UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge8.0 Disc Bowl Centrifuge Faculty Lee Kong Chian Faculty of Engineering and Science Department: Department of Chemical Engineering Unit Code and Name UEMK3431 Chemical Engineering Lab 2 Experiment No.: 8 Title of Experiment: Disc Bowl Centrifuge Laboratory Room No. and Name: KB509 Process Control & Reaction Laboratory Experiment Duration (hour): 4 hours Number of Student per Group 5 Students Equipment and Materials Quantity estimation Item Description *Item category (e.g. per set/group of student) Disc Bowl Centrifuge E 1 Weighting scale E 1 Deionised water C 2.5 LITER Beaker (1 L) W 3 Beaker (500 mL) W 2 Measuring cylinder 500 mL W 3 Spatula W 2 Waste bottle W 5 LITER Cooking oil C 2.5 LITER Dish washing detergent C 1 BOTTLE *Item category SP Sample or specimen C Consumable CH Chemical W Labware, glassware, tool, and components E Equipment S Software To demonstrate the effect of product type as throughput. For disc bowl centrifuge. Separation occurs as the heavy phase liquid experiences a higher magnitude of centrifugal force causing it to settle on the outer collecting ring while the lighter phase liquid is collected on the inner collecting ring. To demonstrate the separation of heavy phase liquid. 2. Both can be used to separate either solids from liquids or two liquids of different density. The solids do not have to travel far before hitting a disc and effectively being separated. There are two main types of centrifuge: tube bowl centrifuge and disc bowl centrifuge. 2. Disc centrifuges range from 10 cm to 75 cm in diameter. the liquids are separate as they flow along the centrifuge or the solids are thrown towards the wall. The tube bowl is simply a tube rotated about its axis. ur of the denser droplets or the particles is given by: r 2 ur 1 2 d 2 18 (1) where = rotational speed of centrifuge . the feed is admitted near the base and passes up through holes in the disc (which are actually inverted cones). Overflow dams at the outlet end allow the two phases to be collected separately.0 OBJECTIVES OF EXPERIMENT To understand disc bowl centrifuge working principle.0 INTRODUCTION Centrifugal separators are used to separate solids from liquid or liquid from liquid using the principle of centrifugal force. Solids then continue to move outwards and are either removed manually or through nozzles on the periphery as concentrated slurry. The discs are about 5 mm apart. To calculate the separation efficiency.1 Operating Equations for Tube Bowl Centrifuge The radial velocity.UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge 1. spin speeds are in the 1000's or rpm range. Liquid-liquid centrifuge separates two liquids of different densities by spinning at relatively high speeds. then half the particles with diameter d will be collected. This gives the distance traveled in the residence time tres as r 2 u r t res 1 2 d 2 t res 18 (2) If the feed is homogeneous and the distance moved is equal to half the total thickness of the liquid layer. V t res Q (4) where V = volumetric holdup Q = volumetric throughput V 2 d 50 r 2 1 2 V Q t res 9 r2 r1 g 1 2 d 502 V r 2 2 18 g r1 r2 2u t 50 (5) where ut = terminal velocity under gravity of the d50 particle . hence we can treat the radius r of rotation as a constant . thus r2 r1 u r t res 2 (3) where r1 = radii of the inner overflow dams r2 = radii of the outer overflow dams In order to compare centrifuges of different design it is convenient to use a relationship which links the throughput with a term which accounts for the nature of the materials and one which accounts for the physical design of the machine. In this case d = d50 (this only applies if the concentration of one phase in the other is very small).UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge The liquid layer thickness is small compared to the tube diameter. feed system and control panel mounted on the stainless steel frame. collecting vessels. For scale up on the same duty Q1 Q2 1 2 (6) Values of are given by manufacturers.UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge V r 2 g r1 r2 = is a characteristic of the centrifuge design only and is equal to the area of gravitational settler required to do the same duty. This is a bench top unit comprises of an epoxy coated frame. . The speed of the motor can be varied from 8500 to 12000 rpm using an electronic speed controller. The throughput of the feed system is at least 150 LPH.0 EQUIPMENT – DISC BOWL CENTRIFUGE The disc bowl centrifuge unit is designed to demonstrate the separation of a heavy phase liquid using the principle of centrifugal force.2 Operating Equations for Disc Bowl Centrifuge 2n r23 r13 2 3 g tan (4) where r1 = inner radii of the disc stack r2 = outer radii of the disc stack n = number of spaces between the discs = cone half-angle 3. feed reservoir. variable speed motor. 2. 1: Disc Bowl Centrifuge Figure 3.2: Disc Bowl Centrifuge Setup Components .UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge Frequency Mixing Inverter Tank Disc rpm Meter Disc Bowl Main Power Switch ON/OFF Liquid Collecting Outlet AC Motor Figure 3. 2. 4.5 L and cooking oil 2.1 Pre-experiment Procedures 1. 3.UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge 4. Read and understand the equipment used in the experiment (disc bowl centrifuge). Prepare the following apparatus and materials needed for the experiment: Disc bowl centrifuge 1 2 L500 mL beaker 1 2 1 L beaker 4 3 Measuring Cylinder 500 mL 2 3 Weighting scale 1 Deionised water 2. Read the safety precautions and chemical hazards before conducting the experiment.0 OPERATING PROCEDURES 4.5 L Spatula 2 Waste bottle 5 L Dish washing detergent 1 bottle . Read and understand the theory of centrifugation. Wipe all the parts and dry them. Check the disc rpm meter and ensure that there is reading shown in the meter when the motor is running.2 General Start-Up Procedures 1. Press the ‘Run’ green button on the frequency inverter. Do not remove the liquid collecting outlet tray when the motor is running. switch off the machine.0 SAFETY PRECAUTIONS Do not use the apparatus for solid-liquid separation. liquid collecting outlet tray and the disc bowl. No body part should be inserted to the belt pulley system when the motor is running. Fill the mixing tank with 3 .3 Cleaning Procedures 1. 2. Run the unit by setting the frequency to about 20 Hz. When all the water is drained out. Ensure the motor is running. Place all the parts back to it original position. 7. .UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge 4. 5. 4. 4. 5. Wear gloves when cleaning the solution container. 2. 4. Remove the mixing tank. Place the apparatus on a level table. Connect the 3-pin plug to main power supply. Test run the motor by adjusting the turning knob on the frequency inverter to around 10 Hz.4 litres of hot water. Avoid oil leaking and spilling on the floor and working surfaces. Turn on the power supply and main power switch at the front of the control panel. 6. Be aware of the slipping hazard when handling cooking oil. The apparatus is ready to use if all the parts and components are working well. 5. Do not attempt to change the setting of the speed meter and frequency inverter. Clean it with cleaning detergent and warm water. 3. 3. UEMK3431 Chemical Engineering Laboratory II Exp 8: Disc Bowl Centrifuge 6. .0 EXPERIMENTS 6. explain why it is not possible.3 Experiment 2: Density Determination Determine the density of the test fluid (take note of the unit used). How does the speed of the bowl affect the separation efficiency? 2. explain how does this affects the separation efficiency. If No. show your estimations. 6. Can we separate two solutions with densities near to each other using a disc bowl centrifuge? Why? 3.0 RESULTS ANALYSIS AND DISCUSSION Discuss all your results. 6.1 Experiment 1A: Investigate the Effect of Frequency on Centrifuge Separation Conduct the experiment with two different solutions at 4 different frequencies (max at 30 Hz). The questions below only serve as a guideline. repeat the experiment using different ratio (mixture with different density). 4. Allow the apparatus to run for 3 minutes then record down the speed of the bowl. As the proportion of water to oil changes. Reminder: Mix both solutions and determine the density before separation. 7. Is it possible to estimate the separation efficiency using the data you obtained in the experiment? If Yes. 1. Your discussion should not only limit to these questions.2 Experiment 1B: Investigate the Effect of Density on Centrifuge Separation By using the same setup as Experiment 1A.