Safety interlock control device and method for sulfur distillation condensing system

Abstract

The present application relates to a kind of safety interlock control device and method of sulfur distillation condensing system, belong to sulfur distillation condensing technical field, specifically including distillation kettle, condenser and liquid sulfur storage tank, also include oxygen content monitoring module, nitrogen protection module, temperature-pressure monitoring module, sulfur vapor concentration monitoring module, cooling water regulating module, heating control module, emergency cooling module and interlock control module, the present application is by oxygen content online monitoring and nitrogen protection interlock, distillation kettle temperature-pressure double parameter interlock protection, condenser sulfur vapor concentration detection and the automatic regulation of multiple-parameter collaborative interlock control of cooling water flow, the safety protection of sulfur distillation-condensing system is promoted from single parameter passive monitoring to multiple-parameter active prevention, realizes the safety interlock protection of distillation-condensing whole process.

Description

Technical Field

[0001] This invention relates to a safety interlock control device and method for a sulfur distillation and condensation system, belonging to the field of sulfur distillation and condensation technology. Background Technology

[0002] Sulfur is an important chemical raw material, widely used in chemical, metallurgical, pesticide, rubber, dye, and paper industries. In the coking industry, coke oven gas, after wet desulfurization, produces sulfur paste (crude sulfur) as a byproduct, which requires further purification to meet industrial requirements. Currently, sulfur purification at home and abroad mainly adopts a five-stage process of "melting-distillation," namely, pressure filtration and dehydration → melting sulfur and removing impurities → filtration and refining → distillation and vaporization → condensation and molding. Among them, the distillation and vaporization and condensation and molding processes are the core links of the entire process. The operating temperature of the distillation kettle is as high as 440~450℃, and the sulfur vapor is condensed into liquid sulfur in the condenser. The system contains hazardous media such as high-temperature sulfur vapor, liquid sulfur, and trace amounts of sulfur-containing gases.

[0003] Sulfur vapor mixed with air is explosive within a certain concentration range, and the lower explosive limit of sulfur dust is only 2.3 g / m³. During operation, if the equipment seals fail, allowing air to seep in, or if the system temperature / pressure becomes uncontrolled, a major safety accident such as a fire or explosion can easily occur in a distillation-condensation system. Therefore, implementing safety interlock control for sulfur distillation-condensation systems is crucial.

[0004] Chinese utility model patent CN205731497U discloses a safety protection system for a sulfur pulverizing process. This system fills the pulverizing equipment with liquid nitrogen and achieves explosion-proof protection through temperature and oxygen content interlocking. However, this patent is limited to localized safety protection in the sulfur pulverizing process and does not address the multi-parameter interlocking control of temperature, pressure, oxygen content, and sulfur vapor concentration in the distillation-condensation system. Therefore, it cannot meet the safety protection requirements of the distillation-condensation system under high temperature, high pressure, and multiphase coexistence conditions.

[0005] Chinese invention patent CN114104733A discloses a nitrogen-filled closed conveying system that uses nitrogen protection to achieve closed conveying in the sulfur conveying process. However, this patent only focuses on nitrogen protection in the conveying process and does not cover the safety interlock control of core distillation-condensation processes such as temperature-pressure dual-parameter interlock protection of the distillation vessel, sulfur vapor concentration detection in the condenser, and automatic adjustment of cooling water.

[0006] While existing distillation safety operating procedures (such as GB 30871-2022) set forth basic requirements for temperature and pressure monitoring during distillation operations, they lack a systematic multi-parameter interlocking control scheme for oxygen content, nitrogen protection, temperature and pressure, and sulfur vapor concentration in sulfur distillation-condensation systems.

[0007] In summary, the existing technology has the following main problems: 1) Blind spots in single-parameter monitoring: Existing technologies mainly rely on monitoring single parameters such as temperature or pressure, which cannot cover multi-dimensional safety risks such as abnormal oxygen content infiltration and sulfur vapor leakage. When a sealing failure occurs in the distillation-condensation system, leading to air infiltration, temperature and pressure monitoring alone cannot provide a timely response.

[0008] 2) The lag of passive protection: Most existing safety measures are passive protection modes of "alarm after exceeding the limit → manual handling", which have a slow response speed. In working conditions where sulfur vapor is extremely explosive and accidents develop rapidly, manual intervention is often too late to prevent the accident from escalating.

[0009] 3) Lack of interlock control for distillation-condensation system: Existing explosion-proof interlock technology is mainly applied to the crushing process and conveying process. There is no systematic safety interlock control scheme for the core process of distillation-condensation, which involves the coexistence of gas-liquid multiphase states, large temperature gradient and strong pressure coupling between the distillation kettle and the condenser.

[0010] 4) Insufficient coordinated control of condensation efficiency and safety: Existing technology does not monitor the concentration of sulfur vapor at the condenser outlet online. When the condensation efficiency decreases and the uncondensed sulfur vapor exceeds the standard, there is a lack of an interlocking mechanism to automatically adjust the cooling water flow, which poses a risk of sulfur vapor leakage. Summary of the Invention

[0011] To address the technical problems existing in the prior art, this invention provides a safety interlock control device and method for a sulfur distillation and condensation system. Through multi-parameter coordinated interlock control, including online monitoring of oxygen content and nitrogen protection interlock, dual-parameter interlock protection of distillation kettle temperature and pressure, and detection of sulfur vapor concentration in the condenser and automatic adjustment of cooling water flow, the safety protection of the sulfur distillation-condensation system is upgraded from passive monitoring of a single parameter to active prevention of multiple parameters, achieving safety interlock protection for the entire distillation-condensation process.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is a safety interlock control device for a sulfur distillation and condensation system, including a distillation kettle, a condenser and a liquid sulfur storage tank, and also including an oxygen content monitoring module, a nitrogen protection module, a temperature-pressure monitoring module, a sulfur vapor concentration monitoring module, a cooling water regulation module, a heating control module, an emergency cooling module and an interlock control module; The oxygen content monitoring module includes online oxygen content monitoring probes installed in the gas phase space at the top of the distillation kettle, the gas phase outlet of the condenser, and the gas phase space at the top of the liquid sulfur storage tank, as well as an oxygen content transmitter connected to the online oxygen content monitoring probes. The nitrogen protection module includes nitrogen pipelines connected to the nitrogen storage tank, distillation kettle, condenser and liquid sulfur storage tank respectively, as well as electric regulating valves, flow meters and nitrogen booster devices installed on each nitrogen pipeline. The temperature-pressure monitoring module includes a temperature sensor and a pressure sensor installed inside the distillation vessel, as well as a temperature transmitter and a pressure transmitter connected to the temperature sensor and the pressure sensor. The sulfur vapor concentration monitoring module includes an online sulfur vapor concentration detector installed in the vapor phase outlet pipe of the condenser, and a concentration transmitter connected to the online sulfur vapor concentration detector. The cooling water regulating module includes an electric regulating valve and a flow meter installed on the condenser cooling water pipeline; The heating control module includes a power supply circuit for the heating source of the distillation kettle and a cut-off switch installed on the power supply circuit; The emergency cooling module includes an emergency cooling water pipeline connected to the jacket of the distillation kettle and a solenoid valve installed on the pipeline. The interlocking control module is electrically connected to the oxygen content monitoring module, nitrogen protection module, temperature-pressure monitoring module, sulfur vapor concentration monitoring module, cooling water regulation module, heating control module, and emergency cooling module, respectively, and is used to receive each monitoring parameter and output control commands to each actuator according to the preset interlocking logic.

[0013] Preferably, it also includes a human-machine interaction module, which includes an operator station and an engineer station, used to display real-time monitoring data, interlock status and alarm information, and to receive reset commands from the operator.

[0014] Preferably, the online oxygen content monitoring probe includes a zirconia-type online oxygen content monitoring probe or an electrochemical-type online oxygen content monitoring probe.

[0015] A method for a safety interlock control device for a sulfur distillation and condensation system includes the following steps. S1. Online monitoring of oxygen content and interlocking control for nitrogen protection: The alarm thresholds for oxygen content are graded, with the first-level alarm threshold set at 1.0%, the second-level alarm threshold at 2.0%, and the third-level interlocking threshold at 3.0% based on volume fraction. The system collects data in real time to determine whether the oxygen content at the monitoring points exceeds the set thresholds, and controls the system to replenish nitrogen and cut off the heating source according to the alarm level. S2. Temperature and pressure dual-parameter interlock protection of the distillation vessel: the normal operating temperature range of the distillation vessel is set to 440-450℃, and the normal operating pressure range is 0.02-0.05MPa; the temperature and pressure data inside the distillation vessel are collected in real time, and temperature and pressure are adjusted according to the alarm range of the temperature and pressure data. S3. Detection of sulfur vapor concentration in condenser and automatic adjustment and control of cooling water flow rate, real-time detection of uncondensed sulfur vapor concentration at condenser outlet; setting the first-level warning value of sulfur vapor concentration at condenser outlet to 50mg / m³, the second-level alarm value to 100mg / m³, and the third-level interlock value to 200mg / m³. When the sulfur vapor concentration reaches the first-level warning value, the cooling water flow rate will be automatically increased by 5%-10%. When the sulfur vapor concentration reaches the level 2 alarm value, the cooling water flow rate will be automatically increased by 15%-25%, and an audible and visual alarm will be issued. When the sulfur vapor concentration reaches the three-level interlock value, the interlock will increase the cooling water flow rate to the maximum rated flow rate and reduce the feed rate of the distillation vessel by 30%. If the sulfur vapor concentration does not drop below 100 mg / m³ within 60 seconds, the interlock will cut off the heating source of the distillation vessel. S4, Interlocking Priority and System Reset The interlocking priority order is set as follows: oxygen content interlocking > pressure interlocking > temperature interlocking > sulfur vapor concentration interlocking. When multiple interlocking conditions are triggered simultaneously, they are executed in order of priority, and high-priority interlocking actions are not overridden by low-priority interlocking actions. After the interlocking action is executed, the system automatically enters the interlocking locked state, and all interlocking equipment remains in a safe position. The system reset operation can only be performed after the fault has been manually confirmed to be eliminated. When resetting the system, proceed in the following order: nitrogen protection confirmation, system sealing test, oxygen content retest, temperature / pressure parameter retest, and gradual resumption of heating. Each step can only be executed after it has been confirmed to be qualified.

[0016] Preferably, in step S1, when the oxygen content at any monitoring point reaches the first-level early warning threshold, the control system issues an early warning signal and records the log. When the oxygen content at any monitoring point reaches the secondary alarm threshold, the nitrogen supply valve of the corresponding equipment is automatically activated to supply nitrogen to the equipment at a nitrogen pressure of 0.3-0.5MPa for inerting protection. At the same time, the control system issues an audible and visual alarm. When the oxygen content at any monitoring point reaches the three-level interlock threshold, the interlock cuts off the heating source of the distillation kettle, and the entire system starts the nitrogen protection mode, simultaneously charging nitrogen into the distillation kettle, condenser and liquid sulfur storage tank. The nitrogen charging flow rate is calculated at 1.5-2.0 times the system volume / minute until the system oxygen content drops below 1.0%.

[0017] Preferably, in step S2, when the temperature of the distillation vessel exceeds 460°C, a first-level temperature alarm is issued, and the heating power is automatically reduced to 50% of the rated power. When the temperature of the distillation vessel exceeds 470℃, a temperature interlock alarm is issued, the heating source is automatically cut off, and the emergency cooling system is activated to introduce cooling water into the jacket of the distillation vessel. The cooling water flow rate is determined according to the heat balance calculation of the distillation vessel, and the initial flow rate is not less than 15m³ / h. When the pressure in the distillation vessel exceeds 0.08 MPa, a level one pressure alarm is issued, and the system exhaust passage is checked for obstruction. When the pressure in the distillation vessel exceeds 0.12 MPa, a pressure interlock alarm is issued, the heating source is automatically cut off, the emergency cooling system is activated, and the safety relief valve of the distillation vessel is opened. The opening pressure of the relief valve is set to 0.15 MPa. When the temperature and pressure of the distillation vessel exceed the limits simultaneously, the pressure interlock protection is activated first, and the temperature-pressure joint emergency response is initiated at the same time: the heating source is cut off, emergency cooling is initiated, the relief valve is opened, and the nitrogen protection of the entire system is initiated. Each action is completed within 5 seconds.

[0018] Preferably, in step S3, when the monitoring of sulfur vapor concentration at the condenser outlet is also adaptively optimized with condensation efficiency, the condensation efficiency η is calculated in real time based on the sulfur vapor temperature and flow rate at the condenser inlet and the sulfur vapor concentration at the outlet. η = (C_in - C_out) / C_in × 100%, where C_in is the sulfur vapor concentration at the condenser inlet and C_out is the sulfur vapor concentration at the condenser outlet; The target condensation efficiency η is set to 98%. When η is lower than 95%, the cooling water flow rate adjustment ΔQ is automatically calculated using a proportional-integral control algorithm. ΔQ=K_p×(95%-η)+K_i×∫(95%-η)dt, Where K_p is the proportionality coefficient set to 2.0 m³ / h·% -1 K_i is the integral coefficient set to 0.5 m³ / h·% -1 ·min -1 ; When the condensation efficiency remains below 90% for more than 10 minutes, a three-level interlock of sulfur vapor concentration is triggered.

[0019] Compared with the prior art, the present invention has the following technical effects: 1. This invention adopts multi-parameter collaborative interlocking to eliminate blind spots in safety monitoring: Through online monitoring and collaborative interlocking of four key safety parameters—oxygen content, temperature, pressure, and sulfur vapor concentration—multi-dimensional safety protection for the entire process of sulfur distillation-condensation system is achieved, eliminating the blind spot problem of single-parameter monitoring in the prior art.

[0020] 2. This invention adopts proactive prevention to improve safety response speed: It upgrades safety protection from the passive mode of "over-limit alarm → manual handling" to the proactive prevention mode of "over-limit early warning → automatic interlocking → graded response". The interlocking action response time is less than 5 seconds, which is about 60 times faster than the traditional manual intervention response time (usually 3 to 5 minutes).

[0021] 3. This invention adopts a system that covers the entire distillation-condensation process: It complements the existing explosion-proof patent for the crushing process and the nitrogen-filling patent for the conveying process, filling the technical gap in the safety interlock control of the core process of sulfur distillation-condensation. It can be linked with the safety systems of crushing, conveying and other processes to achieve safety coverage of the entire sulfur production process.

[0022] 4. This invention adopts interlock priority management to avoid action conflicts: a clear interlock priority order is set (oxygen content > pressure > temperature > sulfur vapor concentration), which effectively avoids the problem of interlock action conflicts when multiple parameters exceed the limit at the same time, and ensures that the most dangerous working conditions (excessive oxygen content → explosion risk) receive the highest priority protection.

[0023] 5. This invention adopts a synergistic optimization of condensation efficiency and safety: by interlocking the detection of sulfur vapor concentration at the condenser outlet with the automatic adjustment of cooling water flow, the risk of sulfur vapor leakage is prevented while ensuring condensation efficiency, thus achieving synergistic optimization of production efficiency and safety. Attached Figure Description

[0024] Figure 1 This is a block diagram of the present invention.

[0025] Figure 2 This is a flowchart of the interlocking control process of the present invention. Detailed Implementation

[0026] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0027] like Figure 1 and Figure 2 As shown, a safety interlock control device for a sulfur distillation and condensation system includes a distillation kettle, a condenser, and a liquid sulfur storage tank. It also includes an oxygen content monitoring module, a nitrogen protection module, a temperature-pressure monitoring module, a sulfur vapor concentration monitoring module, a cooling water regulation module, a heating control module, a human-machine interaction module, an emergency cooling module, and an interlock control module.

[0028] The oxygen content monitoring module includes online oxygen content monitoring probes installed in the gas phase space at the top of the distillation kettle, the gas phase outlet of the condenser, and the gas phase space at the top of the liquid sulfur storage tank, as well as an oxygen content transmitter connected to the online oxygen content monitoring probes. The online oxygen content monitoring probes can be either zirconia-type or electrochemical-type, with redundant configuration, a measurement range of 0-25% (volume fraction), an accuracy of ±0.1%, and a response time of less than 3 seconds. The nitrogen protection module includes nitrogen pipelines connected to the nitrogen storage tank, distillation kettle, condenser and liquid sulfur storage tank respectively, as well as electric regulating valves, flow meters and nitrogen booster devices installed on each nitrogen pipeline; The temperature-pressure monitoring module includes a temperature sensor and a pressure sensor installed inside the distillation vessel, as well as a temperature transmitter and a pressure transmitter connected to the temperature sensor and the pressure sensor; the temperature sensor is a K-type thermocouple temperature sensor, arranged axially inside the distillation vessel, and the median value is taken as the temperature signal for control; the pressure transmitter is a capacitive pressure transmitter, installed at the top of the distillation vessel, and the high value is taken as the pressure signal for control. The sulfur vapor concentration monitoring module includes an online sulfur vapor concentration detector installed in the gas phase outlet pipe of the condenser, and a concentration transmitter connected to the online sulfur vapor concentration detector. The online sulfur vapor concentration detector is an ultraviolet absorption type online sulfur vapor concentration detector. The sampling port is set at 1.5 times the pipe diameter from the outlet flange in the straight pipe section of the condenser outlet. The sampling gas path is equipped with electric heat tracing and insulation to maintain the temperature above 150℃. The cooling water regulating module includes an electric regulating valve and a flow meter installed on the condenser cooling water pipeline. The electric regulating valve adopts an equal percentage flow characteristic, and the pipeline adopts a dual-path parallel design, including a main path regulating valve and a bypass regulating valve. During normal operation, the main path is regulated, and during the three-level interlock, the main path is fully open and the bypass is activated.

[0029] The heating control module includes a power supply circuit for the heating source of the distillation vessel and a cut-off switch installed on the power supply circuit; The emergency cooling module includes an emergency cooling water pipeline connected to the jacket of the distillation vessel and a solenoid valve installed on the pipeline; The human-machine interface module includes an operator station and an engineer station, which are used to display real-time monitoring data, interlock status and alarm information, and receive reset commands from the operator; The interlocking control module is electrically connected to the oxygen content monitoring module, nitrogen protection module, temperature-pressure monitoring module, sulfur vapor concentration monitoring module, cooling water regulation module, heating control module, human-machine interaction module, and emergency cooling module, respectively. It is used to receive each monitoring parameter and output control commands to each actuator according to the preset interlocking logic.

[0030] The following steps are included when implementing safety interlock control: S1. Online monitoring of oxygen content and interlocking control for nitrogen protection: The alarm thresholds for oxygen content are graded, with the first-level alarm threshold set at 1.0%, the second-level alarm threshold at 2.0%, and the third-level interlocking threshold at 3.0% based on volume fraction. The system collects data in real time to determine whether the oxygen content at the monitoring points exceeds the set thresholds, and controls the system to replenish nitrogen and cut off the heating source according to the alarm level. When the oxygen content at any monitoring point reaches the first-level warning threshold, the control system issues a warning signal and records the log. When the oxygen content at any monitoring point reaches the secondary alarm threshold, the nitrogen replenishment valve of the corresponding equipment is automatically activated, and nitrogen is injected into the equipment at a nitrogen pressure of 0.3-0.5MPa for inerting protection. The replenishment flow rate is calculated at 0.5 times the equipment volume per minute. If the oxygen content drops below 1.0% after replenishment for 5 minutes, the replenishment valve is automatically closed, and the control system issues an audible and visual alarm. When the oxygen content at any monitoring point reaches the three-level interlock threshold, the interlock cuts off the heating source of the distillation kettle, and the entire system starts the nitrogen protection mode, simultaneously charging nitrogen into the distillation kettle, condenser and liquid sulfur storage tank. The nitrogen charging flow rate is calculated at 1.5-2.0 times the system volume / minute until the system oxygen content drops below 1.0%.

[0031] S2. Temperature and pressure dual-parameter interlock protection of the distillation vessel: the normal operating temperature range of the distillation vessel is set to 440-450℃, and the normal operating pressure range is 0.02-0.05MPa; the temperature and pressure data inside the distillation vessel are collected in real time, and temperature and pressure are adjusted according to the alarm range of the temperature and pressure data. When the temperature of the distillation vessel exceeds 460℃, a first-level temperature alarm will be issued, and the heating power will be automatically reduced to 50% of the rated power. When the temperature of the distillation vessel exceeds 470℃, a temperature interlock alarm is issued, the heating source is automatically cut off, and the emergency cooling system is activated to introduce cooling water into the jacket of the distillation vessel. The cooling water flow rate is determined according to the heat balance calculation of the distillation vessel, and the initial flow rate is not less than 15m³ / h. When the pressure in the distillation vessel exceeds 0.08 MPa, a level one pressure alarm is issued, and the system exhaust passage is checked for obstruction. When the pressure in the distillation vessel exceeds 0.12 MPa, a pressure interlock alarm is issued, the heating source is automatically cut off, the emergency cooling system is activated, and the safety relief valve of the distillation vessel is opened. The opening pressure of the relief valve is set to 0.15 MPa. When the temperature and pressure of the distillation vessel exceed the limits simultaneously, the pressure interlock protection is activated first, and the temperature-pressure joint emergency response is initiated at the same time: the heating source is cut off, emergency cooling is initiated, the relief valve is opened, and the nitrogen protection of the entire system is initiated. Each action is completed within 5 seconds.

[0032] S3. Detection of sulfur vapor concentration in condenser and automatic adjustment and control of cooling water flow rate, real-time detection of uncondensed sulfur vapor concentration at condenser outlet; setting the first-level warning value of sulfur vapor concentration at condenser outlet to 50mg / m³, the second-level alarm value to 100mg / m³, and the third-level interlock value to 200mg / m³. When the sulfur vapor concentration reaches the first-level warning value, the cooling water flow rate will be automatically increased by 5%-10%. When the sulfur vapor concentration reaches the level 2 alarm value, the cooling water flow rate will be automatically increased by 15%-25%, and an audible and visual alarm will be issued. When the sulfur vapor concentration reaches the three-level interlock value, the interlock will increase the cooling water flow rate to the maximum rated flow rate and reduce the feed rate of the distillation vessel by 30%. If the sulfur vapor concentration does not drop below 100 mg / m³ within 60 seconds, the interlock will cut off the heating source of the distillation vessel.

[0033] When monitoring the sulfur vapor concentration at the condenser outlet is also adaptively optimized with respect to condensation efficiency, the condensation efficiency η is calculated in real time based on the sulfur vapor temperature and flow rate at the condenser inlet and the sulfur vapor concentration at the outlet. η = (C_in - C_out) / C_in × 100%, where C_in is the sulfur vapor concentration at the condenser inlet and C_out is the sulfur vapor concentration at the condenser outlet; The target condensation efficiency η is set to 98%. When η is lower than 95%, the cooling water flow rate adjustment ΔQ is automatically calculated using a proportional-integral control algorithm. ΔQ=K_p×(95%-η)+K_i×∫(95%-η)dt, Where K_p is the proportionality coefficient set to 2.0 m³ / h·% -1 K_i is the integral coefficient set to 0.5 m³ / h·% -1 ·min -1 ; When the condensation efficiency remains below 90% for more than 10 minutes, a three-level interlock of sulfur vapor concentration is triggered.

[0034] S4, Interlocking Priority and System Reset The interlocking priority order is set as follows: oxygen content interlocking > pressure interlocking > temperature interlocking > sulfur vapor concentration interlocking. When multiple interlocking conditions are triggered simultaneously, they are executed in order of priority, and high-priority interlocking actions are not overridden by low-priority interlocking actions. After the interlocking action is executed, the system automatically enters the interlocking locked state, and all interlocking equipment remains in a safe position. The system reset operation can only be performed after the fault has been manually confirmed to be eliminated. When resetting the system, proceed in the following order: nitrogen protection confirmation, system sealing test, oxygen content retest, temperature / pressure parameter retest, and gradual resumption of heating. Each step can only be executed after it has been confirmed to be qualified.

[0035] The first step is nitrogen protection confirmation, confirming that the oxygen content at all monitoring points in the system is below 1.0% and remains stable for more than 5 minutes; the second step is system sealing test, the pressure drop within 10 minutes should not exceed 0.005MPa to be considered a qualified seal; the third step is oxygen content retest, continuously monitoring for 15 minutes to confirm that the oxygen content at all monitoring points is below 1.0%; the fourth step is temperature / pressure parameter retest, confirming that the temperature of the distillation vessel is below 100℃ and the pressure drops to atmospheric pressure; the fifth step is gradual recovery of heating, gradually recovering in a gradient of 10%→30%→50%→75%→100% of rated power, maintaining each gradient for 10 minutes.

[0036] The following analysis will focus on practical application examples: Example 1: Safety interlock control of sulfur distillation-condensation system for sulfur paste production in coking plants 1. System Configuration This embodiment takes a sulfur production project from sulfur paste in a coking plant as an example. The distillation-condensation system includes: a distillation kettle (effective volume 5m³, design temperature 500℃, design pressure 0.3MPa), a condenser (heat exchange area 30m², cooling water inlet temperature 25~32℃), and a liquid sulfur storage tank (effective volume 3m³, insulation temperature 140~150℃).

[0037] 2. Detailed Implementation of Online Oxygen Content Monitoring and Nitrogen Protection Interlock Control (1) Monitoring probe arrangement: Two zirconia oxygen content online monitoring probes (redundant configuration) are installed in the gas phase space at the top of the distillation kettle, with a measurement range of 0~25% (volume fraction), accuracy of ±0.1%, and response time of less than 3 seconds; one electrochemical oxygen content probe is installed in the gas phase outlet pipe of the condenser; and one electrochemical oxygen content probe is installed in the gas phase space at the top of the liquid sulfur storage tank.

[0038] (2) Nitrogen protection pipeline design: The nitrogen storage tank has a capacity of 10 m³, a nitrogen purity of ≥99.99%, and an outlet pressure of 0.6 MPa. Independent nitrogen supply pipelines are installed for the distillation kettle, condenser, and liquid sulfur storage tank, each equipped with a DN25 electric regulating valve and a vortex flow meter. The nitrogen supply pipeline for the distillation kettle is also equipped with a DN50 rapid charging pipeline and an emergency shut-off valve for rapid nitrogen charging during three-level interlocking.

[0039] (3) Interlocking control timing: ① When the oxygen content reaches 1.0%, the interlock control module sends an "oxygen content warning" signal to the human-machine interface module. The operator station pops up a warning dialog box. The system automatically records the warning time, monitoring point number and oxygen content value. It does not execute automatic interlock actions. The operator decides whether to manually start nitrogen replenishment.

[0040] ② When the oxygen content reaches 2.0%: The interlock control module sends an "oxygen content alarm" signal and automatically opens the corresponding DN25 nitrogen replenishment valve. The replenishment flow rate is set to 0.5 times the equipment volume per minute (e.g., for a 5m³ distillation vessel, the replenishment flow rate is 2.5m³ / min), and the replenishment pressure is 0.3MPa. The system's audible and visual alarm is activated. After replenishment continues for 5 minutes, if the oxygen content drops below 1.0%, the replenishment valve is automatically closed; if the oxygen content remains above 1.0%, replenishment continues and the system is upgraded to a three-level interlock.

[0041] ③ When the oxygen content reaches 3.0%: the interlock control module sends an "oxygen content interlock" signal and executes the following sequence of actions (all actions are completed within 5 seconds): a) Disconnect the power supply circuit to the heating source of the distillation vessel (action time ≤ 0.5 seconds); b) Simultaneously open the DN50 rapid charging valve of the distillation kettle, the condenser and the DN25 gas supply valve of the liquid sulfur storage tank. The rapid nitrogen charging flow rate is calculated as 1.5 times the total system volume (distillation kettle + condenser + liquid sulfur storage tank + connecting pipe, approximately 12 m³) per minute, i.e., 18 m³ / min. c) Close the feed valve of the distillation kettle and the product outlet valve of the condenser to isolate the distillation-condensation system; d) The interlock control module continuously monitors the oxygen content at each point. When the oxygen content at all monitoring points drops below 1.0% and remains stable for 3 minutes, it automatically switches to the maintenance gas supply mode (gas supply flow rate drops to 0.2 times the system volume / minute) and enters the interlock lockout state.

[0042] 3. Detailed Implementation of Temperature-Pressure Dual-Parameter Interlock Protection for Distillation Kettle (1) Temperature monitoring: Three K-type thermocouple temperature sensors (top, middle and bottom points) are arranged axially inside the distillation vessel, with a measurement range of 0~600℃ and an accuracy of ±1℃. The median value of the three thermocouples is used as the temperature signal for control, and an alarm is triggered separately when the reading of any thermocouple exceeds the limit.

[0043] (2) Pressure monitoring: Two capacitive pressure transmitters (redundant configuration) are installed on the top of the distillation vessel, with a measurement range of 0~0.5MPa and an accuracy of ±0.075%. The higher value of the two transmitters is used as the control pressure signal.

[0044] (3) Interlocking control timing: ① Temperature Level 1 Alarm (460℃): The interlock control module automatically reduces the heating power of the distillation kettle to 50% of the rated power and issues a "temperature too high" alarm. After the heating power is reduced, if the temperature drops below 450℃ within 10 minutes, it will automatically resume full power operation; if the temperature continues to rise to 470℃, the Level 2 interlock will be triggered.

[0045] ② Temperature Level 2 Interlock (470℃): The interlock control module executes the following sequence of actions (all actions are completed within 5 seconds): a) Disconnect the power supply circuit to the heating source of the distillation vessel; b) Open the emergency cooling water solenoid valve of the distillation vessel jacket. The initial cooling water flow rate is set to 15 m³ / h (according to the heat balance calculation of the distillation vessel, a 5 m³ volume distillation vessel under full load conditions requires about 12~15 m³ / h of cooling water to achieve effective cooling). c) Issue an audible and visual alarm for "temperature interlock", and the operator station will display an interlock confirmation interface; d) Simultaneously activate oxygen content monitoring (abnormal temperature may cause seal failure), and if the oxygen content exceeds 2.0%, trigger nitrogen protection interlock simultaneously.

[0046] ③ Pressure Level 1 Alarm (0.08MPa): The interlock control module issues a "pressure too high" alarm and automatically checks whether the exhaust channel of the sulfur vapor pipeline from the distillation kettle to the condenser is unobstructed (judged by the pressure difference between the two ends of the pipeline). If the pressure difference exceeds 0.02MPa, it indicates a risk of pipeline blockage.

[0047] ④ Pressure Level 2 Interlock (0.12MPa): The interlock control module executes the following sequence of actions (all actions are completed within 5 seconds): a) Disconnect the power supply circuit to the heating source of the distillation vessel; b) Open the emergency cooling water solenoid valve of the distillation vessel jacket, with a cooling water flow rate of 15 m³ / h; c) Open the safety relief valve of the distillation vessel to release the exhaust gas into the tail gas treatment system. The valve opening setting is 0.15 MPa. d) Activate nitrogen protection for the entire system (follow the three-level interlock procedure in S1); e) Issue an audible and visual alarm for "pressure interlock".

[0048] ⑤ When both temperature and pressure exceed limits: Prioritize the execution of the pressure two-level interlock action sequence, and simultaneously increase the emergency cooling water flow rate to 20 m³ / h (33% higher than when only one limit is exceeded) to accelerate cooling and pressure reduction.

[0049] 4. Detailed Implementation of Condenser Sulfur Vapor Concentration Detection and Automatic Cooling Water Flow Regulation (1) Sulfur vapor concentration detection: An online sulfur vapor concentration detector with ultraviolet absorption is installed on the gas phase outlet pipeline of the condenser. The measurement range is 0~500mg / m³, the accuracy is ±5%, and the response time is less than 10 seconds. The sampling port of the detector is set in the straight pipe section of the condenser outlet, 1.5 times the pipe diameter away from the condenser outlet flange. The sampling gas path is equipped with electric heat tracing and insulation (the temperature is maintained above 150℃) to prevent sulfur vapor from condensing and blocking in the sampling pipeline.

[0050] (2) Cooling water regulating pipeline: A DN80 electric regulating valve (equal percentage flow characteristic) is installed on the condenser cooling water pipeline. The cooling water flow rate under normal operating conditions is 10 m³ / h, and the maximum rated flow rate is 25 m³ / h. An electromagnetic flow meter is also installed on the pipeline with a measurement accuracy of ±0.5%.

[0051] (3) Interlocking control timing: ① Sulfur vapor concentration reaches 50mg / m³ (Level 1 warning): The interlock control module automatically increases the cooling water flow rate by 5%~10% (i.e., 10.5~11m³ / h) and simultaneously issues a "decreased condensation efficiency" warning signal. If the sulfur vapor concentration drops back below 50mg / m³ within 5 minutes, the original cooling water flow rate is automatically restored.

[0052] ② When the sulfur vapor concentration reaches 100 mg / m³ (Level 2 alarm): The interlock control module automatically increases the cooling water flow rate by 15%~25% (i.e., 11.5~12.5 m³ / h) and issues an audible and visual alarm for "Sulfur vapor exceeding the standard". At the same time, the cooling water inlet temperature detection is activated. If the inlet temperature exceeds 35℃, an auxiliary alarm for "Cooling water temperature too high" will be issued.

[0053] ③ When the sulfur vapor concentration reaches 200 mg / m³ (three-level interlock): the interlock control module executes the following sequence of actions: a) Increase the cooling water flow rate to the maximum rated flow rate of 25 m³ / h; b) Automatically reduce the feed rate of liquid sulfur in the distillation kettle by 30% (achieved by adjusting the frequency of the feed pump inverter); c) Start a 60-second countdown monitoring. If the sulfur vapor concentration drops below 100 mg / m³ within 60 seconds, maintain the current cooling water flow and issue an "interlock relief" signal. If the sulfur vapor concentration does not drop below 100 mg / m³ within 60 seconds, the heating source of the distillation vessel will be cut off through the interlock, and the entire system will enter the safe shutdown process. d) Issue an audible and visual alarm for "condensation interlock".

[0054] 5. Interlocking priority management and system reset (1) Interlocking priority: Oxygen content interlocking (highest priority) > Pressure interlocking > Temperature interlocking > Sulfur vapor concentration interlocking (lowest priority). When multiple interlocking conditions are triggered simultaneously, the interlocking control module generates an interlocking action sequence according to priority order. The execution result of high-priority interlocking is not overwritten by the action of low-priority interlocking.

[0055] (2) Interlocking and Reset: After any interlocking action is triggered, the system automatically enters the interlocking state, and all interlocking actuators (heating source cut-off switch, nitrogen replenishment valve, emergency cooling water valve, etc.) remain in a safe position and are not affected by manual operation by the operator. The system reset must be performed in the following five steps: Step 1: Nitrogen protection confirmation – Confirm that the oxygen content at all monitoring points in the system is below 1.0% and has remained stable for more than 5 minutes; Step 2: System sealing test - Close the nitrogen supply valve and monitor the system pressure change rate. If the pressure drop does not exceed 0.005MPa within 10 minutes, it is considered to be a qualified seal. Step 3: Oxygen content retest – After the airtightness test is passed, continuously monitor the oxygen content for 15 minutes to confirm that the oxygen content at each monitoring point is below 1.0%; Step 4: Temperature / Pressure Parameter Recheck – Confirm that the temperature of the distillation vessel is below 100℃ and the pressure has dropped to atmospheric pressure; Step 5: Gradually restore heating – restore heating gradually in gradients of 10% → 30% → 50% → 75% → 100% of rated power, maintaining each power gradient for 10 minutes. Only after confirming that the temperature, pressure, and oxygen content are all within the normal range can the next gradient be increased.

[0056] Example 2: Safety Interlock Control of Distillation-Condensation System in Large-Scale Sulfur Recovery Unit This embodiment uses the distillation-condensation system of a sulfur recovery unit in a petrochemical enterprise as an example. The effective volume of the distillation kettle is 20 m³, the heat exchange area of ​​the condenser is 120 m², and the effective volume of the liquid sulfur storage tank is 15 m³. Compared with Embodiment 1, the main differences are as follows: (1) The oxygen content monitoring probes are increased to 4 at the top of the distillation vessel (redundancy is improved), and 2 zirconia probes and 2 electrochemical probes are arranged in a cross pattern to improve the reliability of detection; (2) The nitrogen protection module is equipped with a liquid nitrogen emergency storage tank (5m³). When the oxygen content of the system reaches the 3.0% interlock threshold, in addition to starting the conventional nitrogen replenishment, the liquid nitrogen evaporation system is started simultaneously to achieve faster system inerting. (3) The emergency cooling water flow rate of the distillation kettle is determined to be 40 m³ / h based on the heat balance calculation of large equipment; (4) The condenser cooling water pipeline adopts a dual-circuit parallel design (DN150 main line + DN100 bypass). During normal operation, the main line is regulated, and during the three-level interlock, the main line is fully open and the bypass is opened. The maximum cooling water flow rate can reach 80m³ / h.

[0057] The remaining interlocking control logic is the same as in Example 1.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A safety interlock control method for a sulfur distillation and condensation system, characterized in that: It includes a distillation kettle, a condenser, and a liquid sulfur storage tank, as well as an oxygen content monitoring module, a nitrogen protection module, a temperature-pressure monitoring module, a sulfur vapor concentration monitoring module, a cooling water regulation module, a heating control module, an emergency cooling module, and an interlock control module; The oxygen content monitoring module includes online oxygen content monitoring probes installed in the gas phase space at the top of the distillation kettle, the gas phase outlet of the condenser, and the gas phase space at the top of the liquid sulfur storage tank, as well as an oxygen content transmitter connected to the online oxygen content monitoring probes. The nitrogen protection module includes nitrogen pipelines connected to the nitrogen storage tank, distillation kettle, condenser and liquid sulfur storage tank respectively, as well as electric regulating valves, flow meters and nitrogen booster devices installed on each nitrogen pipeline. The temperature-pressure monitoring module includes a temperature sensor and a pressure sensor installed inside the distillation vessel, as well as a temperature transmitter and a pressure transmitter connected to the temperature sensor and the pressure sensor. The sulfur vapor concentration monitoring module includes an online sulfur vapor concentration detector installed in the vapor phase outlet pipe of the condenser, and a concentration transmitter connected to the online sulfur vapor concentration detector. The cooling water regulating module includes an electric regulating valve and a flow meter installed on the condenser cooling water pipeline; The heating control module includes a power supply circuit for the heating source of the distillation kettle and a cut-off switch installed on the power supply circuit; The emergency cooling module includes an emergency cooling water pipeline connected to the jacket of the distillation kettle and a solenoid valve installed on the pipeline. The interlocking control module is electrically connected to the oxygen content monitoring module, nitrogen protection module, temperature-pressure monitoring module, sulfur vapor concentration monitoring module, cooling water regulation module, heating control module and emergency cooling module respectively, and is used to receive each monitoring parameter and output control commands to each actuator according to the preset interlocking logic; The operation steps are as follows: S1. Online monitoring of oxygen content and interlocking control for nitrogen protection: The alarm thresholds for oxygen content are graded, with the first-level alarm threshold set at 1.0%, the second-level alarm threshold at 2.0%, and the third-level interlocking threshold at 3.0% based on volume fraction. The system collects data in real time to determine whether the oxygen content at the monitoring points exceeds the set thresholds, and controls the system to replenish nitrogen and cut off the heating source according to the alarm level. S2. Temperature and pressure dual-parameter interlock protection of the distillation vessel: the normal operating temperature range of the distillation vessel is set to 440-450℃, and the normal operating pressure range is 0.02-0.05MPa; the temperature and pressure data inside the distillation vessel are collected in real time, and temperature and pressure are adjusted according to the alarm range of the temperature and pressure data. S3. Detection of sulfur vapor concentration in condenser and automatic adjustment and control of cooling water flow rate, real-time detection of uncondensed sulfur vapor concentration at condenser outlet; setting the first-level warning value of sulfur vapor concentration at condenser outlet to 50mg / m³, the second-level alarm value to 100mg / m³, and the third-level interlock value to 200mg / m³. When the sulfur vapor concentration reaches the first-level warning value, the cooling water flow rate will be automatically increased by 5%-10%. When the sulfur vapor concentration reaches the level 2 alarm value, the cooling water flow rate will be automatically increased by 15%-25%, and an audible and visual alarm will be issued. When the sulfur vapor concentration reaches the three-level interlock value, the interlock will increase the cooling water flow rate to the maximum rated flow rate and reduce the feed rate of the distillation vessel by 30%. If the sulfur vapor concentration does not drop below 100 mg / m³ within 60 seconds, the interlock will cut off the heating source of the distillation vessel. S4, Interlocking Priority and System Reset The interlocking priority order is set as follows: oxygen content interlocking > pressure interlocking > temperature interlocking > sulfur vapor concentration interlocking. When multiple interlocking conditions are triggered simultaneously, they are executed in order of priority, and high-priority interlocking actions are not overridden by low-priority interlocking actions. After the interlocking action is executed, the system automatically enters the interlocking locked state, and all interlocking equipment remains in a safe position. The system reset operation can only be performed after the fault has been manually confirmed to be eliminated. When resetting the system, proceed in the following order: nitrogen protection confirmation, system sealing test, oxygen content retest, temperature / pressure parameter retest, and gradual resumption of heating. Each step can only be executed after it has been confirmed to be qualified.

2. The safety interlock control method for a sulfur distillation and condensation system according to claim 1, characterized in that: It also includes a human-machine interaction module, which includes an operator station and an engineer station, used to display real-time monitoring data, interlock status and alarm information, and to receive reset commands from the operator.

3. The safety interlock control method for a sulfur distillation and condensation system according to claim 1, characterized in that: The online oxygen content monitoring probe includes a zirconia-type online oxygen content monitoring probe or an electrochemical-type online oxygen content monitoring probe.

4. The safety interlock control method for a sulfur distillation and condensation system according to claim 1, characterized in that: In step S1, when the oxygen content at any monitoring point reaches the first-level early warning threshold, the control system issues an early warning signal and records the log. When the oxygen content at any monitoring point reaches the secondary alarm threshold, the nitrogen supply valve of the corresponding equipment is automatically activated to supply nitrogen to the equipment at a nitrogen pressure of 0.3-0.5MPa for inerting protection. At the same time, the control system issues an audible and visual alarm. When the oxygen content at any monitoring point reaches the three-level interlock threshold, the interlock cuts off the heating source of the distillation kettle, and the entire system starts the nitrogen protection mode, simultaneously charging nitrogen into the distillation kettle, condenser and liquid sulfur storage tank. The nitrogen charging flow rate is calculated at 1.5-2.0 times the system volume / minute until the system oxygen content drops below 1.0%.

5. The safety interlock control method for a sulfur distillation and condensation system according to claim 1, characterized in that: In step S2, when the temperature of the distillation vessel exceeds 460°C, a first-level temperature alarm is issued, and the heating power is automatically reduced to 50% of the rated power.

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