Is the Souders-Brown equation sufficient for scrubber design? An experimental investigation at elevated pressure with hydrocarbon fluids

Scrubber design practice today is largely based on experimental data generated at ambient conditions with air-water systems. This paper reports experimental results for gas scrubber performance at pressures up to 92 bar using two types of hydrocarbon liquids: Exxsol D60 and a synthesized “live” natural gas condensate. The scrubber has a configuration very commonly used in industry with three types of internals in series: a vane inlet, a mesh pad and a cyclone deck. Results for the separation efficiency and the pressure drop of the internals separately and combined are shown graphically. The relevance of the Souders-Brown K-value, commonly used as scrubber design parameter, is elucidated both theoretically and in light of the results. The results show that the Souders-Brown value is rather good in practise for design of inlet vane and mesh pad, and that results for the two hydrocarbon systems agree reasonably, but also that better design rules are required for high-pressure separation of hydrocarbon liquids.     

Numerical simulation of effect of inlet configuration on square cyclone separator performance

This paper presents a numerical study of the gas-solid flow in square cyclone separators with three types of inlet configuration. Three-dimensional Reynolds Stress Model (RSM) was used to simulate the turbulent flow of gas phase and a Lagrangian equation was used to simulate the particle motion. The resulting velocity, separation efficiency and pressure drops were verified by comparison with measured data. The effect of inlet configurations on the turbulent dynamics in the cyclone and the separation efficiency and pressure drop was analyzed. Results showed that inlet configurations influenced the turbulent dynamics in the cyclone and led to different pressure drop and separation efficiency. The separator with double declining inlets (DDI) had the minimum pressure drop and similar efficiency to the separator with double normal inlets (DNI). The separator with single normal inlet (SNI) had the best separation efficiency and the maximum pressure drop. When a baffle was installed in the inlet of separator SNI, the pressure drop increased by about 191% and 34% for the separator with a straight (SNI-1) and curved (SNI-2) baffle respectively on the basis of the pressure drop of separator SNI. The cut and critical diameter of particles were 2 μm and 14 μm for separator SNI-1 and 4 μm and 14 μm for separator SNI-2, while they were 8 μm and 30 μm for separator SNI at the same inlet conditions.     

Effects of fly ash and bottom ash on the frictional behavior of composites

Immense quantities of coal combustion by-products are produced every year, and only a small fraction of them are currently utilized. Our recent work has focused on developing value-added products especially from fly ash, bottom ash, and flue gas desulfurization (FGD) scrubber sludge. We explored the potential utilization of fly ash, bottom ash, and sulfate-rich scrubber sludge as frictional modifiers and additives for automotive frictional composites. The surfaces of the frictional composites, fabricated from scrubber sludge and fly ash or bottom ash, were characterized with the help of scanning electron microscopy (SEM). The mechanical properties of by-products containing composites were evaluated using a dynamic mechanical analyzer (DMA). The frictional behavior of the composites was probed with the help of friction assessment and screening test (FAST). The frictional results suggested that fly ash or bottom ash had a profoundly different effect on the frictional coefficient (μ) and wear of the composite than those observed for scrubber sludge particles. It appeared that fly ash or bottom ash particles had abrasive characteristics and gave frictional composites a higher μ-value. The FAST test also revealed that the fluctuations in the μ-value were a minimum for composites that contained 20 vol% fly ash or bottom ash among the ash-derived composites. The composites that contained 30 vol% fly ash or bottom ash showed fade after approximately 60 min of continuous FAST test. We compared the frictional and wear performance of our composites with a commercial automotive brake, and it appeared that frictional composites could be formed which contained up to 20 vol% fly ash or bottom ash and 25 vol% scrubber sludge.     

Performance of a Degassing Cyclone with Main and Subsidiary Chambers

Based on the premise that large bubbles are removed in larger cyclones and small bubbles in smaller cyclones, a combined degassing cyclone with main and subsidiary chambers was designed to enhance liquid degassing. The pressure loss, liquid flow rate at the gas outlet, split ratio, gas flow rate at the liquid outlet, and degassing efficiency of the degassing cyclone were measured and calculated. Pressure loss correlations were established which relates the Euler number to the gas and liquid Reynolds numbers in the main chamber. Most cases exhibit a degassing efficiency greater than 0.998 when the liquid flow rate is more than 0.7 m³h^?1. The contours of pressure loss, split ratio, and degassing efficiency provide an effective guidance for designing a degassing cyclone.     

Solids concentration simulation of different size particles in a cyclone separator

To deepen our knowledge of the flow in cyclones, the solids concentrations of different size particles in a scroll cyclone separator were numerically simulated by using the Lagrange approach on the platform of commercial CFD software package, FLUENT 6.1. The numerical calculations visualize that there exists a spiral dust strand near the cyclone wall and a dust ring beneath the cyclone top plate. There are two regions in the radial solids concentration distribution, with which the solids concentration is low in the inner region (r/R(dimensionless radial position) ≤ 0.75) and increases greatly in the outer region (r/R > 0.75). Large particles generally have higher concentration in the wall region and small particles have higher concentration in inner vortex region. The axial distribution of the solids concentration in the inner vortex region (r/R ≤ 0.3) shows that serious fine particle re-entrainment exists within the height of 0.5 D (cyclone diameter) above the dust discharge port. We study the effect of solids particle on the gas flow field by two-way couple. The concepts of back-mixing rate, first escaping rate and second escaping rate are proposed for quantifying the local flow phenomena.     

差异旋风分离器并联性能测量及流场分析

通过改变旋向和芯管直径,设计了3种差异旋风分离器,并按中心对称方式组成了3种并联方案：相同分离器、旋向差异分离器和芯管差异分离器并联。在冷态实验装置上,测量了单分离器和并联分离器的性能,并利用FLUENT软件分析了并联分离器的流场。结果表明,并联分离器的效率均高于单分离器,且效率-气速曲线未出现“驼峰”;与相同分离器并联相比,旋向交替变化时并联总压降较小,分离效率也更低,但各分离器流量分配均匀,未发现“窜流”现象;当芯管有差异时,并联总压降增大,各分离器进口流量分配不均匀,且进、出口流量平均相差6.0%,公共灰斗中存在“窜流”,旋流稳定性变差,效率降低。为了保证并联分离器的性能,应采用相同分离器对称并联的方式。     

Effects of separation space diameter on the performance of a novel reverse flow cyclone

ABSTRACT

A numerical study was carried out to investigate the effect of separation space diameter on the performance of a novel reverse flow tangential inlet cyclone design by using the Eulerian-Lagrangian approach. The design of this cyclone is based on the idea of increasing vortex length and decreasing pressure drop compared with traditional cyclones. This novel cyclone differs from the traditional cyclones with separation space and vortex limiter instead of the conical part. A qualitative numerical study was performed to analyze the effect of separation space diameter on the cyclone performance at different flow rates by evaluating velocity profile, pressure drop, fractional and overall efficiencies. The results show that the collection efficiency of smaller particles increases while pressure drop decreases significantly with the increase in separation space diameter for D₁/D < 0.5.     

Imidazolium-based alkylphosphate ionic liquids - A potential solvent for extractive desulfurization of fuel

N-ethyl-imidazolium-based alkylphosphate ionic liquid (IL), viz. N-ethyl-N-methyl-imidazolium dimethylphosphate ([EMIM][DMP]), N-ethyl-N-ethyl-imidazolium diethylphosphate ([EEIM][DEP]) and N-butyl-N-ethyl-imidazolium dibutylphosphate ([BEIM][DBP]) were demonstrated to be effective for the removal of aromatic sulfur compounds (S-compound) 3-methylthiophene (3-MT), benzothiophene (BT) and dibenzothiophene (DBT) from fuel oils in terms of sulfur partition coefficients (K_N) at 298.15 K. It was shown that the extractive ability of the alkylphosphate ILs was dominated by the structure of the cation and followed the order [BEIM][DBP] > [EEIM][DEP] > [EMIM][DMP] for each S-compound studied with their K_N-value being 1.72, 1.61 and 1.17, respectively for DBT. For a specified IL the sulfur selectivity followed the order DBT > BT > 3-MT with their K_N-value being 1.61, 1.39 and 0.78, respectively for [EEIM][DEP]. The alkylphosphate ILs are insoluble in fuel while the fuel solubility in ILs varies from 20.6 mg(fuel)/g(IL) for [EMIM][DMP] to 266.9 mg(fuel)/g(IL) for [BEIM][DBP]. The results suggest that [EEIM][DEP] might be used as a promising solvent for the extractive desulfurization of fuel, considering its higher sulfur extractive ability, lower solubility for fuel and thus negligible influence on the constituent of fuel, and the ease of regeneration for the spent IL via water dilution process.     

An analytical model for the fractional efficiency of a uniflow cyclone with a tangential inlet

An analytical model was developed to predict the fractional efficiency of a uniflow cyclone with a tangential inlet. The analysis showed that the separation efficiency is a function of particle Stokes number and the geometry of the cyclone body. Six sets of experiments were conducted under different conditions to validate the model. The experimental fractional efficiencies were determined by the total mass efficiency and the corresponding size distributions measured by using an offline particle sizer. Overall the experiments agreed with the modeling results well. Both model and experiments showed that the efficiency of this cyclone reached 99.5% and above when Stk > 1.0.     

Numerical and experimental study on the effect of solid particle sphericity on cyclone pressure drop

The continuous flow inside cyclone separator is usually simulated by solving the Reynolds averaged Navier–Stokes equations in Eulerian reference frame whereas the dispersed phase is modeled using Lagrangian approach. Although these methods have had a remarkable success, more advanced ideas are needed to model particulate phase in cyclones, especially the non-spherical shaped particles. Numerical simulation is verified with experimental results for the gas-solid flow in a cyclone separator. Reynolds Averaged Navier–Stokes equations (RANS) employing the RNG-based k–ε turbulence model are used to simulate the gas phase. 3-D particle tracking procedure is used for the solid phase. Three different equations for the drag coefficient are utilized in the numerical modeling to acquire more understanding of the behavior of non-spherical particles in cyclones. Computations resulted in the difference of pressure between the inlet and exit of the cyclone, and results are compared with experimental data. Experiments included measuring the separation efficiency of different shapes and sizes of particles. The results indicate that the CFD simulation can effectively reveal the pressure drop behavior as well as separation efficiency of gas-non-spherical particle flow in cyclone.     

Multi-object optimization study on the performance of gas cyclones based on heterogeneous condensation and turbulent agglomeration

Improving the separation efficiency of fine particles becomes more and more critical as environmental pollution aggravates. This study aims to investigate the effects of four key parameters on the performance of gas cyclones, including cyclone body height, particle concentration, initial supersaturation degree, and inlet temperature. Then, the two-way coupling numerical model, in which is the process of heterogeneous condensation and agglomeration for insoluble fine particles, was achieved by user defined function. On this basis, the response surface analysis method and multi-objective genetic algorithm were adopted to optimize the cyclone. The results show that when the particle concentration is less than 1000 mg/m³, the separation efficiency can reach above 95%. The initial supersaturation degree has the greatest effect on the separation efficiency and vapour consumption rate, while the cyclone body height is the most critical factor on the pressure drop. As the particle concentration increases, the separation efficiency decreases at first and then keeps almost stable. With the increase of inlet temperature, the separation efficiency is enhanced, and the pressure drop reduces. These research results can provide important guidance for the optimization and engineering application of this technology.     

Liquid entrainment—Droplet size distribution for a low surface tension mixture

The optimization, design and choice of separation technology and the internals of a gas–liquid scrubber are highly dependent on the size of the liquid droplets to be removed. The majority of the liquid entrainment correlations for two-phase flow systems only provide information about the net mass transfer between the phases and not much data are available regarding the drop size distribution of entrained, low surface tension liquids (e.g. hydrocarbons) at working pressures higher than atmospheric.This paper provides a data set with new results for liquid entrainment of a mixture of Exxsol D60^TM as the liquid phase and nitrogen as the gas phase, with the system's pressure ranging from 900 to 1600 kPa. The corresponding surface tensions were 24.0–24.3 mN/m.The paper also reports results of a study on the additional drop size distribution information and provides a correlation that can be taken into consideration in suitable mathematical frameworks in order to increase the level of detail in describing multiphase systems. Further on, a new correlation for the mean droplet diameter was obtained by improving the numerical fitting of data sets which include lower surface tension systems.     

Development and application of a novel swirl cyclone scrubber—(1) Experimental

Conventional cyclones have a lower collection efficiency for smaller particles and conventional wet scrubbers have significant clogging and fouling problems by salt formation at the tip, the inside and outside of the nozzles, the tubes and the walls of scrubbers. Also, many companies and manufacturing sites have been in trouble for collecting their adhesive particulates. The novel swirl scrubber that we have developed consists mainly of a cyclone and a swirl scrubber with an impact cone and plates. This study reports the collection efficiency of particulates and the application of the novel swirl scrubber. The particle collection efficiency as a function of particle size was investigated with changes of plate angles, nozzle size and pressure, and volumetric flow rate of scrubbing medium. The particle collection efficiency increased with a decrease in plate angle, an increase in pressure of scrubbing medium at the nozzle tip, and an increase in volumetric flow rate of the scrubbing medium. The collection efficiency of PM₁₀ by scrubbing effect was much higher than that by cyclonic effect. In particular, the total increase in particle collection efficiency by scrubbing effect was significant (around 2.5 μm) in particle aerodynamic diameter. The developed novel swirl scrubber can be used for significantly increasing the collection efficiency of TSP, PM₁₀, and PM_2.5, in particular, which have adhesive characteristics. The costs for installation, operation and maintenance of the scrubber system are much cheaper than those of cyclones and scrubbers or other particulate collecting devices.     

Use of ferrous powder for increasing the efficiency of solid particle filtration in natural gas cyclones

This paper investigates the experimental feasibility of using magnetic forces to enhance the efficiency of the overall solid–gas separation in cyclone separators used in gas treatment. More specifically, the use of adhesive ferrous powder to further increase the lateral forces on the solid particles is investigated. The size distribution of the escaping solid particles with clean gas is compared between the conventional cyclone design and the proposed technique. It is shown that these additional forces are added to the centrifugal force, enhancing the separation efficiency in conventional cyclones, particularly for smaller particles.     

Bubble column with internals: Effects on hydrodynamics and local heat transfer

Local heat transfer and column hydrodynamics are investigated in a bubble column in presence of internals of different configurations. The liquid phase used is tap water and the gas phase is oil-free compressed air. The gas velocity is varied over a wide range of 0.03–0.35 m/s. The heat transfer variations are measured with a fast response probe capable of capturing bubble dynamics as well as detect local flow direction and deduce local liquid velocity. Measurements obtained in presence of internals are compared with those without internals to elucidate the effects of different internals design. Comparisons are based on average values and temporal variations obtained with the fast response probe. The average gas holdup, local liquid velocity and bubble fractions holdups obtained with and without internals are also compared to further point out the differences. The observed differences are discussed based on the insights provided by these comparisons. The results obtained show influence of internals design on column hydrodynamics which need to be considered for their proper design and modeling.     

并联旋风分离器的旋流稳定性分析

分别选用2台和4台直径300 mm的相同PV型旋风分离器作为分离元件,共用进气管、集气室和排尘室,以中心对称方式组成两种并联分离器,并通过数值模拟比较单分离器与两种并联方案中各分离元件气相流动的特点. 气体介质为常温常压空气,入口气速15~30 m/s. 结果表明,2台或4台并联时各分离元件流量偏差分别不超过0.35%和0.28%,压降最大偏差为0.79%和0.43%,流量分配均匀,灰斗内窜流返混不明显,且4台并联时效果更好. 4台并联时分离元件排尘段的稳定性指数比2台并联或单分离器降低过半,旋流稳定性显著增强. 对称排列的分离元件在公共灰斗中会形成具有自稳定性的对称涡系,对分离元件内旋进涡核的摆动有约束作用,旋流稳定性增强.     

Effects of the Inlet Section Angle on the Flow Field of a Cyclone

The gas flow fields of a cyclone with different inlet section angles have been studied numerically. The gas flow fields were simulated by means of the Reynolds Stress Transport Model (RSTM). The velocities and pressure drop profiles of these cyclones were investigated. The shortcut flow rates at the bottom of the vortex finder were calculated with different inlet section angles. To analyze the relationship between the inlet section angle and the vortex finder insertion deepness, this paper details the shortcut flow rates at the bottom of the vortex finder for three vortex finder insertion depths. The results indicate that the inlet section angle can decrease the shortcut flow from the bottom of the vortex finder, which has practical importance for the improvement of the separation efficiency. The inlet section angle can also decrease the pressure coefficient of a cyclone. When the inlet section angle is 45 °, the level of decrease is up to 30 %. However, the effect of the inlet section angle on the separation performance is related to the dimension of the vortex finder, i.e., the insertion depth and diameter of the vortex finder, and the effect is different when the cyclone has different vortex finder insertion depths.     

Phase transitions in hydrothermal K2HPO4 solutions

A 0.1 M potassium phosphate (K₂HPO₄) solution was reacted in a flow-through cell pressurized to 22 MPa. Reduced light transmission through the cell windows was observed at a setpoint temperature ≥400 °C, along with a decrease in effluent conductivity, but with no effect on flow. These observations suggest solution separation at ∼360 °C, with accumulation of a salt-concentrated liquid in the cell body and transition of a dilute liquid to a supercritical fluid at temperature >374 °C. High-pressure differential scanning calorimetry experiments confirm an onset temperature of 354 °C with an endothermic transition at 377 °C and 22 MPa. For apparent density, ρ = 150-500 kg/m³, the average transition temperature for 0.1 M solutions, 375 ± 5 °C, is slightly elevated relative to that of water at 371 ± 4 °C. Highest deviation for 1.0 M solutions, 365 ± 15 °C, is attributed to increased K₂HPO₄ hydrolysis and polymerization reactions.