US 2010/0071862 A1 · METHOD AND EQUIPMENT FOR THE EVAPORATION OF BLACK LIQUOR THAT IS OBTAINED FROM A DIGESTION PROCESS DURING THE PRODUCTION OF CELLULOSE PULP

Abstract

The method and equipment are for the evaporation of hot black liquor obtained from a digestion process during the production of cellulose pulp. The black liquor is led to a multistage evaporation line with at least five evaporation stages. The black liquor that is to undergo evaporation in the evaporation line is cooled in at least one heat exchange process in a heat exchanger (HE1) against the partially evaporated black liquor that has undergone evaporation in at least one stage (I). The black liquor that is to undergo evaporation is cooled and the partially evaporated black liquor is heated by at least 5-10° C. The risk for the formation of foam and the separation of methanol are reduced. The greater part of the evaporation takes place at low temperature and at the lowest level of dry matter content in the liquor, which also suppresses encrustation in the stage.

Claims19

Dependent claims

A method to evaporate hot black liquor, comprising:

obtaining black liquor from a digestion process during a production of cellulose pulp,
leading the black liquor to a multistage evaporation line having at least five evaporation stages,
at least partially evaporating the black liquor in an evaporation stage in the multistage evaporation line,
cooling hot black liquor that is to undergo evaporation in the multistage evaporation line by exchanging heat with the partially evaporated black liquor.

1 more element

Equipment for evaporation of hot black liquor obtained from a digestion process during a production of cellulose pulp, the hot black liquor being led to a multistage evaporation line that has at least five evaporation stages, comprising:

each evaporation stage having a supply line for black liquor that is to undergo evaporation and maintaining a first level of dry matter content,
each evaporation stage having an outlet line for black liquor that has undergone at least partial evaporation in the evaporation stage and maintaining a second level of dry matter content, the second level being higher than the first level,
a first evaporation stage (I) being provided with a supply line for steam that maintains a first steam temperature and that is used in the first evaporation stage and
the first evaporation stage having an outlet line for steam that has been used in the first evaporation stage and that maintains a second steam temperature, the second temperature being lower than the first temperature,
a first heat exchanger unit (HE1) connected to the first evaporation stage (I), the first heat exchanger unit having a first inlet and a first outlet defined therein to a heating side of the first heat exchanger unit,
the first inlet of the first heat exchanger unit connected to an outlet line for a partially evaporated black liquor from a first evaporation stage (I),
the first outlet of the first heat exchanger unit connected to an inlet line for partially evaporated black liquor that is led to a second evaporation stage (II),
the first heat exchanger unit having a second inlet and a second outlet defined therein to a cooling side of the first heat exchanger unit,
the second inlet of the first heat exchanger unit connected to hot black liquor that has not yet undergone evaporation in any evaporation stage, and
the second outlet connected to an inlet of the first evaporation stage (I).

7 more elements

Dependencies are inferred from the claim text.

Method and equipment for the evaporation of black liquor that is obtained from a digestion process during the production of cellulose pulp

Life of this patent

Method and equipment for the evaporation of black liquor that is obtained from a digestion process during the production of cellulose pulp

Life of this patent

Abstract

Claims19