Electrostatic precipitators (ESPs) simulated with Fluent

Renata Favalli, PhD.Eric Robalinho, MSc.Joel Maia, Eng.Renato Greco, Eng.Jorge Daher, Eng.

2008 ESSS South American ANSYS Users Conference

ENVIRONMENTAL SYSTEMS

MAINTENANCE& ASSEMBLING

STEEL WORKS LASER CUTTING

COMBUSTION AND ENVIRONMENT

Enfil Group of companies

• Founded as C.Greco in 1966 by Prof. Clemente Greco. After 2004 became part of Enfil Group of companies;

• Projects for systems and equipments, such as burners, dryers, gas cleaners and coolers, in different industrial sectors (cement, fertilizers, mining, food stuff, etc.);

• Since its foundation has been developing CFD modelling in a variety of equipments;

• Acting with the Brazilian cement industry since the 80’s;

• Acting with the international cement industry since the 90’s;

• More than 300 burners for rotating kilns installed around the world.

Clients around the world

• Brazilian company based in São Paulo with an office strategically placed in Vitória, ES;• Specialized in maintenance, upgrades, systems optimization and personnel training;• Technological agreement with:

• NSC – Nippon Steel Corporation (Japan)• ENELCO – Environmental Elements Corporation (USA)• Graver Water Systems, Inc. (USA)• DMT – Deutshe Montan Technologie GMBH (Germany)• Bender Corporation, Inc. (USA)• PALL (USA)• LURGI (Germany)

Typical lay-out of an ESP

Electrostatic Precipitator

Dedusting system – Piping lines and ESPs

Distribution pipes; 3 series of ESPs; exit plenum

3D built with AutoCAD/Inventor

Red surfaces: baffles and walls

Blue surfaces: interior for flux control

Green surfaces: perforated plates

Computational reasons: ESPs had to be simulated apart

Computational domain – ESP #2

Inlet perforated plates:

plate1inplate2inplate3in

Inletflange

Hopper baffles

Outlet plates

Exitflange

Computational domain – Collecting plates

ESP mesh

• Gambit –Fluent Ansys

• Hybrid mesh;

• Total of 1.5Mi elements

• Elements of:60mm between collecting plates, 300mm for the restof the domain.

Contours of velocity magnitude in y = 0.15Boundary conditions are taken from the system, and uploaded at inlet flange

through profile rotation and translation

Contours of velocity magnitude in y = 0.45m

Contours of velocity magnitude in y = 0.75m

Contours of velocity magnitude in y = 1.05m

Contours of velocity magnitude in z = 0m

• Rotation and translation of the velocity profile read from the dedusting system resulted in a nearly uniform velocity profile at ESP’s inlet;

• The solution was to rotate and translate the ESP’s geometry and mesh in Gambit to coincide the inlet flange with the position of the written profile.

Contours of velocity magnitude in y = 0.15Boundary conditions are taken from the system, with prior translation and

rotation of ESP’s geometry in Gambit

Contours of velocity magnitude in y = 0.45m

Contours of velocity magnitude in y = 0.75m

Contours of velocity magnitude in y = 1.05m

Contours of velocity magnitude in z = 0m

Perforated platesAssumed as porous media, with pressure loss Re calculated by:

20Re0Re f

l

d

l p

f

p

Perforated plates dataThickness (m) Total area (m2) Free area (m2) Holes diameter (m)

1E 3,00E-03 29,82 12,10 0,07

2E 3,00E-03 62,95 23,80 0,07

3E 3,00E-03 108,30 39,90 0,07

Model parametersSpeed in the holes (m/s) Reynolds (holes) (l/d) Free/Total area ratio (f)

1E 46,015 7,79E+04 0,043 0,40582E 23,394 3,96E+04 0,043 0,37813E 13,954 2,36E+04 0,043 0,3684

Pressure loss coefficient_1E 2864,78_2E 2985,04_3E 2977,92

Contours of velocity magnitude for the first perforated plate at inlet (plate_1in)

Contours of velocity magnitude for the second perforated plate at inlet (plate_2in)

Movie

Contours of velocity magnitude for the third perforated plate at inlet (plate_3in)

Final remarks

• The efficiency of an electrostatic precipitator is strongly dependent on the velocity profile: optimizing the gas flow distribution improves the dedusting process;

• The profile assumed at ESP inlet changes the gas distribution inside the collecting chamber, leading to misinterpretations of flow behaviour;

• The porous jump boundary condition for the perforated plates has demonstrated to be feasible once the actual simulation of the holes is possible but too expensive in terms of computer time;

• A successful optimization work was conducted afterwards in order to reach a more homogenous velocity profile within the ESP, and therefore to reduce the particulate emission.

SEDE

Enfil Engenharia & Serviços Ltda Avenida Brigadeiro Faria Lima, 1912 – 7º

andar Edifício Cal Center IICep: 01451-907Pinheiros – São Paulo – SP BrasilTelefone: 55 11 3093-2727

FILIAL

Enfil Engenharia & Serviços Ltda Avenida Nossa Senhora da Saúde, 381. Cep: 29161-030Carapina – Serra / ES - BrasilTelefone: 55 27 3205-2727

E-mail: enfil_servicos@enfil.com.br