Phenomenological Studies of Fires on Recycling Materials

Abstract

This thesis provides the scientific basis for the waste management industries best practice guidance. The findings have been published by the Waste Industries Safety and Health Forum Guidance 28- Reducing Fire Risk at Waste Management Sites. It details the development of fire in a range of common waste materials at large scale and under realistic storage conditions. This data was used to develop and demonstrate new firefighter tactics now employed by the British Fire Service.
The research was based on a series 27 full scale experiments on common waste materials stored in both loose piled conditions and compressed bales stacked up to 4 m high in line with the UK regulations. The fire tests ranged in masses between 3 tonnes and 18 tonnes of material. The piles were tested in both a fully open condition and within a bunker. The material was ignited on the surface and measures using a bespoke thermocouple array. A series if deep seated ignitions were also examined. A set of self-heating test were con-ducted concurrently with these fire tests. A previously undocumented vortex fire behaviour was discovered during these experiments. CFD was used to confirm the phenomenon associated with the stacked bale fire experiments. The findings were used to develop a new set of firefighting tactics using water, compress air foam system and surfactant water additive these were tested at full scale by members of the fire service from Essex and East Sussex fire and rescue services. A range of different scientific methods were employed to obtain data including thermal imagery along with more traditional thermocouple approach. Video smoke and thermal imagery systems provided very early detection of fire in fuel bed matrix that allow the passage of convection currents such as pre crushed wood but did not prove any more effective than conventional detection technologies in impervious fuel beds. The LEGIO block passive fire separation system was also tested to evaluate the use of movable concrete blocks in the waste environment. K type thermocouples were positioned are regular intervals throughout the depth of the blocks at different points to evaluate conductive heat transfer.
The experiments were used to define the fire development in stored waste materials and provided a range of fire engineering parameters. These include a full analysis of the separation distance using a computer model to establish boundary distances based on the analysis of radiated heat transfer from a range of geometrical orientations of both transmitters and receivers. To provide safe separation distances for stored waste based on the materials and storage conditions. Due to the size of the piles, it was not possible to conduct the tests on a load cell to calculate mass loss. Instead, mass loss was estimated by analysis of the volume loss that could be measured form this mass loss rate and heat release rates were calculated for RDF, SRF, Shredded Tyres, pre crushed timber, wood fines and HDPE bales in ventilated and unventilated conditions. The firefighting tactics explored in the paper have been used to develop the Waste Fire Tactical Advisor role by the National Fire Chiefs Council UK.