A detection device and method for determining the free water content in crystalline salts

Abstract

This invention relates to a filtration device and method for determining the free water content in crystalline salts, comprising a filtration flask; a sand core funnel with an extension cylinder detachably and sealed at its top; a grinding mechanism including a second filter plate detachably and fixedly mounted at the top of the sand core funnel, and a rotatable and downward-moving grinding element; a liquid inlet mechanism including a liquid container screwed onto the upper inner side of the extension cylinder; and a connecting mechanism, wherein when the liquid container is connected to the extension cylinder and rotates downward, the connecting mechanism drives the grinding element to rotate and move downward at an accelerated speed for grinding, and the accelerated rotation of the grinding element also performs rotational mixing and washing. This invention eliminates the interference of crystal water in the detection of free water caused by sample instability, enabling rapid determination of the free water content in the crystalline salt of brine carried during the desalination process of high-salt brine. The equipment is simple, and the method has good accuracy, precision, and applicability, suitable for the detection of free water in different types of crystalline salts.

Description

Technical Field

[0001] This invention relates to the field of analytical testing technology, specifically to a detection and filtration device and method for determining the free water content in crystalline salts, particularly a detection technique for accurately determining the free water content of crystalline salts containing thermally unstable water of crystallization carried by brine during the brine desalination process. Background Technology

[0002] Salt lake brine is one of the main sources of lithium. Its process mainly includes two major steps: lithium extraction and lithium precipitation. Lithium extraction is the core technology, and sun-drying the brine is an indispensable step in the concentration stage of lithium extraction. The main purpose is to increase the lithium concentration of the brine by continuously evaporating water. However, the sun-drying process produces a large amount of crystalline salt precipitation. The water trapped between the crystals during the precipitation of crystalline salt is free water, and the water that exists in the crystals but is carried out is crystal water. The free water comes from the concentrated brine (high-concentration lithium solution). Accurately detecting the amount of free water in the crystalline salt is of great significance for metal balance and production guidance. Moreover, some crystalline salts are unstable and may gain or lose crystal water if stored for a long time. The crystallization forms are diverse, and it is difficult to accurately determine their free water content.

[0003] Currently, moisture content is mainly determined by Karl Fischer moisture determination, coulometric moisture determination, dew point moisture determination, microwave moisture determination, infrared moisture determination, and drying method. However, because crystalline salts contain both free water and water of crystallization, the existing detection methods may cause changes in the properties of the sample during the detection process due to the influence of the physicochemical properties of the crystalline salts, making it difficult to accurately detect the free water, which is quite troublesome.

[0004] Therefore, the research objective of this invention is to design a filtration device and method for determining the free water content in crystalline salt that can overcome the problem of existing detection methods failing to accurately detect free water entrained in thermally unstable crystalline salt, so as to achieve rapid determination of free water content in crystalline salt entrained in brine during the desalination process of high-salt brine, improve detection accuracy, precision and applicability, and be simple, fast, convenient and low-cost to operate. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the present invention provides a detection and filtration device and method for determining the free water content in crystalline salts. This detection and filtration device and method can effectively solve the technical problems existing in the prior art.

[0006] The technical solution of this invention is:

[0007] A detection and filtration device for determining the free water content in crystalline salts, comprising:

[0008] The filtration flask is connected to an external vacuum pump via a corresponding rubber tube.

[0009] A sand core funnel is tightly installed on the mouth of the filtration flask through a perforated rubber stopper, and the outlet tube of the sand core funnel extends through the perforated rubber stopper into the filtration flask. A corresponding first filter plate is integrally formed in the funnel chamber of the sand core funnel, and a corresponding filter paper can be replaced on the first filter plate. An extension cylinder is detachably and sealed on the top of the funnel chamber of the sand core funnel.

[0010] The grinding mechanism includes a second filter plate that is detachably and fixedly installed in the hopper above the first filter plate. The second filter plate is spherical and has a number of sieve holes with a trapezoidal cross-section that is narrow at the top and wide at the bottom. The grinding mechanism also includes a grinding element that can be rotated and moved down to cooperate with the second filter plate for grinding the crystalline salt sample on the second filter plate. The shape of the lower end face of the grinding element is adapted to the second filter plate, and a number of grinding protrusions are integrally formed on its lower surface.

[0011] The liquid inlet mechanism includes a liquid container installed on the upper inner side of the extension cylinder by a threaded connection. The inner wall of the extension cylinder has corresponding liquid guiding grooves evenly distributed in a recessed manner between the second filter plate and the liquid container. An annular connector is fixedly connected inside the extension cylinder, fitting and blocking the outer side of the liquid guiding grooves. The grinding component is fitted and rotatably installed at the position of the annular connector. The top of the annular connector is constricted, forming a corresponding liquid inlet area with the upper part of the liquid guiding grooves. A corresponding liquid guiding pipe is connected to the lower part of the liquid container, and the outlet of the liquid guiding pipe is located within the liquid inlet area. The solution in the liquid container flows through the liquid guiding grooves to the top of the second filter plate.

[0012] A connecting mechanism is used to connect the grinding element and the liquid container. When the liquid container is connected to the extension cylinder and rotates downward, the connecting mechanism drives the grinding element to rotate faster and move downward to grind the crystalline salt sample placed on the second filter plate. The grinding element also rotates faster to mix and wash the ground crystalline salt sample with anhydrous dehydrating agent or volatile detergent.

[0013] The connecting mechanism includes a connecting rod fixed to the bottom of the liquid container. The other end of the connecting rod is rotatably connected to the grinding element through a corresponding bearing. The connecting rod and the grinding element are connected by a corresponding meshing gear set. The meshing gear set includes a first gear and an annular external gear ring respectively fixed to the connecting rod and the grinding element. The annular external gear ring is sleeved on the outside of the connecting rod. The first gear and the annular external gear ring are respectively meshed with a corresponding second gear and a third gear. The second gear and the third gear are connected by a corresponding fixing rod. The fixing rod is rotatably mounted on a mounting plate fixed to the annular connecting element. The first gear and the third gear are both large gears, and the second gear and the annular external gear ring are both small gears.

[0014] The upper inner wall of the extension cylinder is provided with a corresponding internal thread, and the outer wall of the liquid container is provided with a matching external thread. The top of the liquid container is provided with a corresponding cover plate that can be opened and closed, and a corresponding handle is fixedly connected to the cover plate. The liquid container and the extension cylinder are screwed together by rotating and lowering the handle by holding it.

[0015] A method for determining the free water content in crystalline salts, comprising:

[0016] S1, Solvent pretreatment: Add excess salt reagents to the dehydrating agent and detergent respectively, so that the salt reagents soluble in the dehydrating agent and / or detergent are saturated in the dehydrating agent and detergent, and remove water from the dehydrating agent and detergent to obtain anhydrous dehydrating agent and volatile detergent;

[0017] S2, Sample pretreatment: Accurately weigh the crystalline salt sample and place it in the corresponding position of the above-mentioned detection and filtration device with an appropriate amount of anhydrous dehydrating agent. While mixing the crystalline salt sample and the anhydrous dehydrating agent, grind the crystalline salt sample into fine crystal particles.

[0018] S3, Salt washing: The crystalline salt sample, which has been ground into fine crystal particles, is mixed and washed with an anhydrous dehydrating agent.

[0019] S4, First filtration: Filter the mixture from step S3;

[0020] S5, Dehydration agent removal: Add a volatile detergent to the crystalline salt sample after filtration in step S4 and mix and wash.

[0021] S6, Secondary filtration: Use a clean filtration flask to filter the crystalline salt sample washed in step S5.

[0022] The salt reagent is one or more of the following: sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, and calcium chloride.

[0023] The dehydrating agent is an aprotic organic solvent that is miscible with water in any proportion and insoluble in crystalline salts, and has good fluidity, low toxicity, and low odor. The dehydrating agent is one or a mixture of several of amides, ketones, nitriles, dimethyl sulfoxide, and pyridine.

[0024] The detergent is a low-boiling-point, volatile organic solvent that is miscible with the dehydrating agent in any proportion. The detergent is one or a mixture of several of the following: diethyl ether, acetone, and ethyl acetate.

[0025] The salt washing and primary filtration described in steps S3-S4 need to be repeated 3-5 times. The dehydrating agent removal and secondary filtration described in steps S5-S6 need to be repeated 5-8 times. The final filtration must continue until no liquid drips into the filtration flask and continue filtration for 5-8 minutes. Then, replace with a new filtration flask and continue filtration for 15-20 minutes. Remove the sand core funnel and weigh the product. .

[0026] The detection method further includes step S7, blank sample spike verification test: using newly opened commercially available salt crystals as a blank test, the spike verification is performed according to steps S2 to S6 above; wherein, in step S2 of the blank test, the salt crystals and a small amount of pure water need to be accurately weighed, an appropriate amount of pretreated anhydrous dehydrating agent is added to the salt crystals, and during the grinding and stirring of the salt crystals, a small amount of pure water is gradually added dropwise to the salt crystals, and the salt crystals should be kept away from dissolving in the added water as much as possible. The salt crystals are calcium chloride dihydrate crystals.

[0027] The sand core funnels of the detection filtration device must be clean, anhydrous, and dried to constant weight. The mass of the sample must be measured before detection. Mass of the sand core funnel used for sample testing Mass of the sand core funnel used for blank tests Furthermore, the weight of the sample and the sand core funnel after the test was completed was measured. The mass of the sand core funnel after the blank test ,in and Both include the mass of the sand core funnel and the mass of the filter paper; the change in the mass of the sand core funnel after the blank test is as follows: ,in The unit is grams; the percentage of free water in crystalline salts. : .

[0028] Advantages of this invention:

[0029] 1) This invention requires sample grinding, washing, and filtration to detect free water in crystalline salts. Due to the small sample size, large-scale processing equipment cannot be used. Furthermore, existing methods involve grinding the sample in a mortar, dissolving and washing it in beakers, and then transferring it to a sand core funnel for filtration. Personnel hold a pestle and press the sample against the inner wall of the mortar to grind the particles. However, uneven force and pulverization can cause some particles to splash and fall off, and powder particles can easily remain on the mortar and pestle. Multiple transfers of material can also lead to repeated residue buildup, thus affecting the accuracy of free water content detection in crystalline salts. Therefore, this invention employs a detection filtration device consisting of a filtration flask, a sand core funnel, a grinding mechanism, a liquid inlet mechanism, and a connecting mechanism to perform grinding, washing, and filtration of the material. This reduces the number of material transfers, effectively avoiding material loss due to transfer, and thus ensuring detection accuracy.

[0030] 2) This invention connects the corresponding extended cylinder to the hopper of the sand core funnel by sealing and locking it with flanges, gaskets and bolts, and a second filter plate is detachably installed on the upper part of the hopper. By driving the grinding parts to rotate and press down, the second filter plate grinds the crystalline salt sample into fine particles through friction. The grinding parts are set in a spherical arc shape and have many sieve holes with a trapezoidal structure with a narrow upper and wide lower cross section. This not only promotes the material to gather in the center and prevents it from scattering, thus improving the grinding efficiency and effect, but also promotes the smooth passage of the ground material through the second filter plate and avoids clogging.

[0031] 3) This invention uses a spiral connection to install the liquid container while using the liquid container to drive the grinding parts to rotate and move downward for grinding. The uniformity of the threaded track is used to control the grinding force and the even distribution of the applied force. Combined with the closed grinding zone formed by the hopper and the extended cylinder, the force on the material is more uniform during grinding, effectively avoiding material splashing during the grinding process, thereby ensuring the accuracy of the test.

[0032] 4) The present invention has corresponding liquid guiding grooves evenly distributed on the inner sidewall of the inner surface of the extension cylinder, and a ring-shaped connector fixedly attached to the outer side of the liquid guiding groove, forming multiple vertically connected liquid guiding channels, so that the solution in the liquid container can flow smoothly to the grinding zone above the second filter plate to mix and wash with the crystallized salt. The ring-shaped connector forms a corresponding installation area to facilitate the installation and vertical movement of the grinding parts, realizing the liquid feeding and the installation and use of the grinding parts, thus improving the practical effect of the present invention.

[0033] 5) This invention utilizes a connecting structure to connect the grinding component and the liquid container. The grinding component is driven to rotate and move downwards for grinding while the liquid container is installed. A connecting rod is installed between the liquid container and the grinding component. A corresponding first gear is fixed to the outer side of the connecting rod. An annular external gear ring is fixed to the grinding component and sleeved on the outer side of the connecting rod. The first gear and the annular external gear ring mesh with the second gear and the third gear, respectively. The second and third gears are rotatably mounted on the annular connecting component via corresponding fixing rods and mounting plates. The first and third gears are both large gears with a gear ratio of 1:1. The second gear and the annular external gear ring are both small gears with a gear ratio of 1:1. The gear ratio between the first and second gears is 5:1 to 10:1, allowing the grinding component to rotate several times for every one rotation of the liquid container, thus accelerating the grinding speed. The rapidly rotating grinding component also allows the liquid to form a circulating vortex, promoting the mixing of anhydrous dehydrating agents or volatile detergents with crystalline salts, thereby improving the efficiency and effectiveness of washing and removing free water or anhydrous dehydrating agents.

[0034] 6) This invention detects free water in crystalline salt through experimental steps including solvent pretreatment, sample pretreatment, salt washing, primary filtration, dehydrating agent removal, and secondary filtration. The sample is washed with an anhydrous organic solvent that is miscible with water in any proportion and insoluble in crystalline salt to remove free water. Then, a low-boiling-point, volatile detergent is used to remove the anhydrous dehydrating agent. The weight change of the crystalline salt before and after washing is used to calculate the free water content in the crystalline salt sample. This method can detect the free water content in crystalline salt entrained in the brine during the desalination process of high-salt brine, eliminating the interference of crystal water caused by sample instability. It overcomes the problem of existing detection methods failing to accurately detect free water entrained in thermally unstable crystalline salt, achieving rapid determination of the free water content in crystalline salt entrained in the brine during the desalination process of high-salt brine. The method has good accuracy, precision, and applicability; it is simple, fast, and low-cost, and applicable to different types of crystalline salt.

[0035] 7) This invention involves adding excess sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, and calcium chloride salts to the dehydrating agent and detergent, respectively. This allows the salts, soluble in the dehydrating agent and / or detergent, to dissolve in both, removing water from the dehydrating agent and detergent, resulting in anhydrous dehydrating agent and volatile detergent. Since halogen salts, nitrates, and sulfates may be slightly soluble in the dehydrating agent, solvent pretreatment makes the mass of dissolved salts during washing negligible, further improving the accuracy of free water detection. Furthermore, sample pretreatment, grinding the crystalline salt sample into fine particles, promotes the rapid and significant mixing of free water entrained between the crystalline salts into the dehydrating agent for removal, increasing the processing speed of the test. This invention further conducts blank sample spike verification tests, achieving a free water recovery rate of 90%–110% in the blank crystalline salt, thus improving detection accuracy. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the detection and filtration device of the present invention.

[0037] Figure 2 for Figure 1 A cross-sectional schematic diagram of the detection and filtration device (the air pump is omitted).

[0038] Figure 3 This is a cross-sectional enlarged schematic diagram of the sand core funnel and the extension cylinder.

[0039] Figure 4 This is a schematic diagram of the installation of the ring-shaped connector.

[0040] In the attached diagram: 1. Filter bottle; 2. Sand core funnel; 3. Perforated rubber stopper; 4. First filter plate; 5. Filter paper; 6. Grinding mechanism; 601. Second filter plate; 6011. Sieve hole; 602. Grinding part; 6021. Grinding protrusion; 7. Liquid inlet mechanism; 701. Liquid container; 702. Liquid guide tube; 8. Annular connector; 9. Connecting mechanism; 901. Connecting rod; 902. First gear; 903. Annular external gear ring; 904. Second gear; 905. Third gear; 906. Mounting plate; 10. Cover plate; 11. Handle; 12. Extension cylinder; 1201. Liquid guide groove; 13. Air pump. Detailed Implementation

[0041] To facilitate understanding by those skilled in the art, the structure of the present invention will now be described in further detail with reference to the accompanying drawings:

[0042] Example 1

[0043] refer to Figure 1-4 A detection and filtration device for determining the free water content in crystalline salts, comprising:

[0044] The filtration flask 1 is connected to an external vacuum pump 13 via a corresponding rubber tube;

[0045] A sand core funnel 2 is tightly installed on the mouth of the filtration bottle 1 through a perforated rubber stopper 3, and the liquid outlet tube of the sand core funnel 2 extends through the perforated rubber stopper 3 into the filtration bottle 1. A corresponding first filter plate 4 is integrally formed in the funnel chamber of the sand core funnel 2, and a corresponding filter paper 5 can be replaced on the first filter plate 4. An extension cylinder 12 is detachably and sealed on the top of the funnel chamber of the sand core funnel 2.

[0046] The grinding mechanism 6 includes a second filter plate 601 that is detachably and fixedly installed in the hopper above the first filter plate 4. The second filter plate 601 is spherical and arc-shaped, and has a number of sieve holes 6011 with a cross-section that is narrow at the top and wide at the bottom. The grinding mechanism 6 also includes a grinding element 602 that can be rotated and moved down to cooperate with the second filter plate 601 for grinding the crystalline salt sample on the second filter plate 601. The shape of the lower end face of the grinding element 602 is adapted to the second filter plate 601, and a number of grinding protrusions 6021 are integrally formed on its lower surface.

[0047] The liquid inlet mechanism 7 includes a liquid container 701 installed on the upper inner side of the extension cylinder 12 via a threaded connection. The inner wall of the sand core funnel 2 is recessed between the second filter plate 601 and the liquid container 701, with corresponding liquid guiding grooves 1201 evenly distributed. An annular connector 8 is fixedly connected inside the extension cylinder 12, fitting and blocking the outer side of the liquid guiding groove 1201. The grinding part 602 is fitted and rotatably installed at the position of the annular connector 8. The top of the annular connector 8 is constricted and forms a corresponding liquid inlet area with the upper part of the liquid guiding groove 1201. A corresponding liquid guiding pipe 702 is connected to the lower part of the liquid container 701, and the outlet of the liquid guiding pipe 702 is located in the liquid inlet area. The solution in the liquid container 701 flows to the top of the second filter plate 601 through the liquid guiding groove 1201.

[0048] The connecting mechanism 9 is used to connect the grinding element 602 and the liquid container 701. When the liquid container 701 is connected to the extension cylinder and rotates downward, the connecting mechanism 9 drives the grinding element 602 to accelerate its rotation and move downward to grind the crystalline salt sample placed on the second filter plate 601. The grinding element 602 accelerates its rotation to rotate and mix the ground crystalline salt sample with anhydrous dehydrating agent or volatile detergent for washing.

[0049] This invention requires sample grinding, washing, and filtration to detect free water in crystalline salts. Due to the small sample size, large-scale processing equipment cannot be used. Furthermore, existing methods involve grinding the sample in a mortar, dissolving and washing it in beakers, and then transferring it to a sand core funnel 2 for filtration. Personnel hold a pestle and press the sample against the inner wall of the mortar to grind the particles, but uneven force and pulverization can cause some particles to splash and fall off, and powder particles can easily remain on the mortar and pestle. Multiple transfers of material can also lead to repeated residue buildup, thus affecting the accuracy of free water content detection in crystalline salts. Therefore, this invention employs a detection filtration device consisting of a filtration bottle 1, a sand core funnel 2, a grinding mechanism 6, a liquid inlet mechanism 7, and a connecting mechanism 9 to perform grinding, washing, and filtration of the material. This reduces the number of material transfers, effectively avoiding material loss due to transfer, and thus ensuring detection accuracy.

[0050] This invention connects the corresponding extension cylinder 12 to the hopper of the sand core funnel 2 via flanges, gaskets, and bolts for sealing and locking. A second filter plate 601 is detachably installed on the upper part of the hopper. By driving the grinding element 602 to rotate and press down, the second filter plate 601 grinds the crystalline salt sample into fine particles through friction. The grinding element 602 is provided with a spherical arc surface and a number of sieve holes 6011 with a trapezoidal structure that is narrow at the top and wide at the bottom. This not only promotes the material to gather at the center and prevents it from scattering, thus improving the grinding efficiency and effect, but also allows the crushed material to pass smoothly through the second filter plate 601, avoiding blockage.

[0051] This invention utilizes a spiral connection to install the liquid container 701 while simultaneously driving the grinding component 602 to rotate and move downwards for grinding. The uniformity of the threaded track is used to control the grinding force and the even distribution of applied force. Combined with the enclosed grinding zone formed by the hopper and the extension cylinder 12, the force applied to the material during grinding is more uniform, effectively avoiding material splashing during the grinding process, thereby ensuring the accuracy of the detection.

[0052] The present invention has corresponding liquid guiding grooves 1201 evenly distributed on the inner sidewall of the inner surface of the extended cylinder, and an annular connector 8 fixedly connected to the outer side of the liquid guiding grooves 1201, forming multiple vertically connected liquid guiding channels, so that the solution in the liquid container 701 can flow smoothly to the grinding zone above the second filter plate 601 to mix and wash with the crystallized salt. The annular connector 8 forms a corresponding installation area to facilitate the installation and vertical movement of the grinding component 602, realizing the liquid feeding and the installation and use of the grinding components, thus improving the practical effect of the present invention.

[0053] The connecting mechanism 9 includes a connecting rod 901 fixed to the bottom of the liquid container 701. The other end of the connecting rod 901 is rotatably connected to the grinding element 602 through a corresponding bearing. The connecting rod 901 and the grinding element 602 are connected by a corresponding meshing gear set. The meshing gear set includes a first gear 902 and an annular external gear ring 903 respectively fixed to the connecting rod 901 and the grinding element 602. The annular external gear ring 903 is sleeved on the outside of the connecting rod 901. The first gear 902 and the annular external gear ring 903 are respectively meshed with a corresponding second gear 904 and a third gear 905. The second gear 904 and the third gear 905 are connected by a corresponding fixing rod. The fixing rod is rotatably mounted on a mounting plate 906 fixed to the annular connecting element 8. The first gear 902 and the third gear 905 are both large gears, and the second gear 904 and the annular external gear ring 903 are both small gears.

[0054] The upper inner wall of the extension cylinder is provided with a corresponding internal thread, and the outer wall of the liquid container 701 is provided with a matching external thread. The top of the liquid container 701 is provided with a corresponding cover plate 10 that can be opened and closed, and a corresponding handle 11 is fixedly connected to the cover plate 10. The liquid container 701 is screwed to the sand core funnel 2 by rotating and lowering the handle 11 by holding it.

[0055] This invention utilizes a connecting structure to connect the grinding component 602 and the liquid container 701. This allows the grinding component 602 to rotate and move downwards while the liquid container 701 is installed, thus performing grinding. A connecting rod 901 is installed between the liquid container 701 and the grinding component 602. A corresponding first gear 902 is fixedly connected to the outer side of the connecting rod 901. An annular external gear ring 903 is fixedly connected to the grinding component 602 and sleeved on the outer side of the connecting rod 901. The first gear 902 and the annular external gear ring 903 respectively mesh with a second gear 904 and a third gear 905. Both the second gear 904 and the third gear 905 are rotatably mounted via corresponding fixing rods and mounting plates 906. Mounted onto the annular connector 8, the first gear 902 and the third gear 905 are both large gears with a gear ratio of 1:1. The second gear 904 and the annular external gear ring 903 are both small gears with a gear ratio of 1:1. The gear ratio of the first gear 902 and the second gear 904 is 5:1 to 10:1, so that the grinding element 602 rotates several times when the liquid container 701 rotates once, thereby accelerating the grinding speed. The rapidly rotating grinding element 602 can also cause the liquid to form a circulating vortex, which in turn promotes the mixing of anhydrous dehydrating agent or volatile detergent with crystallized salt, thereby improving the efficiency and effect of washing and removing free water or anhydrous dehydrating agent.

[0056] Example 2

[0057] A method for determining the free water content in crystalline salts, comprising:

[0058] S1, Solvent pretreatment: Add excess salt reagents to the dehydrating agent and detergent respectively, so that the salt reagents soluble in the dehydrating agent and / or detergent are saturated in the dehydrating agent and detergent, and remove water from the dehydrating agent and detergent to obtain anhydrous dehydrating agent and volatile detergent;

[0059] S2, Sample pretreatment: Accurately weigh the crystalline salt sample and place it in the corresponding position of the above-mentioned detection and filtration device with an appropriate amount of anhydrous dehydrating agent. While mixing the crystalline salt sample and the anhydrous dehydrating agent, grind the crystalline salt sample into fine crystal particles.

[0060] S3, Salt washing: The crystalline salt sample, which has been ground into fine crystal particles, is mixed and washed with an anhydrous dehydrating agent.

[0061] S4, First filtration: Filter the mixture from step S3;

[0062] S5, Dehydration agent removal: Add a volatile detergent to the crystalline salt sample after filtration in step S4 and mix and wash.

[0063] S6, Secondary filtration: Use a clean filtration flask 1 to filter the crystalline salt sample washed in step S5.

[0064] The salt reagent is one or more of the following: sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, and calcium chloride.

[0065] The dehydrating agent is an aprotic organic solvent that is miscible with water in any proportion and insoluble in crystalline salts, and has good fluidity, low toxicity, and low odor. The dehydrating agent is one or a mixture of several of amides, ketones, nitriles, dimethyl sulfoxide, and pyridine.

[0066] The detergent is a low-boiling-point, volatile organic solvent that is miscible with the dehydrating agent in any proportion. The detergent is one or a mixture of several of the following: diethyl ether, acetone, and ethyl acetate.

[0067] The salt washing and primary filtration described in steps S3-S4 need to be repeated 3-5 times. The dehydrating agent removal and secondary filtration described in steps S5-S6 need to be repeated 5-8 times. The final filtration must continue until no liquid drips into the filtration flask 1 and continue filtration for 5-8 minutes. Then, replace the filtration flask 1 with a new one and continue filtration for 15-20 minutes. Remove the sand core funnel 2 and weigh the product. .

[0068] The detection method further includes step S7, blank sample spike verification test: using newly opened commercially available salt crystals as a blank test, the spike verification is performed according to steps S2 to S6 above; wherein, in step S2 of the blank test, the salt crystals and a small amount of pure water need to be accurately weighed, an appropriate amount of pretreated anhydrous dehydrating agent is added to the salt crystals, and during the grinding and stirring of the salt crystals, a small amount of pure water is gradually added dropwise to the salt crystals, and the salt crystals should be kept away from dissolving in the added water as much as possible. The salt crystals are calcium chloride dihydrate crystals.

[0069] The sand core funnel 2 of the detection filtration device must be clean, anhydrous, and dried to constant weight. The mass of the sample must be measured before detection. 2. Mass of the sand core funnel used for sample testing 2. Mass of the sand core funnel used for blank tests After testing, the weight of the sample and the sand core funnel were measured. The mass of sand core funnel 2 after blank test ,in and Both include the mass of sand core funnel 2 and the mass of filter paper 5; the change in mass of sand core funnel 2 after the blank test is as follows: Percentage of free water in crystalline salt : .

[0070] This invention detects free water in crystalline salt through experimental steps including solvent pretreatment, sample pretreatment, salt washing, primary filtration, dehydrating agent removal, and secondary filtration. The sample is washed with an anhydrous organic solvent that is miscible with water in any proportion but insoluble in crystalline salt to remove free water. Then, a low-boiling-point, volatile detergent is used to remove the anhydrous dehydrating agent. The free water content in the crystalline salt sample is calculated by the weight change before and after washing. This method can detect the free water content in crystalline salt entrained in the brine during the desalination process of high-salt brine, eliminating the interference of crystal water caused by sample instability. It overcomes the problem of existing detection methods failing to accurately detect free water entrained in thermally unstable crystalline salt, achieving rapid determination of the free water content in crystalline salt entrained in the brine during the desalination process of high-salt brine. The method has good accuracy, precision, and applicability; it is simple, rapid, and low-cost, and applicable to different types of crystalline salt.

[0071] This invention involves adding excess sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, and calcium chloride salts to the dehydrating agent and detergent, respectively. This allows the salts, soluble in the dehydrating agent and / or detergent, to dissolve in both, removing water from the dehydrating agent and detergent, resulting in anhydrous dehydrating agent and volatile detergent. Since halogen salts, nitrates, and sulfates may be slightly soluble in the dehydrating agent, solvent pretreatment makes the mass of dissolved salts during washing negligible, further improving the accuracy of free water detection. Furthermore, sample pretreatment, grinding the crystalline salt sample into fine particles, promotes the rapid and significant mixing of free water entrained between the crystals into the dehydrating agent for removal, increasing the processing speed of the test. This invention further conducts blank sample spike verification tests, achieving a free water recovery rate of 90%–110% in the blank crystalline salt, thus improving detection accuracy.

[0072] Examples 3-6

[0073] The difference between this embodiment and Example 2 is that different dehydrating agents and volatile detergents were used for verification: In Example 3, the dehydrating agent was acetone and the detergent was acetone; in Example 4, the dehydrating agent was acetone and the detergent was diethyl ether; in Example 5, the dehydrating agent was dimethyl sulfoxide and the detergent was acetone; in Example 6, the dehydrating agent was dimethyl sulfoxide and the volatile detergent was diethyl ether. Under the same conditions, different dehydrating agents and detergents were used to detect the free water content in the crystalline salt according to the steps of Example 2, and the percentage of free water in the crystalline salt was obtained. The specific results are shown in Tables 1-4 below. This invention needs to be carried out in a suitable operating room to avoid changes in sample properties.

[0074] Table 1. Detection of free water in crystalline salts when both dehydrating agent and detergent are acetone.

[0075]

[0076] Table 2. Detection of free water in crystalline salts when acetone is used as the dehydrating agent and diethyl ether is used as the detergent.

[0077]

[0078] Table 3. Detection of free water in crystalline salts when dimethyl sulfoxide is used as the dehydrating agent and acetone is used as the detergent.

[0079]

[0080] Table 4. Detection of free water in crystalline salts when the dehydrating agent is dimethyl sulfoxide and the detergent is diethyl ether.

[0081]

[0082] As shown in Tables 1-4, the overall spiked recovery rate of blank samples using different dehydrating agents and detergents ranged from 90.44% to 106.5%, indicating that the detection accuracy of this method is good.

[0083] Example 7

[0084] The difference between this embodiment and Embodiment 2 is that this method was used to test the crystalline salt samples at different stages of sun-drying. Acetone was used as the dehydrating agent and ether was used as the detergent to determine the moisture content in the crystalline salt. The test results are shown in Table 5 below. The four samples came from different brine pools and their main components were different: Sample 1 was mainly composed of sodium chloride crystals, Sample 2 was mainly composed of potassium chloride and sodium chloride mixed crystals, and Samples 3 and 4 were mainly composed of calcium chloride crystals. Samples 1, 2, and 3 were freshly taken and prepared from the brine pools, while Sample 4 was obtained from a long-term outdoor salt pile.

[0085] Table 5 Comparison of free water detection for different crystalline salts

[0086]

[0087] The comparison results in Table 5 show that the parallel detection results of this method for detecting free water in crystalline salts have good precision.

[0088] It should be noted that this embodiment is implemented in the same way as the first embodiment in terms of principle and technical effect. For the sake of brevity, any parts not mentioned in this embodiment can be referred to the corresponding content in the first embodiment.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A detection and filtration device for determining the free water content in crystalline salts, characterized in that, include: The filtration flask (1) is connected to an external vacuum pump (13) via a corresponding rubber tube. A sand core funnel (2) is tightly installed on the mouth of the filtration bottle (1) through a perforated rubber stopper (3), and the liquid outlet tube of the sand core funnel (2) extends through the perforated rubber stopper (3) into the filtration bottle (1). A corresponding first filter plate (4) is integrally formed in the hopper of the sand core funnel (2), and a corresponding filter paper (5) can be replaced on the first filter plate (4). An extension cylinder (12) is detachably and sealed on the top of the hopper of the sand core funnel (2). The grinding mechanism (6) includes a second filter plate (601) that is detachably and fixedly installed in the hopper above the first filter plate (4). The second filter plate (601) is spherical and has a number of sieve holes (6011) with a cross-section that is narrow at the top and wide at the bottom. The grinding mechanism (6) also includes a grinding element (602) that can be rotated and moved down to cooperate with the second filter plate (601) for grinding the crystalline salt sample on the second filter plate (601). The shape of the lower end face of the grinding element (602) is adapted to the second filter plate (601), and a number of grinding protrusions (6021) are integrally formed on its lower surface. The liquid inlet mechanism (7) includes a liquid container (701) installed on the upper inner side of the extension cylinder (12) by means of a threaded connection. The inner wall of the extension cylinder (12) is recessed between the second filter plate (601) and the liquid container (701) and has corresponding liquid guiding grooves (1201) evenly distributed. An annular connector (8) is fixedly connected inside the extension cylinder (12) to fit and block the outside of the liquid guiding groove (1201). The grinding part (602) is fitted and rotated. The device is dynamically installed at the location of the annular connector (8). The top of the annular connector (8) is constricted and forms a corresponding inlet area with the upper part of the liquid guiding groove (1201). The lower part of the liquid container (701) is connected to a corresponding liquid guiding pipe (702), and the outlet of the liquid guiding pipe (702) is located in the inlet area. The solution in the liquid container (701) flows through the liquid guiding groove (1201) to the top of the second filter plate (601). The connecting mechanism (9) is used to connect the grinding element (602) and the liquid container (701). When the liquid container (701) is connected to the extension cylinder (12) and rotates downward, the connecting mechanism (9) drives the grinding element (602) to accelerate rotation and move downward to grind the crystalline salt sample placed on the second filter plate (601). The grinding element (602) accelerates rotation to rotate and mix and wash the ground crystalline salt sample with anhydrous dehydrating agent or volatile detergent.

2. The detection and filtration device for determining the free water content in crystalline salts according to claim 1, characterized in that, The connecting mechanism (9) includes a connecting rod (901) fixed to the bottom of the liquid container (701). The other end of the connecting rod (901) is rotatably connected to the grinding element (602) through a corresponding bearing. The connecting rod (901) and the grinding element (602) are connected by a corresponding meshing gear set. The meshing gear set includes a first gear (902) and an annular external gear ring (903) respectively fixed to the connecting rod (901) and the grinding element (602). The annular external gear ring (903) is sleeved on the connecting rod (901) and the grinding element (602). On the outside of the connecting rod (901), the first gear (902) and the annular external gear ring (903) are respectively meshed with the corresponding second gear (904) and third gear (905), and the second gear (904) and third gear (905) are connected by corresponding fixing rods. The fixing rods are rotatably mounted on the mounting plate (906) fixed on the annular connecting member (8). The first gear (902) and the third gear (905) are both large gears, and the second gear (904) and the annular external gear ring (903) are both small gears.

3. The detection and filtration device for determining the free water content in crystalline salts according to claim 1, characterized in that, The upper inner wall of the extension cylinder (12) is provided with a corresponding internal thread, and the outer wall of the liquid container (701) is provided with an external thread that matches it. The top of the liquid container (701) is provided with a corresponding cover plate (10) that can be opened and closed, and a corresponding handle (11) is fixedly connected to the cover plate (10). The liquid container (701) and the extension cylinder (12) are screwed together by rotating and lowering the handle (11) by hand.

4. A method for determining the free water content in crystalline salts, characterized in that, include: S1, Solvent pretreatment: Add excess salt reagents to the dehydrating agent and detergent respectively, so that the salt reagents soluble in the dehydrating agent and / or detergent are saturated in the dehydrating agent and detergent, and remove water from the dehydrating agent and detergent to obtain anhydrous dehydrating agent and volatile detergent; S2, Sample pretreatment: Accurately weigh the crystalline salt sample and place it and an appropriate amount of anhydrous dehydrating agent in the corresponding positions of the detection filtration device as described in any one of claims 1-3. While mixing the crystalline salt sample and the anhydrous dehydrating agent, grind the crystalline salt sample into fine crystalline particles. S3, Salt washing: The crystalline salt sample, which has been ground into fine crystal particles, is mixed and washed with an anhydrous dehydrating agent. S4, First filtration: Filter the mixture from step S3; S5, Dehydration agent removal: Add a volatile detergent to the crystalline salt sample after filtration in step S4 and mix and wash. S6, Secondary filtration: Use a clean filtration flask (1) to filter the crystalline salt sample washed in step S5.

5. The method for determining the free water content in crystalline salts according to claim 4, characterized in that, The salt reagent is one or more of the following: sodium chloride, sodium sulfate, potassium chloride, magnesium chloride, and calcium chloride.

6. The method for determining the free water content in crystalline salts according to claim 4, characterized in that, The dehydrating agent is an aprotic organic solvent that is miscible with water in any proportion and insoluble in crystalline salts, and has good fluidity, low toxicity, and low odor. The dehydrating agent is one or a mixture of several of amides, ketones, nitriles, dimethyl sulfoxide, and pyridine.

7. The method for determining the free water content in crystalline salts according to claim 4, characterized in that, The detergent is a low-boiling-point, volatile organic solvent that is miscible with the dehydrating agent in any proportion. The detergent is one or a mixture of several of the following: diethyl ether, acetone, and ethyl acetate.

8. The method for determining the free water content in crystalline salts according to claim 4, characterized in that, The salt washing and primary filtration described in steps S3-S4 need to be repeated 3-5 times. The dehydrating agent removal and secondary filtration described in steps S5-S6 need to be repeated 5-8 times. The final filtration must continue until no liquid drips into the filtration flask (1) and continue filtration for 5-8 minutes. Then, replace the filtration flask (1) with a new one and continue filtration for 15-20 minutes. Remove the sand core funnel (2) and weigh it to obtain the final product. .

9. The method for determining the free water content in crystalline salts according to claim 4, characterized in that, The detection method further includes step S7, blank sample spike verification test: using newly opened commercially available salt crystals as a blank test, the spike verification is performed according to steps S2 to S6 above; wherein, in step S2 of the blank test, the salt crystals and a small amount of pure water need to be accurately weighed, an appropriate amount of pretreated anhydrous dehydrating agent is added to the salt crystals, and during the grinding and stirring of the salt crystals, a small amount of pure water is gradually added dropwise to the salt crystals, and the salt crystals should be kept away from dissolving in the added water as much as possible. The salt crystals are calcium chloride dihydrate crystals.

10. The method for determining the free water content in crystalline salt according to claim 9, characterized in that, The sand core funnel (2) of the detection filtration device must be clean, anhydrous, and dried to constant weight. The mass of the sample must be measured before detection.

1. Mass of the sand core funnel used for sample testing (2) 1. Mass of the sand core funnel used for blank test (2) And after the test, the weight of the sample and the sand core funnel (2) after the test was completed was measured. The mass of the sand core funnel (2) after the blank test ,in and Both include the mass of the sand core funnel (2) and the mass of the filter paper (5); the change in mass of the sand core funnel (2) after the blank test is as follows: Percentage of free water in crystalline salts : .

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