MTL – Multiple Plug Flow Reactor SOP

Introduction

This experiment is designed to explore how the diameter of a Plug Flow Reactor (PFR) influences the residence time of fluids within the reactor. Residence time is a critical parameter in chemical engineering, as it indicates the average duration a fluid particle spends in the reactor, which directly affects reaction rates, conversion efficiency, and product quality. By understanding how the reactor diameter impacts residence time, we can optimize reactor design and operation for various chemical processes. This information is essential for scaling up reactions from laboratory to industrial scales, ensuring that reactions proceed efficiently and within desired timeframes.

Do not proceed with testing without following all safety procedures. A basic list of safety considerations is provided in Section II of this SOP.

Figure 1. Multiple plug flow reactor setup.

Safety

• All students must wear safety glasses when working in the lab.
• Never leave this equipment operating unattended.
• Mix all chemicals in a fume hood.
• All chemicals, solutions, and standards must be stored in a sealed container. The container must be labeled with the chemical(s) name (not formula) and concentration, the operator/user’s name, hazards, and the date of storage.
• All chemical containers must be sealed when not in use.
• All unwanted material must be placed in an appropriate container. The container must be labeled “Unwanted Material”. The label must include the chemical(s) name and concentration, the user’s name and contact information, and hazards. If you have questions regarding labeling unwanted materials, consult with the lab manager.
• Only pure water (no additives or contaminants) can go down the drains.

Equipment Description

The tubular reactor experiment incorporates the following equipment:

• Masterflex peristaltic pump: This pump has a switch on the rear panel that must be set to external for the computer system to control the pump (Figure 2).
• PVC reactor tubes filled with glass beads (Figure 3). Each reactor tube is labeled with its volume.
• Opto22 Control System: Data is sampled every second and stored in an Excel-compatible file on the Desktop (in a folder labeled “Data” or similar). See the section on viewing your data for more information. Save your data to a flash drive. The computer is not on the network. For more information on saving data, see the “How to View and Save Data in Excel” section.
• Sensorex conductivity measurement system (Refer to Figure 3 – readout devices may vary). The conductivity range and resolution are labeled below the conductivity meter’s digital display

Procedures

1. Determine what chemicals, calibration standards are required, and measurements you will need to make.
2. Determine the desired inlet flow rate for your solution reactants.
3. Refer to the section on pump specifications and tubing to help determine what tubing is appropriate for your flow rates. Be sure to use only Masterflex tubing. If you are unsure about which tubing to use, check with the lab manager. The smaller the inner diameter of the tubing the lower the flow rate.
4. Pumps may be calibrated using a graduated cylinder/calibrated bucket and a stopwatch. Calibration can either be done using the pump’s RPM (internal pump controls), or percent power (external pump controls – using Opto22 control interface).
5. Reactor setup options:
   • Calibration setup (Refer to Figure 4):
     1. Remove the conductivity probe from the right side of the reactor tubes by unscrewing the cap to the black compression fitting.
     2. Replace the probe with one of the short plastic rods.
     3. Rinse the conductivity probe off with DI water, and then dab it dry.
     4. Place the conductivity probe into a beaker with the desired conductivity standard.

Figure 4. Calibration Setup.

• • Reaction setup (Refer to Figure 5):
    1. Attach a tube to the inlet line located on the left side of the desired reactor tube.
    2. Make sure is connected to the outlet at the top of the tee located to the right of the reactor. Insert the other end into the waste container.
    3. Insert the conductivity probe into the crimp fitting on the right side of the desired reactor tube making sure that all of the ferrules and fittings are placed on the probe in the corrector order (Refer to Figure 6).
    4. Tighten down the crimp fitting cap making sure that the probe is inserted just far enough that the left end of the tape on the probe is just touching the crimp fitting after being tightened, and that it is oriented with the black line pointing upwards (Refer to Figure 7).
    5. Open the valve that’s in line with the desired reactor tube and close the two remaining valves.

Figure 5. Reaction Setup.

6. Power up all equipment (the computer should be on):

• • Switch on the power to the pump by using the grey toggle switch located on the front panel for older pumps or the power switch in the back for newer pumps.
  • The Sensorex conductivity module does not have a switch. It is always on.
  • Do not touch the opto22 control hardware located behind the computer.

7. Using the conductivity measurement system:

• • The conductivity probe is enclosed in a tee fitting connected to the outlet of the PFR. The probe connects to the conductivity transmitter (Sensorex Model CX 100) mounted on the PFR frame.
  • Do not attempt to adjust the calibration setting on the CX105 conductivity meter. You need to verify if the conductivity system is working properly by using the provided conductivity standard (following protocols 8.1 to 8.6). Consult the lab manager if you feel that the meter requires adjustment.

8. Calibrating chemical solutions:
   1. In addition to testing the reliability of the conductivity meter using the standard, you will need to prepare individual concentrations of your reactants and products, and then use the conductivity system to build a calibration curve of concentration versus conductivity.
   2. Set up for calibration as depicted in protocol 5a.
   3. Prepare just enough of the solutions that you prepared for calibration or the conductivity standard to fully submerge the tip of the conductivity probe.
   4. Place the conductivity probe in the solution or conductivity standard. Allow the conductivity reading to stabilize before proceeding with the next solution.
   5. Make sure to rinse the probe with DI water between different solutions.
   6. After the calibration curves are obtained and you have also tested system reliability with the standard, set the reactor to the reaction setup as depicted in protocol 5b.
9. Determine the amount of feedstock you will require.
10. Mix all chemicals/feedstock dilutions in a fume hood.
11. Place your feedstock in 8-liter Nalgene containers available in the “A” lab on the shelf above the chemical storage cabinets (Senior Lab).
12. Feed the outlet stream of the system into a different Nalgene waste container.
13. Verify that the pump and tubes are properly connected.
14. For determining residence time, there is a syringe upstream that will allow you to inject a pulse.
15. Proceed with your experiment using the desired flow rates as previously determined

How to view and save data in Excel

• Do not try to view/open your data while the system is running. This will cause it to stop data collection.
• Save data to a flash drive after each trial.
• If you have any questions, please ask for assistance.

If you are running one trial:

1. Once all your required data have been collected, exit the Opto system.
2. Open Excel, click “Open” and navigate to the correct data folder on the desktop (labeled “Data” or something similar).
3. At the bottom of the Excel window, click on the drop-down window and select “All Files”. This will display the data files collected, organized by date.
4. Double-click on the file you wish to open. The Text Import Wizard will open.
5. Select Delimited. Then click Next. Then select Comma Delimited and click Next. Select the General Data format option and click Finish. The data should now be displayed in Excel
6. Save your data to a flash drive by clicking “Save As” and selecting your flash drive as the destination. Ensure that you label your data properly and thoroughly to avoid confusion.
7. Eject the flash drive.
8. Follow the rest of the shutdown procedure specified in the equipment SOP (see the section labeled Shutdown, below).

If you are running several trials in one day:

1. Leave the Opto system running.
2. Open File Explorer and navigate to the correct data folder, on the desktop (labeled “Data” or something similar).
3. Organize/sort by date if you have not already done so. Your data should appear at the top of the list.
4. Right-click on your data file and “cut” the file (or press Ctrl X after clicking once on the file).

Note: this will effectively cut the data that were collected up to that point into a file and begin a new data collection (a new file will be created with the same name as the file you cut) as soon as it is cut.

5. Paste the cut file to a flash drive and rename it with a proper label. Ensure that you are labeling your data thoroughly to avoid confusion.
6. Eject the flash drive and save it to your personal device.

To open in Excel on your personal device:

1. Open Excel. Next, click File/Open and navigate to the saved data on your flash drive or device.
2. At the bottom of the Excel window, click on the drop-down window and select All Files. This will display the data files collected, organized by date.
3. Double-click on the file you wish to open. The Text Import Wizard will open.
4. Select Delimited. Click Next, select Comma Delimited, and then click Next. Select the General Data format option and click Finish.

Shutdown

1. Drain the reactor and store any solution you wish to save in a properly labeled Nalgene container. Consult the lab manager regarding chemical storage.
2. Flush the system with DI until the conductivity meter reads <100 microsiemens, and then drain and dispose of the water. Confirm disposal protocols with the lab manager.

Note: This step must be repeated for each reaction tube used during your experiment.

3. Label all containers, following appropriate labeling protocols.
4. Properly dispose of any unwanted material. Consult the lab manager for guidance.
5. Switch off the power to the pump. Either place the toggle switch in the center for older pumps or flip the power switch on the back of the pump for newer pumps.
6. Do not attempt to switch off the Sensorex conductivity module.
7. Exit the Opto control software. Do Not shut down the computer.
8. Save your data to a flash drive. The computer is not on the network.