3 replies to this topic

[muddu4]

hello friends,

i am working on hysys stimulation from past 3 months but i am not to stimulate distillation column. everything is fine until temp and pressure conditions. but there is a option called as spec in which we have to add certain things like reflux ratio or reflux rate........etc so what exactly it means how many specs should be kept in active and estimate mode???????????? guys please help me out

[darshan]

@mmulla
Distillation column has Degree of freedom 2 for total condensor and 3 for partial one, hence you can specify 2 specs at a time, see that only 2 specs are active at a time. still you dont get solution then try changing your convergence methods ( by cliking on parameters tab and selecting solver->solver methods )

[smalawi]

hi,

the fact that you are designing a distillation column implies that you did some manual calculations to start with then build you simulation. the specs you talk about are design paramters and very important to the final product.

the degree of freedom can be seen in hysys column monitoring window at the bottom right side. hysys tracks this value in order to solve your simulation. slection of the specs for the column simulation are conseaved during consptual desing stage, i.e. do i control the vapor line temperature or the third tray from the top ? what is the rebiler temperature is expected to be and what is % vaporization or reboil ratio ? do i specify a paroduct recovery to component mol fraction? you should have some idea to put meanningful spec that do not conflect with each other. for example, the condenser duty and vapour line temperautre are related in some cases.

typically is specify flow rates, rebiler/condenser dutys to converge the simulation fast and then start tuning the simulation with my criteria. you can build on this and develop your own style

the simluaiton is to check and confirm the detailed engineering of the column design only if you prperly know how to master your simulation and relate it to practical operation.

cheers,

sm

[Padmakar Katre]

Dear,
Just for the addition to the thread is we can have ranged specs in Hysys.Normally we find column either takes much time or doesn't converge for the given/active specs so one option we can use is to have the ranged specs i.e. minimum to maximum and check your column will converged.Once your your column is converged then you can optimize the column by using an optimizer.