Gas Liquid Solid Three-phase Flow Research Articles

Three-phase flow induced vibration characteristics for mining riser in deep-sea natural gas hydrate extraction

During the lifting process of deep-sea natural gas hydrate, the mining riser is susceptible to complex fatigue failure due to the combined effects of internal gas–liquid–solid three-phase flow, external ocean loads, and the large aspect ratio of itself. The gas–liquid–solid three-phase flow induced vibration (FIV) model for deep-sea hydrate extraction riser is established using finite element method and Hamiltonian principle. The simulation experimental device for nonlinear vibration of mining riser under internal and external flow excitation is developed and conducted a simulation experiment for gas–liquid–solid three-phase FIV of vertical pipes. The experimental test results are compared with the theoretical model calculation results to verify the correctness of the model. Using frequency domain and time domain analysis methods, the influences of external environmental parameters and multiphase flow parameters on the nonlinear FIV response of the riser are explored. The results showed that the vibration amplitude in the cross-flow (CF) direction of the riser is larger, and the change in internal flow parameters had a more significant impact on the CF vibration. The longitudinal vibration of the riser is composed of low-frequency high-amplitude vibration caused by gravity and platform heave, and high-frequency low-amplitude vibration induced by internal and external flow field loads. The increase in shear flow velocity will significantly increase the displacement of the riser along in-line flow direction, thereby suppressing CF vibration. The research results can be widely applied to the vibration problems caused by gas liquid solid three-phase flow in the energy collection process, which has important research significance and significant engineering value for improving the safety of operation columns.

A coupled particle dynamics-lattice Boltzmann method model for particle-resolved direct numerical simulation of gas–liquid–solid flow with an irregular particle expressed by multi-sphere algorithm

In this paper, we develop a lattice Boltzmann (LB) model for simulating the gas–liquid–solid three-phase flow. Based on the gas–solid two-phase fluid model in the framework of the lattice Boltzmann method (LBM), a multiphase fluid–solid two-way coupling algorithm is proposed. In this model, the fluid–fluid interface is tracked using a phase-field method. Kinetic-theory-based boundary treatment, such as the interpolated bounce back, combined with the momentum exchange methods handle flow–particle interactions. Particle dynamics (PD) equation depicts the particle's movement and direction. Multi-sphere algorithm is inserted into the LBM frame to efficiently express the irregular particle borrowing from the idea of multi-sphere model in a discrete element method frame. Several typical benchmark cases are used to validate the present model, including the flow around the static and rotating cylinder, the wetting behavior of regular and irregular particles on the liquid–gas interface, the setting of a cylindrical particle, and regular and irregular particles sinking into and pulled out water. The numerical results show that the model agrees well with analytical solutions, experimental data, and published literature. The coupled PD-LBM model is validated and can accurately simulate any gas–liquid–solid three-phase flow system containing moving contact line phenomena.

Numerical Simulation on Hybrid Lifting Operation of Polymetallic Nodules and Rare-Earth Elements-Rich Mud by Air-Lift Pump in Deep Sea Around Minamitorishima Island

Polymetallic nodules and REE-rich mud under the seabed of 5500–5700 m water depth around Minamitorishima island are promising and attractive for exploration and development. Following our previous research, numerical analysis was used to investigate the unsteady flow characteristics and the lifting performance of a commercial production system using an air-lift pump for hybrid lifting, lifting both polymetallic nodules and REE-rich mud. Gas–liquid–solid three-phase flow and gas–liquid two-phase flow in the system were analyzed using the one-dimensional drift–flux model. First, the reliability of the schemes and program was verified by comparing the numerical results with the experimental ones. Next, numerical simulations were conducted, in which the model’s dimensions were related to a commercial production system operated in the deep sea around Minamitorishima island, and the conditions fit the expected production rate. The results revealed the unsteady flow characteristics under the operations, such as start-up, shut-down, feed of polymetallic nodules and REE-rich mud, and those associated with disturbances, such as feed rate fluctuations. We demonstrate that the program and the schemes can simulate the unsteady flow characteristics and the lifting performance of a commercial production system with an air-lift pump well, and they can derive useful information and know-how in advance for the safe and continuous operation of the system.

Research on the Influence of Symmetrical Installation of Blade on the Sediment Erosion in a Multi-Stage Centrifugal Pump

Double suction pumps are widely used in the Yellow River in the China water intake pump stations, which face serious sediment wear. A prediction model for gap erosion in gas-liquid solid three-phase flow was constructed. A gas core factor has been added to the gap erosion model to achieve accurate prediction of particle impact velocity and impact angle caused by cavitation air core deformation. The influence mechanism of cavitation flow and sand-laden suction vortex on the sediment erosion. Usually, double suction pumps are one type. This study aims to explore the effects of the symmetrical and asymmetrical installation of double suction pump impellers on the wear and energy dissipation of pumps under sediment conditions in three-stage centrifugal pumps. The research results indicate that under symmetrical installation, the wear of the impeller caused by sediment impact is significantly intensified with a maximum velocity of 27 m/s. In contrast, asymmetric installation significantly improves sediment wear, with a maximum velocity of 24.3 m/s. By optimizing the staggered angle on both sides of the impeller, it was found that when the staggered angle was set to 10.85°, the performance of the pump under sediment conditions reached its optimal level, with a minimal erosion rate of 0.000008 kg·m−2·s−1. These results provide an important basis for the design and optimization of three-stage centrifugal pumps in sediment transport and have significant theoretical significance and engineering application value.

Air-Lift Pumping System for Hybrid Mining of Rare-Earth Elements-Rich Mud and Polymetallic Nodules around Minamitorishima Island

REE-rich mud under the seabed at a 5500–5700 m water depth around Minamitorishima island and polymetallic nodules buried in the deep seabed are very promising and attractive to explore and develop. REEs are critical to develop due to the recent paradigm shift to renewable energies based on green technologies. Numerical analysis using a one-dimensional drift–flux model for gas–liquid–solid three-phase flow and gas–liquid two-phase flow was conducted to examine the characteristics of an air-lift pumping system for mining these mineral resources. Empirical equations of REE-rich mud and the physical properties of polymetallic nodules around Minamitorishima island were utilized in the analysis. As a result, the characteristics, i.e., the performance of the system, were clarified in three cases: REE-rich mud, polymetallic nodules, and both. The time transient, i.e., the unsteady characteristics of the system, was also shown, such as the start-up and feeding slurry with REE-rich mud and polymetallic nodules. The findings from the unsteady characteristics will be useful in considering the operation of a real project or a commercial system in the future.

Computational fluid dynamics study on first reaction chamber of internal circulation anaerobic reactor

This study aims to investigate the characteristics of gas–liquid-solid three-phase flow in an Internal Circulation (IC) anaerobic reactor during the treatment of wastewater. Through computational fluid dynamics (CFD) simulations of the gas–liquid-solid three-phase in the first reaction chamber and based on the anaerobic granule swarms drag coefficient model, the study investigates the effects of superficial liquid velocity and superficial gas velocity on granules distribution, uniformity index, gas holdup, flow velocities of each phase, and the dimensionless variance of residence time distribution. In addition, the relationship between the fully mixed superficial velocities of gas and liquid in the first reaction chamber is also determined.

Investigation on gas–liquid–solid three-phase flow model and flow characteristics in mining riser for deep-sea gas hydrate exploitation

In response to the problem of gas–liquid–solid three-phase flow in deep-sea hydrate extraction pipelines, a gas–liquid–solid three-phase flow model considering the dynamic decomposition of hydrates is established using continuity equations, momentum equations, and energy equations. The numerical solution of the theoretical model is achieved using the finite difference method. Comparing the theoretical model with the experimental results, the results showed that the average error of gas holdup, liquid holdup, solid phase content, gas phase velocity, liquid phase velocity, and solid phase velocity obtained from the theory and experiment are 8.24%, 0.41%, 1.88%, 5.80%, 2.81%, and 2.22%, respectively, which verified the correctness of the theoretical model. On this basis, the influences of hydrate abundance, liquid phase displacement, and wellhead backpressure on the gas–liquid–solid three-phase flow characteristics in the pipeline were investigated, and it was found that the gas holdup rate will increase with the increase in hydrate abundance, liquid phase displacement, and wellhead backpressure, with the influence of hydrate abundance being more sensitive. The liquid holdup rate increases with the increase in hydrate abundance and liquid phase displacement, but decreases first and then increases toward the wellhead position with the increase in wellhead backpressure. The solid phase content decreases with the increase in hydrate abundance, and first increases and then decreases toward the wellhead position as the liquid phase displacement and wellhead backpressure increase. The influence of gas phase velocity on the abundance of hydrates is relatively small, but it increases with the increase in liquid phase displacement. When the wellhead backpressure increases, the instantaneous increase then tends to flatten out. The influence of hydrate abundance on the liquid phase velocity is also relatively small, but it increases with the increase in liquid phase displacement and decreases with the increase in wellhead backpressure. The solid phase velocity will increase with the increase in hydrate abundance and liquid phase displacement, but it will not show significant changes with the change of wellhead backpressure. The research results can provide a theoretical basis for the safety of hydrate mining.

Simulation of Elbow Erosion of Gas–Liquid–Solid Three-Phase Shale Gas Gathering Pipeline Based on CFD-DEM

Shale gas gathering pipelines often contain liquid water and solid sand in the early stage of production, which leads to the failure of pipeline components easily under the action of gas–liquid–solid three phases. A computational fluid dynamics (CFD) model based on the fluid volume method (VOF) and discrete element method (DEM) was established to study the flow law of gas–liquid–solid three-phase flow in the elbow of shale gas gathering pipeline and the erosion law of the inner surface of the elbow was studied by coupling the Oka erosion prediction model. By comparing the experimental results of erosion damage of the elbow, it is found that the model established can well predict the erosion characteristics and erosion amount under the action of three phases. Combined with the field pipeline parameters and operating conditions, the paper further simulates the elbow erosion behavior under relevant working conditions. The results show that the particles rotate clockwise from the outer wall of the pipe through the bottom of the pipe when passing through the elbow under the action of gas and water phases. When the gas velocity increases, the particles at the elbow mainly gather at the bottom of the elbow and the wall of the outer arch. When the water content increases gradually, the particles gathered on the outer arch wall of the elbow move along the outer arch wall of the elbow and face the inner arch surface gradually, and the erosion area is mainly concentrated on the outer arch wall of the elbow and the outlet horizontal pipe. Under the condition of the liquid phase, the movement characteristics of the water phase and particles in the elbow of the gas gathering pipeline and the erosion characteristics of the pipeline surface are obviously different from those under the condition of the gas–solid two-phase. The model and simulation results established in this paper provide a reference for the erosion damage protection of shale gas gathering pipeline elbow.

Investigation on gas–liquid–solid three-phase flow characteristics in aircraft wastewater pipes

The aircraft wastewater system is an important system for civil aircraft. The wastewater is transported through the pipeline under the pressure difference between the cabin and the vacuum wastewater tank, and its flow time and characteristics are crucial for the system design. In this paper, the gas–liquid–solid flow of aircraft wastewater is investigated using the Euler–Euler–Euler multiphase flow numerical simulation method. The influencing factors of wastewater flow are analyzed. Afterward, the impact of different factors on the flow time and characteristics is analyzed, such as pressure differences between the cabin and the tank, pipeline length, pipeline inner diameter, and the disturbance for a straight long pipeline. The results show that the wastewater flow time is reduced from 6.4 to 2.6 s with the increase in the pressure difference from 20 to 60 kPa and increased from 3.4 to 10.2 s with the increase in the pipeline length from 30 to 70 m. The results obtained provide a modern theoretical basis for the design of such systems of vacuum wastewater and have a wide range of applications not only in aviation but also in other modern kinds of transport (rail, shipping), contributing to reducing their negative impact on the environment.

Interelectrode gas–liquid-solid three-phase flow analysis and simulation for drilling holes with high aspect ratio by micro-EDM

Interelectrode gas–liquid-solid three-phase flow analysis and simulation for drilling holes with high aspect ratio by micro-EDM

Review of bubble dynamics on charged liquid–gas flow

When a fluid is subject to an electric field, it usually processes unique features compared to the conventional fluid that arises from coupling between charged particles and fluid interface. Based on this commonality, we defined the concept of “charged multiphase flow” and constructed a generalized charged multiphase flow system using the “Tai Chi Diagram” to analyze the properties and features of different study objects, with an emphasis on the bubble dynamics on the charged liquid–gas flow object, covering the processes of bubble generation, motion, and interaction, as well as the important dynamic behaviors, involved such as bubble deformation, coalescence, and breakup. Furthermore, in light of the special plasma–liquid interface phenomenon formed by the ionization of the gas/vapor phase in the liquid phase in strong electric fields, the traditional gas–liquid–solid three-phase flow system is expanded into a broader range of multiphase flow systems involving plasma, which enriches the theoretical and frontier scientific problems of the multiphase flow. In addition, technical innovations, remaining work, and future trends in the development of the charged liquid–gas flow, and their potential applications are discussed.

Study on Temporal and Spatial Distribution and Transport Characteristics of Dust in New Composite Spraying Slurry

In view of the problems of traditional spraying technology, such as complex processes, high costs, large dust amounts, and poor air leakage effects, a new composite spraying slurry is proposed in this paper, which takes clay as the main base material and uses water pressure and wind pressure to ensure intrinsic safety. Firstly, the airtightness, bending resistance, and viscosity of the spraying material were measured in the laboratory; secondly, the gas–liquid–solid three-phase flow process involved in the spraying process was simulated by using the CFD-DPM method, adopting the Eulerian two-fluid model for continuous gas–water two-phases and the discrete phase DPM model for dust generation, and the transport, diffusion, and full space-time distribution characteristics of dust generation were studied. The research shows that: (1) the new composite slurry spraying material made of clay as the main material is made by adding a small proportion of cement and engineering fiber to increase the toughness of the material, and finally, determining the mass ratio of the composite material as follows: clay: cement: additive: engineering fiber = 84:14:1.85:0.15. It has good sealing and bending resistance and good adhesion; (2) the water phase distribution under the action of spray determines the distribution of solid-phase dust, and the distribution area of dust is similar to that of the water phase; (3) under the action of spray, the area at the bottom of the roadway is covered by dust flow, and the dust in this area is obviously stratified. The particle size of the dust gradually decreases from bottom to top. The large particle size dust is deposited at the bottom, while the small particle size dust is suspended at a certain height, and the diffusion area gradually increases; (4) the effect of spray angle on dust is mainly manifested in the initial dust flow shape and dust diffusion time. The larger the spray angle, the faster the diffusion; (5) when the water velocity at the nozzle outlet is large, the dust concentration is low in the whole area, but in areas higher than 1.5 m, the PM2.5 concentration also increases with the increase in water flow. The dust suppression effect of larger a water flow is mainly reflected in the bottom area, and the disturbed surrounding airflow can make PM2.5 diffuse to higher areas.

Investigation on the Secondary Generation of Natural Gas Hydrates in Horizontal Wellbore Caused by Pressure Jump during the Depressurization Development of Hydrate Bearing Layers

When the depressurization development of a hydrate-bearing layer is initiated, the temperature of the near-wellbore formation quickly decreases to near the equilibrium temperature due to the dissociation of natural gas hydrate Therefore, the secondary generation of natural gas hydrates in the wellbore easily occurs if pressure jumps to a high value due to the changes of production rates or shutdown of the well. Though hydrate generation in the process of high-pressure drilling and gas and water transportation has been widely investigated, the secondary generation of natural gas hydrates caused by pressure jump during the depressurization development process is not fully understood. In this study, the multiphase pipe flow of a horizontal well, the Vyniauskas–Bishnoi generation dynamics of natural gas hydrate, and a decomposition dynamics model developed by Kim and Bishnoi are combined to build a set of horizontal well gas–liquid–solid three-phase flow models, which consider the phase transition in the wellbore and distinguished the secondary hydrate generation area in the wellbore under different temperature and pressure conditions. The results show that when the toe-end pressure is 7 MPa and the environment temperature is 6.4°C, the secondary hydrate generation exists in the horizontal section of the horizontal well, and the maximum hydrate flow velocity in the wellbore is 0.044 m3/d. A high toe-end pressure, low environment temperature, and high gas output will result in a greater hydrate generation in the wellbore, and the wellbore pressure will have a remarkable influence on the amount generated and its range.

VOF-DPM Simulations of Gas-Liquid-Solid Scrubbing Chambers with Two Gas Intake Modes

The scrubbing tower plays an important role for gas dedusting in the industry. In this study, the VOF-DPM coupled model is applied to investigate the gas—liquid—solid three-phase flow process in the bottom water chamber of the scrubbing tower. Two gas intake modes of guide-pipe mode and tangential-horn mode are numerically compared. Near the outlet surface, the guide-pipe mode scrubber can obtain lower gas velocity and more uniformly distributed gas phase. This is a good protection for the column tray against being overturned. However, there exists a hydrostatic zone in the guide-pipe mode chamber, this may cause dust to accumulate near the wall. The tangential-horn mode chamber obtains a lower pressure drop and a smaller velocity maximum above liquid level. As a result, to a group of particles range from 50 to 1000 μm, the removal efficiency of the tangential-horn mode scrubber is 88.3%, higher than that of 82.0% of the guide-pipe mode scrubber. The tangential-horn mode performs better in lower pressure drop, higher antiblocking and dust removal ability but worse in protecting the column tray against being overturned. This study offers guidance for the research and design of the wet gas scrubbing chamber.

Three-dimensional Eulerian modeling of gas–liquid–solid flow with gas hydrate dissociation in a vertical pipe

The pipe transportation of gas hydrate-bearing sediments (GHBS)1GHBS—gas hydrate-bearing sediments;1 is one of the key problems in mechanical–thermal exploitation of gas hydrate (GH)2GH—gas hydrate.2 in marine stratum. It is a gas–liquid–solid (methane gas–seawater–GHBS particles) three-phase flow, accompanied by GH dissociation. In this study, a three-dimensional Eulerian model combined with the kinetic theory of granular flow (KTGF) was adopted to simulate the gas–liquid–solid flow with GH dissociation. The commercial CFD software FLUENT 16.2 was employed, considering the hydrodynamics, heat and mass transfer, and GH dissociation simultaneously. A kinetic model for GH dissociation in the GHBS particles is presented, considering the influence of multiphase flow on dissociation rate. The model can capture the transition from the initial liquid–solid two-phase flow to gas–liquid–solid three-phase flow, describing the distribution of the phase volume fraction, velocity, temperature, and dissociation rate. The interaction between GH dissociation and multiphase flow is discussed. The simulation results indicate that the continuous production of gas bubbles by GH dissociation leads to more violent fluctuations in the pressure gradient and a more marked elevation of the solid particles compared with the liquid–solid two-phase flow without GH dissociation. In addition, the effect of GH dissociation on the multiphase flow under different hydrate saturations was analyzed.

CFD model simulation of bubble surface area flux in flotation column reactor in presence of minerals

Bubble surface area flux (Sb) is one of the main design parameter in flotation column that typically employed to describe the gas dispersion properties, and it has a strong correlation with the flotation rate constant. There is a limited information available in the literature regarding the effect of particle type, density, wettability and concentration on Sb. In this paper, computational fluid dynamics (CFD) simulations are performed to study the gas–liquid–solid three-phase flow dynamics in flotation column by employing the Eulerian–Eulerian formulation with k-ε turbulence model. The model is developed by writing Fortran subroutine and incorporating then into the commercial CFD code AVL FIRE, v.2014. This paper studies the effects of superficial gas velocities and particle type, density, wettability and concentration on Sb and bubble concentration in the flotation column. The model has been validated against published experimental data. It was found that the CFD model was able to predict, where the response variable as indicated by R-Square value of 0.98. These results suggest that the developed CFD model is reasonable to describe the flotation column reactor. From the CFD results, it is also found that Sb decreased with increasing solid concentration and hydrophobicity, but increased with increasing superficial gas velocity. For example, approximately 28% reduction in the surface area flux is observed when coal concentration is increased from 0 to 10%, by volume. While for the same solid concentration and gas flow rate, the bubble surface area flux is approximately increased by 7% in the presences of sphalerite. A possible explanation for this might be that increasing solid concentration and hydrophobicity promotes the bubble coalescence rate leading to the increase in bubble size. Also, it was found that the bubble concentration would decrease with addition of hydrophobic particle (i.e., coal). For instance, under the same operating conditions, approximately 23% reduction in the bubble concentration is predicted when the system was working with hydrophobic particles. The results presented are useful for understanding flow dynamics of three-phase system and provide a basis for further development of CFD model for flotation column.

CFD simulation of hydrodynamics of gas–liquid–solid three-phase bubble column

A 3D time dependent numerical study was performed to study the gas–liquid–solid three-phase flow dynamics in bubble columns by employing the Eulerian–Eulerian–Eulerian three-fluid approach. The three-phase bubble column of Gandhi et al. (Powder Technol. 1999, 103 (2), 80–94), Rampure et al. (Can. J. Chem. Eng. 2003, 81 (3–4), 692–706) and our previous study (Powder Technol. 2014, 260, 27–35) were studied. A mathematical model of a gas–liquid–solid three-phase flow was built. The effect of numerical schemes (wall boundary conditions, momentum discretization schemes and time steps) was discussed. CFD simulations were performed to study the sensitivity of the interphase drag models (different liquid–solid, gas–solid and gas–liquid drag models), and the predictions were compared with the experiments. The results showed that no-slip conditions for the wall boundary conditions, 0.001s for the calculation time step and second-order Upwind for momentum discretization, had better prediction results. The appropriate interphase drag forces to describe the three phase flow found in this study were the Zhang–Vanderheyden model, which was used as a gas–liquid drag model, Schiller–Naumann model, used as a liquid–solid drag model, and gas–solid drag force, which was not considered. The appropriate numerical schemes and interphase drag models were utilized to simulate the hydrodynamic parameters (time-averaged gas holdup, solid holdup, liquid axial velocity) in a gas–liquid–solid bubble column. The effects of superficial gas velocity, particle volume fraction, particle size and density were analysed and discussed. Four flow regimes of a gas–liquid–solid bubble column were simulated; the CFD results were compared with the experimental flow structures, and it was found that the bubble coalescence regime was better depicted. Superficial gas velocity had a large effect on the gas holdup of the bed, and the effect of solid volume fraction (Vs=0.03–0.30) and particle size (dp=75μm–270μm) on the distributions of time-averaged solid holdup and liquid axial velocity was greater than that of particle density (ρp=2500kg/m3–4800kg/m3). When particle size dp≥150μm and solid volume fraction Vs≥0.09, the hydrodynamic parameters had a strong dependency on dp and Vs. The larger the values of the Vs, dp and ρp were, the larger the axial solid concentration gradient was.

Numerical investigation of flow erosion and flow induced displacement of gas well relief line

High-pressure particle-laden gas flow should be discharged through relief line of gas well timely to ensure safe test and exploitation. Erosion and vibration usually take place on the bend in relief lines, bringing a potential safety hazard to field operation. The majority of this paper investigates the factors affecting the erosion of bend and displacement of relief line in the downstream of bend using the computational fluid dynamics (CFD) methodology. A three-dimensional elbow pipe is selected as computational domain in this investigation. The kinematics and trajectory of discrete solid particles and liquid droplets are described by discrete phase model (DPM) while the hydrodynamic characteristics of continuous phase are obtained based on Reynolds-Averaged-Navier-Stokes (RANS) equations. An empirical erosion model is employed to predict the erosion rate of bend, and a fluid–structure interaction (FSI) model is adopted to calculate the displacement of relief line. The effects of types of multiphase flow (such as gas–solid two-phase flow and gas–liquid–solid three-phase flow), inlet flow rate and pipe diameter on erosion and displacement are discussed. The results show that large displacement and severe erosion present with large inlet flow rate in minor diameter pipe. The increase in liquid droplet content has less effect on flow erosion than that by the same increase in sand particle content.

Numerical simulation of gas–liquid–solid three-phase flow using particle methods

We want to simulate, based on particle methods, the dynamic behavior of multi-phase flows in a gas–solid–liquid mixture system. With the governing equations discretized within the finite volume particle method, the effects of contact and collision between solid particles were modeled by the distinct element method. Applicability of the viscosity model and an empirical drag force model were confirmed for the hydrodynamic interactions between solid particles and fluid. Simulations were performed of a single bubble rising in a tank of stagnant solid particle–liquid. The results for the dynamic behavior indicate that the present computational framework of particle-based simulation method may be useful for numerical simulations of multi-phase flow behavior in a solid particle–fluid mixture system.

Treatment of Catalyst Wastewater in a Three-Phase Flow Airlift Loop Bioreactor

A 12-L gas–liquid–solid three-phase flow airlift loop bioreactor, in which micro-organism immobilization replaced the activated sludge, was used for the nitrifying treatment of the original effluent from Catalyst Complex of Qilu Petrochemical Corp. of SINOPEC, Zibo City, Shandong Province, P.R. China. The original wastewater contained a high strength NH4–N of up to 2,437 mg L−1 and solution electrical conductivity (EC) of nearly 22,000 μScm−1 . The influences of temperature, pH value, superficial gas velocity (ug) and hydraulic residence time (HRT) on the reductions of COD and NH4–N were investigated and discussed, respectively. The optimum operation condition was obtained as temperature 30–35°C, pH value 7.0–7.5, ug 10 mm s−1 , and HRT 15 h at the solid hold-up εs up to 50%. Under this optimum operation condition, the average removal efficiencies of COD and NH4 –N were higher than 85 and 99%, respectively, corresponding to the effluent COD, 25 mg L−1 and NH4 –N, 15 mg L−1 , which was in compliance with the national primary discharge standard of P. R. China as COD ≤ 100 mg L−1 and NH4-N ≤ 15 mg L−1 (GB 8978–1996). Additionally, the radial and axial positions in the reactor showed little influence on the local profiles of COD and NH4 –N.