Gas-Liquid Reaction Precipitation of Calcium Carbonate in MSMPR and Couette-Taylor Reactors

(Journal of the Korean Institute of Chemical Engineers)

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Gas-Liquid Reaction Precipitation of Calcium Carbonate in MSMPR and Couette-Taylor Reactors

Sang Goo Lee, Wang Mo Jung*, Woo-Sik Kim**^† and Chang Kyun Choi*

Hanhwa Ltd., Inchon 405-310, Korea

*School of Chemical Engineering, College of Engineering, Seoul National University, Seoul 151-742, Korea

**Department of Chemical Engineering, Institute of Materials Science & Technology, Kyunghee University, Suwon 449-701, Korea

(Received 14 June 1999; accepted 14 September 1999)

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Abstract−The effect of the operating variables such as mean residence time, agitational speed and surfactant type, on the precipitation of calcium carbonate was experimentally investigated in MSMPR and Couette-Taylor reactors. The precipitates was produced by the gas-liquid reaction of CO₂ gas and Ca(OH)₂ aqueous solution. Under fixed temperature and concentration in MSMPR reactor, it was founded that the surfactant type had the greatest influence on the mean particle size and this effect was represented numerically by the zeta potential. With increasing the impeller speed the mean particle size increased due to decrease of the resistance in mass transfer processes. The vortex flow in Couette-Taylor reactor affected the precipitation of calcium carbonate complicatedly. The homogeneous mixing owing to Taylor vortex in Couette-Taylor reactor led to the more uniform particle size distribution than that in MSMPR reactor.

Key words: Calcium Carbonate, Couette-Taylor Reactor, Gas-liquid Reaction Precipitation, MSMPR Reactor, Rhombohedral Calcite, Surfactant

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Fig. 2. Conceptual diagram of Taylor vortices in Couette-Taylor reactor.

1. Stationary outer cylinder 3. Rotating inner cylinder 2. Taylor vortices

Fig. 3. Schematic diagram of experimental system with MSMPR reactor.

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Table 1. Dimensions of present Couette-Taylor reactor

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Fig. 7. Variation of mean zeta potential with impeller speed, residence time and surfactant type in MSMPR reactor.

Fig. 8. Variation of mean particle size with storage time at 54^oC.

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Ú¦öÛ~ ²*³ê& 400" 700 rpmž öÞ-r¢ >wVöB

*ö Vž pHf ï «¶’V~ æz¢ Fig. 12ö ¾æÚî. pH

& 10š~öB «¶~ W˚ /Ï® Ã&~&b–, ß® "φ © f &¦ª~ – «¶š šrö W>îrj š ª‚¦V r >

öB Ö;z ";ö /ς æz& ¾æ¾, ¸f pHöBº ª~~

‚ Ogino [32]" Kazmierczak [33]ê š‚ *çj þ'b‚

Fig. 9. Comparison of present experimental results with two models of

micromixing in MSMPR reactor. Fig. 10. Variation of mean particle size with inner cylinder speed and surfactant type in Couette-Taylor reactor.

Fig. 11. Comparison of time courses of pH and particle size distribu- tion in MSMPR and Couette-Taylor reactor.

&V~&, š‚ žš pH& 10šçöBº Ö; W˳êš ¾ 

º*¢ ’ª~ Jš¢ ~–, ;çç~ pHö ~šŽj r > ® . 6‚ Ú¦öÛ~ ²*³ê& Ã&†>ƒ pHf «¶’V~ æz

¢ V-‡ bî*š Ã&Žj ~‚. 6‚ Ú¦öÛ~ ²*³ê

& Ã&†>ƒ Ö;WË ê 7 «¶ "*~ bî* &“š 6²

χ~ pHº Fig. 12ö ¾æ :f ?š ;ççö ê~V ç*

ö /Ï® æz‚. >wš ê¯>Ú pH& 12¦"ö ê~š  æ z& Ö †š² ¢Ú¾æ‚, šr Ö;z~ æz¢ 2k~V *š

‡7ê~ æz¢ G;~ Fig. 13ö ¾æÚî. ‡7êº pH& 11

¦"öB ‚&8(0.82)j ¾æږ  šêöº 6²~ ;çç~

W>º ©j ~~–, >&‚ 6²~º ©f WË 5 w÷b‚ žš

>w~ .Vöº ›Wš æV'b‚ B~ ;ççö ê~š

wVÚöB >w 5 ›W ";" Ö;WË 5 w÷ ";j >wV

~ ^šö V¢ ’ª~ &V† > ®º &ËWj ¾æÞ. 6‚

Fig. 14f ?š *ö Vž Bæ**~ æzº pH~ æzf ?f ã

Ëj ¾æÚº–, pH~ æz F¯~  æz& ¾æÎj r >

®. š©f /ς æz& ¢Ú¾º 'öB Bæ**& ;j B چ > ®º æ>‚B wÏF > ®º &ËWj ¾æÞ.

¢>'b‚ Î&B¾ ꚂWBº Ö;~ ;¢ æzʺ ©b

‚ rJ^ ®º–,  ’öB Òς ꚂWB~ ³ê º*öB º Fig. 15f ?š Îv ;O; calcite& W>îrj XRD ªCj ۚ {ž† > ®î.

Fig. 12. Time courses of pH and mean particle size in Couette-Taylor reactor.

Fig. 13. Time courses of pH and absorbance in Couette-Taylor reactor.

Fig. 14. Time courses of pH and zeta potential in Couette-Taylor reactor.

Fig. 15. Micrographs of calcium carbonate particles by SEM.

z B38² B1^ 2000j 2ú

Ã&~&. 6‚ ï Bæ**ö Vž *' «¶’Vªº MSMPR

>wV~ j*b Ξ" j*ªÒ Ξö Vž š†' ªf F ҂ ãËj ¾æÚî. V¢B ꚂWBº êÖ¢¾ Ö;z~ ³ ê†ö 'Ëj ~º ©b‚ ž.

ꚂWB¢ Òς V-‡ >wW êÖ¢¾ Ö;zö &š öÞ -r¢ >wV~ f~ vª~ Î"º ë߂ ßWj ¾æÚî. 6

‚ ï «¶’Vº χ~ pHö "6~² æz~&. öÞ-r¢

 >wVöBº r¢ f~ö ~š ¢‚ b–šj áj > ® Ö ¢~² ¾æÒ.

ÒÏV^

B : nucleation rate [#s-kg]

C : concentration of component in solution [mol/m³] d : gap size between inner and outer cylinder [m]

G : linear growth rate [m/s]

k : rate constant of reaction [m³/mol-s]

L : particle size [m] or Couette-Taylor reactor length [m]

n : population density [#/m-kg]

m₃ : 3-rd moment of population density defined as [dimensionless]

r_A : rate of reaction [mol/m³-s]

r_i : radius of inner cylinder [m]

r_o : radius of outer cylinder [m]

x : conversion of limiting reactant A [dimensionless]

ÒšÊ ^¶

β : input concentration of reactant B defined as C_B0/C_A0 [dimensionless]

γ : Damköhler number defined as kC_A0τ [dimensionless]

θ : age and residence time defined as τ/τ [dimensionless]

τ : mean residence time [s]

ω_i : rotating speed of inner cylinder [rad/s]

~ζ

A : component of OH⁻ B : component of CO₂ 0 : input value

^^ò

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n L( )L³dL

0

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