TNG CNG TY PHN BN & HA CHT DU KH CTY CP CN CTY CP PHN M & HC DK - NH MY M PH M

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CNG NGH SN XUT AMMONIA

PHNG K THUT CNG NGH SN XUT

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MC LC PHN I: TNG QUAN CNG NGH SN XUT NH3 .....................................................3 1. GII THIU .......................................................................................................................3 1.1. Gii thiu chung..................................................................................................................3 1.2. Tng quan sn xut Amnic..............................................................................................3 2. TNH CHT L- HA......................................................................................................4 2.1. Tnh cht vt l ...................................................................................................................4 2.2. Tnh cht ha hc................................................................................................................8 3. TNH CHT NHIT NG............................................................................................10 3.1. Nhit ng hc v ng hc .............................................................................................10 3.2. Cc yu t nh hng n qu trnh tng hp Amnic...................................................12

3.2.1. p sut tng hp.................................................................................................12 3.2.2. Nhit tng hp ...............................................................................................12 3.2.3. Tc khng gian ..............................................................................................12 3.2.4. Thnh phn kh vo ............................................................................................12 3.2.5. Kch thc ht xc tc........................................................................................12

4. SN XUT AMNIC ..................................................................................................13 4.1. Chun b kh tng hp Amnic ......................................................................................13

4.1.1. Cc qu trnh chun b kh tng hp...................................................................13 4.1.2. Cc loi cng ngh oxy ha phn i t cacbon nng .........................................16 4.1.3. Reforming hi nc............................................................................................17 4.1.4. Chi ph vn v nng lng .................................................................................18 4.1.5. Cc loi kh thi giu Hydr dng sn xut kh tng hp .............................19 4.1.6. Cc ngun kh tng hp trong tng lai.............................................................20

4.2. Cng ngh sn xut Amnic t reforming hi nc kh thin nhin..............................21 4.2.1. Tinh ch kh np .................................................................................................21 4.2.2. Reforming s cp v th cp ..............................................................................22 4.2.3. Reforming nhit thi ...........................................................................................24 4.2.4. Chuyn ha.........................................................................................................24 4.2.5. Kh dioxit cacbon ..............................................................................................26 4.2.6. Bc tinh ch cui - Metan ha .........................................................................29 4.2.7. Tng hp v thu hi Amnic............................................................................30

4.3. Hin i ha nh my Amnic........................................................................................34 4.4. Thu hi kh thi .................................................................................................................35 4.5. Chu k nng lng............................................................................................................35 5. MT S VN LIN QUAN .....................................................................................36 5.1. Cc vn v mi trng .................................................................................................36 5.2. Bo qun, vn chuyn v x l .........................................................................................38

5.2.1. Bo qun.............................................................................................................38 5.2.2. Vn chuyn.........................................................................................................38 5.2.3. X l ...................................................................................................................39

5.3. Cc vn v kinh t ........................................................................................................40 5.3.1. Cng sut, mc sn xut v tiu th ...................................................................40 5.3.2. Th trng...........................................................................................................41 5.3.3. Chi ph sn xut ..................................................................................................42 5.3.4. Gi c ..................................................................................................................44 5.3.5. Chi ph vn chuyn v lu thng phn phi .......................................................44

5.4. Tiu chun sn phm v phn tch ....................................................................................45 5.5. Sc khe v an ton ngh nghip......................................................................................46 5.6. ng dng...........................................................................................................................47

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5.6.1. Lm phn bn .....................................................................................................47 5.6.2. Dng trong cng nghip .....................................................................................48

5.7. Amnic sn phm ph .....................................................................................................49 5.8. Cc ngun Amnic khng quy c.................................................................................50 PHN II: CNG NGH SN XUT AMMONIA CA NH MY M PH M- CNG NGH HALDOR TOPSOE........................................................................................51 1. GII THIU CHUNG:.....................................................................................................51 2. CC CNG ON TNG HP AMMONIA ...............................................................52 2.1. Cng on kh lu hunh.................................................................................................52

2.1.1. Qu trnh hydro ho ti thit b 10-R-2001: .......................................................52 2.1.2. Qu trnh hp th lu hunh ti thit b 10-R-2002A/B: ...................................53

2.2. Cng on Reforming .......................................................................................................54 2.2.1. Thit b reforming s cp ...................................................................................55 2.2.2. Thit b reformer th cp....................................................................................56

2.3. Cng on chuyn ho CO ...............................................................................................57 2.3.1. Chuyn ho CO nhit cao..............................................................................58 2.3.2. Thit b chuyn ho nhit thp ......................................................................59

2.4. Cng on tch CO2 .........................................................................................................59 2.5. Cng on Mtan ho .......................................................................................................61 2.6. Cng on Tng hp Amonic .........................................................................................63

2.6.1. Vng tng hp ....................................................................................................64 2.6.2. Thnh phn ammonia u vo thit b chuyn ho ............................................65 2.6.3. Kh tr.................................................................................................................65 2.6.4. T l hydro/nit ..................................................................................................66 2.6.5. Thit b tng hp ammonia ................................................................................67 2.6.6. Xc tc................................................................................................................69 2.6.7. Nhit phn ng trong thit b tng hp .........................................................70 2.6.8. T l tun hon. ..................................................................................................70 2.6.9. p sut vn hnh ................................................................................................70 2.6.10. Chu trnh lm lnh ..........................................................................................71

2.7. Cm chng nc ngng cng ngh ..................................................................................72

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PHN I: TNG QUAN CNG NGH SN XUT NH3 1. GII THIU 1.1. Gii thiu chung

Amnic, cng thc NH3 l mt cht kh kim, c mi sc c trng nh hn khng kh. Sn xut cc mui amn c nhng ngi Ai Cp thc hin t nhng ngy u tin th k th t trc cng nguyn. Kh NH3 c Priestly sn xut ln u di dng hp cht thun khit vo nm 1774.

Gi tr ca cc cht Nit di dng phn bn khong c ngi ta nhn bit t nm 1840. Nit l mt nguyn t chnh gip cho qu trnh pht trin ca cy trng v amnic l mt ngun m ban u c dng lm phn bn. Cho n tn nhng nm u ca thp nin 1900, ngun m cung cp cho t trng u xut pht t cc ngun t nhin nh: ngun khong, nitrat Chilean, t qu trnh phn hy cc cht thi sinh hc v t sunft amn ca qu trnh ccking than, cc sn phm ht, bn thi v cc sn phm hp th ca qu trnh ch bin thc phm.Qu trnh tng hp trc tip amnic t Hydrov Nit trn quy m thng mi c Haber v Bosch i u thc hin vo nm 1913 v h ginh c gii Nobel v vn ny. Vic sn xut lin tc, khng ngng amnic trn quy m thng mi c tc dng lm tng ngun cung cp lng thc trn quy m ton th gii. 1.2. Tng quan sn xut Amnic

Cc hp cht amn c sn xut t nhng nm 1890 trn quy m ln di dng sunfat amn t nguyn liu l kh l cc. Kh l cc cng cn c cung cp lm nguyn liu cho cng ngh Haber-Bosh, cng ngh u tin c dng tng hp amnic trc tip t hydro nguyn t v nit. Thit b Haber-Bosh thng mi u tin i vo vn hnh nm 1913 ti nh my Badische Anilin and Soda Fabrik (BASF) Ludwigshafen-Oppau, c. Thit b ny c cng sut thit k 30 tn/ngy.Vic thng mi ho thnh cng cng ngh ny khng nhng cho ra i c cc loi thit b chu p lc v nhit cao m cn sn xut ra loi xc tc st xc tin, y l loi xc tc chnh c s dng ch yu trong qu trnh tng hp amnic.

Trong giai on t 1930 n 1950, vic ci tin bc u cng ngh amnic ch yu quan tm n lnh vc dng sn xut kh tng hp. Cc m than ln chu u cung cp nguyn liu cho ngnh sn xut amnic. Ngnh cng nghip sn xut amnic Bc M da ch yu vo ngun cung cp kh nguyn liu di do gi thp.

Reforming kh thin nhin thnh cng cc iu kin cao p lm gim nhu cu nn ca cc cng on tip theo. u nhng nm 1960, cng ngh dch ng cng knh tn km kh oxit cacbon cui cng c thay th bng cng ngh methan ho cho php chuyn ho c 2 bc v c r r CO thp. Pht trin xc tc chuyn ho nhit thp-cp th hai lm tng hiu sut ca qu trnh thng qua vic tng sn lng ti u hydro trong kh tng hp.

Nm 1963 ngi ta tin hnh thay i mt bc t mc cng sut trong cc nh my dng n thng qua vic chy th nh my cng sut 544T/ngy do Cng ty MW.Kellogg thit k, sau tip tc c mt nh my c mc cng sut tng t ca Monsanto Luling, Louisiana thc hin. Nh my Monsanto nh du s kin v vic ln u tin cc loi my nn ly tm c a vo s dng cho ton b cc phn vic ca cng ngh bng vic s dng tng th cc h thng ph tr. Cc sng kin ci tin ny l

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nhng sng kin tin phong dng cho vic thit k nh my quy m ln dng n cng sut 907 v 1500 tn ngy trong nhng nm thp k 1970 sau ny.

Cc n lc ci tin k thut c tin hnh vi tc nhanh nhm tho mn nhu cu ca th gii v nit c nh. Cc bc ci tin trong chu k nng lng, k c vic pht sinh hi cao p ca nhit tha v cc tin b k thut v my nn, thit b reforming, thp tng hp lm tng hiu qu sn xut amnic, tn dng hon ton cc th li v mt kinh t thu c trong cc nh my dng n c cng sut ln. 2. TNH CHT L- HA 2.1. Tnh cht vt l

Bng 1 l thnh phn l hc quan trng ca amnic. Bng 2 l t trng amnic lng 15oC. Hnh 1 l th Molier hin th cc s liu nhit ng hc b sung ca amnic. Phm vi chy ca NH3 trong khng kh t 16 n 25% theo th tch; trong xy t 15 n 79%. Cc hn hp ny c th gy n mc d phm vi chy n ca NH3- khng kh hon ton bin thin. Nhit chy vo khong 650oC.

Amnic sn sng hp th nc to ra NH3 lng. Hnh 2 l kt qu tm tt mc cn bng hi-dch ca cc dung dch NH3 c cha nc. Hnh 3 biu th cc mc p sut hi dung dch. Nhit pht trin mnh khi dung dch NH3 c trong nc: xp x 2180 kJ(520 kCal) hnh thnh v pht trin khi ta ha tan 1 kg kh gas NH3.

Amnic l mt dung mi tuyt vi sn xut cc loi mui,v c kh nng ngoi l ion ha cc cht in phn. Cc cht kim loi kim v kim loi t kim ( tr Berily) u ha tan trong NH3. It, lu hunh, phtpho ha tan c trong NH3. Vi s c mt ca xy, ng sn sng phn ng vi NH3. Kali, bc v Uranium ch ha tan rt t trong amnic. C Clorua amn ln Berily amn u ha tan trong khi hu nh ton b cc cht clorua kim loi khc li ch ha tan rt t hoc khng th ha tan trong amnic.

Bromua ni chung ha tan nhiu trong NH3 hn so vi cc cht clorua v hu ht cc It u ha tan nhiu hay t trong NH3. Cc oxt, florua, hydrxt, sunft, sunft, cacbonat u kng tan trong NH3. Cc nitrat (nh nitrat amn) v ur u tan trong NH3 khan ln NH3 lng sn xut ra mt loi hp cht nitr v cc cht axt sunfonic thm cng c th ha tan trong NH3 lng. Amnic tuyt vi hn nc khi sonvt ha cc cht hu c chng hn nh benzen, tetraclorua cacbon, hecxan.

Bng 1: Thnh phn l hc ca Amnic khan Thnh phn Gi tr Trng lng mole 17,03 im si oC -33,35 im ng bng oC -77,7 Nhit ti hn oC 133 p sut ti hn, kPaa 11,425 Nhit c trng, J(kg.K)b 0oC 2097,2 100oC 2226,2 200oC 2105,6 Nhit hnh thnh kh Hi,kJ/molb

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0 K -39,222 298 K -46,222 Tnh ha tan trong nc, % trng lng 0oC 42,8 20oC 33,1 40oC 23,4 60oC 14,1 Trng lng ring -40oC 0,690 0oC 0,639 40oC 0,580 Chuyn n v: PSI=0,145*kPa; cal=J/4,184.

Bng 2: T trng Amnic lng 15oC

Amnic % trng lng T trng, g/L 8 0,970 16 0,947 32 0,889 50 0,832 75 0,733 100 0,618

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2.2. Tnh cht ha hc nhit thng thng, amnic tng i n nh, nhng khi nhit nng cao

n s phn hy thnh Hydr v Nit. Mc phn hy b nh hng rt ln bi bn cht b mt khi kh tip xc vi nhau: thy tinh rt tr, s v bt c hiu ng gia tc ln; cc cht kim loi nh st, km, osmi, uranium c hiu ng mnh hn. iu kin p thng, phn hy bt u xy ra mc nhit khong 450-500oC, kt thc mc T = 500-600oC. 1000oC, vt tch amnic vn cn tn ti. Phn hy amnic, mt ngun nit v hydro thun dng cho nghnh ch bin kim loi c th c xc tin theo phng php quang ha hc hay in nng.

Amnic sn sng phn ng vi cc cht khc nhau. Oxi ha nhit cao l mt trong nhng phn ng quan trng, to ra nit v nc. Amnic kh c xy ha to ra nc v nit khi c t nng ln nhit tng i cao vi s tham gia ca cc oxit c t thnh phn kim loi dng , v d nh oxt ng. Cc cht oxy ha mnh nh permanganate phn ng ging nh cc mc nhit thng thng:

2NH3 + 2KMnO4 2KOH +2MnO2 +2H2O +N2 (1) Phn ng clo trong amnic cng c th xp vo loi phn ng xy ha: 8NH3 + 3Cl2 N2 + 6NH4Cl (2) Mt vn quan trng trong qu trnh sn xut axit nitric l vic oxi ha xc tc

amnic thnh acid nitric v nc. Cn phi c thi gian tip xc rt ngn trn xc tc platium-rhodium vi nhit trn 650oC:

4NH3 + 5O2 4NO + 6H2O (3) 2NO + O2 2NO2 (4) 3NO2 + H2O 2HNO3 + NO (5) Trung ha cc cht axt l mt vn quan trng mang tnh thng mi. C ba loi

phn bn ch yu l Nitrt amn NH4NO3, sunft amn (NH4)2SO4 v phtpht amn (NH4)3PO4 c sn xut bng cch phn ng gia cc acid v amnic.

Phn ng ca NH3 v nc l phn ng thun nghch: NH3 + H2O NH4+ + OH- (6) Khi nhit tng, kh nng ho tan trong nc ca NH3 gim rt nhanh. S c mt

ca Hydrxt amn NH4OH trong dung dch nc l mt vn cn nghi vn d c du hiu cho thy amnic tn ti trong nc di dng cc cht hydrat nh NH3H2O. Ion amn NH4+ cng phn ng ging tng t cc cation kim loi kim. Amnic l mt cht kim tng i yu, tuy nhin ion ho trong nc thp hn so vi hydroxit natri. Trong mt mol amnic c cha nc, nng ca ion hydroxit vo khong 2/100 so vi trong mt mol dung dch hydorxit natri.

Nc amnic cng cn ng vai tr nh mt hydroxit kim loi kt ta kim trong cc dung dch mui ca chng v c tc dng trong vic hnh thnh cc ion hn hp vi s tham gia ca amnic d. V d dng dung dch sunft ng, hydrxt ng trc tin l cho kt ta, ti ho tan trong NH3 d do c s hnh thnh ca ion tetraminecopper(II) phc hp: CuSO4 + 2NH3H2O Cu(OH)2 + (NH4)2SO4 (7) Cu(OH)2 Cu2+ + 2OH- (8) 4NH3 + Cu2+ [Cu(NH3)4]2+ (9)

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Kali ho tan trong nc NH3 nhng li chuyn ho mt lng nh kali kim loi thnh amit kim loi trong vng nhiu ngy. Bng cch p dng k thut tng t s dng kim loi natri, amit natri NaNH2 c th to ra mt cht cng. 2Na + 2NH3 2NaNH2 + H2 (10)

t lithum kim loi trong dng NH3 kh s to ra amit lithum LiNH2. Cc cht kim loi kim c th c xc tin bi cc phn ng phn gii kp trong amnic lng, v d: NaI + KNH2 NaNH2 +KI (11)

t nng NH3 vi mt kim loi phn ng nh manh chng hn s to ra nitrua: 3Mg + 2NH3 Mg3N2 +3H2 (12)

Manh phn ng chm nhit thp to ra amit, cng ging nh phn ng i vi cc kim loi hot tnh khc; phn ng ny c xc tc bng cch chuyn i cc ion kim loi. Nitrua nhm AlN, nitrua bari Ba3N2, nitrua canxi Ca3N2, nitrua stronti Sr3N2 v nitrua titan TiN c th c hnh thnh bng cch t nng cc amt tng ng.

Halogen phn ng vi amnic. Clo hay Brm gii phng nit khi amnic d v sinh ra mui amn tng ng. Trc tin c th xy ra kh nng thay th. Kt qu v d chng hn nh Trihalide kt hp lng lo vi mt mol NH3 khc to ra NCl3.NH3. Cc hp cht ngm amnic ny rt khng n nh v phn hu khi c mt ca amnic d to ra mui amn v nit: NCl3.NH3 + 3 NH3 N2 + 3 NH4Cl (13)

Hp cht it tn ti n nh hn nhiu v phn ly thnh cht gi l monoamoniate triodide nit NI3.NH3, y l mt cht cng nu en khng ho tan, khi phi ra ngoi nh sng, nu c mt ca NH3 s b phn hu. Tuy nhin trong cc phn ng ca halogen vi cc mui amn tng ng, phn ng xy ra hon ton khc nhau. Clorua thay th hydro v clorua nit, NCl3 tch du, cc ht vng ca qu trnh phn hu n t pht. NH4Cl+ 3Cl2 NCl3 + 4HCl (14)

Hydro ca cc mui amn khng th thay th cho brm v it m kt hp vi chng to thnh cc hp cht perhalides: NH4Br + Br2 NH4Br3 (15)

Cc cht perhalides nh chng ta bit, l cht n nh nht, tetrachloroiodide amn NH4ICl4. Amnic phn ng vi clorua trong dch ho tan to ra chloroamine, y l mt phn ng quan trng trong ngnh tinh ch nc. Tu thuc vo pH trong nc m mt trong s 2 cht sau y c hnh thnh, l monocloramine NH2Cl hay dichloramine NHCl2. Trong qu trnh pha long pht sinh trong cc cng tc cp thot nc thng ngi ta vn pht hin thy monochloramine tr trng hp nc c cha nhiu acid.

Amnic phn ng vi hi phtpho trong iu kin nhit nung to ra nit v photphin. 2NH3 + 2P 2PH3 +N2 (16) Hi lu hunh v amnic phn ng to ra sunft amn v nit, lu hunh v amnic lng khan phn ng vi nhau to ra sunfat nit N4S4. 10S +4 NH3 6H2S + N4S4 (17)

Amnic v cacbon phn ng nhit nung s to ra xianide amn NH4Cn. Amnic cn hnh thnh nhiu cc hp cht hn hp hay b sung v c ngi ta

gi l cc amnit, tng t nh cc hydrat. Do c th so snh gia CaCl2.6NH3 vi

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Cl2.6H2O v CuSO4.4H2O, khi c coi l cc cht hn hp th s c gi l cc amin v c vit di dng cc phc hp, v d [Cu(NH3)4]SO4. Tnh ho tan trong nc ca cc hp cht ny thng khc nhau khi ho tan vi cc mui gc. V d clorua bc AgCl l mt cht ho tan hu nh hon ton trong nc v cc mui ng khc. Kt qu ngi ta c th thu c nhiu amin di dng tinh th c bit l ca coban, crm v platinum.

Mt trong nhng vn quan trng chnh ca ngnh cng nghip l phn ng ca NH3 vi CO2 to ra cacbamat amn CH6N2O2 2NH3 + CO2 NH2CO2NH4 (18)

sau phn gii thnh ur v nc: NH2CO2NH4 NH2CONH2 +H2O (19)

y l mt v d v phn ng phn tch amnic trong mt lin kt ho cht b v. iu ny ging nh cc phn ng thu phn nc. C mt lng ln cc hp cht hu c v v c tri qua cng on phn tch amnic. 3. TNH CHT NHIT NG 3.1. Nhit ng hc v ng hc

Amnic c tng hp bng phn ng thun nghch gia hydro v nit: N2 + 3H2 2NH3 (20)

Vn ch yu cn xem xt trong qu trnh tng hp l kh nng xc nh lng NH3 c mt trong hn hp cn bng cc iu kin nhit v p sut khc nhau. Cc s liu tin cy ca cc hn hp cn bng trong gii hn p sut t 1.000 n 101.000 kPa c pht trin v mang li kt qu quyt nh hng s cn bng phn ng.Cc s liu th nghim hin th Kp l hng s ph thuc khng nhng vo nhit , p sut m cn ph thuc vo t l hydro v nit c mt. Bng 3 di y l danh mc cc gi tr v nng cn bng amnic c tnh ton khi np theo t l hydro/nit l 3/1 vi hm lng kh tr t 0-10%.

Bng 3: Phn trm NH3 cn bng i vi kh c cha t l Hydr-Nit 3:1 cc mc p sut

khc nhau Mc % p sut cn bng, kPaa

Nhit ,K 10.133 20.265 30.398 40.530 Dng % kh tr 633 35,1 49,62 58,91 65,72 673 25,37 38,82 48,18 55,39 713 17,92 29,46 38,18 45,26 753 12,55 21,91 29,52 36,03 793 8,32 16,13 22,48 28,14 833 6,27 11,88 16,99 21,73 873 4,53 8,80 12,84 16,72 Dng 10% kh trb 633 28,63 40,53 48,14 53,70 673 20,68 31,71 39,38 45,29 713 14,60 24,06 31,21 37,02

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753 10,22 17,88 24,14 29,48 793 7,18 13,16 18,38 23,04 833 5,10 9,68 13,88 17,79 873 3,69 7,17 10,49 13,68 a Mun chuyn kPa ra at th chia cho 101,3. b C mt 3% agon v 7% methan.

Trong qu trnh thit k cc thit b tng hp cn ch n mc hnh thnh amnic. Phng trnh c p dng thng thng nht tnh ton mc phn ng ni ti l phng trnh Temkin-Pyzher :

( )

=

PP

KPP

PKH

NH

NH

HK 3

2

23

23

32

1

21 2

(21) Trong : w- l mc chuyn ho, c ngha l mc chnh gia mc tng hp v mc phn

gii. K1- l hng s mc tng hp K2- l hng s phn gii P - l p sut ring phn - l hng s (th t phn ng), 0,75 (12) v 0,5-0,7 (13-15). Phng trnh Temkin-Pyzher gi nh mc hp th ho hc ca nit trn b mt

khng ng nht c coi l mc khng ch v khng phi l cc gii hn khuych tn. Mt phng trnh Temkin-Pyzher ci tin c p dng thng thng thit k cc thp tng hp thng mi c cc gii hn khuych tn v c mt ca cc cht nhim c. Di y l phng trnh chc nng nhit phn ng:

H = [2,2523x10-2 + 34,7236/T + 1,89905x107/T3]p -22,3792T-1,057x10-3T2 + 7,08048x10-6T3 -38327,0 (22)

Nhit phn ng H l J trn mi mol amnic c hnh thnh. Phng trnh (22) b qua nhit hn hp m khi ng dng trong cng nghip iu ny bt buc phi lu . Nhit ca qu trnh tng hp khong 370-540 0C tng ng vi khong 54,430 kJ/mol (23,400 Btu/mol).

Phn ng gia hydro v nit trn quy m cng nghip hnh thnh amnic thng c thc hin trn b mt ca mt cht xc tc. Hu ht cc cht xc tc thng mi u da trn st kim loi, c ch to ch yu t cht t tnh, Fe2O4 v tri qua qu trnh xc tin dng kim di dng b tt v kim loi nh nhm, canxi, manh. Xc tc nhy cm vi vic thoi ho nhit v nhim c khc nhau. Oxy chu c cc hp cht c nh hng nhim c tm thi v c th chuyn i c nu thi gian phi ra ngoi rt ngn. Lu hunh, asenic, phtpho, clo v cc hydrocacbon nng c th to ra vic nhim c thng xuyn.

Cc n lc gn y v mt thng mi trng tm ch n cc loi xc tc tng hp hot ho c ci tin, cho php qu trnh tng hp NH3 c thc hin iu

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kin nhit v p sut tng i thp. Cc hng ch to xc tc ch trng n vic ci tin tng cng tnh hot ho ca xc tc gc st thng qua vic dng cc cht xc tin.

Xc tc tng hp amnic c xc tin bng ruteni khc nhau ch yu trn cht mang graphit din tch b mt ln. H thng xc tc to ra tnh hot ho cao vi mc nng amnic m c trong phm vi t l H2-N2 km theo cc u th vn hnh tuyt vi trong iu kin p sut v nhit thp. Cng ngh tng hp amnic hin i ca Kellogg (KAAP) c c th kt hp cc c trng tnh nng nh trn ca xc tc trong vic thit k nh my tng hp amnic hiu qu cao. 3.2. Cc yu t nh hng n qu trnh tng hp Amnic 3.2.1. p sut tng hp

Phn ng amnic xy ra khi th tch gim, bi vy theo nguyn l Le Chatelier khi p sut tng th lng phn trm cn bng amnic s tng. Tc phn ng ng thi cng c gia tc cng vi vic tng p. 3.2.2. Nhit tng hp

Do bn cht to nhit ca phn ng tng hp amnic, khi nhit cao s lm tng tc phn ng nhng lng cn bng NH3 li gim. Thoi ho nhit ca xc tc ng thi cng s tng cng vi nhit . 3.2.3. Tc khng gian

Tc khng gian l mc dung tch kh theo cc iu kin tiu chun so vi dung tch xc tc. Ni chung phn trm amnic trong kh hin c s gim i khi tc th tch tng ln; tuy nhin c cng mt dung tch xc tc cc mc tc th tch tng th kh nng sn xut amnic s t c nhiu hn (Hnh 4). Thng thng tc th tch trong qu trnh vn hnh thng mi s tng trong phm vi t 8000 n 60 000 h-1. 3.2.4. Thnh phn kh vo

nh hng ca thnh phn kh vo bin thin ph thuc vo mc kh tr (xem Bng 3), hm lng amnic v t l hydro-nit. Amnic trong kh vo nh hng n t l phn ng. Hu ht cc thit b thng mi u vn hnh mc t l hydro-nit l 3:1 song ti u hn c l thp hn so vi mc ny. C mt s nh my c thit k vn hnh theo mc t l hydro-nit trong phm vi t 2-2,8. 3.2.5. Kch thc ht xc tc

Tnh hot ho ca xc tc tng ln khi kch thc ht gim v t l din tch b mt so vi th tch s tng. Cc ht xc tc nh cn c kh nng chu c mc di chuyn khi thp trong bn thn cu trc xp ca ht xc tc. Xc tc s dng theo nhiu kch thc khc nhau. Cc loi thp tng hp dng hng trc thng s dng cc loi xc tc c kch thc t 6-10 mm trong khi cc loi thp tng hp c thit k dng nm ngang hng knh th u im v tng tnh hot ho ca xc tc nn thng dng loi ht c kch thc t 1,5 n 3,0 mm.

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4. SN XUT AMNIC 4.1. Chun b kh tng hp Amnic 4.1.1. Cc qu trnh chun b kh tng hp Kh tng hp dng sn xut amnic bao gm hydro v nit theo t l 3/1, methan d, argon c thm vo cng vi kh cng ngh v cc vi lng oxit cacbon. C rt nhiu cng ngh dng pht sinh kh tng hp, mi cng ngh c cc c th ring bi nguyn liu s dng u vo. Thnh phn kh tng hp chun tnh theo th tch gm c: Hydro: 73,65% Nit: 24,55% Methan: < 1ppm-0,8% Argon: 100ppm-0,34% Cc oxit cacbon: 2-10 ppm V hi nc: 0,1 ppm. Ngun nit thng l khng kh, tuy nhin hydro c th ly t nhiu ngun nguyn liu th bao gm nc, nh sng v cc cht hydrocacbon nng ca cc qu trnh tinh lc du th, than, kh thin nhin v tng hp ca mt vi loi nguyn liu th khc. Trong tt c mi trng hp mt phn hydro c sn xut ra bt ngun t nc. Cng tc chun b kh tng hp bao gm ba bc: (1) Chuyn ho nguyn liu, (2) Chuyn ho monoxidcacbon v (3) Tinh ch kh. Bng 4 gii thiu cc cng ngh chnh p dng cho tng loi nguyn liu khc nhau. Trong trng hp ny t in phn nc, cn li u cho thy c cc hin tng phn ng chuyn ho kh- nc din ra: CO +H2O CO2 +H2, H = -41 kJ/mol ( -9,8 kcal/mol) (23) Trong qu trnh reforming hi nc, cn bng nc t c, cn trong cng ngh oxi ha phn mc ny t c gn st.

Bng 4: Nguyn liu th v cng ngh sn xut Hydr.

Nguyn liu th M t cng ngh Phn ng chuyn ha nguyn liu Kh thin nhin Reforming hia CnH(2n+2) + nH2O nCO+ (2n+1)H2 Naptha Reforming hib CnH(2n+2) + nH2O nCO+ (2n+1)H2 Du nhin liu Oxi ha 1 phn CnH(2n+2) + n/2O2 nCO+ (n+1)H2 Than Kh ha than C+1/2 O2 CO Nc in phn H2O 1/2O2 +H2= a: Niken c dng lm xc tc b: Niken xc tin c dng lm xc tc Trong cng ngh Haber-Bosch, ngun kh hydro c cc ha bt ngun t than. Trong ng ngh ny ( nh Hnh 5), trc tin cc c thi cng khng kh v c gii phng nhit bi qu trnh hnh thnh cacbon dioxit nng cc ln thnh chy sng. Sn phm t chy ri khi h thng i ra ngoi. Tip ngi ta thm hi nc vo sn xut ra loi kh c cha CO2, CO v H2. Thng thng Nit c cung cp bng cch b sung mt lng va cho sn phm t chy trong bc thi vo cho dng kh. Bi v hi nc cha phn gii sau c loi tr bng qu trnh ra nc. Kh i thit b cha th nht. CO trong kh c chuyn ha thnh H2 v CO2 bng phn ng vi hi nc c s tham gia ca xc tc, sau kh chuyn ha c cha trong mt thit b

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khc, qua nn v kh CO2 bng ra nc. Kh tip tc c nn, ra bng dung dch ng amnic kh CO cha chuyn ha. Sn phm thu c l loi kh tng i thun c cha ba phn hyr v mt phn Nit v sau np di dng kh mi cho chu trnh tng hp. Nguyn liu cacbon kinh t nht u ging nhau v mc t l hydr-cacbon. Qua Bng 4 ta c th thy vi mt lng cacbon nht nh ( np u vo), v mt t l m ni reforming hi thng to ra nhiu hydro hn so vi oxi ha phn. Do trong qu trnh sn xut hydr tng hp amnic, cng ngh oxy ha phn thng cn phi np nhiu hn do cn phi c cc trang thit b kh CO2 ln. Ngoi ra kh th sn phm ca qu trnh oxy ha phn thng c hm lng CO cao hn so vi qu trnh reforming hi nc. Hm lng CO cao ny cn phi c cc thit b ln, k c dung tch xc tc dng cho vic chuyn ha. V phi kh nhiu CO2 v mc chuyn ha ln nn chi ph u t v chi ph sn xut ca cc qu trnh oxy ha phn ch c ngi ta dng i vi cc loi nguyn liu khng th dng cho cng ngh reforming hi nc c nh than v cc loi nguyn liu np hydrcacbon nng. Hydro c sn xut bng qu trnh in phn nc ch c ngi ta p dng trong cc trng hp c bit: trong nhng trng hp in nng sn, r v khng dng cc cht hydrocacbon nh. Cc loi kh thi ca thit b reforming xc tc ca qu trnh sn xut xng tinh lc du l mt ngun hydr. C nhiu nh my sn xut NH3 c xy dng bng cch dng loi kh thi ny, kh ny c cha khong 85% H2, l mt dng cht np u vo tt. Trong cc cm thit b ca cc nh my ny, h thng ra Nit lng c s dng. Hm lng methan v ioxit cacbon ca l kh ha than Lurgi tiu biu l 10-11% v 28%. Kh th ca l kh ha than Lurgi c x l trong nhiu bc cng ngh bao gm thu hi nhit tha, chuyn ha, kh hc n, phenol v cc sn phm ph khc x l Rectisol ( ra methanol) CO2, kh lu hunh, ra nit lng sn xut kh tng hp c thun cao, nn, v bc tng hp amnic sau cng. Bc ra nit lng kh CO v

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methan v c tun hon tr li cho thit b chuyn ha v reforming hi nc sn xut thm hydr v cung cp nit cn thit cho qu trnh tng hp.

Kh ha tng lng Koppers-Totzek xy ra trong iu kin p sut thp v nhit cao m bo cho vic chuyn ha hon ton hydrocacbon. Hn hp ng nht than nghin, oxy v hi nc phn ng sn sinh ra nhit vng ngn la vo khong 1925oC. Cc phn ng thu nhit gia hi nc v cacbon gim nhit xung vo

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khong 1480oC. Mc d methan nh hn hoc bng 0,1%. Ty thuc vo mc phn ng ca than, c ti 99% cacbon c kh ha; hm lng kh sn phm thu c c cha ch yu hydro v cacbon. Kh th c ch bin trong mt dy cc cng on vn hnh bao gm pht sinh hi ra, nn, kh lu hunh, chuyn ha, kh CO2, ra nit, nn v tng hp. Mi quan tm ca th gii trong nhng thp nin 1970 v cc loi kh tng hp c sn xut t nhiu loi cng ngh s dng than ang c pht trin t ha lng trc tip n kh ha ...Cc loi cng ngh ph hp nht sn xut amnic l cng ngh c th vn hnh mc cao p, chuyn ha than c mc hnh thnh methan v cc sn phm ph thp. Tuy nhin, ngay c i vi cc cng ngh c ci tin, cc nh my sn xut amnic i t than thng t hn so vi cc nh my sn xut i t kh v cc cht lng khc bi v bc vn chuyn thao tc cc cht cng v x l cc dng thi ca n cn phi c nhiu thit b i km. Tr lng nghnh du kh di do cn tr ng k vic dng than lm nguyn liu cho nghnh ha cht. Cng ngh kh ha than Texaco c lun chng ha trn quy m nh vo nm 1982 ti nh my ca Tennessee Valley Authorrity (TVA) ti Alabama. Mt l kh ha than Texaco n c nng cp dng cho cng on u ca mt nh my sn xut amnic i t kh hin c sn xut kh tng hp vi mc cng sut vn hnh tng ng 122 tn/ngy. Nm 1984 cng ty Ube Industries Nht i vo vn hnh mt nh my mi theo cng ngh ny sn xut kh nguyn liu np cho chu trnh tng hp NH3 Kellogg hin ti cng sut 1500 T/ngy. Nh my Ube ni trn hin nay nu cn c kh nng linh hot sn xut amnic i t than cc, du, naptha hay kh ha lng. 4.1.2. Cc loi cng ngh oxy ha phn i t cacbon nng

Hin nay hai cng ngh thuc dng ny ang c thng mi ha, l cng ngh Shell v cng ngh Texaco. Cc iu kin vn hnh ca l sinh kh bin thin t 1200oC n 1370oC v p sut t 3100 n 8270 kPa(450-1200 psig). Ni chung cc loi du nng l cc cht np hydrocacbon, song cng ngh c th thch ng vi cc nguyn liu u vo t kh thin nhin n cc loi cn du. Hnh 8 m t lu trnh cng ngh kh ha tan Shell. Cht np hydrocacbon gia nhit s b cng vi oxy trn ln vi hi nc sau np cho bung t ca l phn ng, ngn la phi xc tc to ra kh tng hp. Dng thot nng ca l kh ha c lm lnh bng vic pht sinh hi cao p trong cc ni hi nhit tha c thit k c bit. Mc d c mt ca cacbon t do, nhng l c thit k m bo cc b mt truyn nhit lun lun sch s ngay c trong trng hp vn hnh lin tc di k. Kh tng hp th sau c a ti cho h thng kh cacbon, h thng ny bao gm thit b thu gom cacbon v thit b ra lm lnh kh, ti y cacbon ca l c kh di dng va nc. Cacbon c chuyn thnh du v sau to thnh cc ht cacbon-du trong mt thit b chuyn dng c ngi ta gi l thit b v vin. Cc ht sn phm ny c ti x l thnh va km vi du np trong mt thit b trn u v ti tun hon di dng va long cho l kh ha. Hnh 9 l s lu trnh cng ngh kh ha Texaco. Hydro qua gia nhit s b c np cng vi oxy cng vi hi nc vo l kh ha than. Kh tng hp th cn nng c lm lnh phn di ca l bng cch dng dng nc nng ca thit b ra. Khi c lm lnh bng nc n nhit bo ha bng cch bc hi v cho php thc hin bc chuyn ha tip theo. Hu ht cc cht cacbon cn li s c kh trong bc vn hnh lm lnh v bc tinh ch b sung trong thit b ra cacbon trong dng nc khi ri khi l kh ha c chit sut bng natha trong thit b tch naptha. Lp naptha cacbon

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nh hn c trn vi hydro cacbon u vo v hn hp c ti sinh trong thit b stripper naptha. T thit b stripper trn cao naptha c tun hon tr li cho bc chit xut. T di y ca thit b stripper, naptha cacbon c ti tun hon tr li cho l kh ha. Nc ca thit b tch naphta sau khi qua kh kh c a tr li cho thit b ra, kh tng hp th sch c dng cho bc ch bin tip theo. Hnh 8 Cng ngh kh ha Shell. Sn xut amnic bng cng ngh oxy ha phn cc cht np hydrocacbon ty thuc vo mc ca qu trnh kh ha. Kh tng hp th sch ca h thng oxy ha phn Shell trc tin c x l kh lu hunh, sau chuyn qua khu chuyn ha v cng on ra nit lng. Kh tng hp th sch bo ha ca cng ngh oxy ha phn Texaco trc tin c chuyn ha bng cch dng xc tc chu lu hunh. Hi nc cn cho chuyn ha c mt sn trong kh bng phng php vn hnh kch lnh trong l kh ha. Kh qua khu chuyn ha sau c ch bin kh sunfit lu hunh v CO2, tip n l bc ra nit lng.

4.1.3. Reforming hi nc D kin s b c chng khong 75-80% sn lng NH3 trn th gii c sn xut t qu trnh reforming hi nc v xp x khong 65-70% trong s ny l dng kh thin nhin lm nguyn liu np u vo. Hnh 10 di y l s khi tiu biu vi ngun nguyn liu np u vo l hydrocacbon nh. Nguyn liu np t kh thin nhin cho n naptha trc tin u phi i qua khu kh lu hunh, sau trn ln vi hi nc v c reforming trong mt thit b reforming th cp. Lng khng kh va c cha nit cn thit dng cho tng hp c a vo trong bc reforming th cp. Lng

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khng kh va c cha nit cn thit dng cho tng hp c a vo trong bc reforming th cp. Kh qua reforming sau c chuyn ha v ra kh CO2. CO v CO2 cn li s c kh bng phn ng ca hydro sinh ra methan v nc trong

cng on methan ha kh tng hp sau qua nn v sn xut ra amnic.

4.1.4. Chi ph vn v nng lng

Cc yu cu v chi ph vn v nng lng cho vic sn xut amnic ph thuc ch yu vo vic s dng nguyn liu np u vo. Bng 6 di y gii thiu v cc yu cu cho nng lng i vi mt nh my sn xut amonic c quy m thng mi, trong nh my ny s dng cc nguyn liu np u vo khc nhau. Vic s dng nng lng tng nhanh do nguyn liu np thay i t kh thin nhin n than hoc nc. Mt nh my kh ha than c nng cp c mc tiu hao nng lng khong 44,3 GJ/T. Cc cng ngh kh ha than mi nh cng ngh Kellogg/KRW c th gim mc tiu hao nng lng khong 10% so vi cc loi cng ngh khc. Bng 6: Nhu cu nng lng cho vic sx NH3 da trn nguyn liu u vo GJ/t Reforming Reforming Oxy ha phn Kh ha in phn kh t nhin naphtha du nh.liu than nc N/m thp nin 1970 35,9 39,6 40,6 48,5 44,3 N/m thp nin 1980 29,0 32,0 43,2

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Chi ph vn ng sau mc tiu hao nng lng c th gp 1,5 ln i vi trng hp oxy ha phn v n hai ln i vi cng ngh kh ha than nu so vi reforming kh thin nhin. Mt nh my reforming naptha c th tng 15-20% so vi i t kh thin nhin bi v nhu cu cn n cc trang thit b x l hydr v kh CO2 cng on u tng i ln. 4.1.5. Cc loi kh thi giu Hydr dng sn xut kh tng hp

T gia nhng nm thp nin 1970 ngi ta ch trng n vic s dng hydr sn phm ph hay cc loi kh thi giu hydr sn xut amnic. Bng 7 l danh mc cc cng ngh sn sinh ra cc loi kh thi giu H2. Cc h thng ny thng c cha nhiu tp cht khc na m ngi ta cn phi kh b trc khi tng hp amnic.

Bng 7- Cc ngun v thnh phn ca cc loi kh giu H2

Thnh phn % th tch Dng kh giu H2 H2 CO CO2 CH4 N2 Kh thi Methanola 80,0 2,00 2,60 14,0 1,0 Kh H2 n/m ethylenb 84,4 0,20 14,5 Kh H2 n/m COc 97,0 1,95 0,4 0,09 H2 n/m sad 99,86 0,02 0,24 N/m cyclar v BTX 96,6 4,0 Kh l ccc 60,0 6,5 2,5 22,5 6,5 a: Kh cn c cha 0,4% th tch methanol b: i t cht np etan c: Nh my CO c hp lnh chuyn ha CO d: Kh cn c cha 0,06 % th tch O2 v 15ppm clo. e: Kh cn c cha 1,5 % th tch cc cht hydrocacbon sau khi qua x l s b v 0,5 % O2. Hnh 11 l lu trnh cng ngh ca cc nh my sn xut amnic tiu biu, nh my ny s dng kh thi ca nh my sn xut methanol l nguyn liu u vo. Nh my ny c cng sut thit k l 545 tn NH3 /ngy c a vo chy th nm 1986 cho cng ty Ocelot Kitimat BC ca Canada. Nh my ny dng chu trnh tng hp nng lng gim ca Kellogg vi thp tng hp amnic lm lnh nm ngang v h thng phn ly lm lnh, cm thit b cht lng cp nht. Mt nh my khc tng t c mc cng sut 750 tn/ngy c xy dng nm 1989 ti vng quc Anh, dng hydro lm sn phm ph ca cc nh my sn xut CO l nguyn liu u vo.

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4.1.6. Cc ngun kh tng hp trong tng lai

Nhu cu pht trin ngy cng nhanh trong qu trnh sn xut amnic v cuc khng hong nng lng trn ton th gii trong thp k 1970 a n mt khi nim mi v sn xut kh tng hp, qu trnh ny khng cn n nguyn liu np hydrocacbon. V d vic dng nhit thi ca cc cm nh my nguyn t c ngi ta xut thay cho nhin liu cn thit sn xut kh tng hp ging nh dng nng lng nhit ca bin. Ngi ta xut mt cm thit b gi l nh my NH3 trn tu/ chuyn ha nng lng nhit bin. Theo lu trnh ny, dch lm vic (NH3) c bm t pha di ngm ( phn lnh) ca bin ln b mt( vng m), ti y n bc hi v hi amnic c pht sinh s c gin n cung cp cng sut trc cho my pht. Sau khi gin n, hi amnic c ngng t v chu trnh tun hon nng lng kt thc. in nng pht ra c dng in phn sn xut H2; nc ca cc t bo in phn i t qu trnh thm thu o nghch ti. Hydro c kt hp vi nit ca nh my ha lng khng kh ti, hn hp H2-N2 c chuyn ti cho chu trnh tng hp amnic quy c. Ton b nh my c h tr bi in nng c sn xut ra bng qu trnh gradient nhit ca bin. Nng lng cha ng trong sng bin nh, nhng khi lng nc ln c cc nh my in hnh thnh trong thi gian ngoi gi cao im, trong gi v.v... c coi l cc phng n la chn sn xut nng lng nhin liu dn ng. Trong nhng nm thuc thp nin 1980 gi du la v kh thin nhin c chiu hng tng cao. Pht hin ra kh thin nhin ngoi khi ln trong t lin lm tng ng k ngun cung cp nng lng cho th gii v vic pht hin ra du la cng vi kh ng hnh gp phn lm tng ngun cung cp nguyn liu cho nghnh cng nghip sn xut amnic. Da vo cc thnh tu pht trin nh nu trn d kin ngun nguyn liu trong tng lai dng sn xut kh tng hp amnic ch yu l reforming hi nc kh thin nhin, c b sung bng kh ng hnh ca qu trnh sn xut du, v cc loi kh thi giu hydr (c bit l ca cc nh my sn xut methanol).

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4.2. Cng ngh sn xut Amnic t reforming hi nc kh thin nhin Kh thin nhin l loi kh nguyn liu th thng thng dng sn xut amnic.

Hnh 12 l s lu trnh cng ngh ca nh my sn xut amnic cng sut ln chu trnh n. Cc bc cng ngh quan trng ca nh my ny bao gm: Tinh ch nguyn liu, reforming s cp v th cp, tinh ch kh tng hp, tng hp amnic v thu hi. 4.2.1. Tinh ch kh np

V cc loi xc tc reforming gc niken l loi xc tc nhy lu hunh, halogen v nhim c kim loi mnh c ngi ta pht hin trong kh thin nhin nn thng thng phi cn n h thng tinh ch nguyn liu. Cc hp cht lu hunh dng hu c ln v c thng l nhng cht gy nhim c xc tc reforming c pht hin thy trong kh thin nhin. Cc tng than hot tnh v cc tng oxit km lnh hoc nng ni chung c dng kh cc hp cht lu hunh. Lu hunh mc thp c th c hp th trn than hot tnh theo cc mc nhit khc nhau ca mi trng. Cht hp th qua s dng c ti sinh bng qu trnh stripping hi nc hay cc loi kh nng. Oxit km l cht dng kh H2S, mercaptan v trong chng mc no kh c clorua rt hu hiu. nhit vo khong 350oC, mercaptan phn hy thnh hydrocacbon v H2S ri sau phn ng vi oxit km to thnh sunfit km: ZnO +H2S ZnS +H2O (24) Oxit km t tiu hy, khng th chuyn i thnh sunfat km, tng dng ri phi loi b. Cc hp cht lu hunh hu c khc nu dng c than hot tnh ln oxit km kh cng khng d dng/ tuy nhin cc hp cht ny c th c hydr ha bng cch dng hydr cho cc loi xc tc coban hay molypden niken. H2S c to ra s c kh bng tng oxit km thng thng nh m t trn. Cc loi xc tc gc molypden cng c th c s dng hydro ha olefin c mt trong mt s cht kh thin nhin. Trong nhng trng hp olefin khng gy nhim c cho xc tc th chng c th crcking hay polime ha mc nhit reforming cao ngn chn tnh hot ha ti ch ca xc tc. Hydro dng cho cc phn ng ny c th c cung cp bng cch tun hon kh tng hp trong qu trnh vn hnh thng thng hay bng cch cracking amnic hay methanol trong qu trnh khi ng, nu khng c ngun bn ngoi s dng thay th. Chi tit c th v cc cu hnh cng ngh cc h thng kh lu hunh nh nu trong ti liu nh km.

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Kh lu hunh tng c nh l phng n khng thc t v khng mang tnh kinh t nu hm lng lu hunh trong kh thin nhin qu ln. Trong trng hp ny thu hi v kh lu hunh khi lng trong h thng hp th-stripping kh axit, tip theo sau thng ngi ta p dng bc lm sch cc cht d tng c nh. Clorua c th pht hin thy trong kh thin nhin, c bit l cc m cha ngoi khi. Cc loi xc tc nhm tng cng c ngi ta nghin cu pht trin hp th cc cht c trong kh np. C mt s cht kh thin nhin cn pht hin thy c cha thy ngn, cht thy ngn ny lm nhim c xc tc khi chng c cha mt lng va . Mt s tng than hot tnh thm lu hunh c kh nng rt hu hiu trong vic kh cht kim loi ny. 4.2.2. Reforming s cp v th cp

Chuyn ha kh thin nhin thnh kh tng hp trong qu trnh reforming c thc hin bng qu trnh reforming hi nc: CH4 +H2O CO +3H2 H= 206 kJ/mol ( 49,2 kcal/mol) (25)

V phn ng chuyn ha nc-kh. Nicken trong cht chng chy hay cht mang nhm lm xc tin cc phn ng ny; phn ng chuyn ha nc- kh t ti mc cn

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bng. Phn ng ton phn ca h thng t phng trnh 23, 25 l phn ng thu nhit, qu trnh chuyn ha c h tr bi nhit cao, p sut thp v t l hi-cacbon cao. Thit b reforming s cp thc ra l mt l cng ngh trong kh nhin liu t vi khng kh cung cp trc tip nhit phn ng cho xc tc c cha trong cc ng. Vng ny ca l thng c ngi ta gi l cng on hng knh, n mang tn gi nh vy bi v y l mt c cu s cp dng truyn nhit vi mc nhit cao theo yu cu ca cng ngh (750-850oC). Mc p sut reforming thng thng trong phm vi 3-4MPa (30-40at), mc ny hp l gia chi ph v cc yu cu nn sau ny. Cc phn ng khng mong mun trong l reforming l cc phn ng hnh thnh cacbon, mt loi sn phm bt c d: CnH(2n+2) nC + (n+1)H2 (26) Cracking nhit c xu hng phn hy cacbon trn b mt xc tc, c kh bng hi nc. Phn hy cacbon theo c cu ny c xu hng xy ra gn st li vo ca cc ng xc tc trc khi sn xut hydro bng cc phn ng reforming trit gim pha phi ca phn ng. Cc cht xc tin nh b tt chng hn c dng h tr cho vic cracking trit tiu trong nguyn liu np kh thin nhin c cha cc cht hydrocacbon nng. Cacbon c th c hnh thnh bng c vic khng cn i ln vic gim monoxit cacbon: 2CO C + CO2 (27) CO +H2 C + H2O (28) Cacbon c sinh ra theo phng trnh phn ng sau c to ra trong cc l xc tc lm cho vic kh gp nhiu kh khn v c bit lm t gy cc b mt l hc. T l hi nc-cacbon c chn trn mc ti thiu cn thit nhm hn ch hnh thnh cacbon theo cc phn ng ta nhit nh nu trn. Hi nc l mt ngun nhim bn mnh, cc loi ha cht ca nc np ni hi hay ca h thng lm lnh l cc cht c i vi xc tc ca l reforming, bi vy lng hi nc cn phi c khng ch cn thn. Hnh 13-Cng on hng knh ca l Reforming hi nc kiu hp Kellogg. Ni chung vt liu ng xc tc chp nhn c dng thit k ch to thit b reforming l loi hp kim nicken c ly tm 25% crm-20% niken c hm lng cacbon c trng khong 0,35 n 0,45% v c kh nng kt hp ti u v bn v kh nng hn. Trong nhng nm thuc thp nin 1980, cc loi vt liu khc c ngi ta chp nhn l loi hp kim 25Cr-35Ni-Nb (cao p ci tin). Vt liu ny cho php hot ng iu kin nhit v p sut cao trong khi gim c chiu dy ca thnh ng. Kt qu cc ng c dy mng v c ng sut vn hnh thp do mc dao ng v profin nhit , ng thi cho php t c dung tch np xc tc ln. Ni chung cc ng c thit k vi tui th l thuyt ti thiu l 100.000h, theo ng tiu chun API 530. Cc kiu s c ng thng gp l cc ng nt hoc gy. Mc p sut reforming cao hn thng c nhiu u im hn, bi v n lm gim nng lng nn cn thit ca chu trnh tng hp, kch thc thit b gim, kh CO2 trong cc iu kin p sut phn thun li ng thi hiu sut thu hi nhit ca qu trnh c ci thin. Cc thit k thit b reforming s cp c p dng thng c s khc nhau v mt b tr ng v cc b phn t, vt liu ch to ng, mc phn phi khi np v h thng gp kh ca thit b reformer. B phn t ca thit b reformer s cp l mt trong nhng c tnh tiu biu ca nh my sn xut amnic. Cng on hng knh ca l reforming hi nc kiu hp Kellogg tiu biu nh nu trong hnh 13. Trong thit b reforming kiu hp ny cc ng xc tc c b tr song song vi nhau, cc dy c rng ring c gia nhit c cc pha bi cc vi t bng dch hay t bng khng kh,

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cc vi ny c t ti ca vo ca l. Hng ICI v Uhde u dng cu hnh l t kiu t nh khi thit k cc thit b reforming s cp ca h. Trong b phn t ca thit b reformer s cp Haldor-Topsoe, cng on hng knh bao gm mt hay nhiu ngn hnh ch nht thon di c cc ng thng ng lp trn gia ng tm ca ngn theo dy thng n hay dy kp ch chi. y l loi l t cnh vi ngn la phn chiu song song vo tng ng vai tr ging nh cc thit b pht x. Cc l t hot ng tt i vi cc loi nhin liu t kh thi giu hydro n cc hn hp naphta bc hi hay hi nc.

Trong l t reforming Foster-Wheeler, cc thnh bc nghing c t thng ng ng nht bng vic tng lung cc loi kh nng. Cc l t trc h ny c th dng c c kh ln du nh chng. Hp hng knh ch c hiu sut khong 50% nhng nhit c gii phng khng b phn ng reforming hp th s c thu hi trong cng on vect cho php tng hiu sut ca l t ti 94% trn c s nhit kh ng khi vo khong 150oC dng np cho cng on kh lu hunh sau . Gii hn thao tc nhit ra ca thit b reformer c quyt nh bi cc vn ca ngnh luyn kim kim loi ng. Qu trnh reforming c hon thin mang tnh cht on nhit trong thit b reforming s cp, y l mt thp c lt mt lp chng oxy c cha xc tc tng c nh. Phn yu cu thu nhit cn li c cung cp bi s t chy trc tip dng thi ca thit b reformer s cp vi khng kh t trong bn thn qu trnh cng ngh. Hn ch b mt truyn nhit dn n nhit qu trnh ti u ra thit b reforming th cp t mc cao hn, khong 1000oC lm cho mc tn tht methan trong kh ra thp, trong gii hn t 0,2-0,3 %. Xc tc ca thit b reforming th cp tng t xc tc c dng trong thit b reforming s cp. y l loi xc tc gc niken v n c cht h tr nhm c kh nng chu c nhit cng ngh cao. Do lng khng kh c thm vo cho thit b reforming c quyt nh bi yu cu v nit cng ngh nn mc hao ht gia thit b reforming s cpv th cp phi trong phm vi cn bng nhit ha hp vi mc nhit thit k thit b ra. 4.2.3. Reforming nhit thi

L reforming s cp c th c hn ch v mt kch thc hay gi n kch thc va bng cch dng nhit trong dng thi ca thit b reforming th cp hay cc loi kh ng khi ca cng on vect cung cp nhit cho qu trnh reforming. C nhiu loi cng ngh khc nhau c xut, trong s c cng ngh mang tnh u vit ha hn nht l cng ngh dng thit b trao i nhit v ng lm phng tin trao i nhit. Tp on ICI a vo thng mi ha loi thit b trao i nhit ny t nm 1988 trong mt phn lu trnh cng ngh nh my tng hp NH3 ca h ( Xem hnh 14). M hnh thit b trao i nhit reforming c p dng cho lin hp sn xut m ca Grodno ti Nga. Hnh 15 l s thit b trao i reforming ng m trong lung kh thi ca thit b reforming th cp chy ngc ln phn cha kh thin nhin i qua cc ng np liu xc tc reforming. Cc dng kh ny c trn ln vi nhau trong bung pha cui ng v i ra pha v ca thit b trao i. Thit b trao i reforming c tnh n gin v mt c hc do thit k c trung ca n. Ngoi ra so vi cc h thng thit b reforming s cp quy c, h thng trn tit kim c cc chi ph vn v chi ph vn hnh. 4.2.4. Chuyn ha

Cc cht xit cacbon s lm kh tnh hot ha ca xc tc tng hp bi vy chng phi c kh ht trc khi i vo chu trnh tng hp. Phn ng chuyn ha nc - kh

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ta nhit to ra mt c cu thch hp tng n mc ti a lng sn xut hydro trong khi c th chuyn ha CO thnh CO2 to iu kin thun li cho qu trnh kh. Ngi ta s dng mt trnh t thit b tng hp on nhit hai cp nng cao nng lc chuyn ha. Lng CO c chuyn ha thnh CO2 trong mt thit b chuyn ha nhit cao(HTS), vi nhit lm vic t 350-400oC tn dng u th v ng lc phn ng trong cc iu kin nhit cao. Cc loi kh sau c lm lnh, CO d cn li trong kh c chuyn ha thnh CO2 trong thp chuyn ha nhit thp hn ch mc r r CO do mc chuyn ha cn bng thch hp. V mt la chn m ni thng cc loi thp chuyn ha ng nhit c ngi ta dng nhiu kh mc cn bng.

Cc loi xc tc chuyn ha nhit cao (HTS) gm ch yu l cc tinh th t tnh n nh bng vic dng cc oxit crom. Phtpho, arsenic v lu hunh l cc cht gy nhim c xc tc. T l hi nc reformer-cacbon thp to iu kin thun li cho vic hnh thnh cacbua st lm xc tc qu trnh tng hp cc cht hydrocacbon trong phn ng Fisher-Tropsch. Cc loi xc tc tng cng st hay khng c st chuyn ha nhit cao v ang c ngi ta nghin cu gii quyt cc vn nan gii ni trn v cho php thit b lm vic vi t l hi nc-cacbon thp khong 2,7. Cc s liu v cn bng trong phn ng chuyn ha kh nc nh nu trong phn tham kho. r r CO t 0,2 n 0,3% th tch mc nhit 200-250oC c gi vng bng vic dng cc thit b chuyn ha nhit thp cho php ta s dng c bc methan ha sau kh cc loi kh tr c trong kh mi ch. Kh ti u vo ca thit b

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chuyn ha nhit thp phi trn mc im sng 20oC nhm ngn nga hin tng mao dn ca dch nc trong xc tc. Xc tc chuyn ha nhit thp l loi xc tc oxit ng mang oxit km v nhm, cc thnh phn CuO, ZnO, Al ni chung l ngang bng nhau. i vi xc tc mi u phi qua mt chu trnh khi ng ban u dng hydro kh oxit ng. C cu nguyn l ca vic kh hot ha l qu trnh thiu t. Xc tc b nhim c bi lu hunh v clorua. Xc tc chuyn ha nhit thp l loi xc tc c mc hot ha cao, c cn bng v cho php hot ng mc thp hn so vi mc nhit thit k. Nhit tng dn dn m bo tui th cho xc tc. 4.2.5. Kh dioxit cacbon

Cc loi kh thi ca thp chuyn ha c cha khong t 17-19% th tch CO2, lng CO2 ny cn phi kh n mt mc cn chng vi ppm, tip n l bc tinh ch cui. Cc h thng kh CO2 thng mi c phn loi da theo cc h thng nh h thng phn ng kt hp l hc v h thng hp th l hc. Ni chung cc qu trnh ny u c cu hnh thit b hp th Stripper. Bng 4 l cc s liu so snh ca cc h thng kh CO2 khc nhau. a. Qu trnh Alkanol amin ( Amin kim )

Dioxit cacbon l mt cht kh phn ng thun nghch vi dung dch kim nc to ra mt sn phm cacbont. Sn phm cng ny phn hy khi ta thm mt lng nhit vo to iu kin cho vic kh CO2 c thun li. Trong cc nh my sn xut amnic thi k u, dung dch nc monoethanolamine ( MEA) 15-20% trng lng c ngi ta coi l phng php dng kh CO2 tiu chun. Cc loi dch kim amin s cp cn phi c mc ti sinh nhit tng i cao. Nhit d qu nhit cc b trong cc ni hi nu li lm cho MEA phn hy v sinh ra cc hp cht n mn. Mt h thng c ch, chng hn nh h thng Bo h Amin do Union Carbide ci tin pht trin l phng php khng ch n mn c hiu qu nht. Cc cht c ch cho php dng cc loi dch MEA c nng cao hn ( 25-35%), iu ny cho php gim c mc tun hon v sau gim c c cc bc ti sinh. Cc loi amin ba hot ha nh triethanolamine (TEA) v methyl diethanolamin (MDEA) c ngi ta chp nhn dng trong qu trnh kh CO2. Cc cht ny c mc nng lng ti sinh thp do vic hnh thnh sn phm cng CO2 amin v khng sn sinh ra cc cht cacbamat v cc hp cht n mn khc. Cc h thng kh CO2 nh h thng MDEA-sunfualan-nc v DIPA-sunfualan-nc, trong DIPA l diisopropylamine l nhng h thng cc dung dch kim nc trong mt dung mi khng c nc v thng thng cc h thng ny c ngi ta s dng theo hng dc cng vi cc h thng khc lm sch cht cn. Cc s liu v tnh ha tan ca cc kh axit trong cc dung dch amin c nu c th trong ti liu. b. Qu trnh cacbonat hot ha

Qu trnh cacbonat hot ha da trn c s hp th CO2 ca cacbonat kali to ra bicacbonat kali. Khi bicacbonat c t nng n s thi ra CO2, lm ti sinh cacbonat kali. Qu trnh cacbonat nng nguyn thy ca U.S.Bureau Mines c ngi ta pht hin n mn thp cacbon. C rt nhiu cht ph da c dng nhm ci tin mc chuyn i vt cht cng nh dng c ch n mn. Cc cng ngh ca Vetrocoke, Carsol, Catacard, Benfied v Lurgi u l cc cng ngh cacbonat hot ha. Cng tc ci tin bng vic thm cc cht ph da v ti u ha qu trnh vn hnh lm cho cc cng ngh cacbonat hot ha mang tnh cnh tranh vi cc h thng MEDA hot ha v h

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thng c gc dung mi phi nc. Yu cu nng lng tiu biu nh trnh by trong Bng 9. Vic la chn h thng kh CO2 c trng ph thuc vo thit k tng th ca ton b nh my NH3. Nhng vn quan trng cn ch bao gm: yu cu

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Cng ngh Dung mi Tun hon dch H.lng kh axt trong kh qua x l (ppm)

MEA MEA DGA MDEA Vetrocoke Carsol Catacarb Benfield Flexorb HP Lurgi Alkazid Sulfinol TEA-MEA MEA-sulfinol-H2O Purisol (NMP) Rectisol Flour Solvent Selexol

20% Monoethanolamin 2-35% monoethanolamine cng thm cht bo h amin 60% Diglycolmine 40% Methyldiethanolamine cng thm cht ph da K2CO3 cng thm As2O3 glycine K2CO3 cng thm ph da 25-30% K2CO3 cng thm ph da 25-30% K2CO3 cng thm diethanolamine v ph da K2CO3 xc tin amin 25-30% K2CO3 cng thm ph da Mui kali aid methylminopropionic 2 ( hoc 3) Cc h thng phn ng l hc kt hp Sulfone v 1.1 imminobis- 2 propanol Triethanolamine v monoethanolamine Cc h thng hp th l hc N-methyl-2-pyrrolidinone Methanol Cacbamat popylen Ete dimethyl prolyethylene glyco

Trung bnh nt nt nt cao cao cao cao cao cao * Trung bnh Cao (TEA) Thp ( MEA) Trung bnh Trung bnh Trung bnh * *

< 50 < 50 < 100 < 50 500- 1000 nt nt nt nt nt * < 100 < 50

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v kh CO2, p sut phn ca CO2 trong kh tng hp, s c mt hay khng c mt ca lu hunh, yu cu nng lng cho cng ngh, chi ph u t, kh nng s dng dung mi v cc yu cu v thu hi CO2. Thng thng CO2 c thu hi l dng sn xut ur v phc v nghnh sn xut nc gii kht c gas v thu hi du theo phng php tuyn ni. c. Cc h thng hp th

Ni chung trong cc iu kin p sut ring phn ca CO2 cao cc dung mi c tnh nng vn hnh tt. Do tnh ha tan ca cc loi kh axit tng khi nhit gim nn hu ht cc h thng hp th u dng qu trnh lm lnh b sung t kh nng hp th nhit thp. Do nhit hp th thp nn kh stripping thng l khng kh do nhu cu nhit cho cc bc ny l khng ng k. Khi gim p thng thng ngi ta c th thu hi c khong 70% dioxit cacbon. Nng sut thu hi CO2 c th t mc cao hn bng phng php phn ly chn khng cao hay ti np li cho thit b stripper trn nh ca thp reforming th cp. Cng ngh Reetisol l cng ngh c th dng c ngay cho bc kh kh axit trong kh tng hp trong qu trnh oxy ha phn nguyn liu nng. Cc loi dung mi dng trong cc cng ngh Purisol, Fluor Solvent v Selexol c cc mc p sut thp nn mc tn tht dung dch c hn ch ti thiu. Cc h thng hp th ni chung khng c hin tng n mn. d. Hp ph p sut dao dng

Dioxit cacbon c th c kh bng qu trnh hp ph trn cc sng phn t. Tuy nhin cc loi sng phn t ny cha phi l ti u i vi CO2, cc loi kh cn phi c tip tc ch bin t ti cht lng yu cu dng cho cng on sn xut ur bc tip theo. S dng qu trnh hp ph p sut dao ng kh CO2 ph hp cho cc nh my c quy m nh v ring bit. 4.2.6. Bc tinh ch cui - Metan ha

Cc cht c cha oxy (CO,CO2,H2O) gy nhim c xc tc v phi c kh ht hay chuyn i sang cc dng kh tr trc khi chng c np vo chu trnh tng hp. Ngoi ra vi s c mt ca CO2 trong kh tng hp c th dn n vic hnh thnh cacbamt amni, cht ny gy nhim bn v cracking ng sut n mn trong my nn. Hu ht cc nh my dng phng php methan ha chuyn i cc oxit cacbon thnh methan. Cc qu trnh kch lnh l rt ph hp cho bc tinh ch kh tng hp c ngi ta nghin cu ci tin v pht trin.

Phn ng methan ha l cc phn ng thn nghch reforming: CO+3H2 CH4 +H2O , H25 .0C = -206,1 kJ/mol (-49,26 kcal/mol) (29) CO2+43H2 CH4 +2H2O,H35 .0C = -164,9 kJ/mol(-39,42 kcal/mol)(30)

Chuyn ha cc oxit cacbon thnh methan, vi s tn tht ca hydro, i n kt thc hon ton v hm lng CO v CO2 ca kh x l cn khong vi ppm. Thit b methan ha tiu biu hot ng trong phm vi nhit t 300- 400oC. Cc phn ng ny l nhng phn ng ta nhit mnh v bi vy CO v CO2 ti li vo ca thit b methan ha phi c khng ch cn thn m bo nhit theo quy nh.

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Cc loi xc tc dng cho thit b methan ha thng mi c cha niken, cht mang nhm, kaolin hay ximng nhm canxi. Lu hunh v asen gy nhim c xc tc, ng thi gy nhim bn do mang dung mi t h thng kh CO2 sang. * Loi nc

Vic dng sng phn t sy kh cho bc lm sch cc oxit cacbon v nc trong kh tng hp xung cn 1 ppm t c kt qu tt trong cc nh my sn xut kh tng hp c bn th thit k tiu hao nng lng thp. Sng phn t t trong cc bc trung gian ca my nn kh tng hp lm gim dung tch cn thit. Kh mi ch qua tinh ch sau c kt hp vi qu trnh tun hon v a tr li trc tip cho thp tng hp. * Kh Nit d tha

C mt s cng ngh nng lng thp s dng khng kh d trong thit b reforming th cp gim cng sut cho thit b refoming s cp. Lng nit d tha s c kh vo khu cht ca qu trnh. Hnh 16 l s lu trnh cng ngh ca thit b tinh ch, cng ngh ny kt hp mt bc lm lnh trc bc nn kh mi ch. Dng thi ca thit b methan ha trc tin c sy kh ti im sng rt thp sau c lm lnh v dn n trong mt turbin ha lng mt phn kh. Sau khi i qua khu lm lnh thm, hi trong dng kh ha lng phn s c ra trong ct tinh ct kh ton b cc tp cht, nhng trong ch c khong 0,2% l argon cn li ch yu l methan. Cc thit k ca cng ngh ICI v Uhde u s dng mt thit b phn ly k thut lnh kh nit d theo p sut ca chu trnh tng hp. Phn ly dao ng p sut c s dng trong nhiu qu trnh khc nhau kh N2, CO2 d v mt phn methan v argon. 4.2.7. Tng hp v thu hi Amnic

Kh tng hp qua tinh ch c cha hydro v nit theo t l 3:1 v c hm lng kh tr d (CH4, Ar v i khi cn c c He). Kh mi tinh ch c ha nhp vi chu trnh tun hon v sau c nn ln p sut tng hp. i vi tt c cc chu trnh tng hp hin i u tun hon c cc loi kh cha phn ng do gii hn cn bng t mc chuyn ha ton phn cao. Cu hnh cng ngh khc nhau v mc s dng p sut v khc nhau v im thu hi amnic.

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u im v p sut tng hp ng lc cao nh ni, bao gm ch yu l v tr cn bng thun li v mc phn ng mnh. Ngoi ra, iu kin p sut v nhit cao, lng amnic s thu hi c nhiu hn bi vy gim c chi ph lm lnh. Nhng nh my thit k trc nm 1964 thng c vn hnh mc p sut 34.500 kPa (5000psi). Theo xut mc p sut thp s thun li v mt kinh t do gim c nng lng nn. Cc nh my amnic cng sut ln hin i thng c thit k vi mc p sut tng hp gim c rt nhiu m khng nh hng n qu trnh chuyn ha amnic thng qua vic s dng cc loi xc tc tng hp hot ha cao. Trc y trong cc nh my cao p dng cc loi my nn piston tha mn c nhu cu cho khu nn cao p, nhng ngc li trong nh my cng sut ln hin i li dng cc loi my nn li tm cho qu trnh tng hp. u th v mt thit k v hiu sut ca my nn li tm l tnh a dng v tin cy cn c i vi nh my c cng sut ln. Thng thng cc loi my nn li tm c dn ng bng cc tuabin hi. Ni chung chu trnh tng hp Ur bao gm 2 loi. Loi th nht l thu hi sn phm amnic sau bc nn kh tun hon kh mi ch. Trong trng hp ny kh tng hp c tinh ch bng qu trnh ra trong amnic ngng t c trong kh mi ch, tuy nhin nhc im ca cu hnh ny l ch n cn n nhiu nng lng nn do dng thi ca thp tng hp i qua qu trnh nn tun hon trc khi ngng t sn phm. Trong hu ht cc nh my sn xut amnic hin i tiu hao nng lng thp u dng cc loi sng phn t lm thit b sy kh ti cng on trung gian ca my nn kh tng hp tinh lc kh mi ch, cho php np trc tip kh tng hp cho thp. Amnic sau c thu hi trong cc cng on tip theo ca thp tng hp. Thit k chu trnh sng phn t gim c nhu cu lm lnh, bi v dng thi ca thp tng hp khng c kh mi ch b sung bo ha, iu ny cho php vic thu hi mt s sn phm c chuyn thnh nc lm lnh. Qu trnh ny cn h bt nng amnic trong kh np cho thp tng hp, kt qu lm tng ng lc cho phn ng tng hp amnic.

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Trong tt c mi phng n b tr ny, kh tng hp cp cho thp tng hp c thun rt ln, bi v qu trnh ra amnic ngng t c trong kh mi ch n b xa thun ca n. Kt qu l tui th ca xc tc c tng ln, thm ch n 20 nm. Trong cc nh my hin i, amnic c thu hi bng qu trnh ngng t theo p sut tng hp hin i, amnic thng l ngun lm lnh cn thit. Nhm duy tr c mc p sut phn mol cao ca cc cht phn ng, cc loi kh tr i cng vi kh mi ch s c ngi ta dng lung thi kh ht. Thp tng hp amnic l trung tm ca nh my tng hp amnic. Thit k s khai ca thp tng hp xut pht t qu trnh lm lnh ng v d nh thp tng hp ca TVA. Mc d cc thp tng hp ny th hin cc c tnh vn hnh nhit ng tng i kh, nhng tnh phc tp v mt c hc hn ch cng sut thit k ca thit b. Cc nh my sn xut amnic cng sut ln trong nhng thp nin 1990 tuyt i ton dng cc loi thp tng hp a tng. Cc thp tng hp ny thng khc nhau v kiu hng dng kh (hng trc, hng knh hay hng ngang), phng php lun khng ch nhit (lm lnh nhanh hay lm lnh gin tip) v cch thu hi nhit phn ng. Trong cc thit k ca thp tng hp kh tng hp lnh vo chy qua mt khong vng trn b ngoi gia v ca thp vi hp xc tc. Dng kh ny duy tr nhit thp cho v v hn ch kh nng dn do hydro xy ra trong iu kin p sut thng thng. Sau khi kh t khong vng ra, n s chy vo thit b trao i nhit bn trong, n lm gia nhit cho dng kh vo n mc nhit tng hp. Nhit ca tng vo c khng ch bng cch lm lnh cc dng thi ca tng vi kh tng hp lnh. Hnh 17a l mt v d c in v cu hnh kiu ny.

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Hu ht cc thp tng hp amnic hin i u c thit k dng hng knh hay dng ngang v nhit c khng ch trc tip bng thit b trao i nhit. Trong thp tng hp amnic nm ngang Kellog ( hnh 18) gas chy qua cc tng xc tc chiu dc thng gi l cc m cha trong cc hp d tho lp. Ton b qu trnh tng hp xy ra tng u c lc dn ng cn bng ln nht. V din tch lu thng hng ngang ln nn kh nng st p cc t ngay c khi ta dng xc tc c kch thc nh. C mt qu trnh tun hon i xung quanh thit b lm lnh trung gian khng ch nhit . Thp tng hp ny a vo vn hnh thnh cng trong nhiu nh my c cng sut ln. Cc loi thp tng hp dng hng knh theo thit k trn do Uhde v Topsoe thit k c tnh nng phn phi kh tt v c st p thp. Cc loi thp tng hp dng hng knh mang Seri 200 ca Topsoe nh nu trong hnh 19. Thp tng

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hp dng hng trc hng knh hn hp ca hng Amnia Casale cng c nhng u th tng t. Thp tng hp dng hng trc c v p lc bn ngoi lm lnh tng trung gian nh nu trong hnh 20. Cc nh my amnic cng sut ln dng cc thp tng hp lm lnh h tng trung gian t hiu sut chuyn ha amnic cao vi thi gian kinh t nht. 4.3. Hin i ha nh my Amnic

Cc vn lm cho cc nh my c vn hnh km hiu qu l do yu t tc ng v th trng. C rt nhiu phng n uc ngi ta la chn nng cp tng cng sut v tit kim nng lng. Cc c tnh thit k nh my c mc tiu hao nng lng thp l vic gim t l hi nc, cacbon, thp tng hp c hiu sut chuyn ha cao s dng cc thit b sy kh sng phn t, gia nhit khng kh t chy, thu hi hydro v c cc h thng dioxit cacbon nhit thp nng cao hiu qu kinh t ci to. Ci to v mt c hc r thp tng hp thnh thit k dng hng knh hay dng phn tch, cng vi vic s dng cc loi xc tc ht nh s lm tng hiu sut chuyn ha amnic cho mi chu trnh trong khi li gim c mc st p. Hnh 17 l mt phng n ci to tiu biu cho mt thp tng hp 4 tng thnh kiu thit k lm lnh trung gian ba tng, da trn nguyn l cng ngh c Amnia Casale. Phng n nng cp th hai l da vo cng ngh Ammonia tn tin ca Kellogg cho php cc nh my amnic s dng hon ton nng lc ca thp tng hp lm tng cng sut cho nh my. Xc tc KAAP c tnh hot ha cao c dng cng vi xc tc t tnh.

35

Cc tin b k thut trong cng ngh khng ch qu trnh lm tng hiu sut vn hnh cho cc nh my sn xut amnic. H thng khng ch phn phi (DCS) gip cho ngi thao tc s dng chnh xc v d dng cc thng tin thi gian thc. Thit b ti u ha amnic ca Kellogg gip ta kim tra gim st cc thng s ti hn nh t l hi nc-cacbon, hydro-nit v mc tn tht methan. H thng cho php ti u ha lin tc cc thng s ti hn v c th c ngi ta dng nng cao nng lc sn xut ammonia v tit kim tiu hao nng lng. Khng ch cng ngh tng cng lm tng thm tnh n nh vn hnh cho nh my v gip nhn vin thao tc kim tra khng ch d dng trong qu trnh nh my xy ra s c, khi khi ng my v ngng my. u t cho phn thit b o lng trong cc nh my hin i thng chim khong 20% chi ph lp t. 4.4. Thu hi kh thi

Cc loi mng khng kn la chn, k thut lnh v cc thit b hp ph p sut dao ng c p dng thu hi hydro v phun kh tr tng cng sut v tng hiu qu nng lng. Vic ti u ha chi ph thit b c bit c cp trong thit k hay nng cp l mt chc nng ca chu trnh, kh tr v nit d cn phi c cng thm thun v phn trm ca cc dng thu hi. Cc h thng thu hi kh thi cn c p dng thu hi argon cn thit. 4.5. Chu k nng lng

Cng ngh amnic c c th l mc yu cu cao v nhit cng ngh v nng lc nn. Tng mc tiu hao nng lng gm c nguyn liu cho cng ngh cng thm cc yu cu khc v nhin liu ph tr. Bi vy hiu sut nng lng ca qu trnh v mt lgic c ti u ha bng cch tng tc tng th vic thu hi nhit tha qu trnh v h thng ph tr bng chu k Rankine, dng hi nc lm mi cht lm vic. Hiu sut ca chu k Rankine t bn thn n c th c tng ln bi p sut hi nc ng lc v nhit qu nhit cao, p sut thit b ngng t b mt thp hn gip cho vic la chn thit b ng. Ni chung cc thng s ny c ti u ha da trn c s vt liu cu trc cng nh kch thc ca thit b. Cc iu kin h thng hi nc p sut cao tiu biu thng vt qu 10,350 kPa(1500psi) v nhit l 510oC. Kt hp hiu qu qu trnh bng h thng thit b ph tr bao hm c vic gim hai khu chnh m t trc ti gi thng tn ti c hu trong chu trnh l: vic truyn nhit qu trnh sang ni hi v vic trn ln dch ni hi bo ha vi kh mi tinh ch ngng t thit b lm lnh. Mc tiu ny c thc hin bng cch thu hi nhit cng ngh mc cao nht c th v chit xut hi nc thit b lm lnh mc thch hp sau khi dn n trong turbin tha mn hi nc cng ngh v lm gim cc yu cu gia nhit.

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Vic chn cc iu kin hi nc cao p l mt phng n ti u ha v mt tit kim nng lng v chi ph thit b. Thu hi nhit thnh h hi cao p thng thng c p dng t qu trnh trong thit b reforming th cp, trong cc dng thi ca thp tng hp v kh ng khi ca cng on vect thit b reformer. Vic thu hi ny di dng n nhit bo ha hay nhit nhy nc np ni hi cao p. Thu hi nhit mc thp b hn ch bi cc iu kin vn hnh ca thit b tch kh. Lu trnh h thng hi nc nh my amnic tiu biu nh trnh by trong hnh 21. Theo y hi nc c s dng tuyt i cho cc thit b dn ng cng ngh. H thng kh CO2 ch cn n lng nhit mc thp, v y l iu kin chnh ci tin gim nng lng u vo. Xut khu nhit mc thp c th c dng cho cc h tiu th ngoi vi nh lm nhit si, d hi hay cho cc thit b loi mui nu c. Mc tiu ca vic gim tiu hao nng lng mc thp nht l vic gim nhin liu t trong l tng mc sn xut hi. Hi nc ca cng on thu hi nhit tha phi t mc yu cu ca cng ngh. Do vn ny c lin quan ti vic chn cc thng s thit k cng ngh. Trong trng hp ny vic t chy ca cm ni hi hay ni hi ph s bng khng mc d cc thit b ny u c c trong dy chuyn vi chc nng nhim v dng khng ch v khi ng. Tng nng lc hi nc cn to iu kin thun li xut khu hi nc ra ngoi cho cc cng on khc trong dy chuyn tng th, v d cho khu Ur chng hn. V vic thit k c tm quan trng lm gim nhu cu tiu hao hi nc nn vic kt hp vi cc chu k in nng khc ng vai tr quan trng v mang tnh kh thi. V d kh x ca thit b dn ng turbin kh c th c dng lm ngun khng kh t chy cho thit b reformer s cp, lm tng hiu sut ca chu k Brayton quy c. Cc phng n lin hp la chn l phng n s dng hi hay ng sn xut in nng. Kt qu ca cc phng n nu trn l mt cch ci tin chu k nng lng tng th. 5. MT S VN LIN QUAN 5.1. Cc vn v mi trng

Sn xut amnic nu so vi cc qu trnh sn xut cc loi ha cht khc l mt qu trnh tng i sch v khng c vn g c bit v mi trng. Sn xut kh tng hp l khu chnh yu cu phi kim tra khng ch cht ch vic nhim mi

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trng, bn cht ca vic kim tra gim st mi trng ny cn ph thuc vo nguyn liu np cng nh cng ngh c s dng. Nguyn liu np u vo bng than th vn nhim mi trng s nng hn. c bit pht x than ca cc thit b vn chuyn, x l cn phi c kim tra v x l nghim ngt. Tro v x cng ca cng on kh ha phi c x l v thi ra ngoi an ton khng gy nhim mi trng. Mt s cng on kh ha cn c cc cht sn phm ph lng nh hc n, phenol,naptha-cc cht ny cn phi kh ht hay t chy. Mt s loi than nguyn liu u vo c hm lng lu hunh cao, lng lu hunh ny cn c tch ht khi kh nguyn liu nh hydro v sunfit cacbonyl v cn c tip tc x l cc cng on sau, thng gi l thit b kh lu hynh. Cc dng ngng t ca l kh ha than cn c cha cyanide hydro, kim loi, NH3 l nhng cht rt kh kh. Oxi ha phn cc cht hydro dch nng th vic x l vn v mi trng c phn n gin hn. Cht ch yu l ccbon hay b hng c hnh thnh do nhit cao ca bc oxy ha. B hng c ra sch khi kh nguyn liu th v mt l tun hon tr li cho l kh ha, hai l c ngi ta thu hi di dng nhin liu cng ng bnh. X l lu hunh v ngng t ging nh qu trnh kh ha than mc d v s lng gy nhim mi trng so vi kh ha than c t hn. Reforming kh thin nhin hay naptha l cc cng ngh sn xut kh tng hp sch nht. Hu ht cc loi kh thin nhin thng c hm lng lu hunh thp, v vic kh c thc hin trong mt h thng hp ph tng c nh n gin. Nu hm lng lu hunh cao th c ngi ta x l trong cc h thng hp th-dung mi quy c kh kh acid nh MEA chng hn. Cng ging nh vy cc hp cht lu hunh v c trong naptha c x l hydro bng xc tc coban-molypden v c stripping tch sunfit hydro. Lu hunh d tha c kh trong mt h thng tng c nh ging nh i vi kh thin nhin trc khi reforming.

Ngng t cng ngh ca qu trnh reforming thng thng c x l bng stripping hi nc. Thit b stripper vn hnh mc p sut thp va cho php hi nc stripping trn cao c th c s dng mt phn cho yu cu hi ca thit b reformer. Ngng t cng ngh c kh ht cc cht nhim bn bng cch stripping sau thi ra ngoi do vy trnh c hin tng gy nhim mi trng. H thng ny khng nhng lm gim c hin tng pht x gy nhim m cn c kh nng lm tng hiu sut ton phn ca cng ngh bng vic thu hi ngng t di dng nc mi ch dng lm nc np cho ni hi, bi v cng ngh c coi l mt h tiu th thc s. S dng ng xon thit b bo ha kh trong cng on vect ca thit b reformer s cp cho php bc hi c 100% ngng t cng ngh. Hi nc c dng lm hi cng ngh trong thit b reformer. Ton b cc thit b t, cho d l l t cng ngh hay ni hi ph tr th u phi tun th quy ch nht nh, thng thng quy ch l gii hn v lu hunh v oxit nit. Cc loi kh ng khi ny c x l bng vic kt hp cc k thut khng ch iu chnh quy c bao gm cc l t c ch s NOx thp, kh xc tc la chn v ra kh ng khi. Dng thi i ra t cc thit b ph tr khc nh thi ca cc thng hi, ca h thng nc lm lnh, thit b tinh ch kh pht sinh ra thng thng s c ngi ta x l bng cch trung ha v gi li trong cc b cha.

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Cc quy ch ca Lin bang c ch o bi cc mc gii hn do EPA quy nh v amnic trong cc dng thi dch trn c s c trng ti thc a. Mc c s ti a hng ngy thng quy nh trong phm vi t 0.05-0.1875 kg NH3 ( dng nit) cho mt tn sn phm; gi tr cho php tng ng trong 30 ngy t 0.025-0.0625 kg NH3 ( nit) cho mt tn sn phm. Ni chung pH ca cc dng thi phi gi mc t 8 n 9. 5.2. Bo qun, vn chuyn v x l 5.2.1. Bo qun

Amnic khan thng thng c bo qun trong cc tc cha lm lnh ti nh my mc nhit -33.30C, p sut mi trng. Trong trng hp cn c th bo qun mt lng ln phc v cho th trng phn bn. Cc loi tc hnh tr dung tch ln ( 27.000 n 50.000 tn) c cu trc vch n hay vch kp c ngi ta lp t phc v cho cc khu vc th trng tiu th s cp. Cc loi tc cha c tn gi l tc cha kp tng th c thit k c c tnh cha th cp an ton ln. Cn phi c h thng bc hi cho amnic m bo duy tr nhit thp cn thit. Kh phng khng s c ha lng ti tun hon hay hp th trong nc phc v cho vic sn xut nc amnic. Mt lng tng i nh amnic khan s c gi li trong bnh cu mc p sut trn 275 kPa p sut ng h o (40psig) v nhit thng. Trong mt tc cha khng c lm lnh khng c cha qu 189 m3 ( Tng ng vi 50.000 galng M). Cc tc khng c cha qu 56% cng sut trng lng nc ca thng 15oC. Xu hng tin ti vic thit k cc loi mng cho cc tc cha trng lng nc tin hnh th thy tnh ton b cho tc cha. Tc cha phi c ch to bng thp, p sut thit k nh nht l 1724 kPa ( 250 psig). Cc loi tc cha p lc c trang b cc van gim p l xo, cc loi tec cha thng c cc loi van p sut chn khng kt hp. Vic nh v p sut cho van gim p khng c vt qu mc p sut thit k ca tc.Cc loi thng cha v kp c mt h thng gim p ph tr: kh tr v nit c dng duy tr mc dao ng p sut dng trong mt khong vng ngn nga khng cho khng kh v m thm nhp vo v n mn b mt kim loi v lm hng bo n. Bi vy cc loi van an ton c dng bo v tng p ca khong vng ny. X nhanh ca cc van an ton c dn qua ng ti ng khi c chiu cao ti thiu 1,83 m so vi sn lm vic xung quanh. Ngoi ra cn c cc thit b gim thanh cho cc van an ton ny. Cc loi tc cha lm lnh c bo n cn thn chng tn tht nhit v ngn nga khng cho khng kh v m thm nhp vo lp bo n v b mt kim loi. i vi cc tc cha v kp, khong khng vng xung quanh ny thng c n y bng perlite, mt ngoi tc c sn chng r bo v. 5.2.2. Vn chuyn

Lu thng phn phi amnic khan ti M c thc hin thng qua mng li ng ng, ng thy, ng st v ng b, trong c ba cng ty phc v cho 11 bang vi h thng ng thy chuyn ch di 4800 km, trong hin nay 4800 km ny vn ang c khai thc thng qua cc phng tin chuyn ch bng x lan, vn chuyn ng st c lin thng vi Canada, Mhic, cn vn chuyn bng t ch yu phc v th trng ni a v giao lu gia cc bang vi nhau.

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H thng ng ng Trung M (MAPCO) dng lu thng amnic c tng chiu di l 1763 km, ng phi 101mm,152mm,203mm c nng lc bm 3885 tn gi v c trang b cc thit b cha ti cc im u cui. Cng sut giao nhn cao nht ca h thng l 4216 tn/ ngy. H thng ng ng trung tm vnh vi chiu di 3220 km, phi ng 152mm, 203mm v 254mm c cng sut bm 2545 tn gi v c cc trang thit b cha ti cc im u cui. Mng li ng ng Vnh Tampa phc v cho cc nh my trn tuyn ng di 133 km. Cng sut ca cc xe ti, toa xe, thng thng t 100-150 m3. X lan thng c mc cha t 400 n 200 tn. Ton b ng ng dn amnic phi l ng ng chun hay thp dy c cc im khp ni c hn li hoc cc khp ni bt vt. Cc loi ng m hay cc khp ni bng ng khng bao gi c ngi ta s dng. Amnic dng vn chuyn bng ng ng phi tha mn cc tiu chun sau: NH3 99,5% th tch min, kh tr ha tan 0,16% max, du 5ppm max v nc di dng ngng t hi 0,2% min hay nc chng ct 0,5% max. Cc h thng ng ng dng vn chuyn amnic khan l cc ng ng dng vn chuyn nitrat amon v nitrat amon ur (UAN) v kh ha lng LNG hin c chu u, Mhyc v M. Cc nc sn xut amnic dng trng tm cho vic xut khu thng s dng cc loi tu i bin c ln c trng ti n 50.000 tn dng lu thng phn phi amnic vi s lng ln. Ngoi ra ngi ta cn vn chuyn km theo trong cc tc kh ha lng. 5.2.3. X l

Vt liu m thng thng ph hp trong cc trng hp x l amnic, nh cc tm aming mi mn cao su chng hn. S dng cc loi vt liu c gc l aming l theo quy nh ca Lin bang. Nhm c ngi ta p dng thnh cng l vt liu m cho cc khp ni mt phng hay khp ni mt bch c rnh, nhng ni chung l khng nn dng. Cc loi vng m cao su cng khng nn s dng. Trong cc trng hp c bit ch nn s dng ch.

Cc loi thc vch nam chm hay thc quay l thch hp cho cc loi ng thy tinh ch mc. Khng c bao gi cho amnic gn st vi ng ch mc, s tng p c th lm v ng thy, cc ng thy ch mc ny phi c bo v cn thn, nu c hin tng v xy ra th lu tc d ca van s lm ngng dng chy amnic, trong trng hp ny cc van ng m t ng phi trng thi m vic quan st c d dng.

Cc loi van gim p phi l loi van c cu trc bng thp c thit k vn hnh trong cc iu kin ti a v ti thiu. Thc vch o p sut phi c cu trc ton b bng gang. Cc loi van gim phi l loi van kiu ti trng l xo. Cc loi a bo him ch c th c s dng lm thit b ph tr. Cc thit b o chnh p dng p k thy ngn tuyt i khng nn dng trong trng hp vn hnh x l amnic. Cc loi vi phi c ch to ring cho trng hp vn chuyn amnic vi p sut lm vic l 2500 kPa (348 psig) v phi c ng nhn dng chuyn dng. Trong cc trng hp vi d b mi mn th nn dng cc loi vi an bn v cc loi vi tng cng . u vi phi c gia c bng ng bt hay khp ni st kim loi c cht lng chp nhn.

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Amnic l loi ha cht n mn cc loi hp kim ng km v bi vy cc vt liu ny khng c dng trong mi trng amnic. St hay gang l kim loi thng thng ch c dng di dng ch to tc cha ng dn v cc chi tit bt cht.

i vi amnic nn c cha hm lng nc t nht khong 0.2% chng n mn ng sut cho thp. Cc loi cp nhit thy ngn nn trnh khng s dng. R r amnic cn phi c pht hin sm bng cch pht hin mi, tr khi c hm lng rt nh pht ra ngoi mi trng. Xc nh chnh xc r r bng cch dng giy phnolphthalalein hay chai axit hydrochloric m, nu pht hin thy r r nhiu, phi dng ct nc ln phun bng vi hp th amnic bc hi. 5.3. Cc vn v kinh t 5.3.1. Cng sut, mc sn xut v tiu th

Sn xut amnic c tm quan trng trn th gii: c khong 85% lng amnic sn xut ra c dng sn xut m. L ngun s cp dng trong qu trnh sn xut m nn n l vn ch cht gii quyt lng thc cho nhn loi. Phn 15% cn li dng cho cc ngnh cng nghip sn xut cc sn phm khc nh si, thc n cho gia sc, thuc n Cho n tn nhng nm thp nin 1960 sn xut amnic mi t con s rt nh ch yu l phc v cho th trng ni a v dng lm nguyn liu trung gian sn xut cc sn phm cng nghip. Do cng ngh khng ngng pht trin , th trng gi kh thin nhin r nn trong nhng nm thp nin 60 chi ph sn xut cng nh mc tiu hao gim i rt nhanh, bt u khi xung t cuc cch mng xanh. Bng 10 l cc s liu mc sn xut amnic v mc tiu th m trn th gii. Mc s dng m hng nm t mc tng trng nhanh, nm 1960-1970: 11,5%; nm 1970-1980 l 6,7% v trong nhng nm 1980 gim xung cn 3,8%. D kin trong nhng nm thp nin 1990 s tng t nht khong 3%.

Bng 10-Cng sut sn xut amnic v mc tiu th phn m ca th gii.

Nm Cng sut sx NH3 danh ngha Mc tiu th phn m 1960 1970 1980 1990

16,23 50,64

101,58 119,57

9,54 28,17 57,19 80,30

Bng 11 di y l cc s liu v lu thng phn phi cc loi sn phm ny theo

a bn a l. Trong nhng nm thuc thp nin 1970, vng Bc M bt u t M v Ty u l nhng nc trng tm sn xut amnic. Tuy nhin sang n thp k 1980 Lin X l nc ng u trong lnh vc ny thay chu M v sang thp k 1990 l nc sn xut amnic ng u th gii. Trung Quc l nc ng th hai th gii ngoi ra cn mt s nc khc mc sn xut cng tng nhanh nh n v Mxic, Indonexia v Trung ng. Vic tng cng sut sn xut cho d nc ang pht trin hay bt k ni no khc th thnh tu ny u bt ngun t vic p dng cng ngh c a vo M t nhng nm thp nin 1990.

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Bng 11: Bng phn phi mc sn xut Amnic trn th gii.

Khu vc Mc phn trm 1975 1990

Chu Phi Chu Chu M Latinh Bc M Ty u ng u Lin X c

3,0 2,1 35,4 25,9 5,3 3,9 13,8 21,4 9,7 12,8 11,3 18,8 21,5 15,1

T nhng nm thp k 1960 vic cung v cu amnic ton cu c chiu hng dao ng, ch yu l do mc cn bng cung v cu cho hai nm 1986 v 1988 v mc d kin cho nm 1991. Nu tnh mc cng sut sn xut bnh thng hay mc cng sut danh ngha ca cc nh my sn xut amnic ca cc khu vc khc nhau th yu t s dng mc cng sut ca cc nh my ny thng thp hn mc thit k danh ngha. V d yu t s dng mc cng sut thng thng ph thuc vo cc kh nng duy tu bo tr, nh hng ca yu t h tng c s v mc s dng cha ht cng sut trong ba nm u ca nh my mi. Cc yu t ny Bc M v Ty u chim 95% cn Chu v Bc chim 80%. Lng amnic dng trong cng nghip chim khong 11% tng mc cng sut sn xut. D kin mc tn tht trong qu trnh chuyn ha c th ln 8% khi dng amnic c cc sn phm khc dng trong nng nghip chng hn. Sn xut phn m t amnic thng c iu chnh hm lng nit ly t cc ngun khc, v d dng thm Nitrat Chile s lm tng hm lng m cho phn bn. Mc tiu th phn bn N thc t trong nm 1986 v 1988 c d v d kin n nm 1991 s t ti mc cn bng.

Bng 12- Mc cung v cu amnic trn th gii

Mc sn xut v s dng 1985-1986 1987-1988 1990-1991 Cng sut danh ngha Kh nng cung cp ( mc sx) Mc s dng cng nghip Tn tht Dng lm phn bn Cung cp m phi NH3 Tng mc cp nit phn bn Tng mc tiu th phn bn D ( - thm ht )

110,85 90,60 10,28 7,60 72,72 0,56 73,28 64,98 8,30

114,15 93,80 10,55 7,92 75,33 0,56 75,89 73,46 2,43

119,18 98,84 10,93 8,40 79,51 0,56 80,07 80,11 -0,66

Cn lu mc cung cp amnic tng l do vic ci tin hiu sut vn hnh ca cc nh my v khc phc c tnh trng tn tht qu mc trong cc cng on chuyn ha v lu thng pha sau. 5.3.2. Th trng

Ty theo tng vng m mc s dng amnic trong cng nghip c mc bin thin khc nhau. V d M v Ty u mc s dng amnic trong cng nghip

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chim khong 20%, cn Lin X chim khong 10%, chu 1-10%, Bc M v Chu M Latinh chim 5%. Mc tiu th phn bn amnic ni a trong hu ht cc quc gia u c chuyn i trc tip sang cc loi phn bn hn hp nh Ur, nitrat amn, photphat diamond hay cc loi phn bn phc hp khc. Tuy vy M c ti 29% nit amnic c tiu th di dng trc tip. Vic dung dch nit nh ur v nitrat amon (UAN) tr nn thng dng ti M v Lin X. Ngay c trong giai on nhng nm 1980 vic cung cp amnic trn th gii t n con s k lc, nhng vn cn nhng vng thiu ht, c bit l Trung Quc, n , Nam M, vng bn Sahara Nam Phi. Vic thiu ht ca cc khu vc ny c nh hng n cn cn bun bn ca th gii. Nm 1984 mc kinh doanh amnic trn th gii t 7 triu tn, Nit t 11,18 triu tn. Amnic c vn chuyn bng cc tu cha lnh, cn Ur c chuyn ch di dng nguyn liu ng bao hay hng ri. Nc xut khu amnic ln nht th gii l Lin X (34%), nc nhp khu ln nht l M (34%). Hng xut khu amnic ln nht th gii l Lin X v Rumani (43%), Trung Quc, M, n v cc quc gia nhp khu Ur ln nht (62%). 5.3.3. Chi ph sn xut

Bng 13- D kin chi ph sn xut amnic

Cc yu t chi ph n v/tn USD/ n gi

Chi ph USD/tn

Chi ph kh bin Kh thin nhin(GJ) Nc m.ch np n. hi, m3 Nc lnh tun hon m3 ( nhit -10oC) Chi ph xc tc Chi ph c nh Cng, ca cng nhn 10USD/h Gim st, 100% cng Li sut vn lu ng,% Cc chi ph trc tip,% Tng chi ph sn xut Thu hi u t trc khi lm thu (ROI)% Gi thnh NH3 ( FOB ti n/m) Chi ph tin mt cho sn xut

28,45 1,1 210 6 10 16 20

1,90 0,25 0,01 10

54,06 0,28 2,10 1,7 1,44 1,44 1,30 44,06 106,38 55,07 161,45 78,84

Bng 13 l cc s liu v cc chi ph sn xut amnic cho nh my sn xut NH3

c cng sut 1000 tn/ngy c xy dng ti b bin Vnh M nm 1990. Chi ph u t c nh k c cc thit b ngoi vi ph tr bao gm nc nguyn, x l nc np ni hi, kho cha amnic v thp lm lnh. Vn lu ng gm c mc d tr sn phm cho 30 ngy mc 150 USD/tn. Kh thin nhin l nguyn liu th cho cng ngh amnic tiu hao t nng lng , c thng mi ha u nhng nm thp nin 1980. Mc thu hi u t 20% trc khi lm thu d kin l hp l cho cc nh my

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cc nc phng Ty v mt kinh t, trong thu hn hp nh vo ngun thu nhp l 50%.

Bng 13-D kin chi ph sn xut amnic. Qua phn tch ta thy kh thin nhin nguyn liu np v vn u t ln ti trn 93% tng chi ph sn xut trc khi thu hi vn u t. Bi vy mc tiu hao nng lng v vn u t l cc yu t chnh quyt nh tnh kinh t trong qu trnh sn xut amnic. Gi kh thin nhin giao l 1,9 USD/Gl ( 2,00/triu BTU), trn c s nhit tr thp (LHV) ti M theo bo co thng 2/1990. V tr xy dng ca nh my sn xut amnic c nh hng n chi ph u t c nh v mc chi ph ny c th cao hn nhng nc c c s h tng yu km. Trong nhng nc di do nng lng nh Cn ng, Lin X v Bc M, gi kh thin nhin thng trong mc 0,47 USD/GJ ( 0,5 USD/triu BTU); tuy nhin chi ph xy dng cc khu vc ny li cao hn so vi vng vnh M.

Trong khi chi ph sn xut li c nh hng rt ln bi gi nng lng, chi ph tin t, vn u t, mc gi thnh amnic bn ra c quyt nh bi cung v cu. Do tnh kinh t ca cc nh my sn xut amnic c quyt nh bi chi ph sn xut v gi NH3 bn ra. Bng 13 l kt qu khi ton chi ph tin mt cho mt tn NH3 l 78,84 USD. Gi FOB amnic ti b bin Vnh M vo thng 2/1990 l 107$/tn. Bi vy cc hng sn xut amnic ti Lousiana, Florida hay Texas c th cn mc tin chnh l 28$ mua kh vo vi gi 1,9 $(2/triu Btu) v mc tiu hao nng lng l 28,45Gj/ tn ( 24,5 triu Btu/tn). Song cc nh my vng b bin vnh M u c xy dng vo cui nhng nm 1960 v u nhng nm 1970 nn mc tiu th nm trong phm vi khong 34,85 Gj/tn ( 30 triu Btu/tn), c ngha l cao hn chi ph sn xut 12$/tn hoc mc tin li ch c 16$/tn.

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5.3.4. Gi c Theo d kin mc gi bn amnic trong nhng nm 1990 s tng, nhng thc t

li dn dn gim xung. c thi k trc y gi amnic ti vng vnh M gim xung mc 66-77 $/tn di mc chi ph sn xut trong hu ht cc nh my sn xut c cng sut ln. Cc nh my nh sn xut km hiu qu, tiu hao nng lng ln buc phi ng ca do vy mnic phi nhp t cc nc nh Mhyc Trinidad, Vnduyla v Lin X. Cc yu t khc c th nh hng n chi ph sn xut hay mc tiu th phn bn l mc thiu ht nh k.V pha tiu th cc iu kin nh kh hu, gi phn bn v n nh v mt chnh tr cng gy nhiu nh hng n nhu cu tiu th. V mt cung ng cc yu t gy nh hng cho vic cung cp amnic l kh nng cung ng nguyn liu th, tin cy ca c s h tng, hiu qu cng sut sn xut ca nh my, tui th ca nh my v vic xy dng hay hin i ha nh my hin c. Gi amnic v ur t nm 1968 n 1988 nh nu trong hnh 22. Gi FOB trung bnh amnic ti b bin Vnh M u nm 1991 l 105$/tn. Trong thi k 1968-1973 do cc nh my c mc sn xut ln nn trn th trng c hin tng p gi. Trong nhng nm sau nhu cu tiu dng phn m cao hn mc cung cp v gi bn li bt u tng ln. Gi kch kim trong nm 1974 l kt qu ca cuc cm vn u nm 1973 v sang nm 1975-1976 gi tr li mc 100-125$/tn, gi ny b xa chi ph sn xut. Tuy nhin mc cung cp li c chiu hng dao ng v gi amnic v ur sang nm 1977 li bt u tng, gi tng ny s d c l do vic cm vn u nm 1978. Cui nm 1977 M, Mehyc, Trung Quc, Indonexia ngi ta tin hnh ci to v m rng cng xut cho cc nh my hin c v sang n nm 1981 mc sn xut li nhiu hn mc tiu th. Nhng nm thp nin 1980 gi NH3 v Ur gim i l kt qu cng sut sn xut tng v sn xut c ngi ta chuyn t dng nguyn liu chi ph cao sang dng nguyn liu gi r. 5.3.5. Chi ph vn chuyn v lu thng phn phi

Mc d c rt nhiu amnic c dng cho cc qu trnh khc, nhng mc s dng amnic n ln nht M, l ch yu dng phn bn trc tip khng qua ch bin thm. Mc tiu th ny dng ch yu cho cc trang tri, amnic c sn xut ti cc quc gia b bin vng Vnh c vn chyn n cc u cu tiu th sau bn l ra ngoi cho cc h nng dn. Amnic vn chuyn ng di bng x lan, ng ng, ng st, vn chuyn ng ngn ch yu dng t. Cc yu t gy nh hng n vic s dng cc trang thit b vn chuyn amnic khan l khong cch, v tr ni t nh my c tnh n khu vc tiu th, kh nng sn c ca thit b chuyn ch v chi ph chuyn ch ca cc thit b .Chi ph tiu biu vic vn chuyn amnic ng di bng ng ng l 0,0153 USD/tn/km, bng x lan l 0,0161 USD/tn/km v ng st l 0,0215 USD/tn/km trong khong cch 1600 km. Chi ph vn ti ng b bng t cao hn nhiu. Chi ph tiu chun thng thng l 0,0365 USD(t/km) vi khong cch l 160km.

V c th ca ngnh cng nghip, mc tiu th amnic mang tnh chu k. Trong thi k bn phn vo ma xun, c khong 75% lng sn phm sn xut ra c tiu th.

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gim chi ph bo qun theo mc tiu th chu k nh nu trn, nn ti cc th trng tiu th ln ngi ta tin hnh xy dng cc cu cha amnic khan lm lnh. Theo bo co, chi ph cui thng tng ln vo khong 11 USD/tn. M vic lu thng bun bn cc loi phn bn cng v lng ch yu do cc i l bn l m nhn. Do vic kinh doanh mang tnh thi v nn cc chi ph marketing cng cao hn. gim cc chi ph qun l ca i l cc hng bn l cn kt hp bn cc sn phm khc cho nng dn nh ging, thuc tr su v thit b my mc nng nghip. Qua nghin cu 47 cng ty bn l phn bn ti Midwestern-M (s liu ti chnh nm 1994), u c mc chi ph amnic trung bnh trong gii hn t 47,4 n 91,5 USD/tn. Vic d tr v thu xp cung ng l nhng yu t chnh nh hng li nhun. Cc chi ph v th trng kinh doanh amnic trn th gii thng mc 35$/tn trong phm vi chuyn ch gia M vi cc nc Ty u. 5.4. Tiu chun sn phm v phn tch

Amnic lng v khan c sn xut ra vi nhiu kiu loi khc nhau ty thuc vo nhu cu s dng. Bng 14 v 15 sau y l c tnh k thut ca cc loi sn phm ny.

Bng 14: Tiu chun k thut amnic khan Hm lng nguyn liu

Cp phn bn hay thng phm

Cp ng lnh Cp luyn kim

NH3 wt% min H2O ppm wt-max Du nt Kh khng ng.t-Max mL/g

99,5 5000

5

99,98 150

3 0,2

99,99 33 2

10

Bng 15: Tiu chun k thut amnic lng.

Cp Amnic % TL Dng cho ngnh dc M Nc amnic Dch th amnic Amnic lng thng thng Tinh khit ha cht K thut,Beo 26 16 18 20

28-30 9,5-10,5

1,7 28

29,4 10,3 14

17,75 Beo: Baum, t trng ring= 145/(14,5 Beo). Amnic khan thng thng c phn tch v hm lng du, m v cc cht cn d tha. Trc tin amnic c bc hi khi mu v c th nghim cc cht d. Trong hu ht cc trng hp, lng du v cc cht lng trong cc mu cn tng i kh nhiu; ton b cc cht d c coi l nc. xc nh hm m chnh xc amnic c th c ngi ta tch khi nit v hydro v thu c im sng ca kh

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phn ly. Th tc ny din ra tng i tri chy khi hm lng nc trong phm vi vi ppm. Trong trng hp hm lng nc c khong vi trm phn trm th axit axetic v methanol c th c ngi ta thm vo cho cht d tha v chun Karl Fischer c p dng cho im cc d theo phng php o in. Du c th c xc nh bng cch chit xut cht cn dng cacbon tetrachloride v sau cho bc hi CCl4. Cc cht cn nh st chng hn c xc nh bng cch cho ha tan trong axit clohyric, tip theo l n phng php tnh so mu. Cc loi kh khng ngng t ha tan c xc nh bng cch phn tch khng kh pha trn amnic lng. Dng kh c phn tch NH3 bng cch to bt v lng kh o c thng qua dung dch axit bc hi hp th NH3. Sau dung dch c nh phn theo axit sunfuaric. Php phn tch ny ch c p dng nu cc cu t khc trong dng kh khng phn ng vi axit boric. Amnic v cc ion amni trong cc dng nc cng nghip bao gm cc dng nc thi c th c xc nh bng mt trong hai phng php. Trong phng php th nht mu c tng dung dch m n pH l 7,4 v c chng thnh dch axit boric trong nit amnic c xc nh bng phng php so mu vi cht kh l Nesler hoc c nh phn bng cch dng axit sunfuric tiu chun. Phng php khc tuy chnh xc c thp hn nhng li nhanh hn, n bao gm phng php Nestelerization ha mu xc nh so mu. Cc php ch th so mu khc c nhy tt hn nh indophenol c dng thay th cho cht th Nessler. Cc in cc st la chn cng c dng trong vic phn tch amnic vi lng. 5.5. Sc khe v an ton ngh nghip

Amnic l cht gy chy da cc b mnh, lm m mt v ph hy cc mng h thng phi. Nng hi n 10.000 ppm c th gy kch thch da, khi nng n 30.000 ppm s lm chy da. Tc dng gy nh hng v mt l hc khi ht phi amnic nh m t trong bng 16 di y. Nng amnic khi r r ra ngoi rt d c pht hin, ch cn mc t 1-5ppm l c th pht hin thy ngay cho nn nng r r mc cao hn khi tip xc trong thi gian di l khng th c.

Bng 16-Tc hi v mt l hc ca Amnic Nng (ppm) Tc hi

20-50 40-100 400-700

1.700

5.000-10.000

Mi cm nhn c Mt v h thng h hp b kch thch Mt v h thng b kch thch mnh, kh nng b hy hoi Ho sc sa cung phi b co tht, nu tip xc khong na gi s gy t vong Gy cht ngi

Amnic khng c xp vo din gy chy n nguy him. Tuy nhin mc d rt kh gy chy nhng n khng c kh nng gy n do r r t h thng lm lnh trong kho gy nn. Amnic khng sn sinh ra cc sn phm phn hy nguy him hay bt n nh. Song nu tip xc vi canxi, vng, thy ngn, bc hay cc cht clorat c th to ra cc hp cht n.

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Cc tiu chun an ton v ngh nghip OSHA hin nay quy nh r ngng nguy him (TLV) khi tip xc trong thi gian 8 ting vi amnic l 50ppm (35mg/m3). Tuy vy t chc ACGIH khuyn co ngng TLV nn mc 25p