Chemical device safety interlocking method and system based on local material balance

Abstract

The invention provides a chemical device safety interlocking method and system based on local material balance. By calculating the material balance liquid level and comparing the material balance liquid level with the actually measured liquid level, the method has high identification sensitivity on the risk of production safety accidents caused by liquid level measurement failure; when liquid level measurement fails, safety accident risks caused by the fact that liquid level interlocking is started to enable equipment to be full of overpressure or empty liquid level of the equipment are timely managed, controlled and eliminated, the situation that liquid level interlocking is adopted to conduct excessive adjustment when slight errors exist in actual liquid level measurement is avoided, on the premise that stable production is guaranteed, the intrinsic safety level of the equipment is improved, and the production cost is reduced. Overpressure accidents caused by full filling of equipment liquid or accidents such as overtemperature and pump evacuation caused by liquid level air compression can be effectively prevented, and great significance is achieved for improving the safety level of chemical production and preventing terrible accidents.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical production process control, and particularly relates to a chemical device safety interlocking method and system based on local material balance. BACKGROUND

[0002] Currently, in the chemical production process, various primary and secondary liquid level measurement devices such as glass tube liquid level meters, magnetic flip plate liquid level meters, sink cylinder liquid level meters, double flange liquid level meters, radar liquid level meters, and servo liquid level meters are often used to monitor the liquid level of the liquid inside the equipment. However, regardless of the liquid level measurement method, under certain conditions, the liquid level measurement may not be accurate. In industry, to prevent safety problems caused by liquid level measurement failures, a combination of on-site primary liquid level measurement and remote secondary liquid level measurement is often used to ensure the accuracy of liquid level measurement. However, even so, liquid level measurement may still fail. Especially during start-up and shut-down, abnormal handling, and other processes, the amount of material in the system is often determined by relying on primary and secondary liquid level measurement instruments, and the local material balance of a single device such as a tower, a tank, a reactor, or a compressor is often overlooked. There is no method for interlocking or control based on local material balance in the prior art. Once the liquid level measurement fails, if the local material balance of the device is not paid attention to, the single device may be filled with liquid or the air pressure may be lost. If the device is filled with liquid, due to the heating process, the temperature of the liquid continues to rise, and due to the incompressibility of the liquid, the device may be over-pressurized, causing a production safety accident. In severe cases, even a malignant accident may occur. If the air pressure of the device is lost, the heating process is still ongoing, which may cause over-temperature. Or if the bottom of the device is connected to a rotating device such as a pump, the pump may be empty, causing leakage of the mechanical seal or dry gas seal, and causing a leakage accident.

[0003] For example, on April 10, 2015 at 10:43, the epoxy ethane refining tower pressure of an epoxy ethane / ethylene glycol device in a chemical plant fluctuated, and the operator took measures such as closing the tower top extraction, adjusting the feed load, and adjusting the amount of heating steam at the tower bottom, but none of these measures achieved stable operation of the tower. The next day at 5:02, the tower top safety valve acted and jumped, at 6:01, a fire occurred near the upper head of the reboiler, and at 6:04, the refining tower exploded. The accident caused 1 person to be slightly injured, the epoxy ethane refining tower to be damaged, and some equipment and facilities to be damaged. The direct cause of the accident was that no epoxy ethane product was extracted for nearly 11 hours, causing the refining tower to be filled with material, the liquid phase to expand due to heating, the pressure to rise sharply, and the tower top pressure pipe to be blocked. The pressure indication was distorted because the pressure interlocking and the pressure control transmitter and the field pressure gauge shared a pressure pipe, the operator did not discover the rising pressure of the tower in time, and the tower pressure interlocking did not act in time, resulting in a malignant accident of the refining tower over-pressurization explosion.

[0004] At 13:20 on March 2005, the isomerization unit of a refinery was restarted after a short maintenance. During the start-up, the operator continuously fed liquid hydrocarbons into the cracking tower through the feed pump. However, the tower bottom level did not reach the high limit alarm during the three-hour feeding process. The operator lacked experience and did not notice that there was no product withdrawal from the tower top and bottom, and the tower bottom level indication might be false. After continuous feed, the liquid feed filled the entire cracking tower, and the tower bottom continued to warm up, causing the liquid phase pressure in the full tower to rise rapidly with temperature, the three safety valves at the top of the tower tripped, a large amount of flammable liquid was discharged into the vent tank, and after the tank was filled, liquid hydrocarbons were sprayed along the tank roof to the ground. After the leaked flammable liquid evaporated, it reached the explosion limit and formed a flammable gas vapor cloud. The spark from the engine of a parked truck near the vent tank, which was not turned off, ignited the flammable vapor cloud, causing a major explosion. At the same time, the accident also caused serious economic losses.

[0005] On April 2022, the first cylinder head and piston of a new hydrogen compressor in a hydrocracking unit of a chemical company flew out, causing a hydrogen leakage flash explosion and fire accident. The main cause of the accident was that the normal condition of the new hydrogen compressor first cylinder outlet separator tank was to drain liquid twice a day, but the false indication of the liquid level in the separator tank had been -0.7% for more than 20 days before the accident. The operator did not accurately identify the abnormal liquid level indication, did not perform the inlet separator tank liquid discharge operation, and the liquid carried by the process gas and the lubricating oil entering the cylinder body accumulated in the system in large quantities, reaching the critical value. The new hydrogen compressor first outlet separator tank liquid level started to rise rapidly from -0.1% to 17.6% in 3 minutes, causing the machine body vibration to reach 11.4 mm / s in an instant, and the cylinder head to burst out.

[0006] The above cases show that in the chemical production process, especially in the start-up and shut-down, abnormal treatment and other processes, the amount of material in the system is often determined by relying on primary and secondary liquid level measuring instruments, and the local material balance of a single device such as a tower, a tank, a reactor, a compressor and the like is easily neglected. There is no method for interlocking or control based on local material balance in the prior art, and once the local material is unbalanced, the single device is filled with liquid, and due to the incompressibility of the liquid, it is very likely to cause a pressure vessel overpressure accident due to the increase of liquid temperature. Or a large amount of liquid is brought into the compressor inlet gas, which can also cause a liquid hammer accident. In addition, if the device is in a liquid pressure empty state, the heating process is still in progress, which may cause over-temperature; or if the bottom of the tank is connected to a rotating device such as a pump, it may cause the pump to be empty, causing mechanical seal or dry gas seal leakage, and causing leakage accidents. It is urgent to propose a method and a supporting system capable of avoiding the device filling overpressure accident caused by liquid level indication failure, the over-temperature accident caused by liquid pressure emptying, and the leakage accident caused by pump emptying. SUMMARY

[0007] In view of the risk of device filling or pressure control that may be caused by liquid level measurement failure in the current chemical production process, the purpose of the present application is to provide a chemical device safety interlocking method and system based on local material balance, which overcomes the major safety hazards of overpressure and over-temperature that may be caused by liquid level measurement failure in the prior art.

[0008] To achieve the above-mentioned purpose, the first aspect of the present application provides a chemical device safety interlocking method based on local material balance, comprising the following steps:

[0009] Step 1. Obtain the actual measured liquid level of the target device;

[0010] Step 2. Calculate the material balance liquid level of the target device based on material balance;

[0011] Step 3. Calculate the deviation between the material balance liquid level and the actual measured liquid level;

[0012] Step 4. Perform liquid level control, liquid level alarm or liquid level interlocking on the target device according to the calculation result of the deviation.

[0013] Optionally, in step 1, the actual measured liquid level is a remote secondary measured liquid level.

[0014] It should be noted that the meaning of the remote secondary measured liquid level referred to in the present application is that the liquid level height obtained by remote secondary measurement accounts for a percentage of the full-scale liquid level height of the target device.

[0015] Optionally, in step 2, the material balance liquid level is calculated according to formula (1):

[0016]

[0017] L 物料平衡 represents the material balance level;

[0018] M i入 represents the total liquid feed amount of the target device in a fixed time period;

[0019] M i出 represents the total liquid discharge amount of the target device in a fixed time period;

[0020] p 液 represents the liquid density in the target device at an average temperature in a fixed time period;

[0021] r represents the internal radius of the target device;

[0022] H 满 represents the full-scale range level of the target device.

[0023] Optionally, in step 3, the deviation between the material balance level and the actual measured level is calculated according to formula (2):

[0024] Δ = L 物料平衡 - L 实际测量 formula (2);

[0025] wherein Δ represents the deviation between the material balance level and the actual measured level;

[0026] L 物料平衡 represents the material balance level;

[0027] L 实际测量 represents the actual measured level.

[0028] Optionally, in step 4, when -15% < Δ < 15%, the level control is performed on the target device;

[0029] When -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the level alarm is performed on the target device;

[0030] When Δ ≤ -50% or Δ ≥ 50%, the level interlock is performed on the target device.

[0031] Optionally, in step 4, the level control comprises:

[0032] When the actual measured level is lower than the set level, the liquid discharge flow is reduced to raise the level in the target device;

[0033] When the actual measured liquid level is higher than the set liquid level, increasing the liquid discharge flow rate to lower the liquid level in the target device.

[0034] Optionally, in step 4, when Δ≤-50%, the liquid level interlock comprises:

[0035] cutting off the liquid discharge path, fully opening the liquid feed path, and raising the liquid level in the target device until -15%<Δ<15%.

[0036] Optionally, in step 4, when Δ≥50%, the liquid level interlock comprises:

[0037] cutting off the liquid feed path, fully opening the liquid discharge path, and lowering the liquid level in the target device until -15%<Δ<15%.

[0038] Optionally, when -15%<Δ<15%, ending the liquid level interlock and performing the liquid level control on the target device.

[0039] The second aspect of the present application provides a local material balance-based safety interlock system for a chemical device, which is used to implement the method according to the first aspect of the present application, wherein the system comprises:

[0040] a liquid level measurement module for measuring the liquid level in the target device to obtain the actual measured liquid level;

[0041] a liquid level control module for performing the liquid level control on the target device;

[0042] a liquid level alarm module for performing the liquid level alarm on the target device;

[0043] a liquid level interlock module for performing the liquid level interlock on the target device to prevent overpressure accidents or overtemperature accidents;

[0044] a selective control module connected to the liquid level measurement module, the liquid level control module, the liquid level alarm module and the liquid level interlock module, respectively, for calculating the material balance liquid level and the deviation between the material balance liquid level and the actual measured liquid level; and selecting the liquid level control, the liquid level alarm or the liquid level interlock on the target device according to the calculation result of the deviation.

[0045] Optionally, the system further comprises:

[0046] a liquid discharge regulating valve for regulating and providing the liquid discharge flow rate;

[0047] a liquid feed regulating valve for regulating and providing the liquid feed flow rate;

[0048] Preferably, the liquid level control module is connected with the liquid level measuring module and the liquid-containing outflow regulating valve respectively, to form a liquid level control loop, so as to realize the liquid level control.

[0049] The liquid level interlocking module is connected with the liquid-containing outflow regulating valve and the liquid-containing inflow regulating valve respectively, to realize the liquid level interlocking.

[0050] The selective control module is connected with the liquid-containing outflow regulating valve and the liquid-containing inflow regulating valve respectively, to obtain the liquid outflow and the liquid inflow of the target device in a fixed time period, and to calculate the total liquid inflow and the total liquid outflow.

[0051] Optionally, the selective control module has the formula (1) stored therein to calculate the material balance liquid level; and / or

[0052] The selective control module also has the formula (2) stored therein to calculate the deviation between the material balance liquid level and the actual measured liquid level.

[0053] Optionally, the selective control module also has the following criteria stored therein:

[0054] When -15%<Δ<15%, the liquid level control is performed on the target device;

[0055] When -50%<Δ≤-15% or 50%>Δ≥15%, the liquid level alarm is performed on the target device;

[0056] When Δ≤-50% or Δ≥50%, the liquid level interlocking is performed on the target device.

[0057] Optionally, the liquid level control module has the following criteria stored therein:

[0058] When the actual measured liquid level is lower than the set liquid level, the liquid outflow is reduced to raise the liquid level in the target device;

[0059] When the actual measured liquid level is higher than the set liquid level, the liquid outflow is increased to lower the liquid level in the target device.

[0060] Optionally, the liquid level interlocking module has the following criteria stored therein:

[0061] When Δ≤-50%, the liquid outflow path is cut off and the liquid inflow path is fully opened to raise the liquid level in the target device until -15%<Δ<15%;

[0062] When Δ≥50%, the liquid inflow path is cut off and the liquid outflow path is fully opened to lower the liquid level in the target device until -15%<Δ<15%.

[0063] The present application has the following advantages or beneficial effects:

[0064] Compared with the prior art, the present application has at least the following advantages or beneficial effects:

[0065] Based on the introduction of the material balance liquid level calculated by the local material balance, by calculating and evaluating the deviation between the material balance liquid level and the actual measured liquid level, the risk of production safety accidents caused by liquid level failure is flexibly controlled in all directions: when the deviation between the material balance liquid level and the actual measured liquid level satisfies -15%<Δ<15%, it reflects that there may be errors in the actual measured liquid level, but the degree of error is small, the risk of production safety accidents caused by liquid level failure is extremely low, the liquid level interlock does not need to be started, and only the liquid level control module needs to adjust the flow size of the liquid discharge to achieve smooth control of the liquid level; when the deviation between the material balance liquid level and the actual measured liquid level satisfies -50%<Δ≤-15% or 50%>Δ≥15%, it reflects that the actual measured liquid level has a large degree of error, and the liquid level in the target device may have a certain degree of abnormality, but it has not reached the severity of liquid level failure, at this time the liquid level alarm is triggered, prompting the staff to check the target device, calibrating the on-site primary liquid level measurement and remote secondary liquid level measurement, investigating the abnormal reasons and processing, controlling the deviation Δ in the range of -15%<Δ<15%, and returning the liquid level to the liquid level control module for control; when the deviation between the material balance liquid level and the actual measured liquid level satisfies Δ≤-50% or Δ≥50% (including the case after alarm processing Δ≤-50% or Δ≥50%), it reflects that the actual measured liquid level has a serious error, and there is a high risk of liquid level failure, in order to prevent equipment overpressure accidents or equipment overtemperature accidents, the target device needs to be liquid level interlocked, the liquid level interlock module determines and executes the liquid level interlock action of raising or lowering the liquid level of the target device according to Δ≤-50% or Δ≥50%, so that the liquid level in the target device is quickly removed from the abnormal condition. The present application has high recognition sensitivity to the risk of production safety accidents caused by liquid level measurement failure by calculating the material balance liquid level and comparing it with the actual measured liquid level, only in the case of liquid level measurement failure of Δ≤-50% or Δ≥50% to start the liquid level interlock to control and eliminate the safety accident risk caused by the full liquid of the single device or the overtemperature, pump emptying and other accidents caused by the empty liquid level, without over-regulation by liquid level interlock when there is a slight error in the actual measured liquid level, affecting production, on the premise of ensuring stable production of the device, the intrinsic safety level of the device is improved, which can effectively prevent overpressure accidents caused by full liquid of single device due to liquid level measurement failure and improper control, overtemperature, pump emptying and other accidents caused by empty liquid level, and plays an important role in improving the safety level of chemical production and preventing serious accidents.

[0066] Additional features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0067] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and together with the description serve to explain the present application. In the drawings:

[0068] Figure 1 The step schematic diagram of the chemical plant safety interlocking method based on local material balance provided by the embodiment of the present application.

[0069] Figure 2 The specific flow schematic diagram of the chemical plant safety interlocking method based on local material balance provided by the embodiment of the present application.

[0070] Figure 3 The structure schematic diagram of the chemical plant safety interlocking system based on local material balance provided by the embodiment of the present application. DETAILED DESCRIPTION

[0071] The embodiments of the present application will be described in detail with reference to the drawings and embodiments below, so that the application can be applied to solve the technical problems and achieve the technical effects by means of technology. It should be noted that, unless there is a conflict, each embodiment in the present application and each feature in the embodiment can be combined with each other, and the technical solutions formed thereby are within the protection scope of the present application.

[0072] In addition, the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer-executable instructions. Moreover, although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0073] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0074] To address the technical problems in the background art, embodiments of the present invention provide a safety interlocking method for chemical plants based on local material balance. This method calculates the equilibrium liquid level based on local material balance and the deviation between the equilibrium level and the actual measured liquid level. Based on the obtained deviation, different liquid level management operations are performed on the target equipment to avoid production safety accidents caused by equipment overpressure or pressure control overheating due to liquid level measurement failure.

[0075] Figure 1 A schematic diagram illustrating the steps of a safety interlocking method for chemical plants based on local material balance, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram illustrating the specific process of a safety interlocking method for chemical plants based on local material balance, provided in an embodiment of the present invention. The following refers to... Figure 1 The steps in, combined Figure 2 The specific steps and procedures of the safety interlocking method for chemical plants based on local material balance provided in the embodiments of the present invention will be described in detail.

[0076] Step S110. Obtain the actual measured liquid level of the target device.

[0077] In step S110, the actual measured liquid level is the remote secondary measured liquid level.

[0078] Step S120. Obtain the material balance level of the target equipment based on material balance calculation.

[0079] It should be noted that, in this embodiment of the invention, the material balance in step S120 only represents the liquid material balance.

[0080] In one embodiment, calculating the liquid material balance of the target device requires obtaining the following technical parameters over a fixed time period: firstly, the total liquid feed rate and total liquid discharge rate of the target device during the fixed time period; secondly, the liquid density of the target device at the average temperature during the fixed time period, the internal radius of the target device, and the full-scale liquid level.

[0081] Based on the obtained technical parameters, the material balance level of the target equipment during the fixed time period is calculated according to formula (1):

[0082]

[0083] In formula (1), L% 物料平衡 This represents the equilibrium liquid level of the material.

[0084] M i入 This represents the total liquid feed rate of the target device during that fixed time period;

[0085] M i出 This represents the total liquid output of the target device within this fixed time period;

[0086] ρ 液 This represents the liquid density in the target device at the average temperature during the fixed time period;

[0087] r represents the internal radius of the target device;

[0088] H 满 This represents the full-scale liquid level of the target device;

[0089] Specifically, M i入 M represents the sum of the liquid feed rate and the liquid feed rate carried by the gas feed rate within the target device during the fixed time period. When either of them is 0, the non-zero value is taken as M. i入 Similarly, M i出 M represents the sum of the liquid output of the target device within the fixed time period and the liquid output carried by the gas output. When either of them is 0, the non-zero value is taken as M. i出 .

[0090] Step S130. Calculate the deviation between the material balance level and the actual measured level.

[0091] It should be noted that, in this embodiment of the invention, the deviation refers to the difference between the material equilibrium level and the actual measured level.

[0092] In step S130, the deviation between the material equilibrium level and the actual measured level is calculated according to formula (2):

[0093] Δ = L% 物料平衡 -L% 实际测量 Formula (2);

[0094] In formula (2), Δ represents the deviation between the material equilibrium level and the actual measured level;

[0095] L% 物料平衡 This represents the equilibrium liquid level of the material.

[0096] L% 实际测量 This represents the actual measured liquid level;

[0097] The deviation Δ between the material balance level and the actual measured level of the target equipment during the fixed time period is calculated according to formula (2).

[0098] Step S140. Based on the calculation result of the deviation, determine whether to perform liquid level control, liquid level alarm or liquid level interlock on the target equipment.

[0099] In step S140, the size of the deviation reflects the dangerous degree of the production activity of the target device in the fixed time period. The deviation can be positive or negative, and the greater the absolute value, the greater the risk of a production safety accident in the production activity of the target device in the fixed time period or thereafter. Of course, excessive risk prevention of the target device in the production activity should also be avoided. Therefore, different levels of liquid level management operations need to be taken for the deviation values in different stages.

[0100] The inventor has found that, by taking 15% and 50% of the absolute value of the deviation as the boundary to divide the stages, and taking liquid level management operations such as liquid level control, liquid level alarm or liquid level interlocking for the deviations in different stages, the accident risk brought by different deviation values can be properly and sufficiently controlled and avoided with a relatively simple process. For example, when the absolute value of the deviation is less than 15%, the difference between the material balance liquid level and the actual measured liquid level of the target device in the fixed time period is small, and the risk of a production safety accident is small, but the actual measured liquid level can still have a small degree of error, and the liquid level needs to be adjusted. When the absolute value of the deviation is not less than 15% but less than 50%, although the deviation between the material balance liquid level and the actual measured liquid level of the target device in the fixed time period has increased, the actual measured liquid level is not likely to reach a very high degree of error such as liquid level measurement failure, and at this time the staff can be prompted to perform relevant checks on the target device through certain means. When the absolute value of the deviation reaches 50% or above, the deviation between the material balance liquid level and the actual measured liquid level of the target device in the fixed time period is large, and a production safety accident can occur, and immediate forced measures need to be taken to remove the risk.

[0101] In one embodiment, when -15% < Δ < 15%, the liquid level control is performed on the target device.

[0102] Specifically, as shown in Figure 2 The liquid level control includes:

[0103] When the actual measured liquid level is lower than the set liquid level, the liquid discharge flow rate is reduced to raise the liquid level in the target device;

[0104] When the actual measured liquid level is higher than the set liquid level, the liquid discharge flow rate is increased to lower the liquid level in the target device;

[0105] Preferably, the liquid level control further includes: when the actual measured liquid level is equal to the set liquid level, the current liquid discharge flow rate is maintained to maintain the liquid level in the target device stable.

[0106] It should be noted that the set liquid level is the optimal liquid level of the target device in normal production, and the set liquid level is determined according to the specific type of the target device and the specific production activities in the target device, and therefore the set liquid level is not specifically limited here. In addition, the reduction of the liquid outflow in the liquid level control does not include the case of reducing the liquid outflow to 0 (i.e. cutting off the liquid outflow path), and the increase of the liquid outflow does not include the case of increasing the liquid outflow to the maximum (i.e. fully opening the liquid outflow path).

[0107] In one embodiment, when -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the liquid level alarm is performed on the target device.

[0108] Specifically, as shown in Figure 2 The liquid level alarm generates a liquid level alarm (such as light, buzzer, etc.), and it is easy to understand that after receiving the liquid level alarm, the on-site liquid level measurement is performed on the target device by the staff, and the remote secondary liquid level measurement is calibrated. After calibration, the actual measured liquid level is obtained again, and the material balance liquid level and the deviation between the material balance liquid level and the actual measured liquid level are calculated according to the above formula (1) and formula (2);

[0109] At this time, if -15% < Δ < 15%, the liquid level alarm is ended, and the liquid level control of the target device is performed;

[0110] If -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the liquid level alarm is continued, and the liquid level alarm is handled by the staff. The way to handle the liquid level alarm should include but not limited to on-site liquid level measurement on the target device, remote secondary liquid level measurement calibration;

[0111] If Δ ≤ -50% or Δ ≥ 50%, the liquid level alarm is ended, and the liquid level interlock of the target device is immediately performed.

[0112] In one embodiment, when Δ ≤ -50% or Δ ≥ 50%, the liquid level interlock of the target device is performed.

[0113] Specifically, as shown in Figure 2 When Δ ≤ -50%, the liquid level interlock includes:

[0114] cutting off the liquid outflow path, fully opening the liquid inflow path, and rising the liquid level in the target device until -15% < Δ < 15%.

[0115] Specifically, as shown in Figure 2 When Δ ≥ 50%, the liquid level interlock includes:

[0116] cutting off the liquid feeding path, fully opening the liquid discharging path, lowering the liquid level in the target equipment until -15%<Δ<15%.

[0117] It should be noted that when the target equipment has no liquid feeding or only liquid feeding carried by gas feeding, only the liquid discharging path is cut off when the liquid level interlocking is performed on the target equipment under the condition of Δ≤-50%; only the liquid discharging path is fully opened when the liquid level interlocking is performed on the target equipment under the condition of Δ≥50%.

[0118] Specifically, as shown in Figure 2 , when -15%<Δ<15% after the liquid level interlocking is performed on the target equipment, the liquid level interlocking is ended, and the liquid level control is performed on the target equipment.

[0119] The embodiment of the present application also provides a chemical plant safety interlocking system based on local material balance. The chemical plant safety interlocking system based on local material balance is used to realize the chemical plant safety interlocking method based on local material balance.

[0120] Figure 3 The structure diagram of the chemical plant safety interlocking system based on local material balance provided by the embodiment of the present application is shown. The target equipment is drawn to better illustrate the internal connection relationship of the chemical plant safety interlocking system based on local material balance and how the system realizes the chemical plant safety interlocking method based on local material balance; the target equipment can be a single equipment such as a chemical production process tower, a tank, a reactor, and a compressor; although not drawn in Figure 3 , the target equipment can also be installed with a field primary measurement device and other supporting devices.

[0121] As shown in Figure 3 , the chemical plant safety interlocking system based on local material balance provided by the embodiment of the present application includes:

[0122] The liquid level measurement module 302 is used to measure the liquid level in the target equipment to obtain the actual measurement liquid level.

[0123] The liquid level control module 303 is used to control the liquid level of the target equipment.

[0124] The liquid level alarm module 304 is used to alarm the liquid level of the target equipment.

[0125] The liquid level interlocking module 305 is used to interlock the liquid level of the target equipment to prevent overpressure accidents or overtemperature accidents.

[0126] The selective control module 301 is connected with the liquid level measuring module 302, the liquid level control module 303, the liquid level alarm module 304 and the liquid level interlock module 305 respectively, and is used for calculating the material balance liquid level and the deviation between the material balance liquid level and the actual measured liquid level; and selecting the liquid level control, the liquid level alarm or the liquid level interlock for the target equipment according to the calculation result of the deviation.

[0127] In one embodiment, the system further comprises:

[0128] The liquid-containing outflow regulating valve 306 is used for regulating and providing the liquid outflow flow rate;

[0129] The liquid-containing inflow regulating valve 307 is used for regulating and providing the liquid inflow flow rate;

[0130] The liquid level control module 303 is connected with the liquid level measuring module 302 and the liquid-containing outflow regulating valve 306 respectively, and constitutes a liquid level control loop to realize the liquid level control;

[0131] The liquid level interlock module 305 is connected with the liquid-containing outflow regulating valve 306 and the liquid-containing inflow regulating valve 307 respectively to realize the liquid level interlock;

[0132] The selective control module 301 is connected with the liquid-containing outflow regulating valve 306 and the liquid-containing inflow regulating valve 307 respectively to obtain the liquid outflow flow rate and the liquid inflow flow rate of the target equipment in a fixed time period, and calculate the total liquid inflow amount and the total liquid outflow amount.

[0133] In one embodiment, the liquid level measuring module 302 adopts a liquid level meter capable of realizing remote secondary liquid level measurement, including but not limited to a sink cylinder liquid level meter, a double-flange liquid level meter, a radar liquid level meter or a servo liquid level meter.

[0134] In one embodiment, the liquid level alarm module 304 comprises a liquid level alarm, and generally commercially available liquid level alarms can be used in the application.

[0135] In one embodiment, the liquid-containing outflow regulating valve 306 comprises a liquid outflow regulating valve;

[0136] Preferably, when the gas outflow carries liquid, the liquid-containing outflow regulating valve further comprises a gas outflow regulating valve.

[0137] In one embodiment, the liquid-containing inflow regulating valve 307 comprises a liquid inflow regulating valve;

[0138] Preferably, when the gas inflow carries liquid, the liquid-containing inflow regulating valve further comprises a gas inflow regulating valve.

[0139] In one embodiment, the selective control module has the formula (1) solidified therein to perform the calculation of the material balance level;

[0140]

[0141] wherein, L 物料平衡 % represents the material balance level;

[0142] M i入 represents the total liquid feed amount of the target device in a fixed time period;

[0143] M i出 represents the total liquid discharge amount of the target device in a fixed time period;

[0144] p 液 represents the liquid density in the target device at an average temperature in a fixed time period;

[0145] r represents the internal radius of the target device;

[0146] H 满 represents the full-scale level of the target device.

[0147] In one embodiment, the selective control module also has the formula (2) solidified therein to calculate the deviation between the material balance level and the actual measured level;

[0148] Δ = L% 物料平衡 - L% 实际测量 Formula (2);

[0149] wherein, Δ represents the deviation between the material balance level and the actual measured level;

[0150] L% 物料平衡 represents the material balance level;

[0151] L% 实际测量 represents the actual measured level.

[0152] In one embodiment, the selective control module also has the following criteria solidified therein:

[0153] when -15% < Δ < 15%, the level control is performed on the target device;

[0154] when -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the level alarm is performed on the target device;

[0155] when Δ ≤ -50% or Δ ≥ 50%, the level interlock is performed on the target device.

[0156] In one embodiment, the following criteria are embedded in the liquid level control module:

[0157] When the actual measured liquid level is lower than the set liquid level, decrease the liquid discharge flow rate to raise the liquid level in the target equipment;

[0158] When the actual measured liquid level is higher than the set liquid level, increase the liquid discharge flow rate to lower the liquid level in the target equipment;

[0159] Preferably, the criteria embedded in the liquid level control module further include: when the actual measured liquid level is equal to the set liquid level, maintain the current liquid discharge flow rate to keep the liquid level in the target equipment stable.

[0160] In one embodiment, the following criteria are embedded in the liquid level interlock module:

[0161] When Δ≤-50%, cut off the liquid discharge path, fully open the liquid feed path to raise the liquid level in the target equipment until -15%≤Δ≤15%;

[0162] When Δ≥50%, cut off the liquid feed path, fully open the liquid discharge path to lower the liquid level in the target equipment until -15%≤Δ≤15%.

[0163] Next, two embodiments are described in detail to illustrate how to implement the above-mentioned local material balance-based chemical plant safety interlocking method on the target equipment through the above-mentioned local material balance-based chemical plant safety interlocking system.

[0164] Embodiment 1

[0165] In this embodiment, a propylene absorption tower is taken as the target equipment, and the above-mentioned local material balance-based chemical plant safety interlocking method is implemented on the propylene absorption tower through the above-mentioned local material balance-based chemical plant safety interlocking system to control the liquid level at the bottom of the propylene absorption tower during the start-up process.

[0166] The relevant information of the propylene absorption tower is as follows:

[0167] Liquid feed: ethylbenzene;

[0168] Liquid feed flow rate: Q 1入 (Kg / h);

[0169] Gas feed: propylene-rich catalytic dry gas, which is composed of 4.06%(m) of liquid components containing C3 and 95.94%(m) of non-condensable gas;

[0170] Gas feed flow rate: Q 2入 (Kg / h);

[0171] Bottom liquid outflow: including 0.46%(m) of liquid component of ≥C3 and 99.54%(m) of ethylbenzene;

[0172] Bottom liquid outflow flow rate: Q 1出 (Kg / h);

[0173] Top gas outflow: including 0.08%(m) of liquid component of ≥C3, 0.58%(m) of ethylbenzene and 99.34%(m) of non-condensable gas;

[0174] Top gas outflow flow rate: Q 2出 (Kg / h);

[0175] Full-scale liquid level: H 满 ;

[0176] Fixed time period: selecting the cumulative time t1 from the start of the propylene absorption tower feed in the start-up stage to the current time point;

[0177] Density of liquid at the average temperature in the fixed time period: p 液 , taking 850kg / m 3 .

[0178] By means of the chemical plant safety interlocking system based on local material balance, the chemical plant safety interlocking method based on local material balance is implemented to control the bottom liquid level of the propylene absorption tower in the start-up process, and the specific steps are as follows:

[0179] Step S110. Obtaining the actual measured liquid level of the target equipment.

[0180] Specifically: the selective control module obtains the actual measured liquid level L 实际测量 of the propylene absorption tower from the liquid level measurement module (i.e. remote secondary liquid level measurement device) online, i.e. remote secondary measured liquid level, and records it.

[0181] Step S120. Calculating the material balance liquid level of the target equipment based on material balance.

[0182] Firstly, the selective control module obtains the technical parameters required for calculating the material balance flow rate from the following devices:

[0183] Obtaining the liquid feed flow rate Q 1入 of the propylene absorption tower in the cumulative time t1 from the liquid feed regulating valve (Kg / h);

[0184] Obtaining the gas feed composition and flow rate Q 2入 of the propylene absorption tower in the cumulative time t1 from the gas feed regulating valve (Kg / h);

[0185] The total liquid feed amount M of the propylene absorber in the cumulative time t1 is obtained by the selective control module according to the above technical parameters 1出 (Kg / h);

[0186] The total liquid feed amount M of the propylene absorber in the cumulative time t1 is obtained by the selective control module according to the above technical parameters 2出 (Kg / h);

[0187] Then, the selective control module on-line calculates the total liquid feed amount M of the propylene absorber in the cumulative time t1 according to the above technical parameters i入 , the total liquid feed amount M i出 :

[0188] M i入 = Q 1入 × 100% × t1 + Q 2入 × 4.06% × t1 (i.e. the total liquid feed amount = the liquid feed amount + the gas feed entrained liquid feed amount);

[0189] M i出 = Q 1出 × 100% × t1 + Q 2出 × 0.66% × t1 (i.e. the total liquid feed amount = the liquid feed amount + the gas feed entrained liquid feed amount);

[0190] Finally, the selective control module on-line calculates the material balance liquid level L 物料平衡 % according to the formula (1) solidified therein and records:

[0191]

[0192] In the formula (1), L 物料平衡 % represents the material balance liquid level;

[0193] M i入 represents the total liquid feed amount of the propylene absorber in the cumulative time t1, which is the sum of the liquid feed amount and the gas feed entrained liquid feed amount of the propylene absorber in the cumulative time t1;

[0194] M i出 represents the total liquid feed amount of the propylene absorber in the cumulative time t1, which is the sum of the liquid feed amount and the gas feed entrained liquid feed amount of the propylene absorber in the cumulative time t1;

[0195] ρ 液 represents the liquid density at the average temperature in the cumulative time t1 of the propylene absorber;

[0196] r represents the internal radius of the propylene absorber;

[0197] H 满represents the full scale liquid level of the propylene absorber.

[0198] Step S130. Calculate the deviation between the material balance liquid level and the actual measured liquid level.

[0199] Specifically, the selective control module utilizes the actual measured liquid level and the material balance liquid level calculated above, and according to the formula (2) solidified therein, calculates the deviation Δ online;

[0200] Δ = L% 物料平衡 - L% 实际测量 Formula (2);

[0201] In formula (2), Δ represents the deviation between the material balance liquid level and the actual measured liquid level;

[0202] L 物料平衡 % represents the material balance liquid level;

[0203] L 实际测量 % represents the actual measured liquid level.

[0204] Step S140. Determine the liquid level control, liquid level alarm or liquid level interlock of the target device according to the calculation result of the deviation.

[0205] Specifically, the selective control module selects the action to be taken by the deviation calculated above according to the following standards solidified therein, which includes:

[0206] When -15% < Δ < 15%, the liquid level control module is selected to perform the liquid level control;

[0207] When -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the liquid level alarm module is selected to perform the liquid level alarm;

[0208] When Δ ≤ -50% or Δ ≥ 50%, the liquid level interlock module is selected to perform the liquid level interlock.

[0209] The selective control module first determines whether the calculated deviation satisfies -15% < Δ < 15%. If yes, the selective control module hands over the liquid level of the propylene absorption tower to the liquid level control module for control. The liquid level control module has the following standards solidified therein: "when the actual measured liquid level is lower than the set liquid level, reduce the liquid discharge flow rate to raise the liquid level in the target device; when the actual measured liquid level is higher than the set liquid level, increase the liquid discharge flow rate to lower the liquid level in the target device; and when the actual measured liquid level is equal to the set liquid level, maintain the current liquid discharge flow rate to stabilize the liquid level in the target device". According to the above standards, the liquid level control module first compares the actual measured liquid level and the set liquid level online. When the actual measured liquid level is lower than the set liquid level, the liquid level control module online controls the liquid discharge adjusting valve to reduce the opening degree, alleviates the slight low liquid level in the propylene absorption tower, and maintains the liquid level stable. When the actual measured liquid level is higher than the set liquid level, the liquid level control module online adjusts the liquid discharge adjusting valve to increase the opening degree, alleviates the slight high liquid level in the propylene absorption tower, and maintains the liquid level stable. When the actual measured liquid level is equal to the set liquid level, the liquid level control module online controls the liquid discharge adjusting valve to maintain the current opening degree, and maintains the liquid level in the propylene absorption tower stable.

[0210] When the selective control module determines that the deviation does not satisfy -15% < Δ < 15%, it continues to determine whether the deviation satisfies -50% < Δ ≤ -15% or 50% > Δ ≥ 15%. If yes, the selective control module online controls the liquid level alarm module to alarm (for example, issue a liquid level warning) and reminds the staff to process the alarm. After receiving the liquid level warning, the staff calibrates the on-site primary liquid level measurement and the remotely transmitted secondary liquid level measurement (i.e. the liquid level measurement module). After calibration, the selective control module continues to calculate the deviation online and determines the deviation according to the standards solidified therein, controls the corresponding liquid level regulating operation, until the deviation satisfies -15% < Δ < 15%, and then the selective control module hands over the liquid level of the propylene absorption tower to the liquid level control module for control.

[0211] When the selective control module determines that the deviation does not satisfy -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, it can be determined that the deviation belongs to the case of Δ ≤ -50% or Δ ≥ 50%, which indicates that the actual measurement liquid level error is large, and there is a risk of failure, so the selective control module immediately hands over the liquid level of the propylene absorption tower to the liquid level interlocking module for liquid level interlocking; then, the liquid level interlocking module needs to further judge the deviation according to the standards fixed therein to determine whether to take liquid level interlocking for abnormal liquid level rise or liquid level interlocking for abnormal liquid level drop: for example, the liquid level interlocking module first determines whether the deviation satisfies Δ ≤ -50%, and if yes, immediately controls the liquid discharge regulating valve to be closed, the liquid feed regulating valve to be fully opened, and the gas feed regulating valve to be fully opened, so as to quickly raise the liquid level in the propylene absorption tower and prevent over-temperature accidents caused by liquid air emptying; during the above liquid level interlocking for the case of Δ ≤ -50%, the selective control module also calculates and monitors the change of the deviation online until the deviation satisfies -15% < Δ < 15%, and the selective control module hands over the liquid level of the propylene absorption tower to the liquid level control module; if the liquid level interlocking module determines that the deviation does not satisfy Δ ≤ -50%, it can be determined that the deviation belongs to the case of Δ ≥ 50%, and at this time, the liquid level interlocking module immediately controls the liquid discharge regulating valve to be fully opened, the liquid feed regulating valve to be closed, and the gas feed regulating valve to be closed, so as to quickly lower the liquid level in the propylene absorption tower and prevent instantaneous overpressure explosion accidents caused by the incompressibility of liquid based on continuous temperature rise; during the above liquid level interlocking for the case of Δ ≥ 50%, the selective control module also calculates and monitors the change of the deviation online until the deviation satisfies -15% < Δ < 15%, and the selective control module hands over the liquid level of the propylene absorption tower to the liquid level control module.

[0212] Example 2

[0213] The embodiment of the present application takes a certain reciprocating fresh hydrogen compressor inlet separation tank as a target device, and controls the liquid level of the reciprocating fresh hydrogen compressor inlet separation tank within 5 days before the implementation time of the embodiment through the above-mentioned chemical plant safety interlocking system based on local material balance and the above-mentioned chemical plant safety interlocking method based on local material balance.

[0214] The relevant information of the reciprocating fresh hydrogen compressor inlet separation tank is as follows:

[0215] Liquid feed: none;

[0216] Liquid feed flow rate: Q 1入 (Kg / h), which is 0 here;

[0217] Gas feed: There are two gas feeds, one of which is a three-to-one line, one of which is composed of 0.06%(m) lubricating oil and 99.94%(m) non-condensable gas, and the other of which is composed of 100%(m) non-condensable gas;

[0218] Gas feed flow rate: Q 1入 (Kg / h);

[0219] Tank bottom liquid discharge: composed of 100%(m) lubricating oil;

[0220] Tank bottom liquid discharge flow rate: Q 1出 (Kg / h);

[0221] Tank top gas discharge: composed of 100%(m) non-condensable gas;

[0222] Tank top gas discharge flow rate: Q 2出 (Kg / h);

[0223] Full-scale liquid level: H 满 ;

[0224] Fixed time period: select the cumulative time t2 of 5 days before the implementation time of the embodiment;

[0225] Density of liquid at average temperature in the fixed time period: p 液 , take 900kg / m 3 .

[0226] By means of the chemical plant safety interlocking system based on local material balance, the chemical plant safety interlocking method based on local material balance is implemented to control the liquid level of the reciprocating new hydrogen compressor inlet separation tank in the cumulative time t2 of 5 days before the implementation time of the embodiment, and the specific steps are as follows:

[0227] Step S110. Obtain the actual measured liquid level of the target device.

[0228] Specifically: the selective control module obtains the actual measured liquid level L 实际测量 of the reciprocating new hydrogen compressor inlet separation tank from the liquid level measurement module (i.e. remote secondary liquid level measurement device) online, i.e. remote secondary measured liquid level, and records it.

[0229] Step S120. Calculate the material balance liquid level of the target device based on material balance;

[0230] First, the selective control module obtains the technical parameters required for calculating the material balance liquid level from the following devices:

[0231] From the liquid feed regulating valve, obtain the liquid feed flow rate Q of the reciprocating new hydrogen compressor inlet separation tank in the cumulative time t21入 (Kg / h), as there is no liquid feed to the inlet knockout drum of the reciprocating fresh hydrogen compressor, the value here is 0;

[0232] The gas feed composition and flow rate Q of the inlet knockout drum of the reciprocating fresh hydrogen compressor at the cumulative time t2 are obtained from the gas feed regulating valve 2入 (Kg / h);

[0233] The bottom liquid discharge flow rate Q of the inlet knockout drum of the reciprocating fresh hydrogen compressor at the cumulative time t2 is obtained from the liquid discharge regulating valve 1出 (Kg / h);

[0234] The top gas discharge composition and flow rate Q of the inlet knockout drum of the reciprocating fresh hydrogen compressor at the cumulative time t2 are obtained from the gas discharge regulating valve 2出 (Kg / h);

[0235] Then, the selective control module calculates the total liquid feed amount M of the inlet knockout drum of the reciprocating fresh hydrogen compressor at the cumulative time t2 according to the above technical parameters i入 , the total liquid discharge amount M i出 :

[0236] M i入 = Q 2入 × 0.06% × t2 (as there is no liquid feed, the total liquid feed amount is the liquid entrained by the gas feed);

[0237] M i出 = Q 1出 × 100% × t2 (as the gas discharge does not carry liquid, the total liquid discharge amount is the liquid discharge amount);

[0238] Finally, the selective control module calculates the material balance liquid level L 物料平衡 % according to formula (1) solidified therein and records:

[0239]

[0240] In formula (1), L 物料平衡 % represents the material balance liquid level;

[0241] M i入 represents the total liquid feed amount of the inlet knockout drum of the reciprocating fresh hydrogen compressor at the cumulative time t2, as there is no liquid feed, M i入 is the liquid entrained by the gas feed of the inlet knockout drum of the reciprocating fresh hydrogen compressor at the cumulative time t2;

[0242] M i出represents the total liquid discharge amount of the reciprocating fresh hydrogen compressor inlet knock-out drum within the cumulative time t2, where the gas discharge does not carry liquid, so M i出 is the liquid discharge amount of the reciprocating fresh hydrogen compressor inlet knock-out drum within the cumulative time t2;

[0243] ρ 液 represents the average temperature of the liquid density of the reciprocating fresh hydrogen compressor inlet knock-out drum within the cumulative time t2;

[0244] R represents the internal radius of the reciprocating fresh hydrogen compressor inlet knock-out drum;

[0245] H 满 represents the full-scale liquid level of the reciprocating fresh hydrogen compressor inlet knock-out drum.

[0246] Step S130. Calculate the deviation between the material balance liquid level and the actual measured liquid level.

[0247] Specifically, the selective control module uses the actual measured liquid level and the material balance liquid level calculated above to calculate the deviation Δ online according to the formula (2) fixed therein;

[0248] Δ = L% 物料平衡 -L% 实际测量 Formula (2);

[0249] In formula (2), Δ represents the deviation between the material balance liquid level and the actual measured liquid level;

[0250] L 物料平衡 % represents the material balance liquid level;

[0251] L 实际测量 % represents the actual measured liquid level.

[0252] Step S140. Determine the liquid level control, liquid level alarm or liquid level interlock of the target device according to the calculation result of the deviation.

[0253] Specifically, the selective control module selects the action to be taken according to the deviation calculated above according to the following standards fixed therein, which include:

[0254] When -15% < Δ < 15%, the liquid level control module is selected to perform the liquid level control;

[0255] When -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the liquid level alarm module is selected to perform the liquid level alarm;

[0256] When Δ ≤ -50% or Δ ≥ 50%, the liquid level interlock module is selected to perform the liquid level interlock.

[0257] The selective control module first determines whether the calculated deviation satisfies -15% < Δ < 15%. If yes, the selective control module hands over the liquid level of the reciprocating fresh hydrogen compressor inlet liquid tank to the liquid level control module for control. The liquid level control module has the following standards solidified therein: "when the actual measured liquid level is lower than the set liquid level, reduce the liquid discharge flow rate to raise the liquid level in the target device; when the actual measured liquid level is higher than the set liquid level, increase the liquid discharge flow rate to lower the liquid level in the target device; when the actual measured liquid level is equal to the set liquid level, maintain the current liquid discharge flow rate to maintain the liquid level in the target device stable", according to the above standards, the liquid level control module first compares the actual measured liquid level and the set liquid level online. When the actual measured liquid level is lower than the set liquid level, the liquid level control module online controls the liquid discharge regulating valve to reduce the opening degree, to alleviate the slight low liquid level in the reciprocating fresh hydrogen compressor inlet liquid tank, and to maintain the liquid level stable. When the actual measured liquid level is higher than the set liquid level, the liquid level control module online adjusts the liquid discharge regulating valve to increase the opening degree, to alleviate the slight high liquid level in the reciprocating fresh hydrogen compressor inlet liquid tank, and to maintain the liquid level stable. When the actual measured liquid level is equal to the set liquid level, the liquid level control module online controls the liquid discharge regulating valve to maintain the current opening degree, to maintain the liquid level in the reciprocating fresh hydrogen compressor inlet liquid tank stable.

[0258] When the selective control module determines that the deviation does not satisfy -15% < Δ < 15%, it continues to determine whether the deviation satisfies -50% < Δ ≤ -15% or 50% > Δ ≥ 15%. If yes, the selective control module online controls the liquid level alarm module to alarm (for example, to issue a liquid level alarm), to remind the staff to handle the alarm. After the staff receives the liquid level alarm, the on-site primary liquid level measurement and the remote secondary liquid level measurement (i.e. the liquid level measurement module) are calibrated. After the calibration is completed, the selective control module continues to calculate the deviation online and determines the deviation according to the standards solidified therein, to control the corresponding liquid level regulating operation, until the deviation satisfies -15% < Δ < 15%, and then the selective control module hands over the liquid level of the reciprocating fresh hydrogen compressor inlet liquid tank to the liquid level control module for control.

[0259] When the selective control module determines that the deviation does not satisfy -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, at this time, it can be determined that the deviation belongs to the case of Δ ≤ -50% or Δ ≥ 50%, which indicates that the actual measurement liquid level error is large, and there is a risk of failure, so the selective control module immediately hands over the liquid level of the reciprocating new hydrogen compressor inlet liquid tank to the liquid level interlocking module for liquid level interlocking; then, the liquid level interlocking module needs to further judge the deviation according to the standard solidified therein to determine to take liquid level interlocking for abnormal rise of the liquid level or liquid level interlocking for abnormal drop of the liquid level: for example, the liquid level interlocking module first determines whether the deviation satisfies Δ ≤ -50%, if yes, immediately online controls to close the liquid discharge regulating valve, and quickly raises the liquid level in the reciprocating new hydrogen compressor inlet liquid tank to prevent the rear overpressure accident caused by liquid pressure emptying; in the process of liquid level interlocking in the above-mentioned case of Δ ≤ -50% of abnormal drop of the liquid level, the selective control module also calculates and monitors the change of the deviation online until the deviation satisfies -15% < Δ < 15%, and the selective control module hands over the liquid level of the reciprocating new hydrogen compressor inlet liquid tank to the liquid level control module; if the liquid level interlocking module determines that the deviation does not satisfy Δ ≤ -50%, it can be determined that the deviation belongs to the case of Δ ≥ 50%, at this time, the liquid level interlocking module immediately online controls to fully open the liquid discharge regulating valve, and quickly lowers the liquid level in the reciprocating new hydrogen compressor inlet liquid tank to prevent the occurrence of malignant accidents such as cylinder damage caused by liquid strike into the reciprocating compressor after the liquid fills the buffer tank; in the process of liquid level interlocking in the above-mentioned case of Δ ≥ 50% of abnormal rise of the liquid level, the selective control module also calculates and monitors the change of the deviation online until the deviation satisfies -15% < Δ < 15%, and the selective control module hands over the liquid level of the reciprocating new hydrogen compressor inlet liquid tank to the liquid level control module.

[0260] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0261] In the description of the application, unless otherwise specified and limited, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the application and simplifying the description, and does 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 a limitation on the application. In addition, the terms "first", "second", "third" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0262] In the description of the application, it should be noted that, unless otherwise specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0263] It should be understood that the embodiments disclosed in the present application are not limited to the specific structure, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those skilled in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing the specific embodiments and do not mean limitation.

[0264] The phrase "one embodiment" or "an embodiment" appearing in the specification means that the specific feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the application. Therefore, the phrase "one embodiment" or "an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0265] Although the embodiments disclosed in the present application are as described above, the content described is only for the purpose of facilitating understanding of the embodiments adopted by the present application, and is not intended to limit the present application. Any person skilled in the art of the present application can make any modification and change in the form and details without departing from the spirit and scope of the present application, but the patent protection scope of the present application shall be subject to the scope defined by the appended claims.

Claims

1. A method for local material balance based safety interlocking of chemical plants, characterized in that, The method comprises the following steps: Step 1. obtaining an actual measured liquid level of a target device; Step 2. calculating a material balance liquid level of the target device based on material balance; Step 3. calculating a deviation between the material balance liquid level and the actual measured liquid level; Step 4. controlling, alarming or interlocking the liquid level of the target device according to the calculation result of the deviation.

2. The method of claim 1, wherein, In Step 1, the actual measured liquid level is a remote secondary measured liquid level.

3. The method according to claim 1 or 2, characterized in that, In Step 2, the material balance liquid level is calculated according to formula (1): wherein L% is the percentage of the liquid level of the material in the tank. 物料平衡 represents the material balance level; M i入 representing a total liquid feed amount for the target device over a fixed time period; M i出 representing a total liquid outflow from the target device over a fixed time period; p 液 representing the density of the liquid at an average temperature in the target device over a fixed time period; r represents the internal radius of the target device; H 满 representing a full scale liquid level of the target device.

4. The method of claim 3, wherein, In Step 3, the deviation between the material balance liquid level and the actual measured liquid level is calculated according to formula (2): Δ = L% 物料平衡 - L 实际测量 Equation (2); wherein Δ represents the deviation between the material balance liquid level and the actual measured liquid level; L% 物料平衡 represents the material balance level; L% 实际测量 represents the actual measured liquid level.

5. The method of claim 4, wherein, In Step 4, when -15% < Δ < 15%, the liquid level of the target device is controlled; when -50% < Δ ≤ -15% or 50% > Δ ≥ 15%, the liquid level of the target device is alarmed; when Δ ≤ -50% or Δ ≥ 50%, the liquid level of the target device is interlocked.

6. The method of claim 5, wherein, In Step 4, the liquid level control comprises: when the actual measured liquid level is lower than a set liquid level, reducing the liquid discharge flow to raise the liquid level in the target device; when the actual measured liquid level is higher than the set liquid level, increasing the liquid discharge flow to lower the liquid level in the target device.

7. The method of claim 5, wherein, In Step 4, when Δ ≤ -50%, the liquid level interlocking comprises: cutting off the liquid discharge path, fully opening the liquid feeding path, raising the liquid level in the target device until -15% < Δ < 15%.

8. The method of claim 5, wherein, In Step 4, when Δ ≥ 50%, the liquid level interlocking comprises: cutting off the liquid feeding path, fully opening the liquid discharge path, lowering the liquid level in the target device until -15% < Δ < 15%.

9. The method according to claim 7 or 8, characterized in that, when -15% < Δ < 15%, ending the liquid level interlocking and controlling the liquid level of the target device.

10. A local material balance based safety interlock system for a chemical plant, characterized in that, The system is used to implement the method as claimed in any one of claims 1 to 9, wherein the system comprises: a liquid level measuring module for measuring the liquid level in the target device to obtain the actual measured liquid level; a liquid level control module for controlling the liquid level of the target device; a liquid level alarming module for alarming the liquid level of the target device; a liquid level interlocking module for interlocking the liquid level of the target device to prevent overpressure or overtemperature accidents; a selective control module connected with the liquid level measuring module, the liquid level control module, the liquid level alarming module and the liquid level interlocking module respectively, for calculating the material balance liquid level and the deviation between the material balance liquid level and the actual measured liquid level, and selecting to control, alarm or interlock the liquid level of the target device according to the calculation result of the deviation.

11. The system of claim 10, wherein, The system further comprises: a liquid discharge regulating valve for regulating and providing the liquid discharge flow; a liquid feeding regulating valve for regulating and providing the liquid feeding flow; Preferably, the liquid level control module is connected with the liquid level measuring module and the liquid-containing outflow regulating valve respectively, to form a liquid level control loop, so as to realize the liquid level control. The liquid level interlocking module is connected with the liquid-containing outflow regulating valve and the liquid-containing inflow regulating valve respectively, to realize the liquid level interlocking. The selective control module is connected with the liquid-containing outflow regulating valve and the liquid-containing inflow regulating valve respectively, to obtain the liquid outflow and the liquid inflow of the target device in a fixed time period, and to calculate the total liquid inflow and the total liquid outflow.

12. The system of claim 10 or 11, wherein, The selective control module is provided with formula (1) to calculate the material balance liquid level; and / or The selective control module is also provided with formula (2) to calculate the deviation between the material balance liquid level and the actual measured liquid level.

13. The system of claim 12, wherein, The selective control module is also provided with the following standards: When -15%<Δ<15%, the liquid level control is performed on the target device; When -50%<Δ≤-15% or 50%>Δ≥15%, the liquid level alarm is performed on the target device; When Δ≤-50% or Δ≥50%, the liquid level interlocking is performed on the target device.

14. The system of claim 13, wherein, The liquid level control module is provided with the following standards: When the actual measured liquid level is lower than the set liquid level, the liquid outflow is reduced to raise the liquid level in the target device; When the actual measured liquid level is higher than the set liquid level, the liquid outflow is increased to lower the liquid level in the target device.

15. The system of claim 13 or 14, wherein, The liquid level interlocking module is provided with the following standards: When Δ≤-50%, the liquid outflow path is cut off and the liquid inflow path is fully opened to raise the liquid level in the target device until -15%<Δ<15%; When Δ≥50%, the liquid inflow path is cut off and the liquid outflow path is fully opened to lower the liquid level in the target device until -15%<Δ<15%.

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