US 12,331,460 B2
Method of replacing sodium losses in a pulp mill, a method of producing bleached cellulosic pulp, and a system
Ari Poukka, Metsä (FI); and Veli-Pekka Tervola, Helsinki (FI)
Assigned to Metsä Fibre Oy, Metsä (FI); and Andritz Oy, Helsinki (FI)
Appl. No. 17/430,737
Filed by Metsä Fibre Oy, Metsä (FI); and Andritz Oy, Helsinki (FI)
PCT Filed Feb. 13, 2020, PCT No. PCT/FI2020/050092
§ 371(c)(1), (2) Date Aug. 13, 2021,
PCT Pub. No. WO2020/165504, PCT Pub. Date Aug. 20, 2020.
Claims priority of application No. 20195108 (FI), filed on Feb. 13, 2019.
Prior Publication US 2022/0106737 A1, Apr. 7, 2022
Int. Cl. D21C 11/00 (2006.01); D21C 9/14 (2006.01)
CPC D21C 11/0078 (2013.01) [D21C 9/142 (2013.01); D21C 11/0057 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method of replacing with sodium make-up chemicals sodium losses caused by outflows in a pulp mill which employs a kraft process for producing cellulosic pulp, wherein the pulp mill includes a unit for conversion of sulphurous compounds, which is fed with sulphurous substances of the kraft process to convert said sulphurous substances into oxidized sulphurous compounds, said method comprising:
using sodium sulphate together with other sodium salts to achieve an essentially sodium hydroxide-free feed of sodium make-up chemicals,
wherein at least a part of the sulphur contained in the sodium make-up chemicals is used for producing oxidized sulphurous compounds in said unit for conversion of sulphurous compounds and,
wherein a majority of the other sodium salts comprises sodium carbonate.