Large-capacity centrifuges are widely used in pharmaceutical applications and are the main equipment for solid-liquid separation in current pharmaceutical raw materials and other production processes. The internal environment in which the flammable solvent is present during the operation of the centrifuge has potential unsafe factors that form a combustion explosion. This potential insecurity factor can lead to an explosion if it encounters the right conditions. Green Prickly Ash,Pricklyash Peel Green Prickly Ash,Green Peppercorns Prickly Ash,Green Chinese Prickly Ash Sichuan Liuhang Agriculture Co.Ltd , https://www.lhagriculture.com
1. Causes of Combustion and Explosion Accidents Combustibles, oxidants and ignition sources are called three elements of combustion. An explosion is a violent combustion. An explosion is a phenomenon in which energy (physical, chemical, or nuclear) is rapidly released or rapidly converted into mechanical work and other energy. The conditions for the explosion are: temperature, pressure, and concentration of explosives. The explosion accidents caused by the centrifuge are mainly the explosion of combustible gas mixture in the confined space, that is, the explosion of explosive substances (chemical explosion).
The explosion process of explosive substances has the following three characteristics: that is, the reaction process is exothermic, the process speed is extremely fast and can be automatically propagated, and a large amount of gas products are generated in the process. These three conditions are necessary for any chemical reaction to become an explosive reaction, and the three are interrelated and indispensable.
2, the basic principle of explosion-proof The basic principle of explosion-proof is to analyze the characteristics of the explosion process, in order to take appropriate preventive measures. Prevent the emergence of the first process, limit the development of the second process, and protect against the hazards of the third process. The basic principles are as follows:
(1) Prevent the formation of explosive mixtures;
(2) Strictly control the source of fire;
(3) cut off the route of the explosion;
(4) Attenuate damage to personnel, equipment and buildings caused by explosion pressure and shock waves;
(5) Detection of alarms.
3. Safety technical measures for explosion protection of centrifuge
3.1 Prevent the formation of flammable and explosive system For the centrifugal flammable and explosive materials, the centrifuge can be filled with flammable gas. Once the centrifuge generates sparks due to static electricity or other reasons, the centrifuge will explode. Therefore, when centrifuging a solution containing flammable and explosive materials, ensure that the centrifuge is sealed and explosion-proof. When using inert gas or other gas protection, such as filling the inside of the centrifuge with nitrogen to replace the air inside, the oxygen concentration is maintained within a safe range. To control the concentration of oxygen, oxygen concentration monitoring is generally used to strictly control the concentration of oxygen.
First of all, it must be ensured that the nitrogen source is stable and operates in strict accordance with the operating procedures. The two accidents mentioned above are due to the operator opening the blanking valve and turning on the centrifuge without the protection of nitrogen. The solution enters the high-speed rotating centrifugal. The machine generates a static spark to detonate the toluene mixture, causing the centrifuge to explode. When the nitrogen pressure is insufficient or the nitrogen supply system fails, an alarm is issued through the alarm device to automatically stop; when the centrifuge is started, the centrifuge system must be replaced with nitrogen gas. When the concentration of oxygen is detected to be 1% to 2% When the centrifuge is in the liquid, the floating liquid and the washing liquid must be protected by nitrogen to prevent the air from entering the centrifuge at the end of the liquid inlet or with the vortex mist of the liquid; when the power is off, the nitrogen is purged. The work can still be carried out normally, and the normally closed solenoid valve is required to ensure that the nitrogen line valve is always open when the power is cut off.
In particular, the company should set up corresponding supporting facilities, such as online oxygen detection system and interlocking protection device, in the process of inerting protection for the centrifuge when the original centrifuge is modified. Otherwise, it is easy to be protected by inertia. The gas source is unstable, mismanagement, misuse, and the system is sealed, which causes a more serious centrifuge explosion accident.
3.2 Elimination and control of ignition sources The main causes of fire and explosion accidents are open flame, high temperature surface, friction and impact, adiabatic compression, chemical reaction heat, electrical spark, static spark, lightning strike and so on. Therefore, in places with fire and explosion hazards, adequate attention should be paid to these sources of fire and strict control measures should be taken.
In the design of the centrifuge, there should be sufficient safety space for the moving parts to eliminate the possible mechanical friction and impact. At the same time, the centrifugal system must have measures to eliminate static electricity. For brake devices, mechanical friction brakes shall not be used, generally in the form of electrical energy braking. In addition, for the drive belt, an anti-static belt is used to eliminate or reduce the possibility of static electricity generation. When purchasing centrifuges, enterprises should propose more precise manufacturing requirements for the configuration of centrifuges, such as: configuration of explosion-proof motors, explosion-proof buttons on site, explosion-proof solenoid valves, explosion-proof proximity switches, explosion-proof barriers, anti-static belts, electrostatic grounding, Inverter control, energy consumption braking, nitrogen protection, on-line detection of oxygen content, etc. However, not all applications with explosion-proof requirements should be configured, and should be properly configured according to the actual process and working environment.
The process of transporting inflammable and explosive materials shall also be carried out in strict accordance with the relevant requirements of GB12158-2006 General Guidelines for Preventing Electrostatic Accidents. In particular, attention should be paid to the antistatic treatment of the discharge tube from the reaction vessel to the centrifuge.
In addition, in the danger zone of explosion, use copper, alloy or other tools that do not produce sparks, use explosion-proof electronic clocks, etc.; smoke is not allowed on the operating site, fireworks are strictly prohibited, and mobile phones are strictly forbidden. The work site should be regularly tested for lightning protection and anti-static to ensure safety.
3.3 Isolation block to prevent accident spread The two accidents mentioned above are caused by the explosion of the centrifuge, which ignited the solution containing flammable and explosive materials released from the bottom valve of the reactor, and quickly spread to the entire workshop. Due to the excessive storage of dangerous chemicals in the workshop, the explosion and combustion accidents caused the indoor equipment to collapse and be destroyed, causing the accident to expand.
First, the centrifugal separation zone should be placed in a separate compartment, separated from other production areas by a fire-resistant solid wall, and should ensure sufficient pressure relief area, and the ventilation of the centrifugal separation zone should be strengthened. The number of on-site operators should be strictly controlled in the centrifugal operation area.
Secondly, enterprises should strictly control the storage of hazardous chemicals in the workplace. Conditional enterprises try to use pipeline transportation. If the job site needs to use the barrel material to directly feed, a special intermediate material storage area should be drawn out. The material storage area and the production operation area should be separated by a fireproof solid wall. Try to use the solvent area without material stacking. It is strictly forbidden to store dangerous chemicals in the centrifuged work area. In particular, it should be noted that the centrifugal residual liquid should not be stored in the centrifuge room.
3.4 Improve the centrifugal process, select the new centrifuge to set the online oxygen detection device and the pressure transmission sensor in the design of the centrifuge nitrogen protection system, detect the oxygen concentration in the centrifuge cavity during the operation, and implement quantitative control to control The oxygen content is within safe limits (ie, the oxygen concentration in the machine is outside the explosion limit of flammable and explosive media). When the centrifugal equipment fails and the personnel misuses to form a dangerous state, the automatic alarm, the interlocking protection device and the safety device are activated to realize a series of operations such as safe discharge of the accident until the shutdown, so as to ensure the safety of the system.
3.5 Effective monitoring and timely processing The centrifugal operation area is strictly in accordance with the requirements of GB 50493-2009 “Design Specification for Petrochemical Gases and Toxic Gas Detection and Alarmâ€, and sets flammable gas and toxic gas detection and alarm devices, and interlocks with forced ventilation facilities. If the centrifuge leaks, the detection alarm can issue an alarm within the set safe concentration range, so that early detection, early elimination, early control, and accident prevention and spread can be prevented.
4. Conclusions Factors affecting safety in the process of safety production Some aspects of unsafe behavior and unsafe conditions of people, while educating and guiding employees to improve their safety awareness, we should put the unsafe state of the object in the first place. Bit. There are many aspects to the influencing factors of human unsafe behavior. At the same time, people's safety awareness is strong, and they may make such mistakes. If we control the unsafe state of the object, we can improve the safety of the system.
The centrifugal separation process in the production of chemical and pharmaceutical industries generally involves inflammable and explosive solvents. The safety of the centrifuge during operation has become the primary requirement for selection. The application of new technologies such as inert gas protection of the centrifuge, online oxygen detection technology, automatic differential pressure transmitter, and special interlock protection make the system safer and the product quality more assured. In particular, the application of intelligent automatic control technology will greatly improve the safety and automation of traditional centrifugal separation equipment, ensuring the safety of the system. More centrifuge information view