Thermal Behaviors and Kinetics of Pingshuo Coal/Biomass Blends during Copyrolysis and Cocombustion

Abstract

The copyrolysis and cocombustion behaviors of Pingshuo coal and the biomasses (sawdust and rice straw) have been investigated using a thermogravimetric analyzer. The experimental results indicate that there exist synergetic effects between the biomasses and Pingshuo coal during their coconversion process. The initial temperature of volatile emission from Pingshuo coal and the temperature corresponding to the maximum conversion rate during the copyrolysis change with the biomass mixture ratio. Moreover, it can be deduced from the comparison between the experimental and the calculated DTG curves that the copyrolysis process is not the sum of Pingshuo coal and the biomass conversion. During their cocombustion process, the larger the mixture ratio of the biomass is, the lower the ignition temperature and the burnout temperature are, and the larger the combustion characteristic index is. In addition, the maximum combustion rate and the combustion performance are the best when the mixture ratio of the biomass is 70 wt % in the research. Moreover, the activation energy and the frequency factor of the copyrolysis and the cocombustion were calculated by the Coats–Redfern method and the first-order reaction model. The results show that the activation energy and the frequency factor change with the mixture ratio of the biomass, and the regularity was consistent with the above-mentioned conclusions. Therefore, it can be deduced that the addition of the biomass can facilitate the pyrolysis and the combustion of Pingshuo coal, and improve the utilization field of Pingshuo coal.

Thermal behavior and the evolution of char structure during co-pyrolysis of platanus wood blends with different rank coals from northern China

“…In the experiment, about 10 mg of the tested sample was first weighed on a Mettler Toledo XA105DU electronic balance, and then put into an Al 2 O 3 ceramic crucible. High purity nitrogen (99.999%) with a preset flow rate of 60 mL min À1 was used in thermogravimetric experiments so as to avert the impact on the heat transfer limitation and weight measurement according to previous literatures [7,14]. All the pyrolysis experiments were executed from ambient temperature to 950°C under three heating rates (10, 20, and 40°C min À1 ).…”

“…These phenomena can also be attributed to the existence of alkali and alkaline-earth metal (AAEM) in PW and coal feedstock [16,34]. These elements can catalyze the decomposition reactions of secondary char in pyrolysis process, leading to the increment of the volatiles yields [4,7]. However, PW would soften and generate large amounts of soft residues during pyrolysis process, which can cohere to the particle surface of the coal before coal initial pyrolysis.…”

“…However, PW would soften and generate large amounts of soft residues during pyrolysis process, which can cohere to the particle surface of the coal before coal initial pyrolysis. Therefore, the pores of coal particles may be congested and pyrolysis of coal was inhibited [4,7]. Consequently, when the PW blending ratio was low (30%), these synergistic effects between PW and coal were not obvious.…”

“…Several studies have been focused on the thermal behavior and kinetic analysis of a variety of coals blended with different biomasses, such as sawdust [7], cypress wood chips [8], and pine chips [9] from forestry residues, cherry pit [10], hazelnut shell [11], sugar beet pulp [12], straw [13], corn and sugarcane [14] from agricultural residues. However, due to the great varieties and heterogeneity of biomass, different conclusions on the thermal behavior were obtained by different researchers.…”

Characteristics and application of co-pyrolysis of coal/biomass blends with solid heat carrier

“…However, the drawbacks of biomass, such as low energy density, seasonal, difficult to collect and transport etc., limit its utilization greatly. One of the most promising solutions is to co-utilize with coal, such as co-combustion [1][2][3][4], co-gasification [5][6][7][8] and co-pyrolysis [8,9]. These solutions cannot only avoid the disadvantages of biomass and coal, but also exert the advantages of them simultaneously.…”