Wet scrubber

Details Wet scrubber Wet scrubber

2001-05-29

2002-12-03

Bushey, C. Scott (Department: 1724)

Gas and liquid contact apparatus

Fluid distribution

Pumping

C261S064100, C261S123000, C261SDIG009, C096S262000, C096S279000, C096S296000, C096S332000

Reexamination Certificate

active

06488269

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scrubber for removing soluble materials from toxic gases, and more particularly to a scrubber for removing soluble materials from harmful gaseous effluents with high efficiency and safety.
2. Description of the Related Art
Semiconductor manufacturing facilities utilize chemical vapor deposition, etching and a wide variety of other unit operations in the fabrication of modern semiconductor devices using process gases such as SF
6
, SiCl
4
, SiH
2
Cl
2
, and WF
6
. The gaseous effluent from processing units in such facilities comprise the unconsumed process gases, as well as by-products of such gases. The gaseous effluent additionally may contain significant quantities of particulates such as silica, which must be removed, in addition to various water soluble components such as hydrochloric acid and residuals of phosphine and arsine.
Water scrubbing is commonly used to remove such particulates and water-soluble gases from the process effluent stream. In such scrubbing, the effluent gas is intimately contacted with water, e.g., by passage of the gaseous effluent through a water spray, to dissolve the soluble gas components and wet and thereby remove the particulates. The scrubbing liquid may then be filtered to remove the scrubbed particulates from the scrubbing medium. The water scrubber unit typically is deployed immediately upstream of a bulk exhaust for the entire plant facility, and is used to treat the process facility effluent, which may vary considerably in concentration of water-soluble components and particulates, depending on the specific types of semiconductor devices or subassembly parts which are being manufactured, and the resulting “mix” of unit operations being carried out in the process facility.
FIG. 1A
shows a conventional fume scrubber
100
. As shown in
FIG. 1A
, a scrubbing chamber
110
having a filter region
120
therein is shown. The filter region
120
comprises an upper perforate diverter plate
122
and a lower perforate plate
124
. A plurality of filter media
126
are packed into the filter region
120
and between the perforate diverter plate
122
and the perforate plate
124
. The detail structure of the filter media
126
is shown in FIG.
1
B and the filter media
126
is comprised of plastic packing spheroids formed of open annular loops as shown in the figure. In the top of the scrubbing chamber
110
, there are a gas inlet
112
a
, an opening
112
b
, fluid inlets
114
a
and
114
b
. A dry exhaust pump
152
exhausts the gaseous effluent from processing units to the scrubbing chamber
110
through a gas exhaust conduit
132
connecting the gas inlet
112
a
. An N
2
purge conduit
133
is connected to the gas exhaust conduit
132
. A gas discharge conduit
134
connecting to a main gas discharge conduit (not shown) is through the top of the scrubbing chamber
110
and the filter region
120
by the opening
112
b
. The gas discharge conduit
134
has a gas inlet
135
with a tilt opening under the perforate plate
124
. A tap water supply pipe
136
connects the scrubbing chamber
110
by the fluid inlets
114
a
. There are also a fluid outlet
116
a
and an opening
116
b
on the bottom of the scrubbing chamber
110
as shown in
FIG. 1A. A
recirculation pump
154
exhausts the scrubbing water from the bottom of the scrubbing chamber
110
back to the filter region
120
via a recirculation pipe
138
. The two ends of the recirculation pipe
138
individually connect the scrubbing chamber
110
at the fluid inlets
114
b
and the fluid outlet
116
a
. An over flow drain pipe
140
used to drain excess scrubbing water is disposed through the bottom of the scrubbing chamber
110
by the opening
116
b
, and the over flow drain pipe
140
has a fluid outlet
142
used to drain the excess scrubbing water.
In the operation of the conventional fume scrubber
100
, the gaseous effluent from processing units is exhausted through the gas exhaust conduit
132
into the scrubbing chamber
110
by the dry exhaust pump
152
, wherein the N
2
purge conduit
133
provides dry N
2
gas to exclude moisture so that less contamination or clump of particulates will precipitate. The gaseous effluent passes the filter region
120
and contacts with the tap water from the tap water supply pipe
136
, and the water-soluble gas components will solve in the tap water. Owing to the open annular loops of the filter media
126
, the water-soluble gas components will solve in the tap water flowing along the open annular loops more effectively. After contacting and adsorbing the gas components, the tap water transfers to scrubbing water and flows to the bottom of the scrubbing chamber
110
. The scrubbing water accumulates at the bottom of the scrubbing chamber
110
until the scrubbing water surface reaches the fluid outlet
142
, and the excess scrubbing water will be drain through the over flow drain pipe
140
to a main drain pipe which is not shown in FIG.
1
A. The scrubbing water also will be exhausted through the recirculation pipe
138
back to the filter region
120
by the recirculation pump
154
. The scrubbing water will remix with the gaseous effluent through the recirculation cycle set forth. After passing the filter region
120
and mixing with the tap water and the scrubbing water, the gaseous effluent will be exhausted through the gas discharge conduit
134
to the main gas discharge conduit (not shown).
However, it is found that the drawbacks of the conventional fume scrubber
100
present environment protection issues and production facility malfunctions, and even result in factory safety problems. For example, the scrubbing water is usually exhausted together with the gaseous effluent through the gas discharge conduit
134
to the main gas discharge conduit (not shown) after passing the filter region
120
thereby results in the pump malfunctions of the production facilities connected to the main gas discharge conduit and even causes serious factory safety problems. Furthermore, the mixing efficiency of the gaseous effluent with the tap water and the scrubbing water is not satisfactory and the environment protection issues will arise from the interruption of the tap water, and thus the production facilities must be shut down. In view of the drawbacks mentioned above, it is desirable to provide an advance scrubber that can prevent the problems of the conventional fume scrubber set forth, it is toward these goals that this invention specially directs.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an advance scrubber having high recirculation efficiency of the harmful gaseous effluent.
It is another object of this invention to provide an advance scrubber which can meet the standards of environment protection and the requirements of factory safety.
It is a further object of this invention to provide a reliable scrubber for removing soluble materials from harmful gaseous effluents with high efficiency and safety.
It is another object of this invention to provide an advance scrubber which renders the production facilities or processing units continually operating as the supply of the scrubbing liquid terminates.
To achieve these objects, and in accordance with the purpose of the invention, a scrubber of the invention for scrubbing gaseous effluents by a scrubbing liquid is provided. The scrubber comprises a scrubbing chamber, a first gas conduit connecting the top of the scrubbing chamber, a manual valve, a second gas conduit connecting the first gas conduit by the manual valve, a gas exhaust pump exhausting a gaseous effluent to the second gas conduit, a check valve, a third gas conduit having a purge conduit used to transit a purge gas, the third gas conduit connecting the second gas conduit by the check valve, the third gas conduit connecting the bottom of the scrubbing chamber to transit the gaseous effluent into the scrubbing chamber, wherein only effluents from the second gas conduit to the third gas conduit can pass said

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