Multi-zone sand bath device for heating soil organic matters

Abstract

The invention relates to the technical field of soil organic matter determination experiments, in particular to a sand bath device for multi-zone heating of soil organic matter, and aims to solve the problem that uneven temperature is easily generated in sand bath heating. Comprising a heating disc, a plurality of detection areas are formed on the heating disc, and the center of each detection area is fixedly connected with a base; closed boxes are detachably connected to the base, the multiple closed boxes are arranged around the base and form heating units, gaps exist between the adjacent heating units and between the heating units and the inner side walls of the adjacent heating plates, heating spaces are formed, and containing cavities are formed in the closed boxes; the heat preservation cover is detachably connected to the top of the heating disc. The containing cavity and the heating space are both filled with sand grains, and the heating unit can rotate along the base. The heating disc is divided into a plurality of detection areas, partitioned and modularized heating is achieved, the closed box surrounds the base to form the heating unit and can rotate along the base, sand grains can relatively move through rotation after heating, and therefore the solid sand grains are evenly mixed after being heated.

Description

Technical Field

[0001] This invention relates to the field of experimental technology for soil organic matter determination, and specifically to a sand bath device for multi-zone heating of soil organic matter. Background Technology

[0002] In a soil organic matter determination experiment, it is necessary to verify whether a sand bath can accurately analyze soil organic matter samples and the feasibility of using a sand bath to digest soil organic matter samples. Sand baths are widely used in chemical analysis, soil sample pretreatment, drying, and heat balance experiments due to their simple structure, large heat capacity, and low risk of sample contamination. Common sand bath forms include a metal pan or deep tank filled with bulk sand placed on a hot plate or heater. Heat is transferred to the sand layer through bottom or side heating elements. As a solid bulk medium, the heat capacity and thermal conductivity of sand can buffer temperature fluctuations to a certain extent and provide a relatively stable temperature field for sample processing.

[0003] In sand bath heating processes used for soil and similar solid samples, it is common to find that the temperature in the central region is significantly higher than that in the peripheral region, resulting in a radial temperature gradient within the sand bath. This temperature inhomogeneity is mainly caused by the following factors: the low thermal conductivity of sand; the heating elements often being concentrated in the center or on one side of the bottom of the pan; the heating process relying primarily on conduction with a lack of effective lateral heat exchange; and the free-floating structure of the sand layer limiting the rapid diffusion of heat within the plane. For soil testing or pretreatment steps requiring strict temperature control (such as moisture determination, volatile matter analysis, or heat balance treatment), the aforementioned radial temperature difference can lead to inconsistencies in sample processing, deviations in test data, and decreased repeatability.

[0004] To improve the temperature uniformity of sand baths, several technical solutions have been adopted: one is to improve lateral heat conduction by setting heat-conducting blocks or metal liners in the sand bath; the other is to promote heat transfer in the medium during the heating process by using mechanical stirring or forced ventilation, such as the electric sand bath device with a sand-turning structure disclosed in patent CN202223399409.4 and the adjustable electric sand bath device disclosed in patent CN202421297375.4, both of which mention using a stirring structure to achieve a uniform temperature effect. The above methods have improved the problem of local temperature difference to a certain extent, but they also have some shortcomings: adding heat-conducting blocks or metal liners in the sand bath, as well as stirring structures left in the sand bath, deviate from the purpose of testing in pure sand bath heating experiments and cannot better test the samples. Summary of the Invention

[0005] The technical problem to be solved by this invention is that uneven temperature is prone to occur in sand bath heating, which affects the accuracy of experimental measurements. A sand bath device for multi-zone heating of soil organic matter is provided, which can divide the heating space of the sand bath into several independent small spaces and can stir the sand particles in the small spaces to avoid the problem of low temperature at the edge of the sand particles and high temperature at the center.

[0006] This invention provides a sand bath device for multi-zone heating of soil organic matter, comprising: A heating pot, wherein a heating plate is provided on the top surface of the heating pot, and a plurality of detection areas of equal area and adjacent to each other are formed on the heating plate, and a base is fixedly connected to the center of each detection area; A plurality of enclosed boxes, each of which is detachably connected to a base, are arranged around the base within the same detection area to form a heating unit. There are gaps between the inner walls of adjacent heating units and adjacent heating plates to form a heating space. A receiving cavity is formed inside the enclosed box. A heat-insulating cover, which is detachably connected to the top of the heating plate; Both the receiving cavity and the heating space are filled with sand particles. The heating unit can rotate along the base. The base is used to place the digestion tube, and the heating unit is used to wrap the digestion tube.

[0007] In the above technical solution, the heating plate is divided into several detection zones, and sand particles are filled in the heating unit and heating space of the detection zone to achieve zoned and modular heating. This facilitates the separate management of temperature in different detection zones and reduces the direct impact of a single heating on the entire plate. The enclosed box surrounds the base to form a wrap-around heating unit and can rotate along the base. After heating, the sand particles can move relative to each other through rotation, thereby achieving uniform mixing of solid sand particles after heating, significantly reducing the radial temperature difference between the center and the edge, and improving the heating uniformity of the digestion tube.

[0008] Preferably, the top of the sealed box is provided with a cover, one side of the sealed box along the width direction is connected with a protrusion, and the other side of the sealed box along the width direction is provided with a slot for engaging with the protrusion.

[0009] In the above technical solution, the snap-fit ​​structure of the top cover of the sealed box and the protrusions and slots on the side provides convenient disassembly and assembly and reliable positioning and locking, ensuring that the sealed boxes will not be misaligned or loosened during rotation or flipping.

[0010] Preferably, the cross-section of the closed box is a fan-shaped structure, and the closed boxes in the same detection area surround the base to form a circular structure. A material-turning protrusion is fixedly connected to the outer circumference of the closed box. The material-turning protrusion is an arc-shaped structure, and the center of the material-turning protrusion is concentric with the center of the closed box.

[0011] In the above technical solution, the annular closed box composed of fan-shaped cross sections and the material turning ridge structure enable each heating unit to turn the sand particles in a regular circumferential path when rotating around the base, thereby achieving continuous and uniform radial mixing and reducing the formation of temperature uneven areas.

[0012] Preferably, multiple material-turning protrusions are arranged parallel to each other along the height direction of the closed box, and the length of the material-turning protrusions on the closed box decreases sequentially downwards.

[0013] In the above technical solution, the design of multiple convex ridges arranged side by side along the height direction with their lengths decreasing sequentially from top to bottom allows for layered and progressive mixing during rotation, thereby simultaneously promoting the radial and vertical mixing of sand particles.

[0014] Preferably, the end of the flipping protrusion away from the closed box is an arc surface, and the end face of the flipping protrusion along the length direction is an inclined surface, with the inclined surface facing the closed box.

[0015] In the above technical solution, the arc surface reduces the impact resistance with the sand, and the inclined surface guides the sand particles back into the closed box, which improves the material turning efficiency and reduces clogging and wear.

[0016] Preferably, the bottom surface of the heat insulation cover is provided with a partition, which is used to divide the bottom surface of the heat insulation cover into several heating zones. Each heating zone corresponds to a detection zone. The bottom surface of the heat insulation cover is provided with several modules. The height of each module is equal to the depth of the heating plate. Four modules are provided for each heating zone. The modules in each heating zone are respectively located at the four corners.

[0017] In the above technical solution, the bottom surface of the heat insulation cover is equipped with a partition, and the partition is divided into sections corresponding to the detection areas. Furthermore, modules with the same depth as the heating plate are set at the four corners of each heating area. The heating areas are aligned with each detection area to reduce thermal crosstalk between adjacent heating areas and enhance the heat insulation effect of each area.

[0018] Preferably, the module's surface along the height direction includes two mutually perpendicular planes and an arc-shaped concave surface, and the rotation path of the turning protrusion passes through the concave surface of the module.

[0019] In the above technical solution, the rotation path of the turning protrusion passes through the concave surface, which can guide the turning protrusion to pass smoothly and provide space for the turned sand to fall back or transition, reducing collisions and obstructions and extending the service life of the parts.

[0020] Preferably, the sidewalls of the partitions and the concave surfaces of the modules within the same heating zone are located on the same arc, and the heating zone is a circular area.

[0021] In the above technical solution, the sidewall of the partition plate and the concave surface of the module are located on the same arc, making the heating zone circular and consistent with the rotation trajectory of the turning protrusion, resulting in a symmetrical and uniform heating area, improving the uniformity and repeatability of rotational mixing.

[0022] Preferably, the inner circumferential surface of the enclosed box is provided with a thread, and the thread of several enclosed boxes in the same heating unit forms a continuous internal thread. A sleeve is fitted on the base wall, and the outer circumferential wall of the sleeve is connected with an external thread for threaded connection with the internal thread. The top thread termination line of the external thread is lower than half the height of the sleeve. A through hole is provided on the heat insulation cover, and a through groove is provided on the bottom surface of the enclosed box.

[0023] In the above technical solution, the inner circumference of the closed box is provided with continuous internal threads, and the base sleeve is provided with external threads and can be threaded together to form an adjustable and detachable connection method, which is convenient for assembly and positioning and can ensure the stability of rotational transmission; the top termination line of the external thread is lower than half the height of the sleeve, which can limit axial loosening and improve safety.

[0024] Preferably, the top surface of the base is provided with a groove, the bottom of the sleeve is connected to a limiting block for engaging with the groove, and the top surface of the heat insulation cover is provided with several grooves around the through hole, and a baffle is rotatably connected in the groove.

[0025] In the above technical solution, the baffle provides positioning and limiting functions to ensure that the closed box and the sleeve are accurately positioned during assembly and will not shift with rotation.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In this invention, by dividing the heating box into several areas and forming several heating zones corresponding to the insulation cover through partitions and modules, each digestion tube has an independent sand bath heating space, and the sealing of the insulation cover can also provide a certain heat preservation effect; after dividing the originally large sand bath heating plate into several areas, the heat transfer efficiency can be better improved and the temperature unevenness can be reduced. 2. In this invention, after the heating plate has been heated for a certain period of time, the closed box can be rotated out to stir and agitate the sand particles in the heating space, so as to fully mix the sand particles with low temperature at the edge and high temperature at the center, avoid uneven temperature, and improve the accuracy of data detection. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a cross-sectional view of the present invention; Figure 3 This is a schematic diagram of the heating box in this invention; Figure 4 This is a schematic diagram of the structure of the heat insulation cover in this invention. Figure 1 ; Figure 5 This is a schematic diagram of the structure of the heat insulation cover in this invention. Figure 2 ; Figure 6 This is a schematic diagram of the structure of the closed box in this invention.

[0028] The attached diagram shows the markings and corresponding component names: 1. Heating plate; 11. Base; 2. Enclosed box; 21. Flipping protrusion; 22. Through groove; 23. Cover; 24. Sleeve; 3. Insulation cover; 31. Partition; 32. Module; 33. Groove; 34. Baffle. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are for illustrative purposes only and are not intended to limit the invention. It should be noted that this invention is already in the actual research and development stage.

[0030] Example 1: like Figures 1 to 6 As shown, this embodiment provides a sand bath device for multi-zone heating of soil organic matter, comprising: A heating pot, with a heating plate 1 on the top surface of the heating pot, and several detection areas of equal area and adjacent to each other formed on the heating plate 1, with a base 11 fixedly connected to the center of each detection area; Several closed boxes 2 are detachably connected to the base 11. Several closed boxes 2 in the same detection area are arranged around the base 11 to form a heating unit. There are gaps between adjacent heating units, heating units and the inner sidewalls of adjacent heating plates 1 to form a heating space. A receiving cavity is formed inside the closed box 2. Insulation cover 3 is detachably connected to the top of heating plate 1; Both the containment cavity and the heating space are filled with sand. The heating unit can rotate along the base 11, which is used to place the digestion tube. The heating unit is used to wrap the digestion tube.

[0031] like Figure 6 As shown, the top of the closed box 2 is provided with a cover 23, one side of the closed box 2 along the width direction is connected with a protrusion, and the other side of the closed box 2 along the width direction is provided with a slot for engaging with the protrusion.

[0032] like Figure 1 and Figure 2 ,and Figure 6 As shown, the cross-section of the closed box 2 is a fan-shaped structure, and the closed boxes 2 in the same detection area surround the base 11 to form a ring structure.

[0033] Specifically, the heating pot is equipped with a temperature sensor and an electronic control device, which can control the heating plate 1 to achieve heating. The heating plate 1 is divided into several detection areas, and a base 11 is fixedly connected to the center of each detection area. The heating plate 1 can be connected to a power source to generate heat. Each detection area is of equal size, and preferably, the detection area is square.

[0034] During the experimental heating, the sealed box 2 is first installed on the base 11. In this embodiment, there are four interconnected sealed boxes 2 in one detection area. Adjacent sealed boxes 2 are connected to each other by protrusions and slots to form a ring-shaped heating unit. Then, the digestion tube is inserted into the center of the heating unit above the base 11. After the digestion tube is placed, sand is filled into the heating space and the receiving cavity. The top layer of sand is smoothed with a tool. Finally, the heat insulation cover 3 is placed in. The heat insulation cover 3 matches the opening area of ​​the heating plate 1, which can cover the sand on the heating plate 1 and prevent heat loss. At the same time, the heat insulation cover 3 can be pressed down to squeeze the sand as much as possible, reduce the gap between adjacent sand particles, and thus improve the heat conduction efficiency between sand particles.

[0035] It should be noted that the sand bath heating inevitably results in a situation where the temperature of the sand particles in the center is high and the temperature of the sand particles at the edges is low. In this invention, after completing the above arrangement and heating the heating plate 1 for a certain period of time, the above-mentioned uneven temperature will also occur. At this time, any one of the closed boxes 2 in the detection area can be rotated, and the other adjacent closed boxes 2 will also rotate accordingly, so that the closed box 2 that is biased towards the center can be rotated to the edge of the heating plate 1, while the closed box 2 at the edge can be rotated to the center. Preferably, the closed box 2 can be higher than the heat preservation cover 3 to facilitate rotation. During the operation, the digestion tube can be fixed with one hand, and the closed box 2 can be rotated with the other hand to achieve the interchange of high and low temperature zones.

[0036] Example 2: like Figure 2 and Figure 6 As shown, a flipping protrusion 21 is fixedly connected to the outer peripheral surface of the closed box 2. The flipping protrusion 21 has an arc-shaped structure, and the center of the flipping protrusion 21 is concentric with the center of the closed box 2.

[0037] like Figure 2 and Figure 6 As shown, multiple material-turning protrusions 21 are arranged parallel to each other along the height direction of the closed box 2, and the length of the material-turning protrusions 21 on the closed box 2 decreases sequentially downwards.

[0038] like Figure 2 and Figure 6As shown, the end of the flipping protrusion 21 away from the closed box 2 is an arc surface, and the end face of the flipping protrusion 21 along the length direction is a slope, with the slope facing the closed box 2.

[0039] like Figure 4 and Figure 5 As shown, the bottom surface of the heat insulation cover 3 is provided with a partition 31. The partition 31 is used to divide the bottom surface of the heat insulation cover 3 into several heating zones. The heating zones correspond one-to-one with the detection zones. The bottom surface of the heat insulation cover 3 is provided with several modules 32. The height of the modules 32 is equal to the depth of the heating plate 1. There are four modules 32 corresponding to each heating zone. The modules 32 in each heating zone are respectively set at the four corners.

[0040] like Figures 2 to 5 As shown, the surface of module 32 along the height direction includes two mutually perpendicular planes and an arc-shaped concave surface, and the rotation path of the flipping protrusion 21 passes through the concave surface of module 32.

[0041] like Figure 4 and Figure 5 As shown, the sidewalls of the partition 31 and the concave surface of the module 32 within the same heating zone are located on the same arc, and the heating zone is a circular area.

[0042] Specifically, during the rotation of the closed box 2 as in Example 1, the material-turning protrusion 21 on the outer periphery of the closed box 2 also moves accordingly. The material-turning protrusion 21 can move the sand particles in the heating space. Multiple closed boxes 2 in the same detection area simultaneously drive the material-turning protrusion 21 to rotate, which can achieve the effect of mixing and stirring. This allows the sand particles with high temperature and low temperature in the heating space to mix, achieve heat exchange, and minimize the situation where the center temperature is high and the edge temperature is low.

[0043] More preferably, a partition 31 is detachably connected to the bottom of the heat insulation cover 3. The partition 31 has a grid-like structure with crisscrossing, and the partition 31 can be removed from the heat insulation cover 3 and assembled onto the heating plate 1 before filling with sand, so as to independently separate the detection area. More preferably, the heat insulation cover 3 also has vent holes corresponding to each heating area.

[0044] In this embodiment, after installing the sealed box 2, the heat insulation cover 3 is installed directly. Then, sand particles are injected into the heating space through the vent holes, and sand particles are injected into the receiving cavity of the sealed box 2 by opening the cover 23. After filling, the heating plate 1 can be shaken to keep the sand particles flat. When the sealed box 2 is rotated later, the flipping protrusion 21 will pass through the partition 31 and the module 32. The concave surfaces of the partition 31 and the module 32 together form the heating zone. The heating zone is a circular area that can abut against the flipping protrusion 21, avoiding dead corners where the flipping protrusion 21 cannot be flipped at the right angle corner of the heating plate 1. The setting of the heating zone not only further reduces the space of the detection area, making the heat transfer faster, but also allows the flipping protrusion 21 to pass through any point, thereby making the sand particles with different temperatures in the heating space fully mixed.

[0045] Example 3: A threaded line is formed on the inner circumferential surface of the sealed box 2. The threaded lines of several sealed boxes 2 in the same heating unit form a continuous internal thread. A sleeve 24 is fitted on the wall of the base 11. An external thread for threaded connection with the internal thread is connected to the outer circumferential wall of the sleeve 24. The top thread termination line of the external thread is lower than half the height of the sleeve 24. A through hole is formed on the heat insulation cover 3. A through groove 22 is formed on the bottom surface of the sealed box 2.

[0046] The top surface of the base 11 is provided with a groove, and the bottom of the sleeve 24 is connected with a limiting block for engaging with the groove.

[0047] Specifically, when the closed box 2 is rotated to mix the sand particles in the heating space, the closed box 2 has a threaded line. The four closed boxes 2 of the same heating unit form a complete internal thread. The base 11 is also fitted with a sleeve 24. When the closed box 2 is rotated, the closed box 2 is rotated and rises vertically at the same time through the cooperation of the internal thread and the external thread on the sleeve 24. The material turning ridge 21 also rotates and rises with it. Multiple material turning ridges 21 can gradually stir and mix the sand particles from the bottom of the heating space upwards, which can make the sand particles more uniformly mixed.

[0048] When the closed box 2 rises to the end line of the external thread of the sleeve 24, it can no longer rotate. At this time, the closed box 2 can be pulled up. The limiting block that is engaged with the base 11 of the sleeve 24 disengages from the groove and rises vertically. During the initial rotation and subsequent vertical rise, the heated sand particles in the closed box 2 gradually leak into the heating space along the through groove 22. During this period, the material turning protrusion 21 will also mix with the leaked sand particles during rotation. During the subsequent vertical rise, the multiple material turning protrusions 21 set along the height direction can also push the leaked sand particles while rising, achieving a certain degree of mixing.

[0049] After the enclosed box 2 rises to a certain height, it stops rising, allowing a certain amount of space at the bottom to remain within the heating space. (This is in conjunction with the attached...) Figure 2It can be seen that after the sealed box 2 rises: firstly, the sealed box 2 and the sleeve 24 block the through hole to prevent heat loss from the heating box; secondly, it can limit the digestion tube to prevent the digestion tube from tilting or deviating during subsequent experiments, thus affecting the experimental results; thirdly, in traditional experiments, the experimental sample usually falls to the bottom of the digestion tube and is heated by the sand bath, rather than filling the digestion tube. After the sealed box 2 and the sleeve 24 rise, they leave the bottom of the digestion tube, thereby allowing the sand particles to wrap around the bottom of the digestion tube, achieving sand bath heating.

[0050] Example 4: like Figure 1 and Figure 2 As shown, the top surface of the heat insulation cover 3 is provided with several grooves 33 around the through hole, and a baffle 34 is rotatably connected in the grooves 33.

[0051] Specifically, after the sealed box 2 rises as in Example 3, the baffle 34 above the heat insulation cover 3 can be moved to the underside of the turning protrusion 21 to restrict the sealed box 2 from falling.

[0052] In this invention, a complete and large heating plate 1 is divided into several detection zones. Within each detection zone, the partition 31 and module 32 of the heat insulation cover 3 further limit the movement of the heating zone, forming a circular and smaller heating zone. It should be noted that the temperature of the heating plate 1 itself is uniform. It is only in traditional sand bath heating that the sand particles are too numerous, have gaps between them, and are in contact with the outside environment, which causes the temperature of the center of the sand particles to be too high and the temperature of the edges to be low. This is not the reason of the heating plate 1.

[0053] In this embodiment, after the heating plate 1 is heated, the temperature is evenly transferred to each heating zone. The heat in each heating zone is further transferred to the sand particles in that area, realizing sand bath heating. The heating efficiency of the heating plate 1 remains unchanged, but the number of sand particles in each heating zone is significantly reduced compared to the complete heating plate 1. It can be understood that the heating efficiency and area of ​​the original heating plate 1 remain unchanged, but it can simultaneously heat multiple small heating zones. The sand particles in each heating zone have a smaller space compared to the traditional loose sand, and are sealed by the insulation cover 3 and the enclosed box, preventing them from contacting the outside world. This allows for better heat conduction and avoids uneven temperature. Furthermore, the metal partition 31 and module 32, as well as the raised enclosed box 2, can provide a certain insulation effect for the sand particles in the heating zone, preventing heat loss and further improving the heating effect.

[0054] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sand bath device for multi-zone heating of soil organic matter, characterized in that, include: A heating pot, the top surface of which is provided with a heating plate (1), and a number of detection areas of equal area and adjacent to each other are formed on the heating plate (1), and a base (11) is fixedly connected to the center of each detection area. A plurality of closed boxes (2), each of the closed boxes (2) being detachably connected to the base (11), the plurality of closed boxes (2) in the same detection area being arranged around the base (11) and forming a heating unit, gaps being present between the inner walls of adjacent heating units, heating units and adjacent heating plates (1) forming a heating space, and a receiving cavity being formed inside the closed box (2); A heat preservation cover (3) is detachably connected to the top of the heating plate (1); Both the containment cavity and the heating space are filled with sand particles. The heating unit can rotate along the base (11). The base (11) is used to place the digestion tube, and the heating unit is used to wrap the digestion tube.

2. The sand bath device for multi-zone heating of soil organic matter according to claim 1, characterized in that, The top of the closed box (2) is provided with a cover (23), and a protrusion is connected to one side of the closed box (2) along the width direction. A slot for engaging with the protrusion is opened on the other side of the closed box (2) along the width direction.

3. The sand bath device for multi-zone heating of soil organic matter according to claim 1, characterized in that, The cross-section of the closed box (2) is a fan-shaped structure. The closed boxes (2) in the same detection area surround the base (11) to form a ring structure. A flipping protrusion (21) is fixedly connected to the outer circumference of the closed box (2). The flipping protrusion (21) is an arc-shaped structure. The center of the flipping protrusion (21) is concentric with the center of the closed box (2).

4. A sand bath device for multi-zone heating of soil organic matter according to claim 3, characterized in that, Multiple material-turning protrusions (21) are arranged parallel to the height direction of the closed box (2), and the length of the material-turning protrusions (21) on the closed box (2) decreases sequentially downwards.

5. A sand bath device for multi-zone heating of soil organic matter according to claim 3, characterized in that, The end of the flipping protrusion (21) away from the closed box (2) is an arc surface, and the end face of the flipping protrusion (21) along the length direction is a slope, with the slope facing the closed box (2).

6. A sand bath device for multi-zone heating of soil organic matter according to claim 3, characterized in that, The bottom surface of the heat insulation cover (3) is provided with a partition (31). The partition (31) is used to separate the bottom surface of the heat insulation cover (3) to form several heating zones. The heating zones correspond one-to-one with the detection zones. The bottom surface of the heat insulation cover (3) is provided with several modules (32). The height of the module (32) is equal to the depth of the heating plate (1). There are four modules (32) corresponding to each heating zone. The modules (32) in each heating zone are respectively set at the four corners.

7. A sand bath device for multi-zone heating of soil organic matter according to claim 6, characterized in that, The module (32) has two mutually perpendicular planes and an arc-shaped concave surface along its height direction. The rotation path of the turning protrusion (21) passes through the concave surface of the module (32).

8. A sand bath device for multi-zone heating of soil organic matter according to claim 7, characterized in that, The sidewalls of the partition (31) and the concave surface of the module (32) within the same heating zone are located on the same arc, and the heating zone is a circular area.

9. A sand bath device for multi-zone heating of soil organic matter according to claim 6, characterized in that, The inner circumferential surface of the closed box (2) is provided with a threaded line. The threaded lines of several closed boxes (2) in the same heating unit form a continuous internal threaded line. A sleeve (24) is fitted on the wall of the base (11). An external thread for threaded connection with the internal threaded line is connected to the outer circumferential wall of the sleeve (24). The top thread termination line of the external thread is lower than half the height of the sleeve (24). A through hole is provided on the heat preservation cover (3). A through groove (22) is provided on the bottom surface of the closed box (2).

10. A sand bath device for multi-zone heating of soil organic matter according to claim 9, characterized in that, The top surface of the base (11) is provided with a groove, and the bottom of the sleeve (24) is connected to a limiting block for engaging with the groove. The top surface of the heat insulation cover (3) is provided with several grooves (33) around the through hole, and a baffle (34) is rotatably connected in the groove (33).

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