Further Discussion on Spontaneous Combustion of Oil Residue in Fryers

In the article 'Safety Issues with Continuous Fryers', the phenomenon of spontaneous combustion of oil residue was discussed, and many have inquired about the reasons behind this. This article aims to provide a further explanation.

First, let's understand some concepts.

Flash Point: Also known as the ignition point, it refers to the minimum temperature at which a combustible substance, whether solid, liquid, or gas, can ignite in the presence of air. When the temperature reaches a certain level, the substance will ignite upon contact with a flame source, and it will continue to burn even after the flame source is removed.

So, why does spontaneous combustion occur? Under normal circumstances, combustible materials undergo a slow oxidation process when they come into contact with air. This process is slow and produces little heat, which dissipates into the surrounding environment and does not emit light like combustion. However, if the temperature increases or other conditions change, the oxidation process speeds up, generating more heat that cannot be dissipated and accumulates, leading to a gradual rise in temperature. When the spontaneous combustion temperature is reached, self-ignition occurs. The minimum temperature at which a material ignites due to heat is referred to as its autoignition point or self-ignition temperature.

At the autoignition temperature, combustible materials can burn in the presence of air without the need for an open flame. The autoignition point is not a fixed value; it primarily depends on the heat generated during oxidation and the efficiency of heat dissipation. The same substance can have different autoignition points depending on varying oxidation conditions and influencing factors.

There are two types of spontaneous combustion: one is heat-induced spontaneous combustion, which occurs due to an external heat source. The other is self-spontaneous combustion, where the combustible material generates heat internally through biological, physical, or chemical processes without an external heat source. Under suitable conditions, this internal heat is sufficient to cause ignition.

The spontaneous combustion of oil residue is a hybrid of the two methods mentioned above, involving both heat-induced spontaneous combustion and self-spontaneous combustion due to the carbonization of the oil residue.

To prevent the spontaneous combustion of oil residue, companies should implement the following measures:

1. Strengthen staff awareness and training on prevention.

2. Timely clean oil residue and submerge it in water within storage tanks.

3. Install temperature sensing probes on oil residue storage tanks next to fryers, connect them to a CO2 fire extinguishing system, and install CO2 fire extinguishing nozzles as well as water spray nozzles to ensure continuous water spraying on the oil residue.

In summary, taking preventative measures is essential to ensure safety.