Desulfurization reaction model and experimental analysis of high sulfur coal under hydrogen atmosphere

Guojie Zhang,Yannian Du,Yongfa Zhang,Ying Xu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.2

The reaction between hydrogen and high-sulfur coal at high temperature was investigated. Crashed andsieved high-sulfur coal sample was placed in a 23 mm I.D. differential reactor. The release of hydrogensulfide at run temperature and under different hydrogen atmospheres was recorded by a hydrogensulfide detector. Desulfurization yield was obtained through the elemental analysis of residual char. Thegrain reaction and random pore models were modified to facilitate the description of reaction kineticscharacteristics. Hydrogen was observed to promote the desulfurization rate considerably; i.e., more than65% of sulfur in coal could be removed. The releasing curves of H2S in the hydropyrolysis processexhibited two peaks. The desulfurization process in the hydropyrolysis of high-sulfur coal could beregarded as two stages based on the evolution profiles of H2S. The first peak at 250–450℃ was derivedfrom the desulfurization of aliphatic sulfide. The second peak at 450–650℃ was produced from thesulfur in pyrite and aromatic thiophenic structure. The desulfurization of high sulfur could be describedmore effectively with the grain reaction model than with the random pore model. The random poremodel was only adopted in the initial stage of sulfur removal of high-sulfur coal under hydrogenatmosphere. The grain reaction model was adequate for the entire stage.

Effects of preparation methods on the properties of cobalt/carbon catalyst for methane reforming with carbon dioxide to syngas

Guojie Zhang,Yongfa Zhang,Yannian Du,Ying Xu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

The effect of different preparation methods on the physicochemical property, reforming reactivity, stability and carbon deposition resistance of cobalt/carbon catalyst was investigated through fixed bed flow reaction. The catalysts were prepared by the impregnation and characterized by the XRD and scanning electron microscopy (SEM). The result indicated that the active components of cobalt/carbon catalyst prepared by using ultrasonic wave distributed evenly, activity was high and the loading time was short. The Co/Carbon catalyst prepared by incipient-wetness impregnation, 10 wt% loading and 300 ℃ calcination, achieved the best activity. Furthermore, the effect of reaction temperature, air speed and CH4/CO2 ratio on the catalyst activity and CO/H2 ratio in products was investigated. It was found that the conversion of CO2 and CH4 increased with the increasing of reaction temperature. However, the conversion of CO2 and CH4 increased first and then decreased with the increasing of air speed. With the increasing of CH4/CO2 in feed gas, both the catalyst activity and the CO/H2 ratio in products decreased.

Hydrogen production from CO2 reforming of methane over high pressure H2O2 modified different semi-cokes

Guojie Zhang,Jiangwen Qu,Yannian Du,Fengbo Guo,Haixiang Zhao,Yongfa Zhang,Ying Xu 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

H2O2 was used under different temperatures and pressures to activate three kinds of different semicokes. FTIR, BET, SEM and Boehm titration were used to analyze properties of the semi-cokes surfaces, finding that catalytic activities of these semi-cokes after modification by high temperature and high pressure H2O2 were improved. FTIR shows that the characteristic infrared absorption peak of functional groups on the semi-cokes surface does not change, but the absorption peak intensity of some functional groups is increased. The strength of –OH absorption peak of Hongce lignite (HCL) semi-coke at 3444 cm-1, carboxyl C55O at 1598 cm-1, aliphatic ether, cyclic ether and other organic functional groups at 1023 cm 1 in the modified Shenmu bituminous(SMB) semi-coke and Jincheng anthracite (JCA) semicoke are increased significantly. BET finds that the specific surface area and pore volume of three semicokes are increased after modification. Boehm titration shows that the basic functional group content in semi-coke is increased after modification, and the net alkali content is increased significantly. Compared with the raw semi-coke, SEM shows that the surface of semi-coke modified with H2O2 becomes rough. Modified JCA semi-coke surface pitted with holes, modified HCL and SMB semi-coke surface present porous.

Development of amine-functionalized hierarchically porous silica for CO2 capture

Guojie Zhang,Peiyu Zhao,Ying Xu 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-

A kind of hierarchical porous silica (HPS) was synthesized in a relatively mild condition and then devoted as the supports to fabricate TEPA-impregnated adsorbents for CO2 adsorption. HPS has different pore size distribution and the huge pore volume. These structure characteristics of HPS can mitigate the mass transfer resistance which occurs more serious in traditional carrier materials with single smaller channel. The CO2 adsorption performances of modified HPS were investigated in a homemade fixed bed reactor under different conditions. The HPS exhibited maximum CO2 adsorption capacities of 5.01 mmol/g when 60 wt.% TEPA loaded. It presented better TEPA loading properties and higher CO2 adsorption capacities than the majority of the single ordered mesoporous adsorbents according to the literature. When the adsorption experiments were repeated ten times, the amount of CO2 capture reduces from 5.01 mmol/g to 4.7 mmol/g, only 6.1% reduction. And the deactivation model which can describe the absorption of CO2 was adopted under different experiment conditions. In all these cases, the experimental data of CO2 adsorption gave a good agreement with the predicted results by the breakthrough model.

Towards understanding the carbon catalyzed CO2 reforming of methane to syngas

Guojie Zhang,Jiangwen Qu,Aiting Su,Yongfa Zhang,Ying Xu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

In this paper, a fixed-bed reactor is used to study the influence of different conditions on carboncatalyzed CO2–CH4 reforming. The surface structure and functional groups of carbonaceous materialhave been characterized through SEM, XPS, XRD, BET and chemical titration before and after the reaction. Studies have revealed that under non-catalytic condition, methane pyrolysis happens first, followed bythe gasification reaction between CO2 and carbon deposit produced from the pyrolysis. While withcarbonaceous material, CO2 gasification, methane pyrolysis and CO2–CH4 reforming can take place at thesame time, with the reforming as the main reaction, CO2 gasification and methane pyrolysis as the sidereaction. Catalytic activity varies from one carbonaceous material to another, but their reaction trend isthe same on the whole. Those high specific surface area carbonaceous materials show higher catalyticactivity. The increase in reaction temperature and residence time of the reforming can improve theconversion of reactant gas. Adjusting the partial pressure of methane can control carbon–hydrogen ratio ofthe synthesis gas. XPS and XRDcharacterizationsdemonstrate that the structural ordering of carbonaceousmaterials becomes a little messier after the reforming reaction, and the number and content of oxygenfunctional groups decrease. That means these oxygen functional groups on the surface of carbonaceousmaterials are involved in the reforming and these groups along with pore structure on the surface are themajor factors influencing the catalytic properties. Different oxygen species make the nature of electricalenergy on the surface different; the catalytic activity depends on the polarity of oxygen from differentspecies. Those whose polarity is strong have strong activity. The dipole force can be associated withmethane in the form of hydrogen bond, so that the material can display strong activity. Those whosepolarity is weak have weak activity, the catalytic activity is weak too. The results of chemical titration andXPS characterization show that the oxygen in the anhydride and lactone structures on the surface ofcarbonaceous materials are active oxygen, and which is the main active component, it can reduce theactivation energy of methane dehydrogenation.

Selective methanation of carbon monoxide over Ru-based catalysts in H2-rich gases

Yongfa Zhang,Liping Wang,Ying Xu,Yaling Sun,Guojie Zhang 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.5

A series of Ru/Al2O3 methanation catalysts containing 0.5–5.0% Ru were prepared by impregnation. This study was designed to investigate the optimization conditions and catalytic activities for the selective methanization of carbon monoxide in hydrogen-containing streams, by use of a catalytically active composition which comprises ruthenium as the active component and a support material based on aluminum oxide. The properties of the catalysts were characterized by XRD, TG and SEM technique. A number of laboratory experiments were performed to clarify the influence of process parameters (Ru loading, calcinations temperature, space velocity and chlorine ions content) on the activities of catalysts. The experimental results showed that the application of ultrasound impregnation could significantly decrease impregnation time and improve the activity of catalyst. The optimum process preparation conditions for these factors were found to be space velocity 3000 h1, calcination temperature 400 8C and 2% Ru loading, respectively. Under these conditions, the CO conversion and CH4 selectivity were 97.2% and 83.3%. The catalyst washed with deionized water and diluted ammonia not only removed chlorine, but also improved the catalytic activity. Overall, the catalyst showed high performance at optimization preparation conditions, and its activity was maintained after 4320 min. It was a promising candidate for utilizing H2-rich gas to produce methane at a wide temperature window.

Synthesis of Trilaminar Core–Shell Au/α-Fe2O3@SnO2 Nanocomposites and their Application for Nonenzymatic Dopamine Electrochemical Sensing

Sai Zhang,Shijun Yue,Jiajia Li,Jian-Bin Zheng,Guojie Gao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.11

Au nanoparticles anchored on core–shell α-Fe2O3@SnO2 nanospindles were successfully constructed through hydrothermal synthesis process and used for fabricating a novel nonenzymatic dopamine (DA) sensor. The structure and morphology of the Au/α-Fe2O3@SnO2 trilaminar nanohybrid film were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the sensor were investigated by cyclic voltammetry and amperometry. The experimental results suggest that the composites have excellent catalytic property toward DA with a wide linear range from 0.5 μM to 0.47 mM, a low detection limit of 0.17 μM (S/N = 3) and high sensitivity of 397.1 μA mM -1 cm -2. In addition, the sensor exhibits long-term stability, good reproducibility and anti-interference.

Weighted Local Naive Bayes Link Prediction

( Jiehua Wu ),( Guoji Zhang ),( Yazhou Ren ),( Xiayan Zhang ),( Qiao Yang ) 한국정보처리학회 2017 Journal of information processing systems Vol.13 No.4

Weighted network link prediction is a challenge issue in complex network analysis. Unsupervised methods based on local structure are widely used to handle the predictive task. However, the results are still far from satisfied as major literatures neglect two important points: common neighbors produce different influence on potential links; weighted values associated with links in local structure are also different. In this paper, we adapt an effective link prediction model―local naive Bayes model into a weighted scenario to address this issue. Correspondingly, we propose a weighted local naive Bayes (WLNB) probabilistic link prediction framework. The main contribution here is that a weighted cluster coefficient has been incorporated, allowing our model to inference the weighted contribution in the predicting stage. In addition, WLNB can extensively be applied to several classic similarity metrics. We evaluate WLNB on different kinds of real-world weighted datasets. Experimental results show that our proposed approach performs better (by AUC and Prec) than several alternative methods for link prediction in weighted complex networks.

Weighted Local Naive Bayes Link Prediction

Wu, JieHua,Zhang, GuoJi,Ren, YaZhou,Zhang, XiaYan,Yang, Qiao Korea Information Processing Society 2017 Journal of information processing systems Vol.13 No.4

Weighted network link prediction is a challenge issue in complex network analysis. Unsupervised methods based on local structure are widely used to handle the predictive task. However, the results are still far from satisfied as major literatures neglect two important points: common neighbors produce different influence on potential links; weighted values associated with links in local structure are also different. In this paper, we adapt an effective link prediction model-local naive Bayes model into a weighted scenario to address this issue. Correspondingly, we propose a weighted local naive Bayes (WLNB) probabilistic link prediction framework. The main contribution here is that a weighted cluster coefficient has been incorporated, allowing our model to inference the weighted contribution in the predicting stage. In addition, WLNB can extensively be applied to several classic similarity metrics. We evaluate WLNB on different kinds of real-world weighted datasets. Experimental results show that our proposed approach performs better (by AUC and Prec) than several alternative methods for link prediction in weighted complex networks.

Damping for Wind Turbine Electrically Excited Synchronous Generators

Tianyu, Wang,Guojie, Li,Yu, Zhang,Chen, Fang The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.4

The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.