Kemira’s Kemform retention system was originally developed for use in fine paper production. It also has a lot to offer for board producers.
The Kemform retention system is an all-in-one solution for enhancing dewatering efficiency, cutting energy costs, and optimizing the furnish mix. Product Line Manager Kimmo Strengell says that demand for Kemform technology, which was patented three years ago, has grown strongly, and it is now in use at multiple mills around the world producing both printing paper and packaging board.
In fact, Kemform has become the undisputed flagship of Kemira’s retention product offering. “Thanks to Kemform, mills can achieve up to a 10–15% savings in energy usage as a result of improved dewatering. Studies have also confirmed that filler content can be increased by 2% in fine paper products,” says Strengell.
“Kemform works equally well with both new and old machines. In the case of new machines, the benefits tend to be seen in better overall productivity, while lower energy usage will be the biggest benefit in older setups with limited dewatering capacity.”
A Kemform system is typically made up of two or three components: inorganic microparticles, either bentonite or colloidal silica, and micropolymers, which are normally anionic in fine paper applications and cationic in packaging ones. The third component is Fennopol retention polymer.
Strengell says that applications based on colloidal silica seem to be growing in all segments, particularly in the fine paper area.
Greater product strength
Kemform was initially developed for use in machines producing fine paper, and its first trial runs were done on these. Following its commercialization, it was tested on some customers’ packaging board machines. The good results achieved with these encouraged Kemira to continue development work to extend Kemform’s scope to board production.
The key benefits Kemform offers in board production are reduced energy usage, as a result of improved dewatering, and an increased level of dry content in the web after the wet press section and further downstream.
“A high level of dry solids after the wet press improves board strength, and makes it possible to keep the elastic modulus as high as possible,” explains Strengell.
“Elastic modulus is an important metaparameter for board manufacturers, as it tells you a lot more about a product’s stiffness and other strength-related characteristics than people generally realize.”
Kemform helps keep elastic modulus as high as the strength potential inherent in the fiber being used will allow, in fact. Each fiber has strength potential as it is. A sheet matrix is formed from the fiber raw material. The final elastic modulus of the matrix is dependent on formation, wet pressing, draws, and drying.
“Board mills typically run headbox consistency very low. Typically half of that used when running fine paper for example. Floc size remains small when using Kemform, and this makes it possible to maintain or improve formation even when operating at a higher consistency in the HB than normally. This translates into better energy efficiency and strength.”
Using Kemform also makes it possible to reduce draw when the paper web travels through the dryer process. The reeler at the end of the dryer runs faster than the wire by a factor of few per cent and reducing this difference, by 50% for example, will improve the strength properties of board significantly.
Text: Jussi-Pekka Aukia
>> Read the full article in Kemira Solutions Magazine 2/2009