Nelson, Norvell (Apartment #14, 3898 Magnolia Avenue Palo Alto, CA, 94306, US)
Steward, Anthony G. (13060 LaPaloma Road, Los Altos Hills, CA, 94022, US)
Bryan, Garry H. (508 S. Fillmore, Kennewick, WA, 99336, US)
EOSYSTEMS, INC. (760 San Aleso Avenue, Sunnyvale, CA, 94086, US)
| 1. | A method of destroying a treatment mixture of an organic phase in an aqueous solution, wherein said organic phase is converted to C°2 and H20, comprising the steps of: (a) providing an electrochemical cell having a cathode compartment with a catholyte and an anode compartment separated by a porous membrane; (b) providing an electrolyte solution of an acid selected from the group consisting of nitric acid and sulfuric acid with an oxidant in an original oxidant state that is substantially nonreactive with the aqueous solution at an operating temperature above about 70° C in an anolyte within said anode compartment; (c) emulsifying the treatment mixture and increasing the surface area of the organic phase, forming an emulsified mixture; (d) passing the emulsified mixture into a liquid phase rection vessel wherein said oxidant reacts with said organic phase to produce said CO2 and said H, O and a reduced form of said oxidant; and (e) flowing said reduced form of said oxidant through said electrochemical cell and electrochemically regenerating said reduced form of said oxidant to the original oxidant state. |
| 2. | The method as recited in claim 1, wherein said organic materials are exoenergetic materials. |
| 3. | The method as recited in claim 2, wherein said exoenergetic materials are selected from the group consisting of chemical warfare agents and high explosives. |
| 4. | The method as recited in claim 1, wherein said operating temperature is from about 80° C to about 100° C in said liquid phase rection vessel. |
| 5. | The method as recited in claim 4, wherein the operating temperature is maintained by a heat exchanger removing thermal energy from the catholyte. |
| 6. | The method as recited in claim 1, wherein the oxidant is cerium IV. |
| 7. | The method as recited in claim 6, wherein the concentration of cerium IV is from about 1. OM to about 1.7M. |
| 8. | The method as recited in claim 1, wherein the electrical current is at least about 4 Kwh/lb of the organic materials. |
| 9. | The method as recited in claim 1, the step of agitating comprises: passing the organic materials through an ultrasonicmixer. |
| 10. | The method as recited in claim 4, wherein the temperature of the catholyte is from about 25° C to about 100° C. |
| 11. | The method as recited in claim 1, further comprising a gas phase rection vessel for receiving a gaseous phase organic material and reacting it with said oxidant. |
| 12. | An apparats for destroying an organic phase within an aqueous solution, comprising: (a) an electrochemical cell having a cathode compartment and an anode compartment separated by a porous membrane; (b) cerium and an acid selected from the group consisting of nitric acid and sulfuric acid in an anolyte within said anode compartment, said cerium present in a concentration of at least about 0.5 M; (c) an agitating emulsifier that increases the surface area of the organic phase; and (d) a liquid phase rection vessel for reacting said organic phase with said cerium and a liquid return to the electrochemical cell for regenerating the reacted cerium. |
| 13. | The apparats as recited in claim 12, further comprising: a heater for raising a temperature of the liquid phase rection vessel. |
| 14. | The apparats as recited in claim 13, wherein said heater has an operating temperature from about 30° C to about 100° C. |
| 15. | The apparats as recited in claim 13, wherein the concentration of cerium is from about 1.5M to about 1.7M. |
| 16. | The apparats as recited in claim 13, wherein said agitating emulsifier is an ultrasonic mixer which mixes the organic materials in advance of the electrochemical cell. |
| 17. | The apparats as recited in claim 13, wherein the heater is the electrode (s) of the electrochemical cell. |
| 18. | The apparats as recited in claim 17, further comprising a heat exchanger for cooling a catholyte. |
| 19. | The apparats as recited in claim 12, further comprising a gas phase rection vessel for reacting gaseous phase organic compound. |
| 20. | An apparats for destroying organic materials, comprising: (a) an electrolyte solution having an acid selected from the group consisting of nitric acid and sulfuric acid, with an oxidant; (b) an ultrasonic mixer for mixing the organic materials with the electrolyte solution into a reactive mixture; (c) a liquid phase rection vessel receiving the reactive mixture wherein the organic materials with the electrolyte solution oxidizes said organic materials to CO2 and H, o and reduces the oxidant; and (d) an electrochemical cell having a cathode compartment and an anode compartment separated by a porous membrane wherein the reduced oxidant is regenerated to an original oxidant state. |
| 21. | A method of destroying a treatment mixture of a gaseous organic phase, wherein said gaseous organic phase is converted to CO2 and H2O, comprising the steps of: (a) providing an electrochemical cell having a cathode compartment with catholyte and an anode compartment separated by a porous membrane; (b) providing an electrolyte solution of an acid selected from the group consisting of nitric acid and sulfuric acid with an oxidant in an original oxidant state that is substantially nonreactive with the aqueous solution at an operating temperature above about 70° C in an anolyte within said anode compartment; (c) passing said gaseous organic phase into a gas phase rection vessel; (d) passing the electrolyte solution into the gas phase rection vessel wherein said oxidant reacts with said gaseous organic phase to produce said C02 and said H20 and a reduced form of said oxidant; and (e) flowing said reduced form of said oxidant through said electrochemical cell and electrochemically regenerating said reduced form of said oxidant to the original oxidant state. |
| 22. | The method as recited in claim 21, wherein said organic materials are exoenergetic materials. |
| 23. | The method as recited in claim 22, wherein said exoenergetic materials are selected from the group consisting of chemical warfare agents and high explosives. |
| 24. | The method as recited in claim 21, wherein said operating temperature is from about 80° C to about 100° C in said rection vessel. |
| 25. | The method as recited in claim 24, wherein the operating temperature is maintained by a heat exchanger for the catholyte. |
| 26. | The method as recited in claim 21, wherein the oxidant is cerium IV. |
| 27. | The method as recited in claim 26, wherein the concentration of cerium IV is from about 1. OM to about 1.7M. |
| 28. | The method as recited in claim 21, wherein the electrical current is at least about 4 kWh/lb of the organic materials. |
| 29. | The method as recited in claim 25, wherein the temperature of the catholyte is from about 25° C to about 100° C. |
| 30. | The method as recited in claim 21, further comprising: a liquid organic rection tank with an emulsifier for mixing a liquid organic compound with said electrolyte solution. |
| 31. | An apparats for destroying a gaseous organic phase, comprising: (a) an electrochemical cell having a cathode compartment and an anode compartment separated by a porous membrane; (b) cerium and an acid selected from the group consisting of nitric acid and sulfuric acid in an anolyte within said anode compartment, said cerium present in a concentration of at least about 0.5 M; and (d) a gas phase rection vessel for reacting said gaseous organic phase with said cerium and a liquid return to the electrochemical cell for regenerating the reacted cerium. |
| 32. | The apparats as recited in claim 31, further comprising: a heater for raising a temperature of the gas phase rection vessel. |
| 33. | The apparats as recited in claim 32, wherein said heater has an operating temperature is from about 30° C to about 100° C. |
| 34. | The apparats as recited in claim 31, wherein the concentration of cerium is from about 1.5M to about 1.7M. |
| 35. | The apparats as recited in claim 32, wherein the heater is electrode (s) of the electrochemical cell. |
| 36. | The apparats as recited in claim 35, further comprising a heat exchanger for cooling a catholyte. |
| 37. | The apparats as recited in claim 31, further comprising a liquid phase rection vessel and an agitating emulsifier for mixing a liquid phase organic material with said cerium and reacting same. |
| 38. | An apparats for destroying organic materials, comprising: (a) an electrolyte solution having an acid selected from the group consisting of nitric acid and sulfuric acid, with an oxidant; (b) an agitating emulsifier for mixing a liquid organic material with the electrolyte solution into a mixture; (c) a liquid phase rection vessel receiving the mixture wherein the mixture is heated and oxidizes said liquid organic material to C02 and H20 and reduces the oxidant; (d) a gas phase rection vessel for receiving a gaseous organic material and the electrolyte solution wherein the gaseous organic material contacts the electrolyte solution and oxidizes said gaseous organic material to COR and H, O and reduces the oxidant; (e) an electrochemical cell having a cathode compartment and an anode compartment separated by a porous membrane wherein the reduced oxidant is regenerated to an original oxidant state. |
| 39. | A method of destroying a treatment mixture of an organic phase in an aqueous solution, wherein said organic phase is converted to COR and H, O, comprising the steps of: (a) providing an electrochemical cell having a cathode loop with a catholyte and an anode loop separated by a porous membrane; (b) providing an electrolyte solution of an acid selected from the group consisting of nitric acid and sulfuric acid with an oxidant in an original oxidant state that is substantially nonreactive with the aqueous solution at an operating temperature above about 70° C in an anolyte within said anode loop; (c) emulsifying the treatment mixture and increasing the surface area of the organic phase; and (d) flowing electrical current through said electrochemical cell and both heating said aqueous solution as a result of passing electrical current through the electrochemical cell and oxidizing said organic phase in said anode loop. |
| 40. | The method as recited in claim 39, wherein said oxidizing in step (d), comprises: passing the emulsified mixture from step (c) into a liquid phase rection vessel wherein said oxidant reacts with said organic phase to produce said CO, and said H, O and a reduced form of said oxidant. |
| 41. | The method as recited in claim 40, wherein said flowing (of electrical curent) is combine with flowing said reduced form of said oxidant through said electrochemical cell and electrochemically regenerating said reduced form of said oxidant to the original oxidant state. |
| 42. | The method as recited in claim 39, further comprising the steps of: passing a gaseous organic phase into a gas phase rection vessel; passing the electrolyte solution into the gas phase rection vessel wherein said oxidant reacts with said gaseous organic phase to produce said C02 and said H20 and a reduced form of said oxidant; and flowing said reduced form of said oxidant through said electrochemical cell and electrochemically regenerating said reduced form of said oxidant to the original oxidant state. |
BACKGROUND OF THE INVENTION Many organic materials are stored and ultimately require disposa. Disposa, however, is becoming more difficult with increasing environmental regulations. In addition, conventional disposa methods, for example incineration, may create additional waste, and may create a hazard especially when the organic materials are exoenergetic materials.
Use of cerium in an electrochemical cell is taught by Silva et al. in U. S. patent 5,420,088 issued 5/30/95. The Silva et al. process is for the purpose of recovering catalyst material from latent catalyst material solids. Oil or organic material is preferably extracted or removed from latent catalyst material solids before the latent catalyst material solids are placed into the electrochemical cell. However, organic material may be reacted in the electrochemical cell together with the latent catalyst material solids, but with a reduced efficiency of recovering catalyst material.
The destruction of cutting oils using catalyzed electrochemical oxidation technology has been studied (Surma et al. 1991) using silver (II) as the catalyst in the HNO3 anolyte solution. That work indicated that near complete (>99.90) destruction of the oil could be achieved.
Optimization of the oil destruction rate by selecting operating parameters of temperature, silver concentration, and electrode current density resulted in destruction efficiencies greater than 99.9%. Operating temperatures up to about 70°C were preferred.
Studies by Bray et al. 1989 have shown that organic compound may be destroyed using electrochemical methods coupled with a catalytic oxidant, such as silver or cerium.
However, the work indicated that cerium may not be kinetically fast enough for an industrial organic oxidation process.
The apparats and method of the co-pending application 08/634,662 has the disadvantage of varying flow rate of the treatment mixture through the electrochemical cell. It has a further disadvantage of inadequate offgas treatment.
Others have used a catalyst/cocatalyst composition for oxidizing organic waste material to produce hydrogen.
Examples include U. S. patent 4,925,540, and European Patent Application 0 246 957 A1 both to Dhooge. Another example is scrubbing of S02 and Nox using a Ce (IV) containing solution as described in the article SCRUBBING OF S02 AND NOX USING A Ce (IV) CONTAINING SOLUTION: A KINETIC INVESTIGATION, M Aurousseau, F Lapicque, The 1995 ICHEME Research Event/First European Conference V.
1562-564,1995.
Accordingly, there is a need for a method of disposa of organic materials that is safe for both the environment and the personnel handling the organic materials, simplifie compare to needing a catalyst/cocatalyst combination and which permits steady flow rate through the electrochemical cell.
SUMMARY OF THE INVENTION The invention is based upon the unexpected discovery that cerium electrooxidation of an organic/water/acid mulsion is specific to the organic phase of the mulsion and therefore exhibits a greater organic rection rate than silver. Thus, the present invention is a method and apparats using high cerium concentration in the anolyte of an electrochemical cell to oxidize organic materials. Organic materials specifically include organic liquids, for example oils, and solid combustible materials, for example paper products, plastics, rubber, cloth, tape, and wood. The invention inclues the discovery that under certain conditions cerium can be at least as effective as silver in the destruction of organic materials, particularly cutting the oils. Specifically, conditions for cerium (IV) oxidation of combustible materials are at elevated temperature (i. e., >85°C) and at increased electrocatalyst concentrations.
The use of cerium as an electrocatalyst has shown that the catalytic electrochemical oxidation process can operate continuously with only minimal electrocatalyst depletion in the anode. The only loss of cerium is due to the slow migration across the membrane into the cathode compartment.
When silver is used as an electrocatalyst for Trimsol destruction, a portion of the catalyst is lost in the precipitation rection with chloride. Also it was observe that the migration of the cerium across the membrane separating the anode for the cathode was much lower than was observe for silver.
The use of cerium as an electrocatalyst has many avantages over silver. Specifically the cerium is not subject to losses due to precipitation as a halide as is silver. Cerium is not a hazardous or listed substance which aids in the disposition of the spent anolyte. Operation of the cell using cerium also has the avantage that higher current densities can be used resulting in higher efficiency than when silver is the electrocatalyst. Other avantages with respect to the operation of the pilot-plant were also
observe that make cerium the electro-catalyst of choice.
Further avantages are realized because cerium is neither a listed or a hazardous compound, making a cerium based electrochemical oxidation process a more attractive alternative than incineration. Another avantage of the present invention is the unexpected result that the oxidant alone (preferably cerium), in the absence of a cocatalyst, is fully sufficient to oxidize organic materials to CO, and H, O.
The method and apparats further use an agitating emulsifier to reduce the size and increase the surface area of the organic phase and enhance the oxidation rate of the organic material in the electrochemical cell. For an stream of an organic material miscible with water or aqueous solution, the agitating emulsifier may not be needed.
A liquid phase rection vessel is used wherein the organic phase is converted to CO, and H, o by rection with the oxidant, and the oxidant is reduced. Reduced oxidant is then passed through the electrochemical cell for regeneration to an original oxidant state and subsequent re-use in the liquid phase rection vessel with fresh organic phase.
In the case wherein the treatment medium is in a gas phase, an agitating emulsifier is not needed. Instead, the gas phase organic is introduced into the gas phase rection vessel and reacted with an oxidant solution.
It is an object of the present invention to provide a method and apparats for oxidizing organic materials in a liquid phase wherein the organic material oxidation rection and the oxidant regeneration are in separate vesses.
It is a further object of the present invention to provide a method and apparats for oxidizing gas phase organic materials.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further avantages and objects thereof, may best be understood by reference to the following description taken in connection
with accompanying drawings wherein like reference characters refer to like elements.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of the apparats of the present invention.
FIG. 2 is a graph of amount of oil destroyed and C02 concentration in the apparats as a function of time.
FIG. 3 is a graph of amount of oil destroyed versus time for various operating temperatures.
FIG. 4 is a graph of coulombic efficiency versus time for various operating temperatures.
FIG. 5 is a graph of power factor as a function of temperature.
FIG. 6 is a graph of amount of oil destroyed, CO2 concentration and coulombic efficiency as a function of time for Example 5.
FIG. 7 is a process flow diagram including a rection tank separate from the anolyte tank and electrochemical cell.
FIG. 7a is a process flow diagram further including a second rection tank for off gas.
DESCRIPTION OF THE PREFERRED EMBODIMENT (S) According to a preferred method of the present invention, organic materials are destroyed by (a) providing an electrochemical cell having a cathode compartment and an anode compartment separated by a porous membrane; (b) providing an oxidant in an anolyte, the oxidant that is not reactive with the aqueous solution but reactive with the organic phase; and (c) heating the mixture together with the oxidant. When the mixture is in a liquid phase, the next step is (d) emulsifying the heated mixture and increasing the surface area of the organic phase. When the mixture is in a gas phase, the next step is (d) contacting the gas phase mixture with the oxidant in a gas phase rection vessel. In one embodiment, the next step is (e) flowing electrical current through the
electrochemical cell and oxidizing the organic material in the anode compartment. In a preferred embodiment, the next steps are (e) flowing the emulsified or contacte mixture through a liquid phase rection vessel wherein the organic material is converted to COR and H, O, and the oxidant is reduced, (f) flowing reduced oxidant through the electrochemical cell to regenerate the oxidant to an original oxidant form. In the case of cerium, cerium in an original oxidant form is Ce4+ which upon reduction becomes Ce3+. The Ce3+ is regenerated in the anode of the electrochemical cell to Ce4+ for re-use with fresh organic material.
The organic material may be any organic material, but the process of the present invention is especially useful for immiscible organic liquids, most especially exoenergetic materials including but not limited to chemical warfare agents, for example sarin (CQHIOFOzP), and high explosives for example HMX (CqHeN808), RDX, nitrocellulose, trinitrotoluene, and nitroglycerin. Of course any combustible organic material is exoenergetic.
The oxidant is preferably cerium. For cerium, the electrochemical cell may be operated at any temperature compatible with the anolyte solution and is preferably from about 30°C to about 100°C and most preferably from about 80°C to about 100°C. The concentration of cerium is at least about 0. 5M. Preferably, the cerium concentration is from about 1. OM to about 1.7M, and most preferably from about 1.5M to about 1.7M. The higher concentrations permit operation of the electrochemical cell at higher current densities and higher current efficiencies. The electrical power consumption ranges from about 4 kWh/lb to about 9 kWh/lb of the organic materials. Most organic materials can be processed at near 100o columbic efficiency, i. e., the amount of electrical power used is very near the theoretical electrical power needed to completely oxidize the organic materials to CO2 and H, O and possible inorganic acids in the anolyte.
Further efficiency is gained when the organic material is mixed in water and the mixture passed through an agitating emulsifier. The agitating emulsifier provides a more thorough
mixing and more even distribution of the organic material in the water. In solution, the agitating emulsifier serves to completely hologenize the organic material water mixture. In a 2-phase mixture, the agitating emulsifier breaks the organic material phase into smaller"bubbles"thereby emulsifying the mixture and increasing its surface area. Whether in solution or multi-phase mixture, the agitating emulsifier improves the physical properties of the mixture for better contact to the electrodes. The agitating emulsifier may be any agitating emulsifier including but not limited to ultrasonic vibrator, and high speed propeller.
In addition, further efficiency may be realized by vibrating the electrodes and increasing the mass/charge transfer coefficient between the liquid and the electrodes.
An apparats of the present inventions is shown in FIG.
1. The electrochemical cell 100 has a cathode compartment 102 and an anode compartment 104 separated by a porous membrane 106. The electrochemical cell 100 is filled with a solution of cerium in a concentration of at least about 1 M. in an anolyte. Because the cerium is generally present as a cerous ion, Ce (III), it is oxidized to ceric ion, Ce (IV) in the anode compartment. The ceric ion reacts with the organic material to destroy it. Electrical current flowing through said electrochemical cell provides the energy to re-oxidize cerous ions in the anode compartment 104. The feed may consist of a liquid organic fed into the anolyte loop 108 with a metering pump 110. Alternatively, solids such as paper pulp and wood chips could be introduced into the anolyte loop via a screened cage (not shown) in the anolyte tank 112.
The anolyte solution is pumped (pump 113) through the anolyte loop 108 having of an agitating emulsifier 114. The agitating emulsifier 114 serves to increase the organic surface area for faster oxidation rates and may provide 100 to 5000 watts or more of energy to the anolyte/organic solution.
After emulsification, the solution enters the electrochemical cell anode compartment 104, where the metal catalyst is oxidized (e. g., Ce3+ to Ce4+). Cerium (IV) is a kinetically rapid, powerful oxidizing agent, which is reduced by reacting
with and oxidizing organic molecules. After the cerium (IV) is reduced, it again is oxidized in the electrochemical cell 100.
In this cyclic manner, cerium acts as an oxidation catalyst, carrying electrons from the material being oxidized to the anode 116. After the electro-chemical cell 100, the anolyte solution enters the anolyte tank 112, which not only serves as a gas/liquid separator and surge tank, but also provides the capability for the oxidation of solids. Gases exiting the anolyte tank 112 pass through a condenser 117. The anolyte tank 112 is provided with an agitato 118 to promote mass transfer if oxidation of solids is evaluated. Temperature, pressure, density, and flowrate of the anolyte and catholyte loops 108,120 are measured.
The cell temperature of the anode and cathode can be independently maintained through heat exchange to fluid jackets 122 on the outside of the electrochemical cell 100.
Operating temperatures of the anolyte may range from about 20°C to about 100°C, but are preferably between about 30°C and about 100°C, and most preferably from about 80°C to about 100°C. Operating pressure is preferably ambient pressure of about 1 atmosphere. Heating may be done separately, or as a result of passing electrical current through the electrochemical cell. Although the catholyte may be about the same temperature as the anolyte, it is preferred to maintain the catholyte at a lower temperature than the anolyte to reduce generation of gaseous nitrous oxide (s) (NOX). The catholyte may be cooled to just above a freezing temperature of the catholyte. Preferably, catholyte temperature is maintained at about 25°C to about 70°C which is approximately 30°C cooler than the anolyte.
The catholyte loop 120 is separated from the anolyte loop 108 with a porous barrier 106 chosen to minimize mixing while maintaining electrical conductivity. The catholyte pump 123 moves catholyte through the catholyte loop 120. The main chemical rection in the catholyte loop 120 is the reduction of nitric acid to HAN02, which is reoxidized in part by bubbling 0, through the solution from the catholyte tank. Make up acid (acid addition unit 125) is added to the catholyte loop 120 to
maintain the acid concentration. The acid is an inorganic acid in which cerium is soluble. Preferably, the acid is nitric acid which has a high solubility for cerium. other acids include sulfuric acid and hydrochloric acid.
The evolved gases from the anolyte and catholyte tanks 112,128 are evacuated to the atmosphere after NOX removal. A gas proportioner (not shown) optionally allows controlled mixing of NOX from the catholyte off-gas and °2 from the anolyte off-gas. Optionally, the evolved gases may be passed through a rection vessel (not shown), where the gas phase catalytic oxidation of NO to N02 takes place. Because N02 is absorbe faster by water than NO, this rection greatly enhances the efficiency of the NO, scrubber 124. After exiting the NOX scrubber 124, the gas is exhausted to the atmosphere.
Scrubber temperature is maintained by a cooling coil 126 running through the scrubber 124.
DATA ACOUISITION FOR EXAMPLES A 386 computer was used with AIMAX-PLUS data acquisition and control software to control the process with minimal operator oversight. Measured parameters were automatically recorde, and the computer had direct control over four final control elements. The anolyte and catholyte temperatures were controlled by motor-operated valves which opened or closed to maintain the anolyte and catholyte temperature set points. A third motor-operated valve minimized the differential pressure between the anolyte and catholyte loops. (In the past, a build-up of pressure in one of the loops had caused the membrane to rupture.) The fourth, and final, control element was the speed of the makeup HNO3 metering pump. Additions of HNO3 maintained acid concentrations at set point and prevented H2 generation. All of the final control elements were controlled via a 4 to 20 milliamp signal generated from the computer.
During normal operation, the computer displays a process diagram by which the operator monitors control parameters.
All measured parameters can be displayed on the process
diagram and provide the operator with real time measurements.
In addition to monitoring parameters, the control system provides the operator with manual control of the anolyte and catholyte pumps, the power supply voltage and amperage, and the capability to override all final control elements from the computer.
Example 1 An expriment was conducted to compare organic phase destruction in an electrochemical cell with cerium or silver, and with or without emulsification. In this experiment, the agitating emulsifier was an ultrasonic mixer Model 800D, Heat Systems-Ultrasonics, Farmingdale, NY. Because the oxidation potential for silver (II) is about 1.98 volts and that for cerium (IV) is about 1.64 volts, it was expected that silver would outperform cerium. The organic material was Trimsol cutting oil.
For tests without emulsification, the organic phase was not effectively destroyed. It was observe that little or no detectable oxidation of an immiscible organic liquid occurred without the use of the ultrasonic mixing. It was also observe that when the operation of the ultrasonic emulsification system was inadvertently interrupted, the oxidation rate of the organic would drop quickly.
For tests with emulsification, the results are shown in Table E-1 Table E-1 Organic Destruction Rate
Oxidant Temperature (C) Amount of Organic Organic Phase Destruction Rate (g/hr) Silver (II) 70 20 ml batch 24 Cerium (IV) 95 10 ml batch 24 Cerium (IV) 85 10 ml batch 6.24 Cerium (IV) 80 10 ml batch 0.4 Silver (II) 70 118 ml 51 continuous Cerium (IV) 95 116 ml 60 continuous The cerium organic destruction rate is strongly affecte by temperature. The silver is shown only for 70°C because above 70°C, the silver causes water separation and release of oxygen. Tests above 70°C were attempted and only reached as high as about 85°C beyond which the oxygen generation from the aqueous solution overwhelmed the test. The organic destruction rate is also a function of the amount or concentration of organic phase present and is less for decreasing amounts of organic phase. Thus, the fact that cerium has a destruction rate for 10 ml of organic phase equal to the destruction rate for silver starting with 20 ml of organic phase illustrates the improved destruction rate of cerium over silver. In the continuous operation tests, the cerium shows a higher destruction rate than silver both operated at optimal operating temperatures. Although cerium does not appreciably react with the aqueous solution at elevated temperatures, it is preferable to avoid boiling the aqueous solution.
Example 2 An expriment was performed to demonstrate destruction of sarin (C4HIOFOzP). For sarin in water, destruction to phosphoric acid, hydrogen fluoride and carbon dioxide requires 26 faradays of charge per mole of sarin or about 5 kWh/lb of
sarin. The electrochemical cell 100 was operated between 40°C and 60°C at ambient pressure. Silver concentration was about 0.5M.
By analyzing the off-gas, it was calculated that the destruction efficiency was better than 99.9999%. Hence, for sarin, it does not appear that using cerium offered any improvement in destruction efficiency compare to silver.
Example 3 An expriment was conducted to demonstrate the destruction of OTTO Fuel II according to the present invention. The elemental analysis for OTTO Fuel II was 32.50 wt% Carbon 5.22 watt Hydrogen 12.87 wt% Nitrogen 49.41 wto-. Oxygen.
Two tests were conducted: 1) a baseline or control, without electrochemical oxidation, and 2) with electrochemical oxidation. The operating conditions were identical for both tests, except for the baseline test wherein no current was passed. Both tests were conducted using silver and cerium as the oxidant to compare destruction performance between silver and cerium.
Operating conditions for silver were: Electro-catalyst Temperature 50°C 4 M Ho,/0.5 M silver initial conc OTTO Fuel a 1000 ppm The destruction rate of OTTO Fuel by silver in terms of total organic carbon (TOC) was-0.004-0.020 ppm TOC per coulomb charge passed through cell.
Operating conditions for cerium were: Electro-Catalyst Temperature 75°C 4 M Ho,/1.5 M cerium initial conc OTTO Fuel ~ 2600 ppm The destruction rate of OTTO fuel by cerium in terms of total organic carbon (TOC) was ~ 0. 025 ppm TOC per coulomb charge passed through cell. This represents an unexpected increase
in destruction rate using cerium compare to silver of at least 25t and as much as a factor of 6.
The electrochemical cell was operated with and without ultrasonic vibration and no difference in destruction performance was observe. This was expected because the concentration of OTTO Fuel in 4M nitric acid was near its solubility limit and therefore the OTTO fuel was in solution.
The electrochemical cell with cerium was operated for about 2 hours which resulted in 281 of the total organic carbon destroyed. Had the expriment been operated to completion, it is estimated that complete destruction would have occurred in about 7 hours under these conditions.
Example 4 Experiments were conducted to demonstrate the destruction of a cutting oil, specifically Trimsol cutting oil.
Experiments were conducted in a catalyzed electrochemical oxidation system as described above and shown in FIG. 1.
The first seven experiments were conducted to determine optimum operating conditions for the oxidation of Trimosol cutting oil. Table E-4 lists the conditions for these seven tests.
Table E-4. Operating Conditions for Parametric Study Using Cerium (IV) as the Electrocatalyst at a concentration of 1.5M/L
Run Current Density Temperature (°C) Identification Amperes/m2 Run 1 3750 80 Run 2 2500 80 Run 3 5000 90 Run 4 5000 80 Run 5 2500 97 Run 6 2500 85 Run 7 3750 95 All seven tests involved the oxidation of 10 ml of Trimsol oil. The Trimsol oil was fed continuously for 10 minutes at a feed rate of 1 m./min. After feeding was terminated, the system operated until the evolution of C02 from the anode compartment approached the baseline prior to the injection of the oil. FIG. 2 presents the data from run 5 showing nearly complete destruction of the Trimsol oil in about an hour. FIG. 3 shows the effect of temperature on destruction rate and FIG. 4 shows the effect of temperature on columbic efficiency. This presentation of data for this run is typical of all subsequent runs in that C02 concentration data is present with a calculated value of oil destroyed, and data on the overall efficiency of destruction and columbic efficiency are presented. The sharp increase in C02 concentration in FIG. 4 at about 10 minutes corresponds to the initial oxidation rate of Trimsol oil which is relatively high. The oxidation rate decreases as the concentration of oil decreases in the anolyte solution. The data show a strong correlation of oxidation rate to the temperature of the anolyte solution. This is evident in the columbic efficiencies presented for each of the runs. In general it is seen that higher columbic efficiencies are obtained when the
cell is operated at elevated temperatures (i. e., above 90°C).
There is an exception to this trend in runs 3 and 4 because the cell operated at higher current densities, resulting in inefficiencies caused by side rections at the anode surface (i. e., the oxidation of water, H20-e-+ H'+ Oz).
A summary of power factor versus temperature is presented in FIG. 5. It is shown that operation of the CEO process above 90°C is required to obtain reasonable and cost effective performance with respect to the oxidation of Trimsol cutting oil.
Under these conditions power requirements for the oxidation of Trimsol cutting oil was observe to the 205 kWh per gallon of cutting oil destroyed. This corresponds to a cost in the range of $6.00 to $10.00 per gallon processed.
Example 5 Three additional tests were performed to evaluate the performance of the pilot plant under continuos operations.
More specifically, the tests were to determine the steady state destruction rate achievable under differing operating conditions. The primary operating parameter of interest was the concentration of cutting oil in the anolyte compartment.
A summary of the runs is presented in Table E-5.
The data from run 8 is shown in FIG. 6. It was observe that as the concentration of oil in the anolyte increased a steady state oxidation rate of 60 ml/hour was achieved during run 8. The columbic efficiency is much higher than in runs 1 through 7 because of the much higher concentration of oil in the anolyte in run 8 relative to the prior runs.
In run 9 data shows that a steady state oil destruction rate was also achieved, evidenced by the flatting of the C02 concentration curve, and the destruction rate was very close to that of Run 8.
Table E-5. Operating Conditions for Continuous Operation of Pilot Plant
Run 8 Run 9 Run 10 Current Density 3750 2500 2500 (ampere/m2) Temperature (°C) 95 95 95 Oil Feed Rate (ml/min) 1.8 4.0 1.0- 4.0 Cerium Concentration 1.5 1.0 1.5 (moles/liter) Duration of Test (hours) 3 5 8 Total Oil Fed (ml) 115.42 507 500 Throughout the duration of Run 9, the feed rate of the oil into the anolyte compartment was altered. However, the average rate was very near that of run 8; therefore, steady state conditions were anticipated to be nearly the same for the two runs. During periods when the feed rate was increased to 4 m./minute, steady state oil destruction rates of 80 ml/hour were observe. It is anticipated that higher rates are achievable by further increasing the organic (oil) concentration in the anolyte.
Second Embodiment Another apparats is shown in FIG. 7. Components common to the apparats of FIG. 1 include the electrochemical cell 100, anolyte loop 108, anolyte tank 112, anolyte pump 113, ultrasonic mixer 114, catholyte loop 120, catholyte pump 123, and the catholyte tank 128. Also common is the organic feed or storage and the feed pump 110. The main new component is the reactor tank 700. The mixer 114 receives organic material and anolyte, mixes them as a rection mixture and passes the rection mixture to the reactor tank 700 wherein the organic material reacts with the anolyte converting the organic material to C02 and H20 and reducing the oxidant in the anolyte. The rection mixture is heated to increase rection rate and rection completeness. Heating may be done with a
heat exchanger (not shown) within the rection tank or by an external jacket (not shown). Additionally, heating may be via electrical resistance losses through the electrochemical cell.
For electrochemical cells with one or a few plates receiving electrical current, an external jacket is preferred. For electrochemical cells with more plates receiving electrical current, the external jacket is not needed and electrical resistance loss provides sufficient thermal energy for the heating. A surplus of thermal energy may be provided necessitating the use of a heat exchanger 701 for removal of surplus thermal energy.
The gas (CO2 and H, O vapor) is drawn off the top of the reactor tank 700 and directe to a chlorine absorber 703.
Chlorine producing materials or compound, for example organochlorine (e. g., chlorobenzene), release the carbon bound chlorine as molecular chlorine C12 which must be removed from the offgas prior to release of the offgas to atmosphere.
Hence, the chlorine absorber 703 is included. The liquid containing reduced oxidant flows back to the anolyte tank and mixed with fresh anolyte. The anolyte mixture is divided between the electrochemical cell 100 and the mixer 114. The portion going to the electrochemical cell 100 is oxidized and thereby refreshed or regenerated, for example Ce3+ is oxidized to Ce4+, and passed back into the anolyte tank 112. An avantage of this embodiment is that the flow through the electrochemical cell may be maintained at a substantially constant rate and the amount of electrical current through the electrochemical cell varied with reduced oxidant concentration, thereby permitting a more energy efficient process. Another avantage is that the rection temperature control is independent of the electrochemical cell temperature control.
A variation of this embodiment (FIG. 7a) is the addition of a second rection tank 702 for handling the gas phase organic materials and off-gas from the liquid phase rection in the rection tank 700. In the second rection tank 702, the liquid anolyte is introduced at the top and sprayed into the second rection tank 702 and the spray droplets fall by
gravit. The gas is introduced at the bottom and passes through a packed bed for distribution of the gas across the cross section of the second rection tank 702. Recovered spray droplet liquid is drained from the bottom and pumped back to the anolyte tank 112 with recovery pump 704.
Alternatively, the gas phase organic materials may be handled independently of any liquid phase organic material. In this alternative embodiment, the emulsifier 114 and the liquid phase rection vessel 700 are omitted.
The catholyte loop 120 is essentially the same as in the embodiment in FIG. 1. A catholyte regenerator 706 is added to regenerate the catholyte. With nitric acid as the catholyte, the catholyte regenerator 706 is a nitric acid distillation apparats, for example a 2-stage vacuum evaporator designed and built by Rosenblad Design Group, Leonardo, N. J. A NOX absorber 708 is added to remove NOX from the off gases, for example a countercurrent packed bed reactor (similar in design to the second rection tank 702) in which an upward flowing stream of NOX and ou ils contacte with a downward flowing liquid of water and nitric acid. The NOIX is converted to nitric acid which is recycle to the process via recycle pump 710.
Closure While a preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appende claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.