Tapered gas inlet for gas treatment system

Details Tapered gas inlet for gas treatment system Tapered gas inlet for gas treatment system

1999-11-15

2001-12-11

Simmons, David A. (Department: 1724)

Gas separation: apparatus

With gas and liquid contact apparatus

Means forming flowing contact liquid film on apparatus...

C261S116000, C261SDIG003, C055S418000, C055S434000

Reexamination Certificate

active

06328790

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the field of systems for treating a flow of gas and is particularly related to an inlet system for providing a uniform flow of gases to a treatment chamber, such as a gas conditioning tower.
BACKGROUND OF THE INVENTION
The treatment of flowing gases is a common requirement of various industrial processes. For example, contaminated effluent gases are commonly generated by industrial processes and require treatment to remove pollutants prior to being exhausted into the atmosphere. While the present invention will be described in connection with a pollution control system, those skilled in the art will appreciate that the invention has application to other systems which require the treatment or processing of flowing gases, particularly high volume gas flows.
Many air pollution treatment systems include a variety of stages, with effluent gases flowing through ducts from one treatment stage to another en route to being discharged. For a variety of reasons, e.g., in order to save space, to avoid settling of dust in horizontal ducts, or because certain treatment processes work best when the gas flow is oriented in a particular way, the gas flow often must be redirected as it moves through the system. Specifically, it is often necessary for the gas flow to make an abrupt or “hard” turn, i.e., greater than 30°, prior to the entrance to the treatment device. Many treatment devices operate most efficiently when the gases flow uniformly from the inlet of the device. This presents a difficult problem when the gas flow must be redirected, sometimes by as much as 180°, prior to entering the treatment stage. Where there is a large volume and relatively high flow rate of gases moving through a treatment system, redirecting the gas flow can create substantial non-uniformities in the flow.
For example, a commonly used device in an air pollution control system is a gas conditioning tower (“GCT”). In a GCT water is injected into a flow of hot gases to reduce the temperature and to humidify the gases. A GCT might be used, for example, to condition gases prior to treatment in an electrostatic precipitator where dust particles are removed. In a GCT, gases normally flow vertically from top to bottom, with water being injected into the gas flow near the upper, entrance end of the tower. The time required to evaporate the water spray can be calculated with considerable accuracy if the gas flow is uniform and the spray droplet size distribution is known. However, if the gas flow is not uniform, the calculation becomes much more difficult, and the efficiency of the system is reduced. Non-uniform gas flow results in non-uniform distribution of the spray within the gas flow, non-uniform transit time of the gases through the GCT, coalescence of the spray droplets and consequently inefficient operation of the system.
FIG. 3
is a depiction of the gas flowing at various locations through a GCT
10
with a prior art inlet
5
calculated using computer modeling. Inlet
5
to GCT
10
of
FIG. 3
merely redirects the gas flow 180° from vertically upward to vertically downward at the entrance to the GCT. Vectors
50
show the direction and speed of the gas flow at the various locations in the system. As can be seen, the gases are very poorly distributed in the GCT, particularly at the entrance to the GCT, with some of the gas flow being in the upward direction opposite to the overall downward flow. The non-uniformity of the gas flow through the prior art GCT degrades the efficiency, operation and performance of the system.
One prior art solution to flow non-uniformity is to use a series of baffles. This approach, however, has the disadvantage of impeding the gas flow, requiring the use of greater energy to move the gases through the treatment system. Baffles also tend to require greater maintenance due to the collection of dust on the baffle surfaces. Dust build-up also degrades performance.
Accordingly, there is a need for an inlet to a gas processing system which is capable of changing the direction of the gas flow in a compact space and introducing the gas flow substantially uniformly into the entrance of a gas processing system.
Another object of the present invention is to avoid the need to use means for improving flow uniformity which substantially impedes gas flow through the system.
Another object of the present invention is to enable the repositioning of the spray nozzles in a GCT closer to the entrance.
SUMMARY OF THE INVENTION
The present invention comprises a gas treatment apparatus having a compact gas inlet apparatus for both redirecting a flow of gas and for making the redirected gas flow uniformly into the entrance to the gas treatment system. In its broad aspect the present invention is directed to a gas inlet chamber having an elongate entrance and a substantially circular outlet coupled to the entrance to a gas processing chamber, said inlet chamber entrance and outlet having different orientations such that the gas flow is redirected, and a tapered body portion between said entrance and outlet. In one embodiment of the invention the gas inlet apparatus changes the gas flow direction by about ninety degrees and the elongate entrance to the inlet chamber is rectangular with an aspect ratio of at least about 2:1. In another aspect of the invention, the outlet is substantially coaxial with the entrance to the gas processing chamber and the taper of the inlet chamber is uniform from the entrance of the inlet apparatus to the end opposite from the entrance. In a preferred embodiment of the present invention the gas processing chamber is a gas conditioning tower having a venturi at the entrance, the throat of the venturi having a diameter D. In the preferred embodiment, the height of the entrance to the gas inlet is no greater than about 0.75 D, the diameter of the circular outlet is greater than about 1.25 D, the narrowest height of the tapered portion is about 0.25 D or less, and the length of the gas inlet apparatus is less than two times the width of the apparatus.
In another aspect, the present invention comprises a system for redirecting a gas flow to a gas processing chamber comprising a divergent transition section, a turning section and the above described gas inlet chamber. When used in connection with a gas conditioning tower having a venturi at the entrance thereof, the gas inlet of the present invention provides sufficient uniformity to allow positioning of the spray nozzles in the throat of the venturi.


REFERENCES:
patent: 3409131 (1968-11-01), Petersen et al.
patent: 3456928 (1969-07-01), Selway
patent: 4790864 (1988-12-01), Kostun
EviroCare International Water Injection Calculation Questionnaire.

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