A method for burning primary fuel (F1), wherein the primary fuel (F1) comprises at least a first compound containing nitrogen and a second compound comprising sulfur. The method comprises producing primary combustion gas (G1) having a temperature of at least 450° C. and comprising oxygen; feeding the primary fuel (F1) and the primary combustion gas (G1) to a primary process zone (Z1) of a furnace (200); feeding tertiary combustion gas (G3) to a secondary process zone (Z2) of the furnace (200); letting the primary fuel (F1), the primary combustion gas (G1), and/or their reaction products to move from the primary process zone (Z1) via the secondary process zone (Z2) to a tertiary process zone (Z3) of the furnace (200); and feeding quaternary combustion gas (G4) comprising oxygen to the tertiary process zone (Z3) of the furnace (200). An embodiment comprises collecting the primary fuel (F1) from a pulp process. A corresponding system.

A method for burning primary fuel (F1), wherein the primary fuel (F1) comprises at least a first compound containing nitrogen and a second compound comprising sulfur. The method comprises producing primary combustion gas (G1) having a temperature of at least 450° C. and comprising oxygen; feeding the primary fuel (F1) and the primary combustion gas (G1) to a primary process zone (Z1) of a furnace (200); feeding tertiary combustion gas (G3) to a secondary process zone (Z2) of the furnace (200); letting the primary fuel (F1), the primary combustion gas (G1), and/or their reaction products to move from the primary process zone (Z1) via the secondary process zone (Z2) to a tertiary process zone (Z3) of the furnace (200); and feeding quaternary combustion gas (G4) comprising oxygen to the tertiary process zone (Z3) of the furnace (200). An embodiment comprises collecting the primary fuel (F1) from a pulp process. A corresponding system.

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.

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.

The present technology is directed to fluff pulps with improved odor control as well as methods of making such fluff pulps. A fluff pulp is provided that includes a bleached kraft fiber and a copper ion content from about 0.2 ppm to about 50 ppm by weight of the bleached kraft fiber. The bleached kraft fiber includes a length-weighted average fiber length of at least about 2 mm, a copper number of less than about 7, a carboxyl content of more than about 3.5 meq/100 grams; an ISO brightness of at least 80; and a viscosity from about 2 cps to about 9 cps.

The present technology is directed to fluff pulps with improved odor control as well as methods of making such fluff pulps. A fluff pulp is provided that includes a bleached kraft fiber and a copper ion content from about 0.2 ppm to about 50 ppm by weight of the bleached kraft fiber. The bleached kraft fiber includes a length-weighted average fiber length of at least about 2 mm, a copper number of less than about 7, a carboxyl content of more than about 3.5 meq/100 grams; an ISO brightness of at least 80; and a viscosity from about 2 cps to about 9 cps.

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.

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.

A method to optimize the chemical balance at a sulfate pulp mill, which produces at least pulp bleached with chlorine dioxide and has a chlorine dioxide plant using at least chlorate, methanol and sulfuric acid for making chlorine dioxide. The method includes: a) gases from the mill's concentrated non-condensable gas system are incinerated in order to form a gas containing sulfur dioxide, which is treated to produce concentrated sulfuric acid, and b) raw methanol from the mill processes is purified to produce methanol, and c) side streams containing sodium compounds and/or sulfur compounds produced by mill processes are used as make-up chemicals, wherein the production of chlorine dioxide uses the sulfuric acid produced in step a) and methanol purified in step b), with a sulfuric acid concentration of 94-99%, preferably 95-98%, and using in step c) sesquisulfate or sodium sulfate produced during the production of chlorine dioxide.

A method to optimize the chemical balance at a sulfate pulp mill, which produces at least pulp bleached with chlorine dioxide and has a chlorine dioxide plant using at least chlorate, methanol and sulfuric acid for making chlorine dioxide. The method includes: a) gases from the mill's concentrated non-condensable gas system are incinerated in order to form a gas containing sulfur dioxide, which is treated to produce concentrated sulfuric acid, and b) raw methanol from the mill processes is purified to produce methanol, and c) side streams containing sodium compounds and/or sulfur compounds produced by mill processes are used as make-up chemicals, wherein the production of chlorine dioxide uses the sulfuric acid produced in step a) and methanol purified in step b), with a sulfuric acid concentration of 94-99%, preferably 95-98%, and using in step c) sesquisulfate or sodium sulfate produced during the production of chlorine dioxide.