Method for improving relative density of iodine by secondary curing of solid iodine

Abstract

The invention discloses a method for increasing relative density of iodine by secondary curing of solid iodine, which comprises the following steps: step 1, firstly heating and liquefying solid iodine, then filling a special storage box with an iodine solution, and uniformly arranging a plurality of groups of heating devices on the side surface and the bottom of the storage box from top to bottom in sequence, the heating surface of each group of heating devices is tightly attached to the surface of the storage box, and the heating devices on the storage box are all in an on state during filling; step 2, keeping an iodine heating device on the storage box in an open heating state to carry out heat preservation and soaking on the whole storage box; 3, after soaking and heat preservation are completed, all the heating devices are gradually and sequentially turned off from bottom to top from the bottom face, waiting is conducted for a period of time after each set of heating device is turned off, the next set of heating devices are turned off after the temperature gradient in the storage box is stable, and after all the heating devices are turned off, cooling is conducted to the room temperature, and target solid iodine is obtained. In this way, the canning density of iodine can be improved, and the space utilization rate of the storage box is increased.

Description

Technical Field

[0001] This invention relates to the field of iodine working medium propulsion systems, and in particular to a method for increasing the relative density of iodine through secondary solidification of solid iodine. Background Technology

[0002] In the field of satellite thrusters, electric propulsion technology is diverse and has attracted significant attention. Both types of thrusters traditionally use xenon as their working fluid. However, obtaining high-purity xenon gas is costly due to its chemical synthesis and separation processes. Furthermore, xenon gas storage requires high-pressure storage under supercritical conditions, limiting the limited spatial layout and functionality of satellites. Therefore, solid iodine, a viable alternative to xenon, directly transforms from a solid to a gaseous state at sublimation temperatures. This sublimation characteristic makes the storage and use of iodine as a working fluid much more convenient, eliminating the need for complex sealing and leak-proof measures required for liquid propellants, and the need for high-pressure sealed storage like xenon. This significantly reduces the complexity and weight of the storage system. Moreover, compared to the rare gas xenon, iodine is much cheaper, which is crucial for reducing the overall cost of satellites, especially for cost-sensitive projects such as microsatellites. This allows more institutions and companies to invest in satellite research and development. Resource abundance: Iodine is relatively abundant on Earth, relatively easy to obtain, and has a high supply stability, unlike rare gases such as xenon, which are limited resources and greatly affected by market supply fluctuations. This makes it more sustainable for large-scale applications. Currently, iodine storage and supply systems directly liquefy solid iodine and inject it into the corresponding storage tanks. However, due to the high solidification temperature of iodine, it solidifies at room temperature and has a high overall density. Iodine solution is also quite viscous. During the injection process, the cavities created by the liquid impact and the dissolved and absorbed air cannot be expelled. This results in a significant difference between the overall density of iodine in the entire storage tank and the standard density, making it impossible to fully utilize the effective volume of the storage tank. This is especially problematic for microsatellites where every inch of space needs to be carefully calculated. Summary of the Invention

[0003] The main technical problem solved by this invention is to provide a method for increasing the relative density of iodine through secondary solidification of iodine, which can increase the density of solidified iodine and save the effective space of the storage tank.

[0004] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: to provide a method for improving the relative density of iodine through secondary solid-state iodine curing, the method comprising the following contents: Step 1: First, the solid iodine is heated and liquefied, and then the iodine solution is filled into a special storage tank. Multiple sets of heating devices are evenly arranged on the side and bottom of the storage tank from top to bottom. The heating surface of each set of heating devices is in close contact with the surface of the storage tank. During filling, the heating devices on the storage tank are all turned on. The iodine heating device on the storage tank described in Step 2 remains in the heating state to keep the entire storage tank warm and evenly heated. After the heat preservation and even heating in Step 3 are completed, starting from the bottom surface, all heating devices are gradually turned off step by step from bottom to top. After each group of heating devices is turned off, wait for a period of time. After the temperature gradient inside the storage tank stabilizes, then turn off the next group of heating devices. After all heating devices are turned off, cool to room temperature to obtain the target solid iodine.

[0005] In a preferred embodiment of the present invention, the number of the heating devices is 3 to 5.

[0006] In a preferred embodiment of the present invention, during filling, the storage tank is in a vacuum state, and the initial temperature of the storage tank is the same as the heating temperature of the heating device. The liquefaction temperature of the iodine in Step 1 is 8 to 15 °C higher than the initial temperature of the storage tank.

[0007] In a preferred embodiment of the present invention, the heating temperature of the heating device in Step 2 is 125 °C to 140 °C, and the time for heat preservation and even heating is 1 h to 4 h.

[0008] In a preferred embodiment of the present invention, the waiting time for each interval in Step 3 is 1 to 4 h.

[0009] In a preferred embodiment of the present invention, the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 115 mm, the height h is 54 mm ≤ h ≤ 143 mm, and the ratio of the bottom diameter d to the height h is 0.8 to 1.2.

[0010] When the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 90 mm and the height h is 54 mm ≤ h ≤ 90 mm, the number of heating devices is 3 groups; When the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 90 mm and the height h is 90 mm < h ≤ 112 mm, the number of heating devices is 4 groups; When the bottom diameter d of the storage tank is 90 mm < d ≤ 115 mm and the height h is 75 mm ≤ h ≤ 115 mm, the number of heating devices is 4 groups; When the bottom diameter d of the storage tank is 90 mm < d ≤ 115 mm and the height h is 115 mm < h ≤ 143 mm, the number of heating devices is 5 groups.

[0011] When the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 90 mm and the height h is 54 mm ≤ h ≤ 90 mm, the heating temperature of the heating device is 130 °C; When the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 90 mm and the height h is 90 mm < h ≤ 112 mm, the heating temperature of the heating device is 125 °C; When the bottom diameter d of the storage tank is 90 mm < d ≤ 115 mm and the height h is 75 mm ≤ h ≤ 115 mm, the heating temperature of the heating device is 140 °C; When the bottom diameter d of the storage tank is 90 mm < d ≤ 115 mm and the height h is 115 mm < h ≤ 143 mm, the heating temperature of the heating device is 135 °C.

[0012] In a preferred embodiment of the present invention, the density of the target iodine is 4.92 g / cm³ to 4.93 g / cm³.

[0013] The beneficial effects of the present invention are as follows: In the present invention, multiple heating devices are sequentially installed on the iodine storage tank from top to bottom, and then the temperature at each position of the storage tank is precisely controlled in cooperation by the multiple heating devices, making the temperature difference in all directions inside the storage tank extremely small, avoiding interference with the precise process of liquefaction crystallization due to local overcooling or overheating, and laying a solid foundation for subsequent cooling control. Moreover, during actual solidification, a segmented cooling method is adopted by sequentially turning off the heating devices from bottom to top, creating a temperature change gradient, driving the liquid iodine to start from the bottom of the storage tank and gradually solidify upward. It's like building a ladder, allowing the liquid iodine to solidify methodically along the designed "temperature ladder" to achieve segmented cooling. In this way, the liquid iodine no longer cools and solidifies disorderly as a whole, but solidifies gradually from bottom to top in an orderly manner. This process avoids the problem of uneven cooling caused by unbalanced heat exchange between the upper and lower layers of liquid in the traditional cooling method, enabling the liquid iodine in the entire storage tank to cool at a more uniform rhythm. With the liquid iodine solidifying in an orderly manner, there is no chance for gas to be "trapped" in the gaps formed by sudden solidification, greatly reducing the bubble cavity phenomenon, and thus making the internal structure of the solidified liquid iodine more compact. After practical inspection, it is found that there is no cavity phenomenon in the storage tank. The relative density of the iodine as a whole also infinitely approaches its standard density of 4.93 g / cm at normal temperature and pressure 3 , greatly improving the space utilization efficiency of the storage tank and enhancing the usage efficiency of the iodine working fluid satellite thruster; moreover, this method can be applied to storage tanks of any shape and structure, greatly simplifying the structure of the storage container, and can be processed and designed according to actual needs to meet different levels of requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of the principle of segmented cooling and solidification of liquid iodine in the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The following describes the preferred embodiments of the present invention in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0016] Please refer to Figure 1The present invention includes: a method for increasing the relative density of iodine through secondary solidification of iodine, the method comprising the following contents: Step 1: First, heat the solid iodine to liquefy it, and then fill the iodine solution into a special storage tank. The side and bottom of the storage tank are evenly arranged with 3 to 5 sets of heating devices from top to bottom. The heating surface of each set of heating devices is in close contact with the surface of the storage tank. During filling, the heating devices on the storage tank are all in the on state. In step 2, the iodine heating device on the storage tank is kept on to maintain uniform heat throughout the entire storage tank. After the heat equalization and heat preservation in step 3 is completed, starting from the bottom, all heating devices are turned off one by one from bottom to top. After each set of heating devices is turned off, the heat preservation is paused for a period of time. After the temperature gradient inside the storage tank stabilizes, the next set of heating devices is turned off. After all heating devices are turned off, the tank is cooled to room temperature to obtain the target iodine with a density of 4.92 g / cm³ to 4.93 g / cm³.

[0017] The reason for installing a heating device on the outside of the storage tank in step 1 is that the cooling of liquid iodine inside the tank mainly depends on the heat exchange process between the tank wall and the outside environment. Therefore, by adding a heating device on the outside, an additional heat source can be provided to the tank wall, which can significantly slow down the rate at which heat is lost from the inside of the tank to the external environment. It can even provide heat to the liquid iodine inside the tank, forming a balance and effectively controlling the cooling rate of the tank wall. As the iodine liquid cools from bottom to top, the density at the bottom is always greater than that at the top. Thus, air bubbles and cavities in the iodine liquid will be gradually driven upwards during the solidification process as the density changes, eventually reaching the top, thereby effectively increasing the overall density.

[0018] After filling in step 1, the storage tank is evacuated to a vacuum state using a vacuum pump. The initial temperature of the storage tank is the same as the heating temperature of the heating device. Evacuating the top of the storage tank minimizes the surface energy of the iodine solution, allowing gas molecules to easily escape. This makes it easier for bubbles rising from the bottom as the density of iodine changes to escape from the solution, preventing bubbles in the solid iodine from affecting subsequent ignition and reducing the unused space in the storage tank. Maintaining the same initial temperature between the storage tank and the heating device effectively avoids rapid heat transfer and localized crystallization caused by excessive temperature differences during filling, thus precisely controlling the overall iodine liquefaction and crystallization process and maintaining the heat supply required for the iodine liquefaction state.

[0019] In step one, the liquefaction temperature of the iodine is 8-15°C higher than the initial temperature of the storage tank. In practice, this is generally controlled at 10°C. This ensures that when the solid iodine is liquefied and enters the storage tank, the temperature of the liquid iodine is higher than both the initial temperature of the tank and the heating temperature of the heating device. Heat will be transferred from the liquid iodine to the surrounding tank walls and the heating device. This heat transfer direction facilitates appropriate "temperature self-regulation" within the storage tank during subsequent heat preservation and homogenization processes. This results in a more uniform temperature distribution as the liquid iodine's temperature gradually approaches the temperature of the heating device, preventing significant temperature gradients and avoiding localized overheating. This provides a stable initial state for subsequent heating and heat preservation operations. As explained above, the temperature difference should not be too large, otherwise localized overheating may occur.

[0020] The heating temperature of the heating device in step 2 is 125℃~140℃, and the heat preservation time is 1h~4h. The waiting time between each step in step 3 is 1~4h. Iodine has a melting point of 113℃ and a boiling point of 184℃. However, since iodine is prone to sublimation, the temperature needs to be controlled slightly above the melting point, that is, 125℃~140℃. The purpose of heat preservation in step 2 is to make the temperature distribution of liquid iodine in the tank more uniform during the heat preservation process, without obvious gradients, providing a stable initial state for subsequent heating and heat preservation operations. The purpose of the waiting time in step 3 is to allow the system in the tank to form a relatively stable temperature gradient after each set of heating devices is turned off. If the interval time is too short, the internal instability will cause convection, which will affect the bubble extrusion speed, resulting in insufficient bubble extrusion in the system, and the density of the target iodine will be difficult to meet the process requirements. Furthermore, during the actual cooling process, this segmented cooling method causes the temperature of the liquid iodine at the bottom of the tank to drop first and gradually reach its freezing point, beginning to solidify. Simultaneously, because heating continues above, the iodine at the top remains liquid and does not begin to solidify. Since the solidified iodine occupies a certain volume, and the liquid iodine gradually fills the space under gravity, the overall liquid level will steadily decrease. Subsequently, once the solidification process of the liquid iodine at the bottom of the tank has achieved the desired effect, the heating device in the middle of the tank's side wall is turned off, and the above process is repeated, causing the overall iodine level to drop further. From the principles of thermal expansion and contraction and phase change, this segmented cooling and solidification process from bottom to top causes the overall iodine level to exhibit a continuous, slow, segmented decrease. Moreover, as the amount of liquid iodine solidified in the tank increases, the overall average density of the iodine also gradually increases. During this process, the average density of the liquid iodine gradually increases from the initial 3.96 g / cm³ to 4.93 g / cm³. The above process can be understood from... Figure 1The cooling trend shown in the figure can be seen that this can effectively reduce the ineffective volume of the storage tank caused by problems such as cavities and air bubbles, and achieve the goal of saving storage tank space. This improves the space utilization rate of the storage tank in the storage of iodine and related chemical processes, and optimizes the economy and efficiency of the entire process.

[0021] The bottom diameter d of the storage tank is 65mm ≤ d ≤ 115mm, and the height h is 54mm ≤ h ≤ 143mm, with the ratio of bottom diameter d to height h being 0.8~1.2. In the entire process of liquefying solid iodine to increase density, the size design of the storage tank needs to undergo multiple rounds of testing and optimization. From a heat transfer perspective, if the storage tank is too tall or too narrow, the temperature difference between the upper and lower layers may exceed expectations when the heating device is turned off from bottom to top and the temperature is reduced in stages, affecting the sequence of liquid iodine solidification and making it difficult to effectively increase the relative density. Within the above-mentioned size range, combined with a surface-fitting heating device, the temperature change of the internal liquid iodine can be more stably and accurately controlled. Smaller storage tanks have shorter heat transfer distances and higher efficiency, facilitating rapid response to heating or cooling operations; larger storage tanks provide more space for liquid iodine to achieve gradual solidification and density increase. Furthermore, actual testing showed that a density increase was most effective when the ratio of the tank's bottom diameter to its height was between 0.8 and 1.2. This is because, from the perspective of heat exchange and changes in the state of matter, this ratio ensures ideal heat conduction and convection during the heating and cooling processes of the liquid iodine within the tank. When the ratio of the tank's bottom diameter to its height increases from 0.8, the tank becomes relatively flatter. This shape provides a larger horizontal surface area for the liquid iodine, allowing it to absorb heat over a larger area when the bottom heating device is operating, which is beneficial for rapid and uniform heat distribution. Simultaneously, during the cooling phase, this shape also facilitates heat dissipation from the surface of the liquid iodine, as the wider surface increases the heat exchange area with the external environment, aiding in the solidification of the liquid iodine. When the ratio of the tank's bottom diameter to its height approaches 1.2, the tank becomes relatively elongated. In this case, when the heating device is gradually shut off from bottom to top for segmented cooling, the temperature gradient of the liquid iodine in the vertical direction is easier to control. The slender shape of liquid iodine allows for more orderly convection under gravity, better aligning with the heating device's shut-off sequence to achieve a gradual solidification process from bottom to top, thus increasing the relative density of iodine. This ratio range matches the layout and operation of the heating device. In the heat preservation and homogenization stage of step 1, this ensures the heat provided by the heating device is evenly distributed within the tank, avoiding localized overheating or undercooling areas, maintaining the temperature of the liquid iodine within a stable range, which is beneficial for precise control of iodine liquefaction and crystallization. In step 3, during the gradual shut-off of the heating device from bottom to top, this ratio allows the liquid iodine to solidify in the expected sequence.

[0022] According to the above-mentioned storage tank dimensions, the preferred dimensions and the matching of the heating device are as follows: When the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 90 mm and the height h is 54 mm ≤ h ≤ 90 mm, the number of heating devices is 3 groups, and the heating temperature of the heating device is 130 °C; when the bottom diameter d of the storage tank is 65 mm ≤ d ≤ 90 mm and the height h is 90 mm < h ≤ 112 mm, the number of heating devices is 4 groups, and the heating temperature of the heating device is 125 °C; when the bottom diameter d of the storage tank is 90 mm < d ≤ 115 mm and the height h is 75 mm ≤ h ≤ 115 mm, the number of heating devices is 4 groups, and the heating temperature of the heating device is 140 °C; when the bottom diameter d of the storage tank is 90 mm < d ≤ 115 mm and the height h is 115 mm < h ≤ 143 mm, the number of heating devices is 5 groups, and the heating temperature of the heating device is 135 °C.

[0023] The reason for adopting the above-mentioned preferred matching structure is that there are differences in the content of liquefied iodine during actual operation, and external factors such as the specification size of the storage tank and the size of the heating device will all affect the liquefaction process of iodine. Therefore, the number of attached heating devices can be appropriately adjusted. Generally speaking, according to the structure of the storage tank, the number range is between 3 and 5 pieces. Moreover, from the perspective of chemical heat transfer and energy conversion, by adjusting the number of heating devices, the iodine liquefaction crystallization can be more accurately controlled.

[0024] The actual implementation according to the above method is as follows: Example 1 The first step: Prepare a storage tank with D = 65 mm, H = 54 mm, D / H = 0.8. Set a heating device at the bottom and evenly arrange two groups of heating devices in a ring on the side. The distance between adjacent heating devices is equal at 20 mm. The heating temperature is 130 °C. Vacuumize the storage tank and preheat it to 130 °C; The second step: Heat iodine to 140 °C. After complete liquefaction, pour it into the preset storage tank. The third step: Turn on all heating devices and keep warm for 1 h until the temperature of all liquid iodine in the storage tank is uniform. The fourth step: Cool down in segments. Starting from the bottom, turn off the heating devices one by one from bottom to top. Pause for heat preservation for 1 h each time a group of heating devices is turned off, and continue to turn off the next group of heating devices after the internal temperature gradient is stable.

[0025] The fifth step: After all heating devices are turned off, cool down to room temperature.

[0026] Example 2 The first step is to prepare the storage tank. The storage tank has a diameter of 90 mm and a height of 112 mm. The diameter of the tank is 0.8. A set of heating devices is installed at the bottom, and three sets of heating devices are evenly arranged around the sides. The distance between adjacent heating devices is equal and is 35 mm. The heating temperature is 125℃. The storage tank is evacuated and preheated to 125℃. The second step involves heating the iodine to 135°C until it is completely liquefied, then pouring it into a pre-designated storage tank. The third step is to turn on all heating devices and maintain the temperature for 2 hours until all the liquid iodine in the storage tank reaches a uniform temperature. The fourth step is to cool down in stages, starting from the bottom and turning off the heating devices one by one from bottom to top. After each set of heating devices is turned off, the heat preservation is paused for 2 hours. After the internal temperature gradient stabilizes, the next set of heating devices is turned off.

[0027] Fifth step: After all heating devices are turned off, cool to room temperature.

[0028] Example 3 The first step is to prepare the storage tank. The storage tank has a diameter of 90 mm and a height of 75 mm. The diameter / height is 1.2. A set of heating devices is installed at the bottom, and three sets of heating devices are evenly arranged around the sides. The distance between adjacent heating devices is equal and is 18 mm. The heating temperature is 130℃. The storage tank is evacuated and preheated to 140℃. The second step involves heating the iodine to 150°C until it is completely liquefied, then pouring it into a pre-designated storage tank. The third step is to turn on all heating devices and maintain the temperature for 3 hours until all the liquid iodine in the storage tank reaches a uniform temperature. The fourth step is to cool down in stages, starting from the bottom and turning off the heating devices one by one from bottom to top. After each set of heating devices is turned off, the heating is paused for 3 hours to maintain the temperature. After the internal temperature gradient stabilizes, the next set of heating devices is turned off.

[0029] Fifth step: After all heating devices are turned off, cool to room temperature.

[0030] Example 4 The first step is to prepare the storage tank. The storage tank has a diameter of 115 mm and a height of 143 mm. The diameter of the tank is 0.8. A set of heating devices is installed at the bottom, and four sets of heating devices are evenly arranged around the sides. The distance between adjacent heating devices is equal and is 40 mm. The heating temperature is 135℃. The storage tank is evacuated and preheated to 135℃. The second step involves heating the iodine to 145°C until it is completely liquefied, then pouring it into a pre-designated storage tank. The third step is to turn on all heating devices and maintain the temperature for 4 hours until all the liquid iodine in the storage tank reaches a uniform temperature. The fourth step is to cool down in stages, starting from the bottom and turning off the heating devices one by one from bottom to top. After each set of heating devices is turned off, the heat preservation is paused for 4 hours. After the internal temperature gradient stabilizes, the next set of heating devices will be turned off.

[0031] Fifth step: After all heating devices are turned off, cool to room temperature.

[0032] Comparative Example The storage tank specifications are the same as in Example 1. After being heated to 140°C and liquefied, the iodine was poured into the storage tank and allowed to cool naturally to room temperature to obtain a solid iodine sample.

[0033] The density detection results of the target iodine obtained in Examples 1-4 above are as follows: As can be seen from the above test results, the solid iodine that has not undergone a staged cooling process inevitably contains air bubbles and cavities. This results in the overall density of the iodine being significantly lower than that of the solid iodine treated by the method described in this invention. However, the density of the target iodine obtained after the above three steps is infinitely close to the standard density of solid iodine. It can be basically considered that the air bubbles and cavities have been completely removed. This not only makes it suitable as a working propellant supply device for satellite thrusters, but also ensures that it is free of any impurities, improving the working stability of the thrusters, and effectively saving valuable application space.

[0034] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for increasing the relative density of iodine through secondary solidification, characterized in that, The content of the method includes the following: Step 1: First, heat solid iodine to liquefy it, and then fill the iodine liquid into a special storage tank. Multiple groups of heating devices are evenly arranged on the side and bottom of the storage tank from top to bottom. The heating surface of each group of heating devices is closely attached to the surface of the storage tank. When filling, the heating devices on the storage tank are all in the on state; Step 2: The iodine heating device on the storage tank remains in the on heating state to keep the entire storage tank warm and evenly heat it; Step 3: After the uniform heating and heat preservation are completed, starting from the bottom surface, gradually turn off all heating devices from bottom to top. Wait for a period of time after turning off each group of heating devices, and then turn off the next group of heating devices after the temperature gradient inside the storage tank is stable. After all heating devices are turned off, cool to room temperature to obtain the target solid iodine.

2. The method for increasing the relative density of iodine through secondary solidification according to claim 1, characterized in that, The number of the heating devices is 3 - 5.

3. The method for increasing the relative density of iodine through secondary solidification according to claim 1, characterized in that, When filling, the storage tank is in a vacuum state, and the initial temperature of the storage tank is the same as the heating temperature of the heating device.

4. The method for increasing the relative density of iodine through secondary solidification according to claim 3, characterized in that, In Step 1, the liquefaction temperature of iodine is 8 - 15°C higher than the initial temperature of the storage tank.

5. The method for increasing the relative density of iodine through secondary solidification according to claim 1, characterized in that, In Step 2, the heating temperature of the heating device is 125°C - 140°C, and the time for heat preservation and uniform heating is 1h - 4h.

6. The method for increasing the relative density of iodine through secondary solidification according to claim 1, characterized in that, In Step 3, the waiting time for each interval is 1 - 4h.

7. The method for increasing the relative density of iodine through secondary solidification according to claim 1, characterized in that, The bottom diameter d of the storage tank is 65mm ≤ d ≤ 115mm, and the height h is 54mm ≤ h ≤ 143mm. The ratio of the bottom diameter d to the height h is 0.8 - 1.

2.

8. The method for increasing the relative density of iodine through secondary solidification according to claim 7, characterized in that, When the bottom diameter d of the storage tank is 65mm ≤ d ≤ 90mm and the height h is 54mm ≤ h ≤ 90mm, the number of heating devices is 3 groups; When the bottom diameter d of the storage tank is 65mm ≤ d ≤ 90mm and the height h is 90mm < h ≤ 112mm, the number of heating devices is 4 groups; When the bottom diameter d of the storage tank is 90mm < d ≤ 115mm and the height h is 75mm ≤ h ≤ 115mm, the number of heating devices is 4 groups; When the bottom diameter d of the storage tank is 90mm < d ≤ 115mm and the height h is 115mm < h ≤ 143mm, the number of heating devices is 5 groups.

9. The method for increasing the relative density of iodine through secondary solidification according to claim 8, characterized in that, When the bottom diameter d of the storage tank is 65mm ≤ d ≤ 90mm and the height h is 54mm ≤ h ≤ 90mm, the heating temperature of the heating device is 130°C; When the bottom diameter d of the storage tank is 65mm ≤ d ≤ 90mm and the height h is 90mm < h ≤ 112mm, the heating temperature of the heating device is 125°C; When the bottom diameter d of the storage tank is 90mm < d ≤ 115mm and the height h is 75mm ≤ h ≤ 115mm, the heating temperature of the heating device is 140°C; When the bottom diameter d of the storage tank is 90mm < d ≤ 115mm and the height h is 115mm < h ≤ 143mm, the heating temperature of the heating device is 135°C.

10. The method for increasing the relative density of iodine through secondary solidification according to claim 1, characterized in that, The density of the target iodine is 4.92g / cm³ - 4.93g / cm³.

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