Abstract
Biomass is an especially reactive fuel. There have been large increases in the transportation and utilization of biomass fuels over the past 10years and this has raised concerns over its safe handling and utilization. Fires, and sometimes explosions, are a risk during all stages of fuel production as well as during the handling and utilization of the product. This paper presents a method for assessing ignition risk and provides a ranking of relative risk of ignition of biomass fuels. Tests involved single particle measurements, thermal analysis, dust layer and basket ignition tests. In all cases, smouldering combustion was observed, whereby the fuels pyrolyse to produce a black char, which then subsequently ignites. Low temperature pyrolysis kinetics have been utilised to predict ignition delay times at low temperatures. A method for evaluating risk was explored based on the activation energy for pyrolysis and a characteristic temperature from TGA analysis. Here, olive cake, sunflower husk and Miscanthus fall into the high risk category, while the woods, plane, pine, mesquite and red berry juniper, fall into the medium risk category. This method is able to capture the impact of low activation energy for pyrolysis on the increased risk of ignition.
Highlights
On a global scale, there is an increasing use of a wide variety of biomass fuels in power and heat generation [1]
The temperature of initial combustion (TIC) method is difficult to implement in cases where there is more than one volatile combustion peak, and temperature of maximum weight loss (TMWL) gives a poor indication of the ease of initial decomposition
This consists of both single particle tests, and dust layer tests, i.e. data is for samples close to or above the critical temperature
Summary
There is an increasing use of a wide variety of biomass fuels in power and heat generation [1]. Biomass shares many properties with coal, there are some disadvantageous features, especially the heightened propensity for low temperature ignition during conveying and processing, and the hazard of spontaneous combustion associated with storage. Coal is far less hydrophilic than biomass; meaning that open-air storage is possible for coal whereas biomass must usually be stored in silos. The friability of biomass means that dust layer ignition is an issue during milling and conveying, and dust accumulates on hot surfaces such as lamps and machinery. Because of the risk of self-heating and low temperature ignition there have been many studies over the past 50 years [4,5,6,7,8] including the development of the underpinning theoretical understanding [9,10]
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