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ICESP X CONFERENCE PAPER ABSTRACTS 6A SERIES

Held in Cairns, Australia
June 25 - 29, 2006

The International Conference on Electrostatic Precipitation (ICESP) is the official conference of the International Society for Electrostatic Precipitation (ISESP).  

The following is a list of the Abstracts for the 6A Series papers from the X ICESP Conference.  

6A1
ENLAGEMENT OF MIST PARTICLES FOR WET TYPE
ELECTROSTATIC PRECIPITATOR
YOSHIHIKO MOCHIZUKI AND TAKAMASA KOJO

Abstract

Gaseous SO3 (H2SO4) condenses into a nucleus and becomes sulfuric acid mist in a cooling process such as the wet flue gas desulfurization system (WFGD). The relation between the temperature condition of this cooling process and particle size of mist was examined by condensation theory and experiment s. In addition, the collecting efficiency and electric current density of a wet electrostatic precipitator (WESP) were examined with the mist generated by the cooling process.

Particle sizes of mist were measured at 30 ppm of SO3 under various cooling conditions, and were measured in the case where fine particles of ammonium sulfate were supplied by spray-drying.

The particle size of the nucleus into which mist condenses depended on the speed at which the gas is cooled. At a slower cooling speed, mist did not condense into small particles. This indicates that the particle size of mist grows in the range where the gas temperature around the SO3 condensation temperature is lowered slowly.

The electric current density of THE model ESP increased when the particle size of mist was larger, and the collecting efficiency was improved, too. This indicates that the specific collecting area of the ESP is influenced by the cooling condition.

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6A2 
ENHANCED FINE PARTICLE COLLECTION
USING THE INDIGO AGGLOMERATOR
RODNEY TRUCE, JOHN WILKINS, ROBERT CRYNACK AND WALLIS HARRISON

Abstract

Fine particles are a major health issue as they remain suspended in the atmosphere for extended periods, are able to penetrate deep into the human lung and contain significant concentrations of heavy metals, such as Arsenic. They are also a significant component of the smog that limits the visibility in many cities and even in some national parks plus scientists believe they have an effect on global weather patterns. The Indigo Agglomerator enhances fine particle collection by attaching the fine particles to the larger particles. These large agglomerated particles are easily collected in existing control devices, such as electrostatic precipitator, fabric filters, scrubbers and cyclones. This paper concentrated on PM2.5 particles, that is particles less than 2.5um in diameter, including data that was collected on particles down to 50nm in diameter. It was found that the reduction in fine particle emission from an electrostatic precipitator provided by installing an Indigo Agglomerator increases with reducing particle size from a factor of 5 at 2um to a factor of 10 at 100nm. Reductions of this magnitude will have a significant effect on the impact of fine particles on both visibility and health. It will also result in a reduction in heavy metal emissions.

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6A3 
REDUCTION OF FINE PARTICULATE EMISSIONS FROM ESPs
KARSTEN S. POULSEN & CARSTEN R. LUND

Abstract

World wide the focus on the health impact of fine particles in the atmosphere is increasing and regulatory restrictions on size dependent emission are expected soon to add to the ever descending total mass limits of all countries. 

The content of hazardous particles may be reduced either by means of sophisticated devices targeting the fine fraction directly or simply aim at reducing the total mass emission to “zero”. The latter may be done by fabric filters or by means of high efficient ESPs and is expected to comply with the demands.

Barrier filters are characterized by having eliminated many of the non-ideal boundary conditions that maintain the ESP on higher emission levels – either due to constant contributions (re-entrainment, sneakage) or intermittent contributions (rapping loss). Many of these effects may be eliminated or minimised in ESPs e.g. by means of an efficient baffling system, electrode optimisation, etc.

This paper describes a series of case stories where dust emission is reduced to the 1-10 mg/Nm3 range and has a low content of fine particles (PM2.5) as well. This shows that in many cases dry ESPs as well as fabric filters are valid alternatives as “best available technology” (BAT) in fine particulate removal.

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6A4 
SUB-MICRON PARTICLE REMOVAL EFFICIENCY OF
ELECTRICALLY ENHANCED WET SCRUBBER
A. LAITINEN, K. VAARASLAHTI AND J. KESKINEN

Abstract

Wet scrubbers are mainly used to remove undesirable gaseous components from flue gases.Normally most scrubbers have low removal efficiency for fine particles. One way to increasethe fine particle removal efficiency is to use pre-charging. Particles can be charged by corona discharge like in an electrostatic precipitator.

Charged fine particles are removed by the combined effect of
i. Inertial impaction of particles and droplets
ii. Diffusion of particles to droplets and scrubber walls
iii. Space charge force
iv. Bipolar attraction between particles and droplets
v. Image force attraction between particles and droplets / scrubber walls.

Particles are also agglomerated in the charger in a precipitation / re-entrance process.Resulting large particles are removed in the scrubber by inertial impaction.

Results from laboratory tests, several pilot installations and a full scale (biomass combustion) electrically enhanced scrubber are presented. For fine particles the removal efficiency was observed to be up to 92% for pilot installations and 86% for full scale installation. For pilot installations the removal efficiency depended strongly on particle properties and varied between 65 - 92%.


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