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Solid Handling

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  EKC 493 Chemical Engineering Laboratory III (Unit Operation Lab) 1 EXPERIMENT 4 SOLIDS HANDLING STUDY EQUIPMENT .   The exercises in this module consist of four separate experiments as follows: Experiment A: Removal of Dust from a Gas Stream Using a Cyclone Experiment B: Size Reduction Using a Ball Mill Experiment C: Screen Analysis Using Sieve Shaker Experiment D: Determination of Mixing Index of Solids All the above experiments are related to solids handling which is an important in many  process operations. The experiments are arranged in a single ring as shown in Figure 4.1  below. Figure 4.1 The Experimental Rig  EKC 493 Chemical Engineering Laboratory III (Unit Operation Lab) 2       −    ×100%   (A1) ∆  12      The rig consists of a cyclone, ball mill, a screen separator and a mixer. Application of the rig for different experiments are detailed below. 4.1 Experiment A: Removal of Dust from a Gas Stream Using a Cyclone. 4.1.1 Introduction: Cyclone is a settling device in which a strong centrifugal force, acting radially, is basically used in place of a relatively weak gravitational force acting vertically. Normally, cyclone is used for removing particles with sizes of greater than 10 µ m. Unless the particles sizes are greater then 25 µ m, the efficiency of a cyclone very often does not exceed 90%. 4.1.2 Theory The collection efficiency n (%) of a cyclone can be calculated from the following equation: where, (mass in - mass out) is the mass collected in the collector. The pressure drop, AP, is given by the following equation: (A2) where      2  (i.e. the column inlet velocity number  P =  pressure drop v 1  = inlet gas velocity   = gas density A = inlet cross-sectional area K = cyclone configuration constant D P  = outlet pipe diameter  EKC 493 Chemical Engineering Laboratory III (Unit Operation Lab) 52 Since gas velocity is proportional to the gas volumetric flow rate Q, the pressure drop is then directly proportional to the square of the velocity. High collection efficiency is normally related to high pressure drop. Simple cyclone usually has pressure drops within 0.5 to 2.0 in. H 2 O to 2.0 in. H 2 O whereas high collection efficiency cyclone usually has pressure drops between 2.0 to 6.0 in. H 2 O. 4.1.2   Experimental Procedure In this experiment students will be demonstrating ejector and cyclone operations. Students must be familiar with each items included in the cyclone system before operating. This experiment requires approximately 100 g of particle sample (e.g. food particles) having size smaller than 22 mesh. 1.   Make sure all connections are tight before starting the experiment and there is no  particles left over in the system. 2.   Place a collecting pan under sieve with 22 mesh number. Sieve the sample and determine the density of the sample collected in the pan. 3.   Switch on the air compressor and close its valve. The compressor will stop automatically when it reaches the pre-set pressure. 4.   Weigh accurately 5.0 gram of particle sample. Fill the particle feed tube with the sample. Put the feed tube into the sample beaker. 5.   Open the air compressor valve and adjust the flow meter reading to 20 liter/min. Notice that pressure drop changes with any variation in the gas flow rate. Record the pressure drop from the manometer. 6.   Insert the flexible feed hose into the feed tube so that the particle sample is sucked out  by the ejector and goes into the cyclone. 7.   When the feed tube is empty, close the air compressor valve. 8.   Determine the weight of the sample collected in the collecting tube, discard the sample. 9.   Before proceeding with a different gas flow rate, remove the sample left over (if any) from the system. This can be done by passing a high velocity air through the  EKC 493 Chemical Engineering Laboratory III (Unit Operation Lab) 4 From equation (A2), Velocity, v 1  system for about 30 seconds. (CAUTION: Very high air velocity might cause the manometer liquid to shoot out). 10.   Repeat steps 4 to 9 for various flow meter readings from 30 to 40 liter/min.  Note: If the pressure is too low, wait until it reaches the pre-set pressure before  proceeding with step 5. 4.1.3   Results 4.1.5 Report 1.   Complete all the data in Table 1.  2.   Record ambient temperature (°C) and pressure (atm.)  3.   Plot (a) (v 1 ) 2  versus experimental AP and (b) Q versus n Flow meter Reading 20 to 40 lit./min. Gas flow rate, = Q lit./min. Weight of sample in feed tube  _   W S,total  gram Weight of empty collecting tube = W c  gram Pressure drop =  P mm H 2 O Weight of collecting tube + sample = W c + s  gram 4.1.4 Calculations  Weight of sample (in collecting tube) = W c + s - W c From equation (A1), Efficiency,   =

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Sep 22, 2019

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