A method for controlling discharges of nitrogen compounds in the production of cellulose carbamate (CCA). Dissolving pulp (DP) or kraft pulp is produced at a pulp mill, and the DP or kraft pulp is activated. The activated pulp is reacted with urea to produce cellulose carbamate whereby ammonia is released. The cellulose carbamate production is integrated into the pulp mill having a flue gas system such that carbon dioxide from the flue gases is reacted with released ammonia to produce urea, which is used in the carbamate production.

A method for controlling discharges of nitrogen compounds in the production of cellulose carbamate (CCA). Dissolving pulp (DP) or kraft pulp is produced at a pulp mill, and the DP or kraft pulp is activated. The activated pulp is reacted with urea to produce cellulose carbamate whereby ammonia is released. The cellulose carbamate production is integrated into the pulp mill having a flue gas system such that carbon dioxide from the flue gases is reacted with released ammonia to produce urea, which is used in the carbamate production.

A method of producing chemical pulp including at least the following steps: a) wood chips or other comminuted ligno-cellulosic fibrous material is treated with a polysulfide-containing cooking liquor in an impregnation stage at a temperature of 90-145° C., and b) slurry of fibrous material from step a) is heated into cooking temperature and cooked for producing pulp having a desired kappa number. After step a) mercaptide ions are added into the slurry of fibrous material and the fibrous material is treated at cooking temperature in step b).

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 specification relates to a method and a system for adjusting pH of green liquor dregs. The method comprises contacting a slurry containing green liquor dregs (100, 200, 300, 400, 500) with flue gas (101, 201, 301, 401, 501). The system comprises a recovery boiler (105) configured to burn black liquor to produce smelt, a smelt dissolving tank (107) configured to dissolve the smelt to produce green liquor comprising green liquor dregs, and a green liquor clarifier/filter (103) and/or a dregs filter (104) configured to separate a slurry containing green liquor dregs (100, 200, 300, 400, 500) from the green liquor. The system further comprises a vessel (102, 202, 302, 402) configured to receive a slurry containing green liquor dregs (100, 200, 300, 400, 500) and a gas inlet (210, 310, 410, 510) configured to convey flue gas (101, 201, 301, 401, 501) to be contacted with the slurry containing green liquor dregs (100, 200, 300, 400, 500).

The present invention relates to a process for treating a feedstock containing tall oil, the process including separation of a light stream from the feedstock, followed by removal of a heavy fraction from the feedstock , in which process the separation of the light stream from the feedstock a fractionator is used and at least one product is collected from the light stream . The invention also relates to an apparatus for use in the process and use of a fractionator in dehydration of a feedstock containing tall oil.

The present invention relates to a process for treating a feedstock containing tall oil, the process including separation of a light stream from the feedstock, followed by removal of a heavy fraction from the feedstock , in which process the separation of the light stream from the feedstock a fractionator is used and at least one product is collected from the light stream . The invention also relates to an apparatus for use in the process and use of a fractionator in dehydration of a feedstock containing tall oil.

An excess heat recovery apparatus and process for high temperature chlorine dioxide bleaching of pulp is provided. The pulp of the high temperature chlorine dioxide bleaching stage enters a tube-side of a chlorine dioxide preheater through a pipeline. The low-temperature chlorine dioxide in the storage tank enters a shell-side pipeline of the chlorine dioxide preheater. 0.5 mol/L of a stabilizer may be added during preheating to prevent ClO.sub.2 from decomposing during the heating process. Preheated chlorine dioxide is then moved into a pulp mixer and the pH is adjusted to 3.2-3.8. The mixed pulp is then moved into a high temperature chlorine dioxide bleaching tower for bleaching. The cooling pulp, now out of the preheater, is washed in an alkaline extraction stage. The waste water from the washing flows directly into an effluent treatment system and is recycled after treatment.

An excess heat recovery apparatus and process for high temperature chlorine dioxide bleaching of pulp is provided. The pulp of the high temperature chlorine dioxide bleaching stage enters a tube-side of a chlorine dioxide preheater through a pipeline. The low-temperature chlorine dioxide in the storage tank enters a shell-side pipeline of the chlorine dioxide preheater. 0.5 mol/L of a stabilizer may be added during preheating to prevent ClO.sub.2 from decomposing during the heating process. Preheated chlorine dioxide is then moved into a pulp mixer and the pH is adjusted to 3.2-3.8. The mixed pulp is then moved into a high temperature chlorine dioxide bleaching tower for bleaching. The cooling pulp, now out of the preheater, is washed in an alkaline extraction stage. The waste water from the washing flows directly into an effluent treatment system and is recycled after treatment.