Combustion limit, explosion limit and flash explosion (2)

Four, flash burst

Flash explosion is also called deflagration or explosion.

Under normal circumstances, only a one-time explosion occurs.

Figure 24-39 A chemical container flash explosion accident occurred in the laboratory of a bioengineering company

5.

(1) Fire shading: alcohol lamp, an oven, hot plate, electric gun, hair dryer and the like

(2) Mars: power switch, lamp starter and ballast, thermal contact, poor electrical contact, voltage regulator, magnetic stirrer, mechanical stirrer, fan connected to the outdoors through pipes, various species motor (pressurizing pump, a vacuum pump, a rotary evaporator, etc.

(3) the heat source: friction (spoon sampling, filtering, stirring), heating jacket, a radiator, a movable heater, a drying oven lamp, heat of crystallization and the like

(4) Static: chemical fiber or wool clothes, high-speed flow of an inert organic solvent (a hydrocarbon such as petroleum ether ), the induced electrostatic charging, thermal electromotive, piezoelectric electrification, Helmholtz layer and the like

6.

Case 1

A R&D personnel processed about 10g of waste lithium aluminum tetrahydrogen

Reason analysis: the mouth of the bag containing tetrahydroaluminum lithium was wet and sparked, and the THF vapor at the mouth of the plastic beaker reached the combustion limit, causing a fire

The concentration of THF vapor varies linearly with the height above the liquid surface, as shown in Figure 24-45 and Figure 24-46.

Figure 24-45 Schematic diagram of the change of THF vapor concentration with the height above the liquid surface

Figure 24-45 The relationship between the concentration of THF vapor and the height above the liquid surface

The same fire accident was also in the process of dealing with expired lithium aluminum tetrahydrofuran.

Figure 24-47 Photos of the accident scene

Reason analysis: because the metal spoon is used instead of the horn spoon, the tetrahydrolithium aluminum sparks due to friction

Case 2

After concentrating the column fraction of petroleum ether and ethyl acetate on the rotary steamer, the speed of rotary steaming suddenly increased, causing the solvent bottle to fall into the pot, and the person concerned quickly picked it up and screwed it back on

The poor contact between the aviation plug and the power output often causes sparks in the water bath base.

Figure 24-48 Screenshot of the accident video