JP2010530793A - System and method for process flow processing - Google Patents

Abstract

Systems and methods for process flow processing. The treatment system can generally include an oxidation unit coupled downstream of the desalination unit. The oxidation unit can oxidize organic reduced sulfur contaminants in the process stream to facilitate downstream processing. The desalination unit can convert the product of the oxidation unit to produce a mineral stream. In some examples, the process stream may be a spent caustic stream from an industrial plant such as an ethylene production facility or an oil refinery. It is possible to isolate a fresh caustic stream, such as a sodium hydroxide stream, in a desalting step and return it to an industrial operation.
[Selection] Figure 1

Description

  The present invention relates generally to process stream processing and, more particularly, to systems and methods for its desalination.

  Oxidation is a well-known technique for treating process streams and is widely used, for example, to eliminate contaminants in wastewater. For example, wet oxidation includes aqueous phase oxidation of undesired components at high temperatures and pressures with an oxidant, typically molecular oxygen from an oxygen-containing gas. This process allows organic pollutants to be converted into biodegradable short chain organic acids such as carbon dioxide, water and acetic acid. Inorganic constituents such as sulfides and mercaptides can also be oxidized, and cyanides can be hydrolyzed. As an alternative to incineration, the process stream can be treated in a wide variety of applications using wet oxidation, for example for subsequent discharge.

  Various ion recovery methods are also widely known. One technique involves a continuous electrical deionization (CEDI) system that is used almost exclusively to produce ultrapure water from an already substantially deionized stream. The CEDI feed stream is typically a reverse osmosis process stream. The CEDI feed stream and product stream have low conductivity, and thus the cells are usually filled with resin to increase the conductivity of the matrix. The cells are arranged in alternating pairs, with each pair typically producing one ultrapure water stream and one saltwater waste stream. The capacity of a CEDI module is defined by the number of cell pairs contained between the electrodes at both ends of the module. Typically, for industrial scale applications, about 30-120 cell pairs are used per module. The CEDI module housing is configured to have a duct system that collects the production water in one stream and the waste ion stream in the other stream. Industrial applications are typically in the range of 10 amps or less.

Each aspect relates generally to a process flow processing system and method.
According to one or more aspects, a system for treating an aqueous feed includes an oxidation unit fluidly connected to a source of the aqueous feed and a product of the oxidation unit fluidly connected downstream of the oxidation unit to the target compound. A desalting unit constructed and arranged to convert to

  In accordance with one or more aspects, a system for treating an aqueous feed containing spent caustic includes an oxidation unit fluidly connected to a source of the aqueous feed and fluidly connected downstream of the oxidation unit. An electrochemical deionization unit constructed and arranged to produce fresh caustic.

  According to one or more aspects, a method for treating an aqueous stream comprises oxidizing the aqueous stream to produce an oxidized product, and converting the oxidized product to produce caustic.

  Other aspects, embodiments, and advantages of these exemplary aspects and embodiments are described in detail below. Further, it should be understood that the above information and the following detailed description are merely examples for the purpose of describing various aspects and embodiments, and illustrate the nature and characteristics of the claimed aspects and embodiments. It is intended to present an overview or configuration for understanding. The accompanying drawings are included to provide a better understanding of various aspects and embodiments, and are incorporated in and constitute a part of this specification. The drawings, together with the remainder of the specification, serve to explain the principles and workings of the aspects and embodiments described and claimed.

  In the following, various aspects of at least one embodiment will be discussed with reference to the accompanying drawings. These figures are not intended to be drawn to scale, but the same or nearly identical components illustrated in the various figures are labeled with like numbers. For clarity, not all components are shown in all drawings. These figures are presented for purposes of illustration and description and are not intended to limit the scope of the invention.

FIG. 2 illustrates a processing system in accordance with one or more embodiments. FIG. 2 illustrates a caustic flow treatment system according to one or more embodiments. FIG. 3 illustrates the operation of a continuous electrical deionization unit according to one or more embodiments. FIG. 3 illustrates piping arrangements of various systems discussed in the accompanying examples. FIG. 3 illustrates piping arrangements of various systems discussed in the accompanying examples. FIG. 3 illustrates piping arrangements of various systems discussed in the accompanying examples. FIG. 3 illustrates piping arrangements of various systems discussed in the accompanying examples. FIG. 3 illustrates piping arrangements of various systems discussed in the accompanying examples. 2 is a table summarizing test conditions and results discussed in the accompanying examples. 2 is a table summarizing test conditions and results discussed in the accompanying examples. Figure 3 is a power chart of a CEDI module discussed in the accompanying examples. Figure 3 is a power chart of a CEDI module discussed in the accompanying examples. Figure 3 is a power chart of a CEDI module discussed in the accompanying examples. Figure 3 is a power chart of a CEDI module discussed in the accompanying examples. Figure 3 is a power chart of a CEDI module discussed in the accompanying examples. 6 is a graph illustrating data regarding the effect of current discussed in the accompanying examples. 6 is a graph illustrating data regarding the effect of current discussed in the accompanying examples. FIG. 4 is a diagram representing mass balance for several different system arrangements in one or more embodiments. FIG. 4 is a diagram representing mass balance for several different system arrangements in one or more embodiments. FIG. 4 is a diagram representing mass balance for several different system arrangements in one or more embodiments. FIG. 4 is a diagram representing mass balance for several different system arrangements in one or more embodiments. FIG. 4 illustrates the measured titer of NaOH in a CEDI product stream required to meet mass balance requirements according to one or more embodiments.

  One or more embodiments are generally associated with processing a process stream. These systems and methods may be generally effective in the treatment of process streams contaminated with one or more readily oxidizable compounds. The systems and methods described herein can be implemented in a wide variety of applications where it may be desirable to desalinate the process stream to facilitate downstream processing and / or produce a product such as a mineral stream. It is. Advantageously, some embodiments may be particularly useful in reducing the amount of new, fresh or supplementary reactants that need to be supplied for upstream industrial applications. For example, in some embodiments, water having sufficient potency and quality to treat a spent caustic feed stream and return it to an upstream ethylene production facility or petroleum refinery for use as a reactant. It is possible to produce a new caustic stream, such as a sodium oxide stream. Some systems and methods have pH levels adjusted to the pH level of the initial process stream so that the need for pH correction is reduced, for example by addition of chemicals, for neutralization prior to discharge. It can also help create a spilled system. In some embodiments, for example, both the oxidation treatment unit and the desalination treatment unit can be used efficiently and recognized synergies between them, providing significant advantages to both the equipment supplier and the end user. Some can bring

  Of course, the system and method embodiments discussed herein are not limited in their application to the details of construction or construction illustrated in the following description or accompanying drawings. These systems and methods can be implemented in other implementations and can be practiced or implemented in various ways. Although specific examples are presented herein for illustrative purposes only, they are not intended to be limiting. That is, the actions, elements and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiments. Also, the expressions and terms used herein are for the purpose of description and should not be regarded as limiting. The use of “including”, “comprising”, “having”, “including”, “with”, and variations thereof herein includes items listed thereafter and equivalents thereof as well as additional items. It represents inclusion.

  According to one or more embodiments, the system can be fluidly connected to a source of process flow to be processed. A process flow may be any process flow that can generally be supplied to the system for processing. In some embodiments, the process stream may be an aqueous feed. In at least one embodiment, the process stream may be a wastewater stream. The process flow can be moved through the system by operations upstream or downstream of the system. The source of the aqueous mixture to be treated by the system, such as a slurry or other feed stream, can take the form of direct piping from the plant or intermediate storage vessel. After treatment, the process stream can be returned to the upstream process or discharged from the system as waste liquid.

  In a typical operation, the disclosed system can obtain a process stream from a community source, an industrial source, or a residential source. In some embodiments, the process stream originates from, for example, a food processing plant, chemical processing facility, gasification business, or pulp and paper mill. In at least one embodiment, the process stream can be an aqueous feed from a process generally associated with polyolefins, such as an ethylene plant or petroleum refinery. For example, in some embodiments, the aqueous feed may be a spent caustic feed stream.

  According to one or more embodiments, the process stream may include dissolved solids, such as minerals. In some embodiments, the mineral may have value as a product stream if it can be separated or converted, as described in more detail below. In other embodiments, the mineral may be considered a contaminant that makes the process stream insufficient for use, treatment or disposal. Accordingly, it may be desirable to desalinate the process stream to extract product and / or facilitate downstream processing. Various other components may be present in the process stream, including but not limited to chloride, sodium hydroxide, sodium carbonate, total organic carbon (TOC), and iron.

  According to one or more embodiments, the process stream may include one or more target ions. As discussed herein, isolation and conversion of target ions may be desirable. For example, target ions in the process stream can be manipulated by the system to produce a valuable or desirable product stream. In some embodiments, target ions are present in the process stream as reaction by-products due to upstream consumption of consumables or reactants. In some embodiments, the target ion is isolated by the system and used to form or generate the target compound. Thus, target ions present in the process stream may be precursors of target compounds. For example, the target compound that is produced may be the original consumable or reactant that produced the target ions in the process stream upstream of the system. The target compound can then be fed upstream of the system and reused. In some embodiments, the target compound may be a caustic compound such as sodium hydroxide or ammonium sulfate. Some systems and methods may generally produce a product stream containing the target compound. In at least one embodiment, the process stream may be a spent caustic stream from an industrial caustic tower or MEROX® type treatment process, such as used in an oil refinery or ethylene production facility. Typically, the spent caustic stream may contain one or more reaction by-products from the consumption of fresh caustic in the caustic tower. In general, according to one or more embodiments, the reaction byproduct may include the target sodium ion of interest. For example, sodium sulfide as a reaction by-product may contain target sodium ions that are problematic. The target ion can then be converted by the system to produce the target compound. For example, target sodium ions can be converted to form the target compound sodium hydroxide. This system is capable of delivering a product stream containing sodium hydroxide in solution. The spent caustic stream to be treated may contain other compounds, including any fresh residual caustic. It may be desirable to generate a fresh caustic stream from the spent caustic stream and send it back to the caustic tower.

  According to one or more embodiments, the process stream to be processed typically includes at least one undesirable component. The unwanted component may be any substance or compound that is to be removed from the aqueous mixture, for example for public health considerations, process design considerations, and / or aesthetic considerations. For example, the unwanted component may be toxic. In some embodiments, undesired components have a tendency to interfere with downstream operation by downstream separation or ion recovery unit membranes. For example, undesired components are generally characterized as causing high chemical oxygen demand (COD) levels in the process stream that can lead to undesirable results. In at least one embodiment, undesirable components in the process stream are generally capable of being oxidized. In some embodiments, the undesirable component that can be oxidized is an organic compound. Some inorganic components such as sulfides, mercaptides and cyanides can also be oxidized. In at least one embodiment, sodium sulfide may be present in the process stream. In one non-limiting embodiment, sodium sulfide may be present at a concentration of up to at least about 25,000 ppm as S.

  According to one or more embodiments of the present invention, the processing system can include a first processing unit. In some embodiments, the first processing unit generally affects the process flow to facilitate its further processing. For example, the first processing unit may be effective to prevent one or more specific chemical bonds in the undesired component or its degradation products. According to one or more embodiments, the first processing unit contributes to a COD that may inhibit the effectiveness, useful life and / or suitability of downstream processing, eg, desalination steps. Oxidizable contaminants can generally be treated. Thus, the first processing unit can reduce or alter the nature of one or more undesirable components, for example, by removing or stabilizing COD. For example, the first processing unit can decompose or remove organic reduced sulfur contaminants. In some embodiments, the first processing unit places at least one target ion in a different or desirable form for downstream extraction, as discussed herein. In at least one embodiment, the first processing unit can typically be incorporated as a pretreatment step prior to the desalting step, as described in more detail below.

  According to one or more embodiments, the first processing unit or stage may be an oxidation unit. Oxidation is one degradation 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 present invention relates to systems and methods for the oxidation treatment of aqueous mixtures containing one or more undesirable components. The oxidation unit can oxidize sulfides to produce non-toxic sulfate ions and oxidize other species present in the process stream, such as a spent caustic stream. Mercaptans can be made substantially harmless and COD contaminants can be converted to less harmful and stable compounds for downstream operation. Since 100% oxidation cannot be achieved, there may still be some undesirable components in the oxidation product of the oxidation unit. There may also be residual target compounds, such as sodium hydroxide and sodium carbonate, in the oxidation product. For some non-limiting embodiments, typical oxidation products can include sodium carbonate and sodium sulfate. Mineralized products such as sulfate and carbonate ions can also be formed. In at least some embodiments, the oxidation process may form at least one salt of a target ion, such as sodium. For example, sodium can form a salt complex with oxidized ions. Thus, the oxidation product may contain target ions, such as sodium, that exist in a different form than in the original process stream. For example, in some embodiments, sodium may normally be present as sodium sulfate upstream of the oxidation unit, but can be discharged from the oxidation unit as sodium sulfate and / or sodium carbonate.

  According to one or more embodiments, any oxidizing agent can be used in the oxidation unit. For example, any oxygen source such as oxygen gas, ozone, peroxides and permanganates and combinations thereof can be used. Similarly, any oxidation technique or technique or combinations thereof can be utilized. For example, in some embodiments, photooxidation techniques can be utilized, in which the conversion of a reduced molecule to an oxidized form in the presence of oxygen is by a series of chemical reactions initiated by photolysis. Usually implemented. In at least one embodiment, for example, ultraviolet light or visible light may be used. According to one or more embodiments, the oxidation unit may generally be a liquid phase oxidation unit. In at least one embodiment, the liquid phase oxidation unit may be a wet oxidation unit, such as a wet air oxidation, wet peroxide oxidation or supercritical water oxidation unit.

  In one embodiment, for example, wet oxidation of an aqueous mixture or process stream that includes at least one undesirable component is performed. The aqueous mixture is oxidized with an oxidant at elevated temperature and superatmospheric pressure for a duration sufficient to treat at least one undesirable component. Some non-limiting embodiments involve process temperatures above about 150 ° C. More specifically, the process temperature may exceed about 200 ° C. In some embodiments, the process temperature is greater than about 250 ° C. Similarly, the duration or residence time can vary. In some embodiments, the residence time varies from about half an hour to 10 hours. In some non-limiting embodiments, a residence time of about 1 hour is required, although shorter or longer residence times can be employed depending on the intended application conditions. The oxidation reaction can substantially destroy the complete state of one or more chemical bonds in the undesired component. As used herein, “substantially destroy” is defined as at least about 95% destruction. The process of the present invention is generally applicable to the treatment of any undesirable component that can be oxidized.

  The disclosed wet oxidation process can be carried out in any known batch or continuous wet oxidation unit suitable for the compound to be oxidized. Typically, water phase oxidation is performed in a continuous flow wet oxidation system. Any oxidizing agent can be used. The oxidant is typically an oxygen-containing gas, such as air, oxygen-enriched air, or substantially pure oxygen. As used herein, the term “oxygen-enriched air” is defined as air having an oxygen content greater than about 21%.

  In a typical process, an aqueous mixture from a source such as a storage tank flows through a conduit to a high pressure pump and is pressurized with this pump. The aqueous mixture is mixed in a conduit with oxygen-containing pressurized gas supplied by a compressor. The aqueous mixture flows through a heat exchanger where it is heated to a temperature at which oxidation begins. The heated feed mixture then flows from the inlet into the reactor. 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 a desired value. Since most of the oxidation reaction occurs in the reactor, sufficient residence time is obtained to achieve the desired degree of oxidation. Next, the oxidized aqueous mixture and the oxygen-reduced gas mixture are transferred from the reactor to the heat exchanger. The hot oxidation effluent traverses the heat exchanger and is cooled by the incoming raw aqueous mixture and gas mixture. The cooled effluent mixture flows into a separation vessel through a conduit regulated by a pressure regulating valve where the liquid and gas are separated. The liquid effluent exits the separation vessel through the lower conduit, while the exhaust gas is discharged from the upper conduit. Treatment of the exhaust gas in the downstream exhaust gas treatment unit may be necessary depending on its composition and requirements for release to the atmosphere. The wet oxidation effluent is typically sent to a processing plant such as a biological or chemical processing plant for purification prior to release. The effluent may be recycled and further processed by a wet oxidation system. In accordance with one or more embodiments of the present invention, the effluent can be sent to a second unit operation, such as a desalination or ion recovery unit as further detailed herein.

  Typically, sufficient oxygen-containing gas is supplied to the system to maintain residual oxygen in the wet oxidation system exhaust gas, and typically the superatmospheric pressure of the gas supplies water at the selected oxidation temperature. Sufficient to keep in liquid phase. For example, the minimum system pressure at about 240 ° C. is about 33 atmospheres, the minimum system pressure at about 280 ° C. is about 64 atmospheres, and the minimum system pressure at about 373 ° C. is about 215 atmospheres. In one embodiment, the aqueous mixture is oxidized under a pressure of about 30 atmospheres to about 275 atmospheres. The wet oxidation process may be performed at a high temperature below about 374 ° C., the critical temperature of water. In some embodiments, the wet oxidation process is performed at a supercritical high temperature. The retention time of the aqueous mixture in the reaction chamber usually must be sufficient to achieve the desired degree of oxidation. In some embodiments, the retention time is greater than about 1 hour and no greater than about 8 hours. In at least one embodiment, the retention time is at least about 15 minutes and no more than 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 one or more embodiments, the wet oxidation process may be a catalytic wet oxidation process. In general, the oxidation reaction in the oxidation unit can be realized by a catalyst. An aqueous mixture containing at least one undesirable component to be treated is generally contacted with the catalyst and oxidant at elevated temperature and superatmospheric pressure. Typically, an effective amount of catalyst is sufficient to increase the reaction rate and / or improve the overall cracking and removal efficiency of the system, including facilitating COD and / or TOC reduction. The catalyst can also help reduce the overall energy requirements of the wet oxidation system. Catalytic wet oxidation has emerged as an effective enhancement method of traditional non-contact wet oxidation. In general, the catalytic wet oxidation process makes it possible to achieve further decomposition at lower temperatures and pressures, and therefore with lower capital costs. The aqueous stream to be treated is mixed with an oxidant and brought into contact with the catalyst under high temperature and pressure. Typically, the heterogeneous catalyst is present on an adsorbent bed through which the aqueous mixture passes or is present in the form of solid particles that are blended with the aqueous mixture prior to oxidation. The catalyst can be recycled from the oxidation effluent downstream of the wet oxidation unit.

  In at least one embodiment, the catalyst may be any transition metal from Group V, Group VI, Group VII and Group VIII of the Periodic Table. For example, in one embodiment, the catalyst may be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, or an alloy or mixture thereof. The transition metal may be an element or may be present in the compound like a metal salt. In one embodiment, the transition metal catalyst is vanadium. In another embodiment, the transition metal catalyst is iron. In yet another embodiment, the transition metal catalyst is copper.

  The catalyst can be added to the aqueous mixture at any point in the wet oxidation system. The catalyst can be mixed with an aqueous mixture. In one embodiment, the catalyst can be added to the source of the aqueous mixture that feeds the wet oxidation unit, which is fluidly connected to the storage tank. In some embodiments, the catalyst is added directly to the wet oxidation unit. In other embodiments, the catalyst is fed to the aqueous mixture prior to heating and / or pressurization.

  A first processing unit, such as an oxidation unit, generally produces a product stream, such as an oxidation product stream. Thus, the oxidation unit can convert the process stream to an oxidation product stream. The oxidation product stream may generally be compatible with subsequent processing as in the ion recovery or desalination unit discussed herein. The oxidation product is generally substantially free of undesirable components. The oxidation product may contain one or more target ions from the original process stream and may be subjected to further processing as discussed herein to produce the desired product. .

  According to one or more embodiments, the second processing unit may be fluidly connected downstream of the first processing unit. The second processing unit may be configured to receive an oxidation product or oxidation product stream and perform further processing. In some embodiments, the second processing unit may generally convert the oxidation product of the first processing unit to form a target compound or target stream. The target compound can generally be isolated for extraction by the system and may be useful as a product stream, or its removal may facilitate downstream operations. In some embodiments, the second processing unit may generally desalinate the oxidation product stream to facilitate downstream processing and / or produce a valuable mineral rich product stream. it can. The second processing unit generally requires any technique capable of extracting the ions to produce an ion rich product stream as well as a reduced mineral content stream. Also good. For example, the second processing unit may be effective in performing ion recovery of compounds including sodium, potassium, calcium, carbonate and sulfate.

  According to one or more embodiments, the desalting unit may include, for example, at least one ion exchange resin bed. Ion exchange can usually involve ion exchange for desalting between a solution and a solid, usually a resin. That is, ion exchange can involve reversible exchange between ions adsorbed on the surface of a mineral or synthetic polymer and ions in solution in contact with the surface. It is possible to remove the target ions and replace them with other ions, such as hydrogen ions. Next, water or other regeneration fluid is periodically passed through the ion exchange resin bed to replenish the resin with new hydrogen ions and produce rinse water containing the target compound such as sodium hydroxide stream. Target ions are recovered from the exchange bed.

  For example, polymer electrolyte structures can be produced by polymerizing cationic monomers within the structure of an anion exchange resin or vice versa. When regenerated, this structure may comprise a cationic group in the form of hydrogen and an anionic group in the form of hydroxyl. The introduction of the electrolyte replaces hydrogen ions and hydroxyl ions, resulting in their neutralization and saturating the resin with ionic species. Regeneration with water causes hydrolysis of the resin groups, during which time the target ions are released and recovered. It is also possible to regenerate the ion exchange resin bed using a lime solution to produce a target compound such as sodium hydroxide.

  According to one or more embodiments, it is also possible to perform ion recovery or desalting using a concentration or separation operation. For example, distillation generally requires evaporation and subsequent condensation to collect steam. It is also possible to carry out a filtration process such as a crystallization process and nanofiltration. It is also possible to utilize a reverse osmosis process involving a filtration process that removes dissolved salts and metal ions from water that is forced through the semipermeable membrane by pressure applied to the concentrate side.

  According to one or more embodiments, examples of demineralization or ion removal techniques include electrochemical operations such as electrodialysis, electrodeionization, capacitive deionization and continuous electrodeionization (CEDI). be able to. According to one or more embodiments, the desalination unit may involve capacitive deionization based on electrostatic processes that are generally operated under low voltage and low pressure. The generated water is pumped through the electrode assembly. The ions in the water are attracted to the electrode charged to the opposite polarity. This concentrates the ions at the electrode, while the ion concentration in the water decreases. The purified water is then passed through the unit. When the electrode capacity is reached, the water flow is stopped and the polarity of the electrode is reversed. This causes the ions to leave the previously stored electrode. Next, a concentrated salt solution is discharged from the unit.

According to one or more embodiments, a continuous electrical deionization (CEDI) process can be performed. CEDI generally utilizes a combination of ion exchange resin and membranes and direct current to continuously deionize water without the need for chemicals. CEDI is an electrochemical process in which a charge is applied to the module. Electrochemical device electrodes can typically be made of various materials such as stainless steel, iridium oxide, ruthenium oxide and platinum. The electrode can also be coated with various materials, such as titanium. The electrodes generate H ⁺ and OH ⁻ ions. These ions move with the ions in the feed stream by the potential applied to the device. A module consists of cells separated by a membrane. The depth of the cell is about 0.1 inch. The membrane allows only one of anions and cations to pass through. Thus, ion species are concentrated in some cells while ions are reduced in other cells. The ion current is directly related to the current applied to the module. Electrons do not flow across the cell. Ions are generated by electrons, but it is these ions that flow across the CEDI module.

  This process typically relies on the use of cells separated by an ionic membrane. Since the conductivity of pure water is very low, the voltage required to transport ions through pure water is very high. The resin is used to increase the electrical conductivity in the water cell, thereby reducing the required voltage. The resin is a sphere of about 0.3 to about 0.5 mm. The resin surface has an ionic charge and is cationic (c) or anionic (a). Cationic resins have anionic functional groups that attract cationic species (ie, cationic resins are so called because they attract cations). Thus, cations can flow across the cell by moving on the cation resin. Similarly, anionic resins allow for the transport of anions. In application, many ion exchange resin beds are mixed with both an anion resin and a cation resin so that both types of ions can be transported across the cell.

  The membrane is also made of a cationic material or an anionic material. The IonPure ™ (Siemens) membrane is made by mixing a resin and polyethylene and extruding it into a sheet. This is called a non-uniform structure. Polyethylene provides mechanical strength and resin provides transport properties. The cation membrane passes only cations, while the anion membrane passes only anions.

When wet, the resin and membrane can swell. When swollen, the resin exerts forces up to about 100 psi on the walls and membranes. The resin material in the film also expands, so that the structure of the heterogeneous film changes permanently. For water purification purposes, a nominal leakage rate of IonPure (TM) membrane is about ^{20mL / hr / ft 2 / 5psi} . The degree of swelling caused by sodium ions is lower than that caused by hydronium ions. Therefore, when the resin of the heterogeneous membrane shrinks in high strength salt water, the porosity of the resin increases. Homogeneous membranes are made only of resin, thus increasing the current flux. Homogeneous membranes are more expensive than heterogeneous membranes, but are otherwise interchangeable.

  The bipolar membrane is an anion membrane on one side and a cation membrane on the other side. Bipolar membranes are the most expensive type of membrane and are used for water splitting. These membranes can be used in place of the water splitting cell. Bipolar membranes rely on water diffusion into the membrane and may not be suitable for high-speed production.

  A direct current is passed through the electrodes of the device by the power source. The electrode is the outermost cell on the opposite side of the module. The electrode cell does not contain a resin and instead uses high strength salt water to provide conductivity to the cell. A plastic screen is placed in the cell to prevent the membrane from contacting the electrode.

The cathode (-) is typically made from stainless steel, although other anode materials can be used. Electrons flow from the power source through this electrode. In the cathode cell, this produces hydroxide ions and hydrogen gas.
4H ₂ O + 4e ⁻ → 2H ₂ (g) + 4OH ⁻

Reduction (plating) of sodium to metallic sodium is an alternative route for consuming electrons. However, this does not occur because the sodium plating potential requirement is higher than that required for the production of H ₂ (g). The hydrogen production rate is calculated from Faraday's law and can be written as:

  here,

Is the molar production rate of hydrogen gas (mol H ₂ / sec), A is the current (ampere), and F is the Faraday constant (96,485 coulomb / mol).

The anode (+) is titanium coated with a corrosion resistant conductor. The conductor is typically platinum, iridium oxide or ruthenium oxide. Iridium oxide is usually used as a coating in C Series modules manufactured by Siemens. For high amperage applications, platinum would be a better material. Electrons are drawn from the water in the cell and returned to the power source. As a result, oxygen gas is generated.
2H ₂ O-4e ⁻ → O ₂ (g) + 4H ⁺

  The oxygen production rate is calculated from the following equation.

  here,

Is the molar production rate of hydrogen gas (mol O ₂ / sec), A is the current (ampere), and F is the Faraday constant (96,485 coulomb / mol).

  Referring to FIG. 1, operation of the processing system 100 involves sending a process stream from the industrial application device 130 to the oxidation unit 110. The oxidation product stream leaving the oxidation unit 110 is directed to the desalting unit 120. The desalting unit 120 produces a target compound stream, such as a sodium hydroxide stream. This compound stream can be sent back to the industrial application device 130 for further use. The target compound stream can be fed directly into the industrial application device 130 or mixed upstream with fresh reactants from the reactant source 140. The discharge stream can be recycled back to the desalination unit 120 for further processing and / or extraction of the target compound. Thus, since the reactants are generated from the process stream by the system, the amount of fresh reactants added to the industrial application device 130 can be reduced.

  In one aspect, spent caustic can be treated to recover a sodium hydroxide product stream. In ethylene plants or petroleum refineries, fresh caustic such as sodium hydroxide can be used to remove or wash acidic gases such as carbon dioxide and hydrogen sulfide from the process gas. Fresh caustic is about 50% NaOH in water and is typically diluted to about 10% for use in caustic towers. About 8 tons of fresh caustic can be consumed per hour. Caustic towers can also condense organic species such as mercaptans, light hydrocarbons, acetaldehyde, naphthenic acid and cresolic acid. As more acid is washed out, the amount of free caustic is reduced until it is no longer useful. At this point, the plant will typically remove caustic from the system, which becomes known as spent caustic.

  A typical spent caustic stream contains sodium carbonate, sulfide and high molecular weight organic compounds dissolved in the solution. This stream holding liquid phase sulfides, carbonates and organic acids typically has a high pH. This stream may have a high content of dissolved solids but is generally not suitable for many desalting processes. This is because reactive sulfides and organic compounds may not be compatible with desalination processes such as CEDI system membrane materials. Removal of cations such as sodium results in the release of sulfide from the liquid, which is often undesirable because hydrogen sulfide is a highly odorous and toxic corrosive gas.

  The spent caustic liquid is oxidized using WAO and then desalted using CEDI. Oxidation converts sulfides into innocuous sulfates and organic compounds into carbonates and short chain organic acids that are relatively stable and less destructive to the desalting process. The oxidized liquor is then sent to the CEDI process where a portion of the sodium is removed resulting in a sodium hydroxide product stream. The residual stream is somewhat desalted by removal of sodium ions, resulting in a decrease in the pH of the effluent.

  It is possible to fluidly connect one or more additional unit operations downstream of the desalination unit. For example, the concentrator can be configured to receive and concentrate the target product stream prior to sending it to an upstream industrial plant for use. There may be a purification unit, such as with chemical or biological treatment, to treat the effluent of the system prior to release.

  According to one or more embodiments, the disclosed system can be operated continuously or intermittently. In some embodiments, the wet oxidation system may include, but is not limited to, a controller for adjusting or adjusting at least one operating parameter of the system or system components, such as an operating valve and pump. Good. The controller may be in electronic communication with at least one sensor configured to detect at least one operating parameter of the system. The controller can generally be configured to generate a control signal for adjusting one or more operating parameters in response to a signal generated by the sensor.

  The controller is typically a microprocessor-based device such as a programmable logic controller (PLC) or a distributed control system that receives input signals or sends output signals to and from components of the wet oxidation system. It is. The communication network allows any sensor or signal generator to be placed at a significant distance from the controller or associated computer system, while still providing data between them. Such a communication mechanism can be implemented using any suitable technique, including but not limited to techniques that use wireless protocols.

  Operational economic considerations include operator time, clean water, power for machinery and instrumentation, and power to provide amperage to the CEDI electrode. The electrical cost to implement CEDI depends on the resistance and the degree of membrane leakage that will cause sodium to return to the brine cell. An economic advantage of implementing CEDI is the generation of valuable NaOH. In addition, in the case of conventional WAO spent caustic applications, a neutralizing acid must be purchased to neutralize the alkalinity of the oxidized spent caustic. Since some of the alkalinity has been removed by CEDI, the consumption of neutralizing acid can be further saved.

  The functionality and advantages of these and other embodiments will be better understood from the following examples. These examples are intended to be illustrative in nature and should not be considered as limiting the scope of the embodiments discussed herein.

EXAMPLE Laboratory tests were performed using standard and improved versions of the Siemens C Series CEDI module. The purpose of the evaluation work was to confirm the effectiveness of the CEDI process for producing a NaOH product stream from a synthetic mixture of inorganic salts and to produce a NaOH product with the intention of reaching a maximum of 18 g / L NaOH. To evaluate the economic significance of this application for the cost of purchasing commercially available NaOH. Test reports were made during the three test periods.

I. Experimental Design A. Tests 1-13
Tests 1-13 were performed on a Siemens C Series CEDI module. The components are described below.
● Aluminum end plate − Cathode end plate ● Cathode − Made of iridium ● Screen used to make S-type cell ● Cation membrane ● Plastic frame filled with 60 / 40v / v mixture of cation resin and anion resin A type 1 cell. The cross-sectional shape of the cell (perpendicular to the current flow) consists of three parallel cells. The two outer chambers are 14 "x 1.3125" and the central chamber is 14 "x 1.25". The total cross-sectional area of the cell is 54.25 ″ ² (350 cm ² ).
● Anionic membrane ● Type 2 cell filled with 60/40 v / v mixture of cation resin (same frame is used, but inverted to flow directly to different duct systems)
● Cation membrane ● S type cell ● Cation membrane ● Type 1 cell ● Anion membrane ● Type 2 cell ● Cation membrane ● S type cell ● Anode-also made of iridium ● Aluminum end plate-Anode end plate

Each cell has one of three supply duct options and one of three discharge duct options.
● The S-type cell was provided with a duct to supply salt water and release the treated salt water. These cells generated H ₂ , O _2, and CO ₂ gases, and therefore these gases were also discharged with this stream.
● Type 1 cells were provided with ducts to supply and discharge DI water.
● Type 2 cells were provided with ducts to supply DI water and release NaOH product. In some cases, the feed stream to the Type 2 cell was recirculated NaOH product rather than pure DI water.

  The notation representing the cell configuration is -S12S12S +. The notation representing the film configuration is -caccac +. In some tests the polarity was reversed, in which case the module would be + S21S21S-. A schematic diagram illustrating the operation of the module is shown in FIG. Each of the three different piping configurations shown in FIGS.

  Power to the module was supplied by a DC power supply and a power control device. The amperage for the module was adjusted by the power controller. The controller displayed the voltage and amperage. Wiring was performed by connecting a negative (black) wire to the cathode tab and connecting a positive (red) wire to the anode tab. The electrical system can only supply 8 or 9 amps of power, beyond which the circuit breaker will fall. The wire was 18 gauge and was warm to the touch after operating for only a short time.

  The supply flow rate was monitored by a rotameter, and the outflow flow rate was monitored using a cylinder and a stopwatch. The pH, gas production rate and gas composition were not monitored. The generated gas was returned to the supply tank together with the recirculated salt water, and degassing was performed by arranging a degassing pipe near the supply tank.

B. Test 14-17
FIG. 4D shows the piping configuration for these tests. This equipment was similar to that described in the previous test, with the following exceptions.
● A stronger power supply and electrical cable were used. This power source was connected to a 220VAC 30A outlet. Utilizing 8 gauge wiring, these wires remained cold to the touch for all tests. Unlike conventional power supplies, this power supply supplied a constant voltage and displayed the resulting amperage.
● New electrode capable of supplying a large current. The electrode plate had a heavy titanium terminal tab and an electrode coated with platinum.
• One of the cells used a homogeneous membrane rather than the conventional IonPure ™ heterogeneous membrane.

C. Test 50-57
Tests 50 to 57 were performed with the piping configuration shown in FIG. 4E. This equipment was similar to that described in the previous test, with the following exceptions.
● A new electrode plate made of titanium mesh electrode plate was used, and it was manufactured in the salt water flow port.
● In the previous test, the salt water flow to the anode, cathode and central screen cell could not be controlled individually. In order to ensure that no cells were bypassed, for tests 50-57, the module was improved by controlling each of these brine streams individually.
● The screen weave in the salt water cell was designed to be diagonal rather than parallel and perpendicular to the fluid flow. This was done in an attempt to minimize vapor locks that were a concern on the screen.

II. Test Procedure Description For each experiment run, the feed tank was first filled with brine. The DI water flow was taken out and the water flow was adjusted using a rotameter needle valve. The main power was then turned on, thereby operating the pump. The flow rate and system back pressure were adjusted using various control valves. The DC power controller was activated and adjusted to the test amperage or voltage. The conductivity and temperature of the feed stream and each effluent were measured using Myron L Co. Measured and recorded using a ULTRAMETER 6P II conductivity meter commercially available from The system could be stabilized over several minutes. Stabilization was monitored using a conductivity meter. The amperage and voltage were recorded and samples of the feed stream, the product NaOH, and the product brine were taken. For some studies, multiple samples were taken over a period of time. The module was shut down by turning off the power and stopping the fresh DI water flow.

H ₂ and O ₂ gases are generated as bubbles in salt water. The explosion lower limit (LEL) of H ₂ is 4%. Fire and explosion hazards were mitigated by providing venting hood vents in the salt return pipe. For the hypothetical 40A full scale unit, it is estimated that 3 standard cubic feet per minute of air is sufficient to dilute H ₂ to less than 10% of LEL. LEL measurement results were not collected in this test operation.

For tests 3-13, feed samples and product samples were analyzed by HACH titration method # 8230. Using this titration, the contents of NaOH, Na ₂ CO ₃ and NAHCO ₃ were measured. Na ₂ SO ₄ concentration was measured by photometry using HACH method # 8051.

For tests 14-57, the pH was monitored using a Myron L Co ULTRAMETER. The contents of NaOH, Na ₂ CO ₃ and NAHCO ₃ were monitored by titration using a Metohm 785 DMP Titrino automatic titrator.

  At the end of test 57, the CEDI membrane was analyzed using an ISI ABT WB-6 scanning electron microscope.

III. Feed stream description The composition of the feed stream is based on the expected content of oxidized spent caustic.
● 55 g / L Na ₂ SO ₄
● 3.1 g / L Na ₂ CO ₃
● 35g / L NaHCO ₃

All chemicals were reagent grade compounds purchased from Sigma-Aldrich, St. Louis, MO. DI water was used as the solvent. Tests 11 and 12 used a higher titer feed stream prepared by doubling the salt dose and decanting the saturated supernatant from the mixing tank. Test 13 used a feed stream with a titer of 1/4. Tests 50 to 57 were performed using an 80 g / L Na ₂ CO ₃ solution.

  In most cases, the feed stream was recirculated through the CEDI module and returned to the feed tank. Therefore, the sodium concentration of the feed stream was not constant.

IV. Test Results Test conditions and results summary tables are shown in Tables 1 and 2 shown in FIGS. 5A and 5B, respectively. The duration of the test is the range of time it takes to record the parameters and take a sample, usually 1-5 minutes. The reported test time was recorded at the end of those steps.

  Current efficiency is the fraction of amperage utilized to transport sodium ions into the NaOH product stream. The current efficiency is calculated from Faraday's law using the following equation:

here,

Is the molar flow rate of sodium in the NaOH product stream (mol Na / sec), A is the current (ampere), F is the Faraday constant (96.485 coulomb / mol), and n ₂ is ₂ in CEDI. Is the number of type cells (in this case 2), Z _Na is the charge of the sodium ion, here +1.

  During some steps, power charts were recorded to monitor amperage as a function of voltage. These charts are shown in FIGS. The power chart was recorded during sustained operation at the following nominal conditions reported in Table 3.

Table 3

  At the end of the test work, the module was disassembled. One of the membranes was analyzed by SEM. The membrane separated salt water in the cathode cell from DI water in the resin bed cell.

V. Discussion of test results Efficacy of the CEDI process for the production of NaOH All tests revealed that the CEDI process can extract sodium ions from brine and produce a NaOH stream. The NaOH titer in the product stream ranged from 0.14 to 8 g / L NaOH. The product NaOH was somewhat contaminated by either or both of carbonate and sulfate. The purity of NaOH in the product stream was 30% to 100% purity. The source of contamination can be due to membrane leakage due to damage or porosity (see below).

Effect of increasing amperage Tests 3, 4 and 5 are the same tests performed under the same conditions with increasing current for each test. The Na recovery and Na concentration in the product stream increased with increasing current. The temperature of the effluent also increased. The current efficiency decreased with increasing current. When the current efficiency decreases, the power utilization efficiency deteriorates, and as a result, the temperature increases.

  The results are shown graphically in FIGS. 7A and 7B.

  During tests 14-57 operated at higher currents, it was observed that as the amperage increased, performance degradation occurred over time. This is illustrated in FIGS. 6A-6E which show the dynamic behavior of current at high voltage. FIG. 6C shows that when the unit is activated, the amperage initially increases with time. This is because NaOH is generated in the product cell, thereby increasing the conductivity and thus increasing the amperage at constant voltage. At around 13:50, the current reached a maximum value of 11 amps. After this, the current gradually decreased.

Next, the system produces H _2, becomes O ₂ and CO ₂ gas is gathered stationary air bubbles, which because is with reduced larger potential vapor lock or eliminate time, the flow and pressure for concern The cell Designed to be controlled individually. Also, sodium carbonate was replaced as a feed stream to reduce or eliminate the production of CO ₂ gas due to Na ⁺ removal. A loss of current over time was observed. The large current may have affected the DI side of the film surface.

Effect of Caustic Flow Rate Tests 11 and 12 were conducted with similar feed flow and amperage. In these tests, the NaOH product stream was recycled through a Type 2 cell. The product NaOH exited the system with a small purge stream and was replenished with DI water (ie feed and discharge). Thus, the flow rate of the flow across the cell was maintained, but the total residence time was extended to produce a smaller flow with a higher titer product.

In Test 12, the product release rate was increased, thus reducing the residence time of the caustic stream. In other respects, these tests were identical. As the residence time was reduced, the titer of the NaOH product stream decreased, but the Na recovery was four times higher than in Test 11 and the current efficiency was also increased. These results suggest that increasing the residence time of the caustic stream may increase the product titer, but may decrease total Na recovery and electrical efficiency. This appears to be due to the high osmotic pressure of the caustic flow resisting the transport of more Na ⁺ ions, but could be overcome by using high currents.

Effect of salt water concentration Test 13 was carried out under the same conditions as 12, but the potency of the supplied salt water was low. Test 13 was performed with careful adjustment of the differential pressure between the cells to minimize leakage between the cells. Test 13 was conducted at a lower product release rate from the Type 2 cell, in which case a decrease in current efficiency and sodium recovery was expected prior to performing this test. Surprisingly, it has been found that this test improves the current efficiency and increases the Na recovery rate compared to Test 12. It appears that sodium recovery is increased when using low-potency feed brine.

Resin Effect Test 7 was performed under the same conditions as Test 4. In Test 4, a resin-filled supply cell was provided at the center of CEDI. In Test 7, the central cell was filled with a screen. The feed stream for Test 7 was a higher titer feed stream that would also affect the results and made it difficult to study. This is because the two parameters are different. However, based on the analysis in Test 13, it was expected that the current efficiency would decrease when the supplied salt water titer increased. However, comparing Test 7 with Test 4, the current efficiency was surprisingly almost The same. This suggests that replacing the resin with a screen does not reduce the efficiency of the process. All subsequent tests were conducted using a screen in a salt water cell.

Membrane Discussion During tests 14-16, homogeneous membranes were used. In these tests, the product was most contaminated. It is not clear whether this was due to porosity / diffusivity or whether the membrane was lacerated.

Effect of increasing saline flow rate Tests 8 and 12 were similar tests. Test 8 was performed at a higher salt water flow rate and caustic flow rate than Test 12. The current efficiency of Test 8 was higher than Test 12, and the potency of the caustic product was similar. These results may indicate that efficiency increases as the brine flow rate increases.

Exhaust Gas Discussion According to this process, exhaust gas was generated in the brine recirculation pipe. The exhaust gas production rate and composition were not measured. According to visual inspection, a considerable gas flow was present in the return pipe, which increased the amperage. This gas mainly contained hydrogen and oxygen generated at the electrode. CO ₂ gas was also generated in tests where the feed stream contained NaHCO ₃ but no Na ₂ CO ₃ .

Scanning Electron Microscopy (SEM) Results A number of different cell packs were tested in this evaluation. After completion of the last test, the last cell pack was cut open and the membrane sample was stored. The cation membrane that isolates the cation cell from the DI water cell was dried, sputtered with gold, and placed in the SEM for analysis. Each side of the membrane was analyzed and the results are shown in FIGS. 7A and 7B. The salt water side image shows how the resin particles suspended in the polyethylene sheet matrix look. Although the cavity is larger than the resin, it is expected because the particles shrunk during the drying process required in sample preparation for SEM. The DI water side image shows the same, but the sheet matrix is different and appears to be possibly damaging.

DI water considerations Over tests 17-57, it was observed that the adjustment of DI water was effective. When the flow rate of DI water was increased under constant conditions, the current decreased (FIG. 6B). Similarly, increasing the relative pressure of DI water resulted in a decrease in current. In this context, in some cases, it was observed that increasing the salt water pressure or flow rate increased the current (FIG. 6E). Decrease in current, in solution and in the resin bed H ⁺ ions and OH ^- may be the result of causing a ion water decomposition reaction. This can increase the conductivity, but increasing the DI water flow rate will wash away these ions and lower the conductivity. Alternatively, in connection with water splitting, ions from salt water and caustic cells can leak through the membrane and into the DI water cell, thereby increasing conductivity. Similarly, increasing the DI water flow rate may wash out these ions faster. Increasing the relative pressure of DI water generally reduces the leak rate. However, leaks cannot be easily detected because the contaminating ions are removed by the CEDI process by the time DI water is released.

VI. Results The effectiveness of CEDI for recovering Na ⁺ as NaOH from oxidized spent caustic was demonstrated. By utilizing recirculation, it is possible to achieve higher recoveries such as 10% Na. Large amperages may be required to produce high potency caustic at the desired flow rate.

Prophetic Example FIG. 2 shows a predicted plant flow diagram (PFD) for an ethylene plant. Table 4 shows the mass balance for a plant in which about 10% of Na is recycled. In this example, the product NaOH from the CEDI unit is about 1.8 weight percent NaOH at a flow rate of about 55% of the total spent caustic stream. Figures 8A-8D show the balance of several different configurations. FIG. 9 illustrates the potency of NaOH in a CEDI product stream that meets mass balance requirements, which can be based, for example, on a similar balance.

Table 4. Sodium balance of ethylene plant with 10% NaOH tower feed and 10% Na recovery.

  Thus, while several aspects of at least one embodiment have been described, it will be appreciated that various changes, modifications and improvements will occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be included within the scope of the present invention. Accordingly, the foregoing description and drawings are for illustrative purposes only, and the scope of the present invention should be determined by proper interpretation of the appended claims and their equivalents.

100 Treatment System 110 Oxidation Unit 120 Desalination Unit 130 Industrial Application Equipment 140 Reactant Source

Claims (42)

An oxidation unit fluidly connected to a source of aqueous feed;
A desalting unit fluidly connected downstream of the oxidation unit and configured and arranged to convert the product of the oxidation unit into a target compound,
A system for processing aqueous feeds.   The system of claim 1, wherein the aqueous feed comprises at least one sodium-based compound.   The system of claim 1, wherein the aqueous feed comprises at least one organic compound.   The system of claim 1, wherein the aqueous feed comprises at least one sulfide.   The system of claim 2, wherein the product of the oxidation unit comprises at least one of sodium carbonate and sodium sulfate.   The system of claim 1, wherein the oxidation unit comprises a liquid phase oxidation unit.   The system of claim 6, wherein the oxidation unit comprises a wet air oxidation unit.   The system of claim 6, wherein the liquid phase oxidation unit comprises a supercritical water oxidation unit.   The system of claim 6, wherein the oxidation unit comprises a catalytic oxidation unit.   The system of claim 1, wherein the oxidation unit comprises a peroxide, permanganate, ultraviolet or visible light oxidation unit.   The system of claim 1, wherein the desalting unit comprises at least one ion exchange resin bed.   The system of claim 1, wherein the desalting unit comprises an electrochemical deionization unit.   13. The electrochemical deionization unit according to claim 12, wherein the electrochemical deionization unit is an electrodialysis, reverse electrodialysis, capacitive deionization, electrodeionization, continuous electrodeionization or reverse continuous electrodeionization unit. system.   The system of claim 13, wherein the electrochemical deionization unit is a continuous electrodeionization unit.   The system of claim 1, wherein the target compound is caustic.   The system of claim 15, wherein the caustic comprises sodium hydroxide.   The system of claim 15, wherein the caustic comprises ammonium sulfate.   The system of claim 15, wherein the caustic is not present in the oxidation unit product.   The system of claim 1, further comprising a concentrator fluidly connected downstream of the desalting unit.   The system of claim 1, wherein the source of the aqueous feed is an industrial operator.   21. The system of claim 20, wherein the source of the aqueous feed is an ethylene production facility.   21. The system of claim 20, wherein an outlet of the deionization unit is fluidly connected to the industrial operation site.   The system of claim 1, further comprising a controller in communication with at least one of the oxidation unit and the desalination unit.   24. The system of claim 23, further comprising a sensor configured to detect a characteristic of a desalted effluent stream and in communication with the controller.   25. The system of claim 24, wherein the controller is configured and arranged to adjust process conditions of one or more of the units in response to detection characteristics of the desalted effluent stream. .   The system of claim 1, further comprising a purification unit fluidly connected downstream of the desalting unit.   27. The system of claim 26, wherein the purification unit comprises a biological processing unit.   The system of claim 14, wherein the continuous electrical deionization device comprises at least one homogeneous membrane.   The system according to claim 7, wherein the desalting unit comprises a continuous electric deionization unit.   30. The system of claim 29, wherein the target compound comprises sodium hydroxide. An oxidation unit fluidly connected to a source of aqueous feed;
An electrochemical deionization unit fluidly connected downstream of the oxidation unit and configured and arranged to produce fresh caustic.
A system for treating an aqueous feed containing spent caustic.   32. The system of claim 31, wherein the oxidation unit comprises a wet air oxidation unit.   32. The system of claim 31, wherein the electrochemical deionization unit comprises a continuous electrodeionization device.   34. The system of claim 33, wherein the system is configured to recycle an effluent stream to the electrochemical deionization unit.   32. The system of claim 31, wherein the fresh caustic comprises sodium hydroxide.   32. The system of claim 31, wherein the source of the aqueous feed is an ethylene production facility. Oxidizing the aqueous stream to produce an oxidation product;
Converting the oxidation product to produce a caustic stream,
A method for treating an aqueous stream.   38. The method of claim 37, wherein the caustic stream comprises sodium hydroxide.   40. The method of claim 38, further comprising supplying the caustic stream to an industrial operation.   38. The method of claim 37, wherein oxidizing the aqueous stream comprises oxidizing the aqueous stream at a temperature of about 150 ° C or higher.   38. The method of claim 37, wherein the conversion of the oxidation product comprises isolating a target ion from the oxidation product.   42. The method of claim 41, wherein the conversion of the oxidation product further comprises associating the isolated target ions with a regeneration fluid to produce the caustic stream.

Images