Operating Instructions Preparation for Start-up 1. If the computer system is logged off, log into the computer system. Log into the operator account on the computer. Please ask your TA for username and password. Click DeltaV Operate on the menu in the center of the screen 2. Check the fluid level in the reboiler using either the sight glass or the sensor data in the control system. The level should be around 50-70%. If the level is too high or too low, seek assistance from the TA/Lab Assistant. 3. Mix the contents of the reboiler: a. Close the transfer valve (see Figure 1). b. Open the recirculation valves (see Figure 1) c. Use the computer control system to turn on the reboiler mixing pump (see Figure 1). Let it mix for about 10 minutes. Figure 1. Overview of the East Column (EC) system on the 1 st floor. 4. While you are waiting: a. Check that the manual bypass valves on the distillate and reflux lines are closed (see Figure 2). 3-1
b. Check that the following control valves are set to the closed position in the control system: Distillate (2 nd floor, see Figure 2) Steam (1 st floor). c. Use the computer system to fully open the reflux control valve (see Figure 2). d. If you will be running at partial reflux conditions, check that the EC distillate tank located on the 1 st floor is empty (see Figure 1). If not, ask the TA to help you transfer content of the distillate tank to the reboiler. 5. Take a sample of the batch in the reboiler from the reboiler sample port (see Figure 1). 6. Use a Gas Chromatograph (GC) to determine composition of the reboiler content. Figure 2. Overview of the EC system on the 2 nd floor. 3-2
Note: Start-up The column should always be started at total reflux. It can be switched to partial reflux after it has reached a steady-state at total reflux. The sequence of turning on the utilities is the following: 1. Compressed air (low cost), required for operating pneumatic control valves. 2. Cooling water (somewhat expensive), required to prevent system from overheating. 3. Steam (highly expensive). The sequence will be reversed while turning the utilities off. Do not leave the column unattended. If a pneumatic valve malfunctions, use its corresponding manual bypass and notify the lab supervisor. Starting-up at Total Reflux 1. Manually open the air valves on the 1 st and 2 nd floors. 2. Manually open the main water valves on the 1 st and 2 nd floors. Water is needed for cooling the steam condensate (1 st floor) and condensing the top product (2 nd floor). 3. Use the control system to open the steam valve. Recommended steam flow rate is about 100 lb/hr. The temperature of the liquid in the reboiler should now be slowly rising. 4. While you are waiting for the column to warm up on Day 1, perform GC calibration. 5. After about 20-30 minutes, you should see flow of the distillate from the condenser. The flow can be directly observed through a glass standpipe connected to the condenser (see Figure 2). 6. Allow a stable liquid level to be attained in the standpipe. If the standpipe starts overfilling, use the control system to turn on the reflux pump (see Figure 2) for a few seconds to drain the excess liquid. Reduce the steam flow rate to prevent recurring overfilling of the standpipe. 7. Start taking product samples to check whether the system has reached a steady-state. It is recommended to use reflux samples for this purpose, since the reflux sample port is located on the 2 nd floor and is close to the control room. Take samples at regular time intervals (10 minutes is recommended). It takes about an hour to reach a steady-state. Switching to Partial Reflux (Week 2) 1. Open and close appropriate manual valves to send distillate from the condenser on the 2 nd floor to the distillate tank on the 1 st floor. In particular, make sure that correct valves are open and closed around the EC distillate tank (see Figure 3). Note that valves with red tags should be kept closed while the column is operated at partial reflux. 3-3
2. Open the distillate control valve and adjust the reflux control valve to achieve a desired reflux ratio. Note that, in order to initialize flow through the distillate line, you may need to briefly turn on the reflux pump after you have opened the distillate valve. This is necessary to flush air out of the piping. Figure 3. East reboiler and distillate tanks (1st floor) 3. Take samples and measure the composition of the distillate and the bottoms at regular time intervals. 4. Periodically adjust the reflux and distillate valves to maintain constant reflux ratio (the valves need to be adjusted due to changes in the product composition over time, which leads to the change of the vapor flow rate). 5. At the end of each run, pump the material from the distillate tank back into the reboiler to ensure that the initial concentration for the next run is the same as in the pervious run. This makes comparison between different runs more meaningful. To transfer the content of the distillate tank back to the reboiler: a. Open the transfer valve (see Figure 1). b. Close the recirculation valves (see Figure 1). c. Ensure that appropriate valves are open and closed to enable fluid flow from the EC distillate tank (see Figure 3) to the transfer pump (located behind the distillate tank) and then to the reboiler. d. Use the computer control system to turn on the transfer pump. e. Stop the pump when the level in the distillate tank reaches zero. 3-4
Shutting Down 1. Use the computer system to close the steam control valve. Important: Use the manual mode of the valve control to ensure that it is fully closed (i.e. it is 0% open). This is necessary because the automatic mode is not guaranteed to fully close the valve, even if you set the flow rate to 0. The automatic valve controller stops closing the valve as soon as the steam flowmeter reads zero. Since the vortex steam flowmeter in our system is not designed to work at low flow rates, it is likely to read zero even when the valve is still slightly open. 2. Turn off the reboiler mixing pump. 3. If the system is running at partial reflux, return it to the total reflux: a. Open the reflux control valve to 100%. b. Close the distillate control valve. 4. Close the manual water and air valves on the 1 st floor. 5. Wait until the liquid flow in the standpipe is negligible. Use the reflux pump to drain any standing liquid from the standpipe. 6. Close the manual water and air valves on the 2 nd floor. 3-5