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Abstract

The CO2 adsorption capacity of the low-cost solid sorbents of waste tire char (TC) and chicken waste char (CW) was compared with commercial active carbon (AC) and 5 Å zeolite (ZA) using thermogravimetric analysis (TG), pressurized TG, and differential scanning calorimetry (DSC). The sorbents were degassed in a TG up to 150 °C to release all gases on the surface of the sample, then cooled down to the designed temperature for adsorption. TG results indicated that the CO2 adsorption capacity of TC was higher than that of CW, but lower than those of AC and ZA. The maximum adsorption rate of TC at 50 °C was 0.61% min−1, lower than that of AC, but higher than that of CW, 0.44% min−1. The maximum adsorption rate of ZA at 50 °C was 3.1% min−1. When the pressure was over 4 bar, the adsorption rate of ZA was lower than that of TC and AC. At 30 bar, the total CO2 uptake of TC was 20 wt%, higher than that of CW and ZA but lower than that of AC. The temperature, nitrogen concentration, and water content also influenced the CO2 adsorption capacity of sorbents to some extent. DSC results showed that adsorption was an exothermic process. The heat of CO2 adsorption per mole of CO2 of TC at 50 °C was 24 kJ mol−1 while the ZA had the largest heat of adsorption at 38 kJ mol−1. Comparing the characteristics of TC and CW, TC may be a promising sorbent for removal of CO2.

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Abstract

The objective of this study was to examine the possible formation of chlorinated organic compounds during the combustion of blends of refuse derived fuels (RDF) and coal under conditions similar to those of an atmospheric fluidized bed combustion (AFBC) system. A series of experiments were conducted using a TG interfaced to FTIR. Additional experiments using a tube furnace preheated to AFBC operating temperatures were also conducted. The combustion products were cryogenically trapped and analyzed with a GC/MS system. The chlorination of phenols and the condensation reactions of chlorophenols were investigated in this study. A possible mechanism for the formation of chlorinated organic compounds such as dibenzodioxins and dibenzofurans, by chlorination and condensation reactions involving phenols, was proposed.

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Journal of Thermal Analysis and Calorimetry
Authors:
Hou-yin Zhao
,
Yan Cao
,
Song P. Sit
,
Quentin Lineberry
, and
Wei-ping Pan

Abstract

The pyrolysis behavior of bitumen was investigated using a thermogravimetric analyzer–mass spectrometer system (TG–MS) and a differential scanning calorimeter (DSC) as well as a pyrolysis-gas chromatograph/mass spectrometer system (Py-GC/MS). TG results showed that there were three stages of weight loss during pyrolysis—less than 110, 110–380, and 380–600 °C. Using distributed activation energy model, the average activation energy of the thermal decomposition of bitumen was calculated at 79 kJ mol−1. The evolved gas from the pyrolysis showed that organic species, such as alkane and alkene fragments had a peak maximum temperature of 130 and 480 °C, respectively. Benzene, toluene, and styrene released at 100 and 420 °C. Most of the inorganic compounds, such as H2, H2S, COS, and SO2, released at about 380 °C while the CO2 had the maximum temperature peaks at 400 and 540 °C, respectively. FTIR spectra were taken of the residues of the different stages, and the results showed that the C–H bond intensity decreased dramatically at 380 °C. Py-GC/MS confirmed the composition of the evolved gas. The DSC revealed the endothermic nature of the bitumen pyrolysis.

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Journal of Thermal Analysis and Calorimetry
Authors:
Hou-yin Zhao
,
Yan Cao
,
Zhi-zhong Kang
,
Yau-bang Wang
, and
Wei-ping Pan

Abstract

Chemical looping combustion (CLC) is a novel combustion technology with the capability for segregation of exhaust products (i.e., carbon dioxide/H2O or N2/O2). The combustion is performed in two interconnected reactors with a solid oxygen carrier circulating between them, transferring oxygen from the air to the fuel. The feasibility of a successful CLC system depends on the selection of an appropriate oxygen carrier. Cu-based oxygen carriers are good oxygen carriers due to high reactivity. However, it faces low melting point, agglomeration problems in fluidized bed. In this study, a circular reduction–oxidation reaction simulated to the cyclic operation of the Cu-based oxygen carrier was conducted on the thermogravimetric analyzer (TG). The thermal behaviors of the potential Cu-based oxygen carrier were investigated by using an X-ray diffraction (XRD), scanning electron microscope (SEM), and surface analyzer. Multiple TG results show that the weight loss was 3.4%, indicating that the loading CuO amount was 17%. Moreover, the weight loss and weight gain was equal during 73 redox cycles, suggesting the good thermal stability of the oxygen carrier. The conversion rate of reduction and oxidation for each redox cycle remained constant even after 73 redox cycles. XRD results show the new phase formation of CuAl2O4 during redox cycles, which promotes the thermal stabilization of the oxygen carrier. The surface area of the oxygen carrier decreased from 105 to 13 m2 g−1 after 73 redox cycles and the particle size distribution shifted from 5–15 nm to 15–30 nm, suggesting that the micorpores were blocked or collapsed. However, the reactivity of the oxygen carrier didn't decrease. SEM results show that CuO was evenly distributed on the surface of Al2O3 after 73 redox cycles. Overall, these results suggested that the Cu-based oxygen carrier was ready for fluidized bed tests.

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Journal of Thermal Analysis and Calorimetry
Authors:
Houyin Zhao
,
Yan Cao
,
William Orndorff
,
Yu-Hsiang Cheng
, and
Wei-ping Pan

Abstract

Biodiesel is a prospective and promising fuel for diesel engines. However, some aspects need improvement, to develop into an ideal fuel, such as flow properties at low temperatures and storage stability at high temperatures with exposure to the air. Thermal analysis is an efficient tool for measuring properties, such as crystallization temperature, and thermal and oxidative stabilities. In this study, the thermal behaviors of biodiesel at low and high temperatures were investigated by using thermogravimetric analyzer, differential scanning calorimetry, pressurized differential scanning calorimetry (PDSC), and sorption analyzer (SA). The soy biodiesel was obtained through a transesterification reaction with a homogeneous catalyst. The constituents of the soy biodiesel as determined by gas chromatography show that methyl esters content was 99 % and of these 84 % were unsaturated fatty acids. TG results illustrate that the total weight loss of the biodiesel was 99 % below 300 °C under nitrogen flow, indicating a high purity biodiesel. The onset decomposition temperature and the peak temperatrue of the soy biodiesel were 193 and 225 °C, respectively, implying the biodiesel has good thermal stability. PDSC results show that the oxidation onset temperature of the soy biodiesel was 152 °C, and the oxidative induction time was 24 min. DSC results demonstrate that the onset crystallization temperature of the soy biodiesel was 1.0 °C. The SA results point out that with increasing temperature and humidity, the soy biodiesel absorbed more water, and in which humidity was the dominant factor. The water absorption and desorption of the soy biodiesel is a non-reversible process. The preferable storage conditions for soy biodiesel occur when humidity is less than 30 % and the temperature is less than 30 °C. In summary, thermal analysis is a faster alternative for thermal behavior studies as compared with conventional standard methods.

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Journal of Thermal Analysis and Calorimetry
Authors:
Hanxu Li
,
Xiang-Zhong Shen
,
B. Sisk
,
W. Orndorff
,
Dong Li
,
Wei-Ping Pan
, and
J. Riley

Abstract  

Improved thermoanalytical methods have been developed that are capable of quantitative identification of various components of fly ash from a laboratory-scale fluidized bed combustion system. The thermogravimetric procedure developed can determine quantities of H2O, Ca(OH)2, CaCO3, CaSO4 and carbonaceous matter in fly ash with accuracy comparable to more time-consuming ASTM methods. This procedure is a modification of the Mikhail-Turcotte methods that can accurately analyze bed ash, with higher accuracy regarding the greater amount of carbonaceous matter in fly ash. In addition, in conjunction with FTIR and SEM/EDS analyses, the reduction mechanism of CaSO4 as CaSO4+4H2 ↔ CaS + 4H2O has been confirmed in this study. This mechanism is important in analyzing and evaluating sulfur capture in fluidized-bed combustion systems.

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Journal of Thermal Analysis and Calorimetry
Authors:
Sheng-Hung Wu
,
Chu-Chin Hsieh
,
Chung-Cheng Chiang
,
Jao-Jia Horng
,
Wei-Ping Pan
, and
Chi-Min Shu

Abstract

Volatile organic compounds (VOCs) and greenhouse gases are the main factors involved in pollution control and global warming. Various treatment methods involving incineration, adsorption, etc., have been employed to reduce VOCs and greenhouse gases concentration in the operating environment and atmosphere. Activated carbon, zeolite, silica gel, and alumina have been broadly used to adsorb pollutants in various industrial applications. Based on the promising effect of adsorption, we analyzed and identified the thermal phenomena of home-made zeolite using various instruments. The endothermic reaction under 100 °C of home-made zeolite was identified as steam adsorption, which is an important discovery. The optimal adsorption temperatures of home-made zeolite have been determined at 200–550 °C.

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