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Development and demonstration plant operation of an opposed multi-burner coal-water slurry gasification technology
WANG Fuchen, ZHOU Zhijie, DAI Zhenhua, GONG Xin, YU Guangsuo, LIU Haifeng, WANG Yifei, YU Zunhong
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 251-258.
https://doi.org/10.1007/s11708-007-0035-5
The features of the opposed multi-burner (OMB) gasification technology, the method and process of the research, and the operation results of a pilot plant and demonstration plants have been introduced. The operation results of the demonstration plants show that when Beisu coal was used as feedstock, the OMB CWS gasification process at Yankuang Cathy Coal Co. Ltd had a higher carbon conversion of 3%, a lower specific oxygen consumption of about 8%, and a lower specific carbon consumption of 2%–3% than that of Texaco CWS gasification at the Lunan Fertilizer Plant. When Shenfu coal was used as feedstock, the OMB CWS gasification process at Hua-lu Heng-sheng Chemical Co. Ltd had a higher carbon conversion of more than 3%, a lower specific oxygen consumption of about 2%, and a lower specific coal consumption of about 8% than that of the Texaco CWS gasification process at Shanghai Coking & Chemical Corporation. The OMB CWS gasification technology is proven by industrial experience to have a high product yield, low oxygen and coal consumption and robust and safe operation.
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Feasibility study on simultaneous removal of sulfur and trace selenium in the MTD-FGD reactor
LI Yuzhong, TONG Huiling, ZHUO Yuqun, LI Yan, CHEN Changhe, XU Xuchang
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 259-263.
https://doi.org/10.1007/s11708-007-0036-4
This study deals with the simultaneous removal of sulfur dioxide (SO2) and trace selenium dioxide (SeO2) from flue gas by calcium oxide (CaO) adsorption in the moderate temperature range, especially the feasibility of simultaneous removal of these two pollutants in a moderate temperature dry flue gas desulfurization (MTD-FGD) reactor. The effect of SO2 presence on selenium capture is studied through the experiments performed on a thermogravimetric analyzer (TGA) and the following conclusions can be obtained. When CaO conversion is relatively low and the reaction rate is controlled by chemical reaction kinetics, the SO2 presence does not affect selenium capture. When CaO conversion is very high and the reaction rate is controlled by product layer diffusion, the SO2 presence and the product layer diffusion resistance jointly reduce selenium capture. Through analyses of some pilot scale MTD-FGD tests, it can be concluded that in the MTD-FGD reactor, the sulfate reaction of sorbent particles is generally kinetically controlled. Therefore, it is feasible that sulfur and trace selenium can be simultaneously removed by Ca-based sorbent in the MTD-FGD reactor.
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Numerical investigation on the dryout point of annular flow in the upward narrow annuli with bilateral heating
SU Guanghui, QIU Suizheng, DUAN Feng, XIAO Zejun, HUANG Yanping
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 264-272.
https://doi.org/10.1007/s11708-007-0037-3
Based on the fundamental conservation principles—the mass, momentum, and energy conservation equtions of liquid films and the momentum conservation equation of vapor core, a theoretical three-fluid model has been developed to predict the dryout point of upward annular flow in vertical narrow annuli with bilateral heating. The range of the parameters are: pressure from 0.5 to 5.0 MPa; mass flow rate from 30 to 150 kg/(m2 · s); gap size from 1.2 to 2.0 mm. Through numerically solving the model, the relationships among the parameters of the critical quality (XC), critical heat flux (QCHF), mass flow rate, system pressure, and the ratio of heat flux on the inner wall of the outer tube to that on the outer wall of the inner tube (qo/qi) are obtained and analyzed. The predicted results accurately match with the experimental data. For a fixed qo, XC will increase with the decreases in the gap size and the tube curvature when the dryout point occurs on the outer wall of the inner tube. However, for a fixed qi, when the dryout point occurs on the inner wall of the outer tube, the parametric trend is reverse. When the dryout point on the inner and outer walls occurs simultaneously, XC reaches a peak value, and the ratio of qo/qi at this position changes with the gap size and the tube curvature.
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Preliminary study of trace element emissions and control during coal combustion
ZHANG Junying, ZHAO Yongchun, DING Feng, ZENG Hancai, ZHENG Chuguang
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 273-279.
https://doi.org/10.1007/s11708-007-0038-2
Hazardous trace element emissions have caused serious harm to human health in China. Several typical high-toxic trace element coals were collected from different districts and were used to investigate the emission characteristics of toxic trace elements (As, Se, Cr, Hg) and to explore preliminary control methods. Coal combustion tests were conducted in several bench-scale furnaces including drop tube furnace (DTF), circulating fluidized bed (CFB) combustion furnace, and fixed-bed combustion furnace. Calcium oxide was used to control the emission of arsenic and selenium. The granular activated carbons (AC) and activated-carbon fibers (ACF) were used to remove mercury in the flue gas from coal combustion. The chemical composition and trace element contents of ash and particulate matter (PM) were determined by X-ray fluorescence (XRF) spectrometry and inductively coupled plasma-atomic emission spectrometry (ICP-AES), respectively. The speciation and concentration of mercury were investigated using the Ontario-Hydro method. X-ray diffraction spectrometry (XRD) was used to determine the mineral composition of production during combustion experiments. With the addition of a calcium-based sorbent, arsenic concentration in PM1 sharply decreased from 0.25–0.11 mg/m3. In fixed-bed combustion of coal, the retention rates of selenium volatiles were between 11.6% and 50.7% using lime. In the circulating fluidized-bed combustion of coal, the content of selenium in ash from the chimney was reduced to one-fourth of its original value and that in leaching water from the chimney decreased by two orders of magnitude using lime. Calcium-based sorbent is an effective additive to control the emission of As and Se during coal combustion. The emission of chromium is influenced by the occurrence mode of Cr in coal. Chromium emission in PM2.5 during coal combustion is 55.5 and 34.7 μg/m3 for Shenbei coal and mixed Pingdingshan coal, respectively. The adsorptive capacity of granular activated carbon for Hg0 is significantly enhanced through ZnCl2-impregnation. The activated carbon fibers showed decent efficiency in mercury adsorption, on which surface oxygen complex showed positive effects on mercury adsorption.
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Fuzzy cascade control based on control’s history for superheated temperature
WANG Guangjun, LI Gang, SHEN Shuguang
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 285-289.
https://doi.org/10.1007/s11708-007-0040-8
To address the characteristics of the large delay and uncertainty of superheated temperature, a new cascade control system is presented based on control’s history. Based on the analysis of the control objects’ dynamic characteristics, historical control information (substituting for the deviation change rate) is used as the basis for decision-making of the fuzzy control. Therefore, the changing trend of the controlled variable can be accurately reflected. Furthermore, a proportional component is introduced, the advantages of PID and fuzzy controllers are integrated, and the structure weaknesses of conventional fuzzy controllers are overcome. Simulation shows that this control method can effectively reduce the adverse impact of the delay on control effects and, therefore, exhibit strong adaptability by comparing the superheated temperature control system by this controller with PID and conventional fuzzy controllers.
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An investigation into the heat transfer characteristics of spiral wall with internal rib in a supercritical sliding-pressure operation once-through boiler
TANG Renhu, YIN Fei, WANG Haijun, CHEN Tingkuan
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 300-304.
https://doi.org/10.1007/s11708-007-0043-5
Within the pressure range of 9–28 MPa, mass velocity range of 600–1 200 kg/(m2 · s), and heat flux range of 200–500 kW/m2, experiments were performed to investigate the heat transfer to water in the inclined upward internally ribbed tube with an inclined angle of 19.5 degrees, a maximum outer diameter of 38.1 mm, and a thickness of 7.5 mm. Based on the experiments, it was found that heat transfer enhancement of the internally ribbed tube could postpone departure from nucleate boiling at the sub-critical pressure. However, the heat transfer enhancement decreased near the critical pressure. At supercritical pressure, the temperature difference between the wall and the fluid increased near the pseudo-critical temperature, but the increase of wall temperature was less than that of departure from nucleate boiling at sub-critical pressure. When pressure is closer to the critical pressure, the temperature difference between the wall and the fluid increased greatly near the pseudo-critical temperature. Heat transfer to supercritical water in the inclined upward internally ribbed tube was enhanced or deteriorated near the pseudo-critical temperature with the variety of ratio between the mass velocity and the heat flux. Because the rotational flow of the internal groove reduced the effect of natural convection, the internal wall temperature of internally ribbed tube uniformly distributed along the circumference. The maximum internal wall temperature difference of the tube along the circumference was only 10 degrees when the fluid enthalpy exceeded 2 000 J/g. Considering the effect of acute variety of the fluid property on heat transfer, the correlation of heat transfer coefficient on the top of the internally ribbed tube was provided.
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Control of homogeneous charge compression ignition combustion in a two-cylinder gasoline direct injection engine with negative valve overlap
WANG Zhi, WANG Jianxin, SHUAI Shijin, MA Qingjun, TIAN Guohong
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 311-315.
https://doi.org/10.1007/s11708-007-0045-3
Homogeneous charge compression ignition (HCCI) has challenges in ignition timing control, combustion rate control, and operating range extension. In this paper, HCCI combustion was studied in a two-cylinder gasoline direct injection (GDI) engine with negative valve overlap (NVO). A two-stage gasoline direct injection strategy combined with negative valve overlap was used to control mixture formation and combustion. The gasoline engine could be operated in HCCI combustion mode at a speed range of 800–2 200 r/min and load, indicated mean effective pressure (IMEP) range of 0.1–0.53 MPa. The engine fuel consumption is below 240 g/(kW-1>/sup> · h-1), and the NOx emission is below 4×10-5 without soot emission. The effect of different injection strategies on HCCI combustion was studied. The experimental results indicated that the coefficient of variation of the engine cycle decreased by using NVO with two-stage direct injection; the ignition timing and combustion rate could be controlled; and the operational range of HCCI combustion could be extended.
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Biological chip technology to quickly batch select optimum cryopreservation procedure
YU Lina, LIU Jing, ZHOU Yixin, HUA Zezhao
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 316-321.
https://doi.org/10.1007/s11708-007-0046-2
In the practices of cryobiology, selection of an optimum freeze/thawing program and an idealistic cryoprotective agent often requires rather tedious, time consuming and repetitive tests. Integrating the functions of sample preparation and viability detection, the concept of biochip technology was introduced to the field of cryopreservation, aiming at quickly finding an optimum freezing and thawing program. Prototype devices were fabricated and corresponding experimental tests were performed. It was shown that microflow-channel chip could not offer a high quality solution distribution. As an alternative, the spot-dropping chip proved to be an excellent way to load the sample quickly and reliably. Infrared thermal mapping on such a chip showed that it had a rather uniform heat transfer boundary. Applying the spot-dropping chip combined with the thermoelectric cooling device, the final output of cryopreservation of multiple samples was tested, and the optimal freeze/thawing program as well as the potentially best concentration of the cryoprotective agent was found by analyzing the results. Further, application of this technique to measure the thermo-physical properties of the cryo-protective agent was also investigated. The study demonstrated that a biochip with integrated automatic loading and inspection units opens the possibility of a massive optimization of the complex cryopreservation program in a quicker and more economical way.
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Hydrogen production from co-gasification of coal and biomass in supercritical water by continuous flow thermal-catalytic reaction system
YAN Qiuhui, GUO Liejin, LIANG Xing, ZHANG Ximin
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 327-330.
https://doi.org/10.1007/s11708-007-0048-0
Hydrogen is a clean energy carrier. Converting abundant coal sources and green biomass energy into hydrogen effectively and without any pollution promotes environmental protection. The co-gasification performance of coal and a model compound of biomass, carboxymethylcellulose (CMC) in supercritical water (SCW), were investigated experimentally. The influences of temperature, pressure and concentration on hydrogen production from co-gasification of coal and CMC in SCW under the given conditions (20–25 MPa, 650vH, 15–30 s) are discussed in detail. The experimental results show that H2, CO2 and CH4 are the main gas products, and the molar fraction of hydrogen reaches in excess of 60%. The higher pressure and higher CMC content facilitate hydrogen production; production is decreased remarkably given a longer residence time.
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Emission characteristics of a turbocharged diesel engine fueled with gas-to-liquids
WU Tao, ZHANG Wugao, FANG Junhua, HUANG Zhen
Frontiers of Energy and Power Engineering in China. 2007, 1 (3): 331-335.
https://doi.org/10.1007/s11708-007-0049-z
Emission characteristics of a turbocharged, inter-cooled, heavy-duty diesel engine operating on neat gas-to-liquids (GTL) and blends of GTL with conventional diesel were investigated and a comparison was made with those of diesel fuel. The results show that nitrogen oxides (NOx), smoke, and particulate matter (PM) emissions can be decreased when operating on GTL and diesel-GTL blends. Engine emissions decrease with an increase of GTL fraction in the blends. Compared with diesel fuel, an engine operating on GTL can reduce NOx, PM, carbon monoxide (CO), and hydrocarbon (HC) by 23.7%, 27.6%, 16.6% and 12.9% in ECE R49 13-mode procedure, respectively. Engine speed and load have great influences on emissions when operating on diesel-GTL blends and diesel fuel in the turbocharged diesel engine. The study indicates that GTL is a promising alternative fuel for diesel engines to reduce emissions.
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