Patent ID: 8052843

Claim:
A system for the steam pre-treatment of chips in association with the production of chemical cellulose pulp, comprising: a vessel having an inlet defined therein at a top of the vessel into which chips are fed into the vessel, the vessel having an outlet defined therein at a bottom of the vessel from which treated chips are fed out from the vessel, a feed arrangement for feeding chips to the vessel such that the chips in the vessel establish an upper chip level between the inlet and the outlet, and a gas phase between the upper chip level and the top of the vessel, at least one nozzle for supplying steam (ST) being arranged in the vessel, the at least one nozzle having an outlet defined therein below the upper chip level, a ventilation channel arranged in an upper part of the vessel and connected to a weak gas system, a gas sensor for detecting a process parameter in the upper part of the vessel, the process parameter being directly or indirectly indicative of a fraction of moisture in the gas phase of the vessel, at least one dilution line connected to the ventilation channel, a first end of the dilution line being in fluid communication with a surrounding atmosphere (ATM) and a second end of the dilution line being in fluid communication with the ventilation channel through a valve, and a control unit (CPU) in operative engagement with the gas sensor and to the valve in the dilution line, the control unit being adapted to open the valve when the process parameter exceeds a pre-determined threshold value wherein a condensation arrangement is connected to the ventilation channel between the vessel and connections of the dilution lines to the ventilation channel.