Abstract:

The ultrasound assisted impregnation at atmospheric pressure and its bleaching properties were studied with eucalyptus and poplar as raw materials by chemical thermomechanical pulp(CTMP) process. The effects of external factors such as impregnation temperatures, impregnation time and impregnation alkali amount on ultrasound assisted impregnation system were explored by continuously monitoring the change of amount of liquid absorbed and residual sodium hydroxide in impregnation system. The experimental results show that the optimum conditions for ultrasonic assisted impregnation were the temperature of 75℃, the time of 30 min and the alkali amount of 6% for eucalyptus, and the temperature of 75℃, the time of 30 min and the alkali amount of 5% for poplar. In this case, for eucalyptus, the brightness increased by 2.83%(ISO) and the residual hydrogen peroxide content increased by 4.4 percent point, the alkali absorption was 41.5 kg/t, which was 5.06% higher than that without ultrasonic treatment; for poplar, the brightness didn't change, the residual hydrogen peroxide content increased by 2.73 percent point and the alkali absorption was 38.75 kg/t, which was 6.15% higher than that without ultrasonic treatment.

Key words: ultrasonic, eucalyptus, poplar, chemimechanical pulp, impregnation at atmospheric pressure