PROCESS FOR REMOVAL OF SOLID NONIFIBROUS MATERIAL FROM PULP
The present invention relates to a process for removal of solid non-fibrous material from an aqueous pulp suspension comprising providing an aqueous pulp suspension comprising solid non-fibrous material, removing at least part of the solid non-fibrous material from the aqueous pulp suspension thereby forming an aqueous pulp suspension depleted in solid non-fibrous material, dewatering the aqueous pulp suspension depleted in solid non-fibrous material thereby forming a web comprising cellulose-containing fibres and a filtrate comprising residual solid non-fibrous material removing at least part of the residual solid non-fibrous material from the filtrate thereby forming a filtrate depleted in residual solid non-fibrous material and an aqueous stream comprising at least part of the removed residual solid non-fibrous material and diluting the aqueous pulp suspension and/or the aqueous pulp suspension depleted in solid non-fibrous material with at least part of the filtrate depleted in residual solid non-fibrous material, whereby the aqueous stream comprising at least part of the removed residual solid non-fibrous material is purged from the system.
1 . A process for removal of solid non-fibrous material from an aqueous pulp suspension comprising the steps of: providing an aqueous pulp suspension comprising solid non-fibrous material, removing at least part of the solid non-fibrous material from the aqueous pulp suspension thereby forming an aqueous pulp suspension depleted in solid non-fibrous material, dewatering the aqueous pulp suspension depleted in solid non-fibrous material thereby forming a web comprising cellulose-containing fibers and a filtrate comprising residual solid non-fibrous material, removing at least part of the residual solid non-fibrous material from the filtrate thereby forming a filtrate depleted in residual solid non-fibrous material and an aqueous stream comprising at least part of the removed residual solid non-fibrous material, and diluting at least one of the aqueous pulp suspension and the aqueous pulp suspension depleted in solid non-fibrous material with at least part of the filtrate depleted in residual solid non-fibrous material, whereby the aqueous stream comprising at least part of the removed residual solid non-fibrous material is purged from the system.
2 . The process according to claim 1 , wherein the process is integrated in a pulping process.
3 . The process according to claim 1 , wherein the pulp of the aqueous pulp suspension has a content of cellulose above about 85% by weight based on total oven dry pulp.
4 . The process according to claim 1 , wherein the pulp has a kappa number of below about 35.
5 . The process according to claim 1 , wherein the consistency of the aqueous pulp suspension is at least about 2.0% by weight based oven dry matter to total weight of pulp suspension.
6 . The process according to claim 1 , wherein the concentration of solid non-fibrous material in the web of cellulose-containing fibers is below about 50 ppm by weight based on total weight oven dry web of cellulosic web.
7 . The process according to claim 1 , wherein the consistency of the filtrate is below about 0.25%.
8 . The process according to claim 1 , wherein the removal of residual solid non-fibrous material from the filtrate is achieved by a process separating solid material from a liquid based on the ratio of centripetal force to fluid resistance.
9 . The process according to claim 1 , wherein the removal of solid non-fibrous material from the aqueous pulp suspension is achieved by a process separating solid material from a liquid based on the ratio of centripetal force to fluid resistance.
10 . The process according to claim 1 , wherein the removal of solid non-fibrous material and residual solid non-fibrous material is achieved by a multistage hydrocyclone system.
11 . The process according to claim 1 , wherein the average particle size of the solid non-fibrous material is below about 1 mm.
12 . The process according to claim 1 , wherein the solid non-fibrous material is silica-based material.
13 . The process according to claim 1 , wherein the consistency of the aqueous pulp suspension after dilution with the filtrate depleted in residual non-fibrous material is from about 0.5 up to about 3.0%, by weight of oven dry matter to total weight of pulp suspension.
14 . The process according to claim 1 , wherein at least part of the pulp of the aqueous pulp suspension originates from recycled paper or board or mixtures thereof.
15 . Pulp comprising less than about 50 ppm of silica-based material, calculated as Si0 2 , by weight based on total oven dry pulp obtainable by a process for removal of solid non-fibrous material from an aqueous pulp suspension comprising the steps of: providing an aqueous pulp suspension comprising solid non-fibrous material, removing at least part of the solid non-fibrous material from the aqueous pulp suspension thereby forming an aqueous pulp suspension depleted in solid non-fibrous material, dewatering the aqueous pulp suspension depleted in solid non-fibrous material thereby forming a web comprising cellulose-containing fibers and a filtrate comprising residual solid non-fibrous material, removing at least part of the residual solid non-fibrous material from the filtrate thereby forming a filtrate depleted in residual solid non-fibrous material and an aqueous stream comprising at least part of the removed residual solid non-fibrous material, and diluting at least one of the aqueous pulp suspension and the aqueous pulp suspension depleted in solid non-fibrous material with at least part of the filtrate depleted in residual solid non-fibrous material, whereby the aqueous stream comprising at least part of the removed residual solid non-fibrous material is purged from the system.