Korean Chem. Eng. Res., Vol. 45, No. 3, June, 007, pp. 58-63 g g o mk m o oi n m oi iii i lo Ç Ç k Ç p *Ç p * o 305-701 re o 373-1 * l v l o rl 305-343 re o q 71- (006 1o 18p r, 007 1o 11p }ˆ) Effect of Precipitation on Operation Range of the Capture Process using Ammonia Water Absorbent Jong Kyun You, Ho Seok Park, Won Hi Hong, Jongkee Park* and Jong-Nam Kim* Department of Chemical and Biomolecular Engineering, KAIST, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea *Chemical Process Research Center, KIER, 71- Jang-dong, Yuseong-gu, Daejeon 305-343, Korea (Receivecd 18 January 006, accepted 11 January 007) k d p ˆ } o r rp n r k k p rn p m. p ˆ n r p rl r k k r m (loading, mol / ) r m. p o l r kl Pitzer p pn l k k r l n r l m. 5 O p p k k r n l s k r p p n p lp pl. k k r l NH 4 rp p p l slp rk m. 5~14 Op k k r 93, 313 Kl 0.5 p l rp m. r p ˆp sl p f k k r d } rl n ppp k pl. n r p l d p ˆ } o r rm k k l 97~31 Kpl. h Abstract Ammoniater was investigated as a new absorbent of the chemical absorption process for the removal of in flue gas. The suitable range of ammoniater concentration and loading (mol CO /mol NH 3 ) were decided in the point of view of absorption capacity and NH 4 precipitation. The absorption capacity of and the precipitation of NH 4 in liquid phase were calculated by the Pitzer model for electrolyte solution. The absorption capacity of the ammoniater over 5 O was higher than that of conventional amine absorbent. The loadings where precipitation occurred were decided at various absorbent concentrations. Theses values were higher than 0.5 in the concentration range of 5-14 O at 93, 313 K. The absorber for the removal of in flue gas could be operated without NH 4 precipitation by using high concentration of ammoniater below these loading values. The optimum temperature of the ammoniater absorbent for removal of in flue gas was 97-31 K depending on the concentration of ammoniater. Key words: Ammonia Water, Absorption, Carbon Dioxide, Precipitation, Pitzer Model 1. p ˆ v m p tnopp k r p. Špr k s ll p ˆ r o p l v p. l v p ˆ } t, k To whom correspondence should be addressed. E-mail: whhong@kaist.ac.kr rl p r p d tp p ˆ } q rp rp k r p [1]. p pn p ˆ p } rl MEA(monoethanolamine), DEA (diethanolamine), MDEA(N-methyldiethanolamine), AMP(-Amino-- methyl-1-propanol) p k r p rp n. Yehm Bai[-3] k k k rl n q l v l qrp v tq k k d 58
k k r pn p ˆ r rl r p sl mll m 59 } n r re m. k k rl n n, k rm k kp ep r p r p. k kp ep, k l p r, p p p opp p. k k d } n r n e r l p lr r. r p p re lp er q l rn m kv l. l l d } n rl k k r p rn p m. p ˆ n r p rl k k rp sl s p r m. p o l rl rp r m, r kl Pitzer p n l k k rl sq p m.. m d t p ˆ k k rm e (1)~(5)p p p k p. H O Ë NH 4 OH (1) H O Ë HCO 3 H () HCO 3 Ë H (3) Ë NH COO H O (4) H O Ë H OH (5) (1)~(5)p p l NH 4, NH COONH 4, (NH 4 p r pp p. pp e (6)~(10), p e (11)p ˆ l. e (11)l Table 1l re l [4, 5]. K 1 m NH4 m -------------------------- γ γ OH NH4 --------------------- OH m NH3 γ NH3 m K HCO3 m H -------------------------- γ HCO3 --------------------- m CO γ H γ CO γ H m K CO3 m H 3 ----------------------- γ CO3 ------------------ K 4 K 5 m γ HCO3 HCO3 m NHCOO ----------------------------- γ a NHCOO w ------------------------- m NH3 m γ NH3 γ HCO3 HCO3 γ γ H OH m H m OH ---------------- C lnk C 1 ----- C T 3 lnt C 4 T (6) (7) (8) (9) (10) (11) e (1)~(5)p pl p r,, H Om NH 4, Table 1. Coefficients for equilibrium constants for reaction (1) to (5) [4, 5] C lnk C 1 ----- C T 3 lnt C 4 T Reaction C 1 C C 3 10 C 4 1 97.976-5,930.7-15.063-1.117 10.8-7,74.6-14.506 -.8104 3 116.73-8,98.0-18.11 -.49 4 19.817 55.69-4.0400 0.46898 5 140.93-13,445.9 -.4773 000 NH COO, HCO 3, 3, H, OH p pmsp r v (electrolyte) nkp. r v nkl p Gibbs energy Pitzer[6]l p e (1) re l [7]. G E ( 0) --------------------- f RTn w M 1 ( I) m i m j β ij w i wj w m i m j i wj wk w ( ( 1) β ij ( )) m k τ ijk (1) e (1)p p p (acivity coefficient) (1) lp p. p rp k lv rp β ij e [4] e (13)p llv. I lnγ i A φ z i ---------------- ( 0) --ln( 1 b I) m 1 b I b j β ij 3 m j m k τ ijk j w j wk w (13) e (13)p m e (6)~(10)p p e 5, e (14)~(16)p v ve, r ve(electroneutrality)p l re p l p (molality) p. m NH3 t m, NH3 m NH4 m NHCOO m CO, t m NH3 t α m m m, CO NHCOO HCO3 m NH4 m H m m NHCOO m HCO3 CO3 m OH 3. y (14) (15) (16) 3-1. nm o rp k rl rp v k mll sl lk. p ml p p p l k k r l rp n, p r p p o l r p m. rp k k r l l rp NMR m. k k rl l NH 4, NH COONH 4, (NH 4 p rp p. p v p t o } o (> 99%)p NMRp r l Fig. 1(A)l ˆ l. NH 4 p n 16 ppm, NH COONH 16, 167, 168 ppm, (NH 4 160 ppm p l r rp m. 95 Kp ml 10~5 wt% k k l tp l rp okp v pe. 10 k v lp snkp ph k k l 8.1~9.m. r l r p NMR Fig. 1(B)l ˆ l. NMR m 16 ppm }l p l r p NH 4 pp p pl. p NH COONH 4 m (NH 4 mp l n NH 4 l j l rp rp n p NH 4 sq p. l NH 4 r l. 3-. h d p ˆ rp ˆ sls p l r f I m CO3 Korean Chem. Eng. Res., Vol. 45, No. 3, June, 007
60 or Ë Ë o Ë s Ë s Fig. 1. NMR spectra of (A) ammonium carbamate, ammonium carbonate, and ammonium bicarbonate, (B) products after the reaction between ammoniater and carbon dioxide at various concentrations from 10 to 5 wt%. m 93~333 K, k k mol NH /kg H O p l k 3 rl sq p m. p o p m p l p l m p kp l [8, 9] l Fig. m 3l ˆ l. r m 93~333 K, k k.1~11.8 Op ol p q p p p. Edward [4] Kurz [8]p e (13)p p o binary interaction parameter / /H O l l m. p k k l l Kurz [8]p re interaction parameter n n p p q m. 3-3. m k k k r d p ˆ rl n o q n p k r p p n p lk. k k l p r k rp MEA(monoethanolamine)m AMP(-Amino--methyl-1- propanol) l Fig. 4l ˆ l. 5 O(8 wt%) p p k k r n l 30 wt%p n k MEA, AMP p n p lp pl. 3-4. n m oiiii i r NH 4 e (17)p pp n (solubility o45 o3 007 6k Fig.. Partial pressure of (A) and (B) in the.1 mol/kg aqueous solution at various temperatures;,, -experimental data (Van Krevelen et al.[8]), Line - prediction, this work. product)p e (18) re l [8]. NH 4 K NH4HCO3 Ë NH 4 (s) (17) m NH4 m γ γ HCO3 NH4 HCO3, 365.3 exp 8.3413 --------------------- T (18) rp (loading) p p p s m. r p v l NH 4 m HCO 3 pm m. pm sp p p e (18)p n ƒv r p [8]. r mll p p o l Kurz [8]p m. Kurz [8]p m 313 K, k k 6.3, 11.8 mol/kgl kl r l m. Fig. 5l ˆ m p rp ml v k mlp q m. Fig. 6l k k l k r l NH 4 rp eq (α precipitation )p ˆ l. r p p lr o l p p l ˆp nr lk. p rp d } rl r
k k r pn p ˆ r rl r p sl mll m 61 Fig. 5. Prediction of solubility limitation of NH 4 at 313 K:, experimental data (Kurz et al.[8]) -without precipitation, - with precipitation, Line - prediction, this work. Fig. 3. Partial pressure of (A) and (B) in the various concentrations aqueous solution;,, -experimental data (Kurz et al.[8], Van Krevelen et al.[9]), Line - prediction, this work. Fig. 6. loading of NH 4 precipitate formation at various concentration of ammoniater. 0.5 p l sl p, slm 93~313 K l l 5 O p p k k k l p r rlp r n ppp k p. Fig. 4. Comparison of absorption capacity between ammoniater and conventional amine absorbents; -experimental data (Shen et al.[10]), -experimental data (Li et al.[11], Seo et al.[1]), Line - prediction, this work. 3-5. oi p rp rp (α max )p p p (α eq )p r. m p p n v α eq v l l o v, p m l NH 4 p r p np r sl Korean Chem. Eng. Res., Vol. 45, No. 3, June, 007
6 or Ë Ë o Ë s Ë s ) r m. p l k k rl rp p p o l 6.5~0 O(10~5 wt%) k k l rp NMR r m. NMR m 16 ppml l r p NH 4 p p p m. Pitzer p pn l k k r l n l r l m. 5 O p p k k r n l s k r p p n p lp pl. k k r l NH 4 rp p p l slp rk m. 5~14 Op k k r 93, 313 Kl 0.5p l rp m. r p ˆp sl p f k k r d } rl n ppp k pl. n r p l d p ˆ } o r rm k k l 97~31 Kpl. 9 O k k 303 Kl n 0.1 kg /kg solution(1.6 kg /kg )p ˆ l. Fig. 7. Maximum (A) loading and (B) absorption capacity of ammoniater at various temperatures (p CO 15 kpa). p rp s (α precipitate )l r p. Fig. 7(A)l k 15 kpap dl l k k rp m, sl p ˆ l. 5 / kgh Op rl rp v kp p p k s (α eq )l p r l. 7 O p p rp n rp mlp s q l p m mll sl rp (α precipitation )p r l. Fig. 7(A)l ˆ m p q p sl p ˆ m 7~13 mol /kg H Ol 97~31 K v m. sl p n (kg /kg solution)p ˆ Fig. 7(B)m. k 15 kpap l d } l l k k l n p v, r p l rp m sq p p. 9 Op n r s 303 Kl n 0.1 kg /kg solution(1.6 kg /kg )p lp pl. 4. d p ˆ } n k k r k k p rn p m. p ˆ n r p rl r k k r m (loading, mol / o45 o3 007 6k l p ˆ r } l (CDRS, Carbon Dioxide Reduction and Sequestration R&D Center)p vop lp pl. k A φ : debye-hückel constant [kg 1/ mol -1/ ] : activity of pure water [mol/kg] b : parameter in equation (13) [kg 1/ mol -1/ ] f 1 (I), f (I) : functions in Pitzer s equation G E : total excess Gibbs free energy I : ionic strength [mol/kg] K : equilibrium constant of reaction with activities expressed in molalities M w : molecular weight of pure water [kg/mol] : molality of species i [mol/kg] m i m CO,t m CO,eq m NH3,t n w : total molality of [mol/kg] : molality of in equilibrium with gas phase [mol/kg] : total molality of [mol/kg] : number of moles of pure water [mol] R : gas constant T : temperature [K] z i : ionic charges on species i [-] m m α : loading moles of /moles of [-] (0) (1) β ij, β ij γ i τ ijk : binary interaction parameters defined by Pitzer : activity coefficient of species i (on molality scale) : ternary interaction coefficient
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