KR20090094041A - Systems and methods for process stream treatment - Google Patents

Abstract

Systems and methods for process stream treatment. The treatment system may generally include an oxidation unit coupled to a downstream demineralization unit. The oxidation unit may oxidize organic and reduced sulfur contaminants in the process stream to facilitate downstream treatment. The demineralization unit may convert a product of the oxidation unit to generate a mineral stream. In some examples, the process stream may be a spent caustic stream from an industrial operation, such as an ethylene production facility or a petroleum refinery. A fresh caustic stream, such as a sodium hydroxide stream, may be isolated in the demineralization step and returned to the industrial operation for use.

Description

System and method for process stream processing {SYSTEMS AND METHODS FOR PROCESS STREAM TREATMENT}

The present invention relates generally to process stream treatment, 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 destroy contaminants in wastewater. Wet oxidation means the aqueous phase oxidation of components that are not desired by, for example, molecular oxygen from an oxidant, generally an oxygen-containing gas, at elevated temperatures and pressures. This process can convert organic pollutants into carbon dioxide, water and biodegradable short chain organic acids such as acetic acid. In addition, inorganic components including sulfides and mercaptide can be oxidized; Cyanide can be hydrolyzed. As an alternative to incineration, wet oxidation can be used in a wide range of fields to process and then discharge process streams.

Various ion recovery methods are also generally known. One technique is already a continuous electrodeionization (CEDI) system which is used almost exclusively for the production of ultrapure water from substantially deionized streams. The CEDI feed is typically a reverse osmosis stream. CEDI feeds and product streams have low conductivity, so that the cells are usually filled with resin to increase the conductivity of the matrix. The cells are arranged in alternating pairs, each pair generally producing one ultrapure water stream and one half brine reject stream. The capacity of the CEDI module is determined by how many cell pairs are included between the electrodes at the module end. Typically, approximately 30 to 120 cell pairs are used per module for commercial scale applications. The housing of the CEDI module is arranged with a piping structure for collecting the product water in one stream and the ionic discharge stream in the other stream. Commercial applications typically range up to 10 amps.

summary

Aspects of the present invention generally relate to systems and methods for process stream processing.

In accordance with one or more aspects, a system for treating an aqueous feed is provided in an oxidation unit fluidly connected to a source of aqueous feed, and in fluid communication downstream of the oxidation unit and converting the product of the oxidation unit to a target compound. And a desalting unit configured and arranged to be.

In accordance with one or more embodiments, a system for treating an aqueous feed containing a caustic material used is an oxidation unit in fluid communication with a source of aqueous feed, and a new caustic material in fluid communication downstream of the oxidation unit. and an electrochemical deionization unit constructed and arranged to produce a fresh caustic.

In one or more embodiments, a method of treating an aqueous stream includes oxidizing the aqueous stream to produce an oxidation product, and converting the oxidation product to produce a corrosive stream.

Still other aspects, embodiments, and advantages of such exemplary embodiments and embodiments are described in detail below. Moreover, it is to be understood that both the above information and the following detailed description are intended primarily to provide an overview or configuration for understanding the nature and features of the claimed aspects and embodiments, as illustrative examples of various aspects and embodiments. The accompanying drawings are included in and constitute a part of this specification as being included to provide illustrations and further understanding of various aspects and embodiments. The drawings, together with the remainder of the specification, are provided to illustrate the principles and processes of the described and claimed aspects and embodiments.

Brief description of the drawings

Various aspects of one or more embodiments are described below with reference to the accompanying drawings. In the drawings, which are not drawn to the original specification, each identical or nearly identical component that is illustrated in various figures is represented by the same numeral. For purposes of clarity, not all parts may be labeled in every drawing. These drawings are provided for purposes of illustration and description, and are not intended as a definition of the limits of the invention.

1 illustrates a processing system according to one or more embodiments.

2 illustrates a corrosive stream treatment system according to one or more embodiments.

3 illustrates a process of a continuous electrodeionization unit in accordance with one or more embodiments.

4A-4E illustrate various system piping arrangements as described in the embodiments.

5A and 5B show tables summarizing test conditions and results as described in the Examples.

6A-6E illustrate CEDI module power charts as described in the embodiments.

7A and 7B show data related to the effect of current as described in the Examples.

8A-8D show mass balances for several different system arrangements in accordance with one or more embodiments.

9 illustrates the determined strength of NaOH in a CEDI product stream that is essential to satisfy material balance needs in accordance with one or more embodiments.

details

One or more embodiments generally relate to the treatment of a process stream. Such systems and methods can generally be effective for treating a process stream contaminated with one or more easily oxidizable compounds. The systems and methods described herein can be practiced in a wide range of applications where it may be desirable to desalting process streams to facilitate downstream processes and / or to produce products such as mineral streams. Advantageously, some embodiments may be particularly useful in reducing the amount of new, newly obtained or constituent reactants required to be supplied for upstream industrial applications. For example, certain embodiments provide new corrosive streams such as sodium hydroxide streams of sufficient strength and quality to process the corrosive feed used and provide it back to an upstream ethylene production facility or crude refinery for use as a reactant. Can be formed. In addition, the present systems and methods may also be useful for producing system effluents with adjusted pH levels relative to the pH of the initial process stream such that, for example, less pH correction is required by chemical addition to neutralize before discharge. . In addition, embodiments can effectively use devices such as both oxidation and desalination units, which are recognized in that synergism between them provides substantial benefits for both device suppliers and end users.

Embodiments of the systems and methods described herein are not limited in their application to the details of construction and arrangement of components described in the detailed description or illustrated in the accompanying drawings. The present systems and methods may perform other embodiments and may be practiced or carried out in various ways. Examples of particular implementations are provided herein for illustrative purposes only and not by way of limitation. In particular, the actions, elements and characteristics described in connection with any one or more embodiments will not be excluded from a similar role in any other embodiments. Also, the phraseology and terminology used herein is for the purpose of description and not of limitation. The use of “comprising”, “having”, “comprising”, “associated with” and variations thereof herein means including the items described after the expression and their equivalents as well as additional items.

According to one or more embodiments, the system may be in fluid communication with a source of process streams to be treated. The process stream may generally be any process stream that can be delivered to a 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 stream may be moved through the system by operation 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, may take the form of direct piping directly from a plant or intermediate holding vessel. After treatment, the process stream can be provided back to the upstream process or discharged from the system as waste.

In a typical process, the described system can accept process streams from local, industrial or residential sources. In some embodiments, the process stream may be from, for example, a food processing plant, a chemical processing facility, a gasification project, or a pulp and paper plant. In at least one embodiment, the process stream may be a process generally associated with polyolefins, such as an ethylene plant process, or an aqueous feed from crude oil refining. For example, the aqueous feed can be the caustic feed used in some embodiments.

According to one or more embodiments, the process stream may contain dissolved solids, for example minerals. In some embodiments, minerals may be valuable as product streams where they can be separated or converted, as described in more detail below. In other embodiments, minerals may be considered contaminants that render the process stream unsatisfactory for handling, processing or disposal. Accordingly, it may be desirable to desalting the process stream to extract the product and / or to facilitate downstream processing. Several other components may be present in the process stream, including, for example, only chloride, sodium hydroxide, sodium carbonate, total organic carbon (TOC), and iron.

According to one or more embodiments, the process stream may contain one or more target ions. Separation and conversion of target ions may be desired as described herein. For example, target ions in the process stream can be manipulated by the system to produce a valuable or otherwise desired product stream. In some embodiments, target ions may be present in the process stream as reactant byproducts due to upstream consumption of the consumable reactants. In some embodiments, the system can separate target ions and use them to generate or generate target compounds. Thus, the target ions present in the process stream can be precursors of the target compound. For example, the resulting target compound may be the original consumable reactant that generates target ions in the process stream upstream of the system. The target compound can then be supplied upstream of the system for reuse. In some embodiments, the target compound can be a caustic compound, such as sodium hydroxide or ammonium sulfate. The present systems and methods are generally capable of forming product streams containing target compounds. In at least one embodiment, the process stream may be an industrial caustic tower, or a corrosive stream used from a MEROX® type treatment process, for example a corrosive stream used in a crude refinery or ethylene production plant. The corrosive streams used may typically contain one or more reaction byproducts due to the consumption of fresh corrosive materials in the caustic tower. According to one or more embodiments, the reaction byproduct may generally comprise target ions. For example, sodium sulfide as a reaction byproduct can include targeted sodium ions under consideration. The target ions can then be converted by the system to produce the target compound. For example, sodium target ions can be converted to produce the sodium hydroxide target compound. The system can produce a product stream containing sodium hydroxide in solution. The used corrosive stream to be treated may also include other compounds, including any residual fresh corrosive material. It may be desirable to produce fresh corrosive streams from the corrosive streams used for delivery back to the caustic tower.

According to one or more embodiments, the process stream to be treated typically contains at least one undesired component. Undesired components may be any targeted material or compound that is removed from the aqueous mixture for public health, process design, and / or aesthetic considerations. For example, undesired ingredients can be toxic. In some embodiments, undesired components can interfere with downstream processes, eg, membranes of downstream separation or ion recovery units. For example, undesired components may be characterized as causing high chemical oxygen demand (COD) levels of the process stream which may generally have negative consequences. In at least one embodiment, the undesirable components of the process stream can generally be oxidized. In some embodiments, the undesirable component that can be oxidized is an organic compound. Special inorganic components such as sulfides, mercaptide and cyanide 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 can be present as S at a concentration of at least about 25,000 ppm or less.

According to one or more embodiments of the present invention, the processing system may comprise a first processing unit. In some embodiments, the first processing unit may generally affect the process stream to facilitate further processing thereof. For example, the first processing unit may be effective at cleaving one or more specific chemical bonds in an undesirable component or degradation product (s) thereof. According to one or more embodiments, the first treatment unit may generally treat oxidizable contaminants, such as contributing to COD, which may interfere with the efficiency, longevity and / or validity of downstream treatments, such as desalination steps. Thus, the first processing unit can reduce the concentration of one or more undesired components or change their properties, for example by changing or stabilizing the COD. For example, the first processing unit can destroy or remove organics and reduce sulfur contaminants. In some embodiments, the first processing unit may also have one or more target ions in different or preferred forms for downstream extraction, as generally described herein. In at least one embodiment, the first treatment unit may be included as a pretreatment step prior to the desalting step as generally described in more detail below.

According to one or more embodiments, the first processing unit or step may be an oxidation unit. Oxidation reactions are one destruction technique that can convert oxidizable organic contaminants to carbon dioxide, water and biodegradable short chain organics such as acetic acid. One aspect of the invention relates to systems and methods for the oxidative treatment of aqueous mixtures containing one or more undesirable components. The oxidation unit can oxidize sulfides to form non-toxic sulfate ions and also oxidize other species present in the process stream, such as the corrosive streams used. Mercaptans can be substantially nontoxic and COD contaminants can be converted to stable compounds that cause less harm to downstream processes. Since oxidation may not be achieved 100%, some undesirable components may still be present in the oxidation product of the oxidation unit. Residual target compounds may also be present in the oxidation product, such as sodium hydroxide and sodium carbonate. In some non-limiting embodiments, conventional oxidation products can include sodium carbonate and sodium sulfate. Mineralized products can be formed, for example sulfate and carbonate ions. In at least some embodiments, at least one salt of the target ion, eg sodium, may be produced by an oxidation process. For example, sodium can form salt complexes with oxidized ions. Accordingly, the oxidation product may comprise target ions, such as sodium, which exist in a different form than in the original process stream. For example, in some embodiments, sodium may generally be present as sodium sulfide upstream of the oxidation unit, but may be released as sodium sulfate and / or sodium carbonate in the oxidation unit.

According to one or more embodiments, any oxidant may be used in the oxidation unit. For example, any oxygen source can be used, such as oxygen gas, ozone, peroxide and permanganate, or combinations thereof. Likewise, any oxidation technique or engineering, or combination thereof may be used. For example, in some embodiments, photooxidation techniques may be used in which the conversion of the reduced molecule to the oxidized form in the presence of oxygen is generally performed by a set of chemical reactions initiated by photolysis. In at least one embodiment, for example UV or visible light can 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, eg, wet air oxidation, wet peroxide oxidation or supercritical oxidation unit.

In one embodiment, an aqueous mixture or process stream, for example comprising at least one undesired component, is wet oxidized. The aqueous mixture is oxidized with an oxidant for a period of time sufficient to process at least one undesired component at elevated temperature and ultrahigh pressure. Non-limiting embodiments include process temperatures above about 150 ° C. More specifically, the process temperature may exceed about 200 ° C. In some embodiments, the process temperature can exceed about 250 ° C. Likewise, the duration or residence time can be changed. In some embodiments, the residence time can be varied from about 30 minutes to 10 hours. Some non-limiting embodiments include a residence time of about 1 hour, but shorter or longer residence times may be used depending on the conditions of the intended application. Oxidation reactions can substantially destroy the intact state of one or more chemical bonds in an undesirable component. As used herein, the phrase "destructively destroying" is defined as at least about 95% destruction. The process of the present invention can generally be applied to the treatment of any undesirable components that can be oxidized.

The wet oxidation process described can be carried out in any known batch or continuous wet oxidation unit suitable for oxidizing the compound. Typically, aqueous phase oxidation is carried out in a continuous flow wet oxidation system. Any oxidant can be used. The oxidant is usually an oxygen-containing gas such as air, oxygen-rich air, or essentially pure oxygen. As used herein, the phrase "oxygen-rich air" is defined as air having an oxygen content of at least 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 that pressurizes the aqueous mixture. The aqueous mixture is mixed in the conduit with the pressurized oxygen-containing gas provided by the pressurizer. The aqueous mixture flows through a heat exchanger, where it is heated to a temperature capable of initiating oxidation. The heated feed mixture then enters the reaction vessel at the inlet. The wet oxidation reaction is generally exothermic and the heat of reaction produced in the reactor can further raise the temperature of the mixture to the desired value. Most oxidation reactions occur in reaction vessels that provide sufficient residence time to achieve the desired degree of oxidation. The oxidized aqueous mixture and the oxygen deficient gas mixture are then passed to a heat exchanger in the reactor. The hot oxidized effluent passes through a heat exchanger, where it is cooled against the incoming raw aqueous mixture and gas mixture. The cooled effluent mixture flows through a conduit controlled by a pressure control valve to a separate vessel where liquid and gas are separated. The liquid effluent exits the separator vessel through the lower conduit and off gas is exhausted through the upper conduit. Treatment of off-gas may be required in the downstream off-gas treatment unit depending on its composition and requirements for discharge to the atmosphere. The wet oxidized effluent may typically be discharged to a treatment plant, such as a biological or chemical treatment plant, for polishing before discharge. The effluent can also be recycled for further processing by the wet oxidation system. According to one or more embodiments of the present invention, the effluent may also proceed to a second unit process, such as a desalination or ion recovery unit, as described in more detail herein.

Sufficient oxygen-containing gas is typically supplied to the system to maintain residual oxygen in the wet oxidation system off-gas, and ultrahigh pressure gas pressure is usually sufficient to maintain the water in the liquid phase at the selected oxidation temperature. For example, the minimum system pressure at about 240 ° C. is about 33 atmospheric pressure, the minimum pressure at about 280 ° C. is about 64 atmospheric pressure, and the minimum pressure at 373 ° C. is about 215 atmospheric pressure. In one embodiment, the aqueous mixture is oxidized at a pressure of about 30 atmospheres to about 275 atmospheres. The wet oxidation process may be operated at elevated temperatures below about 374 ° C., the critical temperature of water. In some embodiments, the wet oxidation process can be operated at supercritical elevated temperatures. The residence time for the aqueous mixture in the reaction chamber should generally be sufficient to achieve the desired degree of oxidation. In some embodiments, the residence time is greater than about 1 hour and up to about 8 hours. In at least one embodiment, the residence time is from about 15 minutes to about 6 hours. In one embodiment, the aqueous mixture is oxidized for about 15 minutes to about 4 hours. In another embodiment, the aqueous mixture is oxidized for about 30 minutes to about 3 hours.

According to one embodiment, the wet oxidation process may be a catalytic wet oxidation process. The oxidation reaction in the oxidation unit can generally be mediated by a catalyst. Aqueous mixtures containing at least one undesired component to be treated are generally contacted with catalyst and oxidant at elevated temperatures and ultrahigh pressures. An effective amount of catalyst may generally be sufficient to improve the overall destruction removal efficiency of the system, including increasing the reaction rate and / or improving the reduction of COD and / or TOC. Catalysts may also be provided to lower the overall energy requirements of the wet oxidation system. Catalytic wet oxidation has been shown to enhance efficiently over conventional noncatalytic wet oxidation. Catalytic wet oxidation processes generally allow more destruction to be achieved at low temperatures and pressures, thus lowering capital costs. The aqueous stream to be treated is mixed with the oxidant and contacted with the catalyst at elevated temperature and pressure. Heterogeneous catalysts are typically present in the form of solid particulates which are combined with the aqueous mixture prior to oxidation or on the layer through which the aqueous mixture passes. The catalyst can be filtered from the oxidative effluent downstream of the wet oxidation unit for reuse.

In at least one embodiment, the catalyst may be any transition metal of groups V, VI, VII and VIII of the periodic table. In one embodiment, for example, the catalyst can be V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, or alloys or mixtures thereof. The transition metal may be an element or present in a compound such as a metal salt. In one embodiment, the transition metal catalyst is vanadium. In another embodiment, the transition metal catalyst is iron. In 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 the aqueous mixture. In one embodiment, the catalyst can be added to a source of an aqueous mixture fed to the wet oxidation unit, where the catalyst source is in fluid communication with the storage tank. In some embodiments, the catalyst can be added directly to the wet oxidation unit. In other embodiments, the catalyst may also be fed to the aqueous mixture prior to heating and / or pressurization.

The first processing unit, for example the oxidation unit, can generally produce a product stream, for example an oxidation product stream. The oxidation unit can thus convert the process stream into an oxidation product stream. The oxidation product stream may generally be suitable for further processing, such as in ion recovery or desalination units as described herein. The oxidation product may be substantially free of components that are generally not desired. The oxidation product may also contain one or more target ions from the original process stream that may be subjected to the further manipulations described herein to produce the desired product.

According to one or more embodiments, the second processing unit may be in fluid communication downstream of the first processing unit. The second treatment unit may be arranged to receive the oxidation product or oxidation product stream for further treatment. In some embodiments, the second processing unit may generally convert the oxidation product of the first processing unit to produce a target compound or target stream. The target compound may generally be separated by a system for extraction and may have value as a product stream or its removal may facilitate downstream processes. In some embodiments, the second processing unit may generally desalting the oxidation product stream to facilitate downstream processing and / or produce a product stream rich in minerals of value. The second processing unit may generally be associated with any technique that can extract ions to produce ion-rich product streams as well as streams with reduced mineral content. For example, the second processing unit may be effective for carrying out ion recovery of the compound, including sodium, potassium, calcium, carbonate, and sulfate.

According to one or more embodiments, the desalting unit may comprise, for example, at least one ion exchange resin layer. Ion exchange may generally involve the exchange of ions between a solution and a solid, typically a resin, for desalting. More specifically, ion exchange can include the reversible exchange of ions adsorbed onto a mineral or synthetic polymer surface with ions in solution in contact with the surface. Target ions can be removed and replaced with other ions, for example hydrogen ions. The target ions are then recovered from the exchange bed by periodically passing water or other regeneration fluid through the bed to continue supplying new hydrogen ions to the resin and to generate wash water containing the target compound, such as a sodium hydroxide stream.

For example, the cationic monomer can be polymerized in the structure of the anion exchange resin or vice versa to result in a polyvalent electrolyte structure. When regenerated, this structure has a cationic group in hydrogen form and may have an anionic group of a hydroxyl group. The introduction of electrolytes will replace hydrogen and hydroxyl ions resulting in their neutralization and will saturate the resin with ionic species. Regeneration with water may hydrolyze the resin groups while the target ions are released and recovered. Lime solutions can also be used to regenerate the layer to produce a target compound, such as sodium hydroxide.

According to one or more embodiments, concentration or separation processes may also be used to achieve ion recovery or desalination. Distillation generally includes evaporation and subsequent condensation, for example, to collect steam. Crystallization and filtration processes such as nanofiltration may also be carried out. A reverse osmosis process can likewise be used, including a filtration process to remove dissolved salts and metallic ions from water where the pressure applied on the concentrated side is pressurized through the semipermeable membrane.

According to one or more embodiments, examples of desalination or ion removal techniques can include electrochemical processes such as electrodialysis, electrodeionization, capacitive deionization and continuous electrodeionization (CEDI). According to one or more embodiments, the desalination unit may comprise capacitive deionization based on electrostatic processes that generally operate at low voltages and pressures. The resulting water is pumped through the electrode assembly. Underwater ions are attracted to the electrode of opposite charge. This reduces the concentration of ions in water while concentrating the ions at the electrode. Clean water then passes through the unit. When the capacity of the electrode is reached, the water flow stops and the polarity of the electrode changes. This moves ions away from previously accumulated electrodes. The concentrated brine solution is then purged from the unit.

In one or more embodiments, a continuous electrodeionization (CEDI) process can be performed. CEDI generally uses a combination of ion exchange resins and membranes and direct current to de-ionize water continuously without the need for chemicals. CEDI is an electrochemical process in which electrical charge is applied across a module. Electrodes of electrochemical devices can generally be made of various materials, such as stainless steel, iridium oxide, ruthenium oxide, and platinum. The electrode can also be coated with various materials, for example titanium. The electrode produces H ⁺ and OH ⁻ ions. Ions are moved by the potential across the device, along with the ions in the feed. The modules are arranged in cells separated by membranes. The cell depth is about 0.1 inches. The membrane can only pass anions or cations. In this way, ionic species are enriched in some cells and deficient in ions in other cells. The flow of ions is directly related to the electrical current applied to the module. Electrons do not flow across the cell. The electrons form ions and the ions flow across the CEDI module.

The process is typically dependent on the use of cells separated by ionic membranes. The conductivity of pure water is very low, so the voltage required to transport ions through pure water is very high. Resins are used to increase conductivity in water cells, which reduces voltage requirements. The resin is about 0.3 to about 0.5 mm spheres. The surface of the resin has an ionic charge which is cationic (c) or anionic (a). Cationic resins have anionic functional groups, which attract cationic species (ie cationic resins are so called because they attract cations). In this way, cations can flow across the cell by moving in the cationic resin. Similarly, anionic resins can migrate anions. In application, numerous layers are mixed with both anionic and cationic resins, which can transport both types of ions across the cell.

The membrane is also made of cationic or anionic material. IonPure ™ (Siemens company) membranes are made by mixing the resin with polyethylene and extruding it into sheets. This is called a heterogeneous structure. Polyethylene provides mechanical strength and resins provide transfer properties. Cationic membranes can pass only cations, and anionic membranes can pass only anions.

When wetted, the resins and membranes can expand. The expansion can cause the resin to exert a force of up to about 100 psi on the walls and membrane. The resin material in the membrane also expands and permanently deforms the structure of the heterogeneous membrane. In clean water application, IonPure ™ membrane nominal leakage (leakage nominal rate) is about ^{20 mL / hr / ft 2/} 5 psi. Sodium ions cause less expansion than hydronium ions. Therefore, in high strength saline, the resin of the dissimilar membrane will shrink, making the resin more porous. Homogeneous membranes are made of resin only, thus allowing higher current flux. They are more expensive than heterogeneous membranes but otherwise replaceable.

The bipolar membrane is an anionic membrane on one side and a cationic membrane on the other side. These are the most expensive type of membranes and are used for water decomposition. Such membranes may be used in place of water decomposition cells. They are dependent on water diffusion into the membrane and may not be suitable for high speed production.

The power supply provides a DC current through the electrodes of the device. The electrodes are the outermost cell on the opposite side of the module. The electrode cell contains no resin but instead uses high strength saline to provide the cell's conductivity. The plastic screen is placed in the cell to protect the membrane from contact of the electrodes.

The cathode (-) is typically made of stainless steel, but other anode materials may also be used. Electrons flow through these electrodes from the power supply. In the cathode cell, this forms hydroxide ions and hydrogen gas.

Sodium reduction (plating) to metallic sodium is an alternative route for consuming electrons. However, this does not occur because the potential requirement for sodium plating is higher than the potential required for H ₂ (g) formation. The production rate of hydrogen is calculated from Faraday's Law, which is as follows:

Where Is the molar generation rate of the hydrogen gas (mol H ₂ / sec), A is the current (Amp) and F is the Faraday constant (96,485 coulombic / mole).

The anode (+) is titanium coated with a corrosion resistant conductor. The conductor is typically platinum, iridium oxide, or ruthenium oxide. Iridium oxide is commonly used as a coating in Siemens C-Series modules. For higher current applications, platinum may be a better material. Electrons are provided from the water in the cell and returned to the power supply. This forms oxygen gas.

The production rate of oxygen is calculated from the following equation.

Where Is the molar generation rate of hydrogen gas (molar O ₂ / sec), A is the current (Amp), and F is the Faraday constant (96,485 coulombic / mole).

Referring to FIG. 1, the operation of the processing system 100 may include a process stream directed from the industrial application 130 to the oxidation unit 110. The oxidation product stream exiting the oxidation unit 110 may be directed to the desalination unit 120. Desalting unit 120 may produce a target compound stream, such as a sodium hydroxide stream. This stream may be directed back to industrial application 130 for another use. The target compound stream may be introduced directly into industrial application 130 or mixed upstream with fresh reactant from reactant source 140. The effluent stream may be recycled back to the desalination unit 120 for further processing and / or extraction of the target compound. Accordingly, lesser reactants need to be added to industrial application 130 due to the generation of reactants from the process stream by the system.

In one aspect, the caustic material used may be treated to recover the sodium hydroxide product stream. Ethylene plants or crude oil refining plants may use new corrosive materials such as sodium hydroxide to remove or clean acid gases such as carbon dioxide and hydrogen sulfide from the process gas. The fresh caustic can be about 50% NaOH in water and can typically be diluted to about 10% for use in caustic towers. About 8 tonnes of new corrosive material per hour can be consumed. The caustic tower can also condense organic species such as mercaptans, light hydrocarbons, acetaldehyde, and naphthalic acid and cresyl acid. As more acid is removed, the amount of free corrosive material is reduced until they are no longer useful. At this point, the plant will typically remove the caustic from the system, which is known as the corrosive material used.

Typical used corrosive streams contain sodium carbonate, sulfides and heavy organic compounds dissolved in solution. Typically streams containing sulfides, carbonates and organic acids in liquid phase may have a high pH. The stream may have a high content of dissolved solids, but is generally not suitable for many desalination processes because reactive sulfides and organic compounds are not compatible with desalination processes such as membrane materials of CEDI systems. The removal of cations such as sodium releases sulfides from the liquid, which is not desired in many cases because hydrogen sulfide is a very nasty and toxic corrosive gas.

The caustic liquid used is oxidized using WAO and then desalted using CEDI. Oxidation converts sulfides into harmless sulfates and organic compounds into carbonates and short-chain organic acids that are relatively stable and less destructive than desalination processes. The oxidized liquid is then passed through a CEDI process where some of the sodium is removed to produce a sodium hydroxide product stream. The residual stream is somewhat desalted by the removal of sodium ions, which also reduces the effluent pH.

One or more further unit processes may be connected in fluid communication downstream of the desalination unit. For example, the concentrator may be arranged to receive and concentrate the target product stream, for example, prior to delivery upstream to the industrial process for use. Polishing units, such as those comprising chemical or biological treatments, may also be present to treat the effluent stream of the system prior to discharge.

According to one or more embodiments, the described system can operate continuously or intermittently. In some embodiments, the wet oxidation system may include a controller for adjusting or adjusting one or more process parameters of the system or parts of the system, including but not limited to, for example, actuating valves and pumps. The controller may be in electrical communication with at least one sensor arranged to detect one or more process parameters of the system. The controller may generally be arranged to generate a control signal to adjust one or more process parameters in response to the signal generated by the sensor.

The controller is typically a microprocessor-based device, for example a programmable logic controller (PLC) or distributed control system, which accepts or provides input and output signals to and from parts of a wet oxidation system. The communication network may place any sensor or signal-generating device at a considerable distance from the controller or associated computer system, and may provide data between them. Such a communication mechanism may be accomplished by using any suitable technique, including but not limited to using a wireless protocol.

Process economics will include operator time, clean water, power for machinery and equipment, and power to provide the amount of current to the CEDI electrode. The electrical cost for operating the CEDI depends on the resistance and the extent of the membrane leak where sodium is returned to the brine cell. Economic benefit from operating CEDI can be in the production of valuable NaOH. In addition, in conventional WAO used caustic applications, neutralized acid must be purchased to neutralize the alkalinity of the oxidized used caustic. Since some alkalinity is removed from the CEDI, it is possible to further save neutral volcanic consumption.

The function and advantages of these and other embodiments will be more fully understood from the following examples. These examples are for illustrative purposes only and do not limit the scope of the embodiments described herein.

Example

Laboratory tests were performed using standard and modified versions of Siemens C-Series CEDI modules. The purpose of the evaluation is to determine the efficiency of the CEDI process for producing a NaOH product stream from the synthetic mixture of inorganic salts, determine the maximum strength of the NaOH product that can be produced with the intention of reaching up to 18 g / L NaOH, and determine the commercial NaOH To assess the economics of its application to the cost of This test was reported for three test times.

I. Experiment Design

A. Test 1 to Test 13

Tests 1 through 13 were performed on Siemens C-Series CEDI Modules. The parts are described below.

● Aluminum End Plates-Cathode End Plates

Cathode electrode made of iridium

Used to manufacture screens, cell type S

● cationic membrane

Cell type 1; It is a plastic frame filled with a 60/40 v / v mixture of cationic and anionic resins. The cross-sectional profile of the cell (perpendicular to the current flow) consists of three cells in parallel. 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

Cell type 2; It is also filled with a 60/40 v / v mixture of cationic resin (same frame is used, but switched to direct the flow to a different conduit system)

● cationic membrane

● S cell type

● cationic membrane

● Cell Type 1

● anionic membrane

● Cell Type 2

● cationic membrane

● S cell type

Anode electrode-made of iridium

Aluminum endplates-anode endplates.

Each cell has one of three feed conduit options and one of three discharge conduit options:

Cell type S has been conduited to supply brine and to drain treated brine. H ₂ , O ₂ , and CO ₂ gases are exhausted from this cell, and therefore these gases are also exhausted with this stream.

• Cell type 1 has a conduit formed to supply DI water and to drain the DI water.

Cell type 2 was formed with conduits to supply deionized water and to discharge NaOH product. In some cases, the feed for cell type 2 is recycled NaOH product instead of pure deionized water.

The symbol for indicating the cell arrangement is -S12S12S +. The symbol for the membrane arrangement is -caccac +. In some tests the polarity was reversed, in which case the module became + S21S21S-. A schematic diagram showing the operation of the module is shown in FIG. 3. Different piping arrangements were evaluated, respectively, as shown in FIGS. 4A-4C.

Power to the module was provided by the DC power supply and the power controller. The power controller regulated the amount of current to the module. The controller showed the voltage and current amount. Wired work was done by connecting the negative (black) wire to the cathode tab and the positive (red) wire to the anode tab. The electrical system can deliver up to 8 or 9 amps of power, in which case the circuit breaker will operate. The wire is 18 gauge and warmed to contact after some operation.

Feed flow rate was monitored by a flow meter, and effluent flow rate was monitored using a cylinder and stopwatch. pH, gas formation rate, and gas composition were not monitored. The gas formed was withdrawn to the feed tank with recycled brine and evacuated by placing a vent hose near the feed tank.

B. Test 14 to Test 17

The piping arrangement for this test is shown in FIG. 4D. This device is similar to that described in the previous test except for the following:

Stronger power supplies and electrical cables were used. This supply is connected to a 220 VAC 30A outlet. 8 gauge wires were used and these wires were kept cool by contact for all tests. Unlike the previous supply, it delivers a constant voltage and represents the amount of current obtained.

New electrodes with high current service. This electrode plate has a heavy titanium end tab and a platinum coated electrode.

One of the cells used a homogeneous membrane rather than the conventional IonPure ™ heterogeneous membrane.

C. Test 50 to Test 57

Tests 50-57 were performed with the tubing arrangement shown in FIG. 4E. The device was similar to that described in the previous test except for the following.

The new electrode plate was used as a titanium mesh electrode plate and built in a brine flow port.

In the previous test, the brine flow to the anode, cathode and central screen cell was not independently controlled. The module was modified for Test 50-57 by controlling each of these streams independently to avoid cell bypass.

The weave of the screen in the saline cell was arranged diagonally with respect to the fluid flow rather than parallel and vertical. This was done in an attempt to minimize vapor locking that is assumed on the screen.

II. Description of the exam process

For each experiment run, the feed tank was filled with brine. The deionized water flow was started and controlled using a flowmeter needle valve. The main power was turned on and the pump was turned on. Flow rate and system back pressure were adjusted using several control valves. Energy was supplied to the DC power controller and the test current amount or voltage was adjusted. The conductivity and temperature of the feed and each effluent were measured and recorded using a ULTRAMETER 6P II conductivity meter commercially available from Myron L Co. The system was stabilized for a few minutes. Stabilization was monitored using a conductivity meter. The amount of current and voltage were recorded and samples of the feed, product NaOH and product brine were collected. For some studies, several samples were collected over a period of time. The module was stopped by turning off the power and stopping the new deionized water flow.

H ₂ and O ₂ gases were generated as bubbles in brine. The explosion limit (LEL) for H ₂ was 4%. The brine recovery line was evacuated with a fume hood to eliminate the risk of flame and explosion. For a hypothetical 40 A total scale unit, 3 SCFM of air was estimated to be sufficient to dilute H ₂ to less than 10% of LEL. LEL measurements were not performed in this test.

For Trials 3 to 13, feed and product samples were analyzed by HACH titration # 8203. The titration was used to determine NaOH, Na ₂ CO ₃ and NaHCO ₃ contents. Na ₂ SO ₄ concentration was measured by photometry using HACH method # 8051.

For trials 14-57, pH was monitored using Myron L Co ULTRAMETER. NaOH, Na ₂ CO ₃ , and NaHCO ₃ contents were monitored by titration using a Metohm 785 DMP Titrino autotitrator.

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

III. Feed Description

The feed composition was based on the possible content of the used corrosive oxidized

● 55 g / L Na ₂ SO ₄

● 3.1 g / L Na ₂ CO ₃

● 35 g / L NaHCO ₃

All chemicals were reagent grade compounds purchased from Sigma-Aldrich (St. Louis, Missouri). Deionized water was used as the solvent. Trials 11 and 12 used feeds of higher strength than those described above, which were prepared by doubling the salt capacity and decanting saturated supernatant from the mixing tank. In test 13 a quarter strength feed was used. Tests 50-57 were performed using a solution of 80 g / L Na ₂ CO ₃ .

In most cases, the feed was recycled through the CEDI module and returned to the feed tank. As a result, the feed sodium concentration was not constant.

IV. Test result

A summary table of test conditions and results is shown in Tables 1 and 2 shown in FIGS. 5A and 5B, respectively. The test period ranged from the time it took to record the parameters and collect the samples, usually 1 to 5 minutes. Daily recorded test time was recorded at the end of this step.

Current efficiency is the ratio of the amount of current used to transfer sodium ions to the product NaOH stream. Current efficiency is calculated from Faraday's law using the following equation:

Where Is the molar flow rate of sodium in the product NaOH stream (molar Na / sec); A is current Amp; F is a Faraday constant (96,485 coulombs / mole); n ₂ is the number of type 2 cells in CEDI (in this case two); Z _Na is the charge of sodium ions that is +1.

During some processes, power charts were recorded to monitor the amount of current as a function of voltage. Such charts are shown in FIGS. 6A-6E. The power chart is recorded during the ongoing process under the following nominal conditions as reported in Table 3 below.

At the end of the test, the module was disassembled. One of the membranes was analyzed by SEM. This membrane separated the brine in the cathode cell from the deionized water in the resin layer cell.

V. Description of Test Results

Efficiency of the CEDI Process for the Production of NaOH

All tests showed that the CEDI process was able to extract sodium ions from the brine and produce a NaOH stream. The strength of NaOH in the product stream was 0.14 to 8 g / L NaOH. The product NaOH was slightly contaminated with carbonate, sulfate or both. The purity of NaOH in the product stream is between 30 and 100% purity. The source of contamination may be due to membrane leakage from damage or porosity (see below).

Increasing Effect of Current

Tests 3, 4 and 5 are the same tests performed under the same conditions with increasing current in each test. Na recovery and the concentration of Na in the product stream increased with increasing current. Effluent temperature also increased. The current efficiency decreased with increasing current. Reduction of current efficiency results in inefficient use of power and results in an increase in temperature.

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

During trials 14-57 operating at higher currents, higher amounts of current were observed to degrade with time. This is shown in Figures 6A-6E, which illustrates the dynamic behavior of current at high voltages. 6C shows that the amount of current initially increases with time at unit initiation. This was due to NaOH formation in the product cell, which increased conductivity and thus vaporized the amount of current at a fixed voltage. At approximately 13:50, the current reached maximum at 11 amps. Thereafter, the current gradually decreased.

The system was then designed with independently controlled flow and pressure to plan the cell to reduce or eliminate possible vapor locking, where the formed H ₂ , O ₂ , and CO ₂ gases grow over time. Can be collected in a fixed bubble. In addition, sodium carbonate has been replaced as a feed to reduce or eliminate CO ₂ gas production from Na ⁺ removal. Over time, current loss was observed. High currents can affect the surface of the film in terms of DI.

Effect of Corrosive Flow Rate

Tables 11 and 12 were performed with similar feeds and current amounts. In this test, the NaOH product stream was recycled through cell type 2. The product NaOH was withdrawn from the system through a small purge stream, which was fed continuously by deionized water (ie feed and discharge). In this way, the flow rate of the stream across the cell remained high, but the overall residence time was increased to form less flow stream of the stream of higher intensity product.

Table 12 has a higher product exit rate, which results in shorter corrosive residence time. These tests were otherwise identical. Short residence times resulted in a weaker NaOH product stream, but% Na recovery was four times greater than test 11 and higher current efficiency. These results mean that longer corrosive retention times can increase the strength of the product, but can reduce overall Na recovery and electrical efficiency. This may be due to the high osmotic pressure of the corrosive streams that impedes the movement of more Na + ions and can be overcome using higher currents.

Effect of brine concentration

Test 13 was conducted under conditions similar to test 12 except that a lower strength feed brine was used. Test 13 was performed at different pressures carefully controlled between cells in an attempt to minimize cell / cell leakage. Test 13 was also performed at a low product evacuation rate from cell type 2, where lower current efficiency and sodium recovery were expected before performing this test. Surprisingly, this test showed better current efficiency, and higher% Na recovery than test 12. The use of weaker strength feed brine has been shown to improve sodium recovery.

Resin effect

Test 7 was performed under conditions similar to test 4. Test 4 had a resin filled feed cell in the middle of CEDI, and in test 7, this intermediate cell was filled with a screen. The test 7 feed was a higher strength feed, which will also affect the difficult reviewed results because the two parameters are different. However, based on the test 13 analysis, higher strength feed brine was expected to produce more current efficiency, but comparing test 4 and test 7, the current efficiency was surprisingly nearly the same. This means that replacing the resin with the screen does not reduce the efficiency of the process. All subsequent tests were performed with screens in saline cells.

Description of the act

Homogeneous membranes were used during trials 14-16. This test has the highest contamination range of the product. If this is due to porosity / diffusion, or the membrane is torn, it is not clean.

Brine flow rate increase effect

Test 8 and test 12 are similar tests. Test 8 was performed at higher salt and corrosive flow rates than test 12. The current efficiency of test 8 was higher than test 12 and the product corrosive material strength was similar. These results may indicate that higher saline flow rates increase efficacy.

Description of Off-Gas

The process produced off-gases in the brine recycle line. Off-gas formation rate and composition were not measured. Visual inspection showed significant gas flow in the recovery line which increased the amount of current. The gas formed at the electrode mainly contains hydrogen and oxygen. The CO ₂ gas was also exhausted in the test with NaHCO ₃ in the feed, but not in the test with Na ₂ CO ₃ .

Scanning electron microscope (SEM) results

Several different cell packs were tested in this evaluation. After the final test was completed, the final cell pack was cut and a sample of the membrane was preserved. The cationic membrane separating the cationic cell from the deionized water cell was dried, gold sputtered 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 saline side image was found to be resin particles suspended in a polyethylene sheet matrix. The cavity is larger than the particles, because it is expected that the particles shrink during the drying process, which is essential for sample preparation for SEM. The deionized water side appears to be similar, but the sheet matrix is different and appears to be damaged.

Description of Deionized Water

Over the course of trials 17-57, adjustments to deionized water were observed to cause effects. Under certain conditions, as the deionized water flow rate increases, the current decreases (FIG. 6B). Similarly, an increase in the relative pressure of DI caused a decrease in current. In this regard, in some cases, an increase in brine pressure or flow was observed to increase the current (FIG. 6E). The decrease in current may be the result of a water separation reaction that produces H ⁺ and OH ⁻ ions in solution and in the resin layer. This can increase the conductivity, and at higher deionized water flow rates, these ions are washed to reduce the conductivity. Alternatively, or in conjunction with water separation, ions from the brine and corrosive cell can leak through the membrane into the deionized water cell, which increases conductivity. Similarly, an increase in deionized water flow may wash these ions faster. Increasing the relative deionized water pressure generally reduces the rate of leakage. However, leaks may not be easily detected and contaminant ions are removed by the CEDI process because deionized water is discharged over time.

VI. result

The efficacy of CEDI for recovering Na ⁺ as NaOH from oxidized used caustic has been demonstrated. Higher recoveries, for example 10% Na, can be achieved by using recycle. High current amounts may be necessary to produce high strong corrosive materials at desired flow rates.

Prediction example

A recognized plant flow diagram (PFD) for an ethylene plant is shown in FIG. 2. Table 4 describes the material balance for the plant where about 10% of Na is recycled. In this prediction, the product NaOH from the CEDI unit would be about 1.8% by weight NaOH at a flow of about 55% of the total used caustic stream. Balances for several different arrangements are shown in FIGS. 8A-8D. FIG. 9 shows the strength of NaOH in a CEDI product stream to meet material balance needs such as may be based on similar validity.

Table 4. Sodium balance for ethylene plant with 10 wt.% NaOH tower feed and 10% recovery.

Thus, while some aspects of one or more embodiments of the inventions have been described, those skilled in the art should recognize that various changes, changes, and improvements may readily occur. Such alterations, changes and improvements are part of this description and are intended to be within the scope of the present invention. Accordingly, the foregoing description and drawings are by way of example only, and the scope of the invention will be determined from the appropriate configuration of the appended claims and their equivalents.

Claims (42)

An oxidation unit in fluid communication with a source of aqueous feed; And A system for processing an aqueous feed connected in fluid communication downstream of an oxidation unit and comprising a demineralization unit constructed and arranged to convert the product of the oxidation unit to a target compound. The system of claim 1, wherein the aqueous feed comprises one or more sodium-based compounds. The system of claim 1, wherein the aqueous feed comprises one or more organic compounds. The system of claim 1, wherein the aqueous feed comprises one or more sulfide compounds. The system of claim 2, wherein the product of the oxidation unit comprises one or more of sodium carbonate and sodium sulfate. The system of claim 1, wherein the oxidation unit comprises a liquid phase oxidation unit. 7. The system of claim 6, wherein the oxidation unit comprises a wet air oxidation unit. 7. 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 catalyzed 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 system of claim 12, wherein the electrochemical deionization unit is an electrodialysis, reverse electrodialysis, capacitive deionization, electrodeionization, continuous electrodeionization or reverse continuous electrodeionization unit. 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 a corrosive material. The system of claim 15, wherein the corrosive material comprises sodium hydroxide. The system of claim 15, wherein the corrosive material comprises ammonium sulfate. The system of claim 15, wherein no corrosive material is present in the oxidation unit product. The system of claim 1, further comprising a concentrator connected in fluid communication downstream of the desalination unit. The system of claim 1 wherein the source of aqueous feed is an industrial process. 21. The system of claim 20, wherein the source of aqueous feed is an ethylene production facility. The system of claim 20, wherein the outlet of the desalting unit is in fluid communication with the industrial process. 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 disposed to communicate with the controller and to detect characteristics of the desalination effluent stream. 25. The system of claim 24, wherein the controller is configured and arranged to adjust one or more process conditions of the one or more units in response to the detected characteristics of the desalination effluent stream. The system of claim 1, further comprising a polishing unit fluidly connected downstream of the desalination unit. 27. The system of claim 26, wherein the polishing unit comprises a biological treatment unit. 15. The system of claim 14, wherein the continuous electrodeionization device comprises one or more homogeneous membranes. 8. The system of claim 7, wherein the desalting unit comprises a continuous electrodeionization unit. The system of claim 29, wherein the target compound comprises sodium hydroxide. An oxidation unit in fluid communication with a source of aqueous feed; And A system for treating an aqueous feed containing used corrosive material in fluid communication downstream of the oxidation unit and comprising an electrochemical deionization unit constructed and arranged to produce new corrosive material. 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 unit. 34. The system of claim 33, wherein the system is configured to recycle the effluent stream to an electrochemical deionization unit. 32. The system of claim 31, wherein the new corrosive material comprises sodium hydroxide. 32. The system of claim 31 wherein the source of aqueous feed is an ethylene production facility. Oxidizing the aqueous stream to produce an oxidation product; A process for treating an aqueous stream comprising converting the oxidation product to produce a corrosive stream. 38. The method of claim 37, wherein the corrosive stream comprises sodium hydroxide. 39. The method of claim 38, further comprising providing the corrosive stream to an industrial process. 38. The method of claim 37, wherein the oxidation of the aqueous stream comprises oxidizing the aqueous stream at a temperature of at least about 150 ° C. 38. The method of claim 37, wherein the conversion of the oxidation product comprises separating target ions from the oxidation product. 42. The method of claim 41, further comprising combining the separated target ions with the regeneration fluid to produce a corrosive stream in the converting of the oxidation product.