CN111392754B - Method and equipment for purifying calcium chloride from fluorine-containing solid waste - Google Patents

Method and equipment for purifying calcium chloride from fluorine-containing solid waste Download PDF

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CN111392754B
CN111392754B CN202010317377.5A CN202010317377A CN111392754B CN 111392754 B CN111392754 B CN 111392754B CN 202010317377 A CN202010317377 A CN 202010317377A CN 111392754 B CN111392754 B CN 111392754B
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leaching
calcium
fluorine
carbonate
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CN111392754A (en
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邵宗强
黄燕生
王淼
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Shenzhen Koala Ecological Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
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    • C01F11/28—Chlorides by chlorination of alkaline-earth metal compounds

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Abstract

Relates to a method and equipment for purifying calcium chloride from fluorine-containing solid waste, which comprises the steps of firstly carrying out carbonation reaction on the fluorine-containing solid waste, and then separating a purification interference source, such as sulfate, in the carbonated fluorine-containing solid waste; and then, carrying out hydrochlorination on the carbonated fluorine-containing solid waste after separation, carrying out solid-liquid separation and cyclic leaching after acid leaching of the hydrochlorination, and purifying calcium chloride from the acid leaching solution and the derived solution of the partial acid leaching in the cyclic leaching, so that the interference of sulfate on the subsequent purification of calcium fluoride can be avoided, and the yield of the intermediate product calcium chloride can be improved.

Description

Method and equipment for purifying calcium chloride from fluorine-containing solid waste
Technical Field
The invention relates to a recovery and regeneration technology of fluorine-containing solid waste, in particular to a method and equipment for purifying calcium chloride from fluorine-containing solid waste.
Background
Industrial solid wastes, particularly hazardous wastes, are called "poisonous nodules" which are harmful to the environment, have large quantity and cause pollution to the environment, and if the industrial solid wastes cannot be effectively treated, the industrial solid wastes not only can harm the environment and physical and mental health of people, but also can greatly restrict the development of economy. At present, the gap of the treatment capacity of the industrial solid waste in China is huge, the high-efficiency utilization is not really realized in the aspect of comprehensive utilization of the industrial solid waste, the treatment method is basically only a part of purification (extraction), most of the waste water and waste residues are still not fully utilized and are discarded, or the waste water and waste residues generated in the process of treating the industrial solid waste cause new secondary pollution to the environment, such as waste water containing high-concentration calcium chloride. The method has the advantages of realizing effective treatment of industrial solid wastes, improving the comprehensive utilization rate, converting all solid wastes into products with economic value as much as possible, changing the solid wastes into valuables, turning the solid wastes into safety, creating huge social value and economic value, reducing unnecessary resource waste and solving the problems urgently at present.
Fluorine-containing solid wastes have serious harm to the environment and human body. And may contaminate surface water, soil and groundwater, causing secondary pollution. Because the content of calcium fluoride in the fluorine-containing solid waste is not high, and the content of compounds of other substances such as silicon dioxide, calcium, aluminum, iron, sulfur and the like is high, the composition is complex, so that the fluorine-containing solid waste cannot be used in the chemical, metallurgical, glass, ceramic, optical and other industrial industries with high requirements on the purity and impurities of calcium fluoride. Can only be used in industries with low-end requirements, such as cement industry, and has low economic value. Even the waste is abandoned due to no economic value, so that excessive stacking is caused, and huge pollution and potential safety hazard are brought to the surrounding environment. on the one hand, with the rapid development of industrialization in China, the demand for fluorite (the main chemical component is calcium fluoride) is increasing. The large-scale over-exploitation of high-quality fluorite ore sources leads to the depletion of the high-quality fluorite ore sources and the reduction of the storage amount, thus leading to the shortage of the resources, the shortage of the supply and the demand and the continuous rising of the price. At present, the fluorite processing industry in China mainly purifies the content of calcium fluoride from medium-low grade fluorite resources by a multi-time flotation method, but the flotation method causes pollution to the environment, and a large amount of tailings generated after flotation cause secondary environmental pollution. The fluorine-containing solid waste is produced and processed in a low-cost, environment-friendly and pollution-free production and processing mode, after comprehensive treatment, the calcium fluoride product can meet the requirement of the grade of the industry, and the byproduct (chemical product) can meet the requirements of other industries. The method can not only solve the contradiction that the prior method has large fluorine-containing solid waste but can meet the narrow application range of the industry, eliminate the pollution of fluorine to the environment, but also solve the serious problem that fluorite concentrate resources are increasingly in short supply. For example, it is known in the art to be able to convert a solution containing calcium chloride into calcium fluoride by reaction with hydrofluoric acid.
Generally, in the process of recovering calcium fluoride from fluorine-containing solid wastes, calcium-containing compounds may be converted into calcium chloride in solution, which may cause wastewater pollution if directly discharged, affect process reaction efficiency if repeatedly recycled, and cause instability of process parameters and decrease of calcium fluoride purity if directly converted into calcium fluoride, because the commercial price of hydrofluoric acid is much higher than that of calcium fluoride, which is not economical. Therefore, calcium fluoride (CaF) is recovered in the solid waste recovery industry2) How to produce high-efficiency separated high-purity calcium chloride (CaCl) at the same time2) Solids are needed.
The invention discloses a method for preparing fluosilicic acid by using calcium fluoride-containing waste, which comprises the following steps of (1) reacting the calcium fluoride-containing waste with fluosilicic acid to generate calcium fluosilicate and hydrofluoric acid; reacting the hydrofluoric acid with silicon dioxide in the calcium fluoride-containing waste to generate fluosilicic acid; (2) adding sulfuric acid into the step (1) to react to generate fluosilicic acid and calcium sulfate; (3) carrying out solid-liquid separation on the fluosilicic acid and the calcium sulfate; and returning part of the fluosilicic acid to the step, and partially outputting. This known patent produces an intermediate product of calcium fluorosilicate by reacting fluorosilicic acid with calcium fluoride such that the sulfuric acid reacts with calcium fluoride silica in the liquid phase to produce fluorosilicic acid. The prior art related to this known patent is to purify low levels of calcium fluoride in fluorine-containing waste to high levels on the basis of converting calcium fluoride in the fluorine-containing waste to fluorosilicic acid. However, the silicification reaction requires a reaction kettle with an acid-resistant and high-temperature-resistant lining material, the reaction temperature is high (up to 120 ℃ F.). As a result, the production cost is high, and in addition, high-concentration sulfuric acid and hydrofluoric acid are required, and a certain production risk exists at high temperature, and a preparation method using calcium chloride solid as an intermediate product is not disclosed.
The invention patent application publication No. CN103241758A discloses a method for producing calcium fluoride by using bottom sludge generated by fluorine-containing wastewater. Separating the components by adopting a one-step alkaline washing and two-step acidification separation method and utilizing different solubilities of the bottom mud in acid to obtain a calcium fluoride product; the processing steps comprise: alkali washing, primary acidification separation, secondary acidification separation, drying and calcining; performing alkali washing to react sodium carbonate solution with the bottom mud to convert calcium sulfate in the bottom mud into calcium carbonate; the primary acidification takes the bottom mud as a raw material; combining filter liquor obtained by secondary acidification separation with washing water to be used as an acid source for primary acidification; the secondary acidification separation adopts new acid as an acid source; and drying and calcining the obtained filter cake. In the secondary acidification, 1:1 hydrochloric acid (concentrated hydrochloric acid: water =1: 1) is added into a secondary acidification reactor, and the hydrochloric acid is utilized to react with calcium carbonate and calcium hydroxide to generate calcium chloride and carbon dioxide dissolved in water, so that the calcium carbonate and the calcium hydroxide are removed. The known patent mainly carries out deacidification treatment on a solid filter cake formed by secondary acidification in a vacuum filtration mode, neutral water from the primary acidification is used for washing to be neutral, filtrate containing calcium chloride in the secondary acidification reacts with hydrofluoric acid to generate calcium fluoride which is insoluble in water, residual filtrate and acidic washing water after filter cake washing are combined and refluxed for primary acidification in the vacuum filtration, so that the filtrate containing calcium chloride is directly subjected to hydrofluoric acid reaction and reflux use, the commercial price of hydrofluoric acid is much higher than that of calcium fluoride, economic benefits are not met, calcium chloride does not take a solid form as an intermediate product, and the recovery purity and yield of calcium chloride cannot be determined, so that a technology for efficiently recovering calcium chloride solid as the intermediate product is not disclosed.
Disclosure of Invention
The invention mainly aims to provide a method for purifying calcium chloride from fluorine-containing solid waste, which avoids interference of sulfate in subsequent calcium fluoride purification by carbonating, separating an interference source and leaching hydrochloric acid, improves the yield of an intermediate product calcium chloride and realizes high-purity recovery of calcium chloride solid.
The invention mainly aims to provide equipment for purifying calcium chloride from fluorine-containing solid waste, and calcium chloride solid is purified from solid-liquid intermediate after hydrochlorination.
The main purpose of the invention is realized by the following technical scheme:
a method for purifying calcium chloride from fluorine-containing solid waste is provided, which comprises the following steps:
the method comprises the following steps of carrying out carbonation reaction on the fluorine-containing solid waste, wherein the fluorine-containing solid waste before carbonation comprises calcium fluoride, calcium-containing sulfate and calcium-containing compounds, and when the reactants specifically but not limited by ammonium carbonate, the carbonation reaction can be represented as the following reaction formula:
CaSO4·2H2O+(NH4)2CO3 = (NH4)2SO4+CaCO3↓+2H2O
Ca(OH)2+(NH4)2CO3 = CaCO3↓ + 2NH3·H2O
separating a purification interference source of carbonated fluorine-containing solid waste, wherein the purification interference source comprises soluble non-calcium sulfate and the carbonated fluorine-containing solid waste comprises calcium fluoride and calcium carbonate;
carrying out hydrochlorination on the carbonated fluorine-containing solid waste after separation, carrying out first solid-liquid separation after acid leaching, carrying out first cyclic leaching on the solid obtained by the first solid-liquid separation, combining an acid leaching filtrate discharged by the first solid-liquid separation with a partial acid leaching lead-out solution with acidity exceeding a lower pH threshold value in the first cyclic leaching, and purifying to obtain calcium chloride solid, wherein the chlorinated fluorine-containing solid waste after the first solid-liquid separation contains calcium fluoride; the possible reaction formula of the hydrochlorination reaction is as follows:
2HCI+CaCO3 = CaCI2+H2O+CO2↑
2HCI+Ca(OH)2 = CaCI2+2H2O 。
by adopting the first technical scheme, firstly, calcium sulfate and calcium hydroxide in the fluorine-containing solid waste are replaced by carbonation reaction to form calcium carbonate, then interference sources such as non-calcium sulfate and the like are separated, acid leaching of hydrochloric acid and first solid-liquid separation are used for converting the calcium carbonate into calcium chloride, acid leaching filtrate obtained by solid-liquid separation and partial acid leaching liquid obtained by solid-liquid separation and having acidity exceeding a lower threshold value under cyclic leaching of the chlorine-containing solid waste are collected, and high-purity calcium chloride solid can be purified finally. More specifically, calcium hydroxide in the fluorine-containing solid waste is consumed in both the carbonation reaction and the hydrochlorination reaction, wherein generally, the calcium hydroxide in the fluorine-containing solid waste is mostly converted into calcium carbonate in the carbonation reaction, calcium chloride is directly or indirectly generated, and the super acid in the circulating leaching of the solid intermediate under the solid-liquid separation is discharged and is combined with the liquid intermediate for collection, so as to improve the yield of the calcium chloride solid as the intermediate product.
The present invention in a preferred example may be further configured to: the total calcium content of the obtained calcium chloride is higher than the calcium content of calcium-containing sulfate in the fluorine-containing solid waste before carbonation, and the first solid-liquid separation and the first cyclic leaching are carried out in the same centrifugal filter.
By adopting the above preferred technical scheme, the fluorine-containing solid waste, except calcium fluoride, is not affected by using a specific process operation, and comprises the best calcium content of calcium sulfate and calcium compound or the most calcium content converted into calcium chloride, and the total calcium content of the obtained calcium chloride is deducted after deducting the used calcium content for acidity adjustment, and whether the total calcium content is higher than the calcium content of the calcium sulfate in the fluorine-containing solid waste or is close to the percentage of the calcium content of the calcium sulfate and the calcium content of the calcium compound and the percentage of the calcium content of the calcium sulfate and the calcium compound are both higher or lower can be used for verifying whether the yield and the purity of the calcium chloride solid in the fluorine-containing solid waste reach the preset standard, namely the yield verification of the technology for recovering the calcium chloride solid from the fluorine-containing solid waste under the variation of various waste compositions.
The present invention in a preferred example may be further configured to: and adjusting acidity and evaporating the acid leaching filtrate and the partial acid leaching derived liquid, wherein the acidity adjusting operation is used for adjusting the acidity of the acid leaching filtrate and the partial acid leaching derived liquid with the acidity exceeding a lower pH threshold value in the first circulation leaching to be neutral in pH value, and preferably, the adjusting agent used for adjusting the acidity is calcium carbonate or/and calcium hydroxide.
By adopting the preferable technical scheme, the acid leaching filtrate obtained by the first solid-liquid separation and the solid obtained by the first solid-liquid separation are combined to generate the partial acid leaching educt with the acidity exceeding the lower pH threshold value through the first circulation leaching, the acidity is adjusted to be neutral under the condition that the pH value is combined, and the mixed liquid is evaporated, so that the obtained calcium chloride solid is generated by crystallization and has high purity. The combination and collection of the acid leaching filtrate and the partial acid leaching effluent can reduce the acidity of the imported substance in advance when entering the acidity adjusting procedure.
The present invention in a preferred example may be further configured to: the threshold value is 5.0 at the pH, and preferably the first cycle of leaching is neutral cycle leaching with water.
By adopting the preferable technical scheme, the setting of the lower pH threshold value and the neutral cyclic leaching are utilized, the working range of the pH value of the first cyclic leaching is kept between 5.0 and 7.0, and calcium chloride and residual acid leaching liquid are dissolved out from the chlorinated fluorine-containing solid waste under the condition of a slightly neutral weak acid.
The present invention in a preferred example may be further configured to: the process of separating the purification interference source comprises second solid-liquid separation and second circular leaching of solids separated by the second solid-liquid separation, leaching filtrate discharged by the second solid-liquid separation and partial alkali leaching educt liquid with alkalinity exceeding an upper pH threshold in the second circular leaching are recycled and combined to purify non-calcium carbonate, and preferably, the recycled non-calcium carbonate is added into a leaching agent for carbonation reaction in a circular use mode.
By adopting the preferable technical scheme, the leaching filtrate obtained by the second solid-liquid separation and the partial alkali leaching effluent liquid generated by leaching the solid obtained by the second solid-liquid separation through the second circulation are recycled and combined, the non-calcium soluble salts are dissolved out, such as non-calcium carbonate and non-calcium sulfate, and the purified non-calcium carbonate can be regenerated and used for carbonation reaction.
The present invention in a preferred example may be further configured to: the upper threshold value of the pH value is 8.5, preferably, the second circulation leaching is neutral circulation leaching using water, the recovery and purification of the non-calcium carbonate comprises mixing, distillation, cooling and third solid-liquid separation, the non-calcium carbonate is formed in solids of the third solid-liquid separation, and liquid discharged by the third solid-liquid separation flows back to the distillation.
By adopting the preferable technical scheme, the setting of the upper pH threshold value and the neutral cyclic leaching are utilized, the working range of the pH value of the second cyclic leaching is kept between 7.0 and 8.5, non-calcium carbonate and residual leachate are dissolved out from carbonated fluorine-containing solid wastes under the condition of partial neutral weak base, liquid discharged by the third solid-liquid separation flows back to a front-stage distillation procedure, and the water resource can be saved and the purity of the non-calcium carbonate can be improved by utilizing the solubility change of the non-calcium carbonate at different temperatures. Furthermore, the recovery of non-calcium carbonate and the separation of non-calcium sulphate are achieved without waste water discharge.
The present invention in a preferred example may be further configured to: the distillation residue is evaporated to obtain non-calcium sulfate, and preferably the carbonation reaction is carried out by blending and leaching, and the leaching agent is ammonium carbonate.
The non-calcium sulfate and the non-calcium carbonate can be separated by adopting the preferable technical scheme and utilizing the characteristic of distillation temperature resistance in distillation and crystallization of a post-evaporation method, ammonia gas and carbon dioxide are decomposed at the distillation temperature (about 70 ℃) by utilizing a leaching agent ammonium carbonate, the ammonia gas, the carbon dioxide and water (water enters in a water vapor mode during distillation) are recombined into an ammonium carbonate solution after cooling, the separation of the non-calcium sulfate and the non-calcium carbonate is facilitated, the supersaturated crystallization is generated in the ammonium carbonate solution at the low temperature, ammonium carbonate crystals can be separated in third solid-liquid separation, and the ammonium carbonate crystal can be recovered and recycled as a leaching agent for carbonic acid reaction.
The second main object of the present invention is also to propose a device for purifying calcium chloride from fluorine-containing solid waste, which is used for implementing the method according to any of the above-mentioned technical solutions.
Alternatively, or in addition, the main object of the present invention is to provide an apparatus for purifying calcium chloride from fluorine-containing solid waste, comprising:
the carbonation reaction device is used for carrying out carbonation reaction on the fluorine-containing solid waste;
the interference source separation device is connected with the carbonation reaction device and is used for separating a purification interference source of carbonated fluorine-containing solid waste;
the hydrochlorination reaction device is connected with the interference source separation device and is used for carrying out hydrochlorination reaction on the carbonated fluorine-containing solid waste after separation, and the hydrochlorination reaction device comprises an acid leaching tank;
the purification device is connected with the hydrochlorination reaction device and is used for purifying the solid-liquid intermediate of the hydrochlorination reaction device to obtain calcium chloride solid;
the purification device comprises a first solid-liquid separator and a first circulating leaching system, wherein the first circulating leaching system is provided with a first leaching head and is used for circularly leaching the chlorinated solid waste of the first solid-liquid separator, and an acid leaching filtrate pipeline of the first solid-liquid separator and a partial acid leaching liquid outlet pipeline of the first circulating leaching system are connected with a common pipeline for purifying calcium chloride.
By adopting the second technical scheme, the purification device is utilized to circularly elute the chlorinated solid waste of the first solid-liquid separator, the acid leaching filtrate pipeline of the first solid-liquid separator is connected with the partial acid leaching liquid outlet pipeline of the first circular elution system, and the solution containing calcium chloride is collected, so that the calcium chloride solid can be purified from the solid-liquid intermediate after the hydrochlorination reaction and can be used as an intermediate product, and the fluorine-containing solid waste can be used for preparing the calcium chloride solid with high yield and high purity at the same time in the process of recovering the calcium fluoride. Under the condition of excessive hydrochloric acid provided by the first solid-liquid separator and the first circulating leaching system, calcium carbonate and calcium hydroxide are converted into soluble calcium chloride completely or mostly.
The present invention in a preferred example may be further configured to: the first solid-liquid separator and the first leaching head are constructed on the same centrifugal filter;
the purification device also comprises an acidity adjusting tank and an evaporator, wherein the acidity adjusting tank is connected with the common pipeline and is used for adjusting the pH value of the solution led out from the common pipeline to be close to neutral so as to purify calcium chloride solids;
preferably, the interference source separation device comprises a second solid-liquid separator and a second circulating leaching system, the second circulating leaching system is provided with a second leaching head for circularly leaching carbonated fluorine-containing solid waste of the second solid-liquid separator, and a leaching filtrate line of the second solid-liquid separator and a partial alkali leaching outlet liquid line of the second circulating leaching system are connected with the carbonate recovery device;
more preferably, the carbonate recovery device comprises a distiller, a cooling chamber and a third solid-liquid separator in order of a recovery path, so that non-calcium carbonate is formed in solids of the third solid-liquid separator, and a liquid discharge pipeline of the third solid-liquid separator returns to the distiller;
more preferably, the carbonate recovery device further comprises an evaporation chamber, the residue obtained by the distiller is evaporated to obtain non-calcium sulfate, the solid outlet of the third solid-liquid separator is connected to the carbonation reaction device, and preferably, the carbonation reaction device comprises a leaching tank adopting ammonium carbonate as a leaching agent.
By adopting the preferable technical scheme, the first solid-liquid separator and the first leaching head are constructed on the same centrifugal filter, compared with vacuum filtration, the solid separation efficiency and the washing effect are better, and the solution after acid leaching is centrifugally filtered to remove solid impurities. Preferably, the calcium chloride solid is purified by using an acidity-adjusting tank and an evaporator without wastewater discharge. Preferably, the carbonated fluorine-containing solid waste of the second solid-liquid separator is circularly leached by the second solid-liquid separator and the second circulating leaching system to dissolve out non-calcium sulfate and non-calcium carbonate, and under the condition of excessive carbonic acid provided by the second solid-liquid separator and the second circulating leaching system, calcium salt, except calcium fluoride, and calcium hydroxide with small partial carbonation incomplete reaction converts the most or most of calcium sulfate which is not easy to separate into insoluble calcium carbonate, and most of calcium hydroxide is also converted into calcium carbonate, so that most of calcium components of calcium hydroxide and calcium components of calcium sulfate can be retained in the fluorine-containing solid waste in a carbonate mode. Preferably, a distiller, a cooling chamber and a third solid-liquid separator are utilized to recover non-calcium carbonate solids, the distiller separates non-calcium carbonate from non-calcium sulfate, each component of the distilled and decomposed non-calcium carbonate can be cooled and recycled to be applied to a carbonation reaction device, and the non-calcium sulfate solution which is relatively high-temperature resistant in the distillation process is evaporated to remove water to obtain the calcium carbonate-based solid. The sulfate radical is replaced by carbonate radical in the solid phase of the solid waste by utilizing a leaching tank which adopts ammonium carbonate as a leaching agent.
In summary, the present invention includes at least one of the following beneficial effects:
1. in the process of purifying calcium fluoride from fluorine-containing solid waste, calcium chloride solid is purified from an acid leaching solution and a metataric acid leaching derived solution in circulating leaching and is used as an intermediate product, and the prepared calcium chloride solid has high yield and purity;
2. calcium-containing compounds, calcium-containing sulfate and the like in the fluorine-containing solid waste are converted into various chemical products which can be used as intermediate products by adopting a chemical production method, such as calcium chloride solid and non-calcium sulfate solid such as ammonium sulfate, and non-calcium carbonate solid such as ammonium carbonate which can be recycled can also be generated;
3. the circulating leaching is adopted after the hydrochlorination and the previous carbonation reaction, and the calcium fluoride is used in a backflow mode before the pH threshold value is not exceeded, so that the water resource is saved, the subsequent evaporation amount is reduced, and the crystallization generation of calcium fluoride solid and non-calcium sulfate solid such as ammonium sulfate is facilitated;
4. the front-stage production process for recovering the fluorine-containing solid waste realizes the purification of calcium chloride in the fluorine-containing solid waste, the recovery of waste liquid and leacheate in the fluorine-containing solid waste, so that more than two compounds can be purified from the fluorine-containing solid waste and can be converted into finished products meeting the requirements of various industrial indexes, and the front-stage production process achieves the purposes of no waste water, no solid waste discharge, no pollution to the environment and environmental protection.
Drawings
FIG. 1 depicts a flow diagram of steps in a process for purifying calcium chloride from fluorine-containing solid waste according to some embodiments of the present invention;
FIG. 2 is a schematic diagram of an apparatus for purifying calcium chloride from fluorine-containing solid waste in accordance with some embodiments of the present invention.
The reference numerals of the device include 10, a carbonation reaction device, 11, a leaching tank, 20, an interference source separation device, 21, a second solid-liquid separator, 22, a second leaching head, 30, a hydrochlorination reaction device, 31, an acid leaching tank, 40, a purification device, 41, a first solid-liquid separator, 42, a first leaching head, 43, an acidity adjusting tank, 44, an evaporator, 50, a carbonate recovery device, 51, a distiller, 52, a cooling chamber, 53, a third solid-liquid separator, 54 and an evaporation chamber.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, 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. Based on the embodiments of the present invention, other embodiments obtained by persons of ordinary skill in the art with the understanding of the inventive concept of the present invention are within the scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In order to facilitate understanding of the technical scheme of the present invention, the method, the using method and the manufacturing method of the present invention for purifying calcium chloride from fluorine-containing solid waste are further described in detail below, but the present invention is not limited to the scope of protection. FIG. 1 is a flow chart showing steps in a method for purifying calcium chloride from fluorine-containing solid waste according to some embodiments of the present invention, and FIG. 2 is a schematic diagram showing an apparatus for purifying calcium chloride from fluorine-containing solid waste according to some embodiments of the present invention.
Referring to fig. 1, a method for purifying calcium chloride from fluorine-containing solid waste includes:
step S1, carrying out carbonation reaction on the fluorine-containing solid waste, wherein the fluorine-containing solid waste before carbonation comprises calcium fluoride, calcium-containing sulfate and calcium-containing compound;
step S2, separating a purification interference source of the carbonated fluorine-containing solid waste, wherein the purification interference source comprises soluble non-calcium sulfate, and the carbonated fluorine-containing solid waste comprises calcium fluoride and calcium carbonate;
and S3, performing a hydrochlorination reaction on the carbonated fluorine-containing solid waste after separation, performing acid leaching, and then performing S4, wherein the method comprises first solid-liquid separation and first cyclic leaching on the solid obtained by the first solid-liquid separation, combining an acid leaching filtrate discharged by the first solid-liquid separation and a partial acid leaching derived solution with acidity exceeding a lower pH threshold value in the first cyclic leaching, and purifying calcium chloride solid, wherein the fluorine-containing chlorine-containing solid waste obtained after the first solid-liquid separation contains calcium fluoride.
The implementation principle of the embodiment is as follows: the method comprises the steps of replacing calcium-containing sulfate and calcium hydroxide in the fluorine-containing solid waste into calcium carbonate by carbonation reaction, separating non-calcium sulfate and other interference sources, converting the calcium carbonate into calcium chloride by using acid leaching of hydrochloric acid and first solid-liquid separation, collecting acid leaching filtrate obtained by solid-liquid separation and a partial acid leaching effluent liquid obtained by solid-liquid separation and having acidity exceeding a lower pH threshold value under cyclic leaching of the chlorine-containing solid waste, and finally purifying high-purity calcium chloride solid. More specifically, calcium hydroxide in the fluorine-containing solid waste can be consumed in both the carbonation reaction and the hydrochlorination reaction, calcium chloride is directly or indirectly generated, and the superacid discharge liquid under the cyclic leaching of the solid intermediate under the solid-liquid separation and the liquid intermediate under the solid-liquid separation are combined and collected, so that the yield of the calcium chloride solid serving as the intermediate product is improved.
In a preferred embodiment, the total calcium content of the obtained calcium chloride is higher than the calcium content of the calcium-containing sulfate in the fluorine-containing solid waste before carbonation, and the first solid-liquid separation and the first cyclic leaching are performed in the same centrifugal filter in step S4. The centrifugal filtering mechanism is similar to the dewatering principle of a pulsator washing machine.
The purity, recovery and yield of calcium chloride obtained when calcium sulfate and calcium compound in the fluorine-containing solid waste are converted into calcium chloride and the acidity is adjusted are shown in the following table:
name (R) Purity of anhydrous calcium chloride% The recovery rate is high Yield%
Purity, recovery, yield of calcium chloride solids from fluorine-containing solid wastes 100 100 31.01
Actually, the purity and the yield of the calcium chloride solid recovered from the fluorine-containing solid waste and the calcium chloride solid obtained in the acidity adjustment are mixed uniformly 95.91 32.99
Purity and yield of calcium chloride obtained by adjusting acidity 96.52 1.15
Purity, recovery, yield of calcium chloride solids from fluorine-containing solid wastes 95.89 98.46 31.84
In a preferred example, step S4 of the method further includes acidity adjustment and evaporation of the acid leach filtrate and the partial acid leach effluent, wherein the acidity adjustment is performed to adjust the acidity of the acid leach filtrate and the partial acid leach effluent having the acidity exceeding the lower pH threshold in the first cycle leach to be neutral, and preferably, the acidity adjustment is performed using calcium carbonate or/and calcium hydroxide as an adjusting agent. The threshold value may be set to 5.0 at the pH, preferably the first cycle rinse is a neutral cycle rinse using water. The calcium chloride solid obtained is produced by crystallization and has high purity. The calcium chloride content of the calcium chloride solid (calculated as anhydrous calcium chloride) obtained in the example of the flow chart is 95.91 percent, which is greater than the standard of not less than 94 percent of the national standard industrial pure grade I product. The combination and collection of the acid leaching filtrate and the partial acid leaching effluent can reduce the acidity of the imported substance in advance when entering the acidity adjusting procedure.
In a preferred example, the step S2 includes a second solid-liquid separation and a second cyclic leaching of the solids from the second solid-liquid separation, and recovering and purifying the non-calcium carbonate from the leaching filtrate from the second solid-liquid separation and the partially alkaline leaching derived solution with alkalinity exceeding the upper pH threshold in the second cyclic leaching, and preferably, the recovered non-calcium carbonate is added to the leaching agent for carbonation reaction in a cyclic manner. The upper pH threshold value can be set to 8.5, preferably, the second circulation leaching is neutral circulation leaching using water, and the recovery and purification of the non-calcium carbonate comprises mixing, distillation, cooling and third solid-liquid separation, wherein the non-calcium carbonate is formed in solids of the third solid-liquid separation, and liquid discharged by the third solid-liquid separation flows back to the distillation.
In a preferred embodiment, the distillation residue is evaporated to obtain non-calcium sulfate, and the carbonation reaction is preferably carried out in a blending and leaching manner in step S1, wherein the leaching agent is ammonium carbonate.
Referring to fig. 2, an apparatus for purifying calcium chloride from fluorine-containing solid waste includes:
the carbonation reaction device 10 is used for carrying out carbonation reaction on the fluorine-containing solid waste;
a disturbance source separation device 20 connected to the carbonation reaction device (10) for separating a purification disturbance source of carbonated fluorine-containing solid waste;
the hydrochlorination reaction device 30 is connected with the interference source separation device 20 and is used for carrying out hydrochlorination on the carbonated fluorine-containing solid waste after separation, and the hydrochlorination reaction device (30) comprises an acid leaching tank 31;
the purification device 40 is connected with the hydrochlorination reaction device 30 and is used for purifying the solid-liquid intermediate of the hydrochlorination reaction device 30 to obtain calcium chloride solid;
the purifying device 40 includes a first solid-liquid separator 41 and a first circulating leaching system, the first circulating leaching system has a first leaching head 42, and is configured to circularly leach the chlorinated solid waste of the first solid-liquid separator 41, and an acid leaching filtrate line of the first solid-liquid separator 41 and a partial acid leaching effluent line of the first circulating leaching system are connected to a common pipeline for purifying calcium chloride.
Preferably, the first solid-liquid separator 41 and the first shower head 42 are constructed in the same centrifugal filter.
Preferably, the purifying device 40 further comprises an acidity adjusting tank 43 and an evaporator 44, wherein the acidity adjusting tank 43 is connected to the common pipeline and is used for adjusting the pH value of the solution led out from the common pipeline to be close to neutral so as to purify calcium chloride.
Preferably, the interference source separation device 20 comprises a second solid-liquid separator 21 and a second circulating washing system, the second circulating washing system has a second washing head 22 for circularly washing the carbonated fluorine-containing solid waste of the second solid-liquid separator 21, and the leaching filtrate line of the second solid-liquid separator 21 and the alkali-biased washing outlet line of the second circulating washing system are connected with the carbonate recovery device 50.
More preferably, the carbonate recovery apparatus 50 includes a distiller 51, a cooling chamber 52 and a third solid-liquid separator 53 in order of a recovery path, so that non-calcium carbonate is formed in the solids of the third solid-liquid separator 53, and a liquid discharge line of the third solid-liquid separator 53 returns to the distiller 51.
More preferably, the carbonate recovering device 50 further comprises an evaporation chamber 54 for evaporating the residue obtained from the distiller 51 to obtain non-calcium sulfate, and the solid outlet of the third solid-liquid separator 53 is connected to the carbonation reaction device 10, and preferably, the carbonation reaction device 10 comprises a leaching tank 11 using ammonium carbonate as a leaching agent.
With respect to the fluorine-containing solid waste, in one example, the fluorine-containing solid waste is limestone (CaCO)3) And limes (e.g., quicklime (CaO) and hydrated lime Ca (OH))2) The slurry liquid absorbs the fluorine-containing and sulfur-containing smoke dust and smoke generated in the industrial production process in a spraying mode and generates a mixture of a plurality of compounds after chemical reaction. The main components of the mixture are three different types of calcium-containing compounds, and small amounts of silica and alumina. The specific content ranges of the various compounds are; the content of calcium fluoride is 30-80%. Less than 40% of calcium sulfate and less than 2% of calcium sulfite. The calcium-containing compounds are less than 40%, and are mainly calcium hydroxide (Ca (OH)2) Calcium carbonate (CaCO)3) Less than 20% of silicon dioxide and less than 2% of aluminum oxide. The fluorine-containing solid waste contains many kinds of compounds and complicated components, and the main physicochemical properties of each compound are 1. calcium hydroxide (consumed by the reaction between step S1 and step S3), calcium sulfate (consumed by the reaction between step S1), calcium carbonate (generated by the reaction between step S1), calcium fluoride (no reaction), and calcium sulfite (generated by the reaction between hydrochloric acid in the acid leaching tank 31 of step S3), which are hardly soluble in water. 2. Calcium carbonate and calcium hydroxide are readily soluble in acids. 3. Calcium sulfate is easy to react with ammonium carbonate to generate calcium carbonate and ammonium sulfate, 4. at normal temperature, calcium fluoride is extremely insolubleWater-soluble, slightly acid-soluble, ammonium carbonate solution. However, when a small amount of calcium ions or fluorine ions exist in the water, acid and ammonium carbonate solution, the same ion effect phenomenon basically affects the solubility of calcium fluoride under the conditions of low concentration of water and hydrochloric acid, normal temperature and long leaching time, high concentration of ammonium salt solution, normal temperature and long leaching time, and high temperature, high concentration of hydrofluoric acid and long leaching time. 5. The silicon dioxide is insoluble in water, a small amount of the silicon dioxide is soluble in concentrated alkali and is soluble in hydrofluoric acid.
The invention designs a front-stage method and front-stage equipment for purifying calcium fluoride from fluorine-containing solid waste by utilizing the main chemical properties of each compound in the fluorine-containing solid waste, and in the process of purifying the calcium fluoride, calcium chloride solid is simultaneously purified by a front-stage process and is used as an intermediate product, so that the aim of completely utilizing each compound in the fluorine-containing solid waste is finally fulfilled. The technical scheme of the previous stage is divided into several aspects, 1, the purified calcium chloride solid adopts an acid leaching mode, then the solid intermediate of the first solid-liquid separation is circularly leached and combined, and the partial acid leaching solution and the liquid intermediate of the first solid-liquid separation are collected (corresponding to steps S3 and S4 in figure 1). b. Other calcium-containing sulfates and compounds are converted into other calcium-free chemical products (corresponding to step S1 in fig. 1) and calcium-containing non-sulfates by chemical production. c. The waste acid and waste liquid generated in the production process are treated in a pollution-free recovery mode and a recycling mode returned to the production flow (corresponding to step S2 in the figure 1). Finally, all compounds in the fluorine-containing solid waste can be utilized, no wastewater and solid waste are generated in the production process, no secondary pollution is caused to the environment, and the requirement of environmental protection is met.
In one example, the fluorine-containing solid waste is white gray in appearance as a wet sludge, but the particle size in aqueous solution is extremely fine. The size distribution is shown in Table 1, and the chemical composition and the content of each element are shown in Table 2.
Figure DEST_PATH_IMAGE001
Figure 914073DEST_PATH_IMAGE002
As is clear from the descriptions of the fluorine-containing solid wastes in tables 1 and 2, the fluorine-containing solid wastes have a high calcium fluoride content and a high calcium-containing sulfate salt (calcium sulfate dihydrate, calcium sulfite) content, and contain a small amount of silicate or quartz (calculated as silica) and other calcium-containing compounds (calculated as CaO). The calcium-containing compounds are various calcium compounds which can react with hydrochloric acid and the reaction product can be dissolved in an aqueous solution, and mainly include calcium carbonate and calcium hydroxide. Because the granularity is too fine, and the content of calcium-containing compounds and calcium sulfate salts is high and the components are complex, the conventional physical ore dressing mode cannot be adopted to purify calcium fluoride and classify and select various compounds in the calcium fluoride, and the aim of purifying various compounds is fulfilled.
According to the situation, the invention exemplifies the former stage process of purifying calcium fluoride in fluorine-containing solid waste, and converts other calcium-containing calcium sulfate salts and compounds into alternative chemical products by adopting a chemical production method, wherein the calcium sulfate salts of calcium are converted into ammonium sulfate chemical products and calcium carbonate, and the compounds of calcium carbonate and calcium are converted into calcium chloride chemical products, so that the fluorine-containing solid waste is effectively utilized, no waste water is discharged in the process, no waste solid waste is generated, and no secondary pollution is caused to the environment.
The front-stage production process flow in the example of the invention is fluorine-containing solid waste → leaching → solid-liquid separation (filtration) → rinsing → acid leaching → solid-liquid separation (filtration) → rinsing → acidity adjustment → evaporation → calcium chloride solid (intermediate product). Wherein, the leaching can correspond to the step S1 in the figure 1, the solid-liquid separation (filtration) and the leaching after the leaching can correspond to the step S2 in the figure 1, the acid leaching can correspond to the step S3 in the figure 1, and the solid-liquid separation (filtration), the leaching, the acidity adjustment and the evaporation after the acid leaching can correspond to the step S4 in the figure 1.
Referring to fig. 1 and 2, step S1 corresponds to the carbonation reaction device 10 obtaining the leached solid, and after the leached solid passes through the second shower head 22 used by the interference source separation device 20 in step S2, the solid contains three substances of calcium carbonate, calcium fluoride and silicon dioxide, and the non-calcium sulfate and the non-calcium carbonate are filtered out in the second solid-liquid separation. In the acid leaching in step S3, the hydrochloric acid is added to the hydrochloric acid reaction apparatus 30 and reacts with calcium carbonate to form calcium chloride dissolved in water, and the hydrochloric acid does not react with calcium fluoride and silicon dioxide. In step S4, the acidity of the liquid obtained by solid-liquid separation (adding calcium carbonate) is adjusted in the acidity adjusting tank 43 so that the pH of the solution rises from about 1 to about 7 in accordance with the purification apparatus 40, wherein the pH of the liquid after washing is greater than 1.0 and the pH of the mixed solution of the filtrate (pH is not greater than 1.0) is about 1.0, calcium carbonate reacts with hydrochloric acid to generate calcium chloride, calcium chloride solid is obtained after evaporation, and the solid obtained by the first solid-liquid separation and the first circulation washing is calcium fluoride and silica, and then the acid leaching operation of the subsequent calcium fluoride purification is performed. The preparation of the acid leaching solution in step S3 may be, mixing commercially available concentrated hydrochloric acid with water, or preparing a filtered solution of meta-acid after the solid-liquid separation process in the recovery process of calcium fluoride purification according to a predetermined preparation ratio, wherein when the concentration of calcium chloride in the filtered solution after the first solid-liquid separation process is higher than or equal to 15%, and the reaction cannot be completed due to the same ion effect, the filtered solution is not returned to be mixed with concentrated hydrochloric acid or/and the solid obtained by the second cyclic leaching, and the liquid used for mixing with the solid obtained by the concentrated hydrochloric acid and the solid obtained by the second cyclic leaching is a filtrate containing hydrochloric acid and a recycle leaching liquid (not shown) after the solid-liquid separation and leaching processes in the second production line (the latter stage process of calcium fluoride purification) in the subsequent calcium fluoride recovery process. Usually, the two liquids contain a small amount of calcium chloride, and the dissolution rate of calcium fluoride is reduced due to the isoionic effect generated by the existence of calcium ions.
Specifically, the solution leached in step S1 contains ammonium sulfate, the solid separated in step S2 generally contains about 30-40% of the leached solution, and the leached solution is washed out by the second solid-waste separator 21 and the second circulation leaching system. If the calcium fluoride is not removed and washed, the ammonium sulfate in the calcium fluoride reacts with the calcium chloride (generated by the reaction of the hydrochloric acid and the calcium carbonate in the step S3) generated subsequently to generate calcium sulfate insoluble in water and acid, which has an adverse effect on the purification purity of the calcium fluoride. When the pH of the leacheate used in the second cycle reaches about 8.5, the concentration of ammonium carbonate in the leacheate is about 0.1% (mass percent), that is, when the pH of the solution is about 8.5, the concentration of ammonium sulfate in the solution is low.
Referring to fig. 2, the fluorine-containing solid waste is subjected to blending, leaching, second solid-liquid separation (filtering), and second cyclic leaching processes in the process, and the leaching pulp solution is prepared by calculating the volume of water and the mass of leaching agent according to a specified preparation ratio according to the mass of the solid (dry basis contains no water) added into the leaching equipment, and then adding the required water and the mass of the leaching agent into the leaching equipment.
The solution after leaching and the second solid-liquid separation enters a carbonate recovery flow according to a route III and a solution (the acid concentration is more than or equal to 8.5) after the second circulation leaching. And when the solution (with the acid concentration of pH less than 8.5) after the second circulation leaching returns to the reflux process of the second circulation leaching system according to a first line, the solution is used for leaching the solid after the second solid-liquid separation (filtration) process again, and the solid after the second circulation leaching process enters an acid leaching process. The filtrate of the second solid-liquid separation (filtration) also enters the carbonate recovery flow according to the route (c). When the pH of the second recycle rinse liquor increases, residual non-calcium carbonate, such as ammonium carbonate, in the solids (carbonated fluorine-containing solid waste) after the second solid-liquid separation (filtration) process continues to be washed out, wherein the calcium carbonate in the solids is insoluble. Therefore, step S1 is to convert calcium sulfate and calcium hydroxide contained in the fluorine-containing solid waste into calcium carbonate, and step S2 is to separate non-calcium carbonate from non-calcium sulfate in a dissolving manner, the non-calcium carbonate can be recycled, and the non-calcium sulfate can be sold as chemicals.
In step S2, there is a recycling step of non-calcium carbonate, and the saturated solution of ammonium carbonate after the third solid-liquid separation (filtration) step is returned to the distillation step in line (line) by using the carbonate recovery apparatus 50 of fig. 2, and the operations of distillation, cooling and solid-liquid separation are performed again.
As a specific example of the hydrochlorination step S3 and the purification step S4, the solid after the leaching step in the leaching process enters the leaching process. And (3) connecting the step (S2) with the step (S3), preparing the acid leaching ore pulp solution, calculating the required added water according to the specified preparation proportion according to the mass of the solid added into the acid leaching equipment (dry basis contains no water), or adding the obtained filtrate after solid-liquid separation in the subsequent calcium fluoride purification recovery process (calcium fluoride purification post-stage process), or/and the obtained filtrate after hydrochloric acid-containing meta acid leaching and liquid after recycling leaching operation, and calculating the appropriate volume and dosage.
The solid after the operation of acid leaching, first solid-liquid separation (filtration) and first cyclic leaching enters acid leaching (not shown) for purifying calcium fluoride. The solution after acid leaching and first solid-liquid separation (filtration) enters the acidity adjustment and evaporation processes in the process according to a line I and a line II when the pH value of the solution after the first circulation leaching is less than or equal to 5.0, and then a chemical product II of calcium chloride solid is obtained by recycling, wherein the product has high enough purity, and in one example, the content of anhydrous calcium chloride is 95.91%, and the product can be sold to required industries. And when the solution in the first cyclic leaching is more than 5.0 in acid concentration, returning the solution to the first cyclic leaching procedure of the flow for leaching the solid after the first solid-liquid separation (filtration) procedure again. Preferably, in addition to the first line, the solution after the first solid-liquid separation step in the process can be treated in two ways; the chemical product II is a chemical product II, wherein calcium chloride solid is obtained after evaporation operation in the evaporation process of the flow. The other is that the filtrate is returned to the acid leaching process (step S3) to replace water to be used for being mixed with concentrated acid to prepare acid leaching solution, or used for diluting the solid after the operation of the second circulation leaching process in the leaching process to prepare ore pulp solution with the solid-liquid ratio (mass percentage) of 1:1 in the mixing process, namely, the bypass line serving as a line (I) returns the filtrate obtained by the first solid-liquid separation to either or both of the two mixing tanks connected in front of the acid leaching tank 31 in fig. 2. When the concentration of calcium chloride in the filtered solution after the operation of the first solid-liquid separation procedure is more than or equal to 15 percent, the calcium chloride is not returned to be uniformly mixed with concentrated hydrochloric acid or/and the solid obtained by the second circulation leaching.
The two leaching solutions used in the respective cyclic leaching working procedure operation of the four process steps are in sequence that the leached reflux solutions meeting the acid concentration and pH requirements of the leaching solutions are leached, and then the leaching is carried out by water until the acid concentration and pH of the leached solutions meet the requirements.
Therefore, the previous stage process for purifying calcium fluoride provided by the example of the present invention may be similar to the production and waste liquid treatment of the chemical industry, and although there are many chemical varieties of leaching agents, concentrated acids, etc. that are needed, new solid compounds may be generated during the leaching and acid leaching processes, and the new solid compounds are dissolved in the leached solution, the acid leached solution, and the leached solution respectively, and the concentration of the generated new solid compounds is high, and does not meet the national relevant wastewater discharge standard. The processing and judging sequence of the various leached solutions, the acid-leached solutions and the leached solutions in the production flow is (1) the acid-leached solutions and the leached solutions meeting the requirements in the flows adopt a mode of returning to each process of each process flow for recycling again, so that the purposes of fully recycling, saving chemical products and water consumption, reducing equipment investment and lowering production cost are achieved. (2) The solution after acid leaching, the solution after leaching and the solution after leaching which do not meet the requirements in each flow are recovered by a recovery treatment method, intermediate product solids such as ammonium carbonate, ammonium sulfate, calcium chloride and the like are obtained after the recovery treatment, various marketable chemical products can be obtained, and profit income can be increased. And can achieve the purposes of no waste water and no solid waste discharge, and meet the requirement of environmental protection.
As for the explanation of the process parameters and production steps of the steps S1 and S2, the process parameters of the leaching process are that the leaching agent adopts ammonium carbonate (solid), the molar ratio of calcium sulfate to ammonium carbonate in the fluorine-containing solid waste is about 1:1.3, and calcium-containing compounds in the fluorine-containing solid waste are Ca (OH)2Meter]The molar ratio to ammonium carbonate was about 1: 1.3. The method for determining the use quality of the leaching agent comprises the following steps of respectively calculating calcium sulfate (calcium sulfite is converted into calcium sulfate) or/and calcium-containing compounds [ Ca (OH) ] in the fluorine-containing solid waste added into the leaching equipment2Meter]Of the respective substancesThe amounts (in moles) were then calculated from their ratios to ammonium carbonate =1:1.3 (mole ratio), the mass of ammonium carbonate that needs to be added each. The solid-to-liquid ratio (mass ratio) of the leaching ore pulp is fluorine-containing solid waste: water =1: 1.5. The preparation of the leaching pulp solution is that according to the mass of the fluorine-containing solid waste added into the leaching equipment, the mass of the water required to be added is firstly added according to the preparation proportion, then the mass of the ammonium carbonate required to be added is added according to the preparation proportion, and the mixture is stirred uniformly. The leaching time is about 60-120 minutes. The leaching temperature can be normal temperature, and the stirring speed is 200 r/min.
As for the source description of the fluorine-containing solid waste, several methods for treating the smoke and fumes are available, among which the principle of the calcium-based treatment method, using limestone (CaCO)3) Or limes [ CaO/Ca (OH) ]2]The serous fluid absorbs the smoke dust containing fluorine and sulfur and the smoke gas generated in the industrial production in a spraying mode and then undergoes chemical reaction to obtain a mixture of a plurality of calcium-containing compounds. With limestone (CaCO)3) The mixture of various calcium-containing compounds obtained after treatment contains calcium fluoride, calcium sulfate, calcium sulfite and the like, and limestone left after reaction with fluorine-containing and sulfur-containing smoke dust and flue gas. With limes [ quicklime (CaO)/hydrated lime (Ca (OH) ]2）]The mixture of various calcium-containing compounds obtained after treatment contains limestone, calcium fluoride, calcium sulfate, calcium sulfite, slaked lime left after reaction with fluorine-containing and sulfur-containing smoke dust and flue gas, and the like. The ammonium carbonate used in the present example reacts only with the hydrated lime and calcium sulfate to form limestone and does not react with limestone. When limestone (CaCO) is used3) The treated fluorine-containing solid waste is substantially free of lime, so that the determination of the quality of the leaching agent does not require the calculation of the calcium-containing compounds [ Ca (OH) ]2Meter]Molar ratio to ammonium carbonate . And lime [ quicklime (CaO)/hydrated lime (Ca (OH))2）]The treated fluorine-containing solid waste contains hydrated lime [ Ca (OH)2]Class, so that the determination of the leachant mass should account for the class of calcium-containing compounds [ in Ca (OH) ]the fluorine-containing solid waste2Meter]Molar ratio to ammonium carbonate . Limestone and limes, fluorine-containing and sulfur-containing smoke and fumeThe chemical reaction is carried out in a reaction scheme (the temperature of the chemical reaction is high);
with limestone (CaCO)3) The reaction formula of the treatment comprises one or more of the following:
2F2+2H2O=4HF+O2↑
CaCO3+2HF=CaF2+CO2↑+H2O
CaCO3+SO2=CaSO3+CO2↑ ; 2CaSO3+O2= 2CaSO4
CaCO3+S03=CaSO4+CO2↑
CaSO4+2H2O= CaSO4·2H2O
with limes [ quicklime (CaO)/hydrated lime (Ca (OH) ]2）]The reaction formula of the treatment comprises one or more of the following:
CaO+H20=Ca(OH)2
Ca(OH)2+2HF=CaF2+2H2O
Ca(OH)2+SO2=CaSO3+H20 ; 2CaSO3+O2= 2CaSO4
Ca(OH)2+S03=CaSO4+H2O
CaSO4+2H2O= CaSO4·2H2O
the specific production steps of the leaching process of step S1 and the separation process of step S2 include, but are not limited to:
firstly, putting a certain mass of fluorine-containing solid waste into leaching equipment, and then adding the mass of water required to be added according to the preparation proportion;
and step two, opening a stirring device of the leaching equipment, and adding the mass of the ammonium carbonate required to be added according to the preparation proportion. The leaching time is kept for 90min, wherein the leaching time is determined according to the content of calcium sulfate and calcium hydroxide in the fluorine-containing solid waste, and the leaching time is long when the content is high;
and thirdly, the leached ore pulp enters solid-liquid separation (filtration) equipment, and the leached ore pulp is subjected to second solid-liquid separation (filtration) and second circulating leaching working procedure operation in the equipment. Firstly, carrying out solid-liquid separation (filtration) operation, leaching the solid after the solid-liquid separation (filtration) operation by using a solution (with the acid concentration of less than 8.5) in the circular leaching of the process, and then leaching by using water until the pH of the leached solution is approximately equal to 7.0;
and fourthly, returning the leached solution (with the acid concentration of pH less than 8.5) in the second circulating leaching process operation to the process leaching process for leaching the solids after a new solid-liquid separation (filtration) process. b. The leached filtered solution after the second solid-liquid separation (filtration) process operation enters the non-calcium carbonate recovery process according to a line III and the leached solution after the second circulating leaching process operation according to a line IV when the acid concentration pH is more than or equal to 8.5. c. And the solid after the operation of the second circulation leaching process enters the acid leaching process of the step S3.
The principle of the leaching process is illustrated by the solubility products of calcium sulfate and calcium carbonate in water (25 ℃) of Lcaso4=4.8 × 10-5、Lcaco3=2.5×10-9The equilibrium constant of the reaction is equal to the ratio of the solubility products of the two substances, K =4820, the reference is the university of Wuhan's project bulletin<Process for preparing ammonium sulfate from phosphogypsum>Pan-Shi-Ma-Shi-Ye, etc. It is possible to react ammonium carbonate with calcium sulfate to form calcium carbonate and ammonium sulfate. And ammonium carbonate and calcium-containing compounds [ Ca (OH) ]2Meter]And reacting to generate calcium carbonate and ammonia water, wherein the calcium carbonate is a substance which is extremely insoluble in water and is insoluble in the leached solution and the solution after the leaching operation, and the ammonium sulfate is dissolved in the leached solution and the solution after the leaching operation. After the solid-liquid separation (filtration) and leaching processes, the calcium carbonate and other solids (mainly calcium fluoride and silicon dioxide) in the fluorine-containing solid waste enter an acid leaching process, and the ammonium sulfate and the ammonium carbonate completely react with the calcium sulfate (and calcium-containing compounds) and then the residual ammonium carbonate enters a carbonate recovery process.
Chemical reaction equations for ammonium carbonate with calcium sulfate and calcium-containing compounds.
CaSO4·2H2O+(NH4)2CO3=(NH4)2SO4+CaCO3↓+2H2O
Ca(OH)2+(NH4)2CO3=CaCO3↓+2NH3·H2O
At normal temperature, the longer the leaching time of the fluorine-containing solid waste is, the better the leaching effect is, but the leaching production cost is increased. When the leaching rate can meet the requirement, the shorter the leaching time is, the better the leaching time is. The effect of leaching time on leaching rate at 20 ℃ under otherwise unchanged conditions is given in the following table:
Figure DEST_PATH_IMAGE003
according to the data in the table, the leaching rate can meet the requirement when the leaching time is 90 min.
Since leaching is a chemical reaction (double decomposition reaction), the reaction speed is slow at normal temperature, and the leaching temperature has an influence on the leaching speed. The leaching rate is faster as the leaching temperature is increased, but the higher the leaching temperature is, the faster ammonium carbonate in the leaching agent is decomposed, and the leaching rate is decreased. And the leaching rate of the calcium fluoride is increased, when the leaching time is 90min and other conditions are not changed, the influence of the leaching temperature on the leaching rate of the fluorine-containing solid waste and the calcium fluoride is shown in the following table:
Figure 627820DEST_PATH_IMAGE004
according to the data in the table; the leaching temperature is optimal at normal temperature.
After the calcium sulfate reacts with the ammonium carbonate, the generated calcium carbonate is adsorbed on the surfaces of calcium sulfate particles, so that the calcium sulfate can not continuously react with the ammonium carbonate, but under the condition of rapid stirring during leaching in the step S1, solid particles in the ore pulp can collide and rub with each other and water flow scours the calcium sulfate particles, so that the calcium carbonate adsorbed on the surfaces of the calcium sulfate particles can be separated from the surfaces of the calcium sulfate particles and enter a solution, and the calcium sulfate can react with the ammonium carbonate to generate the calcium carbonate, thereby achieving the purpose of converting the calcium sulfate into the calcium carbonate.
The process parameters of the non-calcium carbonate recovery flow in the separation step S2 include that the distillation temperature is more than or equal to 100 ℃, the cooling temperature is normal temperature, and the evaporation temperature is more than or equal to 100 ℃. The specific production steps of the recovery process include, but are not limited to:
step one, uniformly mixing a solution leached in the leaching process and a solution (with the acid concentration of more than or equal to 8.5) after circular leaching;
and secondly, introducing steam to volatilize the ammonium carbonate into the cooling equipment in a gas mode. Condensing the cooled ammonium carbonate gas into liquid, wherein the liquid is saturated ammonium carbonate solution or ammonium carbonate crystals appear;
and thirdly, feeding the cooled solution into third solid-liquid separation (filtration) equipment for third solid-liquid separation (filtration). The solid after the third solid-liquid separation (filtration) process is a chemical product such as ammonium carbonate solid, and the liquid is ammonium carbonate saturated solution;
and fourthly, the solution after the ammonium carbonate is completely volatilized enters an evaporation process. And evaporating to obtain chemical products with crystals such as ammonium sulfate.
The non-calcium carbonate recovery process is further described as follows, the leached filtrate and the solution after the circulating leaching (acid concentration pH is more than or equal to 8.5) are fed into the main stream recovery process through the leaching process of step S1 and the second solid-liquid separation of step S2, the leached filtrate and the partial alkali solution in the circulating leaching (acid concentration pH is more than or equal to 8.5) contain two compounds of ammonium carbonate and ammonium sulfate, the ammonium carbonate is fed into a cooling device in a gas mode during distillation operation, and the ammonium carbonate is decomposed into NH at 70 DEG C3And CO2The gas, together with a part of the water vapour, also enters the cooling device. NH (NH)3And CO2The gas is absorbed by the water vapor to generate ammonium carbonate again, a vapor of the ammonium carbonate and the water is formed, and the vapor of the ammonium carbonate and the water after being cooled to the room temperature is changed into a saturated solution of the ammonium carbonate. The solution after the distillation operation is ammonium sulfate solution, so that the purpose of separating ammonium carbonate from ammonium sulfate is achieved. After ammonium carbonate is gasified and enters the cooling equipment together with water vapor to be cooled to room temperature, a solution, such as a saturated solution of ammonium carbonate, may be dissolvedA large amount of ammonium carbonate crystals appear, the ammonium carbonate crystals are separated from the ammonium carbonate saturated solution after the third solid-liquid separation (filtration) operation, the ammonium carbonate crystals are returned to the leaching process of step S1 for leaching new fluorine-containing solid waste, and specifically, the solution of the ammonium carbonate saturated solution can be returned to the distillation process for distillation again. The distilled solution enters an evaporation process. The crystal obtained after water evaporation is an ammonium sulfate chemical product, and the product can be sold to required industries.
Regarding the process parameters and production steps of steps S3 and S4, the process parameters of the acid leaching process of step S3 are specifically described as follows, the acid source of the acid leaching agent may be 17% (mass percentage concentration) of acid, the acid leaching agent is configured in percentage that the acid source is mixed with a solvent in a ratio, and the solvent may be water or filtrate recovery liquid and leaching educt after solid-liquid separation and recycling leaching process operation in the second production line of the later stage recovery process of purifying calcium fluoride. The acid leaching time is about 15-30min, the acid leaching temperature can be normal temperature, the solid-to-liquid ratio (mass ratio) of the acid leaching ore pulp for reacting with the acid leaching agent is obtained by adding equal-ratio water to the solid after the second circulating leaching procedure operation after the leaching procedure of the step S1 or mixing the filtrate recovery liquid and the circulating leaching educt liquid after the solid-liquid separation and leaching procedure operation in the second production line in the rear-stage recovery procedure of the calcium fluoride purification procedure in the step S4, and the hydrochloric acid reaction is prepared in advance. The preparation of the acid leaching pulp solution is to add the mass of the required added water calculated according to the preparation proportion according to the mass of the solid added into the acid leaching equipment after the leaching process of the step S1 and the second circulation leaching process of the step S2, and to stir the mixture evenly. The acidity regulator used in the acidity regulating step of step S4 may be calcium carbonate or calcium hydroxide, and the acidity regulating temperature is about room temperature, and the stirring speed in the acidity regulating process is based on the fact that the solids in the acid leaching pulp do not sink to the bottom of the acid leaching equipment.
The specific production steps from the acid leaching process of step S3 to the calcium chloride purification process of step S4 include, but are not limited to:
a first step of putting a certain mass of solid which passes through the leaching process of the step S1 and is subjected to the second circulating leaching process of the step S2 into acid leaching equipment (a blending tank is led in from the upper right side of an acid leaching tank 31 as shown in figure 2), and then adding the mass number of water required to be added (or filtrate recovery liquid and leaching effluent liquid after solid-liquid separation and circulating leaching process operation in a second production line in the later stage recovery process of purifying calcium fluoride) calculated according to the preparation ratio;
secondly, in the acid leaching tank 31 shown in figure 2, the stirring device of the acid leaching equipment is opened, the acid leaching agent is slowly added for acid leaching, when the acidity pH of the acid leaching ore pulp solution is less than or equal to 1, the upper limit value of the acidity of the acid leaching operation can be set, the acid leaching agent is stopped to be added, and the stirring is carried out for 20 minutes;
thirdly, the ore pulp after acid leaching enters a solid-liquid separation (filtration) device, and the first solid-liquid separation (filtration) and the first cyclic leaching process operation are carried out at the position of a first solid-liquid separator 41 shown in figure 2. And (3) leaching the solid after the operation of the first solid-liquid separation (filtration) procedure by using the solution (with the acid concentration of more than 5.0) leached by the first circulation of the process, and then leaching by using water until the pH of the leached solution is approximately equal to 7.0. The leached solid enters an acid leaching flow (not shown) for purifying calcium fluoride at the later stage; therefore, the solution (with the acid concentration of more than 5.0) after the first circulation leaching is returned to the process leaching procedure according to the line I and is used for leaching the new solid-liquid separation (filtration) procedure;
fourthly, the solution after acid leaching after the first solid-liquid separation (filtration) and the solution after the first circular leaching (the acid concentration pH is less than or equal to 5.0) enter the processes of acidity adjustment and evaporation according to a line II;
fifthly, uniformly mixing the solution after acid leaching in the circuit I and the solution after circular leaching in the circuit II (the acid concentration is less than or equal to 5.0). Under the stirring in the acidity regulating tank 43, slowly adding an acidity regulator into the uniformly mixed solution until the pH value of the solution is preset, and stopping adding the acidity regulator, wherein the pH value of the solution is regulated to be about 5.0 under the 1 st application condition and the pH value of the solution is regulated to be about 7.0 under the 2 nd application condition when calcium carbonate is added;
and sixthly, putting the solution with the adjusted acidity into an evaporation process to obtain crystals as a calcium chloride chemical product.
After the acid leaching process of step S3 and the first solid-liquid separation process of step S4 are further described, the leaching process is performed in step S1 to remove non-calcium carbonate and non-calcium sulfate in step S2, the acid leaching process of step S3 is performed, the calcium carbonate and other solids (mainly calcium fluoride and silicon dioxide) in the fluorine-containing solid waste after the first solid-liquid separation (filtration) and the first cyclic leaching process operation are performed in step S4, and then enter the process, and under the leaching principle of the acid leaching of the process, the hydrochloric acid and the calcium carbonate react to generate calcium chloride, water and carbon dioxide gas. At normal temperature, when hydrochloric acid reacts with calcium carbonate, the higher the concentration of the hydrochloric acid is, the faster the reaction speed of the hydrochloric acid and the calcium carbonate is, because the calcium carbonate is solid, the lower the concentration of the hydrochloric acid is, the slower the reaction speed of the hydrochloric acid and the calcium carbonate is, the longer the time required for the reaction to be complete is, and the longer the reaction time of the hydrochloric acid and the calcium carbonate is, the acid leaching rate of solid calcium fluoride in fluorine-containing solid waste is increased, the concentration of fluoride ions entering into an acid leaching solution is also increased, and the purity of a calcium chloride chemical product is influenced. In order to accelerate the reaction, it is necessary to add an excess of hydrochloric acid so that the acid concentration of the solution is pH 1 or less. And neutralizing the residual hydrochloric acid after the hydrochloric acid completely reacts with the calcium carbonate by using calcium carbonate or calcium hydroxide to obtain calcium chloride. Evaporating the solution after acidity adjustment to obtain a chemical product of calcium chloride.
The chemical reaction equation for the reaction of calcium carbonate or calcium hydroxide with hydrochloric acid is shown below:
2HCI+CaCO3=CaCI2+H2O+CO2↑
2HCI+Ca(OH)2=CaCI2+2H2O
theoretically, the solution obtained after the reaction of equivalent hydrochloric acid with calcium carbonate is completely performed has a pH =7.0, and actually, the hydrochloric acid reacts with calcium carbonate to generate calcium chloride, water and carbon dioxide gas, water can dissolve a part of the carbon dioxide gas to generate carbonic acid, and the carbonic acid is weak acid, so that the pH =4.0 to 4.5 in water, so that the solution obtained after the reaction of hydrochloric acid with calcium carbonate is completely performed is experimentally tested to have a pH =4 to 4.5 instead of the pH = 7.0. In the mixed solution of the filtered solution after acid leaching in the flow line I and the solution (with the acid concentration of less than or equal to 5.0) led out in the first circulation leaching line II. When the acidity regulator is calcium carbonate, the pH of the solution is approximately equal to 5.0, but not pH = 7.0.
Based on the calculation of converting the calcium-containing carbonate in the process into the calcium-containing sulfate before treatment, the higher the contents of the calcium-containing sulfate and the calcium-containing compounds in the fluorine-containing solid waste are, the longer the acid leaching time is, the higher the acid leaching cost is when the contents of the calcium-containing sulfate and the calcium-containing compounds are fixed, and the shorter the acid leaching time is, the better the acid leaching cost is when the leaching rate can meet the requirement. The influence of different acid leaching times on the leaching rate at a temperature of 20 ℃ under otherwise unchanged conditions is shown in the following table.
Figure DEST_PATH_IMAGE005
According to the data in the table, the leaching rate can meet the requirement when the acid leaching time is 20 min.
Because the acid leaching reaction speed is high, the influence of the acid leaching temperature on the leaching speed is small, and a large amount of CO is generated during acid leaching2Bubbles, the higher the temperature, the more violent the reaction, the CO produced2The more vigorous the bubbles, the larger the amount of calcium carbonate powder adsorbed on the splashed bubbles, which adversely lowers the acid leaching rate, and the acid leaching time was 20min under otherwise unchanged conditions. The effect of different acid leaching temperatures on the acid leaching rate is shown in the following table.
Figure 359015DEST_PATH_IMAGE006
According to the data in the table, the leaching rate can meet the requirement when the acid leaching temperature is normal temperature.
It should be added that, without limitation, the leaching process of the present invention using ammonium carbonate in the carbonation reaction has the following advantages:
a. calcium sulfate is an insoluble substance, common acid and alkali cannot dissolve the calcium sulfate, and ammonium carbonate in ammonium salts has the advantages of low price, small dosage, easy purchase, recycling, high reaction speed with the calcium sulfate, only slightly soluble calcium fluoride and the like;
b. the leached solution and the leached solution contain ammonium carbonate and ammonium sulfate, the ammonium carbonate solid can be returned to the leaching process of carbonation reaction to leach the fluorine-containing solid waste again after being separated by distillation, the ammonium sulfate solid obtained after the liquid evaporation can be sold to the required industry, the production process flow is simple, the production process technology is low, and the process is easy to operate.
The leaching agent used in the leaching process in the carbonation reaction can adopt ammonium bicarbonate, sodium carbonate or other non-calcium carbonate which can play an equivalent role without considering the better recovery efficiency.
The embodiments of the present invention are merely preferred embodiments for easy understanding or implementing of the technical solutions of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes in structure, shape and principle of the present invention should be covered by the claims of the present invention.

Claims (6)

1. A method for purifying calcium chloride from fluorine-containing solid waste, comprising:
s1, carrying out carbonation reaction on the fluorine-containing solid waste, wherein the fluorine-containing solid waste before carbonation comprises calcium fluoride, calcium-containing sulfate and calcium-containing compounds;
s2, separating a purification interference source of the carbonated fluorine-containing solid waste, wherein the purification interference source comprises soluble non-calcium sulfate, and the carbonated fluorine-containing solid waste comprises calcium fluoride and calcium carbonate;
s3, carrying out hydrochlorination on the carbonated fluorine-containing solid waste after separation, carrying out first solid-liquid separation after acid leaching, and carrying out first cyclic leaching on the solid obtained by the first solid-liquid separation;
s4, combining the acid leaching filtrate discharged by the first solid-liquid separation and the partial acid leaching educt liquid with acidity exceeding the lower pH threshold value in the first circulation leaching to purify calcium chloride solid, wherein the chlorinated fluorine-containing solid waste after the first solid-liquid separation contains calcium fluoride;
the process of S2 for separating the purification interference source comprises a second solid-liquid separation step, a second circulation leaching step is performed on solids separated by the second solid-liquid separation step, leaching filtrate discharged by the second solid-liquid separation step and a partial alkali leaching derived solution in the second circulation leaching step, wherein the alkalinity of the leaching filtrate exceeds an upper pH threshold value, the partial alkali leaching derived solution is recycled and combined to purify non-calcium carbonate, the recycled non-calcium carbonate is added to a leaching agent for carbonation reaction in a circulation use mode, the upper pH threshold value is 8.5, the second circulation leaching step is a neutral circulation leaching step using water, the recycled and purified non-calcium carbonate comprises mixing, distillation, cooling and third solid-liquid separation, the non-calcium carbonate is formed in solids separated by the third solid-liquid separation step, liquid discharged by the third solid-liquid separation step flows back to the distillation step, a solid outlet of a third solid-liquid separator (53) corresponding to the third solid-liquid separation step is connected to a carbonation reaction device (10), and the non-calcium carbonate return flow back to the carbonation reaction device (S2) is performed In the recovery process, ammonium carbonate is decomposed into NH at 70 DEG C3And CO2The gas and part of the water vapor also enter the cooling device, NH3And CO2The gas is absorbed by water vapor to generate ammonium carbonate and form vapor of the ammonium carbonate and water, the vapor of the ammonium carbonate and the water after being cooled to room temperature is changed into saturated solution of the ammonium carbonate, the non-calcium carbonate is prepared by the third solid-liquid separation, the solution after the distillation operation is ammonium sulfate solution, the purpose of separating the ammonium carbonate from the ammonium sulfate is achieved, the residue obtained by the distillation is evaporated to obtain non-calcium sulfate solid, the non-calcium sulfate solid comprises the ammonium sulfate, the carbonation reaction is carried out in a uniform mixing and leaching mode, and the leaching agent is ammonium carbonate.
2. The method according to claim 1, wherein the total calcium content of the obtained calcium chloride is higher than the calcium content of the calcium-containing sulfate in the fluorine-containing solid waste before carbonation, and the first solid-liquid separation is performed in the same centrifugal filter as the first cyclic rinsing.
3. The method of claim 1, further comprising acidity adjustment and evaporation of the acid leach filtrate and the partial acid leach effluent, wherein the acidity adjustment is performed to adjust the acidity of the acid leach filtrate and the partial acid leach effluent having an acidity exceeding a lower pH threshold in the first cycle leach to a pH neutral, and wherein the acidity adjustment is performed using calcium carbonate or/and calcium hydroxide as an adjusting agent.
4. The method of claim 1, wherein the threshold is 5.0 at the pH and the first cycle of rinsing is a neutral cycle of rinsing with water.
5. An apparatus for purifying calcium chloride from fluorine-containing solid waste, comprising:
the carbonation reaction device (10) is used for carrying out carbonation reaction on the fluorine-containing solid waste;
a disturbance source separation device (20) connected to the carbonation reaction device (10) for separating a purification disturbance source of carbonated fluorine-containing solid waste;
the hydrochlorination reaction device (30) is connected with the interference source separation device (20) and is used for carrying out hydrochlorination reaction on the carbonated fluorine-containing solid waste after separation, and the hydrochlorination reaction device (30) comprises an acid leaching tank (31);
the purification device (40) is connected with the hydrochlorination reaction device (30) and is used for purifying the solid-liquid intermediate of the hydrochlorination reaction device (30) to obtain calcium chloride solid;
wherein the purification device (40) comprises a first solid-liquid separator (41) and a first circulating leaching system, the first circulating leaching system is provided with a first leaching head (42) and is used for circularly leaching the chlorinated solid wastes of the first solid-liquid separator (41), and an acid leaching filtrate pipeline of the first solid-liquid separator (41) and a partial acid leaching outlet liquid pipeline of the first circulating leaching system are connected with a common pipeline for purifying calcium chloride;
the interference source separation device (20) comprises a second solid-liquid separator (21) and a second circulating leaching system, the second circulating leaching system is provided with a second leaching head (22) for circularly leaching carbonated fluorine-containing solid wastes of the second solid-liquid separator (21), and a leaching filtrate line of the second solid-liquid separator (21) and a partial alkali leaching outlet liquid line of the second circulating leaching system are connected with a carbonate recovery device (50);
the carbonate recovery device (50) comprises a distiller (51), a cooling chamber (52) and a third solid-liquid separator (53) in the order of a recovery path, non-calcium carbonate is formed in the solid of the third solid-liquid separator (53), and a liquid discharge pipeline of the third solid-liquid separator (53) returns to the distiller (51);
the carbonate recovery device (50) further comprises an evaporation chamber (54) for evaporating the residue obtained by the distiller (51) to obtain non-calcium sulfate solids, the non-calcium sulfate solids comprise ammonium sulfate, a solid outlet of the third solid-liquid separator (53) is connected to the carbonation reaction device (10), the carbonation reaction device (10) comprises a leaching tank (11) adopting ammonium carbonate as a leaching agent, liquid discharged by the third solid-liquid separator (53) flows back to the distiller (51), and the ammonium carbonate is decomposed into NH at 70 DEG C3And CO2The gas and a part of the water vapor also enter the cooling chamber (52) and NH3And CO2The gas is absorbed by the water vapor to generate ammonium carbonate and form vapor of the ammonium carbonate and the water, the vapor of the ammonium carbonate and the water after being cooled to room temperature is changed into saturated solution of the ammonium carbonate, the saturated solution of the ammonium carbonate and the water passes through the third solid-liquid separator (53) to prepare the non-calcium carbonate, the solution after the distillation operation is ammonium sulfate solution, the purpose of separating the ammonium carbonate from the ammonium sulfate is achieved, and the recovered non-calcium carbonate is added into a leaching agent for carbonation reaction in a recycling mode.
6. The apparatus according to claim 5, characterized in that said first solid-liquid separator (41) and said first showering head (42) are built on the same centrifugal filter;
the purification device (40) further comprises an acidity adjusting tank (43) and an evaporator (44), wherein the acidity adjusting tank (43) is connected to the common pipeline and used for adjusting the pH value of the solution led out from the common pipeline to be close to neutral so as to purify calcium chloride.
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