2 replies to this topic

[mona naser]

Hi,


I am simulating chilling & liquefaction unit in LNG plant as part of my research project. When I switched to the dynamics mode, the flow rates changed from those in the steady state mode. Is there any way I can adjust the flow rates so that I can get the design flows. I tried different combinations of the boundary streams P/F specs and all my attempts were unsuccessful. There are two 2 LNG exchangers (as in the attached image).

I received this reply from an expert but did not have any further explanation:
" The best way would be to initialise the LNG exchangers in isolation from the rest of the simulation and then connect it to the simulation. Specify a flow rate in the inlet and the pressure in the outlet. The k factor should no be specified instead have a constant DP across the exchanger so that the k factor can be restimated. But not that the P-F relationship is not going to be direct since its in a network."

Do you know any way I can adjust the flow rates or if you can explain the mentioned reply??

Thanks,  unit5.png   20.9KB   14 downloads

Mona

[Zauberberg]

A simple flow control loop including the valve and the flow controller will do the work. Your flowsheet is a steady-state flowsheet.

[jmukund]

In dynamic simulation flows are regulated with resistances offered by control valve, LNG exchanger, exchangers, or elevations.

In your case you need to adjust K factors for each layer of LNG exchanger to get desired flow at calculated differential pressure. You can get necessary data from DATASHEET of the exchanger. As suggested by Sir Zauberberg, you need to define the control by PID’s if available.

Mukund