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    • 专利摘要:
    The present invention provides a method for efficiently removing dissolved selenium from water or wastewater of various purification processes. The present invention also provides a new and effective method for oxidizing selenium and organic-selenium complexes to the selenite oxide state so that they can be absorbed as precipitates of metal oxides or metal hydroxides. The present invention includes two continuous stirred tank reactors (CSTR) operating in series. The stream to be treated and one of the various ferric salts (ferric sulphate, ferric chloride) enter the first reactor to form ferric hydroxide and ferric oxalate precipitates. The pH of the first reactor is automatically controlled by adjusting the feed rate of iron salt. The stream from the first reactor is led to a second reactor into which potassium permanganate is introduced. The selenium in the stream to be treated is oxidized to selenic acid, a sediment of Ming Dioxide as a by-product of oxidation. Selenic acid is absorbed into several precipitates, which are removed by centrifugation. The pH of the centrifuged water is automatically adjusted with the addition of sodium hydroxide. The process according to the invention is also effective for treating a second wastewater stream, such as reverse osmosis water discharge and iron exchange regeneration wastewater.
    公开号:KR20010031417A
    申请号:KR1020007004442
    申请日:1998-10-15
    公开日:2001-04-16
    发明作者:스티븐 디. 오버맨
    申请人:홀 케네스 알.；텍사코 디벨롭프먼트 코퍼레이션；
    IPC主号:
    专利说明:

    PROCESS FOR REMOVING SELENIUM FROM REFINERY PROCESS WATER AND WASTE WATER STREAMS
    Selenium compounds are present in trace amounts in petroleum such as high molecular weight, organometallic molecules. The concentration of selenium in petroleum will vary from the manufacturing location and the unread reading to 1.0 ppm by weight. Organic selenium compounds in petroleum are distilled at the fraction of heavy hydrocarbons during purification. Selenium is liberated from heavy hydrocarbons by catalysts or pyrolysis processes such as hydrocrackers and delayed cokers to be removed as inorganic compounds and concentrated to overhead stream products and vapor streams. These inorganic selenium compounds are similar to inorganic sulfur and nitrogen compounds such as hydrogen sulfide and ammonia and are very soluble in water, and are generally removed in the column flow by contact with water. These sulfur and nitrogen components are typically volatile and can be removed from the ″ acidic water ″ stream by distillation (contact of the steam stream with the countercurrent stream of steam). However, some of the selenium components are less volatile, but most of the selenium remains in acidic water after stripping. High concentrations of selenium are toxic and may require some purifier to reduce the concentration of selenium in stripped acidic water.
    Various methods for selenium removal from aqueous and hydrocarbon streams are known. These are three broad and three categories. Selenium compounds already include a method of changing by chemical reaction, a method depending on absorption, and a method depending on membrane separation. Several reaction methods are treated with hydrogen or other reducing agents to convert the dissolved selenium component into elemental selenium. Another method is to employ bacteria which metabolically achieve the same reaction. Other reaction methods include in particular the removal of hydrogen selenide and the oxidation of selenide to selenium. Another additional reaction method is based on the formation of insoluble sulfides by reaction of various sulfur containing compounds with selenium. Alternatively, electrolysis or anion exchange can be employed to extract or replace selenium-containing ions.
    Many methods are known for removing selenium from wastewater by absorbing selenium compounds in solid absorbents. As the material employed as the absorbent, zeolite, dithiocarbamate and polymers thereof may be employed, and metal salts such as ferric chloride and ferric sulfate may also be employed. Most absorption methods are effective in that the selenium is in the form of selenite anions. However, removing the selenocyanate ion SeCN + is not effective. This is because selenium is the predominant form in purified wastewater and stripped acidic water. Attempts have been made to oxidize selenocyanates before introducing the absorbent. Oxidizing agents may include air, ozone, hydrogen peroxide and chlorine dioxide. These oxidants are not entirely satisfactory. Air is not effective for oxidizing selenocyanates. Ozone and peroxides require high alkaline conditions for maximum effectiveness. Chlorine dioxide effectively oxidizes selenocyanate at neutral pH. But it is not stable in aqueous solution.
    U.S. Patent 5,200,082 discloses a selenium removal method. The selenium compound in water is first reduced to elemental selenium and reoxidized to selenite. And by the conventional absorption method mentioned above. These processes are not suitable for water streams such as stripped acidic water that have previously undergone desulfurization because of the need to reintroduce sulfur in water.
    U. S. Patent No. 5,200, 082 discloses a selenium removal method wherein the selenium component in the water is first reduced to basic selenium and then reoxidized to selenite and removed by conventional absorption methods as described above. Because the process requires the re-injection of sulfur into the water, it is inadequate for water streams such as sour water that has previously been removed and decomposed.
    The present invention relates to a continuous process for reducing the concentration of water soluble inorganic and organic selenium components in an aqueous solution. In particular, the process relates to the removal of selenium from various purified water and wastewater streams, such as unwanted acidic water from purified wastewater or unnecessary acidic water, phenolic unnecessary water, reverse osmosis rejection water. The present invention seeks to mass-produce the release rate of selenium in purified wastewater which is recovered and discharged from selenium from this aqueous process or wastewater stream.
    Figure 1 is a schematic process flow diagram of the entire selenium removal process, which shows an example of the chemical additives required to remove the selenium and selenium components from the basic work of the present invention and from refining and other industrial wastewater.
    FIG. 2 is a schematic process flow diagram for the entire selenium removal process similar to FIG. 1, illustrating the use of the process with ferric chloride rather than ferric sulfate.
    It is an object of the present invention to remove selenium from the stream of refined water by oxidizing selenium cation ions in water to selenite ions, which are then absorbed by ferric hydroxide or similar insoluble substances which rise in the water. Oxidation is transferred to a tank reactor which is continuously agitated by the addition of aqueous caustic permanganate solution to the water stream. Another aspect of the invention is that the resulting selenite ions are absorbed not only in the iron precipitate but also in the manganese dioxide produced as a byproduct of oxidation.
    In order to perform the selenium removal process, the selenium-containing water is first cooled to approximately 80 to 90 degrees Fahrenheit (26.6 to 32.3 degrees Celsius) and fed to a continuously stirred tank reactor. Here, water is mixed with an aqueous solution of ferric sulfate or other soluble ferric salts to reduce the pH of the water and produce a deposit that forms ferric hydroxide and ferric oxyhydrogen. The effluent of the reactor is led to a continuously stirred second tank reactor, which is mixed with an aqueous permanganate solution to cause oxidation of selenium with selenite and to form manganese dioxide deposits. The selenite is absorbed by both manganese dioxide and ferric hydroxide and separated from them by centrifugation. Finally, the treated water is mixed with an aqueous base solution to increase the pH of the water to a range suitable for further use or runoff.
    The flow of water to be treated may consist of refinery process water, refinery waste water, reverse osmosis rejection water, ion exchange regeneration wastewater, or any other industrial or agricultural water stream with elevated selenium concentrate. An example of refining water stream suitable for treatment by the present process is phenol-free sour water, which typically occurs with sour water from delayed coke and is produced by the sour water remover as described above, 5.0 mg / l selenium concentrate with a temperature of 150 degrees Fahrenheit (65.5 degrees Celsius). Other streams of water suitable for treatment by the process described herein may or may not require a heat exchanger to reach a target temperature range of 80 to 90 degrees Fahrenheit (26.6 to 32.2 degrees Celsius).
    Preferred ferric salts are ferric chloride and ferric sulfate, most preferably ferric sulfur. However, it will be apparent to one skilled in the art that other water soluble iron (III) components may be used in the process instead.
    The addition of the ferric salt solution to the flow of water is preferably carried out at temperatures below ambient temperature or room temperature. To this end, another aspect of the invention includes cooling means such as a continuous flow heat exchanger for the flow of water to be treated upstream of the point where it comes into contact with the ferric salt solution.
    Since the present invention is most effective when the process is maintained within a narrow pH range of 4.0 to 4.2, another aspect of the present invention is the automatic addition of ferric salt to water occurs before the oxidation step. Thus, the process has inherent means to adjust the pH of the water flow and eliminates any need to inject additional reactants to control the pH prior to the oxidation or precipitation step. Likewise, the present invention includes an automatic means for increasing the pH of the water between 6 and 8 pH units following the oxidation step so that the treated water can be safely discharged or used for other purposes in refining.
    Preferred permanganate compounds for the oxidation step are potassium permanganate. In other strong oxidative mediators such as potassium dichromate or other chlorine dioxide, they are less useful in the present disclosure because they do not form precipitates that aid in the removal of the sulnium compounds. In other words, oxidation containing permanganate produces manganese dioxide precipitate as a by-product, which acts as an additional absorbent capable of removing selenite ions.
    1 illustrates one embodiment of the present invention. The steam containing selenium 1 is led to the heat exchanger 2 at a temperature of 80 to 90 degrees Fahrenheit (26.6 degrees to 32.2 degrees Celsius) if necessary to cool the steam. Cooling water supply flow 3 is led to a heat exchanger to reduce the supply temperature and generate a cooling water return flow 4. Feedwater flow 5 from the heat exchanger is directed to a first continuous stirred tank reactor 6 (CSTR) for handling. The contents of the first CSTR are continuously mixed by the mixer 7. The pH of the effluent of the first CSTR 8 is adjusted in pH units of 4.0 to 4.2 by the pH regulator 9 which controls the addition of 36% ferric sulfate by dissolution by the chemical feed pump 10. The chemical feed pump draws ferric sulfate into the bulk storage tank 11 and leads it to the first CSTR 6. The effluent from the first CSTR 8 is directed to a second CSTR 12 located in series with the first CSTR. The contents of the second CSTR together with the first CSTR are continuously mixed by the mixer 13. The addition rate of the 5% potassium permanganate solution is controlled by the proportional flow regulator 14 to maintain a fixed ratio at the flow rate of the incoming feed stream 5 of the first CSTR. The flow regulator regulates the chemical spray pump 15 which leads potassium permanganate from the bulk storage tank 16 to the second CSTR. The effluent 17 from the second CSTR is led to a solid separation and filtration system 18 capable of separating and recovering all solids to a particle size of 1 micron. The solid separation and filtration system 18 may constitute any single or combination device necessary to achieve the value of this solid separation and filtration. Such equipment may include a settler, clarifier, centrifuge, multimedia or cartridge filter, filter press, or any other comparable separation or combination device. While specific geometries are economical and depend on other process design considerations, the system must remove all solids having a particle size of 1 micron or larger. Treatment solids 19 produced by the separation and filtration system Should not have any liquid, ideally should be less than 50% by heavy water for more effective handling, removal or regeneration. The filtered water stream 20 should be purged and free of any solid particles. At this point, the filtrate still shows the same pH as the effluent of the second CSTR, which pH should be adjusted (raised) in the range of 6.0 to 8.0 pH units. To accomplish this, the effluent 20 from the solid separation and filtration system is led to a pH control system 21. The system can constitute any combination of continuous flow equipment needed to adjust and control pH. Typically, this equipment includes a pH regulator 22 that regulates a chemical feed pump 23 that draws sodium hydroxide solution from the bulk storage tank 24 to the pH control system 21. The final treated water 25 with 0.5 mg / l (or smaller if necessary) selenium condensate and the pH between 6.0 and 8.0 lead to the water recovery use or removal site.
    FIG. 2 shows a second embodiment of the invention in which ferric chloride is replaced with ferric sulfate in the bulk chemical storage tank 11. Ferric chloride provides the same treatment value by the same chemical reaction and structure as ferric sulfate. Generally, ferric chloride is cheaper than ferric sulfate; However, if ferric chloride is used, residual chlorine ions in the last treated steam 25 may limit water recovery use in refining or other industries. While chemical additives are an effective source of ferric ions, the choice between the two can depend on economic factors and water recovery considerations.
    The following examples are intended to illustrate the preferred embodiment of the present invention. Those skilled in the art will recognize that the techniques disclosed in the following examples represent techniques invented by the inventors to function well in practicing the present invention, and thus constitute a preferred aspect in the practice. However, one of ordinary skill in the art will recognize that many modifications are possible within the specific embodiments disclosed by the disclosure herein and similar results may be obtained without departing from the scope and spirit of the invention.
    Example 1
    The jar was filled with 1 liter of phenolic stripped acidic water containing 4.76 ppm of selenium. The acidic water was treated with 1% dose of ferric chloride and then treated with 1% dose of permanganic acid. After a few minutes of stirring, a precipitate precipitated out, which recovered the liquid to rise above the surface, including 2.60 ppm of selenium.
    These results show that 45.4% of selenium was removed.
    Example 2
    The jar was filled with 1 liter of phenolic stripped acidic water containing 4.34 ppm of selenium. The acidic water was treated with 1.50% dose of ferric chloride and then treated with 1.75% dose of permanganate. After a few minutes of stirring the precipitate precipitated out. Liquid was recovered that floated above the surface, including 0.273 ppm of selenium. These results show that 93.7% of selenium was removed.
    Example 3
    During continuous flow pilot testing, 20 gallons per minute (75.7 liters per minute) of phenolic stripped acidic water, containing 4.37 mg of selenium per liter and 3.2 gallons per minute (12.1 liters per minute) of 36% ferric sulfide solution 950 It was fed to a gallon (3596 liters) stirred tank reactor. The reactor was maintained at a temperature of 90 ° F. (32.2 ° C.). Effluent from the reactor was fed to a 950 gallon (3596 liters) stirred tank reactor with 13.6 gallons per minute (51.5 liters per minute) of 5% permanganic acid solution. This second reactor was maintained at a temperature of 90 ° F. (32.2 ° C.). The effluent flowing out of the second reactor was allowed to settle in a portable tank and the liquid floating above the surface had a selenium concentration of 0.32 to 0,75 milligrams of selenium per liter, which would indicate that selenium was removed in the range of 82.8 to 93.1%. Indicates.
    Example 4
    During continuous flow pilot testing, 0.15 gallons per minute (0.56 liters per minute) of reverse osmosis discharged from reverse osmosis of phenolic stripped acidic water from 21 to 26.9 mg of selenium per liter and 0.13 gallons per hour (0.49 liters per hour) ) Was fed to a 12 gallon (45 liter) stirred tank reactor containing 36% ferric sulfide solution. The reactor was maintained at a temperature of 75 ° F. (23.8 ° C.). Effluent from the reactor was fed to a 20 gallon (75 liter) stirred tank reactor with 0.44 to 1.02 gallons per hour (1.67 to 3.86 liters per hour) of 5% permanganate kali solution. This second reactor was maintained at a temperature of 75 ° F. (23.8 ° C.). The effluent flowing out of the second reactor had selenium serfs with 1.02 mg selenium in 0.17 per liter, indicating that selenium was removed in the range of 95.1 to 99.4%.
    Example 5
    During the continuous flow pilot test, 30 gallons per minute (113 liters per minute) of phenolic stripped acidic water containing 4.5 to 5.5 mg of selenium per liter were treated in the same manner as in Example 4. Effluent from the second reactor was sent to a centrifuge to remove the precipitate. The clarified effluent had an average selenium concentration of 0.5 mg per liter, indicating that selenium was removed in the range of 88.9 to 90.9%.
    From the foregoing, those skilled in the art will appreciate that one embodiment of the present invention includes a continuous process for removing selenium from a stream of wastewater comprising selenium. This continuous process preferably comprises adding an aqueous ferric salt to the wastewater, the aqueous ferric salt comprising a solution forming a first stream by means of automatic metering, and preferably adding a second stream to the first stream by means of automatic metering. Adding an aqueous permanganate comprising the forming solution, separating the selenium comprising solids from the second stream, preferably by winch separation, leaving a separate liquid stream, and Preferably, the method comprises adding an aqueous base comprising a solution to form a liquid stream having a pH of approximately 6.0 to 8.0 by automatic metering.
    In one embodiment, the process also cools the stream containing selenium in a continuous flow heat exchanger prior to treating the ferric salt solution such that the temperature is preferably between 80 and 90 ° F. (26.6 and 32.2 ° C.). It includes a method.
    Another embodiment of the invention may include a treatment for removal of selenium from a wastewater stream containing selenium. This treatment cools the stream containing selenium in a continuous flow heat exchanger; Adding an aqueous ferric salt solution to the wastewater by automatic metered addition to form a first stream; Adding a solution containing aqueous permanganate to the first stream by automatic metered addition to form a second stream; Separating the selenium-containing solids from the second stream by centrifugation to extract the centrifuged liquid stream; Adding the aqueous base containing solution to the centrifuged liquid stream by automatic metered addition to increase the pH of the liquid stream to about 6.0 to 8.0. Preferably the treatment is carried out where the ferric salt is selected from ferric sulfate, ferric nitrate, and ferric chloride, more preferably where the ferric salt is ferric sulfate. . In another embodiment, the permanganate is sodium permanganate.
    Another embodiment of the invention may include a continuous process for removing selenium from a liquid stream containing selenium, where the selenium containing stream is first mixed with a solution containing ferric salt to form a first mixture. The first mixture is mixed with a solution containing permanganate to form a second mixture. Preferably the method comprises cooling the liquid stream containing selenium in a continuous flow heat exchanger prior to mixing with the solution containing ferric salt. Moreover, the method separates the solids from the second mixture by centrifugation to extract the centrifuged liquid stream; Finally, the pH of the centrifuged liquid stream between about 6.0 and about 8.0 can be adjusted by adding the aqueous base containing solution to the centrifuged mixture by automatic metered addition. In another embodiment, the ferric salt is selected from ferric sulfate, ferric nitrate, and ferric chloride, preferably the ferric salt is ferric sulfate. The treatment is also preferably carried out where the permanganate is sodium permanganate.
    Yet another embodiment of the present invention may include an apparatus for continuously removing selenium from a liquid stream containing selenium. Such apparatus preferably comprises a heat exchanger for maintaining the temperature of the liquid stream containing selenium at a temperature between 80 and 90 ° F. (26.6 and 32.2 ° C.); The liquid stream containing selenium may be mixed with a solution containing liquid ferric salt to form a first stream. The apparatus is also centrifuged by separating a solid from the second stream with a second reactor in which the first mixture is mixed with an aqueous permanganate solution to oxidize the selenium compound to impart a second stream. Means for imparting a liquid stream. Moreover, means for automatic metered addition of the aqueous base containing solution to the centrifuged liquid stream are also included, preferably to increase the pH of the liquid stream centrifuged to about 6.8 to 8.0. In one embodiment, the ferric salt is selected from ferric sulfate, ferric nitrate, and ferric chloride. More preferably, the ferric salt is ferric sulfate, and the permanganate is sodium permanganate.
    In addition, this invention is not limited to the above-mentioned embodiment, Of course, it can be variously modified and implemented in the range which does not deviate from the summary of this invention.
    权利要求:
    Claims (10)
    [1" claim-type="Currently amended] Adding a solution containing an aqueous ferric salt to the wastewater, preferably at an automatically measured dosage, to form a first stream;
    Adding a solution containing aqueous permanganate to said first stream to form a second stream, preferably at an automatically measured dosage;
    A selenium separation step of separating the selenium-containing solids from the second stream, preferably by centrifugation, and sending the separated liquid stream; And
    Adding selenium-containing wastewater to the separated liquid stream, preferably at an automatically measured dose, preferably adding a solution containing hydroxyl such that the pH of the liquid stream is approximately 6-8 To continuously remove selenium from the product.
    [2" claim-type="Currently amended] The method of claim 1 further comprising the step of cooling the stream containing selenium in a continuous flow heat exchanger such that the temperature is preferably between 26.6-32.2 ° C. prior to treating the iron containing salt. A method for the continuous removal of selenium from wastewater containing selenium.
    [3" claim-type="Currently amended] The iron-containing salt is selected from ferric sulfate, ferric nitrate and ferric chloride. Preferably, the salt containing iron is ferric sulfate. A method of continuously removing selenium from selenium-containing wastewater.
    [4" claim-type="Currently amended] The method of claim 1 wherein the permanganate salt is potassium permanganate.
    [5" claim-type="Currently amended] Cooling the flow containing selenium in a continuous flow heat exchanger;
    Adding a solution containing aqueous aqueous ferric salt to the wastewater to form a first stream at an automatically measured dosage;
    Adding a solution containing aqueous permanganate to the first stream to form a second stream at an automatically measured dosage;
    In the second stream, a selenium separation step of separating the selenium-containing solids and sending the separated liquid stream by centrifugation; And
    To the centrifuged liquid stream, selenium from the selenium-containing wastewater, comprising adding a solution containing a hydroxyl group to increase the pH of the liquid stream to approximately 6-8, at an automatically measured dose. How to get rid of it.
    [6" claim-type="Currently amended] The iron-containing salt is selected from ferric sulfate, ferric nitrate and ferric chloride. Preferably, the salt containing iron is ferric sulfate. A method for continuously removing selenium from selenium-containing wastewater.
    [7" claim-type="Currently amended] 7. The method of claim 6 wherein the permanganate is potassium permanganate.
    [8" claim-type="Currently amended] Heat exchanger for maintaining the temperature of the aqueous stream containing selenium, preferably at 26.6-32.2 ° C;
    A first reactor for mixing said aqueous stream containing selenium with a solution containing a salt containing an aqueous iron component to form a first stream;
    A second reactor for mixing the first mixture above with an aqueous permanganate solution to oxidize the selenium compound to form a second stream;
    Preferably, centrifugation means for separating the solids in the second stream and for separating the centrifuged liquid solution; And
    Continuously administering selenium in an aqueous stream containing selenium, preferably by automatic metered administration, comprising means for administering a solution containing a hydroxyl group to increase the pH to 6-8 in the centrifuged liquid solution. Device for removal.
    [9" claim-type="Currently amended] The salt of claim 8, wherein the salt containing iron is selected from ferric sulfate, ferric nitrate and ferric chloride, and preferably the salt containing iron is ferric sulfate. An apparatus for continuously removing selenium from an aqueous stream containing selenium.
    [10" claim-type="Currently amended] 10. The apparatus of claim 9, wherein the permanganate is potassium permanganate.
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    同族专利:
    公开号 | 公开日
    US5993667A|1999-11-30|
    EA200000437A1|2000-10-30|
    TR200001725T2|2000-10-23|
    JP2001520119A|2001-10-30|
    AU734044B2|2001-05-31|
    AU1091799A|1999-05-10|
    CA2307707A1|1999-04-29|
    CN1279652A|2001-01-10|
    BR9814827A|2001-11-27|
    EP1025051A1|2000-08-09|
    BG104438A|2001-02-28|
    WO1999020569A1|1999-04-29|
    US6156191A|2000-12-05|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1997-10-20|Priority to US8/954,405
    1997-10-20|Priority to US08/954,405
    1998-10-15|Application filed by 홀 케네스 알., 텍사코 디벨롭프먼트 코퍼레이션
    1998-10-15|Priority to PCT/US1998/021835
    2001-04-16|Publication of KR20010031417A
    优先权:
    申请号 | 申请日 | 专利标题
    US8/954,405|1997-10-20|
    US08/954,405|US5993667A|1997-10-20|1997-10-20|Process for removing selenium from refinery process water and waste water streams|
    PCT/US1998/021835|WO1999020569A1|1997-10-20|1998-10-15|Process for removing selenium from refinery process water and wastewater streams|
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