Mechanical OperationsNovember – 2005 Part A ( 10 x 2 = 20 marks) 1) Define volume – surface mean diameter. 2) How individual solid particles are characterized? 3) Define open (or) closed circuit grinding 4) State Rittinger’s law (or) Bond’s law. 5) State the basic rule upon which Tyler standard screens are made. 6) What is the meaning of the rotation 14/20 in mesh analysis? 7) Name some filtration equipments. 8) Define filter cake resistance α (or) Filter medium resistance Rm. 9) Define power number Np 10) Define a bin, silo and mention their uses. Part B ( 5 x 16 = 80 Marks) 11. i) Derive from fundamental mass balance, the equation for the efficiency of a screen (8 marks) ii) A quartz mixture having the screen analysis shown below is screened through a standard 10 mesh screen. The cumulative screen analysis of overflow, feed and underflow are given. Calculate the mass rations of overflow and underflow to feed and the overall efficiency of the screen (8 marks) Mesh No Dp mm Cumulative mass fraction larger than Dp Feed Overflow Underflow 4 4.699 0 0 6 3.327 0.025 0.071 8 2.362 0.15 0.43 0 10 1.651 0.47 0.85 0.195 14 1.168 0.73 0.97 0.58 20 0.833 0.835 0.99 0.83 28 0.589 0.94 1.00 0.91 35 0.417 0.96 0.94 65 0.208 0.98 0.975 Pan 0 1.00 1.000 12. (a) Write short notes on the following 1) Particle shape 2) Particle size 3) Specific surface of mixture 4) No. of particles in mixture (Or) b) i) Discuss in detail with diagram, the principle, operation of pneumatic conveying of solids. the formulae for finding the critical speed of a ball mill ii) With a neat sketch explain the open and closed circuit grinding. Or b) i) Show that power No. ii) With a neat sketch. (Or) b) i)Derive the three laws of crushing from fundamental equation. Np is a function of Reynold’s No Nre and Froude No Nfr by dimensional analysis ii) List out the various equation used for the calculation of power delivered to liquids. Bring out the advantages of each. (Or) b) i) With a diagram. volume of filterate collected V. explain the working of a Top suspended basket centrifuge. November 2002 .(8 marks) ii) List out the different methods of storage of solids and briefly discuss about them (8 marks) 13) a) i) Derive from fundamentals. 15) a) i) With a diagram. explain the working of different kneaders used for mixing of solids and pastes ii) Explain any one blending equipment with a neat sketch. derive an expression connecting time of filteration t. specific cake resistance α and filter medium resistance Rm? Find the relation between α and ∆P and hence define compressibility coefficient of the cake. explain the principle operation to working of a filter press. ( 3 x4 = 12) ii) Define work index (4) 14 (a) (i) From fundamentals. 87 and work index Wi = 19.5 mm cube to 2 mm cube.32 is crushed in gyratory crusher.651 1. Trap rock of specific gravity 2.2 12. Part B – ( 5 x 16 = 80 marks) 11. 80% 10% 10% 3.583 0.5 mm cubes to a product having the following sizes. 5) What is meant by differential analysis in screen analysis? 6) Define angle of nip.6 15.5 4. Mesh 4 4/6 6/8 8/10 10/14 14/20 20/28 28/35 35/48 48/65 65/100 Clear opening (mm) 4. (Or) .208 0.1 10.5 Kg / s from 12.50 mm 2. ii) 5 Kg has to be supplied to a machine crushing material at the rate of 0.147 Product weight fraction retained 3. The differential screen analysis of the product is given below. estimate the power necessary for the grinding.417 0.5 6.2 20. 9) Define terminal settling velocity. 4) Define effectiveness of a screen.168 0.3 0.175 mm 2.295 0. 10) Define mixing index.5 Using the Bond method. 7) What are characteristics of an ideal crusher? 8) Write the Bond’s law of crushing.0 18.699 3.5 Kg / s of the same material form 7.Part A ( 10 x 2 = 20 marks) 1) What do you mean by closed circuit grinding? 2) What are filter aids? 3) Define shape factor.833 0.327 2.0 9.25 mm What would be the power required by this machine to crush 0. (16) 12.362 1. a) i) Derive the basic laws of crushing from a single differential equation defining the energy required for size reduction. (Or) b) Explain the various types of mixtures used in industry and discuss the criteria of mixture effectiveness. ii) Classify filtration equipments and discuss any one of them with a neat sketch.b)i) Derive an expression for theoretical capacity of a Roll Crusher ii) A 60 cms diameter Roll crusher takes a feed equivalent to a sphere of 4 cms diameter. How many hours should each filtration run last between shut down in order to obtain the maximum amount of filtrate in a day if the total time required for each cleaning shut down is 1 hour? (10) (Or) b)i) Derive an expression relations the thickness of the cake and the volume of filtrate for filtration at constant pressure.29. If the coefficient of friction is 0. November – 2002 Part A ( 10 x 2 = 20 marks) . 15) a) Discuss on pneumatic conveying of solids and different methods of storage of solids. ii) The performance of filter press is ( V + 5)2 = 78 (t + 0. 14) a) Explain various industrial dust removal equipments with their sketches. What should be the clearance between the rolls for effective crushing? 13a) i) Describe the working principle of a rotary drum filter. Explain how will you conduct the experiment to obtain the data necessary for the design of thickener. (Or) b) Describe the working of a door thickener.2). 2 inches diameter.15 inches diameter? The mechanical efficiency remains unchanged. What should be the power consumption if the capacity is reduced to 10 tons / hr. the power required to crush 12 tons / hr is 9. 10) What are Buckel elevators? Part B 11) i) How do you determine the nature of the feed for size reduction? ii) What do you know about tumbling mills? iii) With the help of neat diagram describe the functions and working of a smooth roll crusher mentioning its parts and applications.35? 5) List out the types of screening equipments. 6) What do you understand by a Gravity settling process? 7) Give a brief account of classification of centrifuges.1) 2) 3) 4) What is the need to characterize particulate solids Define the terms i) Friability ii) Friction Mention the laws of cominution and state Rittingers law What should be the diameter of a set of rolls to take feed of a size equivalent to 1.75 inches diameter and discharges a product of size 0.3 hp. 8) In what way does Filtration differ from other separation techniques? 9) Specify the factors which influences Rate of Mixing. effectiveness / efficiency and the effect of mesh size on capacity of actual screens. ii) How many methods are involved in screening analysis? iii)Discuss and derive the related expressions for the material balance. 13 a) i) What are said to be stationary screens? ii) Distinguish between ideal and actual screens iii) Give a brief account on general laws of settling? iv) How do you separate course particles from liquids? (OR) b) i) Define settling and enumerate the types of settling and sedimentation operations ii) What are said to be centrifugal methods of separation iii) What is a thickener? iv)Discuss the Kynch theory of sedimentation .5 inches spheres and crush 0. ii) Define the Angle of NIP and Discuss the theory pertaining to Blake Jaw Crusher iii) What is a Rotary knife cutter? (OR) b) i) For a crusher which accepts a feed of rock whose size is 0.5 inches if the coefficient of friction is 0. the product size being 0. 12) a) i) Derive the expressions relating to shape factor and particle size. . The resistance of the cloth can be neglected and a constant pressure is used throughout. What are bulk conveyors? ii) What do you understand by silos? iii) Relate the significance of storage and conveying with respect to chemical industries. (Or) b) Write short notes on any four i) Fluid energy mill ii) Trommels iii) Froth flotation iv) Filter aids and filter media v) Banbury mixer vi) Pneumatic conveyors. Estimate the washing time in seconds if 3 m3 of wash water is used. iii) A plate and frame filter press filtering a slurry. (OR) b) i) How do your classify mixing operation? ii) Discuss the variety of mixing liquids with liquids iii) What are kneaders? iv) Enumerate the characteristics of mixing impellers. 15a) i) List out at least four types of conveyors. gave a total of 8m3 of filtrate in 1800 sec and 11m3 in 3600 sec when the filtration was stopped.14a) i) What are pressure filters? ii) How do you make the selection of filtration equipments. CH 1201 – Mechanical operations November / December 2005 1) Define Shaper factor 2) Write three distinctive properties of solid masses 3) Write the different ways of comminution of solid particles in size reduction machines. 4) 5) 6) 7) What is differential screen analysis State the difference between a clarifier and classifier Name the different types of impellers commonly used for agitation of fluids How will you define Reynolds number of agitator inside an agitated tank with agitator speed. calculate 1) the total load to the crusher 2) the effectiveness of the screen Mesh 4 8 14 28 48 100 on 100 through Feed % 14.25 cm apart at the narrowest point.35. explain the operation of a rotary vacuum filter (10) .0 Oversize (%) 20 28 28 24 0 100. What is centrifuging? (6) (Or) b) i) What are the different laws of crushing? Explain their limitations.9 100.0 12 a) i) Classify the equipments used for size reduction. They are set so that the crushing surfaces are 1.5 8.7 2. 9) Define the term specific cake resistance 10) What are the types of conveyors used for vertical transportation of materials? Part B – ( 5 x 16 = 80 marks) 11)i) Differentiate between differential and cumulative screen analysis( 3) ii) Explain the Tylers standard screen series iii) One tonne per hour of calcite is produced by crushing and then screening through a 14 mesh screen. Discuss their basic principles (10) ii) With the help of a neat sketch. According to the screen analysis given below.3 20.0 Undersize(%) 0 40 30 20 10 100. what should be the maximum permissible size of feed and the maximum actual capacity in tons per hour. if the actual capacity is 15% of the theoretical? (10) 13) a) i) Classify filtration equipments. (6) ii) A set of crushing rolls has rolls of 100 cm diameter by 38 cm width face. With the help of a neat sketch. The recommended speed is maximum 100 rpm and the angle of nip is 300.6 5. N? 8) What are filter aids? Name few commonly used filter aids. If these rolls are used to crush a rock having specific gravity of 2. explain the operation of a conical ball mill.0 20.0 28. Constant pressure was used throughout and resistance of the cloth may be neglected. (Or) b) i) Explain constant pressure and constant rate filtration. prove that NP = f ( NRe. ii) Explain briefly the equipment used for ultra – filtration of sludges / suspensions. explain the principle of belt conveyor. 15a) i) What are the various types of equipments used for conveying of solids in chemical industries? With the help of a neat sketch.0.61 m in diameter. ii) Classify the equipments used for blending and kneading. Tank is filled to a depth of 1. Np and NRe and Nfr represent power number.5 gm / cc and viscosity is 12 CP. each having 19 cm width.arm kneader and explain its working. Draw a neat sketch of Two. filtering a slurry gives 25m3 in 60 min when filtration was stopped.83 m with a solution of 50% caustic soda and the turbine is operated at 90 rpm. Calculate the Reynolds number and power consumption for the operation of the agitator if power function is 6. hoppers and silos? Derive an expression for estimating the pressure exerted by granular solid on the floor of a circular bin. 14a) i) Using dimensional analysis. ii) Explain briefly the working principle of screw conveyor with the help of a neat sketch. . Estimate the washing time in minutes if 10m3 of wash water was used. positioned at 0.61 m from the bottom of the tank.ii) A plate and frame press. Tank is 1. Nfr) for Newtonian liquids during agitation inside a tank. Derive an expression for estimating time for a given volume of filtrate in sludge / slurry.83 m in diameter and the turbine is 0. (Or) b) i) Write short notes on the following 1) Mixer effectiveness 2) Ribbon blenders 3) Tumbling mixers ii) A flat blade turbine with six blades is installed centrally in a vertical tank. Tank is baffled and is having four baffles. Reynolds no and Froudes number respectively. ii) What are the common equipment used for bulk storage of solids? Discuss in detail (Or) b)i) What are bins. Given: Density of 50% caustic soda is 1. Dry cake density 1. each 6 cm thick with a pressure differences of 3 abr. ρ of filtrate = 1 gm /cc. Sp. (Or) b) Discuss about membrane and ultra filtration with suitable examples. Clearly state the assumptions (12) ii) How capacity of a screen affects its efficiency (4) 12)a) Explain the working of the Blake jaw crusher with neat diagram (Or) b) Derive the three laws of crushing from the basic differential equation 13) a) With suitable example discuss about the different methods of size analysis (Or) b) Discuss the working of electro static precipitator with diagram 14) a) A CaCO3 slurry in water containing 0. 2) Explain the difference size analysis techniques used 3) What is comminution? 4) Which size reduction equipment can be used for grinding explosive ore? 5) Explain the sedimentation operation.May / June 2006 Part A 1) Explain the term agglomeration of solids. .73 x 1012 cm / gm. The effective filtering area per frame is 1 sq.0723 weight fraction is to be filtered by a 1 m by 1m plate and frame filter press with forty frames.6 gm / cc.gravity of carbonate = 3. Data: µ filtrate = 1. 6) What is floatation? 7) What is cake porosity? 8) Explain kneaders 9) What are silos? 10) What is power number? Part B – ( 5 x 16 = 80 marks) 11) i) Derive the expression for the effectiveness of screen. Compare the merits and demerits of the same.27 x 10-4 m3.1 cp. α= 1. 15a) Derive the expression for the power consumption by impeller mixer (Or) Discuss about the different methods of storing solids.m and the volume of the filtrate necessary to build up a fictitious filter cake ( The resistance of which is equal to the resistance of the filter medium and piping) is 3. Find the volume of the slurry that will be handled until the frames are full and the time required. For the material between 4 mesh and 299 mesh in particle size calculate Ds and Dw .362 0. The temperature during test cycle is 200C. s = 0. 12a) i) Derive the equation for terminal settling velocity. The pressure drop is 500 mm Hg.0251 8 2. 4) Explain the phenomena of concentrate polarization ? 5) Define Froude number and Power number? 6) Differentiate between Bin and Silo. 10) Name different conveyers used in the industry.751. The density of the particles is 2650 kg / m3 and the shape factors are : α = 2. calculate the filter area required to filter 10 kg / min of slurry when the filter cycle time in 5 min.November / December 2006 Part A 1) Name few techniques used to measure the size of fine particles? 2) Define overall screen efficiency? 3) Define rejection coefficient for ultra filtration process.074 Pan -------- Cumulative Mass fraction Xi 0.000 6 3. .168 0.104 200 0.295 65 0. ii) A rotary drum filter with 25% submergence is to be used to filter concentrate acqueous slurry of CaCO3 containing 250 kg of solids per cubic meter of water. Φs = 0.8868 28 0. Assume that filter medium resistance is negligible.4787 14 1. 8) Why heat removal is necessary in size reduction equipment? 9) Differentiate between Agitation and Mixing. Part B ( 5 x 16 = 80 marks) 11 a) i) Give an account of the characterization of solid particles? (8) ii) The screen analysis shown below applies to a sample of crushed quartz. 7) Write the main classification of size reduction equipment.7278 20 0.651 0. α= α0 (∆ p)s For water µ = 1 CP.1501 10 1.147 150 0.9894 0.25.9925 1. Given: α0 = 12 x 10 11 m / kg .699 0.9795 0.589 0.0000 Or b) i) Define sphericity ii) Characterize the particle size for single particle and mixed particles iii) Describe the differential screen analysis and cumulative screen analysis with a neat graph.417 48 0.9616 0.833 0. ρ = 980 kg / m3 .9718 0.9853 0. If the filter cake contains 50% moisture ( wet basis). (8) Mesh no Screen opening Cumulative Dpi Mass fraction Xi 4 4.208 100 0.9406 Mesh Screen No Opening Dpi 35 0.327 0. (8) . ii) Explain briefly pug mills and ribbon blenders? (Or) b) i) Explain fluid energy mill with neat sketch emphasing mainly on the mechanism of size reduction? ii) Define crushing laws with expression? 14 a) i) Derive the expression for the volumetric flow rate in a centrifugal filtration? (10) ii) Write important characteristics of septum’s in any filtration process and name the few industrial filter mediums? Or b) i) Explain briefly about process of flotation and flotation agents? ii) Explain basket centrifuge with neat sketch 15 a) i) Explain briefly about the screw conveyors? (6) (10) (8) ii) The following data are given for a horizontal screw conveyor for handling moulding sand in a foundry: Bulk density of screw = 1600 kg / m3 . the turbine is 0. Diameter of screw = 0. Speed of screw shaft= 40m Reducer efficiency = 0.(Or) b) i) Discuss the settling characteristics of fine solids from liquid using batch sedimentation test? ii) Explain the cleaning of coal by Sink – Float method? 13a) i) A flat blade turbine with six blades is installed centrally in a vertical tank.4 m Screw pitch = 0. Conveying length = 15 m Filling coefficient = 0.5 m in diameter and is positioned 0.32 m.5 from the bottom of the tank. The tank is baffled.5 m in diameter.125.0 Determine the rate of conveying of the material in kg / hour and the motor power. What power will be required to operate the mixer? The value of KL for this situation is given as 65. The turbine blades are 125 mm wide.5 m with rubber latex compound at 650C having a viscosity of 1200 P and a density of 1129 kg / m3. Total coefficient of resistance = 4.77. The tank is 1. The tank is filled to a depth of 1.The turbine is operated at 95 rpm.