A Study on the Spontaneous Ignition of Some Ligneous Pellets

Abstract

A preliminary non-exhaustive study was conducted on the ignition of some ligneous biomass pellets inside a laboratory scale traveling bed furnace. The experiments consisted in the measurement of the ignition time of volatiles released by six different types of pellets, obtained from wood species found in the Portuguese forest, namely Pinus pinaster, Acacia dealbata, Cytisus scoparius, Cistus ladanifer, Paulownia cotevisa and Eucalyptus globulus. The experiments were carried out at corrected furnace temperatures of 359, 381, 403, 424 and 443 °C, using two different pellet sizes and with batches of 6 and 8 g of pellets. The ignition time was determined measuring the time elapsed between placing the batch of pellets on the traveling grate and the volatiles’ ignition moment. Its dependency was linear, and an increase in ignition time with the furnace temperature was verified. Pinus pinaster was the species that presented a higher ignition time and Cytisus scoparius the shortest. For the same pellets size, an increase in the mass of batches led to shorter ignition times.

Modelling Self-Heating and Self-Ignition Processes during Biomass Storage

“…In contrast, the powder spontaneously ignited after prolonged oxidative heating at the oven temperature of 180 °C, implying its critical self-ignition temperature to be below 180 °C. It is evident in Figure 3 that fir powder was more prone to self-heating and spontaneous combustion than the pellets under the same conditions [33]. The stronger heat transfer…”

“…After heating for 9 h at 180 • C, the central temperature of the fir pellets was stabilised at 173-176 • C without any further rising tendency. However, self-ignition occurred for the pellets when the oven temperature was 185 • C. These indicated the critical self-ignition temperature of the fir pellets sample with the size of 0.001 m 3 to be between 180-185 • C. In contrast, the powder spontaneously ignited after prolonged oxidative heating at the oven temperature of 180 • C, implying its critical self-ignition temperature to be below 180 • C. It is evident in Figure 3 that fir powder was more prone to self-heating and spontaneous combustion than the pellets under the same conditions [33]. The stronger heat transfer performance, as well as lower moisture content of the pellets, resulted in a shorter heating time as compared to the powder, reflecting that the heat transfer and moisture evaporation, to a certain extent, determined the time for the sample to be heated from room temperature to oven temperature.…”

The Experimental Analysis of Biochar Combustion in a Traveling Grate Furnace

“…This furnace comprised a set of instruments enabling the measurement and control of parameters, such as furnace temperature, inlet air mass flow rate, and exhaust gas concentration. Ferreira et al [35] also used this experimental setup in a preliminary study investigating the spontaneous ignition of some ligneous biomass pellets. The furnace body was made of ST37 carbon steel with internal dimensions of 610 mm in length, 320 mm in width, and 4 mm in thickness.…”

Application of Factorial Analysis to the Study of Vented Dust Explosions in Large Biomass Storage Silos

“…Hot surfaces and hot lumps of material, mechanical sparks, electric sparks and electrostatic discharges, lightning, and welding and cutting operations are well-known potential ignition sources [6]. In addition, fires -both open flame fires and smoldering fires-can ignite a dust explosion [6]; these fires can be the result of a self-heating process undergone by the bulk material [7] and the emission of flammable volatiles [8]. Similarly, flames by dust explosions could produce subsequent fires in surrounding facilities, buildings, and vegetation if not addressed properly.…”