Horizontal Settler Research Articles

SIMULATION OF WASTE WATER TREATMENT BASED ON CFD MODEL: EXPRESS CALCULATION

Purpose. Development of CFD model to evaluate the efficiency of wastewater treatment in a horizontal settler. The CFD model can be used to calculate flow hydrodynamics and mass transfer in settlers with complex geometric shape in the area of wastewater flow. Methodology. For numerical simulation of the process of wastewater movement in a horizontal settler, two mathematical models are used. The first model is based on the motion equations of a viscous incompressible fluid – the Navier-Stokes equations. The Navier-Stokes equations are written in the variables «vorticity - flow function». A two-dimensional mass transfer equation is used to calculate the concentration of a pollutant in a horizontal settler. To numerically integrate the two-dimensional mass transfer equation, a finite-difference splitting scheme is used. The splitting of the modeling equation of mass transfer is carried out so that at each fractional step to determine the unknown value of the pollutant concentration by an explicit formula. For numerical integration of the vortex transfer equation and the equation for the flow function (the Navier-Stokes system of equations), finite-difference splitting schemes are used. Findings. Based on the developed CFD model, a complex of computer programs has been developed, which makes it possible to determine the efficiency of water treatment in a horizontal settler with additional elements. The results of a computational experiment to assess the efficiency of water treatment in a horizontal settler with additional elements in the form of plates are presented. Originality. An efficient CFD model has been created, which allows to quickly evaluate the efficiency of wastewater treatment in a horizontal settler with additional elements. The developed CFD model takes into account the geometric shape of the facility and the most significant physical factors, that influence the efficiency of the waste water treatment in horizontal settler: non-uniform flow velocity, diffusion, different position of inlet and outlet openings. Practical value. The developed CFD model belongs to the class of «diagnostic models» and can be used to assess the efficiency of treatment facilities at the stage of their preliminary design.

Simulating separation of a multiphase liquid-liquid system in a horizontal settler by CFD

Microemulsion systems may enable innovative and highly efficient synthesis paths for the chemical industry. When expensive catalysts are involved in the process, an efficient separation of products together with an extremely low catalyst leaching are of utmost importance. In order to optimize the separation process and improve the settler design, a thorough understanding of droplet-droplet interactions is required. In this work, computational fluid dynamics (CFD) has been used to study the multiphase flow in a horizontal settler using the Eulerian two-fluid framework. Droplet coalescence, which is the most important physical phenomenon in gravity-driven separation, has been modeled using a spatially inhomogeneous buoyancy-based kernel, and the resulting population balance equation has been solved using the quadrature-based method of moments (QMOM). After calibrating the model parameters using selected experiments, a very good description of the observed separation is obtained, opening the door for process understanding and optimization.

INVESTIGATION OF ADMIXTURE SEDIMENTATION IN THE HORIZONTAL SETTLER

Purpose.Sedimentation by gravity is the most common and extensively applied treatment process for the removal of solids from water and wastewater and it has been used for over one hundred years. Sedimentation tanks are one of the major parts of a treatment plant especially in purification of turbid flows. Horizontal settlers are mainly used for purification of high quantity of water. In these tanks, the low speed turbid water will flow through the length of the tank and suspended particle have enough time to settle. Finding new and useful methods for calculating and increasing hydraulic efficiency of horizontal settlers is the objective of many theoretical, experimental and numerical studies.But currently used models and methods in Ukraine do not allow taking into account geometrical form and various design features. In this paper the numerical model was developed to evaluate the effectiveness of horizontal settler with modified structure. Methodology. Numerical model is based on: 1) equation of viscous fluid dynamics; 2) mass transfer equation. For numerical simulation the finite difference schemes are used. The numerical calculation is carried out on a rectangular grid. For the formation of the computational domain markers are used. Findings.The model allows obtaining the purification process in the settler with different form and different configuration of baffles. Originality. A new approach to investigate the mass transfer process in horizontal settler was proposed. This approach is based on the developed CFD model. The fluid dynamics model was used for the numerical investigation of flows and waste waters purification. To investigate influence of baffles on settler efficiency physical experiment was carried out. Practical value.The developed model has more capacity than the existing models in Ukraine. The developed model allows computing quickly the efficiency of water purification in settlers. The model is not computationally expensive. Calculation time of one variant of the problem takes few minutes.

NUMERICAL DETERMINATION OF HORIZONTAL SETTLERS PERFORMANCE

Purpose.Horizontal settlers are one of the most important elements in the technological scheme of water purification. Their use is associated with the possibility to pass a sufficiently large volume of water. The important task at the stage of their designing is evaluating of their effectiveness. Calculation of the efficiency of the settler can be made by mathematical modeling. Empirical, analytical models and techniques that are currently used to solve the problem, do not allow to take into account the shape of the sump and various design features that significantly affects the loyalty to a decision on the choice of the size of the settling tank and its design features. The use of analytical models is limited only to one-dimensional solutions, does not allow accounting for nonuniform velocity field of the flow in the settler. The use of advanced turbulence models for the calculation of the hydrodynamics in the settler complex forms now requires very powerful computers. In addition, the calculation of one variant of the settler may last for dozens of hours. The aim of the paper is to build a numerical model to evaluate the effectiveness of horizontal settling tank modified design. Methodology. Numerical models are based on: 1) equation of potential flow; 2) equation of inviscid fluid vortex flow; 3) equation of viscous fluid dynamics; 4) mass transfer equation. For numerical simulation the finite difference schemes are used. The numerical calculation is carried out on a rectangular grid. For the formation of the computational domain markers are used. Findings.The models allow calculating the clarification process in the settler with different form and different configuration of baffles. Originality. A new approach to investigate the mass transfer process in horizontal settler was proposed. This approach is based on the developed CFD models. Three fluid dynamics models were used for the numerical investigation of flows and waste waters purification. Practical value.The developed models have more capacity than the existing models in Ukraine. The developed models allow calculating quickly the efficiency of water purification in settlers. The models are not computationally expensive. Calculation time of one variant of the problem takes few seconds.

CFD SIMULATION OF THE HORIZONTAL SETTLER WITH FIN WORK

Horizontal settlers are one of the most important elements in the technological scheme for drinking water preparing and waste water treatment. Their use is associated with the possibility to pass a sufficiently large volume of water. When remodeling or designing horizontal tanks there is an important task to evaluate their effectiveness. Calculation of the efficiency of the settler can be made by mathematical modeling. Currently used models and methods do not allow take into account the shape of the sump and the various design features. In this paper we consider the construction of a numerical model to evaluate the effectiveness of horizontal settler modified structure. The model is based on equations of motion of an ideal fluid and mass transfer equation. For numerical simulation the finite difference schemes are used. The numerical calculation is carried out on a rectangular grid. For the formation of the computational domain markers are used. The model allows calculate the clarification process in the sump using computers small and medium power. Calculation time of one variant of the problem is a few seconds. The results of a computational experiment are presented.

BASF works on new gas-to-olefin process

Microemulsion systems may enable innovative and highly efficient synthesis paths for the chemical industry. When expensive catalysts are involved in the process, an efficient separation of products together with an extremely low catalyst leaching are of utmost importance. In order to optimize the separation process and improve the settler design, a thorough understanding of droplet-droplet interactions is required. In this work, computational fluid dynamics (CFD) has been used to study the multiphase flow in a horizontal settler using the Eulerian two-fluid framework. Droplet coalescence, which is the most important physical phenomenon in gravity-driven separation, has been modeled using a spatially inhomogeneous buoyancy-based kernel, and the resulting population balance equation has been solved using the quadrature-based method of moments (QMOM). After calibrating the model parameters using selected experiments, a very good description of the observed separation is obtained, opening the door for process understanding and optimization.

The continuous separation of liquid/liquid dispersions

A model allowing for binary and interfacial coalesecence of drops is presented which predicts the variation in dispersion height, throughput, droplet velocity and diameter along the length of a horizontal settler operating at the steady-state. Experimental results obtained in a such a box-settler verify the model which is applicable to both wedge-shaped and deep-bed dispersion bands of varying thickness. The analysis is extended to include the variation in hold-up, drop diameter and relative velocity in the sedimentation zone of a vertical settler under both laminar and turbulent flow conditions. Equations are presented which enable the height of the sedimentation zone to be predicted from the throughput, phase ratio, hold-up and binary coalescence time.