A device and method for eliminating salt deposition in supercritical hydrothermal combustion

Abstract

The application relates to a device and a method for eliminating salt deposition in supercritical hydrothermal combustion, which comprises a premixed feeding area, a supercritical hydrothermal combustion area, a subcritical mixing area and a subcritical material backflow branch which are sequentially connected. The premixed feeding area comprises a feeding pipe, a nozzle, a premixing section and a mixing section, and the feeding pipe is connected with a material pipe. The supercritical hydrothermal combustion area comprises an upper end cover, a cylinder and a contraction section, a tangential inlet is arranged on the upper side wall of the cylinder, one end of the tangential inlet is connected with the subcritical material backflow branch, and the subcritical backflow water is introduced into the tangential inlet and forms a spiral downward subcritical liquid film layer on the inner wall of the supercritical hydrothermal combustion area and the subcritical mixing area. The subcritical mixing area comprises a cylinder and a head, a discharging pipe is arranged below the head, and the other end of the subcritical material backflow branch is connected with the discharging pipe. The side wall of the cylinder of the supercritical hydrothermal combustion area, the contraction section and the cylinder of the subcritical mixing area are all provided with a clamping layer for introducing cooling water.

Description

Technical Field

[0001] This invention relates to the field of chemical saline organic waste liquid treatment, specifically to an apparatus and method for eliminating salt deposition during supercritical hydrothermal combustion. Background Technology

[0002] With the rapid development of industries such as petrochemicals, coal chemicals, fine chemicals, pharmaceuticals, printing and dyeing, and pesticides, high-concentration saline organic wastewater has become a common pollution problem restricting the green and sustainable development of these industries. This type of wastewater has a complex composition, high salt content, and high organic matter concentration. Conventional treatment technologies generally suffer from low treatment efficiency, easy generation of secondary pollution, and difficulty in consistently meeting standards, failing to meet the treatment requirements of harmlessness, volume reduction, and resource recovery.

[0003] Supercritical hydrothermal combustion technology has become a cutting-edge technology for treating high-salt organic wastewater due to its advantages such as thorough oxidation, fast reaction speed, high COD removal rate, and clean products without secondary pollution. However, in the supercritical water environment, the solubility of inorganic salts is extremely low, and the salt in the wastewater is prone to rapid precipitation and deposition on the inner wall of the reactor, pipelines, and the surface of key components, causing equipment blockage, wall overheating, and frequent system shutdowns. This seriously affects the continuous and stable operation of the device and has become the core bottleneck restricting the industrial-scale application of supercritical hydrothermal combustion technology. Summary of the Invention

[0004] The present invention aims to provide a device that can eliminate salt deposition during supercritical hydrothermal combustion, thereby overcoming the shortcomings of the prior art. The technical problem to be solved by the present invention is achieved through the following technical solution.

[0005] An apparatus for eliminating salt deposition in supercritical hydrothermal combustion includes a premixed feed zone, a supercritical hydrothermal combustion zone, a subcritical mixing zone, and a subcritical material return branch connected in sequence. The premixed feeding zone includes a feed pipe, a nozzle, a premixing section, and a mixing section. The feed pipe is connected to a material pipe, which is also connected to an auxiliary fuel pipe. The nozzle extends into the premixing section, and the mixing section extends into the supercritical hydrothermal combustion zone. An oxidant inlet is provided on the side wall of the premixing section. The supercritical hydrothermal combustion zone includes an upper end cover, a cylinder, and a contraction section. A tangential inlet is provided on the upper side wall of the cylinder. The tangential inlet is connected to one end of the subcritical material return branch and is used to introduce subcritical return water and form a spiral downward subcritical liquid film layer on the inner wall of the supercritical hydrothermal combustion zone and the subcritical mixing zone. The subcritical mixing zone includes a cylinder and a head. A discharge pipe is provided below the head and is connected to the other end of the subcritical material return branch. The cylinder walls of the supercritical hydrothermal combustion zone, the contraction section, and the subcritical mixing zone are all provided with jackets for introducing cooling water, and are respectively provided with cooling water inlets and cooling water outlets.

[0006] Preferably, the length of the nozzle is Lp, and Lp = 2.5d. 32 , where d 32 Let be the diameter of the nozzle outlet, and let Lc1 be the distance between the nozzle and the mixing section, where Lc1 = 1.35d. 27 , where d 27 Let be the diameter of the mixing section, and let Lc2 be the length of the mixing section, where Lc2 = 1.1 (d). 27 + d6), where d6 is the diameter of the tangential inlet, and the ratio of the nozzle outlet diameter d32 to the mixing section diameter d27 is 0.58.

[0007] Preferably, the mixing section has an internal spiral groove structure with a spiral groove depth e = 0.4 d. 27 The pitch p = 1.3 d 27 .

[0008] Preferably, the supercritical hydrothermal combustion zone is divided into a subcritical liquid film layer and a combustion flame zone. The thickness of the subcritical liquid film layer is h1, and h1 = -28.3 + 0.15D1 + 0.0002Re, where D1 is the inner diameter of the supercritical hydrothermal combustion zone, Re is the subcritical return water Reynolds number at the tangential inlet, and Re ranges from 1000 to 60000.

[0009] Preferably, the flame height of the combustion flame zone is h2, the flame diameter is D2, and... ,in, F air-fuel ratio, , m f The mass flow rate of the material. f a The mass flow rate of the oxidant. The Reynolds number at the outlet of the mixing section. The range is 6000-50000.

[0010] Preferably, the interlayer width of the supercritical hydrothermal combustion zone is 7-10 mm, the interlayer width of the subcritical mixing zone is 30-50 mm, and the interlayer of the subcritical mixing zone is further provided with a spiral band fixedly connected to the inner cylinder. The spiral band and the outer cylinder are interference-fitted to form a spiral cooling water channel. The groove depth of the spiral band is 30-50 mm, and the pitch is 0.4 times the inner diameter of the subcritical mixing zone inner cylinder.

[0011] Preferably, the subcritical material reflux branch includes a circulation pump, which is connected to a circulation pump inlet pipe and a circulation pump outlet pipe. The circulation pump inlet pipe is connected to a discharge pipe, and the circulation pump outlet pipe is connected to the tangential inlet of the supercritical hydrothermal combustion zone. The circulation pump inlet pipe is also connected to a water supply pipe, and valves are provided on both the water supply pipe and the circulation pump inlet pipe.

[0012] Preferably, valves are provided on both the material pipe and the auxiliary fuel pipe.

[0013] Preferably, there are four tangential inlets, which are symmetrically arranged at equal intervals around the upper side wall of the supercritical hydrothermal combustion zone cylinder. The inlet channel is tangential to the cylinder wall, and the fluid enters the cylinder along the tangential direction.

[0014] This application also provides a method for eliminating salt deposition in supercritical hydrothermal combustion, the method being applied to the aforementioned apparatus for eliminating salt deposition in supercritical hydrothermal combustion, comprising the following steps: Fill the device with supercritical pressure water until it is full; Open the valves of the auxiliary fuel pipe and the oxidant feed valve so that the preheated auxiliary fuel and oxidant are mixed in the premixed feed zone and then enter the supercritical hydrothermal combustion zone for combustion. At the same time, open the valve of the water supply pipe so that the water is pressurized by the circulating pump and then tangentially introduced into the supercritical hydrothermal combustion zone through the tangential inlet to form a swirling subcritical liquid film layer. Start the cooling water circulation in the subcritical mixing zone to maintain the subcritical state in the zone, and at the same time open the discharge pipe; Once the system is stable, close the valve on the water supply pipe and open the valve on the subcritical material return branch. After the system stabilizes again, the valves of the auxiliary fuel pipe and the material pipe are cyclically opened and closed in turn, with each adjustment being 5% of the opening. The auxiliary fuel is gradually replaced by the material in the material pipe until the valve of the auxiliary fuel pipe is completely closed and the valve of the material pipe is completely open, thus entering a stable production state.

[0015] Compared with the prior art, the device of the present invention for eliminating salt deposition in supercritical hydrothermal combustion has the following beneficial effects: By forming a stable helical subcritical liquid film layer on the inner wall of the supercritical hydrothermal combustion zone, solid salts precipitated during combustion can be dissolved in real time, fundamentally preventing salt deposition and blockage on the wall surface. This also effectively prevents reactor wall overheating and improves system operational safety. The thickness of the subcritical liquid film layer provides both sufficient salt-dissolving capacity and wall cooling effect, while avoiding encroachment on the central combustion space, ensuring stable, continuous, and salt-blockage-free operation of the supercritical hydrothermal combustion. The device adopts a premixed feed and subcritical reflux circulation structure, which avoids salt precipitation and pipe blockage in the feed section, ensuring continuous and stable production. Its overall structure is simple and has low processing costs, significantly improving the reliability and economy of supercritical hydrothermal combustion treatment of saline organic waste liquid, making it suitable for industrial-scale application. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the premixed feeding zone of the present invention; Figure 3 This is a schematic diagram of the cross-section of the supercritical hydrothermal combustion zone of the present invention; Figure 4 This is a schematic diagram of the combustion flame size of the present invention; Figure 5 This is a schematic diagram of the inner cylinder of the subcritical mixing zone of the present invention; Figure 6 This is a schematic diagram of the multi-tangential inlet cross-section of the present invention; The reference numerals in the attached figures are as follows: A1. Premixed feeding zone; A2. Supercritical hydrothermal combustion zone; A3. Subcritical mixing zone; 1. Material pipe; 2. Feed pipe; 3. Nozzle; 4. Premixing section; 5. Mixing section; 6. Tangential inlet; 7. Oxidant inlet; 8. Inner cylinder of supercritical hydrothermal combustion zone; 9. Cooling water outlet of supercritical hydrothermal combustion zone jacket; 10. Cooling water inlet of supercritical hydrothermal combustion zone jacket; 11. Outer cylinder of supercritical hydrothermal combustion zone; 12. Contraction section; 13. Outer cylinder of contraction section; 14. Cooling water inlet of contraction section jacket; 15. Cooling water outlet of contraction section jacket; 16. Cooling water outlet of subcritical mixing zone jacket; 17. 18. Subcritical mixing zone inner cylinder; 19. Spiral belt; 20. Subcritical mixing zone outer cylinder; 21. Subcritical mixing zone jacket cooling water inlet; 22. End cap; 23. Discharge pipe; 24. Circulating pump inlet pipe; 25. Circulating pump; 26. Flame; 27. Mixing section outlet; 28. Upper end cover; 29. ​​Discharge port; 30. Subcritical liquid film layer; 31. Combustion flame zone; 32. Nozzle outlet; 33. First jacket; 34. Second jacket; 35. Auxiliary fuel pipe; 36. Auxiliary fuel pipe valve; 37. Material pipe valve; 38. Circulating pump outlet pipe; 39. Circulating pump inlet pipe valve; 40. Makeup water pipe valve. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] Example 1 like Figure 1 As shown, the device for eliminating salt deposition in supercritical hydrothermal combustion of the present invention includes a premixed feed zone A1, a supercritical hydrothermal combustion zone A2, a subcritical mixing zone A3, and a subcritical material reflux branch connected in sequence.

[0019] The premixed feeding zone A1 includes a feed pipe 2, a nozzle 3, a premixing section 4, and a mixing section 5. The feed pipe 2 is connected to a material pipe 1, and a material pipe valve 37 is provided on the material pipe 1. The material pipe 1 is also connected to an auxiliary fuel pipe 35, and an auxiliary fuel pipe valve 36 is provided on the auxiliary fuel pipe 35. The nozzle 3 extends into the premixing section 4, and the mixing section 5 extends into the supercritical hydrothermal combustion zone A2. An oxidant inlet 7 is provided on the side wall of the premixing section 4.

[0020] The supercritical hydrothermal combustion zone A2 includes an upper end cover 28, a cylinder and a contraction section 12. The upper side wall of the cylinder is provided with a tangential inlet 6, which is connected to one end of the subcritical material return branch to introduce subcritical return water and form a spiral downward subcritical liquid film layer on the inner wall of the supercritical hydrothermal combustion zone and the subcritical mixing zone.

[0021] The subcritical mixing zone A3 includes a cylinder and a head 21. A discharge pipe 22 is provided below the head 21 and is connected to the other end of the subcritical material return branch.

[0022] The supercritical hydrothermal combustion zone A2, the contraction section 12, and the subcritical mixing zone A3 all have jackets for introducing cooling water on their side walls, and are respectively provided with cooling water inlets and cooling water outlets.

[0023] For the supercritical hydrothermal combustion zone A2, it includes an inner cylinder 8 and an outer cylinder 11, with a sandwich layer between them. The sandwich layer is 7-10 mm wide and cooling water flows through it. The outer cylinder 11 is provided with a supercritical hydrothermal combustion zone sandwich cooling water inlet 10 and a supercritical hydrothermal combustion zone sandwich cooling water outlet 9.

[0024] The contraction section 12 connected to the supercritical hydrothermal combustion zone A2 is also a double-layer structure, including an outer cylinder 13 and an inner cylinder, with a cooling water interlayer between them. The interlayer width is 7-10 mm, and a cooling water inlet 14 and a cooling water outlet 15 are respectively provided on the outer cylinder 13.

[0025] Similarly, in the subcritical mixing zone A3, there is an inner cylinder 17 and an outer cylinder 19, with a cooling water jacket between them. The jacket width is 30-50 mm. A cooling water inlet 20 and a cooling water outlet 16 are respectively provided on the outer cylinder 19. However, the jacket in subcritical mixing zone A3 also includes a spiral band fixedly connected to the inner cylinder 17. The spiral band is interference-fitted with the outer cylinder 19 to form a spiral cooling water channel. The spiral band groove depth is 30-50 mm, and the pitch is 0.4 times the inner diameter of the inner cylinder 17.

[0026] The subcritical material reflux branch includes a circulation pump 25, which is connected to a circulation pump inlet pipe 23 and a circulation pump outlet pipe 38. The circulation pump inlet pipe 23 is connected to a discharge pipe 22, and the circulation pump outlet pipe 38 is connected to the tangential inlet 6 of the supercritical hydrothermal combustion zone. The circulation pump inlet pipe 23 is also connected to a water supply pipe, which is equipped with a water supply pipe valve 40 and a circulation pump inlet pipe valve 39.

[0027] like Figure 2 As shown, the length of the nozzle 3 is Lp, and Lp = 2.5d. 32 , where d 32 Let be the diameter of nozzle outlet 32, and let Lc1 be the distance between nozzle 3 and mixing section 5, where Lc1 = 1.35d. 27 , where d 27 Let Lc2 be the diameter of mixing segment 5, and Lc2 = 1.1 (d). 27 + d6), where d6 is the diameter of the tangential inlet 6, and the ratio of the nozzle outlet diameter d32 to the mixing section diameter d27 is 0.58. The mixing section 5 has an internal spiral groove structure with a spiral groove depth e = 0.4d. 27 The pitch p = 1.3 d 27 .

[0028] like Figure 3-5 As shown, the supercritical hydrothermal combustion zone A2 is divided into a subcritical liquid film layer 30 and a combustion flame zone 31. The thickness of the subcritical liquid film layer 30 is h1, and h1 = -28.3 + 0.15D1 + 0.0002Re, where D1 is the inner diameter of the supercritical hydrothermal combustion zone A2, and Re is the Reynolds number of the subcritical return water at the tangential inlet 6, with a range of 1000-60000.

[0029] The flame 26 in the combustion flame zone 31 has a height of h2 and a diameter of D2, and ,in, F air-fuel ratio, , m f The mass flow rate of the material. f a The mass flow rate of the oxidant. The Reynolds number at the outlet of the mixed section is 27. The range is 6000-50000.

[0030] Example 2 like Figure 6As shown, based on Example 1, four tangential inlets are arranged symmetrically at 90° along the circumference of the shell, located at 0° (43), 90° (44), 180° (41), and 270° (42) respectively. The inlet channels are tangential to the shell wall, and the fluid enters the shell along the tangential direction. The cross-sectional area of ​​each inlet is equal to ensure uniform fluid distribution and form a symmetrical subcritical liquid film layer 30.

[0031] When the ratio of the height h of the supercritical hydrothermal combustion zone A2 cylinder to the cylinder diameter is greater than or equal to 1.3, four tangential inlets are used in this embodiment; otherwise, a single tangential inlet is used.

[0032] Alternatively, when the circulating flow rate is greater than 1.6 times the maximum single tangential circulating flow rate, the four tangential inlet structure of this embodiment is adopted; otherwise, the single tangential inlet form is adopted.

[0033] The working process of the device for eliminating salt deposition during supercritical hydrothermal combustion of the present invention is as follows: The saline organic wastewater is preheated to a subcritical state to prevent premature salt precipitation and pipe blockage in the premixing section. The preheated wastewater (material) and oxidant enter the premixing feed zone A1 separately, where they are thoroughly mixed in the nozzle section, premixing section, and inner spiral channel mixing section to form a homogeneous combustible mixture. This mixture then enters the supercritical hydrothermal combustion zone A2 from the mixing section outlet. Upon entering A2, the mixture undergoes hydrothermal combustion in the supercritical water environment, completely oxidizing and decomposing the organic matter into harmless substances such as carbon dioxide and water. Inorganic salts in the wastewater have extremely low solubility in supercritical water and precipitate as solid salt particles, distributing around the combustion flame zone. Subcritical return water (circulating material) enters the combustion zone through a tangential inlet on the side wall, spiraling downwards along the inner wall of the cylinder to form a stable and uniform subcritical liquid film. This liquid film continuously dissolves the solid salt particles precipitated during combustion, forming a saline solution that prevents salt deposition and blockage on the wall surface, while simultaneously isolating the high-temperature flame and protecting the cylinder wall from overheating. Combustion products (gas, liquid, and solid salts) and a salt-containing liquid film flow downwards into the subcritical mixing zone A3. This subcritical mixing zone A3 maintains a subcritical environment, dissolving more salt particles that fall due to gravity. Simultaneously, the inner spiral band enhances fluid mixing, ensuring thorough salt dissolution and uniform concentration. Cooling water is circulated through the jacket to control the system temperature and maintain stable operation. The material exiting the mixing zone is divided into two streams: one stream exits the unit and enters the subsequent treatment section, while the other stream mixes with makeup water, is pressurized by a circulating pump, and then reintroduced into the combustion zone through the tangential inlet, circulating to form a liquid film and continuously dissolve salt. It should be noted that during the initial startup of the unit, water is first added to raise the pressure to supercritical pressure, auxiliary fuel is added for ignition, and clean water is simultaneously introduced to form an initial liquid film. After the system stabilizes, wastewater is gradually replaced with auxiliary fuel, eventually switching to a continuous operation state with stable combustion of wastewater and a subcritical liquid film to prevent salt deposition.

[0034] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments described in this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0037] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0038] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.

[0039] In the detailed description above, reference has been made to the accompanying drawings, which form part of this document. In the drawings, similar symbols typically identify similar parts unless the context otherwise indicates otherwise. The illustrated embodiments described in the detailed specification, drawings, and claims are not intended to be limiting. Other embodiments may be used and other changes may be made without departing from the spirit or scope of the subject matter presented herein.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 device for eliminating salt deposition during supercritical hydrothermal combustion, characterized in that, It includes a premixed feeding zone, a supercritical hydrothermal combustion zone, a subcritical mixing zone, and a subcritical material return branch that are connected in sequence. The premixed feeding zone includes a feed pipe, a nozzle, a premixing section, and a mixing section. The feed pipe is connected to a material pipe, which is also connected to an auxiliary fuel pipe. The nozzle extends into the premixing section, and the mixing section extends into the supercritical hydrothermal combustion zone. An oxidant inlet is provided on the side wall of the premixing section. The supercritical hydrothermal combustion zone includes an upper end cover, a cylinder, and a contraction section. A tangential inlet is provided on the upper side wall of the cylinder. The tangential inlet is connected to one end of the subcritical material return branch and is used to introduce subcritical return water and form a spiral downward subcritical liquid film layer on the inner wall of the supercritical hydrothermal combustion zone and the subcritical mixing zone. The subcritical mixing zone includes a cylinder and a head. A discharge pipe is provided below the head and is connected to the other end of the subcritical material return branch. The cylinder walls of the supercritical hydrothermal combustion zone, the contraction section, and the subcritical mixing zone are all provided with jackets for introducing cooling water, and are respectively provided with cooling water inlets and cooling water outlets.

2. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 1, characterized in that, The length of the nozzle is Lp, and Lp = 2.5d. 32 , where d 32 Let be the diameter of the nozzle outlet, and let Lc1 be the distance between the nozzle and the mixing section, where Lc1 = 1.35d. 27 , where d 27 Let be the diameter of the mixing section, and let Lc2 be the length of the mixing section, where Lc2 = 1.1 (d). 27 + d6), where d6 is the diameter of the tangential inlet, and the ratio of the nozzle outlet diameter d32 to the mixing section diameter d27 is 0.

58.

3. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 2, characterized in that, The mixing section has an internal spiral groove structure with a groove depth e = 0.4d. 27 The pitch p = 1.3d 27 .

4. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 1, characterized in that, The supercritical hydrothermal combustion zone is divided into a subcritical liquid film layer and a combustion flame zone. The thickness of the subcritical liquid film layer is h1, and h1 = -28.3 + 0.15D1 + 0.0002Re, where D1 is the inner diameter of the supercritical hydrothermal combustion zone, Re is the subcritical return water Reynolds number at the tangential inlet, and Re ranges from 1000 to 60000.

5. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 4, characterized in that, The flame height of the combustion flame zone is h2, and the flame diameter is D2. ,in, F air-fuel ratio, , m f The mass flow rate of the material. f a The mass flow rate of the oxidant. The Reynolds number at the outlet of the mixing section. The range is 6000-50000.

6. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 1, characterized in that, The interlayer width of the supercritical hydrothermal combustion zone is 7-10 mm, and the interlayer width of the subcritical mixing zone is 30-50 mm. The interlayer of the subcritical mixing zone is also provided with a spiral band fixedly connected to the inner cylinder. The spiral band and the outer cylinder are interference-fitted to form a spiral cooling water channel. The groove depth of the spiral band is 30-50 mm, and the pitch is 0.4 times the inner diameter of the subcritical mixing zone inner cylinder.

7. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 1, characterized in that, The subcritical material reflux branch includes a circulation pump, which is connected to a circulation pump inlet pipe and a circulation pump outlet pipe. The circulation pump inlet pipe is connected to a discharge pipe, and the circulation pump outlet pipe is connected to the tangential inlet of the supercritical hydrothermal combustion zone. The circulation pump inlet pipe is also connected to a water supply pipe, and valves are installed on both the water supply pipe and the circulation pump inlet pipe.

8. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 1, characterized in that, Valves are installed on both the material pipe and the auxiliary fuel pipe.

9. The apparatus for eliminating salt deposition during supercritical hydrothermal combustion according to claim 1, characterized in that, The number of tangential inlets is four, which are symmetrically arranged at equal intervals around the circumference on the upper side wall of the supercritical hydrothermal combustion zone cylinder. The inlet channel is tangential to the cylinder wall, and the fluid enters the cylinder along the tangential direction.

10. A method for eliminating salt deposition during supercritical hydrothermal combustion, characterized in that: This method, applied to the apparatus for eliminating supercritical hydrothermal combustion salt deposition as described in any one of claims 1-9, comprises the following steps: Fill the device with supercritical pressure water until it is full; Open the valves of the auxiliary fuel pipe and the oxidant feed valve so that the preheated auxiliary fuel and oxidant are mixed in the premixed feed zone and then enter the supercritical hydrothermal combustion zone for combustion. At the same time, open the valve of the water supply pipe so that the water is pressurized by the circulating pump and then tangentially introduced into the supercritical hydrothermal combustion zone through the tangential inlet to form a swirling subcritical liquid film layer. Start the cooling water circulation in the subcritical mixing zone to maintain the subcritical state in the zone, and at the same time open the discharge pipe; Once the system is stable, close the valve on the water supply pipe and open the valve on the subcritical material return branch. After the system stabilizes again, the valves of the auxiliary fuel pipe and the material pipe are cyclically opened and closed in turn, with each adjustment being 5% of the opening. The auxiliary fuel is gradually replaced by the material in the material pipe until the valve of the auxiliary fuel pipe is completely closed and the valve of the material pipe is completely open, thus entering a stable production state.

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