Study of lignocellulosic biomass ignition properties estimation from thermogravimetric analysis

Abstract

Abstract In the last decade, the use of renewable resources has increased significantly in order to reduce the energetic dependence on fossil fuels, as they have an important contribution to the global warning and greenhouse gasses effect. Therefore, the role of biomass on the energetic mix is becoming critical nowadays, as it is the only renewable resource, whose characteristics of use match those of the conventional fuel s: solid biomass can be used instead of coals, and biodiesel could replace diesel. But in order to accomplish that goal, it is necessary to improve biomass physical-chemical properties such as high heating value, hygroscopicity, etc., but also to deep study its flammable characteristics in order to define the proper industrial safety measures. Research on solid biomass ignition properties has been considerably developed because of the amount of industrial accidents related to the treatment and use of solid biomass (self-ignition, dust explosions, etc.). On the other hand, thermogravimetric analysis (TGA) is becoming and important characterization technique as it can be used to determine a wide spectrum of properties, such as kinetics, composition, proximate analysis, etc. This research aims to combine both by using the TGA to obtain the elemental composition of lignocellulosic biomass and compare those results to Minimum Ignition Energy (MIE) values test output, so a relation between oxygen, carbon and hydrogen content and MIE can be found; which means that further studies could develop an estimation of MIE by TGA. To achieve this aim, biomass samples from different origins have been used: oil palm wastes (empty fruit bunches, mesocarp fiber and palm kernel shell), agricultural wastes (straw chops) and forestry wastes (wood chips and wood powder). Also, raw materials and torrefied biomass were compared Thermogravimetric analysis was carried on each sample, and so the percentages of cellulose, hemicellulose and lignin were estimated. Afterwards, MIE analysis was carried out and it was observed that torrefied samples presented lower energy values than the original samples. Finally, the hemicellulose/cellulose ratio was calculated and compared to different flammability properties, finding out that the greater the ratio and the lower the onset temperature (temperature at which the pyrolysis reaction accelerates), the lower was the minimum ignition energy. From this basis it was possible to define “tendency areas” that grouped the samples whose MIE was similar. Three tendency areas were found: high minimum ignition energy, medium minimum ignition energy, and low ignition energy.