Note: Descriptions are shown in the official language in which they were submitted.
1~56578
SPECI~ICA~IO~
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This invention relates to improvements
in the treatme~t of waste gases, such as a hot
gaseous mixture, produced b~ combustion in a
~urnace or the like, in which pollutants may
consist of active chemical substances, as well
as solids and other inert gasO
- It is well known that fossil fuels,
such as coal and petroleum products contain, in
addition to the hydrocarbons, sulphur cr ma-terials
combined with sulphur, and the combustion process
combines these m~terials into chemicall~ active
~0 substanc~s in a gaseous form that may contai~ S02
and/or S03, which are highly undesirable, since
these gases are injurious in themselves and in
the presence of moisture may ~orm sulphurous or ~.
sulphuric acidsO
In the present invention, in addition
to providîng means for removing solids from the
flue gases, provision is also made to remove the
sulphurous products by reacting the same with
another substance such as ~a2CO~, and thereby
formulate a dr~ crystalline compound that would
have commercial value.
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In more particularity 9 the chemical
reaction causing such precipitation and the
removal of pollutants from the dust-gas mix-
ture may, in the preferred embodiment, involve
a novel apparatus and method of desulphurization
of hot ~lue gas.
An object of the invention i9 to
provide an improved method and means for treat~
ing a p~luted gaseous mixture, such as hot flue
gas by mechanically removing particulate solid
matter therefrom, and further, by removing other
pollutants in the hot flue gas by chemical
reaction, causing precipitation thereof in a
novel manner.
A further object of the invention is in
the provision of a novel method and apparatus for
removing a pollutant from a hot gaseous mixture
b~ passing the mixture through a channel having
therein at least two non-horizontal portions
wherein the mixture is subaect to reaction wi~h
another chemically active substance to produce
precipitation of the newly formed compound i~ a
step-by-step manner.
A further object of the invention is in
the provision of a novel method and apparatus for
removing a pollutant~ such as S02~ and/or S03
from a hot gaseous mixture wherein the flue gas
is exposed to a strong but mist-like flow o~ a
reagent, such as ~a2C03 in solution, which chemi
call~ reacts with the pollutant to produce preci-
pitation while the gas flow is in one direction,
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such as descension in a passage, during which a
major portion of the sulphurous substance in the
gas is precipitated, and following a substantial
reversal o~ direction of flow of the flue ~as to
expose the remaining S02 and/or S03 in the gas
to a ~urther mist-like spray of the same reagent
solution for ~urther precipitation.
The above and further objects of the
invention may become apparent by re~erence to the
accompa~ying drawing, showing a preferred embodi-
ment thereo~, along with the accompanying descrip-
tion thereo~.
~ he sole figure, comprising the drawing,
shows in a flow diagram a novel method and s~stem
for eliminating pollutants in flue gas emitted
from a furnace.
In said figure, a pollutant removing
system in its entiret~, indicated by general numeral
10, receives hot flue gas from a furnace 129
through a conduit 14~ The flue gas, as it leaves
furnace 12 has a temperature of about 3Q0-350F.,
and includes various pollutants which render the
flue gas below an allowable ecological standard
for delivery to the atmosphere~ Consequently, the
flue gas is delivered to a ~ly-ash collector 16,
wherein a major portion of the entrained solids
are removed and from which the gas flows through
a suitable conduit 18 to a novel separati~g tower 20.
~he separating tower 20 is of generally
sinuous, or U-shaped con~iguration. Its inlet end
22 extends from conduit 18 to a non-hori~ontal
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or descending portion or passage 24 that aoin3
one side of a hopper 26. ~he hopper 26, in turn,
is connected to a non-horizontal or ascending
portion or passage 28 of the tower that has a
discharge opening 30 that joi~s a conduit 32
containing a damper 34~ Conduit 32 extends to a
~iltering device 36, which device is connected b~
a conduit 38 to a further flltering device 40.
~rom the filtering device 40, a conduit 42 ex~ends
to a blower 44 which~ in tur~, connects to a
chi~ney or other gas disposal device 46.
Hopper 26 forms a common connecting
passage between portions 24 and 28 of the tower 20,
and its lower end is connected b~ a conduit 48 to
a discharge trough 50 o~ a product handling system~
Trough 50 is also connected b~ discharge conduits
52 and 54 from the filtering devices 36 and 40,
and extends to a common collecting container 56~
The fl~-ash collector 16 has a discharge
passage 58 which extends to a trough 60, which, in
turn, connecte to a disposal container or fl~-ash
storage hopper 62.
~ o provide a solution to chemically
react with sulphurous substances in the gas~ a
storage bin 64 adapted to receive a chemically
active material, such as Na2C03 9 or o-ther basic
material, is provided with a valve 66 that forms
a controlled passage to a conduit 68 which, in turn~
extends to a hopper 70. Hopper 70 is prov~ded with
a valve 72 connecting to a conduit 74 whlch extends
to a mixing tank 76. A water supply line 78,
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containing a valve 80 also extends to the mixing
tank 76. The tank 76 is provided with an agita-
tor 82~ driven by a motor means 840 .A conduit
86, containing a valve 88 extends from the mixing
tank 76 to a feed tank 90, which contains a screen
or o-ther filtering device 92. A pump 94 has its
inlet connected by a conduit 96 to the feed tank
90, and said pump has its discharge end conne~ted
to a pipe 98 extending to the mixing tank 76, and
contains a Yalve lOOo
A pump 102 has its inlet end connected
to a conduit 104 which extends from a lower e~d
of the feed tank 90. ~aid pump has its discharge
end connected to a conduit 106 which contains a
valve 108 and extends to a spray-head 110 located
in the upper end of portion 24 of tower 20.
Another spra~-head 112 also extends from conduit
106 within the tower portion 24 beneath the spra~-
head 110, bu-t above the hopper portion 26. A con-
duit 114 containing a valve 116 extends from con-
duit 106 to a spray-head 118 that is disposed
within the interior of portion 28 of the tower 20.
Reference numeral 120 designates a sens-
ing device which is reactive to a condition within
portion 24 of the tower 20, such as the proportion
of sulphurous material present in the gases in
that portion of the tower downstream of spra~-
heads 110, 112, in the direction of gas flow.
Reference character 122 indicates a similar sens-
~0 ing device that is reactive to the condition of
the gases in portion 28 of tower 20 downstream of
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spray-head 118. ~he sensor 120 is operatively
connected to valve 108; while sensor 122 is
operatively connected to the valve 116, each of
said sensors being adapted to con-trol the posi-
tioning of the respective valves 108 and 116 so
as to control or modulate the quantit~ of
material such as the reactive solution through
the respective valves. A sensor 124 for se~sing
humidity or other similar conditions wi-thin the
lower portion of hopper 26 is operati~ely con-
nected to a differential control device 126 which
also, like se~sor 120, has the capacity of con-
trolling valve 108.
~he operation of the invention and the
system disclosed in the drawing will now be dis-
cussed. With combustion of fossil fuel occurring
in the furnace 12, hot waste flue gases emitte~
from the furnace at about 300-350~. are trans-
mitted through conduit 14 to the fly-ash collector
16 where a major portion of the solids present in
the gases will be removed. ~he gas, with other
pollutants therein, then passes through conduit
18 to the inlet end of tower 20, where it flows
downwardly through the leg 24. A reactive solu-
tion composed of about 5/~12% of ~a2C03 in water
is formed in the mixing tank 76 and dispensed to
the feed tank 90, The solution is circulated be-
tween the mixing tank and the feed tank to main
tain a relatively uniform solution~ The solution
is then delivered by pump 102 to conduit 106 and
through the valve 108 -therein to the spray-heads
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1 110, 112, where it is sprayed in a mist-like form into the
gases descending through portion 24 of the tower 20, preferably
in opposition to the direction of flow of the gas. The
following chemical reaction occurs:
S2 + Na2C03 -~ > Na2S3 + C2
I + O -----> Na2S04
and
SO3 ~ Na2CO3 ------> Na2S4 -~ C2
In a typical reaction with the products of combustion
1~ of a fossil fuel the above specified compounds produce
approximately 71%-76~ Na2SO3 (sodium sulphite) and 10%-20
Na2SO~ (sodium sulphate), depending upon the combustion
conditions and th~ fuel composition.
Although sodium carbonate in the percentage range
noted in the prior paragraphs is the preferred embodiment,
that is the range of 5~ to 12%, the basic compound obtained from
thermal decomposition of trona (urao) could be used to react
with the SO2 and SO3 to form the by-product. In factl any
suitable strong basic compound which would react with SO2 and
SO3 to form a particular by-product would be suitable.
The gases flowing downwardly from the le~ or portion 24
into hopper 26 will normally not be completely free of the
sulphurous compounds, but these gases then flow upwardly
through the leg or portion 28, where they are again sub~ected to
a spray treatment with the Na2CO3 solution, which in this
instance is sprayed downwardly against the flow path of the gas.
The control of the flow of solution to spray-heads 110, 112 and
118 is by the valves 108 and 116 responding to the sensors 120
and 122.
The total flow of the Na2CO3 solution is controlled so
that a maximum amount of SO2 and/or SO3 are removed from the
flue gas, but in a condition such that the precipitate is
- relatively dry~
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1~565~
The sensor-120 acts to allow flow of solution
through valve 108 -to remove a maJor portion of
the sulphurous substances from the gas, but in
the interes-t of economical use of the ~a2C0
solution there should be a small amount of
sulphurous substance remaining in the flue gas
entering hopper 26 and passing upwardly through
the portion 28. However, the sensin6 device 122,
which reacts ~o the g~ses a~ter treatmen-t b~ the
spray-head 118 should substantially eliminate
free ~2 and/or ~ree S03 from the flue gases. It
is highly desirable that the precipitate be in a
dry dust-like condition, and despite treatment of
the gases with a water-containing solution1 this
is possible because of the high temperature of the
gases. Nonetheless, the control device 124 is
reactive to the humidity conditions in the hopper
25 and its function is to coordinate the total
flow of liquid through the valve 108.
As a further control of the react~n be-
tween the ~a2C03 and the sulphurous oxides within
the flue gases in tower 20, damper 34 is utilized
to control the flow of gases from tower 20 to and
through the filtering devices 36 and 40 to the
chimney 46. Damper 34 controls flow rate of the
gas and thus the time that gases are in tower 20,
thereby yielding more efficient and complete
cleaning of the S02,S03 from the gas. Therefore,
proper control of the chemical reactions and of
the mechanical filtration is su~aect to control
on the one nand by the sensing devices 120, 122
and 124, and also by the flow control device 34D
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A~ter leaving leg or portion 28 of
tower 20, the gases flow through filtering
devices 36 and 40, which are composed of cyclone
separators, or other forms of mechanical separa-
tors that will remove any residual portion o~
the precipitate, or other solids present in the
waste gases before they are discharged b~ blower
44 through the chimney ~6~
m e solid materials constituting the
precipitates and other solid materials, i~ any,
àre gathered in the product storage hopper 56.
As noted above, a major portion of this material
may consist o~ ~a2~0,~ (sodium sulphite), which
will find commercial value in other industries~
such as paper making or the like.
