2 replies to this topic

[Fathy]

My project is naphtha isomerization design and analysis economical of the unit. There is a distillation column in order to separate cracked gases from isomerate. The flow is hydrocarbon mixture from C1 to C7. Please estimate the price of the distillation column.

Temperature = 210 C
tray=31
Diameter 2.9 m
Height 24m
tray space 0.6 m
pressure drop 1.2 bar


Thank you for your kindness. ^ ^ <BR style="mso-special-character: line-break"><BR style="mso-special-character: line-break">

[saeed.s]

To find true answer , please specify design pressure, type of tray, material of shell and tray or any cladding and your region

[katmar]

The list of additional data requested by benham is valid. You must know all that in order to get to an accurate price. I suspect the pressure drop you have listed is actually the operating pressure. It would be most unusual to have such a high pressure drop over a distillation column.

I would like to give you some general advice on estimating fabricated items - eg columns, heat exchangers, tanks and so on. If you know the material of construction and the type of equipment you can often get a reasonable estimate of the price simply from the mass of the item. You need to build up a database (and a "feel") for the fabricated cost per kilogram for each material and equipment type. The cost per kg will be more for a heat exchanger than for a tank. But for heat exchangers of similar sizes the rate per kg will be similar.

For initial estimates this is usually accurate enough because the "true" price of the item is always uncertain. If you have detailed fabrication drawings for the item and issue them to 4 or 5 different workshops for pricing it is not at all unusual to find that the highest price is double the lowest one. In this case, what is the true price? You can't always be sure of getting the lowest cost because it depends on shop loading, and if you always use the highest price your project will be dead before you start. You want to find some reasonable price in the range between the highest and lowest, probably closer to the low end than the high end.

At this stage you obviously do not have this database built up, so you might have to estimate purely from the material cost and a multiplier. It is easy to phone a material supplier to get a price per kg of plate, and then try phoning a workshop to see if they can give you a ratio between the material and labour cost for the type of equipment you are working with.