Process optimization
Process optimization is one of the more pleasant and interesting tasks a professional chemical engineer can be called to perform.
For simplicity we can give you our experience with some of the less complex optimization tasks performed. Hopefully one or more of the remarks will help you in your daily optimization efforts. An optimization job usually follows the following path:
- Problem definition. We try to understand the deliverable first. When the study is over, the modifications made and the bills paid, what will be different? Although we have yet to decline a task at this point, we sometimes find that obtaining definition to the deliverable is a very difficult task.
- Data gathering. As part of the data gathering step we ask as many people involved in the operation as we can what the problem is, what the solution is, what has been tried, and what were the results. Even though this sounds like journalism, we don't compile answers and publish the collective opinion. We do this because there may be a very diverse set of opinions regarding what the troublesome operation is supposed to do and what it actually does, and those opinions may conflict with the recorded process data. Understanding this conflict has on occasion helped us determine the root problem with an operation.
- Next we ask for the material balance for the existing operation. If one is not available we generate one based on the process data. Now that we know what the flow streams are, we ask the direct question "What are the flow steams supposed to be?" The answer to this question may require considerable discussion and agreement by operating forces but it is the key to correcting the problem. In our experience have found a variety of situations such as:
- No problem at all. Once everyone understood what was happening. the situation was accepted,
- A tank level control would not work. The subject item was designed for a purpose no one knew and was being operated arbitrarily. Once we figured out what would happen if the level control was removed, the purpose became clear and operating procedures were revised.
- Filter moisture. Operating personnel had made several attempts to reduce filter cake output moisture by adding dewatering devices prior to the operation. The material balance quickly revealed that the filter was doing all it was capable of doing whether the upstream devices worked or not, The perceived losses were directly associated with a product rate increase, and the only corrective action was to replace the filter with a different devise. The filter operation was accepted once operating forces understood the situation.
- An engineer changed a tower reflux to enhance overhead quality, which was achieved. This changed flow rates in the overhead by five fold, increased overhead pressures, and caused large venting losses. Once it was determined that the overhead quality did not need to be increased, the operation was returned to previous conditions.
We repeatedly find that good people doing a good job have a very hard time objectively analyzing their work. We also repeatedly find that the problem that is not clear on the pump curves, the heat exchange calculations, the pipe flow estimates, the vapor liquid diagrams, or vendor cut sheets are almost always clear on the material balance, one of the most powerful tools for the professional chemical engineer.
If you have good people doing a good job and are still in need of process optimization, consider professional chemical engineering.