Methanol vaporization level control method and methanol vaporizer

Abstract

The present application relates to the technical field of hydrogen production from methanol, and particularly relates to a methanol evaporation liquid level control method, comprising the following steps: S10, heating of a methanol evaporator; S20, feeding of methanol stock solution and evaporation; S30, start of hydrogen production, acquisition of a reference temperature, and detection of an overheating temperature; and S40, adjustment of the feeding amount of the methanol stock solution according to the temperature change of the methanol evaporator during hydrogen production. Meanwhile, the present application also provides a methanol evaporator. The present application discards the direct measurement of the liquid level by a traditional liquid level sensor, and realizes the indirect measurement of the liquid level by a temperature sensor, thereby improving the accuracy of liquid level detection. The temperature sensor is low in price, which is conducive to the compression of equipment cost. The present application not only effectively prevents dry burning due to lack of liquid and overflow due to full liquid, but also effectively assists in the adjustment of hydrogen production flow, thereby maintaining the stability of hydrogen production.

Description

Technical Field

[0001] This invention relates to the field of methanol-to-hydrogen technology, and in particular to a method for controlling the level of methanol evaporation liquid, and a methanol evaporator employing the method for controlling the level of methanol evaporation liquid. Background Technology

[0002] Methanol-to-hydrogen (MTH) is a hydrogen production process that involves reacting methanol with water vapor under controlled temperature and pressure conditions, along with a catalyst, to induce a cracking reaction in methanol and a carbon monoxide conversion reaction, producing hydrogen and carbon dioxide. The hydrogen and carbon dioxide are then separated to obtain the desired hydrogen gas. During the methanol-to-hydrogen process, methanol needs to be vaporized, typically using a methanol evaporator, which heats the methanol to convert it from a liquid to a gaseous state.

[0003] To monitor the methanol level in the methanol evaporator and prevent dry burning due to insufficient liquid or overflow due to excessive liquid, the traditional approach is to install a level sensor inside the methanol evaporator. However, this method has the following drawbacks:

[0004] 1. Liquid level detection is relatively difficult. Due to the two-phase mixture characteristics of the fluid inside the evaporator (coexistence of liquid and gas phases), conventional liquid level sensors cannot accurately detect the liquid level. Temperature changes will affect the accuracy of the measurement.

[0005] 2. Liquid level detection is costly. Although there are various liquid level sensors available, such as capacitive, magnetic float, pressure, and ultrasonic sensors, the cost of instruments is relatively high in small devices with limited size and cost, especially in high-temperature (less than 200°C) and high-pressure (less than 1MPa) environments. Summary of the Invention

[0006] Based on this, the present invention provides a methanol evaporation liquid level control method, which abandons the traditional direct liquid level measurement by liquid level sensor and uses temperature sensor to achieve indirect liquid level measurement, thereby improving the accuracy of liquid level detection. Temperature sensor is inexpensive, which is beneficial to the cost of compression equipment. It not only effectively prevents dry burning due to insufficient liquid and overflow due to full liquid, but also effectively assists in adjusting the hydrogen production flow rate and maintaining the stability of hydrogen production.

[0007] A method for controlling the liquid level of methanol evaporation includes the following steps:

[0008] S10: When the hydrogen production reactor is heated to the reaction temperature, the methanol evaporator is heated to the preset operating temperature with a preset heating power;

[0009] S20: Liquid is fed into the methanol evaporator. After the raw methanol liquid enters the methanol evaporator, it evaporates, and the pressure of the methanol vapor increases.

[0010] S30: The methanol vapor after evaporation enters the hydrogen production reactor and starts to produce hydrogen, obtains the reference temperature required for liquid level control, and detects the superheated temperature of the methanol vapor through the temperature sensor at the top of the inner cavity of the methanol evaporator;

[0011] S40: During the production of hydrogen, the temperature change of the methanol evaporator is monitored through the temperature sensor, and the liquid inflow of the methanol stock solution is adjusted; if the current superheated temperature decreases compared with the reference temperature, it is judged that the liquid inflow is too large, and the liquid inflow of the methanol stock solution needs to be reduced; if the current superheated temperature rises compared with the reference temperature, it is judged that the liquid inflow is too small, and the liquid inflow of the methanol stock solution needs to be increased.

[0012] The above-mentioned methanol evaporation liquid level control method, the inner cavity of the methanol evaporator is divided into an evaporation zone for heating the methanol stock solution and a superheating zone for further heating the methanol vapor, and the temperature sensor detects the temperature of the methanol vapor in the superheating zone. When the liquid level rises, the area of the evaporation zone increases, and correspondingly, the area of the superheating zone decreases. Under a certain heating power, the wet vapor increases and the dry vapor decreases, and the detected vapor temperature will decrease. Conversely, when the liquid level decreases, the wet vapor decreases and the dry vapor increases, and the detected vapor temperature will increase. Therefore, the liquid level can be indirectly detected by the temperature sensor, and the liquid inflow of the methanol stock solution can be adjusted to achieve the purpose of liquid level control. Through the above method, the traditional liquid level direct measurement of the liquid level sensor is abandoned, and the liquid level is indirectly measured by using the temperature sensor, which improves the accuracy of liquid level detection. The temperature sensor is inexpensive, which helps to reduce equipment costs. Not only can it effectively prevent dry burning and full liquid overflow, but it can also effectively assist in adjusting the hydrogen production flow and maintaining the stability of the hydrogen production amount.

[0013] In one embodiment, in step S40, if the current superheated temperature rises compared with the reference temperature and reaches a preset dry burning value, it is judged that the methanol stock solution in the methanol evaporator is short of liquid, at which time the methanol evaporator needs to be stopped heating.

[0014] In one embodiment, in step S40, after the methanol evaporator is stopped heating due to the evaporation of the methanol stock solution, if the current superheated temperature returns to the reference temperature within a preset recovery time, the methanol evaporator is resumed heating; otherwise, an alarm is issued.

[0015] In one embodiment, in step S40, if the current superheated temperature decreases compared with the reference temperature and reaches a preset overflow value, it is judged that the methanol stock solution in the methanol evaporator is too much, at which time the liquid inflow of the methanol stock solution needs to be stopped.

[0016] In one of the embodiments, in step S40, after the methanol evaporator is stopped from heating due to excessive methanol raw solution, if the current superheat temperature returns to the reference temperature within the preset recovery time, the methanol evaporator is recovered into liquid; otherwise, an alarm is sent.

[0017] In one of the embodiments, the measuring point of the temperature sensor is arranged at 8-12 cm above the gas-liquid demarcation point in the inner cavity of the methanol evaporator.

[0018] In one of the embodiments, in step S40, the liquid feeding amount of the methanol raw solution is adjusted by PID control according to the difference between the current superheat temperature and the reference temperature.

[0019] In one of the embodiments, in step S30, the reference temperature is a preset value of 140-150℃.

[0020] Meanwhile, the application also provides a methanol evaporator.

[0021] A methanol evaporator controlled by the methanol evaporator liquid level control method of any of the above embodiments.

[0022] The methanol evaporator directly measures the liquid level by using the temperature sensor to indirectly measure the liquid level, improves the accuracy of liquid level detection, and the temperature sensor is low in price, which is conducive to reducing the equipment cost. Not only can it effectively prevent dry burning and liquid overflow, but also can effectively assist in adjusting the hydrogen production flow and maintaining the stability of the hydrogen production amount.

[0023] In one of the embodiments, the methanol evaporator comprises an outer tube, an inner tube arranged in the outer tube, a heater connected to the outer tube, and a temperature sensor installed on the outer tube; the outer side of the outer tube is provided with a raw solution inlet; the top of the outer tube is provided with a vapor outlet; the inner tube is coaxially arranged with the outer tube, and the outer diameter of the inner tube is smaller than the inner diameter of the outer tube; the inner tube extends from the bottom of the outer tube to the top of the outer tube, and the height of the inner tube is smaller than the height of the outer tube; the heater is provided with heating wires spirally and uniformly wound on the outer side of the outer tube from bottom to top; and the detection end of the temperature sensor is located in the inner cavity of the outer tube and extends downward from the top of the outer tube. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flow chart of the methanol evaporator liquid level control method of one of the embodiments of the application;

[0025] Figure 2 The perspective view of the methanol evaporator of one of the embodiments of the application;

[0026] Figure 3 The perspective view of the methanol evaporator shown in the figure; Figure 2 The perspective view of the methanol evaporator shown in the figure;

[0027] Figure 4 Fig. 1 is a perspective view of a methanol evaporator according to the present application. Figure 3 Fig. 2 is a perspective view of the methanol evaporator shown in Fig. 1 with a heater hidden.

[0028] The meanings of the respective reference numerals in the drawings are as follows:

[0029] 100 - methanol evaporator;

[0030] 10 - outer tube, 11 - raw liquid inlet, 12 - vapor outlet;

[0031] 20 - inner tube;

[0032] 30 - heater, 31 - heating wire;

[0033] 40 - temperature sensor. DETAILED DESCRIPTION

[0034] In order to make the above objectives, features and advantages of the present application more clear and easily understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of different ways from those described herein without departing from the scope of the present application and it is understood that similar improvements can be made by those skilled in the art without departing from the spirit of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0035] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are merely used for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0036] In addition, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0037] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0040] like Figure 1 As shown, this is an embodiment of the methanol evaporation level control method of the present invention.

[0041] like Figure 1 As shown, the methanol evaporation level control method includes the following steps:

[0042] S10: When the hydrogen production reactor is heated to the reaction temperature, the methanol evaporator is heated to the preset operating temperature with a preset heating power.

[0043] S20: Liquid is fed into the methanol evaporator. After the raw methanol liquid enters the methanol evaporator, it evaporates, and the pressure of the methanol vapor increases.

[0044] S30: The evaporated methanol vapor enters the hydrogen production reactor and begins to produce hydrogen. The reference temperature (also known as the reference temperature) required for liquid level control is obtained, and the superheat temperature of the methanol vapor is detected by the temperature sensor at the top of the inner cavity of the methanol evaporator.

[0045] According to the process of the vapor from unsaturated to wet saturated to dry saturated, the temperature of the vapor is not increased, and after the dry saturated, the temperature will quickly rise if the heating continues. The change of the temperature can infer the change of the evaporation liquid level. By comparing the superheated temperature with the reference temperature, the superheat degree of the methanol vapor can be obtained, so as to judge the liquid level of the methanol.

[0046] In the embodiment, the reference temperature is a preset value of 140-150°C, which is the saturated temperature under the pressure, and can be obtained by actual measurement (which may be different according to the equipment of the methanol evaporator). For example, in the embodiment, the reference temperature can be set to 145°C.

[0047] In the embodiment, the measurement point of the temperature sensor is set to 8-12 cm above the gas-liquid demarcation point in the inner cavity of the methanol evaporator. For example, in the embodiment, the measurement point of the temperature sensor is set to 10 cm above the gas-liquid demarcation point in the inner cavity of the methanol evaporator.

[0048] S40: In the process of producing hydrogen, the temperature change of the methanol evaporator is monitored by the temperature sensor, and the liquid feeding amount of the methanol raw solution is adjusted. If the current superheated temperature decreases compared with the reference temperature, it is judged that the liquid feeding amount is too large, and the liquid feeding amount of the methanol raw solution needs to be reduced; if the current superheated temperature increases compared with the reference temperature, it is judged that the liquid feeding amount is too small, and the liquid feeding amount of the methanol raw solution needs to be increased.

[0049] In some embodiments, because the temperature will fluctuate in actual operation, in order to avoid the high-frequency repeated increase and decrease of the liquid feeding adjustment, the reference temperature can be set to a temperature range, or an acceptable preset range can be introduced between the difference between the current superheated temperature and the reference temperature when comparing the two. For example, in step S40, if the current superheated temperature is less than the lower limit value of the reference temperature range, it is judged that the liquid feeding amount is too large, and the liquid feeding amount of the methanol raw solution needs to be reduced; if the current superheated temperature is greater than the upper limit value of the reference temperature range, it is judged that the liquid feeding amount is too small, and the liquid feeding amount of the methanol raw solution needs to be increased.

[0050] In step S40, in special cases, if the normal liquid feeding adjustment cannot timely realize the liquid level adjustment, dry burning or overflow will occur. Therefore, the following supplements can also be made:

[0051] For dry burning:

[0052] In step S40, if the current superheated temperature increases compared with the reference temperature and reaches a preset dry burning value, it is judged that the methanol raw solution in the methanol evaporator is short of liquid, at this time, the methanol evaporator needs to be stopped heating.

[0053] Further, in step S40, after the methanol evaporator is stopped heating due to the methanol stock solution being evaporated dry, if the current superheat temperature returns to the reference temperature within a preset recovery time, the methanol evaporator is resumed heating; otherwise, an alarm is issued.

[0054] For the case of overflow:

[0055] In step S40, if the current superheat temperature drops compared to the reference temperature and reaches a preset overflow value, it is determined that there is too much methanol stock solution in the methanol evaporator, and at this time, the methanol stock solution needs to be stopped.

[0056] Further, in step S40, after the methanol evaporator is stopped heating due to the methanol stock solution being evaporated dry, if the current superheat temperature returns to the reference temperature within a preset recovery time, the methanol evaporator is resumed heating; otherwise, an alarm is issued.

[0057] In addition, in step S40, the methanol stock solution is adjusted in an amount according to the difference between the current superheat temperature and the reference temperature by PID control.

[0058] Working principle:

[0059] The inner cavity of the methanol evaporator is divided into an evaporation zone for heating the methanol stock solution and a superheating zone for further heating the methanol vapor. The temperature sensor detects the temperature of the methanol vapor in the superheating zone. When the liquid level rises, the area of the evaporation zone increases, and correspondingly, the area of the superheating zone decreases. Under a certain heating power, the wet vapor increases and the dry vapor decreases, and the detected vapor temperature will decrease. Conversely, when the liquid level drops, the wet vapor decreases and the dry vapor increases, and the detected vapor temperature will increase. Therefore, the temperature sensor can indirectly detect the liquid level and adjust the amount of methanol stock solution, achieving the purpose of liquid level control.

[0060] The above-mentioned methanol evaporation liquid level control method discards the direct measurement of the liquid level by the traditional liquid level sensor and realizes indirect measurement of the liquid level by the temperature sensor, improving the accuracy of liquid level detection. The temperature sensor is inexpensive, which helps to reduce equipment costs. Not only can it effectively prevent dry burning and overflow, but it can also effectively assist in adjusting the hydrogen production flow to maintain the stability of the hydrogen production amount.

[0061] In addition, the above-mentioned methanol evaporation liquid level control method has the following advantages:

[0062] 1. Controlling the amount of methanol stock solution in the methanol evaporator controls the amount of methanol evaporation in the methanol evaporator, which in turn controls the amount of methanol vapor entering the hydrogen production reactor, further controlling the hydrogen production flow.

[0063] 2. Liquid level detection does not require the use of a liquid level sensor, which directly reduces equipment costs. This is especially suitable for small hydrogen generators. For example, in vehicle hydrogen energy treatment machines, the cost of using a dedicated liquid level sensor for automatic control is very high, while using temperature to indirectly detect the liquid level can reduce costs.

[0064] In addition, the present invention also provides a methanol evaporator.

[0065] The methanol evaporator is controlled using the methanol evaporation level control method described in the above embodiment. This methanol evaporator abandons the traditional direct level measurement using a level sensor and instead utilizes a temperature sensor for indirect level measurement, improving the accuracy of level detection. The low cost of the temperature sensor helps reduce equipment costs. It not only effectively prevents dry burning due to insufficient liquid and overflow due to overfilling, but also effectively assists in regulating the hydrogen production flow rate, maintaining the stability of hydrogen production.

[0066] The following describes an implementation method for a methanol evaporator:

[0067] like Figures 2 to 4 As shown, the methanol evaporator 100 includes: an outer tube 10, an inner tube 20 passing through the outer tube 10, a heater 30 connected to the outer tube 10, and a temperature sensor 40 mounted on the outer tube 10. The outer tube 10 has a raw material inlet 11 on its outer side and a vapor outlet 12 at its top. The inner tube 20 is coaxially arranged with the outer tube 10, and the outer diameter of the inner tube 20 is smaller than the inner diameter of the outer tube 10. The inner tube 20 extends from the bottom to the top of the outer tube 10, and its height is less than the height of the outer tube 10. The heater 30 has a heating wire 31 spirally and evenly wound from bottom to top around the outer side of the outer tube 10. The detection end of the temperature sensor 40 is located inside the outer tube 10 and extends downwards from the top of the outer tube 10.

[0068] In operation, the methanol raw solution enters the evaporation zone between the outer tube 10 and the inner tube 20 from the raw solution inlet 11 on the outer tube 10. The heater 30 is used to heat the outer tube 10, so that the methanol raw solution is heated to gasify into methanol vapor and flow out from the vapor outlet 12 at the top of the outer tube 10. In this design, the inner tube 20 is introduced and the heating wire 31 is uniformly wound on the outside of the outer tube 10. Under the condition of the same liquid storage capacity, the liquid level is increased, so that the contact area of the liquid with the inner wall of the outer tube 10 is larger, thereby improving the heating efficiency and the evaporation efficiency. At the same time, the height of the inner tube 20 is less than the height of the outer tube 10, so that the inner cavity of the outer tube 10 is divided into an evaporation zone and a superheating zone. The liquid methanol is heated to gasify into methanol vapor in the evaporation zone, and the methanol vapor is further heated in the superheating zone, which has the dual functions of an evaporator and a superheater, and the temperature of the outflowing methanol vapor is closer to the temperature of the hydrogen production reactor. Furthermore, the temperature of the methanol vapor can be detected by the temperature sensor 40, so as to judge the evaporation degree of the methanol in the outer tube 10, and indirectly judge the liquid level height of the methanol in the outer tube 10, thereby realizing the function of liquid level monitoring. Therefore, the controllability of the heating power, the superheating degree and the temperature uniformity of this design is strong, the methanol is uniformly heated, the evaporation efficiency is high, the methanol vapor is superheated to close to the temperature of the hydrogen production reactor, and the risk of overflow of the liquid methanol to the hydrogen production reactor or dry burning is effectively reduced.

[0069] The technical features of the above embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present disclosure.

[0070] The above embodiments only express the preferred embodiments of the present application, which are described in detail and specifically, but should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A methanol evaporation level control method, characterized by, The method comprises the steps of: S10: heating the methanol evaporator to a preset working temperature at a preset heating power when the hydrogen production reactor is heated to a reaction temperature; S20: feeding the methanol evaporator with methanol stock solution, which is evaporated after entering the methanol evaporator, and the gas pressure of the methanol vapor rises; S30: the evaporated methanol vapor enters the hydrogen production reactor and starts to produce hydrogen, the reference temperature required for liquid level control is obtained, and the superheating temperature of the methanol vapor is detected by the temperature sensor at the top of the inner cavity of the methanol evaporator; S40: during the production of hydrogen, the temperature change of the methanol evaporator is monitored by the temperature sensor, and the amount of methanol stock solution fed is adjusted; if the current superheating temperature decreases compared with the reference temperature, it is judged that the amount of methanol stock solution fed is too large, and the amount of methanol stock solution fed needs to be reduced; if the current superheating temperature rises compared with the reference temperature, it is judged that the amount of methanol stock solution fed is too small, and the amount of methanol stock solution fed needs to be increased; In step S40, if the current superheating temperature rises compared with the reference temperature and reaches a preset dry burning value, it is judged that the methanol stock solution in the methanol evaporator is short of liquid, at which time the methanol evaporator needs to be stopped heating; The methanol evaporator comprises an outer tube, an inner tube arranged in the outer tube, a heater connected to the outer tube, and a temperature sensor mounted on the outer tube; the outer side of the outer tube is provided with a methanol inlet; the top of the outer tube is provided with a vapor outlet; the inner tube is coaxially arranged with the outer tube, and the outer diameter of the inner tube is smaller than the inner diameter of the outer tube; the inner tube extends from the bottom of the outer tube to the top of the outer tube, and the height of the inner tube is smaller than the height of the outer tube; the heater is provided with heating wires spirally and uniformly wound from bottom to top on the outer side of the outer tube; the detection end of the temperature sensor is located in the inner cavity of the outer tube and extends downward from the top of the outer tube.

2. The methanol boil-off level control method of claim 1, wherein, In step S40, after the methanol evaporator is stopped heating due to the methanol stock solution being evaporated dry, if the current superheating temperature recovers to the reference temperature within a preset recovery time, the methanol evaporator is resumed heating; otherwise, an alarm is issued.

3. The methanol boil-off level control method of claim 1, wherein, In step S40, if the current superheating temperature decreases compared with the reference temperature and reaches a preset overflow value, it is judged that the methanol stock solution in the methanol evaporator is too much, at which time the feeding of the methanol stock solution needs to be stopped.

4. The methanol boil-off level control method of claim 3, wherein, In step S40, after the methanol evaporator is stopped heating due to the methanol stock solution being too much, if the current superheating temperature recovers to the reference temperature within a preset recovery time, the methanol evaporator is resumed feeding; otherwise, an alarm is issued.

5. The methanol boil-off level control method of claim 1, wherein, The measurement point of the temperature sensor is arranged 8-12 cm above the gas-liquid demarcation point in the inner cavity of the methanol evaporator.

6. The methanol boil-off level control method of claim 1, wherein, In step S40, the feeding amount of the methanol stock solution is adjusted in a PID control manner according to the difference between the current superheating temperature and the reference temperature.

7. The methanol boil-off level control method of claim 1, wherein, In step S30, the reference temperature is a preset value of 140-150℃.

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