KR20150144337A - Wet air oxidation process using recycled copper, vanadium or iron catalyst - Google Patents

Abstract

The present invention relates to a system and method for processing process streams. The catalyst enables a wet oxidation process at elevated temperature and pressure to treat at least one undesired component in the aqueous mixture. The aqueous mixture may be contacted with the catalyst and oxidizer at elevated temperature and pressure above atmospheric pressure in reactor 206. At least a portion of the catalyst is precipitated by pH adjustment by the addition of an acid or an alkaline compound from the source 234 of the pH adjusting agent and is contacted with the aqueous mixture via line 238 after clarification in the clarifier 230 It can be recycled again. The pH of the recycled catalyst containing the effluent can be adjusted by the addition of an acid or alkaline compound from the source of the pH regulator 226.

Description

WATER AIR OXIDATION PROCESS USING RECYCLED COPPER, VANADIUM OR IRON CATALYST USING RECONFIGURED COPPER,

Related application

This application claims the benefit of 35 U.S.C. No. 60 / 885,966 entitled " WET AIR OXIDATION PROCESS USING RECYCLED COPPER CATALYST "filed on January 22, 2007 pursuant to §119 (e). PCT Application No. PCT / US2008 / 000784 entitled " WET AIR OXIDATION PROCESS USING RECYCLED CATALYST " filed on January 22, 2008, pursuant to § 371. &Quot; WET AIR OXIDATION PROCESS USING RECYCLED CATALYST "filed on July 21, 2009, each of which is incorporated herein by reference in its entirety.

Field of invention

The present invention generally relates to the treatment of process streams and more particularly to catalytic wet oxidation systems and methods for treating components not desired here.

Discussion of Related Application

BACKGROUND OF THE INVENTION [0002] Wet oxidation is a well known technique for treating process streams and is widely used, for example, to destroy contaminants in wastewater. This method involves the aqueous phase oxidation of the undesired components from the oxygen-containing gas with an oxidizing agent, typically molecular oxygen, at elevated temperatures and pressures. This process can convert organic contaminants to carbon dioxide, water, and biodegradable short chain organic acids, such as acetic acid. Inorganic components including sulfides, mercaptides and cyanides can also be oxidized. As an alternative to incineration, wet oxidation may be used for subsequent emissions, in-process recycling, or for pretreatment to supply a conventional biological treatment plant for polishing Can be used in a wide variety of applications to process the process stream as a step. Catalytic wet oxidation has been shown to be an effective improvement over traditional non-catalytic wet oxidation. Catalytic wet oxidation processes generally allow for greater failure at lower temperatures and pressures and thus lower capital costs. The aqueous stream to be treated is mixed with an oxidizing agent and contacted with the catalyst at elevated temperature and pressure. The heterogeneous catalyst is usually present in the form of solid particulate present on the bed through which the aqueous mixture is passed, or blended with the aqueous mixture prior to oxidation. The catalyst may be filtered from the downstream oxidation effluent of the wet oxidation unit for reuse.

According to one or more aspects or embodiments, the present invention relates to a process and system for catalytic wet oxidation. According to one embodiment, the catalytic wet oxidation process comprises providing an aqueous mixture containing at least one undesired component to be treated. The aqueous mixture is contacted with the catalyst and the oxidizing agent at elevated temperature and pressure above atmospheric pressure to treat at least one undesired component 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 contact the aqueous mixture.

According to another aspect, a catalytic wet oxidation system comprises a wet oxidation unit, a source of an aqueous mixture comprising at least one undesired component fluidly coupled to the wet oxidation unit, A source of a catalyst that is soluble in an aqueous mixture that is fluidly coupled to the wet oxidation unit, positioned between the source of the aqueous mixture and the wet oxidation unit, the pH level of the oxidized aqueous mixture downstream of the wet oxidation unit, Adjusting the pH level of the oxidized aqueous mixture to a level outside the predetermined pH solubility range for the catalyst in response to a pH sensor exhibiting a pH level within a predetermined pH solubility range for the catalyst, A pH controller in communication with the pH sensor, configured to generate a control signal to control the pH of the wet oxidation unit downstream And a separator configured to fluidly communicate therewith and to settle at least a portion of the catalyst positioned downstream of the pH controller, and a fluid flow control device in fluid communication with the outlet of the separator and at the inlet to at least one inlet of the catalyst source and the wet oxidation system And a connected recirculation line.

According to another aspect, a method of promoting recirculation of a catalyst used in a catalytic wet oxidation process comprises providing a pH monitoring system having a controller in communication with a pH sensor, the controller comprising: And to generate a control signal to adjust the pH level of the aqueous mixture in response to a pH sensor exhibiting a pH level within a predetermined pH solubility range.

According to another aspect, a catalytic wet oxidation process is used to treat at least one undesired component in a wet oxidation reactor and to remove the catalyst at a pH in the first range that is substantially soluble in order to form an oxidized aqueous mixture in the wet oxidation reactor And contacting the aqueous mixture containing the at least one undesired component to be treated at elevated temperature and pressure above atmospheric with a catalyst and an oxidizing agent. This process involves recycling at least a portion of the precipitated catalyst to precipitate at least a portion of the catalyst and to contact the aqueous mixture by adjusting the pH level of the oxidized aqueous mixture to a pH in the second range to form a precipitated catalyst .

In some embodiments, the first range of pH and the second range of pH do not overlap.

In some embodiments, contacting the aqueous mixture with the catalyst occurs before the aqueous mixture is brought to an elevated temperature.

In some embodiments, contacting the aqueous mixture with the catalyst occurs before the aqueous mixture is brought under atmospheric pressure.

In some embodiments, this process further comprises monitoring the pH level of the aqueous mixture.

In some embodiments, the aqueous mixture is oxidized in a continuous process.

In some embodiments, such a process further comprises supplementing the catalyst.

In some embodiments, contacting the aqueous mixture with an oxidizing agent comprises contacting the aqueous mixture with an oxygen-containing gas.

In some embodiments, precipitating at least a portion of the catalyst comprises increasing the pH of at least a portion of the oxidized aqueous mixture.

In some embodiments, precipitating at least a portion of the catalyst comprises reducing the pH of at least a portion of the oxidized aqueous mixture.

In some embodiments, the catalyst comprises copper and the first range of pH is selected from the group consisting of less than 6 and greater than about 12.

In some embodiments, the precipitated catalyst comprises copper oxide.

In some embodiments, adjusting the pH level of the oxidized aqueous mixture comprises adjusting the pH level of the oxidized aqueous mixture to a pH range of from about 6 to about 12.

In some embodiments, adjusting the pH level of the oxidized aqueous mixture comprises adjusting the pH level of the oxidized aqueous mixture to a pH range of from about 8 to about 9.

In some embodiments, such a process further comprises adjusting the pH of at least a portion of the precipitated catalyst.

In some embodiments, adjusting the pH of at least a portion of the precipitated catalyst comprises adjusting the pH to a level at which at least a portion of the precipitated catalyst is dissolved.

In some embodiments, this process further comprises purifying the oxidized aqueous mixture to form a first separated solution before precipitating at least a portion of the catalyst from the oxidized aqueous mixture.

In some embodiments, the process further comprises contacting the first separated solution with an aqueous mixture containing at least one undesired component to be treated.

In some embodiments, this process further comprises recovering substantially all of the catalyst.

In some embodiments, the aqueous mixture is oxidized for a time sufficient to treat at least one undesired component.

In some embodiments, the atmospheric pressure excess pressure is from about 30 atmospheres to about 275 atmospheres.

In some embodiments, the elevated temperature is from about 240 ° C to about the critical temperature of water.

In some embodiments, the elevated temperature exceeds the critical temperature of water.

In some embodiments, precipitating at least a portion of the catalyst is accomplished by a two stage catalyst settling process. The two-stage catalyst settling process may be performed by performing a rough clarification in a first clarifier to form a first separate solution comprising a first supernatant and a soluble catalyst, Contacting the solidified catalyst with an aqueous mixture and precipitating at least a portion of the first supernatant in a second clarifier to form a solidified catalyst and an oxidized effluent in which substantially no catalyst is present, And discharging an oxidized effluent substantially free of catalyst from the second clarifier.

In some embodiments, the process further comprises adjusting the pH of at least a portion of the first supernatant before precipitating at least a portion of the first supernatant in the second clarifier.

In some embodiments, the process further comprises adjusting the pH of the solidified catalyst from the second clarifier prior to contacting the aqueous solution.

In some embodiments, the catalyst comprises vanadium and the first range of pH is greater than about 4.5.

In some embodiments, the catalyst comprises iron and the first range of pH is less than about 4.

In some embodiments, the catalyst comprises copper and the first range of pH is selected from the group consisting of less than about 4 and greater than about 12.

In some embodiments, the first range of pH is selected from the group consisting of less than about 2 and greater than about 13.

According to another aspect, a catalytic wet oxidation system includes a source of an aqueous mixture comprising a wet oxidation unit, at least one undesired component fluidly coupled to the wet oxidation unit, a source of an aqueous mixture fluidly connected to the wet oxidation unit, A source of a catalyst that is soluble in an aqueous mixture positioned between a source of an aqueous mixture having a pH in a first range wherein the catalyst is substantially soluble, a sensor configured to detect a pH level of the oxidized aqueous mixture formed in the wet oxidation unit, A pH controller configured to generate a control signal to adjust the pH level of the oxidized aqueous mixture to a pH in a second range in which the catalyst is substantially insoluble in response to a pH sensor communicating with the pH sensor and exhibiting a pH level within the first range, Downstream of the oxidation unit and directly downstream of the pH controller, A separator configured to deposit at least a portion of the catalyst by adjusting the pH level of the aqueous mixture formed and a recycle line fluidly connected to the outlet of the separator and to the inlet of at least one of the sources of the catalyst and the inlet to the wet oxidation system .

In some embodiments, the system further comprises a secondary treatment unit connected downstream of the wet oxidation unit.

In some embodiments, the system further comprises a source of an alkaline compound that is positioned downstream and downstream of at least one of the separator and the wet oxidation unit and is fluidly coupled thereto.

In some embodiments, the system further comprises a source of acid that is positioned downstream and at least one of the separator and the wet oxidation unit and is fluidly coupled thereto.

In some embodiments, the catalyst comprises copper and the first range of pH is selected from the group consisting of less than 6 and greater than about 12.

In some embodiments, the system further comprises a second pH sensor in communication with a pH controller configured to detect a pH level of the oxidized aqueous mixture in the separator, wherein the pH controller adjusts the pH level of the oxidized aqueous mixture in the separator to about Lt; RTI ID = 0.0 > 6 to about 12 < / RTI >

In some embodiments, the pH controller is further configured to generate a control signal to adjust the pH level of the oxidized aqueous mixture in the separator to a range from about 8 to about 9.

In some embodiments, the pH controller is further configured to generate a control signal to adjust the pH level of the oxidized aqueous mixture in the separator to about 9.

In some embodiments, the system further comprises a purifier fluidly connected to and downstream of the separator configured to purify the oxidized aqueous mixture to form a reject.

In some embodiments, the system includes a conduit configured to move at least a portion of the waste to a location upstream of and in fluid communication with the wet oxidation unit in the system and to contact the waste with an aqueous mixture comprising at least one undesired component .

In some embodiments, substantially all of the catalyst is recovered.

In some embodiments, the system further comprises a source of pH adjuster fluidly connected to the recycle line.

In some embodiments, the system further comprises a third pH sensor in communication with a pH controller, configured to detect the pH level of the aqueous mixture in the recycle line, wherein the pH controller is configured to detect a pH above the predetermined pH solubility range for the catalyst Level of the aqueous mixture in the recycle line in response to a third pH sensor indicative of the level of the recycle line.

According to another aspect, a method for promoting recirculation of a catalyst used in a catalytic wet oxidation process includes providing a pH monitoring system having a controller in communication with a pH sensor, the controller comprising: to adjust the pH level of the oxidized aqueous mixture formed in the catalytic wet oxidation process in response to a pH sensor exhibiting a pH level within the pH solubility and to generate a control signal to settle the catalyst only by adjusting the pH of the oxidized aqueous mixture .

The advantages, novel features, and objects of the described aspects and embodiments will become apparent from the following detailed description, taken in conjunction with the accompanying drawings.

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component illustrated in the various figures is represented by a similar number. For the sake of clarity, not every element may be labeled on all drawings. Non-limiting embodiments will be described with reference to the accompanying drawings.
Figure 1 is a system diagram according to one embodiment of a wet oxidation system.
2 is a system diagram according to one embodiment of a wet oxidation system including a catalyst recycle process.
3 is a system diagram according to one embodiment of a wet oxidation system comprising a catalyst recycle process with a two-step precipitation process.
Figures 4 to 6 are Pourbaix diagrams referred to herein for copper, vanadium and iron, respectively.

The aspects and embodiments described herein are not limited in its application to the details of the structure and arrangement of the components described in the following description or illustrated in the drawings. The aspects and embodiments described herein may be of different embodiments and may be practiced or carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the terms "including," "having," "containing," "involving," and variations thereof, as well as the items listed below and their equivalents, It has the meaning to include additional items.

According to one or more embodiments, the present invention relates to one or more systems and methods for processing a process stream. In a typical operation, the described system may receive a process stream from a community, industry or residential source. For example, in embodiments where the system processes wastewater, the process stream may be delivered from a municipal wastewater sludge or other large-scale sewage system. The process stream can also originate from, for example, a food processing plant, a chemical processing facility, a gasification project, or a pulp and paper plant. The process stream may be moved through the system by operation in the upstream or downstream of the system.

The term "process stream" as used herein refers to an aqueous mixture that is transferable to a system for treatment. After processing, the process stream may be returned to the upstream process or may be discharged from the system as waste. The aqueous mixture typically contains at least one undesirable component that can be oxidized. The undesired component may be any targeted matter or compound to be removed from the aqueous mixture for example for public health, process design and / or aesthetic considerations. In some embodiments, the undesirable components that may be oxidized are organic compounds. Certain inorganic components such as sulfides, mercaptides and cyanides can also be oxidized. The source of the aqueous mixture to be treated by the system, for example a slurry, can take the form of direct piping from a plant or holding vessel.

According to one or more embodiments of the present invention, it may be desirable to destroy one or more specific chemical bonds in an undesired component or its degradation product (s). Oxidation reactions are one breakdown technique that can convert oxidizable organic contaminants to carbon dioxide, water, and biodegradable short chain organic acids, such as acetic acid. One aspect of the invention includes a system and method for the oxidative treatment of an aqueous mixture containing one or more undesired components.

In one embodiment, the aqueous mixture comprising at least one undesired component is wet oxidized. The aqueous mixture is oxidized with an oxidizing agent for a period of time sufficient to treat at least one undesired component at elevated temperature and pressure above atmospheric pressure. The oxidation reaction may substantially destroy the integrity of one or more chemical bonds in the undesired component. As used herein, the phrase "substantially destroyed" is defined as at least about 95% failure. The process of the present invention is generally applicable to the treatment of any undesired components that can be oxidized.

The described wet oxidation process may be performed in any known batch or continuous wet oxidation unit suitable for oxidizing the compound. Typically, aqueous phase oxidation is carried out in a continuous flow wet oxidation system, as exemplarily shown in FIG. Any oxidizing agent may be used. The oxidant is usually an oxygen-containing gas, such as air, oxygen-rich air, or essentially pure oxygen. As used herein, the phrase "oxygen-rich air" is defined as air having an oxygen content of greater than about 21%.

In a typical operation and with reference to Figure 1, the aqueous mixture from the source, shown as a storage tank 10, flows through conduit 12 to a high pressure pump 14 which pressurizes the aqueous mixture . The aqueous mixture is mixed with pressurized oxygen-containing gas supplied by compressor (16) in conduit (18). The aqueous mixture flows through heat exchanger 20, where the aqueous mixture is heated to the temperature at which it initiates oxidation. The heated feed mixture then enters the reactor vessel 24 at the inlet 38. The wet oxidation reaction is generally exothermic and the heat of reaction generated in the reactor can further raise the temperature of the mixture to the desired value. Most of the oxidation reactions take place in the reactor vessel 24, which provides a residence time sufficient to achieve the desired degree of oxidation. The oxidized aqueous mixture and the oxygen depleted gas mixture are then discharged from the reactor via conduit 26, which is controlled by a pressure control valve 28. The term " oxidized aqueous mixture "or" oxidized effluent " as used herein refers to an oxidized fluid that is discharged from the reactor vessel 24 prior to any chemical treatment in the downstream of the reactor vessel 24. Liquid-gas separation is not considered a "chemical treatment" as such terms are used herein. The hot oxidized effluent traverses the heat exchanger 20 where it is cooled relative to the incoming feed aqueous mixture and gas mixture. The cooled effluent mixture flows through conduit 30 to separator vessel 32 where the liquid and gas are separated. As the off gas is vented through the upper conduit 36, the liquid effluent is discharged from the separator vessel 32 through the lower conduit 34. The treatment of the off-gas may be required in a downstream off gas treatment unit according to its composition and requirements for discharge into the atmosphere. The wet oxidized effluent can typically be vented to a biological treatment plant for polishing. The effluent can also be recycled for further processing by a wet oxidation system.

A sufficient oxygen-containing gas is typically supplied to the system to maintain the residual oxygen in a wet oxidation system off gas, and the atmospheric pressure excess gas pressure is typically maintained at a selected oxidation temperature to maintain water in the liquid phase It is enough for. For example, the minimum system pressure at 240 ° C is 33 atmospheres, the minimum pressure at 280 ° C is 64 atmospheres, and the minimum pressure at 373 ° C is 215 atm. In one embodiment, the aqueous mixture is oxidized at a pressure of from about 30 atmospheres to about 275 atmospheres. The wet oxidation process may be operated at an elevated temperature of less than 374 < 0 > C, which is the critical temperature of water. In one embodiment, the wet oxidation process may be operated at an elevated temperature of about 150 < 0 > C and a pressure ranging from a pressure of about 6 atmospheres to an elevated temperature of about 320 < 0 > C and a pressure of about 200 atmospheres. In some embodiments, the wet oxidation process may be operated at a supercritical elevated temperature. The residence time for the aqueous mixture in the reaction chamber should generally be sufficient to achieve the desired degree of oxidation. In some embodiments, the residence time is greater than about 1 hour up to about 8 hours maximum. In at least one embodiment, the residence time is at least about 15 minutes up to about 6 hours. In one embodiment, the aqueous mixture is oxidized for about 15 minutes to about 4 hours. In another embodiment, the aqueous mixture is oxidized for about 30 minutes to about 3 hours.

According to at least one embodiment, the wet oxidation process is a catalytic wet oxidation process. The oxidation reaction may be mediated by a catalyst. The aqueous mixture containing at least one undesired component to be treated is generally contacted with the catalyst and the oxidizing agent at elevated temperature and pressure above atmospheric pressure. An effective amount of catalyst may generally be sufficient to increase the rate of reaction and / or to improve the overall destruction removal efficiency of the system, including a chemical oxygen demand (COD) and / or an overall reduction in total organic carbon (TOC). The catalyst may also be provided to lower the overall energy requirement of the wet oxidation system.

In at least one embodiment, the catalyst may be any transition metal of Groups V, VI, VII, and VIII of the Periodic Table. In one embodiment, for example, the catalyst may be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, or alloys or mixtures thereof. The transition metal may be an element or may be present in a compound, e.g., a metal salt. In one embodiment, the transition metal catalyst is vanadium. In another embodiment, the transition metal catalyst is iron. In another embodiment, the transition metal catalyst is copper.

The catalyst may be added to the aqueous mixture at any point in the wet oxidation system. The catalyst may be mixed with an aqueous mixture. In one embodiment, a catalyst may be added to the source of the aqueous mixture to feed the wet oxidation unit as illustrated in Figure 1, where the catalyst source 40 is fluidly connected to the storage tank 10 . In some embodiments, the catalyst may be added directly to the wet oxidation unit. In other embodiments, the catalyst may also be fed to the aqueous mixture prior to heating and / or pressurization.

In another embodiment, the catalyst may already be present in the process stream to be treated. The aqueous mixture fed to the oxidation unit may contain a catalytic material. For example, the transition metal may be in a waste stream to be treated by a catalytic wet oxidation system. An aqueous slurry, for example an aqueous slurry containing volatile organic carbon, may contain a metal that can act as a catalyst. For example, the aqueous mixture may be a slurry of gasification by-products.

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

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

The relationship between solubility and pH level for various catalysts is generally known to those skilled in the art. The potential-pH equilibrium diagram is constructed for a variety of catalyst-water systems and is readily available to those skilled in the art as referenced by those skilled in the art. For example, reproduction thereof is generally referred to as the Pourbaix diagram available from Pourbaix, M.M. The Atlas of Electrochemical Equilibria in Aqeous Solutions, National Association of Corrosion Engineers (Texas 1974), is presented for each of copper, vanadium and iron in FIGS.

According to one or more embodiments, a catalyst that is soluble at the exploited pH level can be selected to enhance the wet oxidation process. Accordingly, referring to FIG. 4, when the pH level of the aqueous mixture detected by the pH sensor 50 is less than about 2 (or, in some embodiments, less than about 4 or less than about 4.5), or greater than about 12 Or greater than about 13, the catalyst comprising copper may be selected for the catalyst source 40 according to one or more embodiments. Likewise, referring to FIG. 5, a catalyst comprising vanadium can be selected when the detected pH level exceeds about 4.5. Referring to FIG. 6, the catalyst comprising iron can be selected when the detected pH level is less than about 4. Other catalysts than those exemplified herein may be used.

In other embodiments, a catalyst may be selected, and one or more characteristics of the aqueous mixture may be manipulated to enhance the presence of the selected catalyst in soluble form to improve the wet oxidation process. For example, the pH level of the aqueous mixture can be detected by the sensor 50 and adjusted to solubilize the selected catalyst in the aqueous mixture. The selected catalyst may be solubilized in the aqueous mixture only by adjusting the pH of the aqueous mixture. The selected catalyst may be dissolved in the aqueous mixture without the addition of any complexing agent, such as ammonia, to facilitate solubilization of the selected catalyst in the aqueous mixture. A pH adjusting agent may be added to the aqueous mixture at any point within the wet oxidation system, but is preferably added such that the catalyst can be dissolved in the aqueous mixture during the oxidation reaction. In some embodiments, the source 60 of the pH adjuster may be fluidly coupled to the source 10 of the aqueous mixture as illustrated in FIG. The source 60 of the pH adjusting agent may generally comprise any substance or compound capable of adjusting the pH level of the aqueous mixture to a desired value or range, such as an acid or base. For example, an alkali metal hydroxide may be used to adjust the pH level of the aqueous mixture. In one embodiment, ammonia can be used to dissolve the catalyst.

In addition, the relationship between solubility and pH levels for various catalysts is generally known to those skilled in the art. As discussed above, the Purbe de Diagram can provide information for determining the desired pH range at which the selected catalyst is soluble. 4, the pH level of the aqueous mixture is adjusted to less than about 2 (or in some embodiments, less than about 4 or less than about 4.5) or greater than about 12 or greater than about 13 when the selected catalyst comprises copper . Similarly, referring to FIG. 5, the pH level of the aqueous mixture can be adjusted above about 4.5 when the selected catalyst comprises vanadium. When a catalyst containing iron is selected, the pH level of the aqueous mixture can be adjusted to a level of less than about 4 with reference to FIG.

In some embodiments, the wet oxidation system includes at least one operating parameter of the system or a component of the system, such as, but not limited to, a controller for adjusting or controlling an actuating valve and pump, (70). The controller 70 may be in electronic communication with the sensor 50 as illustrated in FIG. The controller 70 can be configured to generate a control signal to adjust the pH level of the aqueous mixture in response to a pH sensor 50 that adjusts the pH level beyond the predetermined pH solubility range for the selected catalyst . For example, the controller 70 may provide a control signal to one or more valves associated with the pH adjuster source 60 to add a pH adjuster to the aqueous mixture source 10.

Controller 70 is typically a microprocessor-based device, e.g., a programmable logic controller (PLC), that receives or transmits input and output signals to and from components of a wet oxidation system. Or a distributed control system. A communication network may place any sensor or signal-generating device at a considerable distance from the controller 70 or an associated computer system, ). This communication mechanism may be achieved by using any suitable technique, including, but not limited to, using a wireless protocol.

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

Figure 2 illustrates another embodiment of a wet oxidation system comprising a catalyst recycling system. In this embodiment, the process stream may enter system 200 through line 202. The catalysts that may be used in system 200 may include any transition metal of group 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 may be an element or may be present in a compound, e.g., a metal salt. In one embodiment, the transition metal catalyst is vanadium. In another embodiment, the transition metal catalyst is iron. In another embodiment, the transition metal catalyst is copper.

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

According to one or more embodiments, a catalyst that is soluble at the pH level of the incoming aqueous mixture may be selected to enhance the wet oxidation process. A pH sensor similar to the pH sensor 50 of FIG. 1 may be introduced to the input of the wet oxidation system 200 of FIG. 2 to provide an indication of the pH of the incoming aqueous mixture. Accordingly, with reference to FIG. 4, when the pH level of the aqueous mixture is less than about 2 (or, in some embodiments, less than about 4 or less than about 4.5) or greater than about 12 or greater than about 13, The catalyst may be selected according to one or more embodiments. Likewise, referring to FIG. 5, the catalyst comprising vanadium can be selected when the pH level of the aqueous mixture is higher than about 4.5. Referring to FIG. 6, the catalyst comprising iron can be selected when the pH level of the aqueous mixture is less than about 4. Other catalysts than those exemplified herein may be used.

2, a catalyst may be added to the process stream at the inlet of the system or as it flows through line 202 through line 224, which may be added to the recycle Lt; RTI ID = 0.0 > a < / RTI > catalyst. A new catalyst may also be added with the recycled catalyst.

In other embodiments, a portion of the catalyst or catalyst may already be present in the process stream to be treated. The aqueous mixture fed to the oxidation unit may contain a catalytic material. For example, the transition metal may be present in the waste stream to be treated by a catalytic wet oxidation system. The aqueous slurry containing an aqueous slurry, for example, volatile organic carbon, may contain a metal that can act as a catalyst. For example, the aqueous mixture may be a slurry of gasification by-products.

The process stream may be passed through a heat exchanger 204 where the process stream may be heated to a desired temperature during the residence time provided before entering the reactor 206. After the process is complete, the processed process stream exits the reactor 206 via line 208. The processed process stream may thereafter be cooled by heat exchanger 210, which in some embodiments may be the same heat exchanger as heat exchanger 204. The treated process stream may be pH adjusted by the addition of an acid or an alkaline compound from the source 212 of the pH modifier. a pH sensor (not shown) is provided to monitor the pH of the oxidized aqueous mixture as the pH adjuster is added from the source 212 of the pH adjuster and to provide a signal to interfere with the pH adjustment when the pH reaches a predetermined point, May be provided to communicate with the source 212 of the pH adjuster. In alternative embodiments, a pH sensor (not shown) is located downstream of the source 212 of pH adjuster and is connected to a pH controller (not shown), for example, controller 70 illustrated in FIG. 1 And such a pH controller may be connected to the source 212 of the pH adjuster from the source of the pH adjuster to maintain the pH within a predetermined range and / To control the flow of the pH adjusting agent. In some embodiments, the addition of the pH adjusting agent from the source 212 of the pH adjusting agent can be adjusted by hand. In some embodiments, the source 212 of the pH adjuster may be coupled to a downstream line 218 of the gas / liquid separator 214, instead of upstream of the gas / liquid separator 214 as shown in FIG. 2, As shown in FIG. In another embodiment, the source 212 of the pH adjuster may be configured to directly introduce the pH adjuster into the clarifier 220.

For example, where copper is used as the catalyst, the treated process stream containing soluble copper hydroxide may be cooled to approximately 80 ° C and either upstream or downstream of the gas / liquid separator 214, or A pH adjusted to a range of about 6 to about 12 in the clarifier 220 is conditioned, under which the solubility of copper hydroxide (<1 ppm at 25 ° C) is low. In some embodiments, the pH can be adjusted to a range from about 8 to about 9, and in some embodiments, the pH can be adjusted to about 9. After passing through the gas / liquid separator 214, when the off-gas is discharged through the line 216, the processed process stream can travel through the line 218 to the purifier 220 where it is heated to 80 ° C , In the presence of oxygen at a pH of from about 6 to about 12, at least a portion of the copper hydroxide is converted to copper oxide fine particles. In some embodiments, the copper hydroxide is converted to copper oxide microparticles in a clarifier at a pH in the range of about 8 to about 9, and in some embodiments, the copper hydroxide is converted to a copper oxide microparticle in a clarifier at a pH of about 9 do. The copper oxide microparticles may settle in the clarifier 220 and at least a portion of the concentrated effluent slurry may be removed and recycled back to the inlet of the system 200 via line 224, The oxidized effluent may be removed via line 222. The pH of the recycled copper-containing effluent may be adjusted from acid source 226 of the pH adjuster in response to a signal from a pH sensor (not shown) in communication with line 224 and / or a pH controller (not shown) Or by addition of an alkaline compound. The pH adjuster may be added to the recycled copper-containing effluent to adjust the pH to a level at which the copper catalyst is soluble. For example, if the re-inoculated copper-containing effluent has a pH of from about 6 to about 12, since the copper is generally soluble at a pH level of less than about 6 or greater than about 12, the acid will have a pH for the recycled copper- Level to less than about 6, or alternatively the corrosive compound may be added to increase the pH level of the recycled copper-containing effluent to greater than about 12 to solubilize at least a portion of the copper catalyst. At least a portion of the recycled catalyst may be directed to the source of the catalyst 40 in some embodiments.

In some applications it may be advantageous to use a two-stage catalyst settling process to make the system more efficient and reduce the amount of chemicals used during operation of the system. Figure 3 illustrates one embodiment of a wet air oxidation system using a two-stage catalyst settling process. As illustrated in FIG. 3, a system 300 with a two-stage catalyst settling process can use a set of purifiers 228 and 230. [ In one embodiment, any source 212 of pH modifier may be positioned upstream of the gas / liquid separator 214. In some embodiments of system 300, the source of the pH adjuster and associated transfer pump and / or valves and / or piping may be configured to direct the pH adjuster to upstream or downstream locations of the gas / liquid separator 214 and / The purifier 228, the purifier 230, or both. Several pH sensors (not shown) are located upstream or downstream of any of the components of the system 300 and can be connected to a pH controller (not shown), for example, the controller 70 illustrated in FIG. 1 Which may include one or more pH adjuster sources located throughout the system, for example, the transfer pumps and / or valves associated with the source or sources of the pH adjuster from the source 234 of the pH adjuster, and / And is configured and arranged to control the flow of the pH adjusting agent through the piping.

In the system 300 of FIG. 3, rough clarification may occur at the first clarifier 228. At least a portion of the first separated solution from the first dialing step may be returned to the inlet of the system through lines 236 and 224 as dilution water and catalyst feed for further processing. At least a portion of the supernatant from the first clarification step is transferred via line 232 after adjusting the pH by the addition of an acid or alkaline compound from the source 234 of the pH adjuster and in a purifier 230 to a second purifier Can be precipitated. The source 234 of pH adjuster and associated transfer pump and / or valve and / or piping may be positioned and arranged to adjust the pH of a portion of the supernatant at line 232 or at purifier 230, or both. have. In an alternative embodiment of the system according to FIG. 2 or FIG. 3, any or all of the clarifiers may be replaced by any type of separator capable of separating the precipitated catalyst from the oxidized aqueous mixture. The solution containing the enriched solidified catalyst may be returned to the inlet of the system 300 via lines 238 and 224 to mix with the incoming process stream and the catalyst may be returned to the inlet 222, respectively. At least a portion of the re-calcined catalyst may be derived to the source of the catalyst 40 in some embodiments. The advantage of the two stage system is that only a small fraction of the effluent of the wet oxidation unit will need to be pH adjusted to precipitate the catalyst. A portion of the effluent that may be recycled to the dilution water may have a soluble catalyst remaining therein, which may be desired. The source 226 of the pH modifier can be used to dissolve the catalyst that can migrate through line 224 by adding an acid or a corrosive compound in a manner similar to that discussed for the copper catalyst example. The pH of the recycled effluent of the wet oxidation unit will also be very close to the required pH to keep the catalyst soluble in a wet air oxidation system.

In the system illustrated in Figures 2 and 3, the catalyst can be precipitated by adjusting the pH of the oxidized aqueous mixture only. In some embodiments, the catalyst can only be precipitated by adjusting the pH of the oxidized aqueous mixture in a single direction. In some embodiments, the catalyst can be precipitated by adjusting the pH of the oxidized aqueous mixture to a single pH adjusting agent. In some embodiments, the catalyst can only be precipitated by adjusting the pH of the oxidized aqueous mixture to a pH within a predetermined range of pH that is substantially insoluble or at least partially insoluble in the oxidized aqueous mixture. In some embodiments, pH adjustment can be accomplished without causing the addition of any chemicals, for example, by an electrodeionization process, to cause precipitation of the catalyst. In other embodiments, additional chemicals, such as sources of sulfide ions, such as sodium sulfide or hydrogen sulfide, may be added to the oxidized aqueous mixture to enhance kinetics or otherwise promote precipitation of the catalyst . In some embodiments, the catalyst may be solubilized in an aqueous mixture to cause oxidation at a pH within a first range, and precipitated from the oxidized aqueous mixture at a pH within a second range that does not overlap with the first range.

According to one or more embodiments, the wet oxidized liquid effluent stream may be introduced into the oxidation reactor vessel 24 downstream of the oxidation reactor vessel 24 to remove any undesired components present and / or to polish if necessary or desired, And can be processed by the second processing unit 80 as described above. The second processing unit 80 may be a chemical scrubber, biological scrubber, adsorbent layer, or other unit operation. In some embodiments, an advanced oxidation step including oxidation treatment of the wet oxidation effluent with ozone and ultraviolet light may be performed. This advanced oxidation process is typically carried out at or near ambient temperature and pressure in a vessel or tank. The second processing unit 80 may be sized to provide a surface area consistent with the degree of polishing desired. Alternatively, the liquid effluent may also be recycled back to the reactor vessel 24 for further processing. The treatment of off-gas may also be required in the downstream off-gas treatment unit according to its composition and requirements for discharge into the atmosphere.

Sensors for detecting the concentration of the targeted odorous component may be provided upstream and / or downstream of the wet oxidation unit 24 to facilitate system control. For example, the sensor may be positioned in conduit 26 and may be connected to a controller (not shown) to determine and / or control whether the liquid effluent stream should be switched to a second processing unit 80 to meet established environmental regulations Lt; RTI ID = 0.0 &gt; 70 &lt; / RTI &gt;

It will be appreciated that many alternatives, modifications, and improvements can be made to the illustrated systems and methods. For example, one or more wet oxidation systems may be connected to multiple sources of process streams. In some embodiments, the wet oxidation system may include additional sensors for measuring other properties of the system or operating conditions. For example, the system may include sensors for temperature, pressure drop, and flow rate at different points to facilitate system monitoring. According to one or more embodiments, the catalyst may be re-fed during the wet oxidation process.

The present invention contemplates modifications to existing facilities to provide one or more systems or components for implementing the techniques of the present invention. Existing wet oxidation systems may be modified according to one or more embodiments typically discussed herein using at least some of the devices already present. For example, one or more pH sensors may be provided, and the controller according to one or more embodiments present herein may be implemented in a wet oxidation system that is already present to enhance catalyst solubility or promote catalyst recycle.

The functions and advantages of these and other embodiments of the invention will be more fully understood from the following examples. These embodiments 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 wet oxidation in order to influence the breakdown of the bond here.

Example

Bench Scale Wet Oxidation (Autoclave) Reactor

In the following examples, bench scale wet oxidation tests were performed in laboratory autoclaves. The autoclaves differ from full scale systems in that they are batch reactors, where the full scale unit may be a continuous flow reactor. Because the high air charge must be added to the autoclave to provide sufficient oxygen during the reaction time, the autoclaves typically operate at higher pressures than the full scale unit. The results of the autoclave tests provide an indication of the performance of the wet oxidation technique and are useful for screening the operating conditions for the wet oxidation process.

The autoclaves used were made from titanium, alloy 600 and nickel 200. The choice of autoclaved structural material was based on the composition of the wastewater feed material. The autoclaves are selected for use, each having a total capacity of 500 or 750 ml.

The autoclaves were filled with wastewater and sufficient compressed air to provide an excess of residual oxygen after oxidation (ca. 5%). The filled autoclaves were placed in a heater / shaker mechanism and heated to the desired temperature (280 ° C to 350 ° C) and the temperature was maintained for a desired time in the range of about 60 minutes to about 360 minutes.

During heating and reaction times, the autoclave temperature and pressure were monitored by a computer controlled data acquisition system. Immediately after the oxidation, the autoclaves were removed from the heater / shaker mechanism and cooled to room temperature using tap water. After cooling, the pressure and volume of off-gas in the autoclave head-space was measured. A sample of off-gas was analyzed for permanent gas. After analysis of off-gas, the autoclave was depressurized and opened. The oxidized effluent was removed from the autoclave and placed in a storage vessel. A portion of the effluent was provided for analysis and the remaining sample was used for post-oxidation treatment. A number of autoclave tests were performed on each condition to generate sufficient volume for analytical work and post-oxidation test work.

Example 1

Wet oxidation process using homogeneous copper catalyst

A bench scale wet oxidation test was performed at 280 占 폚 at a temperature of 60 minutes at a temperature to measure the effect of the copper catalyst on the oxidation of acetic acid at various pH levels (pH = 2.2, 8.1, 11.5, 12.5 and 13.5). The data are shown in Table 1 below.

Table 1

The copper catalysts showed 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 breakdown (96.5%, 90%) and TOC breakdown (96.4%, 88.1%). Conversely, when the pH of the solution was maintained in a pH range where the copper was not soluble (pH = 8.1, 11.5 and 12.5), only about 17% to 37% acetic acid destruction was achieved. When the copper was not soluble, lower percentages of COD and TOC breaks were also observed. Data indicated that copper solubility substantially increased oxidation of acetic acid.

Example 2

Wet oxidation process using homogeneous vanadium catalyst

Bench scale wet oxidation tests were performed on aqueous solutions containing acetic acid using vanadium as homogeneous catalyst at two different pH levels. The results are shown in Table 2 below.

Table 2

Under oxidizing conditions, the vanadium is soluble at a pH level of greater than about 4.5. The results show that only 2% TOC breakdown is achieved when the pH of the solution is 2.6 and the vanadium is predominantly insoluble. A low percentage of TOC breakdown is also associated with a pH level of 2.66. The TOC breakthrough was increased to 17.3% when the pH of the solution was increased to 5.3 (solubilization of vanadium) while maintaining the same catalyst capacity, temperature and temperature for the time. By increasing the pH of the solution from 2.66 to 5.3, there was an approximately 64% increase in the total organic carbon breakdown. The data indicate that vanadium solubility substantially increases the oxidation of acetic acid.

Example 3

Wet oxidation process using homogeneous iron catalyst

Bench scale wet oxidation tests were carried out at 230 DEG C for 150 minutes on oxalic acid solution at two different pH levels. The data are shown in Table 3 below.

Table 3

Under oxidative conditions, iron was soluble at a pH level of about 4. The results showed no improvement in oxidation when used at high pH levels (pH = 13.6 and 13.7) where the iron catalyst was insoluble. When the pH of the solution was in the range where iron was soluble (pH = 2.6 and 1.7), the destruction of oxalic acid was increased to about 95% and about 100%, respectively. The data indicate that the solubility of iron substantially increased the oxidation of oxalic acid.

Example 4

Wet oxidation of chlorophenol using homogeneous iron catalysts

Iron catalyzed and non-catalyzed oxidation of chlorophenol was carried out at 150 &lt; 0 &gt; C for 90 minutes at temperature. The data are tabulated in Table 4 below.

Table 4

These tests have shown that increasing the solubility of the iron catalyst by lowering the pH level from 2.9 to 2.3 causes an increase in TOC breakdown from about 7% to about 57%. Similarly, the downward pH level increased the COD breakdown from about 7.4% to about 68.1%. In the data, even a slight adjustment of the pH level indicates a significant increase in the efficiency of the catalytic wet oxidation process.

Example 5

Copper oxide recirculation test

Comparative tests were conducted to evaluate the pH adjustment to recover the copper catalyst. Two sets of tests were performed. In the first set of tests, the non-pH regulated naphthenic consumption caustic was oxidized at 200 DEG C with residence time of 120 minutes and 5000 mg / L of copper added with copper oxide. A second set of tests was conducted with pH controlled naphthenic consumption caustics at 200 DEG C with copper retention time of 120 minutes and 500 mg / L of copper added with copper oxide.

Each set of tests was performed under the same conditions as described below. A sample of naphthenic consumption caustic was oxidized to form an oxidized effluent. The oxidized effluent was pH adjusted to about 8.5 using sodium hydroxide and centrifuged. A portion of the supernatant was removed and the remaining effluent containing copper oxide was re-refilled with dilution water and combined with fresh feed for subsequent oxidation. Each run was repeated several times wherein oxidation of the initial feed resulted in a first recycled effluent containing copper oxide which was combined with a fresh feed and oxidized to form a second recycled effluent containing copper oxide . Each recycle is combined with a fresh feed for oxidation and the formation of a subsequent recycle to the number of cycles is specified in Tables 5 and 6.

The COD and TOC breaks for each recycle loop were calculated in two different ways. The first method was based on the feed mixture placed in the autoclave. Because the oxidized effluent from the previous run was diluted as the consumed caustic that was received, the feed COD was calculated using the ratio of fresh feed to oxidized effluent. The second method is based on feed upon ingestion and is listed as "COD Destruction - Entire ". Since the oxidized effluent was recovered to the WAO system for dilution, the addition was not added to the system to lower total COD.

Results for non-pH and pH controlled recirculation are reported in Tables 5 and 6, respectively.

Table 5

After adjustment of the pH of the oxidized effluent to about 8.5, as described in Table 5, sedimentation by centrifugation recovered 22.9 mg / L soluble copper in recycle 1, which is then used for further oxidation Were combined. The pH of the recycled effluent containing soluble copper was not further controlled with acid or base prior to combining with the fresh feed.

The amount of soluble copper recovered in each recycle was increased from recycle 3 to 55.5 mg / L in each iteration. After three recirculation cycles, the oxidation / recirculation system began to reach a steady state condition with an autoclave COD destruction efficiency of 51.8%, resulting in a total COD destruction efficiency of 88.1%. The autoclave TOC destruction efficiency increased from 8.8% to 38.3% with each repetition with a total TOC destruction efficiency of 81.2% in recycle 3. These results show that the pH control of the oxidized effluent containing copper catalyst can form a recycled effluent containing soluble copper that can be redirected to the oxidation system which can reduce the amount of fresh catalyst to be added to the oxidation system .

Table 6

As shown in Table 6, sedimentation by centrifugation after adjustment of the pH of the oxidized effluent to about 8.5 recovered 152 mg / L soluble copper in recycle 1, which was subsequently combined with fresh feed for further oxidation . Prior to combining with the fresh feed, each recycle 1 to 5 was pH adjusted with an acid as specified. The amount of soluble copper was increased from 152 mg / L to 354 mg / L in recycle 1 to recycle 3 in each recycle, which is the result of the pH adjustment of the oxidized effluent to 8 instead of 8.5 after precipitation at 60 ° C Showed a significantly lower soluble copper at 14.7 mg / L, and a subsequent recycle 5 showing pH control of the oxidized effluent to about 8.5 again showed a significant increase in soluble copper at 289 mg / L.

As shown in Table 6, the addition of acid to the feed and the subsequent addition of acid to each recycle 1 to 5 allowed the system to reach a steady state rather than a pH adjustment not being made in recirculation. The recirculation test carried out with the pH control feed indicated that the steady-state conditions were reached after two cycles of recycle. The overall TOC breaking efficiency stabilized at 90.2% to 89.6% after two cycles. Similarly, the overall COD breaking efficiency stabilized at about 94% after two cycles.

Similarly, the addition of an acid to the feed, and subsequent addition of acid to each recycle 1 to 5, results in higher TOC and COD destruction efficiencies than pH control is not achieved in the recycle. As shown in Table 6, the addition of acid to each recycle increased the overall TOC destruction efficiency to approximately 90% compared to a fracture efficiency of approximately 81% without the addition of acid to each recycle. Similarly, the addition of acid to each recycle increased the overall COD destruction efficiency to approximately 88% compared to approximately 72% in the addition of acid to each recycle. The addition of sulfuric acid to the recycle allowed the pH of the recycle to be in a range where the copper catalyst was more soluble, and this increased level of soluble copper was available in subsequent oxidation cycles to increase the destruction efficiency.

Another advantage of recirculating the deoxidized effluents and catalysts to the WAO unit, both for test runs with and without pH control of the recycle, is that the residence time is increased to make it more difficult to oxidize the components. The residence time is prolonged proportionally to the amount of diluted water added, i.e., if the dilution water is more desired, the residence time becomes longer. The results from the recycling test indicated that this increased residence time was effective in destroying some of the components that were initially tolerant to oxidation. The residence time, which is difficult to oxidize the components, was also very high, as it was necessary to use large amounts of dilution in the autoclave to reduce COD from 260,000 mg / L to approximately 40,000 mg / L on in situ.

Example 6

Wet oxidation process using homogeneous copper catalyst

The bench scale wet oxidation test was conducted at 280 캜 for 60 minutes at such temperature to determine the effect of the copper catalyst on the oxidation of acetic acid at various pH levels (pH = 2.2, 2.9, 4.3, 4.7, 8.1 and 11.5) Respectively. The data are shown in Table 7 below.

Table 7

The results showed that at lower pH values (acidic pH values), the solubility of the copper catalyst decreased with increasing pH. In addition, the degree of acetic acid destruction was also decreased with increasing pH. These data further confirm that the conclusions obtained from Example 1, i.e. mainly copper solubility, substantially increased the oxidation of acetic acid. As described in this example, the oxidation process is enhanced by the presence of a copper catalyst under a wide range of pH values. The copper catalyst can improve the oxidation of undesired components in the aqueous mixture in a wet air oxidation process at a low pH value of about 2 to about 4, or about 4.5.

As used herein, the term " plurality "refers to two or more items or components. The terms " comprising, "" carrying," "having ", and" containing "are non-limiting terms whether they are present in the description or in the claims, ". Accordingly, the use of such terms is intended to encompass the items listed thereafter, and equivalents thereof, as well as additional items. The transitional phrases " consisting of "and" essentially comprising "are each a restrictive or semi-restrictive phrase for the claims.

The use of ordinal terms such as " first, "" second," " third, "or the like, in modifying the claim element in the claims is intended to encompass any prior claim, Does not imply a temporal order in which the acts of an order, gender, order, or method are carried out, and they (except for the use of ordinal terms) It is used as a label to distinguish it from another element having a name.

Those skilled in the art will recognize that the parameters and configurations described herein are exemplary and that actual parameters and / or configurations are dependent upon the particular application for which the systems and techniques of the present invention are used. Those skilled in the art will also recognize or be able to ascertain using equivalent, everyday routine experimentation, specific embodiments of the invention. Accordingly, it is to be understood that the embodiments described herein are presented by way of example only, and that the invention may be practiced as otherwise specifically described within the appended claims and their equivalents.

Claims (20)

Contacting the aqueous mixture containing the at least one undesired component to be treated with the catalyst and the oxidizing agent at a pH within the first range where the catalyst is substantially soluble and at elevated temperature and superatmospheric pressure, Treating the at least one undesired component and forming an oxidized aqueous mixture in the wet oxidation reactor;
Precipitating some or all of the catalyst by adjusting the pH level of the oxidized aqueous mixture to a pH in the second range for forming the precipitated catalyst;
A catalytic wet oxidation process comprising recycling some or all of the precipitated catalyst to the aqueous mixture. The method of claim 1, wherein the first range of pH and the second range of pH do not overlap. 3. The process of claim 2, wherein the catalyst comprises copper and the first range of pH is selected from the group consisting of less than about 4 and greater than about 12. 4. The method of claim 3, wherein the second range of pH is from about 6 to about 12. The process according to claim 1, wherein precipitating part or all of the catalyst
Performing a rough clarification in a first clarifier to form a first separated solution comprising a first supernatant and a soluble catalyst,
Contacting some or all of the first separated solution with an aqueous mixture,
Precipitating some or all of the first supernatant in the second clarifier to form an oxidized effluent essentially free of catalyst and a solidified catalyst,
Contacting the solidified catalyst from the second clarifier with an aqueous mixture,
Wherein the process is accomplished by a two step catalyst settling process that includes discharging an oxidized effluent essentially free of catalyst from the second clarifier. 6. The method of claim 5,
Adjusting the pH of part or all of the first supernatant before precipitating some or all of the first supernatant in the second clarifier,
Further comprising adjusting the pH of the solidified catalyst from the second clarifier prior to contact with the aqueous solution. The method of claim 1, wherein the catalyst comprises vanadium and wherein the first range of pH is greater than about 4.5. The method of claim 1, wherein the catalyst comprises iron and the first range of pH is less than about 4. A wet oxidation unit;
A source of an aqueous mixture comprising at least one undesired component fluidly coupled to the wet oxidation unit;
As a source of a catalyst that is fluidly coupled to a wet oxidation unit and is soluble in an aqueous mixture that is positioned between the source of the aqueous mixture and the wet oxidation unit, the aqueous mixture comprises a source of a catalyst having a pH in a first range wherein the catalyst is substantially soluble ;
A sensor configured to detect a pH level of the oxidized aqueous mixture formed in the wet oxidation unit;
In communication with a pH sensor configured to generate a control signal to adjust a pH level of the oxidized aqueous mixture to a pH within a second range in which the catalyst is substantially insoluble, in response to a pH sensor exhibiting a pH level within the first range pH controller;
A separator configured to communicate fluid directly downstream of the wet oxidation unit and downstream of the pH controller and to precipitate some or all of the catalyst by adjusting the pH of the oxidized aqueous mixture only; And
A catalystic wet oxidation system comprising a recirculation line fluidly connected to an outlet of the separator and to an inlet to at least one of the sources of the catalyst and an inlet to the wet oxidation system. 10. The system of claim 9, further comprising a source of an alkaline compound that is positioned and fluidically coupled to the downstream of at least one of the separator and the wet oxidation unit. 10. The system of claim 9, further comprising a source of acid which is located downstream and in fluid communication with at least one of the separator and the wet oxidation unit. 10. The system of claim 9 wherein the catalyst comprises copper and wherein the first range of pH is less than 6 and greater than about 12. 13. The method of claim 12, further comprising a second pH sensor in communication with a pH controller configured to detect a pH level of the oxidized aqueous mixture in the separator, wherein the pH controller adjusts the pH level of the oxidized aqueous mixture in the separator to about 6 &Lt; / RTI &gt; to about &lt; RTI ID = 0.0 &gt; 12. &Lt; / RTI &gt; 10. The system of claim 9, further comprising a clarifier coupled to and upstream of the separator configured to purify the oxidized aqueous mixture to form a reject. 15. The method of claim 14, further comprising: providing a conduit configured to transfer some or all of the waste to a location upstream of and in fluid communication with the wet oxidation unit and to contact the waste with an aqueous mixture comprising at least one undesired component Further included systems. 10. The system of claim 9, wherein substantially all of the catalyst is recovered. 10. The system of claim 9, further comprising a source of a pH adjuster fluidly connected to the recycle line. 18. The method of claim 17, further comprising a third pH sensor in communication with a pH controller configured to detect a pH level of the aqueous mixture in the recycle line, wherein the pH controller has a predetermined pH solubility And to generate a control signal to adjust the pH level of the aqueous mixture in the recycle line in response to a third pH sensor exhibiting a pH level outside the range. 10. The process of claim 9 wherein the catalyst comprises iron and the first range of pH is less than about 4. & A method for promoting recirculation of a catalyst used in a catalytic wet oxidation method comprising providing a pH monitoring system having a controller in communication with a pH sensor, the method comprising the steps of: and to generate a control signal to adjust the pH level of the oxidized aqueous mixture formed in the catalytic wet oxidation method in response to the pH sensor indicating the pH level and to precipitate only by adjusting the pH of the oxidized aqueous mixture.

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