EKC 217 Mass Transfer [Pemindahan Jisim]

Transcription

1 UIVERSITI SIS MLYSI First Semester Eamination 0/0 ademi Session anuar 0 EKC 7 Mass Transfer [Pemindahan isim] Duration : 3 hours [Masa : 3 jam] Please ensure that this eamination paper ontains SEVE printed pages and FIVE printed pages of ppendi before ou begin the eamination. [Sila pastian bahawa ertas peperisaan ini mengandungi TUUH mua surat ang bereta dan LIM mua surat Lampiran sebelum anda memulaan peperisaan ini.] Instrution: nswer LL 4 questions. [rahan: awab SEMU 4 soalan.] In the event of an disrepanies, the English version shall be used. [Seirana terdapat sebarang peranggahan pada soalan peperisaan, versi Bahasa Inggeris hendalah diguna paai.] /-

2 - - [EKC 7] nswer LL questions. awab SEMU soalan.. [a] n open beaer is filled with liquid benene as shown in Figure Q..[a]. at 5 C. The evaporated benene is arried awa b dr air flowing gentl aross the opening of beaer at 5 C and atm. The evaporated benene is transferred through a stagnant air laer in the beaer. The vapor pressure of benene at 5 C is 0.3 atm. Diffusivit of benene in air at 5 C and atm is m /s. Determine the initial rate of evaporation of benene as a molar flu in mol/m -s. Compute the initial mol-fration profiles in the stagnant air laer for in the range of m. Suatu biar terbua dipenuhi dengan eair benena seperti ang ditunjuan dalam Rajah S..[a] pada 5 C. Benena ang tersejat dibawa oleh udara ering ang mengalir perlahan-lahan melalui pembuaan biar pada 5 C dan atm. Benena ang tersejat dipindahan melalui lapisan udara ang bertaung dalam biar. Teanan wap benena pada 5 C ialah 0.3 atm. Kemeresapan benena dalam udara pada 5 C dan atm ialah sm /s. Tentuan adar awal penejatan benena sebagai flus molar dalam mol/sm.s. Kiraan profil peahan-mol awal dalam lapisan udara bertaung untu dalam julat sm. Figure Q..[a]. Evaporation of benene to air Rajah S..[a]. Penejatan benena e udara [5 mars/marah] 3/-

3 - 3 - [EKC 7] [b] CO is stripped from water b air in a wetted wall tube. t a speifi loation in the stripper with pressure of 0atm and temperature of 5 C, the masstransfer flu of CO is mol/s-m. The partial pressure of CO is 8. atm at the interfae and 0.atm in the bul gas. The diffusivit of CO in air at 0 atm and 5 C is m /s. ssuming turbulent flow of the gas, alulate the mass-transfer oeffient for the gas phase and the film thiness b the film theor. CO diluutan daripada air menggunaan udara dalam tiub dinding basah. Di suatu loasi tertentu dalam peluut dengan teanan 0 atm dan suhu 5 C, flus jisim pemindahan CO ialah mol/s-m. Teanan separa CO adalah 8. atm pada antara mua dan 0. atm dalam gas pual. Kemeresapan CO dalam udara pada 0 atm dan 5 C ialah sm /s. ndaian aliran gelora gas, iraan peali pemindahan jisim bagi fasa gas dan etebalan filem dengan menggunaan teori filem. [0 mars/marah]. [a] tra tower is to be used to remove 95% of the ammonia from an entering air stream ontaining 5 mol% ammonia at 93 K and atm. The entering pure water flow rate is 0.45 gmol H O/h and the inert air flow rate is 4.4 gmol air/h. Suatu turus dulang aan digunaan untu meningiran 95% amonia daripada aliran udara masu ang mengandungi 5 mol% amonia pada 93 K dan atm. Kadar aliran air tulen masu ialah 0.45 gmol H O/j dan adar aliran udara lengai ialah 4.4 gmol udara/j. [i] [ii] Calulate the omposition of the treated air and used water. Kiraan omposisi udara ang telah dirawat dan air ang telah digunaan. Plot the operating lines with intermediate points on the - mol fration equilibrium plot, and determine the number of theoretial tras needed. Plotan garisan operasi dengan titi perantaraan pada plot eseimbangan - peahan mol, dan tentuan bilangan dulang teori ang diperluan. 4/-

4 - 4 - [EKC 7] Table Q..[a]. Equilibrium Data for mmonia-water Sstem adual S..[a]. Data Keseimbangan bagi Sistem mmonia- ir Mole fration of H 3 in liquid, Peahan-mol H 3 dalam Mole fration of H3 in vapor, Peahan-mol H3 dalam wap P atm 0 C 30 C eair, [8 mars/marah] [b] paed tower is used to remove 90% of H 3 from a 85.0 m 3 /min feed gas ontaining 3 mole% of H 3 and 97 mole% of air. Pure water at 93K and atm is used as absorbent. From the given information, estimating the required paed height. ssume it is a dilute sstem. Suatu menara terpadat digunaan untu meningiran 90% H 3 dari gas suapan 85.0 m 3 /min ang mengandungi 3 mol% H 3 dan 97 mol% udara. ir tulen pada 93 K dan atm digunaan sebagai penerap. Daripada malumat ang diberi, anggaran etinggian padatan ang diperluan. nggapan ia adalah satu sistem ang air. Paing.5-inh Rashig rings Henr s Law onstant 0.77 mole ratio H 3 in air/mole ratio H 3 in water Mass flow rate of gas 0.5g/min Mass flow rate of liquid 66.g/min X 0 no reirulated liquid Mole ratio of H3 to H 3 free gas entering the absorber 0.03 Mole ratio of H3 to H 3 free gas leaving the absorber Liquid mass veloit 500lbm/hr-ft Gas mass veloit 500 lbm/hr-ft Padatan inin Rashig.5 ini Pemalar Huum Henr 0.77 nisbah mol H 3 dalam udara / nisbah mol H 3 dalam air Kadar aliran jisim gas 0.5 g/min Kadar aliran jisim eair 66. g/min X 0 tiada eair diitar semula isbah mol H3 untu gas bebas H 3 memasui penerap 0.03 isbah mol H3 untu gas bebas H 3 meninggalan penerap Halaju jisim eair 500 lbm/hr-ft Halaju jisim gas 500 lbm/hr-ft...5/-

5 - 5 - [EKC 7] Figure Q..[b]. Height of a transfer unit for ammonia and water sstem. Rajah S..[b]. Ketinggian unit pemindahan untu sistem amonia dan air. [7 mars/marah] 3. [a] Define the term onstant molar overflow and show that for this ondition the vapour and liquid flows in the upper setion of a distillation olumn an be related b the equation: Tarifan terma limpahan molar malar dan tunjuan bahawa untu eadaan ini wap dan eair ang mengalir di dalam bahagian atas turus penulingan boleh dihubungan dengan persamaan: n+ R R + n D + R + [7 mars/marah] [b] frationation olumn is to separate 30 g/h of a solution of benene and toluene ontaining 0.6 mass fration toluene into an overhead produt ontaining 0.97 mass fration benene and a bottom produt ontaining 0.98 mass fration toluene. reflu ratio of 3.5 is to be used and the feed is liquid at its boiling point. Compute the following, assuming a uniform pressure of atm throughout the olumn: Suatu turus pemeringatan aan memisahan 30 g/j larutan benena dan toluena ang mengandungi 0.6 peahan berat toluena epada produ atas ang mengandungi 0.97 peahan berat benena dan produ bawah ang mengandungi 0.98 peahan berat toluena. Peahan reflus sebana 3.5 aan digunaan dan suapan ialah eair pada titi didihna. Kiraan ang beriut dengan mengandaian teanan seragam atm di sepanjang turus: 6/-

6 - 6 - [EKC 7] [i] [ii] [iii] [iv] [v] mount of distillate and bottom produt umlah sulingan dan produ bawah Minimum number of theoretial tras at total reflu Bilangan minimum dulang teori pada reflus eseluruhan Minimum reflu ratio, R m Peahan reflus minimum, R m Theoretial number of stages required Bilangan peringat teori ang diperluan Optimal loation of the feed Loasi optimum suapan [vi] tual number of tras if the tra effiien is Bilangan dulang sebenar jia eeapan dulang ialah 0.80 Table Q.3.[b].: Equilibrium data for benene-toluene sstem adual S.3.[b]: Keseimbangan data untu sistem benena-toluena Mole fration of benene in vapor Peahan mol benena dalam wap mole fration of benene in liquid Peahan mol benena dalam eair Moleular weight of benene 78 g/mol Berat moleul benena 78 g/mol Moleular weight of toluene 9 g/mol Berat moleul toluena 9 g/mol [8 mars/marah] 7/-

7 - 7 - [EKC 7] 4. [a] Eplain the differenes between distillation and liquid-liquid etration. Terangan perbeaan antara penulingan dan penarian eair-eair. [5 mars/marah] [b] Fresh halibut livers ontaining 5.7 wt% oil are to be etrated with pure ethl ether to remove 95% of the oil in ounterurrent multistage leahing proess. The feed rate is 000 g of fresh livers per hour. The final eit overflow solution is to ontain 70 wt % oil. The retention of solution b the inert solids oil-free liver of the liver varies as given in Table Q.4.[b].: Hati halibut segar ang mengandungi 5.7% berat mina ingin disari dengan etil eter tulen untu meningir 95% mina dalam proses pengurasan berbilang-peringat arus berlawanan. Kadar suapan ialah 000 g hati segar bagi setiap jam. liran eluar terahir bagi larutan aliran atas mengandungi 70% berat mina. Penahan larutan oleh pepejal lengai hati bebas-mina bagi hati berubah-berubah seperti ang diberian dalam adual S.4.[b]: Table Q.4.[b]. adual S.4.[b]. g inert solid/g solution retained g oil/g solution g mina/g larutan g pepejal lengai/g larutan ang tertahan Calulate the amounts and ompositions of the eit streams and the total number of theoretial stages. Kiraan jumlah dan omposisi aliran eluar dan jumlah bilangan peringat teori. [0 mars/marah] - ooooooo -

8 - 8 - [EKC 7] ppendi Formulae and General Data tomi weights: H, C, 4, O 6, S 3, Cl 35:5 Gas onstant: R 8.3 /mol.k L.atm/mol.K 6.36 L.mmHg/mol.K Pressure: 034 Pa atm 760 mm Hg eleration due to gravit: g 9.8 m/s Properties of water unless otherwise stated: ρ 000 g/m 3, μ.00 mpa.s Diffusion Fi s Law: d DB d D B d d D B PT d RT d General equation for diffusion plus onvetion: d DB + + B d Equimolar ounter diffusion: DB i T DB i T DB p p RT Unimoleular diffusion: d DB + d DB ln T i DBPT p p RT pbm pb pb pbm ln pb / pb DBρM BM B B BM ln B / B /-

9 - 9 - [EKC 7] Moleular diffusion of solute in liquids: i T B i T av B D D av BM B M D ρ / ln B B B B BM Film theor bul flow effet is not negligible: ln b b i LM B i B D D δ δ [ ] b i b i LM B LM / ln Mass transfer oeffiients: Turbulent mass transfer with onstant onentration: D M B + ε Turbulent mass transfer with equimolar ounter diffusion: G p p L Turbulent mass transfer with unimoleular diffusion: BM BM G p p L Overall mass transfer: *, K G m K +, * L K m K " + 3/-

10 - 0 - [EKC 7] bsorption or Stripping Stagewise ontating of totall immisible phases: The subsript is often omitted on the omposition variables when no onfusion is possible. Equilibrium General: n f n Gas-liquid Henrs Law: p H or H Liquid - liquid ernst: m Definitions of omposition/flow variables: X / B L 0 L B V V B B inert omponenet For binar mitures: + B Operating line: bsorption fator: L/mV Design of absorber: Transfer from V to L bsorption: When 4/-

11 - - [EKC 7] Transfer from L to V Stripping: When C u S o HETP ρ ρ - ρ lt t General: Manipulation of the above: 5/-

12 - - [EKC 7] Dilute solutions: dditionall Henr s Law holds nalogous equations for gas film basis, and for liquid-phase balane Chilton and Colburn equations: Vave H OG K as OG ln {[ / ][ K / K ] + / } in in / out in