Experimental Study on Chemical Carbon Dioxide Absorption Using …petrotexlibrary.com/wp-content/uploads/2016/03/Vol3... · 2016-03-20 · Aqueous solution of 1-methyl-2-pyrrolidine

American Journal of Oil and Chemical Technologies: Volume 3. Issue 1. May 2015

Industrial And Mining Research Centre – Cycle Science & Industry Company, Tehran, Iran Email: [email protected]–phoneNumber:+982188853416

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American Journal of Oil and Chemical Technologies

Journal Website: http://www.petrotex.us/2013/02/17/317/

American Journal of Oil and Chemical Technologies

Journal Website: http://www.petrotex.us/2013/02/17/317/

Experimental Study on Chemical Carbon Dioxide Absorption Using Porous Polysulfone Gas- Liquid Hollow Fiber Membrane Contactor System

Ehsan kianfar

Ph.D. Student, Department of Chemical Engineering, Arak Branch, Islamic Azad University, Arak, Iran

Abstract

In this study, process asymmetric hollow fiber poly sulfone(PSf) membranes using ethanol (0and 2 wt%) as non-solvent additive in the polymer dope via phase inversion method were fabricated. Aqueous solution of 1-methyl-2-pyrrolidine (NMP, >99.5%) was applied as a bore fluid and water was used as the external coagulant. The morphology of fabricated membranes was examined using field emission scanning electron microscope (SEM).Fabricated membranes were characterized in terms of pore size, critical water entry pressure, and collapsing pressure. The performance of fabricated membranes for carbon dioxide absorbtion from monoethanolamine solution using a gas - liquid membrane contactor system was studied. The results showed that carbon dioxide stripping flux and efficiency increased by increasing liquid velocity .Membranes produced using ethanol to by 2% wt of 𝐶𝑂! excretion rate than other polymer hollow fiber membranes Poly Sulfune. The amount of 𝐶𝑂! gas was (3.9 × 10!!) mol / 𝑚!s that this amount of liquid flow rate300 ml / min respectively.

Keywords: Gas-liquid membrane contactor ,absorbtion CO2, Hollow fiber membrane, Poly Sulfone (PSf)

1.Introduction

Research is ongoing to enhance the pressure-normalized flux and selectivity of asymmetric polymeric gas separation membranes. A thin and effectively undamaged active layer is required and a number of fabrication techniques, which control the conditions of phase inversion in various ways, have been employed to achieve this [1–3]. It is now possible to heighten membrane selectivity beyond the generally recognized intrinsic value for the amorphous polymer [4–6]. This has been accomplished in a number of different ways for various polymers: polysulfone [7–10], polyethersulfone [11], polyestercarbonate [12], polyimide [13], polyamide [14] and cellulose acetate[15]. It has also been recognized that molecular orientation will affect membrane selectivity [5,12] and that orientation can be brought about by altering the rheological conditions during fabrication [16].Shear and elongation during spinning have been shown to affect the permeation performance of polysulfone hollow fiber membranes [17,18] and this was attributed to molecular orientation in the active layer.Molecular orientation in membranes can now be directly measured by spectroscopic techniques [19]. Plane polarized infrared spectroscopy has been used recently to confirm the presence of shear rate induced orientation in gas separation membranes [9,20]. For polysulfone hollow fibers, increased dope extrusion rate (DER) was shown to elevate membrane selectivity beyond the intrinsic value of the polymer [9,21].Altering the internal coagulant system has also been shown to improve the gas separation performance of hollow fiber membranes [11,22]. It is thought that the integrity of the outer skin layer is compromised if solvent migration into the bore is too rapid [3]. A reduction in coagulant water activity in the bore slows down

Kianfar/AmericanJournalofOilandChemicalTechnologies5(2014)1-12

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inward solvent diffusion which protects the active layer from perforation. This paper investigates the effects of increased shear during spinning and decreased coagulant water activity in the bore fluid with a view to producing highly selective polysulfone hollow fiber membranes. A unique dry/wet spinning system was used with a particular forced convection setup in the dry gap. The specific details of the process are given in this paper. The forced convection approach, in general, is one means of producing non-porous active layers in polymeric membranes [23]. Molecular orientation in the membrane active layer was investigated using plane polarized infrared spectroscopy, a technique that has been employed in other fiber applications[24]. 2 mm clearance existed between the top of the forced convection chamber and the bottom plate of the spinneret and also between the bottom of the forced convection chamber and the water level in the first coagulation bath. Pure water at 148C ^ 0.58C was used in the external coagulation baths. The bore coagulant was either pure water or a 20% (w/w) solution of potassium acetate in water at ambient temperature. This equates to water activities of 1 and 0.9 [3] respectively. At both bore water activities, hollow fibers were spun at two DERs and hence at different levels of shear. The stretch ratio (wind up speed/ extrusion speed) was fixed at 1 throughout. The ratio of DER to bore fluid injection rate was also kept constant at a value of 3. After spinning, the membranes were steeped in water and then dried using a methanol solvent exchangetechnique[25]. The objetives of this research are:

1.Fabrication of hollow fibre membranes of poly sulfone (PSF)

2.Analysis of the characteristics of the fabricaled membranes in terms of structure of membrane modulus of contact with water pore size of membrane total porousity rate effective surface porosity critical water entry pressure collapse pressure membrane and gas permeabitity rate.

3.Using the fabricated membranes for absorption of carbon dioxide by monoethanol amine solution in a gas-liguid membrane contactor system and evaluating the performance of the system for absorption of carbon dioxide .

2. Materials

Poly sulfone polymer (PSF udel P-1700-solvay Advance polymer) was used to fabricate hollow fibre membrane .1-methy -2-

pyrrolidine without further purification of polymer was supplied by merk company . Ethanol was purchased from merk

company qermany and was used as an unsoluable additive in polymer solution dape was also used throughowt the process

(spinning process ) as coagulant bathroom .mono-ethanol amine(MEA>98%) was purchased from sigma-Aldrich company and

was used bas liquid absorbent.

3. Fabrication of hollow fibre

The process of spinning hollow fibre via wet-dry phase inversion method is discussed in papers . in figure,1 a schematic of fabricating hollow fibre machine is shown. Polymer solution is degassed prior to spinning . pore fluid (water+NMP) and polymer solution are pumped into the internal pipe of the spinner and into the circular section of the spinner respectively by tow gear pumps. Table 1 shows the parameters of spinning . dope was applied as an external coagulant for solidification of polymer solution resulting in formation of hollow fibre. After that the spinned hollow fibre wasdrowned into the water for three days to remove the remaing ethanol and NMP.then it was naturally hung to be dried in environment temprature for one to two days.


3

Figure1. Hollow fiber membrane spinning apparatus: (1) nitrogen; (2) dope reservoir; (3) gear pump; (4) filter, 7 mm; (5) syringe pump; (6) spinneret; (7) forced convection tube; (8) roller; (9) wind-up drum; (10) refrigeration/heating unit; (11) coagulation bath; (12)washing/treatment bath; (13) wind-up bath; (14)schematic of a spinneret[26].

Table1. characteristics of spinning parameters of hollow fiber membrane of poly sulfone polymer

Output speed polymer solution (ml/min)

4.5

Composition Fluid hole ( %wt) 90/10 NMP+Water Flow rate Fluid hole ( ml/min) 2

external coagulant Tap water Distance air gap (air gap(cm) 0.0

outer diameter of the inner spinner (mm)

5/0/1

Temperature coagulant(℃)

25

3.1. Test of gas permeability It is very important to determine the pore size and the specific level of porosity for study of mass transfer in membrane absorption of gas for an asymmetric poraus membrane[27]. Lee and et at[28] Introduced the method of penetrating modified gas to determine the pore size and surface porosities effecting the length of the pores influeuced by the asymmetric membrane . Assuming the cylindrical pores in the shell layer of asymmetric membranes gas per-meability can be given by the following relation :

(1)

Where it is gas permeability rate (mol/m2 s Pa) rp and Lp are respectively pore radius and the effective pore length (m) is the level of porosity R is constant of gases: 8/314(J/MOL K) µ is the gas viscosity (Kg /m s)M is molocular weight (Kg/mol) T is gas temperature (K) and D is theaverage pressure (Pa).Drawing Ji in terms of mean pressure according to equation (1) the mean pore size is calculated by the following equation via width from initiation (Ko) and slope (Po):


4

(2)

The affective surface porosity to the pore length £/LP can be obtained from the following equation from the slope :

(3)

The test module consisting of two hollow fibers with a length of 10cm was used determine the gas permeability of feed on the shell side. The high pressure was around 1 10 to 4 10 (Pa)(from 1 to 4 bar )(absolute ).Nitrogene was used as the test gas and its penetration rate was measured in 25C w ith the use of soap bubble flow meter connected to the side of the hollow fiber pipe . then gas permeability was calculated on the external diameter of hollow fiber .

Figure 2. A schematic of gas permeability test

3.2. Absorption test of CO2

Gos-liquid membrane contactor system was used to measure the flux rate of CO2 . in total 10 hollow fibers were placed in a stainless steel membrane modale. characteristics of membrane collision module is shown in Table 2. Pure Co2 on the pipe side as feed gas and MEA(1M) on the shell side as absorbent liquid were in non-aligned state.gas and liquid flow rates were controlled in 200 ml/min and so-300ml/min respectively by control taps and flow meters. The pressure of gas side was tuned on 1*10Pa(1 bar ). The pressure of liquid side was hold higher than the gas side by 0.2*40 Pa(1 bar) to prevent bubble formation in the liquid . to Min titration method 10 ml of the sample liquid exited from module was poured in a beaker and some more than that value (about 12ml) of NaOH 0.1molar solution was added to the solution so that the amount of Co2 which is present unsolved in the solution to be completely ionized . then some value of BaCl2 was added to the solution . the resulted solution was then well shaken so that all the carbon dioxide solved in the solution (physically or chemically) to be deposited in the form of BaCO2 . the remaining NaOH in the solution was titrated by HCL and phenolphetalein was used as index . to measure the value of the absorbed Co2 some drops of methyl orange was added to the solution and then the solution was titrated by HCL.the


5

value of used HCL. In this stage is used to calculate the value of MEA.Before sampling all the expriments were conducted for 30 minutes to come to a stable state.

(4)

The total area of membrane was considered as the surface of gas-liquid contact for mass transfer so the experimental absorption flux vale of Co2 valated to is calculated by the following relation :

(5)

Where qL is the vale of absorbeut flow (m/s) Mco2 is Co2 density in absorbent solution (mol/l) and Ai is the surface of gas-liquid contact (m). the absorbent flow rate at the exit of membrane contacting module is measured by a liquid flow meter. Gas- liquid contact surface is measured based on the absorbent flow on the pipe side or modules shell. When the absorbent liquid on the shell side is flown the area of contact surface is calculated from the following relation:

(6)

Where( n) is the number of fiber (10 in this experimeut) di is the internal diameter of fiber (m) and L is the effective fiber length (m) , in figure 3 a drawing of laboratorial pilot flow is shown

Figure 3. laboratorial pilot flow for Co2 absorption


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Table 2. details of gas-liquid membrane cantactor system

Inner diameter module 15mm Length module 250mm

Diameter fiber output 0.9-1mm Diameter fiber input 0.45-0.5mm effective length fiber 18mm

number fibers 10 Collision area 4521inner

4. Results and discussion

4.1. Morphology of hollow fiber membranes

the morphology of hollow fiber membranes poly sulfone hollow fiber membrane was fabricated applying the method of wet spinning with two diffenent additive densities in spinning solution . the morphology of the membranes was studied analyzing the cross-section and inter-section of different amplifications by SEM. The fabricalted hollow fiber membrane have an external diameter of abowt0.75 to 0.9 mm an internal diameter of about 0.4 to 0.45 mm and a well thickness of around 0.175 to 0.225 . the structure of the cross-section and inter-section of the membrane is shown in figures4 (a-b) and figures5 (a-b). of large finger like pores origin of which is frow the external surface of the hollow fiber wall. The internal surface of the membranes also consist of a sponge like layer: usage of aqueous mixture solvent (NMP) as bore fluid and consequently delay of the solidification of membrane is the cause of the sponge like layer. All the membranes show the non-shell internal surface. This is because of high NMP content in internal coagulation . in fact this phenomenon on internal surface results in the construction of open microporous . however since water acts as a strong non-solvent use of water as an external coagulant provides membranes with one layer of external shell. As solution have more pores compared to the membrane without ethanol which is because of the potential of ethanol in creating pores in the time of the solidification of the membrane .


7

(a)

(b)


8

Figure 4.The structure of cross-section of PSf hollow fiber membrane by SEM:(A) without additive (B) ethanol 2 wt%

(a)

(b)

Figure 5. the structure of inter –seetion of PSF hollow fiber membrane by SEM(a) without additive (b) ethanol 2wt%

4.2 .influence of additives on the structure of hollow fiber membrane

The results of experiments related to gas permeability critical water entry pressure ( CEPW) measur ment of porosity rate water contact rate and collapsing pressure are summarized in table 4 porosities are around 70.54 to 74.90 which are high enough and


9

are attributed to low density of polymer in polymer solution (dope). Figure 6 shows the permeability of N2 against average pressure . the data are correlated bya straight line with an acceptable high coefficient of (R). with regard to the method shown in the section of experiment and the given results in table 4 the data were used to calculate the average pore size. Asis seen the penetration of the calculated N2 for all the membranes tends to increase with the increase of the average pressure . this phenomenon shows that both poiseuille and Knudsen are dominant of N2 via PSF membranes :As it is clear the slope related to the orovided membrane with ethanol of 2 wt 40 is very small as an additive which determines that the knudsen leads to more penetration of gas compared to Poiseuille due to small pore size.With regard to the critical water entry pressure all the membranes can resist against the applied additional pressure on the shell side through out the process of disposal of carbon dioxide . the fabricated membrane without ethanol in solution shows a lower critical water entry pressure than the othermembrane which is due to its larger pore size ,that is why that this membrane has a lower rate of water contact than the other fabricaled membrane. Larger pore size has facilitated water entry into the membrane and reduces the rate of water membarane contact.the collapsing pressure for all the fabricated membranes is proportionally high and for all the membranes this pressure is considerably more than the operational pressure in the experiment .as table 4 shows the collapsing pressure of the membrane increases with the increase of the diameter of the membrane pores. The reason why of that is that the nitrogene gas flow passes more easily through the membrane with the increase of the diameter of pores and for that the membrane requives higher pressure to callapse. the influence of additives on the Co2 absorption performance.Figure7 showe the influence of moxoethanol amine solution flow rate (MEA)as sorbeuton Co2 flux increases with the increase of absorbent flow rate .the cause of that is in the case of gas absorption in membrane contactore liquid phase resistance controls the mass transfer process. On the other hand it seems that Co2 gas flow rate has no influence on Co2 flux as there is no resistance for Co2 transfer due to the use of pure carbon dioxide on gas side .A similar procedure has also been reported for the use of common amines for Co2 absorption in membrane contactors of poly tetra fluore ethylene and poly vinyllidine fluoride. It was oserved from figure 8 that Co2 flux related to the fabricated membranes without ethanol was considerably lower than the other

membrane from Table 4 it was seen that the effective porosity of the effective surface of this membrane is smaller than the other membrane. Therefore the surface of gas –liquid contact is smaller and the absorption flux is lower than the other membranes , with the provided solution with ethanol 2 wt% as additive substance in spinning solution maximum flux of (3"q 10) Co2 mol/m in 300ml/min of sorbent fiow rate is obtained.

Table 4. Characteristics of poly sulfone hollow fiber membrane.

Additive Average size Holes (nm)

Porosity surface Effective ε/Lp (m−1)

Entry critical pressure Weather

(×105 Pa)

Total porosity %

Pressure broken Membrane (×105 Pa)

Factor Collision With

Weather

Without additives 24.56 48.57 7.50 70.54 8.5±0.5 68.50

Ethanol(2 wt.%) 19.32 76.30 8.00 74.90 7.5±0.5 73.25


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Figure 6. Shows the permeability of N2 against average pressure

Figure 7. Showe the influence of moxoethanol amine solution flow rate (MEA)as sorbeuton Co2 flux increases with the increase of absorbent flow rate

5E-10x+9E-08y=0.9481R2=

7E-10x+1E-07y=0.9543R2=

0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

3.00E-07

3.50E-07

100 150 200 250 300 350

WithoutaddiLve

PSf+2%Ethanol

Meanpresuure(KPa)

N2P

ermeance(m

ol/m

2 spa)

Meanpresuure(KPa)

N2P

ermeance(m

ol/m

2 spa)

0.00E+00

5.00E-04

1.00E-03

1.50E-03

2.00E-03

2.50E-03

3.00E-03

3.50E-03

4.00E-03

4.50E-03

0 50 100 150 200 250 300 350

PSf+2wt.%Ethanol

WithoutaddiIve

AbsorpIo

nflu

x(m

0l.m

-2.s-1)

Liquidflowrate(ml.m-1)


11

5. Conclusions

1-porosities are around 70.54 to 74.90 which are considered high enough and are attributed to low polymer density in polymer solution (dope).

2-callapsing pressure and critical water entry pressure for all the fabricated membranes are considerably more than the operational pressure in the experiment of gas absorption.

3-permeability of nitvogeue gas for all the membranes increases with the increase of mean pressure .

4-absorption rate of carbon dioxide gas increases with the increase of the of velocity of absorbent liquid .

5-with regard to the critical water entry pressure all the membranes can resist against the additional pressure applied on the shell side (0.2 10 Pa) throughout the process.

6-with the provided solution of ethanol with 2 wt% as additive substance in spinning solution the maximum flux of (3.9 10)Co2 mol/m 300ml/min of sorbent flow rate is obtained.

References

[1] Chung TS, Teoh SK, Hu X. Journal of Membrane Science1997;133:161. [2] van’t Hof JA, Reuvers AJ, Boom RM, Rolevink HHM, Smolders CA.Journal of Membrane Science 1992;70:17. [3] Pesek SC, Koros WJ. Journal of Membrane Science 1994;88:1. [4] Pinnau I, Koros WJ. Journal of Applied Polymer Science1992;46:1195. [5] Pfromm PH, Pinnau I, Koros WJ. Journal of Applied Polymer Science1993;48:2161. [6] Rezac ME, Le Roux JD, Chen H, Paul DR, Koros WJ. Journal ofMembrane Science 1994;90:213. [7] Pesek SC, Koros WJ. Journal of Membrane Science 1993;81:71.[8] Ghosal K, Chern RT, Freeman BD, Daly WH, Negulescu II. Macromolecules1996;29:4360. [9] Ismail AF, Shilton SJ, Dunkin IR, Gallivan SL. Journal of MembraneScience 1997;126:133. [10] Pinnau I, Koros WJ. Journal of Membrane Science 1992;71:81. [11] Li S-G, PhD Thesis, University of Twente, 1994. [12] Pinnau I, Hellums MW, Koros WJ. Polymer 1991;32:2612. [13] Kawakami H, Mikawa M, Nagaoka S. Journal of Applied PolymerScience 1996;62:965. [14] Mohammadi AT, Matsuura T, Sourirajan S. Gas Separation and Purification1995;9:181. [15] Chen Y, Fouda AE, Matsuura T. In: Advances in Reverse Osmosis and Ultrafiltration, National Research Council of Canada, Vancouver,1989. p. 259–278. [16] Puri PS. Gas Separation and Purification 1990;4:29. [17] Shilton SJ, Bell G, Ferguson J. Polymer 1994;35:5327. A.F. Ismail et al. / Polymer 40 (1999) 6499–6506 6505Table 3O2/N2 permeation data (effecof bore coagulant and shear rate)aUncoated Coated(PO2) (PO2/PN2) (PO2) (PO2/PN2)Pure water in the boreDER . 1.0 cm3 min21 (low shear)6.06 1.44 7.96 1.72DER .2.5 cm3 min21 (high shear)25.5 1.14 5.56 4.90Reduced water activity in the boreDER . 1.0 cm3 min21 (low shear)3.94 2.72 2.51 6.41DER . 2.5 cm3 min21 (high shear)29.3 1.11 6.91 7.32a Here P is the pressure-normalized flux £ 106 (cm3 (STP)/(s cm2 cm Hg)), measured at 258C and at a pressure differential of 5 bar. [18] Shilton SJ, Bell G, Ferguson J. Polymer 1996;37:485. [19] Khulbe KC, Gagne´ S, Tabe Mohammadi A, Matsuura T, LamarcheAM. Journal of Membrane Science 1995;98:201. [20] Shilton SJ, Ismail AF, Gough PJ, Dunkin IR, Gallivan SL. Polymer1997;38:2215. [21] Ismail AF, Shilton SJ. Journal of Membrane Science: Rapid Communication1998;139:285. [22] Chung TS, Kafchinski ER. Journal of Applied Polymer Science1997;65:1555. [23] Pinnau I, Koros WJ. Journal of Polymer Science: Part B: PolymerPhysics 1993;31:419. [24] Xue G. Makromol. Chem.: Rapid Commun. 1985;6:811. [25] Manos P. US Patent 4120098, 1978.

[26]. [11].A. F. D. I. G. S. a. S. S. Ismail, "Production of super selective polysulfone hollow fiber membranes for gas Separation," J. Membr. Sci, vol. 40, p. 6499–6506, 1999.


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[27].B. V. d. B. T. V. G. P. Luis, "Non-dispersive absorption for CO2 capture:from the laboratory to industry," J. Chem. Technol. Biotechnol, vol. 86, pp. 769-775, 2011. [28].J. a. C. B. Li, "Review of CO2 absorption using chemical solvents in hollow fiber membrane contactors," Sep. Purif. Technol, vol. 41, pp. 109-122, 2005.

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Experimental Study on Chemical Carbon Dioxide Absorption Using …petrotexlibrary.com/wp-content/uploads/2016/03/Vol3... · 2016-03-20 · Aqueous solution of 1-methyl-2-pyrrolidine