Transcript MSC Development

Allied Environmental Technologies, Inc.
MULTI-STAGE COLLECTOR
(MSC™)
DEVELOPMENT
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Introduction
Multi-Stage Collector

The MSC™ offers a new method and design
for collecting dust or fume from industrial
gases that is virtually independent of
electrical resistivity

This design will be particularly advantages
when the material to be collected consists of
a sub-micron dust or fume
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Evolution of
Electrostatic
Precipitation
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Evolution of Electrostatic Precipitation
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A typical electrostatic precipitator
incorporates two zones:
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the CHARGING zone, where the dust or
aerosol particles are being charged, and

the COLLECTING zone, where the
charged particles are being separated
and transferred from the gas stream to a
collecting electrode
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Evolution of Electrostatic Precipitation

The arrangement of these zones led to
two typical precipitator design
concepts:

an electrostatic precipitator where both
zones are combined in a Single-Stage,
and

a Two-Stage design where these zones
are separated
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Evolution of Electrostatic Precipitation
Two-Stage
Precipitator
Single-Stage
Precipitator
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Evolution of Electrostatic Precipitation
• Here is different design for a
Two-Stage ESP
• It utilizes the unique electrode
design that provides for
separate zones for aerosol
particles charging and
collection in a compact
design
• According to this design, the
dust collecting assembly
comprises of a system of bipolar charged surfaces, which
are engineered in such a way
that they provide alternate
separate zones for hightension non-uniform and
uniform electrostatic fields
The spacing between the surfaces
in the charging and collecting
zones is different, wider in the
charging or corona generating
zones and narrow in the collecting
ones where a uniform high-tension
electric field is being required
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Barrier Filtration
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Barrier Filtration
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Fabric filters are a popular means of
separating particles from a gas stream
because of their relatively high efficiency and
applicability to many situations
Fabric filters can be made of either woven or
felted fabrics and may be in the form of
sheets, cartridges, or bags, with a number of
the individual fabric filter units housed
together in a group
Bags are by far the most common type of
fabric filters, hence the use of the term
"baghouses" to describe fabric filters in
general
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Barrier Filtration
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Ceramic filters have become available that can be
used for high temperature filtration applications
Ceramic material is formed into stiff cylindrical
filter elements, called "candles"
The open ends of the tubes are mounted either
vertically or horizontally on a tubesheet, as with
fabric bags
Tubes are generally cleaned by pulse jets
During the last years, porous metal media had
gained importance in the field of gas dedusting or
product recuperation in gas streams
The two most widely used types of porous metal
media are sintered metal fiber and sintered metal
powder
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Barrier Filtration
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The major particle collection mechanisms of fabric
filters are inertial impaction, diffusion from
Brownian motion, and interception
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Collection may also occur due to gravitational
sedimentation

Electrostatic attraction could play a significant part,
for example in the Electrostatically Augmented or
Enhanced and Hybrid technologies
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The fabric is responsible for some filtration, but
more significantly it acts as support for the dust
layer

The layer of dust, also known as a filter cake, is a
highly efficient filter, even for submicron particles
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Barrier Filtration
Particle Collection Mechanisms in
Barrier Filters
EPA- 450/3-81-005a, NTIS PB83-127498
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Hybrid Particulate
Collection Technology
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Hybrid Particulate Control Technology
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Electrically-charged particles have
been found to form highly porous dust
layers in fabric filters
Efforts to increase barrier filters
efficiency without a corresponding
increase in pressure loss have led to
the development of electrostatically
enhanced fabric filters and so-called
hybrid devices
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Hybrid Particulate Control Technology
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A combination fabric filter/ESP hybrid
device has been developed by EPRI and is
called the Compact Hybrid Particulate
Collector (COHPAC):
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This device involves using pulse jet fabric
filtration to capture dust that escapes an ESP
COHPAC I involves placing a pulse jet filter
downstream from an ESP
 COHPAC II utilizes a fabric filter in place of the
last field(s) of an ESP
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Hybrid Particulate Control Technology
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Advanced Hybrid
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This technology was developed and patented by
the University of North Dakota’s Energy &
Environmental Research Center (EERC)
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The internal geometry consists of alternating
rows of ESP components (discharge electrodes
and collecting plates) and filter bags within the
collector
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The inlet flue gas is directed into the ESP zone,
which removes most of the entrained dust prior
to it reaching the filter bags
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Hybrid Particulate Control Technology
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ESFF
 Electrostatically-stimulated
fabric filters
(ESFF) have been developed by EPA to
reduce fabric filter pressure drop and
particle penetration
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Multi-Stage Collector
(MSC™ )
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Multi-Stage Collector - MSC™
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The principal objective of the MSC™
design is to substantially improve fine
particulate collection by:
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combining electrostatic charging collection and filtration processes, while
separating zones for particles charging
and collecting
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Multi-Stage Collector - MSC™

The MSC™ concept can be broadly
summarized as a system in which
multiple stages are utilized, with
each stage performing a primary
function and multiple stages
operating synergistically to provide
significantly improved overall results
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Multi-Stage Collector - MSC™


The MSC™ offers a uniquely compact concept
utilizing:
 an upstream stage comprised of a conventional
ESP,
 followed by a downstream zone of the parallel
surfaces creating uniform electric field,
 followed by yet another stage, which
incorporates barrier filter, surfaces of which
provide yet additional zone with uniform
electric field
Moreover, by providing continuously repeated
stages in series, the downstream zones
effectively re-charge and re-collect the particles
that are either uncollected or reentrained and
collect those particles after they have been
charged
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Multi-Stage Collector
Stage-2
Filed):
Stage-2(Uniform
(Uniform Filed):
Precipitation
Precipitation
Stage-3 (Barrier Filter):
Filtration
+
+
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+
Stage-1 (Non-Uniform
Field): Charging
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Multi-Stage Collector
Stage-3 (Barrier
Filter): Filtration
Stage-2(Uniform
(Uniform Filed):
Stage-2
Filed):
Precipitation
Precipitation
Stage-1 (Non-Uniform
Field): Charging
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Multi-Stage Collector - MSC™
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The MSC™ assembly
is made up from DE’s
placed between
oppositely charged
corrugated plates
The DE’s are followed
by BFE’s located in
wide zones placed
between the collecting
electrodes
The corrugated plates
are held at a first
electrical potential
while the DE’s and the
Both the flat sides of each of the DE’s,
BFE’s are held at a
corrugated plates and the surfaces
second electrical
of the BFE form collecting surfaces
potential
where the electric field is relatively
uniform
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Multi-Stage Collector - MSC™
At sufficiently high
field strength in
this non-uniform
field region, a
corona discharge
can take place
between the
electrode and the
plates acting as an
ion-charging
source for dust
particles passing
through it
The center region of uniform
field on the other hand
acts in a manner similar to
the field between parallel
capacitor plates with
charged dust particles
collecting on the plates of
opposite polarity
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Evolution of Electrostatic Precipitation
Negative Corona
Positive Corona
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electron
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molecule
particle
Courtesy of Aerosol & Particulate Research Lab
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Evolution of Electrostatic Precipitation
Major Distinctive Points
Gas Flow

The MSC™ is engineered in such a way that the
BFE and the DE are grounded while the
corrugated electrodes are suspended from the
insulators
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By virtue of having the BFE’s at the same potential
as the DE’s, the MSC™ design completely
eliminates any potential sparks from the DE
toward the BFE, thus eradicating any chances of
causing fires and/or puncturing holes in the
porous barrier media

Hence, whether the MSC™ is powered by a
“conventional” or an alternating power source, the
BFE’s remain protected from any sparks from the
DE irrespective of dust concentrations
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Computational
Fluid Dynamics
Modeling
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CFD Simulation
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In order to evaluate the MSC™ design, a
detailed analysis of gas flow dynamics were
performed with an aid of the Computational
Fluid Dynamics (CFD) technique

CFD simulation was conducted for the pilot
MSC™ consisting of four (4) rows of barrier
filters (bags) four (4) bags each for a total of
16 bags and five (5) collecting corrugated
plates
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CFD Simulation
3-D View of the CFD Model
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CFD Simulation

The MSC™ operation was simulated for three (3)
operating conditions with the gas flows of 0.24,
0.47, and 0.69 m3/s at 149 ºC (500, 1,000, and
1,500 acfm at 300 ºF) for the filtration velocity in
the range of 5 – 15 cm/s (10-30 ft/m)

The operating pressure drop supplied by the
bags was assumed about 6” WC

The simulation utilized body-fitted grid approach,
which allows the use of non-orthogonal grids that
can accurately represent geometry of the
simulated object
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CFD Simulation
CFD Model Computational Grid
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CFD Simulation

The simulation was carried out using standard κ-ε
turbulence model with the logarithmic wall functions

The turbulence intensity at the MSC™ inlet was
assumed to be 5 %

Since the pressure drop inside MSC™ is small with
respect to the atmospheric pressure, the equation of
state of the gas used in the simulation was the one of
the constant-density gas

The bags were simulated as the porous media of the
constant resistance, which was adjusted to ensure
predetermined pressure loss for the gas flow
simulated
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CFD Simulation
Velocity Distribution – 500 cfm Case
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CFD Simulation
Velocity Distribution – 1000 cfm Case
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CFD Simulation
Velocity Distribution – 1,500 cfm Case
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CFD Simulation
3D - Velocity Distribution
1,000 acfm
500 acfm
1,500 acfm
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Applications
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MSC™ Applications

One of the most important MSC™
design improvements is very high
collection efficiency in a submicron
(ultra-fine) region, which extends its
potential use to a wide variety of the
fine particulate/dust collection
applications
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MSC™ Applications
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MSC™ Applications
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Ultra clean exhaust gases: “Vision 21”
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Integrated Gasification Combined Cycle (IGCC): superclean de-dusting process (synthetic) gases
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Industrial mineral processing industries:
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In-process capture of the expensive product material
and return to the process, i.e. metals, rock-dust,
gold, etc.
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Post-processing super-clean de-dusting prior to
exhaust to the atmosphere
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Ultra-clean air de-dusting in high-tech, medical, biological
and other similar applications
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Multi-pollutant applications (SOx, NOx, Hg, etc.) via
integrating (or impregnating) catalyst materials within the
barrier filter
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Case Study
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Case Study

A Case Study was conducted in order to evaluate suitability
and size requirements of the MSC™ for the “conventional”
ESP retrofitting

The goal of the study was to evaluate whether it would be
possible to fit the required barrier filter area and the
respective ESP equipment in the existing casing
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500 MW boiler-unit firing sub-bituminous coal was selected
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The existing three (3) field ESP had two (2) casings, four (4)
cells each with 20 gas passages on 229 mm (9”) centers

The collecting plates were 3.66 m (12’) long and 9.14 m (30’)
high

This geometry resulted in a SCA of 38.87 m2/m3/s (197
ft2/kacfm) at a gas flow of 826 m3/s (1,750,000 acfm) at 149 ºC
(300 ºF)
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Case Study
Existing ESP (½)
MSC™ Retrofit (½)
Flue Gas
Cell 1
Cell 2
Cell 3
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Each Cell: 20 GP @ 9” SP
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12’L x 30’H Plates

1,750 kacfm
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SCA=197 ft2/kacfm
Cell 4
Field 3
Field 2
Field 1
Flue Gas
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Case Study
ITEM
UNITS
Barrier Filter Diameter
Gas Flow
MSC™
SIMULATED PERFORMANCE DATA
Case A
Case B
cm - inch
15.24
6
12.7
5
m3/s - acfm
826
1,750,000
826
1,750,000
Systems
2
2
2
2
6
6
6
6
Compartments per MSC™
Compartment Length
m - ft
6.1
20
6.1
20
Compartment Width
m - ft
3.66
12
3.66
12
Effective Height
m - ft
7.32
24
7.32
24
Barrier Filter Elements
No. of Barrier
Compartment
Filter
14 x 24
Elements
Barrier Filter Area per Compartment
Barrier Filter Face Velocity
Total Collecting Area
Effective SCA
per
16 x 27
336
336
432
432
m2 – ft2
1,177
12,667
1,261
13,572
cm/s – ft/m
5.81
11.52
5.46
10.75
m2 – ft2
29,485
317,376
32,950
354,673
m2/m3/s –
ft2/kacfm
34.74
176
38.82
197
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Case Study

Assuming that the MSC™ will be able to operate with
the FV in the 5 - 6 cm/s (10 - 12 ft/m) range a reasonably
suitable retrofit seems possible

Naturally, as the MSC™ operation is independent of the
fly ash resistivity, there will be no need to evaluate the
requirements for the FGC

Hence, this unit would be an ideal candidate for the
“spot market” coal

The expected system performance should be within the
“Vision 21” range; hence the expected outlet emissions
(≤ 0.005 lb/MBtu) should satisfy requirements of any local
air pollution control regulatory office
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Summary &
Conclusions
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Summary



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The MSC™ technology is a novel, compact multistage collector for separating dust or fume from
industrial gases, which is independent of
electrical resistivity
This design should be particularly advantageous
when the material to be collected consists mostly
of a sub-micron and ultra-fine dust or fume
The MSC™ concept offers significant
improvement over conventional ESP’s and BF’s
the MSC™ design completely eliminates any
potential sparks from the DE toward the BFE,
thus eradicating any chances of causing fires
and/or puncturing holes in the porous barrier
media
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Conclusions

MSC™ solves the problem of excessive fineparticle emissions with conventional de-dusting
technology

MSC™ is independent of the dust/fume resistivity

It greatly reduces the problem of higher emissions
from conventional fabric filters and hybrid devices
in the event of partial breaking, leakage or any
system malfunctioning parts, and

It solves the problem of sparking and bags
damaging in the hybrid particulate collectors
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Conclusions

MSC™ overcomes hurdles that prevent operation
of pulsejet filters at high filter velocity ratios

MSC™ requires significantly less BFE surface area
than conventional barrier filter

Consequently, lower vessel size required to
accommodate the MSC™ may result in the lower
capital and operating costs

Finally, in the event the BFE leaks, the overall
MSC™ performance would suffer less, due to the
remaining ESP collection phenomena
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Multi-Stage Collector - MSC™
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