CN215974997U - System for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as raw material - Google Patents
System for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as raw material Download PDFInfo
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Abstract
The utility model discloses a system for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as a raw material, which belongs to the technical field of seawater energy utilization, and comprises a lime slaking device, an alkali dissolving device, a magnesium precipitating device, a calcium precipitating device and a concentrated solution storage tank for storing the concentrated solution of the seawater desalination device, wherein the concentrated solution and lime milk enter the magnesium precipitating device to generate magnesium hydroxide precipitate, and a filter cake separated by a solid-liquid separation device I is dried to obtain a magnesium hydroxide product; clear liquid of the magnesium precipitation device respectively enters a lime slaking device and a calcium precipitation device, sodium hydroxide solution enters the calcium precipitation device, calcium hydroxide precipitate generated in the calcium precipitation device enters a solid-liquid separation device II for separation, a clear liquid outlet is respectively communicated with an alkali dissolving device and a solar salt field, and an obtained calcium hydroxide filter cake is pulped, concentrated and sequentially enters a carbonization device and a filtering device to obtain a high-purity calcium carbonate product. The utility model utilizes the concentrated solution produced by the seawater desalination device to prepare high-purity calcium carbonate and byproduct magnesium hydroxide, recovers the sea salt through the solar salt treatment, and has obvious economic and environmental benefits.
Description
Technical Field
The utility model belongs to the technical field of seawater energy utilization, and particularly relates to a system for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as a raw material.
Background
Seawater is a treasury of inorganic salts, and usually contains inorganic salts up to 35 per mill, mainly NaCl and MgCl2、MgSO4、CaSO4、K2SO4、CaCO3MgBr, etc., as elements per kg of seawater, Cl: 18980mg/kg, Na: 10561Mg/kg, Mg: 1272mg/kg, S: 884mg/kg, Ca: 400mg/kg … …. With the improvement of the living standard of human beings, the development of national economy and the warming of climate, the demand of fresh water is more and more, the supply is not in demand, in order to meet the requirements of human life and economic development, fresh water is extracted from seawater in coastal countries, island countries and regions all around the world, and the development of seawater desalination technology is fast. At present, the fresh water extraction rate by using a membrane technology reaches 65%, and the content of inorganic salt in a concentrated solution is improved by more than 1 time. The inorganic salt directly recovered from the seawater needs to be recovered by a thermal method due to low content, so that the energy consumption is larger; at present, all countries in the world utilize solar energy to recover NaCl and MgCl by using solar salt method on coastal areas2And a salt field is arranged on the coastal beach, the occupied area is large, and other inorganic salt is recycled through bittern.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a system for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as a raw material, and aims to solve the technical problems that in the prior art, a beach salt field is large in occupied area of solar salt, multiple inorganic salts need to be recovered in batches, and the recovery efficiency is low.
In order to solve the technical problems, the technical scheme adopted by the utility model is as follows:
a system for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as a raw material comprises a lime slaking device, an alkali dissolving device, a magnesium precipitating device, a calcium precipitating device and a concentrated solution storage tank for storing the concentrated solution of the seawater desalination device, wherein the top of the lime slaking device is provided with a lime inlet, the lower part of the lime slaking device is provided with a lime milk outlet, the top of the magnesium precipitating device is provided with a lime milk inlet and a concentrated solution inlet connected with the concentrated solution storage tank, a clear solution outlet at the upper part of the magnesium precipitating device is respectively connected with the lime slaking device and the calcium precipitating device, a turbid solution outlet at the bottom of the magnesium precipitating device is connected with a solid-liquid separation device I, and a magnesium hydroxide filter cake of the solid-liquid separation device I is dried to obtain a magnesium hydroxide product;
the top of the alkali dissolving device is provided with a sodium hydroxide inlet, the lower part of the alkali dissolving device is provided with a sodium hydroxide solution outlet, the top of the calcium precipitation device is provided with a mixed filtrate inlet and a sodium hydroxide solution inlet, the mixed filtrate inlet is connected with an upper clear liquid outlet of the magnesium precipitation device, the sodium hydroxide solution inlet is connected with a sodium hydroxide solution outlet of the alkali dissolving device, and the upper clear liquid outlet of the calcium precipitation device is respectively communicated with the alkali dissolving device and a solar salt field and is respectively used for dissolving sodium hydroxide and recovering sodium chloride; and a turbid liquid outlet at the bottom of the calcium precipitation device is connected with a solid-liquid separation device II, and a calcium hydroxide filter cake of the solid-liquid separation device II is beaten, thickened and then sequentially enters a carbonization device and a filtering device to obtain a high-purity calcium carbonate product.
Preferably, the lime slaking device further comprises a lime storage bin and a caustic soda storage bin, wherein the lime storage bin is connected with a lime inlet of the lime slaking device through a metering and conveying device, and a lime milk outlet of the lime slaking device is communicated with a lime milk storage tank; and the caustic soda storage bin is connected with a sodium hydroxide inlet of the alkali dissolving device through a metering and conveying device.
Preferably, a stirrer is arranged in the lime slaking device, a slurry outlet of the lime slaking device is connected with a screening machine, and a screen of the screening machine is 100 meshes and used for screening out lime slag larger than 100 meshes; and a feed liquid outlet of the screening machine is connected with the hydrocyclone separator and is used for separating fine slag with the size less than 100 meshes.
Preferably, a feed liquid outlet of the hydrocyclone separator is connected with a slurry storage tank, and an outlet of the slurry storage tank is connected with a feed inlet of the magnesium precipitation device.
Preferably, the solid-liquid separation device I and the solid-liquid separation device II both adopt a filter press.
Preferably, the magnesium deposition device and the calcium deposition device have the same structure, and a stirrer is arranged inside the magnesium deposition device and the calcium deposition device; the lime milk inlet and the concentrated solution inlet of the magnesium precipitation device are respectively provided with a flowmeter; and a sodium hydroxide solution inlet of the calcium precipitation device is provided with a flowmeter.
Preferably, the calcium hydroxide filter cake of the solid-liquid separation device II sequentially enters a beater and a filter for beating, washing and filtering the calcium hydroxide filter cake.
Preferably, the carbonization device is connected with a carbon dioxide pipeline, a flowmeter is arranged on the carbon dioxide pipeline, the carbonization device is a bubbling carbonization tower, a spraying carbonization tower, a stirring type carbonization tower or a dry-method modified mixer, the bubbling carbonization tower is used for producing light calcium carbonate, the spraying carbonization tower or the stirring type carbonization tower is used for producing superfine calcium carbonate, and the dry-method modified mixer is used for producing active high-purity calcium carbonate.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: compared with the prior art, the method has the advantages that the concentrated solution produced by the seawater desalination device reacts with the lime cream in the magnesium precipitation device to generate magnesium hydroxide precipitate, the magnesium hydroxide product is obtained through solid-liquid separation and drying, the supernatant liquid reacts with the sodium hydroxide solution in the calcium precipitation device to generate calcium hydroxide precipitate, and the calcium hydroxide precipitate reacts with carbon dioxide in the carbonization device to generate the high-purity calcium carbonate product after the solid-liquid separation. The method can extract magnesium and calcium products from the seawater desalination concentrate, can realize industrial production, reduce the quantity of the seawater desalination concentrate discharged back to the sea, reduce the chemical component change of the offshore water quality and the influence on the survival of marine animals and plants, and solve the environmental protection of seawater desalination. The utility model prepares high-purity calcium carbonate and byproduct magnesium hydroxide by taking the seawater desalination concentrated solution as a raw material, and recovers NaCl sea salt through solar salt treatment, and has remarkable economic benefit and environmental benefit.
Drawings
FIG. 1 is a schematic flow chart of a system for preparing high-purity calcium carbonate from a seawater desalination concentrate according to an embodiment of the present invention;
FIG. 2 is a material balance diagram for producing 50kt/a high-purity calcium carbonate from the seawater desalination concentrate in example 1;
FIG. 3 is a material balance diagram of the production of 20.0kt/a activated high-purity calcium carbonate from the concentrated seawater desalination solution in example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly and completely understood, the technical solutions in the embodiments of the present invention are described below with reference to the accompanying drawings and specific embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.
With the development of the seawater desalination technology, the concentrated solution generated in the seawater desalination process contains high-content elements, such as magnesium, calcium and the like, and the salt content of the concentrated solution can be increased by 1-2 times, so that convenient conditions are provided for extracting products such as Mg, Ca and the like by adopting a chemical technology. The utility model adopts the lime milk magnesium precipitation process, can recover magnesium products, simultaneously increases calcium element with medium mol in the concentrated solution, and provides raw material conditions for preparing calcium products by improving calcium concentration. Precipitating calcium with sodium hydroxide, filtering, washing, concentrating, and purifying with CO2Carbonizing to obtain high-purity calcium carbonate product, filtering, drying, grading and packaging.
Through detection, the concentrated solution of the seawater desalination device contains magnesium chloride with the concentration ranging from 10kg/t to 15kg/t and calcium chloride with the concentration ranging from 2.0kg/t to 3.0 kg/t. The utility model utilizes MgCl in the concentrated solution of the seawater desalination device2、CaCl2Respectively with lime milk (Ca (OH)2) The magnesium precipitation reaction is carried out, and the reaction equation is as follows:
digestion reaction: CaO + H2O →Ca(OH)2
Magnesium deposition reaction: MgCl2 + Ca(OH)2→ Mg(OH)2↓ + CaCl2
Calcium deposition reaction: CaCl2 + 2NaOH → Ca(OH)2↓ + 2NaCl
And (3) carbonization reaction: ca (OH)2 + CO2→ CaCO3 + H2O
As shown in figure 1, the system for preparing high-purity calcium carbonate by using seawater desalination concentrated solution as a raw material provided by the utility model comprises the following equipment:
(1) raw material and auxiliary raw material storage pool and bin
a. A concentrated solution storage tank: the concentrated solution discharged by the seawater desalination device is stored in a concentrated solution storage pool for caching, and magnesium and calcium raw materials are provided;
b. lime storage: an outsourcing lime storage bin for storing auxiliary raw materials of the magnesium precipitating agent;
c. caustic soda bin: and (4) purchasing an external caustic soda storage bin for storing the auxiliary raw materials of the calcium precipitating agent.
(2) Lime slaking apparatus: the lime storage bin is connected with a lime inlet of the lime slaking device through a metering and conveying device, lime can be conveyed to the lime slaking device, meanwhile, clear liquid at the upper part of the magnesium deposition device enters the lime slaking device through metering, and the ratio of the lime to the water is 1: 4; and after ash sealing is carried out for 1-2 hours, an internal stirrer is started for fully stirring. Adding water in the stirring process to adjust the slurry concentration to be about 10-20%, and mixing and digesting for 1-2 h to form coarse slurry. A slurry outlet of the lime slaking device is connected with a screening machine, and lime slag larger than 100 meshes is screened out after coarse slurry is coarsely screened by a 100-mesh screen in the screening machine; the feed liquid enters a hydrocyclone separator, and after fine slag with the particle size less than 100 meshes is removed, the feed liquid is sent to a lime milk storage tank for standby. Preparing lime milk according to the process requirements, removing slag, adjusting concentration to prepare 3-12% of calcium hydroxide by weight concentration, and sending the calcium hydroxide into a magnesium precipitation device for magnesium precipitation reaction. The lime slaking apparatus may employ a lime slaker of the prior art.
(3) A magnesium precipitation device: the device belongs to main equipment, has more quantity, large volume, large occupied area and complex structure, a large-scale slow stirrer is arranged in the magnesium precipitation device,respectively provided with a concentrated solution inlet and a lime milk inlet, the upper part is provided with a clear solution outlet, the lower part is provided with a turbid liquid outlet, the stirrer is favorable for uniformly mixing the concentrated solution and the lime milk, and MgCl is added2And Ca (OH)2Contact to produce Mg (OH)2Precipitating and growing crystals, and discharging the suspension from a lower suspension outlet and sending the suspension to a solid-liquid separation device I for filtration and separation; clear liquid is discharged from the upper clear liquid outlet, one part of clear liquid is sent to a lime slaking device for slaking lime, and the most part of clear liquid is sent to a calcium precipitation device for continuous reaction.
In the magnesium precipitation device, the reaction time of concentrated liquid and alkaline agent lime milk is controlled to be 24-48 h, the concentrated liquid and the alkaline agent lime milk gradually sink to the lower half part of the magnesium precipitation device after reaction and crystal growth, the concentration of the liquid is increased, the upper half part of the liquid gradually becomes clear liquid, the clear liquid is respectively discharged from the upper part and the lower part, one part of the clear liquid in the upper layer is used for lime digestion water, and the other part of the clear liquid in the upper layer is discharged into a filtrate tank; the lower half part of the magnesium hydroxide suspension is separated and filtered by a solid-liquid separation device I.
(4) Solid-liquid separation equipment I: discharging magnesium hydroxide turbid liquid formed at the lower part of the magnesium precipitation device, and allowing the magnesium hydroxide turbid liquid to enter a solid-liquid separation device I for solid-liquid separation:
a. sending the filter cake to a magnesium hydroxide preparation process, wherein the water content of the filter cake is 30-40%, and drying to obtain a magnesium hydroxide product, wherein the drying temperature is 200-300 ℃; then the magnesium hydroxide powder product is prepared after crushing and grading, and is packaged for sale.
b. The filtrate enters a filtrate tank, is mixed with clear liquid discharged by a magnesium precipitation device and is sent to a calcium precipitation device.
(5) An alkali dissolving device: the caustic soda and the supernatant of the calcium precipitation device are metered into the alkali dissolving device to be dissolved, sodium hydroxide solution with the concentration of 3% -5% is prepared, and the sodium hydroxide solution is metered into the calcium precipitation device to react with the filtrate (containing the supernatant of the calcium precipitation device) metered from the filtrate tank, so that calcium hydroxide suspension is generated, and the calcium hydroxide suspension is precipitated and concentrated.
A calcium deposition device: is CaCl2Reacting with NaOH to generate Ca (OH) 2And NaCl.
The structure of the calcium precipitation device is approximately the same as that of the magnesium precipitation device, the calcium precipitation device comprises a mixed filtrate inlet, a sodium hydroxide solution inlet, a supernatant outlet, a lower suspension outlet and the like, a small part of the supernatant is used for dissolving caustic soda to prepare sodium hydroxide solution, the suspension discharged from the lower part is sent to the solid-liquid separation device II for separation and filtration, and most of the supernatant is mixed with the filtrate of the lower solid-liquid separation device II and sent to a solar salt field to recover NaCl products.
(6) And (3) solid-liquid separation device II: ca (OH) in suspension discharged by calcium precipitation device2The precipitate is filtered and separated in a solid-liquid separation device II. The calcium hydroxide filter cake contains 30-40% of water, sequentially enters a pulping machine and a filter, is pulped, washed and filtered for 1-2 times, and then filtrate is discharged; adding purified water, beating again, adjusting the concentration to 7-10%, and conveying to a carbonization device for carbonization.
(7) A carbonization device:
according to the preparation of different kinds of high-purity calcium carbonate products, a proper carbonizing device is selected, such as a bubbling carbonizing tower and the like for producing common light calcium carbonate, a spraying carbonizing tower and a stirring carbonizing tower and the like for producing superfine calcium carbonate can be selected, and if active high-purity calcium carbonate products are produced, carbonized slurry is subjected to activation treatment, and a wet or dry activation process and the like are adopted.
In the above process, the filter cake is re-beaten to form Ca (OH) with a certain concentration2The suspension is metered into a carbonizing device and is mixed with CO2CO discharged from the storage tank2After being decompressed by a decompressor, the pressure is controlled to be 2-3 MPa, and CO is controlled to be2Fully contacting gas-liquid in a carbonization device to carry out carbonization reaction to generate CaCO3And (4) suspending the solution. Generally controlling the carbonization reaction time for 1-3 h, discharging the cooked slurry out of the carbonization device, storing the cooked slurry in a cooked slurry pool for a certain time, and then sending the cooked slurry to a filtering device for solid-liquid separation and the like. Wherein, the carbonization reaction temperature is different according to different varieties of the prepared high-purity calcium carbonate, and the control temperature is different:
the carbonization reaction temperature for producing the common light calcium carbonate is controlled to be 50-80 ℃; the carbonization reaction temperature for producing the superfine calcium carbonate is controlled at 20-30 ℃. Carbonization time: the gas-liquid contact time is 1-3 h. Storing, filtering, drying, grading, packaging and selling the reacted cooked slurry.
(8) A filtering device: and (3) feeding the cooked slurry into a filtering device for solid-liquid separation, and drying, crushing, grading and packaging a filter cake to prepare a high-purity calcium carbonate product.
And the solid-liquid separation device I and the solid-liquid separation device II both adopt a filter press to realize solid-liquid separation.
The calcium carbonate is modified by adopting a wet or dry activation process, and the specific process is as follows:
dry modification: some modifiers can not be decomposed in water, can be modified only by a dry method. The dry modification is simple, the calcium carbonate powder is added or continuously fed into a high-speed mixer or a special dry modification machine, the modifier is added into the modification machine or continuously added according to the required addition amount of 1-3 percent, the mixture is stirred and mixed for a certain time, generally 10-15 min, and the modification is finished.
And (3) wet modification: the modification is more complex, but the modification is uniform, and the effect is better. The wet modification is to integrate the modification process into the calcium carbonate process, the modifier is firstly prepared into a solution with a certain concentration, and then the solution can be added into Ca (OH) according to different requirements2And (3) keeping the suspension or the suspension in the carbonized slurry at a certain temperature for a certain time, fully stirring and mixing, filtering and drying, wherein the drying temperature cannot be too high, the heating temperatures of different activators have requirements, the use of different activators is strictly carried out according to the specifications of the activator products, and otherwise, the activation effect is poor or fails. The filtrate can be discharged after being treated by wet modification, and the discharge requirement needs to be met.
The following are two specific examples:
example 1: based on the capability of producing the magnesium-calcium product, the required raw and auxiliary materials are calculated.
(1) The concentrated solution of the seawater desalination device is used as a calcium product raw material, magnesium and calcium elements in the concentrated solution are recovered, and high-purity calcium carbonate series products are produced: the production is 50kt/a high-purity calcium carbonate, the working day is 300d/a, i.e. 7200h/a, and the hourly production is 7 t/h.
(2) Concentrated solution of seawater desalination device contains 2.6kg/m magnesium3Converted to MgCl2Is 10.3kg/m3(ii) a Calcium 0.800kg/m3Converted into CaCl2Is 2.22kg/m3。
（3）The magnesium-precipitating alkali agent is lime milk, the utilization rate of the lime is 90 percent (the raw burning rate and the over-burning rate in the lime are less than or equal to 5 percent, the impurities such as silicon and the like are less than or equal to 3 percent, and the loss in the lime digestion or process is about 2 percent). Wherein, CaO is added at 4.62t/h, Ca (OH)2The concentration of MgOH in the suspension discharged by the magnesium settling device is 5.50t/h, and the concentration of MgOH in the suspension discharged by the magnesium settling device is 4.31 t/h; solid-liquid separation and drying to obtain the magnesium hydroxide product of 4.22 t/h.
(4) The calcium precipitation adopts caustic soda as a calcium precipitation agent, and the loss of caustic soda dissolution and the like is 1 percent; the sodium chloride solution is sent to a solar salt farm, and the recovery rate of NaCl is 95 percent. CaCl entering calcium deposition device28.35t/h, the addition of caustic soda is 5.95t/h, the alkali is dissolved and then enters a calcium precipitation device, filter cakes obtained after solid-liquid separation after precipitation are filtered, washed and pulped, and Ca (OH) enters a carbonization device2Is 5.45 t/h.
(5) CO for carbonisation2The utilization rate was 98%. CO 22CaCO added into the carbonization liquid of a carbonization device at 3.14 t/h37.0t/h, and finally drying and grading to obtain a high-purity calcium carbonate product of 50.4 kt/a.
The balance of materials for producing 50kt/a high-purity calcium carbonate by using concentrated solution of a seawater desalination device as a source of magnesium and calcium is shown in figure 2.
Example 2:
(1) concentrated liquid of a seawater desalination device is taken as raw materials of magnesium and calcium, lime milk is taken as a magnesium precipitation alkali agent, caustic soda is taken as a calcium precipitation alkali agent, and CO is2Is used as auxiliary raw material for carbonization, etc. to produce active high-purity calcium carbonate product and by-product magnesium hydroxide, sodium chloride, etc. Annual productivity: the production of the active high-purity calcium carbonate product is 20.0kt/a, namely the hourly output is 2.8t/h, and the annual work is 300 days, namely 7200 h/a.
(2) Examples (5) to (5) are the same as example 1.
(6) The activating agent is a coupling agent for water, and is modified by a wet method, wherein the addition amount is 1-3%.
The balance of main materials for producing 20.0kt/a active high-purity calcium carbonate products by using concentrated solution of a seawater desalination device as a source of magnesium and calcium is shown in figure 3.
In conclusion, the utility model selects lime milk and caustic soda as the magnesium and calcium precipitation alkali agents, firstly recovers the magnesium element in the concentrated solution and prepares the magnesium hydroxide. In seawaterMagnesium element is recycled, but at the same time, equimolar amount of calcium element is generated and dissolved in the concentrated solution, namely, magnesium element is reduced and calcium element is increased in the concentrated solution. In order to recover the original calcium element and the newly added calcium element together to prepare a high-purity calcium carbonate product and simultaneously generate NaCl sea salt, the concentrated solution obtained by desalting the sea water is subjected to magnesium precipitation by using lime milk to extract magnesium element to generate a magnesium hydroxide series product; then using caustic soda as calcium-precipitating agent to prepare calcium hydroxide, further utilizing CO2Carbonizing to obtain high-purity calcium carbonate products. Through secondary magnesium and calcium deposition reaction, two series products of magnesium hydroxide and high-purity calcium carbonate are prepared, magnesium and calcium in the original concentrated solution are recycled, and waste water of by-product NaCl can be sent to a solar salt pond to produce NaCl sea salt products. The method can recycle Na, Cl, Mg and Ca with the most contents in the seawater desalination concentrated solution, wherein Mg and Ca in the concentrated solution are completely recycled, most Cl is recycled, and part of Na is recycled, so the method can use the concentrated solution of the seawater desalination device as the raw material for preparing magnesium, calcium and sea salt products, not only solves the difficulty of the countries and the regions with magnesium deficiency resources, but also reduces the pollution of calcium-containing wastewater to the ocean, and achieves multiple purposes!
The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (8)
1. A system for preparing high-purity calcium carbonate by taking seawater desalination concentrated solution as a raw material is characterized in that: the device comprises a lime slaking device, an alkali dissolving device, a magnesium depositing device, a calcium depositing device and a concentrated liquid storage pool for storing concentrated liquid of a seawater desalting device, wherein the top of the lime slaking device is provided with a lime inlet, the lower part of the lime slaking device is provided with a lime milk outlet, the top of the magnesium depositing device is provided with a lime milk inlet connected with the lime slaking device and a concentrated liquid inlet connected with the concentrated liquid storage pool, a clear liquid outlet at the upper part of the magnesium depositing device is respectively connected with the lime slaking device and the calcium depositing device, a turbid liquid outlet at the bottom of the magnesium depositing device is connected with a solid-liquid separating device I, and the solid-liquid separating device I is used for separating the turbid liquid to obtain a magnesium hydroxide product;
the top of the alkali dissolving device is provided with a sodium hydroxide inlet, the lower part of the alkali dissolving device is provided with a sodium hydroxide solution outlet, the top of the calcium precipitation device is provided with a mixed filtrate inlet and a sodium hydroxide solution inlet, the mixed filtrate inlet is connected with an upper clear liquid outlet of the magnesium precipitation device, the sodium hydroxide solution inlet is connected with a sodium hydroxide solution outlet of the alkali dissolving device, and the upper clear liquid outlet of the calcium precipitation device is respectively communicated with the alkali dissolving device and a solar salt field and is respectively used for dissolving sodium hydroxide and recovering sodium chloride; and a bottom turbid liquid outlet of the calcium precipitation device is connected with the solid-liquid separation device II, and a calcium hydroxide filter cake separated by the solid-liquid separation device II sequentially enters the carbonization device and the filtering device through the pulping machine to obtain a high-purity calcium carbonate product.
2. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrated solution as the raw material according to claim 1, is characterized in that: the lime storage bin is connected with a lime inlet of the lime slaking device through a metering and conveying device, and a lime milk outlet of the lime slaking device is communicated with a lime milk storage tank; and the caustic soda storage bin is connected with a sodium hydroxide inlet of the alkali dissolving device through a metering and conveying device.
3. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrated solution as the raw material according to claim 1, is characterized in that: the slurry outlet of the lime slaking device is connected with a screening machine, and the screen of the screening machine is 100 meshes and used for screening out lime mud larger than 100 meshes; and a feed liquid outlet of the screening machine is connected with the hydrocyclone separator and is used for separating fine slag with the size less than 100 meshes.
4. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrated solution as the raw material according to claim 3, is characterized in that: and a feed liquid outlet of the hydrocyclone separator is connected with a slurry storage tank, and an outlet of the slurry storage tank is connected with a feed inlet of the magnesium precipitation device.
5. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrated solution as the raw material according to claim 1, is characterized in that: and the solid-liquid separation device I and the solid-liquid separation device II both adopt a filter press.
6. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrated solution as the raw material according to claim 1, is characterized in that: the magnesium deposition device and the calcium deposition device have the same structure, and are internally provided with stirrers; the lime milk inlet and the concentrated solution inlet of the magnesium precipitation device are respectively provided with a flowmeter; and a sodium hydroxide solution inlet of the calcium precipitation device is provided with a flowmeter.
7. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrated solution as the raw material according to claim 1, is characterized in that: and the calcium hydroxide filter cake of the solid-liquid separation device II sequentially enters a beater and a filter for beating, washing and filtering the calcium hydroxide filter cake.
8. The system for preparing high-purity calcium carbonate by using the seawater desalination concentrate as the raw material according to any one of claims 1 to 7, which is characterized in that: the carbonization device is connected with a carbon dioxide pipeline, a flowmeter is arranged on the carbon dioxide pipeline, the carbonization device is a bubbling carbonization tower, a spraying carbonization tower, a stirring type carbonization tower or a dry-method modified mixing machine, the bubbling carbonization tower is used for producing light calcium carbonate, the spraying carbonization tower or the stirring type carbonization tower is used for producing superfine calcium carbonate, and the dry-method modified mixing machine is used for producing active high-purity calcium carbonate.
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