Process for the manufacture of persalt particles

Details Process for the manufacture of persalt particles Process for the manufacture of persalt particles

1999-02-22

2001-07-31

Knode, Marian C. (Department: 1764)

Chemical apparatus and process disinfecting, deodorizing, preser

Physical type apparatus

Crystallizer

C422S224000, C422S225000, C422S226000, C422S227000, C422S252000

Reexamination Certificate

active

06267934

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for the manufacture of solid persalt particles.
The solid persalt particles obtained by the process are used in various types of industry as an active oxygen vehicle in the solid state and, in particular, in the detergents industry.
TECHNOLOGY REVIEW
Processes for the manufacture of persalts by crystallization from a supersaturated aqueous solution obtained by mixing concentrated solutions of hydrogen peroxide and of a water-soluble salt in a crystallizer have been known for a long time (U.S. Pat. No. 2,986,448). In this patent, it is also taught, as a variant, that it is possible to use another type of crystallizer, in which a supersaturated solution flows in a rising movement through a bed of crystals which are being formed and are growing, which makes it possible to carry out a certain classification of the particles (Oslo-type crystallizer, column 3, lines 9 to 12).
These known processes, however, have the disadvantage of providing persalts whose particle size distribution is still relatively broad and whose stability is not very high. Their operation under continuous conditions is, moreover, often made difficult by the deposition of crystals which become firmly attached to the walls of the equipment and come to form crusts which it is necessary to remove periodically.
The invention overcomes the disadvantages of the known processes by providing a process which makes it possible to obtain, under economic conditions, stable SPC with a narrow particle size distribution by means of a continuous process.
SUMMARY OF THE INVENTION
To this end, the invention relates to a continuous process for the manufacture of solid particles of at least one persalt of at least one alkali metal by reaction of a concentrated aqueous hydrogen peroxide solution with a concentrated aqueous solution of at least one salt of at least one alkali metal and crystallization of the persalt formed in a crystallizer-classifier, according to which the crystallizer contains a clarifying region surmounting a stirred region through which passes a rising stream of a supersaturated solution of persalt in which persalt particles move in the contrary direction to that of the solution, the crystallizer being arranged above a classifier in which the solid persalt particles are subjected to elutriation and gather in the lower part of the classifier, where they are drawn off.


REFERENCES:
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Perry's Chemical Engineer's Handbook, Sixth Edition, pp. 19-35 to 19-39, 1984.*
R.H. Perry: “Perry's Chemical Engineer's Handbook”. Sixth Edition, 1985, McGraw-Hill, New York, pp. 19-35 to 19-39.

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