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Method for reducing corrosion in solid sodium hydroxide production

Inactive Publication Date: 2006-04-20
WINDEY GUY FRANCISCUS ELZA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005] 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.

Problems solved by technology

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

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example

[0011] 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.

TABLEInitial NiFinal NiTreatment (NaBH4 level added to caustic)levellevelNone6 ppm6 ppmFormic acid3 ppm12% NaBH4 / 40% NaOH (23 ppm NaBH4)11.5 ppm  0.5 ppm  20% NaBH4 / 20% NaOH (30 ppm NaBH4)8 ppm0.8 ppm  

Note...

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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

Cross Reference to Related Patent Applications [0001] This is a non-provisional application of prior pending U.S. Provisional Application Ser. No. 60 / 619,867 filed on Oct. 18, 2004.BACKGROUND [0002] This invention relates generally to a method for reducing corrosion in equipment used to manufacture solid sodium hydroxide by concentration of aqueous sodium hydroxide. [0003] 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 ma...

Claims

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Application Information

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IPC IPC(8): C23F11/06C23F11/00
CPCC01D1/42C23F11/06
Inventor WINDEY, GUY FRANCISCUS ELZA
Owner WINDEY GUY FRANCISCUS ELZA