Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Reexamination Certificate
2000-01-05
2001-08-21
Mayekar, Kishor (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
C422S186070
Reexamination Certificate
active
06277248
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ozone production facilities employing an ozonizer for generating ozone for use in the treatment of clean water and sewage, as well as the bleaching of pulp; and a method of operating the facilities.
2. Description of the Prior Art
FIG. 1
is a block diagram of conventional ozone production facilities. A starting gas
11
(main component: oxygen) prepared by oxygen production facilities
2
is supplied to an ozonizer
3
. Ozone
12
generated by the ozonizer
3
is fed to ozone treatment facilities (not shown; e.g., facilities for sewage disposal and pulp bleaching). The concentration of ozone is monitored with an ozone analyzer
4
. The amount of ozone generated is calculated by multiplying the flow rate of oxygen (monitored with an oxygen flowmeter
6
) supplied to the ozonizer
3
by the ozone concentration.
FIG. 2
is a block diagram of PSA (pressure swing adsorption) type oxygen production facilities, an example of oxygen production facilities. Air in the atmosphere is pressurized by an air blower
32
, and fed to one adsorption tower
31
with valves
35
and
37
being opened (with valves
35
a
and
37
a
being closed). The adsorption tower
31
is filled with an adsorbent, which adsorbs and removes moisture, carbon dioxide and nitrogen in the air selectively. Oxygen that is minimally adsorbed (the starting gas
11
) passes as such through the adsorption tower
31
. Then, the oxygen is pressurized to a desired pressure by a compressor
34
, and supplied to an ozonizer
3
. As the adsorption proceeds, no further moisture, carbon dioxide and nitrogen can be removed. At this time, the valves
35
and
37
are closed, while other valves
35
a
and
37
a
are opened to switch from the adsorption tower
31
to another adsorption tower
31
a
. Simultaneously, a valve
36
is opened to vacuumize the adsorption tower
31
by means of a vacuum pump
33
. As a result, adsorbed gas components
13
comprising the adsorbed moisture, carbon dioxide and nitrogen are discharged, whereby the adsorbent is regenerated. By so using the adsorption towers alternately, oxygen can be produced continuously.
FIG. 3
is a graph showing the oxygen concentration as a function of the flow rate of oxygen produced by the oxygen production facilities. The oxygen concentration depends on the flow rate of oxygen and the amount of the adsorbent, and decreases as the flow rate of oxygen increases. For example, let the flow rate of oxygen be 1 for a maximum concentration of 95%. At a relative flow rate of 1.5, the oxygen concentration decreases to 60%.
FIGS. 4A and 4B
schematically show a double pipe ozonizer, with
FIG. 4A
being a sectional view in a direction parallel to the common axis, and
FIG. 4B
, a sectional view in a direction perpendicular to the common axis. The double pipe ozonizer has a cylindrical stainless steel housing
101
, which houses a cylindrical stainless steel ground electrode
102
disposed coaxially, and glass as a dielectric layer
103
in intimate contact with the inner surface of the ground electrode
102
, both ends of the ground electrode
102
and the dielectric layer
103
being fixed to the housing
101
. At the center of this ozone generation tube, a cylindrical stainless steel high-voltage electrode
104
is coaxially disposed so as to be separated from the surface of the dielectric layer
103
by a discharge space
105
. A power source connector portion attached to a part of the electrode
104
extends to the outside of the housing
101
, passes through a bushing
106
, and becomes connected to one end of the housing
101
through a high frequency power source
107
. At the center of both side surfaces of the housing
101
, capillaries
111
are passed and fixed. These capillaries
111
are connected to the cylindrical high-voltage electrode
104
via insulating tubes
109
. By this arrangement, cooling water
108
is flowed into the high-voltage electrode
104
in the directions of the arrows in the drawing. Cooling water
108
is also introduced from the outer peripheral surface of the housing
101
to cool the ground electrode
102
.
From one end of the discharge space
105
of the double pipe ozonizer, the starting gas
11
, produced by the aforementioned oxygen production facilities, is supplied. An exhaust valve
110
provided at the other end of the discharge space
105
is adjusted to set the absolute pressure at, approximately, 1.6 atmospheres. An alternating current is applied between the ground electrode
102
and the high-voltage electrode
104
by the high frequency power source
107
. As a result, a silent discharge occurs to generate ozone
12
. The concentration of the generated ozone
12
is monitored with an ozone analyzer
4
. The ozonizer facilities in actual use have several hundred electrodes arranged, therein but their basic structure is the same as the ozonizer illustrated here.
The above ozone production facilities posed the following problems:
Generation of ozone in a large amount requires a large amount of oxygen, the starting material, which in turn requires large-scale and high-cost oxygen production facilities.
Increasing the flow rate of oxygen to the maximum capacity of the oxygen production facilities decreases the concentration of oxygen produced, and also lowers the concentration of ozone.
The concentration of ozone generated by the ozone production facilities is more than 200 g/m
3
, which is applicable to pulp bleaching. In the treatment of clean water and sewage, the ozone concentration must be reduced to about 100 g/m
3
.
SUMMARY OF THE INVENTION
In the light of the above-described problems, the object of the present invention is to provide ozone production facilities which can generate a large amount of ozone, which can always supply an ozone-containing gas having an arbitrary ozone concentration ranging from the maximum to a lower concentration, and which are small in scale.
To attain the above object, the ozone production facilities of the present invention comprise oxygen production facilities as a starting gas supply source, an ozonizer, and an ozone analyzer, and are adapted to supply the starting gas by the oxygen production facilities, ozonize the starting gas by the ozonizer to produce an ozone-containing gas, and monitor the ozone concentration of the ozone-containing gas by the ozone analyzer; the ozone production facilities further including liquid oxygen facilities as another starting gas supply source, and an oxygen flowmeter for monitoring the flow rate of oxygen supplied by the liquid oxygen facilities.
Preferably, the ozonizer is a double pipe ozonizer.
The ozone production facilities have piping for mixing part of the nitrogen exhausted from the oxygen production facilities with the ozone-containing gas, a nitrogen flowmeter for monitoring the flow rate of nitrogen, and a valve for adjusting the flow rate of nitrogen.
Alternatively, the ozone production facilities have piping for mixing air in the atmosphere compressed by a fan with the ozone-containing gas, an air flowmeter for monitoring the flow rate of air, and a valve for adjusting the flow rate of air.
A method of operating the ozone production facilities comprises supplying the starting gas from the oxygen production facilities alone to the ozonizer when the consumption of oxygen is within the production capacity of the oxygen production facilities; or mixing pure oxygen gas from the liquid oxygen facilities with the gas from the oxygen production facilities, and supplying the resulting mixed gas as the starting gas to the ozonizer, when the consumption of oxygen exceeds the production capacity of the oxygen production facilities.
The above method of operation sets the oxygen concentration of the starting gas at 95±5% when the starting gas is supplied only by the oxygen production facilities.
Alternatively, the oxygen concentration of the starting gas is set at 95±5% when the starting gas is supplied by both of the oxygen production facilities and the liquid oxyge
Ishioka Hisamichi
Suzuki Sanae
Toraguchi Makoto
Frank Robert J.
Fuji Electric & Co., Ltd.
Mayekar Kishor
Venable
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