An optimized chip bin provides a smoother production

SCA implemented, by the end of 2013, a comprehensive modernization of its liner factory in Munksund. A larger and more modern pre-steaming bin with a new type of chip conveyor is one piece of that giant puzzle. With an optimized control it gives the new pre-steaming unit improvements regarding economy, energy efficiency and the environment. The operators may focus on optimizing the cooking of the pulp.

Optimisation’s concept for the regulation of the new pre-steaming bin in Munksund has created conditions for a smooth, efficient and automatic operation of the pre-steaming.

"We have made the operation of the pre-steaming bin completely automated," explains Optimation’s project manager, Erik Berg. "The operators can now concentrate on what is most critical to the production, namely to optimize the actual cooking process."

Block engineer Tommy Berglund and production engineer Jan Bengtsson at SCA Munksund, confirm that the process has become smoother and more efficient with the automatic control.

"After the renovation, the temperature throughout the chip bin was very stable, and a sample taken after the chip bin showed that almost all the chips meet the demands we put on the steaming," says Tommy Berglund.

Jan Bengtsson and Tommy Berglund can see many positive effects on the downstream sulphate cooking. Among other things, it now has less dispersion of the amount of residual lignin after the cooking.

Smooth operation is the main thing

The purpose of the pre-steaming is to replace the air among the chips with steam. If this succeed it increases the efficiency of the cooking, where the steam collapses and is replaced with cooking fluid. During the winter, the steam is also used to thaw the chips.

There are several critical points in the pre-steaming. The most important one is to keep a steady operation, so that the subsequent cooking process can run smoothly and efficiently. Other key issues are to use the energy in the steam as effectively as possible and to avoid smelly gases coming up and out of the bin.

"The steam level should be as uniform as possible and lie as high as possible without risking to break through the lid of cold chips that are at the top of the bin," concludes Erik Berg.

In Munksund there is, as additional security, a downdraft and equipment to take care of odorous gases in the chip bin, but with Optimation's concept the regulation ensures that the chip level is optimal and that the steam does not break through the upper chip layer.

To achieve maximum energy efficiency, the valves are set so that the use of live steam will be as low as possible. "You may need to add some fresh steam in the winter but nowadays the regulation makes the need for that minimal. This is fundamental to energy efficiency and economy, "says Erik Berg.

Jan Bengtsson and Tommy Berglund concludes that the energy efficiency has really improved with Optimation's control system.

"Optimation's more stable temperature control, improved the function in the flash tanks, which means that we, to a larger extent, are able to utilize flash steam instead of fresh steam," says Jan Bengtsson.