Process Area Activity – [I See Now-28]: The Thermometer Is Not Broken

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This post was last edited by *lihuagong on 2016-10-26 10:32. Abnormal temperature occurred in the reactor during the first vacuum distillation of the ethylene glycol aqueous solution using the intermittent method. In the later stages of distillation, the temperature inside the reactor rises significantly, remaining around 172 degrees; the temperature at the top of the tower is normal, and no adjustments to the heating system manage to lower this temperature. Moreover, the ethylene glycol sampled at this time had a significantly increased content of high-boiling substances. It’s unclear whether it’s a malfunction in the valves of the heating system or a problem with the thermometer; the cause cannot be determined for now. The equipment was modified from an original reactor; the valves are new, so there should be no problems. The thermometer was also checked and it’s fine. When I had no idea what to do, I wandered around near the kettle; by chance I looked down at the gauge lenses and suddenly realized that the thermometer wasn’t in the liquid. That was the problem – the thermometer wasn’t malfunctioning; what was being measured was the temperature of the gas phase, not that of the liquid. Since it was originally a reaction kettle with the thermometer inserted at a relatively shallow depth, and it has now been converted into a distillation kettle without the thermometer being replaced, as the liquid level dropped the thermometer came out of contact with the liquid. So a longer thermometer was replaced, and the temperature reading became normal.