Valmet has developed a new chip bin, OptiBin, for pulp mills' digester chip feeding. Its task is to serve as a buffer before the digester and to remove air from the chips in an odorless manner. The new design is the result of years of development aimed at a cost-effective solution with as few moving parts as possible.
The first OptiBin was recently started up at the Nordic Paper Bäckhammar pulp and paper mill nearby Kristinehamn, Sweden. In spite of a very tight schedule, the installation and assembly of the new chip bin exceeded expectations at Nordic Paper - everything had to be completed during the regular eight-day mill shutdown.
"The startup was very successful. We started production according to our schedule. What's more, even the startup curve, with a gradual increase in output, followed our plans. A week after the shutdown, we reached full production," says Jonas Lindqvist, Deputy Director of Production and Project Manager at Nordic Paper. "There is still some residual points and, of course, some trimming to ensure that we achieve the goals we have set for the project," he adds.
"For us at Valmet, Bäckhammar was the perfect partner for taking our new development into practice. Partly because the mill is close to our development center in Karlstad, Sweden, and also because we've always had a very good relationship with Bäckhammar," says David Elfman, Sales Manager at Valmet.
Valmet's new OptiBin can be used in various cooking processes. The innovations in the OptiBin design bring several benefits. The design allows chips to flow smoothly and results in even pre-steaming and less runnability problems. Without good pre-steaming before cooking the cooking liquor will not penetrate the whole chip and results in uncooked chips.
The flow design allows a cold top to be used. This means that the bin itself will form a lid of chips that disables gases to flow to the atmosphere which results in less odors to the surroundings.
Thanks to the new chip bin, Nordic Paper estimates an increase in production of about 1,000 Adt/yr. In addition, the OptiBin has led to substantial fiber savings, and as a bonus for those living nearby the mill, it is expected to minimize malodorous emissions into the environment.
