Cocurrent gas—liquid flow in packed columns

Hydrodynamics characteristics of HDS trickle bed test reactor

Gas absorption in a centrifugal reactor: hydrodynamics

The effects of pressure and pipe diameter on gas-liquid two-phase flow behaviors were investigated experimentally and theoretically for horizontal and slightly inclined pipelines. Experimental data of flow pattern, pressure drop and liquid holdup were acquired in the wide range of the gas and liquid flow rates in a large diameter (106.4 mm) pipe for different pressures (592 and 2060 kPa) and different inclination angles (0°, 1°, and 3°). To evaluate effects of the pipe diameter, our previous experimental data of low pressure (490 kPa) and small diameter (54.9 mm), were also used. Based on analysis of the experimental observations, a flow pattern map was developed for each pressure, pipe diameter, and inclination. Major phenomena identified in data analysis include: Pressure and pipe diameter clearly affect the flow pattern transition boundaries. The high pressure tends to shift the boundaries to the lower side of superficial gas velocity in the flow pattern maps. In the large-diameter-pipe experemints, stratified flow was observed at higher superficial liquid velocities than in small diameter. The gas flow rate and inclination angle showed influences on liquid holdup and pressure drop behavior. The average pressure did not show large influences on liquid holdup and pressure drop. Based on the experimental data, a mechanistic model was developed incorporating transition criteria for eight flow patterns, and individual flow models for estimating liquid holdup and pressure drop. The results predicted by the individual models demonstrated excellent agreements with the experimental data for each pressure and each inclination angle.

Gas–liquid two-phase flow distributions in parallel channels for fuel cells

Experimental study on the spray characteristics of an internal-mixing gas-liquid injector

The emission of hydrogen sulphide is a major problem associated with anaerobic treatment of sulphate and sulphite containing wastewaters. Conventional absorbing processes, such as packed towers, spray towers or bubble columns, are all constrained by factors such as flooding and foaming. Membrane systems, on the other hand, enable independent control of the liquid and gas flow rate and a step change order of magnitude increase in the specific surface area of the contact process. The membrane acts as a gas absorber with a design similar to a shell and tube heat exchanger. On the other hand, they are limited by facets of the membrane such as its resistance to mass transfer and permselectivity, as well as its cost. The work presented in this paper refers to an absorption process based on a non-wetted hollow fibre membrane for the scrubbing of hydrogen sulphide from air, with water as the contact solvent. Results presented describe the performance of the unit in terms of overall transfer and outlet liquid concentration as a function of circulation regime, gas flow rate, liquid flow rate and specific surface area. In particular, results are presented using traditional plots of Sherwood number (Sh) against Graetz (Gr) number for the liquid flowing in the lumens, such that experimental and available empirical descriptions of the process performance are directly compared. Results suggest that, as expected, very efficient mass transfer is obtained. However, the mass transfer was found to reach a maximum value against Gr, contrary to available empirical models.

Dynamic tank-in-series modelling and simulation of gas-liquid interaction in trickle bed reactor designed for gas fermentation

Membrane evaporation of amine solution for energy saving in post-combustion carbon capture: Performance evaluation

The effect of free gas on the Electrical Submersible Pump (ESP) performance is well known. At a constant rotational speed and constant liquid flow rate, small amount of gas causes a mild head reduction when compared to the single phase liquid head. However, at higher gas rates, a drastic reduction in the head is observed. This critical condition, known as surging point, is a combination of liquid and gas flow rates that cause a maximum in the head performance curve. The first derivative of the head with respect to the liquid flow rate change sign as the liquid flow rate crosses the surging point. In several works on ESP two-phase flow performance, production conditions to the left of the surging region are described or reported as unstable operational conditions.This paper reviews basic concepts on stability of dynamical systems and shows through simulation that ESP oscillatory behavior may result from two-phase flow conditions. A specific drift flux computation code was developed to simulate the dynamic behavior of ESP wells producing without packer. The code is also able to capture the classical casing-heading phenomenon in natural flowing wells.

Experimental studies on simultaneous removal of CO2 and SO2 in a polypropylene hollow fiber membrane contactor

An experimental study of a shroud type downhole separator for a pumped horizontal or deviated well is presented in this study. The separator is located at high deviation angles (i.e., 45 to 80-degrees from the vertical). The effects of the upstream gas and liquid flow rates are evaluated in the performance of the downhole separator. Traditionally, downhole separators are tested under steady-state conditions in vertical or close to vertical configurations. For those tests, the fluids were injected above or at the bottom of the separator in a vertical setting. The University of Tulsa's outdoor downhole separator facility was used in this study. The facility allows the injection of a two-phase mixture below the separator; the gas and liquid flow rates and the deviation angle can be varied. The global separation efficiency and the liquid holdup in the liquid-rich outlet were recorded and analyzed. The experimental results demonstrated the effects of the gas and liquid flow rates and deviation angle on the behavior of downhole separators. It was found that as the deviation increases, the efficiency of the separator increases. It was also observed that efficiency decreases at deviations close to horizontal. The findings complement previous studies on shroud type downhole separators and demonstrate the operational capability of downhole separators under numerous conditions. Furthermore, the results provide conditions under which and where the separator can be operated efficiently in the field.

The effects of ratio of draft tube to reactor diameter (Dd/D), liquid nozzle diameter (dN), aeration tube diameter (dG) and immersion height of the two‐fluid nozzle into the draft tube (HN) on overall and annulus gas holdups for the air‐water system were evaluated experimentally in a reversed flow jet loop reactor over wide ranges of gas and liquid flow rates. Both the gas holdups increased with increasing gas and liquid flow rates and with decreasing dN and HN. The influence of dG on gas holdups is found to vary with gas flow rates. Correlations are proposed to predict gas holdups.

A radiotracer study was carried out in a trickle bed reactor (TBR) independently filled with two different types of packing i.e., hydrophobic and hydrophilic. The study was aimed at to estimate liquid holdup and investigate the dispersion characteristics of liquid phase with both types of packing at different operating conditions. Water and H2 gas were used as aqueous and gas phase, respectively. The liquid and gas flow rates used ranged from 0.83 × 10−7–16.67 × 10−7 m3/s and 0–3.33 × 10−4 m3 (std)/s, respectively. Residence time distribution (RTD) of liquid phase was measured using 82Br as radiotracer and about 10 MBq activity was used in each run. Mean residence time (MRT) and holdup of liquid phase were estimated from the measured RTD data. An axial dispersion with exchange model was used to simulate the measured RTD curves and model parameters (Peclet number and MRT) were obtained. At higher liquid flow rates, the TBR behaves as a plug flow reactor, whereas at lower liquid flow rates, the flow was found to be highly dispersed. The results of investigation indicated that the dispersion of liquid phase is higher in case of hydrophobic packing, whereas holdup is higher in case of hydrophilic packing.

Results of experimental study of the effect of initial maldistribution of structured packing irrigation on efficiency of binary mixture separation are presented in this article. The studies were carried out in the experimental distillation column with the diameter of 0.9 m using the R114 and R21 freon mixture. Experiments were performed on the structured Mellapak 350.Y packing of stainless steel 316L, containing 19 layers with the total height of 4.016 m at the ratio of mole liquid and vapor flow rates L/V = 1 and 1.7, respectively, and the pressure in the upper part of the column ptop = 3 bars. Nonuniformity at the packing inlet was generated via the blocking of some holes in the liquid distributor. Here, we present some results on efficiency of mixture separation, pressure drop on the packing, distribution of local liquid flow rate under the packing over the cross‐section and on the column wall within the range of vapor loading factor (0.69 < Fv < 1.61 Pa0.5), as well as experimental data on distribution of local concentration of the low‐boiling component over the cross‐section and along the height of the structured packing. It is found out that significant maldistribution of mixture concentration and liquid flow rate over the cross‐section slightly changes along the height in the lower part of the column at a change in the degree of packing irrigation nonuniformity at the inlet. It is shown that efficiency of mixture separation depends considerably on the value of parameter L/V, vapor flow factor Fv, and size of the zone underirrigated by liquid at the inlet. In the studied range of liquid and vapor flow rates, the relative pressure drop on the packing does not depend on the ratio of liquid and vapor flow rates L/V and degree of irrigation maldistribution. © 2013 American Institute of Chemical Engineers AIChE J 60: 690–705, 2014

Liquid flow distribution has been a major concern when scaling up random packed columns. This study concerns the measurements of liquid flow distribution in a large scale column packed with 25.4 mm stainless steel Pall rings. The liquid flow distribution was studied with packed bed height from 0.9 to 3.5 m, liquid flow rate from 2.91 to 6.66 kg/m2·s, and gas flow rate from 0 to 3.0 kg/m2·s. In addition, three systems, water/air, aqueous detergent solution/air and Isopar/air, were used to study the effect of liquid physical properties on liquid flow distribution, and two different liquid distributors were employed to test the effect of liquid distributor design. It was found that liquid flow distribution was strongly influenced by liquid distributor design, packed bed height, gas flow rate and liquid viscosity, slightly influenced by liquid flow rate, but not by liquid surface tension.