2 replies to this topic

[cat]

What could cause the accumulator (flash drum) to deviate from VLE?

Design is a typical cryogenic system. This is a c3 ref system for ethylene. We have an accumulator, downstream of it is JT valve that feeds to a kettle type heat exchanger. This heat ex interchanges with a ethylene (a separate c2 BOG system) and the vapor being generated is fed to c3 BOG compressor. The discharge of the BOG compressor goes to a condenser with CW and goes back to the accumulator.

We are topping up propylene to the accumulator manually.

The incident time, we topped up c3. It was observed that the accumulator temperature dropped significantly. There was still liquid during that time. Closed everything and let the temp and pressure rise. However, temp increased to ambient but pressure (500 kpag) was seen not to be equal to VLE which is supposedly ~1200 kpag and was found to be decreasing. All transmitters are good and validated by local gauges. An attempt to open the vent on top of accumulator led to dropping temperature to zero.

The system was just commissioned and all parameters were running smoothly for three days already. We needed to stop as the external ethylene loop with cryogenic tank is at low pressure already. This event happened on restart.

Can nitrogen be a culprit?

[Bobby Strain]

A picture is worth a thousand words. It's impossible for us to troubleshoot with such little information. All you will get without lots of data are guesses. Not a good method for efficient problem solving. First, you should tabulate the data, including design values. Who designed the system for you? Are they around to help?

 

Bobby

[horatorres]

   Cat

 

A process diagram with design and actual condition (Q,P,T) will be useful to get the trouble in the process , and give you some ideas of what is the issue

 

Horacio