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### M E C H A N I C A L U N I T O P E R A T I O N S I J N T U M O D E L P A P E R{Www

1. 1. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 1 III B.Tech I Semester Regular Examinations, November 2007 MECHANICAL UNIT OPERATIONS-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. Discuss about any four mixers for cohesive solids. [16] 2. Estimate the power consumption for lifting ore particles (speci c gravity = 1.2) pneumatically at the rate of 30 kg/minute to a height of 50 m from the following data: Air: solid ratio (by weight) maintained = 1.5 Diameter of pipe (G.I) = 0.07m Particle size = -0.45 + 0.4 mm Viscosity of air = 0.018 cp Speci c gravity of air = 0.0013 The roughness parameter r for the G.I pipe may be taken to be 0.0112 cm. [16] 3. (a) Explain brie y about the characteristics of comminuted products. (b) Explain brie y about the energy requirements in size reduction equipments. [8+8] 4. (a) Explain brie y the requirements that must meet the lter media. (b) Names the various types of industrial and laboratory lter media. [8+8] 5. What is Continuous ltration? Derive following expression and denote all the terms. [16] • mc = 2C P 1 -s gc fn AT a0 µ 6. (a) Discuss brie y Sludge Separators. (b) Derive Expression for Volumetric ow rate corresponding to cut diameter c in Sedimenting Centrifuge. [8+8] 7. (a) Explain the problems confronting the designer of an agitating equipment. (b) Explain the di erence between Agitation and Mixing. (c) Name the di erent types of impellers commonly used for agitation of uids. [8+4+4] 8. With a neat sketch, describe the D-R Denver Floatation machine. [16]
2. 2. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 2 III B.Tech I Semester Regular Examinations, November 2007 MECHANICAL UNIT OPERATIONS-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) Give a brief account of the characteristics of the Tyler standard screens. (b) The screen analysis shown below applies to samples of crushed quartz. The density of the particles is 2650 kg/ 3 and the shape factors are: a = 2 and Fs = 0.571. What fraction of the total number of particles is in the 150/200 mesh increment? [6+10] Mesh no. pi, mm Mass Mesh no. pi, mm Mass fraction, i fraction, i 4 4.699 1.0000 35 0.417 0.0384 6 30327 0.9749 48 0.295 0.0282 8 2.362 0.8499 65 0.208 0.0205 10 1.651 0.5292 100 0.147 0.0147 14 1.168 0.2722 150 0.104 0.0106 20 0.833 0.1132 200 0.074 0.0075 28 0.589 0.0594 Pan ............ 0.0000 2. An inclined apron conveyor is used to carry crushed dolomite to a discharge point at a horizontal distance and a vertical height of 20 m and 4.0 m respectively from the tail end. Find the width of the apron if the capacity of the conveyor is 85,000 kg/hr at a conveying speed of 0.2 m/s. the height of the side walls is one-fourth of the apron width. The bulk density of the material is 1350 kg/ 3 and its angle of response (static) is 350. Take the inclination factor B to be 0.95. The tractive element for the conveyor is in the form of two laminated wheel chains, with wheels running on plain (sliding) bearings. The wheel diameter is 0.05m and that of wheel shaft is 0.02m. Assume the operating conditions of the conveyor are moderate and take the ange friction factor to be 1.2. Determine the maximum chain tension if the minimum tension is to be 1.5 kN. If there standard hauling wheel chains with rated pressure (breaking) strengths of 56, 80 and 112 kN are available, determine which one will suit best to the purpose. [16] 3. (a) Write in detail about tumbling mills with neat sketch. (b) Why closed circuit is preferred over open circuit grinding. [12+4] 4. Give an account of classi cation of screening equipment and indicate their charac- teristics and uses. [16]
3. 3. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 2 5. For a plate & frame lter press, operated at Constant pressure the relation between the volume of ltrate Vf and the time in operation f is as follows. f2= 6 25×104 ( f +0.11) where Vf is cubic meter of ltrate delivered in ltering time f hrs. The cake formed in each cycle must be washed with an amount of water equal to one sixteenth times the volume of ltrate delivered per cycle. The Washing rate remaining constant and is equal to one fourth of the ltrate delivery rate at the end of the ltration. The time required per cycle for dismantling, dumping & reassembling of the press is 6 hrs. Under the conditions where the preceding information applies, determine the total cycle time necessary to permit the max output of ltrate during each 24 hrs. [16] 6. (a) Distinguish between Clari ers and thickeners. (b) Write brie y about: i. Batch Sedimentation ii. Flocculation. [6+5+5] 7. (a) Derive an Expression for the calculation of Power required to drive the impeller of an agitated vessel. (b) What are the values of typical proportions for a standard turbine design in ordinary agitation problem? Explain with a neat sketch. [8+8] 8. Draw Flow sheet of a typical Floatation plant and explain each process individually in brief. [16]
4. 4. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 3 III B.Tech I Semester Regular Examinations, November 2007 MECHANICAL UNIT OPERATIONS-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. (a) What are the various ways to de ne particle diameter, explain with equations. (b) Develop an expression for determining the speci c surface w and number of particles w of a mixture of particles. [10+6] 2. Write the types of mechanical conveyors. Explain any one of the conveyor. [16] 3. A grinder is to be used (which is 8% e cient) to handle 10 tonnes per hour of a siliceous ore (speci c gravity = 2.65). The feed and product analysis are given below: Screen Size, mm Feed Mass Fraction Product Mass Fraction -3.327+2.362 0.143 0.0 -2.362+1.651 0.211 0.0 -1.651+1.168 0.230 0.0 -1.168+0.833 0.186 0.098 -0.833+0.589 0.120 0.234 -0.589+0.417 0.076 0.277 -0.417+0.295 0.034 0.149 -0.295+0.208 0.0 0.101 -0.208+0.147 0.0 0.068 -0.147+0.104 0.0 0.044 -0.104 0.0 0.029 The grinder cost Rs 40,000/-. It operates on 24 hrs basis for 300 days per year and the maintainance, overload and replacement costs amount to 50% power cost. Electricity costs 70 paise per kW. Estimate the annual processing cost of the ore if the work index of the ore is 13.57 kWh/ton. [16] 4. Explain the theory and principle of centrifugal ltration and describe any one of the equipment with a neat diagram. [16] 5. A Rotary-vacuum drum lter having a 33% submergence of the drum in the slurry is to be used lter a CaCO3 slurry using a Pressure drop of 67.0 kPa. The solids Concentration in the slurry is cx= 0.199 kg solid/kg slurry and the lter cake is such that the kg wet cake /kg dry cake=m=2.0. The density and viscosity of the ltrate can be assumed as those of water at 298 K. Calculate the ltrate area needed to lter 0.478 kg slurry/s. The lter cycle time is 250 sec. The Speci c cake resistance can be represented by = 4.37 ×109 (- )0.3 . Where- is in Pascal and is in m/kg.
5. 5. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 3 Data : The density of water = 996.9 kg/m3 Viscosity of water = 0.8937 × 10-3 Pa-sec. [16] 6. (a) Distinguish between Clari ers and thickeners. (b) Write brie y about: i. Batch Sedimentation ii. Flocculation. [6+5+5] 7. (a) Write Power correlations for speci c Impellers? (b) Draw plots showing Power Number vs Reynolds Number and Discuss brie y about Ba ed and Un ba ed tanks. [6+10] 8. Distinguish between Dissolved Air Floatation & Recycle Dissolved Air Floatation plant For water treatment. [16]
6. 6. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 4 III B.Tech I Semester Regular Examinations, November 2007 MECHANICAL UNIT OPERATIONS-I (Chemical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. Distinguish between: (a) Mixing index and mixing number (b) Pony mixer and Beater mixer (c) Ribbon blenders and Internal screw mixers. [6+6+4] 2. Write in detail about the transport of solids with suitable examples. [16] 3. (a) State and explain Rittingers law. (b) Derive an expression for the estimation of the size of the biggest particle that can be caught and crushed between a pair of rolls as a function of roll sizes, roughness of the rolls and the distance between them. (c) The crushing rolls of 101.6 cm diameter are set so that the crushing faces are 1.27 cm apart. The angle of nip for the feed is 310. Calculate the maximum size of the particles which should be fed to the rolls. [4+6+6] 4. (a) Explain Buchner funnel. (b) What are the zones that will present in continuous rotary vacuum lter and explain function of each zone? [4+12] 5. (a) Write brie y about Constant-Pressure Filtration and Constant-rate ltration. (b) Draw gure showing Pressure gradients (section through lter medium & cake) and Explain pressure drop through lter cake in detail. [6+10] 6. (a) Distinguish Gravity Classi ers & Sorting Classi ers. (b) Di erentiate between Clari er and Classi er? Give Example to each. [10+6] 7. (a) Write brie y about blending in Process vessels. (b) An agitated vessel 1.83 m in diameter contains a six-blade straight-blade tur- bine 0.61 m in diameter, set one impeller diameter above the vesse oor, and rotating at 80 r/min. It is proposed to use this vessel for neutralizing a di- lute aqueous solution of NaOH at 21.1 0C with a stoichiometrically equivalent (T)(e))
7. 7. www.studentyogi.com www.studentyogi.com Code No: R05310802 Set No. 4 8. (a) De ne Floatation? Discuss the concept and principle behind Floatation. (b) Write Thermodynamics of wetting brie y. [8+8]