Armfield Distillation Column Operation Guidelines

Transcription

1 Armfield Distillation Column Operation Guidelines R.Cox Safety SAFETY GLASSES ARE REQUIRED WHEN OPERATING THE DISTILLATION COLUMN Wear gloves when mixing alcohol feedstock The column will become hot, use caution and were gloves when appropriate. THE COLUMN OPERATOR MUST REMAIN AT THE COMPUTER AND CONTROL CONSOLE WHILE THE COLUMN IS IN OPERATION. Equipment / Procedure Overview The distillation column takes about 45 to 90 minutes to reach steady-state. Plan on shutting the column down by 4:30 pm to allow the feedstock to cool. Given the time required for startup and shut down you will want to pay particular attention to planning and preparation. First, operate the column by charging the reboiler with tap water only. Operate the column in total reflux to get a feel for the heater and reflux valve controls. Determine the type of solution you want to distill. Determine calibration standard requirements. Mix the feedstock and calibration standards. Proceed with the distillation process. Before operating the column familiarize yourself with the location of the valves, flowmeters and thermocouples. Temperatures are measured using type K thermocouples. Refer to the column diagram for location of thermocouples. Refer to the equipment photos for clarification of hardware descriptions. Refer to the Distillation Docs folder on the desktop for more info. Valves are labeled as follows: V1 Reboiler outlet to bottoms tank V2 Reboiler Drain V3 Reflux sample V4 Tops sample V5 Condenser water flow control V6 Manometer Valve bottom of column V7 Manometer valve top of column V8 Dosing vessel Not Used V9 N/A V10 Decanter / Tops drain valve V11 Bottoms product drain V12 Tops products drain to reboiler V13 N/A V14 Cooling water to vacuum line Not Used 1

2 Data collection, Stop & Go Buttons Data & Info Icons View Diagram Icon Data Collection Stop / Go Button Enter cooling water flow and column pressure here Enter pump speed here in ml/min. 2

3 Push buttons to light LED s Power on here Set to I/O Port Don t adjust these controls Filtration experiment water valves. Do not open. Condenser drain tube must be inserted into drain pipe. Main distillation condenser water supply valve. CLOSE WHEN FINISHED! 3

4 Sample tube: Discard 1 st sample. Close tube clip and valve V3 after taking sample. Reboiler sight tube with tape indicating minimum fill level 4

5 Lift front pump cover to access tubing area. Make sure pump is off first. Inserting tubing into pump. Don t pinch tubing on corners. 5

6 The drawing above does not show Valve V1 or the reboiler overflow rotameter. 6

7 Run the column with water For your first experience with the column you may want to skip the section on preparing the feed stock and calibration samples and start with the equipment startup procedure. Plan on spending the first lab period operating the column with water. This will give you an opportunity to get a feel for how the column is operated. Filling the Reboiler and Preparing Feed Stock Consult with your professor and determine the concentration of alcohol you require in your feedstock. Use either pure or denatured ethanol or isopropyl alcohol and tap water. Do not use D.I water. Feed stock is pumped to the column from a 5000 ml glass feed vessel. There is a second 5000 ml glass feed vessel that may be used for storing additional feedstock to be used during the day s run. Do not use the second glass feed vessel for storing feedstock overnight. Place the cap with the siphon tube on the glass feed vessel you wish to use. Fill the reboiler with water or feedstock as instructed by your professor. Note the difference between the reboiler and the 5000 ml feed vessel. The recommended volume of solution to place in the reboiler is 5.5 Liters. The reboiler must be filled with approximately 5.5 liters in order for the low level alarm to clear. Preparing Calibration Samples Determine the range and number of calibration standards you will need to build a calibration curve. You will analyze your calibration standards using the densitometer or refractive index instruments. The lab manager will instruct you on the use of these instruments. Storing feedstock and calibration samples Make your calibration standards and store them in an appropriate container. Be sure to label your samples with the material, concentration and group name. Consult the lab manager for assistance on storing your samples and feedstock. Mix the feed stock and store it in an 8 liter Nalgene container. These containers are located in 3520A on top of the cabinets. Label the container with your group name, the type of solution and the concentration. All flammable feedstock must be stored in the flammables cabinet. At the end of each lab period you will need to drain the column and store your feedstock in Nalgene containers. Place the labeled containers in one of the flammables cabinets. Equipment Startup Procedure 1. Turn on the control console by switching on the breaker switches. The up position is on. The gray switch is the main power, followed by individual breaker switches (blue=reboiler heater, red=feed pump/reflux valve, pink=console instrumentation). Turn on the Main breaker first and then the individual breakers. 7

8 2. Ensure all dials on the control console for the Reflux Control, Reboiler Heater, and Feed Pump are turned to the I/O Port position. See photo. 3. Log on to the computer, the user name is administrator the password is password. 4. Open the UOP3CC software (icon is on Desktop). 5. In the lower right-hand corner ensure IFD: OK (F###) is displayed. This indicates the computer and control console are communicating properly. 6. Click on the View Diagram icon (first icon on the right of the grayed out cut/copy/paste icons). This will bring up the GUI, Graphical User Interface. See photo. COLUMN OPERATION PROCEDURE (Batch Total Reflux) 1. Ensure the following valves are CLOSED: V1, V2, V3, V4, V5, V6, V7, V8, V11, V12, V14, V15 2. Ensure that valve V10 is open. (note: there is no valve V9 or V13) 3. Verify that the white tubing condenser drain line- is securely inserted into the blue drain stand-pipe located behind the distillation control module. See photo. 4. The reboiler incorporates a level sensor. If the liquid level in the reboiler is not at least equal to the height of the orange tape on the reboiler sight tube, approximately 5.5 liters, the software will not allow the reboiler to heat. Lack of sufficient liquid in the column is indicated by the low level warning light in the GUI. See photo. 5. Filling the reboiler: Remove the fill cap on the top of the reboiler and, using a funnel add approximately 5.5 liters of tap water or feedstock to the reboiler. Approximately 5.5 liters is the minimum amount of liquid required to clear the low level alarm on the reboiler. Turning on the Condenser Cooling Water Turn on the main condenser cooling water valve located behind the column at the bottom of the water pipe (Red handle ball valve). Do not fully open the valve! Only open the valve about a quarter of the way. Note the yellow handle ball valve next to the Red Valve, DO NOT operate the yellow valve, it is for the filtration experiment. See photo. Adjust valve V5 to set the desired condenser cooling water flow rate, a good starting point is 1000ml/min. Typical operating range is ml/min, adjust this parameter as required. Setting the Controller On the controller, set the Reflux Control, Reboiler Heater and Feed Pump to I/O port and push in the black button above each knob to set the controller to on, the LED above the control knob should lite for each section listed above. See photo. The Column and Process sections on the controller are for manual operation without a computer. You do not need to adjust these controls. Heating the reboiler (PID 1) The reboiler may be operated in either manual or PID (automatic) mode. Click on the PID 1 icon on the main graphic display. This will open the reboiler heater PID controller window. When operating in manual mode you must take care not to allow the column to overheat. It is recommended to operate the reboiler in automatic mode. a) Set the mode of operation to automatic. 8

9 b) Enter the desired set-point. Note that the set-point is the temperature of thermocouple #7, not the temperature of the reboiler liquid. The recommended starting set point is 85 deg C. You will adjust the set-point as you develop your method. Do not adjust the Proportional band, Integral time or Derivative time. c) Click on apply, and then OK. Note the PWR level display is reading 100%. This will gradually reduce as the temperature set-point is reached. d) The warning indicators on the left side of the GUI (Graphic User Interface) should all be green except for the low level indicator on the top. If the low level indicator is red, this indicates that the reboiler does not contain enough liquid. If the other warning lights are not lit green this indicates that the on button for that function is not depressed on the control module. See photo. Reboiler Overflow / Feed Pre-Heat Valve V1 Valve V1 is shown on the left, the overflow rotameter with the feed pre-heater and bottoms vessel are shown on the right. With the reboiler overflow / feed pre-heat valve V1 open, liquid in the reboiler that exceeds the level of the overflow valve will flow through the reboiler overflow rotameter, through the column feed pre-heater and into the bottom vessel. In addition to preheating the feed, setting this valve to the open position allows for the measurement of the bottoms vessel feed flow-rate by reading the flow on the rotameter. The rotameter incorporates a valve that allows for regulation of this reboiler overflow to the bottoms vessel. Valve V1 may be set to the closed position when operating the column in total reflux. 9

10 Valve V1 is often set to the open position when operating in partial reflux. Be sure to check with your professor to determine how this valve should be utilized. Reflux Valve Operation The reflux valve may be operated in either total reflux (OFF) or in Manual mode. In manual mode (partial reflux) the operator may set the reflux ratio to the desired setting. Do not use automatic mode it does not function. Disregard all parameters in the automatic operation section of the PID controller window. Setting the Reflux Valve for Total Reflux (PID 2) Initially you will want to operate the column in total reflux mode. To do this; set the Mode of Operation to OFF, click apply and then OK. Setting the Reflux Valve for Partial Reflux using Manual Mode Control (PID 2) a. Click on the PID2 icon and select manual mode. b. Enter a ratio in the Reflux Ratio Initial window. c. Do not enter a value in the rate of change window d. Click on the start button. e. Click on apply and then ok. f. To stop the reflux valve from operating, click on the stop button. In manual mode (partial reflux) the reflux valve switches at a frequency of 10 seconds. Adjusting the reflux ratio controls the distillate distribution, sending distillate to either the column or the tops container, within the 10 second interval. For example; for a ratio of 4:1 condensate will be directed to the column for 8.0 seconds and to the top product receiver for 2.0 seconds = 5; 10/5 = 2.0; 4 x 2.0 = 8.0 By entering a reflux ratio of 3 : 1 the reflux valve with switch the flow of distillate to the tops vessel for approximately 3.3 seconds and then to the column for approximately 6.7 seconds. A value of 4:1 = ~2.5 secs to tops, ~ 7.5 secs to column. Another example: By entering a value of 1 in the initial window to make the ratio 1:1, the reflux valve will switch every 5 seconds, with 5 seconds of flow going into the column and 5 seconds of flow going into the tops container. Fill the feed bottle Verify that one of the 5000 ml feed stock bottles is filled with your feedstock as described earlier. The feed pump operating rate range is between ml/min. Pumping the feedstock Insert the tubing into the pump a. Verify that the pump speed is set to zero. Enter the pump speed (0) in the drop down window next to the F1 symbol on the GUI. 10

11 b. Lift the top of the peristaltic pump cover and Insert the tubing into the peristaltic pump making sure not to pinch the tubing and then close the cover. See photo. Note the path of the feed line: The feed line connects into a tee fitting; the outlet of the tee connects to the bottom of the bottoms product heat exchanger which allows for pre-heating of the feed stock before it enters the column. The feed exits the top of the bottoms product heat exchanger and is fed to the column. The feed temperature is measured at the center feed location, see T14 on the GUI. Select the column feed port. Typically the column is feed by connecting the pump outlet to the center feed location as labeled on the column. Do not adjust the feed port unless instructed to do so by your instructor. Setting the pump speed / flowrate. It is advisable to calculate the feedstock flow rate before operating the column. Typically the feedstock flowrate is between 5-50 ml/min. This is not a recommended flow rate, just a typical range. If the feed flowrate is too high the flowrate out of the reboiler overflow valve may exceed the range of the reboiler overflow rotameter. The symbol F1 on the distillation GUI represents the pump. Enter the pump speed in the drop down window next to the F1 symbol. The units are milliliters per minute. The range is between 0 and 300 ml/min. Manometer Reading on GUI Pm The window on the GUI next to the letters Pm allow you to manually enter the pressure drop across the column as read from the glass manometer located on the left side of the distillation column frame. You may also use a handheld Dwyer electronic manometer to measure the differential pressure across the column. Consult the lab manager for access to the Dwyer manometer. Whatever value you enter will be saved to the data file. The computer does not automatically update this information. Cooling Water Flow Reading on GUI Fr The window on the GUI next to the letters Fr allow you to manually enter the cooling water flowrate as read from cooling water flowmeter. Whatever value you enter will be saved to the data file. The computer does not automatically update this information. 11

12 Recording Data The system will not record data until you press GO a. To begin recording data, press the green GO button on the GUI (above the condenser on the GUI of the column). See photo. b. Press stop when you wish to end data collection. Operation Guidelines 1. As the column heats you will begin to see vapor rise up the column and start to see bubbling on the lower trays. You will also see liquid flowing from the condenser into the decanter, then back to the column through the feed pipe in the rear of the column above the top tray. 2. Adjust the reboiler heater set point as required to get a consistent amount of bubbling on the trays without flooding the column. A simple definition of column flooding is: the column is flooded or starting to flood if the liquid level in the lower tray(s) has reached the bottom of the tray above it. To stop flooding, lower the heater set point. Adjusting the column temperature to the optimum level is as much an art as a science. The column has reached thermal equilibrium when the temperatures in the column are stable. Liquid samples can be taken using the procedures under Taking Measurements TAKING MEASUREMENTS Sample liquid is hot! Use caution when taking samples. Wear leather gloves and a lab coat as needed. Make sure you click on the Go button to begin data collection. Select the Stop button to stop the data collection. Prior to taking measurements, discuss measurement and sampling procedures with your instructor or lab manager. Column pressure drop is measured by the water manometer on the left of the column. VALVE OPENING AND CLOSING MUST BE DONE IN THE ORDER BELOW TO AVOID GETTING VAPOR IN THE MONOMETER. a. Open valve V6. b. Open valve V7. c. Take a reading. d. Close valve V7. e. Close valve V6. A note on taking samples: Tops products samples may be taken by opening V3 and releasing the tube clip. Discard the first sample as it will be old. Tops products samples may also be accessed through V4 located at the bottom of the tops product vessel. 12

13 Bottom samples can be accessed from the reboiler drain valve, V2 located at the bottom of the reboiler, they may also be taken from the bottoms vessel using valve V2 and the peristaltic pump to drain the bottoms vessel. Samples from each tray may be taken using a syringe. Consult the lab manager for instruction on taking tray samples. Viewing the Data To view the data click on the View Table Icon To view the data as a plot click on the View Graph icon To modify the way the data is plotted on the graph select Format Graph Data. The graph data is of limited valve, the table data is the data that you will export to excel. Saving and Exporting the Data The computer is not on the network save your data to a flash drive after each run. DO NOT plug your flash drive into the USB ports on the front of the computer, doing so will lockup the computer and you will need to reboot the system. Connect your flash drive to the USB extension cable that is visible in front of the control console. If you close the software without saving your data the data will be lost! Once you have collected data, you must save it as an excel file before exporting it. To save the data, click on the stop icon to stop data collection. Go to- file-save as, then click on the drop down menu to select the Excel file type, select save. Save your data as a.vts file if you wish to view it later in the distillation software. Only files saved as a.vts file can be opened by the distillation software. System Shutdown a. Begin shutting down the system at 4:15pm. It will take about 30 minutes for the feedstock to cool down enough to safely store it in the Nalgene containers. b. On the main control unit turn off the three individual break switches and then turn off the main power switch. c. Once the feedstock has cooled to 80 degrees C, drain the contents of the reboiler into an 8 liter Nalgene container using the valve located beneath the reboiler. Use caution and wear gloves when draining the reboiler. The feedstock is HOT. d. If there is liquid in the bottoms vessel, pump it into a Nalgene container using the peristaltic pump located next to the column. e. Close the main condenser water cooling valve (ball valve) located behind the column. f. Save your data to a flash drive. 13