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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/36—Regeneration of waste pickling liquors
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G49/00—Compounds of iron
  • C01G49/02—Oxides; Hydroxides
  • C01G49/06—Ferric oxide [Fe2O3]
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity

Definitions

• the invention relates to a process for the silicification of inorganic aqueous solutions, in particular pickling solutions, and a process for the production of iron oxide with a reduced content of silica, in particular for the production. of ferrites.
• iron oxide (Fe 2 0,) oxide serves as a primary material for the electronics industry (ferrite construction).
• the electronic (electromagnetic) properties of these iron oxide ceramics are primarily dependent on the silica content of the materials.
• SiC silica
• the electronics industry is now demanding a maximum of 0.01% silica (SiC) in iron oxide for soft ferritic applications, whereas a few years ago this limit was 0.02%.
• the development in the iron oxide sector is expected to further lower this limit. Accordingly, the price for very pure iron oxide powder (ax. 0.01% Si0 2 ) can be estimated at about 4,900, - / t, while iron oxide with about 0.05% Si0 2 , as is produced in conventional plants, is only available at around € 700 to € 950 / t.
• JP-PS 59-90688 For the treatment of silicate-containing water, a device and a method is known from JP-PS 59-90688, in which the silicate-containing raw water is passed through two filter stages, the first filter stage containing a microporous membrane or an ultrafilter membrane, and the second filter stage a reverse osmosis membrane having.
• This method detects microparticles in water with a maximum size of one micrometer, and it is therefore not to be expected that silica in its conventional form can be separated off with it, since it is present in particle sizes below 0.02 micrometers. Furthermore, there is no indication that this process could also be applicable to the decilification of pickling solutions with their high content of additional ingredients.
• the object of the present invention was therefore a process which allows the silicic acid contained in any inorganic aqueous solutions to be separated off in a relatively inexpensive manner while avoiding chemicals and labor. Another task was to use this as a basis to specify a simple process for the production of iron oxide, this iron oxide not exceeding the limit values for silica required by the electronics industry. This process should also be suitable for incorporation into existing processes for the regeneration of used pickling solutions, in which iron oxide is preferably obtained.
• the invention provides that the supplied to a cross-flow filter solution to be treated and at a temperature of 60 - 80 * C is passed through the filter - 90 * C, preferably 70th
• micellar structures The silica present in the aqueous solutions is replaced by the Conditions in the cross-flow filter, mainly the prevailing temperatures, converted into micellar structures. These poly eren ' structures are in hydrated form and are kept in suspension by electrostatic charges. Their diameter is several hundredths to tenths of a micron. This size of the micellar structures of the silica makes it also accessible for microfiltration.
• the range of microfiltration for separable particle sizes is between 0.02 and 10 micrometers.
• Membranes for such filters are now made from a wide variety of materials, with cellulose derivatives being used for biochemical applications and, on the other hand, for the technology of cross-flow filtration as used in the process according to the invention, mainly plastic membranes made of polypropylene, polyethylene or polysulfones are used. Hollow fibers, foamed glasses or porous ceramic materials can also be used.
• the principle of cross-flow filtration is also known per se for processing liquids with suspended or emulsified ingredients.
• the top layer of the filter cake on the filter element which is constantly increasing in the case of static filtration and reduces the filtrate flow, is prevented in cross-flow filtration by a shear stress gradient which acts transversely to the direction of filtration beyond the associated equilibrium state.
• This allows long-term filtration at high filtrate flows.
• the cover layer can be largely detached from the surface of the filter element and removed by periodic backwashing, ie brief reversal of the filtration process, whereby the original filtration performance is restored.
• Polypropylene membrane hoses allow an almost complete separation of the silica.
• the process according to the invention can be built into processes for the regeneration of used pickling solutions, the advantage here being that the iron oxide obtained from the pickling solution is largely free of silica and is therefore particularly suitable for the purposes of the electronics industry.
• an inorganic aqueous solution, in particular used pickling solution which predominantly contain dissolved iron and silica, is passed through a crossflow filter at a temperature of 60 to 90 ° C., preferably 70 to 80 ° C., and the permeate is then passed by spray roasting in the corresponding oxides with max. 0.01% silica is transferred.
• the concentrate is cyclically returned to the cross-flow filter. This permits a further increase in the separation efficiency of the filter with an increased degree of purity of the permeate.
• the solution to be prepared is subjected to a spray roasting in the spray roasting reactor 1 after passing through a preconcentrator 2 and the pre-flow container 3, which forms the pre-concentrator sump.
• the resulting solid reaction products, i. H. the metal oxides are drawn off by means of the discharge device 11, while the gaseous reaction products are preferably fed back to the preconcentrator 2 via an electrostatic filter 12.
• a line leads from the pre-concentrator 2, which can be from Lurji or Venturityp, to two droplet separators 4 and finally to absorber columns 5, 6, in which the pickling acid is recovered.
• the exhaust gas from these absorber columns 5, 6 is passed through two droplet separators 7 and then into the open.
• the on-center solution can also be fed to the crossflow filter 8 via a pump 31.
• a pump 81 is used for repeated circulation of the concentrate through said filter 8.
• two (or more) filter units (8a and 8b) can be arranged in series one behind the other.
• the cross flow filter was directly integrated into the concentrate circuit.
• the delivery rate in the concentrate circuit was 2,800 1 / h and the delivery rate in the filter was 2,000 1 / h.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Inorganic Chemistry (AREA)
• Compounds Of Iron (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Applications Claiming Priority (2)

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• 1991
  • 1991-05-13 AT AT0098191A patent/AT395408B/de not_active IP Right Cessation
• 1992
  • 1992-05-13 WO PCT/AT1992/000069 patent/WO1992020834A1/de not_active Ceased
  • 1992-05-13 KR KR1019930703423A patent/KR0138070B1/ko not_active Expired - Fee Related
  • 1992-05-13 CN CN 92104547 patent/CN1037705C/zh not_active Expired - Fee Related
  • 1992-05-13 JP JP4509113A patent/JP2810234B2/ja not_active Expired - Fee Related
  • 1992-05-13 EP EP19920909956 patent/EP0584146A1/de not_active Withdrawn
  • 1992-05-15 TW TW81103811A patent/TW222610B/zh active

Non-Patent Citations (1)

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