Syftet med arbetet var att undersöka hur olika reaktionsbetingelser skulle påverka syrgasdelignifieringen av en sur sulfitmassa. De betingelser som undersöktes var utbyte, slut-pH, viskositet och kappatal. Massan som användes kom från Nordic Paper Seffle och alkalit som användes var magnesiumoxid.  Syrgasdelignifiering av massan gjordes  i autoklaver i ett PEG bad där tid, temperatur och alkalisatser varierades. Resultaten visar att alla utbyten låg mellan 90-97% och att även de mest aggressiva betingelserna bara gav en viskositets reduktion på 260 enheter, motsvarande 19% av den totala viskositeten. Slut-pH för syrgasavluten hamnade mellan 6,5-9,4 beroende på alkalimängd och temperatur under delignifieringen. Slut-pH minskade när mängden alkali hölls konstant men temperaturen varierades mellan 110-140°C. Kappatalet för massan kunde effektivt reduceras från ett startvärde på 23,4 till ett slutvärde på under 5 med en temperatur på 140°C, alkalisats på 10 kg/ODT och en tid på två timmar utan större förluster av vare sig viskositet eller utbyte. En ovanligt resultat som upptäcktes under arbetet var att delignifieringen tappade i effektivitet med ökad alkalimängd och detta samband gällde vid alla betingelser. En teori om detta kan vara att jonstyrkan i lösningen gör att fibrerna i massan drar ihop sig och att syrgasen får svårare att reagera med ligninet. / The purpose of the study was to investigate how different reaction conditions would affect oxygendelignification of an acid sulfite pulp. The conditions being explored were yield, final-pH, viscosity and kappa number. The pulp used in the testing was collected from Nordic Paper Seffle and the active alkali during the delignification was magnesium oxide. The oxygendelignification of the pulp was done with autoclaves suspended in a PEG bath, where they were allowed to rotate, and time, temperature and alkali amount  was varied throughout the testing. Results show that the yield for all pulp samples were between 90-97% for all conditions used in this project while viscosity of the pulps were only decreased by about 260 units for the most severe of conditions. This accounts for a viscosity loss of 19%. Final-pH varied between 6,5-9,4 depedning on temperature and alkali amount chosen. Final-pH levels dropped when the alkali was kept constant but temperature was varied from 110-140°C. The pulps kappa number could effetively be lowered from its starting value of 23,4 to a final value of under 5 when an alkali amount of 10 kg/ODT and a temperature of 140°C was used during 2 hours. This lead to no substantial losses of either viscosity or yield. A strange result that the project also highlighted was that the delignification lost in efficiency when more alkali was added in at a set temperature. This phenomenom was found at all conditions investigated throughout the project. A theory about this is that it might be the increased ionic strength from the magnesium cations in the solution making the fibers shrink and by that lessening the reaction area of the fibres for the oxygen, which will then have a harder time reacting with the lignin.

Esteves et.al. 2020 visade att syrgasdelignifiering ökar den totala fiberladdningen men leder inte alltid till ökad pappersstyrka. Denna studie syftar till att undersöka hur fiberladdning påverkar massans egenskaper.  För att testa hypotesen att ökningen av dragstyrkan beror på den större mängd sekundärt finmaterial som orsakas av malningen, testades vissa egenskaper hos massan, såsom vattenabsorption, med och utan malning avmassan. Två kraftmassor med olika initialt kappatal, 91 respektive 52, syrgasdelignifierades med olika alkalilsats under varierad tid. De massor som hade den lägsta och högsta mängden totala fiberladdningar maldes med PFI-kvarn. Water Retention Value (WRV), Schopper-Riegler (SR), Fiber Saturation Point (FSP) och finmaterial analyserades. WRV testades också efter att finmaterialet avlägsnats från massan.  Resultaten tyder på att massan med en större ökning av den totala fiberladdningen jämfört med den kraftkokta massan vid ett givet kappantal kan resultera i en högre ökning av FSP och WRV. Massor med större ökning av den totala fiberladdningen bildade mer finmaterial vid malning, vilket resulterar i en högre ökning av SR. / According to a previous study from Esteves et. al. 2020, it was found that oxygen delignification can increase the total fiber charge but does not always increase the paper strength. This study aims to investigate how fiber charge has an impact on pulp properties.  To test the hypothesis that the increase in mechanical strength for the fiber is due to the bigger increase of secondary fines caused by the refining process, some properties of the pulp such as water holding capacity were tested with different treatments: refining and no refining. Two kraft cooked pulp with different initial kappa numbers of 91 and 52 were subjected to oxygen delignification with different alkali charges and reaction times. When the characterization tests such as, kappa number and total fiber charge measurement have been determined, the samples which had the lowest and the highest total fiber charge were PFI refined and other analysis such as, water retention value (WRV), Schopper-Riegler degree (SR), fiber saturation point (FSP), and fine content, were done. WRV was also tested without fines.  The results suggest that the pulp with a higher increase in total fiber charge when compared to the kraft cooked pulp at a given kappa number can result in a higher increase in FSP and WRV. A higher increase in total fiber charge can also have a high tendency to create fines, due to the higher swelling ability, resulting in a higher increase in SR.