EP2986570A1 - Procédé d'oxydation d'air humide à l'aide d'un catalyseur recyclé à base de cuivre, de vanadium ou de fer - Google Patents

Procédé d'oxydation d'air humide à l'aide d'un catalyseur recyclé à base de cuivre, de vanadium ou de fer

Info

Publication number
EP2986570A1
EP2986570A1 EP14729758.4A EP14729758A EP2986570A1 EP 2986570 A1 EP2986570 A1 EP 2986570A1 EP 14729758 A EP14729758 A EP 14729758A EP 2986570 A1 EP2986570 A1 EP 2986570A1
Authority
EP
European Patent Office
Prior art keywords
catalyst
aqueous mixture
wet oxidation
range
oxidized
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP14729758.4A
Other languages
German (de)
English (en)
Inventor
Chad L. Felch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Energy Inc
Original Assignee
Siemens Energy Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US13/865,664 external-priority patent/US9315401B2/en
Application filed by Siemens Energy Inc filed Critical Siemens Energy Inc
Publication of EP2986570A1 publication Critical patent/EP2986570A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/06—Treatment of sludge; Devices therefor by oxidation
    • C02F11/08—Wet air oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/008—Control or steering systems not provided for elsewhere in subclass C02F
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F2001/007—Processes including a sedimentation step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/005—Processes using a programmable logic controller [PLC]
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/02—Temperature
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/03—Pressure
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/06—Controlling or monitoring parameters in water treatment pH
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/16—Regeneration of sorbents, filters

Definitions

  • the present disclosure relates generally to the treatment of process streams and, more particularly, to catalytic wet oxidation systems and methods for treatment of undesirable constituents therein.
  • wet oxidation is a well-known technology for treating process streams, and is widely used, for example, to destroy pollutants in wastewater.
  • the method involves aqueous phase oxidation of undesirable constituents by an oxidizing agent, generally molecular oxygen from an oxygen-containing gas, at elevated temperatures and pressures.
  • the process can convert organic contaminants to carbon dioxide, water and biodegradable short chain organic acids, such as acetic acid.
  • Inorganic constituents including sulfides, mercaptides and cyanides can also be oxidized.
  • wet oxidation may be used in a wide variety of applications to treat process streams for subsequent discharge, in-process recycle, or as a pretreatment step to supply a conventional biological treatment plant for polishing.
  • Catalytic wet oxidation has emerged as an effective enhancement to traditional non-catalytic wet oxidation.
  • Catalytic wet oxidation processes generally allow for greater destruction to be achieved at a lower temperature and pressure, and therefore a lower capital cost.
  • An aqueous stream to be treated is mixed with an oxidizing agent and contacted with a catalyst at elevated temperatures and pressures.
  • Heterogeneous catalysts typically reside on a bed over which the aqueous mixture is passed, or in the form of solid particulate which is blended with the aqueous mixture prior to oxidation.
  • the catalyst may be filtered out of the oxidation effluent downstream of the wet oxidation unit for reuse.
  • a catalytic wet oxidation process comprises providing an aqueous mixture containing at least one undesirable constituent to be treated.
  • the aqueous mixture is contacted with a catalyst and an oxidizing agent at an elevated temperature and a superatmospheric pressure to treat the at least one undesirable constituent and form an oxidized aqueous mixture.
  • At least a portion of the catalyst is precipitated by adjusting a 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.
  • a catalytic wet oxidation system comprises a wet oxidation unit, a source of an aqueous mixture comprising at least one undesirable constituent fluidly connected to the wet oxidation unit, a source of a catalyst soluble in the aqueous mixture fluidly 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 registering a pH level within a predetermined pH solubility range for the catalyst, a separator configured to precipitate at least a portion the catalyst positioned downstream of and in fluid communication with the wet oxidation unit and downstream of the pH controller, and a recirc
  • a method of facilitating recycling 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 configured to generate a control signal to adjust a pH level of an aqueous mixture in response to the pH sensor registering a pH level within a predetermined pH solubility range for a utilized catalyst.
  • a catalytic wet oxidation process comprises contacting an aqueous mixture containing at least one undesirable constituent to be treated with a catalyst and an oxidizing agent at an elevated temperature and a superatmospheric pressure at a pH within a first range at which the catalyst is substantially soluble to treat the at least one undesirable constituent within a wet oxidation reactor and form an oxidized aqueous mixture within the wet oxidation reactor.
  • the process further comprises precipitating at least a portion of the catalyst solely by adjusting a pH level of the oxidized aqueous mixture to a pH within a second range to form a precipitated catalyst and recycling at least a portion of the precipitated catalyst to contact the aqueous mixture.
  • the first range of pH and the second range of pH are non-overlapping.
  • contacting the aqueous mixture with the catalyst occurs prior to bringing the aqueous mixture to the elevated temperature.
  • contacting the aqueous mixture with the catalyst occurs prior bringing the aqueous mixture to the superatmospheric pressure.
  • the process further comprises monitoring the pH level of the aqueous mixture.
  • the aqueous mixture is oxidized in a continuous process.
  • the process further comprises replenishing the catalyst.
  • contacting the aqueous mixture with the oxidizing agent comprises contacting the aqueous mixture with an oxygen-containing gas.
  • precipitating at least a portion of the catalyst comprises increasing the pH of at least a portion of the oxidized aqueous mixture.
  • precipitating at least a portion of the catalyst comprises decreasing the pH of at least a portion of the oxidized aqueous mixture.
  • the catalyst comprises copper and the first range of pH is selected from the group consisting of below 6 and above about 12.
  • the precipitated catalyst comprises copper oxide.
  • adjusting the pH level of the oxidized aqueous mixture comprises adjusting the pH level of the oxidized aqueous mixture to range of pH of from about 6 to about 12.
  • adjusting the pH level of the oxidized aqueous mixture comprises adjusting the pH level of the oxidized aqueous mixture to range of pH of from about 8 to about 9.
  • the process further comprises adjusting the pH of at least a portion of the precipitated catalyst.
  • 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 solubilizes.
  • the process further comprises clarifying the oxidized aqueous mixture, thereby forming a first separated solution, prior to precipitating at least a portion of the catalyst from the oxidized aqueous mixture.
  • the process further comprises contacting the first separated solution with the aqueous mixture containing at least one undesirable constituent to be treated.
  • the process further comprises recovering substantially all of the catalyst.
  • the aqueous mixture is oxidized for a period of time sufficient to treat the at least one undesirable constituent.
  • the superatmospheric pressure is from about 30 atmospheres to about 275 atmospheres.
  • the elevated temperature is from about 240° C. to about the critical temperature of water.
  • the elevated temperature is above the critical temperature of water.
  • precipitating the at least a portion of the catalyst is accomplished with a two step catalyst settling process.
  • the two step catalyst settling process comprises performing a rough clarification in a first clarifier to produce a first supernatant and a first separated solution including soluble catalyst, contacting at least a portion of the first separated solution with the aqueous mixture, settling at least a portion of the first supernatant in a second clarifier to produce solidified catalyst and an oxidized effluent essentially free of catalyst, contacting the solidified catalyst from the second clarifier with the aqueous mixture, and withdrawing the oxidized effluent essentially free of catalyst from the second clarifier.
  • the process further comprises adjusting a pH of the at least a portion of the first supernatant prior to settling the at least a portion of the first supernatant in the second clarifier.
  • the process further comprises adjusting a pH of the solidified catalyst from the second clarifier prior to contact with the aqueous solution.
  • the catalyst comprises vanadium and the first range of pH is above about 4.5.
  • the catalyst comprises iron and the first range of pH is below about 4.
  • the catalyst comprises copper and the first range of pH is selected from the group consisting of below about 4 and above about 12.
  • the first range of pH is selected from the group consisting of below about 2 and above about 13.
  • a catalytic wet oxidation system comprises a wet oxidation unit, a source of an aqueous mixture comprising at least one undesirable constituent fluidly connected to the wet oxidation unit, a source of a catalyst soluble in the aqueous mixture fluidly connected to the wet oxidation unit and positioned between the source of the aqueous mixture and the wet oxidation unit, the aqueous mixture having a pH within a first range at which the catalyst is substantially soluble, a sensor configured to detect a pH level of an oxidized aqueous mixture formed in the wet oxidation unit, a pH controller in communication with the pH sensor and configured to generate a control signal to adjust the pH level of the oxidized aqueous mixture to a pH within a second range at which the catalyst is substantially insoluble in response to the pH sensor registering a pH level within the first range, a separator in direct fluid communication downstream of the wet oxidation unit and downstream of the pH controller and configured to precipitate, sole
  • system further comprises a secondary treatment unit connected downstream of the wet oxidation unit.
  • system further comprises a source of an alkali compound positioned downstream of and fluidly connected to at least one of the separator and the wet oxidation unit.
  • system further comprises a source of an acid positioned downstream of and fluidly connected to at least one of the separator and the wet oxidation unit.
  • the catalyst comprises copper and the first range of pH is selected from the group consisting of below 6 and above about 12.
  • system further comprises a second pH sensor in communication with the pH controller configured to detect a pH level of an oxidized aqueous mixture in the separator, the pH controller further configured to generate a control signal to adjust a pH level of the oxidized aqueous mixture in the separator to within a range from about 6 to about 12.
  • the pH controller is further configured to generate a control signal to adjust a 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 further configured to generate a control signal to adjust a pH level of the oxidized aqueous mixture in the separator to about 9.
  • system further comprises a clarifier upstream of and fluidly connected to the separator configured to clarify the oxidized aqueous mixture, thereby forming a reject.
  • system further comprises a conduit configured to transport at least a portion of the reject to a location in the system upstream of and in fluid communication with the wet oxidation unit and to contact the reject with the aqueous mixture comprising at least one undesirable constituent.
  • substantially all of the catalyst is recovered.
  • system further comprises a source of a pH adjuster fluidly connected with the recirculation line.
  • system further comprises a third pH sensor in communication with the pH controller, configured to detect a pH level of an aqueous mixture in the recirculation line, the pH controller further configured to generate a control signal to adjust a pH level of the aqueous mixture in the recirculation line in response to the third pH sensor registering a pH level outside a predetermined pH solubility range for the catalyst.
  • a third pH sensor in communication with the pH controller, configured to detect a pH level of an aqueous mixture in the recirculation line
  • the pH controller further configured to generate a control signal to adjust a pH level of the aqueous mixture in the recirculation line in response to the third pH sensor registering a pH level outside a predetermined pH solubility range for the catalyst.
  • a method of facilitating recycling 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 configured to generate a control signal to adjust a pH level of an oxidized aqueous mixture formed in the catalytic wet oxidation process in response to the pH sensor registering a pH level within a predetermined pH solubility range for the catalyst, and to precipitate the catalyst solely by the adjustment of the pH of the oxidized aqueous mixture.
  • FIG. 1 is a system diagram in accordance with one embodiment of a wet oxidation system
  • FIG. 2 is a system diagram in accordance with an embodiment of a wet oxidation system including a catalyst recycle process
  • FIG. 3 is a system diagram in accordance with an embodiment of a wet oxidation system including a catalyst recycle process with a two step precipitation process;
  • FIGS. 4-6 are Pourbaix diagrams referenced herein for copper, vanadium, and iron, respectively.
  • the present disclosure relates to one or more systems and methods for treating process streams.
  • the disclosed systems may receive process streams from community, industrial or residential sources.
  • the process stream may be delivered from a municipal wastewater sludge or other large-scale sewage system.
  • Process streams may also originate, for example, from food processing plants, chemical processing facilities, gasification projects, or pulp and paper plants.
  • the process stream may be moved through the system by an operation upstream or downstream of the system.
  • the term "process stream" refers to an aqueous mixture deliverable to the system for treatment. After treatment, the process stream may be returned to an upstream process or may exit the system as waste.
  • the aqueous mixture typically includes at least one undesirable constituent capable of being oxidized.
  • the undesirable constituent may be any material or compound targeted to be removed from the aqueous mixture, such as for public health, process design and/or aesthetic considerations.
  • 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 such as a slurry, may take the form of direct piping from a plant or holding vessel.
  • An oxidation reaction is one destruction technique, capable of converting oxidizable organic contaminants to carbon dioxide, water and biodegradable short chain organic acids, such as acetic acid.
  • One aspect of the present disclosure involves systems and methods for oxidative treatment of aqueous mixtures containing one or more undesirable constituents.
  • an aqueous mixture including at least one undesirable constituent is wet oxidized.
  • the aqueous mixture is oxidized with an oxidizing agent at an elevated temperature and superatmospheric pressure for a duration sufficient to treat the at least one undesirable constituent.
  • the oxidation reaction may substantially destroy the integrity of one or more chemical bonds in the undesirable constituent.
  • the phrase "substantially destroy” is defined as at least about 95% destruction.
  • the process of the present disclosure is generally applicable to the treatment of any undesirable constituent capable of being oxidized.
  • the disclosed wet oxidation processes may be performed in any known batch or continuous wet oxidation unit suitable for the compounds to be oxidized.
  • aqueous phase oxidation is performed in a continuous flow wet oxidation system, as exemplarily shown in FIG. 1.
  • Any oxidizing agent may be used.
  • the oxidant is usually an oxygen-containing gas, such as air, oxygen-enriched air, or essentially pure oxygen.
  • oxygen-enriched air is defined as air having an oxygen content greater than about 21%.
  • an aqueous mixture from a source flows through a conduit 12 to a high pressure pump 14 which pressurizes the aqueous mixture.
  • the aqueous mixture is mixed with a pressurized oxygen-containing gas, supplied by a compressor 16, within a conduit 18.
  • the aqueous mixture flows through a heat exchanger 20 where it is heated to a temperature which initiates oxidation.
  • the heated feed mixture then enters a reactor vessel 24 at inlet 38.
  • the wet oxidation reactions are generally exothermic and the heat of reaction generated in the reactor may further raise the temperature of the mixture to a desired value.
  • the bulk of the oxidation reaction occurs within reactor vessel 24 which provides a residence time sufficient to achieve the desired degree of oxidation.
  • the oxidized aqueous mixture and oxygen depleted gas mixture then exit the reactor through a conduit 26 controlled by a pressure control valve 28.
  • oxidized aqueous mixture or “oxidized effluent” refer to the oxidized fluid exiting the reactor vessel 24 prior to any chemical treatment downstream of the reactor vessel 24. Liquid-gas separation is not considered a "chemical treatment” as the term is used herein.
  • the hot oxidized effluent traverses the heat exchanger 20 where it is cooled against incoming raw aqueous mixture and gas mixture.
  • the cooled effluent mixture flows through a conduit 30 to a separator vessel 32 where liquid and gases are separated.
  • the liquid effluent exits the separator vessel 32 through a lower conduit 34 while off gases are vented through an upper conduit 36.
  • Treatment of the off gas may be required in a downstream off gas treatment unit depending on its composition and the requirements for discharge to the atmosphere.
  • the wet oxidized effluent may typically be discharged into a biological treatment plant for polishing.
  • the effluent may 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 wet oxidation system off gas, and the
  • the superatmospheric gas pressure is typically sufficient to maintain water in the liquid phase at the selected oxidation temperature.
  • the minimum system pressure at 240° C. is 33 atmospheres
  • the minimum pressure at 280° C. is 64 atmospheres
  • the minimum pressure at 373° C. is 215 atmospheres.
  • the aqueous mixture is oxidized at a pressure of about 30 atmospheres to about 275 atmospheres.
  • the wet oxidation process may be operated at an elevated temperature below 374° C, the critical temperature of water.
  • the wet oxidation process may be operated at an elevated temperature ranging from about 150° C. and a pressure of about 6 atmospheres to an elevated temperature of about 320° C. and a pressure of about 200 atmospheres.
  • the wet oxidation process may be operated at a supercritical elevated temperature.
  • the retention time for the aqueous mixture within the reaction chamber should be generally sufficient to achieve the desired degree of oxidation. In some embodiments, the retention time is above about one hour and up to about eight hours. In at least one embodiment, the retention time is at least about 15 minutes and 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.
  • 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 undesirable constituent to be treated is generally contacted with a catalyst and an oxidizing agent at an elevated temperature and superatmospheric pressure.
  • An effective amount of catalyst may be generally sufficient to increase reaction rates and/or improve the overall destruction removal efficiency of the system, including enhanced reduction of chemical oxygen demand (COD) and/or total organic carbon (TOC).
  • COD chemical oxygen demand
  • TOC total organic carbon
  • the catalyst may also serve to lower the overall energy requirements of the wet oxidation system.
  • the catalyst may be any transition metal of groups V, VI, VII and VIII of the Periodic Table.
  • the catalyst may be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, or alloys or mixtures thereof.
  • the transition metal may be elemental or present in a compound, such as a metal salt.
  • the transition metal catalyst is vanadium.
  • the transition metal catalyst is iron.
  • the transition metal catalyst is copper.
  • a catalyst may be added to the aqueous mixture at any point in the wet oxidation system.
  • the catalyst may be mixed with the aqueous mixture.
  • the catalyst may be added to the source of the aqueous mixture feeding the wet oxidation unit as illustrated in FIG. 1 in which catalyst source 40 is fluidly connected to storage tank 10.
  • the catalyst may be directly added to the wet oxidation unit.
  • the catalyst may also be supplied to the aqueous mixture prior to heating and/or pressurization.
  • 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.
  • transition metals may be present in a waste stream to be treated by the catalytic wet oxidation system.
  • Aqueous slurries, such as those containing volatile organic carbons, may contain metals capable of acting as a catalyst.
  • the aqueous mixture may be a slurry of gasification byproducts.
  • the catalyst may be soluble in the aqueous mixture to enhance the wet oxidation process.
  • characteristics of the aqueous mixture may impact the solubility of a catalyst in the aqueous mixture.
  • a pH level of the aqueous mixture to be treated may affect the solubility of a particular catalyst in the aqueous mixture.
  • a catalyst may be selected based on a characteristic of the aqueous mixture.
  • the wet oxidation system may include a sensor 50, configured to detect a characteristic of the aqueous mixture to be treated.
  • 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 may be selected based on a detected pH level of the aqueous mixture.
  • solubility and pH level for various catalysts is generally known by those skilled in the art. Potential-pH equilibrium 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.
  • a catalyst soluble at the detected pH level may be selected to enhance the wet oxidation process.
  • a catalyst comprising copper may be selected for catalyst source 40 in accordance with one or more embodiments.
  • a catalyst comprising vanadium may be selected when the detected pH level is above about 4.5.
  • a catalyst comprising iron may be selected when the detected pH level is below about 4.
  • Other catalysts beyond those exemplarily presented herein may be utilized.
  • a catalyst may be selected and one or more
  • characteristics of the aqueous mixture may be manipulated to promote the presence of the selected catalyst in a soluble form to enhance the wet oxidation process.
  • a pH level of the aqueous mixture may be detected by sensor 50 and adjusted to solubilize the selected catalyst in the aqueous mixture.
  • the selected catalyst may be solubilized in the aqueous mixture solely by the adjustment of the pH of the aqueous mixture.
  • the selected catalyst may be solubilized in the aqueous mixture without the addition of any complexing agent, for example, ammonia to facilitate the solubiliztion of the selected catalyst in the aqueous mixture.
  • a pH adjuster may be added to the aqueous mixture at any point within the wet oxidation system but is preferably added such that the catalyst is soluble within the aqueous mixture during the oxidation reaction.
  • a source of pH adjuster 60 may be fluidly connected to the source of the aqueous mixture 10 as illustrated in FIG. 1.
  • the source of pH adjuster 60 may 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 base.
  • an alkali metal hydroxide may be utilized to adjust the pH level of the aqueous mixture.
  • ammonia may be used to solubilize the catalyst.
  • pourbaix diagrams may provide information for determining a desired pH range in which a selected catalyst would be soluble.
  • the pH level of the aqueous mixture may be adjusted to below about 2 (or in some embodiments below about 4 or below about 4.5) or above about 12 or above about 13 when the selected catalyst comprises copper.
  • the pH level of the aqueous mixture may be adjusted to above about 4.5 when the selected catalyst comprises vanadium.
  • the pH level of the aqueous mixture may be adjusted to a level below about 4 with reference to FIG. 6.
  • 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, actuating valves and pumps.
  • Controller 70 may be in electronic communication with sensor 50 as illustrated in FIG. 1.
  • Controller 70 may be generally configured to generate a control signal to adjust the pH level of the aqueous mixture in response to the pH sensor 50 registering a pH level outside a predetermined pH solubility range for the selected catalyst.
  • controller 70 may provide a control signal to one or more valves associated with pH adjuster source 60 to add pH adjuster to aqueous mixture source 10.
  • the controller 70 is typically a microprocessor-based device, such as a programmable logic controller (PLC) or a distributed control system, that receives or sends input and output signals to and from components of the wet oxidation system.
  • Communication networks may permit any sensor or signal-generating device to be located at a significant distance from the controller 70 or an associated computer system, while still providing data therebetween.
  • Such communication mechanisms may be effected by utilizing any suitable technique including but not limited to those utilizing wireless protocols.
  • a liquid effluent is separated from the oxidized aqueous mixture downstream of the oxidation reactor.
  • the catalyst may be recovered from the liquid effluent by a separation process.
  • the catalyst may be precipitated out of the effluent stream.
  • a crystallizer may be used to recover the catalyst. The catalyst may then be recycled back to the wet oxidation system.
  • FIG. 2 illustrates another embodiment of a wet oxidation system including a catalyst recycling system.
  • a process stream may enter the system 200 through line 202.
  • Catalysts that may be utilized in system 200 may include any transition metal of groups V, VI, VII and VIII of the Periodic Table.
  • the catalyst may be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, or alloys or mixtures thereof.
  • the transition metal may be elemental or present in a compound, such as a metal salt.
  • the transition metal catalyst is vanadium.
  • the transition metal catalyst is iron.
  • the transition metal catalyst is copper.
  • the catalyst may be soluble in the aqueous mixture to enhance the wet oxidation process.
  • characteristics of the aqueous mixture may impact the solubility of a catalyst in the aqueous mixture.
  • a pH level of the aqueous mixture to be treated may affect the solubility of a particular catalyst in the aqueous mixture.
  • a catalyst soluble at the pH level of the incoming aqueous mixture may be selected to enhance the wet oxidation process.
  • a pH sensor similar to pH sensor 50 of FIG. 1 may be incorporated into the input of the wet oxidation system 200 of FIG. 2 to provide an indication of the pH of the incoming aqueous mixture.
  • a catalyst comprising copper may be selected in accordance with one or more embodiments.
  • a catalyst comprising vanadium may be selected when the pH level of the aqueous mixture is above about 4.5.
  • a catalyst comprising iron may be selected when the pH level of the aqueous mixture is below about 4.
  • Other catalysts beyond those exemplarily presented herein may be utilized.
  • catalyst may be added to the process stream at the inlet of the system or as it flows through line 202 via line 224, which may carry an aqueous mixture comprising a recycled catalyst as will be discussed further below. Fresh catalyst may also be added along with the recycled catalyst.
  • the catalyst or a portion 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.
  • transition metals may be present in a waste stream to be treated by the catalytic wet oxidation system.
  • Aqueous slurries, such as those containing volatile organic carbons, may contain metals capable of acting as a catalyst.
  • the aqueous mixture may be a slurry of gasification byproducts.
  • the process stream may pass through heat exchanger 204 where it may be heated to the desired temperature for a given residence time before entering reactor 206. After treatment is completed, the treated process stream leaves reactor 206 through line 208. The treated process stream may then 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 alkali compound from source of pH adjuster 212.
  • a pH sensor (not shown) may be provided in communication with the source of pH adjuster 212 in order to monitor the pH of the oxidized aqueous mixture as pH adjuster is added from the source of pH adjuster 212 and give a signal to interrupt pH adjustment when the pH reaches a predetermined point.
  • a pH sensor may be located downstream of the source of pH adjuster 212 and coupled to a pH controller (not shown), such as controller 70 illustrated in FIG. 1, configured to control the flow of pH adjuster from the source of pH adjuster through delivery pumps and/or valves and/or piping associated with the source of pH adjuster 212 into the oxidized aqueous mixture in order to maintain a pH within a predetermined range.
  • a pH controller such as controller 70 illustrated in FIG. 1
  • the addition of pH adjuster from the source of pH adjuster 212 may be manually controlled.
  • the source of pH adjuster 212 may be configured to introduce pH adjuster into line 218 downstream of gas/liquid separator 214 instead of upstream of gas/liquid separator 214 as illustrated in FIG. 2.
  • the source of pH adjuster 212 may be configured to introduce pH adjuster directly into clarifier 220.
  • a treated process stream containing soluble copper hydroxide may be cooled to approximately 80° C. and pH adjusted to a range from about 6 to about 12, either upstream or downstream of gas/liquid separator 214, or within clarifier 220, conditions under which the solubility of copper hydroxide is low ( ⁇ 1 ppm at 25° C).
  • the pH may be adjusted to a range of from about 8 to about 9 and in some embodiments the pH may be adjusted to about 9.
  • the treated process stream may travel through line 218 to clarifier 220 where in the presence of oxygen at 80° C.
  • the copper hydroxide is converted to copper oxide particulate at a pH of from about 6 to about 12, at least a portion of the copper hydroxide is converted to copper oxide particulate.
  • the copper hydroxide is converted to copper oxide particulate in the clarifier at a pH in a range of from about 8 to about 9 and in some embodiments the copper hydroxide is converted to copper oxide particulate in the clarifier at a pH of about 9.
  • the copper oxide particulates may settle in 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 through line 224, while oxidized effluent essentially free of copper may be removed through line 222.
  • the pH of the recycled copper containing effluent may be adjusted by the addition of an acid or alkali compound from source of pH adjuster 226 as is desired in response to a signal from a pH sensor in communication with line 224 (not shown) and/or a pH controller (not shown). pH adjuster may be added to the recycled copper containing effluent in order to adjust the pH to a level at which the copper catalyst is soluble.
  • the recycled copper containing effluent since copper is generally soluble at pH levels of below about 6 or above about 12, if the recycled copper containing effluent has a pH of between about 6 and about 12, acid may be added to decrease the pH level to the recycled copper containing effluent to below about 6, or alternatively, a caustic compound may be added to increase the pH level of the recycled copper containing effluent to above about 12 to solubilize at least a portion of the copper catalyst. At least a portion of the recycled catalyst may be directed to a source of catalyst 40 in some embodiments.
  • FIG. 3 illustrates an embodiment of a wet air oxidation system utilizing a two step catalyst settling process.
  • a system 300 with a two step catalyst settling process may utilize a set of clarifiers 228 and 230.
  • optional source of pH adjuster 212 may be positioned upstream of gas/liquid separator 214.
  • a source of pH adjuster and associated delivery pumps and/or valves and/or piping may be present and configured to deliver pH adjuster to locations upstream or downstream of gas/liquid separator 214 and/or into clarifier 228, clarifier 230, or both.
  • Multiple pH sensors may be located at locations upstream or downstream of any of the components of system 300 and coupled to a pH controller (not shown), such as controller 70 illustrated in FIG. 1, configured and arranged to control the flow of pH adjuster from one or more sources of pH adjuster located throughout the system, such as source of pH adjuster 234, through delivery pumps and/or valves and/or piping associated with the source or sources of pH adjuster.
  • a rough clarification may take place in the first clarifier 228.
  • At least a portion of a first separated solution from the first clarification step may be returned to the inlet of the system via lines 236 and 224 as dilution water and catalyst feed for further treatment.
  • At least a portion of the supernatant from the first clarification step may travel through line 232 and be settled in a second clarifier step in clarifier 230 after being pH adjusted by the addition of acid or alkali compound from source of pH adjuster 234.
  • Source of pH adjuster 234 and associated delivery pumps and/or valves and/or piping may be positioned and arranged to adjust the pH of the portion of the supernatant in line 232 or in clarifier 230, or both.
  • any or all of the clarifiers may be replaced with any form of separator capable of separating precipitated catalyst from the oxidized aqueous mixture.
  • a solution containing concentrated solidified catalyst may be returned to the inlet of system 300 through lines 238 and 224 to be mixed with an incoming process stream, while oxidized effluent essentially free of catalyst may be withdrawn through line 222.
  • At least a portion of the recycled catalyst may be directed to a source of catalyst 40 in some embodiments.
  • a benefit of the two step system is that only a small portion of the effluent of the wet oxidation unit will need to be pH adjusted in order to precipitate catalyst.
  • Source of pH adjuster 226 may be utilized to solubilize catalyst that may travel through line 224 by the addition of an acid or caustic compound in a similar manner as was discussed with regard to the example regarding copper catalyst above.
  • the pH of the recycled effluent of the wet oxidation unit will also be very close to the necessary pH for keeping the catalyst soluble in the wet air oxidation system.
  • catalyst may be precipitated solely by adjusting the pH of the oxidized aqueous mixture.
  • catalyst may be precipitated solely by adjusting the pH of the oxidized aqueous mixture in a single direction.
  • catalyst may be precipitated solely by adjusting the pH of the oxidized aqueous mixture with a single pH adjustment agent.
  • catalyst may be precipitated solely by adjusting the pH of the oxidized aqueous mixture to a pH within a range of pH at which the catalyst is substantially insoluble or at least partially insoluble in the oxidized aqueous mixture.
  • pH adjustment may be
  • catalyst may be solubilized in aqueous mixture to be oxidized at a pH within a first range and precipitated from oxidized aqueous mixture at a pH within a second range which does not overlap the first range.
  • the wet oxidized liquid effluent stream may be processed by a secondary treatment unit 80 as illustrated in FIG. 1 , connected downstream of the oxidation reactor vessel 24 to remove remaining undesirable constituents present and/or polish when necessitated or desired.
  • the secondary treatment unit 80 may be a chemical scrubber, a biological scrubber, an adsorption media bed, or other unit operation.
  • an advanced oxidation step including oxidation treatment of the wet oxidation effluent with ozone and ultraviolet light may be performed. Such advanced oxidation treatment is typically carried out in a vessel or tank at or near ambient temperature and pressure.
  • the secondary treatment unit 80 may be sized to provide a surface area consistent with the desired degree of polishing.
  • the liquid effluent may also be recycled back to reactor vessel 24 for further processing. Treatment of the off gas may also be required in a downstream off gas treatment unit depending on its composition and the requirements for discharge to the atmosphere.
  • Sensors to detect a concentration of a targeted odorous constituent may be provided upstream and/or downstream of the wet oxidation unit 24 to facilitate system control.
  • a sensor may be positioned at conduit 26 and be in
  • controller 70 communication with controller 70 to determine and/or control whether the liquid effluent stream should be diverted to the secondary treatment unit 80 to meet established environmental regulations.
  • one or more wet oxidation systems may be connected to multiple sources of process streams.
  • the wet oxidation system may include additional sensors for measuring other properties or operating conditions of the system.
  • the system may include sensors for temperature, pressure drop, and flow rate at different points to facilitate system monitoring.
  • the catalyst may be replenished during the wet oxidation process.
  • the disclosure contemplates the modification of existing facilities to retrofit one or more systems or components in order to implement the techniques of the disclosure.
  • An existing wet oxidation system can be modified in accordance with one or more embodiments exemplarily discussed herein utilizing at least some of the preexisting equipment.
  • one or more pH sensors may be provided and a controller in accordance with one or more embodiments presented herein may be implemented in a preexisting wet oxidation system to promote catalyst solubility or to facilitate catalyst recycling.
  • bench scale wet oxidation tests were performed in laboratory autoclaves.
  • the autoclaves differ from the full scale system in that they are batch reactors, where the full scale unit may be a continuous flow reactor.
  • the autoclaves typically operate at a higher pressure than the full scale unit, as a high charge of air must be added to the autoclave in order 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 screening operating conditions for the wet oxidation process.
  • the autoclaves used were fabricated from titanium, alloy 600 and Nickel 200. The selection of the autoclave material of construction was based on the composition of the wastewater feed material. The autoclaves selected for use, each have total capacities of 500 or 750 ml.
  • the autoclaves were charged with wastewater and sufficient compressed air to provide excess residual oxygen following the oxidation (ca. 5%).
  • the charged autoclaves were placed in a heater/shaker mechanism, heated to the desired temperature (280° C. to 350° C.) and held at temperature for the desired time, ranging from about 60 minutes to about 360 minutes. During the heating and reacting periods, the autoclave temperature and pressure were monitored by a computer controlled data acquisition system.
  • the autoclaves were removed from the heater/shaker mechanism and cooled to room temperature using tap water. After cooling, the pressure and volume of the off gas in the autoclave head-space were measured. A sample of the off-gas was analyzed for permanent gases. Subsequent to the analysis of the off gas, the autoclave was depressurized and opened. The oxidized effluent was removed from the autoclave and placed into a storage container. A portion of the effluent was submitted for analysis and the remaining sample was used for post- oxidative treatment. In order to generate sufficient volume for analytical work and post-oxidation test work, multiple autoclave tests for each condition were run.
  • the copper catalyst exhibited the highest solubility at pH levels of 2.2 and
  • Fe+2 added g/L Fe - - 2.24 - 2.24 (as FeS0 4 )
  • Comparison tests to evaluate pH adjustment to recover copper catalyst were conducted. Two sets of tests were performed. In a first set of tests, non-pH adjusted naphthenic spent caustic was oxidized at 200° C. with a 120 minute residence time and 5000 mg/L of copper added as copper oxide. The second set of tests were performed with pH adjusted naphthenic spent caustic at 200° C. with 120 minutes residence time and 500 mg/L of copper added as copper oxide.
  • Each set of tests were run under the same conditions as follows.
  • a sample of naphthenic spent caustic was oxidized to produce an oxidized effluent.
  • the oxidized effluent was pH adjusted to about 8.5 using sodium hydroxide and centrifuged. A portion the supernatant was removed and the remaining effluent containing the copper oxide was recycled back as dilution water and combined with fresh feed for a subsequent oxidation.
  • Each run underwent several repetitions, in that the oxidation of the initial feed resulted in a first recycled effluent containing copper oxide, which was combined with fresh feed and oxidized, resulting in a second recycled effluent containing copper oxide.
  • recycled effluent containing soluble copper was not further adjusted with acid or base prior to being combined with the fresh feed.
  • containing copper catalyst may produce a recycled effluent containing soluble copper that may be directed back to the oxidation system which may reduce the amount of fresh catalyst to be added to the oxidation system.
  • a Recycled effluent was pH adjusted to 3.5 with acic
  • the term “plurality” refers to two or more items or components.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)
  • Catalysts (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Treating Waste Gases (AREA)
  • Treatment Of Sludge (AREA)

Abstract

L'invention concerne un système et un procédé de traitement de flux de processus. Un catalyseur intervient dans un procédé d'oxydation humide à des températures et des pressions élevées pour traiter au moins un constituant indésirable présent dans un mélange aqueux. Le mélange aqueux peut être mis en contact avec un catalyseur et un agent oxydant à une température élevée et une pression super-atmosphérique dans un réacteur (206). Au moins une partie du catalyseur peut être précipitée par ajustement du pH, par addition d'un composé acide ou alcalin provenant d'une source d'agent d'ajustement du pH (234), et être recyclée pour être renvoyée au contact du mélange aqueux via la conduite (238), après clarification dans le clarificateur (230). Le pH de l'effluent contenant le catalyseur recyclé peut être ajusté par addition d'un composé acide ou alcalin provenant de la source d'agent d'ajustement du pH (226).
EP14729758.4A 2013-04-18 2014-03-24 Procédé d'oxydation d'air humide à l'aide d'un catalyseur recyclé à base de cuivre, de vanadium ou de fer Withdrawn EP2986570A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US13/865,664 US9315401B2 (en) 2007-01-22 2013-04-18 Wet air oxidation process using recycled copper catalyst
PCT/US2014/031536 WO2014172066A1 (fr) 2013-04-18 2014-03-24 Procédé d'oxydation d'air humide à l'aide d'un catalyseur recyclé à base de cuivre, de vanadium ou de fer

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WO2019101710A1 (fr) 2017-11-23 2019-05-31 Shell Internationale Research Maatschappij B.V. Procédé de traitement des eaux usées
CN109455802A (zh) * 2018-12-12 2019-03-12 中国恩菲工程技术有限公司 废水的处理方法

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US3912626A (en) * 1974-03-18 1975-10-14 Sterling Drug Inc Catalyzed process and catalyst recovery
GB1546681A (en) * 1975-08-14 1979-05-31 Mitsui Toatsu Chemicals Process for the liquid phase oxidation of organic substance-containing aqueous effluents
US7993588B2 (en) * 2006-10-03 2011-08-09 Siemens Industry, Inc. Catalytic wet oxidation systems and methods
WO2008091578A1 (fr) * 2007-01-22 2008-07-31 Siemens Water Technologies Corp. Procédé d'oxydation par voie humide utilisant un catalyseur recyclé

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KR20150144337A (ko) 2015-12-24
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CN105164063A (zh) 2015-12-16
JP2016521203A (ja) 2016-07-21

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