Liquid purification or separation – Processes – Treatment by living organism
Patent
1997-01-23
1999-09-28
Woo, Jay H.
Liquid purification or separation
Processes
Treatment by living organism
210631, 210750, 95169, 95181, 4235766, 4235767, C02F 328
Patent
active
059582383
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for anaerobic removal of a sulphur compound from waste water containing said compound, said method comprising the steps of system in a by-pass channel, said channel comprising a stripper system for stripping the sulphide from the effluent, transporting gas in the stripper system, and
BACKGROUND OF THE INVENTION
Anaerobic biological treatment of waste waters containing sulphates enables the quantitative conversion into sulphide. If the sulphide formed can be converted into useful by-products which can be removed from the liquid, the salt load of waste waters containing sulphate can be decreased dramatically. Application of this technology is of great interest in those cases where sulphates and sulphites are emitted by waste waters resulting from industrial processes, flue gas treatment, leachates etc.
In FR-A-2 484 990 a method is disclosed for stripping of hydrogen sulphide in a by-pass of the anaerobic reactor using biogas that is circulated between a stripper and a desulphurizing apparatus. If however this method will be applied for alkaline waste waters, the pH of the reactor liquid will rise beyond optimum values (for methanogenesis as well as for H.sub.2 S stripping) due to release of carbon dioxide as a consequence of a selective hydrogen sulphide removal. The pH-value of the reactor/stripper circulation liquid will rise if carbon dioxide leaves the system. This will occur in case large amounts of carbon dioxide are removed via the desulphurising apparatus, leading to an important release of carbon dioxide in the stripper. In the publication cited, a release of carbon dioxide is described.
SUMMARY OF THE INVENTION
It is a purpose of the present invention to provide a method for removal of sulphur compounds from waste water, especially waste water being polluted with sulphates in higher concentrations (>500 g S/m.sup.3). In the latter case, recovery of the sulphur compounds might be very attractive.
This purpose is reached in a method of the type mentioned above, in which according to the invention the sulphide is absorbed from the transporting gas in an absorber system by an absorbing liquid, which absorbing liquid is passed in a closed loop through the absorber system, and the transporting gas is passed in a closed loop through the stripper system and the absorber system.
Passing the absorbing liquid in a closed loop through the absorber system provides an effective way of preventing carbon dioxide being released in the step of converting the sulphide into sulphur.
Preferably, the absorbing liquid is passed through a regenerator system and comprises a regenerable redox liquor.
It is preferred that the redox liquor has a pH-value in the range 4 to 7. More preferred, the pH-value is about 6.5.
In an H.sub.2 S absorber in which a regenerable redox liquid having the pH-value as specified is circulated as the absorbing liquid, absorption of carbon dioxide is prevented, whereas oxidation of the sulphide to sulphur can effectively take place.
It was found that the sulphide is well converted by a redox liquor containing a transition metal complex, for example an iron(III)hexacy-anoferrate. Sulphide oxidation by means of a transition metal complex according to the invention is followed by electrode potential controlled electrochemical regeneration of the transition metal complex.
In an embodiment of the invention the sulphide is converted by means of a redox liquor containing a chelated iron, the chelating agent being preferably ethylenediamine tetra-acetic acid (EDTA), having a concentration in the range 0.01-0.1 M, preferably 0.05 M.
It was found that, according to the invention, glycerol, if added to the redox liquor, for example in a suspension of 50 g/l, stabilizes the redox liquor by preventing the occurrence of free radical reactions. Alternatively, suspensions of MnO.sub.2 (e.g. 1 g/l) or MnCl.sub.2.7H.sub.2 O (e.g. 5 g/l) have been found effective in preventing free radical reactions.
It was further found that biological degradation
REFERENCES:
patent: 3754376 (1973-08-01), Kent
patent: 4076621 (1978-02-01), Hardison
patent: 4614588 (1986-09-01), Li
patent: 4735723 (1988-04-01), Mulder
patent: 4774071 (1988-09-01), Jeffrey et al.
patent: 4871520 (1989-10-01), Olson et al.
patent: 5390278 (1995-02-01), Honna et al.
patent: 5422086 (1995-06-01), Bowman
patent: 5474682 (1995-12-01), Buisman
Hydrocarbon Processing, vol. 54, No. 2, Feb. 1975, Houston US pp. 93-95; Takeshi Kasai `Konox Process Removes H.sub.2 S`.
Morrison Betsey J.
Nederlandse Organisatie Voor Toegepast Natuurwetenschappelijk On
Woo Jay H.
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