The invention relates to a method for producing an oil rich fraction (OF) from primary feedstock (FS) that comprises water, first salt, second salt, and biomass. The feedstock (FS) is provided to a first reaction zone (Z1) of a conversion reactor (100), where it is allowed to react at a temperature of at least 350° C. in a pressure of at least 160 bar to form converted primary feedstock. The method comprises separating from the converted primary feedstock a first salt rich fraction (SF1), a second salt rich fraction (SF2), and an oil rich fraction (OF). The method comprises withdrawing the oil rich fraction (OF) from the first reaction zone (Z1) and withdrawing the first salt rich fraction (SF1) and the second salt rich fraction (SF2) from the conversion reactor (100). In the method the first salt rich fraction (SF1) comprises at least some of the first salt dissolved in the water, the second salt rich fraction (SF2) comprises at least some of the second salt in solid form, and at least one of the first salt and the second salt is a salt capable of catalysing the reaction of the biomass of the primary feedstock (FS) with the water of the primary feedstock (FS) to produce the oil rich fraction (OF). A device for the same.

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 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 application relates to a process to obtain fully oxidized white liquor from white liquor used in a Kraft pulp process. Said fully oxidized white liquor is suitable to be used in alkaline steps of certain stages of the Kraft pulp process fiberline in order to partly or totally substitute the purchased sodium hydroxide used in those stages. The presently disclosed process also allows to purge non-process elements (NPE's) by purging alkaline wash filtrates to a wastewater treatment plant.

The invention relates to a method for producing an oil rich fraction (OF) from primary feedstock (FS) that comprises water, first salt, second salt, and biomass. The feedstock (FS) is provided to a first reaction zone (Z1) of a conversion reactor (100), where it is allowed to react at a temperature of at least 350 C. in a pressure of at least 160 bar to form converted primary feedstock. The method comprises separating from the converted primary feedstock a first salt rich fraction (SF1), a second salt rich fraction (SF2), and an oil rich fraction (OF). The method comprises withdrawing the oil rich fraction (OF) from the first reaction zone (Z1) and withdrawing the first salt rich fraction (SF1) and the second salt rich fraction (SF2) from the conversion reactor (100). In the method the first salt rich fraction (SF1) comprises at least some of the first salt dissolved in the water, the second salt rich fraction (SF2) comprises at least some of the second salt in solid form, and at least one of the first salt and the second salt is a salt capable of catalysing the reaction of the biomass of the primary feedstock (FS) with the water of the primary feedstock (FS) to produce the oil rich fraction (OF). A device for the same.

The method and apparatus are for obtaining strong white liquor and lime mud with low residual alkali content from causticized liquor. The first filter (F.sub.WL) receives causticized liquor from causticizing vessels (CT.sub.1-CT.sub.2-CT.sub.3) and is designed as pressurized two stage disc filter with 2 separate vat parts. In the first vat part non-diluted white liquor is obtained as a filtrate from the causticized liquor. The first lime mud cake accumulated on the filter discs in the first vat part is scraped off and diluted before being fed to the second vat part. In the second vat part weak liquor is obtained as a filtrate from the re-slurried first lime mud cake. The second lime mud cake accumulated on the filter discs in the second vat part is washed before being scraped off and diluted before being fed to subsequent lime mud handling.

A process for recausticizing green liquor in a sulphate or Kraft process for wood pulp production, in which a green liquor consisting of an aqueous solution of sodium carbonate as the major component and sodium sulphide is admixed with calcium oxide in a slaker and undergoes a reaction in a recausticizer to form an aqueous suspension containing sodium hydroxide and calcium carbonate as the major components, which suspension is filtered on a first filter and subsequently, after dilution with water in a dilution vessel, is fed over further filters two or three times and filtered to separate solids suspended therein, characterized in that after a first separation of calcium carbonate as the major component and calcium oxide as the minor component, carbon dioxide is added to the aqueous suspension at least during dilution in a dilution vessel and in particular in the dilution vessel (s) upstream of a second and/or a third filter.

The invention is related to improved polysulfide production process wherein a specific second filtration process (F.sub.x) is installed before the polysulfide reactor (R.sub.c). According to the inventive method a cross flow filter (F.sub.x) is used as the second filtration process reaching astonishing low levels of residual solids in the white liquor as well as extended availability of the second filtration process. The subsequent polysulfide reactor, either in form of an electrolytic cell or in form of a bed of active carbon, could then also be operated at increased availability. The invention increases the production volume of polysulfide and the retentate from the cross filtering process may be bled out continuously to a process position ahead of a first filtering or clarification stage, capturing most of the increased content of lime mud particles in the retentate and causing less disturbance of the process with a minimum of tanks and pumps.