The influence of the fabric filter layout of in a flow mass filtrate

doi:10.1016/j.jclepro.2015.09.070

Journal of Cleaner Production

Volume 111, Part A, 16 January 2016, Pages 117-124

https://doi.org/10.1016/j.jclepro.2015.09.070 Get rights and content

Highlights

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In the study of airflow feed position for the industrial fabrick filter, the use of CFD simulations is indispensable, since stopping actual filters in operation is costly. By using the k–ε turbulence model, a transient simulation can be run that shows how the process variables, such as the pressure, velocity and mass flow, vary along the filter.
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The conventional inlet position proved to put excessive stress on the fabric, as evidenced by the concentrated mass flux on certain regions of the filter bags.
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In all, the simple and double inverted feed positions showed the most advantages, by distributing the airflow uniformly on the bags and minimizing the formations of undesirable vortices.

Abstract

Nowadays, more and more companies are forced to control particulate emissions to the atmosphere, due to economic reasons, legal aspects or simply the change in policy that favors ecological commitment. This new trend induces the necessity for better particle capture equipment and has made the environmental control equipment market increase by 20% in the last few years (Rocha et al., 2012). The dry capture of fine particles is carried out by filtration, and the fabric filter has become a very popular equipment because of its high efficiency and low operational cost. In the other hand, this efficiency is dependent upon proper design and layout, and the particle–filter interactions greatly influence the filtration results and the overall efficiency.

In this context, this article presents the computational fluid dynamic (CFD) simulation of the airflow inside an industrial fabric filter with a set of 49 bags and a total surface area of 75 m². The simulations were performed using the ANSYS FLUENT v13.0. This package applies the Finite Volumes Method, using the URANS approach, as well as the realizable k–ε model for the turbulence and the SIMPLE algorithm for the pressure–velocity coupling (Miltner et al., 2015). Four inlet positions were analyzed in order to determine how the internal flow profile and the equipment filtering performance depends on the inlet position. The simulations allowed concluding that the simple and double inverted feed positions led to a more satisfactory flow, considering not only the overall efficiency but also the bag's useful lifespan.

Introduction

The increase in the global population has caused a rise in the exploration of natural resources and in the global pollution levels. This called the attention of environmentalists, government policy makers and academic institutions that have pressured industries to invest in better pollution control equipment. Because of this, cleaner production programs have been numerously implemented around the world, such as in the mining, electronics, base metal industries among others.

According to Yilmaz et al. (2014), in order to choose the right equipment for pollution control, the advantages and the environmental impacts must be analyzed, along with operational costs. Kubota and Rosa (2013) points out that environmental concern taken into account during the development phase result in better environmental performance, cost reduction and process optimization.

As far as the control of particulate material is concerned, the fabric filter has been consistently shown to be the most efficient and to have the best cost-benefit ratio for dry collection. If designed correctly it can also have the less impact in the environment, since the particles can be fed back into production as raw material (in most cases). A drawback is that this high efficiency is very dependent on the choice of filter medium, the equipment geometry and the process variables. In this sense, it becomes clear that the fabric filter should be specifically designed for each application, as opposed to a generic design that tries to accommodate most applications.

Unfortunately due to the high costs and complexity in the project of industrial equipment, the design of the fabric filter is mostly based on empirical prototypes, which can cause under or oversizing problems. The advent of numerical simulations of fluid flow in complex geometries makes it possible to predict the performance of this equipment with a high degree of reliability, and reduced time and cost. The technology that delivers such prediction is called computational fluid dynamics (CFD).

The application of CFD techniques provides results that allow the analysis of the flow behavior inside a filtration system, taking into account important phenomena as turbulence and correlating them to pressure drop in the filter media. Industrial use of these techniques is relatively new (Damian, 2003). Despite recent arrival, the CFD techniques have proven to be effective in not only designing projects for new equipment, but also in improving existing plants and optimizing the operation of traditional equipment (Rocha et al., 2014).

In this context, this work presents the results of the CFD simulation of the airflow inside an industrial fabric filter. The commercial software utilized was ANSYS FLUENT v13.0. Four different inlet configurations were tested for the same fabric filter. Based on CFD results for mass flow and streamlines, it was possible to judge which configuration would have greater potential for optimal performance.

Errors tied with the numerical simulation of this flow and any CFD simulation are of 3 types. They can be iteration/round-off errors, discretization errors, and modeling errors (Fernández-García et al., 2015). In order to guard against the first of these, the simulations were continued until no significant changes in the residuals could be observed, below the standard value of 10⁻⁵ (10⁻³ for the continuity residuals). The mesh geometry was chosen in order to be as fast as possible while still being refined enough to guard against discretization errors. Modeling errors are hard to ascertain, but, judging from previous studies, we feel confident that they are minimized in this simulation and that the assumptions are sound.

Section snippets

Material and methods

The numerical approach used in this study is based on three main steps: the geometry construction and its discretization, the numerical procedure to solve the governing equations starting from the prescribed boundary conditions, and finally the post-processing the results. Experimental studies in this area are scarce, but according to the results of Damian (2003) these simulations yield satisfactory accuracy and provide a useful real world model.

In regards to the geometry of the industrial

Theory

The governing equations are solved using the Unsteady Reynolds Averaged (URANS) approach in which Navier–Stokes and Continuity equations are averaged in a time interval together with the transient term, as shown in Equations (1), (2). $\frac{\partial ρ}{\partial t} + \nabla \cdot (ρ \vec{v})=0$ $\frac{\partial (ρ \vec{v})}{\partial t} + \nabla \cdot (ρ \vec{v} \vec{v}) = - \nabla p + \nabla \cdot \bar{τ}$ Where: $\bar{τ} = μ_{e f f} [(\nabla \vec{v} + \nabla \bar{v^{T}})]$ is the stress tensor for the incompressible flow (kg m⁻¹ s⁻²), $\vec{v}$ is the flow velocity (m s⁻¹), p is the static pressure (kg m⁻¹ s⁻²), and ρ is the gas density (kg m⁻³). The effective viscosity is

Results and discussion

When analyzing a current or new design, the most important variables to verify are velocity, pressure, and mass flux. In points where these variables reach maximum values, the bags tend to wear faster. Therefore, these variables should be as uniform as possible inside the geometry, or in other words, the maximum values should be as low as possible.

The simulations reached a pseudo-steady state at around 15 s (the flow reaches a stable point here, but it can't be called a true steady state as the

Conclusion

The CFD simulation techniques provide valuable qualitative and quantitative data in the analysis of industrial equipment. In this case, the airflow feed position was modified, and the mass flow distribution was used to determine the most appropriate inlet setup. The double inverted setup and the simple setup stood out from the others. The double inverted feed position presented the most uniform mass flow profile at the filter surfaces. The drawback with this option is the formation of vortexes

Acknowledgments

The authors acknowledge CNPq: Conselho Nacional de Pesquisa and FAPES: Fundação de Amparo a Pesquisa do Espírito Santo for financial support for development this work; and the Company PANAN Ind. De Mad. e Móveis LTDA for the fabric filter prototype design.

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The influence of the fabric filter layout of in a flow mass filtrate

Highlights

Abstract

Introduction

Section snippets

Material and methods

Theory

Results and discussion

Conclusion

Acknowledgments

J. Clean. Prod.

Int. J. Mech. Sci.

J. Clean. Prod.

Powder Technol.

Comput. -Aided Chem. Eng.

Development of a Compact Filtration System for Asphalt Plants