US3525665A - Method of transferring impregnated wood chips from an impregnating vessel to a digester - Google Patents

Method of transferring impregnated wood chips from an impregnating vessel to a digester Download PDF

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Publication number
US3525665A
US3525665A US502269A US3525665DA US3525665A US 3525665 A US3525665 A US 3525665A US 502269 A US502269 A US 502269A US 3525665D A US3525665D A US 3525665DA US 3525665 A US3525665 A US 3525665A
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United States
Prior art keywords
liquor
digester
drainer
pressure
transferring
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Expired - Lifetime
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US502269A
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English (en)
Inventor
Adolf W Gessner
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Lummus Technology LLC
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Lummus Co
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Publication date
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Publication of US3525665A publication Critical patent/US3525665A/en
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/24—Continuous processes

Definitions

  • This invention relates generally to the treatment of cellulosic material and, more particularly, the invention relates to an improved method of transferring impregnated wood chips and the like from an impregnating vessel to a digseter, and apparatus therefor.
  • the process results in closer thermal and chemical control of both the impregnation and digestion stages of the pulping process.
  • the chips or other cellulosic material are treated in seriatim in three stages. First, they are impregnated with white liquor and recycle liquor at a first temperature and pressure in an impregnation zone, the chips are then commonly drained of excess liquor in a chip drainer, and lastly they pass to the digestion zone. The chip drainer may also convey the chips to the digester. The liquor is recycled to the impregnating zone.
  • the digester is operated at higher temperatures and pressures than the impregnating vessel.
  • condensation has been considered essentially inescapable.
  • the dilution problem has been overcome by flashing off steam from the hot, diluted impregnating liquor at a lower pressure prior to recycle. While this preserves the liquor at design concentration it does not prevent the loss of high pressure cooking steam. Moreover, it requires the use of an extra stainless steel flash drum, a level controller and a pressure controller.
  • Another object of the present invention is to provide a method and apparatus for transferring impregnated 3,525,665 Patented Aug. 25, 1970 "ice wood chips to a digestion vessel without loss of cooking steam or dilution of the impregnating liquor.
  • Still another object of the invention is to provide a method and apparatus for transferring impregnated Wood chips to a digestion vessel wherein temperature control of impregnation and digestion is improved.
  • impregnated wood chips and excess liquor are fed from the impregnating vessel into a chip drainer, which may be of essentially conventional design. Commonly, this is a screw conveyor having a screen covering a trough in the bottom through which the excess liquor passes.
  • a conduit or conduits and appropriate pumping means return the liquor to the impregnation vessel.
  • the drained chips are dropped from the drainer through an opening and pass into a conduit leading into the digester. It is of course at this point, when the digester feeding valve opens, that cooking steam normally escapes and passes into cooler portions of the system. In the present invention, however, a small amount of high pressure air or inert gas is provided in the discharge end of the drainer.
  • This gas serves to maintain the total pressure in the drainer at the same level as the pressure in the digester.
  • the partial pressure of water vapor in the drainer may be much lower than that in the digester, and the impregnation liquor temperature may thus be at any temperature below the cooking temperature.
  • the difference between the partial pressure of water in equilibrium with the impregnation liquor and the total pressure in the drainer is made up by the partial pressure of the added gas in the drainer.
  • the compressed gas passed into the drainer is vented as required through an opening in the conduit leading to the digester. Any steam which does leak upwardly against the air pressure will also be removed through this opening, so the liquor is never diluted.
  • deaerated wood chips in line 10, fresh cooking liquor and spent liquor recycled from the digester in line 12, and recycle impregnation liquor in line 16, are all passed to the impregnating vessel 18 in the conventional manner.
  • Compressed air or an inert gas in line 20 may be employed to control pressure in impregnator 18, line 22, with a back pressure control valve, being provided for exhaust.
  • a suitable pump 24 below impregnating vessel 18 feeds impregnated chips and liquor via line 26 into chip drainer 28.
  • the chips are conveyed along the length of drainer 28 by screw conveyor 30, which is equipped with a screen in the bottom thereof, indicated generally by dotted line 32, through which the liquor passes.
  • a plurality of conduits 34 collect the liquor and return it to liquor recycle line 16.
  • Compressed gas is supplied to drainer 28, from line 36, which may include a flow indicating controller 38 which opens or closes flow control valve 40 as required. Chips reaching the end of drainer 28, fall into conduit 42 located directly above digester 44, shown only partially. A rotary feed valve 46 may be placed in the top of the digester to pass the chips into the digester, but the invention will work without such a valve. Cooking steam is supplied to digested 44 through line 48. An air vent 50 is located in conduit 42 or in the casing of rotary feed valve 46, these locations assuring that any steam coming from digester 44 will be drawn off before it reaches the cooler chip drainer. Vent S is provided with a suitable back pressure controller and valve 52.
  • drainer 28 is maintained at approximately the same temperature as the impregnator and the same pressure as the digester.
  • the chip slurry entering the drainer via line 26, which is 15% solids by weight, may be at about 120 to 140 C.
  • Impregnating vessel 18 is maintained at only 0.8 to 2.4 atm. gage, however, and immediately on entry into the drainer the chips are subjected to the digester pressure of 511 atm. gage, maintained by compressed gas from line 36. The pressure differential between the drainer and the impregnator reduces the amount of work necessary to recycle the liquor.
  • the compressed gas in line 36 can be air or an inert gas; it is to be noted, however, that air should not be used when the presence of oxygen will adversely afiect the pulp brightness and strength.
  • a gas generated by burning a fuel in air to consume the oxygen may be employed.
  • To completely consume the oxygen there should be a stoichiornetric excess of fuel.
  • CO should :be scrubbed from the combustion gases before injection in line 36 to avoid decreasing the efiective alkalinity of the liquor by absorption of CO and formation of sodium carbonate.
  • other inert gases can be employed when use of air is restricted.

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US502269A 1965-10-22 1965-10-22 Method of transferring impregnated wood chips from an impregnating vessel to a digester Expired - Lifetime US3525665A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US50226965A 1965-10-22 1965-10-22

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US (1) US3525665A (enrdf_load_stackoverflow)
FI (1) FI48763B (enrdf_load_stackoverflow)
SE (1) SE319961B (enrdf_load_stackoverflow)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969184A (en) * 1971-06-04 1976-07-13 Defibrator Ab Digestion odor control
US4050981A (en) * 1974-06-14 1977-09-27 Mo Och Domsjo Aktiebolag Process for the delignification of lignocellulosic material by maintaining a concentration of carbon monoxide in the presence of oxygen and alkali
US4089737A (en) * 1974-02-18 1978-05-16 Toyo Pulp Company, Ltd. Delignification of cellulosic material with an alkaline aqueous medium containing oxygen dissolved therein
US4190490A (en) * 1974-04-03 1980-02-26 Domtar Inc. Impregnation and digestion of wood chips
US4632729A (en) * 1984-05-01 1986-12-30 Laakso Oliver A Chip presteaming and air washing
US4746404A (en) * 1984-05-01 1988-05-24 Laakso Oliver A Chip presteaming and air washing
US4762591A (en) * 1983-01-26 1988-08-09 Mo Och Domsjo Aktiebolag Apparatus for reacting lignocellulosic material with a gas phase comprising a nitrogen oxide and oxygen under controlled gas pressure
US5089086A (en) * 1989-04-27 1992-02-18 Jaakko Poyry Oy Process for continuous cooking of cellulose
US5164042A (en) * 1987-11-04 1992-11-17 Celleco Ab Method and plant for producing high-yield pulp from pulp chip material containing lignocellulose
US5296097A (en) * 1991-08-01 1994-03-22 Union Camp Holding, Inc. Method for reducing contaminants in pulp prior to ozone bleaching

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA463363A (en) * 1950-02-28 Gunnar Fadum Per Process for continuously drawing off digested cellulose in continuous cellulose digestion
US2996422A (en) * 1958-04-23 1961-08-15 Ed Jones Corp Digestion of cellulosic material
US3259538A (en) * 1963-04-22 1966-07-05 Lummus Co Comprehensive pulping system for producing paper pulp
US3446698A (en) * 1965-06-01 1969-05-27 Owens Illinois Inc Method of impregnating and digesting cellulosic materials in a horizontal digestor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA463363A (en) * 1950-02-28 Gunnar Fadum Per Process for continuously drawing off digested cellulose in continuous cellulose digestion
US2996422A (en) * 1958-04-23 1961-08-15 Ed Jones Corp Digestion of cellulosic material
US3259538A (en) * 1963-04-22 1966-07-05 Lummus Co Comprehensive pulping system for producing paper pulp
US3446698A (en) * 1965-06-01 1969-05-27 Owens Illinois Inc Method of impregnating and digesting cellulosic materials in a horizontal digestor

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969184A (en) * 1971-06-04 1976-07-13 Defibrator Ab Digestion odor control
US4089737A (en) * 1974-02-18 1978-05-16 Toyo Pulp Company, Ltd. Delignification of cellulosic material with an alkaline aqueous medium containing oxygen dissolved therein
US4190490A (en) * 1974-04-03 1980-02-26 Domtar Inc. Impregnation and digestion of wood chips
US4050981A (en) * 1974-06-14 1977-09-27 Mo Och Domsjo Aktiebolag Process for the delignification of lignocellulosic material by maintaining a concentration of carbon monoxide in the presence of oxygen and alkali
US4762591A (en) * 1983-01-26 1988-08-09 Mo Och Domsjo Aktiebolag Apparatus for reacting lignocellulosic material with a gas phase comprising a nitrogen oxide and oxygen under controlled gas pressure
US4632729A (en) * 1984-05-01 1986-12-30 Laakso Oliver A Chip presteaming and air washing
US4746404A (en) * 1984-05-01 1988-05-24 Laakso Oliver A Chip presteaming and air washing
US5164042A (en) * 1987-11-04 1992-11-17 Celleco Ab Method and plant for producing high-yield pulp from pulp chip material containing lignocellulose
US5089086A (en) * 1989-04-27 1992-02-18 Jaakko Poyry Oy Process for continuous cooking of cellulose
US5296097A (en) * 1991-08-01 1994-03-22 Union Camp Holding, Inc. Method for reducing contaminants in pulp prior to ozone bleaching
US6126781A (en) * 1991-08-01 2000-10-03 Union Camp Patent Holding, Inc. Process for conditioning ozone gas recycle stream in ozone pulp bleaching
US6315861B1 (en) 1991-08-01 2001-11-13 Union Camp Patent Holding, Inc. Process for conditioning ozone gas recycle stream in ozone pulp bleaching

Also Published As

Publication number Publication date
FI48763B (enrdf_load_stackoverflow) 1974-09-02
SE319961B (enrdf_load_stackoverflow) 1970-01-26

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