Black liquor energy recovery

Claim 3

A method as recited in Claim 1, comprising the further step of effecting countercurrent impregnation of chips in the digester.

Claim 4

A method as recited in Claim 1, wherein step (d) is accomplished by utilizing generated steam for presteaming chips in the digester system before digesting the chips.

Claim 5

A method as recited in Claim 1, wherein step (d) is accomplished by treating chips in the chips bin of the digester system before presteaming thereof.

Claim 6

A method as recited in Claim 1, wherein step (d) is accomplished by utilizing generated steam for heating white liquor being introduced into the digester.

Claim 7

A method as recited in Claim 1, wherein step (f) is accomplished by heating white liquor being introduced into the digester.

Claim 8

A method as recited in Claim 1, comprising the further step of utilizing the clean condensate from evaporation of the black liquor for digester wash liquid.

Claim 9

A method as recited in Claim 1, wherein the temperature of steam in step (b) is 213°F or greater, and wherein the final black liquor solids concentration is about 65%.

Claim 10

Apparatus for recovering heat from black liquor from a digester system for digesting chips, comprising - a digester system for digesting chips including a chips bin, steaming vessel, continuous digester, and heater for heating white liquor introduced in the continuous digester, - means for withdrawing black liquor from the digester, - means for increasing the solids concentration of the withdrawn black liquor to at least about 60% while generating steam having a minimum temperature at or higher than the temperature necessary to treat chips in the digester system, said means comprising a recompression evaporator directly connected to the black liquor withdrawal means, and having a concentrated liquor outlet, and at least one evaporator connected to the recompression evaporator concentrated liquor outlet, - means for recovering essentially all of the steam from said solids concentration increasing and steam generating means, - means for utilizing essentially all of the generated steam recovered by said recovering means for the treatment of chips in said digester system so that condensing of steam with water is avoided, - means for burning the black liquor to generate heat, and - means for utilizing the heat from the black liquor burning in said digester system for chips treatment.

Claim 11

Apparatus for recovering heat from black liquor from a digester system for digesting chips, comprising - a digester system for digesting chips including a chips bin, steaming vessel, continuous digester, and heater for heating white liquor introduced in the continuous digester, - means for withdrawing black liquor from the digester, - means for increasing the solids concentration of the withdrawn black liquor to at least about 60% while generating steam having a minimum temperature at or higher than the temperature necessary to treat chips in the digester system, said means comprising a recompression evaporator directly connected to the black liquor withdrawal means, and having a concentrated liquor outlet, and at least one evaporator connected to the recompression evaporator concentrated liquor outlet, - means for recovering essentially all of the steam from said solids concentration increasing and steam generating means, - means for utilizing essentially all of the generated steam recovered by said recovering means for the treatment of chips in said digester system so that condensing of steam with water is avoided, - means for burning the black liquor to generate heat, and - means for utilizing the heat from the black liquor burning in said digester system for chips treatment.

Claim 12

Apparatus as recited in Claim 9, wherein said recompression evaporator has a steam outlet and wherein said at least one evaporator is connected directly to said recompression evaporator steam outlet, steam supplied by the recompression evaporator steam outlet used to heat the liquor to be concentrated by said at least one evaporator.

Claim 13

Apparatus as recited in Claim 9, wherein said at least one evaporator comprises two evaporators, a first and second evaporator, said first evaporator being connected to said recompression evaporator concentrated liquor outlet, and said second evaporator being connected to a concentrated liquor outlet from said first evaporator, said liquor being concentrated to about at least 60% after passage through said second evaporator, and further comprising means for leading the concentrated liquor from said second evaporator to a furnace.

Claim 14

Apparatus as recited in Claim 9, wherein said at least one evaporator has a gas vent, and further comprising means for directly connecting said gas vent and a gas vent from one of said presteaming vessel and said chips bin to a turpentine decanter.

Claim 15

Apparatus as recited in Claim 9, wherein said means for utilizing the heat from the black liquor burning in said digester system comprises means for supplying heat to said heater for heating white liquor introduced into said continuous digester.

Claim 16

Apparatus as recited in Claim 9, wherein said means for utilizing essentially all of the generated steam recovered by said recovering means comprises means for transporting said steam to said presteaming vessel for steaming of chips therein.

Claim 17

Apparatus as recited in Claim 9, wherein said means for utilizing essentially all of the generated steam recovered by said recovering means comprises means for transporting said steam to said chips bin for pre-heating of chips therein.

Claim 18

Apparatus as recited in Claim 9, wherein said means for utilizing essentially all of the generated steam recovered by said recovering means comprises means for transporting steam to said heater for heating white liquor introducted into said continuous digester.

Claim 19

Apparatus as recited in Claim 9, further comprising means for effecting countercurrent impregnation of chips in said digester.