The issue of draining the jacket of a jacketed reactor
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I currently have a 5M3 enamel-jacketed mixing tank. For process requirements, steam and circulating water are used alternately in the jacket, with the switch between them being controlled via a temperature interlock. The problem is: when switching from circulating water to steam, how should the water in the jacket be drained? If it isn’t drained in time, using steam can pose safety risks. Could you please give some advice on how to handle this issue?
The issue raised by the original poster has been successfully resolved in production: a jacket is equipped with compressed air pipes, and before steam is introduced, compressed air is used to force the circulating water in the jacket back into the main pipeline.
It’s possible to do without compressed air. Install a vent pipe and a vent valve on the steam inlet of the jacket. When the vent valve is opened, the water from the jacket flows out through the outlet at the lower part of the jacket. Close the vent valve again and turn on the steam.
On the second floor, it was mentioned that compressed air could be used, but in practice, it is still necessary to use sight glasses for monitoring; frequent switching between this method and others doesn’t seem to be very efficient. On the third floor, it was suggested to drain the water completely, but 1.5 M3 can be drained in one operation, and if this needs to be done 4-5 times a day, wouldn’t the circulating water be exhausted over time? Are there any other better and feasible solutions?
I am providing my modification design (3M3). For the reactor I use, there are three ports in total: two high and one low. During cooling, one high port and one low port are used, with fluid entering from the low port and exiting from the high port ； When heating, use high inlet and low outlet. Therefore, the cooling water inlet and the condensate water outlet share the same pipe. During cooling, turn off the steam, adjust the process, and use water for cooling. Heating is required; turn off the cold water inlet and outlet, slowly open the steam supply, and use pressure to send the cooling water to the condensate recovery system for reuse as reclaimed water. This process may take some time, but it is very effective. It doesn’t matter if you don’t bother to remove all the remaining water from the jacket; as long as it doesn’t cause any problems, that’s fine. Moreover, the heating and cooling must not be too rapid (this is a requirement for using enamel reaction kettles).
If the heat transfer amount is not large and there is enough space, two sets of jackets can be used. One set for water, one set for steam, with automatic control available. Of course, the manufacturing cost is a bit higher, but it is reasonable considering the frequent need to change water and steam.
The method for the 5th floor should work fine and can be used without issue. As for the concern raised by the original poster regarding water hammer caused by steam, measures can be taken regarding steam intake control; in other words, following the approach used for warming steam pipes, the opening degree of the control valve should be kept very small at the start of steam intake. Once the pressure in the jacket exceeds the back pressure of the drain valve by 0.5 bar, the control valve will switch to its normal operating mode.
I think the suggestion from the second floor is great; that’s exactly what we do, and it works very well!
Following the method mentioned on floor 5 will work fine; that’s how our company does it