EP0369650A2 - Verfahren und Apparat zur Verarbeitung von Kalziumkarbonatsuspension als Rückstand aus der Papierherstellung - Google Patents

Verfahren und Apparat zur Verarbeitung von Kalziumkarbonatsuspension als Rückstand aus der Papierherstellung Download PDF

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Publication number
EP0369650A2
EP0369650A2 EP89311391A EP89311391A EP0369650A2 EP 0369650 A2 EP0369650 A2 EP 0369650A2 EP 89311391 A EP89311391 A EP 89311391A EP 89311391 A EP89311391 A EP 89311391A EP 0369650 A2 EP0369650 A2 EP 0369650A2
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EP
European Patent Office
Prior art keywords
kiln
mesa
riser pipe
smoke gas
raw material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP89311391A
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English (en)
French (fr)
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EP0369650A3 (de
EP0369650B1 (de
Inventor
Jorgen Theil
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
FLSmidth and Co AS
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FLSmidth and Co AS
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Publication date
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Application filed by FLSmidth and Co AS filed Critical FLSmidth and Co AS
Priority to AT89311391T priority Critical patent/ATE88767T1/de
Publication of EP0369650A2 publication Critical patent/EP0369650A2/de
Publication of EP0369650A3 publication Critical patent/EP0369650A3/de
Application granted granted Critical
Publication of EP0369650B1 publication Critical patent/EP0369650B1/de
Anticipated expiration legal-status Critical
Revoked legal-status Critical Current

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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
    • D21C11/00—Regeneration of pulp liquors or effluent waste waters
    • D21C11/0064—Aspects concerning the production and the treatment of green and white liquors, e.g. causticizing green liquor
    • D21C11/0078—Treatment of green or white liquors with other means or other compounds than gases, e.g. in order to separate solid compounds such as sodium chloride and carbonate from these liquors; Further treatment of these compounds

Definitions

  • the invention relates to a method and an apparatus for the treatment of calcium carbonate slurry ("mesa”) as residue from the causticisation of green liquor (Na2CO3) with burnt lime (CaO) during the manufacture of paper pulp after the sulphate process.
  • the burnt lime (CaO) used in the causticisation results from the treatment of a calcareous raw material in a kiln, usually a rotary kiln.
  • Causticisation produces a sodium hydroxide solution (NaOH) or white liquor, which is used for the boiling of the wood pulp from which the paper pulp is produced, and a residue product containing fine calcium carbonate (CaCO3) particles.
  • the residue is washed and filtered thus separating the fine CaCO3-particles in the form of a filter cake or "mesa cake” having a typical water content of 30-35%.
  • the mesa cake is then fed to the rotary kiln where it is burnt to form CaO which is re-utilized in the causticisation. This cycle is generally referred to as the lime cycle of the sulphate process.
  • the uppermost end of a rotary kiln is provided with a number of chains suspended inside the kiln serving to promote the heat trans­fer and the crushing of added, wet mesa cake so as to enhance the removal of water from same within the kiln.
  • the product thus treated in the form of burnt lime is removed from the kiln subsequent to being cooled off in the material cooler coupled after the kiln.
  • the kiln is fuelled with oil, gas or bark powder and during treatment the burnt lime reaches a temperature within the range of 1000-1200°C.
  • the removal of the large amount of water present in the mesa cake through a drying process generates a relatively low exit temperature of 150-200°C in the flue gases thus reducing the stack loss to a minimum.
  • the efficiency of the kiln i.e. the calorific consumption during the drying away of water or the calcining of the treated product, is quite high and, on the whole, the heat economy of the kiln may be said to be quite satisfactory for the purpose.
  • the kiln reacts in the same way when forced beyond its normal production capacity: rising flue gas temperature and augmented dust loss cause the fuel consumption per unit burnt lime produced to increase.
  • the kiln chain system clearly defines the limita­tions of increasing kiln productivity and, similarly, it is associ­ated with the inconvenience that the chains need renewal at regular intervals due to wear, thus entailing not only increases in the material costs proper but also closing down of the kiln and conse­quently production halts and hence an undesirable increase in the total operational costs.
  • the rotary kiln chain system is replaced by a dryer crusher, e.g. of the hammer mill-type, which is mounted before the kiln - as seen in the move­ment direction of the raw material feed - thus permitting an incre­ased production for a given kiln size.
  • a dryer crusher e.g. of the hammer mill-type
  • the sticky, frequently lumpy, wet mesa cake fed to the dryer crusher together with hot smoke from the rotary kiln is ground and dried in the dryer crusher and conveyed by the dryer air and suspended therein as a powder to a separator cyclone, and separated therein from the smoke and fed to the rotary kiln as dry raw material.
  • drying apparatus which is also known in other con­texts, vide e.g. EP 0 041 113, is associated with other major drawbacks.
  • the dust loss is relatively high, the separa­tor cyclone being unable to separate the relatively large portion of fine fraction resulting from the crushing of the mesa cake in the dryer crusher, and the ducts connecting the rotary kiln and the dryer crusher being exposed to cakings, due to the dust from the rotary kiln becoming sticky at temperatures within the range of 600-700°C which is the normal temperature range at the smoke gas outlet.
  • the dryer crusher takes a certain amount of false air into the system and generates a relatively great pressure loss over the equipment proper thus increasing the power consumption of the apparatus.
  • the object is achieved through a method for the treatment of calcium carbonate slurry ("mesa"), wherein the mesa cake is admixed with a suitable amount of pre-dried, powderous raw material (CaCO3), a typical but non-limiting amount being 5-20%, in a mixer in order to form a loose, moist mesa pulp and subsequently subjected to flash drying in suspension using hot kiln smoke gas thus forming a dry, powderous raw material product (CaCO3) which is fed to the kiln for further heat treatment subsequent to having been separated from the smoke gas.
  • mea calcium carbonate slurry
  • drying and pre-heating of the powderous, moist mesa pulp is effected in two steps; the pulp is subjected to initial drying in suspension using hot smoke gas of about 500-600°C in a flash duct in the form of a riser pipe and then, after separation from the smoke gas of the product thus dried, is suspended in the riser pipe connecting the kiln and its separator cyclone for pre-heating up to 500-600°C prior to the dried, powderous product being again separated from the smoke gas and fed to the kiln for further treatment in same.
  • an apparatus for carrying out the above method characterized in comprising a riser pipe con­structed for flash drying of an added, moist raw material ("mesa") which is suspended in hot kiln smoke gas in the riser pipe (flash drying) and which - as seen in the smoke gas flow direction - is mounted immediately after a rotary kiln, a separator mounted after the riser pipe for the separation of dry, powderous product as residue from the smoke gas, a splitting gate for conveying a substream of the separated product through a pipe towards the kiln inlet and for conveying another minor substream through a pipe to a mixer for mixing with added raw material in the form of a filter cake of lime sludge (water-containing "mesa cake”), and means for feeding the loose, moist mesa pulp produced in the mixer to the lowermost end of the riser pipe.
  • mea moist raw material
  • the drying and the preheating are effected in two steps; a first step comprising a riser pipe constructed as a flash duct mounted after a separator cyclone mounted immediately after the rotary kiln, a material inlet in the riser pipe and a separator cyclone mounted after the riser pipe; and a second step comprising the riser pipe connecting the kiln and its separator cyclone, a material inlet in the riser pipe for the separated dry, powderous material resulting from the first step cyclone, and the separated cyclone mounted immediately after the kiln.
  • the invention is characterized in that the movable mechanical parts or units, such as the chain system or the dryer crusher, which are both very wear- and maintenance-demanding, are replaced by a far more simple stationary construction: a riser pipe in the form of a flash duct for instantaneous drying in suspension and pulverizing of a loose, moist mesa pulp.
  • the known apparatus shown in Figure 1 has a rotary kiln 1 with a cooler, here a planetary cooler 2, for cooling the product treated in the kiln, an outlet 3, an oil-, gas or bark powder-fired burner 4, and a smoke chamber 5.
  • a riser pipe 10 the kiln smoke gas is led through a fan 6 to a smoke gas filter 7, whereupon the cleansed smoke is fed to a stack 8.
  • Lime sludge or mesa cake is fed directly to the kiln through an inlet 9 and dried and crushed at the uppermost end of the kiln by means of a chain system 11 mounted in the interior of the kiln prior to the further heat treatment in the kiln.
  • a dryer crusher 12 e.g. of the hammer mill-type, mounted before the kiln 1. Drying air in the form of hot kiln smoke gas enters the dryer crusher through the pipe 10 to which the lime sludge or mesa is fed at 9 and crushed and suspended in the drying air by the dryer crusher whereupon the suspension through a riser pipe 13 is fed to a separator 14, here a cyclone separator, in which the dried, powderous raw material is separated from the smoke gas and through a pipe 15 fed to the kiln 1 for further treatment in same. From the separator 14 the smoke gas is led to the smoke gas filter 7 and the stack 8. If necessary a mixer (not shown) for mixing the mesa cake with solids may here be connected to the inlet 9 to facilitate the feeding of the raw material into the dryer crusher.
  • lime sludge or mesa cake is fed to an inlet 9 of a mixer 21 in which the water­containing mesa cake is mixed with dry, powderous raw material which is fed to the mixer from the cyclone separator 18 via the pipe 19, the splitting gate 20 and the pipe branch 19 ⁇ .
  • the loose, moist mesa pulp produced in the mixer is fed to the inlet 9′ of the lowermost part of a riser pipe 10 constructed as a flash pipe 17 and in direct communication with the smoke chamber 5 of the rotary kiln and is suspended, dried and pulverized in the kiln smoke gas.
  • the separator cyclone 18 the powderous, dried raw material is separated from the smoke gas and through the pipe 19, the splitting gate 20 and a pipe branch 19′ it is fed to the kiln 1 for further treatment.
  • a minor substream of the powderous, dried raw material separated in the separator cyclone 18 is as above described fed through the pipe branch 19 ⁇ to the mixer 21.
  • the smoke gas is via an outlet pipe 16 led to the filter 7 and the stack 8. Separated dust from the smoke gas is removed through outlets 22 and 22′. If desired, dust may be fed to the mixer 21 through a pipe branch 22 ⁇ for further conditioning of the mesa cake in the mixer.
  • FIG 4 shows another embodiment of the invention comprising a two-step drying of the loose, moist mesa pulp from the mixer 21.
  • the "flash-duct" riser pipe is placed after a separator cyclone 18 mounted immediately after the kiln 1.
  • Loose, moist mesa pulp enters at the lowermost end of the flash pipe 25 through the inlet 9′, and is suspended, dried and pulverized in the flash pipe, whereupon the powderous, dried raw material is separated from the smoke gas in the separator cyclone 26 and via the splitting gate 24 and the conduit 27′ fed to the riser pipe 10 connecting the kiln 1 and the separator cyclone 18.
  • the powderous raw material is subjected to a further preheating in the riser pipe 10 and separated from the smoke gas in the cyclone 18 whereupon the dried raw mate­rial is fed to the kiln via the splitting gate 20, a minor part of dried raw material being simultaneously fed via the pipe branch 19 ⁇ to the mixer 21 for being conditioned in same.
  • An elevator 23 conveys the conditioned mesa cake from the mixer to the inlet 9′.
  • the raw material may be conveyed directly to the kiln inlet 5 via the splitting gate 24 and the pipes 27 ⁇ and 19′.
  • the further treatment of smoke gas and filter dust after treatment in the separator cyclone 26 is identical to the one described in connection with Figure 3.
  • the mesa cake consistency prior to the cake being fed into the riser pipe 17 or 25 may be regulated via the splitting gate 20 by changing the amount of dry raw material added for the conditioning of the mesa cake in the mixer 21.
  • both embodiments yield a higher specific production for a given rotary kiln size, a reduced radiation loss from the kiln per unit produced of burnt lime, a lower smoke gas exit temperature and a smaller dust loss, all of which are factors contributing to a reduction of the calorific consumption.
  • the two-step method according to Figure 4 is superior to the one-­step method shown in Figure 3 in yielding an optionally even higher specific production for a kiln of a given size and in permitting adjustment by means of the splitting gate 20 to the lowest possible smoke gas exit temperature for a satisfactory drying to be effected in the riser pipe, thus reducing the specific calorific consumption even more.

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  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
  • Paper (AREA)
  • Processing Of Solid Wastes (AREA)
  • Treatment Of Sludge (AREA)
  • Fertilizers (AREA)
EP89311391A 1988-11-17 1989-11-02 Verfahren und Apparat zur Verarbeitung von Kalziumkarbonatsuspension als Rückstand aus der Papierherstellung Revoked EP0369650B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89311391T ATE88767T1 (de) 1988-11-17 1989-11-02 Verfahren und apparat zur verarbeitung von kalziumkarbonatsuspension als rueckstand aus der papierherstellung.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8804160A SE460728B (sv) 1988-11-17 1988-11-17 Foerfarande och anlaeggning vid behandling av mesa
SE8804160 1988-11-17

Publications (3)

Publication Number Publication Date
EP0369650A2 true EP0369650A2 (de) 1990-05-23
EP0369650A3 EP0369650A3 (de) 1991-05-29
EP0369650B1 EP0369650B1 (de) 1993-04-28

Family

ID=20373977

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89311391A Revoked EP0369650B1 (de) 1988-11-17 1989-11-02 Verfahren und Apparat zur Verarbeitung von Kalziumkarbonatsuspension als Rückstand aus der Papierherstellung

Country Status (10)

Country Link
EP (1) EP0369650B1 (de)
JP (1) JPH0319987A (de)
AT (1) ATE88767T1 (de)
BR (1) BR8905827A (de)
CA (1) CA2003112A1 (de)
DE (1) DE68906243T2 (de)
ES (1) ES2055097T3 (de)
FI (1) FI93751B (de)
PT (1) PT92341A (de)
SE (1) SE460728B (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991000251A1 (en) * 1989-07-03 1991-01-10 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5213496A (en) * 1989-07-03 1993-05-25 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5846378A (en) * 1996-03-29 1998-12-08 Ecc International Ltd. Treatment of solid containing material derived from effluent of wastepaper treating plant
US5989018A (en) * 1996-07-05 1999-11-23 Ahlstrom Machinery Oy Lime sludge feed arrangement
EP1092059A1 (de) * 1998-06-01 2001-04-18 U.S. Borax Inc. Partielle selbstkonstifizierung alkoholischer lauge zum holzaufschluss
US6348128B1 (en) 1998-06-01 2002-02-19 U.S. Borax Inc. Method of increasing the causticizing efficiency of alkaline pulping liquor by borate addition
WO2012126594A1 (de) 2011-03-18 2012-09-27 Ecoloop Gmbh Verfahren zur kontinuierlichen herstellung von gefälltem calciumcarbonat

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020079075A1 (en) 1998-09-04 2002-06-27 Imerys Minerals Limited Treatment of solid containing material derived from effluent
JP4338744B2 (ja) 2007-03-30 2009-10-07 セイコークロック株式会社 からくり時計

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0041113A2 (de) * 1980-06-02 1981-12-09 Krupp Polysius Ag Verfahren und Anlage zur Herstellung von Sintermagnesit aus Magnesiumhydroxid
WO1987003314A1 (en) * 1985-11-22 1987-06-04 Ekono Oy A process for causticizing of an aqueous solution containing alkali carbonate

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0041113A2 (de) * 1980-06-02 1981-12-09 Krupp Polysius Ag Verfahren und Anlage zur Herstellung von Sintermagnesit aus Magnesiumhydroxid
WO1987003314A1 (en) * 1985-11-22 1987-06-04 Ekono Oy A process for causticizing of an aqueous solution containing alkali carbonate

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
TAPPI. vol. 60, no. 11, November 1977, ATLANTA US pages 111 - 115; L.M.BINGHAM et al.: "The modern recausticizing and lime calcining system." *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991000251A1 (en) * 1989-07-03 1991-01-10 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5213496A (en) * 1989-07-03 1993-05-25 A. Ahlstrom Corporation Feeding system for a lime reburning kiln
US5846378A (en) * 1996-03-29 1998-12-08 Ecc International Ltd. Treatment of solid containing material derived from effluent of wastepaper treating plant
AU706803B2 (en) * 1996-03-29 1999-06-24 Ecc International Limited Treatment of solid containing material derived from effluent
US5989018A (en) * 1996-07-05 1999-11-23 Ahlstrom Machinery Oy Lime sludge feed arrangement
EP1092059A1 (de) * 1998-06-01 2001-04-18 U.S. Borax Inc. Partielle selbstkonstifizierung alkoholischer lauge zum holzaufschluss
EP1092059A4 (de) * 1998-06-01 2001-10-24 United States Borax Inc Partielle selbstkonstifizierung alkoholischer lauge zum holzaufschluss
US6348128B1 (en) 1998-06-01 2002-02-19 U.S. Borax Inc. Method of increasing the causticizing efficiency of alkaline pulping liquor by borate addition
US6663749B2 (en) 1998-06-01 2003-12-16 U.S. Borax Inc. Method for regenerating sodium hydroxide by partial autocausticizing sodium carbonate containing smelt by reaction with borate
WO2012126594A1 (de) 2011-03-18 2012-09-27 Ecoloop Gmbh Verfahren zur kontinuierlichen herstellung von gefälltem calciumcarbonat
DE102011014348A1 (de) 2011-03-18 2014-06-18 Ecoloop Gmbh Verfahren zur kontinuierlichen Herstellung von gefälltem Calciumcarbonat

Also Published As

Publication number Publication date
FI895468A0 (fi) 1989-11-16
PT92341A (pt) 1990-05-31
CA2003112A1 (en) 1990-05-17
DE68906243D1 (de) 1993-06-03
FI93751B (fi) 1995-02-15
SE8804160D0 (sv) 1988-11-17
BR8905827A (pt) 1990-06-12
ATE88767T1 (de) 1993-05-15
ES2055097T3 (es) 1994-08-16
EP0369650A3 (de) 1991-05-29
SE460728B (sv) 1989-11-13
JPH0319987A (ja) 1991-01-29
EP0369650B1 (de) 1993-04-28
DE68906243T2 (de) 1993-08-12

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