US 11,807,657 B2
Process for isolating lignin from an alkaline process stream
Marlene Kienberger, Graz (AT); Matthaeus Siebenhofer, Graz (AT); and Thomas Michael Pichler, Gabersdorf (AT)
Assigned to PAPIERHOLZ AUSTRIA GMBH, St. Gertraud (AT)
Appl. No. 17/251,232
Filed by PAPIERHOLZ AUSTRIA GMBH, St. Gertraud (AT)
PCT Filed Jun. 12, 2019, PCT No. PCT/EP2019/065396
§ 371(c)(1), (2) Date Dec. 11, 2020,
PCT Pub. No. WO2019/238783, PCT Pub. Date Dec. 19, 2019.
Claims priority of application No. A 175/2018 (AT), filed on Jun. 15, 2018.
Prior Publication US 2021/0261590 A1, Aug. 26, 2021
Int. Cl. C07G 1/00 (2011.01); B01J 19/24 (2006.01); D21C 11/00 (2006.01)
CPC C07G 1/00 (2013.01) [B01J 19/244 (2013.01); D21C 11/0007 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A process for isolating lignin from an alkaline process stream of thickened black liquor, comprising introducing the alkaline process stream continuously into a lower region of at least one circulation reactor having an interior with an inner tubular reactor zone and an outer tubular reactor zone in a concentric arrangement so that a liquid level of the alkaline process stream in the interior of the at least one circulation reactor is chosen at a level with an upper end of the inner tubular reactor zone which level is higher than the liquid level of the outer tubular reactor zone and therefore prevents foaming; continuously blowing a CO2-containing gas from the lower region into the inner tubular reactor zone of the at least one circulation reactor, so that the CO2-containing gas is absorbed by the alkaline process stream in the at least one inner circulation reactor zone and offgas is drawn off together with residual amounts of the CO2-containing gas at the top of the at least one circulation reactor; running the process at ambient pressure of 1 atm, and drawing off a thickened black liquor with a reduced lignin content together with precipitated lignin present therein after settling at a base of the at least one circulation reactor.