Ethanol pulping of reed canary grass

Abstract: The aim of this study was to investigate the possibility of processing an agricultural crop grown in Sweden to usable pulp. A further purpose was to study ethanol pulping applied to a non-wood raw material.



The first part of this thesis deals with the criteria for selecting a fibre crop for further studies. Based on the content of fibres and the harvested yield reed canary grass was found to be the most interesting crop. The effect on fibre content of the amount of leaves was investigated and it was found that leaves contain a very small amount of fibres. If the amount of leaves in the crop is 25 % or less they have a rather small influence, however.



In the second part of the thesis the studies of ethanol-alkali pulping and autocatalysed acidic ethanol pulping of reed canary grass are reported. The effects of the pulping conditions in the two methods were investigated using a response surface methodology. In ethanol-alkali pulping, the results were compared at the point of fibre liberation, which occurred at a kappa number of about 13. The shortest cooking time (80 min) required to reach kappa number 13 was obtained at an ethanol concentration of about 32 %, a liquor-to-raw material ratio of 4 l/kg and an alkali charge of 25 %. The highest pulp yield at kappa number 13 was obtained at about 38 % ethanol, 15 % alkali and any of the investigated liquor-to-raw material ratios (4 to 10 l/kg). In autocatalysed ethanol pulping, the results were compared at the end of the bulk delignification. The lowest possible kappa number (about 35) was obtained using 60 % ethanol at a liquor-to-raw material ratio of 10 l/kg.



Some paper properties were investigated on an unbleached soda pulp from reed canary grass,

an unbleached ethanol-alkali pulp from reed canary grass, an unbleached ethanol pulp from reed canary grass and a bleached (ODED) ethanol pulp from reed canary grass. For comparison, the properties of an unbleached and a bleached industrial birch kraft pulp were tested. The strength properties of the reed canary grass pulps are generally lower than those of the birch pulps.



The investigated ethanol pulping techniques can be used for the pulping of reed canary grass. The pulps are not suitable in products where strength is important. They may be useful, however, as e.g. a component in printing paper.