Laminar flow electrostatic precipitation system

An electrostatic precipitation system (100) utilizes laminar flow of a particulate-laden gas in order to enhance the removal of sub-micron sized particulates. The system incorporates a vertically oriented housing (105) through which the gas flows downwardly therethrough to a lower outlet port (110). The gas, which may be a flue gas enters the laminar flow precipitator (102) through an inlet port (108) for passage through a charging section (104). The charging section (104) imparts a charge to the particulates carried by the flue gas. The flue gas and charged particles then flow to a collecting section (106) which is downstream and below the charging section (104). The collecting section (106) is formed by a plurality of substantially parallel tubular members, each tubular member defining a collecting passage therein. Each tubular member (118) is electrically coupled to a potential that is of opposite polarity to that imparted to the particulates, so as to attract the charged particulates to an inner surface thereof. The collected particulates are subsequently collected in a hopper (112) or reentrained in the gas stream as agglomerates for subsequent removal from the gas by a secondary filter (120), the gas stream then being conveyed to a stack (14) wherein the particulate-free gas can be emitted into the atmosphere.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention directs itself to an electrostatic precipitation system 
wherein 100% particulate removal can practically be achieved. In 
particular, this invention directs itself to an electrostatic 
precipitation system having a laminar flow precipitator. To achieve 
laminar flow, the precipitator is divided into a charging section for 
imparting a charge to the particulates carried in a gas stream and a 
collecting section having an electrode disposed at a potential that is 
different from than of the charged particles, for attracting the charged 
particles thereto. More in particular, this invention pertains to a 
collecting section of a precipitator formed by a plurality of 
substantially parallel collecting passages, each passage being formed by a 
tubular member which is electrically coupled to the reference potential. 
Further, this invention directs itself to a laminar flow precipitator 
wherein the charging section and collecting section share a common 
reference potential electrode, wherein the charging portion thereof is 
provided with a corona discharge and the collecting portion thereof is 
devoid of corona discharge. 
2. Prior Art 
The governmental requirements for preventing the emission of hazardous air 
pollutants is continually being made more stringent. Most prominent of the 
air pollutants being restricted, are toxic trace metals and their 
compounds. These compounds primarily exist in the form of particulate 
matter. Due to the nature of particulate formation in combustion 
processes, many of the trace metals, such as arsenic, cadmium, nickel, 
etc., as well as the high-boiling point organic hazardous air pollutants 
tend to concentrate on the fine, sub-micron sized particulates present in 
a flue gas. The problem of control of toxic trace metals and heavy organic 
pollutants therefore becomes largely a problem of fine particulate 
control. Other governmental regulations with respect to air emissions 
require control of sub-micron sized particles, as well. 
Conventional collectors, electrostatic precipitators and fabric filters, 
are very capable of fine particulate control, but as the government 
requirements exceed 99.9%, they have difficulty in delivering consistent 
reliable performance, especially for the respirable particles in the 0.2 
to 0.5 micron range. As the government regulations become more stringent, 
adequate control of toxic emissions will require particulate collection 
efficiencies of 99.95% or greater. 
Conventional industrial electrostatic precipitators collect dry 
particulates in a parallel plate, horizontal flow, negative-polarity, 
single-stage system design. Collecting plate spacing generally ranges from 
9 to 16 inches, and plate height can be up to 50 feet. Flow through the 
precipitator is always well into the turbulent range. Due to the turbulent 
flow, precipitator collection efficiency is predicted utilizing the 
Deutsch model, which assumes that the turbulence causes complete mixing of 
the particles in the turbulent core of the flow gas, and electrical forces 
are operative only across the laminar boundary layer. This model leads to 
an exponential equation relating collection efficiency to the product of 
the electrical migration velocity of the particles and the specific 
collecting area of the precipitator. The exponential nature of the 
equation means that increasing of the specific collecting area yields 
diminishing returns in the efficiency at the high collection efficiency 
levels. Therefore, the 100% collection efficiency level is approached only 
asymptotically in the turbulent flow case and cannot in actuality be 
reached, no matter how large the precipitator. 
It has long been known that laminar flow precipitation provides many 
advantages over turbulent flow. In laminar flow, the flow stream lines are 
parallel and in the direction of flow; there is no force causing particles 
near the collecting surface to be thrown back into the central flow 
region. Therefore, the electrical forces tending to move the particles 
toward the collecting surface are effective across the entire flow 
cross-section, not just across the laminar sublayer. As a result, the 
equation which relates collection efficiency to the product of the 
electrical migration velocity of the particles and the specific collecting 
area defines a linear relationship, whereby collection efficiency is 
possible. 
Besides the practical achievement of 100% collection efficiency, equivalent 
efficiencies in a laminar flow system can be achieved with a significantly 
smaller specific collecting area. The striking difference between the 
collection efficiencies of laminar flow, versus turbulent flow can be seen 
utilizing a typical utility fly ash emission system, calculating the 
specific collecting area (in square feet per thousand acfm) versus 
collection efficiency in two cases. In a turbulent flow system a specific 
collecting area of 230 is determined to be required at 99% collection 
efficiency, and is calculated to be over 800 at 99.99%. In a laminar flow 
calculation, on the other hand, the specific collecting area requirement 
is determined to range from 100 at 99% efficiency to only 160 at 99.99%. 
Thus, a turbulent flow precipitator is more than twice the size of an 
equivalent laminar flow precipitator at 99% collection efficiency and at 
99.99% efficiency the turbulent flow precipitator must be more than five 
times larger than an equivalent laminar flow system. Although the 
advantages of laminar flow precipitation have been known, prior attempts 
to incorporate those principles into a working system have been 
unsuccessful or impractical for industrial scale applications. A major 
obstacle to achieving laminar flow in such systems has been the turbulence 
introduced by the corona discharge of the precipitator itself. However, 
the instant invention utilizes a substantially vertically and downwardly 
directed gas flow in combination with a two stage electrostatic 
precipitator design having separate charging and collecting sections to 
achieve a practical laminar flow electrostatic precipitation system. 
The best prior art known to the Applicants include U.S. Pat. Nos. 
1,329,844; 1,413,993; 1,944,523; 2,497,169; 2,648,394; 2,711,225; 
3,495,379; 3,633,337; 3,830,039; 3,853,750; 4,072,477; 4,908,047; 
5,009,677; 5,125,230; and, 5,254,155. 
In some prior art systems, such as that shown in U.S. Pat. No. 5,254,155, 
an electrostatic precipitator system is disclosed wherein a single-stage 
structure is provided. Such systems provide a plurality of passageways 
that are defined by a honeycomb structure for gas flow upwardly 
therethrough. Stationary rods extend into each passageway, the rods being 
coupled to the negative output of a power supply, while the walls of the 
honeycomb passageways are coupled to a reference potential. Removal of the 
collected particulates is accomplished by washing them downwardly 
utilizing a liquid mist (water) collected from the gas stream. The liquid 
mist is introduced into the gas flow upstream of the electrostatic 
precipitator electrodes, and is introduced solely for cleaning 
contaminants from the collecting electrodes. Since a corona discharge is 
maintained throughout the length of the honeycomb passages, laminar gas 
flow is not achieved. 
In other systems, such as that disclosed by U.S. Pat. No. 2,648,394, the 
gas to be cleaned flows downwardly through a housing in order to be 
directed upwardly through the precipitator which is defined by a plurality 
of tubular members having centrally disposed electrodes extending axially 
therethrough. Here again, a single-stage system is provided wherein 
laminar flow of the gas is not achieved. Spray nozzles are also provided 
for introducing water droplets into the gas inlet conduits which serve to 
flush deposited material out of the tubular members. 
In other systems, like those shown in U.S. Pat. Nos. 5,009,677 and 
2,497,169, single-stage electrostatic precipitators are formed utilizing a 
plurality of vertically oriented tubular collecting electrodes through 
which a discharge electrode extends axially therethrough, for establishing 
a corona discharge throughout the length of the tubular electrode. 
None of these prior art systems direct themselves to achieving laminar flow 
of the particulate-laden gas. Additionally, these prior art systems do not 
direct the gas downwardly through electrostatic tubular collecting 
electrodes which are devoid of corona discharge thereby resulting in a 
less efficient system than that provided by the instant invention. 
SUMMARY OF THE INVENTION 
An electrostatic precipitation system using laminar flow for removing 
sub-micron sized particulates entrained in a flue gas is provided. The 
electrostatic precipitation system includes a housing coupled in fluid 
communication with a flue. A power source is provided having a first 
output for supplying a reference potential and at least a second output 
for supplying a potential that is negative with respect to the reference 
potential. The electrostatic precipitation system includes an assembly for 
electrostatically charging particulates disposed within the housing and 
coupled in fluid communication with the flue having flue gas passing 
therethrough. The charging assembly is coupled to the first and second 
outputs of the power supply for imparting a charge that is negative with 
respect to the reference potential to the particulates carried by the flue 
gas. The electrostatic precipitation system further includes an assembly 
for collecting the charged particulates disposed within the housing and 
downstream of the charging assembly. The collecting assembly forms a 
laminar flow of the flue gas therethrough. The collecting assembly is 
coupled to the power source for establishing an electrostatic field to 
attract the charged particulates including sub-micron sized particulates.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1-10, there is shown electrostatic precipitation 
system 100 for removing particulates, including fines, sub-micron sized 
particles, from an emission source. As will be seen in following 
paragraphs, electrostatic precipitation system 100 incorporates a laminar 
flow precipitator 102 capable of substantially 100% collection efficiency. 
The novel features of laminar flow precipitator 102 are suitable for 
incorporation in both wet and dry precipitation systems where high 
particulate removal efficiencies are required. 
Referring to FIG. 1, there is shown, electrostatic precipitation system 100 
coupled in-line between a source 10 of particulates entrained in a gas and 
a stack 14 for emission of the gas to the atmosphere. Although the source 
of particulates 10 may be any type of source, such sources include coal or 
oil fired furnaces or boilers, various types of incinerators, and any 
combustion process wherein hazardous air pollutants in the form of 
particulate matter are produced. As a coal fired furnace, for example, the 
source 10 has a flue pipe 12 which is coupled to the gas inlet 108 of the 
laminar flow precipitator's vertically oriented housing 105. 
The particulates entrained in the flue gas entering the precipitator 102 
through the inlet 108 must first be charged before they can be removed by 
electrostatic attraction, as such is the principal upon which all 
electrostatic precipitators operate. Such charging can be negative or 
positive, however, negative charging is more widely used. Precipitator 102 
is specifically designed to create a laminar flow of flue gas in order to 
increase the efficiency of particulate removal. The particulates are 
charged as they pass through a corona discharge established between one or 
more pairs of parallel or concentric electrodes. The corona discharge 
which is necessary to efficiently impart the desired charge to the 
particulates to be removed, creates a "corona wind" which produces a 
turbulent flow in the gas pattern passing through the precipitator. 
Therefore, precipitator 102 is designed to separate the charging zone of 
the precipitator from the collection zone or agglomeration zone, the 
collection or agglomeration zone being enhanced by laminar flow of the gas 
flowing therethrough. 
As shown in FIG. 1, the precipitator 102 is provided with a charging 
section 104 disposed upstream of the collecting section 106, wherein the 
flue gas entering the inlet 108 passes through charging section 104 and 
collection section 106 to then pass through the gas outlet 110. 
Particulates removed in collecting section 106 are subsequently dispensed 
to the particulate removal hopper 112, from which the waste materials are 
collected and disposed of. The particulates collected in collecting 
section 106 are dispensed to the hopper 112 by methods well known in the 
art. The collecting section may incorporate rappers to mechanically 
dislodge the collected particulates and cause them to drop into the 
hopper, or a wet precipitation method may be employed wherein water is 
supplied through a water inlet 101 to flow down through the collecting 
section 106 into hopper 112 and carry the collected particulates 
therewith. The water inlet may be located upstream of the charging 
section, or alternately at the upstream end of the collecting section. 
Alternately, collecting section 106 may only temporarily collect 
particulates, serving as a agglomerator for system 100. Particulates are 
attracted to the electrode surfaces and as the particulates come in 
contact with one another they agglomerate. The agglomerates then become 
reentrained into the gas stream for subsequent removal by a downstream 
precipitator or filter 120. This process is likewise enhanced by laminar 
flow of the flue gas therethrough. 
As will be described in following paragraphs, the downward flow of gas 
reduces the reentrainment of the collected particles, where such is not 
desired. In the downward flow system gravity and the gas flow provide an 
aid to delivering particulates which come loose from the collecting 
electrodes, to the hopper 112. Such would not be the case where the gas 
directed upwardly or horizontally through the collection passages. 
Where very high collector efficiencies are required, between 99.9% and 
100%, and the precipitator is operated dry, reentrainment of particulates 
may be a design goal of the system, making the collector into an 
agglomerator. For such a system, the collecting section extends a 
sufficient distance beyond the charging section to permit collected 
particles to be reentrained into the gas stream. The collected particles, 
however, will agglomerate before being reentrained. If necessary, the gas 
can be conditioned with one of several known agglomeration promoters to 
ensure adequate agglomeration to form particulates of sufficient size to 
be easily removed. These now larger particles will flow with the gas 
stream through the outlet 110 into a conduit 122 for transport to a 
secondary filter 120 for removal of these larger particles. The secondary 
filter 120 may be a conventional electrostatic precipitator, a fabric 
filter such as a bag house-type filter, or other type of particulate 
removal device. The gas flowing from the secondary filter 120 will flow 
through a conduit 124 to the inlet 16 of the stack 14 to be emitted into 
the atmosphere free of particulates. In a system not specifically designed 
to reentrain particulates, filter 120 may be optionally provided to remove 
any agglomerated particulates which inadvertently become reentrained in 
the gas stream. 
The laminar flow through collecting section 106 of system 100 is achieved 
by passing the gas through a plurality of substantially parallel 
collecting tubes having a predetermined diameter and at a predetermined 
velocity, downstream of the charging section 104 to achieve a Reynolds 
number less than 2,000. The well established Reynolds number is a 
dimensionless factor represented by the equation: 
##EQU1## 
where: 
D is the diameter of the tubes, 
V is the mean velocity, 
v is the kinematic viscosity of the fluid. 
The laminar flow, RE&lt;2,000 must be satisfied. Thus, knowing the mean 
velocity of the gas and its viscosity, a tube diameter can be selected to 
satisfy the aforesaid relationship. 
As shown in FIG. 3, the collecting section 106 is formed by a plurality of 
collecting passages 106, the collecting passages being formed by 
respective tubular collecting members 118. In this particular embodiment, 
each of the tubular members 118 has a circular cross-sectional contour, 
but other shapes may be utilized and still obtain laminar flow. As shown 
in the alternate embodiment of FIG. 4, the collecting section 106" 
includes a plurality of collecting passages 116" disposed within the 
vertical housing 105". Each of the collecting spaces 116" are formed by a 
polygonal tubular collecting member 118". In particular, the 
honeycomb-like structure of collecting section 106" is formed by a 
plurality of hexagonal tubular members. 
Referring now to FIG. 2, there is shown, the electrostatic precipitation 
system 100'. As in the first embodiment, the outlet of a particulate 
source 10, such as a coal-fired furnace, is coupled to a flue 12 which 
brings the flue gas and entrained particulates to the precipitator inlet 
108'. The flue gas and entrained particulates flow through a charging 
section 104' before flowing downwardly through a vertically oriented 
housing portion 105' of the laminar flow precipitator 102'. The vertically 
oriented housing 105' encloses the collecting section 106' for removing 
the particulates entrained in the flue gas. The particulate-free gas flows 
from an outlet 110 through a conduit 122' to the inlet 16 of the stack 14 
for passage therethrough into the environment. The collecting section 106' 
includes a plurality of parallel passageways, as in the embodiment of FIG. 
1, and connection of an optional system for circulating fluid through the 
collecting section for carrying off the particulates removed from the gas 
stream. A fluid such as water enters the vertical portion 105' of 
precipitator 102' through an inlet 101', and directed to flow through the 
plurality of parallel collecting passages contained therein, like those 
shown in FIG. 3 or FIG. 4. The particulate-laden water is collected in the 
hopper 112' and flows to a pump 130 through a conduit 114. Pump 130 
displaces the water through a conduit 132 to a filter 140, wherein the 
particulates are removed from the water and clean water may then be 
recirculated to flow through a conduit 142 back to the inlet 101' or 
alternately out as waste through a conduit 141. Where the filtered water 
is passed through the waste conduit 141, and not recirculated, the conduit 
142 will be coupled to a fresh water source to continually supply water to 
the inlet 101'. As in the embodiment of FIG. 1, precipitator 102' can be a 
dry system. As a dry system, precipitator 102' differs from precipitator 
102 only in the orientation of the charging section 104', such having a 
horizontal flow therethrough. 
The laminar flow precipitator 102, 102' is a two stage structure wherein 
the charging section 104, 104' may be oriented for downward vertical flow, 
as shown in FIG. 1, or oriented for horizontal flow as shown in FIG. 2. 
However, the collecting section 106, 106' is provided in a vertically 
oriented housing 105, 105' wherein the gas is directed to flow downwardly 
through a plurality of substantially parallel collecting passages. Both 
the charging section 104, 104' and the collecting section 106, 106' may be 
formed in any of several different arrangements, however, it is important 
that the collecting section not be subject to corona discharge, as such 
would create turbulence and inhibit achieving laminar flow therethrough. 
As shown in FIG. 5, the charging section 104 may be formed by a plurality 
of parallel electrodes 126, 128 which are respectively coupled to the 
reference voltage output line 152 and negative voltage output line 154 of 
the high voltage power source 150. Power source 150 may represent multiple 
power supplies, with different power supplies being coupled to different 
sections of the precipitator 102, 102'. The reference voltage output line 
152 is coupled to the ground reference terminal 156 so that the high 
voltage potential supplied on line 154 is more negative than the ground 
reference level, to impart the appropriate negative charge on particulates 
passing between the respective electrodes 126, 128. As will be discussed 
in following paragraphs, other configurations of the charging section 104 
may be utilized in the laminar flow precipitator 102, 102'. As previously 
discussed, the collecting section 106 is formed by a plurality of small 
tubular collecting members 118, each having a diameter or width dimension 
in the range of 1 to 3 inches and preferably in the range of 1.5 to 2.0 
inches. Each tubular member 118 defines a respective collecting passage 
116 through which the gas and charged particles pass. Each of the tubular 
members 118 is formed of a conductive material, and electrically connected 
to the reference voltage output line 152a of power source 150, which is 
referenced to ground potential by connection to ground terminal 156. As 
the conductive collecting tubes are coupled to the reference potential, 
and the charged particulates are charged more negatively, the particles 
are attracted to the inner wall surfaces of the tubes 118. A 
non-discharging electrode 125 extends concentrically within each 
collecting passage 116. Each electrode 125 may have a cylindrical 
configuration of predetermined diameter, and each is electrically coupled 
to the voltage output line 154a. Electrode 125 may be in the form of a 
wire-like electrode or other rod-like member, devoid of sharp corners or 
edges which could result in high electric field concentrations. The 
diameter of electrode 125 and the voltage applied thereto is selected to 
maximize an electric field within each space 116 without creating sparking 
or corona discharge. This is particularly important where collecting 
section 106 is used as an agglomerator. Laminar flow through section 106 
is achieved for gas velocities in the range of 2.0 to 7.0 feet/second. 
Referring now to FIG. 6, there is shown an alternate configuration for the 
two stage laminar flow precipitator. FIG. 6 shows an electrode 
configuration of one of the plurality of collection passages wherein the 
charging section 104" is integrated with the collecting section 106" to 
have one electrode 118 in common therebetween. A cylindrically-shaped 
electrode 128' is electrically coupled to the negative voltage output 154 
of the power supply. The electrode 128' extends a predetermined distance 
into the collection passage 116, the electrode being centrally located 
within the passage 116 in concentric relationship with the tubular member 
118. The tubular member 118 is electrically coupled to the power supply 
output line 152. The distance that the electrode 128' extends into the 
tubular member 118 defines the charging section 104". The voltage applied 
between the electrodes 118 and 128', the spacing therebetween, and the 
diameter of electrode 128' being selected to establish a corona discharge 
between electrode 128' and a portion of the tubular member 118a for 
charging the particulates being carried by the flowing gas. 
The remainder 118b of the tubular member 118 defines the collection section 
106", the charged particles being attracted to the inner surface of the 
lower portion 118b of tubular member 118. An electrode 125 is 
concentrically disposed within the passage 116 and electrically coupled to 
the high voltage output line 154a. Electrode 125 has a cylindrical contour 
and provides a strong electrostatic field to act on the charged 
particulates passing through passage 116, without inducing corona 
discharge. 
Another configuration for an integrated two stage laminar flow precipitator 
is shown in FIG. 7 represented by one of the plurality of collection 
passages. In this embodiment the electrode 128" is coupled to the negative 
voltage output line 154 and extends concentrically within the passage 116 
defined by the tubular member 118. The upper portion 127 of electrode 128" 
is of a smaller diameter than the lower portion 129, and thereby 
concentrates the electric field lines directed to the reference electrode 
portion 118a of the charging section 104". The upper portion 127 of 
electrode 128" is dimensioned so as to induce corona discharge between the 
tubular electrode portion 118a and the electrode portion 127 at the 
applied voltage level. In order to increase the electric field between the 
charged particles and the collection electrode portion 118b, the negative 
electrode 128" is designed to extend a predetermined distance into the 
collection section 106". However, as previously discussed, corona 
discharge creates turbulence which would inhibit laminar flow through the 
collection section. Thus, the lower portion 129 of electrode 128" is 
dimensioned differently than that of the upper portion 127, such being 
dimensioned to increase the surface area of the portion 129 to reduce the 
concentration of electric field lines, as compared to upper portion 127, 
to thereby prevent the occurrence of corona discharge. Thus, the 
combination of electrode portion 129 and tubular member portion 118b 
provide an electrostatic field for increasing the electric field between 
the charged particles and the inner surface of the tubular member portion 
118b, without the generation of corona discharge. In this configuration, 
the tubular member 118 is electrically coupled to the reference voltage 
output line 152 (ground) to provide a reference electrode 118a for the 
charging section and a collection electrode 118b for the collection 
section of the laminar flow precipitator. 
Referring now to FIG. 8, there is shown, one of the laminar flow 
precipitator flow passages 116 having the charging section 104" integrated 
with the collection section 106" utilizing a common reference electrode 
118. As was described for the embodiment of FIG. 6, the tubular member 118 
is electrically coupled to the reference voltage output line 152 and the 
centrally disposed negative electrode 128' is electrically coupled to the 
negative voltage output line 154. In the embodiment shown in FIG. 8, 
however, the reference electrode further comprises a conductive fluid 
layer 168 which overlays the inner surface of the tubular member 118. 
Thus, the upper end of each tubular member 118 of the collecting section 
106, 106' of the embodiments of FIGS. 1 and 2, are provided with a fluid 
distributing manifold 160 for dispensing a conductive fluid to the inner 
surface of the tubular members 118. Although any conducting fluid may be 
utilized, including fluidized particulates such as a metallic powder, the 
most economical fluid for such application is water. The manifold 160 
shown is exemplary only and many other means may be employed for 
distributing the fluid to the inner surfaces of the tubular members, 
without departing from the inventive concept disclosed herein. The water 
passes into an inlet 162 and flows about an annular passage 166 to flow 
down through an annular orifice 165, as well as through an outlet 164 for 
passage to other of the manifolds 160. The water flowing from orifice 165 
flows over the inner surface of the tubular member 118. The water that 
flows down the inner surface of each tubular member forms a conductive 
film 168 having the potential of the reference voltage, and thereby 
attracts the charged particulates thereto, as both flow through the 
collection section 106". The water film 168 serves two functions: (1) the 
water serves to carry off the attracted particulates and prevent their 
reentrainment into the gas stream, and (2) acts as a moving electrode, 
thereby aiding in the formation of a laminar flow of the gas stream. By 
directing both the gas and water film 168 downwardly, both can be 
displaced at substantially the same rate, approximately five feet per 
second, providing a net relative movement therebetween of zero. As the gas 
and electrode have no relative movement therebetween, drag is eliminated 
and laminar flow is thereby achieved. 
Thus, by providing a precipitator having a collecting section 106, 106', 
106" disposed within a vertically oriented housing 105, 105' for flow of a 
particulate-laden gas downwardly therethrough, with the gas flow being 
directed at a predetermined rate through a plurality of collecting 
passages 116, 116" devoid of corona discharge, a laminar flow of the gas 
is achieved. With the collecting passages being formed by a plurality of 
tubular members 118, 118" which are electrically coupled to a reference 
voltage output line 152 of a power supply 150, charged particulates 
entrained in the gas will be attracted thereto and removed from the 
downwardly flowing gas. Since corona discharge creates a turbulence which 
would prevent laminar flow, the particulates entrained in the gas are 
charged in a separate charging section 104, 104', 104" disposed upstream 
of the collecting section. The charging section may take the form of 
spaced parallel plates, or may be integrated into an upper portion 118a of 
the respective tubular members 118, 118". By this structure, a practical 
laminar flow precipitator system can be realized, and thereby 100% 
particulate removal can be achieved. 
Referring now to FIG. 9, there is shown, a system block diagram of another 
embodiment of the instant invention. The laminar flow electrostatic 
particulate removal system 200 is provided within a horizontally disposed 
housing or ductwork 205, wherein a particulate laden gas enters through 
one end, in a direction indicated by directional arrow 202, and flows 
horizontally therethrough to exit through the opposing end, as a clean 
gas, in a direction indicated by directional arrow 222. The electrostatic 
system 200 includes a charging section 210 designed to produce corona 
discharge therein and charge the particulates entrained in the gas stream. 
Subsequent to flowing through charging section 210, the gas and charged 
particulates pass through an agglomerator section 215, having a plurality 
of closely spaced passages with no corona discharge in which the gas 
achieves laminar flow, or near-laminar flow therethrough. The charged 
particulates are attracted to wall surfaces in agglomerator 215, and 
collect thereon, agglomerate with other particles, and become re-entrained 
as larger agglomerated particulates to be subsequently removed by the 
collecting section 220. Collecting section 220 may constitute a collection 
structure such as that previously described, or be formed by a 
conventional electrostatic precipitator, or fabric type filter. The 
collecting section may be closely spaced to agglomerator section 215, as 
shown, or disposed more remotely. 
System 200 may be retrofit into an existing conventional electrostatic 
precipitator, wherein at least a portion of the original precipitator 
forms the charging section 210 of system 200. The agglomerator section 215 
of system 200 provides temporary collection of particulates and may 
closely resemble the structure of the charging section 210, however, the 
alternating electrodes will be much more closely spaced and will be devoid 
of any discharge electrodes or other bodies between adjacent electrodes. 
Conventional electrostatic parallel plate precipitators have an electrode 
spacing which ranges from 9-16", with such electrode plates having a 
height which can range up to 50' The agglomerator 215 may be similarly 
constructed from flat parallel plates which are closely spaced, the 
electrode spacing being less than 4" and preferably on the order of 
approximately 2". Each of the charging and agglomerator sections should 
have a sufficient longitudinal dimension such that the gas residence time 
ranges from 0.5 to 2.0 seconds, with a preferred residence time 
approximating 1.0 second. 
Turning now to FIG. 10, the structure of the charging and agglomerator 
sections can be more clearly seen. Charging section 210, disposed within 
the horizontally disposed ductwork 205, is formed by a plurality of 
alternating electrodes 212 and 214 which are coupled to opposing output 
lines of a power supply 150. The electrodes 212 are electrically coupled 
to the power supply output line 152, which is coupled to the ground 
reference 156. The high voltage output line 154 may supply a negative DC 
high voltage, a negative pulsating voltage, or combination thereof. The 
magnitude of the voltage between the output voltage lines 154 and 152 is 
sufficiently high to induce a corona discharge between the electrodes 214 
and 212, without shorting thereacross. Each of the electrodes 214 may 
include a plurality of corona discharge electrode points 216 coupled 
thereto to promote the generation of corona discharge in the charging 
section 210. Agglomerator section 215 includes a plurality of electrodes 
218 and 219 coupled to respective power supply output lines 152a and 154a 
of the power supply 150a. Each of the electrode plates 218, 219 are 
closely spaced, as previously discussed, and devoid of any corona inducing 
type structures. The power supply 150a operates at a different voltage 
than that of power supply 150, supplying sufficient voltage to attract and 
agglomerate particulates carried in the gas stream, without producing any 
corona discharge. The output line 154a of power supply 150a is referenced 
to the output line 152a which is coupled to the ground reference 156 and 
therefore coupled in common with the output line 152 of power supply 150. 
The gas passing through agglomerator 215 with its re-entrained 
agglomerates then flows to the collector section 220, which may be a 
separate and distinct precipitator or filter. By the arrangement shown in 
FIG. 10, system 200 can be retrofit into a process employing a 
conventional horizontal flow parallel plate electrostatic precipitator, 
and result in a system which benefits from laminar flow of the Gas through 
the agglomerator 215, or both the agglomerator 215 and the collector 220. 
Although this invention has been described in connection with specific 
forms and embodiments thereof, it will be appreciated that various 
modifications other than those discussed above may be resorted to without 
departing from the spirit or scope of the invention. For example, 
equivalent elements may be substituted for those specifically shown and 
described, certain features may be used independently of other features, 
and in certain cases, particular locations of elements may be reversed or 
interposed, all without departing from the spirit or scope of the 
invention as defined in the appended claims.