Papers by Keyword: Coking

Abstract: The oil industry increasingly exploits ‘heavy oils’ which are highly viscous and difficult to extract in a ‘clean’ way. Heat and ‘cracking’ catalysts facilitate extraction e.g. by applying the ‘Toe-to-Heel Air Injection’ (THAI) and ‘Catalytic Process In-Situ’ (CAPRI) techniques. Cracking catalysts include palladium. Use of Pd-catalyst is uneconomic but by using palladium deposited on bacterial cells (in combination with other PMs) a waste can be turned into a valuable product. Road dusts contain precious metals (PMs) which arise from automotive catalytic converters. Once washed from roads the PMs are dispersed to the environment. Model r oad dust solutions were produced to simulate acid leaching of road dust to solubilise the PMs. Bacteria cannot directly recover PMs from acidic leachate but by lightly depositing Pd(0) ‘seeds’ enzymatically the resulting ‘bio-Pd’-catalyst accumulates PMs from waste model leachate. The bio-catalyst was assessed in the reduction of heavy oil viscosity compared to a commercial catalyst, achieving this reduction with significantly less coke formation, which was not attributable to the biomass component alone.

Abstract: Cr25Ni35Nb and Cr35Ni45Nb austenitic steels, used as furnace tube material in the ethylene pyrolysis furnace, generally suffer from coking during the long operation period. In the present paper, for coked Cr25Ni35Nb and Cr35Ni45Nb austenitic steel, using the finite element ABAQUS code, a sequentially coupled thermal stress procedure was developed to calculate distribution of the temperature and thermal stress field. The results show that thermal diffusion property of Cr25Ni35Nb and Cr35Ni45Nb steel deteriorates obviously with coking layer increasing. Radial bulge and rupture at local field would generate due to excess temperature for applied subsequent measurement. Maximum stress distribute along the cross-section of coking layer and metal matrix. Finally, the critical depth of coking layer of Cr25Ni35Nb and Cr35Ni45Nb austenitic steel are predicted when decoking measurement must be executed.

Abstract: Effects of pressure of toluene, reaction temperature and nature of catalysts on coking over catalysts in toluene disproportionation are studied by using the method of thermogravimetry. Experiment results show that during the toluene disproportionation, the coking amount over catalysts increases with partial pressure of toluene and reaction temperature and the initial coking temperature decreases with partial pressure of toluene. Coking results mainly from the relatively stronger acid sites on the surface of the catalyst. Both HZSM-5 and HM catalysts have efficiency for toluene disproportionation, but HZM-5 catalyst has higher catalytic activity and stability.

Abstract: Coking characteristics of China RP-3 under high temperature (above 650°C) and long-duration (20 minutes) conditions, especially the effects of temperature, pressure, and inner diameter of cooling channels on coking amount were experimentally investigated. Temperature of kerosene in experiments varied from 650°C to 730°C, pressure varied from 1.8MPa to 3.5MPa, and the mass flow rate was approximately 120g/min. Results showed that temperature has a significant influence on coking amount. Even a small increment of temperature induces remarkable coke formation. However, pressure and inner diameter of the tube has a relatively little effect on it. The coking amount increases as pressure and inner diameter increase, but the increasing rate is decreasing. It is considered that inner diameter mainly affects residence time. When residence time increases to some extent, coking amount begins to grow slowly even stop increasing. This is resulted from two reasons. Firstly, the cracking conversion percentage reaches an upper limit when residence time is adequately long; secondly, coke gradually covers the inner wall of the tube, leading to isolation of kerosene from the metal surface to form coking.

Abstract: This study investigated the improving catalytic effects during tar catalytic reforming by impregnated NiO and CeO₂ onto olivine, and the further reduction of carbon deposition on the catalysts was achieving by the addition of MgO. A series of characters of the catalysts were tested by XRD, TPR and TPD. The experimental results showed the addition of MgO could improve the resistance to carbon deposition and had demonstrated higher reaction activity at higher temperature and lower water-carbon ratio. The activities of catalysts were not only related to the impregnating order of the promoters NiO and CeO₂ but also to the water (steam)-carbon ratio (S/C). Those catalysts impregnated Mg, Ce and Ni in order could achieve highly disperse sites and further promote the interaction between active sites and carriers. Furthermore, those catalysts also had higher reaction activity and better anti-coking abilities under low water (steam)-carbon ratios.

Abstract: The research of all kinds of factors is put up on the inner coking of coal in the plasma reactor during the processing of pyrolysis of coal to acetylene, includ cooking phenomenon, coal of property, coal of grain degree, enter anticipate a speed , power and equip structure. In the arc plasma jet, different kind of coal has different coking character. The aromatics, colloids, asphaltene and carbenes are the precursors of the cokes.The mostly reasons of coking in the plasma reaction equipment are the particle size, the feeding velocity, the power of plasma and the structure of equipment. With the increasing of feeding velocity, the coking of system becomes worse. When the particle size is less than 80~100 mesh, the system will not produce cokes. When the particle size is about 100~120 mesh, the system will begin to produce cokes. When the particle size is larger than 140 mesh, the system will produce a lot of cokes.With the increasing of plasma power, the speed of coking will become smaller.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are discharged into the atmosphere during coking process. They are the typical persistent organic pollutants with their teratogenic, carcinogenetic, and mutagenic. The writer studied the PAHs in blending coal coking process through laboratory sampling and high-performance liquid chromatography analysis, observed and summarized the generation regularity and emission characteristics of PAHs in three kinds of blending coal coking process, and provided the foundation data for the control of PAHs in coking process.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) is a kind of the typical persistent organic pollutants with their teratogenic, carcinogenetic, mutagenic. Coking production process has become one of the main sources of PAHs in the environment. For researching the generation and emission properties of PAHs in coking process, the writer studied the PAHs in single coal coking process through laboratory sampling and high-performance liquid chromatography analysis, observed and summarized the generation regularity and emission characteristics of PAHs in three kinds of single coal coking process, and provided the foundation data for the control of PAHs in coking process.

Abstract: Five representative coal samples used for coking were carbonized in a thermogravimetric analyzer to simulate an industrial coking process. The gaseous organic compounds generated were analyzed with a coupled mass spectrometer. During coal carbonization, thermal detachment of aliphatic side groups causes disintegration of the coal structure. Methyl groups detach at higher temperatures than methylene and methine groups, and the temperatures corresponding to peak generation of these groups increase with the metamorphic grade of the coal. Methane is generated by three mechanisms: below 370 °C, methane adsorbed in coal is thermally released; at about 510 °C, methyl groups are thermally detached from the coal to form CH₃⁺ ions, which further combine with hydrogen to form methane; finally, at about 720 °C, methane is produced as a result of the condensation of aromatic rings to form larger fused rings. Benzene is also generated by three mechanisms: at 400–500 °C, aromatic structures in coal lose side groups (e.g. methylene or methine) to form benzene ions, which subsequently react with hydrogen to form benzene; at 500–700 °C, benzyl structures in coal lose methyl groups to form benzene ions, which then combine with hydrogen to form benzene; finally, at about 800 °C, condensation of fragments in coal also forms benzene.

Abstract: A new adsorption material technology and its adsorption mechanism were studied in this paper. Anthracite and lignite were taken as raw materials in those experiments. Firstly, the coal was made into different sizes by ball mill then cooked in tube furnace so as to obtain the ultrafine coal material for methane adsorption. Secondly, the ultrafine coal powder which fully adsorbed methane was gone through the gas chromatography analysis to choose the best samples. Finally, the characterization of adsorption and adsorption mechanism were researched by the micro-morphology analysis, thermal analysis, X-ray diffraction analysis, BET surface area-aperture-volume analysis and infrared spectral analysis. The results of experiments showed that the ultrafine lignite powder which mainly consists of microporous, is more suitable for methane adsorption. Under the same treatment condition, the adsorption capacity of lignite series is better than that of anthracite series. After milling for 120 minutes and coking in medium temperature, the lignite could be used as the best material of ultrafine coal powder for methane adsorption.