Multi-stage drying method and drying device for superfine nano-calcium

Abstract

The invention discloses a multistage drying method of superfine nano calcium and a drying device thereof, the method comprises the following steps: S1, superfine nano calcium is conveyed into the drying device through a conveying belt for primary drying, mixed gas of fuel gas and air in a combustion chamber is combusted through a combustor and then is heated to enter a drying chamber, convection is formed in the drying chamber, and the superfine nano calcium is dried in the drying chamber; the drying temperature in the drying chamber is uniformly distributed; s2, along with conveying of the multiple layers of conveying belts, calcium carbonate falls into the vertical drying box from the tail end of the conveying belt on the upper layer, and nano-calcium automatically turns over and shakes in the vertical drying box for secondary drying; s3, after being heated in the vertical drying box, the nano-calcium falls onto the next layer of conveying belt from an outlet of the vertical drying box to be subjected to third-stage drying; and S4, the steps S2-S3 are repeated until the water content of the nano-calcium meets the requirement, and the nano-calcium is conveyed out of the drying device through the conveying belt on the bottom layer. The drying device has the characteristics of saving the drying time and improving the drying capacity.

Description

Technical Field

[0001] The invention relates to a processing technology of ultrafine nanometer calcium, in particular to a multi-stage drying method and a drying device of ultrafine nanometer calcium. Background Art

[0002] Nano calcium is the abbreviation of nano calcium carbonate. The commonly used preparation method of nano calcium carbonate is carbonization method, and its steps are as follows: Raw material preparation: Select high-quality limestone as raw material, and go through pretreatment processes such as crushing and screening to ensure that the particle size and purity of the raw material meet the production requirements. Calcination and decomposition: The limestone raw material is sent to the calcining furnace for high-temperature calcination to decompose it to generate calcium oxide (quicklime). This step requires strict control of the calcination temperature and time to ensure the purity and activity of calcium oxide. Digestion and pulping: The calcium oxide obtained by calcination is added with water for digestion reaction to generate calcium hydroxide (slaked lime) emulsion. The amount of water added and the reaction temperature need to be controlled during the digestion process to obtain a stable calcium hydroxide emulsion. Carbonation reaction: Carbon dioxide gas is introduced into the calcium hydroxide emulsion for carbonization reaction to generate calcium carbonate particles. In the carbonization process, by controlling parameters such as reaction temperature, gas flow rate, stirring speed, and adding an appropriate amount of crystal control agent and dispersant, nano calcium carbonate particles with uniform particle size and good dispersibility can be prepared. Subsequent treatment: After filtering, washing, drying and other subsequent treatment processes, impurities and moisture are removed to obtain nano calcium carbonate products.

[0003] The drying process of nano-calcium is mainly to remove the moisture in nano-calcium to improve its stability and application performance. The existing nano-calcium drying usually adopts a one-stage drying method, which has high energy requirements and needs to maintain a certain pressure in the drying room for a long time. If the pressure is insufficient, it will affect the drying effect, resulting in product quality problems and low output, and increased overall costs. Moreover, the one-stage drying devices currently used are mostly static drying methods, and the heat is relatively localized for the heating of nano-calcium. Some nano-calcium agglomerates together, which easily affects the drying effect, resulting in low drying efficiency and long drying time. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-stage drying method and drying device for ultrafine nano calcium, which has the characteristics of saving drying time and improving drying capacity.

[0005] The technical solution of the present invention is a multi-stage drying method for ultrafine nano calcium, comprising the following steps:

[0006] S1. Ultrafine nano-calcium is transported to a drying device through a conveyor belt for primary drying, wherein the gas and air mixture in the combustion chamber is burned by a burner, and then heated up and enters the drying chamber, forming convection in the drying chamber to ensure uniform drying temperature distribution in the drying chamber;

[0007] S2. With the conveying of the multi-layer conveyor belt, calcium carbonate falls from the end of the conveyor belt of the upper layer into the vertical drying oven, and the nano calcium automatically turns and shakes in the vertical drying oven for secondary drying;

[0008] S3, after being heated in the vertical drying oven, the nano calcium falls from the outlet of the vertical drying oven to the conveyor belt of the next layer for three-stage drying;

[0009] S4, repeating steps S2-S3 until the moisture content of the nano-calcium reaches the requirement, and the conveyor belt at the bottom layer conveys the nano-calcium out of the drying device.

[0010] In the aforementioned multi-stage drying method for ultrafine nano-calcium, in step S2, when the nano-calcium is subjected to secondary drying in a vertical drying oven, the nano-calcium falls into a drying tank, the vertical drying oven itself rotates, and the drying tank swings back and forth, turning over and filtering the nano-calcium layer by layer; and while the drying tank swings, a strong magnet moves close to the nano-calcium in the direction of the swing of the drying tank, and adsorbs and removes ferromagnetic impurities in the nano-calcium.

[0011] In the aforementioned multi-stage drying method for ultrafine nano-calcium, during the drying process, the air pressure difference between the inside and outside of the drying chamber entrance is detected in real time. If the air pressure inside the drying chamber entrance is greater than the air pressure outside the drying chamber entrance, the wind speed of the dehumidification fan on the drying chamber is increased, and the pressure in the drying chamber is adjusted so that the pressure in the drying chamber is in a negative pressure state.

[0012] In the aforementioned multi-stage drying method of ultrafine nano-calcium, the waste heat and moisture discharged from the drying chamber is exchanged with the fresh air from the outside through a heat exchange device, and the cooled waste heat gas is discharged for purification treatment, and the hot air formed after the heat exchange with the fresh air is input into the combustion chamber for combustion utilization.

[0013] A multi-stage drying device for ultrafine nano-calcium comprises a drying chamber and a combustion chamber, wherein a burner, a gas pipe and an air pipe are arranged in the combustion chamber, the outlet of the combustion chamber is communicated with the drying chamber, the bottom and the top of the drying chamber are both provided with heat-distributing fans which are staggered up and down, several layers of conveyor belts are arranged in the drying chamber, a vertical drying box is arranged between the end of the conveyor belt of the upper layer and the head end of the conveyor belt of the lower layer, the inlet of the vertical drying box corresponds to the end of the conveyor belt of the upper layer, and the outlet of the vertical drying box corresponds to the head end of the conveyor belt of the lower layer; a fixing frame is arranged on the inner wall of the drying chamber, the vertical drying box is rotatably connected to the fixing frame by being driven by a rotating mechanism, and several layers of drying slots with grid-shaped bottoms are arranged in the vertical drying box.

[0014] In the aforementioned multi-stage drying device for ultrafine nano-calcium, the vertical drying box includes an outer box body, an inner box body is arranged inside the outer box body, an air flow channel is formed between the inner box body and the outer box body, and both the outer box body and the inner box body are provided with vents connected to the air flow channel, and an electric heating tube is also provided on the outer wall of the inner box body.

[0015] In the aforementioned multi-stage drying device for ultrafine nano-calcium, the rotating mechanism includes a gear ring installed on the periphery of the outer box body, the gear ring is meshed with a gear, the gear is provided with a driving shaft, the driving shaft is provided with a worm wheel coaxially distributed with the gear, the worm wheel is meshed with a worm, and one end of the worm is connected to the driving motor.

[0016] In the aforementioned multi-stage drying device for ultrafine nano-calcium, the drying trough is rotatably connected to the inner box body through a rotating shaft, a torsion spring is sleeved on the rotating shaft, one end of the torsion spring is connected to the drying trough, and the other end of the torsion spring is connected to the inner box body; a swing shaft driven by a swing motor is provided on one side or both symmetrical sides below the drying trough, and an eccentric wheel is provided on the swing shaft. The eccentric wheel collides with the drying trough under the rotation of the swing shaft, causing the drying trough to swing back and forth.

[0017] In the aforementioned multi-stage drying device for ultrafine nano-calcium, a transverse screw rotatably connected to the inner box body is provided above the drying tank, one end of the transverse screw is connected to a rotating motor, a movable frame is threadedly connected to the transverse screw, the movable frame moves laterally with the rotation of the transverse screw, a roller driven to rotate by the movable motor is provided on the movable frame, and a ring-shaped strong magnet is provided on the outside of the roller.

[0018] In the aforementioned multi-stage drying device for ultrafine nano-calcium, an exhaust duct is provided on the drying chamber, a dehumidification fan is provided on the exhaust duct, a first air pressure sensor is provided on the inner side of the entrance of the drying chamber, and a second air pressure sensor is provided on the outer side of the entrance of the drying chamber. The detection heads of the first air pressure sensor and the second air pressure sensor are in the same horizontal plane, and the first air pressure sensor and the second air pressure sensor are both connected to the dehumidification fan via a controller.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention allows the gas and air mixture in the combustion chamber to be burned by a burner, and then the mixture is heated and enters the drying chamber. Through the heat-equalizing fan with vertical cross-flow distribution, the hot air flow in the drying chamber forms vertical convection, which is fully in contact with the nano-calcium carbonate, thereby improving the drying effect of the nano-calcium, making the moisture on the surface of the material evaporate quickly, and ensuring that the drying temperature in the drying chamber is evenly distributed.

[0021] Ultrafine nano-calcium is transported through multiple layers of conveyor belts in the drying device. During the transportation process, it is first dried to form pre-drying, and then the nano-calcium falls from the end of the conveyor belt on the upper layer into the vertical drying box and falls into the drying slots distributed in layers. The vertical drying box is driven by the rotating mechanism to rotate, driving the internal drying slots to rotate, and the nano-calcium is dispersed for secondary deep drying, thereby improving the drying effect and comprehensiveness of the nano-calcium; after being heated in the vertical drying box, the nano-calcium falls from the outlet of the vertical drying box to the conveyor belt on the next layer for tertiary drying, and then the above steps are repeated until it is dried to a moisture content that meets the requirements, thereby improving drying efficiency and uniformity and saving drying time.

[0022] Therefore, the present invention has the characteristics of improving drying capacity and saving drying time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention.

[0024] Figure 2 It is a schematic diagram of the internal structure of a vertical drying oven.

[0025] Figure 3 It is a structural diagram of the rotating mechanism.

[0026] Figure 4 It is a structural diagram of a drying tank.

[0027] Figure 5 It is a schematic diagram of the structure of a strong magnet.

[0028] Figure 6 yes Figure 1 A magnified view of the local structure at point A.

[0029] Figure 7 It is a structural schematic diagram of a heat exchange device.

[0030] The markings in the attached drawings are: 1, drying chamber; 11, conveyor belt; 12, heat-saturating fan; 2, combustion chamber; 21, gas pipe; 22, air pipe; 3, vertical drying box; 31, fixed frame; 32, drying trough; 33, outer box; 34, inner box; 35, air flow channel; 36, vent; 37, electric heating tube; 4, rotating mechanism; 41, gear ring; 42, gear; 43, driving shaft; 44, worm gear; 45, worm; 51, rotating shaft; 52, torsion spring; 53, swing motor; 54, swing shaft; 55, Eccentric wheel; 61. transverse screw; 62. rotating motor; 63. movable frame; 64. roller; 65. strong magnet; 7. exhaust duct; 71. dehumidification fan; 72. first air pressure sensor; 73. second air pressure sensor; 8. heat exchange device; 81. casing; 82. first heat exchange space; 83. second heat exchange space; 84. first heat exchange tube; 85. fresh air inlet; 851. sealing cover; 852. sleeve brush; 86. exhaust gas inlet; 87. hot air outlet; 88. exhaust gas outlet; 89. second heat exchange tube. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the embodiments, but they are not intended to limit the present invention.

[0032] Example:

[0033] A multi-stage drying method for ultrafine nano calcium comprises the following steps:

[0034] S1, the ultrafine nano calcium is transported to the drying device through the conveyor belt 11 for primary drying, wherein the gas and air mixture in the combustion chamber 2 is burned by the burner, and then heated up and enters the drying chamber 1, forming convection in the drying chamber 1 to ensure that the drying temperature in the drying chamber 1 is evenly distributed;

[0035] S2, with the conveyance of the multi-layer conveyor belt 11, the nano-calcium is transported from the head end of the conveyor belt 11 to the end of the conveyor belt 11, and the nano-calcium falls from the end of the upper layer of the conveyor belt 11 into the vertical drying box 3, and the nano-calcium automatically turns and shakes in the vertical drying box 3 for secondary drying, so that the nano-calcium is heated more evenly and fully;

[0036] S3, after being heated in the vertical drying oven 3, the nano calcium falls from the outlet of the vertical drying oven 3 to the conveyor belt 11 of the next layer for three-stage drying;

[0037] S4, repeating steps S2-S3 until the moisture content of the nano-calcium reaches the requirement, and the conveyor belt 11 at the bottom layer conveys the nano-calcium out of the drying device.

[0038] When the nano-calcium is subjected to secondary drying in the vertical drying box 3, the nano-calcium falls into the drying slot 32, the vertical drying box 3 itself rotates, and the drying slot 32 swings back and forth, turning over and filtering the nano-calcium layer by layer, so that the nano-calcium in the vertical drying box 3 is evenly and fully heated, ensuring that the nano-calcium particles discharged from the bottom outlet of the vertical drying box 3 meet the requirements; and while the drying slot 32 swings, the strong magnet 65 moves close to the nano-calcium along the swinging direction of the drying slot 32, adsorbs and removes ferromagnetic impurities in the nano-calcium, and improves the quality of the nano-calcium.

[0039] During the drying process, the air pressure difference between the inside and outside of the entrance of the drying chamber 1 is detected in real time. If the air pressure inside the entrance of the drying chamber 1 is greater than the air pressure outside the entrance of the drying chamber 1, the wind speed of the dehumidification fan 71 in the drying chamber 1 is increased, and the pressure in the drying chamber 1 is adjusted so that the pressure in the drying chamber 1 is in a negative pressure state, which is slightly lower than the air pressure outside the entrance of the drying chamber 1, thereby preventing the hot and humid gas and polluted exhaust gas in the drying chamber 1 from being discharged from the entrance of the drying chamber 1 and polluting the working environment.

[0040] The waste heat and moisture discharged from the drying chamber 1 is heat exchanged with the fresh air from the outside through the heat exchange device 8, and the cooled waste heat gas is discharged for purification treatment. The hot air formed after the heat exchange with the fresh air is input into the combustion chamber 2 for combustion utilization, saving natural gas and other fuels and reducing material costs.

[0041] like Figure 1-Figure 7 As shown, a multi-stage drying device for ultrafine nano calcium comprises a drying chamber 1 and a combustion chamber 2, wherein a burner, a gas pipe 21 and an air pipe 22 are arranged in the combustion chamber 2, the outlet of the combustion chamber 2 is communicated with the drying chamber 1, the bottom and the top of the drying chamber 1 are provided with uniform heating fans 12 which are staggeredly distributed up and down, a plurality of layers of conveyor belts 11 are arranged in the drying chamber 1, a vertical drying box 3 is arranged between the end of the conveyor belt 11 of the upper layer and the head end of the conveyor belt 11 of the lower layer, the inlet of the vertical drying box 3 corresponds to the end of the conveyor belt 11 of the upper layer, and the outlet of the vertical drying box 3 corresponds to the head end of the conveyor belt 11 of the lower layer; a fixing frame 31 is arranged on the inner wall of the drying chamber 1, the vertical drying box 3 is rotatably connected to the fixing frame 31 by being driven by a rotating mechanism 4, and a plurality of layers of drying slots 32 with a grid-shaped bottom are arranged in the vertical drying box 3.

[0042] The fuel gas and air mixture in the combustion chamber 2 is burned by the burner and then heated up and enters the drying chamber 1. The hot air flow in the drying chamber 1 forms an upward and downward convection through the heat-equalizing fan 12 with vertical cross-flow distribution, which fully contacts the nano-calcium carbonate, improves the drying effect of the nano-calcium, makes the moisture on the surface of the material evaporate quickly, and ensures that the drying temperature in the drying chamber 1 is evenly distributed.

[0043] Ultrafine nano-calcium is transported through multiple layers of conveyor belts 11 in the drying device. During the transportation process, it is first dried to form pre-baking, and then the nano-calcium falls from the end of the conveyor belt 11 of the upper layer into the vertical drying box 3 and falls into the drying grooves 32 distributed in layers. The vertical drying box 3 is driven by the rotating mechanism 4 to rotate, driving the internal drying grooves 32 to rotate, dispersing the nano-calcium, and performing secondary deep drying of the nano-calcium, thereby improving the drying effect and comprehensiveness of the nano-calcium; after being heated in the vertical drying box 3, the nano-calcium falls from the outlet of the vertical drying box 3 to the conveyor belt 11 of the next layer for tertiary drying, and then the above steps are repeated until it is dried to a moisture content that meets the requirements, thereby improving the drying efficiency and uniformity and saving drying time.

[0044] The vertical drying box 3 includes an outer box body 33, an inner box body 34 is arranged inside the outer box body 33, an air flow channel 35 is formed between the inner box body 34 and the outer box body 33, and vents 36 communicating with the air flow channel 35 are arranged on the outer box body 33 and the inner box body 34, and an electric heating tube 37 is also arranged on the outer wall of the inner box body 34. The vertical drying box 3 allows the hot air in the drying chamber 1 to flow into the inner box body 34 through the vents 36 through the air flow channel 35, and the hot air is further temperature-controlled through the electric heating tube 37 in the air flow channel 35, so as to facilitate the control of the secondary drying of the nano-calcium in the vertical drying box 3.

[0045] The rotating mechanism 4 includes a gear ring 41 installed on the periphery of the outer box body 33, a gear 42 is meshed on the gear ring 41, a driving shaft 43 is provided on the gear 42, a worm wheel 44 is provided on the driving shaft 43 and is coaxially distributed with the gear 42, a worm 45 is meshed on the worm wheel 44, and one end of the worm 45 is connected to the driving motor to rotate. The driving motor drives the worm 45 to rotate, the worm 45 drives the worm wheel 44 to rotate, and the worm wheel 44 drives the gear 42 to rotate through the driving shaft 43, thereby driving the gear ring 41 and the outer box body 33 to rotate, so that the nano calcium inside the vertical drying box 3 is dried in a rotary manner, and the drying is more comprehensive and uniform.

[0046] The drying tank 32 is rotatably connected to the inner box 34 via a rotating shaft 51. A torsion spring 52 is sleeved on the rotating shaft 51. One end of the torsion spring 52 is connected to the drying tank 32, and the other end of the torsion spring 52 is connected to the inner box 34. A swing shaft 54 ​​driven by a swing motor 53 is provided on one side or two symmetrical sides below the drying tank 32. An eccentric wheel 55 is provided on the swing shaft 54. The eccentric wheel 55 collides with the drying tank 32 under the rotation of the swing shaft 54, so that the drying tank 32 swings back and forth. The swing motor 53 drives the swing shaft 54 ​​to rotate, and the swing shaft 54 ​​drives the eccentric wheel 55 to rotate. During the rotation of the eccentric wheel 55, it hits the drying tank 32, so that the drying tank 32 rotates and automatically resets under the drive of the torsion spring 52. Therefore, combined with the structure of the eccentric wheel 55 and the torsion spring 52, the drying tank 32 swings back and forth, driving the nano-calcium inside to flip, reducing the agglomeration phenomenon, adjusting the heating surface of the nano-calcium, and improving the heating efficiency.

[0047] A transverse screw 61 rotatably connected to the inner box 34 is provided above the drying tank 32, one end of the transverse screw 61 is connected to a rotating motor 62, a movable frame 63 is threadedly connected to the transverse screw 61, the movable frame 63 moves laterally with the rotation of the transverse screw 61, a roller 64 driven by the movable motor to rotate is provided on the movable frame 63, and a ring-shaped strong magnet 65 is provided on the outside of the roller 64. The rotating motor 62 drives the transverse screw 61 to rotate, and the movable frame 63 moves back and forth along the transverse screw 61 under the action of the positive and negative rotation of the transverse screw 61, matching the swing of the drying tank 32, driving the roller 64 to approach the nano-calcium, and using the strong magnet 65 to absorb and remove ferromagnetic impurities.

[0048] The drying chamber 1 is provided with an exhaust duct 7, and a dehumidification fan 71 is provided on the exhaust duct 7. A first air pressure sensor 72 is provided on the inner side of the entrance of the drying chamber 1, and a second air pressure sensor 73 is provided on the outer side of the entrance of the drying chamber 1. The detection heads of the first air pressure sensor 72 and the second air pressure sensor 73 are in the same horizontal plane, and the first air pressure sensor 72 and the second air pressure sensor 73 are connected to the dehumidification fan 71 through a controller. The first air pressure sensor 72 and the second air pressure sensor 73 are used to detect the air pressure inside and outside the entrance of the drying chamber 1, respectively. By detecting the pressure difference between the inside and outside of the entrance, if the air pressure inside the entrance of the drying chamber 1 is not less than the air pressure outside the entrance, the dehumidification fan 71 is started to adjust the pressure inside the drying chamber 1, so that a slightly negative pressure state is formed inside the drying chamber 1, so as to prevent the gas inside the drying chamber 1 from overflowing from the entrance, and improve the cleanliness and dryness of the environment outside the drying chamber 1.

[0049] The exhaust pipe 7 is connected to a heat exchange device 8, and a hot air outlet 87 of the heat exchange device 8 is connected to the combustion chamber 2. After the fresh air is heat-exchanged in the heat exchange device 8, the exhausted hot air is connected to the combustion chamber 2 through the hot air outlet 87, providing hot air for the combustion chamber 2, thereby saving dye and reducing costs.

[0050] The heat exchange device 8 includes an outer shell 81, and the inner space of the outer shell 81 is divided into a first heat exchange space 82 and a second heat exchange space 83 by a partition plate. A plurality of first heat exchange tubes 84 are arranged inside the first heat exchange space 82, and a fresh air inlet 85 and an exhaust gas inlet 86 are arranged on the wall of the first heat exchange space 82. A sealing cover 851 connected to the first heat exchange tube 84 and a sleeve brush 852 wrapped around the outside of the first heat exchange tube 84 are arranged at the fresh air inlet 85. One end of the first heat exchange tube 84 is connected to the fresh air inlet 85, and the other end of the first heat exchange tube 84 is connected to the second heat exchange space 83; a hot air outlet 87 and an exhaust gas outlet 88 are arranged on the wall of the second heat exchange space 83, and a second heat exchange tube 89 is arranged inside the second heat exchange space 83. The second heat exchange tube 89 and the first heat exchange tube 84 are staggered, one end of the second heat exchange tube 89 is connected to the first heat exchange space 82, and the other end of the second heat exchange tube 89 is connected to the exhaust gas outlet 88.

[0051] In the heat exchange device 8, the waste heat and moisture first enter the first heat exchange space 82, and the outside fresh air enters the first heat exchange tube 84 to perform a primary heat exchange with the waste heat and moisture. The particulate pollutants in the exhaust gas are easily attached to the outside of the first heat exchange tube 84 and are cleaned; then the fresh air after heat exchange enters the second heat exchange space 83, and the exhaust gas enters the second heat exchange tube 89 for a secondary heat exchange, which improves the heat exchange efficiency and reduces the dust accumulation in the second heat exchange tube 89.

[0052] The outer wall of the first heat exchange tube 84 is rough, and pollutants in the waste heat gas are more likely to adhere to the first heat exchange tube 84. The inner wall of the second heat exchange tube 89 is smooth, and pollutants in the waste heat gas are not easy to adhere to the inner wall of the second heat exchange tube 89. The first heat exchange tube 84 is connected to the sealing cover 851, which is convenient for removal and cleaning. During the removal process, the first heat exchange tube 84 moves in the sleeve brush 852, so that the sleeve brush 852 cleans the outer wall of the first heat exchange tube 84, improving the cleaning convenience of the first heat exchange tube 84.

[0053] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A multi-stage drying method for ultrafine nano calcium, characterized in that: The following steps are involved: S1, transporting the ultrafine nano-calcium to a drying device via a conveyor belt (11) for primary drying, wherein the fuel gas and air mixture in the combustion chamber (2) is burned by a burner, heated up and enters the drying chamber (1), forming convection in the drying chamber (1), thereby ensuring that the drying temperature in the drying chamber (1) is evenly distributed; S2, as the multi-layer conveyor belt (11) is conveyed, the calcium carbonate falls from the end of the upper conveyor belt (11) into the vertical drying oven (3), and the nano calcium automatically turns and shakes in the vertical drying oven (3) to perform secondary drying; S3, after being heated in the vertical drying oven (3), the nano-calcium falls from the outlet of the vertical drying oven (3) onto the conveyor belt (11) of the next layer for three-stage drying; S4, repeating steps S2-S3 until the moisture content of the nano-calcium reaches the required level, and the bottom conveyor belt (11) conveys the nano-calcium out of the drying device.

2. The multi-stage drying method of ultrafine nano calcium according to claim 1, characterized in that: In step S2, when the nano-calcium is subjected to secondary drying in the vertical drying oven (3), the nano-calcium falls into the drying trough (32), the vertical drying oven (3) itself rotates, and the drying trough (32) swings back and forth, turning over and filtering the nano-calcium layer by layer; and while the drying trough (32) swings, the strong magnet (65) moves close to the nano-calcium along the swinging direction of the drying trough (32), and adsorbs and removes ferromagnetic impurities in the nano-calcium.

3. The multi-stage drying method of ultrafine nano calcium according to claim 1, characterized in that: During the drying process, the air pressure difference between the inside and outside of the drying chamber (1) entrance is detected in real time. If the air pressure inside the drying chamber (1) entrance is greater than the air pressure outside the drying chamber (1) entrance, the wind speed of the dehumidification fan (71) on the drying chamber (1) is increased to adjust the pressure inside the drying chamber (1) so that the pressure inside the drying chamber (1) is in a negative pressure state.

4. The multi-stage drying method of ultrafine nano calcium according to claim 1, characterized in that: The waste heat and moisture discharged from the drying chamber (1) is heat exchanged with fresh air from the outside through the heat exchange device (8), and the cooled waste heat gas is discharged for purification. The hot air generated after the heat exchange with the fresh air is input into the combustion chamber (2) for combustion utilization.

5. A multi-stage drying device for ultrafine nano-calcium, used in the multi-stage drying method according to any one of claims 1 to 4, characterized in that: The invention comprises a drying chamber (1) and a combustion chamber (2). The combustion chamber (2) is provided with a burner, a gas pipe (21) and an air pipe (22). The outlet of the combustion chamber (2) is communicated with the drying chamber (1). The bottom and the top of the drying chamber (1) are provided with heat-distributing fans (12) which are staggered up and down. The drying chamber (1) is provided with a plurality of layers of conveyor belts (11). A vertical drying box (3) is provided between the end of the conveyor belt (11) of the upper layer and the beginning of the conveyor belt (11) of the lower layer. The inlet of the vertical drying box (3) corresponds to the end of the conveyor belt (11) of the upper layer, and the outlet of the vertical drying box (3) corresponds to the beginning of the conveyor belt (11) of the lower layer. A fixed frame (31) is provided on the inner wall of the drying chamber (1). The vertical drying box (3) is rotatably connected to the fixed frame (31) by being driven by a rotating mechanism (4). The vertical drying box (3) is provided with a plurality of layers of drying slots (32) with a grid-shaped bottom.

6. The multi-stage drying device for ultrafine nano-calcium according to claim 5, characterized in that: The vertical drying box (3) comprises an outer box body (33), an inner box body (34) is arranged inside the outer box body (33), an air flow channel (35) is formed between the inner box body (34) and the outer box body (33), both the outer box body (33) and the inner box body (34) are provided with vent holes (36) communicating with the air flow channel (35), and an electric heating pipe (37) is also arranged on the outer wall of the inner box body (34).

7. The multi-stage drying device for ultrafine nano-calcium according to claim 6, characterized in that: The rotating mechanism (4) comprises a gear ring (41) mounted on the periphery of the outer box body (33), the gear ring (41) is meshed with a gear (42), the gear (42) is provided with a driving shaft (43), the driving shaft (43) is provided with a worm wheel (44) coaxially distributed with the gear (42), the worm wheel (44) is meshed with a worm (45), and one end of the worm (45) is connected to the driving motor.

8. The multi-stage drying device for ultrafine nano-calcium according to claim 5, characterized in that: The drying trough (32) is rotatably connected to the inner box (34) via a rotating shaft (51); a torsion spring (52) is sleeved on the rotating shaft (51); one end of the torsion spring (52) is connected to the drying trough (32); and the other end of the torsion spring (52) is connected to the inner box (34); a swing shaft (54) driven by a swing motor (53) is provided on one side or two symmetrical sides below the drying trough (32); an eccentric wheel (55) is provided on the swing shaft (54); the eccentric wheel (55) collides with the drying trough (32) under the rotation of the swing shaft (54), so that the drying trough (32) swings back and forth.

9. The multi-stage drying device for ultrafine nano-calcium according to claim 5, characterized in that: A transverse screw (61) rotatably connected to the inner box (34) is provided above the drying tank (32); one end of the transverse screw (61) is connected to a rotating motor (62); a movable frame (63) is threadedly connected to the transverse screw (61); the movable frame (63) moves laterally as the transverse screw (61) rotates; a roller (64) driven to rotate by the movable motor is provided on the movable frame (63); a ring-shaped strong magnet (65) is provided on the outside of the roller (64).

10. The multi-stage drying device for ultrafine nano-calcium according to claim 5, characterized in that: The drying chamber (1) is provided with an exhaust duct (7), and a dehumidification fan (71) is provided on the exhaust duct (7). A first air pressure sensor (72) is provided on the inner side of the entrance of the drying chamber (1), and a second air pressure sensor (73) is provided on the outer side of the entrance of the drying chamber (1). The detection heads of the first air pressure sensor (72) and the second air pressure sensor (73) are located at the same horizontal plane, and the first air pressure sensor (72) and the second air pressure sensor (73) are connected to the dehumidification fan (71) via a controller.

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