Wet air oxidation process using recycled catalyst

(54) Title: HUMID AIR OXIDATION PROCESS USING RECYCLED CATALYST (30) Unionist Priority: 22/01/2007 us 60 / 885,966 (73) Holder (s): Siemens Water Technologies Corp.

(72) Inventor (s): chad l. Feich (74) Attorney (s): Dannemann .Siemsen, Bigler & Ipanema Moreira (86) International Request: pct us2008000784 of 01/22/2008 (87) International Publication: wo 2008 / 09i578de 07/31/2008 (57) Summary : oxidation process with moist air that USES RECYCLED CATALYST. The present invention relates to a system and a process for treating process streams. A catalyst mediates a wet oxidation process at elevated temperatures and pressures to treat at least one undesirable constituent in an aqueous mixture. The aqueous mixture can be in contact with a catalyst and an oxidizing agent at an elevated temperature and superatmospheric pressure. At least part of the catalyst can be precipitated by a pH adjustment and recycled back to contact the aqueous mixture.

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ΡΙ0806724-4

Descriptive Report of the Invention Patent for OXIDATION PROCESS WITH HUMID AIR USING RECYCLED CATALYST. RELATED PATENT APPLICATIONS

This patent application claims priority under 35 USC § 119 (e) to USS Patent Application No. 60/885966 entitled WET AIR OXIDATION PROCESS USING COPPER CATALYST RECYCLED, filed on January 22, 2007, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to the treatment of process streams and, more particularly, to wet catalytic oxidation systems and processes for the treatment of undesirable constituents in that case.

2. Description of the Related Art

Wet oxidation is a well-known technology for treating process currents and is widely used, for example, to destroy pollutants in wastewater. The process involves the aqueous phase oxidation of undesirable constituents by an oxidizing agent, usually molecular oxygen from an oxygen-containing gas, at elevated temperatures and pressures. The process can convert organic contaminants into carbon dioxide, water and biodegradable short chain organic acids, such as acetic acid. Inorganic constituents that include sulfides, mercaptides and cyanides can also be oxidized. As an alternative to incineration, wet oxidation can be used in a wide variety of applications to treat process streams for subsequent discharge, in process recycling or as a pre-treatment step to provide a plant for conventional biological treatment for polishing. Catalytic oxidation in the wet state has emerged as an effective improvement over traditional non-catalytic oxidation in the wet state. The processes of catalytic oxidation in the wet state generally take into account greater destruction to be achieved at a lower temperature and pressure and, therefore, at a lower cost of capital. An aqueous stream to be treated is mixed with an oxidizing agent and comes in contact with a catalyst at elevated temperatures and pressures. Heterogeneous catalysts typically remain in a bed over which the aqueous mixture is passed or in the form of solid particulate which is mixed with the aqueous mixture before oxidation. The catalyst may be removed by filtration of the oxidation effluent downstream of the oxidation unit for reuse in the wet state.

BRIEF SUMMARY OF THE INVENTION

According to one or more embodiments, the present invention relates to processes and systems for catalytic oxidation in the wet state. According to one embodiment, a wet catalytic oxidation process comprises providing an aqueous mixture that contains at least one undesirable constituent to be treated. The aqueous mixture is brought into contact with a catalyst and an oxidizing agent at an elevated temperature and superatmospheric pressure to treat at least one undesirable constituent and form an oxidized aqueous mixture. At least a portion of the catalyst is precipitated by adjusting the pH level of the oxidized aqueous mixture to form a precipitated catalyst. At least a portion of the precipitated catalyst is recycled to contacting the aqueous mixture.

According to another embodiment, the wet catalytic oxidation system comprises a wet oxidation unit, a source of an aqueous mixture comprising at least one undesirable constituent liquidly attached to the wet oxidation unit, a source of a catalyst soluble in the aqueous mixture, liquidly connected to the wet oxidation unit, positioned between the source of the aqueous mixture and the wet oxidation unit, a pH sensor configured to detect a pH level of an oxidized aqueous mixture downstream of the wet oxidation unit, a pH controller in communication with the pH sensor, configured to generate a control signal to adjust the pH level of the oxidized aqueous mixture to a level outside a predetermined pH solubility range for the catalyst in response to the pH sensor that records a pH level within a solubility range predetermined pH for the catalyst, a separator configured to precipitate at least a part of the catalyst positioned downstream and in liquid communication with the wet oxidation unit and downstream from the pH controller and a recirculation line connected liquidly to an outlet of the separator and to an input of at least one of the catalyst source and an input to the wet oxidation system.

According to another modality, a process of facilitating the recycling of a catalyst used in a catalytic oxidation process in the wet state, comprises providing a pH monitoring system that has a controller in communication with a pH sensor, the controller configured to generate a control signal to adjust a pH level of an aqueous mixture in response to the pH sensor that records a pH level within a predetermined pH solubility range for a catalyst used.

The advantages, new aspects and objectives of the invention will become evident from the detailed description below with the accompanying illustrations.

BRIEF DESCRIPTION OF THE DRAWINGS

It is not intended that the accompanying drawings are drawn to scale. In the drawings, each identical or almost identical component that is illustrated in several figures is represented by a similar numeral. For the sake of clarity, not every component can be marked on each drawing. Preferred, non-limiting embodiments of the present invention will be described with reference to the accompanying drawings, in which:

Figure 1 is a diagram of a system according to an embodiment of the oxidation system in the wet state of the present invention;

Figure 2 is a diagram of a system according to an embodiment of the oxidation system in the wet state of the present invention includes a catalyst recycling process;

Figure 3 is a system diagram according to an embodiment of the wet oxidation system of the present invention that includes a catalyst recycling process with a two-step precipitation process and Figures 4-6 are diagrams of Pourbaix cited here for copper, vanadium and iron, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The invention is not limited in its application to the details of construction and arrangement of components as presented in the description below or illustrated in the drawings. The invention is capable of modalities and of being executed or carried out in various ways in addition to those presented here as examples.

According to one or more embodiments, the invention relates to one or more systems and methods for treating process streams. In typical operation, the systems described can receive process currents from community, industrial or residential sources. For example, in modalities where the system is wastewater treatment, the process stream can be released from a municipal wastewater sludge or by another large-scale sewage system. Process streams * 20 can also originate, for example, from food processing plants, chemical processing facilities, gasification projects or pulp and paper plants. The process stream can be carried through the system by an operation upstream or downstream of the system.

As used here the term chain refers to a process aqueous mixture can be supplied to the system for treatment. After treatment, the process stream can be returned to an upstream process or it can leave the system as waste. The aqueous mixture typically includes at least one undesirable constituent capable of being oxidized. The undesirable constituent can be any material or compound intended to be removed from the aqueous mixture, such as for public health, process design and / or for aesthetic considerations. In some embodiments, the undesirable constituents capable of being oxidized are organic compounds. Certain inorganic constituents, for example, sulfides, mercaptides and cyanides can also be oxidized. A source of an aqueous mixture to be treated by the system as a suspension, may take the form of direct piping from a plant or from a holding vessel.

According to one or more embodiments of the present invention, it is desirable to break one or more specific chemical bonds in the undesirable constituent or degradation product (s) thereof. An oxidation reaction is a destruction technique, capable of converting oxidizable organic contaminants to carbon dioxide, water and short chain biodegradable organic acids, such as acetic acid. One aspect of the present invention involves systems and methods for treatment by oxidation of aqueous mixtures containing one or more undesirable constituents.

In one embodiment, an aqueous mixture that includes at least one undesirable constituent is oxidized in a wet state. The aqueous mixture is oxidized with an oxidizing agent at an elevated temperature and superatmospheric pressure for a period sufficient to treat at least one undesirable constituent. The oxidation reaction can substantially destroy the integrity of one or more chemical bonds in the undesirable constituent. As used in this case, the term destroy substantially is defined as at least about 95% destruction. The process of the present invention can generally be applied to the treatment of any undesirable constituents capable of being oxidized.

The described processes of oxidation in the wet state can be carried out in any batch or continuous oxidation suitable for the compounds to be oxidized. Typically, aqueous oxidation is carried out in a continuous-flow oxidation system in the wet state, as shown in Figure 1 as an example. Any oxidizing agent can be used. The oxidant is usually an oxygen-containing gas, such as air, oxygen-enriched air, or essentially pure oxygen. As used in this case, the term oxygen-enriched air is defined as air that has an oxygen content greater than approximately &lt;· 21%.

In typical operation and with reference to Figure 1, an aqueous mixture from a source, presented as a storage tank 10, flows through a conduit 12 to a high pressure pump 14 that pressurizes the aqueous mixture. The aqueous mixture is mixed with a pressurized gas containing oxygen, supplied by a compressor 16, inside a conduit 18. The aqueous mixture flows through a heat exchanger 20 where it is heated to a temperature that initiates oxidation. The heated feed mixture enters a reactor 24 at inlet 38. Wet oxidation reactions are generally exothermic and the reaction heat generated in the reactor can further increase the temperature of the mixture to a desired value. The bulk of the oxidation reaction occurs within reactor 24 which provides sufficient residence time to achieve the desired degree of oxidation. The oxidized aqueous mixture and the aqueous a15 mixture from which the oxygen has been exhausted then leave the reactor through a conduit 26 controlled by a pressure control valve 28. The hot oxidized effluent passes through the heat exchanger 20 in which it is cooled with the raw aqueous mixture and gas mixture that they are entering. The cooled effluent mixture flows through a conduit 30 to a separate container 20 where the liquid and gases are separated. The liquid effluent exits the separator vessel 32 through a lower conduit 34 while the exhaust gases are removed through a conduit 36. The upper gas outlet treatment may be required in a downstream off gas treatment unit depending on composition and requirements for discharge into the atmosphere. The wet oxidized effluent can typically be discharged to a biological treatment plant for polishing. The effluent can also be recycled for further processing by the wet oxidation system.

Sufficient oxygen-containing gas is typically supplied to the system to maintain residual oxygen in the outlet gas of the oxidation system in the wet state and the superatmospheric pressure of the gas is typically sufficient to maintain the water in the liquid phase at the selected oxidation temperature. For example, the minimum system pressure at 240 ° C is 3.34 MPa (33 atmospheres), the minimum pressure at 280 ° C is 6.48 MPa (64 atmospheres) and the minimum pressure at 373 ° C is 21.78 MPa (215 atmospheres). In one embodiment, the aqueous mixture is oxidized at a pressure of around 3.04 MPa (30 atmospheres) to about 275 atmospheres. The oxidation process in the wet state can be operated at an elevated temperature below 374 ° C, the critical temperature of water. In one embodiment, the wet oxidation process can be operated at an elevated temperature in the range of approximately 150 ° C and a pressure of around 0.61 MPa (6 atmospheres) at an elevated temperature of around 320 ° C and a pressure of around 20.26 MPa (200 atmospheres). In some embodiments, the wet oxidation process can be operated at a supercritical high temperature. The retention time for the aqueous mixture within the reaction chamber should generally be sufficient to achieve the desired degree of oxidation. In some modalities, the retention time is above approximately one hour and up to approximately eight hours. In at least one embodiment, the retention time is at least approximately 15 minutes and up to approximately 6 hours. In one embodiment, the aqueous mixture is oxidized for about 15 minutes to 4 hours. In another embodiment, the aqueous mixture is oxidized for approximately 30 minutes to approximately 3 hours.

According to one or more modalities , the process of oxidation in the wet state is a process of catalytic oxidation in the wet state. The oxidation reaction can be mediated by a catalyst. The aqueous mixture containing at least one undesirable constituent to be treated is generally brought into contact with a catalyst and an oxidizing agent at an elevated temperature and superatmospheric pressure. An effective amount of catalyst can generally be sufficient to increase the reaction speeds and / or to improve the efficiency of total removal of destruction from the system, including improved reduction of chemical oxygen demand (COD) and / or total organic carbon ( TOC). The catalyst can also serve to decrease the overall energy requirements of the wet oxidation system.

In at least one embodiment, the catalyst can be any transition metal in groups V, VI, VII and VIII of the Periodic Table.

In one embodiment, for example, the catalyst can be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag or alloys or mixtures thereof. The transition metal can be elemental or present in a compound, such as a metal salt. In one embodiment, the transition metal catalyst is vanadium. In another embodiment, the transition metal catalyst is iron. In yet another embodiment, the transition metal catalyst is copper.

A catalyst can be added to a mixture at any point in the wet oxidation system. The catalyst can be mixed with an aqueous mixture. In one embodiment, the catalyst can be added to the wet oxidation unit of the source of an aqueous mixture supply as illustrated in Figure 1 where the source of catalyst 40 is liquidly connected to the storage tank 10. In some embodiments, the catalyst can be added directly to the wet oxidation unit. In other embodiments, the catalyst can also be supplied to an aqueous mixture before heating - 20 and / or pressurization.

In other embodiments, the catalyst may already be present in the process stream to be treated. The aqueous mixture supplied to the oxidation unit may contain a catalytic material. For example, transition metals may be present in a waste stream to be treated by the catalytic oxidation system in the wet state. Aqueous suspensions, such as those containing volatile organic carbons, may contain metals capable of acting as a catalyst. For example, the aqueous mixture can be a suspension of gasification by-products.

According to one or more embodiments, the catalyst can be soluble in an aqueous mixture to improve the wet oxidation process. In general, the characteristics of the aqueous mixture can impact the solubility of a catalyst in the aqueous mixture. For example, a pH level of an aqueous mixture to be treated can affect the solubility of a particular catalyst in the aqueous mixture.

In some embodiments, a catalyst based on a characteristic of the aqueous mixture can be selected. As illustrated in Figure 1, the wet oxidation system can include a sensor 50, configured to detect a characteristic of the aqueous mixture to be treated. In some embodiments, sensor 50 may be a pH sensor configured to detect a pH level of the aqueous mixture and a catalyst for the wet oxidation process based on a detected pH level of the aqueous mixture may be selected.

The relationship between solubility and pH level for various catalysts is generally known to those skilled in the art. Potential pH balance diagrams have been constructed for various catalyst-water systems and are readily available to those skilled in the art familiar with how to reference them. For example, reproductions of what are commonly cited as Pourbaix diagrams available from Pourbaix, MM, The Atlas of Electrochemical Equilibria in Aqueous Solutions, National Association of Corrosion Engineers: Texas 1974, are shown in Figures 4-6 for copper, vanadium and iron, respectively.

According to one or more modalities, a soluble catalyst can be selected at the pH level detected to improve the oxidation process in the wet state. Thus, with reference to Figure 4, if the pH level of an aqueous mixture detected by the pH 50 sensor is below approximately 2 or above approximately 13, a catalyst comprising copper for catalyst source 40 can be selected according to with one or more modalities. Similarly, with reference to Figure 5, a catalyst comprising vanadium can be selected when the detected pH level is above approximately 4.5. With reference to Figure 6, a catalyst comprising iron can be selected when the pH level detected is below approximately 4. Catalysts other than those shown in this case can be used as an example.

In other embodiments, a catalyst can be selected and one or more characteristics of an aqueous mixture can be manipulated to promote the presence of the selected catalyst in a soluble form to improve the oxidation process in the wet state. For example, a pH level of the aqueous mixture can be detected by the sensor 50 and adjusted to solubilize the selected catalyst in the aqueous mixture. A pH adjusting agent can be added to the aqueous mixture at any point within the oxidation system in the wet state but is preferably added such that the catalyst is soluble within the aqueous mixture during the oxidation reaction. In some embodiments, a source of pH adjusting agent 60 may be liquidly attached to the source of the aqueous mixture 10 as shown in Figure 1. The source of pH adjusting agent 60 can generally include any material or compound capable of adjusting the pH level of the aqueous mixture to a desired value or range, such as an acid or a base. For example, it may be used an alkali metal hydroxide to adjust the pH level of the aqueous mixture. In one embodiment, ammonia can be used to solubilize the catalyst.

Again, the relationship between solubility and pH level for various catalysts is generally known to those skilled in the art. As discussed above, Pourbaix diagrams can provide information to determine a desired pH range in which a selected catalyst is soluble. Referring to Figure 4, the pH level of the aqueous mixture can be adjusted to below approximately 2 or above approximately 13 when the selected catalyst comprises copper. Similarly, with reference to Figure 5, the pH level of the aqueous mixture can be adjusted to above approximately 4.5 when the selected catalyst comprises vanadium. When a catalyst is selected which comprises iron, the pH level of the aqueous mixture can be adjusted to a level below about 4 with reference to Figure 6.

In some embodiments, the wet oxidation system may include a controller 70 for adjusting or regulating at least one operating parameter of the system or a component of the system, such as, but not limited to, active valves and pumps.

Controller 70 can be in electronic communication with sensor 50 as illustrated in Figure 1. Controller 70 can generally be configured to generate a control signal to adjust the pH level of an aqueous mixture in response to the pH 50 sensor that records a pH level outside a predetermined pH solubility range for the selected catalyst. For example, controller 70 can provide a control signal to one or more valves associated with the source of the pH adjusting agent 60 to add the pH adjusting agent to the aqueous mixture source 10.

Controller 70 is typically a microprocessor-based device, such as a programmable logic controller (PLC) or distributed control system, that receives or sends input and output signals to and from components of the oxidation system in the state moist. Communication networks can allow any sensor device or signal generator to be located at a significant distance from controller 70 or a system associated with a computer, while still providing data between them. Such communication mechanisms can be performed using any suitable technique that includes but is not limited to those using wireless protocols.

As discussed above in relation to the typical operation of the oxidation unit, a liquid effluent is separated from the oxidized aqueous mixture downstream of the oxidation reactor. In some embodiments, the catalyst can be recovered from the liquid effluent by a separation process. For example, in some embodiments, the catalyst may be precipitated out of the effluent stream. In one embodiment, a crystallizer can be used to recover the catalyst. The catalyst can then be recycled back to the wet oxidation system.

Figure 2 illustrates another modality of the wet oxidation system that includes a system for recycling the catalyst. In this embodiment, the process current can enter system 200 through line 202. The catalysts that can be used in the 200 po12 system may include any transition metal from groups V, VI, VII and VIII of the Periodic Table. In some embodiments, for example, the catalyst may be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag or alloys or mixtures thereof. The transition metal can be elemental or be present in a compound, such as a metal salt. In one embodiment, the transition metal catalyst is vanadium. In another embodiment, the transition metal catalyst is iron. In yet another embodiment, the transition metal catalyst is copper.

According to one or more embodiments, the catalyst may be soluble in the aqueous mixture to improve the wet oxidation process. In general, the aqueous mixture characteristics may cause an impact on the solubility of a catalyst in an aqueous mix. For example, a pH level of an aqueous mixture to be treated can affect the solubility of a particular catalyst in the aqueous mixture.

According to one or more modalities, a soluble catalyst at the pH level of the incoming aqueous mixture can be selected to improve the oxidation process in the wet state. A pH sensor, similar to the pH sensor 50 of FIG. 1 can be incorporated into the wet oxidation system inlet 200 of Figure 2 to provide an indication of the

-20 pH of the aqueous input mixture. Thus, with reference to Figure 4, if the pH level of the aqueous mixture is below approximately 2 or above approximately 13, a catalyst comprising copper can be selected according to one or more modalities. Similarly, with reference to Figure 5, a catalyst can be selected which comprises vanadium when the pH level of the aqueous mixture is above approximately 4.5. With reference to Figure 6, a catalyst comprising iron can be selected when the pH level of the aqueous mixture is below approximately 4. Catalysts other than those presented as examples in this case can be used.

With reference to Figure 2, the catalyst can be added to the process stream at the entrance of the system or as it flows through line 202 through line 224, which may contain an aqueous mixture comprising 13 recycled catalyst as will be discussed further below. The new catalyst can also be added together with the recycled catalyst.

In other embodiments, the catalyst or a part of the catalyst may already be present in the process stream to be treated. The aqueous mixture supplied to the oxidation unit may contain a catalytic material. For example, transition metals may be present in a tailing stream to be treated by catalytic oxidation in the wet system. Aqueous suspensions, such as those containing volatile organic carbons, may contain metals capable of acting as a catalyst. For example, the aqueous mixture can be a suspension of gasification by-products.

The process current can pass through the heat exchanger 204 where it can be heated to the desired temperature during a given residence time before entering the reactor 206. After the treatment is completed, the treated process current leaves the reactor 206 through line 208. The treated process stream can then be cooled by heat exchanger 210, which in some embodiments can be the same heat exchanger as heat exchanger 204. The treated current process can have its pH adjusted by addition of an acid or alkaline compound from a source of pH adjusting agent 212. A pH sensor (which does not appear in the figure) can be provided in communication with the source of pH adjusting agent 212 to monitor the pH of the oxidized aqueous mixture as a pH adjusting agent is added from the source of the adjusting agent. pH 212 and provide a signal to stop adjusting the pH when the pH reaches a predetermined point. In alternating modalities, a pH sensor (which does not appear in the figure) can be located downstream from the source of pH 212 adjusting agent and coupled to a pH controller (which does not appear in the figure), such as controller 70 illustrated in Figure 1, configured to control the pH adjustment agent flow from the pH adjustment agent source through pumps and / or valves and / or distribution piping associated with the pH adjustment agent source 212 to the oxidized aqueous mixture for maintain a pH within a predetermined range. In some embodiments, the addition of pH adjusting agent from the source of pH adjusting agent 212 can be controlled manually. In some embodiments, the source of pH adjusting agent 212 can be configured to introduce the pH adjusting agent into line 218 downstream of the gas / liquid separator 214 instead of upstream of the gas / liquid separator 214 as illustrated in Figure 2. In other embodiments, the source of pH-adjusting agent 212 can be configured to introduce the pH-adjusting agent directly into clarifier 220.

For example, if copper is used as a catalyst, the treated process stream containing soluble copper hydroxide can be cooled to around 80 ° C and the pH adjusted to a range of from approximately 6 to approximately 12, upstream or downstream of the gas / liquid separator 214 or inside the clarifier 220, conditions under which the copper hydroxide solubility is low (&lt;1 ppm at 25 ° C). In some modalities the pH can be adjusted to a range of from approximately 8 to approximately 9 and in some modalities the pH can be adjusted to approximately 9. After passing through the gas / liquid separator 214, where the outlet gas is released through line 216, the treated process current can travel through line 218 to clarifier 220 where in the presence of oxygen at 80 ° C at a pH from approximately 6 to approximately 12, at least part of the copper hydroxide is converted to particulate copper oxide. In some embodiments, copper hydroxide is converted to particulate copper oxide in the clarifier at a pH in the range of approximately 8 to approximately 9, and in some embodiments, copper hydroxide is converted to particulate copper oxide in the clarifier at a pH of approximately 9. Copper oxide particulates can settle in clarifier 220 and at least part of the concentrated effluent suspension can be removed and recycled back to the system inlet 200 via line 224, while the essentially copper-free effluent can be removed on line 222. The pH of the effluent containing recycled copper can be adjusted by adding an acidic or alkaline compound from the source of pH 226 adjusting agent as desired in response to a signal from a pH sensor in communication with line 224 (which does not appear in the figure) and / or a pH controller (which does not appear in the figure). The pH adjusting agent can be added to the effluent containing recycled copper to adjust the pH to a level at which the copper catalyst is soluble. For example, since copper is generally soluble at pH levels below approximately 6 or above approximately 12, if the effluent containing recycled copper has a pH of between approximately 6 and approximately 12, acid can be added to decrease the level of pH for the effluent containing recycled copper to below approximately 6 or alternatively, a caustic compound can be added to increase the pH level of the effluent containing recycled copper to above approximately 12 to solubilize at least part of the copper catalyst. At least part of the recycled catalyst can be directed to a source of catalyst 40 in some embodiments.

It may be advantageous in some applications to use a two-stage catalyst settling process to make the system more efficient and reduce the amount of chemicals used during the operation of the system. Figure 3 illustrates a modality of a wet air oxidation system that uses a two-stage catalyst sedimentation process. As illustrated in Figure 3, a system 300 with a two-step catalyst settling process can use a set of clarifiers 228 and 230. In one embodiment, the optional source of pH-adjusting agent 212 can be positioned upstream of the separator of gas / liquid 214. In some embodiments of the 300 system, a source of pH adjustment agent and associated pumps and / or valves and / or application piping may be present and configured to apply the pH adjustment agent to locations upstream or downstream of the separator gas / liquid 214 and / or clarifier 228, clarifier 230 or both. Multiple pH sensors (not shown in the figure) can be located in locations upstream or downstream of the system components &lt;· 300 and coupled to a pH controller (not shown in the figure), such as controller 70 shown in Figure 1, configured and arranged to control the flow of pH adjusting agent from one or more sources of adjusting agent pH values ​​located throughout the system, as a source of pH 234 adjusting agent, by means of pumps and / or valves and / or application piping associated with the source or sources of pH adjusting agent.

In system 300 of Figure 3, unfinished clarification can occur in the first clarifier 228. At least part of a first solution separate from the first clarification step can be returned to the system entrance via lines 236 and 224 as dilution water and catalyst feed for further treatment. At least part of the supernatant from the first clarification stage can travel through line 232 and be pelleted in a second clarifier stage in clarifier 230 after having its pH adjusted by the addition of acid or alkaline compound from the source of the cleaning agent. pH adjustment 234. The source of pH 234 adjusting agent and associated pumps and / or valves and / or piping for application may be positioned and arranged to justify the pH of the supernatant part in line 232 or in clarifier 230 or am&gt; 20 bos. In alternate embodiments of the systems according to Figure 2 or Figure 3, any or all of the clarifiers can be replaced with any form of separator capable of separating the precipitated catalyst from the oxidized aqueous mixture. A solution containing concentrated solidified catalyst can be returned to the inlet of system 300 via lines 238 and 224 to be mixed with a stream from the inlet process, while oxidized effluent essentially free of catalyst can be removed via line 222. At least a portion of the recycled catalyst can be directed to a catalyst source 40 in some embodiments. An advantage of the two-step system is that a small portion of the wet oxidation unit's effluent will need to have its pH adjusted to precipitate the catalyst. The part of the effluent that can be recycled for dilution with water may have a soluble catalyst that remains in it, which is desirable. The source of pH adjusting agent 226 can be used to solubilize the catalyst that can travel on line 224 by adding an acidic or caustic compound in a similar manner as was discussed in relation to the example referring to the copper catalyst above. The pH of the recycled effluent from the oxidation unit in the wet state will also be very close to the pH needed to keep the catalyst soluble in the wet air oxidation system.

In the system as illustrated in Figure 2 and Figure 3, the catalyst can be precipitated solely by adjusting the pH of the oxidized aqueous mixture. In some embodiments, the pH adjustment can be carried out without the addition of chemical substances, such as, for example, by an electrodeionization process, to cause the catalyst to precipitate. In other embodiments, an additional chemical substance, such as, for example, a source of sulfide ions such as sodium sulfide or hydrogen sulfide can be added to the oxidized aqueous mixture to improve kinetics or else to facilitate precipitation of the catalyst.

According to one or more modalities, the wet stream of oxidized liquid effluent can be processed by a secondary treatment unit 80 as illustrated in Figure 1, connected downstream of the oxidation reactor 24 to remove the remaining undesirable constituents present and / or polish when needed or desired. The secondary treatment unit 80 can be a chemical scrubber, a biological scrubber, a bed of adsorption medium or another operating unit. In some embodiments, an advanced oxidation step can be performed that includes oxidation treatment of oxidation of the effluent in the wet state with ozone and ultraviolet light. Such advanced oxidation treatment is typically carried out in a container or tank at or near ambient temperature and pressure. The secondary treatment unit 80 can be dimensioned to provide a surface area consistent with the desired degree of polishing. Alternatively, the liquid effluent can also be recycled back to reactor 24 for further processing. Treatment of the outgoing gas may also be necessary in an outgoing gas treatment unit18 downstream depending on its composition and the requirements for discharge into the atmosphere.

Sensors can be provided to detect a concentration of an odorant constituent targeted upstream and / or downstream of the wet oxidation unit 24 to facilitate control of the system. For example, a sensor may be positioned in conduit 26 and be in communication with the controller 70 to determine and / or control whether the liquid effluent stream would be diverted to the secondary treatment unit 80 to comply with the established environmental regulations.

It should be considered that numerous changes, modifications and improvements can be made to the systems and methods illustrated. For example, one or more wet oxidation systems can be linked to multiple sources of process currents. In some embodiments, the wet oxidation system may include additional sensors to measure other properties or operating conditions of the system. For example, the system can include sensors for temperature, pressure drop and flow at different points to facilitate system monitoring. According to one or more embodiments, the catalyst can be replenished during the oxidation process in the wet state.

The invention considers modifying existing installations to improve one or more systems or components to implement the techniques of the invention. An existing wet oxidation system can be modified according to one or more of the modalities discussed here in an ideal way that uses at least part of the pre-existing equipment. For example, one or more sensors and a pH controller can be provided and according to one or more modalities presented here, they can be implemented in a pre-existing wet oxidation system to promote catalyst solubility or to facilitate catalyst recycling .

The function and advantages of these and other embodiments of the present invention will be more fully understood by the following examples. These examples are intended to be illustrative in nature and are not to be construed as limiting the scope of the invention. In the following examples, the compounds are treated by oxidation in the wet state to effect the destruction of the bonds in that case.

EXAMPLES

Reactors for Wet Oxidation in Bench Scale Reactors (Autoclave)

In the following Examples, wet oxidation tests were carried out on a bench scale in laboratory autoclaves. Autoclaves differ from the full-scale system in that they are batch reactors, where the full-scale unit can be a continuous flow reactor. Autoclaves typically operate at a higher pressure than the full scale unit, as a large air charge must be added to the autoclave to provide sufficient oxygen for the duration of the reaction. The results of the autoclave tests provide an indication of the performance of the wet oxidation technology and are useful for selection operating conditions for the wet oxidation process.

The autoclaves used were manufactured with titanium, alloy 600 and Nickel 200. The selection of the construction autoclave material was based on the composition of the wastewater feed material. The autoclaves selected for use, each have a total capacity of 500 or 750 ml.

The autoclaves were loaded with waste water and sufficient compressed air to provide excess residual oxygen after oxidation (about 5%). The loaded autoclaves were placed in a heater / stirrer mechanism, heated to the desired temperature (280 ° C to 350 ° C) and maintained at the temperature for the desired period of time, in the range of approximately 60 minutes to approximately 360 minutes.

During the heating and reaction periods, the temperature and pressure of the autoclave were monitored by a computer-controlled data acquisition system. Immediately after oxidation, the autoclaves were removed from the heater / stirrer mechanism and * cooled to room temperature using tap water. After cooling, the pressure and volume of the outlet gas in the main space of the autoclave were measured. A sample of the outlet gas was analyzed for permanent gases. Subsequent to the analysis of the outlet gas, the auto-key was depressurized and opened. The oxidized effluent was removed from the autoclave and placed in a container for storage. Part of the effluent was subjected to analysis and the rest was used for post-oxidative treatment. To generate enough volume for analytical work and post-oxidation testing, multiple autoclave tests were performed for each condition.

Example 1: Wet oxidation process using a homogeneous copper catalyst

Bench-top wet oxidation tests were carried out at 280 ° C with a time of 60 minutes at temperature to determine the impact of a copper catalyst in relation to the oxidation of acetic acid at various pH levels (pH = 2, 2, 8.1, 11.5, 12.5 and 13.5). The data are presented below in Table 1.

Table 1. Results of wet oxidation (WO) of a solution of acetic acid using copper catalyst.

<td rowspan="5">Oxidation in the Wet State at 280 ° C - 60 minutes</td><td></td><td>Effluent</td><td>II X CL</td><td> 13,5</td><td></td><td>INC 600</td><td> 750</td><td> 200</td><td> 0,5</td><td> 20</td><td>1.79 MPa (260 psig)</td><td> 280 1</td><td> 09</td><td colspan="2"></td><td> 1180</td><td> 90</td>

<td></td><td>Effluent</td><td>II X CL</td><td> 12,5</td><td></td><td>Ni 200</td><td> 500</td><td> 100</td><td> -</td><td>CD</td><td>1.38 MPa (200 psig)</td><td> 280</td><td> 09</td><td colspan="2"></td><td> 0969</td><td>CO</td>

<td></td><td>Effluent</td><td>II X CL</td><td>IO</td><td></td><td>Ni 200</td><td> 500</td><td> 100</td><td> -</td><td>C \ l_</td><td>1.38 MPa (200 psig)</td><td> 280</td><td> 09 1</td><td colspan="2"></td><td> 7300</td><td> 27,7</td>

<td></td><td>Effluent</td><td>II X CL</td><td> 00</td><td></td><td>i—</td><td> 500</td><td> 100</td><td> -</td><td>r-</td><td>1.38 MPa (200 psig)</td><td> 280</td><td> 09</td><td colspan="2"></td><td> 7300</td><td> 27,7</td>

<td></td><td>Effluent _I</td><td>II X CL</td><td> 2,2</td><td></td><td>H</td><td> 500</td><td> 150</td><td> -</td><td>O</td><td>2.14 MPa (310 psig)</td><td> 280</td><td> 09</td><td colspan="2"></td><td> 356</td><td> 96,5</td>

<td></td><td>10g / L</td><td>Acetic</td><td>Acid</td><td>food</td><td></td><td> !</td><td> 1 1</td><td>s</td><td> ! 1</td><td> 1 1</td><td> 1 1 1</td><td>í 1</td><td> 1</td><td colspan="2"></td><td> 10100</td><td> 1 1</td>

<td colspan="5" rowspan="3"></td><td></td><td>I 1</td><td> !</td><td> 1 1 1</td><td>Ass</td><td>NaOH</td><td> 1 1 1</td><td>s 1</td><td> 1</td><td colspan="2">Reported as</td><td> 02</td><td>s</td>

<td></td><td> 1 1</td><td>ml _1</td><td>ml</td><td>O)</td><td>_j O)</td><td>ro σ&gt; £ L co 2 Q;</td><td>O 0</td><td>Min</td><td colspan="2"></td><td>mg / L</td><td>s 1</td>

<td>Carqa Conditions</td><td>Autoclave Material</td><td>| Autoclave Volume</td><td>Volume of Liquid Loaded</td><td>Copper Concentration</td><td>NaOH Loaded</td><td>Air Charged</td><td>Oxidation Temperature</td><td>Temperature Temperature</td><td>Analysis Results I</td><td></td><td>M. COD</td><td>% COD Destruction</td>

Table 1. Continuation

<td rowspan="5">Oxidation in the Wet State at 280 ° C - 60 minutes</td><td></td><td>Effluent</td><td>II X CL</td><td> 13,5</td><td> 485,0</td><td> 88,1</td><td> 84,5</td><td> 13,5</td><td colspan="2"></td><td> 1260</td><td> 87,5</td>

<td></td><td>Effluent</td><td>II X CL</td><td> 12,5</td><td> 2750</td><td> 30,4</td><td>CO O</td><td> 12,50</td><td colspan="2"></td><td> 6480</td><td> 35,5</td>

<td></td><td>Effluent</td><td>II X CL</td><td>I Q</td><td> 2790</td><td> 29,4</td><td> &lt;0,1</td><td> 11,46</td><td colspan="2"></td><td> 7270</td><td> 27,7</td>

<td></td><td>Effluent</td><td>II X Q.</td><td> 00</td><td> 2790</td><td> 29,4</td><td> 1,04</td><td> 8,13</td><td colspan="2"></td><td> 8390</td><td>I 16.5</td>

<td></td><td>Effluent</td><td>II X CL</td><td> 2,2</td><td></td><td> 96,4</td><td> 633</td><td> 2,20</td><td colspan="2"></td><td> 222</td><td> 97,8</td>

<td></td><td>10 g / L</td><td>Acetic</td><td>Acid</td><td>food</td><td> 3950</td><td> 1 1</td><td>1 1 t</td><td> !</td><td colspan="2"></td><td> 10050</td><td> !</td>

<td colspan="5" rowspan="3"></td><td>O</td><td> 1 1 1</td><td>Ass</td><td>s</td><td colspan="2"></td><td>X O O O CO X O</td><td> 1 1</td>

<td>mg / L</td><td> 1 1</td><td>mg / L</td><td>I 1</td><td colspan="2"></td><td>mg / L</td><td>XP</td>

<td>TOC</td><td>% of OCD Destruction</td><td>Soluble Copper</td><td>X CL</td><td>Organic Acids</td><td></td><td>Acetic Acid</td><td>% Acetic Acid Destruction</td>

The copper catalyst exhibited the highest solubility at pH levels of 2.2 and 13.5. When the pH of the oxidized effluent was 2.2 and 13.5, approximately 98% and 88% acetic acid destruction was achieved, respectively. This also corresponded to the highest percentages of COD destruction (96.5%, 90%) and TOC destruction (96.4%, 88.1%). In contrast, when the pH of the solution was maintained in the pH range where copper was not soluble (pH = 8.1, 11.5 and 12.5), only a destruction of approximately 17% to 37% of acid was achieved acetic. When copper was not soluble, lower percentages of COD destruction and TOC destruction were observed in the same way. The data indicated that copper solubility substantially increased the oxidation of acetic acid.

Example 2: Wet oxidation process using a homogeneous vanadium catalyst

Bench-scale wet oxidation tests were carried out in a solution in water containing acetic acid that uses vanadium as a homogeneous catalyst at two different pH levels. The results are shown in Table 2 below.

Table 2. Results of wet oxidation of an acetic acid solution using a vanadium catalyst.

<td>With WO Catalyst at 280 ° C, 60 minutes pH = 5.3</td><td> 197272</td><td> 2790-30-1</td><td></td><td>H</td><td> 500</td><td> 150</td><td> 5000</td><td> 8*9</td><td>2.7 MPa (300 psig)</td><td>O 00 CM</td><td> 09</td><td colspan="2"></td><td> 3093</td><td> 17,3</td><td> 5,29</td>

<td>Without WO Catalyst at 280 ° C, 60 minutes pH = 6.5</td><td> 188420</td><td> 2751-91-1</td><td></td><td>H</td><td> 500</td><td> 150</td><td>O</td><td> 6,8</td><td>2.7 MPa (300 psig)</td><td> 280</td><td> 09</td><td colspan="2"></td><td> 3790</td><td> 5,3</td><td> 6,50</td>

<td>With WO Catalyst at 280 ° C, 60 minutes pH = 2.7</td><td> 197271</td><td> 2790-29-1</td><td></td><td>P</td><td> 500</td><td> 150</td><td> 5000</td><td>O</td><td>2.7 MPa (300 psig)</td><td> 280</td><td> 09</td><td colspan="2"></td><td> 3330</td><td>O</td><td> 2,66</td>

<td>Without WO Catalyst at 280 ° C, 60 minutes pH = 2.7</td><td> 188294</td><td>2751-88-1 _I</td><td></td><td>H</td><td> 500</td><td> 150</td><td>O</td><td>O</td><td>2.7 MPa (300 psig)</td><td> 280</td><td> 09</td><td colspan="2"></td><td> 3710</td><td>CM</td><td> 2,6</td>

<td>10 g / L Acetic Acid Feed for V Races</td><td>197268 _I</td><td> 2790-26-1</td><td></td><td> 1 1</td><td> !</td><td> !</td><td> 1</td><td> !</td><td> 1</td><td> 1 1</td><td> 1</td><td colspan="2"></td><td> 3741</td><td> 1</td><td></td>

<td rowspan="3"></td><td></td><td></td><td></td><td>í 1</td><td> 1 1</td><td>I 1</td><td> &gt;</td><td>NaOH</td><td> 1 1 1</td><td> ! 1</td><td> !</td><td colspan="2">Reported as</td><td>O</td><td>s 1</td><td> 1 1</td>

<td></td><td></td><td></td><td> 1 1</td><td>AND</td><td>AND</td><td>mg / L</td><td>_j O)</td><td>TO 'Õ) ^w2 Q;</td><td>O O</td><td>min</td><td colspan="2"></td><td>Γ mg / L</td><td> 1 1</td><td> 1 1</td>

<td>Lims ¹ _1</td><td>Ref Book</td><td>Carqa Conditions</td><td>Autoclave Material</td><td>Autoclave Volume</td><td>Volume of Liquid Loaded</td><td>Vanadium Concentration</td><td>NaOH Loaded</td><td>Air Charged</td><td>Oxidation Temperature</td><td>Temperature Temperature</td><td>Analysis Results</td><td></td><td>TOC</td><td>% of OCD Destruction</td><td>I CL</td>

I 'Under oxidation conditions, vanadium is soluble at pH levels greater than approximately 4.5. The results show that when the pH of the solution was 2.6 and vanadium was mostly insoluble, only 2% TOC destruction was achieved. A low percentage of TOC destruction was associated with a pH level of 2.66 in the same way. When the pH of the solution increased to 5.3 (vanadium solubilization), while maintaining the same catalyst dosage, temperature and time and the time at temperature, the destruction of TOC was increased by 17.3%. By increasing the pH of the solution from 2.66 to 5.3, there was approximately a 64% increase in the destruction of total organic carbon. The data indicated that the solubility of vanadium substantially increased the oxidation of acetic acid.

Example 3: Wet oxidation process using a homogeneous iron catalyst

Wet oxidation tests were carried out on a bench scale at 230 ° C for 150 minutes in an oxalic acid solution at two different pH levels. The data are presented in Table 3 below.

Table 3. Wet oxidation results of an oxalic acid solution using an iron catalyst

<td>Low pH, Catalyst from Fe</td><td colspan="2"></td><td>i—</td><td> 500</td><td> 200</td><td>3.03 MPa (440 psig)</td><td> 230</td><td> 150</td><td> 2,24</td><td colspan="3"></td><td> &lt; 5,6</td><td> 99,9</td><td> 1</td><td>r-</td>

<td>Low pH, without catalyst</td><td colspan="2"></td><td>H</td><td> 500</td><td> 200</td><td>3.03 MPa (440 psig)</td><td> 230</td><td> 150</td><td> 1 1 1</td><td colspan="3"></td><td> 240,0</td><td> 95,3</td><td> 1 1 1</td><td> 2,6</td>

<td>High pH, catalyst from Fe</td><td colspan="2"></td><td>Inc 600</td><td> 750</td><td> 250</td><td>3.59 MPa (520 psig)</td><td> 230</td><td> 150</td><td> 2,24</td><td colspan="3"></td><td> 3720</td><td> 27,1</td><td> 912,0</td><td> 13,6</td>

<td>High pH, without catalyst</td><td colspan="2"></td><td>Inc 600</td><td> 750</td><td> 250</td><td>3.59 MPa (520 psig)</td><td> 230</td><td> 150</td><td> 1 1</td><td colspan="3"></td><td> 3650</td><td> 28,4</td><td> 955</td><td> 13,7</td>

<td>food 18 g / L Oxalate _________I</td><td colspan="2"></td><td>s 1</td><td> 1 1</td><td> 1 1</td><td> 1 1 1</td><td> 1 1</td><td> 1 1</td><td> 1 1</td><td colspan="3"></td><td> 5100</td><td>í 1</td><td> &lt;20</td><td> 13,7</td>

<td rowspan="3"></td><td colspan="2">Featured as</td><td>ί 1</td><td> 1 1</td><td> 1 1 1</td><td>s 1</td><td> !</td><td>j</td><td>Φ LL</td><td>Featured</td><td colspan="2">as</td><td>O</td><td>i 1</td><td>O</td><td> !</td>

<td>Units</td><td></td><td>i 1</td><td> 2</td><td></td><td>psig (MPa)</td><td>υ O</td><td>min</td><td>_J B)</td><td colspan="2">Units</td><td></td><td>_l AND</td><td>O**</td><td>mg / L</td><td> 1 1</td>

<td>Carqa Conditions</td><td></td><td>Autoclave Material</td><td>Autoclave Volume</td><td>Volume of Liquid Loaded</td><td>Air Charged</td><td>Oxidation Temperature</td><td>Temperature Temperature</td><td>O w ω LL O AND O O Ό CD ç O çj CD CM + ω LL</td><td colspan="2">Analysis Results</td><td></td><td>TOC</td><td>Destruction of OCD</td><td>DIC</td><td>X Q.</td>

Under oxidation conditions, iron is soluble below a pH level of approximately 4. The results indicated that there was no improvement in oxidation when an iron catalyst was used at a high pH level (pH = 13.6 and 13, 7) where it was insoluble. When the pH of the solution was in the range where the iron was soluble (pH = 2.6 and 1.7), the destruction of oxalic acid was increased to approximately 95% and approximately 100%, respectively. The data indicated that the solubility of iron substantially increased the oxidation of oxalic acid.

Example 4: Chlorophenol wet oxidation using a homogeneous iron catalyst

Both catalyzed and non-catalyzed iron oxidation of chlorophenol were carried out at 150 ° C with a time of 90 minutes at temperature. The data are tabulated below in Table 4.

Table 4. Results of oxidation in the wet state of chlorophenol using an iron catalyst.

<td rowspan="3">Chlorophenol WO (1.24 g / L)</td><td>Fe Catalyst</td><td> 182596</td><td> 2751-83-1</td><td colspan="2"></td><td>H</td><td> 500</td><td> 200</td><td>1.38 MPa (200 psig)</td><td> 150</td><td>O O</td><td> 0,5</td><td colspan="2"></td><td> 650</td><td>68.1 I</td><td> 284</td><td>m</td><td> 00</td><td> 09‘3</td>

<td>Without Catalyst</td><td> 182595</td><td> 2751-82-1</td><td colspan="2"></td><td>P</td><td> 500</td><td> 200</td><td>1.38 MPa (200 psig)</td><td> 150</td><td>O O)</td><td> !</td><td colspan="2"></td><td>O O 00</td><td>VL</td><td> 620</td><td>O P</td><td> 1 1 1</td><td> 2,90</td>

<td>food</td><td> 182594</td><td> 2751-51-1</td><td colspan="2"></td><td>s 1</td><td> 1 1 1</td><td>ΐ</td><td> 1 1</td><td> !</td><td> 1 1</td><td> 1 1 1</td><td colspan="2"></td><td> 2040</td><td>I 1</td><td> 667</td><td> 1 1</td><td> 1 1 1</td><td> 5,4</td>

<td colspan="2" rowspan="3"></td><td></td><td></td><td colspan="2">Featured as</td><td> 1</td><td>i</td><td> 1 1</td><td> !</td><td> 1 </td><td>1 i</td><td>O CSI I N- O ω φ LL</td><td colspan="2">Featured as</td><td>CM O</td><td>s 1</td><td>O</td><td>s 1</td><td>Φ LL</td><td> !</td>

<td></td><td></td><td>Units</td><td></td><td> 1 1 1</td><td>AND</td><td> £</td><td>MPa (psig)</td><td>O O</td><td>me</td><td>_J / 3)</td><td>Units</td><td></td><td>Mg / L</td><td>σ '</td><td>Mg / L</td><td>σ '</td><td>Mg / L</td><td>1 I</td>

<td>LIMS</td><td>Book Ref</td><td>Carqa Conditions</td><td></td><td>Autoclave Material 1</td><td>Autoclave Volume</td><td>Volume of Liquid Loaded</td><td>Air Charged</td><td>Oxidation Temperature</td><td>Temperature Temperature</td><td>Fe Catalyst Added</td><td>Analysis Results</td><td></td><td>M. COD</td><td>Destruction of COD</td><td>O O 1-</td><td>Destruction of OCD</td><td>Sol de Fe</td><td>X Ω.</td>

These tests demonstrated that the increased solubility of the iron catalyst, by decreasing the pH level from 2.9 to 2.3, resulted in an increase in TOC destruction from approximately 7% to approximately 57%. Similarly, decreasing the pH level increased DOC destruction from approximately 7.4% to approximately 68.1%. The data indicated that even a slight adjustment in the pH level significantly increases the efficiency of catalytic oxidation in the wet process.

Example 5: Copper Oxide Recycling Testing

Comparison tests were conducted to assess the pH adjustment to recover the copper catalyst. Two sets of tests were performed. In a first set of tests, the exhausted naphthenic caustic without pH adjustment was oxidized at 200 ° C with a residence time of 120 minutes and 5000 mg / L of copper added as copper oxide. The second set of tests was carried out with exhausted naphthenic caustic with pH adjustment at 200 ° C with a residence time of 120 minutes and 500 mg / L of copper added as copper oxide.

Each test set was performed under the same conditions as the following. A sample of exhausted naphthenic caustic was oxidized to produce an oxidized effluent. The pH of the oxidized effluent was adjusted to approximately 8.5 using sodium hydroxide and centrifuged. A portion of the supernatant was removed and the remaining effluent containing copper oxide was recycled back to dilution water and combined with fresh feed for subsequent oxidation. Each run was subjected to several repetitions because the oxidation of the initial feed resulted in a first recycled effluent containing copper oxide, which was combined with new and oxidized feed, resulting in a second recycled effluent containing copper oxide. Each recycling was combined with new feed for oxidation and formation of a subsequent recycling for the number of cycles indicated in Tables 5 and 6.

The destructions of COD and TOC for each repetition of recycling were calculated in two different methods. The first method was &lt;· based on the feed mixture that was placed in an autoclave. As the oxidized effluent from the previous run was used to dilute the exhausted caustic as received, the feed COD was calculated using the ratio of new feed to oxidized effluent. The second method was based on feeding as received and is related to COD - global destruction. As the oxidized effluent was returned to the WAO system for dilution, no additional water was added to the system which would decrease the overall COD.

The results for the recycling product without pH adjustment and with pH adjustment are presented in Tables 5 and 6, respectively.

Table 5: Testing of recycling effluent without pH adjustment in exhausted naphthenic caustic

<td rowspan="4">Recycling pH = 6</td><td>Recycling 3</td><td></td><td> 200</td><td>CM</td><td>m</td><td>O</td><td colspan="2"></td><td> 30900</td><td>51.8 I</td><td> 88,1</td><td> 10900</td><td> 38,3</td><td> 81,2</td><td> 55,5</td><td> 3500</td><td> 6,2</td>

<td>-1 Recycling 2</td><td></td><td> 200</td><td>CM</td><td>m</td><td>O</td><td colspan="2"></td><td> 27500</td><td> 54,2</td><td>1 1 I</td><td> 10100</td><td> 36,7</td><td>s</td><td> 34,3</td><td> 36,4</td><td> 6,1</td>

<td>Recycling 1</td><td></td><td> 200</td><td>CM</td><td>IO</td><td>O</td><td colspan="2"></td><td> 22700</td><td> 42,7</td><td> 1 1 1</td><td>O 00 O 00</td><td>L 8.8</td><td> 1 1 1</td><td> 22,9</td><td> 26,3</td><td> 6,3</td>

<td>I Initial</td><td></td><td> 200</td><td>CM</td><td>io</td><td>O</td><td colspan="2"></td><td>I</td><td> 1 1</td><td> {</td><td>ί 1</td><td>ί 1</td><td> 1</td><td> 1 1 1</td><td>1 I</td><td> 5,7</td>

<td rowspan="5"></td><td>I food Diluted</td><td></td><td></td><td></td><td></td><td></td><td colspan="2"></td><td> 39627</td><td> 1 1</td><td>s 1</td><td> 8859</td><td> 1 1</td><td>s 1</td><td> 1 1</td><td>s 1</td><td> 1 1 1</td>

<td>I KSW</td><td></td><td></td><td></td><td></td><td></td><td colspan="2"></td><td> 259.000</td><td>s 1</td><td> 1 1 1</td><td> 57.900</td><td> 1 1 1</td><td> 1 1 1</td><td> 1</td><td>s</td><td> 13,5</td>

<td></td><td></td><td></td><td></td><td></td><td></td><td colspan="2">Reported as</td><td> 02</td><td> !</td><td> 1 1 1</td><td></td><td>i 1</td><td> 1 1 1</td><td>Ass</td><td>Cu |</td><td> 1 1 1</td>

<td></td><td></td><td>O O</td><td>Hours</td><td>_j σ&gt;</td><td>% in v / v</td><td>Units</td><td></td><td>mg / L</td><td></td><td>O^x</td><td>mg / L</td><td></td><td>X®</td><td>mg / L</td><td>mg / L</td><td>s 1</td>

<td>Sample Label Received</td><td>Carqa Conditions</td><td>Temperature</td><td>Residence time</td><td>Cu Added as CuO</td><td>Ácido Sulfúrico Added</td><td>Analytical Results</td><td></td><td>COD</td><td>Destruction of COD - Autoclave</td><td>Destruction of COD - Global</td><td>O O 1-</td><td>Destruction of TOC - Autoclave</td><td>Destruction of TOC - Global</td><td>Soluble Copper</td><td>Total Copper</td><td>X Q.</td>

&lt;As shown in Table 5, adjusting the pH of the oxidized effluent to approximately 8.5 followed by sedimentation with a centrifuge recovered 22.9 mg / L of soluble copper in Recycling Product 1, which was then combined with new feed for additional oxidation. The pH of the recycled effluent containing soluble copper has not yet been adjusted with acid or base before being combined with the new feed.

The amount of soluble copper recovered at each recycling step increased at each repetition to 55.5 mg / L in Recycling Product 3. After three repetitions of recycling, the oxidation / recycling system began to achieve a steady state condition with an efficiency destruction of COD in an autoclave of 51.8% which resulted in an overall destruction efficiency of COD of 88.1%. The autoclave TOC destruction efficiency increased with each repetition from 8.8% to 38.3% with an overall TOC destruction efficiency of 81.2% with the

Recycling 3. These results demonstrate that adjusting the pH of an oxidized effluent containing copper catalyst can produce a recycled effluent containing soluble copper that can be directed back to the oxidation system which can reduce the amount of new catalyst to be added to the oxidation system.

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<td rowspan="6">Recycling - ρΗ &lt;5</td><td>Recycle- gem 5</td><td></td><td> 200</td><td>CM</td><td> 0,5</td><td>O</td><td colspan="2"></td><td> 15100</td><td> 71,9</td><td> 94,2</td><td> 5850</td><td> 58,9</td><td> 89,9</td><td> 289</td>

<td>Recycling 4</td><td></td><td> 200</td><td>CM</td><td> 0,5</td><td>O</td><td colspan="2"></td><td> 15300</td><td> 71,4</td><td> 94,1</td><td> 6020</td><td> 56,8</td><td> 89,6</td><td>I 14.7</td>

<td>Recycling 3</td><td></td><td> 200</td><td>CM</td><td> 0,5</td><td>GO</td><td colspan="2"></td><td> 14900</td><td> 72,4</td><td> 94,2</td><td> 5670</td><td> 59,4</td><td> 90,2</td><td> 354</td>

<td>Recycling 2 _I</td><td></td><td> 200</td><td>CM</td><td> 0,5</td><td> &lt;</td><td colspan="2"></td><td> 15400</td><td> 69,4</td><td> 94,1</td><td> 5740</td><td> 54,5</td><td>T ~ O</td><td> 108</td>

<td>Recycling 1</td><td></td><td> 200</td><td>CM</td><td> 0,5</td><td> 0,25</td><td colspan="2"></td><td> 11200</td><td> 76,1</td><td> !</td><td> 4130</td><td> 63,7</td><td> 1</td><td> 152</td>

<td>Initial</td><td></td><td> 200</td><td>CM</td><td> 0,5</td><td> 0,25</td><td colspan="2"></td><td> 7110</td><td> 82,1</td><td> 1 1 1</td><td> 2630</td><td> 70,3</td><td> 1 1 1</td><td>CM ~</td>

<td rowspan="5"></td><td>food Diluted</td><td></td><td></td><td></td><td></td><td></td><td colspan="2"></td><td> 39627</td><td> 1 1 1</td><td>i 1 1</td><td> 8859</td><td> 1 1 1</td><td>t 1</td><td> 1 1 1</td>

<td>KSW</td><td></td><td></td><td></td><td></td><td></td><td colspan="2"></td><td> 259.000</td><td> 1 1 1</td><td> 1 1 1</td><td>006'ZS</td><td> 1 1</td><td> 1 1 1</td><td> 1</td>

<td></td><td></td><td></td><td></td><td></td><td></td><td colspan="2">Reported as</td><td> 02</td><td> 1 1</td><td> 1 1 1</td><td></td><td> 1 1 1</td><td> 1 1 1</td><td>Ώ O</td>

<td></td><td></td><td>O O</td><td>Hours</td><td>_J □&gt;</td><td>% in v / v</td><td>Units</td><td></td><td>mg / L</td><td></td><td>s?</td><td>mg / L</td><td>δ?</td><td>vp θ '</td><td>σ&gt; AND</td>

<td>Received Sample Tag</td><td>Carqa Conditions i</td><td>Temperature</td><td>Residence time</td><td>Cu Added as CuO</td><td>Ácido Sulfúrico Added</td><td>Analytical Results</td><td></td><td>COD</td><td>Destruction of COD - Autoclave</td><td>Destruction of COD - Total</td><td>TOC</td><td>Destruction of OCD</td><td>Destruction of TOC - Global</td><td>Soluble Copper</td>

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As shown in Table 6, adjusting the pH of the oxidized effluent to approximately 8.5 followed by sedimentation with a centrifuge recovered 152 mg / L of soluble copper in Recycling Product 1, which was then combined with new feed for further oxidation. Prior to the entry of the new feed, each Recycling Product 1-5 had its pH adjusted with acid as indicated.

The amount of soluble copper recovered in each recycle increased from 152 mg / L to 354 mg / L from Recycle 1 to Recycle

3. Recycling 4, which was a result of a pH adjustment of the oxidized effluent to 8 instead of approximately 8.5 followed by precipitation at 60 ° C, showed significantly less soluble copper at 14.7 mg / L, however, Recycling 5, which resulted from a pH adjustment of the oxidized effluent to approximately 8.5 again, showed a marked increase in soluble copper up to 289 mg / L.

As shown in Table 6, the addition of acid to the feed and the subsequent addition of acid to each Recycling Product 1-5 caused the system to reach a steady state earlier than if no pH adjustment was made in the recycling. The recycling test carried out with the pH-adjusted feed indicated that a steady state condition was reached after two recycling repetitions. The overall destruction efficiency of TOC stabilized between 90.2% and 89.6% after two cycles. Similarly, the overall destruction efficiency of COD has stabilized at around 94% after two cycles.

Similarly, the addition of acid to the feed and the subsequent addition of acid to each Recycling Product 1-5 at higher TOC and COD destruction efficiencies than if no pH adjustment was made to the recycling product. As shown in Table 6, the addition of acid to each Recycle increased the efficiency of the overall destruction of TOC by approximately 90% compared to the destruction efficiency of approximately 81% without the addition of acid to each Recycle. Similarly, the addition of acid to each Recycle increased the efficiency of overall COD destruction to approximately 88% compared to approximately 72% with the addition of acid to each Recycle. The addition of sulfuric acid to the recycling brought the pH of the recycling to a range where the copper catalyst was more soluble and this higher level of soluble copper was available in subsequent oxidation cycles to increase destruction efficiencies.

For both test runs with and without recycling pH adjustment, another advantage to recycling the oxidized effluent and catalyst back to the WAO unit was that this increased the residence time for the most difficult to oxidize components . The residence time was increased in proportion to the amount of dilution water that needed to be added, that is, the greater the need for dilution water, the greater the residence time. The results of the recycling tests indicated that this longer residence time was effective in destroying a part of the components that were initially resistant to oxidation. As it was necessary to use a large amount of dilution in the autoclave to reduce the COD of the caustic as received from from 260,000 mg / L to approximately 40,000 mg / L, the residence time for components difficult to oxidize was also very long.

As used in this case, the term large number refers to two or more elements or components. The terms comprising, including, carrying, having, containing and involving, whether in the report or in the claims and the like, are unlimited terms, that is, to mean including but not limited to. Thus, it is understood that the use of such terms encompasses the elements listed below and their equivalents, as well as additional elements. Only the transition expressions consisting of and consisting essentially of are closed or closed transition expressions, respectively, in relation to the claims.

The use of ordinal terms such as first, second, third and the like in the claims to modify one element of the claim by itself does not imply any priority, precedence or order of one element of the claim over the other or the temporal order37 in that this is a method are performed, however, they are simply used with marks to distinguish an element of the claim that has a certain name from another element that has the same name (but for the use of the term ordinal) to distinguish the elements of the claim5.

Those skilled in the art should consider that the parameters and configurations described herein are examples and that the parameters and / or configurations will depend on the specific application in which the systems and techniques of the invention are used. Those skilled in the art should also recognize or be able to verify, using no more than routine experimentation, equivalent to the specific modalities of the invention. It should therefore be understood that the modalities described herein are presented for purposes of example only and that, within the scope of the appended and equivalent claims thereof; the invention can be carried out in another way than as specifically described.