A molten salt steam generator that transfers heat through heat pipes

Abstract

The present invention provides a molten salt steam generator and an extended molten salt steam generator that transfer heat through heat pipes. The molten salt steam generator has a simple and compact structure, with uniform internal molten salt flow rate and molten salt temperature distribution, high overall heat transfer efficiency, easy to process and manufacture, and the molten salt is not easily frozen and blocked. In particular, it can adapt to heat exchange between two media with a large temperature difference, namely high-temperature molten salt and normal-temperature water, greatly reducing the operation energy consumption of the system itself and improving the overall economy of the system. Further, a molten salt steam generator with a larger tonnage can be extended from multiple molten salt steam generator monomers, sharing a steam drum and enabling standardized production of each steam generator monomer. The steam tonnage can be easily expanded. During steam use, the steam output can be flexibly adjusted by adjusting the number of molten salt steam generator bodies participating in the work, achieving dynamic balance of the steam output.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat exchange, and particularly relates to a structural design of a molten salt steam generator that transfers heat through heat pipes, but is not limited to molten salt as the heat exchange medium only. Background Art

[0002] The molten salt energy storage clean steam and heat supply technology is a new type of green heat storage technology that uses off-peak electricity during periods of abandoned wind and light or at night to heat molten salt, stores the heat using molten salt heat storage technology, and supplies steam and heat during other periods. The heat exchange process is to heat water into hot water or steam by high-temperature molten salt and then supply it to customers for use, and the heat exchange process is completed through a heat exchanger. The heat exchangers in traditional molten salt steam generators usually adopt shell-and-tube heat exchangers, and the traditional shell-and-tube heat exchangers still have the following disadvantages:

[0003] The heat transfer temperature difference of a fixed tube sheet heat exchanger usually cannot exceed 100°C. The U-tube heat exchanger has fewer tube bundles and the tube bundles are not easy to clean and maintain. The floating head heat exchanger has a complex structure and high cost. The spiral wound tube heat exchanger has uneven internal temperature and flow distribution and the tube bundles are not easy to replace and clean. Not only is the heat exchange efficiency low, but also after the equipment is shut down, the molten salt cools and solidifies, making it difficult to preheat again.

[0004] High-temperature molten salt and water are two heat exchange media with extremely large temperature differences, and the maximum temperature difference exceeds more than 500°C. For such a large temperature difference, traditional heat exchangers cannot withstand it, so the effective heat in the molten salt cannot be efficiently extracted at one time. In order to make the best use of the heat energy of high-temperature molten salt, the traditional method is to add an additional molten salt mixer. First, pump the molten salt in the low-temperature molten salt storage tank and the high-temperature molten salt storage tank to the molten salt mixer in proportion for mixing and cooling, cool the molten salt to within the temperature difference range that the traditional heat exchanger can withstand, and then exchange heat between the mixed molten salt and water to generate the required saturated steam. Such a setting not only complicates the process, increases the investment in equipment and pipelines, but more importantly, increases the self-energy consumption of the system after it becomes complex, and the cost per ton of steam also increases significantly, resulting in an unsatisfactory economic benefit for the project. Summary of the Invention

[0005] In order to solve the problems in the background art, the present invention provides a molten salt steam generator that transfers heat through heat pipes. The molten salt steam generator has a simple and compact structure, uniform internal molten salt flow and molten salt temperature distribution, high overall heat exchange efficiency, is easy to process and manufacture, and can especially adapt to heat exchange between two media with extremely large temperature differences, namely high-temperature molten salt and normal-temperature water, greatly reducing the self-operation energy consumption of the system and improving the overall economy of the system.

[0006] To achieve the above object, the present invention is implemented by the following technical solutions: A molten salt steam generator that transfers heat through heat pipes, including a molten salt steam generator body, characterized in that the molten salt steam generator body includes a steam generation chamber in the upper part, a molten salt heater in the lower part, and a number of heat pipes. The heat pipes are cylindrical and are provided with a welded short sleeve at the middle position; the steam generation chamber and the molten salt heater are separated by a heat pipe fixing tube sheet. The heat absorption section of the heat pipe is located in the molten salt heater, and the heat dissipation section of the heat pipe is located in the steam generation chamber. The molten salt heater includes an upper header, a lower header, and a number of molten salt shunt pipes arranged between the two. The upper header is composed of the heat pipe fixing tube sheet, a short shell, and a first molten salt shunt pipe tube sheet, and a molten salt outlet is provided on the short shell. The lower header is composed of a second molten salt shunt pipe tube sheet and a first head, and a molten salt inlet is provided on the first head. The two ends of the molten salt shunt pipe are respectively connected and sealed and fixed to the first molten salt shunt pipe tube sheet and the second molten salt shunt pipe tube sheet by cold extrusion or welding. The tube holes on the panels of the heat pipe fixing tube sheet, the first molten salt shunt pipe tube sheet, and the second molten salt shunt pipe tube sheet have the same number, arrangement method, and the same tube hole pitch. And each heat pipe can pass through the tube holes of the heat pipe fixing tube sheet, the first molten salt shunt pipe tube sheet, the molten salt shunt pipe, and the second molten salt shunt pipe tube sheet in sequence. And the welded short sleeve on the middle section of the heat pipe is welded and sealed to the tube hole on the heat pipe fixing tube sheet. An annular molten salt shunt channel is formed between the inner wall of the molten salt shunt pipe and the outer wall of the heat pipe located therein. After the molten salt enters the lower header from the lower molten salt inlet, it is shunted into each molten salt shunt channel, converges in the upper header, and then flows out concentratedly from the molten salt outlet; A steam outlet is provided at the top of the steam generation chamber, and a water inlet is provided on the side wall of its lower part.

[0007] Further, a spiral guide convex body is provided on the outer surface of the heat absorption section of the heat pipe, and the guide convex body changes the original linear annular molten salt shunt channel into a spiral annular molten salt flow channel.

[0008] Further, a number of heat conduction fins are provided on the outer surface of the heat dissipation section of the heat pipe. Usually, the addition of heat conduction fins is used to increase the heat dissipation area of the heat dissipation section.

[0009] Further, the materials of the heat pipe, the heat pipe fixing tube sheet, and the molten salt heater are high-temperature resistant stainless steel or high-temperature resistant nickel-based alloy or high-temperature resistant titanium alloy.

[0010] Further, an arc-shaped molten salt shunt orifice plate is provided at the inner port of the molten salt inlet. Usually, such a setting makes the molten salt flowing into the lower header can be more evenly shunted into each molten salt shunt pipe.

[0011] Further, a vertical mounting bracket is also provided on the molten salt steam generator body.

[0012] Furthermore, a gas-liquid separator is provided at the upper part of the steam generation chamber, and a demister is provided at the inner port of the steam outlet. An upper liquid level interface, a lower liquid level interface, a blowdown port, a pressure gauge interface, a safety valve interface and a thermometer interface are also provided on the steam generation chamber.

[0013] Furthermore, it includes a plurality of the molten salt steam generator bodies and a shared steam drum. The shared steam drum is provided with a plurality of steam inlets, a steam main outlet, a blowdown port, a pressure gauge interface, a safety valve interface and a thermometer interface. Each steam inlet is connected to one of the molten salt steam generator bodies.

[0014] Furthermore, a mist entrainment molecular sieve is provided at the inner end of the steam main outlet. The mist entrainment molecular sieve is composed of a plurality of isosceles right-angled triangle molecular sieve sheets distributed in a circular shape. Each molecular sieve sheet is provided with sieve holes, and the included angle between the molecular sieve sheet and the flange surface at the outer end of the steam main outlet is 10° - 60°; 5 - 10 layers of square metal meshes are also arranged inside the steam main outlet.

[0015] Furthermore, the shared steam drum includes a cylindrical long shell and second heads welded to both ends of the long shell. A plurality of the steam inlets are evenly and symmetrically arranged at equal intervals on both sides of the lower part of the long shell.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. Creatively, the heat absorption section of each heat pipe is independently inserted into each matching molten salt shunt pipe, abandoning the traditional shell-and-tube structure. Only one heat pipe is inserted into one molten salt shunt pipe. After the high-temperature molten salt enters the lower header, it is evenly shunted into each molten salt shunt channel, ensuring that the molten salt flowing through the surface of the heat absorption section of each heat pipe has a small flow rate and a high flow velocity, enabling each heat pipe to obtain sufficient, efficient and balanced heat supply, and effectively eliminating the large thermal resistance caused by the low thermal conductivity of the molten salt.

[0018] 2. Creatively, spiral guiding convex bodies are provided on the outer surface of the heat absorption section of the heat pipe, making each molten salt shunt channel into a spiral annular flow channel, thereby increasing the flow path of the molten salt flowing through the surface of the heat pipe, and at the same time changing the laminar flow state of the molten salt into a turbulent flow, further enhancing the heat absorption efficiency.

[0019] 3. Inside the molten salt steam generator body, the two ends of the heat pipe can freely expand and contract, which can completely eliminate the influence of thermal stress caused by thermal expansion and contraction due to large temperature differences. Thus, the effective heat stored in the molten salt can be extracted at one time, enabling water to generate saturated steam or superheated steam, which is both simple and efficient.

[0020] 4. The present invention uses heat pipes for heat transfer and heat exchange, featuring fast heat transfer speed and high heat exchange efficiency. Due to the unidirectional heat transfer characteristic of the heat pipes, as long as the temperature of the heat dissipation section of the heat pipes in the steam generation chamber is controlled above the melting point of the molten salt, the risk of molten salt freezing and blocking can be eliminated.

[0021] 5. Further, larger-tonnage molten salt steam generators can be extended from multiple molten salt steam generator bodies. They share a steam drum and can standardize and normalize the production of each steam generator body. The steam tonnage can be easily expanded. During steam use, the steam output can be flexibly adjusted by adjusting the number of molten salt steam generator bodies participating in operation, achieving dynamic balance of steam output. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. The drawings are only provided for reference and explanation, and are not used to limit the present invention.

[0023] Figure 1 is a schematic external structure diagram of a molten salt steam generator body installed on a bracket provided by the present invention;

[0024] Figure 2 is a schematic internal structure diagram of a molten salt steam generator body provided by the present invention;

[0025] Figure 3 is provided by the present invention Figure 2 is a partially enlarged structure diagram of the A part marked in the figure;

[0026] Figure 4 is provided by the present invention Figure 2 is a partially enlarged structure diagram of the B part marked in the figure;

[0027] Figure 5 is a schematic structure diagram of a molten salt heater provided by the present invention;

[0028] Figure 6 is a schematic structure diagram of the outer shell of a steam generation chamber provided by the present invention;

[0029] Figure 7 is a schematic structure diagram of a heat pipe provided by the present invention;

[0030] Figure 8 is a schematic structure diagram of a molten salt steam generator with a gas-liquid separator provided by the present invention;

[0031] Figure 9 It is a schematic structural diagram of a large-tonnage molten salt steam generator formed by combining eight molten salt steam generator bodies provided by the present invention and a shared steam drum;

[0032] Figure 10 provided by the present invention Figure 9 corresponding left view or right view;

[0033] Figure 11 It is a schematic structural diagram of a mist entrainment molecular sieve provided by the present invention.

[0034] The reference numerals are as follows:

[0035] Molten salt steam generator body 1, steam generation chamber 2, molten salt heater 3, heat pipe 4, welded short sleeve 5, heat pipe fixed tube sheet 6, upper tube box 7, lower tube box 8, molten salt shunt pipe 9, short shell 10, first molten salt shunt pipe tube sheet 11, second molten salt shunt pipe tube sheet 12, first head 13, molten salt outlet 14, molten salt inlet 14a, molten salt shunt channel 15, steam outlet 16, water inlet 17, guide convex 18, heat conduction fin 19, molten salt shunt orifice plate 20, gas-liquid separator 21, demister 22, upper liquid level interface 23, lower liquid level interface 24, blowdown port 25, pressure gauge interface 26, safety valve interface 27, thermometer interface 28, steam inlet 29, steam main outlet 30, mist entrainment molecular sieve 31, molecular sieve sheet 32, sieve hole 33, metal mesh 34, shared steam drum 35, long shell 36, second head 37, vertical mounting bracket 38. Specific embodiments

[0036] The following are specific embodiments of the present invention and in combination with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

[0037] Embodiment 1:

[0038] As Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7As shown in the figure, a molten salt steam generator body 1 includes a steam generation chamber 2 at the upper part, a molten salt heater 3 at the lower part, and a number of heat pipes 4. The heat pipes 4 are cylindrical and have a welded short sleeve 5 arranged at the middle section. The steam generation chamber 2 and the molten salt heater 3 are separated by a heat pipe fixing tube sheet 6. The heat absorption section of the heat pipe 4 is located in the molten salt heater 3, and the heat dissipation section of the heat pipe 4 is located in the steam generation chamber 2. The molten salt heater 3 includes an upper header 7, a lower header 8, and a number of molten salt diversion pipes 9 arranged between the two. The upper header 7 is composed of the heat pipe fixing tube sheet 6, a short shell 10, and a first molten salt diversion pipe tube sheet 11. A molten salt outlet 14 is arranged on the short shell 10. The lower header 8 is composed of a second molten salt diversion pipe tube sheet 12 and a first head 13. A molten salt inlet 14a is arranged on the first head 13. The two ends of the molten salt diversion pipe 9 are respectively and hermetically fixed to the first molten salt diversion pipe tube sheet 11 and the second molten salt diversion pipe tube sheet 12 by cold extrusion connection or welding. The tube holes on the panels of the heat pipe fixing tube sheet 6, the first molten salt diversion pipe tube sheet 11, and the second molten salt diversion pipe tube sheet 12 have the same number, arrangement method, and the same tube hole pitch. Each heat pipe 4 can pass through the tube holes of the heat pipe fixing tube sheet 6, the first molten salt diversion pipe tube sheet 11, the molten salt diversion pipe 9, and the second molten salt diversion pipe tube sheet 12 in sequence. The welded short sleeve 5 on the middle section of the heat pipe is hermetically fixed to the tube hole on the heat pipe fixing tube sheet 6. An annular molten salt diversion channel 15 is formed between the inner wall of the molten salt diversion pipe 9 and the outer wall of the heat pipe 4 located therein. After the molten salt enters the lower header from the lower molten salt inlet 14a, it is diverted into each molten salt diversion channel 15, flows to the upper header 7 to converge, and then flows out concentratedly from the molten salt outlet 14.

[0039] A steam outlet 16 is arranged at the top of the steam generation chamber 2, and a water inlet 17 is arranged on the lower side wall thereof.

[0040] Further, a spiral guide convex body 18 is arranged on the outer surface of the heat absorption section of the heat pipe 4. The guide convex body 18 changes the original linear annular molten salt diversion channel 15 into a spiral annular molten salt flow channel. Generally, the guide convex body 18 can be formed by winding stainless steel wires on the outer surface of the heat absorption section of the heat pipe 4, or by integrally forming a thickened heat pipe through machining.

[0041] Further, a number of heat conducting fins 19 are arranged on the outer surface of the heat dissipation section of the heat pipe 4. Generally, the heat conducting fins 19 are added to increase the heat dissipation area of the heat dissipation section.

[0042] Further, the materials of the heat pipe 4, the heat pipe fixing tube sheet 6, and the molten salt heater 3 are high-temperature resistant stainless steel, high-temperature resistant nickel-based alloy, or high-temperature resistant titanium alloy.

[0043] Further, an arc-shaped molten salt flow dividing orifice plate 20 is provided at the inner port of the molten salt inlet 14a. Generally, with such a setting, the molten salt flowing into the lower header 7 can be more evenly divided into each molten salt flow dividing pipe 9.

[0044] Further, a heat preservation layer and a vertical mounting bracket 38 are also provided on the molten salt steam generator body 1.

[0045] Embodiment 2:

[0046] As Figure 8 shown, a gas-liquid separator 21 is further provided in the upper part of the steam generation chamber 2, a demister 22 is provided at the inner port of the steam outlet 16, and an upper liquid level interface 23, a lower liquid level interface 24, a blowdown port 25, a pressure gauge interface 26, a safety valve interface 27 and a thermometer interface 28 are also provided on the steam generation chamber 2.

[0047] This embodiment is a further improvement of Embodiment 1 and can be used as an independent small molten salt steam generator. Other structures are as described in Embodiment 1 and will not be elaborated here one by one.

[0048] Embodiment 3:

[0049] As Figure 9 、 Figure 10 and Figure 11 shown, a molten salt steam generator includes eight molten salt steam generator bodies 1 as described in Embodiment 1 and a shared steam drum 35.

[0050] Eight steam inlets 29, one steam main outlet 30, one blowdown port 25, one pressure gauge interface 26, one safety valve interface 27 and one thermometer interface 28 are provided on the shared steam drum 35, and each steam inlet 29 is connected to a molten salt steam generator body 1.

[0051] Further, a mist entrainment molecular sieve 31 is provided at the inner end of the steam main outlet 30. The mist entrainment molecular sieve 31 is used to remove the trace droplets carried in the gas phase. The mist entrainment molecular sieve 31 is composed of molecular sieve sheets 32 arranged in a 360-degree circumference around the flange at the outer end of the steam main outlet, with a total of thirty-two molecular sieve sheets. Each molecular sieve sheet 32 is provided with tiny sieve holes 33. The diameter φ of the sieve holes 32 is 2.5 mm, and the number of sieve holes is 150. Among them, the molecular sieve sheet 32 is an isosceles right triangle, and the angle between the molecular sieve sheet 32 and the flange surface is 30°. In addition, a metal mesh with a square grid side length of 1 mm is arranged inside the steam main outlet, with ten layers. The molecular sieve sheet has a certain strength and can prevent deformation due to impact force during mist entrainment. The setting of multiple layers of filter screens ensures the pressure drop.

[0052] Further, the shared steam drum 35 includes a long cylindrical shell 36 and second heads 37 welded to both ends of the long shell. Eight steam inlets 29 are evenly and symmetrically arranged at equal intervals on both sides of the lower part of the long shell 36.

[0053] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains may make various modifications or supplements to the described specific embodiments or use similar methods of substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0054] Although terms such as molten salt steam generator body, steam generation chamber, molten salt heater, heat pipe, welded short sleeve, heat pipe fixing tube sheet, upper header, lower header, molten salt diversion pipe, short shell, first molten salt diversion pipe plate, second molten salt diversion pipe plate, first head, molten salt inlet, molten salt diversion channel, steam outlet, water inlet, flow guiding convex body, heat conducting fin, molten salt diversion orifice plate, gas-liquid separator, demister, upper liquid level interface, lower liquid level interface, blowdown port, pressure gauge interface, safety valve interface, thermometer interface, steam inlet, steam main outlet, entrainment molecular sieve, molecular sieve sheet, sieve hole, wire mesh, shared steam drum, long shell, second head, vertical installation bracket are used more frequently herein, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A molten salt steam generator that transfers heat through a heat pipe, comprising a molten salt steam generator body, characterized in that, The described molten salt steam generator body includes a steam generation chamber at the upper part, a molten salt heater at the lower part, and a number of heat pipes. The heat pipes are cylindrical and are provided with a welded short sleeve at the middle position. The steam generation chamber and the molten salt heater are separated by a heat pipe fixing tube sheet. The heat absorption section of the heat pipe is located inside the molten salt heater, and the heat dissipation section of the heat pipe is located inside the steam generation chamber. The molten salt heater includes an upper header, a lower header, and a number of molten salt distribution pipes arranged between the two. The upper header is composed of the heat pipe fixing tube sheet, a short shell, and a first molten salt distribution pipe tube sheet. A molten salt outlet is provided on the short shell. The lower header is composed of a second molten salt distribution pipe tube sheet and a first head. A molten salt inlet is provided on the first head. The two ends of the molten salt distribution pipe are hermetically fixed to the first molten salt distribution pipe tube sheet and the second molten salt distribution pipe tube sheet respectively by cold extrusion connection or welding. The tube holes on the panel surfaces of the heat pipe fixing tube sheet, the first molten salt distribution pipe tube sheet, and the second molten salt distribution pipe tube sheet have the same number, arrangement, and tube hole pitch. Each heat pipe can pass through the tube holes of the heat pipe fixing tube sheet, the first molten salt distribution pipe tube sheet, the molten salt distribution pipe, and the second molten salt distribution pipe tube sheet in sequence. The welded short sleeve on the middle section of the heat pipe is hermetically fixed to the tube hole on the heat pipe fixing tube sheet. An annular molten salt distribution channel is formed between the inner wall of the molten salt distribution pipe and the outer wall of the heat pipe located inside it. After the molten salt enters the lower header from the lower molten salt inlet, it is distributed to each molten salt distribution channel and flows to the upper header. After converging inside the upper header, it then flows out concentratedly from the molten salt outlet. A steam outlet is provided at the top of the steam generation chamber, and a water inlet is provided on the side wall of its lower part. A spiral guide convex body is provided on the outer surface of the heat absorption section of the heat pipe. The guide convex body changes the original straight annular molten salt distribution channel into a spiral annular molten salt flow channel. A number of heat conducting fins are provided on the outer surface of the heat dissipation section of the heat pipe.

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