Method and apparatus for paper stock mixing
View Patent ↗A method of mixing paper stock, having improved outlet consistency, includes: (a) feeding liquid and feeding paper pulp into a vessel to form a mixture; (b) providing at least one counterflow impeller that is submerged in the mixture, the counterflow impeller being capable of simultaneously inducing both upward flow and downward flow; (c) rotating the counterflow impeller such that downward flow from the impeller is partially recirculated by upward flow from the impeller to form a mixing zone; (d) sensing a parameter of the mixture discharged from the vessel; and (e) controlling the feed rate of the liquid and the feed rate of the paper pulp in the feeding step (a) based on the sensing step (d). An apparatus for mixing of paper stock, having improved outlet consistency, includes a vessel for containing liquid and paper pulp, at least one counterflow impeller, and a feedback system for controlling outlet consistency.
1. A method of mixing of paper stock, having improved outlet consistency, comprising the steps of:
(a) feeding liquid and feeding paper pulp into a vessel to form a mixture;
(b) providing at least one counterflow impeller that is submerged in the mixture; the counterflow impeller being capable of simultaneously inducing both upward flow and downward flow;
(c) rotating the counterflow impeller such that downward flow from the impeller is partially recirculated by upward flow from the impeller to form a mixing zone;
(d) sensing a parameter of the mixture that is discharged from the vessel; and
(e) controlling the feed rate of the liquid and the feed rate of the paper pulp in the feeding step (a) based on the sensing step (d).
2. The method of claim 1 , wherein the at least one counterflow impeller of step (b) is two or three counterflow impellers that are mutually spaced apart, such that each impeller produces a substantially separate mixing zone upon rotating step (c).
3. The method of claim 1 , wherein the parameter of sensing step (d) is percent paper pulp by weight or a proxy for percent paper pulp by weight.
4. The method of claim 1 , wherein the paper stock mixture discharged from the vessel contains up to approximately 7% paper pulp by weight.
5. The method of claim 1 , wherein the at least one counterflow impeller has a diameter that is between approximately 70% and approximately 90% of the vessel diameter.
6. The method of claim 1 , wherein an uppermost one of the impellers is adapted to be adjacent to the mixture surface.
7. The method of claim 1 , wherein the speed of the tip of each impeller does not exceed approximately 3 m/s.
8. The method of claim 1 , wherein the vessel includes at least one water injection port.
9. The method of claim 1 , wherein the vessel is a primary machine chest or an unrefined stock chest.
10. The method of claim 1 , wherein the vessel includes:
a vertical orientation;
a top end; and
a bottom end; and the paper pulp enters the vessel near the top end and exits near the bottom end.
11. The method of claim 10 , wherein the at least one counterflow impeller has an axis of rotation that is substantially perpendicular to the vertical orientation of the vessel.
12. The method of claim 1 wherein the counterflow impeller has a first portion adapted for creating upward flow and a second portion adapted for creating downward flow.
13. The method of claim 12 wherein one of the first portion and the second portion is an inner portion of the impeller and the other one of the first portion and the second portion is an outer portion of the impeller.
14. An apparatus for mixing of paper stock, having improved outlet consistency, comprising:
a vessel for containing liquid and paper pulp;
at least one counterflow impeller, the counter flow impeller having a first portion adapted for creating upward flow and a second portion adapted for creating downward flow, said impeller:
adapted for submerging below the liquid and paper pulp surface; and
adapted for simultaneously inducing both upward flow and downward flow; and
a feedback system for controlling outlet consistency, comprising:
a sensor capable of determining a parameter of the mixture that is discharged from the vessel; and
a controller capable of adjusting the feed rate of the liquid and the feed rate of the paper pulp that enters the vessel.
15. The apparatus of claim 14 , wherein the at least one impeller is two or three counterflow impellers that are mutually spaced apart, such that each impeller is capable of producing a substantially separate mixing zone.
16. The apparatus of claim 14 , wherein the parameter is percent paper pulp by weight or a proxy for percent paper pulp by weight.
17. The apparatus of claim 14 , wherein the paper stock mixture discharged from the vessel contains up to approximately 7% paper pulp by weight.
18. The apparatus of claim 14 , wherein the at least one counterflow impeller has a diameter that is between approximately 70% and approximately 90% of the vessel diameter.
19. The apparatus of claim 14 , wherein an uppermost one of the impellers is adapted to be adjacent to the mixture surface.
20. The apparatus of claim 14 , wherein the speed of the tip of each impeller does not exceed approximately 3 m/s.
21. The apparatus of claim 14 , wherein the vessel includes at least one water injection port.
22. The apparatus of claim 14 , wherein the vessel is a primary machine chest or an unrefined stock chest.
23. The apparatus of claim 14 , wherein the vessel includes:
a vertical orientation;
a top end; and
a bottom end; and the paper pulp enters the vessel near the top end and exits near the bottom end.
24. The apparatus of claim 23 , wherein the at least one counterflow impeller has an axis of rotation that is substantially perpendicular to the vertical orientation of the vessel.
25. The apparatus of claim 14 wherein one of the first portion and the second portion is an inner portion of the impeller and the other one of the first portion and the second portion is an outer portion of the impeller.