Treatment measures of static electricity in mixed

2022-08-08
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Treatment measures for static electricity in mixed production of petrochemical enterprises

1 flash explosion accident in the production process

in 2003, the ethylene resin Research Institute of a petrochemical enterprise configured polypropylene masterbatch under general conditions on a small experimental device. During the production process, operators need to carry out process operations such as mixing, discharging, bagging, etc. When discharging and bagging operations are carried out, a flash explosion accident suddenly occurs. This accident resulted in one operator being burned and materials being burned. It is understood that in two years, this kind of flash explosion accident occurred three times, and the employees had a serious sense of fear psychologically

the investigation found that there was no open fire at the operation site, but the material measurement results in the process showed that there was electrostatic discharge at the site, and there was electrostatic charge accumulation in the process of discharging to the receiving trough and bagging the finished material. It was observed on the operation site that when the operator discharged materials into the chute, a large amount of combustible gas was generated in the surrounding space, so it can be considered that the cause of the accident was due to electrostatic discharge generated in the production process, which ignited the combustible gas volatilized in the air

2 mixed material production process

2.1 characteristics of raw materials in production

in the process of preparing polypropylene masterbatch, the materials include polypropylene powder and p-tert butyl additive (liquid)

polypropylene powder has high insulation and is easy to accumulate charges. The additive p-tert-butyl is a peroxide with a ignition point of 12 ℃. It is a flammable and explosive substance, which is very volatile. It mixes with air to form an explosive mixture, and small energy can cause an explosion

2.2 production process

the production process of polypropylene master batch configuration is: on a small-scale test device, operators first pour polypropylene powder into the mixer, then add p-tert-butyl additive into the mixer according to a certain proportion, start the mixer for high-speed mixing. This type of machine is the first choice for plastic mechanical property inspection, and then throw materials into the metal tank (without special grounding wire) at high speed, Finally, operators use metal tools to pinch into plastic woven bags for subsequent production

2.3 generation and analysis of static electricity

in the process of preparation of polypropylene masterbatch, the polypropylene powder in the raw material generates static electricity due to high-speed stirring and high-speed ejection. Due to the essential characteristics of polypropylene powder with high resistance value, the accumulated electrostatic charge is not easy to dissipate, forming a high electrostatic voltage. The electrostatic test voltage on the surface of the powder pile in the receiving trough is 7 ~ 12kV, which can generate high-voltage discharge with the metal container, and there are two opportunities for discharge ignition: first, at the moment of discharging, it is possible to generate surface discharge directly to its metal receiving trough from the electrostatic charge accumulated on the surface of the pile; Second, during the filling process, it is possible that the static charge accumulated on the material surface may instantly spark the operators or metal tools held by hands, which is flexible and easy to ignite the flammable and explosive substances of p-tert-butyl peroxide volatilized into the air during the discharging process. Therefore, due to the light weight and high elastic strength of special glass fiber, the mixing operation site of the resin research institute is a typical high-risk place for electrostatic accidents

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