Thermogravimetric and Kinetic Analysis of Raw and Torrefied Biomass Combustion

Abstract

The use of torrefied biomass as a substitute for untreated biomass may decrease some technological barriers that exist in biomass co-firing technologies e.g. low grindability, high moisture content, low energy density and hydrophilic nature of raw biomass. In this study the TG-MS-FTIR analysis and kinetic analysis of willow (Salix viminalis L.) and samples torrefied at 200, 220, 240, 260, 280 and 300 o C (TSWE 200, 220, 240, 260, 280 and 300), were performed. The TG-DTG curves show that in the case of willow and torrefied samples TSWE 200, 220, 240 and 260 there are pyrolysis and combustion stages, while in the case of TSWE 280 and 300 samples the peak associated with the pyrolysis process is negligible, in contrast to the peak associated with the combustion process. Analysis of the TG-MS results shows m/z signals of 18, 28, 29 and 44, which probably represent H 2 O, CO and CO 2 . The gaseous products were generated in two distinct ranges of temperature. H 2 O, CO and CO 2 were produced in the 500 K to 650 K range with maximum yields at approximately 600 K. In the second range of temperature, 650 K to 800 K, only CO 2 was produced with maximum yields at approximately 710 K as a main product of combustion process. Analysis of the FTIR shows that the main gaseous products of the combustion process were H 2 O, CO 2 , CO and some organics including bonds: C=O (acids, aldehydes and ketones), C=C (alkenes, aromatics), C-O-C (ethers) and C-OH. Lignin mainly contributes hydrocarbons (3000-2800 cm ). Hydrocarbons, aldehydes, ketones and various acids were also generated from hemicellulose (1790-1650 cm −1). In the kinetic analysis, the two-steps first order model (F1F1) was assumed. Activation energy (E a ) values for the first stage (pyrolysis) increased with increasing torrefaction temperature from 93 to 133 kJ/mol, while for the second stage (combustion) it decreased from 146 to 109 kJ/mol for raw willow, as well as torrefied willow at the temperature range of 200-260°C. In the case of samples torrefied at 280 and 300°C, the E a values of the first and second stage were comparable to E a of untreated willow and torrefied at 200°C. It was also found that samples torrefied at a higher temperature, had a higher ignition point and also a shorter burning time.

Furniture wood waste as a potential renewable energy source

“…Samples with higher torrefaction temperatures have a higher ignition temperature and a shorter time of combustion. These results are in accordance with previous research [24]. The performance parameters of the combustion of willow and its torrefied samples have lower values than our samples, except for the ignition temperature.…”

“…2, the physical and chemical properties of torrefied FW strongly depend on the torrefaction temperature. The same trends were observed by other researchers [22][23][24]. Torrefied waste from furniture (TFW), in comparison with non-thermally treated FW, contains lower amounts of moisture, volatile matter, oxygen and nitrogen.…”

“…The DTG peaks of the torrefied biomass are reduced significantly when the torrefaction temperature increases up to 593 K due to the depletion of the majority of the hemicellulosic and cellulosic fractions in the torrefaction process, as was also observed by the authors of other works [36][37][38]. In work [24], the authors investigated the combustion of willow (Salix viminalis L.) and its torrefied samples. The combustion processes of these samples run in the same way as in the case of furniture wood waste and its torrefied samples.…”

“…The small values of the activation energy and pre-exponential factor indicate that the rate of the combustion process is high. In a previous work [24], the kinetics of the combustion process for willow and its torrefied samples was investigated. The same kinetic model was assumed, and the conclusion of the kinetic parameters increasing with the torrefaction temperature of the first stage and decreasing in the second stage was the same.…”

Thermal degradation of some ferrocene-containing poly(aryleneethynylene)s

“…The consideration that thermal decomposition is initiated at the hexadecyloxy lateral chains was also supported by the presence of -CH 2 -characteristic bands at 3000-2800 cm -1 in the FTIR spectra ( Figure 6). The temperature of the FTIR measurement was selected from the corresponding peak value of the first degradation stage (270 C) [22,26,27]. (1), could be also identified [19].…”