Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
1999-06-21
2001-07-10
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S909000
Reexamination Certificate
active
06258281
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for breaking down aromatics in industrial wastewaters that contain small amounts of organic and inorganic nitrogen compounds by reaction with an ozone-containing oxygen stream at from about 40 to 70° C. and at a pH of from about 4 to 7.
BACKGROUND OF THE INVENTION
It is known from EP-A-378 994 that nitrobenzene synthesis wastewaters, which contain various aromatic compounds, in particular nitrophenols, can be purified solely by treatment with ozone at from 20 to 100° C., a pressure of from 1.5 to 10 bar and a pH of from 3 to 12, essentially from 7 to 9, to such an extent that the levels of the original impurities are lowered to below their detection limits.
However, this method is not entirely satisfactory, since the ozone consumption is still relatively high and consequently, because of the high energy requirements of ozone generation, the costs are too high; that is, some of the ozone decomposes without contributing to the breaking down of the aromatics.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a process which will maximize the proportion of ozone that contributes to breaking down the organic and inorganic nitrogen-based compounds.
SUMMARY OF THE INVENTION
It has been found, surprisingly, that this object is achieved in that combination of the following measures leads to an appreciably improved utilization of the ozone used:
a) industrial wastewaters that contain small amounts of aromatics
b) are treated in two stages with an oxygen stream that contains from about 5 to 8% by volume of ozone with thorough mixing by causing the wastewater to flow upward through two reaction zones, the overflow of the wastewater at the top of the first reaction zone entering the second reaction zone at the base, the purified wastewater being obtained at the top of the second reaction zone, the ozone-containing oxygen stream first entering at the base of the second reaction zone, and the waste gas obtained at the top of the second reactor being introduced at the base of the first reaction zone, and, furthermore, a gas containing less than about 0.2% by volume of ozone being at the top of the first reaction zone;
c) the breaking down is carried out in both the reaction zones at from about 40 to 70° C.;
d) the reaction is carried out essentially under atmospheric pressure;
e) the wastewater is introduced at the base of the first reaction zone with a pH of from about 4 to 7 and at the base of the second reaction zone with a pH that is lower by from about 2 to 3 units, or the wastewater is continuously operated between a pH of from about 4 to 7 throughout the ozonization, and
f) the purified wastewater, which is virtually completely free of organic constituents, is discharged without further biological treatment.
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Bittins Klaus
Niedbalski Edmund
Schnur Rudolf
Schuster Ludwig
Thurman Laurance
Barry Chester T.
BASF - Aktiengesellschaft
Nixon & Vanderhye P.C.
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