Nanocellulose Production in a holistic Biorefinery approach

The goal of the NaProBio project was to develop a new and innovative process for production of cellulose nanofibrils (CNF) suitable for oilfield applications, incorporating all steps from wood chips to CNF. Furthermore, the developed process should form the basis for building a demonstration plant for CNF production, with oilfield applications as the primary market. The NaProBio project was in the beginning a cooperation between Treklyngen Holding AS, Elkem AS and the Paper and Fibre Research Institute (PFI, now RISE PFI). After a year, Norske Skog Saugbrugs joined the project. Norske Skog Saugbrugs had an excellent position for realizing the innovation, as the company already had received funding for a pilot/demonstration plant for CNF production from Innovation Norway. This plant was built in the first part of 2016 and started in mid-2016. By including Norske Skog Saugbrugs, the project as a whole took important steps towards commercialization, as they were in the process of implementing a demonstration plant for production of CNF suitable for full scale trials. The process for CNF production was developed, and the CNF material was tested in laboratory scale. These analyzes have been performed both at Elkem and at RISE PFI, with very promising results with respect to use of this CNF as viscosifier for drilling fluids. A short summary of the R&D tasks highlighted in the NaProBio project is given below. Usually, CNF is produced by using standard chemical market pulp as the starting material. The suggested new and innovative process for production of CNF material involved optimizing the production process all the way from wood chips to a final CNF product. The project focused on finding the optimum process conditions for obtaining high yield laboratory pulp suitable for CNF production with required properties for oilfield applications. With nanocellulose as the main product, delignification of the wood chips (production of cellulose fibres) may be done in a much more cost-effective way compared to conventional processes where cellulose fibres for e.g. paper production is the main product. Since brightness is not a quality criterion for the product in this project, bleaching was not necessary. However, to which degree the wood raw material must be delignified in order to be suitable for production of nanocellulose for oilfield applications was a topic of interest. Therefore, the main goal in the project was to produce pulps with various delignification degrees and to investigate the quality of CNF samples produced from them. The results showed that CNF could successfully be produced from a partially delignified pulp with high pulp yield (72%) and that the rheological properties were very good, even after heat aging tests at 150 ºC and 180 ºC, for 16 hours, which is typical test conditions for drilling fluids. CNF is typically produced as dispersions with a solid content of 1-2 %, which gives rise to high transport costs due to the high water content. Therefore, one of the sub goals in the NaProBio project was to increase the solid content of the CNF dispersions. Different additives was added to prevent the fibrils from agglomeration or hornification, during drying. This was tested and analyzed for redispersed samples after drying experiments. Two different drying methods were used in all our experiments: freeze-drying and oven-drying at 60 oC. The results showed that by adding a cellulose derivative before fibrillation of CNF it was possible to dry and then redisperse the CNF after drying. Also, the suspensions were quite stable after redispersion. The redispersed samples were comparable with the reference sample which was not dried. No difference was observed between freeze-dried and oven dried sample. Further, to study the CNF product from Norske Skog Saugbrugs, tests of rheological properties, thermostability and possible influence from temperature on changes in rheological properties were undertaken by Elkem and RISE PFI. Here, the CNF samples produced at the pilot plant at Norske Skog Saugbrugs showed good results, as previously also verified on other CNF materials (work performed in WaterFlu and GreenEOR, two other RCN-funded projects at RISE PFI).

The underlying idea of the innovation is to develop a new and innovative process for production of nanofibrillated cellulose (NFC). The process to be developed shall form the basis for building a demonstration plant for production of NFC for sale to a def ined market. Developing a process for demonstration scale production of NFC is in itself highly innovative, as only a few such processes have been established so far. The selected initial market is also highly interesting. The process to be developed will go beyond producing NFC from standard chemical pulp, and optimize the complete process from wood chips to NFC.