The system is for the oxygen delignification, in at least two reaction stages, of pulp that consists of lignocellulose-containing material having a mean concentration of 8%-18% pulp consistency. Urine is discharged from a urine drainage port formed on the bottom surface of the outer sheet to a sealed urine tank by a vacuum pump through urine drainage tubes. By using the method, seamless handover of intra-BS carriers can be performed in a multi-carrier system for ensuring the service continuity of the mobile station to eliminate carrier handover time delay. A plurality of depressions are formed on the lands.