Gas and liquid contact apparatus – Contact devices – Liquid spray
Reexamination Certificate
1994-08-17
2001-03-20
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Liquid spray
C261SDIG001, C096S257000, C096S366000
Reexamination Certificate
active
06202990
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Art
The present invention relates to a spray tower or cooling, moistening and/or purifying a gas. More particularly, the present invention relates to a dry spray tower and method whereby water and/or an absorbing solution is sprayed by a spray nozzle attached in the vicinity of the top of the spray tower, thereby cooling and moistening a gas and/or removing a harmful component from the gas without producing waste water.
2. Prior Art
To cool and moisten a gas and/or remove a harmful component from the gas, a dry spray tower has heretofore been used.
FIG. 5
, for example, shows a typical conventional dry spray tower in which the gas
5
a
is introduced into the tower from the top
1
thereof through an expanded portion
2
and sprayed with water and/or an absorbing solution by a spray nozzle
4
attached in the vicinity of the top of the tower, and in which the sprayed water and/or absorbing solution is completely evaporated in the tower so that no waste water is produced. In such a spray tower, a swirling motion is often given to the gas when introduced into the tower.
The conventional technique suffers, however, from the problem that liquid droplets sprayed in the vicinity of the top of the spray tower collide with the inner wall of the tower and the liquid flows down as far as the bottom, resulting in waste water.
That is, in the conventional spray tower, as shown in
FIG. 5
, the flow velocity of gas is relatively fast in the central portion of the tower at a position immediately downstream from an expanded portion
2
through which the exhaust gas is introduced into the tower, whereas it is relatively slow in the peripheral portion of the tower. Therefore, at the downstream side of the expanded portion
2
, the gas whirls up from the central portion toward the peripheral portion of the tower as shown by an arrow
5
b.
As a result, sprayed liquid droplets collide with the inner wall of the tower, giving rise to problems as described above. In particular, when the temperature of the exhaust gas, after the sprayed water and/or absorbing solution has evaporated, is lower than the dew point of the gas plus 50° C., it is difficult for liquid droplets having collided with the inner wall to re-evaporate. Therefore, there is a very strong possibility that the liquid droplets colliding with the inner wall will flow down as far as the bottom to become waste water. Further, when the gas contains dust, the dust adheres to the inner wall wetted with the liquid droplets.
Further, in a case where a swirling motion is given to the gas when introduced into the spray tower, the centrifugal force induced by the swirl of the gas tends to encourage the collision of sprayed liquid droplets with the inner wall of the tower, which enhances the problem.
Therefore the object of the present invention is to solve the above-described problems of the conventional technique and to provide a spray tower and method for cooling, moistening and/or purifying a gas, wherein sprayed liquid droplets are prevented from colliding with the inner wall of the tower, thereby preventing generation of waste water and adhesion of dust to the inner wall of the tower.
SUMMARY OF THE INVENTION
To solve the above-described problems, as shown in
FIG. 1
, the present invention provides a dry spray tower without producing waste water, having a top
1
provided with a gas inlet port, an expanded portion
2
extending downwardly from the top while radially gradually enlarging, and a spray nozzle
4
attached to the expanded portion or a portion immediately downstream from the expanded portion to spray water and/or an absorbing solution, thereby cooling and moistening a gas and/or removing a harmful component from the gas, wherein a gas distributing device
6
is disposed in or around the expanded portion at a position upstream from the spray nozzle for making the downward component of flow velocity of the gas faster at the peripheral portion of the spray tower than at the central portion thereof.
An effective example of the above-described gas distributing device may be a perforated plate having a higher opening ratio at the peripheral portion than at the central portion thereof, a perforated plate provided in such a manner that an annular slit or gap is formed between the peripheral portion of the perforated plate and the inner wall of the expanded portion or a straight wall portion of the tower, a combination of a perforated plate crossing the inside of the tower and a distributing grille provided above or below the perforated plate, a combination of a pair of parallel perforated plates disposed in such a manner that an annular slit or gap is formed between the peripheral portion of each plate and the inner wall of the expanded portion or a straight wall portion and a distributing grille sandwiched between said pair of perforated plates, or a device composed of a multiple skirt-shaped guide plate for aiding the spread of exhaust gas and a perforated plate having a diameter smaller than that of the tower and disposed at the bottom of the central portion of the guide plate.
In addition, the present invention provides for a method for cooling, moistening and/or purifying a gas without producing waste water, in which a gas introduced into a spray tower from the top through an expanded portion is sprayed with water and/or an absorbing solution by a spray nozzle attached to the expanded portion or a portion immediately downstream from the expanded portion, thereby cooling and moistening the gas and/or removing a harmful component from the gas, and in which the temperature of exhaust gas after the sprayed water and/or absorbing solution has evaporated is lower than the dew point of the gas plus 50° C., wherein the introduced gas is distributed at a position upstream of the spray nozzle so that the downward component of flow velocity of the gas is faster at the peripheral portion of the spray tower than at the central portion thereof.
In a conventional spray tower, as stated above, the flow velocity of gas is relatively fast in the central portion of the tower at a position immediately downstream from the expanded portion through which the exhaust gas is introduced into the tower. Therefore, at the downstream side of the expanded portion, the gas whirls up from the central portion toward the peripheral portion of the tower and sprayed liquid droplets collide with the inner wall of the tower, giving rise to problems as described above.
On the other hand, in a spray tower and a method for cooling, moistening and/or purifying a gas according to the present invention, as shown in
FIG. 1
, the flow velocity of gas is faster at the peripheral portion than at the central portion of the tower, and the gas whirls up from the peripheral portion toward the central portion in a reverse manner to that of the prior art. As a result, sprayed liquid droplets are prevented from colliding with the inner wall of the tower. Accordingly, there is no possibility that liquid droplets will collide with the inner wall to become waste water or that dust in the gas will adhere to the wall surface wetted with liquid droplets.
In the spray tower of the invention, there is no possibility that liquid droplets will flow down on the inner wall of the tower to produce waste water even under operating conditions where the temperature of the exhaust gas after the sprayed water and/or absorbing solution has evaporated is lower than the dew point of the gas plus 50° C.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative examples.
REFERENCES:
patent: 3396207 (1968-08-01), Bartholome et al.
patent: 3461682 (1969-08-01), Darby
patent: 4293521 (1981-10-01), Isahaya et al.
patent: 4693852 (1987-09-01), Gordon
patent: 4882020 (1989-11-01), Maezawa et al.
patent: 4915712 (1990-04-01), Felsted
patent: 22441
Fujita Kenji
Izutsu Masahiro
Ohbuchi Masashi
Bushey C. Scott
Ebara Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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