Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Organic
Reexamination Certificate
1999-04-15
2001-05-08
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Organic
C205S742000, C588S253000
Reexamination Certificate
active
06228250
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a method and a device for destroying reaction gases. The invention applies notably to the destruction of gases such as the volatile organic compounds (VOCs) and halogenated organic compounds (VOXs) produced by the electro-oxidation of photographic developers in an electrolysis cell. The invention can also be applied to any undesirable reaction gas. By way of example, organic solvents in gas form might be cited.
Patent application FR 95/02729 filed on Mar. 3, 1995 in the name of the applicant describes a method and a device for treating by electrolysis solutions containing one or more used photographic developers so as to degrade and eliminate the components with a high chemical oxygen demand (COD).
FIG. 1
, to which reference is now made, illustrates a device such as the one used in the treatment by electrolysis described in the patent application referred to above. The solution of developers which forms the electrolyte circulates in a closed loop in the installation. The electrolyte initially present in its totality in the expansion tank (
4
) is sent into the cooling coil (
3
) by means of the peristaltic pump (
2
). It then passes into the electrolysis cell (
1
), to emerge and be found in part in the expansion tank (
4
). The electrolysis cell is a closed, non-compartmentalized cell, preferably compact, comprising one or more platinum anodes and one or more titanium or stainless-steel cathodes, separated by an insulating joint. The anodes are SHOWA anodes consisting of titanium covered in pure platinum, which are in the form of metal plates or expanded-metal plates if the electrolyte circulation is parallel to the electrodes, and in the form of one expanded-metal plate if the electrolyte circulation is perpendicular to the electrodes.
The expansion tank is provided with a calibrated orifice which enables a pressure close to atmospheric pressure to be maintained. This tank serves to cushion variations in the volume of the solution and to reduce the pressure of the gases produced during treatment (hydrogen, oxygen, carbon dioxide, volatile organic compounds (VOCs) and volatile halogenated organic compounds (VOXs)) to a pressure close to atmospheric pressure, and is used for the continuous addition of reagents. A device (
5
) enables the temperature in the expansion tank and coil (
3
) to be measured and regulated.
A pH regulation loop is composed of a pH measurement device (
7
) inserted between the electrolysis cell (
1
) and the expansion tank (
4
), and a regulator (
8
) which measures the divergence from the reference value and triggers the pumps, sending an acid (
9
) or base (
9
′) solution to keep the pH constant.
A peristaltic pump (not shown) enables the anti-foaming agent to be introduced into the cell at the outset of electrolysis or as soon as the presence of foam is detected.
The use of the electro-oxidation device described in the application referred to above presents two major problems. The first is related to the treatment of the hydrogen produced by the reaction, which, mixed with air in a proportion of between 4 and 75% by volume, is explosive and may cause, in addition to major damage to equipment, physical injury. Such a problem entails minimizing the quantities of gases produced, keeping them at low pressure and low temperature, and discharging the excess gases following their dilution in air or in nitrogen so that the hydrogen concentration is below the limits presenting a danger of explosion, that is to say below 4%. To this end, equipment and operating procedures are used in which the level of safety substantially increases the cost of the operation. Thus, in the device in
FIG. 1
, an air inlet (
10
) enables gases which present a risk of explosion (hydrogen and oxygen) to be diluted before they are discharged into the atmosphere.
The second problem lies in the generation of toxic gases such as VOCs and VOXs. According to the approach described in this application, the use of a device (
6
) for trapping the VOCs and VOXs is suggested, such as a cartridge containing an adsorbent substance, for example activated carbon. These gases can also be exposed to ultraviolet radiation (EP-A-0 360 941), oxidized catalytically or washed over sulphuric acid.
Numerous combustion techniques have already been used to destroy such reaction gases, in particular with VOCs and VOXs.
According to a first approach, as described in the patent DE-A-3 729 113, the VOCs and VOXs are destroyed by catalytic incineration. The main problem with this technique, apart from the risk of the catalytic reaction running away if the correct gas concentrations for the catalytic mass are not maintained, lies in the fact that, for a large quantity of gases to be destroyed, it necessitates a large quantity of catalyst. Generally, it is used solely to destroy traces. Moreover, catalysts are specific to specific substances to be destroyed, which can entail the use of several catalysts when there is a mixture of different substances. Furthermore, another drawback is the poisoning of the catalysts, either by substances coming from the oxidation reaction or by substances which do not oxidize but which poison the catalyst. By way of example, the halogenated compounds produced by electro-oxidation of photographic developers are reaction inhibitors for catalysts with a noble metal base, such as platinum. According to another approach, described for example in the patent U.S. Pat. No. 5,295,448 and EP-A-490 283, thermal combustion is carried out using external fuels such as natural gas, propane, butane, etc. The problem with this approach lies in the fact that it requires large quantities of such fuels to be stored, which is very onerous from the point of view of safety and space.
According to yet another approach, the VOCs and VOXs are destroyed by corona effect. This approach calls for large quantities of electrical energy.
The patent EP-A-525 974 describes a method of catalytic destruction at medium temperature (400° C.) consisting of passing the gaseous mixture over a catalyst on which adsorption occurs in the presence of oxygen, and subjecting the reactor to a temperature of around 400° C. in order to produce either oxidation or hydrolysis. The main problem with this solution relates to the fact that it could not be applied to a gaseous mixture containing hydrogen such as that produced by electro-oxidation of photographic developers, other than by reducing the hydrogen concentration to below 4%.
Thus one of the objects of the present invention is to provide a method and device for destroying reaction gases by combustion, which do not have the drawbacks referred to above with reference to the known techniques.
Another object of the present invention is to enable a mixture of gases to be destroyed by using as the principal fuel hydrogen generated by the reaction producing the gases to be destroyed, and this in complete safety.
BRIEF SUMMARY OF THE INVENTION
Other objects will emerge in detail in the description which follows.
These objects are attained by means of a method for destroying by combustion a reaction gas or a mixture of reaction gases in which hydrogen is used as the principal fuel in the presence of oxygen, and in which the principal fuel is generated in situ by an electrolysis reaction.
By way of example, the electrolysis reaction consists of an electro-oxidation reaction in a solution comprising one or more used photographic developers, the mixture of reaction gases including volatile organic compounds and halogenated organic compounds produced by the said electro-oxidation reaction.
The invention also concerns a device for destroying by combustion a reaction gas or a mixture of reaction gases, comprising:
a) a combustion unit supplied with reaction gas and fuel and in which the combustion of the gaseous mixture is carried out in the presence of oxygen;
b) supply means designed to supply the combustion unit with reaction gases and with principal fuel required for the combustion of the gaseous mixture;
c) means designed to
Eastman Kodak Company
Phasge Arun S,.
LandOfFree
Method and device for destroying reaction gases by incineration does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and device for destroying reaction gases by incineration, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and device for destroying reaction gases by incineration will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2534573