双流化床煤气化试验研究

建立了一套3米高的双流化床煤气化试验装置,煤在鼓泡流化床中热解气化,生成的半焦送入循环流化床中燃烧,两床间采用气动控制阀连接.分别采用神华烟煤、龙口褐煤和大同烟煤进行了试验.煤中的碳转化成煤气和烟气的总转化率达到90%以上;冷煤气效率随着窄气/煤比的提高而增加;采用神华煤时焦油产率可达到1.5%;采用龙口褐煤时气化效果较好,在气化炉空气/煤比为0.3 kg/kg时,冷煤气热值为10.7 MJ/Nm3,冷煤气效率为48%.经过分析计算,龙口褐煤产生煤气中的可燃成分主要来自热解.     

煤热解气化过程中汞的形态转化和释放规律

本文选用神府和兖州两种烟煤,在400～1000℃的温度范围内,采用程序升温热解反应装置进行了热解和气化实验.实验过程中根据Ontario-Hydro方法捕捉气态汞,采用QM201型原子荧光测汞仪测定汞含量,研究了煤中微量元素汞在热解气化过程中的形态分布和释放规律.结果表明,温度是影响煤中汞释放的主要因素,煤热解过程中气态汞主要以元素汞的形式存在,占气态总汞的64%以上;随着温度的升高和停留时间的延长,元素汞的百分比含量逐渐降低,二价汞的百分比含量逐渐升高.气化过程中,元素汞和二价汞的百分比含量在40%～60%之间变化.气化产生的元素汞占气态总汞的百分比含量低于热解;二价汞则相反.     

纤维素、木质素含量对生物质热解气化特性影响的实验研究

本文采用化学方法测定了六种生物质中纤维素和木质素的含量,通过热重研究了实际生物质及用纤维素、木质素按一定比例混合模拟生物质的热解和气化特性,并结合电子扫描电镜(SEM)对焦样进行了微观形貌分析.结果表明:在本文所选择的生物质中纤维素的含量高于木质素,两者一般在55%～85%和10%～35%.生物质热解分为纤维素热解和木质素分解两个阶段,应于气化过程中挥发份析出和焦炭气化.在热解过程中,首先纤维素发生热解呈现快速失重过程,接着木质素缓慢热解.实验发现生物质中纤维素含量越高,热解反应速率就越大;反之,木质素含量越高,热解反应速率越小.通过对焦形貌与气化研究,发现气化特性与生物质中纤维素和木质素的含量有着密切联系.因此纤维素、木质素含量是影响生物质热解气化特性的重要因素之一.     

塑料和橡胶垃圾的热解机理及动力学分析

利用热分析-质谱联用技术进行了塑料和橡胶垃圾的热解实验研究,探讨了这两种聚合物热解机理,并采用Freman-Carroll法定量分析了垃圾热解动力学.塑料和橡胶主要热解气体产物是烃类CnHm(n≤4～5),CO2和CH4,塑料热解过程以脱链解聚吸热反应为主;而橡胶热解过程分为两个阶段,前期以交联缩聚放热反应为主,后期以脱链解聚吸热反应为主,热解过程总热效应为放热.     

煤温和热解过程中汞释放形态及分布规律研究

本文选取两种贵州高汞煤,在200～800℃的温度范围内,采用程序升温反应系统加热,利用美国EPA推荐的Ontario-Hydro方法捕捉不同形态汞。研究了在N₂气氛和微氧化性气氛下温和热解过程中汞的释放和形态分布规律。实验结果表明:温度是影响煤温和热解过程中汞释放的主要因素,煤中汞释放率随着温度的升高而明显升高,当热解温度为600℃时,汞释放率可达90%左右。在微氧化性气氛下,汞的释放率随着氧气体积分数的升高而增大。元素汞（Hg⁰）是气态汞释放的主要形态,热解停留时间及热解气氛对气态汞的释放形态也存在影响较大。     

纤维素、木质素对生物质与煤混烧特性的影响

利用热重红外分析仪着重分析了生物质中纤维素和木质素含量对混合热解及混烧特性的影响.生物质与煤的混合热解相比于纯煤的单一热解失重明显较大较快,并且纤维素含量越高,混合燃料失重越大;木质素含量较高,则混合燃料失重较慢.当燃烧温度为300～400℃之间时,混合燃料中纤维素含量越高,质量下降幅度越大;当燃烧温度为500～700℃之间时,混合燃料中则是木质素含量越高,质量下降幅度越大.     

煤基化学链燃烧过程中硫的演变

在双阶段流化床反应器内,基于溶胶凝胶法制备的Fe2O3/Al2O3氧载体研究了褐煤化学链燃烧过程中燃料硫的迁移路径及分布特性,并讨论了温度、过氧系数对燃料硫释放分布的影响.结果表明:所有工况下,氧载体均未出现被硫化的现象;在热解气化学链燃烧阶段,气相含硫物质以SO2和H2S为主,煤焦气化气化学链燃烧阶段绝大部分为SO2气体,部分来源于煤焦中CaSO4的分解。另外,部分燃料硫被碱金属固定于煤灰中。同时,提高温度和过氧系数都能导致SO2/H2S值和SO2释放量增大。     

小型流化床内化学链热解煤焦油实验研究

为优化煤焦油化学链热解的工况参数,采用Fe/Al复合载氧体在小型流化床反应器内进行了煤焦油化学链热解实验,考察了燃料反应器温度、载氧体/煤焦油摩尔比及反应时间对热解结果的影响,对炭黑收率、气相产物的体积分数进行分析,并计算了实验系统的碳平衡及能量转化率。结果表明,炭黑收率随温度和载氧体/煤焦油摩尔比升高先增后减,在温度950℃和摩尔比3时达到最大,气相产物中CO和H2体积份额为70%左右,继续升高炉温和摩尔比会降低CO份额。系统碳平衡为95.5%以上,误差较小,则系统能量转化率最高可达到87%.通过表观气速变化改变反应时间从2.1s增大到3.5s时,炭黑收率及能量转化率无明显变化,由此确定了化学链热解煤焦油的优化运行参数.     

微小多孔介质燃烧器的燃烧特性研究

设计了微小多孔介质燃烧器，进行了氢气和空气的扩散燃烧特性实验研究，得到了其燃烧效率、出口尾气温度、外壁面温度和热损失率随燃烧热功率和过量空气系数的变化规律。实验发现，在较宽的操作范围内，微燃烧器具肯较高的燃烧效率和出口尾气温度，同时获得较低的外壁面温度和热损失率，而且随着燃烧热功率和过量卒气系数的增大，外壁而温度和热损...     

稻壳热解的动力学模拟

生物质热解过程的动力学行为研究对于热化学转化过程机理的掌握和热化学转化技术的开发具有重要意义.本文采用Miller模型对稻壳在低升温速率下的热解进行了动力学模拟,并利用热重分析实验结果对模拟过程的有效性进行了对比验证.模拟计算结果显示气体百分含量在650～780K范围内随温度升高迅速增加,炭含量在500～680K之间随温度升高迅速下降,焦油含量随着温度升高在650K左右达到最高值.同时升温速率的提高可以抑制炭的生成,增加气体和焦油最大产量,在100K/min的升温速率下,气体产量在780K达到最大56.3%,焦油产量在678K左右达到最大26.8%.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.