Liquid purification or separation – Processes – Chemical treatment
Patent
1997-01-21
1998-06-09
McCarthy, Neil
Liquid purification or separation
Processes
Chemical treatment
210761, 210908, G02F 172
Patent
active
057628092
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for the chemical oxidative treatment of a medium containing organic constituents.
TECHNOLOGY REVIEW
A medium containing organic constituents is taken to mean, e.g. sludges which arise in biological cleanup of wastewater. For example, primary sludge arises in sewage treatment plants, which is formed in a primary sedimentation of the wastewater. In addition, excess sludge is formed in the biological cleanup stage of the sewage treatment plant. Finally, digested sludge further arises in digestion towers of sewage treatment plants. Usually, these sludges are disposed of by landfilling them, incinerating them or spreading them on fields. However, the landfill space available is in increasingly short supply, as a result of which this method of disposal is constantly becoming more expensive. Incineration of the sludges requires high energy expenditure. Moreover, pollutants are released into the environment by the exhaust air in this method. Spreading on fields is also problematical, since there is the risk of contaminating the soils with heavy metals.
In the present patent application, media containing organic constituents, in addition to sludges from sewage treatment plants, are also taken to mean waste-waters, landfill leachate waters, soils contaminated by organic pollutants etc. For example, polluted soil can be slurried with water and treated in a similar manner to sewage sludge.
A known process for degrading the organic constituents of such media by a chemical oxidative route is so-called wet oxidation. Wet oxidation is taken to mean the reaction of (atmospheric) oxygen with organic compounds in an aqueous phase at temperatures of 150.degree.-370.degree.C. and pressures in the range of 10-220 bar. Such a process is described, for example, in DE-B2-27 28 554. However, because of the high temperatures and pressures required, the conventional processes for wet oxidation result in high capital and operating costs. In processes for wet oxidation which operate in the lower temperature range of 150.degree.-175.degree. C. and at pressures of 10-20 bar, in addition a catalyst must be added and the pH must be decreased to 0.5-1.5, in order to make the oxidation reactions possible. Moreover, in these low-pressure processes, complete oxidation of the organic constituents is not obtainable, which requires an additional downstream treatment process.
SUMMARY OF THE INVENTION
The object underlying the present invention is to provide a process by which media containing organic constituents can be disposed of in an economical manner in an as environmentally friendly manner as possible.
DETAILED DESCRIPTION OF THE INVENTION
This object is achieved according to the invention by the fact that first preset low temperature range and kept in this temperature range for a first preset treatment duration, a second preset low temperature range and pressurized at a pressure within a preset low pressure range and kept in this temperature and pressure range for a second preset treatment duration, an oxygen-containing gas being introduced into the medium at least intermittently, and process step, hydrogen peroxide is added to the medium.
Low temperature and pressure ranges in the context of the present invention are taken to mean those temperature and pressure ranges which are considered low in comparison to the temperatures and pressures conventionally used in chemical oxidative processes. Accordingly, the low temperatures and pressures intended in the two process steps lie below or at most in the lower third of the temperature and pressure ranges of 150.degree.-370.degree. C. and 10-220 bar conventional in wet-oxidation processes.
Preferably, the upper and lower limits of the temperature range preset in the first process step are below the upper and lower limits respectively of the temperature range preset in the second process step.
Thus, in the first process step, a temperature range of approximately 70 to approximately 180.degree. C. and a treatment duration of at le
REFERENCES:
patent: 3649534 (1972-03-01), Schotte
patent: 4155848 (1979-05-01), Sato et al.
patent: 4221661 (1980-09-01), Shimizu et al.
patent: 5364538 (1994-11-01), Stultz et al.
Baur Karl
Gregor Karl-Heinz
Luft Gerhard
Schwarz Hermann
Yadegardjam Farsin
McCarthy Neil
Solvay Interox (Societe Anonyme)
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