Cause analysis of fire and explosion accident of reaction vessel

Cause analysis of fire and explosion accident of reaction vessel

1) Uncontrolled reaction causes fire explosion

Many chemical reactions, such as nitrification, sulfonation, oxidation, chlorination, polymerization and so on, are reactions with greater heat release. When the reaction is carried out in the reaction vessel, if the normal reaction process is out of control, the reaction heat accumulates, the temperature of the reaction system increases, and the reaction speed accelerates. The pressure in the system increases, and when the internal pressure rises sharply and exceeds the pressure resistance of the container, the container breaks, and the high-pressure material spews out from the rupture. Due to the rise of temperature, the reaction materials may decompose and burn, resulting in uncontrolled fire and explosion accidents. Causes of reaction out of control include: reaction heat failed to move out in time, reactants can not be uniformly dispersed and operational errors. Improper selection of coolant, heat transfer equipment can not timely export excessive heat in the reactor, due to the scaling of the wall of the reactor heat transfer effect is poor, coolant supply equipment failure, heat transfer system blockage and other reasons, may lead to the reaction heat can not be removed in time. Power failure, mixing system failure, blade damage, insufficient speed, improper blade form, material crushing degree is not enough, will make the reaction materials in the device dispersed not evenly, resulting in poor heat dissipation or local reaction is too violent and dangerous. Abnormal chemical reaction of materials can be caused by violation of production operation rules, overloading of materials, excessive addition of catalyst, improper raw material ratio, improper feeding sequence and time, failure of coolant valve switch, too fast temperature rise, wrong reading of temperature and pressure, malfunction of metering instruments and other reasons. Many chemical reactions, but also because of the presence of dangerous impurities in the material will lead to violent side reactions, over reactions, and even make the reaction unusually accelerated reaction out of control.

2) Explosive mixture is formed in the reaction vessel

Some feedstock mixtures for gaseous reactions are explosive with feedstock ratios within the explosive limit. For example, the propylene and air of the ammoxidation reaction of propylene account for 6.16% and 677% respectively in the total volume of the raw material, and the concentration of propylene has been within the explosion limit (the explosion limit is 2%-11%); The weight ratio of CAI to air is about 1:9, and the volume concentration of naphthalene vapor in air is 2.25% (the explosion limit of CAI vapor is 0.88-5.9%). The non-displacement or incomplete displacement of combustible gas or flammable liquid vapor in the reaction vessel is also an important reason for the formation of explosive mixture.

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

The reaction vessel is not tightly sealed, the material is rushed out, and burns and explodes in open fire.

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

Stress concentration is caused by unreasonable design of reaction vessel, discontinuous structure shape and improper weld arrangement. Improper selection of equipment material, improper welding quality and improper heat treatment during manufacturing of containers reduce the toughness of materials; The container shell is corroded by the corrosive medium, and the strength decrease may make the container explode in the production process.

5) The high pressure material in the reaction vessel flows into the low pressure system

The atmospheric or low pressure vessel and storage tank connected with the reaction vessel explode due to the rush of high pressure materials in the reaction vessel.