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US 11,619,000 B2Granted
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 pulp mill, wherein an aqueous pulp mill liquor containing sulphides is diverted into a bioreactor and oxidized by means of sulphur-oxidizing microbes, thereby producing an aqueous suspension from which elemental sulphur can be separated as a precipitate and the residual solution may be directed to causticizing. Optionally, prior to oxidation in the bioreactor, the aqueous pulp mill liquor may be first stripped to obtain a gas stream containing H2S which is then scrubbed with a scrubbing solution to obtain an aqueous spent scrubbing solution containing sulphides, in which case the residual solution can be used to replenish the scrubbing solution.
Claims24
A method for adjusting S/Na-balance of a pulp mill, the method comprising:
- providing a sulphate pulp mill producing a gas comprising weak malodorous gas, the sulphate pulp mill comprising a recovery boiler producing an aqueous pulp mill liquor containing sulphides,
- diverting the aqueous pulp mill liquor containing sulphides from the recovery boiler into a bioreactor,
- oxidizing the aqueous pulp mill liquor containing sulphides in the bioreactor biologically in an oxidizing reaction by means of sulphur-oxidizing microbes, thereby producing 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.
2 more elements
A method for adjusting S/Na -balance of a pulp mill, the method comprising:
- providing a sulphate pulp mill producing a gas comprising weak malodorous gas, the sulphate pulp mill comprising a recovery boiler producing an aqueous pulp mill liquor containing sulphides,
- diverting the aqueous pulp mill liquor containing sulphides from the recovery boiler into a stripper,
- stripping the aqueous pulp mill liquor containing sulphides in the stripper with an acidic agent, thereby obtaining a gas stream containing H2S and a residual pulp mill liquor stream,
- scrubbing the gas stream containing H2S in a scrubber located downstream of the stripper with an aqueous scrubbing solution containing an alkaline agent, whereby at least some of the H2S reacts with the alkaline agent, thereby producing a residual gas stream and an aqueous spent scrubbing solution containing sulphides,
- oxidizing the aqueous spent scrubbing solution containing sulphides in a bioreactor biologically in an oxidizing reaction by means of sulphur-oxidizing microbes, thereby producing 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.
4 more elements
A system configured to adjust S/Na-balance of a pulp mill, the system comprising:
- one or more conduits connected to a sulphate pulp mill producing a gas comprising weak malodorous gas, the sulphate pulp mill comprising a recovery boiler producing an aqueous pulp mill liquor containing sulphides, the one or more conduits feeding the aqueous pulp mill liquor containing sulphides from the recovery boiler of the sulphate pulp mill into a bioreactor, the bioreactor configured to oxidize the aqueous pulp mill liquor with sulphur-oxidizing microbes, the bioreactor thereby configured to produce an aqueous suspension containing elemental sulphur,
- a sulphur separation unit located downstream of the bioreactor, the sulphur separation unit configured to produce a residual solution and a precipitate containing the elemental sulphur, and
- at least one conduit connected to the sulphate pulp mill to direct the gas comprising the weak malodorous gas from the pulp mill to the bioreactor, the at least one conduit being configured to aerate the bioreactor with the gas comprising the weak malodorous gas.
A system arranged to adjust the S/Na-balance of a pulp mill, the system comprising:
- one or more conduits connected to a sulphate pulp mill producing a gas comprising weak malodorous gas, the sulphate pulp mill comprising a recovery boiler producing an aqueous pulp mill liquor containing sulphides, the one or more conduits feeding the aqueous pulp mill liquor containing sulphides into a stripper, the stripper being configured to strip the aqueous pulp mill liquor with an acidic agent, thereby producing a gas stream containing H2S and a residual pulp mill liquor stream,
- a scrubber located downstream of the stripper, the scrubber being configured to scrub the gas stream containing H2S with an aqueous scrubbing solution containing an alkaline agent, thereby producing a residual gas stream and an aqueous spent scrubbing solution containing sulphides,
- one or more conduits configured to conduct the aqueous spent scrubbing solution containing sulphides into a bioreactor, the bioreactor being located downstream of the scrubber, the bioreactor being configured to oxidize the aqueous spent scrubbing solution containing sulphides with sulphur-oxidizing microbes, the bioreactor thereby being configured to produce 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, and
- at least one conduit connected to the sulphate pulp mill to direct the gas comprising the weak malodorous gas from the pulp mill to the bioreactor, the at least one conduit being configured to aerate the bioreactor with the gas comprising the weak malodorous gas.
2 more elements
Dependencies are inferred from the claim text.