填料塔泛点/压降模型计算比较

以文献报道的实验数据及关联式为基础 ,比较了Billet模型、S -B -F模型及常用泛点 /压降计算模型在国产散堆和规整填料的泛点 /压降上的计算偏差 ,并对国产散堆和规整填料的泛点 /压降计算模型进行了总结     

散装填料层泛点和压降的新关联

在理论分析的基础上 ,导出了散装填料层泛点气体速度和压降的新关联式 ,由实验数据计算了常用填料新关联式的液泛填料因子和压降常数。新泛点关联式对 8种填料泛点气速的计算值与实验数据的总平均计算误差为 3.5 2 % ;新压降关联式对各种填料的压降平均计算误差一般在 10 %以下。关联值与实验数据吻合很好 ,计算准确性优于文献公式 ,且比文献公式计算简便。     

筛板塔漏液点气速的计算模型

本文从力平衡角度出发,并考虑到筛板上气液混合层的截面含气率和液面波动的影响,指导出筛板的漏液点气速的计算模型,可用于工程设计计算。     

填料因子变化时散堆填料泛点气速数值算法

泛点气速是填料塔设计的重要参数,Eckert关联图为目前工程上运用较为广泛的泛点气速求取方法。文中基于散堆填料的Eckert关联图,在考虑泛点填料因子f随液体泛点喷淋密度Lf变化的条件下,提出了泛点气速uf的数值算法;推导出泛点气速uf的表达式为一个高度非线性化方程,并给出了该方程的2种求解方法。同时举例计算了一个散堆填料的泛点气速,并和著名的塔器流体力学计算软件(WPTR)计算结果做了对比。结果表明:文中的计算结果和WPTR的结果完全吻合;所使用的方程求解方法 Aitken-Steffensen具有快速、稳定的收敛性,可用于散堆填料的泛点气速计算。     

填料塔液泛气速,压力降计算方法的讨论

使用部分Ｄｇ５０瓷质填料在水－空气实验系统中测得的填料塔液泛气速和压力降,根据所确定的液泛气速,压力降的计算方法,推算出９３％Ｈ２ＳＯ４－空气９３％Ｈ２ＳＯ４－ＳＯ２烟气,９８％Ｈ２ＳＯ４－ＳＯ３烟气等操作系统中,填料塔采用不同填料的液泛气和压力降。     

QH-2型扁环填料的流体力学和传质性能研究

在内径60 0填料塔中 ,用空气 富氧水系统对3 8和5 0QH 2型扁环填料的流体力学和传质性能进行了研究 ,得出计算其压降、液泛气速和传质单元高度的关联式。并与3 8鲍尔环、5 0鲍尔环和3 8环矩鞍填料进行了比较 ,结果表明 ,QH 2型扁环具有优良的流体力学和传质特性。     

散装填料层泛点和压降的新关联式

导出了散装填料层泛点和压降的新关联式,将该关联式与通用关联图进行了比较,计算结果表明,新关联式对各种填料的压降平均计算误差在10％以下,泛点计算误差在7％以下,计算准确性优于通用关联图;用通用关联图计算压降有时误差较大。     

计算散装填料层泛点的新方法

在半理论分析的基础上,导出了散装填料层泛点气体速度的关联式,由实验数据计算了常用填料本文关联式的液泛填料因子。本文泛点关联式对8种填料泛点气速的计算值与实验数据的总平均计算误差为3.52%,新关联方法与实验数据吻合很好,计算准确性优于文献公式,且比文献公式计算简便。     

用于高液气比吸收过程的填料优选和数学模型的研究

在(φ)600填料塔中,用空气-富氧水系统在很宽的液体喷淋密度范围内(20～220 m3/(m2·h))对(φ)50QH-2扁环、(φ)63 QH-2扁环、Mellapak 125X、与(φ)38 鲍尔环的流体力学和传质性能进行了研究,结果表明,与鲍尔环相比,QH-2扁环的阻力小,通量大,传质效率高,综合性能优异.而Mellapak 125X通量虽然很高,但传质效率明显低于QH-2扁环和鲍尔环.给出了计算QH-2扁环压降、液泛气速和传质单元高度的关联式.     

QH-1型扁环填料萃取塔的设计计算——液泛速度的计算

在系统实验研究的基础上，选择基于特性速度的方法，得出用于中低界面张力体系的ＱＨ－１扁环填料萃取塔的液泛速度计算公式，可用于工业装置的设计计算。     

超级扁环填料及其在氮肥厂气体净化过程中的应用

国内外最新的研究工作表明,在液液萃取、液气比很大的吸收和高压精馏的情况下,应用散装填料的操作性能优于规整填料和塔盘。其中扁环填料具有独特的结构和优异性能。本文介绍了从阶梯短环到超级扁环的发展过程、技术特点和在合成氨气体净化中的应用。     

Prediction of minimum velocity and minimum bed pressure drop for gas-solid fluidization in conical conduits

Experimental investigations have been carried out for spherical and non-spherical particles using beds comprised of single-sized particles and mixtures in the size and particle density ranges of 439 to 1524 μm and 1303 to 4948 kg/m³, respectively. Five conical fluidizers with varying apex angles of 8.86, 14.77, 19.60, 32.0 and 43.2 degrees were used. Experimental values of minimum velocity and bed pressure drop with air as the fluidizing medium have been compared with their respective values obtained from different models available in the literature. Deviations for each chosen model have been presented.     

上升管内环状流含液体积分数与压降预测模型

对垂直上升管中气液二相环状流的含液体积分数及压降预测进行了研究,在充分考虑了环状流的流型特征以及合理假设的前提下,以二相流动力学理论和Wallis有关经验式为基础,推导出了环状流的数学模型。通过求解力学方程,获得了含液体积分数及压降预测的新模型,将新模型及已有模型与实验数据进行对比,结果表明,新模型不仅与实验结果符合良好,还具有计算速度快的特点,从而为垂直上升管内气液二相环状流含液体积分数与压降的预测提供了一种新的有效方法。     

Effects of cross-flow velocity, capillary pressure and oil viscosity on oil-in-water drop formation from a capillary

The formation of oil drops from a single capillary with a diameter of 200 μm into a cross-flowing continuous water phase has been studied experimentally with the particle image velocimetry (PIV) technique and numerically with the computational fluid dynamics (CFD) software Fluent. The drop formation time and the volume of the detached drop were used as validation parameters and the results from the two methods corresponded well, with a difference of less than 5% for the drop formation time and 10% for the drop volume. The cross-flow velocity has a major impact on drop size, which decreases as the cross-flow increases. An increase in cross-flow, oil viscosity and capillary pressure displace the position of necking and drop detachment away from the capillary opening, which will have a decreasing effect on the final size of the drop.     

Prediction of critical fluidization velocity and maximum bed pressure drop for binary mixture of regular particles in gas–solid tapered fluidized beds

The problems associated with conventional (cylindrical) fluidized beds, viz., fluidization of wider size range of particles, entrainment of particles and limitation of fluidization velocity could be overcome by using tapered fluidized beds. Limited work has been carried out to study the hydrodynamics of single materials with uniform size particles in tapered beds. In the present work, an attempt has been made to study the hydrodynamic characteristics of binary mixtures of homogeneous and heterogeneous regular particles (glass bead and sago) in tapered fluidized beds having different tapered angles. Correlations have been developed for critical fluidization velocity and maximum bed pressure drop for gas–solid tapered fluidized beds for binary mixtures of regular particles. Model predictions were compared with experimental data, which were in good agreement.     

Correlations for critical fluidization velocity and maximum bed pressure drop for heterogeneous binary mixture of irregular particles in gas–solid tapered fluidized beds

The tapered fluidized bed is a remedial measure for certain drawbacks of the gas–solid system, by the fact that a velocity gradient exists along the axial direction of the bed with increase in cross-sectional area. To study the dynamic characteristics of heterogeneous binary mixture of irregular particles, several experiments have been carried out with varying tapered angles and composition of the mixtures with various particles. The tapered angle of the bed has been found to affect the characteristics of the bed. Models based on dimensional analysis have been proposed to predict the critical fluidization velocity and maximum bed pressure drop for gas–solid tapered fluidized beds. Experimental values of critical fluidization velocity and maximum bed pressure drop compare well with that predicted by the proposed models and the average absolute errors are well within 15%.     

Osmotic pretreatment for instant controlled pressure drop dried apple chips: Impact of the type of saccharides and treatment conditions

Instant controlled pressure drop (ICPD) is an emerging drying technique that can produce fruit chips with crispy texture. To improve the qualities of ICPD-dried apple chips, six types of saccharides with different polymerization were used for osmotic pretreatment on apple slices. Firstly, the effects of different saccharides on the osmotic behavior and texture of ICPD-dried apple chips were evaluated. Then, the effects of osmotic conditions of a selected saccharide, i.e. stachyose, on the qualities of ICPD-dried apple chips were studied. The results showed that sucrose, raffinose, and stachyose could significantly enhance the crispness of the ICPD-dried apple chips. In addition, the ICPD-dried apple chips pretreated with stachyose possessed the highest T_g (29.74?°C) and superior porous structure compared with pretreatments using the other saccharides. Moreover, limited color change (ΔE) was found in the samples pretreated with stachyose at 40?°C for 30?min, as well as higher retention of polyphenols. In conclusion, it is confirmed that the types of saccharides significantly influence the qualities of the ICPD-dried apple chips, and osmotic pretreatment at 40?°C for 30?min using stachyose was suggested for improving the overall quality of ICPD-dried apple chips.     

Hydrodynamics of trickle bed reactors at high pressure: Two-phase flow model for pressure drop and liquid holdup, formulation and experimental validation

A large experimental database has been established at IFP on the same experimental setup to measure simultaneously pressure drop and liquid holdup in packed bed reactor operated in trickle for a large range of operating conditions. The varying parameters are liquid viscosity and density, gas density, bed particle shape and size. The range for gas density range is particularly large (from 1.3 to ), thanks to the use of dense gas to simulate very high pressure conditions. This data bank has been first used to compare the prediction accuracy of the different models from the literature. Finally, the mechanistic model proposed by Attou et al. [1999. Modelling of the hydrodynamics of the cocurrent gas-liquid trickle flow through a trickle-bed reactor. Chemical Engineering Science 54, 785-802] has been improved by adding a new formulation for liquid film tortuosity in two-phase flow conditions. This model has been validated over the whole data range and the accuracy has been checked with data external to the data bank. The prediction accuracy is significantly increased when compared with the best available models for pressure drop and liquid retention in trickle flow reactors.