US 2012/0058545 A1 · METHOD OF TREATING AN OFF-GAS STREAM AND AN APPARATUS THEREFOR

Abstract

The present invention provides a method of treating an off-gas stream (80) comprising NH3 and H2S to provide a sulphate stream (910), the method comprising the steps of: (i) providing a first off-gas stream (80) comprising NH3, H2S, CO2 and optionally one or more of HCN, COS and CS2; (ii) passing the first off-gas stream (80) to an incinerator (300) to oxidise NH3, H2S, and optionally one or more of HCN, COS and CS2 to provide a second off-gas stream (310) comprising N2, H2O, SO2 and CO2; (iii) scrubbing the second off-gas stream (310) with a first aqueous alkaline stream (380, 876a) in a caustic scrubber (350) to separate SO2 and a part of the CO2 from the second off-gas stream to provide a spent caustic stream (360) comprising carbonate and one or both of sulphite and bisulphite and a caustic scrubber off-gas stream (370) comprising N2 and CO2; and (iv) passing the spent caustic stream (360) to an aerator (900) comprising sulphur-oxidising bacteria in the presence of oxygen to biologically disc sulphite and bisulphite to sulphate to provide a sulphate stream (910).

Claims12

Dependent claims

A method of treating an off-gas stream comprising NH3 and H2S to provide a sulphate stream, the method comprising the steps of:

(i) providing a first off-gas stream comprising NH3, H2S, CO2 and optionally one or more of HCN, COS and CS2;
(ii) passing the first off-gas stream to an incinerator to oxidise NH3, H2S, and optionally one or more of HCN, COS and CS2 to provide a second off-gas stream comprising N2, H2O, SO2 and CO2;
(iii) scrubbing the second off-gas stream with a first aqueous alkaline stream in a caustic scrubber to separate SO2 and a part of the CO2 from the second off-gas stream to provide a spent caustic stream comprising carbonate and one or both of sulphite and bisulphite and a caustic scrubber off-gas stream comprising N2 and CO2;
and
(iv) passing the spent caustic stream to an aerator comprising sulphur-oxidising bacteria in the presence of oxygen to biologically oxidise sulphite and bisulphite to sulphate to provide a sulphate stream.

2 more elements

An apparatus for treating an off-gas stream comprising H2S to provide a sulphate stream, comprising at least:

an incinerator to oxidise NH3, H2S, and optionally one or more of HCN, COS and CS2 in a first off-gas stream comprising NH3, H2S, CO2 and optionally one or more of HCN, COS and CS2 to provide a second off-gas stream comprising N2, H2O, SO2 and CO2, said incinerator having a first inlet for the first off-gas stream and a first outlet for the second off-gas stream;
a caustic scrubber to separate SO2 and a part of the CO2 from the second off-gas stream, said caustic scrubber having a first inlet for the second off-gas stream connected to the first outlet of the incinerator, a second inlet for a first aqueous alkaline stream and a first outlet for a spent caustic stream comprising carbonate and one or both of sulphite and bisulphite and a second outlet for a caustic scrubber off-gas stream comprising N2 and CO2;
an aerator comprising sulphur-oxidising bacteria in the presence of oxygen to oxidise sulphite and bisulphite to sulphate, said aerator having a first inlet for the spent caustic stream connected to the first outlet of the caustic scrubber, and a first outlet for the sulphate stream.

Dependencies are inferred from the claim text.

Method of treating an off-gas stream and an apparatus therefor

Life of this patent

Method of treating an off-gas stream and an apparatus therefor

Life of this patent

Abstract

Claims12