Improved method and apparatus for processing pulp

Claim 3

The method according to Claim 1, wherein at least one of the deaerating means used in said processing is omitted and its function is carried out by said replacement pump having air or gas removing means.

Claim 4

The method according to Claim 2, wherein the replacement pump is a feed pump for feeding liquor to an evaporator.

Claim 5

The method according to Claim 3, wherein a circulation pump of an evaporator is provided with air removal means for further improving the operation of the evaporator.

Claim 6

The method according to Claim 2, wherein the replacement pump is at least one of a feed pump for chemicals, a liquid circulation pump or a feed pump for washing water for improving the operation of a pump digester.

Claim 7

The method according to Claim 2, wherein the replacement pump is at least one selected from the group of feed pump, filtrate pump and discharge pump for improving the washing and/or bleaching of the pulp.

Claim 8

The method according to Claim 1, wherein the air or gas removing means comprises apparatus for the application of ultrasonic waves to the liquid or liquid fiber suspension.

Claim 11

A centrifugal pumping apparatus for simultaneously pumping and removing entrained gas from a flowable material, comprising: a pump housing having an interior cavity and an inlet opening and an outlet opening communicating through said interior cavity; an impeller mounted for driven rotation on a shaft within said interior cavity of the housing between said inlet and outlet openings; and dual function means on the inlet opening side of said impeller for feeding the gas-entrained flowable material from said inlet opening toward said impeller and for creating a pressure on the inlet opening side of said impeller which is greater than the pressure at said outlet opening so that, as gas is removed from the flowable material through interaction with the rotating impeller, the pressure differential between the inlet opening side of the impeller and the outlet opening causes the removed gas to flow from the inlet opening side to the outlet opening side of the impeller and out of the pump housing through said outlet opening, thereby providing improved efficiency of pump operation by preventing an undesired accumulation of removed gas in the pump interior.

Claim 12

A centrifugal pumping apparatus for simultaneously pumping and removing entrained gas from a flowable material, comprising: a pump housing having an interior cavity and an inlet opening and an outlet opening communicating through said interior cavity; an impeller mounted for driven rotation on a shaft within said interior cavity of the housing between said inlet and outlet openings; and dual function means on the inlet opening side of said impeller for feeding the gas-entrained flowable material from said inlet opening toward said impeller and for creating a pressure on the inlet opening side of said impeller which is greater than the pressure at said outlet opening so that, as gas is removed from the flowable material through interaction with the rotating impeller, the pressure differential between the inlet opening side of the impeller and the outlet opening causes the removed gas to flow from the inlet opening side to the outlet opening side of the impeller and out of the pump housing through said outlet opening, thereby providing improved efficiency of pump operation by preventing an undesired accumulation of removed gas in the pump interior.

Claim 13

The apparatus according to Claim 9, further comprising at least a throughbore defined in the impeller through which the gas removed from the flowable material is drawn by said pressure differential from the inlet to the outlet opening sides of the impeller for passage out of said pump housing through the outlet opening.

Claim 14

The apparatus according to Claim 10, wherein said at least one throughbore is defined in substantially the central portion of said impeller proximate said shaft.

Claim 15

The apparatus according to Claim 9, wherein said dual function means comprises a screw feeder.

Claim 16

The apparatus according to Claim 12, wherein said screw feeder is mounted on said shaft.

Claim 17

The apparatus according to Claim 10, further comprising a passageway defined in said pump housing connecting said interior cavity and said outlet opening of said housing.

Claim 18

The apparatus according to Claim 11, further comprising at least a channel defined in said pump housing and connecting said outlet opening side of the impeller proximate said central portion of the impeller to said outlet opening so that the pressure in said channel and at said outlet opening side of the impeller is substantially equal to the pressure at said outlet opening.

Claim 19

The apparatus according to Claim 12, wherein said screw feeder has a pitch that decreases toward the impeller.

Claim 20

The apparatus according to Claim 9, wherein said inlet opening of the pump housing is tapered toward the pump impeller.

Claim 21

The apparatus according to Claim 9, wherein the capacity of said dual function means for feeding flowable material to said impeller is higher than the capacity of the pump to handle the flowable material.

Claim 24

The method in accordance with Claim 19, wherein said flowable material is advanced toward a pumping means through a conduit wherein the volume of flowable material is being decreased.

Claim 27

The method according to Claim 21, wherein the process is an evaporation process, the flowable material to be treated is black liquor, the black liquor is treated in an evaporator containing a heat transfer surface, the black liquor is withdrawn from and recirculated to the evaporator, and the incoming stream of black liquor is deaerated with a centrifugal pump having deaerating means.

Claim 28

The method according to Claim 22, wherein the treated liquor is recirculated to the evaporator with a forced circulation pump having deaerating means.

Claim 29

The method according to Claim 21, further comprising the step of withdrawing the treatment liquid from the treatment zone and recirculating the treatment liquid into the treatment zone, wherein the process is a digesting process, the material to be treated is cellulosic material, the treatment zone is a digester, the treatment liquid is a digesting chemicals-­containing liquid, the treated material including pulp and waste liquid is withdrawn from the treatment zone, and the incoming stream of digestion chemicals-containing treatment liquid is deaerated with a centrifugal pump comprising deaerating means.

Claim 30

The method according to Claim 24, further comprising the step of introducing washing liquid at the bottom of the treatment zone.

Claim 31

The method of Claim 25, further comprising deaerating the washing liquid prior to its introduction into the treatment zone with a centrifugal pump comprising deaerating means.

Claim 32

The method according to Claim 24, further comprising withdrawing digestion chemicals-containing treatment liquid from the treatment zone at a first level and recirculating said liquid into the treatment zone at a second level above said first level.

Claim 33

The method according to Claim 27, further comprising deaerating said withdrawn treatment liquid prior to its reintroduction into the treatment zone with a centrifugal pump comprising deaerating means.

Claim 34

The method according to Claim 21, wherein said process is a washing process, said material to be treated is a fiber suspension, said treatment liquid is washing liquid, said treatment zone is a washer, and said incoming stream of fiber suspension is deaerated prior to entering the treatment zone with a centrifugal pump comprising deaerating means.

Claim 35

The method according to Claim 29, wherein said washing water is deaerated prior to its introduction into the washer with a centrifugal pump comprising deaerating means.

Claim 36

The method according to Claim 29, wherein the fiber suspension is treated in at least two washers connected in series, and wherein the fiber suspension is deaerated prior to its introduction into each washer with a centrifugal pump comprising deaerating means.

Claim 37

The method according to Claim 21, wherein said process is a bleaching process, said material to be treated is a fiber suspension, said treatment zone is a washer, said treatment liquid is washing water, and said incoming stream of fiber suspension is deaerated prior to its introduction into the washer with a centrifugal pump comprising deaerating means.

Claim 38

The method according to Claim 32, wherein the fiber suspension is further deaerated after its withdrawal from the washer with a centrifugal pump comprising deaerating means.

Claim 39

The process according to Claim 32, further comprising deaerating said washing water prior to its introduction into the washer with a centrifugal pump comprising deaerating means.

Claim 40

The method according to Claim 21, wherein said process includes a treatment zone comprising a hydrocyclone, said treated material is a fiber suspension, said fiber suspension is treated with centrifugal force, and said incoming stream of fiber suspension is deaerated prior to its introduction into the hydrocyclone with a centrifugal pump comprising deaerating means.