CN113200560B - Process method for circularly preparing nano calcium carbonate - Google Patents
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Abstract
The invention relates to the technical field of inorganic synthesis, and discloses a process method for circularly preparing nano calcium carbonate, which adopts limestone as a raw material and acetic acid solution as a solvent, wherein the limestone and the acetic acid solution react to prepare calcium acetate solution and carbon dioxide gas, the prepared calcium acetate solution and potassium bicarbonate solution synthesize the nano calcium carbonate, the solution after liquid-solid separation is potassium acetate solution, the solution is extracted with acetic acid by using an organic phase prepared by high-boiling organic amine under the condition of introducing carbon dioxide, raffinate is potassium bicarbonate solution, is used for synthesis after concentration, and the organic phase is evaporated under negative pressure to obtain acetic acid solution and regenerate the organic phase; the method basically recycles other substances except limestone, consumes little energy, and greatly reduces the energy consumption of concentrating potassium bicarbonate and evaporating acetic acid compared with the traditional synthesis method, so the method realizes the production of the nano calcium carbonate under the production conditions of low energy consumption and low consumption, simultaneously has low raw material cost and low overall process cost, and realizes the green and environment-friendly production of the nano calcium carbonate.
Description
Technical Field
The invention relates to the technical field of inorganic synthesis, in particular to a process method for circularly preparing nano calcium carbonate.
Background
The nano calcium carbonate is also called as superfine calcium carbonate, is a novel superfine solid inorganic chemical material developed in the 80 th of the 20 th century, has the characteristics of environmental protection, low price, no toxicity, outstanding functionality and the like, is widely used in the industries of plastics, rubber, printing ink, paper making and the like, and is a novel superfine powder material developed in the 80 th of the 20 th century. The nano calcium carbonate has many excellent performances, is related to chemical characteristics of the nano calcium carbonate, and is closely related to a preparation method and a microstructure of the nano calcium carbonate, and two process methods, namely a carbonization method and a calcium salt synthesis method, are mainly used for producing the superfine calcium carbonate at present. The carbonization method is to atomize and carbonize calcium hydroxide emulsion in a carbonization tank by a high-pressure injection method, and dry a filter cake after liquid-solid separation to prepare the superfine calcium carbonate, and the method has the advantages of simple process, low cost and no waste water, and has the defect that the purity and the grain diameter of the product depend on the purity and the grain diameter of the calcium hydroxide, so that the high-purity superfine product cannot be prepared; the calcium salt synthesis method is to make calcium chloride and ammonium carbonate into solutions respectively, then mix them and precipitate them to obtain superfine calcium carbonate filter cake, then dry them to obtain calcium carbonate product, and evaporate waste water to obtain ammonium chloride as by-product. Therefore, a process is needed, which can obtain calcium carbonate with high purity and small particle size, and has low process cost and easy control.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a process method for circularly preparing nano calcium carbonate.
In order to solve the technical problem, the invention is solved by the following technical scheme:
a process method for circularly preparing nano calcium carbonate comprises the following steps:
a) Preparing a refined calcium acetate solution;
b) Preparing a potassium bicarbonate solution; the potassium bicarbonate has high solubility, is not easy to crystallize and separate out in the solution, and can reduce the evaporation capacity of the solution;
c) Carrying out synthetic reaction on the refined calcium acetate solution obtained in the step A and the potassium bicarbonate solution obtained in the step B at normal temperature;
d) C, inputting the mixed solution obtained in the step C into a sealed container, stirring, continuing to perform synthetic reaction, collecting carbon dioxide gas generated by the reaction, and filtering the mixed solution after the reaction is completed to respectively obtain filtrate and filter cakes;
e) D, evaporating and concentrating the filtrate obtained in the step D to obtain a potassium acetate solution, and washing and drying the filter cake obtained in the step D to obtain nano calcium carbonate; the obtained nano calcium carbonate is spherical, the particle size is less than 80 nanometers, and the nano calcium carbonate is mainly realized by controlling the concentration of potassium bicarbonate (less than 3mol per liter), the concentration of calcium acetate solution (less than 1.5 mol per liter), the reaction time (the retention time in a pipeline reactor is less than 20 seconds) and the reaction temperature (less than 40 ℃), so that the nano calcium carbonate with good quality, high purity and small particle size is obtained.
F) Preparing an extracting agent, wherein the extracting agent is tri-n-octylamine, n-octanol and No. 260 solvent oil respectively, adding the potassium acetate solution obtained in the step E into a three-phase extractor, introducing the carbon dioxide gas collected in the steps A and D into the three-phase extractor in the three-phase extractor while stirring until the gas pressure is stable, and clarifying and separating to obtain an upper oil phase and a lower water phase after stirring; the stable gas pressure indicates that the carbon dioxide gas is not dissolved any more and the extraction is basically balanced; the n-octanol and the No. 260 solvent oil mainly have the effects of reducing the specific gravity and viscosity of the extracting agent, facilitating oil-water separation and preventing emulsification;
g) The water phase obtained in the step F is a potassium bicarbonate solution, and the potassium bicarbonate solution returns to the step B to be used as the prepared potassium bicarbonate solution for recycling; f, adding the oil phase obtained in the step F into an evaporation tank, evaporating and removing vinegar under the conditions that the pressure is-0.2 to-0.3 MPa and the temperature is 70 to 90 ℃, cooling and absorbing evaporated acetic acid steam with water to obtain an acetic acid solution, and returning the acetic acid solution to the step A to be used as a raw material for preparing the refined calcium acetate solution for recycling; and D, taking the residual oil phase in the evaporating tank as an extracting agent, cooling, and returning to the step F to be used as the extracting agent for recycling.
Preferably, the method for preparing the refined calcium acetate solution in the step A comprises the following steps: adding an acetic acid solution into a container filled with limestone, reacting the acetic acid solution with the limestone to generate a mixture of calcium acetate and acetic acid until the pH value of the solution is 4-5, wherein as the acetic acid is consumed, acid radicals are combined with carbonate radicals in the limestone to generate carbon dioxide gas, the acidity of the mixture is reduced, the pH value is gradually increased along with the reaction, and the generated carbon dioxide gas is collected for the step F; adding calcium hydroxide into a solution with the pH value of 4 to 5, stirring the solution at the same time, filtering the solution when the pH value of the solution is 10 to 12 to obtain a filtrate which is a refined calcium acetate solution, and collecting filter residues. The calcium hydroxide can react with redundant acetic acid to generate calcium acetate and water, the pH value of the solution is adjusted to be alkaline, the acetic acid in the mixed liquid is ensured to fully react, and magnesium ions and other heavy metal ions in the solution are hydrolyzed and removed. The limestone contains a certain amount of magnesium carbonate and a small amount of alumina besides the main component of calcium carbonate, magnesium ions generated by the magnesium carbonate and acetic acid and other heavy metal ions can generate hydroxide precipitates with hydroxide ions in an alkaline solution and are removed when the calcium acetate solution is filtered, so that the calcium acetate solution is refined.
Preferably, the concentration of the acetic acid solution is 0.8 to 2mol/L, preferably 1.25mol/L, and each cubic meter of the acetic acid solution is reacted with 0.2 to 0.4t of limestone, preferably 0.052 to 0.079t of limestone.
Preferably, the preparation method of the potassium bicarbonate solution in the step B comprises the following steps: adding potassium bicarbonate into water, wherein the concentration of the potassium bicarbonate in the solution is 2 to 3mol/L, and preferably 2.5mol/L. The relative molecular mass of the potassium bicarbonate is 100, and the concentration of the potassium bicarbonate in the solution is about 2 to about 3mol/m 3 The potassium bicarbonate is high-purity potassium bicarbonate, and the aim is to improve the purity of calcium carbonate produced subsequently.
Preferably, the synthesis reaction in step C is carried out by feeding the purified calcium acetate solution and the potassium bicarbonate solution into a pipeline reactor, and the flow rate ratio of the calcium acetate solution to the potassium bicarbonate solution is 1.
Preferably, in the step D, after the synthesis reaction in the sealed container is completed, a sodium carbonate solution is added to the mixed solution to detect whether the calcium acetate completely reacts, and a calcium chloride solution is added to detect whether the potassium bicarbonate completely reacts. If excessive potassium bicarbonate is added in the pre-reaction, the completion of the reaction can be checked without adding a sodium carbonate solution and a calcium chloride solution, because the excessive potassium bicarbonate in the solution does not influence the subsequent processes.
Preferably, the volume ratio of the tri-n-octylamine, the n-octanol and the No. 260 solvent oil in the extracting agent in the step F is 1:2.5:3.5, introducing carbon dioxide gas collected from the carbon dioxide in the step A and the step D into the bottom of the extractor by using a gas pump.
Synthesizing nano calcium carbonate by using a calcium acetate solution and a potassium bicarbonate solution, extracting acetic acid by using an organic phase prepared by organic amine with a high boiling point under the condition of introducing carbon dioxide in the solution, concentrating a raffinate, namely the potassium bicarbonate solution, using the concentrated raffinate for synthesis, evaporating the organic phase under negative pressure to obtain an acetic acid solution, and regenerating the organic phase. Tri-n-octylamine is organic amine and has the characteristic of leading reaction with substances with strong acidity and large molecular weight.
The 260# solvent oil is named as wet extraction oil and 260# mine solvent oil/sulfonated kerosene, and features uniform and slow evaporation speed, less aromatic hydrocarbon content, low toxicity and high safety. Small smell, pure quality, no residue after evaporation, and is not easy to be oxidized by heating. The No. 260 solvent oil is widely applied to rare earth and nonferrous metal extraction diluents, electronic, metal and medicine cleaning agents, non-aqueous electroplating solvents, anhydrous cleaning agents, polishing agents and the like.
Preferably, the volume of the acetic acid solution used for preparing the refined calcium acetate solution in the step A is 4 parts by volume, the volumes of the refined calcium acetate solution and the potassium bicarbonate solution in the step C are 4 parts by volume and 2-8 parts by volume respectively, the potassium acetate solution obtained by the concentration in the step E is 4-6 parts by volume, the total amount of the extracting agent used in the step F is 20 parts by volume, and the capacity of the three-phase extractor is at least 30 parts by volume; and G, absorbing 3 parts by volume of water for absorbing the acetic acid vapor to obtain 3.5-4 parts by volume of acetic acid solution.
Preferably, the filter cake is washed twice at least, the total amount of water is 4 parts by volume, the nano calcium carbonate is obtained by drying and packaging after washing, and the filtrate filtered in the washing process is collected for later use. After the filter cake is washed at least twice, potassium acetate and a very small amount of calcium acetate or potassium hydrogen acetate remain in the filtrate.
Preferably, the water used to absorb the acetic acid vapor in step G is the filtrate of the washed filter cake filtered off during the washing process.
Due to the adoption of the technical scheme, the invention has the remarkable technical effects that: the method adopts limestone as a raw material and acetic acid solution as a solvent, the limestone and the acetic acid solution react to prepare calcium acetate solution and carbon dioxide gas, the prepared calcium acetate solution and potassium bicarbonate solution synthesize nano calcium carbonate, the obtained nano calcium carbonate has high purity, small particle size and good product quality, the solution after liquid-solid separation is potassium acetate solution, the solution is extracted with acetic acid by using an organic phase prepared by organic amine with high boiling point under the condition of introducing carbon dioxide, raffinate is potassium bicarbonate solution, the raffinate is used for synthesis after concentration, and the organic phase is evaporated under negative pressure to obtain acetic acid solution and regenerate the organic phase. The method basically recycles other substances except limestone, consumes little energy, and greatly reduces the energy consumption of concentrating potassium bicarbonate and evaporating acetic acid compared with the traditional synthesis method, so the method realizes the production of the nano calcium carbonate under the production conditions of low energy consumption and low consumption, simultaneously has low raw material cost and low overall process cost, and realizes the production method of the green and environment-friendly nano calcium carbonate.
Drawings
FIG. 1 is a schematic of the process flow of the invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
As shown in fig. 1, the process flow of the present invention is shown, and the specific process principle is as follows:
the first step is to react limestone with acetic acid solution to produce calcium acetate and carbon dioxide, the calcium acetate solution is filtered after the pH value is adjusted to 10 to 12 by calcium hydroxide to remove impurities, the refined calcium acetate solution is used for the second step of synthesis, and residues can be sent to a brick factory for further utilization.
The second step of synthesis is that calcium acetate and a pre-prepared potassium bicarbonate solution are subjected to double decomposition reaction to generate nano calcium carbonate precipitate, carbon dioxide gas and a potassium acetate solution, a nano calcium carbonate filter cake is washed, dried and packaged to obtain a nano calcium carbonate product, the potassium acetate solution is concentrated by a triple effect evaporator and then used for the third step of extraction, and the carbon dioxide gas is collected and then also used for the third step of extraction.
The third step is that the extraction process is the key of the production technology in the invention and is completed by two-stage operation of three-phase extraction and organic phase regeneration. The organic phase of the three-phase extraction is prepared by tri-n-octylamine, n-octanol and No. 260 solvent oil, the water phase is a concentrated potassium acetate solution, the carbon dioxide gas phase is introduced into the water phase and the organic phase under the condition of fully stirring and mixing, the carbon dioxide is dissolved in water to generate carbonic acid, the carbonic acid improves the hydrogen ion concentration of the water phase, so the acidity of the water phase is improved, the concentration of acetic acid in the water phase is increased under the condition of excessive acetate ion number, the acetic acid is continuously extracted into the organic phase according to the property that the organic amine can preferentially react with acid with large molecular constitution and strong acidity, the water phase can continuously generate potassium bicarbonate, if the concentration of the tri-n-octylamine in the organic phase and the proportion of the oil phase and the water phase are proper, the acetate in the water phase can be mostly extracted into the organic phase in the form of acetic acid under the participation of the organic amine, the original potassium ions in the water phase are remained in the water phase, and the carbonate generated by introducing the carbon dioxide reacts with the tri-n-octylamine to generate bicarbonate radicals, so most of the substances in the water phase are potassium bicarbonate. Heating and distilling the organic phase containing the acetic acid under the conditions of negative pressure of-0.2 to 0.3MPa and temperature of 70 to 90 ℃, cooling acetic acid steam by water, absorbing to prepare 30 percent acetic acid solution, returning the acetic acid solution to be used for dissolving limestone, cooling the regenerated organic phase, and returning the regenerated organic phase to be used for three-phase extraction again, thereby realizing the recycling of the raw materials.
The main chemical reaction equation of the process is as follows:
CaCO 3 +2HAC=Ca(AC)2+CO 2 +H 2 O (1)
Mg(AC) 2 +Ca(OH) 2 =Ca(AC) 2 +Mg(OH) 2 （2）
Ca(AC) 2 +2KHCO 3 =CaCO 3 +2KAC+CO 2 +H 2 O (3)
2KAC+2 CO 2 +H 2 O+2R-NH 2 =2R-NH 3 AC+2KHCO 3 （4）
R-NH 3 AC= R-NH 2 + HAC （5）
example 1
A process method for circularly preparing nano calcium carbonate comprises the following steps:
a) Preparing a refined calcium acetate solution;
b) Preparing a potassium bicarbonate solution; adding high-purity potassium bicarbonate into water, wherein the concentration of the potassium bicarbonate in the solution is 2 to 3mol/L, and preferably 2.5mol/L.
C) Carrying out synthetic reaction on the refined calcium acetate solution obtained in the step A and the potassium bicarbonate solution obtained in the step B at normal temperature;
d) C, inputting the mixed solution obtained in the step C into a sealed container, stirring, continuing to perform synthetic reaction, collecting carbon dioxide gas generated by the reaction, and filtering the mixed solution after the reaction is completed to respectively obtain filtrate and filter cakes;
e) D, evaporating and concentrating the filtrate obtained in the step D to obtain a potassium acetate solution, and washing and drying the filter cake obtained in the step D to obtain nano calcium carbonate;
f) Preparing an extracting agent, wherein the extracting agent is tri-n-octylamine, n-octanol and No. 260 solvent oil respectively, adding the potassium acetate solution obtained in the step E into a three-phase extractor, stirring while introducing the carbon dioxide gas collected in the steps A-D into the three-phase extractor in the three-phase extractor until the gas pressure is stable, and clarifying and separating to obtain an upper clear oil phase and a lower water phase after stirring;
g) The water phase obtained in the step F is a potassium bicarbonate solution, and the potassium bicarbonate solution returns to the step B to be used as the prepared potassium bicarbonate solution for recycling; adding the oil phase obtained in the step F into an evaporation tank, evaporating and removing vinegar under the conditions that the pressure is-0.2 to-0.3 MPa and the temperature is 70 to 90 ℃, cooling and absorbing the evaporated acetic acid steam with water to obtain an acetic acid solution, and returning the acetic acid solution to the step A to be used as a raw material for preparing the refined calcium acetate solution for recycling; and D, taking the residual oil phase in the evaporating tank as an extracting agent, cooling, and returning to the step F to be used as the extracting agent for recycling.
The method for preparing the refined calcium acetate solution in the step A comprises the following steps: adding an acetic acid solution into a container filled with limestone, reacting the acetic acid solution with the limestone to generate a mixture of calcium acetate and acetic acid until the pH value of the solution is 4-5, and collecting carbon dioxide gas generated by reaction for the step F; adding calcium hydroxide into a solution with the pH value of 4-5, stirring simultaneously, filtering when the pH value of the solution is 10-12 to obtain a filtrate which is a refined calcium acetate solution, and collecting filter residues.
The concentration of the acetic acid solution is 0.8 to 2mol/L, preferably 1.25mol/L, and each cubic meter of the acetic acid solution is reacted with 0.2 to 0.4t of limestone, preferably 0.052 to 0.079t of limestone.
The preparation method of the potassium bicarbonate solution in the step B comprises the following steps: adding potassium bicarbonate into water, wherein the concentration of the potassium bicarbonate in the solution is 2 to 3mol/L, and preferably 2.5mol/L. The relative molecular mass of the potassium bicarbonate is 100, which is equivalent to the concentration of the potassium bicarbonate in the solution of about 0.6 to 0.7mol/m < 3 >, and the potassium bicarbonate adopts high-purity potassium bicarbonate, aiming at improving the purity of calcium carbonate produced subsequently.
And (C) synthesis reaction.
And D, adding a sodium carbonate solution into the mixed solution after the synthesis reaction in the sealed container is finished to detect whether the calcium acetate completely reacts, and adding a calcium chloride solution to detect whether the potassium bicarbonate completely reacts.
And F, preparing the volume ratio of tri-n-octylamine, n-octanol and No. 260 solvent oil in the extracting agent in the step F to be 1:2.5:3.5, introducing the carbon dioxide gas collected from the carbon dioxide in the step A and the step D into the bottom of the extractor by using a gas pump.
The volume of an acetic acid solution used for preparing the refined calcium acetate solution in the step A is 4 parts by volume, the volumes of the refined calcium acetate solution and the potassium bicarbonate solution in the step C are 4 parts by volume and 2-8 parts by volume respectively, the volume of the potassium acetate solution obtained by concentrating in the step E is 4-6 parts by volume, the total amount of an extracting agent used in the step F is 20 parts by volume, and the capacity of a three-phase extractor is at least 30 parts by volume; and G, absorbing 3 parts by volume of water for absorbing the acetic acid vapor to obtain 3.5-4 parts by volume of acetic acid solution.
Washing the filter cake twice at least, wherein the total amount of water is 4 parts by volume, drying and packaging after washing to obtain the nano calcium carbonate, and collecting filtrate filtered in the washing process for later use.
The water used to absorb the acetic acid vapor in step G is the filtrate of the washed filter cake filtered off during the washing process.
Example 2
A process method for circularly preparing nano calcium carbonate comprises the following steps:
a) Preparing a refined calcium acetate solution; adding 4 cubic 5mol of acetic acid solution into a sealed tank filled with 1.2 tons of limestone by using a circulating pump, reacting the acetic acid solution with the limestone to generate a mixture of calcium acetate and acetic acid until the pH value of the solution is 4 to 5, and collecting carbon dioxide gas generated by reaction for the step F, wherein the collection can be performed by using a plastic air bag, a gas tank and the like; and filling the calcium acetate solution generated by the reaction into a reaction tank with a stirring function, adding calcium hydroxide into the reaction tank, stirring simultaneously until the pH value of the solution is 10 to 12, filtering to obtain a filtrate which is a refined calcium acetate solution, collecting filter residues, and sending the filter residues to a brickyard for reuse after collecting the filter residues.
B) Preparing a potassium bicarbonate solution; adding high-purity calcium bicarbonate into clear water for preparation;
c) Carrying out synthetic reaction on the refined calcium acetate solution obtained in the step A and the potassium bicarbonate solution obtained in the step B at normal temperature; feeding a refined calcium acetate solution and a potassium bicarbonate solution into a pipeline reactor, wherein the flow rate ratio of the calcium acetate solution to the potassium bicarbonate solution is 1;
d) C, introducing the slurry after the preliminary reaction in the step C into a sealed synthesis tank with a stirrer, stirring, continuing to perform synthesis reaction, collecting carbon dioxide gas generated by the reaction, sequentially adding 2mol of sodium carbonate solution to detect whether the calcium acetate is reacted completely, and sequentially adding 2mol of calcium chloride solution to detect whether the potassium bicarbonate is reacted completely; after the reaction is completed, filtering the mixed solution to respectively obtain filtrate and filter cakes;
e) D, evaporating and concentrating the filtrate obtained in the step D to obtain a potassium acetate solution, and washing and drying the filter cake obtained in the step D to obtain nano calcium carbonate; concentrating the filtrate to 6 cubic meters, washing the filter cake twice with 2 cubic meters of clear water each time, drying after washing, and packaging to obtain a nano calcium carbonate product, wherein the yield of the nano calcium carbonate is about one ton;
f) Preparing an extracting agent, and mixing tri-n-octylamine, n-octanol and 260# solvent oil according to the proportion of 1:2.5:3.5 preparing 20 cubic meters of extracting agent, adding the extracting agent and the 6-square potassium acetate solution concentrated in the third step into a 30 cubic meter closed three-phase extractor, continuously introducing carbon dioxide gas from the bottom of the extractor by using an air pump under the conditions of normal temperature and strong stirring until the gas pressure is not reduced, stopping the air pump, stirring, clarifying and separating the oil phase and the water phase, and obtaining the oil phase and the water phase
G) F, the water phase obtained in the step F is a potassium bicarbonate solution, the water phase is clear, and the potassium bicarbonate solution returns to the step B to be used as the prepared potassium bicarbonate solution for recycling; adding the oil phase obtained in the step F into an evaporation tank, evaporating and removing vinegar under the conditions that the pressure is-0.2 to-0.3 MPa and the temperature is 70 to 90 ℃, cooling and absorbing the evaporated acetic acid steam by using washing water (about 3 cubic meters) for washing nano calcium carbonate to prepare an acetic acid solution with the concentration of about 30 percent to obtain about 4 cubic meters of the acetic acid solution, and returning the acetic acid solution to the step A to be used as a raw material for preparing the refined calcium acetate solution for recycling; and D, taking the residual oil phase in the evaporating tank as an extracting agent, cooling, and returning to the step F to be used as the extracting agent for recycling.
Therefore, about 1 ton of nano calcium carbonate product can be produced by comprehensively synthesizing every 1.2 ton of limestone, the raw materials which cannot be recycled in the step are limestone, calcium hydroxide and clear water, whether the reaction is complete or not is detected, and the generated by-product is residue after the limestone reaction, so that the method has the advantages of high utilization rate, low reaction raw material cost and capability of recycling the raw materials, the steps of evaporation concentration and acetic acid distillation are not required to be heated in the reaction process, and the heating temperature in the step is very low, so the production cost is low.
In summary, the above-mentioned embodiments are only preferred embodiments of the present invention, and all equivalent changes and modifications made in the claims of the present invention should be covered by the claims of the present invention.
Claims (9)
1. A process method for circularly preparing nano calcium carbonate is characterized by comprising the following steps:
a) Preparing a refined calcium acetate solution: adding an acetic acid solution into a container filled with limestone, reacting the acetic acid solution with the limestone to generate a mixture of calcium acetate and acetic acid until the pH value of the solution is 4-5, and collecting carbon dioxide gas generated by reaction for the step F; adding calcium hydroxide into a solution with the pH value of 4-5, stirring simultaneously, filtering when the pH value of the solution is 10-12 to obtain a filtrate which is a refined calcium acetate solution, collecting filter residues, wherein the concentration of the acetic acid solution is 0.8-2mol/L, and the acetic acid solution per cubic meter reacts with 0.04-0.1t limestone;
b) Preparing a potassium bicarbonate solution: adding potassium bicarbonate into water, wherein the concentration of the potassium bicarbonate in the solution is 2-3mol/L;
c) Carrying out a synthesis reaction on the refined calcium acetate solution obtained in the step A and the potassium bicarbonate solution obtained in the step B at normal temperature, and inputting the refined calcium acetate solution and the potassium bicarbonate solution into a pipeline reactor, wherein the flow rate ratio of the calcium acetate solution to the potassium bicarbonate solution is 1;
d) C, inputting the mixed solution obtained in the step C into a sealed container, stirring, continuing to perform synthetic reaction, collecting carbon dioxide gas generated by the reaction, and filtering the mixed solution after the reaction is completed to respectively obtain filtrate and filter cakes;
e) D, evaporating and concentrating the filtrate obtained in the step D to obtain a potassium acetate solution, and washing and drying the filter cake obtained in the step D to obtain nano calcium carbonate;
f) Preparing an extracting agent, wherein the extracting agent is tri-n-octylamine, n-octanol and No. 260 solvent oil respectively, adding the potassium acetate solution obtained in the step E into a three-phase extractor, introducing the carbon dioxide gas collected in the steps A and D into the three-phase extractor in the three-phase extractor while stirring until the gas pressure is stable, and clarifying and separating to obtain an upper oil phase and a lower water phase after stirring;
g) The water phase obtained in the step F is a potassium bicarbonate solution, and the potassium bicarbonate solution returns to the step B to be used as the prepared potassium bicarbonate solution for recycling; adding the oil phase obtained in the step F into an evaporation tank, evaporating and removing vinegar under the conditions that the pressure is-0.2 to-0.3 MPa and the temperature is 70 to 90 ℃, cooling and absorbing the evaporated acetic acid steam with water to obtain an acetic acid solution, and returning the acetic acid solution to the step A to be used as a raw material for preparing the refined calcium acetate solution for recycling; and D, taking the residual oil phase in the evaporating tank as an extracting agent, cooling, and returning to the step F to be used as the extracting agent for recycling.
2. The process method for cyclically preparing nano calcium carbonate according to claim 1, which is characterized in that: and (B) the concentration of the acetic acid solution in the step (A) is 1.25mol/L, and each cubic meter of the acetic acid solution reacts with 0.052 to 0.079t of limestone.
3. The process method for cyclically preparing nano calcium carbonate according to claim 1, which is characterized in that: the concentration of the potassium bicarbonate in the solution in the step B is 2.5mol/L.
4. The process method for cyclically preparing nano calcium carbonate according to claim 1, which is characterized in that: and C, the flow rate ratio of the calcium acetate solution to the potassium bicarbonate solution is 1.
5. The process method for cyclically preparing nano calcium carbonate according to any one of claims 1 to 4, which is characterized in that: and D, adding a sodium carbonate solution into the mixed solution after the synthesis reaction in the sealed container is finished to detect whether the calcium acetate completely reacts, and adding a calcium chloride solution to detect whether the potassium bicarbonate completely reacts.
6. The process method for cyclically preparing nano calcium carbonate according to claim 5, which is characterized in that: the extracting agent in the step F comprises tri-n-octylamine, n-octanol and 260# solvent oil in a volume ratio of 1:2.5:3.5, introducing the carbon dioxide gas collected from the carbon dioxide in the step A and the step D into the bottom of the extractor by using a gas pump.
7. The process method for cyclically preparing nano calcium carbonate according to claim 6, which is characterized in that: the volume of the acetic acid solution used for preparing the refined calcium acetate solution in the step A is 4 parts by volume, the volumes of the refined calcium acetate solution and the potassium bicarbonate solution in the step C are 4 parts by volume and 2-8 parts by volume respectively, the potassium acetate solution obtained by concentration in the step E is 4-6 parts by volume, the total amount of the extracting agent used in the step F is 20 parts by volume, and the capacity of the used three-phase extractor is at least 30 parts by volume; and G, absorbing 3 parts by volume of water for absorbing the acetic acid vapor to obtain 3.5-4 parts by volume of acetic acid solution.
8. The process method for cyclically preparing nano calcium carbonate according to claim 7, which is characterized in that: washing the filter cake twice at least, wherein the total amount of water is 4 parts by volume, drying and packaging after washing to obtain the nano calcium carbonate, and collecting filtrate filtered in the washing process for later use.
9. The process method for cyclically preparing nano calcium carbonate according to claim 8, which is characterized in that: the water used to absorb the acetic acid vapor in step G is the filtrate of the washed filter cake filtered off during the washing process.
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