Chemistry: electrical and wave energy – Processes and products
Patent
1992-11-03
1995-02-21
Niebling, John
Chemistry: electrical and wave energy
Processes and products
C25B 122
Patent
active
053912667
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of regulating the throughput in the electrochemical regeneration of chromosulfuric acid by the metered addition of hot chromium (III ) sulfate solution containing sulfuric acid in continuously operated flow-type electrolysis cells.
2. Description of the Prior Art
It is known to convey the hot solution (hot chromium (III) sulfate solution), into stock containers disposed in an elevated position and to feed the electrolyte to the individual cell cascades from said stock containers by means of glass siphons and long flexible pipes. (cf. M. Kappel, Elektrolytische Regeneration von Chromsaure [Electrolytic Regeneration of Chromic Acid], Chem. Ing. Technik 35 (1963), 386-389). Said siphons are glass tubes bent in a U-shape and having an elongated limb which terminates with a capillary-type tapering of the glass tube diameter. The amount of liquid flowing through is dependent on the difference in height between the liquid level in the stock vessels and the end of the longer limb of the glass siphon, and also on the diameter of the capillary. If it is intended to alter the amount of liquid, the glass siphons have to be replaced by others having greater capillary diameter (for more passage of liquid) or smaller capillary diameter (for less passage of liquid).
This type of metered addition has a number of disadvantages: containing sulfuric acid are an accident risk in the event of leakages. fed to the electrolyte cells via long flexible pipes. Owing to entrained air and evolving gases, the flexible pipes have to be degassed in a suitable way. In addition, the gases can result in the breakdown of the liquid column in the glass siphon. electrolyte to be fed through has to be adapted by replacing the glass siphon. That requires some time and results in defects in the quality of the regenerated chromosulfuric acid. arriving from the montan wax bleaching often contains traces of wax which has not been separated off. Since the working temperature of the electrochemical regeneration (less than 100.degree. C.) is below the melting point of the wax, wax may deposit in the glass siphons and, in particular, in the capillaries of the glass siphons. This alters the diameter of the glass tubes and the amount of liquid flowing through, and consequently the quality of the final product (constant changes in concentration).
SUMMARY OF THE INVENTION
A process is furthermore known for the electrolytic regeneration of reduced chromium compounds in which the solution of the chromium compound to be regenerated is introduced continuously into the cathode chamber of an electrolytic cell containing a porous polytetrahaloethylene diaphragm, and is passed into the anode chamber through at least one opening in the diaphragm, and, after anodic oxidation of the chromium compound, the regenerated solution is removed from the anode chamber of the cell (cf. DE-A-1804956). The process operates virtually without pressure and has similar problems as described above.
There was therefore the object of finding a method which does not have the above defects.
It was found that the object can be achieved if the chromium (III) sulfate solution containing sulfuric acid is fed in under pressure, the amount of electrolyte fed in making it possible to produce a uniform product quality by controlling regulation.
The invention consequently relates to a method of regulating the throughput in the electrochemical regeneration of chromosulfuric acid by continuously feeding chromium (III) sulfate solution containing sulfuric acid to the electrolysis cells, comprising keeping the chromium (III) sulfate solution containing sulfuric acid under pressure in a closed pipe system and passing it through replaceable orifices in the cell feed lines into the anode chamber of the first cell in each case of a cell cascade, the amount of electrolyte fed into the cells being controlled via the pressure in the pipe system and the diameter of the opening in the orifices, and the level in the acid
REFERENCES:
patent: 3423300 (1969-01-01), Joo et al.
patent: 3450623 (1969-06-01), Joo et al.
patent: 3595765 (1971-07-01), Joo et al.
patent: 3761369 (1973-09-01), Tirrell
patent: 3909381 (1975-09-01), Ehrsam
patent: 4031001 (1977-06-01), Bosa
patent: 4557811 (1985-12-01), Furst et al.
Chemical Abstracts, Band 84, No. 10, Mar. 8, 1976, p. 513, Zusammenfassung Nr. 66896n, E. S. Letskikh et al.: "Electrochemical regeneration of chromium sulfate waste during oxidation (purification) of mineral was", & Khim. Tverd. Topl, 1976.
Chemical Abstracts, Band 87, No. 26, Dec. 26, 1977, p. 450, Zusammenfassung Nr. 208652t; & SU-A-574 482 (E. S. Letskikh et al.), Sep. 30, 1977.
Herbst Hans
Stenzel Jurgen
Hoechst Aktiengesellschaft
Mee Brendan
Niebling John
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