Wiped Film Distillation Operation - Post 3

Wiped Film Distillation Operation - Post 3

Maintaining Your Distillation

Once your distillation is established, it is important to maintain it. Distillations can change over time, so monitoring them is critical to obtain desired results.

There are several reasons for this. The biggest reason is it takes time for all parts of the system to completely warm up. The large flanges are big heat sinks, so it can take several hours or even an 8 hour shift for the system to stop changing outputs slightly. In addition, systems need to be monitored to make sure nothing has gone wrong. Vacuum pumps can seize up, gear pumps can stop working, chillers can kick out. The only way to make sure everything is going well is to physically check the entire system every couple of hours.

A check of the system should look like this: Create a data sheet and record the critical setpoints and ACTUAL readings for the system. This generally includes vacuum, evaporator temperature, feed rate, condenser temperature and cold trap temperature. Then see if anything has changed. Finally, if possible, collect a timed sample of each product stream and verify that the desired distillate split has stayed constant.

If the distillate split has changed, make an adjustment to return to the desired split. For instance, if you started with 20% distillate, and now you have 22% distillate, the correct response would be to turn down the evaporator temperature a degree or two to bring the split back to 20%.

One quick note: Many operators run their systems overnight without personnel present. They do this because wiped film distillation is a robust, dependable process. If you have large enough receivers, this should be ok, IN THEORY. But this is not recommended. Power outages happen. Heaters kick out. Gear pumps clog and back up. When you run up to 7 wiped film still systems every day for over 6 years, you see all the things that can happen. This approach is a gamble, and one that should come with a risk assessment. If it won't be prohibitively expensive to lose that entire batch and dangerous to clean it off the floor, perhaps the risk would be worth it. But it is BETTER to check in at least every 2 hours.

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Picture courtesy of Pope Scientific, Inc.