Available online at ScienceDirect. Energy Procedia 114 (2017 )

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1 Aville online t ScienceDirect Energy Procedi 4 (27 ) th Interntionl Conference on Greenhouse Gs Control Technologies, GHGT-3, 4-8 Novemer 26, Lusnne, Switzerlnd Experimentl Results of Pressure Swing Adsorption (PSA) for Precomustion CO 2 Cpture with Metl Orgnic Frmeworks Crlos A. Grnde *, Richrd Blom, Kri Anne Andressen nd Ruth E. Stensrød SINTEF Mterils nd Chemistry, Forskningsveien, Oslo, Norwy Astrct Vcuum Pressure Swing Adsorption (VPSA) hs lredy proved tht it cn e used for cpture of CO2 from the til gs of the PSA process for hydrogen purifiction. The demo operted in Port Arthur y Air Products hs lredy cptured more thn million metric tons of CO2. In this work we re evluting the utiliztion of formulted metl-orgnic frmework (UTSA-6) for cpture of CO2 from stem-methne reforming off-gses with the im of selectively cpture CO2, while llowing hydrogen nd other components to pss through it, iming to remove the requirement of vcuum for CO2 cpture in this ppliction. We hve mesured quternry rekthrough curves with 76% H2, 7% CO2, 3% CH4 nd 4% CO simulting the off-gs of typicl stem-methne reformer. We hve lso simulted the results using mthemticl model tht constitutes the sis for design nd improvement of the PSA unit. 27 The Authors. Pulished y Elsevier Ltd. This is n open ccess rticle under the CC BY-NC-ND license 27 The Authors. Pulished y Elsevier Ltd. ( Peer-review under responsiility of the orgnizing committee of GHGT-3. Peer-review under responsiility of the orgnizing committee of GHGT-3. Keywords: H 2 purifiction; CO 2 cpture; dsorption; metl-orgnic frmework. Introduction One of the lrgest demo plnts for CO 2 cpture is instlled in Port Arthur, United Sttes nd uses n dsorption process s selective method to cpture ulk CO 2 from stem-methne reforming (SMR) off-gs []. This demo unit hs lredy cptured over million tons of CO 2 without reported prolems demonstrting tht dsorption is mture technique tht should e considered for CO 2 cpture technologies. * Corresponding uthor. Tel.: ; fx: E-mil ddress: crlos.grnde@sintef.no The Authors. Pulished y Elsevier Ltd. This is n open ccess rticle under the CC BY-NC-ND license ( Peer-review under responsiility of the orgnizing committee of GHGT-3. doi:.6/j.egypro

2 2266 Crlos A. Grnde et l. / Energy Procedi 4 ( 27 ) Specificlly, the technology used is dul Pressure Swing Adsorption (PSA). The first PSA unit is stte-of-thert technology for purifiction of hydrogen llowing hydrogen purity of >99.9% [2]. The til gs from the first PSA is ville t low pressure nd is constituted y mixture of some lost hydrogen nd ll unconverted methne, cron oxides (CO nd CO 2) nd wter. This strem is normlly urned to recover clorific power to the SMR rector. In this plnt, it is routed to second PSA unit tht opertes under vcuum nd for this reson is denoted s VPSA. From this unit is possile to recover purified CO 2 on one end nd ll other gses on the other. The ide of such dul PSA technology ws to retrofit CO 2 cpture unit in n existing refinery. The necessity of using vcuum is due to the vilility of the til gs contining CO 2 t low pressure. However, if the purifiction section cn e designed for new plnt, different pproch cn e dopted. Since the SMR off-gs is ville t reltively high pressures, it is possile to cpture CO 2 first without the need of using vcuum [3]. The gs exiting this unit cn e treted y norml PSA unit for H 2 purifiction, with reduced mount of CO 2 to process. The difference etween oth process schemes is shown in Figure. SMR off gses H 2, CO, CO 2, CH 4, H 2 O Stndrd PSA Purified hydrogen SMR off gses H 2, CO, CO 2, CH 4, H 2 O PSA for CO 2 cpture CO 2 for cpture (+H 2 O) Intermedites (H 2 ), CO, CO 2, CH 4 Til gs VPSA for CO 2 cpoture CO 2 for cpture (+H 2 O) Intermedites (H 2 ), CO, CO 2, CH 4 PSA for H 2 purifiction Purified hydrogen Figure. () PSA + CO 2 cpture VPSA unit retrofitted to Port Arthur; () dul PSA scheme for CO 2 cpture nd hydrogen purifiction. For pre-comustion schemes, the mount of intermedites (CO nd CH 4) is smller nd then, there is even the possiility of using only one PSA unit, provided tht some CO 2 cn e llowed to the hydrogen strem for power genertion. In ny cse, the design of the PSA for CO 2 cpture is similr in oth cses. The prtil pressure of CO 2 in SMR off gses or in pre-comustion schemes is reltively high in the order of severl tmospheres. This is very importnt specifiction in order to select the right dsorent mteril. For exmple, zeolites dsor lrge quntities of cron dioxide [4-6] ut its desorption requires very low vcuum or temperture. Activted crons re the dsorents lredy used in PSA unit for CO 2 removl in the hydrogen purifiction PSA nd thus re importnt cndidtes [7]. Despite its low density nd selectivity, the dsorent cost is very positive indictor of this mteril. On the other hnd, novel mterils cn offer desired properties of selectivity, cpcity nd cost. Metl-orgnic frmeworks re reltively new mterils where comintions of orgnic linkers nd inorgnic metls re grouped. Due to this comintion, there re siclly thousnds of possile structures tht cn e synthesized. Indeed, the numer of pulictions of MOF structures is very high. Unfortuntely, mny of these mterils is not stle in ir or wter. Additionlly, mny of them re synthesized with very expensive linkers nd thus they should e proper for other pplictions thn CO 2 cpture. Finlly, the numer of MOFs tht were formulted without dmging their high surfce re nd CO 2 selectivity is very reduced. One MOF mteril termed UTSA-6 [8] cn e very interesting cndidte for this ppliction. It hs reltively high dsorption cpcity for CO 2, with not so steep isotherms nd good selectivity towrds other gses. The linker of this mteril is citric cid (not so expensive linker). Moreover, we hve lredy demonstrted tht is possile to scle-up this mteril nd lso to formulte it with miniml decy in surfce re nd CO 2 dsorption cpcity [9]. Furthermore, nd differently from mny MOF mterils, hs density comprle to zeolites (nd higher thn ctivted crons). This mens tht when isotherms normlly reported in mol/kg re converted to mol/m 3, the vlue

3 Crlos A. Grnde et l. / Energy Procedi 4 ( 27 ) is still ttrctive nd very competitive. We hve lredy mesured fundmentl properties of single gs dsorption nd diffusion on pellets of this mteril nd used this dt to simulte the ehvior of H 2 PSA unit []. In this work we hve extended our previous study y mesuring dsorption rekthrough curves of the quternry mixture of gses exiting the SMR process (dry strem). The mesurements were done using more thn grms of formulted dsorent iming to understnd if the properties mesured from single components cn e relly extended to rel systems nd lso to understnd if the UTSA-6 formultion procedure hs een homogeneous for lrger smples. The results were lso used to clirte het nd mss trnsfer prmeters of mthemticl model tht is used to determine proper PSA scheduling for CO 2 cpture. 2. Experimentl Adsorption isotherms of the formulted (extrudtes) UTSA-6 re shown in Figure 2. The CO 2 dsorption cpcity is much lrger thn the ones of other gses. The steepness of the CO 2 isotherm is intermedite etween n ctivted cron nd zeolite. 2 CH4 CO CO2 N2 H2 Amount dsored [cm 3 /g] Pressure [kp] Figure 2. Adsorption equilirium isotherms of CH 4, CO, CO 2, N 2 nd H 2 on UTSA-6 extrudtes t 298K. Quternry rekthrough curves of gs mixture of 76% H 2, 7% CO 2, 3% CH 4 nd 4% CO were mesured in 4-column PSA unit ville in SINTEF. The gs ws provided s redy mixture from Yr, Norwy. Experiments were performed t totl pressure of 6 rs nd temperture of 35 K. Vrile flowrtes were used in order to understnd the effect of dispersion nd diffusion in the finl shpe of the rekthrough curves. The operting conditions used for mking the experiments re listed in Tle.

4 2268 Crlos A. Grnde et l. / Energy Procedi 4 ( 27 ) Tle. Experimentl conditions for quternry rekthrough curves. Condition Vlue Temperture [K] 35 Pressure [r] 6 Composition [%] 76% H 2, 7% CO 2, 3% CH 4 nd 4% CO Flowrte [SLPM].5,.,.5, 2. Column length [m].56 Column dimeter [m].22 m Adsorent mss [g] Theoreticl The isotherms were fitted with the Dul Lngmuir model nd the prmeters re ville in literture []. The single component isotherms were used in the theoreticl expression for prediction of the multicomponent ehvior. The rekthrough curves were modelled with n existing fixed ed model tht hs een vlidted for mny systems [,2]. For the ske of revity, we will not include the model in this puliction since is lredy pulished in mny different pulictions. This 2D model (time nd xil coordinte) consist of seven prtil differentil equtions (PDEs) corresponding to mss lnce in the gs, mcropores nd micropores of the dsorent, energy lnce in the gs, the solid nd the column wll nd the momentum lnce, simplified y the Ergun eqution. These PDEs re coupled with the idel gs nd isotherm equtions. The mthemticl model ws solved in gproms (PSE, UK) using the centered finite element method with t lest elements on the xil xis. 4. Results nd Discussion Brekthrough curves mesured t four different flowrtes re displyed in Figures 3-6. In the imges we show the molr frction of the different gses exiting the column s well s the temperture in four different plces in the column Molr frction (CO 2, CO, CH 4 ) H 2 Molr frction Temperture [K] Figure 3. Quternry rekthrough curve of H 2, CO, CO 2 nd CH 4 in UTSA-6 extrudtes t 6 r nd 35K with totl flowrte of.5 SLPM. () molr flowrte of gses exiting the column; () temperture in 4 thermocuples in the column. Solid lines re the results otined from the mthemticl model.

5 Crlos A. Grnde et l. / Energy Procedi 4 ( 27 ) Molr frction (CO 2, CO, CH 4 ) H 2 Molr frction Temperture [K] Figure 4. Quternry rekthrough curve of H 2, CO, CO 2 nd CH 4 in UTSA-6 extrudtes t 6 r nd 35K with totl flowrte of. SLPM. () molr flowrte of gses exiting the column; () temperture in 4 thermocuples in the column. Molr frction (CO 2, CO, CH 4 ) H 2 Molr frction Temperture [K] Figure 5. Quternry rekthrough curve of H 2, CO, CO 2 nd CH 4 in UTSA-6 extrudtes t 6 r nd 35K with totl flowrte of.5 SLPM. () molr flowrte of gses exiting the column; () temperture in 4 thermocuples in the column. Molr frction (CO2, CO, CH4) H 2 Molr frction Temperture [K] Figure 6. Quternry rekthrough curve of H 2, CO, CO 2 nd CH 4 in UTSA-6 extrudtes t 6 r nd 35K with totl flowrte of 2. SLPM. () molr flowrte of gses exiting the column; () temperture in 4 thermocuples in the column.

6 227 Crlos A. Grnde et l. / Energy Procedi 4 ( 27 ) The results indicte tht cron dioxide is indeed much more dsored thn the other gses, even in the quternry mixture. Also it cn e oserved tht the het genertion due to dsorption of cron dioxide is considerle with temperture increse in the column etween 35 K for low flowrte nd 55K for higher flowrtes. The min reson of the temperture increse when the flowrte increses is due to fster het genertion while the trnsfer of het is mostly limited y nturl convection from the column wll to the oven surroundings. The importnt result here is tht it is possile to descrie the system with the mthemticl model used tht will llow us to design PSA unit for CO 2 cpture, in principle, not requiring vcuum for CO 2 desorption. 4. Conclusions Adsorption of multicomponent gs mixtures hs een studied in formulted metl-orgnic frmework UTSA-6. In this mteril, CO 2 is much more dsored thn the other gses, lthough is possile to remove it just y reducing its prtil pressure (not requiring therml tretments). The cpcity of this mteril towrds CO is lso high when compred with zeolites. For this reson, this mteril cn e used for simultneous production of hydrogen nd cpture of cron dioxide. Adsorption processes hve the dvntge of eing le to e retrofitted to hydrogen production plnts where there is one existing unit for hydrogen purifiction. However, in new plnts, more efficient redesign of the seprtion schemes cn result in importnt svings of energy. Acknowledgements The support of the Reserch Council of Norwy through the CLIMIT progrm y the SINTERCAP project (23388). This puliction hs een produced with support from the BIGCCS Centre, performed under the Norwegin reserch progrm Centres for Environment-friendly Energy Reserch (FME). The uthor cknowledge the following prtners for their contriutions: ConocoPhillips, Gssco, Shell, Sttoil, TOTAL, GDF SUEZ nd the Reserch Council of Norwy (9386/S6). References [] Wde W, Frnnd S, Hutchison R, Welch K. CO 2 Cpture from SMRs: A Demonstrtion project. Hydrocron Processing, Septemer 22. [2] Grnde CA. PSA Technology for H2 Seprtion. In Hydrogen Science nd Engineering Mteril, Processes, Systems nd Technology. Editors: D. Stolten nd B. Emonts. Wiley VCH, 26. p [3] Voss C. CO 2 removl y PSA: n industril view on opportunities nd chllenges. Adsorption 24; 2: [4] Delgdo JA, Águed VI, Uguin MA, Sotelo JL, Bre P, Grnde CA. Adsorption nd diffusion of H 2, CO, CH 4 nd CO 2 in BPL ctivted cron nd zeolite 3X: evlution of performnce in PSA hydrogen purifiction y simultion. Ind. Eng. Chem. Res. 24; 53: [5] Ntimoh A, Ling J, Xio P, Weley PA, Zhi Y. CO 2 cpture y temperture swing dsorption: use of hot CO 2-rich gs for regenertion. Ind. Eng. Chem. Res. 26;55: [6] Mrx D, Joss L, Hefti M, Mzzotti M. Temperture swing dsorption for postcomustion CO 2 cpture: single- nd multicolumn experiments nd simultions. Ind. Eng. Chem. Res. 26; 55:4-42 [7] Lopes FVS, Grnde CA, Rieiro AM, Loureiro JM, Rodrigues AE. Enhncing Cpcity of Activted Crons for Hydrogen Purifiction. Ind. Eng. Chem. Res. 29;48: [8] Xing S, He Y, Zhng Z, Wu H, Zhou W, Krishn R, Chen B. Microporous metl-orgnic frmework with potentil for cron dioxide cpture t mient conditions. Nture Communictions 22; 3:954. [9] Grnde CA, Águed VI, Spjelkvik A, Blom R. An Efficient Recipe for Formultion of Metl-orgnic Frmeworks. Chem. Eng. Sci. 25; 24:54-58 [] Águed VI, Delgdo JA, Uguin MA, Bre P, Spjelkvik A, Blom R, Grnde CA. Adsorption nd diffusion of H 2, N 2, CO, CH 4 nd CO 2 in UTSA-6 metl-orgnic frmework extrudtes. Chem. Eng. Sci. 25; 24:59-69 [] Liu Z, Grnde CA, Li P, Yu J, Rodrigues AE. Multi-ed Vcuum Pressure Swing Adsorption for Cron Dioxide Cpture from Flue Gses. Sep. Purif. Technol. 2; 8: [2] Lopes FVS, Grnde CA, Rodrigues AE. Fst-cycling VPSA for Hydrogen Purifiction. Fuel 22; 93:5-523.