Issues regarding the layout of air separation units

At around 10 a.m. on April 14, 2005, the Maintenance Department of a company in Anhui Province organized a team of 8 people (the chief dispatcher, the head of the Maintenance Department, the person in charge of instruments, and production maintenance workers) to enter the pressure regulation station to carry out the replacement of pneumatic control valves. The operator first closed the valves at both ends of the pipeline to cut off the gas supply, then loosened the flange bolts of the pneumatic control valve. While loosening the bolts, it was found that the inlet valve was not properly closed and there was still gas leakage; the inlet valve was then closed using an F-shaped wrench. After the air leakage was resolved, the technician removed the faulty pneumatic control valve and replaced it with a new one that had been degreased. The power cables for the instruments as well as the pipelines connecting to the control cylinder of the pneumatic control valve were installed, and a multimeter was used to make measurements. Once the above tasks were completed, Zhang, the supervisor in charge of the oxygen production process, received an approval order from the on-site shift manager. He went to the back of the explosion-proof wall and opened the pneumatic pressure regulator for about 2–3 seconds; shortly after that, a loud explosion was heard, and fierce flames erupted from the other side of the explosion-proof wall. Zhang tried to turn around and close the valve, but was prevented by the intense fire; he then ran quickly to the oxygen production workshop, calling for help to put out the fire while also shutting down the oxygen compressors in order to cut off the supply of oxygen at the scene of the accident and prevent the fire from spreading. Later, Zhang remembered that the oxygen came from an oxygen tank, so he climbed up to the tank and closed the valve, thereby cutting off the source of oxygen at the accident site. By then, the fire was finally brought under control. 　　Afterward, an investigation of the explosion site revealed that the oxygen pipelines inside the pressure regulation station had been completely burned out, while there were no signs of combustion on the inner surface of the bypass pipelines, indicating that these pipelines had been blown open. There were 8 workers at the accident site, 7 of whom died (3 died on the spot, and 4 died despite efforts to save them in the hospital). At the time of the accident, another person was in the nitrogen room of the pressure regulation station; a firewall separated this room from the oxygen room, and that person was not injured. 　　Upon investigation, it was found that the pneumatic control valve of that pressure regulation pipeline frequently suffered from internal leakage of its valve core; at least 3 pneumatic control valves had been replaced since it came online. Furthermore, the pressure pipelines at this plant were not subjected to installation supervision inspections. In response, the local special equipment supervision authorities issued safety inspection orders requiring that the use of these pipelines be halted and that they be restored to their original state. The city mayor in charge also attempted to coordinate matters on several occasions, but for various reasons, the corrective actions required to address these safety hazards were not properly carried out. Cause of the accident: Following the explosion of the oxygen pipeline on April 14, and considering the exothermic nature and rapidity of the explosion, the accident investigation team determined that it was a chemical explosion. Furthermore, due to phenomena such as the formation of jets when pressurized flammable substances leak and being ignited at the leakage site, resulting in instantaneous jet fires, investigators believe that combustion, explosions, and jet fires were the main characteristics of this accident. Jet fires, in turn, were a key factor contributing to numerous casualties as well as the melting of pipes and valves. 　　The three basic elements of combustion and explosion are an oxidizer, a combustible substance, and ignition energy. Among the 3 basic elements, the absence of any one of them will not cause combustion or explosion. 　　1. Oxidizing agents Oxygen is a gas with relatively reactive chemical properties; it provides oxygen in oxidation reactions and is therefore a commonly used oxidizer. 　　In production environments, standard chemical plant maintenance practices require that the oxygen level be maintained between 17% and 23%. It is necessary to prevent both low oxygen levels and high oxygen levels, as either condition can lead to accidents. This accident met all the conditions of an oxygen-enriched environment. The pneumatic control valve is removed, and the remaining air inside the pipe is released into the atmosphere ； During the maintenance process, it was found that the valve was not fully closed, allowing oxygen to escape ； During the oxygen leak test, there was no evidence indicating that the flange seal of the pneumatic control valve was reliable; therefore, there is a possibility of oxygen leakage ； Oxygen must be present inside the pipeline during maintenance at the time of the explosion. It can be seen that during maintenance, environments and conditions with an oxygen-rich atmosphere can occur. By checking the shift records from the pipeline maintenance and pressure testing, it was found that before the accident, the oxygen tanks and delivery pipelines contained oxygen at a pressure of 2.5 MPa, with a concentration of 99.0%–99.5%. During the pressure testing that day, the pressure in the oxygen pipelines ranged from a minimum of 1.3 MPa to a maximum of 1.8 MPa ； The air flow velocity is greater than 15 m/s. 　　2. Combustible materials In an environment with high oxygen concentrations, the human body, clothing, and metals can all act as reducing agents, undergoing redox reactions with oxygen. In other words, the human body, clothing, and metal become combustible in an oxygen-rich environment. 　　Although the replaced pneumatic control valves were degreased, they were not fully degreased in accordance with relevant safety regulations. Upon disassembling and inspecting the pneumatic control valves from the same batch, it was found that there was a large amount of grease inside them. During the degreasing process, the workers simply used cotton yarn dipped in a small amount of carbon tetrachloride to wipe the external surfaces that could be reached; there was no disassembly, soaking, or cleaning. Of the 500 ml of cleaning agent provided, only 75 ml was used. The degreasing method and the amount of degreasing agent used were not sufficient to ensure complete degreasing, so it is possible that grease remains. Additionally, the worker’s tools, clothing, and gloves may also be contaminated with oil (grease). Therefore, in the working environment, there are conditions for flammable substances that can cause explosions. 　　3. Ignition energy 　　Based on the accident scene, there are various conditions that can serve as ignition energy for explosions and fires: static electricity generated by the workers’ clothing made of synthetic fibers ； Use non-explosion-proof tools ； Use non-explosion-proof lighting ； Under certain pressure and temperature conditions, pure oxygen can react with fats and oils; the heat released as a result of this reaction can cause the fats and oils to catch fire on their own ； The operator opens the intake valve to perform an oxygen leak test; the temperature rises due to the adiabatic compression of the gas ； When operating the valve, opening it too quickly can result in high-speed air currents that cause friction with the pipe fittings and the valve, thereby generating static electricity; all of these factors can serve as energy sources that trigger combustion and explosions. 　　4. Analysis and inference of the cause of the accident 　　All three basic factors for combustion and explosion were present, making it difficult to avoid such an incident. Based on the analysis of information obtained after the accident, it is inferred that the accident occurred because, under conditions of pure oxygen inside the pipeline or an oxygen-rich environment outside the pipeline due to a leak, the presence of an ignition source triggered intense chemical reactions (combustion, explosion). The explosion caused a large amount of oxygen to be released, and the heat generated by these reactions led to the melting of the steel pipes, intensifying the combustion further and resulting in the destruction of the entire pipeline as well as casualties. 　　It can be concluded that incomplete degreasing of the newly replaced pneumatic control valve was not the direct cause of the accident, while the illegal use of oxygen for leak testing was another important factor that led to the explosion. Preventive measures: 1. Oxygen production and delivery pipelines must undergo safety performance inspections in accordance with the ***Regulations on the Supervision of Special Equipment; they can only be put into use after passing such inspections. The purpose of inspection is to check the manufacturing and installation quality of special equipment, in order to prevent equipment that does not meet safety requirements from being put into use. Special equipment that does not meet safety technical specifications must be stopped from use. During the safety supervision of special equipment, inspections must be carried out in strict accordance with the requirements of safety technical specifications. Equipment that does not meet the safety standards for use should be stopped from being used immediately, and enterprises should be urged to make corrections. 　　2. For enterprises involved in chemical production, oxygen manufacturing, and transportation, it is necessary to urge them to earnestly assume their primary responsibility for the safe management of special equipment. The phenomenon of some enterprise leaders having a weak awareness of their responsibilities regarding safe production and being complacent must be corrected promptly. By improving various management systems related to special equipment in enterprises, it is possible to ensure that safety responsibilities are fulfilled, with clear accountability at each level and strict oversight, thereby reducing the occurrence of accidents and eliminating illegal operations. Any issues identified should be addressed immediately to effectively remove potential hazards. Equipment with unresolved hazards or lacking adequate safety measures must be shut down until such time as they are rectified. 　　3. For chemical and oxygen production equipment designated as key monitoring targets, the production and usage units must appoint specific persons in charge and implement specific monitoring measures ； Strengthen inspections of key areas, develop corresponding early-warning and emergency response plans, and conduct drills from time to time to improve the ability to handle emergencies. The special equipment safety supervision agencies and the industry authorities in charge should strengthen supervision and inspection. 　　4. The departments responsible for the safety supervision of special equipment should maintain active contact, exchange information, and communicate with safety supervision agencies and industry regulatory bodies in order to enhance their joint enforcement capabilities. For chemical and oxygen production enterprises that fall under overlapping regulatory frameworks, it is necessary to eliminate any gaps in the safety supervision of special equipment, thereby preventing major accidents. 　　5. In dealing with accidents involving special equipment, it is necessary to focus not only on post-incident accountability but also on preventive measures beforehand. In most production safety accidents, criminal and administrative liability is imposed on those responsible only after an accident occurs or serious consequences arise; moreover, insufficient penalties are imposed on those who fail to fulfill their safety management duties as required by law, fail to carry out their safety responsibilities, or violate the regulations regarding the safety management of special equipment, thereby creating hazards or threatening public safety. This fosters a mentality of recklessness among some enterprises, organizations, and individuals, who are inclined to carry out operations in a risky manner or give orders that violate regulations, leading to frequent serious accidents involving special equipment. Therefore, it is essential to hold them accountable after such incidents, with the aim of serving as a deterrent to prevent similar actions in the future. “\"Light penalties and heavy profits\" have led some leaders to prioritize the economy over safety. The countermeasures include frequent inspections, constant supervision, ensuring implementation of measures, thorough rectification efforts, and strict law enforcement. Only in this way can preventive actions against accidents involving special equipment be effectively carried out, thereby reducing the occurrence of such accidents.

The relevant standards involved include: GB 50489-2009 Code for General Layout and Transportation Design of Chemical Enterprises, HGT 20546-2009 Regulations for the Layout Design of Chemical Plant Equipment, GB50029-2003 Code for Design of Compressed Air Stations, GB 50030-1991 Code for Design of Oxygen Stations, GB 50160-2008 Code for Fire Protection Design of Petrochemical Enterprises, and GB 50016-2006 Code for Fire Protection Design of Buildings

Could someone share the layout diagram for reference? Please share the diagram showing filtration, compression, pre-cooling, purification, separation, and storage

For the newly installed air separation units in the park, which are affected by the existing units of various companies, if they cannot meet the requirements specified in the oxygen station regulations regarding the wind direction at the minimum frequency, is it feasible to move the intake ports to an area with cleaner air? Are there any reference cases for investment and operation? Thank you!