Analysis of liquefied gas leakage and explosion accident in Hunan

On February 9 this year, the day before Lunar New Year's Eve, Zuo Mou, a 21-year-old female student from Hunan Normal University Law School, returned to Suining County in southern Hunan. In the evening, when she changed into 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 it, and took a bath with a water heater. After taking a shower, I used a hair dryer to dry my hair. I didn't expect that 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. Both Zuo and her father were severely burned. She was completely burned, and the burn area reached 91%, which was terrible and was on the verge of shock.

This is a typical accident of burning and explosion caused by the leakage of liquefied petroleum gas. Although liquefied petroleum gas (LPG) is a non-toxic gas because it does not contain CO, many components of LPG are easy to poison and even suffocate people and animals. 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. There must be three conditions for combustible materials to burn and explode:

First, there must be combustible materials;

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

thirdly, there is an ignition source and the minimum ignition energy is achieved. In the above two accidents, the first condition is beyond doubt.

household liquefied petroleum gas (LPG) is a by-product produced by petrochemical plants, and it is a complex mixture of various hydrocarbons (alkanes, cycloalkanes and aromatic hydrocarbons), mainly flammable hydrocarbons such as propane, butane, propylene and butene. The second condition is also easy to achieve. As we know, although combustible gas and air are not in danger of fire and explosion in any mixing ratio, the lower limit of the explosion limit of liquefied petroleum gas mixed with air is low and the upper and lower limit ranges are 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 28.61%). The minimum ignition energy in air is also low (for example, 1.282 mj for propylene and 1.315 mj for propane). As long as the concentration of the leaked liquefied gas mixed with air reaches any concentration point in the range of 2%-28% (which is easy to reach in the kitchen of urban buildings), it will explode when it encounters a fire source. In the first accident, it was known that the liquefied gas bottle leaked, and after a long bath, the liquefied gas leakage easily reached the lower limit of the explosion limit, and it 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 "empty bottle" that was replaced 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 an absolute atmospheric pressure, i.e. 1kgf/m2 or 1.1mpa), and it is in a micro-equilibrium state. When removing the pressure reducing valve and moving the "empty bottle", this balance was broken. Without the relevant valve, the 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, the accident of burning and explosion will inevitably happen.

in view of the above-mentioned burning and explosion accidents caused by liquefied gas leakage and its mechanism, we should take the following safety precautions at ordinary times:

1. LPG cylinders must be inspected and maintained according to the regulations, and all unqualified cylinders shall be scrapped, and those with leakage are not allowed to continue to use.

2. The pressure reducing valve for home use 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 upper master valve to prevent the residual liquid in the bottle from leaking out during handling or when the weather becomes warm or heated.

4. If liquefied gas or gas leaks at home, first of all, pay attention not to ignite with any fire source, including not to plug in the electrical switch, not to start the ventilator, washing machine, hair dryer, microwave oven, disinfection cabinet, etc. that cause electric sparks; Immediately close the site to prevent people from entering;