A process for isolating lignin from an alkaline process stream of thickened black liquor which is introduced continuously into a lower region of at least one circulation reactor having two reactor zones in concentric arrangement, liquid level of the alkaline process stream in the interior of the reactor is at a level with an upper end of an inner tubular reactor zone, a CO.sub.2-containing gas is blown continuously from the bottom into the inner tubular reactor zone of the reactor, wherein the CO.sub.2-containing gas is absorbed by the alkaline process stream in the inner circulation reactor zone and offgas is drawn off with residual amounts of the CO.sub.2 at the top of the reactor, the process is run at 1 atm, and thickened black liquor with a reduced lignin content together with precipitated lignin present are drawn off optionally after settling at the base of the reactor.

There is described a process for the recovering of inorganic chemicals of pulp and paper making processes (IC) and the production of biochemicals from black liquor (BL) using microwaves (MW) comprising: (a) filtration of BL to produce filtered BL, in a media, (b) drying of said filtered BL with MW in said media to produce dried BL, (c) pyrolysis of said dried BL with MW in said media to produce bio-oil, biogas, and solid residue, (d) recovering of said bio-oil, and (e) recovering of IC and biocarbon from said solid residue. The disclosed process does not require chemical additives compared to processes rely on precipitation of lignin to recover said IC. The disclosed process supports efficient, direct, and long-lasting reductions in greenhouse gas emissions and local air pollutants resulting from the current processes rely on burning BL in recovery boilers to recover said IC.

There is described a process for the recovering of inorganic chemicals of pulp and paper making processes (IC) and the production of biochemicals from black liquor (BL) using microwaves (MW) comprising: (a) filtration of BL to produce filtered BL, in a media, (b) drying of said filtered BL with MW in said media to produce dried BL, (c) pyrolysis of said dried BL with MW in said media to produce bio-oil, biogas, and solid residue, (d) recovering of said bio-oil, and (e) recovering of IC and biocarbon from said solid residue. The disclosed process does not require chemical additives compared to processes rely on precipitation of lignin to recover said IC. The disclosed process supports efficient, direct, and long-lasting reductions in greenhouse gas emissions and local air pollutants resulting from the current processes rely on burning BL in recovery boilers to recover said IC.

A method for removing hydrogen sulphide ions (HS.sup.−) from a liquor (300) of a pulp mill process, the method comprising pumping the liquor (300) to an injector arrangement (710) using a pump arrangement (720) such that the pumping of the liquor (300) through a jet nozzle (115) generates suction at a gas inlet (130), whereby reagent gas (310) is mixed with the liquor (300), and letting out the treated liquor (300) from the injector arrangement (710) to a vessel (200). In this way, the liquor (300) is treated to form at least partly treated liquor (300). A corresponding use of an injector arrangement. A system for performing the method.

A method for removing hydrogen sulphide ions (HS.sup.−) from a liquor (300) of a pulp mill process, the method comprising pumping the liquor (300) to an injector arrangement (710) using a pump arrangement (720) such that the pumping of the liquor (300) through a jet nozzle (115) generates suction at a gas inlet (130), whereby reagent gas (310) is mixed with the liquor (300), and letting out the treated liquor (300) from the injector arrangement (710) to a vessel (200). In this way, the liquor (300) is treated to form at least partly treated liquor (300). A corresponding use of an injector arrangement. A system for performing the method.

A method to purify black liquor soap (BLS) from sulfur compounds is disclosed. In the BLS desulfurization method, a BLS composition is heated in an inert atmosphere and sulfur is removed via aqueous extractions with inorganic base in the absence of other chemicals such as brine, sulfate salts and carbonate salts. The purified BLS composition exhibits favorable properties, including reduced sulfur content, lower color, and improved odor characteristics. The resulting tall oil compositions, depitched tall oil compositions, tall oil distillation fractions, and products derived therefrom also show reduced sulfur content, lower color, and improved odor characteristics.

Embodiments herein relate to a system (200; 300; 400; 500) for obtaining methanol from foul condensate (101) of a pulping process. The system (200; 300; 400; 500) comprises a primary stripper (102) arranged to strip the foul condensate (101) from pollutants, whereby a first methanol-containing condensate is obtained from the polluted stripper off gases (SOGs). The system (200; 300; 400; 500) also comprises a first acidification unit (202) arranged to acidify the first methanol-containing condensate. Further, the system (200; 300; 400; 500) comprises a secondary stripper (204) arranged to strip the acidified first methanol-containing condensate from pollutants to obtain a second methanol-containing condensate, and a distillation column (107) arranged to distil the second methanol-containing condensate from the secondary stripper (204) so as to obtain methanol. Embodiments herein also relate to a method performed in a system (200; 300; 400; 500) for obtaining methanol from foul condensate (101) of a pulping process.

The disclosure provides methods and compositions for reducing the viscosity of black liquor. Also provided are methods of inhibiting deposition of scale and methods of processing black liquor. In some embodiments, the compositions include a carboxylate-containing polymer and an inorganic salt. In some embodiments, the compositions include a carboxylate-containing polymer, an inorganic salt, and a surfactant.

A method and apparatus for protecting a furnace floor of a black liquor recovery boiler, where the furnace floor is covered by a protective layer, the protective layer being formed of a salt mixture including at least two different salts.

The invention relates to a process for isolation of hemicelluloses from biomass pulping process waters or spent liquors with removal of suspended solids, concentration of the product and purification of the product by removal of inorganic salts and low molecular weight substances. It is characterized in that the hemicellulose isolation process conditions at several separation/purification stages are adjusted separately by e.g. pH adjustment. The invention further relates to a plant for carrying out the process. With such process and plant it is possible to recover most of the suspended solids, especially xylan and other hemicelluloses.