The invention discloses a process for treating black liquor comprising pyrolysing black liquor in a fluidized bed reactor to obtain solid particles and pyrolysed black liquor gas, heating the solid mass, returning the heated solid mass to the fluidized bed reactor for use in the pyrolysis reaction; condensing the pyrolysed black liquor gas to obtain a condensate and recover heat and a residual gas released during condensation for heating the solid mass to a predetermined temperature for that is required for the pyrolysis.

Disclosed is a process for reducing slag in a black liquor recovery boiler, the process comprising: injecting and burning black liquor in a boiler by contacting it with primary air and secondary air; introducing a slag-reducing chemical into the gases above the injection locations through interlaced, tangential or concentric secondary, tertiary, and/or quarternary air ports.

A process for the preparation of small aromatic compounds from black liquor comprising: providing black liquor that derives from alkaline treatment of wood chips; subjecting the black liquor to a pyrolysis treatment to yield a pyrolysed black liquor gas and a solid mass comprising char and salts in a first reactor, wherein the salts substantially derive from the treatment of black liquor; contacting at least part of the pyrolysed black liquor gas with a catalyst in a second reactor, which is different from the first reactor to provide a conversion treatment to yield a conversion product; and recovering small aromatic compounds from the conversion product.

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 for transforming a black liquor, comprising the following steps: a) supplying a black liquor, b) gasifying the black liquor by means of supercritical water gasification in the presence of a hydrogenated carbon-free fuel, by means of which reaction products are formed, c) cooling the reaction products, by means of which a gaseous mixture is obtained which comprises at least methane and a green liquor comprising at least sulphur in the form of NaHS, Na.sub.2S and H.sub.2S.

Scale build-up on metal surfaces of a black liquor evaporator is prevented or mitigated by treating the black liquor with a deposit inhibiting concentration of a water-soluble polymer containing a polycarboxylate chain and a 3-mercaptopropionic acid end group.

A process for depolymerization of lignin, the process including using at least one catalyst internal to a pulp mill for performing catalytic treatment and separation of biomass components into cellulose and lignin rich material is provided.

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.

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.

Compositions and methods for minimizing fouling and/or reducing the viscosity of black liquor in a Kraft pulping process are provided. An exemplary composition includes an anionic sulfate or sulfonate surfactant; an anionic sulfate or sulfonate dispersant; and a nonionic alkoxylated surfactant.