Flammability properties of thermally dried sewage sludge

Abstract

HIGHLIGHTS• Flammability parameters of sludge are presented.• Relationships between chemical and flammability properties of sludge are analyzed.• Physical and chemical properties of sludge dusts affects their explosibility.• Seasons and origins of sludge should lead to a differentiation among samples. ABSTRACTThe treatment and disposal of sewage sludge is becoming an urgent need whereby different technologies were developed and integrated into the waste cycle all over the world. One ofthe most used technologies is the thermal drying ofthe sludge. Thermally dried sewage sludge has interesting properties that allow its use as an alternative fue!, but also needs some consideration from the point of view of its safe operation.The aim ofthis study was the research on the flammability properties of sewage sludge, including ignition sensitivity, explosion severity, thermal sensitivity and thermal stability. Furthermore relationships among those properties and composition parameters have been determined, added to the study of their variation depending on their origin or season. Finally, properties related to spontaneous combustion were determined. To study these relationships and characteristics sludge samples were selected from different locations in Spain and taken during different seasons.

A field study of lignite as a drying aid in the superheated steam drying of anaerobically digested sludge

“…The critical temperature for dried sludge is a little lower than the Ignition Temperatures reported by Fernandez-Anez et al (2014), who measured the flammability of 21 samples of dried sewage sludge using a range of techniques, none identical to the method used in this work. The Ignition Temperature measured by thermo-gravimetric analysis is the most similar of the methods used by similar Fernandez-Anez et al, where the Ignition Temperature was around 230 C. Fig.…”

Ignition sensitivity of solid fuel mixtures

“…the higher the amount of volatiles and the lower the ash, sulphur and nitrogen contents, the more reactive the sample is. It is well-known that the addition of inert dust is a common technique used to avoid the ignition risk mainly of coals [39], so the influence of the ash content on this parameter has been previously seen in many materials, as organic dusts [40] or sewage sludge [26]. The influence of nitrogen and sulphur is due to their origin, since they are mainly present on the coal and sewage the sludge samples, which have higher amounts of these components than the wood has.…”

“…The flammability properties that characterize coal [25], waste [26] and biomass [27] dusts have to be carefully determined in each single case due to their heterogeneity, but mean values show that they present a high ignition risk. This risk will also be present in the mixtures of these materials, and will depend on the proportion of each component in the mixture [24,28].…”

Experimental measurement of particle size effects on the self-heating ignition of biomass piles: Homogeneous samples of dust and pellets

“…The influence of particle size on the storage of materials has to consider the following two countering properties: When the particle size increases, the gaps between the particles with oxidizer present increase, so self-heating ignition becomes easier since oxidation is promoted. But on the other hand, air is less conductive than the material, decreasing the heat transfer and therefore the chance of self-heating ignition [14].…”