Remote Distillation Experiments via the Internet
Jim Henry and Murat Ozkaya
and
Chemical Engineering
University of Tennessee at Chattanooga
Chattanooga, Tennessee, USA
Introduction
As an outgrowth to remote control systems applications (see other chapter in this book on that), a much more complex system with many inputs and outputs was developed for a distillation column. The remote distillation column consists of 12 bubble-cap trays, 3kW electric resistance heater (tubular heating rods) inside a 15L partial reboiler, and feed tray located between trays 6 and 7. The schematic of the distillation column is shown below in Figure 1.
Figure 1: Schematic of Distillation Column
The computer shown above in Figure 1 is connected to the distillation column and is able to send input commands to start an experiment with initial specifications (reboiler power, reflux %, and feed rate) and receive many outputs including all tray temperatures, reboiler power and pressure, cooling water flow rates and temperatures entering/leaving the condenser, and distillate, feed, bottoms flow rates. All of this is sent to an internet database where the output data can be seen on several graphs. This allows for the user to analyze what is happening at all times.
Scenario
The faculty, staff and studnets involved in the development of this system are in the chemical engineering department at UTC. Distillation is a required course for chemical engineers and this is a way of applying the knowledge to run experiments in the lab and then analyze the data received. This can either be done by the main computer connected to the distillation column or by anyone, anywhere in the world with an Internet connection.
Remote experimentationinvolves at least two personnel; one would be the user anywhere in the world that wants to run an experiment, the other is the operator of the distillation column who prepares the distillation column for operated. The operator gets initial specs for the experiment from the user either by e-mail or phone. Communication is the most important part of this process to flow smoothly. Having a device that receives emails, text messages, and phone calls at all times is important for both personnel; international users can use Internet communications. This way an experiment can be scheduled for a certain date and time, all preliminary questions about the experiment can be answered beforehand and both student and operator communicate at least 30 minutes before scheduled time for confirmation.
For a scheduled distillation experiment, the student informs the operator of the initial specifications which include: batch or continuous process and the initial concentrations of each liquid in the mixture to be distilled. The student should plan ahead on what reboiler power and reflux ratio will be used once the system reaches steady-state. In the next step; the operator prepares the mixture with the specified concentrations and fills the reboiler up with this initial mixture. After the reboiler is filled and the column is checked for safety, the operator runs a few tests to ensure the column is operating properly. Then the operator sends an email to the student to let them know the column is ready for the scheduled experiment and give detailed instructions to follow.
The control panel of the program which both personnel and anyone else can see is shown in Figure 2below:
Figure 2: Control Panel of Distillation Column
The information that needs to be input on the screen includes username, power, reflux %, and feed pump. For a batch experiment the feed pump will remain at 0. Any username can be entered, but in order to run an experiment for longer than 20 minutes a 4 digit PIN code must be entered anywhere within the username box.
Initial settings for reboiler power and reflux % should always be 3000W and 100% respectively. These settings will be changed once the mixture reaches boiling point and the trays reach a steady-state temperature. Once the student is ready, the experiment can begin by clicking the green “START” button on the control panel. The distillation control panel can be opened by going to downloading the necessary plug-in run time engine, and opening the website again. Control will then be transferred to the student. The operator can anytime regain control from the main computer in case the student makes mistakes. More than one student or any other person can go to the same website and be an observer of the experiment’s control panel.
Once the START button is pressed, LabVIEW will send signals to start the distillation column. An experiment ID will appear (or change) on the top right hand of the control panel which indicates that the output data is being saved into a database which can be accessed from the internet.The output data given by LabVIEW include all the tray temperatures, reboiler power, pump settings, reflux ratio and %, cooling water temperatures, and reboiler pressure. On the top right of the distillation panel in Figure 2, the student can see what the total time allowed for the experiment is. If the pin code is not entered, this time will indicate one minute which means the experiment will only last a minute. If the correct PIN code is entered in the username slot, then the total time indicated should say 20 minutes.
A “Continue” button will appear on the control panel. By clicking this button the experiment will be extended by another 20 minutes which will change the total time to 40 minutes and so on. This is our method of making sure the student is there and paying attention to what’s going on. It’s important for the student to know that this is not a simulation program, but rather operating an actual distillation column remotely thru the internet. If the student forgets to click continue, then he/she must restart the experiment with a new PIN code that only the operator has. ThisPIN code gets sent to the operator program every time a new experiment is started. The student can run the experiment for up to 9999 minutes by simply clicking the “Continue” button every 19th minute of 20 minutes. Once the experiment is complete, the user must click “STOP” button and LabVIEW will shut down the distillation column.
All of the data output by LabVIEW is sent to an internet database, which can be accessed easily by the user or other team members so that he/she/they can analyze what’s happening at all times. It is recommended that the student should view both the control panel and the graphs from the website just mentioned since the control panel only shows the reboiler and the reflux tray temperatures. A sample graph of an experiment is shown below in Figure 3.Anyone can review experimental data of any of the experiments of the past several years by going to that web site; type in “Illinois” or “WPI” in the search box and click on the arrow.
Figure 3: Sample graph of output results by LabVIEW into Internet Webpage
The figure above is a sample of what the user can access through the internet. The graphs on the left can be left-clicked with the mouse to show as the main graph. The “Pumps” graph is very important analyze since it shows how often the distillate, feed, and reboiler pumps came on and off which leads to the calculation of those flow rates.
There are several web cams that students can continuously view what is going on in the column. There is a camera focused on the reboiler, the condenser and feed port. (The column is made of glass, so all these can be observed from an external camera.) The link to these cameras is on the web site at .
Technical description
Scheduling
The user must schedule a day and a time to run an experiment with the operator of the distillation column via e-mail. This must be done at least one day in advance so that the operator can schedule to be free at the time of the experiment.
Security
The remote distillation column is secured by a program called WatchDog. WatchDog shuts the distillation column down in the event of any failure of the control computer. Anytime the server loses internet connection with the server, the reboiler shuts off at the end of that 20 minute period to avoid continuous heating of liquid contents inside.
When a user wants to run an experiment, he/she must type in a 4-digit PIN code inside the “User Name” box on the control panel in order to run a 20 minute experiment. This 4-digit code is reset anytime the “START” button is clicked on the control panel and a new code is generated. This code is sent to the cell phone and email of the operator which allows the operator to receive the new code instantly as a text message on the cell phone. Without this PIN code, LabVIEW is programmed to run only a 1 minute experiment. The column will shut down after 1 minute. This means that without permission and email confirmation by the operator, the user cannot run an experiment. This recent security change was made due to internet users trying to start experiments without knowledge of the operator, which is a safety hazard since this is not a simulation but rather an actual operation of the distillation column. Once the PIN code is typed in and experiment is started, the user can run the experiment for an unlimited time as long as the “CONTINUE” button is clicked 1 minute prior to stop time as mentioned before. This recent security change was made so that the system makes sure the user is aware and alert of the experiment taking place. Also, as long as the user is aware, the experiment can run for any time and this allows one smooth graph on the internet database.
How to access it
User access to the remote distillation column begins by going to Internet Explorer. Then the user is informed to download a certain (free) plug-in named LVRun.exe. After the installation of this plug-in, the webpage is refreshed to allow connection with the control panel. From there, the user has access to the distillation column although the operator can regain control at any time using the host control computer. In our most recent papers, we have looked at learning gains by the students.
Quality
We believe the remote distillation operation in labs is very useful, besides applying the theory learned in unit operations course, in teaching good communication and team work in education. The users learn what to do and how to react when unexpected errors occur.
Experiences
We have had teams of users from several USA universities (Michigan, Illinois and Worchester Polytechnic University). With the latter two institutions over the past few years we have assessed students’ learning (Henry, 2009, DiBiasio, 2010 and 2011). Statistically speaking, we have found no significant difference in students’ learning whether they ran experiment locally (at WPI) or remotely (at UTC). The students in these studies were sophomores running canned experiments. The student reports had mistakes with energy balance calculations and typical confusion over quantitative comparison of experiment to Rayleigh analysis. Students expect exact comparisons yet reality is never that predictable.
Economics
This distillation column (at UTC) was purchased in 1982 for a cost of US$40,000. Adding in installation, upgrades and maintenance, it is reasonable to estimate the cost of the column to be not far from US$200,000. This does not include a building and floor space. For remote operation of the column, users are charged at approximately the marginal cost of operation (supplies and labor); which is MUCH less that the column’s cost.
Future work and conclusions
Future work involves improving the distillation column operation by upgrading to a new computer with a much faster processor and updated software (LabVIEW 2009) which is already in progress.
References
DiBiasio, David (2010), Jim Henry, William M. Clark and Marina Miletic, “Student Learning in Hands-On, Remote, and Virtual Laboratory Experiences: What Works (or doesn't),” American Institute of Chemical Engineers, Annual Meeting, Salt Lake City, UT, USA, 2010.
DiBiasio, David(2011), Jim Henry, Murat Ozkaya, Jerrod A. Henderson, William M. Clark and Marina Miletic,
“Hands-on, Remote, and Simulated Labs: Is There a Productive Synergy?” American Institute of Chemical Engineers, Annual Meeting, Minneapolis, MN, USA, 2011.
Henry, Jim (2009), Marina Miletic andDavid DiBiasio, (2009). Understanding StudentLearning in Remote andHands-on LaboratoryExperiences,” American Institute of Chemical Engineers, Annual Meeting, Nashville, TN, USA, 2009.