Sep 2007, Volume 1 Issue 3
    

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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
    2007, 1(3): 251-258. https://doi.org/10.1007/s11708-007-0035-5
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    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.
  • 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
    2007, 1(3): 259-263. https://doi.org/10.1007/s11708-007-0036-4
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    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.
  • 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
    2007, 1(3): 264-272. https://doi.org/10.1007/s11708-007-0037-3
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    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.
  • Preliminary study of trace element emissions and control during coal combustion
    ZHANG Junying, ZHAO Yongchun, DING Feng, ZENG Hancai, ZHENG Chuguang
    2007, 1(3): 273-279. https://doi.org/10.1007/s11708-007-0038-2
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    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.
  • Experimental study on low temperature thermal treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in fly ash
    YAN Jianhua, CHEN Tong, LU Shengyong, LI Xiaodong, GU Yueling, CEN Kefa
    2007, 1(3): 280-284. https://doi.org/10.1007/s11708-007-0039-1
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    The effects of temperature and time on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) distribution in fly ash of a municipal solid waste incinerator (MSWI) were studied in a tubular oven under nitrogen atmosphere. The PCDD/Fs in the gas phase and solid phase were detected by high-resolution gas chromatography coupled with low resolution mass spectrometry (HRGC/LRMS) se para tely. The experimental results showed that the major congener was octa-chlorinated dibenzo-ρ-dioxin (OCDD) in the gas phase and the low chlorinated congeners were the major products in the solid phase. There were high levels of OCDD in the gas phase in several experimental conditions although the PCDD/Fs in the solid phase could be decomposed. The optimum condition for PCDD/Fs decomposition in fly ash was a heating time of 60 min at 400 vH under nitrogen atmosphere.
  • Fuzzy cascade control based on control’s history for superheated temperature
    WANG Guangjun, LI Gang, SHEN Shuguang
    2007, 1(3): 285-289. https://doi.org/10.1007/s11708-007-0040-8
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    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.
  • Investigation into the influence of diffuser stagger angles on the flow field and performance of a centrifugal compressor
    XI Guang, DING Haiping, YUAN Minjian, ZHANG Chunmei, ZHOU Li
    2007, 1(3): 290-294. https://doi.org/10.1007/s11708-007-0041-7
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    The performance graphs of a centrifugal compressor under different diffuser stagger angles were measured, and the influence of different stagger angles of vanes on the stage performance as well as flow field was investigated numerically. The results show that the performance graph shifts when the diffuser stagger angle is altered; the influence of different stagger angles of vanes on the flow field inside the centrifugal compressor is great. Large scale vortices appear on the diffuser vane under larger incidence. An optimal diffuser stagger angle should exist at a specified flow rate to make the characteristic of the flow optimized. The incidence corresponding to the highest efficiency is not 0º at the design condition.
  • High pressure air spray assistant power supply control strategies and their effects on diesel engine under transient operations
    HAN Yongqiang, LIU Zhongchang, WANG Zhongshu, ZHU Ruoqun
    2007, 1(3): 295-299. https://doi.org/10.1007/s11708-007-0042-6
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    In order to reduce smoke from direct-injection (DI) turbo-charged and after-cooled (TCA) diesel engines under transient operations, the real-time controlling and measuring system of a high pressure air spray assistant power supply (HPAS) was developed. Effects of HPAS on a DI TCA diesel engine under constant engine speed and increased torque (CSIT) transient operations were studied by using different control strategies. Pre-spray (PS) strategy, which means supplying highly pressurized air into the exhaust manifold two seconds before the accelerating-graph begins to rise and stopping spraying air when the accelerating-graph stops rising. Two other strategies—full-time-spray (FTS) and middle-time-spray (MTS)—were used to fully exploit HPAS potential. With the FTS and MTS strategies, the HPAS system can remarkably decrease smoke from DI TCA diesel engines under transient operations.
  • 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
    2007, 1(3): 300-304. https://doi.org/10.1007/s11708-007-0043-5
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    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.
  • Numerical simulation of three-dimensional gas/liquid two-phase flow in a proton exchange membrane fuel cell
    ZHUGE Weilin, ZHANG Yangjun, LAO Xingsheng, CHEN Xiao, MING Pingwen
    2007, 1(3): 305-310. https://doi.org/10.1007/s11708-007-0044-4
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    Investigation into the formation and transport of liquid water in proton exchange membrane fuel cells (PEMFCs) is the key to fuel cell water management. A three-dimensional gas/liquid two-phase flow and heat transfer model is developed based on the multiphase mixture theory. The reactant gas flow, diffusion, and chemical reaction as well as the liquid water transport and phase change process are modeled. Numerical simulations on liquid water distribution and its effects on the performance of a PEMFC are conducted. Results show that liquid water distributes mostly in the cathode, and predicted cell performance decreases quickly at high current density due to the obstruction of liquid water to oxygen diffusion. The simulation results agree well with experimental data.
  • 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
    2007, 1(3): 311-315. https://doi.org/10.1007/s11708-007-0045-3
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    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.
  • Biological chip technology to quickly batch select optimum cryopreservation procedure
    YU Lina, LIU Jing, ZHOU Yixin, HUA Zezhao
    2007, 1(3): 316-321. https://doi.org/10.1007/s11708-007-0046-2
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    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.
  • Research and development of a high-quality thermal-stress online monitoring model for the 600 MW turbine
    ZHANG Hengliang, XIE Danmei, XIONG Yangheng, SUN Kunfeng
    2007, 1(3): 322-326. https://doi.org/10.1007/s11708-007-0047-1
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    To monitor and control its thermal state, a rotor s temperature and thermal stress fields must be calculated in real time. After some reasonable assumptions and simplification, iterative models of the rotor s temperature and thermal stresses were obtained with an integral transform based on a two-dimensional axis-symmetry thermal conduction differential equation. The models can deal with some nonlinear factors such as material and boundary condition. An example is given to compare results computed by the finite element method (FEM) and one-dimensional models. The result shows that the analytical model gained has high quality and the computing course is very short. The iterative formulas could be used not only to analyze the rotor’s thermal states of turbine, but to monitor and control them online. The method adopted can be used to analyze the thermal state of other axis-symmetry objects having similar boundary conditions.
  • 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
    2007, 1(3): 327-330. https://doi.org/10.1007/s11708-007-0048-0
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    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.
  • Emission characteristics of a turbocharged diesel engine fueled with gas-to-liquids
    WU Tao, ZHANG Wugao, FANG Junhua, HUANG Zhen
    2007, 1(3): 331-335. https://doi.org/10.1007/s11708-007-0049-z
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    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.
  • Simulation of horizontal slug-flow pneumatic conveying with kinetic theory
    GU Zhengmeng, GUO Liejin
    2007, 1(3): 336-340. https://doi.org/10.1007/s11708-007-0050-6
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    Wavelike slug-flow is a representative flow type in horizontal pneumatic conveying. Kinetic theory was introduced to establish a 3D kinetic numerical model for wavelike slug gas-solid flow in this paper. Wavelike motion of particulate slugs in horizontal pipes was numerically investigated. The formation and motion process of slugs and settled layer were simulated. The characteristics of the flow, such as pressure drop, air velocity distribution, slug length and settled layer thickness, and the detailed changing characteristics of slug length and settled layer thickness with air velocity were obtained. The results indicate that kinetic theory can represent the physical characteristics of the non-suspension dense phase flow of wavelike slug pneumatic conveying. The experiment in this paper introduced a new idea for the numerical calculation of slug-flow pneumatic conveying.
  • Improvement of the cascading closed loop cycle system
    ZHANG Guoqiang, CAI Ruixian
    2007, 1(3): 341-346. https://doi.org/10.1007/s11708-007-0051-5
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    Aspen Plus was used to simulate and get more information about the cascading closed loop cycle (CCLC) system [1–3]. Following evaluation of the variable temperature heat source (e.g. gas turbine flue gas) utilized by the CCLC, both qualitative and quantitive comparisons between the system and simple steam Rankine cycle, were made. The results indicate that CCLC has the advantage in recuperating exergy from flue gas, but it cannot sufficiently convert the recuperated exergy to useful work. To improve the utilization of low temperature flue gas heat, the properties and parameters of the working substance must match conditions of the low temperature heat source. A better cycle scheme and pressure distribution was proposed to raise the efficiency of the CCLC. In addition, the multifunction system concept was introduced to improve the performance of CCLC with solar energy.
  • Experimental research on dynamic operating characteristics of a novel silica gel-water adsorption chiller
    WANG Dechang, WU Jingyi, WANG Ruzhu, DOU Weidong
    2007, 1(3): 347-351. https://doi.org/10.1007/s11708-007-0052-4
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    A novel silica gel-water adsorption chiller consisting of two adsorption/desorption chambers and an evaporator with one heat-pipe working chamber is experimentally studied. The dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are obtained. The experimental results show that the dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are satisfactory and that the cycle is a novel and effective adsorption cycle. A mass recovery process increases the cyclic adsorption capacity of the system and improves adaptability of the chiller to a low-grade heat source. In addition, the experiment indicates that this novel chiller is highly suitable for an air conditioning system with a low dehumidification requirement or a system with a large cycle flowrate and an industrial cooling water system.
  • Numerical analysis of 3-D unsteady flow in a vaneless counter-rotating turbine
    ZHAO Qingjun, WANG Huishe, ZHAO Xiaolu, XU Jianzhong
    2007, 1(3): 352-358. https://doi.org/10.1007/s11708-007-0053-3
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    To reveal the unsteady flow characteristics of a vaneless counter-rotating turbine (VCRT), a three-dimensional, viscous, unsteady computational fluid dynamics (CFD) analysis was performed. The results show that unsteady simulation is superior to steady simulation because more flow characteristics can be obtained. The unsteady effects in upstream airfoil rows are weaker than those in downstream airfoil rows in the VCRT. The static pressure distribution along the span in the pressure surface of a high pressure turbine stator is more uniform than that in the suction surface. The static pressure distributions along the span in the pressure surfaces and the suction surfaces of a high pressure turbine rotor and a low pressure turbine rotor are all uneven. The numerical results also indicate that the load of a high pressure turbine rotor will increase with the increase of the span. The deviation is very big between the direction of air flow at the outlet of a high pressure turbine rotor and the axial direction. A similar result can also be obtained in the outlet of a low pressure turbine rotor. This means that the specific work of a high pressure turbine rotor and a low pressure turbine rotor is big enough to reach the design objectives.
  • Partitioning of heavy metals during municipal solid waste incineration on a laboratory fluid bed furnace
    LI Jianxin, YAN Jianhua, CHI Yong
    2007, 1(3): 359-364. https://doi.org/10.1007/s11708-007-0054-2
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    The content of heavy metals in the main physical compositions of municipal solid waste (MSW) is analyzed. The effects of temperature, chlorine and water on the partitioning of heavy metals are studied using a laboratory fluidized-bed (FB) furnace with simulated MSW composition. The experimental results show that temperature and chloride content in the feed have significant influence on the volatility of heavy metals, especially those of lower boiling point such as Hg, Cd and Zn. The influence of water is slight.
  • Numerical analysis on heat transfer enhancement by longitudinal vortex based on field synergy principle
    WU Junmei, TAO Wenquan
    2007, 1(3): 365-369. https://doi.org/10.1007/s11708-007-0055-1
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    Three-dimensional numerical simulation results are presented for a fin-and-tube heat transfer surface with vortex generators. The effects of the Reynolds number (from 800 to 2 000) and the attack angle (30º and 45º) of a delta winglet vortex generator are examined. The numerical results are analyzed on the basis of the field synergy principle to explain the inherent mechanism of heat transfer enhancement by longitudinal vortex. The secondary flow generated by the vortex generators causes the reduction of the intersection angle between the velocity and fluid temperature gradients. In addition, the computational evaluations indicate that the heat transfer enhancement of delta winglet pairs for an aligned tube bank fin-and-tube surface is more significant than that for a staggered tube bank fin-and-tube surface. The heat transfer enhancement of the delta winglet pairs with an attack angle of 45º is larger than that with an angle of 30º. The delta winglet pair with an attack angle of 45º leads to an increase in pressure drop, while the delta winglet pair with the 30º angle results in a slight decrease. The heat transfer enhancement under identical pumping power condition for the attack angle of 30º is larger than that for the attack angle of 45º either for staggered or for aligned tube bank arrangement.