Problems in Chemical Industry Safety Production and Accident Prevention Strategies
Introduction
With the rapid development of China's economy, the chemical industry has made remarkable progress. However, safety issues and accidents during the chemical production process have become factors affecting the sustainable development of the industry. This article aims to enhance the emphasis on chemical industry safety production, analyze existing problems and improvement strategies, in order to provide a reference for chemical enterprises to improve their safety production levels.
1. The Importance of Chemical Production Safety
The chemical industry is an important part of the national economy and plays an irreplaceable role in economic construction and social development. However, the chemical production process is extremely complex, involving hazardous factors such as high temperature, high pressure, flammability, and explosiveness. Once a safety accident occurs, it will not only cause serious damage to production equipment and the environment but also endanger the lives of operators and the surrounding areas. Therefore, strengthening chemical production safety is of great significance for ensuring the safety of people's lives and property, maintaining social stability, and promoting sustainable economic development.
Chemical safety accidents can lead to huge economic losses. For example, in 2013, an explosion occurred in a chemical enterprise in Zhangjiagang, Jiangsu Province, resulting in a direct economic loss of up to 370 million yuan. The toxic gas released by the accident polluted an area of 2 km², seriously affecting the health of surrounding residents, and the treatment cost was as high as 120 million yuan. The "8·12" particularly serious fire and explosion accident at Tianjin Port in 2015 caused 165 deaths, 795 people were injured to varying degrees, and the direct economic loss exceeded 6.5 billion yuan, having a significant impact on society.
Therefore, from the perspective of maintaining social stability, strengthening safety production is of great significance. Chemical enterprises must attach great importance to safety production work, establish and improve safety management systems, increase safety investment, actively take effective measures, and strive to reduce the accident rate.
2. Analysis of Existing Problems in Chemical Industry Safety Production
During the safety production process of chemical enterprises, there are various potential hazards. If these hazards develop into accidents, they are likely to lead to serious consequences. Firstly, the pipeline system in chemical enterprises is of paramount importance for safety production. Thousands of pipelines of different materials and diameters operate for a long time in an environment of high temperature, high pressure, and strong corrosion, and are prone to corrosion and leakage. Especially for those old pipelines that have been in operation for more than 10 years, the probability of leakage will increase significantly. For example, in a chemical park in Jinan, a pipeline with a 20-year history used for carbon steel pickling cracked due to corrosion, resulting in the leakage of a large amount of toxic gas. Secondly, the failure of the automated control system is also a common cause of accidents in chemical enterprises. During the chemical reaction process, the monitoring of various parameters is crucial. Once the measurement is inaccurate or the actuator malfunctions, the consequences will be disastrous. For example, under long-term high-temperature conditions, if the calibration of the sensor loses accuracy, it may become a factor triggering an accident. Finally, various safety valves responsible for overpressure protection also have the risk of slow response or failure. Fatigue of the operating spring, blockage of the piston by the medium, etc., are common reasons for valve failure. For example, in 2021, the safety valve of a chemical plant in Laizhou, Shandong Province failed to respond due to severe scaling of the filter element, and eventually, an explosion occurred in the device.
3. Prevention and Control Strategies for Chemical Industry Safety Production Accidents
3.1 Pipeline Anti-corrosion and Maintenance
The main solutions to the problems of pipeline corrosion and leakage are as follows: First, the selection of pipeline materials should fully meet the process requirements. For different media, corrosion-resistant materials with good chemical compatibility should be selected. Inferior pipeline materials should not be chosen solely for economic reasons. For example, for media containing H₂S and CO₂, cast steel or stainless steel pipelines resistant to H₂S corrosion should be selected. Second, strengthen the anti-corrosion design of pipelines. In addition to material selection, pipeline structure optimization, addition of inhibitors, internal coating, etc., should also be considered. For example, high-quality epoxy coal tar paint can be sprayed on the inner wall of high-temperature pipelines to improve their resistance to temperature aging and corrosion. For underground pipelines, a double-layer polyethylene anti-corrosion and thermal insulation layer should be used. Third, establish a regular inspection, anti-corrosion monitoring, and evaluation mechanism for pipelines. For example, conduct a comprehensive risk assessment and anti-corrosion inspection of pipelines once a year, either regularly or irregularly, especially focusing on old pipelines that have been in operation for more than 10 years. The inspection content includes line patrol, thickness testing, coating integrity inspection, etc. Once a problem is found, it should be dealt with in a timely manner. Fourth, strengthen the maintenance of pipelines. Focus on the maintenance of key parts such as valves, flanges, and supports to ensure their sealing performance. Regularly replace the consumables in the pipeline, and increase the maintenance frequency of pipelines with more demanding operating parameters. Fifth, establish a pipeline safety information management system. Use technologies such as GPS and RFID to conduct real-time positioning and monitoring of pipelines, obtain online parameters such as flow, pressure, and temperature, and facilitate the evaluation of pipeline operation status. Sixth, increase investment in pipeline operation, maintenance, and renovation. Reasonably use the pipeline depreciation reserve fund to renovate or replace pipelines to reduce the probability of accidents.
Through the above comprehensive strategies, the leakage risk of chemical pipelines can be effectively reduced, the operation safety and reliability can be improved, and serious accidents can be avoided.
3.2 Real-time Monitoring of Process Parameters
To address the problems of parameter drift and process abnormalities caused by the failure of the automatic control system, the focus is on strengthening the real-time monitoring and early warning of process parameters. Specific measures include: First, increase the online detection points for key process parameters to achieve comprehensive process monitoring, and focus on monitoring key parameters such as the pressure, temperature, and liquid level of the reactor. At the same time, the frequency of manual sampling should be increased, for example, sampling and testing once an hour as an effective supplement to online monitoring. Second, optimize the control system to achieve pre-alarm and complementary control of key parameters. For example, set high-high limit, high limit, and low limit alarm devices to respond quickly when the limit is exceeded, and establish redundant control loops to prevent the expansion of an accident due to the failure of a single system. Establish a dynamic mathematical model and use online data for model calibration to simulate process trends and determine parameter abnormalities. Third, strengthen the maintenance of the control system, regularly calibrate sensors, detect controller signals, etc., and deal with failures quickly if found. In addition, regularly train operators and maintenance personnel to improve their ability to deal with system failures and conduct accident drills. Develop a complete emergency plan and start the response quickly when parameters are abnormal. Finally, increase investment in the research and development of process control technology, and use new technologies such as artificial intelligence to improve the intelligence level of the system.
In summary, the above measures can continuously improve the safe and stable operation level of the process control system and avoid chemical accidents caused by parameter abnormalities.
3.3 Optimization of Safety Valve Performance
To address the problem of the decline in the response performance of safety valves, the following measures are mainly taken for optimization: First, select valves with sensitive action and corrosion resistance. Focus on spring-loaded safety valves, use stainless steel or bimetallic/alloy springs made of special materials to improve the reaction speed. For media prone to scaling, select porcelain-tipped safety valves with good anti-wear performance. Second, establish a regular maintenance system for safety valves. Conduct surface cleaning and action testing at least once a month, and conduct a complete disassembly and inspection once a year to promptly discover and replace problematic components. Key valves can be equipped with online monitoring to obtain real-time opening pressure parameters and determine whether the response time limit is extended. Third, when conducting action performance testing, gradually approach the set value and conduct multiple repeated tests instead of just one test. Keep a complete record of the test results as a basis for judgment. Synchronously monitor the action sensitivity index during the test and calibrate it in a timely manner. Determine a reasonable overpressure setting value according to different media to ensure that the probability of sudden changes in action parameters is very low. Finally, regularly train operators to improve their ability to test, record, and judge the action of safety valves. Any abnormal signs found should be dealt with or replaced in a timely manner, and the behavior of delaying replacement due to cost concerns should be eliminated.
By comprehensively implementing measures such as selecting high-quality safety valves, strengthening maintenance and testing, setting reasonable parameters, and training personnel, the response performance of safety valves can be significantly improved, chemical accidents caused by valve failure can be avoided, and the stable and reliable operation of the process system can be ensured.
4. Case Practice of Problems in Chemical Industry Safety Production and Accident Prevention
In recent years, thermal runaway and over-temperature explosion accidents during the molecular sieve conversion process have occurred frequently, seriously threatening the lives of employees and the property of enterprises. According to incomplete statistics, such accidents account for about 15% of all chemical accidents, and more than 65% of over-temperature explosion accidents are directly related to the failure of the automated system. This case analyzes in detail a typical accident that occurred in a chemical enterprise in Shandong Province, aiming to identify the cause of the accident and propose targeted safety management countermeasures.
The enterprise has 2 sets of molecular sieve devices with an annual output of 100,000 tons of crude phthalodinitrile. The accident occurred in the toluene conversion reactor of the #1 device. The reactor is vertically arranged, with an effective volume of 1500 m³, filled with TM-2 type molecular sieve catalyst. The conversion temperature is 420°C, and the pressure is 0.25 MPa. The top of the reactor is connected to the condensation system, and the bottom is heated by heat transfer oil. Under normal production conditions, the temperature of the reactor will fluctuate by ±10°C. To prevent overheating, in addition to the high-temperature limit alarm of the control system, a TRS-25 type safety relief valve is installed on the side line of the reactor, which will automatically relieve pressure and discharge when the temperature is higher than 450°C to avoid the rapid rise of pressure and temperature.
Before the accident occurred, the detection data showed that the controlled temperature and liquid level of the reactor were basically normal, and the opening pressure of the relief valve conformed to the set value of 1.4 MPa, as shown in Table 1. However, one week before the accident, on-site inspectors found that the temperature fluctuation range displayed by the control system was slightly larger than usual. To find out the cause, the manhole was opened on-site for inspection, and it was found that the top of the catalyst layer of the molecular sieve was severely agglomerated locally. At this time, the temperature at the top of the reactor had reached 435°C, higher than the set high-high temperature alarm value of 420°C, but the control room did not receive an alarm. The maintenance personnel determined that the temperature sensor of the control system had failed, so they turned off the heating of the reactor, and at the same time, turned off the relevant feed and refrigeration to try to cool it down. However, 10 minutes later, an explosion accident occurred in the reactor. The accident investigation and analysis believed that the failure of the temperature sensor was the direct cause of the accident. Under long-term high-temperature conditions, the accuracy of the thermocouple sensor gradually declined, resulting in inaccurate measurement and failure to feed back the real temperature to the control system. At the same time, the carbon deposition layer inside the reactor was agglomerated, causing a sudden increase in local temperature. The combined effect of these two factors ultimately led to severe overheating and triggered an explosion. Insufficient regular calibration of sensors and other safety management deficiencies were also one of the causes of the accident.
Table 1 Comparison of Detection Data before the Accident
| Detection Items |
Data 3 Months before the Accident |
Data 1 Week before the Accident |
| Controlled Temperature/℃ |
418 ±5 |
422 ± 8 |
| Liquid Level/m |
12.5 |
12.3 |
| Flow Rate/(m³/h) |
152 |
148 |
| Opening Pressure of Relief Valve/MPa |
1.45 |
1.41 |
To prevent such accidents, the enterprise has formulated the following safety management countermeasures: (1) Add a main and backup dual-system temperature monitoring. Once the difference exceeds the limit, an automatic alarm will be issued to prompt calibration, reducing the risk of single-point dependence. (2) Increase the maintenance frequency of key instruments and conduct manual comparison and calibration every month. At the same time, establish a database of instrument aging characteristics to evaluate the accuracy decay trend. (3) Optimize the operation procedures and strictly implement the verification system of safety work permits to avoid on-site operators from arbitrarily turning off or bypassing the alarm device. (4) Replace the molecular sieve catalyst once a year to reduce the risk of agglomeration and carbon deposition in the reactor and control the thermal effect. (5) Add an online monitoring system for carbon deposition and thermal runaway on key equipment such as reactors and storage tanks to achieve early warning.
Through in-depth investigation and analysis of this typical accident, the direct cause of the accident and related management deficiencies have been clarified, and targeted improvement measures have been formulated. In particular, the inspection of sensors, operation procedures, etc., have been standardized and optimized, which is conducive to reducing the recurrence of such accidents and provides valuable reference for the safety risk prevention and control of other chemical enterprises.
5. Conclusion
The safety production of chemical enterprises is related to the safety of people's lives and property and also to the sustainable development of the local economy and society. Currently, problems such as pipeline corrosion, automated system failure, and safety valve failure still frequently lead to accidents, and we must remain highly vigilant. In the next step, chemical enterprises need to fully implement the requirements of the new "Work Safety Law" and other relevant laws and regulations, deeply carry out safety risk classification management and control, implement the concept of intrinsic safety, increase the maintenance and detection efforts of pipelines and instruments, establish and improve accident emergency plans, improve the level of intelligence and informatization, and systematically promote various safety production work. We must resolutely prevent major and particularly serious accidents and achieve a continuous improvement in the safety production situation.
Cited from "Chemical Industry Management" (Journal), August 2024, Issue 22. Authors: Zheng Cuicui, Wang Hao, Sha Shuai, Hu Zehua
