Preparation method and preparation device of calcium-removed magnesium-rich recrystallized dolomite

Abstract

The invention discloses a preparation method and a preparation device of calcium-removed magnesium-rich recrystallized dolomite. The method comprises the following steps: preparing a reaction liquid I, wherein the concentration of Ca < 2 + >, Mg < 2 + > and Na < + > ions in the reaction liquid I is equal to the concentration value of Ca < 2 + >, Mg < 2 + > and Na < + > ions in standard seawater; preparing a reaction solution II, wherein the concentration of CO3 < 2-> ions in the reaction solution II is consistent with that of Ca < 2 + > ions in the reaction solution I, and the concentration of Na < + > ions in the reaction solution II is consistent with that of Na < + > ions in the reaction solution I; adding the prepared basic reaction solution into a reactor; adding the prepared magnesium-rich carbonate rock seeds into the basic reaction solution in the reactor; and injecting the reaction liquid I and the reaction liquid II into a reaction container through a peristaltic pump, supplying gas sources with different components in the reaction process to adjust the pH value of the solution in the reaction container, performing pH reduction and pH increase adjustment in a day-night continuous alternating manner, and obtaining a dolomite sample with a high magnesium-calcium ratio after 30-60 days. According to the method, dolomite is prepared in a calcium-removing magnesium-rich recrystallization mode under the conditions of normal temperature and normal pressure in a laboratory.

Description

Technical Field

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

[0002] Under laboratory conditions at room temperature and pressure, it is difficult to synthesize stoichiometric raw dolomite, but under specific conditions such as microbial mediation and catalysis by negatively charged substances, raw dolomite can be precipitated in brine with a relatively high Mg:Ca ratio. In modern sediments and ancient sedimentary strata, there are also dolomite deposits of microbial and inorganic origin. However, the "raw dolomite" formed by the initial precipitation is of low purity and low order. It is a mixture of calcium-magnesium carbonates and needs to go through repeated dissolution-precipitation cycles before it can 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 strata, magnesium-rich carbonates such as high-magnesium calcite are widely distributed, but because of their insignificant characteristics, they have not received widespread attention and have not been associated with 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 the surface of the disordered cations that dolomite initially precipitates. When the dolomite layer grows on the disordered dolomite substrate, the strain energy generated by the atomic mismatch between the surface growth layer and the disordered substrate below is as high as 15kJ / mol. This high stress can inhibit the further growth of the crystal. The weakly acidic unsaturated solution with a low pH value will preferentially dissolve these disordered regions, thereby increasing the order during reprecipitation.

[0004] However, in the current prior art, there is no method or device that can prepare dolomite by calcium-removal and 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 a device for preparing calcium-removed magnesium-rich 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 in that:

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

[0008] Step 1: Prepare reaction solution 1. The Ca in reaction solution 1 2+ Mg 2+ 、Na+ The ion concentration is equal to 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 reaction solution 2 + Ion concentration and Na in reaction solution 1 + The 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 into the basic reaction solution in the reactor;

[0012] Step 5, injecting reaction solution 1 and reaction solution 2 into a reaction container through a peristaltic pump, and reacting with the basic reaction solution added with magnesium-rich carbonate rock seeds; during the reaction, the pH value of the solution in the reaction container 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, and add water to a preset volume. After stirring evenly, pour into a previously cleaned injection container 1 to complete the preparation of reaction solution 1.

[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 previously 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] Further, 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 by the peristaltic pump at a speed of 7 μl / min; and 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 alternately lower and raise the pH during the 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, and CaCO3 is preferentially dissolved;

[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 the pH value and raising the pH value during the day and night, the step further includes:

[0025] In 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 container at a first flow rate v1; from the second day to the fifth day, the first gas cylinder supplies cleaned air into the reaction container 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 one, an injection container two, a first gas cylinder, a second gas cylinder and a third gas cylinder.

[0028] Furthermore, the reaction container is used 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 arranged on the liquid supply pipeline, and reaction liquid one and reaction liquid two are supplied into the reaction container by the peristaltic pump 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 the 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 into the reaction container; the second gas cylinder is an N2 gas cylinder, which is filled with pure N2 gas with a certain pressure; the third gas cylinder is a CO2 gas cylinder, which is filled with pure CO2 gas with 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 and 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 evenly distributed with a plurality of air vents, and the air vents are connected to the air storage cavity.

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

[0033] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the 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 The operation flow chart of the method for preparing calcium-removed and magnesium-rich recrystallized dolomite provided by the present invention;

[0036] Figure 2 A schematic diagram of the structure of a 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 preparation device for calcium-removed and magnesium-rich recrystallized dolomite provided by the present invention;

[0038] Figure 4 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 container; 21. Injection container 1; 22. Injection container 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. Air vent; 52. Air pipe; 53. Rotary joint; 54. Driven gear; 61. Motor; 62- Driving gear. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0042] To facilitate the understanding of the embodiments of the present application, the following will be further explained with reference to the accompanying drawings, and the embodiments do not constitute a limitation on 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 a different order than described. For example, two continuously described processes may be performed substantially simultaneously or in an order opposite to the described order. In addition, the same reference numerals represent the same components.

[0043] The terms used here are for the purpose of describing specific embodiments, and are not intended to be restrictive. As used here, 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, it is explained that there are stated features, integral bodies, steps, operations, parts, assemblies and / or their groups, but it is not excluded that there are or add one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups. It should also be noted that, as used here, 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 frequently fluctuates above and below the saturation of calcium magnesium carbonate (CaMg(CO3)2-CaCO3), and the dissolution-reprecipitation cycle of magnesium-rich carbonates triggered is a key factor in the precipitation and formation of dolomite in the laboratory and natural environment. This process not only occurs in the syn-sedimentation stage of magnesium-rich carbonates, but can also occur after diagenesis. With magnesium-rich carbonate rock as the seed, when the pH value of the solution decreases, CaCO3 preferentially dissolves (decalcifies), allowing MgCO3 with strong anti-dissolution ability to be 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 laboratory conditions at normal temperature and pressure, 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-removed 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 in reaction solution 1 2+ Mg 2+ 、Na + The ion concentration is equal to Ca in standard seawater 2 + Mg 2+ 、Na + Ion concentration value.

[0048] According to the standard seawater Ca 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 less 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 one 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 a previously cleaned injection container one to complete the preparation of reaction solution one.

[0054] Step 2: Prepare reaction solution 2, the volume of which is equal to that of reaction solution 1; 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] Exemplarily, the volume of the reaction solution 2 is 0.5 L, according to CO3 2- With Ca 2+ The concentration of Na in 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 a preset volume, such as 0.5L. After stirring evenly with a rotor, pour the prepared reaction solution 2 into the previously 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] Exemplarily, the basic reaction solution is a NaCl solution with a concentration of 0.45M and a volume of 0.5L. 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 into 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 seeds, then peel and pour in the basic reaction solution prepared in step 3, add a rotor, and cover the reaction container with a container cover. Use a marker to draw a mark 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, injecting reaction solution 1 and reaction solution 2 into a reaction container through a peristaltic pump, and reacting with the basic reaction solution added with magnesium-rich carbonate rock seeds; during the reaction, the pH value of the solution in the reaction container 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, and a dolomite sample with a high magnesium-calcium ratio is obtained after 30-60 days.

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

[0068] Before injecting the prepared reaction liquid 1 and reaction liquid 2, first turn off the switches on injection container 1 and injection container 2, and connect injection container 1 and injection container 2 to the silicone tube (inner diameter 0.38mm) on the peristaltic pump respectively. After connection, turn on the switches on injection container 1 and injection container 2 and the peristaltic pump switch, and exhaust quickly! The gas source adopts three gas cylinders to supply gas, and the three gas cylinders are connected to the reaction container through the gas supply pipeline (such as silicone tube).

[0069] In this embodiment, the three gas cylinders can each independently supply gas sources of different components to the reaction container, or two or three can simultaneously supply gas sources of different components to the reaction container. Among them, the first gas cylinder is a cleaning bottle, which is connected to the atmosphere. The cleaning bottle is pre-filled with a NaCl solution with a concentration of 0.1-0.2M. The air is cleaned by bubbling with the NaCl solution in the cleaning bottle and then supplied to the mixed reaction solution in the reaction container; the second gas cylinder is an N2 gas cylinder, and the third gas cylinder is a CO2 gas cylinder. Through the gas pipeline or the valve on the gas cylinder mouth, N2 or pure CO2 gas can be supplied separately, or a mixture of N2 and CO2 can be supplied simultaneously.

[0070] In one of the optional embodiments, during the reaction, reaction solution 1 and reaction solution 2 are injected into the reaction container via 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 by NaCl solution is continuously supplied to the reaction container 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 container at a first flow rate v1, and the reaction continues 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 container at a second flow rate v2, v2 = (1.1-1.5) · v1. During this process, due to the entry of CO2 in the air, the pH of the mixed reaction solution in the reaction container will decrease. After 5 consecutive days of reaction, the pH value of the mixed reaction solution in the reaction container is basically stabilized at 8.1 to 8.4, and carbonate mineral precipitation (CaMg(CO3)2-CaCO3) is generated;

[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 drop 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 to 6-6.3 again; 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 value of the solution decreases, the precipitated CaCO3 is preferentially dissolved (decalcified), so that the Mg-CO3 with strong anti-dissolution ability is enriched in the sediment (magnesium-rich), and the "decalcified and magnesium-rich recrystallization" process is started, and no additional addition of external magnesium is required; during the day, pure CO2 gas or a mixture of CO2 and N2 is continuously supplied to lower the pH and start the "decalcified and magnesium-rich recrystallization" process, and at night, pure N2 gas is supplied to increase the pH, and carbonate minerals are precipitated and recrystallized. After repeated cycles, the pH value changes periodically, and the magnesium-rich carbonate is continuously "decalcified and magnesium-rich recrystallized", and finally a high Mg / Ca ratio dolomite is formed. The experimental method of frequent pH fluctuations and multiple cycles of carbonate dissolution-reprecipitation can improve the order of precipitated dolomite. In the mixed growth zone of calcium-magnesium carbonate, calcium-rich domains, hydrated carbonate domains and disordered domains are preferentially dissolved; once stronger Mg-CO3 bonds are formed in the structure, they will resist dissociation during dissolution, resulting in magnesium enrichment in the carbonate. The preferential dissolution order of carbonate minerals under weakly acidic conditions is: aragonite → calcite → disordered dolomite → magnesite → ordered dolomite. High mol% MgCO3 carbonate precursors are required, and non-equilibrium local dissolution is the process of preferentially removing low-magnesium minerals. Weakly acidic unsaturated solutions with lower pH values ​​preferentially dissolve these disordered regions, thereby increasing order during reprecipitation.

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

[0077] Place the reaction container (sealed container lid) in an ultrasonic cleaner and perform ultrasonic cleaning. Then, separate the dolomite sample from the reaction container in the following steps: TM A 0.2 μm cellulose nitrate filter membrane is placed in the filter device, and all the solutions in the reaction container are poured into the filter device. The lower part of the filter device is connected to a suction pump, and the suction pump is turned on, and the pressure knob is increased to accelerate the filtration. Pay attention to flushing the sediment on the inner wall of the filter device onto the filter membrane. The last rinse is done with alcohol to accelerate the drying of the sample. Turn off the suction pump, return the pressure knob to zero, separate and disassemble the filter device, clean the upper part and set it aside for later use, remove the filtered sample with tweezers, put it in an oven, and dry it overnight at 35°C to complete the collection of dolomite samples with a high magnesium-calcium ratio.

[0078] In one optional embodiment, LiCl is added to the prepared reaction solution 1 as a tracer, and then the prepared dolomite sample is subjected to a lithium isotope test, and the relationship between the lithium isotope and the pH is obtained according to 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 the B isotope and the pH, and the corresponding LiCl and B(OH)3 are also added to the prepared basic reaction solution.

[0079] Step five also includes: regularly collecting liquid samples during the reaction process. If a rotor is used to stir the reaction mixed solution, 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 sampling number is determined, the pH value of each sample is measured separately. After the sampling is completed, turn on the rotor switch, turn up the knob, continue stirring, and the rotor speed (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 over time can also be observed by electron microscopy, which helps to understand the formation and growth process of dolomite.

[0080] Compared with the prior art, 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 at normal temperature and pressure, which has positive significance for the in-depth study of 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, and the reaction vessel 10 is pre-filled with a basic reaction solution;

[0084] The injection container 1 21 and the injection container 2 22 are connected to the reaction container 10 through a liquid supply pipeline 23, respectively. The liquid supply pipeline 23 adopts a silicone tube with an inner diameter of 0.38 mm. The injection container 1 21 is filled with a reaction liquid 1, and the injection container 2 22 is filled with a reaction liquid 2. A peristaltic pump 24 is provided on the liquid supply pipeline 23. The reaction liquid 1 and the reaction liquid 2 are supplied to the reaction container 10 through the peristaltic pump 24 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; wherein the first gas cylinder 31 is a cleaning bottle connected to the atmosphere, and the cleaning bottle is pre-filled with NaCl solution for cleaning the air supplied into the reaction container; the second gas cylinder 32 is an N2 gas cylinder, which is filled with pure N2 gas of a certain pressure; the third gas cylinder 33 is a CO2 gas cylinder, which is filled with pure CO2 gas of a certain pressure.

[0086] In this embodiment, the basic reaction solution is a NaCl solution with a concentration of 0.45 M; the Ca 2+ Mg 2+ 、Na + The ion concentration is equal to 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 a main gas line 35. The first gas cylinder 31, the second gas cylinder 32 and the third gas cylinder 33 are respectively 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 container. 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 container, or two or three gas cylinders can simultaneously supply gas sources of different components to the reaction container, and the type of gas source supplied is selected according to specific needs.

[0088] In the reaction vessel 10, multiple solutions are mixed, and multiple gases are used to adjust the pH value of the mixed solution, triggering a dissolution-reprecipitation cycle of magnesium-rich carbonate, and realizing calcium-removal and magnesium-rich recrystallization to prepare dolomite. When the cleaned air is continuously introduced through the first gas cylinder, the pH in the reaction vessel 10 can be stabilized at 8.1-8.4, and carbonate minerals are precipitated; when switching to pure CO2 gas or a mixture of CO2 and N2, the pH decreases, CaCO3 is preferentially dissolved to remove calcium, and MgCO3 is enriched to enrich magnesium, starting the calcium-removal and magnesium-rich recrystallization process.

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

[0090] In one optional embodiment, a stirrer is provided in the reaction vessel 10, and the solution in the reaction vessel 10 is stirred by the stirrer. For example, the stirrer includes a rotor and a driving part for driving the rotor to rotate, the driving part is outside the reaction vessel 10, and the rotor is inside the reaction vessel 10, and the driving part drives the rotor to rotate to achieve solution stirring. The driving part and the rotor adopt the electromagnetic driving principle to make the rotor rotate in the solution, thereby achieving stirring of the solution. This can be achieved by using a magnetically driven stirrer 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 has a disc 51 and an air pipe 52. The disc 51 is horizontally arranged in the reaction vessel 10 and is close to the middle and lower position. The disc 51 has a gas storage cavity inside, and the air pipe 52 is arranged to penetrate 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 the bottom surface of the disc 51 are evenly distributed with a plurality of vents 511, and the vents 511 are connected to the gas storage cavity. By providing a plurality of dispersed vents 511 on the disc 51, the gas can enter the reaction mixed solution 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, and 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, thereby realizing the three gas cylinders supplying gas to the disk 51 of the gas distribution mechanism, and the supplied gas enters the reaction mixed solution through the air vents 511 dispersedly arranged on the disk 51, thereby increasing the contact area and contact opportunity between the gas and the solution.

[0093] In one of the optional embodiments, the disc 51 of the gas distribution mechanism is rotatably disposed in the reaction vessel 10. The rotation of the disc 51 allows the gas supplied from the vent 511 to contact the solution more evenly, avoiding the problem of local gas aggregation or uneven distribution, which helps to improve the uniformity of the reaction, allowing the reaction to proceed more evenly in the entire reaction vessel 10, reducing local reaction differences caused by uneven gas distribution, thereby improving the efficiency and quality of the dolomite preparation reaction, making the 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, and the axis of the air pipe 52 coincides with the axis of the disc 51. Exemplarily, 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 gas storage cavity in the disc 51. The air pipe 52 is arranged at 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, and the rotary sealing structure can achieve the sealing of the connection between the outer wall of the air pipe 52 and the bottom wall of the reaction vessel 10, and can also ensure 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 arranged on a support seat. The support seat 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 rotating 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 rotated manually outside the reaction container 10 to realize the rotation of the disc 51; or the air pipe 52 can be driven to rotate by an electric drive mechanism outside the reaction container 10, thereby realizing the rotation of the disc 51. Optionally, in the technical solution using the electric drive mechanism, the air distribution mechanism also includes an electric drive mechanism, and the electric drive mechanism 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 output shaft of the motor, the motor 61 is provided on a motor seat (not shown in the figure), the driving gear 62 is meshed with a driven gear 54 fixedly provided 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 realizing 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, and the gas flow control valve is used to control the amount of gas entering the inside of the disc 51. The gas flow control valve in the prior art can be used.

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

[0098] Since the first gas cylinder is a cleaning cylinder, it is necessary to clean the outside atmosphere before supplying it to the reaction container. The first gas cylinder needs to be equipped with a vacuum assembly, which includes an air inlet pipe and an air pump arranged on the air inlet pipe. The air inlet end of the air inlet pipe is located in the air, and the air outlet end of the air 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, and the air enters the reaction container after bubbling and cleaning. The second gas cylinder is an N2 gas cylinder, and the third gas cylinder is a CO2 gas cylinder. These two gas cylinders have a certain air pressure, so there is no need to set up an additional air pump, and the pressure in the bottle can be used to achieve the power of gas supply.

[0099] In one optional embodiment, a sampling channel 40 is further provided on the side wall of the reaction container 10. The sampling channel 40 is located above the disc 51 and below the liquid level in the reaction container 10. A sampling valve is provided on the sampling channel 40, and a liquid sample in the reaction container 10 is taken out through the sampling channel 40 and the sampling valve. When it is necessary to collect a sample, the sampling valve is opened to obtain a liquid sample from the reaction container 10. The stirring of the solution in the reaction container 10 is stopped 30 minutes before sampling to allow the particles in the solution to settle, so as to facilitate the extraction of solution samples.

[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 a fixed time. 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 fixed 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, lowering the pH value of the solution in the reaction vessel 10 and starting the calcium-removing magnesium-enriching 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 by signal control. That is to say, 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 preset program, thereby achieving feedback adjustment of the pH value of the solution, so that the pH is maintained within the set range during the reaction (the pH value range is differentiated during the day and at night) to avoid the pH being too low or too high.

[0102] Compared with the prior art, the decalcified and 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 decalcified and magnesium-rich recrystallization under normal temperature and pressure laboratory conditions, which has positive significance for the in-depth study of the causes of dolomitization.

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

Claims

1. A method for preparing calcium-removed magnesium-rich recrystallized dolomite, characterized in that: include: Step 1: Prepare reaction solution 1. The Ca in reaction solution 1 2+ Mg 2+ 、Na + The ion concentration is equal to 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 reaction solution 2 + Ion concentration and Na in reaction solution 1 + The ion concentration is consistent; Step 3, adding the configured basic reaction solution into the reactor; Step 4, adding the prepared magnesium-rich carbonate rock seeds into the basic reaction solution in the reactor; Step 5, injecting reaction solution 1 and reaction solution 2 into a reaction container through a peristaltic pump, and reacting with the basic reaction solution added with magnesium-rich carbonate rock seeds; during the reaction, the pH value of the solution in the reaction container 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.

2. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 1, characterized in that: 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, and add water to a preset volume. After stirring evenly, pour into a previously cleaned injection container 1 to complete the preparation of reaction solution 1.

3. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 1, characterized in that: 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 previously cleaned injection container 2 to complete the preparation of reaction solution 2.

4. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 1, characterized in that: In step 3, the basic reaction solution is a NaCl solution with a concentration of 0.45M.

5. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 1, characterized in that: 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.

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

7. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 1, characterized in that: In step 5, the following gas supply method is used to continuously alternately lower and raise the pH during the 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, and CaCO3 is preferentially dissolved; 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.

8. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 7, characterized in that: In step 5, before continuously alternating between lowering pH and raising pH during the day and night, the step further includes: In 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.

9. The method for preparing calcium-free and magnesium-rich recrystallized dolomite according to claim 8, characterized in that: In step five, on the first day of the initial reaction, the first gas cylinder supplies cleaned air into the reaction container at a first flow rate v1; from the second day to the fifth day, the first gas cylinder supplies cleaned air into the reaction container at a second flow rate v2, v2 = (1.1-1.5)·v1.

10. A device for preparing calcium-free and magnesium-rich recrystallized dolomite applied to the method for preparing calcium-free and magnesium-rich recrystallized dolomite according to any one of claims 1 to 9, characterized in that: It includes a reaction container 10, an injection container 1, an injection container 2, a first gas cylinder, a second gas cylinder and a third gas cylinder.

Images