Operating Instructions

Transcription

1 Operating Instructions 1. Preparation of Organic Feed. 1. To avoid flooding the columns during start-up, check that the main valves for water (VS1) and organic phase feed (VF2) on the 1 st floor are closed (see Figure 1). Figure 1. Front view of the LLE system (1 st floor). 2. Check the liquid level in the Isopar M/MEK feed tank located on the 3 rd floor (see Figure 2a). 3. If amount of feed is insufficient for the entire lab period, transfer the content of the raffinate tank (located on the 1 st floor) to the feed tank: On the 3 rd floor (see Figure 2a and Figure 3): Open valves V34 and V36 Close valves V31, V32, V33, and V35. On the 1 st floor (see Figure 1 and Figure 2b): Open valves VR3 and VR4 Close valves VF1 and VF2. Turn on the return pump located next to the raffinate tank. Wait until all liquid is pumped out of the raffinate tank. Turn off the return pump. 4-1

2 Figure 2. LLE tanks: (a) Feed and solvent tanks on the 3 rd floor; (b) raffinate tank on the 1 st floor. Figure 3. Piping around the feed mixing pump (3 rd floor). 4. If the amount of feed is still insufficient after the transfer from the raffinate tank, ask the lab technician to transfer some of Isopar M from storage to the feed tank. 5. Mix the feed (see Figure 2a and Figure 3): Open valves V31, V33, V35, and V36. Close valves V32, V34, and V37. Turn on the mixing pump and let it run for about 20 minutes. Note: If the feed is poorly mixed, there may be large fluctuations in the feed composition, which would make it difficult to reach a steady-state. 6. While the mixing pump is running, go down to the 1 st floor and prepare the waste drums (see Section 2). 7. After mixing is complete, take a sample from the feed tank and measure concentration of the MEK in it. Recommended concentration is 10-20% by volume. 4-2

3 8. If the MEK concentration is too low, transfer the necessary amount of MEK from the nearby MEK tank (see Figure 2a and Figure 3): Open valves V33, V35, V36, and V37. Close valves V31, V32, and V34. Turn on the mixing pump and monitor the level changes in the feed and solute tanks. Turn off the mixing pump after the level in the feed tank has reached a desired valve. Repeat steps 5 and Prepare to feed the LLE system: Open valves V31 and V32 Close valves V33, V34, and V

4 2. Handling Waste Water/MEK Mixture The waste water/mek mixture should be collected in 55-gallon drums located outside on the containment pad (Figure 4). WARNING: Do not jump off the loading dock to access waste collection drums use the stairs. Before the experiment 1. Get the drum wrench, the red float assembly, hazardous waste labels, and a pen from one of the drawers of the desk in front of the fume hood. 2. Get the key to the cover of the waste drums from the lab technician. 3. Unlock and remove the drum cover (see Figure 4). The cover should be lifted by at least two students. Lift the cover straight up until it clears the drum tops and then place it on the ground near the drums. 4. Check the drum usage log and choose a (partially) empty drum. Do not start a new waste drum if there are drums that are only partially full fill up those drums first! 5. If you need to use a new waste drum, fill out the yellow hazardous waste label and attach it to the drum. Do not date the label until the tank is full and is ready to be picked up by EH&S. 6. After choosing a drum, use the drum wrench to remove the large and the small caps from the drum (see Figure 5). WARNING: Unscrew the caps slowly to bleed the pressure from the drum. Keep your face away from the caps and wear eye protection. 7. Check the level of liquid in the drum by the measuring stick (usually located near the fume hood). Each tick mark on the stick corresponds to 1 gallon in the standard 55 gallon drum. Record the level in the log. 8. Attach the grounding clip (located in the center of the platform) to the drum to be used. 9. Screw the red float level indicator into the small opening in the drum top (see Figure 5). 10. Place the metal hose into the large opening in the drum top (see Figure 5) and open the waste valve VE4 (see Figure 4). Figure 4. Waste drums outside of the building. Waste drums are under the cover. The cover should be removed at the start of the experiment and placed back and locked when done. 4-4

5 During the Experiment 1. Monitor the red float which begins to rise when the drum is nearly full. Note that this happens very quickly. Do not let the level rise above two inches from the top of the drum. IMPORTANT: One on the group members should watch the drums constantly to avoid spills. If a drum overflows, the group must pour absorbent to cover the spill and contact the lab technician. The clean-up procedure takes about 1.5 hours and must be done before anyone can leave the lab. Figure 5. Waste drum setup. The drum caps should be unscrewed using the drum wrench. The waste hose and the level indicator should be placed into the large and small openings, respectively. 2. When a drum is full a) Date the yellow hazardous waste label attached to the drum. b) Open another drum and move the waste hose and indicator into it. Be careful when transferring the hose to avoid spills! c) Cap both of the openings in the top of the full drum. d) Fill out the yellow hazardous waste label for the new drum: specify the chemicals and their approximate concentrations and attach the label to the drum. Do not date the label until the drum is full. After the Experiment 1. Measure the liquid level in the waste drum and record it in the log. 2. Close the waste valve VE4, remove the hose and the level indicator, and cap both openings in the drum top. 3. Place the plastic cover on the drums and lock it. 4-5

6 3. Start Up 1. Make sure that the feed valves on the 3 rd floor are set correctly (see Section 1) and that the mixing pump is turned off. 2. Purge the liquid left in the feed line from the previous lab: a) Open the purge valve VF1 (see Figure 6). b) Close the valves VF2 (see Figure 1) and VR2, VR3, VR4, and VR5 (see Figure 6). c) Let the fluid flow into the raffinate tank for several minutes. d) Close the purge valve VF1. Figure 6. Feed, feed purge, raffinate, and extract lines near the raffinate tank. 3. Calibrate the rotameter for the organic feed. This is necessary because the density and viscosity of the organic feed is different from that of water (used in the factory calibration of the rotameter): a) Make sure that the column feed inlet valves (VF6) are closed for all columns. b) Open the main feed valve VF2. c) Use the feed control valve VF3 and the feed rotameter R F to control and monitor the flow rate of the organic phase. d) Place a beaker below the calibration port and open the valve VF5 (see Figure 1). 4-6

7 e) Collect the organic phase for a set period of time and close the valve VF5 when done. f) Measure the volume of the collected organic feed and calculate the flow rate. Note the rotameter reading corresponding to this flow rate. g) Repeat steps (c)-(f) for several flow rates. 4. Select a column for the run. Check that the inlet valves (VF6 and VS3) to other columns are closed. 5. Set up the selected column: a) Open the outlet valves for the raffinate (VR1, see Figure 7) and the extract (VE1). b) Open the inlet valves for the feed (VF6) and the solvent (VS3, see Figure 7) 6. Close the extract valves VE2 (see Figure 6). 7. Introduce water by rotameter into the column: a) Open the main solvent valve VS1. Water will flow into the column through the solvent line connected to the column top (see Figure 7). Figure 7. Top of a column. b) Control the water flow rate using the solvent control valve VS2 and monitor the flow rate using the solvent rotameter R S (see Figure 8). c) Fill the column with water until water covers all column packing. d) Open one of the extract control valves VE2 (see Figure 6). e) Use the solvent control valve VS2 to adjust the water flow rate to the desired value. f) Adjust the extract valve VE2 to stabilize the water level. The stabilized water interface should be located above the packing and below the raffinate line (see Figure 7). 4-7

8 Figure 8. Controls for feed and solute flow rates. Important: Make sure that water does not flow into the raffinate line. If this happens, we will have to separate water from the organic phase in the raffinate tank. Adjustments to the extract valve VE2 often need to be very small, ¼ turn or less. One of the group members should be responsible for observing and controlling the water level with this valve at all times during the experiment. 8. When the water level is stable, introduce the organic feed into the column: a) Open the main feed valve VF2 (see Figure 1) b) Use the feed control valve VF3 and the feed rotameter R F to control and monitor the feed flow rate (see Figure 8). 9. Wait until an interface between the aqueous and organic phases is formed near the top of the column. 10. Adjust the extract control valve VE2 to stabilize the interface above the top of the column packing but below the interface line. Do not change the inlet flow rates of water and the feed while adjusting valve VE2. The goal is to stabilize the interface while maintaining desired feed and solvent flowrates. However, if the interface keeps rising and you cannot control it with the extract valve VE2, shut off the main water valve (VS1) to drop the interface level and prevent water from getting into the raffinate tank. It is recommended to start the experiment with low feed and water flow rates in order to learn how to control the organic/water interface level at the top of the column. 4-8

9 4. During an Experimental Run Adjust the flow rates of water and organic feed using the corresponding control valves. Recommended flow rates are: For organic feed: 5 to 15 l/h For water: 15 to 25 l/h 2. Control the interface level by adjusting the extract control valve (VE2) to maintain the level above the column packing but below the raffinate line. 3. Samples of the organic feed, raffinate, and extract should be taken through sample ports by opening valves VF4, VR2, and VE3, respectively, every minutes until the system reaches a steady-state. 4. Determine MEK concentration in each sample by measuring its (i) refractive index and (ii) density. Note that the density measurements are useful for determination of the MEK concentration in water but not in Isopar M (make sure you understand why!). Refractive index should be measured using a table-top refractometer Density of water/mek mixtures should be measured by a hydrometer. 5. Once the concentrations are measured, check the mass balance for MEK to determine if the column is at a steady state. You can assume that the system has reached a steady state if the flow rates of MEK entering and leaving the column differ by less than 5%. 5. Changing Columns 1. Shut off the organic feed by closing the main feed valve VF2. 2. Close the extract valve VE2, but keep the solvent inlet line open. This will increase the water level in the column so that the organic phase (located above the interface) is pushed into the raffinate line at the top of the column. 3. When the organic phase/water interface is about to reach the raffinate line, close the main water inlet valve (VS1) immediately. 4. Close the column s raffinate valve VR1. 5. Open the extract valve VE2 and drain the liquid from the column to the waste drum outside. 6. Close the column s extract valve VE1. 7. Close the extract valve VE2. 8. Prepare another column, following steps 4-10 of Section Shutting Down 1. Shut down the column by following steps 1-8 of instructions for changing columns. 2. Close the organic feed valves V31 and V32 on the 3 rd floor. 3. Close waste valve VE4 outside, remove the hose from the waste drum, and cap both openings of the drum with correct plugs. If the drum is full, date the yellow hazardous waste label attached to the drum. This will let EH&S know that this drum is ready to be picked up.

10 4. Dispose of the remaining hazardous waste: a) Place used Kimwipes, pipette tips, and gloves into the container for hazardous solid waste. b) Empty beakers and graduated cylinders containing samples into the appropriate waste containers and close the containers. c) Place used sample vials into the appropriate waste container. The vials do not need to be emptied. Notes: Make sure that a waste container is labeled before you start using it. If you need to start a new container, fill out and attach a yellow hazardous waste label to it before use. A hazardous waste label attached to the waste container with vials should read used sample vials containing Water, Isopar M, and Methyl Ethyl Ketone. The containers for liquid waste and vials should be closed when not in use. Do not fill the containers all the way up. 7. Turn off the light in the fume hood and close the hood sash. 4-10