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 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.

Systems and techniques can be used to control malodorous emissions from pulp mills, such as Kraft pulp mills discharging sulfur and/or nitrogen-based compounds displeasing to persons living or working in areas neighboring the pulp mill. In some examples, one or more sensors are used to measure air characteristics around the pulp mill. Example sensors include wind sensors and gas sensors. The sensors can provide data indicating whether malodorous emissions will likely blow toward a population concentration area or away from a population concentration area and/or the indicating the concentration of a malodorous compound in the measured air. Control actions can be taken based on the measured sensor data, such as controlling delivery of an odor control agent to reduce or eliminate the malodorous emissions.

Systems and techniques can be used to control malodorous emissions from pulp mills, such as Kraft pulp mills discharging sulfur and/or nitrogen-based compounds displeasing to persons living or working in areas neighboring the pulp mill. In some examples, one or more sensors are used to measure air characteristics around the pulp mill. Example sensors include wind sensors and gas sensors. The sensors can provide data indicating whether malodorous emissions will likely blow toward a population concentration area or away from a population concentration area and/or the indicating the concentration of a malodorous compound in the measured air. Control actions can be taken based on the measured sensor data, such as controlling delivery of an odor control agent to reduce or eliminate the malodorous emissions.

A method for removing ammonia (NH.sub.3) from a gas produced in a pulp mill (100). The method comprises producing raw non-condensable gas comprising ammonia (NH.sub.3) in the pulp mill (100) and transferring at least some of the raw non-condensable gas to a scrubber (200) containing aqueous scrubbing solution (130, 140). The method comprises adding a compound capable of decreasing a pH of the scrubbing solution to the scmbbing solution (130, 140) and in the scrubber (200), contacting the raw non-condensable gas with the scmbbing solution (130, 140), to react the ammonia (NH.sub.3) of the raw non-condensable gas with the scmbbing solution to produce clean non-condensable gas and ammonium (NH.sub.4.sup.+). A pulp mill comprising equipment for performing the method.

A method for removing ammonia (NH.sub.3) from a gas produced in a pulp mill (100). The method comprises producing raw non-condensable gas comprising ammonia (NH.sub.3) in the pulp mill (100) and transferring at least some of the raw non-condensable gas to a scrubber (200) containing aqueous scrubbing solution (130, 140). The method comprises adding a compound capable of decreasing a pH of the scrubbing solution to the scmbbing solution (130, 140) and in the scrubber (200), contacting the raw non-condensable gas with the scmbbing solution (130, 140), to react the ammonia (NH.sub.3) of the raw non-condensable gas with the scmbbing solution to produce clean non-condensable gas and ammonium (NH.sub.4.sup.+). A pulp mill comprising equipment for performing the method.

Processes and systems for treating Kraft pulping foul condensate are provided. The processes comprise removing volatile compounds from the foul condensate to produce a resulting condensate and removing methanol from the resulting condensate. The systems comprise a volatile compound removal stage and a methanol removal stage downstream of and in fluid communication with the volatile removal stage.

Processes and systems for treating Kraft pulping foul condensate are provided. The processes comprise removing volatile compounds from the foul condensate to produce a resulting condensate and removing methanol from the resulting condensate. The systems comprise a volatile compound removal stage and a methanol removal stage downstream of and in fluid communication with the volatile removal stage.

According to an example aspect of the present invention, there is provided a method of removing volatile compounds from a lignin-containing material, the method comprising: providing a material comprising lignin and volatile compounds; treating the material by a distillation method in order to vaporize at least a part of the volatile compounds.

According to an example aspect of the present invention, there is provided a method of removing volatile compounds from a lignin-containing material, the method comprising: providing a material comprising lignin and volatile compounds; treating the material by a distillation method in order to vaporize at least a part of the volatile compounds.