M; the Ca 2+ Mg 2+ 、Na + The ion concentration is equal to the Ca in standard seawater 2+ Mg 2+ 、Na + Ion concentration value; CO3 in reaction solution 2 2- Ion concentration and Ca in reaction solution 1 2+ The ion concentration is consistent, and the Na + Ion concentration and Na in reaction solution 1 + The ion concentration is consistent.

[0087] In one optional embodiment, the gas supply pipeline includes three branch gas lines 34 and one main gas line 35. The first gas cylinder 31, the second gas cylinder 32, and the third gas cylinder 33 are each connected to a branch gas line 34. The three branch gas lines 34 are connected to the main gas line 35, and the main gas line 35 is connected to the reaction vessel. Furthermore, a valve is provided on each branch gas line 34, and a main valve can also be provided on the main gas line 35. The valves on the branch gas lines 34 allow the three gas cylinders to independently supply gas sources of different components to the reaction vessel, or two or three gas cylinders can simultaneously supply gas sources of different components to the reaction vessel, and the type of gas source to be supplied is selected according to specific needs.

[0088] In reaction vessel 10, multiple solutions are mixed, and the pH of the mixed solution is adjusted using multiple gases, triggering a dissolution-reprecipitation cycle of magnesium-rich carbonate, achieving calcium-removal and magnesium-rich recrystallization to produce dolomite. When cleaned air is continuously introduced through the first gas cylinder, the pH in reaction vessel 10 can be stabilized at 8.1-8.4, and carbonate minerals precipitate. When switching to pure CO2 gas or a mixture of CO2 and N2, the pH decreases, CaCO3 preferentially dissolves to remove calcium, and MgCO3 enriches magnesium, initiating the calcium-removal and magnesium-rich recrystallization process.

[0089] Preferably, the reaction container 10 is provided with a pH meter, and the pH value change of the mixed solution in the reaction container 10 is monitored in real time by the pH meter.

[0090] In one optional embodiment, a stirrer is provided within the reaction vessel 10 to stir the solution within the reaction vessel 10. For example, the stirrer includes a rotor and a drive unit that drives the rotor to rotate. The drive unit is located outside the reaction vessel 10, while the rotor is located within the reaction vessel 10. The drive unit drives the rotor to rotate to stir the solution. The drive unit and the rotor utilize an electromagnetic drive principle to rotate the rotor within the solution, thereby stirring the solution. This can be achieved using a magnetically driven stirrer known in the prior art.

[0091] In one optional embodiment, a gas distribution mechanism is provided in the reaction vessel 10, and the gas distribution mechanism includes a disc 51 and an air pipe 52. The disc 51 is horizontally arranged in the reaction vessel 10 and is near the lower middle portion. The disc 51 has a gas storage cavity inside, and the air pipe 52 is provided through the bottom wall of the reaction vessel 10. The gas storage cavity is connected to the main gas path 35 through the air pipe 52. The top surface and / or bottom surface of the disc 51 are uniformly distributed with a plurality of air vents 511, and the air vents 511 are connected to the gas storage cavity. By providing a plurality of dispersed air vents 511 on the disc 51, the gas can enter the reaction mixture more evenly, increasing the contact area and contact opportunity between the gas and the solution.

[0092] Specifically, the first gas cylinder 31, the second gas cylinder 32 and the third gas cylinder 33 are respectively connected to the main gas circuit 35 through a branch gas circuit 34. The main gas circuit 35 is connected to the lower gas inlet of the gas pipe 52. The upper gas outlet of the gas pipe 52 is connected to the center of the bottom surface of the disk 51 and is connected to the gas storage cavity. In this way, the three gas cylinders supply gas to the disk 51 of the gas distribution mechanism. The supplied gas enters the reaction mixed solution through the air vents 511 dispersedly arranged on the disk 51, increasing the contact area and contact opportunity between the gas and the solution.

[0093] In one optional embodiment, the disc 51 of the gas distribution mechanism is rotatably disposed within the reaction vessel 10. The rotation of the disc 51 allows the gas supplied through the vents 511 to contact the solution more evenly, avoiding localized gas accumulation or uneven distribution. This helps improve the uniformity of the reaction, allowing the reaction to proceed more evenly throughout the reaction vessel 10, reducing localized reaction variations caused by uneven gas distribution, thereby improving the efficiency and quality of the dolomite preparation reaction, making experimental results more stable and reliable, and providing better reaction conditions for dolomite preparation.

[0094] In one optional embodiment, the air pipe 52 is fixedly connected to the disc 51, and the two can rotate simultaneously, with the axis of the air pipe 52 coinciding with the axis of the disc 51. For example, the air outlet end of the air pipe 52 is fixedly connected to the center of the bottom wall of the disc 51 and communicates with the air storage cavity within the disc 51. The air pipe 52 is disposed through the center of the bottom wall of the reaction vessel 10, and the air inlet of the air pipe 52 is connected to the main air path 35. A rotary sealing structure is provided at the connection between the bottom wall of the reaction vessel 10 and the air pipe 52. The rotary sealing structure can achieve a seal at the connection between the outer wall of the air pipe 52 and the bottom wall of the reaction vessel 10, while also ensuring the rotation of the air pipe 52. The air inlet of the air pipe 52 is connected to the main air path 35 through a rotary joint 53. The rotary joint 53 is set on a support seat, which supports the air pipe 52. The rotary joint 53 can connect the main air path 35 and the air inlet of the air pipe 52, and can ensure the rotation of the air pipe 52; the air pipe 52 can rotate through the rotary joint 53 and the rotary sealing structure, thereby driving the disc 51 to rotate.

[0095] In the technical solution in which the turntable can rotate, the air pipe 52 can be manually rotated outside the reaction vessel 10 to achieve the rotation of the disc 51; or the air pipe 52 can be driven to rotate by an electric drive mechanism outside the reaction vessel 10, thereby achieving the rotation of the disc 51. Optionally, in the technical solution using an electric drive mechanism, the air distribution mechanism also includes an electric drive mechanism, which is configured to drive the air pipe 52 to rotate, thereby driving the disc 51 to rotate. Specifically, the electric drive mechanism includes a motor 61 and a driving gear 62 provided on the motor output shaft, the motor 61 is provided on a motor base (not shown in the figure), the driving gear 62 is engaged with a driven gear 54 fixed outside the air pipe 52, and the motor drives the air pipe 52 to rotate through the driving gear 62 and the driven gear 54, thereby achieving the rotation of the driving disc 51.

[0096] In one optional embodiment, a gas flow control valve is provided at the gas outlet of the gas pipe 52 to control the amount of gas entering the disc 51. The gas flow control valve can be used as known in the art.

[0097] Because the supplied gas has a certain pressure, liquid will not flow back through the vent hole during normal gas supply. To more reliably prevent liquid backflow, a one-way vent valve can be installed on the vent hole of the disc 51. In addition, a gas flow control valve can be installed at the outlet of the air pipe 52 to prevent liquid backflow.

[0098] Because the first gas cylinder is a purge cylinder and needs to be cleaned from the outside atmosphere before being supplied to the reaction vessel, it needs to be equipped with a vacuum assembly. The vacuum assembly includes an air inlet pipe and an air pump mounted on the inlet pipe. The air inlet end of the inlet pipe is located in the air, and the air outlet end of the inlet pipe is inserted below the liquid level of the NaCl solution in the first gas cylinder. The air pump is used to supply air into the NaCl solution, bubbling and cleaning it before entering the reaction vessel. The second gas cylinder is an N2 gas cylinder, and the third gas cylinder is a CO2 gas cylinder. These two gas cylinders already have a certain air pressure, so there is no need to set up an additional air pump. The pressure inside the cylinders can be used to provide the power for gas supply.

[0099] In one optional embodiment, a sampling channel 40 is further provided on the sidewall of the reaction vessel 10. The sampling channel 40 is located above the disk 51 and below the liquid level in the reaction vessel 10. A sampling valve is provided on the sampling channel 40, through which a liquid sample in the reaction vessel 10 is removed. When a sample is required, the sampling valve is opened to obtain a liquid sample from the reaction vessel 10. Stirring of the solution in the reaction vessel 10 is stopped 30 minutes before sampling to allow particulate matter in the solution to settle, facilitating the extraction of a sample.

[0100] In one of the optional embodiments, a flow meter and an electric valve are provided on the branch gas circuit 34, which can automatically switch the gas combination or separate gas supply in the first gas cylinder 31, the second gas cylinder 32 and the third gas cylinder 33 at regular intervals. The flow meter in the branch gas circuit 34 monitors the gas flow in real time, and the electric valve switches the gas supply combination or separate gas supply in a regular manner according to the set time (such as 12 hours). For example, during the day, it automatically switches to supplying pure CO2 gas alone or supplying a mixture of CO2 and N2 at the same time to lower the pH value of the solution in the reaction vessel 10 and start the calcium-removal and magnesium-enriched recrystallization process; at night, it automatically switches to supplying pure N2 gas to increase the pH value and promote the precipitation and recrystallization of carbonate minerals.

[0101] In one of the optional embodiments, a controller is further included, and the controller is connected to the acidity meter, flow meter, and electric valve using signal control. That is, the pH value measured by the acidity meter and the gas volume value measured by the flow meter can be transmitted to the controller in real time. The controller can control the type, composition, and supply duration of the supplied gas according to a pre-set program, thereby realizing feedback adjustment of the pH value of the solution, so that the pH is maintained within the set range during the reaction process (the pH value range is set differently during the day and at night), and the pH is prevented from being too low or too high.

[0102] Compared with the existing technology, the calcium-depleted magnesium-rich recrystallized dolomite preparation device provided in this embodiment has a simple structure and is easy to operate. It realizes the preparation of dolomite by calcium-depleted magnesium-rich recrystallization under normal temperature and pressure laboratory conditions, which has positive significance for in-depth research on the causes of dolomitization.

[0103] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of this application. It should be understood that the above description is only the specific implementation methods of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A method for preparing calcium-depleted magnesium-rich recrystallized dolomite, characterized in that: include: Step 1: Prepare reaction solution 1. The Ca 2+ Mg 2+ 、Na + The ion concentration is equal to the Ca in standard seawater 2+ Mg 2 + 、Na + Ion concentration value; Step 2: Prepare reaction solution 2. CO3 in reaction solution 2 2- Ion concentration and Ca in reaction solution 1 2+ The ions are the same, Na in the reaction solution 2 + Ion concentration and Na in reaction solution 1 + Ion concentration is consistent; Step 3: Add the prepared basic reaction solution into the reactor; the basic reaction solution is a NaCl solution with a concentration of 0.45M; Step 4: adding the prepared magnesium-rich carbonate rock seeds to the basic reaction solution in the reactor; Step 5: Injecting the reaction solution 1 and the reaction solution 2 into a reaction vessel through a peristaltic pump to react with the basic reaction solution added with magnesium-rich carbonate rock seeds; during the reaction, the pH value of the solution in the reaction vessel is adjusted by supplying a gas source of different components, and the pH is lowered and raised in a continuous alternating manner day and night to obtain a dolomite sample with a high magnesium-calcium ratio after 30-60 days; In step 5, the following gas supply method is used to continuously lower and raise the pH value day and night: During the day, pure CO2 gas or a mixture of CO2 and N2 is continuously supplied to maintain the solution pH at 6-6.3, allowing CaCO3 to dissolve preferentially. Pure N2 gas is continuously supplied at night to maintain the solution pH at 7.5-7.8, and MgCO3 with strong anti-dissolution ability continues to be enriched in the sediment.

2. The method for preparing calcium-free magnesium-rich recrystallized dolomite according to claim 1, wherein: In step 1, prepare reaction solution 1 according to the following steps: Weigh the required weight of NaCl, CaCl2, and MgCl2 compound powders, add deionized water to a container to dissolve them, and add water to the preset volume. After stirring evenly, pour it into the pre-cleaned injection container one to complete the preparation of reaction solution one.

3. The method for preparing calcium-free magnesium-rich recrystallized dolomite according to claim 1, wherein: In step 2, prepare reaction solution 2 according to the following steps: First, add 1 / 4 deionized water to a container, then add the required weight of NaCl powder and the remaining 3 / 4 deionized water in sequence, mix well, then add Na2CO3 powder, add water to the preset volume, stir evenly, and pour the prepared reaction solution 2 into the pre-cleaned injection container 2 to complete the preparation of reaction solution 2.

4. The method for preparing calcium-free magnesium-rich recrystallized dolomite according to claim 1, wherein: In step 4, the steps of preparing magnesium-rich carbonate rock seeds are: High-magnesium calcite or magnesium-containing limestone with uniform composition and structure and Mg / Ca ratio>5 is selected, crushed to 60-80 mesh, washed and dried to obtain the prepared magnesium-rich carbonate rock seeds.

5. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 1, wherein: In step 5, the reaction solution 1 and the reaction solution 2 are injected into the reaction container by a peristaltic pump at a rate of 7 μl / min; the gas supply pressure of the gas source is 1-1.2 bar.

6. The method for preparing calcium-free magnesium-rich recrystallized dolomite according to claim 1, wherein: In step 5, before continuously alternating between lowering and raising the pH value day and night, the following steps are further included: At the initial stage of the reaction, air cleaned with NaCl solution was continuously supplied to the reaction vessel for 5 consecutive days to stabilize the pH value of the solution at 8.1-8.4.

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