What is the cause analysis of the fire and explosion accident of the reaction vessel?

1) The reaction is out of control, causing fire and explosion

Many chemical reactions such as nitration, sulfonation, oxidation, chlorination, polymerization and other reactions are reactions with large exothermic heat. When the reaction is carried out in the reaction vessel, if the normal reaction process is out of control, the reaction heat will accumulate, the temperature of the reaction system will increase, and the reaction speed will increase. , the container ruptures, and the high-pressure material is ejected from the rupture. Due to the increase of temperature, the reaction materials may also decompose and burn, resulting in uncontrolled fire and explosion accidents. The reasons for the runaway reaction include: the heat of reaction could not be removed in time, the reactants could not be dispersed evenly, and the operation was wrong. Improper selection of the coolant, the heat exchange equipment cannot export the excessive heat in the reactor in time, the heat transfer effect is deteriorated due to the scaling of the wall, the failure of the coolant supply equipment, the blockage of the heat exchange system, etc., may cause the reaction heat to fail. Can be removed in time. Power failure, stirring system failure, damage to the blades, insufficient rotation speed, improper blade form, insufficient material pulverization, etc., will cause the reaction material to be unevenly dispersed in the vessel, resulting in poor heat dissipation or excessive local reaction, which may cause danger. Violation of production operation rules, overfilling of materials, excessive addition of catalysts, ratio of raw materials, improper feeding sequence and time, incorrect switching of coolant valves, excessive heating speed, wrong reading of temperature and pressure, faulty measuring instruments, etc. Abnormal chemical reaction of materials. Many chemical reactions also lead to violent side reactions, overreactions due to the presence of dangerous impurities in the materials, and even make the reactions unusually accelerated and lead to runaway reactions.

2) An explosive mixture is formed in the reaction vessel

The raw material mixture of some gaseous reactions is explosive because the raw material ratio is within the explosion limit range. For example: propylene and air in the ammoxidation reaction of propylene account for 6.16% and 677% of the total volume of raw materials, respectively, and the concentration of propylene is already within the explosion limit (its explosion limit is 2% to 11%); Cai and air in the production of benzene intoxication The weight ratio of naphthalene vapor is about 1:9, and the volume concentration of naphthalene vapor in the air is 2.25% (Cai vapor explosion limit is 0.88%-5.9%). Incomplete replacement or incomplete replacement of flammable gas or flammable liquid vapor in the reaction vessel is also an important reason for the formation of explosive mixtures.

3) The reaction vessel is not tightly sealed, and material leakage causes combustion and explosion

The reaction container is not tightly sealed, the material is flushed out, and it burns and explodes in case of an open flame.

4) The reaction vessel exploded due to design and manufacturing defects

The unreasonable design of the reaction vessel, discontinuous structure and shape, improper welding seam layout, etc. cause stress concentration; improper selection of equipment materials, unsatisfactory welding quality and improper heat treatment during the manufacture of the vessel reduce the toughness of the material; the vessel shell is corroded by corrosive media, Decreased strength, etc., may cause the container to explode during production.

5) The high-pressure material in the reaction vessel enters the low-pressure system

Atmospheric or low pressure containers and storage cabinets connected to the reaction container exploded due to the entry of high-pressure materials in the reaction container.

6) Danger of water vapor or water leaking into the reaction vessel

The reaction vessel heated by water vapor or cooled by water, if water vapor or cooling water leaks into the vessel, the material in the vessel will release heat when exposed to water, and the temperature and pressure will rise sharply, resulting in material flushing and fire. For example, in the nitrification reaction, when there is water in the nitrifying agent, it will cause a large amount of decomposition and evaporation, which will strongly corrode the equipment and cause an explosion. When water penetrates into the nitrification material through the equipment coil and the shell is not tight, it will cause the temperature and air pressure of the liquid material to rise.

7) The unreasonable discharge system of the reaction vessel causes an accident

When the material is discharged, the position and height of the discharge port are not set as required, and the discharged material drifts into the room and burns and explodes in case of an open fire.

8) Improper materials in and out of the reaction vessel cause accidents

Most hydrocarbon materials are insulating materials with poor electrical conductivity. When entering and leaving the reaction vessel, the materials flow at a high speed, and the electrostatic accumulation and discharge cause combustion and explosion. The reaction vessel adopts pressurized discharge, which is easy to cause the gas or vapor in the vessel to escape and leak into the workshop, forming an explosive gas mixture

9) The reaction vessel is heated to cause an explosion

Due to the fire of the external combustibles, the radiant heat causes the temperature in the reaction vessel to rise sharply, the vapor pressure increases, and the charge or explosion occurs.

10) Fire and explosion accidents occur continuously

When the reaction vessel is damaged due to uncontrolled reaction, external flame action or equipment defect, the internal pressure is often higher than atmospheric pressure, and some can reach 3.0MPa-10.0MPa or higher, the liquid in the vessel is overheated, and the container bursts causing the material The equilibrium state of the vapor pressure is destroyed, and a secondary explosion (called a vapor explosion) caused by an unstable superheated liquid occurs; the sprayed reaction material spreads rapidly, and the space around the container is enveloped by droplets or vapors of flammable liquids. In case of fire, a third explosion (mixed gas explosion) will occur. These three explosions are often completed in an instant, but they are three successive explosions of different properties.