Wood chip steaming system for chemical pulp production, has chip bin dilution pipe extending between atmosphere and valve regulated by sensor for measuring process parameter

摘要

A dilution pipe (5a-5d) is connected to the ambient atmosphere (ATM) at one end and to the chip bin ventilation channel (2A, 2B) via a valve (4a-4d) at the other end. A control device (CPU) connected to a gas sensor (3) and the valve is used to open the valve when the process parameter being measured by the sensor exceeds a predetermined threshold value. A system for steaming wood chips as part of a chemical pulp production process comprises a vessel (1) with an inlet in the top for the chips and an outlet in its base for the treated chips, a feed device for supplying chips to the vessel so that the level of chips is maintained between the vessel inlet and outlet and so that a gas phase is present between the chips and the top of the vessel, at least one nozzle for introducing steam (ST) into the chips beneath the upper chip level, a ventilation channel located in the upper part of the vessel and connected to a diluted non-condensable gas system (DNCG sys) and a gas sensor for detecting a process parameter in the upper part of the vessel which is directly or indirectly linked to the amount of moisture present in the vessel gas phase. At least one dilution pipe is connected to the ventilation channel and has one end connected to the ambient atmosphere and the other end connected to the ventilation channel via a valve. A control device is connected to the gas sensor and valve and used to open the valve when the process parameter exceeds a predetermined threshold value. An independent claim is also included for a method for steaming wood chips as part of a chemical pulp production process, comprising continuously adding wood chips to the top of a vessel in order to form a chip column between the top and bottom of the vessel, adding steam to the column, removing the treated chips from the bottom of the vessel and removing a gas comprising steam, air and non-condensable gases from the top of the vessel. In this method a process parameter linked to the moisture content in the gas in the top of the vessel is detected and air for diluting the gas is introduced, the amount of air added being increased if the moisture content in the gas increases.