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Effects of recycle and split ratios on the performance of CO2 utilized gas-to-methanol process
( Chundong Zhang ),전기원,곽근재,이윤조,박해구 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Two process models for CO2 utilized gas-to-methanol (GTM) process (CGTM), primarily producing methanol were developed by Aspen Plus. Both models are mainly comprised of a reforming unit, a methanol synthesis unit and a recycle unit, with the feeding point of the fresh CO2 as the main configurational difference. With recycling, it was found that the thermal and carbon efficiencies increased, less amount of CO2 was emitted from the process and more methanol was produced. It was shown that the process efficiency was sensitive to the recycle ratio and more recycle seemed to be beneficial for improving process efficiency and reducing CO2 emissions. However, the process efficiency was not very sensitive to the split ratio, and the optimum split ratio was determined to be zero.
Intrusion Detection for Black Hole and Gray Hole in MANETs
( Chundong She ),( Ping Yi ),( Junfeng Wang ),( Hongshen Yang ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.7
Black and gray hole attack is one kind of routing disturbing attacks and can bring great damage to the network. As a result, an efficient algorithm to detect black and gray attack is important. This paper demonstrate an adaptive approach to detecting black and gray hole attacks in ad hoc network based on a cross layer design. In network layer, we proposed a path-based method to overhear the next hop`s action. This scheme does not send out extra control packets and saves the system resources of the detecting node. In MAC layer, a collision rate reporting system is established to estimate dynamic detecting threshold so as to lower the false positive rate under high network overload. We choose DSR protocol to test our algorithm and ns-2 as our simulation tool. Our experiment result verifies our theory: the average detection rate is above 90% and the false positive rate is below 10%. Moreover, the adaptive threshold strategy contributes to decrease the false positive rate.
Technical and economic analysis for a modular gas-to-liquids process
( Chundong Zhang ),( Ruxing Gao ),이윤조,전기원 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Two process models for modular GTL process, mainly producing Fischer-Tropsch (F-T) synthetic oils were developed by Aspen Plus. Both models mainly comprised a reforming unit, an F-T synthesis unit, and a recycle unit, with the syngas generation and syngas ratio conditioning methods as the main difference. In the reforming unit, steam reforming or CO2/Steam-mixed reforming was selected to generate the desired syngas. Then, the Co-based microchannel F-T synthesis was applied to convert the obtained syngas to synthetic oils. After F-T synthesis, a portion of the unreacted syngas was recycled to improve energy efficiency, and reduce CO2 emissions. Both technical and economic analysis were implemented to investigate the two modular GTL options. It was shown that the increased energy efficiency and reduced CO2 emissions were achieved by recycling. Meanwhile, both options were economically viable at 2,500 BPD, and were more competitive in case of high carbon tax.
Effects of crude methanol recycling on the performance of novel methanol-to-dimethyl ether process
( Chundong Zhang ),김성탁,전기원,곽근재,김용태 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Two Methanol-to-Dimethyl ether (MTD) process scenarios 1 and 2 were proposed to develop new MTD processes with improved energy efficiency, by using crude methanol (i.e., water-containing methanol) combined with a water-tolerant K-modified HZSM-5 catalyst. Process modeling was implemented to obtain the quantitative energy analysis results via Aspen Plus software. Both scenarios mainly comprise units of methanol preheating, methanol dehydration, DME separation, methanol separation, and crude methanol recycling. While, the main difference is the way of methanol recycling. The process performance was investigated by varying the recycle ratio or the recycled methanol purity in scenarios 1 and 2, respectively, and compared with the conventional γ-Al2O3 based MTD process. Both Scenarios were shown to be more energy-efficient, and scenario 2 seems to be more beneficial for saving energy as well as CAPEX and OPEX.
Zhang, Chundong,Jun, Ki-Won,Gao, Ruxing,Kwak, Geunjae,Park, Hae-Gu Elsevier Ltd 2017 Fuel Vol.190 No.-
<P><B>Abstract</B></P> <P>Conceptual design for two options of carbon-dioxide-utilized gas-to-methanol process (CGTM) was implemented by using process simulation software Aspen Plus. The overall mass and energy stream results as well as the thermal and carbon efficiency were obtained from the developed process models. Before the following economic evaluation and sensitivity analysis, total capital investment (TCI) and total product cost (TPC) of both CGTM options were determined. Then, economic evaluation were conducted to assess the economic profitability of the base cases for both CGTM options, using the economic evaluation indicators such as net present value (NPV), internal rate of return (IRR), and discounted payback period (DPBP). Furthermore, sensitivity analysis as well as break-even analysis were also applied to investigate the economic performance of both CGTM options under different circumstances, by changing parameters such as methanol and NG prices, plant scale, and carbon tax. It was shown that the methanol price, CAPEX, and NG price are the most sensitive factors, and the two CGTM options were economically feasible in the plant scale range of 2500–5000 ton per day, according to the economic evaluation indicators NPV, IRR, and DPBP, and were more economically competitive in the case of higher plant scale and carbon tax.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two options of CO<SUB>2</SUB> utilized gas-to-methanol (CGTM) process are proposed. </LI> <LI> CO<SUB>2</SUB> is converted via CO<SUB>2</SUB>/Steam-mixed reforming and CO<SUB>2</SUB> hydrogenation. </LI> <LI> Process simulation and conceptual design are implemented using Aspen Plus. </LI> <LI> Techno-economic analysis is implemented to evaluate the economic feasibility. </LI> <LI> Both options are economically feasible in the plant scale range of 2500–5000TPD. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Zhang Chundong ),전기원 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Two process models for carbon dioxide (CO<sub>2</sub>) utilized gas-to-liquids (GTL) process mainly producing methanol were developed by Aspen Plus software. Both models are mainly comprised of a reforming unit, a methanol synthesis unit and a recycle unit. With recycling, it was found that the energy efficiency was successfully improved and the net CO<sub>2</sub> emission was significantly reduced, compared to the conventional GTL process. Meanwhile, the energy efficiency was sensitive to the recycle ratio and more recycle seemed to be favorable for improving CO<sub>2</sub> conversion, enhancing energy efficiency and reducing CO<sub>2</sub> emission.
Zhang, Chundong,Jun, Ki-Won,Ha, Kyoung-Su,Lee, Yun-Jo,Kang, Seok Chang American Chemical Society 2014 Environmental science & technology Vol.48 No.14
<P>Two process models for carbon dioxide utilized gas-to-liquids (GTL) process (CUGP) mainly producing light olefins and Fischer-Tropsch (F-T) synthetic oils were developed by Aspen Plus software. Both models are mainly composed of a reforming unit, an F T synthesis unit and a recycle unit, while the main difference is the feeding point of fresh CO2. In the reforming unit, CO2 reforming and steam reforming of methane are combined together to produce syngas in flexible composition. Meanwhile, CO2 hydrogenation is conducted via reverse water gas shift on the Fe-based catalysts in the F-T synthesis unit to produce hydrocarbons. After F-T synthesis, the unreacted syngas is recycled to F-T synthesis and reforming units to enhance process efficiency. From the simulation results, it was found that the carbon efficiencies of both CUGP options were successfully improved, and total CO2 emissions were significantly reduced, compared with the conventional GTL processes. The process efficiency was sensitive to recycle ratio and more recycle seemed to be beneficial for improving process efficiency and reducing CO2 emission. However, the process efficiency was rather insensitive to split ratio (recycle to reforming unit/total recycle), and the optimum split ratio was determined to be zero.</P>
Jia Fu,Yuejiang Shi,Yingying Li,Fudi Wang,Sheng Liu,Jian Zhang,Jun Li,Yiyyun Huang,Yuanlai Xie,Zhimin Liu,Chundong Hu,Chundong Hu,DNB Team,William Rowan,He Huang 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.5
A diagnostic neutral beam (DNB) has been installed on the HT-7 tokamak for the measurement of charge exchange recombination spectroscopy (CXRS). The H_α-light Doppler shift spectroscopy from the drifted duct is measured to determine the components of the neutral beam. The fractions of neutral beam species are investigated under a wide range of arc voltages and extraction high voltages of the beam aimed to the optimized species fractions for the CXRS applications. A magnet ring is used to improve the magnetic property of the ion source. The result shows that the full-energy component fractions increase from 19 to 25 percent with optimization of the beam operation, but with a dramatic increase of the water component. There are nine optical fiber channels observing one section of the beam simultaneously for this spectroscopy, which provides information of the power profiles of the beam. The full width at half maximum (FWHM) of the beam profile is 8 cm, as measured by using the spectroscopy.