Who gave a case of burning and explosion accident, which was well analyzed?

Analysis of liquefied gas leakage and explosion accident in Hunan

On February 19 this year, the day before Lunar New Year's Eve, Zuo Mou, a 20-year-old female student from Hunan Normal University Law School, returned to Suining County in southern Hunan. In the evening, when she put on a new liquefied gas cylinder, she found that the gasket of the pressure reducing valve joint connecting the cylinder was broken and leaked a little, thinking that it had nothing to do with herself, so she took a bath with a water heater. After taking a shower, I dry my hair with a hair dryer. Unexpectedly, the hot red resistance wire in front of the hair dryer was the fire source, which immediately triggered the sudden burning and explosion of indoor liquefied gas. Zuo and her father were badly burned, and she was completely burned. The burn area reached 9 1%, which was terrible and was on the verge of shock.

This is a typical liquefied petroleum gas leakage, combustion and explosion accident. Although liquefied petroleum gas is a non-toxic gas because it contains no carbon monoxide, many components of liquefied petroleum gas are easy to poison people and animals and even suffocate them. Especially when a certain proportion of liquefied petroleum gas is mixed in the air, it is easy to catch fire and explode. This kind of explosion belongs to chemical explosion. The combustion and explosion of combustible materials must meet three conditions:

First, there are flammable substances;

Second, the concentration of combustible substances is within the explosion limit;

Third, there is a little fire source to achieve the minimum ignition energy. Of the above two accidents, the first condition is beyond doubt.

Household liquefied petroleum gas (LPG) is a by-product produced by petrochemical plants and a complex mixture of various hydrocarbons (alkanes, cycloalkanes and aromatics), mainly flammable hydrocarbons such as propane, butane, propylene and butene. The second condition is also easy to achieve. We know that although combustible gas and air are not in danger of fire and explosion at any mixing ratio, the lower limit of explosion of LPG mixed with air is relatively low, and the upper and lower limits are relatively wide (for example, the lower limit of butane is 1.86%, and the upper limit is 8.41%; The lower limit of ethylene is 2.75% and the upper limit is 28.60%). The minimum ignition energy in air is also very low (for example, 0.282 mj for propylene and 0.305 mj for propane). When the leaked liquefied gas is mixed with air, as long as the concentration reaches any concentration point within the range of 2%-28% (which is easy to reach in the kitchen of urban buildings), it will explode when it meets a fire source. In the first accident, it was known that the liquefied gas cylinder leaked. After a long bath, the liquefied gas leakage easily reached the lower limit of the explosion limit and was within the concentration range of the upper and lower limits. When it met the ignition source of the hair dryer, a combustion explosion occurred. In the second accident, the replaced "empty bottle" was not empty, and there was liquefied gas in the bottle. This is because the pressure in the bottle is equal to the local atmospheric pressure (about one absolute atmospheric pressure, that is, 1kgf/m2 or 0. 1mpa), and it is in a micro-equilibrium state. This balance was broken when the pressure reducing valve was removed and the "empty bottle" was moved. Without relevant valves, liquefied gas in the bottle leaked out and gradually reached the explosion limit. When a new bottle of gas is used to strike a fire and there is a fire source, a burning and explosion accident will inevitably occur.

In view of the above-mentioned combustion and explosion accidents caused by liquefied gas leakage and its mechanism, the following safety precautions should be taken at ordinary times:

1, LPG cylinders must be inspected and maintained according to regulations. Unqualified gas cylinders should be scrapped, and those with leakage are not allowed to continue to use.

2. The domestic pressure reducing valve must be a qualified product, and the rubber gasket connected and sealed between the front end of the pressure reducing valve and the liquefied gas bottle must be intact without leakage.

3. For the "empty bottle" after use, be sure to tighten the master valve to prevent the residual liquid in the bottle from leaking out during handling or when the weather becomes warm or hot.

4. If liquefied gas or gas leaks at home, first of all, be careful not to ignite it with any fire source, including not plugging in the electrical switch plug, and not starting the ventilator, washing machine, hair dryer, microwave oven, disinfection cabinet, etc. Will produce an electric spark; Immediately close the site to prevent personnel from entering;