Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator Mr.Dharmendra Dekate 1 Mr.K.M.Narkar 2

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1 IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 01, 015 ISSN (online): Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator Mr.Dharmendra Dekate 1 Mr.K.M.Narkar 1, Department of Mechanical Engineering 1 Thermax Ltd. Enviro Division, Pune, Maharashtra, India D.Y. Patil College of Engineering, Pune, Abstract The Electrostatic Precipitator s (ESP s) are widely used for controlling particulate emissions from boilers and industrial process sources. The Electrostatic precipitation consists of three fundamental steps: (1) particle charging, () particle collection, and (3) removal of the collected dust. Electrostatic Precipitator is the device used for controlling air pollution. Process gases contain suspended dust particles. These dust particles are collected on collecting electrodes. The effectiveness of Electrostatic Precipitators is affected by various fact like gas flow condition, electric field generation and geometric parameters. The industrial ESP are capable of handling large gas volumes with a wide range of inlet temperatures, pressures, dust volumes and gas conditions and exhibit complex interaction mechanism between electric field, fluid flow and particulate flows. Flow pattern of electrostatic precipitator and effect of different boundary conditions on flow pattern has been studied by using Ansys fluent. So that the flow distribution should be improved and it should meet ICAC (Institute of Clean Air Companies) guidelines. This paper presents the Ansys Fluent (CFD) concept for modeling and analysis of Electro static precipitator. Experimental testing is done for validation. The result of CFD concept and physical measurement are discussed. Key words: Electrostatic Precipitator (ESP), CFD, GD screen, Nozzle, Guide Vanes I. INTRODUCTION The rapid increase in developing industrial processes is accompanied by the release of substantial quantities of pollutants. These pollutants often have detrimental effects, directly or indirectly, on human health, animals, natural resources, the biosphere and construction materials and metal structures. New industrial processes must therefore be designed so that emissions are minimized. The requirement that the development of new processes must be balanced by the development of suitable technologies that eliminate or at least reduce the amount of pollutants released to the atmosphere. Many approaches have been devised to control pollutants in the atmosphere. Often times, different types of technologies can control a given source in order to achieve a given emission limit given by the emission control board. The most popular air pollution equipment is Electrostatic precipitator amongst all other available equipments like Bag filters, Cyclones, Mechanical dust collector etc. to remove the dust from process gases. The effectiveness of Electrostatic Precipitator is depends of parameters like gas flow condition, electric field generation and geometric parameters. The time to time cleaning is a major activity which is rather the cause of dust collection. The collecting electrodes are cleaned periodically on which dust is Maharashtra, India collected. Efficiency of ESP depends on the periodic cleaning of collecting electrodes. The Proper flow pattern of electrostatic precipitator and effect of different boundary conditions on flow pattern. Plays major role and improves the ESP effectiveness and performance and it should meet ICAC (Institute of Clean Air Companies) guidelines. Perforated plates/ GD screens help to promote uniform gas distribution inside the ESP, as good uniform gas distribution is important to ESP performance. Poor gas distribution can diminish ESP performance by creating high zones which reduce treatment time of the gases. Perforated plates are very important in ESP. These are having hole of different sizes arranged in specific manner. The entire plate is divided into no. of parts and as per cross section it has been perforated with specific openings. Researchers have done various experimental studies to ensure the proper flow distribution in Electrostatic precipitator by selecting proper opening in GD screens from that they derived various useful conclusions for further study and work. However this experimental approach has major drawbacks of higher time lines and cost involved in physical testing. To overcome this drawback there is need to develop a quick and reliable process to properly distribute the flow pattern and study of different boundary conditions on flow pattern to maintain the Flow uniformity at the ESP inlet and outlet at per ICAC Guidelines. II. LITERATURE REVIEW The paper reviewed are referred and used directly or indirectly for completing this work The present project work is based on the studies carried out by various researchers on Flow distribution in ESP and Detail study of ESP. These papers are. A Mizuno [1] have studied role of ESP in environmental protection. Performance of ESP deteriorates by abnormal phenomena, including back corona for treating high resistivity dust, abnormal re-entrainment for low resistivity dust, and corona quenching for fine dusts. Electrostatic precipitator (ESP) has been used widely in various industries such as utility boilers, cements kilns, etc., and also has been applied in cleaning of indoor air in houses, offices, hospitals, and factories for food processing. ESP can be operated with high collection efficiency and a low pressure drop. The collection efficiency is usually >%. Sub micrometer particles also can be collected effectively. The pressure drop is normally t1000 Pa. This is an important advantage of ESP, resulting in low operation cost. Feng Z. et.al. [] have studied the performance of several turbulence models, including the standard k-ε model, low Reynolds number k-ε models, Large Eddy Simulation (LES) models, and Detached Eddy Simulation (DES) All rights reserved by 40

2 Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator models, for simulating the pressure drop and transitional flows through pleated filters both with and without an electrostatic precipitator. The simulated results from the models were compared with the experimental data from the literature and measurements. Niles F. Nielsen [3] performed stimulation of ESPs including inlet nozzle with gas distributions screens, precipitation sections with collector curtains and baffle plates, hoppers with partition plates and outlet nozzle with gas distribution screen. Flow management by gas distribution screens are needed in inlet and outlet nozzle. The study has focused on modeling of different ESPs. The gas flow distribution as well as particle transport has been investigated and discussed in terms of different designs. Robert G. Mudry et.al. [4] have examined the accuracy of CFD models of electrostatic precipitators. Flow simulation results from ten distinct precipitator CFD models are compared with actual field measurements of patterns. In five of these cases, data from a physical scale modeling effort for the same ESP are available and are also compared to the field measurements. The distribution predicted by the CFD and physical models within the ESP collection regions are accurate to within and 33% of actual test data, respectively Zhengwei Long et.al. [5] The initial design of the ESP was studied with the help of commercial CFD tool ANSYS Fluent and after understanding its ineffectiveness, the design was modified by the addition of a filter. The insertion of filter at the inlet helped delay the flow separation at the inlet improved distribution of in a more uniform pattern around all the electrode plates thus improving the efficiency of the ESP. III. DETAIL OF ESP The ESP is so arranged that the nozzle is placed in line with gas flow where GD-Screens are located. The dusty gas is allowed to pass thru this GD-screen. ESP design conditions are well evaluated while sizing ESP, inlet/outlet duct routing along with nozzle design & orientation may play a major role in spoil in performance of ESP. Even correctly sized ESP, through uneven gas and dust flow distribution will affect ESP performance. That is where CFD study plays a major role in improving gas distribution in ESP. IV. ANSYS FLUENT AND ITS DETAILS The ESP model are made up by collecting plate, baffle plates, girders and perforated sheets, Nozzle, etc. with exact dimensions. Guide vanes, gas distribution screens, wall plates and other flow obstructions are modeled as bafflethat are effectively zero thickness, two dimensional cells.model are mesh with ratio 0.3 with 3-d hexahedral mesh. The model is defined as Turbulent as K-epsilon and fluid properties of flow are defined. Atmospheric air is considered as working fluid, analysis is done for steady state condition and single phase. Boundary condition is defined as at ESP inlet and Pressure at ESP outlet. Perforated sheet is define as Porous jump condition (minimum of 3% opening and a maximum 0% opening is considered for CFD). The properties of working fluid (air) are given as per the operating conditions. All other components like baffle Fig. 1: ESP Model plates, girders collecting plates, outer casing and nozzle are given as Wall type boundary condition A. Gas Distribution Screen Percentage as Per Standard: Fig. : GD Screen Details All rights reserved by 40

3 Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator B. Mesh Model of ESP: Mesh generation is basically the discretization of the computational domain. The 3D CFD model is discretized into small fluid cells called mesh. Models are meshed 3D hexahedral mesh to capture the fluid domain using ICEM CFD. measured at those points and then check for ICAC guidelines & RMS value. A. Velocity Readings: All the ESP s should follow the ICAC guidelines for uniform flow distribution for attaining maximum efficiency. The pattern shall have a minimum of 5% of the velocities not more than 1.15 times the average and % of the velocities not more than 0 times the average. Average refers to the mean of all measurements made at a given face of the precipitator. As per ICAC guidelines all this velocities should be measured near the inlet and outlet faces of the precipitator collection chamber, where as we measured at the end of first field. B. RMS Value: The percent RMS is calculated by the following formula Fig. 3: Mesh Model in CFD V. EXPERIMENTAL RESULT Solution are iterate up to convergence. Test points are generate at the end of first field and flow pattern are checked to meet ICAC guidelines. The number of points created is equal to the number of gas passages along the x-axis and at y-axis a maximum of 1 meter distance between each point along the height of collecting plates. Velocities are ( ) Equation 1 Where V i = Velocity at selected Grid Point V avg = Average Velocity over Entire plane i = Grid Point Center The typical goal in industry is to achieve a Percent RMS of less than 15% at the ESP inlet and outlet planes where as we measured RMS value at the end of first field. C. Velocity Measurement Plane Considered: Fig. 4: Model with Velocity Measurement Plane D. Velocity Contour at Plane 1: Fig. 5: Velocity Contour Plane All rights reserved by 40

4 Poin ts 1 H T G P Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator Average Velocity 1.15 Times V avg 1.14 Times V avg Table 1: Velocity Result at Plane 1 For 100% Load Condition 1.0 Flow uniformity at the ESP inlet and outlet ICAC test planes m/sec 5% of test points within 115% of measured 1.1 average (ICAC EP- criterion) m/sec % of test points within 140% of measured average (ICAC EP- criterion) m/sec 15% RMS at the ESP inlet and outlet test 1 Nos. planes. 145 % % as per ICAC Minimize system pressure loss Criteria 1 % 3 % as per ICAC Criteria Total Velocity Reading No of reading Within 1.15 Times V avg No of reading Within 1.14 Times V avg Standard Deviation.4 RMS in % 4 % Table : Velocity readings & RMS value tabulated data VI. VALIDATION RESULT In order to ensure that the design of the ESP fulfills the performance requirements, the physical model is constructed, and tested a physical model as below. The flow models are used to design flow control devices to meet the following criteria: Uni t Loa d 100 % Loa d Actu al Unit Flow Volu me, 00 Am3/ Actual Unit Temperat ure 140oC Mode l Flow Volu me, Am3/ hr Table 3: Design Data Model Temperat ure 0oC / 0oF Tests Perfor med Velocity, Pressure, All rights reserved by 410

5 Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator A. Model Flow Condition: The model flow rates are correctly scaled from the unit design flow rate to match the head (dynamic pressure) of the full-scale unit. Since only one-half of the Fig. : Physical model of ESP unit is evaluated, the model flow rate is derived from onehalf of the full unit flow rate. All testing are performed on 100% Load condition the are measured at air heater outlet TL-1, at Inlet TL-, at ESP outlet TL-3. Fig. : Typical View of ESP Model with test Points Following are the result for average, RMS, and total pressure Model Result Location Target Goal (100% Load) ICAC Inlet ICAC Inlet 5% of test points 115% of average % of test points 140% of average.% 100% ICAC Inlet Velocity RMS 15% 1.% ICAC Outlet 5% of test points 115% of average.% ICAC Outlet % of test points 140% of average 100% ICAC Outlet Velocity RMS 15% 1.% Total pressure drop 5 mmho ESP Flange-to-flange at 100% Load Table 4: Physical Model test result 4.0 mmho Result Show that at 100% load the final model design achieves the ICAC requirements at both the ESP inlet and outlet planes, and it achieves the RMS target at the ESP inlet plane. VII. CONCLUSION 1) Results are presented for the physical model ESP. Tests performed included and pressure measurements at 100 % load conditions and design achieves the result as per ICAC ) The pressure loss across the ESP from the beginning of the inlet nozzle to the outlet of the outlet nozzle (ESP flange-to-flange) is within the specified target at 100% Load. REFERENCES [1] A Mizuno, Electrostatic Precipitation, IEEE Transactions on Dielectrics and Electrical Insulation Vol. No. 5, October 000. [] Feng Z., Long Z., and Chen Q, Assessment of various CFD models for predicting airflow and All rights reserved by 411

6 pressure drop through pleated filter system, Building and Environment, 5, (014) [3] Niles F. Nielsen, Leif Lind, CFD simulation of gas flow and particle movement in ESPs, Institute of clean air companies, electrostatic precipitator gas flow model studies, publication EP- January 1. [4] Robert G. Mudry, Brian J. Dumont, Computational fluid dynamic modeling of electrostatic precipitators, Electric Power 003 Conference 05 March 003. [5] Zhengwei Long, Qiang Yao, Electrostatic Precipitators (ESP) analysis using CFD, Journal of Aerosol Science 41 (010), 0 1. Verification and Validation of Preliminarily Result of CFD of Electrostatic Precipitator All rights reserved by 41