Operating Instructions

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Cleopatra Bond
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1 Operating Instructions Determining Sample Composition Using Refractive Index (RI) Analysis Throughout this experiment, you will use a refractometer to determine compositions of water-eg mixtures. Concentration of ethylene glycol in a sample is determined by comparing the refractive index (RI) of the sample to the refractive indices of water and ethylene glycol using the following formula: volume (10) Preparation for Start-up Feed Preparation 1. Check that the feed valve on the 2 nd floor is closed. 2. Check that sufficient amount of feed is available in the supply tank on the third floor. 3. Check with the TA whether the feed needs to be mixed. If so, perform the following operations: a. Close valve V-a and open valves V-b, V-c, and V-d (see Figure 6). b. Plug in the mixing pump and mix the feed for about five minutes. c. Unplug the mixing pump. 4. Open valves V-a and V-b for flow leaving the supply tank and close the recycling valve V-c. 5. Take a feed sample from the supply tank and determine the feed composition using the RI analysis. Pump power supply V-a V-b V-d V-c Figure 6. Feed Tanks. 3 1

2 Emptying the Product Tanks NOTE: You need to empty the product tanks both before you start the experiment as well as during the experiment due to the limited tank capacity. 1. Close all air valves V20-23 and intake valves V11-V14 connected to the product tanks (see Figure 7). 2. Open vacuum valves V15-18 connected to the product tanks (see Figure 7). Steps 1 and 2 are necessary to prevent flow of liquid from the product tanks back into the system. 3. Open the air supply valve VA (see Figure 8). 4. Open the air valve (V20-23) connected to the product tank (see Figure 7). 5. Drain each product tank (one at a time) following these steps: (Wear safety goggles while draining product tanks!) a. Open the air valve on the product tank. Let the tank pressurize. b. Tilt the black receiving bucket toward the outlet tap to minimize splashing. c. Open the outlet valve at the bottom of the tank. Let all liquid drain into the bucket. d. Close the air valve and then the outlet valve for the product tank. e. Empty buckets in the appropriate waste bins. 6. Keep valve V19 open! Valve V19 Vacuum valve V15-18 (green line) Pressure Intake valve (V11-14) gauge Air valve V20-23 (white line) Outlet valve (V24-27) Figure 7. Product tank. Configurations of all product tanks are similar. Different numbers for each valve shown in this figure refer to similar valves on different tanks. 3 2

3 Supplying Water to the system There are several sets of water supply valves to be turned on: 1. Main water supply (Figure 8): Open the valves V2, V3 Water valves V2, V3 Keep this air valve closed at all times Air Valve (VA) Keep these water valves closed at all times Main steam valve (V8) Figure 8. Air, water, and steam valves. 2. Water Supply for the heat exchanger for cooling the bottom product (Figures 9, 10): Open the valve V4 3. Water supply for the condenser for the top product (Figures 9, 10): Open the valve V5. Use the needle valve to adjust the flow rate of the cooling water. Recommended setting: about 8 gpm. 4. Water supply for the steam injector (Figure 11): Open the main valve (V6) and the supply valve (V7). 3 3

4 Valve V4 Cooling water bottom product Valve V5 Needle valve Cooling water for top product Figure 10. Heat exchanger for cooling the bottom product. Figure 9. Water controls for the heat exchanger and the condenser Valve V6 Valve V7 Figure 11.Water valves for the steam injector 3 4

5 Supplying Steam and Evacuating the System Steam in this system is used for two purposes: (1) heat the evaporator walls and (2) create vacuum using the steam injector. 1. The first time steam is used, ask the lab assistant for assistance. 2. Open the main steam valve V8 (see Figure 8). Wear gloves! This line will be hot! 3. Supply steam to the heating jacket of the evaporator by opening the valves V9 on the steam line (see Figure 12). Close when sending steam to the system Keep these valves fully open Figure 12. Valves for steam supply to the evaporator Valves V9 Open to send steam to TFE 4. Supply steam to the injector by SLOWLY opening the valve V10 valve. This valve is located at the back of the apparatus (see Figure 13). Wear gloves! This line will be hot! Condenser for steam injector Steam pressure indicator Steam injector Steam valve V10 Figure 13. Steam injector setup. 3 5

6 The steam pressure gauge should read about psi. You can control pressure in the TFE chamber by adjusting the steam pressure in the injector. 5. Create vacuum in the product tanks by opening all vacuum valves (V15-18) on the product tanks and the condenser (see Figure 7). Evacuation vacuum pressure should be between 15 in Hg and 30 in Hg Start-up 1. Open the intake valves on the back of the product tanks. 2. Open feed valve VF (see Figure 14) to start flow of the feed solution to the evaporator from the third floor. Use the feed valve to adjust the feed flow rate. Recommended flow rate: below Important: the numbers on the feed rotameter do not correspond to the actual flow rate of the water-eg mixture. Therefore, it is necessary to calibrate the rotameter prior to starting the experiment. This can be done by the bucket and stopwatch method. 3. Turn on the motor driving the evaporator rotor blades with the motor switch (see Figure 14). If necessary, see lab manager for key to open the lockout switch. 4. Wait until temperature of the top product stream reaches 88 and temperature of the bottom product becomes larger than that of the top product. Motor switch Feed valve (VF) The thin film evaporator is now fully operational. Feed rotameter Figure 14. TFE feed valve and motor switch. 3 6

7 Switching between Product Tanks during the TFE Operation It is important that you do not perturb the continuous operation of the system when you switch between the tanks. Otherwise, you may not be able to reach a steady-state. 1. Simultaneously close the intake valves on the full tank and open the intake valves on the empty tank (see Figure 7). 2. Empty the full tank following the instructions for Emptying the Product Tanks given above. 3. Re-establish the vacuum on the emptied product tanks by opening the vacuum valves V20-23 while the air valves are closed. 4. Make sure the vacuum valves V15-18 are open and the condensed air valve is closed while the tanks under them are collecting the product. 5. After emptying the tank, obtain the mass of the product. Use this information to estimate the products flow rate. 6. Determine the product composition using the RI analysis Shutting Down 1. Turn off the motor for the rotor blades (see Figure 14). 2. Close the feed valve VF (see Figure 14). 3. Close the main steam valve V8 (see Figure 8). Wear gloves! This line will be hot! 4. Close the steam valves V9 to the evaporator (see Figure 12). Wear gloves! This line will be hot! 5. Close the steam valve V13 to the steam injector (see Figure 8). Wear gloves! This line will be hot! 6. Close water valves V2-7 (see Figures 8, 9, and 11). 7. Close valves V-a and V-b on the line leaving the bottom of the supply tank (see Figure 6). 8. Empty the product tanks (instructions for emptying the product tanks are given in the Startup procedure). 9. Close all valves (air, vacuum, intake, and outlet) on the product tanks. 10. Close the master air valve VA (see Figure 8). 11. Check the tanks for pressurization. If they are pressurized, open the outlet valve to relieve the pressure. 3 7

8 Data Collection and Analysis 1. Record experimental conditions for each experimental run, including: steam pressure, pressure in the TFE chamber, feed flow rate, and feed composition. 2. This system takes long time to reach a steady state. In order to ensure that the steady state has been reached, take samples periodically (15-20 minutes) during each experimental run and record results of your measurements in the following table: Measurement Time RI top RI bottom W top W bottom T top T bottom Here, W is the weight and T is the temperature. 4. Use the information collected in the above table to compute the compositions and flow rates of the product streams. 5. Due to long time required to reach a steady-state, you will not have enough time to repeat each experiment 3 times in order to estimate the experimental error. Instead, you can use the time-averaging, i.e. use the last 3 samples taken from each run to estimate the mean values and standard deviations of the measured quantities. Of course, you need to verify that the last 3 measurements correspond to a steady-state! 6. To verify reproducibility of your results, run at least one experiment under the same conditions on two different lab days. 3 8

UNIVERSITY OF MINNESOTA DULUTH DEPARTMENT OF CHEMICAL ENGINEERING ChE 3211-4211 ABSORPTION OF CARBON DIOXIDE INTO WATER

UNIVERSITY OF MINNESOTA DULUTH DEPARTMENT OF CHEMICAL ENGINEERING ChE 3211-4211 ABSORPTION OF CARBON DIOXIDE INTO WATER OBJECTIVE The objective of this experiment is to determine the equilibrium line,