Jian C Jiang

US Patent:

53264339, Jul 5, 1994

Filed:

May 22, 1992

Appl. No.:

7/887004

Inventors:

Rolf Ryham - Roswell GA
James W. Smith - Toronto, CA
Jian E. Jiang - Glens Falls NY
Kaj Henricson - Kotka, FI

Assignee:

Ahlstrom Recovery Inc. - Roswell GA

International Classification:

D21C 1100

US Classification:

162 14

Abstract:

Paper pulp (e. g. kraft pulp) is produced utilizing at least two different supplies of cooking liquor, one having low sulfide content, and the other high sulfide content. The high sulfide content supply is typically used to impregnate the pulp or otherwise treat it first, while the second supply is used in other cooking stages (e. g. a digester), whether co-current or countercurrent. The different sulfur content liquors are obtained by heat treating (under pressure) black liquor to drive off sulfur compounds, and absorbing them into white liquor to produce a high sulfide stream. The low sulfide stream is made by conventional treatment of the black liquor after heat treating and evaporation. Utilizing multiple sulfide content supplies results in an optimum viscosity/kappa ratio and/or pulp strength properties for the pulp produced.