Method and a system for adjusting S/Na-balance of a pulp mill
AssigneeValmet Technologies Oy
InventorsRisto Hämäläinen, Seppo Tuominiemi
Life of this patent
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Abstract
The invention relates to a method and a system for adjusting S/Na-balance of a sulphate pulp mill, wherein a pulp mill CNCG stream containing sulphur compounds is first scrubbed with an aqueous scrubbing solution containing an alkaline agent, thereby producing an aqueous spent scrubbing solution containing sulphides, which is then oxidized in a bioreactor by means of sulphur-oxidizing microbes, thereby obtaining an aqueous suspension containing elemental sulphur from which the elemental sulphur can be separated as a precipitate and the residual solution may be used for replenishing the aqueous scrubbing solution.
Claims18
A method for adjusting S/Na-balance of a sulphate pulp mill, the method comprising:
- providing a sulphate pulp mill producing a pulp mill CNCG stream containing sulphur compounds and a gas comprising weak malodorous gas;
- transporting, via one or more conduits, the pulp mill CNCG stream containing sulphur compounds from the sulphate pulp mill into a scrubber,
- scrubbing the pulp mill CNCG stream containing sulphur compounds in the scrubber with an aqueous scrubbing solution containing an alkaline agent, whereby at least some of the sulphur compounds react with the alkaline agent, thereby producing a CNCG stream derivate and an aqueous spent scrubbing solution containing sulphides,
- introducing the aqueous spent scrubbing solution containing sulphides into a bioreactor located downstream of the scrubber,
- oxidizing the aqueous spent scrubbing solution containing sulphides in the bioreactor biologically in an oxidizing reaction by means of sulphur-oxidizing microbes, thereby obtaining an aqueous suspension containing elemental sulphur,
- separating the elemental sulphur from the aqueous suspension in a sulphur separation unit located downstream of the bioreactor, thereby obtaining a residual solution and a precipitate containing the elemental sulphur, and
- aerating the bioreactor with the gas comprising the weak malodorous gas, the weak malodorous gas being directed via at least one conduit connected to the pulp mill, from the pulp mill to the bioreactor.
A system configured to adjust S/Na-balance of a sulphate pulp mill, the system comprising:
- one or more conduits connected to a sulphate pulp mill producing a pulp mill CNCG stream containing sulphur compounds and a gas comprising weak malodorous gas, the one or more conduits feeding the pulp mill CNCG stream containing sulphur compounds from the sulphate pulp mill into a scrubber, the scrubber being configured to separate sulphur compounds from the pulp mill CNCG stream with an aqueous scrubbing solution containing an alkaline agent, thereby producing a CNCG stream derivate and an aqueous spent scrubbing solution containing sulphides,
- a bioreactor located downstream of the scrubber, the bioreactor being configured to oxidize the aqueous spent scrubbing solution with sulphur-oxidizing microbes, thereby producing an aqueous suspension containing elemental sulphur,
- a sulphur separation unit located downstream of the bioreactor, the sulphur separation unit being configured to produce a residual solution and a precipitate containing the elemental sulphur from the aqueous suspension, and
- at least one conduit connected to the sulphate pulp mill to direct the gas comprising the weak malodorous gas from the sulphate pulp mill to the bioreactor, the at least one conduit being configured to aerate the bioreactor with the gas comprising the weak malodorous gas from the pulp mill.
Dependencies are inferred from the claim text.