CN111960439B - Extraction crystallization method for preparing potassium sulfate crystal, fluidizing device and application thereof - Google Patents
Extraction crystallization method for preparing potassium sulfate crystal, fluidizing device and application thereof Download PDFInfo
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Abstract
The invention discloses an extraction crystallization method for preparing potassium sulfate crystals, a fluidization device and application thereof. The fluidized bed fractional crystallization process production device for coupled extraction crystallization, which is designed by the invention, has the advantages that the contact probability between crystals and between the crystals and the wall of the device in a fluidized crystallizer is greatly reduced, so that secondary nucleation can be effectively reduced, and crystals with larger size can be obtained. The device has the advantages of greatly simplifying the production process, enabling the operation to be coherent and convenient, regularly removing a small amount of waste residues in the crystallizer, having no three-waste discharge and having extremely environment-friendly process flow.
Description
Technical Field
The invention relates to the technical field of inorganic materials, in particular to an extraction crystallization method for preparing potassium sulfate crystals, a fluidizing device and application thereof.
Background
Potassium sulfate has a relative molecular weight of 174, and is usually colorless or white hexagonal or orthorhombic crystal or white granular powder; the chemical property is inactive, and the product is stable in the air; melting point of 1069 deg.C, density of 2.66g cm -3 . At normal temperature, the water solution is neutral, and the pH value is about 7;1g potassium sulfate dissolved in 83mL of water, 4mL of boiling water, 75mL of glycerol, but not ethanol. Potassium sulfate is common in chemical products and raw materials, and is widely applied in various industrial fields such as agriculture, industry, medicine and the like. As a potassium content (in K) 2 Calculated as O) is about 50 percent, the sulfur content is about 18 percent, and the fertilizer is mainly applicable to the planting industry of various chlorine-avoiding crops. The potassium sulfate can be used as a precipitating agent in the glass industry, can be used as an intermediate in the dye industry, can be used as an auxiliary agent in the spice industry, and can also be used for preparing various potassium salts such as potassium carbonate, potassium persulfate and the like. Potassium sulfate is used as a raw material in the pharmaceutical industry for the production of certain drugs such as laxatives and even for biochemical tests.
Crystallization of potassium sulfate is a very critical step in the potassium salt industry. Because the crystallization process of potassium sulfate is a key step from the beginning to the end no matter taking ore as a raw material or taking brine as a raw material. The most common crystallization process of potassium sulfate is reactive crystallization, and the most widely used process of reactive crystallization is extractive crystallization. The crystallization process combines the traditional association method process and the crystallization transformation theory researched at present, and skillfully utilizes the operation characteristics of the two processes. Potassium chloride and concentrated sulfuric acid are used as raw materials, and the potassium chloride and the concentrated sulfuric acid are placed in an extraction crystallizer under a certain reaction condition and are stirred by an extracting agent so as to be in full contact. Under the influence of stirring driving force, potassium sulfate crystals are promoted to be continuously precipitated from the mixed solution. However, at present, most of the extraction crystallization modes are stirring crystallization, and the system can cause certain influence on the granularity of a final product due to the existence of the collision force between the stirring paddle and the crystal, so that the granularity of the obtained potassium sulfate crystal is too small, and the crystal appearance is irregular. In industrial production, besides strict requirements on the purity of potassium sulfate, the method also has high requirements on the granularity and the appearance of potassium sulfate crystals, and the potassium sulfate particles are enlarged by adding a hardening agent, a coating agent, a surfactant or an adhesive and the like, but the methods have high energy consumption, large loss and serious dust pollution in a processing site.
Therefore, how to obtain potassium sulfate crystals with larger crystal particles and better crystal form with low energy consumption is a technical problem to be solved by the technical personnel in the field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an extraction crystallization method for preparing potassium sulfate crystals, which avoids the problems of a large amount of fine crystals, over-small product crystal particle size and irregular crystal morphology caused by collision and crushing among the crystals and secondary nucleation.
Furthermore, the invention also provides a fluidized bed fractional crystallization device for realizing the coupling extraction crystallization of the method, and a device for eliminating the influence of the stirring effect on the crystal granularity.
Furthermore, the invention also provides an application method of the potassium sulfate crystal preparation device.
The invention adopts the following technical scheme:
an extraction crystallization method for preparing potassium sulfate crystals comprises the following steps:
mixing and dissolving: mixing concentrated sulfuric acid and potassium oxide in proportion, and dissolving to obtain a mixed solution;
extraction: extracting the mixed solution by using an extracting agent, and extracting hydrogen chloride in the solution by using the extracting agent at normal temperature;
and (3) cyclic phase separation: respectively circulating the mixed solution and the extracting agent to continuously crystallize and separate out potassium sulfate crystals in the circulating process;
crystallization after filtration and drying: and carrying out suction filtration on the solution after the circulating phase splitting, and drying the crystals after the suction filtration to obtain potassium sulfate crystals.
Preferably, the ratio of the concentrated sulfuric acid to the potassium chloride is 1:1 to 4.
Preferably, the extracting agent comprises trioctylamine, tributylphosphate and octanol, wherein the mass fraction ratio of trioctylamine, trioctyl ester and octanol is 5.
Preferably, potassium sulfate seed crystals are added into the mixed solution in the circulation, the particle size of the potassium sulfate seed crystals is 40-50 meshes, and the addition amount of the seed crystals is 5-10 g/L.
Preferably, the extraction also comprises back extraction of an extractant containing hydrogen chloride under the condition of dilute ammonia water, and after stationary phase separation, the upper layer feeds back to the extraction liquid, and the lower layer obtains a byproduct ammonium chloride.
A fluidization device for preparing potassium sulfate crystals comprises a water phase tank, an oil phase tank, a buffer tank, a phase separation tank and a crystallizer; the water phase tank is connected with the water inlet end of the water phase circulating pump, and the water outlet end of the water phase circulating pump is connected with the bottom of the crystallizer; the oil phase tank is connected with the water inlet end of the oil phase circulating pump, and the water outlet end of the oil phase circulating pump is connected with the bottom of the crystallizer; the upper part of the crystallizer is connected with a buffer tank through a pipeline, and the buffer tank is connected with a phase separation tank through a pipeline; the upper part of the phase separation groove is connected with the oil phase groove through a pipeline, and the bottom of the phase separation groove is connected with the water phase groove through a pipeline; and heating devices are arranged at the bottoms of the water phase tank and the oil phase tank.
Preferably, the crystallizer is funnel-shaped, the lower section of the crystallizer comprises a plurality of mixing sections with different diameters, the diameter of the outlet of the crystallizer is at least twice of the diameter of the inlet of the crystallizer, and the diameter of the outlet of the phase separation groove is at least twice of the diameter of the inlet of the phase separation groove. The sizes of the outlet of the crystallizer and the outlet of the phase splitting groove are large, so that the mixed solution can flow in time at a high flow rate, and the stagnation phenomenon is avoided.
Preferably, a guide shell is arranged in the phase separation groove, and a plurality of guide holes are formed in the shell of the guide shell.
The application of the fluidizing device for preparing potassium sulfate crystals, which is disclosed by the invention, in the preparation of the potassium sulfate crystals by the extraction and crystallization method for preparing the potassium sulfate crystals, comprises the following steps of:
s1: adding a saturated potassium sulfate solution serving as a mother solution into a water phase tank, starting a water phase circulating pump and a water bath kettle to perform water phase circulation, and heating the water phase tank until the temperature is constant;
s2: when the temperature in the phase separation tank reaches 45 ℃, adding an extracting agent into the phase separation tank until the liquid level of the oil phase rises to a level capable of automatically flowing into the oil phase tank, starting an oil phase circulating pump, and starting oil phase circulation until the oil phase is stable;
s3: observing whether the water phase and the oil phase in the phase splitting tank are obviously layered and whether a layered interface is stable;
s4: after the phase splitting is stable, adding concentrated sulfuric acid and potassium chloride into the newly prepared potassium sulfate mother liquor, stirring and mixing uniformly until the solid is completely dissolved to obtain mixed liquor, and slowly adding the mixed liquor into the water phase tank;
s5: adding a certain amount of potassium sulfate as seed crystal into the water phase tank, and observing the crystallization process of the crystal in the crystallizer;
s6: measuring the pH value of the mixed liquid at the upper section of the crystallizer at intervals, observing the fluidization state of crystals in the crystallizer and the phase separation condition in a phase separation groove in the fluidized bed crystallizer, keeping the pH of the mixed liquid stable after the raw material and the extractant are dripped, stopping the operation of a circulating system when the pH of the mixed liquid finally reaches 4.5, taking out crystal particles from the crystallizer, and washing with clean mother liquid to remove the extractant adhered to the crystals;
s7: and filtering the crystals containing the mother liquor, collecting crystallized particles, drying, screening, and observing the phase of the crystals.
Preferably, in the step S4, the mixed material liquid is added into the water phase tank through a peristaltic pump, and the speed of the peristaltic pump is 5-10 mL/min -1 。
Compared with the prior art, the invention has the following beneficial effects:
1. the fluidization method is adopted to replace stirring to generate driving force to enable the crystal to grow on the surface of the seed crystal, so that the environment is more uniform and stable, each crystal face of the crystal is uniformly supplied with solute in the supersaturated solution, the solution phase continuously flows, the supersaturation degree of the solution in the bed is basically maintained unchanged, the crystal grows at a basically constant speed, and the obtained crystal is better in crystal form and higher in quality.
2. According to the fluidized bed fractional crystallization process production device for coupled extraction crystallization, which is designed by the invention, because no stirring device is arranged, the crystals do not contact with the stirring paddle in the fluidized crystallizer, and the contact probability between the crystals and the wall of the device is greatly reduced, so that secondary nucleation can be effectively reduced, and crystals with larger size can be obtained; the fluidization device provided by the invention provides a circulation process in a fluidization state, closed circulation is basically realized, the extraction and crystallization processes are carried out under a continuous condition, the production process is greatly simplified, the operation is coherent and convenient, a small amount of waste residues in the crystallizer is removed periodically, no three wastes are discharged, and the process flow is extremely environment-friendly.
3. According to the vulcanizing device, a plurality of mixing sections with different diameters are arranged at the lower section of the crystallizer, so that an extracting agent and a water phase can be fully mixed and reacted, and the extraction effect is further improved; the buffer tank prolongs the retention time, improves the phase splitting effect of the water phase and the oil phase, and ensures the smooth operation of the whole process flow; the sizes of the outlet of the crystallizer and the outlet of the phase splitting groove are large, so that the mixed solution can flow in time at a high flow rate, the stagnation phenomenon is prevented from affecting the whole process circulation, and the waste of the extracting agent is avoided.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
FIG. 2 is a schematic view of a sulfurizing apparatus for preparing potassium sulfate crystals according to the present invention.
In the figure: 1-water phase tank, 2-oil phase tank, 3-water phase circulating pump, 4-buffer tank, 5-phase separation tank, 6-crystallizer, 7-thermometer, 8-material taking port, 9-heating device, 10-three-way pipe and 11-oil phase circulating pump.
Detailed Description
The invention will be further explained with reference to the drawings and the embodiments.
1. An extraction crystallization method for preparing potassium sulfate crystals comprises the following steps:
mixing and dissolving: mixing concentrated sulfuric acid and potassium oxide in proportion, and dissolving to obtain a mixed solution.
And (3) extraction: and extracting the mixed solution by using an extracting agent, and extracting hydrogen chloride in the solution by using the extracting agent at normal temperature.
And (3) cyclic phase separation: and respectively circulating the mixed solution and the extracting agent, and crystallizing and circulating the mixed solution to continuously crystallize and separate out potassium sulfate crystals in the circulating process. And (3) performing extraction and back extraction on the extractant, performing back extraction on the extractant after the mixed solution is extracted, and performing hydrogen chloride extraction on the mixed solution again by the extract liquid after the back extraction so as to achieve recycling.
Crystallization after filtration and drying: and carrying out suction filtration on the solution after the circulating phase splitting, and drying the crystals after the suction filtration to obtain potassium sulfate crystals.
The reaction for preparing the potassium sulfate by the reaction of the potassium chloride and the sulfuric acid is carried out in two steps:
KCl(s)+H 2 SO 4 →KHSO 4 (l)+HCl(g) (1)
KCl(s)+KHSO 4 (l)→K 2 SO 4 (l)+HCl(g) (2)
the reaction (1) is exothermic and can be carried out spontaneously, and the reaction (2) is endothermic, so that in order to improve the equilibrium constant and accelerate the reaction speed, the reaction temperature needs to be improved within a certain range, and the water bath kettle is used for keeping the constant temperature of the system so as to ensure that the extracting agent is extracted at the optimal extraction temperature.
The reaction principle of oil phase extraction in the crystallizer is as follows:
2KCl(s)+H 2 SO 4 (l)+2R 3 N→K 2 SO 4 ↓+2[R 3 NH]Cl(g)
r is an extracting agent, the extracting agent comprises trioctylamine, trioctyl ester and octanol, and the mixture of the trioctylamine, the trioctyl ester and the octanol comprises 50w%, 30w% and 20w% of the extracting agent respectively by mass fraction.
In the system, the extraction reaction is changed from 'static' to 'dynamic', and the problem of blockage caused by untimely extraction can be effectively prevented. At the same time, according to the principle of crystallization kinetics, the "dynamic" state of the extraction reaction can promote K 2 SO 4 The formation and growth of crystal particles are favorable to the organic phase R with smaller specific gravity 3 NH]CI floats up and overflows from the upper part of the reactor, and the later HCI further recovery is facilitated.
Wherein the proportion of the concentrated sulfuric acid to the potassium chloride is 1:1 to 4.
The extractant comprises one or a mixture of more than two of trioctylamine, tributyl phosphate and octanol.
And adding potassium sulfate seed crystals into the circulating mixed solution, wherein the particle size of the potassium sulfate seed crystals is 40-50 meshes, the addition amount of the seed crystals is 5-10 g/L, and 5g of the seed crystals are preferably added into 1 liter of mother solution.
The extraction also comprises back extraction of an extractant containing hydrogen chloride under the condition of dilute ammonia water, and after standing and phase splitting, the upper layer feeds back to the extraction liquid, and the lower layer obtains a byproduct ammonium chloride. Adding a certain amount of dilute ammonia water into the used extractant to perform back extraction until the pH value is 7 and stable, and after separation, the upper oil phase (namely the extractant) can be reused in the previous cycle, and the lower water phase is a byproduct ammonium chloride solution.
2. Fluidizing device for preparing potassium sulfate crystal for implementing method
A fluidizing device comprises a water phase tank 1, an oil phase tank 2, a buffer tank 4, a phase separation tank 5 and a crystallizer 6; the water phase tank 1 is connected with the water inlet end of the water phase circulating pump 3, and the water outlet end of the water phase circulating pump 3 is connected with the bottom of the crystallizer 6. The oil phase tank 2 is connected with the water inlet end of an oil phase circulating pump 11, and the water outlet end of the oil phase circulating pump 11 is connected with the bottom of the crystallizer 6. The upper part of the crystallizer 6 is connected with the buffer tank 4 through a pipeline, and the buffer tank 4 is connected with the phase separation tank 4 through a pipeline. The upper part of the phase separation tank 4 is connected with the oil phase tank 2 through a pipeline, and the bottom of the phase separation tank 5 is connected with the water phase tank 1 through a pipeline. The bottoms of the water phase tank 1 and the oil phase tank 2 are both provided with a heating device 9.
Wherein, the crystallizer is hopper-shaped, and the crystallizer hypomere includes the different mixed section of multistage diameter, and the diameter of crystallizer export is the twice of its diameter of import at least, and the diameter of phase separation groove export is the twice of its diameter of import at least, can accelerate the double-phase mixed degree of water oil like this, and then accelerate the crystallization process to crystallizer export and phase separation groove export size are great, are favorable to mixing solution's timely flow under the high velocity of flow. A guide cylinder is arranged in the phase separation groove 5, and a plurality of guide holes are formed in the cylinder body of the guide cylinder, so that the axial speed of fluid in the phase separation groove can be increased, and crystal suspension is avoided.
The whole crystallization system consists of two pipelines, wherein one pipeline is filled with saturated potassium sulfate mother liquor, and the other pipeline is filled with an extracting agent, and the saturated potassium sulfate mother liquor and the extracting agent are uniformly mixed and then enter a fluidized bed crystallizer together. Potassium chloride and concentrated sulfuric acid in certain proportion are added into saturated potassium sulfate crystallization mother liquor, and the saturated potassium sulfate crystallization mother liquor and fresh extracting agent are pumped into a circulating device by a peristaltic pump simultaneously, and are uniformly mixed by a circulating pump. By utilizing the difference of the distribution coefficients of substances in two mutually incompatible systems of water and oil, hydrogen ions in sulfuric acid and chloride ions in potassium chloride are combined into hydrogen chloride and continuously transferred from water phase to oil phase, and the extractant has very low selectivity to hydrogen sulfate ions and sulfate ions, so that the hydrogen chloride and the chloride ions are hardly extracted, thereby continuously increasing the concentration of potassium ions and sulfate ions in the water phase, and continuously precipitating fine potassium sulfate crystals when the set temperature is reached. The water phase and the oil phase are easy to separate after leaving the extraction section, and are mixed and extracted again by a complete flow mixing device until the pH value of the water phase is stable, and the generated potassium sulfate crystal is taken out and filtered. Adding a certain amount of dilute ammonia water into the used extractant for back extraction until the pH value is 7 and stable, wherein the upper oil phase (namely the extractant) can be recycled after separation, and the water phase is a byproduct ammonium chloride solution.
Compared with other process technologies, the process technology adopted in the fluidized bed device has the advantages that the energy consumption is low, the reaction can be carried out at about 40 ℃, the extraction and crystallization processes are carried out in the same equipment, uniform and thick potassium sulfate crystal particles can be obtained without other processes such as concentration, the device is a continuous circulating device, except for the fact that a pump and a pipeline need to be cleaned regularly, the emission of three wastes is basically avoided, the process flow adopted by the device is relatively environment-friendly, the requirement on the equipment is low, the investment of environment-friendly facilities is small, and the production cost is low. On the other hand, the used extractant can be recycled by back extraction of the dilute ammonia water, and the ammonium chloride in the water phase after back extraction can be used for agricultural production, so that the economic benefit is more remarkable.
In order to eliminate the influence of other factors, the experimental operating conditions are as follows: the water-oil rate ratio was 9.5:8.5, the reaction temperature is 40 ℃, the retention time is 4320s, and the mother liquor feeding rate is 7 mL/min -1 The fluidization velocity is 0.422 m.s -1 ～0.5m·s -1 In the meantime.
3. Application of fluidizing device for preparing potassium sulfate crystals
The specific application method of the fluidizing device for preparing potassium sulfate crystals comprises the following steps:
s1: and (3) adding a potassium sulfate saturated solution (with the pH value of approximately 4) serving as a mother solution into a water phase tank, starting a water phase circulating pump and a water bath kettle to perform water phase circulation, and heating the water phase tank until the temperature is constant.
S2: and when the temperature in the phase separation tank reaches the required temperature, adding an extracting agent into the phase separation tank until the liquid level of the oil phase rises to a level capable of automatically flowing into the oil phase tank, starting an oil phase circulating pump, and starting oil phase circulation until the oil phase is stable.
S3: and (5) observing whether the water phase and the oil phase in the phase separation tank are obviously layered and whether the layered interface is stable.
S4: after the phase separation is stable, taking the reconfigured potassium sulfate mother liquor (about 275 mL) into a beaker, adding 25g (0.25 mol) of concentrated sulfuric acid and 37.25g (0.5 mol) of potassium chloride, and stirring and mixing uniformly until all the solid is dissolved. The raw material solution was dropped into the aqueous phase tank by a peristaltic pump (rate: about 8 mL. Min. -1), and the back-extracted extractant was dropped into the oil phase tank by a peristaltic pump (rate: about 16 mL. Min. -1).
S5: adding 20g of potassium sulfate with 40-50 meshes as seed crystals into the water phase tank, observing the crystallization process of the crystals in the crystallizer, and recording the time when the crystals grow obviously.
S6: and measuring the pH value of the mixed liquid at the upper section of the crystallizer by using a precise pH meter every 5 minutes through a three-way pipe 10, observing the vulcanization state of crystals in the crystallizer and the phase separation condition in a phase separation groove, keeping the pH of the mixed liquid stable after the raw material and the extractant are dripped, stopping the operation of a circulating system when the pH of the mixed liquid finally reaches 4.5, measuring the pH value of the mixed liquid through a material taking port 8 on the crystallizer, taking out crystal particles from the crystallizer, and washing with clean mother liquor to remove the extractant adhered to the crystals.
S7: the crystals containing the mother liquor were filtered with a suction filter and the crystallized particles were collected. Drying in a 90 ℃ oven for about 2 hours to obtain a dried product, then sieving by using a screen, comparing and recording the mass percentages of crystals with the grain diameters of more than 20 meshes, 20-30 meshes, 30-40 meshes and less than 50 meshes at different circulation rates, and observing the phase of the crystals.
The extracting agent comprises a mixture of trioctylamine, tributylphosphate and octanol, wherein the mass fraction ratio of trioctylamine to trioctyl alcohol is 5.
And when the extraction of the extractant is saturated, starting an oil phase tank heating device, adding ammonia water at 45 ℃, stirring for back extraction, and continuously allowing the upper oil phase obtained after back extraction to enter the oil phase for recycling.
3. Examples and comparative examples
TABLE 1 EXAMPLES 1-5 AND COMPARATIVE EXAMPLES
Therefore, the fluidization method of the invention replaces stirring to generate driving force to enable the crystal to grow on the surface of the seed crystal, so that the environment is more uniform and stable, each crystal face of the crystal is uniformly supplied with solute in the supersaturated solution, the solution phase continuously flows, the supersaturation degree of the solution in the bed is basically maintained unchanged, the crystal grows at a basically constant speed, and the crystal form of the obtained crystal is better. In addition, the fluidized bed fractional crystallization process production device for coupled extraction crystallization avoids the contact between the crystals and the stirring paddle, and greatly reduces the contact probability between the crystals and the wall of the device, thereby effectively reducing secondary nucleation and obtaining the crystals with larger size. It can also be seen from the examples that the crystals of examples 1 to 5 had an increased number of crystals of 50 mesh or less, the crystal sizes were mostly concentrated in 20 to 30 mesh and 30 to 40 mesh, the number of crystals having a small size of 20 mesh or less was small, and the overall quality of the crystals was high, and that the number of crystals having a small size of 20 mesh or less was large and the number of crystals having a large size was small, and the overall quality of the crystals was poor in the comparative example, as compared with the comparative example using the conventional stirring crystallization technique. The fluidizing device provided by the invention provides a circulating process in a fluidizing state, closed circulation is basically realized, the extraction and crystallization processes are carried out under a continuous condition, the production process is greatly simplified, the operation is coherent and convenient, a small amount of waste residues in a crystallizer are removed regularly, no three wastes are discharged, and the process flow is extremely environment-friendly.
It should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that the technical solutions of the present invention can be modified or substituted with equivalent solutions without departing from the spirit and scope of the technical solutions, and all should be covered in the claims of the present invention.
Claims (8)
1. An extraction crystallization method for preparing potassium sulfate crystals is characterized by comprising the following steps:
mixing and dissolving: mixing concentrated sulfuric acid and potassium chloride in proportion, and dissolving to obtain a mixed solution;
and (3) extraction: extracting the mixed solution by using an extracting agent, and extracting hydrogen chloride in the solution by using the extracting agent at normal temperature;
and (3) cyclic phase separation: respectively circulating the mixed solution and the extracting agent to continuously crystallize and separate out potassium sulfate crystals in the circulation process;
crystallization after filtration and drying: carrying out suction filtration on the solution after the cyclic phase splitting, and drying the crystals after the suction filtration to obtain potassium sulfate crystals;
the device comprises a water phase tank, an oil phase tank, a buffer tank, a phase separation tank and a crystallizer; the water phase tank is connected with the water inlet end of the water phase circulating pump, and the water outlet end of the water phase circulating pump is connected with the bottom of the crystallizer; the oil phase tank is connected with the water inlet end of the oil phase circulating pump, and the water outlet end of the oil phase circulating pump is connected with the bottom of the crystallizer; the upper part of the crystallizer is connected with a buffer tank through a pipeline, and the buffer tank is connected with a phase separation tank through a pipeline; the upper part of the phase separation groove is connected with the oil phase groove through a pipeline, and the bottom of the phase separation groove is connected with the water phase groove through a pipeline; heating devices are arranged at the bottoms of the water phase tank and the oil phase tank;
the fluidization device for preparing the potassium sulfate crystal is adopted to prepare the potassium sulfate crystal and comprises the following steps:
s1: adding a saturated potassium sulfate solution serving as a mother solution into a water phase tank, starting a water phase circulating pump and a water bath kettle to perform water phase circulation, and heating the water phase tank until the temperature is constant;
s2: when the temperature in the phase separation tank reaches 45 ℃, adding an extracting agent into the phase separation tank until the liquid level of the oil phase rises to a level where the oil phase can automatically flow into the oil phase tank, starting an oil phase circulating pump, and starting oil phase circulation until the oil phase is stable;
s3: observing whether the water phase and the oil phase in the phase splitting tank are obviously layered and whether a layered interface is stable;
s4: after the phase separation is stable, taking another reconfigured potassium sulfate mother liquor, adding concentrated sulfuric acid and potassium chloride, stirring and mixing uniformly until the solid is completely dissolved to obtain a mixed feed liquid, and slowly adding the mixed feed liquid into the water phase tank;
s5: adding a certain amount of potassium sulfate as seed crystals into the water phase tank, and observing the crystallization process of crystals in the crystallizer;
s6: measuring the pH value of the mixed liquid at the upper section of the crystallizer at intervals, observing the fluidization state of crystals in the crystallizer and the phase separation condition in a phase separation groove in the fluidized bed crystallizer, keeping the pH of the mixed liquid stable after the raw material and the extractant are dripped, stopping the operation of a circulating system when the pH of the mixed liquid finally reaches 4.5, taking out crystal particles from the crystallizer, and washing with clean mother liquid to remove the extractant adhered to the crystals;
s7: and filtering the crystals containing the mother liquor, collecting crystallized particles, drying, screening, and observing the phase of the crystals.
2. The extractive crystallization method for preparing potassium sulfate crystals as claimed in claim 1, wherein the ratio of concentrated sulfuric acid to potassium chloride is 1:1 to 4.
3. The extractive crystallization method for preparing potassium sulfate crystals as claimed in claim 1, wherein the extractant comprises trioctylamine, tributylphosphate and octanol, wherein the mass fraction ratio of trioctylamine, trioctylamine and octanol is 5.
4. The extraction crystallization method for preparing potassium sulfate crystals according to claim 1, characterized in that potassium sulfate seed crystals are added into the mixed solution in the circulation, the particle size of the potassium sulfate seed crystals is 40-50 meshes, and the addition amount of the seed crystals is 5-10 g/L.
5. The extraction crystallization method for preparing potassium sulfate crystals according to claim 1, characterized in that the extraction further comprises back-extraction of an extractant containing hydrogen chloride under the condition of dilute ammonia water, and after stationary phase separation, the upper layer feeds back to the extraction liquid, and the lower layer obtains a byproduct ammonium chloride.
6. The method for the extractive crystallization of potassium sulfate crystals as defined in claim 1, wherein the crystallizer is funnel-shaped, and the lower section of the crystallizer comprises a plurality of mixing sections having different diameters, the diameter of the outlet of the crystallizer is at least twice the diameter of the inlet thereof, and the diameter of the outlet of the phase separation tank is at least twice the diameter of the inlet thereof.
7. The extractive crystallization method for preparing potassium sulfate crystals as claimed in claim 1, wherein a guide shell is arranged in the phase separation tank, and a plurality of guide holes are formed on the shell of the guide shell.
8. The method for the extractive crystallization of potassium sulfate crystals as defined in claim 1, wherein the mixed solution is fed into the aqueous phase tank through a peristaltic pump at a rate corresponding to the rate of the peristaltic pump in step S45 to 10mL/min -1 。
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| CN101434402A (en) * | 2007-11-13 | 2009-05-20 | 张建华 | Method of producing potassium sulfate by reaction, extraction and crystallization one-step method |
| CN101746783A (en) * | 2008-12-19 | 2010-06-23 | 中国科学院兰州化学物理研究所 | Method for co-production of potassium sulphate and ammonium chloride through liquid extraction |
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2020
- 2020-08-31 CN CN202010898999.1A patent/CN111960439B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101434402A (en) * | 2007-11-13 | 2009-05-20 | 张建华 | Method of producing potassium sulfate by reaction, extraction and crystallization one-step method |
| CN101746783A (en) * | 2008-12-19 | 2010-06-23 | 中国科学院兰州化学物理研究所 | Method for co-production of potassium sulphate and ammonium chloride through liquid extraction |
Non-Patent Citations (1)
| Title |
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| 尹建良等.萃取法生产硫酸钾.《内蒙古石油化工》.1999,第35-37页. * |
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