Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
10,785-1-C
~066659
; The present invention relates to corona reaction
systems, and more particularly to method and apparatus
which may be used to increase the electrical efficiency
of corona induced chemical reactions. - -
It is well known that many chemical reactions,
such as the conversion of oxygen to ozone may be
effectively conducted in the presence of an electrical
corona discharge. While it is found that high voltage
corona is in many instances a convenient means by which
to induce chemical reactions, corona discharge processes
are extremely inefficient in terms of electrical energy
- required,per unit of desired reaction product produced.
For example, in the case of ozone produced from oxygen,
,
the theoretical energy required to produce a Kg of
ozone is 0.~7 KWH per Kg while in practice it iB found
that about 6.6 KWH per Kg sre needed with oxygen feed
and 17.0 KWH/Kg with dry air feed.
Prior workers have attempted to decrease the amount
of energy required to produce a corona reaction by
varying many of the operational parameters of the
corona generation system. For example, it is known
that the use of pulsed high voltage energy having a
pulse duration of 1 microsecond and a frequency as high
as 1 Khz will more efficiently decompose carbon dioxide
than a conventional 60 Hz AC waveform. However, it
has also been shown that the use of an extremely high
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1066659
freguency corona power in the radiofrequency range,
that is, 1-20 MHz, doe~ not result in increased
offieiency in the production of ozone
~ hile the pr$or art suggests that change~ in
effieieney may be obtained in corona induced ch~mical
roaetions by the manipulation of freguency and waveform,
it has been found that these attempts have resulted in
; proee~ses that show no improvement and are in fact
lopraetical from the commercial standpoint This i~
primarily aue to the faet that the use of high
fr~queneies and voltages result in the production of
exe ~ heat whi~h is unmanageable when large scale
op ration and high unit eapacities which reguire high
po~er den-ities per unit of electrode Jurface are
eontomplated
It 18 therefore an ob~ect of the pre~ent invention
- to provid~ an ~mproved eorona discharge Jy~tem
It i- a furth r ob~ect to provide a method by
~hleh tho overall l-etrical enerQ required to produce
a eorona di~eharge chemieal reaction may be minimized
It i~-till a further ob~eet to provide a means by
~hich th a~ount of exce~s he~t whieh results from a
eorona di-charge reaetion proeess is substantially
doer-a~ed
~ t i~ xet another ob~ect to provide a method by
~hieh the operation and ~quipment parameters involved in
a oorona diseharge ehemical reaction ~ystem may be
optimized to produce maximum product and minimum wa~te
hnat
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1066~59
It i8 still a further ob~ect to provide an
$mproved corona generator ~ystem which will make
feas~ble corona reaction processes which are conducted
at h$gh unit capacities and mRximum electrical
offic$-ncies
It $8 still another ob~ect to provide an improved
ozone generation gystem which is capable of efficiently
produc$ng ozone in large quantit1es from an oxygen
contain$ng re~ctant gas, such aR a$r, which contains
cons$der ble quant$t$es of moisture and other impurities
It is ~till a further ob~ect to provide economic~l, -`'
rel$~ble, h$gh volt~ge, high frequency narrow pulse
'; ' po~er supp'lies which are cap~ble of driving large size - ' ~'
corona gener~tors to produce comm~rcial quantitie~ of
. ~
ozone
It i~ still yet ~nother ob~ect to provide a ~ystom _
by wh$ch ozon- may be safely gonerated in concentrat$ons
; ` o~ 10 percent by we$ght w$thout undue decompo-$tion of
o~o~ . , _ ~,
-- ~ .
Th~se and ~till furt~er ob~ect~ of the present
invention will b-come readily ~pparent to one ~killed
$n th art from ~h- following det~iled description ''
and drawings wh-rein's --
'1 Figure 1 represents a cross-sectional view with
parts brokon aw~y of a typ$cal corona d$scharge cell
.. . .:
whlch may be used $n the practice of the present
lnvent$ont
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: ~066659
- Figure 2 is a graphic representation wherein
supplied, applied, dielectric and gap voltages are
plotted on the vertical axis versus time on the
borizontal axi~, and represents the preferred waveform
of the electrical energy pulses used to generate corona
aischarge;
P~gures 3 and 4 are circuit diagrams of preferred
power supplies whi d may be used to obtain the desired
corona aischarge;
n gure 5 $8 a plot in which specific ozone yield
1~ plotted on the vertical ~cale versus duty factor on
the horizontal scale, which may be used to select ;~
; oertain preferred operational parameters of the present
~y~tem;
Figure 6 is a plot in which percënt-energy 10BS i~
plottod on the vertical scale versu~ duty factor on
th~ borizontal ~cale, which may be used to ~elect
cortain proferr-d operational parameters used in the
practico of the pre~ent invention; and
~0 Figure 7 is a block process diagram which
lllw trate~ preferred methods for practicing the
pr--ont invontion.
Broadly, ~y invention comprises a method for
lncroasing the electrical efficiency of a corona
discharge reaction system, and corre~pondingly
ubstantially reducing the amount of waste heat produced
thereby, wherein a narrow pulse high voltage waveform
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~066659
is applied to a gas filled corona discharge gap along
with means to remove gas ions from the gap
More specifically, I have invented a corona
roaction system wherein the corona is produced in a gas
filled gap between opposing electrodes by a high
voltage, narrow pul~e electrical discharge in which
the electrical pulse width is less than the ga~ ion
tran-lt time between the electrode~, and wherein means
ar produced to remove or neutralize the gas ions which
are formed auring the afscharge in a manner which
d nimizes the electrical energy which is normally
~a-ted in th- accelera~ion of the ion~ -
In a particularly preferred practice of my invention
a low voltage bia~ potential is maintained between the
electrode~ wh~ch i8 ~ufficient to subst~ntially remove
ga~ $on~ from the gap in the time interval between
. . _
pul~e- Additional mean~ or methods for removing gas
lon- from th aischarge gap before an exce~sive amount
o~ rgy i~ xpend d in the acceleration thereof
; ~0 Include removing the gas from the gap after exposure to ~ ~
a l$mit-d number of narrow pulses and holding the gas
- ln a non-corona zone to perm$t recombination, i e
n utralization, of th- ion- before exposing the gas to
aad~t~onal corona ditc~arge It i8 also envlsioned
that gas ion~ may be n~utralized vithin the gap by
~-lective application of an added neutralizing component
v~ - n!gativ ly ch~rg d finely dLvided liguid or
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'106Ç659
solid particles such as silica gel, water and carbon
black having a particle size of less than about 0 1
~icron, ~nd preferably on the order of 0 001 to 0 01
microns To obta$n the negatively charged
neutralization component, a finely divided solid is
pa~d through an electrical field which i8 created
by a pair of oppositely charged plates such as used
in electrostatic precipitator~ Alternatively, an
, . . . . .
ato-lz-d liquid ~uch as water may be used wherein
water i8 dispersed as an Jerosol having droplets on
th- order of about 0 01 m~cron Electrical
n turalization of non-productive gas ~ons may also
be a¢hieved by application of a minor energizing
el ctrical puls- of a polarity opposite to that of the
corona pulse ?Se applicJtion of the bias potential -
~ay b- advantageoud y applied to the corona aischarge --
l ctrode~ of a corona cell or to a grid which i~
plac d b-tw ~n th l-ctrod 8
- ln ~o~t conventional corona aischarge systems the
20 high volt~ge el-ctrical potential i8 ~pplied across the
di~charg- gap $n the form of rel~tively wide electric~l
` pul-~s ~ypic~lly, the electrical enerqy waveform i a
conventional sine wave,`while in other instances pulse
nergy having ~ pul-e duration o 1 to 200 ~icroseconds
i!? ~u -c) have been utiliz-d
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It i,s observed that these prior art ~y~tems are
xtremely inefficient and that 90 to 99~ of the'
lectrical energy i5 wasted in the form of excess heat
'~ I have determined that the excess heat generated in ,'
, these conventional systems may be attributed to the
- kinetic energy which is imparted to the charged gas
~olecules ~ions) which Are pre~ent in the corona ,~
d~scharge gap The electrons which are responsible
,' for the formation of the desired react'ion product are
' 10 formed and acceler~'ed to reaction potential during
, . ,
- the initial part of the conventional electrical power ';
pul~e The remainder of the pulse supplies kinetic
,~, energy to the charged gas molecule~ which result from
'' 'th- formation,of~electrons and which do not contribute
to tho formatlon of roaction product These ionizcd
qDs ~olecule~ di~sipate their kinetic energy in non~
productlv coll~ion which appears as waste heat in -
t~- r-action ~y~t~
~; In ~y proces~ I have substantially reduced the ''
2~ ~mount of waste hoat by modifying the applied olectrical
w~voorm in two w~ys~ '
.
~ ho duration o the electrical power pulse (I~)
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- ~066659
is selected to be substantially less than the gas ion
tran~it time across the discharge gap (T+)
~2) A relatively low voltage bias potential (Vb)
~J malntained between the discharge electrodes to -
remove the m~jority of ~he charged gas molecules
By ~electlng an extremely narrow energy pulse at -
thc re~uired ~parking potential to produce ozone (Vs~ -
~t ~ found that the electrons which are formed are -
acc-lerated to an energy lovel required to do useful
~or~ ~o~ever, the energy pul~e i~ not of sufficient
duratlon to impart any ~ignificant wa~te energy to the
charqed g~ molecules which are correspondingly formed
It ~8 recognized, however, that the g~s ions which
are pre~ent in the di~charge gap must be removed before
th- next appli~d energy pulse, or a substantial portion -~
of th- nergy pul-e will be wasted in further acceleration
of th- non-productive ga~ ions To achieve re~oval of
g-- lon ~debr$~, 1 apply a relatively low voltage bias
pot-nt~al or ~d bri~ lon ~weeping~ potential during the -
20 lnterv-l between high energy eleotrical pulse~ This ~~
lo~ voltage bi-~ pot-ntial i~ applied for a period which
ub~tantlally gr-ater than th- high energy pul~e
Ho~ever, since the nergy applied to a charged particle - -
ln an lectrical field i~ a function of only the particle
chargo and the fi-ld potential, the energy requ~red to
~w~ep the ~on debrl~ fro~ the discharqe gap is relatively
~lnor. --
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'- 10 66659 ' ~-
..
' The relationship which defines the preferred low ~
,~,.
voltage bias potentlal Vb is as follows '
Tr Vb ~ T~ Vs
:
., ~ , Vb P _ VS , . ..
Tr - . .;
wh~re'~n Tr represents the pulse repetition period, T+ is
the calculated gas ion transit time to ~weep substantially "'~
. . .
ll the ga ion~ from the gap at the sparking ~corona n
d~scharge) potential V~
In order to determine the actual pulse width and
"' ~0 fr-quency which is employed in the production of the ' --
.~ . . .
high frequency narrow pulse energy it ~s neeessary to ~'
select a pulse width which is ~ub~tantially -less than --~
ibV
the pulse r-p~tition period (which is the reciprocal of
th- ~r quen Q) ~n general, the actual pulse width Tw '
j ~- selected 50 a8 to be a small percentage of the overall ' '' ''
pulse repQtition rate Tr In general it is found that
ln ~4st applications the Tw will be from about 0 1 to ' ',
'~ lO p-r cent o~ Tr. Furthermore, it i~ noted that in
ordar toi produce th- deeired chemicaI reaction the pulse ~'
20 width ~hould be of sufficient duration and magnitude to - '
..~ .
l~p~rt Jufficient kin-tic energy to electrons whlch '''''
produce the desired chemical reaction Therefore, th¢ .. J~
de-~red narrow pulse width Tw will be somewhat greater
than the pulso width required to accelerate the electrons
~cro-~ the di charg¢ gap, this time being referred to
~n order to implement my novel method and to
optimize the dcsign o~ the equipment and electrical ~;
circuits which are uitlized herein, it is found that the
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0 66659
operational and circuit parameters of the system may
be conveniently selected in accordance with the
following consideration of a circuit which employs a
conventional heated cathode vacuum switch tube type --
power supply
; .
For mo~t heated filament vacuum tube switch
device~ it is well kns~wn that the optimum electrical
eff$ciencie~ are obtained when a duty cycle tD) is
-lected which iQ a~ high as possible That is a
rel-tion-hip
D - Tw ~~
Tr
i- maxi~ized commen~urate with the energy losses which
re~ult in corona generation due to a pulse width TW ~ -
which i8 nece~sarily larger than the electron trS~nsit
t~e T ~nd substantially les~ than the gas ion tran~it
. . .
t~e T+.
To opti~lze the parameters of duty cycle D and
pul~e width Tw, pul~e repetition time Tr which i~ the
r-ciprocal of th- pul~se frequency,f, I have found the -
20 following relation~hip exi~ts: -
~2 D tl) ,`
relns
. ~.
~ - TW ~2~ ~ ~
.~ :
and T+ i~ the ga~ ion transit ti~e which mS~y be readily
c~lculatQd for any ga~ ion using the well known principle~
typics~lly ~et forth in ~G~eou~ Conductorss~ by
J. D. Cob$ne, Dover Publicsations, N Y ~i958) -
Equation ~1) S~ay be rewritten
D ~ t~2 ~3)
T+
. , . . s
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1066659 `~
For air it is found by using the relationships
- provided by Cobine, that
Tl ~ 4)
. . Xp ' ' . ' -:'
The product Xp is constant for any gas For air
; ~p - 1064 (cm~sec ) ~m m Hg) ~5)
vo cm -
A rea~onable approximation of Tl is - - -
T~ - 1 83 x 10-S tg ~6)
Aecord$ngly, to give an example of how the
j.
; op rational parameter~ may be optimized for a eorona
di~eharge sy~tem which is operating on air to produce
020ne at a pressure ~p) of 1520 m m Hg absolute with a
dlseharge gap of 0 115 cm the following calculations
; -
ar~ maae, u~ing equat~on ~6) above
S~ - 2.10 usec
, ,
' The parking voltage Vs or gap potential require~
r~
to produee eoron- $~ ealculated from the following
r l~tlon~hip which appears in Cobine: -
;
V~ ~ ~0 p tg
- ~0 x 1520 x 0 115 - 6992 volts - ~~
20Sh- pul~ width Iw is determined using equation ~2)
j~l , . . ~, .
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~h-re$n ~ $~ les~ than 1 Furth-rmore, Tw is seleeted
to be ~o~ what greater than the eleetron transit time To
aero~ the discharge gap whlch may bc readily calculated
by eomparing the mas8cs of the eleetron with the mass of ~,
th~ gas ion ~oxygen) used ~n the ealculation of the gas
lon transit time T~. This caleulation is as follows
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0 66659 ' '' ,~
Te ~ Tl
1840 x 16
, , , ~ 0 012Jusec
It can be shown that the amount of power consumed
ln th- production of ozone, that is, specific 020ne ',
y$eld, Sy, which is due to pulse width losse and pulse
ias losses i8 approximately
' ,~ Sy - 0 6 ~
. .
and is a mini~um when
i . .
Accordingly . `~
8y 1m$n)~ - 0 6 (1+4~S)2 , ' --
- 0 6 ~l14~)2
and if Sy in XMH per pound of ozone produced is plotted
qainst D, the duty factor, a curv such as is shown in
f$gur 5 results From figur- S lt is een that-D should
be as low as possible to obtain the lowest 020ne speclfic
yl~ld ~y in'terms of XW8/lbs 03 produced ~s,'far as the ' " ~'
pul-- g-ometry 1- concerned
To ~lect a specif$c valu for th- duty cycl- D ' -
~h n uslng a typical h-atcd cathode vacuum tube power
upply'c$rcuit wh-re$n th- ~acuum tub- filament 108s is ''
ot primary consideration, a plot such as is shown in --
t$gur 6 1~ prepared. In figur~ 6 the duty factor D ls
plotted a~ a solid line !gainst th per cent energy loss
which i- atrr$buted to pulse geometry ~which may be - "
r-ad$1y determined from flgure 5) Also plotted are a
serles of broken lines in figure 6 whlch represent the ' ~, ' -
per cent energy loss du- to filament heatlnq in two '"' '
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1066659 ;
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typical vacu'um tube switch devices rated at 100 and 150
KW respectively. It is seen from figure 6 that the
preferred duty cycle D for the 150 KW tube is about
0.001 and it i~ at approximately that point where the
tube fllament loss i~ equal to the pulse geometry, that
i~, process, loss.
~' When the duty cycle D has been chosen to be 0.001 ~
$~ calculated a-~ folIows: -' ' -
,, ,cl~ ~ ~
10' ~ ' - ~1 ' '' '
- 0.0317
From ~ and Tl the desired pulse width Tw and
,,, ' fr-quency f may be calculated as follows:
w - Tl
- 0.0317 x 2.09 - 0.066 ~sec.
.
,~ and
f , 1 , D
Tr Tw
,.. ~ , . . .
- 0.001 - 15100 Hz
' '0.066
~o determine the preferred,,low vol'tage bias potential
._ .
Vb'which is used to remove positively charged gas
~bl-cule- from the discharge gap between pul~es, the
,
follow~ng relationship i8 us~d~
Vb - T~ V~ and Tr
Vb - 2.09 x 697S
5100
315 V.
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1066659 .- ~
In aecordance with the above calculations, it is
seen that the preferred operational parameters may be
.~ . .
summar~zed as follows
D - 0 001 ~-
Ys ~ 6975 v
f - lS100 Itz
, ~ Ub - 315 v - -
A more elear under~tanding of the pre~ent invention
- say Se obt~ined by r fer~nee to the drawings in whieh
figur 1 18 a erw ~-~ectional view of a corona cell witb
partr broken ~way whieh may be us~a in th eorona
.
!~ 'r ~etions sy~tem~ eontemplated herein The eorona
r -otlon eQll of fi~ure 1 ineluaes a gas tight hou~ing 1
-- $n wh$eh ar~ plaeed two oppos1ng eleetrode~ 2 and 3
¦ ~ Between eleetrod~ 2 and 3 are plao d dieleetrie plates
~ 4 and 5, th~ inner ~urfae~ of whieh defin~ a eorona
! . diseharg~ gap havlng a thieknes~ tg, a~ indicated in
'l f~gure 1~ The dieleetric plate- 4 and 5 posse~ a
ehlekn -~ td, the aetual dimen-ion of which is enlarged
20 oonsld-rably for purpo~e~ of elarity Likewi~e, the- `~
;x ~
~, d~n lon tg is eon-id-rably xpanded in the drawing 4i-
j lor purpos-J of elarity Typieally, the dieleetric
thleknos-, td, ~ay r ng- 8 sm~ll a~ 0 1 ~ ~nd in
o rt~ln in~t~nees may b- a~ large a 24 to 50 mm Tho
d$seharg- gap tg ~ay range from about 0 1 to S0 mm
5h eleetrode plates 2 and 3 are eonneeted to an
xt-rnal pow~r soure~ through eonduetor~ 6 and 7
respoetively, whleh enter th~ housing 1 through in~ulated
bu~hings 7 and 8 ~rnile ln t~e pre~ent drawing it 1
~:
,''.
_ 15
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0 666 59
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shown that the electrodes 2 and 3 are not in contact '
with the housing 1, it is found that in actual practice '-
lf the housing 1 is constructed of essentially --
electr~cally non-conductlng material, the electrode
plates may be in contact therewith Furthermore, it is
found in actual practice that either of the electrodes
2 or 3 may be grounded, and in the event the hous-ing -
1~ constructed of conductive material, may support
either of the electrodes ' - ~'
A~ shown in figure 1, reactant gas enters the
hou~lng 1 through conduit 10 and the reactant product ~'
'' exlt~ through conduit 11 The arrow 12 indicates ~'
d~rection of flow into the housing 1, while arrow 13
lnd~cate~ the direction of the existing reaction products
Furthermore, ln figure 1, 14 indicates the corona
discharge zone which ls defined between the electrodes
2 and 3 and the dielectrlc plat-s 4 and S While the
pr---nt drawlng shows the use of two dielectric plates,
oach of whlch 1~ es~entially in contact with the
20'' opposing electrodes 2 and 3, it should be understood '~
that d-vice~ whereln the electrode plate~ are spaced
from the electrode~,'or whereln a single dielectric
plate ls located between, may also be utilized In
practice lt is found that satisfactory re~ults may be
obtalned when the dlelectrics are constructed of
materials having good dielec~ric qualities, that is
dlelectric strength of from about 100,000 to 1,000,000
volts per cm, sucb as gla'ss lt is also found that
xtremely thin d~electric layers formed from fired'on '
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1 066659
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porcelain enamel coatings having a thickness of from
about 0 1 to 0 5 mm produces particularly satisfactory
r -ults
Also shown in figure 1 is a grid 15 which is
optionally placed between electrodes 2 and 3 In some
instances it is found to be advantageou~ to apply a
relativ-ly low bias potential to the grid 15 for
purpose of ol~minating heavy gas ions from the reactant
ga~ tream While a single ~creen type grid 15 is
~0 ~hown in figur 1, it is contemplated that a s-ries of
grid~ may be prov~ded which may be energized to provide
a ol-ctive ion neutralization electrical field in the
gap 14
Figure 2 shows in graphic idealized form the shape
of th d ~ired narrow electrical power pulses which a~e
u -d in tho practic- of the present invention. It i~
noto~ ~n figur ~ that 4 curves are plotted, with
voltag on th v rt$cal axis and time on the horizontal
~xl- Th- curv El ~--t forth as a solid line)
r pr 8 nt- th voltage of the preferred sguare wave
~ul~- whid ~ initially produced mo~t efficiently by
th high p -d ~witch devic- of a suitable power ~upply
~h curvo E2 (~hown a- a ~er$es of X'sl represents the
~oltago of th init$al power pulse El ~fter pas~ing
through a suitable inductance which ha~ a value
-l-cted to minimize the power loss wh$ch normally
r -ults from the charging of a resistance-capacitance
~ 17 -
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1066659
circuit E2 is the power pulse which is applied to the
olectrodes of the corona cell shown in figure 1 The
ourve Vg ~dashed line) represents the voltage which
appears across the discharge gap 14 of the corona cell
and ha~ a maximum value of Vs which is the sparking or
ionization potential of the gap Vg has a lower value
of Vb which is the bias potential, a pulse width of Tw
. ana a ropetition period of Tr The curve indicated as
; Vd (dottod line) i8 the valvo of the potential which
appears across the dielectrics of the corona cell As
will bo discussed heroin an understanding of the various
pr ferred volt ge wave forms which appear at various
point~ in the corona celI will provide a basis by which
on- skilled in the art may design a circuit suitablo
for practice of the present irvention
~ hil- the preferred wavoform shown in figure 2
indicat~ tho pul~e- to be monopolar, it is to be
und r~tood that bipolar pu180s in which oach succeeding
pul~ of alternating polarity may also be utilized
~t 1~ to b- also unaerstood that while figure 2 shows
th bia- potential to be groater than 0, that i8 a +
bla- potontial, it i- found that ~b may al~o b-
utllized in th fonm of à negative bias potential, that
1-, a value le~s than 0 Furthermore, it is shown that
Vb i- ~8 ntially con~tant in the wavoform shown in
figure 2 It -hould be undorstood that Vb may be
ithor increasing or docreas$ng between powor pulses,
that i8, Vb does not necessarily have to remain constant,
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1066659 .~ .
and in fact may alternate to some extent --
The waveform shown in figure 2 may be produced by
a vari-ty of well known high voltage power supplies -~
which utilize high speed switch devices æuch as solid
tate transistors, silicon controlled rectifiers,
; varactors, vacuum t~be~ of both the heated filament
and non-fil~nt types, ~uch as thyratrons and ignitrons, ~.
as well as high speed mechanical switches
In figures 3 and 4 two typical circuits are
10 diaclosed which u~e heated cathode vacuum switch tube~ -~
; It i~ to be understood, however, that the w e of non- -~
filament switch devices such as thyratrons and ignitrons
have Jub~tantially no stanaby power 1088-8 and use
th~reof enables the operation of a more efficient
proc-~s
f rence to figur- 3 r-veals a corona generation _-
~y~t~m which includes a power supply of the typical
vacuu~ tub- pliti-r type In figure 3 a pulse
g n rator 24 i~ conn-cted to a DC power Jupply by means
20 of l-ctrical conduit 26 Pulse generator 24 is ~-
typlcally a comm rclal pul-e g-nerator unit such as is ~'
old by Cober ElectronicJ Inc , which is capable of
producing pulJe~ of a voltage up to 300 volts at
fr quenci-- ranging from 1 ~z to 3 N~2 ThQ pulse
g-nerator 24 typically comprises a trigger circuit in
~amhination with suitabl- vacuum tube amplif$er stages
The DC power supply 25 i8 also commercially available
and typically produces from ~bout 0 to l3000 volts DC
at a pow r level of up to 10 kw
'~i
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1066659
.
~ . . ..
Pulse generator 24 is used to control the output
of vacuum ~witch tube 27 Vacuum switch tube 27 is a
typical heated cathode tetrode device which is readily
commercially available Tube 27 includes a heated
cathode 28 which $~ connected to a source of power by
leaas 29 or 30 Typically the heating power means, not
rhown, range from about 4 to 40 volts The vacuum tube
.
27 $~ provided with a plate lead 32, a secondary grid
lead 33 and a primary grid lead 34 The secondary grid
10 33 i~ connected to a source of bias potential which is ~!
confined within broken line 35 The bias potential
~upply comprises a diode 36 which i~ connected to a
power transformer 37 which in turn i~4,supplied through
a variable resistance 38 by means of power leads 39
. . . .
and 40 which are connected to a convenient 6Q cycle ~C
ourco, not hown. The biaQ potential means 35 also
lnclud-~ a capacitance 41 which serves to even out the
`` output th-reof
, Th- ~witching grid 34 of the vacuu~ tube 27 i~ -
20 connect-d to the pul8e generator 24 The plate lead 32 t
1- connoctod to a DC p~wer supply 45 through a conductor '~
~6 which i~ connected to an inductance coil 47 in series
wlth a rosistance 48 The DC' pawer supply 45 is also
conn-cted through conductor 46 and conduc~or 54 in series
with conductance coil 53 and conductor 52 to a corona
cell 50 'rhe coil 53 ~spreads out~ the ~quare genera~ed
waveform such to minimize the energy'loss normally
..... , ~ :
.
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- 20 -
.
- ... .. . .
,
. ' : , '. :, : . :
1066659
. .... . ... ~
associated with charging up a capacitor Icell capacitance
in this case) through a charging resistor In general,
tho value of the preferred inductance of the co~l 53 '-
is obtained by the readily recognized relationship
L - tw2
f~c . ~ ,
A power supply 55 may be used to supply a bias
potential to the plates of corona cell 50 through
conductor 56 and inductance 57 which connect through
inductance 53 and conductor 52 The capacitance 58
.. ... . . . . . .
;10 ~erve- to isolate a DC bias voltage from the remainder
of the power ~upply circuit In the event the bias
potential i~ suppl~ed through the sw,itch tube 27, the
powcr supply 55 may be eliminated The corona cell 50
i~ typically con~tructed in the manner shown in figure 1
- ~h- circuit through the corona cell 50 i~ completed by
, co~ductor 51 which i8 connected to the g~te lead 32
' ' , ~n op-ration th- d-vice of figure 3 requires that
'; _ th- output of DC power supply 45''be switched at a
' d~ired frequency whlch i~ produced by the pulse
~ n-rator 24, which in turn i8 powered by the DC power
~upply 25 Typically, the DC power supply 45 i8 '
ad~,ust-d to oper~te about 5000 to 30,000 vol~s DC The
po~itive output ~ide of the DC power supply 45 i8
applled to th- corona cell a8 shown through th-
lnductance 53 which typically ha~ a value of 1 0 to
''-~ ' ~ 10.0 microh-nry The positive side of the power ~upply
. _ .
. .. ~ ,. .
:,. ..
- 21 - ~,
' ' ~'.:
, . . -' ' - - , : ' ' : ~ .
- 10 666~9
~5 also appears as being applied to the q~e lead 32
through the inductance 47 which has a value of 0 1 to
1 0 henry and through the resistance 48 which has a
value of 100 to 100,000 ohms It is noted that switching
o tho output of vacuum tube 27 by means of the grid 34
which is connected to the pulse generator 24 produces
n,arrow high frequency pul~e to appear across the
plate~ of the corona cell 50 Typically,'the pulse
g nerator 25 iQ operated at a frequency of from 0 1 to
100 XHz Al~o, for vacuum switch tubes of
appropriate design the grid 33 of the power tube 27 is -'
maintained at a ~ultable potential from about ~50 to
' ~SOO volt~ 80 that ,a bia~ voltage of about 10 to 5000
, volt~ ~ay be maintained acro~s the plates of the corona
c ll 50 Other methods of supplying,a Iow pulse to
pul-- bia~ are pos~ible; as shown in Figure 4 In this
nn-r the op-rational parametors of the corona cell
ln t~rm- o~ fr-quency, bia~ voltage, ~pa'rking voltage
and,pul~e width may be conveniently selected within the
'' 2~ it~ lndicat d by th present invention The circuit
.. .. ~
o~ gur~ 3 i~ cla~sically called a hard tube modulator
" Anoth-r ~uitable type of power ~upply i~ ~how~n in
~igure 4, wh rein a triode type vacuum switch tube 60
lnclude~ a heated cathode 61, a plate 6i and a grid 63 ,,
m~ a cla~ical line pul~er type modulator The
grid 63 i8 conn-cted to a pul~e gener~tor 64 and a '
,......... . ~
. .
- 22 - -
: - . ,, ~ ~ : : .
.
1066659
.. . . . ...
grounded conductor 65 which is also connected to the-
cathoae 61. The cathode 61 is provided with heater. --
'l~ads 66 and 67 wh~Ch are connected to a suitable source
of power, not shown. . .-
~~' .A high voltage DC power supply 70 is connected .-
through ~ts positive lead to the cathode lead 62 of the . '
witch tube 60. The negative side of the DC power supply . '~
70 i8 grounded. A DC bias voltage power ~upply 80 is
negative grounded and the positive lead thereof is
. 10. connected through an inductance 81 to conductor 82.
The DC power supplies 70 and 80 as well as the ..
~witch to circuit is connected to a c'onventional'pulse
.. . . . . .
~- forming network which i5 confined with$n.the ~roken line
8i and includec select'ëd-inductances 85, 86'and 87 which
. , . . . . . _ .
,' ~'''" ar connected in series with each other through
' conductors 88, 89 and 90. Also included in the pulse
. for~ng network 85 are capacitances 91, 92 and 93 whlch
r respectively connected to the conductors 88, 89 and
~. _
.~ 90 by means of conductors 94, 95 and 96. m e pulse
20. for~ing network 84 i~ connected to the DC power supply
tch circuit by ~ean~ of conductors 95'and 98. The , '
, output of the pul5e forming network 84 i~ connected
., through to the primary side of a step-down tran~former
.i ~3 100 by ~eans of lead8 101 and 102. The ~tep-down
tr~nsformer secondary is connected to a corona cell 105
by ~ean~ of conductors 106 and 107. The step-down ' ~ :
:, .
.
- 23 -
. . . .
,
,. ~
,: : ' . -
: ) ?
1066659 -~
.
~equirement is necessary at power levels greater than a
few kilowatts It $s found to be impractical to build
~tep-up pulse transformers with the required
characteristics of band width, inductance, etc at
hig~er power level~ Step-down transformers are possible,
however ~he output of the bias power supply 80 is ~-
rupplied to the corona cell 105 through the conductors
82 and 107
In operatlon the system of figure 4 i8 adjusted -
~o that the power ~upply 70 produces a voltage from
bout 10,000 to 100,000 volts DC which appears across
the plate 62 of switch tube 60 and one slde of pulse
network 84 m e DC power supply 80 is ad~usted to
provide a voltage of from about I0 to 10,000 volts DC
ich app-ar~ acros3 the electrodc~ of corona-cell 105
~he pul~e g-ner~tor 64 i~ ad~u ted to provide a
.. .. .. _ ,, ,
fr qu ncy output $n the range of 0.1 to 200 RHz at a
volt~g- of from about 100 to 10,000 v
A the pulse forming network 84 the inductances 85, ~ ;~
86 and 87 ar ~el-cted to have a value of from about
~ . . .
1.0 to 1000 microhenry, while the capacitances 91, 92
and 93 are -lect-d to have a v~lue of from about 10-6
to 1 microfarads. It is seen that by pulsing the pulse
~or~ing network from the sw~tch tube circult the output
of the pulJe forming n-twork appears acro~s the stepdown
tran~former 100 Slnc- the transformer 100 ~ of a step-
do~n type, preferably the primary to secondary winding
....
..
' 4
:,'
.
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.. -. - . . .. . ~
- - - . . . .
.
~ . . . , , ,
. l ~
~066659
ratio will have a value of from about 1 2 to 1 100 and
it is seen that the inductance characteristics of the
power supply may be readily matched to those of the
corona cell
In one preferred practice of my invention a
reaction system is utilized wherein a reactant gas
~tream is passed through a corona reaction gap in
~hich narrow pulse electrical power is dissipated in
the gap at a frequency such that the reactant gas i8
sub~ect to a limited number of corona pul~es, preferably
not more than about 5 to 100 electrical pulses prior
to removal from the gap The gas is then preferably
held in a non-corona zone or receiver for sufficient
time to permit recombination of the heavy gas ions
Preforably ~he reaçtant ga~ is held;under positive
pr ~sure to incroase the rate of recombination
A~ ind~cated abov , th~ duration and magnitude
of tho pow r pul~o i8 ~ufficient to accelerate electrons
_ to produco a desired chemical roaction but is
~ub-tantially 1088 than the time required for a gas
lon to be acc-lorated to a level whore appreciable
n-rgy i~ ai~sipated thereon The reactant gas is
pr ferably maintained at a high rate of flow through
th corona discharge gap 80 that gas ions formed
during given corona pulses aro removed, that is, ~swept~, ;
~rom the gap by movement of the reactant gas stre~m
prior to b-ing sub~ected to subsequent corona pulsos
1066659
In this manner the charged gas molecules or ions are
not accelorated by ~uccess`i~e energy pulses to a
point wherein a substantial amount of kinetic energy
i~ imparted thereto, which in turn $8 dissipated as
wa~te heat
A more clear understandiAg of my present invention
~ay be obtained by reference to figure 7, which
- comprise~ a block diagram which represents preferred
~ thod~ for pract~cing the present invention In
figure 7, lll repre~ents a reactant gas source ~uch
a- an oxygen-containing gas when ft is desired to
; produce ozone, which i8 connected by mean~ of conduit
112 to a corona gen rator 113 Preferably, the corona
r action zone of generator 113 is short with respect
to gas flow, that i~, the width to iength ratio is
- gr ater th~n 2 to 1 and pr-ferably up to 100 to 1 with
~-~p-ct to th dire¢t$on of ga- flow The r-actant
- ga- pro~d d at 111 i~ und-r pressur ~uffici-nt to
cau~- the d ~ired rate of flow ~hrough the generator
113 Corona generator 113 is in turn connected by
~ean- of conduit 11~ to a reaction product recoiver 115
Th r action product rec~iver 115 i~ in turn connected
by ~ean- of a conduit 116 to a second corona generator
117, which in turn i- provided with an outlet conduit
118. The u~- of the ~econd corona generator 117 is
optlonal and is ut$1iz-d when it is desired to produce
a high concentration of desired reactant species and
'~ \ '
'-
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" ' . ' :'
- 26 -
', , , . ' - ' `,
~,
- ~ ,,
1066659 . -
the reaction product It i~ also to be understood
that more than 2 corona generators may be utilized, as
long a~ an additional receiver accompanies each
additional corona generator
Figure 7 also show~ another alternative preferred
practice of the present invention, wherein the
reaction product contained in the reaction product
receiver 115 may be recycled by means of conduit 119
through the corona generator 113 This recycle
feature, which iJ optional, is ut$1ized to produce a
higher concentration of ozone or reactant product than
would normally be produced by a once-through pa~s
through the corona generator
The use of the reaction product receiver 115 in
addition to prov$ding means for s~oring the reaction
product which ex$ts from a given corona generator,
~uch as 113, may provide the add$tional funct$on of -
holding the ga~ for an ~nterim period between xposure
to corona to permit recombination of positive and
; ~Q n-gative charged particle ion debris which is produced
~t any giv n corona generat$on step Furthermore, the
corona r action product receiver 115 may be provided
~lth cooling m an~ to provide a method for el~m~nating
or r moving any excess heat which may be formed
A~ indicated abov , the present invention
¢ont~mplate~ the u~- of multiple corona generators
~hich are preferably provided with interim reaction
.
'
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:- '':' ''
.
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1066659
~;product holding means 80 that the reaction product of
any given corona generator may be permitted to stand
prior to being sub~eeted to additional treatment by
eorona. The present method may also be practiced
u ing a single eorona generator, particularly when it
is de~ired to produee a reaetion produet eontaining
only a small guantity of the desired product
Figure 7 also describes another preferred practlce
of my~invention wherein heavy gas ions are managed,
; 10 that i~, neutralized, by the addition of a neutralizing
., .
partieulato solid or liguid component In figure 7 a
neutralization component source 120 i~ conneeted to ~ - the eonnecting eonduit 112 by means of a conduit 121
In operation, a neutralizing component compris~ng
n gatively eharged particles of a finely divided solid
or liguid ~ueh as ~iliea gel, earbon blaek or water in
th ~ize range of about 0.001 to 0.1 mieron is supplied
trom the ~oure- i20 a~ hown in ~igure 7 and metered
through th eonduit 121 into the feed gas ~tream. The
20 amount of neutralizing eomponent added is approximately ~~
that amount whieh will provide a negative eharge for
aeh po~itively eharged gas ion present in the eorona
; di~eharge gap
~ n a typieal preferred praetiee of the invention
a wat r aerosol i8 added as the neutralizing a~ent in
an amount to provide a water to ozone weight ratio
of about 25 To arrive at thi~ e~timate, it i8 a8~Umed
-- .
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1066659
that ln producing 2 percent ozone from oxygen feed,
- one free accelerated electron produces about 500
ozone molecules If water is added to the oxygen feed
ga~ as droplets having a diameter of 0 01 micron, it
18 calculated that one droplet will weigh lO~19g and
comprise 0 3 x 105 water molecules Since each
lectron (which i~ a~sumed to produce about 500
ozone lecules) results in the formation of one
p w itively charged gas ion, it i~ rea~oned that 60
water lecule~, that i~
:'' ' ' '' :
~ - 0 3 x-105 ~ 60-, -
- 3 500
,
e r~gu~red per ozone lecule On a weight basis,
it ~- calculated that 1 part by weight of ozone reguires
bout 25 part~ by weight of water to produce the
d-~ir d r -ult, that is
.. . .
~- ~ x Nol Nt ~0 - 60 tl8~ ~ 25
~ 03 Mol Wt 03 48
'- .. ,~ .
The fln-ly divided water may be conveniently added
to th reactant gas stream in the form of an aerosol
obtained from saturated ~team It i~ estimated that
~her the feed ga~ is used to produce 2 percent by
ight ozone, ~ufficient moisture (steam) should be
added to yield a feed ga~ having about a ~175-F dewpoint
-~.
~ .
~'-' ' .
:; :
1066659
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