# US 5,705,032 A · Black liquor viscosity control > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,705,032 A - Document ID: US5705032A - Status: Granted - Kind: A - Application number: 08/605,865 - Filed: 1996-02-23 - Granted: 1998-01-06 - Earliest claimed: 1995-02-23 - Assignees: Thor Technology Corporation - Inventors: John N. Harbinson; David Todd R. Ellenor - Web page: https://patentgrep.com/patent/US5705032A ## CPC - D21C 11/10: Concentrating spent liquor by evaporation (evaporators B01D) - D21C 11/12: Combustion of pulp liquors - D21C: PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR ## Abstract Black liquor is subjected to high shear to cause a breakdown of macromolecules contained therein and provide a reduction in viscosity, thereby improving the processability of the black liquor and enabling the solids content to be increased. ## Claims ### Claim 1 A process of controlling the viscosity of black liquor from a pulping operation, which comprises subjecting the black liquor to physical conditions to effect shearing of black liquor macromolecules to decrease their molecular size and produce a decrease in viscosity of the black liquor of at least about 5%. ### Claim 2 (depends on 1) The process of claim 1 wherein said black liquor has a concentration of about 15 to about 90 wt%. ### Claim 3 (depends on 2) The process of claim 2 wherein said black liquor has a concentration of about 40 to about 80%. ### Claim 4 (depends on 3) The process of claim 3 wherein said black liquor is subjected to said physical conditions at an elevated temperature of about 75.degree. to about 300.degree. C. ### Claim 5 (depends on 4) The process of claim 4 wherein the elevated temperature is about 140.degree. to about 200.degree. C. ### Claim 6 (depends on 1) The process of claim 1 wherein said decrease in viscosity is effected by multiple ones of the shearing steps. ### Claim 7 (depends on 1) The process of claim 1 wherein the alkalinity of the black liquor is controlled to a value of at least about 2% following shearing of the black liquor. ### Claim 8 (depends on 1) The process of claim 1 which is carried out in the presence of a catalyst for degradation of said macromolecules under shear conditions. ### Claim 9 A process of controlling the viscosity of black liquor from a pulping operation, which comprises subjecting the black liquor to physical conditions by passing the black liquor through a gap between a rotor and stator of a high shear mixer operating at a peripheral velocity of rotor of at least about 10 m/s with a gap between the rotor and stator at less than about 1 mm to effect shearing of black liquor macromolecules to decrease their molecular size and produce a decrease in viscosity of the black liquor of at least about 5%. ### Claim 10 (depends on 9) The process of claim 9 wherein said peripheral velocity is at least about 15 m/s and the gap is less than about 0.6 mm. ### Claim 11 A process of decreasing the viscosity of black liquor from a pulping operation, which comprises: providing a concentrated black liquor from the pulping of hardwood or softwood pulps having a solids content of about 40 to about 85 wt%, heating said concentrated black liquor to a temperature of about 75.degree. to about 300.degree. C., passing said concentrated black liquor through a high shear zone wherein macromolecules in said concentrated black liquor are subjected to physical conditions of high shear to effect, in a gap between a rotor and a stator of a high shear mixer operating at a peripheral velocity of rotor of at least about 10 m/s with the gap between rotor and stator of less than about 1 mm, molecular size reduction and achieve a decrease in viscosity of said concentrated black liquor of at least about 5%, and recovering the treated black liquor having decreased viscosity. ### Claim 12 (depends on 11) The process of claim 11 wherein said temperature is about 140.degree. to about 200.degree. C. ### Claim 13 (depends on 11) The process of claim 11 wherein said peripheral velocity is at least about 15 m/s and said gap is less than about 0.6 mm. ### Claim 14 (depends on 13) The process of claim 13 wherein said gap is about 0.2 to about 0.4 mm. ### Claim 15 (depends on 11) The process of claim 11 wherein the black liquor has an alkalinity which is controlled to a value of at least about 2% following shearing of the black liquor. ### Claim 16 (depends on 15) The process of claim 15 wherein said alkalinity is about 2.5 to about 4%. ### Claim 17 (depends on 11) The process of claim 11 which is carried out in the presence of a catalyst for molecular size reduction. ### Claim 18 (depends on 11) The process of claim 11 including the subsequent step of concentrating the recovered black liquor and repeating the process on the concentrated black liquor. ### Claim 19 (depends on 11) The process of claim 11 wherein multiple ones of said shearing steps is effected. ### Claim 20 A process for decreasing the viscosity of black liquor from a pulping operation, which comprises processing the black liquor in equipment primarily intended to shear molecules for a time and at a temperature sufficient to effect a decrease in viscosity. ### Claim 21 (depends on 20) The process of claim 20 wherein said equipment comprises a high shear mixer comprising a rotor and a stator and said processing is effected by passing the black liquor through a gap between a rotor and stator. ### Claim 22 (depends on 20) The process of claim 20 wherein said black liquor has a concentration of about 40 to about 85% and said processing is effected at a temperature of about 140.degree. to about 200.degree. C. for a time sufficient to effect a decrease in viscosity of at least about 5%. ### Claim 23 A process for decreasing the viscosity of black liquor from a pulping operation, which comprises processing the black liquor in equipment primarily intended to shear molecules and comprises a high shear mixer comprising a rotor and a stator by passing the black liquor through a gap between the rotor and stator wherein said high speed mixer is operated at a peripheral rotor velocity of at least about 10 m/s with a gap between rotor and stator of less than about 1 mm. ### Claim 24 (depends on 23) The process of claim 23 wherein said rotor velocity is at least about 15 m/s and said gap is less than about 0.6 mm. ### Claim 25 (depends on 24) The process of claim 24 wherein slid gap is about 0.2 to about 0.4 mm.