Mapping of causations for edospore formation and process optimization at pulp-and paper mill
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Kartläggning av sporbildning och processutveckling inom pappersindustrin (Swedish)
BillerudKorsnäs is a manufacturer of fiber-based cartonboard and liquid packaging board. Microbial growth occurs at several steps in cartonboard production due to favourable environment and the good access to nutrients from the raw material, and additives such as starch. Vegetative bacteria are usually not harmful in the production and die in the hot drying end of the cartonboard machine. The most abundant microflora at paper- and cartonboard factories consists largely of sporeforming microorganisms from the genera Bacillus and Paenibacillus. The endospores are highly resistant and can stay in the final end product, which is undesirable. Levels of endospores from these species at BillerudKorsnäs production unit KM5 are usually low, but an occational increase can be seen when a new cartonboard product, KW1 is produced. Today, the method used for controlling the microbiology is by adding biocides to broke towers. This has shown to be both expensive and non-effective at KM5. A new method is needed for controlling the microbiology at KM5 that is more effective, costbeneficial and environmental friendly.The aim of this project was to test a hypothesis for spore formation at a paper board factory in lab-scale experiments. A suggestion of a technical change in the process would be made that could minimize spore formation and the use of biocides at KM5. A model organism Bacillus licheniformis (E-022052) was used to study effects of environmental conditions on spore formation. Experiments were also performed in controlled bioreactor trials, where methods to minimize spore formation were tested.The experiments showed that nutrient deficiency of a primary carbon source was the major reason for spore formation and should be avoided at KM5. Further, the experiments showed that oxygen limitation significantly decreases the endospore formation.The conclusion reached, was that spore formation could be minimized by a feed addition of glucose to Broke tower 1 during the few days production of KW1. A second alternative includes using a feed of concentrated pulp that could be used to minimize spore formation without the use of biocides and without the need for rebuilding of the mill.
Place, publisher, year, edition, pages
Endospore, process design, Bacillus, simulation
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-150698OAI: oai:DiVA.org:kth-150698DiVA: diva2:744734