TCT bleached pulps from Miscanthus sinensis by the impregnation rapid steam pulping (IRSP) process

The production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated in this work. The impregnation rapid steam pulping process (IRSP) involves impregnating of the lignocellulosic material with the pulping liquor, withdrawing the excess liquor and rapidly steaming the impregnated material at 180-200degreesC for a short time. In this paper the process variables and their effect on the kappa number, yield and viscosity of the unbleached pulps are discussed. Bleaching by an ozone-based TCF sequence was tested, and the papermaking properties of the bleached pulp were determined. A kappa number of 19 was obtained by impregnating at an alkali charge of 30 + 0.1% anthraquinone carboxylic. acid (AQCA) and pulping at 180degreesC for only 15 min. Kappa was reduced to 16 by extending pulping time to 26 min. The alkali consumption during impregnation and pulping was 10.2 g NaOH/ 100 g of dry Miscanthus. Screened pulp yield, viscosity and brightness for this pulp were 54.6%, 913mL/g and 37.3%, respectively. After bleaching, the pulp had an ISO brightness of 87.4% and a viscosity of 700 mL/g. Refining in a PFI mill provided optimal strength properties of the bleached pulp at 4500 revolutions (7 I'S R): breaking length 7.2 km, tensile index 72Nm/g, and burst index 4.3 kN/g. Tear index was 7.9 mNm(2)/g at this degree of refining.