ESC170_FALL_EXAM1__[0] - THE COOPER UNION Department of...

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Unformatted text preview: THE COOPER UNION Department of Chemical Engineering ESC 170 Principles of Material and Energy Balances Mid Semester Exams Answer all questions Time Allowed: 11/2 h l Crystallization may sometimes be used to separate sylvinite, a mixed salt containing 42.7% NaCl and the remainder KCl, is dissolved in 1000 kg of water and cooled to induce crystallization. The composition of the crystals is 72.1% KCl, 0.5% NaCl and 27.4% H2O. A crystal yield of 727 kg is obtained. The mother liquor remaining behind contains 50% H20 and the remainder is salts. N ‘ i. How much sylvinite was originally dissolved Sufi VlZ vvl M C" m f {.3 ii. What is the composition of the mother liquor? 5 (l a?) “'5‘ “300%; iii. What is the percentage recovery of KCl? 31)“ E is [V K 2. Styrene, a monomer of polystyrene can be manufactured by alkylating benzene with ethylene to form ethylbenzene which is further dehydrogenated to styrene. The primary reactions of the process are: Catalyst + C2H4 _——-> C6H5C2H5 Ethylene Ethylbenzene C6H6 Benzene (1) Catalyst & Heat ———~———~—> C6H5C2H3 + H2 Styrene C6H5C2H5 Ethylbenzene The benzene is and thenfignt to an alkylatng reactor where it is combined with ethylene. The effluent from the reactor is sent to a separator where the catalyst is separated and recycled to the reactor. The other effluent products are washed with water and caustic, and then sent to a train of three ethylbenzene distillation columnl In the first column, the unconverted benzene is separated and returned to the benzene drying column to dry, then sent to the alkylation reactor\ In the second column the ethylbenzene is removed as the distillate and sent to a dehydrogenation reactor with steam}. The effluent from the dehydrogenation reactor is cooled, condensed and sent to a separator where the uncondensed hydrogen is removed. \The dehydrogenated mixture is sent to a train of distillation columns where the styrene is separated from the mixture as crude styrene. The unconverted ethylbenzene is recycled to the dehydrogenation column. The other products such as toluene and tar are sent to waste treatment units.\In some cases, some polyethylbenzene may be formed and have to be removed in the third column of the ethylbenzene distillation train and returned to the alkylation reactor. i. Sketch a flowchart for this process. ii. List all the major pieces of equipment and x . . . Vt ‘vi-Erix‘fi, I" k .1 111. Allthe recycled streams. at K M l3 "3 ('5', ID (v Mr'flv\ 3. A tank is fed by two streams. Each stream contains cyclohexanol and benzene. During a two-hour test, the following data were obtained. Start of test End of test Tank contents, gal 2000 6000 Specific gravity of contents 0.920 0.880 Weight % benzene 47.0 63.0 During the test no material was removed from the tank. Due to an operator’s error, only the following data were obtained for the entering streams. Stream 1 Stream 2 Flow rate, gal/hr 1000 ? 7‘ Weight % benzene 90.0 ? Us Specific gravity 0.870 0.900 3 Calculate a. the flow rate of stream 2 in gal/hr b. the weight percent benzene in stream 2. The Cooper Union Department of Chemical Engineering ESC 170: Principles of Material and Energy Balances Final Examination Answer all questions Time allowed: 11/2 h 1. cm em 0'» or A gaseous fuel containing only methane and ethane is burned with air to yield a flue gas (dry basis) containing 4.62% C02, 3.08% CO, 8.91% 02 and 81.39% N2. Calculate . . I"? "0 i, O 2’ a. the analysis of the fuel in mole percent 4 a (3 Li A" (“Q Q Kai—“iii” ,v ‘Q 1, b. the percentage excess air. if. a M -»::.b»;:vi 132‘} a! {3 1% x y , 0% 2 / IV?“ Propane is catalytically dehydrogenated to propylene in a fixed bed reactor. As the reaction proceeds a carbonaceous material is deposited on the catalyst. In a laboratory experimentl‘l;2_l:t>m of pure propane is fed to a fixed reactor. The reactor effluent analyzes (i.n,~m01§_/9_9) 25.4 H2, CH4 , C2H4, 5.3 Csz, 21.3 C3H6, C3H8. An analysis Of the deposit on the catalyst indicates that it is 96% carbon and 4% hydrogen by weight. Calculate the amount of deposit on the catalyst. Express your answer as a weight percentage of the propane feed. Methane is burned in a poorly designed combustion chamber. One thousand mol/h of the gas is fed to the chamber at 25°C, along with the theoretical required amount of air “preheated to 200°C. Calculate the heat transferred from the reactor if 90% of the methane is burned, the mole ratio of C02 to CO in the product gas is 10:1, and the combustion gas leaves the chamber at 400°C. 0 The Cooper Union Department of Chemical Engineering ESC 170: Principles of Material and Energy Balances Final Examination Answer all questions Time Allowed: 11/2 h The flue gas from a burner has the following dry-basis molar composition: 80.35 mole%, C02, 4.73% CO, 0.033% 802, 14.89% 02. IO % excess oxygen is fed to the burner and the fuel achieved complete combustion. There is no oxygen in the fuel. Calculate the elemental composition (mole% of the various elements) of the fiiel. 2. \ In the nitric acid production process, p eheated air is mixed with ammonia to form a '3. l 2:: gas made up gflglgmoleféfifiéwatfiggf (Note; the ammonia is not preheateclwsince it maydempose to N2 and H2). The mixture is then catalytically oxidized to form N02, which is further absorbed in water to form HNO3. If ammonia enters the gas blending unit at 25°C at a rate of 520 kg/h, and heat is lost from the mixer to its surroundings at a rate of 7 kW, determine the temperature to which the air must be preheated. (Use the first two terms of the heat capacity formula for air). 3. A gas containing 85mole% methane and 15mole% ethane at 25°C is burned in a constant volume reactor, and the products are brought back down to 25°C. Calculate the net heat (kJ) transferred from the reactor. ...
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This note was uploaded on 02/27/2012 for the course CHEMISTRY/ CH/ECE/PH/ taught by Professor Faculty during the Spring '08 term at Cooper Union.

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ESC170_FALL_EXAM1__[0] - THE COOPER UNION Department of...

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