A computational fluid dynamics(CFD)model was developed to accurately predict the flash reduction process,which is considered an efficient alternative ironmaking process.Laboratory-scale experiments were conducted in d...A computational fluid dynamics(CFD)model was developed to accurately predict the flash reduction process,which is considered an efficient alternative ironmaking process.Laboratory-scale experiments were conducted in drop tube reactors to verify the accuracy of the CFD model.The reduction degree of ore particles was selected as a critical indicator of model prediction,and the simulated and experimental results were in good agreement.The influencing factors,including the particle size(20–110μm),peak temperature(1250–1550°C),and reductive atmosphere(H_(2)/CO),were also investigated.The height variation lines indicated that small particles(50μm)had a longer residence time(3.6 s)than large particles.CO provided a longer residence time(~1.29 s)than H_(2)(~1.09 s).However,both the experimental and analytical results showed that the reduction degree of particles in CO was significantly lower than that in H2 atmosphere.The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50μm and 1350°C in H2 atmosphere,and40μm and 1550°C in CO atmosphere,respectively.展开更多
Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） techn...Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.展开更多
为准确描述下降管反应器内生物质颗粒与高温陶瓷球之间的瞬态传热与热解行为,该研究提出了一种基于分布活化能模型(distributed activation energy model,DAEM)的多物理场耦合数值模型。该模型在颗粒能量平衡框架下,引入接触导热、气膜...为准确描述下降管反应器内生物质颗粒与高温陶瓷球之间的瞬态传热与热解行为,该研究提出了一种基于分布活化能模型(distributed activation energy model,DAEM)的多物理场耦合数值模型。该模型在颗粒能量平衡框架下,引入接触导热、气膜导热、对流与辐射多种传热机制,并与质量转化过程和活化能分布特征相耦合,建立了用于描述生物质快速热解过程的常微分方程模型。基于热重分析试验数据,对高斯、洛伦兹及逻辑斯谛3种活化能分布函数进行了参数反演与对比分析。结果表明,洛伦兹分布能够更准确地再现试验热重曲线,其平均绝对误差(mean absolute error,MAE)和均方根误差(root mean square error,RMSE)分别为0.0116和0.0138。数值模拟结果显示,生物质颗粒在初始阶段经历了极高的升温速率(峰值达到2.14×10^(3)℃/s),但热解反应相对于温度演化存在明显的动力学滞后特征。传热机制分析表明,对流与导热在整个热解过程中占主导地位,而在高温阶段辐射传热的贡献不可忽略。参数敏感性分析进一步揭示,陶瓷球温度和生物质颗粒粒径对热解效率具有显著影响,反应焓和颗粒碰撞概率次之,而辐射视角因子的影响相对有限。研究结果表明,在传热条件充分的快速热解工况下,过程控制机理由传热受限逐渐转变为化学反应动力学受限。研究为深入理解下降管反应器内多物理场耦合热解行为特征及反应器结构与工艺参数优化提供了理论依据和数据支持。展开更多
A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) r...A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) radicals into HO2 radicals.It can conduct different measurement modes through altering the reagent gases,achieving the speciated measurement of RO2 and RO2^#(RO2 radicals derived from the long-chain alkane,alkene and aromatic hydrocarbon).An example of field measurement results was given,with a maximum concentration of 1.88 × 10^(8) molecule/cm^(3) for RO2 and 1.18×10^(8) molecule/cm^(3) for RO2^(#).Also,this instrument quantifies the local ozone production rates directly,which can help to deduce the regional ozone control strategy from an experimental perspective.The new device can se rve as a potent tool for both the explo ration of frontier chemistry and the diagnosis of the control strategies.展开更多
In our previous work, a low-shear stirred bioreactor was explored. With a pitched blade turbine impeller downflow(PBTD) used, the shear stress generated is high compared with that in some low shear axial flow impeller...In our previous work, a low-shear stirred bioreactor was explored. With a pitched blade turbine impeller downflow(PBTD) used, the shear stress generated is high compared with that in some low shear axial flow impellers. KHX impeller is an efficient axial flow impeller, which provides large onflow diffusivity and low shear force. In this work, the KHX impeller was applied in a lower-shear bioreactor and the performance of this reactor was evaluated and compared with that of the PBTD impeller. The experimental results show that the KHX impeller can disperse gas at lower power consumption and gives greater gas–liquid volumetric mass transfer coefficients than PBTD at the same power consumption. An empirical correlation for evaluating the mass transfer coefficient of the KHX impeller in the bioreactor is presented to provide reference for its industrial application.展开更多
钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)控制棒通道套管是典型的承受外压的高温薄壁长圆柱壳,蠕变-屈曲失稳是其主要失效模式。本文旨在利用数值模拟方法研究控制棒通道套管高温下的蠕变屈曲失稳行为。首先基于UNS N10003合金的...钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)控制棒通道套管是典型的承受外压的高温薄壁长圆柱壳,蠕变-屈曲失稳是其主要失效模式。本文旨在利用数值模拟方法研究控制棒通道套管高温下的蠕变屈曲失稳行为。首先基于UNS N10003合金的高温蠕变试验数据获得了该材料的Norton蠕变模型及材料参数;然后利用有限元分析软件ABAQUS进行了TMSR控制棒通道套管的特征值屈曲分析与蠕变屈曲分析,并对屈曲失稳的关键因素进行了敏感性分析,获得了蠕变屈曲寿命的经验公式。分析结果表明,温度、压力、结构尺寸均会对套管的蠕变屈曲寿命产生显著影响。本文的研究结果对TMSR控制棒通道套管以及复杂结构与载荷条件下的高温结构的稳定性设计提供了工程指导依据,也为其他高温薄壁结构的蠕变屈曲寿命预测提供了依据。展开更多
基金financially supported by the National Key Research and Development Project(No.2016YFB0601304)the National Natural Science Foundation of China(No.51804030)。
文摘A computational fluid dynamics(CFD)model was developed to accurately predict the flash reduction process,which is considered an efficient alternative ironmaking process.Laboratory-scale experiments were conducted in drop tube reactors to verify the accuracy of the CFD model.The reduction degree of ore particles was selected as a critical indicator of model prediction,and the simulated and experimental results were in good agreement.The influencing factors,including the particle size(20–110μm),peak temperature(1250–1550°C),and reductive atmosphere(H_(2)/CO),were also investigated.The height variation lines indicated that small particles(50μm)had a longer residence time(3.6 s)than large particles.CO provided a longer residence time(~1.29 s)than H_(2)(~1.09 s).However,both the experimental and analytical results showed that the reduction degree of particles in CO was significantly lower than that in H2 atmosphere.The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50μm and 1350°C in H2 atmosphere,and40μm and 1550°C in CO atmosphere,respectively.
文摘Different mathematical models for ethylene furnace reactor tubes were reviewed. On the basis of these models a new mathematical simulation approach for reactor tubes based on computational fluid dynamics （CFD） technique was presented. This approach took the flow, heat transfer, mass transfer and thermal cracking reactions in the reactor tubes into consideration. The coupled reactor model was solved with the SIMPLE algorithm. Some detailed information about the flow field, temperature field and concentration distribution in the reactor tubes was obtained, revealing the basic characteristics of the hydrodynamic phenomena and reaction behavior in the reactor tubes. The CFD approach provides the necessary information for conclusive decisions regarding the production optimization, the design and improvement of reactor tubes, and the new techniques implementation.
文摘为准确描述下降管反应器内生物质颗粒与高温陶瓷球之间的瞬态传热与热解行为,该研究提出了一种基于分布活化能模型(distributed activation energy model,DAEM)的多物理场耦合数值模型。该模型在颗粒能量平衡框架下,引入接触导热、气膜导热、对流与辐射多种传热机制,并与质量转化过程和活化能分布特征相耦合,建立了用于描述生物质快速热解过程的常微分方程模型。基于热重分析试验数据,对高斯、洛伦兹及逻辑斯谛3种活化能分布函数进行了参数反演与对比分析。结果表明,洛伦兹分布能够更准确地再现试验热重曲线,其平均绝对误差(mean absolute error,MAE)和均方根误差(root mean square error,RMSE)分别为0.0116和0.0138。数值模拟结果显示,生物质颗粒在初始阶段经历了极高的升温速率(峰值达到2.14×10^(3)℃/s),但热解反应相对于温度演化存在明显的动力学滞后特征。传热机制分析表明,对流与导热在整个热解过程中占主导地位,而在高温阶段辐射传热的贡献不可忽略。参数敏感性分析进一步揭示,陶瓷球温度和生物质颗粒粒径对热解效率具有显著影响,反应焓和颗粒碰撞概率次之,而辐射视角因子的影响相对有限。研究结果表明,在传热条件充分的快速热解工况下,过程控制机理由传热受限逐渐转变为化学反应动力学受限。研究为深入理解下降管反应器内多物理场耦合热解行为特征及反应器结构与工艺参数优化提供了理论依据和数据支持。
基金the National Key R&D Program of China(No.2017YFC0209402)the Beijing Natural Science Foundation,China(No.JQ19031)。
文摘A low-pressure reactor(LPR) was developed for the measurement of ambient organic peroxy(RO2)radicals with the use of the laser-induced fluorescence(LIF) instrument.The reactor converts all the RO_(x)(=RO2+HO2+RO+OH) radicals into HO2 radicals.It can conduct different measurement modes through altering the reagent gases,achieving the speciated measurement of RO2 and RO2^#(RO2 radicals derived from the long-chain alkane,alkene and aromatic hydrocarbon).An example of field measurement results was given,with a maximum concentration of 1.88 × 10^(8) molecule/cm^(3) for RO2 and 1.18×10^(8) molecule/cm^(3) for RO2^(#).Also,this instrument quantifies the local ozone production rates directly,which can help to deduce the regional ozone control strategy from an experimental perspective.The new device can se rve as a potent tool for both the explo ration of frontier chemistry and the diagnosis of the control strategies.
基金Supported by the National Basic Research Program of China(2010CB630904)the National Natural Science Foundation of China(21276004,20990224)+1 种基金the National Natural Science Fund for Distinguished Young Scholars(21025627)the National High Technology Research and Development Program of China(2012AA061503)
文摘In our previous work, a low-shear stirred bioreactor was explored. With a pitched blade turbine impeller downflow(PBTD) used, the shear stress generated is high compared with that in some low shear axial flow impellers. KHX impeller is an efficient axial flow impeller, which provides large onflow diffusivity and low shear force. In this work, the KHX impeller was applied in a lower-shear bioreactor and the performance of this reactor was evaluated and compared with that of the PBTD impeller. The experimental results show that the KHX impeller can disperse gas at lower power consumption and gives greater gas–liquid volumetric mass transfer coefficients than PBTD at the same power consumption. An empirical correlation for evaluating the mass transfer coefficient of the KHX impeller in the bioreactor is presented to provide reference for its industrial application.
文摘钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)控制棒通道套管是典型的承受外压的高温薄壁长圆柱壳,蠕变-屈曲失稳是其主要失效模式。本文旨在利用数值模拟方法研究控制棒通道套管高温下的蠕变屈曲失稳行为。首先基于UNS N10003合金的高温蠕变试验数据获得了该材料的Norton蠕变模型及材料参数;然后利用有限元分析软件ABAQUS进行了TMSR控制棒通道套管的特征值屈曲分析与蠕变屈曲分析,并对屈曲失稳的关键因素进行了敏感性分析,获得了蠕变屈曲寿命的经验公式。分析结果表明,温度、压力、结构尺寸均会对套管的蠕变屈曲寿命产生显著影响。本文的研究结果对TMSR控制棒通道套管以及复杂结构与载荷条件下的高温结构的稳定性设计提供了工程指导依据,也为其他高温薄壁结构的蠕变屈曲寿命预测提供了依据。
