文丘里洗涤器压力损失模型

通过理论分析,在考虑气体摩擦压力损失和扩散段液滴减速的压力回收基础上,推导出了一个准确、实用的文丘里洗涤器压力损失计算模型,并分别对3个具有不同喉管长度的文丘里洗涤器模型在液气比为0.4—1.0L/m3与喉管气速为33—58m/s条件下的压力损失进行了试验测量。结果表明:模型的理论预测值和试验值吻合良好,可以为工程设计或优化操作时文丘里洗涤器压力损失的预测方法。     

天然气净化用多管旋风分离器的分离性能

为了系统评价天然气净化用多管旋风分离器的分离性能,在线测量了入口气速6~24 m/s、入口颗粒浓度30~2000 mg/m3范围内多管旋风分离器的分离效率和分级效率. 结果表明,多管旋风分离器的分离效率和分级效率都随入口气速和入口颗粒浓度增大而提高. 与单管旋风分离器相比,在相同实验条件下,多管旋风分离器的分离效率下降2%~15%;单管旋风分离器基本能除净粒径大于10 mm的颗粒,而多管旋风分离器只能去除15 mm以上的颗粒. 多管旋风分离器的压降主要是内部单管旋风分离器的压降,占整个压降的80%~90%.     

Experimental investigations on a cyclone separator performance at an extremely low particle concentration

In order to evaluate the influence of extremely low particle concentration on separation performance of cyclone separator, the overall collection efficiencies and grade efficiencies of a cyclone separator with particle concentrations of 5-2000 mg/m³ and inlet velocities of 6-30 m/s have been investigated under ambient temperature and atmospheric pressure conditions. Aerosol spectrometer based on measuring particle number is used to measure the particle concentrations and particle size distributions of the inlet and outlet of the cyclone separator. The overall efficiency is equal to the ratio of the particle concentration difference between the inlet and outlet of the cyclone separator to the inlet particle concentration. The grade efficiency is obtained by comparing the particle size distributions of the inlet and outlet of the cyclone separator. The effects of particle concentration on separation performance are predicted by Smolik empirical model. Particle agglomeration, which has been found in the inlet and outlet of the cyclone separator, has a very important influence on the collection efficiencies and grade efficiencies of the cyclone separator at the particle concentration of 5-2000 mg/m³. The cut sizes for different inlet gas velocity with extremely low particle concentration can be quantitatively calculated by Barth model, Mothes and Loffer model and Muschelknautz model, respectively. Experimental results show that the overall collection efficiencies and grade efficiencies increased with the increasing particle concentrations and inlet velocities, and most of the particles with the diameter bigger than 10 μm can be removed by cyclone separator.     

文氏栅洗涤器除尘脱硫实验研究

采用双碱法脱硫技术 ,在自行设计的多通道文丘里洗涤器 (简称文氏栅洗涤器 )进行模拟燃煤烟气的除尘脱硫试验。其试验过程是 :先在三种不同喉部参数 (分别称为 1# ,2 # ,3 # )的文氏栅洗涤器进行除尘试验 ,经过优选后 ,在 2 #文氏栅洗涤器上进行脱硫试验。试验结果表明经过优选的 2 #文氏栅洗涤器有着较高的除尘脱硫效率。当文氏栅洗涤器的运行参数为 :pH =12、液气比为 0 .75L/m3、 [Na+ ]=0 .3mol/L、 [SO2 ]=12 0 0× 10 -6,文氏栅洗涤器的除尘效率大于 96 % ,脱硫效率大于 80 %。经过完善后可用作中小型燃煤锅炉烟气的除尘脱硫     

High-Volume Aerosol Filtration and Mitigation of Inertial Particle Rebound

The performance of electrostatically charged blown microfiber filter media was characterized for high-volume sampling applications. Pressure drop and aerosol collection efficiency were measured at air pressures of 55.2 and 88.7 kilopascals (kPa) and filter face velocities ranging from 2.5 to 11.25 meters per second (m/s). Particle penetration was significant for particles above 0.5 micrometers (μm) in aerodynamic diameter where the onset of particle rebound was observed as low as 200 nanometers (nm). Particle retention was enhanced by treating filters in an aqueous solution of glycerol. Adding this retention agent eliminated electrostatic capture mechanisms but mitigated inertial rebound. Untreated filters had higher nanoparticle collection efficiencies at lower filter face velocities where electrostatic capture was still significant. At higher filter face velocities, nanoparticle collection efficiencies were higher for treated filters where inertial capture was dominant and particle rebound was mitigated. Significant improvements to microparticle collection efficiency were observed for treated filters at all air flow conditions. At high air pressure, filter efficiency was greater than 95% for particles less than 5 μm. At low air pressure, performance enhancements were not as significant since air velocities were significantly higher through the fiber mat. Measured single fiber efficiencies were normalized by the theoretical single fiber efficiency to calculate adhesion probability. The small fiber diameter (1.77 μm) of this particular filter gave large Stokes numbers and interception parameters forcing the single fiber efficiency to its maximum theoretical value. The adhesion probability was plotted as a function of the ratio of Stokes and interception parameter similar to the works of others. Single fiber efficiencies for inertial nanoparticle collection were compared to existing theories and correlations.

Copyright 2014 American Association for Aerosol Research     

The pipeline flow of paste slugs: Part II. Pressure gradients and velocities of trains of slugs

Previous studies of the pipeline movement of single paste slugs of coal have been extended to determine the velocities of, and the pressure gradients along, trains of slugs. The measurements were taken in a 70-foot long, closed-loop line made from 0.95-inch bore, rigid plastic tubing. Flow in the line could be switched to maintain continuous movement of a train of slugs. Tests were made with slugs of 80:20 (w/w) coal-water paste which was extruded through a 0.775-inch die and also with slugs which were stabilized by the addition of agar to the water used for making the slugs. Slugs made from coal and agar solution were formed in cylindrical molds having diameters of 0.567, 0.661 and 0.756 inches and were intended to show more clearly the influence of slug diameter on the behavior of the trains. Individual slugs were five inches in length and were formed into trains with lengths of up to fifteen feet for the tests. The oil used as carrier fluid was a light mineral oil (μ = 5.92 cp,σ = 0.826 at 70°F.), which was circulated through the pipeline loop at velocities ranging from 1.0 to 10.0 ft./sec.     

Friction and friction-generated temperature at a polymer-metal interface

Results are presented of friction and thermal tests of molded polyimide and pyrrone polymers. The coefficient of sliding friction up to surface velocities of 2 m/sec (394 ft/min) and the coefficient of thermal expansion from 300 to 500°K (80 to 440°F) were measured. An apparatus was constructed to measure simultaneously the coefficient of sliding friction and the friction-generated temperature. Measurements were made at a nominal pressure-velocity product of 0.25 MN/msec (7100 lb/in.² × ft/min) and at temperatures between 300 and 500°K (80 and 440°F).     

Growth of aerosol particles by adiabatic expansion at the throat of a venturi scrubber

The condensational growth of aerosol particles in the throat section of a venturi scrubber and the contribution of it to the dust collection efficiency were discussed.The condensable water vapor produced in the throat of venturi was quantitatively obtained for various conditions assuming the change in pressure and temperature to be adiabatic process. In terms of this condensable water vapor and the particle number concentration, the diameter of grown particles was determined, and the degree of contribution due to particle growth to the particle collection by venturi scrubber was evaluated as the change in particle collection efficiency involved in the particle growth.Experimental verification of the above results was qualitatively made by changing the humidity of the inlet gas, which is the most important property dominating the particle growth, in the particle collection by venturi scrubber.     

ATOMIZATION IN A VENTURI SCRUBBER

High speed motion pictures were made or the breakup of a single jet of water in the throat of a venturi scrubber for various air and water jet velocities and different nozzle diameters. Atomization seemed to occur as the result of several different mechanisms, depending on the flow conditions, the most common mechanisms being breakup due to either capillary or acceleration waves and also breakup by “steady shear,” all of which have been observed by other investigators. The so-called “cloud-type” atomization proposed by Hesketh (1970) was not observed despite several attempts to achieve it. Measured values of pressure drop across the test section of the scrubber compare well with previously published results.     

FURTHER STUDIES OF GLASS FRACTURE WITH HIGH-SPEED PHOTOGRAPHY*

Photoelastic photographs, with exposures of approximately one-millionth of a second, were taken of transient stresses in glass before, during, and after fracture. The longitudinal and transverse waves in glass have been photographed and their velocities measured (18,000 and 11,000 ft. per sec, respectively). It was also found that under special conditions cracks may travel slower than .5000 ft. per sec, the value previously given as the crack propagation velocity.     

旋流板分离器的三维流场测定及结构改进

为了增加旋流板分离器的断面气速,减小分离粒径,使其适应水泥生料粉预热器的要求,对分离器空间三维旋转流场进行了测定和分析.根据实测流场的特点,对其结构作了如下改进:加挡板以防止颗粒的二次夹带;加筋以消除灰环,从而使断面气速增加到3m/s,临界分离粒径减小到10～15μm,本文运用流场实测结果所推导的旋流板分离器的临界分离粒径公式及所测压降数据,可供生产上参考.     

Friction factors in pulsed turbulent flow

An apparatus for investigating pulsed turbulent liquid flow in a 2 in. diameter, 80 ft. pipeline is described. The pulsation unit was powered by compressed air with a consumption of up to 2.7 std. cu.ft./min. at 35 lb/in² gauge. The pressure drop for water flowing at mean velocities of 7.66 to 12.28 ft./sec. has been measured, both for steady flow and for pulsed flow, at frequencies between 0.48 and 0.82 Hz. The experimentally measured pressure versus time curves for pulsed flow can be matched fairly closely by a solution of Euler's equation employing the friction factors measured under steady flow conditions.     

Investigation of a wet dust scrubber with a pneumatic nozzle: Dust collection based on turbulent diffusion

The “nozzle scrubber” is a wet scrubber in which the scrubbing water is dispersed in dust laden gas stream by means of one or more pneumatic nozzle. This scrubber is distinguished by an excellent collection efficiency for submicron dust at an unusually low energy and water consumption. So far, the physical effects affecting the separation cannot be explained by a well-defined theory. Therefore, it is sensible to investigate the collection efficiency with regard to the mechanisms of inertial impaction, turbulent diffusion and coalescence induced by turbulence. The experimental equipment is of a very simple design. A light scattering device was used to measure the particle distributions. In addition, electron micrographs were analyzed to obtain information about the submicron particles. The influence of operating parameters on grade efficiency has been demonstrated by their systematic variation. The contribution of turbulent diffusion to the collection efficiency has been confirmed; nevertheless, grade efficiencies were also measured when inertial impaction prevailed.     

Mercury Speciation in Flue Gases after an Oxidative Acid Wet Scrubber

Flue gases from a hazardous waste incinerator have been sampled in three campaigns, before and after, an oxidative acid wet scrubber working with the MercOx‐process. A continuous emission monitor for mercury speciation was used before the scrubber in the first campaign. In all campaigns, impingers with KCl and KMnO₄ were used. A solid adsorption method was used in the last campaign. The mercury leaving the scrubber is oxidized at > 90 % efficiency (independent of the inlet speciation). A substantial decrease in the redox potential of the scrubber liquid caused an increased fraction of elemental gaseous mercury to be present in the clean gas. The measurements also show that the scrubber has the ability to readily absorb mercury peaks. During one extreme peak of 3,600 μg/m³ (dry gas) in the raw gas, the removal efficiency was above 99.9 %.     

Evaluation of the three phase transport reactor

A high aspect ratio chemical reactor for reacting a liquid with a gas in the presence of a finely divided catalyst was tested. The gas was sparged into the bottom of a tubular reactor with the slurry of liquid and catalyst flowing countercurrent to the gas. The liquid phase hydrogenation of alpha-methylstyrene to cumene on a Pd. catalyst was studied in semibatch operation of the reactor with slurry recycle. The reacor was 1 1/2-in. I.D. by 6-ft. long. The following variables were studied at a temperature of 28°C and a pressure of 1 atm: superficial gas velocities of 1.1 to 3.3 cm/sec., and catalyst loadings from 0.4 to 2.0 gm. catalyst per liter. A model of the reactor was developed and successfully compared with the data.     

ATOMIZATION IN A VENTURI SCRUBBER

High speed motion pictures were made or the breakup of a single jet of water in the throat of a venturi scrubber for various air and water jet velocities and different nozzle diameters. Atomization seemed to occur as the result of several different mechanisms, depending on the flow conditions, the most common mechanisms being breakup due to either capillary or acceleration waves and also breakup by “steady shear,” all of which have been observed by other investigators. The so-called “cloud-type” atomization proposed by Hesketh (1970) was not observed despite several attempts to achieve it. Measured values of pressure drop across the test section of the scrubber compare well with previously published results.     

Holdup in vertical two and three phase flow Part II: Experimental investigation

Experimental data on air-water-glass beads system flowing cocurrently and countercurrently in a vertical column 1.5-in. ID and 5-ft. long at 1 atm. and room temperature are presented. The ranges of variables studied were: superficial gas velocity 0 to 2.55 cm/sec upward, superficial liquid velocity 7.6 cm/sec downward to 32.2 cm/sec upward, input solid concentration in the the slurry 0 to 6% by volume and the mean diameter of solid particles 0.0118 and 0.0059-in. All flows involving gas were in the bubbly regime. The experimental data were in good agreement with the theory presented in Part 1.     

纯化天然气水合物螺旋分离器流场与性能分析

基于海洋天然气水合物固态流化开采方法的井下原位除砂提纯回填工艺,本文结合试采所得水合物浆体特征,设计用于解决设备磨损、储层坍塌等问题的井下除砂螺旋分离器,利用CFD数值模拟方法研究了入口速度和水合物体饱和度对井下除砂螺旋分离器流场和性能的影响,得到了随着入口速度增加,流场中流体的速度急剧增大,特别是切向速度、分离效率增加。当分离效率为70%以上,分离器内压降急剧增大,表明分离器内部的能量损耗不断增加;随着入口水合物体积分数的增加,螺旋分离器内流场变化微小,水合物分离效率降低,砂分离效率增加;分离效率为80%以上,压降逐渐降低。说明该分离器的最佳操作区为入口速度范围为3～5m/s,水合物入口体积分数15%以下。研究结果表明：本螺旋分离器具有极佳的除砂效果;切向速度是决定分离器分离性能的关键速度,处理量的增大有利于水合物的提纯;海底水合物储层中水合物饱和度变化对螺旋分离器分离效率具有一定的影响,但螺旋分离器对其具有一定的适应能力;揭示了水合物井下螺旋分离器除砂的分离机理,为其设计提供了一定的依据,为海洋水合物储层开采防砂提了一种新的技术及装备。     

Simultaneous removal of SO2, NO and particulate by pilot-scale scrubber system

SO _x and NO _x have both previously been identified as primary precursors of acid rain, and thus the abatement of SO _x and NO _x emissions constitutes a major target in the field of air pollution control. In this study, the efficacy of a pilot-scale scrubber was evaluated with regard to the simultaneous removal of SO₂, NO and particulate with wet catalysts. The removal efficiencies of particulate were measured to be 83, 92 and 97% with catalyst flux of 0.5, 0.8 and 1.5 L/min, respectively. The average removal efficiencies of particulate with different nozzles were approximately 94 and 90% with FF6.5 (5/8 in.) and 14 W (1.0 in.) nozzles, respectively. At least 96–98% of particulate and SO₂ were removed, regardless of the stage number of reactor. In a one-stage scrubber, 83.3% removal efficiency of NO was achieved after 48 hours; however, the two-stage scrubber achieved an NO removal efficiency of 95.7%. Regardless of the liquid-gas ratio, SO₂ and particulate were removed effectively, whereas NO was removed about 84% and 74% under liquid-gas ratio conditions of 39.32 L/m³ and 27.52 L/m³, respectively. In experiments using STS and P.P. pall ring as packing material, particulate and SO₂ removal efficiency values in excess of 98% were achieved; however, NO removal was correlated with the different packing materials tested in this study. With the above optimum operation conditions, even after 20 hours, the removal efficiency for NO stayed at 95% or higher, the removal efficiency for SO₂ stayed at 97% or higher, and the removal efficiency for particulate stayed at 92% or higher. In accordance, then, with the above results, it appears that this process might be utilized in scrubber systems, as well as systems designed to simultaneously remove particulate, SO₂ and NO from flue gas.