Nghiên cứu mô phỏng giảm khí thải độc hại khi lắp bộ DOC SCR cho động cơ diesel

NGHIEN CLfU - TRAO e l NGHIEN C d u MO PHdNG G I A M K H I T H A I DOC HAI KHI LAP BO DOC-SCR CHO DONG CO DIESEL RESEACH ON SIMULATION OF EMISSION REDUCTION FOR DIESEL ENGINE USING DOC-SCR Nguyln Tung LSm', Nguyin Tien Han^ 'Khoa Ca khi, Tmong Dai hgc Giao thong Van tai ^Khoa Cong nghe to, Tnrong Dai hoc Cong nghiep Ha Noi TOM TAT Bai bdo giai thieu phucmg phap mo phong biin phap gidm phdt thai lap DOC-SCR (Diesel Oxydation Catalyst - Selective Catalytic Reduction) de gidm phdt thdi NOx cho dong ca diesel Tren ca sa dua cdc gidi phdp thiet ke cum xu ly thdi DOC-SCR de lap cho dong ca diesel tren phucmg tien giao thong van tdi dang su dung a nuac ta Tir khoa: Phdt thdi, DOC-SCR, thdi, iong ca diesel ABSTRACT This paper introduces simulation how to decrease NOx in the exhaust gas of diesel engine by using DOC-SCR Based on results ofthe simulation, the solutions for designing the DOC-SCR dre provided to dpplyfor diesel vehicles in our country Keywords: Emission, DOC-SCR, exhdust gas, diesel engine DAT VAN DE Tren thS gioi noi chung va o Viet Nam noi rieng, nghien ctiu nh Sm giam phat thai doc hai tir dpng co d6t trong, nhSm dap img cac tieu chuin cang ngat ngheo vg thai tir dpng CO d6t Ben canh nhimg giai phap giam thilu tai ngu6n, tire la truoc va qua trinh chay thi giai phap xir ly thai sau ctia xa ciing mang lai hieu qua dang ke Voi dpng CO xang thi dupc biet dSn vcri bp xu ly xuc tac ba duong, dpng co diesel thuong sir dung bp oxy hoa (DOC) de tiep tuc oxy hoa HC va CO k a hop bo khir (SCR) da khu NO, NO^ [1-3] Tuy nhien, bo DOC qua trinh lam viec lai c6 anh hucmg den bo SCR Anh huong thi mang tinh tich cue nang cao hieu qua khii NOx, nhien ciing co truong hpp mang den nhihig hieu img tieu cue Phuong phap xir ly xiic tac chon lpc khir NOx (SCR-Selective Catalytic Reduction) la phucmg phap khir lien tuc NOx [4] Duoi ^^ tae dung cua chat xiic tac, NOx bi khir ISSN 0866 - 7056 TAP CHl CO KHi VlfiT NAM, S67nam2017 www.cokhivietnam.vn NGHIEN CU'U-TRAODOI NjVa HjO, thircmg dung chat khu la NH^ Tuy vay, viec lim trir NH^ la rat kho khan nen nguai ta tao NH^ mot each gian tiep tu phan ung thuy phan urea Tuy nhien, urea cr dang tinh chat la dang bot kho c6 the dua vao thai vai lugng xac dinh dugc Do la H nguai ta phai Sli dung urea duoi dang dung dich Mot nhung san pham thuang mai dugc sii dung nhieu nhat hien la dung dich Adblue (32,5% urea) DOC den hieu qua Iam viec ctia bg urea-SCR (hinh 2) Bo DOC-SCR dugc xay dimg lip d^t tren dgng ca 6.7L CUMMINS ISB (bang 1) Day chinh la mgt ngi dung lign quan dgn qua trinh tinh toan thiet ke bg DOC trgn thuc tS nham kiem soat va toi uu hieu qua Iam viec cua cum DOC-SCR Dong thai, qua qua trinh khao sat vai mgt so truong hgp thai: Kha nang giam phat thai NOx cua bg DOC-SCR cac nhiet dg va luu Iugng thai khac nhau; phan nito oxit sau bg DOC XAY DlTNG MO HINH KHAO SAT BO DOC-SCR 2.1 L5p dat DOC-SCR tren dirfrng thai Cac ket qua nghign cuu da cho thay bg DOC va SCR thi dat bg DOC dat truoc bg SCR CO nhieu uu diem ro ret nhu la nang cao hieu suat khu, dac biet voi truang hgp nhiet dp thai thap Tuy nhien, hieu qua khii cua bo SCR tot nhdt bg DOC sinh r^^ ^„ = 50% Hinh Md hinh md phdng bd DOC-SCR Trong do: ATBl: Dieu kien bien dau vao, bao gom cac thong so: Nhiet do, ap suit, Iuu lugng va cac phan Ichi thai; CATl: Mo hinh bp khu xuc tac SCR; CAT2: Mo hinh bg xi hoa DOC; ATB2: Dieu kien bign dau ra, bao gom cac thong so: Nhiet va ap suat moi truong Bang Thdng sd cua dgng ca tham khdo: N0,flJO.N5-10W ^fO^'NO.=Sll% Hinh I Sa lap ddt SCR tren du&ng thdi: a) Chi CO he thong SCR; b) Trudc hi thdng SCR cd bg oxy hda tgo NO^ 2.2 Xay dung mo hinh mo phong Su dung phan mem mo phong cho dong ca dot AVL-Boost thi ta co thg xay dung mo hinh de khao sat anh huang ciia the tich bg Ma so dgng ca Loai dong ca The tich cong tac Ducmg kinh x hanh trinh Ty so nen 6.7L CUMMINS ISB xy lanh thang hang V„-6,71 10,7x12,4 (cm xem) 17,3 Dua vao cong thuc tinh toan DOC va SCR Clia [4-6], ta co thg tinh toan sa bg thg tich Clia hai bg trinh bay Bang ISSN 0866 - 7056 TAP CHI CO KHI VIET NAM, S6 nam 2017 www.cokhivietnam.vn NGHIEN CLfU - TRAO DOI Bang Thong so DOC-SCRDOC Thong so The tich (1) Chieu dai (mm) SCR 4,5 6,5 153,5 228,6 So luong 16/linch (cpsi) 400 400 Kicii thuac 16 (mm) 0,1905 0,1905 Be day 16 (mm) 0,01905 0,01905 Dieu kien bign cho mo hinh bao gom: Trang thai va phdn thai va digu kien moi truong, dugc cho Bang Bang Ma trdn khdo sdt dnh hudng ciia the tich bo DOC din SCR Thong so Casel Case Case Case The tich bp DOC (1) 45 5; 2.5; 3.5; 4.5 45 Ap suat thai (bar) 1.2 1.2 1.2 1.2 Nhiet thai (°C) 200; 250; 300; 350; 400; 450; 500 200; 250; 300; 350; 400; 450; 500 Liru luong thai (kg/h) 200; 300,400 500 300 400 Nong phan t6ng HC; CO (ppm) 200 320 200 200 TyleHC/CO(%) 50 50 50 50 Nong dp phan NOx (ppm) 200; 500; 800,1100 200; 500; 800; UOO 800 200,1100 Ty le mol NO,/NO (%) 10 10 10 5,10, 15 200; 250; 300; 200; 250; 300; 350; 400; 450; 500 350; 400; 450; 500 KET QUA MO PHONG DOC-SCR 3.1 Anh hirong cua the tich bo DOC Hinh Hieu sudt oxy hda NO theo nhiit dd thdi cua bd BOC v&i thi tich bd DOC khdc nhau: VDOC = 4.Siit, VDOC = Slit vd VBOC=2 Slit vd nong NOx thdi lan lu0 Id: [NOx] ^ SOOppm, muc luu lugng thdi khdc nhau: Qx = 300kg/h cr ISSN 0866 - 7056 TAP CHI CO KHi VIET NAM, S6 nam 2017 wvtTv.cokhivietnam.vn NGHIEN CO'U-TRAO DOI Dac tinh lam viec cua bg oxy hoa theo nhiet dugc thg hien tren hinh 3, voi cac muc thg tich bg oxy hoa khac day, hieu suat oxy hoa tot nhat la vung trgn dudng man xanh, khoang 45% dg tao ty le 'HOJ NOx=50% sau bg oxy hoa Khi miic oxy hoa NO NO, cang cao han 45% thi cang khong tot vi lugng NOj Ian han lugng NOx bao nhieu thi se chinh la Iugng du sau phan ung a bg SCR Kich thuac the tich cua bg DOC, anh hudng nhigu a viing nhiet thap, tir 200 dgn 300''C, giam the tich bg xi hoa thi Iugng NO bi oxy hoa NO, cang giam Giam the tich bg oxy hoa DOC thi CO Igi vg hieu suat khu NOx vgi viing nhiet dg thap, nhien qua trinh su dung thi khong tranh khoi su suy giam ciia cac phan tir xiic tac, suy giam hieu nang xuc tac thi phucmg an giam the thich la khong kha quan, chi nen tranh viing nhiet thap la tot han 3.2 Anhfau-ongciia nhi|t Idii thai va liru lirgng thai Hieu suat khu NOx co anh huang rat lan tii nhiet thai Hinh 4, la kgt qua mo phong hieu suat khli NOx vdi cac the tich bg DOC Ian lugt la Vpp^=4,5I va V^^=l,5\ Ket qua mo phong cho thay, hieu qua khii cao nhat nhiet thai khoang 350-^450*'C Vdi nhiet cao Idn han 450^ hieu suat khu Iai co xu huong giam Nguygn nhan la qua trinh chgn Igc khir NOx giam ma qua trinh oxy hoa NH^ lai tang len ngn lam hieu qua chuyen doi NOx ciia SCR giam Hinh Hieu sudt khu NOx theo nhi^t thdi cua bo BOC-SCR vai the lich bg DOC khdc nhau: V^^ = 4.Slit vd V ^2.Slit vd ndng NOx thdi ldn lugt Id: [NOx] = 200ppm, [NOx] = SOOppm [NOx] = SOOppm, [NOx] = 11 OOppm, miec luu luang thai khdc nhau: Qx = SOOkg/h 3.3 Khao sat v ^ cac nong d^ khac cua NOi thai Anh hudng cua phan NOx ban dSu thai nham muc dich danh gia nhay anh hudng Clia thong so dau vao vdi dau Thanh phan NO, anh hudng dgn hieu qua chuyen doi NOx ro ret nhat vdi viing nhiet thap cua bg xiic tac: Tir 200-300*^ Thanh phan NO^ tang Ien lam phan ung chgn lgc khii NOx tang so lugng phan iing nhanh nen Iam tang hieu qua chuyen doi NOx (hinh 5) iH.iu n i l m vS ihinK Dhiii "O^ aflu V I D bh cnl.mj /