Magnesium nitrate thermal decomposition device based on resistance heating

Abstract

The utility model discloses a magnesium nitrate thermal decomposition device based on resistance heating, which comprises a dilute magnesium nitrate storage tank, a primary evaporator, a secondary evaporator, a concentrated magnesium nitrate storage tank and a magnesium nitrate decomposition tank, each section of the resistance heating furnace is divided into three parts which are circumferentially distributed around the outer side wall of the magnesium nitrate decomposition tank, and a fire-resistant heat-insulating material and a resistance heating wire are sequentially arranged on the inner wall of a furnace body of each part of the resistance heating furnace from outside to inside; three temperature testers are arranged on the outer side wall of the magnesium nitrate decomposition tank at equal intervals in the circumferential direction, and one temperature tester is arranged between every two parts of the resistance heating furnace. The temperature fluctuation in the magnesium nitrate decomposition tank can be limited in an extremely small range, the stability and uniformity of the temperature in the whole magnesium nitrate decomposition tank are effectively ensured through the cooperation of the resistance heating furnace and the temperature tester, the whole decomposition process is ensured to be carried out in a stable constant-temperature environment, and the production efficiency is improved. The decomposition efficiency of magnesium nitrate and the product quality are improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to metallurgical technical field relates to thermal decomposition device, concretely relates to a kind of magnesium nitrate thermal decomposition device based on resistance heating. BACKGROUND

[0002] Nickel, as a key strategic metal, plays a crucial role in the fields of stainless steel manufacturing and new energy development. In recent years, with the rapid development of the new energy industry, the demand for nickel-based batteries has surged, therefore, improving the extraction efficiency of nickel resources has profound significance for the sustainable development of China's new energy industry. Currently, due to the gradual depletion of nickel sulfide ore, laterite nickel ore has surpassed nickel sulfide ore and become the main source of nickel extraction. Among these deposits, about 70% are brown iron-type laterite nickel ores, and the market generally uses sulfuric acid pressure leaching method for treatment. Although this method can efficiently leach nickel and cobalt, it produces a large amount of iron and aluminum leaching residue after reaction. These residues contain excessive sulfur elements, which are difficult to further utilize and can only be treated by deep-sea landfill or tailings storage, which not only brings huge environmental pressure but also causes serious waste of iron resources.

[0003] Therefore, high-pressure nitric acid leaching technology has made significant progress in recent years. This technology not only ensures efficient leaching of nickel and cobalt, but also has high iron content in the leaching residue, which can be directly sold as iron powder. The leaching solution uses magnesium oxide as a neutralizing agent, and through fractional precipitation, aluminum hydroxide, nickel-cobalt hydroxide, and manganese hydroxide are obtained. The main component of the precipitated liquid is magnesium nitrate, which can be regenerated through evaporation, drying, and pyrolysis cycles. The regeneration of magnesium oxide and nitric acid can be achieved. Magnesium nitrate, as a key intermediate in the regeneration of nitric acid and magnesium oxide, has important scientific value and practical application significance in the study of its pyrolysis process.

[0004] Chinese patent CN108862218A discloses a method and device for producing nitric acid by pyrolysis of metal nitrate. The method is carried out in a closed and negative pressure rotary kiln, causing the metal nitrate powder to undergo pyrolysis reaction, generating oxygen (O2), nitrogen dioxide (NO2), and corresponding metal oxide powder. Subsequently, the generated O2 and NO2 are introduced into an absorption tower, where they are effectively absorbed by the circulating absorption liquid, ultimately obtaining a nitric acid solution with a specific concentration. This method has the following technical problems: first, the heating of nitrate in the furnace is uneven, and the decomposition is not complete, so part of the nitrate may not be completely converted into the target product, affecting the quality and yield of the final product; second, the metal oxide particles obtained by this method are large and have low activity, which is not conducive to subsequent application or further processing.

[0005] A method and device system for recovering nitric acid from nitrate pyrolysis are disclosed in Chinese Patent CN109721038B. First, the nitrate is preheated to obtain a nitrate hot fluid. Then, the fluid is introduced into a decomposer through an atomizing device and heated to generate a gas-solid mixture of metal oxide powder, nitrogen oxide gas, and oxygen. Part of the mixed gas is directly recycled and converted into nitric acid, and the other part is heated to a higher temperature as a heat source for recycling, avoiding the interference of additional heat sources on the pyrolysis of nitrate. This method uses mixed gas as the heat source during the decomposition of nitrate. First, using mixed gas as the heat source, the thermal conductivity is relatively low, the heat transfer efficiency is not high, and a large amount of heat will be lost to the environment during gas transportation, thereby reducing the overall energy utilization efficiency. Second, when using mixed gas as the heat source, it is difficult to maintain uniform and stable temperature distribution in the entire decomposer, which may cause local hot spots or cold spots. This temperature fluctuation not only affects the decomposition rate of nitrate, but also may cause the temperature in some areas to be too high or too low, thereby affecting the running stability and safety of the entire system. Finally, due to low thermal efficiency and temperature control difficulties, the decomposition rate of nitrate is difficult to reach the ideal level, which means that there may be more un-decomposed nitrate residues in the actual production process, which not only wastes raw materials, but also may adversely affect the subsequent processing steps.

[0006] Chinese Patent CN112250092A discloses a magnesium nitrate pyrolysis device and method based on resource recycling. The technical solution contains two main steps: first, remove most of the water through a spray drying process to obtain anhydrous magnesium nitrate and a small amount of magnesium oxide; second, perform a pyrolysis reaction in a direct-fired cyclone dynamic calcination furnace to decompose the magnesium nitrate into magnesium oxide, nitrogen dioxide, and oxygen. The obtained gas-solid mixture is then sent to a cyclone separator for separation treatment, and the gas part is further treated by acid absorption method to recover the nitric acid therein, thereby achieving the resource recycling goal in the entire process. In this patent, magnesium nitrate is processed in two stages: the first stage uses spray drying technology to reduce the water content of the material and form fine solid particles. The second stage uses a cyclone dynamic calcination furnace to pyrolyze magnesium nitrate to generate a mixture of magnesium oxide and nitrogen oxide gas. This scheme combines two different technical means to optimize the processing flow of magnesium nitrate, but due to its complex process arrangement and some unavoidable defects in actual operation (such as quality fluctuations during calcination), the scheme faces great uncertainty in actual application.

[0007] It can be seen that the decomposition process of magnesium nitrate is extremely complex, and the current technical solution has significant deficiencies in temperature control, which often leads to local temperature abnormalities in the decomposition system, thereby affecting the decomposition efficiency of magnesium nitrate. In addition, the heat transfer mode also has certain limitations. In most cases, heat is transferred through an intermediate medium, and in this process, heat is inevitably lost to the surrounding environment, which not only causes waste of energy, but more importantly, reduces the utilization efficiency of heat energy. At the same time, in the existing technical solution, gas is used as an intermediate medium to transfer heat, in order to achieve the specific temperature required for the complete decomposition of magnesium nitrate, the temperature of the intermediate gas often needs to be heated to more than 400℃ higher than the decomposition temperature of magnesium nitrate, which consumes a large amount of fuel gas, not only increasing the cost, but also causing certain pressure on the environment. SUMMARY

[0008] In view of the deficiencies of the prior art, the utility model provides a magnesium nitrate thermal decomposition device based on resistance heating to solve the technical problem of uneven internal temperature of the magnesium nitrate decomposition tank in the prior art.

[0009] In order to solve the above technical problems, the utility model adopts the following technical scheme to achieve:

[0010] A magnesium nitrate thermal decomposition device based on resistance heating, comprising a dilute magnesium nitrate storage tank, the dilute magnesium nitrate storage tank is connected with a first evaporator through a first pipeline, the first evaporator is connected with a second evaporator through a second pipeline, the second evaporator is connected with a concentrated magnesium nitrate storage tank through a third pipeline, the concentrated magnesium nitrate storage tank is connected with one end of a fourth pipeline, the other end of the fourth pipeline extends into the inside of a magnesium nitrate decomposition tank and is connected with a sprayer, and the sprayer is located at a middle upper position in the magnesium nitrate decomposition tank.

[0011] The outer side wall of the magnesium nitrate decomposition tank is vertically provided with multiple resistance heating furnaces, each resistance heating furnace is circumferentially arranged in three parts around the outer side wall of the magnesium nitrate decomposition tank, and a refractory heat insulation material and a resistance heating wire are sequentially arranged on the inner wall of the furnace body of each resistance heating furnace from the outside to the inside.

[0012] Three temperature testers are circumferentially and equidistantly arranged on the outer side wall of the magnesium nitrate decomposition tank, and one temperature tester is arranged between every two resistance heating furnaces.

[0013] The utility model also has the following technical features:

[0014] The outer side wall of the magnesium nitrate decomposition tank is provided with an air outlet below the resistance heating furnace, the air outlet is connected with one end of a fifth pipeline, the other end of the fifth pipeline is connected with a waste heat recovery device, the waste heat recovery device is connected with a cyclone dust collector through a sixth pipeline, the cyclone dust collector is connected with a bag-type dust collector through a seventh pipeline, the bag-type dust collector is connected with one end of an eighth pipeline, the other end of the eighth pipeline is divided into a first branch and a second branch, the first branch is connected with the top wall of the magnesium nitrate decomposition tank, and the second branch leads to a nitric acid recovery tank.

[0015] The bottom of the magnesium nitrate decomposition tank is provided with a first discharge port, the first discharge port is connected with a screw propeller through a ninth pipeline, and a first valve is arranged at the first discharge port of the magnesium nitrate decomposition tank, and the first valve is used to control the communication between the first discharge port and the ninth pipeline.

[0016] The bottom of the cyclone dust collector is provided with a second discharge port, the second discharge port is connected with a screw propeller through a tenth pipeline, and a second valve is arranged at the second discharge port of the cyclone dust collector, and the second valve is used to control the communication between the second discharge port and the tenth pipeline.

[0017] The bottom of the bag-type dust collector is provided with a third discharge port, the third discharge port is connected with a screw propeller through an eleventh pipeline, and a third valve is arranged at the third discharge port of the bag-type dust collector, and the third valve is used to control the communication between the third discharge port and the eleventh pipeline.

[0018] The screw propeller is connected with a magnesium oxide storage tank.

[0019] The first pipeline is provided with a first conveying pump, the second pipeline is provided with a second conveying pump, the third pipeline is provided with a third conveying pump, and the fourth pipeline is provided with a fourth conveying pump.

[0020] The fifth pipeline is provided with a fourth valve.

[0021] The first branch is provided with a first induced draft fan, and the second branch is provided with a second induced draft fan.

[0022] Compared with the prior art, the magnesium nitrate decomposition tank has the following beneficial technical effects:

[0023] (Ⅰ) The multi-section resistance heating furnace can limit the temperature fluctuation in the magnesium nitrate decomposition tank within a very small range, and the resistance heating furnace and the temperature tester are cooperated to effectively ensure the stability and uniformity of the temperature in the magnesium nitrate decomposition tank, so that the decomposition process is carried out in a stable constant temperature environment, and the decomposition efficiency of the magnesium nitrate and the product quality are improved.

[0024] (II) The utility model discloses a resistance heating furnace is directly arranged on the outside wall of magnesium nitrate decomposition tank, and the resistance heating furnace directly contacts with the magnesium nitrate decomposition tank, and the heat is directly transferred from the heating source to the magnesium nitrate decomposition tank, so that the heat loss of intermediate link is reduced, the heat is more efficiently utilized, and the thermal efficiency of the system is improved.

[0025] (III) The utility model can accurately control temperature, so that the heating temperature can be appropriately reduced to meet the requirement of sufficient decomposition of magnesium nitrate, the heat input required by the system is reduced, the consumption of energy is reduced, the production cost is reduced, and the environmental protection concept of energy saving and emission reduction is met. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the structure schematic diagram of magnesium nitrate thermal decomposition device based on resistance heating.

[0027] Figure 2 It is the structure schematic diagram of magnesium nitrate decomposition tank and resistance heating furnace.

[0028] Figure 3 It is the cross section structure schematic diagram of resistance heating furnace outside wall.

[0029] The meanings of various reference numerals in the drawing are as follows: 1 - dilute magnesium nitrate storage tank, 2 - first pipeline, 3 - primary evaporator, 4 - second pipeline, 5 - secondary evaporator, 6 - third pipeline, 7 - concentrated magnesium nitrate storage tank, 8 - magnesium nitrate decomposition tank, 9 - resistance heating furnace, 10 - temperature tester, 11 - resistance heating wire, 12 - refractory insulating material, 13 - gas outlet, 14 - fifth pipeline, 15 - waste heat recovery device, 16 - sixth pipeline, 17 - cyclone dust collector, 18 - seventh pipeline, 19 - bag dust collector, 20 - eighth pipeline, 21 - first branch, 22 - second branch, 23 - nitric acid recovery tank, 24 - first discharge port, 25 - ninth pipeline, 26 - screw propeller, 27 - first valve, 28 - second discharge port, 29 - tenth pipeline, 30 - second valve, 31 - third discharge port, 32 - eleventh pipeline, 33 - third valve, 34 - magnesium oxide storage tank, 35 - first conveying pump, 36 - second conveying pump, 37 - third conveying pump, 38 - fourth conveying pump, 39 - fourth valve, 40 - first induced draft fan, 41 - second induced draft fan, 42 - atomizer, 43 - fourth pipeline.

[0030] The specific content of the utility model is further explained and described in detail in connection with the following embodiments. DETAILED DESCRIPTION

[0031] It should be noted that all the equipment and materials in the utility model are known in the prior art, and no special description is given.

[0032] According to the above technical scheme, the following specific embodiments of the present application are given, and it should be noted that the present application is not limited to the following specific embodiments, and any equivalent transformation based on the technical scheme of the present application falls within the protection scope of the present application.

[0033] Embodiment:

[0034] The embodiment provides a magnesium nitrate thermal decomposition device based on resistance heating, which comprises a dilute magnesium nitrate storage tank 1, as shown in the drawings. Figure 1 The dilute magnesium nitrate storage tank 1 is connected with a first evaporator 3 through a first pipeline 2, the first evaporator 3 is connected with a second evaporator 5 through a second pipeline 4, the second evaporator 5 is connected with a concentrated magnesium nitrate storage tank 7 through a third pipeline 6, the concentrated magnesium nitrate storage tank 7 is connected with one end of a fourth pipeline 43, the other end of the fourth pipeline 43 extends into the inside of a magnesium nitrate decomposition tank 8 and is connected with a sprayer 42, and the sprayer 42 is located at a middle upper position in the magnesium nitrate decomposition tank 8.

[0035] As shown in the drawings, Figures 1 to 3 A plurality of resistance heating furnaces 9 are vertically arranged on the outer side wall of the magnesium nitrate decomposition tank 8, each resistance heating furnace 9 is circumferentially arranged in three parts around the outer side wall of the magnesium nitrate decomposition tank 8, and a refractory insulating material 12 and a resistance heating wire 11 are sequentially arranged on the inner wall of the furnace body of each resistance heating furnace 9 from the outside to the inside.

[0036] As shown in the drawings, Figure 3 Three temperature testers 10 are circumferentially and equidistantly arranged on the outer side wall of the magnesium nitrate decomposition tank 8, and one temperature tester 10 is arranged between every two resistance heating furnaces 9.

[0037] In the embodiment, the magnesium nitrate decomposition tank 8 is made of stainless steel by welding, has good corrosion resistance and high temperature resistance, and provides stable and reliable basic guarantee for the whole production process.

[0038] In the embodiment, a plurality of resistance heating furnaces 9 are vertically arranged around the outer side wall of the magnesium nitrate decomposition tank 8, in the heating process, the resistance heating furnace 9 converts electric energy into heat energy through the heat effect of electric current, and the different regions of the magnesium nitrate decomposition tank 8 are heated in a targeted manner. Meanwhile, a plurality of temperature testers 10 are arranged on the outer side wall of the magnesium nitrate decomposition tank 8, the temperature change at different positions is monitored in real time, once the temperature deviation of a certain region is found, the power of the corresponding resistance heating furnace 9 is adjusted immediately. The segmented arrangement of the plurality of resistance heating furnaces 9 not only can independently control the temperature of each furnace body, accurately control the reaction temperature, but also can flexibly adjust the segmented arrangement of the plurality of resistance heating furnaces 9 according to the heat demand of different parts of the magnesium nitrate decomposition tank 8, and improve the energy utilization efficiency.

[0039] In this embodiment, each section of the electric resistance heating furnace 9 is circumferentially arranged in three parts around the outer sidewall of the magnesium nitrate decomposition tank 8, and each part of the electric resistance heating furnace 9 from the outside to the inside is sequentially the furnace body of the electric resistance heating furnace 9 (made of carbon steel material), the refractory insulation material 12, and the electric resistance heating wire 11. This design allows each part to be independently disassembled and assembled, facilitating the maintenance of the equipment and the replacement of the electric resistance heating wire 11.

[0040] In this embodiment, the temperature tester 10 can obtain the furnace body temperature of the electric resistance heating furnace 9 in real time during the production process. Once a deviation is found in a certain area, the power of the corresponding electric resistance heating furnace 9 can be immediately adjusted to ensure that the temperature of the entire system remains within a stable and suitable range.

[0041] In this embodiment, the sprayer 42 finely processes the magnesium nitrate molten salt and atomizes it into uniformly distributed fine particles, so that it is uniformly heated during the reaction process, thereby improving the magnesium nitrate decomposition rate and product quality.

[0042] As shown in Figure 1 The outer sidewall of the magnesium nitrate decomposition tank 8 is provided with a gas outlet 13, the gas outlet 13 is located below the electric resistance heating furnace 9, the gas outlet 13 is connected in communication with one end of a fifth pipeline 14, the other end of the fifth pipeline 14 is connected with a waste heat recovery device 15, the waste heat recovery device 15 is connected with a cyclone dust collector 17 through a sixth pipeline 16, the cyclone dust collector 17 is connected with a bag dust collector 19 through a seventh pipeline 18, the bag dust collector 19 is connected with one end of an eighth pipeline 20, the other end of the eighth pipeline 20 is divided into a first branch 21 and a second branch 22, the first branch 21 is connected in communication with the top wall of the magnesium nitrate decomposition tank 8, and the second branch 22 leads to a nitric acid recovery tank 23.

[0043] In this embodiment, the gas-solid mixture generated during the reaction process can be promptly discharged through the gas outlet 13, which can prevent the pressure in the furnace from abnormally rising and orderly transport the generated gas to the next process.

[0044] As shown in Figure 1 The bottom of the magnesium nitrate decomposition tank 8 is provided with a first discharge port 24, the first discharge port 24 is connected with a screw propeller 26 through a ninth pipeline 25, and a first valve 27 is arranged at the first discharge port 24 of the magnesium nitrate decomposition tank 8. The first valve 27 is used to control the communication between the first discharge port 24 and the ninth pipeline 25.

[0045] As shown in Figure 1 The bottom of the cyclone dust collector 17 is provided with a second discharge port 28, the second discharge port 28 is connected with the screw propeller 26 through a tenth pipeline 29, and a second valve 30 is arranged at the second discharge port 28 of the cyclone dust collector 17. The second valve 30 is used to control the communication between the second discharge port 28 and the tenth pipeline 29.

[0046] As shown in Figure 1 , the bottom of the bag filter 19 is provided with a third discharge port 31, the third discharge port 31 is connected with the screw propeller 26 through an eleventh pipeline 32, and the third discharge port 31 of the bag filter 19 is provided with a third valve 33, which is used to control the communication between the third discharge port 31 and the eleventh pipeline 32.

[0047] As shown in Figure 1 , the screw propeller 26 is connected with a magnesium oxide storage tank 34, and the screw propeller 26 is used to deliver the solid magnesium oxide powder into the magnesium oxide storage tank 34.

[0048] In this embodiment, the first discharge port 24, the second discharge port 28 and the third discharge port 31 are used to collect and deliver a part of the solid magnesium oxide powder obtained by the reaction to the magnesium oxide storage tank 34.

[0049] As shown in Figure 1 , the first pipeline 2 is provided with a first delivery pump 35, the second pipeline 2 is provided with a second delivery pump 36, the third pipeline 2 is provided with a third delivery pump 37, and the fourth pipeline 2 is provided with a fourth delivery pump 38.

[0050] In this embodiment, the first delivery pump 35, the second delivery pump 36, the third delivery pump 37 and the fourth delivery pump 38 are respectively used to deliver the dilute magnesium nitrate solution, the magnesium nitrate solution and the dihydrate magnesium nitrate molten salt fluid to the next process.

[0051] As shown in Figure 1 , the fifth pipeline 14 is provided with a fourth valve 39 for controlling the delivery of the mixed gas and the solid magnesium oxide powder. In this embodiment, the mixed gas is the gas generated by the decomposition of magnesium nitrate.

[0052] As shown in Figure 1 , the first branch 21 is provided with a first induced draft fan 40, and the second branch 22 is provided with a second induced draft fan 41.

[0053] In this embodiment, the first induced draft fan 40 and the second induced draft fan 41 are respectively used to blow the mixed gas into the magnesium nitrate decomposition tank 8 and the nitric acid recovery tank 23.

[0054] In this embodiment, the method for using the magnesium nitrate thermal decomposition device based on resistance heating includes the following steps:

[0055] Step one, the dilute magnesium nitrate solution after leaching the laterite nickel ore with nitric acid is concentrated by different methods in stages, MVR (mechanical vapor recompression) evaporation is carried out in the first evaporator 3, and multi-effect evaporation is carried out in the second evaporator 5, so as to remove the free water and part of the crystallization water in the dilute magnesium nitrate solution.

[0056] Step two, the concentrated magnesium nitrate solution after evaporation and concentration in step one is heated in the concentrated magnesium nitrate storage tank 7, and heated to below the decomposition temperature of the concentrated magnesium nitrate solution (the decomposition temperature is the decomposition temperature of the magnesium nitrate solution known in the art) to obtain a magnesium nitrate dihydrate molten salt fluid.

[0057] Step three, the magnesium nitrate dihydrate molten salt fluid obtained in step two is transported into the magnesium nitrate decomposition tank 8 by the atomizer 42, and heated by the resistance heating furnace 9, so as to maintain the internal temperature of the magnesium nitrate decomposition tank 8 between 550-750℃, so as to ensure that the magnesium nitrate dihydrate molten salt fluid is fully decomposed to generate mixed gas and solid magnesium oxide powder, the solid magnesium oxide powder deposited at the bottom of the magnesium nitrate decomposition tank 8 is transported to the magnesium oxide storage tank 34 by the first valve 27 from the ninth pipeline 25 to the screw propeller 26, and the screw propeller 26 transports the solid magnesium oxide powder to the magnesium oxide storage tank 34.

[0058] Step four, part of the heat in the mixed gas and solid magnesium oxide powder in step three is recovered by the waste heat recovery device 15.

[0059] Step five, the mixed gas and solid magnesium oxide powder in step four are sequentially introduced into the cyclone dust collector 17 and the bag dust collector 19 for gas-solid separation, the solid magnesium oxide powder deposited at the bottom of the cyclone dust collector 17 is dropped into the screw propeller 26 by the second valve 30 from the tenth pipeline 29, the solid magnesium oxide powder deposited at the bottom of the bag dust collector 19 is dropped into the screw propeller 26 by the third valve 33 from the eleventh pipeline 32, and the screw propeller 26 transports the solid magnesium oxide powder to the magnesium oxide storage tank 34.

[0060] Step six, part of the mixed gas in step five is transported to the nitric acid recovery tank 23, and the remaining mixed gas is returned to the magnesium nitrate decomposition tank 8 as a carrier of the decomposed solid magnesium oxide, which is taken out of the magnesium nitrate decomposition tank 8.

Claims

1. A magnesium nitrate thermal decomposition device based on resistance heating, comprising a dilute magnesium nitrate storage tank (1), characterized in that, The dilute magnesium nitrate storage tank (1) is connected to the first-stage evaporator (3) through the first pipe (2), the first-stage evaporator (3) is connected to the second-stage evaporator (5) through the second pipe (4), the second-stage evaporator (5) is connected to the concentrated magnesium nitrate storage tank (7) through the third pipe (6), the concentrated magnesium nitrate storage tank (7) is connected to one end of the fourth pipe (43), and the other end of the fourth pipe (43) extends into the magnesium nitrate decomposition tank (8) and is connected to the sprayer (42). The sprayer (42) is located in the upper middle position inside the magnesium nitrate decomposition tank (8). The magnesium nitrate decomposition tank (8) is vertically arranged with multiple resistance heating furnaces (9). Each resistance heating furnace (9) is arranged in three parts around the outer wall of the magnesium nitrate decomposition tank (8). The inner wall of each resistance heating furnace (9) is provided with refractory heat insulation material (12) and resistance heating wire (11) from the outside to the inside. Three temperature testers (10) are circumferentially equidistantly arranged on the outer wall of the magnesium nitrate decomposition tank (8), and one temperature tester (10) is arranged between every two resistance heating furnaces (9).

2. The magnesium nitrate thermal decomposition device based on resistance heating as described in claim 1, characterized in that, The magnesium nitrate decomposition tank (8) has an outlet (13) on its outer wall. The outlet (13) is located below the resistance heating furnace (9). The outlet (13) is connected to one end of the fifth pipe (14). The other end of the fifth pipe (14) is connected to the waste heat recovery unit (15). The waste heat recovery unit (15) is connected to the cyclone dust collector (17) through the sixth pipe (16). The cyclone dust collector (17) is connected to the bag dust collector (19) through the seventh pipe (18). The bag dust collector (19) is connected to one end of the eighth pipe (20). The other end of the eighth pipe (20) is divided into a first branch (21) and a second branch (22). The first branch (21) is connected to the top wall of the magnesium nitrate decomposition tank (8). The second branch (22) leads to the nitric acid recovery tank (23).

3. The magnesium nitrate thermal decomposition device based on resistance heating as described in claim 2, characterized in that, The magnesium nitrate decomposition tank (8) is provided with a first discharge port (24) at the bottom. The first discharge port (24) is connected to the screw propeller (26) through the ninth pipe (25). A first valve (27) is provided at the first discharge port (24) of the magnesium nitrate decomposition tank (8). The first valve (27) is used to control the connection between the first discharge port (24) and the ninth pipe (25). The cyclone dust collector (17) has a second discharge port (28) at its bottom. The second discharge port (28) is connected to the screw propeller (26) through the tenth pipe (29). A second valve (30) is provided at the second discharge port (28) of the cyclone dust collector (17). The second valve (30) is used to control the connection between the second discharge port (28) and the tenth pipe (29). The bag dust collector (19) has a third discharge port (31) at its bottom. The third discharge port (31) is connected to the screw propeller (26) through the eleventh pipe (32). A third valve (33) is provided at the third discharge port (31) of the bag dust collector (19). The third valve (33) is used to control the connection between the third discharge port (31) and the eleventh pipe (32). The propeller (26) is connected to the magnesium oxide storage tank (34).

4. The magnesium nitrate thermal decomposition device based on resistance heating as described in claim 1, characterized in that, A first delivery pump (35) is installed on the first pipeline (2), a second delivery pump (36) is installed on the second pipeline (4), a third delivery pump (37) is installed on the third pipeline (6), and a fourth delivery pump (38) is installed on the fourth pipeline (43).

5. The magnesium nitrate thermal decomposition device based on resistance heating as described in claim 2, characterized in that, A fourth valve (39) is installed on the fifth pipe (14).

6. The magnesium nitrate thermal decomposition device based on resistance heating as described in claim 2, characterized in that, The first branch (21) is equipped with a first induced draft fan (40), and the second branch (22) is equipped with a second induced draft fan (41).

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