Arrangement and method for degassing a pump

A method comprising:

• pumping a suspension of medium-consistency pulp flowing through a conduit having an inlet receiving the suspension from a first reactor and an outlet delivering the suspension to a second reactor;
• separating gas from the suspension of medium-consistency pulp in the pump to form a separated gas flow;
• discharging the separated gas flow from the pump to a degassing conduit having an inlet receiving the separated gas flow from the pump;
• determining a pressure difference between a pressure of the suspension of medium-consistency pulp at an inlet to the pump and a pressure of the separated gas flow in the degassing conduit and upstream of a degassing valve connected to the degassing conduit;
• maintaining the pressure difference within a certain pressure difference range by adjusting the degassing valve;
• feeding the separated gas flow from the degassing conduit to a pressurized degassing vessel downstream of the degassing valve;
• determining a pressure difference between a pressure of the separated gas flow in the degassing conduit downstream of the degassing valve and a pressure of the gas in the degassing vessel, and
• maintaining the pressure of the gas in the pressurized degassing vessel within a pressure range above atmospheric pressure using a pressure control valve at or downstream of an outlet of the pressurized degassing vessel.

A method to control a gas flow separated from a suspension of medium consistency pulp in a pulp treatment apparatus, the method comprising:

• pumping the suspension with the first pump to a first reactor,
• pumping the suspension from the first reactor to a second reactor with a second pump, wherein the second pump includes a degassing centrifugal pump and a degassing system,
• separating gasses from the suspension with the second pump and diverting the gases into a degassing conduit separate from a flow of the suspension;
• regulating, with a degassing valve in the degassing conduit, a pressure difference between a pressure of the suspension at a suction side of the second pump and a pressure of the gases in the degassing conduit upstream in a flow of the gases in the degassing conduit of the degassing valve,
• directing the gasses from the degassing conduit into a pressurized degassing vessel downstream of the degassing valve in the flow of the gases through the degassing conduit, and
• maintaining a pressure in the pressurized degassing vessel to above atmospheric pressure, wherein the pressure is maintained using a pressure control valve fluidically connected to an outlet of the degassing vessel.