Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WET SCRUBBING DEVICE, IN PARTICULAR FOR
SEPARATING GASES AND/OR LIQUID AND/OR SOLID
IMPURITIES FROM GAS STREAMS
The invention refers to a wet scrubbing device, in
particular for separating gases and/or liquid and/or solid
impurities from gas streams, with two-component noz~les being
O provided for introducing the washing liquid.
2 The necessity to increasingly minimize the emission of
3 pollutants from industrial plants to reduce any health hazard
4 to the population in densely populated areas and the pollutant
~5 level of air, water and ground requires an almost complete
6 purification of these pollutant-laden gases and poses a
17 challenge to the modern environmental technology.
9 Besides existing dry dust removal systems, dust scrubber
O systems were increasingly developed over the last years which
1 are applicable especially for great amounts of exhaust gas
2 because of their low energy consumption and water consumption
3 and, moreover, because good separating capacities in the
4 superfine dust range are achieved.
6 The operation of these wet scrubbers is based on the
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.1transformation of the dust particles in the dust-removing
2compartment from the aerodispersion in a liquid.
~3
4Especially advantageous proved the separation by means of
~5washing liquid droplets which form a mist of superfine
~6droplets when spraying the liquid into the dust-removing
7 compartment. A very fine and narrow droplet spectrum with a
-~8 droplet size between 5 and 50 ym is attained through use of
~9 particular two-component nozzles.
~10
~11The DE-OS 30 31 951 shows several nozzles in a nozzle
~12plane which, however, are commonly connected to a central feed
~13pipe.
~14 -
~15The DE-OS 26 23 033 discloses two planes with several
16nozzles per plane in the inlet conduit or in the subsequent
~17pipe nozzle, respectively, which, however, are also supplied
18with wash water via a central feed pipe.
~19 ::
i20The construction according to the DE-AS 24 34 664 includes
~21an annular arrangement of several spray nozzles located on one
;122plane. In particular, it is referred to the relative small
~23distance between individual nozzles relative to each other and
~24 relative to the wall surface of the nozzle compartment.
~Iowever, there is no reference to the return flow attained
26 thereby. Also here, a central feed pipe is described
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1 for the washing liquid which is directly connected to the
nozzles without any additional control device - presumably via
~3 feed pipes which radiate from the central pipe to the nozzles.
Furthermore, the use of a nozzle lance for a particular
geometric cross-section is illustrated.
j7 All these known devices have the characteristic of
-~8 allowing adaptation of the optimum mean droplet diameter via
the respective liquid/gas-mass streams in dependence on the
~0 dust load and dust size, but they are not or only
1 insufficiently secured against mishaps.
~2
-~13 The previously mentioned two-component nozzles are subject
~i4 - in particular during use of circulation liquid - to an
~5 increased stress through corrosion and erosion. Further, there
~6 exists an increased danger for clogging.
~8 All these disturbing circumstances cause a shutdown of the
~9 wet scrubber in order to allow replacement of the defective
~0 nozzle, or that the breakdown of a nozzle in an arrangement of
~21 several nozzles in a plane remains unnoticed since the
22 corresponding pressure change is too low and, moreover, is
~3 compensated through pressure changes and thus modified
24 operational conditions in the remaining nozzles. The mishap is
~25 only noticeable at simultaneous breakdown of several nozzles.
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I It is an object of the invention to create a wet scrubber
which operates with two-component nozzles, as well as supply
~3 units for these two-component nozzles to enable a continuous
`~ operation of the plant upon breakdown of a nozzle without
:5 interruption and without limitation of the cleaning
,6 performance, and to replace the defective nozzle without
7 interruption of the operation.
'~8
9 This object is attained in accordance with the invention
by arranging the two-component nozzles at the outflow sides of
lances, with each lance being provided with one or more
~12 nozzles wherein the center axes of the lances lie on a plane
~13 perpendicular to the gas flow direction, and by allowing
~14 withdrawal and reinsertion of each individual nozzle lance
~15 from the washing area of the device, preferably by means of
~16 flanges. In this manner, an even distribution of the washing
~il7 liquid over the whole gas stream cross section is attained
~18 while, at breakdown of a nozzle or a nozzle group along a
~19 nozzle lance, the nozzle lance which is provided with the
~20 nozzle or nozzles is withdrawable individually from the
~21 washing area of the device so that the operation can proceed
22 with the same cleaning effect, possibly while changing the
-~23 particular supply of the neighboring nozzles.
~24
Advantageously, one or more further nozzle planes with
~26 same or different number of nozzles can be arranged in
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succession of the first nozzle plane so that through
cooperation between several nozzle planes the tasks of the
individual nozzle planes can be controlled in such a manner
that the nozzle plane provided upstream in flow direction
initiates an enveloping of the dust particles to be separated
and the succeeding further nozzle plane then terminates the
`l enveloping to bring the liquid particles, laden with solid or3 other pollutants to be separated, in an easy to separate
j state. The nozzles may be combined individually or in groups
LO with separate supply conduits for the washing liquid as well
~Ll as for the atomizing gas. This enables an individual control
~2 of the atomizing conditions of the individual nozzles or
fil3 nozzle groups. Thus, the scrubber casing is provided in one or
~4 several planes, preferably in two planes, with a number of
~n 5 nozzles on so-called nozzle lances, with each individual
q~6 nozzle or several nozzles of a lance including a separate
il7 supply conduit for the washing liquid and a further separate
-l18 supply conduit for the gaseous atomizing gas. Distinct
i19 measuring devices and control devices for the individual
At20 supply may be incorporated in each of the supply conduits. In~21 this manner, each individual nozzle is separately controllable
22 or adjustable so that the droplet size and the droplet number323 per time unit for each nozzle or each nozzle group can be
~24 individually controlled through modification of these
~25 operational parameters. Thus, the wet scrubber can be best
526 suited to the respective cleaning problem - in particular
.
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1 during breakdown of a neighboring nozzle - and can be
2 controlled over a great range upon changes of concentration of
3 the material being washed out (solid dust, liquid droplets or
~4 pollutant) in the gas stream. The wet scrubber can be
~5 precisely adapted in an optimum manner to the prevailing
~6 separation problem through the mutual distance of individual
~7 nozzle lances and through the distance of nozzles per nozzle
~8 lance, i.e. through the mutual distance between neighboring
~9 nozzles. A defect in the plant because of a defective nozzle
~10 (e.g. through clogging or through wear) is indicated through
11 the pressure change or change of the amount of washing liquid
~ 12 in the respective supply conduit. During a disturbance, the
-,13 one nozzle lance which contains the defective nozzle is then
~ 14 withdrawn from the wet scrubber. The operation of the scrubber
`~ 15 can be continued undisturbed. Since the obtained wall opening
16 is very small compared to the inner diameter of the scrubber,
17 and the wet scrubber is preferably operated at low pressure,
18 no uncontrolled gas discharge through the wall opening occurs
19 during removal and replacement of a nozzle lance. This wall
opening may also be closed in a known manner temporarily
21 through a dummy flange or the like.
22
~- 23 Since all other nozzles continue to operate unchanged, and
,
24 only in the are& of the temporarily removed nozzle lance a
slightly different turbulence gas stream is created which
;~ 26 however results primarily in a gas return flow, the effect of
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' the missing nozzle lance on the degree of separation is
2 negligibly small. However, in case the prescribed pollutant
~3 level is exceeded, it is possible to compensate this by
-4 variations of the operational fluids (pressure, throughflow of
the washing liquid as well as of the atomizing gas) of
6 neighboring nozzles. This nozzle arrangement and operation
7 ensures a highest possible degree of safety and reliability of
8 the wet scrubber.
' 9
According to a preferred embodiment, each of the
11 two-component nozzles may include a nozzle body set in a
12 nozzle holder and having a rear end connected to a liquid
13 supply conduit and a preferably central casing area which
14 includes bores for connecting the interior of the nozzle body
with the atomizing gas conduit. Thus, the atomizing gas is
16 introduced in the nozzle transversely to the direction of the
17 liquid flow so as to create a respectivzly high impulse of the
18 washing liquid in flow direction and to guide the respectively
19 superfinely distributed washing liquid exiting the outlet
opening of the nozzle into the gas stream to be cleaned. The
21 casing area of the nozzle body, provided with the bores, may
22 be enclosed by an annular space which is provided in the
23 nozzle holder and communicates with the atomizing gas conduit
24 so that the introduction of the atomizing gas is attained
evenly all around the wa~hing liquid stream.
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1 In the area of the nozzle flow, contact between washing
2 liquid droplets and pollutants to be separated, e.g. dust
3 particles, occurs in a mixing zone with high turbulence. The
4 suction effect of the atomizing gas and the impulse transfer
of the atomizing gas to the pollutant-laden gas generates a
~6 forward acceleration of particles of the pollutant-laden gas
7 stream which forward acceleration must be compensated through
8 a return flow between the nozzles or between nozzle and
~9 scrubber inner wall, respectively (pulse conservation). This
~10 means that parts of the gas stream being cleaned circulates
~11 until finally flowing through the energy-rich nozzle flow
12 zone. The distance between nozzles as well as the number of
13 nozzles is randomly variable and depends on the respective
14 cleaning problem of the wet scrubber.
~;j16 An exemplified embodiment of the subject matter of the
J 17 invention is illustrated in the drawing.
5~ 18
19 FIG. 1 shows schematically a longitudinal section
~20 through the gas scrubber in the area of a nozzle lance.
~21
-~ 22 FIG. 2 is a cross section through the gas scrubber,
23 with individual nozzles and nozzle lances being illustrated in
24 a bottom view.
26 FIG. 3 shows a section through a nozzle body.
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1 A gas scrubber 1 includes two-component nozzles 2, 2', 2''
- 2 which are mounted to a common nozzle lance 3 incorporating the
, 3 liquid feed conduits 4, 4', 4'' and atomizing gas feed
4 conduits 5, 5', 5''. The nozzle lance 3 is attached at the
- 5 inner side of a flange 6 which is inserted in the gas
6 scrubber 1 via an opening in the wall thereof. The flange is
7 mounted in a conventional manner to the gas scrubber, e.g. by
~8 not shown screws. As can be seen from FIG. 1, each of the
9 nozzles 2, 2' and 2'' is associated with a separate washing
liquid conduit 4, 4', 4'', and an atomizing gas feed
11 conduit 5, 5' and 5''. The separate feed conduits 4, 4'
12 and 4'' for the washing liquid are connected to a washing
; 13 liquid feed conduit 7 and the atomizing gas feed conduits 4,
14 4' and 4'' with an atomizing gas feed conduit 8 (see FIG. 2).
~iY 15 Incorporated between the feed conduits 7 and 8 and the
~-1 16 conduits 4, 4', 4'' and 5, 5' and 5'' which communicate with
17 the individuàl nozzles are not shown special measuring and
18 control devices ~uch as valves, flow rate gages and the like
19 which enable a separate control of supply to the individual
320 nozzles.
~21
~,22 The two-component nozzle 2 shown in detail in FIG. 3
~23 includes a nozzle holder 10 and a nozzle body 11 which is
~24 snugly fitted in the nozzle holder, e.g. bolted therein as in
the present case. The nozzle body 11 includes a nozzle head 14
J 26 and a nozzle throat 15 provided with an external thread and
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1 bolted in the nozzle holder 10. The nozzle throat 15
.;.2 preferably has in its center area bores 12 by which an annular
3 space 13 which surrounds this center area is connected to the
'4 interior of the nozzle body 11. The annular space 13 is
connected with the gas feed conduit 5 via a connecting channel
;6 16. For supply of washing liquid, the rear end of the nozzle
7 throat 15 enters the washing liquid fee conduit 4.
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