Papers by Keyword: Lignite

Abstract: Experience, current situation and the prospects for operation of mining and processing enterprises for production of montan wax from brown coal are analyzed. Classification of the main technologies for the use of solid fossil fuel mineral has been performed. The features the technological process for production of montan wax, taking into account the experience of leading enterprises in Germany and Ukraine, are considered. Prospective directions for renewing the production of montan wax on the basis of brown coal reserves of Dneprovskiy brown coal basin are indicated. The evaluation of the attractiveness of production montan wax with the application of cash flow projection methods was carried out. Recommendations on the integrated development of brown coal deposits and processing of brown coal in order to attract foreign investment and support the competitiveness of the country's market have been developed.

Abstract: Oxygen-enriched Combustion behavior of indigenous lignite was investigated by using thermo gravimetric analyzer (TG). Combustion tests were carried out in six different atmospheres. The experiment results showed the oxygen–enriched atmosphere can improve the combustion rate of the lignite and expand the application scope of the lignite. Determine the Combustibility index to reveal the oxygen-enriched combustion process in detail.

Abstract: Drying is an important way to improve the quality of lignite with high moisture. In this paper, a single-shaft paddle dryer experimental system was built to investigate the drying characteristics of fine-particle lignite with diameter 0-5mm. The experimental results show that with the increasing in shaft rotation speed the flow rate of lignite increases linearly approximately and the residence time decreases correspondingly. Increasing the inclination angle of dryer frame helps increase the flow rate. Both shaft rotation speed and heating source (heat transfer oil) temperature have significant effects on outlet moisture content of lignite. Shaft rotation speed affects the average heat transfer coefficient greatly and heating source temperature affects it weakly for specified conditions. It is found that for 5-12mm coarse-particle lignite, flow is not smooth and the average heat transfer coefficient is much less than that of fine-particle lignite. This research shows that it is feasible technically to dry fine-particle lignite by using paddle dryers, but not suitable to dry coarse-particle lignite.

Abstract: Aliphatic mercaptans (R-SH) are organic sulfur containing functional groups in coal maceral that makes up lignite. Prior and after specific bioprocess on the lignite, namely multistage artificial biotreatment (A-Bmt), organic sulfur rich lignite sample was treated and analyzed by spectroscopic methods. To determine the qualitative change in aliphatic mercaptans on lignite maceral surface, Fourier transform infrared (FTIR) method at transmittance spectrum of 400-4000 cm^-1 was used on lignite sample in the form of pellet with a KBr mixture. The results of FTIR analysis indicate significant spectrum gradations between natural samples, samples from biooxidation, and samples from column bioflotation. This can be seen in the spectrum distribution pattern of transmittance at 620-690 cm^-1 and 1530-1580 cm^-1, which gradually and significantly change. The results of biotreatment with the addition of bioreagent Pseudoclavibacter sp. strain SKC/XLW-1 both at biooxidation and column bioflotation stage on A-Bmt method showed that there was a significant difference on spectrum pattern compared to the results with no biotreatment. The spectrum distribution pattern resulted from FTIR analysis also showed a strong correlation with the distribution pattern of decreased levels of organic sulfur and trace elements.

Abstract: This study focuses on the biodesulfurization of lignite specifically the reduction of organic sulfur, namely aliphatic mercaptans/thiols via bioprocess methods. The process was conducted by using multistage artificial biotreatment (A-Bmt) and Pseudoclavibacter sp. SKC/XLW-1 strains as biocatalysts. The aims are to improve the recovery of clean coal by reducing the organic sulfur both in nodules and globular forms on the maceral surface during the stage of coal biooxidation prior to column bioflotation stage, in which it is still possible to achieve higher recovery of fine coal grains without sulphide mineral. The results shows that the A-Bmt method carried out through biooxidation stage followed by column bioflotation stage has better performance compared to the method without biooxidation stage. The results of this study show that the content of organic sulfur are lower by 25%.

Abstract: The effect of Ca (OH)₂ prepared by the wet-mixing method on acid-washed and raw lignite steam gasification process at 800°C were analyzed in a spout-fluid bed reactor. The addition of Ca (OH)₂ on acid-washed lignite obviously increased the coal conversion, gas yield and reduced the tar yield, and the Ca (OH)₂ addition on raw lignite significantly reduced the tar yield but just slightly increased the coal conversion and gas yield. As a catalyst, Ca (OH)₂ can promote the tar steam reforming in the gasification process. Based on GC-MS data, it can be deduced that Ca (OH)₂ has different catalytic activity on the steam reforming of tar with different molecular structures. Aliphatic hydrocarbons, Class 2 and Class 5 tars were clearly catalytic reformed, while the concentration of Class 4 tars increased. The CO concentration decreased and the CO₂ and H₂ concentration increased with the addition of Ca (OH)₂ on both acid-washed and raw lignites, which was mainly caused by the catalytic effect of Ca (OH)₂ on WGS reaction. The effect of Ca (OH)₂ addition on acid-washed lignite was more significant than on raw lignite, and no adsorption of CO₂ was detected in the process by using active carbon as a model compound_.

Abstract: The Hesigewula lignite was studied by heat treatment in a fixed bed and moisture absorption experiment. The temperature of heat treatment was considered as a factor to investigate its influence on product yield. Under the gas carrier (N₂) flow rate of 200 SCCM, 0.5 MPa and holding for 20 min, the yield of tar firstly increased and reached the maximum of 5.67 wt% at 500 °C, then came to a decrease with the increasing temperature. The proximate and ultimate analyses of the solid products had been measured. As to the moisture adsorption experiment, the equilibrium moisture content of the solid products at different humidity (30 °C) had been calculated. It was shown that the char of 600 °C adsorbed the least moisture with the minimum content of oxygen. It indicated that heat treatment can remove the oxygen-containing functional group and to some extent upgraded the coal rank.

Abstract: Hesigewula lignite was studied by fixed bed pyrolysis to achieve the optimal conditions for pyrolysis under low temperature. It was found that the maximum tar yield 6.60wt% under 50 mL/min of gas carrier, 500 °C, 0.5 MPa and holding for 15 min. By column chromatography, we extracted aromatics of the tar generated under the optimal condition. Aromatics with 2 and 3 rings are predominant in the tar from Hesigewula lignite pyrolysis by gas chromatography-mass spectrometry analysis (GC-MS), however, the tetracyclics and above compounds were very few. Naphthalene and its derivatives had pivotal position in aromatics.

Abstract: Simulation experiments on biogenic coalbed methane were conducted under an anaerobic condition provided by an anaerobic glove chamber and using parent anaerobic methanogen. These experiments aimed to analyze the isotope fractionation behavior of secondary biogenic coalbed methane generated from the lignite samples collected from Zhaotong Basin, Yunnan Province, China. Results showed that the δ¹³C₁ values of the simulated biomethane varied from −52.31‰ to −58.41‰, which were in the normal distribution range compared with those of biogenic methane. Given the organic maceral in the parent rock, the methanogen used, and the biological generation pathway of CH4, δ¹³C₁ values continued to decrease as the simulation experiment proceeded. The carbon isotope ratio transferred from raw coals to biogenic methane in the simulation, indicating the significant relationship of source material inheritance. The fractional degree of δ¹³C₁ was probably controlled by the organic maceral component in coal, which was manifested by the positive correlation between δ¹³C₁ and humic matter content, as well as the negative correlation between δ¹³C₁ and inertinite content.

Abstract: Drying of lignite alters the physical and chemical structure of coal, and influences the oxygen transport on the low temperature oxidation process. This paper provides a comprehensive overview on low-temperature oxidation of lignite and its dried products, including oxygen transport during the oxidation process, changes of physical structure and chemical compositions occurring at the drying process and its effects on the oxygen transport, and restraint of dried lignite oxidation.