US20060083656A1 - Method for reducing corrosion in solid sodium hydroxide production - Google Patents
Method for reducing corrosion in solid sodium hydroxide production Download PDFInfo
- Publication number
- US20060083656A1 US20060083656A1 US11/250,127 US25012705A US2006083656A1 US 20060083656 A1 US20060083656 A1 US 20060083656A1 US 25012705 A US25012705 A US 25012705A US 2006083656 A1 US2006083656 A1 US 2006083656A1
- Authority
- US
- United States
- Prior art keywords
- sodium hydroxide
- sodium borohydride
- ppm
- caustic
- aqueous sodium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 title claims abstract description 144
- 239000007787 solid Substances 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000005260 corrosion Methods 0.000 title claims abstract description 10
- 230000007797 corrosion Effects 0.000 title claims abstract description 10
- 238000004519 manufacturing process Methods 0.000 title description 6
- 229910000033 sodium borohydride Inorganic materials 0.000 claims abstract description 43
- 239000012279 sodium borohydride Substances 0.000 claims abstract description 43
- 238000001704 evaporation Methods 0.000 claims abstract description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 229910000990 Ni alloy Inorganic materials 0.000 claims description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 21
- 239000003518 caustics Substances 0.000 description 18
- 229910052759 nickel Inorganic materials 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 6
- 229910052796 boron Inorganic materials 0.000 description 6
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 239000007788 liquid Substances 0.000 description 5
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 3
- 235000019253 formic acid Nutrition 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000012267 brine Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/06—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in markedly alkaline liquids
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
- C01D1/04—Hydroxides
- C01D1/42—Concentration; Dehydration
Definitions
- This invention relates generally to a method for reducing corrosion in equipment used to manufacture solid sodium hydroxide by concentration of aqueous sodium hydroxide.
- Concentrated aqueous sodium hydroxide (caustic) is manufactured commercially by electrolysis of brine and concentration in evaporators to produce concentrated (45-50%) aqueous sodium hydroxide.
- a method for reducing corrosion in evaporators by addition of sodium borohydride is disclosed in U.S. Pat. No. 4,585,579.
- Solid sodium hydroxide typically is produced at a purity of approximately 98% by further evaporation of water from caustic, often in two stages, with initial evaporation to approximately 75% followed by further concentration in an evaporator designed to handle solids. Evaporators used to produce solid materials are in contact with higher concentrations of aqueous sodium hydroxide than other evaporators, and also are in contact with solid sodium hydroxide.
- the problem addressed by this invention is corrosion of evaporator equipment under the extreme conditions used to produce solid sodium hydroxide.
- the present invention is directed to a method for reducing corrosion in evaporators used to produce solid sodium hydroxide.
- the method comprises adding sodium borohydride to aqueous sodium hydroxide and evaporating water from the aqueous sodium hydroxide on a contact surface having a temperature from 300° C. to 450° C.
- Sodium borohydride can be added to the concentrated aqueous sodium hydroxide (caustic) in any form.
- solid sodium borohydride can be used, as well as stabilized aqueous solutions of sodium borohydride containing sodium hydroxide.
- these stabilized solutions contain from 1-25% sodium borohydride and 15-50% sodium hydroxide.
- stabilized aqueous solutions of sodium borohydride contain 10-25% sodium borohydride and 15-45% sodium hydroxide.
- a stabilized sodium borohydride solution is a solution containing approximately 12% sodium borohydride and 40% sodium hydroxide.
- Other stabilized sodium borohydride solutions would be suitable, including approximately 20% sodium borohydride and 20% sodium hydroxide.
- Sodium borohydride provided in any of the forms mentioned above may be diluted with aqueous sodium hydroxide prior to or during addition to the caustic product stream.
- the sodium borohydride is added to the caustic in an amount sufficient to produce a sodium borohydride concentration of at least 10 ppm in the caustic, but no more than 500 ppm.
- concentration of added sodium borohydride varies within this range depending on the exact operating conditions of the evaporator.
- the concentration of sodium borohydride added is at least 15 ppm, and more preferably at least 20 ppm.
- concentration of sodium borohydride added is no more than 200 ppm, and most preferably no more than 100 ppm.
- the actual concentration of sodium borohydride in the caustic after the addition is likely lower than the aforementioned values, and possibly even zero, due to reactions that consume sodium borohydride.
- liquid sodium borohydride is added using a caustic-resistant dosage pump. Dilution of liquid sodium borohydride with aqueous sodium hydroxide, e.g., 20-40% sodium hydroxide, may increase efficiency by improving mass transport of the sodium borohydride.
- Sodium borohydride-containing solution may be injected into the caustic process stream at any point where the equipment allows introduction of an additive. One preferred addition point is prior to the steam heat exchanger. Preferably, addition is done after the preliminary concentration of caustic to approximately 75%.
- the method of the present invention is applicable to any evaporator having a contact surface, i.e., a surface in contact with liquid sodium hydroxide and having a temperature of 300° C. to 450° C., that is subject to corrosion by sodium hydroxide.
- a contact surface i.e., a surface in contact with liquid sodium hydroxide and having a temperature of 300° C. to 450° C.
- Materials of construction for evaporator contact surfaces include, for example, nickel alloys, such as low-carbon nickel; nickel; and stainless steels, such as E-BriteTM.
- the contact surfaces are constructed of low-carbon nickel.
- a typical evaporator used in production of solid sodium hydroxide is a forced draft evaporator.
- the method of the present invention is applicable to an evaporator operating at a contact-surface temperature from 300° C. to 450° C.
- the temperature is at least 350° C.
- the temperature is no more than 400° C.
- Concentrated caustic (75% NaOH) was treated with a solution containing 12% sodium borohydride and 40% sodium hydroxide, a solution containing 20% sodium borohydride and 20% sodium hydroxide, and with formic acid (a compound known to reduce corrosion in aqueous sodium borohydride manufacturing equipment).
- the treated caustic was evaporated in a forced-draft evaporator at a contact-surface temperature of 380° C.
- the solid sodium hydroxide products produced without any treatment of the caustic, with treatment by formic acid, and with treatment by sodium borohydride were analyzed for nickel content by inductively-coupled plasma atomic emission spectroscopy (ICP), before (Initial Ni level) and after treatment (Final Ni level), to give the results displayed in the Table below.
- ICP inductively-coupled plasma atomic emission spectroscopy
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Inorganic Chemistry (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
- Heat Treatment Of Water, Waste Water Or Sewage (AREA)
Abstract
A method for reducing corrosion in evaporators used to produce solid sodium hydroxide. The method comprises adding sodium borohydride to aqueous sodium hydroxide and evaporating water from the aqueous sodium hydroxide on a contact surface having a temperature from 300° C. to 450° C.
Description
- This is a non-provisional application of prior pending U.S. Provisional Application Ser. No. 60/619,867 filed on Oct. 18, 2004.
- This invention relates generally to a method for reducing corrosion in equipment used to manufacture solid sodium hydroxide by concentration of aqueous sodium hydroxide.
- Concentrated aqueous sodium hydroxide (caustic) is manufactured commercially by electrolysis of brine and concentration in evaporators to produce concentrated (45-50%) aqueous sodium hydroxide. A method for reducing corrosion in evaporators by addition of sodium borohydride is disclosed in U.S. Pat. No. 4,585,579. Solid sodium hydroxide typically is produced at a purity of approximately 98% by further evaporation of water from caustic, often in two stages, with initial evaporation to approximately 75% followed by further concentration in an evaporator designed to handle solids. Evaporators used to produce solid materials are in contact with higher concentrations of aqueous sodium hydroxide than other evaporators, and also are in contact with solid sodium hydroxide. Moreover, while liquid sodium hydroxide products are produced in evaporators operating at 100-165° C., much higher temperatures are employed in evaporators used to produce solid sodium hydroxide. Production of solid sodium hydroxide is also accompanied by much higher turbulence. Corrosion of nickel or nickel-containing alloys in the evaporators used to produce solid product causes undesirable nickel contamination in the solid sodium hydroxide. Maintenance and replacement of corroded equipment can be costly and can have an adverse effect on production output
- The problem addressed by this invention is corrosion of evaporator equipment under the extreme conditions used to produce solid sodium hydroxide.
- The present invention is directed to a method for reducing corrosion in evaporators used to produce solid sodium hydroxide. The method comprises adding sodium borohydride to aqueous sodium hydroxide and evaporating water from the aqueous sodium hydroxide on a contact surface having a temperature from 300° C. to 450° C.
- Unless otherwise specified, all percentages herein are stated as weight percentages and temperatures are in ° C.
- Sodium borohydride can be added to the concentrated aqueous sodium hydroxide (caustic) in any form. For example, solid sodium borohydride can be used, as well as stabilized aqueous solutions of sodium borohydride containing sodium hydroxide. Preferably, these stabilized solutions contain from 1-25% sodium borohydride and 15-50% sodium hydroxide. More preferably, stabilized aqueous solutions of sodium borohydride contain 10-25% sodium borohydride and 15-45% sodium hydroxide. One example of a stabilized sodium borohydride solution is a solution containing approximately 12% sodium borohydride and 40% sodium hydroxide. Other stabilized sodium borohydride solutions would be suitable, including approximately 20% sodium borohydride and 20% sodium hydroxide. Sodium borohydride provided in any of the forms mentioned above may be diluted with aqueous sodium hydroxide prior to or during addition to the caustic product stream.
- In the method of this invention, the sodium borohydride is added to the caustic in an amount sufficient to produce a sodium borohydride concentration of at least 10 ppm in the caustic, but no more than 500 ppm. The concentration of added sodium borohydride varies within this range depending on the exact operating conditions of the evaporator. Preferably, the concentration of sodium borohydride added is at least 15 ppm, and more preferably at least 20 ppm. Preferably, the concentration of sodium borohydride added is no more than 200 ppm, and most preferably no more than 100 ppm. The actual concentration of sodium borohydride in the caustic after the addition is likely lower than the aforementioned values, and possibly even zero, due to reactions that consume sodium borohydride. Typically, liquid sodium borohydride is added using a caustic-resistant dosage pump. Dilution of liquid sodium borohydride with aqueous sodium hydroxide, e.g., 20-40% sodium hydroxide, may increase efficiency by improving mass transport of the sodium borohydride. Sodium borohydride-containing solution may be injected into the caustic process stream at any point where the equipment allows introduction of an additive. One preferred addition point is prior to the steam heat exchanger. Preferably, addition is done after the preliminary concentration of caustic to approximately 75%.
- The method of the present invention is applicable to any evaporator having a contact surface, i.e., a surface in contact with liquid sodium hydroxide and having a temperature of 300° C. to 450° C., that is subject to corrosion by sodium hydroxide. Materials of construction for evaporator contact surfaces include, for example, nickel alloys, such as low-carbon nickel; nickel; and stainless steels, such as E-Brite™. In a preferred embodiment of the invention, the contact surfaces are constructed of low-carbon nickel. A typical evaporator used in production of solid sodium hydroxide is a forced draft evaporator.
- The method of the present invention is applicable to an evaporator operating at a contact-surface temperature from 300° C. to 450° C. Preferably, the temperature is at least 350° C. Preferably, the temperature is no more than 400° C.
- Concentrated caustic (75% NaOH) was treated with a solution containing 12% sodium borohydride and 40% sodium hydroxide, a solution containing 20% sodium borohydride and 20% sodium hydroxide, and with formic acid (a compound known to reduce corrosion in aqueous sodium borohydride manufacturing equipment). The treated caustic was evaporated in a forced-draft evaporator at a contact-surface temperature of 380° C. The solid sodium hydroxide products produced without any treatment of the caustic, with treatment by formic acid, and with treatment by sodium borohydride were analyzed for nickel content by inductively-coupled plasma atomic emission spectroscopy (ICP), before (Initial Ni level) and after treatment (Final Ni level), to give the results displayed in the Table below.
TABLE Initial Ni Final Ni Treatment (NaBH4 level added to caustic) level level None 6 ppm 6 ppm Formic acid 3 ppm 12% NaBH4/40% NaOH (23 ppm NaBH4) 11.5 ppm 0.5 ppm 20% NaBH4/20% NaOH (30 ppm NaBH4) 8 ppm 0.8 ppm
Notes: Initial levels of Ni in the product varied somewhat, probably due at least in part to varying levels of Ni present in the 75% caustic. The final Ni level reported is the average of the approximately steady-state levels attained after addition of NaBH4, usually after several days. Analysis of boron levels in the solid caustic, with back-calculation, revealed that some boron is consumed in reactions with the evaporator surface. For example, a treatment rate of 23 ppm NaBH4 based on 75% caustic would be expected to yield 31 ppm boron (calculated as NaBH4) in the final solid NaOH product if all of the boron were concentrated into and remained in the solid NaOH. Instead, based on the total boron in the solid NaOH product, the concentrations of NaBH4 was 14 ppm. Likewise, a treatment rate of 30 ppm in the liquid caustic would be expected to yield 40 ppm in the solid NaOH; however, the actual boron content was only 24 ppm, calculated as NaBH4.
Claims (7)
1. A method for reducing corrosion in evaporators used to produce solid sodium hydroxide; said method comprising adding sodium borohydride to aqueous sodium hydroxide and evaporating water from said aqueous sodium hydroxide on a contact surface having a temperature from 300° C. to 450° C.
2. The method of claim 1 in which sodium borohydride is added to said aqueous sodium hydroxide in a concentration of at least 10 ppm in said aqueous sodium hydroxide, and no more than 500 ppm.
3. The method of claim 2 in which sodium borohydride is provided as a stabilized aqueous solution.
4. The method of claim 3 in which the temperature is from 350° C. to 400° C.
5. The method of claim 4 in which contact surfaces of the evaporator are constructed of a nickel alloy.
6. The method of claim 5 in which the stabilized aqueous solution contains 1-25% sodium borohydride and 15-50% sodium hydroxide.
7. The method of claim 6 in which said aqueous sodium hydroxide has an initial concentration of 75%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US11/250,127 US20060083656A1 (en) | 2004-10-18 | 2005-10-13 | Method for reducing corrosion in solid sodium hydroxide production |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US61986704P | 2004-10-18 | 2004-10-18 | |
| US11/250,127 US20060083656A1 (en) | 2004-10-18 | 2005-10-13 | Method for reducing corrosion in solid sodium hydroxide production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US20060083656A1 true US20060083656A1 (en) | 2006-04-20 |
Family
ID=35735278
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US11/250,127 Abandoned US20060083656A1 (en) | 2004-10-18 | 2005-10-13 | Method for reducing corrosion in solid sodium hydroxide production |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US20060083656A1 (en) |
| EP (1) | EP1647523A3 (en) |
| JP (1) | JP2006111528A (en) |
| CN (1) | CN100384736C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3196165A1 (en) * | 2013-11-12 | 2017-07-26 | Solvay SA | Concentrated aqueous sodium hydroxide solution and process for treating a sodium carbonate purge |
| CN114231962A (en) * | 2021-12-16 | 2022-03-25 | 厦门华弘昌科技有限公司 | Chromium-free passivator, preparation method thereof and passivating method |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4883794B2 (en) * | 2006-07-05 | 2012-02-22 | ローム アンド ハース カンパニー | High temperature stable borohydride compound |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1786516A (en) * | 1928-02-29 | 1930-12-30 | Ig Farbenindustrie Ag | Process for the continuous production of fused caustic alkalies |
| US1883211A (en) * | 1930-10-20 | 1932-10-18 | Standard Oil Co | Concentration of caustic soda |
| US3298797A (en) * | 1965-11-29 | 1967-01-17 | Hooker Chemical Corp | Alkali metal hydroxide evaporation |
| US3600316A (en) * | 1968-08-20 | 1971-08-17 | Lachema Np | Method of producing a descaling composition from sodium hydroxide,sodium and hydrogen under pressure |
| US4585579A (en) * | 1984-10-01 | 1986-04-29 | Occidental Chemical Corporation | Suppression of corrosion in caustic manufacturing systems |
| US5154860A (en) * | 1991-09-16 | 1992-10-13 | Occidental Chemical Corporation | Corrosion suppression of stainless steel in caustic media |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2735750A (en) * | 1956-02-21 | Method of reducing the chlorate content of aqueous | ||
| DE2437290C3 (en) * | 1974-08-02 | 1979-05-31 | Paul Dipl.-Ing. 6497 Steinau Janisch | Process for the high concentration of alkaline solutions |
| US6080299A (en) * | 1999-10-14 | 2000-06-27 | Pioneer (East) Inc. | Method for removal of nickel and iron from alkali metal hydroxide manufacturing process requiring the use of sodium borohydride |
-
2005
- 2005-10-08 CN CNB200510113777XA patent/CN100384736C/en not_active Expired - Fee Related
- 2005-10-10 EP EP05256290A patent/EP1647523A3/en not_active Withdrawn
- 2005-10-13 US US11/250,127 patent/US20060083656A1/en not_active Abandoned
- 2005-10-17 JP JP2005301239A patent/JP2006111528A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1786516A (en) * | 1928-02-29 | 1930-12-30 | Ig Farbenindustrie Ag | Process for the continuous production of fused caustic alkalies |
| US1883211A (en) * | 1930-10-20 | 1932-10-18 | Standard Oil Co | Concentration of caustic soda |
| US3298797A (en) * | 1965-11-29 | 1967-01-17 | Hooker Chemical Corp | Alkali metal hydroxide evaporation |
| US3600316A (en) * | 1968-08-20 | 1971-08-17 | Lachema Np | Method of producing a descaling composition from sodium hydroxide,sodium and hydrogen under pressure |
| US4585579A (en) * | 1984-10-01 | 1986-04-29 | Occidental Chemical Corporation | Suppression of corrosion in caustic manufacturing systems |
| US5154860A (en) * | 1991-09-16 | 1992-10-13 | Occidental Chemical Corporation | Corrosion suppression of stainless steel in caustic media |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3196165A1 (en) * | 2013-11-12 | 2017-07-26 | Solvay SA | Concentrated aqueous sodium hydroxide solution and process for treating a sodium carbonate purge |
| CN114231962A (en) * | 2021-12-16 | 2022-03-25 | 厦门华弘昌科技有限公司 | Chromium-free passivator, preparation method thereof and passivating method |
Also Published As
| Publication number | Publication date |
|---|---|
| CN100384736C (en) | 2008-04-30 |
| EP1647523A2 (en) | 2006-04-19 |
| EP1647523A3 (en) | 2010-12-29 |
| JP2006111528A (en) | 2006-04-27 |
| CN1778678A (en) | 2006-05-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |