Thermal Decomposition and Kinetics Analysis of Microwave Pyrolysis of Dunaliella salina Using Composite Additives
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Thermal Decomposition and Kinetics Analysis of Microwave Pyrolysis of Dunaliella salina Using Composite Additives Chunxiang Chen 1,2
&
Xiaoyan Bu 1,2 & Dengchang Huang 1,2 & Yuting Huang 1,2 & Haozhong Huang 1
Received: 14 March 2020 / Accepted: 1 June 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The thermal characteristics and kinetics of the microalgae Dunaliella salina were evaluated through microwave catalytic pyrolysis under composite additives (blends of graphite (GP) and Na2CO3 (NC)). GP was blended with NC of 0%, 30%, 50%, 70%, and 100%, which were named as NC, 3GP7NC, 5GP5NC, 7GP3NC, and GP. Then different amounts (5%, 10%, and 15%) of NC and 5GP5NC were also studied. The pyrolysis characteristic parameters, characteristic index (D) and activation energy (E), and thermodynamic parameters, including enthalpy (ΔH) and Gibbs free energy (ΔG), were studied in this paper. In all the groups with the amount of 5%, the initial decomposition temperature (Ti) decreased with the NC proportion of the composite additive increased. The 5GP5NC group obtained the largest values of maximum weight loss rate (Rmax), average weight loss rate (Rmean), and D, which were 3.78%/min, 1.67%/min, and 12.35 × 10−7, respectively. However, the NC group achieved a small value of E (66.28 kJ/mol), ΔH (60.46 kJ/mol), and ΔG (175.97 kJ/mol). When changing the amounts of 5GP5NC, the suitable amount was 15%, based on its largest D (13.76 × 10−7), smallest E (52.49 kJ/mol), excellent weight loss, and thermodynamic characteristic. For NC, the maximum Rmax was obtained at 15%, while the greatest D and minimum E were achieved at 5%. Keywords Microwave-assisted pyrolysis . Dunaliella salina . Composite additive . Kinetics analysis . Thermodynamics
Introduction With population growth and economic development, the demand for energy is rapidly increasing globally [1]. The largescale use of conventional energy resources like coal, petroleum, and natural gas has caused environmental issues [2]. Biomass is a renewable energy that has the potential to replace traditional fossil fuels due to the high biological CO2 fixation and energy production [3]. Biomass can be converted into fuel products by a biological or thermochemical method. Among these methods, pyrolysis is considered as an effective technology [4]. There are primarily two major pathways for biomass pyrolysis, which are conventional heating and
* Chunxiang Chen [email protected] 1
College of Mechanical Engineering, Guangxi University, University Road 100, Xixiangtang District, Nanning City 530004, People’s Republic of China
2
Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, Guangxi University, Nanning City 530004, People’s Republic of China
microwave-induced pyrolysis [5]. The essence of microwave heating is to transfer energy directly to the reacting molecules or atoms inside the material [6], and the heated material generates dielectric loss, followed by a thermal effect formed, further hea
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