Process for high temperature peroxide bleaching of pulp with cool discharge

Abstract From the Canadian patent

A process for high temperature peroxide bleaching of pulp in which pulp is retained at high temperature and pressure to increase bleaching activity but in which the pulp is cooled prior to discharge from the retention tower below the flash point thereby resulting in lower energy nonviolent discharge. Through the use of a heat exchanger the cooling of the pulp can be performed using recycled filtrate containing residual peroxide which encourages further bleaching during atmospheric retention. The heat exchanger is also used to heat a water stream which can be used earlier in the pulping process resulting in cost savings because energy within the system is retained to a greater degree.