In two vessel cooking the first impregnation vessel is the biggest consumer of liquor. Controlling liquor to wood ratio (L/W) here is of the essence for optimal woodchip impregnation, for runnabillity and for pulp quality. L/W ratios are managed by black liquor re-circulations from the digester to various points along the impregnation vessel. But current situation today have many of those operating without individual flow control. This creates negative effects on chip column movement and lead to gas channeling in the top part. Extra challenging for atmospheric vessels where top section is running at cold conditions to maintain an odor free process. With an even woodchip plug flow the chip column act as a lid and prevents malodorous gas channeling. Failure to maintain uniform plug flow velocity cause varying retention time, leading to kappa variations and high reject. We offer consultancy and technology for woodchip and black liquor areas: - Black liquor flow control with non-invasive 3G Acoustic PROSONIC - Chip buffer level monitoring with non contact Radar - Impregnation vessel level with non contact Radar - Chip overfill detection, vibronic and microwave - Woodchip feed moisture inline analyzer - Nucleonic chip level (gamma). - Multitemp chip/liquor interface #Consultancy #Woodchip #BlackLiquor #ProcessOptimization #Pulpandpaper #Kraftpulp #Flowcontrol #Moistureanalyzer
Interesting project, however, are investment and return together? it would not generate an even greater proportion of liquor, even if the first pre-cooking removes some of it and the secondary cooking also, even in a smaller quantity, also accumulates liquor. Congratulations on the Project and Success.
Having seperate impregnation is superior. Less reject, better yeild and no need for heating in digester circulation. But steaming is just as important as the mass flow is.
Thomas Holm
2w
Good stuff! Continuous digesters have always been a bit of a "black box", primarily because of lack of reliable, real-time data. Reliable Chip moisture measurement is a key facet to good operation. What is your yield? You can't possibly know without knowing how much dry wood material is going in.
Interesting!
Vice President & Principal Engineer at Engineering Design Services LLC
2wThe mechanical and process design for continuous digesters has always been intriguing to me. It’s cool to see this process well controlled and operational at peak performance in mills. To your point Ulf Johansson, several mills struggle to perform optimally.