KHOA HOC - CONG NGHE MO HlNH LY THUYET SIT DUNG VO TRAU TRONG LO DOT TANG SOI CHO SAN XUAT NHIET VA DIEN VIET NAM Nguyen Dinh Titng' TOM TAT Bdi bdo ndy dua mdl ldng quan ngdn ggn cua md hinh vd ky thudi cua nhd mdy nhiel dien dugc dung vd trdu Id dot ldng sdi (FBC) de Igo nhiel vd di?n Nd md id ca sd ly thuyet md hinh cho nhirng ihdnh phdn nhd mdy nhiet dien Nhu mgt vi du, md hinh ly thuyet nhd mdy nhiel dien ddt sinh khdi cdng sudt Megawal dien da dugc xdy dung vd khdo sdt lu ddng vdi str irg giup cua md hinh EXCEL dugc hd trg bdi Visual Basic Vdi gid thiet ban ddu quy dinh nhiel dot FBC Tfn = 800 - 850° C (vdi vd trdu) Kel qud tinh lodn cho thdy rdng: lugng nguyen li?u cdn cung cdp m Vut/ ~ 0,75 kg/s, tuong ung vdi ndng lugng sa cdp cita nguyen lieu ~ 9688 kW, ndng dg oxy khdi thdi Oz.dr ~ H Vol %, nhiet cita khdi Ihdi hdi luu dirac giir khdng thay doi Tuc ^ 170° C = const, ty le cua khdi thdi hdi liru RC ^ 0,9, hieu sudt nhiel cue dgi cua nhd mdy nhiet dien Tjfh,si ~ 33,6%, hieu sudt dien cue dgi rjei ~ 18,5% THEORY MODELING UTILIZED RICE HUSKS IN THE FLUIDIZED BED COMBUSTOR FOR PRODUCTION OF HEAT AND ELECTRICITY IN VIETNAM Nguyen Dinh Tung' SUMMARY This paper gives a brief review ofthe modeling and techniques of steam power plant utilized rice husks in the fluidized bed combuslor (FBC) for production of heal and electricity, ll describes basis theory model for power plant components As an example, a theory model for a MWd biomass fired power plant has been built and automatically investigated by the help ofthe EXCEL model supported by Visual Basic With (he assumed initial condition temperature in FBC TFB = 800 - 850° C (for rice husks) The calculation results showed that; ihe fuel mass need to supply mVue/ ~ 0.75 kg/s, corresponding to primary energy of fuel 9688 kW, the oxygen concentration in exhaust gas 02,dr ~ H Vol %, the temperature of recirculation exhaust was kept at TRZ = 170° C = const, Ihe ratio ofthe recirculation exhaust RC ~ 0.9 the maximal of thermal efficiency ofthe steam power plant 7},h.si ~ 33.6%, the maximal of electrical efficiency r]ei ~ 18.5% I DAT VAN BE Viet Nam la mot s6 nuac dang phat TW vao nam 2010, va 160-200 TW nam 2020 tri8n vai luong dien nang tieu thu a mirc thap, (EVN, 2003 Ng-LTmong and Tran O.Cu 2004) uac tinh khoang 210 kg dau quy d6i/ngirai/nam Da dap ijng dugc nhu chu nang luang Trong thai ky tiJ 1995-2000, tieu thu nang lugng cang lan nay, thi c5n thiSt phai dSu tu xay dung dien tang rSt nhanh, trung binh khoang 15%/nam, nhieu nha may phat dien sii dung tu nhieu nguon nhung nam sau len tai gin 17% Ty le tang cao nguyen lieu khac Cac nha may dien su nhat la a nganh cong nghiep khoang 19,5%, khu dung cac nguon nguyen lieu truygn th6ng (than, vuc dich vu 18,3%, ITnh vuc gia dinh khoang dSu, khi, thuy dien ) cang can kiet 14,2%/nam (Ei'N 2003: Ng LTruong and Tran Q Cu Chinh Vl vay, viec SU dung cac ngufin nang 2004) Theo (Ng Le Truong and Tran Q Cu 2004) nam lugng sinh kh6i tdi tao de tao nang lugng dien 2002 t6ng cong sudt dien dugc xay dung vao la viec lam rSt cSn thiet vao thai diem hien cf khoang 8.860 MW, % la tir thuy dien, Viet Nam No hoan toan co the thay th£ dugc 17% tCr nhiet dien, 27% tir Gas turbine va tCr dong phan nao cho ngu6n nguyen lieu truygn th6ng ya ca Diesel, va tCr cac ngudn doc lap khac la 5% cac nguon nhien lieu khac Ngoai gop phan Theo cac nha quan ly vg chuyen mon thi yeu chi dang ke vao muc tieu chong thay doi hau, cho su phat trien nang lugng dien khoang 89-93 biSn chat thai (phu pham) cua nganh Nong, Lam ;—\—; nghiep nang lugng nhiet dien ' Vi?n nghien curu thiSt k£ chS tao may nong nghiep-RIAM TAP CHi CONG NGHIEP NONG THON - SO - 2013 27 J? KHOA HOC - CONG N G H | Bai bao de cap den van de xay dung, tinh toan mo hinh ly thuyet nha may d6ng phat nhiet dien (CHP) su dung ngu6n nguyen lieu tu vo trau, nh5m tim cac thong so ky thuat, hieu suat nhiet, dac bi?t la hieu sudt di^n co the su dung dugc n VAT L I | U VA PHU'ONG PHAP 2.1 Vdt lieu Bdng I Thdnh phdn Thanh phan nguyen lieu Vo trau (C) (kg/kg) 0,3979 (H) (kg/kg) 0,0523 (0) (kg/kg) 0,3863 Ptidntlch giri flilng B$im Vo trau la nguyen lieu dugc sCr dung de tinh toan cho mo hinh Cac dac tinh ly, hoa, dac biet la cac phan hoa hgc co chung: ham lugng cua cac bon (C), oxy (O), hydro (H), nita (N), luu huynh (S), tro cua nguyen lieu (a), nuac CO nguySn li?u (w) va nhiet trj th5p cua nguyen lieu (Hu) [6 7] dugc the hien a bang va hinh hda hgc cua vd Irdu (N) (kg/kg) 0,0013 (S) (kg/kg) (a) (kg/kg) 0,1392 (w) (kg/kg) 0,0230 (Hu) (kJ/kg) 15.196 90% 80% cac thdnh phSn bay no'i 70% (Cdc chdt b6c) 40% 60% so% Lu'vng carbon cd fljnh cBTbon c i flinh Hinh Cdc thdnh phdn hda hgc cua vdt lieu thi nghiem 2.2 Phuffng plidp D6t tSng soi tTnh (khong h6i luu) dugc lya chpn cho mo hinh tinh toan Vi phuang phap d6t co mot so uu diem, duai day la uu nhugc diem cua he thSng dot t^ng s6i,su dung nguyen lieu ran (bang 2) Voi phuang phap d6t ting soi, nhiet dp cua vat lieu trg dot "6 vung soi" (nhiet dp dot chay) ben 16 nam khoang 800 - 900°C Day la mpt cac thong so chfnh ban dau phai lira chgn Lya chgn nhiet dp phai can cu vao nhiet chay loang "tro cCia nguyen lieu" day nhiet dp dugc lya chpn T,i, - 800°C [7] Bdng lfu vd nhirgc diem ciia he thdng dot tdng sdi Uu diem 1- Khdng CO phSn di chuyen bu6ng ddt nong 2- Co hi$u qua/kha nSng giam thilu phSn NO^ nVxs viec kiem soat lugng kh6ng cung cap (vao) 3- Tinh linh hoat cao doi vai cac hat co kieh thuac ldn, dp am cao cua cac loai nguyen lieu ran, 4- Giam lugng oxy thira, tang hi^u su§.t 5- Cac chat xuc tac them vao rdt dan gian 6- Hieu qua "hgp nhat/hoa nhap" luu huynh vao tro, neu CO (ton tai) dii lugng Ca 28 Nhugc diem 1- Gia dau tucao 2- Ty le (lugng) bui khoi cao 3- D6 bj* hu hong vl sir chay loang/nong chay cua tro 4- De bj an mon cua cac ong trao doi nhiet ben vat lieu trg dot/ "lap cat soi" 5- Hao hut v^t lieu trg dot (cat) lan tro TAP CHi CONG NGHIEP NONG THON - SO - 2013 KHOA HOC - CONG NGHE Sa nguySn ly cua nha may/mo hinh dong phat nhiet dien dugc kSt noi 16 dot tang soi dugc trinh bay nhu tren hinh Hinh Sa md hinh ddng phdt nhiel dien ket ndi Id dot ldng soi lmh 2.3 Md hinh ~ tt'nh todn De xay dyng mo hinh toan hgc cho he thdng, mo hinh dugc xay dung tu cac quan he nguyen nhan-ket qua gi&a cac thong s6 dau vao va cac thong so dau vai mpt so dieu kien giai han ban dau nao Ap suat cua nuac a sau bg trao d6l nhiet Condensator, doi vai hai dau vao cua turbine nhu la nhiet dp hai, ap suit hoi Day la cac thong so dieu kien ban dau lam ca so de tinh toan tim cac thong so nhu: nhiet do, ap suat, enthalpy, entropy va cong suat nhiet tai cac diem lam viec cua tru trinh cung nhu la hieu suat nhiet cua he thong Sa phae hpa/minh hpa cua mo hinh va cac diem lam viec cua chu trinh dugc bieu dien/dugc chi tren hinh a muc Dua vao chu trinh '"Rankine Cycle process" de tinh toan cac thong so vai sy trg giup cua truang trinh tinh toan nhiet dpng lyc hgc dugc viet bang ngon ngiJ VB- Excel (Visual Basic-Excel) 2.3.1 Tinh loan qud trinh chay [4, 5, 7] Duai day tuang ung la diln ta cho sy chay cua cac phan carbon (C), hydro (H) va luu huynh a) Chay cua phSn Carbon (vai khoi lugng moi, M = 12 kg C/kmol): C + O j ^ C O i (+nhiet) kmol C+1 kmol O2 -^ kmol C03(+ nhiet) 12 kg C + 22,4 m^ (N) O2 -» 22,4 m^ (N) CO, kg C + 1,867 m' (N) O2 -^ 1,867 m^ (N) CO2 I kg nguyen lieu co chiia c kg carbon, nhu vay ta co: c kg C + 1,867 X c m^(N) O2 -^ 1,867 x c m'(N) CO, b) Chay cija phiin hydro (vai kh6i lugng moi, M = kg H2/kmol): H: + 0,5 O2 -^ H2O (+ nhiet) kmol H2+ 0,5 kmol O2 -» kmol H2O (+ nhiet) kg H2 + 0,5 X 22,4 m^ (N) O2 -* 22,4 m' (N) H2O kg H2 + 5,56 m^ (N) O2 -* 11,2 m^ (N) HjO kg nguyen lieu co chtia h kg hydro, nhu vay ta co: h kg H2 + 5,56 X h m^(N) O2 -* 11,2 x h m^(N) H2O c) Chay cua phSn luu huynh (vai khoi lugng moi, M = 32 kg S/kmol): S + O2 -» SOi (+ nhiet) I kmol S + ikmol O2 ->1 kmol SO2 (+ nhiet) 32 kg S + 22,4 m-' (N) O2 ^ 22,4 m'' (N) SO, kg S + 0,7 m' (N) O2 -» 0,7 m' (N) SO, kg nguyen lieu co chua s kg luu huynh, nhu vay ta co: s kg S + 0,7 x s m^(N) O2 ^ 0,7 x s m^(N) SO2 Nhu vay, ta co cac phuang chay nhu sau: c kg C + 1,867 X c m^(N) O, -> 1,867 x c m^(N) CO2 TAP CHl CONG NGHIEP NONG THON - SO - 2013 (S) (1) (2) (3) (4) (5) (6) (7) 29 KHOA HQC - CONG NGHE h kg H; + 5,56 X h m'(N) O2 -> 11,2 x h m'(N) H2O s kg S + 0,7 X s m-'(N) O2 ^ 0,7 x s m'(N) SO, (8) (9) ( Thanh phan chat chay duac + Lirong oxy tieu thu —• Thanh phan phat thai + Nhiet) Nhu cau oxy toi thieu (0mm), (vai khoi lugng rieng cua oxy P02 = 1,429 kg/m^(N) O2): 0„,.= l , x c + , x l i + , x s - ( ) xo [m'(N)02/kgNL] (10) Poj 0„, = 1,867 X c + 5,56 x h +0,7 x s - 0,7 x o [m'(N)02/kg NL] Nhu cau khong toi thieu cho qua trinh chay (Lmin): Voi moi truong khong binh thuang ta co: - Khoang 21 Vol-% oxy do yo2,KK = 0,21 m' (N)02/m' (N) KK - Khoang 79 Vol-% nito do yN2,KK = 0,79 m> (N)N2/m" (N) KK (| i) Do vay: i „ „ = — = [m'(N) KK/kg NL] (12) yth.nn Theo [4, 5, 7], nhu cau khong cho qua trinh chay (L): Ty le giila luong khong thuc cjn cung cdp (L) vai lugng khong khf ly thuySt (Lmm) chung dugc dien ta nhu la ty le khong du X: ^ =— [ - ] (13) Do vay: L = X X L„,„ [m= (N) KK/kg NL] Lim Iugng kh6i cua khong dugc ti'nh nhu sau: mKK = L x p „ „ [kgKK/kgNL] The ti'ch va sir hgp cua cac phan phat thai, ton tai nguyen lieu: H2O: w kg/kg NL (p„= 0,804 kg/m' (N))l,245 xw (m' (N)/kg NL] N2: n kg/kg NL (p„= 1,2505 kg/m' (N))0,8 xn [m' (N)/kgNL] Khi thai sinh ciia qua trinh chay: CO;: 1,867x0 [m'(N)/kgNL] H2O: ll,2xh[m'(N)/kgNL] SO2: 0,7 XS [m' (N)/kgNL] Vgi Iugng khong chay cung cdp: N2: yN2.KK X L = yN2,KK X X X L,„,„ [m' (N)/kg NL] O2: yo2.KK X L - 0„,„ =yo2,KK X X X £BS- - 0,„,„=(X-1) X Om,„ [ffl' (N)/kg NL] (14) (15) (16) (17) (18) (19) (20) (21) (22) yn.jtK The tich cua khoi "am" tCr qua trinh chay hoan toan bao g6m: Ka, =K= Veo, + y,t,o + Vso, + VN, + Vo, Vai: F,.„_ = 1,867 x c [m' (N)/kg NL] V„j,, = 1,245 x(9 X h + w) [m' (N)/kg NL] K^^ = 0,7xs[m'(N)/kgNL] K„^ = , x n + yN2,KKX>.xL,„i„[m'(N)/kgNL] ''o, =(''-l)xO.,„ Nhu vay thS tfch cua kh6i "am" (VAG/): 30 [m'(N)/kgNL] (23) (24) (25) (26) (27) (28) TAP CHf CONG NGHI6P NONG THON - SO - 2013 KHOA HQC - CONG NGHE V „ , , - l g X c+ 1,245 X (9 X h+ w) + 0,7 x s + (0,8 X n + yNi.KKX IX L,„„) + (l-l) x , |m' (N)/ke NL] -)xO,.i.|xl|m-'(N)/kgNL] Hoac: V»c,.-(l,867xc+l,245 x(9 x h+ w)+ 0,7 xs + 0,8 xn - 0„,.) + [(1 + (29) (30) >V;„^ The tich cua khoi "kho" (VAo.kh): y„;j.„ = K, =K-VHP = V,v, + V^,^ + K,, + K„_ [m'(N)/kgNL] (31) Hoac: Vu, = (1,867 xc + 0,7 xs + 0,8 xn Thanh phan CO2 cue dai khoi "kho": Nong CO2 cue dai se dat dugc khi/boi ty le khong khf du X - Do the tfch khoi "kho" se (dugc) V n | i | , = Vii.mm VcJi: Vki,,m,„ = Vco2+Vso2+V„(i.ii= l,867xc - 0,7 X s + 0,8 X n + ^^^^^^ X 0,n,„ Do ta co: C0^ „,.,, = (34) '— 2.3.2 Tinh todn qud trinh tgo hai Mo ta qua trinh: Cac phan va cong doan chinh cua qua trinh tao dien nang dugc kit n6i vai 16 d6t tSng soi bao gom: ham nong, qua nhiet turbine hai dugc ket noi vcri may phat dien, binh ngung (condenser), va bom cap nucrc (feed pump), hinh Muc tieu chinh cua mo hinh doi vai qua trinh tao hai la tim lugng nhiet tieu thu cho qua trinh tao hai ducri cac thong so hai dua vao ban dau (muc nhiet dp, ap su5t cua hoi sach vao turbine hai) cSn thiet dk tao nang lugng dien dau tieu thu theo yeu chi cua mo hinh de Phan tich chu trinh thuc dan gian ciia qua trinh tao hai: Day la chu trinh (Clauslus-RankineCycle) dugc diln ta tren cac thi nhiet doentropy (T, s) va enthalpy-entropy (h, s) (hinh 3) [2,3,7] Qua trinh 0->l la qua trinh d^ng entropy, ap suat tai diSm "0" la bSng vcri ap suat tai diem " " (Po = Ps) (trong truang hgp ly thuya ) tang len din ap suat lam viec/van hanh (ps = pi) Qua trinh l->2 la qua trinh cap nhiet dang ap, nhiet cung cSp dk lam nong/ham nong nuac Trang thai dugc tinh toan bcri bilu thiic (35) Q,2=m,,.{h,-^) = fyisri^^a).{h^-h,) (35) (33) Qua trinh 2->3 la qua trinh cap nhiet dang apdang nhiet suot gia! doan "soi" Hai va nang lugng nhiet se duoc tao giai doan Trang thai dugc linh toan boi bieu thuc (36) Q2^=m,,.{H,-hj) (36) Qua trinh 3->4 la giai doan qua nhiet, nhiet dugc cung cap a trang thai dugc tinh toan bai bieu thuc (37) Q,,=m„.{h,-h^ (37) Do do, nang lugng nhiet can thiet cung c5p cho tong cac qua trinh tao hoi dk tao dien n3ng dugc tinh toan bai bieu thuc (38) fi;,,.;,.sv=e;2+&+a (38) Mo hinh co the tinh toan dugc: lugng nguyen lieu tieu thu, kh6i lugng hai nudc c5n tao ra, san lugng dien tao dugc va hi?u suat nhiet cua qua trinh Cac thong so tinh toan ban dau dugc gia dinh nhu sau: Nhiet cCia nguon nuac c5p tai dilm "0" (tsrw = 104°C) (htnh 3, 5) Vai dilu kien ky thuat cr Viet nam, cac thong so ap suSt va nhief ciia ha! qua nhiet cung cap vao turbine hai de tao dien cong suat MWel se dugc lua chgn nhu sau: Cac thong s6 hai p4 = 26 bar, T4 = 350°C tuong ung vai viing cong suat nhiet 5-50MW, TAP CHI CONG NGHIEP NONG THON - SO 8- 31 KHOA H O C - CONG N G H E hon nua vai viing cong suat thi cac hieu suat neu sau day co thl lua chon nhu sau [2, 3, 7]: hieu suat nhiet cua Turbine hai TIT ^ 0,82, hieu suat ca rimech ^ 0,99 va hieu suat cua may phat dien TIG = 0,98 Nang Iirgng nhiet ciia khoi thai sau budng dot: 0-V =(l + ^O-«;.i,,,.n,U,-'-WA-^W;.(kW)(43) Nang lugng nhiet tro [2, 4, 5, 7): Q,u„='"',.d-'J,.„.i-^',+G^,„+Q„,+a.v (kw) (52) |e a='«;.we,.w7',,„,(kW) (47) Phuang trinh can bang nang lugng cua he th6ngla(48)hoac(51): P > Q , (%) (53) Pel- Tong cong suat nhiet sinh (kW) Hieu suat nhiet thai cua khoi co thi sudung tiip: av3 ^'-Cl'"' (54) III KET QUA VA THAO LUAN Qua trinh dugc khao sat voi su trg giiip ciia/bdi mo hinh "EXCEL-VISUAL BASIC" Loi giai cho ket qua cu6i cung ciia cac thong so ciia qua trinh dugc diln ta nhu tren bang va cac hinh 5, hlnh va hinh Lugng nhiet dau vao can thiit/lugng nhiet cung cSp cSn thiet cua qua trinh Q'loBi.si = 8345 kJ/s, hi?u suSt chuySn d6i nang lugng cua nha may/ciia he thong nhiet dien iiEcst = 24.7% =fia-.«r =^C.»);,,„.(^,„„.A,,,„ (kW)(42) TAP CHf CONG NGHIEP NONG THON • SO - 2013 KHOA HOC - CONG NGHE Bdng Cdc thdng so ket qud ti'nh todn ciia md hinh ddng phdi nhiel dien Diem 104,00 To Po h'o Tspipi Diem Pi h i (pi, TSp) Tiipi Diem Diem CO Diem AD /ill, 2372,40 (kJ/kg) 2211,30 6,824 7,316 0,837 2211,30 914,80 731,90 (kJ/kg) (kJ/(kg.K)) (kJ/(kg.K)) (kg/kg) (kJ/kg) (kJ/kg) (kJ/kg) 2394,30 7,383 0.914 1390,10 5906,60 (kJ/kg) (kJ/(kg.K)) (kg/kg) (kW) (kW) (kW) (kW) (kg/s) (kg/s) Vll 1048,30 8345,00 3,36 3,23 30,90 '/E^apdlunii 24,70 hAt , j - a , „ , „ „ S4 = Ss s'"s X5 h,= h(p,.v) AhAD=h4-ll.,|j P: 26,00 971,70 26,00 226,05 2801.40 1830.70 (bar) (kJ/kg) (bar) (°C) (kJ/kg) (kJ/kg) 26.00 350.00 3126,10 6,8240 0,15 (ban (°C) (kJ/kg) (kJ/(kg.K)) (bar) 54,00 rc) 225,90 (kJ-kg) 7, 24,00 '/.I 23,80 Tjip) h"j Ah, P4 Diem CO (bar) (kJ/kg) (°C) (bar) (kJ/kg) h'j Pj Di^mS 1,17 436,00 132,3 26,00 557,70 226,05 T4 = TpD il4 = hFD h+ = hpD Ps = Ts PAD (PAD) h'j Ah,e.i hs S\d -'^\d 0\.„„, Q'D.„,PI Q\b Q-„ m\up mVo (%) (%) (%) (%) H/n/i Sff dd cong nghi; cdc kit qud linh loan vd cdc thong w ip thudt cua cim ky Igo hai lai cdc diem lrong chu trinh W\ Hinh Cdc kel qud linh lodn cho/doi vdi cdc qud Irinh ddng entropy vd gian ihuc Irang turbine hai duac bieu dien Iren thi enthalpy-entropy (h s) Hinh 7, Cdc ket qud linh lodn cho cdc qud rinh dang dpddng nhiel vci qua irlnh gian ihirc lrong turbine hai duac bieu dien tren ihi nhiet do-entropy (T sj TAP CHI CONG NGHIEP NONG THON - SO - 2013 33 KHOA H O C - CONG N G H E TCr ket qua tinh toan: Ty le tao nang lugng dien [2, 7]: y aw.„, {0 do: +0, 8345ir e* u , ,) (Gv, +G/.1O