NGHISN CLIU-TRflOBOI
TIEN BO TRONG NGHltN CtU QUA TRINH REFORMING METAN VA HOI NOfiC DE SAN XUAT HYDRO SACH i NHIET DO THAP
CONG NGOC T H A N G ddrrdnlQC- Wia dlu. Ktaa Vki - tH
Bai bao te'ng l<e't cac ke't qua nghi6n ci}u qua trinh reforming mStan va iioi nirdc diToic tang cifcrng qua trinh hap phu de san xuS't hydr6 b nhiet dO thSp dung ca h i thie't bj ph^n i}ng d i m c6' djnh la hdn hop cua cac h^t chat xuc tac va chat hip phu CO^ difOc lai sinh djnli ky (triffifng hop 1) va he thie't bj phan Ung d i m xuc tac cO'djnh ke't hop \i6i cac hat cha't hS'p phu chuydn ddng diTgfc tuan hoan va tai sinh liSn tuc, hay cong nghf tu3'n hoan cha't tin (trifdng hdp 2), trong do cac phan tfch nhiet dQng hpc, danh gia thdc nghiim va mo phdng dddc tie'n hanh dfi'ng thdi. Trong cac nghien cdu nay, hSn hdp cOa cha't xuc lac chda niken cong nghidp va hydrStanxit hS'p phu CO^ tao thanh Idp dim xuc tac c6' djnh cho trddng hop 1 , trong khi cung cha't xuc tac chda niken cong nghiep nay lao thanh Idp dem xuc tac co'djnh cdn hydrStanxit tao thanh cac hat ch3't ha'p pliu COj d tr^ng thai chuyS'n dfing cho trddng hdp 2. Cac ke't qua nghien cdu chi ra ring, dfi chuyfi'n hda metan can bing va 6n dinh tang len dang ke khi qua trinh phSn dng dddc thuc hien dong thdi vdi qua Irinh loai bd ca'u td CO^ ra khdi vung phin dng va sd tSiig cddng do chuydn hda phu thufic vao difi'u kien hoat dgng. Khi tang ap sua't phan dng, ty le mol bdi nddc/metan bay tfi'c do the tich se lam tang do tang cddng chuydn hda nhdng dfi tang cddng cbuyfi'n hda se giam kbi tang nhiel dfi phan dng va lu'u Iddng dong nitd.
Ldong CO^ bj loai bd nhd ha'p phu cang Idn tbi dfi cbuyfi^n boa m6tan cang cao va Iddng hydrfi dddc tao ra cang ldn va cang tinh kbie't. Td cac k6't qui nghien cdu cho tha'y, cd sd phu hop gida cac kfi't qui phan ticb nhifit dong bpc, thdc nghi$m va mfi phdng ciing nhd tinh kbi tbi cda cac cfing nghfi nghifin cdu.
THIfhoa: phin Ung hoa hoc dugc tang cadng hS'p phu, san xua't hydro, metan, chai hap phu CO^.
Dat van de h§'t sufc nghiem ngat. Do cac quan ngai ve cac v^n Trong nhBng thap ky g^n day, 6 nhilm moi tmflng ' ' ^ ' " * ' ^'.'^^"^ ™ ^'"'" '^' " * " "''" '=^" ^^ "'^"^ *^i"'I*
dac biet la phat thai khi nha kinh CO da trS thanh m6t "^^^ ' ^ ' " ' " " '""" "'""S '^°"9 '^'- ^^'^"^ "^"' S^"
van de dU(?c quan tam toan cau. Nhieu nghien cilu ''^^' ^^°^"3 50% iuong hydr6 duoc sSn xuat bSng da chi ra rang, nhien iieu hydro la nguon nhien iieu "'"^ "''"'^ reforming metan va hfli nudc (SIMR) - m6t viJdt troi de giiim ptiat thai CO^. Ben canh do, nhu c^u 'i"^ ' " " ^ ^'^f'^ *y<= ^'^" d nhiet d6 r^t cao (khoSng SII dgng hydro cho cac nha may ioc dau cung tang 900-1.000»C) [1, 2]. Qua trinh san xuat n4y co nhiSu ien nhanh cMng do phSi tien hanh che bien cao loai diem han che nhu tieu thu nhiSu nang luflng, hieu qu4 dau chua nang va cac yeu cau chat IUdng nhien lieu sil dung nang ii/ong thSp... BSn canh dd, nang lUflng
NGHIGN COU-TRRO DOI
PKOGDE&S IN STEAM-METHANE DEFORMING FOD GDEEN HYDDOGEN PRODUCTION AT LOW TEMPEDATUDE
Suntnary
Adsorption-enhanced steam-methane reforming process has recently been investigated for low temperature hydrogen production from hydrocarbons with simultaneous CO^ abatement.
This process is based on a concept involving simultaneous hydrogen production and CQ^
removal, which can combine both catalyst and adsorbent in the stationary phase for in turn reaction stage and regeneration stage of adsorbent (case 1) or can use a stationary catalyst phase in combination with a continuously circulated and regenerated moving adsorbent phase (case 2). This paper summaries the recent technology development including experimental results and simulating work on adsorption-enhanced steam-methane reforming for low temperature hydrogen production using both cases with two different fixed-bed reactors.
This work uses a mixture of an industrial nickel- based catalyst and hydrotalcite as the packed and COj adsorbent particles (case 1) and an Industrial nickel-based catalyst as the packed particles and hydrotalcite as the suspended CO^
adsorbent particles (case 2), whereas methane (main composition of natural gas) is used as the model feedstocks for technological experiments.
The results show that an equilibrium methane conversion increases when increasing reaction temperature, steam-to-methane ratio, nitrogen flowrate and decreases when increasing the reactor pressure. The removal of CO, from reaction zone enhances the equilibrium methane conversion and the more the amount of CO, has been removed, the hiylier methane conversion and the more hydrogen with higher purity have been producet^ ^i^-^ results also show that the thermodypf perimental and simulation rf,ia ^' '^Eched with each other.
m
, option enhanced chemical jgen production, methane, CO^cung cap cho cac qua trinh san xuat thLfdng do viec dot chay dau m6 va khf ta nhien nen ban than qua trinh chay cung tao ra cac tac d6ng dang ke den moi tracing do phat th^i NO,, SO^, va CO^. Mot phadng phap de khac phuc cac van de tren la tich hdp qua trinh phan tach vao trong qua trinh SMR thong qua cac phadng phap hap phLi, mang dam xuy§n chpn Ipc hoac thong qua vi§c phiin ling dong thdi giQa cac phan tii chat phan iing va cac chat tiep nhan. Cac qua trinh dUa tren phadng phap hap phu the hien cac ldi the vUdt troi so vdi cac he thong dua vao mang phan tach khi xet den kha nang ben nhiet va chju ap cao cua vat lieu cung nha khk nang laa chpn rpng rai va kh^ nang cung cap cac chat hap phij cho viec thac hien qua trinh phan tach mong mu6'n 6 cac dieu kien phkn ilng. Nghien ciiu gan day cilia Ding va Alpay [3] khi sCf diing thiet bi ph&n ang dadc nhoi h5n hdp chat xuc tac va chat hap phu da chi ra rSng, nhiet dp lam viec cua qua trinh phkn Ong co the gi^m dang ke {ta 900-1.000°C) xuong cdn 400-500°C.
Bai vi^t gidi thieu t6ng quan ve nhSng ti§'n bp trong viec nghien cau cdng nghe SMR khi sD dung nguon nguyen lieu metan va hydrotanxit lam chat hS'p phy COg. Metan dapc laa chon lam nguyen lieu cho qua trinh nghien cau vi day la hdp phan chinh cua khi ta nhien, mot nguon nguyen lieu chinh de san xuat hydro.
Hydrotanxit la loai set anion tao b6i cac Idp dxi't kim loai tfch di§n dadng va cac Idp anion trung gian. Qua trinh trao doi giOa cac cation kim logi cung nha tUdng tac giOa cac ldp anion giup cho hydrotanxit co nhieu tfnh chat co ldi cho qua trinh xuc tac va hap phy. Hydrotanxit dadc lua chon lam chat hap phu vi sau khi xii ly no co dien tfch be mat rieng Idn, tich bazd m^nh, ben vOng trong dieu kien khf adt va nhiet dp cao ngay ca vdi cac hat tinh the rat nho [4].
Noi dung nghien ciifu
Qua trinh reforming nguyen lieu hydro cacbon (C^H ) va hdi nadc co sD dyng xuc tac la mpt trong nhu'ng qua trinh cd ban dadc SL( dung de san xuat hydrd. Cac phan ang cd ban cua qua trinh dapc chi ra nha sau [4]:
Trade tien la phan ang reforming C^H vdi hdi nadc (1) vasau do la phan ang chuyen djch khi- nadc (2):
C^H^ + xHgO = xCO + (x + y/2)H, (1) CO + HgO = CO, + H, (2) Nha veiy, phan ang t6ng quat cua qua trinh reforming
C^H^ ly tadng co the bilu diln nha sau:
C,H^ + (2x)Hp = xCOg + {2x + y/2)H, (3) Vdi nguyen lieu metan, phkn (Ing tong quat cua qua
— C O N S S ^ h '
NGHIGN COU - TRflO BOI
trinh san xuat hydro bang phan ang SMR cd the dapc Viet nha sau:
CH, + 2H,0 = CO, + 4H, (4)
Phan ang tong neu tren gdi y rang, theo nguyen ly chuyen dich can bang Le Chatelier, neu dioxft cacbon dadc loai bo ngay khi no dddc tao ra trong vung phan dng, cac phan iJng thuan co the dadc tang cadng neu cac phan ang d trang thai can bang gidi hgn Day chfnh la cd sd ciia khai niem cac qua trinh phan u'ng dddc tang cadng qua trinh hap phu da dapc nghien ciiu rpng rai c^ thac nghi§m va md hinh toan trong nhieu tai lieu tham khio [5, 6]. Nhffng nghien cau nay chf ra rang, cac qua trinh phan dng dapc tang cadng qua trinh h^p phu cd the tang cudng dang ke lupng hydro tao ra va giam nong dd 00^ trong san pham. Hdn nOa, viec sii dung qua trinh hap phy CO^ co the giam dang ke nhiet do tig'n hanh phan dng, va nha vky cd the giam dang k l lapng nang lapng tieu thy, giam thilu siJ mat hoat tinh xuc tac va chi phi van hanh. Tuy nhien, nhQng nghien cdu trade day cd bin dQa tren cac thiet bi phan dng dem cd djnh (trddng hdp 1) khi ma cae chat xue tac va hap phLi gan nhu khdng ehuyin dpng va do do thilt bi phan Qng phai hoat dpng theo chu ky [7, 8]. Sd do ddn giiin cDa he thd'ng thiet bj thi/c nghiem cho tradng hdp 1 dape chf ra trong hinh 1 a va 1 b; trong do, hinh 1 a gidi thi§u sd do ddn gian cua he thd'ng thf nghiem va hinh lb la he thdng thi nghiem da dddc xay dung trong thiJe te.
Hlnh la: stJ d6 dan gian h§ thdng Hinh lb: tie thong thuc ngtii§m trong thiJc nghiim (tnJdng h0p1) thdc fe {trudng hgp 1)
Vdi tradng hdp nghien cdu nay, thiet bi phan dng dadc che tgo bang ong thep 304 cd dudng kfnh ngoai la 12,7 mm va dai 1.200 mm trong do dUdc nhoi khoang 85 gam chat xiic tac va 25 gam chat hap phy. Thiet bi phan dng cd nhiet dp va ap suat lam viec toi da den 550°C va 400 kPa. Chat xuc tac dUde sd dyng cho thae nghiem la chat xuc tac reforming cdng nghiep cd chaa niken do Cong ty Johnson Matthew Catalysts (Anh) cung cap (dien tfch be mat rieng BET la 123 mVg), eon ehS't ha'p phy CO^ la hydrotanxit dadc cung cap bdi Sigma-Aldrich (dien tfeh be mat ri§ng BET la 108 m^/g).
Chat xuc tac va chat hap phu dddc SLf dung 6 dang hat cd kich thadc td 0,5 den 2 mm. Hydro, metan va nitd SLT
dyng dUdc chda trong cac binh khi nen 40 lit do Cong ty Cryotech Vietnam cung cap va dapc dieu khiln iuu lapng bang cac bp do va dieu khiln lau lapng MFC cCia Hang Aalborg (My). Hdi nddc dape tgo ra nhd Id hda hdi nadc va dupc dilu chinh IUu lupng thdng qua bdm cao ap HPLC LabAlliance 110SFN01. Cac phim dng dapc thD nghiem d khoang nhiet dd 400-550°C vk ap suat 0-400 kPa. May sae ky khf (GC-CP9001) co trang _bi detector din nhiet dddc sCf dung de phan tieh cac mau skn pham.
De vapt qua cac thach thUc lien quan den he thing lam viee theo ehu ky nhu tren, mpt qua trinh khac da dupc de nghj va nghi§n edu nhU hinh 2a [4]. CP sd cua qua trinh mdi nay la viec sCf diing ket hdp dem chat xuc tac cd' djnh va hat ehat hap phu chuyen ddng (trddng hpp 2). Do dd, he thong thiJc nghiem bao gom mpt thiet bi ph&n Ung lam viec lien tyc, mdt thiet bj nha hap phu va mpt he thd'ng ph&n tach ran - khi. Cac hgt chat hap phLi kfch thadc nhd dapc van ehuyin bdi hdn hpp ehat ph^n dng va san phim qua cau true dem xuc tac d l loai bd tdc thdi, lien tuc CO,. Qua trinh tai sinh chat hip phu dupc thuc hien ben ngoai thiet bj phkn dng. NhU vay, cd t h i taeh biet cac pha phSn dng vdi pha tai sinh cLJng nha d^m b^o he thong hogt dpng lien tye In djnh hay thu hoi va IUu trQ CO^ neu sijf dung hai thiet bj nhk hip phy.
CH4 + 2HiO ?
,»,».»';tr^_
^ d i i S d u n g " •"
M S r g r g a n - f . C h l , h S p B ^ u i ThSp A
: : 1 V
CH,+ H,0 COj + 4Hz
-T*".*«"?o,
Chat m c tac
Th.pR
...
h$p phu
Hlnh 2a- so dd dan giin qua trinh Hinh 2b: he thdng thUc nghiem san xuat H^ d nhiet do Mp qua trinh san xuat H^ d nhiSt 0 thip
(trudng hap 2) (trudng ftpp 2)
Hinh 2b gidi thieu h§ thong thac nghiem qua trinh san xuat hydro 6 nhiet dp thap (tradng hpp 2). H§ thing dapc xay dung diia tr§n cau hinh nhiet dp cao vdi cae dac trung sau: (i) bp phan nap liSu dUde dilu ehinh de cho phep SLf dLing hdn hdp nguyen lieu khi (metan) cung nhd eac ddng khi nguyen lieu, khf lam saeh, khfde khd chat xuc tac va khf thSi; (ii) khdng ehf thilt bj phkn dng ma cac thiet bi khac nha thiet bi nha hip phy, cac binh chda, cac xycldn, cac mang Ipc va dadng dng deu dddc gia nhiet d l giQ eho cac chit phan Qng va skn pham khdng bj ngang ty trUdc khi ra khoi h& thing; (iii)
60
CONilfcHS^^^---^
NGHIGN COU^ TRno BOI
mdt may phan tfch khi nhieu kenh kit noi true tiep lam viee lien tyc ABB ddpc ldp dat de kiem tra thanh phan ddng khi di ra. Be tien h^nh thyc nghiem trUdng hdp 2, chat xiic tac tddng ta nhU trudng hdp 1 (KATALCO CRG-LHR, Johnson Matthey Catalysts, Anh) da dapc sii dung. Trong tradng hpp nay, eac hat ehat xue tac nguyen ban (vien try cd dudng kfnh 1/8 inch; dien tfch be mat rieng BET la 123 m^/g) dupc nhoi ngau nhien trong thiet bj phkn dng. Chat hap phu CO, sd dung cho tradng hpp 2 la loai hydrotanxit Mg-AI dupe kich hogt bang hydroxft kali cung cap bdi Cdng ty MEL Chemicals (Anh) va da dupc kilm tra dung lapng hap phy va dp ben. Chat hap phy dUdc nghien nhd va phan loai thanh nhdm hat ed kfch thadc 38-180 pm trade khi sd dung (di§n tieh be mat rieng BET la 130 mVg).
Trade mil lan thd nghiem, chat xuc tac dapc khd lien tye trong 4 gid bang ddng hdn hpp H, vdi Idu IUdng 2 lit/phut va ddng nitd vdi IUu IUdng 3 liVphut d nhiet do 600 "C va ap suit khi quyen. Chat hap phy hydrotanxit da^c tai sinh bang each tuan hoan cac hat chat hap phu vdi ddng hon hpp hdi nudc (5 Ift/phut) va ddng nitd (45 lit/phut) 6 nhiet do 500°C trong 2 gid dudi dilu kien ap suit thap. Tong cpng khoang 1.700 g chat xuc tac da dUde nhoi trong thiet bj phan Qng va khoang 1.500 g hydrotanxit dapc dung trong qua trinh phan dng cd tang cUdng hap phy.
Ket qua va ttiao luan Phan tich nhi$t dgng hgc
Trade tien, cac phan tfch nhietddng hpc da dupc thac hien d l cung cap cae ehi dan cho viec nghien cau thae nghi§m ph§n Qng. Hinh 3 gidi thipu quan he giQa dd ehuyen hda metan can bang va nong dp CO, 6 dieu kien nhiet do 400°C va ap suat 300 kPa. Trong nghien cQu nay, ty so mol hdi nddc/mdtan la 6,5 va luu lupng ddng nitd la 50 va 70 Ift/phut. De cd so lieu so sanh, cac kit qua khi khdng cd ddng khf mang nitd cung dddc ehi ra trong hinh 3.
Cd the thay td hinh 3 rang, cho ca hai logi
> ^ ^ '":. thiet bi phan ang gian Y.» '•• doan va ddng lien tuc, 71 I *^^ '*^' ^° ^^ khdng cd
" ^ ^ dong nitd, dp chuyin
^ ^ hoa can bang tang s 1. l^•'rf:•:t™:::^".^_ J khi nong dp CO, giam
.,„,..,'" " di nha mong dpi. Dp chuyen hda can bang
; a nong dd CO, den d lUu lUdng ddng nitd tieiancinbang |a 50 Ift/phut hoSc ldn nop 1.2} [^(jn cao hdn dang ke
Hinh 4: quan he giUa hieu suat tao hydro va luang 00^ bi loai bd (trudng h^p 2)
SO vdi khi khdng cd dong nitd. Kit qua nay dung nha du doan vi sa ed mat eila dong nitd da pha loang nong dd CO, va nhu vay dp chuyen hda metan eao hdn.
Hinh 4 gidi thieu cac ket quk nghi§n edu phan Qng SMR d dllu kien luu IUdng dong metan va nitd (khf mang) lan lupt la 0,5 lit/phut metan va 50 lit/phut nitP, ty sd mol hdi nudc/metan la 6,5, nhiet dp 400°C va ap suat 300 kPa. Cac dieu kien khac cung ehi ra cae kit qu^ cd xu hadng thay doi tUdng ty. Cd the thay rang, hieu suat tgo thanh hydrd (so mol hydrd/s6 mol nguyen lieu metan) tang len khi phan CO^ bi loai di tang len. Neu 100% COj, bi loai bo, ca hieu suat tgo thanh hydrd cua metan tiln den hieu suat tgo thanh hydrd ly tUdng theo he so ty lupng (4 mol hydrd/1 mol metan). NhQng so' lieu nay khang dmh ve mat ly thuylt rang, vi§e loai bo CO, ra khoi vung phan dng cd the tang cddng qua trinh san xuat hydrd vdi ca hai logi nguyen lieu nghi§n cdu. Hinh 4 eung chl ra cac xu hudng biln doi tUdng ta trong kit qua nghi§n edu lien quan den phan ang khdng cd ddng khi mang. Cac phan tfch ly thuylt cung da dUde thac hien d l xem xet anh hudng cua nhiet dp, ap suat va ty so' mol hdi nUde/nguyen lieu din nong dp can bSng trong cae he phan dng. Cd t h i nhan thay rang, cac dieu kien nhiet dp thap hPn, ap suit cao hPn va ty so mol hdi ndde/nguyen lieu thap hdn ed ldi hdn cho viee hap phy CO,, trong khi cac dieu kien ngUdc iai cd Idl hPn eho viee tao thanh hydrd.
Ket qua tht/c nghl$m
Dua tren cac kit quci phan tich nhiet ddng hoc cho ca hai trddng hdp, eae nghien edu thde nghiem da dape tien hanh 6 cac nhiet dp 400, 450, 500°C va ap suit khoang 100 den 400 kPa.
Anh hudng cija ap suat den do chuyen hoa va dp tang cUdng ehuyin hda eho trddng hpp 2 dupc minh hpa trong hinh 5a khi cac dilu kien thde nghiem co djnh d nhiet dp = 400-0, ty so mol hdi nudc/metan = 6,5, IUu lupng ddng nitd = 50 Ift/phut, toe dp the tich m§tan = 20,74 g-xuc tac x phut/mol-CH^, va IUu Iddng chat hap phy trung binh = - 52,8 g/phut. Cd the thay rang, do tang eddng chuyen hda on dinh trung binh tang len khi ap suit phan dng tang len va gia tri dd tang cadng chuyen hda kha ldn b ap suat tren 300
QAcnnSr^om,, TapcH KHOflHCrC 61
NGHIAN COU-TRflO DOI
kPa. Tuy nhien, dd chuyen hda metan Igi giam di khi ap suat ph^n Ung tang len. Cac gia trj can bing tfnh dUdc the hien xu hudng thay doi tUdng ta nha cae gia trj thac nghiem dUdc do cho hai bp dQ lieu thuc nghiem khac nhau, dac biet d ap suit cao hdn. Cac kit qu^
chi ra trong hinh 5a gdi y rang, mac du dp tang cddng ehuyin hda la co ldi hdn d ap suat cao hdn nhdng dd chuyen hoa lai thap hdn. Nha vay, d dieu kien thac nghiem trong nghien cQu, ap suit 300 kPa dddng nhU la ap suit lam viec tii Uu ma tai dd c^ dd chuyin hda va dp tang cUdng ehuyen hoa deu tUdng dd'i eao.
Cac anh hudng cua nhiet dp va ap suat din dp ehuyen hda va do tang cddng chuyen hda eho trudng hpp 1 dddc trinh bay trong hinh 6a va 6b khi eac dieu kien thae nghiem eho hinh 6a dupc co djnh d nhiet dd = 5do°C, ty sd' mol hPi nudc/metan = 6,5, IUu lupng ddng metan = 0,1 lit/phut, IUu lupng dong nitp = 2,0 lit/phut;
cdn cac dieu ki§n thuc nghiem cho hinh 6b dupc c l djnh d ap suit = 100 kPa vdi ty so mol hpi nudc/metan
= 6,5, luu lupng ddng metan = 0,1 lit/phut va IUu lupng dong nitP = 2,0 Ift/phut.
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Hhh 5a- int) tiUdng cua Ap sudt den ad Hlnh 5b: anh bUdng cua nhiel do den chuydn hoa va iing cUdng chuyen /ida do chuyen hoa va ISng cUdng
(SMR - trudng h0p 2) chuySn hda fSMfl - trUdng hi^p 2)
Hinh 5b minh hpa anh hudng cCia nhiet dp din dp chuyen hda va tang cddng ehuyen hda trgng thai on djnh eho trUdng hpp 2. Thiet bi phan Ung hogt dpng 6 dilu kien khoang 300 kPa vdi ty so mol hdi nude/mdtan
= 6,5, luu lupng ddng nitP = 50 lit/phut, toe dp t h i tfch metan = 20,74 g-xuc tac x phut/mol-CH^ va IUu IUdng chat hip phy trung binh = - 52,8 g/phut. Td kit qui thue nghidm, cd the rut ra cac nhan xet sau: sU phu thude cda dd chuyen hda metan vao nhidt dd do dupe td thyc nghiem cd khuynh hadng thay doi tUdng tiJ nliu quy lugt phy thudc nhiet dp tinh toan dUdc nhdng dp ehuyin hda can bang tinh toan cua ck thilt bj phan dng gian doan va dong lien tyc deu cao hdn eac gia tn thuc nghiem. Dp tang cudng chuyen hda giam di khi nhiet dd tang len. 6 nhiet dp 400°C, dp tang cddng chuyin hda la - 51,2%, sau dd giam nhanh xuong - 15,5% 6 450°C va giim chl cdn - 3,6% tai 500°C. Dilu nay cd t h i dapc giai thich nhU sau: d nhiet dp thlp hdn, chit hip phu cd dung lupng hap phy cao hdn va IUdng CO, dupc tgo ra it hdn. Phan tram dd chuyen hoa can bang tang khi nhi^t dp tang len. 6 400°C, dp chuyen hda metan trong phan dng reforming metan va hpi nudc dupc tang cadng qua trinh hap phy (SE-SMR) lln lUdt la khoang 67,2% va 75,4% so vdi dp chuyen hda can bang tinh toan dli vdi thilt b| ph^n Qng ddng lien tuc va gian doan. Cac gia tn nay tang len den ~ 86,0% va 93,5% S 450OC, va den ~ 95,6% va 99,2% d 500°C.
Dieu dd cd nghTa la d nhi§t dp cang eao, qua trinh SMR dupe tang cadng hap phy cang nhanh chdng tien din trgng thai can bang.
Hinh 6a anh hUdng cda ap suat ddn Hinti 6b: anh hudng c6a nhiet do den ad chuyin hda va tSng cUdng dd chuySn hda va tSng cUdng chuyen hda fSMR - trUdng hi?p 1) chuyen hda (SMR - trUdng hpp I)
Co the thay td hlnh 6a va 6b rang, cac xu hudng ve dp chuyen hda metan va dp tang cudng ehuyin hda la tddng tu nhu chl ra trong hinh 5a va 5b m^ tren da mieu ta. Do vay, trong phan cdn lai eCia bai bao, cac thao luan chi tiet chu yeu tap trung vao trudng hpp 2.
Hinh 7 gidi thieu quan h§ giQa ap suit va thanh phan pha khf do dddc I n djnh dien hinh va khi tfnh toan can bang, Cae kit qua nay la cac tfnh toan dua tren trgng thai khd va da loai bo nitd va CO de d l dang so sanh giQa eac nghien cQu khac nhau. Cac dieu kien thae nghiem de nhan dapc eae kit quk trong hinh 7 tUdng tu cac dieu kien thde nghiem d i nhSn dUde eac kit qua cho trong hinh 5a. C^c moi quan he tUdng tU giQa nhiet dd va thanh phan pha khi can bang cung nhu thanh phan pha khf do dUde I n djnh dien hinh cua cac qua trinh SMR va SE-SMR cijng dUde quan sat nhu d hinh 8. Hinh 7 cung chl ra rang, sy phu thudc do dapc bang thac nghiem giQa nong dd metan, CO, va hydrd va ap suat la tddng ta quan he phy thudc tfnh toan theo ly thuylt nhUng khac nhau v l lapng. Vi dy, d 300 kPa, nong dp metan on djnh trung binh cua qua trinh SE-SMR la - 7,5% mol, gia trj nay thap hdn nong dp metan on dinh trung binh cua qua trinh SMR (~
8,6% mol). Ly do la qua trinh SE-SMR cd dd chuyen hda metan cao hdn (~ 42%) so vdi qua trinh SMR (~
28%). Tai ap suit nay, nong dd CO, dn dinh trung binh cua qua trinh SE-SMR la nho hdn nong dp CO, on djnh trung binh cua qua trinh SMR (- 19,7% so vdi 23,1%) do mpt IUdng CO, da bj hip phy va nong
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NGHIAN CQU-TRflO DOI
dd H, on dmh trung binh cOa qua trinh SE-SMR cao hdn nong dp hydro on dmh trung binh eua qua trinh SMR (~ 72,7% so vdi 71,4%). Cd mpt s i yeu to ed t h i ddng gdp vao sy khac nhau nay, bao gom ch§nh lech nhiet dp giQa gla tn cai d§t va nhidt dp ph^n dng thyc te, sy cd mat cija mpt lUpng nhd chat hip phy CO, trong thiet bj phan dng do bi mac ket lai, va eae ldi thuc nghidm khac. Do vung phkn dng kha dai, rat khd tranh khdi su khong dong nhat cua nhiet dp phan dng theo chieu dai thiet bj phan Qng va theo hadng ban kfnh thiet bi.
Hlnh 7: inh hudng cua ap suat ddn nong do phin mol (SMR - irt/dng hpp 2)
Hinh 8- anti hudng ciia nhiet d nong do phan mol (SMR - trudng hap 2)
Cac ket qua tddng ta cung thu dUpc khi xem xet anh hudng cCia nhi§t dp nhU ehi ra trong hinh 10, trong dd hieu suit tgo thanh hydro la cao hdn d nhiet dp cao nhdng dd tang eudng tgo thanh hydro thi thap hdn.
Nhu vay, can td'i du hda cae thong so van hanh eua he tho'ng.
Mo phong
Ckc nghien edu mo phong dua tren md hinh thilt bi phan dng c&n bang (Equilibrium Reactor) trong phan mIm HYSYS 2.4 cung da dupe thuc hi§n vdi qua trinh SMR de so sanh vdi eae kit qua thtJc nghiem phkn iing va eae k i t quk phan tich nhiet ddng hpc [8]. Cac hinh 11 va 12 md ta anh hudng cua ap suit den dp chuyen hda can bang tfnh toan va dp ehuyen hda md phdng khi cd va khdng ed dong khi trd (nitd) va ehit hip phu. Phin nay chl nghien cdu thiet bj phan Qng dong lien tuc. Thiet bj lam viec d nhiet dp 400°C vdi ty so' mol hdi nddc/metan la 6,5.
06 the nh§n thay td eae kit quk md phdng nha chi
Cac hinh 9 va 10 gidi thieu hieu suit tao thanh hydro (so mol hydro/so mol metan) va dp tang cUdng sin xuat hydrd cCia qua trinh SMR. Cac dieu kien lam viec de thu dade cac k i t quk cho trong hinh 9 bao gom luu IUdng metan la 0,5 Ift/phut, lau IUdng nitd la 50 lit/phut, ty so hdi nUdc/metan la 6,5 va nhiet dp la 40000; cdn cac dieu kien lam viec d l thu dupc cac kit qua cho trong hinh i o bao gom IUu IUdng metan la 0,5 lit/phut, Idu IUdng nitd la 50 lit/phut, ty so hdi nUdc/metan la 6,5 va ap suit la 300 kPa.
Hlnh Q- Anh hudna cua ap suat ddn Hinh 10. inh hudng cua nhi?t do den
!^!!^'uifymVM^ - ^''^"9 '•CP2) "'^^ ^"3'^>^™ fSMH - tnJdng hap 2)
Co the thay rang, viee sd dung chat hip phy ludn d i n den viec tao ra IUdng hydro nhieu hdn so vdi khi khona SLf dung chat hap phu. KhS nang t§ng eddng dd chuven hda tang len khi ap suit tang, bdi vl ap si'ilt cao -• c§n trd qua trinh tao ra CO, va tang kh^
khi^Hnq ap suat, hieu suat tgo thanh hydrd gjam di, , i/rt ' hadng cua dp tang cudng chuyen hda.
Hmh 11: inh tiUdng ciJa ap sudt den Hinti 12. anti hUdng cua ip suat den do ctiuyen hoa vi tSng cUdng chuyen dd chuyen hda va tang cUdng chuyen hoa (md phdng SMR cd nita) hoa (md phdng SMR I(h6ng co nita)
ra trong hinh 11 va 12 rang, khi ap suat tang td 140 kPa len 400 kPa thi dd chuyen hoa md phong khi cd va khong ed ddng nitd lan Iddt g\km 18,24% (tQ 68,49 xuong edn 50,25%) va 9,71% (tQ 29,65 xuong cdn 19,94%) cho thiet bi phkn iing ddng lien tue vdi IQu lUdng dong nitd la 50 Ift/phut va khong cd chat hip phu (hlnh 11) cung nhu thiet bj phan dng ddng lien tue khdng sd dyng ca khf trd va chat hip phu (hinh 12). 6 nhiet dp 400°C va ty so mol hdi nudc/metan 6,5, khi cd ehat hap phu, dp chuyen hda giam lln lupt la 10,23% (td 82,02 xuong 71,79%) va 10,13%
(ta 56,04 xud'ng 45,91%) cho thiet bj phan dng dong lien tuc vdi luu lu^ng ddng nitd la 50 lit/phut va thilt bi phkn iing dong lien tuc khong sCf dyng khf trd. Cung trong cac hinh nay, dp chuyin hda can bang giam td 74,5% xud'ng 54,6% cho thiet bj phan dng ddng lien tyc vdi IUu lUpng ddng nitd la 50 Ift/phut, nghTa la giam 19,9% va sd g\km nay doi vdi thilt bj phan Qng ddng li§n tue khdng ed ddng nitd la 10,9% (td 33,9%
6 140 kPa xud'ng 23,0% 6 400 kPa). NhOng kit qua nay chi ra rang, ap suit ed Inh hudng mgnh hdn den
S620 nam 2014 . Topchi KHOflHCtt I 83 CONG NGHE VIET N M I
NGHIGN cOU-TRRO DOI
he thilt bj phkn Qng ddng lien tue khi khdng cd ehat hip phu, dgc biet khi cd ddng khf trd. Khi so sanh eac kit quk md phdng vdi eae ket qua trong hlnh 5 cd t h i thay rang, cac kit qua md phong, thuc nghiem va phan tich nhidt dpng hoc kha phu hpp vdi nhau.
Cac moi quan he tUdng tU giQa cac dp chuyen hoa md phdng va can bang vdi nhiet dp eung dUdc nhan thiy nha chi ra trong cac hlnh 13,14.
Hinh 13- inti tiUdng cua nhi§t a$ (Jen Hinh 14 anh hudng cDa nhiet dd den ad ctiuyin hda vA tSng cUdng chuyen dd chuyen hda va ting cUdng ctiuydn
hoa (md phdng SMR khong cd nitaj hda (md ptiong SMR cd nita)
Cac hinh 13 va 14 ehi ra cac quan he giQa dp chuyen hda md phdng va can bang vdi nhiet dp 6 ap suat 300 kPa cho thiet bj phan Qng ddng lien tuc lan lapt khi khong cd va khi cd ddng nitd. Ty so mol hdi nudc/metan dUde sd dung la 6,5 va Idu lapng ddng nitd la 50 li't/phut eho trudng hpp cd sQ dung khi mang. Cd t h i nhan thiy td hinh 13 va 14 rang, vdi thilt bj phkn iing ddng lien tue khi ed va khi khdng cd ddng nitd, dd chuyen hda md phong va can bang tang khi nhiet dp tang dung nhd mong dpi Dp chuyen hda md phdng va can bang khi IUu lUpng dong nitd la 50 lit/phut cao hpn dang k l khi khdng cd ddng nitd.
Dieu nay eung dung nhU mong muon vi sU ed mat cua nitP da pha loang hieu qua nong dp CO, va do dd lam tang dp chuyen hda mdtan. So sanh vdi cac kit quk thlic nghiem trong hinh 6, dp chuyin hda thuc nghiem on djnh dien htnh eua qua trinh SMR va SE-SMR, mdt lln nQa cd the thay rang cac so' lieu mo phong, thyc nghiem va phan tich nhi§t dong hpc tUdng doi phu hpp vdi nhau.
Ket luan
Cdng ngh§ de san xult hydrd 6 nhiet dd thap kem theo viec loai bo CO, da dape tac gia nghien edu bang each sQ dyng nguyen lieu la m§tan va hydrotanxit lam chit liap phy CO,. Cac nghien cdu nhiet ddng hpc, thUc nghiem va mo phdng doi vdi phan ufng SMR d l s^n xult hydrd d nhiet dp thap va khong gay 6 nhilm mdi tradng da dupc thyc hien cho ck hai trudng hdp sd dyng hdn hdp chat xLic tac va ehat hap phu (trddng hdp 1) va cdng nghe tuan hoan ehIt hap phu ran (tradng hpp 2). Cac ket luan chinh
dupe rut ra td k i t qua nghien edu nay bao gom:
- Trong ck hai trudng hpp, dd chuyen hoa nguyen ligu thanh hydrd khi cd sQ dung chat hip phy COg ludn Idn hdn dp chuyin hoa nguyen lieu thanh hydro khi khdng sit dyng ehIt hap phy CO,.
- Trong cac dieu kien cija nghi§n cdu, dd tang cddng chuyen hda on d[nh gikm khi tang nhiet dp phan dng, td'c dp t h i tfcli nguyen lidu, ty so mol hdi nUdc/nguyen lieu va luu lupng ddng khf trd. Tuy nhien, khi tang ap suat thi dd tang cddng chuyen hda t&ng len. NhOng k i t quk thdc nghigm kha phu hpp vdi eac nghien edu nhiet dpng hpc va md phong mkc du eac ket qua thUc nghiem luon nho hdn cac gia tn mo phdng va phan tfch nhigt ddng hpe.
- Cac nghien cOu thOc nghiem, mo phong va phkn tfch nhiet dpng hpc da khang djnh tinh khk thi cija cdng nghe mdi dUde nghien cOu ^
Tai lieu tham khan
[1] IPHE (2011), IPHE Renewable Hydrogen Report, International Partnership for Hydrogen va Fuel Cells in the Economy.
[2] Patwardhan K.V , Dhumal V.D. and Balaramakrishna P., (2014). Revamping the hydrogen generation unit • Hydrogen plants can be modilied for higher production by employing innovative process schemes, Petroleum technology quarterly, 02.25-31.
[3] Ding Y,L, v^ Alpay E. (2000). Adsorption-enhanced steam-methane reforming, Chemical Engineering Science, 55, 3929-3940.
[4] Cong N.T. (2009). Adsorption enhanced steam methane reforming for low temperature hydrogen production using solids circulation, the University of Leeds, PhD thesis.
[5] Cong H.T. (2011 a). Adsorption enhanced steam methane reforming for low temperature hydrogen production using solids circulation. Part 1; Thermodynamic analyses, Vietnam Journal of Chemistry, 49 (5AB), 130-136.
[6] Cong N.T. (2011 b). Adsorption enhanced steam methane reforming for low temperature hydrogen production using solids circulation Part 2. Experiments (I), Vietnam Journal of Chemistry, 49 (SAB), 137-143.
[7] Cong Ngoc Thang (2013), Khko sat m6t s6 yeu t6^nh hL/3ng den qua trinh sSn xua't tiydrS Xii metan tren h§ thiet bi phSn iJng d&m c6 dinh co tang cifdng qua trinh hap phy, Tap chl Hoa hpc, 51 (6ABC), 498-503.
[8] CSng Ngpc Thang, Nguyin Tht Mmh Hi^n, Phgm Trung Kien (2013) M6 ph6ng qua trinh reforming m6tan va hdi ni/dc dU0c tang cudng qua trinh h&p phu di sin xui't hydr6 sgch 6 nhiel dp thgp, Tgp chi Hoa hpc, 51 (6ABC), 492-497.
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