陶瓷过滤器滤管外瞬态流场

在由 3根陶瓷滤管组成的实验装置上 ,利用热线风速仪对脉冲反吹时滤管外瞬态流场进行了测定 ,分析了喷吹压力和脉冲宽度对滤管外流场的影响。结果表明 ,滤管外流场存在严重的气体回流区 ,回流速度峰值数倍于正常过滤气速。随着离开滤管壁面距离的增加 ,喷吹速度和回流速度逐渐减小 .随着喷吹压力的增加 ,反吹速度和回流速度也显著增加 .     

陶瓷过滤器滤管脉冲反吹过程的流动特性

在由三根陶瓷滤管组成的实验装置上 ,利用热线风速仪对脉冲反吹时滤管外瞬态流场进行了测定 ,分析了喷吹压力、脉冲宽度、过滤气速和喷吹距离对滤管外流场的影响。随着离开滤管距离的增加 ,喷吹速度和回流速度逐渐减小。结果表明 ,回流现象和喷吹气流沿轴向的不均匀性是影响过滤器脉冲反吹性能的重要因素     

陶瓷过滤器脉冲反吹系统的流场的数值模拟

In the commercial utilization of rigid ceramic filters, the performance of pulse cleaning has crucial effects on the long-term stable operation. In order to get a clear insight into the nature of this cleaning process and provide a solid basis for industrial applications, the flow in ceramic candle filter was investigated. The flow in the pulse-jetspace and inside the ceramic candle is regarded as two- dimensional, unsteady, compressible flow, and numerical simulation is carried out by computational fluid dynamics. The numerical predictions of flow field are in good agreement with the experimental measurements. Effects of the candle diameter, the separation distance between the nozzle and the candle injector and the length of the candle on the flowfield have been numerically analyzed to provide the basis for the optimum design of the pulse cleaning system.     

联箱式陶瓷滤管排的脉冲喷吹系统的研究

对共用一个喷嘴和引射器的联箱式陶瓷滤管排的喷吹性能进行了实验研究并得出结论,认为扩压管式引射器动态性能优于文氏管引射器和直管引射器,且喷嘴至引射器有一最佳距离     

陶瓷过滤器脉冲反吹全过程的瞬变流场计算

采用二维轴对称非稳态流动模型对陶瓷过滤器脉冲反吹全过程中滤管内外的瞬变流场进行了数值模拟,所计算的滤管外径向速度波形与实验测定结果基本吻合,给出了从正常过滤过程到脉冲反吹结束的全过程中引射区域和滤管内速度场及温度场的变化, 分析了反吹气体温度对滤管内温度分布的影响.模拟结果表明,过滤器的操作温度与反吹气体温度差提高,会加剧滤管轴向方向脉冲清灰不均匀性.     

行列式刚性陶瓷过滤器脉冲反吹系统中的压力特性

利用高频动态压力传感器测定脉冲反吹系统中各位置的压力特性,研究了反吹压力和喷嘴孔径对压力特性的影响,提出了解决反吹不均匀的设计方案,采用过滤循环实验进行验证. 结果表明,采用相同孔径的喷嘴时,喷吹管内、喷嘴出口及过滤管内的压力特性存在较大差异,各喷嘴的反吹不均匀性随反吹压力升高而增大,反吹强度随喷嘴孔径增大而减小,喷吹管内的静压沿喷吹方向逐渐增大. 沿喷吹方向将喷嘴孔径递减能改善反吹不均匀的状况,喷嘴截面积与喷吹管截面积之比s/S对脉冲反吹均匀性的影响较大,s/S=48%~55%较佳.     

陶瓷过滤器脉冲反吹系统引射性能的实验测定（Ⅰ）：喷吹气体？…

采用热线风速铁瓷过滤器脉冲反吹喷同口的流场得以了喷吹气体流量,分析了喷吹压力和脉冲宽度对喷吹气体流量的影响。实验结果吹气体流量随喷吹压力的增加而显著增加,而脉冲宽度的增加对喷吹气体流量的影响较小,只是增加了所体喷吹持续时间。同时证明由热线风速仪测得的一次脉冲反映的压缩气体耗量与将储气罐排气过程简化为绝热排气过程所计算出的结果非常吻合,推荐采用绝热排气过程估算压缩气体耗量。     

陶瓷滤管运行过程中的振动特性测定与分析

为分析实际生产中陶瓷滤管断裂的原因,利用电涡流位移传感器测定了陶瓷滤管在气体反吹时的振动,并测量了操作参数对陶瓷滤管振动的影响. 结果表明,陶瓷滤管在反吹时会产生径向位移,由于陶瓷滤管抗形变能力弱,可能会导致滤管发生断裂;另外,改变反吹压力对滤管振幅影响较大,反吹压力从0.3 MPa升至0.5 MPa时,滤管的振幅增加约40%;而改变过滤速度、脉冲宽度对滤管振幅影响较小,但会影响滤管振动的持续时间.     

刚性过滤器脉冲反吹过程中滤管内动态压力特性

催化汽油吸附脱硫（S-Zorb）装置中反应器过滤器的脉冲反吹性能直接影响吸附剂的分离与循环。利用建立的滤管过滤性能实验装置,采用高频动态压力传感器,测定脉冲反吹过程中沿滤管长度方向不同位置处滤管内动态压力随时间的变化特性,分析了滤管长度、反吹压力和脉冲宽度对滤管内动态压力特性的影响规律。结果表明：自开口端至盲端,滤管内动态压力的压力峰值先逐渐变大后基本不变;相同反吹条件下,随着滤管长度的增加,滤管内沿长度方向各位置处的压力峰值均降低。实验范围内,1750～2000 mm滤管开口端附近的动态压力在达到压力峰值后降低为负压,并在反吹气流和脉冲压力波的共同作用下持续振荡。适当提高反吹压力以及增加脉冲宽度可以改善长滤管的反吹效果。     

陶瓷过滤器脉冲反吹系统引射性能的实验测定(Ⅰ)──喷吹气体流量的测定和分析

采用热线风速仪测量陶瓷过滤器脉冲反吹喷嘴出口的流场得到了喷吹气体流量,分析了喷吹压力和脉冲宽度对喷吹气体流量的影响。实验结果表明,喷吹气体流量随喷吹压力的增加而显著增加,而脉冲宽度的增加对喷吹气体流量的影响较小,只是增加了气体喷吹持续时间。同时证明由热线风速仪测得的一次脉冲反吹的压缩气体耗量与将储气罐排气过程简化为绝热排气过程所计算出的结果非常吻合,推荐采用绝热排气过程估算压缩气体耗量。     

陶瓷过滤管用扩压管式引射器脉冲喷吹系统的研究

通过对陶瓷过滤管用扩压管式引射器脉冲喷吹系统的动态特性研究，分析了引射器结构参数和操作参数对其反吹性能的影响，为研究扩压管式引射器的机理及其优化设计提供了依据     

Experimental investigation into compression properties of integrated coal gasification combined cycle fly ashes on a ceramic filter

The compression properties of IGCC (integrated coal gasification combined cycle) fly ash cake on a ceramic filter were carefully investigated under well-controlled conditions. Overall cake porosity and pressure drop of dust cake of three different particles of geometric mean diameters of 3.7, 6.2, and 12.1 Μm, and dynamic shape factors of 1.37, 1.57 and 1.65, respectively, were investigated, at face velocities of 0.02-0.06 m/s. Overall cake porosity was strongly dependent on face velocity, mass load, and particle size. The expressions for overall cake porosity, considering the compression effect, and pressure drop across the dust cake were developed with good agreement with experimental results.     

Temperature effect on the pressure drop across the cake of coal gasification ash formed on a ceramic filter

In order to predict the pressure drop across the cake of coal gasification (CG) ash formed on ceramic filter, an empirical equation was developed taking into account several factors, such as the face velocity, ash load, shape factor and size of particles, and especially the operating temperature. The hot air stream of well classified fine particles of CG ash was simulated as the syngas derived from the coal gasification process. The pressure drop behavior and cleaning efficiency of the filter were carefully investigated within the temperature range from room temperature to 673 K. The pressure drop across the ash cake was dominantly governed by the air viscosity, which increased with temperature. It was well expressed by the previously reported-empirical equation [J.H. Choi, Y.C. Bak, H.J. Jang, J.H. Kim, and J.H. Kim, Korean J. Chem. Eng., 21(3) (2004) 726.] with the modification of the viscosity term in the equation for different temperatures. The residual pressure drop rate across the ash cake also increased while the cleaning efficiency of the ceramic filter decreased as temperature increased.     

Filtration and dust cake experiment by ceramic candle filter in high temperature conditions

Particulate collection at high temperature and high pressure (HTHP) is important in an advanced coal power generation system not only to improve the thermal efficiency of the system, but also to prevent the gas turbine from erosion and to meet the emission limits of the effluent gas. The specifications for particulate collection in those systems such as Integrated Gasification Combined Cycle (IGCC) and Pressurized Fluidized Bed Combustion (PFBC) require absolutely high collection efficiency and reliability. Advanced cyclone, granular bed filter, electrostatic precipitator, and ceramic filter have been developed for particulate collection in the advanced coal power generation system. However, rigid ceramic filters and granular bed filters among them show the best potential. The problems experienced of these systems on performance, materials, and mechanical design were investigated. Ceramic candle filters have the best potential for IGCC at this moment because they have nearly the highest efficiency compared with other filtering systems and have accumulated many reliable design data from many field experiences. The purpose of this study was to investigate the efficiency of ceramic filters and stability of material against high temperature and longterm operation condition by applying fly ash on the surface of the filter and relation of pressure drop and dust cake thickness. Experimental conditions were 50 hours at 450 °C, 650 °C and 850 °C.     

Numerical analysis of flow field in the hot gas filter vessel during the pulse cleaning process

The flow field is simulated for a ceramic filter vessel containing three candle filters which are arranged in the form of an equilateral triangle. Grids generated by GAMBIT are adopted for the simulations. The Reynolds stress model provided by FLUENT code is applied to evaluate gas flow and temperature field in the filter vessel. The temperature profiles in the ceramic candle filter cavity during the pulse cleaning process are analyzed under different operating conditions and for different lengths of candle filter. The evolution of radial velocity in the porous wall of the filters being cleaned and the normal working filters as well as around the filters is discussed. Sharp temperature change takes place in the top of the candle filter which is subject to thermal stress. The phenomenon of temperature increase during the pulse cleaning process has been carefully observed and interpreted based on the effect of gas compression. The simulated results show qualitative agreement with the experimental field observations with the filter vessel.     

The preparation of V2O5/TiO2 catalyst supported on the ceramic filter candle for selective reduction of NO

In order to prepare the catalytic filters based on V₂O₅/TiO₂ for the removal of NO_x and participate simultaneously from the flue gas stream, the experimental study was carried out. The effective method to support TiO₂ layer in the pore of the commercial ceramic filter element was developed. TiO₂ layer was supported on the filter element by three methods; impregnation with Ti solution, sol-gel dip coating and sol-gel centrifugal coating. As the model test to check the catalytic activity, NO reduction in the oxidizing stream was investigated. The catalytic filter prepared by applying the centrifugal force showed the best NO conversion more than 90% when the face velocity was 0.02 m/sec. This was a very promising result for the application of catalytic filter for the flue gas control at high temperature. The supporting methods by the impregnation and dip coating were not recommended because the TiO₂ layer was concentrated in the exterior layer of the filter element. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8–10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University     

Experimental and numerical study of fluid dynamic parameters in a jetting fluidized bed of a binary mixture

The solid circulation pattern, the voidage profile, and the jet penetration height have been investigated experimentally and computationally in a cold-flow model of jetting fluidized beds (JFBs) of a binary mixture in this paper. This rectangular two-dimensional bed is 0.30 m wide and 2.05 m high with a central jet and a conical distributor, which roughly stands for the ash-agglomerating fluidized-bed coal gasifier. A video camera and coloured particle tracer method were employed to explore the fluid dynamics in the bed. In terms of the average physical properties of binary mixtures, a hydrodynamic model describing the gas-solid flow characteristics in a jetting bed is resolved by using a modified Semi-Implicit Method for Pressure-Linked Equation (SIMPLE) algorithm. This paper focuses on three features of the fluid dynamics—solid circulation pattern, voidage profile, and jet penetration height. The solid circulation pattern is composed of three regions: the jetting region, the bubble street, and the annular region. Above the central nozzle the time-averaged isoporosity contours are almost elliptic, while near the walls of the bed, the voidage in high solid concentration region is approximately equal to that at the minimum fluidization state. The jet penetration height increases with increasing jet gas velocity and with decreasing average particle diameter. The increase in weight percentage of the lighter component in the binary system reveals that reduction of average density causes the enlargement of jet penetration height. The simulated results show good agreement with the experimental data.     

Incoloy 800H钢制集气管裂纹失效的原因分析及修复方法

通过分析发现,Ｉｎｃｏｌｏｙ８００Ｈ钢制集气管裂纹产生的原因在于晶界条带特征的形成。采用局部切除更换新管的方法进行修复,焊接的关键在于背面氩气保护的效果。     

Synthesis,pyrolysis of a novel liquid SiBCN ceramic precursor and its application in ceramic matrix composites

SiBCN ceramic precursor, polyborosilazane, was synthesized through a novel method which used sodium borohydride as boron source. Vinyl silazane with SiCl was converted to vinyl silazane with SiH structure, followed by hydroboration reaction and subsequent high-temperature reaction to form soluble polyborosilazane liquid. The process of precursor-to-ceramic conversion was almost completed before 800 °C and the cross-linked polyborosilazane precursor exhibited higher ceramic yield 75.6% at 1200 °C. The SiBCN ceramic annealed at 1400 °C contained BN, SiN and SiC bonds with smooth and dense surface and still retained principally amorphous structure up to 1600 °C. In addition, the viscosity of the polyborosilazane was 65 mPa.s, which can efficiently prepare ceramic matrix composite by means of precursor infiltration and pyrolysis (PIP). The density of as-obtained ceramic matrix composite (CMC) was 1.82 g/cm³, and the average bending strength, bending modulus and tensile strength were 265.2 MPa, 37.5 GPa and 158.6 MPa, respectively.