5 replies to this topic

[paidis]

dears , 

 

if we want to use an existing tower instead of tower , what we should check ?

 

before feed flow of this tower was about ten times more than new feed flow . we simulate it with hysys and it can separate exactly . but as i say new feed flow ( and therefore reflux and reboiler rate ) are  less than design and operation condition of tower . 

 

 

thanks. 

[Bobby Strain]

Probably best to use a new tower. Although you could put in some special trays to operate at the lower rate.

 

Bobby

[latexman]

I've learned time and time again, that it only cost a little extra to use surplus equipment.

[Bobby Strain]

Its my experience of 50 years, too.

 

Bobby

[Pilesar]

If you are planning on rerouting a new feed to an existing installed tower, there can be substantial savings. A few things to check (not exhaustive)

- design pressure and temperature

- materials of construction

- recent inspections for corrosion, thinning, structural problems

 

A ten to one turndown is radical and difficult to achieve without modification unless your column has bubble caps. Consider whether you will need to over-reflux the tower to stay in its operating range and how that will affect the economics. You should rate the tower, condenser, reboiler, pumps, instrumentation, piping, internals, etc for the new design conditions. Distillation efficiency may change with the lower flow rate. Will you have enough distillation stages? Does some of the tray active area need blanking? Are your internal distributors adequate or do they need modification? Is the feed location adequate? With lower internal flows, check for tray weeping or dry packing sections. The tower internals vendors should be able to help with some of these rating questions. Relief valves need to be checked for the new conditions. Instrumentation may need re-ranging. Control valves may need new trim. If you have piping with two-phase flow, check that you are not in the slug flow regime or at least have proper support for the piping. 

[paidis]

dears , thanks for reply .

 

dear pilesar thanks for your help. i will check .