目的:应用彩色多普勤显像(color Doppler flow imaging,CDFI)对磁共振血管显像(magnetic resonance artery,MRA)诊断的椎动脉优势患者进行再评估,探讨CDFI对椎动脉优势的再评估价值.方法:选取150例经MRA诊断并经CT血管造影(computer technology angiography,CTA)或数字减影血管造影(digital subtraction angiography,DSA)确认为椎动脉优势的住院患者,测量双侧椎动脉内径(DMRA),椎动脉CDFI测及双侧椎动脉内径(DCDFI内)、外径(DCDFI外),并测量收缩期峰值流速(Vs)、舒张期末期血流速度(Vd)、平均血流速度(Vm)、搏动指数(PI)、阻力指数(RI)等血流动力学参数.对测及数据进行统计,分析其与后循环缺血的关系.结果:根据超声检查结果,MRA诊断为椎动脉优势的患者可分为两组:椎动脉先天性发育不良型(134例),椎动脉管壁增厚而引起的椎动脉弥漫性狭窄型(16例),前组两侧椎动脉血流速度(包括Vs、Vd和Vm)均高于后者,PI和RI小于后者,差异具有统计学意义(P＜0.05);同时,两组人群的基础资料和PCI的发生率具有明显差异(P＜0.05).结论:CDFI对MRA诊断的椎动脉优势的再评估具有重要临床价值,可鉴别椎动脉优势的产生根本原因,从而为临床治疗提供依据.

In order to obtain sorbent that can remove HCl with high efficiency at medium-high tem-perature,the removal efficiency of hydrotalcite-like sorbent (HTL)prepared domestically was com-pared with traditional sorbents such as CaO,NaHCO3 under different temperatures (300 to 700 ℃), initial concentrations of HCl (750 to 1 500 mg/m3 ),and reaction times.The results show that,with the increase of initial concentrations of HCl and the extension of reaction time,the removal efficien-cies of CaO,NaHCO3 decrease.With the temperature increasing,the removal efficiency of CaO de-clines.However,the removal efficiency of NaHCO3 falls at the beginning,and then rises after 550℃.And when the temperature is high than 600 ℃,NaHCO3 and CaO are sintered and melted. However,the above conditions have little influence on HTL.The removal efficiency of HTL under different conditions always keeps more than 95%.

Applying an underfeed system,the underfeed circulating spouted bed(UCSB) is an improved dry desulfurization technology.The UCSB system feeds the fresh agent from the center of the bottom bed in order to uniform the particle concentration distribution,and therefore advance the calcium utility.In this article,the influence of different feed styles on the movement and mixing of the solids in the reaction bed was simulated and analyzed by the Euler/Lagrange method.The results indicate: The existence of injecting flow can obviously optimize the gas-solid two-phase flow fields in the bottom zone of the UCSB.Comparing with the facefeed style,the technology can uniform the distribution concentration of fresh agent on sections especially at the lower part of the reaction bed.The gas-solid mixing is distinctly enhanced with the application of the underfeed system.Applying the underfeed nozzle with six orifices,the improvement is more satisfying.

An underfeed circulating spouted bed (UCSB) reactor was used as a desulfurization apparatus. In this study, an attempt was made to build a mathematical 3D model which couples the complicated flow and chemical reactions in the interest of system analysis and sulfur removal data analysis. A simplified reaction model was developed to describe the SO2 absorption process. Humidifying, evaporation, neutralization reaction have been considered in the model while the dissolution and ionization of calcium hydroxide are neglected. The effect of operating parameters including feed style, injecting velocity, jet water flow rate, humidifying style on sulfur removal efficiency were investigated. The results show that the calculation gives a good description of the experimental data under the range of operating conditions. It indicates that the model is successful in predicting the desulfurization efficiency of the UCSB system.

A detailed model for flue gas desulfurization by spray-dry absorption with calcium hydro agent is presented. The model refers to a steady state one-dimensional model by means of infinitesi-mal analysis, incorporating with the model of droplet evaporation, shrinking core and sulfur absorp-tion. The trends of moisture, temperature field, SO_2 and vapor concentration along the axial direc-tion are calculated and the results are compared with the experimental data. It is shown that applying multi-level humidifying, the temperature field in the riser gets more tempered and the outlet tempera-ture is 3 to 6℃ lower comparing to 1-level humidifying; As the droplet evaporation gets slower, thedesulfurization efficiency increases by 7% to 11% ; The total droplet mass in the riser is found to be very important factor for the sulfur removal efficiency and it is of reference value for the design and operation of the humidifying system.

The underfeed circulating spouted bed (UCSB) was designed as a new dry desulfurization reactor. In this article, pressure fluctuations along the axial direction were measured and time, frequency and Shannon entropy analysis of pressure signals were studied under different operation parameters. The results indicate: the pressure fluctuations express different characteristics at various axial locations. And the operation parameters have significant influence on the flow characteristic in the riser. Advancing the spouting velocity or the circulating ratio, the solid concentration in the riser increases and the amplitude of the pressure fluctuations rises. With higher injecting velocity or nozzle position, the gas–solid turbulence in the bottom bed gets more intense. It shows that the existence of injecting flow near the underfeed nozzle has a distinct effect on strengthening the particle mixing. The power spectrum density acquired from the signals can coincidently reflect the dynamic behavior of the gas–solid flow in the riser. Analysis of Shannon entropy also corresponds to the above summarization of flow characteristic very well.

With quartz sand and calcium hydroxide serving as the feed and return material respectively, studied were the particle mixing characteristics of a φ0.6 m×15 m underfeed circulating spouted bed in a desulfurization tower. The mixing entropies at various locations and its mixing indexes of the underfeed and return material at various elevations were calculated by utilizing the solubility difference of the quartz sand and calcium hydroxide in water, and the influence of various operating parameters on the particle mixing behavior of particles in the tower was analyzed. The research results show that the mixing index can reflect very well the mixing quality of the feed and return material particles in the tower. With an increase of the fluidization speed, the mixing indexes at various elevations in the tower assume an ascending tendency. The spouting velocity and circulation ratio conspicuously affect the particle distribution characteristics in the tower, especially at its bottom. When a relatively high spouting speed and a comparatively high circulation ratio are adopted, the mixing index will go up accordingly, indicating that the mixing quality in the tower has been improved.

In order to investigate the effect of underfeed style on improving the symmetry and uniformity of solid distribution,a series of experiments were conducted in a φ0.6 m× 15 m underfeed circulating spouted bed and the solid upflow flux distribution on sections was acquired by means of isokinetic sampling.The influence of operation parameters on the radial distribution of solid fluxes was also studied.The results indicate:Comparing with the face-feed style,the technology can distinctly improve the distribution of particle fluxes in the riser.The fluidizing and spouting velocity have significant influence on the radial distribution of solid particles.As the fluidizing velocity advances,the solid distribution gets more uniform.Applying higher spouting velocity,the symmetry of solid flux distribution in the radial direction can be obviously improved.

To study the gas-solid two phase flow characteristics of an underfed circulating spouted bed,the authors have measured the pressure fluctuation signals at various heights in the axial direction of a reaction tower through a cold-state test,analyzed the pressure signals by using Shannon information entropy and compared the influence of different operating conditions on the gas-solid two-phase flow in the tower.It has been found that the pressure fluctuation and its power spectrum display different characteristics at different heights of bed layers and Shannon information entropy can reflect very well the complexity and stability degree of the characteristic signals.Enhancing the fluidized velocity and circulation ratio can lead to an increase of particle concentration in the axial direction of the tower,thus enhancing the amplitude of the pressure fluctuation.To increase the jet flow velocity and heighten the nozzle location can intensify the gas-solid turbulent flow at the bottom of the tower and Shannon information entropy can be increased accordingly.

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