Extinguishing smoldering fires in waste facilities

Abstract

Waste facilities are filled with a range of combustible materials, and fires have been an issue for a long time. Fire is a risk, not only for economic reasons, but also for the consequences the toxic smoke and extinguishing water may have on the local environment. Smoldering fire in waste facilities are difficult to extinguish as the fire often sit deep in the waste piles and it can spread over a large area before it is detected or transitions to a flaming fire. This thesis studies extinguishing methods that are based on viscous liquids to investigate whether this is more effective on smoldering fires than water, which traditionally is used by the fire department. Viscous liquids adhere better to material and might spread in a different way than water, as water tends to flow in the path of least resistance and forms channels. Therefore, water may not always reach the smoldering fire in a waste pile and large amounts of water are usually required. Small-scale experiments were performed with wood waste placed in a steel tube. Inside the tube, seven thermocouples recorded the temperature changes in the sample. Sugar water was chosen as the viscous extinguishing agent because of well-documented viscosity of different mixtures. The extinguishing agent was applied to the smoldering fire one hour into the experiments, and temperatures were recorded for two more hours after extinguishing agent was applied to observe the extinguishing effect. Results from the experiments indicates that liquids with a viscosity higher than water may be more effective on smoldering fires than water. The smoldering fire was extinguished in all three experiments where the mixture of water and 20 % sugar by mass was used as extinguishing agent. For the experiments with higher viscosity, the fire intensity was higher and fewer smoldering fires were extinguished. This is probably because the water evaporated, and the sugar contributed to the fire. The viability of viscous liquids as extinguishing agent should be examined further with up-scaled experiments and other viscous agents. High-viscosity extinguishing agents may be useful for smoldering fires at waste facilities and there are other areas where it may be an more effective extinguishing agent than water, such as for densely built wooden settlements or bush fires to limit the fire spread.