RESUMO
Easily soluble organic components in Santanghu long flame coal (SLFC) from Hami (Xinjiang, China) were separated by CS2 and acetone mixed solvent (v/v = 1:1) under ultrasonic condition, and the extract residue was stratified by carbon tetrachloride to obtain the light raffinate component (SLFC-L). The effect of solvent treatment on the composition and structure of the coal and its rapid pyrolysis products was analyzed. Solvent treatment can reduce the moisture content in coal from 9.48% to 6.45% and increase the volatile matter from 26.59% to 28.78%, while the macromolecular structure of the coal changed slightly, demonstrating the stability of coal's complex organic structure. Compared with raw coal, the relative contents of oxygen-containing functional groups and aromatic groups in SLFC-L are higher, and the weight loss rates of both SLFC and SLFC-L reached the maximum at about 450 °C. In contrast, the loss rate of SLFC-L is more obvious, being 33.62% higher than that of SLFC. Pyrolysis products from SLFC at 450 °C by Py-GC/MS are mainly aliphatic hydrocarbons and oxygenated compounds, and the relative contents of aliphatic hydrocarbons decreased from 48.48% to 36.13%, while the contents of oxygenates increased from 39.07% to 44.95%. Overall, the composition and functional group in the coal sample were changed after solvent treatment, resulting in a difference in the composition and distribution of its pyrolysis products.
RESUMO
Oily sludge (OS) was extracted with petroleum ether (PE), methanol, carbon disulfide (CDS), acetone, and isometric CDS/acetone mixture (IMCDSAM), respectively, to obtain soluble species (E1-E5) and extraction residues (R1-R5). The soluble species were analyzed by gas chromatography/mass spectrometry (GC/MS), and the extraction residues were characterized by Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA). Results showed that the extract yield of the soluble species from OS using CDS and IMCDSAM as the solvent was 61.0 and 67.3%, respectively. GC/MS results exhibited that the compounds detected in E1-E5 are mainly hydrocarbons and oxygen-containing compounds. E1-E5 are rich in alkanes, alkenes, ketones, alcohols, and other oxygen-containing compounds. Double-bond equivalence (DBE) and carbon numbers (CNs) of the compounds detected in E1, E2, and E4 are distributed in 0-4 (DBE) and 10-20 (CNs), respectively, while the DBE and CNs of the detected compounds in E3 and E5 are concentrated in 0-6 and 15-35, respectively. Thermogravimetry-differential thermogravimetry (TG-DTG) profiles presented that pyrolysis of OS occurred mainly in the temperature range of 150-750 °C, while pyrolysis of R1-R5 took place in the range of 350-750 °C. In the temperature range of 150-550 °C, the weight losses of OS and each extraction residue differ significantly, with OS having a much higher weight loss than the extraction residues. Meanwhile, the possible mechanism of oily sludge extraction was considered. Results revealed that selecting a low-polar or nonpolar solvent capable of selectively destroying hydrogen bonds and/or aromatic interactions is critical for improving the extract yield of OS.
RESUMO
Karamay oily sludge (KOS), Zhundong subbituminous coal (ZSBC), and their equal mass mixture (M KOS/ZSBC) were selected as the research samples, and composition characteristics and pyrolysis performance of KOS, ZSBC, and its mixture were investigated by means of various analytical methods. Results showed that yields of fixed carbon and volatile matter from ZSBC are higher than those from KOS, and the content of moisture in ZSBC is also higher; most of the components in KOS are inorganic minerals, with the ash yield of 71.4%, and the fixed carbon yield of nearly 0. According to Fourier transform infrared spectrometer (FTIR) analysis, the types of functional groups in KOS and ZSBC are basically the same, while the contents of which are different. Thermogravimetry-differential thermogravimetry (TG-DTG) analysis indicated that the mass loss of ZSBC, KOS, and M KOS/ZSBC are 41.1%, 25.7%, and 32.8% with a heating temperature up to 990 °C, respectively. By analyzing the theoretical pyrolysis and combustion TG-DTG profiles of M KOS/ZSBC and the measured composition of the flue gas produced during the tested processes, it is found that the mixture of oily sludge and coal helps generate remarkable combustible gases with significantly reduced CO2, indicating that there is an effective "synergistic effect" between KOS and ZSBC. Based on the Coats-Redfern (CR) model, in the main pyrolysis temperature range, when the reaction order is selected as 1, the kinetic fitting effect of pyrolysis and combustion profiles for ZSBC is better, with the correlation coefficient R 2 > 0.98. While for KOS and M KOS/ZSBC, in N2 atmosphere, the fitting effect is satisfactory as the reaction order is set to 5, in air atmosphere, the better fitting effect is considered that reaction order is selected as 1.