Segmented heating high-voltage high-power fused salt electric heater and optimization method thereof

Abstract

The invention discloses a segmented heating high-voltage high-power fused salt electric heater and an optimization method thereof.The segmented heating high-voltage high-power fused salt electric heater comprises a barrel, the barrel comprises an upper barrel body and a lower barrel body, one end of the upper barrel body communicates with one end of the lower barrel body through a connecting barrel, and tube plates are installed at the two ends of the upper barrel body and the two ends of the lower barrel body correspondingly; a fused salt outlet is formed in the end, opposite to the end connected with the connecting cylinder, of the upper cylinder, a fused salt inlet is formed in the end, opposite to the end connected with the connecting cylinder, of the bottom of the lower cylinder, electric heating elements distributed in the axial direction are arranged in the upper cylinder and the lower cylinder respectively, the electric heating elements are connected with the tube plate, and baffle plates distributed in a staggered mode are installed in the cylinders; molten salt flowing holes are formed in the baffle plates, and the electric heating elements are divided into a plurality of groups. According to the electric heater, the multi-stage electric heating elements are arranged in the electric heater, molten salt area heating is achieved, on the premise that the flow of molten salt is guaranteed, the phenomenon that the molten salt is heated and decomposed due to overtemperature of the molten salt can be obviously relieved, and therefore the safety of a molten salt system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt electric heaters, and in particular to a segmented heating high-voltage and high-power molten salt electric heater and an optimization method thereof. Background Art

[0002] In recent years, the development of renewable energy such as wind power and solar power generation has been continuously increased in order to achieve the goal of reducing the use of fossil energy. However, renewable energy generally has the characteristics of intermittent and strong volatility, which makes its power output extremely unstable, and in serious cases will impact the safety of the power grid. In order to improve the stability of solar power generation and wind power generation and stabilize power output, energy storage devices have begun to be used on a large scale in renewable energy generation. Molten salt energy storage uses the temperature difference of molten salt during the process of heat absorption and heat release to achieve heat storage. It has very little hysteresis and can quickly convert electrical energy into thermal energy. It is especially suitable for large-scale wind power and solar power generation systems.

[0003] Molten salt electric heaters are devices that convert electrical energy into thermal energy. Currently, common types include resistive, electrode and inductive types. Among them, resistive molten salt electric heaters are widely used because of their simple structure, high reliability and high heating efficiency. With the increasing scale of energy storage, the disadvantages of traditional low-voltage resistive heaters, such as low heating power and high cost of power distribution equipment, have become increasingly obvious, and high-voltage heaters have emerged. Compared with low-voltage electric heaters, high-voltage electric heaters can be directly connected to the high-voltage power grid, eliminating the cost of power distribution equipment. At the same time, the same power requires lower cable diameter, which greatly reduces the manufacturing cost. However, high-voltage electric heaters have high heating power and high surface power of electric heating elements, which puts high demands on the flow rate of molten salt: if the flow rate of molten salt is low, local overheating is likely to occur inside the electric heater, resulting in overheating and decomposition of molten salt, which seriously affects the safety of the equipment; and if the flow rate of molten salt is increased, the pressure drop of the equipment increases sharply, and the flow distance of molten salt will inevitably increase, resulting in a large size of the electric heater, which is not convenient for engineering application. For this reason, a high-voltage and high-power molten salt electric heater with segmented heating is needed to improve the above problems. Summary of the invention

[0004] In order to solve the above technical problems, the present invention designs a segmented heating high-voltage and high-power molten salt electric heater and an optimization method thereof, so as to solve the problem that the high-voltage resistive heater in the prior art is prone to local overheating.

[0005] The present invention adopts the following technical solution: A segmented heating high-voltage high-power molten salt electric heater comprises a cylinder, the cylinder comprises an upper cylinder and a lower cylinder, one end of the upper cylinder and the lower cylinder are connected through a connecting cylinder, tube sheets are respectively installed at both ends of the upper cylinder and the lower cylinder, a molten salt outlet is arranged at the opposite end connected to the connecting cylinder on the upper cylinder, a molten salt inlet is arranged at the bottom of the lower cylinder at the opposite end connected to the connecting cylinder, electric heating elements arranged along the axial direction are respectively arranged in the upper cylinder and the lower cylinder, the electric heating elements are connected to the tube sheet, staggered baffles are installed inside the cylinder, molten salt flow holes are arranged on the baffles, the electric heating elements are divided into multiple groups and placed in the upper cylinder and the lower cylinder, each group of electric heating elements is connected and controlled by an independent control box, and the heating power of electric heating elements of different groups gradually decreases along the flow direction of the molten salt. At the molten salt inlet position, the molten salt temperature is low, the risk of molten salt overheating is small, and a larger electric heating power can be set to quickly increase the molten salt temperature; at the molten salt outlet position, the molten salt temperature is high, and setting a smaller electric heating power can reduce the possibility of molten salt overheating. The molten salt flow holes can weaken the local flow dead zone of the baffle and avoid the problem of excessively high molten salt temperature.

[0006] Preferably, the barrel is composed of two cylinders with the same or different diameters, and the two cylinders are arranged parallel to each other.

[0007] Preferably, the two cylinders are arranged in a stacked manner.

[0008] Preferably, the cylinder forms a certain angle with the horizontal direction, and a sewage outlet is provided at the bottom of the cylinder, so as to quickly discharge the internal molten salt in emergency conditions.

[0009] Preferably, the angle between the cylinder and the horizontal direction is 0.5-1°.

[0010] Preferably, a connecting plate is provided between the upper cylinder and the lower cylinder.

[0011] Preferably, a base is provided at the bottom of the cylinder.

[0012] An optimization method is applicable to the above-mentioned segmented heating high-voltage and high-power electric heater, comprising the following steps: determining the structural parameters of the electric heater, then determining the segmented heating power distribution coefficient, determining the curve of the segmented heating power distribution coefficient of the electric heater and the maximum temperature, and selecting the heating power distribution coefficient with the lowest temperature in the curve as the heating distribution ratio of the segmented high-voltage and high-power molten salt electric heater.

[0013] Preferably, the method for setting the segmented heating power distribution coefficient is: first determine the percentage of the electric heating power of the upper cylinder and the lower cylinder, and on this basis determine the heating ratio of the two-stage electric heating elements in the same cylinder.

[0014] Preferably, the electric heating power of the lower cylinder is greater than that of the upper cylinder, and the electric heating power on the upstream side of the molten salt flow is greater than that on the downstream side.

[0015] The beneficial effects of the present invention are as follows: (1) the present invention adopts a segmented multi-stage heating method and sets different heating powers for different heating sections, thereby improving the heating efficiency of the molten salt while ensuring that the molten salt does not overheat, reducing the size of the molten salt electric heating equipment, and making the project site layout more convenient; (2) the baffle is provided with molten salt flow holes, which weakens the flow dead zone caused by the baffle and improves the temperature distribution of the electric heater; (3) by optimizing and selecting the optimal heating distribution coefficient, the problem of local overheating of the molten salt in the electric heater is suppressed to the greatest extent, thereby improving the safety and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the electric heater of the present invention; Figure 2 It is a schematic diagram of the internal structure of the electric heater of the present invention; Figure 3 It is a structural schematic diagram of the baffle in the present invention; In the figure: 1. cylinder, 11. upper cylinder, 12. lower cylinder, 13. connecting cylinder, 2. connecting plate, 3. base, 4. tube sheet, 5. electric heating element, 51. first-stage electric heating element, 52. second-stage electric heating element, 53. third-stage electric heating element, 54. fourth-stage electric heating element, 6. baffle, 61. molten salt flow hole, 71. first control box, 72. second control box, 73. third control box, 74. fourth control box, 8. sewage outlet, 111. molten salt outlet, 121. molten salt inlet. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: Figure 1 and Figure 2As shown, a segmented heating high-voltage high-power molten salt electric heater comprises: a cylinder 1, the cylinder comprises an upper cylinder 11 and a lower cylinder 12, one end of the upper cylinder 11 and the lower cylinder 12 are connected through a connecting cylinder 13, and a connecting plate 2 is arranged between the two cylinders; a base 3 for supporting the electric heater is installed at the bottom of the lower cylinder; a molten salt outlet 111 is arranged at the opposite end of the upper cylinder 11 connected to the connecting cylinder, and a molten salt inlet 121 is arranged at the opposite end of the lower cylinder 12 connected to the connecting cylinder; tube sheets 4 are installed at both ends of the upper cylinder 11 and the lower cylinder 12; electric heating elements 5 arranged along the axial direction of the cylinder are installed inside the upper cylinder 11 and the lower cylinder 12, and the electric heating elements 5 are connected to the tube sheets 4; staggered baffles 6 are installed inside the upper cylinder 11 and the lower cylinder 12, and molten salt flow holes 61 are arranged on the baffles 6. The molten salt flow holes 61 can weaken the local flow dead zone of the baffles and avoid the problem of excessive molten salt temperature.

[0018] like Figures 1 to 3 As shown, a plurality of groups of electric heating elements are arranged in sequence in the cylinder along the flow direction of the molten salt, including a first-stage electric heating element 51, a second-stage electric heating element 52, a third-stage electric heating element 53, and a fourth-stage electric heating element 54, respectively. Each group of electric heating elements is connected to its own control box, namely, a first control box 71, a second control box 72, a third control box 73, and a fourth control box 74, and is independently controlled by the control box; the electric heating power gradually decreases from the first-stage electric heating element 51 to the fourth-stage electric heating element 54. The principle is that the molten salt temperature is relatively low near the molten salt inlet 121. Setting a larger electric heating power can rapidly increase the molten salt temperature and increase the total heating capacity of the equipment. The molten salt temperature is relatively high near the molten salt outlet 111, and the risk of molten salt overheating increases. Using a smaller electric heating power can reduce the possibility of molten salt overheating.

[0019] like Figure 1 As shown, a sewage outlet 8 is provided below the cylinder, and the cylinder forms a certain angle with the horizontal direction, preferably 0.5-1°, so as to quickly discharge the internal molten salt under emergency conditions.

[0020] An optimization method is suitable for the segmented heating high-voltage and high-power molten salt electric heater. First, the electric heater structural parameters are determined, and then the segmented heating power distribution coefficient is determined; the segmented heating power distribution coefficient consists of two parts: first, the electric heating power percentage of the upper and lower cylinders is determined, for example, the heating ratio of the lower cylinder 12 is 80%, that is, the total heating power of the lower cylinder 12 is 80% of the designed power, and the heating power of the upper cylinder 11 accounts for 20%. On this basis, the heating ratio of the two-stage electric heating elements in the same cylinder is determined, that is, the heating power ratio of the first-stage electric heating element 51 and the second-stage electric heating element 52, and the third-stage electric heating element 53 and the fourth-stage electric heating element 54. Determine the curve of the segmented heating power distribution coefficient of the electric heater and the highest temperature, and select the heating power distribution coefficient with the lowest temperature in the curve as the heating distribution ratio of the segmented high-voltage and high-power molten salt electric heater.

[0021] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A segmented heating high voltage high power molten salt electric heater, characterized in that: It includes a cylinder body, which includes an upper cylinder body and a lower cylinder body. One end of the upper cylinder body and the lower cylinder body are connected through a connecting cylinder. Tube sheets are installed at both ends of the upper cylinder body and the lower cylinder body respectively. A molten salt outlet is arranged on the upper cylinder body at the opposite end connected to the connecting cylinder. A molten salt inlet is arranged on the bottom of the lower cylinder body at the opposite end connected to the connecting cylinder. Electric heating elements arranged along the axial direction are respectively arranged in the upper cylinder body and the lower cylinder body, and the electric heating elements are connected to the tube sheets. Staggered baffles are installed inside the cylinder body, and molten salt flow holes are arranged on the baffles. The electric heating elements are divided into multiple groups and placed in the upper cylinder body and the lower cylinder body. Each group of electric heating elements is connected and controlled by an independent control box, and the heating power of electric heating elements of different groups gradually decreases along the flow direction of the molten salt.

2. According to claim 1, a segmented heating high voltage high power molten salt electric heater is characterized in that: The cylinder body is composed of two cylinders with the same or different diameters, and the two cylinders are arranged parallel to each other.

3. A segmented heating high voltage high power molten salt electric heater according to claim 2, characterized in that: The two cylinders are arranged in a stacked manner.

4. The segmented heating high voltage and high power molten salt electric heater according to claim 2 is characterized in that: The cylinder forms a certain angle with the horizontal direction, and a sewage outlet is arranged at the bottom of the cylinder.

5. The segmented heating high voltage and high power molten salt electric heater according to claim 4 is characterized in that: The angle between the cylinder and the horizontal direction is 0.5-1°.

6. The segmented heating high voltage and high power molten salt electric heater according to claim 1 is characterized in that: A connecting plate is arranged between the upper cylinder and the lower cylinder.

7. The segmented heating high voltage and high power molten salt electric heater according to claim 1 is characterized in that: A base is arranged at the bottom of the cylinder.

8. An optimization method, applicable to a segmented heating high voltage and high power electric heater as claimed in any one of claims 1 to 7, characterized in that: The optimization method comprises the following steps: determining the structural parameters of the electric heater, then determining the segmented heating power distribution coefficient, determining the curve of the segmented heating power distribution coefficient of the electric heater and the maximum temperature, and selecting the heating power distribution coefficient with the lowest temperature in the curve as the heating distribution ratio of the segmented high-voltage and high-power molten salt electric heater.

9. An optimization method according to claim 8, characterized in that: The method for setting the segmented heating power distribution coefficient is as follows: firstly determine the percentage of the electric heating power of the upper cylinder and the lower cylinder, and on this basis determine the heating ratio of the two-stage electric heating elements in the same cylinder.

10. An optimization method according to claim 9, characterized in that: The electric heating power of the lower cylinder is greater than that of the upper cylinder, and the electric heating power of the upstream side of the molten salt flow is greater than that of the downstream side.

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