Patent ID: 8545674
Filing Date: 2013-10-01
Classification: D21C,Y02P

Abstract:
1. A method to retrieve heat from black liquor, comprising: withdrawing black liquor from a digester in association with a production of cellulose pulp, the black liquor when withdrawn from the digester maintaining a first withdrawal temperature, the digester maintaining a digestion temperature of 130-180° C., subsequent to withdrawal of the black liquor, reducing the first withdrawal temperature of the black liquor to a second temperature in a range of 90-125° C., leading at least a part of the black liquor at the second temperature to a primary heat exchanger, exchanging heat in the primary heat exchanger between the black liquor and a bleaching filtrate that has been obtained from a bleaching plant and increasing a filtrate temperature of the bleaching filtrate to produce a heated bleaching filtrate, and conveying the heated bleaching filtrate to the bleaching plant.