Patent ID: 8888955

Claim:
A method to evaporate hot black liquor, comprising: providing a multistage evaporation line having at least two evaporation stages, obtaining hot black liquor from a digestion process during a production of cellulose pulp, conveying the hot black liquor to a heat exchanger, cooling the hot black liquor to form a cooled black liquor by exchanging heat in the heat exchanger with a partially evaporated black liquor from a first evaporation stage, and the cooling of the hot black liquor in the heat exchanger reducing foam formation during subsequent evaporation by cooling the hot black liquor, conveying the cooled black liquor from the heat exchanger to the first evaporation stage, evaporating the cooled black liquor in the first evaporation stage to produce the partially evaporated black liquor, conveying the partially evaporated black liquor from the first evaporation stage to the heat exchanger, and conveying the partially evaporated black liquor from the heat exchanger to a second evaporation stage.