Device and method for treating green liquor

1 . A method for treating green liquor in a green liquor treatment arrangement, the method comprising:

providing the green liquor treatment arrangement, which comprises:

a flocculation device,

a clarifying vessel,

an inlet conduit that extends from the flocculation device to the clarifying vessel, and

a first flocculation measuring device located directly in a path of the inlet conduit that extends from the flocculation device to the clarifying vessel;

in the flocculation device, adding a flocculation agent to green liquor to form flocculated green liquor;

after adding the flocculation agent, supplying the flocculated green liquor from the flocculation device to the clarifying vessel via the inlet conduit;

measuring, with the first flocculation measuring device, a flocculation of the flocculated green liquor that is flowing in the inlet conduit from the flocculation device to the clarifying vessel,

in the clarifying vessel, separating the flocculated green liquor into flocculated matter and clear green liquor;

removing the flocculated matter through a sludge outlet; and

removing the clear green liquor from the clarifying vessel.

2 . The method according to claim 1 , further comprising:

selecting a flocculation pre-treatment setpoint;

determining a difference between a measured flocculation value and the flocculation pre-treatment setpoint; and

adjusting an amount of the flocculation agent added to the green liquor based on said difference.

3 . The method according to claim 1 , further comprising:

before adding the flocculation agent, measuring a flocculation of the green liquor using the first flocculation measuring device;

determining a difference between a measured flocculation value before adding the flocculation agent and a measured flocculation value after adding the flocculation agent; and

adjusting an amount of the flocculation agent added to the green liquor based on said difference.

4 . The method according to claim 1 , wherein:

the green liquor treatment arrangement further comprises:

a clear green liquor conduit extending from an outlet of the clarifying vessel, and

a second flocculation measuring device located directly in a path of the clear green liquor conduit that extends from the outlet of the clarifying vessel; and

the method further comprises:

selecting a flocculation setpoint;

after removing the clear green liquor from the clarifying vessel, measuring, with the second flocculation measuring device, a flocculation of the clear green liquor that is flowing in the clear green liquor conduit from the outlet of the clarifying vessel;

determining a difference between the measured flocculation of the clear green liquor and the flocculation setpoint; and

adjusting an amount of the flocculation agent added to the green liquor based on said difference.

5 . The method according to claim 2 , further comprising:

adjusting at least one parameter of the green liquor treatment arrangement based on said difference and/or based on the flocculation measurement after adding the flocculation agent.

6 . The method according to claim 5 , wherein said at least one parameter is a rotational speed of a stirring device in the flocculation device.

7 . The method according to claim 1 , comprising measuring, using the first flocculation measuring device, the flocculation of the green liquor at predetermined intervals during operation of the green liquor treatment arrangement.

8 . The method according to claim 1 , comprising measuring, using the first flocculation measuring device, the flocculation of the flocculated green liquor continuously during operation of the green liquor treatment arrangement.