Air make-up control method for catalytic oxidation dehydrogenation reaction in dehydrogenation system

Abstract

The application discloses a kind of catalytic oxidation dehydrogenation reaction air supplement control method in dehydrogenation system, comprising: collection real-time data, at least including the hydrogen content data and flow data in BOG gas input dehydrogenation system and the oxygen content data in gas after catalytic oxidation reaction by dehydrogenation system;According to the real-time data, the opening degree of regulating valve is controlled using PID control mode, and the oxygen content in the air input into the dehydrogenation system is controlled, and the regulating valve is installed in the oxygen supplement branch of the dehydrogenation system;The application based on PID control can well adapt to catalytic oxidation reaction oxygen supplement condition, so that catalytic oxidation reaction is stably and efficiently operated.

Description

Technical Field

[0001] This invention relates to the chemical industry, specifically to a method for controlling the air supply to the catalytic oxidation dehydrogenation reaction in a dehydrogenation system based on a BOG gas helium extraction device. Background Technology

[0002] Helium, a non-renewable strategic rare resource, is widely used in defense, aerospace, medical, fiber optics, semiconductors, low-temperature superconductivity, scientific research, and precision instrument leak detection, fulfilling irreplaceable functional requirements. Helium is primarily found in natural gas, which is the main source of commercially available helium products. Helium purification mainly involves membrane separation, adsorption, and cryogenic processes. However, because hydrogen and helium coexist and have similar molecular weights, they are difficult to separate, making the above processes ineffective for hydrogen-helium separation. Existing helium purification methods primarily involve catalytic oxidation to remove hydrogen from BOG (Boiling Point Gas).

[0003] Catalytic oxidation requires oxygen. By supplementing oxygen and hydrogen in a specific ratio, a catalytic oxidation reaction is carried out under the action of a special catalyst to produce water, thereby removing hydrogen from the helium-containing BOG gas. However, hydrogen is a flammable and explosive gas with an explosion limit of 4%-74.2% in air. Supplementing air poses a safety hazard. Therefore, it is crucial to ensure a stable supply of air to participate in the reaction and to guarantee the safety of subsequent production processes. Summary of the Invention

[0004] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a method for controlling the air supply to the catalytic oxidation dehydrogenation reaction in a dehydrogenation system. The dehydrogenation system is applicable to BOG gas helium extraction devices. This method, based on PID control, can well adapt to the oxygen supply conditions of the catalytic oxidation dehydrogenation reaction, enabling the catalytic oxidation dehydrogenation reaction to operate stably and efficiently.

[0005] Specifically, a method for controlling air supply to the catalytic oxidation dehydrogenation reaction in a dehydrogenation system, wherein the dehydrogenation system is applicable to a BOG gas helium extraction device, the control method comprising: Collect real-time data, which includes at least the hydrogen content data in the BOG gas input to the dehydrogenation system and the oxygen content data in the gas after the catalytic oxidation reaction through the dehydrogenation system. The amount of oxygen in the air input to the dehydrogenation system is controlled by the opening and closing degree of the regulating valve using the real-time data and the regulating valve is installed in the oxygen replenishment branch of the dehydrogenation system.

[0006] Optionally, the real-time data may also include flow rate data of BOG gas input to the dehydrogenation system.

[0007] Optionally, the oxygen supply branch is also equipped with an emergency shut-off valve, the opening and closing of which is determined according to the oxygen content data.

[0008] Optionally, values ​​are assigned to the opening degree of the regulating valve and the emergency shut-off valve in the PID control. The following factors need to be considered when assigning the opening degree of the regulating valve: The oxygen content value entering the subsequent process after catalytic oxidation reaction is adjusted by regulating the P value, I value, and D value to ensure that the opening and closing speed and reaction speed of the regulating valve can match the air supply amount. After catalytic oxidation reaction, the oxygen content value entering the subsequent process is guaranteed. When the positive fluctuation exceeds a specific value, the emergency shut-off valve is triggered, leaving a safety margin and adjustment space. The following factors need to be considered when assigning values ​​to the emergency shut-off valve: Due to the influence of analyzer lag, an inertial margin needs to be allowed to determine the analyzer, which is an oxygen analyzer that collects oxygen content data.

[0009] Preferably, the opening degree of the regulating valve is set to 20% of the standard safety value, and the interlocking emergency shut-off valve is set to 90% of the standard safety value.

[0010] Optionally, in PID control, the hydrogen content data is divided into multiple segments from small to large, and each segment is assigned a range value; the opening degree of the control valve is divided into multiple segments, and each segment opening degree is assigned a range value from small to large. The low value and the high value are the lower limit and upper limit of the opening degree of the control valve, respectively, and the minimum opening degree is not zero. The hydrogen content data segment corresponds one-to-one with the upper and lower limits of the control valve's opening and closing degree, thus limiting the control valve, which is slowly opening and closing, to a reasonable range.

[0011] Optionally, in PID control, the flow data is segmented, and the opening and closing degree of the control valve, which has already been divided into multiple segments, is copied as a whole into multiple large segments corresponding to the flow data segments.

[0012] Optionally, the oxygen replenishment branch is connected to an oxygen replenishment source, which is instrument air. Instrument air is an essential auxiliary project for factory production, and air is inexhaustible. The successful application of the control system for replenishing air in the helium extraction device by utilizing oxygen in the air to participate in the catalytic oxidation reaction rationally utilizes the factory's public resources, reduces the high investment in pure oxygen replenishment and the long-term operating and depreciation costs, and saves the land occupied by building a pure oxygen device and the safety hazards associated with it.

[0013] The present invention has the following advantages: This invention addresses the problem of air supply interruption and oxygen deficiency in the catalytic oxidation reaction caused by excessive air supply triggered by fully opening or closing the control valve, which in turn leads to product quality issues. It addresses the issues arising from the rational combination of BOG gas flow rate data, hydrogen content data in the BOG gas, and oxygen content data in the gas after the catalytic oxidation reaction. Furthermore, it resolves the lag effects caused by long analytical sampling pipelines, low pressure, slow flow rates, and the reaction cycle of analytical data. It also ensures that the minimum opening value of the control valve is not zero, preventing the control valve from being fully closed during normal production when the hydrogen content is at its lowest, thus avoiding air supply interruption and oxygen deficiency in the catalytic oxidation reaction. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the present invention; Figure 2 This is a schematic diagram of the dehydrogenation system described in this invention; Figure 3 This is a diagram showing the correspondence between the segmented flow rate data, the segmented hydrogen content data, and the segmented opening / closing degree of the regulating valve as described in this invention. In the diagram: 100, make-up air branch; 101, make-up air regulating valve; 102, make-up air temperature sensor; 103, make-up air pressure sensor; 104, make-up air flow meter; 105, make-up air emergency shut-off valve; 200, mixing branch; 201, mixer; 202, catalytic oxidation reactor; 203, mixed gas thermometer; 204, make-up inlet; 205, check valve; 206, outlet thermometer; 300, hydrogen-containing BOG branch; 301, feed gas buffer tank; 302, hydrogen-containing BOG flow meter; 303, hydrogen analyzer; 304, BOG gas flow meter; 400, reaction branch; 401, cooler; 402, gas-liquid separator; 403, reaction thermometer; 404, oxygen analyzer; 500, heat exchanger; 600, electric heater. Detailed Implementation

[0015] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0016] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0017] As described in the background section, catalytic oxidation requires oxygen. By supplementing oxygen and hydrogen in a specific ratio, a catalytic oxidation reaction is carried out under the action of a special catalyst to produce water, thereby removing hydrogen from the helium-containing BOG gas. However, hydrogen is a flammable and explosive gas with an explosion limit of 4%-74.2% in air. Supplementing air poses a safety hazard. It is particularly important to ensure a stable supply of air to participate in the reaction and to guarantee the safety of subsequent production processes.

[0018] For the reasons mentioned above, such as Figure 1 As shown, this embodiment provides a method for controlling air replenishment in a catalytic oxidation dehydrogenation reaction within a dehydrogenation system. The dehydrogenation system is applicable to BOG gas helium extraction devices. The control method includes... Step S100: Collect real-time data, which includes at least the hydrogen content data in the BOG gas input to the dehydrogenation system and the oxygen content data in the gas after the catalytic oxidation reaction through the dehydrogenation system. Step S200: Based on the real-time data, the opening and closing degree of the regulating valve is controlled using PID control to control the amount of oxygen in the air input to the dehydrogenation system. The regulating valve is installed in the oxygen replenishment branch of the dehydrogenation system, and the oxygen replenishment branch is connected to the oxygen replenishment source, which is instrument air.

[0019] In one embodiment, the real-time data also includes flow data of BOG gas input to the dehydrogenation system; the oxygen supplement branch is also equipped with an emergency shut-off valve, the opening and closing of which is determined according to the amount of oxygen content data.

[0020] For example, the opening and closing degree of the regulating valve is simultaneously controlled by data on the oxygen content in the gas after catalytic oxidation in the dehydrogenation system, the hydrogen content in the BOG gas input to the dehydrogenation system, and the flow rate of the BOG gas input to the dehydrogenation system. Assuming PID control uses oxygen content data to regulate the valve's opening and closing degree, a higher oxygen content results in a slower valve closure, and vice versa. The interlocking control of the oxygen content data on the valve's opening and closing degree and the emergency shut-off valve's opening and closing is related to the production safety of subsequent processes. The interlocking valve opening degree should be assigned to 20% of the standard safety value, and the interlocking emergency shut-off valve should be assigned to 90% of the standard safety value. This solves the lag effect caused by the data analysis reaction cycle, providing a buffer period for the oxygen content data to reach the standard safety value, thus ensuring production safety.

[0021] The following factors need to be considered when assigning the opening degree of the regulating valve: The oxygen content value entering the subsequent process after catalytic oxidation reaction is adjusted by regulating the P value, I value, and D value to ensure that the opening and closing speed and reaction speed of the regulating valve can match the air supply amount. After catalytic oxidation reaction, the oxygen content value entering the subsequent process is guaranteed. When the positive fluctuation exceeds a specific value, the emergency shut-off valve is triggered, leaving a safety margin and adjustment space.

[0022] For example, based on the process characteristics of this dehydrogenation system, the oxygen content entering the subsequent process after catalytic oxidation must be ≤0.6%. Therefore, the opening and closing degree of the interlocking control valve should be assigned 0.6×0.2=0.12. By adjusting the P value, I value, and D value, the opening and closing speed and reaction speed of the control valve can be matched with the air supply amount. After the catalytic oxidation reaction, the oxygen content entering the subsequent process is controlled between 0.12±0.05. The value of 0.12±0.05 meets the oxygen demand of the subsequent process, while leaving a large safety margin and adjustment space for triggering the emergency shut-off valve when the positive fluctuation exceeds +0.05.

[0023] The following factors need to be considered when assigning values ​​to the emergency shut-off valve: Due to the influence of analyzer lag, an inertial margin needs to be allowed to determine the analyzer, which is an oxygen analyzer that collects oxygen content data.

[0024] For example, the value assigned to the interlocked emergency shut-off valve should be 0.6 × 0.9 = 0.54 because when the oxygen content reaches 0.54 and triggers the emergency shut-off valve to close, the rise does not completely stop due to the lag effect of the analyzer, and it will eventually rise to 0.6. Therefore, a certain amount of inertial space should be left when assigning the value to ensure safety.

[0025] Because the opening and closing of the control valve is inversely proportional to the real-time measurement of the oxygen content after the reaction—that is, the valve is always closed when the oxygen content is high and always open when the content is low—this causes large fluctuations in the real-time oxygen content that are difficult to control. Therefore, the real-time measurement of the hydrogen content at the front end is introduced to limit the upper and lower limits of the control valve's opening and closing, so that the control valve continuously opens and closes within a certain range, thereby effectively controlling the real-time oxygen analysis data value after the reaction stably at 0.12±0.05. Since the real-time hydrogen content data value of BOG gas is relatively fixed, the greater the flow rate, the greater the demand for oxygen. Therefore, the fixed upper and lower limits of the valve must also be adjusted accordingly. Thus, the upper and lower limits of the multi-segment hydrogen content control are treated as a whole and then divided into multiple segments corresponding to the flow rate.

[0026] like Figure 3 As shown, the hydrogen content data is divided into multiple segments from smallest to largest, with each segment assigned a range value; the opening degree of the control valve is also divided into multiple segments, with each segment assigned a range value from smallest to largest. The low value and the high value are the lower limit and upper limit of the control valve opening, respectively, and the lowest opening degree cannot be zero. The hydrogen content data segments correspond one-to-one with the upper and lower limit segments of the control valve opening degree, so that the control valve, which is slowly opening and closing, is limited to a reasonable range. The more segments there are in the hydrogen content data and the control valve opening degree, the more precise the control.

[0027] When the hydrogen content of the BOG feed gas is constant, the larger the flow rate, the more air needs to be supplemented, and vice versa. The upper and lower limits of the fixed opening and closing range of the regulating valve cannot meet the oxygen demand requirements for dehydrogenation. At this time, it is necessary to treat the opening and closing range of the regulating valve, which has been divided into multiple segments, as a whole and then replicate it into multiple large segments to correspond one-to-one with the flow data segments, thus forming a complete dehydrogenation oxygen supplementation control method.

[0028] like Figure 2 As shown, the dehydrogenation system is used for BOG gas helium extraction devices, including: a hydrogen-containing BOG branch 300, a venting branch 100, a mixing branch 200, and a reaction branch 400. One end of the hydrogen-containing BOG branch 300 is connected to the raw material gas buffer tank 301, and the other end is connected to the heat exchanger 500 and the electric heater 600 in sequence before being connected to the mixing branch 200. One end of the supplementary branch 100 is connected to the oxygen source, and the other end is connected to the supplementary inlet 204 opened on the mixing branch after passing through the electric heater. The mixing branch 200 is connected to the mixer 201 and then to the catalytic oxidation reactor 202; One end of the reaction branch 400 is connected to the catalytic oxidation reactor 202, and the other end is connected in sequence to the heat exchanger 500, the cooler 401 and the gas-liquid separator 402 before being connected to the subsequent process components.

[0029] An outlet thermometer 206 and a check valve 205 are also installed at the outlet end of the electric heater, and the replenishment inlet 204 is located at the rear end of the outlet of the check valve 205; the oxygen source is instrument air.

[0030] When the dehydrogenation system is in use, BOG gas enters the hydrogen-containing BOG branch through the feed gas buffer tank, and is heated by a heat exchanger (using gas-to-gas heat exchange). It then enters the heater (using electric heating) and enters the mixing branch. The air to be added enters from the air replenishment branch, is heated by the electric heater, and then enters the mixing branch through the replenishment inlet. After the gas is mixed in the mixer (using a static mixer) in the mixing branch, it enters the catalytic oxidation reactor. After the reaction is completed, the gas is heated by a heat exchanger again, and after the heat exchange, it passes through the cold zone of the cooler. Then, the gas and liquid are separated by a gas-liquid separator to obtain the dehydrogenated BOG gas.

[0031] By installing an electric heater at the cold end outlet of the heat exchanger, the electric heater serves as the heat source for the reaction during production startup, consuming a certain amount of electrical energy. Once the dehydrogenation reaction is normal, the heat energy generated by the reaction is recovered through heat exchange in a gas-to-gas heat exchanger, making reasonable use of the heat energy. When the temperature of the cold gas exceeds the outlet temperature of the electric heater after heat exchange, the electric heater stops working and enters a hot standby state, consuming no electrical energy. Conversely, it promptly heats up to replenish the heat energy to maintain a constant temperature entering the reactor and ensure the stable progress of the catalytic oxidation reaction. The electric heater adopts precise PID automatic adjustment when replenishing heat energy, resulting in extremely low energy consumption.

[0032] The air inlet is located between the electric heater outlet and the catalytic oxidation reactor. The incoming air is effectively mixed with the heated BOG feed gas via a static mixer before entering the reactor. Under the action of the catalyst, hydrogen reacts with oxygen in the air to produce water, thus achieving hydrogen removal. A mixed gas thermometer 203 is installed on the mixing branch between the inlet 204 and the mixer, accurately measuring the actual temperature entering the reactor, facilitating timely adjustment of the electric heater temperature and the gas-to-gas heat exchanger temperature during production.

[0033] To obtain hydrogen content data, flow rate data, and oxygen content data, a hydrogen-containing BOG flow meter 302 and a hydrogen analyzer 303 are sequentially installed on the hydrogen-containing BOG branch 300 from the raw material gas buffer tank 301 to the heat exchanger. The raw material gas buffer tank 301 is connected to the hydrogen-containing BOG gas branch and the downstream return gas branch. A BOG gas flow meter 304 is installed on the hydrogen-containing BOG gas branch. A purging regulating valve 101, a purging temperature sensor 102, a purging pressure sensor 103, a purging flow meter 104, and a purging emergency shut-off valve 105 are sequentially installed from the inlet to the outlet on the purging branch. A reaction thermometer 403 and an oxygen analyzer 404 are installed on the reaction branch 400, wherein the reaction thermometer 403 is located between the catalytic oxidation reactor 202 and the heat exchanger 500, and the oxygen analyzer 404 is located at the outlet of the gas-liquid separator 402.

[0034] This invention addresses the problem of air supply interruption and oxygen deficiency in the catalytic oxidation reaction caused by excessive air supply triggered by fully opening or closing the control valve, which in turn leads to product quality issues. It addresses the issues arising from the rational combination of BOG gas flow rate data, hydrogen content data in the BOG gas, and oxygen content data in the gas after the catalytic oxidation reaction. Furthermore, it resolves the lag effects caused by long analytical sampling pipelines, low pressure, slow flow rates, and the reaction cycle of analytical data. It also ensures that the minimum opening value of the control valve is not zero, preventing the control valve from being fully closed during normal production when the hydrogen content is at its lowest, thus avoiding air supply interruption and oxygen deficiency in the catalytic oxidation reaction.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling air supply to the catalytic oxidative dehydrogenation reaction in a dehydrogenation system, characterized in that, The dehydrogenation system is suitable for BOG gas helium extraction devices, and the control method includes: Collect real-time data, which includes at least the hydrogen content data in the BOG gas input to the dehydrogenation system and the oxygen content data in the gas after the catalytic oxidation reaction through the dehydrogenation system. The amount of oxygen input to the dehydrogenation system is controlled by using PID control to control the opening and closing degree of the regulating valve based on the real-time data. The regulating valve is installed in the oxygen replenishment branch of the dehydrogenation system. In the PID control, values ​​are assigned to the opening degree of the regulating valve and the emergency shut-off valve. The following factors need to be considered when assigning the opening degree of the regulating valve: The oxygen content value entering the subsequent process after catalytic oxidation reaction is adjusted by regulating the P value, I value, and D value to ensure that the opening and closing speed and reaction speed of the regulating valve can match the air supply amount. After catalytic oxidation reaction, the oxygen content value entering the subsequent process is guaranteed. When the positive fluctuation exceeds a specific value, the emergency shut-off valve is triggered, leaving a safety margin and adjustment space. The following factors need to be considered when assigning values ​​to the emergency shut-off valve: Due to the influence of analyzer lag, an inertial margin needs to be allowed to determine the analyzer, which is an oxygen analyzer that collects oxygen content data. The real-time data also includes flow rate data of BOG gas input to the dehydrogenation system; In PID control, the hydrogen content data is divided into multiple segments from small to large, and each segment is assigned a range value; the opening degree of the control valve is divided into multiple segments, and each segment's opening degree is assigned a range value from small to large. The low value and the high value are the lower limit and upper limit of the control valve's opening degree, respectively, and the minimum opening degree is not zero. The hydrogen content data segment corresponds one-to-one with the upper and lower limits of the control valve's opening and closing degree, thus limiting the control valve, which is slowly opening and closing, to a reasonable range.

2. The method for controlling air supply to the catalytic oxidative dehydrogenation reaction in the dehydrogenation system according to claim 1, characterized in that, The oxygen supply branch is also equipped with an emergency shut-off valve, the opening and closing of which is determined by the oxygen content data.

3. The method for controlling air supply to the catalytic oxidative dehydrogenation reaction in the dehydrogenation system according to claim 1, characterized in that, The opening degree of the regulating valve is set at 20% of the standard safety value, and the interlocking emergency shut-off valve is set at 90% of the standard safety value.

4. The method for controlling air supply to the catalytic oxidative dehydrogenation reaction in the dehydrogenation system according to claim 3, characterized in that, In PID control, the flow data is segmented, and the opening and closing degree of the control valve, which has already been divided into multiple segments, is copied as a whole into multiple large segments corresponding to the flow data segments.

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